Intensity Modulated Radiation Therapy (IMRT):
Intensity modulated radiation therapy, or IMRT, is a specialized form of 3D-CRT that allows radiation to be more exactly shaped to fit the tumor. With IMRT, the radiation beam can be broken up into many beamlets, and the intensity of each beamlet can be adjusted individually. The radiation intensity of these beams is modulated, or controlled, with a system of movable leaves called a multi-leaf collimator (MLC). The leaves conform to the shape of the tumor and block out unwanted radiation. With sophisticated dose calculation methods each leaf can move independently to create tiny beamlets of radiation that specifically target a tumor. This treatment technique provides the means to escalate tumor doses while significantly sparing normal tissue. Less radiation to normal tissues translates into fewer complications for patients. IMRT is ideal for stationary tumors situated near critical structures such as the spinal cord, heart and eyes. Some typical treatment sites include the prostate, brain and breast.