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  • 1995-1999  (5,863)
  • 1905-1909  (1,027)
  • Organic Chemistry  (3,717)
  • Analytical Chemistry and Spectroscopy  (2,287)
  • Magnetic resonance imaging  (885)
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  • 101
    ISSN: 1432-1920
    Keywords: Key words Spinal subdural haematoma ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Chronic spinal subdural haematoma is a uncommon. We describe the CT and MRI appearances of chronic spinal and intracranial subdural haematomas following minor trauma. The aetiology, pathogenesis and differential diagnosis are discussed.
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  • 102
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 41 (1999), S. 129-133 
    ISSN: 1432-1920
    Keywords: Key words Cryptococcosi ; Acquired immunodeficiency syndrome ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract CT and MRI in one case of Cryptococcus neoformans infection showed contrast-enhancing parenchymal lesions resembling granulomata or abscesses. After an initial phase without contrast enhancement, the full extent of the lesions was visible within 2 weeks of presentation. The enhancing masses were assumed to represent intracerebral cryptococcomas. Despite evidence of massive meningeal infection on cerebrospinal fluid (CSF) examination, no radiological signs of meningitis, invasion of the Virchow-Robin spaces or ventriculitis could be demonstrated. With antimycotic treatment the contrast enhancement disappeared and cystic, partly calcified lesions remained. Recurrence of meningeal infection without radiological correlates was apparent in this stage. In a second case of proven cryptococcus meningitis, dilation of Virchow-Robin spaces or cysts in the adjacent parenchyma were the main abnormalities on MRI. Enhancing masses were not detected. These cases may represent two different reactions of the immunocompromised hosts to infection with C. neoformans: widening of the perivascular spaces as a correlate of the more typical meningeal infection and enhancing parenchymal lesions as a sign of further invasion from the CSF spaces. Enhancement of cryptococcomas, indicating an inflammatory response in the surrounding brain, is not typical in patients with impairment of immune function.
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  • 103
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 41 (1999), S. 158-162 
    ISSN: 1432-1920
    Keywords: Key words Midbrain ; tumours ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We diagnosed 60 cases of midbrain tumours by MRI between 1993 to 1997. There were 39 males and 21 females, aged 2–64 years, mean 25.6 years. We found 38 patients with true intramedullary midbrain tumours, 11 predominantly in the tectum, 20 in the tegmentum and 7 with a downward extension to the pons; there were 7 within the cerebral aqueduct. There were 22 patients with infiltrating midbrain tumours extending from adjacent structures, 11 cases each from the thalamus and pineal region. All patients received surgical treatment. Gross total resection was achieved in 42 cases, subtotal (〉 75 %) resection in 18. Pathological diagnoses included 16 low-grade and 15 high-grade astrocytomas; 5 oligodendroastrocytomas; 2 ependymomas; 11 glioblastomas; and 11 pineal parenchymal or germ-cell tumours. Midbrain tumours are a heterogeneous group of neoplasms, with wide variation in clinical and MRI features, related to the site and type of tumour. MRI not only allows precise analysis of their growth pattern, but also can lead to a correct preoperative diagnosis in the majority of cases.
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  • 104
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 41 (1999), S. 175-178 
    ISSN: 1432-1920
    Keywords: Key words Infarct ; cerebral ; Computed tomography ; Magnetic resonance imaging ; diffusion-weighted
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We compared CT and MRI obtained within the first 3 h of onset of a cerebral infarct. Echo-planar diffusion-weighted MRI delineated the infarcted areas most clearly, and subtle low-density areas on CT were consistent with those shown to be abnormal by diffusion-weighted MR. The signal changes of affected areas on fast spin-echo proton-density, T2-weighted and fast FLAIR images were subtler than the low density on CT.
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  • 105
    ISSN: 1432-1920
    Keywords: Key words Shunt ; portosystemic ; Globus pallidus ; Manganese ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report two toddlers with portosystemic shunts who had symmetrical high-signal globus pallidus lesions on T1- but not T2-weighted MRI, and measurement of whole blood manganese at 2 years of age. These cases suggest that portosystemic shunts can cause elevation of blood manganese and result in manganese accumulation in the globus pallidus, causing high signal on T1-weighted images even in asymptomatic toddlers.
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  • 106
    ISSN: 1432-1920
    Keywords: Key words Cerebral infarcts ; Magnetic resonance imaging ; Contrast enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We compared contrast enhancement on T1-weighted MRI of acute cerebral infarcts after conventional bolus administration and continuous infusion of gadolinium. We examined 12 patients with a history of acute stroke with contrast-enhanced MRI once a week for a 1 month. Only ischaemic lesions were investigated after cerebral haemorrhage had been excluded by CT. Each MRI study included T2- and proton density-weighted sequences for determination of the size and site of the infarct, immediate postinjection T1-weighted imaging after bolus administration of 0.1 mmol/kg gadolinium-DPTA and delayed T1-weighted imaging after additional continuous infusion of 0.1 mmol/kg over 2 h. A total of 42 MRI studies was performed. In the first week after the onset of stroke, most infarcts (8 of 10) did not enhance after bolus administration, whereas all showed distinct contrast enhancement after the infusion. In the following weeks all but two infarcts showed contrast enhancement after bolus administration; after continuous infusion contrast enhancement could be seen in all cases. While contrast enhancement after bolus administration showed the typical gyriform pattern, enhanced areas were more extensive after the infusion and usually covered the entire infarcted area shown on T2- and proton density-weighted images. We presume that the disturbed blood-brain barrier in ischaemic areas favours delivery of contrast medium to the infarcted tissue if it is offered continuously so that a steady state can develop.
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  • 107
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 41 (1999), S. 428-432 
    ISSN: 1432-1920
    Keywords: Key words Tuberous sclerosis ; Magnetic resonance imaging ; Focal cortical dysplasia ; Cortical dysgenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There is immense variability in the clinical presentation of tuberous sclerosis and many incomplete forms (formes frustes) exist. To investigate the imaging characteristics of cortical tubers seen in tuberous sclerosis unaccompanied by other stigmata, we reviewed MRI and CT of six patients who met the criteria for a definitive diagnosis of TS, established solely by the presence of a histologically confirmed cortical tuber. Five of the patients had a solitary cortical tuber and the last had three lesions, one of which was resected and confirmed histologically. The other two lesions were included in our study. CT showed five tubers as low density, but three were not identified. No calcified or dense lesions were observed. MRI revealed peripheral components and inner cores of seven cortical tubers in five patients, with differing signal characteristics. The subcortical cores, with T1 and T2 prolongation, were separated from the overlying cortex. Abnormal inhomogeneous high signal was observed in both the cortex and subcortical white matter on proton-density weighted or FLAIR images. A radially orientated white-matter band was observed in one patient, and central depression of the expanded gyri in another. In one patient, a cortical tuber was atypical, with a thick cortex on T1-weighted images and a blurred grey/white matter junction with diffusely increased signal on T2-weighted images. Cortical tubers without other stigmata of tuberous sclerosis are shown to be distinct from focal cortical dysplasia.
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  • 108
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 41 (1999), S. 443-446 
    ISSN: 1432-1920
    Keywords: Key words Langerhans cell histiocytosis ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Langerhans cell histiocytosis (LCH) is a disease of unknown cause characterised by proliferation of histiocytic granulomas in tissues; the primary cerebral manifestation is diabetes insipidus caused by hypothalamic infiltration. We present a patient in whom, except for the absence of high signal on T 1 weighting in the posterior pituitary, consistent with central diabetes insipidus, MRI showed no evidence of hypothalamic involvement by histiocytosis, despite the long duration of the disease. However, there was bilateral, symmetrical involvement of the cerebellum and globus pallidus in addition to a calvarial lesion. High signal in the cerebellar white matter on T 2-weighted images may represent demyelination, gliosis and cell loss, as previously reported on pathologic examination.
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  • 109
    ISSN: 1432-1920
    Keywords: Key words Dural arteriovenous fistula ; Craniocervical junction ; Magnetic resonance imaging ; Venous hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a 62-year-old woman who presented with a myelopathy at the lower thoracic level. Left vertebral angiography revealed a dural arteriovenous fistula (DAVF) at the craniocervical junction, draining into an anterior spinal vein. Below the T 7 level, the spinal cord gave high signal on T 2-weighted images and enhanced with Gd-DTPA. The patient was successfully treated by simple clipping of vein draining the DAVF. The abnormal signal intensity and contrast enhancement rapidly regressed, except in the conus medullaris. Regression of the parenchymal abnormality on serial MRI following treatment corresponded closely with postoperative improvement of neurological function.
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  • 110
    Electronic Resource
    Electronic Resource
    Springer
    Der Radiologe 39 (1999), S. 828-837 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Zerebrovaskuläre Erkrankungen ; Intrazerebrale Blutung ; Magnetresonanztomographie ; Computertomographie ; Key Words Cerebrovascular diseases ; Intracerebral hemorrhage ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Intracerebral hemorrhage is a common cause of acute neurological deterioration and a frequent indication for emergency neuroimaging. Stroke symptoms are caused in 10 to 15% by intracerebral hemorrhage. It is often not possible to differentiate intracerebral hemorrhage from cerebral ischemia by clinical examination. The therapeutic decision between thrombolysis or conservative therapy is comprised by the etiology. To exclude intracerebral hemorrhage as the cause of clinical symptoms, a CT is usually performed. Localisation and extension of the acute intracerebral hemorrhage are easy to detect. Subacute and chronic intracerebral hemorrhage are better delineated with magnetic resonance imaging. The different signal of the hemorrhage can be used for the age of the intracerebral hemorrhage. The cause of a non-traumatic intracerebral hemorrhage is in over 60% hypertony, less frequent alcoholism, malformation, or amyloid angiopathy. Uncommon causes of hemorrhage are head trauma, blood dyscrasia, tumor or venous thrombosis. Non-traumatic intracerebral hemorrhage are most common in patients between 50 and 70 years. In younger patients a malformation should be excluded with a cerebral angiography. Intracerebral hemorrhages are usually conservatively treated, in some cases an operative decompression is performed.
    Notes: Zusammenfassung Die intrazerebrale Blutung ist eine häufige Ursache akut auftretender neurologischer Symptome und führt oft zu einer notfallmäßigen neuroradiologischen Untersuchung. Etwa 15% der „Schlaganfälle” sind auf eine intrazerebrale Blutung zurückzuführen. Intrazerebrale Blutungen sind klinisch oft nicht von ischämischen Infarkten zu unterscheiden. Eine Computertomographie ist zur Zeit für die Diagnosesicherung – und damit auch zur weiterführenden Therapie – unerläßlich. Ausdehnung und Lokalisation der akuten intrazerebralen Blutung können damit schnell und sicher erfaßt werden. Subakute und chronische Blutungen sind dagegen verläßlicher mit der Magnetresonanztomographie nachweisbar. Aus der unterschiedlichen Signalgebung in den verschiedenen MR-Sequenzen kann auf das Alter der Blutung geschlossen werden. Die Ursache einer nicht-traumatischen intrazerebralen Blutung ist in über 60% der Fälle eine Hypertonie, weniger häufig die Folgen des Alkoholismus, Gefäßfehlbildungen oder die Amyloidangiopathie. Seltener sind Blutgerinnungsstörungen, Traumen, Tumoren, Venenthrombosen oder Intoxikationen die Ursachen einer intrazerebralen Blutung. Nicht-traumatische intrazerebrale Blutungen treten am häufigsten zwischen dem 5.–7. Lebensjahrzehnt auf. Bei jüngeren Patienten sind vor allem Gefäßfehlbildungen als Ursache zu berücksichtigen. Insbesondere bei jüngeren Patienten sollte zur ätiopathogentischen Klärung eine zerebrale Angiographie durchgeführt werden. Spontane intrazerebrale Blutungen werden in der Regel konservativ behandelt, außer man verspricht sich von der operativen Dekompression eine Verbesserung des klinischen Zustandes.
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  • 111
    Electronic Resource
    Electronic Resource
    Springer
    Der Radiologe 39 (1999), S. 889-893 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Sarkoidose ; Neurosarkoidose ; Magnetresonanztomographie ; Key words Sarcoidosis ; Neurosarcoidosis ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Neurological involvement is a significant cause of morbidity and mortality in patients with sarcoidosis. The aim of this study was to evaluate the role of magnetic resonance imaging (MRI) in the diagnosis of patients with neurosarcoidosis. The MRI brain scans of 22 patients with sarcoidosis were retrospectively reviewed, along with the clinical information provided in the request form. All patients had signs and symptoms referable to the head and were examined with gadolinium enhancement. Cranial (facial) nerve paralysis was the most common clinical manifestation identified in 10 patients. A wide spectrum of MR findings was noted: periventricular and white matter lesions on T2 W spin echo images, mimicking multiple sclerosis (46%); multiple supratentorial and infratentorial brain lesions, mimicking metastases (36%); solitary intraaxial mass, mimicking high-grade astrocytoma (9%); solitary extraaxial mass, mimicking meningioma (5%); leptomeningeal enhancement (36%). The diagnosis of neurosarcoidosis is often difficult, particularly so in patients who lack either pulmonary or systemic manifestations of sarcoidosis. MRI shows a wide spectrum of brain abnormalities associated with neurosarcoidosis. These findings, however, are not specific for sarcoidosis and one must consider appropriate clinical circumstances in arriving at the correct diagnosis. In selected cases with isolated brain involvement, meningeal or cerebral biopsy may be required.
