Reproducibility of localized 2D correlated MR spectroscopy

Abstract

The test-retest reliability of two-dimensional (2D) correlated spectroscopy (COSY) was studied on a whole-body 1.5T MRI scanner. Single-voxel localized 2D proton spectra were recorded in vitro as well as in vivo using a recently implemented localized chemical shift correlated spectroscopic (L-COSY) sequence. A total of 40 in vitro and 40 human brain (10 volunteers, four times each) 2D L-COSY spectra were recorded. The coefficients of variation (CVs) of selected brain metabolites (raw volume integrals) recorded in 10 healthy volunteers were less than 9% for creatine, choline, and N-acetyl aspartate, and less than 17% for myo-inositol, glutamine/glutamate, aspartate, and threonine/lactate. The 2D metabolite ratios and the raw volume integrals of 2D diagonal and cross peaks in healthy human brain were very well reproduced. The intraclass correlation coefficients were greater than 0.4 (P < 0.05) for the major metabolites, indicating that the 2D peak volumes were stable enough within individuals to detect reliable differences between normal subjects. In the past decade, MR spectroscopy (MRS) has become a reliable clinical tool for the diagnosis of selected diseases (1-7). An important feature of any diagnostic tool is its reproducibility. Many studies on the reproducibility of one-dimensional (1D) 1 H MRS have reported the ratios and absolute concentrations of the metabolites (8 -13). Although these studies have shown small errors (3-6%) in the measurement of metabolites in vitro (8,9), the in vivo studies showed higher coefficients of variation (7-26%) in a maximum of only five metabolites (9 -13). Severe overlap of brain metabolites is a major hindrance in 1D MRS.Localized and nonlocalized versions of 2D MRS were reported a decade ago (14 -18); however, only recently have 2D proton spectra been recorded in healthy human subjects and patients with brain tumors (19 -25). Compared to 1D MRS, 2D MR spectra allow less ambiguous assignment of several metabolite resonances in human brain and prostate (25)(26)(27). In a previous study (25), the resonances caused by glutamine/glutamate (Glx) were clearly separated from the dominant singlet resulting from N-acetyl aspartate (NAA) and myo-inositol (mI) in the human brain. Even though identification of "free" aspartate (Asp) was not possible with 1D MRS, the peaks were separated from NAA in 2D MRS (25). 2D cross peaks caused by phosphoethanolamine and ethanolamine (PE), phosphoryl choline (PCh), threonine and lactate (Thr/Lac), and ␥-aminobutyric acid (GABA) were also identified in the 2D L-COSY spectra of the brain. However, to date there has been no report on the reproducibility of 2D MRS. The goal of this work was to investigate the reproducibility of 2D peak volumes and 2D metabolite ratios recorded in phantom solutions and healthy brain using the L-COSY sequence (25). MATERIALS AND METHODS A 1.5 T GE Horizon (5.8) MRI/MRS scanner (GE MedicalSystems, Waukesha, WI) with echo-speed gradients was used with a body coil for transmission and a 3-inch surface coil for reception. ...

Evaluation of two‐dimensional L‐COSY and JPRESS using a 3 T MRI scanner: from phantoms to human brain in vivo

“…In order to calculate the reproducibility of 2D L-COSY spectra, the following coefficients of variation (CV) of the ratios with respect to the diagonal peak of Cr (Cr_d) were calculated: (a) 14%; (b) 16%; (c) 15%; (d) 8%; (e) 13%; (f) 12%; (h) 19%; and (i) 16%. An improvement with these CVs compared with our recent findings using a 1.5 T MRI scanner 27 was most probably due to the improved spectral dispersion at 3 T. The 2D L-COSY spectra were also recorded in the occipito-parietal white matter of five healthy volunteers and the following CVs were calculated: 27, 21, 35, 10, 21, 19, 5 and 8% for the metabolite ratios of NAA, Glx, mICh, mI, Asp, GSH, Ch_d and NAA_d with the diagonal peak volume of Cr Cr_d). Owing to the proximity of the MRS voxel to skull marrow, the contamination of lipids was more prominent in the occipito-parietal white matter.…”

1H‐MRS can detect aberrant glycosylation in tumour cells: a study of the HeLa cell line

“…According to previous studies (18,20), the size of each rectangle marking the area used for the peak volume integration was determined just to cover the peak (above the noise) but not the neighbouring peaks. After few spectra evaluation, the optimized rectangle sizes (areas of integration) were fixed and applied to all the spectra.…”

“…In particular, the use of 2D experiments improves metabolite specificity and can solve most one-dimensional (1D) co-resonating signals while keeping good sensitivity, especially in association with high resolution coils. Recently, 2D spectroscopy entered the field of metabolomics in cells, in ex vivo samples and in vivo studies, making it possible to detect 20 to 40 metabolites in tissue samples (18)(19)(20)(21)(22).…”

Localized two‐dimensional 1H magnetic resonance exchange spectroscopy: A preliminary evaluation in human muscle

“…The 2D raw data were processed using a Felix-2000 package (Accelrys, San Diego, CA). The volumes under the 2D diagonal and cross peaks were calculated using manual peak picking on contours (25) The study group included six healthy volunteers (four males and two females). Healthy controls were aged between 27 and 53 years old, with a mean age of 38 years.…”

“…1 is a 2D L-EXSY sequence with three slice-selective 90°RF pulses (90°S S ) combined with the conventional TE-and TM-crushers that are commonly used in a STEAM sequence (22). This sequence mirrors the three-pulse technique proposed by Jeener et al 25 years ago except that the earlier sequence used three hard RF pulses (16). An incremental delay (t 1 ) to encode the second spectral axis was inserted between the refocusing gradient pulse after the first 90°S S pulse and the first column of TE-crusher gradients prior to the second 90°S S pulse.…”