Objective: The objective of our study was to compare standard breath-held, free-breathing, and compressed sensing (CS) accelerated 2D gradient-recalled echo (GRE) MR elastography (MRE) techniques for measuring liver stiffness.
Subjects and methods: Twenty-five adult volunteers (20 without liver disease and five with liver disease) underwent MRE with five different 2D GRE techniques: breath-held; free-breathing; and CS with acceleration factors of 1.5, 2, and 3. Four axial images were obtained through the mid liver with each technique, and liver stiffness measurements (in kilopascals) were made by three blinded readers using elastograms with 95% confidence maps. Liver stiffness measurements were compared between techniques using repeated-measures ANOVA. Absolute agreement between techniques was evaluated for each reader using single-measure intraclass correlation coefficients (ICCs). Bland-Altman analyses were performed to assess bias between techniques using breath-held MRE as the reference.
Results: Individual subject mean liver stiffness values ranged from 1.35 to 5.25 kPa for the population. There was no significant difference in mean liver stiffness values between MRE techniques for readers 1 and 3 (p > 0.05). A significant difference (p = 0.02) due to higher stiffness measurements using free-breathing MRE was observed for reader 2. There was excellent absolute agreement between MRE techniques for each reader (all ICCs > 0.940). Bias between techniques ranged from -0.102 to 0.089 kPa for reader 1, -0.119 to 0.121 kPa for reader 2, and -0.074 to 0.085 kPa for reader 3.
Conclusion: Free-breathing and CS accelerated 2D GRE MRE techniques yield similar results to the conventional breath-held technique with only slight bias and may be useful in pediatric and adult patients with limited ability to breath-hold.
Keywords: MR elastography; comparative research; compressed sensing; gradient-recalled echo; liver.