Characterization of a Next-Generation Poly (Methacrylic Acid)-Coated Iron Oxide Nanoparticle Coupling Medium for Transcranial MRI-Guided Focused Ultrasound

Presenter: Nathan Sambo, Engineering Mechanics

Authors: N. Sambo, A. Sayyah, L. Ruger, H. Wang, A. Maxwell, S. Allen, R.M. Davis, E. Vlaisavljevich

Abstract: Objective: This study characterizes the physical properties and assesses the acoustic feasibility of using poly(methacrylic acid)-coated iron oxide nanoparticles as a coupling bath for transcranial MRI-guided focused ultrasound. Methods: Synthesized nanoparticles were characterized to determine their physical properties. Thereafter, cavitation thresholding (pressure at which probability of cavitation = 0.5) was conducted under histotripsy parameters with a 500 kHz transducer at peak negative pressures ranging from ~1 - 35 MPa to determine the acoustic feasibility. Results: The IBCM particles were found to be ~33 nm in size and have a surface tension of ~72.5 mN/m. Cavitation thresholding experiments of the IBCM at different gas saturations did not significantly differ from the water controls (27.02 MPa < p- water < 28.59 MPa, 26.86 MPa < p- IBCM < 28.30 MPa). Higher concentration experiments followed a similar trend indicating no dependence between the cavitation threshold and iron concentration (p- water = 25.59 ± 0.07 MPa, 24.33 MPa < p- IBCM < 26.28 MPa). Conclusion: These findings support the feasibility of the IBCM as a replacement for the degassed water bath to improve imaging quality of tMRgFUS procedures without introducing negative acoustic effects.