    Notes: Zusammenfassung Klinische Untersuchungen an Patienten mit systemischer Sarkoidose sprechen in 5%, Autopsieberichte in 25% für eine Beteiligung des Zentralnervensystems. Ziel der Studie ist eine Beurteilung der Beitrags der Magnetresonanztomographie (MRT) in der Diagnostik der Neurosarkoidose. Die MR-Tomogramme von 22 Patienten mit gesicherter Sarkoidose und neurologischer Symptomatik wurden retrospektiv ausgewertet. Häufigstes klinisches Symptom der Neurosarkoidose war eine Fazialisparese (10 Patienten). MR-tomographisch konnte eine Vielzahl verschiedener Befunde erhoben werden: periventrikuläre und Marklagerläsionen in T2-gewichteten Bildern in 46%, multiple bzw. miliare supratentorielle und infratentorielle Läsionen in 36%, solitäre intraaxiale Raumforderungen in 9%, solitäre extraaxiale Raumforderungen in 5% und meningeale Kontrastmittelanreicherung (nodulär oder diffus) in 36%. Schlußfolgerung: Die MR-tomographischen Befunde bei Neurosarkoidose sind oft wenig spezifisch. Die Diagnose wird meist bei gleichzeitigem Nachweis sarkoidosetypischer Granulome in anderen Organen gestellt, eine isolierte zerebrale Manifestation kann erhebliche diagnostische Schwierigkeiten bereiten. Die Neurosarkoidose sollte bei unklaren zerebralen Symptomen und Befunden stets in die Differentialdiagnose einbezogen werden, weil sie behandelbar ist.
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  • 112
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Kalkaneus ; Talus ; Gelenkinstabilität ; Radiologische Diagnostik ; Ultraschall ; Magnetresonanztomographie ; Sprunggelenk ; Synovialmembran ; Arthritis ; Diagnose ; Bildgebende Diagnostik ; Key words Calcaneus ; Joint instability ; Plain film radiography ; Ultrasonography ; Magnetic resonance imaging ; Subtalar joint ; Ankle joint ; Arthritis ; Synovial membrane ; Synovitis ; Diagnosis ; Differential ; Diagnostic imaging ; Rheumatic disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Diseases of the hindfoot are associated with considerable functional impairment and therefore may hamper patients’ movements during gait considerably. Because of biomechanical overload, articular structures, tendons and ligaments are prone to early degenerative changes during the course of rheumatic diseases as visible with plain film radiography, sonography (US), or magnetic resonance imaging (MRI). Findings may occur as arthritis of major joints or in the form of fibroostitis and bursitis of the os calcis. Despite the progressive course of rheumatic diseases and characteristic imaging findings, high variability of X-ray signs may occur. Plain film radiograms and high-resolution ultrasonography play a key role in imaging rheumatic diseases of the hindfoot. MRI supports imaging diagnosis in selected cases. The principal goals of diagnostic imaging are precise and reproducible documentation of morphologic abnormalities and differentiated analysis for planning proper conservative or surgical treatment.
    Notes: Zusammenfassung Erkrankungen des Sprunggelenks und der Fußwurzel sind, da mit einer deutlichen Einschränkung der Beweglichkeit dieser Region einhergehend, für den Patienten meist sehr belastend. Bei rheumatischen Krankheitsbildern steht neben der Funktionseinschränkung vor allem in späteren Stadien die Destruktion biomechanisch stark beanspruchter Strukturen (hyaliner Knorpel, subchondraler Knochen, Bänder und Sehnen) im Vordergrund des klinischen wie auch des radiologischen Bildes. Grundsätzlich sind Arthritiden der großen Gelenke und die Calcaneopathia rheumatica zu beobachten. Trotz des meist stadienhaften Verlaufes mit charakteristischem Befallsmuster ist die bildgebende Diagnostik wegen der großen Formvariabilität der unterschiedlich ausgeprägten Veränderungen oft schwierig. Zusätzlich zu nativröntgenologischen Aufnahmen gehören die hochauflösende Sonographie, ergänzt durch die MRT, mit denen Gelenke und Sehnen direkt darstellbar sind, heute zur Standarddiagnostik. Ziel der Diagnostik ist einerseits die präzise reproduzierbare Dokumentation morphologischer Veränderungen zur Verlaufskontrolle, andererseits ihre möglichst differenzierte Analyse zur Einleitung adäquater konservativer oder operativer Therapiemaßnahmen, um Patienten zu einer aktiveren Lebensweise verhelfen zu können.
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  • 113
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Intrazerebrale Blutung ; Kernspintomographie ; MR-Angiographie ; Key words Intracerebral hematoma ; Magnetic resonance imaging ; Magnetic resonance angiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary We review the signal characteristics of intracerebral hematomas (ICH) on magnetic resonance imaging (MRI), with special emphasis on the diagnosis of intracerebral hemorrhage within the first hours after stroke. The detection of peracute ICH was evaluated in 42 patients of a prospective, MR randomized stroke trial. These patients underwent a protocol of T1 and T2 weighted sequences, diffusion weigthed sequences and MR – angiography within 6 hours after onset of acute hemiparesis. The signal behaviour of ICH in any stage after bleeding was additionally reviewed in a retrospective series of 63 patients, who were submitted for MRI over a 12 months period because of known ICH. MRI correctly identified 4 hyperacute ICH in the prospective group and 4 hyperacute ICH in the retrospective group. These ICHs had high signal on T2 weighted images, were isointense in T1 weighted images and had signal voids on the diffusion weighted sequences. The signal intensities of acute, subacute and chronic ICHs correlated to previous experiences as reported in the literature. In conclusion, MRI reliably identified all hematomas even in the hyperacute stage. Diffusion weighted images were most sensitive to the presence of deoxyhemoglobine and helpful for the differentiation and characterization of acute ischemia. Therefore, MRI at 1.5 T can be employed as an alternative to CT for the emergency diagnosis of acute stroke.
    Notes: Zusammenfassung In dieser Übersicht wird das kernspintomographische (KST) Erscheinungsbild der intrazerebralen Blutung (IZB) anhand eigener Erfahrungen und der Literatur diskutiert. Besonderes Gewicht wurde auf den KST Nachweis der hyperakuten IZB innerhalb der ersten Stunden gelegt. Es wurden einerseits die Befunde von 42 Patienten einer prospektiven, KST randomisierten Schlaganfallstudie ausgewertet, bei denen die KST als Erstuntersuchung innerhalb von 6 Stunden durchgeführt worden war. Andererseits werteten wir retrospektiv jene KST Untersuchungen aus, die im Jahr 1998 unter der Fragestellung einer IZB (n=63) erfolgten. Die KST erwies sich als sensitiv im Nachweis auch der hyperakuten IZB. Es wurden weder falsch-negative noch falsch-positive Befunde erhoben. Die hyperakute IZB kommt in der T2-Gewichtung hyperintens und in der T1-Gewichtung isointens zur Darstellung. Auf den diffusionsgewichteten Sequenzen führen minimale Deoxyhämoglobinkonzentrationen bereits in dieser Phase zu Signalauslöschungen. Das Erscheinungsbild der akuten, subakuten und chronischen IZB entsprach dem, in der Literatur mitgeteilten, Signalverhalten. Zusammenfassend waren alle IZB, unabhängig vom Stadium in der KST nachweisbar. Die Diffusionsgewichtung war in der hyperakuten Blutungsdiagnose und deren Abgrenzung von der akuten Ischämie hilfreich. Zumindest bei 1,5T erscheint die KST somit für die Diagnostik des akuten Schlaganfalls geeignet und sollte, da Ischämien besser als mit der Computertomographie charakterisiert werden können, für die Akutdiagnostik verfügbar gemacht werden.
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  • 114
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Schlaganfall ; Intrazerebrale Blutung ; Magnetresonanztomographie ; Computertomographie ; Ratten ; Key words Cerebrovascular diseases ; Intracerebral hemorrhage ; Magnetic resonance imaging ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Background and Purpose: Stroke symptoms are caused in 10 to 15% by intracerebral hemorrhage. From the clinical examination it is often impossible to differentiate intracerebral hemorrhage from cerebral ischemia. To exclude intracerebral hemorrhage as the cause of clinical symptoms a CT is usually performed. The aim of our study was a direct comparison of the sensitivity of Computed Tomography and MRI using different MR sequences for the detection of acute intracerebral hemorrhage. Methods: In 8 male Wistar rats intracerebral hemorrhage was induced by infusion of collagenase into the caudate nucleus. After 1hour the brains were subsequently imaged with CT and MRI using T2- and T1-weighted Spin Echo sequences, diffusion-weighted sequences, T2*-weighted gradient echo sequences and FLAIR-sequences. Visibility of the intracerebral hemorrhage was examined using a scoring system from 1=not visible to 5=excellent visible. Finally, the intracerebral hemorrhage was verified by histological staining. Results: In all animals, intracerebral hemorrhage was visible in T2*-weighted gradient echo and diffusion weighted MR images 1 h after infusion of collagenase. T2- and PD-weighted SE images were positive in 7/8 rats. T1-weighted images revealed signal changes in 5/8 rats, and FLAIR sequence was positive in 8/8 rats. In CT intracerebral hemorrhage was only visible in 3/8 rats. When measuring the increase of Hounsfield units within the suspected hemisphere we saw a mean increase of 7% compared to the normal hemisphere in 3/8 rats. Conclusions: In this animal model, T2*-weighted magnetic resonance imaging proved to be the most sensitive imaging modality in the detection of acute intracerebral hemorrhage and is by far more sensitive than CT.
    Notes: Zusammenfassung Hintergrund und Ziel: Die Symptome eines Schlaganfalls sind in 10 bis 15% durch eine intrazerebrale Blutung verursacht. Oft ist es in der klinischen Untersuchung nicht möglich, zwischen einer intrazerebralen Blutung und einer zerebralen Ischämie zu differenzieren. Um eine intrazerebrale Blutung bei Schlaganfallsymptomatik auszuschließen, wird in der Regel zuerst eine Computertomographie (CT) durchgeführt. Ziel der vorliegenden Studie ist ein direkter Vergleich der Sensitivität der CT mit verschiedenen magnetresonanztomographischen (MR) Sequenzen in der Diagnostik der akuten intrazerebralen Blutung. Material und Methoden: Durch intrazerebrale Applikation von Kollagenase wurde bei 8 männlichen Wistar-Ratten eine intrazerebrale Blutung im linken Nucleus caudatus induziert. Nach einer Stunde wurden die Gehirne zunächst im CT und direkt anschließend in einem klinischen MR-Tomographen unter Verwendung von Protonendiche-, T2- und T1-gewichteten Spinechosequenzen, T2*-gewichten Gradientenechosequenzen, FLAIR-Sequenzen sowie diffusions- und perfusionsgewichteten Gradientenechosequenzen untersucht. Die Visibilität der Blutung wurde anhand einer Skala von 1 (=nicht sichtbar) bis 5 (=klar sichtbar) bewertet. Die Größe der Blutungsherde wurde für jede Untersuchungstechnik bestimmt und mit der Histologie verglichen. Ergebnisse: Bei allen Tieren konnte die Blutung in den T2*-gewichteten Gradientenecho-, FLAIR- sowie diffusionsgewichteten MRT-Bildern 1 h nach Kollagenaseinfusion erkannt werden. Auch in den T2- und Protonendichte-gewichteten Bildern konnte die Blutung bei 8/8 Ratten erkannt werden, wohingegen sie in den T1-gewichteten Aufnahmen nur bei 5/8 Ratten zu erkennen war. In der CT war die intrazerebrale Blutung nur bei 3/8 Ratten sichtbar, wobei bei diesen Tieren eine Zunahme der Dichte in Hounsfield-Einheiten (HE) in der Läsion um 15% auftrat. Schlußfolgerung: In dem verwendeten Tiermodell erwiesen sich T2*-und diffusionsgewichtete Aufnahmen sowie FLAIR-Sequenzen als sehr sensitive Methode in der Diagnostik der akuten intrazerebralen Blutung. Sie waren hierbei sensitiver als die CT. Deshalb sollte ein MR-tomographisches Untersuchungsprotokoll zur Diagnostik des akuten Schlaganfalls T2*- und diffusionsgewichtete Sequenzen beinhalten. Hierdurch gelingt eine rasche Unterscheidung zwischen der akuten intrazerebralen Blutung und der Frühphase der zerebralen Ischämie.
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  • 115
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    Experimental brain research 125 (1999), S. 417-425 
    ISSN: 1432-1106
    Keywords: Key words Motor learning ; Motor cortex ; Magnetic resonance imaging ; Musicians ; Hand motor skill
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In this study, we investigated blood-flow-related magnetic-resonance (MR) signal changes and the time course underlying short-term motor learning of the dominant right hand in ten piano players (PPs) and 23 non-musicians (NMs), using a complex finger-tapping task. The activation patterns were analyzed for selected regions of interest (ROIs) within the two examined groups and were related to the subjects’ performance. A functional learning profile, based on the regional blood-oxygenation-level-dependent (BOLD) signal changes, was assessed in both groups. All subjects achieved significant increases in tapping frequency during the training session of 35 min in the scanner. PPs, however, performed significantly better than NMs and showed increasing activation in the contralateral primary motor cortex throughout motor learning in the scanner. At the same time, involvement of secondary motor areas, such as bilateral supplementary motor area, premotor, and cerebellar areas, diminished relative to the NMs throughout the training session. Extended activation of primary and secondary motor areas in the initial training stage (7–14 min) and rapid attenuation were the main functional patterns underlying short-term learning in the NM group; attenuation was particularly marked in the primary motor cortices as compared with the PPs. When tapping of the rehearsed sequence was performed with the left hand, transfer effects of motor learning were evident in both groups. Involvement of all relevant motor components was smaller than after initial training with the right hand. Ipsilateral premotor and primary motor contributions, however, showed slight increases of activation, indicating that dominant cortices influence complex sequence learning of the non-dominant hand. In summary, the involvement of primary and secondary motor cortices in motor learning is dependent on experience. Interhemispheric transfer effects are present.
