Jinjun Xia - Academia.edu (original) (raw)
Papers by Jinjun Xia
Optical Sensors and Sensing Systems for Natural Resources and Food Safety and Quality, 2005
An objective and reliable method for meat quality measurement will benefit both consumers and mea... more An objective and reliable method for meat quality measurement will benefit both consumers and meat industry. Among various techniques, optical methods have the advantage of being fast, flexible, inexpensive and nondestructive, which are important characteristics for online quality control. Although there have been great progress in this area, many results are inconsistent and controversial because of the lack of fundamental understanding of in light-meat interactions. Optical measurements on meat tissues are affected by both meat scattering and absorption properties. In the project, a method based on diffuse approximation solution of light transport in tissue was used to derive meat scattering and absorption coefficients. Differentiating muscle scattering properties from absorption properties are important for muscle characterization because they represent distinctly different aspects of muscle physical and chemical components. Our preliminary results showed that scattering coefficients can detect variations in beef steak tenderness. This new technique is promising to be used as an indicator for beef tenderness. However, a more extensive study with larger sample population will be necessary to fully test the capability of using optical scattering for beef tenderness characterization.
Photons Plus Ultrasound: Imaging and Sensing 2013, 2013
ABSTRACT Photoacoustic (PA) imaging has been widely used in molecular imaging to detect diseased ... more ABSTRACT Photoacoustic (PA) imaging has been widely used in molecular imaging to detect diseased cells by targeting them with nanoparticle-based contrast agents. However, the sensitivity and specificity are easily degraded because contrast agent signals can be masked by the background. Magnetomotive photoacoustic imaging uses a new type of multifunctional composite particle combining an optically absorptive gold nanorod core and magnetic nanospheres, which can potentially accumulate and concentrate targeted cells while simultaneously enhancing their specific contrast compared to background signals. In this study, HeLa cells molecularly targeted using nanocomposites with folic acid mimicking targeted rare circulating tumor cells (CTCs) were circulated at a 6 ml/min flow rate for trapping and imaging studies. Preliminary results show that the cells accumulate rapidly in the presence of an externally applied magnetic field produced by a dual magnet system. The sensitivity of the current system can reach up to 1 cell/ml in clear water. By manipulating the trapped cells magnetically, the specificity of detecting cells in highly absorptive ink solution can be enhanced with 16.98 dB background suppression by applying motion filtering on PA signals to remove unwanted background signals insensitive to the magnetic field. The results appear promising for future preclinical studies on a small animal model and ultimate clinical detection of rare CTCs in the vasculature.
2011 IEEE International Ultrasonics Symposium, 2011
ABSTRACT In deep tissue photoacoustic (PA) imaging, a large beam size with large pulse energy is ... more ABSTRACT In deep tissue photoacoustic (PA) imaging, a large beam size with large pulse energy is typically used as a broad band acoustic signal excitation source. However, widely used solid state Q-switched laser systems are limited by their repetition rate for real-time applications. An emerging fiber laser with nanosecond level pulse width, hundreds of kilohertz repetition rate, and up to 1mJ pulse energy is a potential candidate for a new PA signal excitation source. However, the inherent drawbacks of narrow beam size and low pulse energy of a fiber laser make it hard to be directly applied to deep tissue imaging. To overcome this issue, a narrow beam scanning scheme is proposed in this study. However, the lower light penetration capability may still limit the depth at which this technique can be applied. The objective of this study is to compare the general quality of reconstructed images in terms of signal to noise ratio (SNR) for multiple narrow beam scanning PA excitation and conventional one shot, high pulse energy and large beam size excitation at depths appropriate for peripheral vascular applications.
