pencil‑beam fluence evaluation based on monte carlo simulations algorithm of high energetic treatment photons

Background: the accurate calculation of doses during external radiotherapy sessions is necessary. recently, the models used for this purpose have been the point kernel, pencil‑beam, and collapsed cone superposition/convolution combination models. methods: in this study, it is aimed to determine point/pencil‑beam kernels to be used in dose calculations. for this purpose, tallying pencil‑beam fluence based on monte carlo (mc) simulations is investigated by scoring a volume of interest centered in a cubic water phantom at a depth of 10 cm and the irradiated field of 10 cm × 10 cm. the fluence is calculated for each mono‑energetic photon ranging from 0.25–6 mv at increments of 250 kev. results: the output of the four fluence kernels along the depth z around the central axis is categorized for both the primary and secondary photons and electrons. here, a database for pencil‑beam kernels is established for each category. for validation purposes, other mc simulations are carried out for fluence calculations as produced by the predetermined poly‑energetic spectra for a varian 6 mv linear accelerator. conclusions: the net results show a good fit of the two convoluted fluence spectra quantities for both mono‑energetic and poly‑energetics‑based simulations except little singular peaks.