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  • 116
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    European radiology 9 (1999), S. 457-459 
    ISSN: 1432-1084
    Keywords: Key words: Retroperitoneal neoplasms ; Retroperitoneal space ; Computed tomography ; Magnetic resonance imaging ; Ultrasonography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. We report a rare case of pseudomyxoma retroperitonei in a 58-year-old woman with a past history of severe appendicitis. The imaging showed a multicystic mass similar to pseudomyxoma peritonei, but the tumor was located in the retroperitoneal space.
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  • 117
    ISSN: 1432-1459
    Keywords: Key words Parkinson’s disease ; Depression ; Brainstem midline ; changes ; Transcranial sonography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recent studies using transcranial sonography (TCS) have provided evidence of alterations in the mesencephalic midline structures in patients with unipolar depression and depression in Parkinson’s disease (PD), suggesting an involvement of the basal limbic system in primary and secondary mood disorders. This study tested the hypothesis of brainstem midline abnormality in depression and investigated 31 PD patients by magnetic resonance imaging (MRI) and TCS. Signal intensity of the pontine and mesencephalic brainstem midline was rated on T2-weighted images and measured by relaxometry. In addition, two blinded investigators assessed the echogenicity of the brainstem midline by TCS. The severity of motor symptoms and depression were graded independently using standard research scales. Rating of signal intensity and T2 relaxometry of the pontomesencephalic midline structures revealed significant difference between depressed and nondepressed PD patients (P 〈 0.05). This corresponded to a significant reduction in mesencephalic midline echogenicity of depressed PD patients on TCS images. No correlation was found between raphe signal intensity, T2 relaxation times, or TCS echogenicity and the severity of motor symptoms or depression. This study is the first to show changes in signal intensity and T2 relaxation time of the pontomesencephalic midline structures on MRI in depressed PD patients confirming previous TCS findings. As these midline structures comprise fiber tracts and nuclei of the basal limbic system, the findings may support the hypothesis of an alteration in the basal limbic system in mood disorders.
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  • 118
    ISSN: 1432-1459
    Keywords: Key words Multiple sclerosis ; Magnetic resonance imaging ; Enhancing lesions ; Interferon-β1a
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. We investigated whether interferon-β1a modifies the course of new enhancing lesions in relapsing-remitting multiple sclerosis. Sixty-eight patients were studied by monthly magnetic resonance imaging (MRI) in a pretest-posttest design including 6 months of observation and 6 months of treatment. We examined the course of new Gd-enhancing lesions on two consecutive scans during observation and during treatment. Lesions detected during treatment were also analyzed by MRI 1 year later for persistence of enhancement, persistence of T2 hyperintensity, development of T1 hypointensity, or disappearance. Among the enhancing lesions detected by observation and treatment MRI, respectively, Gd-enhancement persisted at 2 months in 20% and 3% (P 〈 0.001), T2 hyperintensity persisted in 86% and 63% (P 〈 0.03), and T1 hypointensity developed in 49% and 15% (P 〈 0.01). Progression to T1 hypointensity was significantly more frequent in larger lesions during both the observation and treatment periods (P 〈 0.01). No reenhancement of plaques was present at 1-year follow-up; a further reduction in T2 hyperintensity (63% vs. 39%) was observed while T1 hypointensity remained unchanged. Both the duration of Gd enhancement and the short-term MRI course of new enhancing lesions benefited by treatment with recombinant interferon-β1a treatment.
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  • 119
    ISSN: 1432-1459
    Keywords: Key words Multiple sclerosis ; Magnetic resonance imaging ; Disease activity ; Fast spin echo ; Fast fluid-attenuated inversion ; recovery ; Reproducibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous studies have addressed the question of the precision in assessing multiple sclerosis (MS) activity by counting enhancing lesions on gadolinium enhanced brain magnetic resonance imaging (MRI). However, counting the active lesions on serial unenhanced MRI obtained by various pulse sequences has not been yet considered. We compared the interobserver levels of agreement in reporting active MS lesions on serial enhanced and unenhanced MRI to assess whether the use of various unenhanced techniques may change the degree of interobserver measurement reproducibility. Dual-echo conventional spin echo (CSE), dual-echo fast spin echo (FSE), fast fluid-attenuated inversion recovery (FLAIR) and Gd-enhanced T1-weighted brain MRI were obtained from five MS patients at baseline and monthly for 2 months. Six experienced observers independently identified and counted active MS lesions on the two follow-up MRI scans. Active lesions were considered to be all the enhancing lesions and any new or enlarging lesion on enhanced and unenhanced scans. Interobserver levels of agreement were calculated by weighted κ values. Very good agreement was reached only for counting total and new Gd-enhancing lesions. Good agreement was achieved for counting new lesions on the three unenhanced techniques, whereas the agreement for counting enlarging lesions was poor with all the MRI techniques. The level of agreement was significantly heterogeneous for various MRI techniques but not for various lesion sites. These results confirm that counting enhancing lesions is the most reliable method for assessing MS activity, but the use of any of the available unenhanced MRI techniques did not result in different levels of interobserver agreement when reporting new and enlarging MS lesions on serial scans.
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  • 120
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    Journal of neurology 246 (1999), S. 1169-1171 
    ISSN: 1432-1459
    Keywords: Key words European tick-borne encephalitis ; Magnetic resonance imaging ; Central nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a case of central European tick-borne encephalitis with cervical myelitis presenting clinically as a lower motor neuron syndrome of the upper limbs with proximal asymmetrical pareses and atrophies. There were no sensory deficits nor signs of lesions of the spinal pathways or signs of encephalitis or meningitis. The affected motor fibers of the upper limbs were electrically inexcitable, but sensory findings were normal. Electromyography of the paralyzed muscles revealed pathological denervation activity without voluntary activation. The initial magnetic resonance imaging (MRI) showed a large hyperdense lesion in the anterior part of the cervical cord from C3 to T1. Despite the fact that MRI changes disappeared completely within 6 weeks the patient showed only little improvement in the paralyzed muscles after 6 months. To our knowledge, these MRI changes in patients with tick-borne encephalitis, consistent with an isolated anterior horn lesion, have never been reported previously. The course may have been aggravated by an initial antibiotic treatment with cephalosporins.
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  • 121
    ISSN: 1432-1459
    Keywords: Key words Temporal lobe epilepsy ; Hippocampus ; Magnetic resonance imaging ; Fluoro-2-deoxy-d-glucose positron-emission tomography ; Wada test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In refractory temporal lobe epilepsy (TLE) temporal lobe structures and functions are continuously or intermittently affected by abnormal brain electrical events, noxious neurochemical agents, and metabolic disturbances. There is conflicting evidence regarding the relationship between the duration of refractory mesial TLE and quantitative measures of temporal lobe functions and volumes of the hippocampi. Twenty patients (aged 28 ± 7 years, 14 males) with an initial precipitating injury before the age of 5 years were subjected to high-resolution magnetic resonance imaging, fluoro-2-deoxy-d-glucose positron-emission tomography (PET), and the Wada test. We investigated whether the duration of unilateral refractory TLE (12 left, 8 right) affects hippocampal volume, glucose metabolism, or Wada hemispheric memory performance. Ipsilateral to the epileptogenic zone the hippocampal volume, metabolism, and Wada hemispheric memory performance were reduced compared to the corresponding contralateral measures. The duration of epilepsy controlled for age at investigation, side of seizure origin, underlying cause, and sex were negatively correlated with ipsi- and contralateral hippocampal volume, hippocampal metabolism, and Wada hemispheric memory performance. Moreover, ipsilateral Wada hemispheric memory performance and contralateral hippocampal glucose metabolism were correlated with the frequency of habitual seizures. Refractory TLE seems to be associated with a slow but ongoing bilateral temporal lobe damage. These cross-sectional results require verification by longitudinal studies carried out over a period of more than two decades.
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  • 122
    ISSN: 1432-1459
    Keywords: Key words Multiple sclerosis ; Magnetic resonance imaging ; Gadolinium-DTPA ; Triple dose ; Blood-brain barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study assessed whether dysfunction of the blood-brain barrier is an obligatory early event in lesion formation in multiple sclerosis. Dual-echo and T1-weighted magnetic resonance imaging after the injection of a triple dose (0.3 mmol/kg) of gadolinium-DTPA were obtained from ten patients with relapsing-remitting multiple sclerosis every week for 2 months. Sixty-four newly active lesions were detected by the two techniques. All the 44 new lesions seen on dual-echo scans enhanced during the early phases of their formation: 33 at their first appearance, 10 1 week before their appearance on the dual-echo scans, and one the week thereafter. When the every fourth (monthly) scan was analyzed, a total of 55 newly active lesions were detected (i.e., 14% active lesions would have been missed compared to the number found on weekly scanning). Thirty-one of them were detected by both dual-echo and triple-dose scans, 15 only by enhanced scans, and nine only by dual-echo scans. This study confirms that with highly sensitive magnetic resonance imaging techniques dysfunction of the blood-brain barrier is an obligatory early event in new lesion formation in relapsing-remitting multiple sclerosis.
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  • 123
    ISSN: 1432-1327
    Keywords: Gadolinium(III) complexes ; Contrast agents ; Magnetic resonance imaging ; Human serum albumin ; Proton relaxation enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: N,N′,N″,N‴ -pentaacetic acid) bearing different substituents for binding to human serum albumin (HSA) are compared. In spite of the structural differences of the recognition synthon and of the residual electric charge, the two chelates display an analogous binding affinity for the serum protein. Upon formation of the adducts with HSA, the exchange rates of the coordinated water appear slowed down by an amount corresponding to ca. 50% of the rates found for the free complexes. The relaxivity of [Gd(BOM)3DTPA (H2O)]2 −  is significantly higher than that of MS-325 either in the free complex or in the macromolecular adduct. Finally, the effect of pH on the stability of the HSA adducts and on the values of their relaxivities has been investigated.
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  • 124
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    Child's nervous system 15 (1999), S. 624-634 
    ISSN: 1433-0350
    Keywords: Key words Brain imaging ; Magnetic resonance imaging ; brain ; Magnetic resonance spectroscopy ; brain ; Computed tomography ; brain ; Diffusion imaging ; brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The last century has seen the evolution of neuroimaging from nonexistent to a group of techniques that, in our eyes, appears to be highly sophisticated. The rapidity of advancement in imaging has been concentrated in the last quarter century. There is no reason to expect this continual forward expansion of neuroradiology to abate; rather it seems likely that it will continue to increase at an even faster rate. The near future is one of refinement in imaging, faster and higher resolution as well as a much greater emphasis on physiology and biochemistry.
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  • 125
    ISSN: 1433-0350
    Keywords: Key words Abscess ; Spinal cord ; Dermal sinus ; Epidermoid ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intramedullary abscesses of the spinal cord are uncommon. Most of them occur in association with heart, pulmonary or urogenital infections. We report two cases of intramedullary spinal cord abscesses secondary to congenital dermal sinus. Only 14 cases of such an association have previously been reported. In our cases, dermal sinus was associated with an epidermoid tumour. The clinical presentation, pathogenesis, magnetic resonance imaging findings, surgical management and outcome are discussed.
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  • 126
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    Child's nervous system 15 (1999), S. 359-361 
    ISSN: 1433-0350
    Keywords: Key words Computerized tomography ; Intracranial tumor ; Magnetic resonance imaging ; Posterior fossa ; Teratoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In this study we report a rare case of a giant midline posterior fossa teratoma; its clinical presentation, radiological appearance, treatment and outcome, with an extensive review of the literature.
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  • 127
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    Skeletal radiology 28 (1999), S. 383-389 
    ISSN: 1432-2161
    Keywords: Key words Allografts ; Osteoarticular ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To investigate the magnetic resonance imaging (MRI) features of allografts at various time intervals after surgery in patients with osteoarticular allografts. Design and patients. Sixteen patients who were treated with osteoarticular allografts and who were followed over time with MRI studies as part of their long-term follow-up were retrospectively selected for this study. T1-weighted images were obtained both before and after gadolinium administration along with T2-weighted images. All images were reviewed by an experienced musculoseletal radiologist, with two other experienced radiologists used for consultation. Imaging studies were organized into three groups for ease of discussion: early postoperative period (2 days to 2 months), intermediate postoperative period (3 months to 2 years), and late postoperative period (greater than 2 years). Results. In the early postoperative period, no gadolinium enhancement of the allograft was visible in any of the MR images. A linear, thin layer of periosteal and endosteal tissue enhancement along the margin of the allograft was visible in images obtained at 3–4 months. This enhancement apeared gradually to increase in images from later periods, and appears to have stabilized in the images obtained approximately 2–3 years after allograft placement. The endosteal enhancement diminished after several years, with examinations conducted between 6 and 8 years following surgery showing minimal endosteal enhancement. However, focal enhancement was noted adjacent to areas of pressure erosion or degenerative cysts. All the cases showed inhomogeneity in the marrow signal (scattered low signal foci on T1 with corresponding bright signal on T2), and a diffuse, inhomogeneous marrow enhancement later on. Conclusion. We have characterized the basic MRI features of osteoarticular allografts in 16 patients who underwent imaging studies at various time points as part of routine follow-up. We believe that the endosteal and periosteal enhancement observed on MRI during the first few months to 2 years following surgery represents vascular ingrowth and early skeletal repair. The zone of periosteal enhancement could also include the new bone laid on the surface of the allograft through which the soft tissues bind to the cortex. The exact reason for the inhomogeneity in the marrow signal, and the diffuse, inhomogeneous marrow enhancement is not clear. This may represent saponified and/or necrotic marrow fat interspersed with the fibrovascular tissue. The features noted here should provide radiologists with useful information regarding imaging characteristics they can expect to see in other allograft replacement patients.
