Biomedical subjects
Publications and source records attributed to R Felix.
The diagnostic possibilities of intraarterial DSA are demonstrated by means of 76 investigated haemodialysis shunts. No complications were seen. In 85% of the cases venous stenoses or occlusions were proved. 18% of these were localised in the proximal part of the draining veins. For this reason, investigation of the venous inflow into the V. cava superior is recommended in every case.
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40 patients with a definite diagnosis and 16 patients with an initial manifestation of multiple sclerosis were investigated by cerebral nuclear magnetic resonance imaging (NMR) and compared. The initial manifestation is predominantly characterized in the NMR by significantly less periventricular involvement, especially within the region of the occipital horns, by significantly rarer appearance of confluent, periventricular lesions within the region of the pars centralis and the temporal horns of the lateral ventricles and by significantly rarer appearance of circumscribed non-periventricular lesions. Unlike those in definite multiple sclerosis, the morphology and distribution of the initial lesions do not show a stereotypical and diagnostically characteristic pattern. The importance of the cerebral NMR for the early diagnosis of multiple sclerosis lies primarily in the indication of disseminated lesions.
In a single-blind intraindividual cross-over comparative study the influence of two systemic-mucolytic agents, 2-(pyridyl-3-methylthio)pyrimidine (tasuldine, HE 10004-succinate) vs. N-acetyl-L-cysteine (acetylcysteine) on the mucociliary clearance and lung function was investigated in 15 patients with chronic obstructive respiratory disease. The overall treatment period was 14 days with the drug being changed after 7 days in each group. Under tasuldine and acetylcysteine treatment a tendency to an improvement of mucociliary clearance was observed compared with the control pointing to an increase in adoral velocity. The direct comparison between both drugs revealed that 120 min after medication mucociliary clearance was stimulated significantly stronger by intake of tasuldine than by acetylcysteine. There was no influence on lung function.
21 patients with clinical and CT diagnoses of intracranial tumor were studied by MRI (NMR) prior to and after administration of intravenous Gadolinium-DTPA. Resultant MRI images were compared with corresponding CT sections with respect to lesion detection, contrast enhancement, tumor delineation and visualization of perifocal edema. All intracranial lesions shown on CT were identified on MRI. Contrast enhancement in MRI images was achieved in 19 out of 21 patients, as it was also with CT. In these cases improved differentiation between tumor, perifocal edema and adjacent brain structures were obtained. In most cases sufficient visualization of perifocal edema in MRI required T2 weighted images (SE 1600/70) in addition to spin echo scans routinely performed prior to and after contrast medium (SE 400/30 or 800/30). No side effects were encountered following administration of Gadolinium-DTPA. The good tolerance and the efficacy justifies the use of Gadolinium-DTPA for contrast enhanced MRI imaging.
Patients with a brain-stem tumor were studied with NMR. The full extent of the lesion as well as its relationship with the adjacent structures was clearly demonstrated in all cases. Although NMR is, in many aspects, superior to CT and angiography, these examinations remain useful complementary methods.
Gadolinium DTPA was evaluated as an intravenous contrast agent for magnetic resonance imaging in 15 patients with primary or secondary intracranial neoplastic disease. T1 and T2 weighted images were obtained prior to contrast administration. T1 weighted spin echo 35/800 (TE/TR) images were utilized to detect enhancement. The increase in signal intensity observed, identifying areas of breakdown of the blood-brain barrier (BBB), was similar in magnitude to the contrast enhancement observed on CT. This permitted differentiation of neoplastic tissue from surrounding cerebral edema on MRI. Direct visualization of otherwise "isomagnetic" lesions was also demonstrated. The use of intravenous contrast media should significantly extend the diagnostic potential and specificity of magnetic resonance imaging.
Bisphosphonates are potent inhibitors of bone resorption and also inhibit prostaglandin (PG) E2 synthesis in bone cells. Therefore we have investigated whether a correlation exists between inhibition of bone resorption and inhibition of PGE2 formation. Initially, bisphosphonates were tested for their effect on the release of [14C]PGE2 from rat calvaria cells labelled with [14C]arachidonic acid and stimulated by bradykinin, thrombin and mechanical manipulation. The effect on [14C]-PGE2 synthesis was not correlated with the known inhibitory activity of bisphosphonates on bone resorption. Mouse calvaria were then treated with epidermal growth factor (EGF) to induce PGE2 synthesis and bone resorption, with or without bisphosphonates. The bisphosphonates either decreased, had no effect or increased PGE2 production, but all inhibited the release of calcium. Finally, the bisphosphonates were given in vivo to mice before explantation of the calvaria. Some of the bisphosphonates decreased the production of PGE2, suggesting that these compounds may have such an effect in vivo. But again no relationship between the effect on PGE2 synthesis and bone resorption was found. Thus, these experiments show the inhibitory effect of bisphosphonates on bone resorption is unlikely to be explained only by their effect on PGE2 synthesis.
