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Peter Kaczkowski

Principal Engineer

Email

peter@apl.washington.edu

Phone

206-543-1283

Research Interests

Medical Acoustics, Wave Scattering, Electromagnetic Induction Methods, Inverse Problems

Biosketch

Dr. Kaczkowski studies applications of ultrasound in medical diagnostic imaging and therapy. Current projects include developing high-intensity focused ultrasound (HIFU) for minimally invasive surgery, and the development of new methods of imaging with ultrasound. He has developed an electromagnetic induction system for detecting and identifying unexploded ordnance on land. Previous work also includes a theoretical and numerical investigation of a new method for computing rough surface scattering, numerical modeling of wave propagation through random media, and inverse problems. Dr. Kaczkowski joined the Laboratory as a graduate student in 1988 and as a staff member in 1992.

Education

B.S. Electrical Engineering, University of Colorado, 1977

M.S. Geophysics, Colorado School of Mines, 1986

Ph.D. Electrical Engineering, University of Washington, 1993

Publications

2000-present and while at APL-UW

Ultrasound intensity to propel stones from the kidney is below the threshold for renal injury

Wang, Y.-N., J.C. Simon, B. Cunitz, F. Starr, M. Paun, D. Liggit, A. Evan, J. McAteer, J. Williams, Z. Liu, P. Kaczkowski, R. Hsi, M. Sorensen, J. Harper, and M.R. Bailey, "Ultrasound intensity to propel stones from the kidney is below the threshold for renal injury," Proc., Meetings on Acoustics., 19, 075066, doi:10.1121/1.4800361, 2013.

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3 Jun 2013

Therapeutic ultrasound has an increasing number of applications in urology, including shockwave lithotripsy, stone propulsion, tissue ablation, and hemostasis. However, the threshold of renal injury using ultrasound is unknown. The goal of this study was to determine kidney injury thresholds for a range of intensities between diagnostic and ablative therapeutic ultrasound. A 2 MHz annular array generating spatial peak pulse average intensities (ISPPA) up to 28,000 W/cm2 in water was placed on the surface of in vivo porcine kidneys and focused on the adjacent parenchyma. Treatments consisted of pulses of 100 μs duration triggered every 3 ms for 10 minutes at various intensities. The perfusion-fixed tissue was scored by 3 blinded independent experts. Above a threshold of 16,620 W/cm2, the majority of injury observed included emulsification, necrosis and hemorrhage. Below this threshold, almost all injury presented as focal cell and tubular swelling and/or degeneration. These findings provide evidence for a wide range of potentially therapeutic ultrasound intensities that has a low probability of causing injury. While this study did not examine all combinations of treatment parameters of therapeutic ultrasound, tissue injury appears dose-dependent.

Evidence for trapped surface bubbles as the cause for the twinkling artifact in ultrasound imaging

Lu, W., O.A. Sapozhnikov, M.R. Bailey, P.J. Kaczkowski, and L.A. Crum, "Evidence for trapped surface bubbles as the cause for the twinkling artifact in ultrasound imaging," Ultrasound Med. Biol., 39, 1026-1038, doi:10.1016/j.ultrasmedbio.2013.01.011, 2013.

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1 Jun 2013

The mechanism of the twinkling artifact (TA) that occurs during Doppler ultrasound imaging of kidney stones was investigated. The TA expresses itself in Doppler images as time-varying color. To define the TA quantitatively, beam-forming and Doppler processing were performed on raw per channel radio-frequency data collected when imaging human kidney stones in vitro. Suppression of twinkling by an ensemble of computer-generated replicas of a single radio frequency signal demonstrated that the TA arises from variability among the acoustic signals and not from electronic signal capture or processing. This variability was found to be random, and its suppression by elevated static pressure and return when the pressure was released suggest that the presence of bubbles on the stone surface is the mechanism that gives rise to the TA.

Focused ultrasound to expel calculi from the kidney

Shah, A., J.D. Harper, B.W. Cunitz, Y.-N. Wang, M. Paun, J.C. Simon, W. Lu, P.J. Kaczkowski, and M.R. Bailey, "Focused ultrasound to expel calculi from the kidney," J. Urol., 187, 739-743, doi:10.1016/j.juro.2011.09.144, 2012.

1 Feb 2012

More Publications

Heat diffusion constrained inversion of backscattered ultrasound data to image temperature rise during high intensity focused ultrasound therapy

Kaczkowski, P.J., G. Speyer, A.A. Brayman, L.A. Crum, and A. Anand, "Heat diffusion constrained inversion of backscattered ultrasound data to image temperature rise during high intensity focused ultrasound therapy," J. Acoust. Soc. Am., 129, 2439, doi:10.1121/1.3587982, 2011.

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1 Apr 2011

Noninvasive ablative high intensity focused ultrasound (HIFU) therapy must be guided with precision, and monitored in real time. Magnetic resonance imaging (MRI) can provide both high resolution tissue-specific images and temperature maps, but even the most recently developed MRI methods cannot do so in less than a few seconds. Ultrasonic imaging techniques using a sequence of rf frames to measure heating-induced apparent strain have been developed to produce heating maps, but the approach is challenging due to lack of sensitivity and substantial variability in tissue properties. To improve estimates of temperature rise, constraints based on heat diffusion modeling are imposed, thus minimizing the effects of noise and nonmonotonicity of the speed of sound with respect to temperature throughout the therapeutic range. Furthermore, noninvasive protocols for measuring relevant HIFU field and tissue properties in the region of interest enable patient-calibrated mapping of temperature rise during HIFU, at ultrasonic imaging frame rates. Further analysis of the heat-induced apparent strain leads to a modal decomposition of the strain, greatly reducing the computational load for use in real-time feedback and therapy control. Finally, a Rytov approximation applied to the problem leads to further improvement in computational efficiency and physical understanding.

Holographic reconstruction of therapeutic ultrasound sources

Kreider, W., O.A. Sapozhnikov, M.R. Bailey, P.J. Kaczkowski, and V.A. Khokhlova, "Holographic reconstruction of therapeutic ultrasound sources," J. Acoust. Soc. Am. Vol. 129, 2403, doi: 10.1121/1.3587826, 2011.

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1 Apr 2011

Clinical therapeutic ultrasound systems rely on the delivery of known acoustic pressures to treatment sites. Assessing the safety and efficacy of these systems relies upon characterization of ultrasound sources in order to determine the acoustic fields they produce and to understand performance changes over time. While direct hydrophone measurements of intense acoustic fields are possible, data acquisition throughout a treatment volume can be time-consuming and is only applicable to the specific source conditions tested. Moreover, measuring intense acoustic fields poses challenges for the hydrophone. An alternate approach combines low-amplitude pressure measurements with modeling of the nonlinear pressure field at various transducer power levels. In this work, low-intensity measurements were acquired for several therapeutic transducers. Pressure amplitude and phase were measured on a plane near the test transducer; the Rayleigh integral was used to back-propagate the acoustic field and mathematically reconstruct relative vibrations of the transducer surface. Such holographic reconstructions identified the vibratory characteristics of different types of transducers, including a 256-element clinical array. These reconstructions can be used to define boundary conditions for modeling and to record characteristics of transducer performance.

In vivo tissue emulsification using millisecond boiling induced by high intensity focused ultrasound

Khokhlova, T.D., J.C. Simon, Y.-N. Wang, V.A. Khokhlova, M. Paun, F.L. Starr, P.J. Kaczkowski, L.A. Crum, J.H. Hwang, and M.R. Bailey, "In vivo tissue emulsification using millisecond boiling induced by high intensity focused ultrasound," J. Acoust. Soc. Am., 129, 2477, doi:10.1121/1.3588149, 2011.

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1 Apr 2011

Shock-wave heating and millisecond boiling in high intensity focused ultrasound fields have been shown to result in mechanical emulsification of ex-vivo tissue. In this work, the same in situ exposures were applied in vivo in pig liver and in mice bearing 5-7 mm subcutaneous tumors (B16 melanoma) on the hind limb. Lesions were produced using a 2-MHz annular array in the case of pig liver (shock amplitudes up to 98 MPa) and a 3.4-MHz single-element transducer in the case of mouse tumors (shock amplitude of 67 MPa). The parameters of the pulsing protocol (1-500 ms pulse durations and 0.01-0.1 duty factor) were varied depending on the extent of desired thermal effect. All exposures were monitored using B-mode ultrasound. Mechanical and thermal tissue damage in the lesions was evaluated histologically using H&E and NADH-diphorase staining. The size and shape of emulsified lesions obtained in-vivo agreed well with those obtained in ex-vivo tissue samples using the same exposure parameters. The lesions were successfully produced both in bulk liver tissue at depths of 1-2 cm and in superficial tumors at depths less than 1 mm without damaging the skin.

Investigation of the effect of signal amplitude on twinkling artifact

Lu, W., B.W. Cunitz, O.A. Sapozhnikov, P.J. Kaczkowski, J.C. Kucewicz, N.R. Owen, M.R. Bailey, and L.A. Crum, "Investigation of the effect of signal amplitude on twinkling artifact," J. Acoust. Soc. Am., 129, 2376, doi: 10.1121/1.3587698, 2011.

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1 Apr 2011

Twinkling artifact on color Doppler ultrasound is the color labeling of hard objects, such as kidney stones, in the image. The origin of the artifact is unknown, but clinical studies have shown that twinkling artifact can improve the sensitivity of detection of stones by ultrasound. Although Doppler detection normally correlates changes in phase with moving blood, here the effect of amplitude on the artifact is investigated. Radio-frequency and in-phase and quadrature (IQ) data were recorded by pulse-echo ensembles using a software-programmable ultrasound system. Various hard targets in water and in tissue were insonified with a linear probe, and rectilinear pixel-based imaging was used to minimize beam-forming complexity. In addition, synthesized radio-frequency signals were sent directly into the ultrasound system to separate acoustic and signal processing effects. Artifact was observed both in onscreen and post-processed images, and as high statistical variance within the ensemble IQ data. Results showed that twinkling artifact could be obtained from most solid objects by changing the Doppler gain, yet signal amplitude did not have to be sufficiently high to saturate the receive circuits. In addition, low signal but high time gain compensation created the largest variance.

