Your radiation setup refers to the planning stage of your radiation therapy. During this session, your radiation oncologist will map out the area of your breast that will be treated. Your radiation oncologist may use a special x-ray machine, called a simulator, to determine the treatment field, which is the area where radiation will be applied. The properties that constitute the treatment field are called treatment field parameters.
The treatment field is selected carefully to ensure that:
The areas of your body that need treatment will receive the maximum dose
Unaffected areas of your body will receive minimum exposure, so that side effects will be minimized
Once the radiation oncologist has established the treatment fields, he or she will mark the edges of the field on your body with either a small, permanent tattoo or a marker containing non-washable ink. The markings are usually no larger than the head of a pin. These marks will help the radiation technician target the treatment areas each time you come in for your doses of radiation.