Paul L Carson - Academia.edu (original) (raw)

Papers by Paul L Carson

Research paper thumbnail of Effects of nonlinear ultrasound propagation on output display indices

Journal of Ultrasound in Medicine, 1999

, in Boston, Massachusetts. This workshop addressed the effects of nonlinear ultrasound propagati... more , in Boston, Massachusetts. This workshop addressed the effects of nonlinear ultrasound propagation in the measurement medium (water) on the reported output display indices, MI and TI. Key questions of the workshop, addressed in these six papers, included the following: What are the magnitude of the effects? "What approaches might be possible to correct for the effects?" Finally, do the effects appeared significant enough to warrant accounting for them in the measurements and reporting as specified by the 1992 AIUM/NEMA ODS and its later revision and related standards 1-3 and the Federal Drug Administration 510(k) approval process for diagnostic ultrasound systems.

Research paper thumbnail of Estimation of Ultrasonic Attenuation and Mean Backscatterer Size via Digital Signal Processing

Research paper thumbnail of Interlaboratory comparison of ultrasonic attenuation and speed measurements

Journal of Ultrasound in Medicine, 1986

Research paper thumbnail of Limited-Angle Computer Tomography with Truncated Projection Artifacts Removal

Applied sciences, Nov 16, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Biomedical Imaging Research Opportunities Workshop: Report and Recommendations

Research paper thumbnail of A micromachined diaphragm structure for integrated ultrasound transducers

Proceedings., IEEE Ultrasonics Symposium

A diaphragm structure for integrated ultrasound transducers based on micromachining of Si is pres... more A diaphragm structure for integrated ultrasound transducers based on micromachining of Si is presented. This device significantly reduces a large parasitic capacitance compared to a nonmicromachined structure, improving transducer sensitivity and minimum detectable signal. It also reduces acoustical crosstalk between transducer elements. Micromachined transducer elements are also shown to be less directive in an array, an indication of crosstalk reduction

Research paper thumbnail of Normalizing Fractional Moving Blood Volume Estimates with Power Doppler US: Defining a Stable Intravascular Point with the Cumulative Power Distribution Function

Journal of Diagnostic Medical Sonography, 1998

To normalize the power Doppler ultrasound (US) signal to the expected signal from 100% blood in t... more To normalize the power Doppler ultrasound (US) signal to the expected signal from 100% blood in the calculation of a fractional moving blood volume estimate. To locate the signal from flowing blood with a consistent backscatter coefficient, the authors estimated the knee of the cumulative Doppler power distribution function. They used a flow-tube phantom to test the use of this knee to locate a radial position that would fall into a region of high shear stress and minimal rouleaux formation. They also studied how well the method normalized fractional moving blood volume estimates of the right renal cortex in a volunteer when simulating different body habitus and in a group of six healthy volunteers to estimate variability. Over five flow velocities and over undersaturated to severely oversaturated receiver gains, the calculated flow-tube area was a mean 89% +/- 7 (+/- standard deviation) of a standard. In humans, the technique normalized the fractional moving blood volume estimates over an 8-dB receiver gain variation; the mean +/- standard deviation of fractional moving blood volume estimates for the six volunteers was 37.6% +/- 3.6. Vascularity estimates with power Doppler US are feasible with a normalization scheme based on the cumulative Doppler power distribution function.

Research paper thumbnail of Characterization of acoustic droplet vaporization and inertial cavitation thresholds in acoustically-responsive tissue scaffolds

Hydrogel scaffolds are commonly used in tissue engineering as a substrate for cells or to deliver... more Hydrogel scaffolds are commonly used in tissue engineering as a substrate for cells or to deliver regenerative growth factors. We have previously demonstrated that acoustically responsive scaffolds can be developed by incorporating sonosensitive emulsions into hydrogel scaffolds. Growth factors, contained within the sonosensitive emulsions, can be released using ultrasound. Since ultrasound can be applied with both spatial and temporal control, this enables spatio-temporal release of growth factors within the ARS, which is unattainable with conventional hydrogel scaffolds. In this study, we expand this previous work by studying the thresholds associated with acoustic droplet vaporization (ADV) and inertial cavitation (IC) - two processes relevant to growth factor release. Acoustically-responsive scaffolds (ARS) were cast in OptiCells by doping fibrin hydrogels with perfluorocarbon droplets. ADV was generated in the ARS using a 2.5 MHz single element transducer. B-mode ultrasound was used to detect the onset of ADV whereas IC was detected with a broadband hydrophone. Results showed that ADV and IC thresholds are dependent on the number of acoustic cycles, the concentration of the ARS, and the structure of the droplets.

Research paper thumbnail of Drug delivery monitoring by photoacoustic tomography with an ICG encapsulated double emulsion

Proceedings of SPIE, Feb 9, 2012

We successfully encapsulated ICG in an ultrasound-triggerable perfluorocarbon double emulsion tha... more We successfully encapsulated ICG in an ultrasound-triggerable perfluorocarbon double emulsion that prevents ICG from binding with plasma proteins. Photoacoustic spectral measurements on point target as well as 2-D photoacoustic images of blood vessels revealed that the photoacoustic spectrum changes significantly in blood when the ICG-loaded emulsion undergoes acoustic droplet vaporization (ADV), which is the conversion of liquid droplets into gas bubbles using ultrasound. Other than providing a new photoacoustic contrast agent, the ICG encapsulated double emulsion, when imaged with photoacoustic tomography, could facilitate spatial and quantitative monitoring of ultrasound initiated drug delivery.

