Comparison of differential diagnostic capabilities of 201Tl scintigraphy and fine-needle aspiration of thyroid nodules.

We assessed the ability of 201 TI planar scintigraphy and fine-needle aspiration (FNA) biopsy to differentiate malignant from benign lesions by comparing the findings of these techniques with those of surgical histopathology for 107 patients with 109 thyroid nodules. Methods: 201 TI (74 MBq) was injected intravenously, and an early image and a delayed image were acquired after 10 and 120 min, respectively, for 10 min each. For 201 TI planar scintigraphy, accumulation of the tracer in the nodules was visually scored and the nodules were grouped. Group A showed high activity in both early and delayed images. Group B revealed high activity in only the early image. Group C showed activity in the early image equal to that in normal tissues. Quantitative calculation of the washout rate was less than 0 in group Cl and 0 or higher in group CII. Group D revealed low activity in the early image and variable activity in the delayed image. Three differential diagnosis methods were used for 201 TI planar scintigraphy: method 1, in which only group A was considered malignant; method 2, in which both group A and group B were considered malignant; and method 3, in which groups A, B and Cl were considered malignant. FNA results were assessed and classified by experienced pathologists. Two differential diagnosis methods were used for FNA: method a, in which malignancy was assigned to class IV (probably malignant or higher), and method b, in which malignancy was assigned to class II (possibly malignant or higher). Results: Conceming 201 TI methods 1, 2 and 3, sensitivity was 74.0%, 84.0% and 92.0%, respectively; specificity was 83.1%, 64.4% and 54.2%, respectively; and accuracy was 78.9%, 73.4% and 71.6%, respectively. For FNA, method a and method b had a sensitivity of 36.0% and 50.0%, respectively, and a specificity of 96.6% and 84.7%, respectively. The accuracy of both methods was 68.8%. For follicular lesions, sensitivity ranged from 80.0% to 90.0% for 201 TI scintigraphy and from 10.0% to 30.0% for FNA. Conclusion: 201 TI planar scintigraphy was found to be easier to use and more accurate than FNA in the differentiation of diagnosis of benign and malignant thyroid nodules based on visual scoring combined with quantitative evaluation.