To evaluate the respective value of dual- phase helical CT arterial portography （CTAP） and conventional angiography in preoperative predicting resectability of pancreatic ductal adenocarcinoma. Subjects and methods. Tumor resectability was prospectively evaluated in 54 patients with pathologically proven pancreatic ductal adenocarcinoma who later underwent surgery. Both dual- phase helical CT scanning and selective angiography were obtained in each patient preoperatively. For optimal enhancement of pancreas and major peripancreatic vessels

two catheters connected to an automatic injector via a Y- shaped tube were placed after selective angiography

one in celiac trunk

the other in superior mesenteric artery. Then the patient underwent dual- phase helical CTAP of pancreas and liver. The criteria of irresectability for CTAP include: tumor diameter≥ 5 cm

extrapancreatic invasion

distant metastases and vascular involvement（occlusion

stenosis or semicircular encasement of superior mesenteric artery

hepatic artery

splenic artery

celiac axis; portal vein

superior mesenteric vein or splenic vein）. The results of both modalities were correlated with findings from surgery or pathology. Results. Thirty- eight of 54 patients had nonresectable disease. In prediction the irresectability

sensitivity

specificity

positive predictive value

negative predictive value and overall accuracy were 94.7％

100％

100％

88.9％

96.3％ respectively for helical CTAP and 63.2％

93.8％

96.0％

51.7％

72.2％ respectively for selective angiography. In assessing vascular involvements

dual- phase helical CTAP was also superior to selective angiography. Conclusion. Dual- phase helical CTAP is superior to angiography in assessing resectability of pancreatic ductal adenocarcinoma. The combination of the two modalities may further improve overall accuracy of assessment.