Spectral analysis of Monte Carlo calculated fluence correction and cema conversion factors for high-energy photon beams at different depths

Purpose: The aim of this study is to investigate the depth-dependent detector response detailed thimble air-filled ionization chambers by calculating spectral charged particle fluence correction factors at different depths in water. Those will help understand, how varies and what kind influences disparate effects have on response. Methods: cema-approach can be used obtain fluence-based for various measurement conditions substituting commonly well-known dose conversion factor with a based dosimetric quantity cema (“converted-energy per unit mass”). resulting were calculated EGSnrc software toolkit analyzed two cylindrical (PTW type 31021 Semiflex 3D, SNC125c™) water phantom irradiated 6 MV linear accelerator x-ray spectrum. chamber models been stepwise decomposed perturbation caused internal external distribution within detector. Results: Monte Carlo revealed that all investigated detectors, considerable disturbances occur, especially build-up region depth-dose curves. Our results shown even slight variations depth major consequences differential chamber, mainly due cavity-specific effects. Furthermore, showed case relative measurements, depth-depending significantly differ from unity range 1.4%–2.8% depending design. Conclusion: complexity disturbance could broken down regard their influence sensitive volume detectors. It demonstrated, displacement effect, which not compensated or corrected ideally each shift effective point measurement. Generally, analysis those energy-dependent serves deeper understanding under conditions.