Man Zhang - Academia.edu (original) (raw)
Papers by Man Zhang
Color Imaging Conference, 2004
Journal of Imaging Science and Technology, 2006
... ZHHuang, WYLong, GYXie, OLKwan, and ANDeMaria, Comparison of gray-scale and B-color ultrasou... more ... ZHHuang, WYLong, GYXie, OLKwan, and ANDeMaria, Comparison of gray-scale and B-color ultrasound images in evaluating left ventricular systolic function in coronary artery disease, Am. Heart J. 123, 2 (1992). ... (Permission from Dr. Deborah J. Rubens.). ...
PURPOSE To test the accuracy of real-time 3D angle-independent measurements of volume flow at car... more PURPOSE To test the accuracy of real-time 3D angle-independent measurements of volume flow at cardiac blood flow rates. METHOD AND MATERIALS We utilized a 4D (real-time 3D) color Doppler ultrasound scanner (Vivid 7, GE Healthcare, Milwaukee, WI) equipped with a 2D phased array (3V, GE Healthcare) to acquire bench top cardiac-type output under pulsatile flow conditions. In 3D, the color flow constant-depth plane (C-plane) resolution was 3 and 2.25 pixels/cm in the lateral and elevational directions respectively, while recording 10 volumes/second. Experiments were performed with a 2.5-cm diameter, thin-walled latex tube mounted in a water tank. Blood-mimicking fluid (CIRS Inc., Norfolk, VA) was circulated at up to 108 mL/s using a calibrated cardiac bypass pump set at 60 and 80 beats/min. Data was acquired randomly throughout the pump cycle with sweeps of 10, 25, 50, and 100 volumes. For each acquisition, a mean volume flow estimate was computed from C-plane integration and Doppler po...
Proceedings - IEEE Ultrasonics Symposium, 2008
Ultrasound can be used to phase transition perfluorocarbon (PFC) droplets into gas bubbles, a pro... more Ultrasound can be used to phase transition perfluorocarbon (PFC) droplets into gas bubbles, a process known as acoustic droplet vaporization (ADV). In vivo blood flow reductions can then be achieved using the ADV bubbles. An in situ ultrasonic measurement of this blood flow reduction is desirable. Since, in a simple model, initial flow reduction is proportional to the number of bubbles, and the mean echo power (MEP) in a B-mode image is related to the number of bubbles (off resonant scattering), it is hypothesized that the MEP can be used to estimate the relative flow reduction. To test this hypothesis, three canines were anesthetized and a laparotomy performed to externalize the left kidney and renal artery. An ultrasonic flow probe was placed on the renal artery. PFC droplets were injected intravenously and a focused 3.5 MHz single-element transducer was used to vaporize the PFC droplets, just downstream of the flow probe. The flow in the renal artery was recorded with the flowmeter as the vaporized droplets became lodged in the renal capillary beds. Simultaneously, B-mode cine loops were recorded. The cine loops were processed to determine the echogenicity, as measured by the MEP, in the kidney cortex. It was found that the MEP and renal arterial flow did not correlate quantitatively. However it was found that the MEP could be used to determine when the renal arterial flow had recovered to a steady state.
Medical Imaging 2008: Ultrasonic Imaging and Signal Processing, 2008
The capability of sonoelastography to detect lesions based on elasticity contrast can be applied ... more The capability of sonoelastography to detect lesions based on elasticity contrast can be applied to monitor the creation of thermally ablated lesion. Currently, segmentation of lesions depicted in sonoelastographic images is performed manually which can be a time consuming process and prone to significant intra-and inter-observer variability. This work presents a semi-automated segmentation algorithm for sonoelastographic data. The user starts by planting a seed in the perceived center of the lesion. Fast marching methods use this information to create an initial estimate of the lesion. Subsequently, level set methods refine its final shape by attaching the segmented contour to edges in the image while maintaining smoothness. The algorithm is applied to in vivo sonoelastographic images from twenty five thermal ablated lesions created in porcine livers. The estimated area is compared to results from manual segmentation and gross pathology images. Results show that the algorithm outperforms manual segmentation in accuracy, inter-and intra-observer variability. The processing time per image is significantly reduced.
