Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 541 records · Page 30Linked to original sources

PubMed1992

["Surgical projection" in the gadolinium-DTPA (Gd-DTPA)-supported NMR tomographic diagnosis of lateral lumbar disk prolapse].

In a group of 25 patients the coronal views of plain and Gd-DTPA-enhanced MRI studies were correlated with CT and operative findings. All series included sagittal, transverse and coronal FLASH sequences (GE 500/6, flip angle 70 degrees), sagittal proton density-(SE 2500/15) and T2-(SE 2500/70) weighted images. MR diagnosis proved to be correct in all cases. Compared to CT and axial MRI herniated disk material in the lateral intravertebral space and its relationship to nerve roots was demonstrated more clearly on coronal views.

Adult↗

PubMed1992

[The regional cerebral circulation in infarct patients. Rapid dynamic T2*-weighted MRT after a bolus injection of gadolinium-DTPA].

The aim was to validate the MRI assessment of regional cerebral blood flow. Measurements were performed on a 1.5 T imaging system using a fast T2*-weighted gradient-echo sequence. After intravenous injection of gadolinium-DTPA 30 images were acquired in the same slice position during 84 seconds. In 12 volunteers we observed a symmetrical cortical decrease of signal intensity during the passage of the contrast medium. In 9/23 patients with impairment of cerebral blood flow a circumscribed area of reduced signal intensity decrease (hypoperfusion) was found. In 4/23 patients the decrease of signal intensity was more pronounced than in normals (hyperfusion). In 9/23 patients signal intensity changes were normal. HMPAO-SPECT confirmed successful MRI assessment of cerebral blood flow in 22/23 patients.

Cerebral Infarction↗

PubMed1992

[Magnetic resonance tomographic screening studies of the bone marrow with gradient-echo sequences. II. Gadolinium-DTPA-supported studies of plasmocytoma patients].

MR imaging was performed in 19 patients with proven multiple myeloma. Both plain and Gd-DTPA enhanced in-phase and opposed-phase gradient-echo techniques were used (0.1 mmol Magnevist/kg body weight). Plain, opposed-phase imaging demonstrated more lesions than plain in-phase imaging (35 vs. 16); enhanced opposed-phase imaging demonstrated more lesions than plain opposed-phase and enhanced in-phase imaging (47 vs. 35 and 17 lesions). These results suggest that enhanced opposed-phase images which have a high contrast between normal and infiltrated bone marrow are especially suited for MR screening in multiple myeloma.

Bone Marrow↗

PubMed1992

[Computed tomography: the TNM staging of laryngeal carcinoma].

In 64 patients with malignant lesions of the larynx, CT and microlaryngoscopy (ML) were evaluated in terms of T-staging. Histological information was present in all cases following operation. CT showed an accuracy of 90% in T-staging. ML showed an accuracy of only 71% of correct T-staging. CT is superior to ML particularly in distinguishing between stages T3 and T4 and T1 and T2. CT tends to overestimate tumour stage whereas ML tends to underestimate it. CT was also compared with palpation and sonography as regards N-staging. In this respect sonography has the highest accuracy (94%) followed by palpation (76%) and CT (74%).

Carcinoma↗

PubMed1992

[Magnetic resonance tomography (MRT) in pleural diseases. A comparison with CT and histopathological findings].

The MRI and CT appearances in 48 patients with histologically confirmed benign and malignant pleural abnormalities were compared retrospectively. Abnormal pleural changes were shown in 47 out of the 48 patients by high signal intensity of the pleura in T2-weighted sequences and in contrast enhanced T1-weighted sequences on MRI. CT showed abnormalities in 45 out of 48 patients. Delineation of pleural and pulmonary changes by CT was possible in 13 out of 23 cases, and pleural disease from effusions in 15 out of 28 cases. T2-weighted MRI was successful in 14 out of 23 and 4 out of 28 cases, respectively. T1-weighted images after contrast were successful in 20 out of 23 and 22 out of 28 cases, respectively. Indications of malignant pleural disease were the presence of mediastinal or circumferential involvement or involvement of the entire pleura, thickness of more than 10 mm and nodular changes. The most reliable sign of malignancy was infiltration of the thoracic wall and the diaphragm; this was better demonstrated by MRI (18 out of 19 and 2 out of 2 cases) than by CT (14 out of 19 and 0 out of 2 cases).

