Model planning for laser thermal therapies: Developments and optimization of thermal models for tumor laser ablation

As the second greatest cause of mortality in USA, cancer is an important problem for global public health. Significant reductions in mortality have been observed over the past ten years as a result of enhanced therapies, detection methods, and targeted treatment development. A variety of cancer treatments already exist which exploit various tactics and scientific concepts such as chemotherapy, radiation therapy, photodynamic therapy, hormone therapy, immunotherapy, stem cell therapy, and targeted therapy. Most of them have been consolidated over the last few years; nevertheless, other therapies for curing liver and lung cancer, for example, are still unreliable and mostly, too invasive. Hence, a great interest has growth in minimally invasive treatments that aim to target metastases while causing the least amount of harm to the patients. This thesis examined the process of laser ablation, in which cancerous cells are directly targeted with lasers to raise their temperature and induce necrosis. In fact, living cells can develop and survive in temperatures ranges between 30 and 40 °C, and they evaporate at temperatures exceeding 100 °C. Because fiber-optic biomedical laser applications have so many benefits over traditional ones, they have grown significantly in the last several years. Their resilience, compact dimensions, and high energy efficiency make them suitable for a wide range of biomedical applications. Their energy here is used to cause specific cells to necrotize, enabling accurate non-invasive treatments that benefit patients more. This master's thesis sought to create a realistic thermal model that could simulate biological tissue interaction with a laser, its propagation range and the temperature rise it causes, to serve as a mock-up for medical personnel administering treatments. To obtain the numerical solutions and compare them with the analytical ones, a model was first made up and implemented into Comsol Multiphysics. Secondly, the heat pulse method was exploited to assess the model's thermal biological properties, which are crucial for determining the accurate heat distribution across the media under study. Then, Matlab codes were used to extract temperature data in real time. The distortion caused by the monitoring fibre over the measured temperature values was also a subject of investigation. As a result of this study, experimental tests employing fibre laser beam delivery and FBG sensors were required in order to validate the distortion temperature maps previously produced. Lastly, an investigation on a more realistic delivery system was conducted. Therefore, the heat source was constructed as a linearly distributed superposition of various Gaussians, taking advantage of the linearity of the heat equation.