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

ABSTRACT 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 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 and 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 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 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 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 ‐test. In the phantom study, a small positive bias in of was observed compared with inversion recovery spin‐echo and with MOLLI, while for biases of compared with spin‐echo and with prep bSSFP were found. In vivo, statistically similar values of and values of were obtained, with differences versus MOLLI of () and versus prep bSSFP of (). 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.