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1

Thermal Properties of Porcine Tissues Determined by Modified Photoacoustic Piezoelectric Technique  

NASA Astrophysics Data System (ADS)

Using the modified photoacoustic piezoelectric (PAPE) technique, the influence of the piezoelectric transducer on the vibrations of the sample is taken into account. The modified PAPE technique is employed to determine the average thermal diffusivities of the porcine tissues, which include fresh and dry skin, fat, and muscle. The values of the thermal diffusivities of all measured porcine tissues determined by the modified PAPE technique are smaller than those of the conventional ones, especially for the dry skin and fresh fat samples. The thermal diffusivity of the fresh skin sample is the biggest, and the dry samples of different tissues have similar thermal properties with each other. These results show that the modified PAPE technique can provide thermal characterization of the porcine tissues more effectively.

Zhao, Binxing; Wang, Yafei; Gao, Chunming; Liu, Ting; Sun, Qiming

2013-09-01

2

Differential photoacoustic microscopy technique.  

PubMed

Photoacoustic microscopy (PAM), whose image quality largely depends on the optical absorption of samples, provides endogenous information for structural and functional imaging. However, PAM technology in general can not provide edge enhancement imaging for absorbing objects. Therefore, PAM and differential microscopy are integrated for the first time in a single technique to obtain an edge enhancement image. The resolution test target RTA-07 and red blood cells are used as samples to achieve the desired spatial differential photoacoustic imaging. The feasible biomedical application of edge enhancement from the improved differential PAM was demonstrated. PMID:23632532

Tang, Hongchun; Tang, Zhilie; Wu, Yongbo; Cai, Qiuxia; Wu, Liru; Chi, Yan

2013-05-01

3

A piezoelectric cell for simultaneous photoacoustic and fluorescence measurements  

SciTech Connect

A piezoelectric cell based on a bifurcated fiber optic has been designed and implemented for simultaneous photoacoustic and fluorescence measurements. The analytes were ethanolic solutions of anthracene. Quartz rod configurations were evaluated to reduce the amount of scattered light impinging on the piezoelectric crystal. 14 refs., 7 figs., 1 tab.

Williamson, C.K.; Coleman, G.N. [Univ. of Alabama, Tuscaloosa, AL (United States)

1994-12-31

4

Pulse shapes of nanosecond photoacoustic signals in liquids detected by piezoelectric foil  

SciTech Connect

A nonringing detection system based on 28-..mu..m-thick piezoelectric, poly(vinylidene difluoride) foil has been constructed for studying photoacoustic signals in liquids. Excellent agreement between theoretical and experimental photoacoustic pulse shapes has been observed. This system is well suited for monitoring radiationless relaxation processes in solutions on a nanosecond time scale.

Komorowski, S.J.; Eyring, E.M.

1987-10-01

5

Recent Progress on Infrared Photoacoustic Spectroscopy Techniques  

Microsoft Academic Search

Analogous to most new methods in science, photoacoustic spectroscopy (PAS) grew out of an advance in technology, in this case the dramatic improvement in the novel light sources, modulators and acoustic detectors, as well as signal recovery electronics, which in turn was made possible by the development of modern PAS techniques. PAS as a promising technique can be used to

Jingsong Li; Weidong Chen; Benli Yu

2011-01-01

6

Photoacoustic technique applied to the study of skin and leather  

SciTech Connect

In this paper the photoacoustic technique is used in bull skin for the determination of thermal and optical properties as a function of the tanning process steps. Our results show that the photoacoustic technique is sensitive to the study of physical changes in this kind of material due to the tanning process.

Vargas, M.; Varela, J.; Hernandez, L.; Gonzalez, A. [Instituto de Fisica, Universidad de Guanajuato P.O. Box E-143, Leon, Gto. (Mexico)

1998-08-28

7

Photoacoustic measurement technique using acoustic phase perturbation  

SciTech Connect

A novel photoacoustic measurement technique is introduced, which is based on the phase perturbation of an external acoustic wave that propagates through a region of material irradiated by an optical beam. The mechanism of the perturbation is the local change in acoustic velocity due to heating of the irradiated sample. Because the acoustic phase perturbation may be calibrated directly, it is found that the absolute optical absorption coefficient of the irradiated sample may be determined using the technique. Both the experimental phase detection system and a theoretical analysis of the acoustic perturbation are discussed. Finally, an experiment is described in detail, where the measurement technique is used to determine the absolute optical absorption coefficient of a liquid.

Stearns, R.G.

1988-02-01

8

Skin absorption studied by photoacoustic techniques  

NASA Astrophysics Data System (ADS)

In this work we propose for the particular problem of penetration of substance into skin, a setup which is based on the conventional photoacoustic cell. In order to avoid some problems, intrinsic to the material under study and the sensibility of the technique, we use the thermal effusivity of the skin-substance system to monitor this phenomenon, in vivo and in situ. We measure the changes of thermal effusivity due to the absorption of some topical medicaments. These values are compared with those from an adjacent sample of clean skin (without medicament, natural fats or transpiration). This experiment was performed on a volunteer in different parts of the human skin. We use stainless steel (250 mm thickness) as the thermally thin light absorbance surface. The values for this parameter are in agreement with some reported in the literature. Besides the measurements described above. .

Vargas-Luna, M.; Córdova-Fraga, T.; Varela-Nájera, J. B.; Gutiérrez-Juárez, G.

2000-10-01

9

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

10

Numerical homogenization techniques applied to piezoelectric composites.  

PubMed

With the recent availability of piezoelectric fibers, the design and the analysis of piezoelectric composites needs new modeling tools. Therefore, a numerical homogenization technique has been developed, based on the ATILA finite element code, that combines two techniques: one relying upon the representative volume element (RVE) the other relying upon the wave propagation (WP). The combination of the two methods allows the whole tensor of the homogenized properties of the piezoelectric composite to be found. Considering a fiber embedded in epoxy, the numerical results are compared to the results obtained using previous analytical models, thus validating the models. Even if the method is presented in a particular case, its extension to any piezoelectric composite is straightforward. PMID:12597177

Lenglet, Eve; Hladky-Hennion, Anne-Christine; Debus, Jean-Claude

2003-02-01

11

Multicolor photoacoustic imaging by a single transducer with piezoelectric copolymer film in a wide frequency range  

NASA Astrophysics Data System (ADS)

We built a photoacoustic tomographic (PAT) imaging system by scanning a single detector (? 3.5 mm) made of piezoelectric copolymer poly(vinylidene difluoride-trifluoroethylene), P(VDF-TrFE), which had been fabricated for diagnostic photoacoustic measurement of cartilage tissues in our group. The PAT images of a phantom were obtained at two excitation wavelength of 687.5 nm and 795 nm. The phantom was made of agar including a black hair and agarose gels dissolving indocyanine green (ICG) and methylene blue (MB). Laser pulses (685-900 nm) were generated from a Ti:Sappire tunable laser to excite ICG and MB molecules. The PAT image at 687.5 nm shows signals due to all absorption sources. This is good agreement with dimension of the phantom. The PAT image at 795 nm shows a strong signal due to the ICG-dyed gel and almost no signal due to the MB-dyed gel. This result indicated that absorption sources were extracted by excitation wavelength according to their absorption spectra. The signal/noise ratio of the PAT images were compared between the P(VDF-TrFE) transducer in our group and a PZT transducer (Parametrics V309, 5 MHz, ? 12.7 mm) which is commercially available. The P(VDF-TrFE) transducer was more sensitive by 9 times (120 times per area) than the PZT transducer. By using this imaging system with a P(VDF-TrFE) transducer which is highly sensitive in a wide frequency range, we will achieve frequency analysis of the PAT images to associate photoacoustic waveforms with physical properties of sample tissues.

Ohmori, Tsutomu; Ishihara, Miya; Tsujita, Kazuhiro; Bansaku, Isao; Kikuchi, Makoto

2010-02-01

12

Optimal piezoelectric switching technique for vibration damping  

NASA Astrophysics Data System (ADS)

This paper describes piezoelectric switching techniques for vibration damping. The dynamical behaviour of a piezoceramics connected to a switching LR shunt and the dissipated energy are obtained using a fundamental piezoelectric model. All calculations are performed in a normalized way and highlight the influence of the electromechanical coupling coefficient of the piezoceramics and the shunt parameters. For the first time, a precise result for the dynamics of a shunted piezoceramics is derived. The analytic results are used to determine the optimal switching sequence and external branch parameters in order to maximize the damping performance. The results are validated by measurements of a clamped beam.

Neubauer, Marcus; Oleskiewicz, Robert

2007-03-01

13

Study of Photoacoustic Techniques for Detection of Mercaptans  

Microsoft Academic Search

Studies were performed utilizing photoacoustic techniques for the quantitative detection of mercaptans in natural gas. An experimental spectrophone was designed and constructed. Its performance was analyzed using samples of methane gas containing differing concentrations of normal propyl mercaptan, one of the odorants commonly injected into natural gas. The spectrophone performed the necessary analyses and reported the concentration of mercaptans present

Randle Lee Overbey

1986-01-01

14

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

15

Thermal NDE techniques-from photoacoustics to thermosonics  

NASA Astrophysics Data System (ADS)

The evolution of thermal wave imaging and materials characterization is traced from its origins during the time of the First International Workshop on Photoacoustics and Photothermal Phenomena in Ames, Iowa in 1979 to the present, and with an eye to the future. In the early days, the heat sources consisted of amplitude-modulated lasers, focused to a spot, and step-scanned across the surface of the object under evaluation. A variety of lock-in detection schemes were used, including microphones in gas cells (photoacoustics), laser optical probes (the mirage effect), photothermal defection, thermoreflectance, and infrared (IR) detection. With the commercial availability of IR cameras, rapid and wide-area synchronous imaging became possible, both in the frequency domain (lock-in imaging), and the time-domain (box-car imaging). Recently, the photoacoustic technique has been ``flipped,'' with a pulse of sound being used as the energy source, and with an IR camera monitoring the subsequent photons emitted in the vicinity of a surface or subsurface defect. This new technique (thermosonics) is described, along with selected applications to crack detection in a variety of materials and objects. .

Thomas, Robert L.

2002-05-01

16

Photoacoustic imaging using a frequency domain synthetic aperture focusing technique  

NASA Astrophysics Data System (ADS)

This paper describes the application of a frequency domain synthetic aperture focusing technique to photoacoustic imaging. The photoacoustic probe consisted of a laser delivery fiber-optic (diameter of 600 ?m, plastic coated silica) combined with a polymer (PVDF) transducer for ultrasonic detection. This system had a broadband frequency response in the MHz region. Such an integral probe was designed to optically transmit and receive near on-axis ultrasonic transients simultaneously, in under water applications. A frequency domain synthetic aperture method was successfully applied using phantom samples to produce 2D images from A-scan signals received from the probe. A range of samples were examined, including black nylon with 1 mm circular holes at a depth of 5.9 mm from the surface. A comparison was made with conventional B-scan images and with time domain synthetic aperture images. Results showed that synthetic focusing apertures, in time or frequency domains, offer better signal-to-noise ratios with improved capabilities in lateral resolution.

Boonsang, S.; Zainal, J.; Dewhurst, Richard J.

2004-07-01

17

Study of photoacoustic techniques for detection of mercaptans  

SciTech Connect

Studies were performed utilizing photoacoustic techniques for the quantitative detection of mercaptans in natural gas. An experimental spectrophone was designed and constructed. Its performance was analyzed using samples of methane gas containing differing concentrations of normal propyl mercaptan, one of the odorants commonly injected into natural gas. The spectrophone performed the necessary analyses and reported the concentration of mercaptans present in the gas samples. The test obtained from the spectrophone closely followed the theoretical response curve. The decrease in signal voltage was determined to be directly proportional to the decrease in mercaptan concentration. The lowest concentration of mercaptan analyzed by the spectrophone was approximately 25% of the typical concentration level of mercaptan occurring in odorized natural gas. Thus, the studies indicated the analytical range of the spectrophone was sufficient to allow the instrument to be utilized ion performing quantitative analyses of mercaptans in natural gas.

Overbey, R.L.

1986-01-01

18

Study of Photoacoustic Techniques for Detection of Mercaptans  

NASA Astrophysics Data System (ADS)

Studies were performed utilizing photoacoustic techniques for the quantitative detection of mercaptans in natural gas. An experimental spectrophone was designed and constructed. Its performance was analyzed using samples of methane gas containing differing concentrations of normal propyl mercaptan, one of the odorants commonly injected into natural gas. The spectrophone performed the necessary analyses and reported the concentration of mercaptans present in the gas samples. The test data obtained from the spectrophone closely followed the theoretical response curve. The decrease in signal voltage was determined to be directly proportional to the decrease in mercaptan concentration. The lowest concentration of mercaptan analyzed by the spectrophone was approximately 25 percent of the typical concentration level of mercaptan occurring in odorized natural gas. Thus, the studies indicated the analytical range of the spectrophone was sufficient to allow the instrument to be utilized in performing quantitative analyses of mercaptans in natural gas.

Overbey, Randle Lee

1986-08-01

19

Application of lasers in photoacoustic and photothermal microscopy of solids with residual stresses  

NASA Astrophysics Data System (ADS)

Photoacoustic and photothermal techniques which can be used for the investigation and imaging of solids with residual stresses are described. Photoacoustic and photothermal images of different types (photodeflection, photoreflectance, photoacoustic piezoelectric) are presented. By imaging Vickers indented samples it is demonstrated that the photoacoustic piezoelectric microscopy has a high sensitivity to residual stresses. It is also shown that thermal wave images do not reveal a strong influence of residual stress on thermophysical properties of materials. Presented results of the photoacoustic and photothermal imaging of samples under direct loading and annealing demonstrate some specific features of the residual stress influence on the photoacoustic signals. The possibility of development of new non-destructive evaluation systems based on application of modern lasers for residual stress detection is discussed.

Muratikov, Kyrill L.; Glazov, Alexej L.

2002-02-01

20

Thermal Properties of Melanin Determined from Photoacoustic Techniques.  

National Technical Information Service (NTIS)

Photoacoustic signals from synthetic melanin powders and films were detected and analyzed; their signification to vision research is discussed. Consistency between results from our experimental arrangement and Rosencwaig-Gersho theory was confirmed. The l...

J. M. Gallas R. G. Allen E. T. Schmeisser M. Eisner P. Talley

1988-01-01

21

Applications of photoacoustic techniques to the study of jet fuel residue  

NASA Technical Reports Server (NTRS)

It has been known for many years that fuels for jet aircraft engines demonstrate thermal instability. One manifestation of this thermal instability is the formation of deleterious fuel-derived thermally-induced deposits on surfaces of the aircraft's fuel-handling system. The results of an investigation of the feasibility of applying photoacoustic techniques to the study of the physical properties of these thermal deposits are presented. Both phase imaging and magnitude imaging and spectroscopy were investigated. It is concluded that the use of photoacoustic techniques in the study of films of the type encountered in this investigation is not practical.

Claspy, P. C.

1983-01-01

22

Multi-element synthetic aperture focusing photoacoustic imaging system with real-time digital beamformer technique  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging takes the merits of simultaneous high optical contrast and low acoustical scattering, and has been proven to be a potential tool for noninvasive diagnosis of cancer tumors in an early stage. An integrated prototype multi-element synthetic aperture focusing photoacoustic imaging system using real-time digital beamformer (96 scan lines of each frame image) is designed, fabricated and tested. The combined system with multi-channel signal acquisition and real-time digital beam-formation module implements real-time dynamic receiving focus and apodization technique to process the photoacoustic signal, which is captured by a 128-element linear ultrasonic transducer array. The data acquisition and synthesis time can be accelerated in less than 4 s of each view without data average. The in vivo experiments were performed with a clear view of the blood vessels network of mouse tumor. The results demonstrate that the multi-element synthetic aperture focusing photoacoustic imaging system with real-time digital beamformer technique has the potential in the practical fast photoacoustic imaging for clinical diagnosis.

Ji, X.; Yang, S.

2010-12-01

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

Determination of thin film optical properties by the photoacoustic OPC technique  

Microsoft Academic Search

Through the use of maxima and minima of interference fringes in transmittance spectra registered by the open photoacoustic cell (OPC) detection technique, we have determined the refraction index n and thickness d of aluminium nitride thin films which had previously been deposited on opaque and transparent substrates. The results for the transparent substrate are in agreement with those obtained from

C. García-Segundo; M. Villagrán-Muniz; S. Muhl

1998-01-01

25

Comparison of low-frequency piezoelectric switching shunt techniques for structural damping  

Microsoft Academic Search

In this paper, the performances of two novel low-frequency piezoelectric switching shunt techniques for structural damping are compared to the traditional passive tuned resonant shunt circuit technique. The first novel technique, state switching, is a semi-active variable stiffness technique in which bonded piezoelectric elements are switched from the short circuit to open circuit states. This technique changes the stiffness of

Lawrence R. Corr; William W. Clark

2002-01-01

26

Thermal effusivity of human skin by photoacoustic technique  

NASA Astrophysics Data System (ADS)

In this work, we show a particular setup, which is based on the conventional photoacoustic cell, to measure thermal effusivity of human skin in-vivo and in-situ. We measure the changes of thermal effusivity due to the absorption of sunscreen into the skin and these values are compared with those from an adjacent sample of clean skin. This experiment was performed on a volunteer's forearm and stainless steel as the thermally thin absorption surface. The values for this parameter are in good agreement with those reported in the literature. Besides the measurements described above, with the same setup we got the thermal effusivity of the sunscreen itself as a reference parameter. R

Varela-Najera, Jose B.; Cordova-Fraga, Teodor; Vargas-Luna, Miguel; Gutierrez-Juarez, Gerardo

2000-05-01

27

The photophysics of some UV-MALDI matrices studied by using spectroscopic, photoacoustic and luminescence techniques  

NASA Astrophysics Data System (ADS)

The photophysical behaviour of classical UV-MALDI matrices 2,5-dihydroxybenzoic acid (gentisic acid; GA), 2,4,6-trihydroxyacetophenone (THAP), trans-3,5-dimethoxy-4-hydroxycinnamic acid (SA), trans-4-hydroxy-?-ciano-4-hydroxycinnamic acid (CHC), 9H-pirido[3,4-b]indole (nor-harmane; norHo) and 1-methyl-9H-pirido[3,4-b]indole (harmane; Ho) in acetonitrile was studied by using spectroscopic, luminescence and photoacoustic techniques.

Mesaros, Mariana; Tarzi, Olga I.; Erra-Balsells, Rosa; Bilmes, Gabriel M.

2006-08-01

28

Improved piezoelectric switch shunt damping technique using negative capacitance  

NASA Astrophysics Data System (ADS)

This paper proposes an adaptive shunt damping circuit for improved damping performance. It consists of a switched inductance-resistance network (SSDI), which is connected in parallel to a negative capacitance. This circuit is in the following called 'synchronized switching damping on negative capacitor and inductor' (SSDNCI). It combines the adaptive nature of the SSDI technique and the improved performance of a negative capacitance. By the action of the switch device, the piezoelectric element is periodically held under both states of the nonlinear shunt and therefore adapts to the frequency of excitation. The analysis in this publication is performed based on the typical assumptions of a single degree-of-freedom oscillator. The stationary charge signal and energy dissipation are derived as functions of the ratio between the negative capacitance and piezoelectric capacitance. Calculation results show that the dissipated energy grows with the negative capacitance up to the stability boundary of the system. Measurements are conducted on a clamped beam test rig to validate the theoretical results. In the operative range of the negative capacitance which is used in this research, an increase in nearly 220% in energy dissipation compared to the standard SSDI technique is achieved.

Han, Xu; Neubauer, Marcus; Wallaschek, Jörg

2013-01-01

29

Piezoelectric active sensing techniques for damage detection on wind turbine blades  

Microsoft Academic Search

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

Kevin M. Farinholt; Stuart G. Taylor; Charles R. Farrar

2011-01-01

30

Piezoelectric immunosensor with gold nanoparticles enhanced competitive immunoreaction technique for quantification of aflatoxin B 1  

Microsoft Academic Search

A simple, rapid and highly sensitive piezoelectric immunosensor has been proposed and applied to detect aflatoxin B1 (AFB1). It is unlikely that direct binding of small molecules such like AFB1 to the piezoelectric sensor surface could result in a satisfactory detection limit and sensitivity. Thus, indirect competitive immunoassay technique had been used for the detection of the target and gold

Xiaoyong Jin; Xuefang Jin; Liguo Chen; Jianhui Jiang; Guoli Shen; Ruqin Yu

2009-01-01

31

Thermal diffusivity measurements in the photoacoustic open-cell configuration using simple signal normalization techniques  

NASA Astrophysics Data System (ADS)

A generalized model for the open photoacoustic cell configuration (OPC) technique, involving one-dimensional heat diffusion across two layers, is presented. The analytical results are particularly suitable for applications with dielectric solids, such as polymers and resins. Two effective normalization procedures for simple and reliable measurement of the thermal diffusivity of this kind of materials using an OPC are also presented. The thermal diffusivity of three different materials (a dental resin, an epoxy resin, and a polymer foil) was measured and excellent agreement was obtained with some values reported in the literature.

Balderas-López, J. A.; Mandelis, A.

2001-09-01

32

Adaptive synthetic-aperture focusing technique for microvasculature imaging using photoacoustic microscopy.  

PubMed

To improve the lateral resolution of the blood vessels along arbitrary direction out of focus in photoacoustic microscopy (PAM), we propose an adaptive synthetic-aperture focusing technique (ASAFT) for microvasculature imaging which can be automatically applied to each branch of blood vessels, based on our previous two-dimensional (2D) SAFT. The ASAFT is validated both in the phantom study and in vivo imaging. The results demonstrate that ASAFT can provide images of blood vessels with better lateral resolution both at different depths and along various directions compared with one-dimensional and 2D SAFT. PMID:22453434

Deng, Zilin; Yang, Xiaoquan; Gong, Hui; Luo, Qingming

2012-03-26

33

Piezoelectric in situ transmission electron microscopy technique for direct observations of fatigue damage accumulation in constrained metallic thin films  

Microsoft Academic Search

A piezoelectric in situ transmission electron microscopy (TEM) technique has been developed to observe the damage mechanism in constrained metallic thin films under cyclic loading. The technique was based on the piezoelectric actuation of a multilayered structure in which a metallic thin film was sandwiched between a piezoelectric actuator and a silicon substrate. An alternating electric field with a static

X. Tan; T. Du; J. K. Shang

2002-01-01

34

Photoacoustic effect and its applications  

NASA Astrophysics Data System (ADS)

Photoacoustic detection characteristics, as well as the principle and applications of the photoacoustic effect in gases and solids are introduced. Figures show a gas photoacoustic detection system; a photoacoustic spectrum of benzene and Lamb's depression for methyl alcohol as displayed by a CO2 laser; a correlation curve of pure CH4; resonance curves for (C-12)O2 and (C-13)O2; a photoacoustic resonator of a microphone detection system; a transducer-specimen assembly of detection system of a piezoelectric transducer; a weak-absorption set-up for photoacoustic detection of solids; an optico-acoustical spectrum for the epidermis of guinea-pigs; and determination of photoelectric quantum efficiency Q of thin dye films. Tables give the P (tau) values of the oscillatory relaxation of CH4 determined by several methods, and a comparison of results of weak absorption determination.

Wei, M.; Qian, M.

1985-03-01

35

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

36

Nd3+ fluorescence quantum-efficiency measurements with photoacoustics  

NASA Astrophysics Data System (ADS)

We have investigated the use of photoacoustic techniques for obtaining absolute values of fluorescence quantum efficiencies in lightly doped Nd3+ laser materials. We have found that surface absorptions play an important role in gas-microphone measurements, and that thermal profiles are important in piezoelectric measurements. We have obtained fluorescence quantum efficiencies for Nd3+ in yttrium aluminum garnet, and in silicate and borate glasses that are in good agreement with lifetime measurements and Judd-Ofelt calculations.

Rosencwaig, Allan; Hildum, Edward A.

1981-04-01

37

Three-dimensional photoacoustic imaging of blood vessels in tissue  

Microsoft Academic Search

We applied photoacoustics as a tissue tomography technique for the detection of blood concentrations, e.g., angiogenesis around tumors. We imaged blood vessels in highly scattering samples, using 532-nm light, to depths of ,1 cm. The samples were real tissue (chicken breast) or 10% dilutions of Intralipid-10%. The blood flowed through nylon capillaries. Polyvinylidene difluoride (PVdF) piezoelectric detectors were used in

C. G. A. Hoelen; Mul de F. F. M; R. Pongers; A. Dekker

1998-01-01

38

Consideration of Impedance Matching Techniques for Efficient Piezoelectric Energy Harvesting  

Microsoft Academic Search

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 times 10-3 V m\\/N. Second, a transducer structure, cymbal, was optimized and fabricated to

Hyeoungwoo Kim; Shashank Priya; Harry Stephanou; Kenji Uchino

2007-01-01

39

Evaluation of Her2 status using photoacoustic spectroscopic CT techniques  

NASA Astrophysics Data System (ADS)

Purpose: The purpose of this study is to determine the feasibility of using photacoustic CT spectroscopy(PCT-s) to track a near infrared dye conjugated with trastuzumab in vivo. Materials and Methods: An animal model was developed which contained both high and low Her2 expression tumor xenografts on the same mouse. The tumors were imaged at multiple wavelengths (680- 950nm) in the PCT scanner one day prior to injection of the near infrared conjugated probe. Baseline optical imaging data was acquired and the probe was then injected via the tail vein. Fluorescence data was acquired over the next week, PCT spectroscopic data was also acquired during this timeframe. The mice were sacrificed and tumors were extirpated and sent to pathology for IHC staining to verify Her2 expression levels. The optical fluorescence images were analyzed to determine probe uptake dynamics. Reconstructed PCT spectroscopic data was analyzed using IDL routines to deconvolve the probe signal from endogenous background signals, and to determine oxygen saturation. Results: The location of the NIR conjugate was able to be identified within the tumor utilizing IDL fitting routines, in addition oxygen saturation, and hemoglobin concentrations were discernible from the spectroscopic data. Conclusion: Photacoustic spectroscopy allows for the determination of in vivo tumor drug delivery at greater depths than can be determined from optical imaging techniques.

