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Yak-Nam Wang

Senior Engineer

Email

ynwang@apl.washington.edu

Phone

206-616-6673

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.

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23 Mar 2017

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

Safety and effectiveness of a longer focal beam and burst duration in ultrasonic propulsion for repositioning urinary stones and fragments

Janssen, K.M., T.C. Brand, B.W. Cunitz, Y.-N. Wang, J.C. Simon, F. Starr, H.D. Liggitt, J. Thiel, M.D. Sorensen, J.D. Harper, M.R. Bailey, and B. Dunmire, "Safety and effectiveness of a longer focal beam and burst duration in ultrasonic propulsion for repositioning urinary stones and fragments," J. Endourol., 31, 793-799, doi:10.1089/end.2017.0167, 2017.

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1 Aug 2017

Purpose: In the first-in-human trial of ultrasonic propulsion, subjects passed collections of residual stone fragments repositioned with a C5-2 probe. Here, effectiveness and safety in moving multiple fragments are compared between the C5-2 and a custom (SC-50) probe that produces a longer focal beam and burst duration.

Materials and Methods: Effectiveness was quantified by the number of stones expelled from a calyx phantom consisting of a 30-mm deep, water-filled well in a block of tissue mimicking material. Each probe was positioned below the phantom to move stones against gravity. Single propulsion bursts of 50 ms or 3 s duration were applied to three separate targets: 10 fragments of 2 different sizes (1–2 and 2–3 mm) and a single 4 x 7 mm human stone. Safety studies consisted of porcine kidneys exposed to an extreme dose of 10-minute burst duration, including a 7-day survival study and acute studies with surgically implanted stones.

Results: Although successful in the clinical trial, the shorter focal beam and maximum 50 ms burst duration of the C5-2 probe moved stones, but did not expel any stones from the phantom's 30-mm deep calyx. The results were similar with the SC-50 probe under the same 50 ms burst duration. Longer (3 s) bursts available with the SC-50 probe expelled all stones at both 4.5 and 9.5 cm "skin-to-stone" depths with lower probe heating compared to the C5-2. No abnormal behavior, urine chemistry, serum chemistry, or histological findings were observed within the kidney or surrounding tissues for the 10 min burst duration used in the animal studies.

Conclusions: A longer focal beam and burst duration improved expulsion of a stone and multiple stone fragments from a phantom over a broad range of clinically relevant penetration depths and did not cause kidney injury in animal studies.

Effect of carbon dioxide on the twinkling artifact in ultrasound imaging of kidney stones: A pilot study

Simon, J.C., Y.-N. Wang, B.W. Cunitz, J. Thiel, F. Starr, Z. Liu, and M.R. Bailey, "Effect of carbon dioxide on the twinkling artifact in ultrasound imaging of kidney stones: A pilot study," Ultrasound Med. Bill. 43, 877-883, doi:10.1016/j.ultrasmedbio.2016.12.010, 2017.

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1 May 2017

Bone demineralization, dehydration and stasis put astronauts at increased risk of forming kidney stones in space. The color-Doppler ultrasound "twinkling artifact," which highlights kidney stones with color, can make stones readily detectable with ultrasound; however, our previous results suggest twinkling is caused by microbubbles on the stone surface which could be affected by the elevated levels of carbon dioxide found on space vehicles. Four pigs were implanted with kidney stones and imaged with ultrasound while the anesthetic carrier gas oscillated between oxygen and air containing 0.8% carbon dioxide. On exposure of the pigs to 0.8% carbon dioxide, twinkling was significantly reduced after 9–25 min and recovered when the carrier gas returned to oxygen. These trends repeated when pigs were again exposed to 0.8% carbon dioxide followed by oxygen. The reduction of twinkling caused by exposure to elevated carbon dioxide may make kidney stone detection with twinkling difficult in current space vehicles.

Noninvasive characterization of pancreatic tumor mouse models using magnetic resonance imaging

Farr, N., Y.-N. Wang, S. D'Andrea, K.M. Gravelle, J.H. Hwang, and D. Lee, "Noninvasive characterization of pancreatic tumor mouse models using magnetic resonance imaging," Cancer Med., 6, 1082-1090, doi:10.1002/cam4.1062, 2017.

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1 May 2017

The preclinical models of pancreatic adenocarcinoma provide an alternative means for determining the mechanisms of malignancy and possibilities for treatments, thus representing a resource of immense potential for cancer treatment in medicine. To evaluate different tumor models, quantifiable magnetic resonance imaging (MRI) techniques can play a significant role in identifying valuable in vivo biomarkers of tumor characteristics. We characterized three models of pancreatic cancer with multiparametric MRI techniques. Tumor stromal density of each tumor was measured using diffusion-weighted imaging and magnetization transfer (MT-MRI). Histologic measurement showed a similar trend with tumor fibrosis levels. Results indicated that MRI measurements can serve as a valuable tool in identifying and evaluating tumor characteristics.

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Inventions

MRI-Guided Lithotripsy of Urinary Tract Stones

Record of Invention Number: 47984

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

Disclosure

23 Feb 2017

Methods of Soft Tissue Emulsification using a Mechanism of Ultrasonic Atomization Inside Gas or Vapor Cavities and Associated Systems and Devices

Patent Number: 9,498,651

Oleg Sapozhnikov, Mike Bailey, Larry Crum, Vera Khokhlova, Yak-Nam Wang

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Patent

22 Nov 2016

The present technology is directed to methods of soft tissue emulsification using a mechanism of ultrasonic atomization inside gas or vapor cavities, and associated systems and devices. In several embodiments, for example, a method of non-invasively treating tissue includes pulsing ultrasound energy from the ultrasound source toward the target site in tissue. The ultrasound source is configured to emit high intensity focused ultrasound (HIFU) waves. The target site comprises a pressure-release interface of a gas or vapor cavity located within the tissue. The method continues by generating shock waves in the tissue to induce a lesion in the tissue at the target site. The method additionally includes characterizing the lesion based on a degree of at least one of a mechanical or thermal ablation of the tissue.

Noninvasive Disintegration of Peyronie's Plaque with Focused Ultrasound

Record of Invention Number: 47233

Hunter Wessells, Mike Bailey, Mahri Haider, Tatiana Khokhlova, Frank Lee, Adam Maxwell, George Schade, Yak-Nam Wang

Disclosure

23 Feb 2015

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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