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    Skeletal radiology 28 (1999), S. 447-452 
    ISSN: 1432-2161
    Keywords: Key words Plantar fascia ; aponeurosis ; Fasciitis ; Fasciotomy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To determine the postoperative appearance of the plantar fascia on MR imaging after a fasciotomy has been performed, and to compare the postsurgical appearance of the fascia after an open and endoscopic procedure.〈@head-abs-p1.lf〉Design and patients. Fifteen asymptomatic volunteers (12 women, 3 men; age range 22–49 years, mean age 33 years) with prior fasciotomies for treatment of longstanding plantar fasciitis were studied. Fourteen volunteers had a unilateral release and one volunteer had bilateral releases, allowing for assessment of 16 ankles. Eight fasciotomies were performed through an open incision and eight were performed endoscopically. The average time between surgery and imaging was 24 months (range 11–46 months). The site of surgery was established from the operative reports. Proton density (PD)-weighted and T2-weighted images in three orthogonal planes were obtained on a 1.5-T magnet. In eight studies, T1-weighted sagittal and STIR sagittal images were included. The fascia in each ankle was assessed for morphology and signal intensity. Perifascial soft tissues and bone marrow were assessed for edema. Preoperative MR studies were available in five volunteers.〈@head-abs-p1.lf〉Results. There was no apparent difference in the postoperative appearance of the ankle after an open or endoscopic procedure except for scar formation in the subcutaneous fat which was common after an open procedure (P〈0.05). Three ankles had a gap in the fascia (one open, two endoscopic). The plantar fascia measured a mean of 7.0 mm (range 5–10 mm) at the fasciotomy, and 8.3 mm (range 6–12 mm) at the enthesis. At the fasciotomy, 11 of 13 ankles had an indistinct deep contour and 9 of 13 had an indistinct superficial contour. At the enthesis, 13 of 16 ankles had an indistinct deep contour and 6 of 16 had an indistinct superficial contour. Compared with preoperative MR studies there was an average reduction in the fascial thickness at the enthesis of 14% (range 9–20%), but the thickness at the fasciotomy nearly doubled. No edema was evident in the fascia, perifascial tissues, deep plantar muscles, or calcaneal bone marrow.〈@head-abs-p1.lf〉Conclusions. The average thickness of the plantar fascia in asymptomatic volunteers after surgery is nearly 2–3 times that of normal. While there is increased thickness at the site of surgery, the changes in morphology and signal intensity were most prominent at the enthesis. The key observation was absence of edema in the fascia and perifascial soft tissues. This baseline information may be of value when assessing MR studies of symptomatic patients.
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  • 129
    ISSN: 1432-2161
    Keywords: Key words Hand ; Wrist ; Magnetic resonance imaging ; Soft tissue mass ; Neoplasm ; Tumour ; Tendon diseases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract   Objective. To assess the utility of magnetic resonance imaging (MRI) in the investigation of palpable masses in the hand or wrist.〈@head-abs-p1.lf〉Design and patients. We retrospectively reviewed the MRI examinations and case records of 134 patients referred because of a palpable mass in the hand or wrist. MRI was performed on a 1.0 T magnet using an extremity coil. Intravenous gadolinium-DTPA was injected when considered appropriate.〈@head-abs-p1.lf〉Results and conclusions. MRI demonstrated the cause of the palpable mass in 126 cases (94.02%). Soft tissue neoplasms were found in 34 cases (25.37%). The majority were benign and included giant cell tumours of tendon sheath, lipomas and hemangiomas and had a characteristic appearance. There were three malignant tumours (myxoid liposarcoma, malignant fibroushistiocytoma and rhabdomyosarcoma). Ganglia were found in 36 cases (26.86%) and non-tumour tendon pathology in 31 cases (23.13%). Less common causes included articular diseases (5.97%) and anatomical variants (4.47%). No focal lesion was present in 8 cases (5.97%). In conclusion, MRI is an accurate diagnostic technique in patients who present with a palpable mass of the hand and wrist.
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    Skeletal radiology 28 (1999), S. 96-99 
    ISSN: 1432-2161
    Keywords: Key words Computed tomography ; Granular cell tumor ; Magnetic resonance imaging ; Subcutis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Three cases of granular cell tumor (GCT) of the subcutis are presented. Computed tomography showed a mass isodense with muscle with an ill-defined margin. Magnetic resonance imaging showed a mass with inhomogeneous low signal intensity on both T1- and T2-weighted images. Another characteristic feature of subcutaneous GCT is its attachment in part to muscle. Histological examination confirmed the diagnosis in all cases.
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  • 131
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    Child's nervous system 15 (1999), S. 8-10 
    ISSN: 1433-0350
    Keywords: Key words Cavernous sinus ; Meningioma ; Child ; Ophthalmoplegia ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intracranial meningiomas in children are rare, representing 1–4.2% of central nervous system tumors and 1.5–1.8% of all intracranial meningiomas. Meningiomas arising from the lateral wall of the cavernous sinus account for less than 1% of all intracranial meningiomas. To our knowledge, only one case of a meningioma arising from the cavernous sinus has been reported in childhood. A 6-year-old boy presented with left ophthalmoplegia. A slight drooping of the left eyelid was noted at the age of 1 year. Magnetic resonance imaging (MRI) with contrast administration revealed an enhancing mass lesion located in the left cavernous sinus. The tumor, arising from the lateral wall of the cavernous sinus, was totally removed and the oculomotor nerve was reconstructed with a sural nerve graft. MRI displayed total tumor removal 1 month after the surgery. The pathological diagnosis was of a psammomatous meningioma.
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    Child's nervous system 15 (1999), S. 209-211 
    ISSN: 1433-0350
    Keywords: Key words Anterior sacral meningocele ; Epidermoid tumor ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A 2-year-old girl presented with an anterior sacral meningocele completely occupied by an epidermoid tumor. Preoperative magnetic resonance imaging had shown the meningocele with contents of the same intensity as cerebrospinal fluid. Surgery via a posterior sacral approach disclosed the tumor beneath an unexpected membrane inside the meningocele. Additionally, the presence of pus inside epidermoid tumor suggested that possible episodes of asymptomatic meningitis or other infection might have occurred before treatment, these being the major complication in anterior sacral meningocele. Therefore, we recommend that surgical treatment should be performed at the earliest possible stage in childhood, once the diagnosis is established, and dural plasty carried out to prevent infectious complications.
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    Der Radiologe 39 (1999), S. 847-854 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Zerebrale Amyloidangiopathie ; Intrazerebrale Blutung ; Computertomographie ; Kernspintomographie ; Key words Cerebral amyloid angiopathy ; Intracerebral hemorrhage ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The purpose of our study was to evaluate the characteristic findings of acute hemorrhage due to amyloid angiopathy with computed tomography. 14 patients of intracranial hemorrhage with histologically confirmed cerebral amyloid angiopathy were observed over a period of 4 years. Characteristic findings were a lobar hemorrhage in superficial localisation, cortical involvment, subarachnoid hemorrhage, the multiplicity of hemorrhages and repeated episodes. Severe cerebral amyloid angiopathy is often accompanied by multiple petechial hemorrhages, restricted to a cortical-subcortical distribution, detectable by magnetic resonance imaging. These findings suggest that cerebral amyloid angiopathy is not a rare cause of atraumatic lobar hemorrhage. Amyloid angiopathy should be considered in any elderly patient with superficial intracerebral hemorrhage in an atypical location.
    Notes: Zusammenfassung In der Arbeit werden die computertomographischen Befunde der intrazerebralen Blutung im Rahmen der Amyloidangiopathie untersucht. 14 Patienten mit Massenblutung und histologisch bestätigter Amyloidangiopathie wurden in einem Zeitraum von 4 Jahren beobachtet. Charakteristische Befunde waren eine lobäre, oberflächlich gelegene Blutung, eine kortikale Beteiligung, eine begleitende Subarachnoidalblutung sowie ein mehrfaches und mehrzeitiges Auftreten der Blutungen. Eine schwere Amyloidangiopathie geht oft mit multiplen petechialen Blutungen in kortiko-subkortikaler Lokalisation einher, die sich kernspintomographisch nachweisen lassen. Die Befunde zeigen, daß die Amyloidangiopathie keine seltene Ursache einer nicht traumatischen lobären Blutung ist. Sie sollte daher bei jedem älteren Patienten mit einer intrazerebralen, oberflächlich gelegenen Blutung in atypischer Lokalisation in Betracht gezogen werden.
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  • 134
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Staging thorakoabdominaler Tumoren ; Kinder ; Computertomographie (CT) ; Magnetresonanztomographie (MRT) ; Malignome ; Key words Staging of tumors ; Thoracoabdominal tumors ; Childhood ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Thoracoabdominal tumors in childhood can arise from all organs and affect children from the neonate to the adolescent. Better prognosis of childhood tumors, due to better biological understanding and improvement of chemotherapy, require sufficient radiological staging. Sufficiency in radiological staging needs modern cross-sectional techniques with high resolution, good availability and lower radiation dose. In general computed tomography (CT) is being used for radiological staging; increasingly MR imaging is being used because of multiplanar imaging techniques. Replacement of invasive techniques such as myelography and lymphography and modern cross-sectional techniques create painless staging conditions. Nevertheless, scintigraphy will always be a major examination technique, especially for evaluation of metastases and postoperative control examinations. The most common thoracoabdominal tumors in childhood and their staging are described.
    Notes: Zusammenfassung Thorakale und abdominale Tumoren im Kindesalter nehmen ihren Ausgang von allen Organsystemen und können vom Neugeborenen bis zum Adoleszenten auftreten. Verbesserte Prognose, bedingt durch das bessere biologische Verständnis der Tumorerkrankung, sowie der effiziente Einsatz von Chemotherapeutika machen ein radiologisches Staging unumgänglich. Üblicherweise wird zum Staging die Computertomographie (CT) eingesetzt. Durch die Möglichkeit der multiplanaren Schnittführung und die bessere Auflösung bei Tumoren mit Beteiligung des ZNS wird in zunehmendem Maße die Magnetresonanztomographie (MRT) eingesetzt. Diese modernsten Schnittbildverfahren haben invasive Methoden wie Lymphographie und Angiographie in den Hintergrund gedrängt. Im weiteren werden die häufigsten thorakalen und abdominalen Tumoren im Kindesalter besprochen und deren Stagingsysteme erläutert.
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    Der Radiologe 39 (1999), S. 562-567 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Kolorektales Karzinom ; Präoperatives Staging ; Endosonographie ; CT ; MRT ; Key words Colorectal cancer ; Preoperative staging ; Endosonography ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Carcinoma of the colorectum is one of the most frequent neoplasias, with an incidence of 40 in 100 000. For the effective use of new, differentiated, less invasive treatment options, exact preoperative staging of the tumor is essential. The introduction of endosonography in rectal tumor staging allows for exact differentiation of the rectal wall layers and thus of tumor stages 1–3 with median accuracy of 89%. Magnetic resonance imaging of the rectum, especially in double-contrast technique, can also be employed in high and stenosing tumors and leads to an average accuracy of 85% for the stages 1–4. Computed tomography is the method of choice in screening for metastases. In lymph node staging, all modalities show only moderate accuracy around 75%.
    Notes: Zusammenfassung Das kolorektale Karzinom stellt mit einer Inzidenz von 40 auf 100000 eine der häufigsten Neoplasien dar. Für den effektiven Einsatz neuer differenzierter Therapien mit geringerer Invasivität ist ein exaktes präoperatives Staging erforderlich. Die Einführung der Endosonographie im Tumorstaging erlaubt eine exakte Differenzierung der Wandschichten und damit der Tumorstadien 1–3 mit einer mittleren Genauigkeit von 89%, die Magnetresonanztomographie des Rektums, insbesondere in Doppelkontrasttechnik, kann auch bei hohen und stenosierenden Tumoren angewendet werden, bei einer Genauigkeit von durchschnittlich 85% für die Stadien 1–4. Die Computertomographie ist Methode der Wahl im Metastasenscreening. Im Lymphknotenstaging zeigen alle Modalitäten nur bescheidene Genauigkeiten um 75%.
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  • 136
    ISSN: 1433-7347
    Keywords: Key words Donor site morbidity ; Anterior cruciate ligament ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Sports Science
    Notes: Abstract The aim of this prospective study was to follow the development of repair tissue in the donor-site area using serial magnetic resonance imaging (MRI) evaluation and to assess whether the MRI findings were correlated with donor-site morbidity. Thirty-seven consecutive patients with unilateral anterior cruciate ligament injuries undergoing elective reconstruction of the ligament were included in the study. They were aged 27 (range 14–50) years. The graft was harvested through two 25-mm vertical incisions with the aim of protecting the infrapatellar nerve and sparing the paratenon. The tendon defect was left open. The patients underwent MRI evaluation at 6 weeks, 6 months and 27 months postoperatively. A final clinical follow-up was made 25 (range 23–29) months postoperatively. MRI demonstrated that the donor-site gap, i.e. the area corresponding to a pathological non-tendinous-like tissue signal, was 9 (range 4–18) mm at 6 weeks, 5 (range 2–14) mm at 6 months and 2 (range 0–5) mm at 27 months. The size of the donor-site gap had significantly decreased at 6 months compared with 6 weeks (P = 0.0001), as well as at 27 months compared with 6 months (P = 0.0001). We conclude that the patellar tendon at the donor site healed gradually, as expressed by a decrease in the area of non-tendinous-like tissue signal on the serial MRI evaluations.
