Biomedical subjects
Publications and source records attributed to W Steinbrich.
MRA (magnetic resonance angiography) is besides duplex sonography at present the only noninvasive method for vascular visualisation. The technical fundamentals and our initial experiences with this new technique of angiography in the visualisation of the basilar artery are presented in the following article.
42 MRI of 36 patients with cerebral aneurysms were analysed retrospectively and compared with selective angiography. 92% of aneurysms proven by angiography were also detected by MRI. The smallest and surgically confirmed aneurysms had a diameter of 2-3 mm on MRI. 3 aneurysms were only demonstrated by selective angiography (8%). This concerned 5 mm sized aneurysms located at the anterior communicating artery (2) and middle cerebral artery (1). On the other hand 2 thrombosed aneurysms were only delineated by MRI (6%). Because partial thrombosis could not be demonstrated by angiography extensions of aneurysms were underestimated in 44% (n = 16) angiographically. A 2.5 cm sized lobulated aneurysm of the internal carotid artery was initially evaluated by MRI as being thrombosed subtotally, due to flow-phenomena. Angiography though showed a wide perfused lumen without visible thrombosis. A progressive thrombosis of a mycotic aneurysm of the internal carotid artery was shown by MRI during septic thrombosis of the cavernous sinus. In this case the number of angiographic controls could be reduced by use of MRI. Nevertheless, MRI was not able to substitute selective angiography, especially to exclude under 6 mm sized cerebral aneurysms. MRI could not demonstrate clearly the vessels in the neighbourhood of saccular aneurysms preoperatively.
The relation between white-matter lesions (WMLs), demonstrated with magnetic resonance imaging, and regional cerebral blood flow (CBF), measured with dynamic positron emission tomography and [18F] fluoromethane, was investigated in 20 patients with atherosclerotic disease of the internal carotid artery. There was no correlation between the extent of small patchy WMLs and hemispheric CBF, but hemispheric CBF was significantly reduced in 5 patients with multiple large or confluent lesions. Distinct focal cortical CBF reductions were observed when large WMLs (greater than 5 mm) were located directly beneath the cortex, whereas large WMLs in deeper white matter were associated with a more diffuse decrease of cortical perfusion. There was no evidence of preferential CBF reduction in vascular border zones with increasing severity of WMLs or stenosis of the internal carotid artery. The side of previous transient ischemic symptoms correlated significantly with hemispheric CBF asymmetries, but not with asymmetries of WMLs and internal carotid artery stenosis. It can be concluded from these results that the presence of small patchy WMLs shown by magnetic resonance imaging cannot be used as evidence of impaired cerebral perfusion, while large lesions indicate clinically relevant cerebrovascular disease affecting cortical blood flow.
120 double-contrast barium enemas were obtained by both digital luminescent radiography (DLR) and conventional screen-film systems, the digital exposure dose being 50% of the conventional one. In DLR two differently post processed images were obtained from one x-ray exposure: a display with low spatial frequency enhancement was processed to look like a conventional radiograph and was complemented by a display with high spatial frequency enhancement. Analysing the results statistically DLR proved to be diagnostically equivalent to conventional radiography despite the reduction in exposure dose and a slightly diminished image quality. High spatial frequency enhancement did not provide further diagnostic information and is therefore superfluous in barium enemas.
A new method for image-guided localized phosphorus NMR spectroscopy of superficial tissues has been investigated using a 1.5 Tesla whole-body-MR-System. We used a surface coil combined with adiabatic excitation pulses and a modified ISIS sequence. This approach is related to imaging sequences and thus permits a flexible and accurate determination of the volume of interest from "conventional" proton images. The scope and advantages of the method are demonstrated by phantom studies. Clinical applications to the liver, renal transplants, and the mediastinum are described.
The image quality of digital luminescent radiography (DLR) is sufficient for routine biplane chest radiography and for follow-up studies of heart size, pulmonary congestion, coin lesions, infiltrations, atelectasis, pleural effusions, and mediastinal and hilar lymph node enlargement. Chest radiography in the intensive care unit may in most cases be performed using the DLR technique. There is no need for repeat shots because of incorrect exposure, and the position of catheters, tubes, pacemakers, drains and artificial heart valves, the mediastinum, and the retrocardiac areas of the left lung are more confidently assessed on the edge-enhanced DLR films than on conventional films. Nevertheless, DLR is somewhat inferior to conventional film-screen radiography of the chest as it can demonstrate or rule out subtle pulmonary interstitial disease less confidently. There is no reduction of radiation exposure of the chest in DLR compared with modern film-screen systems. As a consequence, DLR is presently not in a position to replace traditional film-screen radiography of the chest completely.
