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Biomedical subjects

W Semmler

Publications and source records attributed to W Semmler.

At least 55 records · Page 3Linked to original sources
PubMed1995

[Brain SPECT with 123I-lisuride in patients with Parkinson's disease and controls].

The goal was to visualize cerebral dopamine-D2 receptors in 6 patients with Parkinson's disease and in 3 healthy controls using iodine-123-Lisuride-SPECT. In addition, we performed receptor-replacement studies using 123I-Lisuride and cold Lisuride as competitive ligands. The highest uptake of 123I-Lisuride was observed in the striatum, a region with known high dopamine receptor density. In two patients premedication with cold Lisuride displaced 123I-Lisuride from the dopamine receptor. 123I-Lisuride is valuable as a radiotracer in cerebral dopamine-D2 receptor scintigraphy. Whether or not it is possible to determine dynamic changes of dopamine receptor density or function by receptor replacement studies needs further evaluation in larger patient populations.

Adult↗
PubMed1994

Drug monitoring of 5-fluorouracil: in vivo 19F NMR study during 5-FU chemotherapy in patients with metastases of colorectal adenocarcinoma.

The metabolism of 5-fluorouracil (5-FU) is complex and the reason for the low response rate of tumor patients to 5-FU is currently unknown. The aim of this study was to evaluate whether spectral parameters obtained noninvasively by in vivo 19F nuclear magnetic resonance (NMR) spectroscopy can be used to assess individual response to 5-FU chemotherapy. Eighteen patients with metastases of colorectal carcinoma treated with 5-FU were examined by 19F NMR at 1.5 T. The NMR signal intensity versus time curves were observed for the cytostatic and its catabolite alpha-fluoro-beta-alanine (FBAL). Clinical response to treatment was monitored by CT/MR imaging of the liver and carcinoembryonic antigen (CEA) levels in the serum. 5-FU levels observed in IV-treated patients correlate with volumes of metastases in the liver region examined with the 19F NMR coil (k = 0.77, p < .0001). 5-FU levels in patients at their initial 5-FU chemotherapy were related with clinical response determined after three cycles of treatment. In the group of patients with extensive liver involvement and IV treatment, responders (n = 3) had enhanced 5-FU levels compared to nonresponders (n = 3). FBAL data indicate an apparent saturation of 5-FU catabolism in the liver for 5-FU doses > 1 g infused during 10 min. Mean absolute concentrations of FBAL were about 1 mumol per gram liver tissue. 19F NMR spectroscopy could be used to guide dose escalation schemes or to assess the modulation of 5-FU metabolism by other drugs in combined chemotherapy.

Adenocarcinoma↗
PubMed1994

Dopamine D2 receptor imaging with iodine-123-iodobenzamide SPECT in idiopathic rotational torticollis.

UNLABELLED: The cause of idiopathic rotational torticollis (IRT) is not completely understood to date. However, basal ganglia are believed to be involved in the pathophysiology of IRT. To elucidate this disorder further, the value of iodobenzamide (IBZM) SPECT was studied for the evaluation of striatal dopamine D2 receptors in these patients. METHODS: Striatal dopamine D2 receptor density was assessed in 10 patients with IRT using 123I-IBZM SPECT. The images were interpreted by a nuclear medicine physician initially to determine IBZM binding within the striatum and the cerebellum and, secondly, interstriatal IBZM binding. The results were correlated with the clinical parameters of the patients and compared with the results obtained from normal controls. RESULTS: No difference was found in average, specific striatal IBZM binding (basal ganglia/cerebellum ratio) between patients and controls. However, interstriatal analysis of IBZM binding revealed a significantly higher binding in the striatum contralateral to the direction of the torticollis (p = 0.026, by chi-square test). CONCLUSION: It was concluded that the striatal dopamine D2 receptor status is altered in patients with IRT.

Adult↗
PubMed1994

[Effects of a nucleotide-nucleoside mixture on ischemic muscle metabolism in patients with stage II peripheral arterial occlusive disease. MR spectroscopic and biochemical analytic results].

In order to assess the acute metabolic effects of an intra-arterial infusion of nucleotide-nucleoside-mixture (NNM), 31P-mr-spectroscopy at the site of m. gastrocnemius and metabolite determinations from blood of the femoral artery and vein were carried out in 10 patients with PAOD stage II during ergometric calf exercise to the claudication pain limit. The spectroscopic measurements revealed a greater exercise-induced fall of PCr and a higher increase of Pi in calf muscles during supply of NNM compared with control ergometry. Post-exercise recovery of PCr was distinctly delayed during infusion of NNM. The anaerobic production of energy, however, was sufficient to maintain the ATP concentration to the same extent as under control ergometry. On the other hand, intramuscular lactate acidosis developed to a lower degree with NNM infusion than without NNM. A reduced muscular release of lactate, pyruvate, ammonia and alanine followed from the evaluation of the arteriovenous balance of these metabolites in the femoral vessels indicating a favourable global metabolic effect of NNM infusion in the extremity. The apparent contradiction in the spectroscopic and analytic-biochemical findings can be explained by local blood shunts induced by maximum vasodilation. Noninvasive mr-spectroscopy allows to detect directly and continuously the metabolic impact of ischemia in the calf muscles afflicted by arterial occlusion, whereas the metabolite concentrations in femoral blood are altered by afflux from non-ischemic areas. The known clinical benefit of frequently repeated intra-arterial infusions of NNM is thought to be due to an expansion of collateral circulation and to a favourable influence on endothelial functions.