Phase propagation in ultrasonic backscatter monitoring of high-intensity focused ultrasound therapy

Speyer, G., P. Kaczkowski, A. Brayman, and L. Crum, "Phase propagation in ultrasonic backscatter monitoring of high-intensity focused ultrasound therapy," J. Acoust. Soc. Am., 129, 2439, doi:10.1121/1.3587983, 2011.

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1 Apr 2011

Phase propagation using the Rytov method has recently been proposed as a means for modeling the time-of-flight changes induced by thermal therapy [Speyer et al., J. Acoust. Am. 127]. These results are extended to measurements from a linear array, under which the general problem of imaging material changes is cast. The linear array offers several design components, which can be exploited for therapy monitoring, including the apodization and probing frequency. Phase propagation models are shown to be consistent with many aspects of conventional modeling, linearizing material changes around the same operating points as have been proposed by other researchers, and providing time-of-flight changes linearly related to the temperature distribution under these conditions. Beyond expanding on model properties, experimental evidence is presented, which indicates that phase propagation modeling is significantly more consistent with backscattered ultrasound data than conventional ray approaches

Prototype for expulsion of kidney stones with focused ultrasound

Shah, A., J.D. Harper, B.W. Cunitz, J.C. Kucewicz, Y.N. Wang, J.C. Simon, W. Lu, P.J. Kaczkowski, and M.R. Bailey, "Prototype for expulsion of kidney stones with focused ultrasound," J. Acoust. Soc. Am., 129, 2376, doi:10.1121/1.3587694, 2011.

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1 Apr 2011

Residual fragments remain in over 50% of treatments for lower pole kidney stones. A second-generation device based on a diagnostic ultrasound system and scanhead has been developed with a unique algorithm for stone detection and the capability to focus ultrasound to expel residual fragments. Focused ultrasound was applied to a bead on string in a water tank as well as to human stones (<5 mm) implanted in the lower pole of a live porcine model via retrograde ureteroscopy. Histological samples were collected and scored in a blinded fashion for therapeutic exposures and for super-therapeutic levels. The in-vitro bead was visually observed to move under focused ultrasound. Even with progressive manual displacement of the bead, the system continuously tracked and caused bead movement in real time. In the live porcine model, stones were expelled from the lower pole to the ureteropelvic junction in seconds to minutes using pulses at a duty factor of 0.02 and 8 W total acoustic power. Injury was observed no more frequently than in controls. Occurrence of injury rose slightly above control at a duty factor of 0.02 and 80 W and at a duty factor of 1 and 8 W.

Real-time tracking of renal calculi displaced by the radiation force of focused ultrasound

Illian, P.R., Jr., B.W. Cunitz, J.C. Kucewicz, M.R. Bailey, and P.J. Kaczkowski, "Real-time tracking of renal calculi displaced by the radiation force of focused ultrasound," J. Acoust. Soc. Am., 129, 2377, doi:10.1121/1.3587701, 2011.

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1 Apr 2011

An area of active research involves using the radiation force of ultrasound to expel small kidney stones or fragments from the kidney. The goal of this work is real-time motion tracking for visual feedback to the user and automated adaptive pushing as the stone moves. Algorithms have been designed to track stone movement during patient respiration but the challenge here is to track the stone motion relative to tissue. A new algorithm was written in MATLAB and implemented on an open-architecture, software-based ultrasound system. The algorithm was first trained then implemented in real-time on B-mode IQ data recorded from phantom experiments and animal studies. The tracking algorithm uses an ensemble of image processing techniques (2-D cross-correlation, phase correlation, and feature-edge detection) to overlay color on the stone in the real-time images and to assign a color to indicate the confidence in the identification of the stone. Camera images as well as ultrasound images showed that the system was able to locate a moving stone, re-target, and apply a new focused push pulse at that location.

The Verasonics ultrasound system as a pedagogic tool in teaching wave propagation, scattering, beamforming, and signal processing concepts in physics and engineering

Kaczkowski, P.J., and R.E. Daigle, "The Verasonics ultrasound system as a pedagogic tool in teaching wave propagation, scattering, beamforming, and signal processing concepts in physics and engineering," J. Acoust. Soc. Am., 129, 2648, doi: 10.1121/1.3588831, 2011.

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1 Apr 2011

The Verasonics ultrasound system is a highly programmable data acquisition and processing platform designed to facilitate development of new medical ultrasound imaging methods. In contrast to conventional commercial ultrasound systems, individual element digitized rf data are available to the developer. All beamforming and postprocessing are done in software, and both the hardware data acquisition sequence and the host computer processing flow are programmable by the user using a MATLAB interface. Because the system is designed to be highly flexible, it can also be useful as a practical tool in teaching acoustic wave physics, transducer and array design, and data processing concepts, using benchtop scale homemade acoustic and elastic media, including flow models. For script evaluation and testing, the Verasonics system includes a hardware simulator that uses a simple point scatterer numerical model to compute rf backscatter data. rf data can also be recorded during a hardware acquisition, and then reprocessed using different user-developed algorithms for comparative study. Because the system is easy to learn, many fundamental concepts can be explored in a laboratory setting, using scattering media or custom transducers fabricated as part of the student experimental plan. The system enables sophisticated hands-on experience with acoustics beyond the numerical world.

Novel ultrasound method to reposition kidney stones

Shah, A., N. Owen, W. Lu, B. Cunitz, P. Kaczkowski, J. Harper, M. Bailey, and L. Crum, "Novel ultrasound method to reposition kidney stones," Urol. Res., 38, 491-495, doi:10.1007/s00240-010-0319-9, 2010.

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1 Dec 2010

The success of surgical management of lower pole stones is principally dependent on stone fragmentation and residual stone clearance. Choice of surgical method depends on stone size, yet all methods are subjected to post-surgical complications resulting from residual stone fragments. Here we present a novel method and device to reposition kidney stones using ultrasound radiation force delivered by focused ultrasound and guided by ultrasound imaging. The device couples a commercial imaging array with a focused annular array transducer.

Feasibility of repositioning stones was investigated by implanting artificial and human stones into a kidney-mimicking phantom that simulated a lower pole and collecting system. During experiment, stones were located by ultrasound imaging and repositioned by delivering short bursts of focused ultrasound. Stone motion was concurrently monitored by fluoroscopy, ultrasound imaging, and video photography, from which displacement and velocity were estimated. Stones were seen to move immediately after delivering focused ultrasound and successfully repositioned from the lower pole to the collecting system. Estimated velocities were on the order of 1 cm/s. This in vitro study demonstrates a promising modality to facilitate spontaneous clearance of kidney stones and increased clearance of residual stone fragments after surgical management.

Detection of blunt force trauma liver injuries using shear wave elastography

Yu, J., P. Kaczkowski, L. Crum, and S. Mitchell, "Detection of blunt force trauma liver injuries using shear wave elastography," J. Acoust. Soc. Am., 128, 2362-2362, 2010

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1 Oct 2010

Violent impacts, such as vehicle accidents, frequently yield injuries of the liver due to its size and its location in the abdominal cavity. Frequently these injuries are fractures which may lead to life-threatening hemorrhage. Currently, a fast means of non-invasively visualizing areas of injuries in the liver due to blunt force trauma does not exist; hence there is a need to develop better imaging modalities of hepatic injuries to assist in clinical assessments. In this study, we investigate the feasibility of visualizing liver fractures using shear wave elastography.

We hypothesize that there is a shear modulus discontinuity between the two edges of a fracture, and we expect that these discontinuities can be observed from the imaging at the boundary of the split. In testing the hypothesis, we first use optical methods to track and study the displacements and motion trajectories of different regions of a hepatic injury phantom in response to shear wave excitations. Then, following Fink et al. [Proc. IEEE Ultrason. Symp. 1767 (2002)], we implement similar methods with a Verasonics ultrasound system and examine the propagation of shear waves induced by the acoustic radiation force in tissue-mimicking phantoms and ex vivo liver.

Displacement analysis of diagnostic ultrasound backscatter: A methodology for characterizing, modeling, and monitoring high intensity focused ultrasound therapy

Speyer, G., P.J. Kaczkowski, A.A. Brayman, and L.A. Crum, "Displacement analysis of diagnostic ultrasound backscatter: A methodology for characterizing, modeling, and monitoring high intensity focused ultrasound therapy," J. Acoust. Soc. Am., 128, 104-120, 2010.

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1 Jul 2010

Accurate monitoring of high intensity focused ultrasound (HIFU) therapy is critical for widespread clinical use. Pulse-echo diagnostic ultrasound (DU) is known to exhibit temperature sensitivity through relative changes in time-of-flight between two sets of radio frequency (RF) backscatter measurements, one acquired before and one after therapy. These relative displacements, combined with knowledge of the exposure protocol, material properties, heat transfer, and measurement noise statistics, provide a natural framework for estimating the administered heating, and thereby therapy.

The proposed method, termed displacement analysis, identifies the relative displacements using linearly independent displacement patterns, or modes, each induced by a particular time-varying heating applied during the exposure interval. These heating modes are themselves linearly independent. This relationship implies that a linear combination of displacement modes aligning the DU measurements is the response to an identical linear combination of heating modes, providing the heating estimate. Furthermore, the accuracy of coefficient estimates in this approximation is determined a priori, characterizing heating, thermal dose, and temperature estimates for any given protocol. Predicted performance is validated using simulations and experiments in alginate gel phantoms. Evidence for a spatially distributed interaction between temperature and time-of-flight changes is presented.

