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  • Electronic Resource  (237)
  • 2000-2004  (237)
  • 1920-1924
  • Magnetic resonance imaging  (158)
  • kinetics  (79)
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  • Electronic Resource  (237)
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Year
  • 101
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 42 (2000), S. 586-590 
    ISSN: 1432-1920
    Keywords: Key words Spine ; Subdural haematoma ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present MRI findings in three patients with acute spontaneous subdural haematomas of the spine. Acute haematomas (1–3 days) were isointense or gave slightly high signal on T1- and heterogeneous signal on T2-weighted images. MRI precisely defined the level and extent of the haematoma preoperatively. The MRI was prospectively correctly interpreted as acute subdural haematomas in all patients. As a specific, noninvasive modality, MRI is the preferred imaging technique in this rare clinical entity.
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  • 102
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 42 (2000), S. 9-13 
    ISSN: 1432-1920
    Keywords: Key words Haemochromatosis ; Magnetic resonance imaging ; Computed tomography ; Transcranial ultrasound ; Nucleus, lentiformis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Haemochromatosis is characterised by deposition of iron-containing pigment in various organs, but little is known about possible deposition in the brain and its clinical impact. We therefore investigated 14 patients with hereditary haemochromatosis with MRI, CT and transcranial ultrasound (TCS) and examined them neurologically. In six of the patients dense lesions were found within the lentiform nucleus on CT, all of whom displayed hyperechogenic lesions in the same area on TCS, as did one other patient. In these patients the relative signal intensities of the lentiform nucleus measured by MRI relaxometry were higher. No patient had clinical signs of basal ganglia disorders.
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  • 103
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 42 (2000), S. 48-50 
    ISSN: 1432-1920
    Keywords: Key words Gaucher's disease ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present the cranial MRI findings in a 6-month-old girl with biopsy-proven acute neuropathic Gaucher's disease, which include unilateral cerebral atrophy and dural thickening with contrast enhancement.
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  • 104
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 42 (2000), S. 54-55 
    ISSN: 1432-1920
    Keywords: Key words Brain, hypoxia ; Blood-aqueous barrier ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The MRI findings of a patient with diffuse cortical hypoxic brain damage (Adams pattern III) are presented. Besides intense cortical contrast enhancement, a peculiar leakage of contrast medium at the anterior chambers of the eye was observed. The pathogenetic mechanism of this enhancement is discussed.
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  • 105
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 42 (2000), S. 746-748 
    ISSN: 1432-1920
    Keywords: Key words Granulation, arachnoid ; Sinuses, venous ; Computed tomography ; Magnetic resonance imaging ; Magnetic resonance venography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report CT, MRI and angiographic findings of an arachnoid granulation in the straight sinus in a young man. Its density and signal intensity were isodense and isointense with cerebrospinal fluid on CT and MRI, respectively. The lesion appeared as a filling defect on MR venography and conventional angiography.
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  • 106
    ISSN: 1432-1920
    Keywords: Key words Spinal cord, central canal ; Syringomyelia ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The central canal of the spinal cord is present at birth and becomes progressively obliterated. Cadaver studies have shown that it may persiste partially or completely. To our knowledge, this entity has not been described on MRI. We reviewed 794 MRI studies of the spinal cord, and found 12 patients (aged 14 to 65 years) who had an intramedullary cavity. The cavity was at the junction of the ventral 1/3 and dorsal 2/3 of the spinal cord, except at the level of the lumbar enlargement, where it was central. It was filiform in most cases, although sometimes fusiform (3 to 4 mm in diameter), and had regular contours. The cavity were thoracic in 69 % of cases. The clinical features were totally unrelated to the image, and there were no anatomical factors (Chiari malformation, dysraphism) predisposing to syringomyelia. The images were perfectly compatible with a persistent central canal, which we interpret as a variant of normal anatomy. Therefore it is important to regard these findings as normal, to avoid unnecessary treatment and follow-up.
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  • 107
    ISSN: 1432-1920
    Keywords: Key words Hemimegalencephaly ; Positron emission tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report hemimegalencephaly in a 44-year-old woman with mental retardation, epilepsy and a mild hemiparesis. In addition to typical findings on MRI, 2-deoxy-2[18F]fluorodeoxyglucose positron-emission tomography (PET) demonstrated glucose hypometabolism of the affected hemisphere. The results of PET have been coregistered with morphological information from the MRI studies by image fusion.
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  • 108
    ISSN: 1432-1920
    Keywords: Key words Cerebral palsy ; Birth asphyxia ; Magnetic resonance imaging ; Single-photon emission computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We describe the findings on single-photon emission computed tomography (SPECT) in patients with perinatal asphyxia at term, with perirolandic cortico-subcortical changes on MRI, and to correlate them with clinical features. SPECT of 7 patients was obtained after injection of 185–370 MBq of Tc-99m-ECD (ethyl cysteinate dimer). The patients had spastic quadriplegia (7/7) with perinatal asphyxia (6/7) at term (7/7). The results were correlated with the MRI findings. Hypoperfusion of the perirolandic cortex was clearly seen on SPECT in all patients, even in two with subtle changes on MRI. SPECT demonstrated a more extensive area of involvement than MRI, notably in the cerebellum (in 4), the thalamus (in 7) and basal ganglia (in 5), where MRI failed to show any abnormalities.
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  • 109
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 42 (2000), S. 917-922 
    ISSN: 1432-1920
    Keywords: Key words Mouth, cysts ; Neck, cysts ; Glands, salivary ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We reviewed the MRI of 20 patients with a ranula (8 simple and 12 plunging) and ten with other cystic masses in the floor of the mouth and/ or suprahyoid portion of the neck (three haemangiomas, two neuromas, one monomorphic adenoma, one lipoma, two lateral cervical cysts and one dermoid cyst). Histological diagnoses were obtained in all cases with the exception of one presumed haemangioma. Ranulas were all well-defined, homogeneous masses giving low signal on T1-and markedly high signal on T2-weighted images. While simple ranulas were all confined to the sublingual space, plunging ranulas were centered on the submandibular space and tended to spill into one or more adjacent spaces. They extended into the sublingual space anteriorly (producung a so-called tail sign) in eight of 12 cases and into the parapharyngeal space superiorly in five. Although they sometimes filled a considerable part of the parapharyngeal space, displacement of surrounding muscles or vessels was usually slight, which was thought to reflect the nature of extravasation pseudocysts. All other cystic masses in our study had one or more MRI finding different from those of ranulas and could be easily differentiated from them.
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  • 110
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 42 (2000), S. 112-114 
    ISSN: 1432-1920
    Keywords: Key words Hypophosphataemia ; Brain ; Myelinolysis, extrapontine ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a 38-year-old woman with extreme hypophosphataemia in whom CT and MRI disclosed bilateral lesions within the basal ganglia, thalamus and occipital lobes. After adequate substitution of phosphate the lesions grossly resolved and the patient recovered. This case is the first to demonstrate that profound changes of serum phosphate may be associated with reversible brain lesions.
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  • 111
    ISSN: 1432-1920
    Keywords: Key words Carcinoma nasopharyngeal ; Radionecrosis ; Magnetic resonance imaging ; Pulse sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We examined nine patients with histologically proven nasopharyngeal carcinoma (NPC), treated with radiotherapy, using dynamic susceptibility contrast MRI (DSC-MRI). In eight there was clinical evidence of radionecrosis of the temporal lobe, and one was examined for local recurrence in the nasopharynx. All patients had either high-signal finger-like or cystic lesions in the temporal lobes on T2-weighted images. Heterogeneous contrast enhancement occurred in all patients. Relative regional cerebral blood volume (rrCBV) mapping revealed marked hypoperfusion in all patients. One underwent bilateral temporal lobectomy and radionecrosis was confirmed histologically.
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  • 112
    ISSN: 1432-1920
    Keywords: Key words Dysplasia, focal cortical ; Hamartomas ; Epilepsy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Focal cortical dysplasia (FCD) is a pathological entity first described in 1971. Other more subtle cortical malformations found in patients with epilepsy include microdysgenesis (MD), and glioneuronal hamartias. Although these glial and neuronoglial malformations have distinct histological features, there is terminological confusion in the radiological literature. Few cases have been reported in adults with both imaging and histology. We address these issues, giving a radiological-pathological correlation of histologically proven cortical malformations in adults. We describe clinical, radiological and histological features of 12 cases (five FCD, five MD with glioneuronal hamartias, and two hamartomas), unassociated with other conditions, and discuss them in the light of the literature. FCD is usually seen on MRI as cortical thickening, with or without signal change, which may extend into the adjacent white matter. On histology, abnormal neurons and/or glial cells, blurring of the grey-white matter interface, myelin pallor, demyelination, and gliosis may be found. Glioneuronal hamartias and hamartomas usually appear as complex masses on MRI. FCD and hamartias may be associated, and a combination of imaging findings may be seen on MRI. Atrophy of the ipsilateral hippocampus may be present on MRI in patients with hamartias, and minor cell loss on histology, but not definitive hippocampal sclerosis. Although the imaging findings of cortical malformations are protean, some characteristic MRI features, with histological correlates, may be found. The relevance of most of these observations remains unclear.
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  • 113
    ISSN: 1432-1920
    Keywords: Key words Acquired immunodeficiency syndrome ; Magnetic resonance imaging ; Contrast-enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Our purpose was to determine whether triple-dose delayed contrast-enhanced images would improve lesion detection in patients with symptomatic human immunodeficiency virus (HIV) infection. We reviewed 33 MRI studies on 29 patients. Single-dose immediate T 1-weighted spin-echo (1x-T 1) images were compared with delayed triple-dose images (D3x-T 1). Two neuroradiologists decided which technique showed more lesions, increased lesion conspicuity and/or altered the radiologic diagnosis. The D3x-T 1 technique improved lesion detection in 14 of 29 patients (48 %). In two patients (7 %), the improvement changed the radiologic diagnosis by showing new meningeal lesions.
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  • 114
    ISSN: 1432-1920
    Keywords: Key words Cerebral autosomal dominant arteriopathy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Clinical data and MRI findings are presented on 18 subjects from two families with neuropathologically confirmed CADASIL. DNA analysis revealed mutations in exon 4 of Notch 3 gene in both families. All family members with mutations in Notch 3 gene had extensive abnormalities on MRI, principally lesions in the white matter of the frontal lobes and in the external capsules. Of several family members in whom a diagnosis of CADASIL was suspected on the basis of minor symptoms, one had MRI changes consistent with CADASIL; none of these cases carried a mutation in the Notch 3 gene. MRI and clinical features that may alert the radiologist to the diagnosis of CADASIL are reviewed. However, a wide differential diagnosis exists for the MRI appearances of CADASIL, including multiple sclerosis and small-vessel disease secondary to hypertension. The definitive diagnosis cannot be made on MRI alone and requires additional evidence, where available, from a positive family history and by screening DNA for mutations of Notch 3 gene.
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  • 115
    ISSN: 1432-1920
    Keywords: Key words Rhombencephalosynapsis ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rhombencephalosynapsis is an unusual disorder characterised by maldevelopment of the rhombencephalon, sometimes with supratentorial midline anomalies. We report MRI findings in a 39-year-old woman, the oldest in the literature. MRI demonstrated hypoplasia of the cerebellar vermis, with fusion of the cerebellar hemispheres and abnormally oriented folia. Supratentorial anomalies were also seen.
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  • 116
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 42 (2000), S. 360-362 
    ISSN: 1432-1920
    Keywords: Key words Cyst, cavum septi pellucidi ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A 20-year-old woman with secondary amenorrhoea and an empty sella turcica was found to have a cyst of the cavum septi pellucidi (CSP) on MRI. The cyst had regressed spontaneously on follow-up MRI.
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  • 117
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 42 (2000), S. 406-412 
    ISSN: 1432-1920
    Keywords: Key words Lymphoma, primary central nervous system ; Chemotherapy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract On MRI, primary brain tumors are commonly seen as contrast-enhancing masses surrounded by areas of abnormal signal on T2-weighted images. Following successful treatment tumors may no longer show contrast enhancement. The residual abnormalities are assumed to be represent “edema” and infiltrating tumor cells. We report nine patients with primary lymphoma of the central nervous system who had complete responses to intravenous methotrexate, but did not receive intrathecal chemotherapy or cranial irradiation. After complete resolution of contrast-enhancing lesions, persistent abnormalities on T2-weighted images in the region of prior tumor were initially assumed to reflect residual viable tumor. As they remained unchanged for years, however, this may not hold true in the cases in which primary central nervous system lymphoma responds to chemotherapy alone.
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  • 118
    ISSN: 1432-1920
    Keywords: Key words Corpus callosum ; White matter lesions ; Cerebral ischaemia ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Many studies of white matter high signal (WMHS) on T2-weighted MRI have disclosed that it is related to cerebral ischaemia and to brain atrophy. Atrophy of the corpus callosum (CC) has also been studied in relation to ischaemia. Our objective was to test the hypothesis that CC atrophy could be due to ischaemia. We therefore assessed CC, WMHS and brain atrophy in patients with risk factors without strokes (the risk factor group) and in those with infarcts (the infarct group), to investigate the relationships between these factors. We studied 30 patients in the infarct group, 14 in the risk factor group, and 29 normal subjects. Using axial T1-weighted MRI, cortical atrophy and ventricular enlargement (brain atrophy) were visually rated. Using axial T2-weighted MRI, WMHS was assessed in three categories: periventricular symmetrical, periventricular asymmetrical and subcortical. Using the mid-sagittal T1-weighted image, the CC was measured in its anterior, posterior, midanterior and midposterior portions. In the normal group, no correlations were noted between parameters. In the infarct group, there were significant correlations between CC and brain atrophy, and between CC atrophy and WMHS. After removing the effects of age, gender and brain atrophy, significant correlations were noted between some CC measures and subcortical WMHS. In the risk factor group, there were significant correlations between CC and brain atrophy and between CC atrophy and WMHS. After allowance for age, gender and brain atrophy, significant correlations between some CC measures and periventricular WMHS remained. The hypothesis that CC atrophy could be due to cerebral ischaemia was supported by other analyses. Namely, for correlations between the extent of infarcts and partial CC atrophy in patients with anterior middle cerebral artery (MCA) and with posterior MCA infarcts, there were significant correlations between the extent of infarct and midanterior CC atrophy in the former, and posterior CC atrophy in the latter. Our findings could indicate that CC atrophy is associated with cerebral ischaemia.
