Thyroid nodule other imaging findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. 
Thyroid nodules may also be diagnosed via radionuclide thyroid scan, whole-body radioactive iodine scan, positron emission tomography (PET scan) or iodine-131 single photon emission computed tomography (SPECT).
Other Imaging Studies
Radionuclide thyroid scan/scintigraphy
- Using either technetium 99 mTc pertechnetate or I123
- Radionuclide scan is contraindicated during pregnancy
- Thyroid scintigraphy is useful to determine the functional status of a nodule. It is specifically indicated in patients with thyroid nodule and a low serum TSH to determine if the nodule has autonomous functioning.
- In scintigraphy, iodine radioisotopes (more commonly used; usually I-123) or technetium pertechnetate (99Tc), are injected and then the radioisotope uptake time by the thyroid gland is measured.
- High radioisotope uptake=Hot nodule:
- Hyperfunctioning nodules
- Low radioisotope uptake=Cold nodule:
- Post therapy whole-body iodine scanning is typically conducted approximately 1 week after RAI therapy to visualize metastases.
Diagnostic whole-body RAI scans
- Diagnostic whole body scanning (DxWBS), either following thyroid hormone withdrawal or recombinant hormone TSH (rhTSH), 6–12 months after remnant ablation may be of value in the follow-up of patients with high or intermediate risk of persistent disease, but should be done with I-123 or low activity I-131.
- Improved diagnostic accuracy of indeterminate thyroid nodules
- In patients with thyroid PET incidentaloma, the incidence of primary thyroid malignancy is very high 
- There is insuffiecient evidence to recommend to or against routine clinical use
- Usage indications:
- Simple disease localization in thyroglobulin (Tg) positive, RAI scan–negative patients
- Initial staging and follow-up of high-risk patients with poorly differentiated thyroid cancers unlikely to concentrate RAI in order to identify sites of disease that may be missed with RAI scanning and conventional imaging.
- Initial staging and follow-up of invasive or metastatic Hurthle cell carcinoma.
- As a powerful prognostic tool for identifying which patients with known distant metastases are at highest risk for disease-specific mortality.
- As a selection tool to identify those patients unlikely to respond to additional RAI therapy.
- As a measurement of post treatment response following external beam irradiation, surgical resection, embolization, or systemic therapy.
Larson SM, Robbins R 2002 Positron emission tomography in thyroid cancer management. Semin Roentgenol 37:169–174. 316. 
False-positive 18FDG-PET findings can be due to:
- Inflammatory lymph nodes
- Suture granulomas
- Increased muscle activity
Therefore, cytologic or histologic confirmation is required before one can be certain that an 18FDG-positive lesion represents metastatic disease.
Iodine 131 single photon emission computed tomography (SPECT)=CT fusion imaging
- May provide superior lesion localization after remnant ablation, but it is still a relatively new imaging modality
- ↑ Reschini E, Ferrari C, Castellani M, Matheoud R, Paracchi A, Marotta G, Gerundini P (2006). "The trapping-only nodules of the thyroid gland: prevalence study". Thyroid. 16 (8): 757–62. doi:10.1089/thy.2006.16.757. PMID 16910877.
- ↑ Shambaugh GE, Quinn JL, Oyasu R, Freinkel N (1974). "Disparate thyroid imaging. Combined studies with sodium pertechnetate Tc 99m and radioactive iodine". JAMA. 228 (7): 866–9. PMID 4406304.
- ↑ Torlontano M, Crocetti U, D'Aloiso L, Bonfitto N, Di Giorgio A, Modoni S, Valle G, Frusciante V, Bisceglia M, Filetti S, Schlumberger M, Trischitta V (2003). "Serum thyroglobulin and 131I whole body scan after recombinant human TSH stimulation in the follow-up of low-risk patients with differentiated thyroid cancer". Eur. J. Endocrinol. 148 (1): 19–24. PMID 12534353.
- ↑ Gavriel H, Tang A, Eviatar E, Chan SW (2015). "Unfolding the role of PET FDG scan in the management of thyroid incidentaloma in cancer patients". Eur Arch Otorhinolaryngol. 272 (7): 1763–8. doi:10.1007/s00405-014-3120-5. PMID 24902804.
- ↑ Leboulleux S, Schroeder PR, Busaidy NL, Auperin A, Corone C, Jacene HA, Ewertz ME, Bournaud C, Wahl RL, Sherman SI, Ladenson PW, Schlumberger M (2009). "Assessment of the incremental value of recombinant thyrotropin stimulation before 2-[18F]-Fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography imaging to localize residual differentiated thyroid cancer". J. Clin. Endocrinol. Metab. 94 (4): 1310–6. doi:10.1210/jc.2008-1747. PMID 19158200.