Utilization of Chemical Deposition Technique for Preparation of Miniature 170Tm Sources and Preliminary Quality Assessment for Potential Use in Brachytherapy

Monte Carlo-based dosimetric studies of a locally developed170Tm LDR brachytherapy seed source

¹⁷⁰Tm is being explored as a source for applications in brachytherapy. Although it has adequate physical properties, such as a short half-life (128.6 d), high specific activity and a mean photon energy of about 66 keV, it has a drawback of low photon yield (only about six photon emissions/100 beta emissions). The objective of this work is to study the dosimetric characteristics of a locally developed¹⁷⁰Tm brachytherapy seed source using the Monte Carlo-based EGSnrc code system. In this study, we calculate the dose rate constant, air-kerma strength, radial dose function, anisotropic function and 2D dose-rate distributions in water. Separate simulations are carried out by considering the photon (gamma and characteristic x-ray) and beta spectra of the source. For regions close to the source (surface of the source <r< 0.4 cm), the dose is solely due to direct dose deposition by beta particles. At larger distances (0.4 cm <r<10 cm), the dose is due to bremsstrahlung photons produced by beta particles and photon emissions. The calculated value of the dose rate constant is 1.217 ± 0.052 cGy h^-1U^-1. The value ofS_kper mCi is 0.029 ± 0.0009 U mCi^-1. The contributions of the inherent photon emission and the bremsstrahlung photons to the totalS_kare 0.58 and 0.42, respectively.

Fabrication of miniature 141Ce sources by chemical deposition towards possible use in the performance evaluation of gamma cameras - A feasibility study

¹⁴¹Ce sources were fabricated for quality assurance of gamma cameras. The fabrication process consisted of electro-deposition of Ni on a Cu sphere in 0.01 N H₂SO₄ containing 30 mg/mL H₃BO₃ and 50 μg of NiSO₄·7H₂O at pH 2-3 followed by deposition of ¹⁴¹Ce on it. > 95% deposition of ¹⁴¹Ce on substrate could be achieved at pH 5. Source core was loaded in custom-made Al holder. Autoradiography confirmed uniform activity distribution. SEM and EDS analyses confirmed deposition of Cerium on substrate.