Backscatter monitoring of high intensity focused ultrasound therapy using a parametric treatment model

Speyer, G., P. Kaczkowski, A. Brayman, and L. Crum, "Backscatter monitoring of high intensity focused ultrasound therapy using a parametric treatment model," In Proceedings, Ninth International Symposium on Therapeutic Ultrasound, Aix-en-Provence, 24-26 September 2009, K. Hynynen and J. Souquet, eds.,62-65 (AIP, 2010).

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9 Mar 2010

Accurate monitoring of high intensity focused ultrasound (HIFU) surgery is critical to ensuring proper treatment. Pulse-echo diagnostic ultrasound (DU) is a recognized modality for identifying temperature differentials using speckle tracking between two DU radio frequency (RF) frames [2], [4]. This observation has motivated non-parametric temperature estimation, which associates temperature changes directly with the displacement estimates.

We present an estimation paradigm termed displacement mode analysis (DMA), which uses physical modeling to associate particular patterns of observed displacement, called displacement modes, with corresponding modes of variation in the administered therapy. This correspondence allows DMA to estimate therapy directly using a linear combination of displacement modes, imbuing these displacement estimates into the reference using interpolation, and by aligning with the treatment frame, providing a therapy estimate with the heating modes. Since DMA is maximum likelihood estimation (MLE), the accuracy of its estimates can be assessed a priori, providing error bounds for estimates of applied heating, temperature, and thermal dose. Predicted performance is verified using both simulation and experiment for a point exposure of 4.2 Watts of electrical power in alginate, a tissue mimicking phantom.

Noninvasive determination of in situ heating rate using kHz acoustic emission and focused ultrasound

Anand, A., and P.J. Kaczkowski, "Noninvasive determination of in situ heating rate using kHz acoustic emission and focused ultrasound," Ultrasound Med. Biol., 35, 1662-1671, 2009.

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1 Oct 2009

For high-intensity focused ultrasound (HIFU) to be widely applicable in the clinic, robust methods of treatment planning, guidance and delivery need to be developed. These technologies would greatly benefit if patient specific tissue parameters could be provided as inputs so that the treatment planning and monitoring schemes are customized and tailored on a case by case basis. A noninvasive method of estimating the local in situ acoustic heating rate using the heat transfer equation (HTE) and applying novel signal processing techniques is presented in this article.

The heating rate is obtained by experimentally measuring the time required to raise the temperature of the therapeutic focus from a baseline temperature to boiling (here assumed to be 100 degrees C for aqueous media) and then solving the heat transfer equation iteratively to find the heating rate that results in the onset of boiling. The onset of boiling is noninvasively detected by measuring the time instant of onset of acoustic emissions in the audible frequency range due to violent collapse of bubbles. In vitro experiments performed in a tissue mimicking alginate phantom and excised turkey breast muscle tissue demonstrate that the noninvasive estimates of heating rate are in good agreement with those obtained independently using established methods. The results show potential for the applicability of these techniques in therapy planning and monitoring for therapeutic dose optimization using real-time acoustic feedback.

Radiation pressure from ultrasound to help kidney stones pass

Lu, W., A. Shah, B.W. Cunitz, P.J. Kaczkowski, O.A. Sapozhnikov, and M.R. Bailey, "Radiation pressure from ultrasound to help kidney stones pass," J. Acoust. Soc. Am., 126, 2213, doi:10.1121/1.3248749, 2009.

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1 Oct 2009

Residual kidney stone fragments often remain months after treatment. These fragments may nucleate new stones and contribute to a 50% recurrence within 5 years. Here, a research focused ultrasound device was used to generate fragment motion with the goal of facilitating passage. Natural and artificial stones 1–8 mm in length were surgically placed in the urine space in pig kidneys. The ultrasound source was a 2.75-MHz, eight-element annular array with a 6-cm radius of curvature. At adjustable focal depths of 5–8 cm, the focal pressure beam width in water was about 2 mm, and peak pressure was about 4 MPa. Targeting was done by ultrasound using B-mode and twinkling artifact that stones produce in Doppler mode. The commercial imaging probe was placed within and oriented down the axis of the therapy probe. Ultrasound and fluoroscopy showed the stones moving in real-time under the influence of the focused ultrasound. Stones moved on the order of 1 cm/s away from the source and several stones moved several centimeters down the ureter. It appeared that stones were affected only when directly in the focal beam, perhaps indicating that radiation pressure not streaming caused the motion.

Bounds on thermal dose estimates using ultrasonic backscatter monitoring of heating

Speyer, G., P. Kaczkowski, A. Brayman, M. Andrew, and L. Crum, "Bounds on thermal dose estimates using ultrasonic backscatter monitoring of heating," Proceedings, 8th International Symposium on Therapeutic Ultrasound, Minneapolis, MN, 10-13 September 2008, 251-255, doi:10.1063/1.3131424 (AIP, 2009).

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14 Apr 2009

Diagnostic ultrasound provides a means for estimating the spatial distribution of temperature in tissue in response to HIFU therapy. One approach to estimating the temperature is to distort backscattered ultrasound between two frames, one preceding and one following the treatment, in a manner consistent with the heat equation, the exposure protocol, the beam pattern, and the specific material properties of the tissue. Ascribing a probability distribution to the measurements taken after treatment, the Cramer Rao bound may be determined for coefficient estimates in a functional expansion for the applied heating during therapy. This formulation also identifies the function with coefficient estimates having least variance, providing the lower bound. We study the implications of this characterization for heat deposition from a linear scan, examining how estimation accuracy is influenced by the lesion length and the delay following treatment and preceding acquisition. It is shown that for these studies, temperature estimates with accuracy well below 1°C are possible. In addition, the thermal dose can be estimated to tens of equivalent minutes, referenced to 43°C.

A Schlieren system for optical visualization of ultrasonic fields

Kaczkowski, P.J., M.R. Bailey, V.A. Khokhlova, and O.A. Sapozhnikov, "A Schlieren system for optical visualization of ultrasonic fields," J. Acoust. Soc. Am., 125, 2742, 2009.

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1 Apr 2009

Ultrasonic field mapping is an essential component of transducer characterization and of beam forming verification. Such measurements are commonly performed by displacing a hydrophone over a range of points within the field; these procedures can be time consuming. A calibrated hydrophone can provide accurate measurements of the field, subject to limitations of bandwidth and aperture of the device. A rapid qualitative 2D measurement of the spatial acoustic field can be obtained by optical means, in which the change in optical index due to the presence of acoustic pressure is imaged using a Schlieren approach.

This technique illuminates a transparent refracting acoustic medium using a plane collimated source and then focuses the transmitted light using a lens or mirror. In the absence of acoustic field, all of the light focuses to a small spot; acoustically induced refractive index perturbations cause some of the light to focus elsewhere. Obscuring the primary focal spot of unperturbed light with a mask permits imaging only the perturbations in the acoustic medium. We will describe a mirror-based Schlieren system for imaging continuous as well as pulsed fields and with color corresponding qualitatively to the intensity of the field.

Focused ultrasound: Concept for automated transcutaneous control of hemorrhage in austere settings

Kucewicz, J.C., M.R. Bailey, P.J. Kaczkowski, and S.J. Carter, "Focused ultrasound: Concept for automated transcutaneous control of hemorrhage in austere settings," Aviat. Space Environ. Med., 80, 391-394, 2009.

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1 Apr 2009

BACKGROUND:
High intensity focused ultrasound (HIFU) is being developed for a range of clinical applications. Of particular interest to NASA and the military is the use of HIFU for traumatic injuries because HIFU has the unique ability to transcutaneously stop bleeding. Automation of this technology would make possible its use in remote, austere settings by personnel not specialized in medical ultrasound. Here a system to automatically detect and target bleeding is tested and reported.

METHODS:
The system uses Doppler ultrasound images from a clinical ultrasound scanner for bleeding detection and hardware for HIFU therapy. The system was tested using a moving string to simulate blood flow and targeting was visualized by Schlieren imaging to show the focusing of the HIFU acoustic waves.

RESULTS:
When instructed by the operator, a Doppler ultrasound image is acquired and processed to detect and localize the moving string, and the focus of the HIFU array is electronically adjusted to target the string. Precise and accurate targeting was verified in the Schlieren images.

CONCLUSIONS:
An automated system to detect and target simulated bleeding has been built and tested. The system could be combined with existing algorithms to detect, target, and treat clinical bleeding.

Noninvasive measurement of local thermal diffusivity using backscattered ultrasound and focused ultrasound heating

Anand, A., and P.J. Kaczkowski, "Noninvasive measurement of local thermal diffusivity using backscattered ultrasound and focused ultrasound heating," Ultrasound Med. Biol., 34, 1449-1464, 2008.

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30 Sep 2008

Previously, noninvasive methods of estimating local tissue thermal and acoustic properties using backscattered ultrasound have been proposed in the literature. In this article, a noninvasive method of estimating local thermal diffusivity in situ during focused ultrasound heating using beamformed acoustic backscatter data and applying novel signal processing techniques is developed. A high intensity focused ultrasound (HIFU) transducer operating at subablative intensities is employed to create a brief local temperature rise of no more than 10 degrees C. Beamformed radio-frequency (RF) data are collected during heating and cooling using a clinical ultrasound scanner. Measurements of the time-varying "acoustic strain", that is, spatiotemporal variations in the RF echo shifts induced by the temperature related sound speed changes, are related to a solution of the heat transfer equation to estimate the thermal diffusivity in the heated zone. Numerical simulations and experiments performed in vitro in tissue mimicking phantoms and excised turkey breast muscle tissue demonstrate agreement between the ultrasound derived thermal diffusivity estimates and independent estimates made by a traditional hot-wire technique. The new noninvasive ultrasonic method has potential applications in thermal therapy planning and monitoring, physiological monitoring and as a means of noninvasive tissue characterization.