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  • 137
    ISSN: 1433-7347
    Keywords: Key words Meniscus ; Degeneration ; Magnetic resonance imaging ; Histology ; Chronicity of the meniscal tear
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Sports Science
    Notes: Abstract Signal anomalies observed in magnetic resonance imaging of the intrameniscal tissue adjacent to the tear were compared between stable knees (group 1, 54 menisci) and anterior cruciate ligament (ACL) deficient knees (group 2, 98 menisci). The histological significance of these signal anomalies was also studied (n = 25). The frequency of intrameniscal signal anomalies adjacent to the tear was significantly lower in ACL-deficient knees than in ACL-stable knees (P = 0.0022). There was a close correlation between the imaging anomalies and the presence of histological lesions (fissures, degeneration) within meniscal tissues adjacent to the tear (sensitivity: 0.95, specificity: 0.60). Our results suggest that the severity of intrameniscal degenerative changes adjacent to the tear are lower in ACL-deficient knees than in ACL-stable knees.
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  • 138
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    Journal of neurology 246 (1999), S. 16-20 
    ISSN: 1432-1459
    Keywords: Key words Dementia ; Alzheimer’s disease ; Neuroimaging ; Magnetic resonance imaging ; Single photon emission computed tomography ; Atrophy ; Hippocampus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The use of neuroimaging is reviewed in the diagnosis of dementia, especially Alzheimer’s disease (AD). Computed tomography (CT) may be used to exclude other causes of dementia than AD. The finding of cortical or subcortical atrophy on CT or magnetic resonance imaging (MRI) itself does not indicate AD. Hippocampal atrophy on CT/MRI provides a useful early marker, although further longitudinal and neuropathological study is required. CT- and MRI-based measurements of hippocampal atrophy show promise in providing useful diagnostic information for discriminating patients with probable AD from normal elderly individuals. Using a standardized imaging protocol, including some assessment of hippocampal atrophy, can save costs since patients with suspected AD must undergo a cross-sectional imaging study to exclude other (treatable) causes of dementia. Combining an assessment of hippocampal atrophy with cerebral blood flow measurements by single photon emission computed tomography is not warranted either from a clinical or from an economic point of view.
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  • 139
    ISSN: 1432-1459
    Keywords: Key words Spinocerebellar ataxia type 2 ; Magnetic resonance imaging ; Cerebral atrophy ; Disease duration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There have been only few studies of brain magnetic resonance imaging (MRI) in spinocerebellar ataxia (SCA) type 2. We investigated 20 SCA2 patients, from 11 Sicilian families, and 20 age-matched control subjects using MRI. Our data confirm that olivopontocerebellar atrophy (OPCA) is the typical pattern in SCA2. We found no significant correlation between infratentorial atrophy, disease duration, or the number of CAG repeats in our SCA2 patients, but there was supratentorial atrophy in 12 patients, with a significant correlation between supratentorial atrophy and disease duration. OPCA appears to represent the “core” of the SCA2: however, central nervous system involvement is not limited to pontocerebellar structures. We therefore consider central nervous system degeneration in SCA2 as a widespread atrophy. MRI is helpful in diagnosing SCA, but it is not diagnostic in the absence of clinical and molecular studies. We suggest that serial MRI may play a role in evaluating “in vivo” the progressive steps of neurodegeneration in SCA2, for a better comprehension of the pathophysiology of this disorder.
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  • 140
    ISSN: 1615-3146
    Keywords: Kerspintomographie ; Kollateralbandruptur ; Knorpelläsion ; Hochauflösende Oberflächenspule ; Magnetic resonance imaging ; Collateral ligament rupture ; Cartilage lesion ; High-resolution coil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Aim of this study was the evaluation of a prototype of a new high-resolution MRI coil for the detection of finger trauma. The practicability of this new coil for the assessment of traumatic lesions of the finger joints and the diagnostic value of this new method in clinical practice was assessed. Twenty patients between 13 and 50 years of age (mean 28 years) were examined with a 1.5-T whole-body-imager Magnetom SP 63 scanner (Siemens, Erlangen, Germany). A prototype of a high-resolution MRI coil with a diameter of 2.5 cm was used. T1- and T2-weighted images with an in plane resolution of 0.I95 x 0.098 mm were acquired. Bone structures, joint cartilage and capsule, ligaments, tendons and soft tissue alterations were assessed. All 19 patients with pathological changes at the finger joints had a joint effusion. With MR imaging, fractures were detected in almost all patients, compared with the X-ray examinations. Cartilage contusion showed high signal intensity. The collateral ligaments could best be assessed in the transversal, and ligament ruptures in the coronal plane. Hemorrhage in the tendon showed an increased signal intensity in T1- and T2-weighted, edema only in T2-weighted images. Especially traumatic lesions of cartilage and of ligaments can be sufficiently assessed by the high-resolution MRI due to its high anatomic resolution compared to common methods like X-ray. High-resolution MRI is practicable in clinical routine.
    Notes: Zusammenfassung Ziel der vorliegenden prospektiven Untersuchung war es, die Wertigkeit der hochauflösenden Kernspintomographie mittels einer speziellen Oberflächenspule in der Beurteilung von traumatischen Veränderungen der Fingergelenke zu evaluieren. Ferner sollte die Praktikabilität der Methode in der klinischen Routine überprüft werden. Es wurden 20 Patienten im Alter zwischen 13 und 50 Jahren (im Mittel 28 Jahre) an einem 1,5-T-Ganzkörpertomographen (Magnetom SP 63, Firma Siemens, Erlangen) untersucht. Als Spule wurde ein Prototyp einer hochauflösenden Oberflächenspule mit einem Durchmesser von 2,5 cm benutzt. T1- und T2-gewichtete Sequenzen mit einer maximalen Auflbsung in der Bildebene von 0,195 x 0,098 mm wurden zur Beurteilung von Knochen, Gelenkknorpel und -kapsel, der Sehnen und des Weichteilgewebes akquiriert. Kernspintomographisch fand sich bei 19 Patienten ein pathologischer Befund. Bei all diesen Patienten konnte ein Gelenkerguß nachgewiesen werden. Knöcherne Absprengungen, die anhand konventioneller Röntgenaufnahmen diagnostiziert wurden, zeigten sich kernspintomographisch als dislozierte signalreiche Strukturen. Gelenkknorpelkontusionen stellten sich hyperintens dar. Zur Beurteilung der Kollateralbānder eignete sich vor allem die koronare Schichtebene, da in dieser die Kollateralbdnder per continuitatem darstellbar sind. Sehneneinblutungen wiesen eine Signalerhöhung in T1- und T2-Wichtung auf. Ödeme der Weichteile und Bandstrukturen imponierten in T2-gewichteten Aufnahmen als signalreiche Strukturveränderungen. Aufgrund der hohen anatomischen Detailerkennbarkeit eignet sich die hochauflbsende Kernspintomographie als ergänzendes diagnostisches Verfahren zur nichtinvasiven Diagnostik von traumatischen Knorpel- und Bandläsionen. Unter Berücksichtigung des Zeitaufwandes handelt es sich dabei um eine im klinischen Alltag praktikable Methode.
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  • 141
    ISSN: 1619-7089
    Keywords: Key words: Autism ; Brain ; Technetium-99m ethyl cysteinate dimer ; Single-photon emission tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The neuro-anatomical substrate of autism has been the subject of detailed investigation. Because previous studies have not demonstrated consistent and specific neuro-imaging findings in autism and most such studies have been performed in adults and school-aged children, we performed a retrospective review in young children in search of common functional and anatomical abnormalities with brain single-photon emission tomography (SPET) using technetium-99m ethyl cysteinate dimer (ECD) and correlative magnetic resonance imaging (MRI). The patient population was composed of 23 children aged 28–92 months (mean: 54 months) who met the diagnostic criteria of autism as defined in the DSM-IV and CARS. Brain SPET was performed after intravenous injection of 185–370 MBq of 99mTc-ECD using a brain-dedicated annular crystal gamma camera. MRI was performed in all patients, including T1, T2 axial and T1 sagittal sequences. SPET data were assessed visually. Twenty patients had abnormal SPET scans revealing focal areas of decreased perfusion. Decreased perfusion of the cerebellar hemisphere (20/23), thalami (19/23), basal ganglia (5/23) and posterior parietal (10/23) and temporal (7/23) areas were noted on brain SPET. By contrast all patients had normal MRI findings without evidence of abnormalities of the cerebellar vermis, cerebellar hemisphere, thalami, basal ganglia or parietotemporal cortex. In conclusion, extensive perfusion impairments involving the cerebellum, thalami and parietal cortex were found in this study. SPET may be more sensitive in reflecting the pathophysiology of autism than MRI. However, further studies are necessary to determine the significance of thalamic and parietal perfusion impairment in autism.
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  • 142
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    European journal of applied physiology 79 (1999), S. 367-373 
    ISSN: 1439-6327
    Keywords: Key words Cerebral edema ; Cerebrospinal fluid ; Head-down tilt ; Intracranial pressure ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Vascular and tissue fluid dynamics in the microgravity of space environments is commonly simulated by head-down tilt (HDT). Previous reports have indicated that intracranial pressure and extracranial vascular pressures increase during acute HDT and may cause cerebral edema. Tissue water changes within the cranium are detectable by T 2 magnetic resonance imaging. We obtained T 2 images of sagittal slices from five subjects while they were supine and during −13° HDT using a 1.5-Tesla whole-body magnet. The analysis of difference images demonstrated that HDT leads to a 21% reduction of T 2 in the subarachnoid cerebrospinal fluid (CSF) compartment and a 11% reduction in the eyes, which implies a reduction of water content; no increase in T 2 was observed in other brain regions that have been associated with cerebral edema. These findings suggest that water leaves the CSF and ocular compartments by exudation as a result of increased transmural pressure causing water to leave the cranium via the spinal CSF compartment or the venous circulation.
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  • 143
    ISSN: 1573-9686
    Keywords: Blood flow ; Magnetic resonance imaging ; Numerical flow modeling ; Carotid artery ; Three-dimensional ; Wall shear stress ; Atherosclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Purpose: Combining computational blood flow modeling with three-dimensional medical imaging provides a new approach for studying links between hemodynamic factors and arterial disease. Although this provides patient-specific hemodynamic information, it is subject to several potential errors. This study quantifies some of these errors and identifies optimal reconstruction methodologies. Methods: A carotid artery bifurcation phantom of known geometry was imaged using a commercial magnetic resonance (MR) imager. Three-dimensional models were reconstructed from the images using several reconstruction techniques, and steady and unsteady blood flow simulations were performed. The carotid bifurcation from a healthy, human volunteer was then imaged in vivo, and geometric models were reconstructed. Results: Reconstructed models of the phantom showed good agreement with the gold standard geometry, with a mean error of approximately 15% between the computed wall shear stress fields. Reconstructed models of the in vivo carotid bifurcation were unacceptably noisy, unless lumenal profile smoothing and approximating surface splines were used. Conclusions: All reconstruction methods gave acceptable results for the phantom model, but in vivo models appear to require smoothing. If proper attention is paid to smoothing and geometric fidelity issues, models reconstructed from MR images appear to be suitable for use in computational studies of in vivo hemodynamics. © 1999 Biomedical Engineering Society. PAC99: 8719Uv, 8761-c, 0705Pj, 8710+e
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  • 144
    ISSN: 1573-9686
    Keywords: Medical imaging ; Magnetic resonance imaging ; Biomechanics ; Tendon moment arm ; Functional neuromuscular stimulation ; Tendon transfer surgery ; Hand biomechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract New three-dimensional (3D) magnetic resonance imaging (MRI) methods for measuring the tendon moment arm were created and were evaluated on the tendon moment arm of the flexor digitorum profundus at the third metacarpophalangeal joint. Using an open magnet MRI system and a hand holder, a series of static images were acquired at four joint angles and analyzed using specially created computer programs. Three methods were evaluated: (1) a 3D tendon excursion method that extended the method of Landsmeer; (2) a 3D geometric method whereby the moment arm was the perpendicular distance between the joint axis of rotation and the tendon path, and (3) a two-dimensional (2D) geometric method whereby single image slices were analyzed. Repeating the imaging and measurement processes, the 3D tendon excursion method was more reproducible (6% variation) than the 3D geometric method (12%), and both were much more reproducible than the 2D geometric method (27%). By having three operators analyze a single set of image data, we found that the precision of the 3D tendon excursion method was much less affected by segmentation error than the 3D geometric method. With the 3D imaging methods, tendon bowstringing and a displacement of the joint center of rotation toward the dorsal side of the hand were evident, leading to as much as a 60% increase in moment arm with joint flexion. Because of the dependence on flexion and variation between subjects, we recommend patient-specific measurements for target applications in functional neuromuscular stimulation interventions and tendon transfer surgery. © 1999 Biomedical Engineering Society. PAC99: 8761Pk, 8719Rr, 0705Pj
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  • 145
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    Journal of High Resolution Chromatography 22 (1999), S. 11-16 
    ISSN: 0935-6304
    Keywords: Pyrolysis gas chromatography ; microstructure determination ; syndiotactic copolymers ; styrenes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The composition and microstructure of syndiotactic para-methylstyrene/styrene copolymer was determined by a pyrolysis gas chromatography (Py-GC) method. This method uses the styrene and para-methylstyrene monomer peak intensities to determine the styrene and para-methylstyrene composition in the copolymer. The number average sequence length of styrene was calculated by using the triad peak intensities. Because of the low concentration of para-methylstyrene in the copolymer, the number average sequence length of para-methylstyrene was determined with formulas that incorporate the copolymer composition and the number average sequence length of styrene. The distribution of para-methylstyrene defined by the terms “percent of single units” and “percent of desired distribution” was calculated by the number average sequence of para-methylstyrene. This method has been tested with copolymers containing up to 24 mole% of para-methylstyrene. The composition results from Py-GC of para-methylstyrene and styrene copolymers used in this study were in excellent agreement with 1H-NMR results.
    Additional Material: 3 Ill.
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  • 146
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    Journal of High Resolution Chromatography 22 (1999), S. 24-28 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; ECD ; Micro-ECD ; GC detector ; organochlorine pesticides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A new ECD, the HP 6890 Series Micro-ECD, was designed to address inherent deficiencies in classical electron capture detectors (ECD), especially with respect to sensitivity, linearity, dynamic range, and ruggedness. Several novel technologies were incorporated in the totally new design and were refined through practical testing and user feedback. Validation of the micro-ECD performance was accomplished through side-by-side testing of the Micro-ECD with previous ECDs following US EPA Contract Laboratory Program methods for pesticides and PCBs. In addition, extensive interviews were conducted with early users of the Micro-ECD who also had experience with other designs running a variety of ECD methods. The design and resulting performance improvements are described.
    Additional Material: 6 Ill.
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  • 147
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    Journal of High Resolution Chromatography 22 (1999), S. 33-38 
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; chiral separation ; negatively charged chiral selectors ; capillary filling methods ; dual systems ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Data on the use of two chiral selectors, namely 18-crown-6 tetracarboxylic acid and a negatively charged cyclodextrin derivative (sulfated-β-cyclodextrin or carboxymethyl-β-cyclodextrin), in the same background electrolyte are presented. The use of such dual systems has a considerable influence on the resolution, as illustrated for the separation of tryptophan derivatives. Reduction of the consumption of chiral selector without significant loss in resolution was obtained by only partly filling the capillary and applying a run buffer without selector. This is illustrated for the chiral separation of tryptophan hydroxamate and the diastereomeric and enantiomeric separation of the dipeptide α/b-AspPhe-OMe.
    Additional Material: 5 Ill.
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  • 148
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    Journal of High Resolution Chromatography 22 (1999), S. 43-46 
    ISSN: 0935-6304
    Keywords: Green and roasted coffee ; diterpenes ; cafestol ; kahweol ; 16-O-methylcafestol ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The three coffee diterpenes cafestol, kahweol, and 16-O-methylcafestol are mostly esterified with fatty acids. Little has been published about the diterpenes occurring in the free form. By means of gel permeation chromatography on Bio Beads S-X3, it is now possible to simultaneously analyze and quantify the small amounts of these compounds by RP-HPLC. In this way, free kahweol was first proved to be an ingredient of Robusta coffee. Various Arabica and Robusta coffees - both green and roasted - were investigated. Free diterpenes were found in green coffees in amounts below 200 mg/kg dry matter. In comparison to the respective total diterpene content determined by the same HPLC method after saponification of the coffee oil, the proportion of free diterpenes ranged from 0.7 to 3.5 %. During the roasting process, the three uncombined diterpenes behaved similarly: free 16-O-methylcafestol, cafestol as well as kahweol were degraded with increasing roasting temperature.
    Additional Material: 6 Ill.
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  • 149
    ISSN: 0935-6304
    Keywords: Ethanol ; mobile phase ; factorial planning ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 150
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    Journal of High Resolution Chromatography 22 (1999), S. 177-180 
    ISSN: 0935-6304
    Keywords: Fresh water systems ; burbot ; organotin compounds ; speciation analysis ; GC-AED ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 151
    ISSN: 0935-6304
    Keywords: RP-HPLC ; GC-MS ; trioxanes ; thermolysis products ; quantitative analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 152
    ISSN: 0935-6304
    Keywords: Multidimensional Gas Chromatography ; orthogonal separations ; GC×GC ; comprehensive two-dimensional chromatography ; characterization of gasoline ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In comprehensive two-dimensional gas chromatography (GC×GC), two capillary columns are connected in series through an interface known as a “thermal modulator”. This device transforms effluent from the first capillary column into a series of sharp injection-like chemical pulses suitable for high-speed chromatography on the second column. Dramatic increases in the resolving power, sensitivity, and speed of the gas chromatograph result. This paper describes the development of a robust and reliable thermal modulator for GC×GC.
    Additional Material: 5 Ill.
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  • 153
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    Journal of High Resolution Chromatography 22 (1999), S. 74-78 
    ISSN: 0935-6304
    Keywords: Polypeptides ; subcritical fluid chromatography ; supercritical fluid chromatography ; carbon dioxide ; additives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The effect of mobile phase modifier and additive on the chromatographic properties of various small polypeptides was explored under subcritical conditions. A polymeric column was used to separate various enkephalin analogs, bradykinin, and oxytocin using a carbon dioxide-based mobile phase with either an ethanol or a 2-methoxyethanol modifier. The role of the modifier was found to be secondary to that of the mobile phase additive. As progressively stronger acidic mobile phase additives were used, the peak profiles of the various polypeptides improved and retention decreased. Heptadecafluorooctanesulfonic acid was found to be the most useful additive for these types of solutes under near-critical conditions, while the potassium salt of heptadecafluorooctanesulfonic acid failed to elute any of the polypeptides. At low temperatures, pressure gradients with a carbon dioxide/ethanol/heptadecafluorooctanesulfonic acid ternary mobile phase produced reasonably good peak profiles with the polymeric column.
    Additional Material: 7 Ill.
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  • 154
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    Journal of High Resolution Chromatography 22 (1999), S. 89-92 
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin ; heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin ; γ(δ)-thionolactones ; olfactometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The even numbered γ(δ)-thionolactones (C6-C12) were investigated, using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)- and heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as chiral stationary phases in capillary gas chromatography. The odor characteristics of γ(δ)-thionolactone enantiomers were investigated by enantioselective gas chromatography/olfactometry.
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  • 155
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    Journal of High Resolution Chromatography 22 (1999), S. 93-96 
    ISSN: 0935-6304
    Keywords: Capillary GC ; PTV and on-column injectors ; milk fat triglycerides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The PTV (Programmable Temperature Vaporizer) is a split/splitless injector which allows the sample to be introduced at a relatively low temperature, thus affording accurate and reproducible sampling. After injection the PTV is rapidly heated to transfer the vaporized components into the capillary column. This type of injector has proved to be an efficient tool for the evaluation of fatty acids, essential oils, and pesticides in food analysis. In this work the suitability of PTV for the analysis of milk fat purity by the Official EU method was evaluated. This method is based on the gas chromatographic determination of triglycerides only according to their total number of carbon atoms followed by the application of formulae deriving from multiple linear regressions. The analysis is currently carried out with a packed column or a short capillary column and an on-column injection system. Several samples of pure milk fat and mixtures of milk fat with foreign fat were analyzed with the same capillary column and by using both PTV and on-column injection systems. The results show that the gas chromatographic profile obtained by PTV is comparable with that obtained by the on-column injector, while repeatability and reproducibility data meet the requirements indicated in the Official Method. Therefore, this study demonstrates that it is possible to use the PTV instead of the on-column injector to determine the purity of milk fat with this method.
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  • 156
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    Journal of High Resolution Chromatography 22 (1999), S. 217-221 
    ISSN: 0935-6304
    Keywords: HPLC ; UV detection ; linear range ; method validation ; Beer-Lambert law ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Determination of the linear range is one of the main concerns in validation of an HPLC analysis method. It is particularly important since single point calibration will be then used routinely. We proposed an iterative methodology to handle this problem. The idea was, at each step, to test statistically whether the following point belonged to the same regression line. The methodology was then used to evaluate quantitatively the effect on linear range of a shift in detection wavelength or of the detector bandwidth. Although experimental results were globally in accordance with spectroscopic theory, magnitudes observed were rather large. So the linear range could vary by a factor of over 2 with changes in conditions that remained within the range of current practical values. Changes in detection wavelength were limited to about fifteen nm around λmax and the detector used was considered to be representative of modern high-performance UV detectors. The question of how to take consequences in method validation into account was raised. The solution proposed recommended that the validation was undertaken in conditions as close as possible to those where the method would be conducted routinely. This means with the same instrumentation and on the product of interest for analyses.
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  • 157
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    Journal of High Resolution Chromatography 22 (1999), S. 231-234 
    ISSN: 0935-6304
    Keywords: Trace analysis ; air samples ; BTX ; equilibrium-sorptive enrichment ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
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  • 158
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    Journal of High Resolution Chromatography 22 (1999), S. 119-122 
    ISSN: 0935-6304
    Keywords: Fast gas chromatography ; multi-capillary column ; band broadening ; simulation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 159
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    Journal of High Resolution Chromatography 22 (1999), S. 129-130 
    ISSN: 0935-6304
    Keywords: GC-MS ; kava pyrones ; Alpinia zerumbet ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 160
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    Journal of High Resolution Chromatography 22 (1999), S. 135-143 
    ISSN: 0935-6304
    Keywords: Chromatographic separation techniques ; High Performance Liquid Chromatography (HPLC) ; Gel Permeation Chromatography (GPC) ; Supercritical Fluid Chromatography (SFC) ; Capillary HPLC ; Nuclear Magnetic Resonance (NMR) spectroscopy ; hyphenation of chromatography with NMR spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The hyphenation of chromatographic separation techniques with NMR spectroscopy is one of the most powerful and time-saving methods for the separation and structural elucidation of unknown compounds and molecular compositions of mixtures. Most of the routinely used NMR flow-cells have detection volumes between 40-180 μL for conventional separations with analytical columns, and the newest designs employ detection volumes in the order of 200 nL for capillary separations. The low flow rates used in capillary chromatography permit the use of deuterated solvents. Unequivocal structural assignment of unknown chromatographic peaks is possible by two-dimensional stopped-flow capillary HPLC-NMR experiments.
    Additional Material: 14 Ill.
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  • 161
    ISSN: 0935-6304
    Keywords: Conjugated linoleic acid (CLA) ; silver-ion high performance liquid chromatography (Ag+-HPLC) ; cheese ; analysis ; silver-ion chromatography ; tandem-column Ag+-HPLC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A commercial mixture of conjugated linoleic acid (CLA) isomers, reportedly consisting of six components, was recently resolved into 12 peaks attributed to CLA isomers using silver-ion high performance liquid chromatography (Ag+-HPLC). In this study, the coupling of two analytical silver-ion high performance liquid chromatography columns (tandem-column Ag+-HPLC) in series led to the enhanced resolution of CLA isomers. Many CLA isomers were baseline resolved and the pair 18 : 2 8,10 c/t and 18 : 2 7,9 c/t found in cheese products, was resolved for the first time. In this work, a similar commercial CLA mixture was separated into 16 peaks, while CLA isomers from cheese also gave rise to 16 peaks. As expected, the CLA isomers were separated into three geometric groups in the order trans,trans, cis/trans, and cis,cis. Semi-preparative Ag+-HPLC, followed by gas chromatography-mass spectroscopy of the dimethyloxazoline derivatives, was used to confirm the identity of the newly resolved positional CLA isomers. The double bond configuration of CLA isomers was established by gas chromatography-Fourier transform infrared spectroscopy. Two minor t,t CLA isomers found in cheese, presumably 18 : 2 t6t8 and 18 : 2 t13t15, were also separated. The CLA isomeric composition of 16 commercial cheese products was determined.
    Additional Material: 5 Ill.
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  • 162
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    Journal of High Resolution Chromatography 22 (1999), S. 159-163 
    ISSN: 0935-6304
    Keywords: Multi-dimensional chromatography ; LC-GC ; AED ; memory effects ; fossil fuel ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Conventional operation of the GC Atomic Emission Detector (AED) system involves backflushing of the microwave induced plasma (MIP) during the elution of small volumes of solvent from the GC column. When performing multi-dimensional, on-line LC-GC-AED, significantly larger solvent volumes are introduced into the system and must subsequently be removed. Thus solvent venting procedures are required and the backflushing of the plasma must be extended to facilitate solvent but not solute removal. This study demonstrates the significance of memory effects imparted upon the MIP of the AED if solvent venting is incomplete. Comparison of conventional GC-AED and multi-dimensional LC-GC-AED is made with respect to a fossil fuel sample.
    Additional Material: 3 Ill.
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  • 163
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    Journal of High Resolution Chromatography 22 (1999), S. 171-176 
    ISSN: 0935-6304
    Keywords: Micellar electrokinetic chromatography (MEKC) ; solid phase extraction (SPE) ; phenylurea(s) ; herbicide(s) ; monuron ; linuron ; diuron ; isoproturon ; monolinuron ; drinking water ; environmental water ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The present paper describes the application of capillary electrophoresis in the micellar mode to the separation and quantitative determination of five phenylurea herbicides, viz. monuron, linuron, diuron, isoproturon, and monolinuron, in water samples. Using uncoated fused silica capillary and phosphate-borate buffer (pH 7.0) containing SDS, the five pesticides are resolved in less than 15 min and quantitatively determined by an ultraviolet detector at 244 nm. Method optimization and validation parameters are presented. Good linearity and repeatability were observed for all the compounds studied (correlation coefficients 0.999). The feasibility of the method developed was tested by simultaneous determination of these herbicides in environmental and drinking water samples at the minimum residue levels (MRLs) (0.1 μg/L) after solid-phase extraction (SPE) preconcentration procedure.
