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Yak-Nam Wang

Research Scientist Engineer - Principal






B.S. Biomedical Materials Science & Engineering, Queen Mary & Westfield College, University of London, UK, 1996

Ph.D. Biomedical Materials, Queen Mary & Westfield College, University of London, UK, 2000


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.

Non-invasive Treatment of Abscesses with Ultrasound

Abscesses are walled-off collections of fluid and bacteria within the body. They are common complications of surgery, trauma, and systemic infections. Typical treatment is the surgical placement of a drainage catheter to drain the abscess fluid over several days. Dr. Keith Chan and researchers at APL-UW's Center for Industrial + Medical Ultrasound are exploring how to treat abscesses non-invasively, that is, from outside the body, with high-intensity focused ultrasound (HIFU). This experimental therapy could reduce pain, radiation exposure, antibiotic use, and costs for patients with abscesses. Therapeutic ultrasound could also treat abscesses too small or inaccessible for conventional drainage.

20 Jun 2016


2000-present and while at APL-UW

Comparative study of histotripsy pulse parameters used to inactivate Escherichia coli in suspension

Ambedkar, P.A., Y.-N. Wang, T. Khokhlova, M. Bruce, D.F. Leotta, S. Totten, A.D. Maxwell, K.T. Chan, W.C. Liles, E.P. Dellinger, W. Monsky, A.A. Adedipe, and T.J. Matula, "Comparative study of histotripsy pulse parameters used to inactivate Escherichia coli in suspension," Ultrasound Med. Biol., 49, 2451-2458, doi:10.1016/j.ultrasmedbio.2023.08.004, 2023.

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1 Dec 2023

Bacterial loads can be effectively reduced using cavitation-mediated focused ultrasound, or histotripsy. In this study, gram-negative bacteria (Escherichia coli) in suspension were used as model bacteria to evaluate the effectiveness of two regimens of histotripsy treatments: cavitation histotripsy (CH) and boiling histotripsy (BH).

The results of this study suggest that both CH and BH can be used to inactivate E. coli in suspension, with the optimal regimen depending on the attainable peak negative focal pressure at the target.

Development of a burst wave lithotripsy system for noninvasive fragmentation of ureteroliths in pet cats

Maxwell, A.D., G.W. Kim, E. Furrow, J.P. Lulich, M. Torre, B. MacConaghy, E. Lynch, D.F. Leotta, Y.-N. Wang, M.S. Borofsky, and M.R. Bailey, "Development of a burst wave lithotripsy system for noninvasive fragmentation of ureteroliths in pet cats," BMC Vet. Res., 141, doi:10.1186/s12917-023-03705-1, 2023.

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2 Sep 2023

Upper urinary tract stones are increasingly prevalent in pet cats and are difficult to manage. Surgical procedures to address obstructing ureteroliths have short- and long-term complications, and medical therapies (e.g., fluid diuresis and smooth muscle relaxants) are infrequently effective. Burst wave lithotripsy is a non-invasive, ultrasound-guided, handheld focused ultrasound technology to disintegrate urinary stones, which is now undergoing human clinical trials in awake unanesthetized subjects.

In this study, we designed and performed in vitro testing of a modified burst wave lithotripsy system to noninvasively fragment stones in cats. The design accounted for differences in anatomic scale, acoustic window, skin-to-stone depth, and stone size. Prototypes were fabricated and tested in a benchtop model using 35 natural calcium oxalate monohydrate stones from cats. In an initial experiment, burst wave lithotripsy was performed using peak ultrasound pressures of 7.3 (n = 10), 8.0 (n = 5), or 8.9 MPa (n = 10) for up to 30 min. Fourteen of 25 stones fragmented to < 1 mm within the 30 min. In a second experiment, burst wave lithotripsy was performed using a second transducer and peak ultrasound pressure of 8.0 MPa (n = 10) for up to 50 min. In the second experiment, 9 of 10 stones fragmented to < 1 mm within the 50 min. Across both experiments, an average of 73–97% of stone mass could be reduced to fragments < 1 mm. A third experiment found negligible injury with in vivo exposure of kidneys and ureters in a porcine animal model.

These data support further evaluation of burst wave lithotripsy as a noninvasive intervention for obstructing ureteroliths in cats.

