Intensity Modulated Radiotherapy (IMRT)

IMRT is an advanced form of three-dimensional conformal radiation (3DCRT)  that reduces the dose of radiation received by healthy tissue, and allows doctors to deliver radiation to difficult-to-reach areas. A "fourth dimension" of tumor movement can be incorporated in a procedure called 4DCR for more advanced tumors confined to the chest.

The use of CT scanning in the treatment simulation process permits the development of a three-dimensional treatment plan that allows the design of a complex combination of radiation beams focusing on a cancer. This is particularly useful in treating cancers that are adjacent to vital structures or near organs that are sensitive to the effects of radiation. Completion of a three-dimensional treatment plan requires CT scanning equipment, essential computer hardware and software, as well as skilled radiation oncologists and radiation dosimetrists.

Stanford doctors and researchers were pioneers in the development and implementation of IMRT, a method of delivering radiation to tumors with unprecedented precision.

How IMRT works

IMRT combines extremely precise tumor imaging techniques with special linear accelerators that can deliver hundreds of thin beams of radiation from any angle. Information fed into the linear accelerator allows it to revolve around the patient, delivering radiation in a three-dimensional patterns that corresponds to the exact tumor location.

The benefits of IMRT

Targeting radiation to the tumor allows doctors to deliver the maximum dose of radiation to the cancer, while sparing healthy tissues. In addition, such accurate patterning of the radiation allows doctors to deliver radiation to places in the body that have been traditionally difficult to treat with radiation, such as the spinal cord, head (e.g., paranasal sinuses), neck, brain, liver, lungs, and prostate. In some cases, doctors can even deliver radiation to tumors that had been considered untreatable because they were too intertwined with vital organs.

In addition, IMRT can sometimes be combined with respiratory gating to precisely deliver radiation to tumors that could move when a patient breathes.