This web form calculates the potential dose to other individuals based on Appendix B of RegGuide 8.39.
D(t) = Accumulated dose to time t, in rems
34.6 = Conversion factor of 24 hrs/day times the total integration of decay (1.44)
Γ = Exposure rate constant for a point source, R/mCi x hr at 1 cm
Qo = Initial activity at the start of the time interval
Tp = Physical half-life in days
r² = Distance in centimeters - typically 100 cm
E1 = Occupancy factor for the first 8 hours
E2 = Occupancy factor from 8 hours to total decay
F1 = Extrathyroidal uptake fraction
F2 = Thyroidal uptake fraction
Equation B-1

Equation B-5

For I-131 patients there are three factors that must be determined: