These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Thermal Diffusivity of Reduced Activation Ferritic/Martensitic Steel Determined by the Time Domain Photoacoustic Piezoelectric Technique  

NASA Astrophysics Data System (ADS)

The thermal diffusivity of reduced activation ferritic/martensitic steel (CLF-1), which is recognized as the primary candidate structural material for the test blanket module of the international thermal-nuclear experimental reactor, has been studied by the time-domain (TD) photoacoustic piezoelectric (PAPE) technique. The TD PAPE model based on a simplified thermoelastic theory under square-wave modulated laser excitation is presented, relating the TD PAPE signal to the modulation frequency, thermal diffusivity, and other material parameters. Thermal diffusivities of reference samples such as copper and nickel were measured and analyzed, by which the validity of the technique is verified. The thermal diffusivity of the CLF-1 sample was measured to be 8.2 {mm}2{\\cdot }{s}^{-1} , which is at a medium level among the ordinary steel materials (3 {mm}2{\\cdot }{s}^{-1} to 14 {mm}2{\\cdot }{s}^{-1}) and has decent heat-dissipation ability. The results show that the TD PAPE technique can provide a fast and economic way for the investigation of the thermophysical properties of fusion reactor structural materials.

Zhao, Binxing; Wang, Yafei; Gao, Chunming; Sun, Qiming; Wang, Pinghuai

2014-07-01

2

Piezoelectric cantilever microphone for photoacoustic gas detector  

Microsoft Academic Search

New micromachined pressure sensors based on PZT coated silicon cantilevers have been fabricated and integrated in a photoacoustic gas detector. PZT Sol-gel thin films texture and composition were optimized with respect to the transverse piezoelectric coefficient e31,f. A best value of -12 C\\/m was obtained with (100)\\/(001) textured thin films at the MPB composition. Optimum stress compensation between the different

Nicolas Ledermann; Jacek Baborowski; Andreas Seifert; Bert Willing; Stephane Hiboux; Paul Muralt; Nava Setter; Martin Forster

2001-01-01

3

Phase correction in piezoelectric photoacoustic Fourier transform infrared spectroscopy of mica  

Microsoft Academic Search

Piezoelectric photoacoustic IR spectra of mica are obtained using a Fourier transform IR spectrometer and lead zirconate titanate (PZT) as a detector. The spectra exhibit negative intensities and transmission like bands, instead of more conventional absorption bands generally observed with a gas- microphone cell. Correct spectra of mica\\/PZT are calculated only when the interferogram phase is constrained to the first

S. L. Zhang; Kirk H. Michaelian; James A. Burt

1997-01-01

4

Phase correction in piezoelectric photoacoustic Fourier transform infrared spectroscopy of mica  

NASA Astrophysics Data System (ADS)

Piezoelectric photoacoustic IR spectra of mica are obtained using a Fourier transform IR spectrometer and lead zirconate titanate (PZT) as a detector. The spectra exhibit negative intensities and transmission like bands, instead of more conventional absorption bands generally observed with a gas- microphone cell. Correct spectra of mica/PZT are calculated only when the interferogram phase is constrained to the first and fourth quadrants, similar to the case in differential spectroscopy where negative intensities occur.

Zhang, S. L.; Michaelian, Kirk H.; Burt, James A.

1997-02-01

5

A photoacoustic technique to measure the properties of single cells  

NASA Astrophysics Data System (ADS)

We demonstrate a new technique to non-invasively determine the diameter and sound speed of single cells using a combined ultrasonic and photoacoustic technique. Two cell lines, B16-F1 melanoma cells and MCF7 breast cancer cells were examined using this technique. Using a 200 MHz transducer, the ultrasound backscatter from a single cell in suspension was recorded. Immediately following, the cell was irradiated with a 532 nm laser and the resulting photoacoustic wave recorded by the same transducer. The melanoma cells contain optically absorbing melanin particles, which facilitated photoacoustic wave generation. MCF7 cells have negligible optical absorption at 532 nm; the cells were permeabilized and stained with trypan blue prior to measurements. The measured ultrasound and photoacoustic power spectra were compared to theoretical equations with the cell diameter and sound speed as variables (Anderson scattering model for ultrasound, and a thermoelastic expansion model for photoacoustics). The diameter and sound speed were extracted from the models where the spectral shape matched the measured signals. However the photoacoustic spectrum for the melanoma cell did not match theory, which is likely because melanin particles are located around the cytoplasm, and not within the nucleus. Therefore a photoacoustic finite element model of a cell was developed where the central region was not used to generate a photoacoustic wave. The resulting power spectrum was in better agreement with the measured signal than the thermoelastic expansion model. The MCF7 cell diameter obtained using the spectral matching method was 17.5 ?m, similar to the optical measurement of 16 ?m, while the melanoma cell diameter obtained was 22 ?m, similar to the optical measurement of 21 ?m. The sound speed measured from the MCF7 and melanoma cell was 1573 and 1560 m/s, respectively, which is within acceptable values that have been published in literature.

Strohm, Eric M.; Berndl, Elizabeth S. L.; Kolios, Michael C.

2013-03-01

6

Photoacoustic Techniques for Trace Gas Sensing Based on Semiconductor Laser Sources  

PubMed Central

The paper provides an overview on the use of photoacoustic sensors based on semiconductor laser sources for the detection of trace gases. We review the results obtained using standard, differential and quartz enhanced photoacoustic techniques. PMID:22303143

Elia, Angela; Lugara, Pietro Mario; Di Franco, Cinzia; Spagnolo, Vincenzo

2009-01-01

7

Adaptive and robust techniques (ART) for thermoacoustic and photoacoustic tomography  

Microsoft Academic Search

In this paper, we present new Adaptive and Robust Techniques (ART) for microwave-based thermoacoustic tomography (TAT) and laser-based photo-acoustic tomography (PAT), and study their performances for breast cancer detection. TAT and PAT are emerging medical imaging techniques that combine the merits of high contrast due to electromagnetic or laser stimulation and high resolution offered by thermal acoustic imaging. The current

Yao Xie; Bin Guo; Jian Li; Geng Ku; Lihong V. Wang

2007-01-01

8

Percutaneous permeation measurement of topical phthalocyanine by photoacoustic technique  

NASA Astrophysics Data System (ADS)

This investigation have studied photoacoustic (PA) technique to percutaneous permeation of topical hydroxy-(29H,31H-phthalocyaninate) aluminum (PcAlOH) on pig ear skin. The PcAlOH was incorporated in an emulsion (O/W) (1 mg/dl) with assessed stability parameters of: pH, short and long term stability tests (in the several conditions). The skin was prepared through a heat separation technique, and with a scalpel, the outer skin of the cartilage was removed. The skins were then cut into 4 cm2 pieces and treated with sodium bromide 2 mol/L for 6 h at 37 °C. The epidermis layer was washed with purified water, dried, and stored under reduced pressure until use. The skin permeation kinetics was determined by photoacoustic technique in an open photoacoustic cell. Short (after preparation) and long-term stability tests showed no phase separation. The emulsion developed pH 7.6 and after incorporating the pH was unchanged. The typical times for percutaneous permeation of the emulsion base and emulsion + PcAlOH were 182 (±6) and 438 (±3) s, respectively. This study indicated that the formulations containing PcAlOH have stabile characteristics and show promising results in absorption into the skin. The presence of the photosensitive agent in the formulation contributed significantly to the greater absorption time than observed in the base formulation. The used photoacoustic technical to examine the penetration kinetics of PcAlOH in pig ear skin was adequate and may be employed in the determination of the percutaneous permeation of phthalocyanines.

Silva, Emanoel P. O.; Barja, Paulo R.; Cardoso, Luiz E.; Beltrame, Milton

2012-11-01

9

Experimental Research of Gruneisen Parameter of Fullerite C60 Single Crystal Near Structural Phase Transition at 260 K Using Photoacoustic Technique  

Microsoft Academic Search

The work is devoted to experimental research of Gruneisen parameter of fullerite C60 (100) single crystal near structural phase transition at 260 K using photoacoustic technique. For measurements automated set-up with laser excitation and piezoelectric registration was used. For illumination of a sample the He-Ne laser was used, which radiation (with wavelength 0.63 microns and power 25 mW) was modulated

Aleksandr Korobov; Natalya Odina; Vladimir Chegnov; Mikhail Chukichev

2008-01-01

10

Advancement of a MEMS photoacoustic chemical sensor  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is a useful monitoring technique that is well suited for trace gas detection. The technique also possesses favorable detection characteristics when the system dimensions are scaled to a micro-system design. The objective of present work is to incorporate two strengths of the Army Research Laboratory (ARL), piezoelectric microelectromechanical systems (MEMS) and chemical and biological sensing into a monolithic MEMS photoacoutic trace gas sensor. We initially miniaturized a macro-cell design as a means to examine performance and design issues as the photoacoustics is scaled to a dimension approaching the MEMS level. A miniature non-MEMS photoacoutic resonance cell was fabricated and tested with resonator dimensions: diam.=1.5 mm, length = 30mm. Knowledge gained in these initial tests provide the basic information required to fabricate a MEMS scale device while maintaining the sensor integrity. Initial MEMS work is centered on fabrication of a lead zirconate titanate (PZT) microphone subsystem to be incorporated in the full photoacoustic device. PZT membrane microphones have been designed, fabricated and acoustically tested. Presently, the piezoelectric microphone performance has revealed the possibility of using a PZT microphone as the passive acoustic detection mechanism of a photoacoustic resonant cavity. Preliminary designs of the MEMS photoacoustic resonator incorporate a three-wafer design to create a monolithic MEMS photoacoustic cavity. Results will be presented describing the miniature photoacoustic cell capabilities and initial MEMS microphone performance. Preliminary results concerning the MEMS photoacoustic cell design will also be discussed.

Pellegrino, Paul M.; Polcawich, Ronald G.

2003-08-01

11

Force control in piezoelectric microactuators using self scheduled H technique  

E-print Network

Force control in piezoelectric microactuators using self scheduled H technique Micky Rakotondrabe the manipulation force applied by piezoelectric microactuators by using a parameter dependent approach of the piezoelectric microactuator was compensated and the derived model is therefore linear. Afterwards, we design

Boyer, Edmond

12

Nonlinear photoacoustic microscopy via a loss modulation technique: from detection to imaging.  

PubMed

In order to achieve high-resolution deep-tissue imaging, multi-photon fluorescence microscopy and photoacoustic tomography had been proposed in the past two decades. However, combining the advantages of these two imaging systems to achieve optical-spatial resolution with an ultrasonic-penetration depth is still a field with challenges. In this paper, we investigate the detection of the two-photon photoacoustic ultrasound, and first demonstrate background-free two-photon photoacoustic imaging in a phantom sample. To generate the background-free two-photon photoacoustic signals, we used a high-repetition rate femtosecond laser to induce narrowband excitation. Combining a loss modulation technique, we successfully created a beating on the light intensity, which not only provides pure sinusoidal modulation, but also ensures the spectrum sensitivity and frequency selectivity. By using the lock-in detection, the power dependency experiment validates our methodology to frequency-select the source of the nonlinearity. This ensures our capability of measuring the background-free two-photon photoacoustic waves by detecting the 2nd order beating signal directly. Furthermore, by mixing the nanoparticles and fluorescence dyes as contrast agents, the two-photon photoacoustic signal was found to be enhanced and detected. In the end, we demonstrate subsurface two-photon photoacoustic bio-imaging based on the optical scanning mechanism inside phantom samples. PMID:24515013

Lai, Yu-Hung; Lee, Szu-Yu; Chang, Chieh-Feng; Cheng, Yu-Hsiang; Sun, Chi-Kuang

2014-01-13

13

Recovery of the Elastic Constants from Wavespeed Measurements in Viscoelastic Composites by Photoacoustic Technique  

NASA Astrophysics Data System (ADS)

Mixtures of black rubber (natural rubber) vulcanizates containing various concentrations of sand particles, as hard fillers, were prepared to determine their elastic constants at low and high frequency using the photoacoustic technique. These parameters are related with the degree of sand filler dispersion which determines the changes in stiffness, as well as its potential as reinforcement material for treads in tires. The constants are recovered through measurements of the longitudinal wave and complemented with the predictions from the Kerner model to obtain the Poisson’s ratio. Some results are corroborated with tension and compression tests. The acoustic waves are acquired by two piezoelectric transducers, one centered at 3 kHz and the other at 240 kHz. The results show a slight increase in Young’s modulus at low frequencies; meanwhile at high frequencies, it increases by two orders of magnitude. In addition, we found that on adding small amounts of prepared sand, the stiffness increases and this is particularly convenient to reduce the energy losses by the rolling resistance in automotive vehicles.

Navarrete, M.; Mejía-Uriarte, E. V.; Villagrán-Muniz, M.

2013-09-01

14

Piezoelectric ceramics and composites via rapid prototyping techniques  

Microsoft Academic Search

Reviews the inherent advantages, i.e. design flexibility and processing, of manufacturing piezoelectric ceramics and composites with numerous architectures via rapid prototyping techniques. Reports on processing in which piezoelectric ceramics and composites with novel and conventional designs were fabricated using rapid prototyping techniques. Fused deposition of ceramics, fused deposition modeling, and Sanders prototyping techniques were used to fabricate lead-zirconate-titanate ceramics and

A. Bandyopadhyay; R. K. Panda; T. F. McNulty; F. Mohammadi; S. C. Danforth; A. Safari

1998-01-01

15

Adaptive and robust techniques (ART) for thermoacoustic and photoacoustic tomography  

NASA Astrophysics Data System (ADS)

In this paper, we present new Adaptive and Robust Techniques (ART) for microwave-based thermoacoustic tomography (TAT) and laser-based photo-acoustic tomography (PAT), and study their performances for breast cancer detection. TAT and PAT are emerging medical imaging techniques that combine the merits of high contrast due to electromagnetic or laser stimulation and high resolution offered by thermal acoustic imaging. The current image reconstruction methods used for TAT and PAT, such as the widely used Delay-and-Sum (DAS) approach, are data-independent and suffer from low resolution, high sidelobe levels, and poor interference rejection capabilities. The data-adaptive ART can have much better resolution and much better interference rejection capabilities than their data-independent counterparts. By allowing certain uncertainties, ART can be used to mitigate the amplitude and phase distortion problems encountered in TAT and PAT. Specifically, in the first step of ART, RCB is used for waveform estimation by treating the amplitude distortion with an uncertainty parameter. In the second step of ART, a simple yet effective peak searching method is used for phase distortion correction. Compared with other energy or amplitude based response intensity estimation methods, peak searching can be used to improve image quality with little additional computational costs. Moreover, since the acoustic pulse is usually bipolar: a positive peak, corresponding to the compression pulse, and a negative peak, corresponding to the rarefaction pulse, we can further enhance the image contrast in TAT or PAT by using the peak-to-peak difference as the response intensity for a focal point. The excellent performance of ART is demonstrated using both simulated and experimentally measured data.

Xie, Yao; Guo, Bin; Li, Jian; Ku, Geng; Wang, Lihong V.

2007-02-01

16

New technique for investigating ferroelectric phase transitions: The photoacoustic effect  

NASA Astrophysics Data System (ADS)

Measurements of the photoacoustic (PA) effect in properly oriented triglycine sulfate (TGS) crystals from 30 to 60 °C show clearly the ferroelectric phase transition in this crystal manifested by the pronounced thermal expansion anomalies. The same method is generally applicable to similar phase transitions.

Tocho, Jorge O.; Ramírez, Rafael; Gonzalo, J. A.

1991-09-01

17

Piezoelectric cantilevers energy harvesting in MEMS technique  

NASA Astrophysics Data System (ADS)

Piezoelectric cantilevers energy harvesting made by micro-electromechanical system (MEMS) technology can scavenge power from low-level ambient vibration sources. The developed cantilevers energy harvesting are featured with resonate frequency and power output in microwatt level, which is sufficient to the self-supportive sensors for in-service integrity monitoring of large social and environmental infrastructures at remote locations. In this paper, piezoelectric energy harvesting based on thick-film piezoelectric cantilevers is investigated to resonate at specific frequencies of an external vibration energy source, which creating electrical energy via the piezoelectric effect. Our cantilever device has a multiple structure with a proof mass added to the end. The thick film lead zirconate titanate Pb(Zr,Ti)O3 (PZT) coated on the top of Au/Cr/SiO2/Si substrates by sol-gel-spin method. The thickness of the PZT membrane was up to 2?m and the cantilevers substrates thickness 50?m, wideness 1.5mm, length 4mm. The Au/Ti top electrode is patterned on top of the sol-gel-spin coated PZT thick film in order to employ the d31 mode. The prototype energy generator has a measured performance of 0.74?W effective electrical power, and 4.93 DC output voltages to resistance load. The effect of proof mass, beam shape and damping on the power generating performance are modeled to provide a design guideline for maximum power harvesting from environmentally available low frequency vibrations. A multiple structure cantilever is designed to achieve compactness, low resonant frequency and minimum damping coefficient, simultaneously. This device is promising to support networks of ultra-low-power sensor.

Shang, Yingqi; Qiu, Chengjun; Liu, Hongmei; Chen, Xiaojie; Qu, Wei; Dou, Yanwei

2012-04-01

18

Piezoelectric cantilevers energy harvesting in MEMS technique  

NASA Astrophysics Data System (ADS)

Piezoelectric cantilevers energy harvesting made by micro-electromechanical system (MEMS) technology can scavenge power from low-level ambient vibration sources. The developed cantilevers energy harvesting are featured with resonate frequency and power output in microwatt level, which is sufficient to the self-supportive sensors for in-service integrity monitoring of large social and environmental infrastructures at remote locations. In this paper, piezoelectric energy harvesting based on thick-film piezoelectric cantilevers is investigated to resonate at specific frequencies of an external vibration energy source, which creating electrical energy via the piezoelectric effect. Our cantilever device has a multiple structure with a proof mass added to the end. The thick film lead zirconate titanate Pb(Zr,Ti)O3 (PZT) coated on the top of Au/Cr/SiO2/Si substrates by sol-gel-spin method. The thickness of the PZT membrane was up to 2?m and the cantilevers substrates thickness 50?m, wideness 1.5mm, length 4mm. The Au/Ti top electrode is patterned on top of the sol-gel-spin coated PZT thick film in order to employ the d31 mode. The prototype energy generator has a measured performance of 0.74?W effective electrical power, and 4.93 DC output voltages to resistance load. The effect of proof mass, beam shape and damping on the power generating performance are modeled to provide a design guideline for maximum power harvesting from environmentally available low frequency vibrations. A multiple structure cantilever is designed to achieve compactness, low resonant frequency and minimum damping coefficient, simultaneously. This device is promising to support networks of ultra-low-power sensor.

Shang, Yingqi; Qiu, Chengjun; Liu, Hongmei; Chen, Xiaojie; Qu, Wei; Dou, Yanwei

2011-11-01

19

Non-restrained measurement of Young's modulus for soft tissue using a photoacoustic technique  

NASA Astrophysics Data System (ADS)

A miniaturized sensor was developed to determine the Young's modulus of tumors based on photoacoustic spectroscopy. The sensor had a chamber height of 5.3 mm and diameter of 5.8 mm; thus, this device is smaller than conventional endoscopes, the outer diameters of which are typically about 10 mm. A non-restrained methodology for determining the Young's modulus of tumors was proposed based on the resonance frequency of the photoacoustic signal. The proposed approach was applied to silicone rubbers with six different Young's moduli (30, 64, 123, 224, 396, and 574 kPa) and showed good resolution (±2 kPa) and high reproducibility. These results show that the photoacoustic technique can be applied to mechanically characterize soft tissue by diagnostic endoscopy.

Wadamori, Naoki

2014-09-01

20

Nonlinear scattering studies of carbon black suspensions using photoacoustic Z-scan technique  

NASA Astrophysics Data System (ADS)

Nonlinear scattering properties of carbon black suspensions (CBS) are studied using nanosecond photoacoustic (PA) and optical z-scan techniques. When the laser is operated in multi-pulse mode, no nonlinear behavior is observed in PAZ-scans. However, in the single-pulse mode, we observed the nonlinear scattering in both PAZ and optical z- scans. Our results are in agreement with the well-known bleaching effect in CBS and demonstrate the importance of pulse repetition frequency for studying nonlinear scattering using photoacoustics. The effective nonlinear extinction coefficients of CBS were determined, and we found that PAZ-scan data are more sensitive and offer information on higher nonlinearities.

Kislyakov, Ivan M.; Yelleswarapu, Chandra S.

2013-10-01

21

Study of photoreaction in dichromated gelatin by laser photoacoustic technique  

Microsoft Academic Search

. An experimental method to study the photochemical reaction in solid-state dichromated gelatin during exposure is proposed, in which two laser sources with different wavelengths are used to induce photoreaction and to excite photoacoustic signal, respectively. This method is to obtain the real-time characteristics during the formation of the photoreaction product. The curve is fitted using the Rosencwaig-Gersho (R-G) theory

H. Du; J. W. Fang; G. J. Chen; T. Q. Cai; J. J. Zheng

1996-01-01

22

Study of photoreaction in dichromated gelatin by laser photoacoustic technique  

Microsoft Academic Search

.  ?An experimental method to study the photochemical reaction in solid-state dichromated gelatin during exposure is proposed,\\u000a in which two laser sources with different wavelengths are used to induce photoreaction and to excite photoacoustic signal,\\u000a respectively. This method is to obtain the real-time characteristics during the formation of the photoreaction product. The\\u000a curve is fitted using the Rosencwaig-Gersho (R-G) theory and

H. Du; J. W. Fang; G. J. Chen; T. Q. Cai; J. J. Zheng

1997-01-01

23

Piezoelectric energy harvesting using a series synchronized switch technique  

NASA Astrophysics Data System (ADS)

An alternative switching technique for piezoelectric energy harvesting is presented. The energy harvester based on piezoelectric elements is a promising method to scavenge ambient energy. Several non-linear techniques such as SSHI have been implemented to improve the global harvested energy. However, these techniques are sensitive to load and should be tuned to obtain optimal power output. This technique, called Series Synchronized Switch Harvesting (S3H), has both the advantage of easy implementation and independence of the harvested power with the load impedance. The harvesting circuit simply consists of a switch in series with the piezoelement and the load. The switch is nearly always open and is triggered-on each time the piezoelectric voltage reaches an extremum. It is opened back after an arbitrary on-time t0. The energy scavenging process happens when switch is closed. Based on linear motion assumption, the harvester structure is modeled as a "Mass-Spring-Damper" system. The analysis of S3H technique is considered with harmonic excitation. An analytical model of S3H is presented and discussed. The main advantage of this approach compared with the usual standard technique is that the extracted power is independent of the load within a wide range of load impedance, and that the useful impedance range is simply related to the defined switch on-time. For constant displacement excitation condition, the optimal power output is more than twice the power extracted by the standard technique as long as the on-time interval is small comparatively with the vibration period. For constant force excitation, an optimal on-time can be defined resulting in an optimally wide load bandwidth. Keywords: piezoelectric; energy harvesting; non-linear harvesting techniques; switching techniques.

Li, Yang; Lallart, Mickaël.; Richard, Claude

2014-04-01

24

In vivo evaluation of drug delivery after ultrasound application: A new use for the photoacoustic technique  

NASA Astrophysics Data System (ADS)

Ultrasound application is a therapeutical resource widely employed in physiotherapy. One of its applications is the phonophoresis, a technique in which the ultrasound radiation is utilized to deliver drugs through the skin to soft tissues. The proposal of our study was to employ the Photoacoustic Technique to evaluate the efficacy of such treatment, analyzing if phonophoresis could enhance drug delivery through skin when compared to the more traditional method of manual massage. The configuration of the system employed was such that it was possible to perform in vivo measurements, which is a pre-requisite for this kind of study. The changes observed in the photoacoustic signal amplitude after each form of drug application were attributed to changes in the thermal effusivity of the system, due to penetration of the drug. The technique was able to detect differences in drug delivery between the specified physiotherapy treatments, indicating that phonophoresis enhances drug absorption by tissue.

Barja, P. R.; Acosta-Avalos, D.; Rompe, P. C. B.; Dos Anjos, F. H.; Marciano, F. R.; da Silva, M. D.

2005-06-01

25

Probe beam deflection technique as acoustic emission directionality sensor with photoacoustic emission source.  

PubMed

The goal of this paper is to demonstrate the unique capability of measuring the vector or angular information of propagating acoustic waves using an optical sensor. Acoustic waves were generated using photoacoustic interaction and detected by the probe beam deflection technique. Experiments and simulations were performed to study the interaction of acoustic emissions with an optical sensor in a coupling medium. The simulated results predict the probe beam and wavefront interaction and produced simulated signals that are verified by experiment. PMID:24514140

Barnes, Ronald A; Maswadi, Saher; Glickman, Randolph; Shadaram, Mehdi

2014-01-20

26

Piezoelectric Pb(Zrx, Ti1-x)O3 thin film cantilever and bridge acoustic sensors for miniaturized photoacoustic gas detectors  

NASA Astrophysics Data System (ADS)

Novel, highly sensitive piezoelectric acoustic sensors based on partially unclamped Pb(Zrx, Ti1-x)O3 (PZT) coated cantilever and bridge have been fabricated by silicon micromachining. High sensitivity at low frequencies (5-100 Hz) has been achieved by patterning very narrow slits (3 to 5 µm) around the structures. A typical response of 100 mV Pa-1 and a noise equivalent pressure of 1.6 mPa Hz1/2 at 20 Hz have been measured using a 10 pF charge amplifier. Stress compensation, dry etching and integration of high performance piezoelectric thin films were the key issues. PZT/Pt/SiO2 stacks have been patterned by reactive ion etching and stress compensation has been achieved by compensating the PZT film's tensile stress by adjusting the thickness of a thermal SiO2 layer. The integration of sol-gel PZT films with a transverse piezoelectric coefficient e31,f of -12.8 C m-2 has been realized without any degradation of the properties. The microphones were successfully integrated into a miniature photoacoustic detector and tested for CO2 detection. Concentrations down to 330 ppm could be measured with significant signals.

Ledermann, Nicolas; Muralt, Paul; Baborowski, Jacek; Forster, Martin; Pellaux, Jean-Paul

2004-12-01

27

Miniature photoacoustic chemical sensor using microelectromechanical structures  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is a useful monitoring technique that is well suited for trace gas detection. The technique also possesses favorable detection characteristics when the system dimensions are scaled to a micro-system design. The objective of present work is to incorporate two strengths of the Army Research Laboratory (ARL), piezoelectric microelectromechanical systems (MEMS) and chemical and biological sensing into a monolithic MEMS photoacoustic trace gas sensor. A miniaturized macro-cell design was studied as a means to examine performance and design issues as the photoacoustics is scaled to a dimension approaching the MEMS level. Performance of the macro-cell was tested using standard organo-phosphate nerve gas simulants, Dimethyl methyl phosphonate (DMMP) and Diisoprpyl methyl phosphonate (DIMP). Current MEMS work centered on fabrication of a multi-layer cell subsystem to be incorporated in the full photoacoustic device. Preliminary results were very positive for the macro-cell sensitivity (ppb levels) and specificity indicating that the scaled cell maintains sensitivity. Several bonding schemes for a three-dimension MEMS photoacoustic cavity were investigated with initial results of a low temperature AuSn bond proving most feasible.

Pellegrino, Paul M.; Polcawich, Ronald G.; Firebaugh, Samara L.

2004-08-01

28

Switching Delay Effects on Nonlinear Piezoelectric Energy Harvesting Techniques  

Microsoft Academic Search

Energy harvesting using piezoelectric elements re- ceived much attention as vibrations are widely available and as piezoelectric transducers feature high-power densities and promising integration potentials. It has also been shown that applying a nonlinear treatment on the output voltage of the piezo- electric material can significantly enhance the performance of the device. This process consists of inverting the piezoelectric voltage

Mickaël Lallart; Yi-Chieh Wu; Daniel Guyomar

2012-01-01

29

Analytical Method for Selecting a Rectification Technique for a Piezoelectric Generator based on Admittance Measurement  

NASA Astrophysics Data System (ADS)

AC-DC converters employed for harvesting power from piezoelectric transducers can be divided into linear (i.e. diode bridge) and non-linear (i.e. synchronized switch harvesting on inductor, SSHI). This paper presents an analytical technique based on the measurement of the impedance circle of the piezoelectric element to determine whether either diode bridge or SSHI converter harvests more of the available power at the piezoelectric element.

Mateu, Loreto; Zessin, Henrik; Spies, Peter

2013-12-01

30

Photoacoustic method for measuring concentration of chemical species  

DOEpatents

The present invention is a transducer for photoacoustic detection having at least two piezoelectric elements wherein at least a first piezoelectric element has a first frequency and at least a second piezoelectric element has a second frequency. The improvement according to the present invention is that at least two piezoelectric elements are longitudinal elements for longitudinal waves; and the first frequency is different from said second frequency. In other words, the invention is a multi-frequency longitudinal transducer for photoacoustic detection.

Autrey, S. Thomas (West Richland, WA) [West Richland, WA; Posakony, Gerald J. (Richland, WA) [Richland, WA; Amonette, James E. (Richland, WA) [Richland, WA; Foster-Mills, Nancy S. (Richland, WA) [Richland, WA

2001-01-01

31

Reflective and photoacoustic infrared spectroscopic techniques in assessment of binding media in paintings  

NASA Astrophysics Data System (ADS)

This study proposes a method to estimate the lipid content in binding media in paintings that can be used at any laboratory equipped with an infrared spectrometer. The lipid content estimator, termed greasiness index (GI), is defined as a ratio of lipid ?(C=O) and protein amide I bands at 1743 and 1635 cm-1, respectively. Three Fourier transform infrared (FTIR) sampling techniques were evaluated for GI determination: reflective attenuated total reflection—ATR, specular reflection microscopy— ?SR and photoacoustic—PAS. A set of model painting samples containing three tempera binding media (casein, egg, egg + oil), seven pigments and one varnish type were used in the study. Multivariate analysis was used to evaluate the resulting data. A good reproducibility of GI was obtained by ATR and PAS but not with ?SR. The discriminative power of the technique is higher for unvarnished samples, but, generally, the GI estimator can be used for the categorisation of binding media in large populations of painting samples analysed with the same FTIR technique (sampling technique, detection, etc.).

?ojewski, Tomasz; Bagniuk, Jacek; Ko?odziej, Andrzej; ?ojewska, Joanna

2011-11-01

32

The wafer flexure technique for the determination of the transverse piezoelectric coefficient ( d 31) of PZT thin films  

Microsoft Academic Search

This paper describes a simple and inexpensive method for evaluating the transverse piezoelectric coefficient (d31) of piezoelectric thin films. The technique is based upon the flexure of a coated substrate which imparts an ac two-dimensional stress to the piezoelectric film. The surface charge generated via the mechanical loading is converted to a voltage by an active integrator. Plate theory and

J SHEPARDJR; P. J. Moses; S. Trolier-McKinstry

1998-01-01

33

Dual-wavelength photoacoustic technique for monitoring tissue status during thermal treatments  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) techniques have been exploited for monitoring thermal treatments. However, PA signals depend not only on tissue temperature but also on tissue optical properties which indicate tissue status (e.g., native or coagulated). The changes in temperature and tissue status often occur simultaneously during thermal treatments, so both effects cause changes to PA signals. A new dual-wavelength PA technique to monitor tissue status independent of temperature is performed. By dividing the PA signal intensities obtained at two wavelengths at the same temperature, a ratio, which only depends on tissue optical properties, is obtained. Experiments were performed with two experimental groups, one with untreated tissue samples and the other with high-intensity focused ultrasound treated tissue samples including thermal coagulated lesion, using ex vivo porcine myocardium specimens to test the technique. The ratio of PA signal intensities obtained at 700 and 800 nm was constant for both groups from 25 to 43°C, but with distinct values for the two groups. Tissue alteration during thermal treatment was then studied using water bath heating of tissue samples from 35 to 60°C. We found that the ratio stayed constant before it exhibited a marked increase at around 55°C, indicating tissue changes at this temperature.

Hsiao, Yi-Sing; Wang, Xueding; Deng, Cheri X.

2013-06-01

34

Dual-wavelength photoacoustic technique for monitoring tissue status during thermal treatments  

PubMed Central

Abstract. Photoacoustic (PA) techniques have been exploited for monitoring thermal treatments. However, PA signals depend not only on tissue temperature but also on tissue optical properties which indicate tissue status (e.g., native or coagulated). The changes in temperature and tissue status often occur simultaneously during thermal treatments, so both effects cause changes to PA signals. A new dual-wavelength PA technique to monitor tissue status independent of temperature is performed. By dividing the PA signal intensities obtained at two wavelengths at the same temperature, a ratio, which only depends on tissue optical properties, is obtained. Experiments were performed with two experimental groups, one with untreated tissue samples and the other with high-intensity focused ultrasound treated tissue samples including thermal coagulated lesion, using ex vivo porcine myocardium specimens to test the technique. The ratio of PA signal intensities obtained at 700 and 800 nm was constant for both groups from 25 to 43°C, but with distinct values for the two groups. Tissue alteration during thermal treatment was then studied using water bath heating of tissue samples from 35 to 60°C. We found that the ratio stayed constant before it exhibited a marked increase at around 55°C, indicating tissue changes at this temperature. PMID:23733048

Hsiao, Yi-Sing; Wang, Xueding; Deng, Cheri X.

2013-01-01

35

Analysis of Piezoelectric Structural Sensors with Emergent Computing Techniques  

NASA Technical Reports Server (NTRS)

The purpose of this project was to try to interpret the results of some tests that were performed earlier this year and to demonstrate a possible use of emergence in computing to solve IVHM problems. The test data used was collected with piezoelectric sensors to detect mechanical changes in structures. This project team was included of Dr. Doug Ramers and Dr. Abdul Jallob of the Summer Faculty Fellowship Program, Arnaldo Colon-Lopez - a student intern from the University of Puerto Rico of Turabo, and John Lassister and Bob Engberg of the Structural and Dynamics Test Group. The tests were performed by Bob Engberg to compare the performance two types of piezoelectric (piezo) sensors, Pb(Zr(sub 1-1)Ti(sub x))O3, which we will label PZT, and Pb(Zn(sub 1/3)Nb(sub 2/3))O3-PbTiO, which we will label SCP. The tests were conducted under varying temperature and pressure conditions. One set of tests was done by varying water pressure inside an aluminum liner covered with carbon-fiber composite layers (a cylindrical "bottle" with domed ends) and the other by varying temperatures down to cryogenic levels on some specially prepared composite panels. This report discusses the data from the pressure study. The study of the temperature results was not completed in time for this report. The particular sensing done with these piezo sensors is accomplished by the sensor generating an controlled vibration that is transmitted into the structure to which the sensor is attached, and the same sensor then responding to the induced vibration of the structure. There is a relationship between the mechanical impedance of the structure and the resulting electrical impedance produced in the in the piezo sensor. The impedance is also a function of the excitation frequency. Changes in the real part of impendance signature relative to an original reference signature indicate a change in the coupled structure that could be the results of damage or strain. The water pressure tests were conducted by pressurizing the bottle on a test stand, and running sweeps of excitations frequencies for each of the piezo sensors and recording the resulting impedance. The sweeps were limited to 401 points by the available analyzer, and it was decided to perform individual sweeps at five different excitation frequency ranges. The frequency ranges used for the PZTs were different in two of the five ranges from the ranges used for the SCP. The bottles were pressurized to empty (no water), 0psig, 77 psig, 155 psig, 227 psig in nearly uniform increments of about 77psi. One of each of the two types of piezo sensors was fastened on to the bottle surface at two locations: about midway between the ends on cylindrical portion of the bottle and at the very edge of one of the end domes. The data was collected in files by sensor type (2 cases), by location (2 cases), by frequency range (5 cases), and pressure (5cases) to produce 100 data sets of 401 impedances. After familiarization with the piezo sensing technology and obtaining the data, the team developed a set of questions to try to answer regarding the data and made assignments of responsibilities. The next section lists the questions, and the remainder of the report describes the data analysis work performed by Dr. Ramers. This includes a discussion of the data, the approach to answering the question using statistical techniques, the use of an emergent system to investigate the data where statistical techniques were not usable, conclusions regarding the data, and recommendations.

Ramers, Douglas L.

2005-01-01

36

Fabrication techniques and performance of piezoelectric energy harvesters  

Microsoft Academic Search

Energy harvesting devices which convert ambient energy to electrical energy has attracted a lot of attention in commercial sectors. Due to the environmental consciousness, energy harvesting devices or so called micro generators promise a cleaner environment by avoiding the usage of batteries. Piezoelectric energy harvesters are the most promising solution because they can efficiently convert mechanical strain to electrical charge

A. A. M. Ralib; A. Nurashikin; H. Salleh

2009-01-01

37

Development of novel piezoelectric composites by solid freeform fabrication techniques  

Microsoft Academic Search

Piezoelectric ceramic\\/polymer composites have been widely used for ultrasonic transducers because of their superior properties as compared to bulk piezoceramics or polymers. The electromechanical Properties of the composites can be tailored for various applications by changing the design and connectivity of the piezoceramic skeleton. The goal of this project was to utilize the design flexibility provided by solid freeform fabrication

Rajesh Kumar Panda

1998-01-01

38

Consideration of impedance matching techniques for efficient piezoelectric energy harvesting.  

PubMed

This study investigates multiple levels of impedance-matching methods for piezoelectric energy harvesting in order to enhance the conversion of mechanical to electrical energy. First, the transduction rate was improved by using a high piezoelectric voltage constant (g) ceramic material having a magnitude of g33 = 40 x 10(-3) V m/N. Second, a transducer structure, cymbal, was optimized and fabricated to match the mechanical impedance of vibration source to that of the piezoelectric transducer. The cymbal transducer was found to exhibit approximately 40 times higher effective strain coefficient than the piezoelectric ceramics. Third, the electrical impedance matching for the energy harvesting circuit was considered to allow the transfer of generated power to a storage media. It was found that, by using the 10-layer ceramics instead of the single layer, the output current can be increased by 10 times, and the output load can be reduced by 40 times. Furthermore, by using the multilayer ceramics the output power was found to increase by 100%. A direct current (DC)-DC buck converter was fabricated to transfer the accumulated electrical energy in a capacitor to a lower output load. The converter was optimized such that it required less than 5 mW for operation. PMID:17941391

Kim, Hyeoungwoo; Priya, Shashank; Stephanou, Harry; Uchino, Kenji

2007-09-01

39

Time resolved high frequency spectrum of Br2 molecules using pulsed photoacoustic technique.  

PubMed

The paper reports the time resolved spectral distribution of higher order acoustic modes generated in Br2 molecules using pulsed Photoacoustic (PA) technique. New time resolved vibrational spectrum of Br2 molecules are recorded using a single 532nm, pulses of 7ns duration at 10Hz repetition rate obtained from Q-switched Nd:YAG laser. Frank-Condon principle based assignments confirms the presence of 12 numbers of (??-?') vibrational transitions covered by a single 532+2nm pulse profile. Inclusions of higher order zeroth modes in Bassel's function expansion series shows the probability of overlapping of different types of acoustic modes in the designed PA cells. These modes appear in the form of clusters which occupies higher frequency range. The study of decay behavior of PA signal with respect to time confirms the photolysis of Br2 at 532nm wavelength. In addition, the shifting and clustering effect of cavity eigen modes in Br2 molecules have been studied between 1 and 10ms time scale. The estimated Q-factor of PA cell (l=16cm, R=1.4cm) is 145±4 at 27kHz frequency. PMID:23871982

Yehya, Fahem; Chaudhary, A K

2013-11-01

40

Time resolved high frequency spectrum of Br2 molecules using pulsed photoacoustic technique  

NASA Astrophysics Data System (ADS)

The paper reports the time resolved spectral distribution of higher order acoustic modes generated in Br2 molecules using pulsed Photoacoustic (PA) technique. New time resolved vibrational spectrum of Br2 molecules are recorded using a single 532 nm, pulses of 7 ns duration at 10 Hz repetition rate obtained from Q-switched Nd:YAG laser. Frank-Condon principle based assignments confirms the presence of 12 numbers of (??-??) vibrational transitions covered by a single 532 + 2 nm pulse profile. Inclusions of higher order zeroth modes in Bassel's function expansion series shows the probability of overlapping of different types of acoustic modes in the designed PA cells. These modes appear in the form of clusters which occupies higher frequency range. The study of decay behavior of PA signal with respect to time confirms the photolysis of Br2 at 532 nm wavelength. In addition, the shifting and clustering effect of cavity eigen modes in Br2 molecules have been studied between 1 and 10 ms time scale. The estimated Q-factor of PA cell (l = 16 cm, R = 1.4 cm) is 145 ± 4 at 27 kHz frequency.

Yehya, Fahem; Chaudhary, A. K.

2013-11-01

41

Real-time full-field photoacoustic imaging using an ultrasonic camera  

NASA Astrophysics Data System (ADS)

A photoacoustic imaging system that incorporates a commercial ultrasonic camera for real-time imaging of two-dimensional (2-D) projection planes in tissue at video rate (30 Hz) is presented. The system uses a Q-switched frequency-doubled Nd:YAG pulsed laser for photoacoustic generation. The ultrasonic camera consists of a 2-D 12×12 mm CCD chip with 120×120 piezoelectric sensing elements used for detecting the photoacoustic pressure distribution radiated from the target. An ultrasonic lens system is placed in front of the chip to collect the incoming photoacoustic waves, providing the ability for focusing and imaging at different depths. Compared with other existing photoacoustic imaging techniques, the camera-based system is attractive because it is relatively inexpensive and compact, and it can be tailored for real-time clinical imaging applications. Experimental results detailing the real-time photoacoustic imaging of rubber strings and buried absorbing targets in chicken breast tissue are presented, and the spatial resolution of the system is quantified.

Balogun, Oluwaseyi; Regez, Brad; Zhang, Hao F.; Krishnaswamy, Sridhar

2010-03-01

42

Internal Water Vapor Photoacoustic Calibration  

NASA Technical Reports Server (NTRS)

Water vapor absorption is ubiquitous in the infrared wavelength range where photoacoustic trace gas detectors operate. This technique allows for discontinuous wavelength tuning by temperature-jumping a laser diode from one range to another within a time span suitable for photoacoustic calibration. The use of an internal calibration eliminates the need for external calibrated reference gases. Commercial applications include an improvement of photoacoustic spectrometers in all fields of use.

Pilgrim, Jeffrey S.

2009-01-01

43

Thermal intravascular photoacoustic imaging  

PubMed Central

Intravascular photoacoustics (IVPA)—a minimally invasive imaging technique with contrast related to optical absorption properties of tissue, can be used to visualize atherosclerotic plaques. However, the amplitude of photoacoustic signals is also related to a temperature dependent, tissue specific parameter—the Grüneisen parameter. Therefore, photoacoustic signals measured at different temperatures may reveal information about tissue composition. In this study, thermal IVPA (tIVPA) imaging was introduced. The imaging studies were performed using an ex vivo atherosclerotic rabbit aorta. Temperature dependent photoacoustic responses from lipid in plaques and lipid in periadventitial tissue were different, thus allowing tIVPA images to delineate the location of lipid-rich plaques. The results indicate that tIVPA imaging has a potential to characterize tissue composition in atherosclerotic vessels. PMID:22076268

Wang, Bo; Emelianov, Stanislav

2011-01-01

44

Thermal intravascular photoacoustic imaging.  

PubMed

Intravascular photoacoustics (IVPA)-a minimally invasive imaging technique with contrast related to optical absorption properties of tissue, can be used to visualize atherosclerotic plaques. However, the amplitude of photoacoustic signals is also related to a temperature dependent, tissue specific parameter-the Grüneisen parameter. Therefore, photoacoustic signals measured at different temperatures may reveal information about tissue composition. In this study, thermal IVPA (tIVPA) imaging was introduced. The imaging studies were performed using an ex vivo atherosclerotic rabbit aorta. Temperature dependent photoacoustic responses from lipid in plaques and lipid in periadventitial tissue were different, thus allowing tIVPA images to delineate the location of lipid-rich plaques. The results indicate that tIVPA imaging has a potential to characterize tissue composition in atherosclerotic vessels. PMID:22076268

Wang, Bo; Emelianov, Stanislav

2011-11-01

45

Photoacoustic measurement of epidermal melanin  

NASA Astrophysics Data System (ADS)

Most dermatologic laser procedures must consider epidermal melanin, as it is a broadband optical absorber which affects subsurface fluence, effectively limiting the amount of light reaching the dermis and targeted chromophores. An accurate method for quantifying epidermal melanin content would aid clinicians in determining proper light dosage for therapeutic laser procedures. While epidermal melanin content has been quantified non-invasively using optical methods, there is currently no way to determine the melanin distribution in the epidermis. We have developed a photoacoustic probe that uses a Q-switched, frequency doubled Nd:YAG laser operating at 532nm to generate acoustic pulses in skin in vivo. The probe contained a piezoelectric element that detected photoacoustic waves which were then analyzed for epidermal melanin content, using a photoacoustic melanin index (PAMI). We tested 15 human subjects with skin types I--VI using the photoacoustic probe. We also present photoacoustic data for a human subject with vitiligo. Photoacoustic measurement showed melanin in the vitiligo subject was almost completely absent.

Viator, John A.; Svaasand, Lars O.; Aguilar, Guillermo; Choi, Bernard; Nelson, J. Stuart

2003-06-01

46

Optical absorption measurements in a new composite material by combined photoacoustic and beam transmission techniques  

NASA Astrophysics Data System (ADS)

The absorption coefficient of a highly absorbing (?>105 cm-1) new composite produced in our laboratory, namely manganese dioxide surface-impregnated polyethylene (MnO2-PE) film, has been measured in the visible range. We have employed a combination of concurrently taken photoacoustic and beam transmission data. This combination proved to be an effective means for the optical evaluation of highly absorptive samples which dispenses with the need for prior knowledge of the sample reflectivity. Theoretical interpretation of MnO2-PE absorption profile, with due account of the processes underlining the photoacoustic signal generation, reveals a semiconductor behavior with an estimated effective gap wavelength of 8050 Å. Technical implications of the availability of these highly absorptive flexible films are briefly considered.

Cesar, C. L.; Lima, C. A. S.; Leite, N. F.; Vargas, H.; Rubira, A. F.; Galembeck, F.

1985-05-01

47

A photoacoustic technique applied to detection of ethylene emissions in edible coated passion fruit  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy was applied to study the physiological behavior of passion fruit when coated with edible films. The results have shown a reduction of the ethylene emission rate. Weight loss monitoring has not shown any significant differences between the coated and uncoated passion fruit. On the other hand, slower color changes of coated samples suggest a slowdown of the ripening process in coated passion fruit.

Alves, G. V. L.; dos Santos, W. C.; Waldman, W. R.; Oliveira, J. G.; Vargas, H.; da Silva, M. G.

2010-03-01

48

An automated setup for investigation of anisotropy of the Gruneisen parameter of solids in the temperature range 77–350 K using the photoacoustic technique  

Microsoft Academic Search

An automated setup for studying the anisotropy of the Gruneisen parameter of solids in the temperature range 77–350 K using\\u000a the photoacoustic technique is described. The serviceability of the setup was tested at low (77–300 K) and high (300–350 K)\\u000a temperatures on strontium titanate and triglycine sulphate single crystals, respectively.

N. I. Odina; A. I. Korobov; D. N. Semenov; A. N. Knysh; T. V. Ageeva

2008-01-01

49

Photoacoustic angiography of the breast  

PubMed Central

Purpose: The authors report a noninvasive technique and instrumentation for visualizing vasculature in the breast in three dimensions without using either ionizing radiation or exogenous contrast agents, such as iodine or gadolinium. Vasculature is visualized by virtue of its high hemoglobin content compared to surrounding breast parenchyma. The technique is compatible with dynamic contrast-enhanced studies. Methods: Photoacoustic sonic waves were stimulated in the breast with a pulsed laser operating at 800 nm and a mean exposure of 20 mJ?pulse over an area of ?20 cm2. These waves were subsequently detected by a hemispherical array of piezoelectric transducers, the temporal signals from which were filtered and backprojected to form three-dimensional images with nearly uniform k-space sampling. Results: Three-dimensional vascular images of a human volunteer demonstrated a clear visualization of vascular anatomy with submillimeter spatial resolution to a maximum depth of 40 mm using a 24 s image acquisition protocol. Spatial resolution was nearly isotropic and approached 250 ?m over a 64×64×50 mm field of view. Conclusions: The authors have successfully visualized submillimeter breast vasculature to a depth of 40 mm using an illumination intensity that is 32 times less than the maximum permissible exposure according to the American National Standard for Safe Use of Lasers. Clearly, the authors can achieve greater penetration depth in the breast by increasing the intensity and the cross-sectional area of the illumination beam. Given the 24 s image acquisition time without contrast agent, dynamic, contrast-enhanced, photoacoustic breast imaging using optically absorbing contrast agents is conceivable in the future. PMID:21158321

Kruger, Robert A.; Lam, Richard B.; Reinecke, Daniel R.; Del Rio, Stephen P.; Doyle, Ryan P.

2010-01-01

50

Design, modeling and control of a piezoelectric ultrasonic microdissection technique for the molecular analysis of tissue  

NASA Astrophysics Data System (ADS)

Molecular techniques are transforming our understanding of cellular function and disease. However, accurate molecular analysis methods will be limited if the input DNA, RNA or protein is not derived from a pure population of cells or is contaminated by the wrong cells. The modeling and control of the piezoelectric actuator, with an objective application towards ultrasonic vibration cutting (UVC), is addressed in this paper. The piezoelectric actuator is used in realizing the fast and precise movements of the developed UVC so as to procure a pure population of targeted cells from tissue sections for subsequent pathology analysis with precision and without causing a large deformation. To address the nonlinearities and uncertainties of the piezoelectric actuator, an adaptive controller based on a hysteresis model is proposed to yield robust control performance. A multilayer piezoelectric actuator is used to actuate a sharp needle vibrating at high frequency and low amplitude to cut the tissue. Experimental results showed that the embedded tissue can be quickly and precisely cut with this ultrasonic vibration microdissection method.

Chen, Liguo; Ru, Changhai; Rong, Weibin; Liu, Yaxin; Sun, Lining

2010-02-01

51

Multimodal in vivo imaging of oral cancer using fluorescence lifetime, photoacoustic and ultrasound techniques  

PubMed Central

This work reports a multimodal system for label-free tissue diagnosis combining fluorescence lifetime imaging (FLIm), ultrasound backscatter microscopy (UBM), and photoacoustic imaging (PAI). This system provides complementary biochemical, structural and functional features allowing for enhanced in vivo detection of oral carcinoma. Results from a hamster oral carcinoma model (normal, precancer and carcinoma) are presented demonstrating the ability of FLIm to delineate biochemical composition at the tissue surface, UBM and related radiofrequency parameters to identify disruptions in the tissue microarchitecture and PAI to map optical absorption associated with specific tissue morphology and physiology. PMID:24049693

Fatakdawala, Hussain; Poti, Shannon; Zhou, Feifei; Sun, Yang; Bec, Julien; Liu, Jing; Yankelevich, Diego R.; Tinling, Steven P.; Gandour-Edwards, Regina F.; Farwell, D. Gregory; Marcu, Laura

2013-01-01

52

Grueneisen Relaxation Photoacoustic Microscopy  

NASA Astrophysics Data System (ADS)

The temperature-dependent property of the Grueneisen parameter has been employed in photoacoustic imaging mainly to measure tissue temperature. Here we explore this property using a different approach and develop Grueneisen relaxation photoacoustic microscopy (GR-PAM), a technique that images nonradiative absorption with confocal optical resolution. GR-PAM sequentially delivers two identical laser pulses with a microsecond-scale time delay. The first laser pulse generates a photoacoustic signal and thermally tags the in-focus absorbers. When the second laser pulse excites the tagged absorbers within the thermal relaxation time, a photoacoustic signal stronger than the first one is produced, owing to the temperature dependence of the Grueneisen parameter. GR-PAM detects the amplitude difference between the two colocated photoacoustic signals, confocally imaging the nonradiative absorption. We greatly improved axial resolution from 45 ?m to 2.3 ?m and, at the same time, slightly improved lateral resolution from 0.63 ?m to 0.41 ?m. In addition, the optical sectioning capability facilitates the measurement of the absolute absorption coefficient without fluence calibration.

Wang, Lidai; Zhang, Chi; Wang, Lihong V.

2014-10-01

53

Piezoelectric thick film ultrasonic transducers fabricated by a spray technique  

Microsoft Academic Search

Thick film broadband ultrasonic transducers (UTs) produced using sol-gel spray technique, operating below 10 MHz are presented. These UTs are formed by dispersing PZT and LiTaO3 particles, respectively in Al2O3 and PZT sol-gel solution. The 50-100 ?m thick films have been deposited on curved steel, flat steel and aluminum substrates and steel rods. Ultrasonic pulse-echo signals with a signal to

M. Kobayashi; T. R. Olding; L. Zou; M. Sayer; C.-K. Jen; A.-U. Rehman

2000-01-01

54

Photoacoustic technique for simultaneous measurements of thermal effusivity and absorptivity of pigments in liquid solution.  

