Biomedical subjects
Publications and source records attributed to T Krahe.
Kallmann's syndrome is characterized by hypogonadotropic hypogonadism and anosmia. Postmortem studies have revealed either hypoplasia or aplasia of the rhinencephalon, respectively, in patients with hyposmia and anosmia. This anatomical defect has now been demonstrated in vivo in four patients with Kallmann's syndrome by magnetic resonance imaging.
The authors present an extremely pronounced involvement of the orbita in malignant uveal melanoma with a ten-year course of disease. The results of imaging diagnostics (ultrasound, computed tomography, magnetic resonance tomography) are discussed.
CT scans were made prior to and following radiotherapy in eleven patients with primary or secondary malignant lymphomas of the CNS. Six patients were additionally submitted to MR tomography with calculated T1 and T2 images. Radiotherapy induced a very rapid regression of the lymphomas. A measurable quantitative influence of the irradiation could thus not be visualized in the MR scans. The survival curve of our patients was calculated, too. The median survival after radiotherapy is 17.4 months.
Surface doses received by patients and operators were measured during 30 interventional radiological procedures (ten percutaneous transhepatic biliary drainages, ten percutaneous nephrostomies, ten percutaneous transluminal angioplasties). In addition, organ doses to the patient were determined using an Alderson-Rando phantom. These served as a basis for calculating the so-called somatic dose indices. It was found that the somatic radiation risk to the patient is relatively small despite prolonged periods of fluoroscopy. However, exposure of the hands and lenses of the operator could easily reach the limits thought acceptable while carrying out these procedures with additional angiography.
By means of serial computer tomography it is possible to show changes in normal and abnormal tissues in the liver, pancreas, and kidney with characteristic contrast kinetics. Diagnosis can be improved by evaluating intra-vascular parenchymal contrast within the first minute after an intravenous bolus injection. A tissue diagnosis is not possible in the majority of lesions in the liver, but can usually be made in lesions of the pancreas and kidneys.
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Our purpose was to analyze and compare the image quality and contrast-to-noise ratio (CNR) of different fast T1- and T2-weighted sequences with conventional spin-echo sequences in renal MRI. Twenty-three patients with focal renal lesions were examined with a T2-weighted ultrafast turbo spin-echo (UTSE) sequence with and without frequency selective fat suppression (SPIR), a combined gradient-and-spin-echo sequence (GraSE), and a conventional spin-echo sequence (SE). In addition, T1-weighted images were obtained pre- and postcontrast, using a fast spin-echo sequence (TSE) with and without SPIR and the conventional SE sequence. Among the T2-weighted images, the highest CNR and the best image quality were obtained with the UTSE sequence, followed by the fat-suppressed UTSE sequence. GraSE and conventional SE sequences showed a significantly lower CNR and image quality (p < 0.05). The T1-weighted sequences did not show significant differences, in either precontrast or postcontrast measurements. T2-weighted UTSE with and without fat suppression combined excellent image quality and high CNR for imaging and detection of renal lesions. The T1-weighted fast sequences provided no alternative to the gradient-echo or to the conventional SE sequences. The results of this systematic study suggest the use of T2-weighted fast techniques for improved diagnostic accuracy of renal MRI.
