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Biomedical subjects

E Moser

Publications and source records attributed to E Moser.

252 records · Page 14Linked to original sources
PubMed1980

Effects of obstruction on single-kidney function: clinical and experimental results with 131I-hippurate and 99mTc-DMSA.

In 35 patients, renography with 131I-o-hippurate (OIH) and static renal imaging with 99mTc-dimercaptosuccinic acid (DMSA) were used to measure differential renal function (DRF). The results were compared. Depth correction was applied in both methods. In non-obstructed kidneys (19 patients), both methods revealed nearly identical kidney function (r = 0.98). For completely obstructed kidneys (16 patients), OIH gave a significantly better DRF (14 ml/min) than DMSA. This small difference was of no clinical value. Because DMSA is reported to give unreliable results in unilateral obstructed kidneys, the right ureter was ligated in 8 dogs for 10 days and DRF was measured before and after opening an ureteral fistula. The difference in DRF was about 1% and could be accounted for by the amount of urinary radioactivity collected from the pelvic system after the ligature had been opened. Although DMSA appears to give reliable values in determining DRF, even in obstructed kidneys, OIH is preferred since total clearance values and postrenal urinary dynamics can be determined simultaneously.

Animals↗
PubMed1980

[Evaluation of renal transplant function by 99mTc-DTPA dynamic imaging (author's transl)].

In 60 patients with a kidney transplant 86 perfusion studies with 99mTc-DTPA were performed during the early postoperative period. Correlative data and clinical differentiation were obtained by isotope nephrograms, laboratory values and clinical presentation. In addition to evaluation of scintiphotos, time-activity curves were derived from the transplant and evaluated quantitatively, obtaining a perfusion ratio by a computer program. A ratio of greater than 0.80 was found to be normal. In 20 patients with acute rejection, the ratio was decreased. In 13 patients with acute tubular necrosis, the perfusion ratio was between 0.39 and 0.65, decreasing further during an added rejection crisis. Follow-up examinations confirmed rejection through a decrease of the perfusion ratio (mean difference 0.44; p less than 0.025). In 9 cases, successful rejection therapy was documented by an increase (mean difference 0.29; p less than 0.005). In addition to quantitative evaluation, visual analysis revealed acute occlusion of the renal artery, renal infarction, urinoma, ureteral stenosis or necrosis. Quantitative scintigraphy with 99mTc-DTPA broadened the methods of describing kidney transplant function. Its quantitative evaluation enables the definition of acute rejection and its differentiation from acute tubular necrosis combined with acute rejection in the early postoperative period. Since the method recognizes morphological alterations as well, it usefully complements isotope nephrography.

Acute Kidney Injury↗
PubMed1979

[Automatic recognition of hemisphere-borderlines in cerebral radionuclide angiography (author's transl)].

The diagnostic value of brain perfusion studies with radionuclides is based upon the careful determination of intracerebral vascular supply areas in sequential scintigraphic frames. This paper describes an automatic algorithm to determine cerebral hemisphere-borderlines (Regions of Interest). In 134 randomized brain perfusion studies, regions of interest were set by three techniques: automatically by a computer program at the beginning of the venous phase, automatically by using all images derived from the total bolus passage (40 sec.), and manual marking with a light pen at the beginning of the venous phase. A good correlation of these different techniques was obtained (r = 0.87). Furthermore, we found the bilateral perfusion index independent within a wide range, from the size of the marked regions and the quality of the injected indicator bolus. Time saving and lesser carefulness, concomitant with higher precision and reliability, in addition to the standardisation of the marking technique increase the diagnostic value of cerebral radionuclide angiography.

Brain↗
PubMedDate not supplied

Reproducibility of PET brain mapping of cancer patients.

