Purpose or Case Report:
Multiple noninvasive magnetic resonance imaging (MRI) methods have been described to detect liver fibrosis, including diffusion-weighted imaging (DWI). The purpose of our study was to evaluate predictors of liver MRI DWI apparent diffusion coefficient (ADC) measurements in pediatric patients with autoimmune liver disease, including the relationship between ADC measurements and liver stiffness.

Methods & Materials: Fifty-seven research liver MRI examinations performed between January 2017 and August 2018 that included DWI, liver MR elastography (MRE), and spleen MRE in pediatric patients enrolled in an autoimmune liver disease registry were identified. DWI ADC values were measured by manually drawing regions of interests (ROI) in the right hepatic lobe while avoiding visible vessels and artifacts at four anatomic levels using IntelliSpace (Philips Healthcare). Liver and spleen stiffness (kPa) were measured at the same anatomic levels. Iron-corrected T1 (cT1) was measured using LiverMultiScan (Perspectum Diagnostics). Patient age, sex, laboratory data (ALT, bilirubin, alkaline phosphatase, and GGT) were recorded. Spearman’s rank-order correlation (r) and multiple linear regression (stepwise model selection) were used to evaluate the association between liver ADC measurements and liver predictor variables.

Results: Mean (SD) patient age was 15.0 (3.9) years. 23/57 (40%) examinations were performed in girls. Mean liver DWI ADC was 1.34 (0.14) x 10^-3 mm²/s. Mean liver stiffness was 3.42 (1.62) kPa. Liver ADC measurements showed weak to moderate significant inverse correlations with liver stiffness (r=-0.42, p=0.001), spleen stiffness (r=-0.34; p=0.015), ALT (r=-0.5; p=0.0001); GGT (r=-0.48; p=0.0004), and cT1 mean (r=-0.39; p=0.007). Multiple linear regression showed liver stiffness (p=0.0009) and sex (p=0.023) to be independent predictors of liver ADC measurements.

Conclusions:
Liver DWI ADC values are significantly associated with liver and spleen stiffness, ALT and GGT, cT1, and patient sex, with liver stiffness and sex remaining significant at multivariable regression. Liver ADC may ultimately play a role in multi-parametric prediction of chronic liver disease/fibrosis severity.