Quantitative evaluation of vascularity on power Doppler US may not identify malignancy of the thyroid

Abstract

Purpose: To evaluate the usefulness of vascular index (VI) and in predicting thyroid malignancy.Materials & Methods: This retrospective study was approved by our institutional review board, and informed consent was waived. A total of 1,309 thyroid nodules in 1,257 patients (mean age, 50.2 years; range, 18-83 years) were included. Clinical characteristics of the patients and grayscale US were reviewed. Vascularity pattern on Doppler US was classified as none, peripheral, and intranodular. VI was measured with a quantification software from Power Doppler images obtained prior to biopsy. Diagnostic performances of grayscale US alone, US combined with vascularity patterns or VI was calculated and compared. Results: Of the 1,309 thyroid nodules, 927 (70.8%) were benign and 382 (29.2%) were malignancy. Mean value of VI was significantly higher in benign compared to malignancy, 19.1±19.3% to 15.4±17.9% (P<0.001). When cutoff of VI was set at 9.6% in discriminating between benign and malignant thyroid nodules, sensitivity of US combined to vascularity pattern (91.4%) or VI (95.8%) was significantly higher than US alone (89.0%, P<0.001), with lower specificity (62.1% and 28.2% to 74.3%, respectively, P<0.001). Area under the receiver operating characteristics curve (Az) of grayscale US was significantly higher than US combined to vascularity pattern or VI, 0.82 to 0.77 and 0.70, respectively (all P<0.001).Conclusion: Quantified vascularity values were higher in benign than malignant nodules. Neither vascularity patterns nor VI are not predictive of malignancy, and does not improve the diagnostic performances of US in the predicting thyroid malignancy.