Abstract
PURPOSE: To evaluate the test-retest repeatability of a rapid, free-breathing two-dimensional (2D) MR elastography (MRE) technique and to assess the reliability of the liver-stiffness measurements compared with conventional breath-hold MREs. METHODS: Fifteen and 115 participants were enrolled in the technical repeatability and measurement equivalence assessment cohorts, respectively. All participants underwent rapid free-breathing and conventional breath-hold 2D MRE (twice in repeatability cohort) on 1.5T scanners. Both methods have four phase offsets over one harmonic motion cycle at 60 Hz; one and 10 cycles were collected and processed in breath-hold and free-breathing MREs, respectively. The liver stiffness measurements of free-breathing (LS(F)) and breath-hold MRE (LS(B)) were calculated from manually drawn regions of interest. The repeatability coefficients and Spearman correlation were used to assess technical repeatability and measurement agreement between LS(F) and LS(B). Univariable and multivariable linear regressions were performed to identify potential influencing factors, including age, sex, body mass index, and fat fraction, in the measurement agreement between LS(B) and LS(F). RESULTS: The repeatability coefficient of free-breathing 2D MRE is comparable to breath-hold MRE (LS(F): 20.8%, LS(B): 20.4%). LS(F) showed a strong agreement and significant correlation with LS(B) (LS(F) = 1.01 × LS(B), ρ = 0.94, p < 0.001). The measurement agreement between LS(F) and LS(B) was only significantly affected by sex (p = 0.047) after adjusting for confounding factors of age, body mass index, and fat fraction. CONCLUSIONS: The nongated, free-breathing, multislice 2D MRE technique can provide reliable liver stiffness measurements compared with conventional breath-hold 2D MRE. It could provide a comfortable alternative method with reliable liver stiffness measurements for patients who have difficulty in suspending respiration.