ABSTRACT
PURPOSE: Frequency encoded Doppler ultrasound (DUS) imaging has allowed identification of flow in thyroid tumours, but its role in evaluation of thyroid nodules for malignancy has not been accurately defined. We wanted to investigate the possible role of DUS in differentiation of benign and malignant nodules. MATERIALS AND METHODS: DUS and spectral parameters were analysed in 50 benign and 20 malignant thyroid nodules. The following patterns of vascularity were identified: pattern 0--no visible flow; pattern 1--minimal internal flow without a peripheral ring; pattern 2--peripheral ring of flow but minimal or no internal flow; pattern 3--peripheral ring of flow and a small-to moderate amount of internal flow; pattern 4--extensive internal flow with or without a peripheral ring. Peak systolic velocity (PSV) and end diastolic velocity (EDV) was measured and resistance index (RI) was calculated. RESULTS: Significantly more benign nodules had vascularisation patterns 1.2 and 3. Significantly more malignant nodules had vascularisation patterns 3 and 4, and only pattern 4. EDV was significantly lower in malignant than in benign nodules (6.06 +/- 4 cm/sec vs. 13.01 +/- 8.74 cm/sec). RI was significantly higher in malignant than in benign thyroid nodules (0.75 +/- 0.08 vs. 0.56 +/- 0.09). For RI > or = 0.70: 80% sensitivity, 92% specificity, 80% positive predictive value, 92% negative predictive value, and 88.6 % accuracy, were calculated in characterising malignant thyroid nodules. CONCLUSION: We believe that internal flow without or with minimal peripheral flow on DUS and RI > or = 0.70 can be used to distinguish between malignant and benign thyroid nodules fairly reliably. Nodules with prevailing peripheral vascularisation and minimal or no internal vascularisation, and RI below 0.70 are probably benign.