SPIE Proceedings, 2006
Our recent studies indicated that the optical scattering has the ability to characterize the micr... more Our recent studies indicated that the optical scattering has the ability to characterize the micro structures in beef muscles. In this study, optical scattering spectra of beef semimembranosus and longissimus muscle samples were measured at different cooking temperatures along with the corresponding Warner-Bratzler shear force values. Overall, scattering coefficients increased first and then decreased. The increase was likely due to
Meat Science, 2007
We developed a fiber optical probe to measure spatially resolved diffuse reflectance from beef sa... more We developed a fiber optical probe to measure spatially resolved diffuse reflectance from beef samples in VIS-NIR bandwidth of 450-950 nm. The optical scattering and absorption coefficients were obtained by fitting the measurements with diffuse equation. Beef absorption coefficients are related to the sample chemical compositions such as the concentration of myoglobin and its derivatives; while scattering coefficients depend on meat structural properties such as sarcomere length and collagen concentration. Structural properties are also key factors in determining beef tenderness, therefore we hypothesize that a correlation exists between optical scattering and cooked Warner-Bratzler shear (WBS) force. Thirty-two, unfrozen beef muscle samples obtained from different animals were used in the correlation study. We found a higher scattering coefficient was associated with a higher cooked WBS. A linear regression analysis showed that sample scattering coefficients were significantly (p < 0.0001) correlated to the corresponding WBS with a coefficient of determination (R 2) of 0.59.
SPIE Proceedings, 2014
ABSTRACT Due to the high scattering coefficient of tissue over the wavelength range used for phot... more ABSTRACT Due to the high scattering coefficient of tissue over the wavelength range used for photoacoustic (PA) imaging, most studies employ bulky, low repetition rate lasers to provide sufficient pulse energies at depth to image within the body. The size and cost of these lasers has impeded integration of photoacoustics into conventional, routinely-used ultrasound (US) scanners. Here, we present an approach leveraging the capabilities of modern, high repetition rate fiber lasers to produce a clinically translatable system providing integrated US/PA images at frame rates > 30 Hz. The system uses a portable, low-cost, low pulse-energy (1 mJ/pulse), high repetition rate (1 kHz), 1064 nm laser and is designed for integrated US/PA imaging of the peripheral vasculature or any relevant diseased region, such as a tumor. Using a rotating galvo-mirror system, the incident laser beam is quickly scanned over the imaging area. Multiple PA images covering the scan area are integrated to form a single PA image. Additionally, ultrasound firings are integrated into the scan sequence to provide an US image reconstructed over the same frame period. We acquired PA images of a 1.5-mmdiameter cylindrical absorber (absorption coefficient 5 cm-1) embedded in a tissue-mimicking gelatin phantom at 6-cm depth. A 2 cm × 1 cm (depth × lateral) area was reconstructed. We obtained a signal-to-noise ratio of more than 30 dB, comparable to conventional PA methods using high energy, low repetition rate lasers. The current system produces an integrated US/PA frame at a 32 Hz rate, and 100 Hz frame rates are possible with our present approach.
This study investigates the feasibility of non-contact ultrasound shear wave generation and detec... more This study investigates the feasibility of non-contact ultrasound shear wave generation and detection using a line focused air-coupled transducer and miniaturized fiber optic-based Sagnac system for soft tissue mechanical characterization. This paper focused on the measuring ultrasound shear wave velocity on a phantom tissue surface. Different phantoms with different stiffness were used as samples. The group velocity and phase velocity of the generated ultrasound surface wave were measured. The results showed that the proposed system was efficient in ultrasound shear wave generation and detection. It has potential applications in non-contact and non-invasive soft tissue mechanical properties characterizations.
Sensors
In shear wave-based material mechanical characterization, the transmit/receiver transducer is gen... more In shear wave-based material mechanical characterization, the transmit/receiver transducer is generally in contact with the material through a coupling medium. In many applications, especially in biological tissue-related characterization, the application of the coupling medium and the contact method are not ideal, sometimes even unacceptable, due to contamination or stress response concerns. To avoid contact, we developed a 1 MHz air-coupled focused PZT transducer as a moderate pressure generator that could induce a shear wave in soft material and a fiber optic-based Sagnac system for the detection of the propagating shear wave. A calibration indicated that the fabricated air-coupled focused PZT transducer could generate pressure above 1 KPa within its focal range. This pressure is three to five times as much as the pressure generated by a 1 MHz air-coupled transducer currently available on the market. The integrated system was demonstrated through shear wave generation by the fabr...
