Free‐breathing simultaneous T1, T2, and T2∗ quantification in the myocardium

Purpose To implement a free‐breathing sequence for simultaneous quantification of T1, T2, and T2∗ for comprehensive tissue characterization of the myocardium in a single scan using a multi‐gradient‐echo readout with saturation and T2 preparation pulses. Methods In the proposed Saturation And T2‐prepared Relaxometry with Navigator‐gating (SATURN) technique, a series of multi‐gradient‐echo (GRE) images with different magnetization preparations was acquired during free breathing. A total of 35 images were acquired in 26.5 ± 14.9 seconds using multiple saturation times and T2 preparation durations and with imaging at 5 echo times. Bloch simulations and phantom experiments were used to validate a 5‐parameter fit model for accurate relaxometry. Free‐breathing simultaneous T1, T2, and T2∗ measurements were performed in 10 healthy volunteers and 2 patients using SATURN at 3T and quantitatively compared to conventional single‐parameter methods such as SASHA for T1, T2‐prepared bSSFP, and multi‐GRE for T2∗. Results Simulations confirmed accurate fitting with the 5‐parameter model. Phantom measurements showed good agreement with the reference methods in the relevant range for in vivo measurements. Compared to single‐parameter methods comparable accuracy was achieved. SATURN produced in vivo parameter maps that were visually comparable to single‐parameter methods. No significant difference between T1, T2, and T2∗ times acquired with SATURN and single‐parameter methods was shown in quantitative measurements (SATURN T1=1573±86ms, T2=33.2±3.6ms, T2∗=25.3±6.1ms; conventional methods: T1=1544±107ms, T2=33.2±3.6ms, T2∗=23.8±5.5ms; P>.2) Conclusion SATURN enables simultaneous quantification of T1, T2, and T2∗ in the myocardium for comprehensive tissue characterization with co‐registered maps, in a single scan with good agreement to single‐parameter methods.