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Adam Maxwell

Research Assistant Professor, Urology

Email

maxwell@apl.washington.edu

Phone

206-221-6530

Videos

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.

PIXUL: PIXelated ULtrasound Speeds Disease Biomarker Search

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26 Apr 2018

Accurate assessment of chromatin modifications can be used to improve detection and treatment of various diseases. Further, accurate assessment of chromatin modifications can have an important role in designing new drug therapies. This novel technology applies miniature ultrasound transducers to shear chromatin in standard 96-well microplates. PIXUL saves researchers hours of sample preparation time and reduces sample degradation.

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Publications

2000-present and while at APL-UW

Noninvasive acoustic manipulation of objects in a living body

Ghanem, M.A., A.D. Maxwell, Y.-N. Wang, B.W. Cunitz, V.A. Khokhlova, O.A. Sopozhnikov, and M.R. Bailey, "Noninvasive acoustic manipulation of objects in a living body," Proc. Nat. Acad. Sci. USA, EOR, doi:10.1073/pnas.2001779117, 2020.

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6 Jul 2020

In certain medical applications, transmitting an ultrasound beam through the skin to manipulate a solid object within the human body would be beneficial. Such applications include, for example, controlling an ingestible camera or expelling a kidney stone. In this paper, ultrasound beams of specific shapes were designed by numerical modeling and produced using a phased array. These beams were shown to levitate and electronically steer solid objects (3-mm-diameter glass spheres), along preprogrammed paths, in a water bath, and in the urinary bladders of live pigs. Deviation from the intended path was on average <10%. No injury was found on the bladder wall or intervening tissue.

Design, fabrication, and characterization of broad beam transducers for fragmenting large renal calculi with burst wave lithotripsy

Randad, A., M.A. Ghanem, M.R. Bailey, A.D. Maxwell, "Design, fabrication, and characterization of broad beam transducers for fragmenting large renal calculi with burst wave lithotripsy, " J. Acoust. Soc. Am., 148, 44-50, doi:10.1121/10.0001512, 2020.

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1 Jul 2020

Burst wave lithotripsy (BWL) is a technology for comminuting urinary stones. A BWL transducer's requirements of high-pressure output, limited acoustic window, specific focal depth, and frequency to produce fragments of passable size constrain focal beamwidth. However, BWL is most effective with a beam wider than the stone. To produce a broad-beam, an iterative angular spectrum approach was used to calculate a phase screen that was realized with a rapid prototyped lens. The technique did not accurately replicate a target beam profile when an axisymmetric profile was chosen. Adding asymmetric weighting functions to the target profile achieved appropriate beamwidth. Lenses were designed to create a spherically focused narrow-beam (6 mm) and a broad-beam (11 mm) with a 350-kHz transducer and 84-mm focal depth. Both lenses were used to fragment artificial stones (11 mm long) in a water bath, and fragmentation rates were compared. The linearly simulated and measured broad beamwidths that were 12 mm and 11 mm, respectively, with a 2-mm-wide null at center. The broad-beam and the narrow-beam lenses fragmented 44 ± 9% and 16 ± 4% (p = 0.007, N = 3) of a stone by weight, respectively, in the same duration at the same peak negative pressure. The method broadened the focus and improved the BWL rate of fragmentation of large stones.

Modeling of photoelastic imaging of mechanical stresses in transparent solids mimicking kidney stones

Sapozhnikov, O.A., A.D. Maxwell, and M.R. Bailey, "Modeling of photoelastic imaging of mechanical stresses in transparent solids mimicking kidney stones," J. Acoust. Soc. Am., 147, 3819-3829, doi:10.1121/10.0001386, 2020.

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1 Jun 2020

Theoretical and numerical models were developed to calculate the polariscopic integrated light intensity that forms a projection of the dynamic stress within an axisymmetric elastic object. Although the model is general, this paper addressed its application to measurements of stresses in model kidney stones from a burst wave lithotripter for stone fragmentation. The stress was calculated using linear elastic equations, and the light propagation was modeled in the instantaneous case by integrating over the volume of the stone. The numerical model was written in finite differences. The resulting images agreed well with measured images. The measured images corresponded to the maximum shear stress distribution, although other stresses were also plotted. Comparison of the modeled and observed polariscope images enabled refinement of the photoelastic constant by minimizing the error between the calculated and measured fields. These results enable quantification of the stress within the polariscope images, determination of material properties, and the modes and mechanisms of stress production within a kidney stone. Such a model may help in interpreting elastic waves in structures, such as stones, toward improving lithotripsy procedures.

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Inventions

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

Broadly focused ultrasonic propulsion probes, systems, and methods

Disclosed herein are ultrasonic probes and systems incorporating the probes. The probes are configured to produce an ultrasonic therapy exposure that, when applied to a kidney stone, will exert an acoustic radiation force sufficient to produce ultrasonic propulsion. Unlike previous probes configured to produce ultrasonic propulsion, however, the disclosed probes are engineered to produce a relatively large (both wide and long) therapy region effective to produce ultrasonic propulsion. This large therapy region allows the probe to move a plurality of kidney stones (or fragments from lithotripsy) in parallel, thereby providing the user the ability to clear several stones from an area simultaneously. This "broadly focused" probe is, in certain embodiments, combined in a single handheld unit with a typical ultrasound imaging probe to produce real-time imaging. Methods of using the probes and systems to move kidney stones are also provided.

Patent Number: 10,667,831

Mike Bailey, Bryan Cunitz, Barbrina Dunmire, Adam Maxwell, Oren Levy

Patent

2 Jun 2020

Systems and Methods for Measuring Pressure Distributions of Acoustic Beams from Ultrasound Sources

The present technology relates generally to receiving arrays to measure a characteristic of an acoustic beam and associated systems and methods.

Patent Number: 10,598,773

Oleg Sapozhnikov, Wayne Kreider, Adam Maxwell, Vera Khokhlova

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Patent

24 Mar 2020

The present technology relates generally to receiving arrays to measure a characteristic of an acoustic beam and associated systems and methods. The receiving arrays can include elongated elements having at least one dimension, such as a length, that is larger than a width of an emitted acoustic beam and another dimension, such as a width, that is smaller than half of a characteristic wavelength of an ultrasound wave. The elongated elements can be configured to capture waveform measurements of the beam based on a characteristic of the emitted acoustic beam as the acoustic beam crosses a plane of the array, such as a transverse plane. The methods include measuring at least one characteristic of an ultrasound source using an array-based acoustic holography system and defining a measured hologram at the array surface based, at least in part, on the waveform measurements. The measured hologram can be processed to reconstruct a characteristic of the ultrasound source. The ultrasound source can be calibrated and/or re-calibrated based on the characteristic.

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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