Quantitative assessment of thermal dose using photographic measurements of tissue discoloration

Speyer, G., P. Kaczkowski, A. Brayman, M. Andrew, S. Kargl, and L.A. Crum, "Quantitative assessment of thermal dose using photographic measurements of tissue discoloration," J. Acoust. Soc. Am., 123, 3223, 2008.

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1 May 2008

High Intensity Focused Ultrasound (HIFU) is rapidly gaining widespread clinical use in China, and is undergoing regulatory evaluation in Europe and the US for many target diseases. Nevertheless, tools for therapy planning, monitoring, and assessment remain at a rudimentary level. In particular, measurement of thermal dose in tissues exposed with HIFU has not been sufficiently quantitative to make detailed comparisons with numerical simulations, required for validation of therapy planning models. Indeed, model validation is complicated by high sensitivity of the results to small changes in parameter values and by the general difficulty of performing geometrical registration with sufficient precision to meaningfully compare millimeter scale features typical of HIFU lesions. Our work uses photographic measurement of visible tissue discoloration so that it can be used to accurately and rapidly quantify HIFU-induced bioeffects at scales of several centimeters for comparison with the prior therapy plan. Precise comparison between nonlinear acoustic simulation and macroscopic lesion data indicates that a newly defined "blanching index" is nearly linearly proportional to the logarithm of predicted thermal dose over a very wide range of exposure, including well below the 240 minute (at 43 degrees) necrotic threshold up to about 10,000 minutes.

Therapeutic ultrasound induced cell death from a histological perspective

Brayman, A., P. Kaczkowski, Y.-N. Wang, M. Andrew, L.A. Crum, S. Kargl, and G. Speyer, "Therapeutic ultrasound induced cell death from a histological perspective," J. Acoust. Soc. Am., 123, 2996, doi:10.1121/1.2932547, 2008.

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1 May 2008

High-power, short-exposure time, High Intensity Focused Ultrasound (HIFU) treatment protocols are under development that offer the potential to increase procedure throughput and optimize individual therapies. Histological examination and optical image analysis of tissues following dynamic HIFU exposure in ex vivo bovine liver have revealed that cells undergo a fundamentally different form of cell death. The rapid temperature rise due to the HIFU exposure leaves the cells structurally intact but no longer viable, similar to the cell "fixation" induced by snap-freezing. These results suggest that careful choice of both staining technique and metric for determining cell death are important in quantifying type and morphology of cell ablation, and more broadly, safety and efficacy of treatment. This finding is similar to those obtained and under discussion in the laser and RF ablation communities. Specifically, the NADH staining technique is superior to H&E for assessing cell viability, and an alternative measure of cell death may be preferable to the binary thermal dose threshold currently the standard for HIFU treatment.

Use of a bovine eye lens for observation of HIFU-induced lesions in real-time

Lafon, C., V.A. Khokhlova, O.A. Sapozhnikov, P.J. Kaczkowski, A.A. Brayman, M.R. Bailey, and L.A. Crum, "Use of a bovine eye lens for observation of HIFU-induced lesions in real-time," Ultrasound Med. Biol. 32, 1731-1741, 2006.

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1 Nov 2006

Study of coagulative lesion formation by high intensity focused ultrasound (HIFU) in tissue usually requires performing a sequence of experiments under different exposure conditions followed by tissue sectioning. This paper, inspired by the pioneering work of Frederic L. Lizzi, reports on the use of the bovine eye lens as a laboratory model to observe visually the development of HIFU-induced lesions. The first part of this work describes the measurement of the lens shape, density, sound speed and attenuation. The measured values were within the range of previously published values. In the second part, HIFU-induced lesion development was observed in real-time and compared with good agreement with theoretical simulation. Theoretical modeling included acoustic propagation, absorptive heating and thermal dose, as well as the experimentally measured lens characteristics. Thus, the transparent eye lens can be used as a laboratory phantom to facilitate the understanding of HIFU treatment in other tissues.

Effects of nonlinear propagation, cavitation, and boiling in lesion formation by high intensity focused ultrasound in a gel phantom

Khokhlova, V.A., M.R. Bailey, J.A. Reed, B.W. Cunitz, P.J. Kaczkowski, and L.A. Crum, "Effects of nonlinear propagation, cavitation, and boiling in lesion formation by high intensity focused ultrasound in a gel phantom," J. Acoust. Soc. Am., 119, 1834-1848, 2006.

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1 May 2006

The importance of nonlinear acoustic wave propagation and ultrasound-induced cavitation in the acceleration of thermal lesion production by high intensity focused ultrasound was investigated experimentally and theoretically in a transparent protein-containing gel. A numerical model that accounted for nonlinear acoustic propagation was used to simulate experimental conditions. Various exposure regimes with equal total ultrasound energy but variable peak acoustic pressure were studied for single lesions and lesion stripes obtained by moving the transducer. Static overpressure was applied to suppress cavitation. Strong enhancement of lesion production was observed for high amplitude waves and was supported by modeling. Through overpressure experiments it was shown that both nonlinear propagation and cavitation mechanisms participate in accelerating lesion inception and growth. Using B-mode ultrasound, cavitation was observed at normal ambient pressure as weakly enhanced echogenicity in the focal region, but was not detected with overpressure. Formation of tadpole-shaped lesions, shifted toward the transducer, was always observed to be due to boiling. Boiling bubbles were visible in the gel and were evident as strongly echogenic regions in B-mode images. These experiments indicate that nonlinear propagation and cavitation accelerate heating, but no lesion displacement or distortion was observed in the absence of boiling.

Microbubble cavitation, boiling, and nonlinear acoustic propagation in high-intensity focused ultrasound therapy

Kaczkowski, P.J., M.R. Bailey, L.A. Crum, V.A. Khokhlova, and A. Anand, "Microbubble cavitation, boiling, and nonlinear acoustic propagation in high-intensity focused ultrasound therapy," J. Acoust. Soc. Am., 119, 3211, 2006.

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1 May 2006

The investigation of high-intensity focused ultrasound (HIFU) as a tool for noninvasive thermally ablative therapy has required deeper understanding of the relative roles of nonlinear mechanisms involved in heat deposition. Attempts at quantifying the dose response to particular exposure conditions in vitro are complicated by the interplay of several mechanisms. These include microbubble cavitation, nonlinear acoustic propagation and attenuation, dependence of tissue parameters on temperature and temperature history, and formation and evolution of vapor bubbles due to boiling. One immediately evident consequence of such effects is distortion of coagulative lesion shape and size, colloquially evolving from cigars to tadpoles. Developing a quantitative understanding of the relative roles of relevant nonlinear mechanisms is not straightforward, yet is desirable for design of algorithms for therapy planning and real-time monitoring using ultrasound. A historical perspective of research toward this end will be presented along with a recommendation for suitable terminology for the various physical acoustic regimes encountered in HIFU therapy.

Nonlinear mechanisms of heating by high-intensity focused ultrasound

Khokhlova, V.A., M.R. Bailey, M.S. Canney, P.J. Kaczkowski, and L.A. Crum, "Nonlinear mechanisms of heating by high-intensity focused ultrasound," J. Acoust. Soc. Am., 119, 3227, 2006.

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1 May 2006

Two major nonlinear mechanisms are known to influence HIFU heating: acoustic nonlinearity and cavitation. Heating may also result in formation of boiling vapor bubbles that grow much larger than the cavitation bubbles. The relevant role of these phenomena was investigated experimentally and numerically in a gel phantom. HIFU pressure thresholds for shock formation, cavitation, and boiling were measured using a fiber-optic probe hydrophone, passive cavitation detection, ultrasound and optical imaging, and thermocouples. The KZK and Bio-heat equations were employed to simulate experimental conditions. Elevated static pressure was applied to suppress bubbles and increase the boiling temperature, thus isolating the pure effect of acoustic nonlinearity in comparison of heating between short, high-amplitude and long, low-amplitude pulses of equal average intensity. The experimental results indicated that both nonlinear mechanisms accelerated lesion production with acoustic nonlinearity responsible for the greater effect. It was observed that lesion distortion and migration was due to boiling detected in as little as 40 ms within the center of the lesion, in agreement with nonlinear acoustic simulations. These data indicate that acoustic nonlinearity and the boiling play a significant role earlier in HIFU treatments than previously anticipated.

Effects of nonlinear propagation, cavitation, and boiling in lesion formation by high intensity focused ultrasound in a gel phantom

Khokhlova, V.A., M.R. Bailey, J.A. Reed, B.W. Cunitz, P.J. Kaczkowski, and L.A. Crum, "Effects of nonlinear propagation, cavitation, and boiling in lesion formation by high intensity focused ultrasound in a gel phantom," J. Acoust. Soc. Am., 119, 1834-1848, doi:10.1121/1.2161440, 2006.

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1 Mar 2006

The importance of nonlinear acoustic wave propagation and ultrasound-induced cavitation in the acceleration of thermal lesion production by high intensity focused ultrasound was investigated experimentally and theoretically in a transparent protein-containing gel. A numerical model that accounted for nonlinear acoustic propagation was used to simulate experimental conditions. Various exposure regimes with equal total ultrasound energy but variable peak acoustic pressure were studied for single lesions and lesion stripes obtained by moving the transducer. Static overpressure was applied to suppress cavitation. Strong enhancement of lesion production was observed for high amplitude waves and was supported by modeling. Through overpressure experiments it was shown that both nonlinear propagation and cavitation mechanisms participate in accelerating lesion inception and growth. Using B-mode ultrasound, cavitation was observed at normal ambient pressure as weakly enhanced echogenicity in the focal region, but was not detected with overpressure. Formation of tadpole-shaped lesions, shifted toward the transducer, was always observed to be due to boiling. Boiling bubbles were visible in the gel and were evident as strongly echogenic regions in B-mode images. These experiments indicate that nonlinear propagation and cavitation accelerate heating, but no lesion displacement or distortion was observed in the absence of boiling.

