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Biomedical subjects

J Weis

Publications and source records attributed to J Weis.

At least 91 records · Page 5Linked to original sources
PubMed1997

Fasting improves discrimination of grade 1 and atypical or malignant meningioma in FDG-PET.

UNLABELLED: We investigated the use of PET with 2[18F]fluoro-2-deoxy-D-glucose (FDG) to discriminate between atypical or malignant and grade 1 meningiomas. The influence of fasting state and high-dose corticosteroid medication was analyzed retrospectively. METHODS: Preoperative PET scans of 75 patients with suspected diagnosis of intracranial meningioma were evaluated using standardized uptake values (SUV) and tumor-to-contralateral gray matter ratios (TGR) of FDG uptake. Fifty-one of 75 patients fasted before the PET scan, and 27 of 75 patients were studied under high-dose corticosteroid medication. Eighteen tumors had recurred. PET results were compared to histopathological grading. RESULTS: PET correctly identified 8/9 atypical or malignant meningiomas and 58/66 grade 1 meningiomas using TGR and a threshold of 1.05 in primary meningioma and 0.85 in tumor recurrence. This corresponds to a specificity of 0.88 for the detection of higher tumor grading. Specificity was significantly higher in fasting compared to nonfasting subjects (0.96 versus 0.73; p < 0.025). SUV quantification lead to a reduced specificity of 0.77 at the same level of sensitivity. The only false-negative PET finding occurred in a recurrent meningioma, which had been operated on four times before. CONCLUSION: Overnight fasting before injection is needed to improve the diagnostic accuracy of FDG-PET for noninvasive metabolic grading of meningioma. Hyperglycemia in nonfasting patients and in diabetic patients may lead to overestimation of meningioma grading.

Adolescent↗
PubMed1997

Long-term angiographic and histopathologic findings in experimental aneurysms of the carotid bifurcation embolized with platinum and tungsten coils.

PURPOSE: To evaluate the long-term outcome of endovascular occlusion of arterial aneurysms effected with metal coils. METHODS: Microsurgical methods were used to produce carotid bifurcation aneurysms in 20 rabbits and the radiologic and histologic changes were examined. Eight of these aneurysms were occluded with electrically detachable platinum coils (Guglielmi detachable coils [GDCs] and nine were treated with mechanically detachable tungsten coils (mechanical detachable system [MDS]). Three aneurysms remained untreated and served as controls. One animal died of embolic complications 12 hours after endovascular treatment. After observation periods of 3 to 6 months, the remaining animals were examined by intraarterial digital subtraction angiography and subsequent fixation and light and electron microscopy. RESULTS: Large open spaces without signs of thrombosis were found between the loops of the coil baskets in 12 aneurysms (six treated with GDCs and six treated with MDS) regardless of the observation period. In very densely packed aneurysms (four cases with complete occlusion as determined by angiographic criteria), the coil surfaces were for the most part covered by thin cell layers; however, complete endothelialization was never seen. In aneurysms with an initial partial occlusion of 70% to 90%, coil compaction and/or recanalization was a consistent finding. A comparison of the radiologic findings with the histologic aspect revealed that the degree of occlusion was often overrated on the radiographs (in eight of 17 cases). In general, the fibrous tissue reaction appeared to be slightly more pronounced in aneurysms occluded with tungsten coils. CONCLUSIONS: Platinum and tungsten coils were not always effective in causing endoluminal thrombosis leading to long-term occlusion by organized thrombus.

Angiography, Digital Subtraction↗
PubMed1997

Isolated cerebral aspergilloma--long-term survival of a renal transplant recipient.

