DCE-MRI in clinical trials: data acquisition techniques and analysis methods.
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Angiogenesis Inhibitors↗
Biomedical subjects
M Büchert
Publications and source records attributed to M Büchert.
Functional magnetic resonance imaging evidence for binocular interactions in human visual cortex.
Using functional magnetic resonance imaging (fMRI), we explored the binocular interactions occurring when subjects viewed dichoptically presented checkerboard stimuli. A flickering radial checkerboard was presented to each eye of the subject, while T2*-weighted images were acquired over the visual cortex with gradient-echo, echoplanar sequences. We compared responses in striate and extrastriate visual cortex under four conditions: both eyes were stimulated at the same time (binocular condition), each eye was stimulated in alternation (monocular condition) or first the one eye then the other eye was stimulated (left eye first - right eye trailing, or vice versa). The results indicate that only the striate area, in and near the calcarine fissure, shows significant differences for these stimulation conditions. These differences are not evident in more remote extrastriate or associational visual areas, although the BOLD response in the stimulation-rest comparison was robust. These results suggest that the effect could be related to inhibitory interactions across ocular dominance columns in striate visual cortex.
Adult↗
MRI-diffusion imaging of neuroblastomas: first results and correlation to histology.
The purpose of this study was to evaluate diffusion-weighted MR imaging in neuroblastomas. We prospectively examined seven children (age range 1-3 years) with seven solid body neuroblastomas. Diagnosis was established histologically. Diffusion-weighted echo-planar imaging (EPI) sequence was performed in all patients, with a repetition time of 5400 ms and an echo time of 103 ms, and with a b-value of 1000 s/mm(2). The contrast of tumour tissue depicted with T2-weighted images and diffusion-weighted images were evaluated by means of region-of-interest measurements and a calculation of the apparent diffusion coefficient (ADC) was done. The ADC calculation showed a mean ADC of 1.1x10(-3) (SD 0.14x10(-3), range 0.9-1.2x10(-3)) mm(2)/s of all tumours. Diffusion-weighted images showed an increased tumour signal. Water proton diffusion within the tumour matrix of neuroblastomas is especially restricted by the molecular and macromolecular barriers due to the very dense structure of this tumour tissue. We hypothesize that high nuclear-to-cytoplasm ratio of neuroblastoma cells limits intracellular motion. Furthermore, the very densely packed tumour cells inhibit effective motion of extracellular water protons. Restricted proton motion leads to a reduction in the rate of apparent diffusion and to a marked increase in signal on diffusion-weighted EPI MR images.
Adrenal Gland Neoplasms↗
Lhermitte-Duclos disease: assessment with MR imaging, positron emission tomography, single-photon emission CT, and MR spectroscopy.
SUMMARY: Lhermitte-Duclos disease (LDD) is a rare cerebellar lesion with features of both malformation and benign neoplasm. However, the fundamental nature of the entity, its pathogenesis, and the exact genetic alterations remain unknown. We describe MR findings (including perfusion- and diffusion-weighted images) in two patients with LDD, as well as findings from single-photon emission CT (SPECT), MR spectroscopy (MRS), and fluorodeoxyglucose (FDG) positron emission tomography (PET) that give additional information about tumor pathophysiology. MR imaging usually distinguishes the LDD by its characteristic "tiger-striped" appearance. The regions of increased regional cerebral blood volume (rCBV) within the lesion correlated closely to the regions of FDG-hypermetabolism and high thallium (201-Tl) uptake. Proton MRS revealed an increased level of lactate and decreased level of myo-inositiol and N-acetyl-aspartate, as observed in low-grade gliomas, but decreased levels of choline. Our cases indicate that the functional investigations give additional information about tumor pathophysiology and reflect the histopathologic controversial entity with both characteristics found in low-grade gliomas and characteristics not typical for tumors.
Adult↗
TSE-sequences with spin-echo contrast.
The article presents a discussion of the basic signal behavior of contrast-modified RARE(TSE,FSE...)-sequences which have been modified such that the echo train used for image encoding is preceded by a long echo interval in order to introduce the T(2)-contrast of conventional spin-echo sequences while maintaining the high imaging speed of TSE. Sequences aimed at breathhold abdominal imaging as well as for the detection of hemorrhages in the CNS have been implemented and optimized. The significant difference in image contrast at identical echo times compared to unmodified TSE is demonstrated for different tissues.
Brain↗
Reproducibility and validity of electric source localisation with high-resolution electroencephalography.
The present study investigates the reproducibility and validity of the EEG source localisation of somatosensory evoked potentials (SEPs) using high-resolution EEG (61 scalp electrodes) and a source reconstruction on the basis of the individual brain morphology as obtained from magnetic resonance images (MRIs). The somatosensory evoked potentials (SEPs) to electrical stimulation of the right median nerve were repeatedly collected from the scalp of one healthy subject in 9 replications run on 9 different days. The source reconstruction for the 19 ms SEP component was performed by using a single moving dipole model as a source model. Two different head models were used: a spherical 3 shell model and a more realistically shaped 3 compartment model computed using the boundary element method (BEM). The source locations of the 19 ms SEP component were found to be highly reproducible using both head models: the mean standard deviation of the dipole locations was found to be 2.6 mm for the 3 shell model and 4 mm for the more realistically shaped head model. By projection into the individual MRI, the dipoles resulting from either head models were found to be located within the postcentral gyrus. The electric source locations were consistent with the maximum of the task-specific changes seen in a functional magnetic resonance imaging (fMRI) experiment when using the same somatosensory stimulation protocol.
Brain Mapping↗
Breath-hold projection magnetic resonance-cholangio-pancreaticography (MRCP): a new method for the examination of the bile and pancreatic ducts.
Breath-hold MR cholangio-pancreaticography using the RARE method was evaluated as a noninvasive alternative to direct cholangio-pancreaticography in 30 healthy volunteers and in 30 patients with various diseases of the respective duct systems. In contrast to 3D MR cholangiography, RARE MRCP generates projection images requiring a 4-s acquisition time and no postprocessing. Diagnostic information gained from the cholangio-pancreaticograms was fully equivalent to that of conventional x-ray imaging by invasive procedures. Additional information was gained whenever endoscopic access was impossible and/or cystic malformations were present.
Adult↗