As many as 50% of patients with cancer receive treatment with radiation therapy with the goal of cure or reducing pain and other symptoms. During a presentation at the inaugural ONS Bridge™ virtual conference, Sotiri Stathakis, PhD, DABR, offered nurses insights into the field from the perspective of a medical physicist.

“Radiation therapy is a multidisciplinary treatment approach. Understanding the roles of each team member makes the overall patient treatment more effective and safer,” Stathakis, professor in the Department of Radiation Oncology and Radiology at the University of Texas Health Science Center in San Antonio, said.

He reviewed the principles of radiobiology, which is the study of the action of ionizing radiation on living organisms. The field elucidates the physics and chemistry of the processes by which radiation is absorbed as well as the response to radiation, which may be dependent on various parameters:

  • Physical factors (e.g., total dose, radiation type, overall time of exposure, patient anatomy, organs at risk)
  • Biological factors (e.g., tissue type, age, species)

Medical physicists in radiation oncology consider all of those factors to determine dosing for optimal outcomes with reduced side effects. Side effects, Stathakis noted, occur when healthy tissue near a tumor is affected. Most side effects are localized to the area treated and usually are short-term, although he said that some effects can be system-wide, such as fatigue.

The Role of a Radiation Oncology Medical Physicist

To help nurses better understand their medical physicist colleagues in radiation oncology, Stathakis reviewed their role in detail.

Dosimetry, which is vital to quality assurance, is one of their key responsibilities. Dosimetrists create and review treatment plans and take in vivo radiation measurements to ensure accuracy of each patient’s specific treatment plan. They also take absolute and relative radiation measurements to monitor that linear accelerators and radiation vaults are operating properly and within established guidelines.

In vivo treatment verification is one of their essential functions. Medical physicists in radiation oncology record the dose received, ensure that the prescribed dose was delivered, detect errors, and assess any clinically relevant differences between planned and delivered doses. Based on treatment verification over time, medical physicists make recommendations to treating physicians for adaptations if necessary.

Another aspect of the role involves choosing immobilization devices to quickly and accurately restrict motion during treatments and create reproducible conditions for treatments. Stathakis said that his team uses both simple devices (e.g., straps, grip rings, headrests) and more complex options (e.g., face and shoulder masks, head frames, compression paddles, wing and breast boards). They select devices that are lightweight and durable, have minimal effects on the treatment field, and will not cause image artifacts.

Other responsibilities of medical physicists in radiation oncology include:

  • Review patients’ treatment plans to make sure they are optimal.
  • Take images from planning computed tomography scans and fuse them with other medical images for treatment planning purposes.
  • Review and segment organs at risk.
  • Create blocks in various shapes to protect organs.
  • Plan treatments that involve special procedures such as brachytherapy and stereotactic radiosurgery.
  • Test new equipment.
  • Cover the floor and answer questions about patient treatments.
  • Coordinate with nurses as patients start and end treatment, as well as for considerations with special populations such as pediatric patients.