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BACKGROUND: The gold standard treatment for colorectal cancer liver metastases (CRCLM) is surgical resection. Unfortunately, the majority of patients with colorectal hepatic metastases are not candidates for resection. In recent years, several alternatives have emerged for patients whom are not resection candidates including modern systemic chemotherapy, targeted biologic treatments, regional therapies and local tumor ablation options. Microwave ablation (MWA) therapy is one such treatment alternative, based on thermal tissue ablation. This modality in concert with the most recent published literature on its use for patients with CRCLM will be reviewed in this paper. LITERATURE REVIEW FINDINGS: A structured review of the literature on ablative technologies was performed. In recent years, there has been an evolution from radiofrequency ablation (RFA) to microwave ablation therapy for the treatment of CRCLM. RFA has several limitations to its use and MWA theoretically avoids such limitations making it the currently preferable treatment option. There are limited publications comparing the use of RFA to MWA and limited publications on the use of microwave ablation for CRCLM. This paper will focus on the most recent data on MWA for CRCLM. This data can then be compared to the already published data on RFA. PROPOSED METHODS: Given the relative novel status for MWA as a treatment option for CRCLM, a potential disadvantage for its use is the perceived lack of knowledge across the medical professional spectrum. In an effort to expand the knowledge of MWA, the proposed outcomes for this study include creating a curriculum to be offered as a CME course focused for Primary Care Providers (PCPs) to provide a basis of clinical familiarity for its use. This effort will familiarize providers who may have patients diagnosed with CRCLM and also allow them to initiate the conversation about this therapy with their patients who may be candidates for this treatment. CONCLUSIONS: MWA therapy is a safe and effective treatment modality for CRCLM. Due to this new development in treating liver lesions originating from colorectal cancer, it’s imperative for providers to become familiar with these new technologies especially considering the high incidence of CRCLM. Therefore, a curriculum for PCPs will allow for a better understanding of this new technology and foster better provider-patient relationships.

The increasing demand for efficient cancer treatment inspired the researchers for new investigations about an alternative treatment of cancer. Microwave ablation is the newest ablation technique to cure cancer. This method is minimally noninvasive and inexpensive compared to the other methods. However, current microwave ablation systems suffer due to narrowband nature of the antenna (dipole or slot) placed at the tip of the probe. Therefore, this study developed an ultra-wideband ablation probe that operates from 300MHz to 10 GHz. For this purpose, a small wideband antenna is designed to place at the tip of the probe and fabricated. These probes are tested at ISM frequencies (2.4 GHz and 5.8GHz) in skin mimicking gels and pig liver. Microwave ablation probe design, simulation results, and experiment results are provided in this thesis.

Master of Science / Department of Electrical and Computer Engineering / Punit Prakash / Microwave ablation (MWA) is a minimally invasive thermal therapy predominantly used in the treatment of localized cancer. Previous studies have demonstrated clinical use of MWA for treating lung tumors, however, these procedures have relied upon the use of rigid percutaneous MWA applicators which can limit the range of accessible tumors and may have inherent disadvantages for use in lung tissue. The objective of this work was to develop and characterize a bronchoscopic MWA applicator suitable for use in a system that enables bronchoscopic transparencymal nodule access (BTPNA). A 3D coupled FEM electromagnetic-heat transfer model was implemented to optimize the antenna design and evaluate the expected ablation size and shape. A prototype device was fabricated and experimentally evaluated in ex vivo tissue to verify simulation results and demonstrate proof-of-concept. Simulated and experimental results indicate the proposed device could create ablation zones 19.3 – 31.0 mm in diameter with 30 – 45 W of power applied for 5 – 10 minutes. Future bronchoscopic MWA applicators based on the design proposed in this study could allow physicians an even less invasive treatment option for lung cancer with increased accuracy and efficacy and reduced risk of procedural complications immediately following a positive bronchoscopic lung biopsy.

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Master of Science / Department of Electrical and Computer Engineering / Punit Prakash / Thermal therapies employing interstitial microwave applicators for hyperthermia or ablation are in clinical use for treatment of cancer and benign disease in various organs. However, treatment of targets in proximity to critical structures with currently available devices is risky due to unfocused deposition of energy into tissue. For successful treatment, complete thermal coverage of the tumor and margin of surrounding healthy tissue must be achieved, while precluding damage to critical structures. This thesis investigates two approaches to increase precision of microwave thermal therapy. Chapter 2 investigates a novel coaxial antenna design for microwave ablation (MWA) employing a hemi-cylinderical reflector to achieve a directional heating pattern. A proof of concept antenna with an S₁₁ of -29 dB at 2.45 GHz was used in ex vivo experiments to characterize the antennas’ heating pattern with varying input power and geometry of the reflector. Ablation zones up to 20 mm radially were observed in the forward direction, with minimal heating (less than 4 mm) behind the reflector. Chapter 3 investigates the use of magnetic nanoparticles (MNP) of varying size and geometry for enhancing microwave tissue heating. A conventional dipole, operating at 2.45 GHz and radiating 15 W, was inserted into a 20 mm radius sphere of distributed MNPs and heating measurements were taken 5 mm, 10 mm, and 15 mm radially away. A heating rate of 0.08°C/s was observed at 10 mm, an increase of 2-4 times that of the control measurement. These approaches provide strong potential for improving spatial control of tissue heating with interstitial and catheter-based microwave antennas.