Research paper thumbnail of TU-C-220-06: Photoacoustic Imaging of Deep Targets in the Breast Using a Multi-Channel 2D Array Transducer

Medical Physics, Jun 1, 2011

Purpose: To pave the road toward successful application of photoacoustic imaging(PAI) to breast c... more Purpose: To pave the road toward successful application of photoacoustic imaging(PAI) to breast cancer, an initial evaluation of a home fabricated PAIsystem designed deliberately to achieve high sensitivity for the detection and characterization of vascular anomalies in the breast in the mammographic geometry was completed. Method and Materials: Signal detection from deep breast was achieved by a broadband 2D PVDF planar array that has a round shape with one side trimmed straight to improve fit near the chest wall. This array has 572 active elements and a −6dB bandwidth of 0.6–1.7 MHz. The low frequency of the array enhances imaging depth and increases the size of vascular collections displayed without edge enhancement. The photoacoustic signals from all the elements go through low noise preamplifiers in the probe that are very close to the array elements for optimized noise control. Driven by 20 independent on‐probe signal processing channels, imaging with both high sensitivity and good speed was achieved. Results: According to our measurements, the end of cable sensitivity was 2.5mV/Pa. Without averaging, the minimum detectable pressure was 80 Pa. Based on the measurements of a point object at different distances from the surface of the array, the lateral resolution of the system ranges from 2.9 mm to 4.2mm and axial resolution ranges from 1.9 mm to 3.7 mm within the distance of 60 mm. To evaluate the imaging depth of this system, artificial vessels embedded deeply in ex vivo breasts harvested from fresh cadavers were imaged. Using near‐infrared laser light with incident energy density within the ANSI safety limit, imaging depth of up to 49 mm in human breasts was achieved. To validate the multi‐modality imaging possibility, PAIimages of a compressed breast containing a catheter balloon filled with blood was coregistered with ultrasoundimages acquired from the same specimen. PAI, based on the intrinsic tissue optical contrast, successfully presented some breast tissue features, including the interfaces on both sides of the skin, the connective tissue sheet in subcutaneous fat, and the lobar capsule. Conclusions: The current imaging speed of this system is adequate for laboratory research and in vivo human studies with small numbers of cooperative volunteers. With a high power tunable laser working on multiple wavelengths, this system might contribute to 3D noninvasive imaging of morphological and physiological tissue features throughout the breast.

Research paper thumbnail of Limited angle breast ultrasound tomography with a priori information and artifact removal

Proceedings of SPIE, Mar 13, 2017

In B-mode images from dual-sided ultrasound, it has been shown that by delineating structures sus... more In B-mode images from dual-sided ultrasound, it has been shown that by delineating structures suspected of being relatively homogeneous, one can enhance limited angle tomography to produce speed of sound images in the same view as X-ray Digital Breast Tomography (DBT). This could allow better breast cancer detection and discrimination, as well as improved registration of the ultrasound and X-ray images, because of the similarity of SOS and X-ray contrast in the breast. However, this speed of sound reconstruction method relies strongly on B-mode or other reflection mode segmentation. If that information is limited or incorrect, artifacts will appear in the reconstructed images. Therefore, the iterative speed of sound reconstruction algorithm has been modified in a manner of simultaneously utilizing the image segmentations and removing most artifacts. The first step of incorporating a priori information is solved by any nonlinearnonconvex optimization method while artifact removal is accomplished by employing the fast split Bregman method to perform total-variation (TV) regularization for image denoising. The proposed method was demonstrated in simplified simulations of our dual-sided ultrasound scanner. To speed these computations two opposed 40-element ultrasound linear arrays with 0.5 MHz center frequency were simulated for imaging objects in a uniform background. The proposed speed of sound reconstruction method worked well with both bent-ray and full-wave inversion methods. This is also the first demonstration of successful full-wave medical ultrasound tomography in the limited angle geometry. Presented results lend credibility to a possible translation of this method to clinical breast imaging.

Research paper thumbnail of Combined photoacoustic and ultrasound imaging of human breast in vivo in the mammographic geometry

Proceedings of SPIE, Mar 4, 2013

ABSTRACT This photoacoustic volume imaging (PAVI) system is designed to study breast cancer detec... more ABSTRACT This photoacoustic volume imaging (PAVI) system is designed to study breast cancer detection and diagnosis in the mammographic geometry in combination with automated 3D ultrasound (AUS). The good penetration of near-infrared (NIR) light and high receiving sensitivity of a broad bandwidth, 572 element, 2D PVDF array at a low center-frequency of 1MHz were utilized with 20 channel simultaneous acquisition. The feasibility of this system in imaging optically absorbing objects in deep breast tissues was assessed first through experiments on ex vivo whole breasts. The blood filled pseudo lesions were imaged at depths up to 49 mm in the specimens. In vivo imaging of human breasts has been conducted. 3D PAVI image stacks of human breasts were coregistered and compared with 3D ultrasound image stacks of the same breasts. Using the designed system, PAVI shows satisfactory imaging depth and sensitivity for coverage of the entire breast when imaged from both sides with mild compression in the mammographic geometry. With its unique soft tissue contrast and excellent sensitivity to the tissue hemodynamic properties of fractional blood volume and blood oxygenation, PAVI, as a complement to 3D ultrasound and digital tomosynthesis mammography, might well contribute to detection, diagnosis and prognosis for breast cancer.

