Many treatment options are available in eliminating tumors including surgery, radiation, and chemotherapy. These treatments, however, have heavy financial constraints and/or significant systemic side effects. Focused ultrasound (FUS) is a new method that has been implemented for targeted cancer treatments. Chemotherapeutic drugs are stored in temperature sensitive liposomes and injected near the target tumor area. FUS is used to heat the target tissue to a temperature range that causes the liposomes to burst and release their drugs. This methodology allows targeted drug delivery to the tumor region while sparing the surrounding tissue, preventing the systemic side effects of traditional chemotherapy.

We used COMSOL to optimize the duty cycle and pulse repetition frequency (PRF) of FUS to maximize induced heating in a tissue analog, a bovine serum albumin phantom, from 21°C to a specified temperature range, 23-28°C, while minimizing heating to the surrounding tissues. We used a homologous tissue-mimicking phantom to have uniformity in parameters and to compare our results with the experimental results from literature [1]. In tissue, body temperature is 37°C and the liposomes are engineered to break at temperatures between 39°C and 44°C [1]. Therefore, we used a different initial temperature for the phantom but the same change in temperature. In the model, as the pressure waves from the ultrasound transducer pass into the phantom, some energy is lost. This attenuation of acoustic energy was assumed to be equal to the heat energy gained by the phantom and thus was used as a heat source term. We were able to determine the optimal duty cycle and PRF of the FUS to reach a high enough temperature that would release chemotherapeutic agents from the liposomes into only the target region of the phantom.