Abstract
The American Association of Physicists in Medicine (AAPM) Working Group on TG‐51 published an Addendum to the AAPM's TG‐51 protocol (Addendum to TG‐51) in 2014, and the Japan Society of Medical Physics (JSMP) published a new dosimetry protocol JSMP 12 in 2012. In this study, we compared the absorbed dose to water determined at the reference depth for high‐energy photon beams following the recommendations given in AAPM TG‐51 and the Addendum to TG‐51, IAEA TRS‐398, and JSMP 12. This study was performed using measurements with flattened photon beams with nominal energies of 6 and 10 MV. Three widely used ionization chambers with different compositions, Exradin A12, PTW 30013, and IBA FC65‐P, were employed. Fully corrected charge readings obtained for the three chambers according to AAPM TG‐51 and the Addendum to TG‐51, which included the correction for the radiation beam profile (P rp), showed variations of 0.2% and 0.3% at 6 and 10 MV, respectively, from the readings corresponding to IAEA TRS‐398 and JSMP 12. The values for the beam quality conversion factor k Q obtained according to the three protocols agreed within 0.5%; the only exception was a 0.6% difference between the results obtained at 10 MV for Exradin A12 according to IAEA TRS‐398 and AAPM TG‐51 and the Addendum to TG‐51. Consequently, the values for the absorbed dose to water obtained for the three protocols agreed within 0.4%; the only exception was a 0.6% difference between the values obtained at 10 MV for PTW 30013 according to AAPM TG‐51 and the Addendum to TG‐51, and JSMP 12. While the difference in the absorbed dose to water determined by the three protocols depends on the kQ and P rp values, the absorbed dose to water obtained according to the three protocols agrees within the relative uncertainties for the three protocols.
Highlights
The incidence and death rates of cancer have recently been increasing worldwide,[1] highlighting the need for effective cancer treatment methods
The values for the absorbed dose to water obtained for the three protocols agreed within 0.4%; the only exception was a 0.6% difference between the values obtained at 10 MV for PTW 30013 according to Association of Physicists in Medicine (AAPM) Task Group 51 (TG-51) and the Addendum to TG-51, and Japan Society of Medical Physics (JSMP) 12
The differences that may exist among these protocols could have important consequences for dosimetric evaluation; in this study, we compared the absorbed dose to water determined for high-energy photon beams according to AAPM TG-51 and the Addendum to TG-51, JSMP 12, and International Atomic Energy Agency (IAEA) Technical Report Series No 398 (TRS-398)
Summary
The incidence and death rates of cancer have recently been increasing worldwide,[1] highlighting the need for effective cancer treatment methods. A highaccuracy dose is required to be delivered to the patient to achieve a favorable clinical outcome.[2,3] high-energy radiation sources are commonly calibrated under certain reference conditions according to a protocol based on the ionization chambers, which are calibrated using the standards for the absorbed dose to water. During the last two decades, the International Atomic Energy Agency (IAEA), the American Association of Physicists in Medicine (AAPM), and other national organizations from various countries have published clinical reference dosimetry protocols for external beam radiation therapy using high-energy photon and electron beams.
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