Age-dependent Radiation Dose Rates from Canine Sn-117m Treatments

Tin-117 m (Sn-117m) is used to treat dogs with osteoarthritic joints by radiosynoviorthesis. The decay process for Sn-117m is internal conversion wherein IC electrons and auger electrons provide the therapeutic effect. Additionally, the most prominent gamma emission is 158.6 keV. The effective dose rate received by a person interacting at close distances with a treated dog is needed to determine the person's total dose and thus regulatory compliance. Simple measurement of the dose rate at a given distance does not provide an accurate measurement of the effective dose to a person due to the non-uniform nature of the radiation field at close distances. MNCP models of the interactions of five ages of humans at three distances were created to determine the effective dose rates using the methodology from NRC Regulatory Guide 8.40. Ratios of the effective dose rate to the person to the measured dose rate at 1 m from the same source were calculated.