Biliary tract cancer refers to malignant tumors of the extrahepatic bile duct originating from the confluence of the left and right hepatic ducts to the lower end of the common bile duct. If the cancer is located in one side of the hepatic duct, the cancer is often asymptomatic at the beginning, and obstructive jaundice appears only when it affects the opening of the opposite hepatic duct. The examination shows that the liver is enlarged and hard, and the gallbladder is not enlarged; if it is the lower part of the common bile duct, the enlarged gallbladder can be found, and if the tumor breaks and bleeds, there may be black stool or positive stool occult blood test and anemia. It is understood that Gamma Knife treatment has certain effect on advanced biliary tract cancer because it will cause cancer cells to degenerate and necrosis and inhibit their growth, which can prolong the survival of patients with advanced biliary tract cancer. So, what is Gamma Knife? The treatment principle of Gamma Knife is similar to the focusing process of a magnifying glass. When a magnifying glass is placed in the sunlight, a dazzling and eye-catching spot of light, the focal point, is formed under the magnifying glass. Outside the focal point, the person feels as normal, but at the focal point there is very high heat, enough to set some objects on fire. Using the gamma ray geometric focusing method, the energy of 30 planned cobalt 60 is focused on the pre-illuminated target according to the calculated dose, and the tissue in the target is destroyed in a one-time, lethal manner, which can have the same effect as surgical resection and avoid the risk of surgery.