Optimal targetb-value on computed diffusion-weighted magnetic resonance imaging for visualization of pancreatic ductal adenocarcinoma and focal autoimmune pancreatitis

Purpose To compare computed diffusion-weighted imaging (cDWI) feasibility with that of directly acquired DWI for visualizing pancreatic ductal adenocarcinoma (PDAC) and focal autoimmune pancreatitis (AIP). Methods From April 2012 to January 2017, 135 patients with PDAC (n = 111) or focal AIP (n = 24) were retrospectively enrolled. They underwent DWI withb-values of 0, 500, and 1000 s/mm(2). From DWI(0)and DWI1000, we generated cDWIs with targetedb-values of 1500, 2000, and 3000 s/mm(2). The lesions' signal intensities, image quality, signal intensity ratio (SIR) of lesions and pancreatic parenchyma to spinal cord, and lesion-to-pancreatic parenchyma contrast ratio (CR) were compared among the five DWI protocols (DWI500, DWI1000, cDWI(1500), cDWI(2000), and cDWI(3000)). SIR was analyzed by receiver operating characteristic (ROC) analyses. Results DWI500, DWI1000, and cDWI(1500)had higher image quality than cDWI(2000)and cDWI(3000)(P< 0.001). The incidence of clear hyperintense PDAC was highest on cDWI(2000), followed by cDWI(1500), and cDWI(3000)(P< 0.001-0.002), while the incidence of clear hyperintense AIP was higher on DWI1000, cDWI(1500), and cDWI(2000)than on DWI(500)and cDWI(3000)(P= 0.001-0.022). SIRs decreased whereas CRs increased as theb-value increased, for both PDAC and AIP. The area under the ROC curve (AUC) of SIR(lesion)was significantly lower on cDWI(1500)than on cDWI(2000)and cDWI(3000)(P< 0.001). Conclusion cDWI(1500)or cDWI(2000)generated fromb-values of 0 and 1000 s/mm(2)were the most effective for visualizing PDAC and focal AIP; however, the SIR(lesion)AUC was significantly lower on cDWI(1500)than on cDWI(2000)and cDWI(3000).