SPIE Proceedings, 2011
Current systems designed for deep photoacoustic (PA) imaging typically use a low repetition rate,... more Current systems designed for deep photoacoustic (PA) imaging typically use a low repetition rate, high power pulsed laser to provide a ns-scale pulse illuminating a large tissue volume. Acoustic signals recorded on each laser firing can be used to reconstruct a complete 2-D (3-D) image of sources of heat release within that region. Using broad-beam excitation, the maximum frame rate
2010 IEEE International Ultrasonics Symposium, 2010
Filtering estimated displacements is widely used in ultrasonic strain imaging. To minimize spatia... more Filtering estimated displacements is widely used in ultrasonic strain imaging. To minimize spatial resolution loses due to filtering, we propose an adaptive, weighted least squares filtering scheme driven by a confidence index indicating estimation quality. Compared to traditional, non-adaptive median filtering, the variance of displacement estimation was reduced 61%. Moreover, this adaptive filtering scheme is particularly helpful in accumulating displacement and strain estimates.
Biomedical Optics and 3-D Imaging, 2012
ABSTRACT Magnetic trapping and manipulation of polystyrene beads mimicking magnetically targeted ... more ABSTRACT Magnetic trapping and manipulation of polystyrene beads mimicking magnetically targeted circulating tumor cells (CTCs) has been demonstrated using magnetomotive photoacoustic (mmPA) imaging. These techniques appear promising for the detection of rare CTCs in the vasculature.
Photons Plus Ultrasound: Imaging and Sensing 2015, 2015
Ultrasound-guided photoacoustic imaging has shown great potential for many clinical applications ... more Ultrasound-guided photoacoustic imaging has shown great potential for many clinical applications including vascular visualization, detection of nanoprobes sensing molecular profiles, and guidance of interventional procedures. However, bulky and costly lasers are usually required to provide sufficient pulse energies for deep imaging. The low pulse repetition rate also limits potential real-time applications of integrated photoacoustic/ultrasound (PAUS) imaging. With a compact and low-cost laser operating at a kHz repetition rate, we aim to integrate photoacoustics (PA) into a commercial ultrasound (US) machine utilizing an interleaved scanning approach for clinical translation, with imaging depth up to a few centimeters and frame rates > 30 Hz. Multiple PA sub-frames are formed by scanning laser firings covering a large scan region with a rotating galvo mirror, and then combined into a final frame. Ultrasound pulse-echo beams are interleaved between laser firings/PA receives. The approach was implemented with a diode-pumped laser, a commercial US scanner, and a linear array transducer. Insertion of an 18-gauge needle into a piece of chicken tissue, with subsequent injection of an absorptive agent into the tissue, was imaged with an integrated PAUS frame rate of 30 Hz, covering a 2.8 cm × 2.8 cm imaging plane. Given this real-time image rate and high contrast (> 40 dB at more than 1-cm depth in the PA image), we have demonstrated that this approach is potentially attractive for clinical procedure guidance.
Photoacoustics, 2014
Laser-ultrasonics is an attractive and powerful tool for the non-destructive testing and evaluati... more Laser-ultrasonics is an attractive and powerful tool for the non-destructive testing and evaluation (NDT&E) of composite materials. Current systems for non-contact detection of ultrasound have relatively low sensitivity compared to contact peizotransducers. They are also expensive, difficult to adjust, and strongly influenced by environmental noise. Moreover, laser-ultrasound (LU) systems typically launch only about 50 firings per second, much slower than the kHz level pulse repetition rate of conventional systems. As demonstrated here, most of these drawbacks can be eliminated by combining a new generation of compact, inexpensive, high repetition rate nanosecond fiber lasers with new developments in fiber telecommunication optics and an optimally designed balanced probe beam detector. In particular, a modified fiber-optic balanced Sagnac interferometer is presented as part of a LU pump-probe system for NDT&E of aircraft composites. The performance of the all-optical system is demon...
