Diagnostic value of b value threshold maps based on diffusion weighted imaging images for pancreatic cancer

Objective To investigate the feasibility of b value threshold maps based on MRI diffusion weighted imaging (DWI) in the diagnosis of pancreatic adenocarcinoma. Methods The preoperative MRI DWI [b value=0(b0) and 1000 (b1000) s/mm2] data of 14 patients who were postoperatively histologically confirmed as pancreatic ductal adenocarcinoma from September 2016 to May 2015 admitted in Shanghai Changhai Hospital were retrospectively analyzed. The b value threshold maps were calculated. Computed DWI images at b value of 1500 s/mm2 (cDWIb1500) was calculated based on the scanned DWI images of b0 and b1000s/mm2. The efficacy of DWIb1000, b value threshold map and cDWIb1500 in manifesting pancreatic adenocarcinoma was assessed by a four-point scale. The non-parametric Friedman test was used to compare the three methods, and Conover adjusted method was applied to compare any two of the three methods. Results The conspicuity score of DWIb1000, b value threshold map and cDWIb1500 in showing pancreatic cancer was 2.9±0.8, 3.7±0.5 and 3.6±0.5, respectively, and the differences among the three methods were statistically significant (F=19.5, P value<0.001), but the differences on tumor conspicuity scores of b value threshold map and cDWIb1500 were not statistically different. Conclusions The calculation of b value threshold map based on DWI images could show pancreatic cancer in high contrast quickly by adjusting window width and window level, and could achieve comparable performance as cDWIb1500. Key words: Pancreatic neoplasms; Magnetic resonance imaging; Diffusion weighted imaging; b-value map