Absorbed dose estimation to cohabitants and co-travelers of patients treated with radioiodine for differentiated thyroid carcinoma.

OBJECTIVE Thyroid remnant ablation with radioiodine is a well-established treatment for patients with differentiated thyroid carcinoma (DTC) after thyroidectomy. After hospitalization of approximately 2-4 days, these patients return home presenting a possible radiation hazard to the people around them. This work aims to estimate the possible radiation burden to people (co-travelers and cohabitants) which came in contact with the patients after their release from the hospital, analyzing data obtained during their hospitalization. MATERIALS AND METHODS Data from 1065 patients were used to estimate the possible radiation burden to family members and people that came in contact with the patients, grouping them according to their age, type of contact with the patient (co-traveler, cohabitant) and patient family status, assuming different exposure scenarios for each group and based on the written precautions given to all patients before discharge. Relations between the iodine effective half-life (Teff), estimated from patient dose rate measurements during hospitalization, patient age and the method used for thyroid preparation for ablation (thyroid hormone withdrawal-THW or administration of recombinant human thyroid stimulating hormone-rhTSH) were also investigated. RESULTS Median absorbed dose to adult cohabitants was estimated to be 8.3μSv (0.1-117.2μSv), to babies (0-5yr) 15.7μSv (1.2-196.1μSv), to young children (5-10yr) 13.1μSv (0.8-100.7μSv), to children (10-18yr) 8.4μSv (0.5-116.8μSv) and to co-travelers 4.8μSv (0.2-114.9μSv). The highest doses to cohabitants were estimated in the few cases where the patient was a single parent of one or more children (median children dose 28.9μSv, range 11.2-279.4μSv). A statistically significant difference in median Teff between THW (15.1h) and rhTSH (13.9h) patient groups was found. CONCLUSION Provided necessary precautions are followed, radiation burden to the family members and co-travelers of DTC patients treated with radioiodine following thyroidectomy can be kept well below the corresponding dose limits and constraints.