Optimizing b-values for accurate depiction of pancreatic cancer with tumor-associated pancreatitis on computed diffusion-weighted imaging

Abstract

PurposeTo determine the optimal b-value for accurate depiction of pancreatic cancer (PC) in patients with active tumor-associated pancreatitis (TAP), using computed diffusion-weighted imaging (cDWI) with a range of b-values up to 3000 s/mm2. MethodsThe study protocol was approved by the institutional review board. We retrospectively analyzed 34 consecutive PC cases with active TAP who underwent pancreatectomy without preoperative therapy. Four cDWI datasets with b-values of 1500–3000 s/mm2 (cDWI1500–cDWI3000) were generated from the original DWI datasets with b-values of 0 and 1000 s/mm2 obtained using a 3-T scanner. Two board-certified radiologists evaluated images qualitatively (tumor conspicuity and total image quality), and another two board-certified radiologists placed regions of interest for quantitative evaluations (apparent diffusion coefficient [ADC] values of both lesions, contrast ratio [CR] of PC to active TAP, and volume ratio [VR] of PC to surgical specimen). ResultsAs the b-value increased, tumor conspicuity improved significantly in cDWI2000 and cDWI2500 (P = 0.0121 and 0.0015, respectively), although total image quality decreased in all cDWIs compared with DWI1000 (P < 0.0001). Significantly lower ADC values were seen in PC (P < 0.0001). All cDWI groups showed positive correlation between the tumor conspicuity and ADC difference between PC and TAP. CR increased with the b-value, while VR decreased. Significant equivalence of VR to the surgical specimen was seen on cDWI2000 (P = 0.0031). ConclusionAccurate depiction of PC was optimal with cDWI2000 in the presence of active TAP.