Room: AAPM ePoster Library
Purpose: Our private practice medical physics group consisting of 8 diagnostic and 9 therapeutic medical physicists discovered we were using different methods, forms, and instructions for outpatient I-131 restrictions. Our goal was to standardize, simplify, and improve consistency on I-131 thyroid therapy workflows. Practice environments include site-based and consulting physicists.
Methods: Based on results from a patient questionnaire, patients were placed into one of three categories based on potential risk. Category 1 patients are thyroid cancer remnant-ablation patients with a separate bedroom and bathroom at home who don’t have continual contact with children. Category 2 patients are thyroid cancer patients that don’t meet the requirements of Category 1 or hyperthyroid patients with a separate bedroom and bathroom at home who don’t have continual contact with children. Category 3 patients are hyperthyroid patients with complicating factors, including but not limited to, young children at home, work in food service or around young children, or dialysis.
Results: Category 1 patients received discharge instructions completed in advance representing six different scenarios (50, 100, and 200 mCi doses modeled as 2% or 5% slow-clearance compartment uptake depending on the presence or absence of metastatic nodules). Category 2 patients had restrictions calculated using the NCRP 155 example spreadsheets. Fractional uptake in the slow-clearance compartment for hyperthyroid patients was assumed to be equal to the 24 hour uptake value. If no uptake study was available, 60% was used.
Conclusion: In spite of regulatory permissiveness, generic discharge instructions should be discouraged for all hyperthyroid patients. Keeping doses to children below 1 mSv results in restrictions for hyperthyroid patients that will be substantially longer than those for thyroid cancer. In our group, we chose to limit restriction calculations with Category 3 patients to a sub-group of four physicists with more experience in challenging scenarios.