Research paper thumbnail of Adaptive optimization on ultrasonic transmission tomography-based temperature image for biomedical treatment

Chinese Physics B, Jun 1, 2017

Hyperthermia has proven to be beneficial to treating superficial malignancies, particularly chest... more Hyperthermia has proven to be beneficial to treating superficial malignancies, particularly chest wall recurrences of breast cancer. During hyperthermia, monitoring the time–temperature profiles in the target and surrounding areas is of great significance for the effect of therapy. An ultrasound-based temperature imaging method has advantages over other approaches. When the temperature around the tumor is calculated by using the propagation speed of ultrasound, there always exist overshoot artifacts along the boundary between different tissues. In this paper, we present a new method combined with empirical mode decomposition (EDM), similarity constraint, and continuity constraint to optimize the temperature images. Simulation and phantom experiment results compared with those from our previously proposed method prove that the EMD-based method can build a better temperature field image, which can adaptively yield better temperature images with less computation for assistant medical treatment control.

Research paper thumbnail of American Institute of Ultrasound in Medicine Consensus Report on Potential Bioeffects of Diagnostic Ultrasound

Journal of Ultrasound in Medicine, Apr 1, 2008

The continued examination of potential biological effects of ultrasound and their relationship to... more The continued examination of potential biological effects of ultrasound and their relationship to clinical practice is a key element in evaluating the safety of diagnostic ultrasound. Periodically, the American Institute of Ultrasound in Medicine (AIUM) sponsors conferences bringing experts together to examine the literature on ultrasound bioeffects and to develop conclusions and recommendations related to diagnostic ultrasound. The most recent effort included the examination of effects whose origins were thermal or nonthermal, with separate evaluations for potential effects related to fetal ultrasound. In addition, potential effects due to the introduction of ultrasound contrast agents were summarized. This information can be used to assess risks in comparison to the benefits of diagnostic ultrasound. The conclusions and recommendations are organized into 5 broad categories, with a comprehensive background and evaluation of each topic provided in the corresponding articles in this issue. The following summary is not meant as a substitute for the detailed examination of issues presented in each of the articles but rather as a means to facilitate further study of this consensus report and implementation of its recommendations. The conclusions and recommendations are the result of several rounds of deliberations at the consensus conference, subsequent review by the Bioeffects Committee of the AIUM, and approval by the AIUM Board of Governors.

Research paper thumbnail of Temperature imaging with speed of ultrasonic transmission tomography for medical treatment control: A physical model-based method

Chinese Physics B, Sep 29, 2015

Hyperthermia is a promising method to enhance chemo and radiation therapy of breast cancer. In th... more Hyperthermia is a promising method to enhance chemo and radiation therapy of breast cancer. In the process of hyperthermia, temperature monitoring is of great importance to assure the effectiveness of treatment. The transmission speed of ultrasound in biomedical tissue changes with temperature. However, when mapping the speed of sound directly to temperature in each pixel as desired for using all speeds of ultrasound data, temperature bipolar edge enhancement artifacts occur near the boundary of two tissues with different speeds of ultrasound. After the analysis of the reasons for causing these artifacts, an optimized method is introduced to rebuild the temperature field image by using the continuity constraint as the judgment criterion. The significant smoothness of the rebuilding image in the transitional area shows that our proposed method can build a more precise temperature image for controlling the medical thermal treatment.

Research paper thumbnail of TU-B-220-03: Development of CMUT Transducer Array Assemblies for Medical Diagnostics

