Radiation Oncologists, P.C. Our Specialties

Intensity Modulated Radiation Therapy (IMRT)


The rationale for IMRT is to deliver radiation while minimizing the potentially detrimental side effects. In general, with increasing doses of radiation there is increasing probability of eliminating a tumor. However, our ability to increase the radiation dose has been limited by toxicity to the normal organs/structures that are located close to the tumor. For example, the rectum is the dose-limiting normal structure for prostate cancer. The salivary glands and spinal cord are critical normal structures of cancer when treating head and neck cancer.

By altering the radiation intensity across each beam, IMRT creates the desired radiation dose distributions which allows radiation to be delivered into complex shapes, thus decreasing radiation to adjacent critical organs.

When is it used?

IMRT is a technological advancement in the planning and delivery of radiation. It enables the radiation oncologist to deliver high doses to the tumor while adjacent normal structures get a relatively lower dose. Its benefit has been demonstrated for head and neck cancers and is felt to be potentially superior for select prostate, breast, lung, and gynecological tumors. In addition, it may be appropriate in select cases of recurrent tumors that are near sensitive structures such as the spinal cord.

Planning and delivery

The planning and delivery of IMRT involves the following:

  • Selection by the radiation oncologist of appropriate patients in regard to tumor location, stage (i.e., not all patients need IMRT in order to do well)
  • Meticulous patient positioning so that treatment can be delivered in a reproducible manner
  • Detailed delineation of relevant anatomy in three dimensions by using CT/MRI/PET imaging
  • Prescribing “goals” in regards to desired dose for tumor versus dose to normal structures
  • Computerized optimization process
  • Evaluation of proposed plan with reiteration of the optimization process until the “optimal” plan is achieved
  • Quality assurance (i.e., verification of accuracy of the treatment plan)
  • Daily delivery of the treatment with frequent verification of appropriate positioning of the radiation beam
  • Weekly evaluation of patient’s response and tolerance to the treatment

Leaders in your IMRT treatment

  • Radiation Oncologists has the most experience in Oregon with IMRT for head and neck, breast, and prostate cancers, operating 6 IMRT facilities in Portland, Vancouver, and the Columbia Gorge
  • Knowledgeable team of professionals who can help you for the duration of treatment as well as after the treatment
  • State-of-the-art-equipment
  • In 2001, Radiation Oncologists became the first group in Oregon or Washington to deliver IMRT with a dynamic multi-leaf collimator, and the first group in Oregon to operate community centers accredited by the Radiation Therapy Oncology Group (RTOG) for treating patients using IMRT on clinical trials sponsored by the National Cancer Institute (NCI). RTOG is a nationally recognized organization, under the auspices of the NCI, which is involved in implementation of radiation protocols and technology