Pages: 220-225

Authors: Hong-Lam Pham, Thanh-Phi-Hung Hoang, Jin Sunjun, Duy-Linh Bui, Tuan-Khai Nguyen, Van-Loat Bui, Tuan-Anh Le, Huu-Quyet Nguyen, Duc-Khue Pham, Viet-Cuong Phan, Tien-Dung Phan, Quang-Trung Pham, Hoai-Nam Tran, and Ngoc-Thiem Le

Abstract

Ionization chambers were calibrated regarding absorbed dose to water in MeV X-ray fields of a medical linear accelerator, with nominal maximum energies of 6 MeV and 15 MeV. Whereas, absorbed doses to water at a depth of 10 cm below the water surface were measured using the same ionization chamber (referred to as IC-1) in two different manners (i. e., applying the old beam quality correction factor k_Q0from the old IAEA/TRS-398 protocol, referred to as D_10^1–old and using the new one, k_Q from the updated protocol, referred to as D_10^1–new. The calibration factors of IC-1, N_¹D,w,Qwere deduced (for beam qualities Q of MeV X-ray fields with maximum energies of 6 MeV and 15 MeV). The identical procedure was applied to two other ionization chambers
(IC-i, i = 2, 3) to obtain absorbed doses to water at a depth of 10 cm (referred to as D_10^i–new) using the new beam quality correction factor. A comparison between D_10^1–new and D_10^i–new was conducted to derive the calibration factors of the IC-i,N_ⁱD,w,Q. The combined standard uncertainties of N_ⁱD,w,Q (i =1, 2, 3) were estimated within 1.22 % and 2.30 %, respectively.

Key words: absorbed dose, beam quality, nominal maximum energy

FULL PAPER IN PDF FORMAT (546 KB)