Presentation Information
[10p-A13-1]Helical acoustic field using a tapered ultrasonic transducer for optical waveguiding
Keiya Suzuki1, Yuji Kato1, Nobuki Kudo1, 〇Mamoru Hashimoto1 (1.IST Hokkaido Univ.)
Keywords:
acoustic vortex,ultrasound-induced optical waveguide,near-infrared photoimmunotherapy
Near-infrared photoimmunotherapy selectively destroys cancer cells, but light delivery to deep tissue is hindered by strong optical scattering. We propose a non-invasive light-transmission scheme that uses a helical acoustic field (acoustic vortex), in which a high-refractive-index region induced by ultrasound continues coaxially along the propagation direction, as an optical waveguide. To improve transmission efficiency, we developed a tapered cylindrical transducer. k-Wave simulations show that, while the peak pressure is comparable to that of a concave transducer, the path-length ratio is reduced from 3-4 to below 1.5. We fabricated a transducer with a 3D-printed phase plate (topological charge TC = 1), achieving 98.0% power-transmission efficiency and an axially continuous helical high-pressure region usable as a waveguide. In a transmission experiment through a 1-mm scatterer, an intensity enhancement of about 3% was observed.