Twenty German cancer patients (56.9+/-12.7 years old) without brain metastasis underwent neurological PET. The acquired brain data were compared to the data of ten age and sex-matched controls (53.6+/-15. 7). Scores of Zung's Self-rating Depression Scale (SDS) obtained from 15 out of the 20 patients suggested they might be mildly depressed. Scores of Taylor's Manifest Anxiety Scale (MAS), used for additional psychological evaluation, were close to normal distribution. Hypometabolic areas in the German cancer patients were compared with those demonstrated in our previous study in Japanese cancer patients. Common findings in both studies were observed in the limbic structures, such as the anterior and posterior cingulate gyri, the basolateral frontal cortices, as well as in the basal ganglia (especially the caudate nucleus) and frontal cortex. These results are in accordance with many previous PET studies on major depression. The results show that the positron emission tomography and (18)F-fluoro-deoxyglucose ((18)FDG-PET) brain mapping results could be partially reproduced, and suggest that PET brain mapping of cancer patients has a potential clinical application to the field of psycho-oncology and cancer patient care.

Adult↗
PubMedDate not supplied

Three-dimensional reconstruction of the liver venous system using the preservation solution as contrast agent.

To investigate whether MRI without using artificial contrast agents can provide sufficient image contrast to visualize the venous tree in the cold stored liver graft, two pig liver grafts were scanned with a multislice turbo spin-echo sequence with long TE (200 msec). The quality of the data obtained at 1-T field strength was sufficient for three-dimensional reconstruction of the hepatic vascular system, potentially useful for liver splitting surgery.

Animals↗
PubMedDate not supplied

Fuzzy clustering of gradient-echo functional MRI in the human visual cortex. Part I: reproducibility.

Reproducibility of human functional MRI (fMRI) studies is essential for clinical and neuroresearch applications of this new human brain mapping method. Based on a recently presented study on reproducibility of gradient-echo fMRI in the human visual cortex (Moser et al. Magn Reson Imaging 1996; 14:567-579), comparing the performance of three different threshold strategies for correlation analysis, we demonstrate that (a) fuzzy clustering is a robust, model-independent method to extract functional information in time and space; (b) intertrial reproducibility of cortical activation is significantly improved by the capability of fuzzy clustering to separate signal contributions from larger vessels, running perpendicular to the slice orientation, from activation apparently close to the primary visual cortex; and (c) for repeated single subject studies, SDs of <20% for signal enhancement in approximately 80% of the studies and SDs of <30% for activated area size in approximately 65% of the studies are obtained. This, however, depends also on signal-to-noise ratio, (motion) artifacts, and subject cooperation.

Adult↗
PubMedDate not supplied

Fuzzy clustering of gradient-echo functional MRI in the human visual cortex. Part II: quantification.

Fuzzy cluster analysis (FCA) is a new exploratory method for analyzing fMRI data. Using simulated functional MRI (fMRI) data, the performance of FCA, as implemented in the software package Evident, was tested and a quantitative comparison with correlation analysis is presented. Furthermore, the fMRI model fit allows separation and quantification of flow and blood oxygen level dependent (BOLD) contributions in the human visual cortex. In gradient-recalled echo fMRI at 1.5 T (TR = 60 ms, TE = 42 ms, radiofrequency excitation flip angle [theta] = 10 degrees-60 degrees) total signal enhancement in the human visual cortex, ie, flow-enhanced BOLD plus inflow contributions, on average varies from 5% to 10% in or close to the visual cortex (average cerebral blood volume [CBV] = 4%) and from 100% to 20% in areas containing medium-sized vessels (ie, average CBV = 12% per voxel), respectively. Inflow enhancement, however, is restricted to intravascular space (= CBV) and increases with increasing radiofrequency (RF) flip angle, whereas BOLD contributions may be obtained from a region up to three times larger and, applying an unspoiled gradient-echo (GRE) sequence, also show a flip angle dependency with a minimum at approximately 30 degrees. This result suggests that a localized hemodynamic response from the microvasculature at 1.5 T may be extracted via fuzzy clustering. In summary, fuzzy clustering of fMRI data, as realized in the Evident software, is a robust and efficient method to (a) separate functional brain activation from noise or other sources resulting in time-dependent signal changes as proven by simulated fMRI data analysis and in vivo data from the visual cortex, and (b) allows separation of different levels of activation even if the temporal pattern is indistinguishable. Combining fuzzy cluster separation of brain activation with appropriate model calculations allows quantification of flow and (flow-enhanced) BOLD contributions in areas with different vascularization.