PURPOSE: To prospectively analyze the effectiveness of computed tomography-guided percutaneous lumbar sympathectomy (CTLS) in patients with peripheral arterial occlusive disease in relation to angiographic findings and vascular risk factors. METHODS: Eighty-three patients were treated by CTLS. After clinical evaluation of the risk profile and diagnostic intraarterial digital subtraction arteriography, 14 patients underwent unilateral, and 69 bilateral one-level treatment. Follow-up studies took place on the day following the intervention, after 3 weeks, and after 3 months. RESULTS: A total of 152 interventions were performed in 83 patients. After 3 months, clinical examination of 54 patients (5 patients had died, 24 were lost to follow-up) revealed improvement in 46% (25/54), no change in 39% (21/54), and worsening (amputation) in 15% (8/54). There was no significant statistical correlation among any of the analyzed factors (diabetes mellitus, arterial hypertension, smoking, hyperlipidemia, obesity, hyperuricemia, number of risk factors, ankle-arm index, and angiography score) and the outcome after CTLS. Three major complications occurred: one diabetic patient developed a retroperitoneal abscess 2 weeks after CTLS, and in two other patients ureteral strictures were detected 3 months and 2 years after CTLS, respectively. CONCLUSION: As no predictive criteria for clinical improvement in an individual patient could be identified, CTLS, as a safe procedure, should be employed on a large scale in patients who are unsuitable for treatment by angioplasty or revascularization.
PURPOSE: The treatment of inoperable tracheobronchial stenoses with Palmaz stents is analyzed in terms of the clinical effect, typical complications, and long-term follow-up. METHODS: Twenty-seven Palmaz stents were placed in 22 patients with the help of a rigid bronchoscope. RESULTS: Stents were implanted in the distal trachea, the main bronchi, and the lower lobe bronchi. Twenty-one of 22 patients reported an immediate subjective improvement in their respiratory situation. The mean survival time was 12 months; in two patients the stents were well tolerated for up to 40 months. A redilation of three stents was successful up to 33 months. In three cases a dislocation of the stent was observed; after bronchoscopic retraction a new stent was successfully implanted in each case. CONCLUSIONoff Treatment of inoperable tracheobronchial stenoses with the Palmaz stent is a safe procedure that provides an immediate improvement of the patient's pulmonary situation. The Palmaz stent shows a minimal complication rate in the long-term follow-up.
OBJECTIVE: Our goal was to optimize the efficiency of contrast material (CM) application in routine examinations of the neck by the use of spiral CT and slow power injection. MATERIALS AND METHODS: Dynamic studies were performed in 14 patients to establish a set protocol for spiral CT examinations of the neck. Prospectively, 100 patients were examined either by use of the spiral technique with 100 ml CM (30 g iodine) injected in two phases or in conventional CT with 150 ml CM (45 g iodine). Vascular and parenchymal enhancement was evaluated at three distinct levels of the neck. RESULTS: Despite the reduced CM volume in spiral CT, vascular enhancement was significantly higher at all three levels. Parenchymal enhancement was comparable in both groups. CM exploitation in vascular opacification (ratio of mean enhancement to applied CM volume) was 0.87 in spiral CT compared with 0.43 in conventional CT. CONCLUSION: Spiral CT significantly increases the efficiency of CM application and is well suited for routine examinations of the neck.
PURPOSE: Our goal was to investigate the value of T2-weighted fast SE (FSE) sequences, FSE sequences with shortened echo spacing (UFSE), combined gradient and spin echo sequences (GRASE), and segmented T1-weighted echo planar imaging (EPI) in comparison with conventional SE sequences in the detection of focal liver lesions. METHOD: Thirty-five patients with malignant focal liver lesions underwent MRI at 1.0 T. RESULTS: All fast T2-weighted imaging techniques (FSE, UFSE, GRASE) showed fewer artifacts and overall better image quality than the conventional SE sequence. Quantitative analysis demonstrated that UFSE imaging had the highest tumor/liver contrast/noise ratio (C/N) (13.9 +/- 5.5) followed by FSE (12.7 +/- 4.5), T2 SE (10.9 +/- 4.2), and GRASE (10.0 +/- 4.8) sequences. The differences in C/N between the UFSE and T2 SE sequences was statistically significant (p < 0.05). C/N was significantly higher (p < 0.01) for the T1 SE (-7.4 +/- 3.8) than for the EPI sequence (-0.5 +/- 5.6). CONCLUSION: FSE sequences with shortened echo spacing are valuable for liver imaging at 1.0 T. In comparison with the T2 SE sequence, they yielded better image quality and comparable tumor/liver C/N.