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Yak-Nam Wang

Research Scientist Engineer - Principal

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

Fracture and fragmentation of vascular calcifications by focused ultrasound

Chen, L.S., G. Koh, Y.-N. Wang, G.W. Kim, Z. Singh, A. Lehnert, R. Miyaoka, H.S. Gurm, and A.D. Maxwell, "Fracture and fragmentation of vascular calcifications by focused ultrasound," J. Cardiovasc. Transl. Res., EOR, doi:10.1007/s12265-025-10611-4, 2025.

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21 Apr 2025

Peripheral artery disease results in ischemia necessitating interventions such as balloon angioplasty. However, calcified lesions resist balloon and stent expansion, leading to poor outcomes. We hypothesized that focused ultrasound can fracture vascular calcifications and enable balloon angioplasty. In a first experiment, focused ultrasound was applied to ex vivo human calcified plaque specimens to determine its effects based on micro-CT imaging. In a second experiment, ultrasound was applied to an in vitro phantom to evaluate whether the effects enable balloon expansion. Fractures, thinning, and disintegration of calcified sections were observed in 15 of 18 treated human plaque samples. Minor mechanical disruption to soft plaque was found in 33% of samples. In tissue phantoms, n = 10/10 samples were successfully expanded by a water-filled angioplasty balloon with ultrasound applied prior to or during expansion. No controls (n = 0/10) were expanded. These results indicate focused-ultrasound plaque fracture is feasible and may enhance balloon angioplasty.

Facilitated clearance of small, asymptomatic renal stones with burst wave lithotripsy and ultrasonic propulsion

Harper, J.D., and 18 others including B. Dunmire, J. Thiel, Y.-N. Wang, S. Totten, J.C. Kucewicz, and M.R. Bailey, "Facilitated clearance of small, asymptomatic renal stones with burst wave lithotripsy and ultrasonic propulsion," J. Urol., EOR, doi:10.1097/JU.0000000000004533, 2025.

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17 Mar 2025

We tested feasibility of burst wave lithotripsy (BWL) and ultrasonic propulsion to noninvasively fragment and expel small, asymptomatic renal stones in awake participants.

Adult patients suspected of having 2- to 7-mm stones were consented and screened for eligibility. BWL and ultrasonic propulsion were applied to up to 3 stones in 1 kidney of qualifying participants for a 30-minute total exposure. Participants completed a CT scan and the Wisconsin Stone Quality-of-Life (WISQOL) questionnaire within 90 days before and 120 days after the procedure. Participants were contacted weekly for 3 weeks after the procedure to assess adverse events (AEs). Outcomes included (1) no fragment > 2 mm, (2) unanticipated health care visits, (3) change in stone volume, (4) reported AEs, and (5) WISQOL score.

Forty-one participants were enrolled between April 2023 and October 2024. Twenty-one participants failed screening because no stones were seen, stones were too large or small, stone visibility was too deep or obstructed, or they declined to participate. Twenty participants with 31 stones received the research procedure with 7 undergoing a single repeat procedure. Twenty-two of 31 stones (71%) met the primary effectiveness outcome of no fragment > 2 mm, with 17 of 31 stones (55%) reported as stone free. Median stone volume reduction (IQR) was 100% (88%–100%). No participants returned unexpectedly for care related to the procedure. AEs were all Grade I by modified Clavien classification. WISQOL scores improved on 10 of 15 completed questionnaires.

Small, asymptomatic renal stones were effectively and safely removed in awake participants in a clinic setting.

Advancing boiling histotripsy dose in ex vivo and in vivo renal tissues via quantitative histological analysis and shear wave elastography

Ponomarchuk, E., G. Thomas, M. Song, Y.-N. Wang, S. Totten, G. Schade, J. Thiel, M. Bruce, V. Khokhlova, and T. Khokhlova, "Advancing boiling histotripsy dose in ex vivo and in vivo renal tissues via quantitative histological analysis and shear wave elastography," Ultrasound Med. Biol., 50, 1936-1944, doi:10.1016/j.ultrasmedbio.2024.08.022, 2024.

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1 Dec 2024

Objective
In the context of developing boiling histotripsy (BH) as a potential clinical approach for non-invasive mechanical ablation of kidney tumors, the concept of BH dose (BHD) was quantitatively investigated in porcine and canine kidney models in vivo and ex vivo.

Methods
Volumetric lesions were produced in renal tissue using a 1.5-MHz 256-element HIFU-array with various pulsing protocols: pulse duration tp = 1–10 ms, number of pulses per point ppp = 1–15. Two BHD metrics were evaluated: BHD1 = ppp, BHD2 = tp × ppp. Quantitative assessment of lesion completeness was performed by their histological analysis and assignment of damage score to different renal compartments (i.e., cortex, medulla, and sinus). Shear wave elastography (SWE) was used to measure the Young's modulus of renal compartments in vivo vs ex vivo, and before vs after BH treatments.

Results
In vivo tissue required lower BH doses to achieve identical degree of fractionation as compared to ex vivo. Renal cortex (homogeneous, low in collagen) was equal or higher in stiffness than medulla (anisotropic, collagenous), 5.8–12.2 kPa vs 4.7–9.6 kPa, but required lower BH doses to be fully fractionated. Renal sinus (fatty, irregular, with abundant collagenous structures) was significantly softer ex vivo vs in vivo, 4.9–5.1 kPa vs 9.7–15.2 kPa, but was barely damaged in either case with any tested BH protocols. BHD1 was shown to be relevant for planning the treatment of renal cortex (sufficient BHD1 = 5 pulses in vivo and 10 pulses ex vivo), while none of the tested doses resulted in complete fractionation of medulla or sinus. Post-treatment SWE imaging revealed reduction of tissue stiffness ex vivo by 27–58%, increasing with the applied dose, and complete absence of shear waves within in vivo lesions, both indicative of tissue liquefaction.

Conclusion
The results imply that tissue resistance to mechanical fractionation, and hence required BH dose, are not solely determined by tissue stiffness but also depend on its composition and structural arrangement, as well as presence of perfusion. The SWE-derived reduction of tissue stiffness with increasing BH doses correlated with tissue damage score, indicating potential of SWE for post-treatment confirmation of BH lesion completeness.

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Inventions

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

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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.

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

Patent

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

Patent

7 Jul 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
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