Water–fat Dixon cardiac magnetic resonance fingerprinting

Abstract

Purpose Cardiac magnetic resonance fingerprinting (cMRF) has been recently introduced to simultaneously provide T1, T2, and M0 maps. Here, we develop a 3‐point Dixon‐cMRF approach to enable simultaneous water specific T1, T2, and M0 mapping of the heart and fat fraction (FF) estimation in a single breath‐hold scan. Methods Dixon‐cMRF is achieved by combining cMRF with several innovations that were previously introduced for other applications, including a 3‐echo GRE acquisition with golden angle radial readout and a high‐dimensional low‐rank tensor constrained reconstruction to recover the highly undersampled time series images for each echo. Water–fat separation of the Dixon‐cMRF time series is performed to allow for water‐ and fat‐specific T1, T2, and M0 estimation, whereas FF estimation is extracted from the M0 maps. Dixon‐cMRF was evaluated in a standardized T1–T2 phantom, in a water–fat phantom, and in healthy subjects in comparison to current clinical standards: MOLLI, SASHA, T2‐GRASE, and 6‐point Dixon proton density FF (PDFF) mapping. Results Dixon‐cMRF water T1 and T2 maps showed good agreement with reference T1 and T2 mapping techniques (R2 > 0.99 and maximum normalized RMSE ~5%) in a standardized phantom. Good agreement was also observed between Dixon‐cMRF FF and reference PDFF (R2 > 0.99) and between Dixon‐cMRF water T1 and T2 and water selective T1 and T2 maps (R2 > 0.99) in a water–fat phantom. In vivo Dixon‐cMRF water T1 values were in good agreement with MOLLI and water T2 values were slightly underestimated when compared to T2‐GRASE. Average myocardium septal T1 values were 1129 ± 38 ms, 1026 ± 28 ms, and 1045 ± 32 ms for SASHA, MOLLI, and the proposed water Dixon‐cMRF. Average T2 values were 51.7 ± 2.2 ms and 42.8 ± 2.6 ms for T2‐GRASE and water Dixon‐cMRF, respectively. Dixon‐cMRF FF maps showed good agreement with in vivo PDFF measurements (R2 > 0.98) and average FF in the septum was measured at 1.3%. Conclusion The proposed Dixon‐cMRF allows to simultaneously quantify myocardial water T1, water T2, and FF in a single breath‐hold scan, enabling multi‐parametric T1, T2, and fat characterization. Moreover, reduced T1 and T2 quantification bias caused by water–fat partial volume was demonstrated in phantom experiments.

3D free‐breathing cardiac magnetic resonance fingerprinting

“…3D cMRF T 1 values were generally higher than those of MOLLI (mean bias of +38 ms) and lower than those of SASHA (mean bias of −55 ms), which has also been observed in previous 2D cMRF studies. 27,54 There are several confounding factors that may account for these differences, F I G U R E 5 A, Whole-heart T 2 mapping (20 short-axis slices) produced with 3D cMRF for representative subject B (RR interval = 1069 ± 62 ms). B, Corresponding basal, mid-and apical slices for T 2 -GraSE F I G U R E 4 A, Whole-heart T 1 mapping (20 short-axis slices) produced with 3D cMRF for representative subject B (RR interval = 1069 ± 62 ms).…”

Multi‐parametric liver tissue characterization using MR fingerprinting: Simultaneous T1, T2, T2*, and fat fraction mapping

“…MRF time‐series reconstruction was performed using a multi‐contrast patch‐based high‐order low‐rank reconstruction (HD‐PROST) 23 with temporal dictionary based compression. Temporally compressed singular images approximating the MRF time‐series 24,25 are reconstructed for each echo i using HD‐PROST, where are the left singular vectors of the MRF dictionary matrix truncated to rank R. Reconstruction parameters included a rank R = 6 and a sparsity promoting parameter 17,23 …”

“…The dictionary contained signal evolutions corresponding to combinations of T 1 and T 2 of interest (ie, [50:10:1400, 1430:30:1600, 1700:100:2200, 2400:200:3000] ms for T 1 and [5:2:80, 85:5:150, 160:10:300, 330:30:600] ms for T 2 as well as the standardized T 1 /T 2 phantom 32 reference values. The FF map is estimated from the water and fat M 0 and phase images (for noise bias correction 17,33 ).…”

“…Here, we propose to jointly map T 1 , T 2 , T 2 *, and FF for comprehensive liver tissue characterization. This is achieved by extending our previous work on 3‐echo Dixon cardiac MRF 17 to a 9‐echo gradient rewound echo (GRE) acquisition and graphcut method 18 for estimation of B 0 and T 2 * and water‐fat separation. To the best of our knowledge, this is the first time that liver T 1 , T 2 , T 2 *, and FF are simultaneously quantified in a single acquisition.…”

Myocardial T1 and T2 quantification and water–fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T

“…29 Among various methods providing the potential for multiple tissue property characterization, the MR fingerprinting (MRF) framework has shown promise for myocardial mapping. [30][31][32] Previous studies have also explored simultaneous relaxation time quantification and water-fat separation/fat fraction quantification in the skeletal muscle, liver, brain, breast, and heart [33][34][35][36][37][38] by combining the MRF framework with variable TE or multiecho acquisition.…”