Shaffer, Michael; Kruger, Robert; Reinecke, Daniel; Chin-Sinex, Helen; Mendonca, Marc; Stantz, Keith M.

2010-02-01

40

Photoacoustic methods for real-time measurement of laser beam diameter and position, and for laser cavity alignment  

Microsoft Academic Search

Photoacoustic signals generated in absorbing media can be used for real-time alignment of laser cavity components, for measurements of positions and diameters of pulsed laser beams, and for control of the degree of overlap of two or more, focused and unfocused pulsed laser beams. The developed techniques require an absorbing medium and a piezoelectric detector. Measurements and control can be

M. Villagra´n-Muniz; C. Garci´a-Segundo; H. F. Ranea-Sandoval; G. M. Bilmes

1995-01-01

41

Determining the thermophysical properties of Al-doped ZnO nanoparticles by the photoacoustic technique  

NASA Astrophysics Data System (ADS)

The thermal conductivity and specific heat capacity of undoped and Al-doped (1-10 at.%) ZnO nanoparticles prepared using the solvent thermal method are determined by measuring both thermal diffusivity and thermal effusivity of a pressed powder compact of the prepared nanoparticles by using the laser-induced photoacoustic technique. The impact of Al doping versus the microstructure of the samples on such thermal parameters has been investigated. The results reveal an obvious enhancement in the specific heat capacity when decreasing the particle size, while the effect of Al doping on the specific heat capacity is minor. The measured thermal conductivities are about one order of magnitude smaller than that of the bulk ZnO due to several nested reducing heat transfer mechanisms. The results also show that Al doping significantly influences the thermal resistance. Using a simple thermal impedance model, the added thermal resistance due to Al dopant has been estimated.

El-Brolossy, T. A.; Saber, O.; Ibrahim, S. S.

2013-07-01

42

Analysis of Maize Seed Germs by Photoacoustic Microscopy and Photopyroelectric Technique  

NASA Astrophysics Data System (ADS)

A knowledge about thermal parameters of structural components of maize seed is of great relevance in the seed technology practice. The objective of the present study was to determine the thermal effusivity of germs of maize ( Zea mays L.) of different genotypes by means of the photopyroelectric technique (PPE) in the inverse configuration and obtaining the thermal imaging of these samples by photoacoustic microscopy (PAM). Germs from crystalline maize (white pigment), semi-crystalline maize (yellow pigment), and floury maize (blue pigment) were used in this investigation. The results show differences between germs of maize seeds mainly in the values of their thermal effusivities. The thermal images showed minimum inhomogeneity of these seed germs. Characterizations of thermal parameters in seeds are important in agriculture and food production and could be particularly useful to define their quality and determine their utility. PPE and PAM can be considered as potential diagnostic tools for the characterization of agriculture seeds.

Pacheco, A. Domínguez; Aguilar, C. Hernández; Cruz-Orea, A.

2013-05-01

43

Analysis of Piezoelectric Structural Sensors with Emergent Computing Techniques.  

National Technical Information Service (NTIS)

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 sen...

D. L. Ramers

2005-01-01

44

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.

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

2013-01-01

45

Dynamics of Acetaldehyde Production during Anoxia and Post-Anoxia in Red Bell Pepper Studied by Photoacoustic Techniques  

Microsoft Academic Search

Acetaldehyde (AA), ethanol, and CO, production in red bell pepper (Capsicum annum 1.) fruit has been measured in a contin- uou~ flow system as the fruit was switched between 20% O, and anaerobic conditions. Minimum gas phase concentrations of 0.5 nL L-l, 10 nL 1-', and 1 mL L-', respectively, can be detected em- ploying a laser-based photoacoustic technique. This

Hanna Zuckermann; Frans J. M. Harren; Joerg Reuss; David H. Parker

46

Analytical and experimental investigation of the frequency ratio and switching law for piezoelectric switching techniques  

NASA Astrophysics Data System (ADS)

Piezoelectric shunt damping with mechanical structures has been an active research topic for several years. Standard passive techniques suffer from a very limited and frequency-dependent damping performance. Recently, semi-active switching techniques—namely SSDI (synchronized switch damping on inductor) and SSDV (synchronized switch damping on voltage source) techniques—have been proposed, which are capable of adapting to variations of the excitation frequency without reduction in performance. Crucial for the damping performance is the tuning of the shunt parameters and the precise switching sequence. In this paper, an analytical analysis of the switching technique is presented, which includes the influence of all shunt parameters and the switching times. New results concerning the optimal tuning of the inductance and the switching sequence are obtained, and it is shown that the enhanced SSDV technique can be equated with the SSDI technique, albeit with an increased effective piezoelectric force factor. Measurements are conducted to validate the theoretical results.

Neubauer, M.; Wallaschek, J.

2008-06-01

47

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

48

Signal processing techniques for damage detection with piezoelectric wafer active sensors and embedded ultrasonic structural radar  

Microsoft Academic Search

Embedded ultrasonic structural radar (EUSR) algorithm is developed for using piezoelectric wafer active sensor (PWAS) array to detect defects within a large area of a thin-plate specimen. Signal processing techniques are used to extract the time of flight of the wave packages, and thereby to determine the location of the defects with the EUSR algorithm. In our research, the transient

Lingyu Yu; Jingjing Bao; Victor Giurgiutiu

2004-01-01

49

Effect of boundary (support) conditions on piezoelectric damping in the case of SSDI vibration control technique  

NASA Astrophysics Data System (ADS)

Piezoelectric transducers in conjunction with appropriate electric networks can be used as a mechanical energy dissipation device. If a piezoelectric element is attached to a structure, it is strained as the structure deforms and converts a portion of the vibration energy into electrical energy that can be dissipated through a shunt network in the form of heating. These vibration control devices experienced a great development in recent years, due to their performances and advantages compared with active techniques. One of them is the synchronized switch damping (SSD) and derived techniques, which were developed in the field of piezoelectric damping, and which lead to a very good trade-off between the simplicity, the required power supply and their performances. This technique consists in a non-linear processing of the piezoelectric voltage, which induces an increase in electromechanical energy conversion. The control law consists in triggering the inverting switch on each extremum of voltage (or displacement). In this study, the proposed method for the switching sequence is based on the statistical evaluation of structural deflection. The purpose of this paper is to present an experimental study of the synchronized switch damping on inductance (SSDI) control technique sensitivity to the system boundary conditions. It is observed that the fundamental natural frequency greatly depends on these conditions. The effect of these constraints is distributed all over the system and significantly affects the results.

Guyomar, D.; Mohammadi, S.; Richard, C.

2009-02-01

50

Miniaturization and integration of photoacoustic detection  

Microsoft Academic Search

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

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

2002-01-01

51

Real-time photoacoustic imaging with optical ultrasound detection  

NASA Astrophysics Data System (ADS)

Optical ultrasound detection has become an attractive alternative to piezoelectric ultrasound detection for photoacoustic imaging. The favorable properties of optical detection are high resolution, complete optical and acoustical transparency. Recently, it has been shown that optical phase contrast full field detection in combination with a CCD-camera can be used to record acoustic fields. This allows to obtain two-dimensional photoacoustic projection images in real-time. The present work shows an extension of the technique towards full three-dimensional photoacoustic tomography. The specifications of the detection system, resolution and sensitivity, are 66?m and 3.4kPa. The reconstruction of the initial three dimensional pressure distribution is a two step process. First of all, projection images of the initial pressure distribution are acquired. This is done by back propagating the observed wave pattern in frequency space. In the second step the inverse Radon transform is applied to the obtained projection dataset to reconstruct the initial three dimensional pressure distribution. Simulations and experiments are performed to show the overall applicability of this technique for real-time photoacoustic imaging.

Nuster, R.; Paltauf, G.

2012-02-01

52

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

53

Nanosecond laser-induced explosive boiling studied by photoacoustic and plume transmission techniques  

NASA Astrophysics Data System (ADS)

A model experimental "thin variable thickness transparent liquid layer on opaque (absorbing) solid substrate" geometry has been chosen to study explosive boiling and lift-off of a pre-deposited 2-propanol (isopropanol, IPA) layer on a crystalline Si substrate heated by a nanosecond KrF excimer laser using contact photoacoustic and optical plume transmission techniques. The threshold-like transition from the low-amplitude (sub-MPa) bipolar to the intense (near GPa) unipolar temporal shape of acoustic transients has been observed above the ablation threshold of 0.17 J/cm2 ("universal" for micron-thick IPA layers used) due to sub-nanosecond explosive near-critical expansion and boiling in the nanometer-thick liquid IPA sub-layer near the film/substrate interface heated by conduction from the Si substrate. This pressure build-up exceeding many times the critical pressure of 2-propanol (4.8 MPa) exerted a reactive force on the cooler liquid overlay of the IPA layer and accelerated it to lift-off (ablative plume) velocities from several m/s to several tens m/s depending on the film thickness, while the initial expansion velocity of the superheated IPA sub-layer was about 1 km/s. In a good agreement with experimental data, calculations of the IPA/substrate interface temperatures versus laser fluence have shown near-critical state of the IPA sub-layer near the ablation threshold. These data allow testing the general sub-surface explosive boiling mechanism, characteristic for pulsed laser ablation of both opaque and weakly-absorbing materials.

Kudryashov, Sergey I.; Allen, Susan D.

2004-09-01

54

Photorespiration and temperature dependence of oxygen evolution in tomato plants monitored by open photoacoustic cell technique  

Microsoft Academic Search

The open photoacoustic cell was used to monitor the evolution rate of oxygen from tomato leaves. Estimates of the relative amount of released oxygen in vivo and in situ conditions as influenced by ambient temperature are being presented. Photorespiration phenomenon is shown to dominate above a critical temperature. The evolution of this critical point is analyzed as a function of

M. Vargas-Luna; L. Madueńo; G. Gutiérrez-Juárez; J. Bernal-Alvarado; M. Sosa; J. L. González-Solís; S. Sánchez-Rocha; V. Olalde-Portugal; J. J. Alvarado-Gil; P. Campos

2003-01-01

55

Caracterization of color centers and dichroism in some Brazilian species of tourmaline using photoacoustic technique  

Microsoft Academic Search

Photoacoustic Spectroscopy (PAS) experiments in the visible and ultraviolet regions of the electromagnetic spectrum were carried out on a variety of tourmaline species. The results of our investigation show that PAS can be seen as a powerful alternative spectroscopic tool in the identification and characterization of color centers in mineral specimens.

R. J. S. Lima; A. S. Vasconcelos; R. R. Wegner; J. F. Suassuna

2005-01-01

56

Optimized energy harvesting from mechanical vibrations through piezoelectric actuators, based on a synchronized switching technique  

NASA Astrophysics Data System (ADS)

Increasing demand in mobile, autonomous devices has made energy harvesting a particular point of interest. Systems that can be powered up by a few hundreds of microwatts could feature their own energy extraction module. Energy can be harvested from the environment close to the device. Particularly, the ambient mechanical vibrations conversion via piezoelectric transducers is one of the most investigated fields for energy harvesting. A technique for optimized energy harvesting using piezoelectric actuators called "Synchronized Switching Harvesting" is explored. Comparing to a typical full bridge rectifier, the proposed harvesting technique can highly improve harvesting efficiency, even in a significantly extended frequency window around the piezoelectric actuator's resonance. In this paper, the concept of design, theoretical analysis, modeling, implementation and experimental results using CEDRAT's APA 400M-MD piezoelectric actuator are presented in detail. Moreover, we suggest design guidelines for optimum selection of the storage unit in direct relation to the characteristics of the random vibrations. From a practical aspect, the harvesting unit is based on dedicated electronics that continuously sense the charge level of the actuator's piezoelectric element. When the charge is sensed, to come to a maximum, it is directed to speedily flow into a storage unit. Special care is taken so that electronics operate at low voltages consuming a very small amount of the energy stored. The final prototype developed includes the harvesting circuit implemented with miniaturized, low cost and low consumption electronics and a storage unit consisting of a super capacitors array, forming a truly self-powered system drawing energy from ambient random vibrations of a wide range of characteristics.

Tsampas, P.; Roditis, G.; Papadimitriou, V.; Chatzakos, P.; Gan, Tat-Hean

2013-05-01

57

Carbon nanotubes as photoacoustic molecular imaging agents in living mice  

Microsoft Academic Search

Photoacoustic imaging of living subjects offers higher spatial resolution and allows deeper tissues to be imaged compared with most optical imaging techniques. As many diseases do not exhibit a natural photoacoustic contrast, especially in their early stages, it is necessary to administer a photoacoustic contrast agent. A number of contrast agents for photoacoustic imaging have been suggested previously, but most

Adam De La Zerda; Cristina Zavaleta; Shay Keren; Srikant Vaithilingam; Sunil Bodapati; Zhuang Liu; Jelena Levi; Bryan R. Smith; Te-Jen Ma; Omer Oralkan; Zhen Cheng; Xiaoyuan Chen; Hongjie Dai; Butrus T. Khuri-Yakub; Sanjiv S. Gambhir

2008-01-01

58

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.

Wang, Bo; Emelianov, Stanislav

2011-01-01

59

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

60

Fast, limited-data photoacoustic imaging for multiplexed systems using a frequency-domain estimation technique  

PubMed Central

Purpose: A new frequency-domain estimation algorithm has been developed that uses a priori information to simultaneously improve imaging quality and time resolution in photoacoustic tomography with incomplete data sets. Methods: The method involves application of a single-stage Wiener optimal filter to augment data sets by interpolation between measurement locations using relationships determined in a reference scan. The filter can be applied in real-time using FFT methods using either fixed or dynamic references and used with any imaging algorithm. The performance of the method is compared to a modified version of constrained backprojection algorithms using simulations and experimental investigations. Results: Simulations demonstrate the effectiveness of the approach for tracking dynamic photoacoustic activity for data sets with limited views (90°) or tomographic views with a reduced number of acquisition angles at any given time (?32). Experimental data of contrast uptake and washout using a 512-element curved transducer with 8:1 electronic multiplexing with the algorithm demonstrate full two-dimensional tomographic imaging with a temporal resolution better than 130 ms. Conclusions: The estimation algorithm enables high spatial resolution, real-time imaging of dynamic physiological events or volumetric regions for photoacoustic systems employing multiplexing or scanning.

Gamelin, John K.; Aguirre, Andres; Zhu, Quing

2011-01-01

61

Characterisation by Inverse Techniques of Elastic, Viscoelastic and Piezoelectric Properties of Anisotropic Sandwich Adaptive Structures  

NASA Astrophysics Data System (ADS)

In this article we present recent developments regarding parameter estimation in sandwich structures with viscoelastic frequency dependent core and elastic laminated skin layers, with piezoelectric patch sensors and actuators bonded to the exterior surfaces of the sandwich. The frequency dependent viscoelastic properties of the core material are modelled using fractional derivative models, with unknown parameters that are to be estimated by an inverse technique, using experimentally measured natural frequencies and associated modal loss factors. The inverse problem is formulated as a constrained minimisation problem, and gradient based optimization techniques are employed. Applications are presented and discussed, focused on the identification of viscoelastic frequency dependent core material properties.

Araújo, Aurelio L.; Mota Soares, Cristovao M.; Mota Soares, Carlos A.; Herskovits, Jose

2010-10-01

62

A piezoelectric micro-cantilever bio-sensor using the mass-micro-balancing technique with self-excitation  

Microsoft Academic Search

A biosensor was developed for using in a Lab-On-a-Chip (LOC). The sensor detects the change in the resonance frequency of\\u000a a micro-cantilever with a piezoelectric film. This is the mass micro-balancing technique, which has been successfully used\\u000a for detecting bio-materials in the quartz crystal microbalance (QCM). The PZT film, a piezoelectric film, is designed to act\\u000a as both sensor and

Yeolho Lee; Geunbae Lim; Wonkyu Moon

2007-01-01

63

Micromachining Techniques in Developing High-Frequency Piezoelectric Composite Ultrasonic Array Transducers  

PubMed Central

Several micromachining techniques for the fabrication of high-frequency piezoelectric composite ultrasonic array transducers are described in this paper. A variety of different techniques are used in patterning the active piezoelectric material, attaching backing material to the transducer, and assembling an electronic interconnection board for transmission and reception from the array. To establish the feasibility of the process flow, a hybrid test ultrasound array transducer consisting of a 2-D array having an 8 × 8 element pattern and a 5-element annular array was designed, fabricated, and assessed. The arrays are designed for a center frequency of ~60 MHz. The 2-D array elements are 105 × 105 ?m in size with 5-?m kerfs between elements. The annular array surrounds the square 2-D array and provides the option of transmitting from the annular array and receiving with the 2-D array. Each annular array element has an area of 0.71 mm2 with a 16-?m kerf between elements. The active piezoelectric material is (1 ? x) Pb(Mg1/3Nb2/3)O3?xPbTiO3 (PMN-PT)/epoxy 1–3 composite with a PMN-PT pillar lateral dimension of 8 ?m and an average gap width of ~4 ?m, which was produced by deep reactive ion etching (DRIE) dry etching techniques. A novel electric interconnection strategy for high-density, small-size array elements was proposed. After assembly, the array transducer was tested and characterized. The capacitance, pulse–echo responses, and crosstalk were measured for each array element. The desired center frequency of ~60 MHz was achieved and the ?6-dB bandwidth of the received signal was ~50%. At the center frequency, the crosstalk between adjacent 2-D array elements was about ?33 dB. The techniques described herein can be used to build larger arrays containing smaller elements.

Liu, Changgeng; Djuth, Frank T.; Zhou, Qifa; Shung, K. Kirk

2014-01-01

64

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.

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

65

Photoacoustic imaging in biomedicine  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging (also called optoacoustic or thermoacoustic imaging) has the potential to image animal or human organs, such as the breast and the brain, with simultaneous high contrast and high spatial resolution. This article provides an overview of the rapidly expanding field of photoacoustic imaging for biomedical applications. Imaging techniques, including depth profiling in layered media, scanning tomography with focused ultrasonic transducers, image forming with an acoustic lens, and computed tomography with unfocused transducers, are introduced. Special emphasis is placed on computed tomography, including reconstruction algorithms, spatial resolution, and related recent experiments. Promising biomedical applications are discussed throughout the text, including (1) tomographic imaging of the skin and other superficial organs by laser-induced photoacoustic microscopy, which offers the critical advantages, over current high-resolution optical imaging modalities, of deeper imaging depth and higher absorption contrasts, (2) breast cancer detection by near-infrared light or radio-frequency-wave-induced photoacoustic imaging, which has important potential for early detection, and (3) small animal imaging by laser-induced photoacoustic imaging, which measures unique optical absorption contrasts related to important biochemical information and provides better resolution in deep tissues than optical imaging.

Xu, Minghua; Wang, Lihong V.

2006-04-01

66

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.

2011-03-01

67

Piezoelectric surgery in mandibular split crest technique with immediate implant placement: a case report  

PubMed Central

SUMMARY Implant supported rehabilitation of thin edentulous ridges with horizontal atrophy necessitates a regenerative approach. Within the procedures for horizontal bone defects augmentation, ridge expansion techniques permit dislocation of the buccal bone plate in a labial direction and simultaneous implant insertion in single-stage surgery, abbreviating overall treatment time. The piezoelectric ridge expansion technique permits to obtain the expansion of very mineralized bone crests without excessive traumas or the risk of ridge fractures. The case reported shows an implant treatment for partial edentulous lower arch rehabilitation. A full-split thickness flap was raised. The mucoperiosteal reflection permitted to identify alveolar crest contour where osteotomies had to be performed. Split thickness dissection allowed periosteal blood supply to be mainteined on the buccal bone plate. After horizontal and vertical osteotomies were performed with OT7 piezoelectric microsaw (Piezo-surgery, Mectron), a single-bevel scalpel was used to move the buccal bone plate to the labial. Two Straumann TE 3.3/4.8 mm wide implants were inserted in the lower right premolar area, and 1 Straumann 4.8 mm Wide Neck implant was inserted to replace lower right first molar. The amount of bone expansion was equal to the cervical diameter of the placed implants (4.8 mm) and residual bone gap was packed with Bio-Oss granules (Geistlich). Healing was uneventful and 3 months later final restorations with implant-supported porcelain-fused-to-metal crowns were cemented.

BELLEGGIA, F.; POZZI, A.; ROCCI, M.; BARLATTANI, A.; GARGARI, M.

2009-01-01

68

Photoacoustic technique applied to ethylene emission in passion fruit seedlings: An experimental approach  

NASA Astrophysics Data System (ADS)

It is well known that plants respond to mechanical perturbation, such as swaying in the wind, touching or brushing, by a reduction in stem length and an increase in stem diameter. Brushing provides a tactile or thigmic stimulation of the plant growing points and undergo physiological and developmental changes that increase stress tolerance. One of the main hormones released by brushing plants is thought to be ethylene, a plant hormone difficult to trace and monitor because it is a gas. The emission rate of ethylene was monitored using a photoacoustic spectrometer based on the infrared absorption of the line 10P12 and 10P14 of CO2 LASER. In response to the brushing treatment, seedlings of passion fruit (Passiflora edulis L.) showed a increase in the ethylene emission. The aim of this work was to investigate the effect of brushing on the ethylene emission rate of passion fruit seedlings.

Pereira, T.; Baptista-Filho, M.; Corręa, S. F.; de Oliveira, J. G.; da Silva, M. G.; Vargas, H.

2005-06-01

69

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

70

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

71

Detection of aqueous glucose based on a cavity size- and optical-wavelength-independent continuous-wave photoacoustic technique.  

PubMed

Toward the achievement of noninvasive and continuous monitoring of blood glucose level, we developed a new measurement method based on the continuous-wave photoacoustic (CW-PA) technique and performed the first validation in vitro with calibrated aqueous glucose solutions. The PA technique has been studied in the past but exclusively based on the pulse setup since the CW one exhibits dependence on the cavity dimensions, which is not compatible with the final application requirements. This paper describes a new strategy relying on the monitoring of the resonant-frequency relative shift induced by the change of glucose concentrations rather than amplitude signal levels at a fixed frequency. From in vitro results, we demonstrate a stable and reproducible response to glucose at various cavity dimensions and optical wavelengths, with a slope of 0.19 ±0.01%/g/dL. From theoretical considerations, this method is consistent with a relative acoustic velocity measurement, which also explains the aforementioned stability. The proposed method then resolves most of the issues usually associated with the CW-PA technique and makes it a potential alternative for the noninvasive and continuous monitoring of glycemia levels. However, experimental determination of sensor responses to albumin and temperature as two potential interferents shows similar levels, which points to the selectivity to glucose as a major issue we should deal with in future development. PMID:22548281

Camou, S; Haga, T; Tajima, T; Tamechika, E

2012-06-01

72

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

73

Environment-dependent generation of photoacoustic waves from plasmonic nanoparticles.  

PubMed

Nanoparticle-augmented photoacoustics is an emerging technique for molecular imaging. This study investigates the fundamental process of the photoacoustic signal generation by plasmonic nanoparticles suspended in a weakly absorbing fluid. The photoacoustic signal of gold nanospheres with varying silica shell thicknesses is shown to be dominated by the heat transfer between the nanoparticles and the surrounding environment. PMID:22114029

Chen, Yun-Sheng; Frey, Wolfgang; Aglyamov, Salavat; Emelianov, Stanislav

2012-01-01

74

Photoacoustic signal generation based on self-oscillation method  

Microsoft Academic Search

.  In conventional photoacoustic experiments a signal \\u000a generated by photoacoustic phenomenon is produced by a forced stimulation of \\u000a the investigated sample by electromagnetic radiation energy (light) which \\u000a intensity is modulated at a user selected frequency. Resultant photoacoustic \\u000a signal has the same frequency as the light modulation frequency. The paper \\u000a presents a new technique of photoacoustic signal generation, based on \\u000a self-oscillations resulting

T. Borowski; T. Starecki

2008-01-01

75

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

76

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

77

A low-loss hybrid rectification technique for piezoelectric energy harvesting  

NASA Astrophysics Data System (ADS)

Embedded systems have decreased in size and increased in capability; however, small-scale energy storage technologies still significantly limit these advances. Energy neutral operation using small-scale energy harvesting technologies would allow for longer device operation times and smaller energy storage masses. Vibration energy harvesting is an attractive method due to the prevalence of energy sources in many environments. Losses in efficiency due to AC-DC rectification and conditioning circuits limit its application. This work presents a low-loss hybrid rectification technique for piezoelectric vibration energy harvesting using magnetically actuated reed switches and a passive semiconductor full-bridge rectifier. This method shows the capability to have higher efficiency levels and the rectification of low-voltage harvesters without the need for active electrical components. A theoretical model shows that the hybrid rectification technique performance is highly dependent on the proximity delay and the hysteresis behavior of the reed switches. Experimental results validate the model and support the hypothesis of increased performance using the hybrid rectification technique.

