Intensity Modulated Radiation Therapy (IMRT)

Intensity modulated radiation therapy (IMRT) "sculpts" the dose of radiation to conform to the unique shape of a tumor. This highly precise approach uses computer-controlled linear accelerators to maximize the therapy's impact on a malignant tumor, while minimizing the effects radiation can have on your healthy tissues and organs.

Treatment with IMRT is slightly longer than that with conventional radiation, but generally produces fewer side effects.

How does IMRT work?

IMRT is an advanced form of 3-D conformal radiotherapy. It uses sophisticated software and hardware to vary the shape and intensity of radiation delivered to different parts of the treatment area. It is one of the most precise forms of external beam radiation therapy available.

Like conventional radiation, IMRT links CT scans to treatment planning software, allowing the cancerous area to be visualized in 3-D. Conventional radiation and IMRT differ in how the pattern and volume of radiation delivered to the tumor is determined. In conventional radiation, clinicians input delivery patterns into the computer. In IMRT, the physician carefully delineates the tumor and normal tissue, and designates specific doses of radiation (constraints) that each area should receive. The physics team then uses a sophisticated computer program to develop an individualized plan to meet the constraints. This process is known as inverse treatment planning.

As a unique feature, IMRT also involves dynamic multi-leaf collimators (MLCs), computer-controlled devices that use up to 120 movable "leaves" to conform the radiation beam to the shape of the tumor from any angle, while protecting normal adjacent tissue as much as possible.

These MLCs allow the dose of radiation to vary within a single beam. In other words, a single beam can deliver higher radiation in some areas and lower radiation in others.

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