Calibration of helical tomotherapy machine using EPR/alanine dosimetry

摘要: Purpose: Current codes of practice for clinical reference dosimetry high-energy photon beams in conventional radiotherapy recommend using a 10 × cm 2 square field, with the detector at depth water and 100 source to surface distance (SSD) (AAPM TG-51) or source-to-axis (SAD) (IAEA TRS-398). However, maximum field size helical tomotherapy (HT) machine is 40 5 defined 85 SAD. These nonstandard conditions prevent direct implementation these protocols. The purpose this study twofold: To check absorbed dose rate calibration unit as well accuracy treatment planning system (TPS) calculations specific test case. Method: Both topics are based on use electron paramagnetic resonance(EPR) alanine transfer dosimeter between Laboratoire National Henri Becquerel (LNHB) C 60 o- γ -ray beam Institut Curie’s HT beam. Irradiations performed LNHB allowed setting up method, which was then implemented tested 6 MV linac x-ray beam, resulting deviation 1.6% (at 1% standard uncertainty) relative value determined IAEA TRS-398 protocol. Results: estimation shows difference 2% stated by manufacturer uncertainty. A 4% measured calculation from TPS found. latter originated an inadequate representation phantom CT-scan values and, consequently, mass densities within phantom. This has been explained density given used were not true ones. Once corrected Monte Carlo N-Particle simulations validate process, found be around (with uncertainty doses 1.5% EPR measurements). Conclusion: Beam results good agreement Moreover, determination method set uncertainty).