[Evaluation of thyroid scan with 99mTc-MIBI in selected patients candidate for thyroid surgery]

Thyroid scan with sestamibi is used for evaluation of thyroid nodules with the aim of increasing specificity before surgery. In this study we evaluated the role of Sestamibi thyroid scan in candidates for thyroid surgery. Methods and patients: During two years, 37 patients were studied with solitary thyroid nodules, referred for thyroid surgery due to malignant or suspicious FNAB results (66/7%), compressive effects or failure of medical therapy. Thyroid scan was performed after IV injection of 15mCi of Tc-99m-MIBI in 4 phases (Angiography-First 10 minutes-15min and 2-3 hours after injection). Thyroid MIBI uptake was scaled in 5 scores (0-4) with no uptake as score 0 and hot nodule as score 4. Patients underwent thyroid surgery and results of pathology are correlated with MIBI uptake. From 37 patients (27 female, 10 male, mean age=35.5 years+/- 13.6) 16 malignant and 21 benign nodules were detected. In another classification, we had 26 neoplastic and 11 non-neoplastic nodules. MIBI uptake score 3-4 was noted in 11 out of 16 malignant nodules and 13 out of 21 benign nodules(P=0.73). Sensitivity and specificity of high MIBI uptake (score 3-4) for diagnosis of malignancy was 68.7% and 38% respectively. The values for sensitivity and specificity were 69.2% and 30.7% in diagnosis of neoplasm respectively. Washout index (considered as difference in uptake scores of late and early phases) was 0.45 in benign and 0.09 in malignant nodules (P=0.07). The values were 0.26 and 0.37 in neoplastic and non-neoplastic nodules respectively (P=0.65). Thyroid MIBI scan has a low specificity for differentiating malignant from benign or neoplastic from non-neoplastic nodules in patients who are candidates for thyroid surgery according to clinical evaluation. Analysis of wash out index may increase specificity.