In vivo measurement of T1rho dispersion in the human brain at 1.5 tesla.

Abstract

To measure T1rho relaxation times and T1rho dispersion in the human brain in vivo. Magnetic resonance imaging (MRI) was performed on a 1.5-T GE Signa clinical scanner using the standard GE head coil. A fast spin-echo (FSE)-based T1rho-weighted MR pulse sequence was employed to obtain images from five healthy male volunteers. Optimal imaging parameters were determined while considering both the objective of the study and the guarantee that radio-frequency (RF) power deposition during MR did not exceed Food and Drug Administration (FDA)-mandated safety levels. T1rho-weighted MR images showed excellent contrast between different brain tissues. These images were less blurred than corresponding T2-weighted images obtained with similar contrast, especially in regions between brain parenchyma and cerebrospinal fluid (CSF). Average T1rho values for white matter (WM), gray matter (GM), and CSF were 85 +/- 3, 99 +/- 1, and 637 +/- 78 msec, respectively, at a spin-locking field of 500 Hz. T1rho is 30% higher in the parenchyma and 78% higher in CSF compared to the corresponding T2 values. T1rho dispersion was observed between spin-locking frequencies 0 and 500 Hz. T1rho-weighted MRI provides images of the brain with superb contrast and detail. T1rho values measured in the different brain tissues will serve as useful baseline values for analysis of T1rho changes associated with pathology.