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  • 119
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    Springer
    Neuroradiology 42 (2000), S. 551-563 
    ISSN: 1432-1920
    Keywords: Key words Acquired immune deficiency syndrome ; Spine ; infections ; Spine ; neoplasms ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Our purpose was to describe the range of MRI findings in infectious and neoplastic involvement of the spine and spinal cord in symptomatic patients with the acquired immunodeficiency syndrome (AIDS). MRI studies in 55 patients with AIDS and neurological signs and symptoms thought to be related to the spine or spinal cord were reviewed. We categorized the findings according to the spinal compartment involved. There were 29 patients with extradural, 11 with intradural-extramedullary and 9 with intramedullary disease. In 6 patients more than one compartment was involved simultaneously, and patients presented with multiple lesions in the same compartment. The most common causes of extradural disease were bone lesions (28); an epidural mass was seen in 14 and spondylodiscitis in 4 patients. Cytomegalovirus polyradiculitis was the most common cause of intradural-extramedullary disease (in 10 cases); herpes radiculitis was seen in two, and tuberculous infection in another two. In three cases leptomeningeal contrast enhancement was due to lymphoma. Human immunodeficiency virus (HIV) myelitis was seen in two patients, presumed vacuolar myelopathy in two, toxoplasma myelitis in four, intramedullary lymphoma in one, and herpes myelitis in one. Familiarity with the various potential pathological entities that can affect the spine and spinal cord in the AIDS population and their imaging characteristics is crucial for initiation of further diagnostic tests and appropriate medical or surgical treatment.
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  • 120
    ISSN: 1432-1920
    Keywords: Key words Progressive supranuclear palsy ; Magnetic resonance imaging ; Diffusion-weighted imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We measured the apparent diffusion coefficient (ADC), using diffusion-weighted imaging (DWI) and signal intensity on T2-weighted MRI in the cerebral white matter of patients with progressive supranuclear palsy (PSP) and age-matched normal subjects. In PSP, ADC in the prefrontal and precentral white matter was significantly higher than in controls. There was no significant difference in signal intensity on T2-weighted images. The ADC did correlate with signal intensity. The distribution of the elevation of ADC may be the consequence of underlying pathological changes, such as neurofibrillary tangles or glial fibrillary tangles in the cortex. Our findings suggest that ADC measurement might be useful for demonstrating subtle neuropathological changes.
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  • 121
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    Springer
    Neuroradiology 42 (2000), S. 676-678 
    ISSN: 1432-1920
    Keywords: Key words. Syringomyelia, spontaneous drainage ; Cerebrospinal fluid, hydrodynamics ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. We present five cases of syringomyelia associated with Chiari I or other causes of partial obstructions at the cervicomedullary junction, with spontaneous disruption of the wall of a cervical syrinx and formation of a communication between the cavity and the subarachnoid space, shown on axial MRI. MRI can be used to investigate the hydrodynamics, showing the liquid inside the disrupted syrinx wall and the pathway of drainage. The finding of spontaneous drainage may be important for understanding the pathogenesis of syringomyelia and may be helpful for choosing a surgical approach.
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  • 122
    ISSN: 1432-198X
    Keywords: Key words Henoch-Schönlein purpura ; Methylprednisolone ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Neurological complications are rare during the course of Henoch-Schönlein purpura (HSP). We report a 7-year-old girl with HSP who presented with seizures, loss of vision and disturbance of consciousness. Magnetic resonance imaging (MRI) showed high signal intensity in the gray and white matter over the left parietal and both occipital lobes, compatible with MRI findings of cerebral vasculitis. The eye fundi revealed multiple branches of retinal artery occlusion. Intravenous pulse methylprednisolone (MTP) followed by oral steroid therapy was initially administered for HSP nephritis. Cerebral vasculitis developed 10 days post-MTP treatment, with progressive worsening of consciousness. Oral steroid was discontinued and plasmapheresis was performed alone. Her level of consciousness dramatically improved after plasmapheresis. The brain MRI and eye fundi findings were consistent with her clinical improvement. To the best of our knowledge, this is the first description of MRI abnormalities and multiple retinal artery branch occlusion of cerebral vasculitis in a patient with HSP that was successfully treated by plasmapheresis alone. In conclusion, we propose that plasmapheresis may be used as a first-line therapy or rescue therapy for cerebral vasculitis in HSP.
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  • 123
    ISSN: 1432-198X
    Keywords: Key words Hemolytic uremic syndrome ; Cerebral hypoxia ; Magnetic resonance imaging ; Central nervous system lesions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report a 20-month-old girl with post- diarrheal (Shiga toxin) hemolytic uremic syndrome and severe encephalopathy. Magnetic resonance (MR) images were obtained in the acute phase of the disease and after 10 months. The first MR images showed widespread high signal intensity on T2-weighted and low signal intensity on T1-weighted images, in deep and subcortical white matter; the splenium of the corpus callosum was also involved, as well as cerebellar hemispheres. Neurological symptoms and signs gradually disappeared within 35 days. Follow-up MR imaging showed almost complete resolution of the previous findings, and the patient recovered without central nervous system impairment. The neurological lesions were probably due to hypoxia, although several other mechanisms could be involved, such as metabolic derangements and the action of Shiga toxin. In spite of the dramatic clinical manifestations, we observed a good outcome, indicating that patients with similar lesions do not necessarily have a poor prognosis.
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  • 124
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    Springer
    Der Radiologe 40 (2000), S. 904-915 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Leber ; Sonographie ; Computertomographie ; Magnetresonanztomographie ; Szintigraphie ; Positronenemissionstomographie ; Keywords Liver ; Ultrasonography ; Computed tomography ; Magnetic resonance imaging ; Radionuclide imaging ; Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Highly specific methods are required for the diagnostic workup of focal hepatic lesions, since benign circumscribed liver changes are very common. Although cross-sectional imaging techniques have a high diagnostic accuracy, radionuclide imaging techniques such as colloid, red blood cell, or hepatobiliary scan are commonly performed when a benign lesion is assumed since these permit a definite diagnosis with high specificity. The diagnosis of a primary or secondary malignant liver tumor, however, usually relies on radiological imaging techniques alone, supported by needle biopsy. Whether positron emission tomography as a primary or supplementary diagnostic tool will have a role in the routine staging of malignant tumors remains to be determined.
    Notes: Zusammenfassung Die Abklärung umschriebener Leberveränderungen erfordert den Einsatz von Methoden hoher Spezifität, da die Prävalenz benigner, fokaler Läsionen sehr hoch ist. Hierfür sind radiologische Schnittbildtechniken grundsätzlich gut geeignet. Wenn aufgrund der sonographischen, computertomographischen oder magnetresonanztomographischen Befunde eine gutartige Läsion anzunehmen ist, werden jedoch häufig ergänzend die Kolloiderythrozyten- oder hepatobiliäre Szintigraphie – ggf. in Kombination – eingesetzt, da hiermit rasch eine abschließende Diagnose mit hoher Spezifität gestellt werden kann. Bei malignen primären oder sekundären Lebertumoren hingegen werden nuklearmedizinische Zusatzuntersuchungen seltener angefordert, da der radiologische Befund, ggf. gestützt durch eine Ultraschall- oder CT-gezielte Biopsie, eine Diagnose in den meisten Fällen erlaubt. Inwieweit sich der primäre oder ergänzende Einsatz der Positronenemissionstomographie im Vergleich zu radiologischen Schnittbildtechniken beim Staging bösartiger Tumoren bewährt, ist noch nicht abschließend geklärt.
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  • 125
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    Der Radiologe 40 (2000), S. 1064-1076 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Sarkoidose ; Neurosarkoidose ; Granulom ; MRT ; Keywords Sarcoidosis ; Sarcoidosis complications ; Neurosarcoidosis ; Granuloma ; Brain diseases complications ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract The central nervous system is frequently affected during the course of sarcoidosis. Many of these lesions remain without clinical correlates. Unenhanced and contrast enhanced CT and MRI play an important role during the diagnostic work-up of patients with sarcoidosis and suspected or proved CNS involvement. This article summarizes the most frequent manifestations of neurosarcoidosis and provides illustrative examples of MRI findings.
    Notes: Zusammenfassung Das Nervensystem ist bei der Sarkoidose häufiger mitbeteiligt als nach klinischen Gesichtspunkten zu vermuten wäre. Den bildgebenden Untersuchungsverfahren kommt eine große Bedeutung beim Nachweis der pathologischen Veränderungen zu. Insbesondere die Kernspintomographie sichert die Diagnosestellung und dient der Verlaufsbeurteilung. In dieser Übersichtsarbeit werden die typischen klinischen und bildgebenden Befunde bei der Neurosarkoidose vorgestellt.
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  • 126
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    Der Radiologe 40 (2000), S. 870-877 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Lunge ; Perfusion ; Ventilation ; Computertomographie (CT) ; Magnetresonanztomographie (MRT) ; Keywords Lung ; Perfusion ; Ventilation ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Radiological cross-sectional imaging modalities, particularly computed tomography (CT) have become the mainstays for diagnosing lung disease in recent years. These enable morphological visualization of pathological processes with the greatest possible spatial resolution. Modern technical developments and complementary strategies have led to new applications and new functional assessments which need to be reviewed together with state-of-the-art techniques in nuclear imaging. The diagnosis of pulmonary embolism using spiral CT angiography and magnetic resonance (MR) angiography certainly belongs in this category. CT has become the an alternative modality of first choice, and it is also challenging pulmonary angiography as the gold standard. Direct visualization of patent pulmonary arteries and thromboembolic material is complemented by that of effects on the pulmonary parenchyma and right heart function; it also provides perfusion studies and MR-based flow measurement to assess hemodynamic compromise. Ventilation studies have long been a domain of nuclear imaging, and new techniques for the direct visualization of ventilation are emerging from recent developments in the field of MR imaging, for example, using hyperpolarized inert gases. New functional parameters of ventilation can be derived from these studies. For the diagnosis of metabolically active disease, such as tumor and pneumonia, CT offers very high sensitivity, for example, in screening for intrapulmonary nodules using low-dose CT and in the early detection of pulmonary infiltrates in high-risk patients. Especially for characterizing pulmonary nodules there is a need to combine nuclear medicine techniques, such as in positron-emission tomography.
    Notes: Zusammenfassung Die radiologischen Schnittbildverfahren, insbesondere die CT, haben sich innerhalb kurzer Zeit einen herausragenden Stellenwert in der Diagnostik von Lungenerkrankungen erworben. Dies umfasst in erster Linie die morphologische Darstellung pathologischer Prozesse mit hoher räumlicher Auflösung. Moderne technische Entwicklungen und kombinierte Untersuchungsstrategien eröffnen neue Einsatzgebiete und auch funktionelle Aussagen, die nach einer aktuellen Standortbestimmung gemeinsam mit den nuklearmedizinischen Verfahren verlangen. Dazu gehört die Diagnostik der Lungenembolie mittels Spiral-CT-Angiographie und MR-Angiographie der Pulmonalarterien. Hier hat sich mittlerweile die CT als alternatives Verfahren der Wahl etabliert und die Rolle der Pulmonalisangiographie als Goldstandard infrage gestellt. Die reine direkte Darstellung der durchströmten Pulmonalarterien und des thromboembolischen Materials wird durch Diagnostik intrapulmonaler und kardialer Veränderungen, Perfusionsuntersuchungen sowie MR-basierte Flussmessungen zur hämodynamischen Beurteilung erweitert. Nachdem Untersuchungen der Ventilation lange Zeit eine Domäne der Nuklearmedizin waren, eröffnen aktuelle Entwicklungen in der MRT neue Verfahren zur direkten Visualisierung der Lungenbelüftung, z. B. mittels polarisierter Edelgase. Aus diesen Verfahren lassen sich auch neue funktionelle Parameter der Ventilation ableiten. In der Diagnostik von Tumoren und Entzündungen überzeugt die CT insbesondere durch ihre hohe Sensitivität, z. B. beim Screening auf intrapulmonale Rundherde mittels Niedrigdosis-CT oder bei der Früherkennung pneumonischer Infiltrate bei Risikopatienten. Insbesondere bei der Charakterisierung intrapulmonaler Rundherde ist eine Kombination mit nuklearmedizinischen Verfahren (PET) grundsätzlich anzustreben.
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  • 127
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Koronare Herzkrankheit ; Magnetresonanztomographie ; Myokardperfusion ; SPECT ; Key words ; Coronary artery disease ; Magnetic resonance imaging ; Myocardial perfusion ; SPECT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Aim: Performance of combined rest/stress MR perfusion studies and the analysis of qualitative signal intensity parameters in comparison with 99mTc-SestaMIBI SPECT in patients with known coronary artery disease (CAD). Methods: Sixteen patients with CAD underwent MR myocardial perfusion assessment at rest and after dipyridamole-induced hyperemia. Qualitative parameters (SI increase, SI upslope) of the SI time-curves were evaluated and characteristics of normal, reversible and persistent hypoperfused myocardium as assessed by 99mTc-SestaMIBI SPECT were compared. Results: Compared with the rest values, normal myocardium showed a significant increase of the SI upslope during hyperemia (P〈0.001), whereas persistent (P=0.07) and reversible (P=0.15) hypoperfusions showed only minor changes. SI increase over baseline also showed a significant increase only in normal myocardium (P〈0.001). At rest, reversible ischemic areas showed no significant differences from normal myocardium, whereas during hyperemia SI increase was significantly lower (P=0.02). Conclusions: Qualitative SI parameters of a combined rest/stress MR myocardial perfusion study allow to differentiate normal from reversibly or persistently hypoperfused myocardium.
    Notes: Zusammenfassung Fragestellung: Die kombinierte Ruhe- und Belastungsuntersuchung der myokardialen Durchblutung in der MRT sowie die Analyse qualitativer SI-Parameter der MR-Myokardperfusion bei Patienten mit koronarer Herzkrankheit wurden mit der 99mTc-SestaMIBI SPECT verglichen. Methode: Bei 16 Patienten mit koronarer Herzkrankheit (KHK) wurde in der MRT mit einer Mehrschichtgradientenechotechnik die Myokardperfusion unter Ruhe- und Belastungsbedingungen untersucht. Qualitative Signalintensitätsparameter der Kontrastmittelanflutung wurden berechnet und die Parameter in normalen, reversibel und persistierend minderperfundierten Myokardarealen miteinander verglichen. Ergebnisse: Normales Myokard zeigte im Gegensatz zu reversiblen (P=0,15) und persistierenden (P=0,07) Ischämien eine signifikante Zunahme der SI-Anstiegssteilheit unter Belastung (P〈0,001). Die SI-Zunahme zeigte ebenfalls nur in normal perfundierten Arealen eine signifikante Zunahme (P〈0,001) nach Belastung. Unter Belastung zeigte sich bei reversiblen Ischämien eine signifikant niedrigere SI-Zunahme als in normalem Myokard (P=0,02), während sich in Ruhe kein Unterschied zeigte. Schlussfolgerung: Qualitative SI-Parameter der kombinierten MR-Perfusionsuntersuchung des Myokards in Ruhe und unter Belastung erlauben die Differenzierung zwischen normalem sowie reversibel oder persistierend minderperfundiertem Myokard.
