Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 595 records · Page 33Linked to original sources

PubMed1990

[Scintigraphic quantification of pulmonary pressure increase in mitral valve stenoses based thallium uptake by the lung].

30 patients (24 fm, 6 m) with angiographically proven mitral stenosis as well as 10 healthy controls were investigated by wedge catheterism and thallium-201-scintigraphy to calculate the heart-lung quotient of the isotope. All patients with mitral stenosis could be discriminated from controls by a pathological increase of isotope concentration in the lungs. 4 groups could be subdivided: the first consisted of 8 patients with normal pulmonary artery pressure of x = 13.06 mm Hg and a normal heart-lung quotient less than 1.1. The second group of 15 patients showed passive pulmonary hypertension with a PAm of x = 27.57 mm Hg and heart-lung quotients between 1.1 and 1.4. A third group of 9 patients showed PAm of 36.76 mm Hg with reactive hypertension and a HLQ between 1.4 and 1.6. The last group of patients showed pulmonary hypertension of x = 45 mmHgPAm and a heart-lung quotient of greater than 1.6. Scintigraphy alone allowed classification of the patients, so the value of this method is proven for pre- and postoperative strategy.

Exercise Test↗

PubMed1990

Impairment of macrophage colony-stimulating factor production and lack of resident bone marrow macrophages in the osteopetrotic op/op mouse.

Mouse calvaria-derived osteoblastlike cells have been shown to produce macrophage colony-stimulating factor (M-CSF). This factor may be involved in osteoclastogenesis and thus in bone resorption. In the present study we investigated whether the production of M-CSF was altered in the osteopetrotic mouse mutant strain op/op, characterized by a decrease in osteoclast number and an impairment of bone resorption. Whole calvariae and cells, as well as skin and lung fibroblasts, of the op/op mouse were found to produce no measurable M-CSF, in contrast to tissue and cells derived from normal littermates. M-CSF was identified by colony assay in semisolid media and by inhibition of the biologic activity with antiserum against M-CSF. Furthermore, the number of resident macrophages, identified by F4/80 antigen (F4/80 Ag) immunohistochemistry, was drastically decreased in bone and bone marrow of the op/op mouse, but in skin these cells were normal in number and morphology. These findings suggest that both M-CSF and resident macrophages play a role in the mechanism of bone resorption. The op/op mouse appears to be a valuable model to further investigate such a hypothesis.

Animals↗

PubMed1990

"Meningeal sign": a characteristic finding of meningiomas on contrast-enhanced MR images.

In meningiomas, a flat, contrast-enhancing, probably dural structure adjacent to the tumor can occasionally be observed on Gadolinium-DTPA enhanced MR images. This so called "meningeal sign" was evaluated with respect to the differential diagnosis of meningiomas in MR imaging. The study included 29 patients with intracranial meningiomas and 24 patients with non-meningeal brain tumors. In all meningiomas, MR studies included T2-weighted as well as unenhanced and Gadolinium-DTPA-enhanced T1-weighted images. In all non-meningeal tumors, Gd-DTPA-enhanced MR images were available. All images were evaluated with respect to the presence of the "meningeal sign". In meningiomas, a "meningeal sign" was seen in 15/29 cases on Gadolinium-DTPA-enhanced images. No abnormalities corresponding to the areas of contrast enhancement were found on unenhanced T2- and T1-weighted MR images. In non-meningeal tumors only 2/24 cases showed a "meningeal sign". In conclusion, with a sensitivity of 52% and a specificity of 92%, the demonstration of the "meningeal sign" improved the differential diagnosis of intracranial meningiomas in contrast-enhanced MR imaging.

Adult↗

PubMed1990

Intracranial meningiomas. Comparison of plain and contrast-enhanced examinations in CT and MRI.

Fifty patients with intracranial meningiomas underwent plain and contrast-enhanced examinations with CT and MRI. Each of the MR studies consisted of three plain (T1, proton density and T2-weighted) and a post-contrast series (0.1 mmol Gd-DTPA/kg body weight). All techniques (plain CT, plain MRI, contrast-enhanced CT, contrast-enhanced MRI) proved to be highly efficient as regards tumour detection: depending on the technique, an intracranial lesion was demonstrated in 47-50 cases. The image contrast was assessed as good or excellent in 21 cases having plain CT and in 33 cases having plain MRI, but in 46 and 50 of the contrast-enhanced CT and MRI studies respectively. Adequate tumour delineation was achieved in 18 cases with plain CT, in 35 cases with plain MRI and in 46 and 50 cases of the contrast-enhanced CT and MRI examinations. The contrast-enhanced studies proved to be superior to the plain CT and MRI studies as regards image contrast and tumor delineation. Because of the methodological advantages of the MRI technique, contrast-enhanced MRI was judged to be slightly superior to contrast-enhanced CT.