Schlichting, A. D.; Fink, E.; Garcia, E.

2013-09-01

78

Innovative technique for tailoring intrinsic stress in reactively sputtered piezoelectric aluminum nitride films  

SciTech Connect

Novel technical and technological solutions enabling effective stress control in highly textured polycrystalline aluminum nitride (AlN) thin films deposited with ac (40 kHz) reactive sputtering processes are discussed. Residual stress in the AlN films deposited by a dual cathode S-Gun magnetron is well controlled by varying Ar gas pressure, however, since deposition rate and film thickness uniformity depend on gas pressure too, an independent stress control technique has been developed. The technique is based on regulation of the flux of the charged particles from ac plasma discharge to the substrate. In the ac powered S-Gun, a special stress adjustment unit (SAU) is employed for reducing compressive stress in the film by means of redistribution of discharge current between electrodes of the S-Gun leading to controllable suppression of bombardment of the growing film. This technique is complementary to AlN deposition with rf substrate bias which increases ion bombardment and shifts stress in the compressive direction, if required. Using SAU and rf bias functions ensures tailoring intrinsic stress in piezoelectric AlN films for a particular application from high compressive -700 MPa to high tensile +300 MPa and allows the gas pressure to be adjusted independently to fine control the film uniformity. The AlN films deposited on Si substrates and Mo electrodes have strong (002) texture with full width at half maximum ranging from 2 degree sign for 200 nm to 1 degree sign for 2000 nm thick films.

Felmetsger, V. V.; Laptev, P. N.; Tanner, S. M. [Tegal Corporation, 51 Daggett Drive, San Jose, California 95134 (United States)

2009-05-15

79

Validation of the piezoelectric rosette technique for locating impacts in complex aerospace panels  

NASA Astrophysics Data System (ADS)

In this paper an approach based on an array of macro-fiber composite (MFC) transducers arranged as rosettes is proposed for high-velocity impact location on isotropic and composite aircraft panels. Each rosette, using the directivity behavior of three MFC sensors, provides the direction of an incoming wave generated by the impact source as a principal strain angle. A minimum of two rosettes is sufficient to determine the impact location by intersecting the wave directions. The piezoelectric rosette approach is easier to implement than the well known time-of-flight based triangulation of acoustic emissions because it does not require knowledge of the wave speed in the material. Hence the technique does not have the drawbacks of time-of-flight triangulation associated to anisotropic materials or tapered sections. The experiments reported herein show the applicability of the technique to high-velocity impacts created with a gas-gun firing spherical ice projectiles. The experimental testing involved the following six specimens: an aluminum panel, a quasi-isotropic CFRP composite panel, a highly anisotropic CFRP composite panel, a stiffened aluminum panel, a stiffened quasi-isotropic CFRP composite panel, and a stiffened anisotropic CFRP composite panel.

Salamone, Salvatore; Bartoli, Ivan; Rhymer, Jennifer; Lanza di Scalea, Francesco; Kim, Hyonny

2011-03-01

80

Study on Detection of SF6 Gas Leakage Based on Photoacoustic Spectrometry  

Microsoft Academic Search

In view of the problems of using traditional monitoring method for SF6 gas leakage in electrical equipments, according to the photoacoustic spectrometry technology, the photoacoustic spectrometry experiment system is designed for detecting SF6 gas concentration. The generation of photoacoustic spectrum is presented, the photoacoustic technique is used to survey the photoacoustic characteristic of SF6 molecule at 10.6 mum wavelength, resonance

Yuanzhe Xu; Hongjing Zhou; Bo Li; Xin Zhao

2009-01-01

81

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

82

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

83

Photoacoustic computed microscopy  

PubMed Central

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

2014-01-01

84

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

85

A piezoelectric micro-cantilever bio-sensor using the mass-micro-balancing technique with self-excitation  

Microsoft Academic Search

A micro biosensor, which can be applied to a lab-on-a-chip (LOC), is developed in order to detect biomaterials such as protein or DNA. The biomaterials are detected by the mass micro-balancing technique, which measures the change of the resonant frequency of the sensor structure. The sensor structure consists of a micro cantilever actuated by piezoelectric PZT film. The PZT film

Yeolho Lee; Geunbae Lim; Wonkyu Moon

2005-01-01

86

NOTES ON EXPERIMENTAL TECHNIQUE AND APPARATUS: A method for continuous observation of frequency-capacitance change around resonance and anti-resonance for piezoelectric material  

Microsoft Academic Search

A method of displaying the dielectric behaviour of piezoelectric materials near resonance is described. It is pointed out that the technique offers certain advantages when rapid changes in behaviour are expected.

J. Storry; J. R. Kirkman

1966-01-01

87

Bulk Crystal Growth of Piezoelectric PMN-PT Crystals Using Gradient Freeze Technique for Improved SHM Sensors  

NASA Technical Reports Server (NTRS)

There has been a growing interest in recent years in lead based perovskite ferroelectric and relaxor ferroelectric solid solutions because of their excellent dielectric, piezoelectric and electrostrictive properties that make them very attractive for various sensing, actuating and structural health monitoring (SHM) applications. We are interested in the development of highly sensitive and efficient PMN-PT sensors based on large single crystals for the structural health monitoring of composite materials that may be used in future spacecrafts. Highly sensitive sensors are needed for detection of defects in these materials because they often tend to fail by distributed and interacting damage modes and much of the damage occurs beneath the top surface of the laminate and not detectable by visual inspection. Research is being carried out for various combinations of solid solutions for PMN-PT piezoelectric materials and bigger size crystals are being sought for improved sensor applications. Single crystals of this material are of interest for sensor applications because of their high piezoelectric coefficient (d33 greater than 1700 pC/N) and electromechanical coefficients (k33 greater than 0.90). For comparison, the commonly used piezoelectric ceramic lead zirconate titanate (PZT) has a d33 of about 600 pC/N and electromechanical coefficients k33 of about 0.75. At the present time, these piezoelectric relaxor crystals are grown by high temperature flux growth method and the size of these crystals are rather small (3x4x5 mm(exp 3). In the present paper, we have attempted to grow bulk single crystals of PMN-PT in a 2 inch diameter platinum crucible and successfully grown a large size crystal of 67%PMN-33%PT using the vertical gradient freeze technique with no flux. Piezoelectric properties of the grown crystals are investigated. PMN-PT plates show excellent piezoelectric properties. Samples were poled under an applied electric field of 5 kV/cm. Dielectric properties at a frequency of 1 kHz are examined. The grown PMN-PT crystals show typical relaxor dielectric properties. Additionally, the thermal properties of the sample are tested. The results are in good agreement with those found in the literature and some are reported for the first time.

Aggarwal, Mohan D.; Kochary, F.; Penn, Benjamin G.; Miller, Jim

2007-01-01

88

Quantitative Photoacoustic Image Reconstruction using Fluence Dependent Chromophores  

PubMed Central

In biomedical photoacoustic imaging the images are proportional to the absorbed optical energy density, and not the optical absorption, which makes it difficult to obtain a quantitatively accurate image showing the concentration of a particular absorbing chromophore from photoacoustic measurements alone. Here it is shown that the spatially varying concentration of a chromophore whose absorption becomes zero above a threshold light fluence can be estimated from photoacoustic images obtained at increasing illumination strengths. This technique provides an alternative to model-based multiwavelength approaches to quantitative photoacoustic imaging, and a new approach to photoacoustic molecular and functional imaging.

Cox, B.T.; Laufer, J.G.; Beard, P.C.

2010-01-01

89

Photoacoustic cystography.  

PubMed

Conventional pediatric cystography, which is based on diagnostic X-ray using a radio-opaque dye, suffers from the use of harmful ionizing radiation. The risk of bladder cancers in children due to radiation exposure is more significant than many other cancers. Here we demonstrate the feasibility of nonionizing and noninvasive photoacoustic (PA) imaging of urinary bladders, referred to as photoacoustic cystography (PAC), using near-infrared (NIR) optical absorbents (i.e. methylene blue, plasmonic gold nanostructures, or single walled carbon nanotubes) as an optical-turbid tracer. We have successfully imaged a rat bladder filled with the optical absorbing agents using a dark-field confocal PAC system. After transurethral injection of the contrast agents, the rat's bladders were photoacoustically visualized by achieving significant PA signal enhancement. The accumulation was validated by spectroscopic PA imaging. Further, by using only a laser pulse energy of less than 1 mJ/cm(2) (1/20 of the safety limit), our current imaging system could map the methylene-blue-filled-rat-bladder at the depth of beyond 1 cm in biological tissues in vivo. Both in vivo and ex vivo PA imaging results validate that the contrast agents were naturally excreted via urination. Thus, there is no concern regarding long-term toxic agent accumulation, which will facilitate clinical translation. PMID:23792925

Jeon, Mansik; Kim, Jeehyun; Kim, Chulhong

2013-01-01

90

Carotenoids and flavonoids identification in Brazilian tropical fruits and vegetables using photoacoustic technique  

Microsoft Academic Search

In this work we present results of the application of PAS technique in the UV-Vis region in a variety of organic materials in natural form such as plant leaves, fruits and vegetables. The observed PAS spectra were associated to the presence of several carotenoids and flavonoids molecules in leaves, fruits and vegetables. Our results confirm PAS as a rapid direct

R. J. S. Lima; A. S. Vasconcelos; J. F. Suassuna

2005-01-01

91

Laser damage threshold of SiO{sub 2} films by the photoacoustic mirage technique  

SciTech Connect

SiO{sub 2} thin films of 240 nm thickness have been deposited by a dual-ion-beam sputtering technique using argon or xenon ions mixed with oxygen ions in the assisting ion beam and the role of the assisting ion beam and of the substrate temperature on the laser damage threshold at 308 nm (XeCl excimer laser) has been investigated by the photo acoustic mirage technique. It has been found that the laser damage threshold was quite dependent on the film deposition conditions. The sample grown at a substrate temperature of 300 deg. C and with the argon ion assisting beam was characterized by the highest damage threshold ( congruent with 10 J/cm{sup 2})

Alvisi, M.; Vasanelli, L. [Dipartimento di Scienza dei Materiali, Universita di Lecce, 73100 Lecce (Italy); De Nunzio, G.; Diso, D.; Perrone, M. R.; Protopapa, L. [Dipartimento di Fisica, Universita di Lecce, 73100 Lecce (Italy); Rizzo, A. [PASTIS-CNRSM, ss 7 Appia, km 713, 72100 Brindisi (Italy); Scaglione, S. [Laboratorio Film Sottili, Enea Casaccia, 00060 S. Maria di Galeria, Roma (Italy)

1999-03-15

92

Pure optical photoacoustic microscopy.  

PubMed

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 the refinements of the microring's working wavelength and in the resonator structure and mold fabrication, an ultrahigh Q factor of 3.0×10(5) was achieved which provided high sensitivity with a noise equivalent detectable pressure(NEDP) value of 29 Pa. 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 with 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, which is not now imageable with current optical or acoustic microscopes of comparable resolution. PMID:21643156

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

2011-05-01

93

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

94

Application of photoacoustic and photothermal techniques for heat conduction measurements in a free-standing chemical vapor-deposited diamond film  

SciTech Connect

Heat conduction in a free-standing chemical vapor-deposited polycrystalline diamond film has been investigated by means of combined front and rear photoacoustic signal detection techniques and also by means of a mirage' photothermal beam deflection technique. The results obtained with the different techniques are consistent with a value of [alpha] = (5.5 [+-] 0.4) [times] 10[sup [minus]4]m[sup 2][center dot]s[sup [minus]1] for thermal diffusivity, resulting in a value of k -(9.8 [+-] 0.7) [times] 10[sup 2]W m[sup [minus]1]. K[sup [minus]1] for thermal conductivity when literature values for the density and heat capacity for natural diamond are used. 25 refs., 7 figs.

Glorieux, C.; De Groote, J.; Lauriks, W.; Thoen, J. (Katholieke Universiteit Leuven (Belgium.)); Fivez, J. (Katholieke Universiteit Leuven (Belgium.) EHSAL, Brussel (Belgium.) Universitaire Faculteiten St. Ignatius, Antwerpen (Belgium.))

1993-11-01

95

High-temperature piezoelectric film ultrasonic transducers by a sol-gel spray technique and their application to process monitoring of polymer injection molding  

Microsoft Academic Search

Thick-film (90 ?m) piezoelectric ceramic high-temperature ultrasonic transducers (HTUTs) have been successfully deposited on metallic substrates by a sol-gel spray technique. The gel is composed of fine powders of bismuth titanate dispersed in a lead-zirconate-titanate solution. The films with desired thickness have been obtained through multilayer coating approach. Piezoelectricity is achieved using the corona discharge poling method. The center frequencies

Makiko Kobayashi; Yuu Ono; Cheng-Kuei Jen; Chin-Chi Cheng

2006-01-01

96

Photoacoustic Spectroscopy of Dielectric and Semiconducting Solids.  

National Technical Information Service (NTIS)

The recently developed techniques of solid state photoacoustic spectroscopy have been applied to the study of absorption processes in dielectric and semiconducting solids which are of interest in high power laser or electronic applications. The photoacous...

S. S. Yee

1981-01-01

97

Characterisation by Inverse Techniques of Elastic, Viscoelastic and Piezoelectric Properties of Anisotropic Sandwich Adaptive Structures  

Microsoft Academic Search

In this article we present recent developments regarding parameter estimation in sandwich structures with viscoelastic frequency dependent core and elastic laminated skin layers, with piezoelectric patch sensors and actuators bonded to the exterior surfaces of the sandwich. The frequency dependent viscoelastic properties of the core material are modelled using fractional derivative models, with unknown parameters that are to be estimated

Aurelio L. Araújo; Cristovao M. Mota Soares; Carlos A. Mota Soares; Jose Herskovits

2010-01-01

98

Photoacoustic imaging using an ultrasonic Fresnel zone plate transducer  

Microsoft Academic Search

A photoacoustic (PA) imaging system based on an ultrasonic Fresnel zone plate (FZP) transducer is developed for the purpose of imaging biological tissue. This FZP transducer has a two-zone negative zone plate piezoelectric material pattern, and an optical fibre is integrated with the transducer on the symmetric axis of the zone plates to deliver laser pulses to the sample. The

Hui Wang; Da Xing; Liangzhong Xiang

2008-01-01

99

Fourier transform photoacoustic visible spectroscopy of solids and liquids  

SciTech Connect

Fourier transform photoacoustic spectroscopy (FTPAS) can be carried out in the visible using either a piezoelectric crystal or a microphone to detect the interferogram produced in a sample when the latter is illuminated by white light passed through a Michelson interferometer. Spectra of lanthanide oxides and whole human blood are reported that illustrate benefits and limitations of visible FTPAS.

Lloyd, L.B. (Univ. of Utah, Salt Lake City); Burnham, R.K.; Chandler, W.L.; Eyring, E.M.; Farrow, M.M.

1980-09-01

100

Features of photoacoustic transformation in microporous nanocrystalline silicon  

NASA Astrophysics Data System (ADS)

Results of a study of the photoacoustic transformation in microporous nanocrystalline silicon are described. The amplitude-frequency and phase-frequency characteristics of the photoacoustic signal from microporous silicon samples on a monocrystalline substrate exposed to illumination at various wavelengths are experimentally determined. Informative response was measured by the gas-microphone and piezoelectric detection methods. In terms of the proposed mathematical model, it is shown that the difference in the parameters of the photoacoustic signal for different wavelengths of exciting radiation is attributed to a shift of the fundamental absorption edge in nanocrystalline silicon. It is pointed out that the piezoelectric detection method is more sensitive to changes in the thermophysical and optical parameters of the porous layer.

Tytarenko, A. I.; Andrusenko, D. A.; Kuzmich, A. G.; Gavril'chenko, I. V.; Skryshevskii, V. A.; Isaiev, M. V.; Burbelo, R. M.

2014-03-01

101

Photoacoustic endoscopic imaging of the rabbit mediastinum  

NASA Astrophysics Data System (ADS)

Like ultrasound endoscopy, photoacoustic endoscopy (PAE) could become a valuable addition to clinical practice due to its deep imaging capability. Results from our recent in vivo transesophageal endoscopic imaging study on rabbits demonstrate the technique's capability to image major organs in the mediastinal region, such as the lung, trachea, and cardiovascular systems. Here, we present various features from photoacoustic images from the mediastinal region of several rabbits and discuss possible clinical contributions of this technique and directions of future technology development.

Yang, Joon-Mo; Favazza, Christopher; Chen, Ruimin; Yao, Junjie; Cai, Xin; Li, Chiye; Maslov, Konstantin; Zhou, Qifa; Shung, K. Kirk; Wang, Lihong V.

2013-03-01

102

Förster resonance energy transfer photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

Förster resonance energy transfer (FRET) provides fluorescence signals sensitive to intra- and inter-molecular distances in the 1-10 nm range. Widely applied in the optical imaging environment, FRET enables visualization of physicochemical processes in molecular interactions and conformation changes. We reported photoacoustic imaging of FRET, based on non-radiative decay that produces heat and subsequent acoustic waves. The experimental results show that photoacoustic imaging offers better penetration into scattering biological tissue. Through its ability to three-dimensionally image tissue with scalable resolution, photoacoustic microscopy provides a beneficial biomedical tool to broaden the in vivo application of the FRET technique.

Wang, Yu; Wang, Lihong V.

2013-03-01

103

Robust Passive Piezoelectric Shunt Dampener  

Microsoft Academic Search

This paper 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 to variations in environmental conditions that can severely eect the performance of other controllers. The proposed control scheme is validated experimentally on a piezoelectric laminated plate structure.

S. Behrens; A. J. Fleming; S. O. R. Moheimani

104

Robust passive piezoelectric shunt dampener  

Microsoft Academic Search

This paper introduces a new multiple mode passive piezoelectric shunt damping technique. The robust passive piezoelectric shunt controller is capable of damping multiple structural modes and maybe less susceptible to variations in environmental conditions that can severely effect the performance of other controllers. The proposed control scheme is validated experimentally on a piezoelectric laminated plate structure.

Sam Behrens; Andrew J. Fleming; S. O. R. Moheimani

2003-01-01

105

Finite element homogenization technique for the characterization of d15 shear piezoelectric macro-fibre composites  

NASA Astrophysics Data System (ADS)

A finite element homogenization method for a shear actuated d15 macro-fibre composite (MFC) made of seven layers (Kapton, acrylic, electrode, piezoceramic fibre and epoxy composite, electrode, acrylic, Kapton) is proposed and used for the characterization of its effective material properties. The methodology is first validated for the MFC active layer only, made of piezoceramic fibre and epoxy, through comparison with previously published analytical results. Then, the methodology is applied to the seven-layer MFC. It is shown that the packaging reduces significantly the shear stiffness of the piezoceramic material and, thus, leads to significantly smaller effective electromechanical coupling coefficient k15 and piezoelectric stress constant e15 when compared to the piezoceramic fibre properties. However, it is found that the piezoelectric charge constant d15 is less affected by the softer layers required by the MFC packaging.

Trindade, M. A.; Benjeddou, A.

2011-07-01

106

Characterisation by Inverse Techniques of Elastic, Viscoelastic and Piezoelectric Properties of Anisotropic Sandwich Adaptive Structures  

Microsoft Academic Search

In this article we present recent developments regarding parameter estimation in sandwich structures with viscoelastic frequency\\u000a dependent core and elastic laminated skin layers, with piezoelectric patch sensors and actuators bonded to the exterior surfaces\\u000a of the sandwich. The frequency dependent viscoelastic properties of the core material are modelled using fractional derivative\\u000a models, with unknown parameters that are to be estimated

Aurelio L. Araújo; Cristovao M. Mota Soares; Carlos A. Mota Soares; Jose Herskovits

2010-01-01

107

Temperature mapping using photoacoustic and thermoacoustic tomography  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) and thermoacoustic (TA) effects are based on the generation of acoustic waves after tissues absorb electromagnetic energy. The amplitude of the acoustic signal is related to the temperature of the absorbing target tissue. A combined photoacoustic and thermoacoustic imaging system built around a modified commercial ultrasound scanner was used to obtain an image of the target's temperature, using reconstructed photoacoustic or thermoacoustic images. To demonstrate these techniques, we used photoacoustic imaging to monitor the temperature changes of methylene blue solution buried at a depth of 1.5 cm in chicken breast tissue from 12 to 42 °C. We also used thermoacoustic imaging to monitor the temperature changes of porcine muscle embedded in 2 cm porcine fat from 14 to 28 °C. The results demonstrate that these techniques can provide noninvasive real-time temperature monitoring of embedded objects and tissue.

Ke, Haixin; Erpelding, Todd N.; Jankovic, Ladislav; Wang, Lihong V.

2012-02-01

108

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

2014-01-01

109

Influence of Bipolar Pulse Poling Technique for Piezoelectric Vibration Energy Harvesters using Pb(Zr,Ti)O3 Films on 200 mm SOI Wafers  

NASA Astrophysics Data System (ADS)

Piezoelectric vibration energy harvester arrays using Pb(Zr,Ti)O3 thin films on 200 mm SOI wafers were fabricated. In-plane distribution of influence of bipolar pulse poling technique on direct current (DC) power output from the harvesters was investigated. The results indicate that combination poling treatment of DC and bipolar pulse poling increases a piezoelectric property and reduces a dielectric constant. It means that this poling technique improves the figure of merit of sensors and harvesters. Maximum DC power from a harvester treated by DC poling after bipolar pulse poling is about five times larger than a one treated by DC poling only.

Moriwaki, N.; Kobayashi, T.; Suzuki, Y.; Makimoto, N.; Fujimoto, K.; Suzuki, K.; Itoh, T.; Maeda, R.

2013-12-01

110

Investigational detection of pharmacological agents in the eye using photoacoustic spectroscopy  

Microsoft Academic Search

This research reports progress in our earlier investigation of detecting specific drug diffusion into eye tissue using photoacoustic spectroscopy (PAS). A key improvement to the technique is using short pulse tunable laser source to stimulate the photoacoustic effect in tissue. An optical parametric oscillator (OPO) laser system was used as a pumping source to generate ultrasonic photoacoustic signals and employed

Saher M. Maswadi; Randolph D. Glickman; Norman Barslou; Rowe W. Elliott

2007-01-01

111

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

112

Miniaturization and integration of photoacoustic detection with a microfabricated chemical reactor system  

Microsoft Academic Search

Photoacoustic spectroscopy is a useful technique for monitoring chemical composition in mesoscale analysis systems because the detection limit scales favorably with miniaturization. The key element of a photoacoustic spectrometry system is the detector. This work focuses on the miniaturization of photoacoustic detection. In particular, we are using 3.4 ?m light to detect propane in a carbon dioxide background-a system that

Samara L. Firebaugh; Martin A. Schmidt

2001-01-01

113

Study of methods for automated crack inspection of electrically poled piezoelectric ceramics.  

SciTech Connect

The goal of this project was to identify a viable, non-destructive methodology for the detection of cracks in electrically poled piezoelectric ceramics used in neutron generator power supply units. The following methods were investigated: Impedance Spectroscopy, Scanning Acoustic Microscopy, Lock-in Thermography, Photo-acoustic Microscopy, and Scanned Vicinal Light. In addition to the exploration of these techniques for crack detection, special consideration was given to the feasibility of integrating these approaches to the Automatic Visual Inspection System (AVIS) that was developed for mapping defects such as chips, pits and voids in piezoelectric ceramic components. Scanned Vicinal Light was shown to be the most effective method of automatically detecting and quantifying cracks in ceramic components. This method is also very effective for crack detection in other translucent ceramics.

Yang, Pin; Hwang, Stephen C.; Jokiel, Bernhard, Jr.; Burns, George Robert

2004-06-01

114

FT-IR-cPAS--New Photoacoustic Measurement Technique for Analysis of Hot Gases: A Case Study on VOCs  

PubMed Central

This article describes a new photoacoustic FT-IR system capable of operating at elevated temperatures. The key hardware component is an optical-readout cantilever microphone that can work up to 200 °C. All parts in contact with the sample gas were put into a heated oven, incl. the photoacoustic cell. The sensitivity of the built photoacoustic system was tested by measuring 18 different VOCs. At 100 ppm gas concentration, the univariate signal to noise ratios (1?, measurement time 25.5 min, at highest peak, optical resolution 8 cm?1) of the spectra varied from minimally 19 for o-xylene up to 329 for butyl acetate. The sensitivity can be improved by multivariate analyses over broad wavelength ranges, which effectively co-adds the univariate sensitivities achievable at individual wavelengths. The multivariate limit of detection (3?, 8.5 min, full useful wavelength range), i.e., the best possible inverse analytical sensitivity achievable at optimum calibration, was calculated using the SBC method and varied from 2.60 ppm for dichloromethane to 0.33 ppm for butyl acetate. Depending on the shape of the spectra, which often only contain a few sharp peaks, the multivariate analysis improved the analytical sensitivity by 2.2 to 9.2 times compared to the univariate case. Selectivity and multi component ability were tested by a SBC calibration including 5 VOCs and water. The average cross selectivities turned out to be less than 2% and the resulting inverse analytical sensitivities of the 5 interfering VOCs was increased by maximum factor of 2.2 compared to the single component sensitivities. Water subtraction using SBC gave the true analyte concentration with a variation coefficient of 3%, although the sample spectra (methyl ethyl ketone, 200 ppm) contained water from 1,400 to 100k ppm and for subtraction only one water spectra (10k ppm) was used. The developed device shows significant improvement to the current state-of-the-art measurement methods used in industrial VOC measurements.

