Calculation of beam quality correction factors for various thimble ionization chambers using the Monte Carlo code PENELOPE

The beam quality correction factor k(Q,Q0) and the perturbation factor p(Q), commonly considered in dosimetry with ionization chambers, were calculated for the NE2571 and the Standard Imaging A19 and Al2S chambers, using the Monte Carlo simulation code PENELOPE. For the NE2571 chamber, the values of k(Q,Q0) obtained are in very good agreement with those found in previous works by Wulff et al. and Muir and Rogers with the code EGSnrc and also with the experimental results summarized in the NCS code of practice. For p(Q), a difference of similar to 0.4% has been found between our results and those obtained with EGSnrc for Co-60 and this difference increases slightly with TPR1020 values. These factors have been calculated also for the A19 and Al2S chambers of Standard Imaging. The values of k(Q,Q0) show reasonable agreement with those recently calculated by Muir and Rogers and the measurements of McEwen. (C) 2012 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.