Thyroid volumetric measurement and quantitative thyroid scintigraphy in dogs.

Thyroid volumetric measurement combined with quantitative 99mTc-per-technetate thyroid scintigraphy was performed in 62 clinical canine patients having suspected thyroid abnormalities. Euthyroid dogs (n = 22) had a total thyroid size of 3.60 +/- 1.36 cm3, the thyroid/salivary gland region of interest (ROI) ratio was 2.01 +/- 0.55, the thyroid/background ROI ratio was 3.86 +/- 0.90, and 20-min thyroid radioactivity uptake was 1.17 +/- 0.71% of the injected dose (I. D.). By Student's unpaired test, thyroid size of the hypothyroid group (n = 36) was not statistically different from that of the euthyroid dogs, but all other quantitative data (e.g., thyroid/salivary gland ROI ratio = 1.08 +/- 0.56, thyroid/background ROI ratio = 2.32 +/- 0.70, and 20-min thyroid radioactivity uptake = 0.34 +/- 0.22% of the I. D.) were significantly (p < 0.001) lower in hypothyroid than in euthyroid dogs. Evaluating the above-listed quantitative data of separated thyroid lobes by Student's paired test, there was no significant difference between the left and the right lobe either in the euthyroid or in the hypothyroid group.