The Medical Dosimetrist is a member of the radiation oncology team who has knowledge of the overall characteristics and clinical relevance of radiation oncology treatment machines and equipment, is cognizant of procedures commonly used in brachytherapy and has the education and expertise necessary to generate radiation dose distributions and dose calculations in collaboration with the medical physicist and radiation oncologist.

After the Radiation Oncologist has consulted with the patient on their plan of treatment, the oncologist will write a prescription of radiation dose to a defined tumor volume.  The medical dosimetrist will then design a treatment plan by means of computer and/or manual computation to determine a treatment field technique that will deliver that prescribed radiation dose.  When designing that plan, also taken into consideration are the dose-limiting structures.  These structures could include the eye when treating the brain, the heart when treating the lung, or the spinal cord when it is included in the area of treatment.

Following the planning process, the patient will have a simulation for tumor localization to ensure reproducibility of treatment set up and plan delivery. Here, it may be necessary to produce moulds, casts, and other immobilization devices for accurate treatment delivery.  A medical dosimetrist may supervise, perform, or assist in this process.  The medical dosimetrist will then work with the radiation therapists in the implementation of the patient treatment plans including: the correct application of immobilization devices, beam modification devices, approved field arrangements, and other treatment variables.

In summation, the medical dosimetrist performs calculations for the accurate delivery of the Radiation Oncologist's prescribed dose, documents pertinent information in the patient record, and verifies the mathematical accuracy of all calculations using a system established by the Medical Physicist.  Also, dosimetrists often take on the role of educator in the department for radiation oncology residents, radiation therapy students or medical dosimetry students.