Evaluation of IMRT for institutions participating in NCI sponsored clinical trials

Abstract

Materials/Methods The phantoms consist of a plastic outer shell and internal structures to represent anatomy. A thorax phantom contains lung-equivalent regions, one of which contains a GTV. A pelvic phantom contains structures representing the prostate, rectum, and bladder. A third IMRT phantom mimics the head and neck region and contains structures representing a planning target volume (PTV) close to an organ at risk (OAR), simulating an orophanryngeal tumor and the spinal cord. The phantom contains a secondary PTV that simulates peripheral nodes. In each phantom, thermoluminescence dosimeters (TLDs) were embedded in each target volume and several of the OARs, and GafChromic® film was inserted in two or three planes through the PTVs. Institutions were instructed to fill the shell with water on-site, image the phantom, plan a treatment according to RPC guidelines and irradiate the phantom. The institutions were also asked to follow the QA procedures that would be done for a patient. Upon completion the institutions returned the phantom to the RPC. The TLD and film were evaluated by the RPC. Conclusion Failures occurred in irradiations delivered by a variety of models of linear accelerator and planned with several treatment planning systems (TPS). Somewhat consistent behavior was seen among the TPSs, although no trends were apparent among the delivery devices. The phantom was valuable for evaluating IMRT treatments at institutions preparing to participate in advanced technology clinical trials.