Evaluation of Pancreatic Fibrosis Grading by Multimodal Functional Magnetic Resonance Imaging.

BACKGROUND Early detection and grading of pancreatic fibrosis (PF) are important and challenging clinical goals. PURPOSE To determine main pancreatic duct (MPD) diameter, pancreatic thickness, and grades of PF via magnetic resonance elastography (MRE), T1 mapping, and intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI), assessing respective diagnostic performances. STUDY TYPE Prospective. SUBJECTS Histopathologic and imaging records (MRE, T1 mapping, and IVIM-DWI) generated by 144 patients between December 2018 and May 2020 were collected for analysis. Grades of PF were distributed as follows: F0, 82; F1, 22; F2, 22; and F3, 18. FIELD STRENGTH/SEQUENCE 3 T pancreatic MRI, encompassing MRE, T1 mapping, and IVIM-DWI. ASSESSMENT In all patients, T1 relaxation times, pancreatic stiffness values, IVIM-DWI parameters, MPD diameter, and pancreatic thickness were measured. STATISTICAL TESTS Receiver operating characteristic (ROC) analysis served to assess imaging parameters useful in diagnosing PF. To identify relations between specific parameters and grades of PF, logistic regression analysis was invoked. RESULTS Both pancreatic stiffness (r = 0.754; P < 0.001) and T1 relaxation time (r = 0.433; P < 0.001) correlated significantly with PF (%). To determine PF grades ≥F1, a combined model (area under the curve [AUC] = 0.906) performed significantly better than pancreatic stiffness (AUC = 0.855; P < 0.001) or T1 relaxation time (AUC = 0.754; P < 0.001) alone. For PF grades ≥F2 or grade F3, both the combined model (≥F2: AUC = 0.910; F3: AUC = 0.939) and pancreatic stiffness (≥F2: AUC = 0.906; F3: AUC = 0.929) outperformed T1 relaxation time (≥F2: AUC = 0.768 [P = 0.005 and P = 0.004, respectively]; F3: AUC = 0.816 [both P < 0.005]). All IVIM-DWI parameters generated AUC values <0.700. DATA CONCLUSION A combination of MRE and T1 mapping seems promising in diagnosing various grades of PF, particularly at an early stage. LEVEL OF EVIDENCE 1 TECHNICAL EFFICACY: Stage 2.