MRS Examination (mrs + examination)

Distribution by Scientific Domains

Selected Abstracts

Magnetic resonance spectroscopy (MRS) and its application in Alzheimer's disease

Pravat K. Mandal
Abstract Magnetic resonance spectroscopy (MRS) is a noninvasive tool to measure the chemical composition of tissues (in vivo) and characterize functional metabolic processes in different parts of the human organs. It provides vital biological information at the molecular level. Combined with magnetic resonance imaging (MRI), an integrated MRI/MRS examination provides anatomical structure, pathological function, and biochemical information about a living system. MRS provides a link between the biochemical alterations and the pathophysiology of disease. This article provides a comprehensive description of the MRS technique and its application in Alzheimer's disease (AD) research. This review is a primer for students and researchers seeking a firm theoretical understanding of MRS physics as well as its application in clinical AD research. 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 40,64, 2007. [source]

3T MR of the prostate: Reducing susceptibility gradients by inflating the endorectal coil with a barium sulfate suspension

Yael Rosen
Abstract Most prostate MRI/MRS examinations are performed with an endorectal coil inflated with air, leading to an air,tissue interface that induces magnetic susceptibility gradients within the gland. Inflation of the coil with a barium sulfate suspension is described and compared to inflation with air or liquid perfluorocarbon (PFC). The B0 field in the prostate gland was mapped for five healthy volunteers when the endorectal coil was inflated with each of the three agents. A marked decrease in the posterior-anterior (P-A) field gradient and a significant improvement in field homogeneity were evident in the presence of a barium suspension and PFC relative to air. MRS data acquired from the prostate gland in the presence of air, PFC, and a barium suspension in the endorectal coil showed similar trends, demonstrating improvement in line-widths and spectral resolution when the barium suspension or the PFC were inflating the endorectal coil. On this basis we conclude that a barium suspension provides an available, cheap, and safe alternative to PFC, and we suggest that inflating the endorectal coil with a barium suspension should be considered for prostate MR studies, especially at high field strengths (such as 3T). Magn Reson Med 57:898,904, 2007. 2007 Wiley-Liss, Inc. [source]

Pitfalls and advantages of different strategies for the absolute quantification of N -acetyl aspartate, creatine and choline in white and grey matter by 1H-MRS

E. Malucelli
Abstract This study extensively investigates different strategies for the absolute quantitation of N -acetyl aspartate, creatine and choline in white and grey matter by 1H-MRS at 1.5,T. The main focus of this study was to reliably estimate metabolite concentrations while reducing the scan time, which remains as one of the main problems in clinical MRS. Absolute quantitation was based on the water-unsuppressed concentration as the internal standard. We compared strategies based on various experimental protocols and post-processing strategies. Data were obtained from 30 control subjects using a PRESS sequence at several TE to estimate the transverse relaxation time, T2, of the metabolites. Quantitation was performed with the algorithm QUEST using two different metabolite signal basis sets: a whole-metabolite basis set (WhoM) and a basis set in which the singlet signals were split from the coupled signals (MSM). The basis sets were simulated in vivo for each TE used. Metabolites' T2s were then determined by fitting the estimated signal amplitudes of the metabolites obtained at different TEs. Then the absolute concentrations (mM) of the metabolites were assessed for each subject using the estimated signal amplitudes and either the mean estimated relaxation times of all subjects (mean protocol, MP) or the T2 estimated from the spectra derived from the same subject (individual protocol, IP). Results showed that MP represents a less time-consuming alternative to IP in the quantitation of brain metabolites by 1H-MRS in both grey and white matter, with a comparable accuracy when performed by MSM. It was also shown that the acquisition time might be further reduced by using a variant of MP, although with reduced accuracy. In this variant, only one water-suppressed and one water-unsuppressed spectra were acquired, drastically reducing the duration of the entire MRS examination. However, statistical analysis highlights the reduced accuracy of MP when performed using WhoM, particularly at longer echo times. Copyright 2009 John Wiley & Sons, Ltd. [source]

MRI and 1H MRS of The Breast: Presence of a Choline Peak as Malignancy Marker is Related to k21 Value of the Tumor in Patients with Invasive Ductal Carcinoma

Patricia R. Geraghty MD
Abstract:, To assess which specific morphologic features, enhancement patterns, or pharmacokinetic parameters on breast Magnetic Resonance Imaging (MRI) could predict a false-negative outcome of Proton MR Spectroscopy (1H MRS) exam in patients with invasive breast cancer. Sixteen patients with invasive ductal carcinoma of the breast were prospectively included and underwent both, contrast-enhanced breast MRI and 1H MRS examination of the breast. The MR images were reviewed and the lesions morphologic features, enhancement patterns and pharmacokinetic parameters (k21-value) were scored according to the ACR BI-RADS-MRI lexicon criteria. For the in vivo MRS studies, each spectrum was evaluated for the presence of choline based on consensus reading. Breast MRI and 1H MRS data were compared to histopathologic findings. In vivo 1H MRS detected a choline peak in 14/16 (88%) cancers. A false-negative 1H MRS study occurred in 2/16 (14%) cancer patients. K21 values differed between both groups: the 14 choline positive cancers had k21 values ranging from 0.01 to 0.20/second (mean 0.083/second), whereas the two choline-negative cancers showed k21 values of 0.03 and 0.05/second, respectively (mean 0.040/second). Also enhancement kinetics did differ between both groups; typically both cancers that were choline-negative showed a late phase plateau (100%), whereas this was only shown in 5/14 (36%) of the choline positive cases. There was no difference between both groups with regard to morphologic features on MRI. This study showed that false-negative 1H MRS examinations do occur in breast cancer patients, and that the presence of a choline peak on 1H MRS as malignancy marker is related to the k21 value of the invasive tumor being imaged. [source]