Regional cerebral blood flow in patients with leuko-araiosis and atherosclerotic carotid artery disease.

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.

Lower extremity angiography: improved image quality and outflow vessel detection with bilaterally antegrade selective digital subtraction angiography. A blinded prospective intraindividual comparison with aortic flush digital subtraction angiography.

RATIONALE AND OBJECTIVES: To introduce routine bilaterally antegrade selective stationary digital subtraction angiography (DSA), and prospectively compare it with unselective stationary DSA in the detection of calf arteries and assess additional time and complication rate. METHODS: Twenty-five patients received one unselective and two separate antegrade selective studies of each calf. Images were evaluated for image quality, number of depicted run-off vessels, and potential crural bypass recipient arteries. RESULTS: Bilaterally antegrade selective DSA was significantly superior in image quality and motion artifacts (P < 0.01). The number of adequately depicted run-off arteries per calf increased from 79% (2.37 of 3) to 96% (2.89 of 3) for legs with advanced peripheral vascular disease (PVD). Seventy-nine instead of 62 potential bypass recipients were identified (P = 0.002). Mean procedure time needed for selective catheterizations was 7 minutes. No adverse events were seen. CONCLUSIONS: Bilaterally antegrade selective DSA clearly is superior to aortic run-off DSA depicting tibial arteries. It requires comparatively small additional effort. Outflow vessel detection essentially is independent of advanced PVD.

Contrast-enhanced magnetic resonance angiography of peripheral vessels. Different contrast agent applications and sequence strategies: a review.

In this article the relation between contrast medium (CM) application and sequence parameters will be discussed with respect to clinical use of the contrast-enhanced magnetic resonance angiography (CE-MRA) in the peripheral vessel region. The adjustment of the sequence parameters, the CM application timing and the bolus geometry is necessary for an effective use of CE-MRA. Investigation protocols for several vascular regions differ mainly corresponding to varying fields of view and slab thickness. Restrictions of increasing the measurement time are expected in peripherally localized vessels if fast arteriovenous transit time occurs. The vessel contrast depends from (1) optimal CM bolus timing and (2) bolus geometry defined by the parameters of the intravenous bolus injection (flow rate, dose and NaCl flush volume). Our study results have shown that the bolus remains compact but also shorter if a higher flow rate is being applied at equal dose. The enlargement of the NaCl flush volume has evidently caused an increased intraarterial CM concentration and a slightly bolus lengthening. The exact timing regimen requires an automated mechanical CM injection pump. In most countries, a total dose of 0.3 mmol/kg Gd is allowed for application during one investigation. Therefore, obtaining an angiogram of the entire iliac and leg region this total dose must be separated. 0.1 mmol/kg for each of the three measurements can be recommended. Otherwise, using this lower CM dose results in less spatial resolution. At least a dosage of 0.2 mmol/kg Gd is necessary to achieve a higher spatial resolution. The calculation of CM dosage should be also related to the dedicated vessel region of interest than to the body weight only.

Serial proton MR spectroscopy of contrast-enhancing multiple sclerosis plaques: absolute metabolic values over 2 years during a clinical pharmacological study.

BACKGROUND AND PURPOSE: The time courses of total creatine (Cr), N-acetylaspartate (NAA), choline (Cho), and myo-inositol have not previously been investigated in the follow-up of contrast-enhancing multiple sclerosis (MS) plaques. Therefore, over a period of 2 years, we compared the absolute concentrations of these metabolites between patients treated with a placebo or 15 +/- deoxyspergualin (DSG) and between clinical groups with relapsing-remitting or secondary-progressive MS. METHODS: Sixteen patients, recruited from a pharmacological study of DSG, and 11 healthy control subjects were investigated by a stimulated-echo acquisition mode sequence (TR/TE = 3000/20). The selected volume initially contained a contrast-enhancing plaque, which was followed up for a period of 2 years. RESULTS: In contrast-enhancing plaques, Cho was significantly elevated and showed a significant reduction after both 3 and 12 months. The initially normal Cr significantly increased between 3 and 12 months, and was negatively correlated with plaque volume on T1-weighted MR images. NAA initially showed normal values, a significant decrease at 1 month, and a slow recovery over 2 years. Myo-inositol did not show a clear tendency. The placebo group did not differ from the treated group, nor did the relapsing-remitting group differ from the secondary-progressive group. CONCLUSION: The contradictory time courses of Cr and NAA show that an absolute quantification in proton MR spectroscopy in MS is necessary to avoid a false interpretation of reduced NAA/Cr ratios. The increase in Cr is probably due to remyelination. The initial dip and later recovery of NAA seem to be related to diminishing edema and remyelination.

