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

ABSTRACT

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.