Der Radiologe
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The vertebral bodies consist of two main structures, trabecular and cortical bone. The histological changes within the spine, especially in cortical bone, leading to osteoporotic fractures remain, however, poorly understood. Therefore, the complete front column of the spine was removed in 26 autopsy cases without skeletal diseases and in 11 cases with proven osteoporosis. ⋯ This decrease in cortical thickness was more marked in the dorsal shell (P < 0.05) than in the ventral shell (ventral from C3 to T6 (P < 0.05) below T6 (P = n.s.). We therefore conclude that in osteoporosis, biomechanical competence is affected by both trabecular bone loss and decrease of cortical thickness. This suggests that, in addition to trabecular bone measurements, the cortical thickness is of special interest for diagnostic radiological examinations (CT) to yield clues about the risk of vertebral fractures.
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Contrast enhanced (CE) magnetic resonance angiography (MRA) provides high resolution angiograms within 20-40 sec. The technique is based on the acquisition of heavily T1-weighted three-dimensional (3D) gradient-echo data sets (FISP) with ultrashort echo-(< 2ms) and repetition times (< 5 ms) during arterial phase of an intravenously injected bolus of a T1-shortening agent such as Gd-DTPA. For MR-angiography of abdominal vessels CE-MRA is better suited than "time-of flight" (TOF) and phase-contrast (PC) MRA because motional artifacts can be obviated with breath-held acquisitions. ⋯ Whilst CE-MRA provides reliable diagnostic accuracy in the aorta and the proximal sections of its branches, small peripheral arteries cannot be assessed accurately. The portal vein and its tributaries can often be depicted better with CE-MRA than with conventional angiography but, like conventional angiography, CE-MRA is hampered by slow and reversed flow, conditions under which TOF or "true FISP" MRA may perform bst. We have also investigated FLASH-echo-planar imaging (EPI) hybrid techniques, a further technical development which due to shorter acquisition times of 12-15 sec. allows semi-dynamic imaging of the arterial and venous phase and provide better vessel contrast due to the use of fat-suppression.
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Time-of-flight MR-angiography of large volumes is limited by the occurrence of saturation effects, which lead to low signal in both veins and arteries. Alternatively to a number of other MRA-techniques, intravenous application of paramagnetic contrast media in combination with 3D-pulse sequences with or without flow refocussing allows the depiction of slow vessels in large volumes without technical extra expenses. The main intracranial indication is anatomical 3D-imaging of normal and dysplastic cerebral veins with high spatial resolution, and the additional depiction of the venous drainage in AVMs, when unenhanced MRA shows only the arteriel supply and the nidus. ⋯ Signal loss due to spin dephasing in vessels with complex flow is not influences by contrast media. Results of contrast-enhanced MRA are determined by the timing of injection. Since arteries and veins are both imaged with high signal intensity, improvements of postprocessing procedures for secondary vessel segmentation are necessary.
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From 1989 to 1995 high-resolution ultrasonography (US) was performed in 3,546 children (age: 1-17 years) with clinically suspected appendicitis. A total of 518 patients underwent laparotomy; 420 had histologically proven acute or perforated appendicitis (prevalence 11.8%). In these children, the sensitivity, specificity and overall accuracy of US examination were 90%, 97% and 96% respectively. The use of US in clinically doubtful acute abdomen may allow earlier diagnosis of acute appendicitis; in 1995 the rate of unnecessary appendectomy was reduced to 13%.