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Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 415 records · Page 23Linked to original sources
PubMed1995

[Spontaneous osteonecrosis of the knee joint: MRT compared to CT, scintigraphy and histology].

PURPOSE: We compared MR imaging with scintigraphy and CT in eight patients with spontaneous osteonecrosis of the knee. The histological changes accounting for the MR signal abnormalities were evaluated. METHODS: Eight patients with spontaneous osteonecrosis of the knee joint underwent MR imaging before and after i.v. administration of Gd-DTPA. Nuclear scintigraphy was performed in all 8 patients, three patients also had CT scans of the knee area. Histologic correlation was available in three patients. RESULTS: Increased radionuclide uptake was observed in all patients. In one patient, however, scintigraphy showed increased radionuclide uptake consistent with osteonecrosis only in the medial femoral condyle, while MR imaging demonstrated osteonecrosis both in the medial as well as the lateral femoral condyles. MR demonstrated areas of low signal intensity on precontrast T1-weighted images in the femoral condyle in all patients. All these areas showed high signal intensity on T2-weighted images. On postcontrast T1-weighted images, signal intensity increase was either homogeneous throughout the lesion or it was seen at the periphery of the lesion in a band-like pattern. Histologically, the areas of high signal intensity on T2-weighted and on postcontrast T1-weighted images corresponded to granulation tissue. CONCLUSION: MR imaging detects granulation tissue adjacent to the necrotic zone. Using morphological and signal intensity criteria, MR imaging can be utilised to differentiate spontaneous osteonecrosis of the knee from osteochondritis dissecans, degenerative osteoarthritis, and other conditions affecting the knee joint.

Aged↗
PubMed1995

[Spiral CT of the pancreas. A clinical comparison with conventional CT and dynamic CT].

PURPOSE: Spiral CT is compared with the dynamic CT and the conventional CT with regard to the enhancement of the pancreas and peripancreatic vessels and the visualisation of anatomic details. METHODS: In 15 patients spiral CT of the pancreatic region was performed in the arterial phase followed by spiral CT of the upper abdomen in the arterial-venous phase. In 30 patients dynamic CT (n = 15) and spiral CT (n = 15) of the pancreatic region was performed in the arterial phase followed by conventional CT of the upper abdomen. RESULTS: Compared with dynamic CT, spiral CT of the pancreatic region in the arterial phase (flow 4 ml/s, delay 15-18 s) leads to a stronger contrast of the peripancreatic vessels (p < 0.001) and the pancreas (108 vs. 86 HU) (p < 0.05). In the following spiral CT of the upper abdomen (flow 1 ml/s, delay 70 s), a high enhancement of both arteries and veins could be achieved. Intrapancreatic structures and peripancreatic vessels were better seen in the spiral CT than in the conventional CT (p < 0.05) and p < 0.005, respectively). CONCLUSION: The combination of spiral CT of the pancreatic region in the arterial perfusion phase and spiral CT of the upper abdomen in the arterial-venous phase enables an optimal enhancement of the pancreas and the abdominal vessels and a reliable visualisation of anatomic details.

Artifacts↗
PubMed1995

[MR-guided laser-induced thermotherapy in tumors of the head and neck region: initial clinical results].

PURPOSE: To analyse the value of MR-guided laser-induced thermotherapy (LITT) for palliative treatment of recurrent tumours of the head and neck region. MATERIAL AND METHODS: 8 patients with recurrent tumours of the head and neck region (squamous cell carcinomas n = 6, pleomorphic adenomas n = 2) underwent MR-controlled LITT. A 7 French laser applicator was inserted under local anaesthesia into the centre of the recurrent tumour. A Nd:YAG laser with a wavelength of 1064 nm was used. Therapy was monitored on-line using special MR thermosequences. RESULTS: Preinterventional contrast-enhanced MRI revealed a recurrent tumour of the head and neck region for all eight patients. All patients tolerated the procedures well under local anaesthesia, with no clinically relevant side effects. The MR thermosequences depicted up to 15 mm diameter areas of less signal near the laser tip. Postinterventional contrast-enhanced MRI revealed hypovascularized areas due to the resulting coagulative necrosis. Coagulative necrosis of 4 cc to 28 cc occurred in all patients, and a reduction of clinical symptoms was achieved in five. CONCLUSION: The results obtained indicate that minimal invasive LITT can be a therapeutic alternative for palliative treatment of head and neck tumours.

