Abstract
Objective: To compare visual and semiquantitative indices of double phase thallium-201 thyroid scintigraphy(DTS) for differentiation of malignant nodules by indeterminate fine needle aspiration biopsy (FNAB) results.Design: DTS (early; 15 minutes; delayed, 2 hour) were performed after injection of 37MBq of thallium-201 in 60 patients with indeterminate FNAB. Main outcome: With grade 4 and 5, sensitivity and specificity were 51.4% and 78.3%, respectively. With early lesion to nonlesion ratio (L/N) 1.49, sensitivity and specificity were 97.3% and 39.1%, respectively. With delayed L/N 1.89, sensitivity and specificity were 70.3% and 78.3%, respectively. With wash-out rate (WR) 18.93%, sensitivity and specificity were 89.2% and 82.6%. Early L/N was superior to delayed L/N and WR for the detection of malignant thyroid nodules. Conclusion: Visual assessment had a limited value for differentiation of follicular nodules. The optimal semiquantitative indices were 1.49 for early L/N and 1.89 for delayed L/N. Also, optimal WR was 18.93%. The early L/N was superior to delayed L/N and WR for the detection of malignant thyroid nodular lesions. However, visual assessment and early L/N of DTS showed similar results. Visual analysis and semiquantitative indices of DTS could not differentiate follicular carcinoma and follicular variant of papillary thyroid cancer.
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