DESIGN AND FABRICATION OF A PEDIATRIC THYROID PHANTOM FOR USE IN RADIO-IODINE UPTAKE MEASUREMENT, IMAGE QUALITY CONTROL AND DOSIMETRY.

Abstract

Estimating internal contamination from 131I for children in nuclear accidents is a crucial subject in the radiation protection field. Throughout this paper, an urgent and simple method was proposed for measuring 131I inside the pediatric thyroid gland by constructing a neck and thyroid phantom. For this purpose, CT scan images of healthy child's thyroids were obtained, and the sizes of different parts were determined by a 3D slicer image processing software. Girls with the body surface area between 0.95 and 1.05 were involved in this study. The fabricated phantom is composed of 5 cylindrical slabs of 2-cm thickness, and several small holes were constructed for TLD dosemeters near the thyroid gland and all other parts of the neck. The phantom was constructed utilizing a 3D printer with acrylonitrile butadiene styrene plastic. The thyroid phantom was filled with radioiodine-131, and calibration curves were plotted for contamination estimation. A nodular thyroid phantom was also constructed. The nodular phantom or the resolution phantom has 4 removable parts containing cylindrical holes with diameters of 3, 6, 9 and 12 mm. These holes on the thyroid glands can be filled with different activities of radionuclides to serve as hot and cold spots for quality control of nuclear medicine images. The results show that the designed phantom is applicable in different fields such as nuclear image quality and resolution tests, dosimetry and iodine thyroid uptake estimation in nuclear medicine departments, and nuclear emergency monitoring.