Caren van Roekel

16 Chapter 2 ABSTRACT Radioembolization is a therapy during which radioactive microspheres are injected into the hepatic artery. A microcatheter is placed in the hepatic arterial vasculature and millions of microspheres are administered. Hepatic malignancies are fed mainly by arterial blood and because of preferential arterial flow, the microspheres lodge in small tumor arterioles. There, they emit high-energy β-radiation to induce cell death. This way, the hepatic tumors are selectively irradiated and the healthy liver tissue is relatively spared. The essential steps for radioembolization include [1] visceral angiography to map tumor-perfusing vessels, embolize collateral vessels and assess portal vein patency, [2] assessment of pulmonary and gastrointestinal shunts by intra- arterial administration of a scout dose, and [3] determination of the optimal therapeutic activity, e.g. dosimetry (1). Key words: radioembolization, microspheres, hepatic tumors, yttrium-90, holmium-166, angiography, dosimetry