PubMed

A photoacoustic (PA) methodology, in the transmission configuration, for simultaneous measurements of thermal effusivity and molar absorption coefficient (absorptivity) for pigments in liquid solution is introduced. The analytical treatment involves a self-normalization procedure for the PA signal, as a function of the modulation frequency, for a strong absorbing material in the thermally thin regime, when the light travels across the sample under study. Two fitted parameters are obtained from the analysis of the self-normalized PA amplitude and phase, one of them proportional to the sample's optical absorption coefficient and from which, taking it for a series of samples at different concentrations, the pigment's absorptivity in liquid solution can be measured, the other one yields the sample's thermal effusivity. Methylene blue's absorptivity in distilled water was measured with this methodology at 658 nm, finding good agreement with the corresponding one reported in the literature. PMID:22225240

Balderas-López, J A; Díaz-Reyes, J; Zelaya-Angel, O

2011-12-01

55

Spontaneous High Piezoelectricity in Poly(vinylidene fluoride) Nanoribbons Produced by Iterative Thermal Size Reduction Technique.  

PubMed

We produced kilometer-long, endlessly parallel, spontaneously piezoelectric and thermally stable poly(vinylidene fluoride) (PVDF) micro- and nanoribbons using iterative size reduction technique based on thermal fiber drawing. Because of high stress and temperature used in thermal drawing process, we obtained spontaneously polar ? phase PVDF micro- and nanoribbons without electrical poling process. On the basis of X-ray diffraction (XRD) analysis, we observed that PVDF micro- and nanoribbons are thermally stable and conserve the polar ? phase even after being exposed to heat treatment above the melting point of PVDF. Phase transition mechanism is investigated and explained using ab initio calculations. We measured an average effective piezoelectric constant as -58.5 pm/V from a single PVDF nanoribbon using a piezo evaluation system along with an atomic force microscope. PVDF nanoribbons are promising structures for constructing devices such as highly efficient energy generators, large area pressure sensors, artificial muscle and skin, due to the unique geometry and extended lengths, high polar phase content, high thermal stability and high piezoelectric coefficient. We demonstrated two proof of principle devices for energy harvesting and sensing applications with a 60 V open circuit peak voltage and 10 ?A peak short-circuit current output. PMID:25133594

Kanik, Mehmet; Aktas, Ozan; Sen, Huseyin Sener; Durgun, Engin; Bayindir, Mehmet

2014-09-23

56

Use of time history speckle pattern and pulsed photoacoustic techniques to detect the self-accommodating transformation in a Cu-Al-Ni shape memory alloy  

SciTech Connect

Continuous and pulsed electromagnetic radiation was used to detect the self-accommodation mechanism on a polycrystalline Cu-13.83 wt.%Al-2.34 wt.%Ni shape memory alloy. Rectangular samples of this alloy were mechanically polished to observe the austenite and martensite phases. The samples were cooled in liquid nitrogen prior to the experiments to obtain the martensite phase. Using a dynamic speckle technique with a continuous wave laser we obtained the time history of the speckle pattern image and monitored the surface changes caused by the self-accommodation mechanism during the inverse (martensitic to austenitic) transformation. Using a photoacoustic technique based on a pulsed laser source it was also possible to detect the self-accommodation phenomena in a bulk sample. For comparison purposes, we used differential scanning calorimetry (DSC) to detect the critical temperatures of transformation and use these as reference to evaluate the performance of the optical and photoacoustical techniques. In all cases, the same range of temperature was obtained during the inverse transformation. From these results, we conclude that time history speckle pattern (THSP) and pulsed photoacoustic are complementary techniques; they are non-destructive and useful to detect surface and bulk martensitic transformation induced by a temperature change.

Sanchez-Arevalo, F.M., E-mail: fsanchez@iim.unam.mx [CCADET - Universidad Nacional Autonoma de Mexico, A.P. 70-186, Mexico D.F., C.P. 04510 (Mexico); Aldama-Reyna, W. [Departamento Academico de Fisica, Universidad Nacional de Trujillo, Trujillo (Peru); Lara-Rodriguez, A.G. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico (Mexico); Garcia-Fernandez, T. [Universidad Autonoma de la Ciudad de Mexico (UACM), Prolongacion San Isidro 151, Col. San Lorenzo Tezonco, Mexico DF, C.P. 09790 (Mexico); Pulos, G. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico (Mexico); Trivi, M. [Centro de Investigaciones Opticas, Universidad de la Plata (Argentina); Villagran-Muniz, M. [CCADET - Universidad Nacional Autonoma de Mexico, A.P. 70-186, Mexico D.F., C.P. 04510 (Mexico)

2010-05-15

57

The evolution of the longitudinal modulus during the photo-polymerisation of a bis-GMA\\/TEGDMA resin by pulsed photoacoustic technique  

Microsoft Academic Search

A pulsed photoacoustic (PA) technique was implemented to study the evolution of the longitudinal modulus, C11, during the polymerisation of a methacrylate co-monomer system, induced by UV light. A laser pulse was used as a standard source of ultrasound waves to monitor the changes in the longitudinal velocity of the acoustic signal during the photo-polymerisation (PP) a bis-GMA\\/TEGDMA co-monomer system

M. Navarrete; F. Rivera Torres; R. Vera-Graziano; M. Villagrán-Muniz

2005-01-01

58

Wireless drive of piezoelectric components.  

E-print Network

??To widen the application range of piezoelectric devices, various new techniques including wireless drive of piezoelectric components by parallel plate capacitor structure, focused electric field,… (more)

Satyanarayan Bhuyan.

2011-01-01

59

Exploration of noninvasive determination of blood glucose concentration by using photoacoustic technique  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) noninvasive detection has become a research hotspot of measuring blood glucose concentration (BGC) in recent years. This novel method overcomes greatly the scattering light interference problem must be faced in near infrared (NIR) spectroscopy. A PA based BGC measurement set-up was established, in which a Q switched Nd: YAG pumped optical parametric oscillator (OPO) pulsed laser is used as the excitation source and lateral detection model was used to detetct the PA signals of glucose. To validate the profile model of real time PA signal, determine the characteristic wavelengths of glucose, a series of vitro experiments of glucose aqueous solutions were perfromed. Several wavelengths were preliminarily determined as the characteristic wavelengths via the peak-to-peak values difference. The prediction concentration model was established via least square fitting algorithm between PA peak-to-peak values with their different concentrations. The experimental results demonstrated that the PA profile of glucose is consistent with PA meachnism and the root-mean-squre error (RMSE) of prediction concentration can reach 0.77mmol/L. Therefore, this PA based set-up and scheme has the potential value in the BGC monitoring research.

Ren, Zhong; Liu, Guodong; Liu, Ying; Huang, Zhen

2013-09-01

60

Photoacoustic molecular imaging  

NASA Astrophysics Data System (ADS)

It is well documented that photoacoustic imaging has the capability to differentiate tissue based on the spectral characteristics of tissue in the optical regime. The imaging depth in tissue exceeds standard optical imaging techniques, and systems can be designed to achieve excellent spatial resolution. A natural extension of imaging the intrinsic optical contrast of tissue is to demonstrate the ability of photoacoustic imaging to detect contrast agents based on optically absorbing dyes that exhibit well defined absorption peaks in the infrared. The ultimate goal of this project is to implement molecular imaging, in which Herceptin TM, a monoclonal antibody that is used as a therapeutic agent in breast cancer patients that over express the HER2 gene, is labeled with an IR absorbing dye, and the resulting in vivo bio-distribution is mapped using multi-spectral, infrared stimulation and subsequent photoacoustic detection. To lay the groundwork for this goal and establish system sensitivity, images were collected in tissue mimicking phantoms to determine maximum detection depth and minimum detectable concentration of Indocyanine Green (ICG), a common IR absorbing dye, for a single angle photoacoustic acquisition. A breast mimicking phantom was constructed and spectra were also collected for hemoglobin and methanol. An imaging schema was developed that made it possible to separate the ICG from the other tissue mimicking components in a multiple component phantom. We present the results of these experiments and define the path forward for the detection of dye labeled Herceptin TM in cell cultures and mice models.

Kiser, William L., Jr.; Reinecke, Daniel; DeGrado, Timothy; Bhattacharyya, Sibaprasad; Kruger, Robert A.

2007-02-01

61

Piezoelectric active sensing techniques for damage detection on wind turbine blades  

NASA Astrophysics Data System (ADS)

This paper presents the performance of a variety of structural health monitoring (SHM) techniques, based on the use of piezoelectric active sensors, to determine the structural integrity of a 9m CX-100 wind turbine blade (developed by Sandia National Laboratory). First, the dynamic characterization of a CX-100 blade is performed using piezoelectric transducers, where the results are compared to those by conventional accelerometers. Several SHM techniques, including Lamb wave propagations, frequency response functions, and time series based methods are then utilized to analyze the condition of the wind turbine blade. The main focus of this research is to assess and construct a performance matrix to compare the performance of each method in identifying incipient damage, with a special consideration given the issues related to field deployment. Experiments are conducted on a stationary, full length CX-100 wind turbine blade. This examination is a precursor for planned full-scale fatigue testing of the blade and subsequent tests to be performed on an operational CX-100 Rotor Blade to be flown in the field.

Park, Gyuhae; Farinholt, Kevin M.; Taylor, Stuart G.; Farrar, Charles R.

2011-04-01

62

Miniaturization and integration of photoacoustic detection  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is an absorption spectroscopy technique that is currently used for low-level gas detection and catalyst characterization. It is a promising technique for chemical analysis in mesoscale analysis systems because the detection limit scales favorably with miniaturization. This work focuses on the scaling properties of photoacoustic spectroscopy, and on the miniaturization of gas-phase photoacoustic detection of propane in a nitrogen ambient. The detection system is modeled with a transmission line analogy, which is verified experimentally. The model includes the effects of acoustic leaks and absorption saturation. These two phenomena degrade the performance of the photoacoustic detector and must be controlled to realize the scaling advantages of photoacoustic systems. The miniature brass cells used to verify the model employ hearing aid microphones and optical excitation from a mechanically chopped, 3.39 mum He-Ne laser, transmitted into the cells with an optical fiber. These cells are able to detect 10 ppm of propane in nitrogen (a signal level of approx1 Pa/W). We also describe the development of a miniaturized photoacoustic system formed by microfabrication. In this case, the pressure-driven deflection of the detection membrane is measured optically. These systems show that photoacoustic detection may be inappropriate for systems with large variations in gas concentration because of absorption saturation and changing gas acoustic properties. Nevertheless, photoacoustic spectroscopy is a promising technique for the analysis of dilute mixtures in miniature chemical systems.

Firebaugh, Samara L.; Jensen, Klavs F.; Schmidt, Martin A.

2002-08-01

63

Influence of the size, geometry and temporal response of the finite piezoelectric sensor on the photoacoustic signal: the case of the point-like source  

NASA Astrophysics Data System (ADS)

Most photoacoustic (PA) work assumes a point-like detection of generated pressure waves; this assumption results in important differences between predicted and experimental signals, as shown in this paper. We used the geometry of a real sensor in the theoretical signal generation through the discretization of the sensing surface, considering each element as a point-like sensor. We modeled the interaction between the wavefront and the real sensor, starting from a well-known PA pressure relation for a point-like source and punctual detection. We obtained the electrical response of the real sensor experimentally and modeled it as a summation of Gaussian functions. The impulse response was convolved with the total PA pressure to obtain the theoretical PA signal. We analyzed the dependence of the source-sensor distance on the discretization size. Then the predicted signal and experimental data were compared for two different frequency response transducers. We found differences in shape and temporal width of simulated PA signals for point-like-source/punctual-detection model and for point-like-source/finite-sensor model.

Bravo-Miranda, C. A.; González-Vega, A.; Gutiérrez-Juárez, G.

2014-06-01

64

Photoacoustic computed microscopy.  

PubMed

Photoacoustic microscopy (PAM) is emerging as a powerful technique for imaging microvasculature at depths beyond the ~1?mm depth limit associated with confocal microscopy, two-photon microscopy and optical coherence tomography. PAM, however, is currently qualitative in nature and cannot quantitatively measure important functional parameters including oxyhemoglobin (HbO2), deoxyhemoglobin (HbR), oxygen saturation (sO2), blood flow (BF) and rate of oxygen metabolism (MRO2). Here we describe a new photoacoustic microscopic method, termed photoacoustic computed microscopy (PACM) that combines current PAM technique with a model-based inverse reconstruction algorithm. We evaluate the PACM approach using tissue-mimicking phantoms and demonstrate its in vivo imaging ability of quantifying HbO2, HbR, sO2, cerebral BF and cerebral MRO2 at the small vessel level in a rodent model. This new technique provides a unique tool for neuroscience research and for visualizing microvasculature dynamics involved in tumor angiogenesis and in inflammatory joint diseases. PMID:24828539

Yao, Lei; Xi, Lei; Jiang, Huabei

2014-01-01

65

Photoacoustic computed microscopy  

NASA Astrophysics Data System (ADS)

Photoacoustic microscopy (PAM) is emerging as a powerful technique for imaging microvasculature at depths beyond the ~1 mm depth limit associated with confocal microscopy, two-photon microscopy and optical coherence tomography. PAM, however, is currently qualitative in nature and cannot quantitatively measure important functional parameters including oxyhemoglobin (HbO2), deoxyhemoglobin (HbR), oxygen saturation (sO2), blood flow (BF) and rate of oxygen metabolism (MRO2). Here we describe a new photoacoustic microscopic method, termed photoacoustic computed microscopy (PACM) that combines current PAM technique with a model-based inverse reconstruction algorithm. We evaluate the PACM approach using tissue-mimicking phantoms and demonstrate its in vivo imaging ability of quantifying HbO2, HbR, sO2, cerebral BF and cerebral MRO2 at the small vessel level in a rodent model. This new technique provides a unique tool for neuroscience research and for visualizing microvasculature dynamics involved in tumor angiogenesis and in inflammatory joint diseases.

Yao, Lei; Xi, Lei; Jiang, Huabei

2014-05-01

66

Photoacoustic spectroscopy of condensed matter  

NASA Technical Reports Server (NTRS)

Photoacoustic spectroscopy is a new analytical tool that provides a simple nondestructive technique for obtaining information about the electronic absorption spectrum of samples such as powders, semisolids, gels, and liquids. It can also be applied to samples which cannot be examined by conventional optical methods. Numerous applications of this technique in the field of inorganic and organic semiconductors, biology, and catalysis have been described. Among the advantages of photoacoustic spectroscopy, the signal is almost insensitive to light scattering by the sample and information can be obtained about nonradiative deactivation processes. Signal saturation, which can modify the intensity of individual absorption bands in special cases, is a drawback of the method.

Somoano, R. B.

1978-01-01

67

Nanoscale piezoelectric response of ZnO nanowires measured using a nanoindentation technique.  

PubMed

We report the piezoelectric properties of ZnO nanowires (NWs) obtained by using a nanoindenter with a conductive boron-doped diamond tip. The direct piezoelectric effect was measured by performing nanoindentations under load control, and the generated piezoelectric voltage was characterized as a function of the applied loads in the range 0.2-6 mN. The converse piezoelectric effect was measured by applying a DC voltage to the sample while there was a low applied force to allow the tip being always in physical contact with the NWs. Vertically aligned ZnO NWs were grown on inexpensive, flexible, and disposable paper substrates using a template-free low temperature aqueous chemical growth method. When using the nanoindenter to measure the direct piezoelectric effect, piezopotential values of up to 26 mV were generated. Corresponding measurement of the converse piezoelectric effect gave an effective piezoelectric coefficient d33(eff) of ?9.2 pm V(-1). The ZnO NWs were also characterized using scanning electron microscopy, X-ray diffraction, and high-resolution transmission electron microscopy. The new nanoindentation approach provides a straightforward method to characterize piezoelectric material deposited on flexible and disposable substrates for the next generation of nanodevices. PMID:23722480

Broitman, Esteban; Soomro, Muhammad Yousuf; Lu, Jun; Willander, Magnus; Hultman, Lars

2013-07-14

68

Absorption Enhancement of Coated Absorbing Aerosols: Validation of the Photo-Acoustic Technique for Measuring the Enhancement  

Microsoft Academic Search

A photo-acoustic absorption spectrometer (PAS) and a cavity ring down aerosol extinction spectrometer (CRD-AES) were used, in conjunction with Mie Theory, to measure the refractive index (RI) of absorbing polystyrene spheres (APSS). The PAS and CRD-AES were also used to measure the absorption and extinction enhancement after these APSS were coated in oleic acid. The experimental enhancements were then compared

Daniel A. Lack; Christopher D. Cappa; Eben S. Cross; Paola Massoli; Adam T. Ahern; Paul Davidovits; Timothy B. Onasch

2009-01-01

69

Ultrafast optical technique for measuring the electrical dependence of the elasticity of piezoelectric thin film: demonstration on AlN.  

PubMed

We present a technique based on ultrafast acoustics which permits us to measure the electrical dependence of the elastic properties of a thin piezoelectric layer. Ultrafast acoustics offers a unique way of measuring elastic properties of thin-layer in a non-destructive way using ultrashort optical pulses. We apply this technique to a thin layer to which a dc voltage is simultaneously applied. Both the film thickness and the sound velocity are affected. The two effects can be separated by use of a semi-transparent top electrode. A demonstration is made on a thin aluminum nitride (AlN). From that the d(33) piezoelectric coefficient and the stiffness variation induced by the bias in AlN are measured. PMID:23387687

Devos, A; Emery, P; Defay, E; Ben Hassine, N; Parat, G

2013-01-01

70

Isolation of circulating tumor cells using photoacoustic flowmetry and two phase flow  

NASA Astrophysics Data System (ADS)

Melanoma is the deadliest form of skin cancer, yet current diagnostic methods are inadequately sensitive. Patients must wait until secondary tumors form before malignancy can be diagnosed and treatment prescribed. Detection of cells that have broken off the original tumor and flow through the blood or lymph system can provide data for diagnosing and monitoring cancer. Our group utilizes the photoacoustic effect to detect metastatic melanoma cells, which contain the pigmented granule melanin. As a rapid laser pulse irradiates melanoma, the melanin undergoes thermo-elastic expansion and ultimately creates a photoacoustic wave. Thus, melanoma patient's blood samples can be enriched, leaving the melanoma in a white blood cell (WBC) suspension. Irradiated melanoma cells produce photoacoustic waves, which are detected with a piezoelectric transducer, while the optically transparent WBCs create no signals. Here we report an isolation scheme utilizing two-phase flow to separate detected melanoma from the suspension. By introducing two immiscible fluids through a t-junction into one flow path, the analytes are compartmentalized. Therefore, the slug in which the melanoma cell is located can be identified and extracted from the system. Two-phase immiscible flow is a label free technique, and could be used for other types of pathological analytes.

O'Brien, Christine M.; Rood, Kyle D.; Gupta, Sagar K.; Mosley, Jeffrey D.; Goldschmidt, Benjamin S.; Sharma, Nikhilesh; Sengupta, Shramik; Viator, John A.

2011-03-01

71

Research on key technique of microscopy three-dimensional image reconstruction based on piezoelectric ceramics  

NASA Astrophysics Data System (ADS)

Due to the limited depth of focus of microscope objective, a series of images taken from different sections and directions are needed to reconstruct 3D microscopy image. In this paper, we present a novel method which utilizes piezoelectric actuator, high magnification microscopy system without mirror and single CCD to observe micro-objects and reconstruct its three-dimensional image. Inverse piezoelectric effect of piezoelectric ceramics have some superior characteristics, such as high positioning resolution, high positioning accuracy, etc. And piezoelectric actuator possess the advantage of small-size, strong-power and easy- to-integrated as well. Based on these points, we designed a 360° rotation and tilt positioning platform. In this platform, Piezoelectric actuator is employed to ensure the positioning accuracy at axis-Z direction. At the same time, Motion of 360° rotation and tilt can be controlled precisely using stepping motor controlling technology. Furthermore, finite element methods (FEM) analyze software--ANSYS is used to analyze the rigidity, stress and structure optimization of the platform. This rotation and tilt mechanical positioning platform can help the single CCD to get clear, complete-view two dimensional images. This method paves the way for three-dimensional reconstruction of micro objects. Experiments demonstrate that this 360° rotation and tilt positioning stage is structure-simple and high-accurate. It can be widely used in micro-structure observing and three-dimensional image reconstruction among mechanics, materials and biology, etc.

Wang, Jianhua; Xiao, Zexin

2011-11-01

72

Photoacoustic thermography of tissue.  

PubMed

Photoacoustic (PA) techniques can measure temperature in biological tissues because PA signal amplitude is sensitive to tissue temperature. So far, temperature-measuring PA techniques have focused on sensing of temperature changes at a single position. In this work, we photoacoustically measured spatial distribution of temperature in deep tissue. By monitoring the temperature at a single position using a thermocouple, the relationship between the PA signal amplitude and the actual temperature was determined. The relationship was then used to translate a PA image into a temperature map. This study showed that it is possible to calibrate the system for the temperature range of hyperthermia using single-point measurements over a smaller temperature range. Our experimental results showed a precision of -0.8±0.4°C (mean±standard error) in temperature measurement, and a spatial resolution as fine as 1.0 mm. PA techniques can be potentially applied to monitor temperature distribution deep in tissue during hyperthermia treatment of cancer. PMID:24522803

Ke, Haixin; Tai, Stephen; Wang, Lihong V

2014-02-01

73

Biomedical photoacoustics in China?  

PubMed Central

During the last decade, along with its explosive growth globally, biomedical photoacoustics has become a rapidly growing research field in China as well. In particular, photoacoustic tomography (PAT), capable of imaging intact biological tissue in vivo at great depths, has generated intense interest among Chinese researchers. This review briefly summarizes the current status and recent progress of the research in PAT in China. The focus is on the technology development and biomedical applications of three representative embodiments of PAT: photoacoustic microscopy, photoacoustic computed tomography, and photoacoustic endoscopy. In addition, recent development and studies in other related areas are also reviewed shortly.

Meng, Jing; Song, Liang

2013-01-01

74

Biomedical photoacoustics beyond thermal expansion using triggered nanodroplet vaporization for contrast-enhanced imaging  

Microsoft Academic Search

Since being discovered by Alexander Bell, photoacoustics may again be seeing major resurgence in biomedical imaging. Photoacoustics is a non-ionizing, functional imaging modality capable of high contrast images of optical absorption at depths significantly greater than traditional optical imaging techniques. Optical contrast agents have been used to extend photoacoustics to molecular imaging. Here we introduce an exogenous contrast agent that

Katheryne Wilson; Kimberly Homan; Stanislav Emelianov

2012-01-01

75

4-D Photoacoustic Tomography  

PubMed Central

Photoacoustic tomography (PAT) offers three-dimensional (3D) structural and functional imaging of living biological tissue with label-free, optical absorption contrast. These attributes lend PAT imaging to a wide variety of applications in clinical medicine and preclinical research. Despite advances in live animal imaging with PAT, there is still a need for 3D imaging at centimeter depths in real-time. We report the development of four dimensional (4D) PAT, which integrates time resolutions with 3D spatial resolution, obtained using spherical arrays of ultrasonic detectors. The 4D PAT technique generates motion pictures of imaged tissue, enabling real time tracking of dynamic physiological and pathological processes at hundred micrometer-millisecond resolutions. The 4D PAT technique is used here to image needle-based drug delivery and pharmacokinetics. We also use this technique to monitor 1) fast hemodynamic changes during inter-ictal epileptic seizures and 2) temperature variations during tumor thermal therapy. PMID:23346370

Xiang, Liangzhong; Wang, Bo; Ji, Lijun; Jiang, Huabei

2013-01-01

76

4-D Photoacoustic Tomography  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography (PAT) offers three-dimensional (3D) structural and functional imaging of living biological tissue with label-free, optical absorption contrast. These attributes lend PAT imaging to a wide variety of applications in clinical medicine and preclinical research. Despite advances in live animal imaging with PAT, there is still a need for 3D imaging at centimeter depths in real-time. We report the development of four dimensional (4D) PAT, which integrates time resolutions with 3D spatial resolution, obtained using spherical arrays of ultrasonic detectors. The 4D PAT technique generates motion pictures of imaged tissue, enabling real time tracking of dynamic physiological and pathological processes at hundred micrometer-millisecond resolutions. The 4D PAT technique is used here to image needle-based drug delivery and pharmacokinetics. We also use this technique to monitor 1) fast hemodynamic changes during inter-ictal epileptic seizures and 2) temperature variations during tumor thermal therapy.

Xiang, Liangzhong; Wang, Bo; Ji, Lijun; Jiang, Huabei

2013-01-01

77

Photoacoustic thermal diffusion flowmetry  

PubMed Central

Thermal Diffusion Flowmetry (TDF) (also called Heat Clearance Method or Thermal Clearance Method) is a longstanding technique for measuring blood flow or blood perfusion in living tissues. Typically, temperature transients and/or gradients are induced in a volume of interest and the temporal and/or spatial temperature variations which follow are measured and used for calculation of the flow. In this work a new method for implementing TDF is studied theoretically and experimentally. The heat deposition which is required for TDF is implemented photothermally (PT) and the measurement of the induced temperature variations is done by photoacoustic (PA) thermometry. Both excitation light beams (the PT and the PA) are produced by directly modulated 830 nm laser diodes and are conveniently delivered to the volume under test by the same optical fiber. The method was tested experimentally using a blood-filled phantom vessel and the results were compared with a theoretical prediction based on the heat and the photoacoustic equations. The fitting of a simplified lumped thermal model to the experimental data yielded estimated values of the blood velocity at different flow rates. By combining additional optical sources at different wavelengths it will be possible to utilize the method for non-invasive simultaneous measurement of blood flow and oxygen saturation using a single fiber probe. PMID:22574267

Sheinfeld, Adi; Eyal, Avishay

2012-01-01

78

Advances in Clinical and Biomedical Applications of Photoacoustic Imaging  

PubMed Central

Importance of the field Photoacoustic imaging is an imaging modality that derives image contrast from the optical absorption coefficient of the tissue being imaged. The imaging technique is able to differentiate between healthy and diseased tissue with either deeper penetration or higher resolution than other functional imaging modalities currently available. From a clinical standpoint, photoacoustic imaging has demonstrated safety and effectiveness in diagnosing diseased tissue regions using either endogenous tissue contrast or exogenous contrast agents. Furthermore, the potential of photoacoustic imaging has been demonstrated in various therapeutic interventions ranging from drug delivery and release to image-guided therapy and monitoring. Areas covered in this review This article reviews the current state of photoacoustic imaging in biomedicine from a technological perspective, highlights various biomedical and clinical applications of photoacoustic imaging, and gives insights on future directions. What the reader will gain Readers will learn about the various applications of photoacoustic imaging, as well as the various contrast agents that can be used to assist photoacoustic imaging. This review will highlight both pre-clinical and clinical uses for photoacoustic imaging, as well as discuss some of the challenges that must be addressed to move photoacoustic imaging into the clinical realm. Take home message Photoacoustic imaging offers unique advantages over existing imaging modalities. The imaging field is broad with many exciting applications for detecting and diagnosing diseased tissue or processes. Photoacoustics is also used in therapeutic applications to identify and characterize the pathology and then to monitor the treatment. Although the technology is still in its infancy, much work has been done in the pre-clinical arena, and photoacoustic imaging is fast approaching the clinical setting. PMID:21344060

Su, Jimmy L.; Wang, Bo; Wilson, Katheryne E.; Bayer, Carolyn L.; Chen, Yun-Sheng; Kim, Seungsoo; Homan, Kimberly A.; Emelianov, Stanislav Y.

2010-01-01

79

Quantitative Photoacoustic Imaging of Nanoparticles in Cells and Tissues  

PubMed Central

Quantitative visualization of nanoparticles in cells and tissues, while preserving the spatial information, is very challenging. A photoacoustic imaging technique to depict the presence and quantity of nanoparticles is presented. This technique is based on the dependence of the photoacoustic signal with both the nanoparticle quantity and the laser fluence. Quantitative photoacoustic imaging is a robust technique that doesn’t require knowledge of the local fluence, but a relative change in the fluence. This eliminates the need for sophisticated methods or models to determine the energy distribution of light in turbid media. Quantitative photoacoustic imaging was first applied to nanoparticle-loaded cells and quantitation was validated by inductively coupled plasma mass spectrometry. Quantitative photoacoustic imaging was then extended to xenograft tumor tissue sections, and excellent agreement with traditional histopathological analysis was demonstrated. Our results suggest that quantitative photoacoustic imaging may be used in many applications including the determination of the efficiency and effectiveness of molecular targeting strategies for cell studies and animal models, the quantitative assessment of photoacoustic contrast agent biodistribution, and the validation of in vivo photoacoustic imaging. PMID:23312348

Cook, Jason R.; Frey, Wolfgang; Emelianov, Stanislav

2013-01-01

80

Photoacoustic imaging in cancer detection, diagnosis, and treatment guidance  

PubMed Central

Imaging modalities play an important role in the clinical management of cancer, including screening, diagnosis, treatment planning, and therapy monitoring. Owing to increased research efforts in the past two decades, photoacoustic imaging – a non-ionizing, non-invasive technique capable of visualizing optical absorption properties of tissue at reasonable depth, with spatial resolution of ultrasound – has emerged. Ultrasound-guided photoacoustics is regarded for its ability to provide in vivo morphological and functional information about the tumor within the surrounding tissue. With the recent advent of targeted contrast agents, photoacoustics is capable of in vivo molecular imaging, thus facilitating further molecular and cellular characterization of cancer. This review examines the role of photoacoustics and photoacoustic-augmented imaging techniques in comprehensive cancer detection, diagnosis and treatment guidance. PMID:21324541

Mallidi, Srivalleesha; Luke, Geoffrey P.; Emelianov, Stanislav

2011-01-01

81

A study of several vortex-induced vibration techniques for piezoelectric wind energy harvesting  

NASA Astrophysics Data System (ADS)

This paper discusses a preliminary study on harnessing energy from piezoelectric transducers by using bluff body and vortex-induced vibration phenomena. Structures like bridges and buildings tend to deform and crack due to chaotic fluid-structure interactions. The rapid variation of pressure and velocity can be tapped and used to power structural health monitoring systems. The proposed device is a miniature, scalable wind harvesting device. The configuration consists of a bluff body with a flexible piezoelectric cantilever attached to the trailing edge. Tests are run for different characteristic dimensions or shapes for the bluff body and optimized for maximum power over a wide range of flow velocities. The main motive here is to seek a higher synchronized region of frequencies for the oscillation amplitudes. The multi-physics software package COMSOL is used to vary the design parameters to optimize the configuration and to identify the significant parameters in the design. The simulation results obtained show a wider lock-in bandwidth and higher average power for the cylindrical bluff body compared to the other two bluff body shapes investigated, the greatest average power being 0.35mW at a Reynolds number of 900, beam length of 0.04m, and bluff body diameter of 0.02m.

Sivadas, Vishak; Wickenheiser, Adam M.

2011-03-01

82

Photoacoustic photocalorimetry of a solid state reaction  

Microsoft Academic Search

We have developed a new photocalorimetric technique for the study of photoinduced chain reactions. This technique is based on photoacoustic detection and is applied to the solid-state photopolymerization of diacetylenes. At early stages of the polymerization process, the thermal energy evolved is as much as four times greater than the total light energy deposited in the sample. This result is

R. R. Chance; M. L. Shand

1980-01-01

83

Photoacoustic chemical sensing: ultracompact sources and standoff detection  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy (PAS) is a useful monitoring technique that is well suited for trace detection of gaseous and condensed media. We have previously demonstrated favorable PAS gas detection characteristics when the system dimensions are scaled to a micro-system design. This design includes quantum cascade laser (QCL)-based microelectromechanical systems (MEMS)-scale photoacoustic sensors that provide detection limits at parts-per-billion (ppb) levels for chemical targets. Current gas sensing research utilizes an ultra compact QCL, SpriteIR, in combination with a MEMS-scale photoacoustic cell for trace gas detection. At approximately one tenth the size of a standard commercially available QCL, SpriteIR is an essential element in the development of an integrated sensor package. We will discuss these results as well as the envisioned sensor prototype. Finally, expanding on our previously reported photoacoustic detection of condensed phase samples, we are investigating standoff photoacoustic chemical detection of these materials and will discuss preliminary results.

Marcus, Logan S.; Holthoff, Ellen L.; Schill, John F.; Pellegrino, Paul M.

2014-05-01

84

Photoacoustic cell for ultrasound contrast agent characterization  

NASA Astrophysics Data System (ADS)

Photoacoustics has emerged as a tool for the study of liquid gel suspension behavior and has been recently employed in a number of new biomedical applications. In this paper, a photoacoustic sensor is presented which was designed and realized for analyzing photothermal signals from solutions filled with microbubbles, commonly used as ultrasound contrast agents in echographic imaging techniques. It is a closed cell device, where photothermal volume variation of an aqueous solution produces the periodic deflection of a thin membrane closing the cell at the end of a short pipe. The cell then acts as a Helmholtz resonator, where the displacement of the membrane is measured through a laser probe interferometer, whereas photoacoustic signal is generated by a laser chopped light beam impinging onto the solution through a glass window. Particularly, the microbubble shell has been modeled through an effective surface tension parameter, which has been then evaluated from experimental data through the shift of the resonance frequencies of the photoacoustic sensor. This shift of the resonance frequencies of the photoacoustic sensor caused by microbubble solutions is high enough for making such a cell a reliable tool for testing ultrasound contrast agent, particularly for bubble shell characterization.

Alippi, A.; Bettucci, A.; Biagioni, A.; D'Orazio, A.; Germano, M.; Passeri, D.

2010-10-01

85

A photoacoustic and ultrasonic study on jatropha oil  

NASA Astrophysics Data System (ADS)

Using the photoacoustic technique, the thermal diffusivity of a dimethoxymethane + jatropha liquid mixture and pure jatropha oil is measured at room temperature. The result is correlated with the result of ultrasonic measurements.

Krishna Bama, G.; Ramachandran, K.

2010-03-01

86

Characterization of photoacoustic sources in tissue using time domain measurements  

NASA Astrophysics Data System (ADS)

Photoacoustic phenomenon in tissue and tissue phantoms is investigated with the particular goal of discrimination of diseased and healthy tissue. Propagation of broadband photoacoustic sources in tissue phantoms is studied with emphasis on attenuation, dispersion, and diffraction. Attenuation of photoacoustic waves induced by a circular laser spot on an absorber/air interface is modeled by the on-axis approximation of the acoustic field of a baffled piston source. Dispersion is studied in a diffraction free situation, where the disk of irradiation was created by a 5 mm laser spot on a 200 cm -1 solution. The genesis of diffraction in an absorbing solution was displayed by showing the merging of a boundary wave with a plane wave from a circular laser spot on an absorbing solution. Depth profiling of absorbing tissue phantoms and stained tissue was shown using a photoacoustic method. Acrylamide gels with layers of different optical absorption and stained elastin biomaterials were irradiated with stress confined laser pulses. The resulting acoustic waves were detected with a lithium niobate wideband acoustic transducer and processed in an algorithm to determine absorption coefficient as a function of depth. Spherical photoacoustic sources were generated in optically clear and turbid tissue phantoms. Propagation time and acoustic pulse duration were used to determine location and size, respectively. The photoacoustic sources were imaged using a multiplicative backprojection scheme. Image sources from acoustic boundaries were detected and dipole sources were detected and imaged. Finally an endoscopic photoacoustic probe was designed, built, and tested for use in determining treatment depth after palliative photodynamic therapy of esophageal cancer. The probe was less than 2.5 mm in diameter and consisted of a side firing 600 mum optical fiber to deliver laser energy and a 890 mum diameter, side viewing piezoelectric detector. The sensitivity of the probe was determined. The probe was also tested on coagulated and non-coagulated liver, ex vivo and on normally perfused and underperfused human skin, in vivo.

Viator, John Andrew

87

Enhanced photoacoustic detection using photonic crystal substrate  

NASA Astrophysics Data System (ADS)

This paper demonstrates the enhanced photoacoustic sensing of surface-bound light absorbing molecules and metal nanoparticles using a one-dimensional photonic crystal (PC) substrate. The PC structure functions as an optical resonator at the wavelength where the analyte absorption is strong. The optical resonance of the PC sensor provides an intensified evanescent field with respect to the excitation light source and results in enhanced optical absorption by surface-immobilized samples. For the analysis of a light absorbing dye deposited on the PC surface, the intensity of photoacoustic signal was enhanced by more than 10-fold in comparison to an un-patterned acrylic substrate. The technique was also applied to detect gold nanorods and exhibited more than 40 times stronger photoacoustic signals. The demonstrated approach represents a potential path towards single molecule absorption spectroscopy with greater performance and inexpensive instrumentation.

Zhao, Yunfei; Liu, Kaiyang; McClelland, John; Lu, Meng

2014-04-01

88

Piezoelectric valve  

DOEpatents

A motorized valve has a housing having an inlet and an outlet to be connected to a pipeline, a saddle connected with the housing, a turn plug having a rod, the turn plug cooperating with the saddle, and a drive for turning the valve body and formed as a piezoelectric drive, the piezoelectric drive including a piezoelectric generator of radially directed standing acoustic waves, which is connected with the housing and is connectable with a pulse current source, and a rotor operatively connected with the piezoelectric generator and kinematically connected with the rod of the turn plug so as to turn the turn plug when the rotor is actuated by the piezoelectric generator.

Petrenko, Serhiy Fedorovich

2013-01-15

89

Piezoelectrically Enhanced Photocathodes  

NASA Technical Reports Server (NTRS)

Doping of photocathodes with materials that have large piezoelectric coefficients has been proposed as an alternative means of increasing the desired photoemission of electrons. Treating cathode materials to increase emission of electrons is called "activation" in the art. It has been common practice to activate photocathodes by depositing thin layers of suitable metals (usually, cesium). Because cesium is unstable in air, fabrication of cesiated photocathodes and devices that contain them must be performed in sealed tubes under vacuum. It is difficult and costly to perform fabrication processes in enclosed, evacuated spaces. The proposed piezoelectrically enhanced photocathodes would have electron-emission properties similar to those of cesiated photocathodes but would be stable in air, and therefore could be fabricated more easily and at lower cost. Candidate photocathodes include nitrides of elements in column III of the periodic table . especially compounds of the general formula Al(x)Ga(1.x)N (where 0< or = x < or =.1). These compounds have high piezoelectric coefficients and are suitable for obtaining response to ultraviolet light. Fabrication of a photocathode according to the proposal would include inducement of strain in cathode layers during growth of the layers on a substrate. The strain would be induced by exploiting structural mismatches among the various constituent materials of the cathode. Because of the piezoelectric effect in this material, the strain would give rise to strong electric fields that, in turn, would give rise to a high concentration of charge near the surface. Examples of devices in which piezoelectrically enhanced photocathodes could be used include microchannel plates, electron- bombarded charge-coupled devices, image tubes, and night-vision goggles. Piezoelectrically enhanced photocathode materials could also be used in making highly efficient monolithic photodetectors. Highly efficient and stable piezoelectrically enhanced, ultraviolet-sensitive photocathodes and photodetectors could be fabricated by use of novel techniques for growing piezoelectrically enhanced layers, in conjunction with thinning and dopant-selective etching techniques.

Beach, Robert A.; Nikzad, Shouleh; Bell, Lloyd Douglas; Strittmatter, Robert

2011-01-01

90

Photoacoustic active ultrasound element for catheter tracking  

NASA Astrophysics Data System (ADS)

In recent years, various methods have been developed to improve ultrasound based interventional tool tracking. However, none of them has yet provided a solution that effectively solves the tool visualization and mid-plane localization accuracy problem and fully meets the clinical requirements. Our previous work has demonstrated a new active ultrasound pattern injection system (AUSPIS), which integrates active ultrasound transducers with the interventional tool, actively monitors the beacon signals and transmits ultrasound pulses back to the US probe with the correct timing. Ex vivo and in vivo experiments have proved that AUSPIS greatly improved tool visualization, and provided tool-tip localization accuracy of less than 300 ?m. In the previous work, the active elements were made of piezoelectric materials. However, in some applications the high driving voltage of the piezoelectric element raises safety concerns. In addition, the metallic electrical wires connecting the piezoelectric element may also cause artifacts in CT and MR imaging. This work explicitly focuses on an all-optical active ultrasound element approach to overcome these problems. In this approach, the active ultrasound element is composed of two optical fibers - one for transmission and one for reception. The transmission fiber delivers a laser beam from a pulsed laser diode and excites a photoacoustic target to generate ultrasound pulses. The reception fiber is a Fabry-Pérot hydrophone. We have made a prototype catheter and performed phantom experiments. Catheter tip localization, mid-plan detection and arbitrary pattern injection functions have been demonstrated using the all-optical AUSPIS.

Guo, Xiaoyu; Tavakoli, Behnoosh; Kang, Hyun-Jae; Kang, Jin U.; Etienne-Cummings, Ralph; Boctor, Emad M.

2014-03-01

91

EARLY-AGE CONCRETE STRENGTH ESTIMATION TECHNIQUE USING EMBEDDED PIEZOELECTRIC SELF-SENSING IMPEDANCE  

E-print Network

Engineering, Sungkyunkwan University, 2066, Seobu-Ro, Suwon, Korea 440-746 2 Dept. of u-City Design in "EWSHM - 7th European Workshop on Structural Health Monitoring (2014)" #12;The recent advent of smart infrastructures [5-12]. This technique utilizes high-frequency structural excitation, which is typically > 20 k

Paris-Sud XI, Université de

92

POWER HARVESTING PIEZOELECTRIC SHUNT DAMPING 1  

E-print Network

POWER HARVESTING PIEZOELECTRIC SHUNT DAMPING 1 A. J. Fleming ¤ S. O. R. Moheimani ¤ ¤ School piezoelectric transducer. Typical shunt networks require inductance values of up to thousands of Henries introduces an e±cient, light weight, and small-in-size technique for implementing piezoelectric shunt damping

Fleming, Andrew J.

93

Photoacoustic correlation spectroscopy for in vivo blood flow speed measurement  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging has been widely used in structural and functional imaging. Because of its safety, high resolution, and high imaging depth, it has great potential for a variety of medical studies. Capillaries are the smallest blood vessels and enable the exchange of oxygen and nutrients. Noninvasive flow speed measurement of capillaries in vivo can benefit the study of vascular tone changes and rheological properties of blood cells in capillaries. Recently, there has been a growing interest in photoacoustic velocimetry, such as photoacoustic Doppler and M-mode photoacoustic flow imaging. Methods capable of high-resolution imaging and low-speed flow measurement are suitable to measure blood speeds in capillaries. Previously we proposed photoacoustic correlation spectroscopy (PACS) and shown its feasibility for lowspeed flow measurement. Here, in vivo measurement of blood speeds in capillaries in a chick embryo model by PACS technique is demonstrated. The laser-scanning photoacoustic microscopy system is used for fast imaging acquisition and high-resolution imaging. The measured speed in capillaries is similar to those found in literatures, which confirm the feasibility of the PACS method for blood velocimetry. This technique suggests a fairly simple way to study blood flow speeds in capillaries.

Chen, Sung-Liang; Xie, Zhixing; Carson, Paul L.; Wang, Xueding; Guo, L. Jay

2012-02-01

94

Biomedical photoacoustic imaging.  

PubMed

Photoacoustic (PA) imaging, also called optoacoustic imaging, is a new biomedical imaging modality based on the use of laser-generated ultrasound that has emerged over the last decade. It is a hybrid modality, combining the high-contrast and spectroscopic-based specificity of optical imaging with the high spatial resolution of ultrasound imaging. In essence, a PA image can be regarded as an ultrasound image in which the contrast depends not on the mechanical and elastic properties of the tissue, but its optical properties, specifically optical absorption. As a consequence, it offers greater specificity than conventional ultrasound imaging with the ability to detect haemoglobin, lipids, water and other light-absorbing chomophores, but with greater penetration depth than purely optical imaging modalities that rely on ballistic photons. As well as visualizing anatomical structures such as the microvasculature, it can also provide functional information in the form of blood oxygenation, blood flow and temperature. All of this can be achieved over a wide range of length scales from micrometres to centimetres with scalable spatial resolution. These attributes lend PA imaging to a wide variety of applications in clinical medicine, preclinical research and basic biology for studying cancer, cardiovascular disease, abnormalities of the microcirculation and other conditions. With the emergence of a variety of truly compelling in vivo images obtained by a number of groups around the world in the last 2-3 years, the technique has come of age and the promise of PA imaging is now beginning to be realized. Recent highlights include the demonstration of whole-body small-animal imaging, the first demonstrations of molecular imaging, the introduction of new microscopy modes and the first steps towards clinical breast imaging being taken as well as a myriad of in vivo preclinical imaging studies. In this article, the underlying physical principles of the technique, its practical implementation, and a range of clinical and preclinical applications are reviewed. PMID:22866233

Beard, Paul

2011-08-01

95

Biomedical photoacoustic imaging  

PubMed Central

Photoacoustic (PA) imaging, also called optoacoustic imaging, is a new biomedical imaging modality based on the use of laser-generated ultrasound that has emerged over the last decade. It is a hybrid modality, combining the high-contrast and spectroscopic-based specificity of optical imaging with the high spatial resolution of ultrasound imaging. In essence, a PA image can be regarded as an ultrasound image in which the contrast depends not on the mechanical and elastic properties of the tissue, but its optical properties, specifically optical absorption. As a consequence, it offers greater specificity than conventional ultrasound imaging with the ability to detect haemoglobin, lipids, water and other light-absorbing chomophores, but with greater penetration depth than purely optical imaging modalities that rely on ballistic photons. As well as visualizing anatomical structures such as the microvasculature, it can also provide functional information in the form of blood oxygenation, blood flow and temperature. All of this can be achieved over a wide range of length scales from micrometres to centimetres with scalable spatial resolution. These attributes lend PA imaging to a wide variety of applications in clinical medicine, preclinical research and basic biology for studying cancer, cardiovascular disease, abnormalities of the microcirculation and other conditions. With the emergence of a variety of truly compelling in vivo images obtained by a number of groups around the world in the last 2–3 years, the technique has come of age and the promise of PA imaging is now beginning to be realized. Recent highlights include the demonstration of whole-body small-animal imaging, the first demonstrations of molecular imaging, the introduction of new microscopy modes and the first steps towards clinical breast imaging being taken as well as a myriad of in vivo preclinical imaging studies. In this article, the underlying physical principles of the technique, its practical implementation, and a range of clinical and preclinical applications are reviewed. PMID:22866233

Beard, Paul

2011-01-01

96

Piezoelectric thick film ultrasonic transducers fabricated by a sol–gel spray technique  

Microsoft Academic Search

Thick film broadband ultrasonic transducers (UTs) produced by a sol–gel spray technique and operated below 10 MHz are presented. These UTs are formed by dispersing PZT and LiTaO3 particles, respectively in Al2O3 and PZT sol–gel solution. The 50–100 ?m thick films have been deposited on curved steel, flat steel and aluminum substrates and steel rods. Ultrasonic pulse-echo signals with a

M Kobayashi; T. R Olding; M Sayer; C.-K Jen

2002-01-01

97

Stimulated Raman photoacoustic imaging  

PubMed Central

Achieving label-free, molecular-specific imaging with high spatial resolution in deep tissue is often considered the grand challenge of optical imaging. To accomplish this goal, significant optical scattering in tissues has to be overcome while achieving molecular specificity without resorting to extrinsic labeling. We demonstrate the feasibility of developing such an optical imaging modality by combining the molecularly specific stimulated Raman excitation with the photoacoustic detection. By employing two ultrashort excitation laser pulses, separated in frequency by the vibrational frequency of a targeted molecule, only the specific vibrational level of the target molecules in the illuminated tissue volume is excited. This targeted optical absorption generates ultrasonic waves (referred to as stimulated Raman photoacoustic waves) which are detected using a traditional ultrasonic transducer to form an image following the design of the established photoacoustic microscopy. PMID:21059930

Yakovlev, Vladislav V.; Zhang, Hao F.; Noojin, Gary D.; Denton, Michael L.; Thomas, Robert J.; Scully, Marlan O.

2010-01-01

98

Piezoelectric thick film ultrasonic transducers fabricated by a sol-gel spray technique.  

PubMed

Thick film broadband ultrasonic transducers (UTs) produced by a sol-gel spray technique and operated below 10 MHz are presented. These UTs are formed by dispersing PZT and LiTaO3 particles, respectively in Al2O3 and PZT sol-gel solution. The 50-100 microm thick films have been deposited on curved steel, flat steel and aluminum substrates and steel rods. Ultrasonic pulse-echo signals with a signal to noise ratio of more than 25 dB are experimentally obtained for the operating temperatures up to 250 degrees C. PMID:12479598

Kobayashi, M; Olding, T R; Sayer, M; Jen, C K

2002-10-01

99

Urogenital photoacoustic endoscope  

PubMed Central

Photoacoustic endoscopy for human urogenital imaging has the potential to diagnose many important diseases, such as endometrial cancer and prostate cancer. We have specifically developed a 12.7 mm diameter, rigid, side-scanning photoacoustic endoscopic probe for such applications. The key features of this endoscope are the streamlined structure for smooth cavity introduction and the proximal actuation mechanism for fast scanning. Here, we describe the probe’s composition and scanning mechanism, and present in vivo experimental results suggesting its potential for comprehensive clinical applications. PMID:24690816

Chen, Ruimin; Yeh, Cheng-Hung; Zhu, Liren; Maslov, Konstantin; Zhou, Qifa; Shung, K. Kirk; Wang, Lihong V.

2014-01-01

100

Structure of adsorbed polyelectrolyte monolayers investigated by combining optical reflectometry and piezoelectric techniques.  

PubMed

Polyelectrolyte monolayers on solid substrates are studied with optical reflectivity and the quartz crystal microbalance (QCM). In particular, we investigate the adsorption of anionic poly(styrene sulfonate) (PSS) on amino-functionalized silica as well as cationic poly(allylamine hydrochloride) (PAH) and poly-L-lysine (PLL) on bare silica. By comparing the dry and wet masses measured on identical substrates with these two techniques, we obtain information on the layer thickness and water content of these layers. Monolayers typically feature an adsorbed dry mass of about 0.1-2 mg/m(2), a layer thickness of 0.5-2 nm, and a water content of 20-50%. One finds that the layer thickness increases with increasing concentrations of monovalent salts and polyelectrolytes. PMID:22283688

Porus, Maria; Maroni, Plinio; Borkovec, Michal

2012-04-01

101

Photoacoustics study of the degree of polimerization of resins and restoration materials  

Microsoft Academic Search

In this work is presented the use of Photoacoustic as an alternative technique to monitor the curing process of odontological materials, emphasizing the resins chemically activated (RCA). Through photoacoustic measurements, it is possible to study optical and thermal properties of samples, and to obtain information on the characteristic times involved in the curing processes. For this study the samples were

Elaine C. dos Reis Coloiano; Airton Abrahao Martin; Marcos Dias da Silva; Paulo Roxo Barja; Daniel Acosta-Avalos

2003-01-01

102

Human teeth model using photoacoustic frequency response  

NASA Astrophysics Data System (ADS)

In this paper, a novel photo-acoustic technique modality utilizing a frequency- modulated Q-switch Nd:YAG laser at 1064 nm and coherent frequency domain signal processing is introduced for impulse and frequency responses of biological tissues. We present a photoacoustic technique to monitor the temporal behavior of temperature and pressure in an excised sample of human teeth after either a single laser pulse or during multiple laser pulses at pulse repetition frequencies (PRF) from 5 Hz to 100 Hz. Knowledge of the dynamic characteristics of structural elements often means the difference between normal and abnormal tissue. The determination of the resonance characteristics of structures is termed "modal analysis." The results of our study suggest that it is possible to identify the impulse, frequency response and resonance modes of simplified human teeth. This data provided a powerful tool to differentiate between normal and decay teeth.

El-Sharkawy, Yasser H.; El-Sherif, Ashraf F.

2012-03-01

103

Piezoelectric Film.  

ERIC Educational Resources Information Center

Presents activities that utilize piezoelectric film to familiarize students with fundamental principles of electricity. Describes classroom projects involving chemical sensors, microbalances, microphones, switches, infrared sensors, and power generation. (MDH)

Garrison, Steve

1992-01-01

104

Photoacoustic section imaging with an integrating cylindrical detector  

PubMed Central

A piezoelectric detector with a cylindrical shape is investigated for photoacoustic section imaging. Images are acquired by rotating a sample in front of the cylindrical detector. With its length exceeding the size of the imaging object, it works as an integrating sensor and therefore allows reconstructing section images with the inverse Radon transform. Prior to the reconstruction the Abel transform is applied to the measured signals to improve the accuracy of the image. A resolution of about 100 µm within a section and of 500 µm between sections is obtained. Additionally, a series of images of a zebra fish is shown. PMID:22076260

Gratt, Sibylle; Passler, Klaus; Nuster, Robert; Paltauf, Guenther

2011-01-01

105

Development of real-time photoacoustic microscopy  

Microsoft Academic Search

Photoacoustic tomography detecting ultrasound signals generated from photon absorption provides optical absorption contrast in vivo for structural, functional and molecular imaging. Although photoacoustic tomography technology has grown fast in recent years, real-time photoacoustic imaging with cellular spatial resolution are still strongly demanded. We developed a photoacoustic microscopy which has video-rate imaging capability with cellular spatial resolution. The system consists of

Lidai Wang; Konstantin Maslov; Junjie Yao; Li Li; Lihong V. Wang

2011-01-01

106

Catheter-based photoacoustic endoscope.  

