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Oleg Sapozhnikov

Senior Principal Engineer






M.S. Physics, Moscow State University, 1985

Ph.D. Acoustics, Moscow State University, 1988


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.

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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.

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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

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2000-present and while at APL-UW

Elastic properties of aging human hematoma model in vitro and its susceptibility to histotripsy liquefaction

Ponomarchuk, E.M., and 12 others including T.D. Khokhlova, O.A. Sapozhnikov, and V.A. Khokhlova, "Elastic properties of aging human hematoma model in vitro and its susceptibility to histotripsy liquefaction," Ultrasound Med. Biol., 50, 927-938, doi:10.1016/j.ultrasmedbio.2024.02.019, 2024.

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1 Jun 2024

Tissue susceptibility to histotripsy disintegration has been reported to depend on its elastic properties. This work was aimed at investigation of histotripsy efficiency for liquefaction of human hematomas, depending on their stiffness and degree of retraction over time (0–10 d).

It was found that clotting time decreased from 113 to 25 min with the increase in blood temperature from 10°C to 37°C. The shear modulus increased to 0.53 ± 0.17 kPa during clotting and remained constant within 8 d of incubation at 2°C. Sample volumes decreased by 57% because of retraction within 10 d. SEM revealed significant echinocytosis but unchanged ultrastructure of the fibrin meshwork. Liquefaction rate and lesion dimensions produced with the same histotripsy protocols correlated with the increase in the degree of retraction and were lower in retracted samples versus freshly clotted samples. More than 80% of residual fibrin fragments after histotripsy treatment were shorter than 150 μm; the maximum length was 208 μm, allowing for unobstructed aspiration of the lysate with most clinically used needles.

The results indicate that hematoma susceptibility to histotripsy liquefaction is not entirely determined by its stiffness, and correlates with the retraction degree.

Dynamic mode decomposition for transient cavitation bubbles imaging in pulsed high-intensity focused ultrasound therapy

Song, M.H., O.A Sapozhnikov, V.A. Khokhlova, and T.D. Khokhlova, "Dynamic mode decomposition for transient cavitation bubbles imaging in pulsed high-intensity focused ultrasound therapy," IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 71, 596-606, doi:10.1109/TUFFC.2024.3387351, 2024.

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1 May 2024

Pulsed high-intensity focused ultrasound (pHIFU) can induce sparse de novo inertial cavitation without the introduction of exogenous contrast agents, promoting mild mechanical disruption in targeted tissue. Because the bubbles are small and rapidly dissolve after each HIFU pulse, mapping transient bubbles and obtaining real-time quantitative metrics correlated with tissue damage are challenging. Prior work introduced Bubble Doppler, an ultrafast power Doppler imaging method as a sensitive means to map cavitation bubbles. The main limitation of that method was its reliance on conventional wall filters used in Doppler imaging and its optimization for imaging blood flow rather than transient scatterers. This study explores Bubble Doppler enhancement using dynamic mode decomposition (DMD) of a matrix created from a Doppler ensemble for mapping and extracting the characteristics of transient cavitation bubbles. DMD was first tested in silico with a numerical dataset mimicking the spatiotemporal characteristics of backscattered signal from tissue and bubbles. The performance of DMD filter was compared to other widely used Doppler wall filter-singular value decomposition (SVD) and infinite impulse response (IIR) high-pass filter. DMD was then applied to an ex vivo tissue dataset where each HIFU pulse was immediately followed by a plane wave Doppler ensemble. In silico DMD outperformed SVD and IIR high-pass filter and ex vivo provided physically interpretable images of the modes associated with bubbles and their corresponding temporal decay rates. These DMD modes can be trackable over the duration of pHIFU treatment using k-means clustering method, resulting in quantitative indicators of treatment progression.

Treatment planning and aberration correction algorithm for HIFU ablation of renal tumors

Rosnitskiy, P.B., T.D. Khokhlova, G.R. Schade, O.A. Sapozhnikov, and V.A. Khokhlova, "Treatment planning and aberration correction algorithm for HIFU ablation of renal tumors," IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 71, 341-353, doi:10.1109/TUFFC.2024.3355390, 2024.

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1 Mar 2024

High-intensity focused ultrasound (HIFU) applications for thermal or mechanical ablation of renal tumors often encounter challenges due to significant beam aberration and refraction caused by oblique beam incidence, inhomogeneous tissue layers, and presence of gas and bones within the beam. These losses can be significantly mitigated through sonication geometry planning, patient positioning, and aberration correction using multielement phased arrays. Here, a sonication planning algorithm is introduced, which uses the simulations to select the optimal transducer position and evaluate the effect of aberrations and acoustic field quality at the target region after aberration correction. Optimization of transducer positioning is implemented using a graphical user interface (GUI) to visualize a segmented 3-D computed tomography (CT)-based acoustic model of the body and to select sonication geometry through a combination of manual and automated approaches. An HIFU array (1.5 MHz, 256 elements) and three renal cell carcinoma (RCC) cases with different tumor locations and patient body habitus were considered. After array positioning, the correction of aberrations was performed using a combination of backpropagation from the focus with an ordinary least squares (OLS) optimization of phases at the array elements. The forward propagation was simulated using a combination of the Rayleigh integral and k-space pseudospectral method (k-Wave toolbox). After correction, simulated HIFU fields showed tight focusing and up to threefold higher maximum pressure within the target region. The addition of OLS optimization to the aberration correction method yielded up to 30% higher maximum pressure compared to the conventional backpropagation and up to 250% higher maximum pressure compared to the ray-tracing method, particularly in strongly distorted cases.

More Publications


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


13 Feb 2024

Real-Time Cell-Surface Marker Detection

Cell-separation systems and methods utilizing cell-specific microbubble tags and ultrasound-based separation are described. The methods are useful for simplification of time consuming and costlyu cell purification procedures and real time apoptosis detection.

Patent Number: 11,698,364

Tom Matula, Oleg Sapozhnikov


11 Jul 2023

Noninvasive Fragmentation of Urinary Tract Stones with Focused Ultrasound

Patent Number: 11,583,299

Adam Maxwell, Bryan Cunitz, Wayne Kreider, Oleg Sapozhnikov, Mike Bailey


21 Feb 2023

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