Adenoma, Pleomorphic↗
PubMed1995

Changes of fluid-dynamic parameters in peripheral stenoses with transcutaneous interventions.

UNLABELLED: Peripheral vessels provide a useful in vivo haemodynamic model allowing evaluation of local intravascular fluid dynamics. Velocity measurements using a 0.018 inch Doppler-tipped angioplasty guidewire, quantitative angiography and laboratory data were gathered from 45 patients with a total of 48 percutaneous transluminal laser assisted angioplasties (PTLA) in the superficial femoral, in the iliac, in the popliteal artery and in the peroneal artery. From these data, blood flow, whole blood viscosity, Reynold's numbers, Womersley numbers and shear stress were calculated, evaluated as to their changes post PTLA and correlated with clinical improvement at early follow-up. The clinical result was quantified as categorial improvement according to the American Heart Association guidelines. The primary angiographic results of angioplasty were satisfactory in all patients. Clinically 17/45 patients showed a marked, 6/45 a moderate, 18/45 a minimal, and 4/45 no improvement. The mean values of maximal peak velocity at stenosis decreased from 235 +/- 28 cms-1 to 84 +/- 8 cms-1 after PTLA (P < 0.01). The minimal intrastenotic cross section increased from 7.7 +/- 0.9 to 21.9 +/- 1.6 mm2 (P < 0.01). Mean trans-stenotic flow increased after intervention by about 50% (P < 0.01) and improved further by 135% after administration of adenosine triphosphosphate i.a. (P < 0.01). Reynold's numbers were elevated intrastenotically (1285 +/- 198) pre-intervention as compared to values proximal (564 +/- 81) and distal (449 +/- 66) to the stenosis and were reduced significantly (P < 0.05) at stenosis by PTLA, whereas values proximally and distally increased significantly (P < 0.01) post PTLA (proximal 829 +/- 84, intra 773 +/- 107, distal 676 +/- 98). Shear stress, reflecting mechanical interaction between flow and vessel wall, was elevated at stenosis pre-intervention to 44 +/- 8.9 Pa and reduced at post-stenoric vessel sites to 2.4 +/- 0.5 Pa. PTLA caused a decrease in stenosis to 6.3 +/- 1 Pa (P < 0.01) and an increase distally to 4.6 +/- 1 Pa (P < 0.01). Whereas in single stenoses removal of the obstruction was associated with a significant (P < 0.05) increase in trans-stenotic flow and shear stress distally, there was only auenuated increase in trans-stenotic flow in multiple lesions despite an angiographically good PTLA result. Shear stress distally remained low in those patients. Velocities and Reynold's numbers were lower in these vessels even pre PTLA. Residual flow, Reynold's number and minimal cross-section pre-intervention correlated significantly with clinical outcome. Pooling cases with no or minimal, as opposed to those with marked or moderate improvement, 81% of patients were correctly classified using the Reynold's numbers pre- and post-PTLA. CONCLUSION: Peak velocity monitoring is feasible and safe during angioplasty. Velocity provides clinically relevant physiological information in addition to angiography. Combining quantitative angiography, velocity measurements and laboratory data allow the calculation of blood flow, Reynold's numbers and shear stress, thereby providing complex fluid dynamic information. Thus the evaluation of haemo-dynamics in single and multiple obstructions before and after intervention is improved. Fluid dynamic parameters pre-and post-PTLA are significantly correlated with clinical short-term result.

Adult↗
PubMed1995

Role of high-resolution magnetic resonance imaging for differentiating melanin-containing skin tumors.

RATIONALE AND OBJECTIVES: The aim of the study was to evaluate the use of high resolution magnetic resonance imaging (MRI) for differentiation of melanin-containing skin tumors. METHODS: Twenty-seven melanocytic nevi and 18 malignant melanomas were examined by high resolution MRI. Signal intensities and signal-to-noise (SNR) and contrast-to-noise ratios (CNR) of the tumors were determined in enhanced (T1, T2, water-suppression, and fat-suppression sequences) and contrast-enhanced images (T1 and fat-suppression sequences). The differences were tested for significance by a Wilcoxon test. RESULTS: Malignant melanomas differed from melanocytic nevi in that they displayed a higher SNR in T2-weight and unenhanced and contrast-enhanced fat-suppression scan. Malignant melanomas exhibited a higher CNR than did benign lesions in unenhanced and contrast-enhanced fat-suppression sequences with dermis as reference tissue (P < 0.05) and in enhanced fat-suppression sequences with subcutis as reference tissue (P < 0.05). CONCLUSIONS: The usefulness of SNR and CNR analysis on MRI for the differentiation of malignant skin tumors from benign skin tumors of the melanin-containing system is limited. Clinical and histologic examinations are, further, the important step in evaluation of melanin-containing skin tumors.

