Dosimetry is the process where the doctor and the radiation therapist decide on the amount of radiation you need and the best ways to aim it at the cancer with the least effect on normal tissue. This is called a treatment plan. They base this on the size of the tumour, how sensitive the tumour is to radiation, and the ability of the normal tissue in the area to tolerate the treatment.

Image Above: Information from the planning CT scan and/or simulator is used to create an individual map of where the radiation is to be delivered.