A renal transplant recipient with isolated cerebral aspergilloma 4 months after allograft transplantation is reported. On admission cerebral computed tomography showed a ring-enhancing mass in the left frontal hemisphere and aspirated purulent material revealed A. fumigatus hyphae. He was cured by short-term antifungal therapy and neurosurgical removal of the well demarcated lesion. He is still alive more than two years later and the renal transplant is well functioning. This is the first report of a renal transplant recipient with isolated cerebral aspergillosis without any relapse and only the third patient who has survived longer than 3 months. Early diagnostic procedures with rapid confirmation of aspergillus infection are pivotal for a benign clinical course.

Amphotericin B↗
PubMed1996

Detection of Anisotropic Pulsating Flow and Its Velocity-Fluctuation Rate in Fertilized Bird Eggs by NMR Microimaging

Coherent and incoherent flows in fertilized quail and bantam eggs have been studied with the aid of NMR microimaging techniques in the course of incubation until the end of the sixth day. The methods employed were multiplane tagging NMR imaging and a NMR gradient-echo imaging pulse sequence supplemented by bipolar gradient pulses in the coherence-evolution interval. The latter technique is suited for recording of velocity maps as well as for localizing of regions with enhanced echo attenuation by incoherent motions. Slight coherent displacements in the middle of the upper part of the egg white were found after the fourth day of incubation with the aid of both pulse schemes. The maximum velocity was estimated to be 1 mmsoliduss. More pronounced effects revealed themselves in the examination of incoherent motions. After the same time of incubation and in a somewhat more restricted area of the upper part of the egg white, distinct motions could be localized consistently with either technique. It is shown that these motions are directed to and from the yolk. Furthermore, the analysis of the time fluctuations of the local signals with the aid of a Fourier transformation showed that the flow is largely of a pulsating nature. The pulsation frequency was found to be 0.4 Hz.

Journal Article↗
PubMed1996

PET-study of intracranial meningiomas: correlation with histopathology, cellularity and proliferation rate.

The glucose metabolism of 62 meningiomas was measured by fluorine -18-2-fluorodeoxyglucose (FDG) PET and correlated with proliferation rate (Ki-67 index) and tumor cellularity. The mean metabolic rate (MRGlu) for meningiomas was 0.26 +/- 0.13 mikromol/g/min (range 0.08-0.62 mikromol/g/min). The relative tumor FDG-uptake (Q-MRGlu) (tumor/contralateral cortex) of all meningiomas was calculated with 0.73 +/- 0.37 (0.24-1.79). Differences of Q-MRGlu were significant between the groups with high vs. low cellularity (p < 0.01), increased vs. normal proliferation rate (p < 0.025) and low (WHO grade I) vs. higher (WHO grades II, III) graded tumors. In recurrent meningiomas (14 tumors) the glucose metabolism was not increased. The data show that 18 FDG-PET is suitable to serve as non-invasive predictor of tumor growth characteristics in meningiomas.

Adult↗
PubMed1996

[Sensory Jacksonian seizures as initial manifestation of sarcoidosis].

A 46-year old patient is reported presenting with somatosensory focal seizures of either arm as the only manifestation of an otherwise clinically inapparent sarcoidosis. MRI showed signs of a granulomatous leptomeningeal affection. Histological examination of a meningeal biopsy proved the diagnosis of sarcoidosis by demonstrating noncaseating granulomas. There was no other clinical manifestation of sarcoidosis. Chest X-ray was normal and the serum level of angiotensin-converting-enzyme was only slightly elevated. The CD4/CD8 ratio in the bronchoalveolar lavage cell population, however, was clearly abnormal, supporting the role of this diagnostic tool in the diagnosis of sarcoidosis.

Biopsy↗
PubMed1996

Mitochondrial abnormalities and intrafamilial variability of sural nerve biopsy findings in adrenomyeloneuropathy.

Clinical and sural nerve biopsy findings in two brothers and their mother affected by adrenomyeloneuropathy/adrenoleukodystrophy (AMN/ALD) illustrate the variability of histopathological changes in this disorder. The number of diagnostic inclusions, i.e., trilaminar leaflets, varied considerably from case to case and showed no correlation to the extent of neurological symptoms. In addition, mitochondrial abnormalities (granular and filamentous inclusions and abnormal cristae), which have not previously been described in AMN/ALD, were detected. These alterations could be secondary to the peroxisomal defect and the increased amount of very long chain fatty acids or could be caused by a more generalized defect.

