Cancerous Tumor Ablation Using Different Microwave Ablation Applicators

Abstract

While there are several chronic diseases more destructive to life than cancer, none is more feared. Despite significant progress in understanding, diagnosing, treating, and preventing the disease in the past decades, cancer still remains the major threat to human beings. Microwave ablation (MWA) modality is a newly emerged minimally invasive thermal therapy technique for the treatment of various malignant tumors up to 3 cm in diameter. The ablation region obtained during MWA mainly depends on the type and efficiency of the trocar as well as the energy transfer from the generator to the biological tissue. The trocar plays an essential role in the MWA system by governing the energy distribution during tissue ablation. The present study analysed the microwave ablation of cancerous tumors located in six vital organs and estimated the significance of tissue properties in relation to the importance of appropriate positioning of the trocar during treatment. The six major organs are lungs, breast, stomach/gastric, liver, liver (with colon metastasis), and kidney. The input power (100 W) and ablation times (4 minutes) with apt and inapt positioning of the trocar have been considered to compare the ablation volume of various cancerous tissues. The highest values of the ablation region have been observed for the liver, colon metastatic liver and breast cancerous tissues compared with other organs at the same operating conditions. The positioning of the trocar is more important for the breast, liver, and kidney, as they produce a more rapid zone of heating in a shorter span of time. The present study addresses one of the major problems clinicians face: the proper placement of the trocar due to poor imaging techniques and human error, resulting in incomplete tumor removal and increased surgical procedures. In addition, the present work also consists of a new MWA trocar design proposed to overcome the above-mentioned issues. A numerical analysis of MWA using the new medical applicator (also referred to as trocar or antenna) in L and U shaped has been presented in this work. The novel microwave applicator consists of a flexible dual tine trocar, with each tine supplied with energy at equal and/or different frequencies, 2.45/6 GHz. Once the trocar is inserted into the tumor, the flexible tines can be deployed independently with varying lengths. With the proposed trocar design, large size ablation zones can be obtained by varying the frequency of the supplied energy and the deployment length of the tines. Various combinations of supplied energy and deploying lengths result in tumor ablations ranging from 2.7 to 4 cm in diameter. Supplying energy at high-frequency (6 GHz) to the trocar results in ablating tumors (> 4 cm) with spherical ablation region. The use of high-frequency energy in MWA (6 GHz) further addresses the issue of collateral damage to the tissue and the low spherical shaped ablation region associated with the MWA procedure at 2.45 GHz frequency. In addition, the present study has been designed to assess the ablation region obtained using multiple MWA trocars both numerically and experimentally. Further, multiple trocars have been inserted into the tissue in parallel and non-parallel positions operating at 2.45 GHz and 6 GHz frequencies. Internal trocar cooling mechanism has been considered in this study. Experimental analysis has been performed on egg white with added albumin protein. It has been found from the present study that MWA operated at 2.45/6 GHz with the non-parallel position of multiple trocars into the tissue leads to a considerable increase in the ablation region as compared to the parallel insertion of trocars. Hence, it may be concluded that non-parallel insertion of trocars is suitable to treat irregular-shaped large cancerous tumours (>3 cm). The non-parallel simultaneous insertion of trocars can overcome the healthy tissue ablation issue as well as the problem associated with indentation.