Temporally resolved parametric assessment of Z-magnetization recovery (TOPAZ): Dynamic myocardial T1 mapping using a cine steady-state look-locker approach.

ABSTRACT: PURPOSE:To develop and evaluate a cardiac phase-resolved myocardial T1 mapping sequence. METHODS:The proposed method for temporally resolved parametric assessment of Z-magnetization recovery (TOPAZ) is based on contiguous fast low-angle shot imaging readout after magnetization inversion from the pulsed steady state. Thereby, segmented k-space data are acquired over multiple heartbeats, before reaching steady state. This results in sampling of the inversion-recovery curve for each heart phase at multiple points separated by an R-R interval. Joint T1 and B1+ estimation is performed for reconstruction of cardiac phase-resolved T1 and B1+ maps. Sequence parameters are optimized using numerical simulations. Phantom and in vivo imaging are performed to compare the proposed sequence to a spin-echo reference and saturation pulse prepared heart rate-independent inversion-recovery (SAPPHIRE) T1 mapping sequence in terms of accuracy and precision. RESULTS:In phantom, TOPAZ T1 values with integrated B1+ correction are in good agreement with spin-echo T1 values (normalized root mean square error?=?4.2%) and consistent across the cardiac cycle (coefficient of variation?=?1.4?±?0.78%) and different heart rates (coefficient of variation?=?1.2?±?1.9%). In vivo imaging shows no significant difference in TOPAZ T1 times between the cardiac phases (analysis of variance: P?=?0.14, coefficient of variation?=?3.2?±?0.8%), but underestimation compared with SAPPHIRE (T1 time?±?precision: 1431?±?56 ms versus 1569?± 65 ms). In vivo precision is comparable to SAPPHIRE T1 mapping until middiastole (P?>?0.07), but deteriorates in the later phases. CONCLUSIONS:The proposed sequence allows cardiac phase-resolved T1 mapping with integrated B1+ assessment at a temporal resolution of 40 ms. Magn Reson Med 79:2087-2100, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

SUBMITTER: Weingartner S 

PROVIDER: S-EPMC5811329 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature