Correlation Between Exposure Rate and Residual Activity in Felines Undergoing 131I Thyroid Ablation Therapy.

Radioiodine thyroid ablation therapy is a common method for treatment of felines exhibiting hyperthyroidism. Due to the high gamma-ray emission rate of radioiodine (I), patients following treatment must be held in isolation for several days before release to prevent unnecessary dose to owners and members of the public. Dose rate measurement on the external surface of the patient of ≤ 20 µSv h is maintained as the patient release criterion without regard to residual activity. However, the Texas Department of State Health Services regulatory guide recommends a release limit of 3.7 MBq to households with non-pregnant women and children over the age of 18 y, and a limit of 925 kBq to households of pregnant women and children who can be supervised. In this paper, Monte Carlo computational radiation transport techniques are employed to predict and standardize the patient isolation time at the clinic by correlating the thyroid burden and surface dose rates of felines. Measurements of patient dose rate as a function of time are used to determine the patient-specific effective half-life experimentally and to validate the model results. Results show that an average holding time of 8 to 9 d is sufficient to reduce the residual activity to 3.7 MBq levels. Additionally, contact dose rate measurements of 20 µSv h or less correlate to residual activity levels of approximately 925 kBq. Based on the model and measurements, a protocol was developed for clinical use at Texas A&M University Veterinary Medical Teaching Hospital to allow estimation of residual activity following injection. This in turn confirms that the surface dose rates used as the release criteria follow the release limits recommended in the regulatory guide.

Radiological safety concerns for the accelerator production of diagnostic and therapeutic radionuclides in a university setting.

Accelerator production of radionuclides for diagnostic and therapeutic research at a university has many advantages. Radionuclides not commonly available through commercial suppliers may be readily produced for innovative research applications. Loss of material due to decay in transit is minimized, and product lead times may be significantly reduced. Furthermore, graduate students and research assistants have the opportunity to gain considerable hands-on experience during the production, extraction, and processing operations. However, the benefits of implementing accelerator production into an existing radiological protection program must be balanced against increased safety procedures and maintenance of as-low-as-reasonably-achievable work practices. This article outlines the basics for radioactive material production and corresponding issues in radiological protection associated with the production, use, and disposal on a college campus.

Radiological safety at a broad scope radioactive materials license: Texas A&M University.

Operating a radiological safety program under a broad-scope license at a major research university introduces many elements not encountered by general or industrial licenses. This article outlines elements of the radiological safety program in place at Texas A&M University.