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Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 397 records · Page 22Linked to original sources
PubMed1996

[Spiral-CT of the liver: optimizing contrast medium administration and examination technique].

AIM OF STUDY: To analyze different protocols for spiral-CT with regard to the enhancement of liver parenchyma and vessels of the upper abdomen. To compare the achieved density values with those obtained by conventional CT. METHODS: 30 CT-examinations of the abdomen of different patients with normal findings of the liver were selected. In all examinations the upper abdomen was scanned before injection of contrast agent in conventional technique. In 10 patients spiral-CT of the liver was performed in the arterial phase at a delay of 15 sec and a flow of 4 ml/sec with 100 ml contrast agent, in 10 other patients in the portal-venous phase at a delay of 35 sec and a flow of 4 ml/sec with 100 ml contrast agent, followed by a spiral-CT of the upper abdomen in the arterial-venous phase at a delay of 70 sec and a flow of 1 ml/sec with 85 ml contrast agent. In 10 patients conventional CT of the upper abdomen was performed at a delay of 30 sec and a flow of 1 ml/sec with 200 ml contrast agent. RESULTS: The highest density of the aorta was achieved by the arterial spiral-CT (p < 0.001). In the portal-venous spiral-CT the density of liver parenchyma was lower than in the arterial-venous spiral-CT and conventional CT (p < 0.001). Both arterial-venous spiral-CT and conventional CT achieved the same contrast in the aorta (216 +/- 10 vs. 217 +/- 23 HE) and in liver parenchyma (110 +/- 3 vs. 112 +/- 16 HE), but arterial-venous spiral-CT showed a lower density in the inferior vena cava than conventional CT (138 +/- 9 vs. 162 +/- 21 HE) (p < 0.002). CONCLUSIONS: The spiral-CT-protocol for the examination of the liver in arterial and arterial-venous phase enables a reliable and adequate enhancement of liver parenchyma and all vessels of the upper abdomen with a lower dose of contrast agent than is possible with conventional CT. Together with unenhanced CT, this protocol promises a better detection of focal lesions of the liver with different enhancement modes in the arterial and venous phases.

Adult↗
PubMed1996

[Diagnostic value of magnetic resonance tomography of the upper ankle joint--imaging of ligaments and tendons in standard slice orientation].

PURPOSE: Evaluation of the capability of high field strength MRI in depicting clinically important tendons and ligaments of the ankle joint using slice orientations parallel to the standard space directions without angulation. MATERIALS AND METHODS: 65 patients whose ankle joint complaints were not sufficiently clarified by conventional radiology sphere underwent MRI using plain T1-weighted spin echo sequences. Tendons and ligaments were classified by three independent radiologists with regard to their perceptibility on images of the different slice orientations. RESULTS: Good perceptibility of at least two-thirds of each structure with the possibility for a decision regarding continuity or rupture of the remaining part was given most frequently in the following slice orientations: Axially for the tendons of peroneus longus, peroneus brevis, tibialis posterior, flexor digitorum longus, flexor hallucis longus, tibialis anterior, extensor digitorum longus, and extensor hallucis longus muscles, and for the calcanear tendon (each over 94% of cases), anterior (68%) talofibular ligament, deltoid (77%), anterior (63%), and posterior (72%) tibiofibular ligaments and coronally for the calcaneofibular (39%) and posterior talofibular ligaments (70%). The sagittal orientation was never the favoured one. CONCLUSIONS: All tendons and ligaments of the ankle joint, except for the calcaneofibular and anterior tibiofibular ligaments, can be sufficiently visualized in the majority of cases by non-angulated spin echo sequences in standard slice orientations if the examination is performed in at least two slice directions. Thus, the minimal examination program should be: one T2-weighted sequence, T1-weighted sequences axially and in a further orientation, i.e. slightly angulated coronally for depicting the calcaneofibular ligament.

Achilles Tendon↗
PubMed1996

Intraaneurysmal flow: evaluation with Doppler guidewires.

Flow dynamics in cerebral aneurysms were studied with the use of Doppler guidewires in two patients. In both cases it was possible to reach the aneurysmal sac and to assess intraaneurysmal flow. Torquability and flexibility of the new Doppler guidewires permitted continuous assessment of flow velocity and flow pattern at the dome as well as in the neck area. Flow velocities were higher at the neck than within the aneurysmal sac (88 cm/s > 28 cm/s). Because of the limited area of interrogation (sample volume, 5 mm) it was not possible to investigate the complete intraaneurysmal space.

