Investigating the effect of the geometry of the Valencia large field applicator collimators on the dose distribution of the 75Se source using the Monte Carlo method

Document Type : Original Article

Authors

1 Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran

2 Islamic Azad University, Science and Research Branch, Department of Medical Radiation Engineering, Tehran, Iran.

Abstract

Recently, multi-position applicators with interchangeable collimators have been proposed for the treatment of skin lesions in the range of 3 cm to 5 cm; for this purpose, in this research, for investigating the effect of collimators(3 cm ×  5 cm, 4 cm, 5 cm) geometry of the large field Valencia applicator on the dose distribution of 75Se source, dosimetry parameters of the skin applicator were evaluated by the Monte Carlo method. Finally, it was found that by decreasing the diameter of the collimator, there was no significant effect on the output factor, treatment time, and depth dose percentage on the surface, and with the increase in depth, the depth dose percentage decreased sharply. The amount of penumbra increased by 17.2% and 42.2% for 4cm and 3 cm × 5 cm (x-axis) collimators, respectively, and decreased by 5.6% for  3 cm × 5 cm (y-axis) collimator. The amount of flatness for 4cm and 3cm×5cm(x-axis) collimators has improved by 57% and 23.8%, respectively, and for the 3 cm × 5 cm(y-axis) collimator it has increased by 3.8%; the amount of symmetry for other collimators has improved compared to the 5cm collimator.

Keywords

References

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Journal of Radiation Safety and Measurement
Volume 13, Issue 3 - Serial Number 51
December 2025
Pages 129-119

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