Effects of nonlinear propagation, cavitation, and boiling in lesion formation by high intensity focused ultrasound in a gel phantom

Khokhlova, V.A., M.R. Bailey, J.A. Reed, B.W. Cunitz, P.J. Kaczkowski, and L.A. Crum, "Effects of nonlinear propagation, cavitation, and boiling in lesion formation by high intensity focused ultrasound in a gel phantom," J. Acoust. Soc. Am., 119, 1834, 2006.

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1 Mar 2006

The importance of nonlinear acoustic wave propagation and ultrasound-induced cavitation in the acceleration of thermal lesion production by high intensity focused ultrasound was investigated experimentally and theoretically in a transparent protein-containing gel. A numerical model that accounted for nonlinear acoustic propagation was used to simulate experimental conditions. Various exposure regimes with equal total ultrasound energy but variable peak acoustic pressure were studied for single lesions and lesion stripes obtained by moving the transducer. Static overpressure was applied to suppress cavitation. Strong enhancement of lesion production was observed for high amplitude waves and was supported by modeling. Through overpressure experiments it was shown that both nonlinear propagation and cavitation mechanisms participate in accelerating lesion inception and growth. Using B-mode ultrasound, cavitation was observed at normal ambient pressure as weakly enhanced echogenicity in the focal region, but was not detected with overpressure. Formation of tadpole-shaped lesions, shifted toward the transducer, was always observed to be due to boiling. Boiling bubbles were visible in the gel and were evident as strongly echogenic regions in B-mode images. These experiments indicate that nonlinear propagation and cavitation accelerate heating, but no lesion displacement or distortion was observed in the absence of boiling.

Gel phantom for use in high-frequency focused ultrasound dosimetry

Lafon, C., V. Zderic, M.L. Noble, J.C. Yuen, P.J. Kaczkowski, O.A. Sapozhnikov, F. Chavrier, L.A. Crum, and S. Vaezy, "Gel phantom for use in high-frequency focused ultrasound dosimetry," Ultrasound Med. Biol., 31, 1383-1389, 2005

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11 Oct 2005

An optically transparent phantom was developed for use in high-intensity focused ultrasound (US), or HIFU, dosimetry studies. The phantom is composed of polyacrylamide hydrogel, embedded with bovine serum albumin (BSA) that becomes optically opaque when denatured. Acoustic and optical properties of the phantom were characterized as a function of BSA concentration and temperature. The speed of sound (1544 m/s) and acoustic impedance (1.6 MRayls) were similar to the values in soft tissue. The attenuation coefficient was approximately 8 times lower than that of soft tissues (0.02 Np/cm/MHz for 9% BSA). The nonlinear (B/A) coefficient was similar to the value in water. HIFU lesions were readily seen during formation in the phantom. In US B-mode images, the HIFU lesions were observed as hyperechoic regions only if the cavitation activity was present. The phantom can be used for fast characterization and calibration of US-image guided HIFU devices before animal or clinical studies.

Monitoring high-intensity focused ultrasound (HIFU) therapy using radio frequency ultrasound backscatter to quantify heating

Kaczkowski, P.J., and A. Anand, "Monitoring high-intensity focused ultrasound (HIFU) therapy using radio frequency ultrasound backscatter to quantify heating," J. Acoust. Soc. Am., 118, 1882, 2005

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1 Sep 2005

The spatial distribution and temporal history of tissue temperature is an essential indicator of thermal therapy progress, and treatment safety and efficacy. Magnetic resonance methods provide the gold standard noninvasive measurement of temperature but are costly and cumbersome compared to the therapy itself. We have been developing the use of ultrasound backscattering for real-time temperature estimation; ultrasonic methods have been limited to relatively low temperature rise, primarily due to lack of sensitivity at protein denaturation temperatures (50–70<th>°C). Through validation experiments on gel phantoms and ex vivo tissue we show that temperature rise can be accurately mapped throughout the therapeutic temperature range using a new BioHeat Transfer Equation (BHTE) model-constrained inverse approach. Speckle-free temperature and thermal dose maps are generated using the ultrasound calibrated model over the imaged region throughout therapy delivery and post-treatment cooling periods. Results of turkey breast tissue experiments are presented for static HIFU exposures, in which the ultrasound calibrated BHTE temperature maps are shown to be very accurate (within a degree) using independent thermocouple measurements. This new temperature monitoring method may speed clinical adoption of ultrasound-guided HIFU therapy.

Processing ultrasound backscatter to monitor high-intensity focused ultrasound (HIFU) therapy

Kaczkowski, P.J., A. Anand, and M.R. Bailey, "Processing ultrasound backscatter to monitor high-intensity focused ultrasound (HIFU) therapy," J. Acoust. Soc. Am., 118, 1876, 2005

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1 Sep 2005

The development of new noninvasive surgical methods such as HIFU for the treatment of cancer and internal bleeding requires simultaneous development of new sensing approaches to guide, monitor, and assess the therapy. Ultrasound imaging using echo amplitude has long been used to map tissue morphology for diagnostic interpretation by the clinician. New quantitative ultrasonic methods that rely on amplitude and phase processing for tissue characterization are being developed for monitoring of ablative therapy. We have been developing the use of full wave ultrasound backscattering for real-time temperature estimation, and to image changes in tissue backscatter spectrum as therapy progresses. Both approaches rely on differential processing of the backscatter signal in time, and precise measurement of phase differences. Noise and artifacts from motion and nonstationary speckle statistics are addressed by constraining inversions for tissue parameters with physical models. We present results of HIFU experiments with static point and scanned HIFU exposures in which temperature rise can be accurately mapped using a new heat transfer equation (HTE) model-constrained inverse approach. We also present results of a recently developed spectral imaging method that elucidates microbubble-mediated nonlinearity not visible as a change in backscatter amplitude.

Bioheat Transfer Model (BHTE) based temperature estimation technique for high intensity focused ultrasound therapy monitoring

Kaczkowski, P.J., and A. Anand, "Bioheat Transfer Model (BHTE) based temperature estimation technique for high intensity focused ultrasound therapy monitoring," J. Acoust. Soc. Am., 117, 2444, 2005

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2 Apr 2005

The spatial distribution of tissue temperature is an essential indicator of thermal therapy progress, treatment safety and efficacy. Here, it is shown through in vitro experiments that temperature rise can be accurately measured during therapy delivery and post-treatment cool down phases using RF backscatter data collected with a modified ultrasound scanner. RF data is acquired prior to, during, and after HIFU exposures, in tissue mimicking phantoms and excised animal tissue. Through two calibration experiments, initial estimates for key BHTE parameters (local thermal diffusivity, and magnitude of the HIFU heat source) and the temperature dependence of ultrasonic travel time are obtained prior to therapy. Tissue heterogeneity over a larger targeted region of interest is modeled as a change in the magnitude of the focal heat source. During therapy this magnitude is updated using an iterative optimization technique that minimizes the difference between predicted and measured travel time values. Temperature and thermal dose maps are generated throughout therapy delivery and post-treatment cooling periods. The ultrasound derived estimates are validated against independent thermocouple measurements close to but not at the HIFU focus. This model-based technique permits noninvasive temperature estimation throughout the entire therapeutic range, and is thus a departure from previously reported techniques.

Vector-Doppler ultrasound for the detection of internal bleeding

Cunitz, B.W., P.J. Kaczkowski, and A.A. Brayman, "Vector-Doppler ultrasound for the detection of internal bleeding," J. Acoust. Soc. Am., 117, 2584, 2005

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2 Apr 2005

A vector Doppler (VDop) ultrasound system uses a transmitter and a spatially separated pair of receivers to measure bistatic scattering from blood. VDop has two principal advantages over color-flow Doppler in identifying internal bleeding: (1) measures flow direction, and thus absolute magnitude of flow velocity (2) does not require special orientation to detect and measure flow, thus can measure flows perpendicular to the transmitter. Our hypothesis is that real-time flow direction and magnitude can be used to detect and characterize internal bleeding. A real-time vector Doppler system has been built and tested in vitro. The system is capable of measuring flow magnitude and direction up to 145 cm/s at a depth of 3.6 cm at a processing rate of 10 Hz. Accuracy was measured using a calibrated moving string phantom and the system performs well within a useful range. A blood flow phantom was developed to mimic arterial flow into an open cavity as well as into tissue and replicate both pulsatile flow as well as the energy storage due to vascular elasticity. Flow signature data is gathered under conditions of normal branching flow, and vessel breach. The talk will describe the VDop system and the flow phantom and summarize results.

Design and evaluation of complex moving HIFU treatment protocols

Kargl, S.G., M.A. Andrew, P.J. Kaczkowski, A.A. Brayman, and L.A. Crum, "Design and evaluation of complex moving HIFU treatment protocols," Proceedings, American Institute of Physics Conference, number 754, 140-142, doi:10.1063/1.1901621 (2005).

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28 Mar 2005

The use of moving high-intensity focused ultrasound (HIFU) treatment protocols is of interest in achieving efficient formation of large-volume thermal lesions in tissue. Judicious protocol design is critical in order to avoid collateral damage to healthy tissues outside the treatment zone. A KZK–BHTE model, extended to simulate multiple, moving scans in tissue, is used to investigate protocol design considerations. Prediction and experimental observations are presented which 1) validate the model, 2) illustrate how to assess the effects of acoustic nonlinearity, and 3) demonstrate how to assess and control collateral damage such as prefocal lesion formation and lesion formation resulting from thermal conduction without direct HIFU exposure. Experimental data consist of linear and circular scan protocols delivered over a range of exposure regimes in ex vivo bovine liver.