Ultrasound in Medicine & Biology, 2007
Biomechanical properties of soft tissues are important for a wide range of medical applications, ... more Biomechanical properties of soft tissues are important for a wide range of medical applications, such as surgical simulation and planning and detection of lesions by elasticity imaging modalities. Currently, the data in the literature is limited and conflicting. Furthermore, to assess the biomechanical properties of living tissue in vivo, reliable imaging-based estimators must be developed and verified. For these reasons we developed and compared two independent quantitative methods -crawling wave estimator (CRE) and mechanical measurement (MM) for soft tissue characterization. The CRE method images shear wave interference patterns from which the shear wave velocity can be determined and hence the Young's modulus can be obtained. The MM method provides the complex Young's modulus of the soft tissue from which both elastic and viscous behavior can be extracted. This article presents the systematic comparison between these two techniques on the measurement of gelatin phantom, veal liver, thermal-treated veal liver, and human prostate. It was observed that the Young's moduli of liver and prostate tissues slightly increase with frequency. The experimental results of the two methods are highly congruent, suggesting CRE and MM methods can be reliably used to investigate viscoelastic properties of other soft tissues, with CRE having the advantages of operating in nearly real time and in situ.
ABSTRACT Spatial and temporal control over the expression of growth/differentiation factors is of... more ABSTRACT Spatial and temporal control over the expression of growth/differentiation factors is of great interest for regeneration of bone, but technologies capable of providing tight and active control over gene expression remain elusive. We propose the use of focused ultrasound for the targeted activation of heat shock-sensitive expression systems in engineered bone. We report in vitro results with cells that express firefly luciferase (fLuc) under the control of a heat shock protein promoter. Cells were embedded in fibrin scaffolds and exposed to focused ultrasound, using a custom 3.3MHz transducer (focal length 4", f-number 1.33", focal dimension 1.2mm lateral FWHM) in CW mode for 2-20 minutes at intensities ISPTA=120-440 W/cm2. The kinetics of ultrasound-mediated activation of the cells was compared with that of strictly thermal activation. Bioluminescence imaging revealed fLuc expression in an area >=2.5mm in diameter at the position of the ultrasound focus, and the diameter and intensity of the signal increased with the amplitude of the acoustic energy. We also found that ultrasound activated fLuc expression with substantially shorter exposures than thermal activation. Our results demonstrate the potential for focused ultrasound to selectively activate the expression of a gene of interest in an engineered tissue and suggest that focused ultrasound activates the heat shock pathway by a combination of thermal and non-thermal mechanisms.
Ultrasound in Medicine & Biology, 2008
Quantification of mechanical properties of human prostate tissue is important for developing sono... more Quantification of mechanical properties of human prostate tissue is important for developing sonoelastography for prostate cancer detection. In this study, we characterized the frequency-dependent complex Young's modulus of normal and cancerous prostate tissues in vitro by using stress relaxation testing and viscoelastic tissue modeling methods. After radical prostatectomy, small cylindrical tissue samples were acquired in the posterior region of each prostate. A total of 17 samples from eight human prostates were obtained and tested. Stress relaxation tests on prostate samples produced repeatable results that fit a viscoelastic Kelvin-Voigt fractional derivative (KVFD) model (r 2 >0.97). For normal (n ؍ 8) and cancerous (n ؍ 9) prostate samples, the average magnitudes of the complex Young's moduli (|E*|) were 15.9 ؎ 5.9 kPa and 40.4 ؎ 15.7 kPa at 150 Hz, respectively, giving an elastic contrast of 2.6:1. Nine two-sample t-tests indicated that there are significant differences between stiffness of normal and cancerous prostate tissues in the same gland (p < 0.01). This study contributes to the current limited knowledge on the viscoelastic properties of the human prostate, and the inherent elastic contrast produced by cancer. (
Tissue Engineering Part C: Methods, 2014
Temporal and spatial control of growth factor gradients is critical for tissue patterning and dif... more Temporal and spatial control of growth factor gradients is critical for tissue patterning and differentiation. Reinitiation of this developmental program is also required for regeneration of tissues during wound healing and tissue regeneration. Devising methods for reconstituting growth factor gradients remains a central challenge in regenerative medicine. In the current study we develop a novel gene therapy approach for temporal and spatial control of two important growth factors in bone regeneration, vascular endothelial growth factor, and bone morphogenetic protein 2, which involves application of high intensity focused ultrasound to cells engineered with a heat-activated- and ligand-inducible gene switch. Induction of transgene expression was tightly localized within cell-scaffold constructs to subvolumes of ∼30 mm³, and the amplitude and projected area of transgene expression was tuned by the intensity and duration of ultrasound exposure. Conditions for ultrasound-activated transgene expression resulted in minimal cytotoxicity and scaffold damage. Localized regions of growth factor expression also established gradients in signaling activity, suggesting that patterns of growth factor expression generated by this method will have utility in basic and applied studies on tissue development and regeneration.
