RESEARCH COMMUNICATIONS OF THE 28th ECVIM-CA CONGRESS

We prospectively included 937 cats referred to the Animal Endocrine Clinic for 131I treatment. Following quantitative thyroid scintigraphy, we calculated thyroid volume and percent thyroidal uptake of pertechnetate for each cat. We administered a radioiodine dose based on an algorithm that considers the serum T4 and T3 concentrations, percent uptake of pertechnetate, and calculated thyroid volume. Twenty‐four hours later, we then determined the percent 131I thyroid uptake by measuring radioactive counts directly on the skin surface over the thyroid tumor. After correction for background (thigh count), the thyroid radioactivity (in counts per minute) was compared with the activity measured from a standard containing ≈350 μCi 131I. To evaluate the effect of 131I uptake on final outcome, cats were divided into 4 quartiles, based on thyroid uptake values.