    Additional Material: 7 Ill.
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  • 164
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    Journal of High Resolution Chromatography 22 (1999), S. 181-182 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; microwave induced emission spectrometry ; speciation ; mercury ; SPME, headspace SPME ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
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  • 165
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; interfacing ; sample treatment ; serum ; solid-phase extraction ; sulfonamides ; urine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
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  • 166
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    Journal of High Resolution Chromatography 22 (1999), S. 191-194 
    ISSN: 0935-6304
    Keywords: TLC/FID ; simple and double migration ; triangle of solvent selectivity ; lipochemical media ; fatty acid esters ; esterification ; transesterification ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 3 Ill.
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  • 167
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    Journal of High Resolution Chromatography 22 (1999), S. 201-204 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; flame ionization detection ; solvent effects ; aqueous injection ; toluene analysis ; dioxane ; sample preparation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A gas chromatographic method is presented for determining from 1 to 100 μg/mL of 1,4-dioxane in toluene with purities ranging from commercial to high-purity grades. This method relies on extracting 1,4-dioxane from toluene into water. The water extract is analyzed for 1,4-dioxane content by gas chromatography/flame ionization detection and a capillary column coated with a bonded polyethylene glycol stationary phase. Splitless injection is used to achieve a 1 μg/mL detection limit. Purging extracts with nitrogen after an initial analysis is suggested as an extract clean-up procedure and as a means to confirm the identification of 1,4-dioxane. However, for absolute identification of dioxane, gas chromatography/mass spectroscopy should be considered.
    Additional Material: 2 Ill.
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  • 168
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    Journal of High Resolution Chromatography 22 (1999), S. 213-216 
    ISSN: 0935-6304
    Keywords: Average velocity ; characteristic parameters ; flow rate ; high pressure drop ; low pressure drop ; outlet velocity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When the column pressure drop is high, the average velocity of a carrier gas is proportional to the square root of the outlet velocity and the flow rate. Characteristic velocity, flow rate and pressure - the boundary conditions between low and high pressure drop regions - are introduced. Previously derived equations for average velocity vs. outlet velocity were modified to include the flow rate and to become more suitable for the separate studies of the low and high pressure drop regions.
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  • 169
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    Journal of High Resolution Chromatography 22 (1999), S. 225-230 
    ISSN: 0935-6304
    Keywords: Green tea ; black tea ; composition ; stability ; capillary electrophoresis ; MEKC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 6 Ill.
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  • 170
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    Journal of High Resolution Chromatography 22 (1999), S. 235-238 
    ISSN: 0935-6304
    Keywords: Cryogenic modulation ; LMCS ; GC×GC ; multidimensional GC ; comprehensive gas chromatography ; petroleum analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 4 Ill.
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  • 171
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    Journal of High Resolution Chromatography 22 (1999), S. 242-244 
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; 6-O-ethyl-2,3-O-pentyl-β-cyclodextrin ; essential oils ; carboxylic acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 3 Ill.
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  • 172
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    Journal of High Resolution Chromatography 22 (1999), S. 247-249 
    ISSN: 0935-6304
    Keywords: High performance liquid chromatography-ultraviolet detection (HPLC-UV) ; Amitraz ; cattle dipping bath ; pesticide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 173
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    Journal of High Resolution Chromatography 22 (1999), S. 261-264 
    ISSN: 0935-6304
    Keywords: On-line coupled LC-GC ; normal phase liquid chromatography ; process samples ; oxygenated compounds ; partially concurrent solvent evaporation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Normal phase liquid chromatography-gas chromatography was used with on-column interfacing and partially concurrent solvent evaporation in the analysis of process samples. Samples were taken from reaction mixtures, where the solvent was toluene. The analytes were oxygenated compounds: methyl isobutyrate, methyl methacrylate, methyl α-formyl isobutyrate, and methyl β-formyl isobutyrate. The analytes were transferred from LC to GC using back-flush with a solvent mixture of pentane and diethyl ether. Linearity, repeatability, and transfer efficiency were determined for the method. The method was applied in the determination of the analytes of two different process samples. The results were in good agreement with results obtained by the gas chromatographic method currently in use for the analysis of the process samples.
    Additional Material: 2 Ill.
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  • 174
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    Journal of High Resolution Chromatography 22 (1999), S. 265-270 
    ISSN: 0935-6304
    Keywords: Critical micelle concentration ; cationic surfactant ; capillary electrophoresis ; tetradecyltrimethylammonium bromide ; dodecyltrimethylammonium bromide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The determination of the critical micelle concentration (CMC) of cationic surfactants by capillary electrophoresis was demonstrated. In this study, tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DoTAB) were selected as cationic surfactants and propazine was chosen as test solute. In the evolution of the effective electrophoretic mobility of propazine as a function of surfactant concentration, a dramatic change in slope at a particular concentration is a good indication of the CMC of this surfactant. The CMC values determined experimentally were further confirmed by a curve-fitting approach. Simulation of the electrophoretic mobility curves as a function of surfactant concentration in both micellar electrokinetic chromatography and capillary zone electrophoresis using cationic surfactants as an electrolyte modifier was performed for propazine, and the intersection of these two mobility curves allowed us to precisely predict the CMC of the surfactant. The CMC values determined for TTAB and DoTAB are 1.6 ± 0.1 and 11.0 ± 0.1 mM, respectively, in the case of an electrolytic solution consisting of 70 mM phosphate buffer at pH 6.0. Moreover, the applicability of the electroosmotic mobility as a parameter for the determination of the CMC was examined.
    Additional Material: 6 Ill.
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  • 175
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    Journal of High Resolution Chromatography 22 (1999), S. 271-275 
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction ; enhanced solvent extraction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A supercritical fluid extraction/enhanced solvent extraction system (SFE/ESE) was used to remove polar and non-polar analytes from various matrices. Extraction of environmental pollutants from soil, additives from low density polyethylene, sulfa drugs from animal tissue, and drug from tablet was performed using both SFE and ESE. Results showed that a single instrumental system can be used to perform both ESE with organic solvents and SFE with carbon dioxide-based fluids. Each method has its own unique advantages and applications. The ability to carry out both solvent extraction and supercritical fluid extraction with one system has obvious economical advantages.
    Additional Material: 5 Ill.
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  • 176
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    Journal of High Resolution Chromatography 22 (1999), S. 279-282 
    ISSN: 0935-6304
    Keywords: Solid phase microextraction (SPME) ; SPME/HPLC interface ; C-8 refocusing unit ; explosives analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 177
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    Journal of High Resolution Chromatography 22 (1999), S. 294-296 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; capillary ; fused silica ; rotenone ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 3 Ill.
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  • 178
    ISSN: 0935-6304
    Keywords: Deproteinization ; polychlorobiphenyls ; polychlorodibenzo-p-dioxins ; restricted-access reversed-phase packings ; sample preparation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
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  • 179
    ISSN: 0935-6304
    Keywords: Mycotoxin ; T2 ; solid phase microextraction ; GC/FID ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
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  • 180
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    Journal of High Resolution Chromatography 22 (1999), S. 438-442 
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; micro-HPLC ; preparation of on-column frits ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Existing methods for preparing frits in packed fused silica capillaries as used for electrochromatography and micro HPLC are not applicable to all silica based packing materials and involve a high thermal stress for both the stationary phase and the fused silica tubing including the polyimide coating. A new procedure for the production of such on-column frits under mild conditions by a sol-gel type reaction of polydimethoxysiloxane (PDMOS) is described in this paper. Reaction conditions were established for optimum mechanical stability and high permeability of the frits. Frits produced in this manner showed no noticeable effect on the overall efficiency.
    Additional Material: 1 Ill.
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  • 181
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    Journal of High Resolution Chromatography 22 (1999), S. 443-448 
    ISSN: 0935-6304
    Keywords: Micellar electrokinetic capillary chromatography ; temperature programming ; applied voltage programming ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Temperature and voltage programming modes were utilized to optimize selectivity and increase the eluting rate of strongly retained compounds in micellar electrokinetic chromatography. Separations obtained by applying temperature, voltage, and a simultaneous combination of temperature and voltage gradient in micellar electrokinetic capillary chromatography were compared with separations performed under isothermal and constant voltage conditions. A complete separation of all the constituents of the test mixture was only achieved in the temperature programming run and in a combination of temperature and voltage programming modes. Simultaneous variations of column temperature and applied voltage during a separation run, yielded a 30% reduction in the total analysis time when compared to a temperature gradient alone. Temperature programming and voltage programming modes may be the gradient methods of choice because of the considerable technical difficulties involved in performing linear solvent gradient elution in micellar electrokinetic chromatography.
    Additional Material: 7 Ill.
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  • 182
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    Journal of High Resolution Chromatography 22 (1999), S. 459-464 
    ISSN: 0935-6304
    Keywords: Fast gas chromatography ; gas chromatography ; resistive heating ; organophosphorus pesticides ; PAHs ; triazines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The features of a resistive-heated capillary column for fast temperature-programmed gas chromatography (GC) have been evaluated. Experiments were carried out using a commercial available EZ Flash GC, an assembly which can be used to upgrade existing gas chromatographs. The capillary column is placed inside a metal tube which can be heated, and cooled, much more rapidly than any conventional GC oven. The EZ Flash assembly can generate temperature ramps up to 1200°/min and can be cooled down from 300 to 50°C in 30 s. Samples were injected via a conventional split/splitless injector and transferred to the GC column. The combination of a short column (5 m×0.25 mm i. d.), a high gas flow rate (up to 10 mL/min), and fast temperature programmes typically decreased analysis times from 30 min to about 2.5 min. Both the split and splitless injection mode could be used. With n-alkanes as test analytes, the standard deviations of the retention times with respect to the peak width were less than 15% (n = 7). First results on RSDs of peak areas of less than 3% for all but one n-alkane indicate that the technique can also be used for quantification. The combined use of a short GC column and fast temperature gradients does cause some loss of separation efficiency, but the approach is ideally suited for fast screening as illustrated for polycyclic aromatic hydrocarbons, organophosphorus pesticides, and triazine herbicides as test compounds. Total analysis times - which included injection, separation, and equilibration to initial conditions - were typically less than 3 min.
    Additional Material: 7 Ill.
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  • 183
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    Journal of High Resolution Chromatography 22 (1999), S. 465-468 
    ISSN: 0935-6304
    Keywords: Amino acid ; stable isotope ; GC-MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In order to study protein digestibility by means of noninvasive tracer techniques (stable isotopes), a representative oral tracer, i.e. a stable isotope labeled protein, is needed. Therefore, egg white containing L-[ring-2H5]phenylalanine and L-[ring-2H4]tyrosine was prepared. The aim of this study was to measure the isotopic enrichment of the labeled amino acids in the egg white. The use of a standard GC-MS, based on ion trap technology was found to be a reliable technique. The enrichment of L-[ring-2H5]phenylalanine and L-[ring-2H4]tyrosine, expressed in Molar Percent (MP) amounted to 23.2 MP and 2.8 MP respectively.
    Additional Material: 4 Ill.
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  • 184
    ISSN: 0935-6304
    Keywords: Adhesives ; GC/MS ; headspace analysis ; poly(vinyl acetate) ; volatile organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 185
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    Journal of High Resolution Chromatography 22 (1999), S. 483-486 
    ISSN: 0935-6304
    Keywords: HPLC ; alumina ; evaporative light-scattering detection ; non-polar lipids ; wax esters ; sterol esters ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This study describes the performance and capacity of alumina as stationary phase in an HPLC-ELSD (evaporative light-scattering detection) method optimized for the separation of the non-polar lipid classes hydrocarbons, wax esters, sterol esters, triacylglycerols, and sterols, including quantitative determination of these lipid classes in natural samples. By using gradient elution and constant equilibration times between injections, highly reproducible separations of triacontane, stearyl oleate, and cholesterol oleate were accomplished with a binary mobile phase system. Phase A contained 0.5% tetrahydrofuran in hexane and phase B 20% isopropanol and 20% tetrahydrofuran in hexane. The same system was also used to determine the non-polar lipid classes in a zooplankton sample, the major lipid class being wax esters, followed by triacylglycerols, sterol esters, sterols, and hydrocarbons. Substantial amounts of an unknown compound, possibly acylated glyceryl ethers, were also found. The equilibration time of alumina was relatively slow compared to a polyvinyl alcohol stationary phase used earlier by the authors and calibration curves for different lipid classes were more uniform and linear with alumina.
    Additional Material: 4 Ill.
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  • 186
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    Journal of High Resolution Chromatography 22 (1999), S. 495-500 
    ISSN: 0935-6304
    Keywords: CZE ; mobility ratio ; migration time prediction ; mathematical model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The electrophoretic mobility ratio (R value) of any two ions is constant and independent of the capillary type and electrophoretic conditions if their electrical charges and hydration radii are constant. The use of strong acid salts and quaternary ammonium salts is therefore proposed for the determination of R values. Such analytes are called markers. The following determinations can be carried out: (i) the determination of the migration time corresponding to the electroosmotic flow (EOF) in any capillary under any electrophoretic condition by measuring the migration times of two markers in the condition studied (useful when the EOF is weak); (ii) the determination of the migration time of an analyte in any capillary by knowing the migration time of the markers in the capillary studied. If the pH is changed and the ionization of the analyte is pH dependent, the resulting migration time for the analyte can be calculated. The constancy of the mobility ratios of seven markers was checked experimentally at eight different pH values (between pH 3 and 10), at three temperatures, and for two buffer concentrations. The predicted and experimental migration times were also compared in two different types of capillaries.