Hirschmann, Christian Bernd; Koivikko, Niina Susanna; Raittila, Jussi; Tenhunen, Jussi; Ojala, Satu; Rahkamaa-Tolonen, Katariina; Marbach, Ralf; Hirschmann, Sarah; Keiski, Riitta Liisa

2011-01-01

115

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

116

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

117

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.

Sheinfeld, Adi; Eyal, Avishay

2012-01-01

118

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.

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

119

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.

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

2013-01-01

120

Photoacoustic Point Source  

SciTech Connect

We investigate the photoacoustic effect generated by heat deposition at a point in space in an inviscid fluid. Delta-function and long Gaussian optical pulses are used as sources in the wave equation for the displacement potential to determine the fluid motion. The linear sound-generation mechanism gives bipolar photoacoustic waves, whereas the nonlinear mechanism produces asymmetric tripolar waves. The salient features of the photoacoustic point source are that rapid heat deposition and nonlinear thermal expansion dominate the production of ultrasound.

Calasso, Irio G.; Craig, Walter; Diebold, Gerald J.

2001-04-16

121

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

122

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.

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

2011-01-01

123

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

NASA Astrophysics Data System (ADS)

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 (70/30 %w/w) containing camphorquinone as photo-initiator, and N,N-dimethyl-p-toluidine as reducing agent. C11 was determined on real time conditions after irradiating the system for predetermined periods. The kinetics of the PP reaction was also studied by infrared spectroscopy in order to compare the evolution of C11 with the rate of conversion of the double bounds of the methacrylate groups. The evolution of C11 reflects the whole polymerisation process: The technique permits to determine the transitions of the resin during polymerisation from viscous to viscoelastic state and further to a glassy polymer.

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

2005-06-01

124

Modeling and experimental verification of synchronized discharging techniques for boosting power harvesting from piezoelectric transducers  

NASA Astrophysics Data System (ADS)

This paper presents analytical models for studying the transient behavior of several power harvesting circuit topologies for use with piezoelectric bending transducers. Specifically, the problem of charging a large storage capacitor, which is inherently a time-varying process, is considered. Three circuit designs are studied—direct charging, synchronized switching and discharging to a storage capacitor, and synchronized switching and discharging to a storage capacitor through an inductor (SSDCI)—and they are compared to a matched resistive load case. Analytical models are developed for these cases to predict the charging rates and output power for various values of storage capacitance and quality factor. Experimental circuit designs are given and their results are compared to the theoretical predictions. It is shown that these predictions are accurate when the losses in the circuit are considered in the model. In spite of these losses, it is demonstrated that the SSDCI design can produce about 200% the output power of the idealized, matched resistive load case throughout the charging process and substantially reduce the charging time of the storage capacitor.

Wu, W. J.; Wickenheiser, A. M.; Reissman, T.; Garcia, E.

2009-05-01

125

Photoacoustic Studies on Iodine.  

NASA Astrophysics Data System (ADS)

A photoacoustic cavity was constructed which employs a temperature-controlled cylindrical cavity with optical windows at either end. It was operated in the lowest longitudinal mode using a small electret microphone for detecting the acoustic signal and a photomultiplier tube for detecting the optical signal. Molecular Iodine was used as the specimen gas and argon as the buffer gas. The photoacoustic characteristics of the system were studied. Iodine molecules, excited periodically by intensity modulated optical radiation (xenon discharge), de-excited by non-radiative processes which result in pressure waves having the same modulation frequency as that of the light. These pressure waves are detected as acoustical pulses by the microphone situated in the wall of the cavity. Studies were conducted for different pressures of buffer gas (100 torr to 800 torr) at several different Iodine pressures in the range between 0.3 and 1 torr. The longitudinal mode of excitation provides an opportunity to compare the response of the cavity under acoustical excitation with that under optical excitation. The relevant parameters in the investigation were: Q, the quality factor of the cavity; the resonant frequency, partial pressures of argon and Iodine; temperature; and the signal amplitude. It was found that the Q of the cavity was well -behaved following the theoretically predicted dependence on SQRT.(P and on T('- 3/4). The absorption coefficient of Iodine determined photometrically, increased with increasing argon pressure up to a limiting value of pressure that depended on Iodine concentration. The photoacoustic signal showed a similar increase with increasing argon pressure. This signal reached a limiting value at a pressure which corresponded closely with that found optically. This is taken to indicate that the extinction coefficient of Iodine in argon, at the level of dilution used in these studies, depends on the argon pressure. A method was developed for measuring the concentration of Iodine at low levels through application of the shift in the frequency of the longitudinal mode resonance of the cavity. Also, resonance technique was employed for determining the velocity of sound in argon. A value of 307.7 M/sec was established as compared with the value of 319 M/sec as reported in various standard handbooks.

Bhan, Avtar N.

126

Design considerations for ultrasound detectors in photoacoustic breast imaging  

NASA Astrophysics Data System (ADS)

The ultrasound detector is the heart of a photoacoustic imaging system. In photoacoustic imaging of the breast there is a requirement to detect tumors located a few centimeters deep in tissue, where the light is heavily attenuated. Thus a sensitive ultrasound transducer is of crucial importance. As the frequency content of photoacoustic waves are inversely proportional to the dimensions of the absorbing structures, and in tissue can range from hundreds of kHz to tens of MHz, a broadband ultrasound transducer is required centered on an optimum frequency. A single element piezoelectric transducer structurally consists of the active piezoelectric material, front- and back-matching layers and a backing layer. To have both high sensitivity and broad bandwidth, the materials, their acoustic characteristics and their dimensions should be carefully chosen. In this paper, we present design considerations of an ultrasound transducer for imaging the breast such as the detector sensitivity and frequency response, which guides the selection of active material, matching layers and their geometries. We iterate between simulation of detector performance and experimental characterization of functional models to arrive at an optimized implementation. For computer simulation, we use 1D KLM and 3D finite-element based models. The optimized detector has a large-aperture possessing a center frequency of 1 MHz with fractional bandwidth of more than 80%. The measured minimum detectable pressure is 0.5 Pa, which is two orders of magnitude lower than the detector used in the Twente photoacoustic mammoscope.

Xia, Wenfeng; Piras, Daniele; Singh, Mithun K. A.; van Hespen, Johan C. G.; van Veldhoven, Spiridon; Prins, Christian; van Leeuwen, Ton G.; Steenbergen, Wiendelft; Manohar, Srirang

2013-03-01

127

Determination of Tequila Quality by Photoacoustic Analysis  

NASA Astrophysics Data System (ADS)

A pulsed laser photoacoustic (PLPA) technique is proposed to distinguish original from adulterated tequila. In fact, it brings a reliable cheaper and more sensible method in adulteration detection, in comparison with traditional techniques. The method proposed is comparative and non-destructive, and it is based on a correlation analysis of photoacoustic signals, obtained by exciting tequila samples with short laser pulses (7 ns), in the UV region (355 nm). Eleven samples of tequila were analyzed. From a reference sample, all other samples were classified.

Ruiz-Pérez, Atzin; Pérez-Castańeda, J. I.; Castańeda-Guzmán, R.; Pérez-Ruiz, S. J.

2013-09-01

128

Thermoacoustic and photoacoustic sensing of temperature  

PubMed Central

We present a novel temperature-sensing technique using thermoacoustic and photoacoustic measurements. This noninvasive method has been demonstrated using a tissue phantom to have high temporal resolution and temperature sensitivity. Because both photoacoustic and thermoacoustic signal amplitudes depend on the temperature of the source object, the signal amplitudes can be used to monitor the temperature. A temperature sensitivity of 0.15°C was obtained at a temporal resolution as short as 2 s, taking the average of 20 signals. The deep-tissue imaging capability of this technique can potentially lead us to in vivo temperature monitoring in thermal or cryogenic applications.

Pramanik, Manojit; Wang, Lihong V.

2009-01-01

129

Photoacoustic detection of gases using microcantilevers  

NASA Astrophysics Data System (ADS)

We describe a new technique for measuring the infrared absorption spectra of gases using atomic force microscope microcantilevers. This photoacoustic system is demonstrated for a dilute acetylene/helium mixture by recording the acetylene ?1+?3 infrared overtone transitions using a wavelength modulated tunable diode laser as the infrared light source. The technique presents significant advantages over existing methods in terms of size, simplicity, speed and insensitivity to ambient vibrations. The maximum achievable signal-to-noise for resonant and non-resonant photoacoustic excitation of the microcantilever is examined and is found to be limited by the microcantilever's Brownian noise.

Adamson, Brian D.; Sader, John E.; Bieske, Evan J.

2009-12-01

130

Fourier transform infrared photoacoustic spectroscopy study of physicochemical interaction between human dentin and etch-&-rinse adhesives in a simulated moist bond technique  

NASA Astrophysics Data System (ADS)

The purpose of this study was to provide the physicochemical interactions at the interfaces between two commercial etch-&-rinse adhesives and human dentin in a simulated moist bond technique. Six dentin specimens were divided into two groups (n=3) according to the use of two different adhesive systems: (a) 2-hydroxyethylmethacrylate (HEMA) and 4-methacryloxyethyl trimellitate anhydrate (4-META), and (b) HEMA. The Fourier transform infrared photoacoustic spectroscopy was performed before and after dentin treatment with 37% phosphoric acid, with adhesive systems and also for the adhesive systems alone. Acid-conditioning resulted in a decalcification pattern. Adhesive treated spectra subtraction suggested the occurrence of chemical bonding to dentin expressed through modifications of the OH stretching peak (3340 cm-1) and symmetric CH stretching (2900 cm-1) for both adhesives spectra; a decrease of orthophosphate absorption band (1040 to 970 cm-1) for adhesive A and a better resolved complex band formation (1270 to 970 cm-1) for adhesive B were observed. These results suggested the occurrence of chemical bonding between sound human dentin and etch-&-rinse adhesives through a clinical typical condition.

Ubaldini, Adriana L. M.; Baesso, Mauro L.; Sehn, Elizandra; Sato, Francielle; Benetti, Ana R.; Pascotto, Renata C.

2012-06-01

131

Fourier transform infrared photoacoustic spectroscopy study of physicochemical interaction between human dentin and etch-&-rinse adhesives in a simulated moist bond technique.  

PubMed

The purpose of this study was to provide the physicochemical interactions at the interfaces between two commercial etch-&-rinse adhesives and human dentin in a simulated moist bond technique. Six dentin specimens were divided into two groups (n=3) according to the use of two different adhesive systems: (a) 2-hydroxyethylmethacrylate (HEMA) and 4-methacryloxyethyl trimellitate anhydrate (4-META), and (b) HEMA. The Fourier transform infrared photoacoustic spectroscopy was performed before and after dentin treatment with 37% phosphoric acid, with adhesive systems and also for the adhesive systems alone. Acid-conditioning resulted in a decalcification pattern. Adhesive treated spectra subtraction suggested the occurrence of chemical bonding to dentin expressed through modifications of the OH stretching peak (3340 cm(-1)) and symmetric CH stretching (2900 cm(-1)) for both adhesives spectra; a decrease of orthophosphate absorption band (1040 to 970 cm(-1)) for adhesive A and a better resolved complex band formation (1270 to 970 cm(-1)) for adhesive B were observed. These results suggested the occurrence of chemical bonding between sound human dentin and etch-&-rinse adhesives through a clinical typical condition. PMID:22734756

Ubaldini, Adriana L M; Baesso, Mauro L; Sehn, Elizandra; Sato, Francielle; Benetti, Ana R; Pascotto, Renata C

2012-06-01

132

Improvement of depth resolution on photoacoustic imaging using multiphoton absorption  

NASA Astrophysics Data System (ADS)

Commercial imaging systems, such as computed tomography and magnetic resonance imaging, are frequently used powerful tools for observing structures deep within the human body. However, they cannot precisely visualized several-tens micrometer-sized structures for lack of spatial resolution. In this presentation, we propose photoacoustic imaging using multiphoton absorption technique to generate ultrasonic waves as a means of improving depth resolution. Since the multiphoton absorption occurs at only the focus point and the employed infrared pulses deeply penetrate living tissues, it enables us to extract characteristic features of structures embedded in the living tissue. When nanosecond pulses from a 1064-nm Nd:YAG laser were focused on Rhodamine B/chloroform solution (absorption peak: 540 nm), the peak intensity of the generated photoacoustic signal was proportional to the square of the input pulse energy. This result shows that the photoacoustic signals can be induced by the two-photon absorption of infrared nanosecond pulse laser and also can be detected by a commercial low-frequency MHz transducer. Furthermore, in order to evaluate the depth resolution of multiphoton-photoacoustic imaging, we investigated the dependence of photoacoustic signal on depth position using a 1-mm-thick phantom in a water bath. We found that the depth resolution of two-photon photoacoustic imaging (1064 nm) is greater than that of one-photon photoacoustic imaging (532 nm). We conclude that evolving multiphoton-photoacoustic imaging technology renders feasible the investigation of biomedical phenomena at the deep layer in living tissue.

Yamaoka, Yoshihisa; Fujiwara, Katsuji; Takamatsu, Tetsuro

2007-07-01

133

Piezoelectric scanners  

NASA Astrophysics Data System (ADS)

Bimorph piezoelectric elements show relative large axial displacements at moderate voltages. Their response to voltage variations is very fast. The reproducibility of the displacement is practically limited only by the mechanical and electrical supplementary equipment. In combination with a deflection mirror linear scans or two-dimensional scan pattern can be generated. Fast scanning with good linearity and repeatability is possible, either in a resonant mode or in a random access mode. However, the hysteresis of the piezoelectric material and the large capacitance of the elements impose some constraints on the applicability of the piezoelectric scanners. In the first part of the paper the properties of piezoelectric elements are discussed in view of scanner application; in the second part an experimental single mirror two-axis piezoelectric scanner is described. Some suggestions for future applications of piezoelectric scanners are made.

Hohner, M.; Manhart, S.

1987-03-01

134

Vibration control efficiency of piezoelectric shunt damping system  

Microsoft Academic Search

The piezoelectric shunt damping technique based on the direct piezoelectric effect has been known as a simple, low-lost, lightweight,\\u000a and easy to implement method for passive damping control of structural vibration. In this technique, a piezoelectric material\\u000a is used to transform mechanical energy to electrical energy. When applying the piezoelectric shunt damping technique to passively\\u000a control structural vibration, the piezoelectric

Dan Wu; Zhichun Yang; Hao Sun

2009-01-01

135

Multiparameter measurement of absorbing liquid by time-resolved photoacoustics.  

PubMed

Measuring constituent concentrations of processing liquids provides highly useful data for industrial process control. Techniques that allow online measurement will greatly save resources and energy, making them highly attractive for enterprises. In this paper, we develop a technique based on time-resolved photoacoustics for simultaneously measuring the optical absorption coefficient, acoustic speed, and thermal-acoustic transformation coefficient of an absorbing liquid, using an experimental setup that merely employs a nanosecond pulsed laser with millijoule energy and a single piezoelectric transducer with a wide frequency bandwidth. As investigated samples, we use potassium chromate, glucose, and their mixing solutions. Experimental results show that the value of each parameter measured in a mixed solution is approximately equal to the sum value of the same parameter in the constituent solutions. This means that a simultaneous measurement of these parameters enables us to calculate two or three constituent concentrations in a mixed liquid, if the constituent substances differ clearly from one another in terms of their optical absorption, acoustic speed, or thermal-acoustic transformation properties. PMID:22410983

Zhao, Zuomin; Myllylä, Risto

2012-03-10

136

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

137

Photothermal and photoacoustic measurement and imaging of cracks and residual stresses in opaque ceramics  

NASA Astrophysics Data System (ADS)

The feasibility of using photothermal microscopy to detect subsurface lateral and vertical cracks in silicon nitride ceramic is demonstrated. It is shown that the photoreflectance method is especially sensitive to the grain structure of ceramics. The possibility of using the photoacoustic microscopy with a piezoelectric detection for study of a residual stress field near Vickers indentation zone is demonstrated.

Muratikov, K. L.; Glazov, A. L.; Rose, D. N.; Dumar, J. E.

1999-03-01

138

Early detection of dental caries using photoacoustics  

Microsoft Academic Search

For decades, visual, tactile and radiographic examinations have been the standard for diagnosing caries. Nonetheless, the extent of variation in the diagnosis of dental caries is substantial among dental practitioners using these traditional techniques. Therefore, a more reliable standard for detecting incipient caries would be desirable. Using photoacoustics, near-infrared (NIR) optical contrast between sound and carious dental tissues can be

K. Kim; R. Witte; I. Koh; S. Ashkenazi; M. O'Donnell

2006-01-01

139

Standoff chemical detection using quantum cascade lasers and photoacoustic sensing  

NASA Astrophysics Data System (ADS)

We report in this paper the feasibility of standoff chemical detection using quantum cascade lasers (QCLs) and photoacoustic technique. In the experiment, we use a QCL with an emission wavelength near 7.9 ?m, an electret condenser microphone, and isopropanol (IPA) vapor as a safer experimental substitute of the explosive, RDX. The QCL is operated at pulsed mode and the laser beam focused on the IPA vapor sample. The photoacoustic sound wave is generated and detected by the microphone at a remote distance. With less than 40 mW laser power, standoff photoacoustic chemical detection distance over 35 cm is achieved.

Chen, Xing; Janssen, Douglas; Choa, Fow-Sen

2011-05-01

140

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

141

High-Temperature Piezoelectric Sensing  

PubMed Central

Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented.

Jiang, Xiaoning; Kim, Kyungrim; Zhang, Shujun; Johnson, Joseph; Salazar, Giovanni

2014-01-01

142

Piezoelectric osteotomy in hand surgery: first experiences with a new technique  

PubMed Central

Background In hand and spinal surgery nerve lesions are feared complications with the use of standard oscillating saws. Oral surgeons have started using a newly developed ultrasound bone scalpel when performing precise osteotomies. By using a frequency of 25–29 kHz only mineralized tissue is cut, sparing the soft tissue. This reduces the risk of nerve lesions. As there is a lack of experience with this technique in the field of orthopaedic bone surgery, we performed the first ultrasound osteotomy in hand surgery. Method While performing a correctional osteotomy of the 5th metacarpal bone we used the Piezosurgery® Device from Mectron [Italy] instead of the usual oscillating saw. We will report on our experience with one case, with a follow up time of one year. Results The cut was highly precise and there were no vibrations of the bone. The time needed for the operation was slightly longer than the time needed while using the usual saw. Bone healing was good and at no point were there any neurovascular disturbances. Conclusion The Piezosurgery® Device is useful for small long bone osteotomies. Using the fine tip enables curved cutting and provides an opportunity for new osteotomy techniques. As the device selectively cuts bone we feel that this device has great potential in the field of hand- and spinal surgery.

Hoigne, Dominik J; Stubinger, Stefan; Kaenel, Oliver Von; Shamdasani, Sonia; Hasenboehler, Paula

2006-01-01

143

Photoacoustic spectroscopy of ?-hematin  

PubMed Central

Malaria affects over 200 million individuals annually, resulting in 800,000 fatalities. Current tests use blood smears and can only detect the disease when 0.1–1% of blood cells are infected. We are investigating the use of photoacoustic flowmetry to sense as few as one infected cell among 10 million or more normal blood cells, thus diagnosing infection before patients become symptomatic. Photoacoustic flowmetry is similar to conventional flow cytometry, except that rare cells are targeted by nanosecond laser pulses to induce ultrasonic responses. This system has been used to detect single melanoma cells in 10 ml of blood. Our objective is to apply photoacoustic flowmetry to detection of the malaria pigment hemozoin, which is a byproduct of parasite-digested hemoglobin in the blood. However, hemozoin is difficult to purify in quantities greater than a milligram, so a synthetic analog, known as ?-hematin was derived from porcine haemin. The specific purpose of this study is to establish the efficacy of using ?-hematin, rather than hemozoin, for photoacoustic measurements. We characterized ?-hematin using UV-vis spectroscopy, TEM, and FTIR, then tested the effects of laser irradiation on the synthetic product. We finally determined its absorption spectrum using photoacoustic excitation. UV-vis spectroscopy verified that ?-hematin was distinctly different from its precursor. TEM analysis confirmed its previously established nanorod shape, and comparison of the FTIR results with published spectroscopy data showed that our product had the distinctive absorbance peaks at 1661 and 1206 cm?1. Also, our research indicated that prolonged irradiation dramatically alters the physical and optical properties of the ?-hematin, resulting in increased absorption at shorter wavelengths. Nevertheless, the photoacoustic absorption spectrum mimicked that generated by UV-vis spectroscopy, which confirms the accuracy of the photoacoustic method and strongly suggests that photoacoustic flowmetry may be used as a tool for diagnosis of malaria infection.

Samson, Edward B.; Goldschmidt, Benjamin S.; Whiteside, Paul J. D.; Sudduth, Amanda S. M.; Custer, John R.; Beerntsen, Brenda

2012-01-01

144

Differential mode excitation photoacoustic spectroscopy: A new photoacoustic detection scheme  

Microsoft Academic Search

A robust and simple gas sensor based on a novel photoacoustic scheme named ``differential mode excitation photoacoustic spectroscopy (DME-PAS)'' is presented. This method takes advantage of the selective excitation of two different modes in a resonant photoacoustic cell. A blackbody light source is used for simplicity in combination with optical correlation to provide a good selectivity. The frequency response of

J. M. Rey; M. W. Sigrist

2007-01-01

145

Differential mode excitation photoacoustic spectroscopy: A new photoacoustic detection scheme  

Microsoft Academic Search

A robust and simple gas sensor based on a novel photoacoustic scheme named “differential mode excitation photoacoustic spectroscopy (DME-PAS)” is presented. This method takes advantage of the selective excitation of two different modes in a resonant photoacoustic cell. A blackbody light source is used for simplicity in combination with optical correlation to provide a good selectivity. The frequency response of

J. M. Rey; M. W. Sigrist

2007-01-01

146

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

147

Photoacoustic measurements of water–gas shift reaction on ferric oxide catalyst  

Microsoft Academic Search

A photoacoustic spectroscopic (PAS) technique was applied to the kinetic study of the water–gas shift reaction in the presence of ?-Fe2O3 catalyst. The catalytic reaction was performed in the temperature range from 523 to 673K at various partial pressures of carbon monoxide and water–vapor in a closed-circulation reactor system using a differential photoacoustic cell. The variation of CO2 photoacoustic signal

Su-Jin Kim; In-Sik Byun; Ho-Youn Han; Hong-Lyoul Ju; Sung Han Lee; Joong-Gill Choi

2002-01-01

148

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

149

Simultaneous optical and photoacoustic measurement of nonlinear absorption  

NASA Astrophysics Data System (ADS)

A measurement technique to perform optical Z-scan and photoacoustic Z-scan simultaneously called OPAZ-scan is demonstrated. It is found that the simultaneous measurement of the optical and photoacoustic Z-scan signals provides substantially better insight into the mechanism of optical nonlinearity. The system is able to identify mixed nonlinear processes within a mixture of nonlinear scattering species and nonlinear absorbers.

Chantharasupawong, Panit; Philip, Reji; Thomas, Jayan

2013-01-01

150

Photoacoustic detection of stimulated emission pumping in p-difluorobenzene  

SciTech Connect

Photoacoustic detection has been used to monitor a stimulated emission pumping process in p-difluorobenzene. Using the A /sup 1/B/sub 2u/5/sup 1/ state as an intermediate, several vibrational levels of the ground electronic state were populated. The photoacoustic method is an attractive alternative to other detection techniques because of its sensitivity, simplicity, and its ability to differentiate between stimulated emission pumping and excited state absorption. An example of excited state absorption in aniline is given.

Moll, D.J.; Parker, G.R. Jr.; Kuppermann, A.

