Continuous measurement of radioactivity for a patient with chronic kidney disease during radioactive iodine therapy and hemodialysis: a case report

The half-life of radioactive iodine (RAI) is prolonged in patients with chronic kidney disease (CKD) because RAI is mainly excreted by the kidneys. There is little information on the RAI half-life in patients with dialysis-dependent CKD (CKDG5d). Estimating the RAI half-life in a patient's body provides important information for treatment planning. In this paper, we report a 68-year-old woman of CKDG5d who underwent postsurgical RAI therapy for papillary adenocarcinoma of the thyroid. We administered 15 mCi (0.56 GBq) RAI (¹³¹I) and continuously measured the dose equivalent rate. The results were summarized into hourly values of dose equivalent rate. Based on the measurements, we estimated the RAI half-life in the patient's body using a semi-log plot and linear regression analysis. In addition, we calculated the integrated doses for caregivers and the public using coefficients of 0.5 and 0.25, respectively. The half-life in the patient's body was 7.2 days (95% confidence interval, 4.8-14.4). The integrated doses for caregivers and the public were 0.23 mSv and 0.11 mSv, respectively. RAI therapy for a CKDG5d patient should be planned on the basis of the biological dynamics of ¹³¹I. Accumulation of more cases should lead to the establishment of a treatment strategy for patients undergoing RAI therapy and hemodialysis.