Release of Patients Administered Radioactive Materials
Procedures for Calculating Doses Based on Patient-Specific Factors
Based on NRC Regulatory Guide 8.39 RegGuide 8.39 (revised April 1997)
This form calculates the potential dose to other individuals based on Appx B of RegGuide 8.39.
Equation B-1
Equation B-5
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
For I-131 patients there are three factors that must be determined:
Initial Activity (in millicuries)
Medical Condition
Occupancy Factor from 8 hours to total decay
University of Arkansas for Medical Sciences
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