SPIE Proceedings, 2006
We recently found that optical scattering coefficients of beef muscle can be used as a predictor ... more We recently found that optical scattering coefficients of beef muscle can be used as a predictor for beef tenderness. However, it is still not clear what specific muscle properties are responsible for optical scattering. As an effort to answer these questions, we conducted several controlled experiments in which we studied the changes of scattering coefficient with muscle sarcomere length and
2010 IEEE International Ultrasonics Symposium, 2010
Photoacoustic (PA) imaging is rapidly evolving as a functional and molecular imaging tool. Contra... more Photoacoustic (PA) imaging is rapidly evolving as a functional and molecular imaging tool. Contrast agents with high optical absorption, such as gold nanoparticles, have been used to target diseased cells and increase the specific contrast of PA imaging. However, background tissue absorption greatly limits the detection of PA signals and the specificity of these contrast agents. To sensitively identify PA
SPIE Proceedings, 2013
ABSTRACT A new technique using pulsed laser heating of a nanocomposite contrast agent resulting i... more ABSTRACT A new technique using pulsed laser heating of a nanocomposite contrast agent resulting in local bubble formation and concomitant harmonic generation in a scattered probe ultrasound (US) beam is proposed to increase specific contrast in both US imaging and laser-induced photoacoustic (PA) imaging. The composite combines an emulsion bead core with amphiphilic gold nanospheres (GNSs) assembled at the interface. Clustered GNSs result in a broadened absorption spectrum in the near infrared range (700-1000 nm) compared to the typical 520 nm peak of distributed GNSs, enabling their use at depth in tissue. Illuminating the composite with a pulsed laser with appropriately chosen parameters heats the composite through optical absorption by the GNSs and results in a phase transition of the emulsion bead to form a transient bubble. By delivering a probe US pulse simultaneously, or immediately after the laser pulse is delivered, harmonic signals are produced in the scattered US beam. The results show that a residual signal created by subtracting a US signal from the simultaneous US/laser probing signal of the emulsion bead sample is 1.7 dB higher than the laser alone generated PA signal and 20 dB higher than the PA signal of a control homogeneous GNSs dispersion with the same optical absorption, indicating the nonlinear contrast enhancement from bubble dynamics. The proposed technique of local activation of this designed contrast agent can be used to dramatically enhance both the specificity and sensitivity of integrated US/PA molecular imaging.
2013 IEEE International Ultrasonics Symposium (IUS), 2013
ABSTRACT The possibility of manipulating inertial cavitation induced in a new type of nanoemulsio... more ABSTRACT The possibility of manipulating inertial cavitation induced in a new type of nanoemulsion contrast agent with simultaneous nanosecond pulsed laser and ultrasound illumination is described. The contrast agent consists of an encapsulated emulsion core coated with a layer of 12nm-diameter gold nanospheres. A low-cost, high repetition-rate, low-energy 1064 nm fiber laser transiently heated the emulsion beads to help initiate inertial cavitation due to a phase transition in the emulsion core. It has been shown that inertial cavitation can be initiated at a very low acoustic pressure (0.43MPa) with laser irradiation applied at the rarefaction phase of the incident acoustic wave. The significantly decreased inertial cavitation threshold in this nanoemulsion suggests that it could be an effective tool for site-targeted, molecular therapeutics in addition to its proposed use as a highly specific molecular imaging agent for photoacoustics.
2013 IEEE International Ultrasonics Symposium (IUS), 2013
ABSTRACT A new technique using a composite contrast agent is proposed to increase specific contra... more ABSTRACT A new technique using a composite contrast agent is proposed to increase specific contrast in photoacoustic (PA) molecular imaging. The composite particle has an emulsion bead core with a surface-assembled monolayer of gold nanospheres (GNSs), which efficiently absorbs optical energy under laser irradiation and promotes a phase transition of the emulsion bead to form a transient bubble. Much stronger PA signals are generated by the phase transition process than those from thermal expansion, the most common mechanism of laser-sound conversion. By applying a differential scheme of images, recorded at a series of variable fluences, assuming a linear relation between laser fluence and the PA signal amplitude, a nearly perfect suppression of a linear agent can be obtained, while large residues for the nonlinear emulsion beads remain. This result clearly indicates enhanced PA sensitivity and specificity. Localized bubble generation activated by a short laser pulse was also demonstrated using a microscope coupled with a high-speed camera. With simultaneous ultrasound/laser probing, i.e., delivering a probe ultrasound beam after bubble formation, the nonlinear agent shows great potential for ultrasound contrast-enhanced imaging and harmonic imaging.
