Purpose To develop a novel respiratory motion compensated three‐dimensional (3D) cardiac magnetic resonance fingerprinting (cMRF) approach for whole‐heart myocardial T1 and T2 mapping from a free‐breathing scan. Methods Two‐dimensional (2D) cMRF has been recently proposed for simultaneous, co‐registered T1 and T2 mapping from a breath‐hold scan; however, coverage is limited. Here we propose a novel respiratory motion compensated 3D cMRF approach for whole‐heart myocardial T1 and T2 tissue characterization from a free‐breathing scan. Variable inversion recovery and T2 preparation modules are used for parametric encoding, respiratory bellows driven localized autofocus is proposed for beat‐to‐beat translation motion correction and a subspace regularized reconstruction is employed to accelerate the scan. The proposed 3D cMRF approach was evaluated in a standardized T1/T2 phantom in comparison with reference spin echo values and in 10 healthy subjects in comparison with standard 2D MOLLI, SASHA and T2‐GraSE mapping techniques at 1.5 T. Results 3D cMRF T1 and T2 measurements were generally in good agreement with reference spin echo values in the phantom experiments, with relative errors of 2.9% and 3.8% for T1 and T2 (T2 < 100 ms), respectively. in vivo left ventricle (LV) myocardial T1 values were 1054 ± 19 ms for MOLLI, 1146 ± 20 ms for SASHA and 1093 ± 24 ms for the proposed 3D cMRF; corresponding T2 values were 51.8 ± 1.6 ms for T2‐GraSE and 44.6 ± 2.0 ms for 3D cMRF. LV coefficients of variation were 7.6 ± 1.6% for MOLLI, 12.1 ± 2.7% for SASHA and 5.8 ± 0.8% for 3D cMRF T1, and 10.5 ± 1.4% for T2‐GraSE and 11.7 ± 1.6% for 3D cMRF T2. Conclusion The proposed 3D cMRF can provide whole‐heart, simultaneous and co‐registered T1 and T2 maps with accuracy and precision comparable to those of clinical standards in a single free‐breathing scan of about 7 min.
Purpose To develop a free‐breathing isotropic‐resolution whole‐heart joint T1 and T2 mapping sequence with Dixon‐encoding that provides coregistered 3D T1 and T2 maps and complementary 3D anatomical water and fat images in a single ~9 min scan. Methods Four interleaved dual‐echo Dixon gradient echo volumes are acquired with a variable density Cartesian trajectory and different preparation pulses: 1) inversion recovery‐preparation, 2) and 3) no preparations, and 4) T2 preparation. Image navigators are acquired to correct each echo for 2D translational respiratory motion; the 8 echoes are jointly reconstructed with a low‐rank patch‐based reconstruction. A water/fat separation algorithm is used to obtain water and fat images for each acquired volume. T1 and T2 maps are generated by matching the signal evolution of the water images to a simulated dictionary. Complementary bright‐blood and fat volumes for anatomical visualization are obtained from the T2‐prepared dataset. The proposed sequence was tested in phantom experiments and 10 healthy subjects and compared to standard 2D MOLLI T1 mapping, 2D balance steady‐state free precession T2 mapping, and 3D T2‐prepared Dixon coronary MR angiography. Results High linear correlation was found between T1 and T2 quantification with the proposed approach and phantom spin echo measurements (y = 1.1 × −11.68, R2 = 0.98; and y = 0.85 × +5.7, R2 = 0.99). Mean myocardial values of T1/T2 = 1116 ± 30.5 ms/45.1 ± 2.38 ms were measured in vivo. Biases of T1/T2 = 101.8 ms/−0.77 ms were obtained compared to standard 2D techniques. Conclusion The proposed joint T1/T2 sequence permitted the acquisition of motion‐compensated isotropic‐resolution 3D T1 and T2 maps and complementary coronary MR angiography and fat volumes, showing promising results in terms of T1 and T2 quantification and visualization of cardiac anatomy and pericardial fat.
