The primary objective of this study is to derive electron fluence correction factors for cylindrical and parallel plate ion chambers made of polystyrene, lucite/acrylic and electron equivalent solid water wall materials placed inside matching phantom materials. The correction factors will be derived theoretically by performing Monte Carlo calculations using EGS code on a VAX computer. The calculated data will be experimentally verified for electron beams 6-22 MeV and ion chambers of various dimensions applying Harder's multiple scattering effect. The findings will be compared with Harder's theoretical calculations and Johnson's experimental results. The proposed study will provide significant information to supplement the data relevant to the new electron beam calibration protocol recently proposed by the American Association of Physicists in Medicine. The new protocol seeks to standardize the electron beam calibration procedures recommending the use of parallel plate ionization chamber. Although it does allow the use of cylindrical chambers as well, the protocol however does not provide necessary correction factors for these chambers and even for parallel plate chambers of plate separation greater than 2mm. This information is not available in the literature. Our study proposes to generate comprehensive information on electron fluence correction for electron beam calibrations and thus support the proper usage of the new AAPM protocol and promote accuracy and precision in the delivery of radiation treatments in radiation oncology.
