Analysis of Radiometry on Patients Undergoing Radioactive Iodine Therapy

The treatment for differentiated thyroid cancer consists of thyroidectomy followed by radioactive iodine therapy (RIT), in which the patient remains in isolation until the dose rate of the radioactive iodine reduces to a certain limit. The present research intends to estimate the length of stay of patients who undergo RIT, with radiometry analysis performed throughout the patient's admission. Methods: Information such as age, sex, weight, height, prescribed activity, volume of liquids ingested, and the use of recombinant human thyrotropin was gathered from 204 patients with differentiated thyroid cancer who underwent RIT. During the admission, the dose rate was periodically measured. The data served as variables for a multiple regression, in which the coefficients (the term coefficient in this paper is related to the multiplicative factor of each considered variable used in Eqs. 1-4) and significance of each were verified as a function of the dose rate. Results: The results showed that length of stay, administered activity, volume of liquids ingested, use of recombinant human thyrotropin, and patient weight impacted significantly on the dose rate. The average effective half-life of the ¹³¹I, considering all patients, was 12.61 ± 3.28 h, and the average time for their radiologic release was 15.23 ± 5.50 h. On the basis of the results, it was possible to develop a tool to estimate a patient's length of stay and effective half-life. Conclusion: The results can contribute to optimization of the radiologic protection of patients who undergo RIT, as well as allow better logistics regarding their admission, which can lead to more appropriate accommodation for the patient and a better use of resources.