Adult↗
PubMed1996

MR characteristics of primary extramedullary plasmacytoma in the head and neck.

PURPOSE: To define MR characteristics of primary extramedullary plasmacytoma in the head and neck using a variety of plain and contrast-enhanced MR protocols. METHODS: Six patients with primary extramedullary plasmacytoma in the head and neck were examined clinically and with MR imaging at 1.5 T. The morphologic appearance and signal intensities of the lesions were analyzed and the results of the imaging findings were compared with histopathologic findings. RESULTS: Qualitative analysis showed that five lesions were oval and sharply demarcated without signs of infiltration; the other lesion filled the parapharyngeal space bilaterally. On t2-weighted sequences, the lesions had moderate signal intensity. On plain T1-weighted sequences, the tumors were isointense or slightly hyperintense with respect to surrounding muscles; after administration of contrast medium, four lesions notable enhancement, with distinct central inhomogeneity. CONCLUSION: Although morphologic features or evidence of contrast enhancement do not assure certain diagnosis of extramedullary plasmacytoma, these MR imaging characteristics should prompt the radiologist to include this rare lesion in the differential diagnosis.

Adolescent↗
PubMed1996

[Determining the depth of infiltration in urinary bladder carcinoma with contrast medium enhanced dynamic magnetic resonance tomography. With reference to postoperative findings and inflammation].

OBJECTIVE: The purpose of this study was to evaluate dynamic contrast-enhanced magnetic resonance imaging for the staging of urothelial bladder carcinoma and to compare it with plain and contrast-enhanced spin-echo MRI. METHODS: Pre-operative MRI was carried out in 62 patients. Post-operative histological examination confirmed bladder carcinoma in 50/62 patients. Carcinoma was excluded in 12 patients. Beside spinecho MRI a dynamic contrast-enhanced study was performed immediately after IV application of Gd-DTPA using 10 sequential FLASH-2Dsequences, each with a duration of 15 s. Images were evaluated visually by three radiologists in a blinded fashion. RESULTS: In 41/62 patients pre-operative tumor staging with the dynamic contrast-enhanced study was confirmed by the histological examination after surgery. MRI with spinecho sequences yielded correct staging in 30/62 patients (P = 0.028). Staging of superficial bladder cancer was more accurate with dynamic contrast-enhanced MRI than with conventional MRI (P = 0.024). Overstaging was observed in some patients with stage pT1 tumors. Furthermore, postoperative changes of the bladder wall could be differentiated from cancer due to significantly earlier contrast enhancement of bladder cancer compared with postoperative and inflammatory alterations (P < 0.001). CONCLUSION: Contrast-enhanced dynamic MRI is a helpful addition in the presurgical T-staging of bladder cancer.

Adult↗
PubMed1996

[An interstitial miniature antenna for localized in vivo P-31 MR spectroscopy].

BACKGROUND: Phosphorus spectroscopy can be used to assess response in tumor therapy and to monitor response. An additional response parameter would be useful for individualization in oncological therapy. Methodical problems of localisation and contamination make it more difficult to interpret and reproduce the spectra. Interstitial and endoluminal spectroscopy antennas placed directly within or close to the tumor could provide help in this problem. MATERIAL AND METHOD: We developed an interstitial 31P MRS antenna together with a tuning network which can be used in thermometry catheters for hyperthermia within an internal lumen of 1.1 mm in diameter. A prototype of this type of miniature antenna suitable for use in Siemens MRI scanners at 1.5 T was described spectroscopically with regard to excitation profile, range and SNR. RESULTS: In terms of quality, the excitation profiles of the interstitial antennas in relation to orientation correspond to those of comparable but considerably larger endocavitary antennas and catheter coils for MR imaging and spectroscopy. Maximum sensitivity was achieved by aligning the coil normal perpendicular to the B0 field. Signal losses of up to 50% have to be reckoned with when using other orientations. The maximum range of the interstitial antenna was determined using spectroscopy and was found to be 5 mm, i.e. 9 times coil radius. The sensitivity (SNR, detection sensitivity) of the studied type of interstitial antenna allows in vivo 31P spectroscopy to be performed despite the unusually low axial dimension (coil radius r = 0.55 mm). The prototype of the described interstitial antenna was used to measure an in vivo spectrum from the back muscle of a rabbit in 10 min. Nevertheless, the detection volume of at least some ml necessary for 31P spectroscopy results mainly from the large antenna length. CONCLUSION: The sensitivity (SNR, detection sensitivity) of the interstitial antenna needs to be further improved in order to assess treatment response in patients. However, the construction principle is suitable for intracavitary 31P spectroscopy antenna with larger diameters, which can be used for advanced rectal, cervical and prostate carcinomas.