Purpose:To enable free-breathing whole-heart 3D T 2 mapping with high isotropic resolution in a clinically feasible and predictable scan time. This 3D motioncorrected undersampled signal matched (MUST) T 2 map is achieved by combining an undersampled motion-compensated T 2 -prepared Cartesian acquisition with a high-order patch-based reconstruction. Methods: The 3D MUST-T 2 mapping acquisition consists of an electrocardiogramtriggered, T 2 -prepared, balanced SSFP sequence with nonselective saturation pulses.Three undersampled T 2 -weighted volumes are acquired using a 3D Cartesian variabledensity sampling with increasing T 2 preparation times. A 2D image-based navigator is used to correct for respiratory motion of the heart and allow 100% scan efficiency.Multicontrast high-dimensionality undersampled patch-based reconstruction is used in concert with dictionary matching to generate 3D T 2 maps. The proposed framework was evaluated in simulations, phantom experiments, and in vivo (10 healthy subjects, 2 patients) with 1.5-mm 3 isotropic resolution. Three-dimensional MUST-T 2 was compared against standard multi-echo spin-echo sequence (phantom) and conventional breath-held single-shot 2D SSFP T 2 mapping (in vivo). Results: Three-dimensional MUST-T 2 showed high accuracy in phantom experiments (R 2 > 0.99). The precision of T 2 values was similar for 3D MUST-T 2 and 2D balanced SSFP T 2 mapping in vivo (5 ± 1 ms versus 4 ± 2 ms, P = .52). Slightly longer T 2 values were observed with 3D MUST-T 2 in comparison to 2D balanced SSFP T 2 mapping (50.7 ± 2 ms versus 48.2 ± 1 ms, P < .05). Preliminary results in patients demonstrated T 2 values in agreement with literature values. Conclusion:The proposed approach enables free-breathing whole-heart 3D T 2 mapping with high isotropic resolution in about 8 minutes, achieving accurate and precise T 2 quantification of myocardial tissue in a clinically feasible scan time.
PurposeTo develop an accelerated motion corrected 3D whole‐heart imaging approach (qBOOST‐T2) for simultaneous high‐resolution bright‐ and black‐blood cardiac MR imaging and quantitative myocardial T2 characterization.MethodsThree undersampled interleaved balanced steady‐state free precession cardiac MR volumes were acquired with a variable density Cartesian trajectory and different magnetization preparations: (1) T2‐prepared inversion recovery (T2prep‐IR), (2) T2‐preparation, and (3) no preparation. Image navigators were acquired prior the acquisition to correct for 2D translational respiratory motion. Each 3D volume was reconstructed with a low‐rank patch‐based reconstruction. The T2prep‐IR volume provides bright‐blood anatomy visualization, the black‐blood volume is obtained by means of phase sensitive reconstruction between first and third datasets, and T2 maps are generated by matching the signal evolution to a simulated dictionary. The proposed sequence has been evaluated in simulations, phantom experiments, 11 healthy subjects and compared with 3D bright‐blood cardiac MR and standard 2D breath‐hold balanced steady‐state free precession T2 mapping. The feasibility of the proposed approach was tested on 4 patients with suspected cardiovascular disease.ResultsHigh linear correlation (y = 1.09 × −0.83, R2 = 0.99) was found between the proposed qBOOST‐T2 and T2 spin echo measurements in phantom experiment. Good image quality was observed in vivo with the proposed 4x undersampled qBOOST‐T2. Mean T2 values of 53.1 ± 2.1 ms and 55.8 ± 2.7 ms were measured in vivo for 2D balanced steady‐state free precession T2 mapping and qBOOST‐T2, respectively, with linear correlation of y = 1.02x+1.46 (R2 = 0.61) and T2 bias = 2.7 ms.ConclusionThe proposed qBOOST‐T2 sequence allows the acquisition of 3D high‐resolution co‐registered bright‐ and black‐blood volumes and T2 maps in a single scan of ~11 min, showing promising results in terms of T2 quantification.
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