The translation of MRS to clinical practice has been impeded by the lack of technical standardization. There are multiple methods of acquisition, post-processing, and analysis whose details greatly impact the interpretation of the results. These details are often not fully reported, making it difficult to assess MRS studies on a standardized basis. This hampers the reviewing of manuscripts, limits the reproducibility of study results, and complicates meta-analysis of the literature. In this paper a consensus group of MRS experts provides minimum guidelines for the reporting of MRS methods and results, including the standardized description of MRS hardware, data acquisition, analysis, and quality assessment. This consensus statement describes each of these requirements in detail and includes a checklist to assist authors and journal reviewers and to provide a practical way for journal editors to ensure that MRS studies are reported in full.
Keywords:Proton single voxel spectroscopy Ultra high magnetic field of 14.1 T Rat brain LCModel Quantification accuracy a b s t r a c t Ultra-short echo-time proton single voxel spectra of rat brain were obtained on a 14.1 T 26 cm horizontal bore system. At this field, the fitted linewidth in the brain tissue of adult rats was about 11 Hz. New, separated resonances ascribed to phosphocholine, glycerophosphocholine and N-acetylaspartate were detected for the first time in vivo in the spectral range of 4.2-4.4 ppm. Moreover, improved separation of the resonances of lactate, alanine, c-aminobutyrate, glutamate and glutathione was observed. Metabolite concentrations were estimated by fitting in vivo spectra to a linear combination of simulated spectra of individual metabolites and a measured spectrum of macromolecules (LCModel). The calculated concentrations of metabolites were generally in excellent agreement with those obtained at 9.4 T. These initial results further indicated that increasing magnetic field strength to 14.1 T enhanced spectral resolution in 1 H NMR spectroscopy. This implies that the quantification of the neurochemical profile in rodent brain can be achieved with improved accuracy and precision.
Keywords:Phase imaging In vivo rat brain High field MRI Contrast mechanisms Recent studies at high magnetic fields using the phase of gradient-echo MR images have shown the ability to unveil cortical substructure in the human brain. To investigate the contrast mechanisms in phase imaging, this study extends, for the first time, phase imaging to the rodent brain. Using a 14.1 T horizontal bore animal MRI scanner for in vivo micro-imaging, images with an in-plane resolution of 33 μm were acquired. Phase images revealed, often more clearly than the corresponding magnitude images, hippocampal fields, cortical layers (e.g. layer 4), cerebellar layers (molecular and granule cell layers) and small white matter structures present in the striatum and septal nucleus. The contrast of the phase images depended in part on the orientation of anatomical structures relative to the magnetic field, consistent with bulk susceptibility variations between tissues. This was found not only for vessels, but also for white matter structures, such as the anterior commissure, and cortical layers in the cerebellum. Such susceptibility changes could result from variable blood volume. However, when the deoxyhemoglobin content was reduced by increasing cerebral blood flow (CBF) with a carbogen breathing challenge, contrast between white and gray matter and cortical layers was not affected, suggesting that tissue cerebral blood volume (and therefore deoxyhemoglobin) is not a major source of the tissue phase contrast. We conclude that phase variations in gradient-echo images are likely due to susceptibility shifts of nonvascular origin.
Proton T 1 relaxation times of metabolites in the human brain have not previously been published at 7 T. In this study, T 1 values of CH 3 and CH 2 group of N-acetylaspartate and total creatine as well as nine other brain metabolites were measured in occipital white matter and gray matter at 7 T using an inversion-recovery technique combined with a newly implemented semi-adiabatic spin-echo full-intensity acquired localized spectroscopy sequence (echo time 5 12 ms). The mean T 1 values of metabolites in occipital white matter and gray matter ranged from 0.9 to 2.2 s. Among them, the T 1 of glutathione, scylloinositol, taurine, phosphorylethanolamine, and N-acetylaspartylglutamate were determined for the first time in the human brain. Significant differences in T 1 between white matter and gray matter were found for water (228%), total choline (214%), N-acetylaspartylglutamate (229%), N-acetylaspartate (14%), and glutamate (18%). An increasing trend in T 1 was observed when compared with previously reported values of N-acetylaspartate (CH 3 ), total creatine (CH 3 ), and total choline at 3 T. However, for N-acetylaspartate (CH 3 ), total creatine, and total choline, no substantial differences compared to previously reported values at 9.4 T were discernible. The T 1 values reported here will be useful for the quantification of metabolites and signal-to-noise optimization in human brain at 7 T. Magn Reson Med 69:931-936, 2013. V C 2012 Wiley Periodicals, Inc.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.