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Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 577 records · Page 32Linked to original sources
PubMed1991

[A 3-dimensional reconstructive procedure in lumbar computed tomography].

In this study, 50 patients were examined by a Siemens' "Somatom Plus"; continuous 2 mm sections between the third lumbar and first sacral vertebra were obtained. The accuracy of the 3-D reconstruction software programme was checked by measuring a polyethylene phantom of a second lumbar vertebra. Reconstruction was carried out with a threshold definition of 150 Hu. In each case, four standard projections and medio-sagittal, medio-lateral and coronary sections were reconstructed, photographed and compared with axial CT sections and conventional radiographs. All these imaging procedures were suitable for the diagnosis of osteochondrosis and chondrosis. Spondylosis was diagnosed more frequently on 3-D CT. Spondylarthrosis, with narrowing of the intervertebral foramina and root canals is shown particularly well by 3-D CT, since the entire extent of these structures can be seen. 3-D surface reconstruction of the lumbar spine is useful in the diagnosis of lumbar spondylarthrosis with narrowing of the root canals and of the spinal canal. This method of axial Ct is superior to conventional radiography of the lumbar spine in the usual two planes.

Adult↗
PubMed1991

[More rapid MRT with T2-weighted spin-echo sequences through variation of the flip angle].

In the present study the influence of the flip angle on image contrast in spin echo imaging was investigated. It was evaluated, whether variation of the flip angle allows for shorter repetition and imaging times in T2-weighted spin echo sequences. 10 patients with cerebral white matter lesions were investigated with an 1.5 Tesla whole body tomograph using a conventional double-spin echo sequence (TR = 2500 ms, TE = 15 and 70 ms) and time-optimized double-spin echo sequences (TR = 1900 ms, TE 15 and 70 ms) at flip angles of 90, 80, 70, 60 and 50 degrees. A reduction of the flip angles resulted in a decrease of T1-weighting and a relative increase of T2-weighting of the images. Despite the reduced repetition time at a flip angle of 70 degrees visually and quantitatively assessed contrast between lesions and brain as well as image artifacts of the time-optimized sequence were comparable to the conventional spin echo sequence; however, imaging time was shortened about 25%.

Adult↗
PubMed1991

[The place of angiography and radiologic intervention before and after liver transplantation].

The study demonstrates the value of angiography and radiological interventions before and after liver transplantation. From September 1988 till February 1991 84% out of 124 hepatic transplant recipients underwent pretransplant angiography evaluation for the exact demonstration of arterial and portal venous blood supply of the liver. Posttransplant angiography was performed in cases with suspected vascular complications, chronic rejection, and spleno-hepatic steal syndrome. Radiological interventions were performed for bacteriological examination and percutaneous drainage of encapsulated fluid collections.

Angiography↗
PubMed1991

[Lymphocytic infiltrations of the orbit in MRT and CT. Lymphoma, pseudolymphoma and inflammatory pseudotumor].

MR and CT examinations of 16 patients with lymphoma, pseudolymphoma and inflammatory pseudotumours were analysed to describe morphologic features of lymphocytic infiltration. Density and signal did not allow for differentiation, but localisation was the most important criterion: lymphoma and pseudolymphoma were located in the anterior superior orbit, inflammatory pseudotumours being retrobulbar lesions. Differentiation is of clinical importance, since both lymphoma and pseudolymphoma are accompanied by generalised malignant lymphoma while inflammatory pseudotumours are localised. Imaging of topographic relations of lens, optic nerve and lesion on sagittal MR images was found helpful for radiation therapy planning.

Adult↗
PubMed1991

Gadopentetate dimeglumine as a bowel contrast agent: safety and efficacy.

To determine the safety and efficacy of gadopentetate dimeglumine as a bowel contrast agent, magnetic resonance (MR) imaging (0.5 T) was performed with a formulation of gadopentetate dimeglumine (1.0 mmol/L of gadopentetate dimeglumine, 15 g/L of mannitol, 6-17 mL/kg) in 133 patients with intraabdominal mass lesions. Mostly short-lived gastrointestinal side effects were noted in 32% of patients. Gadopentetate dimeglumine provided uniform hyperintense marking of the bowel and contrast enhancement in the region of interest in 81% of patients. Among 78 patients with images obtained both before and after administration of contrast material, post-contrast improvement of lesion delineation was found in 62%. Among 55 patients with only postcontrast images, gadopentetate dimeglumine proved useful in 65%. Intravenous injection of scopolamine or glucagon effectively eliminated "ghost" images of the opacified bowel in 105 of 109 cases. The authors conclude that gadopentetate dimeglumine is a safe and effective bowel contrast agent for MR imaging.

