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M Barth

Publications and source records attributed to M Barth.

72 records · Page 4Linked to original sources
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

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

Vision affects mushroom bodies and central complex in Drosophila melanogaster.

The brain of Drosophila is structurally altered by sensory stimuli that the flies receive during their adult life. Size and fiber number of the mushroom bodies, central complex, and optic lobes are influenced by social, spatial, or olfactory cues. Recently, the optic lobes have been shown to depend on the light regime that flies experience. Structural plasticity in the brain is thought to be a correlate of functional adaptations and long-term memory. We therefore extend our investigation of volume changes to the calyces of the mushroom bodies and the central complex. We show that rearing flies in constant light for 4 days increases the volume of both structures by up to 15% compared to rearing them in total darkness. Much of this difference develops during the first day. The effect of light is not hormonally mediated, as monocularly deprived flies develop a smaller ipsilateral calyx. Mutant analysis suggests that light generates its effects through known visual pathways. In contrast to the optic lobes, in the calyx and central complex structural changes can be linked to cAMP signaling, as in the mutants dunce1 and amnesiac1 no volume differences are observed. Surprisingly, the mutant rutabaga1 shows a prominent light-dependent volume increase in the calyx and central complex, dissociating structural from behavioral plasticity. In complete darkness wild-type flies grow larger calyces under crowded conditions in their normal culture vials than if kept in small groups on fresh food. This stimulating effect of crowding is not observed in any of the cAMP mutants, including rutabaga1.

Aging↗
PubMedDate not supplied

[Diagnosis of a non-functioning kidney pelvis in adults: a report on 12 cases (author's transl)].

Two types of non-functioning supernumerary kidney pelvis are defined by analyzing 12 cases discovered in adult life. Those of congenital origin from glomerular aplasia, sometimes associated with a ureterocele or an ectopic anastomosis, and those due to an acquired lesion such as lithiasis, vesico-ureteral reflux, or secondary infection of a pocket of fluid. Radiological diagnosis is made by IVU with descending cystography and films taken during micturition. Cystoscopy and possibly retrograde ureteropyelography are essential in order to confirm the diagnosis.

Cystoscopy↗