Abstract

The calibration of different types of ionization chambers in radiotherapy level is done using different beam qualities i.e. {\gamma}-rays from 137Cs and 60Co. The most common reference beam quality (Qo) used for the calibration of ionization chambers in therapy level is 60Co {\gamma}-rays to calculate calibration coefficient factor either in air (NK) or water (ND,W). In this study we determine NK for two types of ionization chambers PTW-30013 and NE-2561 in beam quality (Q) of 137Cs. The reference values of NK for ionization chamber type M-32002 which determine in beam qualities Q and Qo were 24.8{\mu}Gy/nC and 25.4 {\mu}Gy/nC respectively. These values were used to determine the NK and ND,W for unknown chambers in beam quality Q. The beam quality correction factor KQQo in terms of air and absorbed dose to water for different ionization chambers used was 0.980±0.01, 0.983±0.009 and 1.0001±0.008, 1.0005±0.006 for TM-30013 and NPL 229 respectively.

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