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  • 128
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    Der Radiologe 40 (2000), S. 465-468 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Fäkale Inkontinenz ; Magnetresonanztomographie ; Endoanalspule ; Key words Faecal incontinence ; Magnetic resonance imaging ; Endoanal coil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Purpose. Within the recent years several studies have been performed to determine the value of endoanal magnetic resonance imaging (MRI) in faecal incontinence. Methods. MRI is performed using a 0.5 – 1.5T unit. A surface coil with a maximum diameter of 19 mm is placed in the anal canal. T2* 3D gradient-echo-sequences and T2-weighted turbo-spin-echo-sequences in coronal, axial und sagittal orientation are acquired. Results. Compared to endoanal ultrasound (EUS), which is the gold standard for diagnosis in faecal incontinence, endoanal MRI is better in visualization of the external sphincter. The accurate delineation of the external sphincter has led to the possibility to evaluate sphincter atrophy. Preliminary results have shown, that endoanal MRI has an accuracy of 90–95% in the demonstration of lesions in the external sphincter. In detection of lesions of the internal sphincter EUS is still superior to endoanal MRI. Conclusion. EUS and endoanal MRI are currently the optimal imaging techniques for faecal incontinenc, with the advantage of detecting external sphincter atrophy with endoanal MRI.
    Notes: Zusammenfassung Zielsetzung. In den letzten Jahren wurden mehrere Studien durchgeführt, deren Ziel es war, den Stellenwert von Endoanalspulen in der Magnetresonanztomographie (MRT) zur Abklärung von Sphinkterdefekten bei fäkaler Inkontinenz (FI) zu bestimmen. Methode. Die endoanale MRT wird an 0,5–1,5-Tesla-Geräten durchgeführt. Zur Darstellung der Sphinkteren werden Oberflächenspulen mit einem maximalen Querdurchmesser von 19 mm endoanal appliziert. T2*-gewichtet 3D-Gradientenechosequenzen und T2-gewichtete Turbospinechosequenzen in koronaler, axialer und sagittaler Schnittführung werden zur Darstellung des Analkanals angefertigt. Ergebnisse. Im Vergleich zum endoanalen Ultraschall (EUS), der den Goldstandard bei der Abklärung einer FI darstellt, kann mit der endoanalen MRT v. a. der M. sphincter externus besser abgegrenzt werden. Die exakte Differenzierung des M. sphincter externus vom ischiorektalem Fettgewebe ermöglicht die Diagnose einer Atrophie des äußeren Schließmuskels. Erste Studienergebnisse haben gezeigt, daß die endoanale MRT eine Treffsicherheit von 90–95% bei der Detektion von Defekten im M. sphincter externus erreicht. Die Abklärung einer Kontinuitätsunterbrechung im M. sphincter internus ist nach wie vor eine Domäne des EUS. Schlussfolgerung. Die endoanale MRT stellt eine ergänzende Methode zum EUS dar und ist diesem in der Beurteilung der Morphologie des M. sphincter externus überlegen.
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  • 129
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    Der Radiologe 40 (2000), S. 625-631 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Computertomographie ; Magnetresonanztomographie ; Pharynx ; Tumoren ; Key words Computed tomography ; Magnetic resonance imaging ; Pharynx ; Tumors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Background. Malignant tumors of the head and neck region are amongst the six most often occurring tumors of the body. They can be associated with the different anatomical compartments as well as different histologic types. The way of tumor spread of these malignancies depends on their histologic type and on the region. These compartments can be separated into the nasopharynx, the oropharynx, and the hypopharynx. Most of the malignant tumors belong to the squamous cell carcinomas, other histologic types are depicted less frequently. The histologic types of the other groups which are seen more often comprise of lymphomas and adenoidcystic carcinomas. The undifferentiated carcinoma of the nasopharynx is supposed to be a special type of tumor. The malignant tumors of the pharynx can also involve all three compartments. Beside these tumors, malignancies of mesenchymal origin can also be delineated. Imaging modalities. The imaging modalities most frequently used to detect these tumors and to clarify their extension are contrast enhanced computed tomography, magnetic resonance imaging, nuclearmedicine imaging modalities such as positron emission tomography. Other scintigraphic imaging methods play a less important role. Conclusion. The different imaging modalities of malignant pharyngeal tumors and of potentially infiltrated lymphnodes with the weightness on computed tomography and magnetic resonance imaging and their appearance in these imaging techniques shall be enhanced in this paper.
    Notes: Zusammenfassung Hintergrund. Der Kopf-Hals-Bereich zählt weltweit zu den 6 am häufigsten von malignen Tumoren befallenen Körperregionen. Maligne Tumoren des Pharynx können dabei entsprechend der anatomischen Unterteilung – d. h. Nasopharynx, Oropharynx und Hypopharynx – diesen Regionen zugeordnet werden. Neben der grundsätzlich heterogenen Wachstumstendenz weisen diese Tumoren je nach histologischer Herkunft ein recht unterschiedliches Ausbreitungsmuster auf. Bei der überwiegenden Mehrzahl handelt es sich um Plattenepithelkarzinome, die anderen histologischen Typen – wie adenoidzystische Karzinome oder Lymphome – sind weitaus seltener vertreten. Daneben kommen sehr selten auch noch maligne Tumoren mesenchymalen Ursprungs wie z. B. die Rhabdomyosarkome vor. Bildgebung. Die bildgebende Abklärung erfolgt mit der kontrastmittelverstärkten CT, der MRT und in jüngster Zeit mit nuklearmedizinischen Methoden, z. B. PET. Andere szintigraphische Untersuchungsmethoden spielen eine untergeordnete Rolle. Resümee. Verschiedene bildgebende Methoden (schwerpunktmäßig CT und MRT) und die entsprechenden Erscheinungsbilder sowie Lokalisations- bzw. Ausbreitungsdiagnostik der malignen Tumoren und evtl. befallener Lymphknoten dieser Regionen werden vorgestellt.
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  • 130
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Zerebrovaskuläre Erkrankung ; Arteriosklerose ; Magnetresonanztomographie ; Magnetresonanzangiographie ; Digitale Subtraktionsangiographie ; A. carotis ; Keywords Cerebrovascular disease ; Arteriosclerosis ; Magnetic resonance imaging ; Magnetic resonance angiography ; Digital subtraction angiography ; Carotid artery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Purpose. To compare high resolution contrast-enhanced MR angiography (MRA) and digital subtraction angiography (DSA) in the assessment of supraaortic vessel stenosis. Methods. 14 patients with suspicion of cerebrovascular disease or upper limb ischemia underwent selective DSA and high resolution contrast enhanced MRA employing a new Panoramic-Array coil. Stenosis assessment in comparison to DSA followed NASCET criteria. Additionally signal-/noise ratios (SNR) were evaluated to assess contrast enhancement. Results. Diagnostic image quality was achieved in all patients. Sensitivity and specificity for assessing high-grade stenosis of the supraaortic vessels were 100% and 96% respectively. In the assessment of high-grade common or internal carotid artery stenosis sensitivity and specificity was 100%. Conclusion. High resolution contrast enhanced supraaortic MRA combined with new coil sytems allow for a reliable assessment of stenoses along the whole vessel course including the aortic arch. Previous stent procedures limit its use in post-interventional follow-up.
    Notes: Zusammenfassung Fragestellung. Ziel der Studie war ein Vergleich zwischen hochauflösender kontrastverstärkter MR-Angiographie (MRA) und digitaler Subtraktionsangiographie (DSA) in der Diagnostik von Stenosen der supraaortalen Gefäße. Methoden. 14 Patienten mit Verdacht auf eine zerebrovaskuläre Erkrankung oder Durchblutungsstörung der oberen Extremität wurden mit DSA und hochaufgelöster, kontrastverstärkter MR-Angiographie mit Verwendung einer Panoramic-Array-Spule untersucht. Neben der Beurteilung der Kontrastierung erfolgte die Bestimmung der Stenosegrade im Vergleich zur selektiven DSA nach den NASCET-Kriterien. Ergebnisse. Bei allen Patienten konnte mit der MRA eine diagnostisch ausreichende Bildqualität erzielt werden. In der Diagnostik hochgradiger Stenosen der supraaortalen Gefäße ergab sich eine Sensitivität von 100% und eine Spezifität von 96%. In der Erkennung hochgradiger Stenosen der A. carotis communis oder interna lagen Sensitivität und Spezifität bei 100%. Schlussfolgerung. Die ultraschnelle MRA der supraaortalen Gefäße in Kombination mit einer geeigneten Spulenkombination ermöglicht die zuverlässige Erkennung stenotischer Veränderungen im gesamten Gefäßverlauf einschließlich des Aortenbogens. Stentimplanationen limitieren derzeit den Einsatz in der postinterventionellen Kontrolle.
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  • 131
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    Journal of neurology 247 (2000), S. 943-948 
    ISSN: 1432-1459
    Keywords: Key words Transverse myelitis ; Motor evoked potentials ; Somatosensory evoked potentials ; Electromyography ; Prognosis ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A systematic evaluation of anterior horn cell, motor and sensory pathways is possible by electromyography (EMG), motor (MEPs) and somatosensory (SEPs) evoked potentials, respectively, which may provide valuable information on acute transverse myelitis (ATM). In a prospective hospital-based study, EMG, MEP and SEP studies were carried out on admission and after 3 months in 39 patients with ATM. All the patients also underwent detailed clinical evaluation, and spinal magnetic resonance imaging (MRI) was performed in 28. Outcome was defined at the end of 3 months as poor, partial or complete recovery on the basis of functional status. Spinal MRI revealed hyperintense signal changes in T2 extending for two segments to the entire spinal cord. Central motor conduction time to tibialis anterior (CMCT-TA) was more frequently abnormal (90%), followed by tibial SEP (77%). CMCT to abductor digiti minimi (ADM) was abnormal in 30% and median SEP in 15% of patients. Evidence of denervation on EMG was present in 51% of patients. The CMCT-TA improved in 48% patients and tibial SEP in 32%. Median SEP improved in all patients, and CMCT-ADM remained prolonged in two. At 3 months 2 patients had died, and 18 had poor, 10 partial and 9 complete recovery. CMCT was correlated with miscle power, tone, reflec and MRI changes. Patients' outcome of was correlated with CMCT, SEP and EMG. These results are consistent with pronounced involvement of dorsal region of spinal cord in ATM. MEP is more frequently abnormal than SEP.
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  • 132
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    Journal of neurology 247 (2000), S. 252-258 
    ISSN: 1432-1459
    Keywords: Key words Cerebral venous ¶thrombosis ; Dural sinuses ; Magnetic resonance imaging ; Heparin ; Thrombolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In contrast to arterial stroke, cerebral venous thrombosis (CVT) is an infrequent condition which presents with a wide spectrum of signs and with a highly variable mode of onset. The clinician must therefore consider it systematically in all brain syndromes and perform the appropriate neuroimaging investigations: computed tomography (CT) with computed tomography angiography and/or magnetic resonance imaging with magnetic resonance angiography and, if necessary intra-arterial angiography. Once the diagnosis is established, a wide investigation for should be carried out in search of the cause, and treatment started as soon as possible. Treatment is based on the combination of intravenous heparin (followed by oral anticoagulants for 3–6 months), symptomatic treatment (anticonvulsants, analgesics, treatment of increased intracranial pressure) and treatment of the cause. Local thrombolysis is indicated if there is deterioration due to thrombosis extension despite adequate anticoagulation. Diagnosis and treatment of CVT should be considered as an emergency because of the considerable potential for full recovery in this condition.
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  • 133
    ISSN: 1432-1459
    Keywords: Key words Multiple sclerosis ; Neuropsychological ; Cognitive ; Magnetic resonance imaging ; Lesion load
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Neuropsychological deficits and the relationship to brain pathology were examined in 13 primary progressive (PP) and 12 secondary progressive (SP) multiple sclerosis patients with a similar duration of the progressive phase and comparable physical disability. A battery of neuropsychological tests to assess attention, short-term and working memory was administered to the patients, and their performance was compared to that of 20 healthy controls matched for age and premorbid IQ. Total cerebral lesion load on T2-weighted magnetic resonance imaging was measured in the patients. Both PP and SP patients performed significantly worse than controls in most of the neuropsychological tests. There were only subtle differences between SP and PP on the working memory task although magnetic resonance imaging lesion load was significantly higher in SP than in PP patients. In this exploratory study only subtle differences in cognitive impairment were detected between SP and PP patients matched for physical disability and relevant illness features. The results also suggest that the severity of cognitive impairment cannot be fully explained by the extent of abnormalities detected on conventional T2-weighted magnetic resonance images, and that other pathological abnormalities such as in normal-appearing white matter are likely to be involved.
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  • 134
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    Keywords: Key words Leukoaraiosis ; Aged ; Atherosclerosis ; Magnetic resonance imaging ; Carotid artery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cerebral white matter lesions are frequently observed on magnetic resonance imaging of elderly, nondemented persons. There is evidence that white matter lesions are involved in the pathophysiology of cognitive decline and dementia. White matter lesions can be divided into those in the periventricular and those in the subcortical region. Pathological and epidemiological studies suggest that atherosclerosis is involved in the pathogenesis of these lesions. Our study reports on the association between atherosclerosis in the carotid arteries and white matter lesions in a population-based study among 1077 elderly subjects. We randomly sampled 1077 subjects aged between 60–90 years from two prospective population-based studies. All subjects underwent ultrasonography of the carotid artery. In addition, 1.5 T magnetic resonance imaging was performed; white matter lesions in the subcortical and periventricular regions were rated separately. With increasing number of plaques in the carotid artery the severity of periventricular white matter lesions increased (P trend = 0.03), but not the severity of subcortical white matter lesions (P trend = 0.19). In addition, an increase in intima media thickness was borderline significantly associated with an increased severity of periventricular white matter lesions (P trend = 0.09), but not of subcortical white matter lesions (P trend = 0.68). These findings suggest that partly dissimilar pathogenetic mechanisms are involved in the etiology of periventricular and subcortical white matter lesions.