Medical Physics, Jun 1, 2011

Purpose: Significant work in the last 10 years has been directed towards the development of capac... more Purpose: Significant work in the last 10 years has been directed towards the development of capacitive Micromachined Ultrasound Transducer (cMUT) arrays and associated assemblies for medical imaging. These implementations are intended to address a spectrum of applications including Intra‐Vascular (IVUS), Low Cost Portable and large area arrays for breast imaging among others. The close integration of cMUT arrays with associated processing electronics is intended to alleviate a series of issues having direct bearing on product arrays: Electrical loading of the cMUTs during transmit and receive leads to a reduction in round‐trip sensitivity as well as increased power dissipation. Large 2D arrays required for real‐time volumetric imaging require 10's of thousands of elements resulting in a significant bottleneck for traditional cable‐based interconnects. The cost of interconnect and processing channels built using standard techniques in current ultrasound machines when scaled from 100's of elements to 10's of thousands is prohibitive. This talk will examine the issues around close integration and explore the proposed solutions to address these challenges. Method and Materials: The close integration of cMUT transducers with associated processing electronics promises to yield improvements in image quality, probe manufacturability and reduction in cost for point of care and large area arrays. To date there have been at least three solutions to these issues proposed: i) Fabrication of cMUTs directly on top of the electronic devices, ii) Direct assembly of cMUT chips to the associated electronics, and iii) Double‐sided flip‐chip assembly of both the cMUT arrays and the electronics to an intervening substrate made of organic or other materials. Each of these methods has associated benefits and disadvantages and these will be reviewed along with the presentation of the results of our work in some of these areas. Results: To date we have explored the direct attach of cMUTs to electronics as well as double‐sided flip‐chip attach using rigid interposers. Interposers promis to provide the ability to realize seamless tiling of array modules for fabrication of large array areas for full field of view automated breast ultrasound. However, due to the very large number of interconnects and through substrate vias needed via density remains challenging. We will present the results of our latest work in this area. Direct attach of cMUTs to associated electronics is promising for point of care low cost probes. However large area arrays based on this approach rely on the availability of high voltage TSVs which are not yet available in volume production. Fabrication of cMUTs directly on top of device electronics has been explored by other groups and some recent results will be briefly reviewed. Conclusions: Significant challenges remain in close integration of cMUTs with associated interface electronics for complex transducer array assemblies. Three currently proposed solutions to close integration have been reviewed. It is likely that each of these will find a niche in specific applications.

Research paper thumbnail of Real-time, volumetric imaging of radiation dose delivery deep into the liver during cancer treatment

Nature Biotechnology

Ionizing radiation acoustic imaging (iRAI) allows online monitoring of radiation’s interactions w... more Ionizing radiation acoustic imaging (iRAI) allows online monitoring of radiation’s interactions with tissues during radiation therapy, providing real-time, adaptive feedback for cancer treatments. We describe an iRAI volumetric imaging system that enables mapping of the three-dimensional (3D) radiation dose distribution in a complex clinical radiotherapy treatment. The method relies on a two-dimensional matrix array transducer and a matching multi-channel preamplifier board. The feasibility of imaging temporal 3D dose accumulation was first validated in a tissue-mimicking phantom. Next, semiquantitative iRAI relative dose measurements were verified in vivo in a rabbit model. Finally, real-time visualization of the 3D radiation dose delivered to a patient with liver metastases was accomplished with a clinical linear accelerator. These studies demonstrate the potential of iRAI to monitor and quantify the 3D radiation dose deposition during treatment, potentially improving radiotherapy...

Research paper thumbnail of Radiological Society of North America/Quantitative Imaging Biomarker Alliance Shear Wave Speed Bias Quantification in Elastic and Viscoelastic Phantoms

Journal of Ultrasound in Medicine, 2021

ObjectivesTo quantify the bias of shear wave speed (SWS) measurements between different commercia... more ObjectivesTo quantify the bias of shear wave speed (SWS) measurements between different commercial ultrasonic shear elasticity systems and a magnetic resonance elastography (MRE) system in elastic and viscoelastic phantoms.MethodsTwo elastic phantoms, representing healthy through fibrotic liver, were measured with 5 different ultrasound platforms, and 3 viscoelastic phantoms, representing healthy through fibrotic liver tissue, were measured with 12 different ultrasound platforms. Measurements were performed with different systems at different sites, at 3 focal depths, and with different appraisers. The SWS bias across the systems was quantified as a function of the system, site, focal depth, and appraiser. A single MRE research system was also used to characterize these phantoms using discrete frequencies from 60 to 500 Hz.ResultsThe SWS from different systems had mean difference 95% confidence intervals of ±0.145 m/s (±9.6%) across both elastic phantoms and ± 0.340 m/s (±15.3%) acr...

Research paper thumbnail of Three-dimensional US for Quantification of Volumetric Blood Flow: Multisite Multisystem Results from within the Quantitative Imaging Biomarkers Alliance

Radiology, 2020

Strengthening and stretching for rheumatoid arthritis of the hand (SARAH): Design of a randomised... more Strengthening and stretching for rheumatoid arthritis of the hand (SARAH): Design of a randomised controlled trial of a hand and upper limb exercise intervention-ISRCTN89936343. BMC Musculoskeletal Disorders, 13(230), [230].

Research paper thumbnail of An ionizing radiation acoustic imaging (iRAI) technique for real‐time dosimetric measurements for FLASH radiotherapy

Medical Physics, 2020

PurposeFLASH radiotherapy (FLASH‐RT) is a novel irradiation modality with ultra‐high dose rates (... more PurposeFLASH radiotherapy (FLASH‐RT) is a novel irradiation modality with ultra‐high dose rates (>40 Gy/s) that have shown tremendous promise for its ability to enhance normal tissue sparing while maintaining comparable tumor cell eradication toconventional radiotherapy (CONV‐RT). Due to its extremely high dose rates, clinical translation of FLASH‐RT is hampered by risky delivery and current limitations in dosimetric devices, which cannot accurately measure, in real time, dose at deeper tissue. This work aims to investigate ionizing radiation acoustic imaging (iRAI) as a promising image‐guidance modality for real‐time deep tissue dose measurements during FLASH‐RT. The underlying hypothesis is that iRAI can enable mapping of dose deposition with respect to surrounding tissue with a single linear accelerator (linac) pulse precision in real time. In this work, the relationship between iRAI signal response and deposited dose was investigated as well as the feasibility of using a proo...

