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

Abstract Background To assess the feasibility of biventricular SAPPHIRE T1 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 3T. Left and right ventricular (LV, RV) T1 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 T1 times (1.5T then 3T results) were significantly longer by diastolic SAPPHIRE (1283±11|1600±17ms) than any of the other SAPPHIRE variants: systolic (1239±9|1595±13ms), 0th order DB (1241±10|1596±12) and 2nd order DB (1251±11|1560±20ms, all p<0.05). In the mid septum MOLLI and diastolic SAPPHIRE exhibited significant T1 signal contamination (longer T1) 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 T1 times across the mid septum when compared to diastolic SAPPHIRE (interquartile ranges respectively: 25ms, 71ms, 73ms vs 143ms, all p<0.05). RV T1 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 T1 mapping. Further work is needed to understand the robustness of these sequences and their potential clinical utility.