Double-parabolic-reflectors acoustic waveguides for high-power medical ultrasound

High-Power Ultrasonic Transducer for Effective Hemolysis

To realize compact and portable hemolysis devices, an ultrasonic transducer with a blood channel is proposed in this study. Ultrasound waves are focused by a parabolic reflector to generate high sound pressure inside the channel for hemolysis. The hemolysis performance of the transducer is evaluated using simulations and experiments. Experiments are performed with various voltages and flow rates to verify the feasibility of hemolysis. The hemolysis rate is more than 93% at an applied voltage of 80 Vp-p, a flow rate of 0.25 mL/min, and a driving frequency of 1.28 MHz.

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 mm ×1 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.

An Ultrasonic Tweezer With Multiple Manipulation Functions Based on the Double-Parabolic-Reflector Wave-Guided High-Power Ultrasonic Transducer

The development of ultrasonic tweezers with multiple manipulation functions is challenging. In this work, multiple advanced manipulation functions are implemented for a single-probe-type ultrasonic tweezer with the double-parabolic-reflector wave-guided high-power ultrasonic transducer (DPLUS). Due to strong high-frequency (1.49 MHz) linear vibration at the manipulation probe's tip, which is excited by the DPLUS, the ultrasonic tweezer can capture microobjects in a noncontact mode and transport them freely above the substrate. The captured microobjects that adhere to the probe's tip in the low-frequency (154.4 kHz) working mode can be released by tuning the working frequency. The results of the finite-element method analyses indicate that the manipulations are caused by the acoustic radiation force.

Wideband Multimode Excitation by a Double-Parabolic-Reflector Ultrasonic Transducer

This research presents double-parabolic-reflector wave-guided ultrasonic transducers in order to realize wideband (0-2.5 MHz), multiharmonic mode excitations (over 20 modes), and to obtain large mechanical/acoustic outputs. The double-parabolic-reflector mechanism serves as a horn structure at low frequencies and acoustic-focusing structure at high frequencies to enhance the energy density of the incident ultrasound. Upon combining simulation and experimental methods, we examined and verified the basic performance and working mechanisms of the double-parabolic-reflector waveguides: multimode excitation belongs to the harmonic modes from the thin waveguide. At the megahertz range near the thickness mode of the piezoelectric element (PZT), energy density of the incident ultrasound is enhanced by double-parabolic reflections, and the amplification ranges 10 to 40× between 1 and 2.5 MHz. At burst excitations, the amplification performance is independent of the length of the thin waveguide. Compared with conventional Langevin transducers and high-intensity focused ultrasound (HIFU) transducers, our transducers possess a wide working frequency with large mechanical/acoustic outputs and large vibration velocity amplification. By introducing these new features, our proposed method is a promising candidate for examining basic physics parameters, such as frequency dependence, in the fields of medicine, biology, industry, etc.