Adolescent↗
PubMed1996

NMR imaging of thermal convection patterns.

Two special magnetic resonance imaging techniques were applied to the Rayleigh/Bénard problem of thermal convection for the first time. The methods were tested using a water cell with horizontal bottom and top covers kept at different temperatures with a downward gradient. Using Fourier encoding velocity imaging (FEVI) a five-dimensional image data set was recorded referring to two space dimensions of slice-selective images and all three components of the local velocity vector. On this basis, the fields of the velocity components or of the velocity magnitude were evaluated quantitatively and rendered as gray shade images. Furthermore the convection rolls were visualized with the aid of two- or three-dimensional multistripe/multiplane tagging imaging pulse sequences based on two or three DANTE combs for the space directions to be probed. Movies illustrating the fluid motions by convection in all three space dimensions were produced. It is demonstrated that the full spatial information of the convection rolls is accessible with microscopic resolution of typically 100 x 100 x 100 microns3. This resolution is effectively limited by flow displacements in the echo time, which should be well within the voxel dimension. The main perspective of this work is that the combined application of FEVI and multistripe/multiplane tagging imaging permits quantitative examinations of thermal convection for arbitrary boundary conditions and with imposed through-flow apart from the direct visualization of convective flow in the form of movies.

Convection↗
PubMed1996

Correlation of histology, cytogenetics and proliferation fraction (Ki-67 and PCNA) quantitated by image analysis in meningiomas.

Sixty meningiomas were classified histologically according to the WHO criteria and analyzed cytogenetically. The Ki-67 and PCNA proliferation fractions (PRFs) were assessed by immunhistochemistry. The staining results were quantified by TV-image analysis (Miamed, Leica, Germany). Within meningiomas of WHO-grade II/III and those with complete or partial deletion of # 1p, we found a significantly higher mean and maximal Ki-67 PRFs than in those of WHO-grade I and those with all other karyotypes. This was not the case for PCNA PRFs. No differences in PRFs were detectable between histological subtypes. Although these results were obtained after measurement of five high power fields (HPFs) only, the heterogeneity of PRF distribution within the tumors was high. Even after the measurement of 100 HPFs, the 95% confidence intervals were in a range of 18% to 34.3% PRF. This finding seems to be responsible for the moderate interobserver reproducibility of image analytical determination of PRF (r = 0.74). Nevertheless, there was a good correlation between subjective and objective image analytical assessment of PRF (r = 0.83). The significance of the maximum Ki-67 PRF per specimen implies the possibility of selecting those areas which show the highest fraction of positively stained nuclei for measurement, avoiding the problem of intraslide heterogeneity. Thus the time needed for image analytical quantification may be reduced.

Biomarkers, Tumor↗
PubMed1996

Visualization of anisotropic pulsations in extraembryonic compartments of incubated quail eggs by NMR microimaging.

Multi-plane tagging time-of-flight and bipolar gradient phase-encoding and amplitude-weighting NMR microimaging techniques have been employed to study transport in extraembryonic compartments of fertilized quail eggs during the first seven days of incubation. After the fourth day coherent and incoherent motions became visible in certain regions, in particular in the upper part of the albumen. Coherent motions as visualized by deformations of multiplane tagging grids were specified by local velocities less than 1 mm/s at most. On the other hand, incoherent motions led to much more pronounced phenomena. The multiplane tagging grid completely faded in a region comprising the upper third of the albumen after 4.5 incubation days. Images weighted by signal attenuation owing to incoherent displacements indicate motions in the same region. The fact that a reproducible localization of the motions is only possible when signals from different transients are averaged indicates that the incoherence at least partly is temporal in nature. The signal intensity of a volume selected in the incoherent-motion region consequently fluctuates with time. The Fourier analysis of these fluctuations revealed a distinct pulsation with a frequency of 0.4 Hz.

