Perturbation Correction Factors For Cylindrical Ionization Chambers In High-energy Electron Beams
Published 2010 · Medicine
The aim of the study was to evaluate the perturbation correction factors at a reference depth for cylindrical ionization chambers in high-energy electron beams by means of the EGSnrc Monte Carlo user code cavity. The cylindrical chambers used in this study were the Farmer-type of PTW30010, PTW30011, PTW30012, and PTW30013 models. We calculated the wall correction factor, Pwall, the cavity or electron fluence correction factor, Pcav, the stem correction factor, Pstem, the central electrode correction factor, Pcel, and the overall perturbation correction factor, PQ, for each chamber. The calculated Pcav values were higher by from 2 to 1% than those recommended by the IAEA-TRS-398 code of practice, in an energy range of 6–18 MeV. The Pwall values almost agreed with the analytical calculation performed with IAEA-TRS-398. The Pcel values agreed with those of Ma and Nahum, performed with IAEA-TRS-398. The Pstem values were approximately 0.995 on average and were independent of the electron beam energy. Pstem needs to be considered in future dosimetry protocols. The PQ values were higher from 1 to 2% than those of IAEA-TRS-398 in an energy range of 6–18 MeV.