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Adam Maxwell

Research Assistant Professor, Urology

Email

maxwell@apl.washington.edu

Phone

206-221-6530

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.

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.

Burst Wave Lithotripsy: An Experimental Method to Fragment Kidney Stones

CIMU researchers are investigating a noninvasive method to fragment kidney stones using ultrasound pulses rather than shock waves. Consecutive acoustic cycles accumulate and concentrate energy within the stone. The technique can be 'tuned' to create small fragments, potentially improving the success rate of lithotripsy procedures.

20 Nov 2014

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.

An investigation of elastic waves producing stone fracture in burst wave lithotripsy

Maxwell, A.D., B. MacConaghy, M.R. Bailey, and O.A. Sapozhnikov, "An investigation of elastic waves producing stone fracture in burst wave lithotripsy," J. Acoust. Soc. Am., 147, 1607-1622, doi:, 2020.

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1 Mar 2020

Burst wave lithotripsy is a method to noninvasively fragment urinary stones by short pulses of focused ultrasound. In this study, physical mechanisms of stone fracture during burst wave lithotripsy were investigated. Photoelasticity imaging was used to visualize elastic wave propagation in model stones and compare results to numerical calculations. Epoxy and glass stone models were made into rectangular, cylindrical, or irregular geometries and exposed in a degassed water bath to focused ultrasound bursts at different frequencies. A high-speed camera was used to record images of the stone during exposure through a circular polariscope backlit by a monochromatic flash source. Imaging showed the development of periodic stresses in the stone body with a pattern dependent on frequency. These patterns were identified as guided wave modes in cylinders and plates, which formed standing waves upon reflection from the distal surfaces of the stone model, producing specific locations of stress concentration in the models. Measured phase velocities compared favorably to numerically calculated modes dependent on frequency and material. Artificial stones exposed to bursts produced cracks at positions anticipated by this mechanism. These results support guided wave generation and reflection as a mechanism of stone fracture in burst wave lithotripsy.

Defining thermally safe laser lithotripsy power and irrigation parameters: In vitro model

Aldoukhi, A.H., K.M. Black, T.L. Hall, K.R. Ghani, A.D. Maxwell, B. MacConaghy, and W.W. Roberts, "Defining thermally safe laser lithotripsy power and irrigation parameters: In vitro model,"J. Endourol., 34, 76-81, doi:10.1089/end.2019.0499, 2020.

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16 Jan 2020

High-power laser settings are commonly employed for stone dusting techniques. Previous in vitro and in vivo studies have demonstrated that a toxic thermal dose can result from treatment within a renal calix without adequate irrigation. Hence, both laser power and irrigation rate must be considered together to determine safe laser lithotripsy parameters. The objective of this in vitro study was to map parameter safety boundaries and create guidelines for selection of safe laser and irrigation settings.

The experimental system consisted of in vitro models simulating ureter, renal calix, and renal pelvis placed in a water bath maintained at 37°C. Temperature was recorded during ureteroscopy with laser activation for 60 seconds. Trials were conducted at strategically selected power levels and irrigation rates. Thermal dose for each trial was calculated based on Sapareto and Dewey t43 methodology with thermal dose >120 equivalent minutes considered to result in thermal tissue injury. A parameter safety boundary was established by plotting the maximal safe power level for each irrigation rate.

The parameter safety boundary was found to be linear for each scenario with the renal pelvis able to tolerate the highest laser power and the renal calix the least power without injury.

This study describes the methodology to determine parameter safety boundaries that can be used to guide proper selection of thermally safe laser settings and irrigation rates during ureteroscopy with laser lithotripsy. This work provides a framework to assess the effectiveness of various strategies to control and mitigate thermal dose.

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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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