1984-05-15

151

Fine-resolution photoacoustic imaging of the eye  

NASA Astrophysics Data System (ADS)

Purpose: Ultrasound and optical coherence tomography (OCT) are widely used techniques for diagnostic imaging of the eye. OCT provides excellent resolution, but limited penetration. Ultrasound provides better penetration, but an order-of-magnitude poorer resolution than OCT. Photoacoustic imaging is relatively insensitive to scattering, and so offers a potential means to image deeper than OCT. Furthermore, photoacoustic imaging detects optical absorption, a parameter that is independent of that detected by conventional ultrasound or OCT. Our aim was to develop a photoacoustic system suitable for imaging the eye. Methods: We developed a prototype system utilizing a focused 20 MHz ultrasound probe with a central aperture through which optics were introduced. The prototype system produced 1-?J, 5-nsec pulses at 532 or 1064 nm with a 20-?m spot size at a 500 Hz repetition rate. The photoacoustic probe was mounted onto computer-controlled linear stages and pulse-echo ultrasound and photoacoustic images obtained on ex vivo pig eyes and in vivo mouse eyes. Results: Lateral resolution was significantly improved by use of a laser spot size much smaller than the acoustic beamwidth. Photoacoustic signals were obtained primarily from melanin in ex vivo tissues and from melanin and hemoglobin in vivo. Image fusion allowed superposition of photoacoustic signals upon the anatomic features detected by conventional ultrasound. Conclusion: Photoacoustic imaging detects the presence of clinically relevant pigments, such as melanin and oxyand deoxy-hemoglobin, and, potentially, from other pathologic pigments occurring in disease conditions (tumors, nevii, macular degeneration). Fine-resolution photoacoustic data provides information not detected in current ophthalmic imaging modalities.

Silverman, Ronald H.; Kong, Fanting; Lloyd, Harriet O.; Chen, Y. C.

2010-02-01

152

Eliminating the Temperature Effect of Piezoelectric Transformer in Backlight Electronic Ballast by Applying the Digital Phase-Locked-Loop Technique  

Microsoft Academic Search

A new controller for eliminating the temperature effect of a piezoelectric transformer (PT) in a backlight electronic ballast is proposed in this paper. First, a class-D backlight inverter is employed to simplify the circuit configuration and to raise system efficiency. Next, to reduce the dimensions of the backlight module for satisfying the thin-shaped design trend and to overcome the drawbacks

Chang-Hua Lin; Ying Lu; Huang-Jen Chiu; Chung-Lun Ou

2007-01-01

153

Piezoelectricity in polymers  

SciTech Connect

Piezoelectricity and related properties of polymers are reviewed. After presenting a historical overview of the field, the mathematical basis of piezo- and pyroelectricity is summarized. We show how the experimentally measured quantities are related to the changes in polarization and point out the serious inequlity between direct and converse piezoelectric coefficients in polymers. Theoretical models of the various origins of piezo- and pyroelectricity, which include piezoelectricity due to inhomogeneous material properties and strains, are reviewed. Relaxational effects are also considered. Experimental techniques are examined and the results for different materials are presented. Because of the considerable work in recent years polyimylidene fluoride, this polymer receives the majority of the attention. The numerous applications of piezo-and pyroelectric polymers are mentioned. This article concludes with a discussion of the possible role of piezo- and pyroelectricity in biological system.

Kepler, R.G.; Anderson, R.A.

1980-11-01

154

Pharmacokinetic Monitoring of Indocyanine Green for Tumor Detection Using Photoacoustic Imaging  

NASA Astrophysics Data System (ADS)

We report tumor detection using a photoacoustic technique for the imaging of angiogenesis and monitoring of agent pharmacokinetics on an animal model. We take 532-nm laser pulses to excite photoacoustic signals of blood vessels with acquisition by a broadband hydrophone, and the morphological characteristics of tumor angiogenesis are successfully image depicted. Furthermore, tumor pharmacokinetics is preformed and analyzed with fast multielement photoacoustic imaging of the intravenous-injected indocyanine green (ICG). Photoacoustic signals of ICG are excited with 805 nm laser pulses and recorded by transducer array as a function of time. The difference between the photoacoustic signal from the tumor side and that from the normal side is observed, and the ICG clearance velocity in the tumor area is found to lag behind that in the normal area. Experimental results demonstrate that photoacoustic imaging of morphological parameter and pharmacokinetics with specific agent may provide high sensitive approach for tumor detection and localization.

Yang, Si-Hua; Yin, Guang-Zhi; Xing, Da

2010-09-01

155

Intravascular ultrasound and photoacoustic imaging.  

PubMed

There is a need for an imaging technique that can reliably identify and characterize the vulnerability of atherosclerotic plaques. Catheter-based intravascular ultrasound (IVUS) is one of the imaging tools of the clinical evaluation of atherosclerosis. However, histopathological information obtained with IVUS imaging is limited. We present and discuss the applicability of a combined intravascular photoacoustic (IVPA) and intravascular ultrasound (IVUS) imaging approach to assess both vessel structure and tissue composition thus identifying rupture-prone atherosclerotic plaques. Photoacoustic (or optoacoustic and, generally, thermoacoustic) imaging relies on the absorption of electromagnetic energy, such as light, and the subsequent emission of an acoustic wave. Therefore, the amplitude and temporal characteristics of the photoacoustic signal is primarily determined by optical absorption properties of different types of tissues and can be used to differentiate the lipid, fibrous and fibro-cellular components of an inflammatory lesion. Simultaneous IVUS and IVPA imaging studies were conducted using 40 MHz clinical IVUS imaging catheter interfaced with a pulsed laser system. The performance of the IVPA/IVUS imaging was assessed using phantoms with point targets and vessel-mimicking phantoms. To detect the lipids in the plaque, ex-vivo IVPA imaging studies of a normal and an atherosclerotic rabbit aorta were performed at a 532 nm wavelength. To assess plaque composition, multi-wavelength (680-950 nm) spectroscopic IVPA imaging studies were carried out. Finally, molecular and cellular IVPA imaging was demonstrated using plasmonic nanoparticles. Overall, our studies suggest that plaque detection and characterization can be improved using the combined IVPA/IVUS imaging. PMID:19162578

Emelianov, Stanislav; Wang, Bo; Su, Jimmy; Karpiouk, Andrei; Yantsen, Evgeniya; Sokolov, Konstantin; Amirian, James; Smalling, Richard; Sethuraman, Shriram

2008-01-01

156

Combined photoacoustic and oblique-incidence diffuse reflectance system for quantitative photoacoustic imaging in turbid media.  

PubMed

While photoacoustic imaging is capable of producing high-resolution biomedical images with optical absorption contrast, optical property quantification has thus far remained challenging. One reason for this is that laser-induced photoacoustic signal amplitudes are proportional to not only the local optical absorption coefficient, but also the local laser fluence in the tissue. Unfortunately, local laser fluence is often unknown, but could possibly be estimated if local bulk tissue optical properties were known. One method to estimate tissue optical properties is a technique known as oblique incidence diffuse reflectance (OIR). We report on an integrated OIR and photoacoustic imaging system and demonstrate, using phantom experiments, improved ability to quantitatively estimate optical properties of a turbid medium. PMID:20799818

Ranasinghesagara, Janaka C; Zemp, Roger J

2010-01-01

157

Spectroscopic intravascular photoacoustic imaging to differentiate atherosclerotic plaques.  

PubMed

The potential of intravascular photoacoustic (IVPA) imaging to detect atherosclerosis was previously demonstrated using a 532 nm nanosecond pulsed laser and an intravascular ultrasound (IVUS) imaging catheter. However, to differentiate vulnerable plaques, the composition of plaques needs to be imaged. Therefore, we introduce a multi-wavelength photoacoustic imaging method to distinguish various types of plaques. Multi-spectral IVPA imaging of ex vivo samples of normal and atherosclerotic rabbit aorta was performed at several wavelengths within 680-900 nm range. The spectral variation of photoacoustic response was extracted and a spectroscopic analysis was performed. The results of our preliminary study suggest that the spectroscopic intravascular photoacoustic imaging technique can be used to differentiate fibrous and lipid components of the atherosclerotic plaques. PMID:18542427

Sethuraman, Shriram; Amirian, James H; Litovsky, Silvio H; Smalling, Richard W; Emelianov, Stanislav Y

2008-03-01

158

Elastic property attributes to photoacoustic signals: an experimental phantom study.  

PubMed

We report an experimental study that shows the attribution of the elastic property of light absorbing targets to the generation of ultrasound signals induced due to the photoacoustic effect. We investigated the variation in strength of the detected photoacoustic signals for various targets embedded in a background phantom with: (1) different elastic coefficients (94-346 kPa) and (2) various sizes (0.25-1.5??mm2). The results show that photoacoustic signals increase with an increase in elastic coefficient (i.e., showing to contrast in elastic property) while it is independent of variation in target sizes. Quantitative (analysis) study, and 2D and 3D reconstructed images are also presented. This study demonstrates the feasibility of imaging elastic property using photoacoustic technique. PMID:24978784

Singh, Mayanglambam Suheshkumar; Jiang, Huabei

2014-07-01

159

The Radiative Transfer Equation in Photoacoustic Imaging  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography is a rapidly developing medical imaging technique that combines optical and ultrasound imaging to exploit the high contrast and high resolution of the respective individual modalities. Mathematically, photoacoustic tomography is divided into two steps. In the first step, one solves an inverse problem for the wave equation to determine how tissue absorbs light as a result of a boundary illumination. The second step is generally modeled by either diffusion or transport equations, and involves recovering the optical properties of the region being imaged. In this paper we, we provide an overview of mathematical progress in photoacoustic and thermoacoustic tomography, as well as inverse problems for the radiative transfer equation. We then address quantitative photoacoustic tomography modeled by the radiative transfer equation, and in particular, we show that the absorption coefficient in the stationary transport equation can be recovered given certain internal information about the solution. Our new result will consider the variable index of refraction case, which will correspond to an inverse transport problem on a Riemannian manifold with internal data and a known metric. We will prove a stability estimate for a functional of the absorption coefficient of the medium by finding a singular decomposition for the distribution kernel of the measurement operator. Finally, we will use this estimate to recover the desired absorption properties.

Patrolia, Lee

160

Molecular specific photoacoustic imaging with plasmonic nanosensors  

NASA Astrophysics Data System (ADS)

Gold nanoparticles functionalized with anti-EGFR antibodies undergo molecular specific aggregation on the cellular membrane and later within the cell that leads to a red shift in the plasmon resonance frequency of the gold nanoparticles. Capitalizing on this effect, we previously demonstrated on tissue phantoms that highly sensitive and selective detection of cancer cells can be achieved using the combination of photoacoustic imaging and molecular specific gold nanoparticles. To further evaluate the efficacy of molecular specific photoacoustic imaging technique in detecting deeply situated tumors, small animal experiments were performed. In this study, two gelatin solutions mixed with cells labeled with gold nanoparticles and cells mixed with polyethylene glycol-thiol (mPEG-SH) coated gold nanoparticles were injected in a mouse abdomen ex-vivo. The photoacoustic and ultrasound images from the same crosssection of the region before and after the injections were obtained using a 25 MHz single element ultrasound transducer interfaced with pulsed laser system. The results of our study suggest that the molecular specific photoacoustic imaging with plasmonic nanosensors could be used to detect deeply embedded tumors.

Mallidi, Srivalleesha; Yantsen, Evgeniya; Larson, Timothy; Sokolov, Konstantin; Emelianov, Stanislav

2008-03-01

161

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.

Beard, Paul

2011-01-01

162

Contactless photoacoustic imaging of biological samples  

NASA Astrophysics Data System (ADS)

In this paper we report on remote photoacoustic imaging using an interferometric technique. By utilizing a two-wave mixing interferometer ultrasonic displacements are measured without any physical contact to the sample. This technique allows measurement of the displacements also on rough surfaces. Mixing a plane reference beam with the speckled beam originating from the sample surface is done in a Bi12SiO20 photorefractive crystal. After data acquisition the structure of the specimen is reconstructed using a Fourier-domain synthetic focusing aperture technique. We show three-dimensional imaging on tissue-mimicking phantoms and biological samples. Furthermore, we show remote photoacoustic measurements on a human forearm in-vivo.

Berer, Thomas; Hochreiner, Armin; Grün, Hubert; Burgholzer, Peter

2012-02-01

163

High resolution photoacoustic spectra of Ho(2)O(3) and Nd(2)O(3).  

PubMed

A piezoelectric detection system for recording photoacoustic (PA) spectra of materials in the condensed phase was designed and fabricated. A Nd-YAG laser pumped tunable dye laser with a bandwidth of 0.05 nm was used for recording the fine structure of bands in the region between 610-680 nm in powdered microcrystalline samples of Ho(2)O(3) and Nd(2)O(3). Analysis of high resolution photoacoustic spectra obtained new information on the Stark components of the ground and excited states of Ho(3+) and Nd(3+) in the oxide matrix. PMID:20563193

Narayanan, K; Thakur, S N

1990-06-01

164

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.

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

2014-01-01

165

Measurement of Broadband Temperature-Dependent Ultrasonic Attenuation and Dispersion Using Photoacoustics  

Microsoft Academic Search

The broadband ultrasonic characterization of biological fluids and tissues is important for the continued development and application of high-resolution ultrasound imaging modalities. Here, a photoacoustic technique for the transmission measurement of temperature-dependent ultrasonic attenuation and dispersion is described. The system uses a photoacoustic plane wave source constructed from a polymethylmethacrylate substrate with a thin optically absorbent layer. Broadband ultrasonic waves

Bradley E. Treeby; Benjamin Cox; Edward Zhang; Sarah Patch; Paul Beard

2009-01-01

166

A non-contact and online ink thickness sensor for printing machines using the photoacoustic effect  

Microsoft Academic Search

We have developed an ink thickness sensor by employing a photoacoustic technique in order to enable the online measurement of ink thickness for printing machines such as a sheet-fed press. This sensor enables the online measurement of black ink thickness, which was impossible using the conventional methods. In order to detect the photoacoustic signals from the ink on a rotating

Koichi Kurita

2008-01-01

167

Additive Processes for Piezoelectric Materials: Piezoelectric MEMS  

Microsoft Academic Search

\\u000a Piezoelectricity has been underutilized in the MEMS world. Fabrication process compatibility, complexity, and the limited\\u000a availability of repeatable and reliable piezoelectric thin films have limited the incorporation of piezoelectric thin films\\u000a in MEMS. Advances in materials processing and a move toward system-in-package (SIP) concepts have pushed piezoelectric thin\\u000a film devices toward mainstream acceptance. The advances in piezoelectric aluminum (AlN) thin

Ronald G. Polcawich; Jeffrey S. Pulskamp

168

3D photoacoustic imaging  

Microsoft Academic Search

Our group has concentrated on development of a 3D photoacoustic imaging system for biomedical imaging research. The technology employs a sparse parallel detection scheme and specialized reconstruction software to obtain 3D optical images using a single laser pulse. With the technology we have been able to capture 3D movies of translating point targets and rotating line targets. The current limitation

Jeffrey J. L. Carson; Michael Roumeliotis; Govind Chaudhary; Robert Z. Stodilka; Mark A. Anastasio

2010-01-01

169

A broadband controller for shunt piezoelectric damping of structural vibration  

Microsoft Academic Search

In this paper a broadband active shunt technique for controlling vibration in piezoelectric laminated structures is proposed. The effect of the negative capacitance controller is studied theoretically and then validated experimentally on a piezoelectric laminated simply supported plate. The 'negative capacitance controller' is similar in nature to passive shunt damping techniques, as a single piezoelectric transducer is used to dampen

S. Behrens; A. J. Fleming; S. O. R. Moheimani

2003-01-01

170

A broadband controller for shunt piezoelectric damping of structural vibration  

Microsoft Academic Search

In this paper a broadband active shunt technique for controlling vibration in piezoelectric laminated structures is proposed. The effect of the negative capacitance controller is studied theoretically and then validated experimentally on a piezoelectric laminated simply supported plate. The ‘negative capacitance controller’ is similar in nature to passive shunt damping techniques, as a single piezoelectric transducer is used to dampen

S Behrens; A J Fleming; S O R Moheimani

2003-01-01

171

A self diagnostic system for piezoelectric sensors  

Microsoft Academic Search

A technique for determining the mounting conditions of a piezoelectric accelerometer is presented. This technique electrically stimulates the piezoelectric element in the 'diagnostic' frequency band measuring the electrical frequency response characteristics across a capacitive load impedance. The diagnostic frequency band is tipically much higher than the operating bandwidth of the accelerometer. The resonant frequencies of the accelerometer are included in

William J. Atherton; Patrick M. Flanagan

1989-01-01

172

Cross-optical-beam nonlinear photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

We present a photoacoustic microscopy (PAM) technique with an optical sectioning capability. By combining crossoptical- beam illumination with nonlinear PAM, an axial resolution of 8.7 ?m was measured, demonstrating a fourfold improvement over the acoustically determined value. Compared to methods relying on high-frequency ultrasound transducers to improve the axial resolution, our approach offers a greater working distance and a higher signal-to-noise ratio.

Zhu, Liren; Gao, Liang; Li, Lei; Wang, Lidai; Ma, Teng; Zhou, Qifa; Shung, K. Kirk; Wang, Lihong V.

2014-03-01

173

Photoacoustic section imaging with an integrating cylindrical detector.  

PubMed

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

2011-11-01

174

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

175

Design of a self-diagnostic beam-mode piezoelectric accelerometer  

Microsoft Academic Search

A technique was developed for detecting in situ real-time soft failures in a beam-mode piezoelectric accelerometer. The new technique can be used to detect changes in the piezoelectric capacitance, the equivalent mechanical stiffness of the piezoelectric element and the surface mounting impedance, and the piezoelectric efficiency.

Patrick M. Flanagan

1992-01-01

176

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

177

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.

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

2014-01-01

178

Determining two-photon absorption cross sections via nonresonant multiphoton photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

Multiphoton excitation of exogenous dyes and endogenous biochemical species has been used extensively for tissue diagnosis by fluorescence spectroscopy. Unfortunately, the majority of endogenous biochemical chromophores have low quantum yields, less than 0.2, therefore determining two-photon cross sections of weakly luminescencing molecules is difficult using two-photon fluorescence spectroscopy. Accurate determination of two-photon cross sections of these biochemicals could provide insight into fluorescence signal reduction caused by the absorption of excitation energy by non-target intracellular species. Non-resonant multiphoton photoacoustic spectroscopy (NMPPAS) is a novel technique we have developed for condensed matter measurements that has the potential for accurately determining two-photon absorption cross-sections of chemicals with small or non-existant fluorescence quantum yields. In this technique, near infrared light is used to generate an ultrasonic signal following a non-resonant two-photon excitation process. This ultrasonic wave is directly related to the non-radative relaxation of the chromophore of interest and is measured using a contact piezoelectric ultrasonic transducer. The signal from the ultrasonic transducer can then be used to calculate two-photon absorption cross sections. This paper will describe the validation of this technique by measuring the two-photon absorption cross- sections of well characterized chromophores such as rhodamine B and coumarin 1 in solution as well as riboflavin in a gelatin tissue phantom.

Kiser, John B.; Chandrasekharan, Nirmala; Cullum, Brian M.

2007-10-01

179

Towards nonionizing photoacoustic cystography  

NASA Astrophysics Data System (ADS)

Normally, urine flows down from kidneys to bladders. Vesicoureteral reflux (VUR) is the abnormal flow of urine from bladders back to kidneys. VUR commonly follows urinary tract infection and leads to renal infection. Fluoroscopic voiding cystourethrography and direct radionuclide voiding cystography have been clinical gold standards for VUR imaging, but these methods are ionizing. Here, we demonstrate the feasibility of a novel and nonionizing process for VUR mapping in vivo, called photoacoustic cystography (PAC). Using a photoacoustic (PA) imaging system, we have successfully imaged a rat bladder filled with clinically being used methylene blue dye. An image contrast of ~8 was achieved. Further, spectroscopic PAC confirmed the accumulation of methylene blue in the bladder. Using a laser pulse energy of less than 1 mJ/cm2, bladder was clearly visible in the PA image. Our results suggest that this technology would be a useful clinical tool, allowing clinicians to identify bladder noninvasively in vivo.

Kim, Chulhong; Jeon, Mansik; Wang, Lihong V.

2012-02-01

180

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.

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

2012-01-01

181

A Comparative Study of Photoacoustic and Reflectance Methods for Determination of Epidermal Melanin Content  

Microsoft Academic Search

Although epidermal melanin content has been quantified non-invasively using visible reflectance spectroscopy (VRS), there is currently no way to determine melanin distribution in the epidermis. We have developed a photoacoustic probe that uses a Q-switched, frequency-doubled Nd:YAG (neodymium, yttrium, aluminum, garnet) laser operating at 532 nm to generate acoustic pulses in skin in vivo. The probe contained a piezoelectric element

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

2004-01-01

182

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

183

Pulse photoacoustic spectroscopy of water vapor in UV spectral region with space-time resolution of photo-acoustic signals  

Microsoft Academic Search

New technique for measurement of the water vapor absorption coefficient for pulse UV radiation is described. This technique allows the useful signal caused by gas absorption to be separated from the signal caused by absorption by walls and windows of the cell. Both the photoacoustic and photoionization signals are observed in the cell by the action of radiation at the

Venedict A. Kapitanov; Boris A. Tikhomirov; V. O. Troitskii; I. S. Tyryshkin

1997-01-01

184

An autonomous piezoelectric shunt damping system  

Microsoft Academic Search

Passive shunt damping involves the connection of an electrical shunt network to a structurally attached piezoelectric transducer. In recent years, a large body of research has focused on the design and implementation of shunt circuits capable of significantly reducing structural vibration. This paper introduces an efficient, light weight, and small-in-size technique for implementing piezoelectric shunt damping circuits. A MOSFET half

Andrew J. Fleming; Sam Behrens; S. O. R. Moheimani

2003-01-01

185

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

186

Three-dimensional photoacoustic imaging of vascular anatomy in small animals using an optical detection system  

NASA Astrophysics Data System (ADS)

A 3D photoacoustic imaging instrument for characterising small animal models of human disease processes has been developed. The system comprises an OPO excitation source and a backward-mode planar ultrasound imaging head based upon a Fabry Perot polymer film sensing interferometer (FPI). The mirrors of the latter are transparent between 590 - 1200nm but highly reflective between 1500-1600nm. This enables nanosecond excitation laser pulses in the former wavelength range, where biological tissues are relatively transparent, to be transmitted through the sensor head into the tissue. The resulting photoacoustic signals arrive at the sensor where they modulate the optical thickness of the FPI and therefore its reflectivity. By scanning a CW focused interrogating laser beam at 1550nm across the surface of the sensor, the spatial-temporal distribution of the photoacoustic signals can therefore be mapped in 2D enabling a 3D photoacoustic image to be reconstructed. To demonstrate the application of the system to imaging small animals such as mice, 3D images of the vascular anatomy of the mouse brain and the microvasculature in the skin around the abdomen were obtained non invasively. It is considered that this system provides a practical alternative to photoacoustic scanners based upon piezoelectric detectors for high resolution non invasive small animal imaging.

Zhang, Edward Z.; Laufer, Jan; Beard, Paul

2007-03-01

187

Sunscreen effects in skin analyzed by photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

In the photoacoustic technique, the signal is proportional to the heat produced in a sample as a consequence of modulated light absorption. This technique allows the spectroscopic characterization of multilayer systems: as the thermal diffusion length varies with the light modulation frequency, one can obtain the depth profile of the sample by analyzing the frequency-dependence of the signal. As the photoacoustic signal depends on thermal and optical properties of the sample, structural changes in the system under analysis account for signal variations in time. In this work, photoacoustic spectroscopy was used to characterize samples of sunscreen and the system formed by sunscreen plus skin. We used photoacoustic spectroscopy to monitor the absorption kinetics of sunscreen applied to samples of human skin, characterizing alterations in the human skin after application of sunscreen. Measurements used 250W Xe arc lamp as light source, for wavelengths between 240nm and 400nm. This range corresponds to most of the UV radiation that reaches Earth. Skin samples were about 0,5cm diameter. The absorption spectra of sunscreen was obtained. Finally, photoacoustics was employed to monitor the absorption kinetics of the sunscreen applied to skin samples. This was done by applying sunscreen in a skin sample and recording the photoacoustic spectra in regular time intervals, up to 90 minutes after application. According to measurements, light absorption by the system sunscreen plus skin stabilizes between 25 and 45 minutes after sunscreen application. Results show that this technique can be utilized to monitor drug delivery and farmacokinetics in skin samples.

dos Anjos, Fernanda H.; Rompe, Paula C. B.; Batista, Roberta R.; Martin, Airton A.; Mansanares, Antonio M.; da Silva, Edson C.; Acosta-Avalos, Daniel; Barja, Paulo R.

