Absolute metabolite quantification by in vivo NMR spectroscopy: III. Multicentre 1H MRS of the human brain addressed by one and the same data-analysis protocol.
Explore the source record for details and available documents.
Body Water↗
Biomedical subjects
K W Langenberger
Publications and source records attributed to K W Langenberger.
Absolute metabolite quantification by in vivo NMR spectroscopy: V. Multicentre quantitative data analysis trial on the overlapping background problem.
The goal of this study was to establish the best approach for quantifying nuclear magnetic resonance (NMR) lines, that in the frequency domain are overlapping with broad, unwanted background features. To perform the quantitative data analysis in a controlled way, test signals were designed and utilised, derived from two different real-world in vivo nuclear magnetic resonance signals. One of the main conclusions of the study was that the quantification methods currently available to the biomedical research groups can deliver the correct values of the quantitative parameters, but that great care should be taken in using optimal input parameters for the computer programs concerned.
Bayes Theorem↗
Nonlinear motion artifact reduction in event-triggered gradient-echo FMRI.
Event-triggered FMRI was designed to yield good spatial and time resolution on conventional hardware. However, due to longer overall measurement time this method is even more prone to motion artifacts than regular FLASH-based methods. We demonstrate a simple and efficient method to detect and reduce linear and non-linear motion artifacts by manipulating k-space MR data. Results show that (a) motion artifacts may be reduced from typically 10% to noise level (2-3%); (b) small, well-localized hemodynamic changes may be differentiated from motion artifacts; and (c) are visualized with high contrast using an appropriate model function. This way, hemodynamic changes detected by event-triggered FMRI can be quantitated reliably in the lower percent range.
Adult↗
[Quality control for localized in-vivo proton spectroscopy on clinical MR equipment].
The localisation techniques STEAM and PRESS using echo times of 135 ms were tested for their performance. The selection parameters selection efficiency, contamination and outer volume suppression factor were determined as well as the quality of water suppression and the linearity of signal intensities versus concentrations. Using a voxel size of 2 x 2 x 2 cm3 PRESS localisation showed better values for the selection parameters than STEAM: selection efficiency: 6.0 vs. 4.6%, contamination: 0.70 vs. 3.26%, outer volume suppression factor: 220,000 vs. 60,000. Signal intensities showed good linearity (r2 = 0.9996) with concentrations of more than 10 mM, but below that concentration deviation of more than 10% should be taken into account. Measurements for quality assessment are important to optimise measurement protocols and for estimating the clinical value of in vivo measurements.
Humans↗