Optical Sensors and Sensing Systems for Natural Resources and Food Safety and Quality, 2005
An objective and reliable method for meat quality measurement will benefit both consumers and mea... more An objective and reliable method for meat quality measurement will benefit both consumers and meat industry. Among various techniques, optical methods have the advantage of being fast, flexible, inexpensive and nondestructive, which are important characteristics for online quality control. Although there have been great progress in this area, many results are inconsistent and controversial because of the lack of fundamental understanding of in light-meat interactions. Optical measurements on meat tissues are affected by both meat scattering and absorption properties. In the project, a method based on diffuse approximation solution of light transport in tissue was used to derive meat scattering and absorption coefficients. Differentiating muscle scattering properties from absorption properties are important for muscle characterization because they represent distinctly different aspects of muscle physical and chemical components. Our preliminary results showed that scattering coefficients can detect variations in beef steak tenderness. This new technique is promising to be used as an indicator for beef tenderness. However, a more extensive study with larger sample population will be necessary to fully test the capability of using optical scattering for beef tenderness characterization.
Photons Plus Ultrasound: Imaging and Sensing 2013, 2013
ABSTRACT Photoacoustic (PA) imaging has been widely used in molecular imaging to detect diseased ... more ABSTRACT Photoacoustic (PA) imaging has been widely used in molecular imaging to detect diseased cells by targeting them with nanoparticle-based contrast agents. However, the sensitivity and specificity are easily degraded because contrast agent signals can be masked by the background. Magnetomotive photoacoustic imaging uses a new type of multifunctional composite particle combining an optically absorptive gold nanorod core and magnetic nanospheres, which can potentially accumulate and concentrate targeted cells while simultaneously enhancing their specific contrast compared to background signals. In this study, HeLa cells molecularly targeted using nanocomposites with folic acid mimicking targeted rare circulating tumor cells (CTCs) were circulated at a 6 ml/min flow rate for trapping and imaging studies. Preliminary results show that the cells accumulate rapidly in the presence of an externally applied magnetic field produced by a dual magnet system. The sensitivity of the current system can reach up to 1 cell/ml in clear water. By manipulating the trapped cells magnetically, the specificity of detecting cells in highly absorptive ink solution can be enhanced with 16.98 dB background suppression by applying motion filtering on PA signals to remove unwanted background signals insensitive to the magnetic field. The results appear promising for future preclinical studies on a small animal model and ultimate clinical detection of rare CTCs in the vasculature.
2011 IEEE International Ultrasonics Symposium, 2011
ABSTRACT In deep tissue photoacoustic (PA) imaging, a large beam size with large pulse energy is ... more ABSTRACT In deep tissue photoacoustic (PA) imaging, a large beam size with large pulse energy is typically used as a broad band acoustic signal excitation source. However, widely used solid state Q-switched laser systems are limited by their repetition rate for real-time applications. An emerging fiber laser with nanosecond level pulse width, hundreds of kilohertz repetition rate, and up to 1mJ pulse energy is a potential candidate for a new PA signal excitation source. However, the inherent drawbacks of narrow beam size and low pulse energy of a fiber laser make it hard to be directly applied to deep tissue imaging. To overcome this issue, a narrow beam scanning scheme is proposed in this study. However, the lower light penetration capability may still limit the depth at which this technique can be applied. The objective of this study is to compare the general quality of reconstructed images in terms of signal to noise ratio (SNR) for multiple narrow beam scanning PA excitation and conventional one shot, high pulse energy and large beam size excitation at depths appropriate for peripheral vascular applications.
