Evaluations for Determination of Optimum Shields in Nuclear Medicine

Background: ۱۳۱I source is widely used in the treatment of hyperthyroidism and thyroid cancers. ۱۳۱I emits both beta and gamma-rays. Radiation protection is considered for gamma rays emitted by ۱۳۱I. It seems no special shield against ۱۳۱I source to be designed. Objective: This research aims to evaluate determination of optimum shields in nuclear medicine against ۹۹Tcm and ۱۳۱I sources by dosimetric method. Additionally, Monte Carlo simulation was used to find the optimum thickness of lead for protection against ۱۳۱I source.Material and Methods: This is an experimental research in the field of radiation protection. A calibrated model of GraetzX۵C Plus dosimeter was used to measure exposure rates passing through the shields. The efficiency of the shields was evaluated against ۹۹Tcm and ۱۳۱I. Furthermore, Monte Carlo simulation was used to find the optimum thickness of lead for protection against ۱۳۱I source. Results: The findings of the dosimetric method show that the minimum and maximum efficiencies obtained by the lead apron with lead equivalent thickness of ۰.۲۵ mm and the syringe holder shields with thickness of ۰.۵ mm lead were ۵۰.۸۶% and ۹۹.۵۰%, respectively. The results of the simulations show that the minimum and maximum efficiencies obtained by lead thicknesses of ۱ mm and ۴۳ mm were ۱۹.۳۶% and ۹۹.۷۹%, respectively. Conclusion: The optimum shields against ۹۹Tcm are the syringe holder shield, the tungsten syringe shield, and the lead partition, respectively. Furthermore, based on simulations, the thicknesses of ۱۱-۲۸ mm of lead with efficiencies between ۹۰.۶% to ۹۹% are suggested as the optimum thicknesses to protect against ۱۳۱I source.

کلیدواژه ها:

Nuclear medicine ، Shield ، Efficiency ، Dosimetry ، Monte Carlo Simulation ، Iodine-۱۳۱ ، ۹۹Tcm