Radiation exposure from outpatient radioactive iodine (I-131) therapy for thyroid carcinoma

Context In May 1997, the US Nuclear Regulatory Commission (NRC) revised its patient release regulations, allowing for outpatient administration of lar ger activities of sodium iodide I-131 than previously permitted. Objective To measure the radiation exposure to household members from patie nts receiving outpatient I-131 therapy for thyroid carcinoma in accordance with the new regulations, Design Consecutive case series from October 1998 to June 1999. Setting and Patients Thirty patients who received outpatient I-131 therapy following thyroidectomy for differentiated thyroid carcinoma were enrolled, along with their 65 household members and 17 household pets. Main Outcome Measure Radiation exposure to household members and 4 rooms in each home, as monitored with dosimeters for 10 days following I-131 admini stration. Results The patients received I-131 doses ranging from 2.8 to 5.6 GBq (mean , 4.3 GBq). The radiation dose to 65 household members ranged from 0.01 mSv to 1.09 mSv (mean, 0.24 mSv). The dose to 17 household pets ranged from 0. 02 mSv to 1.11 mSv (mean, 0.37 mSv). The mean dose to the 4 rooms ranged fr om 0.17 mSv (kitchen) to 0.58 mSv (bedroom). Conclusion In our study, I-131 doses to household members of patients recei ving outpatient I-131 therapy were well below the limit (5.0 mSv) mandated by current NRC regulations.