Research paper thumbnail of Effects of nonlinear ultrasound propagation on output display indices

Journal of Ultrasound in Medicine, 1999

, in Boston, Massachusetts. This workshop addressed the effects of nonlinear ultrasound propagati... more , in Boston, Massachusetts. This workshop addressed the effects of nonlinear ultrasound propagation in the measurement medium (water) on the reported output display indices, MI and TI. Key questions of the workshop, addressed in these six papers, included the following: What are the magnitude of the effects? "What approaches might be possible to correct for the effects?" Finally, do the effects appeared significant enough to warrant accounting for them in the measurements and reporting as specified by the 1992 AIUM/NEMA ODS and its later revision and related standards 1-3 and the Federal Drug Administration 510(k) approval process for diagnostic ultrasound systems.

Research paper thumbnail of Estimation of Ultrasonic Attenuation and Mean Backscatterer Size via Digital Signal Processing

Research paper thumbnail of Interlaboratory comparison of ultrasonic attenuation and speed measurements

Journal of Ultrasound in Medicine, 1986

Research paper thumbnail of Limited-Angle Computer Tomography with Truncated Projection Artifacts Removal

Applied sciences, Nov 16, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Biomedical Imaging Research Opportunities Workshop: Report and Recommendations

Research paper thumbnail of A micromachined diaphragm structure for integrated ultrasound transducers

Proceedings., IEEE Ultrasonics Symposium

A diaphragm structure for integrated ultrasound transducers based on micromachining of Si is pres... more A diaphragm structure for integrated ultrasound transducers based on micromachining of Si is presented. This device significantly reduces a large parasitic capacitance compared to a nonmicromachined structure, improving transducer sensitivity and minimum detectable signal. It also reduces acoustical crosstalk between transducer elements. Micromachined transducer elements are also shown to be less directive in an array, an indication of crosstalk reduction

Research paper thumbnail of Normalizing Fractional Moving Blood Volume Estimates with Power Doppler US: Defining a Stable Intravascular Point with the Cumulative Power Distribution Function

Journal of Diagnostic Medical Sonography, 1998

To normalize the power Doppler ultrasound (US) signal to the expected signal from 100% blood in t... more To normalize the power Doppler ultrasound (US) signal to the expected signal from 100% blood in the calculation of a fractional moving blood volume estimate. To locate the signal from flowing blood with a consistent backscatter coefficient, the authors estimated the knee of the cumulative Doppler power distribution function. They used a flow-tube phantom to test the use of this knee to locate a radial position that would fall into a region of high shear stress and minimal rouleaux formation. They also studied how well the method normalized fractional moving blood volume estimates of the right renal cortex in a volunteer when simulating different body habitus and in a group of six healthy volunteers to estimate variability. Over five flow velocities and over undersaturated to severely oversaturated receiver gains, the calculated flow-tube area was a mean 89% +/- 7 (+/- standard deviation) of a standard. In humans, the technique normalized the fractional moving blood volume estimates over an 8-dB receiver gain variation; the mean +/- standard deviation of fractional moving blood volume estimates for the six volunteers was 37.6% +/- 3.6. Vascularity estimates with power Doppler US are feasible with a normalization scheme based on the cumulative Doppler power distribution function.

Research paper thumbnail of Characterization of acoustic droplet vaporization and inertial cavitation thresholds in acoustically-responsive tissue scaffolds

Hydrogel scaffolds are commonly used in tissue engineering as a substrate for cells or to deliver... more Hydrogel scaffolds are commonly used in tissue engineering as a substrate for cells or to deliver regenerative growth factors. We have previously demonstrated that acoustically responsive scaffolds can be developed by incorporating sonosensitive emulsions into hydrogel scaffolds. Growth factors, contained within the sonosensitive emulsions, can be released using ultrasound. Since ultrasound can be applied with both spatial and temporal control, this enables spatio-temporal release of growth factors within the ARS, which is unattainable with conventional hydrogel scaffolds. In this study, we expand this previous work by studying the thresholds associated with acoustic droplet vaporization (ADV) and inertial cavitation (IC) - two processes relevant to growth factor release. Acoustically-responsive scaffolds (ARS) were cast in OptiCells by doping fibrin hydrogels with perfluorocarbon droplets. ADV was generated in the ARS using a 2.5 MHz single element transducer. B-mode ultrasound was used to detect the onset of ADV whereas IC was detected with a broadband hydrophone. Results showed that ADV and IC thresholds are dependent on the number of acoustic cycles, the concentration of the ARS, and the structure of the droplets.

Research paper thumbnail of Drug delivery monitoring by photoacoustic tomography with an ICG encapsulated double emulsion

Proceedings of SPIE, Feb 9, 2012

We successfully encapsulated ICG in an ultrasound-triggerable perfluorocarbon double emulsion tha... more We successfully encapsulated ICG in an ultrasound-triggerable perfluorocarbon double emulsion that prevents ICG from binding with plasma proteins. Photoacoustic spectral measurements on point target as well as 2-D photoacoustic images of blood vessels revealed that the photoacoustic spectrum changes significantly in blood when the ICG-loaded emulsion undergoes acoustic droplet vaporization (ADV), which is the conversion of liquid droplets into gas bubbles using ultrasound. Other than providing a new photoacoustic contrast agent, the ICG encapsulated double emulsion, when imaged with photoacoustic tomography, could facilitate spatial and quantitative monitoring of ultrasound initiated drug delivery.