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  • 135
    ISSN: 1432-1459
    Keywords: Key words Multiple sclerosis ; Fatigue ; Magnetic resonance imaging ; Motor evoked potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fatique is a common symptom of multiple sclerosis (MS) even in the early phases of the disease, when neurological disability is usually still not present. To investigate the pathophysiology of fatigue we compared neurophysiological (motor evoked potentials of the four limbs, MEPs) and brain magnetic resonance imaging (MRI) findings in two groups of nondisabled MS patients, those with (n=15) and those without (n=15) fatigue. Fatigue was assessed by an interview and scored by the Fatigue Severity Scale. The two groups were matched for sex, age, disease duration, Expanded Disability Status Scale score, pyramidal Functional System (FS) score, and depression score. MEPs were abnormal in five patients with fatigue and in one patient without fatigue. A significant association was found between the patient scores on the Fatigue Severity Scale, and the burden of MRI lesions (r=0.5; P〈0.005). Significantly higher parietal lobe (P〈0.05), internal capsule (P〈0.05), and periventricular trigone (P〈0.05) lesion loads were found in patients with fatigue than in those without. Our results agree with a central nervous system origin of fatigue in MS patients. This symptom might be a consequence either of a functional deafferentation of the cortex due to cortico-subcortical interconnection damage or of a demyelination in critical sites of the CNS, such as the cortico-spinal tract.
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  • 136
    ISSN: 1432-1459
    Keywords: Key words Small subcortical ¶infarction ; Large-vessel disease ; Magnetic resonance imaging ; Silent white-matter hyperintensity ; Lacunar infarction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Small subcortical infarctions resulting from large-vessel disease are often observed. It is important to distinguish these from pure lacunar infarction resulting from small-vessel disease because the investigations and examinations differ. We investigated the differences on brain magnetic resonance imaging (MRI) between small subcortical ¶“lacunar-like” infarcts resulting from large-vessel disease and pure lacunar infarcts. Thirteen subjects with small lacunar-like infarcts (size 〈 2 cm), resulting from large-vessel disease, ¶and 30 subjects with lacunar infarcts (〈 2 cm), without large-vessel disease were studied. We measured infarction size using a 1.5-T MRI device and evaluated silent subcortical hyperintensity lesions using the modified Scheltens’ score. Large-vessel lesion was confirmed by conventional angiography, duplex carotid scan, and magnetic resonance angiography. There was no difference in the mean age of the two groups. Cerebrovascular risk factors and atherosclerotic complications were also comparable for the two groups. Progressive stroke was more common ¶in the lacunar-like infarction group than in the lacunar infarction group ¶(P = 0.004). Scores for periventricular hyperintensity, white matter hyperintensity, basal ganglia hyperintensity, and total subcortical hyperintensity scores were significantly higher in the lacunar infarction group than in the lacunar-like infarction group. The difference in basal ganglia hyperintensity scores was remarkable (P = 0.001). The enlargement of the perivascular space was also significantly greater in the lacunar infarction group than in the lacunar-like infarction group. These findings seem to reflect differences in the pathogenesis of infarction between the two groups. Silent subcortical hyperintensity lesions and enlargement of perivascular space are useful for between distinguishing small lacunar-like infarct resulting from large-vessel disease and pure lacunar infarction. This may have significant implications for the management of patients with lacunar-sized infarctions. It suggests that the pathogenesis of lacunar-sized infarction is variable.
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  • 137
    ISSN: 1432-1459
    Keywords: Key words Sarcoidosis ; Spinal cord ; Magnetic resonance imaging ; Corticosteroid therapy ; Prognosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spinal cord sarcoidosis is a rare disorder whose natural history and therapeutic outcome are not fully known. We examined four patients with spinal cord sarcoidosis both clinically and radiologically, particularly in relation to corticosteroid treatment. The initial manifestation was cervical myelopathy in three and uveitis in one. All four patients progressed slowly until corticosteroid therapy was initiated. The cervial spine was involved in all patients. Magnetic resonance imaging (MRI) showed spinal cord swelling with T2-weighted high intensity and linear leptomeningeal and patchy or diffuse intramedullary enhancement with gadolinium diethylene triaminepentaacetic acid. With corticosteroid therapy, dramatic improvement was seen on MRI, including disappearance or marked reduction of swelling and enhancement. Plasma levels of angiotensin-converting enzyme (ACE) were also markedly improved. In contrast, the clinical symptoms were little improved in one patient, unchanged in two, and rather worsened in one patient. Recurrence was seen on MRI at the maintenance dose in all four patients, without any dramatic change in clinical manifestation. MRI findings and plasma ACE are well correlated with active leasion of the spinal cord sarcoidosis, providing a useful marker for recurrence, but do not parallel the clinical manifestations.
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    Skeletal radiology 29 (2000), S. 726-728 
    ISSN: 1432-2161
    Keywords: Keywords Developmental dysplasia ; Hip ; Membrane ; Interposition ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Intra-articular membranous interposition was detected by MRI in the hip joint with residual subluxation of a girl aged 5 years 10 months. This structure, which had low signal intensity on both T1- and T2-weighted images, separated the femoral head from the acetabulum. Histological examination revealed chondrometaplasia, which suggested that this interposition might be transformed to a surface cartilaginous tissue of the secondary acetabulum often observed in residual subluxation of the hip.
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  • 139
    ISSN: 1432-2161
    Keywords: Key words Rheumatoid arthritis ; Cervical spine ; Magnetic resonance imaging ; Dynamic imaging ; Flexion views
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To determine whether MR imaging in flexion adds value relative to imaging in the neutral position with respect to displaying involvement of the subarachnoid space, brainstem and spinal cord. Design and patients. T1-weighted MR images of the cervical spine in 42 rheumatoid arthritis patients with cervical spine involvement were obtained and analyzed prospectively. We assessed changes between images obtained in the neutral position and following active flexion, especially horizontal atlantoaxial and subaxial motion, presence or absence of brainstem compression, subarachnoid space involvement at the atlantoaxial and subaxial level and the cervicomedullary angle. Vertical atlantoaxial subluxation and the amount of pannus were correlated with motion and change in subarachnoid space. Results. The flexion images showed horizontal atlantoaxial motion in 21 patients and subaxial motion in one patient. The flexion view displayed brainstem compression in only one patient. Involvement of the subarachnoid space increased at the atlantoaxial level in eight (19%) patients (P=0.004) and at the level below C2 in five (12%) patients (P=0.03). There were no patients with a normal subarachnoid space in neutral position and compression in the flexed position. The cervicomedullary angle changed significantly with flexion. Vertical atlantoaxial subluxation and the amount of pannus did not show a significant correlation with motion or subarachnoid space involvement. Conclusion. MR imaging in the flexed position shows a statistically significant narrowing of the subarachnoid space at the atlantoaxial level and below C2. Cord compression is only observed on flexion views if the subarachnoid space in neutral position is already decreased. MR imaging in the flexed position might be useful, since subarachnoid space involvement may be an indicator for the development of neurologic dysfunction.
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    Skeletal radiology 29 (2000), S. 104-108 
    ISSN: 1432-2161
    Keywords: Key words Adult teratoma ; Dumb-bell type tumor ; Lumbar spine ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report a case of a lumbar teratoma in a 50-year-old woman. The teratoma showed a dumb-bell-type expansion at the level of the left L3/4 foramen with massive erosion of the L3 vertebral body. MRI revealed inhomogeneous signal changes in the tumor, which were histologically compatible with a mixture of bone, muscle, fat, and cyst containing sebaceous material. Complete resection of the tumor and spinal arthrodesis with pedicle screw fixation was necessary to obtain stability of the affected spinal segment.
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    Child's nervous system 16 (2000), S. 138-142 
    ISSN: 1433-0350
    Keywords: Key words Craniopharyngioma ; Posterior fossa tumors ; Microsurgery ; Magnetic resonance imaging ; Computerized tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Between 1991 and 1998, 24 patients underwent surgery for a craniopharyngioma in our department. This group included two patients who had tumors with extensive growth along the midline, and along the posterior fossa in particular. In both cases suprasellar calcifications were typical features on magnetic resonance imaging (MRI) and computed tomography (CT). A 7-year-old boy presented with a 6-month history of headache, nausea, and progressive unilateral hearing loss. With a suboccipital approach it was possible to remove the main part of the tumor. In a 13-year-old boy headache and visual deterioration led to the diagnosis of a craniopharyngioma, which was removed with a pterional approach. For the neuroimaging work-up in such cases of atypically growing craniopharyngiomas MRI is the method of choice. Additional CT scanning is recommended, which provides valuable information about bony changes at the skull base due to space-occupying growth. CT substantiates the differential diagnosis if typical calcifications are seen.
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  • 142
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    Child's nervous system 16 (2000), S. 398-401 
    ISSN: 1433-0350
    Keywords: Keywords Primitive neuroectodermal tumor ; Diffuse leptomeningeal neoplasia ; Magnetic resonance imaging ; Pseudotumor cerebri ; Sinus thrombosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Primitive neuroectodermal tumors are easily detected by neuroradiologic imaging, as a rule. We report on two patients with early diffuse leptomeningeal primitive neuroectodermal tumors which escaped detection by contrast-enhanced magnetic resonance imaging.
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  • 143
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    Child's nervous system 16 (2000), S. 551-554 
    ISSN: 1433-0350
    Keywords: Keywords Acute myelitis of childhood ; Fibrocartilaginous embolism ; Magnetic resonance imaging ; Spinal cord infarction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Fibrocartilaginous embolus causing acute spinal cord infarction is a rare cause of acute-onset paraplegia or quadriplegia. Few cases of survivors have been reported in the neurosurgical literature, with most reports involving post-mortem or biopsy findings. There is little information on MRI findings in such patients. We present the youngest patient ever reported, and discuss the important differences between fibrocartilaginous embolus and acute myelitis of childhood. A 6-year-old girl with a history of back pain presented with sudden-onset nontraumatic paraplegia, with a clinical anterior spinal artery syndrome. Initial MRI scan revealed intervertebral disc disease at L1–2 and an incidental thoracic syrinx, but no cause for her acute-onset paraplegia was identified. Cerebrospinal fluid and other investigations were all negative. Sequential MRI scans revealed development of spinal cord expansion from T10 to the conus medullaris, with increased cord signal in the anterior aspect of the spinal cord. The intervertebral disc disease was unchanged. The imaging and clinical findings were caused by fibrocartilaginous embolus, which meant there was no need for spinal cord biopsy. The report describes the clinical and imaging criteria for diagnosis of fibrocartilaginous embolus, highlighting the case for avoiding an unnecessary biopsy. The clinical pattern in the paediatric group is discussed, with features differentiating it from acute myelitis of childhood.
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  • 144
    ISSN: 1433-0350
    Keywords: Keywords Cavernous angioma ; Cerebral angiography ; Dynamic scan ; Magnetic resonance imaging ; Sinus pericranii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objects: Sinus pericranii is only a symptom complex, and it can have a variety of etiologies. Therefore, it is important to differentiate these etiologies preoperatively by means of radiological examinations. A 5-year-old boy was admitted with a soft and fluctuant tumor in the right parietal region near the midline. The tumor appeared when the child was in a recumbent position, distending noticeably with the Valsalva maneuver and disappearing completely when the patient was in the sitting position. Methods: Magnetic resonance imaging showed the lesion with honeycomb-like heterogeneous iso- and low-intensity signals on the T1-weighted image and with heterogeneous high- and iso- intensity signal on the T2-weighted image. Dynamic study with an injection of gadolinium diethylene-triaminopentaacetic acid demonstrated and nodular peripheral enhancement at early phase and subsequent progressive enhancement towards the center of tumor. The internal carotid angiogram was normal. The external carotid angiogram, however, showed a tumor stain fed by the superficial temporal arteries. The stain was retained until the late phase and drained into the scalp veins and into the superior sagittal sinus. Following direct injection of contrast medium into the tumor there was prolonged retention of the medium in the tumor and leakage into scalp veins and the superior sagittal sinus. The mass under the periosteum was totally removed and proved to be a cavernous angioma. Conclusions: Scalp cavernous angioma is one of the etiologies of sinus pericranii and may be diagnosed preoperatively by cerebral angiography or magnetic resonance imaging. Serial dynamic magnetic resonance imaging will be particularly helpful for this diagnosis.
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  • 145
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Diffusionsgewichtete Kernspintomographie ; Wirbelkörpermetastasen ; Diffusionskoeffizient ; Keywords Diffusion weighted imaging (DWI) ; Magnetic resonance imaging ; Vertebral metastases ; Diffusion coefficient ; ADC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Aim of the study. The aim of the study was the evaluation of the diffusion coefficient (ADC) of vertebral metastasis and regular vertebral bodies with diffusion weighted MRI (DWI). DWI evaluates the tissue-specific molecular diffusion of protons. In tissues with high cell densities (neoplasm) a decreased ADC can be expected due to restricted diffusion according to an exaggerated amount of intra- and intercellular membranes (i. e. diffusion barriers). Methods. In 5 breast cancer patients the ADC of both known vertebral metastases and of adjacent regular vertebral bodies were measured with DWI (1.0 T; Phased-Array-Body-Coil; b: 880 and 440 s/mm2). Results. The ADC of regular vertebral bodies (1.3±0.23×10–,3s/mm2) was significantly (p≤0.0002) higher than in vertebral metastases (0.39±0.11×10–3s/mm2). Conclusions. These data demonstrate that the ADC can be reliably measured in vertebral bodies. The quantitative evaluation of the ADC in vertebral bodies seems to be an objective and comparable parameter for differentiating malign from benign vertebral tissue.
    Notes: Zusammenfassung Ziel. Ziel der Arbeit war die Messung des Diffusionskoeffizienten (ADC) mittels diffusionsgewichteter (DW) MRT in Wirbelkörpermetastasen und in MR-morphologisch unauffälligen Wirbelkörpern. Die DW-MRT misst den für ein Gewebe spezifischen ADC, welcher der Eigendiffusion von Wasserstoffmolekülen entspricht. In zellreichem Tumorgewebe mit zahlreichen intra- und interzellulären Membranen (d. h. Diffusionsbarrieren) ist ein niedriger, in zellarmen oder nekrotischem Gewebe, ein hoher ADC zu erwarten. Methode. Bei 5 Patientinnen mit Mammakarzinom wurde der ADC von Lendenwirbelkörpermetastasen sowie von angrenzenden, MR-morphologisch unauffälligen Wirbelkörpern ermittelt (1,0 T; Phased-Array-Body-Coil; b: 880 und 440 s/mm2). Ergebnisse. Der ADC in MR-morphologisch unauffälligen Wirbelkörpern (1,3±0,23×10–3s/mm2) war signifikant (p≤0,0002) höher als in Wirbelkörpermetastasen (0,39±0,11×10–3s/mm2). Schlussfolgerung. Anhand dieser Daten konnte gezeigt werden, dass der ADC von Wirbelkörpern verlässlich gemessen werden kann, und dass durch die quantitative Bestimmung des ADC ein objektiv vergleichbarer Parameter zur Verfügung steht, der zur Differenzierung von malignem und benignem Gewebe gut geeignet erscheint.