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  • 187
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    Journal of High Resolution Chromatography 22 (1999), S. 509-513 
    ISSN: 0935-6304
    Keywords: Fast GC ; fast temperature programming ; resistive heating techniques ; short columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---One possible way to speed up a gas chromatographic analysis is the application of fast temperature programming by using resistive heating techniques. With this heating technique programming rates up to 20° per second can be reached. A relative standard deviation of retention times better than 0.2% is obtained. Using fast temperature programming the analysis-times of a mineral oil sample, an industrial oligomer sample, and toxic compounds in diesel fuel have been reduced 5 to 20 times, compared to a standard temperature programmed analysis. In most cases resistive heating cannot be applied to reduce the analysis time of a complex sample. The use of fast temperature programming is preferable to the use of short columns and columns operated at above-optimum carrier gas velocities.
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  • 188
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    Journal of High Resolution Chromatography 22 (1999), S. 521-526 
    ISSN: 0935-6304
    Keywords: Multichannel silicone trap ; water analysis ; flow rate ; methanol ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of Multichannel Silicone Rubber Traps for the direct analysis of organic compounds in water was studied. The optimum collection flow rate for a 10 mL sample was found to be ca. 150 μL·min-1. The effect of methanol on the retention power of the trap was evaluated. The addition of a methanol fraction of up to 40% to the water standards did not show any loss in collection efficiency. It was shown that the extraction of organic compounds from water with the multichannel trap is uncomplicated, i. e. methanol is not required to achieve accurate analyses, concentration of the sample onto the trap is by gravity flow, and excess water remaining in the multichannel trap after water extraction is removed by centrifugation. With the use of the multichannel silicone rubber trap a wide boiling point range of compounds were analyzed from aqueous samples at levels of 1-4 μg·L-1.
    Additional Material: 5 Ill.
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  • 189
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 533-540 
    ISSN: 0935-6304
    Keywords: Chlorobiphenyl congeners ; Aroclor 1254 ; DB-XLB phase ; GC-MS-SIM ; PCB 126 ; toxic equivalency ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Complete PCB congener distributions in a panel of Aroclor mixtures were previously obtained by combining data from several HRGC systems. In that study quantitation of minor components may have been unreliable due to single level calibration against high levels of individual congener standards. Two lots of Aroclor 1254 had markedly different congener distributions. In this study, the design and performance of a congener-specific PCB analysis method employing GC-MS-SIM detection of congeners separated on a DB-XLB capillary column are discussed. Quantitation is carried out against a 6-level inclusive standard curve of a mixture of 144 congeners found in Aroclors. A separate procedure to measure trace levels of PCB 126 in Aroclors using the same system, combined with levels initially acquired for other congeners, facilitates estimation of TEQ values (Toxic Equivalencies of the PCB mixtures to 2,3,7,8-TCDD). PCB congener profiles of 15 Aroclor 1254 mixtures are presented. These profiles show that the less common, high TEQ variety of Aroclor 1254 was manufactured by an atypical, two-stage chlorination process that was apparently used during the final 1% of Aroclor 1254 production (ca. 1974-1976).
    Additional Material: 5 Tab.
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  • 190
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 547-552 
    ISSN: 0935-6304
    Keywords: Water analysis ; polar pollutants ; solid-phase extraction ; chemically-modified polymeric resins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This study assesses how the physical characteristics of styrene-divinylbenzene (PS-DVB) resins affect the extent to which they are modified when they are functionalized, and how they affect recoveries in on-line solid-phase extraction (SPE) of some polar phenolic compounds, pesticides, and metabolites from water samples which were analyzed by liquid chromatography and UV detection. For this purpose, three commercial PS-DVB resins with different physical characteristics (Amberchrom GC-161m and two different PLRP-S resins) were chemically modified by placing a hydrophilic group, an o-carboxybenzoyl moiety, on their surface; although the physical characteristics are different, the extent of modification did not vary significantly. The results from the SPE process with each sorbent were related to their physical and chemical properties. The polymers with higher surface area provided better recoveries. Moreover, the recoveries for these analytes were better with the chemically-modified polymers due to the higher polarity of these sorbents. The best recovery values were with the sorbent obtained from the chemical modification of Amberchrom GC-161m, the commercial sorbent with higher surface area. For instance, in the analysis of 50 mL of a sample of 2 μg L-1, the recovery of phenol was 40% with Amberchrom GC-161m and 65% with the chemically-modified Amberchrom GC-161m.
    Additional Material: 3 Ill.
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  • 191
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 421-423 
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; 2,3-di-O-methyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin ; 2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin ; γ-dithiolactones ; olfactometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 192
    ISSN: 0935-6304
    Keywords: HPLC ; nitrotyrosine ; nitrotocopherol ; analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---For three decades, high performance liquid chromatography has proven itself to be a powerful, flexible, and inexpensive tool for basic and clinical research. Recent advances in our understanding of disease have prompted a demand for more sensitive and selective methods of routine bioanalysis, particularly with respect to the determination of oxidative metabolites and biomarkers of oxidative stress. Multidimensional detectors utilizing coulometric arrays offer a solution to these research needs. The challenge to the bioanalyst is now to creatively apply HPLC-ECD technology to promising research and clinical enterprises.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 193
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 449-453 
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; experimental design ; cyclodextrin ; chiral separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Orthogonal design and uniform design were used for the optimization of separation of enantiomers using 2,6-di-O-methyl-β-cyclodextrin (DM-β-CD) as a chiral selector by capillary zone electrophoresis. The concentration of DM-β-CD, buffer pH, running voltage, and capillary temperature were selected as variable parameters, their different effects on peak resolution were studied by the design methods. It was concluded that orthogonal design offers a rapid and efficient means for testing the importance of individual parameters and for determining the optimum operating conditions. However, for a large number of both factors and levels, uniform design is more efficient. The effect of addition of methanol and citric acid buffer on the separation of enantiomers was also examined.
    Additional Material: 5 Ill.
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  • 194
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 454-458 
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; reversed phase ; prototypical substances ; retention parameter model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A set of four prototypical substances (naphthalene, acetanilide, phenol, and benzonitrile) is selected from 26 different analytes used by Seibert and Poole for characterization of the retention behavior of 20 liquid chromatographic systems of a C18 reversed phase with methanol/water and acetonitrile/water as mobile phases. Retention data of 22 different analytes can be calculated from the retention data of the set of prototypical substances with a mean standard deviation of 5.4%. Two phase system maps similar to that suggested by Poole et al. are provided for an octadecylsiloxane-bonded silica sorbent with methanol and acetonitrile as cosolvents with water.
    Additional Material: 2 Ill.
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  • 195
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 475-476 
    ISSN: 0935-6304
    Keywords: Organic peroxides ; gas chromatography ; FID ; cold on-column injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
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  • 196
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 469-474 
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction ; SFE modifiers ; pseudoephedrine ; suphedrine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The effect of modifier and additive composition upon pseudoephedrine recovery from spiked-sand and Suphedrine tablets was examined. Recovery was shown to be dependent on CO2 density as well as on the addition of an ion pairing agent to the matrix. The presence of methanol in the extraction vessel prior to SFE was shown to play a significant role in the ion-pair extraction process. Recovery was also shown to be a function of ion-pairing reagent composition and concentration. The most successful recovery was obtained in the presence of 1-heptanesulfonic acid (HSA), sodium salt in methanol at a 5:1 molar ratio (reagent to drug). The increased extractability in the presence of ion-pairing reagent was attributed to reduced analyte polarity and analyte-matrix displacement. Alternatively, a matrix-spiked mixture of methanol and 1% water by itself was just as effective as a matrix-spiked mixture of methanol and HSA for attaining efficient extraction. Several in-cell (e. g. to the matrix) and in-line (e. g. to the fluid) modifiers were examined for the extraction of pseudoephedrine from Suphedrine tablets. The greatest pseudoephedrine recovery from Suphedrine tablets of 82% (7.0%) was achieved with 10% (l% H2O) methanol-modified CO2 in the presence of 400 μL of methanol (l% H2O). Finally AgCl tests and infrared analyses were performed on two tablet extracts. It was confirmed that even in the absence of any in-cell modifier, a small fraction of pseudoephedrine hydrochloride could be extracted.
    Additional Material: 5 Ill.
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  • 197
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 487-489 
    ISSN: 0935-6304
    Keywords: Carboxymethyl derivatives of amines ; dodecyl-L-hydroxyproline ; chelate ring ; chemiluminescence ; ruthenium complex ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Carboxymethyl derivatives of amines containing a chiral α-carbon were separated into enantiomers by high-performance liquid chromatography using octadecylsilanized silica gel coated with N-n-dodecyl-L-hydroxyproline as the stationary phase and an aqueous solution containing copper(II) as the mobile phase. Detection was by post-column reaction involving derivatization to tertiary amine and chemiluminescence reaction of ruthenium bipyridine complex.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 198
    ISSN: 0935-6304
    Keywords: Large volume injection ; packed capillary LC ; temperature programming ; retinyl esters ; vitamin A ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A non-aqueous isocratic reversed-phase packed capillary high performance liquid chromatography method for the determination of retinyl esters, utilizing temperature programming and on-column focusing large volume injection, has been developed. The stationary phase material was C30, and the mobile phase consisted of acetonitrile-dichloromethane (70 : 30, v/v). A three-step temperature program, starting at 10°C for 10 min, then 1°/min to 30°C, and finally 2.5°/min to 70°C, was found most appropriate. Compared to an isothermal separation at 25°C, this temperature program provided improved peak resolution, enhanced peak shapes of the last eluting compounds, and a reduction of the overall elution time. A mass limit of detection of 27 pg was found with respect to retinyl palmitate, using UV detection with an “U” shaped flow cell at 327 nm. This corresponds to a concentration limit of detection of 2.7 pg/μL, when utilizing an injection volume of 10 μL. The concentration of retinyl palmitate in arctic seal liver samples was estimated to be 62.6 μg/g liver.
    Additional Material: 2 Ill.
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  • 199
    ISSN: 0935-6304
    Keywords: A,C- and A,D-bridged calix[6]arene ; stationary phase ; capillary gas chromatography ; geometric and positional isomer separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A,C-Bridged (ACCX) and A,D-bridged isopropyldimethylsilylcalix[6]arene (ADCX) dissolved in OV-1701 were used as stationary phases in isothermal capillary gas chromatographic separation of some positional isomers. Retention factors and separation factors for the isomers were measured. The isomers investigated are well resolved on the two phases. Retention of all the solutes investigated is longer on ACCX than on ADCX. The longer retention on A,C-bridged calix[6]arene is probably due to extra inductive interactions of the solute molecule with the carbonyl moieties in the phase. Separation factors for closely eluting isomer pairs are similar on the two phases. This seems to indicate that the carbonyl moieties do not play an appreciable role in discriminating the isomer molecules on entering the cavity of the calixarene if the solute is retained by the inclusion process.
    Additional Material: 2 Tab.
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  • 200
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 647-665 
    ISSN: 0935-6304
    Keywords: Two-dimensional GC ; statistical method of overlap ; petroleum ; fuels ; enviromental samples ; organochlorine compounds ; flavors ; aromas ; foods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The writer of this review published in 1978 a three-part article on two-dimensional gas chromatography in the first three issues of this journal [1]. The review was written at a time when capillary column GC was still in its infancy. Commercial columns were (essentially) unavailable and sample introduction into capillary columns was done exclusively in the split mode. Two-dimensional separations were explored in only a few laboratories. The limitations of capillary column technology made this exercise rather difficult. The introduction of fused silica capillary columns in the early eighties drastically changed the landscape in which gas chromatography was practiced. It took the chromatographic community just a few years to convert from packed columns to capillary columns. Instrumentation and accessories specifically designed for capillary column use came onto the market. This writer had great hopes that the revolution in capillary column GC would be mirrored in the development of instrumentation for Two-Dimensional Gas Chromatography. This never materialized. On the contrary, tentative steps taken by a few manufacturers and suppliers of chromatographic equipment fizzled out. It was perhaps the introduction of relatively inexpensive and user friendly GC/MS instrumentation, in combination with nearly indestructible fused silica capillary columns that took away the incentive to develop commercially viable Two-Dimensional Gas Chromatography. Much of the thinking went like this: why insist on good chromatography if mass spectrometry can do the job without the need for complete separation. Some progress in the further development of conventional Two-Dimensional Gas Chromatography has certainly been made over the last 20 years but there has not been a great deal of excitement. Applications have also been relatively sparse and they are limited to just a few areas. Science does not remain static and chromatography is no exception. Progress in gas chromatography is driven by new technology and ideas. Substantial improvements in two-dimensional GC were not forthcoming until Phillips and his research group introduced and implemented an entirely new form of Two-Dimensional Gas Chromatography, called comprehensive two-dimensional GC, or GC×GC. This breakthrough occurred only in 1991 [2]. It does take some time before scientists change attitudes and habits. There is always a time lag between the introduction of new technology and its general acceptance. The public's attitude toward comprehensive Two-Dimensional Gas Chromatography is probably no exception. The number of scientists who are actively pursuing this new branch of gas chromatography is still very small. It is often a single individual who carries the torch. J.B. Phillips' name is synonymous with comprehensive Two-Dimensional Gas Chromatography. He is not only its inventor and proponent but his fertile mind has initiated research in other related areas. Sadly, he passed away shortly before this review was written. This contribution is dedicated to his memory.
    Additional Material: 16 Ill.
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