Three-dimensional Conformal Radiation Therapy (3-D CRT)
3-D CRT combines digital diagnostic imaging, powerful computers and specialized software to conform the radiation beam to the shape of the tumor. It’s used to treat cancers in most parts of the body, and most commonly for prostate cancer, lung cancer and certain brain tumors.
Treatment planning begins with CT or MR images that show the anatomy of the tumor and surrounding normal structures. The images are put into a special treatment planning computer that produces an accurate three-dimensional image of the tumor and surrounding organs. Multiple radiation beams can be aimed at the tumor from different directions, matching the contour of the treatment area. The plan is made to deliver a prescribed dose across all three dimensions (height, width and depth) of the tumor and spreads the dose around the surrounding areas, sparing nearby healthy tissue.
Dosimetrists use the computer to model the effect of a predetermined treatment on a patient, selecting various beam angles and intensity and observing the virtual outcome, before prescribing the best dosage.
Radiation therapy usually is given five days a week for six or seven weeks. The total radiation dose and number of treatments varies with each patient and depends on the size, location and type of tumor, as well as the patient's general health and other medical treatments he or she is receiving.