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

We assessed the ability of (TI)-T-201 planar scintigraphy and fine-needle a spiration (FNA) biopsy to differentiate malignant from benign lesions by co mparing the findings of these techniques with those of surgical histopathol ogy for 107 patients with 109 thyroid nodules. Methods: (TI)-T-201 (74 MBq) was injected intravenously, and an early image and a delayed image were ac quired after 10 and 120 min, respectively for 10 min each. For (TI)-T-201 p lanar scintigraphy, accumulation of the tracer in the nodules was visually scored and the nodules were grouped. Group A showed high activity in both e arly and delayed images. Group B revealed high activity in only the early i mage. Group C showed activity in the early image equal to that in normal ti ssues. Quantitative calculation of the washout rate was less than 0 in grou p CI and 0 or higher in group CII. Group D revealed low activity in the ear ly image and Variable activity in the delayed image. Three differential dia gnosis methods were used for (TI)-T-201 planar scintigraphy: method 1, in w hich 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 CI were considered malignant. FNA results were assessed and classified by experienced pathologists. Two differential diagnosis methods were used f or FNA: method a, in which malignancy was assigned to class IV (probably ma lignant or higher), and method b, in which malignancy was assigned to class III (possibly malignant or higher). Results: Concerning (TI)-T-201 methods 1,2 and 3, sensitivity was 74.0%, 84.0% and 92.0%, respectively; specifici ty 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 o f 36.0% and 50.0%, respectively, and a specificity of 96.6% and 84.7%, resp ectively The accuracy of both methods was 68.8%. For follicular lesions, se nsitivity ranged from 80.0% to 90.0% for (TI)-T-201 scintigraphy and from 1 0.0% to 30.0% for FNA. Conclusion: (TI)-T-201 planar scintigraphy was found to be easier to use and more accurate than FNA in the differentiation of d iagnosis of benign and malignant thyroid nodules based on visual scoring co mbined with quantitative evaluation.