Intensity Modulated Radiation Therapy (IMRT)
MEDICAL ANIMATION TRANSCRIPT: Your doctor may recommend intensity modulated radiation therapy, a procedure that treats certain forms of cancer to kill cancer cells or control their growth. The cells in the body grow and divide as part of the normal cell cycle. The cell's nucleus controls this process. Inside each nucleus genetic material called DNA contains the instructions for directing this process. Sometimes the cell's DNA becomes damaged. Normally the DNA responds by either repairing itself or instructing the cell to die. In cancer, however, the parts of the cell's DNA that direct cell division become damaged. When these sections are damaged the DNA is unable to repair itself. Instead the unrepaired DNA causes the cell to grow and divide uncontrollably into more damaged cells called cancer cells. A tumor forms as the cancer cells multiply and displace the normal cells. Radiation kills cancer cells by inflicting overwhelming damage to their DNA. The tumor shrinks as the cells stop dividing and die. If the tumor is in your head your radiation therapist may make a mesh frame or mask that will keep you positioned correctly during the IMRT. Or you will get small permanent tattoos to help align the IMRT. Next your therapist will do a CT scan of your head to get a detailed picture of your tumor and its borders. Your doctor will use the scans to specify the three-dimensional shape of your tumor and vital tissues nearby. The tumor's shape, size, type, and location help your doctor determine how the IMRT beam should be adjusted to hit your tumor and avoid healthy tissue. During your procedure a medical linear accelerator will deliver an x-ray beam to your tumor. A computer inside the accelerator will adjust the beam with a device called a collimator. The collimator will adjust or modulate the intensity, direction, and shape of the radiation beam. This feature allows higher doses of radiation to be delivered to your tumor while sparing your healthy tissue around it. You may receive many radiation treatments over days or weeks. This allows your body to recover between treatments and to kill as many cancer cells as possible. Side effects are usually mild and occur only in the treatment area. Common side effects include localized skin irritation, localized hair loss, or inflammation and swelling near the tumor location.
, intensity modulated radiation therapy