PubMed

We report a flexible shaft-based mechanical scanning photoacoustic endoscopy (PAE) system that can be potentially used for imaging the human gastrointestinal tract via the instrument channel of a clinical video endoscope. The development of such a catheter endoscope has been an important challenge to realize the technique's benefits in clinical settings. We successfully implemented a prototype PAE system that has a 3.2-mm diameter and 2.5-m long catheter section. As the instrument's flexible shaft and scanning tip are fully encapsulated in a plastic catheter, it easily fits within the 3.7-mm diameter instrument channel of a clinical video endoscope. Here, we demonstrate the intra-instrument channel workability and in vivo animal imaging capability of the PAE system. PMID:24887743

Yang, Joon-Mo; Li, Chiye; Chen, Ruimin; Zhou, Qifa; Shung, K Kirk; Wang, Lihong V

2014-06-01

107

Catheter-based photoacoustic endoscope  

NASA Astrophysics Data System (ADS)

We report a flexible shaft-based mechanical scanning photoacoustic endoscopy (PAE) system that can be potentially used for imaging the human gastrointestinal tract via the instrument channel of a clinical video endoscope. The development of such a catheter endoscope has been an important challenge to realize the technique's benefits in clinical settings. We successfully implemented a prototype PAE system that has a 3.2-mm diameter and 2.5-m long catheter section. As the instrument's flexible shaft and scanning tip are fully encapsulated in a plastic catheter, it easily fits within the 3.7-mm diameter instrument channel of a clinical video endoscope. Here, we demonstrate the intra-instrument channel workability and in vivo animal imaging capability of the PAE system.

Yang, Joon-Mo; Li, Chiye; Chen, Ruimin; Zhou, Qifa; Shung, K. Kirk; Wang, Lihong V.

2014-06-01

108

Quartz-enhanced photoacoustic spectroscopy: a review.  

PubMed

A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis. PMID:24686729

Patimisco, Pietro; Scamarcio, Gaetano; Tittel, Frank K; Spagnolo, Vincenzo

2014-01-01

109

Photoacoustic spectroscopy of Baru Dipteryx alata Vog  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy (PAS) was used to investigate samples produced from Baru (Dipteryx alata Vog.), a typical fruit from the Brazilian Cerrado, which is considered as a good source of nutrients. The photoacoustic (PA) spectra of samples prepared from Baru seeds present three different absorption bands in the wavelength range 0.3 1.0 ?m, named Band-C, Band-S, and Band-L. We found that PAS can be useful for monitoring the strong absorption of visible light by Baru's seeds constituents mainly in the shorter wavelength measured range. This study is important from both agricultural and commercial point of view once it introduces PAS as a potential characterization technique allowing better control of fruit and seed selection, storage and transportation.

Rodriguez, A. F. R.; Santos, J. G.; Silveira, L. B.; Oliveira, A. C.; Morais, P. C.; Nunes, O. A. C.

2008-01-01

110

Quartz-Enhanced Photoacoustic Spectroscopy: A Review  

PubMed Central

A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis. PMID:24686729

Patimisco, Pietro; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, Vincenzo

2014-01-01

111

Towards single molecule detection using photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

Recently, a number of optical imaging modalities have achieved single molecule sensitivity, including photothermal imaging, stimulated emission microscopy, ground state depletion microscopy, and transmission microscopy. These optical techniques are based on optical absorption contrast, extending single-molecule detection to non-fluorescent chromophores. Photoacoustics is a hybrid technique that utilizes optical excitation and ultrasonic detection, allowing it to scale both the optical and acoustic regimes with 100% sensitivity to optical absorption. However, the sensitivity of photoacoustics is limited by thermal noise, inherent in the medium itself in the form of acoustic black body radiation. In this paper, we investigate the molecular sensitivity of photoacoustics in the context of the thermal noise limit. We show that single molecule sensitivity is achievable theoretically at room temperature for molecules with sufficiently fast relaxation times. Hurdles to achieve single molecule sensitivity in practice include development of detection schemes that work at short working distance, <100 microns, high frequency, <100 MHz, and low loss, <10 dB.

Winkler, Amy M.; Maslov, Konstantin; Wang, Lihong V.

2013-03-01

112

TIR-based photothermal/photoacoustic deflection  

NASA Astrophysics Data System (ADS)

We report on a new experimental technique for monitoring laser-induced shock waves and thermal waves above the sample surface called total internal reflection based photothermal or photoacoustic deflection (TIR based PTD/PAD deflection). It is based on the changes in transmissivity of a prism which is operated near the condition of total internal reflection for a HeNe laser beam propagating parallel to the sample surface at a small distance. The HeNe laser beam is probing photoacoustic or photothermal waves originating from a sample surface due to interaction with a pulsed Nd:YAG laser beam. The method is compared with standard online detection techniques like scatter probe monitoring and plasma detection, and found to be a very sensitive and practical tool. It also showed its suitability for selectively monitoring several surfaces (e. g. front and rear surface) of optical components, and attributing the damage starting point. Therefore, the method might be used for monitoring of surface damage on laser crystals or valuable components. Keywords: photothermal deflection, photoacoustic deflection, laser damage, total internal reflection.

Riede, Wolfgang; Allenspacher, Paul; Franck, J.

2008-10-01

113

Sensitivity of photoacoustic microscopy  

PubMed Central

Building on its high spatial resolution, deep penetration depth and excellent image contrast, 3D photoacoustic microscopy (PAM) has grown tremendously since its first publication in 2005. Integrating optical excitation and acoustic detection, PAM has broken through both the optical diffusion and optical diffraction limits. PAM has 100% relative sensitivity to optical absorption (i.e., a given percentage change in the optical absorption coefficient yields the same percentage change in the photoacoustic amplitude), and its ultimate detection sensitivity is limited only by thermal noise. Focusing on the engineering aspects of PAM, this Review discusses the detection sensitivity of PAM, compares the detection efficiency of different PAM designs, and summarizes the imaging performance of various endogenous and exogenous contrast agents. It then describes representative PAM applications with high detection sensitivity, and outlines paths to further improvement.

Yao, Junjie; Wang, Lihong V.

2014-01-01

114

Lifetime-based photoacoustic oxygen sensing in vivo  

PubMed Central

Abstract. The determination of oxygen levels in blood and other tissues in vivo is critical for ensuring proper body functioning, for monitoring the status of many diseases, such as cancer, and for predicting the efficacy of therapy. Here we demonstrate, for the first time, a lifetime-based photoacoustic technique for the measurement of oxygen in vivo, using an oxygen sensitive dye, enabling real time quantification of blood oxygenation. The results from the main artery in the rat tail indicated that the lifetime of the dye, quantified by the photoacoustic technique, showed a linear relationship with the blood oxygenation levels in the targeted artery. PMID:22612143

Ray, Aniruddha; Rajian, Justin Rajesh; Lee, Yong-Eun Koo; Wang, Xueding; Kopelman, Raoul

2012-01-01

115

Nondestructive evaluation of structural ceramics by photoacoustic microscopy  

NASA Technical Reports Server (NTRS)

A photoacoustic microscopy (PAM) digital imaging system was developed and utilized to characterize silicon nitride material at the various stages of the ceramic fabrication process. Correlation studies revealed that photoacoustic microscopy detected failure initiating defects in substantially more specimens than microradiography and ultrasonic techniques. Photoacoustic microscopy detected 10 to 100 micron size surface and subsurface pores and inclusions, respectively, up to 80 microns below the interrogating surface in machined sintered silicon nitride. Microradiography detected 50 micron diameter fracture controlling pores and inclusions. Subsurface holes were detected up to a depth of 570 microns and 1.00 mm in sintered silicon nitride and silicon carbide, respectively. Seeded voids of 20 to 30 micron diameters at the surface and 50 microns below the interrogating surface were detected by photoacoustic microscopy and microradiography with 1 percent X-ray thickness sensitivity. Tight surface cracks of 96 micron length x 48 micron depth were detected by photoacoustic microscopy. PAM volatilized and removed material in the green state which resulted in linear shallow microcracks after sintering. This significantly limits the use of PAM as an in-process NDE technique.

Khandelwal, Pramod K.

1987-01-01

116

Functional photoacoustic microscopy of pH  

NASA Astrophysics Data System (ADS)

pH is a tightly regulated indicator of metabolic activity. In mammalian systems, imbalance of pH regulation may result from or result in serious illness. Even though the regulation system of pH is very robust, tissue pH can be altered in many diseases such as cancer, osteoporosis and diabetes mellitus. Traditional high-resolution optical imaging techniques, such as confocal microscopy, routinely image pH in cells and tissues using pH sensitive fluorescent dyes, which change their fluorescence properties with the surrounding pH. Since strong optical scattering in biological tissue blurs images at greater depths, high-resolution pH imaging is limited to penetration depths of 1mm. Here, we report photoacoustic microscopy (PAM) of commercially available pH-sensitive fluorescent dye in tissue phantoms. Using both opticalresolution photoacoustic microscopy (OR-PAM), and acoustic resolution photoacoustic microscopy (AR-PAM), we explored the possibility of recovering the pH values in tissue phantoms. In this paper, we demonstrate that PAM was capable of recovering pH values up to a depth of 2 mm, greater than possible with other forms of optical microscopy.

Chatni, M. Rameez; Yao, Junjie; Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin I.; Wang, Lihong V.

2012-02-01

117

1662 Piezoelectric Microdispenser  

E-print Network

using the high-temperature flux technique is a notable example of another approach. For ceramic materials, there are many approaches available to a researcher for fabrication, including the simple pellet press, tape casting, screen printing, sputter deposition (especially PZT and ZnO), sol-gel techniques for thin films, pulsed-laser deposition, and the hygrothermal technique [10] for deposition of quality PZT onto titanium. Key Research Findings During World War II, the discovery of PZT was a fortuitous and remarkable improvement on the state of the art in piezoelectric materials engineering. Since then, modest improvements in performance of piezoelectric materials have been made, with the discovery of single-crystal high-strain PMN-PT materials [8] an important milestone.

unknown authors

118

High-sensitivity detection of trace gases using dynamic photoacoustic spectroscopy  

E-print Network

Lincoln Laboratory of Massachusetts Institute of Technology has developed a technique known as dynamic photoacoustic spectroscopy (DPAS) that could enable remote detection of trace gases via a field-portable laser-based ...

Wynn, Charles M.

119

Photoacoustic spectroscopic differences between normal and malignant thyroid tissues  

NASA Astrophysics Data System (ADS)

The thyroid is one of the main endocrine glands of human body, which plays a crucial role in the body's metabolism. Thyroid cancer mortality ranks only second to ovarian cancer in endocrine cancer. Routine diagnostic methods of thyroid diseases in present clinic exist misdiagnosis and missed diagnosis to varying degrees. Those lead to miss the best period of cancer treatment--early. Photoacoustic spectroscopy technology is a new tool, which provides an effective and noninvasive way for biomedical materials research, being highly sensitive and without sample pretreatment. In this paper, we use photoacoustic spectroscopy technology (PAST) to detect the absorption spectrum between normal and malignant thyroid tissues. The result shows that the photoacoustic spectroscopy technology (PAST) could differentiate malignant thyroid tissue from normal thyroid tissue very well. This technique combined with routine diagnostic methods has the potential to increase the diagnostic accuracy in clinical thyroid cancer diagnosis.

Li, Li; Xie, Wengming; Li, Hui

2012-12-01

120

Photoacoustic Study of Fungal Disease of Acai ( Euterpe oleracea) Seeds  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is introduced as a promising experimental technique to investigate fungus infected Acai ( Euterpe oleracea) seeds. Photoacoustic spectra of healthy and infected Acai seeds with the fungus Colletotrichum gloeosporioides were recorded firstly in the modulation frequency range of 5Hz to 700 Hz, while keeping the wavelength of excitation radiation of a Xe arc-lamp constant, to ascertain the depth of penetration of infection within the seed and secondly, at variable wavelength (wavelength scanning) in the interval 250nm to 1,000 nm, while keeping the modulation frequency constant. In the former, the photoacoustic signal strength from the infected seed was found higher than that of the healthy one, and has been associated with the appearance of new biomolecules associated with the pathogen infection. In the latter, characteristics peaks and bands were observed in the range from 650 nm to 900 nm ascribed to organic compounds with carboxylates and amines (functional groups) forming the typical metabolic structures of the fungus.

Rezende, Denise V.; Nunes, O. A. C.; Oliveira, A. C.

2009-10-01

121

Photoacoustic spectroscopy for trace vapor detection and molecular discrimination  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy (PAS) is a useful monitoring technique that is well suited for trace gas detection. This method routinely exhibits detection limits at the parts-per-million (ppm) or parts-per-billion (ppb) level for gaseous samples. PAS also possesses favorable detection characteristics when the system dimensions are scaled to a microsystem design. Current research utilizes quantum cascade lasers (QCLs) in combination with micro-electromechanical systems (MEMS)-scale photoacoustic cell designs. This sensing platform has provided favorable detection limits for a standard nerve agent simulant. The objective of the present work is to demonstrate an extremely versatile MEMS-scale photoacoustic sensor system that is able to discriminate between different analytes of interest.

Holthoff, Ellen; Bender, John; Pellegrino, Paul; Fisher, Almon; Stoffel, Nancy

2010-04-01

122

Application of photoacoustic, photothermal and fluorescence spectroscopies in signal enhancement and the kinetics, chemistry and photophysics of several dyes  

SciTech Connect

Modified photoacoustic and photothermal spectroscopies are applied in analytical studies of liquid and solid systems. Quenching of benzophenone by potassium iodide is used to demonstrate application of time resolved photothermal spectroscopies in study of fast (submicrosecond) deexcitation processes. Inherently weak X-ray photoacoustic signals at a synchrotron are enhanced by the introduction of a volatile liquid into a gas-microphone photoacoustic cell. Traditionally, photoacoustic signals have been detected either by gas coupling with a microphone or with a piezoelectric detector. However, optically detected photoacoustic signals have been used in the determination of physical properties of a liquid sample system and are successfully applied to the study of deexcitation processes of a number of dye molecules. Photothermal beam deflection photoacoustic (PBDPA), fluorescence and absorbance measurements are utilized to study the chemistry and photophysics of cresyl violet in aqueous, aqueous micellar and methanolic solutions. A concentration dependence of the fluorescence quantum yield of cresyl violet is investigated. Aspects of chemistry and photophysics relating to potential use of several diazo dyes as photothermal sensitizing dyes in photodynamic therapy are explored experimentally and discussed. Photothermal beam deflection, fluorescence and absorbance measurements are again utilized. The dyes are found to have a number of interesting chemical and photophysical properties. They are also determined to be ideal photothermal sensitizing dye candidates.

Isak, S.J.

1992-06-01

123

Photoacoustic measurement of methane concentrations with a compact pulsed  

E-print Network

of lasers in trace-gas monitoring. The optical techniques com- monly used in trace-gas detection of trace quan- tities of methane in nitrogen by photoacoustic spectroscopy with a novel differential was achieved with a 15-mW He­Ne laser. In subsequent development of PA trace-gas detection, chiefly CO2 and CO

Kung, Andy

124

Electrical Power Generation Using Piezoelectric Crystal  

E-print Network

Abstract- The usefulness of most high technology devices such as cell phones, computers, and sensors is limited by the storage capacity of batteries. In the future, these limitations will become more pronounced as the demand for wireless power outpaces battery development which is already nearly optimized. Thus, new power generation techniques are required for the next generation of wearable computers, wireless sensors, and autonomous systems to be feasible. Piezoelectric materials are excellent power generation devices because of their ability to couple mechanical and electrical properties. For example, when an electric field is applied to piezoelectric a strain is generated and the material is deformed. Consequently, when a piezoelectric is strained it produces an electric field; therefore, piezoelectric materials can convert ambient vibration into electrical power. Piezoelectric materials have long been used as sensors and actuators; however their use as electrical generators is less established. A piezoelectric power generator has great potential for some remote applications such as in vivo sensors, embedded MEMS devices, and distributed networking. Developing piezoelectric generators is challenging because of their poor source characteristics (high voltage, low current, high impedance) and relatively low power output. This paper presents a theoretical analysis to increase the piezoelectric power generation that is verified with experimental results. Index Terms-Piezoelectric materials, piezoelectricity, power generation, PZT ceramics.

unknown authors

125

Virus-based piezoelectric energy generation  

NASA Astrophysics Data System (ADS)

Piezoelectric materials can convert mechanical energy into electrical energy, and piezoelectric devices made of a variety of inorganic materials and organic polymers have been demonstrated. However, synthesizing such materials often requires toxic starting compounds, harsh conditions and/or complex procedures. Previously, it was shown that hierarchically organized natural materials such as bones, collagen fibrils and peptide nanotubes can display piezoelectric properties. Here, we demonstrate that the piezoelectric and liquid-crystalline properties of M13 bacteriophage (phage) can be used to generate electrical energy. Using piezoresponse force microscopy, we characterize the structure-dependent piezoelectric properties of the phage at the molecular level. We then show that self-assembled thin films of phage can exhibit piezoelectric strengths of up to 7.8 pm V-1. We also demonstrate that it is possible to modulate the dipole strength of the phage, hence tuning the piezoelectric response, by genetically engineering the major coat proteins of the phage. Finally, we develop a phage-based piezoelectric generator that produces up to 6 nA of current and 400 mV of potential and use it to operate a liquid-crystal display. Because biotechnology techniques enable large-scale production of genetically modified phages, phage-based piezoelectric materials potentially offer a simple and environmentally friendly approach to piezoelectric energy generation.

Lee, Byung Yang; Zhang, Jinxing; Zueger, Chris; Chung, Woo-Jae; Yoo, So Young; Wang, Eddie; Meyer, Joel; Ramesh, Ramamoorthy; Lee, Seung-Wuk

2012-06-01

126

Evaluation of Ferroelectric Properties of Piezoelectric Ceramics Based on Crystallographic Homogenization Method and Crystal Orientation Analysis by SEM·EBSD Technique  

NASA Astrophysics Data System (ADS)

Macroscopic ferroelectric properties of piezoelectric polycrystals are strongly affected by microscopic inhomogeneous crystal structure. In our previous study, a multi-scale finite element method based on crystallographic homogenization method has been developed to estimate macroscopic properties considering microscopic crystal morphology. In this paper, the crystal orientation distribution of polycrystalline barium titanate has been measured by SEM·EBSD technique, and the measured crystal orientation distribution has been introduced to the microscopic finite element model. As the prediction of macroscopic properties depends on the sampling conditions of the measured crystal orientations, the effects of number of sampling points and sampling area have been investigated. As a result, the effective sampling conditions have been clarified to estimate macroscopic ferroelectric properties.

Uetsuji, Yasutomo; Yoshida, Toshihiro; Yamakawa, Takayuki; Tsuchiya, Kazuyoshi; Ueda, Sei; Nakamachi, Eiji

127

Photoacoustics study of the degree of polimerization of resins and restoration materials  

NASA Astrophysics Data System (ADS)

In this work is presented the use of Photoacoustic as an alternative technique to monitor the curing process of odontological materials, emphasizing the resins chemically activated (RCA). Through photoacoustic measurements, it is possible to study optical and thermal properties of samples, and to obtain information on the characteristic times involved in the curing processes. For this study the samples were analyzed to evaluate the polymerization of the RCA for different temperature. The results obtained show the viability of applying the Photoacoustic Techinques to monitor the polyermization kinetic of odontological resins, allowing for a qualitative and quantitative interpretation.

dos Reis Coloiano, Elaine C.; Abrahao Martin, Airton; Dias da Silva, Marcos; Roxo Barja, Paulo; Acosta-Avalos, Daniel

2003-06-01

128

Measurement of cardiac output by use of noninvasively measured transient hemodilution curves with photoacoustic technology.  

PubMed

We present the theoretical basis and experimental verification for cardiac output measurements using noninvasively measured hemodilution curves afforded with an indicator dilution technique and the emerging photoacoustic technology. A photoacoustic system noninvasively tracks a transient hemodilution effect induced by a bolus of isotonic saline as an indicator. As a result, a photoacoustic indicator dilution curve is obtained, which allows to estimate cardiac output from the developed algorithm. The experiments with a porcine blood circulatory phantom system demonstrated the feasibility of this technology towards the development of a noninvasive cardiac output measurement system for patient monitoring. PMID:24877007

Kang, Dongyel; Huang, Qiaojian; Li, Youzhi

2014-05-01

129

Label-free photoacoustic nanoscopy.  

PubMed

Super-resolution microscopy techniques - capable of overcoming the diffraction limit of light - have opened new opportunities to explore subcellular structures and dynamics not resolvable in conventional far-field microscopy. However, relying on staining with exogenous fluorescent markers, these techniques can sometimes introduce undesired artifacts to the image, mainly due to large tagging agent sizes and insufficient or variable labeling densities. By contrast, the use of endogenous pigments allows imaging of the intrinsic structures of biological samples with unaltered molecular constituents. Here, we report label-free photoacoustic (PA) nanoscopy, which is exquisitely sensitive to optical absorption, with an 88 nm resolution. At each scanning position, multiple PA signals are successively excited with increasing laser pulse energy. Because of optical saturation or nonlinear thermal expansion, the PA amplitude depends on the nonlinear incident optical fluence. The high-order dependence, quantified by polynomial fitting, provides super-resolution imaging with optical sectioning. PA nanoscopy is capable of super-resolution imaging of either fluorescent or nonfluorescent molecules. PMID:25104412

Danielli, Amos; Maslov, Konstantin; Garcia-Uribe, Alejandro; Winkler, Amy M; Li, Chiye; Wang, Lidai; Chen, Yun; Dorn, Gerald W; Wang, Lihong V

2014-08-01

130

An experimental and theoretical approach to the study of the photoacoustic signal produced by cancer cells  

NASA Astrophysics Data System (ADS)

The distinctive spectral absorption characteristics of cancer cells make photoacoustic techniques useful for detection in vitro and in vivo. Here we report on our evaluation of the photoacoustic signal produced by a series of monolayers of different cell lines in vitro. Only the melanoma cell line HS936 produced a detectable photoacoustic signal in which amplitude was dependent on the number of cells. This finding appears to be related to the amount of melanin available in these cells. Other cell lines (i.e. HL60, SK-Mel-1, T47D, Hela, HT29 and PC12) exhibited values similar to a precursor of melanin (tyrosinase), but failed to produce sufficient melanin to generate a photoacoustic signal that could be distinguished from background noise. To better understand this phenomenon, we determined a formula for the time-domain photoacoustic wave equation for a monolayer of cells in a non-viscous fluid on the thermoelastic regime. The theoretical results showed that the amplitude and profile of the photoacoustic signal generated by a cell monolayer depended upon the number and distribution of the cells and the location of the point of detection. These findings help to provide a better understanding of the factors involved in the generation of a photoacoustic signal produced by different cells in vitro and in vivo.

Solano, Rafael Pérez; Ramirez-Perez, Francisco I.; Castorena-Gonzalez, Jorge A.; Anell, Edgar Alvarado; Gutiérrez-Juárez, Gerardo; Polo-Parada, Luis

2012-03-01

131

Remote Temperature Estimation in Intravascular Photoacoustic Imaging  

PubMed Central

Intravascular photoacoustic (IVPA) imaging is based on the detection of laser-induced acoustic waves generated within the arterial tissue under pulsed laser irradiation. Generally, laser radiant energy levels are kept low (20 mJ/cm2) during photoacoustic imaging to conform to general standards for safe use of lasers on biological tissues. However, safety standards in intravascular photoacoustic imaging are not yet fully established. Consequently, monitoring spatio-temporal temperature changes associated with laser-tissue interaction is important to address thermal safety of IVPA imaging. In this study we utilize the IVUS based strain measurements to estimate the laser induced temperature increase. Temporal changes in temperature were estimated in a phantom modeling a vessel with an inclusion. A cross-correlation based time delay estimator was used to assess temperature induced strains produced by different laser radiant energies. The IVUS based remote measurements revealed temperature increases of 0.7±0.3°C, 2.9±0.2 °C and 5.0±0.2 °C, for the laser radiant energies of 30 mJ/cm2, 60 mJ/cm2 and 85 mJ/cm2 respectively. The technique was then used in imaging of ex vivo samples of a normal rabbit aorta. For arterial tissues, a temperature elevation of 1.1°C was observed for a laser fluence of 60 mJ/cm2 and lesser than 1°C for lower energy levels normally associated with IVPA imaging. Therefore, the developed ultrasound technique can be used to monitor temperature during IVPA imaging. Furthermore, the analysis based on the Arrhenius thermal damage model indicates no thermal injury in the arterial tissue; suggesting the safety of IVPA imaging PMID:17935861

Sethuraman, Shriram; Aglyamov, Salavat R.; Smalling, Richard W.; Emelianov, Stanislav Y.

2008-01-01

132

Reverse photoacoustic standoff spectroscopy  

SciTech Connect

A system and method are disclosed for generating a reversed photoacoustic spectrum at a greater distance. A source may emit a beam to a target and a detector measures signals generated as a result of the beam being emitted on the target. By emitting a chopped/pulsed light beam to the target, it may be possible to determine the target's optical absorbance by monitoring the intensity of light collected at the detector at different wavelengths. As the wavelength of light is changed, the target may absorb or reject each optical frequency. Rejection may increase the intensity at the sensing element and absorption may decrease the intensity. Accordingly, an identifying spectrum of the target may be made with the intensity variation of the detector as a function of illuminating wavelength.

Van Neste, Charles W. (Kingston, TN); Senesac, Lawrence R. (Knoxville, TN); Thundat, Thomas G. (Knoxville, TN)

2011-04-12

133

Photoacoustic point spectroscopy  

SciTech Connect

A system and method are disclosed for generating a photoacoustic spectrum in an open or closed environment with reduced noise. A source may emit a beam to a target substance coated on a detector that measures acoustic waves generated as a result of a light beam being absorbed by the target substance. By emitting a chopped/pulsed light beam to the target substance on the detector, it may be possible to determine the target's optical absorbance as the wavelength of light is changed. Rejection may decrease the intensity of the acoustic waves on the detector while absorption may increase the intensity. Accordingly, an identifying spectrum of the target may be made with the intensity variation of the detector as a function of illuminating wavelength.

Van Neste, Charles W. (Kingston, TN); Senesac, Lawrence R. (Knoxville, TN); Thundat, Thomas G. (Knoxville, TN)

2011-06-14

134

Piezoelectric Effect  

NSDL National Science Digital Library

In this activity, by the Concord Consortium's Molecular Literacy project, students explore the piezoelectric effect, which is the conversion between electricity and mechanical motion. The model used in this activity shows this conversion and users can manipulate the model to change the voltage and observe changes to a crystal. The activity itself is a java-based interactive resource built upon the free, open source Molecular Workbench software. In these activities, students are allowed to explore at their own pace in a digital environment full of demonstrations, illustrations, and models they can manipulate. In addition to the activity, visitors will find an overview of the activity and central and key concepts.

2008-10-23

135

Region-of-interest breast images with the Twente Photoacoustic Mammoscope (PAM)  

NASA Astrophysics Data System (ADS)

The Twente Photoacoustic Mammoscope (PAM) is based on generating laser-induced ultrasound from absorbing structures in the breast. The heart of the instrument is a flat PVDF based detector matrix comprising 590 active elements. The exciting source is an Nd:YAG laser operating at 1064 nm with 5 ns pulses. The instrument is built around a hospital bed. A study protocol was designed to explore the feasibility of using the photoacoustic technique as embodied in PAM to detect cancer in the breasts of patients with suspect/symptomatic breasts. The protocol was approved by a Medical Ethics testing committee and the instrument approved for laser and electrical safety. The protocol was executed at the Medisch Spectrum Twente by using the mammoscope to obtain photoacoustic region-of-interest (ROI) images of the suspect/symptomatic breasts. We report on one case and compare the photoacoustic images obtained with x-ray mammograms and ultrasound images.

Manohar, Srirang; Vaartjes, Sanne E.; van Hespen, Johan G. C.; Klaase, Joost M.; van den Engh, Frank M.; The, Andy K. H.; Steenbergen, Wiendelt; van Leeuwen, Ton G.

2007-02-01

136

Study of solids and surfaces by photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy has been employed to study the electronic spectra of a variety of solids. The systems studied include powders of intensely coloured dyes, amorphous chalcogenides and oxide gels besides polycrystalline samples of several oxide materials. Surface sensitivity of the technique has been examined by study of dye adsorption on oxide surfaces and determination of surface areas of active oxides. Acidic and basic sites on catalyst surfaces have also been estimated by this technique.

Rao, C. N. R.; Ganguly, P.; Jagannathan, K.

137

Investigations of intraband quantum cascade laser source for a MEMS-scale photoacoustic sensor  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is a useful monitoring technique that is well suited for trace gas detection applications. A sensitive and compact differential photoacoustic method for trace gas measurements is proposed. The technique possesses favorable detection characteristics that suggest the system dimensions may scale to a micro-system design. The objective of present work is to incorporate two strengths of the Army Research Laboratory (ARL); Interband Quantum Cascade Laser (ICL) source development and Chemical and Biological Sensing; we then applied them into a monolithic micro-electromechanical systems (MEMS) photoacoustic trace gas sensor. Previous data has shown that reducing the size of the photoacoustic cell can produce a very sensitive sensor using a CO II laser. Recent work has shown that with further reduction in the size of the photoacoustic cell in combination with an ICL as the source, produces favorable detection limits for Dimethyl Methyl Phosphonate (DMMP) a precursor to a nerve agent. These studies involve the incorporation of an ICL source operating at ~3.45 ?m. This experimentation is expected to culminate in the creation of an extremely versatile MEMS photoacoustic sensor.

Heaps, David A.; Pellegrino, Paul M.

2007-04-01

138

Single-cell photoacoustic thermometry  

PubMed Central

Abstract. A novel photoacoustic thermometric method is presented for simultaneously imaging cells and sensing their temperature. With three-seconds-per-frame imaging speed, a temperature resolution of 0.2°C was achieved in a photo-thermal cell heating experiment. Compared to other approaches, the photoacoustic thermometric method has the advantage of not requiring custom-developed temperature-sensitive biosensors. This feature should facilitate the conversion of single-cell thermometry into a routine lab tool and make it accessible to a much broader biological research community. PMID:23377004

Gao, Liang; Wang, Lidai; Li, Chiye; Liu, Yan; Ke, Haixin; Zhang, Chi; Wang, Lihong V.

2013-01-01

139

Single-cell photoacoustic thermometry.  

PubMed

A novel photoacoustic thermometric method is presented for simultaneously imaging cells and sensing their temperature. With three-seconds-per-frame imaging speed, a temperature resolution of 0.2°C was achieved in a photo-thermal cell heating experiment. Compared to other approaches, the photoacoustic thermometric method has the advantage of not requiring custom-developed temperature-sensitive biosensors. This feature should facilitate the conversion of single-cell thermometry into a routine lab tool and make it accessible to a much broader biological research community. PMID:23377004

Gao, Liang; Wang, Lidai; Li, Chiye; Liu, Yan; Ke, Haixin; Zhang, Chi; Wang, Lihong V

2013-02-01

140

Using Diffusion Bonding in Making Piezoelectric Actuators  

NASA Technical Reports Server (NTRS)

A technique for the fabrication of piezoelectric actuators that generate acceptably large forces and deflections at relatively low applied voltages involves the stacking and diffusion bonding of multiple thin piezoelectric layers coated with film electrodes. The present technique stands in contrast to an older technique in which the layers are bonded chemically, by use of urethane or epoxy agents. The older chemical-bonding technique entails several disadvantages, including the following: It is difficult to apply the bonding agents to the piezoelectric layers. It is difficult to position the layers accurately and without making mistakes. There is a problem of disposal of hazardous urethane and epoxy wastes. The urethane and epoxy agents are nonpiezoelectric materials. As such, they contribute to the thickness of a piezoelectric laminate without contributing to its performance; conversely, for a given total thickness, the performance of the laminate is below that of a unitary piezoelectric plate of the same thickness. The figure depicts some aspects of the fabrication of a laminated piezoelectric actuator by the present diffusion- bonding technique. First, stock sheets of the piezoelectric material are inspected and tested. Next, the hole pattern shown in the figure is punched into the sheets. Alternatively, if the piezoelectric material is not a polymer, then the holes are punched in thermoplastic films. Then both faces of each punched piezoelectric sheet or thermoplastic film are coated with a silver-ink electrode material by use of a silkscreen printer. The electrode and hole patterns are designed for minimal complexity and minimal waste of material. After a final electrical test, all the coated piezoelectric layers (or piezoelectric layers and coated thermoplastic films) are stacked in an alignment jig, which, in turn, is placed in a curved press for the diffusion-bonding process. In this process, the stack is pressed and heated at a specified curing temperature and pressure for a specified curing time. The pressure, temperature, and time depend on the piezoelectric material selected. At the end of the diffusion-bonding process, the resulting laminated piezoelectric actuator is tested to verify the adequacy of the mechanical output as a function of an applied DC voltage.

Sager, Frank E.

2003-01-01

141

Variational Asymptotic Micromechanics Modeling of Heterogeneous Piezoelectric  

E-print Network

Variational Asymptotic Micromechanics Modeling of Heterogeneous Piezoelectric Materials Tian Tang-4130, USA Abstract In this paper, a new micromechanics model is developed to predict the effective method for unit cell homogenization (VAMUCH), a recently developed micromechanics modeling technique

Yu, Wenbin

142

COMPAS: Compositional mineralogy with a photoacoustic spectrometer  

NASA Astrophysics Data System (ADS)

There is an important need for an in situ method of mineral and rock identification and quantification that provides true absorption spectra for a wide spectral range for lunar lander/rover missions. Many common minerals such as feldspars, magnetite, ilmenite, and amorphous fine solids or glasses, can exhibit flat spectral reflectances in the 400-2500 nm spectral region that render inaccurate or difficult their spectral detection and quantitative analysis. Ideal rock and mineral spectra are, of course, pure absorption spectra that are independent of the spectral effects of scattering, particle size, and distribution that can result in a suppression or distortion of their spectral features. This ideal seldom pertains to real samples. Since sample preparation is difficult and may fundamentally alter the observed diffuse spectral reflectance, an in situ spectral measurement method for rocks and minerals on the Moon, insensitive to the sample morphology, would be invaluable. Photoacoustic spectroscopy is a well-established technique appropriate for this task that has been widely applied in condensed-phase spectral studies of complex, highly light scattering, unprepared samples of everything from coal to whole blood, including rock and mineral characterization. A Compositional Mineralogy Photoacoustic Spectrometer, or COMPAS, can enable in situ spectral measurement of rocks and minerals, bypassing the major limitations of diffuse reflectance spectroscopy. COMPAS spectral capabilities for rock and mineral samples will be incorporated into an instrument prototype specifically for lunar measurements, compatible with rover capabilities.

Smith, W. Hayden

1992-12-01

143

COMPAS: Compositional mineralogy with a photoacoustic spectrometer  

NASA Technical Reports Server (NTRS)

There is an important need for an in situ method of mineral and rock identification and quantification that provides true absorption spectra for a wide spectral range for lunar lander/rover missions. Many common minerals such as feldspars, magnetite, ilmenite, and amorphous fine solids or glasses, can exhibit flat spectral reflectances in the 400-2500 nm spectral region that render inaccurate or difficult their spectral detection and quantitative analysis. Ideal rock and mineral spectra are, of course, pure absorption spectra that are independent of the spectral effects of scattering, particle size, and distribution that can result in a suppression or distortion of their spectral features. This ideal seldom pertains to real samples. Since sample preparation is difficult and may fundamentally alter the observed diffuse spectral reflectance, an in situ spectral measurement method for rocks and minerals on the Moon, insensitive to the sample morphology, would be invaluable. Photoacoustic spectroscopy is a well-established technique appropriate for this task that has been widely applied in condensed-phase spectral studies of complex, highly light scattering, unprepared samples of everything from coal to whole blood, including rock and mineral characterization. A Compositional Mineralogy Photoacoustic Spectrometer, or COMPAS, can enable in situ spectral measurement of rocks and minerals, bypassing the major limitations of diffuse reflectance spectroscopy. COMPAS spectral capabilities for rock and mineral samples will be incorporated into an instrument prototype specifically for lunar measurements, compatible with rover capabilities.

Smith, W. Hayden

1992-01-01

144

A transparent broadband ultrasonic detector based on an optical micro-ring resonator for photoacoustic microscopy  

PubMed Central

Photoacoustic microscopy (PAM) does not rely on contrast agent to image the optical absorption contrast in biological tissue. It is uniquely suited for measuring several tissue physiological parameters, such as hemoglobin oxygen saturation, that would otherwise remain challenging. Researchers are designing new clinical diagnostic tools and multimodal microscopic systems around PAM to fully unleash its potential. However, the sizeable and opaque piezoelectric ultrasonic detectors commonly used in PAM impose a serious constraint. Our solution is a coverslip-style optically transparent ultrasound detector based on a polymeric optical micro-ring resonator (MRR) with a total thickness of 250??m. It enables highly-sensitive ultrasound detection over a wide receiving angle with a bandwidth of 140?MHz, which corresponds to a photoacoustic saturation limit of 287?cm?1, at an estimated noise-equivalent pressure (NEP) of 6.8?Pa. We also established a theoretical framework for designing and optimizing the MRR for PAM. PMID:24675547

Li, Hao; Dong, Biqin; Zhang, Zhen; Zhang, Hao F.; Sun, Cheng

2014-01-01

145

Patterned thin metal film for the lateral resolution measurement of photoacoustic tomography  

PubMed Central

Background Image quality assessment method of photoacoustic tomography has not been completely standardized yet. Due to the combined nature of photonic signal generation and ultrasonic signal transmission in biological tissue, neither optical nor ultrasonic traditional methods can be used without modification. An optical resolution measurement technique was investigated for its feasibility for resolution measurement of photoacoustic tomography. Methods A patterned thin metal film deposited on silica glass provides high contrast in optical imaging due to high reflectivity from the metal film and high transmission from the glass. It provides high contrast when it is used for photoacoustic tomography because thin metal film can absorb pulsed laser energy. An US Air Force 1951 resolution target was used to generate patterned photoacoustic signal to measure the lateral resolution. Transducer with 2.25?MHz bandwidth and a sample submerged in water and gelatinous block were tested for lateral resolution measurement. Results Photoacoustic signal generated from a thin metal film deposited on a glass can propagate along the surface or through the surrounding medium. First, a series of experiments with tilted sample confirmed that the measured photoacoustic signal is what is propagating through the medium. Lateral resolution of the photoacoustic tomography system was successfully measured for water and gelatinous block as media: 0.33?mm and 0.35?mm in water and gelatinous material, respectively, when 2.25?MHz transducer was used. Chicken embryo was tested for biomedical applications. Conclusions A patterned thin metal film sample was tested for its feasibility of measuring lateral resolution of a photoacoustic tomography system. Lateral resolutions in water and gelatinous material were successfully measured using the proposed method. Measured resolutions agreed well with theoretical values. PMID:22794510

2012-01-01

146

Noninvasive monitoring of traumatic brain injury and post-traumatic rehabilitation with laser-induced photoacoustic imaging  

NASA Astrophysics Data System (ADS)

A photoacoustic imaging system was used for noninvasive monitoring of traumatic mouse brain in vivo with high-quality reconstructed images. Traumatic lesions accompanying with hemorrhage in the mouse cortical surface were accurately mapped, and foreign bodies of two small copper wires inserted in the mouse brain were also detected. Furthermore, the time course of morphological changes of cerebral blood during rehabilitation process of a mouse brain with traumatic brain injury was obtained using a series of photoacoustic images. Experimental results demonstrate that photoacoustic technique holds the potential for clinical applications in brain trauma and cerebrovascular disease detection.

Yang, Sihua; Xing, Da; Lao, Yeqi; Yang, Diwu; Zeng, Lvming; Xiang, Liangzhong; Chen, Wei R.

2007-06-01

147

Coregistered three-dimensional ultrasound and photoacoustic imaging system for ovarian tissue characterization  

PubMed Central

Ovarian cancer has the highest mortality of all gynecologic cancers, with a five-year survival rate of only 30% or less. Current imaging techniques are limited in sensitivity and specificity in detecting early stage ovarian cancer prior to its widespread metastasis. New imaging techniques that can provide functional and molecular contrasts are needed to reduce the high mortality of this disease. One such promising technique is photoacoustic imaging. We develop a 1280-element coregistered 3-D ultrasound and photoacoustic imaging system based on a 1.75-D acoustic array. Volumetric images over a scan range of 80 deg in azimuth and 20 deg in elevation can be achieved in minutes. The system has been used to image normal porcine ovarian tissue. This is an important step toward better understanding of ovarian cancer optical properties obtained with photoacoustic techniques. To the best of our knowledge, such data are not available in the literature. We present characterization measurements of the system and compare coregistered ultrasound and photoacoustic images of ovarian tissue to histological images. The results show excellent coregistration of ultrasound and photoacoustic images. Strong optical absorption from vasculature, especially highly vascularized corpora lutea and low absorption from follicles, is demonstrated. PMID:19895116

Aguirre, Andres; Guo, Puyun; Gamelin, John; Yan, Shikui; Sanders, Mary M.; Brewer, Molly; Zhu, Quing

2009-01-01

148

Functional photoacoustic microscopy Muhammad Rameez Chatni  

E-print Network

agents, e.g., inorganic phosphate (Pi), intracellular amide proteins, chemical exchange saturation. Photoacoustic microscopy (PAM), an emerging biomedical imaging modality for noninvasive in vivo studies, has

Wang, Lihong

149

Photoacoustic signal amplification through plasmonic nanoparticle aggregation  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging, using targeted plasmonic metallic nanoparticles, is a promising noninvasive molecular imaging method. Analysis of the photoacoustic signal generated by plasmonic metallic nanoparticles is complex because of the dependence upon physical properties of both the nanoparticle and the surrounding environment. We studied the effect of the aggregation of gold nanoparticles on the photoacoustic signal amplitude. We found that the photoacoustic signal from aggregated silica-coated gold nanoparticles is greatly enhanced in comparison to disperse silica-coated gold nanoparticles. Because cellular uptake and endocytosis of nanoparticles results in their aggregation, these results have important implications for the application of plasmonic metallic nanoparticles towards quantitative molecular imaging.

Bayer, Carolyn L.; Nam, Seung Yun; Chen, Yun-Sheng; Emelianov, Stanislav Y.

2013-01-01

150

Measurements of thermal effusivity of liquids using a conventional photoacoustic cell  

NASA Astrophysics Data System (ADS)

In this article, we present a new photoacoustic technique, based on the conventional photoacoustic configuration, to characterize the thermal effusivity of liquid samples. This new technique is applicable for all kind of liquid samples, including the nontransparent ones. In order to show the usefulness of this new technique, we measured the thermal effusivity of a variety of liquid samples including: distilled water, ethanol, methanol, chloroform, glycerol, and car oil. The comparison with literature values shows a remarkable agreement. Also, we show measurements of the thermal effusivity of acetone in distilled water mixtures, showing the graphical dependence of this thermal property with the concentration of one of the components.

Balderas-López, J. A.; Gutiérrez-Juárez, G.; Jaime-Fonseca, M. R.; Sánchez-Sinencio, Feliciano

1999-04-01

151

"Mighty Worm" Piezoelectric Actuator  

NASA Technical Reports Server (NTRS)

"Mighty Worm" piezoelectric actuator used as adjustable-length structural member, active vibrator or vibration suppressor, and acts as simple (fixed-length) structural member when inactive. Load force not applied to piezoelectric element in simple-structural-member mode. Piezoelectric element removed from load path when not in use.

Bamford, Robert M.; Wada, Ben K.; Moore, Donald M.

1994-01-01

152

Piezoelectric Crystals: Future Source  

E-print Network

With the increase in energy consumption due to evergrowing number of electronic devices, the concept of harvesting renewable energy in human surrounding arouses a renewed interest. In this context, we have highlighted use of piezoelectricity and its generation. The other alternative thought is shared at the end. Key words Mechanical pressure, piezoelectric effect, piezoelectric, material, ferroelectrics, crystals thermocouple. I.

unknown authors

153

Piezoelectric paint sensor for real-time structural health monitoring  

NASA Astrophysics Data System (ADS)

Sensors, which collect data for further information processing, are core component of any viable structural health monitoring system. Continuous on-line structural health monitoring can be achieved through the use of advanced sensors developed for real-time structural health monitoring applications. To overcome the problems associated with traditional piezoelectric ceramics, a polymer-based piezoelectric paint material has been developed and recently used for sensors. The piezoelectric paint is composed of tiny piezoelectric particles mixed within polymer matrix and therefore belongs to "0-3" piezoelectric composite. Because of the electro-mechanical coupling properties of piezoelectric paint, the dynamic responses of host structures can be monitored by measuring the output voltage signals from the piezoelectric paint sensor. Piezoelectric paint sensors hold a great potential for dynamic strain sensing applications due to the ease with which their mechanical properties can be adjusted, low fabrication cost, ease of implementation, and conformability to curved surface Additionally, a novel surface crack detection technique has been conceived and validated experimentally, in which cracks of the host structure is detected by observing the measured signals from an piezoelectric paint sensor with multi-electrode configuration. This paper presents this piezoelectric paint-based crack monitoring method as well as validation test data. The piezoelectric paint sensor is ideal for surface crack detection in locations with complex geometry, such as welded joints, which conventional sensors are ill equipped to do.

Zhang, Yunfeng

2005-05-01

154

Amplitude-masked photoacoustic wavefront shaping and application in flowmetry  

PubMed Central

Optical-resolution photoacoustic flowmetry allows non-invasive single-cell flow measurements. However, its operational depth is limited by optical diffusion, which prevents focusing beyond shallow depths in scattering media, as well as reducing the measurement signal-to-noise ratio (SNR). To overcome this limitation, we used binary-amplitude wavefront shaping to enhance light focusing in the presence of scattering. Here, the transmission modes that contributed constructively to the intensity at the optical focus were identified and selectively illuminated, resulting in a 14-fold intensity increase and a corresponding increase in SNR. This technique can potentially extend the operational depth of optical-resolution photoacoustic flowmetry beyond 1 mm in tissue. PMID:25360912

Tay, Jian Wei; Liang, Jinyang; Wang, Lihong V.

2014-01-01

155

Photoacoustic spectroscopy study of Blepharocalyx salicifolius (Kunt) O. Berg  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy (PAS) has revolutionized the fields of biological, environmental, and agricultural sciences. It is a very simple, sensitive, and non-destructive technique that allows the determination of optical properties of bio-samples. The in vivo chlorophylls of the leaf have a recorded maximum absorption peak at 675 nm as against 665 nm of the in vitro chlorophylls. The intensity of purple pigmentation in leaves of Blepharocalyx salicifolius (Kunt) O. Berg, is inversely correlated to the soil moisture levels, leaf water content and leaf water potentials. The applicability of PAS to biological samples was discussed. It allows the validation of existing emission models which are important for atmospheric process. A portable device for photoacoustic spectroscopy of plants and other photosynthetic tissues, cells and organelles is provided. Further, there is provided a method to measure photosynthesis of such tissues, cells and organelles.

Rodriguez, A. F. R.; Jacobson, T. K. B.; Moraes, J. S. F.; Faria, F. S. E. D. V.; Cunha, R. M.; Santos, J. G.; Oliveira, A. C.; Azevedo, R. B.; Morales, M. A.; Morais, P. C.

156

Photoacoustic imaging in both soft and hard biological tissue  

NASA Astrophysics Data System (ADS)

To date, most Photoacoustic (PA) imaging results have been from soft biotissues. In this study, a PA imaging system with a near-infrared pulsed laser source has been applied to obtain 2-D and 3-D images from both soft tissue and post-mortem dental samples. Imaging results showed that the PA technique has the potential to image human oral disease, such as early-stage teeth decay. For non-invasive photoacoustic imaging, the induced temperature and pressure rises within biotissues should not cause physical damage to the tissue. Several simulations based on the thermoelastic effect have been applied to predict initial temperature and pressure fields within a tooth sample. Predicted initial temperature and pressure rises are below corresponding safety limits.

Li, T.; Dewhurst, R. J.

2010-03-01

157

Determination of optical absorption coefficient with focusing photoacoustic imaging.  

PubMed

Absorption coefficient of biological tissue is an important factor for photothermal therapy and photoacoustic imaging. However, its determination remains a challenge. In this paper, we propose a method using focusing photoacoustic imaging technique to quantify the target optical absorption coefficient. It utilizes the ratio of the amplitude of the peak signal from the top boundary of the target to that from the bottom boundary based on wavelet transform. This method is self-calibrating. Factors, such as absolute optical fluence, ultrasound parameters, and Gru?neisen parameter, can be canceled by dividing the amplitudes of the two peaks. To demonstrate this method, we quantified the optical absorption coefficient of a target with various concentrations of an absorbing dye. This method is particularly useful to provide accurate absorption coefficient for predicting the outcomes of photothermal interaction for cancer treatment with absorption enhancement. PMID:22734746

Li, Zhifang; Li, Hui; Zeng, Zhiping; Xie, Wenming; Chen, Wei R

2012-06-01

158

Ultrasound and photoacoustic image-guided photothermal therapy using silica-coated gold nanorods: In-vivo study  

Microsoft Academic Search

In nanoparticle mediated photothermal therapy, confirmation of nanoparticle delivery\\/deposition in a tumor before therapy and temperature monitoring during therapy are needed to optimize therapeutic outcomes. In this paper, we demonstrate that ultrasound and photoacoustic imaging techniques can plan and guide photothermal cancer therapy, using an in-vivo mouse model of subcutaneous cancer intravenously administrated with silica-coated gold nanorods. Spectroscopic photoacoustic imaging

Seungsoo Kim; Yun-Sheng Chen; Geoffrey P. Luke; Mohammad Mehrmohammadi; Jason R. Cook; Stanislav Y. Emelianov

2010-01-01

159

An Efficient Piezoelectric Energy Harvesting Interface Circuit Using a Bias-Flip Rectifier and Shared Inductor  

E-print Network

Harvesting ambient vibration energy through piezoelectric means is a popular energy harvesting technique which can potentially supply 10-100's of [mu]W of available power. One of the main limitations of existing piezoelectric ...

Ramadass, Yogesh Kumar

160

Photoacoustic thermometry for therapeutic hyperthermia  

Microsoft Academic Search

Local hyperthermia is widely studied as a treatment option for small tumors. This study investigates the feasibility of exploiting the photoacoustic (PA) effect to monitor the in situ temperature rise during high-intensity focused ultrasound (HIFU) exposures for therapeutic hyperthermia. Polyacrylamide phantoms with a cylindrical inclusion (3 ?? 20 mm) of graphite (0.01 g\\/ml) were heated using 30 s exposures from

Parag V. Chitnis; Jonathan Mamou; J. McLaughlan; T. Murray; R. A. Roy

2009-01-01

161

Depth and resolution characterization of two-photon photoacoustic spectroscopy for noninvasive subsurface chemical diagnostics  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is a powerful optical biopsy technique that enables rapid tumor diagnosis in situ. It has also been reported that photoacoustic spectroscopy can be used to diagnose pre-malignant tissue based on the chemical differences between healthy and pre-malignant tissues. Since the acoustic signals obtained from tissues in these analyses suffer from minimum damping, photoacoustic spectroscopy can be highly sensitive. This paper focuses on the characterization of a novel multiphoton excited photoacoustic methodology for margining of malignant and pre-malignant tissues. The two-photon excitation process in tissues using nanosecond laser pulses produces ultrasonic signals that transmit through tissue with minimal attenuation. Additionally, the two-photon excitation process is highly localized since only ballistic photons contribute to the excitation process; thereby eliminating potential absorption events in tissue not of interest (i.e., along the beam path) and increasing the spatial resolution of the diagnostic technique to that achievable via optics. This work characterizes the two-photon excitation process for photoacoustic signal measurements on a model dye. Using gelatin phantoms to mimic real tissues, tissue penetration studies were performed, revealing chemical species as deep as 1.3 cm in the tissue can easily be detected using this methodology. Furthermore, the resolution of this multiphoton excitation process was determined to be as great as 50 ?m (near cellular level resolution).

Dahal, Sudhir; Kiser, John B.; Cullum, Brian M.

