Fusion of segmental right-lobe IVIM-DWI metrics and GPR for non-invasive assessment of chronic hepatitis B–related hepatic fibrosis: a pilot study

PURPOSE: A segmental intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI)/gamma-glutamyl transpeptidase-to-platelet ratio (GPR) fusion model was evaluated for the non-invasive assessment of chronic hepatitis B (CHB) fibrosis (controls vs. early; early vs. advanced) and compared with the aspartate aminotransferase-to-platelet ratio index (APRI) and Fibrosis-4 (FIB-4). METHODS: This retrospective study included 139 participants: 42 healthy controls (HCs), 46 with early hepatic fibrosis (EHF), and 51 with advanced hepatic fibrosis (AHF). IVIM-DWI parameters (apparent diffusion coefficient, slow diffusion component, fast diffusion component, and perfusion fraction) were extracted from segmental analysis of the right hepatic lobe (segments V-VIII). The GPR, APRI, and FIB-4 were calculated from laboratory values. The IVIM + GPR fusion model was developed using logistic regression. Model performance was assessed using receiver operating characteristic analysis with bootstrap internal validation. RESULTS: For HCs vs. EHF, FIB-4 achieved the highest area under the curve [AUC; 0.911, 95% confidence interval (CI): 0.844-0.969) followed by APRI (0.843, 95% CI: 0.755-0.923). The IVIM + GPR fusion model (AUC = 0.745, 95% CI: 0.643-0.847) outperformed IVIM alone (AUC = 0.652) and GPR alone (AUC = 0.730) but did not outperform APRI or FIB-4. For EHF vs. AHF, the IVIM + GPR fusion model (AUC = 0.698) was comparable to APRI (0.573) and FIB-4 (0.637), with no significant differences among methods. CONCLUSION: FIB-4/APRI outperformed the fusion model for controls vs. early fibrosis, whereas fusion added no value over GPR for early vs. advanced fibrosis. In the absence of a biopsy-proven S0 CHB group, HCs vs. EHF discriminates between HCs and established fibrosis rather than detecting incident fibrosis. The model should be considered, at most, a supplementary, opportunistic adjunct during abdominal magnetic resonance imaging (MRI) rather than a replacement for FIB-4/APRI. CLINICAL SIGNIFICANCE: The GPR uses only gamma-glutamyl transpeptidase and platelets, making it practical in resource- limited settings. The fusion model may provide supplementary, opportunistic information during abdominal MRI or when serum markers are confounded by extrahepatic factors, but it should remain complementary pending validation in larger cohorts; FIB-4 and APRI remain first-line where laboratory panels are available.