B₀ Magnetic Field Conditions in the Human Heart at 3 T Across One Thousand Subjects: A Numerical Simulation Study

Functional scans in cardiovascular magnetic resonance (CMR) adopting bSSFP sequences suffer from dark band artifacts due to B₀ inhomogeneity. The best remedy to mitigate this issue is through cardiac B₀ shimming. The development of an optimal B₀ shim strategy for the human heart is hindered by a limited understanding of B₀ conditions in clinical diagnostic orientations of CMR. Here, we present high-resolution B₀ distributions in cardiac imaging planes, derived from simulations utilizing high-resolution computed tomography (CT) images from 1008 subjects, and present an oblique slicing method to derive such B₀ distributions. This study also presents a theoretical analysis of spherical harmonic B₀ shimming at 3 T using a static global approach and slice-specific dynamic shim updating in the short-axis view of human hearts. The characteristics of cardiac B₀ conditions along with spherical harmonic shimming were correlated with the subjects' demographic parameters, with weak or no correlations, suggesting limited demographic commonality and predominantly subject-specific characteristics in cardiac B₀. The segmented lung volume shows more significant associations and relatively higher correlations with B₀ conditions, indicating that B₀ conditions in the heart rely on the anatomy surrounding the heart more than overall body shape and size. This research provides a basis for the development of optimized cardiac B₀ shim strategies.