2011-05-01

162

Methodical study on plaque characterization using integrated vascular ultrasound, strain and spectroscopic photoacoustic imaging  

NASA Astrophysics Data System (ADS)

Carotid atherosclerosis has been identified as a potential risk factor for cerebrovascular events, but information about its direct effect on the risk of recurrent stroke is limited due to incomplete diagnosis. The combination of vascular ultrasound, strain rate and spectroscopic photoacoustics could improve the timely diagnosis of plaque status and risk of rupturing. Current ultrasound techniques can noninvasively image the anatomy of carotid arteries. The spatio-temporal variation in displacement of different regions within the arterial wall can be derived from ultrasound radio frequency data; therefore an ultrasound based strain rate imaging modality can be used to reveal changes in arterial mechanical properties. Additionally, spectroscopic photoacoustic imaging can provide information on the optical absorption properties of arterial tissue and it can be used to identify the location of specific tissue components, such as lipid pools. An imaging technique combining ultrasound, strain rate and spectroscopic photoacoustics was tested on an excised atherosclerotic rabbit aorta. The ultrasound image illustrates inhomogeneities in arterial wall thickness, the strain rate indicates the arterial segment with reduced elasticity and the spectroscopic photoacoustic image illustrates the accumulation of lipids. The results demonstrated that ultrasound, strain rate and spectroscopic photoacoustic imaging are complementary. Thus the integration of the three imaging modalities advances the characterization of atherosclerotic plaques.

Graf, Iulia M.; Su, Jimmy; Yeager, Doug; Amirian, James; Smalling, Richard; Emelianov, Stanislav

2011-03-01

163

Development and Application of Stable Phantoms for the Evaluation of Photoacoustic Imaging Instruments  

PubMed Central

Photoacoustic imaging combines the high contrast of optical imaging with the spatial resolution and penetration depth of ultrasound. This technique holds tremendous potential for imaging in small animals and importantly, is clinically translatable. At present, there is no accepted standard physical phantom that can be used to provide routine quality control and performance evaluation of photoacoustic imaging instruments. With the growing popularity of the technique and the advent of several commercial small animal imaging systems, it is important to develop a strategy for assessment of such instruments. Here, we developed a protocol for fabrication of physical phantoms for photoacoustic imaging from polyvinyl chloride plastisol (PVCP). Using this material, we designed and constructed a range of phantoms by tuning the optical properties of the background matrix and embedding spherical absorbing targets of the same material at different depths. We created specific designs to enable: routine quality control; the testing of robustness of photoacoustic signals as a function of background; and the evaluation of the maximum imaging depth available. Furthermore, we demonstrated that we could, for the first time, evaluate two small animal photoacoustic imaging systems with distinctly different light delivery, ultrasound imaging geometries and center frequencies, using stable physical phantoms and directly compare the results from both systems. PMID:24086557

Bohndiek, Sarah E.; Bodapati, Sandhya; Van De Sompel, Dominique; Kothapalli, Sri-Rajasekhar; Gambhir, Sanjiv S.

2013-01-01

164

Examination of quantum cascade laser source for a MEMS-scale photoacoustic chemical sensor  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is a useful monitoring technique that is well suited for trace gas detection. The technique also possesses favorable detection characteristics when the system dimensions are scaled to a micro-system design. The objective of present work is to incorporate two strengths of the Army Research Laboratory (ARL), Quantum Cascade Laser (QCL) source development and chemical and biological sensing into a monolithic micro-electromechanical systems (MEMS) photoacoutic trace gas sensor. Past examination of a one quarter scale photoacoustic (PA) macro-cell has indicated a pathway to incorporate a photoacoustic resonance structure in a micro-mechanical platform. Initial studies involve the incorporation of a QCL source operating @ ~3.45 ?m into the PA macro-cell system as a means to discern proper operational characteristics in relation to the photoacoustic cell design. Results will be presented describing beam conditioning, modulation control and wavelength selection associated with the QCL source. Some preliminary information regarding MEMS-scale designs based off of hybrid concept, involving commercially available microphone and fully fabricated MEMS photoacoustic resonator will be described.

Heaps, David A.; Pellegrino, Paul M.

2006-05-01

165

Coherent photoacoustic-ultrasound correlation and imaging.  

PubMed

Both photoacoustics and ultrasound have been researched extensively but separately. In this letter, we report an initial study on the coherent correlation between pulsed photoacoustic wave and pulse-echo ultrasound wave. By illuminating an object with a pulsed laser and external ultrasound sequentially, both the endogenous photoacoustic wave and pulse-echo ultrasound wave are received and coherently correlated, demonstrating enhanced signal-to-noise ratio. Image contrast of the proposed coherent photoacoustic-ultrasound imaging is also demonstrated to be improved significantly on vessel-mimicking phantom, due to fusion of the optical absorption and ultrasound reflection contrasts by coherent correlation of either conventional laser-induced photoacoustic imaging or pulse-echo ultrasound imaging separately. PMID:24801584

Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin

2014-09-01

166

Photoacoustic Spectroscopy Analysis of Traditional Chinese Medicine  

NASA Astrophysics Data System (ADS)

Chinese medicine is a historic cultural legacy of China. It has made a significant contribution to medicine and healthcare for generations. The development of Chinese herbal medicine analysis is emphasized by the Chinese pharmaceutical industry. This study has carried out the experimental analysis of ten kinds of Chinese herbal powder including Fritillaria powder, etc., based on the photoacoustic spectroscopy (PAS) method. First, a photoacoustic spectroscopy system was designed and constructed, especially a highly sensitive solid photoacoustic cell was established. Second, the experimental setup was verified through the characteristic emission spectrum of the light source, obtained by using carbon as a sample in the photoacoustic cell. Finally, as the photoacoustic spectroscopy analysis of Fritillaria, etc., was completed, the specificity of the Chinese herb medicine analysis was verified. This study shows that the PAS can provide a valid, highly sensitive analytical method for the specificity of Chinese herb medicine without preparing and damaging samples.

Chen, Lu; Zhao, Bin-xing; Xiao, Hong-tao; Tong, Rong-sheng; Gao, Chun-ming

2013-09-01

167

Photoacoustic tomography of ex vivo mouse hearts with myocardial infarction  

NASA Astrophysics Data System (ADS)

In the present study, we evaluated the applicability of ex vivo photoacoustic imaging (PAI) on small animal organs. We used photoacoustic tomography (PAT) to visualize infarcted areas within murine hearts and compared these data to other imaging techniques [magnetic resonance imaging (MRI), micro-computed tomography] and histological slices. In order to induce ischemia, an in vivo ligation of the left anterior descending artery was performed on nine wild-type mice. After varying survival periods, the hearts were excised and fixed in formaldehyde. Samples were illuminated with nanosecond laser pulses delivered by a Nd:YAG pumped optical parametric oscillator. Ultrasound detection was achieved using a Mach-Zehnder interferometer (MZI) working as an integrating line detector. The voxel data were computed using a Fourier-domain based reconstruction algorithm, followed by inverse Radon transforms. The results clearly showed the capability of PAI to visualize myocardial infarction and to produce three-dimensional images with a spatial resolution of approximately 120 ?m. Regions of affected muscle tissue in PAI corresponded well with the results of MRI and histology. Photoacoustic tomography utilizing a MZI for ultrasound detection allows for imaging of small tissue samples. Due to its high spatial resolution, good soft tissue contrast and comparatively low cost, PAT offers great potentials for imaging.

Holotta, Markus; Grossauer, Harald; Kremser, Christian; Torbica, Pavle; Völkl, Jakob; Degenhart, Gerald; Esterhammer, Regina; Nuster, Robert; Paltauf, Günther; Jaschke, Werner

2011-03-01

168

Wood pulp characterization by a novel photoacoustic sensor  

NASA Astrophysics Data System (ADS)

In this paper we introduce a novel photoacoustic sensing technique that captures a photoacoustic signal excited by a laser light pulse after the light has propagated through a turbid medium. Simultaneously, the ultrasonic sound wave is captured after it has propagated through the same turbid medium. By combining the two signals, more information on the investigated medium can be obtained. Applications can be found in the pulp and paper industry where monitoring wood pulp compositions is of interest. Depending on its origin, pulp suspension contains different compositions of fibres and fibre fragments (fines). Poor control of the pulp composition leads to an unstable process that compromises the production, quality and energy efficiency in the pulp mill. The result shows the feasibility of the photoacoustic sensor in monitoring the mass fractions of fibres and fines in a pulp suspension. The first received echo, corresponding to the light interaction with the sample, showed a stronger correlation to the fines mass fraction compared to fibre mass fraction. The second echo, corresponding to the sound wave interaction with the sample, showed a much stronger correlation to fibre mass fraction than to fines mass fraction. Hence, it is proposed that by combining these two echoes, more information about the pulp suspension could be extracted than from any other sensor built on a single sensing principle.

Niemi, Jan; Löfqvist, Torbjörn

2012-08-01

169

3D high resolution pure optical photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

The concept of pure optical photoacoustic microscopy(POPAM) was proposed based on optical rastering of a focused excitation beam and optically sensing the photoacoustic signal using a microring resonator fabricated by a nanoimprinting technique. After some refinedment of in the resonator structure and mold fabrication, an ultrahigh Q factor of 3.0×105 was achieved which provided high sensitivity with a noise equivalent detectable pressure(NEDP) value of 29Pa. This NEDP is much lower than the hundreds of Pascals achieved with existing optical resonant structures such as etalons, fiber gratings and dielectric multilayer interference filters available for acoustic measurement. The featured high sensitivity allowed the microring resonator to detect the weak photoacoustic signals from micro- or submicroscale objects. The inherent superbroad bandwidth of the optical microring resonator combined with an optically focused scanning beam provided POPAM of high resolution in the axial as well as both lateral directions while the axial resolution of conventional photoacoustic microscopy (PAM) suffers from the limited bandwidth of PZT detectors. Furthermore, the broadband microring resonator showed similar sensitivity to that of our most sensitive PZT detector. The current POPAM system provides a lateral resolution of 5?m and an axial resolution of 8?m, comparable to that achieved by optical microscopy while presenting the unique contrast of optical absorption and functional information complementing other optical modalities. The 3D structure of microvasculature, including capillary networks, and even individual red blood cells have been discerned successfully in the proof-of-concept experiments on mouse bladders ex vivo and mouse ears in vivo. The potential of approximately GHz bandwidth of the microring resonator also might allow much higher resolution than shown here in microscopy of optical absorption and acoustic propagation properties at depths in unfrozen tissue specimens or thicker tissue sections not now imageable with current optical or acoustic microscopes of comparable resolution.

Xie, Zhixing; Chen, Sung-Liang; Ling, Tao; Guo, L. Jay; Carson, Paul L.; Wang, Xueding

2012-02-01

170

Retrospective respiration-gated whole-body photoacoustic computed tomography of mice  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography (PAT) is an emerging technique that has a great potential for preclinical whole-body imaging. To date, most whole-body PAT systems require multiple laser shots to generate one cross-sectional image, yielding a frame rate of <1 Hz. Because a mouse breathes at up to 3 Hz, without proper gating mechanisms, acquired images are susceptible to motion artifacts. Here, we introduce, for the first time to our knowledge, retrospective respiratory gating for whole-body photoacoustic computed tomography. This new method involves simultaneous capturing of the animal's respiratory waveform during photoacoustic data acquisition. The recorded photoacoustic signals are sorted and clustered according to the respiratory phase, and an image of the animal at each respiratory phase is reconstructed subsequently from the corresponding cluster. The new method was tested in a ring-shaped confocal photoacoustic computed tomography system with a hardware-limited frame rate of 0.625 Hz. After respiratory gating, we observed sharper vascular and anatomical images at different positions of the animal body. The entire breathing cycle can also be visualized at 20 frames/cycle.

Xia, Jun; Chen, Wanyi; Maslov, Konstantin; Anastasio, Mark A.; Wang, Lihong V.

2014-01-01

171

Development of a MEMS-scale photoacoustic chemical sensor for trace vapor detection  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy (PAS) is a useful monitoring technique that is well suited for trace gas detection. This method routinely exhibits detection limits at the parts-per-million (ppm) or parts-per-billion (ppb) level for gaseous samples. PAS also possesses favorable detection characteristics when the system dimensions are scaled to a microsystem design. Micro-electromechanical systems (MEMS)-scale designs offer the possibility to develop photoacoustic sensors in which the signals would remain at sensitivities similar to or greater than those typically found in macro-scale devices. The objective of the present work is to develop a monolithic MEMS-scale photoacoustic trace gas sensor utilizing the Army Research Laboratory's chemical and biological sensing capability. In order to realize the advantage of photoacoustic sensor miniaturization, light sources of comparable size are required. Quantum cascade lasers (QCLs) have been tested in combination with MEMS-scale photoacoustic cells. This sensing platform has provided favorable detection limits for a standard nerve agent simulant. Current research employs this sensor scheme for the detection of 2,4-dinitrotoluene, a degradation product of TNT. Preliminary results describing the sensor capabilities and performance for the detection of this compound will be presented.

Holthoff, Ellen L.; Pellegrino, Paul M.

2009-05-01

172

In vitro determination of glucose concentration based on photoacoustic spectroscopy and chemometrics  

NASA Astrophysics Data System (ADS)

Noninvasive blood glucose level (BGL) monitoring has recently become a research hotspot in the world. Photoacoustic spectroscopy is a well-established, hybrid and promising noninvasive technique, which has already drawn many researchers' attentions in recent years due to the advantage of overcoming the scattering light interference. As the preliminary exploration of photoacoustic BGL monitoring, a photoacoustic BGL monitoring set-up based on nanosecond pulsed laser with repetition rate of 20Hz and ultrasound transducer with central frequency of 9.55MHz was established in this paper. To explore the mechanism of the time resolved BGL photoacoustic signal, a series of in vitro experiments of glucose aqueous solutions were tested, the time resolved photoacoustic signals for different concentrations of glucose solutions under different output wavelengths were captured with the data average of 512 times. The peak-to-peak values of each solution were gotten at the wavelength interval of 10nm. Difference with the peak-to-peak value of pure water via subtractive spectroscopy, the characteristic wavelengths of glucose were gotten, and the optimum characteristic wavelengths were determined via data pre-processing and principle component analysis(PCA) algorithm, the calibration equation between concentration and the peak-to-peak value was gotten via multiple linear regression(MLR), and the calibration root mean square error(CRMSE) and the prediction root mean square error(PRMSE) of glucose level is all less than 10mg/dl under the correction equation.

Ren, Zhong; Liu, Guodong; Huang, Zhen

2014-09-01

173

Calibration-free quantification of absolute oxygen saturation based on the dynamics of photoacoustic signals.  

PubMed

Photoacoustic tomography (PAT) is a hybrid imaging technique that has broad preclinical and clinical applications. Based on the photoacoustic effect, PAT directly measures specific optical absorption, which is the product of the tissue-intrinsic optical absorption coefficient and the local optical fluence. Therefore, quantitative PAT, such as absolute oxygen saturation (sO?) quantification, requires knowledge of the local optical fluence, which can only be estimated through invasive measurements or sophisticated modeling of light transportation. In this Letter, we circumvent this requirement by taking advantage of the dynamics in sO?. The new method works when the sO? transition can be simultaneously monitored with multiple wavelengths. For each wavelength, the ratio of photoacoustic amplitudes measured at different sO? states is utilized. Using the ratio cancels the contribution from optical fluence and allows calibration-free quantification of absolute sO?. The new method was validated through both phantom and in vivo experiments. PMID:23903146

Xia, Jun; Danielli, Amos; Liu, Yan; Wang, Lidai; Maslov, Konstantin; Wang, Lihong V

2013-08-01

174

Intravascular photoacoustic imaging of exogenously labeled atherosclerotic plaque through luminal blood  

PubMed Central

Abstract. Combined intravascular ultrasound and intravascular photoacoustic (IVUS/IVPA) imaging has been previously established as a viable means for assessing atherosclerotic plaque morphological and compositional characteristics using both endogenous and exogenous contrast. In this study, IVUS/IVPA imaging of atherosclerotic rabbit aortas following systemic injection of gold nanorods (AUNRs) with peak absorbance within the tissue optical window is performed. Ex vivo imaging results reveal a high photoacoustic signal from localized AUNRs in regions with atherosclerotic plaques. Corresponding histological staining further confirms the preferential extravasation of AUNRs in atherosclerotic regions with compromised luminal endothelium and acute inflammation. The ability to detect AUNRs using combined IVUS and photoacoustic imaging in the presence of luminal saline and luminal blood is evaluated using both spectroscopic and single wavelength IVPA imaging techniques. Results demonstrate that AUNR detection within the arterial wall can be achieved using both methods, even in the case of imaging through luminal blood. PMID:23224013

Yeager, Doug; Karpiouk, Andrei; Wang, Bo; Amirian, James; Sokolov, Konstantin; Smalling, Richard; Emelianov, Stanislav

2012-01-01

175

Estimating optical absorption, scattering, and Grueneisen distributions with multiple-illumination photoacoustic tomography.  

PubMed

While photoacoustic methods offer significant promise for high-resolution optical contrast imaging, quantification has thus far proved challenging. In this paper, a noniterative reconstruction technique for producing quantitative photoacoustic images of both absorption and scattering perturbations is introduced for the case when the optical properties of the turbid background are known and multiple optical illumination locations are used. Through theoretical developments and computational examples, it is demonstrated that multiple-illumination photoacoustic tomography (MI-PAT) can alleviate ill-posedness due to absorption-scattering nonuniqueness and produce quantitative high-resolution reconstructions of optical absorption, scattering, and Gruneisen parameter distributions. While numerical challenges still exist, we show that the linearized MI-PAT framework that we propose has orders of magnitude improved condition number compared with CW diffuse optical tomography. PMID:21743514

Shao, Peng; Cox, Ben; Zemp, Roger J

2011-07-01

176

Photoacoustic image reconstruction from few-detector and limited-angle data  

PubMed Central

Photoacoustic tomography (PAT) is an emerging non-invasive imaging technique with great potential for a wide range of biomedical imaging applications. However, the conventional PAT reconstruction algorithms often provide distorted images with strong artifacts in cases when the signals are collected from few measurements or over an aperture that does not enclose the object. In this work, we present a total-variation-minimization (TVM) enhanced iterative reconstruction algorithm that can provide excellent photoacoustic image reconstruction from few-detector and limited-angle data. The enhancement is confirmed and evaluated using several phantom experiments. PMID:21991554

Yao, Lei; Jiang, Huabei

2011-01-01

177

Structural, optical and photoacoustic study of milled and melted Bi2Se3  

NASA Astrophysics Data System (ADS)

Powder Bi2Se3 was produced through Mechanical Alloying (MA) and Melting Technique (MT) routes. Structural, optical and photoacoustic properties were evaluated by X-ray diffraction (XRD), Raman Spectroscopy (RS) and Photoacoustic Absorption Spectroscopy (PAS). Minority Bi2O2Se phase was nucleated in both samples. PAS measurements showed a thermal diffusivity reduction of 40% for Bi2Se3 produced through MA when compared with Bi2Se3 produced by MT. In addition, thermal diffusivity of Bi2Se3 obtained by MA and MT was a new report in literature.

Poffo, C. M.; de Lima, J. C.; Souza, S. M.; Trichês, D. M.; Nogueira, T. P. O.; Borges, Z. V.; Manzato, L.

2014-11-01

178

Nonlinear photoacoustic signal increase from endocytosis of gold nanoparticles.  

PubMed

Nonlinear photoacoustic effects, rarely seen in biomedical photoacoustic imaging of tissues, can manifest themselves strongly when plasmonic nanoparticles are used as imaging contrast agents. Specifically, nonlinear behavior of photoacoustic signal with modest laser fluences can occur when nanoparticles undergo cellular endocytosis and aggregation leading to thermal coupling and subsequent localized temperature enhancement. Our study demonstrated this effect using in vitro tissue models containing cells. While the photoacoustic signal amplitude was linearly proportional to the cell/nanoparticle concentration, the photoacoustic signal increased nonlinearly as the laser fluence increased. Our results, therefore, suggest that the nonlinear effects can be exploited in molecular/cellular photoacoustic imaging. PMID:23164887

Nam, Seung Yun; Ricles, Laura M; Suggs, Laura J; Emelianov, Stanislav Y

2012-11-15

179

An analytical and experimental study to investigate flutter suppression via piezoelectric actuation  

Microsoft Academic Search

The objective was to analytically and experimentally study the capabilities of adaptive material plate actuators for suppressing flutter. The validity of analytical modeling techniques for piezoelectric materials was also investigated. Piezoelectrics are materials which are characterized by their ability to produce voltage when subjected to a mechanical strain. The converse piezoelectric effect can be utilized to actuate a structure by

Jennifer Heeg

1991-01-01

180

Robust Passive Piezoelectric Shunt Dampener S. Behrens, A. J. Fleming and S. O. R. Moheimani  

E-print Network

Robust Passive Piezoelectric Shunt Dampener S. Behrens, A. J. Fleming and S. O. R. Moheimani School introduces a new multiple mode passive piezoelectric shunt damping technique. The robust pas- sive piezoelectric shunt controller is capable of damping multiple structural modes and maybe less susceptible

Fleming, Andrew J.

181

Photoacoustic resonance spectroscopy for biological tissue characterization  

NASA Astrophysics Data System (ADS)

By "listening to photons," photoacoustics allows the probing of chromosomes in depth beyond the optical diffusion limit. Here we report the photoacoustic resonance effect induced by multiburst modulated laser illumination, which is theoretically modeled as a damped mass-string oscillator and a resistor-inductor-capacitor (RLC) circuit. Through sweeping the frequency of multiburst modulated laser, the photoacoustic resonance effect is observed experimentally on phantoms and porcine tissues. Experimental results demonstrate different spectra for each phantom and tissue sample to show significant potential for spectroscopic analysis, fusing optical absorption and mechanical vibration properties. Unique RLC circuit parameters are extracted to quantitatively characterize phantom and biological tissues.

Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin; Ohl, Claus-Dieter

2014-06-01

182

Photoacoustic effect in a periodically modulated structure  

NASA Astrophysics Data System (ADS)

We discuss the photoacoustic effect in one-dimensional phononic structures with sinusoidal modulation of its acoustic properties. The periodic structure is considered to have a modulation in its density or compressibility of the form 1-2?(2?xa), where ? is the modulation factor and a is the periodic length of the phononic structures. The properties of the photoacoustic waves are determined by an inhomogeneous Mathieu equation. We give several different methods including Green's function solutions, series expansions, and variation of parameters solutions for determining closed from solutions to the inhomogeneous Mathieu equation to obtain the properties of the photoacoustic effect.

Wu, Binbin; Diebold, Gerald

2011-04-01

183

Photoacoustic location of optical absorbers in phantom tissue  

NASA Astrophysics Data System (ADS)

Pulsed photoacoustic (PA) signals may be used for the detection and imaging of blood vessels in tissue. A relatively strong absorption by red blood cells and low absorption by the surrounding tissue, combined with a reasonable penetration depth of the light is found at a wavelength of ca. 577 nm. Experiments were performed with a pulsed frequency doubled Nd:YAG laser which delivered 10 ns pulses at 532 nm wavelength. Ten percent dilutions of India ink and 50% suspensions of red blood cells in PBS were used as optical absorbers. Blood vessels were simulated by hollow nylon fibers with an inner diameter of ca. 250 micrometer through which these suspensions flow. The optical scattering of the surrounding tissue was simulated by a 12% dilution of Intralipid-10% to get a solution with a reduced scattering coefficient of 1.8 mm-1. The PA signals were detected with a hydrophone that contained four wide band piezoelectric transducers made of 9 micrometer thick PVdF film with an effective diameter of 200 micrometers. Laser pulses with energies up to 8 microjoules were delivered to the sample by a 50 or 100 micrometer core diameter glass fiber. Pulsed optical heating of red blood cells up to 30 - 35 degrees for more than 12,000 times did not affect the photoacoustic response of the cells. If a single fiber is used to illuminate the sample, then even at a depth of 1 mm the PA signals show that the volume that is effectively illuminated is laterally restricted to a diameter of ca. 1 mm. Vessels with blood or ink dilutions were detected up to a depth of more than 1 mm in the scattering medium. Monte- Carlo (MC) simulations were used to simulate the spatial distribution of light absorption in phantom tissue. From this distribution the PA response of blood vessels was simulated. A delay-and-sum beam forming algorithm was developed for 3-D near field configurations and applied to a PA image reconstruction program. The images based on MC simulations as well as experimental data show that the side of larger vessels that is facing the illuminating fiber can be located with a resolution that depends on the configuration and varies between 0.1 and 1 time the inner vessel diameter. This shows the principle and the feasibility of three dimensional photoacoustic dermal tissue imaging.

Hoelen, Christoph G.; Hamhuis, G.; Pagoulatos, Niko; van den Ham, Iris; de Mul, Frits F. M.; Greve, Jan

1996-12-01

184

Plates made of piezoelectric materials: when are they really piezoelectric?  

E-print Network

Plates made of piezoelectric materials: when are they really piezoelectric? Giuseppe Geymonat with the simplified but accurate modeling of linearly piezoelectric thin plates. It is shown how mathematical tools the fact that for some piezoelectric crystal classes, the coupling between the electrical

Boyer, Edmond

185

Piezoelectric angular acceleration sensor  

Microsoft Academic Search

This paper deals with a piezoelectric angular acceleration sensor, which might be proposed by us, first, as a new concept of the sensor to detect a rotational motion only. In the first part of this paper are dealt with some concrete constructions of this new concept of angular acceleration sensor, composed of piezoelectric transducers. The second part contains their basic

Y. Tomikawa; S. Okada

2003-01-01

186

Piezoelectric transducer materials  

Microsoft Academic Search

Properties of piezoelectric crystals and ceramics are reviewed as they affect use of such materials in electroacoustic transducers. Extensive data on lead titanate-zirconate ceramics are presented to help in selection of the appropriate material for a variety of applications in the lower and medium frequency range, up to several megacycles per second. Quartz and several recently discovered piezoelectric crystals will

H. Jaffe; D. A. Berlincourt

1965-01-01

187

Piezoelectric micromotors for microrobots  

Microsoft Academic Search

The authors have begun research into piezoelectric ultrasonic motors using ferroelectric thin films. The authors have fabricated the stator components of these millimeter diameter motors on silicon wafers. Ultrasonic motors consist of two pieces: a stator and a rotor. The stator includes a piezoelectric film in which bending is induced in the form of a traveling wave. A small glass

Anita M. Flynn; Lee S. Tavrow; Stephen F. Bart; Rodney A. Brooks; Daniel J. Ehrlich; K. R. Udayakumar; L. Eric Cross

1992-01-01

188

Microfabrication of Piezoelectric MEMS  

Microsoft Academic Search

In this chapter an overview of processes for fabrication of MEMS using piezoelectric thin films as active layer in planar structures is presented. These structures are used in cantilever-like and membrane configurations for sensing and actuation. Key issues consist in findings of a compatible dry etching sequence for piezoelectric layer, electrodes and silicon. The method of compensation of the gradient

J. Baborowski

189

Quartz enhanced photoacoustic spectroscopy (QEPAS) with antimonide compounds in very compact systems  

NASA Astrophysics Data System (ADS)

We present in this paper measurements made by quartz enhanced photoacoustic spectroscopy (QEPAS) technique with antimonide laser diodes emitting at 2.3 ?m and 3.3 ?m. These measurements dedicated to environmental purposes allow us sensitive detection of ethylene and methane. Two experimental setups are reported: a laboratory and brand new compact benches. The detection limits are mentioned.

Nguyen Ba, T.; Triki, M.; Gaimard, Quentin; Rouillard, Y.; Vicet, A.

2014-05-01

190

Photoacoustic excitation profiles of gold nanoparticles?  

PubMed Central

The wavelength dependence of the laser-induced photoacoustic signal amplitude has been measured for water dispersions of 10, 61, and 93 nm diameter gold nanospheres. The whole region of the localized surface plasmon resonance has been covered. This “photoacoustic excitation profile” can be overlayed with the extinction spectrum between 450 nm and 600 nm in the case of the smallest nanoparticles. At variance, the larger-sized nanoparticles display a progressive deviation from the extinction spectrum at longer wavelength, where the photoacoustic signal becomes relatively smaller. Considering that photoacoustics is intrinsically insensitive to light scattering, at least for optically thin samples, the results are in agreement with previous theoretical work predicting (i) an increasing contribution of scattering to extinction when the nanoparticle size increases and (ii) a larger scattering component at longer wavelengths. Therefore, the method has a general validity and can be applied to selectively determine light absorption by plasmonic systems. PMID:25302155

Feis, Alessandro; Gellini, Cristina; Salvi, Pier Remigio; Becucci, Maurizio

2014-01-01

191

Photoacoustic Imaging for Cancer Detection and Staging  

PubMed Central

Cancer is one of the leading causes of death in the world. Diagnosing a cancer at its early stages of development can decrease the mortality rate significantly and reduce healthcare costs. Over the past two decades, photoacoustic imaging has seen steady growth and has demonstrated notable capabilities to detect cancerous cells and stage cancer. Furthermore, photoacoustic imaging combined with ultrasound imaging and augmented with molecular targeted contrast agents is capable of imaging cancer at the cellular and molecular level, thus opening diverse opportunities to improve diagnosis of tumors, detect circulating tumor cells and identify metastatic lymph nodes. In this paper we introduce the principles of photoacoustic imaging, and review recent developments in photoacoustic imagingas an emerging imaging modality for cancer diagnosis and staging. PMID:24032095

Mehrmohammadi, Mohammad; Yoon, Soon Joon; Yeager, Douglas; Emelianov, Stanislav Y.

2013-01-01

192

Photoacoustic photonic crystal fiber gas sensor  

E-print Network

Photoacoustic spectroscopy (PAS) is a form of laser spectroscopy that has demonstrated very high sensitivity for gas detection. Typically, PAS involves the absorption of a modulated laser beam by the gas species of interest, ...

Chen, Raymond, M. Eng. Massachusetts Institute of Technology

2007-01-01

193

Noise-equivalent sensitivity of photoacoustics  

PubMed Central

Abstract. The fundamental limitations of photoacoustic microscopy for detecting optically absorbing molecules are investigated both theoretically and experimentally. We experimentally demonstrate noise-equivalent detection sensitivities of 160,000 methylene blue molecules (270 zeptomol or 2.7×10?19??mol) and 86,000 oxygenated hemoglobin molecules (140 zeptomol) using narrowband continuous-wave photoacoustics. The ultimate sensitivity of photoacoustics is fundamentally limited by thermal noise, which can present in the acoustic detection system as well as in the medium itself. Under the optimized conditions described herein and using commercially available detectors, photoacoustic microscopy can detect as few as 100s of oxygenated hemoglobin molecules. Realizable improvements to the detector may enable single molecule detection of select molecules. PMID:24026425

Winkler, Amy M.; Maslov, Konstantin; Wang, Lihong V.

2013-01-01

194

Photoacoustic spectroscopic studies of polycyclic aromatic hydrocarbons  

NASA Astrophysics Data System (ADS)

Because of their involvement in environmental pollutants, in carcinogenic activity, plastics, pharmaceuticals, synthesis of some laser dyes and presence in interstellar space etc., Polycyclic aromatic hydrocarbons (PAHs) are important. As their structure and properties can be varied systematically, they form a beautiful class of molecules for experimental and quantum chemical investigations. These molecules are being studied for last several years by using conventional spectroscopy. In recent years, Photoacoustic (PA) spectroscopy has emerged as a new non-destructive technique with unique capability and sensitivity. The PA effect is the process of generation of acoustic waves in a sample resulting from the absorption of photons. This technique not only reveals non- radiative transitions but also provides information about forbidden singlet-triplet transitions which are not observed normally by the conventional spectroscopy. The present paper deals with the spectroscopic studies of some PAH molecules by PA spectroscopy in the region 250 - 400 nm. The CNDO/S-CI method is used to calculate the electronic transitions with the optimized geometries. A good agreement is found between the experimental and calculated results.

Zaidi, Zahid H.; Kumar, Pardeep; Garg, R. K.

1999-02-01

195

Functional photoacoustic tomography of animal brains  

E-print Network

the most rewarding experience in my life. I would like to thank Dr. Lihong Wang for supporting me through his research funding and for providing me this great opportunity to study in his lab. His broad knowledge and acute insight guided me all through...-animal Brains in situ............................................................ 13 3.1 Photoacoustic imaging of mouse brains in situ................................... 13 3.2 Photoacoustic imaging of rat brains in situ...

Wang, Xueding

2005-11-01

196

Reflection-mode multiple-illumination photoacoustic sensing to estimate optical properties?  

PubMed Central

Objectives We analyze a reflection-mode multiple-illumination photoacoustic method which allows us to estimate optical scattering properties of turbid media based on fitting light-transport models and explore its limits in optical property estimation and depth-dependent fluence compensation. Background Recent simulation results show significant promise for a technique called multiple-illumination photoacoustic tomography (MI-PAT) to quantitatively reconstruct both absorption and scattering heterogeneities in turbid medium. Prior to experiments, it is essential to develop and analyze a measurement technique and probe capabilities of quantitative measurements that focus on sensing rather than imaging. Methods This technique involved translation of a 532 nm pulsed-laser light spot while focusing an ultrasound receiver on a sub-surface optical absorber immersed in a scattering medium at 3, 4 and 5 mm below the surface. Measured photoacoustic amplitudes for media with different reduced scattering coefficients are fitted with a light propagation model to estimate optical properties. Results When the absorber was located at 5 mm below the membrane in media with a reduced scattering coefficient of 4.4 and 5.5 cm?1, the true values were predicted with an error of 5.7% and 12.7%, respectively. We observe accuracy and the ability of estimating optical scattering properties decreased with the increased reduced scattering coefficient. Nevertheless, the estimated parameters were sufficient for demonstrating depth-dependent fluence compensation for improved quantitation in photoacoustic imaging. PMID:25302153

Ranasinghesagara, Janaka C.; Jiang, Yan; Zemp, Roger J.

2013-01-01

197

Noninvasive functional photoacoustic tomography of blood-oxygen saturation in the brain  

NASA Astrophysics Data System (ADS)

Since optical contrast is sensitive to functional parameters, including the hemoglobin oxygen saturation and the total concentration of hemoglobin, imaging based on optical contrast has been widely employed for the real-time monitoring of tissue oxygen consumption and hemodynamics in biological tissues. However, due to the overwhelming scattering of light in tissues, traditional optical imaging modalities cannot provide satisfactory spatial resolution. Functional photoacoustic tomography is a novel technique that combines high optical contrast and high ultrasonic resolution. Here, we present our study of a laser-based photoacoustic technique that, for the first time to our knowledge, monitors blood oxygenation in the rat brain in vivo. The cerebral blood oxygenation in the rat brain was imaged by photoacoustic detection at two wavelengths. The change in the hemoglobin oxygen saturation in the brain vessels as a result of the alternation from hyperoxia status to hypoxia status was visualized successfully with satisfactory spatial resolution. This work demonstrates that photoacoustic technique, based on the spectroscopic absorption of oxy- and deoxy-hemoglobin, can provide accurate functional imaging of cerebral blood oxygenation in the small-animal brain non-invasively with the skin and skull intact.

Wang, Xueding; Ku, Geng; Xie, Xueyi; Wang, Yiwen; Stoica, George; Wang, Lihong V.

2004-07-01

198

Toward in-vivo photoacoustic imaging of human ovarian tissue for cancer detection  

NASA Astrophysics Data System (ADS)

Currently, most of the cancers in the ovary are detected when they have already metastasized to other parts of the body. As a result, ovarian cancer has the highest mortality of all gynecological cancers with a 5-year survival rate of 30% or less [1]. The reason is the lack of reliable symptoms as well as the lack of efficacious screening techniques [2,3]. Thus, there is an urgent need to improve the current diagnostic techniques. We have investigated the potential role of co-registered photoacoustic and ultrasound imaging in ovarian cancer detection. In an effort to bring this technique closer to clinical application, we have developed a co-registered ultrasound and photoacoustic transvaginal probe. A fiber coupling assembly has been developed to deliver the light from around the transducer for reflection geometry imaging. Co-registered ultrasound and photoacoustic images of swine ovaries through vagina wall muscle and human ovaries using the aforementioned probe, demonstrate the potential of photoacoustic imaging to non-invasively detect ovarian cancer in vivo.

Aguirre, Andres; Kumavor, Patrick; Ardeshirpour, Yasaman; Sanders, Mary M.; Brewer, Molly; Zhu, Quing

2011-03-01

199

Development of real-time photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography detecting ultrasound signals generated from photon absorption provides optical absorption contrast in vivo for structural, functional and molecular imaging. Although photoacoustic tomography technology has grown fast in recent years, real-time photoacoustic imaging with cellular spatial resolution are still strongly demanded. We developed a photoacoustic microscopy which has video-rate imaging capability with cellular spatial resolution. The system consists of a single-element focused ultrasound transducer, a fiber-based light-delivery subsystem, a voice-coil translation stage, a motion controller, and a data acquisition subsystem. A compact cube is employed to split optical and acoustic beams. The mass of the entire scanning photoacoustic probe is less than 40 grams, which minimizes potential vibrations and inertial effects, therefore, makes it capable to scan fast. The imaging system is capable of acquiring 20 cross-sectional (B-scan) images per second over 9 mm, and up to 40 B-scan images per second over 1 mm. Focused laser beams provide a lateral resolution of five microns. Confocal deployment of optical and acoustic focuses provides higher SNR than optical scanning approach. Micron-sized carbon particles flowing in silicone tubing and in vivo blood flows were imaged in video-rate, which demonstrated the capability to image highly dynamic biological processes in vivo with cellular resolution. This real-time high-resolution photoacoustic imaging system provides a promising approach for various in vivo imaging and quantitative studies.

Wang, Lidai; Maslov, Konstantin; Yao, Junjie; Li, Li; Wang, Lihong V.

2011-03-01

200

Piezoelectric cantilever sensors  

NASA Technical Reports Server (NTRS)

A piezoelectric cantilever with a non-piezoelectric, or piezoelectric tip useful as mass and viscosity sensors. The change in the cantilever mass can be accurately quantified by monitoring a resonance frequency shift of the cantilever. For bio-detection, antibodies or other specific receptors of target antigens may be immobilized on the cantilever surface, preferably on the non-piezoelectric tip. For chemical detection, high surface-area selective absorbent materials are coated on the cantilever tip. Binding of the target antigens or analytes to the cantilever surface increases the cantilever mass. Detection of target antigens or analytes is achieved by monitoring the cantilever's resonance frequency and determining the resonance frequency shift that is due to the mass of the adsorbed target antigens on the cantilever surface. The use of a piezoelectric unimorph cantilever allows both electrical actuation and electrical sensing. Incorporating a non-piezoelectric tip (14) enhances the sensitivity of the sensor. In addition, the piezoelectric cantilever can withstand damping in highly viscous liquids and can be used as a viscosity sensor in wide viscosity range.

Shih, Wan Y. (Inventor); Shih, Wei-Heng (Inventor); Shen, Zuyan (Inventor)

2008-01-01

201

Piezoelectricity of biopolymers.  

PubMed

The piezoelectricity of semicrystalline biopolymers was first discovered for wood and bone in the 1950's. Piezoelectric properties have since been investigated for a number of biological substances, including polysaccharides, proteins and deoxyribonucleates. The shear piezoelectric constants -d14 = d25 were determined for their oriented structures with a uniaxial symmetry Dinfinity. From studies of synthetic polypeptides and optically active polymers, it was concluded that the origin of piezoelectricity lies in the internal rotation of dipoles such as CONH. Values of d14 = -10 pC/N were determined for highly elongated films of poly-L-lactic acid, optically active and biodegradable. The implantation of this polymer induced the growth of bone, possibly because ionic current caused by piezoelectric polarization stimulated the activity of bone cells. Submicron-thick polyurea films were prepared by evaporating diisocyanate and diamine monomers in vacuum. After poling, the films exhibited pyro- and piezoelectric effects. The tensile piezoelectric constant d31 = 10 pC/N persisting up to 200 degrees C was also observed for aliphatic polyurea films. PMID:8857351

Fukada, E

1995-01-01

202

Adaptive piezoelectric sensoriactuator  

NASA Technical Reports Server (NTRS)

An adaptive algorithm implemented in digital or analog form is used in conjunction with a voltage controlled amplifier to compensate for the feedthrough capacitance of piezoelectric sensoriactuator. The mechanical response of the piezoelectric sensoriactuator is resolved from the electrical response by adaptively altering the gain imposed on the electrical circuit used for compensation. For wideband, stochastic input disturbances, the feedthrough capacitance of the sensoriactuator can be identified on-line, providing a means of implementing direct-rate-feedback control in analog hardware. The device is capable of on-line system health monitoring since a quasi-stable dynamic capacitance is indicative of sustained health of the piezoelectric element.

Clark, Jr., Robert L. (Inventor); Vipperman, Jeffrey S. (Inventor); Cole, Daniel G. (Inventor)

1996-01-01

203

Theoretical and experimental investigation of multispectral photoacoustic osteoporosis detection method  

NASA Astrophysics Data System (ADS)

Osteoporosis is a widespread disorder, which has a catastrophic impact on patients lives and overwhelming related to healthcare costs. Recently, we proposed a multispectral photoacoustic technique for early detection of osteoporosis. Such technique has great advantages over pure ultrasonic or optical methods as it allows the deduction of both bone functionality from the bone absorption spectrum and bone resistance to fracture from the characteristics of the ultrasound propagation. We demonstrated the propagation of multiple acoustic modes in animal bones in-vitro. To further investigate the effects of multiple wavelength excitations and of induced osteoporosis on the PA signal a multispectral photoacoustic system is presented. The experimental investigation is based on measuring the interference of multiple acoustic modes. The performance of the system is evaluated and a simple two mode theoretical model is fitted to the measured phase signals. The results show that such PA technique is accurate and repeatable. Then a multiple wavelength excitation is tested. It is shown that the PA response due to different excitation wavelengths revels that absorption by the different bone constitutes has a profound effect on the mode generation. The PA response is measured in single wavelength before and after induced osteoporosis. Results show that induced osteoporosis alters the measured amplitude and phase in a consistent manner which allows the detection of the onset of osteoporosis. These results suggest that a complete characterization of the bone over a region of both acoustic and optical frequencies might be used as a powerful tool for in-vivo bone evaluation.

Steinberg, Idan; Hershkovich, Hadas Sara; Gannot, Israel; Eyal, Avishay

2014-03-01

204

Ultrasonic attenuation of biomaterials for compensation in photoacoustic imaging  

NASA Astrophysics Data System (ADS)

Ultrasonic attenuation in biomaterials limits the quality and resolution of ultrasonic imaging. This work presents a simple and reliable method to investigate acoustic attenuation of biological tissue samples and liquids in order to improve reconstruction algorithms for photoacoustic imaging. For this purpose broadband high-frequency single transmission measurements were performed. The spectra of the acquired signals were compared to reference measurements in distilled water. Unfocused broadband piezoelectric transducers were used as ultrasound source and detector. Moreover, laser generated ultrasound, which provides more intensity and signals with higher bandwidth, was used to measure acoustic attenuation. Only few studies concerned with attenuation of fat tissue performed broadband high frequency measurements and to our knowledge none of those used the simple and reliable single transmission approach with unfocused ultrasound. Our results for acoustic attenuation in olive oil show good agreement with literature. Many studies indicate linear frequency increase of attenuation of fat tissue. However, we observed significant non-linear frequency behaviour of porcine subcutaneous fat tissue at room temperature with a power-law exponent of around 1.45.

Bauer-Marschallinger, Johannes; Berer, Thomas; Roitner, Heinz; Grün, Hubert; Reitinger, Bernhard; Burgholzer, Peter

2011-03-01

205

Broadband pulsed flow using piezoelectric microjets  

NASA Astrophysics Data System (ADS)

A piezohydraulic microjet design and experimental results are presented to demonstrate broadband active flow control for applications on various aircraft structures including impinging jets, rotor blades, cavity bays, etc. The microjet actuator includes a piezoelectric stack actuator and hydraulic circuit that is used to throttle a 400 ?m diameter microjet using hydraulic amplification of the piezoelectric stack actuator. This system is shown to provide broadband pulsed flow actuation up to 800 Hz. Unsteady pressure measurements of the microjet's exit flow are coupled with high-speed phase imagery using micro-Schlieren techniques to quantify the flow field. These results are compared with in situ stack actuator displacements using strain gauge measurements.

Hogue, Joshua; Solomon, John; Hays, Michael; Alvi, Farrukh; Oates, William

2010-04-01

206

Piezoelectric Energy Harvesting Solutions  

PubMed Central

This paper reviews the state of the art in piezoelectric energy harvesting. It presents the basics of piezoelectricity and discusses materials choice. The work places emphasis on material operating modes and device configurations, from resonant to non-resonant devices and also to rotational solutions. The reviewed literature is compared based on power density and bandwidth. Lastly, the question of power conversion is addressed by reviewing various circuit solutions. PMID:24618725

Caliò, Renato; Rongala, Udaya Bhaskar; Camboni, Domenico; Milazzo, Mario; Stefanini, Cesare; de Petris, Gianluca; Oddo, Calogero Maria

2014-01-01

207

Laminated piezoelectric transformer  

NASA Technical Reports Server (NTRS)

A laminated piezoelectric transformer is provided using the longitudinal vibration modes for step-up voltage conversion applications. The input portions are polarized to deform in a longitudinal plane and are bonded to an output portion. The deformation of the input portions is mechanically coupled to the output portion, which deforms in the same longitudinal direction relative to the input portion. The output portion is polarized in the thickness direction relative its electrodes, and piezoelectrically generates a stepped-up output voltage.

Vazquez Carazo, Alfredo (Inventor)

2006-01-01

208

Photoacoustic imaging of brachytherapy seeds using a channel-domain ultrasound array system  

NASA Astrophysics Data System (ADS)

Brachytherapy is a technique commonly used in the treatment of prostate cancer that relies on the precise placement of small radioactive seeds near the tumor location. The advantage of this technique over traditional radiation therapies is that treatment can be continuous and uniform, resulting in fewer clinic visits and a shorter treatment duration. Two important phases of this treatment are needle guidance for implantation, and post-placement verification for dosimetry. Ultrasound is a common imaging modality used for these purposes, but it can be difficult to distinguish the seeds from surrounding tissues, often requiring other imaging techniques such as MRI or CT. Photoacoustic imaging may offer a viable alternative. Using a photoacoustic system based on an L7- 4 array transducer and a realtime ultrasound array system capable of parallel channel data acquisition streamed to a multi-core computer via PCI-express, we have demonstrated imaging of these seeds at an ultrasound depth of 16 mm and laser penetration depths ranging up to 50 mm in chicken tissue with multiple optical wavelengths. Ultrasound and photoacoustic images are coregistered via an interlaced pulse sequence. Two laser pulses are used to form a photoacoustic image, and at these depths, the brachytherapy seeds are detected with a signal-to-noise ratio of over 26dB. To obtain this result, 1064nm light was used with a fluence of 100mJ/cm2, the ANSI limit for human skin exposure at this wavelength. This study demonstrates the potential for photoacoustic imaging as a candidate technology for brachytherapy seed placement guidance and verification.

Harrison, Tyler; Zemp, Roger J.

2011-03-01

209

Fabrication and characteristics of thin disc piezoelectric transformers based on piezoelectric buzzers with gap circles.  

PubMed

This paper investigates design, fabrication and test of thin disc piezoelectric transformers (PTs) based on piezoelectric buzzers with gap circles at different diameters of the gap circles. The performance test is focused on characteristics of voltage gains, including maximum voltage gains and maximum-gain frequencies, for each piezoelectric transformer under different load conditions. Both a piezoelectric buzzer and a gap circle on a silver electrode of the buzzer are needed to build any type of the PTs. Here, the gap circle is used to form a ring-shaped input electrode and a circle-shaped output electrode for each piezoelectric transformer. To do so, both structure and connection of a PT are first expressed. Then, operating principle of a PT and its related vibration mode observed by a carbon-power imaging technique are described. Moreover, an experimental setup for characterizing each piezoelectric transformer is constructed. Finally, effects of diameters of the gap circles on characteristics of voltage gains at different load resistances are discussed. PMID:18221977

Chang, Kuo-Tsai; Lee, Chun-Wei

2008-04-01

210

Photoacoustic Imaging of Animals with an Annular Transducer Array  

NASA Astrophysics Data System (ADS)

A photoacoustic system with an annular transducer array is presented for rapid, high-resolution photoacoustic tomography of animals. An eight-channel data acquisition system is applied to capture the photoacoustic signals by using multiplexing and the total time of data acquisition and transferring is within 3 s. A limited-view filtered back projection algorithm is used to reconstruct the photoacoustic images. Experiments are performed on a mouse head and a rabbit head and clear photoacoustic images are obtained. The experimental results demonstrate that this imaging system holds the potential for imaging the human brain.

Yang, Di-Wu; Zhou, Zhi-Bin; Zeng, Lv-Ming; Zhou, Xin; Chen, Xing-Hui

2014-07-01

211

TOPICAL REVIEW: Photoacoustic tomography and sensing in biomedicine  

NASA Astrophysics Data System (ADS)

Photoacoustics has been broadly studied in biomedicine, for both human and small animal tissues. Photoacoustics uniquely combines the absorption contrast of light or radio frequency waves with ultrasound resolution. Moreover, it is non-ionizing and non-invasive, and is the fastest growing new biomedical method, with clinical applications on the way. This review provides a brief recap of recent developments in photoacoustics in biomedicine, from basic principles to applications. The emphasized areas include the new imaging modalities, hybrid detection methods, photoacoustic contrast agents and the photoacoustic Doppler effect, as well as translational research topics.

Li, Changhui; Wang, Lihong V.

2009-10-01

212

Design of a portable noninvasive photoacoustic glucose monitoring system integrated laser diode excitation with annular array detection  

NASA Astrophysics Data System (ADS)

A near-infrared photoacoustic glucose monitoring system, which is integrated dual-wavelength pulsed laser diode excitation with eight-element planar annular array detection technique, is designed and fabricated during this study. It has the characteristics of nonivasive, inexpensive, portable, accurate location, and high signal-to-noise ratio. In the system, the exciting source is based on two laser diodes with wavelengths of 905 nm and 1550 nm, respectively, with optical pulse energy of 20 ?J and 6 ?J. The laser beam is optically focused and jointly projected to a confocal point with a diameter of 0.7 mm approximately. A 7.5 MHz 8-element annular array transducer with a hollow structure is machined to capture photoacoustic signal in backward mode. The captured signals excitated from blood glucose are processed with a synthetic focusing algorithm to obtain high signal-to-noise ratio and accurate location over a range of axial detection depth. The custom-made transducer with equal area elements is coaxially collimated with the laser source to improve the photoacoustic excite/receive efficiency. In the paper, we introduce the photoacoustic theory, receive/process technique, and design method of the portable noninvasive photoacoustic glucose monitoring system, which can potentially be developed as a powerful diagnosis and treatment tool for diabetes mellitus.

Zeng, Lvming; Liu, Guodong; Yang, Diwu; Ren, Zhong; Huang, Zhen

2008-12-01

213

Using high-power light emitting diodes for photoacoustic imaging  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging will become an important supplement to conventional ultrasound imaging. However, the equipment needed is still too delicate to bring this technique into the daily clinical work. The pulsed light source is the area of interest in the present report. Usually, large and costly laser systems are used to provide high-energy light pulses with a chosen wavelength. Pulsed semiconductor lasers have been demonstrated as a possible alternative light source for the photoacoustic imaging purpose. As an alternative to laser sources, the preliminary result of using a pulsed high-power light emitting diode, LED, for photoacoustic imaging is presented here. The pulsed light source is created from a Luxeon LXHL_PD09 red LED (250mW optical output power at 1 Amp current). The LED is supplied with current pulses 60ns wide and 40A peak. The LED delivers 60ns light pulses with approximately 6W peak power. The phantom used consists of a thin stripe (3mm high x 5mm wide) of green colored gelatin overlaid by a 3cm layer of un-colored gelatin. The light pulses from the LED are collected by a lens system and focused on the green gelatin from beneath the sample. The acoustic response from the green gelatin is detected with a single focused transducer on the upper surface of the 3cm thick colorless gelatin layer. The response is clearly observed when the measurement is taken as an average of 50,000 pulses. Is it concluded that despite the relatively low pulse power, for some purposes, a combination of of LED's could be a candidate for an inexpensive light source.

Skov Hansen, René

2011-03-01

214

Power enhancement of piezoelectric transformers by adding heat transfer equipment.  

PubMed

It is known that piezoelectric transformers have several inherent advantages compared with conventional electromagnetic transformers. However, the maximum power capacity of piezoelectric transformers is not as large as electromagnetic transformers in practice, especially in the case of high output current. The theoretical power density of piezoelectric transformers calculated by stress boundary can reach 330 W/cm(3), but no piezoelectric transformer has ever reached such a high power density in practice. The power density of piezoelectric transformers is limited to 33 W/cm(3) in practical applications. The underlying reason is that the maximum passing current of the piezoelectric material (mechanical current) is limited by the temperature rise caused by heat generation. To increase this current and the power capacity, we proposed to add a thermal pad to the piezoelectric transformer to dissipate heat. The experimental results showed that the proposed techniques can increase by 3 times the output current of the piezoelectric transformer. A theoretical-phenomenological model which explains the relationship between vibration velocity and generated heat is also established to verify the experimental results. PMID:23143563

Su, Yu-Hao; Liu, Yuan-Ping; Vasic, Dejan; Wu, Wen-Jong; Costa, François; Lee, Chih-Kung

2012-10-01

215

HYPR-spectral photoacoustic CT for preclinical imaging  

NASA Astrophysics Data System (ADS)

We have designed and built a prototype PCT (photoacoustic CT) scanner suitable for small animal imaging that acquires a sparse set of 128 photoacoustic, radial "projections" uniformly distributed over the surface of a hemisphere in response to optical absorption from a tunable, pulsed NIR (near-infrared) laser. Acquisition of a denser set of projections is achieved by rotating the hemispherical array about its vertical axis and acquiring additional, interleaved projections. Each detector in the array is a 3-mm diameter, piezo-composite with a center frequency of 5 MHz and 70% bandwidth. Spatial resolution is < 300 ?m and nearly isotropic, owing to the array geometry. Preliminary results acquired at half of the allowable laser power and with no system optimizations show a low contrast sensitivity sufficient to detect a 350 nM concentration of a NIR-absorbing organic dye embedded in 12.5 mm of soft tissue. This scanner design will allow our group to take advantage of HYPR (HighlY constrained backPRojection) reconstruction techniques, which can significantly improve temporal (or spectral) resolution, without sacrificing signal-to-noise or spatial resolution. We will report how these accelerated reconstruction techniques can be implemented with this PCT scanner design. Using this approach, we may be able to achieve 100-ms temporal resolution for dynamic studies throughout a 20-mm-diameter imaging volume.