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  • 146
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Diffusion ; Magnetresonanztomographie ; Encephalitis disseminata ; Keywords Diffusion ; Magnetic resonance imaging ; Multiple sclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Magnetic resonance (MR) imaging is one of the best methods in diagnosis of multiple sclerosis, particularly in disclosure of active demyelinating lesions. Aim of this study was to compare diffusion weighted imaging and contrast enhancement in the detection of active lesions. A MR study with a contrast enhanced T1-weighted pulse sequence with magnetization transfer presaturation and a diffusion weighted echoplanar pulse sequence (b=1000 s/mm2) was performed in 17 patients (11 women, 6 men) with multiple sclerosis. 29 of 239 lesions showed an increased signal intensity in diffusion weighted imaging, 24 lesions a contrast enhancement, but only 16 lesions were visible in both pulse sequences. In patients with short clinical symptomatology significant more lesions could be detected with diffusion-weighted pulse sequence in comparison to patients with long standing symptomatology showing more lesions with contrast enhancement. Hence it is likely, that both pulse sequences detect different histopathologic changes. The early detection of demyelinating lesions in diffusion weighted imaging is attributed to the extracellular edema, however the contrast enhancement is caused by a blood brain barrier abnormality. It can be expected that diffusion weighted imaging will have a high impact on imaging of multiple sclerosis not only in therapeutic trials, but also in clinical routine.
    Notes: Zusammenfassung Die Magnetresonanztomograpie ist eine der wichtigsten Untersuchungsmethoden in der Diagnostik der Encephalitis disseminata, insbesondere im Nachweis aktiver Entmarkungsherde. Ziel der Untersuchung war es, diffusionsgewichtete und kontrastverstärkte Untersuchungen bezüglich der Erkennung aktiver Läsionen zu vergleichen. Bei 17 Patienten (11 Frauen, 6 Männer) mit bekannter Encephalitis disseminata wurden sowohl eine kontrastverstärkte T1-gewichtete Sequenz mit Magnetization-Transfer-Sättigung als auch eine diffusionsgewichtete Echoplanar-Sequenz (b=1000 s/mm2) durchgeführt. 29 der 239 Läsionen zeigten eine Signalsteigerung in der diffusionsgewichteten Sequenz, 24 eine Kontrastmittelaufnahme, jedoch waren nur 16 Läsionen in beiden Techniken nachweisbar. Bei Patienten mit kurzzeitig bestehender Symptomatik zeigten sich signifikant mehr Entmarkungsherde mit Signalsteigerung in der Diffusionswichtung im Vergleich zu Patienten mit länger bestehender neurologischer Symptomatik, die mehr kontrastmittelaffine Läsionen aufwiesen. Dies lässt darauf schließen, dass mit beiden Verfahren unterschiedliche histopathologische Veränderungen beobachtet werden. Das sehr frühe Auftreten der Diffusionsänderung in den Entmarkungsherden wird auf das Ödem zurückgeführt, während die Kontrastmittelaufnahme durch eine Blut-Hirnschranken-Störung verursacht wird. Es ist zu erwarten, dass die diffusionsgewichtete Magnetresonanztomographie einen hohen Stellenwert in der Bildgebung der Encephalitis disseminata nicht nur in Therapiestudien, sondern auch in der klinischen Routinediagnostik erlangen wird.
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  • 147
    ISSN: 1433-7347
    Keywords: Key words Osteonecrosis ; Bone marrow edema ; Knee ; High tibial osteotomy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Sports Science
    Notes: Abstract Symptoms in patients suffering from spontaneous osteonecrosis of the knee (SONK) may be reduced by high tibial osteotomy (HTO). However, the fate of the necrotic lesion is unknown and needs further investigation. We conducted a prospective study to evaluate magnetic resonance imaging (MRI) changes after operative and nonoperative treatment. Ten consecutive patients suffering from SONK of the medial compartment were given two treatment options: either HTO (n = 6) or conservative treatment with partial weight bearing for 3 months (n = 4). We measured the greatest extent of well-defined subchondral low signal intensity abnormality, considered to represent necrosis, and the surrounding area of intermediate signal intensity, considered to represent perifocal bone marrow edema, on T1-weighted coronal MRI images before and after treatment. The MRI follow-up period was 17.5 months (range 12–¶27) in the HTO group and 14.5 months (range 8–25) in the nonoperative group. At follow-up the MRI evaluation revealed a decrease in the low signal intense areas (necrosis) in five of the six patients in the HTO group. Only one of the four nonoperative patients showed a decrease in the low signal intense area. The intermediate intense areas (edema) decreased in all patients in the HTO group and in three of four in the nonoperative group. The mean decrease in the area of perifocal edema was significantly greater in the HTO group than in the nonoperative group (P = 0.019). No statistically significant difference was found for the area of necrosis between the two groups (P = 0.171). A clinical improvement was observed in all patients of the HTO group but in only two of the four patients of the nonoperative group. We conclude that the decrease in perifocal bone marrow edema seems to be associated with improved patient comfort. The MRI appearance of the necrotic lesion does not alter with either treatment mode.
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  • 148
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    Child's nervous system 16 (2000), S. 829-831 
    ISSN: 1433-0350
    Keywords: Keywords Intraoperative imaging ; Magnetic resonance imaging ; Anatomical and functional neuronavigation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The Erlangen-concept of image-guided-surgery is based on the installation of an open magnetic resonance (MR) scanner (Magnetom Open, 0.2 T, Siemens AG) in a twin operating room in combination with two neuronavigation systems (Stealth NeuroStation, Sofamor Danek, MKM Zeiss). Since March 1996 this method has been used for a total of 402 patients, among them 44 children. In 214 patients, mainly with gliomas or pituitary adenomas or who needed surgery for epilepsy, we performed intraoperative MR imaging to monitor the extent of resection, allowing a second look for possible tumor remnants and also compensating for brain shift by an intraoperative update of neuronavigation. Functional neuronavigation, i.e. the combination of anatomical neuronavigation with functional imaging [e.g. magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI)] was used in patients with lesions in brain areas such as the motor and speech areas. For MEG we used a MAGNES II biomagnetometer (Biomagnetic Technologies, San Diego, Calif.) and for fMRI a 1.5 T Siemens Symphony MR scanner. So far we have treated 89 patients with functional neuronavigation. Our preliminary experience indicates that intraoperative MR imaging, especially in combination with functional neuronavigation, allows more radical resections with lower morbidity.
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  • 149
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    European archives of psychiatry and clinical neuroscience 250 (2000), S. 76-78 
    ISSN: 1433-8491
    Keywords: Key words Septum pellucidum ; Developmental ¶disorder ; Schizophrenia ; Magnetic resonance imaging ; Cavum veli interpositi ; Cavum septi pellucidi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The case of monocygotic twins discordant for a psychotic disorder is presented. An anomaly of the septum pellucidum, a so-called cavum veli interpositi was found in the psychotic twin while his brother showed no such anomaly. Previous studies have shown a higher prevalence of septum pellucidum anomalies in schizophrenic patients. Abnormalities of the septum pellucidum may be associated with disturbed neuronal development in distinct limbic brain areas which cannot yet be visualized yet by brain imaging techniques. The finding of the cavum veli interpositi in the psychotic twin could be incidental; however, it may indicate a dysgenic process in early brain development and, thus, play a significant role in the etiology of psychosis.
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  • 150
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    Pflügers Archiv 440 (2000), S. r200 
    ISSN: 1432-2013
    Keywords: Key words oxygen uptake ; kinetics ; threshold
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The linear relationship between oxygen consumption (Vo2) and exercise intensity is a well established phenomenon observed during incremental exercise. Recently, a non-linear increase in Vo2 has been reported by Zoladz et al., who used a relatively complicated method to describe the phenomenon. In this study, we tried to ascertain whether the same phenomenon, which we named the oxygen uptake threshold (OUT), could be described by a simple method, using the two best fitting lines adopted for the less and more steep parts of the Vo2 increase. Our hypothesis was that the non-linear Vo2 increase was the result of a continuous Vo2 increase (oxygen drift) occurring during the more intense steps only. Therefore, we analysed the Vo2 time course during each step. Six cyclists performed an incremental exercise test on a cyclo - ergometer. The lactate threshold (LT) was calculated by using the intersection point of the two best fitting lines in the diagram of log LA (lactate concentration) dependence on log P (Power). The time course of Vo2 during each step was analysed by an exponential rise to the maximum model. The results showed that OUT could be determined in five of the six subjects, whereas LT could be determined in all six subjects. The power output determined by OUT (168 ± 13 W) was similar to that determined by LT (180 ± 25 W). The Vo2 time course during each step showed steady values during low intensity exercise. At intensities above LT and OUT, however, Vo2 increased continuously, showing oxygen drift. It may be concluded that OUT is a realistic phenomenon, which is based on oxygen drift.
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  • 151
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    Journal of thermal analysis and calorimetry 59 (2000), S. 633-642 
    ISSN: 1572-8943
    Keywords: cadmium ; dialkyldithiocarbamate ; kinetics ; thermal decomposition ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition kinetics of the solid complexes Cd(S2 CNR2 )2 , where R =C2 H5 , n -C3 H7 , n -C4 H9 or iso -C4 H9 , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R1 . The thermal analysis data suggested the thermal stability sequence Cd(S2 CNBun 2 )2 〉Cd(S2 CNPrn 2 )2 〉Cd(S2 CNBui 2 )2 〉Cd(S2 CNEt2 )2 , which accords with the sequence of stability of the apparent activation energies.
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  • 152
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    Journal of thermal analysis and calorimetry 59 (2000), S. 807-814 
    ISSN: 1572-8943
    Keywords: facial and meridional Co(III) complexes ; kinetics ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal properties of facial and meridional uns-cis-[Co(eddp)gly]0.5H2O complexes were investigated by means of DSC and TG techniques. It wasshown that the processes of thermal decomposition of these complexes are multi-stepdegradation processes, which can also be well separated into individual steps, depending onthe molecular symmetry. Thus, the process of thermal degradation of the meridional isomerof the above complex consists of 4 well-separated steps in the temperature interval from 100to 500°C. The corresponding kinetic and thermodynamic parameters of this process weredetermined, and a possible mechanism is discussed.
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  • 153
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    Journal of thermal analysis and calorimetry 61 (2000), S. 955-965 
    ISSN: 1572-8943
    Keywords: kinetics ; metal complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermogravimetry (TG) and differential thermal analysis (DTA) were performed on the complexes with general formula (M(DEBT)n (where M =Fe, Co, Ni, Cu or Ru; n =2, or 3 and DEBT=N,N-diethyl-N'-benzoylthiourea). Derivative thermogravimetric (DTG) curves were also recorded in order to obtain decomposition data on the complexes. The complexes of Fe(III), Co(II), Ni(II), Cu(II) and Ru(III) displayed two- or three-stage decomposition patterns when heated in a dynamic nitrogen atmosphere. Mass loss considerations relating to the decomposition stages indicated the conversion of the complexes to the sulfides or to the corresponding metal alone (Cu, Ru, NiS, CoS or FeS). Mathematical analysis of the TG and DTG data showed that the order of reaction varied between 0.395 and 0.973. Kinetic parameters such as the decomposition energy, the entropy of activation and the pre-exponential factor are reported.
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  • 154
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    Journal of thermal analysis and calorimetry 62 (2000), S. 429-433 
    ISSN: 1572-8943
    Keywords: adsorption ; fast measurement ; gravimetry ; kinetics ; sorption ; kw6
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms. After each pressure change he measured the adsorbed mass three times and calculated its equilibrium value at the new pressure. In the present paper, we discuss the applicability of this method in a broader scope without starting from a given combination of sorptive and adsorbent and the influence of measuring inaccuracies. The method is applied to detect whether the adsorption process is based on more than one adsorption mechanism or not.
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  • 155
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    Journal of thermal analysis and calorimetry 63 (2000), S. 375-386 
    ISSN: 1572-8943
    Keywords: activation energy ; ammonium perchlorate ; decompositon ; isothermal ; kinetics ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method. From the maximum decomposition rate – temperature dependence two different decomposition stages, corresponding to two different structural phases of ammonium perchlorate, are identified. For the first region (215–235°C), corresponding to the orthorhombic phase, the mean value of the activation energy of 146.3 kJ mol–1, and the pre-exponential factor of 3.43⋅1014 min–1 are obtained, whereas for the second region (240–260°C), corresponding to the cubic phase, the mean value of the activation energy of153.3 kJ mol–1, and the pre-exponential factor of 4.11⋅1014 min–1 are obtained.
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  • 156
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    Journal of thermal analysis and calorimetry 60 (2000), S. 35-43 
    ISSN: 1572-8943
    Keywords: kinetics ; 10-methylacridinium halides ; thermodynamics ; thermogravimetric investigations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 10-Methylacridinium chloride, bromide and iodide were prepared in crystalline forms (the first two salts as monohydrates) and subjected to thermogravimetric investigations. Decomposition of the compounds is initially accompanied by the liberation of water (in case of monohydrates), halomethanes and acridine molecules. As decomposition proceeds, side reactions occur which are reflected in a complex pattern of thermogravimetric curves. TG traces corresponding to the initial decomposition stage were used to determine the kinetic characteristics of the thermal dissociation of the salts. MNDO/d, AM1 and PM3 methods were employed independently to examine reaction pathways and to predict thermodynamic and kinetic barriers for the thermal decomposition of the compounds. These data were subsequently supplemented with theoretically determined crystal lattice energies, which enabled the relevant characteristics for the decomposition of crystalline phases to be predicted. The theoretically predicted characteristics are qualitatively comparable with those originating from thermogravimetric investigations, which allows one to believe that both are valid.
