Patient safety is very important and is assured in several ways.
Before we deliver treatment to a patient, we develop a treatment plan. The radiation oncologist in collaboration with the radiation dosimetrist and medical physicist approve this plan. We also double-check and perform quality-assurance procedures to ensure that we can deliver the treatment as planned.
Quality assurance of the linear accelerator is very important. There are several systems built into the accelerator so that it will not deliver a higher dose than the radiation oncologist has prescribed. Each morning before any patients are treated, the radiation therapist performs checks on the machine. He or she ensures that the radiation intensity is uniform across the beam and is working properly. In addition, the medical physicist conducts more detailed monthly and annual checks of the linear accelerator.
Modern linear accelerators also have internal checking systems. These systems do not allow the machine to be turned on unless all the prescribed treatment requirements are met.
During treatment, the radiation therapist continuously observes the patient using a closed-circuit television monitor. There is also a microphone in the treatment room so that the patient can speak to the therapist if needed. Port films (x-rays taken with the treatment beam) or other imaging tools such as cone beam CT are checked regularly to ensure the beam position doesn’t vary from the original plan.
Safety of the staff operating the linear accelerator is also important. The linear accelerator sits in a room with lead and concrete walls so that the high-energy x-rays are shielded and no one outside of the room is exposed to the x-rays. The radiation therapist must turn on the accelerator from outside the treatment room. Because the accelerator only emits radiation when it is actually turned on, the risk of accidental exposure is extremely low.