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Determination of Dosimetric Parameters for Vacuum-Sealed Miniature X-Ray Tube Based On Carbon Nanotube Field Emitters

S Kang1*, J Chung2 , K Kim1 , S Kang2 , K Eom2 , C Song2 , J Kim2 , T Suh1 , (1) The Catholic University of Korea College of Medicine, Seoul, Seoul, (2) Seoul National University Bundang Hospital, Seongnam, Kyeonggi-do


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: Aim of this study is to determine dosimetric parameters of a newly developed X-ray tube for high-dose-rate (HDR) brachytherapy.

Methods: Our collaborative research institute developed a vacuum-sealed miniature X-ray tube (mXT) based on a novel carbon nanotube to alternate radioactivity source used conventional brachytherapy. In order to apply the mXT for clinical HDR brachytherapy, dosimetric parameters such as air kerma strength, dose rate constant, radial-dose and anisotropic function should be determined. In this study, dosimetirc parameters were measured with EBT3 film and the manufactured phantom made acrylonitrile butadiene styrene (ABS) material. Also, those were calculated in virtual ABS and water phantom with MCNP6.1 code. Correlation factors about the calculated parameters between both phantoms are obtained. The measured parameters with ABS phantom are corrected to the corresponding values with water phantom using the correlation factors.

Results: The dose-rate constant measured by EBT3 film was 1104.28 cGy·h�¹·μA�¹ in ABS phantom. The converted dose-rate constant in water was 1344.14 cGy·h�¹·μA�¹. The measured radial-dose function was 0.49, 0.33, 0.22, and 0.15 at depth 2.0, 3.0, 4.0, and 5.0 cm, respectively. Difference between the measured and calculated radial-dose function was within -0.09, and then the average difference was -0.04. Values for anisotropic function were increased with approaching 0˚ degree and increasing radial-distance. The ratio between measured and calculated values for anisotropic function ranged from 0.94 to 1.09 within 3.8 cm of radial distance. Acceptable azimuthal angular dependence was observed within 1.06.

Conclusion: Overall difference between the measured and calculated dosimetric parameters was into tolerance level. Therefore, this study demonstrated that the determined dosimetric parameters for the mXT were suitable for applying clinical HDR brachytherapy.


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