Imaging Anatomy for the Radiation Oncologist

Abstract

To facilitate comprehension on cross-sectional imaging, we introduce appropriate imaging protocols for computed tomography (CT) and magnetic resonance imaging (MRI). On cross-sectional images of CT and MRI, hepatic segments can be located by several anatomical indices and portal vein branching. The majority of hepatic lymph drains into the portal lymphatic system, and regional lymph nodes for hepatocellular carcinoma include the hepatic hilar, hepatoduodenal ligament, inferior phrenic, and caval lymph nodes. Intrahepatic bile ducts are not usually seen on CT due to their small caliber, but bilateral hepatic ducts and the common hepatic duct can be identified at the hepatic hilum and need to be delineated to avoid potential biliary stricture after radiotherapy. For luminal organs at risk, an external surface contouring is recommended, and the drawn contour needs to include partial volume artifacts to ensure that the entire wall is included. Imaging features of the arterioportal shunt, malignant portal vein thrombosis, intraductal growing hepatocellular carcinoma, intrahepatic metastasis, and viable tumor after locoregional treatment are also summarized in this chapter because they can aid in the exact evaluation of tumor extent.