Animals↗
PubMed1996

[Computer graphics methods for 3-dimensional imaging of intrapulmonary space-occupying lesions of CT and MRI images].

AIM: To improve the pre-operative planning of interventional procedures in thorax surgery different methods of computer-graphical visualization of intrapulmonary lesions and adjacent anatomical structures based on CT and MR data were realized and compared to each other. DESIGN: In 21 patients with intrapulmonary lesions the image data was segmented by interactive and automatic algorithms and different reconstruction techniques were applied (maximum intensity projection; color-encoded and transparent surfaces; volume rendering). Based on these three-dimensional reconstructions, different views from arbitrary perspectives (including simulated endoscopic images) were generated and animated film sequences of the 3D scene were displayed with 30 frames/second. RESULTS: For all patients under review, a high-quality presentation of the relevant structures was obtained by use of the applied computer-graphical techniques. Even combinations of different visualization methods in one image can be generated with the software we developed. CONCLUSIONS: The various methods for image segmentation allow a fast and comfortable processing even of large data sets. The calculated values of tumor surface and volume can be used for quantitative studies and therapy control. The planning of surgical and interventional procedures can be supported by the simultaneous visualization of the intrathoracic lesion and the surrounding structures.

Aged↗
PubMed1996

[Perioperative evaluation of internal carotid artery stenoses: value of multislab MR angiography].

PURPOSE: Evaluation of the diagnostic potential of high resolution multislab 3D-TOF-magnetic resonance angiography (MRA) in the pre- and postoperative assessment of carotid artery stenosis in comparison to conventional angiography. METHODS: 120 Patients were evaluated with MRA and DSA prior to carotid endarterectomy (CEA). Additionally 26 patients underwent MRA after CEA. All MRA examinations were carried out on a 1.5 T MR-unit (Siemens Magnetom SP63) using a Helmholtz surface coil. For the visualization of the vascular structures in the head and neck region, flow compensated GE-sequences were employed. Both original MRA data set and MIP angiograms were included in the evaluation. The determination of the extent of stenoses was performed according to the recommendation of NASCET. RESULTS: In 195 (92.9%) of 210 cases included in the review MRA revealed the same results as DSA (grade I+II: 114, grade III: 24, grade IV: 44, grade V: 13). None of the cases showed a deviation higher than one grade. The sensitivity and specificity of hemodynamic relevant stenoses (> 60%) was 0.964 respectively 0.952. 23 out of 26 patients with postoperative follow-up examination revealed regular reperfusion of the former affected internal carotid artery. The remaining 3 patients showed a restenosis of the operated vessel (n = 2) and a reocclusion of the ICA after surgery (n = 1). MRA proofed to be an accurate and reliable method for the perioperative evaluation of vascular structures in the head and neck region. Despite of some drawbacks MRA reached a high accuracy in the diagnostic imaging before and after CEA. MRA is accurate and useful in screening carotid artery diseases. The indication of MRA employment therefore not only covers the screening of vascular structures but also includes pre- and postoperative evaluation of vascular stenoses.

Adult↗
PubMed1995

Downregulation of colony-stimulating factor-1 (CSF-1) binding by CSF-1 in isolated osteoclasts.

Colony-stimulating factor-1 (CSF-1), also called macrophage colony-stimulating factor, is the growth factor for the cells of the mononuclear phagocytic system. Furthermore, CSF-1 is essential in osteoclastogenesis and also affects mature osteoclasts. The receptor for CSF-1 was demonstrated on cells of the osteoclast lineage, with highest levels on the mature cells. This study investigated whether the binding of CSF-1 to isolated rat osteoclasts is modulated by the growth factor itself. Exposure of osteoclasts to CSF-1 for 1 hour virtually abolished binding of the growth factor. After removal of CSF-1, binding sites were restored within 4 hours. This recovery was blocked by cycloheximide, indicating the dependence on new protein synthesis for reexpression of receptors on the cell surface. The observed downregulation of CSF-1 binding sites might be a mechanism to control the effects of the growth factor on mature osteoclasts.

