Power Doppler improves the diagnostic accuracy of color Doppler ultrasonography in cold thyroid nodules: follow-up results

The usefulness of a recent color Doppler (CD) ultrasonography technique, named power Doppler (PD), was evaluated in the diagnosis of thyroid nodules showing low or absent uptake of (99m)Tc-pertechnetate, in order to investigate the possibility to improve the diagnostic accuracy of ultrasonography. The rationale was the evidence that at PD the color map displays the total integrated Doppler power in color, while CD generally displays an estimate of the mean Doppler shift. The vascular patterns recorded at PD and CD evaluation of 322 thyroid nodules were compared to the results of cytology and/or histology, when surgery was performed. In respect to the results of cytology, PD has a higher sensitivity (100 vs. 91%) and specificity (95.1 vs. 86.2%) than CD. A similar result was found when PD and CD were compared to the results of histology, sensitivity being 100 vs. 89% and specificity 98.1 vs. 93.7%, respectively. During the follow-up the 2 nodules considered false positive at PD resulted to be tumoral lesions. On this basis, the final specificity of PD in our series was 100%. In conclusion, in the current series including 322 thyroid nodules characterized by a low or absent uptake of (99m)Tc-pertechnetate, PD seems to provide a better characterization of thyroid nodules, possibly allowing a more accurate selection of the patients to subject to fine-needle biopsy.