Kruger, Robert; Reinecke, Daniel; Kruger, Gabe; Thornton, Michael; Picot, Paul; Morgan, Timothy; Stantz, Keith; Mistretta, Charles

2009-02-01

216

Total internal reflection photoacoustic detection spectroscopy  

NASA Astrophysics Data System (ADS)

Total Internal Reflection Photoacoustic Spectroscopy (TIRPAS) is a method that exploits the evanescent field of a nanosecond duration laser pulse reflecting off a glass/water interface to generate photoacoustic responses. These photoacoustic events are generated in light absorbing analytes suspended in the fluid medium in contact with the glass that are within the penetration depth of the evanescent wave. This method has been employed in previous studies by Hinoue et al. Hinoue et al. used an optically chopped HeNe laser at 632.8 nm to detect Brilliant Blue FCF dye at different angles of incidence. In recent years, the advent of high power nanosecond pulsed tunable lasers has allowed for the re-visitation of the TIRPAS idea under stress confinement and orders of magnitude larger peak energy conditions. Compared to conventional detection methods, this approach has the potential to detect much smaller quantities of disease indicators, such as circulating tumor cells and hemazoin crystals in malaria, than other optical methods. The detection limit of the TIRPAS system was quantified using chlorazol black solution with an absorption coefficient of 55 cm-1 at 532 nm. Interaction with the evanescent field was verified by varying the angle of incidence of the probe laser beam that generated the photoacoustic waves, thereby changing the penetration depth of the evanescent field as well as the photoacoustic spectroscopy effect from angled excitation.

Sudduth, Amanda S. M.; Goldschmidt, Benjamin S.; Samson, Edward B.; Whiteside, Paul J. D.; Viator, John A.

2011-03-01

217

Molecular Photoacoustic Imaging of Follicular Thyroid Carcinoma  

PubMed Central

Purpose To evaluate the potential of targeted photoacoustic imaging as a non-invasive method for detection of follicular thyroid carcinoma. Experimental Design We determined the presence and activity of two members of matrix metalloproteinase family (MMP), MMP-2 and MMP-9, suggested as biomarkers for malignant thyroid lesions, in FTC133 thyroid tumors subcutaneously implanted in nude mice. The imaging agent used to visualize tumors was MMP activatable photoacoustic probe, Alexa750-CXeeeeXPLGLAGrrrrrXK-BHQ3. Cleavage of the MMP activatable agent was imaged after intratumoral and intravenous injections in living mice optically, observing the increase in Alexa750 fluorescence, and photoacoustically, using a dual wavelength imaging method. Results Active forms of both MMP2 and MMP-9 enzymes were found in FTC133 tumor homogenates, with MMP-9 detected in greater amounts. The molecular imaging agent was determined to be activated by both enzymes in vitro, with MMP-9 being more efficient in this regard. Both optical and photoacoustic imaging showed significantly higher signal in tumors of mice injected with the active agent than in tumors injected with the control, non-activatable, agent. Conclusions With the combination of high spatial resolution and signal specificity, targeted photoacoustic imaging holds great promise as a noninvasive method for early diagnosis of follicular thyroid carcinomas. PMID:23349314

Levi, Jelena; Kothapalli, Sri-Rajashekar; Bohndiek, Sarah; Yoon, Joon-Kee; Dragulescu-Andrasi, Anca; Nielsen, Carsten; Tisma, Aleksandra; Bodapati, Sunil; Gowrishankar, Gayatri; Yan, Xinrui; Chan, Carmel; Starcevic, Daniela; Gambhir, Sanjiv Sam

2013-01-01

218

Micromachined piezoelectric acoustic transducers  

NASA Astrophysics Data System (ADS)

The feasibilities and functionalities of three different types of diaphragm-based piezoelectric MEMS acoustic transducers (produced by combining micromachining procedures with piezoelectric ZnO thin-film processing) have been successfully demonstrated for audio and ultrasound applications. They are based on a dome-shaped diaphragm, parylene-supported diaphragm and parylene-held cantilever-like diaphragm, and have been fabricated compatibly with an IC fabrication processing that allows a cost-effective mass production of the transducer elements. Dome-shaped-diaphragm piezoelectric acoustic transducers have successfully been fabricated on a 1.5 ?m thick silicon nitride diaphragm (2,000 ?m in radius, with a circular clamped boundary on a silicon substrate) with electrodes and piezoelectric ZnO film. Due to the 3- dimensional nature of a dome diaphragm, the dome- diaphragm transducer has a stress-releasing capability and generates the high frequency sound effectively. The transducer's sound output (measured with B&K 4135 microphone 2 mm away from the transducer) is 70-113 dB SPL in 10-200 kHz ranges. We have successfully fabricated piezoelectric acoustic transducers built on 1.5 ?m thick parylene diaphragms (both flat 5,000*5,000 ?m 2 square diaphragm and dome-shaped 2,000 ?m-radius diaphragm with circular clamped boundary on a silicon substrate) with electrodes and piezoelectric ZnO film. Parylene-held cantilever-like diaphragm acoustic transducers have been fabricated and demonstrated to release the residual stress (and also to make the diaphragm mechanically flexible) much like a cantilever, and yet is itself a diaphragm with its four edges clamped. We have successfully fabricated and tested various piezoelectric acoustic transducers built on a silicon nitride layer (either in cantilever form and/or freely-suspended island form) with electrodes and piezoelectric ZnO film. Finite element modeling (FEM) is used to simulate the responses of the three different types of the micromachined acoustic transducers based on a piezoelectric active component. Full three-dimensional elements are used to model the piezoelectric acoustic transducers because such devices are not only anisotropic, but also couple electric and elastic fields, and satisfy the boundary conditions of the two fields independently. The finite element analysis accounts for the interaction (coupling) between electric and structural fields.

Han, Cheol-Hyun

219

Handheld probe integrating laser diode and ultrasound transducer array for ultrasound/photoacoustic dual modality imaging.  

PubMed

Ultrasound and photoacoustics can be utilized as complementary imaging techniques to improve clinical diagnoses. Photoacoustics provides optical contrast and functional information while ultrasound provides structural and anatomical information. As of yet, photoacoustic imaging uses large and expensive systems, which limits their clinical application and makes the combination costly and impracticable. In this work we present and evaluate a compact and ergonomically designed handheld probe, connected to a portable ultrasound system for inexpensive, real-time dual-modality ultrasound/photoacoustic imaging. The probe integrates an ultrasound transducer array and a highly efficient diode stack laser emitting 130 ns pulses at 805 nm wavelength and a pulse energy of 0.56 mJ, with a high pulse repetition frequency of up to 10 kHz. The diodes are driven by a customized laser driver, which can be triggered externally with a high temporal stability necessary to synchronize the ultrasound detection and laser pulsing. The emitted beam is collimated with cylindrical micro-lenses and shaped using a diffractive optical element, delivering a homogenized rectangular light intensity distribution. The system performance was tested in vitro and in vivo by imaging a human finger joint. PMID:25401669

Daoudi, K; van den Berg, P J; Rabot, O; Kohl, A; Tisserand, S; Brands, P; Steenbergen, W

2014-10-20

220

Multicontrast photoacoustic in vivo imaging using near-infrared fluorescent proteins  

NASA Astrophysics Data System (ADS)

Non-invasive imaging of biological processes in vivo is invaluable in advancing biology. Photoacoustic tomography is a scalable imaging technique that provides higher resolution at greater depths in tissue than achievable by purely optical methods. Here we report the application of two spectrally distinct near-infrared fluorescent proteins, iRFP670 and iRFP720, engineered from bacterial phytochromes, as photoacoustic contrast agents. iRFPs provide tissue-specific contrast without the need for delivery of any additional substances. Compared to conventional GFP-like red-shifted fluorescent proteins, iRFP670 and iRFP720 demonstrate stronger photoacoustic signals at longer wavelengths, and can be spectrally resolved from each other and hemoglobin. We simultaneously visualized two differently labeled tumors, one with iRFP670 and the other with iRFP720, as well as blood vessels. We acquired images of a mouse as 2D sections of a whole animal, and as localized 3D volumetric images with high contrast and sub-millimeter resolution at depths up to 8 mm. Our results suggest iRFPs are genetically-encoded probes of choice for simultaneous photoacoustic imaging of several tissues or processes in vivo.

Krumholz, Arie; Shcherbakova, Daria M.; Xia, Jun; Wang, Lihong V.; Verkhusha, Vladislav V.

2014-02-01

221

A Micro-Cantilever Based Photoacoustic Detector of Terahertz Radiation for Chemical Sensing  

NASA Astrophysics Data System (ADS)

In this paper we describe a novel photoacoustic detector that can detect radiation in the Terahertz/sub-millimeter (THz/smm) spectral range, is immune to the effect of standing waves, and potentially can have spectral response that is independent of the absorption path length, thus offering crucial advantages for acquisition of THz/smm molecular spectra. The photoacoustic effect occurs when the energy from electromagnetic waves is absorbed by molecules and collisionally transferred into translational energy, thus resulting in local heating induced by the radiation. If radiation produced by the source is modulated, an acoustic wave results which can be detected by a pressure sensitive device such as a microphone or a cantilever. This transduction of the THz signal into a photoacoustic wave is what makes this approach insensitive to the detrimental standing waves associated with traditional THz sensors and allows for a significant reduction in the size of the absorption cell. A Microelectromechanical system (MEMS) cantilever pressure sensor was designed, modeled, fabricated, and tested for sensing the photoacoustic response of gases to THz/smm radiation. Here we present our manufacturing, experimental set-up and most recent spectroscopic results, which demonstrate the capabilities of this spectroscopic technique.

Glauvitz, Nathan E.; Coutu, Ronald A. Coutu, Jr.; Kistler, Michael N.; Hamilton, Ryan F.; Petkie, Douglas T.; Medvedev, Ivan R.

2013-06-01

222

Multicontrast photoacoustic in vivo imaging using near-infrared fluorescent proteins  

PubMed Central

Non-invasive imaging of biological processes in vivo is invaluable in advancing biology. Photoacoustic tomography is a scalable imaging technique that provides higher resolution at greater depths in tissue than achievable by purely optical methods. Here we report the application of two spectrally distinct near-infrared fluorescent proteins, iRFP670 and iRFP720, engineered from bacterial phytochromes, as photoacoustic contrast agents. iRFPs provide tissue-specific contrast without the need for delivery of any additional substances. Compared to conventional GFP-like red-shifted fluorescent proteins, iRFP670 and iRFP720 demonstrate stronger photoacoustic signals at longer wavelengths, and can be spectrally resolved from each other and hemoglobin. We simultaneously visualized two differently labeled tumors, one with iRFP670 and the other with iRFP720, as well as blood vessels. We acquired images of a mouse as 2D sections of a whole animal, and as localized 3D volumetric images with high contrast and sub-millimeter resolution at depths up to 8?mm. Our results suggest iRFPs are genetically-encoded probes of choice for simultaneous photoacoustic imaging of several tissues or processes in vivo. PMID:24487319

Krumholz, Arie; Shcherbakova, Daria M.; Xia, Jun; Wang, Lihong V.; Verkhusha, Vladislav V.

2014-01-01

223

Photo-acoustic imaging of blue nanoparticle targeted brain tumor for intra-operative glioma delineation  

NASA Astrophysics Data System (ADS)

Distinguishing the tumor from the background neo-plastic tissue is challenging for cancer surgery such as surgical resection of glioma. Attempts have been made to use visible or fluorescent markers to delineate the tumors during surgery. However, the systemic injection of the dyes requires high dose, resulting in negative side effects. A novel method to delineate rat brain tumors intra-operatively, as well as post-operatively, using a highly sensitive photoacoustic imaging technique enhanced by tumor targeting blue nanoparticle as contrast agent is demonstrated. The nanoparticles are made of polyacrylamide (PAA) matrix with covalently linked Coomassie-Blue dye. They contain 7.0% dye and the average size is 80nm. Their surface was conjugated with F3 peptide for active tumor targeting. These nanoparticles are nontoxic, chemically inert and have long plasma circulation lifetime, making them suitable as nanodevices for imaging using photoacoustics. Experiments on phantoms and rat brains tumors ex-vivo demonstrate the high sensitivity of photoacoustic imaging in delineating the tumor, containing contrast agent at concentrations too low to be visualized by eye. The control tumors without nanoparticles did not show any enhanced signal. This study shows that photoacoustic imaging facilitated with the nanoparticle contrast agent could contribute to future surgical procedures for glioma.

Ray, Aniruddha; Wang, Xueding; Koo Lee, Yong-Eun; Hah, HoeJin; Kim, Gwangseong; Chen, Thomas; Orrienger, Daniel; Sagher, Oren; Kopelman, Raoul

2011-07-01

224

Capture of circulating tumor cells using photoacoustic flowmetry and two phase flow  

NASA Astrophysics Data System (ADS)

Melanoma is the deadliest form of skin cancer, yet current diagnostic methods are unable to detect early onset of metastatic disease. Patients must wait until macroscopic secondary tumors form before malignancy can be diagnosed and treatment prescribed. Detection of cells that have broken off the original tumor and travel through the blood or lymph system can provide data for diagnosing and monitoring metastatic disease. By irradiating enriched blood samples spiked with cultured melanoma cells with nanosecond duration laser light, we induced photoacoustic responses in the pigmented cells. Thus, we can detect and enumerate melanoma cells in blood samples to demonstrate a paradigm for a photoacoustic flow cytometer. Furthermore, we capture the melanoma cells using microfluidic two phase flow, a technique that separates a continuous flow into alternating microslugs of air and blood cell suspension. Each slug of blood cells is tested for the presence of melanoma. Slugs that are positive for melanoma, indicated by photoacoustic waves, are separated from the cytometer for further purification and isolation of the melanoma cell. In this paper, we evaluate the two phase photoacoustic flow cytometer for its ability to detect and capture metastastic melanoma cells in blood.

O'Brien, Christine M.; Rood, Kyle D.; Bhattacharyya, Kiran; DeSouza, Thiago; Sengupta, Shramik; Gupta, Sagar K.; Mosley, Jeffrey D.; Goldschmidt, Benjamin S.; Sharma, Nikhilesh; Viator, John A.

2012-06-01

225

Capture of circulating tumor cells using photoacoustic flowmetry and two phase flow  

PubMed Central

Abstract. Melanoma is the deadliest form of skin cancer, yet current diagnostic methods are unable to detect early onset of metastatic disease. Patients must wait until macroscopic secondary tumors form before malignancy can be diagnosed and treatment prescribed. Detection of cells that have broken off the original tumor and travel through the blood or lymph system can provide data for diagnosing and monitoring metastatic disease. By irradiating enriched blood samples spiked with cultured melanoma cells with nanosecond duration laser light, we induced photoacoustic responses in the pigmented cells. Thus, we can detect and enumerate melanoma cells in blood samples to demonstrate a paradigm for a photoacoustic flow cytometer. Furthermore, we capture the melanoma cells using microfluidic two phase flow, a technique that separates a continuous flow into alternating microslugs of air and blood cell suspension. Each slug of blood cells is tested for the presence of melanoma. Slugs that are positive for melanoma, indicated by photoacoustic waves, are separated from the cytometer for further purification and isolation of the melanoma cell. In this paper, we evaluate the two phase photoacoustic flow cytometer for its ability to detect and capture metastastic melanoma cells in blood. PMID:22734751

O'Brien, Christine M.; Rood, Kyle D.; Bhattacharyya, Kiran; DeSouza, Thiago; Sengupta, Shramik; Gupta, Sagar K.; Mosley, Jeffrey D.; Goldschmidt, Benjamin S.; Sharma, Nikhilesh; Viator, John A.

2012-01-01

226

Photoacoustic Brain Imaging: from Microscopic to Macroscopic Scales  

PubMed Central

Human brain mapping has become one of the most exciting contemporary research areas, with major breakthroughs expected in the following decades. Modern brain imaging techniques have allowed neuroscientists to gather a wealth of anatomic and functional information about the brain. Among these techniques, by virtue of its rich optical absorption contrast, high spatial and temporal resolutions, and deep penetration, photoacoustic tomography (PAT) has attracted more and more attention, and is playing an increasingly important role in brain studies. In particular, PAT complements other brain imaging modalities by providing high-resolution functional and metabolic imaging. More importantly, PAT’s unique scalability enables scrutinizing the brain at both microscopic and macroscopic scales, using the same imaging contrast. In this Review, we present the state-of-the-art PAT techniques for brain imaging, summarize representative neuroscience applications, outline the technical challenges in translating PAT to human brain imaging, and envision potential technological deliverables. PMID:25401121

Yao, Junjie; Wang, Lihong V.

2014-01-01

227

Piezoelectric Ceramics and Their Applications  

ERIC Educational Resources Information Center

Describes the piezoelectric effect in ceramics and presents a quantitative representation of this effect. Explains the processes involved in the manufacture of piezoelectric ceramics, the materials used, and the situations in which they are applied. (GS)

Flinn, I.

1975-01-01

228

Intravascular photoacoustic imaging of human coronary atherosclerosis  

NASA Astrophysics Data System (ADS)

We demonstrate intravascular photoacoustic imaging of human coronary atherosclerotic plaque. We specifically imaged lipid content, a key factor in vulnerable plaques that may lead to myocardial infarction. An integrated intravascular photoacoustics (IVPA) and ultrasound (IVUS) catheter with an outer diameter of 1.25 mm was developed. The catheter comprises an angle-polished optical fiber adjacent to a 30 MHz single-element transducer. The ultrasonic transducer was optically isolated to eliminate artifacts in the PA image. We performed measurements on a cylindrical vessel phantom and isolated point targets to demonstrate its imaging performance. Axial and lateral point spread function widths were 110 ?m and 550 ?m, respectively, for PA and 89 ?m and 420 ?m for US. We imaged two fresh human coronary arteries, showing different stages of disease, ex vivo. Specific photoacoustic imaging of lipid content, is achieved by spectroscopic imaging at different wavelengths between 1180 and 1230 nm.

Jansen, Krista; van der Steen, Antonius F. W.; Springeling, Geert; van Beusekom, Heleen M. M.; Oosterhuis, J. Wolter; van Soest, Gijs

2011-03-01

229

Quantitative Photoacoustic Spectroscopy in the Frequency Domain  

NASA Astrophysics Data System (ADS)

In this paper, the development of a new methodology for the quantitative determination of the optical absorption coefficient in simple systems in which the light absorption follows Beer’s law is described. An approximation of the heat diffusion model of the photoacoustic effect for thermally thick samples is explored. It was found that we could combine the amplitude and the phase of the photoacoustic signal to obtain a new analytical expression for the optical absorption coefficient. This expression is directly proportional to the normalized photoacoustic signal amplitude, the sine of the phase difference, and the heat capacity per unit of volume of the sample. The theoretical results were experimentally verified in the visible range (300 nm to 700 nm). The optical absorption coefficient obtained with this methodology was comparable to that obtained by UV-Vis spectroscopy.

Gutiérrez-Juárez, G.; Vela-Lira, H. A.; Yánez-Limón, J. M.; García-Rodríguez, F. J.; Polo-Parada, L.

2013-09-01

230

Ultrasonically encoded photoacoustic flowgraphy in biological tissue  

PubMed Central

Blood flow speed is an important functional parameter. Doppler ultrasound flowmetry lacks sufficient sensitivity to slow blood flow (several to tens of millimeters per second) in deep tissue. To address this challenge, we developed ultrasonically encoded photoacoustic flowgraphy combining ultrasonic thermal tagging with photoacoustic imaging. Focused ultrasound generates a confined heat source in acoustically absorptive fluid. Thermal waves propagate with the flow and are directly visualized in pseudo color using photoacoustic computed tomography. The Doppler shift is employed to calculate the flow speed. This method requires only acoustic and optical absorption, and thus is applicable to continuous fluid. A blood flow speed as low as 0.24 mm·s?1 was successfully measured. Deep blood flow imaging was experimentally demonstrated under 5-mm-thick chicken breast tissue. PMID:24289689

Wang, Lidai; Xia, Jun; Yao, Junjie; Maslov, Konstantin I.; Wang, Lihong V.

2014-01-01

231

Ultrasonically Encoded Photoacoustic Flowgraphy in Biological Tissue  

NASA Astrophysics Data System (ADS)

Blood flow speed is an important functional parameter. Doppler ultrasound flowmetry lacks sufficient sensitivity to slow blood flow (several to tens of millimeters per second) in deep tissue. To address this challenge, we developed ultrasonically encoded photoacoustic flowgraphy combining ultrasonic thermal tagging with photoacoustic imaging. Focused ultrasound generates a confined heat source in acoustically absorptive fluid. Thermal waves propagate with the flow and are directly visualized in pseudo color using photoacoustic computed tomography. The Doppler shift is employed to calculate the flow speed. This method requires only acoustic and optical absorption, and thus is applicable to continuous fluid. A blood flow speed as low as 0.24mm·s-1 was successfully measured. Deep blood flow imaging was experimentally demonstrated under 5-mm-thick chicken breast tissue.

Wang, Lidai; Xia, Jun; Yao, Junjie; Maslov, Konstantin I.; Wang, Lihong V.

2013-11-01

232

Laser-induced photothermal technique used for detection of caries in human tooth  

NASA Astrophysics Data System (ADS)

Thermal monitoring during laser-irradiated hard tissues is fundamental to enable real time feedback control and automated adjustment of laser power to maintain a constant, predetermined tissue temperature. We present an experimental technique to produce thermal wave generated in human tooth by irradiation of a high power Q-switched Nd:YAG laser operating at 1064 nm, with variable pulse energy in the range of 50-250 mJ/pulse providing laser fluences of 0.4-2 J/cm2 for the laser beam with diameter of less than 1 mm, and short pulse duration down to 100 ?sec (or 0.1 ms) at FWHM. A comparison of the measured time-dependent thermal wave for normal and carious human tooth using infrared thermal detector is investigated, simultaneously we have measure the photoacoustic response of the sample using piezoelectric transducer. Calculations of the results demonstrate that the faster temperature decay is for caries one with higher thermal conductivity and thermal diffusivity than the normal one. So the normal tooth has the largest absorption coefficient causing a purely surface heating effect, but for the carious one, the heat source resulting from the relatively low absorption coefficient does not resemble surface heating, but describes a heating effect extending some distance into the irradiated material. These results are in good agreement with the simultaneous measured photoacoustic response, so we can differentiate between the normal and carious ones.

El-Sherif, Ashraf F.; El-Sharkawy, Yasser H.

2008-02-01

233

Photoacoustic array imaging of calcifications: phantom study  

NASA Astrophysics Data System (ADS)

Breast calcification is one of the most important indicators for early breast cancer detection. In this study, based on a medical ultrasound array imaging platform, we attempt to develop a real-time and high penetration photoacoustic (PA) array imaging system for visualization of breast calcifications. Phantom studies were used to verify the imaging capability and penetration depth of the developed PA array system for calcification imaging. Intralipid gelatin phantoms with different-sized hydroxyapatite (HA) particles - major chemical composition of the breast calcification associated with malignant breast cancers - embedded were imaged. Laser at 750 nm was used for photoacoustic excitation and a custom-made 5-MHz photoacoustic array transducer with linear light guides was applied for photoacoustic signal detection. Experimental results demonstrated that this system is capable of calcification imaging of 0.3-0.5 mm HA particles. For the 0.5-mm HA particles, the imaging contrast was about 34 dB and the achievable penetration was 20 mm where the axial, lateral, and elevational resolution of this PA array imaging system is 0.39 mm, 0.38 mm, and 1.25 mm, respectively. The highest frame rate was 10 frames/sec limited by the laser pulse rate. Overall, our results demonstrate that it is promising for PA imaging as a real-time diagnosis and biopsy guidance tool of breast micro-calcifications outside mass lesion. Future work will focus on optimization of the photoacoustic transducer to further improve the penetration depth and development of photoacoustic and ultrasound dual-modal imaging to enhance the calcification imaging capability.

Cheng, Yao-You; Hsiao, Tsai-Chu; Tien, Wan-Ting; Luo, Shih-Bin; Chiou, De-Yi; Li, Meng-Lin

2012-02-01

234

In vivo virtual intraoperative surgical photoacoustic microscopy  

SciTech Connect

We developed a virtual intraoperative surgical photoacoustic microscopy system by combining with a commercial surgical microscope and photoacoustic microscope (PAM). By sharing the common optical path in the microscope and PAM system, we could acquire the PAM and microscope images simultaneously. Moreover, by employing a beam projector to back-project 2D PAM images onto the microscope view plane as augmented reality, the conventional microscopic and 2D cross-sectional PAM images are concurrently mapped on the plane via an ocular lens of the microscope in real-time. Further, we guided needle insertion into phantom ex vivo and mice skins in vivo.

Han, Seunghoon, E-mail: hsh860504@gmail.com; Kim, Sehui, E-mail: sehui0916@nate.com; Kim, Jeehyun, E-mail: jeehk@knu.ac.kr, E-mail: chulhong@postech.edu [School of Electrical Engineering and Computer Science, Kyungpook National University, Daegu 702-701 (Korea, Republic of)] [School of Electrical Engineering and Computer Science, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Lee, Changho, E-mail: ch31037@postech.edu; Jeon, Mansik, E-mail: msjeon@postech.edu [Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of)] [Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Kim, Chulhong, E-mail: jeehk@knu.ac.kr, E-mail: chulhong@postech.edu [Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of) [Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Department of Biomedical Engineering, The State University of New York at Buffalo, Buffalo, New York 14221 (United States)

2013-11-11

235

Photoacoustic effect in a sinusoidally modulated structure  

NASA Astrophysics Data System (ADS)

We derive solutions to an inhomogeneous Mathieu equation that describes the photoacoustic effect in a one-dimensional phononic structure whose acoustic properties vary sinusoidally in space. Solutions show splitting of resonances, the space equivalent of subharmonic generation, and spatial confinement. Properties of the photoacoustic effect including the damping of waves inside the band gaps, the dispersion relation, the positions and widths of the gaps, the frequencies of resonances, and the space dependence of the acoustic waves can be found in closed form from known properties of Mathieu functions.

Wu, Binbin; Diebold, Gerald J.

2012-04-01

236

PREFACE: 15th International Conference on Photoacoustic and Photothermal Phenomena (ICPPP15)  

NASA Astrophysics Data System (ADS)

Conference banner Although the roots of this scientific field go back to the end of the nineteenth century when A G Bell discovered the photoacoustic effect generated by the absorption of modulated light in a sample, major and rapid progress only occurred since the mid-1970's when the photoacoustic effect in condensed matter was put on a firm theoretical basis by A Rosencwaig and A Gersho. Since that time the fields of photoacoustics and the related fields of photothermal phenomena and laser ultrasonics have grown enormously. A multitude of ways of generating the effects has emerged using all kinds of radiation. Likewise, the diversity in methods for the detection of the generated thermal and acoustic waves has increased dramatically. One of the reasons for the popularity of the photoacoustic and photothermal field is the wide applicability of these techniques for fundamental and applied research. At this moment, the field has become really multidisciplinary and it is safe to say that it has reached a mature state with an established position in measurement technology and materials characterization. This conference as well as the ones before reflected this large diversity in the program topics and the research disciplines of the participants. This 15th International Conference on Photoacoustic and Photothermal Phenomena was held on a campus of the Catholic University of Leuven in Belgium in the week of 19-23 July 2009. During the conference 15 tutorial lectures, 8 plenary lectures, 36 invited talks, 120 oral and 172 poster communications were presented. The conference was attended by 252 participants from 38 countries from all over the world. During a special session award lectures were presented by winners of the prizes of the International Photoacoustic and Photothermal Association (IPPA). Winners of the senior prize were A Mandelis, D Fournier and A C Boccara. The winner of the junior prize was T W Murray. The editors of the proceedings of this conference believe that the published papers provide significant contributions to the field of photoacoustic and phothermal phenomena and can serve as a good introduction to scientists outside of the field. C Glorieux J Thoen Editors Conference photograph

Glorieux, Christ; Thoen, Jan

2010-01-01

237

Piezoelectric wave motor  

DOEpatents

A piezoelectric motor having a stator in which piezoelectric elements are contained in slots formed in the stator transverse to the desired wave motion. When an electric field is imposed on the elements, deformation of the elements imposes a force perpendicular to the sides of the slot, deforming the stator. Appropriate frequency and phase-shifting of the electric field will produce a wave in the stator and motion in a rotor. In a preferred aspect, the piezoelectric elements are configured so that deformation of the elements in the direction of an imposed electric field, generally referred to as the d.sub.33 direction, is utilized to produce wave motion in the stator. In a further aspect, the elements are compressed into the slots so as to minimize tensile stresses on the elements in use.

Yerganian, Simon Scott (Lee's Summit, MO)

2003-02-11

238

Piezoelectric wave motor  

DOEpatents

A piezoelectric motor having a stator in which piezoelectric elements are contained in slots formed in the stator transverse to the desired wave motion. When an electric field is imposed on the elements, deformation of the elements imposes a force perpendicular to the sides of the slot, deforming the stator. Appropriate frequency and phase shifting of the electric field will produce a wave in the stator and motion in a rotor. In a preferred aspect, the piezoelectric elements are configured so that deformation of the elements in direction of an imposed electric field, generally referred to as the d.sub.33 direction, is utilized to produce wave motion in the stator. In a further aspect, the elements are compressed into the slots so as to minimize tensile stresses on the elements in use.

Yerganian, Simon Scott (Lee's Summit, MO)

2001-07-17

239

Photoacoustic microscopy of human teeth  

NASA Astrophysics Data System (ADS)

Photoacoustic microscopy (PAM) utilizes short laser pulses to deposit energy into light absorbers and sensitively detects the ultrasonic waves the absorbers generate in response. PAM directly renders a three-dimensional spatial distribution of sub-surface optical absorbers. Unlike other optical imaging technologies, PAM features label-free optical absorption contrast and excellent imaging depths. Standard dental imaging instruments are limited to X-ray and CCD cameras. Subsurface optical dental imaging is difficult due to the highly-scattering enamel and dentin tissue. Thus, very few imaging methods can detect dental decay or diagnose dental pulp, which is the innermost part of the tooth, containing the nerves, blood vessels, and other cells. Here, we conducted a feasibility study on imaging dental decay and dental pulp with PAM. Our results showed that PAM is sensitive to the color change associated with dental decay. Although the relative PA signal distribution may be affected by surface contours and subsurface reflections from deeper dental tissue, monitoring changes in the PA signals (at the same site) over time is necessary to identify the progress of dental decay. Our results also showed that deep-imaging, near-infrared (NIR) PAM can sensitively image blood in the dental pulp of an in vitro tooth. In conclusion, PAM is a promising tool for imaging both dental decay and dental pulp.

Rao, Bin; Cai, Xin; Favazza, Christopher; Yao, Junjie; Li, Li; Duong, Steven; Liaw, Lih-Huei; Holtzman, Jennifer; Wilder-Smith, Petra; Wang, Lihong V.

2011-03-01

240

Photo-acoustic excitation and detection of guided ultrasonic waves in bone samples covered by a soft coating layer  

NASA Astrophysics Data System (ADS)

Photo-acoustic (PA) excitation was combined with skeletal quantitative ultrasound (QUS) for multi-mode ultrasonic assessment of human long bones. This approach permits tailoring of the ultrasonic excitation and detection so as to efficiently detect the fundamental flexural guided wave (FFGW) through a coating of soft tissue. FFGW is a clinically relevant indicator of cortical thickness. An OPO laser with tunable optical wavelength, was used to excite a photo-acoustic source in the shaft of a porcine femur. Ultrasonic signals were detected by a piezoelectric transducer, scanning along the long axis of the bone, 20-50 mm away from the source. Five femurs were measured without and with a soft coating. The coating was made of an aqueous gelatin-intralipid suspension that optically and acoustically mimicked real soft tissue. An even coating thickness was ensured by using a specific mold. The optical wave length of the source (1250 nm) was tuned to maximize the amplitude of FFGW excitation at 50 kHz frequency. The experimentally determined FFGW phase velocity in the uncoated samples was consistent with that of the fundamental antisymmetric Lamb mode (A0). Using appropriate signal processing, FFGW was also identified in the coated bone samples, this time with a phase velocity consistent with that theoretically predicted for the first mode of a fluid-solid bilayer waveguide (BL1). Our results suggest that photo-acoustic quantitative ultrasound enables assessment of the thickness-sensitive FFGW in bone through a layer of soft tissue. Photo-acoustic characterization of the cortical bone thickness may thus become possible.

Zhao, Zuomin; Moilanen, Petro; Karppinen, Pasi; Määttä, Mikko; Karppinen, Timo; Hæggström, Edward; Timonen, Jussi; Myllylä, Risto

2012-12-01

241

Photoacoustic imaging of prostate brachytherapy seeds.  

PubMed

Brachytherapy seed therapy is an increasingly common way to treat prostate cancer through localized radiation. The current standard of care relies on transrectal ultrasound (TRUS) for imaging guidance during the seed placement procedure. As visualization of individual metallic seeds tends to be difficult or inaccurate under TRUS guidance, guide needles are generally tracked to infer seed placement. In an effort to improve seed visualization and placement accuracy, the use of photoacoustic (PA) imaging, which is highly sensitive to metallic objects in soft tissue, was investigated for this clinical application. The PA imaging properties of bare (i.e., embedded in pure gelatin) and tissue-embedded (at depths of up to 13 mm) seeds were investigated with a multi-wavelength (750 to 1090 nm) PA imaging technique. Results indicate that, much like ultrasonic (US) imaging, an angular dependence (i.e., seed orientation relative to imaging transducer) of the PA signal exists. Despite this shortcoming, however, PA imaging offers improved contrast, over US imaging, of a seed in prostate tissue if sufficient local fluence is achieved. Additionally, although the PA signal of a bare seed is greatest for lower laser wavelengths (e.g., 750 nm), the scattering that results from tissue tends to favor the use of higher wavelengths (e.g., 1064 nm, which is the primary wavelength of Nd:YAG lasers) when the seed is located in tissue. A combined PA and US imaging approach (i.e., PAUS imaging) shows strong potential to visualize both the seed and the surrounding anatomical environment of the prostate during brachytherapy seed placement procedures. PMID:21833361

Su, Jimmy L; Bouchard, Richard R; Karpiouk, Andrei B; Hazle, John D; Emelianov, Stanislav Y

2011-08-01

242

Induced piezoelectricity in isotropic biomaterial.  

PubMed

Isotropic material can be made to exhibit piezoelectric effects by the application of a constant electric field. For insulators, the piezoelectric strain constant is proportional to the applied electric field and for semiconductors, an additional out-of-phase component of piezoelectricity is proportional to the electric current density in the sample. The two induced coefficients are proportional to the strain-dependent dielectric constant (depsilon/dS + epsilon) and resistivity (drho/dS - rho), respectively. The latter is more important at frequencies such that rhoepsilonomega less than 1, often the case in biopolymers. Signals from induced piezoelectricity in nature may be larger than those from true piezoelectricity. PMID:990389

Zimmerman, R L

1976-12-01

243

Photoacoustic FTIR spectroscopic study of undisturbed human cortical bone  

NASA Astrophysics Data System (ADS)

Chemical pretreatment has been the prevailing sample preparation procedure for infrared (IR) spectroscopic studies on bone. However, experiments have indicated that chemical pretreatment can potentially affect the interactions between the components. Typically the IR techniques have involved transmission experiments. Here we report experimental studies using photoacoustic Fourier transform infrared spectroscopy (PA-FTIR). As a nondestructive technique, PA-FTIR can detect absorbance spectrum from a sample at controllable sampling depth and with little or no sample preparation. Additionally, the coupling inert gas, helium, which is utilized in the PA-FTIR system, can inhibit bacteria growth of bone by displacing oxygen. Therefore, we used this technique to study the undisturbed human cortical bone. It is found that photoacoustic mode (linear-scan, LS-PA-FTIR) can obtain basically similar spectra of bone as compared to the traditional transmission mode, but it seems more sensitive to amide III and ?2 carbonate bands. The ?3 phosphate band is indicative of detailed mineral structure and symmetry of native bone. The PA-FTIR depth profiling experiments on human cortical bone also indicate the influence of water on OH band and the cutting effects on amide I and mineral bands. Our results indicate that phosphate ion geometry appears less symmetric in its undisturbed state as detected by the PA-FTIR as compared to higher symmetry observed using transmission techniques on disturbed samples. Moreover, the PA-FTIR spectra indicate a band at 1747 cm-1 possibly resulting from Cdbnd O stretching of lipids, cholesterol esters, and triglycerides from the arteries. Comparison of the spectra in transverse and longitudinal cross-sections demonstrates that, the surface area of the longitudinal section bone appears to have more organic matrix exposed and with higher mineral stoichiometry.

Gu, Chunju; Katti, Dinesh R.; Katti, Kalpana S.

2013-02-01

244

Photoacoustic analysis of the ultrasonic irradiation effect in the photosynthetic activity in aquatic lirium plants.  

PubMed

We report, the application of the photoacoustic technique for monitoring the photosynthesis evolution in aquatic lirium (Eichhornia Crassipes), before and after it was exposed to ultrasonic irradiations. We obtained the disappearance of the phototobaric contribution in the PA signal measured for the irradiated samples with ultrasound of 17 kHz, and therefore of a possible damage in the centers producing the photosynthesis, due to the irradiation. These results show the utility of the ultrasonic irradiation, as well as, of the photosynthesis monitoring by means of the photoacoustic technique, for the elaboration and establishment of methodologies in the control of this aquatic plant, whose propagation causes many consequences extremely unfavorable for the environment, as well as for the diverse human activities that are developed in the bodies of water in the tropical and sub-tropical regions of the world. PMID:23916598

Calderón, A; Cardona, A; Nogal, U; Juárez Gracia, A G; Marín, E; Muñoz Hernández, R A

2014-01-01

245

Noncontact photoacoustic tomography imaging using a low-coherence interferometer with rapid detection of phase modulation  

NASA Astrophysics Data System (ADS)

A photoacoustic tomography imaging system using a low-coherence interferometer with rapid detection of phase modulation was designed, fabricated, and tested for biologic imaging. A noncontact probing technique was applied to improve the practicability of the system. The technique is experimentally verified by the image of a simulated tissue sample and the blood vessels within a mouse ear flap (pinna) in vivo. The system's axial and lateral resolutions are evaluated at 45 and ~15 ?m, respectively. The system's imaging depth is 1mm in a special phantom. The results show that the system has the feasibility to be used as a photoacoustic tomography imaging method, and it may provide a kind of possibility of noncontact real-time PAT.

Liu, Jun; Tang, Zhilie; Tang, Hongchun; Wu, Yongbo; Wang, Yi

2014-09-01

246

Extensions of quartz-enhanced photoacoustic spectroscopy  

E-print Network

The goal of this thesis was to perform quartz-enhanced photoacoustic spectroscopy (QEPAS) on trace concentrations of NH3 in the 1.53 pm region with a DFB laser without the use of a resonating cavity. I analyzed the process ...

Masurkar, Amrita V

2009-01-01

247

Photoacoustic tomography of a rat cerebral cortex  

E-print Network

Photoacoustic tomography of a rat cerebral cortex with a ring-based ultrasonic virtual point Engineering, Optical Imaging Laboratory, Saint Louis, Missouri 63130 Abstract. We image a rat cerebral cortex. In this work, we apply the virtual point detector to PAT of a rat cerebral cortex and show its advantages over a

Wang, Lihong

248

Boundary conditions for axisymmetric piezoelectric cylinder  

NASA Astrophysics Data System (ADS)

For axisymmetric piezoelectric cylinder, the reciprocal theorem and the axisymmetric general solution of piezoelasticity are applied in a novel way to obtain the appropriate stress and mixed boundary conditions accurate to all orders for the cylinder of general edge geometry and loadings. A decay analysis technique developed by Gregory and Wan is converted into necessary conditions on the end-data of axisymmetric piezoelectric circular cylinder, and the rapidly decaying solution is established. The prescribed end-data of the circle cylinder must satisfy these conditions in order that they could generate a decaying state within the cylinder. When stress and mixed conditions are imposed on the end of cylinder, these decaying state conditions for the case of axisymmetric deformation of piezoelectric cylinder are derived explicitly. They are then used for the correct formulation of boundary conditions for the theory solution (or the interior solution) of axisymmetric piezoelectric cylinder. The results of the present paper enable us to establish a set of correct boundary conditions, most of which are obtained for the first time.

Zhao, Baosheng; Wu, Di; Chen, Xi

2013-12-01

249

Vessel segmentation analysis of ischemic stroke images acquired with photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

We have applied optical-resolution photoacoustic microscopy (OR-PAM) for longitudinal monitoring of cerebral metabolism through the intact skull of mice before, during, and up to 72 hours after a 1-hour transient middle cerebral artery occlusion (tMCAO). The high spatial resolution of OR-PAM enabled us to develop vessel segmentation techniques for segment-wise analysis of cerebrovascular responses.

Soetikno, Brian; Hu, Song; Gonzales, Ernie; Zhong, Qiaonan; Maslov, Konstantin; Lee, Jin-Moo; Wang, Lihong V.

2012-02-01

250

Photoacoustic spectral characterization of perfluorocarbon droplets  

NASA Astrophysics Data System (ADS)

Perfluorocarbon droplets containing optical absorbing nanoparticles have been developed for use as theranostic agents (for both imaging and therapy) and as dual-mode contrast agents. Droplets can be used as photoacoustic contrast agents, vaporized via optical irradiation, then the resulting bubbles can be used as ultrasound imaging and therapeutic agents. The photoacoustic signals from micron-sized droplets containing silica coated gold nanospheres were measured using ultra-high frequencies (100-1000 MHz). The spectra of droplets embedded in a gelatin phantom were compared to a theoretical model which calculates the pressure wave from a spherical homogenous liquid undergoing thermoelastic expansion resulting from laser absorption. The location of the spectral features of the theoretical model and experimental spectra were in agreement after accounting for increases in the droplet sound speed with frequency. The agreement between experiment and model indicate that droplets (which have negligible optical absorption in the visible and infrared spectra by themselves) emitted pressure waves related to the droplet composition and size, and was independent of the physical characteristics of the optical absorbing nanoparticles. The diameter of individual droplets was calculated using three independent methods: the time domain photoacoustic signal, the time domain pulse echo ultrasound signal, and a fit to the photoacoustic model, then compared to the diameter as measured by optical microscopy. It was found the photoacoustic and ultrasound methods calculated diameters an average of 2.6% of each other, and 8.8% lower than that measured using optical microscopy. The discrepancy between the calculated diameters and the optical measurements may be due to the difficulty in resolving the droplet edges after being embedded in the translucent gelatin medium.

Strohm, Eric; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael

2012-02-01

251

Measurement of Grüneisen parameter of tissue by photoacoustic spectrometry  

NASA Astrophysics Data System (ADS)

The Grüneisen parameter of tissue is a constitutive parameter in photoacoustic tomography. Here, we applied photoacoustic spectrometry (PAS) to directly measure the Grüneisen parameter. In our PAS system, laser pulses at wavelengths between 460 and 1600 nm were delivered to tissue samples, and photoacoustic signals were detected by a 20 MHz flat water-immersion ultrasonic transducer. By fitting photoacoustic spectra to light absorption spectra, we found that the Grüneisen parameter was 0.73 for porcine subcutaneous fat tissue, and 0.15 for oxygenated bovine red blood cells at room temperature (24°C).

Yao, Da-Kang; Wang, Lihong V.

2013-03-01

252

Origin of piezoelectricity in monolayer halogenated graphane piezoelectrics  

NASA Astrophysics Data System (ADS)

Periodic patterning with adatoms or defect is one of the methods for opening the band gap of graphene. In particular, under certain configurations controlled by the order of hydrogen and halogen atoms attached on graphene, inversion symmetry of graphene can be broken to give piezoelectricity as well as pyroelectricity. Using first-principles calculations, we examine the structural stability and electronic properties of four polar conformations of halogenated graphane (C2HX)n to understand the origin of piezoelectricity in this two-dimensional system. The formation energies and piezoelectric coefficients manifest that the four conformations of (C2HF)n are energetically stable with considerable piezoelectricity. We find that the electronic contribution of the proper piezoelectricity in (C2HF)n is mainly related to the change of the electron distribution around F atoms. By substituting flourine with chlorine, we confirm that the piezoelectricity enhances at the expense of stability degradation.

Kim, Hye Jung; Noor-A-Alam, Mohammad; Son, Jong Yeog; Shin, Young-Han

2014-05-01

253

Piezoelectric Energy Harvesting From Flutter  

NASA Astrophysics Data System (ADS)

With the increasing need for alternative sources of energy, a great deal of attention is drawn to harvesting energy from ambient vibration. These vibrations may be caused by fluid forces acting upon a structure. When a flexible structure is subject to a fluid flow, it loses stability at a certain flow velocity and starts to vibrate. This self-induced motion is called flutter where energy is continuously transferred from the fluid to the structure. In this study a piezoelectric film sensor is used as a fluttering object, to convert the motion to electrical energy, and the energy harvesting capacity of the proposed concept is investigated. An experimental setup, composed of data acquisition methods, is designed and the findings are validated by original test data. The results are also compared to similar literature and it is concluded that the proposed energy harvesting technique meets the requirements of the intended application.

Norouzi, Soroush

254

Materials characterization using frequency domain photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

A frequency domain photoacoustic microscopy system is developed for the characterization of micro- and nanoscale materials. An amplified, intensity modulated continuous wave (CW) laser source is used to generate narrow-bandwidth acoustic waves through the thermoelastic effect. The displacement resulting from acoustic wave interaction with material boundaries is measured using a path-stabilized Michelson interferometer. The signal from the interferometer is coupled to a RF lock-in amplifier or vector network analyzer, allowing for the bandwidth of the detection system to be matched to that of the acoustic signals. Measurements are made over an extremely narrow bandwidth by modulating the excitation laser source on the sample surface over a long time interval and selecting a corresponding integration time for the detection system. An analysis of the signal-to-noise ratio (SNR) of this system indicates that it offers substantial improvements over existing systems that incorporate pulsed laser sources to generate broad bandwidth acoustic waves. Using a bandwidth of 1.0 Hz, for instance, experimental results show a minimum detectable displacement of 3.1 fm. Extracting quantitative material parameters from the complex acoustic spectrum can be difficult when multiple acoustic modes are excited, or in the presence of reflections from sample boundaries. Two techniques are used to process the measured signals. In the first technique, the modulation frequency of the excitation laser is scanned over the bandwidth of interest, and a transient sample response is constructed from the frequency domain data. Acoustic arrivals that are separated in the time domain are time gated for further analysis. In the second approach, the modulation frequency of the excitation laser is fixed, but the source to receiver distance is varied. The spatial frequencies of the acoustic modes are found by analyzing the spatial variation of the phase, allowing for the velocity of each mode generated at a given frequency to be determined. Several promising materials characterization applications are explored including the measurement of the thickness of nanometer scale films, the inspection of thin plates using both bulk waves and guided waves, and the imaging of subsurface features in micron scale membranes using high frequency (700 MHz) resonant acoustic spectroscopy.

Balogun, Oluwaseyi Oladeinde

255

An efficient piezoelectric energy-harvesting interface circuit using a Bias-Flip rectifier and shared inductor  

E-print Network

Energy harvesting is an emerging technology with applications to handheld, portable and implantable electronics. Harvesting ambient vibration energy through piezoelectric (PE) means is a popular energy harvesting technique ...

Ramadass, Yogesh Kumar

256

Characterization of reconstructed human skin using Photoacoustic Spectroscopy  

NASA Astrophysics Data System (ADS)

Recent progress in skin culture techniques has led to the development of systems in which the reconstructed human skin obtained exhibits morphologic characteristics similar to those observed in vivo. Reconstructed human skin may be the best substrate for pharmacological tests of topically applied drugs; besides, it can be employed in the treatment of burns wounds and chronic skin ulcers. However, this newly developed material must be validated by comparison with human skin, in order to show that reconstructed skin presents characteristics similar to those of human skin. This was accomplished in the present work, through photoacoustic spectroscopy (PAS) measurements. Results show similarity between reconstructed skin and ex-vivo human skin, validating possible therapeutic and cosmetic treatments to be developed using the reconstructed human skin analyzed in this work.

Taube, T. P.; Puzzi, M. B.; Rehder, J.; Mansanares, A. M.; da Silva, E. C.; Acosta-Avalos, D.; Barja, P. R.

2008-01-01

257

Label-free oxygen-metabolic photoacoustic microscopy in vivo  

NASA Astrophysics Data System (ADS)

Almost all diseases, especially cancer and diabetes, manifest abnormal oxygen metabolism. Accurately measuring the metabolic rate of oxygen (MRO2) can be helpful for fundamental pathophysiological studies, and even early diagnosis and treatment of disease. Current techniques either lack high resolution or rely on exogenous contrast. Here, we propose label-free metabolic photoacoustic microscopy (mPAM) with small vessel resolution to noninvasively quantify MRO2 in vivo in absolute units. mPAM is the unique modality for simultaneously imaging all five anatomical, chemical, and fluid-dynamic parameters required for such quantification: tissue volume, vessel cross-section, concentration of hemoglobin, oxygen saturation of hemoglobin, and blood flow speed. Hyperthermia, cryotherapy, melanoma, and glioblastoma were longitudinally imaged in vivo. Counterintuitively, increased MRO2 does not necessarily cause hypoxia or increase oxygen extraction. In fact, early-stage cancer was found to be hyperoxic despite hypermetabolism.

Yao, Junjie; Maslov, Konstantin I.; Zhang, Yu; Xia, Younan; Wang, Lihong V.

2011-07-01

258

Photoacoustic microscopy for quantitative evaluation of angiogenesis inhibitor  

NASA Astrophysics Data System (ADS)

We present the photoacoustic microscopy (PAM) for evaluation of angiogenesis inhibitors on a chick embryo model. Microvasculature in the chorioallantoic membrane (CAM) of the chick embryos was imaged by PAM, and the optical microscopy (OM) images of the same set of CAMs were also acquired for comparisons, serving for validation of the results from PAM. The angiogenesis inhibitors, Sunitinib, with different concentrations applied to the CAM result in the change in microvascular density, which was quantified by both PAM and OM imaging. Similar change in microvascular density from PAM and OM imaging in response to angiogenesis inhibitor at different doses was observed, demonstrating that PAM has potential to provide objective evaluation of anti-angiogenesis medication. Besides, PAM is advantageous in three-dimensional and functional imaging compared with OM so that the emerging PAM technique may offer unique information on the efficacy of angiogenesis inhibitors and could benefit applications related to antiangiogenesis treatments.

Chen, Sung-Liang; Burnett, Joseph; Sun, Duxin; Xie, Zhixing; Wang, Xueding

2014-03-01

259

Intracellular temperature mapping with fluorescence-assisted photoacoustic-thermometry  

PubMed Central

Measuring intracellular temperature is critical to understanding many cellular functions but still remains challenging. Here, we present a technique–fluorescence-assisted photoacoustic thermometry (FAPT)–for intracellular temperature mapping applications. To demonstrate FAPT, we monitored the intracellular temperature distribution of HeLa cells with sub-degree (0.7?°C) temperature resolution and sub-micron (0.23??m) spatial resolution at a sampling rate of 1?kHz. Compared to traditional fluorescence-based methods, FAPT features the unique capability of transforming a regular fluorescence probe into a concentration- and excitation-independent temperature sensor, bringing a large collection of commercially available generic fluorescent probes into the realm of intracellular temperature sensing. PMID:23825801

Gao, Liang; Zhang, Chi; Li, Chiye; Wang, Lihong V.

2013-01-01

260

Photolyses of mammalian carboxy-hemoglobin studied by photoacoustic calorimetry  

NASA Astrophysics Data System (ADS)

The enthalpy and conformational volume changes in the photolyses of carboxy-hemoglobin (HbCO) of human, bovine, pig, horse and rabbit are investigated by photoacoustic calorimetry. Considering the time scales of the exciting laser pulse and the receiving ultrasound transducers (PVDF films and PZT ceramics), as well as the reaction lifetimes in the photolysis processes of HbCO, the measured results are related to the geminate recombination and tertiary relaxation in photolyses of HbCO. Moreover, the quantum yields of the five mammals are also measured by laser pump-probe technique. The results show that the dynamic parameters, such as enthalpy and conformational volume changes, differ between the processes of the geminate recombination and tertiary relaxation. Also, the dynamic parameters differ among the five mammals although some of them may be consistent with each other.

