An oncologist who wants to treat a cancer patient using radiation will need to work with a dosimetrist. A dosimetrist is a medical professional whose expertise is radiation dosage and how to deliver it most effectively to a patient. He or she evaluates the prescription for radiation from the doctor and calculates the best plan to apply it to the tumor while avoiding harm to the patient's surrounding tissues and organs.
A dosimetrist must be knowledgeable in the practices of brachytherapy and teletherapy. Brachytherapy is a method of treatment which involves applying a source of radiation very near to a tumor, sometimes within the patient's body. This practice helps localize the application of radiation to the tumor, limiting possible damage from irradiation of other healthy tissues. Teletherapy is the practice of targeting a tumor using a beam from outside the body. Both techniques can be utilized depending on which is more appropriate to the situation.
When the dosimetrist receives the oncologist's prescription for radiation, he or she must then evaluate the needs of the patient to design a course of treatment. Calculations done manually or using a computer must be performed to plan for the correct dosage. Special consideration must be taken for any healthy tissues or organs near to the treatment site. Known as dose-limiting structures, the dosimetrist must be cognizant of them and design a plan that will effectively apply the radiation without hurting them. Often, 3-D images or scans such as MRIs or PET scans are used to help clearly define the location of the tumor and its position relative to these structures.
After creating a plan, the dosimetrist may set up a simulation of the treatment to confirm it will work as expected. During the test, he or she may determine if it is necessary to immobilize parts of the patient's body during treatment to keep healthy tissues safe and assure the radiation is applied correctly. In these cases, casts or molds may need to be created for this purpose.
Another area where a dosimetrist must have significant training is in the use of equipment for radiation therapy. He or she is responsible for calibrating the machinery used in treatment and assuring it is up to standard. The dosimetrist often works with another medical professional known as a medical physicist to implement the treatment using the appropriate equipment, ensuring that it is done safely and correctly.