Reproducibility and sensitivity of in vivo human brain R1 map at ultralow field 64 mT

MR parameter mapping provides objective biomarkers for living tissues. However, long scan times and high field MR imaging are typically required, whereas few ultralow field MR scanner studies have been performed. Here we propose a simplified R1 mapping protocol with only two inversion delay time points (R1approx), taking advantage of the fast R1 at ultralow field. The R1 characteristics of human brain were largely preserved in R1approx compared to standard inversion recovery R1 mapping. R1approx. required under 30 minutes vs. ~two hours for standard R1 mapping. In addition, R1approx. shows high reproducibility and good sensitivity to an R1 contrast agent.