Adipose Tissue↗
PubMed1995

Telemedicine in rural areas. Experience with medical desktop-conferencing via satellite.

Cooperation between physicians in hospitals in rural areas can be assisted by desktop-conferencing using a satellite link. For six weeks, medical desktop-conferencing was tested during daily clinical conferences between the Virchow-Klinikum, Berlin, and the Medical Academy, Wroclaw. The communications link was provided by the German Telekom satellite system MCS, which allowed temporary connections to be established on demand by manual dialling. Standard hardware and software were used for videoconferencing, as well as software for medical communication developed in the BERMED project. Digital data, such as computed tomography or magnetic resonance images, were transmitted by a digital data channel in parallel to the transmission of analogue video and audio signals. For conferences involving large groups of people, hardware modifications were required. These included the installation of a video projector, adaptation of the audio system with improved echo cancellation, and installation of extra microphones. Learning to use an unfamiliar communication medium proved to be uncomplicated for the participating physicians.

Germany↗
PubMed1995

Induction of classical lactotropes by epidermal growth factor in rat pituitary cell cultures.

Long term incubation of pituitary tumor GH3 cultures with epidermal growth factor (EGF) induces reciprocal changes in PRL and GH production. However, it is not known whether EGF alters the cellular composition of these cultures. Another unanswered question is whether chronic treatment with EGF stimulates PRL secretion from nonneoplastic pituitary cells. In this study, GH3 cells and pituitary cells from neonatal (10-day-old) rats were cultured for 6 and 2 days, respectively, in the absence or presence of 5 nM EGF. Cells containing PRL and/or GH were then enumerated using light microscopic immunocytochemistry. In addition, neonatal pituitary cells were subjected to reverse hemolytic plaque assays for PRL. EGF treatment drastically increased the proportion of classical lactotropes (cells that secrete only PRL) in the GH3 cultures, from about 0.5% to 8% of all cells, without modifying the percentage of GH-positive cells. A similar action of EGF was observed in the primary cultures. Moreover, EGF enhanced by 240% the amount of PRL secreted from the neonatal lactotrope population during 1-h incubations under basal conditions. This effect was mediated by a selective increase in the relative number of PRL secretors forming large plaques. The results suggest that EGF promotes the differentiation of classical lactotropes in both GH3 cultures and pituitary cultures from neonatal rats, and that these cells are characterized by a high basal rate of PRL secretion.

Animals↗
PubMed1995

Cervical lymphadenopathy: ratio of long- to short-axis diameter as a predictor of malignancy.

The purpose of this study was to evaluate short- and long-axis diameters of enlarged cervical lymph nodes with ultrasonography and to determine whether the long-to-short axis (l/s) ratio is a valid diagnostic parameter in the differentiation between benign and malignant nodal disease. 730 enlarged cervical lymph nodes in 285 patients were examined with ultrasound. The short- and the long-axis diameters of each enlarged node were measured and the l/s ratio calculated. Definite diagnoses of the nodes were obtained by histological examination following neck dissection. 95% of enlarged cervical nodes shown on ultrasound to have a l/s ratio of more than 2 were correctly diagnosed as benign. Nodes presenting with a more circular shape and a l/s ratio of less than 2 were diagnosed correctly as metastases with 95% accuracy. The l/s ratio of lymph nodes thus provides an excellent criterion for differentiation between benign and malignant enlargement in cervical lymphadenopathy.

Adult↗
PubMed1995

[Ultrasound detection of breast cancer with normal mammogram].

In eleven patients with breast cancer the diagnosis was made by using ultrasound as the only method. In none of the patients could mammography show the malignoma. Although six of the patients underwent additional tube X-ray investigation, no radiological criteria of malignancy were found on the mammograms. In ten patients a lump of the breast was palpable and/or retraction of the skin was visible. In one woman, neither the clinical investigation nor the mammography could reveal the tumor. The ultrasound of the breast is a indispensable and useful method for diagnosing breast cancer.

Adult↗
PubMed1995

[Megadolichobasilar artery as a rare cause of hydrocephalus internus: synopsis of modern imaging methods].