2004-06-01

188

Fabrication and properties of PZT and PMN-PT piezoelectric fibers and piezoelectric fiber composites  

Microsoft Academic Search

PZT powder is synthesized by solid reaction and PMN-PT is synthesized by columbite method. PZT and PMN-PT piezoelectric fibers are prepared by sol-powder mixture extrusion. 1-3 piezoelectric fiber composites are fabricated by arraying-casting technique. The influence of fiber composition on dielectric properties and piezoelectric properties are studied. The results show that the values of kt and kt\\/kp of 1-3 composite

Jun Liu; Yan-qing Qiu; Xiang-ling Xu; Cai-feng Chen; Ying Luo

2009-01-01

189

Determining the location and severity of a beam crack based on piezoelectric guided wave  

Microsoft Academic Search

In recent years, structural health monitoring has received extensive attention in civil and mechanical engineering communities. Due to direct and converse piezoelectric effect, piezoelectric materials, such as, PZT has provided a efficient sensing technique- piezoelectric guided wave for structural health monitoring. In this paper, a numerical study on crack identification of a cantilever steel beam based on piezoelectric guided wave

Dan-sheng Wang; Hong-yuan Song; Dan-yan Shen; Hong-ping Zhu

2011-01-01

190

Characterization and matched-field processing localization of photoacoustic signals  

NASA Astrophysics Data System (ADS)

This dissertation presents the results of an investigation performed to characterize photoacoustic sound from gases in an open environment and to determine its utility for localizing small gas clouds. Photoacoustics is the generation of acoustic waves due to unsteady heating from a light source. It is well understood for trace gas detection and spectroscopy when the gases are placed in chambers. However, it is poorly understood in an open environment. Leak detection and localization are critical quality control processes because many industrial and domestic machines use or convey pressurized gases or liquids. Unintended leaks from machine components may be detrimental to consumers, manufacturers, and the environment. Current leak testing methods are either subjective, time consuming, or lack automated localization capability. The use of photoacoustic signals measured with multiple microphones for the localization of leaks is examined to address the shortcomings of the current leak testing methods. Scaling laws for photoacoustic sound pressure are developed with dimensional analysis and verified with experiments using a carbon dioxide laser and sulfur hexafluoride as the tracer gas to generate the photoacoustic sound. A photoacoustic signal model based on first principles is developed and takes in to account gas cloud shape and realistic gas absorption. For acoustically distributed gas clouds, the model and experiments agree to within 3 dB in a 10-120 kHz bandwidth. For acoustically compact gas clouds, the model and experiments agree to within 3 dB in a 30-120 kHz bandwidth. Matched-field processing is applied to photoacoustic measurements made by a four-microphone array. The photoacoustic sound is generated by scanning a carbon dioxide laser beam over a calibrated leak source of sulfur hexafluoride. The results of this study indicate that measured photoacoustic signals processed using matched-field processing can be used to accurately localize gas clouds from leak sources that leak at a rate of 1.19 × 10-5 CM3/S to within +/-1 mm Different processing techniques are demonstrated and acoustic propagation model robustness studies are performed.

Yonak, Serdar Hakki

2000-09-01

191

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

192

Characteristic absorption peak of the human blood measured with differential photoacoustic spectroscopy  

Microsoft Academic Search

A new highly sensitive spectroscopy technique-differential photoacoustic spectroscopy (PAS) is presented in this paper. The\\u000a blood samples from 3 healthy persons, patients with leukemia, patients with pregnancy-induced hypertension (PIH), and 40 patients\\u000a with nasopharyngeal carcinoma were measured by the PAS technique. The normalized, the first order, and the second order differential\\u000a photoacoustic spectroscopy of the blood were gained. The results

Zhilie Tang; Jinlong Liu; Yunfei Xia; Yong Su; Luisheng Liang; Gengsheng Chen

2002-01-01

193

Neurovascular Photoacoustic Tomography  

PubMed Central

Neurovascular coupling refers to the relationship between neuronal activities and downstream hemodynamic responses. Photoacoustic tomography (PAT), enabling comprehensive label-free imaging of hemodynamic activities with highly scalable penetration and spatial resolution, has great potential in the study of neurovascular coupling. In this review, we first introduce the technical basis of hemodynamic PAT – including label-free quantification of total hemoglobin concentration, blood oxygenation, and blood flow – as well as its applications in hemodynamic monitoring. Then, we demonstrate the potential application of PAT in neurovascular imaging by highlighting representative studies on cerebral vascular responses to whisker stimulation and Alzheimer's disease. Finally, potential research directions and associated technical challenges are discussed.

Hu, Song; Wang, Lihong V.

2010-01-01

194

Standoff photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

Here, we demonstrate a variation of photoacoustic spectroscopy that can be used for obtaining spectroscopic information of surface adsorbed chemicals in a standoff fashion. Pulsed light scattered from a target excites an acoustic resonator and the variation of the resonance amplitude as a function of illumination wavelength yields a representation of the absorption spectrum of the target. We report sensitive and selective detection of surface adsorbed compounds such as tributyl phosphate and residues of explosives such as trinitrotoluene at standoff distances ranging from 0.5-20 m, with a detection limit on the order of 100 ng/cm2.

van Neste, C. W.; Senesac, L. R.; Thundat, T.

2008-06-01

195

Photoacoustic imaging with attenuation rectification of different frequent components of photoacoustic signal  

Microsoft Academic Search

Photoacoustic tomography is a potential and noninvasive medical imaging technology. It combines the advantages of pure optic imaging and pure ultrasound imaging. Photoacoustic signals induced by a short pulse laser cover a wide spectral range. We have explored the influences of attenuation of photoacoustic signals, which vary according to frequencies, to the quality of reconstructed photoacoustic images. It reveals that

Yi Tan; Da Xing; Yi Wang; Diwu Yang

2005-01-01

196

Improvement of depth resolution on photoacoustic imaging using multiphoton absorption  

Microsoft Academic Search

Commercial imaging systems, such as computed tomography and magnetic resonance imaging, are frequently used powerful tools for observing structures deep within the human body. However, they cannot precisely visualized several-tens micrometer-sized structures for lack of spatial resolution. In this presentation, we propose photoacoustic imaging using multiphoton absorption technique to generate ultrasonic waves as a means of improving depth resolution. Since

Yoshihisa Yamaoka; Katsuji Fujiwara; Tetsuro Takamatsu

2007-01-01

197

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

PubMed Central

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.

Kang, Dongyel; Huang, Qiaojian; Li, Youzhi

2014-01-01

198

Electronics for Piezoelectric Smart Structures  

NASA Technical Reports Server (NTRS)

This paper briefly presents work addressing some of the basic considerations for the electronic components used in smart structures incorporating piezoelectric elements. After general remarks on the application of piezoelectric elements to the problem of structural vibration control, three main topics are described. Work to date on the development of techniques for embedding electronic components within structural parts is presented, followed by a description of the power flow and dissipation requirements of those components. Finally current work on the development of electronic circuits for use in an 'active wall' for acoustic noise is introduced.

Warkentin, D. J.; Tani, J.

1997-01-01

199

PHOTOACOUSTIC SPECTROSCOPY USING A SYNCHROTRON LIGHT SOURCE.  

SciTech Connect

We have investigated the use of a synchrotron as a source for infrared photoacoustic spectroscopy. A synchrotron has an intrinsically high radiance, which is beneficial when photoacoustic spectroscopy is applied to small samples, especially at long wavelengths.

JACKSON, R.S.; MICHAELIAN, K.H.; HOMES, C.C.

2001-02-05

200

Investigation of the photoacoustic effect in micellar solutions by the picosecond transient grating method  

NASA Astrophysics Data System (ADS)

This thesis comprises studies of viscosity and thermal conductivity effects on the photoacoustic wave from a droplet, generation of photoacoustic waves from reversed micellar solutions, and acoustic attenuation in reverse micellar solutions at GHz frequencies. In the first part of the thesis, the coupled equations for pressure and temperature, that describe the photoacoustic effect, are solved for a laser irradiated droplet surrounded by a second fluid to determine the effects of heat conduction and viscosity on the emitted ultrasonic wave. A numerical method of solving the coupled equations is used to give frequency domain expressions for the photoacoustic wave emitted by the droplet. The results show that the range of diameters over which the solution to the wave equation remains valid is quite large, and that deviations from the wave equation solution in experimentally recorded photoacoustic waveforms is not expected until the diameter of the droplet is so small as to approach the viscous or thermal heat conduction lengths of the fluid. Photoacoustic waves can be generated by submicron sized particles that absorb radiation and transmit heat to a surrounding fluid. When the thermal expansion coefficient of the absorbing body is small, a photoacoustic effect is not produced until heat diffuses into the surrounding fluid. Effects of the micelle size, acoustic wave-length and the thermal conductivity ratio on the generation of photoacoustic waves are discussed. The qualitative results both from theory and experiment show that the photoacoustic technique should thus form a diagnostic technique for determining particle radii and two thermal parameters for dilute slurries of particulate matter that can be excited by optical radiation. The propagation properties of ultrasonic waves have been studied by a picosecond transient grating method in AOT reversed micellar solutions. Ultrasonic attenuation exhibits peak values. Experiments show that peak values appear at the GHz frequencies when the micelle size is in the nanometer range. A new sizing method thus is proposed.

Cao, Yanni

1997-12-01

201

Photoacoustic imaging with integrating line detectors  

Microsoft Academic Search

Photoacoustic Tomography is an emerging imaging technology mainly for medical and biological applications. A sample is illuminated by a short laser pulse. Depending on the optical properties the electromagnetic radiation is distributed and absorbed. Thereby local temperature increase generates thermal expansion and broadband ultrasonic signals, also called photoacoustic signals. Unlike conventional ultrasound in photoacoustic imaging the contrast depends on the

Hubert Grün; Thomas Berer; Armin Hochreiner; Robert Nuster; Günther Paltauf; Peter Burgholzer

2009-01-01

202

Fundamental considerations for multiwavelength photoacoustic molecular imaging  

Microsoft Academic Search

Photoacoustic technology offers great promise for molecular imaging in vivo since it offers significant penetration, and optical contrast with ultrasonic spatial resolution. In this article we examine fundamental technical issues impacting capabilities of photoacoustic tomography for molecular imaging. First we examine how reconstructed photoacoustic tomography images are related to true absorber distributions by studying the modulation transfer function of a

Roger J. Zemp; Li Li; Lihong V. Wang

2006-01-01

203

Photoacoustic measurement of iron in composite coagulant  

Microsoft Academic Search

Iron concentrations of composite coagulant powders were measured by means of the photoacoustic effect. The onset of photoacoustic signal saturation for iron in the powders was 5 wt.%. This problem was solved by adding one of the components of the composite coagulant as a diluent to the samples. Based on the findings of this research, photoacoustic response of composite coagulant

Maohong Fan; Robert Brown; Shih-Wu Sung

2003-01-01

204

Photoacoustic investigations on thermal anisotropy in urea l-malic acid single crystals  

Microsoft Academic Search

Laser-induced photoacoustic technique in the closed cell configuration has been employed to study the anisotropy in thermal parameters of urea l-malic acid, a nonlinear optical crystal. Thermal diffusivity values of the specimen along different crystallographic axes are evaluated from the measured amplitude and phase spectra of photoacoustic signal using one-dimensional model of Rosencwaig and Gersho. Thermal conductivity of the crystal

A. Deepthy; S. Vanishri; D. Ambika; Sajan D. George; V. P. N. Nampoori; H. L. Bhat; E. de Matos Gomes; M. Belsley

2008-01-01

205

Diffuse reflectance and photoacoustic Fourier transform infrared spectra of silica surfaces under polarizable gases  

SciTech Connect

It has been reported that the use of an infrared transparent polarizable gas such as xenon enhances the FT-IR photoacoustic signal of some species adsorbed on a sample surface. Diffuse reflectance and photoacoustic FT-IR methods were used to obtain spectra of silica surfaces under helium, nitrogen, and xenon. Absence of the reported effect with both techniques is shown, and a tentative explanation for these results is given.

Story, W.C.; Masujima, T.; Liang, J.; Liu, G.; Eyring, E.M.; Harris, J.M.; Anderson, L.L.

1987-09-01

206

Reverse photoacoustic standoff spectroscopy  

DOEpatents

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

207

Photoacoustic point spectroscopy  

DOEpatents

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

208

Intravascular Photoacoustic Imaging  

PubMed Central

Intravascular photoacoustic (IVPA) imaging is a catheter-based, minimally invasive, imaging modality capable of providing high-resolution optical absorption map of the arterial wall. Integrated with intravascular ultrasound (IVUS) imaging, combined IVPA and IVUS imaging can be used to detect and characterize atherosclerotic plaques building up in the inner lining of an artery. In this paper, we present and discuss various representative applications of combined IVPA/IVUS imaging of atherosclerosis, including assessment of the composition of atherosclerotic plaques, imaging of macrophages within the plaques, and molecular imaging of biomarkers associated with formation and development of plaques. In addition, imaging of coronary artery stents using IVPA and IVUS imaging is demonstrated. Furthermore, the design of an integrated IVUS/IVPA imaging catheter needed for in vivo clinical applications is discussed.

Wang, Bo; Su, Jimmy L.; Karpiouk, Andrei B.; Sokolov, Konstantin V.; Smalling, Richard W.; Emelianov, Stanislav Y.

2011-01-01

209

Piezoelectric drive circuit  

DOEpatents

A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes.

Treu, Jr., Charles A. (Raymore, MO)

1999-08-31

210

Piezoelectric drive circuit  

DOEpatents

A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes. 7 figs.

Treu, C.A. Jr.

1999-08-31

211

"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

212

In-Situ Measurements of Aerosol Optical Properties using New Cavity Ring-Down and Photoacoustics Instruments and Comparison with more Traditional Techniques  

NASA Technical Reports Server (NTRS)

Carbonaceous species (BC and OC) are responsible for most of the absorption associated with aerosol particles. The amount of radiant energy an aerosol absorbs has profound effects on climate and air quality. It is ironic that aerosol absorption coefficient is one of the most difficult aerosol properties to measure. A new cavity ring-down (CRD) instrument, called Cadenza (NASA-ARC), measures the aerosol extinction coefficient for 675 nm and 1550 nm light, and simultaneously measures the scattering coefficient at 675 nm. Absorption coefficient is obtained from the difference of measured extinction and scattering within the instrument. Aerosol absorption coefficient is also measured by a photoacoustic (PA) instrument (DRI) that was operated on an aircraft for the first time during the DOE Aerosol Intensive Operating Period (IOP). This paper will report on measurements made with this new instrument and other in-situ instruments during two field recent field studies. The first field study was an airborne cam;oaign, the DOE Aerosol Intensive Operating Period flown in May, 2003 over northern Oklahoma. One of the main purposes of the IOP was to assess our ability to measure extinction and absorption coefficient in situ. This paper compares measurements of these aerosol optical properties made by the CRD, PA, nephelometer, and Particle Soot Absorption Photometer (PSAP) aboard the CIRPAS Twin-Otter. During the IOP, several significant aerosol layers were sampled aloft. These layers are identified in the remote (AATS-14) as well as in situ measurements. Extinction profiles measured by Cadenza are compared to those derived from the Ames Airborne Tracking Sunphotometer (AATS-14, NASA-ARC). The regional radiative impact of these layers is assessed by using the measured aerosol optical properties in a radiative transfer model. The second study was conducted in the Caldecott Tunnel, a heavily-used tunnel located north of San Francisco, Ca. The aerosol sampled in this study was characterized by fresh automobile and diesel exhaust. Measurements from Cadenza and from an aethalometer are presented. The aethalometer is a filter-based photometer and the infrared channel is calibrated to produce a measure of BC mass loading.

Strawa, A. W.; Arnott, P.; Covert, D.; Elleman, R.; Ferrare, R.; Hallar, A. G.; Jonsson, H.; Kirchstetter, T. W.; Luu, A. P.; Ogren, J.

2004-01-01

213

Photoacoustic tomography and sensing in biomedicine  

PubMed Central

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 article provides a brief review 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.

2010-01-01

214

Piezoelectric hydraulic pump with innovative active valves  

NASA Astrophysics Data System (ADS)

The development of a piezoelectric hydraulic pump with innovative active valves is presented in this study. The pump structure basically consists of a diaphragm type piezoelectric stack actuator and two specially designed unimorph disc valves acting as inlet and delivery valves. Static and dynamic piezoelectric finite element analyses were used to maximize the delivered fluid volume per stroke and to predict the resonance characteristics of the pump, respectively. A structural optimization technique was performed to optimize the efficiency of the pump versus its geometrical dimensions. A transient CFD model was used to predict flow rates. Dynamic experiments were also conducted and results are in good agreement with those obtained from the simulation.

Lee, Donggun; Or, Siu W.; O'Neill, Conal H.; Carman, Gregory P.

2002-07-01

215

Differential mode excitation photoacoustic spectroscopy: a new photoacoustic detection scheme.  

PubMed

A robust and simple gas sensor based on a novel photoacoustic scheme named "differential mode excitation photoacoustic spectroscopy (DME-PAS)" is presented. This method takes advantage of the selective excitation of two different modes in a resonant photoacoustic cell. A blackbody light source is used for simplicity in combination with optical correlation to provide a good selectivity. The frequency response of the proposed resonant cell is modeled using the extended Helmholtz resonator theory. The DME-PAS device is tested using acetone vapor and a model developed to describe its response when the gas concentration is varied. The obtained limit of detection is 25 ppm m(-1) for acetone in room air. Using DME-PAS, the derived gas concentration is affected neither by intensity fluctuations of the light source nor by any microphone drifts. PMID:17614602

Rey, J M; Sigrist, M W

2007-06-01

216

Differential mode excitation photoacoustic spectroscopy: A new photoacoustic detection scheme  

NASA Astrophysics Data System (ADS)

A robust and simple gas sensor based on a novel photoacoustic scheme named ``differential mode excitation photoacoustic spectroscopy (DME-PAS)'' is presented. This method takes advantage of the selective excitation of two different modes in a resonant photoacoustic cell. A blackbody light source is used for simplicity in combination with optical correlation to provide a good selectivity. The frequency response of the proposed resonant cell is modeled using the extended Helmholtz resonator theory. The DME-PAS device is tested using acetone vapor and a model developed to describe its response when the gas concentration is varied. The obtained limit of detection is 25 ppm m-1 for acetone in room air. Using DME-PAS, the derived gas concentration is affected neither by intensity fluctuations of the light source nor by any microphone drifts.

Rey, J. M.; Sigrist, M. W.

2007-06-01

217

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.

2007-03-01

218

Photoacoustic characterization of carbon nanotube array thermal interfaces  

Microsoft Academic Search

This work describes an experimental study of thermal conductance across multiwalled carbon nanotube (CNT) array interfaces, one sided (Si-CNT-Ag) and two sided (Si-CNT-CNT-Cu), using a photoacoustic technique (PA). Well-anchored, dense, and vertically oriented multiwalled CNT arrays have been directly synthesized on Si wafers and pure Cu sheets using plasma-enhanced chemical vapor deposition. With the PA technique, the small interface resistances

Baratunde A. Cola; Jun Xu; Changrui Cheng; Xianfan Xu; Timothy S. Fisher; Hanping Hu

2007-01-01

219

Photoacoustic imaging and temperature measurement for photothermal cancer therapy  

PubMed Central

Photothermal therapy is a noninvasive, targeted, laser-based technique for cancer treatment. During photothermal therapy, light energy is converted to heat by tumor-specific photoabsorbers. The corresponding temperature rise causes localized cancer destruction. For effective treatment, however, the presence of photoabsorbers in the tumor must be ascertained before therapy and thermal imaging must be performed during therapy. This study investigates the feasibility of guiding photothermal therapy by using photoacoustic imaging to detect photoabsorbers and to monitor temperature elevation. Photothermal therapy is carried out by utilizing a continuous wave laser and metal nanocomposites broadly absorbing in the near-infrared optical range. A linear array-based ultrasound imaging system is interfaced with a nanosecond pulsed laser to image tissue-mimicking phantoms and ex-vivo animal tissue before and during photothermal therapy. Before commencing therapy, photoacoustic imaging identifies the presence and spatial location of nanoparticles. Thermal maps are computed by monitoring temperature-induced changes in the photoacoustic signal during the therapeutic procedure and are compared with temperature estimates obtained from ultrasound imaging. The results of our study suggest that photoacoustic imaging, augmented by ultrasound imaging, is a viable candidate to guide photoabsorber-enhanced photothermal therapy.

Shah, Jignesh; Park, Suhyun; Aglyamov, Salavat; Larson, Timothy; Ma, Li; Sokolov, Konstantin; Johnston, Keith; Milner, Thomas; Emelianov, Stanislav Y.

2009-01-01

220

Structural health monitoring using piezoelectric impedance measurements  

Microsoft Academic Search

This paper presents an overview and recent advances in impedance-based structural health monitoring. The basic principle behind this technique is to apply high-frequency structural excitations (typically greater than 30kHz) through surface-bonded piezoelectric transducers, and measure the impedance of structures by monitoring the current and voltage applied to the piezoelectric transducers. Changes in impedance indicate changes in the structure, which in

Daniel J. Inman

2007-01-01

221

Quantitative photoacoustic measurement of tissue optical absorption spectrum aided by an optical contrast agent.  

PubMed

In photoacoustic imaging, the intensity of photoacoustic signal induced by optical absorption in biological tissue is proportional to light energy deposition, which is the product of the absorption coefficient and the local light fluence. Because tissue optical properties are highly dependent on the wavelength, the spectrum of the local light fluence at a target tissue beneath the sample surface is different than the spectrum of the incident light fluence. Therefore, quantifying the tissue optical absorption spectrum by using a photoacoustic technique is not feasible without the knowledge of the local light fluence. In this work, a highly accurate photoacoustic measurement of the subsurface tissue optical absorption spectrum has been achieved for the first time by introducing an extrinsic optical contrast agent with known optical properties. From the photoacoustic measurements with and without the contrast agent, a quantified measurement of the chromophore absorption spectrum can be realized in a strongly scattering medium. Experiments on micro-flow vessels containing fresh canine blood buried in phantoms and chicken breast tissues were carried out in a wavelength range from 680 nm to 950 nm. Spectroscopic photoacoustic measurements of both oxygenated and deoxygenated blood specimens presented an improved match with the references when employing this technique. PMID:19293919

Rajian, Justin Rajesh; Carson, Paul L; Wang, Xueding

2009-03-16

222

Listening to light by fast photoacoustic tomography based on a digital phased array system  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging technique, which provided high ultrasonic resolution and high optical contrast tissue images, can overcome the disadvantages of pure optical imaging by measurement of laser-induced sound waves. The waves produced by tissue are high-frequency ultrasounds, meaning that they cannot be heard by human ear. However, it can be picked up with ultrasonic transducer and analyze them with a computer. The laser-induced ultrasonic signals from a biological sample can be used to reveal the tissues structure based on optical contrast. In current experiment system, an integrity multi-element synthetic aperture focusing (M-SAF) photoacoustic imaging system using real-time digital beamformer is developed. This system relies on pumping laser source to irradiate the biological tissue to produce photoacoustic signal, a linear ultrasonic transducer array is connected to a multichannel signal acquisition and real-time digital beam-formation system providing techniques of real-time dynamic receiving focus and dynamic receiving apodization to process the photoacoustic signal. Each element of the transducer array has a thin cylinder ultrasonic lens to select 2D image plane and suppress the out-of-plane signals to realize photoacoustic computed tomography. This method and system can provide a fast and reliable photoacoustic tomography approach that could be applied to noninvasive imaging and clinic diagnosis.

Xiang, Liangzhong; Xing, Da; Yang, Diwu; Yang, Sihua; Hua, Guo

2007-10-01

223

Quantitative photoacoustic measurement of tissue optical absorption spectrum aided by an optical contrast agent  

PubMed Central

In photoacoustic imaging, the intensity of photoacoustic signal induced by optical absorption in biological tissue is proportional to light energy deposition, which is the product of the absorption coefficient and the local light fluence. Because tissue optical properties are highly dependent on the wavelength, the spectrum of the local light fluence at a target tissue beneath the sample surface is different than the spectrum of the incident light fluence. Therefore, quantifying the tissue optical absorption spectrum by using a photoacoustic technique is not feasible without the knowledge of the local light fluence. In this work, a highly accurate photoacoustic measurement of the subsurface tissue optical absorption spectrum has been realized for the first time by introducing an extrinsic optical contrast agent with known optical properties. From the photoacoustic measurements with and without the contrast agent, a quantified measurement of the chromophore absorption spectrum can be achieved in a strongly scattering medium. Experiments on micro-flow vessels containing fresh canine blood buried in phantoms and chicken breast tissues were carried out in a wavelength range from 680 to 950 nm. Spectroscopic photoacoustic measurements of both oxygenated and deoxygenated blood specimens presented an improved match with the reference when employing this technique.