Zhao, JinYu; Li, JiaHuang; Zhang, Zheng; Zhang, ShuYi; Qu, Min; Fang, JianWen; Hua, ZiChun

2013-07-01

261

Intracellular temperature mapping with fluorescence-assisted photoacoustic-thermometry  

NASA Astrophysics Data System (ADS)

Measuring intracellular temperature is critical to understanding many cellular functions but still remains challenging. Here, we present a technique-fluorescence-assisted photoacoustic thermometry (FAPT)-for intracellular temperature mapping applications. To demonstrate FAPT, we monitored the intracellular temperature distribution of HeLa cells with sub-degree (0.7 °C) temperature resolution and sub-micron (0.23 ?m) spatial resolution at a sampling rate of 1 kHz. Compared to traditional fluorescence-based methods, FAPT features the unique capability of transforming a regular fluorescence probe into a concentration- and excitation-independent temperature sensor, bringing a large collection of commercially available generic fluorescent probes into the realm of intracellular temperature sensing.

Gao, Liang; Zhang, Chi; Li, Chiye; Wang, Lihong V.

2013-05-01

262

Intracellular temperature mapping with fluorescence-assisted photoacoustic thermometry  

NASA Astrophysics Data System (ADS)

Measuring intracellular temperature is critical to understanding many cellular functions but still remains challenging. Here we present a technique - fluorescence-assisted photoacoustic thermometry (FAPT) - for intracellular temperature mapping applications. To demonstrate FAPT, we monitored the intracellular temperature distribution of HeLa cells with sub-degree (0.7 °C) temperature resolution and sub-micron (0.23 ?m) spatial resolution at a sampling rate of 1 kHz. Compared to traditional fluorescence-based methods, FAPT features the unique capability of transforming a regular fluorescence probe into a concentration- and excitation-independent temperature sensor, bringing a large collection of commercially available generic fluorescent probes into the realm of intracellular temperature sensing.

Gao, Liang; Zhang, Chi; Li, Chiye; Wang, Lihong

2014-03-01

263

Functional photoacoustic imaging to observe regional brain activation induced by cocaine hydrochloride  

NASA Astrophysics Data System (ADS)

Photoacoustic microscopy (PAM) was used to detect small animal brain activation in response to drug abuse. Cocaine hydrochloride in saline solution was injected into the blood stream of Sprague Dawley rats through tail veins. The rat brain functional change in response to the injection of drug was then monitored by the PAM technique. Images in the coronal view of the rat brain at the locations of 1.2 and 3.4 mm posterior to bregma were obtained. The resulted photoacoustic (PA) images showed the regional changes in the blood volume. Additionally, the regional changes in blood oxygenation were also presented. The results demonstrated that PA imaging is capable of monitoring regional hemodynamic changes induced by drug abuse.

Jo, Janggun; Yang, Xinmai

2011-09-01

264

Interlaced photoacoustic and ultrasound imaging system with real-time coregistration for ovarian tissue characterization  

NASA Astrophysics Data System (ADS)

Coregistered ultrasound (US) and photoacoustic imaging are emerging techniques for mapping the echogenic anatomical structure of tissue and its corresponding optical absorption. We report a 128-channel imaging system with real-time coregistration of the two modalities, which provides up to 15 coregistered frames per second limited by the laser pulse repetition rate. In addition, the system integrates a compact transvaginal imaging probe with a custom-designed fiber optic assembly for in vivo detection and characterization of human ovarian tissue. We present the coregistered US and photoacoustic imaging system structure, the optimal design of the PC interfacing software, and the reconfigurable field programmable gate array operation and optimization. Phantom experiments of system lateral resolution and axial sensitivity evaluation, examples of the real-time scanning of a tumor-bearing mouse, and ex vivo human ovaries studies are demonstrated.

Alqasemi, Umar; Li, Hai; Yuan, Guangqian; Kumavor, Patrick; Zanganeh, Saeid; Zhu, Quing

2014-07-01

265

Imaging of blood vessels with CCD-camera based three-dimensional photoacoustic tomography  

NASA Astrophysics Data System (ADS)

An optical phase contrast full field detection setup in combination with a CCD-camera is presented to record acoustic fields for real-time projection and fast three-dimensional imaging. When recording projection images of the wave pattern around the imaging object, the three-dimensional photoacoustic imaging problem is reduced to a set of two-dimensional reconstructions and the measurement setup requires only a single axis of rotation. Using a 10 Hz pulse laser system for photoacoustic excitation a three dimensional image can be obtained in less than 1 min. The sensitivity and resolution of the detection system was estimated experimentally with 5 kPa mm and 75?m, respectively. Experiments on biological samples show the applicability of this technique for the imaging of blood vessel distributions.

Nuster, Robert; Slezak, Paul; Paltauf, Guenther

2014-03-01

266

Tunable fiber laser and fiber amplifier based photoacoustic spectrometer for trace gas detection.  

PubMed

A new wavelength modulated photoacoustic spectrometer based on a near-infrared tunable erbium doped fiber laser (TEDFL) and an erbium doped fiber amplifier (EDFA) is first developed for trace gas detection. This sensor has been applied to the detection of ammonia using a first longitudinal resonant photoacoustic cell with double absorption optical path (L=20cm) and lock-in harmonic detection technique. The minimum detectable limit of 3 parts-per-billion volume (signal-to-noise ratio=1) and response time of approximately 1min is achieved at room temperature and atmospheric pressure with 100ms time constant and 500mW optical power at the 1531.7nm transition line. PMID:19781982

Peng, Yong; Zhang, Wang; Li, Liang; Yu, Qingxu

2009-11-01

267

Improved Piezoelectric Loudspeakers And Transducers  

NASA Technical Reports Server (NTRS)

Loudspeakers and related acoustic transducers of improved type feature both light weight and energy efficiency of piezoelectric transducers and mechanical coupling efficiency. Active component of transducer made from wafer of "rainbow" piezoelectric material, ceramic piezoelectric material chemically reduced on one face. Chemical treatment forms wafer into dishlike shallow section of sphere. Both faces then coated with electrically conductive surface layers serving as electrodes. Applications include high-fidelity loudspeakers, and underwater echo ranging devices.

Regan, Curtis Randall; Jalink, Antony; Hellbaum, Richard F.; Rohrbach, Wayne W.

1995-01-01

268

In situ measurements of the thermal properties of heterogenous materials using transmission photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

Transmission photoacoustic microscopy (TPAM) was developed as an analytical technique for the in-situ measurement of the thermal properties of heterogeneous materials. In TPAM, a modulated light is focused on a polished surface of a heterogeneous material using the objective lens of an optical reflectance microscope. The heat generated at the front or illuminated surface of the sample diffuses to the back surface. This diffusion introduces a phase delay in the temperature of the back surface relative to that of the front surface. The temperature phase delay produces a phase delay in the photoacoustic signal, which is measured by a highly sensitive microphone placed in a closed chamber containing the sample and the coupling gas. The phase of the photoacoustic signal as a function of the modulation frequency constitutes the desired experimental data. Using TPAM, the thermal diffusivities of a rank series of coal were measured. These thermal diffusivity data were used to calculate the thermal conductivity of coal and to infer the structure of coal as a function of its rank. The TPAM technique was also used to measure the in-situ thermal diffusivities of the constituents of a 3-D carbon-carbon composite material. Thermal diffusivities were measured for the three different yarns in the directions parallel and perpendicular to the fibers. The average thermal diffusivities in the three octagonal directions were measured.

Ahmed, Tasdiq

269

High Temperature Piezoelectric Drill  

NASA Technical Reports Server (NTRS)

Venus is one of the planets in the solar systems that are considered for potential future exploration missions. It has extreme environment where the average temperature is 460 deg C and its ambient pressure is about 90 atm. Since the existing actuation technology cannot maintain functionality under the harsh conditions of Venus, it is a challenge to perform sampling and other tasks that require the use of moving parts. Specifically, the currently available electromagnetic actuators are limited in their ability to produce sufficiently high stroke, torque, or force. In contrast, advances in developing electro-mechanical materials (such as piezoelectric and electrostrictive) have enabled potential actuation capabilities that can be used to support such missions. Taking advantage of these materials, we developed a piezoelectric actuated drill that operates at the temperature range up to 500 deg C and the mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) configuration. The detailed results of our study are presented in this paper

Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom

2012-01-01

270

Optical coherence photoacoustic microscopy: accomplishing optical coherence tomography and photoacoustic microscopy with a single light source.  

PubMed

We developed optical coherence photoacoustic microscopy (OC-PAM) to demonstrate that the functions of optical coherence tomography (OCT) and photoacoustic microscopy (PAM) can be achieved simultaneously by using a single illuminating light source. We used a pulsed broadband laser centered at 580 nm and detected the absorbed photons through photoacoustic detection and the back-scattered photons with an interferometer. In OC-PAM, each laser pulse generates both one OCT A-line and one PAM A-line simultaneously; as a result, the two imaging modalities are intrinsically co-registered in the lateral directions. In vivo images of the mouse ear were acquired to demonstrate the capabilities of OC-PAM. PMID:22502553

Zhang, Xiangyang; Zhang, Hao F; Jiao, Shuliang

2012-03-01

271

Modeling piezoelectric actuators  

Microsoft Academic Search

The piezoelectric actuator (PEA) is a well-known device for managing extremely small displacements in the range from 10 pm to 100 ?m. When developing a control system for a piezo-actuated positioning mechanism, the actuator dynamics have to be taken into account. An electromechanical piezo model, based on physical principles, is presented in this paper. In this model, a first-order differential

H. J. M. T. S. Adriaens; W. L. De Koning; R. Banning

2000-01-01

272

Piezoelectrically enhanced photocathode  

NASA Technical Reports Server (NTRS)

A photocathode, for generating electrons in response to incident photons in a photodetector, includes a base layer having a first lattice structure and an active layer having a second lattice structure and epitaxially formed on the base layer, the first and second lattice structures being sufficiently different to create a strain in the active layer with a corresponding piezoelectrically induced polarization field in the active layer, the active layer having a band gap energy corresponding to a desired photon energy.

Beach, Robert A. (Inventor); Nikzad, Shouleh (Inventor); Strittmatter, Robert P. (Inventor); Bell, Lloyd Douglas (Inventor)

2009-01-01

273

Black Branes as Piezoelectrics  

NASA Astrophysics Data System (ADS)

We find a realization of linear electroelasticity theory in gravitational physics by uncovering a new response coefficient of charged black branes, exhibiting their piezoelectric behavior. Taking charged dilatonic black strings as an example and using the blackfold approach we measure their elastic and piezolectric moduli. We also use our results to draw predictions about the equilibrium condition of charged dilatonic black rings in dimensions higher than six.

Armas, Jay; Gath, Jakob; Obers, Niels A.

2012-12-01

274

Black branes as piezoelectrics.  

PubMed

We find a realization of linear electroelasticity theory in gravitational physics by uncovering a new response coefficient of charged black branes, exhibiting their piezoelectric behavior. Taking charged dilatonic black strings as an example and using the blackfold approach we measure their elastic and piezolectric moduli. We also use our results to draw predictions about the equilibrium condition of charged dilatonic black rings in dimensions higher than six. PMID:23368298

Armas, Jay; Gath, Jakob; Obers, Niels A

2012-12-14

275

Integrated Photoacoustic Ophthalmoscopy and Spectral-domain Optical Coherence Tomography  

PubMed Central

Both the clinical diagnosis and fundamental investigation of major ocular diseases greatly benefit from various non-invasive ophthalmic imaging technologies. Existing retinal imaging modalities, such as fundus photography1, confocal scanning laser ophthalmoscopy (cSLO)2, and optical coherence tomography (OCT)3, have significant contributions in monitoring disease onsets and progressions, and developing new therapeutic strategies. However, they predominantly rely on the back-reflected photons from the retina. As a consequence, the optical absorption properties of the retina, which are usually strongly associated with retinal pathophysiology status, are inaccessible by the traditional imaging technologies. Photoacoustic ophthalmoscopy (PAOM) is an emerging retinal imaging modality that permits the detection of the optical absorption contrasts in the eye with a high sensitivity4-7 . In PAOM nanosecond laser pulses are delivered through the pupil and scanned across the posterior eye to induce photoacoustic (PA) signals, which are detected by an unfocused ultrasonic transducer attached to the eyelid. Because of the strong optical absorption of hemoglobin and melanin, PAOM is capable of non-invasively imaging the retinal and choroidal vasculatures, and the retinal pigment epithelium (RPE) melanin at high contrasts 6,7. More importantly, based on the well-developed spectroscopic photoacoustic imaging5,8 , PAOM has the potential to map the hemoglobin oxygen saturation in retinal vessels, which can be critical in studying the physiology and pathology of several blinding diseases 9 such as diabetic retinopathy and neovascular age-related macular degeneration. Moreover, being the only existing optical-absorption-based ophthalmic imaging modality, PAOM can be integrated with well-established clinical ophthalmic imaging techniques to achieve more comprehensive anatomic and functional evaluations of the eye based on multiple optical contrasts6,10 . In this work, we integrate PAOM and spectral-domain OCT (SD-OCT) for simultaneously in vivo retinal imaging of rat, where both optical absorption and scattering properties of the retina are revealed. The system configuration, system alignment and imaging acquisition are presented. PMID:23354081

Jiao, Shuliang; Zhang, Hao F.

2013-01-01

276

Multimaterial piezoelectric fibres  

NASA Astrophysics Data System (ADS)

Fibre materials span a broad range of applications ranging from simple textile yarns to complex modern fibre-optic communication systems. Throughout their history, a key premise has remained essentially unchanged: fibres are static devices, incapable of controllably changing their properties over a wide range of frequencies. A number of approaches to realizing time-dependent variations in fibres have emerged, including refractive index modulation, nonlinear optical mechanisms in silica glass fibres and electroactively modulated polymer fibres. These approaches have been limited primarily because of the inert nature of traditional glassy fibre materials. Here we report the composition of a phase internal to a composite fibre structure that is simultaneously crystalline and non-centrosymmetric. A ferroelectric polymer layer of 30?m thickness is spatially confined and electrically contacted by internal viscous electrodes and encapsulated in an insulating polymer cladding hundreds of micrometres in diameter. The structure is thermally drawn in its entirety from a macroscopic preform, yielding tens of metres of piezoelectric fibre. The fibres show a piezoelectric response and acoustic transduction from kilohertz to megahertz frequencies. A single-fibre electrically driven device containing a high-quality-factor Fabry-Perot optical resonator and a piezoelectric transducer is fabricated and measured.

Egusa, S.; Wang, Z.; Chocat, N.; Ruff, Z. M.; Stolyarov, A. M.; Shemuly, D.; Sorin, F.; Rakich, P. T.; Joannopoulos, J. D.; Fink, Y.

2010-08-01

277

Ultrahigh resolution photoacoustic microscopy via transient absorption  

PubMed Central

We have developed a novel, hybrid imaging modality, Transient Absorption Ultrasonic Microscopy (TAUM), which takes advantage of the optical nonlinearities afforded by transient absorption to achieve ultrahigh-resolution photoacoustic microscopy. The theoretical point spread function for TAUM is functionally equivalent to confocal and two-photon fluorescence microscopy, potentially enabling cellular/subcellular photoacoustic imaging. A prototype TAUM system was designed, built, and used to image a cross-section through several capillaries in the excised cheek pouch of a Syrian Hamster. The well-resolved capillaries in the TAUM image provided experimental evidence of the spatial resolution. These results suggest that TAUM has excellent potential for producing volumetric images with cellular/subcellular resolution in three dimensions deep inside living tissue. PMID:21258499

Shelton, Ryan L.; Applegate, Brian E.

2010-01-01

278

Multiple passive element enriched photoacoustic computed tomography.  

PubMed

Recently, we presented a method using laser-induced ultrasound from an external absorber (passive element) to image the ultrasound transmission parameters of an object under photoacoustic tomographic investigation. The method suffers from long measurement times due to the requirement for a large number of views and consequently physical projections around the object. Here we propose and validate an approach that permits a multitude of views to be obtained within a limited projection scenario. The approach uses a plurality of spatially distributed external absorbers in the path of the light, that results in multiple laser-induced ultrasound sources to interrogate the object from a number of angles. This reduces the required number of rotation angles or physical projections around the object, permitting a considerable reduction in imaging time without significant degradation in image quality. The approach brings the concept of hybrid imaging of ultrasound transmission parameters together with photoacoustic imaging, into the realm of practical application. PMID:21808320

Resink, Steffen; Jose, Jithin; Willemink, Rene G H; Slump, Cornelis H; Steenbergen, Wiendelt; van Leeuwen, Ton G; Manohar, Srirang

2011-08-01

279

CO 2-laser photoacoustic detection of gaseous n-pentylacetate  

NASA Astrophysics Data System (ADS)

The absorption spectra of gaseous n-pentylacetate were investigated by FT IR spectroscopy as well as CO 2-laser photoacoustic spectroscopy for simulation of the dispersion of a nerve agent (sarin) within a modeled atmospheric boundary layer. Three CO 2-laser emission lines were used for photoacoustic detection of n-pentylacetate with detection limit in the range of 1-3 ppm.

Herecová, Lenka; Hejzlar, Tomáš; Pavlovský, Ji?í; Mí?ek, Dalibor; Zelinger, Zden?k; Kubát, Pavel; Jane?ková, Radmila; Nevrlý, Václav; Bitala, Petr; St?ižík, Michal; Klouda, Karel; Civiš, Svatopluk

2009-07-01

280

In vivo imaging of subcutaneous structures using functional photoacoustic microscopy  

E-print Network

In vivo imaging of subcutaneous structures using functional photoacoustic microscopy Hao F Zhang1.2007.108 Functional photoacoustic microscopy (fPAM) is a hybrid technology that permits noninvasive. Although various methods for light delivery can be applied, an optical-ultrasonic confocal illumination

Wang, Lihong

281

Spectroscopic photoacoustic microscopy using a photonic crystal fiber supercontinuum source  

E-print Network

performed at seven different wavelengths from 575 to 875 nm. A simple discriminant analysis(5), 054033 (2008). 2. J. L.-S. Su, B. Wang, and S. Y. Emelianov, "Photoacoustic imaging of coronary artery. Cox, J. G. Laufer, and P. C. Beard, "The challenges for quantitative photoacoustic imaging," Proc

Buma, Takashi

282

Multifunctional Photosensitizer-Based Contrast Agents for Photoacoustic Imaging  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging is a novel hybrid imaging modality combining the high spatial resolution of optical imaging with the high penetration depth of ultrasound imaging. Here, for the first time, we evaluate the efficacy of various photosensitizers that are widely used as photodynamic therapeutic (PDT) agents as photoacoustic contrast agents. Photoacoustic imaging of photosensitizers exhibits advantages over fluorescence imaging, which is prone to photobleaching and autofluorescence interference. In this work, we examined the photoacoustic activity of 5 photosensitizers: zinc phthalocyanine, protoporphyrin IX, 2,4-bis [4-(N,N-dibenzylamino)-2,6-dihydroxyphenyl] squaraine, chlorin e6 and methylene blue in phantoms, among which zinc phthalocyanine showed the highest photoacoustic activity. Subsequently, we evaluated its tumor localization efficiency and biodistribution at multiple time points in a murine model using photoacoustic imaging. We observed that the probe localized at the tumor within 10 minutes post injection, reaching peak accumulation around 1 hour and was cleared within 24 hours, thus, demonstrating the potential of photosensitizers as photoacoustic imaging contrast agents in vivo. This means that the known advantages of photosensitizers such as preferential tumor uptake and PDT efficacy can be combined with photoacoustic imaging capabilities to achieve longitudinal monitoring of cancer progression and therapy in vivo.

Ho, Chris Jun Hui; Balasundaram, Ghayathri; Driessen, Wouter; McLaren, Ross; Wong, Chi Lok; Dinish, U. S.; Attia, Amalina Binte Ebrahim; Ntziachristos, Vasilis; Olivo, Malini

2014-06-01

283

Nonionizing photoacoustic cystography in vivo Chulhong Kim,1,  

E-print Network

cystography (PAC). A healthy rat bladder filled with Methylene Blue (MB) was photoacoustically a photoacoustic imaging system, we have successfully imaged a rat bladder filled with clinically used Methylene Blue (MB) dye. An image contrast of 8 was achieved. Further, spectroscopic PAC con- firmed

Wang, Lihong

284

Photoacoustic lifetime contrast between methylene blue monomers and self-  

E-print Network

Photoacoustic lifetime contrast between methylene blue monomers and self- quenched dimers/03/2013 Terms of Use: http://spiedl.org/terms #12;Photoacoustic lifetime contrast between methylene blue-state lifetime of methylene blue (MB), a fluorophore widely used in clinical therapeutic and diagnostic

Thomas, David D.

285

Photoacoustic spectroscopy of short-period gyrotropic superlattices  

SciTech Connect

The Rosencwaig-Gersho photoacoustic transformation is extended to the case of the short-period superlattices formed by gytropic nonmagnetic cubic crystals. The potentialities of photoacoustic spectroscopy when applied to superlattices and the control of their parameters are considered. 18 refs., 4 figs.

Mityurich, G.S.; Starodubtsev, E.G. [Frantsisk Skorina State Univ., Gomel (Belarus)

1994-12-31

286

Multifunctional photosensitizer-based contrast agents for photoacoustic imaging.  

PubMed

Photoacoustic imaging is a novel hybrid imaging modality combining the high spatial resolution of optical imaging with the high penetration depth of ultrasound imaging. Here, for the first time, we evaluate the efficacy of various photosensitizers that are widely used as photodynamic therapeutic (PDT) agents as photoacoustic contrast agents. Photoacoustic imaging of photosensitizers exhibits advantages over fluorescence imaging, which is prone to photobleaching and autofluorescence interference. In this work, we examined the photoacoustic activity of 5 photosensitizers: zinc phthalocyanine, protoporphyrin IX, 2,4-bis [4-(N,N-dibenzylamino)-2,6-dihydroxyphenyl] squaraine, chlorin e6 and methylene blue in phantoms, among which zinc phthalocyanine showed the highest photoacoustic activity. Subsequently, we evaluated its tumor localization efficiency and biodistribution at multiple time points in a murine model using photoacoustic imaging. We observed that the probe localized at the tumor within 10 minutes post injection, reaching peak accumulation around 1 hour and was cleared within 24 hours, thus, demonstrating the potential of photosensitizers as photoacoustic imaging contrast agents in vivo. This means that the known advantages of photosensitizers such as preferential tumor uptake and PDT efficacy can be combined with photoacoustic imaging capabilities to achieve longitudinal monitoring of cancer progression and therapy in vivo. PMID:24938638

Ho, Chris Jun Hui; Balasundaram, Ghayathri; Driessen, Wouter; McLaren, Ross; Wong, Chi Lok; Dinish, U S; Attia, Amalina Binte Ebrahim; Ntziachristos, Vasilis; Olivo, Malini

2014-01-01

287

Compressed sensing in photoacoustic tomographyin vivo  

PubMed Central

The data acquisition speed in photoacoustic computed tomography (PACT) is limited by the laser repetition rate and the number of parallel ultrasound detecting channels. Reconstructing an image with fewer measurements can effectively accelerate the data acquisition and reduce the system cost. We adapt compressed sensing (CS) for the reconstruction in PACT. CS-based PACT is implemented as a nonlinear conjugate gradient descent algorithm and tested with both phantom and in vivo experiments. PMID:20459233

Guo, Zijian; Li, Changhui; Song, Liang; Wang, Lihong V.

2010-01-01

288

In vivo optically encoded photoacoustic flowgraphy.  

PubMed

We present an optically encoded photoacoustic (PA) flow imaging method based on optical-resolution PA microscopy. An intensity-modulated continuous-wave laser photothermally encodes the flowing medium, and a pulsed laser generates PA waves to image the encoded heat pattern. Flow speeds can be calculated by cross correlation. The method was validated in phantoms at flow speeds ranging from 0.23 to 11??mm/s. Venous blood flow speed in a mouse ear was also measured. PMID:24978744

Zhang, Ruiying; Wang, Lidai; Yao, Junjie; Yeh, Cheng-Hung; Wang, Lihong V

2014-07-01

289

Quantitative imaging of bilirubin by photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

Noninvasive detection of both bilirubin concentration and its distribution is important for disease diagnosis. Here we implemented photoacoustic microscopy (PAM) to detect bilirubin distribution. We first demonstrate that our PAM system can measure the absorption spectra of bilirubin and blood. We also image bilirubin distributions in tissuemimicking samples, both without and with blood mixed. Our results show that PAM has the potential to quantitatively image bilirubin in vivo for clinical applications.

Zhou, Yong; Zhang, Chi; Yao, Da-Kang; Wang, Lihong V.

2013-03-01

290

Imaging hypoxia using 3D photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

Purpose: The objective is to develop a multivariate in vivo hemodynamic model of tissue oxygenation (MiHMO2) based on 3D photoacoustic spectroscopy. Introduction: Low oxygen levels, or hypoxia, deprives cancer cells of oxygen and confers resistance to irradiation, some chemotherapeutic drugs, and oxygen-dependent therapies (phototherapy) leading to treatment failure and poor disease-free and overall survival. For example, clinical studies of patients with breast carcinomas, cervical cancer, and head and neck carcinomas (HNC) are more likely to suffer local reoccurrence and metastasis if their tumors are hypoxic. A novel method to non invasively measure tumor hypoxia, identify its type, and monitor its heterogeneity is devised by measuring tumor hemodynamics, MiHMO2. Material and Methods: Simulations are performed to compare tumor pO2 levels and hypoxia based on physiology - perfusion, fractional plasma volume, fractional cellular volume - and its hemoglobin status - oxygen saturation and hemoglobin concentration - based on in vivo measurements of breast, prostate, and ovarian tumors. Simulations of MiHMO2 are performed to assess the influence of scanner resolutions and different mathematic models of oxygen delivery. Results: Sensitivity of pO2 and hypoxic fraction to photoacoustic scanner resolution and dependencies on model complexity will be presented using hemodynamic parameters for different tumors. Conclusions: Photoacoustic CT spectroscopy provides a unique ability to monitor hemodynamic and cellular physiology in tissue, which can be used to longitudinally monitor tumor oxygenation and its response to anti-angiogenic therapies.

Stantz, Keith M.

2010-02-01

291

Photoacoustic imaging and characterization of the microvasculature  

PubMed Central

Photoacoustic (optoacoustic) tomography, combining optical absorption contrast and highly scalable spatial resolution (from micrometer optical resolution to millimeter acoustic resolution), has broken through the fundamental penetration limit of optical ballistic imaging modalities—including confocal microscopy, two-photon microscopy, and optical coherence tomography—and has achieved high spatial resolution at depths down to the diffusive regime. Optical absorption contrast is highly desirable for microvascular imaging and characterization because of the presence of endogenous strongly light-absorbing hemoglobin. We focus on the current state of microvascular imaging and characterization based on photoacoustics. We first review the three major embodiments of photoacoustic tomography: microscopy, computed tomography, and endoscopy. We then discuss the methods used to characterize important functional parameters, such as total hemoglobin concentration, hemoglobin oxygen saturation, and blood flow. Next, we highlight a few representative applications in microvascular-related physiological and pathophysiological research, including hemodynamic monitoring, chronic imaging, tumor-vascular interaction, and neurovascular coupling. Finally, several potential technical advances toward clinical applications are suggested, and a few technical challenges in contrast enhancement and fluence compensation are summarized. PMID:20210427

Hu, Song; Wang, Lihong V.

2010-01-01

292

Acoustic and Photoacoustic Molecular Imaging of Cancer  

PubMed Central

Ultrasound and combined optical and ultrasonic (photoacoustic) molecular imaging have shown great promise in the visualization and monitoring of cancer through imaging of vascular and extravascular molecular targets. Contrast-enhanced ultrasound with molecularly targeted microbubbles can detect early-stage cancer through the visualization of targets expressed on the angiogenic vasculature of tumors. Ultrasonic molecular imaging can be extended to the imaging of extravascular targets through use of nanoscale, phase-change droplets and photoacoustic imaging, which provides further molecular information on cancer given by the chemical composition of tissues and by targeted nanoparticles that can interact with extravascular tissues at the receptor level. A new generation of targeted contrast agents goes beyond merely increasing imaging signal at the site of target expression but shows activatable and differential contrast depending on their interactions with the tumor microenvironment. These innovations may further improve our ability to detect and characterize tumors. In this review, recent developments in acoustic and photoacoustic molecular imaging of cancer are discussed. PMID:24187042

Wilson, Katheryne E.; Wang, Tzu Yin; Willmann, Jurgen K.

2014-01-01

293

An optimized ultrasound detector for photoacoustic breast tomography  

E-print Network

Photoacoustic imaging has proven to be able to detect vascularization-driven optical absorption contrast associated with tumors. In order to detect breast tumors located a few centimeter deep in tissue, a sensitive ultrasound detector is of crucial importance for photoacoustic mammography. Further, because the expected photoacoustic frequency bandwidth (a few MHz to tens of kHz) is inversely proportional to the dimensions of light absorbing structures (0.5 to 10+ mm), proper choices of materials and their geometries, and proper considerations in design have to be made for optimal photoacoustic detectors. In this study, we design and evaluate a specialized ultrasound detector for photoacoustic mammography. Based on the required detector sensitivity and its frequency response, a selection of active material and matching layers and their geometries is made leading to a functional detector models. By iteration between simulation of detector performances, fabrication and experimental characterization of functional...

Xia, Wenfeng; Van Hespen, Johan; Van Veldhoven, Spiridon; Prins, Christian; Van Leeuwen, Ton; Steenbergen, Wiendelt; Manohar, Srirang

2012-01-01

294

THREE-DIMENSIONAL ANALYSIS OF AN ELLIPSOIDAL INCLUSION IN A PIEZOELECTRIC MATERIAL  

Microsoft Academic Search

In this paper. the Green's function technique is used to develop a solution For an inlinite. piezoelectric medium containing a piezoelectric. ellipsoidal inclusion. The coupled elastic and clcctric fields both inside the inclusion and on the boundary of the inclusion and matrix are obtained. Thcsc results are used to calculate the ektive constants of pinoelectric composite materials. It is found

BIAO WANG

295

Practical implementation of piezoelectric energy harvesting synchronized switching schemes  

NASA Astrophysics Data System (ADS)

Many closed-loop control methods for increasing the power output from piezoelectric energy harvesters have been investigated over the past decade. Initial work started with the application of Maximum Power Point Tracking techniques (MPPT) developed for solar power. More recent schemes have focused on taking advantage of the capacitive nature of piezoelectric harvesters to manipulate the transfer of energy from the piezoelectric to the storage element. There have been a couple of main techniques investigated in the literature: Synchronous Charge Extraction (SCE), Synchronized Switching and Discharging to a Capacitor through an Inductor (SSDCI), Synchronized Switch Harvesting on an Inductor (SSHI), and Piezoelectric Pre-Biasing (PPB). While significant increases in harvested power are seen both theoretically and experimentally using powerful external control systems, the applicability of these methods depends highly on the performance and efficiency of the system which implements the synchronized switching. Many piezoelectric energy harvesting systems are used to power devices controlled by a microcontroller (MCU), making them readily available for switching control methods. This work focuses on the practical questions which dictate the applicability of synchronized switching techniques using MCU-based switching control.

Schlichting, Alexander D.; Phadke, Ajay; Garcia, Ephrahim

2013-04-01

296

Photoacoustic intra-operative nodal staging using clinically approved superparamagnetic iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

Detection of tumor metastases in the lymphatic system is essential for accurate staging of various malignancies, however fast, accurate and cost-effective intra-operative evaluation of the nodal status remains difficult to perform with common available medical imaging techniques. In recent years, numerous studies have confirmed the additional value of superparamagnetic iron oxide dispersions (SPIOs) for nodal staging purposes, prompting the clearance of different SPIO dispersions for clinical practice. We evaluate whether a combination of photoacoustic (PA) imaging and a clinically approved SPIO dispersion, could be applied for intra-operative nodal staging. Metastatic adenocarcinoma was inoculated in Copenhagen rats for 5 or 8 days. After SPIO injection, the lymph nodes were photoacoustically imaged both in vivo and ex vivo whereafter imaging results were correlated with MR and histology. Results were compared to a control group without tumor inoculation. In the tumor groups clear irregularities, as small as 1 mm, were observed in the PA contrast pattern of the nodes together with an decrease of PA response. These irregularities could be correlated to the absence of contrast in the MR images and could be linked to metastatic deposits seen in the histological slides. The PA and MR images of the control animals did not show these features. We conclude that the combination of photoacoustic imaging with a clinically approved iron oxide nanoparticle dispersion is able to detect lymph node metastases in an animal model. This approach opens up new possibilities for fast intra-operative nodal staging in a clinical setting.

Grootendorst, Diederik J.; Fratila, Raluca M.; Visscher, Martijn; Ten Haken, Bennie; van Wezel, Richard; Steenbergen, Wiendelt; Manohar, Srirang; Ruers, Theo J. M.

2013-02-01

297

Breast imaging using the Twente photoacoustic mammoscope (PAM): new clinical measurements  

NASA Astrophysics Data System (ADS)

Worldwide, yearly about 450,000 women die from the consequences of breast cancer. Current imaging modalities are not optimal in discriminating benign from malignant tissue. Visualizing the malignancy-associated increased hemoglobin concentration might significantly improve early diagnosis of breast cancer. Since photoacoustic imaging can visualize hemoglobin in tissue with optical contrast and ultrasound-like resolution, it is potentially an ideal method for early breast cancer imaging. The Twente Photoacoustic Mammoscope (PAM) has been developed specifically for breast imaging. Recently, a large clinical study has been started in the Medisch Spectrum Twente in Oldenzaal using PAM. In PAM, the breast is slightly compressed between a window for laser light illumination and a flat array ultrasound detector. The measurements are performed using a Q-switched Nd:YAG laser, pulsed at 1064 nm and a 1 MHz unfocused ultrasound detector array. Three-dimensional data are reconstructed using a delay and sum reconstruction algorithm. Those reconstructed images are compared with conventional imaging and histopathology. In the first phase of the study 12 patients with a malignant lesion and 2 patients with a benign cyst have been measured. The results are used to guide developments in photoacoustic mammography in order to pave the way towards an optimal technique for early diagnosis of breast cancer.

Heijblom, Michelle; Piras, Daniele; Ten Tije, Ellen; Xia, Wenfeng; van Hespen, Johan; Klaase, Joost; van den Engh, Frank; van Leeuwen, Ton; Steenbergen, Wiendelt; Manohar, Srirang

2011-07-01

298

Photoacoustic discrimination of vascular and pigmented lesions using classical and Bayesian methods  

PubMed Central

Discrimination of pigmented and vascular lesions in skin can be difficult due to factors such as size, subungual location, and the nature of lesions containing both melanin and vascularity. Misdiagnosis may lead to precancerous or cancerous lesions not receiving proper medical care. To aid in the rapid and accurate diagnosis of such pathologies, we develop a photoacoustic system to determine the nature of skin lesions in vivo. By irradiating skin with two laser wavelengths, 422 and 530 nm, we induce photoacoustic responses, and the relative response at these two wavelengths indicates whether the lesion is pigmented or vascular. This response is due to the distinct absorption spectrum of melanin and hemoglobin. In particular, pigmented lesions have ratios of photoacoustic amplitudes of approximately 1.4 to 1 at the two wavelengths, while vascular lesions have ratios of about 4.0 to 1. Furthermore, we consider two statistical methods for conducting classification of lesions: standard multivariate analysis classification techniques and a Bayesian-model-based approach. We study 15 human subjects with eight vascular and seven pigmented lesions. Using the classical method, we achieve a perfect classification rate, while the Bayesian approach has an error rate of 20%. PMID:20210465

Swearingen, Jennifer A.; Holan, Scott H.; Feldman, Mary M.; Viator, John A.

2010-01-01

299

Detection, isolation, and capture of circulating breast cancer cells with photoacoustic flow cytometry  

NASA Astrophysics Data System (ADS)

According to the CDC, breast cancer is the most common cancer and the second leading cause of cancer related deaths among women. Metastasis, or the presence of secondary tumors caused by the spread of cancer cells via the circulatory or lymphatic systems, significantly worsens the prognosis of any breast cancer patient. In this study, a technique is developed to detect circulating breast cancer cells in human blood using a photoacoustic flow cytometry method. A Q-switched laser with a 5 ns pulse at 532 nm is used to interrogate thousands of cells with one pulse as they flow through the beam path. Cells which are pigmented, either naturally or artificially, emit an ultrasound wave as a result of the photoacoustic (PA) effect. Breast cancer cells are targeted with chromophores through immunochemistry in order to provide pigment. After which, the device is calibrated to demonstrate a single-cell detection limit. Cultured breast cancer cells are added to whole blood to reach a biologically relevant concentration of about 25-45 breast cancer cells per 1 mL of blood. An in vitro photoacoustic flow cytometer is used to detect and isolate these cells followed by capture with the use of a micromanipulator. This method can not only be used to determine the disease state of the patient and the response to therapy, it can also be used for genetic testing and in vitro drug trials since the circulating cell can be captured and studied.

Bhattacharyya, Kiran; Njoroge, Martin; Goldschmidt, Benjamin S.; Gaffigan, Brian; Rood, Kyle; Viator, John A.

2013-03-01

300

Photoimprint Photoacoustic Microscopy for Three-Dimensional Label-Free Subdiffraction Imaging  

NASA Astrophysics Data System (ADS)

Subdiffraction optical microscopy allows the imaging of cellular and subcellular structures with a resolution finer than the diffraction limit. Here, combining the absorption-based photoacoustic effect and intensity-dependent photobleaching effect, we demonstrate a simple method for subdiffraction photoacoustic imaging of both fluorescent and nonfluorescent samples. Our method is based on a double-excitation process, where the first excitation pulse partially and inhomogeneously bleaches the molecules in the diffraction-limited excitation volume, thus biasing the signal contributions from a second excitation pulse striking the same region. The differential signal between the two excitations preserves the signal contribution mostly from the center of the excitation volume, and dramatically sharpens the lateral resolution. Moreover, due to the nonlinear nature of the signal, our method offers an inherent optical sectioning capability, which is lacking in conventional photoacoustic microscopy. By scanning the excitation beam, we performed three-dimensional subdiffraction imaging of varied fluorescent and nonfluorescent species. As any molecules have absorption, this technique has the potential to enable label-free subdiffraction imaging, and can be transferred to other optical imaging modalities or combined with other subdiffraction methods.

Yao, Junjie; Wang, Lidai; Li, Chiye; Zhang, Chi; Wang, Lihong V.

2014-01-01

301

Photoacoustic discrimination of vascular and pigmented lesions using classical and Bayesian methods  

NASA Astrophysics Data System (ADS)

Discrimination of pigmented and vascular lesions in skin can be difficult due to factors such as size, subungual location, and the nature of lesions containing both melanin and vascularity. Misdiagnosis may lead to precancerous or cancerous lesions not receiving proper medical care. To aid in the rapid and accurate diagnosis of such pathologies, we develop a photoacoustic system to determine the nature of skin lesions in vivo. By irradiating skin with two laser wavelengths, 422 and 530 nm, we induce photoacoustic responses, and the relative response at these two wavelengths indicates whether the lesion is pigmented or vascular. This response is due to the distinct absorption spectrum of melanin and hemoglobin. In particular, pigmented lesions have ratios of photoacoustic amplitudes of approximately 1.4 to 1 at the two wavelengths, while vascular lesions have ratios of about 4.0 to 1. Furthermore, we consider two statistical methods for conducting classification of lesions: standard multivariate analysis classification techniques and a Bayesian-model-based approach. We study 15 human subjects with eight vascular and seven pigmented lesions. Using the classical method, we achieve a perfect classification rate, while the Bayesian approach has an error rate of 20%.

Swearingen, Jennifer A.; Holan, Scott H.; Feldman, Mary M.; Viator, John A.

2010-01-01

302

Photoimprint photoacoustic microscopy for three-dimensional label-free subdiffraction imaging.  

PubMed

Subdiffraction optical microscopy allows the imaging of cellular and subcellular structures with a resolution finer than the diffraction limit. Here, combining the absorption-based photoacoustic effect and intensity-dependent photobleaching effect, we demonstrate a simple method for subdiffraction photoacoustic imaging of both fluorescent and nonfluorescent samples. Our method is based on a double-excitation process, where the first excitation pulse partially and inhomogeneously bleaches the molecules in the diffraction-limited excitation volume, thus biasing the signal contributions from a second excitation pulse striking the same region. The differential signal between the two excitations preserves the signal contribution mostly from the center of the excitation volume, and dramatically sharpens the lateral resolution. Moreover, due to the nonlinear nature of the signal, our method offers an inherent optical sectioning capability, which is lacking in conventional photoacoustic microscopy. By scanning the excitation beam, we performed three-dimensional subdiffraction imaging of varied fluorescent and nonfluorescent species. As any molecules have absorption, this technique has the potential to enable label-free subdiffraction imaging, and can be transferred to other optical imaging modalities or combined with other subdiffraction methods. PMID:24483902

Yao, Junjie; Wang, Lidai; Li, Chiye; Zhang, Chi; Wang, Lihong V

2014-01-10

303

Deconvolution-based deblurring of reconstructed images in photoacoustic/thermoacoustic tomography.  

PubMed

Photoacoustic/thermoacoustic tomography is an emerging hybrid imaging modality combining optical/microwave imaging with ultrasound imaging. Here, a k-wave MATLAB toolbox was used to simulate various configurations of excitation pulse shape, width, transducer types, and target object sizes to see their effect on the photoacoustic/thermoacoustic signals. A numerical blood vessel phantom was also used to demonstrate the effect of various excitation pulse waveforms and pulse widths on the reconstructed images. Reconstructed images were blurred due to the broadening of the pressure waves by the excitation pulse width as well as by the limited transducer bandwidth. The blurring increases with increase in pulse width. A deconvolution approach is presented here with Tikhonov regularization to correct the photoacoustic/thermoacoustic signals, which resulted in improved reconstructed images by reducing the blurring effect. It is observed that the reconstructed images remain unaffected by change in pulse widths or pulse shapes, as well as by the limited bandwidth of the ultrasound detectors after the use of the deconvolution technique. PMID:24322855

Rejesh, Nadaparambil Aravindakshan; Pullagurla, Harish; Pramanik, Manojit

2013-10-01

304

Wide-field two-dimensional multifocal optical-resolution photoacoustic computed microscopy  

PubMed Central

Optical-resolution photoacoustic microscopy (OR-PAM) is an emerging technique that directly images optical absorption in tissue at high spatial resolution. To date, the majority of OR-PAM systems are based on single focused optical excitation and ultrasonic detection, limiting the wide-field imaging speed. While one-dimensional multifocal OR-PAM (1D-MFOR-PAM) has been developed, the potential of microlens and transducer arrays has not been fully realized. Here, we present the development of two-dimensional multifocal optical-resolution photoacoustic computed microscopy (2D-MFOR-PACM), using a 2D microlens array and a full-ring ultrasonic transducer array. The 10 × 10 mm2 microlens array generates 1800 optical foci within the focal plane of the 512-element transducer array, and raster scanning the microlens array yields optical-resolution photoacoustic images. The system has improved the in-plane resolution of a full-ring transducer array from ?100 µm to 29 µm and achieved an imaging time of 36 seconds over a 10 × 10 mm2 field of view. In comparison, the 1D-MFOR-PAM would take more than 4 minutes to image over the same field of view. The imaging capability of the system was demonstrated on phantoms and animals both ex vivo and in vivo. PMID:24322226

Xia, Jun; Li, Guo; Wang, Lidai; Nasiriavanaki, Mohammadreza; Maslov, Konstantin; Engelbach, John A.; Garbow, Joel R.; Wang, Lihong V.

2014-01-01

305

PIEZOELECTRIC POWER SCAVENGING OF MECHANICAL VIBRATION ENERGY  

E-print Network

PIEZOELECTRIC POWER SCAVENGING OF MECHANICAL VIBRATION ENERGY PIEZOELECTRIC POWER SCAVENGING and magneticand magnetic field.field. Piezoelectric Materials as Smart Material- Among the all smart materials, piezoelectric materials are of great interest, as they are commonly used as sensors, actuators and memory

Ervin, Elizabeth K.

306

Using Piezoelectric Materials for Wearable Electronic Textiles  

E-print Network

Using Piezoelectric Materials for Wearable Electronic Textiles Joshua Edmison, Mark Jones, Zahi Oct. 8, 2002 Tom Martin, ISWC 2 Overview · Introduction · Piezoelectric materials · Glove prototype Piezoelectric materials · Piezoelectric film (PVDF) · Produce voltage based upon applied force (10mV ­ 100V

307

A least-squares fixed-point iterative algorithm for multiple illumination photoacoustic tomography  

PubMed Central

The optical absorption of tissues provides important information for clinical and pre-clinical studies. The challenge in recovering optical absorption from photoacoustic images is that the measured pressure depends on absorption and local fluence. One reconstruction approach uses a fixed-point iterative technique based on minimizing the mean-squared error combined with modeling of the light source to determine optical absorption. With this technique, convergence is not guaranteed even with an accurate measure of optical scattering. In this work we demonstrate using simulations that a new multiple illumination least squares fixed-point iteration algorithm improves convergence - even with poor estimates of optical scattering. PMID:24156078

Harrison, Tyler; Shao, Peng; Zemp, Roger J.

2013-01-01

308

Piezoelectric ceramic implants: in vivo results.  

PubMed

The suitability of barium titanate (BaTiO3) ceramic for direct substitution of hard tissues was evaluated using both electrically stimulated (piezoelectric) and inactive (nonpolarized) test implants. Textured cylindrical specimens, half of them made piezoelectric by polarization in a high electric field, were implanted into the cortex of the midshaft region of the femora of dogs for various periods of time. Interfacial healing and bio-compatibility of the implant material were studied using mechanical, microradiographical, and histological techniques. Our results indicate that barium titanate ceramic shows a very high degree of biocompatibility as evidenced by the absence of inflammatory or foreign body reactions at the implant-tissue interface. Furthermore, the material and its surface porosity allowed a high degree of bone ingrowth as evidenced by microradiography and a high degree of interfacial tensile strength. No difference was found between the piezoelectric and the electrically neutral implant-tissue interfaces. Possible reasons for this are discussed. The excellent mechanical properties of barium titanate, its superior biocompatibility, and the ability of bone to form a strong mechanical interfacial bond with it, makes this material a new candidate for further tests for hard tissue replacement. PMID:7348700

Park, J B; Kelly, B J; Kenner, G H; von Recum, A F; Grether, M F; Coffeen, W W

1981-01-01

309

Plucked piezoelectric bimorphs for energy harvesting applications  

NASA Astrophysics Data System (ADS)

The modern drive towards mobility and wireless devices is motivating intense research in energy harvesting (EH) technologies. In an effort to reduce the battery burden of people, we are investigating a novel piezoelectric wearable energy harvester. As piezoelectric EH is significantly more effective at high frequencies, in opposition to the characteristically low-frequency human activities, we propose the use of an up-conversion strategy analogous to the pizzicato musical technique. In order to guide the design of such harvester, we have modelled with Finite Elements (FE) the response and power generation of a piezoelectric bimorph while it is "plucked", i.e. deflected, then released and permitted to vibrate freely. An experimental rig has been devised and set up to reproduce the action of the bimorph in the harvester. Measurements of the voltage output and the energy dissipated across a series resistor are reported and compared with the FE predictions. As the novel harvester will feature a number of bimorphs, each plucked tens of times per step, we predict a total power output of several mW, with imperceptible effect on the wearer's gait.

Pozzi, Michele; Zhu, Meiling

2011-06-01

310

Design, Synthesis and Imaging of an Activatable Photoacoustic Probe  

PubMed Central

Photoacoustic tomography is a rapidly growing imaging modality that can provide images of high spatial resolution and high contrast at depths up to 5 cm. We report here the design, synthesis and evaluation of an activatable probe that shows great promise in enabling detection of the cleaved probe in the presence of the high levels of non-activated, un-cleaved probe, a difficult task to attain in absorbance-based modality. Before the cleavage by its target, proteolytic enzyme MMP-2, the probe, an activatable cell penetrating peptide, Ceeee[Ahx]PLGLAGrrrrrK, labeled with two chromophores, BHQ3 and Alexa750, shows photoacoustic signal of similar intensity at the two wavelengths corresponding to the absorption maxima of the chromophores, 675 and 750 nm. Subtraction of the images taken at these two wavelengths makes the probe effectively photoacoustically silent as the signals at these two wavelengths essentially cancel out. After the cleavage, the dye associated with the cell penetrating part of the probe(CPP), BHQ3, accumulates in the cells, while the other dye diffuses away, resulting in photoacoustic signal seen only at one of the wavelengths, 675 nm. The subtraction of the photoacoustic images at two wavelengths reveals the location of the cleaved (activated) probe. In the search for the chromophores that are best suited for photoacoustic imaging we have investigated photoacoustic signal of five chromophores absorbing in the NIR region. We have found that the photoacoustic signal did not correlate with the absorbance and fluorescence of the molecules, as the highest photoacoustic signal arose from the least absorbing quenchers BHQ3 and QXL 680. PMID:20698693

Levi, Jelena; Kothapalli, Sri Rajasekhar; Ma, Te-Jen; Hartman, Keith; Khuri-Yakub, Butrus T.; Gambhir, Sanjiv Sam

2010-01-01

311

Considering sources and detectors distributions for quantitative photoacoustic tomography  

PubMed Central

Photoacoustic tomography (PAT) is a hybrid imaging modality that takes advantage of high optical contrast brought by optical imaging and high spatial resolution brought by ultrasound imaging. However, the quantification in photoacoustic imaging is challenging. Multiple optical illumination approach has proven to achieve uncoupling of diffusion and absorption effects. In this paper, this protocol is adopted and synthetic photoacoustic data, blurred with some noise, were generated. The influence of the distribution of optical sources and transducers on the reconstruction of the absorption and diffusion coefficients maps is studied. Specific situations with limited view angles were examined. The results show multiple illuminations with a wide field improve the reconstructions.

Song, Ningning; Deumié, Carole; Da Silva, Anabela

2014-01-01

312

Vibrational Photoacoustic Tomography: Chemical Imaging beyond the Ballistic Regime  

PubMed Central

Proof-of-concept of vibrational photoacoustic tomography is demonstrated with a homebuilt Raman laser generating greater than 100 mJ of energy per pulse at 1197 nm wavelength. We employed this system for excitation of second overtone transition of C-H bonds. Vibrational photoacoustic signal from C-H rich polyethylene tube phantom placed under 3 cm thick chicken breast tissue was obtained with a signal to noise ratio of 2.5. Further, we recorded photoacoustic image of a polyethylene ring placed under 5 mm chicken tissue with excellent contrast. This development opens new opportunities of performing label free vibrational imaging in the deep tissue regime. PMID:24224071

Wang, Pu; Cheng, Ji-Xin

2013-01-01

313

Blood pulse wave velocity measured by photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

Blood pulse wave velocity (PWV) is an important indicator for vascular stiffness. In this letter, we present electrocardiogram-synchronized photoacoustic microscopy for in vivo noninvasive quantification of the PWV in the peripheral vessels of mice. Interestingly, strong correlation between blood flow speed and ECG were clearly observed in arteries but not in veins. PWV is measured by the pulse travel time and the distance between two spot of a chose vessel, where simultaneously recorded electrocardiograms served as references. Statistical analysis shows a linear correlation between the PWV and the vessel diameter, which agrees with known physiology. Keywords: photoacoustic microscopy, photoacoustic spectroscopy, bilirubin, scattering medium.

Yeh, Chenghung; Hu, Song; Maslov, Konstantin; Wang, Lihong V.

2013-03-01

314

Photoacoustic tomography extracted from speckle noise in acoustically inhomogeneous tissue.  

PubMed

Photoacoustic tomography is usually limited to acoustically homogeneous tissue. A hybrid scheme is developed to break this limitation by utilizing ultrasound to determine the unknown Green's function of inhomogeneous tissue. The method can effectively decrease the distortion and false contrast in images by extracting information from speckle noise. The method does not depend on the prior knowledge of tissue and the medium complexity. Moreover, the estimation of Green's function and the photoacoustic detection are performed by the same transducer. Therefore, the scheme could be easily integrated into a classical photoacoustic tomography system and extend its application in speckle environment. PMID:23938677

Wu, Dan; Tao, Chao; Liu, Xiaojun

2013-07-29

315

Micro-optical-mechanical system photoacoustic spectrometer  

DOEpatents

All-optical photoacoustic spectrometer sensing systems (PASS system) and methods include all the hardware needed to analyze the presence of a large variety of materials (solid, liquid and gas). Some of the all-optical PASS systems require only two optical-fibers to communicate with the opto-electronic power and readout systems that exist outside of the material environment. Methods for improving the signal-to-noise are provided and enable mirco-scale systems and methods for operating such systems.