Surface Science, 2003
The decomposition of NO has been studied on clean W(1 1 1), carbide-modified W(1 1 1), and oxycar... more The decomposition of NO has been studied on clean W(1 1 1), carbide-modified W(1 1 1), and oxycarbide-modified W(1 1 1) surfaces. The decomposition pathways are investigated using a combination of temperature programmed desorption, Auger electron spectroscopy, high-resolution electron energy loss spectroscopy, and soft X-ray photoelectron spectroscopy. All these surfaces exhibit high activity toward the decomposition of NO, and the only N-containing products are N 2 and N 2 O. Furthermore, all three surfaces preferentially produce N 2 over N 2 O from the decomposition of NO. Oxygen atoms, produced from the decomposition of NO, react with carbide surfaces to produce gas-phase CO at high temperatures. In addition, our results demonstrate that cycles of alternate NO/hydrocarbon treatments can regenerate the carbide overlayer on W(1 1 1), and the regenerated C/W(1 1 1) surface remains active in the decomposition of NO.
Medical Physics, 2008
Sonoelastography has been developed as an ultrasound-based elasticity imaging technique. In this ... more Sonoelastography has been developed as an ultrasound-based elasticity imaging technique. In this technique, external vibration is induced into the target tissue. In general, tissue stiffness is inversely proportional to the amplitude of tissue vibration. Imaging tissue vibration will provide the elasticity distribution in the target region. This study investigated the feasibility of using real-time sonoelastography to detect and estimate the volume of thermal lesions in porcine livers in vivo. A total of 32 thermal lesions with volumes ranging from 0.2 to 5.3 cm 3 were created using radiofrequency ablation ͑RFA͒ or high-intensity focused ultrasound ͑HIFU͒ technique. Lesions were imaged using sonoelastography and coregistered B-mode ultrasound. Volumes were reconstructed from a sequence of two-dimensional scans. The comparison of sonoelastographic measurements and pathology findings showed good correlation with respect to the area of the lesions ͑r 2 = 0.8823 for RFA lesions, r 2 = 0.9543 for HIFU lesions͒. In addition, good correspondence was found between threedimensional sonoelastography and gross pathology ͑3.6% underestimate͒, demonstrating the feasibility of sonoelastography for volume estimation of thermal lesions. These results support that sonoelastography outperforms conventional B-mode ultrasound and could potentially be used for assessment of thermal therapies.
The Journal of the Acoustical Society of America, 2010
ABSTRACT Clinical volumetric blood flow estimation relies on several assumptions. Among them are ... more ABSTRACT Clinical volumetric blood flow estimation relies on several assumptions. Among them are cylindrical vessel geometry, symmetric flow profile, and Doppler angle. None of them are known well enough to obtain clinically relevant estimates. 3-D color flow acquisition circumvents these assumptions, posing a viable tool for in vivo blood volume flow analysis. A 4-D cardiac scanner operating a 2-D array for real-time 3-D color flow imaging [GE Healthcare, Milwaukee, WI] was used. The array was positioned to fully intersect a 2-cm-diameter flow tube with the constant-depth plane (CPlane). Blood mimicking fluid was circulated at up to 6 l∕min using a cardiac bypass pump (60 and 80 beats∕min). A trigger source synchronized the pump and scanner. Data volumes were acquired equally spaced throughout the cardiac cycle. Temporally resolved volume flow was derived from CPlane data integration using Doppler power partial volume correction. Results show less than 7% mean flow error for temporally resolved volume flow (100 points per cardiac cycle and 50 averages). Single points in the cardiac cycle (10 max total), including systolic and diastolic flow, can be acquired within 50 heartbeats. Average, nontime-resolved flow can be estimated within 5 s.
