Double-parabolic-reflectors Ultrasonic Transducer with Flexible Waveguide for Minimally Invasive Treatment.

Objective To treat tissues that are difficult to access, ultrasound based minimally invasive treatment (MIT) is promising. However, high-power ultrasound delivery through waveguides had been difficult which can increase treatment duration. It is our effort to design the waveguide that can transmit powerful ultrasound. Methods The waveguide with two parabolic reflectors was proposed by us to produce high-energy-density plane wave. Use of flexible and long thin waveguide was demonstrated here. Results Double Parabolic refLectors wave-guided high-power Ultrasonic tranSducer (DPLUS) including a ϕ1 mmx1 m Nitinol thin waveguide was fabricated. It was shown that high-power ultrasound between 1 to 2 MHz can be propagated through the thin waveguide. Low-loss waveguide material was confirmed to be important to enhance output. As ultrasound is transmitted into working medium, energy mainly flows from the side surface. Temperature of target soft tissue was demonstrated to drastically increase by 10 degree in 30 seconds. Conclusion The developed DPLUS makes high-power ultrasound transmission in long and flexible thin waveguide possible. Significance The concept of DPLUS for delivering high-power ultrasound is powerful in the field of Ultrasonics.