Effect of respiratory motion on free‐breathing 3D stack‐of‐radial liver relaxometry and improved quantification accuracy using self‐gating

PURPOSE: To develop an accurate free-breathing 3D liver R 2 * mapping approach and to evaluate it in vivo. METHODS: A free-breathing multi-echo stack-of-radial sequence was applied in 5 normal subjects and 6 patients at 3 Tesla. Respiratory motion compensation was implemented using the inherent self-gating signal. A breath-hold Cartesian acquisition was the reference standard. Proton density fat fraction and R 2 * were measured and compared between radial and Cartesian methods using Bland-Altman plots. The normal subject results were fitted to a linear mixed model (P .234). For patients, Bland-Altman plots exhibited mean R 2 * differences of 14.4 and 0.1 s(-1) for free-breathing stack-of-radial without self-gating and with self-gating, respectively, but no substantial proton density fat fraction differences. CONCLUSION: The proposed self-gating method corrects the respiratory motion bias and enables accurate free-breathing stack-of-radial quantification of liver R 2 * .