Monte Carlo Method for Electron and Photon Absorbed Dose Distributions and Beam Quality

for Radiotherapy Applications


J. Ghassoun*, B. Chkillou, A. Jehouani

Nuclear Physics and Techniques Laboratory, Faculty of Sciences Semlalia, BP. 2390, University Cadi Ayyad, Marrakech, Morocco

* Corresponding author.

Received: 02 April 2006; revised version accepted: 26 June 2006



     In radiotherapy using gamma-rays, the electron contamination and secondary photons produced by the photon interaction with the material surrounding the photons source causes, an unexpected excess dose at the irradiated surface of the patient. In this study the Monte Carlo method was used to simulate a photon beam system for therapy applications. The MNCP code was used to calculate the absorbed dose at different depths in a water phantom due to 60Co ?-rays at 80 cm source to-surface-distance SSD. To study the influence of both electron contamination and secondary photons on the absorbed dose distribution, the energy spectra of both electron and photon at the entrance surface of a water phantom were examined for different material filters. Our analysis showed that the use of an appropriate filter leads to an electron flux reduction without affecting the primary photon beam quality.


Keywords:  Monte Carlo; Photon; Electron; Depth dose; Radiotherapy; Phantom; Cobalt.

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