External Auditing on Absorbed Dose Using a Solid Water Phantom for Domestic Radiotherapy Facilities

作者：Chang Heon Choi, Jung-In Kim, Jong Min Park, Yang Kyun Park, Kun-Woo Cho, Woon-Kap Cho, Chun-Il Lim, Sung‐Joon Ye · 发表于：Radiation Oncology Journal · 年份：2010 · DOI：10.3857/jkstro.2010.28.1.50 · 被引用次数：4 · 研究领域：Advanced Radiotherapy Techniques、Radiation Therapy and Dosimetry、Radiation Detection and Scintillator Technologies

Purpose: We report the results of an external audit on the absorbed dose of radiotherapy beams independently performed by third parties. For this effort, we developed a method to measure the absorbed dose to water in an easy and convenient setup of solid water phantom. Materials and Methods: In 2008, 12 radiotherapy centers voluntarily participated in the external auditing program and 47 beams of X-ray and electron were independently calibrated by the third party's American Association of Physicists in Medicine (AAPM) task group (TG)-51 protocol. Even though the AAPM TG-51 protocol recommended the use of water, water as a phantom has a few disadvantages, especially in a busy clinic. Instead, we used solid water phantom due to its reproducibility and convenience in terms of setup and transport. Dose conversion factors between solid water and water were determined for photon and electron beams of various energies by using a scaling method and experimental measurements. Results: Most of the beams (74%) were within 2% of the deviation from the third party's protocol. However, two of 20 X-ray beams and three of 27 electron beams were out of the tolerance (3%), including two beams with a 10% deviation. X-ray beams of higher than 6 MV had no conversion factors, while a 6 MV absorbed dose to a solid water phantom was 0.4% less than the dose to water. The electron dose conversion factors between the solid water phantom and water were determined: The higher the electron energy, the les...