Free-breathing simultaneous T1, T2, and T2* quantification in the myocardium

Purpose To implement a free-breathing sequence for simultaneous quantification of T-1, T-2, and T-2* for comprehensive tissue characterization of the myocardium in a single scan using a multi-gradient-echo readout with saturation and T-2 preparation pulses. Methods In the proposed Saturation And T-2-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 T-2 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 T-1, T-2, and T-2* 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 T-1, T-2-prepared bSSFP, and multi-GRE for T-2*. 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 T-1, T-2, and T-2* times acquired with SATURN and single-parameter methods was shown in quantitative measurements (SATURN T-1=1573 +/- 86ms, T-2=33.2 +/- 3.6ms, T-2*=25.3 +/- 6.1ms; conventional methods: T-1=1544 +/- 107ms, T-2=33.2 +/- 3.6ms, T-2*=23.8 +/- 5.5ms; P>.2) Conclusion SATURN enables simultaneous quantification of T-1, T-2, and T-2* in the myocardium for comprehensive tissue characterization with co-registered maps, in a single scan with good agreement to single-parameter methods.