Liver

Liver

Many clinicians choose thermal ablation as a minimally invasive treatment option for hepatocellular carcinoma in patients with cirrhosis, hepatic metastases in non-operative patients, and debulking of symptomatic liver tumors. Despite promising clinical results, current clinical standard is fundamentally limited by its mechanism of heating. Tissue temperatures during electrical conduction must be kept below 100 °C to prevent charring and a subsequent rise in electrical impedance, which contributes to a high susceptibility to the heat-sink effect of local blood flow. Several studies^1-6 have demonstrated the following advantages that 2.45GHz have over other energy frequencies for ablation of liver tumors:

• Larger ablation zones: 2.45GHz actively heat a larger volume of tissue and create larger ablation zones in liver than electrical frequencies.
• Higher tissue temperatures: While electrical conduction ablation is limited to temperatures below 100 °C, 2.45GHz can heat tissue to temperatures in excess of 150 °C. Higher tissue temperatures can help overcome cooling due to blood flow and increase heat transfer to the periphery leading to larger ablation zones.
• Faster heat generation: 2.45GHz heat tissue at a much faster rate than lower radio frequencies does. Faster tissue heating leads to shorter treatment times, and also helps overcome cooling from nearby blood vessels.
• More effective heating near blood vessels: The liver is a highly vascular organ and contains several large blood vessels including hepatic arteries and veins as well as the portal vein. Cancerous cells are often spared near large blood vessels due to the “heat-sink” effect of local blood flow, which can lead to local tumor recurrences. 2.45GHz are less susceptible to cooling from nearby vessels. In fact, several studies have demonstrated that higher frequencies preferentially heat along blood vessels
• Multiple-antenna support: Multiple 2.45GHz antennas can be used simultaneously without concern for undesirable electrical interactions encountered with  electrodes. Several closely spaced 2.45GHz antennas can be used to create extremely large ablation zones (greater than would be expected by doing sequential ablations). Multiple 2.45GHz antennas can also be used independently to reduce treatment time by treating several tumors simultaneously. Arrays of 2.45GHz antennas can also be used to increase the efficiency of energy delivery and create more uniform thermal profiles.