In vivo quantitative MRI: T1 and T2 measurements of the human brain at 0.064 T

Abstract

Objective: To measure healthy brain T1 and T2 relaxation times at 0.064 T. Materials and methods: T1 and T2 relaxation times were measured in vivo for 10 healthy volunteers using a 0.064 T magnetic resonance imaging (MRI) system and for 10 test samples on both the MRI and a separate 0.064 T nuclear magnetic resonance (NMR) system. In vivo T1 and T2 values are reported for white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF) for automatic segmentation regions and manual regions of interest (ROIs). Results: T1 sample measurements on the MRI system were within 10% of the NMR measurement for 9 samples, and one sample was within 11%. Eight T2 sample MRI measurements were within 25% of the NMR measurement, and the two longest T2 samples had more than 25% variation. Automatic segmentations generally resulted in larger T1 and T2 estimates than manual ROIs. Discussion: T1 and T2 times for brain tissue were measured at 0.064 T. Test samples demonstrated accuracy in WM and GM ranges of values but underestimated long T2 in the CSF range. This work contributes to measuring quantitative MRI properties of the human body at a range of field strengths.