Medical dosimetry is the subspecialty of radiation oncology that focuses on treatment planning, dose measurement, dose calculations and quality assurance for radiotherapy treatments designed to treat cancer. The medical dosimetrist is an integral member of the "treatment team" that includes a radiation oncologist, a medical physicist and radiotherapy technologists.
Under the direction of the medical physicist and the radiation oncologist, the dosimetrist determines the beam arrangements, beam shapes, beam weights and beam energies that provide the highest-quality treatment plan. The dosimetrist also contributes to quality assurance and to the construction of special treatment devices. In addition, the medical dosimetrist plays an important role in brachytherapy procedures, providing technical assistance and completing any necessary calculations.