Does diffusion-weighted imaging improve magnetic resonance evaluation of pancreatic neuroendocrine tumors?

Purpose: To assess the diagnostic value of diffusion-weighted imaging (DWI) to evaluate pancreatic neuroendocrine tumors (PNETs) regarding identi ca- tion, characterization, and staging. Material and Methods: The MR ndings of 30 consecutive patients with surgically resected pancreatic neuroendocrine tumors (PNETs) were retrospectively compared to those of 30 consecutive patients with pancreatic ductal adenocarcinomas (PDACs). T1- and T2-weighted, arterial, portal and delayed phase, b800 and ADC map images were evaluated by two readers in consensus, who performed a quantita- tive and a qualitative analysis. The latter was completed by a con dence assessment for PNET diagnosis and liver metastases diagnosis by two separate blinded readers. Results: PDACs had statistically signi cantly higher mean ADC value com- pared to PNETs (1.40 vs. 1.19 x 10-3mm2/s; p = 0.001). b800 images provided the highest lesion conspicuity (p <0.05). On blinded readers’ analysis, DWI did not provide signi cant advantages over other sequences for PNET diagnosis. Regarding liver metastases diagnosis, substantial agreement between readers for DWI and an overall lower diagnostic con dence for conventional sequenc- es vs. DWI were found (both p <0.001). DWI had high AUC values for both readers (0.879 and 0.824) regarding liver metastases diagnosis. Conclusion: DWI may be of value for the identi cation of PNETs and for the detection of liver metastases, while it does not seem to provide signi cant improvements regarding diagnosis. Nevertheless, ADC quanti cation may be helpful for differential diagnosis.