Usefulness of power Doppler in the diagnostic management of hypoechoic thyroid nodules.

Objective: The usefulness of power Doppler (PD), a new color Doppler ultrasonography technique, namely in the diagnosis and management of hypoechoic thyroid nodules in comparison with color Doppler (CD) is investigated in this study. Patients and methods: 157 hypoechoic thyroid nodules were studied by CD and PD. The distribution of vascular patterns was compared with the results obtained at cytology and/or histology. Results: Three characteristic PD patterns were found: type A=ring sign, defined as the perilesional vascular signal; type B=complex ring sign, subdivided into B1 for the perilesional and moderate intralesional vascular signal with regular vessels course and B2 for the perilesional and high intralesional vascularization, with anarchic structure and winding vessels course; C=delta sign, defined as a small vascular perilesional halo with a large afferent vessel and winding course and flow. All tumors, benign and malignant, showed a pattern type B2, except one which showed a pattern type C and another with a type B1. All the lesions with patterns A and B1 were hyperplasias. Forty-six hyperplastic lesions showed a pattern B2: in these cases the analysis of flow indices predicted the negative cytology. In fact, Doppler measurements showed that all 117 nodules with CD pattern type II and III had systolic peak velocity (Pv)<50 cm/s, 116/117 had resistance index (RI)50 cm/s and 9/10 had RI50 cm/s and among these, four had RI>0.75 and two <0.75, while the patients with Pv<50 cm/s had RI>0.75. In this series of 157 thyroid nodules, both sensitivity and specificity of PD were higher than CD technique (95% versus 75% and 66.4% versus 38.7%). Conclusions: PD, when compared with CD allowed a more accurate characterization of hypoechoic thyroid nodules. Copyright 1997 Elsevier Science Ireland Ltd.