Intravoxel incoherent motion diffusion-weighted imaging of the pancreas: Characterization of benign and malignant pancreatic pathologies

Purpose: To evaluate the diagnostic value of apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM) parameters in differentiating patients with either a normal pancreas (NP), pancreatic ductal adenocarcinoma (PDAC), neuroendocrine tumor (NET), solid pseudopapillary tumor (SPT), acute pancreatitis (AcP), vs. autoimmune pancreatitis (AIP). Materials and Methods: In all, 84 pathologically confirmed pancreatic tumors (60 PDACs, 15 NETs, 9 SPTs), 20 pancreatitis (13 AcPs, 7 AIPs), and 30 NP subjects underwent IVIM diffusion-weighted imaging using 10 b-values (0–900 sec/mm²) at 1.5T. The ADC, pure molecular diffusion coefficient (D_slow), perfusion fraction (f), and perfusion-related diffusion coefficient (D_fast) were calculated and compared using a Kruskal–Wallis test and post-hoc Dunn procedure. Receiver operating characteristic (ROC) analysis was performed to assess diagnostic performance. Results: The f and D_fast of the PDAC were significantly lower than that of the NP (f = 0.10 vs. 0.24; D_fast = 42.21 vs. 71.74 × 10⁻³mm²/sec; P < 0.05). In ROC analysis, f showed the best diagnostic performance (area-under-the-curve, 0.919) among all parameters in differentiating PDAC from NP (P ≤ 0.001). The f values of AcP (0.11) and AIP (0.13) and the D_fast values of SPT (20.48 × 10⁻³mm²/sec) and AcP (24.49 × 10⁻³mm²/sec) were significantly lower compared with NP (f = 0.24; D_fast = 71.74 × 10⁻³mm²/sec; P < 0.05). For NET, the f (0.21) was significantly higher than that of PDAC (0.10, P < 0.01). Conclusion: Perfusion-related parameters f and D_fast are more helpful in characterizing pancreatic diseases than ADC or D_slow. The PDCA, SPT, AcP, and AIP were characterized by reduced f and D_fast values compared with normal pancreas. The f value might help in differentiating between PDAC and NET. Level of Evidence: 3. J. Magn. Reson. Imaging 2017;45:260–269.