T1 and T2 Metabolite Relaxation Times in Normal Brain at 3T and 7T

Abstract

This study was designed to measure T1 and T2 relaxation times of the singlets in normal brain at 7T. Our results demonstrated that the T 1 relaxation values of total creatine (tCr)-CH 3 and N-acetyl aspartate (NAA) in the parietal white matter significantly increased at 7T compared to 3T, while the T 1 of Choline-containing compounds (Cho) was similar between field strengths. T 2 values of all metabolites investigated were significantly shorter at 7T. To compare signal-to-noise ratio (SNR) values between different field strengths, data were corrected for the effects of T 1 and T 2 relaxation. The average SNR ratio between 7T and 3T was 1.6. The increase in peak height SNR was less than linear with respect to B 0 , primarily due to the differences in linewidth. The average linewidth of tCr-CH 3 in TE-averaged spectra was 18.62 Hz while it was 8.38 Hz in the single echo time using spectral-spatial RF pulses at 7T. The Cramer-Rao lower bounds (CRLBs) of metabolites were much lower at 7T compared to 3T. These data are important for the optimization of acquisition parameters for future spectroscopy studies in clinical applications at 7T.

Comparison of single voxel brain MRS AT 3T and 7T using 32-channel head coils

“…Consistent with prior studies of the occipital lobe using surface coils [2, 6] and one study of parietal white matter using an 8-channel head coil [9], this study confirms the improved SNR and generally lower metabolite CRLBs at 7T compared to 3T, across three brain regions using 32-channel receiver coil arrays. Improvements in SNR seen in the cortical regions (63–66%) in the current study were similar to those seen in reference [6], slightly lower than those reported in reference [2] and also lower than the linear prediction from simple theory (a factor of 2.3).…”

“…In particular, previous studies using surface coils have shown that the SNR, spectral resolution and measurement precision in the occipital lobe are all superior at 7T compared to lower field strengths (either 3T or 4T) [2, 6]. However, to our knowledge, there has only been one comparison MRS study [9] between field strengths that used multi-channel receiver head coils, which compared measurements made in the parietal white matter at 3T and 7T using an 8- channel head coil. The current study compared measurements made in multiple-brain regions using 32-channel head coils at 3T and 7T.…”

Comparison between Short and Long Echo Time Magnetic Resonance Spectroscopic Imaging at 3T and 7T for Evaluating Brain Metabolites in Patients with Glioma

“…The differences in relaxation times of brain metabolites between the T2 lesion and normal brain 20 and shortening of T2 relaxation times at 7T 21 could change the contrast between metabolites in the different regions. These effects have not previously been evaluated for patients with glioma.…”

In vivo proton magnetic resonance spectroscopy of liver metabolites in non-alcoholic fatty liver disease in rats: T2 relaxation times in methylene protons

“…An increase in SNR Abbreviations: MRI, magnetic resonance imaging; 1 H-MRS, proton magnetic resonance spectroscopy; NC, normal-chow; HF, high-fat; PRESS, point-resolved spectroscopy; VOI, volume of interest; TR, repetition time; TE, echo time; NSA, number of signal averages; VAPOR, variable pulse power and optimized relaxation delays; SE, spin echo; SNR, signal-to-noise ratio; STEAM, stimulated echo acquisition mode. shortens the total acquisition time and increases spectral resolution, thus improving quantification of metabolites and relaxation time (Li et al, 2008). For minimizing signal loss, localized point-resolved spectroscopy (PRESS) and short echo time (TE) produce better SNR of metabolite peaks and their T2 relaxation times rather than stimulated echo acquisition mode (STEAM) sequence with long TE (Yahya and Fallone, 2010).…”