## 2 Materials and Methods
### Innovative Aspects of This MW-Assisted Ablation Technology Approach  
Ethanol was chosen since it can be an effective chemical ablation substance on its own. However, when combined with MW energy, it becomes more effective. The toxicity of ethanol also increases as the temperature increases. Its permittivity varies from ca. 10 to 1 as the temperature varies from ca. 35 to ca. 80 degrees, which augments the field by a factor of ca. 5 over liver tissues (\(\epsilon^{\prime}\) of ca. 45) at the ethanol introduction point. The loss factor (\(\epsilon^{\prime\prime}\)) of ethanol is ca. 7.7 and varies little as the temperature varies from ca. 35 to its boiling point. Thus, its ability to heat remains constant until it reaches its boiling point; then, the surrounding tissues act as a natural microwave reflector.  
The boiling point of ethanol (78 \({}^{\circ}\)C) is lower than that of water (100 \({}^{\circ}\)C); thus, the maximum temperature attainable during ablation will be lower. This property of ethanol is beneficial for ablation as it reduces the potential of off-target tissue damage due to thermal diffusion. Additionally, the heat capacity of ethanol (2.3 J/g\(\cdot\)K) is about half that of water (4.2 J/g\(\cdot\)K) which further reduces the potential for collateral damage due to thermal diffusion. Its density is about 80% that of water; thus, a smaller mass of ethanol is required per unit volume to be treated. The flow rate of ethanol allows a single protocol to adapt to the varying dielectric characteristics of tissues.  
In MW ablation procedures, susceptors are used to enhance the heating speed and to increase the temperature gradient. Variable frequency is used to adapt to the tissues' influence on field propagation, and a variable phase is used to adapt to the tissues' influence on field patterns.  
This technology comprises innovative features to enhance the efficiency of ablation procedures. As stated, one of these features is an additional channel in the antenna that is located directly in the centre of the coaxial emitting unit and used to deliver substances that enhance the ablation efficiency. Optionally, the antenna can comprise a resonator, with the latter enabling matching of the impedance of each tissue. This reduction in the loss of energy delivery also reduces the time required to complete the ablation process with reduced collateral damage.  
For this research project, the antennas were designed specifically for the delivery of susceptors during the IR procedure. In certain cases, a susceptor may be chosen with the intent to improve the delivery of thermal energy; however, we believe that the added benefit of chemical toxicity may be advantageous in many applications. Ideally, an ablative approach would include a susceptor to project the field where required, and thus, offer additional thermal energy while allowing for enhanced control within the ablation zone. In many instances, the addition of a chemical ablation agent would result in the combined benefits of chemical toxicity and thermal necrosis. Another benefit is that once the ablation procedure is completed, the centre channel can then be used for injecting additional substances to accelerate the healing process or to enhance the long-term efficiency of the treatment, thus reducing the risk for recurrence. Specific examples of this would include the delivery of antibiotic prophylaxis and/or immune modulating agents.