Accelerated k‐space shift calibration for free‐breathing stack‐of‐radial MRI quantification of liver fat and R2

• Published in: Magnetic resonance in medicine Vol. 87; no. 1; pp. 281 - 291
• Main Authors: Zhong, Xiaodong, Armstrong, Tess, Gao, Chang, Nickel, Marcel D., Han, Fei, Dale, Brian M., Li, Xinzhou, Kafali, Sevgi G., Hu, Peng, Wu, Holden H., Deshpande, Vibhas
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.01.2022
• Subjects: acceleration; Bayesian analysis; Calibration; Cartesian coordinates; Evaluation; In vivo methods and tests; k‐space shift calibration; Liver; Magnetic resonance imaging; Normal distribution; proton‐density fat fraction; quantification; R 2; radial MRI; Statistical analysis; Uncertainty
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.28981

Purpose To develop an accelerated k‐space shift calibration method for free‐breathing 3D stack‐of‐radial MRI quantification of liver proton‐density fat fraction (PDFF) and R2∗. Methods Accelerated k‐space shift calibration was developed to partially skip acquisition of k‐space shift data in the through‐plane direction then interpolate in processing, as well as to reduce the in‐plane averages. A multi‐echo stack‐of‐radial sequence with the baseline calibration was evaluated on a phantom versus vendor‐provided reference‐standard PDFF and R2∗ values at 1.5T, and in 13 healthy subjects and 5 clinical subjects at 3T with respect to reference‐standard breath‐hold Cartesian acquisitions. PDFF and R2∗ maps were calculated with different calibration acceleration factors offline and compared to reference‐standard values using Bland‐Altman analysis. Bias and uncertainty were evaluated using normal distribution and Bayesian probability of difference (P < .05 considered significant). Results Bland‐Altman plots of phantom and in vivo data showed that substantial acceleration was highly feasible in both through‐plane and in‐plane directions. Compared to the baseline calibration without acceleration, Bayesian analysis revealed no significant differences on biases and uncertainties of PDFF and R2∗ measurements with all acceleration methods in this study, except the method with through‐plane acceleration equaling slices and averages equaling 20 for PDFF and R2∗ (both P < .001) for the phantom. A six‐fold reduction in equivalent calibration acquisition time (time saving ≥25 s and ≥80.7%) was achieved using recommended acceleration factors for the in vivo protocols in this study. Conclusion This proposed method may allow accelerated calibration for free‐breathing stack‐of‐radial MRI PDFF and R2∗ mapping.