Adult↗

PubMed1992

[The regional blood flow in intracranial tumors: a comparison of HMPAO-SPECT with a newer magnetic resonance tomographic procedure].

We compared the value of gadolinium-enhanced first-pass MRI perfusion studies and HMPAO-SPECT for the assessment of regional cerebral blood flow in a prospective study of 23 intracranial tumour patients. In five tumours with homogeneous hypoperfusion and eight tumours with homogeneous hyperperfusion, tumour blood flow patterns in MRI and HMPAO-SPECT were similar. By contrast, in ten patients with inhomogeneous tumour blood flow pattern only MRI was able to differentiate between tumour areas with no or low flow, tumour tissue with high flow, and perifocal oedema with reduced flow. In HMPAO-SPECT, these inhomogeneous tumours were represented as areas of homogeneously reduced tracer retention corresponding to different tumour constituents and perifocal oedema. In conclusion, the high spatial resolution of MRI enables a detailed analysis of tumour blood flow.

Brain↗

PubMed1992

[The determination of cerebral dopamine (D2) receptor density by using 123I-IBZM-SPECT in Parkinson disease patients].

An alteration of the dopaminergic nigrostriatal system is believed to be the main pathogenetic factor of Parkinson's disease (PD). We report on our initial results on the determination of the post-synaptic dopamine-D2-receptor binding of 123I-IBZM in patients with PD. Drug-native patients showed a significantly higher IBZM binding in the basal ganglia as compared to patients on specific dopaminergic medication. Age, duration of the disease and the severity of the disease do not seem to influence the IBZM-receptor binding. We conclude that 123I-IBZM-SPECT is an extremely useful tool for the evaluation of the functional state of cerebral dopamine-D2-receptors.

Aged↗

PubMed1992

[The magnetic resonance tomographic differential diagnosis between reactively enlarged lymph nodes and cervical lymph node metastases].

A prospective study was carried out involving 27 patients to determine whether MRT can distinguish between lymph node metastases and reactive lymph node enlargement. The results of MRT were compared with the pathological findings. Using T1 and T2 weighted sequences and proton density sequences it was not possible to differentiate between reactively enlarged lymph nodes and lymph node metastases. Following the administration of Gd-DTPA the observation of central hypo-intensity with marginal hyper-intensity is a reliable sign of a lymph node metastasis. Using the criterion of length greater than 10 mm for lymph node metastases results in a specificity of 32% and sensitivity of 75%. The use of the sonographic maximal/cross measurement quotient > 2 in the axial/coronary/sagittal dimension improves specificity and sensitivity to 94%.

Contrast Media↗

PubMed1992

[Magnetic resonance tomography in the follow-up after the embolization of arteriovenous malformations of the central nervous system].

Interventional embolisation is an accepted treatment for intracranial or spinal arteriovenous malformations. Since multiple embolizations are often required, noninvasive repeatable follow-up studies are desirable. The aim of this study is to demonstrate the usefulness of T2-weighted images, MR angiography, and gadolinium-DTPA first-pass studies for post-embolisation follow-up studies. Five patients with arteriovenous malformations, four cerebral and one spinal, were studied prospectively before and repeatedly after single or multiple embolizations. A total of 26 MRI studies (1.5 T Magnetom, Siemens AG) were performed. The combination of T2-weighted images, MR angiography, and gadolinium-DTPA first-pass studies nicely demonstrated the arteriovenous malformations and the effect of embolisation which ranged from negligible to almost complete. While contrast-enhanced T1-weighted images and contrast-enhanced MR-angiography seemed to be of little more value than unenhanced studies, gadolinium-DTPA first-pass studies appeared to be more sensitive than T2-weighted images or MR-angiography because of their high intrinsic sensitivity to regional blood flow and volume. In the spine, T2-weighted images and MR-angiography were too insensitive to detect arteriovenous malformations, whereas gadolinium-DTPA first-pass studies sensitively detected the malformation and the changes after embolizations.

Adult↗

PubMed1992

Acetazolamide stimulation test in patients with unilateral internal carotid artery obstructions using transcranial Doppler and 99mTc-HM-PAO-Spect.