The Journal of the Acoustical Society of America, 2014
One application of acoustic droplet vaporization (ADV), a method of converting biocompatible micr... more One application of acoustic droplet vaporization (ADV), a method of converting biocompatible microdroplets into microbubbles, is to enhance locally high intensity focused ultrasound (HIFU) therapy. Two objectives are pursued here: (1) the controlled creation of a bubble trench prior to HIFU using ADV and (2) use of the trench for increasing ablation volumes, lowering acoustic powers, and decreasing therapy duration. Thermally responsive phantoms were made with perfluorocarbon emulsion. Compound lesions were formed in a laboratory setting and a clinical magnetic resonance imaging (MRI)-guided HIFU system. Linear and spiral patterned compound lesions were generated in trenches. A larger fraction of the HIFU beam is contained to increase the generation of heat. Using the laboratory system, a 90 mm linear length spiral trench was formed in 30 s with mechanical beam steering. Comparatively, the clinical HIFU system formed a 19.9 mm linear length spiral trench in approximately 1 s with electronic beam steering. Lesions were imaged optically and with MRI. A uniform thermal ablation volume of 3.25 mL was achieved in 55.4 s (4-times faster than standard clinical HIFU and 14-times larger volume versus sum of individual lesions). Single lesions showed a 400% volume increase.
The Journal of the Acoustical Society of America, 2010
Applications of acoustic droplet vaporization in diagnostic and therapeutic ultrasound. [The Jour... more Applications of acoustic droplet vaporization in diagnostic and therapeutic ultrasound. [The Journal of the Acoustical Society of America 127, 1975 (2010)]. Mario L. Fabiilli, Oliver D. Kripfgans, Man Zhang, Kevin J. Haworth, Andrea H. Lo, Paul L. Carson, J. Brian Fowlkes. Abstract ...
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
As ultrasound imagers become increasingly portable and lower cost, breakthroughs in transducer te... more As ultrasound imagers become increasingly portable and lower cost, breakthroughs in transducer technology will be needed to provide high-resolution, real-time 3-D imaging while maintaining the affordability needed for portable systems. This paper presents a 32 x 32 ultrasound array prototype, manufactured using a CMUT-in-CMOS approach whereby ultrasonic transducer elements and readout circuits are integrated on a single chip using a standard integrated circuit manufacturing process in a commercial CMOS foundry. Only blanket wet-etch and sealing steps are added to complete the MEMS devices after the CMOS process. This process typically yields better than 99% working elements per array, with less than ±1.5 dB variation in receive sensitivity among the 1024 individually addressable elements. The CMUT pulseecho frequency response is typically centered at 2.1 MHz with a -6 dB fractional bandwidth of 60%, and elements are arranged on a 250 μm hexagonal grid (less than half-wavelength pitch). Multiplexers and CMOS buffers within the array are used to make on-chip routing manageable, reduce the number of physical output leads, and drive the transducer cable. The array has been interfaced to a commercial imager as well as a set of custom transmit and receive electronics, and volumetric images of nylon fishing line targets have been produced.
Academic Radiology, 2011
Rationale and Objectives-Acoustic droplet vaporization (ADV) shows promise for spatial control an... more Rationale and Objectives-Acoustic droplet vaporization (ADV) shows promise for spatial control and acceleration of thermal lesion production. Our hypothesis was that microbubbles generated by ADV could enhance high intensity focused ultrasound (HIFU) thermal ablation by controlling and increasing local energy absorption.
Ultrasound in medicine …, Jan 1, 2010
Acoustic droplet vaporization (ADV) shows promise for spatially and temporally targeted tissue oc... more Acoustic droplet vaporization (ADV) shows promise for spatially and temporally targeted tissue occlusion. In this study, substantial tissue occlusion was achieved in operatively exposed and transcutaneous canine kidneys by generating ADV gas bubbles in the renal arteries or segmental arteries. Fifteen canines were anesthetized, among which 10 underwent laparotomy to externalize the left kidney and 5 were undisturbed for transcutaneous ADV. The microbubbles were generated by phase conversion of perfluoropentane droplets encapsulated in albumin or lipid shells in the blood. A 3.5 MHz single-element therapy transducer was aligned with an imaging array in a water tank with direct access to the renal artery or a segmental artery. In vivo color flow and spectral Doppler imaging were used to identify the target arteries. Tone bursts of 1 kHz pulse repetition frequency with 0.25% duty cycle vaporized the droplets during bolus passage. Both intracardiac (IC) and intravenous (IV) injections repeatedly produced ADV in chosen arteries in externalized kidneys, as seen by B-mode imaging. Concurrent with this in two cases was the detection by pulse wave Doppler of blood flow reversal, along with a narrowing of the waveform. Localized cortex occlusion was achieved with 87% regional flow reduction in one case using IC injections. Vaporization from IV injections resulted in a substantial echogenicity increase with an average half-life of 8 minutes per droplet dose. Gas bubbles sufficient to produce some shadowing were generated by transcutaneous vaporization of intra renal artery or IV administered droplets, with a tissue path up to 5.5 cm.
