VTH-D - Special Session: Veterinary Medicine Health Physics 10:00 - 12:00
NOTE: ALL VIRTUAL SESSIONS WILL TAKE PLACE DURING PACIFIC STANDARD TIME.
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VTH-D.1
10:00 Public Dose Assessment from Canine Sn-117m Treatment MG Arno*, Foxfire Scientific
; J Simon, Isotherapeutics Group; NR Stevenson, Exubrion; J Donecker, Exubrion; Ma Arno
Abstract: 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. 117mSn 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 towards the opposite side of the dog’s body. This leads to a radiation field which is significantly non-isotropic.
Part 1, The Source. 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 5th percentile of the shielding effectiveness distribution. The 5th percentile shielding effectivenesses are 27% and 21% at 0.3 and 1.0 m respectively.
Part 2, The Receptor. 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 5 ages of human at 3 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 at the 3 distances to the measured dose rate at 1 meter from the source were calculated.
Part 3, Time and Motion Study. 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 and determined effective dose rates to a person based on those radiation fields. The third piece needed is to determine how long a person spends at various distances from a dog. Typical behaviors such as feeding, walking, petting, grooming, sleeping, etc. were evaluated with regard to the distance at which these activities occur and how long each activity typically last. With this information, calculations were made of the dose to a person and written release instructions developed to demonstrate compliance with public dose limits.
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VTH-D.2
10:30 Veterinary Practice and the System of Radiological Protection NE Martinez*, Clemson University, Oak Ridge National Laboratory
; L Van Bladel, Federal Agency for Nuclear Control, Retired
Abstract: Veterinary use of radiation in the diagnosis, management, and treatment of disease has progressively expanded and diversified over the past several years, as have the corresponding radiological protection concerns. The ICRP’s system of radiological protection has always been applicable to personnel or bystanders involved in veterinary procedures making use of radiation or radioactive material, but due to the modern complexities associated with veterinary practice, it has been determined that the associated radiological protection issues warrant dedicated consideration. Moreover, there is a widely recognized need for clarifying and strengthening the application of radiological protection principles in this area. This presentation discusses the ICRP’s on-going work related to veterinary practice, which includes the recommendation that the system of radiological protection be applied in veterinary practice principally for the protection of humans but also with explicit attention to the protection of the exposed animals and the environment, where applicable. The report in development focuses primarily on justification and optimization in veterinary practice along with the underlying ethical values, and it sets the scene for more detailed guidance to follow in potential future recommendations.
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VTH-D.3
11:00 Improving Radiation Protection and Safety in Veterinary Medicine D Gilley*, IAEA
Abstract: Purpose: With the increasing use of ionizing radiation in veterinary medicine, the IAEA recognized that there needed to be radiation protection and safety guidance provided to veterinary medicine professionals and regulators.
Methods: At the request of Members States, the IAEA was asked to complete a guidance document for veterinary professionals and regulators on the safe use of radiation in veterinary practices. The publications was completed using the skills of veterinary experts, three veterinarians, one radiation protection officer and one regulator from a national regulatory authority. Consultancy for drafting the publication were held in 2018 and 2019. The publication addresses the use of ionizing radiation in veterinary medicine.
Results: In March 2020 the publication was released. The publication addresses the generic use of radiation in veterinary medicine and the specific used in radiology, nuclear medicine and radiotherapy. The publication addresses training and education, facility design and all aspects of the safe and secure use of radiation sources in the industry.
Conclusion: The safety report addresses the needs for veterinary professionals and regulatory authority in the authorization and inspection of radiation sources used in veterinary medicine.
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VTH-D.4
11:30 Evaluating Release Criteria for Feline Patients Following Radioactive Iodine Treatment for Hyperthyroidism AR Davila*, Tulane University Office of Environmental Health and Safety
; JF Fletcher, MedVet; KM Matthews, Louisiana State University Department of Physics & Astronomy; WW Wang, Louisiana State University Center for Energy Studies
Abstract: Hyperthyroidism is an endocrine disorder that commonly afflicts both humans and cats. Ablative radionuclide therapy using iodine-131 is the preferred treatment option in both human medicine and veterinary medicine. This treatment option results in the patient becoming an ambulatory radiation source, so the patient’s release needs to be carefully considered. In human medicine the regulation is clear: 10 CFR 35.75 specifies a total effective dose equivalent limit to the maximally exposed person of 5 mSv. This limit is only applicable in human medicine; therefore, veterinary medicine defaults to following 10 CFR 20.1301 which limits the total effective dose equivalent to 1 mSv for any member of the public. This discrepancy in the regulations for similar applications of iodine-131 has not been satisfactorily addressed in the regulations nor in the literature. This difference has resulted in feline patients requiring hospitalization despite receiving lower doses than those used for human patients who are able to be released immediately after treatment. Having a more restrictive release criteria places a burden on the veterinary staff, animal caretaker, and animal patient. In this study, hyperthyroid cats undergoing iodine-131 treatment at Louisiana State University Veterinary Teaching Hospital had their administered activities, exposure rates, and eliminated activities measured and were checked for the presence of contamination. Using this information along with the Nuclear Regulatory Commission’s equation from NU-REG1556 Vol 9, estimates for the pet owner’s total effective dose equivalent were calculated in order to evaluate the release criteria. The results of the total effective dose equivalent estimates indicate that same-day release of feline patients may be possible without its caretaker exceeding their 1 mSv limit.
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VTH-D.5
11:45 Comparison of veterinary medicine radiation safety programs across the United States RP Nichols*, University of Missouri
Abstract: Due to emerging radiopharmaceuticals and techniques, diagnostic and therapeutic procedures in veterinary medicine are becoming more common. Treating animals with sources of radiation not only benefits the animal but provides data applicable to medical human uses. While regulations for human use applications of radioactive material are clear, the same cannot be said for animal procedures; regulations do not specifically address veterinary requirements and guidance often only skims the surface of basic applications. The goal of this presentation is to evaluate various radiation safety departments with veterinary medicine programs and assess the implementation of regulations and best practices in the field.
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