A novel myocardial T1 analysis method robust to fluctuations in longitudinal magnetization recovery due to heart rate variability in polarity-corrected inversion time preparation

Abstract

Myocardial T1 mapping is useful for characterizing the myocardial tissues. Polarity-corrected inversion time preparation (PCTIP), one of the T1 mapping techniques, was expected to reduce measurement underestimation versus the MOLLI method. However, measurement accuracy is reportedly reduced, especially at high heart rates (HR), owing to the shorter time interval of inversion recovery (IR) pulses. This phantom-based experiment aimed to evaluate the dependence of T1 mapping with PCTIP on HR. Here we proposed and evaluated the effectiveness of a novel HR-independent analysis method for T1 mapping. A PCTIP scan using a 3-T magnetic resonance imaging scanner was performed on a T1 measurement phantom. The virtual HR were set at 50, 60, 75, and 100bpm. The T1 of the phantom was estimated by a least-squares fit of the PCTIP data for each obtained inversion time and a theoretical longitudinal relaxation formula. This analysis was performed for the conventional and proposed formulas. The proposed formula was derived for adapting to the transient state of longitudinal magnetization recovery caused by the trigger interval as a recurrence formula. The estimated T1 measurements using the conventional formula varied widely with HR and the accuracy decreased, especially at a high HR. However, the proposed analysis showed good accuracy versus the conventional method independent of HR. T1 mapping using the PCTIP method combined with the novel method proposed here showed good accuracy.