Color Imaging Conference, 2004
Journal of Imaging Science and Technology, 2006
... ZHHuang, WYLong, GYXie, OLKwan, and ANDeMaria, Comparison of gray-scale and B-color ultrasou... more ... ZHHuang, WYLong, GYXie, OLKwan, and ANDeMaria, Comparison of gray-scale and B-color ultrasound images in evaluating left ventricular systolic function in coronary artery disease, Am. Heart J. 123, 2 (1992). ... (Permission from Dr. Deborah J. Rubens.). ...
PURPOSE To test the accuracy of real-time 3D angle-independent measurements of volume flow at car... more PURPOSE To test the accuracy of real-time 3D angle-independent measurements of volume flow at cardiac blood flow rates. METHOD AND MATERIALS We utilized a 4D (real-time 3D) color Doppler ultrasound scanner (Vivid 7, GE Healthcare, Milwaukee, WI) equipped with a 2D phased array (3V, GE Healthcare) to acquire bench top cardiac-type output under pulsatile flow conditions. In 3D, the color flow constant-depth plane (C-plane) resolution was 3 and 2.25 pixels/cm in the lateral and elevational directions respectively, while recording 10 volumes/second. Experiments were performed with a 2.5-cm diameter, thin-walled latex tube mounted in a water tank. Blood-mimicking fluid (CIRS Inc., Norfolk, VA) was circulated at up to 108 mL/s using a calibrated cardiac bypass pump set at 60 and 80 beats/min. Data was acquired randomly throughout the pump cycle with sweeps of 10, 25, 50, and 100 volumes. For each acquisition, a mean volume flow estimate was computed from C-plane integration and Doppler po...
Proceedings - IEEE Ultrasonics Symposium, 2008
Ultrasound can be used to phase transition perfluorocarbon (PFC) droplets into gas bubbles, a pro... more Ultrasound can be used to phase transition perfluorocarbon (PFC) droplets into gas bubbles, a process known as acoustic droplet vaporization (ADV). In vivo blood flow reductions can then be achieved using the ADV bubbles. An in situ ultrasonic measurement of this blood flow reduction is desirable. Since, in a simple model, initial flow reduction is proportional to the number of bubbles, and the mean echo power (MEP) in a B-mode image is related to the number of bubbles (off resonant scattering), it is hypothesized that the MEP can be used to estimate the relative flow reduction. To test this hypothesis, three canines were anesthetized and a laparotomy performed to externalize the left kidney and renal artery. An ultrasonic flow probe was placed on the renal artery. PFC droplets were injected intravenously and a focused 3.5 MHz single-element transducer was used to vaporize the PFC droplets, just downstream of the flow probe. The flow in the renal artery was recorded with the flowmeter as the vaporized droplets became lodged in the renal capillary beds. Simultaneously, B-mode cine loops were recorded. The cine loops were processed to determine the echogenicity, as measured by the MEP, in the kidney cortex. It was found that the MEP and renal arterial flow did not correlate quantitatively. However it was found that the MEP could be used to determine when the renal arterial flow had recovered to a steady state.
Medical Imaging 2008: Ultrasonic Imaging and Signal Processing, 2008
The capability of sonoelastography to detect lesions based on elasticity contrast can be applied ... more The capability of sonoelastography to detect lesions based on elasticity contrast can be applied to monitor the creation of thermally ablated lesion. Currently, segmentation of lesions depicted in sonoelastographic images is performed manually which can be a time consuming process and prone to significant intra-and inter-observer variability. This work presents a semi-automated segmentation algorithm for sonoelastographic data. The user starts by planting a seed in the perceived center of the lesion. Fast marching methods use this information to create an initial estimate of the lesion. Subsequently, level set methods refine its final shape by attaching the segmented contour to edges in the image while maintaining smoothness. The algorithm is applied to in vivo sonoelastographic images from twenty five thermal ablated lesions created in porcine livers. The estimated area is compared to results from manual segmentation and gross pathology images. Results show that the algorithm outperforms manual segmentation in accuracy, inter-and intra-observer variability. The processing time per image is significantly reduced.
Ultrasound in Medicine & Biology, 2007
Biomechanical properties of soft tissues are important for a wide range of medical applications, ... more Biomechanical properties of soft tissues are important for a wide range of medical applications, such as surgical simulation and planning and detection of lesions by elasticity imaging modalities. Currently, the data in the literature is limited and conflicting. Furthermore, to assess the biomechanical properties of living tissue in vivo, reliable imaging-based estimators must be developed and verified. For these reasons we developed and compared two independent quantitative methods -crawling wave estimator (CRE) and mechanical measurement (MM) for soft tissue characterization. The CRE method images shear wave interference patterns from which the shear wave velocity can be determined and hence the Young's modulus can be obtained. The MM method provides the complex Young's modulus of the soft tissue from which both elastic and viscous behavior can be extracted. This article presents the systematic comparison between these two techniques on the measurement of gelatin phantom, veal liver, thermal-treated veal liver, and human prostate. It was observed that the Young's moduli of liver and prostate tissues slightly increase with frequency. The experimental results of the two methods are highly congruent, suggesting CRE and MM methods can be reliably used to investigate viscoelastic properties of other soft tissues, with CRE having the advantages of operating in nearly real time and in situ.
ABSTRACT Spatial and temporal control over the expression of growth/differentiation factors is of... more ABSTRACT Spatial and temporal control over the expression of growth/differentiation factors is of great interest for regeneration of bone, but technologies capable of providing tight and active control over gene expression remain elusive. We propose the use of focused ultrasound for the targeted activation of heat shock-sensitive expression systems in engineered bone. We report in vitro results with cells that express firefly luciferase (fLuc) under the control of a heat shock protein promoter. Cells were embedded in fibrin scaffolds and exposed to focused ultrasound, using a custom 3.3MHz transducer (focal length 4", f-number 1.33", focal dimension 1.2mm lateral FWHM) in CW mode for 2-20 minutes at intensities ISPTA=120-440 W/cm2. The kinetics of ultrasound-mediated activation of the cells was compared with that of strictly thermal activation. Bioluminescence imaging revealed fLuc expression in an area >=2.5mm in diameter at the position of the ultrasound focus, and the diameter and intensity of the signal increased with the amplitude of the acoustic energy. We also found that ultrasound activated fLuc expression with substantially shorter exposures than thermal activation. Our results demonstrate the potential for focused ultrasound to selectively activate the expression of a gene of interest in an engineered tissue and suggest that focused ultrasound activates the heat shock pathway by a combination of thermal and non-thermal mechanisms.
Ultrasound in Medicine & Biology, 2008
Quantification of mechanical properties of human prostate tissue is important for developing sono... more Quantification of mechanical properties of human prostate tissue is important for developing sonoelastography for prostate cancer detection. In this study, we characterized the frequency-dependent complex Young's modulus of normal and cancerous prostate tissues in vitro by using stress relaxation testing and viscoelastic tissue modeling methods. After radical prostatectomy, small cylindrical tissue samples were acquired in the posterior region of each prostate. A total of 17 samples from eight human prostates were obtained and tested. Stress relaxation tests on prostate samples produced repeatable results that fit a viscoelastic Kelvin-Voigt fractional derivative (KVFD) model (r 2 >0.97). For normal (n ؍ 8) and cancerous (n ؍ 9) prostate samples, the average magnitudes of the complex Young's moduli (|E*|) were 15.9 ؎ 5.9 kPa and 40.4 ؎ 15.7 kPa at 150 Hz, respectively, giving an elastic contrast of 2.6:1. Nine two-sample t-tests indicated that there are significant differences between stiffness of normal and cancerous prostate tissues in the same gland (p < 0.01). This study contributes to the current limited knowledge on the viscoelastic properties of the human prostate, and the inherent elastic contrast produced by cancer. (
Tissue Engineering Part C: Methods, 2014
Temporal and spatial control of growth factor gradients is critical for tissue patterning and dif... more Temporal and spatial control of growth factor gradients is critical for tissue patterning and differentiation. Reinitiation of this developmental program is also required for regeneration of tissues during wound healing and tissue regeneration. Devising methods for reconstituting growth factor gradients remains a central challenge in regenerative medicine. In the current study we develop a novel gene therapy approach for temporal and spatial control of two important growth factors in bone regeneration, vascular endothelial growth factor, and bone morphogenetic protein 2, which involves application of high intensity focused ultrasound to cells engineered with a heat-activated- and ligand-inducible gene switch. Induction of transgene expression was tightly localized within cell-scaffold constructs to subvolumes of ∼30 mm³, and the amplitude and projected area of transgene expression was tuned by the intensity and duration of ultrasound exposure. Conditions for ultrasound-activated transgene expression resulted in minimal cytotoxicity and scaffold damage. Localized regions of growth factor expression also established gradients in signaling activity, suggesting that patterns of growth factor expression generated by this method will have utility in basic and applied studies on tissue development and regeneration.