Animals↗
PubMed1995

Washout and redistribution between immediate and two-hour myocardial images using technetium-99m sestamibi.

The aim of this study was to assess whether a clinically relevant change in myocardial sestamibi activity could be documented within the first 120 min following injection (p.i.). In 17 patients planar anterior imaging of the heart was performed 5 min and 120 min p.i. During this time interval, mean decay-corrected myocardial activity declined to 77.9% +/- 9.7% after stress and to 85.7% +/- 7.9% after injection at rest (P < 0.05). In 19 patients with angiographically documented coronary artery disease, single-photon emission tomography was performed 5 min and 120 min after injection at maximum stress. For analysis, sestamibi activity was scored semiquantitatively in six left ventricular segments. Furthermore, sestamibi uptake was assessed quantitatively using a circumferential profile method. In 35 of 114 segments the score improved within 120 min p.i. (early fill-in); in these segments relative sestamibi activity rose from 69.9% +/- 22.5% to 74.5% +/- 20.8% (P < 0.01). In five patients this early fill-in was the only sign of exercise-induced hypoperfusion. In 7 of 114 segments the score deteriorated 120 min p.i. (early tracer washout); in these segments relative sestamibi activity declined from 85.6% +/- 9.9% to 80.1% +/- 10.7% (P < 0.02). In three of four patients with early tracer washout the corresponding coronary artery was significantly narrowed. In conclusion, a global myocardial sestamibi washout was registered within the first 120 min after injection. A fill-in of initial defects as well as an early tracer loss could be detected in a relevant number of patients with chronic coronary artery disease during the first 2 h p.i.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Circulation↗
PubMed1995

Cytokine production by calvariae of osteopetrotic mice.

In the osteopetrotic op/op mouse, the absence of macrophage colony-stimulating factor (M-CSF) prevents the growth of macrophages and osteoclasts and, consequently, bone resorption. In the present study, we investigated whether this deficiency in M-CSF production alters the production of cytokines in op/op bones. Calvariae of phenotypically normal (+/?) and op/op mice were stimulated in vitro with lipopolysaccharide or Pasteurella multocida toxin to produce cytokines. Interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) synthesis was the same both in calvaria from osteopetrotic and phenotypically normal animals. However, the production of granulocyte colony-stimulating factor (G-CSF), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF alpha) was lower in calvaria from op/op animals than was the case in +/? calvaria. Thus, the lack of biologically active M-CSF causes defects which are not compensated by cells independent of M-CSF.

Animals↗
PubMed1995

Detection of transcripts and binding sites for colony-stimulating factor-1 during bone development.

Colony-stimulating factor-1 (CSF-1), originally characterized as the growth factor for the cells of the mononuclear phagocytic system, has been shown to be essential for osteoclast formation. The aim of the present study was twofold: (i) to investigate the expression of transcripts encoding CSF-1; and (ii) to detect binding sites for CSF-1 during bone development. As a model, metatarsal rudiments from embryonic mice of different ages were used, an in vivo system allowing one to follow osteoclast formation. In 16-day-old embryos, proliferating osteoclast precursors are located on the outer surface of the rudiments. They differentiate subsequently to post-mitotic precursors. At 18 days, the precursors fuse and the mature osteoclasts invade the mineralized cartilage of the rudiments to excavate the future bone marrow cavity. Within this study, in situ hybridization on sections of whole paws from 17-day-old embryos revealed CSF-1 transcripts to be present in cells lining the outside of the midregion of the metatarsals. One day later, cells containing CSF-1 mRNA were found within the mineralized cartilage. The levels of transcripts encoding CSF-1 were further increased in the bone rudiments of newborn animals. Binding sites for CSF-1 on cells in close proximity of the metatarsals were detected at embryonic age 17 days, but not before. At this stage, cells binding CSF-1 were located on the periosteum of the midregion of the metatarsal rudiment. At 18 days, cells expressing high levels of CSF-1 binding sites had invaded the mineralized cartilage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[The correction for motion and visualization of subtraction angiographic data from the spiral CT].

