It is stereotactic radiotherapy given in one single dose of radiotherapy to the tumour, rather than in a number of small doses. The treatment is usually given using the same machine, called a linear accelerator, which is used to give standard radiotherapy. It is especially adapted for the purpose of giving stereotactic radiotherapy and is then sometimes called the x-knife. The machine gives concentrated beams of radiation to the brain tumour from several different angles to be as precise as possible. This is done either by moving the machine during treatment or by aiming individual beams from a number of different directions.
Cobalt is a radioactive source which gives off a particular type of radiation called gamma rays.
The effect of irradiation to the particular tumour area with both x-knife and gamma knife is the same. During sterotactic radiotherapy or radiosurgery you may need to wear a frame to prevent movement. This also helps to locate the tumour precisely on a CT or MRI scan. Side effects of radiotherapy Side effects can be mild or more troublesome depending on the strength of the radiotherapy dose and the length of your treatment. There are some side effects which are specific to having radiotherapy to the head.