TWO-PARAMETRIC BEAM MODEL FOR DOSIMETRY OF THE PROCESS OF ELECTRON IRRADIATION OF MATERIALS WITH LOW DENSITY AND ATOMIC NUMBER

The work is devoted to studying the possibility of using a two-parametric model of an electron beam to describe the depth distributions of the electron dose in materials with a low density and an effective atomic number. In this model, the parameters are determined by fitting the semi-empirical model (PFSEM-method) to the results of meas-urements of the depth-dose distribution in a dosimetric wedge. The depth-dose distributions in a birchwood wedge were measured at the Institute of Nuclear Chemistry and Technology in Warsaw, Poland. The parameters of the electron beam incident on the wedge were determined by the PFSEM method. The Monte Carlo simulations of the depth-dose distribution in the wedge for the process of electron irradiation, the characteristics of which are deter-mined by the PFSEM method, have been carried out. It is shown that there is a satisfactory agreement between the measurement results and the Monte Carlo simulation of the depth-dose distribution. The advantages of describing depth-dose distributions in a wedge based on a two-parametric model of an electron beam in comparison with tradi-tional methods of polynomial approximation of measurement results are discussed.

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Comparison between the calculated and measured dose distributions for four beams of 6 MeV linac in a human-equivalent phantom

Nuclear Technology and Radiation Protection ◽

10.2298/ntrp0602067r ◽

2006 ◽

Vol 21 (2) ◽

pp. 67-72

Author(s):

Sonia Reda ◽

Eman Massoud ◽

Ibrahem Bashter ◽

Esmat Amin

Keyword(s):

Monte Carlo ◽

Dose Distribution ◽

Calculated Data ◽

The Body ◽

X Rays ◽

Dose Distributions ◽

Depth Dose ◽

Thermoluminescence Dosimetry ◽

Depth Dose Distribution ◽

Good Agreement

Radiation dose distributions in various parts of the body are of importance in radiotherapy. Also, the percent depth dose at different body depths is an important parameter in radiation therapy applications. Monte Carlo simulation techniques are the most accurate methods for such purposes. Monte Carlo computer calculations of photon spectra and the dose ratios at surfaces and in some internal organs of a human equivalent phantom were performed. In the present paper, dose distributions in different organs during bladder radiotherapy by 6 MeV X-rays were measured using thermoluminescence dosimetry placed at different points in the human-phantom. The phantom was irradiated in exactly the same manner as in actual bladder radiotherapy. Four treatment fields were considered to maximize the dose at the center of the target and minimize it at non-target healthy organs. All experimental setup information was fed to the MCNP-4b code to calculate dose distributions at selected points inside the proposed phantom. Percent depth dose distribution was performed. Also, the absorbed dose as ratios relative to the original beam in the surrounding organs was calculated by MCNP-4b and measured by thermoluminescence dosimetry. Both measured and calculated data were compared. Results indicate good agreement between calculated and measured data inside the phantom. Comparison between MCNP-4b calculations and measurements of depth dose distribution indicated good agreement between both.

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