Respiratory Motion‐Corrected Model‐Based 3D Water‐Fat MRA of the Thorax at 0.55 T

ABSTRACT Purpose The goal of this study was to develop a 5‐min 3D MRA acquisition at 0.55 T with predictable scan time, 100% data efficiency, and robust water‐fat separation. Methods For full data efficiency, the proposed method combined self‐gating with retrospective motion correction while ensuring a predictable 5‐min scan time. Water‐fat separation was implemented using a model‐based Dixon reconstruction. Evaluation in 18 volunteers compared results to navigator‐gated reference scans with nominal scan times of 5 and 10 min via a Likert scale blinded expert rating. Susceptibility to irregular breathing patterns was also analyzed. Results The expert rating for image quality was 4.22 for the proposed method, 3.89 for the 5‐min navigator‐gated scan and 4.43 for the 10‐min navigator‐gated scan. Ranking the three methods revealed moderate inter‐rater reliability of 0.46, suggesting only minor differences. While navigator‐gated acquisitions deviated from the expected scan time by −2.26 to 2.86 min and −3.91 to 4.54 min for the 5‐ and 10‐min protocols respectively, the proposed method deviated only by −0.17 to 0.45 min. The self‐gated method further avoided saturation artifacts from the cross‐beam navigator, allowing better distinction of the right pulmonary veins. Image quality for the proposed method was also less susceptible to irregular breathing patterns. Conclusion Whole‐thorax MRA acquisitions with water‐fat separation and predictable scan times were successfully acquired in 18 volunteers at 0.55 T. The proposed method demonstrated on average better image quality than navigator‐gated acquisitions of the same nominal scan time while mitigating limitations of prospective navigator gating.