Feasibility of Noncontrast 3D MR Angiography on a Commercial Wide-Bore 0.55-T System: Comparison with 1.5-T MR Angiography.

Purpose To evaluate a noncontrast electrocardiographically triggered, navigator-gated, three-dimensional, balanced steady-state free precession MR angiography (MRA) research sequence on a wide-bore 0.55-T commercial low-field-strength system, by comparing image quality and aortic dimension measurements against images obtained at 1.5 T. Materials and Methods Ten healthy volunteers (28.8 years ± 9.0 [SD]; four male) and 10 participants being evaluated for dilated thoracic aorta (53.6 years ± 10.7; six male) underwent noncontrast MRA scans at both 1.5 T and 0.55 T. Overall image quality, intrarater and interrater agreement in aortic dimensions, and diagnostic accuracy were evaluated between field strengths for both groups of individuals using Wilcoxon test, intraclass correlation coefficient, and Bland-Altman plots. Results Median image quality scores remained comparable between volunteers and participants across field strengths. Blood signal variability was greater at the ascending aorta at 1.5 T for volunteers (P = .01) and participants (P = .02). Blood-myocardium contrast was significantly higher at the ascending aorta and proximal arch at 1.5 T for volunteers and participants (P < .05). Excellent intra- and interrater agreement (intraclass correlation coefficient > 0.9) was demonstrated at 0.55 T and 1.5 T. Aortic dimensions (intraclass correlation coefficient > 0.9) and diagnosis of aortic dilatation did not demonstrate significant interfield differences. Conclusion Noncontrast, three-dimensional, balanced steady-state free precession MRA at 0.55 T demonstrated adequate image quality and no significant differences in quantitative measurements or diagnostic accuracy compared with 1.5 T. Keywords: Noncontrast MR Angiography, Low Field, 0.55 T, Obesity, Thoracic Aorta © RSNA, 2025.