Transcranial MR guided FUS Cooling

Focused ultrasound thalamotomy is a novel therapy that uses sound waves to kill neurons in the thalamus, treating conditions such as essential tremor and tremor-dominant Parkinson’s disease. However, the treatment can result in high temperatures at the skull-brain interface, leading to damaged tissues within or near the skull. Currently, this risk is reduced by keeping stationary chilled water around the skull during treatments. However, many patients are still unable to receive treatment due to unfavorable subject-specific characteristics, including low skull density ratio. Our long-term goal is to increase the number of potential patients by exploring how convective water flow around the skull might improve cooling efficiency.

We have developed a finite-difference time-domain (FDTD) numerical solver to simulate convective water flow around the skull during focused ultrasound therapies. To validate model performance, we have designed a laboratory experiment to imitate focused ultrasound thalamotomy.

The experimental setup consists of a hemispherical 3D-printed (PLA) skull containing a brain surrogate, placed into a mock transcranial focused ultrasound transducer. Heating is achieved by pumping hot water at a constant temperature across the inside of the brain surrogate. Both the temperature and flow rate of the chilled water between the skull and mock transducer will be varied across experimental trials. Thermocouple temperatures are recorded throughout the setup.

Beyond model validation, these data will be used to quantify convection heat transfer between the skull and chilled water bath. Determining the quality of this predictive model and the potential impact of convective flow over the skull are important steps to reducing the risk of skull lesions and improving the lives of additional focused ultrasound thalamotomy patients.