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The quality of MR-Spectroscopy data can easily be affected in in vivo applications. Several factors may produce signal artefacts, and often these are not easily detected, not even by experienced spectroscopists. Reliable and reproducible in vivo MRS-data requires the definition of quality requirements and goals, implementation of measures to guarantee quality standards, regular control of data quality, and a continuous search for quality improvement. The first part of this review includes a general introduction to different aspects of quality management in MRS. It is followed by the description of a series of tests and phantoms that can be used to assure the quality of the MR system. In the third part, several methods and strategies used for quality control of the spectroscopy data are presented. This review concludes with a reference to a few interesting techniques and aspects that may help to further improve the quality of in vivo MR-spectra., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Introduction: Deep brain stimulation (DBS) nowadays is a well-established treatment of motor symptoms in Parkinson's disease. The subthalamic nucleus (STN) is a common target for DBS, because motor improvements have been shown to be superior to best medical therapy, if DBS electrodes have been appropriately positioned. DBS target identification can be assisted by MRI beyond structural imaging by spatially resolved measurement of T2-relaxation times (T2r)., Aim: We pose the question, whether T2r of the STN is linked to the severity of the disease and whether outcome of DBS may be correlated to an asymmetric manifestation of the disease. Further, we investigated if abnormal T2r in the STN may be predictive for outcome of DBS., Methods: Twelve patients underwent preoperative MR imaging including a multi echo relaxometry sequence (3 Tesla, Siemens Medical Systems, Erlangen, Germany) ahead of DBS. T2r were determined for STN, substantia nigra (SN), red nucleus (RN) and centrum semiovale (CSO). Unified Parkinson's disease Rating Scale (UPDRS) scores were tested before and after DBS. Patients' T2r and deduced values representing left-right asymmetry of measurements were correlated with UPDRS scores and measures for outcome of DBS. Furthermore, patients' T2r were compared with T2r measurements in 12 healthy controls (HC)., Results: Patients' T2r for SN (mean 45.4 ms ± 4.4 ms) and STN (mean 56.4 ms ± 3.8 ms) were significantly shorter than T2r in HCs for SN (mean 60.7 ± 4.6) and STN (mean 66.1 ms ± 4.0 ms). While no mean T2r asymmetry was found in the SN, patients' mean T2r for STN showed a weakened left-right correlation (Pearson correlation coefficient 0.19 versus 0.72 in HC) indicating asymmetric degeneration. T2r asymmetry was not linked to the more severely affected hemisphere. The respective lower T2r within the left or right target region was significantly correlated to the outcome in terms of UPDRS III improvement in "off" state (Pearson correlation 0.82 corresponding to p ≪ 0.01). Patients with T2r of STN lower than 50 ms showed no response to DBS in the UPDRS. The maximum T2r for SN correlated to the improvement between UPDRS "off" minus and "on" (Dopamine response) but failed to predict DBS outcome., Conclusions: The lower boundaries of T2r in the STN predict motor outcome in DBS. T2r asymmetry in the STN is not associated with increased clinical symptoms, but with response to therapy. Thus, patients with very low T2r may be inappropriate candidates for DBS.

There is a need for absolute quantitation methods in (31)P magnetic resonance spectroscopy, because none of the phosphorous-containing metabolites is necessarily constant in pathology. Here, a method for absolute quantitation of in vivo (31)P MR spectra that provides reproducible metabolite contents in institutional or standard units is described. It relies on the reciprocity principle, i.e., the proportionality between the B(1) field map and the map of reception strength for a coil with identical relative current distributions in receive and transmit mode. Cerebral tissue contents of (31)P metabolites were determined in a predominantly white matter-containing location in healthy subjects. The results are in good agreement with the literature and the interexamination coefficient of variance is better than that in most previous studies. A gender difference found for some of the (31)P metabolites may be explained by different voxel composition., (Copyright 2001 Academic Press.)

1H MR spectra of human muscles were recorded before, during, and after fatiguing exercise. In contrast to expectations, it was found that the spectral contributions of creatine/phosphocreatine (Cr/PCr) were subject to change as a function of exercise. In particular, the dipolar-coupled methylene protons of Cr/PCr were found to be reduced in intensity in proportion to the co-registered PCr levels. Recovery after exercise and behavior under ischemic conditions provide further evidence to suggest that the contributions of the CH2 protons of Cr/PCr to 1H MR spectra of human muscle in vivo reflect PCr rather than Cr levels. Variation of experimental parameters showed that this effect is not due to a trivial change in relaxation times. At present it can only be speculated about why the Cr resonances have reduced NMR visibility. If temporary binding to macromolecules should be involved, the free Cr concentration-important for equilibrium calculations of the creatine kinase reaction-might be different from what was previously assumed., (Copyright 1999 Academic Press.)

The difference between the experimental and theoretical spatial response function (SRF) of a narrow tube with water is used for a localization test for magnetic resonance spectroscopic imaging (MRSI). From this difference a quantitative performance parameter is derived for the relative amount of signal within a limited region in the field of view. The total signal loss by the MRSI experiment and eddy currents is described by a parameter SL derived from the signal intensities of two echoes. Results of a European multi-centre trial show that this approach is suited for assessment of MRSI localization performance.

This paper reports the results of multicentre studies aimed at designing, constructing, and evaluating prototype test objects for performance assessment in small-bore MRS systems, by utilizing the test protocols already proposed by the EEC COMAC-BME Concerted Action for clinical MRS equipment. Three classes of test objects were considered: (1) a multicompartment test object for 31P MRS measurements performed with slice-selective sequences; (2) a two-compartment test object for volume-selection 1H MRS; and (3) two-compartment test objects for assessing the performance of experimental systems using ISIS as volume localization sequence in 31P MRS. The results suggested the interest of adopting some of these prototypes for improving the comparison of spectroscopy data obtained from different sites, for providing useful means of quality assurance in experimental MRS, and facilitating the validation of new localization sequences.