Update and Extension of Release Criteria for Canine 117m Sn Treatments.

ABSTRACT: Tin-117 m ( 117m Sn) is used to treat dogs with osteoarthritic joints by radiosynoviorthesis. The internal conversion and Auger electrons emitted by the 117m Sn provide the therapeutic effect. Sn-117 m also emits x rays and gamma rays, of which the most significant is 158.6 keV. Accurate information regarding the interactions of a person with a treated dog is needed to determine the person's total dose and thus regulatory compliance; i.e., a time and motion study. Prior studies have characterized the radiation field emitted by a treated dog, determined the effective dose rates to a person based on those radiation fields, and evaluated dog-human interactions. These studies have been tied together to calculate the prospective dose to the owner of a treated dog. The behavior modifications needed to comply with public dose limits were identified, and a template for written instructions limiting dose was developed. Further calculations based on the written instructions were made to determine the necessary duration of the instructions. The result is guidance that may be used by veterinary practitioners to release treated dogs in accordance with the public dose limits.

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

ABSTRACT: 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.

Anisotropy of the Radiation Field Following Canine Sn-117m Treatment.

ABSTRACT: Tin-117m (117mSn) is used to treated dogs with osteoarthritic joints by radiosynoviorthesis. The internal conversion and Auger electrons emitted by the 117mSn provide the therapeutic effect. Sn-117m also emits gamma rays, of which the most significant is 158.6 keV. The external radiation field around a treated dog is of interest to limit the dose to the owners/caretakers of the dog. The dog's torso attenuates the radiation being emitted toward the opposite side of the dog's body. This leads to a radiation field that is significantly non-isotropic. This study characterizes the anisotropy of this field to permit maximum dose rate measurements to be used to calculate the dose to individuals in the vicinity of the dog. Measurements were made in nine directions and at two distances, 0.3 and 1.0 m, to characterize common distances and spatial orientations for human-dog interactions. From these measurements, the percent reduction in the average dose rate compared to the maximum dose rate was determined. From a radiation safety perspective, the important factor is the minimum amount of shielding effectiveness or percent reduction that can be expected. A reasonable measure for this value is the fifth percentile of the shielding effectiveness distribution. The fifth percentile shielding effectiveness measures are 27% and 21% at 0.3 and 1.0 m, respectively.