Pancreatic-phase versus portal vein-phase helical CT of the pancreas: Optimal temporal window for evaluation of pancreatic adenocarcinoma

OBJECTIVE. Our objective was to use helical CT to compare the enhancement a ttenuation values of pancreatic adenocarcinoma, adjacent normal pancreas, a nd critical vascular structures during the pancreatic phase and portal vein phase. SUBJECTS AND METHODS. Forty-one patients with pathologically proven pancrea tic adenocarcinoma underwent dual-phase thin-section dynamic helical CT usi ng a pancreatic-phase and portal vein-phase protocol, The scan delay after initiation of the contrast bolus was 40 sec for the pancreatic phase and 70 sec for the portal vein phase, Attenuation values after IV contrast admini stration were calculated during both phases of scanning for normal pancreas , pancreatic tumor, celiac axis, superior mesenteric artery, superior mesen teric vein, splenic vein, and portal vein. Quantitative values were assesse d using regions of interest. RESULTS. Mean differences of enhancement between tumor and normal pancreas were significantly greater in the pancreatic phase (57 H) than the portal v ein phase (35 H) (p =.0001). Enhancement values of all the critical vascula r structures were also significantly greater in the pancreatic phase than t he portal vein phase (p <.001). CONCLUSION, With dynamic thin-section helical CT, pancreatic-phase scanning provides greater differences in contrast enhancement between normal pancre as and pancreatic tumor and between pancreatic tumors and surrounding criti cal vascular structures than does portal vein-phase scanning.