Quantitative T1 and Effective Proton Density (PD*) mapping in children and adults at 7T from an MP2RAGE sequence optimised for uniform T1-weighted (UNI) and FLuid And White matter Suppression (FLAWS) contrasts.

Quantitative T1 and PD mapping is important for non-invasive tissue characterisation. Here, we aimed to calculate effective proton density (PD*) and quantitative T1 relaxation maps at 7T using the MP2RAGE sequence and an analytical formula. This was applied to a short repetition time (TRMP2RAGE) protocol developed to produce both Fluid And White Matter Suppression (FLAWS) and T1-weighted uniform image (UNI) images. T1 and PD* were estimated from analytical MP2RAGE signal equations for partial Fourier acquisitions. The sensitivity with respect to the TRMP2RAGE and B1 + effects on both excitation flip angles and inversion efficiency was evaluated. T1 and PD* alteration with age (10-54 years) were evaluated at the shortest TRMP2RAGE (4000 ms) in white matter (WM), cortical and deep grey matter regions. The T1 values were insensitive to the choice of different TRMP2RAGE. T1 values varied over development into adulthood, especially for the deep grey matter regions whereas only a very small difference was observed for WM T1. Effective PD maps were produced which did not show a significant difference between children and adults for the age range included. PD* maps and high precision T1 maps were produced at 7T with 0.65 mm resolution in 7:18 min:s from an MP2RAGE protocol, previously optimised for UNI and FLAWS-related contrasts by incorporating the excitation flip angle and inversion efficiency B1 + effects into the fit. Average WM T1 values of adults and children were very similar (1092 vs. 1117 ms) while expected reductions in T1 with age were found in deep GM.