SPIE Proceedings, 2006
Our recent studies indicated that the optical scattering has the ability to characterize the micr... more Our recent studies indicated that the optical scattering has the ability to characterize the micro structures in beef muscles. In this study, optical scattering spectra of beef semimembranosus and longissimus muscle samples were measured at different cooking temperatures along with the corresponding Warner-Bratzler shear force values. Overall, scattering coefficients increased first and then decreased. The increase was likely due to
Meat Science, 2007
We developed a fiber optical probe to measure spatially resolved diffuse reflectance from beef sa... more We developed a fiber optical probe to measure spatially resolved diffuse reflectance from beef samples in VIS-NIR bandwidth of 450-950 nm. The optical scattering and absorption coefficients were obtained by fitting the measurements with diffuse equation. Beef absorption coefficients are related to the sample chemical compositions such as the concentration of myoglobin and its derivatives; while scattering coefficients depend on meat structural properties such as sarcomere length and collagen concentration. Structural properties are also key factors in determining beef tenderness, therefore we hypothesize that a correlation exists between optical scattering and cooked Warner-Bratzler shear (WBS) force. Thirty-two, unfrozen beef muscle samples obtained from different animals were used in the correlation study. We found a higher scattering coefficient was associated with a higher cooked WBS. A linear regression analysis showed that sample scattering coefficients were significantly (p < 0.0001) correlated to the corresponding WBS with a coefficient of determination (R 2) of 0.59.
SPIE Proceedings, 2014
ABSTRACT Due to the high scattering coefficient of tissue over the wavelength range used for phot... more ABSTRACT Due to the high scattering coefficient of tissue over the wavelength range used for photoacoustic (PA) imaging, most studies employ bulky, low repetition rate lasers to provide sufficient pulse energies at depth to image within the body. The size and cost of these lasers has impeded integration of photoacoustics into conventional, routinely-used ultrasound (US) scanners. Here, we present an approach leveraging the capabilities of modern, high repetition rate fiber lasers to produce a clinically translatable system providing integrated US/PA images at frame rates > 30 Hz. The system uses a portable, low-cost, low pulse-energy (1 mJ/pulse), high repetition rate (1 kHz), 1064 nm laser and is designed for integrated US/PA imaging of the peripheral vasculature or any relevant diseased region, such as a tumor. Using a rotating galvo-mirror system, the incident laser beam is quickly scanned over the imaging area. Multiple PA images covering the scan area are integrated to form a single PA image. Additionally, ultrasound firings are integrated into the scan sequence to provide an US image reconstructed over the same frame period. We acquired PA images of a 1.5-mmdiameter cylindrical absorber (absorption coefficient 5 cm-1) embedded in a tissue-mimicking gelatin phantom at 6-cm depth. A 2 cm × 1 cm (depth × lateral) area was reconstructed. We obtained a signal-to-noise ratio of more than 30 dB, comparable to conventional PA methods using high energy, low repetition rate lasers. The current system produces an integrated US/PA frame at a 32 Hz rate, and 100 Hz frame rates are possible with our present approach.
This study investigates the feasibility of non-contact ultrasound shear wave generation and detec... more This study investigates the feasibility of non-contact ultrasound shear wave generation and detection using a line focused air-coupled transducer and miniaturized fiber optic-based Sagnac system for soft tissue mechanical characterization. This paper focused on the measuring ultrasound shear wave velocity on a phantom tissue surface. Different phantoms with different stiffness were used as samples. The group velocity and phase velocity of the generated ultrasound surface wave were measured. The results showed that the proposed system was efficient in ultrasound shear wave generation and detection. It has potential applications in non-contact and non-invasive soft tissue mechanical properties characterizations.
Sensors
In shear wave-based material mechanical characterization, the transmit/receiver transducer is gen... more In shear wave-based material mechanical characterization, the transmit/receiver transducer is generally in contact with the material through a coupling medium. In many applications, especially in biological tissue-related characterization, the application of the coupling medium and the contact method are not ideal, sometimes even unacceptable, due to contamination or stress response concerns. To avoid contact, we developed a 1 MHz air-coupled focused PZT transducer as a moderate pressure generator that could induce a shear wave in soft material and a fiber optic-based Sagnac system for the detection of the propagating shear wave. A calibration indicated that the fabricated air-coupled focused PZT transducer could generate pressure above 1 KPa within its focal range. This pressure is three to five times as much as the pressure generated by a 1 MHz air-coupled transducer currently available on the market. The integrated system was demonstrated through shear wave generation by the fabr...