One hundred and forty-six intracranial hematomas in 129 patients were examined by MRI (136 examinations) and CT (147 examinations). Even using a high field MR system (1.5 T) and gradient-echo sequences, CT was the more sensitive method during the acute phase (46% compared with 93%). During the sub-acute phase, MR was superior to CT (97% compared with 58%), as it was in the chronic phase (93% compared with 17%). Petechial bleedings and discreet foci of contusion could only be demonstrated by MRI. Moreover, MRI showed evidence of residues from hemorrhage (signal reduction due to hemosiderin deposition) long after CT has become normal. Analyses of MRI images allows one to date the bleed and to distinguish between a) the formation of clot in a haemorrhagic cavity, b) bleeding into the tissues and c) a liquefying hematoma. Bearing in mind this classification, the localisation of the hematoma and the clinical findings mostly allow it is possible to determine the cause of the bleeding. Another advantage is the certain detection of vessels supplying arterio-venous malformations and cavernous hemangiomas.
The results of 27 percutaneous transluminal angioplasties (PTA) of the subclavian artery are reported in 25 patients. 13 patients complained of claudicatio brachii, 7 also demonstrated symptoms of vertebral-basilar insufficiency. In 5 cases this was the sole indication for PTA. 23 (85.2%) of 27 interventions were limited to the proximal section of the subclavian artery. In 22 (81%) the obstructions were localized on the left side. A technical success could be achieved in 24 (88.9%) of 27 interventions. The angiographic appearance of the homolateral vertebral arteries before and after PTA differed significantly. No PTA led to an occlusion of the previously patent vertebral artery. A retrograde flow was no longer seen after PTA. The haemodynamic significance was also demonstrated by the differences in brachial-occlusion pressures (mean 51 mmHg before, 7 mmHg after PTA). Complete or partial relief was achieved after technically successful PTA in 90% of patients with brachial symptoms and in 50% with vertebral-basilar insufficiency. Complications occurred in one (3.7%) of 27 procedures. Published data on PTA of the subclavian artery are discussed.
The results of percutaneous transluminal angioplasty (PTA) (n = 13) of the lower abdominal aorta are reported in 12 patients. The mean patient age was relatively low (46 years). In 7 cases there were isolated aortic obstructions (6 stenoses, 1 occlusion). In the remaining 6 aortic stenoses, there were also major atherosclerotic lesions distally. The mean diameter of the aortic section in which PTA was performed, measured 8.2 mm. The total diameter of the PTA balloon(s) averaged 19.1 mm. The arterial gradient dropped significantly from 41.4 mm Hg (mean) to 2 mm Hg after PTA. The arm-ankle index increased significantly from 0.64 to 0.97. The follow-up included 9 patients; 1 showed restenosis 38 month after PTA. There were no clinically relevant complications. The data published on abdominal PTA in atherosclerotic lesions are summarized.
For the first time a controlled double-blind study was performed to compare side effects and complications of i.v. DSA with central venous application of iopamidol and iopromide. 200 consecutive patients 15-85 years of age were studied. The randomisation brought up two homogeneously structured groups of 100 patients each. Using a given protocol, 66% of the patients were classified as high-risk patients. Side-effects and complications were registered by an extensive, standardised protocol. In 71 (35.5%) of 200 patients contrast-media related side effects and complications were noted. 37 reactions in 24 patients (9 iopamidol, 15 iopromide group) were classified as clinically relevant. In four patients (4%) of each group a drug therapy was initiated. Contrast-media related reactions occurred with delay in 5.5% of initially symptom-free patients. In no case intensive care or hospital admission became necessary. There were no significant differences between the two non-ionic contrast media in the incidence of side effects and complications. Both substances were well tolerated in i.v. DSA. In the total population patients with diseases known as auto-immune diseases and prior drug reactions demonstrated clinically relevant reactions significantly more often.
CT and MR imaging are of minor importance for the preoperative diagnosis of rectosigmoid carcinoma. A synchronous colon tumor can be excluded with a barium enema, while an accurate diagnosis of liver metastases is possible using real-time ultrasonography. However, post-operative management requires the use of tomographic methods: MR imaging has proved to be more accurate than CT for differentiation between local recurrence and post-operative scars. Therefore MRI should be the method of choice after surgery for rectosigmoid carcinoma in all patients without postoperative baseline examinations.