The quality of intravenous digital subtraction angiograms was sufficient for diagnostic evaluation in 90%. The accuracy of the method was 90% for the internal carotid artery. 40% of the internal carotid arteries showed stenoses, whereas the common and external carotid arteries were not narrowed in 90%. On behalf of these data the authors consider that i.v. DSA of the carotid vessels is a suitable screening method for carotid arterial occlusive disease.
In a clinical study with 663 patients the influence of compression and compound technique of the visualisation of the abdomen was tested with a real-time-scanner Combison 100, compound scanner Combison 202 and the Octoson-machine. In 66 patients the retroperitoneal space was not demonstrated. Compression with the real-time-transducer improves demonstration in 50% (33/66), compound-technique 20% (19/66). Compound-technique was handicapped in 30% (19/66) by velocity errors and reflection which causes a deterioration in resolution.
Contrast media can significantly improve the diagnostic value of MR tomography. The basis of using contrast material for MR depends on totally different physical principles from those employed in conventional radiological diagnosis. The physical factors underlying the use of these contrast media are described, various suitable substances are discussed, and experience so far gained with some contrast agents is outlined.
The examination of 91 patients was undertaken in order to establish the relevance of tomographical measurement of the regional cerebral blood-flow, following inhalation of 133Xenon, as a complementary method to the conventional carotis-angiography. In many cases the findings revealed a more precise or even deviating judgement on the hemodynamic relevance of stenosis and obliteration than was proved only by angiography. Especially in the stages I and IV of cerebrovascular disease of the a. cerebri anterior, a. carotis interna and a. carotis communis the rCBF-measurement seemed to be an important parameter for the decision between conservative and surgical therapy as a prognostic parameter for the individual risk of many patients to suffer a cerebral infarction.
A comparative study between magnetic resonance tomography (MRT) and CT was carried out in 16 patients with temporal lobe epilepsy. The MRT studies were performed on a 0.35 T Magnetom with T.1 modes in a coronal plane. MRT proved to the superior to CT. CT demonstrated a discreet temporal lobe lesion in three patients and MRT in four patients. In addition, unilateral atrophy of the temporal lobe was demonstrated by MRT in six cases; these could not be diagnosed by CT. The lack of artifacts near the skull base, the possibility of producing coronal sections and the excellent tissue differential of MRT provide the basis for improved diagnosis of lesions in the temporal lobes.
We performed magnetic resonance tomography (MRT) on 22 patients with multiple sclerosis (MS) using varying scan sequences. In 21 patients MRT produced abnormal findings demonstrating multiple lesions, giving varying signals. The MRT appearances of MS have the following characteristics: circular configuration and homogeneous structure of individual lesions, multiple foci, with involvement of all parts of the brain, but with preference for the periventricular region and white matter. This constellation of MRT features is characteristic for MS, but is largely independent of the varying clinical symptoms. The appearance of the individual lesions and the distribution pattern of the foci is sufficiently characteristic to support the clinical diagnosis of MS in younger patients.
The principles underlying contrast media for MR tomography are totally different from those for conventional contrast media. Substances suitable for MR tomography are paramagnetic complexes which alter the relaxation times of the tissues. Signal intensity on the MR images are influenced correspondingly. The mode of action of MR contrast media is explained. Gadolinium-DTPA, the first MR contrast medium in clinical use by means of intravenous injection, is described. Its tolerance has been investigated by animal experiments and its effectiveness as an contrast agent has been studied in normal individuals. In the second part of the paper, early results from the use of gadolinium DTPA are given. The additional information which can be obtained by using MR contrast media is discussed.
The early results of the use of the MR specific contrast medium gadolinium-DTPA in 40 patients with intracranial tumours are reported. Optimal pulse sequences, contrast dose and timing are discussed. The relationship between the blood-brain barrier and contrast distribution within tumour tissue is elaborated. The clinical significance of the application of contrast agents in the diagnosis of brain tumours is evaluated.
By means of ECG triggering, it is possible to demonstrate various phases of cardiac action. It is then possible to derive a measure for cardiac function. The disadvantage of the method consists of the long measurement period required and the creation of movement artifacts. A method is discussed which would permit the demonstration of normal cardiac movement during a short time span and which reduces artifacts. In order to obtain optimum results, a new sequence of measurements is suggested. This is based on spin-echo sequences and can readily be used with any type of MRT apparatus.
Object movement influences the images in MRT, producing phantom images and blurred contours, while also affecting the intensity of the signal. Phantom images and blurring of contours can be largely prevented by suitable signal triggering in case of rhythmic movements caused, for example, by cardiac pulsation or respiration. However, the intensity of the signal follows a different pattern. Periodic movement in the image plane (sagittal plane) has no effect on signal intensity if the exposures are triggered. Object movement across the image plane causes changes in signal intensity, even with triggered exposures.