Intensity modulated radiation therapy or IMRT is one of the most advanced treatment methods available in external beam radiation therapy. Initially a CT scan is performed on the affected region in order to establish the exact contours of the tumor and the surrounding healthy tissue and therefore determine the dose of radiation.
Based on this data the radiation beam is modulated to different levels of intensity by computer-controlled multileaf collimator. The leaves of this device periodically move in and out contouring the radiation beam to the shape of the tumor. The beams enter the body from different angles in order to maximize tumor dosage.
The IMRT technology helps to protect the adjacent healthy tissue by only exposing it to small doses of radiation while the tumor receives a larger, potentially more effective dose. This flux of radiation is changing throughout the area with the net effect being that the shape of radiation around the tumor is more precise with IMRT than with conventional radiation.
This medical animation illustrates intensity modulated radiation therapy (IMRT). When this treatment is administered, beams of radiation strike the tumor target after passing through a component in the IMRT machine which acts much like a filter. It shapes the radiation beams to the size and contour of the tumor. This helps to keep the radiation distribution tightly controlled, avoiding healthy tissue close to the tumor.
IMRT can treat difficult-to-reach tumors in areas such as the spine, head, neck, prostate, lung, liver and brain.