Thyroid Scintigrams

Thyroid scintigrams are performed by acquiring lateral and ventral images of the neck 20 to 30 minutes after subcutaneous injection of Technetium 99m pertechnetate. Technetium 99m pertechnetate is a radionuclide that emits gamma radiation that can be measured with a gamma camera. Technetium 99m pertechnetate preferentially deposits in organs high in iodide (such as the thyroid gland) and chloride (such as the salivary glands). When the deposition of radioinuclide is significantly greater in the thyroid gland than it is in the salivary glands, the thyroid tissue is considered hyperactive.

Normal scintigram in a cat

The areas of the zygomatic salivary glands (red) and thyroid lobes (yellow) are circled on ventral image.

Normal scintigram

Unilateral hyperthyroidism

Unilateral hyperthyroidism scintigram

Bilateral hyperthyroidism

Bilateral hyperthyroidism scintigram