Surface Science, 2003
The decomposition of NO has been studied on clean W(1 1 1), carbide-modified W(1 1 1), and oxycar... more The decomposition of NO has been studied on clean W(1 1 1), carbide-modified W(1 1 1), and oxycarbide-modified W(1 1 1) surfaces. The decomposition pathways are investigated using a combination of temperature programmed desorption, Auger electron spectroscopy, high-resolution electron energy loss spectroscopy, and soft X-ray photoelectron spectroscopy. All these surfaces exhibit high activity toward the decomposition of NO, and the only N-containing products are N 2 and N 2 O. Furthermore, all three surfaces preferentially produce N 2 over N 2 O from the decomposition of NO. Oxygen atoms, produced from the decomposition of NO, react with carbide surfaces to produce gas-phase CO at high temperatures. In addition, our results demonstrate that cycles of alternate NO/hydrocarbon treatments can regenerate the carbide overlayer on W(1 1 1), and the regenerated C/W(1 1 1) surface remains active in the decomposition of NO.
Medical Physics, 2008
Sonoelastography has been developed as an ultrasound-based elasticity imaging technique. In this ... more Sonoelastography has been developed as an ultrasound-based elasticity imaging technique. In this technique, external vibration is induced into the target tissue. In general, tissue stiffness is inversely proportional to the amplitude of tissue vibration. Imaging tissue vibration will provide the elasticity distribution in the target region. This study investigated the feasibility of using real-time sonoelastography to detect and estimate the volume of thermal lesions in porcine livers in vivo. A total of 32 thermal lesions with volumes ranging from 0.2 to 5.3 cm 3 were created using radiofrequency ablation ͑RFA͒ or high-intensity focused ultrasound ͑HIFU͒ technique. Lesions were imaged using sonoelastography and coregistered B-mode ultrasound. Volumes were reconstructed from a sequence of two-dimensional scans. The comparison of sonoelastographic measurements and pathology findings showed good correlation with respect to the area of the lesions ͑r 2 = 0.8823 for RFA lesions, r 2 = 0.9543 for HIFU lesions͒. In addition, good correspondence was found between threedimensional sonoelastography and gross pathology ͑3.6% underestimate͒, demonstrating the feasibility of sonoelastography for volume estimation of thermal lesions. These results support that sonoelastography outperforms conventional B-mode ultrasound and could potentially be used for assessment of thermal therapies.
The Journal of the Acoustical Society of America, 2010
ABSTRACT Clinical volumetric blood flow estimation relies on several assumptions. Among them are ... more ABSTRACT Clinical volumetric blood flow estimation relies on several assumptions. Among them are cylindrical vessel geometry, symmetric flow profile, and Doppler angle. None of them are known well enough to obtain clinically relevant estimates. 3-D color flow acquisition circumvents these assumptions, posing a viable tool for in vivo blood volume flow analysis. A 4-D cardiac scanner operating a 2-D array for real-time 3-D color flow imaging [GE Healthcare, Milwaukee, WI] was used. The array was positioned to fully intersect a 2-cm-diameter flow tube with the constant-depth plane (CPlane). Blood mimicking fluid was circulated at up to 6 l∕min using a cardiac bypass pump (60 and 80 beats∕min). A trigger source synchronized the pump and scanner. Data volumes were acquired equally spaced throughout the cardiac cycle. Temporally resolved volume flow was derived from CPlane data integration using Doppler power partial volume correction. Results show less than 7% mean flow error for temporally resolved volume flow (100 points per cardiac cycle and 50 averages). Single points in the cardiac cycle (10 max total), including systolic and diastolic flow, can be acquired within 50 heartbeats. Average, nontime-resolved flow can be estimated within 5 s.
