3-D Conformal and Intensity Modulated Radiation Therapy
Among the newer treatment options for cancer of the prostate, brain, lung, and head and neck are 2 methods of focusing radiation on the tumor and surrounding at-risk tissues while optimally sparing nearby normal tissues, 3-dimensional (3-D) conformal radiation therapy, and intensity modulated radiation therapy (IMRT). This approach uses anatomic computed tomographic and/or magnetic resonance images of the patient, computer-generated radiation dose calculations, and a computer-controlled linear accelerator to conform or “paint” the radiation dose very precisely to match the shape of the tumor to be treated, avoiding critical structures that may be only millimeters away.
When the linear accelerator radiation beam intensity is varied, or modulated, over space and time during the patient’s treatment, hence the term “Intensity Modulated” radiation therapy. In combination with advanced imaging techniques like magnetic resonance spectroscopy and positron emission tomography that image both tumor anatomy and biology, IMRT holds great promise for improving local tumor control and survival, even in the most resistant and aggressive human cancers.