Anatomic evaluation of the circle of Willis: MR angiography versus intraarterial digital subtraction angiography.

PURPOSE: To evaluate the reliability of source images and maximum intensity projection images of MR angiography in showing the arterial segments of the circle of Willis. METHODS: In 62 patients, 526 arterial segments of the circle of Willis were determined to be present, partially present, or absent by blinded observers evaluating MR angiographic source images and maximum intensity projection images. Vessel diameter was measured on source images. These results were then compared with the results from intraarterial digital subtraction angiography. RESULTS: MR angiographic maximum intensity projection images had a sensitivity of 87% and a specificity of 88% and MR angiographic source images had a sensitivity of 89% and a specificity of 63% in depicting the presence of a vessel segment. The positive predictive value of an arterial segment with a diameter of at least 1 mm was 99%. CONCLUSION: MR angiography is a sensitive technique for detecting the anatomy of the circle of Willis. Maximum intensity projection images are more specific than source images. An arterial segment with a diameter of at least 1 mm on the source image is almost always present and patent.

MRI of facial skeleton and parapharyngeal space.

The diagnostic value of magnetic resonance imaging is examined in relation to computed tomography on the basis of 66 patients, who had pathological processes in the midfacial and nasopharyngeal space. The high power of contrast resolution in imaging soft tissue masses and the direct multiplanar capability of magnetic resonance offer advantages over computed tomography in respect of space occupying lesions in the median and lower parts of the craniofacial skull. Lymph nodes of more than 1 cm. in diameter were detected by both modalities. A disadvantage is the poorer detectability of tumour conditioned bone destruction at the base of the skull. In such cases, computed tomography remains the method of choice.

Evaluation of the clinical safety and efficacy of iobitridol (Xenetix) in intravenous urography.

The aim of this study is to report on the clinical safety and diagnostic efficacy of iobitridol (Xenetix) in intravenous urography compared to iohexol (Omnipaque) or iopamidol (Iopamiro). A total of 120 patients underwent intravenous urography (i.v.u.); 60 received Xenetix and 60 either Omnipaque (30 patients) or Iopamiro (30 patients) according to the center where they were treated. Clinical safety was assessed by the reporting of adverse events and diagnostic efficacy was evaluated. Warmth sensation was the most commonly reported adverse event. Two cases of nausea and vomiting were reported. Concerning diagnostic efficacy, 72-74% of the i.v.u. examinations were rated good or excellent by the physician. These studies confirm that Xenetix is a suitable contrast agent for i.v.u.

[CT of the lesser pelvis--normal and abnormal anatomy, indications, results (author's transl)]. / CT der Organe des kleinin Beckens -- normale und pathologische Anatomie, Indikationen, Ergebnisse.

385 abnormal computer tomograms of the organs in the lesser pelvis were analysed; the normal anatomy, indications for CT and its value are discussed. Particular attention is paid to the relevance of the computer tomographic information for treatment.

[Magnetic resonance tomography of brain tumors--comparison of the results using the multi-echo technic and gadolinium-DTPA]. / Magnetische Resonanztomographie (MR) bei Hirntumoren--Gegenüberstellung der Ergebnisse Multiechotechnik und Gadolinium-DTPA.

In thirty-seven MR examinations of intracranial tumours equivalent sections were obtained in a multi-echo technique before and after intravenous injection of 0.1 mmol. gadolinium DTPA/kg body weight. From this comparison the following preliminary conclusions have been drawn concerning the demonstration of the tumour, its delineation and type: Contrast administration does not unequivocally improve the sensitivity. In 55% of the cases, differentiation between tumour and oedema respectively normal brain tissue was easier after Gd-DTPA. Diffusely infiltrating gliomas remain a problem, since their extent is uncertain with or without contrast medium. The structure of the tumour can already be adequately characterized by the multi-echo technique. In order to diagnose the type of tumour, the criteria which apply to Gd-DTPA are similar to those used for iodine-containing contrast media in CT.

