Saturation-pulse prepared heart-rate independent inversion-recovery (SAPPHIRE) biventricular T1 mapping: inter-field strength, head-to-head comparison of diastolic, systolic and dark-blood measurements

Background To assess the feasibility of biventricular SAPPHIRE T-1 mapping in vivo across field strengths using diastolic, systolic and dark-blood (DB) approaches. Methods 10 healthy volunteers underwent same-day non-contrast cardiovascular magnetic resonance at 1.5 Tesla (T) and 3 T. Left and right ventricular (LV, RV) T-1 mapping was performed in the basal, mid and apical short axis using 4-variants of SAPPHIRE: diastolic, systolic, 0th and 2nd order motion-sensitized DB and conventional modified Look-Locker inversion recovery (MOLLI). Results LV global myocardial T-1 times (1.5 T then 3 T results) were significantly longer by diastolic SAPPHIRE (1283 +/- 11|1600 +/- 17 ms) than any of the other SAPPHIRE variants: systolic (1239 +/- 9|1595 +/- 13 ms), 0th order DB (1241 +/- 10|1596 +/- 12) and 2nd order DB (1251 +/- 11|1560 +/- 20 ms, all p < 0.05). In the mid septum MOLLI and diastolic SAPPHIRE exhibited significant T-1 signal contamination (longer T-1) at the blood-myocardial interface not seen with the other 3 SAPPHIRE variants (all p < 0.025). Additionally, systolic, 0th order and 2nd order DB SAPPHIRE showed narrower dispersion of myocardial T-1 times across the mid septum when compared to diastolic SAPPHIRE (interquartile ranges respectively: 25 ms, 71 ms, 73 ms vs 143 ms, all p < 0.05). RV T-1 mapping was achievable using systolic, 0th and 2nd order DB SAPPHIRE but not with MOLLI or diastolic SAPPHIRE. All 4 SAPPHIRE variants showed excellent re-read reproducibility (intraclass correlation coefficients 0.953 to 0.996). Conclusion These small-scale preliminary healthy volunteer data suggest that DB SAPPHIRE has the potential to reduce partial volume effects at the blood-myocardial interface, and that systolic SAPPHIRE could be a feasible solution for right ventricular T-1 mapping. Further work is needed to understand the robustness of these sequences and their potential clinical utility.