The peculiar ultrasonographic and elastographic features of thyroid nodules after treatment with laser or radiofrequency: similarities and differences.

The aim of percutaneous thermal ablation with laser (LA) or radiofrequency (RFA) is to reduce the volume of benign thyroid nodules. Little is known about ultrasonographic and elastographic appearances of thyroid lesions after treatment. For the first time, we report in detail the main ultrasonographic and elastographic characteristics of thermally ablated nodules and their underlying similarities and differences. Both thermal treatments usually produce a marked hypoechoic area of coagulative necrosis. LA-treated lesions usually become highly heterogeneous due to the presence of cavitations and charring; they then evolve into hyperechoic scars. In RFA-treated nodules, instead, the necrotic area is more homogeneous but presents more irregular margins compared to those observed in LA-treated lesions. Regardless of the thermal method used, vascularity is typically reduced in all treated nodules and stiffness, evaluated with qualitative elastography, increases. In conclusion, ultrasonographic and elastographic appearances of the thermally ablated thyroid lesions differ slightly according to the adopted procedure. Furthermore, they are peculiar, changeable over time, and potentially misleading.