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Yak-Nam Wang

Senior Engineer

Email

ynwang@apl.washington.edu

Phone

206-616-6673

Education

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

Videos

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

Publications

2000-present and while at APL-UW

Sonographic features of abscess maturation in a porcine model

Lotta, D.F., M. Bruce, Y.-N. Wang, J. Kucewicz, T.K. Khokhlova, K. Chan, W. Monsky, and T.J. Matula, "Sonographic features of abscess maturation in a porcine model," Ultrasound Med. Biol., 47, 1920-1930, doi:10.1016/j.ultrasmedbio.2021.03.011, 2021.

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1 Jul 2021

Abscesses are walled-off collections of infected fluids that often develop as complications in the setting of surgery and trauma. Treatment is usually limited to percutaneous catheterization with a course of antibiotics. As an alternative to current treatment strategies, a histotripsy approach was developed and tested in a novel porcine animal model. The goal of this article is to use advanced ultrasound imaging modes to extract sonographic features associated with the progression of abscess development in a porcine model. Intramuscular or subcutaneous injections of a bi-microbial bacteria mixture plus dextran particles as an irritant led to identifiable abscesses over a 2 to 3 wk period. Selected abscesses were imaged at least weekly with B-mode, 3-D B-mode, shear-wave elastography and plane-wave Doppler imaging. Mature abscesses were characterized by a well-defined core of varying echogenicity surrounded by a hypoechoic capsule that was highly vascularized on Doppler imaging. 3-D imaging demonstrated the natural history of abscess morphology, with the abscess becoming less complex in shape and increasing in volume. Furthermore, shear-wave elastography demonstrated variations in stiffness as phlegmon becomes abscess and then liquefies, over time. These ultrasound features potentially provide biomarkers to aid in selection of treatment strategies for abscesses.

Mechanical characterization of fibrotic and mineralized tissue in Peyronie's disease

Brady, L., C.J. Stender, Y.-N. Wang, G.R. Schade, A.D. Maxwell, H. Wessells, and W.R. Ledoux, "Mechanical characterization of fibrotic and mineralized tissue in Peyronie's disease," Int. J. Impotence Res., EOR, 10.1038/s41443-021-00439-2, 2021.

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25 May 2021

Peyronie's disease affects penile mechanics, but published research lacks biomechanical characterization of affected tunica albuginea. This work aims to establish mechanical testing methodology and characterize pathological tissue mechanics of Peyronie's disease. Tunica albuginea was obtained from patients (n = 5) undergoing reconstructive surgery for Peyronie's disease, sectioned into test specimens (n = 12), stored frozen at –20°C, and imaged with micro-computed tomography (μCT). A tensile testing protocol was developed based on similar soft tissues. Correlation of mechanical summary variables (force, displacement, stiffness, work, Young’s modulus, ultimate tensile stress, strain at ultimate tensile stress, and toughness) and μCT features were assessed with linear regression. Specimens empirically grouped into hard or soft stress–strain behavior were compared using a Student's t-test. Surface strain and failure patterns were described qualitatively. Specimens displayed high inter- and intra-subject variability. Mineralization volume was not correlated with mechanical parameters. Empirically hard tissue had higher ultimate tensile stress. Failure mechanisms and strain patterns differed between mineralized and non-mineralized specimens. Size, shape, and quantity of mineralization may be more important in determining Peyronie's disease plaque behavior than presence of mineralization alone, and single summary variables like modulus may not fully describe mechanical behavior.

Treating porcine abscesses with histotripsy: A pilot study

Matula, T.J., Y.-N. Wang, T. Khokhlova, D.F. Leotta, J. Kucewicz, A.A. Brayman, M. Bruce, A.D. Maxwell, B.E. MacConaghy, G. Thomas, V.P. Chernikov, S.V. Buravkov, V.A. Khokhlova, K. Richmond, K. Chan, W. Monsky, "Treating porcine abscesses with histotripsy: A pilot study," Ultrasound Med. Biol., 47, 603-619, doi:10.1016/j.ultrasmedbio.2020.10.011, 2021.

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1 Mar 2021

Infected abscesses are walled-off collections of pus and bacteria. They are a common sequela of complications in the setting of surgery, trauma, systemic infections and other disease states. Current treatment is typically limited to antibiotics with long-term catheter drainage, or surgical washout when inaccessible to percutaneous drainage or unresponsive to initial care efforts. Antibiotic resistance is also a growing concern. Although bacteria can develop drug resistance, they remain susceptible to thermal and mechanical damage. In particular, short pulses of focused ultrasound (i.e., histotripsy) generate mechanical damage through localized cavitation, representing a potential new paradigm for treating abscesses non-invasively, without the need for long-term catheterization and antibiotics. In this pilot study, boiling and cavitation histotripsy treatments were applied to subcutaneous and intramuscular abscesses developed in a novel porcine model. Ultrasound imaging was used to evaluate abscess maturity for treatment monitoring and assessment of post-treatment outcomes. Disinfection was quantified by counting bacteria colonies from samples aspirated before and after treatment. Histopathological evaluation of the abscesses was performed to identify changes resulting from histotripsy treatment and potential collateral damage. Cavitation histotripsy was more successful in reducing the bacterial load while having a smaller treatment volume compared with boiling histotripsy. The results of this pilot study suggest focused ultrasound may lead to a technology for in situ treatment of acoustically accessible abscesses.

More Publications

Inventions

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

Patent

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

Patent

30 Jun 2020

Audio Feedback for Improving the Accuracy of BWL Targeting

Record of Invention Number: 48254

Mike Bailey, Bryan Cunitz, Barbrina Dunmire, Christopher Hunter, Wayne Kreider, Adam Maxwell, Yak-Nam Wang

Disclosure

25 Jan 2018

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
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