Fast myocardial T1 mapping using shortened inversion recovery based schemes

Abstract

Background: Myocardial T₁ mapping shows promise for assessment of cardiomyopathies. Most myocardial T₁ mapping techniques, such as modified Look-Locker inversion recovery (MOLLI), generate one T₁ map per breath-held acquisition (9-17 heartbeats), which prolongs multislice protocols and may be unsuitable for patients with breath-holding difficulties.

Purpose: To develop and characterize novel shortened inversion recovery based T₁ mapping schemes of 2-5 heartbeats.

Study type: Prospective.

Population/phantom: Numerical simulations, agarose/NiCl₂ phantom, 16 healthy volunteers, and 24 patients.

Field strength/sequence: 1.5T/MOLLI.

Assessment: All shortened T₁ mapping schemes were characterized and compared with a conventional MOLLI scheme (5-(3)-3) in terms of accuracy, precision, spatial variability, and repeatability.

Statistical tests: Kruskal-Wallis, Wilcoxon rank sum tests, analysis of variance, Student's t-tests, Bland-Altman analysis, and Pearson correlation analysis.

Results: All shortened schemes provided limited T₁ time variations (≤2% for T₁ times ≤1200 msec) and limited penalty of precision (by a factor of ~1.4-1.5) when compared with MOLLI in numerical simulations. In phantom, differences between all schemes in terms of accuracy, spatial variability, and repeatability did not reach statistical significance (P > 0.71). In healthy volunteers, there were no statistically significant differences between all schemes in terms of native T₁ times and repeatability for myocardium (P = 0.21 and P = 0.87, respectively) and blood (P = 0.79 and P = 0.41, respectively). All shortened schemes led to a limited increase of spatial variability for native myocardial T₁ mapping with respect to MOLLI (by a factor of 1.2) (P < 0.0001). In both healthy volunteers and patients, the two-heartbeat scheme and MOLLI led to highly linearly correlated T₁ times (correlation coefficients ≥0.83).

Data conclusion: The proposed two-heartbeat T₁ mapping scheme yields a 5-fold acceleration compared with MOLLI, with highly linearly correlated T₁ times, no significant difference of repeatability, and limited spatial variability penalty at 1.5T. This approach may enable myocardial T₁ mapping in patients with severe breath-holding difficulties and reduce the examination time of multislice protocols.

Level of evidence: 1 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2019;50:641-654.

Keywords: Look-Locker; MOLLI; T1 mapping; inversion recovery; myocardial tissue characterization.