Estimation of Absorbed Dose of Salivary Glands in Radioiodine Therapy and Its Reduction Using Pilocarpine

The use of radioactive iodine (131I) has become an important adjunct to the treatment of thyroid cancer and hyperthyroidism. Salivary gland has the ability to concentrate radioactive iodine under normal circumstances. Salivary gland dysfunction and dry mouth are the common side effects of high-dose radioiodine therapy. The purpose of this study was to determine the absorbed dose of salivary glands. Twenty patients who were divided into two groups of 10 were studied (A group without pilocarpine and the B group received pilocarpine during treatment). The absorbed dose of parotid glands and the submandibular glands of patients was measured using thermoluminescent dosimeter (TLD) at three different times (24 hours, 8 days and 3 months after treatment). The attenuation coefficient of patients and the effects of pilocarpine were also determined. In group A total attenuation coefficient was 0.335, 0.323, and 0.357 for parotid glands and the right and left submandibular glands, respectively. In group B total attenuation coefficient was 0.462, 0.482, and 0.514 for parotid glands and the right and left submandibular glands, respectively. The results also showed the dose decreases to 1 cGy after 3 and 2 half life for A and B group, respectively. The findings showed that the dose decreases to 1 cGy after 3 half life of Iodine therapy. The exponential coefficient attenuation of salivary glands varied 3% to 4%. Pilocarpine appears to be effective in increasing excretion of radioactive iodine and enhancing coefficient attenuation (up to 1.5 to 2 times).