Kotovsky, Jack; Benett, William J.; Tooker, Angela C.; Alameda, Jennifer B.

2013-01-01

316

Dynamic photoacoustic spectroscopy for trace gas detection  

NASA Astrophysics Data System (ADS)

We present a method of photoacoustic spectroscopy in which a laser beam tuned to an absorption feature of a gas is swept through its plume at the speed of sound. The resulting coherent addition of acoustic waves leads to an amplification of the signal without the need for a resonant chamber, thus enhancing the ability to remotely sense the gas. We demonstrate the concept using a tunable CO2 laser and SF6 gas in conjunction with a microphone. Sound pressure levels of 83 dB (relative to 20 ?Pa) are generated from a 15-ppm plume.

Wynn, C. M.; Palmacci, S.; Clark, M. L.; Kunz, R. R.

2012-10-01

317

Alternative Method to Characterize Corn Grain by Means of Photoacoustic Spectroscopy  

NASA Astrophysics Data System (ADS)

The application of photothermal (PT) techniques to obtain the optical and thermal properties of different materials has been widely reported in the literature. Among the PT techniques, photoacoustic spectroscopy stands out because this technique has been used to characterize different types of materials in solid, liquid, and gaseous phases, as well as homogeneous and inhomogeneous samples as biological materials which present great complexity in their structure. In particular, the seeds and corn kernels comprise different structural components such as endosperm, pericarp, embryo, and pedicel. The color attribute is very important in the grains because it gives information about the chemical composition and nutritional quality attributes which are important in consumer acceptance. In this investigation optical absorption spectra of corn grains were obtained by using photoacoustic spectroscopy in a wavelength range from 325 nm to 800 nm. Two varieties of corn grains were studied, establishing a complete block design at random for the measurements. From the obtained optical absorption spectra, the optical absorption coefficient () was calculated as a function of the wavelength for each sample. A complementary study of the percentage of reflectance for these samples was carried out by using ultraviolet/visible spectrometry with an integrating sphere. The data were subjected to an analysis of the variance using software of the statistical analysis system. The results revealed significant differences () between corn varieties in the range of 325 nm to 670 nm. The application of the photoacoustic spectroscopy technique as an alternative to conventional methods for the characterization of maize grain through an analysis of could be important for characterizing non-homogeneous materials like grains of corn, whose characterization is relevant in the food industry.

Molina, Ricardo Rico; Aguilar, Claudia Hernández; Pacheco, Arturo Dominguez; Cruz-Orea, Alfredo; Canseco, Miguel Angel

2013-09-01

318

Micromechanics of piezoelectric composites with improved effective piezoelectric constant  

Microsoft Academic Search

This paper is concerned with the derivation of a micromechanics model of a new type of piezoelectric fiber reinforced composite\\u000a (PFRC) materials. A continuum mechanics approach is employed to determine the effective properties of these composites. The\\u000a piezoelectric fibers of these composites are considered to be electroded at the fiber–matrix interface such that the electric\\u000a fields in the fiber and

Manas Chandra Ray

2006-01-01

319

In vivo photoacoustic imaging of chemotherapy-induced apoptosis in squamous cell carcinoma using a near-infrared caspase-9 probe  

E-print Network

by utilizing a noninvasive photoacoustic imaging (PAI) technique. Nude mice bearing head and neck tumors received cisplatin chemotherapy (10 mg/kg) and were imaged by PAI after tail vein injection of the contrast agent. In vivo PAI indicated a strong apoptotic...

Yang, Qiuhong; Cui, Huizhong; Cai, Shuang; Yang, Xinmai; Forrest, Marcus Laird

2011-10-27

320

Photoacoustic Trace Detection of Methane Using Compact Solid-State Lasers Geng-Chiau Liang, Hon-Huei Liu, and A. H. Kung  

E-print Network

Photoacoustic Trace Detection of Methane Using Compact Solid-State Lasers Geng-Chiau Liang, Hon sensitive devices for monitoring and analyzing trace gases has been of primary importance in applications as an ultrasensitive technique.1-3 Tunable solid-state light sources, such as diode lasers (DL) and optical parametric

Kung, Andy

321

Functional photoacoustic tomography for non-invasive imaging of cerebral blood oxygenation and blood volume in rat brain in vivo  

NASA Astrophysics Data System (ADS)

Based on the multi-wavelength laser-based photoacoustic tomography, non-invasive in vivo imaging of functional parameters, including the hemoglobin oxygen saturation and the total concentration of hemoglobin, in small-animal brains was realized. The high sensitivity of this technique is based on the spectroscopic differences between oxy- and deoxy-hemoglobin while its spatial resolution is bandwidth-limited by the photoacoustic signals rather than by the optical diffusion as in optical imaging. The point-by-point distributions of blood oxygenation and blood volume in the cerebral cortical venous vessels, altered by systemic physiological modulations including hyperoxia, normoxia and hypoxia, were visualized successfully through the intact skin and skull. This technique, with its prominent intrinsic advantages, can potentially accelerate the progress in neuroscience and provide important new insights into cerebrovascular physiology and brain function that are of great significance to the neuroscience community.

Wang, Xueding; Xie, Xueyi; Ku, Geng; Stoica, George; Wang, Lihong V.

2005-04-01

322

Thermal Image of Coffee-Seed Germ Obtained by Photoacoustic Microscopy  

NASA Astrophysics Data System (ADS)

Photoacoustic microscopy (PAM) has been shown to be a suitable technique to obtain thermal images of a wide variety of samples from semiconductors to biological material. In PAM, the incidence of a modulated laser beam on a sample within a photoacoustic (PA) cell, hermetically sealed, produces a PA signal which depends on the thermal and optical properties of the studied sample. By making a sweep of the modulated laser beam on the sample surface, it is possible to obtain the PA signal as a function of their x- y coordinates, and from this signal, it is possible to reconstruct thermal images of the sample. In this study, thermal images of a coffee-seed germ were obtained, with a difference of 12 h between them, by using the PAM technique. Thermal differences observed between images give information which reflects degradation due to the fact that germ cells undergo changes as a function of time. The thermal images obtained by the PAM technique could be applied to biological materials that have a complex constitution (not homogeneous) in their structures, and thermal differences can be observed. PAM is a non-destructive technique, which is an important feature for this type of study. Other applications of this technique can be performed in the agricultural and biotechnological areas.

Domínguez-Pacheco, A.; Hernández Aguilar, C.; Cruz-Orea, Alfredo; Isaac Alemán, E.; Martínez Ortiz, E.

2013-09-01

323

Improved current and charge amplifiers for driving piezoelectric loads  

E-print Network

Improved current and charge amplifiers for driving piezoelectric loads Andrew J. Fleming and S. O, Callaghan 2308, Australia. ABSTRACT Piezoelectric transducers are known to exhibit less hysterisis when, Piezoelectric, Capacitive, Load, Amplifier, Zero Offset, Compliance, Feedback 1. INTRODUCTION Piezoelectric

Fleming, Andrew J.

324

Piezoactuator Design Considering the Optimum Placement of FGM Piezoelectric Material  

E-print Network

Piezoactuator Design Considering the Optimum Placement of FGM Piezoelectric Material Ronny C has been explored in piezoelectric materials to improve properties and to increase the lifetime of piezoelectric actuators. Elastic, piezoelectric, and dielectric properties are graded along the thickness

Paulino, Glaucio H.

325

Stabilization of a piezoelectric system  

E-print Network

We consider a stabilization problem for a piezoelectric system. We prove an exponential stability result under some Lions geometric condition. Our method is based on an identity with multipliers that allows to show an appropriate observability estimate.

Ammari, K

2010-01-01

326

Modeling of Piezoelectric Tube Actuators  

E-print Network

A new dynamic model is presented for piezoelectric tube actuators commonly used in high-precision instruments. The model captures coupling between motions in all three axes such as bending motion due to a supposedly pure ...

El Rifai, Osamah M.

327

Piezoelectric MEMS for energy harvesting  

E-print Network

Piezoelectric microelectromechanical systems (MEMS) have been proven to be an attractive technology for harvesting small magnitudes of energy from ambient vibrations. This technology promises to eliminate the need for ...

Kim, Sang-Gook

328

Piezoelectric Rotary Tube Motor  

NASA Technical Reports Server (NTRS)

A custom rotary SQUIGGLE(Registered TradeMark) motor has been developed that sets new benchmarks for small motor size, high position resolution, and high torque without gear reduction. Its capabilities cannot be achieved with conventional electromagnetic motors. It consists of piezoelectric plates mounted on a square flexible tube. The plates are actuated via voltage waveforms 90 out of phase at the resonant frequency of the device to create rotary motion. The motors were incorporated into a two-axis postioner that was designed for fiber-fed spectroscopy for ground-based and space-based projects. The positioner enables large-scale celestial object surveys to take place in a practical amount of time.

Fisher, Charles D.; Badescu, Mircea; Braun, David F.; Culhane, Robert

2011-01-01

329

A Resonant Damping Study Using Piezoelectric Materials  

NASA Technical Reports Server (NTRS)

Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.

Min, J. B.; Duffy, K. P.; Choi, B. B.; Morrison, C. R.; Jansen, R. H.; Provenza, A. J.

2008-01-01

330

Optical wavelength selection for improved spectroscopic photoacoustic imaging?  

PubMed Central

Spectroscopic photoacoustic imaging has the potential to become a powerful tool that can estimate distributions of optically absorbing chromophores in the body. We have developed an algorithm to select imaging wavelengths for spectroscopic photoacoustics given the spectra of expected chromophores. The algorithm uses the smallest singular value of a matrix constructed from the absorption spectra as a criterion to remove extraneous wavelengths. The method performed significantly better than an approach where evenly spaced wavelengths were used in the presence of noise and wavelength-dependent attenuation of light in tissue. Finally, the algorithm was applied to photoacoustic imaging of a phantom containing indocyanine green dye and silica-coated gold nanorods, demonstrating significant improvements in the ability to estimate relative contrast agent concentrations compared to the case where evenly spaced wavelengths were chosen. In summary, our work provides a versatile framework to select optical wavelengths and evaluate sets of absorbers for spectroscopic photoacoustic imaging.

Luke, Geoffrey P.; Nam, Seung Yun; Emelianov, Stanislav Y.

2013-01-01

331

Thermal stability of biodegradable plasmonic nanoclusters in photoacoustic imaging  

PubMed Central

The photothermal stability of plasmonic nanoparticles is critically important to perform reliable photoacoustic imaging and photothermal therapy. Recently, biodegradable nanoclusters composed of sub-5 nm primary gold particles and a biodegradable polymer have been reported as clinically-translatable contrast agents for photoacoustic imaging. After cellular internalization, the nanoclusters degrade into 5 nm primary particles for efficient excretion from the body. In this paper, three different sizes of biodegradable nanoclusters were synthesized and the optical properties and photothermal stability of the nanoclusters were investigated and compared to that of gold nanorods. The results of our study indicate that 40 nm and 80 nm biodegradable nanoclusters demonstrate higher photothermal stability compared to gold nanorods. Furthermore, 40 nm nanoclusters produce higher photoacoustic signal than gold nanorods at a given concentration of gold. Therefore, the biodegradable plasmonic nanoclusters can be effectively used for photoacoustic imaging and photothermal therapy. PMID:23388774

Yoon, Soon Joon; Murthy, Avinash; Johnston, Keith P.; Sokolov, Konstantin V.; Emelianov, Stanislav Y.

2012-01-01

332

Photoacoustic image-guided needle biopsy of sentinel lymph nodes  

NASA Astrophysics Data System (ADS)

We have implemented a hand-held photoacoustic and ultrasound probe for image-guided needle biopsy using a modified clinical ultrasound array system. Pulsed laser light was delivered via bifurcated optical fiber bundles integrated with the hand-held ultrasound probe. We photoacoustically guided needle insertion into rat sentinel lymph nodes (SLNs) following accumulation of indocyanine green (ICG). Strong photoacoustic image contrast of the needle was achieved. After intradermal injection of ICG in the left forepaw, deeply positioned SLNs (beneath 2-cm thick chicken breast) were easily indentified in vivo and in real time. Further, we confirmed ICG uptake in axillary lymph nodes with in vivo and ex vivo fluorescence imaging. These results demonstrate the clinical potential of this hand-held photoacoustic system for facile identification and needle biopsy of SLNs for cancer staging and metastasis detection in humans.

Kim, Chulhong; Erpelding, Todd N.; Akers, Walter J.; Maslov, Konstantin; Song, Liang; Jankovic, Ladislav; Margenthaler, Julie A.; Achilefu, Samuel; Wang, Lihong V.

2011-03-01

333

Photoacoustic measurement of the Grüneisen parameter of tissue  

NASA Astrophysics Data System (ADS)

The Grüneisen parameter, a constitutive parameter in photoacoustics, is usually measured from isobaric thermal expansion, which may not be valid for a biological medium due to its heterogeneity. Here, we directly measured the Grüneisen parameter by applying photoacoustic spectroscopy. Laser pulses at wavelengths between 460 and 1800 nm were delivered to tissue samples, and photoacoustic signals were detected by flat water-immersion ultrasonic transducers. Least-squares fitting photoacoustic spectra to molar optical absorption spectra showed that the Grüneisen parameter was 0.81±0.05 (mean±SD) for porcine subcutaneous fat tissue and 0.69±0.02 for porcine lipid at room temperature (22°C). The Grüneisen parameter of a red blood cell suspension was linearly related to hemoglobin concentration, and the parameter of bovine serum was 9% greater than that of water at room temperature.

Yao, Da-Kang; Zhang, Chi; Maslov, Konstantin; Wang, Lihong V.

2014-01-01

334

Photoacoustic measurement of the Grüneisen parameter of tissue.  

PubMed

The Grüneisen parameter, a constitutive parameter in photoacoustics, is usually measured from isobaric thermal expansion, which may not be valid for a biological medium due to its heterogeneity. Here, we directly measured the Grüneisen parameter by applying photoacoustic spectroscopy. Laser pulses at wavelengths between 460 and 1800 nm were delivered to tissue samples, and photoacoustic signals were detected by flat water-immersion ultrasonic transducers. Least-squares fitting photoacoustic spectra to molar optical absorption spectra showed that the Grüneisen parameter was 0.81±0.05 (mean±SD) for porcine subcutaneous fat tissue and 0.69±0.02 for porcine lipid at room temperature (22°C). The Grüneisen parameter of a red blood cell suspension was linearly related to hemoglobin concentration, and the parameter of bovine serum was 9% greater than that of water at room temperature. PMID:24474512

Yao, Da-Kang; Zhang, Chi; Maslov, Konstantin; Wang, Lihong V

2014-01-01

335

Fabrication and characterization of piezoelectric thick film elements and arrays  

Microsoft Academic Search

PZT thick film discs have been produced in the range of 100-200 ?m using screen printing technology and suitable new ink prepared with piezoelectric powder as main active component. After poling, characterization of electrical impedance was made and an acoustic spectroscopy technique used to analyze the vibrating behavior of PZT discs over different substrates in order to know typical parameters

Sergio Gwirc; S. Tropea; C. Negreira; N. Perez; F. M. de Espinosa

2000-01-01

336

Development of novel piezoelectric ceramics and composites for transducer applications  

Microsoft Academic Search

Over the last decade, several methods were utilized to develop novel piezoelectric ceramic\\/polymer composites for transducer applications. Solid freeform fabrication (SFF) is one of the methods that have been emphasized recently. SFF techniques have been used to fabricate polymer, metal or ceramic structures on a fixtureless platform, directly from a computer aided design file. During design verification or the product

Ahmad Safari; Stephen C. Danforth

1998-01-01

337

Piezoelectric lead zirconate titanate ceramic fiber\\/polymer composites  

Microsoft Academic Search

This papers on piezoelectric lead zirconate titanate (PZT) ceramic fiber\\/polymer composite were fabricated by a novel technique referred to as relic processing. Basically, this involved impregnating a woven carbon-fiber template material with PZT precursor by soaking the template in a PZT stock solution. Careful heat treatment pyrolized the carbon, resulting in a PZT ceramic relic that retained the fibrous template

David J. Waller; P. Safari

1992-01-01

338

Non-contact photoacoustic tomography and ultrasonography for brain imaging  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography (PAT) and ultrasonography (US) of biological tissues usually rely on transducer arrays for the detection of ultrasound. Obtaining the best sensitivity requires a physical contact with the tissue using an intermediate coupling fluid (water or gel). This type of contact is a major drawback for several applications such as neurosurgery. Laser-ultrasonics is an established optical technique for the non-contact generation and detection of ultrasound in industrial materials. In this paper, the non-contact detection scheme used in laser-ultrasonics is adapted to allow probing of ultrasound in biological tissues while remaining below laser exposure safety limits. Both non-contact PAT (NCPAT) and non-contact US (NCUS) are demonstrated experimentally using a single-frequency detection laser emitting suitably shaped pulses and a confocal Fabry-Perot interferometer. It is shown that an acceptable sensitivity is obtained while remaining below the maximum permissible exposure (MPE) of biological tissues. Results obtained ex vivo with a calf brain specimen show that sub-mm endogenous and exogenous inclusions can be detected at depths exceeding 1 cm. When fully developed, the technique could be a unique diagnostic tool in neurosurgery providing deep imaging of blood vessels, blood clots and blood oxygenation.

Rousseau, Guy; Blouin, Alain; Monchalin, Jean-Pierre

2012-02-01

339

Some carcinogenic polycyclic aromatic hydrocarbons by photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

Polycyclic aromatic hydrocarbons (PAHs) have attracted spectroscopists, astrophysicts and environmentalist because of their importance in our day to day life. It is well known that epoxides are produced during the metabolism of PAHs and have the requisite chemical reactivity to qualify them for the role as an ultimate carcinogenic form of PAHs. Several carcinogenic PAHs such as 3.4-benzopyrene, 1.2,3.4-dibenzopyrene, 3.4,9.10- dibenzopyrene etc. are found to be present in tobacco smoke and among air pollutants. Although PAH molecules are being studied for last several years by using conventional spectroscopy but no systematic attempt has been made to study non-radiative transitions. In our laboratory, we have studied many PAH molecules by a non-destructive technique with unique capability and sensitivity, known as Photoacoustic (PA) spectroscopy. PA spectroscopy is an analytical and research tool to get information about non-radiative transitions and singlet-triplet electronic transitions, where the conventional spectroscopic technique fails. The study of electronic transitions of some carcinogenic molecules are reported using PA and optical absorption spectra in boric acid glass in the region 250 - 400 nm. The electronic transitions of these molecules observed experimentally, have been interpreted using the optimized geometries and CNDO/S-CI method. A good agreement is found between the experimental and calculated results. Assignments of observed electronic transitions are made on the basis of singlet-triplet electronic transitions. Vibrations attached to these electronic transitions are attributed to the ground state vibrational modes.

Garg, R. K.; Kumar, Pardeep; Ram, R. S.; Zaidi, Zahid H.

1999-12-01

340

Compact photo-acoustic chemical sensor  

NASA Astrophysics Data System (ADS)

The present security environment has created a need for robust, sensitive, portable gas-phase chemical sensors. The ready availability of high performance quantum cascade lasers, which can operate at ambient temperatures with only thermoelectric cooling, has made the possibility of such sensors quite realistic. A compact, sensitive, cost-effective photo-acoustic sensor capable of sub-part-per-million sensitivity is described. The sensor can be entirely selfcontained in a small volume weighing only a few pounds. The quantum cascade laser is enclosed in a sealed package incorporating a collimating lens and thermoelectric cooler. The package sits on an external thermoelectric cooler. Both the laser and thermoelectric coolers are driven by a self-contained power supply and controller specifically designed for the purpose. The photo-acoustic gas cell contains input and output ports and anti-reflection coated optical windows. Details of the sensor's configuration and performance will be described as it relates to explosive detection using thermal fragmentation.

Wells, David N.

2009-05-01

341

Functional photoacoustic microscopy of diabetic vasculature  

PubMed Central

Abstract. We used functional photoacoustic microscopy to image diabetes-induced damage to the microvasculature. To produce an animal model for Type 1 diabetes, we used streptozotocin (STZ), which is particularly toxic to the insulin-producing beta cells of the pancreas in mammals. A set number of ND4 Swiss Webster mice received intraperitoneal injections of STZ for five consecutive days at 50?mg/kg. Most mice developed a significant rise in blood glucose level (?400?mg/dL) within three weeks of the first injection. Changes in vasculature and hemodynamics were monitored for six weeks. The mouse ear was imaged with an optical-resolution photoacoustic microscope at a main blood vessel branch from the root of the ear. There are noticeable and measurable changes associated with the disease, including decreased vessel diameter and possible occlusion due to vessel damage and polyurea. We also observed an increase in the blood flow speed in the vein and a decrease in the artery, which could be due to compensation for the dehydration and vessel diameter changes. Functional and metabolic parameters such as hemoglobin oxygen saturation, oxygen extraction fraction, and oxygen consumption rate were also measured, but showed no significant change. PMID:22734725

Krumholz, Arie; Wang, Lidai; Yao, Junjie; Wang, Lihong V.

2012-01-01

342

Functional photoacoustic microscopy of diabetic vasculature.  

PubMed

We used functional photoacoustic microscopy to image diabetes-induced damage to the microvasculature. To produce an animal model for Type 1 diabetes, we used streptozotocin (STZ), which is particularly toxic to the insulin-producing beta cells of the pancreas in mammals. A set number of ND4 Swiss Webster mice received intraperitoneal injections of STZ for five consecutive days at 50 mg/kg. Most mice developed a significant rise in blood glucose level (? 400 mg/dL) within three weeks of the first injection. Changes in vasculature and hemodynamics were monitored for six weeks. The mouse ear was imaged with an optical-resolution photoacoustic microscope at a main blood vessel branch from the root of the ear. There are noticeable and measurable changes associated with the disease, including decreased vessel diameter and possible occlusion due to vessel damage and polyurea. We also observed an increase in the blood flow speed in the vein and a decrease in the artery, which could be due to compensation for the dehydration and vessel diameter changes. Functional and metabolic parameters such as hemoglobin oxygen saturation, oxygen extraction fraction, and oxygen consumption rate were also measured, but showed no significant change. PMID:22734725

Krumholz, Arie; Wang, Lidai; Yao, Junjie; Wang, Lihong V

2012-06-01

343

Photoacoustic microtomography using optical interferometric detection.  

PubMed

A device for three-dimensional (3-D) photoacoustic tomography with resolution in the range of tens of micrometers is presented that uses a light beam for interferometric detection of acoustic waves. Reconstruction of the 3-D initial pressure distribution from the signals representing line integrals of the acoustic field is a two-step process. It uses an inversion of 2-D wave propagation to obtain line projections of the initial pressure distribution and the inverse Radon transform. The light beam, propagating freely in a water bath, is scanned either in an arc- or box-shaped curve around the object. Simulations are performed to compare the two scanning procedures. The projection images are obtained either using the filtered back projection algorithm for the pi-arc scanning mode or the frequency domain algorithm for the box scanning mode. While the former algorithm provides slightly better image quality, the latter is about 20 times faster. The ability of the photoacoustic tomography device to create 3-D images with constant resolution throughout the reconstruction volume is demonstrated experimentally using a human hair phantom. These measurements revealed a 3-D resolution below 100 mum. In a second experiment, 3-D imaging of an isolated mouse heart is demonstrated to show the applicability for preclinical and biological research. PMID:20459229

Nuster, Robert; Holotta, Markus; Kremser, Christian; Grossauer, Harald; Burgholzer, Peter; Paltauf, Günther

2010-01-01

344

Functional photoacoustic microscopy of diabetic vasculature  

NASA Astrophysics Data System (ADS)

We used functional photoacoustic microscopy to image diabetes-induced damage to the microvasculature. To produce an animal model for Type 1 diabetes, we used streptozotocin (STZ), which is particularly toxic to the insulin-producing beta cells of the pancreas in mammals. A set number of ND4 Swiss Webster mice received intraperitoneal injections of STZ for five consecutive days at 50 mg/kg. Most mice developed a significant rise in blood glucose level (~400 mg/dL) within three weeks of the first injection. Changes in vasculature and hemodynamics were monitored for six weeks. The mouse ear was imaged with an optical-resolution photoacoustic microscope at a main blood vessel branch from the root of the ear. There are noticeable and measurable changes associated with the disease, including decreased vessel diameter and possible occlusion due to vessel damage and polyurea. We also observed an increase in the blood flow speed in the vein and a decrease in the artery, which could be due to compensation for the dehydration and vessel diameter changes. Functional and metabolic parameters such as hemoglobin oxygen saturation, oxygen extraction fraction, and oxygen consumption rate were also measured, but showed no significant change.

Krumholz, Arie; Wang, Lidai; Yao, Junjie; Wang, Lihong V.

2012-06-01

345

Photoacoustic study of the photostability of sunscreens  

NASA Astrophysics Data System (ADS)

Although solar radiation is essential for maintenance of life in Earth, excessive exposition to the ultraviolet radiation emitted by the sun may cause sunburns, early aging and even cancer lesions. Sunscreens act absorbing or reflecting ultraviolet radiation; in this way, they protect the skin against the damages caused by excessive absorption of ultraviolet radiation. Sunscreens must present photostability, that is the capacity of a product to be retained in skin without degradation by light incidence. The present study aimed to evaluate, through photoacoustic spectroscopy (PAS) measurements, the photostability of a sunscreen commercially available in Brazil. PAS measurements were performed at 19 Hz, for wavelengths between 270 nm and 400 nm, using a sunscreen with solar protection factor (SPF) 15 applied in skin samples. Photoacoustic spectra of the sunscreen applied to the skin were obtained and analyzed as a function of time after application. Photostability was then evaluated by the comparative study of the integrated areas of the absorption curves for the sunscreen applied to the skin. Results indicate that the sunscreen analyzed was photostable for a large period and was not completely removed by cleaning.

da Cruz, V. M. F. R.; Acosta-Avalos, D.; Barja, P. R.

2008-01-01

346

First-principles based multiscale model of piezoelectric nanowires with surface effects  

NASA Astrophysics Data System (ADS)

A continuum model of nanowires incorporating surface piezoelectricity is proposed which extends the electric enthalpy energy with surface terms. The corresponding equations are solved by a numerical method using finite elements technique. A methodology is introduced to compute the surface piezoelectric coefficients by first-principles calculations through the Berry phase theory. We provide the e33s, e31s, and e15s piezoelectric coefficients of (101¯0) surfaces for hexagonal wurtzite nanowires made of GaN, ZnO, and AlN. The effective piezoelectric coefficient along the axis of the nanowire is found to increase when the diameter decreases, for the three studied materials. Finally, the solution of the continuum model is compared with large-size first-principles calculations on piezoelectric nanowires.

Hoang, M.-T.; Yvonnet, J.; Mitrushchenkov, A.; Chambaud, G.

2013-01-01

347

Photoacoustic imaging using a two-dimensional CMUT array  

Microsoft Academic Search

Photoacoustic imaging is a promising complement to pulse-echo ultrasound imaging because it provides contrast between areas with different light absorption characteristics. Specifically, regions with higher blood concentration can be identified, which is useful for imaging vascularization and the early detection of cancer. Here we present volumetric photoacoustic images of a vessel-like phantom. The phantom consists of three 1.3-mm diameter tubes

I. O. Wygant; X. Zhuang; P. S. Kuo; D. T. Yeh; O. Oralkan; B. T. Khuri-Yakub

2005-01-01

348

Fast-scanning ultrasonic-photoacoustic biomicroscope: in vivo performance  

NASA Astrophysics Data System (ADS)

The combination of ultrasonic and photoacoustic imaging modalities has yet to be realized in the high-frequency regime (>20MHz) where spatial resolution may permit visualization of the microvasculature. In this work, we characterize the in-vivo performance of a custom ultrasound-photoacoustic B-scanning imaging system. This system utilizes a combined ultrasound/photoacoustic probe attached to a voice-coil capable of approximately 1cm lateral translation at a rate of up to 15Hz. The probe is comprised of a 25MHz ultrasound transducer, configured confocally with a conical mirror-based dark-field laser delivery system. The fast-scanning mode permits realtime ultrasound imaging. The imaging speed of the photoacoustic mode is limited by the repetition rate of the 532nm laser (up to 20Hz). Signals from the transducer are amplified by a 39dB preamp with an additional time-gain compensation stage of up to 24dB. Control of the system is through a digital input-output PCI card, which acts as a pulse-sequencer and permits software control of time-gain compensation. This setup permits interlaced pulse sequences for excellent registration of ultrasonic and photoacoustic data, as well as separate timegain compensation curves for photoacoustic and ultrasound modalities. We have managed to achieve a lateral resolution of 155 ?m and an axial resolution of 40 ?m. The system is used to visualize the finger and palm of a hand to almost 1cm ultrasound depths and multiple millimeter-scale photoacoustic depths. Photoacoustic images are overlaid on the ultrasound images for simultaneous visualization of the microvasculature and surrounding tissue.

Harrison, Tyler; Ranasinghesagara, Janaka; Lu, Huihong; Zemp, Roger J.

2010-02-01

349

Photoacoustic computed tomography in biological tissues: algorithms and breast imaging  

E-print Network

PHOTOACOUSTIC COMPUTED TOMOGRAPHY IN BIOLOGICAL TISSUES: ALGORITHMS AND BREAST IMAGING A Dissertation by MINGHUA XU Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of DOCTOR OF PHILOSOPHY August 2004 Major Subject: Biomedical Engineering PHOTOACOUSTIC COMPUTED TOMOGRAPHY IN BIOLOGICAL TISSUES: ALGORITHMS AND BREAST IMAGING A Dissertation by MINGHUA XU Submitted to Texas A...

Xu, Minghua

2004-11-15

350

Mechanical Design and Material Characterization of the Piezoelectric Energy Harvestor  

NASA Astrophysics Data System (ADS)

This paper is on the proposal of the methodology for the design and fabrication of the piezoelectric energy harvesting devices in viewpoint of the justification both structural and material properties. There has been developing various kinds of energy harvesting techniques using piezoelectric films. Most of them are for the justification of the design or the circuit. The output of the piezoelectric harvester is the product of the material and structural parts. It is, therefore, necessary to justify both of them simultaneously. In this paper cantilever structure was fabricated for the improvement of the power generation in the low frequency region. The resonant frequency and output voltage and charge from the following theory formula were calculated in this study.

Ichiki, M.; Komine, E.; Sueshige, K.; Iimura, K.; Kobayashi, T.; Kitahara, T.; Fujimoto, S.

2013-12-01

351

The piezoelectric sorption technique: a practical method  

E-print Network

-cut crystals to a mass addition of 130 micrograms of silicone oil, arbitrary F LIST OF TABLES TABLE PAGE 1. PRESSURE AND VISCOUS EFFECTS FOR NITROGEN. . . . . 2. VISCOUS EFFECT FOR SOME COMMMON HYDROCARBONS AND NITROGEN AT 0. 1 MPa. 54 55 3. Q... LLI CI 0 O -25 F- Fo, Hz 25 Figure 10. Power dissipation for a typical 10 MHz AT-cut quartz crystal. 46 Crystal PT4 Fo = 9. 990909 MHz Power = O. IOmW Q= II, 900 I- a I- O LIJ O 0 Cl -5 -4 -3 -2 -I 0 I 2 3 4 5 F-Fo, kHz Figure 11...

Flipse, Eugene Charles

2012-06-07

352

Characterization of ultrathin films by laser-induced sub-picosecond photoacoustics with coherent extreme ultraviolet detection  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is a powerful tool for characterizing thin films. In this paper we demonstrate a new photoacoustic technique that allows us to precisely characterize the mechanical properties of ultrathin films. We focus an ultrafast laser onto a nano-patterned thin film sample, launching both surface acoustic waves (SAWs) and longitudinal acoustic waves (LAWs). Coherent extreme ultraviolet pulses are then used to probe the propagation dynamics of both the SAWs and LAWs. The resulting photoacoustic signal on both short (picosecond) and long (nanosecond) time scales yields important information. In the first 100ps, a fast oscillation followed by an echo signal corresponds to LAWs traveling inside the nanostructures and the thin film, from which the LAW velocities in the two materials can be extracted. On longer time-scales, SAW oscillations are observed. By combining the measured SAW frequency with the wavelength (determined by the nanostructure period) the SAW velocity can be accurately determined, even for very short wavelength surface acoustic waves with very small penetration depths. Using this technique, the elastic properties, including the Young's modulus and Poisson ratio for the thin film, can be obtained in a single measurement, this technique can be extended to sub-10nm thin films.

Li, Qing; Hoogeboom-Pot, Kathleen; Nardi, Damiano; Deeb, Chris; King, Sean; Tripp, Marie; Anderson, Erik; Murnane, Margaret M.; Kapteyn, Henry C.

2012-03-01

353

Sensitive absorption measurements in bulk material and coatings using a photothermal and a photoacoustic spectrometer  

NASA Astrophysics Data System (ADS)

Bulk and surface absorption in lithium triborate (LBO) and lithium niobate (LiNbO3) are measured using two sensitive measurement techniques, a photoacoustic spectrometer (PAS) and a photothermal common-path interferometer (PCI). As pump light sources, optical parametric oscillators are employed, covering the wavelength ranges 212 - 2500 nm (PAS) and 1460 - 1900 nm and 2460 - 3900 nm (PCI). The spectrometers are used to measure absorption spectra of optical materials across this wide spectral range and to compare the methods in the shared wavelength regime.

Fieberg, S.; Waasem, N.; Kühnemann, F.; Buse, K.

2014-02-01

354

Detection of soybean rust contamination in soy leaves by FTIR photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

In this work the Photoacoustic Infrared Spectroscopy from 4000 to 400 cm-1 was applied, by the first time to our knowledge, to diagnostic the soy bean rust or Asian rust contamination on soy leafs caused by the fungi Phakopsora pachyrhizi. The obtained results shown that a premature, fast and precise diagnosis can be achieved using this technique before it can be detect by the conventional visual method. The early identification of the fungi infection avoid massive lost in the soy production and decrease the intense use of fungicide whose is necessary when the infection is in advanced stagy.

Andrade, L. H. C.; Freitas, P. G.; Mantovani, B. G.; Figueiredo, M. S.; Lima, R. A.; Lima, S. M.; Rangel, M. A. S.; Mussury, R. M.

2008-01-01

355

3D high resolution photoacoustic imaging based on pure optical photoacoustic microscopy with microring resonator  

NASA Astrophysics Data System (ADS)

For three-dimensional imaging of optical absorbance, the existing technology of photoacoustic microscopy (PAM) has quite poor axial resolution, the tens of microns to hundreds of microns. This is despite the fact that PAM has recently achieved lateral resolutions on the order of a micron or submicron, comparable to that of optical microscopy. In this paper, a pure optical photoacoustic microscopy (POPAM) with optical rastering of a focused excitation beam and optically sensing of the photoacoustic signal using a microring resonator was developed with the super broad bandwidth of the system more than 350MHz. With unprecedented broad bandwidth of POPAM, 3.8?m axial resolution was achieved without deconvolution processing. Sectioning imaging ability along axial direction presenting 3D morphologic features was shown based on imaging printed phantom. The impact of this approach will be similar to how confocal optical microscopy revolutionized the conventional optical microscopy by enabling the axial sectioning capability. Tissue imaging comparing POPAM and conventional PAM based on needle hydrophone demonstrated that though such broad bandwidth compromised the sensitivity of POPAM 4.35 times than that of conventional PAM, the noise equivalent detectable pressure (NEDP) was estimated as 74Pa, still able to get the tissue imaging.

Xie, Zhixing; Tian, Chao; Chen, Sung-Liang; Ling, Tao; Zhang, Cheng; Guo, L. Jay; Carson, Paul L.; Wang, Xueding

2014-03-01

356

Calibration of piezoelectric positioning actuators using a reference voltage-to-displacement transducer based on quartz tuning forks  

E-print Network

We use a piezoelectric quartz tuning fork to calibrate the displacement of ceramic piezoelectric scanners which are widely employed in scanning probe microscopy. We measure the static piezoelectric response of a quartz tuning fork and find it to be highly linear, non-hysteretic and with negligible creep. These performance characteristics, close to those of an ideal transducer, make quartz transducers superior to ceramic piezoelectric actuators. Furthermore, quartz actuators in the form of a tuning fork have the advantage of yielding static displacements comparable to those of local probe microscope scanners. We use the static displacement of a quartz tuning fork as a reference to calibrate the three axis displacement of a ceramic piezoelectric scanner. Although this calibration technique is a non-traceable method, it can be more versatile than using calibration grids because it enables to characterize the linear and non-linear response of a piezoelectric scanner in a broad range of displacements, spanning fro...

Castellanos-Gomez, Andres; Agraït, Nicolás; Rubio-Bollinger, Gabino; 10.1017/S1431927611012839

2012-01-01

357

Piezoelectrically Initiated Pyrotechnic Igniter  

NASA Technical Reports Server (NTRS)

This innovation consists of a pyrotechnic initiator and piezoelectric initiation system. The device will be capable of being initiated mechanically; resisting initiation by EMF, RF, and EMI (electromagnetic field, radio frequency, and electromagnetic interference, respectively); and initiating in water environments and space environments. Current devices of this nature are initiated by the mechanical action of a firing pin against a primer. Primers historically are prone to failure. These failures are commonly known as misfires or hang-fires. In many cases, the primer shows the dent where the firing pin struck the primer, but the primer failed to fire. In devices such as "T" handles, which are commonly used to initiate the blowout of canopies, loss of function of the device may result in loss of crew. In devices such as flares or smoke generators, failure can result in failure to spot a downed pilot. The piezoelectrically initiated ignition system consists of a pyrotechnic device that plugs into a mechanical system (activator), which on activation, generates a high-voltage spark. The activator, when released, will strike a stack of electrically linked piezo crystals, generating a high-voltage, low-amperage current that is then conducted to the pyro-initiator. Within the initiator, an electrode releases a spark that passes through a pyrotechnic first-fire mixture, causing it to combust. The combustion of the first-fire initiates a primary pyrotechnic or explosive powder. If used in a "T" handle, the primary would ramp the speed of burn up to the speed of sound, generating a shock wave that would cause a high explosive to go "high order." In a flare or smoke generator, the secondary would produce the heat necessary to ignite the pyrotechnic mixture. The piezo activator subsystem is redundant in that a second stack of crystals would be struck at the same time with the same activation force, doubling the probability of a first strike spark generation. If the first activation fails to ignite, the device is capable of multiple attempts. Another unique aspect is in the design of the pyrotechnic device. There is an electrode that aids the generation of a directed spark and the use of a conductive matrix to support the first-fire material so that the spark will penetrate to the second electrode.

Quince, Asia; Dutton, Maureen; Hicks, Robert; Burnham, Karen

2013-01-01

358

Photoacoustic Spectroscopy of Candida albicans Treated with Methylene Blue  

NASA Astrophysics Data System (ADS)

In the present work the phototoxic effect of methylene blue (MB) on Candida albicans cultures was studied using the photoacoustic spectroscopy (PAS) technique. An aliquot of 50 ?L of C. albicans suspension—strain ATCC 10-231—was incubated with 50 ?L of MB solution (0.5 mg/mL), at room temperature. After the proper incubation time, a colony forming unit (CFU) with approximately 3 mm diameter was chosen in each plate. The CFU selected was irradiated using an InGaAlP laser during 20 s. After irradiation and new incubation, the CFUs were collected and stored at -70 °C, until spectroscopy analysis. The spectroscopy analysis was performed using an open PAS setup. The study was conducted in different groups: (1) control (non-treated); (2) irradiated with laser light; (3) treated with MB (non-irradiated); and (4) treated with MB and irradiated with laser light. The PAS measurements were performed on C. albicans in a sterile physiological solution. The measurements indicate that the presence of MB and irradiation promotes a change in the redox state of the cells to the reduced state. The absorption spectrum after photodynamic therapy (PDT) was observed 12 h and 36 h later. It was inferred that PDT can be related to structural changes in cytochrome molecules after 36 h. It is concluded that MB can be an efficient photosensitizer in C. albicans through modification of the cytochrome molecule affecting the cell metabolism.

Acosta-Avalos, D.; Jedlicka, L. D. L.; Costa, M. S.; Barja, P. R.; da Silva, E. C.

2012-11-01

359

Photoacoustic diagnosis of human teeth using interferometric detection scheme  

NASA Astrophysics Data System (ADS)

We have investigated the mechanical and acoustic properties of human teeth using the laser generation of surface acoustic wave (SAW) technique. The materials investigated included normal and decayed teeth, which have similar grain sizes and different thicknesses. The tissue responds to the laser-induced stress by thermoelastic expansion. The informative features of this method allow one to determine sample thermal, optical, and acoustical properties that depend on the peculiarities of the sample compositional structure. An interferometric detection experimental scheme is applied for detection generated SAW pulses. The surface displacement curves shape of normal and decayed human teeth are shown. The dispersion curves for SAW pulses were determined by Fourier analysis. The result is an almost linear dependence of SAW velocity on frequency for a normal tooth, the magnitude of the thermoelastic expansion of the normal tooth reaches its peak at 0.344 ?s, a SAW phase velocity of 2500 ms-1 between 0.0008 and 5 MHz was determined. For abnormal teeth, the magnitude of thermoelastic expansion of the normal tooth reaches its peak at 1.3 ?s, the measured velocity was 3225 ms-1. Due to the inhomogeneity of abnormal teeth perpendicular to the propagation direction, strong differences in their dispersion curves were obtained. The detection of acoustic waves is the basis of photoacoustic methods, which can be used for diagnostic purposes.

El-Sharkawy, Yasser H.; El Sherif, Ashraf F.

2012-07-01

360

Small-animal whole-body photoacoustic tomography: a review.  

PubMed

With the wide use of small animals for biomedical studies, in vivo small-animal whole-body imaging plays an increasingly important role. Photoacoustic tomography (PAT) is an emerging whole-body imaging modality that shows great potential for preclinical research. As a hybrid technique, PAT is based on the acoustic detection of optical absorption from either endogenous tissue chromophores, such as oxyhemoglobin and deoxyhemoglobin, or exogenous contrast agents. Because ultrasound scatters much less than light in tissue, PAT generates high-resolution images in both the optical ballistic and diffusive regimes. Using near-infrared light, which has relatively low blood absorption, PAT can image through the whole body of small animals with acoustically defined spatial resolution. Anatomical and vascular structures are imaged with endogenous hemoglobin contrast, while functional and molecular images are enabled by the wide choice of exogenous optical contrasts. This paper reviews the rapidly growing field of small-animal whole-body PAT and highlights studies done in the past decade. PMID:24108456

Xia, Jun; Wang, Lihong V

2014-05-01

361

Fiber optics photoacoustic generation using gold nanoparticles as target  

NASA Astrophysics Data System (ADS)

Ultrasound transducers have been used in various applications such as nondestructive testing, acoustic response analysis of vascular tissues, and medical imaging. Most recent applications lead to a demand of more advanced ultrasound generators featuring higher central frequency, wider bandwidth and miniature size. In this paper, a novel ultrasound generator on an optical fiber tip is designed, fabricated and characterized. The ultrasound generator was fabricated by coating several layers of gold nanoparticles (Au NPs) on the end face of a piece of commercially available optical fiber via a layer-by-layer (L-b-L) technique. The Au NPs were synthesized by a traditional sodium citrate reduction method and the diameter of Au NPs was controlled at 20 nm. The ultrasound is generated through photoacoustic procedure. By introducing excitation laser pulses on the Au NPs layer, the energy of laser is converted into the heat through photothermal mechanism. Then, the heat transforms into kinetic energy through thermalelastic mechanism. Thus, ultrasound can be generated. The experiment results showed that this kind of ultrasound generator shows wide bandwidth, high frequency and miniature size. By comparing to the conventional energy absorption material such as graphite, the Au NPs show high energy absorption efficiency and high thermal expansion rate. Therefore, the generator exhibits great potentials in intravascular imaging due to its miniature size.

Wu, Nan; Sun, Kai; Wang, Xingwei

2011-04-01

362

Photothermal and photoacoustic Raman cytometry in vitro and in vivo  

PubMed Central

An integrated Raman-based cytometry was developed with photothermal (PT) and photoacoustic (PA) detection of Raman-induced thermal and acoustic signals in biological samples with Raman-active vibrational modes. The two-frequency, spatially and temporally overlapping pump–Stokes excitation in counterpropagating geometry was provided by a nanosecond tunable (420–2300 nm) optical parametric oscillator and a Raman shifter (639 nm) pumped by a double-pulsed Q-switched Nd:YAG laser using microscopic and fiberoptic delivery of laser radiation. The PA and PT Raman detection and imaging technique was tested in vitro with benzene, acetone, olive oil, carbon nanotubes, chylomicron phantom, and cancer cells, and in vivo in single adipocytes in mouse mesentery model. The integration of linear and nonlinear PA and PT Raman scanning and flow cytometry has the potential to enhance its chemical specificity and sensitivity including nanobubble-based amplification (up to 10- fold) for detection of absorbing and nonabsorbing targets that are important for both basic and clinically relevant studies of lymph and blood biochemistry, cancer, and fat distribution at the single-cell level. PMID:20389713

Shashkov, Evgeny V.; Galanzha, Ekaterina I.; Zharov, Vladimir P.

2010-01-01

363

Photo-acoustic analysis of dental materials and tissue  

NASA Astrophysics Data System (ADS)

The goal of the presented study is the investigation of the feasibility of using optically generated acoustic waves for analysis of dental material below laser-ablation threshold. The temperature rise of dental material and tissue has been modeled analytically and numerically, and measured experimentally. Following interactions with nano- and femto-second laser radiation the temperature rises at a rate of typically 1°C per J/cm 2, along with the generation of an acoustical wave. The results from the models agree with the experiment. The acoustic measurements show differences in the acoustic signal strength and the frequency spectrum when the canal in the porcelain phantom is empty or filled with intralipid solution. The photo-acoustic technique is found to be suitable for detection of liquids under a layer of dental porcelain material, consequently it can be the basis for building an imaging tool for dental diagnostic applications. By generating sound waves in the pulp, one would be able to evaluate it's state and the overall health of the tooth. This is of vital importance for diagnosing initial-stage inflammation.

Jeleva, Pavlina Jetchkova

364

Intravascular photoacoustic imaging: a new tool for vulnerable plaque identification.  

PubMed

The vulnerable atherosclerotic plaque is believed to be at the root of the majority of acute coronary events. Even though the exact origins of plaque vulnerability remain elusive, the thin-cap fibroatheroma, characterized by a lipid-rich necrotic core covered by a thin fibrous cap, is considered to be the most prominent type of vulnerable plaque. No clinically available imaging technique can characterize atherosclerotic lesions to the extent needed to determine plaque vulnerability prognostically. Intravascular photoacoustic imaging (IVPA) has the potential to take a significant step in that direction by imaging both plaque structure and composition. IVPA is a natural extension of intravascular ultrasound that adds tissue type specificity to the images. IVPA utilizes the optical contrast provided by the differences in the absorption spectra of plaque components to image composition. Its capability to image lipids in human coronary atherosclerosis has been shown extensively ex vivo and has recently been translated to an in vivo animal model. Other disease markers that have been successfully targeted are calcium and inflammatory markers, such as macrophages and matrix metalloproteinase; the latter two through application of exogenous contrast agents. By simultaneously displaying plaque morphology and composition, IVPA can provide a powerful prognostic marker for disease progression, and as such has the potential to transform the current practice in percutaneous coronary intervention. PMID:24631379

Jansen, Krista; van Soest, Gijs; van der Steen, Antonius F W

2014-06-01

365

Coupled Simulation of Circuit and Piezoelectric Laminates  

E-print Network

In this paper, an algorithm for the coupled simulation of circuit and piezoelectric laminate devices is presented. A finite element solver for piezoelectric laminates is included in the SPICE framework as a capacitor. The charge of this capacitor is a function of both the terminal voltage and the mechanical strain in the piezoelectric material. The coupled simulator allows simulation of novel micropower generation circuits based on piezoelectric laminates. 1.

unknown authors

366

Disc piezoelectric ceramic transformers.  

PubMed

In this contribution, we present our study on disc-shaped and homogeneously poled piezoelectric ceramic transformers working in planar-extensional vibration modes. Transformers are designed with electrodes divided into wedge, axisymmetrical ring-dot, moonie, smile, or yin-yang segments. Transformation ratio, efficiency, and input and output impedances were measured for low-power signals. Transformer efficiency and transformation ratio were measured as a function of frequency and impedance load in the secondary circuit. Optimum impedance for the maximum efficiency has been found. Maximum efficiency and no-load transformation ratio can reach almost 100% and 52 for the fundamental resonance of ring-dot transformers and 98% and 67 for the second resonance of 2-segment wedge transformers. Maximum efficiency was reached at optimum impedance, which is in the range from 500 ? to 10 k?, depending on the electrode pattern and size. Fundamental vibration mode and its overtones were further studied using frequency-modulated digital holographic interferometry and by the finite element method. Complementary information has been obtained by the infrared camera visualization of surface temperature profiles at higher driving power. PMID:25004532

Erhart, Jirií; P?lpán, Petr; Dole?ek, Roman; Psota, Pavel; Lédl, Vít

2013-08-01

367

Cryogenic Piezoelectric Actuator  

NASA Technical Reports Server (NTRS)

In this paper, PMN-PT single crystal piezoelectric stack actuators and flextensional actuators were designed, prototyped and characterized for space optics applications. Single crystal stack actuators with footprint of 10 mm x10 mm and the height of 50 mm were assembled using 10 mm x10mm x0.15mm PMN-PT plates. These actuators showed stroke > 65 - 85 microns at 150 V at room temperature, and > 30 microns stroke at 77 K. Flextensional actuators with dimension of 10mm x 5 mm x 7.6 mm showed stroke of >50 microns at room temperature at driving voltage of 150 V. A flextensional stack actuator with dimension of 10 mm x 5 mm x 47 mm showed stroke of approx. 285 microns at 150 V at room temperature and > 100 microns at 77K under driving of 150 V should be expected. The large cryogenic stroke and high precision of these actuators are promising for cryogenic optics applications.

Jiang, Xiaoning; Cook, William B.; Hackenberger, Wesley S.

2009-01-01

368

Wideband piezoelectric pressure transducer  

NASA Astrophysics Data System (ADS)

A piezoelectric pressure transducer for pressures of up to 100 MPa was developed, with an operating frequency range from 100 Hz to 1 MHz on the electrical side - sufficiently wide to reproduce pressure profiles of arc discharges with microsecond rise times and millisecond fall times. The sensing element is a disk of TsTS-19 piezoceramic material, 1 mm thick and 5 mm in diameter. It is thermally and electrically insulated from the arc plasma by a compound transmission rod consisting of two quartz crystals 5 mm in diameter and freely sliding inside a teflon sleeve. The 50 mm long waveguide for absorbing acoustic vibrations and thus separating the valid signal from the reflected one consists of brass wires acoustically insulated with epoxy resin and encapsulated into a textolite sleeve with epoxy resin at the other end. A copper housing shields the transducer from electromagnetic interference. The transducer output signal passes through a matching circuit and then a high-impedance voltage divider to a differential amplifier, the latter being shunted by a stabilizing low 1 Mohm resistance at the input. A special feature of this transducer is low-frequency compensation by means of a corrective RC-circuit. After calibration of oscillograms, the transducer has a sensitivity of 1 V/MPa over the 10(-2) to 10 MPa range. Its resolution corresponds to the 2 microsecond maximum rise time of its output signal, with the sensing element located at the end of a shock tube.

Godonyuk, V. A.; Zhuravlev, B. V.; Shedko, I. P.

1986-02-01

369

Piezoelectric Water Drop Energy Harvesting  

NASA Astrophysics Data System (ADS)

Piezoelectric materials convert mechanical deformation directly into electrical charges, which can be harvested and used to drive micropower electronic devices. The low power consumption of such systems on the scale of microwatts leads to the possibility of using harvested vibrational energy due to its almost universal nature. Vibrational energy harvested using piezoelectric cantilevers provides sufficient output for small-scale power applications. This work reports on vibrational energy harvesting from free-falling droplets at the tip of lead zirconate titanate piezoelectric-based cantilevers. The harvester incorporates a multimorph clamped-free cantilever made of lead zirconate titanate piezoelectric thick films. During the impact, the droplet's kinetic energy is transferred to the form of mechanical stress, forcing the piezoelectric structure to vibrate and thereby producing charges. Experimental results show an instantaneous drop-power of 2.15 mW cm-3 g-1. The scenario of a medium intensity of falling water drops, i.e., 200 drops per second, yielded a power of 0.48 W cm-3 g-1 per second.