Based on 46 enosteal cartilaginous tumours of the long tubular bones (43 patients) the established radiological and Mirra's histopathological criteria of tumour status are assessed independently and compared retrospectively. In lesions of Lodwick's type I B (37 cases) with mineralisation of the cartilaginous matrix and facultatively cortical arrosion, lack of periosteal reaction, destruction of the corticalis and parosseal tumour extension none of Mirra's histopathological criteria of malignancy was found. It may be expected that biopsy and histopathological examination will not give valuable additional information in this radiological constellation, because there are no known definite histopathological criteria of benignity. Suspicious radiological findings should prompt complete resection of the lesion. Biopsy and histopathological classification are always crucial when matrix mineralisation is lacking and therefore the diagnosis of a cartilaginous tumour cannot be established radiologically.
Abdominal x-ray examinations represent a variety of indications with different demands on exposure latitude, contrast resolution and spatial resolution of screen-film system combinations. The diagnostic value of digital luminescent radiography (DLR) was thus compared to conventional x-ray examinations carried out with screen-film systems, speed class 200, by analysing matched digital and conventional exposures in 46 abdominal and 25 pelvic x-ray examinations in supine and left lateral view, 156 contrast examinations of the gastrointestinal tract, 140 excretory urographies, 8 cholecystographies, 22 lymphographies and in 6 phlebographies. The digital exposure dose was 50% of the conventional one. In DLR two differently post-processed images were obtained from one x-ray exposure: a display with low spatial frequency enhancement was processed to look like a conventional radiograph and was complemented by a display with high spatial frequency enhancement. Analysing the results statistically, DLR proved to be diagnostically equivalent to conventional radiography despite the reduction in exposure dose and the lower digital spatial resolution. Since high spatial frequency enhancement did not provide further diagnostic information and eventually resulted in border line artifacts, high spatial frequency enhancement is superfluous in abdominal x-ray examinations.
The use of fast gradient echo sequences enable reduction of the acquisition times in MR imaging, allowing examinations during suspended respiration. Furthermore, repeated single slices in the same position after administration of a paramagnetic contrast agent provide dynamic evaluation of tissue perfusion. These new diagnostic modalities were applied for imaging normal adrenal glands in 128 cases and for differentiation of 83 adrenal tumors in 74 patients. CT remains the imaging method of choice for the detection of adrenal masses, due to the higher spatial resolution. Fast gradient echo MRI offers the possibility of differentiation between benign and malignant adrenal lesions. The 70% accuracy reached with precontrast scans can be augmented to 90% using dynamic contrast-enhanced studies.
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In 25 patients sialographies were obtained by both conventional film-screen system combinations and computed radiography (CR), the digital exposure dose being 50% of the conventional one. In CR two differently post processed images were obtained from one x-ray exposure: one "conventionally" processed image resembling a conventional film-screen system combination and a complementary "enhanced" image showing a higher edge enhancement at the same spatial resolution. CR proved to be equivalent to conventional radiography despite the reduction in exposure dose. Using high edge enhancement the peripheral glandular ducts as well as the central ducts superimposed by bony structures were optically accentuated. However, diagnostical information exceeding the conventional film-screen system combination was not obtained by CR. Artefacts by post processing procedures relevant for diagnosis were not observed.
Amongst 1.345 MR examinations of the skull 49 patients were suspected of a cerebral infection. With a knowledge of the clinical situation, the abnormal findings were classified according to their localization, number, extent and distribution. The final diagnoses included meningitis, meningoencephalitis, and abscesses of varying etiology. CT was carried out in 29 patients; it was found that MRI was more sensitive and able to show the lesion at an earlier stage (sensitivity 90% compared with 66%). Observations of proton density and relaxation time combined with morphological criteria and clinical history reduced differential diagnoses. On the other hand, the changes due to intracranial infections lead to an inflammatory reaction that may be similar to the findings in degenerative or even tumorous cerebral lesions. This explains why twelve patients with abnormal MRI findings were erroneously diagnosed as having cerebral infections.
Fast gradient-echo magnetic resonance (MR) imaging of 38 adrenal masses with proved diagnosis was performed during suspended respiration with various repetition times (TRs), echo times (TEs), and flip angles. Dynamic perfusion studies after gadolinium diethylenetriamine-pentaacetic acid (DTPA) administration were performed by repeated imaging at short time intervals. With more T2 weighting (TR = 60 msec, TE = 30 msec, and flip angle = 15 degrees), malignant tumors and pheochromocytomas had a significantly higher relative signal intensity than adenomas; overlap of signal intensity led to equivocal findings in nine cases. After administration of Gd-DTPA, adenomas showed only mild enhancement and quick washout; malignant tumors and pheochromocytomas showed strong enhancement and slower washout. Five of the nine cases that were equivocal in precontrast images could thus be correctly classified. In addition to this improved classification of adrenal masses, fast, dynamic contrast material-enhanced MR imaging resulted in a reduction in total examination time.