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Bismuth-based nanoparticles as radiosensitizer in low and high dose rate brachytherapy

Rajaee Azimeh, Wang Shi, Zhao Lingyun

Polish Journal of Medical Physics and Engineering

2019

Vol. 25, Iss. 2

79--85

Background: Recently bismuth-based nanoparticles have attracted increasing attention as a dose amplification agent in radiation therapy due to high atomic number, high photoelectric absorption, low cost, and low toxicity. Objectives: This study aims to calculate physical aspects of dose enhancement of bismuth-based nanoparticles in the presence of brachytherapy source by Monte Carlo simulation and an analytical method for low mono-energy. Materials and methods: After simulation and validation brachytherapy sources (Iodine-125 and Ytterbium-169) by Monte Carlo code, bismuth-based nanoparticles (bismuth, bismuth oxide, bismuth sulfide, and bismuth ferrite) were modeled in the sizes of 50 nm and 100 nm for two concentrations of 10 and 20 mg/ml. Dose enhancement factors for the bismuth-based nanoparticles were measured at both brachytherapy sources. Furthermore, the dose amplification was calculated with an analytic method at 30 keV mono-energy. Results: Dose enhancement factor was greatest with pure bismuth nanoparticles, followed by bismuth oxide, bismuth sulfide and bismuth ferrite for both radiation source and simulation methods. The dose amplification for the bismuth-based nanoparticles increased with increasing size and concentration of nanoparticles. Conclusion: The physical aspect dose enhancement of the nanoparticles was shown by Monte Carlo and analytic method. The results have proved bismuth-based nanoparticles deserve further study as a radiosensitizer.

An approach to the preparation of iodine-125 seed-type sources

Cieszykowska I., Piasecki A., Mielcarski M.

Nukleonika

2005

Vol. 50, nr 1

17-22

The deposition of iodine-125 on silver bars to be sealed in titanium capsules as seed-type sources for brachytherapy was studied. For this purpose, a method of internal electrolysis was applied. The cell consisted of a silver anode contained in a Pt crucible serving as cathode. The plating solution contained sodium iodide-125 and sodium hydroxide. The yield of iodine-125 deposition for carrier-containing and carrier-free electrolyte solutions was determined. The deposition on uncutted Ag wires and on those cutted into 3 mm long bars was investigated. The influence of visible light on the coating process was examined. The leachability of iodine-125 from the silver wires as well as the activity distribution on the wires was measured. The obtained results indicate that the silver wire should be first coated with iodine-125 and then cutted into 3 mm long pieces. Based on this observation, a device for a batch-type procedure of manufacturing I-125 plated silver bars was designed and made. A design for simultaneous cutting and positioning of the activity-carrying bars into the titanium capsules is presented. This arrangement has been built and tested in trials. The tests confirmed that contamination of the source capsules can be minimized. Laser weldings of the titanium capsules were performed and the cross section of the welds examined by the use of an optical microscope.