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  • 1
    ISSN: 1432-1084
    Keywords: Key words: Brain ; MR ; Fast sequences ; FSE ; GRASE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The aim of our study was to compare gradient-spin-echo (GRASE) to fast-spin-echo (FSE) sequences for fast T2-weighted MR imaging of the brain. Thirty-one patients with high-signal-intensity lesions on T2-weighted images were examined on a 1.5-T MR system. The FSE and GRASE sequences with identical sequence parameters were obtained and compared side by side. Image assessment criteria included lesion conspicuity, contrast between different types of normal tissue, and image artifacts. In addition, signal-to-noise, contrast-to-noise, and contrast ratios and were determined. The FSE technique demonstrated more lesions than GRASE and with generally better conspicuity. Smaller lesions in particular were better demonstrated on FSE because of lower image noise and slightly weaker image artifacts. Gray–white differentiation was better on FSE. Ferritin and hemosiderin depositions appeared darker on GRASE, which resulted in better contrast. Fatty tissue was less bright on GRASE. With current standard hardware equipment, the FSE technique seems preferable to GRASE for fast T2-weighted routine MR imaging of the brain. For the assessment of hemosiderin or ferritin depositions, GRASE might be considered.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0827
    Keywords: Key words: Dual-energy X-ray Absorptiometry — Degenerative factors — Postmenopausal women — Bone mineral density — Osteoporosis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The purpose of this study is to evaluate degenerative factors in a postmenopausal patient group and differentiate the influence on bone mineral density (BMD) measurements by dual-energy X-ray absorptiometry (DXA). The patients and methods included an investigation of 144 postmenopausal women (mean 63.3 years) with PA-DXA of the spine. Degenerative factors (osteophytes, osteochondrosis, scoliosis, and vascular calcification) were evaluated from plain lumbar radiographs, their estimated probability was analyzed as a function of age, and their influence on BMD measured by PA-DXA was determined. The results of the study revealed osteophytes in 45.8%, vascular calcifications in 24.3%, scoliosis in 22.2%, osteochondrosis in 21.5%. The estimated probability for degenerative factors increased from 35 to 80% in the 55- to 70- year age group. Osteophytes and osteochondrosis were associated with up to a 14% increase in BMD values (P 〈 0.001). Vascular calcifications showed a positive trend, whereas scoliosis did not show a discernible influence. We concluded that degenerative factors, except for scoliosis, showed an influence on BMD as measured by DXA. Their prevalence increased rapidly between 55 and 70 years of age. Interpretation of PA-DXA spine data for subjects of or above this age range should be complemented by plain film radiographs.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 38 (1996), S. 360-366 
    ISSN: 1432-1920
    Keywords: Infratentorial brain maturation ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Our purpose was to establish parameters for normal infratentorial brain maturation at 0.5 and 1.5T and to evaluate the field strength criteria for the assessment of infratentorial brain maturation with MRI. We examined 27 children with normal psychomotor development (3 days to 24 months) with a 1.5T system and 22 (4 days to 29 months) with a 0.5T system; standard T2-weighted spin-echo sequences (TR/TE 2500/90 ms at 1.5T and TR/TE 2200/90 ms at 0.5T) were obtained. The signal intensity of infratentorial anatomical structures compared to their surroundings was classified as high, isointense or low by three neuroradiologists. For anatomical structures with age-related contrast changes, the time of these changes was determined statistically for the 0.5T and 1.5T system independently. The delineation of the structures without age-related contrast changes at the two field strengths was compared using a χ2 test. Age-related contrast changed were found in the same anatomical structures (“marker sites”) at 0.5 and 1.5T. Generally, these changes were apparent in larger structures (pons, middle cerebellar peduncles, medulla, cerebellar folia, red nuclei, cerebral peduncles), with only slight field-strength-dependent differences in the time of the contrast changes. Contrast changes from high to isointense signal were observed slightly earlier at 0.5T and changes from isointense to low signal slightly later at 0.5T. The delineation of the smaller anatomical structures was significantly better at 1.5T but these structures did not show age-related contrast changes. The differences in the assessment of infratentorial brain maturation between 0.5 and 1.5T can be attributed to a lower signal-to-noise ratio at lower magnetic field strengths. These differences do not complicate temporal classification of the stage of infratentorial brain maturation using the same “marker sites” and the same temporal criteria at 0.5 or 1.5T. However, higher field strengths are preferable for the assessment of smaller structures with physiological signal differences; this may imply better detection of small lesions at higher field strengths.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 38 (1996), S. S178 
    ISSN: 1432-1920
    Keywords: Key words GM2 gangliosidosis ; Sandhoff's disease ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An 18-month-old girl was examined by MRI for progressive psychomotor retardation. T2-weighted images demonstrated abnormal high signal in the putamina and low signal in the thalamus (due probably to calcification). Although the cerebral cortex was markedly atrophic, there were signs of brain enlargement because of swelling of the extensively diseased white matter. The diagnosis of Sandhoff's disease was established by low serum levels of hexosaminidase A and B.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 38 (1996), S. S178 
