How does radioembolization works? Radioembolization allows for internal delivery of radiation through the arteries supplying the cancer, thereby allowing concentration of high doses of radiation to the cancer with minimal effect on the surrounding healthy tissues. In addition, radioembolization requires at least two treatment sessions. The first session is a mapping angiogram, where a catheter is passed into the liver artery from the groin and angiography is used to “map out” all the arteries in the liver circulation. At this time, any arteries passing from the liver circulation to non-target structures, such as the stomach or bowel, can be embolized (blocked off) with coils, to prevent radiation damage to these organs. A test will also be