Quantitative T1 mapping using multi-slice multi-shot inversion recovery EPI

An efficient multi-slice inversion–recovery EPI (MS-IR-EPI) sequence for fast, high spatial resolution, quantitative T(1) mapping is presented, using a segmented simultaneous multi-slice acquisition, combined with slice order shifting across multiple acquisitions. The segmented acquisition minimises the effective TE and readout duration compared to a single-shot EPI scheme, reducing geometric distortions to provide high quality T(1) maps with a narrow point-spread function. The precision and repeatability of MS-IR-EPI T(1) measurements are assessed using both T(1)-calibrated and T(2)-calibrated ISMRM/NIST phantom spheres at 3 and 7 T and compared with single slice IR and MP2RAGE methods. Magnetization transfer (MT) effects of the spectrally-selective fat-suppression (FS) pulses required for in vivo imaging are shown to shorten the measured in-vivo T(1) values. We model the effect of these fat suppression pulses on T(1) measurements and show that the model can remove their MT contribution from the measured T(1), thus providing accurate T(1) quantification. High spatial resolution T(1) maps of the human brain generated with MS-IR-EPI at 7 T are compared with those generated with the widely implemented MP2RAGE sequence. Our MS-IR-EPI sequence provides high SNR per unit time and sharper T(1) maps than MP2RAGE, demonstrating the potential for ultra-high resolution T(1) mapping and the improved discrimination of functionally relevant cortical areas in the human brain.