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  • 157
    ISSN: 1572-8943
    Keywords: cyanazine ; DSC ; kinetics ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyanazine was taken as an example for investigations under the influence of different conditions on thermal decomposition of triazine herbicides. DSC measurements were carried out under atmospheric pressure and hermetically closed, under pressure 1.3 kPa. The influence of the pressure on the constant reaction rate of decomposition of cyanazine was discussed. It was also proved that the predicted reaction constant rates from isothermal and non-isothermal measurements are consistent.
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  • 158
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    Journal of thermal analysis and calorimetry 60 (2000), S. 247-255 
    ISSN: 1572-8943
    Keywords: desulfuration ; gas atmosphere ; kinetics ; thermal decomposition ; titanium dioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The studies were devoted to determination of the effect of gas atmosphere and its pressure on the second step of decomposition of hydrated titanium dioxide (HTD) promoted by sulfate groups. It has been found that thermal decomposition of HTD at temperatures above 300°C consists of a number of processes such as dehydroxylation, desulfuration, recrystallization and sintering of solid grains, photochemical processes (if the decomposition proceeds in the presence of light) and adsorption of gas phase components (in the presence of air or SO2). Kinetic parameters characterizing this step of decomposition have been determined for processes carried out in vacuum and in argon or air atmospheres (at a pressure of 13.33hPa). The kinetic curves of decomposition carried out in the presence of gases capable of being adsorbed on the surface of partly dehydrated HTD are featured by local extrema due to simultaneous processes of decomposition and adsorption of gas components.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 9-15 
    ISSN: 1572-8943
    Keywords: coordination compounds ; kinetics ; thermal dissociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Physicalo-chemical importance of the quantitative study of kineticliability of coordination compounds in thermal dissociation processes is considered. Muchattention is given to the proof of the physicalo-chemical meaning and validity of kineticparameters calculated from thermoanalytical data. Experimental data (thermal dissociation ofcoordination compounds and clathrates with such a matrix) are discussed.
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  • 160
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    Journal of thermal analysis and calorimetry 60 (2000), S. 401-407 
    ISSN: 1572-8943
    Keywords: cross-linking ; isothermal crystallization ; kinetics ; modification ; polypropylene ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of addition of silica on the parameters of isothermal crystallization of polypropylene has been investigated. It was found that the covering of the silica surface by a layer of low-density polyethylene leads to a deactivation of the filler regarding the positive effect on the polypropylene crystallization rate parameters. Cross-linking of the surface polyethylene layer results in a stronger attachment of the modifying polymer to the filler surface and the deactivation effect of the silica surface modification is more pronounced.
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  • 161
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    Journal of thermal analysis and calorimetry 60 (2000), S. 541-547 
    ISSN: 1572-8943
    Keywords: Cr(II) ; chromium trioxide ; kinetics ; reduction ; thermal analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal behaviour of CrO3 on heating up to 600°C in dynamic atmospheres of air, N2 and H2 was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy (DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i) melting of CrO3 near 215°C (independent of the atmosphere), (ii) decomposition into Cr2(CrO4)3 at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr2O3 at 415–490°C (significantly dependent). The decomposition CrO3 → Cr2(CrO4)3 is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr2(CrO4)3 → Cr2O3 involves endothermic reductive deoxygenation reactions in air (or N2) which are greatly accelerated and rendered exothermic in the presence of H2. TG measurements as a function of heating rate (2–50°C min−1) demonstrated the acceleratory role of H2, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H2 molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function of the heating rate (2–50°C min−1) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 667-674 
    ISSN: 1572-8943
    Keywords: accommodation function ; crystal growth ; glass-ceramics ; kinetics ; number of nuclei ; thermal history
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Kinetic modeling of the crystal growth from pre-existing nuclei was reexamined to obtain a fundamental information about the controlled crystallization of glasses during formation of advanced inorganic glass-ceramics. Methods of kinetic analysis were reviewed by taking account of thermal history of the sample within the temperature range of nucleation. An accommodation function depending on the thermal history was introduced in the kinetic equation. The role of the accommodation function was reinvestigated when determining the activation energy from a series of kinetic curves. The kinetic description of the crystal growth in the samples with different thermal history was generalized by extrapolating the rate behavior to infinite temperature.
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  • 163
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    Journal of thermal analysis and calorimetry 60 (2000), S. 333-343 
    ISSN: 1572-8943
    Keywords: base line ; DSC ; kinetics ; modeling ; thermodynamics ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The application of non-linear heating program to a heat-flux DSC apparatus has attracted much attention. From thermodynamics viewpoint, it is shown that the variation of enthalpy of a sample changing with temperature change is due, to both the true heat capacity of the sample and the enthalpy of some transformations occurring in the sample, characterized by its degree of advance. Using the simple assumption that the rate of the transformation is proportional to the distance from the thermodynamic equilibrium, an electrical model of the thermal event is given. Using the coupled cell model of the DSC apparatus, we show how to obtain the rate of transformation of the sample and heat capacity, which is directly related to the base line of the experiment.
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  • 164
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    Journal of thermal analysis and calorimetry 60 (2000), S. 759-778 
    ISSN: 1572-8943
    Keywords: decomposition temperature ; error sources ; gas-flow and vapor control ; kinetics ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The well-known divergence between the present ‘state of the art’ of thermogravimetry and industrial requirements is discussed. Sources of errors are analyzed and the optimization of measuring conditions is discussed regarding the problems associated with static and dynamic (flow) atmospheres, and interactions between materials and gases or vapors. Recommendations for gas-flow control systems and vapor sources are given. Thermal stability and the kinetics of gas-evolving, reversible, thermal decompositions of solids are discussed. The scope of TG-derived kinetics for practical use is examined. Some new characteristic points of TG curves are proposed and defined, e.g. ‘procedure-independent decomposition temperature’ and ‘augmented decomposition temperature’ (obtained at pseudo-equilibrium conditions).
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  • 165
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    Journal of thermal analysis and calorimetry 60 (2000), S. 879-886 
    ISSN: 1572-8943
    Keywords: driving force ; kinetics ; rate equation ; reversible reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper outlines the different ways of taking the distance from thermodynamic equilibrium into account in kinetic studies based on thermoanalytical experiments. The three main approaches are: (i) avoiding or neglecting the effect of the reverse reaction, (ii) describing the influence of distance from equilibrium on apparent kinetic parameters, and (iii) incorporating a driving force factor in the rate equation. Finally, the contradiction of the microscopic nature of the processes and the macroscopic character of the usual rate equation are briefly discussed.
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  • 166
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    Journal of thermal analysis and calorimetry 60 (2000), S. 943-954 
    ISSN: 1572-8943
    Keywords: CRTA ; kinetics ; self-generated atmospheric conditions ; synthetic malachite ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetic behavior of the thermal decomposition of synthetic malachite was investigated by means of CRTA under different conditions of reduced pressure, flowing gases and quasi-isobaric atmospheres. The thermal decomposition was found to proceed at lower temperatures under the influence of the self-generated gases, CO2 and H2O. From a viewpoint of chemical equilibrium, the normal and opposite effects on the overall kinetics were observed for the self-generated CO2 and H2O, respectively. The complexity of the present reaction is also reflected by the variations of the apparent kinetic parameters which depend on the applied and self-generated atmospheric conditions. The practical usefulness of CRTA when applied to a complicated thermal decomposition is discussed as exemplified by the kinetic approaches to the present reaction.
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  • 167
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    Journal of thermal analysis and calorimetry 61 (2000), S. 151-156 
    ISSN: 1572-8943
    Keywords: complexes ; kinetics ; TG-DTA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal behaviour of a few lanthanide complexes of the type ML3(I) [M=Eu,Gd; HL=4,4,4-trifluoro- 1-(2-napthyl)-1,3-butanedione and EuL30.5dmm dmm=2,6-dimethylmorpholine(II)], has been investigated. From thermogravimetric(TG) curves, the decomposition pattern of the compounds has been analysed on the basis of mass loss data. The order and activation energy of the thermal decomposition reactions have been elucidated. From differential thermal analysis (DTA) studies, the heat of reaction and rate of thermal decomposition reaction have been enumerated.
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  • 168
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    Journal of thermal analysis and calorimetry 61 (2000), S. 239-242 
    ISSN: 1572-8943
    Keywords: kinetics ; Mannich compounds ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The authors present data concerning the evaluation of kinetic parameters of the decomposition of a Mannich compound by using the classical method of constant heating rate thermal analysis and the new one of controlled rate thermal analysis (CRTA). The data processed using the CRTA method allow to obtain more reliable kinetic parameters according to the proposed reaction mechanism.
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  • 169
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    Journal of thermal analysis and calorimetry 61 (2000), S. 437-450 
    ISSN: 1572-8943
    Keywords: crystallization ; EPDM ; kinetics ; morphology ; PP ; rubber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of the incorporation of an amorphous immiscible polymer (ethylene-propylene-diene- terpolymer) on the PP crystallization kinetics and thermodynamics is investigated by thermal analysis. The results of the investigation have shown that EPDM acts as a nucleant agent. A marked decrease of the half time of PP crystallization, τ1/2 , as well as a sensible increase of the overall crystallization rate, K n , has been observed in the presence of EPDM. Moreover, at any crystallization temperature, a minimum of τ1/2 , is obtained at 25% EPDM content in the blend. The Avrami model has been successfully applied to describe the crystallization kinetics of the blend. The kinetic curves obtained under non-isothermal conditions confirm the results obtained under isothermal conditions and demonstrate the nucleant action of the EPDM phase on the PP crystallization.
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  • 170
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    Journal of thermal analysis and calorimetry 62 (2000), S. 721-727 
    ISSN: 1572-8943
    Keywords: kinetics ; metal exchange ; thermaldehydration ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolite-4A is a hydrated aluminosilicate which becomes more hydrated when exchanged with transition metals. In this work, the dehydration kinetics of cobalt, nickel and copper(II)-exchanged zeolite-4A were studied by means of TG and DTA over the temperature range from 20 to 500°C, and the numbers of water molecules in the metal-exchanged zeolite samples were calculated. It was observed that, as the ionic radius of the hydrated metal increased, the number of water molecules also increased. The loss of water from the zeolite samples generally occurred in the temperature range 100–300°C and was manifested in the DTA graphs by an extended endothermic effect. The DTA curves demonstrated that the peak position shifted towards lower temperatures as the metal concentration increased or, in other words, the water of hydration increased. The kinetic parameters (order of reaction and activation energy) were calculated via the Coats and Redfern method. The process of dehydration was found to follow first-order kinetics.
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  • 171
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    Journal of thermal analysis and calorimetry 63 (2000), S. 359-374 
    ISSN: 1572-8943
    Keywords: KEKAM equation ; kinetics ; thermal dissociation of solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Relationships have been established between the average conversion degree and the dissociation time for polydisperse granular material, taking its grain size distribution into account. It has been checked in which cases the kinetic curves obtained by a numerical solution can be described in terms of KEKAM equation.
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  • 172
    ISSN: 1572-8943
    Keywords: isoconversional methods ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An analysis is presented of the consequences of the use of a one term equation containing apparent activation parameters, instead of the true rate equation to describe two successive decomposition reactions undergone by a solid compound. It is demonstrated that the apparent activation energy, obtained by means of isoconversional differential and integral methods, varies with the conversion degree for a relatively narrow temperature range and with temperature at a given value of the conversion degree. The activation energy values obtained with the isoconversional differential method are higher than the corresponding values obtained with the isoconversional integral method.
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  • 173
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    Journal of thermal analysis and calorimetry 59 (2000), S. 869-875 
    ISSN: 1572-8943
    Keywords: decomposition ; kinetics ; plumbo-jarosite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An investigation was carried out on the kinetics of thermal decomposition of plumbo-jarosite. The kinetic models of dissociation of the compounds in the ore were identified. The results of the kinetic studies and the mechanism of the process are discussed. The thermal decomposition of plumbo-jarosite occurs in three stages: the first up to 763, the second up to 1023 and the third up to 1223 K, the corresponding activation energy values being 62.2, 60.3 and 98.0 kJ mol–1 , respectively.
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  • 174
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    Journal of thermal analysis and calorimetry 61 (2000), S. 805-818 
    ISSN: 1572-8943
    Keywords: aluminium ; ARC ; DSC ; kinetics ; nanometric size ; SDT ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal properties of Alex, a nanosized Al powder, were determined using various techniques, including DSC, TG, simultaneous TG-DTA (SDT) and accelerating rate calorimetry (ARC). The results demonstrate that the specific heat capacities of nano and micron size Al powders are similar between 30 and 400°C. Dynamic and isothermal methods were used to determine the kinetic parameters for the oxidation reaction of Alex, which was detected at an onset temperature of 481°C. The results obtained were in good agreement with each other. From the ARC experiments, exotherms were detected near 340 and 260°C for experiments started at ambient pressure and at 0.72 MPa, respectively.
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  • 175
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    Journal of thermal analysis and calorimetry 61 (2000), S. 861-871 
    ISSN: 1572-8943
    Keywords: DAGN ; kinetics ; mechanism and IR spectroscopy ; TAGN ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Diaminoguanidine nitrate (DAGN) and triaminoguanidine nitrate (TAGN),potential energetic materials in emerging propulsion technology with high mass impetus at low isochoric flame temperature have been studied as regards kinetics and mechanism of thermal decomposition using thermogravimetry (TG), differential thermal analysis (DTA),infrared spectroscopy (IR) and hot stage microscopy. Kinetics of thermolysis has been followed by isothermal TG and IR. For the initial stage of thermolysis of DAGN the best linearity with a correlation coefficient of 0.9976 was obtained for the Avrami-Erofe'evequation, n=2, by isothermal TG. The activation energy was found to be 130 kJ mol–1 and logA=11.4. The initial stage of thermolysis of TAGN also obeyed the Avrami-Erofe'ev equation, n=2, with a correlation coefficient of 0.9975by isothermal TG and the kinetic parameters are E=160.0 kJ mol–1 and logA=16.0. High temperature IR spectra showed exquisite preferential loss in intensity of the NH2, NH, N–N stretching and CNN bending. Spectroscopic and other results favour deamination reaction involving the rupture of the N–N bond as the primary step in the thermal decomposition.
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  • 176
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    Journal of thermal analysis and calorimetry 61 (2000), S. 979-984 
    ISSN: 1572-8943
    Keywords: kinetics ; nucleation-growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The author presents some applications of the fractal geometry in the kinetics of heterogeneous decomposition of solids.
