Semester of Graduation

Fall 2019


Master of Science (MS)


Physics & Astronomy

Document Type



Hyperthyroidism is a very common endocrine disorder in both humans and cats. Radioactive iodine ablation therapy is considered the gold standard; however, the patient becomes a radiation source and poses a potential radiological risk to others. The regulations governing when the patient can be released differ between human medicine and veterinary medicine. A human patient can receive up to 33 mCi of I-131 and be discharged the same day; yet a feline patient can receive a dose as low as 2 mCi and require multiple days of hospitalization. This discrepancy has not been satisfactorily addressed; and overly restrictive release criteria can place a burden on the veterinary staff, the patient, and the pet owner. In this study, administered activities and exposure rates are measured for hyperthyroid cats undergoing treatment at Louisiana State University Veterinary Teaching Hospital to determine if current criteria are too restrictive for releasing cats to their owners. Additionally, radioassays are performed on the surface of the cat, its excreta, and its environment to characterize the potential exposures to the pet owners. Annual total effective dose equivalents for the pet owners are calculated using the NRC’s equation from NUREG-1556 Vol 9. The results of the assays show that minimal radioactivity is present. The results of the TEDE estimates indicate that the majority of cats can be released the same day of injection and that the resulting TEDE to the pet owner is unlikely to exceed 100 mrem, suggesting that current release criteria are overly conservative.

Committee Chair

Wang, Wei-Hsung