Fifteen patients with symptoms of cerebral ischaemia and angiographically confirmed unilateral stenoses or occlusions of the extracranial internal carotid artery (ICA) and 20 controls were studied by a 2 MHz transcranial Doppler (TCD) at rest and after stimulation with 1 g acetazolamide i.v., a cerebral vasodilator. In addition, the patients underwent 99mTc-HM-PAO-Spect measurement of regional cerebral blood flow (rCBF) at rest and after stimulation with 1 g acetazolamide. In 10 patients with ICA stenoses greater than 80% or occlusions, time-mean velocity (Vmean) increase and pulsatility index (PI) decrease in the postobstructive middle cerebral artery (MCA) as well as the increase of the ipsilateral rCBF were reduced in comparison with the contralateral side. The remaining 5 patients showed a normal Vmean increase and PI decrease in TCD.

Acetazolamide↗

PubMed1992

Effect of Pasteurella multocida toxin on bone resorption in vitro.

Pasteurella multocida toxin (PMT), which is the primary etiologic factor in the pathogenesis of progressive atrophic rhinitis in pigs, was found to stimulate bone resorption in vitro. This stimulation was observed both in cultures of murine calvaria by measuring the release of calcium and of the lysosomal enzyme beta-glucuronidase and in murine long bone cultures by measuring the release of calcium. Both systems showed the same dose response curve, with the maximal effect at a concentration of 5 ng/ml. The effect on calvaria was studied in more detail. PMT increased bone resorption 24 h after its addition and always had to be present to express an effect. Calcitonin was able to inhibit this increase of resorption completely, and inhibitors of prostaglandin synthesis suppressed it partially. Although the data show an effect of PMT on bone tissue, the results do not exclude an action on cells in the nasal cavity, which could indirectly stimulate bone resorption.

Animals↗

PubMed1992

Effect of macrophage colony-stimulating factor on in vitro osteoclast generation and bone resorption.

To investigate the role of recombinant human macrophage colony-stimulating factor (rhM-CSF) on in vitro bone resorption, two bone explants, each at a different developmental stage, were adopted, namely 1) radii and 2) metatarsals of 17-day-old embryonic mice. At this stage of gestation, bone resorption in the radii is exclusively dependent upon fusion of osteoclast precursors and activation of mature osteoclasts, whereas in metatarsals it is dependent upon the generation of new osteoclasts. rhM-CSF showed no effect in radii, but stimulated 45Ca release in metatarsals, when they were either intact or periosteum stripped in coculture with embryonal liver as a source of hemopoietic progenitors. The rhM-CSF-induced increase in 45Ca release was paralleled by a higher number of osteoclasts. The stimulating effect was found to be in a concentration range between 250-500 U/ml M-CSF. The action of rhM-CSF was blocked by irradiation, indicating that it is dependent upon cell proliferation. These results, thus, show that M-CSF stimulates bone resorption only when it is dependent on generation of new osteoclasts. M-CSF does not appear to have any effect on the activity of mature osteoclasts. The mechanism of action might be direct on osteoclast precursors or indirect on accessory cells influencing osteoclast generation.

Animals↗

PubMed1992

[The value of nuclear magnetic resonance tomography in tumor staging of laryngeal-/hypopharyngeal cancer].

Twenty-four patients with tumors of the larynx and hypopharynx were examined with magnetic resonance imaging (MRI) and laryngoscopy. The results of MRI and laryngoscopy were then correlated with the pathology reports. Diagnostic findings of 84% of the MRI studies correlated with the pathology report, while laryngoscopy provided exact classification in 79%. MRI tended to overestimate tumor size because edema or inflammatory reactions of surrounding tissues simulated tumors. However, normal mucosa also enhanced contrast medium, restricting the value of this technique. Laryngoscopy tended to underestimate tumor size, because deep extensions of tumor and cartilage involvement were difficult to detect. Nonetheless, the utility of MRI in obtaining axial, coronal and sagittal slices was found to facilitate the preoperative staging of tumor extensions.

Carcinoma, Squamous Cell↗

PubMed1992

[Radioimmunoscintigraphy: fundamentals (1)].

