Absorbed dose to water calibration coefficient by types of ionization chambers

Purpose: In Japan, calibration of therapy-level dosimeter with absorbed dose to water have been performed by Association for Nuclear Technology in Medicine (ANTM) as the Secondary Dosimeter Laboratory (SSDL) since 2012. Purpose of this study is to investigate the variation in absorbed dose to water calibration coefficients among chambers of the same type.Results: For shallow type chambers, PTW 34001 is the least variable (1.2% standard deviation. IBA NACP-02 and PTW 23343 chamber exhibit the most variation (3.9% and 4.3% standard deviation) respectively. For almost all types of cylindrical chambers, variations of coefficients are less than those of shallow type chambers. And it is showed that both for cylindrical chamber and for shallow chamber, the smaller collecting volume leads to the more variation of coefficients.Conclusion: Absorbed dose to water calibration coefficient by types of ionization chamber were collected by ANTM. It is found that a tendency of coefficients distribution is different for each chamber type, and small chamber volume leads to more variable of coefficients.8th Japan-Korea Joint Meeting on Medical Physics (114th Scientific Meeting of JSMP