Rajian, Justin Rajesh; Carson, Paul L; Wang, Xueding

2009-01-01

224

High Power Piezoelectric Characterization for Piezoelectric Transformer Development  

NASA Astrophysics Data System (ADS)

The major goal was to develop characterization techniques to identify and define guidelines to manufacture high power density actuators. We particularly aim at improving the strengths of piezoelectric transformers, namely the high efficiency, ease of manufacturing, low electromagnetic noise, and high power to weight ratio resulting in an adaptor application by identifying material limitations, geometrical limitations and offer guidelines to counter drawbacks limiting the power density. There are 3 losses present in piezoelectrics. Namely dielectric, elastic and piezoelectric losses. These losses can be calculated using mechanical quality factors of the resonating piezoelectric actuator. But in order to calculate all three losses, the mechanical quality factor for resonance and anti resonance need to be measured. Although the mechanical quality factor for resonance is conventionally measured, measurements in antiresonance have been ignored. Since there was no unique measurement technique to address antiresonance and resonance Q in one single sweep, in this study constant vibration velocity method was developed. During the constant vibration velocity measurement, the input electrical energy is monitored and significant differences between resonance and antiresonance drives are observed. For the same output work (identical vibration velocity) significant differences in the losses were observed. Thermographic images have shown increasing temperature differences for resonance and antiresonance nodal point temperatures, with higher vibration velocities. The theoretical evaluation identified the difference observed in the mechanical quality factors at resonance and antiresonance to stem from the piezoelectric loss. In order to investigate losses in the absence of thermal effects a transient characterization technique was adopted. The burst technique, originally developed for characterization of the mechanical quality factor at resonance, has been modified with a switch circuit to leave the resonator in an open circuit condition. The newly introduced open circuits burst have resulted in antiresonance quality factor measurements along with resonance quality factors in a "non-heating" sample. In this technique too, resonance and antiresonance losses showed significant difference. Resonance burst mode characterizations at elevated ambient temperatures have shown that the lower vibration velocity mechanical quality factors appear to be more sensitive to the ambient temperature. Design criteria's to produce the most power dense structure were investigated. Common device shapes were investigated to see which one does enhance the power density of the piezoelectric device. Disk shaped piezoelectric actuators have proven to have lower matching impedances and higher, farther persisting mechanical quality factors with respect to vibration velocities. In order to achieve identical power level, plate shaped samples will have been to strain ~3.5 times more than disk shaped samples. Thus the most power dense structure has been concluded to be a disk shape ~1W/cm3 Once the actuators shape was fixed, further design on structure were conducted with (c)ATILA finite element method. For the transformer application, the design considered following key factors; 1-Controlling the output impedance by optimizing number of layers and layer thicknesses of the multilayer and 2- Evaluation of various electrodes and their affect on high power performance was evaluated. As the thickness of active layers decreased, the number of electrode layers increases. This increase in the metal to piezoelectric ratio and the relative increase in the electrode resistance under high current loads, both will have to be accounted for. Thus; with the piezoelectric composition and the device structure optimized, the research input electrical power. Once the actuators shape was fixed, further design on structure were conducted with (c)ATILA finite element method. For the transformer application, the design considered following key factors; 1-Controlling the output imped

Ural, Seyit O.

225

In-situ measurement of sensitivity for a piezoelectric sensor  

Microsoft Academic Search

The paper presents a technique for the in situ and real-time measurement of sensitivity change in a piezoelectric accelerometer. This technique involves the electrical stimulation of the accelerometer's piezoelectric element in a 'diagnostic' frequency band and the measurement of the frequency response of the sensor's electromechanical properties. It is found that changes in the piezomechanical properties of a compression-mode accelerator,

Patrick M. Flanagan

1991-01-01

226

Developing a self-diagnostic system for piezoelectric sensors  

Microsoft Academic Search

Measurement techniques for developing a self-diagnostic system for piezoelectric sensors are presented. The self-diagnostic system uses two types of measurement techniques based on passive and active evaluation of the piezoelectric element. Both hard and soft failures can be detected by this system. Hard failures such as loss of sensor signal and change in sensor output resistance are determined by monitoring

Patrick M. Flanagan; William J. Atherton

1990-01-01

227

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

228

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.

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

2014-01-01

229

Experimental study of the Grüneisen parameter of a fullerite C60 single crystal near phase transitions at 90 and 260 K by the photoacoustic method  

NASA Astrophysics Data System (ADS)

The behavior of the Grüneisen parameter of single-crystal fullerite C60 has been studied experimentally near orientational phase transitions at 90 and 260 K. The measurements have been performed by the photoacoustic method using an automated photoacoustic device with laser excitation (the intensity was modulated by a harmonic law) and shadow piezoelectric detection. The temperature dependence of the relative change in the Grüneisen parameter in the fullerite C60 single crystal has been measured near the phase transitions at 90 and 260 K. The results have been analyzed.

Odina, N. I.; Korobov, A. I.

2014-04-01

230

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.

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

2013-01-01

231

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

232

Label-free photoacoustic microscopy of cytochromes  

PubMed Central

Abstract. Photoacoustic microscopy (PAM) has achieved submicron lateral resolution in showing subcellular structures; however, relatively few endogenous subcellular contrasts have so far been imaged. Given that the hemeprotein, mostly cytochromes in general cells, is optically absorbing around the Soret peak (?420??nm), we implemented label-free PAM of cytochromes in cytoplasm for the first time. By measuring the photoacoustic spectra of the oxidized and reduced states of fibroblast lysate and fitting the difference spectrum with three types of cytochromes, we found that the three cytochromes account for more than half the optical absorption in the cell lysate at 420 nm wavelength. Fixed fibroblasts on slides were imaged by PAM at 422 and 250 nm wavelengths to reveal cytoplasms and nuclei, respectively, as confirmed by standard staining histology. PAM was also applied to label-free histology of mouse ear sections by showing cytoplasms and nuclei of various cells. PAM of cytochromes in cytoplasm is expected to be a high-throughput, label-free technique for studying live cell functions, which cannot be accomplished by conventional histology.

Zhang, Chi; Zhang, Yu Shrike; Yao, Da-Kang; Xia, Younan; Wang, Lihong V.

2013-01-01

233

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

234

Improvement of Piezoelectricity in Piezoelectric Paper Made With Cellulose.  

National Technical Information Service (NTIS)

This report deals with the improvement of piezoelectricity in the piezoelectric paper made with cellulose. Piezoelectric paper fabrication process is composed of cellulose dissolving, wet cellulose casting, regenerating cellulose, stretching and drying pr...

J. Kim

2009-01-01

235

A self diagnostic system for piezoelectric sensors  

NASA Technical Reports Server (NTRS)

A technique for determining the mounting conditions of a piezoelectric accelerometer is presented. This technique electrically stimulates the piezoelectric element in the 'diagnostic' frequency band measuring the electrical frequency response characteristics across a capacitive load impedance. The diagnostic frequency band is tipically much higher than the operating bandwidth of the accelerometer. The resonant frequencies of the accelerometer are included in the diagnostic band. By monitoring the shift in these resonant frequencies, via electrical stimulation techniques, certain diagnostic conditions including mounting conditions can be determined. Experimental data from a compression mode accelerometer is used to demonstrate this technique.

Atherton, William J.; Flanagan, Patrick M.

1989-01-01

236

A piezoelectric transformer  

NASA Technical Reports Server (NTRS)

This work describes a modeling and design method whereby a piezoelectric system is formulated by two sets of second-order equations, one for the mechanical system, and the other for the electrical system, coupled through the piezoelectric effect. The solution to this electromechanical coupled system gives a physical interpretation of the piezoelectric effect as a piezoelectric transformer that is a part of the piezoelectric system, which transfers the applied mechanical force into a force-controlled current source, and short circuit mechanical compliance into capacitance. It also transfers the voltage source into a voltage-controlled relative velocity input, and free motional capacitance into mechanical compliance. The formulation and interpretation simplify the modeling of smart structures and lead to physical insight that aids the designer. Due to its physical realization, the smart structural system can be unconditional stable and effectively control responses. This new concept has been demonstrated in three numerical examples for a simple piezoelectric system.

Won, C. C.

1993-01-01

237

Contrast agents for photoacoustic imaging  

Microsoft Academic Search

In photoacoustic imaging, a pulsed laser is used to irradiate tissue but instead of measuring photons to obtain an image of anatomical structures hidden inside, ultrasound is measured. This is because different structures situated in the tissue can absorb light to different extents; this absorbed energy is converted into ultrasonic waves through the thermoelastic effect. The resulting pressure build up

Constantin Ungureanu

2007-01-01

238

Saturation effect in functional photoacoustic imaging  

PubMed Central

We investigate the saturation effect, which describes the violation of the linearity between the measured photoacoustic amplitude and the object’s optical absorption coefficient in functional photoacoustic imaging when the optical absorption in the object increases. We model the optical energy deposition and photoacoustic signal generation and detection in a semi-infinite optical absorbing object. Experiments are carried out by measuring photoacoustic signals generated from an ink-filled plastic tube. The saturation effect is studied by varying the optical absorption coefficient in the model and the ink concentration in the photoacoustic experiments. By changing the center frequency of the ultrasonic detector, the requirement to minimize the saturation effect in functional photoacoustic imaging is established.

Wang, Jing; Liu, Tan; Jiao, Shuliang; Chen, Ruimin; Zhou, Qifa; Shung, K. Kirk; Wang, Lihong V.; Zhang, Hao F.

2010-01-01

239

Kelvin and piezoelectricity  

NASA Astrophysics Data System (ADS)

This paper presents a résumé of the history of piezoelectricity during the 19th and 20th centuries. By examining the experiments, concepts and theories presented in Lord Kelvin's scientific communications and those of his contemporaries, this paper aims to show that he played an important role in the development of piezoelectricity. Kelvin's contribution was that he produced the measurement instrumentation that led to the discovery of piezoelectricity and laid some of the essential theoretical groundwork that led to the important applications of piezoelectricity in the 20th century.

Trainer, Matthew

2003-09-01

240

Developing a self-diagnostic system for piezoelectric sensors  

NASA Astrophysics Data System (ADS)

Measurement techniques for developing a self-diagnostic system for piezoelectric sensors are presented. The self-diagnostic system uses two types of measurement techniques based on passive and active evaluation of the piezoelectric element. Both hard and soft failures can be detected by this system. Hard failures such as loss of sensor signal and change in sensor output resistance are determined by monitoring the sensor's output resistance, voltage or current. These are passive measurements of the sensor's output condition. Soft failures include changes in sensor calibration and mounting conditions. Soft failures are detected by measuring structural/electrical impedance of the piezoelectric sensor. Active measurement techniques are used to calculate changes in piezoelectric element properties related to soft failures. This paper describes the general operating principles of a self-diagnostic system and discusses the design of an active/passive measurement technique required for this system to function. Experimental results using two types of piezoelectric accelerometers are presented.

Flanagan, Patrick M.; Atherton, William J.

1990-07-01

241

Developing a self-diagnostic system for piezoelectric sensors  

NASA Technical Reports Server (NTRS)

Measurement techniques for developing a self-diagnostic system for piezoelectric sensors are presented. The self-diagnostic system uses two types of measurement techniques based on passive and active evaluation of the piezoelectric element. Both hard and soft failures can be detected by this system. Hard failures such as loss of sensor signal and change in sensor output resistance are determined by monitoring the sensor's output resistance, voltage or current. These are passive measurements of the sensor's output condition. Soft failures include changes in sensor calibration and mounting conditions. Soft failures are detected by measuring structural/electrical impedance of the piezoelectric sensor. Active measurement techniques are used to calculate changes in piezoelectric element properties related to soft failures. This paper describes the general operating principles of a self-diagnostic system and discusses the design of an active/passive measurement technique required for this system to function. Experimental results using two types of piezoelectric accelerometers are presented.

Flanagan, Patrick M.; Atherton, William J.

1990-01-01

242

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

243

Label-free oxygen-metabolic photoacoustic microscopy in vivo  

Microsoft Academic Search

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

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

2011-01-01

244

High frequency photoacoustic microscopy for high resolution imaging  

Microsoft Academic Search

\\u000a Photoacoustic imaging (also called optoacoustic imaging) is a new hybrid imaging modality which offers tremendous potential\\u000a for research and clinical applications and features main advantages of optical and acoustical techniques. It combines ultrasonic\\u000a resolution with high optical contrast since signal generation is due to light absorption depending on the physiology of the\\u000a examined biological tissue. The acoustic signal reports tissue-specific

W. Bost; F. Stracke; Y. Kohl; M. Fournelle; R. Lemor

245

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.

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

2009-01-01

246

Usefulness of the photoacoustic measurement method for monitoring the regenerative process of full-thickness defects in articular cartilage using tissue-engineering technology  

NASA Astrophysics Data System (ADS)

We demonstrated the capability of photoacoustic measurement for viscoelastic characterization. Since tissue viscoelasticity affects the propagation and attenuation of photoacoustic waves generated in the tissue, the relaxation times of the photoacoustic waves give the viscosity-elasticity ratio of the tissue. The relaxation times of photoacoustic waves of articular cartilage tissues engineered under various culture conditions were closely correlated with intrinsic viscosity-elasticity ratios measured by using a conventional viscoelastic analyzer (R > 0.98). In order to apply the photoacoustic measurement method to evaluation of the regeneration of articular cartilage as a method to validate the surgery, the method should enable not only evaluation of engineered tissue during cultivation in vitro but also evaluation after transplantation of engineered tissue in vivo. The aim of this study was to verify the usefulness of the photoacoustic method for repeated measurement of viscoelastic properties in order to evaluate the process of regeneration of a full-thickness defect in rabbit articular cartilage using allografted tissue-engineered cartilage. Photoacoustic waves were induced by 266- and 355-nm, 5-7 ns, light pulses delivered through an optical silica fiber from an Q-switched Nd:YAG laser and were detected by a piezoelectric transducer, which we had designed. About a 40% difference between the viscosity-elasticity ratio of allografted cartilage that of tissue surrounding the defect was shown just after surgery. The difference was significantly reduced at 4 and 12 postoperative weeks. Therefore, since the photoacoustic measurement method enables assessment of the progress of restoration of the viscoelasticity of articular cartilage, its main function, this method would be useful as an evaluation method in regenerative medicine.

Ishihara, Miya; Sato, Masato; Sato, Shunichi; Kikuchi, Toshiyuki; Mitani, Genya; Kaneshiro, Nagatoshi; Ishihara, Masayuki; Mochida, Joji; Kikuchi, Makoto

2005-04-01

247

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

248

Photoacoustics, thermoacoustics, and acousto-optics for biomedical imaging.  

PubMed

Recently there have been significant advances in developing hybrid techniques combining electromagnetic waves with ultrasound for biomedical imaging, namely photoacoustic, thermoacoustic, and acousto-optic (or ultrasound modulated optical) tomography. All three techniques take advantage of tissue contrast offered by electromagnetic (EM) waves, while achieving good spatial resolution in deeper tissue facilitated by ultrasound. In this review the principles of the three techniques are introduced. A description of existing experimental and image reconstruction techniques is provided. Some recent key developments are highlighted and current issues in each of the areas are discussed. PMID:20349820

Tang, M-X; Elson, D S; Li, R; Dunsby, C; Eckersley, R J

2010-01-01

249

Piezoelectric-assisted removal of a benign fibrous histiocytoma of the mandible: An innovative technique for prevention of dentoalveolar nerve injury  

PubMed Central

In this article, we present our experience with a piezoelectric-assisted surgical device by resection of a benign fibrous histiocytoma of the mandible. A 41 year-old male was admitted to our hospital because of slowly progressive right buccal swelling. After further radiographic diagnosis surgical removal of the yellowish-white mass was performed. Histologic analysis showed proliferating histiocytic cells with foamy, granular cytoplasm and no signs of malignancy. The tumor was positive for CD68 and vimentin in immunohistochemical staining. Therefore the tumor was diagnosed as primary benign fibrous histiocytoma. This work provides a new treatment device for benign mandibular tumour disease. By using a novel piezoelectric-assisted cutting device, protection of the dentoalveolar nerve could be achieved.

2011-01-01

250

Photoacoustic reflectivity spectra of layered semiconductors  

NASA Astrophysics Data System (ADS)

The Photoacoustic (PA) spectra in several layered compounds such as HfSe2, ZrS2, HfS2, WSe2, MoSe2 and MoS2 have been measured at energies above the fundamental absorption edge. In this optical region the PA signal is regarded to be independent of the optical absorption coefficient and the dips in the PA spectra may be ascribed to optical reflection effects inherent the band structure. Generally, our experimental data prove that the information on the band structure of the layered semiconductors is in good agreement with that obtainable by means of conventional spectroscopic techniques, and moreover it is comparable with the data which are usually obtained by means of modulatory spectroscopy.

Baldassarre, L.; Cingolani, A.

1988-03-01

251

Photoacoustic tomography in a rectangular reflecting cavity  

NASA Astrophysics Data System (ADS)

Almost all known image reconstruction algorithms for photoacoustic and thermoacoustic tomography assume that the acoustic waves leave the region of interest after a finite time. This assumption is reasonable if the reflections from the detectors and surrounding surfaces can be neglected or filtered out (for example, by time-gating). However, when the object is surrounded by acoustically hard detector arrays, and/or by additional acoustic mirrors, the acoustic waves will undergo multiple reflections. (In the absence of absorption, they would bounce around in such a reverberant cavity forever.) This disallows the use of the existing free-space reconstruction techniques. This paper proposes a fast iterative reconstruction algorithm for measurements made at the walls of a rectangular reverberant cavity. We prove the convergence of the iterations under a certain sufficient condition, and demonstrate the effectiveness and efficiency of the algorithm in numerical simulations.

Kunyansky, L.; Holman, B.; Cox, B. T.

2013-12-01

252

Adaptive piezoelectric shunt damping  

Microsoft Academic Search

Piezoelectric shunt damping systems reduce structural vibration by shunting an attached piezoelectric transducer with an electrical impedance. Current impedance designs result in a coupled electrical resonance at the target modal frequencies. In practical situations, variation in structural load or environmental conditions can result in significant changes in the structural resonance frequencies. This variation can severely reduce shunt damping performance as

Andrew J. Fleming; S. O. Reza Moheimani

2002-01-01

253

Adaptive piezoelectric shunt damping  

Microsoft Academic Search

Piezoelectric shunt damping systems reduce structural vibration by shunting an attached piezoelectric transducer with an electrical impedance. Current impedance designs result in a coupled electrical resonance at the target modal frequencies. In practical situations, variation in structural load or environmental conditions can result in significant changes in the structural resonance frequencies. This variation can severely reduce shunt damping performance as

A. J. Fleming; S. O. R. Moheimani

2003-01-01

254

3K-1 Integrated and Flexible Piezoelectric Ultrasonic Transducers  

Microsoft Academic Search

Thick (>40 mum) ceramic films as piezoelectric and ultrasonic transducers (UTs) have been successfully deposited on metallic and non-metallic substrates by a spray technique. In the film fabrication a composite consisting of piezoelectric powders well mixed with solution of high dielectric constant is directly sprayed onto the substrate. It is then dried, fired or annealed by heat. Multiple coating is

M. Kobayashi; C.-K. Jen

2006-01-01

255

Structural vibration damping experiments using improved piezoelectric shunts  

Microsoft Academic Search

The theoretical analysis of an improved piezoelectric shunt using a piezoelectric PZT element shunted with a parallel resistor and inductor circuit for passive structural damping and vibration control was studied. In this paper, we report results of the experiments of the improved shunting technique which were performed and demonstrated successfully for passive vibration control in the ARPA consortium SPICES program

Shu-Yau Wu; Andrew S. Bicos

1997-01-01

256

Broadband piezoelectric shunts for passive structural vibration control  

Microsoft Academic Search

This paper reports an advanced passive piezoelectric shunt damping technique called broadband piezoelectric shunting. The shunt circuit for the broadband shunting is built with a reactance neutralizing circuit, which is designed with operational amplifier circuits to maximize the parallel reactance of the shunt circuit over a wide frequency band. It is different from the earlier shunt circuits, either used for

Shu-yau Wu

2001-01-01

257

Sensorless vibration suppression and scan compensation for piezoelectric tube nanopositioners  

Microsoft Academic Search

Piezoelectric tube scanners are employed in high-resolution positioning applications such as scanning probe microscopy and nanofabrication. Much research has proceeded with the aim of reducing hysteresis and vibration-the two foremost problems associated with piezoelectric tube scanners. In this paper, two simple techniques are proposed for simultaneously reducing hysteresis and vibration: 1) A new dc accurate charge amplifier is shown to

Andrew J. Fleming; S. O. Reza Moheimani

2006-01-01

258

Simultaneous dual-frequency excitation of a resonant photoacoustic cell  

Microsoft Academic Search

Simultaneous amplitude modulation of the exciting light beam with two different frequencies enables the excitation of two acoustic modes of a resonant photoacoustic cell. The photoacoustic amplitudes at both resonance frequencies and the corresponding photoacoustic amplitude ratio are obtained continuously without changing the modulation frequency. The photoacoustic mode amplitude ratio is affected neither by intensity fluctuations of the light source

Julien M. Rey; Markus W. Sigrist

2008-01-01

259

Photoacoustic imaging: consideration of bandwidth of ultrasonic transducer  

Microsoft Academic Search

Photoacoustic tomography is a potential and noninvasive medical imaging technology. It combines the advantages of pure optic imaging and pure ultrasound imaging. Photoacoustic signals induced by a short pulse laser cover a wide spectral range. We have explored the frequency spectrum of absorbers with different sizes and the influence of photoacoustic signals with different spectral components on photoacoustic imaging. The

Yi Tan; Da Xing; Yi Wang; Huaiming Gu; Diwu Yang; Qun Chen

2005-01-01

260

Determination of optical absorption coefficient with focusing photoacoustic imaging  

NASA Astrophysics Data System (ADS)

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 Grüneisen 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.

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

2012-06-01

261

Photoacoustic spectroscopy of standard explosives in the MIR region  

NASA Astrophysics Data System (ADS)

An emerging and important topic of interest in the field of homeland security is the identification and quantification of explosives. This paper brings new elements in the Laser Photoacoustic Spectroscopy (LPAS) based characterisation of some classical explosives (2,4-DNT; 2,6-DNT; HMX; TATP; PETN) in solid phase at CO 2 laser wavelengths, not yet reported in the literature to our knowledge. Moreover, we report our LPAS analysis of TNT and RDX, already previously studied with the same technique in the same spectral interval by different authors. The reported photoacoustic signals from standard commercial samples of the classical explosive substances were recorded in the 9-11 ?m region, by a CO 2 laser based homemade optical apparatus. The underlying experimental activity was performed in the molecular spectroscopy laboratory of the ENEA Research Centre in Frascati.

Giubileo, Gianfranco; Puiu, Adriana

2010-11-01

262

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

263

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.

264

Development of a combined intravascular ultrasound and photoacoustic imaging system  

NASA Astrophysics Data System (ADS)

Intravascular ultrasound (IVUS) imaging has emerged as an imaging technique to evaluate coronary artery diseases including vulnerable plaques. However, in addition to the morphological characteristics provided by IVUS imaging, there is a need for functional imaging capability that could identify the composition of vulnerable plaques. Intravascular photoacoustic (IVPA) imaging, in conjunction with clinically available IVUS imaging, may be such a technique allowing vulnerable plaque characterization and differentiation. We have developed an integrated intravascular ultrasound and photoacoustic imaging system to visualize clinically relevant structural and functional properties of the coronary arteries. The performance of the combined IVUS and IVPA imaging system was evaluated through images of arterial phantoms. Experiments were performed using high frequency IVUS imaging catheters operating at 20 MHz, 30 MHz and 40 MHz. The IVPA imaging was successful in highlighting inclusions based on differential optical absorption while these lesions did not have sufficient contrast in the IVUS images. Finally, initial IVUS and IVPA imaging studies were performed on ex vivo samples of a rabbit artery using the 40 MHz IVUS imaging catheter. Results of the above studies demonstrate the feasibility of combining intravascular ultrasound and photoacoustic imaging and suggest clinical utility of the developed imaging system in interventional cardiology.

Sethuraman, S.; Aglyamov, S. R.; Amirian, J. H.; Smalling, R. W.; Emelianov, S. Y.

2006-03-01

265

Resonant photoacoustic simultaneous detection of methane and ethylene by means. of a 1.63-?m diode laser  

Microsoft Academic Search

A compact multi-component trace-gas detector based on the resonant photoacoustic technique and a NIR external cavity diode laser has been developed. It has been characterized using a mixture of ethylene and methane diluted in ambient air. A spectroscopic investigation of combination bands and overtones between 5900 and 6250 cm-1, obtained with an IR pulsed laser photoacoustic spectrometer, allowed us to find

A. Boschetti; D. Bassi; E. Iacob; S. Iannotta; L. Ricci; M. Scotoni

2002-01-01

266

Photoacoustic investigations of CO 2–CH 4 reaction catalyzed by nickel particles embedded into SBA15 mesopores  

Microsoft Academic Search

A photoacoustic spectroscopy technique was employed to the kinetic study of the CO2\\/CH4 reaction catalyzed by Ni particles embedded into the mesochannels of SBA15. The catalytic CO2\\/CH4 reaction was performed in a closed-circulating reactor system at various partial pressures of CO2 and CH4 (40Torr total pressure) in the temperature range of 500–700°C. The CO2 photoacoustic signal that varied with the

Hun Jung; Ji-Woong Kim; Young-Gil Cho; Jin-Seung Jung; Sung-Han Lee; Joong-Gill Choi

2009-01-01

267

Photoacoustic Microscopy in Tissue Engineering  

PubMed Central

Photoacoustic tomography (PAT) is an attractive modality for noninvasive, volumetric imaging of scattering media such as biological tissues. By choosing the ultrasonic detection frequency, PAT enables scalable spatial resolution with desired imaging depth up to ~7 cm while maintaining a high depth-to-resolution ratio of ~200 and consistent optical absorption contrasts. Photoacoustic microscopy (PAM), the microscopic embodiment of PAT, aims to image at millimeter depth and micrometer-scale resolution. PAM is well-suited for characterizing three-dimensional scaffold-based samples, including scaffolds themselves, cells, and blood vessels, both qualitatively and quantitatively. Here we review our previous work on applications of PAM in tissue engineering and then discuss its future developments.

Cai, Xin; Zhang, Yu Shrike; Xia, Younan; Wang, Lihong V.

