Evaluations for Determination of Optimum Shields in Nuclear Medicine

Abstract

Background: 131 I source is widely used in the treatment of hyperthyroidism and thyroid cancers. 131 I emits both beta and gamma-rays. Radiation protection is considered for gamma rays emitted by 131 I. It seems no special shield against 131 I source to be designed. Objective: This research aims to evaluate determination of optimum shields in nuclear medicine against 99 Tc m and 131 I sources by dosimetric method. Additionally, Monte Carlo simulation was used to find the optimum thickness of lead for protection against 131 I source. Material and Methods: This is an experimental research in the field of radiation protection. A calibrated model of GraetzX5C Plus dosimeter was used to measure exposure rates passing through the shields. The efficiency of the shields was evaluated against 99 Tc m and 131 I. Furthermore, Monte Carlo simulation was used to find the optimum thickness of lead for protection against 131 I 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 0.25 mm and the syringe holder shields with thickness of 0.5 mm lead were 50.86% and 99.50%, respectively. The results of the simulations show that the minimum and maximum efficiencies obtained by lead thicknesses of 1 mm and 43 mm were 19.36% and 99.79%, respectively. Conclusion: The optimum shields against 99 Tc m are the syringe holder shield, the tungsten syringe shield, and the lead partition, respectively. Furthermore, based on simulations, the thicknesses of 11-28 mm of lead with efficiencies between 90.6% to 99% are suggested as the optimum thicknesses to protect against 131 I source.

Evaluation of Shielding Performance of Gamma Ray Shielding Tungsten Polymer Composite with LBL-Type Layered Structure

“…Radioisotopes widely used in medical institutions include 18 F at 511 keV, which is used in PET imaging. The shielding performance was evaluated for 99m Tc at 140 keV, which is most commonly used in imaging tests, and for 131 I at 364 keV, which is widely used in thyroid tumor treatment [40]. Therefore, in the shielding performance evaluation, the shielding performance was 67.54% for 99m Tc, 29.12% for 18 F, and 9.21% for 131 I at 0.1 m, based on the 1.0 mm thickness of the shielding material.…”

Development of ultra-thin radiation-shielding paper through nanofiber modeling of morpho butterfly wing structure

“…In recent years, plate flexibility has been obtained by using composite materials and the plate manufactured in this manner has been widely used as a material for applications such as shielding walls 13 . Materials for other applications of shields, such as blocks, syringe shields, and apertures used in medical institutions, are manufactured by injection molding by mixing a shielding material and polymer 14 . The miscibility of the metal particles with the polymer is a crucial factor affecting processability and shielding performance of composite materials.…”