Repeatability of Open‐MOLLI: An open‐source inversion recovery myocardial T1 mapping sequence for fast prototyping

Abstract

AbstractPurposeTo develop an open‐source prototype of myocardial T1 mapping (Open‐MOLLI) to improve accessibility to cardiac T1 mapping and evaluate its repeatability. With Open‐MOLLI, we aim to enable faster implementation and testing of sequence modifications and to facilitate inter‐scanner and cross‐vendor reproducibility studies.MethodsOpen‐MOLLI is an inversion‐recovery sequence using a balanced SSFP (bSSFP) readout, with inversion and triggering schemes based on the 5(3)3 MOLLI sequence, developed in Pulseq. Open‐MOLLI and MOLLI sequences were acquired in the ISMRM/NIST phantom and 21 healthy volunteers. In 18 of those subjects, Open‐MOLLI and MOLLI were repeated in the same session (test–retest).ResultsPhantom T1 values were comparable between methods, specifically for the vial with reference T1 value most similar to healthy myocardium T1 (T1vial3 = 1027 ms): T1MOLLI = 1011 ± 24 ms versus T1Open‐MOLLI = 1009 ± 20 ms. In vivo T1 estimates were similar between Open‐MOLLI and MOLLI (T1MOLLI = 1004 ± 33 ms vs. T1Open‐MOLLI = 998 ± 52 ms), with a mean difference of −17 ms (p = 0.20), despite noisier Open‐MOLLI weighted images and maps. Repeatability measures were slightly higher for Open‐MOLLI (RCMOLLI = 3.0% vs. RCOpen‐MOLLI = 4.4%).ConclusionThe open‐source sequence Open‐MOLLI can be used for T1 mapping in vivo with similar mean T1 values to the MOLLI method. Open‐MOLLI increases the accessibility to cardiac T1 mapping, providing also a base sequence to which further improvements can easily be added and tested.