[The importance of magnetic resonance tomography in the diagnosis of cerebral infections]. / Die Bedeutung der Kernspintomographie in der Diagnostik zerebraler Infektionen.

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.

[Image-guided localized 31P NMR spectroscopy of the human brain at 1.5T]. / Bildgesteuerte lokalisierte 31P-NMR-Spektroskopie des menschlichen Gehirns bei 1,5 Tesla.

Using a 1.5 Tesla whole body system, image-guided localized 31P NMR spectra of normal brain tissue and of various intracranial tumours have been obtained. The spectra of normal brain tissue were reproducible, although further studies are necessary to determine physiological variability. Compared with the normal spectrum, the spectra of tumours usually showed reduced intensity of the phosphocreatine peaks and increased intensity of the peaks of inorganic phosphate, of phosphodiesters and particularly phosphomonoesters. To our limited experience there has been no correlation between the spectra and tumour histology. In follow-up studies of brain tumours undergoing treatment by chemotherapy or radiotherapy 31P MR spectroscopy demonstrated metabolic changes at a time when 1H MR imaging did not show any changes in tumour size or structure. Further investigations have to be done in order to evaluate the usefulness of 31P MRS for detecting therapeutic response in follow-up studies.

[Initial findings with magnetic resonance tomography of mediastinal and hilar tumors]. / Erste Erfahrungen mit der magnetischen Resonanztomographie (MR) bei tumorösen Erkrankungen des Mediastinums und der Lungenhili.

Twenty-six tumours of the mediastinum and hilar regions were examined by magnetic resonance; the technique and initial experience in distinguishing normal from pathological appearances are described. ECG triggering has proved essential, whereas respiratory triggering was found to be unnecessary. Spin-echo images were found to be best for tumour delineation but, for further characterisation, the inversion recovery mode and multi-echo technique were most satisfactory. In general, the space-occupying lesion was seen as well as it would be with CT. The advantages of the new method are the excellent differentiation of vascular structures and the ability to image in multiple planes, whereas CT possesses better resolution which, in some cases, may be of diagnostic advantage.

[Efficient procedure for diagnosing abdominal abscesses using imaging technics]. / Rationelles Vorgehen bei der Diagnostik abdomineller Abszesse mit Hilfe bildgebender Verfahren.

In 56 patients with abdominal abscess typical radiological abscess sings were analized to establish a rational and stepwise use of imaging procedures. Plain radiographs of the abdomen should be carried out at first because of their large diagnostic possibilities and standardized practicability. In addition with ultrasonography the diagnosis is possible in almost 90% of the cases. Contrast medium examination are rarely of diagnostic value. Computed tomography should be used in the remaining unclear cases and for planning of further surgical treatment.

[Diagnosis of recurrent rectal cancer: Comparison of CT and MR]. / Rezidivdiagnostik der Rektumkarzinome: Vergleich CT/MR.

For the assessment of local recurrence after surgical treatment of rectal carcinoma the results of MR and CT examinations in 29 patients were analyzed. Diagnosis was confirmed by surgery, by multiple biopsies and by follow-up examinations. CT yielded in only 11 cases clearly positive or negative findings. There were 4 false positive and 2 false negative results; in 12 cases the diagnosis remained uncertain. On the other hand, a clear differentiation was possible by MR in 23 cases with characteristically prolonged T2 in recurrent tumour and low signal intensities in fibrosis. Difficulties in differentiation were found only in early fibrotic reactions after surgery, inflammation or radiotherapy and in rare fibrotic tumours.

[Results and consequences of frequent quality control of quantitative clinical 1H-MR-spectroscopy]. / Resultate und Konsequenzen regelmässiger Qualitätskontrollen für die quantitative klinische 1H-MR-Spektroskopie.