Adult↗

PubMed1990

Multiple slice FLASH imaging: an improved pulse sequence for contrast enhanced MR brain studies.

A multisclice gradient echo sequence (FLASH) was compared with a conventional spin-echo (SE) technique with regard to its value for contrast enhanced brain studies. In 50 patients with contrast enhancing intracranial lesions, MR studies (0.5 Tesla MR tomograph) were performed with SE images (SE 400/30; four images/3.4 min) and FLASH scans (FLASH 315/14, 90 degrees; 15 images/1.4 min) before and after Gd-DTPA. Based on visual and quantitative assessment diagnostic results of postcontrast SE- and FLASH images were equivalent with respect to contrast enhancement, lesion/brain-contrast, lesion/edema-contrast, and lesion delineation. Although image quality generally was excellent on postcontrast FLASH images, susceptibility artifacts were more severe on FLASH scans than on SE images. However, with the exception of postoperative patients with artifacts due to metal remains, diagnostic information was not decreased by artifacts on postcontrast FLASH images. In conclusion, because of the clearly higher efficiency of the multisclice FLASH technique, this pulse sequence offers the opportunity to speed up contrast enhanced brain imaging.

Adult↗

PubMed1990

[High-resolution computerized tomography of the petrous bone with two-dimensional and three-dimensional reconstruction].

Fifty patients with various diseases of the petrous bone were examined by HR-CT with a 1024 x 1024 matrix. It is demonstrated that the improved spacial resolution results in a better discrimination of subtle anatomical structures and therefore leads to an expansion of the diagnostic possibilities in diseases of the auditory and vestibular organs. Evaluation of the two-dimensional reconstructed images shows that best quality is obtained with contiguous 1 mm, sections in the primary scans. In most cases these reconstructed images are diagnostically sufficient. In addition they help to reduce patient strain (no problem with patient positioning, no further x-ray exposure, time-saving). Three-dimensional reconstructions from the base of the skull allow a good visualization of complex and extensive osseous destructions of the temporal bone. The disadvantage of this method is on the one hand the lacking representation of soft tissue and the poor spacial resolution (no 3-D imaging of the ossicular chain), and on the other hand the smoothing of contours because of arithmetical filters. Thus tumor expansion and finer osseous erosions may not be distinguishable. Consequently, 2D primary or reconstructed images must continue to be the basis of diagnosis.

Adult↗

PubMed1990

[Optimization of gadolinium-DTPA dose: an inter-individual study of patients with intracranial tumors].

The diagnostic value of various doses of Gd-DTPA was compared intra-individually. Thirty-three patients with cerebral tumours were randomly allocated to three groups. Group 1 was given a dose of 0.025, group 2 a dose of 0.05 and group 3 a dose of 0.1 mmol GD-DTPA/kg body weight. Following administration of Gd-DTPA the average tumor/brain contrast in group 1 was -4.5%, in group 2 +8.4% and in group 3 +43.0%. Diagnostically useful tumour delineation was obtained in two out of 11 in group 1, in seven out of 11 in group 2 and in 10 out of 11 in group 3. A further increase in the dose to 0.2 mmol/kg body weight in group 3 resulted in a further increase in tumour/brain contrast of +62.5% and improved tumour delineation in one case. As a result of these findings a dose of 0.1 mmol Gd-DTPA/kg body weight is recommended for the routine investigation of intracranial tumours.

Adult↗

PubMed1990

[Value of radioimmunoscintigraphy compared to computed tomography in the diagnosis and follow-up of primary ovarian carcinoma].

In this prospective study the diagnostic merit of radioimmunoscintigraphy (RIS) was compared with computed tomography (CT) and operation in the primary diagnostic procedure and follow-up of women with suspected ovarian cancer. In primary diagnosis, sensitivity, specificity, and diagnostic accuracy was 100%, 60% and 90% for RIS. In follow-up, sensitivity for local recurrence was slightly higher in CT than in RIS. It was possible to detect peritoneal carcinosis in the pelvis and lower abdominal region better with RIS, but in the upper abdominal region, peritoneal carcinosis was detected better with CT. If no differentiation between benign or malignant lesion, is possible with CT, differentiation will in many cases be possible with RIS.

