Non-enhanced ultrasound is not a satisfactory modality for measuring necrotic ablated volume after radiofrequency ablation of benign thyroid nodules: a comparison with contrast-enhanced ultrasound.

• Va measured by gray-scale and Doppler US was significantly larger than that by CEUS. • Va measured by gray-scale and Doppler US lacked intra- and inter-observer reliability and agreement with CEUS. • CEUS should be preceded to gray-scale and Doppler US for the measurement of Va.