Annals of Oncology 10 Suppl. 4: S12-S17, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. Review Computed tomography in the diagnosis and staging of cholangiocarcinoma and pancreatic carcinoma Patrick C. Freeny University of Washington School of Medicine, Department of Radiology, Seattle, WA, U.S.A. Summary This paper is a review of the current techniques and results of helical CT in the diagnosis and staging of pancreatic adenocarcinoma and cholangiocarcinoma of the intra and extra- hepatic biliary ducts. CT has a diagnostic accuracy rate of over 95% for detection and diagnosis of pancreatic carcinoma and close to 100% in staging unresectable tumors. The accuracy of staging surgically resectable tumors is about 80%. Accuracy of determining the level of biliary obstruction caused by cholangiocarcinoma is close to 100%. The accuracy of making a specific diagnosis is about 78%. Key words: bile ducts, cholangiocarcinoma, computed tomography, pancreas, pancreatic carcinoma Introduction Cross-sectional imaging techniques have become the cornerstone for primary and initial evaluation of most patients with suspected pancreatic and biliary tract neoplasms. During the past few years, significant advances in imaging have occurred, including the development of helical computed tomography (CT), magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP), Doppler and intraductal pancreatic sonography, and positron emission tomography (PET). This paper will discuss the techniques and applications of CT in diagnosis and staging of pancreatic and biliary tract malignancies. Techniques of computed tomography CT of the pancreas and bile ducts can be accomplished using conventional portal phase imaging or the newer technique of helical CT dual phase scan acquisition. Dual phase imaging acquires scans during both the arterial and portal phases of contrast enhancement, producing high detail images which can be used for diagnosis and staging of pancreatic and biliary tract neoplasms as well as for precise definition of visceral arterial anatomy. Dual phase helical CT acquires images during rapid IV bolus injection of 180mL of nonionic contrast medium (300-320 mg of Iodine per ml) using a power injector and an injection rate of 5.0 mL/sec. The initial helical acquisition (3-5mm collimation; pitch adjusted to cover the pancreas and liver in a single breathhold) is obtained during the arterial phase of contrast enhancement. The arterial phase scan delay is determined by administering a test bolus of contrast (20mL at 5mL/sec) and measuring the time to peak enhancement of the aorta at the level of the celiac axis. The scan delay is calculated to equal the time of aortic peak plus 5 sec. Pancreatic parenchymal enhancement as high as 85-90 HU above baseline can be obtained during arterial phase helical CT, thus optimizing contrast enhancement for detection of small, hypodense pancreatic carcinomas (Figure 1) and hyperdense islet cell tumors, for demonstration of tumor infiltration around arteries (Figure 2), and for differential diagnosis of pancreatic masses [1]. Figure 1. Small resectable pancreatic carcinoma. A. Arterial phase helical CT at the level of the pancreatic head shows a 1.5 cm hypodense mass (arrowheads) adjacent to a biliary stem (arrow) placed for obstructive jaundice. B. Portal phase scan shows the mass to have become nearly isodense with the surrounding normal pancreatic parenchyma and thus difficult to detect. The second helical CT acquisition is obtained at 60 sec after contrast delivery during the portal phase of contrast enhancement. In this phase, the peripancreatic veins show maximal contrast enhancement, facilitating delineation of tumor involvement of venous vessels (Figure 2). The liver parenchyma also shows maximal enhancement during the portal phase, which is optimal for detection of hepatic metastases or tumor infiltration into adjacent hepatic parenchyma from biliary tract neoplasms. In some cases, a peripheral rim of contrast enhancement can be seen during the early arterial phase, enhancing the ability to differentiate small metastases from other benign hepatic lesions. The volumetric acquisition of helical CT also permits the arterial phase scan data to be used for computer reconstruction of 3-D maximal intensity projection, shaded- surface display, and volume rendered images of the upper
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