Non-invasive measurement of in situ thermal diffusivity and local heat source using backscattered ultrasound for thermal therapy planning and monitoring

Anand, A., and P. Kaczkowski, "Non-invasive measurement of in situ thermal diffusivity and local heat source using backscattered ultrasound for thermal therapy planning and monitoring," J. Acoust. Soc. Am., 117, 2445, 2005.

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30 Jan 2005

Bioheat transfer equation (BHTE) estimates of applied dose during HIFU therapy typically use prior knowledge or assume standard values for tissue properties that determine thermal diffusivity (K) and heat source (Q). We have developed a novel signal-processing based technique to noninvasively estimate these parameters in situ based on analysis of raw backscattered RF data from two localized HIFU exposures, one at sub-ablative intensities to determine K, and another at therapeutic intensities to obtain Q. Both exposures are performed prior to therapy. To estimate K, a short HIFU exposure is applied resulting in a temperature rise of less than 15°C. The Gaussian radius of the temperature induced apparent strain profile during cool down is estimated and fit to an approximate analytical heat diffusion expression to obtain K. Independent estimates of K derived using the transient hotwire technique validated the ultrasonic measurements. To estimate Q, an audio range hydrophone was acoustically coupled to the sample to detect the onset of boiling. The time required to bring the sample to boiling was used to estimate Q by iteration of a numerical BHTE model. These results are validated against in situ measured values using thermocouples and linear acoustic calculations.

Cavitation detection and suppression in HIFU

Bailey, M.R., J. Reed, A. Anand, P. Kaczkowski, W. Kreider, S. Vaezy, L.A. Crum, R. Seip, J. Tavakkoli, and N.T. Sanghvi, "Cavitation detection and suppression in HIFU," Proceedings of the 3rd International Symposium on Therapeutic Ultrasound, edited by J.Y. Chapelon and C. Lafon, 42-48 (Lyon, France, INSERM, 2004).

15 Sep 2004

Circular scanned thermal lesions in ex vivo bovine liver

Andrew, M., S. Kargl, P. Kaczkowski, B. Cunitz, and A. Brayman, "Circular scanned thermal lesions in ex vivo bovine liver," Proceedings of the 3rd International Symposium on Therapeutic Ultrasound, edited by J.Y. Chapelon and C. Lafon, 359-364 (Lyon, France, INSERM, 2004).

15 Sep 2004

Nonlinear effects in HIFU lesion production in tissue-mimicking phantom

Khokhlova, V., P.J. Kaczkowski, B.W. Cunitz, M.R. Bailey, J.A. Reed, M. Nakazawa, and L.A. Crum, "Nonlinear effects in HIFU lesion production in tissue-mimicking phantom," Proceedings of the 3rd International Symposium on Therapeutic Ultrasound, edited by J.Y. Chapelon and C. Lafon, 275-280 (Lyon, France, INSERM, 2004).

15 Sep 2004

Monitoring formation of high intensity focused ultrasound (HIFU) induced lesions using backscattered ultrasound

Anand, A., and P.J. Kaczkowski, "Monitoring formation of high intensity focused ultrasound (HIFU) induced lesions using backscattered ultrasound," ARLO, 5, 88-94, doi:10.1121/1.1652131, 2004.

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16 Mar 2004

Backscattered radio frequency (RF) data collected in a series of in vitro experiments, in which HIFU lesions were created in bovine liver tissue, were analyzed using two signal processing approaches to visualize temporal evolution of lesion formation. Change in round-trip travel time provides information related to temperature change during and after therapy. Changes in the RF spectrum related to changes in scattering properties of the heated region were observed before visible changes appeared on B-mode images. Effect of increased attenuation in the necrosed tissue region was also observed. Results demonstrate potential for these two techniques in image-guided HIFU therapy.

Acoustic hemostasis

Crum, L., M. Andrew, M. Bailey, K. Beach, A. Brayman, F. Curra, P. Kaczkowski, S. Kargl, R. Martin, and S. Vaezy, "Acoustic hemostasis," J. Acoust. Soc. Am., 113, 2280, 2003.

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1 Oct 2003

Over the past several years, the Center for Industrial and Medical Ultrasound (CIMU) at the Applied Physics Laboratory in the University of Washington has undertaken a broad research program in the general area of High Intensity Focused Ultrasound (HIFU). Our principal emphasis has been on the use of HIFU to induce hemostasis; in particular, CIMU has sought to develop a small, lightweight, portable device that would use ultrasound for both imaging and therapy. Such a technology is needed because nearly 50% of combat casualty mortality results from exsanguinations, or uncontrolled bleeding. A similar percentage occurs for civilian death due to trauma. In this general review, a presentation of the general problem will be given, as well as our recent approaches to the development of an image-guided, transcutaneous, acoustic hemostasis device.

Study of a scanning HIFU therapy protocol, Part II: Experiment and results

Andrew, M.A., P.J. Kaczkowski, B.W. Cunitz, A.A. Brayman, and S.G. Kargl, "Study of a scanning HIFU therapy protocol, Part II: Experiment and results," J. Acoust. Soc. Am., 113, 2309, 2003.

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1 Oct 2003

Instrumentation and protocols for creating scanned HIFU lesions in freshly excised bovine liver were developed in order to study the in vitro HIFU dose response and validate models. Computer control of the HIFU transducer and 3-axis positioning system provided precise spatial placement of the thermal lesions. Scan speeds were selected in the range of 1 to 8 mm/s, and the applied electrical power was varied from 20 to 60 W. These parameters were chosen to hold the thermal dose constant. A total of six valid scans of 15 mm length were created in each sample; a 3.5 MHz single-element, spherically focused transducer was used. Treated samples were frozen, then sliced in 1.27 mm increments. Digital photographs of slices were downloaded to computer for image processing and analysis. Lesion characteristics, including the depth within the tissue, axial length, and radial width, were computed. Results were compared with those generated from modified KZK and BHTE models, and include a comparison of the statistical variation in the across-scan lesion radial width.

Polyacrylamide gel as an acoustic coupling medium for focused ultrasound therapy

Prokop, A.F., S. Vaezy, M.L. Noble, P.J. Kaczkowski, R.W. Martin, and L.A. Crum, "Polyacrylamide gel as an acoustic coupling medium for focused ultrasound therapy," Ultrasound Med. Biol., 29, 1351-1358, doi:10.1016/S0301-5629(03)00979-7 , 2003.

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1 Sep 2003

A hydrogel acoustic coupling medium was investigated as a practical alternative to water for clinical applications of focused ultrasound (US) therapy. Material characterization and functional testing of polyacrylamide gel couplers were performed. Acoustic, bulk and thermal properties were measured. Conical couplers were designed and fabricated to fit a 3.5-MHz, spherically concave transducer for functional tests, including Schlieren imaging, power efficiency measurements and in vivo hemostasis experiments. Polyacrylamide was shown to have favorable acoustic properties that varied linearly with acrylamide concentration from 10% to 20% weight in volume. Attenuation coefficient, sound speed and impedance ranged from 0.08 to 0.14 dB/cm at 1 MHz, 1546 to 1595 m/s and 1.58 to 1.68 Mrayl, respectively. An intraoperative in vivo hemostasis experiment in a sheep model demonstrated that the gel-coupled transducer was capable of inducing hemostasis in actively bleeding splenic and hepatic incisions. The results of this study show that polyacrylamide may be a promising coupling material for focused US therapy.

Experimental apparatus and methods for in vitro HIFU dose response studies

Andrew, M., P. Kaczkowski, A Brayman, B. Cunitz, A. Anand, C. Lafon, and L. Crum, "Experimental apparatus and methods for in vitro HIFU dose response studies," in Therapeutic Ultrasound, Proceedings of the 2nd International Symposium, M.A. Andrew, L.A. Crum and S. Vaezy, eds., 330-340 (American Institute of Physics Press, 2003).

1 Jun 2003

In vitro examination of nonlinear heat deposition in HIFU lesion formation

Kackzkowski, P., M. Andrew, A. Brayman, S. Kargl, B. Cunitz, C. Lafon, V. Khokhlova, and L.A. Crum, "In vitro examination of nonlinear heat deposition in HIFU lesion formation," in Therapeutic Ultrasound, Proceedings of the 2nd International symposium, M.A. Andrew, L.A. Crum, and S. Vaezy, eds., 341-352 (American Institute of Physics Press, 2003).

1 Jun 2003

Ultrasound rf signal analysis of HIFU-induced lesions

Anand, A., and P.J. Kaczkowski, "Ultrasound rf signal analysis of HIFU-induced lesions," Ultrason. Imaging, 25, 50-51, 2003.

1 Jun 2003

Using the ATL HDI-1000 ultrasound scanner to collect demodulated RF data for monitoring HIFU lesion formation

Anand, A.J., P.J. Kaczkowski, R.E. Daigle, L. Huang, M. Paun, K.W. Beach, and L.A. Crum, "Using the ATL HDI-1000 ultrasound scanner to collect demodulated RF data for monitoring HIFU lesion formation," Proc. SPIE, 5035, 316-326, doi:10.1117/12.479879, 2003

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18 Feb 2003

The ability to accurately track and monitor the progress of lesion formation during HIFU (High Intensity Focused Ultrasound) therapy is important for the success of HIFU-based treatment protocols. To aid in the development of algorithms for accurately targeting and monitoring formation of HIFU induced lesions, we have developed a software system to perform RF data acquisition during HIFU therapy using a commercially available clinical ultrasound scanner (ATL HDI 1000, Philips Medical Systems, Bothell, WA). The HDI 1000 scanner functions on a software dominant architecture, permitting straightforward external control of its operation and relatively easy access to quadrature demodulated RF data. A PC running a custom developed program sends control signals to the HIFU module via GPIB and to the HDI 1000 via Telnet, alternately interleaving HIFU exposures and RF frame acquisitions. The system was tested during experiments in which HIFU lesions were created in excised animal tissue. No crosstalk between the HIFU beam and the ultrasound imager was detected, thus demonstrating synchronization. Newly developed acquisition modes allow greater user control in setting the image geometry and scanline density, and enables high frame rate acquisition. This system facilitates rapid development of signal-processing based HIFU therapy monitoring algorithms and their implementation in image-guided thermal therapy systems. In addition, the HDI 1000 system can be easily customized for use with other emerging imaging modalities that require access to the RF data such as elastographic methods and new Doppler-based imaging and tissue characterization techniques.

