Heat sink effects in thyroid bipolar radiofrequency ablation: an ex vivo study

The study aimed to investigate heat sink effects in radiofrequency ablation (RFA) under thyroid-specific conditions. In an ex vivo model, bovine thyroid lobes were ablated using bipolar RFA with 2.0 kJ energy input at a power level set to 10 W (n = 35) and 25 W (n = 35). Glass vessels (3.0 mm outer diameter) placed within the ablation zone were used to deliver tissue perfusion at various flow rates (0, 0.25, 0.5, 1, 5, 10, 20 ml/min). Temperature was measured in the proximity of the vessel (Tv) and in the non-perfused contralateral region of the ablation zone (Tc), at equal distances to the ablation electrode (d = 8 mm). Maximum temperature within the perfused zone was significantly lowered with Tv ranging from 54.1 +/- 1.5 degrees C (20 ml/min) to 56.9 +/- 1.5 degrees C (0.25 ml/min), compared to Tc from 63.2 +/- 3.5 degrees C (20 ml/min) to 63.2 +/- 2.6 degrees C (0.25 ml/min) (10 W group). The cross-sectional ablation zone area decreased with increasing flow rates from 184 +/- 12 mm2 (0 ml/min) to 141 +/- 20 mm2 (20 ml/min) at 10 W, and from 207 +/- 22 mm2 (0 ml/min) to 158 +/- 31 mm2 (20 ml/min) in the 25 W group. Significant heat sink effects were observed under thyroid-specific conditions even at flow rates <= 1 ml/min. In thyroid nodules with prominent vasculature, heat dissipation through perfusion may therefore result in clinically relevant limitations to ablation efficacy.

Automated summary

The study aimed to investigate heat sink effects in radiofrequency ablation (RFA) under thyroid-specific conditions and found that significant heat sink effects were observed under thyroid-specific conditions, which may limit the efficacy of ablation even at low flow rates.