Arterial versus portal venous helical CT for revealing pancreatic adenocarcinoma: conspicuity of tumor and critical vascular anatomy.

OBJECTIVE: The purpose of this study was to determine the conspicuity of pancreatic adenocarcinoma and surrounding critical pancreatic vascular structures on helical CT scans obtained during the arterial and portal venous phases of enhancement. SUBJECTS AND METHODS: Forty patients with pancreatic adenocarcinomas under-went dual-phase helical CT (3-mm collimation; l-mm overlapping reconstructions; 160 ml contrast medium injected at 4 ml/sec; scan delay: 18 sec for arterial phase, 60 sec for portal venous phase). Tissue enhancement and differences in tumor-to-pancreas contrast were compared. Quantitative evaluation was also done for the aorta, the superior mesenteric artery and vein, and the splenic and portal veins.
RESULTS: Tumor conspicuity was significantly greater in the portal venous phase, when the tumor-to-pancreas contrast difference was 54 +/- 31 H, than in the arterial phase, when the difference was 31 +/- 29 H. Enhancement values of critical pancreatic venous structures were significantly greater in the portal venous phase than in the arterial phase.
CONCLUSION: Arterial-phase helical CT in patients with pancreatic adenocarcinoma is of limited benefit: lesion conspicuity is suboptimal and depiction of venous anatomy is inferior to the depiction possible with venous-phase helical CT.