Optimal Power for Microwave Slotted Probes in Ablating Different Hepatocellular Carcinoma Sizes.

Thermal ablation is currently used to treat tumors, whether benign or malignant. The most common types of thermal ablation procedures are the radiofrequency ablation (RFA) and the microwave ablation (MWA). Both generate heat in the tissues leading to an elevation in the tissue temperature level from 50-60∘C causing tissues death. In this work, the finite-element method (FEM) is used to model the human liver with a Hepatocellular Carcinoma to obtain the relationship between the power used in microwave radiation, exposure time, and resultant temperature at three microwave frequencies: 433, 915 MHz, and 2.45 GHz. Different hepatic tumor diameters from 20 to 50 mm and the best position to place the probe in the tumor are studied for complete tumor ablation using the lowest required power. A comparison is carried out for four different slotted probes: single slot (SS), multi slot (MS), single slot with 1T ring (SS1T), and single slot with shifted 1T ring (SSST) using the same conditions. The results indicate that the thermal distribution varies according to the type of the used probe. In addition, a relation is deduced between the power and time to assist the physician while using those probes to ablate different tumor sizes. The results reported a reflection coefficient -19.072 dB using the SSS1T probe, while the SS1T provided -4.5582 dB. It is found that a tumor with a diameter of 24, 28, 36, and 39 mm can be completely ablated using power 20 W for a period of 3, 5, 10 and 15 min, respectively, using the SSS1T probe. However, using the same conditions with the SS1T probe, a tumor with diameter 19, 24, 30, and 33 can be ablated, respectively.