In every case, the treatment is stereotactic , meaning that the radiation field is concentrated right on the tumor and is very weak in other parts of the brain. This is accomplished by having rays converge on the tumor, according to a treatment plan that is calculated with the help of a computer, based on a patient's MRI and CT scans. In practice, only some of the combinations are available. The following grid shows all the combinations that we are aware of. The type of radiation is shown along the top, the dosage is shown on the left, and the positioning method is inside.
Some combinations have a better track record than others.
Track records of different treatments are a controversial topic. Gamma Knife falls somewhere between these two. This means that the radiation field is concentrated right on the tumor and is very weak in other parts of the brain. Fractionated Radiosurgery Fractionated means that instead of a single session, the radiation is broken up into smaller doses delivered over several separate sessions. This has been done for cancer treatments for a long time, since the tumor tissue responds more readily to radiation that the healthy tissue.