The Journal of the Acoustical Society of America, 2014
One application of acoustic droplet vaporization (ADV), a method of converting biocompatible micr... more One application of acoustic droplet vaporization (ADV), a method of converting biocompatible microdroplets into microbubbles, is to enhance locally high intensity focused ultrasound (HIFU) therapy. Two objectives are pursued here: (1) the controlled creation of a bubble trench prior to HIFU using ADV and (2) use of the trench for increasing ablation volumes, lowering acoustic powers, and decreasing therapy duration. Thermally responsive phantoms were made with perfluorocarbon emulsion. Compound lesions were formed in a laboratory setting and a clinical magnetic resonance imaging (MRI)-guided HIFU system. Linear and spiral patterned compound lesions were generated in trenches. A larger fraction of the HIFU beam is contained to increase the generation of heat. Using the laboratory system, a 90 mm linear length spiral trench was formed in 30 s with mechanical beam steering. Comparatively, the clinical HIFU system formed a 19.9 mm linear length spiral trench in approximately 1 s with electronic beam steering. Lesions were imaged optically and with MRI. A uniform thermal ablation volume of 3.25 mL was achieved in 55.4 s (4-times faster than standard clinical HIFU and 14-times larger volume versus sum of individual lesions). Single lesions showed a 400% volume increase.
The Journal of the Acoustical Society of America, 2010
Applications of acoustic droplet vaporization in diagnostic and therapeutic ultrasound. [The Jour... more Applications of acoustic droplet vaporization in diagnostic and therapeutic ultrasound. [The Journal of the Acoustical Society of America 127, 1975 (2010)]. Mario L. Fabiilli, Oliver D. Kripfgans, Man Zhang, Kevin J. Haworth, Andrea H. Lo, Paul L. Carson, J. Brian Fowlkes. Abstract ...
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
As ultrasound imagers become increasingly portable and lower cost, breakthroughs in transducer te... more As ultrasound imagers become increasingly portable and lower cost, breakthroughs in transducer technology will be needed to provide high-resolution, real-time 3-D imaging while maintaining the affordability needed for portable systems. This paper presents a 32 x 32 ultrasound array prototype, manufactured using a CMUT-in-CMOS approach whereby ultrasonic transducer elements and readout circuits are integrated on a single chip using a standard integrated circuit manufacturing process in a commercial CMOS foundry. Only blanket wet-etch and sealing steps are added to complete the MEMS devices after the CMOS process. This process typically yields better than 99% working elements per array, with less than ±1.5 dB variation in receive sensitivity among the 1024 individually addressable elements. The CMUT pulseecho frequency response is typically centered at 2.1 MHz with a -6 dB fractional bandwidth of 60%, and elements are arranged on a 250 μm hexagonal grid (less than half-wavelength pitch). Multiplexers and CMOS buffers within the array are used to make on-chip routing manageable, reduce the number of physical output leads, and drive the transducer cable. The array has been interfaced to a commercial imager as well as a set of custom transmit and receive electronics, and volumetric images of nylon fishing line targets have been produced.
Academic Radiology, 2011
Rationale and Objectives-Acoustic droplet vaporization (ADV) shows promise for spatial control an... more Rationale and Objectives-Acoustic droplet vaporization (ADV) shows promise for spatial control and acceleration of thermal lesion production. Our hypothesis was that microbubbles generated by ADV could enhance high intensity focused ultrasound (HIFU) thermal ablation by controlling and increasing local energy absorption.
Ultrasound in medicine …, Jan 1, 2010
Acoustic droplet vaporization (ADV) shows promise for spatially and temporally targeted tissue oc... more Acoustic droplet vaporization (ADV) shows promise for spatially and temporally targeted tissue occlusion. In this study, substantial tissue occlusion was achieved in operatively exposed and transcutaneous canine kidneys by generating ADV gas bubbles in the renal arteries or segmental arteries. Fifteen canines were anesthetized, among which 10 underwent laparotomy to externalize the left kidney and 5 were undisturbed for transcutaneous ADV. The microbubbles were generated by phase conversion of perfluoropentane droplets encapsulated in albumin or lipid shells in the blood. A 3.5 MHz single-element therapy transducer was aligned with an imaging array in a water tank with direct access to the renal artery or a segmental artery. In vivo color flow and spectral Doppler imaging were used to identify the target arteries. Tone bursts of 1 kHz pulse repetition frequency with 0.25% duty cycle vaporized the droplets during bolus passage. Both intracardiac (IC) and intravenous (IV) injections repeatedly produced ADV in chosen arteries in externalized kidneys, as seen by B-mode imaging. Concurrent with this in two cases was the detection by pulse wave Doppler of blood flow reversal, along with a narrowing of the waveform. Localized cortex occlusion was achieved with 87% regional flow reduction in one case using IC injections. Vaporization from IV injections resulted in a substantial echogenicity increase with an average half-life of 8 minutes per droplet dose. Gas bubbles sufficient to produce some shadowing were generated by transcutaneous vaporization of intra renal artery or IV administered droplets, with a tissue path up to 5.5 cm.