Adenocarcinoma, Mucinous↗

PubMed1990

[Cerebral and meningeal manifestations of AIDS: sensitivity of CT and T2-weighted MRT (129 patients)].

We studied 129 AIDS patients with suspected or proved intracranial manifestations of the disease. The purpose of this study was to compare the diagnostic sensitivity of unenhanced and contrast enhanced CT and unenhanced T2-weighted MR. In 35/129 patients CT and MR findings were normal. In 37/129 patients equivalent findings were obtained with both methods. Although CT and MR demonstrated intracranial pathology in 25 cases, MR was clearly superior. Six of these cases had solitary lesions in CT, while MR demonstrated multiple lesions. MR detected more foci than CT. In 24 patients with normal CT, MR detected intracranial manifestations of AIDS, namely solitary lesions in 8, multiple lesions in 12 and meningeal alterations in 4 patients. In only 8 patients with normal MR findings, CT revealed pathological contrast enhancement in 2 and parenchymal calcifications in 6 patients. Thus, in 20% of our patients MR but not CT was diagnostic. In another 20% MR provided additional diagnostic information. In conclusion, MR is recommended as the imaging modality of choice in AIDS patients with non-conclusive cranial CT.

Acquired Immunodeficiency Syndrome↗

PubMed1990

[MRT of brain metastases. (I) What is the place of screening with T2-weighted sequences?].

Sensitivity and specificity of plain T2-WI and Gd-DTPA enhanced T1-WI were compared by evaluating MR exams of 30 patients with brain metastases. Large lesions with high signal on T2-WI always enhanced (43/43) when a structure (perifocal edema, tumor tissue, central necrosis) was found. Large lesions nearly always enhanced (53/55) even if no such structure was found. 65% of small unstructured white matter lesions with high signal on T2-WI, which are generally considered vascular, did not enhance. Surprisingly, 35% did enhance. Demonstration of blood brain barrier disturbance in these lesions suggested a metastatic origin. In 3 patients with multiple metastases, Gd-DTPA enhanced T1-WI disclosed more than 140 lesions not seen on T2-WI. All of them were located in or adjacent to grey matter. Our results indicate that enhanced T1-WI should be obtained even if T1-WI are normal or show only small white matter lesions.

Adult↗

PubMed1990

[Dynamic CT and angio-CT following liver transplantation].

This is a prospective study of the value of dynamic CT with a rapid scan frequency for the control of liver transplants. In 28 patients dynamic CT was performed with table movement and angio-CT without table movement, using a standard contrast bolus. In 97% of cases the central portions of the portal and hepatic veins could be delineated. The peripheral vessels were better demonstrated by angio-CT (79%) than by dynamic studies with table movement (47%). Parenchymal lesions, such as infarcts, and changes round the liver, such as lymphoedema or haematomas, were adequately demonstrated by either method. In addition, angio-CT provided information on abnormalities of perfusion within the transplant.

Adult↗

PubMed1990

[MRI of the cervical spine using T1-weighted multislice FLASH sequences].

A study has been carried out to evaluate contrast and image quality of cervical structures using multislice 2D-flash sequences with long repetition times (TR = 400 ms.) and short echo delay times (TE = 5.8 ms.). The examinations were carried out using ten normals with an MRI of 1.5 Tesla and flip angles of 10, 20, 30, 50, 70 and 90 degrees. The best contrast between intervertebral disc and surrounding tissue was obtained between 50 and 70 degrees, best contrast between compact bone and CSF with 10 degrees. In order to demonstrate degenerative changes of the cervical spine, it appears sensible to use a combination of these angles. The described sequences produce good images of the cervical structures with little image degradation. Compared to T1-weighted spin-echo sequences, the method has a number of significant advantages, such as variations in image contrast, higher maximal number of slices, contiguous imaging and less imaging time.

Adult↗

PubMed1990

[A NMR tomographic follow-up assessment of the replacement plastic repair of the anterior cruciate ligament with an autologous ligamentum patellae transplant].

