Sains Malaysiana 49(3)(2020): 693-701

http://dx.doi.org/10.17576/jsm-2020-4903-24

Monte Carlo Investigation on Neutron Dosimetry Parameters of ²⁵²Cf Isotron Brachytherapy Source

(Kajian Monte Carlo ke atas Parameter Dosimetri Neutron Sumber Brakiterapi ²⁵²Cf Isotron)

OME LEILA AHMADI & HOSSEIN TAVAKOLI-ANBARAN*

Faculty of Physics and Nuclear Engineering, Shahrood University of Technology, Shahrood, Iran

Diserahkan: 22 Jun 2019/Diterima: 11 November 2019

Abstract

In the present study, all dosimetry parameters around the ²⁵²Cf Isotron source for neutron brachytherapy were calculated. The ²⁵²Cf neutron energy spectrum was modeled using the Maxwellian spectrum. The calculations were performed using MCNPX.2.6.0 code based on the TG-43U1 protocol in the water medium. The neutron air kerma strength for the ²⁵²Cf Isotron source was computed as 0.3098 ± 0.0002 cGy cm²/µgh and the neutron dose rate constant was 6.559 ± 0.003 cGy/Uh. The anisotropy functions were calculated at intervals of 1, 2, 3, 4, and 5cm at different polar angles in the range of θ = 0̊ to 90º in respect to the source long axis in a water Phantom. The uncertainty of the calculated data at all distances is less than 1%. The radial dose function at different distances from the source for the Isotron model was compared with the theoretical HDR ²⁵²Cf source model. The discrepancies between the results were the highest at the distance of 0.5 cm, with relative differences of 5.64 %. For the ²⁵²Cf Isotron source, the data presented in this study provides better understanding on the dosimetric distribution of a theoretical neutron brachytherapy source, for potential clinical application.

Keywords: Brachytherapy; Isotron; neutron dosimetry; ²⁵²Cf

Abstrak

Dalam kajian ini, semua parameter dosimetri sekitar sumber Isotron ²⁵²Cf  untuk brakiterapi neutron dihitung. Spektrum tenaga neutron ²⁵²Cf dimodelkan menggunakan spektrum Maxwellian. Pengiraan dilakukan menggunakan kod MCNPX.2.6.0 berdasarkan protokol TG-43U1 dalam medium air. Kekuatan kerma udara neutron untuk sumber Isotron ²⁵²Cf dihitung sebagai 0.30986 ± 0.0002 cGy cm²/µgh dan kadar dos neutron tetap ialah 6.559 ± 0.003 cGy/Uh. Fungsi anisotropi dihitung pada selang 1, 2, 3, 4 dan 5 cm pada sudut polar yang berbeza dalam julat θ = 0º hingga 90º berkenaan dengan paksi panjang sumber dalam Phantom air. Ketidakpastian data yang dihitung pada semua jarak adalah kurang daripada 1%. Fungsi dos radial pada jarak yang berbeza daripada sumber untuk model Isotron dibandingkan dengan model sumber HDR ²⁵²Cf teoritis. Perbezaan antara keputusan adalah yang tertinggi pada jarak 0.5 cm, dengan perbezaan relatif 5.64%. Bagi sumber Isotron ²⁵²Cf, data yang dibentangkan dalam kajian ini memberikan pemahaman yang lebih baik mengenai pengagihan dosimetri sumber brakiterapi neutron teoritis, untuk aplikasi klinikal yang berpotensi.

Kata kunci: Brakiterapi; dosimetri neutron; Isotron; ²⁵²Cf

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*Pengarang untuk surat-menyurat; email: tavakoli-anbaran@shahroodut.ac.ir