Different methods exist for an absolute quantification of in vivo proton MR spectra. According to the principle of reciprocity a simple method has been suggested previously, comprising the multiplication of the spectral signals with the unlocalised reference amplitude of the measurement as a correction for the different coil load. Afterwards, the result can be compared to measurements on phantoms in order to obtain in vivo metabolite concentrations. Thus, only one calibration would be sufficient in principle for all measured spectra. However, during a previous serial study on humans and phantoms we observed significant changes in transmitter amplitudes over time, although metabolite peak areas remained quite constant. Hence, the method led to incorrect metabolite concentrations. Since these effects are mostly underestimated or even neglected in clinical spectroscopy, the purpose of the present study was to investigate these instabilities over time in order to find a new correction method for quantitative MRS. According to this new method, the spectra corrected by the coil load have to be modified additionally by dividing by the reference amplitude of a phantom.

[Computer tomography in the diagnosis of local recurrences after resection for carcinoma of the rectum (author's transl)]. / Computertomographische Diagnostik lokaler Rezidive nach Operationen von Rektumkarzinomen.

Presacral or pelvic floor tumour recurrence after abdomino-perineal resection for rectal or anal carcinomas has not been amenable to early radiological diagnosis. Computer tomography is a procedure which can demonstrate recurrences of two to three cm. Within the pelvis with certainty. The reliability of the method has been demonstrated in 27 patients suspected of having recurrences. The effect of demonstrating or excluding a recurrence on subsequent treatment is discussed. The value of computer tomographic examination of the pelvis for demonstrating the position and extent of a recurrence, the displacement of neighbouring organs, destruction of the pelvis and involvement of iliac lymph nodes is shown.

[The findings and value of computed tomography in pleural empyema]. / Befunde und Stellenwert der Computertomographie beim Pleuraempyem.

Chest radiographs and CT images of 25 patients with pleural empyemas were compared retrospectively with those of 20 patients with pleural exudates and transudates in order to determine criteria for differential diagnosis and to define the place of CT in the diagnosis of pleural empyemas. The sign which was most suggestive of an empyema on a chest radiograph was an encapsulated effusion in an atypical position (18/25); this was found in only 4 out of 20 exudates and in none of the transudates. On CT, changes in the pleura, the subcostal tissues and the configuration and position of the fluid were suggestive of an empyema. In nearly all patients with a pleural empyema there was thickening and increased contrast uptake of the parietal pleura (22/25) and thickening and increased density oft the subcostal tissues (23/25). Usually, empyemas were encapsulated and biconvex (20/25). None of the patients with pleural transudates showed any of these changes. In the presence of some pleural exudates, pleural (14/20) or thoracic (11/20) changes were noted. In part, these changes were due to previous treatment (sclerotherapy) or tumour infiltration (7/20). An attempt to correlate the CT findings with changes in the pleura and subcostal tissues with the clinical empyema stages I-III, according to Light, showed that CT was unable to distinguish between early and late empyemas. Consequently, diagnostic aspiration remains necessary for correct treatment.

[A comparison of digital luminescence radiography and conventional radiodiagnosis in sialography]. / Vergleich der digitalen Lumineszenzradiographie (DLR) und der konventionellen Röntgendiagnostik bei Sialographien.

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.

[Localization of cerebrospinal fluid fistulas with CT cisternography]. / Lokalisation von Liquorfisteln mit der CT-Zisternographie.

Positive CT cisternography has proved a useful method for the accurate pre-operative localisation of liquor fistulae from the skull base. In this way, planning of surgery can be improved with respect to the operative approach and the area to be covered. The risk of a recurrence is also reduced. It is necessary, however, to have a clinically recognisable leak at the time of the examination, since it is otherwise difficult to indicate the flow during the examination. We regard persistent or recurrent liquorrhoea as an indication for this examination, irrespective of its cause, provided it is intended to proceed to surgery after a positive finding. The method has few complications, is easy to perform and, in case of recurrence, can be repeated.

[Intracranial aneurysms. A comparison between magnetic resonance tomography and arteriography]. / Intrakranielle Aneurysmen. Vergleich zwischen magnetischer Resonanztomographie und Arteriographie.

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.