## 4 Discussion  
In performing the ablation procedure, one of the key aims was to ensure adequate control of the ethanol elution in order to maintain good control over the ablated volume. In the ablations performed with ethanol, we first created a small cavity in the tissue before dispensing the ethanol. The cavity was formed by applying microwave power via the ablation antenna for a determined period of time prior to beginning the addition of the ethanol. The strategy was to create a small \"empty\" sphere surrounded by necrosed tissues. The latter were hard and used to control, or at least limit, the diffusion of the ethanol when it was being dispensed. We found that there were numerous advantages to this method. From empirical data, we know the size of the cavity formed by this initial energy impulse. The ethanol can be added prior to or while applying the power. The ethanol diffusion away from the dispensing location is greatly hindered, thus reducing the potential for harming tissues that are remote from the target area. We know that we induced a significantly lower value of permittivity at the microwave-emitting point, thus effectively creating a reflection \"mirror\" from the untreated tissues surrounding the ethanol-filled cavity; this would lead to more spherical ablation zones and reduced collateral damage to healthy tissue. All trials were performed using a single pre-beta antenna type. This probe was equipped with an additional hollow lumen surrounding the MW-emitting coaxial antenna. While this is not the optimal design configuration, it allowed for preliminary validation of the theory. In our view, the optimal configuration would incorporate a hollow lumen at the very centre of the MW-emitting coaxial antenna. A single application of MW power of 100 W (120 s) with no addition of ethanol was performed as a basic reference; a non-spherical ablation zone was created showing elongation along the shaft of the antenna. This is typical of an antenna showing significant reflection. All the following comparisons were made with respect to this trial. A test was performed where a MW power of 100 W was applied for 30 s, followed by a period of 60 s with no applied power, and then, followed by another application of 100 W for 90 s (same 12,000 Joules applied) with no addition of ethanol. This demonstrates the effect resulting from the pause period, which caused the tissue to harden and contract. An enlarged non-spherical ablation zone was created showing elongation along the shaft of the antenna, which is also typical of an antenna showing significant reflection. Figure 5: Thermal and photographic imaging of ablation. Ablation conditions: 100 W for 30 s with no ethanol addition; 0 W for 60 s with no ethanol addition; 100 W for 30 s with no ethanol addition; and 100 W for 60 s with an elution of 5.0 mL of ethanol. Figure 6: Thermal and photographic imaging of ablation. Ablation conditions: 100 W for 30 s with no ethanol addition; 0 W for 60 s with no ethanol addition; 100 W for 30 s with no ethanol addition; 0 W for 30 s with elution of 2.5 mL of ethanol; and 100 W for 60 s with an elution of 5.0 mL of ethanol. A test with similar MW power parameters to the previous one was performed, this time with 5.0 mL of ethanol being introduced during the final application of MW energy (60 s) (same energy of 12,000 Joules). The ablation zone was enlarged and revealed improved sphericity. Energy reflection along the antenna path was still visible. A multi-step test with an initial MW power of 100 W for 30 s, followed by a pause period of 60 s, and then, 100 W of MW for 30 s, followed by no power for 30 s and the addition of 2.5 mL of ethanol during that period, and a final MW application of 100 W for 60 s with a further addition of 5.0 mL of ethanol during that period (same energy of 12,000 Joules). These conditions produced a much larger ablation zone, better sphericity, and clear evidence of the limiting effect of ethanol on thermal runaway. Some of the main findings in these experiments were as follows:  
1.