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Biomedical subjects

Robert Becker

Publications and source records attributed to Robert Becker.

9 recordsLinked to original sources
PubMed2005

Visual evoked potentials recovered from fMRI scan periods.

Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) may allow functional imaging of the brain at high temporal and spatial resolution. Artifacts generated in the EEG signal during MR acquisition, however, continue to pose a major challenge. Due to these artifacts, an interleaved modus has often been used for "evoked potential" experiments, i.e., only EEG signals recorded between MRI scan periods were assessed. An obvious disadvantage of this approach is the loss of a portion of the EEG information, which might be relevant for the specific scientific issue. In this study, continuous, simultaneous EEG-fMRI measurements were carried out. Visual evoked potentials (VEPs) could be reconstructed reliably from periods during MR scanning and in between successive scans. No significant differences between both VEPs were detected. This indicates sufficient artifact removal as well as physiological correspondence of VEPs in both periods. Simultaneous continuous VEP-fMRI recordings are thus shown to be feasible.

Adult↗
PubMed2005

Short stories.

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Palliative Care↗
PubMed2004

Predicting the precipitation of poorly soluble weak bases upon entry in the small intestine.

Solubility and dissolution relationships in the gastrointestinal tract can be critical for the oral bioavailability of poorly soluble drugs. In the case of poorly soluble weak bases, the possibility of drug precipitation upon entry into the small intestine may also affect the amount of drug available for uptake through the intestinal mucosa. To simulate the transfer out of the stomach into the intestine, a transfer model was devised, in which a solution of the drug in simulated gastric fluid is continuously pumped into a simulated intestinal fluid, and drug precipitation in the acceptor medium is examined via concentration-time measurements. The in-vitro precipitation of three poorly soluble weakly basic drugs, dipyridamole, BIBU 104 XX and BIMT 17 BS, was investigated. For all three, extensive supersaturation was achieved in the acceptor medium. Under simulated fasted-state conditions, precipitation occurred for all three compounds whereas under simulated fed-state conditions, the higher concentrations of bile components and the lower pH value in the acceptor medium inhibited precipitation at concentrations corresponding to usual doses in all cases. Comparison with pharmacokinetic data indicated that a combination of transfer model data with solubility and dissolution profiles should lead to better predictions of in-vivo behaviour of poorly soluble weak bases.

Benzimidazoles↗