Adult↗
PubMedDate not supplied

Characterization of BOLD activation in multi-echo fMRI data using fuzzy cluster analysis and a comparison with quantitative modeling.

A combination of multiple gradient-echo imaging and exploratory data analysis (EDA), i.e. fuzzy cluster analysis (FCA), is proposed for separation and characterization of BOLD activation in single-shot spiral functional magnetic resonance imaging (fMRI) experiments at 3 T. Differentiation of functional activation using FCA is performed by clustering pixel signal changes (DeltaS) as a function of echo time (TE). Further vascular classification is supported by the localization of activation and the comparison with a single-exponential decay model. In some subjects, an additional indication for large vessels within a voxel was found as oscillation of the fMRI signal difference vs echo time (TE). Such large vessels may be separated from small vessel activation and, therefore, our proposed procedure might prove useful if a more specific functional localization is desired in fMRI. In addition to the signal change DeltaS, DeltaT(2)*/T(2)* is significantly different between activated regions. Averaged over all eight subjects DeltaT(2)* is 1.7 +/- 0.2 ms in ROIs with the highest signal change characterized as containing large vessels, whereas in ROIs corresponding to microvascular environment average DeltaT(2)* values are 0.8 +/- 0.1 ms.

Brain↗
PubMedDate not supplied

Relationship between trait anxiety, brain activity and natural killer cell activity in cancer patients: a preliminary PET study.

The purpose of this study is to examine the relationship between psychological factors, regional brain activity and natural killer cell activity (NKA). Eight patients with malignant diseases were studied by FDG-PET under a resting condition. NKA and degree of anxiety and depression were measured using Taylor's manifest anxiety scale (MAS) and Zung's self-rating depression scale (SDS). Linear correlation of NKA and psychological measures to the regional brain metabolism in cancer patients was examined using statistical parametric mapping (SPM). Positive linear correlation between NKA and regional metabolic rate ratios was identified in the visual association cortex, anterior cingulate gyrus (CG) and sensorimotor area, and negative correlation was identified in the inferolateral prefrontal cortex (ILPFC), prefrontal cortex (PFC), orbitofrontal cortex (OFC) and anterior temporal cortex. Positive linear correlation to the MAS score was identified in the visual association cortex, anterior CG, primary sensorimotor area and the posterior parietal cortex, and negative correlation was detected in the ILPFC, PFC, OFC and anterior temporal cortex. The NKA and MAS scores positively correlated with each other (p<0.001). The result might serve as supporting data for a hypothesis that psycho-immune interaction is also mediated by the cerebral cortex and limbic system.

Adult↗
PubMedDate not supplied

Quantification of statistical type I and II errors in correlation analysis of simulated functional magnetic resonance imaging data.

The potential of statistical analyses of functional magnetic resonance images using various threshold strategies in combination with correlation analysis was studied by simulating brain activation. Differences in statistical Type I (alpha) and II (beta) errors are substantial for the various thresholds. Absolute thresholds and individualized thresholds based on the assumption of a gaussian noise distribution are producing constant alpha-errors and thus do not sufficiently improve discrimination of "truly" activated pixels even for very high contrast-to-noise ratios (CNR). Only relative threshold strategies related to the maximum correlation coefficient and thus the individual data quality and activation level, i.e., a data-driven approach, can perfectly discriminate true positives, at least for CNR > 2.5. To further improve discrimination of activated and non-activated pixel in studies with lower CNR, additional prior knowledge would be necessary. From the data presented, one would also expect that the best performing threshold strategy in this simulation study would perform best under in vivo conditions.

Biometry↗
PubMedDate not supplied

Myo-inositol in depressive and healthy subjects determined by frontal 1H-magnetic resonance spectroscopy at 1.5 tesla.