Research paper thumbnail of TU-C-220-06: Photoacoustic Imaging of Deep Targets in the Breast Using a Multi-Channel 2D Array Transducer

Medical Physics, Jun 1, 2011

Purpose: To pave the road toward successful application of photoacoustic imaging(PAI) to breast c... more Purpose: To pave the road toward successful application of photoacoustic imaging(PAI) to breast cancer, an initial evaluation of a home fabricated PAIsystem designed deliberately to achieve high sensitivity for the detection and characterization of vascular anomalies in the breast in the mammographic geometry was completed. Method and Materials: Signal detection from deep breast was achieved by a broadband 2D PVDF planar array that has a round shape with one side trimmed straight to improve fit near the chest wall. This array has 572 active elements and a −6dB bandwidth of 0.6–1.7 MHz. The low frequency of the array enhances imaging depth and increases the size of vascular collections displayed without edge enhancement. The photoacoustic signals from all the elements go through low noise preamplifiers in the probe that are very close to the array elements for optimized noise control. Driven by 20 independent on‐probe signal processing channels, imaging with both high sensitivity and good speed was achieved. Results: According to our measurements, the end of cable sensitivity was 2.5mV/Pa. Without averaging, the minimum detectable pressure was 80 Pa. Based on the measurements of a point object at different distances from the surface of the array, the lateral resolution of the system ranges from 2.9 mm to 4.2mm and axial resolution ranges from 1.9 mm to 3.7 mm within the distance of 60 mm. To evaluate the imaging depth of this system, artificial vessels embedded deeply in ex vivo breasts harvested from fresh cadavers were imaged. Using near‐infrared laser light with incident energy density within the ANSI safety limit, imaging depth of up to 49 mm in human breasts was achieved. To validate the multi‐modality imaging possibility, PAIimages of a compressed breast containing a catheter balloon filled with blood was coregistered with ultrasoundimages acquired from the same specimen. PAI, based on the intrinsic tissue optical contrast, successfully presented some breast tissue features, including the interfaces on both sides of the skin, the connective tissue sheet in subcutaneous fat, and the lobar capsule. Conclusions: The current imaging speed of this system is adequate for laboratory research and in vivo human studies with small numbers of cooperative volunteers. With a high power tunable laser working on multiple wavelengths, this system might contribute to 3D noninvasive imaging of morphological and physiological tissue features throughout the breast.

Research paper thumbnail of Limited angle breast ultrasound tomography with a priori information and artifact removal

Proceedings of SPIE, Mar 13, 2017

In B-mode images from dual-sided ultrasound, it has been shown that by delineating structures sus... more In B-mode images from dual-sided ultrasound, it has been shown that by delineating structures suspected of being relatively homogeneous, one can enhance limited angle tomography to produce speed of sound images in the same view as X-ray Digital Breast Tomography (DBT). This could allow better breast cancer detection and discrimination, as well as improved registration of the ultrasound and X-ray images, because of the similarity of SOS and X-ray contrast in the breast. However, this speed of sound reconstruction method relies strongly on B-mode or other reflection mode segmentation. If that information is limited or incorrect, artifacts will appear in the reconstructed images. Therefore, the iterative speed of sound reconstruction algorithm has been modified in a manner of simultaneously utilizing the image segmentations and removing most artifacts. The first step of incorporating a priori information is solved by any nonlinearnonconvex optimization method while artifact removal is accomplished by employing the fast split Bregman method to perform total-variation (TV) regularization for image denoising. The proposed method was demonstrated in simplified simulations of our dual-sided ultrasound scanner. To speed these computations two opposed 40-element ultrasound linear arrays with 0.5 MHz center frequency were simulated for imaging objects in a uniform background. The proposed speed of sound reconstruction method worked well with both bent-ray and full-wave inversion methods. This is also the first demonstration of successful full-wave medical ultrasound tomography in the limited angle geometry. Presented results lend credibility to a possible translation of this method to clinical breast imaging.

Research paper thumbnail of Combined photoacoustic and ultrasound imaging of human breast in vivo in the mammographic geometry

Proceedings of SPIE, Mar 4, 2013

ABSTRACT This photoacoustic volume imaging (PAVI) system is designed to study breast cancer detec... more ABSTRACT This photoacoustic volume imaging (PAVI) system is designed to study breast cancer detection and diagnosis in the mammographic geometry in combination with automated 3D ultrasound (AUS). The good penetration of near-infrared (NIR) light and high receiving sensitivity of a broad bandwidth, 572 element, 2D PVDF array at a low center-frequency of 1MHz were utilized with 20 channel simultaneous acquisition. The feasibility of this system in imaging optically absorbing objects in deep breast tissues was assessed first through experiments on ex vivo whole breasts. The blood filled pseudo lesions were imaged at depths up to 49 mm in the specimens. In vivo imaging of human breasts has been conducted. 3D PAVI image stacks of human breasts were coregistered and compared with 3D ultrasound image stacks of the same breasts. Using the designed system, PAVI shows satisfactory imaging depth and sensitivity for coverage of the entire breast when imaged from both sides with mild compression in the mammographic geometry. With its unique soft tissue contrast and excellent sensitivity to the tissue hemodynamic properties of fractional blood volume and blood oxygenation, PAVI, as a complement to 3D ultrasound and digital tomosynthesis mammography, might well contribute to detection, diagnosis and prognosis for breast cancer.