Megadolichobasilarartery (MDB), i.e. the widened, elongated and tortuous course of the basilar artery, has been the topic of numerous publications; about 350 cases have been reported world-wide. It can cause many symptoms; isolated or combined cranial nerve lesions and ischemic or hemorrhagic changes are the most frequent. A hydrocephalus internus is a rare occurrence and many patients do not exhibit any symptoms. To date, angiography, computed tomography, and to an increasing extent magnetic resonance imaging (MRI) are the principal methods for diagnosis of MDB. Angiographic-like representations with CT and MRI are further developments which represent an alternative to angiography. With the help of special MRI sequences, furthermore, non-invasive CSF flow measurements for the etiologic evaluation of a hydrocephalus can be performed. For the example of a patient with MDB and hydrocephalus internus, the possibilities of modern imaging techniques are presented and discussed.

Basilar Artery↗
PubMed1995

[MR urography with the T2-weighted turbo-spin-echo sequence].

Tumor-induced dilatation of the urinary tract is difficult to diagnose in the distal part of the ureter, including the stenosis, by ultrasound and X-ray. Often on account of renal insufficiency and allergy, i.v.-contrast media cannot be used. The present study should show the suitability of fast T2-weighted (turbo-) spin-echo sequences (T2-TSE) for MR-urography (MRU). Seven patients (62.3 +/- 6.1 years) were examined in the coronal plane with T2-TSE sequence (TR = 4500 ms, TE = 160 ms) and an MRU was calculated by using the MIP method (maximal intensity projection). This technique enabled urogram-like morphological representation of dilated urinary tract including stenosis in 6 of 7 patients. Assuming a high magnetic field homogeneity, MRU by using a T2-TSE-sequence, without i.v.-contrast media administration, can visualize the urinary tract dilatation and localize tumor-induced stenosis.

Adult↗
PubMed1995

[Comparison of the diagnostic value of CT and MRI in injuries of the cervical vertebrae].

The aim of our study was to compare the diagnostic capacities of computed tomography (CT) and magnetic resonance imaging (MRI) in the diagnostic evaluation of acute cervical spinal column injuries. We examined 39 patients with cervical spine injury suspected either clinically or by plain radiography, or even confirmed. In 30 patients, 86 acute traumatic lesions were observed in the area of the cervical spine, 83% of which were retrospectively recognisable by CT and 95% on MRI films. In nine patients, no acute traumatic pathologic pattern could be found either by CT or by MRI or any other subsequently employed diagnostic methods. CT yielded 100% of the osseous acute traumatic findings, the degenerative lesions narrowing the spinal channel, and of the dislocations, but only 33% of the lesions of the longitudinal ligaments, 50% of intramedullary haemorrhages, 60% of paravertebral soft tissue haematomas, 83% of vertebral disc herniations of protrusions, and none of the six nonhaemorrhagic spinal cord contusions. Without exception, MRI revealed all the traumatic medullary and paravertebral soft tissue changes, dislocations, and spondylophytes narrowing the spinal channel, but only 50% of the C2-odonteous fractures, 89% of the transverse processes', and 92% of the vertebral lamina fractures. Basing on these results, after primary plain film radiograph imaging, the performance of MRI seems to be recommendable prior to CT in diagnostic evaluation of traumatic cervical spinal lesions, if possible with regard to the patient's clinical state and the global organization, unless immediate CT imaging of other body regions (i.e. of the head) is already being planned anyway, Nevertheless, MRI should not be abandoned within the overally framework of this disease pattern.

Adult↗
PubMed1995

[Radioisomorphisms of sclerosing cholangitis].

For differentiation of Primary Sclerosing Cholangitis (PSC) from AIDS-associated cholangitis (AAC), 95 CT or Cholangiography studies of 37 patients were reviewed and signs of biliary disease analysed. Only two each of PSC and AIDS-subjects were free from biliary lesions compatible with some kind of sclerosing cholangitis. Subgroup analysis revealed wide overlapping of morphological findings in PSC and AAC. We conclude that radioisomorphism of etiologically different forms of sclerosing cholangitis may indicate pathophysiologically similar courses.

AIDS-Related Opportunistic Infections↗
PubMed1995

[Estimating patient dose in computerized tomography].

This paper presents a model for the estimation of the effective patient dose in computed tomography. It is demonstrated how equivalent organ doses for selected examination can be estimated on the basis of the scanner-specific axis dose and published conversion factors. Problems and limitations of this method are discussed. The determination of the effective dose from the organ equivalent dosis is explained. The explanations are illustrated by an exemplary calculation, and the doses of the most important CT examinations are summarised.

