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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

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.

Pilot in vivo studies on transcutaneous boiling histotripsy in porcine liver and kidney

Khokhlova, T.D., G.R. Schade, Y.-N. Wang, S.V. Buravkov, V.P. Chernikov, J.C. Simon, F. Starr, A.D. Maxwell, M.R. Bailey, W. Kreider, and V.A. Khokhlova, "Pilot in vivo studies on transcutaneous boiling histotripsy in porcine liver and kidney," Sci. Rep., 9, 20176, doi:10.1038/s41598-019-56658-7, 2019.

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27 Dec 2019

Boiling histotripsy (BH) is a High Intensity Focused Ultrasound (HIFU) method for precise mechanical disintegration of target tissue using millisecond-long pulses containing shocks. BH treatments with real-time ultrasound (US) guidance allowed by BH-generated bubbles were previously demonstrated ex vivo and in vivo in exposed porcine liver and small animals. Here, the feasibility of US-guided transabdominal and partially transcostal BH ablation of kidney and liver in an acute in vivo swine model was evaluated for 6 animals. BH parameters were: 1.5 MHz frequency, 5–30 pulses of 1–10 ms duration per focus, 1% duty cycle, peak acoustic powers 0.9–3.8 kW, sonication foci spaced 1–1.5 mm apart in a rectangular grid with 5–15 mm linear dimensions. In kidneys, well-demarcated volumetric BH lesions were generated without respiratory gating and renal medulla and collecting system were more resistant to BH than cortex. The treatment was accelerated 10-fold by using shorter BH pulses of larger peak power without affecting the quality of tissue fractionation. In liver, respiratory motion and aberrations from subcutaneous fat affected the treatment but increasing the peak power provided successful lesion generation. These data indicate BH is a promising technology for transabdominal and transcostal mechanical ablation of tumors in kidney and liver.

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Inventions

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.

Focused Ultrasound Apparatus and Methods of Use

Patent Number: 10,350,439

Adam Maxwell, Mike Bailey

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Patent

16 Jul 2019

Methods for diagnosing a pathologic tissue membrane, as well as a focused ultrasound apparatus and methods of treatment are disclosed to perform ureterocele puncture noninvasively using focused ultrasound-generated cavitation or boiling bubbles to controllably erode a hole through the tissue. An example ultrasound apparatus may include (a) a therapy transducer having a treatment surface, wherein the therapy transducer comprises a plurality of electrically isolated sections, (b) at least one concave acoustic lens defining a therapy aperture in the treatment surface of the therapy transducer, (c) an imaging aperture defined by either the treatment surface of the therapy transducer or by the at least one concave acoustic lens and (d) an ultrasound imaging probe axially aligned with a central axis of the therapy aperture.

Device and Method to Break Urinary Stones in Pets

Record of Invention Number: 48640

Mike Bailey, Dan Leotta, Elizabeth Lynch, Brian MacConaghy, Adam Maxwell

Disclosure

28 May 2019

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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