Al Ahmad, Mahmoud

2014-02-01

370

Optical clearing in photoacoustic flow cytometry  

PubMed Central

Clinical applications of photoacoustic (PA) flow cytometry (PAFC) for detection of circulating tumor cells in deep blood vessels are hindered by laser beam scattering, that result in loss of PAFC sensitivity and resolution. We demonstrate biocompatible and rapid optical clearing (OC) of skin to minimize light scattering and thus, increase optical resolution and sensitivity of PAFC. OC effect was achieved in 20 min by sequent skin cleaning, microdermabrasion, and glycerol application enhanced by massage and sonophoresis. Using 0.8 mm mouse skin layer over a blood vessel in vitro phantom we demonstrated 1.6-fold decrease in laser spot blurring accompanied by 1.6-fold increase in PA signal amplitude from blood background. As a result, peak rate for B16F10 melanoma cells in blood flow increased 1.7-fold. By using OC we also demonstrated the feasibility of PA contrast improvement for human hand veins. PMID:24409398

Menyaev, Yulian A.; Nedosekin, Dmitry A.; Sarimollaoglu, Mustafa; Juratli, Mazen A.; Galanzha, Ekaterina I.; Tuchin, Valery V.; Zharov, Vladimir P.

2013-01-01

371

Terahertz quartz enhanced photo-acoustic sensor  

NASA Astrophysics Data System (ADS)

A quartz enhanced photo-acoustic sensor employing a single-mode quantum cascade laser emitting at 3.93 Terahertz (THz) is reported. A custom tuning fork with a 1 mm spatial separation between the prongs allows the focusing of the THz laser beam between them, while preventing the prongs illumination. A methanol transition with line-strength of 4.28 × 10-21 cm has been selected as target spectroscopic line. At a laser optical power of ˜ 40 ?W, we reach a sensitivity of 7 parts per million in 4s integration time, corresponding to a 1? normalized noise-equivalent absorption of 2 × 10-10 cm-1W/Hz½.

Borri, S.; Patimisco, P.; Sampaolo, A.; Beere, H. E.; Ritchie, D. A.; Vitiello, M. S.; Scamarcio, G.; Spagnolo, V.

2013-07-01

372

Photoacoustic tomography: fundamentals, advances and prospects.  

PubMed

Optical microscopy has been contributing to the development of life science for more than three centuries. However, due to strong optical scattering in tissue, its in vivo imaging ability has been restricted to studies at superficial depths. Advances in photoacoustic tomography (PAT) now allow multiscale imaging at depths from sub-millimeter to several centimeters, with spatial resolutions from sub-micrometer to sub-millimeter. Because of this high scalability and its unique optical absorption contrast, PAT is capable of performing anatomical, functional, molecular and fluid-dynamic imaging at various system levels, and is playing an increasingly important role in fundamental biological research and clinical practice. This review discusses recent technical progress in PAT and presents corresponding applications. It ends with a discussion of several prospects and their technical challenges. PMID:22025335

Yao, Junjie; Wang, Lihong V

2011-01-01

373

Absolute Photoacoustic Thermometry in Deep Tissue  

PubMed Central

Photoacoustic (PA) thermography is a promising tool for temperature measurement in deep tissue. Here, we propose an absolute temperature measurement method based on the dual temperature dependences of the Grüneisen parameter and the speed of sound in tissue. By taking ratiometric measurements at two adjacent temperatures, we can eliminate the factors that are temperature irrelevant but difficult to correct for in deep tissue. To validate our method, absolute temperatures of blood-filled tubes embedded ~9 mm deep in chicken tissue were measured in a biologically relevant range from 28 °C to 46 °C. The temperature measurement accuracy was ~0.6 °C. The results suggest that our method can be potentially used for absolute temperature monitoring in deep tissue during thermotherapy. PMID:24322224

Tai, Stephen; Zhou, Yong; Wang, Lihong V.

2013-01-01

374

Absolute photoacoustic thermometry in deep tissue.  

PubMed

Photoacoustic thermography is a promising tool for temperature measurement in deep tissue. Here we propose an absolute temperature measurement method based on the dual temperature dependences of the Grüneisen parameter and the speed of sound in tissue. By taking ratiometric measurements at two adjacent temperatures, we can eliminate the factors that are temperature irrelevant but difficult to correct for in deep tissue. To validate our method, absolute temperatures of blood-filled tubes embedded ~9 mm deep in chicken tissue were measured in a biologically relevant range from 28°C to 46°C. The temperature measurement accuracy was ~0.6°C. The results suggest that our method can be potentially used for absolute temperature monitoring in deep tissue during thermotherapy. PMID:24322224

Yao, Junjie; Ke, Haixin; Tai, Stephen; Zhou, Yong; Wang, Lihong V

2013-12-15

375

Photoacoustic microscopy of bilirubin in tissue phantoms  

NASA Astrophysics Data System (ADS)

Determining both bilirubin's concentration and its spatial distribution are important in disease diagnosis. Here, for the first time, we applied quantitative multiwavelength photoacoustic microscopy (PAM) to detect bilirubin concentration and distribution simultaneously. By measuring tissue-mimicking phantoms with different bilirubin concentrations, we showed that the root-mean-square error of prediction has reached 0.52 and 0.83 mg/dL for pure bilirubin and for blood-mixed bilirubin detection (with 100% oxygen saturation), respectively. We further demonstrated the capability of the PAM system to image bilirubin distribution both with and without blood. Finally, by underlaying bilirubin phantoms with mouse skins, we showed that bilirubin can be imaged with consistent accuracy down to >400 ?m in depth. Our results show that PAM has potential for noninvasive bilirubin monitoring in vivo, as well as for further clinical applications.

Zhou, Yong; Zhang, Chi; Yao, Da-Kang; Wang, Lihong V.

2012-12-01

376

Piezoelectric Bimorph Optical-Fiber Sensor  

Microsoft Academic Search

We propose and demonstrate a novel high-voltage optical-fiber sensor. This sensor consists of an emitting fiber, a receiving fiber, and a piezoelectric bimorph transducer. The emitting fiber is fixed in a base, whereas the receiving fiber is mounted on the free end of the piezoelectric bimorph transducer. When a voltage is applied to the piezoelectric bimorph transducer, its free end

Fengguo Sun; Gaozhi Xiao; Zhiyi Zhang; Chander P. Grover

2004-01-01

377

Recent developments of polar piezoelectric polymers  

Microsoft Academic Search

Following the extensive studies on the piezoelectric, pyroelectric and ferroelectric properties of polyvinylidene fluoride and its copolymers, a vast number of polymers were investigated for these properties. Piezoelectric thin films of polyurea were prepared by vapor deposition polymerization in vacuum and stable up to 200 degC. Piezoelectric odd nylon was characterized by the field induced rotation of amide dipoles in

Eiichi Fukada

2006-01-01

378

Light focusing and two-dimensional imaging through scattering media using the photoacoustic transmission matrix with an ultrasound array  

NASA Astrophysics Data System (ADS)

We implement the photoacoustic transmission-matrix approach on a two-dimensional photoacoustic imaging system, using a 15 MHz linear ultrasound array. Using a black leaf skeleton as a complex absorbing structure, we demonstrate that the photoacoustic transmission-matrix approach allows to reveal structural features that are invisible in conventional photoacoustic images, as well as to selectively control light focusing on absorbing targets, leading to a local enhancement of the photoacoustic signal.

Chaigne, Thomas; Gateau, Jérôme; Katz, Ori; Bossy, Emmanuel; Gigan, Sylvain

2014-05-01

379

Light Focusing and Two-Dimensional Imaging Through Scattering Media using the Photoacoustic Transmission-Matrix with an Ultrasound Array  

E-print Network

We implement the photoacoustic transmission-matrix approach on a two-dimensional photoacoustic imaging system, using a 15 MHz linear ultrasound array. Using a black leaf skeleton as a complex absorbing structure, we demonstrate that the photoacoustic transmission-matrix approach allows to reveal structural features that are invisible in conventional photoacoustic images, as well as to selectively control light focusing on absorbing targets, leading to a local enhancement of the photoacoustic signal.

Chaigne, Thomas; Katz, Ori; Bossy, Emmanuel; Gigan, Sylvain

2014-01-01

380

A Micro-Opto-Mechanical Photoacoustic Spectrometer  

SciTech Connect

This report describes progress achieved in a one-year LDRD feasibility study of a Photo Acoustic Spectrometer (PAS). Specifically, this team sought to create an all-optical and very small PhotoAcoustic Spectrometer Sensing system (PASS system). The PASS system includes all the hardware needed within a gas environment to analyze the presence of a large variety of molecules. The all-optical PASS system requires only two optical-fibers to communicate with the opto-electronic power and readout systems that exist outside of the gas environment. These systems can be at any distance from the PASS system as signal loss through the optical fibers is very small. The PASS system is intended to be placed in a small space where gases need to be measured and thus must be very small. The size and all-optical constraints placed on the PASS system demand a new design. The PASS system design includes a novel acoustic chamber, optical sensor, power fiber coupling and sensing fiber coupling. Our collaborators at the Atomic Weapons Establishment (AWE) have proven the capabilities of a complete photoacoustic spectrometer that uses a macro-scale PASS system (first 2 references). It was our goal to miniaturize the PASS system and turn it into an all-optical system to allow for its use in confined spaces that prohibit electrical devices. This goal demanded the study of all the system components, selection of an appropriate optical readout system and the design and integration of the optical sensor to the PASS system. A stretch goal was to fabricate a completed PASS system prototype.

Kotovsky, J

2008-10-17

381

Fabrication of zinc oxide nanoneedles on conductive textile for harvesting piezoelectric potential  

NASA Astrophysics Data System (ADS)

Keeping the fact in mind that different morphologies have strong influence on piezoelectric properties, ZnO NNs were synthesized on textile for harvesting piezoelectricity. Piezoelectric potential was captured from ZnO NNs grown on textile by using AFM in contact mode. Structural study was carried out by using FESEM, HRTEM and XRD techniques. The recorded output potential and current was more than 45 mV and 150 nA. The combination of ZnO NNs and textile can be used effectively for energy harvesting applications and the use of textile fabric can pave the way for cheap, flexible, wearable, washable and environment friendly nanodevices.

Khan, Azam; Hussain, Mushtaque; Nur, Omer; Willander, Magnus

2014-09-01

382

Silica-coated super paramagnetic iron oxide nanoparticles (SPION) as biocompatible contrast agent in biomedical photoacoustics  

PubMed Central

In this study, we report for the first time the use of silica-coated superparamagnetic iron oxide nanoparticles (SPION) as contrast agents in biomedical photoacoustic imaging. Using frequency-domain photoacoustic correlation (the photoacoustic radar), we investigated the effects of nanoparticle size, concentration and biological media (e.g. serum, sheep blood) on the photoacoustic response in turbid media. Maximum detection depth and the minimum measurable SPION concentration were determined experimentally. The nanoparticle-induced optical contrast ex vivo in dense muscular tissues (avian pectus and murine quadricept) was evaluated and the strong potential of silica-coated SPION as a possible photoacoustic contrast agents was demonstrated. PMID:23082291

Alwi, Rudolf; Telenkov, Sergey; Mandelis, Andreas; Leshuk, Timothy; Gu, Frank; Oladepo, Sulayman; Michaelian, Kirk

2012-01-01

383

Doppler photoacoustic and Doppler ultrasound in blood with optical contrast agent  

NASA Astrophysics Data System (ADS)

Photoacoustic Doppler flowmetry as well as Doppler ultrasound were performed in acoustic resolution regime on tubes filled with flowing blood with indocyanine green (ICG) at different concentrations. The photoacoustic excitation utilized a pair of directly-modulated fiber-coupled 830nm laser-diodes, modulated with either CW or tone-bursts for depthresolved measurements. The amplitude of the Doppler peak in photoacoustic Doppler measurements was found to be proportional to the ICG concentration. Photoacoustic Doppler was measured in ICG at human safe concentrations, but not in whole blood. Comparing the results between the two modalities implied that using a wavelength with higher optical absorption may improve the photoacoustic signal in blood.

Sheinfeld, Adi; Eyal, Avishay

2013-03-01

384

Silica-coated super paramagnetic iron oxide nanoparticles (SPION) as biocompatible contrast agent in biomedical photoacoustics.  

PubMed

In this study, we report for the first time the use of silica-coated superparamagnetic iron oxide nanoparticles (SPION) as contrast agents in biomedical photoacoustic imaging. Using frequency-domain photoacoustic correlation (the photoacoustic radar), we investigated the effects of nanoparticle size, concentration and biological media (e.g. serum, sheep blood) on the photoacoustic response in turbid media. Maximum detection depth and the minimum measurable SPION concentration were determined experimentally. The nanoparticle-induced optical contrast ex vivo in dense muscular tissues (avian pectus and murine quadricept) was evaluated and the strong potential of silica-coated SPION as a possible photoacoustic contrast agents was demonstrated. PMID:23082291

Alwi, Rudolf; Telenkov, Sergey; Mandelis, Andreas; Leshuk, Timothy; Gu, Frank; Oladepo, Sulayman; Michaelian, Kirk

2012-10-01

385

Near Infrared Photoacoustic Detection of Sentinel Lymph Nodes with Gold Nanobeacons  

PubMed Central

Detection of sentinel lymph node (SLN) using photoacoustic imaging is an emerging technique for noninvasive axillary staging of breast cancer. Due to the absence of intrinsic contrast inside the lymph nodes, exogenous contrast agents are used for photoacoustic detection. In this work, we have demonstrated near infrared detection of SLN with gold nanobeacons (GNB) providing the photoacoustic contrast in a rodent model. We found that size dictates the in vivo characteristics of these nanoparticles in SLN imaging. Larger nanobeacons with high pay loads of gold were not as efficient as smaller size nanobeacons with lower pay loads for this purpose. Colloidal GNBs were designed as a nanomedicine platform with “soft” nature that is amenable to bio-elimination, an essential feature for in vivo efficacy and safety. The GNBs were synthesized as lipid- or polymer-encapsulated colloidal particles incorporating tiny gold nanoparticles (2–4 nm) in three tunable sizes (90 nm, 150 nm and 290 nm). Smaller GNBs were noted trafficking through the lymphatic system and accumulating more efficiently in the lymph nodes in comparison to the bigger nanoagents. At 20 min, the GNBs reached the SLN and were no longer observed within the draining lymphatic vessel. Within one hour post injection, the contrast ratio of the lymphnodes with the surrounding blood vessels was 9:1. These findings were also supported by analytical measurements of the ex vivo tissue samples. Results indicate that cumulative nanoparticle deposition in lymph nodes is size dependent and that high payloads of gold, although offering greater contrast in vitro, may yield nanoagents with poor intradermal migration and lymphatic transport characteristics. PMID:20172607

Pan, Dipanjan; Pramanik, Manojit; Senpan, Angana; Ghosh, Soumojit; Wickline, Samuel A.; Wang, Lihong V.; Lanza, Gregory M.

2010-01-01

386

Linear and nonlinear photo-acoustic spectroscopy with extreme ultraviolet radiation  

NASA Astrophysics Data System (ADS)

Photo-Acoustic spectroscopy is a universally used method for determining material parameters in condensed matter systems. This experimental method relies on laser excitation and the subsequent frequency domain measurement of acoustic phenomenon. Within the last two decades, ultrafast lasers have been employed within the framework of photo-acoustic spectroscopy to study the time evolution characteristics of these acoustic phenomenon. Ultrafast lasers are currently being used in studying acoustic dynamics in both fundamental and applied research. The present work contains experimental results wherein ultrafast Extreme Ultraviolet (EUV) Radiation has been incorporated into photo-acoustic spectroscopy for the first time. The use of ultrafast EUV radiation in studying acoustic dynamics exhibits high signal-to-noise ratios and high sensitivity to surface corrugation. Both of these features are directly attributable to the reduced probing wavelength of EUV, where even sub-nanometer topological changes in the sample induce large phase changes for EUV radiation. The experimental results fall into two categories. The first of these are experiments performed on heterostructured samples, where uniform optical irradiation induces dynamics due to the differing material properties of the structure. These experiments were used as an introduction to acoustic spectroscopy with EUV and facilitated the measurement of signal-to-noise and surface sensitivity. The second set of experiments were performed on homogeneous samples where the excitation of acoustic behavior was done using the transient grating geometry. Periodically modulated surface excitation led to the generation and subsequent propagation of narrow band surface acoustic waves (SAW). These experiments approach the highest frequency SAWs ever generated using the transient grating technique.

Tobey, Ra'anan Itzhak

387

Multiscale Photoacoustic Microscopy of Single-Walled Carbon Nanotube-Incorporated Tissue Engineering Scaffolds  

PubMed Central

Three-dimensional polymeric scaffolds provide structural support and function as substrates for cells and bioactive molecules necessary for tissue regeneration. Noninvasive real-time imaging of scaffolds and/or the process of tissue formation within the scaffold remains a challenge. Microcomputed tomography, the widely used technique to characterize polymeric scaffolds, shows poor contrast for scaffolds immersed in biological fluids, thereby limiting its utilities under physiological conditions. In this article, multiscale photoacoustic microscopy (PAM), consisting of both acoustic-resolution PAM (AR-PAM) and optical-resolution PAM (OR-PAM), was employed to image and characterize single-walled carbon-nanotube (SWNT)–incorporated poly(lactic-co-glycolic acid) polymer scaffolds immersed in biological buffer. SWNTs were incorporated to reinforce the mechanical properties of the scaffolds, and to enhance the photoacoustic signal from the scaffolds. By choosing excitation wavelengths of 570 and 638?nm, multiscale PAM could spectroscopically differentiate the photoacoustic signals generated from blood and from carbon-nanotube-incorporated scaffolds. OR-PAM, providing a fine lateral resolution of 2.6??m with an adequate tissue penetration of 660??m, successfully quantified the average porosity and pore size of the scaffolds to be 86.5%±1.2% and 153±15??m in diameter, respectively. AR-PAM further extended the tissue penetration to 2?mm at the expense of lateral resolution (45??m). Our results suggest that PAM is a promising tool for noninvasive real-time imaging and monitoring of tissue engineering scaffolds in vitro, and in vivo under physiological conditions. PMID:22082018

Cai, Xin; Paratala, Bhavna S.; Hu, Song

2012-01-01

388

Non-invasive monitoring of ultrasound-stimulated microbubble radiation enhancement using photoacoustic imaging.  

PubMed

Modulation of the tumour microvasculature has been demonstrated to affect the effectiveness of radiation, stimulating the search for anti-angiogenic and vascular-disrupting treatment modalities. Microbubbles stimulated by ultrasound have recently been demonstrated as a radiation enhancer when used with different cancer models including PC3. Here, photoacoustics imaging technique was used to assess this treatment's effects on haemoglobin levels and oxygen saturation. Correlations between this modality and power doppler assessments of blood flow, and histology measurements of vascular integrity and cell death were also investigated. Xenograft prostate tumours in SCID mice were treated with 0, 2, or 8 Gy radiation combined with microbubbles exposed to 500 kHz ultrasound at a peak negative pressure of 0, 570, and 750 kPa. Tumours were assessed and levels of total haemoglobin, oxygen saturation were measured using photoacoustics before and 24 hours after treatment along with power doppler measured blood flow. Mice were then sacrificed and tumours were assessed for cell death and vascular composition using immunohistochemistry. Treatments using 8 Gy and microbubbles resulted in oxygen saturation decreasing by 28 ± 10% at 570 kPa and 25 ± 29% at 750 kPa, which corresponded to 44 ± 9% and 40 ± 14% respective decreases in blood flow as measured with power doppler. Corresponding histology indicated 31 ± 5% at 570 kPa and 37 ± 5% at 750 kPa in terms of cell death. There were drops in intact vasculature of 15 ± 2% and 20 ± 2%, for treatments at 570 kPa and 750 kPa. In summary, photoacoustic measures of total haemoglobin and oxygen saturation paralleled changes in power doppler indicators of blood flow. Destruction of tumour microvasculature with microbubble-enhanced radiation also led to decreases in blood flow and was associated with increases in cell death and decreases in intact vasculature as detected with CD31 labeling. PMID:24000993

Briggs, K; Al Mahrouki, A; Nofiele, J; El-Falou, A; Stanisz, M; Kim, H C; Kolios, M C; Czarnota, G J

2014-10-01

389

Piezoelectric Driver for Incremental Motion  

NASA Technical Reports Server (NTRS)

Vibrating device containing two piezoelectric ceramic slabs acts as mechanical driver. Eventually substitutes for small continuous or stepping electric motors of slow to moderate speeds. Piezoelectric driver simple in construction, requires no precise dimensions, inexpensive to make, and needs no lubrication. Not damaged by stalling or overloads and safe for use in explosive atmospheres; Motion controllable in micron-size increments, and holds position when power turned off. Potential applications as positioner or mover. Used to position instrument pointers, antennas, or solar panels; to focus lenses; or operate tuners, recording instruments, or valves.

Bruman, Joseph R.

1987-01-01

390

Multimodal Sentinel Lymph Node Mapping with SPECT/CT and Photoacoustic Tomography  

PubMed Central

Identification of cancer cells in the lymph nodes surrounding a tumor is important in establishing prognosis. Optical detection techniques such as fluorescence and photoacoustic tomography (PAT) have been reported in preclinical studies for noninvasive sentinel lymph node (SLN) mapping. A method for validation of these techniques is needed for clinical trials. We report the use of a multimodal optical-radionuclear contrast agent as a validation tool for PAT in a preclinical model. Methylene blue (MB) was radiolabeled with 125I for multimodal SLN mapping and used in conjunction with MB to assess the feasibility of multimodal SLN mapping in a rat model by PAT and SPECT. MB provided sufficient contrast for identifying SLNs non-invasively with a PAT system adapted from a clinical ultrasound imaging system. The signal location was corroborated by SPECT using 125I labeled MB. The translation of PAT into the clinic can be facilitated by direct comparison with established imaging methods using a clinically relevant dual SPECT and photoacoustic imaging agent. The new high resolution PAT is a promising technology for sensitive and accurate SLN detection in cancer patients. PMID:22340767

Akers, Walter J.; Edwards, W. Barry; Kim, Chulhong; Xu, Baogang; Erpelding, Todd N.; Wang, Lihong V.; Achilefu, Samuel

2012-01-01

391

Photoacoustic Non-Destructive Evaluation and Imaging of Caries in Dental Samples  

NASA Astrophysics Data System (ADS)

Dental caries is a disease wherein bacterial processes damage hard tooth structure. Traditional dental radiography has its limitations for detecting early stage caries. In this study, a photoacoustic (PA) imaging system with the near-infrared light source has been applied to postmortem dental samples to obtain 2-D and 3-D images. Imaging results showed that the PA technique can be used to image human teeth caries. For non-destructive photoacoustic evaluation and imaging, the induced temperature and pressure rises within biotissues should not cause physical damage to the tissue. For example, temperature rises above 5 °C within live human teeth will cause pulpal necrosis. Therefore, several simulations based on the thermoelastic effect have been applied to predict temperature and pressure fields within samples. Predicted temperature levels are below corresponding safety limits, but care is required to avoid nonlinear absorption phenomena. Furthermore, PA imaging results from the phantom provide evidence for high sensitivity, which shows the imaging potential of the PA technique for detecting early stage disease.

Li, T.; Dewhurst, R. J.

2010-02-01

392

Analysis of pollutant chemistry in combustion by in situ pulsed photoacoustic laser diagnostics  

NASA Astrophysics Data System (ADS)

A technique for gas analysis based on pulsed-laser-induced photoacoustic spectroscopy in the UV and the visible is presented. The laser-based technique and the associated analysis probe have been developed for the analysis of pollutant chemistry in fluidized beds and other combustion environments with limited or no optical access. The photoacoustic-absorption spectrum of the analyzed gas is measured in a test cell located at the end of a tubular probe. This test cell is subject to the prevailing temperature and pressure in the combustion process. The instrument response has been calibrated for N2O, NO, NO2, NH3, SO2, and H2 S at atmospheric pressure between 20 and 910 deg C. The response of the probe was found to increase with pressure for N2O, NO, NH 3, and NO2 up to 1.2 MPa pressure. The method and the probe have been used for detection and ranging of gas concentrations in a premixed methane flame. Some preliminary tests in a large 12-MW circulating bed boiler have also been done.

Stenberg, Jari; Hernberg, Rolf; Vattulainen, Juha

1995-12-01

393

Photoacoustic Tomography Reconstruction in a 2-D Chaotic Cavity using Time Reversal  

NASA Astrophysics Data System (ADS)

In photoacoustic tomography, a scanning setup or an array of transducers is usually needed to record the photoacoustic signal on a closed trajectory surrounding the region of interest. Such a measurement configuration may increase the complexity or expense of the photoacoustic tomography system. In this study, a one-channel photoacoustic tomography using time reversal invariance of photoacoustics in a chaotic cavity is proposed. In no need of the scanning setup or transducer array, the method utilizes only one fixed small-size transducer to collect the photoacoustics in the cavity. The method is verified by two-dimensional numerical simulations. Moreover, the influence of noise and the diameter of the transducer are also taken into account to verify the robustness and practicality of the proposed method. The proposed method could be helpful for improving the image quality of photoacoustic tomography using a few data channels.

Wu, Dan; Tao, Chao; Liu, Xiaojun; Zhang, Shuyi

2013-09-01

394

Characterization of Piezoelectric Stack Actuators for Vibrothermography  

NASA Astrophysics Data System (ADS)

Vibrothermography, also known as Sonic IR and thermosonics, is an NDE technique for finding cracks and flaws based on vibration-induced frictional rubbing of unbonded surfaces. The vibration is usually generated by a piezoelectric stack actuator which transduces electrical energy into large amplitude mechanical vibrations. The amplitude and impedance transfer characteristics of the transducer system control the vibration of the sample. Within a linear contact (no tip chatter) model, the interaction between the transducer system and the specimen can be characterized using the theory of linear time-invariant (LTI) systems and electro-mechanical Norton equivalence. We present quantitative measurements of the performance of piezoelectric stack actuators in a vibrothermography excitation system and investigate the effect of actuator performance and specimen characteristics on the induced vibration in the specimen. We show that the system resonances generated because of metal-metal contact of specimen and actuator are broken by adding a couplant between specimen and actuator. Finally, we give criteria for actuator and couplant selection for vibrothermography.

Vaddi, Jyani; Reusser, Ricky; Holland, Stephen D.

2011-06-01

395

Elastic properties of spherically anisotropic piezoelectric composites  

NASA Astrophysics Data System (ADS)

Effective elastic properties of spherically anisotropic piezoelectric composites, whose spherically anisotropic piezoelectric inclusions are embedded in an infinite non-piezoelectric matrix, are theoretically investigated. Analytical solutions for the elastic displacements and the electric potentials under a uniform external strain are derived exactly. Taking into account of the coupling effects of elasticity, permittivity and piezoelectricity, the formula is derived for estimating the effective elastic properties based on the average field theory in the dilute limit. An elastic response mechanism is revealed, in which the effective elastic properties increase as inclusion piezoelectric properties increase and inclusion dielectric properties decrease. Moreover, a piezoelectric response mechanism, of which the effective piezoelectric response vanishes due to the symmetry of spherically anisotropic composite, is also disclosed.

Wei, En-Bo; Gu, Guo-Qing; Poon, Ying-Ming

2010-09-01

396

Method of Fabricating a Piezoelectric Composite Apparatus  

NASA Technical Reports Server (NTRS)

A method for fabricating a piezoelectric macro-fiber composite actuator comprises providing a piezoelectric material that has two sides and attaching one side upon an adhesive backing sheet. The method further comprises slicing the piezoelectric material to provide a plurality of piezoelectric fibers in juxtaposition. A conductive film is then adhesively bonded to the other side of the piezoelectric material, and the adhesive backing sheet is removed. The conductive film has first and second conductive patterns formed thereon which are electrically isolated from one another and in electrical contact with the piezoelectric material. The first and second conductive patterns of the conductive film each have a plurality of electrodes to form a pattern of interdigitated electrodes. A second film is then bonded to the other side of the piezoelectric material. The second film may have a pair of conductive patterns similar to the conductive patterns of the first film.

Wilkie, W. Keats (Inventor); Bryant, Robert (Inventor); Fox, Robert L. (Inventor); Hellbaum, Richard F. (Inventor); High, James W. (Inventor); Jalink, Antony, Jr. (Inventor); Little, Bruce D. (Inventor); Mirick, Paul H. (Inventor)

2003-01-01

397

Measurement of piezoelectric constants of lanthanum-gallium tantalate crystal by X-ray diffraction methods  

SciTech Connect

A method for measuring piezoelectric constants of crystals of intermediate systems by X-ray quasi-multiple-wave diffraction is proposed and implemented. This technique makes it possible to determine the piezoelectric coefficient by measuring variations in the lattice parameter under an external electric field. This method has been approved, its potential is evaluated, and a comparison with high-resolution X-ray diffraction data is performed.

Blagov, A. E.; Marchenkov, N. V., E-mail: marchenkov@ns.crys.ras.ru; Pisarevsky, Yu. V.; Prosekov, P. A.; Kovalchuk, M. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)] [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2013-01-15

398

Piezoelectric-Crystal-Resonator High-Frequency Gravitational Wave Generation and Synchro-Resonance Detection  

Microsoft Academic Search

Here we show the generation of high-frequency-gravitational-waves (HFGWs) utilizing piezoelectric elements such as the ubiquitous Film-Bulk-Acoustic-Resonators (FBARs), found in cell phones, as energized by inexpensive magnetrons, found in microwave ovens, generating GWs having a frequency of about 4.9GHz and their detection by means of new synchro-resonance techniques developed in China. In the 1960s Weber suggested piezoelectric crystals for gravitational-wave (GW)

Robert M. L. Baker; R. Clive Woods; Fangyu Li

2006-01-01

399

Use of a Laser-Driven Photoacoustic Detection System for Measurement of Ethylene Production in Cymbidium Flowers  

PubMed Central

A laser-based photoacoustic method was used for determination of ethylene (C2H4) production of emasculated orchid (Cymbidium) flowers in a flow-through system. The laser photoacoustic equipment consisted of a line-tuneable CO2 laser in conjunction with a single-pass resonant acoustic cell. The minimum detection limit of the system for C2H4 in air was 0.03 nanoliter per liter. C2H4 production of intact Cymbidium (cv Mary Pinchess `Del Rey') flowers was very low (0.015 nanoliter per gram per hour) and showed an increase within 3 hours following emasculation (removal of pollinia plus anthercap). Production peaked (0.14 nanoliter per gram per hour) 8 hours after emasculation and decreased thereafter. Production again increased 45 hours after emasculation. Coloration of the labellum appeared shortly after the first peak; wilting of the petals and sepals appeared during the second rise in ethylene production. The use of the laser photoacoustic technique in plant physiological studies is discussed. PMID:16666335

Woltering, Ernst J.; Harren, Frans; Boerrigter, Henrie A. M.

1988-01-01

400

Measuring non-radiative relaxation time of fluorophores with biomedical applications by intensity-modulated laser-induced photoacoustic effect  

PubMed Central

Modulated tone-burst light was employed to measure non-radiative relaxation time of fluorophores with biomedical importance through photoacoustic effect. Non-radiative relaxation time was estimated through the frequency dependence of photoacoustic signal amplitude. Experiments were performed on solutions of new indocyanine green (IR-820), which is a near infrared dye and has biomedical applications, in two different solvents (water and dimethyl sulfoxide (DMSO)). A 1.5 times slower non-radiative relaxation for the solution of dye in DMSO was observed comparing with the aqueous solution. This result agrees well with general finding that non-radiative relaxation of molecules in triplet state depends on viscosity of solvents in which they are dissolved. Measurements of the non-radiative relaxation time can be used as a new source of contrast mechanism in photoacoustic imaging technique. The proposed method has potential applications such as imaging tissue oxygenation and mapping of other chemophysical differences in microenvironment of exogenous biomarkers. PMID:22025981

Soroushian, Behrouz; Yang, Xinmai

2011-01-01

401

A review of piezoelectric polymers as functional materials for electromechanical transducers  

NASA Astrophysics Data System (ADS)

Polymer based MEMS and microfluidic devices have the advantages of mechanical flexibility, lower fabrication cost and faster processing over silicon based ones. Also, many polymer materials are considered biocompatible and can be used in biological applications. A valuable class of polymers for microfabricated devices is piezoelectric functional polymers. In addition to the normal advantages of polymers, piezoelectric polymers can be directly used as an active material in different transduction applications. This paper gives an overview of piezoelectric polymers based on their operating principle. This includes three main categories: bulk piezoelectric polymers, piezocomposites and voided charged polymers. State-of-the-art piezopolymers of each category are presented with a focus on fabrication techniques and material properties. A comparison between the different piezoelectric polymers and common inorganic piezoelectric materials (PZT, ZnO, AlN and PMN-PT) is also provided in terms of piezoelectric properties. The use of piezopolymers in different electromechanical devices is also presented. This includes tactile sensors, energy harvesters, acoustic transducers and inertial sensors.

Ramadan, Khaled S.; Sameoto, D.; Evoy, S.

2014-03-01

402

Photoacoustic system for NH3 detection in a selective catalytic reactor  

NASA Astrophysics Data System (ADS)

A new instrument specifically developed for measuring NH3 concentrations at the inlet and outlet of an SCR reactor is described. It is based on the photoacoustic technique and can perform an online and in-situ n-point measurement grid. The major problem is the severe interference of CO2 combustion gas that absorbs at the same wavelength used for NH3, lowering the sensitivity of the technique. A 13CO2 tunable laser emitting at three wavelengths has been used in order to evaluate simultaneously the CO2 and NH3 concentration. The integrated measurements have been done by a simple differential absorption technique by using a pyroelectric detector; the spatially resolved measurements have been carried out through the analysis of the acoustic wave generated by the laser beam and collected by four microphones perpendicularly disposed. Experimental tests on a 35 MW industrial plant and comparison with traditional sampling methods are presented.

Pintus, Nice; Carrer, Isabella; Del Corno, Ada; Fiorina, Lorenzo; Zanzottera, Eugenio

1995-09-01

403

Open Photoacoustic Cell Configuration Applied to the Thermal Characterization of Liquid CdS Nanocomposites  

NASA Astrophysics Data System (ADS)

CdS nanofluids were prepared by the gamma-radiation method at different radiation doses. The samples were characterized by UV-Vis spectroscopy and transmission electron microscopy. The open cell photoacoustic technique was used to measure the thermal effusivity of the CdS nanocomposites. In this technique a He-Ne laser was used as the excitation source and was operated at 632.8 nm with an output power of 70 mW. The precision and accuracy of this technique were initially established by measuring the thermal effusivity of distilled water and ethylene glycol. The thermal-effusivity values of these two samples were found to be close to the values reported in the literature. The thermal effusivity of CdS nanofluids decreased from (0.453 to 0.268) with increased dosage of gamma radiation.

Faraji, Nastaran; Mahmood Mat Yunus, W.; Kharazmi, Alireza; Saion, Elias; Behzad, Kasra

2014-01-01

404

Nonlinear photoacoustic signal amplification from single targets in absorption background?  

PubMed Central

Photoacoustic (PA) detection of single absorbing targets such as nanoparticles or cells can be limited by absorption background. We show here that this problem can be overcome by using the nonlinear photoacoustics based on the differences in PA signal dependences on the laser energy from targets and background. Among different nonlinear phenomena, we focused on laser generation of nanobubbles as more efficient PA signal amplifiers from strongly absorbing, highly localized targets in the presence of spatially homogenous absorption background generating linear signals only. This approach was demonstrated by using nonlinear PA flow cytometry platform for label-free detection of circulating melanoma cells in blood background in vitro and in vivo. Nonlinearly amplified PA signals from overheated melanin nanoclusters in melanoma cells became detectable above still linear blood background. Nonlinear nanobubble-based photoacoustics provide new opportunities to significantly (5–20-fold) increase PA contrast of single nanoparticles, cells, viruses and bacteria in complex biological environments. PMID:24921062

Sarimollaoglu, Mustafa; Nedosekin, Dmitry A.; Menyaev, Yulian A.; Juratli, Mazen A.; Zharov, Vladimir P.

2013-01-01

405

Intravascular photoacoustic tomography for characterization of atherosclerotic lipid and inflammation  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging is a fast growing imaging technology depending on its high optical resolution of optics while taking the advantage of the high penetration depth of ultrasound. In this paper, we demonstrate the new progress in the photoacoustic imaging. Atherosclerosis is characterized by a progressive build-up of lipid in the arterial wall, which is known as plaque. Histological studies demonstrate that the primary cause of acute cardiovascular events is the rupture of atherosclerotic plaques. Lipid and inflammation within the plaque are related to influence the propensity of plaques to disrupt. Photoacoustic intravascular tomography (IVPAT) holds a great advantage in providing comprehensive morphological and functional information of plaques. Lipid relative concentration maps of atherosclerotic aorta were obtained and compared with histology. Furthermore, by selectively targeting the intravascular inflammatory cytokines, IVPAT is also capable of mapping the inflamed area and determining the degree of inflammation.

Zhang, Jian; Qin, Huan; Shi, Yujiao; Yang, Sihua; Xing, Da

2014-09-01

406

Understanding climate: the role of photoacoustic spectroscopy at NIST  

NASA Astrophysics Data System (ADS)

Sophisticated climate models predict that soot aerosols have a significant impact on Earth's energy budget; however, the uncertainty of these predictions is large, in part, because soot in the atmosphere and in the laboratory is poorly characterized. In the atmosphere, soot's optical and physical properties change as it combines with water vapor and sulfuric acid. We will describe a novel photoacoustic spectrometer system that measures the optical absorption cross section of various soots as they age in diverse environments. We also measure the albedo (optical scattering) of aerosols ranging from black-carbon-like to brown-carbon-like using simultaneous photoacoustic spectroscopy and cavity ring-down spectroscopy. Lastly, we developed a photoacoustic spectrometer system that measures the concentration of carbon dioxide in atmospheric air with sub-ppm uncertainty. We will report results of field tests of this spectrometer.

Gillis, Keith

2012-02-01

407

High frequency label-free photoacoustic microscopy of single cells?  

PubMed Central

Photoacoustic measurements of melanoma cells and red blood cells (RBCs) using ultra-high frequency (UHF) wide-bandwidth transducers are reported. In this detection system, the resolution typically depends on the parameters of the receiving transducer, and not the focus of the laser. A single melanoma cell was imaged with 200, 375 and 1200 MHz transducers. As the frequency increased, the resolution increased, resulting in greater detail observed. A single RBC was imaged at 1200 MHz, showing the contours of the cell. While lateral and axial resolutions approaching 1 ?m are possible with this microscope, the key advantage is the ability to perform a wide-bandwidth quantitative signal analysis of the photoacoustic signals. The power spectrum of the signals measured from RBCs showed distinct spectral minima around 800 and 1500 MHz which are directly related to the RBC geometry. This study reports on the high-resolution imaging capabilities and quantitative analyses using UHF photoacoustic microscopy.

Strohm, Eric M.; Berndl, Elizabeth S.L.; Kolios, Michael C.

2013-01-01

408

Photoacoustic microscopy of tyrosinase reporter gene in vivo  

PubMed Central

Photoacoustic tomography is a hybrid modality based on optical absorption excitation and ultrasonic detection. It is sensitive to melanin, one of the primary absorbers in skin. For cells that do not naturally contain melanin, melanin production can be induced by introducing the gene for tyrosinase, the primary enzyme responsible for expression of melanin in melanogenic cells. Optical resolution photoacoustic microscopy was used in the ex vivo study reported here, where the signal from transfected cells increased by more than 10 times over wild-type cells. A subsequent in vivo experiment was conducted to demonstrate the capability of photoacoustic microscopy to spectrally differentiate between tyrosinase-catalyzed melanin and various other absorbers in tissue. PMID:21895303

Krumholz, Arie; VanVickle-Chavez, Sarah J.; Yao, Junjie; Fleming, Timothy P.; Gillanders, William E.; Wang, Lihong V.

2011-01-01

409

Noninvasive photoacoustic computed tomography of mouse brain metabolism in vivo.  

PubMed

We have demonstrated the feasibility of imaging mouse brain metabolism using photoacoustic computed tomography (PACT), a fast, noninvasive and functional imaging modality with optical contrast and acoustic resolution. Brain responses to forepaw stimulations were imaged transdermally and transcranially. 2-NBDG, which diffuses well across the blood-brain-barrier, provided exogenous contrast for photoacoustic imaging of glucose response. Concurrently, hemoglobin provided endogenous contrast for photoacoustic imaging of hemodynamic response. Glucose and hemodynamic responses were quantitatively decoupled by using two-wavelength measurements. We found that glucose uptake and blood perfusion around the somatosensory region of the contralateral hemisphere were both increased by stimulations, indicating elevated neuron activity. While the glucose response area was more homogenous and confined within the somatosensory region, the hemodynamic response area had a clear vascular pattern and spread wider than the somatosensory region. Our results demonstrate that 2-NBDG-enhanced PACT is a promising tool for noninvasive studies of brain metabolism. PMID:22940116

Yao, Junjie; Xia, Jun; Maslov, Konstantin I; Nasiriavanaki, Mohammadreza; Tsytsarev, Vassiliy; Demchenko, Alexei V; Wang, Lihong V

2013-01-01

410

Prediction of absorption coefficients by pulsed laser induced photoacoustic measurements.  

PubMed

In the current study, a pulsed laser induced photoacoustic spectroscopy setup was designed and developed, aiming its application in clinical diagnostics. The setup was optimized with carbon black samples in water and with various tryptophan concentrations at 281nm excitations. The sensitivity of the setup was estimated by determining minimum detectable concentration of tryptophan in water at the same excitation, and was found to be 0.035mM. The photoacoustic experiments were also performed with various tryptophan concentrations at 281nm excitation for predicting optical absorption coefficients in them and for comparing the outcomes with the spectrophotometrically-determined absorption coefficients for the same samples. Absorption coefficients for a few serum samples, obtained from some healthy female volunteers, were also determined through photoacoustic and spectrophotometric measurements at the same excitations, which showed good agreement between them, indicating its clinical implications. PMID:24632160

Priya, Mallika; Satish Rao, B S; Ray, Satadru; Mahato, K K

2014-06-01

411

Silver Nanoplate Contrast Agents for In Vivo Molecular Photoacoustic Imaging  

PubMed Central

Silver nanoplates are introduced as a new photoacoustic contrast agent that can be easily functionalized for molecular photoacoustic imaging in vivo. Methods are described for synthesis, functionalization, and stabilization of silver nanoplates using biocompatible (“green”) reagents. Directional antibody conjugation to the nanoplate surface is presented along with proof of molecular sensitivity in vitro with pancreatic cancer cells. Cell viability tests show the antibody-conjugated silver nanoplates to be nontoxic at concentrations up to 1 mg/ml. Furthermore, the silver nanoplates' potential for in vivo application as a molecularly sensitive photoacoustic contrast agent is demonstrated using an orthotopic mouse model of pancreatic cancer. Results of these studies suggest that the synthesized silver nanoplates are well suited for a host of biomedical imaging and sensing applications. PMID:22188516

Homan, Kimberly A.; Souza, Michael; Truby, Ryan; Luke, Geoffrey P.; Green, Christopher; Vreeland, Erika; Emelianov, Stanislav

2012-01-01

412

Coregistered photoacoustic-ultrasound imaging applied to brachytherapy.  

PubMed

Brachytherapy is a form of radiation therapy commonly used in the treatment of prostate cancer wherein sustained radiation doses can be precisely targeted to the tumor area by the implantation of small radioactive seeds around the treatment area. Ultrasound is a popular imaging mode for seed implantation, but the seeds are difficult to distinguish from the tissue structure. In this work, we demonstrate the feasibility of photoacoustic imaging for identifying brachytherapy seeds in a tissue phantom, comparing the received intensity to endogenous contrast. We have found that photoacoustic imaging at 1064 nm can identify brachytherapy seeds uniquely at laser penetration depths of 5 cm in biological tissue at the ANSI limit for human exposure with a contrast-to-noise ratio of 26.5 dB. Our realtime combined photoacoustic-ultrasound imaging approach may be suitable for brachytherapy seed placement and post-placement verification, potentially allowing for realtime dosimetry assessment during implantation. PMID:21895302

Harrison, Tyler; Zemp, Roger J

2011-08-01

413

Photoacoustic microscopy of tyrosinase reporter gene in vivo  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography is a hybrid modality based on optical absorption excitation and ultrasonic detection. It is sensitive to melanin, one of the primary absorbers in skin. For cells that do not naturally contain melanin, melanin production can be induced by introducing the gene for tyrosinase, the primary enzyme responsible for expression of melanin in melanogenic cells. Optical resolution photoacoustic microscopy was used in the ex vivo study reported here, where the signal from transfected cells increased by more than 10 times over wild-type cells. A subsequent in vivo experiment was conducted to demonstrate the capability of photoacoustic microscopy to spectrally differentiate between tyrosinase-catalyzed melanin and various other absorbers in tissue.

Krumholz, Arie; Vanvickle-Chavez, Sarah J.; Yao, Junjie; Fleming, Timothy P.; Gillanders, William E.; Wang, Lihong V.

2011-08-01

414

Silver nanoplate contrast agents for in vivo molecular photoacoustic imaging.  

PubMed

Silver nanoplates are introduced as a new photoacoustic contrast agent that can be easily functionalized for molecular photoacoustic imaging in vivo. Methods are described for synthesis, functionalization, and stabilization of silver nanoplates using biocompatible ("green") reagents. Directional antibody conjugation to the nanoplate surface is presented along with proof of molecular sensitivity in vitro with pancreatic cancer cells. Cell viability tests show the antibody-conjugated silver nanoplates to be nontoxic at concentrations up to 1 mg/mL. Furthermore, the silver nanoplates' potential for in vivo application as a molecularly sensitive photoacoustic contrast agent is demonstrated using an orthotopic mouse model of pancreatic cancer. Results of these studies suggest that the synthesized silver nanoplates are well suited for a host of biomedical imaging and sensing applications. PMID:22188516

Homan, Kimberly A; Souza, Michael; Truby, Ryan; Luke, Geoffrey P; Green, Christopher; Vreeland, Erika; Emelianov, Stanislav

2012-01-24

415

Piezoelectric measurement of laser power  

DOEpatents

A method for measuring the energy of individual laser pulses or a series of laser pulses by reading the output of a piezoelectric (PZ) transducer which has received a known fraction of the total laser pulse beam. An apparatus is disclosed that reduces the incident energy on the PZ transducer by means of a beam splitter placed in the beam of the laser pulses.

Deason, Vance A. (Idaho Falls, ID); Johnson, John A. (Idaho Falls, ID); Telschow, Kenneth L. (Idaho Falls, ID)

1991-01-01

416

V-stack piezoelectric actuator  

NASA Astrophysics Data System (ADS)

Aeroelastic control of wings by means of a distributed, trailing-edge control surface is of interest with regards to maneuvers, gust alleviation, and flutter suppression. The use of high energy density, piezoelectric materials as motors provides an appealing solution to this problem. A comparative analysis of the state of the art actuators is currently being conducted. A new piezoelectric actuator design is presented. This actuator meets the requirements for trailing edge flap actuation in both stroke and force. It is compact, simple, sturdy, and leverages stroke geometrically with minimum force penalties while displaying linearity over a wide range of stroke. The V-Stack Piezoelectric Actuator, consists of a base, a lever, two piezoelectric stacks, and a pre-tensioning element. The work is performed alternately by the two stacks, placed on both sides of the lever. Pre-tensioning can be readily applied using a torque wrench, obviating the need for elastic elements and this is for the benefit of the stiffness of the actuator. The characteristics of the actuator are easily modified by changing the base or the stacks. A prototype was constructed and tested experimentally to validate the theoretical model.

Ardelean, Emil V.; Clark, Robert L.

2001-07-01

417

Cylindrical Piezoelectric Fiber Composite Actuators  

NASA Technical Reports Server (NTRS)

The use of piezoelectric devices has become widespread since Pierre and Jacques Curie discovered the piezoelectric effect in 1880. Examples of current applications of piezoelectric devices include ultrasonic transducers, micro-positioning devices, buzzers, strain sensors, and clocks. The invention of such lightweight, relatively inexpensive piezoceramic-fiber-composite actuators as macro fiber composite (MFC) actuators has made it possible to obtain strains and displacements greater than those that could be generated by prior actuators based on monolithic piezoceramic sheet materials. MFC actuators are flat, flexible actuators designed for bonding to structures to apply or detect strains. Bonding multiple layers of MFC actuators together could increase force capability, but not strain or displacement capability. Cylindrical piezoelectric fiber composite (CPFC) actuators have been invented as alternatives to MFC actuators for applications in which greater forces and/or strains or displacements may be required. In essence, a CPFC actuator is an MFC or other piezoceramic fiber composite actuator fabricated in a cylindrical instead of its conventional flat shape. Cylindrical is used here in the general sense, encompassing shapes that can have circular, elliptical, rectangular or other cross-sectional shapes in the planes perpendicular to their longitudinal axes.

Allison, Sidney G.; Shams, Qamar A.; Fox, Robert L.

2008-01-01

418

Epitaxial piezoelectric MEMS on silicon  

NASA Astrophysics Data System (ADS)

This paper reports on the microfabrication and characterization of piezoelectric MEMS structures based on epitaxial Pb(Zr0.2Ti0.8)O3 (PZT) thin films grown on silicon wafers. Membranes and cantilevers are realized using a sequence of microfabrication processes optimized for epitaxial oxide layers. Different issues related to the choice of materials and to the influence of the fabrication processes on the properties of the piezoelectric films are addressed. These epitaxial PZT transducers can generate relatively large deflections at low bias voltages in the static mode. Estimations of the piezoelectric coefficient d31 of the epitaxial PZT thin film (100 nm) yield 130 pm V-1. In the dynamic mode, the performance of the epitaxial PZT transducers in terms of the resonant frequency, modal shape and quality factor are examined. An epitaxial PZT/Si cantilever (1000 × 2500 × 40 µm3) resonating in air and in vacuum exhibits a deflection of several microns with quality factors of 169 and 284, respectively. For a 1500 µm diameter membrane, the quality factor is 50 at atmospheric pressure, and this rises to 323 at a pressure of 0.1 mbar. These results indicate the high potential of epitaxial piezoelectric MEMS, which can impact a variety of technological applications.

Isarakorn, D.; Sambri, A.; Janphuang, P.; Briand, D.; Gariglio, S.; Triscone, J.-M.; Guy, F.; Reiner, J. W.; Ahn, C. H.; de Rooij, N. F.

2010-05-01

419

Electrically Tunable Y-type Hexaferrite-Piezoelectric Microwave Resonator  

NASA Astrophysics Data System (ADS)

An electrically tunable Y-type hexaferrite-piezoelectric resonator has been designed and characterized. Such Y-type hexagonal ferrites have large in-plane anisotropy that would facilitate the observation of ferromagnetic resonance (FMR) over 5-25 GHz with external bias fields of 0-5 kOe. In a ferrite-piezoelectric bilayer the FMR could be tuned with an electric field E applied to the piezoelectric layer. The piezoelectric deformation manifests as an internal magnetic field in the ferrite and will lead to a shift in FMR. Single crystal ferrites of the composition Ba2Zn2Fe12O22 (Zn2Y) were used. The crystals were grown by the floating zone technique. The resonator consisted of a 100 micron thick 1 mm x 3 mm Zn2Y bonded to 10 mm diameter ,200 micron thick lead zirconate titanate (PZT). The resonator was placed in a micorstripline and excited with 1 mW of microwaves. The reflected or transmitted power was measured with a a vector network analyzer. Reflected power versus frequency profiles at 5-25 GHz for a series of in-plane bias magnetic field H showed an increase in the FMR frequency by 60 MHz for E = 7 kV/cm. These resonators can be used as filters or phase shifters. -- work supported by grants from ARO and ONR.

Tatarenko, Alexander; Srinivasan, G.

2010-03-01

420

Design and Modelling a Mini-System with Piezoelectric Actuation  

E-print Network

1 Design and Modelling a Mini-System with Piezoelectric Actuation S. Noveanu1 , V.I. Csibi1 , A. I.ivan@femto-st.fr Abstract. In this paper a new mini-system with piezoelectric actuation is presented. The piezoelectric the input displacement, with facile connection with the piezoelectric actuator. The piezoelectric actuator

Paris-Sud XI, Université de

421

PPF Control of a Piezoelectric Tube Scanner (Invited Paper)  

E-print Network

PPF Control of a Piezoelectric Tube Scanner (Invited Paper) M. Ratnam, B. Bhikkaji, A. J. Fleming and S. O. R. Moheimani Abstract-- Piezoelectric tubes are commonly used in Scan- ning Tunnelling to a piezoelectric tube or placing the sample on the top of a piezoelectric tube, and actuating the piezoelectric

Fleming, Andrew J.

422

Modeling photoacoustic spectral features of micron-sized particles  

NASA Astrophysics Data System (ADS)

The photoacoustic signal generated from particles when irradiated by light is determined by attributes of the particle such as the size, speed of sound, morphology and the optical absorption coefficient. Unique features such as periodically varying minima and maxima are observed throughout the photoacoustic signal power spectrum, where the periodicity depends on these physical attributes. The frequency content of the photoacoustic signals can be used to obtain the physical attributes of unknown particles by comparison to analytical solutions of homogeneous symmetric geometric structures, such as spheres. However, analytical solutions do not exist for irregularly shaped particles, inhomogeneous particles or particles near structures. A finite element model (FEM) was used to simulate photoacoustic wave propagation from four different particle configurations: a homogeneous particle suspended in water, a homogeneous particle on a reflecting boundary, an inhomogeneous particle with an absorbing shell and non-absorbing core, and an irregularly shaped particle such as a red blood cell. Bioc