Adolescent↗
PubMed1991

Transcranial Doppler sonography: collateral pathways in internal carotid artery obstructions.

Fifty-four patients with stenoses and occlusions of the extracranial internal carotid artery (ICA) demonstrated by intravenous digital subtraction angiography (IVDSA) were studied by extracranial duplex and transcranial Doppler. Two hundred healthy volunteers served as control group. Intracranial collateralization was demonstrated in 32 patients with ICA stenoses greater than 80% and occlusions. Twelve patients with unilateral and 8 patients with bilateral ICA obstructions greater than 80% showed collateral supply via the anterior (ACA) and/or posterior cerebral artery (PCA). In 5 cases of unilateral ICA occlusion and in 7 patients with bilateral ICA stenoses greater than 80% and occlusions, the ophthalmic artery and ACA and/or PCA served as collateral vessels. Five patients with ICA occlusions showed leptomeningeal anastomoses in the region of the postocclusive middle cerebral artery (MCA). All 54 patients showed normal time-mean flow velocity in the post-obstructive MCA. In unilateral ICA stenoses greater than 80% and occlusions, the pulsatility index in the ipsilateral MCA was reduced in comparison with the contralateral side, indicating that this parameter is more sensitive to hemodynamic effects of ICA obstructions than time-mean velocity.

Angiography, Digital Subtraction↗
PubMed1991

Production of granulocyte-macrophage (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) by rat clonal osteoblastic cell population CRP 10/30 and the immortalized cell line IRC10/30-myc1 stimulated by tumor necrosis factor alpha.

Previously, we have shown that primary cultures of murine calvarial cells produce both granulocyte macrophage (GM) and granulocyte (G) colony stimulating factor (CSF). Because of the heterogeneity of cell types in these cultures the osseous origin of these cytokines was not certain. Thus a non-transformed rat clonal osteoblastic cell population CRP 10/30 and the immortalized cell line IRC10/30-myc1 derived from it, which both express the osteoblastic phenotype, were now investigated. Both produced hemopoietic growth activity after treatment with recombinant murine tumor necrosis factor alpha. This activity eluted from diethylaminoethyl Sephacel at 0.2-0.3 M NaCl, and migrated on Sephacryl S-200 at a mol wt of around 30 k, as described for murine GM- and G-CSF. On a Phenyl Sepharose CL-4B column, it was separated into two peaks appearing at position where GM (peak I) and G-CSF (peak II) are expected to be eluted. Antisera against GM-CSF inhibited the activity of peak I. In the colony assay in semisolid medium, peak I induced colonies of the GM-type and peak II of the G-type. These data indicate that cloned osteoblasts produce GM- and G-CSF. Through CSF production, osteoblasts might regulate osteoclast formation, influence hemopoiesis and/or participate in local inflammatory reactions of bone.

Animals↗
PubMed1991

[Three-dimensional computerized tomography of fractures].

In 32 patients with fractures of different localisation the transverse CT layers were compared with three-dimensional reconstructions. Evaluation showed that three-dimensional CT can better visualize complicated anatomical conditions especially if there are dislocated fragments in the facial part of the skull and in the trunk of the body. Hence, 3-D CT is a valuable complement to axial CT which, however, remains the basis of the findings. Misinterpretations are possible of the reconstructions are used alone because of the lack if visualization of the lesions of the soft parts that accompany fractures and because there may be pseudoforamina at thin osseous lamellae.

Adolescent↗
PubMed1991

[Intra-arterial chemoembolization of non-resectable hepatocellular carcinoma].

During a period of nine months, fifteen patients with extensive hepato-cellular carcinomas were subjected to palliative arterial chemo-embolisation using doxorubicin and cisplatin in an emulsion with Lipiodol and/or Spherex particles. Two patients (stage Child C) died within two weeks as the result of liver failure. The remaining thirteen patients showed improvement in their general condition. Subsequent CT showed evidence of tumour reduction and reduction of ascites. Gas production in the tumour was considered as evidence of tumour necrosis. Biochemical results confirmed these findings with a fall of AFP as tumour marker indicating tumour regression.

