Free-breathing hepatic 2D magnetic resonance elastography

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.

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.

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.

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.