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Thyroid

Thyroid

In this newsletter, we focus on thyroid scintigraphy. Thyroid function tests, ultrasound and scintigraphy form the basis for investigation of thyroid disease.
Technetium-99m pertechnetate is administered intravenously and is taken up into the thyroid tissue by the Na/I symporter and allows imaging of thyroid function.

Figure 1: Normal thyroid scan. Note the normal symmetric uptake in both lobes of thyroid (arrow). Mild normal uptake in submandibular salivary glands superiorly.

 

Indications:
Assessment of thyrotoxicosis Differentiates between Graves’ disease (Fig. 2), thyroiditis and toxic adenomas (Fig.3) Assessment of thyroid nodules Not used for surveillance of thyroid cancer (I-123/I-131 are used)

Figure 2: Graves’ disease: There is intensely increased tracer uptake throughout both lobes of the thyroid gland.

Preparation:
No intravenous X-ray contrast for 6 weeks prior to the test Avoid iodine loading for at least 6 weeks e.g. supplements or medications with a high iodine content Withhold anti- thyroid medications for at least 3 days prior to the test The thyroid scan is usually not performed on hypothyroid patients on thyroid hormone replacement, however if required please contact NMI.

Figure 3: Toxic adenoma: A rounded focus of intense tracer uptake in the mid and lower pole of the left lobe of thyroid with complete suppression of tracer uptake in the remainder of the thyroid.

 

SPECT CT for thyroid imaging?
SPECT CT has no role in thyroid scintigraphy. The optimal method is with a pinhole collimator (routinely used at NMI) for small parts imaging Thyroid morphology is best assessed by ultrasound
Nuclear Medicine and treatment of thyroid disease:
I-131 is a radioactive isotope of iodine and is highly effective for treatment of thyrotoxicosis particularly due to Graves’ disease and toxic adenomas For more information and patient consultation please contact NMI.
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