|Discussion: It is an aggressive and usually fatal tumor. Most pancreatic cancers occur in the pancreatic head (60%)and less commonly in the body (15%) or tail (5%). 20% diffusely involve the entire gland. The overall 5 year survival rate is less than 5%. The only realistic hope for cure is in early detection and aggressive surgery (Whipple procedure). Imaging modalities utilized in the detection and evaluation of pancreatic carcinoma include ultrasound, MRI, and CT. Contrast enhanced CT is the most frequently performed study for the evaluation of pancreatic carcinoma. Characteristic findings include a minimally enhancing, hypodense mass that commonly produces the "double-duct" sign - a dilated common bile duct and pancreatic duct. The uncinate process often appears blunted. There may be stranding in the peripancreatic mesentery signaling peri-pancreatic invasion. Vascular encasement of the nearby superior mesenteric vessels, portal vein, hepatic artery, or celiac trunk renders the tumor inoperable.
Imaging often begins with transabdominal sonography to identify a cause of abdominal pain or jaundice. Sonography can screen for gallstones, signs of cholecystitis, and for the presence and level (intrahepatic, suprapancreatic, or intrapancreatic) of common bile duct obstruction. However, the presence of obscuring overlying bowel gas and the variable skill of the operator limit the sensitivity of this technique for identification and staging of pancreatic tumors.
After sonography, CT is the modality most used as the primary modality for diagnosis and staging. Optimal imaging by helical CT (single-or multidetector) for pancreatic cancer is obtained after the rapid injection of iodinated contrast material (140–150 mL at 4–5 mL/sec). The relatively hypovascular tumor is best detected during the pancreatic parenchymal phase of enhancement, approximately 35–50 sec after the beginning of contrast medium injection . On the other hand, liver metastases are best imaged during the portal venous phase of liver enhancement, approximately 60–70 sec after the beginning of contrast medium injection. A "dual-phase" technique is therefore often used to obtain information regarding staging and metastases. Unfortunately, circulation times vary between patients, and simple rules for timing may not always be effective. Currently available computer-based automated scanning techniques can be used to compensate; however, they incur an additional expense and are dependent on equipment and software.