Thyroid scintigraphy

Thyroid scintigraphy is performed 20 min after intravenous injection. 

The effective (whole body) dose equivalent for pertechnetate " Tc is 0.013 mSv/MBq (International Commission on Radiological Protection 1987). The effective dose in adults (70 kg) resulting from 75 MBq of intravenously injected Tc-pertechnetate for thyroid scintigraphy is approximately 1 mSv. The absorbed radiation dose to the thyroid (without a blocking agent) resulting from an intravenous injection of 75 MBq of 99mTc-pertechnetate corresponds to 1.7 mCy. 

Figure 56.4 The figure shows thyroid scintigraphy with and a perchiorate (KCiOd testing in a ohiid affected with TiOD due to TPO mutations. A high radioiodine uptake (12.63%, normai vai-ues 1 -5) is observed at the seoond hour, and a totai discharge 1 h after the administration of 400 mg of KCi04 is aiso documented.

Thyroid scintigraphy separates hyperfunctioning (hot) and hypofunctional (cold) nodules. Hypofunctioning nodules are much more likely to harbor mafignancy than hyperfunctioning nodules. 

NIS-mediated iodide accumulation allows diagnostic thyroid scintigraphy, as well as therapeutic radioiodine application, in benign and malignant thyroid disease. 

Brain scintigraphy 550 MBq, after blocking thyroid and choroid plexus to avoid nonspecific uptake of Tc-pertechnetate... 

Several drugs interfere with the normal biodistribution of Tc-pertechnetate (Hla-dik et al. 1987). Thus, cancer chemotherapeutic agents (methotrexate) can affect brain scintigraphy atropine, isoprenaline, and analgesics interfere in abdominal imaging iodine and other blockers (perchlorate, perrhenate) can modify thyroid uptake. 

Normal TSH excludes the diagnosis of hyperthyroidism. However, it does not necessarily exclude small autonomous areas in a (nodular) goiter. Larger autonomous areas may be detectable by scintigraphy in patients with palpatory thyroid nodules or goiter and thus at increase risk for IIH in formerly iodine-deficient areas. 

Before ultrasound-guided fine-needle aspiration came into use, scintigraphy was believed to be the most important test for the evaluation of nodules in the thyroid gland. Scintigraphy should, however, still be used when the patient with a nodule has low serum thyroid-stimulating hormone (TSH) value, to confirm the diagnosis of a toxic adenoma. 

Mandart G., Erbsman F. 1975 Estimation of thyroid weight by scintigraphy. Int.J.Nucl.Biol. 2 185-188. 

An X-ray fluorescence scanner is at least as expensive as an analogous piece of equipment for the classical scintigraphy complete with all the necessary accessories. The latter is therefore suitable for use in all field in which in vivo nuclear medicine diagnostics are valuable. An X-ray fluorescence scanner developed and built for thyroid investigations may be used to obtain morpho-functional images only of the thyroid besides, these images show a not better resolution than that of radionuclides images. 

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