Photoneutron and capture gamma dose calculations for a radiotherapy room made of high density concrete

• Published in: Nuclear Technology and Radiation Protection Vol. 26; no. 2; pp. 147 - 152
• Main Authors: Mesbahi, Asghar, Ghiasi, Hosein, Mahdavi, Rabee
• Format: Journal Article
• Language: English
• Published: VINCA Institute of Nuclear Sciences 01.09.2011
• Subjects: Monte Carlo modeling; photoneutrons; radiation therapy
• DOI: 10.2298/NTRP1102147M
• ISSN: 1451-3994

Neutron and capture gamma ray dose equivalent along the maze and entrance door of a radiation therapy room made of high density concrete was calculated using analytical and Monte Carlo methods. The room geometry and the 18 MV photon beam of a Varian 2100C/D linac were simulated using MCNPX MC code. Four analytical methods including Kersey, French, McCall, and Wu-McGinley methods were used in the current study. Average difference of 13-30% was seen between analytical and MC methods along the maze for photoneutron calculations. The difference between Wu-McGinley and MC methods was about 17% for capture gamma ray calculations. It was concluded that the analytical methods overestimate both neutron and capture gamma ray dose equivalents compared to MC. Moreover, it was shown that the analytical methods can be used as conservative estimators for neutron and capture gamma calculations. Primenom analitickih i Monte Karlo metoda izracunate su ekvivalentne doze od neutrona i prateceg gama zracenja duz lavirinta i ulaznih vrata sobe za radioterapiju, nacinjene od betona velike gustine. Geometrija sobe i snop 18 MeV-skih fotona iz linearnog akceleratora Varian 2100C/D, simulirani su koriscenjem MCNPX Monte Karlo programa. Cetiri analiticke metode - Kersijeva, Frencova, Mekkolova i Vu-Mekginlijeva, koriscene su u ovoj studiji. Razlike izmedju analitickih i Monte Karlo metoda u proracunu fotoneutrona duz lavirinta iznosila su 13-30%, u srednjem. U proracunu prateceg gama zracenja, razlika izmedju Vu-Mekginlijeve metode i Monte Karlo simulacije bila je oko 17%. Zakljuceno je da analiticke metode uporedjene sa Monte Karlo simulacijom, precenjuju ekvivalentnu dozu i neutrona i prateceg gama zracenja, te da mogu biti upotrebljene u cilju konzervativne procene doza.