Reconstruction of the anterior crucial ligament can be performed by using an autogenous transplant from the patellar ligament. Employing postoperative MR investigation, reaction of the non-vascularised tendon was studied. In 16 patients 20 knees were investigated by applying a 1.5 tesla magnet with T1-weighted (TR 500 ms, TE 15 ms) and a T2*-weighted (FISP 3D: TR 30 ms, TE 10 ms, flip angle 40 degrees). Postoperative MR follow-up showed an increase in signal intensity and diameter in T1-weighted images. This represents revascularisation of the transplant.

Anterior Cruciate Ligament↗

PubMed1990

[Differentiation of malignant liver tumors using rapid dynamic CT].

In this prospective study 39 patients with malignant liver tumours were examined by rapid CT. CT was performed before contrast, as dynamic CT, with and without table movement and, in some patients, images were obtained four hours after contrast injection. Time/density curves of hepato-cellular carcinomas (nine cases) showed more rapid and more intense enhancement of the tumour than of the liver parenchyma, whereas tumours of biliary origin (ten cases) showed a slower and less marked enhancement than surrounding tissue. In addition, it was possible to differentiate hypovascular metastases (18 cases) and hypervascular lesions by means of the time-density curve. Best diagnostic information was obtained by dynamic bolus CT. This method without table movement is best for differentiating focal lesions, whereas dynamic CT with table movement shows the extent and number of tumour lesions.

Adenoma, Bile Duct↗

PubMed1990

[Transcranial Doppler sonography. Normal values and physiologic changes].

In 100 normal subjects mean flow velocity in the middle (MCA), anterior (ACA), and posterior (PCA) cerebral arteries and mean pulsatility index were examined by transcranial Doppler ultrasound. Age-dependent normal reference values were assessed. The measured parameters showed a large variation increasing with age. The highest flow velocities were found in the MCA, the lowest in the PCA. The highest mean side difference in flow velocity was observed in the ACA. An increase of pulsatility index and a decrease of flow velocities in all examined vessels were found with increasing age. The influence of ventilation and heart function on flow velocity and pulsatility index was demonstrated by the investigation of 10 normal subjects in different phases of ventilation and 1 patient with aortic valve insufficiency.

Adult↗

PubMed1990

[Magnetic resonance tomographic differentiation of ocular muscle changes in endocrine orbitopathy].

In 50 patients with Graves' Ophthalmopathy and 9 controls both orbits were examined by MR Imaging at 0.5 Tesla using a surface coil. T1-weighted spin-echo images were obtained in transverse and coronal orientation; additionally, a T2-image was calculated from a multi-echo sequence (8 echoes). Signal intensity of eye muscles on both T1-weighted and T2-weighted MR images was evaluated qualitatively. T2-times were then calculated for all inferior rectus muscles. Eye muscle enlargement was found in 28 out of 50 patients. T2-times of inferior rectus muscles in stage III and IV patients were evaluated significantly (p less than 0.05). Areas of high signal intensity were accordingly found in enlarged eye muscles in 19 out of 50 patients; they were interpreted as edematous tissue changes. Areas of low signal intensity were found in enlarged eye muscles of 5 out of 50 patients; these eye muscles were considered fibrotic. Differentiation of eye muscle changes by MR imaging might help to decide between antiinflammatory medication and surgical therapy in patients with Graves' Ophthalmopathy.

Adolescent↗

PubMed1990

[The value of 3D-CT in maxillary surgical diagnosis and therapy planning].

In 25 patients in whom oral surgery was required, we examined what additional information can be obtained via three-dimensional CT compared with conventional transverse CT scans. We showed that D-3 CT facilitated the spatial orientation by complex osseous destructions. Better therapy planning and postoperative control was therefore feasible. However, CT diagnosis continued to be based on transverse scans.

Aged↗

PubMed1990

[Magnetic resonance tomography in orthotopic liver transplantation].

14 patients with orthotopic liver transplantation were prospectively studied with MR imaging. MR imaging demonstrated a perivascular collar surrounding central portal venous branches in 14 patients. The perivascular collar had low signal intensity on T1-weighted and high signal intensity on T2-weighted images. In 10 of the 14 patients, a perivascular collar was also observed around peripheral portal venous branches. The perivascular collar is probably caused by intraoperative interruption of hepatic lymph vessels and resultant impaired lymph drainage. It is a normal postoperative phenomenon in hepatic transplants. MR imaging is particularly useful in the distinction of postoperative hematoma from other intra- and extrahepatic fluid collections and may provide a noninvasive assessment of liver transplant rejection.

Adult↗