Adenosine Triphosphate↗
PubMed1993

Preliminary evaluation: magnetic resonance of urography using a saturation inversion projection spin-echo sequence.

A saturation inversion projection (SIP) spin-echo technique is reported which allows a reliable direct visualization of the urogenital system as well as its functional performance in magnetic resonance imaging. We used an imaging sequence with a 90 degree saturation pulse and two 180 degree inversion pulses followed by a short spin-echo (SE) pulse sequence. The three time intervals in the 90 degree-180 degree-180 degree-SE pulse train were adjusted to suppress the signals of soft tissues and fat. After intravenous injection of the contrast agent Gd-DTPA, a shortening of the kidney T1 and the T1 of the urogenital system is obtained below the T1 values of fat and soft tissues, and these remaining ultra-short T1 tissues were imaged with the SIP sequence. Using a sequential measuring technique a quantitative evaluation of the glomerular filtration rate seems to be possible with a time resolution of 18 sec per image. In addition, magnetic resonance urography using the SIP sequence provided a good visualization of the urogenital system and may show several clinical utilities in further clinical studies.

Contrast Media↗
PubMed1993

Recurrent rectal cancer: diagnosis with dynamic MR imaging.

PURPOSE: To evaluate whether dynamic magnetic resonance (MR) imaging can increase the diagnostic accuracy in suspected local recurrence of rectal carcinoma. MATERIALS AND METHODS: Eighteen patients (seven men, 11 women, aged 26-78 years) with 19 suspect lesions were examined. T1-weighted (pre- and postcontrast) and T2-weighted spin-echo images were read by three observers. Computed tissue-specific enhancement parameters were obtained and displayed on gray-scale images (pharmacokinetic mapping). RESULTS: Reading of the spin-echo images yielded a sensitivity of 91%-100% (confidence interval, 67%, 100%), a specificity of 29%-43% (12%, 67%), and an accuracy of 71%-75% (48%, 91%). Analysis of the MR data showed greater (P = .0038) and faster (P = .0018) enhancement of malignant lesions (n = 12) compared with benign lesions (n = 7). CONCLUSION: Pharmacokinetic mapping of dynamic MR imaging data allows in vivo insight into tissue physiopathology, helping differentiate benign from malignant pelvic lesions in rectal cancer.

Adult↗
PubMed1993

[Pulmonary sequestration: use of MR-angiography].

The confirmation of the diagnosis of intralobar pulmonary sequestration usually requires angiographic demonstration of the systemic arterial supply, and venous drainage. Magnetic resonance angiography (MR angiography) is a new, non-invasive imaging modality for examinations of the vasculature. In this report we describe its successful application in intralobar pulmonary sequestration demonstrating the feeding systemic artery, including its intrapulmonary branching, and the type of the venous return.

Adult↗
PubMed1992

[MR angiography. Its use in pulmonary and mediastinal space-occupying lesions].

MR angiography (MRA) proved to be promising combined to MR imaging (MRI) in the assessment of intrathoracic masses. Sequential FLASH 2D angiograms were acquired in breath-hold technique using the following parameters: TR = 30 ms, TE = 10 ms, FA = 30 degrees. Section thickness was 5 mm with 1 mm overlap between sequential sections. Individual conditions of the examination were achieved by an automatized control procedure. Targeted MIP postprocessing resulted in 3D reconstructions illustrating vascular anatomy and avoiding superimposition. Presentation should be done by cine-mode for better spatial impression. This method was evaluated in a prospective study of 21 patients with malignant pulmonary and mediastinal masses in addition to spin-echo imaging. The diagnostic contribution concerning the relationship between the mass and the vasculature like displacement, stenosis, and poststenotic perfusion defect were assessed.

Adult↗
PubMed1992

[MR tomography and MR angiography--a new method for the planning of the irradiation of large abdominal fields].

Subdiaphragmatic radiation therapy in malignant lymphoma requires complete irradiation of retroperitoneal lymph nodes, spleen and splenic pedicle and optimal shielding of radiosensitive structures. The aim of our study was to develop a new method for individual field definition by using MR tomography and MR angiography. In 38 patients with malignant lymphoma coronal MR tomograms and MR angiograms of the abdominal vessels were obtained and superimposed by a specially created computer program. By using a Subtraskop the MRT/MRA superposition was geometrically projected onto the simulation film in correct scale. The target volume could individually be defined and was compared to standard treatment planning according to the definition by Abbatucci. In all patients an exact irradiation of the spleen, the splenic pedicle and prominent lymphatic masses was possible. Furthermore, this resulted in a 32% reduction of treated kidney volume in the average of patients. Noninvasiveness, acceptable costs and high accuracy support the application of this new method in clinical routine.