Animals↗
PubMed1996

Six-dimensional spin density/velocity NMR microscopy of percolation clusters.

Using computer-simulated random-site percolation networks as templates, three-dimensional percolation cluster objects were fabricated. The pore space was filled with water and experimentally investigated with the aid of NMR microimaging. A pulse sequence for six-dimensional spin density/velocity NMR imaging was employed for the combined record of the three-dimensional spin-density distribution and the three-dimensional velocity vector field of water percolating through the pore space. An evaluation procedure for the NMR image data was established that reliably renders the characteristic parameters (fractal dimensionality, fractal dimensionality of the backbone, correlation length).

Computer Simulation↗
PubMed1996

Susceptibility, field inhomogeneity, and chemical shift-corrected NMR microscopy: application to the human finger in vivo.

Spectroscopic proton image data recorded with the aid of a gradient-echo spectroscopic imaging pulse sequence are reported. A postdetection processing method is suggested which permits correction of artifacts due to inhomogeneity, susceptibility, and chemical-shift resonance offsets. That is, apart from the spectral information available in this way, better spatial resolutions can be achieved. The method is demonstrated by resonance-offset corrected images of the human finger in vivo. Moreover, resonance-line selective and spectroscopically resolved diffusion-weighted images and diffusivity maps rendered with the aid of the same postdetection procedure are shown.

Artifacts↗
PubMed1996

Microsurgically produced bifurcation aneurysms in a rabbit model for endovascular coil embolization.

The authors present a detailed account of the microsurgical production of bifurcation aneurysms in chinchilla rabbits for basic studies of endovascular coil embolization of aneurysms. End-to-side anastomoses of both common carotid arteries (CCAs) were performed, and a venous pouch was fitted into the newly created bifurcation. These experimental aneurysms closely mimic human cerebral aneurysms in size and hemodynamic features. Sixty-three animals underwent operation. Fifteen animals died in the course of the experiment and 15 were excluded because of a CCA occlusion within the carotid bifurcation. Electrical detachable platinum coils, also known as Guglielmi detachable coils (GDCs), and tungsten mechanical detachable coils (MDCs) were used for the endovascular occlusion of 26 bifurcation aneurysms (16 rabbits were treated with GDCs and 10 with MDCs). Initially, complete angiographic obliteration (95%-100% occlusion of the aneurysm) was achieved in nine rabbits and incomplete obliteration (< 95% occlusion) was seen in 17 animals. Final angiography 3 to 6 months later demonstrated complete occlusion in only four and partial occlusion in 22 aneurysms. At present, the histopathological examination of 17 embolized aneurysms has revealed incomplete obliteration of all aneurysms, even in those three cases that were thought to be completely embolized according to angiographic criteria. A general overestimation of the radiological degree of aneurysm obliteration was found.

Animals↗
PubMed1995

Human CNTF and related cytokines: effects on DRG neurone survival.

Ciliary neurotrophic factor (CNTF), leukaemia inhibitory factor (LIF), oncostatin M (OSM), interleukin-6 (IL-6), and interleukin-11 (IL-11) are structurally and functionally related cytokines. We compared their survival-promoting activities on embryonic chick and newborn rat dorsal root ganglion (DRG) neurones. Human CNTF showed the well known trophic effect on both chick and rat DRG neurones. Human and murine LIF and, at unphysiologically high doses, human OSM were trophic for rat neurones, but failed to promote chick DRG cell survival. Human IL-11, murine IL-6 and human IL-6 did not improve chick or rat DRG neurone survival; soluble human IL-6 receptor alpha did not increase sensitivity to human IL-6. Thus, human CNTF as well as murine and human LIF had special neurotrophic properties compared with other related cytokines.

Animals↗