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Background: Scanning with technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) is recommended for evaluating thyroid nodule metabolism. In addition, it may help differentiate between benign and malignant nodules; however, the efficacy of this technique has not been fully elucidated. Therefore, it is not currently performed for routine clinical application. This prospective study was conducted to investigate the clinical significance of 99mTc-MIBI scintigraphy in the assessment of patients with cold thyroid nodules.

Patients and methods: This prospective study was conducted on 104 patients with cold thyroid nodules greater than 1 cm in diameter as detected on 99mTc-pertechnetate scintigraphy. Uptake of MIBI in thyroid nodules was compared with that in the surrounding normal thyroid tissue for both early and delayed images, and a score of 0-3 was assigned to each nodule as follows: 0, cold; 1, decreased; 2, equal; 3, increased. The thyroid scan was performed 20 and 40 min after intravenous injection of 555 MBq of 99mTc-MIBI. The patients underwent fine-needle aspiration cytology (FNAC). Detailed statistical parameters were determined on a per-nodule basis for each qualitative and quantitative scan analysis, as defined by histology.

Results: A total of 104 patients (93 women and 11 men; mean age 40.76 /-11.40 years, range 20-73) with a total number of 167 cold nodules were included in this study. When 99mTc-MIBI uptake was regarded as the criterion of malignancy in 99mTc-MIBI scintigraphy, the accuracy was between 69.46 and 92.21% on using seven different methods. In addition, FNAC findings indicated a sensitivity of 66.66%, a specificity of 100%, a negative predictive value of 95.72%, a positive predictive value of 100%, and an accuracy of 96.06%. Six malignant cold nodules were detected on a positive 99mTc-MIBI scan, which were determined as benign nodules on FNAC examinations.

Conclusion: The study demonstrated that 99mTc-MIBI scanning can be complementary to other diagnostic techniques in patients with cold thyroid nodules. In addition, because of its availability, rather low cost, simple protocol, and objective semiquantitative information, 99mTc-MIBI scanning seems to hold promise in routine imaging of cold thyroid nodules.

(C) 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins