APL-UW Home

Jobs
About
Campus Map
Contact
Privacy
Intranet

Oleg Sapozhnikov

Senior Principal Engineer

Email

olegs@apl.washington.edu

Phone

206-543-1385

Education

M.S. Physics, Moscow State University, 1985

Ph.D. Acoustics, Moscow State University, 1988

Videos

Ultrasonic tweezers: Technology to lift and steer solid objects in a living body

In a recent paper, a CIMU team describes successful experiments to manipulate a solid object within a living body with ultrasound beams transmitted through the skin.

More Info

15 Jul 2020

A collaborative, international research teams developed and tuned an ultrasound transducer to create vortex shaped beams that can trap, grab, levitate, and move in three dimensions mm-scale objects. The team is working to apply this technology to their all-in-one kidney stone treatment system that, in clinical trials, uses ultrasound to non-invasively break, erode, and move stones and stone fragments out of the kidney so that they may pass naturally from the body.

Mechanical Tissue Ablation with Focused Ultrasound

An experimental noninvasive surgery method uses nonlinear ultrasound pulses to liquefy tissue at remote target sites within a small focal region without damaging intervening tissues. A multi-institution, international team led by CIMU researchers is applying the method to the focal treatment of prostate tumors.

More Info

19 Mar 2020

Boiling histotripsy utilizes sequences of millisecond-duration HIFU pulses with high-amplitude shocks that form at the focus by nonlinear propagation effects. Due to strong attenuation of the ultrasound energy at the shocks, these nonlinear waves rapidly heat tissue and generate millimeter-sized boiling bubbles at the focus within each pulse. Then the further interaction of subsequent shocks with the vapor cavity causes tissue disintegration into subcellular debris through the acoustic atomization mechanism.

The method was proposed at APL-UW in collaboration with Moscow State University (Russia) and now is being evaluated for various clinical applications. It has particular promise because of its important clinical advantages: the treatment of tissue volumes can be accelerated while sparing adjacent structures and not injuring intervening tissues; it generates precisely controlled mechanical lesions with sharp margins; the method can be implemented in existing clinical systems; and it can be used with real-time ultrasound imaging for targeting, guidance, and evaluation of outcomes. In addition, compared to thermal ablation, BH may lead to faster resorption of the liquefied lesion contents.

Characterizing Medical Ultrasound Sources and Fields

For every medical ultrasound transducer it's important to characterize the field it creates, whether for safety of imaging or efficacy of therapy. CIMU researchers measure a 2D acoustic pressure distribution in the beam emanating from the source transducer and then reconstruct mathematically the exact field on the surface of the transducer and in the entire 3D space.

11 Sep 2017

More Videos

Publications

2000-present and while at APL-UW

Synthesized acoustic holography: A method to evaluate steering and focusing performance of ultrasound arrays

Williams, R.P., W. Kreider, F.A. Nartov, M.M. Karzova, V.A. Khokhlova, O.A. Sapozhnikov, and T.D. Khokhlova, "Synthesized acoustic holography: A method to evaluate steering and focusing performance of ultrasound arrays," J. Acoust. Soc. Am., 157, 2750-2762, doi:10.1121/10.0036225, 2025.

More Info

11 Apr 2025

Acoustic holography is a commonly used tool to characterize the three-dimensional acoustic fields and the vibration patterns of ultrasound (US) transducers and arrays. It involves recording the pressure distribution over a transverse plane in front of the transducer via a two-dimensional hydrophone scan, and subsequent forward or backward field projection. For multi-element arrays capable of electronic focus steering, a separate hologram is needed to describe each beam configuration of interest. Since medical US arrays commonly use tens to hundreds of beam configurations, their characterization is very time consuming. Here, we show that holograms for the field of each array element can be recorded with a single hydrophone scan by pulsing the elements sequentially at each location. This approach was validated using a 1 MHz 64-element diagnostic-therapeutic linear array. Holograms of each element combined with backpropagation to the array surface revealed the variability of vibration patterns and crosstalk between channels and elements. Electronically steered beam configurations resulting from boundary conditions synthesized from elemental holograms and directly measured holograms were found to be in excellent agreement. The results demonstrate the method's potential in detecting defects and other nonideal array behavior and in rapid and accurate characterization of all relevant beam configurations.

Method for measuring acoustic radiation force of a focused ultrasound beam acting on an elastic sphere

Kotelnikova, L.M., S.A. Tsysar, D.A. Nikolaev, and O.A. Sapozhnikov, "Method for measuring acoustic radiation force of a focused ultrasound beam acting on an elastic sphere," J. Acoust. Soc. Am., 157, 1391-1402, doi:10.1121/10.0035939, 2025.

More Info

21 Feb 2025

Acoustic radiation force (ARF) is a nonlinear phenomenon resulting from the wave momentum transfer to an absorbing or scattering target. ARF allows objects to be remotely manipulated, pushed, trapped, or pulled, which is used in medical applications such as kidney stone expulsion or acoustic tweezers. Such applications require development of methods for precision ARF measurements and calculations. The purpose of this paper is to present a method for direct measurement of the axial component of the ARF exerted by an ultrasound beam on its axis acting on a millimeter-sized spherical particle in a liquid. The method consists of weighing a rigid frame with a scatterer on electronic scales, similar to the radiation force balance method of measuring the total acoustic beam power. The capabilities of the method are demonstrated by applying it to spheres of different diameters (2–8 mm) and compositions (steel, glass). The additional objective is to provide experimental validation of the theoretical model of Sapozhnikov and Bailey [J. Acoust. Soc. Am. 133, (2013)], previously developed to calculate the ARF of an arbitrary acoustic beam on an elastic sphere in a liquid or gaseous medium based on the angular spectrum approach.

Dynamic mode decomposition based Doppler monitoring of de novo cavitation induced by pulsed HIFU: An in vivo feasibility study

Song, M., O.A. Sapozhnikov, V.A. Khokhlova, H. Son, S. Totten, Y.-N. Wang, and T.D. Khokhlova, "Dynamic mode decomposition based Doppler monitoring of de novo cavitation induced by pulsed HIFU: An in vivo feasibility study," Sci. Rep., 14, doi:10.1038/s41598-024-73787-w, 2024.

More Info

27 Sep 2024

Pulsed high-intensity focused ultrasound (pHIFU) has the capability to induce de novo cavitation bubbles, offering potential applications for enhancing drug delivery and modulating tissue microenvironments. However, imaging and monitoring these cavitation bubbles during the treatment presents a challenge due to their transient nature immediately following pHIFU pulses. A planewave bubble Doppler technique demonstrated its potential, yet this Doppler technique used conventional clutter filter that was originally designed for blood flow imaging. Our recent study introduced a new approach employing dynamic mode decomposition (DMD) to address this in an ex vivo setting. This study demonstrates the feasibility of the application of DMD for in vivo Doppler monitoring of the cavitation bubbles in porcine liver and identifies the candidate monitoring metrics for pHIFU treatment. We propose a fully automated bubble mode identification method using k-means clustering and an image contrast-based algorithm, leading to the generation of DMD-filtered bubble images and corresponding Doppler power maps after each HIFU pulse. These power Doppler maps are then correlated with the extent of tissue damage determined by histological analysis. The results indicate that DMD-enhanced power Doppler map can effectively visualize the bubble distribution with high contrast, and the Doppler power level correlates with the severity of tissue damage by cavitation. Further, the temporal characteristics of the bubble modes, specifically the decay rates derived from DMD, provide information of the bubble dissolution rate, which are correlated with tissue damage level—slower rates imply more severe tissue damage.

More Publications

Inventions

Noninvasive fragmentation of urinary tract stones with focused ultrasound

Patent Number: 12,167,864

Bryan Cunitz, Wayne Kreider, Oleg Sapozhnikov, Mike Bailey

More Info

Patent

17 Dec 2024

A method for attempting to fragment or comminute an object in a body using ultrasound includes producing a burst wave lithotripsy (BWL) waveform by a therapy transducer. The BWL waveform is configured to fragment or comminute the object. The BWL waveform includes a first burst of continuous ultrasound cycles and a second burst of continuous ultrasound cycles. A burst frequency corresponds to a frequency of repeating the bursts of the BWL waveform. The method also includes determining a cycle frequency f of the continuous ultrasound cycles within the first burst and the second burst based on a target fragment size D, where the cycle frequency is: f(MHz)=0.47/D(mm).

Boiling histotripsy methods and systems for uniform volumetric ablation of an object by high-intensity focused ultrasound waves with shocks

Patent #12,157,018

Patent Number: 12,157,018

Vera Khokhlova, Mike Bailey, Wayne Kreider, Oleg Sapozhnikov, Yak-Nam Wang

More Info

Patent

3 Dec 2024

An example method includes generating an acoustic ultrasound wave that is focused at a focal point. The method further includes sequentially directing the focal point upon distinct portions of an object to form respective shock waves at the distinct portions of the object. The method further includes, via the respective shock waves, causing the distinct portions of the object to boil and form respective vapor cavities. The method further includes causing substantially uniform ablation of a region of the object that comprises the distinct portions. The substantially uniform ablation is caused via interaction of the respective shock waves with the respective vapor cavities. An example ablation system and an example non-transitory computer-readable medium, both related to the example method, are also disclosed.

Transrectal Ultrasound Probe for Boiling Histotripsy Ablation of Prostate, and Associated Systems and Methods

Inventors: V. Khokhlova, P. Rosnitskiy (Seattle), P.V. Yuldashev (Moscow), T.D. Khokhlova (Seattle), O. Sapozhnikov, and G.R. Schade (Seattle)

Patent Number: 11,896,853

Vera Khokhlova, Oleg Sapozhnikov

Patent

13 Feb 2024

More Inventions

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
Close

 

Close