Authors: Elizabeth M J Allen, Steven P Allen, Henrik C A Odeen
Mentors: Steven P Allen
Insitution: Brigham Young University
Background
The focus of this project was creating phantoms with customizable attenuation and stiffness for visualizing histotripsy lesions created with magnetic resonance guided focused ultrasound surgery (MRgFUS). Having phantoms with varying mechanical and acoustic properties is important because they affect cavitation and allow for testing of different histotripsy mechanisms. Creating a tunable phantom with red blood cells (RBCs) spread throughout it is valuable because it allows us to visualize High Intensity Focused Ultrasound (HIFU) lesions from MRgFUS in three dimensions throughout the gel.
Materials and Methods
We produced gels with tunable acoustic and mechanical properties by mixing 5 different ratios of evaporated milk and deionized water with 5 different ratios of agarose powder to create 25 different gels.
Gel attenuation was measured using a through transmission setup and Young’s Modulus was obtained using a tensile tester in compression. The MR properties, including T1, T2, and T2* of each gel were also measured prior to creating histotripsy lesions.
Results
In general, the agarose gels had an increase in attenuation as the amount of evaporated milk increased, and an increase in mechanical stiffness as the amount of agarose powder increased. They also provided excellent lesioning contrast for visualizing MRgFUS lesions.
Conclusions
We successfully created a series of tunable gels for visualizing MRgFUS lesions. These gels are also useful for characterizing ultrasound transducers and can be used to test emerging MRgFUS technology as it becomes more widely used and is further developed.