[Clinical Approach for Thyroid Radiofrequency Ablation]

Abstract

Radiofrequency ablation (RFA) is a non-surgical treatment for symptomatic, benign thyroid nodules. This treatment works by heating and destroying the nodule tissue, which results in reduction of its size and alleviation of the symptoms involved. RFA is indicated for nodules which are confirmed to be benign on two or more cytological or histological examinations, and which result in clinical symptoms requiring medical treatment. It is associated with good short-term outcomes on one-year follow-up; however, 20%-30% of the nodules regrow after more than three years. Therefore, on the basis of long-term follow-up, management of regrowth is key to patient care following RFA. Regrowth is more likely to occur in nodules that are large in size prior to RFA, and in those with high or increased vascularity. Recently, new techniques such as hydrodissection, artery-first ablation, and venous ablation have been introduced to inhibit regrowth. In addition, appropriate criteria for additional RFA should be applied to manage regrowth and prolong its therapeutic effects. RFA is essentially an alternative to surgery; therefore, the ultimate goal of this procedure is to avoid surgery permanently, rather than to achieve temporary effects.

Fig. 1. Diagram of benign thyroid nodules after radiofrequency ablation using the moving-shot technique.

The small circles at the center represent conceptual units ablated by the moving-shot technique, which combine to form Va; to safeguard the surrounding structures from thermal damage, the periphery of the nodule is left unablated and the remaining viable nodule tissue constitutes Vv, which can be calculated by measuring Vt and Va, then using the equation Vv = Vt – Va. Va = ablated volume, Vt = total nodule volume, Vv = viable volume

Fig. 2. US image of a 35-year-old female taken 1 month after the treatment of a 27 mL benign thyroid nodule with radiofrequency ablation.

The centrally located ablated area (Va) appears hypoechoic, while the viable nodule tissue that is left unablated (Vv) is distributed in the peripheral area; it is predominantly located in the medial aspect, near the carotid sheath and in the posterior aspect, while the anterior aspect, with relatively few critical structures, shows minimal viable tissue. Va = ablated volume, Vv = viable volume