Multiparametric Free-Breathing 3D Whole-Heart Cardiac MR for Anatomical Bright- and Black-Blood Imaging With Co-Registered T1/T2 Myocardial Tissue Mapping at 0.55 T.

内容摘要

Low-field MRI has recently gained interest due to its potential for increased accessibility, reduced cost, and improved safety. However, high-quality anatomical imaging and robust tissue characterization remains an active area of research, particularly when aiming for a simple, one-click scan that captures all relevant information in a single acquisition. Bright-blood imaging is widely used for visualizing cardiac structures and coronary arteries, whereas black-blood is optimal for delineating the myocardium, atrial and vessel walls. High-resolution imaging is required for the accurate detection and segmentation of small anatomical structures, such as the coronary arteries, to enable assessment of narrowing or blockages. Co-registered T 1 / T 2 $$ {T}_1/{T}_2 $$ mapping enables quantitative myocardial tissue characterization, offering valuable clinical information for the detection of myocardial abnormalities. In this study, we sought to develop a novel free-breathing, motion-compensated 3D multi-contrast high-resolution cardiac MR sequence for simultaneous assessment of whole-heart cardiovascular anatomy via bright- and black-blood imaging and myocardial tissue quantification by joint T 1 $$ {T}_1 $$ and T 2 $$ {T}_2 $$ mapping at 0.55 T in a single scan. Data were acquired over six interleaved contrasts with various preparation modules using a variable flip angle bSSFP spiral-like readout with 2D image-based navigation for translational motion correction, resulting in a predictable acquisition time of ≈ 12 $$ \approx 12 $$ min. Images were reconstructed using non-rigid motion corrected iterative sensitivity encoding followed by high-dimensional patch-based low-rank denoising, resulting in the acquisition, reconstruction and quantitative mapping time of ≈ 31 $$ \approx 31 $$ min. In the phantom study, sequence performance was evaluated using correlation and Bland-Altman analysis against reference gold-standard and clinical mapping methods. In vivo, 3D bright- and black-blood volumes were assessed in multiple views, and vessel sharpness was quantified from multiplanar images. For joint T 1 / T 2 $$ {T}_1/{T}_2 $$ mapping, bull's-eye plots were generated to evaluate the mean, standard deviation, and coefficient of variation for apical, mid-cavity, and basal segments, and results were summarized using violin plots. Differences between the proposed 3D sequence and established 2D methods were analyzed with a two-tailed t $$ t $$ -test. In the phantom study, a small positive bias in T 1 $$ {T}_1 $$ of 6 . 3 ms $$ 6.3\kern0.3em \mathrm{ms} $$ was observed compared with inversion recovery spin-echo and 23 . 5 ms $$ 23.5\kern0.3em \mathrm{ms} $$ with MOLLI, while for T 2 $$ {T}_2 $$ biases of 7 . 3 ms $$ 7.3\kern0.3em \mathrm{ms} $$ compared with spin-echo and 0 . 8 ms $$ 0.8\kern0.3em \mathrm{ms} $$ with T 2 $$ {T}_2 $$ prep bSSFP were found. In vivo, statistically similar T 1 $$ {T}_1 $$ values of ( 648 ± 26 ) ms $$ \left(648\pm 26\right)\kern0.3em \mathrm{ms} $$ and T 2 $$ {T}_2 $$ values of ( 56 . 9 ± 3 . 2 ) ms $$ \left(56.9\pm 3.2\right)\kern0.3em \mathrm{ms} $$ were obtained, with differences versus MOLLI of - 3 ms ± 15 ms $$ -3\kern0.3em \mathrm{ms}\pm 15\kern0.3em \mathrm{ms} $$ ( p = 0 . 75 $$ p=0.75 $$ ) and versus T 2 $$ {T}_2 $$ prep bSSFP of - 0 . 5 ms ± 2 . 1 ms $$ -0.5\kern0.3em \mathrm{ms}\pm 2.1\kern0.3em \mathrm{ms} $$ ( p = 0 . 63 $$ p=0.63 $$ ). The proposed sequence demonstrated high image quality and accurate mapping despite the inherent limitations of low-field strength, suggesting its feasibility for comprehensive cardiac assessment in resource-limited environments.