Monitoring evolution of HIFU-induced lesions with backscattered ultrasound

Anand, A., and P.J. Kaczkowski, "Monitoring evolution of HIFU-induced lesions with backscattered ultrasound," J. Acoust. Soc. Am., 113, 2310, 2003.

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30 Jan 2003

Backscattered radio frequency (rf) data from a modified commercial ultrasound scanner were collected in a series of in vitro experiments in which high intensity focused ultrasound (HIFU) was used to create lesions in freshly excised bovine liver tissue. Two signal processing approaches were used to visualize the temporal evolution of lesion formation. First, apparent tissue motion due to temperature rise was detected using cross-correlation techniques. Results indicate that differential processing of travel time can provide temperature change information throughout the therapy delivery phase and after HIFU has been turned off, over a relatively large spatial region. Second, changes in the frequency spectrum of rf echoes due to changes in the scattering properties of the heated region were observed well before the appearance of hyper-echogenic spots in the focal zone. Furthermore, the increase in attenuation in the lesion zone changes the measured backscatter spectrum from regions distal to it along the imaging beam. Both effects were visualized using spectral processing and display techniques that provide a color spatial map of these features for the clinician. Our results demonstrate potential for these ultrasound-based techniques in targeting and monitoring of HIFU therapy, and perhaps post-treatment visualization of HIFU-induced lesions.

High-intensity focused ultrasound (HIFU) array system for image-guided ablative therapy (IGAT)

Kaczkowski, P.J., G.W. Keilman, B.W. Cunitz, R.W. Martin, S. Vaezy, and L.A. Crum, "High-intensity focused ultrasound (HIFU) array system for image-guided ablative therapy (IGAT)," Proceed., SPIE, 4954, 209-219, doi:10.1117/12.476539, 2003.

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26 Jan 2003

Recent interest in using High Intensity Focused Ultrasound (HIFU) for surgical applications such as hemostasis and tissue necrosis has stimulated the development of image-guided systems for non-invasive HIFU therapy. Seeking an all-ultrasound therapeutic modality, we have developed a clinical HIFU system comprising an integrated applicator that permits precisely registered HIFU therapy delivery and high quality ultrasound imaging using two separate arrays, a multi-channel signal generator and RF amplifier system, and a software program that provides the clinician with a graphical overlay of the ultrasound image and therapeutic protocol controls. Electronic phasing of a 32 element 2 MHz HIFU annular array allows adjusting the focus within the range of about 4 to 12 cm from the face. A central opening in the HIFU transducer permits mounting a commercial medical imaging scanhead (ATL P7-4) that is held in place within a special housing. This mechanical fixture ensures precise coaxial registration between the HIFU transducer and the image plane of the imaging probe. Recent enhancements include development of an acoustic lens using numerical simulations for use with a 5-element array. Our image-guided therapy system is very flexible and enables exploration of a variety of new HIFU therapy delivery and monitoring approaches in the search for safe, effective, and efficient treatment protocols.

Nonlinear regimes of lesion formation by HIFU in tissue-mimicking phantom

Khokhlova, V.A., P.J. Kaczkowski, B.W. Cunitz, M.R. Bailey, and L.A. Crum, "Nonlinear regimes of lesion formation by HIFU in tissue-mimicking phantom," Proceedings, 16th International Symposium on Nonlinear Acoustics, Moscow, Russia, 19-23 August, 129 (2002).

23 Aug 2002

A multi-channel high-intensity focused ultrasound (HIFU) system for image-guided therapy (IGT)

Kaczkowski, P.J., S. Vaezy, R. Martin, L.A. Crum, and G. Keilman, "A multi-channel high-intensity focused ultrasound (HIFU) system for image-guided therapy (IGT)," J. Acoust. Soc. Am., 110, 2614, 2001.

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1 Nov 2001

Recent success in using high-intensity focused ultrasound (HIFU) for surgical applications has stimulated the development of image-guided systems for noninvasive therapy. With the goal of developing an all ultrasound modality, we have developed a clinical HIFU system comprising an integrated transducer probe that permits precisely registered HIFU therapy delivery and high-quality ultrasound imaging, a multi-channel signal generator and rf amplifier system, and a software program that provides the clinician with a graphical overlay of the ultrasound image and therapeutic protocol controls. Electronic phasing of the 2-MHz HIFU annular array allows adjusting the focus within the range of about 4–12 cm from the face. A central opening in the transducer permits mounting of a commercial medical imaging scanhead (ATL P7-4) that is held in place within a special housing. This mechanical fixture ensures precise registration between the HIFU transducer axis and the image plane of the imaging probe. We will present a description of the various system components along with experimental in vitro results of therapy targeting and lesion visualization.

An innovative synthetic tissue-mimicking material for high-intensity focused ultrasound

Lafon, C., O.A. Sapozhnikov, P.J. Kaczkowski, S. Vaezy, M. Noble, and L.A. Crum, "An innovative synthetic tissue-mimicking material for high-intensity focused ultrasound," J. Acoust. Soc. Am., 110, 2613, 2001.

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1 Nov 2001

A dosimetry study of the high-temperature and pressure regimes involved in high-intensity focused ultrasound (HIFU) requires experiments on biological tissues because no synthetic tissue-mimicking phantom is available. Unfortunately, the development of coagulative lesions cannot be observed in real-time in opaque tissues. Furthermore, the natural heterogeneous structure of tissue complicates direct comparison with numerical models. In this study, a new optically transparent phantom is evaluated. It is principally composed of a polyacrylamide gel, and includes a thermally sensitive indicator protein that becomes optically diffusive when denatured. Various tests were undertaken to characterize the acoustical, thermal, and optical properties of this material for a range of protein concentrations. The attenuation coefficient can be usefully modified by adjusting the quantity of embedded proteins to permit some selection of acoustic regime. It is also possible to emphasize cavitation activity at lower BSA concentrations, or thermal effects at higher concentrations. This new phantom adequately matches tissue for most of the measured parameters and facilitates the study of the HIFU bioeffects.

Bubbles and acoustic image-guided high intensity focused ultrasound

Bailey, M.R., S. Vaezy, J.C. Yuen, A. Anand, N.A. Miller, P.J. Kaczkowski, and L.A. Crum, "Bubbles and acoustic image-guided high intensity focused ultrasound," J. Acoust. Soc. Am., 110, 2643, 2001.

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1 Nov 2001

Clinical diagnostic ultrasound (US) can be used to target and to monitor in real-time high-intensity focused ultrasound (HIFU) therapy. In our system, the HIFU transducer (3.5 MHz, 35 mm aperture, 55 mm radius of curvature) and US scan head (several were tested, center frequencies 3–8 MHz) are fixed with the HIFU focus in the imaging plane. HIFU and US are either synchronized real time to relegate interference to the image fringe or HIFU and US are interlaced for nearly real-time imaging. HIFU produces a localized hyperechoic region visible on B-mode US. Coagulatively necrosed lesions produced have similar size, shape, and location to measurements made from the corresponding US images. Thresholds are also comparable. However, in vivo, if HIFU is turned off as soon as hyperecho appears, no lesion is seen (the tissue was fixed within four hours of treatment). Thus, a short HIFU burst can be used to target treatment. Bubbles appear to be largely but perhaps not entirely responsible for the increase in echogenicity. Times for dissipation of the hyperecho and dissolution of a bubble as a function of hydrostatic pressure compare well. Significant overpressure (50 bar) can suppress hyperecho produced by HIFU.

Color Doppler detection of acoustic streaming in a hematoma model

Shi, X., R.W. Martin, S. Vaezy, P. Kaczkowski, and L.A. Crum, "Color Doppler detection of acoustic streaming in a hematoma model," Ultrasound Med. Biol., 27, 1255-1264, 2001.

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1 Sep 2001

Accurate differentiation between stagnant blood and soft tissue or clotted and unclotted blood has potential value in managing trauma patients with internal hemorrhage. Determination by regular ultrasound (US) imaging is sometimes difficult because the sonographic appearance of blood, clots and soft tissue may be similar. A hematoma model was developed to investigate the use of acoustic streaming for hematoma diagnosis in an in vivo environment. The results showed that a derated spatial peak temporal average (SPTA) intensity of 30 W/cm2 was needed to generate color-Doppler-detectable streaming in stirred blood. The streaming velocity increased in proportion to the derated intensity. Streaming was also detected in stagnant blood, but at higher intensities. In clots, streaming was not detected even at high intensities. The streaming detection may be a valuable tool for improving the distinction between liquid blood and clots or soft tissue in hematoma diagnosis.

Image-guided acoustic therapy

Vaezy, S., M. Andrew, P. Kaczkowski, and L.A. Crum, "Image-guided acoustic therapy," Annu. Rev. Biomed. Eng., 3, 375-390, 2001.

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1 Aug 2001

The potential role of therapeutic ultrasound in medicine is promising. Currently, medical devices are being developed that utilize high-intensity focused ultrasound as a noninvasive method to treat tumors and to stop bleeding (hemostasis). The primary advantage of ultrasound that lends the technique so readily to use in noninvasive therapy is its ability to penetrate deep into the body and deliver to a specific site thermal or mechanical energy with submillimeter accuracy. Realizing the full potential of acoustic therapy, however, requires precise targeting and monitoring. Fortunately, several imaging modalities can be utilized for this purpose, thus leading to the concept of image-guided acoustic therapy. This article presents a review of high-intensity focused ultrasound therapy, including its mechanisms of action, the imaging modalities used for guidance and monitoring, some current applications, and the requirements and technology associated with this exciting and promising field.