Pilot ex vivo study on non-thermal ablation of human prostate adenocarcinoma tissue using boiling histotripsy

Rosnitskiy, P.B., and 16 others including O.A. Sapozhnikov, A.D. Maxwell, Y.-N. Wang, and V.A. Khokhlova, "Pilot ex vivo study on non-thermal ablation of human prostate adenocarcinoma tissue using boiling histotripsy," Ultrasonics, 133, doi:10.1016/j.ultras.2023.107029, 2023.

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1 Aug 2023

Focused ultrasound technologies are of growing interest for noninvasive ablation of localized prostate cancer (PCa). Here we present the results of the first case study evaluating the feasibility of non-thermal mechanical ablation of human prostate adenocarcinoma tissue using the boiling histotripsy (BH) method on ex vivo tissue. High intensity focused ultrasound field was generated using a 1.5-MHz custom-made transducer with nominal F#=0.75. A sonication protocol of 734 W acoustic power, 10-ms long BH-pulses, 30 pulses per focal spot, 1 % duty cycle, and 1 mm distance between single foci was tested in an ex vivo human prostate tissue sample containing PCa. The protocol used here has been successfully applied in the previous BH studies for mechanical disintegration of ex vivo prostatic human tissue with benign hyperplasia. BH treatment was monitored using B-mode ultrasound. Post-treatment histologic analysis demonstrated BH produced liquefaction of the targeted tissue volume. BH treated benign prostate parenchyma and PCa had similar tissue fractionation into subcellular fragments. The results of the study demonstrated that PCa tumor tissue can be mechanically ablated using the BH method. Further studies will aim on optimizing protocol parameters to accelerate treatment while maintaining complete destruction of the targeted tissue volume into subcellular debris.

More Publications


High Intensity Focused Ultrasound Systems for Treating Tissue

Inventors: Y.-N. Wang, M.R. Bailey, T.D. Khokhlova (Seattle), W. Kreider, A.D. Maxwell, G.R. Schade (Seattle), and V.A. Khokhlova

Patent Number: 11,857,813

Yak-Nam Wang, Mike Bailey, Wayne Kreider, Adam Maxwell, Vera Khokhlova


2 Jan 2024

Histotripsy Treatment of Hematoma

A rapid, definitive intervention aiming at evacuation of the space-occupying hematoma would reduce pain, improve function, and avoid long term sequelae. Ultrasound is known to promote intravascular clot breakdown, as both a standalone procedure and used in conjunction with thrombolytic drugs and/or microbubbles. In-vitro and in-vivo studies have been conducted over the years, and acoustic cavitation is widely accepted as the dominant mechanism for mechanical disruption of the clot integrity and partial or complete recanalization of the vessel. Recently, a technique termed histotripsy that employs high-intensity focused ultrasound (HIFU) has been demonstrated to dissolve large in vitro and in vivo vascular clots without thrombolytic drugs within 1.5-5 minutes into debris 98% of which were smaller than 5 microns. However, this approach cannot be applied to the large extravascular hematomas due to their large volume (20-50 cc's) compared to intravascular clots, which necessitates much higher thrombolysis rates to complete the treatment within clinically relevant times (.about.15-20 minutes).

Patent Number: 10,702,719

Tatiana Khokhlova, Tom Matula, Wayne Monsky, Yak-Nam Wang


7 Jul 2020

Method and System for MRI-based Targeting, Monitoring, and Quantification of Thermal and Mechanical Bioeffects in Tissue Induced by High Intensity Focused Ultrasound

Example embodiments of system and method for magnetic resonance imaging (MRI) techniques for planning, real-time monitoring, control, and post-treatment assessment of high intensity focused ultrasound (HIFU) mechanical fractionation of biological material are disclosed. An adapted form of HIFU, referred to as "boiling histotripsy" (BH), can be used to cause mechanical fractionation of biological material. In contrast to conventional HIFU, which cause pure thermal ablation, BH can generate therapeutic destruction of biological tissue with a degree of control and precision that allows the process to be accurately measured and monitored in real-time as well as the outcome of the treatment can be evaluated using a variety of MRI techniques. Real-time monitoring also allow for real-time control of BH.

Patent Number: 10,694,974

Vera Khokhlova, Wayne Kreider, Adam Maxwell, Yak-Nam Wang, Mike Bailey


30 Jun 2020

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