SPIE Proceedings, 2011
Current systems designed for deep photoacoustic (PA) imaging typically use a low repetition rate,... more Current systems designed for deep photoacoustic (PA) imaging typically use a low repetition rate, high power pulsed laser to provide a ns-scale pulse illuminating a large tissue volume. Acoustic signals recorded on each laser firing can be used to reconstruct a complete 2-D (3-D) image of sources of heat release within that region. Using broad-beam excitation, the maximum frame rate
2010 IEEE International Ultrasonics Symposium, 2010
Filtering estimated displacements is widely used in ultrasonic strain imaging. To minimize spatia... more Filtering estimated displacements is widely used in ultrasonic strain imaging. To minimize spatial resolution loses due to filtering, we propose an adaptive, weighted least squares filtering scheme driven by a confidence index indicating estimation quality. Compared to traditional, non-adaptive median filtering, the variance of displacement estimation was reduced 61%. Moreover, this adaptive filtering scheme is particularly helpful in accumulating displacement and strain estimates.
Biomedical Optics and 3-D Imaging, 2012
ABSTRACT Magnetic trapping and manipulation of polystyrene beads mimicking magnetically targeted ... more ABSTRACT Magnetic trapping and manipulation of polystyrene beads mimicking magnetically targeted circulating tumor cells (CTCs) has been demonstrated using magnetomotive photoacoustic (mmPA) imaging. These techniques appear promising for the detection of rare CTCs in the vasculature.
Photons Plus Ultrasound: Imaging and Sensing 2015, 2015
Ultrasound-guided photoacoustic imaging has shown great potential for many clinical applications ... more Ultrasound-guided photoacoustic imaging has shown great potential for many clinical applications including vascular visualization, detection of nanoprobes sensing molecular profiles, and guidance of interventional procedures. However, bulky and costly lasers are usually required to provide sufficient pulse energies for deep imaging. The low pulse repetition rate also limits potential real-time applications of integrated photoacoustic/ultrasound (PAUS) imaging. With a compact and low-cost laser operating at a kHz repetition rate, we aim to integrate photoacoustics (PA) into a commercial ultrasound (US) machine utilizing an interleaved scanning approach for clinical translation, with imaging depth up to a few centimeters and frame rates > 30 Hz. Multiple PA sub-frames are formed by scanning laser firings covering a large scan region with a rotating galvo mirror, and then combined into a final frame. Ultrasound pulse-echo beams are interleaved between laser firings/PA receives. The approach was implemented with a diode-pumped laser, a commercial US scanner, and a linear array transducer. Insertion of an 18-gauge needle into a piece of chicken tissue, with subsequent injection of an absorptive agent into the tissue, was imaged with an integrated PAUS frame rate of 30 Hz, covering a 2.8 cm × 2.8 cm imaging plane. Given this real-time image rate and high contrast (> 40 dB at more than 1-cm depth in the PA image), we have demonstrated that this approach is potentially attractive for clinical procedure guidance.
Photoacoustics, 2014
Laser-ultrasonics is an attractive and powerful tool for the non-destructive testing and evaluati... more Laser-ultrasonics is an attractive and powerful tool for the non-destructive testing and evaluation (NDT&E) of composite materials. Current systems for non-contact detection of ultrasound have relatively low sensitivity compared to contact peizotransducers. They are also expensive, difficult to adjust, and strongly influenced by environmental noise. Moreover, laser-ultrasound (LU) systems typically launch only about 50 firings per second, much slower than the kHz level pulse repetition rate of conventional systems. As demonstrated here, most of these drawbacks can be eliminated by combining a new generation of compact, inexpensive, high repetition rate nanosecond fiber lasers with new developments in fiber telecommunication optics and an optimally designed balanced probe beam detector. In particular, a modified fiber-optic balanced Sagnac interferometer is presented as part of a LU pump-probe system for NDT&E of aircraft composites. The performance of the all-optical system is demon...