Research paper thumbnail of Adaptive optimization on ultrasonic transmission tomography-based temperature image for biomedical treatment

Chinese Physics B, Jun 1, 2017

Hyperthermia has proven to be beneficial to treating superficial malignancies, particularly chest... more Hyperthermia has proven to be beneficial to treating superficial malignancies, particularly chest wall recurrences of breast cancer. During hyperthermia, monitoring the time–temperature profiles in the target and surrounding areas is of great significance for the effect of therapy. An ultrasound-based temperature imaging method has advantages over other approaches. When the temperature around the tumor is calculated by using the propagation speed of ultrasound, there always exist overshoot artifacts along the boundary between different tissues. In this paper, we present a new method combined with empirical mode decomposition (EDM), similarity constraint, and continuity constraint to optimize the temperature images. Simulation and phantom experiment results compared with those from our previously proposed method prove that the EMD-based method can build a better temperature field image, which can adaptively yield better temperature images with less computation for assistant medical treatment control.

Research paper thumbnail of American Institute of Ultrasound in Medicine Consensus Report on Potential Bioeffects of Diagnostic Ultrasound

Journal of Ultrasound in Medicine, Apr 1, 2008

The continued examination of potential biological effects of ultrasound and their relationship to... more The continued examination of potential biological effects of ultrasound and their relationship to clinical practice is a key element in evaluating the safety of diagnostic ultrasound. Periodically, the American Institute of Ultrasound in Medicine (AIUM) sponsors conferences bringing experts together to examine the literature on ultrasound bioeffects and to develop conclusions and recommendations related to diagnostic ultrasound. The most recent effort included the examination of effects whose origins were thermal or nonthermal, with separate evaluations for potential effects related to fetal ultrasound. In addition, potential effects due to the introduction of ultrasound contrast agents were summarized. This information can be used to assess risks in comparison to the benefits of diagnostic ultrasound. The conclusions and recommendations are organized into 5 broad categories, with a comprehensive background and evaluation of each topic provided in the corresponding articles in this issue. The following summary is not meant as a substitute for the detailed examination of issues presented in each of the articles but rather as a means to facilitate further study of this consensus report and implementation of its recommendations. The conclusions and recommendations are the result of several rounds of deliberations at the consensus conference, subsequent review by the Bioeffects Committee of the AIUM, and approval by the AIUM Board of Governors.

Research paper thumbnail of Temperature imaging with speed of ultrasonic transmission tomography for medical treatment control: A physical model-based method

Chinese Physics B, Sep 29, 2015

Hyperthermia is a promising method to enhance chemo and radiation therapy of breast cancer. In th... more Hyperthermia is a promising method to enhance chemo and radiation therapy of breast cancer. In the process of hyperthermia, temperature monitoring is of great importance to assure the effectiveness of treatment. The transmission speed of ultrasound in biomedical tissue changes with temperature. However, when mapping the speed of sound directly to temperature in each pixel as desired for using all speeds of ultrasound data, temperature bipolar edge enhancement artifacts occur near the boundary of two tissues with different speeds of ultrasound. After the analysis of the reasons for causing these artifacts, an optimized method is introduced to rebuild the temperature field image by using the continuity constraint as the judgment criterion. The significant smoothness of the rebuilding image in the transitional area shows that our proposed method can build a more precise temperature image for controlling the medical thermal treatment.

Research paper thumbnail of TU-B-220-03: Development of CMUT Transducer Array Assemblies for Medical Diagnostics

Medical Physics, Jun 1, 2011

Purpose: Significant work in the last 10 years has been directed towards the development of capac... more Purpose: Significant work in the last 10 years has been directed towards the development of capacitive Micromachined Ultrasound Transducer (cMUT) arrays and associated assemblies for medical imaging. These implementations are intended to address a spectrum of applications including Intra‐Vascular (IVUS), Low Cost Portable and large area arrays for breast imaging among others. The close integration of cMUT arrays with associated processing electronics is intended to alleviate a series of issues having direct bearing on product arrays: Electrical loading of the cMUTs during transmit and receive leads to a reduction in round‐trip sensitivity as well as increased power dissipation. Large 2D arrays required for real‐time volumetric imaging require 10's of thousands of elements resulting in a significant bottleneck for traditional cable‐based interconnects. The cost of interconnect and processing channels built using standard techniques in current ultrasound machines when scaled from 100's of elements to 10's of thousands is prohibitive. This talk will examine the issues around close integration and explore the proposed solutions to address these challenges. Method and Materials: The close integration of cMUT transducers with associated processing electronics promises to yield improvements in image quality, probe manufacturability and reduction in cost for point of care and large area arrays. To date there have been at least three solutions to these issues proposed: i) Fabrication of cMUTs directly on top of the electronic devices, ii) Direct assembly of cMUT chips to the associated electronics, and iii) Double‐sided flip‐chip assembly of both the cMUT arrays and the electronics to an intervening substrate made of organic or other materials. Each of these methods has associated benefits and disadvantages and these will be reviewed along with the presentation of the results of our work in some of these areas. Results: To date we have explored the direct attach of cMUTs to electronics as well as double‐sided flip‐chip attach using rigid interposers. Interposers promis to provide the ability to realize seamless tiling of array modules for fabrication of large array areas for full field of view automated breast ultrasound. However, due to the very large number of interconnects and through substrate vias needed via density remains challenging. We will present the results of our latest work in this area. Direct attach of cMUTs to associated electronics is promising for point of care low cost probes. However large area arrays based on this approach rely on the availability of high voltage TSVs which are not yet available in volume production. Fabrication of cMUTs directly on top of device electronics has been explored by other groups and some recent results will be briefly reviewed. Conclusions: Significant challenges remain in close integration of cMUTs with associated interface electronics for complex transducer array assemblies. Three currently proposed solutions to close integration have been reviewed. It is likely that each of these will find a niche in specific applications.

