Usefulness of the helical CT in the diagnosis of periampullary malignant tumors

To evaluate the usefulness of the helical CT in the differentiation of periampullary malignant tumors. Fifty-five periampullary carcinoma patients (pancreatic head carcinoma (n=18); distal CBD carcinoma (n=17) ; carcinoma of the ampulla of Vater (n=16) ; periampullary duodenal cancers,(n=4), all diagnosed by histopathologic study) underwent helical CT with 5mm scan thickness and 5mm/sec table speed. After scanning, retrospective reconstruction was performed at 2mm intervals, followed by multiplanar reformation. In both retrospective reconstructed axial and multiplanar reformation images, the authors analyzed the detection rate and size of the mass, and associated findings including invasion of peripancreatic fat, dilatation of CBD and its narrowing pattern, dilatation of the pancreatic duct and its degree of dilatation, wall thickening of CBD, extension of dilated bile duct into the ampulla, and of protruding mass into the duodenal lumen, and 1ymph node metastasis all according to the origin sites of tumors. Differential points were thus determined. The detection rate of the masses was 96% (53/55). Their size was 1-5cm, with a mean size of 2.4±0.5cm in carcinoma of of ampulla of Vater and 3.5±1.0cm in pancreatic head carcinoma. Invasion of peripancreatic fat was most commonly observed in pancreatic head carcinoma (100%, 18/18) (p<0.05), dilatation of CBD was observed in all cases except one of periampullary duodenal cancer (98%, 54/55), and abrupt termination of dilated bile duct was noted in all cases except one of the pancreatic head carcinoma (98%, 53/54). Dilatation of pancreatic duct was commonly observed in pancreatic head carcinoma (94%, 17/18) and carcinoma of the ampulla of Vater (75%, 12/16). Its degree of dilatation was mostly moderate in pancreatic head carcinoma (56%, 10/18) and mostly mild in carcinoma of the ampulla of Vater (63%, 10/16) (p<0.05). Wall thickening of the distal CBD was most commonly observed in distal CBD carcinoma (76%, 13/17). Extension of dilated bile duct into the ampulla was commonly observed in the carcinoma of the ampulla of Vater (81%, 13/16) and periampullary duodenal cancer (75%, 3/4) (p<0.05). A mass protruding into the duodenal lumen was commonly observed in periampullary duodenal cancer (100%, 4/4) and carcinoma of the ampulla of Vater (94%, 15/16) (p<0.05). Lymph node meatastasis was observed in pancreatic head carcinoma (17%, 3/18) and distal CBD carcinoma (6%,1/17). Because of improvement in the rate at which the mass is detected, and a clear demonstration of associated findings, helical CT in useful in the differentiation of periampullary carcinomas