Myo-inositol (mI) as a precursor in the phosphatidylinositol second messenger system has been reported to be reduced in depression. By means of proton-magnetic resonance spectroscopy (1H-MRS) the mI levels in the frontal brain were investigated in vivo in the present study. Twenty-two patients (mean age: 42.8 +/- 10.7 years) with depressive episodes according to ICD 10 (HAMD score > 17) were compared to 22 healthy subjects (28.0 +/- 5.3 years). Two voxels (30 x 20 x 20 mm3) in the frontal lobes were examined in a Siemens Magnetom SP 4000 at 1.5 T (STEAM sequence: TR = 3500 ms, TE = 55 ms). With the total creatine (Cr) as an internal standard, mI/Cr ratios were calculated to follow the mI levels. In the left frontal lobe, mI/Cr was 0.43 +/- 0.06 in depressive patients and 0.46 +/- 0.07 in healthy subjects; concerning the right frontal lobe, mI/Cr was 0.46 +/- 0.08 and 0.48 +/- 0.06, respectively. There were neither significant differences between the two groups nor between the hemispheres. Since there was a significant positive correlation (R = 0.6) between the age and the mI/Cr in the right frontal lobe of depressed patients, age matched pairs analysis was performed (n = 2 x 10, in each group: nine females, one male, < 40 years). In the right frontal lobe, the patients' mI/Cr of 0.40 +/- 0.05 was now significantly lower than the controls' mI/Cr of 0.45 +/- 0.06. However, most of the patients were on antidepressive medication. Interestingly, it was exactly this group of patients which showed significantly lower mI levels. We regard our investigation as a pilot study which suggests an influence of age and antidepressants on mI levels and should be taken into consideration in further investigations in depressive patients.

Adult↗
PubMedDate not supplied

Combined thallium 201/technetium 99m-labeled pyrophosphate tomography for identification of the "culprit" vessel in acute myocardial infarction.

BACKGROUND: Many previous investigations have used the presence of transient ischemic 201Tl perfusion defect to localize coronary artery stenosis. This study reports the results of 201Tl tomography alone and combined 201Tl/99mTc-labeled pyrophosphate (99mTc PYP) tomography employed to identify the infarct-related vessel in patients with acute myocardial infarction (AMI). METHODS AND RESULTS: All short-axis images were evaluated by dividing each left ventricular slice into eight equal sectors. In addition, for combined 201Tl/99mTc PYP tomography, two sectors were added to evaluate involvement of the right ventricle. In a preevaluation phase of the study, the sectors were assigned to the supplying coronary arteries in 75 patients with single chronic myocardial infarction related to the left anterior descending coronary artery (LAD), left circumflex artery (LCX), or right coronary artery (RCA). In this pilot phase, 201Tl tomograms were reviewed in conjunction with the angiographic data. This assignment was then tested prospectively in 117 patients with AMI. As confirmed by angiography, the AMI was related to the LAC, LCX, and RCA in 54, 17, and 46 patients, respectively. Sensitivity and specificity for 99mTc PYP accumulation on combined 201Tl/99mTc PYP tomography were 98% a nd 100% for the LAD, 88% and 99% for the LCX, and 98% and 96% for the RCA, respectively. For 201Tl tomography, sensitivity and specificity for identification of the culprit vessel were 94% and 89% for the LAD, 82% and 91% for the LCX, and 72% and 96% for the RCA, respectively. CONCLUSION: This prospective study demonstrates that combined 201Tl/99mTc PYP tomography is highly accurate for identification of the infarct-related artery in AMI, even in patients with multivessel disease. Positive contrast visualization of myocardial necrosis in both the left and right ventricle allows for reliable differentiation between AMI related to the LCX or RCA territory. In comparison, for 201Tl tomography the sensitivity to detect the culprit vessel, particularly the LCX and RCA, appears to be lower than for 201Tl 99mTc PYP imaging, particularly in patients with prior infarction or right dominant coronary artery.

Coronary Vessels↗
PubMedDate not supplied

High-resolution MR venography at 3.0 Tesla.