A new high intensity focused ultrasound applicator for surgical applications

Brentnall, M.D., R.W. Martin, S. Vaezy, P. Kaczkowski, F. Forster, and L.A. Crum, "A new high intensity focused ultrasound applicator for surgical applications," IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 48, 53-63, 2001.

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1 Jan 2001

Improved high-intensity focused ultrasound (HIFU) surgical applicators are required for use in a surgical environment. We report on the performance and characteristics of a new solid-cone HIFU applicator. Previous HIFU devices used a water-filled stand-off to couple the ultrasonic energy from the transducer to the treatment area. The new applicator uses a spherically-focused element and a solid aluminum cone to guide and couple the ultrasound to the tissue. Compared with the water-filled applicators, this new applicator is simpler to set up and manipulate, cannot leak, prevents the possibility of cavitation within the coupling device, and is much easier to sterilize and maintain during surgery. The design minimizes losses caused by shear wave conversion found in tapered solid acoustic velocity transformers operated at high frequencies. Computer simulations predicted good transfer of longitudinal waves. Impedance measurements, beam plots, Schlieren images, and force balance measurements verified strong focusing and suitable transfer of acoustic energy into water. At the focus, the -3 dB beam dimensions are 1.2 mm (axial) x 0.3 mm (transverse). Radiation force balance measurements indicate a power transfer efficiency of 40%. In vitro and in vivo tissue experiments confirmed the applicator's ability to produce hemostasis.

Real-time observation of inception and growth of HIFU-induced tissue lesions

Lafon, C., M.R. Bailey, L.N. Couret, P.J. Kaczkowski, A.A. Brayman, L.A. Crum, and O.A. Sapozhnikov, "Real-time observation of inception and growth of HIFU-induced tissue lesions," J. Acoust. Soc. Am., 108, 2546, 2000.

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1 Nov 2000

To study the biological effects of high-intensity focused ultrasound (HIFU), experiments are usually performed on isolated or perfused tissues. Indeed, the complex phenomena occurring in tissue during HIFU-induced coagulation necrosis is difficult to mimic with synthetic phantoms. A good phantom should first match the acoustical and thermal properties of tissues. Furthermore, heating above a thermal threshold should induce a permanent, localized and observable change corresponding to protein denaturing in tissue. Lastly, the choice of a transparent material makes possible real-time examination of the development of coagulation necroses. We have used bovine eye lenses in this aim. The density, sound speed, attenuation, and thermal threshold for irreversible damage to the bovine lens were measured and found to be similar to those for liver or muscle, common tissues for HIFU experiments, although acoustic attenuation is slightly higher in the lens. Transparency of the lens allowed us to observe HIFU-induced lesion evolution in real time. The shape and size of the lesions obtained in the lens agreed well with results obtained in liver. In conclusion, the transparent bovine eye lens is a useful model for visualization of thermal lesions.

Acoustic hemostasis

Crum, L.A., K. Beach, S. Carter, W. Chandler, F.P. Curra, P. Kaczkowski, G. Keilman, V. Khokhlova, R. Martin, P.D. Mourad, and S. Vaezy, "Acoustic hemostasis," in Nonlinear Acoustics at the Turn of the Millennium, edited by W. Lauterborn and T. Kurz, 13-22 (American Institute of Physics, New York, 2000).

1 Aug 2000

Inventions

Multilayer Ultrasound Transducer Devices for High Power Transmission and Wide-band Reception and Associated Systems and Methods

Patent Number: 8,500,643

Francesco Curra, Peter Kaczkowski, Neil Owen

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Patent

6 Aug 2013

Multilayer ultrasound transducer devices for high power transmission and wide-band reception and associated methods and systems are disclosed herein. An ultrasound transducer device in accordance with an embodiment of the present technology, for example, can include a first array of first transducers and a second array of second transducers that are oriented substantially parallel to one another. The first transducers can include a first piezoelectric material that is configured to transmit acoustic waves, and the second transducers can include a second piezoelectric material that is configured to receive echoes from the acoustic waves. The ultrasound transducer device can further include an electrical connection layer between the first and second arrays that is electrically coupled to the first and second transducers.

Method for Testing the Functionality of an Ultrasound Probe

Record of Invention Number: 45890

Peter Kaczkowski, John Kucewicz, Francesco Curra, Justin Reed

Disclosure

20 Dec 2011

Filtering Method for Supression of Non-stationary Reverberation in Ultrasound Images

Record of Invention Number: 45889

Francesco Curra, Justin Reed, John Kucewicz, Peter Kaczkowski

Disclosure

15 Dec 2011

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Non-invasive Temperature Estimation Technique for HIFU Therapy Monitoring Using Backscattered Ultrasound

Patent Number: US 8,016,757 B2

Peter Kaczkowski, Ajay Anand

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Patent

13 Sep 2011

Ultrasound data are collected from a thermal source and a mass of tissue before initiating therapy to measure two parameters of the bio-heat transfer equation (BHTE). The parameters are the thermal diffusivity (K) of the tissue and the magnitude of the thermal source (Q). Once the parameters have been obtained, the BHTE can be calibrated to the specific mass of tissue and the specific thermal source. The calibrated BHTE can be used to generate a temperature dependence curve calibrated to the thermal source and tissue, and spatio-temporal temperature maps, to facilitate pre-therapy planning. During therapy, ultrasound data are collected to determine if Q changes during therapy, and if so, the BHTE is recalibrated using the new Q value, increasing an accuracy of the temperature estimations.

Portable Acoustic Holography System for Therapeutic Ultrasound Sources

Record of Invention Number: 45469

Mike Bailey, Peter Kaczkowski, Vera Khokhlova, Wayne Kreider, Oleg Sapozhnikov

Disclosure

21 Dec 2010

Multilayer Ultrasound Transducer for High-Power Transmission of Wideband Reception

Record of Invention Number: 8412D

Francesco Curra, Peter Kaczkowski, Neil Owen

Disclosure

7 Jul 2009

Method for Diagnostic Ultrasound-based Monitoring of High Intensity Focused Ultrasound Therapy

Record of Invention Number: 8309D

Andrew Brayman, Larry Crum, Peter Kaczkowski, Gavriel Speyer

Disclosure

9 Mar 2009

Solid Hydrogel Coupling for Ultrasound Imaging and Therapy

Patent Number: US 7,070,565 B2

Shahram Vaezy, Adrian Prokop, Roy W. Martin, Peter Kaczkowski, Misty Noble

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Patent

4 Jul 2006

The present invention employs hydrogels as acoustic couplings for clinical applications of ultrasound imaging and therapy, but is particularly applicable to high intensity focused ultrasound (HIFU) based therapy. While other materials can be used, it has been determined that polyacrylamide is sufficiently robust and transmissive to withstand the high temperatures encountered in HIFU therapy. One embodiment of a hydrogel coupling is configured in shape and size (length) to ensure that a focal region of an ultrasound transducer is disposed proximate the target area when the distal tip of the transducer is in contact with tissue. These couplings can be shaped to correspond to the beam focus characteristics of specific transducers. Water can be applied to hydrate the tip of the hydrogel coupling during use, and medication absorbed into the hydrogel material can be applied to the tissue in contact with the distal surface of the hydrogel.

Method and Apparatus for Medical Procedures Using High-Intensity Focused Ultrasound

Patent Number: US 6,432,067 B1

Roy W. Martin, Larry Crum, Shahram Vaezy, Stephen J. Carter, W. Scott Helton, Michael Gaps, Peter Kaczkowski, Andrew Proctor

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Patent

13 Aug 2002

Methods and apparatus for enabling substantially bloodless surgery and for stemming hemorrhaging. High intensity focused ultrasound (HIFU) is used to form cauterized tissue regions prior to surgical incision, for example, forming a cauterized tissue shell around a tumor to be removed. The procedure is referred to as "presurgical volume cauterization." In one embodiment, the method is particularly effective for use in surgical lesion removal or resection of tissue having a highly vascularized constitution, such as the liver or spleen, and thus a propensity for hemorrhaging. In further embodiments, methods and apparatus for hemostasis using HIFU is useful in both surgical, presurgical, and medical emergency situations. In an apparatus embodiment, a telescoping, acoustic coupler is provided such that depth of focus of the HIFU energy is controllable. In other embodiments, apparatus characterized by portability are demonstrated, useful for emergency medical situations.

Method and Apparatus for Medical Procedures Using High-Intensity Focused Ultrasound

Patent Number: US 6,315,741 B1

Roy W. Martin, Larry Crum, Shahram Vaezy, Stephen J. Carter, W. Scott Helton, Michael Gaps, Peter Kaczkowski, Andrew Proctor

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Patent

13 Nov 2001

Methods and apparatus for enabling substantially bloodless surgery and for stemming hemorrhaging. High intensity focused ultrasound (HIFU) is used to form cauterized tissue regions prior to surgical incision, for example, forming a cauterized tissue shell around a tumor to be removed. The procedure is referred to as "presurgical volume cauterization." In one embodiment, the method is particularly effective for use in surgical lesion removal or resection of tissue having a highly vascularized constitution, such as the liver or spleen, and thus a propensity for hemorrhaging. In further embodiments, methods and apparatus for hemostasis using HIFU is useful in both surgical, presurgical, and medical emergency situations. In an apparatus embodiment, a telescoping, acoustic coupler is provided such that depth of focus of the HIFU energy is controllable. In other embodiments, apparatus characterized by portability are demonstrated, useful for emergency medical situations.

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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