The goal of three-dimensional conformal radiotherapy (3D-CRT) is to deliver a conformal dose distribution to tumors, while sparing surrounding normal structures. The use of patient specific 3D images in the treatment planning process distinguishes 3D-CRT from conventional radiotherapy. Typically CT and/or MRI images are used for defining the areas of concern as well as adjacent normal structures. Based on this, complex plans are developed to deliver a radiation dose distribution within the patient, where the regions of high dose are concentrated within the tumors. Higher doses of radiation can be delivered to cancer cells while significantly reducing the amount of radiation received by surrounding healthy tissues.
3D-CRT is used to treat tumors that in the past might have been considered too close to vital organs and structures for radiation therapy. For example, 3D-CRT allows radiation to be delivered to head and neck tumors in a way that minimizes exposure of the spinal cord, optic nerve, salivary glands and other important structures.