Conventional image subtraction of CT sequences is hampered by extended motion artifacts. In this paper a motion correction procedure for the subtraction of images from two time-separate CT investigations is introduced. Native images are obtained in the first CT sequence, and a contrast medium examination is imaged in the second. The aim of image subtraction is sole presentation of the contrast medium. In contrast to conventional digital subtraction angiography (DSA), CT angiography rules out the possibility of direct image subtraction due to occurrence of extended motion artifacts in the time-shifted images. Such shortcomings can now be corrected by means of a new registration method developed for determination of local displacement vectors between the two images. This motion pattern is used to compute a new synthetic mask of maximum congruence with the contrast medium image. The resulting three-dimensional data record is presented by means of a special-purpose hardware enabling fast rotations and cut planes. New diagnostic possibilities can be achieved such as the creation of views that are not obtainable with conventional modalities and the assessment of calcified vessels.

Angiography, Digital Subtraction↗
PubMed1995

[Quantification of signal modulation of hematopoietic bone marrow in gradient echo sequences. Results of phantom and proband studies with simultaneous determination of T2* relaxation times].

The signals from spongy bone on gradient echo sequences depend on the fat and water proton content as well as the differences in magnetic susceptibility at the border between the trabeculae and the bone marrow. From the signal intensities for different echo times, signal modulation was quantified by a special algorithm and at the same time the T2 relaxation time was calculated. Using a fat-water phantom, it was shown that the product of the initial fat and water signal intensity (modulation coefficient) is applicable to indicate the extent of signal modulation and thereby the chemical shift and, moreover, to indicate changes in the fat/water ratio sensitively. In 16 individuals of different ages (23 to 64 years, average 42.4 years) there was a tendency for the T2 relaxation time from the spongiosa of lumbar vertebrae to increase with age, this can be explained by a reduction in the trabecular content, causing reduction in the magnetic inhomogeneity of the bone marrow. The results indicate the usefulness of the sequence and the mathematical model for evaluating the spongy bone in cases of osteoporosis and of malignant haematological disorders.

Adult↗
PubMed1995

[High-resolution magnetic resonance tomography (HR-MRT) of the pleura and thoracic wall: normal findings and pathological changes].

AIM: To determine the value of high-resolution MRI in pleural and chest wall diseases, the normal and pathologic costal pleura and adjacent chest wall between paravertebral and the axillary region were examined with contrast enhanced high-resolution T1-weighted MRI images using a surface coil. MATERIAL AND METHODS: Normal anatomy was evaluated in 5 healthy volunteers and a normal specimen of the thoracic wall, and correlation was made with corresponding HR-CT and histologic sections. CT-proved focal and diffuse changes of the pleura and the chest wall in 36 patients underwent HR-MRI, and visual comparison of MRI and CT was done retrospectively. RESULTS: Especially sagittal T1-weighted HR-MRI images allowed accurate delineation of the peripleural fat layer (PFL) and the innermost intercostal muscle (IIM), which served as landmarks of the intact inner chest wall. PFL and IIM were well delineated in 3/4 patients with tuberculous pleuritis, and in all 7 patients with non-specific pleuritis, as opposed to impairment of the PFL and/or the IIM, which was detected in 15/18 malignancies as a pattern of malignant chest wall involvement. In one case of tuberculous pleural empyema with edema of the inner chest wall HR-MRI produced false positive diagnosis of malignant disease. CONCLUSION: HR-MRI images improved non-invasive evaluation of pleural and chest wall diseases, and allowed for differentiation of benign and malignant changes.

Adult↗
PubMed1995

[The value of in-vivo 31-phosphorus spectroscopy in the diagnosis of generalized muscular diseases. The clinical results and the differential diagnostic aspects].

PURPOSE: In a prospective study, characteristics and the diagnostic potential of in vivo 31-phosphorus spectroscopy in cases of generalised muscle diseases were analysed. METHOD: 41 patients with myogenic and neurogenic muscle diseases and 11 healthy volunteers were examined using MRI and in vivo 31-phosphorus spectroscopy by means of a 50 mm double-tuned surface coil. RESULTS: The spectra showed significant changes of the metabolite ratios depending on the degree of the disease. Inflammatory muscle diseases were characterised by increased PME and PDE peaks, which indicates that there is a higher conversion of the cell membrane. The spectra of muscular dystrophy showed a slight increase of PDE and Pi. A strongly reduced PCr and an increased Pi peak were demonstrated in cases of muscle atrophy depending on their degree of markedness. The pH values were minimally increased in comparison to the volunteers. In other muscle diseases, such as glycogenosis or myotonia, no significant changes were detected. CONCLUSION: Standardised in vivo 31-phosphorus spectroscopy of generalised muscle diseases provides noninvasive prognostic information on the type and behaviour of the disease and is complementary to clinical and histological findings.

Adolescent↗