Quality assurance for 3D conformal radiation therapy.

Three-dimensional conformal radiation therapy (3D CRT) can be considered as an integrated process of treatment planning, delivery, and verification that attempts to conform the prescription dose closely to the target volume while limiting dose to critical normal structures. Requiring the prescription dose to conform as closely as possible to the target volume raises the level of the precision and accuracy requirements generally found in conventional radiation therapy. 3D CRT treatment planning requires robust patient immobilization/repositioning systems and volumetric image data (CT and/or MR) acquired in the treatment position. 3D treatment planning more explicitly details the particulars of a patient's treatment than was ever possible with 2D treatment planning. In 1992, we implemented a formal 3D treatment planning service in our clinic and at that same time instituted a formal quality assurance (QA) program addressing the individual procedures that make up the 3D CRT process. Our 3D QA program includes systematic testing of the hardware and software used in the 3D treatment planning process, careful review of each patient's treatment plan, careful review of the physical implementation of the treatment plan, a peer review 3D QA Case Conference, and a formal continuing education program in 3D CRT for our radiation therapy staff. This broad 3D QA program requires the involvement of physicians, physicists, dosimetrists, and the treating radiation therapists that complete the team responsible for 3D CRT. 3D CRT capabilities change the kinds of radiation therapy treatments that are possible and that changes the process with which treatment planning and treatment delivery are performed. There is no question that 3D CRT shows significant potential for improving the quality of radiation therapy and improving the efficiency with which it can be delivered. However, its implementation and wide spread use is still in its initial stages. The techniques used for 3D treatment planning and the associated QA procedures and tests should still be considered developmental and changes are likely to continue to occur over the next several years.