Abstract
PurposeTo 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.MethodsIn 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∗.ResultsSimulations 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)ConclusionSATURN 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.
Highlights
Quantitative mapping in the myocardium has received major clinical interest, as markers related to myocardial relaxation time yield promising sensitivity to a broad spectrum of cardiomyopathies
T1, T2, and T2∗ mapping are routinely used in advanced CMR centers and received increasing interest in community recommendations and consensus statements for the assessment of ischemia, fibrosis, edema, and amyloidosis or iron deposition.1-4
A wide variety of mapping sequences was proposed in the last decades for noninvasively studying the myocardial tissue state.5-9 Myocardial T1 mapping is most commonly performed based on a series of inversion or saturation recovery images and has shown promise for the assessment of ischemic and nonischemic cardiomyopathies.[1,4,10,11]
Summary
Quantitative mapping in the myocardium has received major clinical interest, as markers related to myocardial relaxation time yield promising sensitivity to a broad spectrum of cardiomyopathies. A wide variety of mapping sequences was proposed in the last decades for noninvasively studying the myocardial tissue state.5-9 Myocardial T1 mapping is most commonly performed based on a series of inversion or saturation recovery images and has shown promise for the assessment of ischemic and nonischemic cardiomyopathies.[1,4,10,11] While inversion recovery-based methods have shown improved precision and map quality, saturation recovery methods yield more accurate T1 maps insensitive to the heart rate, the magnetization evolution, and other confounders.12-14. Myocardial T2∗ quantification has demonstrated high clinical value for the assessment of myocardial iron accumulation.19-21 According to relevant guidelines, T2∗ measurements in the myocardium is most commonly performed by acquiring 8 echoes with a multi-gradient-e cho readout and performing an exponential fit.[19]. The accuracy of the proposed technique is evaluated in phantom measurements and in vivo image quality is assessed in healthy subjects and a small cohort of patients
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