Evaluation of the heat sink effect after transarterial embolization when performed in combination with thermal ablation of the liver in a rabbit model

Abstract

Purpose:

To assess the contribution of the heat sink effect when combining thermal ablation with transarterial embolization(TAE).

Materials and Methods:

Radiofrequency ablation(RFA) or microwave ablation(MWA) were performed in the liver of non-tumor bearing rabbits. Three perfusion groups were used: rabbits that were sacrificed then immediately ablated (non-perfused liver group to simulate embolized tumor with no heat sink), rabbits that underwent hepatic TAE followed by ablation (embolized liver group), and rabbits that underwent ablation while alive (normally perfused liver control group). For each perfusion group, 8 RFAs and 8 MWAs were performed. Probes were inserted using ultrasound guidance to avoid areas with major blood vessels. During ablation, temperatures were obtained from a thermocouple located 1 centimeter away from the ablation probe to assess heat conduction. With MWA, temperatures were also measured from the antennae tip.

Results:

For RFA, embolization of normal liver did not increase temperature conduction when compared to the control group. However, temperature conduction was significantly increased in the nonperfused group (simulating embolized tumor) compared to controls(p=0.007). For MWA, neither embolization nor nonperfusion increased temperature conduction compared to controls. With MWA, the probe tip temperature was significantly higher in the nonperfused group compared to the control and embolized group.

Conclusions:

In nonperfused tissue simulating tumor, RFA demonstrated modest enhancement of temperature conduction, whereas MWA did not. Embolization of normal liver did not affect RFA or MWA. Findings suggest that heat sink mitigation plays a limited role with combination embolization-ablation therapies, albeit more with RFA than MWA.