    ISSN: 1432-1920
    Keywords: GM2 gangliosidosis ; Sandhoff's disease ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An 18-month-old girl was examined by MRI for progressive psychomotor retardation. T2-weighted images demonstrated abnormal high signal in the putamina and low signal in the thalamus (due probably to calcification). Although the cerebral cortex was markedly atrophic, there were signs of brain enlargement because of swelling of the extensively diseased white matter. The diagnosis of Sandhoff's disease was established by low serum levels of hexosaminidase A and B.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 38 (1996), S. 360-366 
    ISSN: 1432-1920
    Keywords: Key words Infratentorial brain maturation ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Our purpose was to establish parameters for normal infratentorial brain maturation at 0.5 and 1.5 T and to evaluate the field strength criteria for the assessment of infratentorial brain maturation with MRI. We examined 27 children with normal psychomotor development (3 days to 24 months) with a 1.5 T system and 22 (4 days to 29 months) with a 0.5 T system; standard T2-weighted spin-echo sequences (TR/TE 2 500/90 ms at 1.5 T and TR/TE 2 200/90 ms at 0.5 T) were obtained. The signal intensity of infratentorial anatomical structures compared to their surroundings was classified as high, isointense or low by three neuroradiologists. For anatomical structures with age-related contrast changes, the time of these changes was determined statistically for the 0.5 T and 1.5 T system independently. The delineation of the structures without age-related contrast changes at the two field strengths was compared using a χ 2 test. Age-related contrast changed were found in the same anatomical structures (“marker sites”) at 0.5 and 1.5 T. Generally, these changes were apparent in larger structures (pons, middle cerebellar peduncles, medulla, cerebellar folia, red nuclei, cerebral peduncles), with only slight field-strength-dependent differences in the time of the contrast changes. Contrast changes from high to isointense signal were observed slightly earlier at 0.5 T and changes from isointense to low signal slightly later at 0.5 T. The delineation of the smaller anatomical structures was significantly better at 1.5 T but these structures did not show age-related contrast changes. The differences in the assessment of infratentorial brian maturation between 0.5 and 1.5 T can be attributed to a lower signal-to-noise ratio at lower magnetic field strengths. These differences do not complicate temporal classification of the stage of infratentorial brain maturation using the same “marker sites” and the same temporal criteria at 0.5 or 1.5 T. However, higher field strengths are preferable for the assessment of smaller structures with physiological signal differences; this may imply better detection of small lesions at higher field strengths.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Der Radiologe 39 (1999), S. 93-99 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter CT Angiographie ; Kontrastmittelbolus ; Optimierung ; Computer ; Diskrete Fourier-Transformation ; Key words CT angiography ; Contrast bolus ; Optimization ; Computer ; Discrete Fourier transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary This paper compares different contrast injection techniques for optimizing vessel contrast in CT angiography (CTA). The optimal vessel contrast shall be defined as constant strong enhancement confined to the scanning interval. This ”plateau enhancement” guarantees high-quality CTA images and should therefore be approximated during every CTA examination by an appropriate contrast injection protocol. With well-established injection techniques such as the standard bolus technique (constant uniphasic contrast bolus for all patients) or adjustment of the scan delay, considerable individual differences in the arterial enhancement can be observed, and a nondiagnostic examination or an inefficient use of contrast agent might be the result in a particular patient. Therefore, two sophisticated mathematical models have recently been developed for analyzing the individual enhancement characteristics. These models can be exploited to predict the arterial enhancement for any given intravenous contrast bolus in any patient and to optimize the contrast bolus in order to approach the ideal ”plateau enhancement”. These techniques have to prove their effectiveness in larger clinical series.
    Notes: Zusammenfassung Diese Arbeit stellt verschiedene Techniken der Kontrastmittelinjektion zur Optimierung der Gefäßdarstellung bei der CT-Angiographie (CTA) gegenüber. Einleitend wird als angestrebtes Ziel der Kontrastmittelgabe eine gleichbleibend hohe und auf die Zeit der CT-Messung beschränkte Gefäßkontrastierung definiert. Diese „Plateauanfärbung” garantiert hochqualitative CTA-Bilder bei minimalem Kontrastmittelverbrauch und soll deshalb bei jeder CTA-Untersuchung durch eine geeignete Art der Kontrastmittelgabe angestrebt werden. Bei etablierten Injektionstechniken wie der Standardbolustechnik (gleichbleibendes uniphasisches Injektionsprotokoll für alle Patienten) oder der Anpassung der CT-Verzögerung allerdings werden beträchtliche individuelle Unterschiede in der Gefäßanfärbung beobachtet, und das Resultat kann im Einzelfall eine unzureichende Untersuchungsqualität oder eine ineffiziente Kontrastmittelausnutzung sein. Es wurden deshalb kürzlich 2 mathematische Modelle zur Analyse der individuellen Anfärbecharakteristik entwickelt, welche die arterielle Anfärbung für einen gegebenen Kontrastmittelbolus beim jeweiligen Patienten vorhersagen können und so eine individuelle Bolusoptimierung im Hinblick auf die gewünschte Plateauanfärbung erlauben. Diese Techniken müssen allerdings noch ihre Effektivität in größeren klinischen Studien beweisen.
    Type of Medium: Electronic Resource
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