Skip to main content
Department of Radiation Oncology

Department of Radiation Oncology

Intensity Modulated Radiation Therapy (IMRT)


The UC Davis Department of Radiation Oncology is among the first facilities to use this sophisticated, 3-D conformal radiation therapy and has been successfully providing treatment for many years.

IMRT is an advanced, precise form of radiation therapy that delivers higher doses of radiation to the tumor and lower doses to nearby healthy tissue.  IMRT allows patients to receive more concentrated radiation each day, potentially shortening the overall treatment time and improving treatment success.  Some patients also experience fewer side effects during IMRT than more conventional treatment.

The radiation is delivered by a linear accelerator equipped with a multileaf collimator which helps to shape or sculpt the beams of radiation.  The machine producing radiation can be rotated around the patient so that beams can be delivered from the best angles.  Carefully planned and precisely manipulated beams conform as closely as possible to the shape of the tumor.

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.  Instead of radiation coming out of the machine via a single beam, IMRT uses as many as 80-120 sliding metal leaves 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 prevent radiation from getting to nearby healthy tissue.

Although IMRT is primarily used to treat tumors in the brain, head and neck, nasopharynx, breast, liver, lung, prostate and uterus, this new technology is not always appropriate or necessary for every patient and/or type of cancer.

UC Davis provides three IMRT modalities, two using Elekta Synergy linear accelerators and the other using the helical TomoTherapy.  For planning, the team employs the Varian Eclipse and Philips Pinnacle Planning systems.