Clinic based transfer of the calibration coefficient using a linear accelerator

Abstract

Ionization chambers used for reference dosimetry require a local secondary standard ionization chamber with a absorbed dose to water calibration coefficient traceable to a national primary standards dosimetry laboratory or an accredited secondary dosimetry calibration laboratory. Clinic based (in‐house) transfer of this coefficient to tertiary reference ionization chambers has traditionally been accomplished with chamber cross calibration in water using a beam; however, access to teletherapy machines has become increasingly limited for clinic based physicists. In this work, the accuracy of alternative methods of transferring the calibration coefficient using 6 and 18 MV photon beams from a linear accelerator in lieu of has been investigated for five different setups and four commonly used chamber types.