Embolization refers to the passage and lodging of an embolus within the bloodstream. It may be of natural origin (pathological), in which sense it is also called embolism, for example a pulmonary embolism; or it may be artificially induced (therapeutic), as a haemostatic treatment for bleeding or as a treatment for some types of cancer by deliberately blocking blood vessels to starve the tumour cells. In the cancer management application, the embolus, besides blocking the blood supply to the tumour, also often includes an ingredient to attack the tumour chemically or with irradiation. When it bears a chemotherapy drug, the process is called chemoembolization. Tran’s catheter arterial chemoembolization (TACE) is the usual form. When the embolus bears a radiopharmaceutical for unsealed source radiotherapy, the process is called radio embolization or selective internal radiation therapy (SIRT).