An optimized Monte Carlo (PENELOPE) code for the characterization of gel-layer detectors in radiotherapy

Monte Carlo (MC) simulation of radiation transport is considered to be one of the most accurate methods of radiation therapy dose calculation. A basic requirement for MC treatment planning is a detailed knowledge of the characteristics of radiation beam generated from medical linear accelerators (LINACs). One of the most important input parameters is the photon fluence of the beam, usually not determinable experimentally. Thus, an MC simulation code based on the PENELOPE package was developed in order to survey the influence of the incident spectrum on the in-phantom dose distributions. Different spectra for the incident photon fluence have been considered in order to establish the most adequate one. The resulting planned dose distributions have been compared with those determined experimentally with ionization chamber measurements and gel dosimeter layers analyzed with optical technique. The specific gel composition has been implemented in the MC simulation code. Comparisons between experimental measurements, approximated simulations (water) and specific simulations (gel composition) have been performed.