National Medical Dosimetrist’s Day Date in the current year: August 19, 2026

Radiation therapy, also known as radiotherapy, is a primary treatment for several types of cancer. It is also commonly used as an adjuvant therapy after the surgical removal of a malignant tumor or as a neoadjuvant therapy before removal. It uses ionizing radiation to damage the DNA of cancerous cells, leading to their death.

Because ionizing radiation can damage healthy cells and cause side effects, treatment must be planned and delivered carefully on a case-by-case basis. A radiation oncology team typically includes several professionals, such as a radiation oncologist, medical physicist, medical dosimetrist, and radiation therapists. Other medical professionals may be included as needed.

Radiation oncologists and medical physicists play a more general role in patients’ treatment. The radiation oncologist is the physician responsible for the overall radiation treatment, while medical physicists are responsible for the physics and technical safety of the treatment. While their work is extremely important, it is the medical dosimetrist who is primarily responsible for developing the detailed, individualized treatment plans under the direction of the radiation oncologist and in collaboration with the medical physicist.

Many people see the term “dosimetrist” and assume that calculating radiation doses is the only responsibility of a medical dosimetrist. In reality, however, their role is more complex. Medical dosimetrists take prescriptions from radiation oncologists, use patients’ imaging results and other clinical information, and employ specialized software to determine how to deliver the prescribed dose of radiation to maximize the effect of radiation therapy while minimizing damage to healthy tissues.

The work of medical dosimetrists on a treatment plan may involve selecting beam directions, arrangements, energies, field shapes, intensity patterns, and dose distributions. They may create one plan or several for comparison, which are reviewed by radiation oncologists and medical physicists. If the plan meets the clinical objectives and passes the required technical checks and approvals, it can then be used to deliver the treatment.

Although working as a staff medical dosimetris, i.e. the specialist responsible for developing radiotherapy treatment plans, is the traditional career path for medical dosimetrists, it is not the only one. Medical dosimetrists may work in particle therapy as proton dosimetrists, work as radiation oncology vendors, take on administrative roles within radiation oncology departments, focus on research and development, or work in education.

In 2021, the American Association of Medical Dosimetrists (AAMD) established National Medical Dosimetrist’s Day to honor medical dosimetry professionals in the United States and worldwide. The day also aims to raise awareness about their roles within radiation therapy teams and in other medical and academic settings.