Body Burden↗
PubMed1995

[Diagnosis of cerebral metastasis with standard dose gadobutrol vs. a high dose protocol. Intraindividual evaluation of a phase II high dose study].

PURPOSE: To assess the effectiveness and safety of normal and high doses of Gadobutrol versus a standard dose of Gadolinium DTPA in the MR evaluation of patients with brain metastases. MATERIAL AND METHODS: In a clinical phase-II study 20 patients who had been diagnosed as having brain metastases with CT or MRT were studied prospectively with Gadobutrol, a new nonionic, low osmolality contrast agent. Each patient received an initial injection of 0.1 mmol/kg body weight and an additional dose of 0.2 mmol/kg Gadobutrol 10 min later. Spin-echo images were obtained before and after the two applications of Gadobutrol. Dynamic scanning (Turbo-FLASH) was performed for 3 min after each injection of the contrast agent. Both quantitative and qualitative data were intraindividually evaluated. The primary tumor was a bronchial carcinoma in 11 cases; in 9 other cases there were different primary tumors. RESULTS: Forty-eight hours after the use of Gadobutrol there were no adverse signs in the clinical examination, vital signs or blood and urine chemistry. Statistical analysis (Friedman test and Wilcoxon test) of the C/N ratios between tumor and white matter, percentage enhancement, and visual assessment rating revealed statistically significant superiority of high-dose Gadobutrol injection in comparison to the standard dose. The percentage enhancement increased on average from 104% after 0.1 mmol/kg to 162% after 0.3 mmol/kg Gadobutrol. Qualitative delineation and contrast of the lesions increased significantly. The use of high-dose Gadobutrol improved the detection of 36 additional lesions in 6 patients. CONCLUSION: The first in vivo results prove the excellent contrast capacity of the nonionic contrast agent Gadobutrol for the diagnosis of intracerebral metastases.

Adult↗
PubMed1995

[The use of an early postoperative interstitial-hyperthermia combination therapy in malignant gliomas].

BACKGROUND: The survival of people suffering from malignant gliomas (WHO level III and IV) is predominantly limited by local progress in the primary tumor region. Interstitial hyperthermia combined with radiotherapy or chemotherapy is one approach for the intensification of local therapy. It is possible to combine (partial) tumor resection with hyperthermia as well as with brachytherapy by implanting catheters intraoperatively. PATIENTS AND METHODS: A pilot study was performed to examine practicality, tolerability, effectiveness and scope for improvement in early postoperative hyperthermia treatment following catheter implantation as part of (partial) tumor resection. Each CT data set was transferred into a VAX 3100 workstation for retrospective analysis of the hyperthermia treatment. The implanted catheters were segmented and the distributions of power density and temperature were simulated. We sought to achieve the best possible temperature distributions by optimising the catheter arrangement in the planning calculations. The corresponding Ir-192-source brachytherapy treatments were simulated in a similar way using the implanted, as well as optimised catheter arrays. RESULTS: Intraoperative catheter implantation in 4 patients was problem-free. Postoperative complications were not observed, neither were infections. Interstitial microwave hyperthermia in combination with percutaneous irradiation or chemotherapy a few days after the operation was also tolerated well by all patients. Effective temperatures (of at least 42 degrees C) were regularly achieved at measurement points, but the temperature distributions were unsatisfactory, with T90 values (the temperature reached in at least 90% of the target volume) of under 38 degrees C. Measured temperature/position curves showed qualitative correlation with the simulated calculations. The catheter positions determined by optimisation varied significantly from the positions clinically used. CONCLUSIONS: Early postoperative combination therapy using hyperthermia for the treatment of malignant gliomas is a very practical approach. The optimisation strategies described should be used preoperatively to plan catheter arrays for interstitial hyperthermia and brachytherapy, and these arrays should be implanted using stereotaxic surgery.

Antineoplastic Agents↗
PubMed1995

[Roentgen diagnosis of body packers--radiological and forensic considerations].

The diagnostic value of abdominal ultrasonography and plain abdominal radiographs for the detection or exclusion of body smugglers was investigated prospectively. Both methods showed equally high sensitivity and specificity in the detection of swallowed drug packages. Possibilities for misinterpretation of physiological abdominal contents are illustrated. In addition to the radiological aspects, the legal implications of the subject are discussed.

Adult↗