Research paper thumbnail of Real-time, volumetric imaging of radiation dose delivery deep into the liver during cancer treatment

Nature Biotechnology

Ionizing radiation acoustic imaging (iRAI) allows online monitoring of radiation’s interactions w... more Ionizing radiation acoustic imaging (iRAI) allows online monitoring of radiation’s interactions with tissues during radiation therapy, providing real-time, adaptive feedback for cancer treatments. We describe an iRAI volumetric imaging system that enables mapping of the three-dimensional (3D) radiation dose distribution in a complex clinical radiotherapy treatment. The method relies on a two-dimensional matrix array transducer and a matching multi-channel preamplifier board. The feasibility of imaging temporal 3D dose accumulation was first validated in a tissue-mimicking phantom. Next, semiquantitative iRAI relative dose measurements were verified in vivo in a rabbit model. Finally, real-time visualization of the 3D radiation dose delivered to a patient with liver metastases was accomplished with a clinical linear accelerator. These studies demonstrate the potential of iRAI to monitor and quantify the 3D radiation dose deposition during treatment, potentially improving radiotherapy...

Research paper thumbnail of Radiological Society of North America/Quantitative Imaging Biomarker Alliance Shear Wave Speed Bias Quantification in Elastic and Viscoelastic Phantoms

Journal of Ultrasound in Medicine, 2021

ObjectivesTo quantify the bias of shear wave speed (SWS) measurements between different commercia... more ObjectivesTo quantify the bias of shear wave speed (SWS) measurements between different commercial ultrasonic shear elasticity systems and a magnetic resonance elastography (MRE) system in elastic and viscoelastic phantoms.MethodsTwo elastic phantoms, representing healthy through fibrotic liver, were measured with 5 different ultrasound platforms, and 3 viscoelastic phantoms, representing healthy through fibrotic liver tissue, were measured with 12 different ultrasound platforms. Measurements were performed with different systems at different sites, at 3 focal depths, and with different appraisers. The SWS bias across the systems was quantified as a function of the system, site, focal depth, and appraiser. A single MRE research system was also used to characterize these phantoms using discrete frequencies from 60 to 500 Hz.ResultsThe SWS from different systems had mean difference 95% confidence intervals of ±0.145 m/s (±9.6%) across both elastic phantoms and ± 0.340 m/s (±15.3%) acr...

Research paper thumbnail of Three-dimensional US for Quantification of Volumetric Blood Flow: Multisite Multisystem Results from within the Quantitative Imaging Biomarkers Alliance

Radiology, 2020

Strengthening and stretching for rheumatoid arthritis of the hand (SARAH): Design of a randomised... more Strengthening and stretching for rheumatoid arthritis of the hand (SARAH): Design of a randomised controlled trial of a hand and upper limb exercise intervention-ISRCTN89936343. BMC Musculoskeletal Disorders, 13(230), [230].

Research paper thumbnail of An ionizing radiation acoustic imaging (iRAI) technique for real‐time dosimetric measurements for FLASH radiotherapy

Medical Physics, 2020

PurposeFLASH radiotherapy (FLASH‐RT) is a novel irradiation modality with ultra‐high dose rates (... more PurposeFLASH radiotherapy (FLASH‐RT) is a novel irradiation modality with ultra‐high dose rates (>40 Gy/s) that have shown tremendous promise for its ability to enhance normal tissue sparing while maintaining comparable tumor cell eradication toconventional radiotherapy (CONV‐RT). Due to its extremely high dose rates, clinical translation of FLASH‐RT is hampered by risky delivery and current limitations in dosimetric devices, which cannot accurately measure, in real time, dose at deeper tissue. This work aims to investigate ionizing radiation acoustic imaging (iRAI) as a promising image‐guidance modality for real‐time deep tissue dose measurements during FLASH‐RT. The underlying hypothesis is that iRAI can enable mapping of dose deposition with respect to surrounding tissue with a single linear accelerator (linac) pulse precision in real time. In this work, the relationship between iRAI signal response and deposited dose was investigated as well as the feasibility of using a proo...