P0202 Effect of non-parallel placement of incircle bipolar radiofrequency ablation probes on volume of tissue ablated with heat sink

Abstract

<h3>Background</h3> Percutaneous bipolar radiofrequency ablation (RFA) is a minimally invasive technique for treating liver tumours. It is not always possible to insert the bipolar probes parallel to each other on either side of a tumour, since such placement could restrict manoeuvrability away from vital structures or the ability to ablate certain tumour shapes. Therefore, we investigated how non-parallel placement of probes affected ablation. <h3>Methods</h3> Bipolar RFA probes in parallel and in divergent positions were submerged in a tissue model (800mL egg white) at 37°C and ablated. Temperature probes T1 and T2 were placed 8.00mm below the tip of the RFA probes, T3 in between the probe coil elements, and T4 and T5 at the water inlet and outlet, respectively. Models with a heat sink (+HS) and without a heat sink (−HS) were investigated. <h3>Findings</h3> The mean ablated tissue volume, mass, density, and height increased linearly with unit angle increase in probe position for the −HS model. For the +HS model, a smaller increase in mean volume and mass, a slightly greater increase in mean density, and a reduction in height of tissue ablated per unit angle increase was seen. The mean ablation time and duration of maximum temperature with +HS was slightly longer than with −HS, whereas −HS ablated at a slightly higher temperature. The heat sink was minimal for probes in parallel position compared with non-parallel positions. <h3>Interpretation</h3> Divergence from parallel insertion of bipolar RFA probes increased the mean volume, mass, and density of tissue ablated. However, the presence of large heat sinks may limit the application of this technique, when tumours border on larger vessels.