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

Abstract

Abstract Objective To measure healthy brain $${T}_{1}$$ T 1 and $${T}_{2}$$ T 2 relaxation times at 0.064 T. Materials and methods $${T}_{1}$$ T 1 and $${T}_{2}$$ T 2 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 $${T}_{1}$$ T 1 and $${T}_{2}$$ T 2 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 $${T}_{1}$$ T 1 sample measurements on the MRI system were within 10% of the NMR measurement for 9 samples, and one sample was within 11%. Eight $${T}_{2}$$ T 2 sample MRI measurements were within 25% of the NMR measurement, and the two longest $${T}_{2}$$ T 2 samples had more than 25% variation. Automatic segmentations generally resulted in larger $${T}_{1}$$ T 1 and $${T}_{2}$$ T 2 estimates than manual ROIs. Discussion $${T}_{1}$$ T 1 and $${T}_{2}$$ T 2 times for brain tissue were measured at 0.064 T. Test samples demonstrated accuracy in WM and GM ranges of values but underestimated long $${T}_{2}$$ T 2 in the CSF range. This work contributes to measuring quantitative MRI properties of the human body at a range of field strengths.