Low dose radioiodine therapy: A review of dosimetry and evaluation of potential shielding materials for neck collars

Abstract

Radioactive Iodine (131I) has become the most widely used radionuclide for the treatment of patients with thyroid cancer in Sri Lanka. This study aims to measure radiation dose rate emitted from the131I treated patients at the Nuclear Medicine Unit (NMU), University of Peradeniya, Sri Lanka and synthesise a lead-free material to be used as a shielding collar to minimize the radiation exposure to the family members and the general public. Routinely, an average activity of 1110 MBq (30 mCi) is administered orally to thyroid cancer patients following a thyroidectomy. A total number of 40 patients including 17.5% males and 82.5% females were monitored for radiation dose rate after administering the radioiodine. The dose rate was measured at 1.0 m distance from the patient’s neck, after 1 hour of131I administration. The results showed moderately high dose rates (mean 50.01 ± 11.50 µSv h-1) from these patients when compared to permissible dose rates to the general public in other countries. Hence, measures should be taken to reduce the dose rates at the releasing time of the patients. Four types of shielding materials were synthesised to make a collar. The best shielding material identified was iodine incorporated silicon-based rubber with a reduction percentage of 38.48%.