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.

The future of cardiovascular magnetic resonance: All-in-one vs. real-time (Part 1)

“…Model-based formulations allow for high acceleration factors and have demonstrated high resolution (1 × 1 × 8 mm 3 ) T 1 mapping in ∼4 s scan time [22] , with negligible biases relative to MOLLI (∼20 ms) and a CoV of approximately 3%. Joint T 1 /T 2 /T 2 * mapping has been demonstrated in free-breathing using SR, T2prep, multi-gradient-echo and navigator gating, for 2x2x8 mm 3 resolution multi-parametric mapping in a ∼26.5 s scan [23] . Minor differences were observed relative to SASHA (∼30 ms), T2prep-bSSFP (∼0 ms) and multi-echo-gradient-echo (∼1.5 ms), for T 1 , T 2 and T 2 * , respectively; corresponding precisions were ∼68 ms, ∼1.1 ms and ∼ 3.3 ms.…”

Improved reproducibility for myocardial ASL: Impact of physiological and acquisition parameters

“…In a FAIR‐myoASL measurement, the imaging signal can be modeled with blood ($$$ {I}_B $$$) and myocardial contributions ($$$ {I}_M $$$) weighted by the blood‐volume‐fraction $$$ {V}_B $$$ and its complement $$$ {V}_M=1-{V}_B $$$, respectively. Due to differences in the relaxation times, 25,26 the coefficients $$$ {A}_M $$$ and $$$ {A}_B $$$ in the MMF (Equations and ) differ between $$$ {I}_B $$$ and $$$ {I}_M $$$.…”

“…In a FAIR-myoASL measurement, the imaging signal can be modeled with blood (I B ) and myocardial contributions (I M ) weighted by the blood-volume-fraction V B and its complement V M = 1 − V B , respectively. Due to differences in the relaxation times, 25,26 the coefficients A M and A B in the MMF (Equations 3and 4) differ between I B and I M . Using the approach of Buxton's GKM (Equation 1) and the image signals as derived in the Appendix (Equations B2-B9), the ratio of control, tag, and baseline signal can be given as:…”

MyoFold: Joint myocardial tissue composition and wall motion quantification via a highly folded sequence

“…8 Most of the current approaches are designed for simultaneous myocardial T 1 and T 2 mapping. [9][10][11][12][13][14][15][16] Within a single breath-holding scan, these sequences acquire 10 to 12 hybrid T 1 /T 2 -weighted images to ensure robust estimation of T 1 and T 2 . However, additional cine scans are required for LV function.…”

“…To address these limitations, multitasking techniques have been introduced to shorten imaging time and enhance diagnostic capabilities through the coregistered tissue MR properties 8 . Most of the current approaches are designed for simultaneous myocardial T 1 and T 2 mapping 9–16 . Within a single breath‐holding scan, these sequences acquire 10 to 12 hybrid T 1 /T 2 ‐weighted images to ensure robust estimation of T 1 and T 2 .…”