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Effect of respiratory motion on free‐breathing 3D stack‐of‐radial liver R 2 ∗ relaxometry and improved quantification accuracy using self‐gating
Author(s) -
Zhong Xiaodong,
Armstrong Tess,
Nickel Marcel D.,
Kannengiesser Stephan A.R.,
Pan Li,
Dale Brian M.,
Deshpande Vibhas,
Kiefer Berthold,
Wu Holden H.
Publication year - 2020
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.28052
Subject(s) - gating , breathing , nuclear medicine , nuclear magnetic resonance , chemistry , mathematics , medicine , physics , anatomy , physiology
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 < .05 considered significant). Results Free‐breathing stack‐of‐radial without self‐gating exhibited signal attenuation in echo images and artifactually elevated apparent R 2 ∗ values. In the Bland‐Altman plots of normal subjects, compared to breath‐hold Cartesian, free‐breathing stack‐of‐radial acquisitions of 22, 30, 36, and 44 slices, had mean R 2 ∗ differences of 27.4, 19.4, 10.9, and 14.7 s −1 with 800 radial views, and they had 18.4, 11.9, 9.7, and 27.7 s −1 with 404 views, which were reduced to 0.4, 0.9, −0.2, and −0.7 s −1 and to −1.7, −1.9, −2.1, and 0.5 s −1 with self‐gating, respectively. No substantial proton density fat fraction differences were found. The linear mixed model showed free‐breathing radial R 2 ∗ results without self‐gating were significantly biased by 17.2 s −1 averagely ( P = .002), which was eliminated with self‐gating ( P = .930). Proton density fat fraction results were not different ( 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 ∗ .