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Adam Maxwell

Research Assistant Professor, Urology






Ultrasonic Kidney Stone Treatment for Pet Cats and Marine Mammals

A research kidney stone treatment system that is now undergoing clinical trials in humans was modified to noninvasively fragment stones in pet cats. The design accounted for differences in anatomic scale, acoustic window, skin-to-stone depth, and stone size. Veterinarian collaborators at the University of Minnesota have treated ureteral stones successfully in three cats.

The human system has also been used to treat a dolphin with a ureteral stone blockage and a harbor seal to reduce the stone burden in his kidneys.

20 Dec 2023

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.

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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.

Assessment of urostomy parastomal herniation forces using incisional prevention strategies with an abdominal fascia model

Kanabolo, D.L., A.D. Maxwell, Y.N. Kumar, and G.R. Schade, "Assessment of urostomy parastomal herniation forces using incisional prevention strategies with an abdominal fascia model," Eur. Urol. Open Sci., 54, 66-71, doi:10.1016/j.euros.2023.05.019, 2023.

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1 Aug 2023

Approximately 10 000 patients undergo cystectomy/ileal conduit annually in the USA, of whom over 70% subsequently develop a parastomal hernia (PSH). Still, no well-established "best" practice for stoma creation to prevent a PSH exists.

To measure the relationship between incision size/type/material and axial tension force (ATF) as a surrogate for herniation force, using several models to mimic abdominal fascia.

Abdominal fascia models included silicone membrane, ex vivo porcine, and embalmed human cadaveric fascia. A dynamometer pulled a Foley catheter (20 mm/min) with the balloon inflated to 125% incision (linear, cruciate, and circular) diameter using a motorized positioning system. The maximum ATF before herniation was recorded. The study was repeated in unused silicone/tissue for suture reinforcement. We evaluated silicone, ex vivo porcine, and human abdominal fascia.

Incision sizes (1–3 cm) in 0.5-cm increments were evaluated in silicone. A 3-cm incision was used in porcine/human tissue.

ATF for herniation was recorded/compared across incision types/sizes using Mann-Whitney U and Kruskal-Wallis tests as appropriate, with α = 0.05.
Results and limitations

Linear incision ATF was significantly greater than cruciate and circular incisions. A cruciate incision had significantly greater ATF than a circular incision. In cadaveric tissue, incisions were significantly greater for linear (34.5 ± 12.8 N) versus cruciate (15.3 ± 2.9 N, p = 0.004) and for cruciate versus circular (p = 0.023) incisions. Results were similar in ex vivo porcine fascia and silicone. Reinforcement with a suture significantly increased ATF in all materials/incision sizes/types. The ex vivo nature is this study's main limitation.

This study suggests that urostomy fascial incision type may influence ATF required for herniation. Linear incisions may be preferable. Urostomy reinforcement may significantly increase ATF required for a PSH. These data may help establish best practices for PSH risk reduction.

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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

Ultrasound System for Shearing Cellular Material in a Microplate

Patent Number: 11,592,366

Tom Matula, Adam Maxwell


28 Feb 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