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.

Double-blind crossover study with physostigmine in patients with degenerative cerebellar diseases.

OBJECTIVE: To determine whether treatment with physostigmine can improve the conditions of patients with ataxia. DESIGN: A double-blind crossover study with physostigmine was performed in 19 patients with degenerative cerebellar diseases. SETTING: Patients were selected from an ongoing prospective follow-up study at the university hospital in Lübeck, Germany. PATIENTS: Eleven patients with autosomal dominant cerebellar ataxia and 8 patients with idiopathic cerebellar ataxia. INTERVENTION: Physostigmine was administered by using a transdermal system (patch) containing 30 mg of physostigmine as a base, of which about 6 mg is released during 24 hours along a diffusion gradient. Each treatment phase with the physostigmine patch or the placebo lasted 4 weeks, after which the treatment of patients was crossed over to the other phase. MAIN OUTCOME MEASURES: Ataxia was documented and quantified by using a clinical score and posturographic measures. RESULTS: Physostigmine patches had no significant effect on cerebellar symptoms. CONCLUSION: Treatment with physostigmine does not improve the conditions of patients with ataxia.

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.

Method for the quantitative assessment of contrast agent uptake in dynamic contrast-enhanced MRI.

In previous papers relative signal intensity increase was used as a quantitative assessment parameter for contrast uptake in contrast-enhanced MRI. However, relative signal intensity increase does not only reflect contrast uptake but depends also on tissue parameters (native T1 relaxation time) and sequence parameters (repetition time and flip angle); thus, the contrast uptake cannot be assessed accurately using relative signal intensity increase. Based on an analysis of the contrast behavior of spoiled gradient echo sequences, a method is described in this paper that overcomes the limitations of relative signal intensity increase measurement. A parameter, called "enhancement factor" (EF) is introduced that approximates differential T1 relaxation rate. The enhancement factor scales linearly with contrast uptake and is independent of tissue and sequence parameters. The additional measurement time involved in determining the enhancement factor is less than 1 min and computation is straightforward. The practicality of the new method was confirmed by phantom measurements using T1-weighted and proton density-weighted spoiled gradient echo sequences (FLASH-2D). Enhancing tissues were simulated by water phantoms doped with increasing concentrations of Gd-DTPA.

[Quality control for localized in-vivo proton spectroscopy on clinical MR equipment]. / Qualitätskontrolle für die lokalisierte In-vivo-Protonenspektroskopie an klinischen MR-Geräten.

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.