Multiparametric Magnetic Resonance Elastography Improves the Detection of NASH Regression Following Bariatric Surgery

Abstract

Disease monitoring in nonalcoholic steatohepatitis (NASH) is limited by absence of noninvasive biomarkers of disease regression or progression. We aimed to examine the role of multiparametric three-dimensional magnetic resonance elastography (3D-MRE) and magnetic resonance imaging proton density fat fraction (MRI-PDFF) in the detection of NASH regression after interventions. This is a single-center prospective clinical trial of 40 patients who underwent bariatric surgery. Imaging and liver biopsies were obtained at baseline and 1 year after surgery. The imaging protocol consisted of multifrequency 3D-MRE to determine the shear stiffness at 60 Hz and damping ratio at 40 Hz, and MRI-PDFF to measure the fat fraction. A logistic regression model including these three parameters was previously found to correlate with NASH. We assessed the model performance in the detection of NASH resolution after surgery by comparing the image-predicted change in NAFLD activity score (delta NAS) to the histologic changes. A total of 38 patients (median age 43, 87% female, 30 of 38 with NAS ≥ 1, and 13 of 38 with NASH) had complete data at 1 year. The NAS decreased in all subjects with NAS ≥ 1 at index biopsy, and NASH resolved in all 13. There was a strong correlation between the predicted delta NAS by imaging and the delta NAS by histology (r = 0.73, P < 0.001). The strength of correlation between histology and the predicted delta NAS using single conventional parameters, such as the fat fraction by MRI-PDFF or shear stiffness at 60 Hz by MRE, was r = 0.69 (P < 0.001) and r = 0.43 (P = 0.009), respectively. Conclusion: Multiparametric 3D-MRE and MRI-PDFF can detect histologic changes of NASH resolution after bariatric surgery. Studies in a nonbariatric setting are needed to confirm the performance as a composite noninvasive biomarker for longitudinal NASH monitoring.

Figure 1

Distribution of NAFLD activity scores before and after weight‐loss surgery.

Figure 2

Histologic NAS at the time of bariatric surgery (index) and 1 year after.

Figure 3

Correlation between changes in NAFLD activity score by histology (x‐axis) and changes predicted by imaging (y‐axis). (A) Multiparametric 3D‐MRE and MRI‐PDFF. (B) MRI‐PDFF. (C) Single‐parameter 3D‐MRE (shear stiffness). Change was determined by subtracting the postbariatric surgery NAS from prebariatric NAS.

Figure 4

Longitudinal assessment of NASH probability and NAS prediction by multiparametric 3D‐MRE and MRI‐PDFF in 3 study patients. The three imaging parameters included in the predictive model are shown: mf3D‐MRE depiction of shear stiffness, mf3D‐MRE depiction of damping ratio, and MRI‐PDFF depiction of fat fraction. The horizontal boxes illustrate the predicted NAS values ranging from 0 to 8. The shaded part of the boxes represents the predicted range of NAS, which were derived from the regression model as the highest probabilities within the 68% CI.