Comparison of longitudinal metabolite relaxation times in different regions of the human brain at 1.5 and 3 Tesla

Abstract

In vivo longitudinal relaxation times of N‐acetyl compounds (NA), choline‐containing substances (Cho), creatine (Cr), myo‐inositol (mI), and tissue water were measured at 1.5 and 3 T using a point‐resolved spectroscopy (PRESS) sequence with short echo time (TE). T₁ values were determined in six different brain regions: the occipital gray matter (GM), occipital white matter (WM), motor cortex, frontoparietal WM, thalamus, and cerebellum. The T₁ relaxation times of water protons were 26–38% longer at 3 T than at 1.5 T. Significantly longer metabolite T₁ values at 3 T (11–36%) were found for NA, Cho, and Cr in the motor cortex, frontoparietal WM, and thalamus. The amounts of GM, WM, and cerebrospinal fluid (CSF) within the voxel were determined by segmentation of a 3D image data set. No influence of tissue composition on metabolite T₁ values was found, while the longitudinal relaxation times of water protons were strongly correlated with the relative GM content. Magn Reson Med 50:1296–1301, 2003.