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  • 177
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    Journal of thermal analysis and calorimetry 59 (2000), S. 935-942 
    ISSN: 1572-8943
    Keywords: CoSO46H2O ; kinetics ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermogravimetry (TG-DTG), and differential thermal analysis (DTA) were used in the study of the kinetics of decomposition of cobalt sulphate hexahydrate under an air atmosphere. The kinetics of the particular stages of CoSO4 6H2 O decomposition were evaluated from the dynamic mass loss data. The values of the kinetic parameters for each stage of the thermal decomposition were calculated from the α(T) data by using the integral method, applying the Coats-Redfern approximation.
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  • 178
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    Journal of thermal analysis and calorimetry 62 (2000), S. 681-685 
    ISSN: 1572-8943
    Keywords: coal-burning additive ; combustion ; graphite ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The catalytic and accelerating effects of three coal-burning additives (CBA) on the burning of graphite were studied with the help of thermogravimetric (TG) analysis. The kinetic study on the catalytic oxidation of the graphite doped with CBA was carried out and the results were presented. The results show that the CBA can change the carbon oxidation/combustion course by catalytic action and change the activation energy, thus improving the combustion efficiency.
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  • 179
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    Journal of thermal analysis and calorimetry 63 (2000), S. 457-463 
    ISSN: 1572-8943
    Keywords: isoconversional methods ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is demonstrated that, if the activation energy depends on the degree of conversion, its values obtained by isoconversional differential and integral methods are different.
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  • 180
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    Journal of materials synthesis and processing 8 (2000), S. 139-144 
    ISSN: 1573-4870
    Keywords: TiO2 ; phase transformations ; mechanical alloying ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A high-pressure and high-temperature phase of TiO2 : TiO2 II is formed transiently during room-temperature high-energy ball milling of anatase TiO2 : TiO2 anatase → TiO2 II → TiO2 rutile. Rutile is the only phase present after prolonged ball milling. The present paper focuses on the influences of physical and chemical processing conditions on the transformation kinetics. The effects of two milling parameters on the kinetics of phase transformation of anatase TiO2 were investigated: the nature of milling tools and the powder-to-ball weight ratio R. Granulometric characterizations and TEM observations have demonstrated that the transformation of TiO2 anatase into TiO2 II occurs without fracturing of particles and that TiO2 II nanograins form at the surface of anatase particles. The parameter R affects only the transformation rate. For a given R, the transformation rate is the largest with alumina grinding tools, intermediate with zirconia tools, and the smallest with steel tools. The parameters involved in current models of the mechanical alloying process do not suffice to explain the differences in transformation rates observed here. A parameter, which takes into account the influence of the mechanical properties of grinding materials, is considered.
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  • 181
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    Journal of materials synthesis and processing 8 (2000), S. 271-277 
    ISSN: 1573-4870
    Keywords: Comminution ; kinetics ; mechanical alloying ; phase transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract It has been shown that structural evolution occurring in powder mixtures subjected to mechanical treatment by milling follow well-defined conversion trends as a function of milling time. Sigmoidal curves were observed in the case of the mechanical alloying of transition metal mixtures, whereas a simpler kinetic course with a progressively decreasing transformation rate was found to characterize the disordering process of intermetallic equilibrium compounds by mechanical milling. Under the stipulation that collisions are the dominant energy transfer events, a kinetic model is developed to relate the observed macrokinetic features to the discrete powder fractions, which transform at each impact. Because of its intrinsic qualities, the milling process was regarded as discrete processing. A statistical approach was followed to work out a set of differential equations, solutions of which provide a sound description of the transformation kinetics in terms of conventional rate expressions. The model allows one to reproduce the different kinetic behaviors by means of a single, unifying mathematical formalism. Furthermore, quantifying the structural evolution rate by suitable kinetic constants permits the exploration of the reactive behavior of a system treated under different milling regimes or to compare, on an absolute basis, different systems processed under similar conditions.
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  • 182
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    Oxidation of metals 53 (2000), S. 351-360 
    ISSN: 1573-4889
    Keywords: Co-base superalloy ; high-temperature oxidation ; kinetics ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of the Co-base superalloy DZ40M was studied in air at900–1100°C for times of up to 2000 hr. The results indicated thatthis alloy can grow a protective oxide scale at 900 and 1000°C duringisothermal oxidation, but not at 1100°C because of serious cracking andspalling of the oxide scales. Moreover, an internal-precipitate zone formedin the subsurface region of the alloy at all temperatures and times. Theprecipitates were rich in Cr in the vicinity of the alloy–scaleinterface and rich in Al deep in the alloy. The internal-precipitatemorphology changed from a granular to needlelike shape with increasingoxidation temperature.
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  • 183
    ISSN: 1573-4943
    Keywords: Aluminum ; yeast hexokinase ; preferential interactions ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The aluminum and yeast hexokinase interaction was studied. Structural changes were correlated with variations in protein functionality. Results show two different behaviors: At low metal concentrations preferential adsorption of metal (and water exclusion) induces aggregate formation. No significant changes in the protein structure occur, but there is a continuous loss of activity (from the first concentration). At large salt concentrations a monomerization process and a conformational change in the secondary structure as well as in the three-dimensional structure take place. This change reduces the percentage of α-helix conformation, gives thermal stability to the protein, and allows the exposure of some tryptophan residue and hydrophobic regions. The protein inhibition increases. Conformational change and monomerization may allow access of the metal to the substrate site, mainly the ATP site. The inhibition in any case is of mixed type with a competitive component.
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  • 184
    ISSN: 1573-4943
    Keywords: Creatine kinase ; human ; expression ; brain ; muscle ; purification ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We report the expression of the human muscle (CK-MM) and brain (CK-BB) creatine kinases in Escherichia coli. The proteins have been purified to apparent homogeneity and several of their physical and kinetic properties investigated. In the process, we have conclusively verified the correct DNA sequence of the genes encoding the respective isozymes, and determined the correct primary structure and mass of the gene products. Alignment of the primary sequences of these two enzymes shows 81% sequence identity with each other, and no obvious gross structural differences. However, Western blot analyses demonstrated the general lack of antigenic cross-reactivity between these isozymes. Preliminary kinetic analyses show the K m and k cat values for the creatine and MgATP substrates are similar to values reported for other isozymes from various tissues and organisms. The human muscle and brain CKs do not, however, exhibit the synergism of substrate binding that is observed, for example, in rabbit muscle creatine kinase.
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  • 185
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    Russian chemical bulletin 49 (2000), S. 1974-1976 
    ISSN: 1573-9171
    Keywords: ammonium dinitramide ; thermal decomposition ; kinetics ; stabilization ; isotope composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of accumulation of the main products of thermal decomposition of ammonium dinitramide in the melt was investigated. The isotope composition of nitrogen-containing gases evolved by the decomposition of 15NH4N(NO2)2 and NH4 15N(NO2)2 was found. Easily oxidized salts, amines, amides, iodides, and other compounds soluble in the melt interfere with the liquid-phase decomposition of ammonium dinitramide.
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  • 186
    ISSN: 1573-9171
    Keywords: 2-alkylthiopropenals ; Diels–Alder reaction ; kinetics ; reaction mechanism ; 2,5-dialkylthio-3,4-dihydro-2H-pyran-2-carbaldehyde ; IR spectroscopy ; ab initio calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of 2-alkylthiopropenals cyclodimerization was studied in the temperature range from -7 to +42 °C in heptane and at 20 °C in various solvents. The rate constants for cyclodimerization of 2-alkylthiopropenals are four orders of magnitude higher than those for dimerization of the oxygen-containing analogs, 2-alkoxypropenals, and are independent of the solvent polarity and substituent steric constant. The activation parameters for 2-butylthiopropenal cyclodimerization were estimated. The distribution of electron density in the 2-methoxy- and 2-methylthiopropenals molecules was calculated by the ab initio method. From comparison of the HOMO and LUMO energies for these aldehydes it was concluded that the ratio between the cyclodimerization rates for 2-alkylthio-, 2-ethoxypropenals, and propenal is determined by the HOMO–LUMO gap.
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  • 187
    ISSN: 1608-3245
    Keywords: DNA ; kinetics ; oligonucleotide derivatives ; photomodification ; sensitization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Quantitative characteristics of thermodynamic and kinetic cooperativity arising in the process of photomodification of a single-stranded DNA fragment with binary systems of oligonucleotide conjugates forming an active site on the target were studied. Oligonucleotides of the binary system were complementary to adjacent segments of the DNA target, and contained arylazide (X) and perylene (S) residues covalently attached to their terminal phosphates. Upon irradiation at the perylene absorption wavelength, the target was modified by the arylazide residue, which was activated owing to the contiguity with the sensitizing perylene group in the tandem complex. Basing on the kinetic data, the constants of association of both derivatives of oligonucleotides with the target were determined: K x = 1.13 · 106 M–1, K s = 1.49 · 104 M–1. It was determined that association of both oligonucleotides with the target proceeded with a positive cooperativity characterized by parameter α = 45. The kinetic cooperativity parameter β was found to be approximately equal to 200; this characterized the acceleration of target modification in complex with the binary reagent versus that in the absence of sensitizer.
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  • 188
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    Herz 25 (2000), S. 384-391 
    ISSN: 1615-6692
    Keywords: Key Words Cardiomyopathy ; Magnetic resonance imaging ; Schlüsselwörter Kardiomyopathie ; Magnetresonanztomographie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die kardiale Magnetresonanztomographie (MRT) bietet als nichtinvasives Verfahren die Möglichkeit, innerhalb einer Untersuchung die für die verschiedenen Formen der Kardiomyopathien charakteristischen funktionellen und morphologischen Veränderungen darzustellen. In dieser Übersicht werden die Einsatzmöglichkeiten der MRT bei den verschiedenen Formen dieser Erkrankung diskutiert. Die geringe Variabilität der MRT-Messungen gestattet ge-naue Verlaufskontrollen im klinischen Alltag, eröffnet aber auch die Möglichkeit, Therapiestudien mit einer geringeren Anzahl von einzuschließenden Patienten zu sicheren Ergebnissen zu führen. Damit erweitert sich das Spektrum der Indikationen über die Präzisierung unklarer Befunde hinaus auf die Verlaufsbeobachtung während einer pharmakologischen Intervention und auf alle wissenschaftlichen Fragestellungen. Der Vorzug der MRT, nichtinvasiv Gewebe charakterisieren zu können, verdeutlicht das Potential dieser Technik bei sekundären Kardiomyopathien sowie bei entzündlichen und infiltrativen Formen myokardialer Erkrankungen.
    Notes: Abstract Cardiac magnetic resonance imaging (MRI) is a noninvasive tool which is able to diagnose and differentiate cardiomyopathies in a single study. The assessment of essential information such as alterations of myocardial and ventricular geometry and function is possible with a high degree of accuracy and reproducibility, based on a small inter- and intraobserver variability. Thus, very small morphological and functional changes in different types of cardiomyopathy are detectable, thereby enabling the cardiologist to increase the safety of therapeutic decisions. Furthermore, MRI bears the potential to characterize tissue transformation in the different types of myocardial affections including ischemic, toxic, infiltrative or inflammatory forms.
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    Heart and vessels 15 (2000), S. 44-45 
    ISSN: 1615-2573
    Keywords: Key words Pericardial hydatid cyst ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 190
    ISSN: 1615-2573
    Keywords: Key words Three-dimensional echocardiography ; Magnetic resonance imaging ; Left ventricular volume ; Stereology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The objective of this study was to investigate the degree of bias with coaxial three-dimensional echocardiography in an experimental animal setup and to establish the minimum number of sections needed for estimation of left ventricular (LV) volume. Epicardial coaxial echocardiography and magnetic resonance imaging (MRI) was used to measure LV volume in 14 pigs, with chronic remodeled left ventricles induced by repeated intracoronary microembolizations. In addition, six animals underwent serial MRI at baseline, immediately after intracoronary microembolization, and after 119–165 days (mean 129 days). Coaxial echocardiography was performed by rotational acquisition of long-axis sections starting from an arbitrary angle. Planimetered MRI contours of LV endocardial borders were analyzed to investigate the relationship between the number of coaxial sections, and the precision of volume estimates. The mean ± 2SD of the differences between coaxial epicardial echocardiography with six sections and MRI were −2.5 ± 16.4 ml, 0.8 ± 13. 1 ml, and 2% ± 14% for end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF), respectively. Numerical analysis conducted on MRI contours of LV endocardial borders showed that with six coaxial sections the average coeffi-cient of error was 〈1% for the EDV and ESV. Three-dimensional echocardiography with six coaxial sections provides unbiased LV volume estimation with minimal geometric error.
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  • 191
    ISSN: 1608-3407
    Keywords: Dunaliella salina ; lactate dehydrogenase ; kinetics ; glycerol synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dependence of the catalytic properties of lactate dehydrogenase (LDH, EC 1.1.1.27) from a halophilic alga Dunaliella salina, a glycophilic alga Chlamydomonas reinhardtii, and from porcine muscle on glycerol concentration, medium pH, and temperature was investigated. Several chemical properties of the enzyme from D. salina differentiated it from the LDH preparation obtained from C. reinhardtii and any homologous enzymes of plant, animal, and bacterial origin. (1) V max of pyruvate reduction manifested low sensitivity to the major intracellular osmolyte, glycerol. (2) The affinity of LDH for its coenzyme NADH dropped in the physiological pH region of 6–8. Above pH 8, NADH virtually did not bind to LDH, while the enzyme affinity for pyruvate did not change considerably. (3) The enzyme thermostability was extremely low: LDH was completely inactivated at room temperature within 30 min. The optimum temperature for pyruvate reduction (32°C) was considerably lower than with the enzyme preparations from C. reinhardtii (52°C) and porcine muscle (61°C). (4) NADH greatly stabilized LDH: the ratio of LDH inactivation constants in the absence of the coenzyme and after NADH addition at the optimum temperature in the preparation from D. salina exceeded the corresponding indices of LDH preparations from C. reinhardtii twelve times and from porcine muscle eight times. The authors believe that these LDH properties match the specific metabolism of D. salina which is set at rapid glycerol synthesis under hyperosmotic stress conditions. The increase of cytoplasmic pH value produced in D. salina by the hyperosmotic shock can switch off the terminal reaction of the glycolytic pathway and thus provide for the most efficient utilization of NADH in the cycle of glycerol synthesis. As LDH is destabilized in the absence of NADH, this reaction is also switched off. In the course of alga adaptation to the hyperosmotic shock, glycerol accumulation and the neutralization of intracellular pH stabilize LDH, thus creating the conditions for restoring the complete glycolytic cycle.
