A model for frequency optimization in high intensity focused ultrasound therapy and its verification using magnetic resonance thermometry

High Intensity Focused Ultrasound (HIFU) is a promising technology for the treatment of various diseases. The techniques that have been studied mostly include tissue ablation and drug delivery in which application duration and dosage are critical. Tissue ablation requires very high temperatures reached within seconds whereas, drug delivery applications require low temperatures over longer durations. It is also critical to not damage any other tissue than target tissue in both applications (i.e. skin). Therefore, many studies focused on reducing unnecessary heating of the tissue. One of the promising solutions is frequency optimization. Frequency optimization technique, utilizes the frequency of the acoustic pressure depending on the target tissue depth. In literature, there is an analytic solution for this problem; however, this has not been shown experimentally with the calculated solution. This thesis focuses on modeling of a HIFU system with tissue model while using Magnetic Resonance (MR) thermometry for experimental data. So that an efficient HIFU therapy can be delivered to the target knowing how much the tissue is going to be heated. For the experiments, ex vitro chicken breast was used. The model uses COMSOL software and experimental environment can be mimicked properly. The model benefits from 2-D axisymmetric structure of the acoustic and heat problem. The model was then validated using MR thermometry. Frequency dependence was shown both analytically and experimentally. As a result, a HIFU model for tissue heating, which can be used for treatment planning, has been developed and has been shown to predict temperature rise correctly.