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 (I) 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 I. Accumulation of more cases should lead to the establishment of a treatment strategy for patients undergoing RAI therapy and hemodialysis.