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  • 192
    ISSN: 1573-4986
    Keywords: β-glycosidase ; temperature dependence ; kinetics ; glucose ; transglycosylation ; (Thermus thermophilus)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A β-glycosidase of a thermophile, Thermus thermophilus, belonging to the glycoside hydrolase family 1, was cloned and overexpressed in Escherichia coli. The purified enzyme (Ttβgly) has a broad substrate specificity towards β-D-glucoside, β-D-galactoside and β-D-fucoside derivatives. The thermostability of Ttβgly was exploited to study its kinetic properties within the range 25–80[emsp4 ]°C. Whatever the temperature, except around 60[emsp4 ]°C, the enzyme displayed non-Michaelian kinetic behavior. Ttβgly was inhibited by high concentrations of substrate below 60[emsp4 ]°C and was activated by high concentrations of substrate above 60[emsp4 ]°C. The apparent kinetic parameters (k cat and K m ) were calculated at different temperatures. Both k cat and K m increased with an increase in temperature, but up to 75[emsp4 ]°C the values of k cat increased much more rapidly than the values of K m . The observed kinetics might be due to a combination of factors including inhibition by excess substrate and stimulation due to transglycosylation reactions. Our results show that the substrate could act not only as a glycosyl donor but also as a glycosyl acceptor. In addition, when the glucose was added to reaction mixtures, inhibition or activation was observed depending on both substrate concentration and temperature. A reaction model is proposed to explain the kinetic behavior of Ttβgly. The scheme integrates the inhibition observed at high concentrations of substrate and the activation due to transglycosylation reactions implicating the existence of a transfer subsite.
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  • 193
    ISSN: 1439-6327
    Keywords: Key words Human ; Muscle function ; Physiological cross-sectional area ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of the present study was to investigate the effect of recruitment on the relationship between peak torque and physiological cross-sectional area (PCSA) in human muscle. A group of 11 healthy men participated in this study. Isokinetic knee extension torques at seven (0, 30, 60, 120, 180, 240, and 300° · s−1) velocities were determined. Magnetic resonance imaging (MRI) was performed to calculate PCSA of right quadriceps femoris (QF) muscle. Exercise-induced contrast shifts in spin-spin relaxation time (T2)-weighted MRI were taken at rest and immediately after repetitive knee-extension exercise and T2 of QF were calculated. The MRI pixels with T2 values more than 1 SD greater than the means at rest were considered to represent QF muscle that had contracted. The area of activated PCSA within the total in QF was expressed as percentage activated PCSA and used as an index of muscle recruitment. The PCSA correlated with peak torque at 0° · s−1 (r=0.615, P 〈 0.05); in contrast, activated PCSA correlated with peak torque at 120° · s−1 (r=0.603, P 〈 0.05) and 180° · s−1 (r=0.606, P 〈 0.05). Additionally, there was a significant difference in correlation coefficients between the activated PCSA-peak torque relationship and the PCSA-torque relationship (P 〈 0.05). These results suggested that muscle recruitment affects the PCSA-torque relationship.
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  • 194
    Electronic Resource
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    Springer
    European journal of applied physiology 82 (2000), S. 391-396 
    ISSN: 1439-6327
    Keywords: Key words B-mode ultrasound ; Bioelectrical impedance ; Data acquisition system ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study aimed to investigate the validity of bioelectrical impedance and ultrasonographic methods for predicting the muscle volume of the upper arm. Bioelectrical impedance of the right upper arm and the thickness of elbow flexor and extensor muscles were measured from 26 healthy young adult men using a specially designed bioelectrical impedance data acquisition system and brightness-mode ultrasound apparatus, respectively. As reference data, the muscle volume (MVMRI) of the right upper arm was determined using a magnetic resonance imaging method. The impedance index was calculated as L 2/Z, where L is the upper arm length and Z is the impedance of the shoulder to the elbow. The muscle volume (MVULT) was calculated as π·(d/2)2·L, where d is muscle thickness. L 2/Z and MVULT were significantly correlated with MVMRI with correlation coefficients of 0.971 and 0.962, respectively. In these relationships, the standard errors of estimation were 44.2 cm3 (6.3%) for L 2/Z and 50.7 cm3 (7.2%) for MVULT. There was no significant difference between the absolute errors of muscle volumes estimated by L 2/Z and MVULT: 36.2 (4.8, SEM) cm3 for L 2/Z versus 40.3 (5.8) cm3 for MVULT. The present results suggest that both bioelectrical impedance and ultrasonographic methods may be useful for predicting the muscle volume of the upper arm.
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  • 195
    Electronic Resource
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    Springer
    Journal of applied spectroscopy 67 (2000), S. 981-989 
    ISSN: 1573-8647
    Keywords: nonlinear regime of stimulated Raman scattering ; fluctuation ; Stokes radiation ; kinetics ; spectrum ; distribution function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Statistical properties of the Raman scattering of an intense step pulse are investigated by numerical solution of the equations of a semi-classical theory with assignment of a random Gaussian distribution of the initial polarization over the sample. The probability density functions of the intensity, energy, delay time, and width of a Stokes pulse and also of the position, height, and width of the spectral peaks of the first incidental Stokes component with the preservation of the phase memory of scattering centers are calculated. The influence of collisional dephasing on the fluctuation of these characteristics is considered.
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  • 196
    Electronic Resource
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    Powder metallurgy and metal ceramics 39 (2000), S. 540-544 
    ISSN: 1573-9066
    Keywords: compaction ; facing ; cumulative charge ; powder ; composite ; heterogeneous structure ; particle ; kinetics ; surface ; die ; model ; xeroradiogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental and numerical (finite element method) study is carried out for the effect of forming scheme on property distribution for cumulative charge facings made from composite heterogeneous powder material. An experimental procedure is developed for studying powder particle flow kinetics. It is shown that use of composite punches and partition of the moulded material into a number of sub-divisions with their successive compaction achieves a more uniform density distribution for an article. It is demonstrated how the direction of the force of friction on the die walls during compaction affects the compaction of articles with faces that are not perpendicular to the direction of the pressing. The results obtained make it possible to select the optimum compaction regime taking account of production features connected with powder material composition as well as service characteristics.
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  • 197
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    Pharmaceutical research 17 (2000), S. 701-706 
    ISSN: 1573-904X
    Keywords: vapor sorption ; molar heat of adsorption ; kinetics ; isothermal microcalorimetry ; recrystallization ; hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. In this study, instrumentation for measuring vapor sorptionenthalpies and sorption uptakes simultaneously with an isothermalmicrocalorimeter is introduced. Various pharmaceutical modelsubstances undergoing phase transitions when exposed to humid conditions(25°C), were employed to evaluate the usefulness and sensitivity ofthe constructed experimental method. Methods. The sample is placed in the sample vessel of a RH cell andthe moisture content of the air flow is controlled. From the RH cellthe air flow is conducted into a subsequent perfusion cell in which asaturated salt solution has been loaded. The RH cell and perfusioncells are positioned in the sample sides of two twin calorimetric units.Depending on the moisture content in the outlet flow leaving thepreceding RH cell, the heat flow signal from the subsequent perfusioncell will vary. By means of blank measurement with identical settings,the rate of water sorption can be calculated and, by integration, theamount of sorbed water is obtained. Results. Amorphous lactose and cefadroxil undergo recrystallizationwhen the moisture level in the surroundings exceeds the thresholdvalues specific to each compound. During the sorption phase, heat isevolved fairly linearly as a function of consumed moisture, and alsoafter the recrystallization, the heats indicate linear behavior. The heatvalues for the desorption phase of amorphous lactose and the adsorptionof crystalline lactose coincide. With the different anhydrous forms oftheophylline, the hydration takes place more rapidly in the metastableform I, and generally, the process is more energetic in form I. In allcases, the gravimetric results agree with the water sorption uptakescalculated from the calorimetric data. Conclusions. The technique introduced offers a rapid and sensitivemethod to gain new insights into the transitions in which vapors areinvolved. In addition, different kinds of surfaces with various energeticscan now be studied more closely.
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  • 198
    ISSN: 1615-6692
    Keywords: Key Words Right ventricle ; Arrhythmias ; Left bundle branch block ; Dysplasia ; Fatty infiltration ; Magnetic resonance imaging ; Schlüsselwörter Rechter Ventrikel ; Arrhythmien ; Linksschenkelblock ; Dysplasie ; Fettige Degeneration ; Kernspintomographie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die arrhythogene rechtsventrikuläre Dysplasie (ARVD), eine Herzmuskelerkrankung unlarer Ätiologie, ist pathologisch durch fettige Degeneration des rechtsventrikulären Myokards gekennzeichnet. Die klinischen Symptome umfassen strukturelle und funktionelle Malformationen des rechten Ventrikels, krankhafte elektrokardiographische Befunde und das Auftreten ventrikulärer Tachykardien mit Linksschenkelblock oder plötzlichem Herztod. Die Krankheit tritt familiär gehäft auf und wird autosomal vererbt. Neben der rechtsventrikulären Dilatation stellen rechtsventrikuläre Aneurysmen typische Fehlbildungen bei ARVD dar. Sie sind im so genannten “Dysplasiedreieck”, das heißt rechtem ventrikulärem Ausflusstrakt, Herzspitze und Infundibulum, verteilt. Dort lokalisierte ventrikuläre Aneurysmen können als pathognomonisch für die ARVD angesehen werden. Ein weiteres typisches Merkmal der ARVD ist die fettige Degeneration der freien rechten Ventrikelwand. Diese funktionellen und strukturellen Charakteristika sind bei der klinischen Untersuchung mit bildgebenden Verfahren wie Kontrastangiographie, Echokardiographie, Radionuklidangiographie, ultraschneller Computertomographie und Magnetresonanztomographie (MRT) von Bedeutung. Unter diesen Verfahren erlaubt die MRT die deutlichste Darstellung des Herzens, insbesondere bei Beteiligung des rechten Ventrikels, der sich mit den anderen bildgebenden Methoden in der Regel schwerer untersuchen lässt. Darüber hinaus bietet die MRT den wesentlichen Vorteil der Darstellung der fettigen Degeneration als helles Signal im rechtsventrikulären Myokard. Die MRT liefert die wichtigsten anatomischen, funktionellen und morphologischen Kriterien zur Diagnose einer ARVD in einem einzigen Untersuchungsgang. Daher scheint sie das beste bildgebende Verfahren zur Identifizierung und Nachsorge von Patienten mit klinischem Verdacht auf ARVD zu sein.
    Notes: Abstract Arrhythmogenic right ventricular dysplasia (ARVD) is a heart muscle disorder of unknown cause that is characterized pathologically by fibrofatty replacement of the right ventricular myocardium. Clinical manifestations include structural and functional malformations of the right ventricle, electrocardiographic abnormalities, and presentation with ventricular tachycardias with left bundle branch pattern or sudden death. The disease is often familial with an autosomal inheritance. In addition to right ventricular dilatation, right ventricular aneurysms are typical deformities of ARVD and they are distributed in the so-called “triangle of dysplasia”, i. e., right ventricular outflow tract, apex, and infundibulum. Ventricular aneurysms at these sites can be considered pathognomonic of ARVD. Another typical hallmark of ARVD is fibrofatty infiltration of the right ventricular free wall. These functional and morphologic characteristics are relevant to clinical imaging investigations such as contrast angiography, echocardiography, radionuclide angiography, ultrafast computed tomography, and magnetic resonance imaging (MRI). Among these techniques, MRI allows the clearest visualization of the heart, in particular because the right ventricle is involved, which is usually more difficult to explore with the other imaging modalities. Furthermore, MRI offers the specific advantage of visualizing adipose infiltration as a bright signal of the right ventricular myocardium. MRI provides the most important anatomic, functional, and morphologic criteria for diagnosis of ARVD within one single study. As a result, MRI appears to be the optimal imaging technique for detecting and following patients with clinical suspicion of ARVD.
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  • 199
    ISSN: 1573-9686
    Keywords: Heart ; Left ventricle ; LV contractility ; ESPVR ; Pig ; Rat ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The end systolic pressure–volume relation (ESPVR) has been shown to be a relatively load independent measure of left ventricular (LV) contractility. Recently, several single-beat ESPVR computation methods have been developed, enabling the quantification of LV contractility without the need to alter vascular loading conditions on the heart. Using a single-beat ESPVR method, which has been validated previously in humans and assumes that normalized elastance is constant between individuals of a species, we studied the effects of myocardial infarction on LV contractility in two species, the rat and the pig. In our studies, LV pressure was acquired invasively and LV volume determined noninvasively with magnetic resonance imaging, at one week postinfarction in pigs and at 12 weeks postinfarction in rats. Normalized systolic elastance curves in both animal species were not statistically different from that of humans. Also, the slope of the ESPVR $$\left( {E_{es} } \right)$$ decreased significantly following infarction in both species, while the volume-axis intercept $$\left( {V_0 } \right)$$ was unaffected. These results indicate that a single-beat ESPVR method can be used to measure the inotropic response of the heart to myocardial infarction, and that the basis for this method (i.e., constant normalized elastance) is applicable to a variety of mammalian species. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8761Lh, 8719Hh, 8719Rr, 8719Ff
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  • 200
    ISSN: 1573-515X
    Keywords: gaseous ; kinetics ; mercury ; methods ; speciation ; waters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Mercury evasion from water is commonly modeled using measurements of dissolved gaseous mercury (DGM). We developed a method using a recently available automated field-ready mercury vapor analyzer to rapidly measure the concentrations of DGM in surface waters. We summarize here results of laboratory tests of the method, field intercomparisons with a manual method, and selected data from recent sampling campaigns in Florida and Michigan. The method uses the 1.5 lpm flow of a Tekran® Model 2537A mercury analyzer to purge and analyze discrete water samples, generating near real time (5-min) data on DGM in samples and blanks. Application of the Tekran allowed for detailed analysis of DGM removal kinetics and short-term diel studies characterizing the influence of sunlight and precipitation on DGM production in surface waters. Gas removal kinetics for dozens of samples indicates a first-order rate constant, and supports a 20-min. purge time for surface water samples from Florida (40-min for Michigan samples). Blanks are measured during a second such purge. Our results indicate that DGMs determined by both automated and manual methods are generally comparable, and that DGM in Florida samples is unstable during storage (loss rate constant ∼0.1--0.2 h-1), probably due to oxidation. This suggests that rapid in-field analysis is preferred to storage with delayed analysis. Our data indicate that DGM at the Florida site is influenced by inputs of reactive Hg in rainwater, and by production of surface DGM during photoreduction of oxidized Hg in the water column.
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