SPIE Proceedings, 2006
We recently found that optical scattering coefficients of beef muscle can be used as a predictor ... more We recently found that optical scattering coefficients of beef muscle can be used as a predictor for beef tenderness. However, it is still not clear what specific muscle properties are responsible for optical scattering. As an effort to answer these questions, we conducted several controlled experiments in which we studied the changes of scattering coefficient with muscle sarcomere length and
2010 IEEE International Ultrasonics Symposium, 2010
Photoacoustic (PA) imaging is rapidly evolving as a functional and molecular imaging tool. Contra... more Photoacoustic (PA) imaging is rapidly evolving as a functional and molecular imaging tool. Contrast agents with high optical absorption, such as gold nanoparticles, have been used to target diseased cells and increase the specific contrast of PA imaging. However, background tissue absorption greatly limits the detection of PA signals and the specificity of these contrast agents. To sensitively identify PA
SPIE Proceedings, 2013
ABSTRACT A new technique using pulsed laser heating of a nanocomposite contrast agent resulting i... more ABSTRACT A new technique using pulsed laser heating of a nanocomposite contrast agent resulting in local bubble formation and concomitant harmonic generation in a scattered probe ultrasound (US) beam is proposed to increase specific contrast in both US imaging and laser-induced photoacoustic (PA) imaging. The composite combines an emulsion bead core with amphiphilic gold nanospheres (GNSs) assembled at the interface. Clustered GNSs result in a broadened absorption spectrum in the near infrared range (700-1000 nm) compared to the typical 520 nm peak of distributed GNSs, enabling their use at depth in tissue. Illuminating the composite with a pulsed laser with appropriately chosen parameters heats the composite through optical absorption by the GNSs and results in a phase transition of the emulsion bead to form a transient bubble. By delivering a probe US pulse simultaneously, or immediately after the laser pulse is delivered, harmonic signals are produced in the scattered US beam. The results show that a residual signal created by subtracting a US signal from the simultaneous US/laser probing signal of the emulsion bead sample is 1.7 dB higher than the laser alone generated PA signal and 20 dB higher than the PA signal of a control homogeneous GNSs dispersion with the same optical absorption, indicating the nonlinear contrast enhancement from bubble dynamics. The proposed technique of local activation of this designed contrast agent can be used to dramatically enhance both the specificity and sensitivity of integrated US/PA molecular imaging.
2013 IEEE International Ultrasonics Symposium (IUS), 2013
ABSTRACT The possibility of manipulating inertial cavitation induced in a new type of nanoemulsio... more ABSTRACT The possibility of manipulating inertial cavitation induced in a new type of nanoemulsion contrast agent with simultaneous nanosecond pulsed laser and ultrasound illumination is described. The contrast agent consists of an encapsulated emulsion core coated with a layer of 12nm-diameter gold nanospheres. A low-cost, high repetition-rate, low-energy 1064 nm fiber laser transiently heated the emulsion beads to help initiate inertial cavitation due to a phase transition in the emulsion core. It has been shown that inertial cavitation can be initiated at a very low acoustic pressure (0.43MPa) with laser irradiation applied at the rarefaction phase of the incident acoustic wave. The significantly decreased inertial cavitation threshold in this nanoemulsion suggests that it could be an effective tool for site-targeted, molecular therapeutics in addition to its proposed use as a highly specific molecular imaging agent for photoacoustics.
2013 IEEE International Ultrasonics Symposium (IUS), 2013
ABSTRACT A new technique using a composite contrast agent is proposed to increase specific contra... more ABSTRACT A new technique using a composite contrast agent is proposed to increase specific contrast in photoacoustic (PA) molecular imaging. The composite particle has an emulsion bead core with a surface-assembled monolayer of gold nanospheres (GNSs), which efficiently absorbs optical energy under laser irradiation and promotes a phase transition of the emulsion bead to form a transient bubble. Much stronger PA signals are generated by the phase transition process than those from thermal expansion, the most common mechanism of laser-sound conversion. By applying a differential scheme of images, recorded at a series of variable fluences, assuming a linear relation between laser fluence and the PA signal amplitude, a nearly perfect suppression of a linear agent can be obtained, while large residues for the nonlinear emulsion beads remain. This result clearly indicates enhanced PA sensitivity and specificity. Localized bubble generation activated by a short laser pulse was also demonstrated using a microscope coupled with a high-speed camera. With simultaneous ultrasound/laser probing, i.e., delivering a probe ultrasound beam after bubble formation, the nonlinear agent shows great potential for ultrasound contrast-enhanced imaging and harmonic imaging.