GEM and cholangiocarcinoma: The representative in vivo metabolic response of cholangiocarcinoma-afflicted rats to various treatments as detected by 18F-fludeoxyglucose micro-positron emission tomography (18F-FDG microPET) is shown in Fig. 4A. The Gem+Rad group had the most significant metabolic response after two cycles of treatment (Fig. 4B).