PURPOSE: The aim of this study was to investigate the visualization of small venous vessels in the normal human brain at a field strength of 3 Tesla. METHODS: T2*-weighted, three-dimensional gradient-echo images were acquired by exploiting the magnetic susceptibility difference between oxygenated and deoxygenated hemoglobin in the vasculature and microvasculature. The spatial resolution was 0.5 x 0.5 x 1 mm3, and sequence parameters were varied to obtain good vessel delineation. Improved visibility of venous vessels was obtained by creating phase mask images from the magnetic resonance phase images and multiplying these by the magnitude images. Venograms were created by performing a minimum intensity projection over targeted volumes. RESULTS: Highly detailed visualization of venous structures deep in the brain and in the superficial cortical areas were obtained without administration of an exogenous contrast agent; compared with similar studies performed at 1.5 T, the echo time could be reduced from typically 40-50 ms to 17-28 ms. CONCLUSION: Imaging at high-field strength offers the possibility of improved resolution and the delineation of smaller vessels compared with lower field strengths.

Adult↗
PubMedDate not supplied

Depressive state and regional cerebral activity in cancer patients - a preliminary study.

BACKGROUND: The aim of this study was to investigate influences of depressive states, chemotherapy and existence of remaining tumors on the regional brain activity of cancer patients. MATERIAL AND METHODS: Positron emission tomography with 18F-fluorodeoxyglucose was performed on 21 patients with various types of cancer. Their brain images were compared to 10 age- and gender-matched control data using statistical parametric mapping (SPM). The patients were subgrouped into the with and without depression based on the scores on Zung's self-rating depression scale (SDS), with and without previous chemotherapy, and with and without existence of remaining tumors. RESULTS: Significant metabolic reduction was detected in the cingulate gyrus, prefrontal, dorsolateral prefrontal, temporoparietal cortices and basal ganglia in cancer patients. These findings were close to known lesions of major depression. Intra-group comparisons showed that these hypometabolic findings were associated with the depth of depressive state. Influences of chemotherapy and remaining tumors on the cerebral cortex seemed to be weaker than that of psychological factors. CONCLUSIONS: The present pilot study suggests that frontal hypoactivity commonly seen in cancer patients is likely to be associated with depression rather than chemotherapy or remaining tumors. A brain mapping technique might be useful in evaluating neuropsychiatric problems in cancer patients.

Adult↗
PubMedDate not supplied

Whole-body MRI in comparison to skeletal scintigraphy in detection of skeletal metastases in patients with solid tumors.

AIM: To evaluate the diagnostic value of whole-body magnetic resonance imaging (MRI) and skeletal scintigraphy in the detection of skeletal metastases in patients with solid tumors. MATERIALS AND METHODS: One hundred and twenty-nine tumor patients were examined with whole-body MRI using coronal TIRM sequences for the different anatomical regions. Skeletal scintigraphy was performed with 99mTc-DPD. RESULTS: In 105/129 (81%) patients, the whole-body MRI and skeletal scintigraphy findings were concordant. In 56/129 (43%) patients, both imaging modalities excluded skeletal metastases. In 49/129 (38%) patients, whole-body MRI and skeletal scintigraphy revealed metastases, however whole-body MRI demonstrated more extensive disease in 22/49 (45%) cases. In 6/49 (12%) cases, skeletal scintigraphy was superior to whole-body MRI in detecting more skeletal metastases. In 24/129 (19%) cases, the imaging findings were discordant. In 15 cases, skeletal scintigraphy was negative, whereas whole-body MRI revealed skeletal metastases. In 9 cases, skeletal scintigraphy was positive, whereas whole-body MRI failed to detect these metastases. In 77/129 (60%) patients, whole-body MRI revealed additional tumor-related findings. CONCLUSION: Whole-body MRI, as a new staging method, is superior to skeletal scintigraphy with respect to the detection of skeletal metastases and the extent of metastastic disease. Furthermore, whole-body MRI yields additional tumor-related findings. Therefore, whole-body MRI should be performed as an alternative to skeletal scintigraphy for the assessment of skeletal metastases.

Adolescent↗