Fast cardiac T_1ρ,adiab mapping using slice-selective adiabatic spin-lock preparation pulses

Purpose: Myocardial T_1ρ mapping techniques commonly acquire multiple images in one breathhold to calculate a single-slice T_1ρ map. Recently, non-selective adiabatic pulses have been used for robust spin-lock preparation (T_1ρ,adiab). The objective of this study was to develop a fast multi-slice myocardial T_1ρ,adiab mapping approach.

Methods: The proposed-sequence reduces the number of breathholds required for whole-heart 2D T_1ρ,adiab mapping by acquiring multiple interleaved slices in each breathhold using slice-selective T_1ρ,adiab preparation pulses. The proposed-sequence was implemented with two interleaved slices per breathhold scan and was quantitatively evaluated in phantom experiments and 10 healthy-volunteers against a single-slice T_1ρ,adiab mapping sequence. The sequence was demonstrated in two patients with myocardial scar.

Results: The phantom experiments showed the proposed-sequence had slice-to-slice variation of 1.62% ± 1.05% and precision of 4.51 ± 0.68 ms. The healthy volunteer cohort subject-wise mean relaxation time was lower for the proposed-sequence than the single-slice sequence (137.7 ± 5.3 ms vs. 148.4 ± 8.3 ms, p < 0.001), and spatial-standard-deviation was better (18.7 ± 1.8 ms vs. 21.8 ± 3.4 ms, p < 0.018). The mean within-subject, coefficient of variation was 5.93% ± 1.57% for the proposed-sequence and 6.31% ± 1.92% for the single-slice sequence (p = 0.35) and the effect of slice variation (0.81 ± 4.87 ms) was not significantly different to zero (p = 0.61). In both patient examples increased T_1ρ,adiab (maximum American Heart Association-segment mean = 174 and 197 ms) was measured within the myocardial scar.

Conclusion: The proposed sequence provides a twofold acceleration for myocardial T_1ρ,adiab mapping using a multi-slice approach. It has no significant difference in within-subject variability, and significantly better precision, compared to a 2D T_1ρ,adiab mapping sequence based on non-selective adiabatic spin-lock preparations.