Dosimetric Parameters Estimation for I-125 (model 6711) Brachytherapy Source

Ali Yadollahpour¹, Mansour Zabihzadeh^1,2*, Hadi Rezaee³ and Mostafa Feghhi⁴

1Assistant Professor of Medical Physics, Department of Medical Physics, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. 2Assistant Professor of Radiotherapist and Oncologist. Department of Radiation Oncology, Golestan Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. 3M.Sc. Student of Medical Physics, Department of Medical Physics, School of Medicine, Jundishapur University of Medical Sciences, Ahvaz, Iran. 4Associate Professor of Ophthalmology, Department of Ophthalmology, Imam khomeini Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

DOI : http://dx.doi.org/10.13005/bbra/1190

ABSTRACT:

Determining dose distribution around the applied sources in brachytherapy, especially ones with low-energy is so crucial in treatment designing. In this study dosimetric parameters of a brachytherapy source I-125 (model6711) were calculated using Monte Carlo simulation method.A homogeneity water phantom with dimensions of 30´30´30 cm3 were simulated with MCNPX(2.6.0) code. A brachytherapy source I-125 (model6711) considering its details (materials, dimensions and its emitted spectrum) was located in the center of phantom. Positioning the source inside the vacuum sphere its air kerma strength, Sk, was calculated. Recommended dosimetric parameters were calculated by AAPM, TG-43 protocol in this phantom.The air kerma strength of the source I-125 (model 6711)was estimated equal to 0.557 cGycm2h-1mCi-1 in activity unit anddose rate constant was 0.885 cGyh-1U-1. The Radial dose function with 5 degree equation and correlation coefficient of 0.9989 was estimated by g(r)=-0.0001r4+0.0026r3-0.0178r2-0.0970r+1.0995. Numerical amounts of the anisotropy dose functions and related equations were calculated and compared with the reported data.In spite of low-energy emission photons and high dose gradients with radial distance, dosimetric parameters of source I-125 (model 6711)can be calculated by MCNPX Monte Carlo code with an acceptable accuracyand this can be used in brachytherapy treatment planning.

KEYWORDS: Brachytherapy; Source I-125 (model 6711); Radiation dosimetry; Monte Carlo simulation

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