Abdomen↗
PubMed1991

Detection of bone marrow infiltration by non-Hodgkin's lymphoma--comparison of histological findings, analysis of gene rearrangements, and examination by magnetic resonance imaging.

The histological examination of bone marrow specimens is one of the standard procedures in staging non-Hodgkin's lymphoma. To investigate the validity of a conventional unilateral iliac crest biopsy, we performed a prospective study comparing histological findings with analysis of gene rearrangements in bone marrow samples and magnetic resonance imaging of bone marrow. Twenty-seven consecutive patients with non-Hodgkin's lymphoma (ten with high grade, seventeen with low grade) were studied. In twelve patients, histological examination revealed bone marrow infiltration. Results of histology and magnetic resonance imaging were discordant in three of the twenty-seven patients. With magnetic resonance imaging, suspected infiltration was found in two patients without histological evidence for bone marrow involvement in the disease. In one patient, an infiltration was described by histology but MRI revealed no pathological findings. In this case, DNA analysis confirmed bone marrow infiltration by detection of a clonal rearrangement of the immunoglobulin heavy chain gene. Analysis of gene rearrangements was performed in ten patients. As examined by histology, five of them had bone marrow involvement in the disease and five had not. In all these cases, analysis of gene rearrangements confirmed the histological findings. Our data show that, despite the small volume of bone marrow specimens, the sensitivity of an iliac crest biopsy seems to be high in staging non-Hodgkin's lymphoma.

Adult↗
PubMed1991

Three-dimensional time-of-flight MR-angiography and the surgical indication of brainstem cavernomas.

This study was designed to assess the diagnostic value of 3D time-of-flight MR-angiography in cerebral cavernomas. In seven patients, nine out of ten cavernomas were removed by microsurgery. While MR-angiography demonstrated well branches of brain arteries adjacent to the lesions, no flow signal in the vascular malformations was observed. On the other hand, there was a high intensity signal induced by methaemoglobin in those three patients with brainstem cavernomas who had experienced a significant bleeding attack seven months prior to admission. It had a spotted appearance in MR-angiography with volumes of the largest spots around 1.8 cm3. It is suggested that this spot signal could be used as a path marker for the surgical approach in brainstem cavernomas.

Adult↗
PubMed1991

Kinetic modeling of in vivo--nuclear magnetic resonance spectroscopy data: 5-fluorouracil in liver and liver tumors.

Kinetic modeling has been applied to the time course of the nuclear magnetic resonance signal intensities of 5-fluorouracil and the sum of its catabolites, alpha-fluoro-beta-ureido propanoic acid and alpha-fluoro-beta-alanine, as monitored in liver tumors of seven patients with cancer after brief intraarterial infusion of 5-fluorouracil. Because these data represent only relative tissue concentrations, only ratios of clearance and volume parameters can be estimated (e.g., clearance/central volume of distribution or central volume of distribution/steady-state volume of distribution). On the other hand, parameters that do not refer to volumes, such as half-lives or maximal velocity of metabolic conversion of a nonlinear model, can be estimated in absolute terms. A nonlinear three-compartment model gave satisfactory fits with all of the individual data sets. Kinetics of 5-fluorouracil and catabolites were similar in five patients with metastases of colorectal adenocarcinomas but differed from those of two patients with cholangiocarcinoma and metastases of an anaplastic carcinoma of unknown origin, respectively.

Adult↗
PubMed1991

[MR tomography and MR angiography in cerebral arteriovenous malformations].

Av malformations are cerebral abnormalities with a high risk of bleeding. The role of MRI and MR angiography (MRA) for demonstrating these congenital vascular malformations has been studied. It has been shown that MRI/MRA can provide a rapid and certain diagnosis. MRA can demonstrate arteries to the second set of branches beyond the main cerebral vessels. It has the advantage of being able to produce rapidly and noninvasively 3-D images and, unlike conventional angiography, it can be repeated at will. The disadvantage is the limited special resolution and the difficulty in distinguishing between arteries and veins.

Adolescent↗
PubMed1991

Assessment of bone marrow infiltration by magnetic resonance imaging in patients with hairy cell leukemia treated with pentostatin or alpha-interferon.

The bone marrow of five patients with progressive hairy cell leukemia was examined histologically and by magnetic resonance imaging in a prospective study. Iliac crest biopsies and magnetic resonance scans were performed before and after nine months of therapy with pentostatin (four patients) and alpha-interferon (one patient). T1-weighted scans were evaluated quantitatively and in terms of their visual appearance in three regions of interest (lumbar spine, pelvis and femur). In contrast to bone marrow histology, it was possible to detect differences in the degree of infiltration between these marrow regions in four patients by magnetic resonance imaging. After treatment, three patients had no residual bone marrow infiltration as determined histologically; in parallel, the magnetic resonance images had normalized. The remaining two patients achieved partial remission: marrow infiltration was estimated to be 20% histologically, corresponding well to the signal reduction obtained by magnetic resonance imaging. These data suggest that magnetic resonance imaging of the bone marrow is a sensitive method for assessing responses to treatment with pentostatin and alpha-interferon in patients with hairy cell leukemia.

Adult↗