Evaluation of effect on output factor in customized electron fields collimation in radiotherapy for various energies

Electrons are widely used in combination with photon beams or as standalone modality for radiotherapy with energy ranging from 4MeV-15MeV. The electron beams are applied using varies sizes of applicator with cutouts to match the tumor topology and conform to the clinical requirements. However, in routine clinical practices customized electron cutouts of cerrobend are prepared which may be circular, rectangular or of any other geometry to meet the need of the target volume. The electron cutouts in combination with applicators affect the output, PDD and other dosimetric parameters. It has been reported that the changes in beam characteristic of high energy and small cutouts are more profound due to lack of lateral scattering contribution. In this study it was propose to evaluate the dosimetric parameters of cutout and compare it with electron beam characteristics obtain from the various algorithm of the treatment planning system (TPS). The measured data and the TPS generated values have been compared to obtain the perturbation that may be induced in clinical practice. This study attempts to demonstrate that small cutout dosimetry in electron is critical when used as standard alone modality or in combination with photon beam abutment