Intensity-modulated radiation therapy (IMRT) is an advanced, highly precise way of delivering radiation treatments. IMRT uses computer-controlled X-ray accelerators to deliver precise radiation doses to a tumor site or to the cancer. The radiation dose is designed to conform in 3-D to the shape of the tumor or targeted area by modulating or controlling the intensity of the beam, focusing more on the tumor and less on the surrounding tissues.

The first difference is how we plan treatment. With IMRT, planning is done using sophisticated computer software that shapes the radiation dose to what the radiation oncologist specifies. Treatment is planned using 3-D computed tomography (CT) images of the patient in conjunction with computerized dose calculations to determine the dose intensity pattern that will best conform to the tumor shape.

The second difference is how treatment is delivered.  Instead of radiation coming out of the machine uniformly using a single beam, in IMRT there are as many as 80-120 sliding metal leaves that are used to shape the beam to fit the specific shape of the tumor or treatment site. The beam is actually composed of thousands of tiny beamlets. The metal leaves and manipulability of the beam prevents radiation from getting to nearby healthy tissue.

UC Davis provides three IMRT modalities, two using Elekta Synergy linear accelerators and the other using the helical Tomotherapy unit. Our IMRT employs the Varian Eclipse and Philips Pinnacle Planning systems.

Research studies will compare the two IMRT modalities.

The radiation oncology team that provides IMRT consists of a radiation oncologist, a medical radiation physicist, a dosimetrist, a radiation therapist and an oncology nurse. 

Your radiation oncologist heads the treatment team and plans your individualized course of treatment with the assistance of the radiation physicist, who ensures the linear accelerator delivers the precise radiation dose and that computerized dose calculations are accurate. The physicist also supervises a dosimetrist who calculates the exposures and beam configurations necessary to deliver the dose prescribed by the radiation oncologist. On the day of the treatment, you will be positioned on the treatment table by the radiation therapist who then operates the machine. Before and after the treatment, our highly trained nurses provide information and care.

Currently, IMRT is being used to treat cancers of the prostate, head and neck, breast, and lung, as well as in gynecologic and brain tumors and lymphomas and sarcomas. IMRT is also beneficial for treating pediatric malignancies.

One of our highly trained radiation therapists will position you precisely on treatment table. The radiation beam will be directed at the specific region from several different angles just as it would with a more standard treatment such as 3-D CRT. However, there may be more or fewer angles depending on your treatment plan. Overall, IMRT may require a few more minutes on the treatment table per day than 3-D CRT (approximately 25-30 minutes, compared with 20-25 minutes), due to the improved shaping of the beam.