Radioimmunoscintigraphy (scintigraphy of benign and malignant diseases with radioactively labelled monoclonal antibodies) is being performed via clinically controlled studies in Germany since 1985. In this review the immunological fundamentals and diagnostic possibilities of this new diagnostic approach are given described.

Contrast Media↗

PubMed1992

[Radioimmunoscintigraphy of colorectal tumors: state of the art (2)].

Radioimmunoscintigraphy (RIS) of colorectal carcinomas is under investigation in controlled clinical studies in Germany since 1985. With the availability of 99mTc labelled monoclonal antibodies against the carcinoembryonic antigen (CEA), there is an increasing acceptance of this new technique; nevertheless, the merits of RIS in comparison to established methods of staging and restaging of patients with colorectal carcinomas as computed tomography, endoscopy and sonography are still under discussion. In this review the current "State of the Art" of radioimmunoscintigraphy of colorectal carcinomas is given in respect of whether there is additional information which can be gained only by Ris but not by the established diagnostic procedure.

Colorectal Neoplasms↗

PubMed1992

[Bladder tumors--Magnevist-assisted magnetic resonance tomography].

Magnetic resonance imaging (MRI, Magnetom 0.5 Tesla) using a high-resolution surface coil was performed on 10 healthy volunteers, 16 patients with bladder tumours, 2 patients with cystitis and 15 patients with bladder tumours and cystitis. Lesion delineation versus urine, bladder wall and surrounding organs was evaluated in plain and contrast-enhanced (IV Magnevist, 0.1 mmol/kg) T1-weighted, plain proton-density and T2-weighted spin-echo images. Surface-coil MRI proved very sensitive since all lesions were found in plain scans. Cystitis and 27 of 31 tumours exhibited contrast enhancement, however, differentiation of tumours and cystic lesions was not improved. Plain T2 and contrast-enhanced T1-weighted images demonstrated bladder wall disruption and perivesical tumour spread with equal sensitivity. Post-contrast images permitted unequivocal visualisation of perivesical tumour spread in surrounding peritoneal fat. The authors conclude that T2-weighted imaging may be restricted to non-enhancing bladder tumours thus significantly reducing imaging time.

Aged↗

PubMed1992

[Brain scintigraphy (SPECT) with thallium-201 in primary brain tumors].

We evaluated the role of thallium-201 single-photon emission-computed tomography (SPECT) in diagnosis, differential diagnosis and follow-up of 33 patients with primary brain tumors. 27 of 33 lesions were detectable by Tl-201 SPECT because only two of eight low-grade (grade 1 and 2) astrocytomas showed Tl-201 accumulation up to a tumor to nontumor ratio of 2.6. High grade (grade 3 and 4) astrocytomas showed Tl-201 accumulation in the range of 2.2 up to 13.0 and were different from low-grade astrocytomas. Noninvasive grading of astrocytomas is therefore possible, whereas differential diagnosis of oligodendrogliomas and astrocytomas or meningiomas was not possible with Tl-201. In the follow-up of six patients, we could demonstrate, that tumor progression is correlated with increasing and tumor regression with decreasing Tl-201 accumulations. This functional changing proceed morphological findings in CT. But vanishing of Tl-201 accumulation during therapy does not mean vanishing of tumor as could be demonstrated by follow-up.

Adult↗

PubMed1992

[Reactive enlargement of cervical lymph nodes and cervical lymph node metastases: sonography (M/Q quotient) and computed tomography].

Ranking of sonographic maximum/transverse diameter quotients was compared with the ranking of CT in respect of identification and exclusion of cervical lymph node metastases. Both sonography and CT are distinguished by a high degree of sensitivity in the imaging of cervical lymph node metastases. Sonography, with the assistance of the maximum/transverse diameter quotient, can differentiate between benign enlarged and non-enlarged lymph nodes on the one hand and cervical lymph node metastases on the other, with a safety of 95 per cent. CT can yield definite information regarding the tumour status only after contrast medium administration under the criteria of central hypodensity and peripheral marginal enhancement. CT is much less specific than the sonographic M/T quotient (66% vs 95%). Accuracy of sonography (94%) is clearly superior to that of CT (79%).

Adult↗