Aged↗
PubMed1991

Vascular graft infection: detection by 123I-labeled antigranulocyte antibody (anti-NCA95) scintigraphy.

A total of 40 scintigraphic examinations were performed after vascular reconstructive surgery in 27 patients in whom there was a clinical suspicion of vascular graft infection. Whole-body gamma camera images were obtained at 4 and 24 h after i.v. administration of 111 MBq 123I-labeled antigranulocyte antibody Anti-NCA95. Scan results were interpreted without clinical information and were subsequently correlated with computed tomography. Prosthetic vascular graft infection was confirmed in 9 patients and excluded in 18 by surgical findings, bacteriology and/or clinical course. Scintigraphy revealed true-positive results in 16 of 40 and false-negative results in 1 of 40 examinations. True-negative results were found in 19 and 16, false-positive results in 4 and 7 examinations at 4 and 24 h p.i., resp. The sensitivity was calculated to be 94% for both early (4 h) and late (24 h) images whereas the specificity was 83% and 70%, resp. In all cases the application of the murine antibody was safe and no side effects or complications were noted. Limitations of this diagnostic procedure are accumulations of granulocytes in hematomas which may be observed in the non-complicated early course following reconstructive surgery.

Aged↗
PubMed1991

[A histologically controlled study of the value of sonography and palpation for the detection and exclusion of neck lymph node enlargements and metastases].

Preoperative evaluation of cervical lymph nodes by ultrasound and palpation was compared retrospectively in 123 patients with tumours on the head and neck. The diagnostic accuracy was higher by ultrasound (96.5%) than by palpation (85.5%). Hence, the sensitivity for detecting cervical metastases was also higher for ultrasound than for palpation (96% versus 83%), because of the reduced false negative findings. Specificity, however, was higher for palpation (82%) than for ultrasound (74%). Ultrasound was superior in delineating the relationship of metastases to adjacent tissues (vessels). Major disadvantages of ultrasound were the higher percentage of false positive findings (26%) and absence if delineation of the relationship to bony structures.

Adult↗
PubMed1991

[Magnetic resonance tomographic differentiation of eye muscle enlargement. Study technique, characteristic images, literature review].

Multiplanar facilities of MR imaging allow for a detailed analysis of eye muscle enlargement. For taking full advantage of MRI's diagnostic possibilities, thorough knowledge of pathological anatomy is necessary. The paper describes examination technique and criteria for analysis. Diseases leading to eye muscle enlargement are illustrated by exemplary cases.

Humans↗
PubMed1991

[Determinant factors and disturbances in controlling power distribution patterns by the hyperthermia-ring system BSD-2000. 2. Measuring techniques and analysis].

Clinical observables and phantom measurements (part 1) have suggested that the control of power deposition patterns can still be improved for the hyperthermia system BSD-2000. This is addressed to system-specific phase errors as well as inadequacies of phase selection (target point method), which might be corrected by modifications of the manufacturer. Furthermore, frequency-dependent physical effects (coupling, mode excitation) are existing, which might cause distortions and asymmetries of current distribution on antennas and consequently deteriorate the power deposition pattern (e.g. focussing capability). The application of a network analyzer system is described in order to determine electrical material constants, phase errors, coupling coefficients, reflection coefficients and current distributions on antennas. The analysis of the measurement datas suggests that ring-applicator has a variable frequency-optimum (supposed around 80 ... 95 MHz) characterized by minimal coupling and asymmetries.

Humans↗
PubMed1990

Malondialdehyde formation by blood platelets: a diagnostic test to assess acetylsalicylic acid induced thrombocytopathy?

We investigated whether the measurement of N-ethylmaleimide stimulated malondialdehyde (MDA) formation by blood platelets from normal subjects is equally sensitive to acetylsalicylic acid intake as are platelet aggregation studies. MDA production and platelet aggregation by collagen and arachidonate were assayed in ten healthy volunteers before and up to ten days after a single oral dose of 500 mg aspirin. Discordant results of the two tests were seen in several subjects 4 to 6 days after aspirin intake. In three cases with still suppressed MDA values on day 4, collagen or arachidonate induced aggregation was normalized. However, on day 6, when MDA was normalized in all subjects, the aggregation response to arachidonate was still pathologic in 5 of the ten volunteers. In case of a patient with abnormal aggregation response to arachidonate and/or collagen, therefore, a normal MDA value does not permit to exclude aspirin as the cause of the platelet dysfunction.

Adult↗