2013-01-01

268

Thermally nonlinear laser photoacoustic tomography  

SciTech Connect

The formation of a laser photoacoustic response in an inhomogeneous medium is considered taking into account the temperature dependence of the coefficient of thermal expansion. It is shown that in the one-dimensional or three-dimensional cases in the presence of individual absorbing centres (spherical particles), the shape of the photoacoustic response is the wavelet transform of the spatial distribution of heat sources. The parameters (level) of the wavelet expansion are determined by the characteristics of the laser pulse. The possibility of multiscale wavelet analysis of the medium structure is demonstrated by the example of a numerical model. The possibility of direct visualisation of individual cells in biological tissues is discussed. (laser applications and other topics in quantum electronics)

Oshurko, Vadim B [Moscow Engineering Physics Institute (State University), Moscow (Russian Federation)

2005-02-28

269

A photoacoustic study of water infiltrated leaves  

Microsoft Academic Search

Photoacoustic measurements of photosynthetic energy storage were conducted on water infiltrated pea and sugar maple leaves. The samples were vacuum infiltrated with pure water or with a suitable buffer. The use of such methodology permitted an accurate determination of the energy storage parameter at low modulation frequencies, where in non-infiltrated leaves oxygen evolution dominates the photoacoustic signal and does not

Shmuel Malkin; Marc Charland; Roger M. Leblanc

1992-01-01

270

Photoacoustic microscopy of human teeth  

Microsoft Academic Search

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

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

2011-01-01

271

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

272

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.

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

2013-01-01

273

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

274

Differential Open Photoacoustic Helmholtz Cell  

NASA Astrophysics Data System (ADS)

There are very few designs of the open photoacoustic Helmholtz cells, and most of them exhibit very strong penetration of the external acoustic noise inside the cell. So far the best values of external acoustic noise suppression obtained in such cells were reported at the level of about 40 dB to 50 dB. This paper presents an open photoacoustic Helmholtz cell design with a differential signal detection. Both Helmholtz resonator cavities are equipped with microphones and connected with the exterior via duct-buffer-duct structures. The length and diameter of the ducts as well as volume of the acoustic buffers are selected in such a way that the acoustic impedance of the duct-buffer-duct structure at the frequency of light modulation is relatively high. As a result, the resonance of the cell is not damped, while penetration of the external acoustic noise inside the cell is strongly reduced. Preliminary analysis predicts attenuation of the external acoustic noise at the resonance frequency of the cell with a single microphone to be at the level of at least 60 dB. Additional rejection of the external acoustic noise can be obtained with differential detection, which simultaneously doubles the photoacoustic signal component; as in the Helmholtz resonator, pressure changes in the cavities are in counterphase.

Starecki, Tomasz; Geras, Antonina

2014-02-01

275

Magnetocaloric piezoelectric composites for energy harvesting  

NASA Astrophysics Data System (ADS)

Magnetocaloric alloy, Gd5Si2Ge2, was developed into a composite with the poly(vinylidene fluoride) (PVDF) piezoelectric polymer. This multifunctional material possesses unique properties that are suitable for energy conversion and harvesting. Experimental approaches include using an arc melting technique to synthesize the Gd5Si2Ge2 (GSG) alloy and the spinning casting method to fabricate the composite. The materials were characterized using various techniques at different length scales. These include atomic force microscopy (AFM), optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The results indicated that the phase transformation of the magnetocaloric material close to its Curie temperature induced a significant increase in power generation in the piezoelectric polymer. The power output of a laminated structure was 1.1 mW, more than 200 thousand times higher than the piezoelectric materials alone (5.1 nW).

Cleveland, Michael; Liang, Hong

2012-04-01

276

A photoacoustic technique to measure speeds of sound from high-pressure fluids and solids: On the detonation chemistry of boron  

NASA Astrophysics Data System (ADS)

We predict detonation, propellant, and combustion chemistry using a thermochemical computational model derived from interatomic potentials constructed from shockwave, thermodynamic, and speeds of sound (SoS) data from highly compressed reaction product fluids and mixtures, e.g., H2O, CO2, NH3, simple hydrocarbons, etc. Typically we employ impulsive stimulated light scattering to measure SoS. Here we discuss how an acoustic wave can be launched from a thin platinum film by absorption of a focused 1064 nm laser pulse. (Platinum lines were deposited onto diamond anvil culets using a focused ion beam.) Light scattered from a time-delayed probe pulse is phase modulated by a traveling acoustic pulse and collected using a PMT. Fourier transformations of measured time-domain series yield the frequency of acoustic waves. We demonstrate the utility of this technique applied to metaboric acid (HBO2). Corresponding predictions of extreme condition boron chemistry are given on the basis of our HBO2 equation of state.

Zaug, Joseph M.; Bastea, Sorin; Crowhurst, Jonathan; Teslich, Nick

2010-03-01

277

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

278

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

279

Light scattering effects in photoacoustic spectroscopy  

SciTech Connect

The influence of light scattering on photoacoustic signals is treated. Theoretical and experimental results are compared. The theoretical results are based on a model in which the photons diffuse through the sample. An equation governing the diffusion process is solved with appropriate boundary conditions. This gives the distribution of photons in the sample. The photoacoustic signal is then calculated and the result is compared with the result for nonscattering samples, giving the influence of the light scattering. The experimental results are obtained by measuring the photoacoustic signal for both scattering and nonscattering samples. The experimental and theoretical results are in good agreement. The differences are mainly due to the incompleteness of the original diffusion theory. An improved theory incorporating internal reflection at the sample surface is also analyzed. The paper illustrates the effects of light scattering on photoacoustic signals. It also shows how to estimate theoretically the photoacoustic signal from a light-scattering sample.

Helander, P.; Lundstroem, I.; McQueen, D.

1980-07-01

280

Photoacoustic measurement of refractive index of dye solutions and myoglobin for biosensing applications  

PubMed Central

Current methods of determining the refractive index of chemicals and materials, such as ellipsometry and reflectometry, are limited by their inability to analyze highly absorbing or highly transparent materials, as well as the required prior knowledge of the sample thickness and estimated refractive index. Here, we present a method of determining the refractive index of solutions using the photoacoustic effect. We show that a photoacoustic refractometer can analyze highly absorbing dye samples to within 0.006 refractive index units of a handheld optical refractometer. Further, we use myoglobin, an early non-invasive biomarker for malignant hyperthermia, as a proof of concept that this technique is applicable for use as a medical diagnostic. Comparison of the speed, cost, simplicity, and accuracy of the techniques shows that this photoacoustic method is well-suited for optically complex systems.

Goldschmidt, Benjamin S.; Mehta, Smit; Mosley, Jeff; Walter, Chris; Whiteside, Paul J. D.; Hunt, Heather K.; Viator, John A.

2013-01-01

281

Photoacoustic imaging with a commercial ultrasound system and a custom probe.  

PubMed

Building photoacoustic imaging (PAI) systems by using stand-alone ultrasound (US) units makes it convenient to take advantage of the state-of-the-art ultrasonic technologies. However, the sometimes limited receiving sensitivity and the comparatively narrow bandwidth of commercial US probes may not be sufficient to acquire high quality photoacoustic images. In this work, a high-speed PAI system has been developed using a commercial US unit and a custom built 128-element piezoelectric-polymer array (PPA) probe using a P(VDF-TrFE) film and flexible circuit to define the elements. Since the US unit supports simultaneous signal acquisition from 64 parallel receive channels, PAI data for synthetic image formation from a 64- or 128-element array aperture can be acquired after a single or dual laser firing, respectively. Therefore, two-dimensional (2-D) B-scan imaging can be achieved with a maximum frame rate up to 10 Hz, limited only by the laser repetition rate. The uniquely properties of P(VDF-TrFE) facilitated a wide -6 dB receiving bandwidth of over 120% for the array. A specially designed 128-channel preamplifier board made the connection between the array and the system cable, which not only enabled element electrical impedance matching but also further elevated the signal-to-noise ratio (SNR) to further enhance the detection of weak photoacoustic signals. Through the experiments on phantoms and rabbit ears, the good performance of this PAI system was demonstrated. PMID:21276653

Wang, Xueding; Fowlkes, J Brian; Cannata, Jonathan M; Hu, Changhong; Carson, Paul L

2011-03-01

282

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

283

Pulsed photoacoustic Doppler flowmetry using a cross correlation method  

NASA Astrophysics Data System (ADS)

The feasibility of making spatially resolved measurements of blood flow using pulsed photoacoustic Doppler techniques has been explored. Doppler time shifts were quantified via cross-correlation of pairs of photoacoustic waveforms generated within a blood-simulating phantom using pairs of laser light pulses. The photoacoustic waves were detected using a focussed or planar PZT ultrasound transducer. This approach was found to be effective for quantifying the linear motion of micron-scale absorbers imprinted on an acetate sheet moving with velocities in the range 0.15 to 1.50 ms-1. The effect of the acoustic spot diameter and the time separation between the laser pulses on measurement resolution and the maximum measurable velocity is discussed. The distinguishing advantage of pulsed rather than continuous-wave excitation is that spatially resolved velocity measurements can be made. This offers the prospect of mapping flow within the microcirculation and thus providing insights into the perfusion of tumours and other pathologies characterised by abnormalities in flow status.

Brunker, J.; Beard, P.

2010-02-01

284

Photoacoustic tomography of ex vivo mouse hearts with myocardial infarction.  

PubMed

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. PMID:21456870

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

2011-03-01

285

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

286

Dynamic contrast-enhanced 3D photoacoustic imaging  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging (PAI) is a hybrid imaging modality that integrates the strengths from both optical imaging and acoustic imaging while simultaneously overcoming many of their respective weaknesses. In previous work, we reported on a real-time 3D PAI system comprised of a 32-element hemispherical array of transducers. Using the system, we demonstrated the ability to capture photoacoustic data, reconstruct a 3D photoacoustic image, and display select slices of the 3D image every 1.4 s, where each 3D image resulted from a single laser pulse. The present study aimed to exploit the rapid imaging speed of an upgraded 3D PAI system by evaluating its ability to perform dynamic contrast-enhanced imaging. The contrast dynamics can provide rich datasets that contain insight into perfusion, pharmacokinetics and physiology. We captured a series of 3D PA images of a flow phantom before and during injection of piglet and rabbit blood. Principal component analysis was utilized to classify the data according to its spatiotemporal information. The results suggested that this technique can be used to separate a sequence of 3D PA images into a series of images representative of main features according to spatiotemporal flow dynamics.

Wong, Philip; Kosik, Ivan; Carson, Jeffrey J. L.

2013-03-01

287

Piezoelectric Pulsed Microjets.  

National Technical Information Service (NTIS)

This reports summarizes an investigation of coupling broadband piezoelectric actuators with large force microjet actuators to achieve pulsed flow control over a broad frequency range. The development is relevant to a range of flow control problems for rot...

F. Alvi W. S. Oates

2011-01-01

288

Resonance in Piezoelectric Vibrators.  

National Technical Information Service (NTIS)

The electrical behavior of a piezoelectric vibrator leads to criteria by which to describe onset and extent of the resonance region. The equi-immittance point is convenient for delimiting the resonance range and assesses the validity of circle representat...

A. Ballato

1969-01-01

289

New Piezoelectric Polymers  

Microsoft Academic Search

Four kinds of piezoelectric polymers are introduced. Submicron thin films of polyurea are prepared by vapor deposition polymerization. Poled films of aromatic polyurea exhibit the piezoelectric constant d31=20 pC\\/N, which is almost independent of temperature in the range of 100 to 200°C. Aliphatic polyureas show a ferroelectric hysteresis with a coercive field of about 100 MV\\/m. Single crystalline films of

Eiichi Fukada

1998-01-01

290

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.

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

2014-01-01

291

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

292

Appearance of breast cysts in planar geometry photoacoustic mammography using 1064-nm excitation.  

PubMed

In the search for improved imaging modalities for detection and diagnosis of breast cancer, a high negative prediction value is also important. Photoacoustic (optoacoustic) imaging is a relatively new technique that has high potential for visualizing breast malignancies, but little is known about the photoacoustic appearance of benign lesions. In this work, we investigate the visibility of benign breast cysts in forward-mode photoacoustic mammography using 1064-nm light, as currently applied in the Twente photoacoustic mammoscope. Results from (Monte Carlo and k-wave) simulations and phantom measurements were used to interpret results from patient measurements. There was a strong agreement among the results from simulations, phantom, and patient measurements. Depending on the absorption contrast between cyst and breast tissue, cysts were visible as either one or two confined high-contrast areas representing the front and the back of the cyst, respectively. This edge enhancement is most likely the consequence of the local sudden change in the absorbed energy density and Grüneisen coefficients. Although the current forward-mode single-wavelength photoacoustic mammoscope cannot always unambiguously discriminate cysts from malignancies, this study reveals specific features of cysts compared to malignancies, which can be exploited for discrimination of the two abnormalities in future modifications of the imager. PMID:24343440

Heijblom, Michelle; Piras, Daniele; Maartens, Erik; Huisman, Erik J J; van den Engh, Frank M; Klaase, Joost M; Steenbergen, Wiendelt; Manohar, Srirang

2013-12-01

293

Three-dimensional photoacoustic imaging with a clinical two-dimensional matrix ultrasound transducer  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography provides both structural and functional imaging in vivo based on optical absorption contrast. A novel imaging system that incorporates a two-dimensional matrix ultrasound probe for combined photoacoustic and ultrasonic three-dimensional (3D) volumetric imaging is presented. The system consists of a tunable dye laser pumped by a Nd:YAG laser, a commercial ultrasound imaging system (Philips iU22) with a two-dimensional matrix transducer (Philips X7-2, 2500 elements, 2-7 MHz), and a multichannel data acquisition system which allows us to acquire RF channel data. Compared with alternative 3D techniques, this system is attractive because it can generate co-registered 3D photoacoustic and ultrasound images without mechanical scanning. Moreover, the lateral resolution along the azimuth and elevational directions are measured to be 0.77 +/- 0.06 mm and 0.96 +/- 0.06 mm, respectively, based on reconstructed photoacoustic images of phantoms containing individual human hairs. Finally, in vivo 3D photoacoustic sentinel lymph node mapping using methylene blue dye in a rat model is demonstrated.

Erpelding, Todd N.; Wang, Yu; Jankovic, Ladislav; Guo, Zijian; Robert, Jean-Luc; David, Guillaume; Kim, Chulhong; Wang, Lihong V.

2011-02-01

294

Appearance of breast cysts in planar geometry photoacoustic mammography using 1064-nm excitation  

NASA Astrophysics Data System (ADS)

In the search for improved imaging modalities for detection and diagnosis of breast cancer, a high negative prediction value is also important. Photoacoustic (optoacoustic) imaging is a relatively new technique that has high potential for visualizing breast malignancies, but little is known about the photoacoustic appearance of benign lesions. In this work, we investigate the visibility of benign breast cysts in forward-mode photoacoustic mammography using 1064-nm light, as currently applied in the Twente photoacoustic mammoscope. Results from (Monte Carlo and k-wave) simulations and phantom measurements were used to interpret results from patient measurements. There was a strong agreement among the results from simulations, phantom, and patient measurements. Depending on the absorption contrast between cyst and breast tissue, cysts were visible as either one or two confined high-contrast areas representing the front and the back of the cyst, respectively. This edge enhancement is most likely the consequence of the local sudden change in the absorbed energy density and Grüneisen coefficients. Although the current forward-mode single-wavelength photoacoustic mammoscope cannot always unambiguously discriminate cysts from malignancies, this study reveals specific features of cysts compared to malignancies, which can be exploited for discrimination of the two abnormalities in future modifications of the imager.

Heijblom, Michelle; Piras, Daniele; Maartens, Erik; Huisman, Erik J. J.; van den Engh, Frank M.; Klaase, Joost M.; Steenbergen, Wiendelt; Manohar, Srirang

2013-12-01

295

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

2010-03-01

296

An Autonomous Piezoelectric Shunt Damping System  

Microsoft Academic Search

Passive shunt damping involves the connection of an electrical shunt network to a structurally attached piezoelec- tric transducer. In recent years, a large body of research has focused on the design and implementation of shunt circuits capable of significantly reducing structural vibration. This paper introduces an efficient, light weight, and small-in-size technique for implementing piezoelectric shunt damping circuits. A MOSFET

Andrew J. Fleming; Sam Behrens; S. O. Reza Moheimani

297

Characterization of a Piezoelectric Buzzer Using a Michelson Interferometer  

NASA Astrophysics Data System (ADS)

A piezoelectric material generates an electric potential across its surface when subjected to mechanical stress;1 conversely, the inverse piezoelectric effect describes the expansion or contraction of the material when subjected to some applied voltage. Piezoelectric materials are used in devices such as doorbell buzzers, barbeque igniters, and also as the scanning and approach mechanisms in scanning probing microscopy. The assembly of a scanning tunnelling microscope (STM)2 at Thompson Rivers University has motivated a characterization of the sensitivity and hysteresis3 of piezoelectric discs using a Michelson interferometer. The investigation uses an interferometer4 and a simple photodiode circuit to track the fringes. As a possible undergraduate lab, the measurement provides an introduction to piezoelectric materials (including hysteresis), the Michelson interferometer, and data acquisition techniques.

Lloyd, S.; Paetkau, M.

2010-12-01

298

Initial results of imaging melanoma metastasis in resected human lymph nodes using photoacoustic computed tomography  

NASA Astrophysics Data System (ADS)

The pathological status of the sentinel lymph node is important for accurate melanoma staging, ascertaining prognosis and planning treatment. The standard procedure involves biopsy of the node and histopathological assessment of its status. Drawbacks of this examination include a finite sampling of the node with the likelihood of missing metastases, and a significant time-lag before histopathological results are available to the surgeon. We studied the applicability of photoacoustic computed tomographic imaging as an intraoperative modality for examining the status of resected human sentinel lymph nodes. We first applied the technique to image ex vivo pig lymph nodes carrying metastases-simulating melanoma cells using multiple wavelengths. The experience gained was applied to image a suspect human lymph node. We validated the photoacoustic imaging results by comparing a reconstructed slice with a histopathological section through the node. Our results suggest that photoacoustics has the potential to develop into an intraoperative imaging method to detect melanoma metastases in sentinel lymph nodes.

Jose, Jithin; Grootendorst, Diederik J.; Vijn, Thomas W.; Wouters, Michel W.; van Boven, Hester; van Leeuwen, Ton G.; Steenbergen, Wiendelt; Ruers, Theo J. M.; Manohar, Srirang

2011-09-01

299

The effects of optical scattering on pulsed photoacoustic measurement in weakly absorbing liquids  

NASA Astrophysics Data System (ADS)

In this article, a photoacoustic technique, excited by a pulsed diode laser, is used in a study of optically absorbing and scattering liquids. The article discusses the effects of optical scattering on the photoacoustic source and signal. In the empirical part, varying amounts of milk and carbon powder were added to water to control the absorption and scattering coefficients of the resulting liquids. The results showed that scattering increases the duration of the photoacoustic signal while decreasing the signal amplitude to some degree. This paper also shows a quite simple method for measuring the scattering coefficient in weakly absorbing materials using a PZT transducer, which can be used to determine the concentration of highly scattering compositions in some cases.

Zhao, Zuomin; Myllylä, Risto

2001-12-01

300

Gold nanoparticle targeted photoacoustic cavitation for potential deep tissue imaging and therapy  

PubMed Central

The laser generation of vapor bubbles around plasmonic nanoparticles can be enhanced through the application of an ultrasound field; a technique referred to as photoacoustic cavitation. The combination of light and ultrasound allows for bubble formation at lower laser fluence and peak negative ultrasound pressure than can be achieved using either modality alone. The growth and collapse of these bubbles leads to local mechanical disruption and acoustic emission, and can potentially be used to induce and monitor tissue therapy. Photoacoustic cavitation is investigated for a broad range of ultrasound pressures and nanoparticle concentrations for gold nanorods and nanospheres. The cavitation threshold fluences for both nanoparticle types are found to drastically reduce in the presence of an ultrasound field. The results indicate that photoacoustic cavitation can potentially be produced at depth in biological tissue without exceeding the safety limits for ultrasound or laser radiation at the tissue surface.

Ju, Hengyi; Roy, Ronald A.; Murray, Todd W.

2012-01-01

301

Photoacoustic spectroscopy (PAS) system for remote detection of explosives, chemicals, and special nuclear materials  

NASA Astrophysics Data System (ADS)

This paper describes a practical photoacoustic spectroscopy technique applied to remote sensing of chemicals in an open environment. A laboratory system that consists of a high-power CO2 laser and an open-field acoustic resonator is described. The acoustic resonator is a combination of a parabolic reflector and a narrow-band cylindrical acoustic resonator that resonates at the laser modulation frequency. The performance of the resonator is theoretically analyzed and experimentally verified. Significant improvement in signal-to-noise ratio has been achieved. Detection of gas-phase photoacoustic signals was demonstrated at a remote distance of several meters from the target. Potential applications to the detection of condensed-phase chemicals are discussed; the detection of the photoacoustic spectrum of trinitrotoluene (TNT) in an open environment is presented.

Chien, Hual-Te; Wang, Ke; Sheen, Shuh-Haw; Raptis, A. C. Paul

2012-05-01

302

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

303

A Combined Reconstruction Algorithm for Limited-View Multi-Element Photoacoustic Imaging  

NASA Astrophysics Data System (ADS)

We present a photoacoustic imaging system with a linear transducer array scanning in limited-view fields and develop a combined reconstruction algorithm, which is a combination of the limited-field filtered back projection (LFBP) algorithm and the simultaneous iterative reconstruction technique (SIRT) algorithm, to reconstruct the optical absorption distribution. In this algorithm, the LFBP algorithm is exploited to reconstruct the original photoacoustic image, and then the SIRT algorithm is used to improve the quality of the final reconstructed photoacoustic image. Numerical simulations with calculated incomplete data validate the reliability of this algorithm and the reconstructed experimental results further demonstrate that the combined reconstruction algorithm effectively reduces the artifacts and blurs and yields better quality of reconstruction image than that with the LFBP algorithm.

Yang, Di-Wu; Xing, Da; Zhao, Xue-Hui; Pan, Chang-Ning; Fang, Jian-Shu

2010-05-01

304

Gold nanoparticle targeted photoacoustic cavitation for potential deep tissue imaging and therapy.  

PubMed

The laser generation of vapor bubbles around plasmonic nanoparticles can be enhanced through the application of an ultrasound field; a technique referred to as photoacoustic cavitation. The combination of light and ultrasound allows for bubble formation at lower laser fluence and peak negative ultrasound pressure than can be achieved using either modality alone. The growth and collapse of these bubbles leads to local mechanical disruption and acoustic emission, and can potentially be used to induce and monitor tissue therapy. Photoacoustic cavitation is investigated for a broad range of ultrasound pressures and nanoparticle concentrations for gold nanorods and nanospheres. The cavitation threshold fluences for both nanoparticle types are found to drastically reduce in the presence of an ultrasound field. The results indicate that photoacoustic cavitation can potentially be produced at depth in biological tissue without exceeding the safety limits for ultrasound or laser radiation at the tissue surface. PMID:23304648

Ju, Hengyi; Roy, Ronald A; Murray, Todd W

2013-01-01

305

Study of the diffusion of some emulsions in the human skin by pulsed photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

We previously used pulsed photoacoustic spectroscopy (PPAS) to quantify sunscreen diffusion into human skin, and suggested a methodology to evaluate the time and the depth diffusion profile. These results were obtained by the analysis of the photoacoustic maximum response signal Pmax decrease, the time delay tmax and the Fourier transform representation of the photoacoustic signal. In this study we present the results obtained for diffusion of four typical emulsions used in sunscreen compositions that show, for the first time, a particular behaviour for one of these emulsions due to a chemical reaction inside the skin during the diffusion process. This result provides a particularly interesting technique through the PPAS, to evaluate in situ the eventual chemical reactions that can occur during drug diffusion into human skin.

Lahjomri, F.; Benamar, N.; Chatri, E.; Leblanc, R. M.

2003-08-01

306

Correcting photoacoustic signals for fluence variations using acousto-optic modulation.  

PubMed

We present a theoretical concept which may lead to quantitative photoacoustic mapping of chromophore concentrations. The approach supposes a technique capable of tagging light in a well-defined tagging volume at a specific location deep in the medium. We derive a formula that expresses the local absorption coefficient inside a medium in terms of noninvasively measured quantities and experimental parameters and we validate the theory using Monte Carlo simulations. Furthermore, we performed an experiment to basically validate the concept as a strategy to correct for fluence variations in photoacoustics. In the experiment we exploit the possibility of acousto-optic modulation, using focused ultrasound, to tag photons. Results show that the variation in photoacoustic signals of absorbing insertions embedded at different depths in a phantom, caused by fluence variations of more than one order of magnitude, can be corrected for to an accuracy of 5%. PMID:22714476

Daoudi, K; Hussain, A; Hondebrink, E; Steenbergen, W

2012-06-18

307

Multiwavelength Photoacoustic Imaging and Plasmon Resonance Coupling of Gold Nanoparticles for Selective Detection of Cancer  

PubMed Central

Gold nanoparticles targeting epidermal growth factor receptor via antibody conjugation undergo molecular specific aggregation when they bind to receptors on cell surfaces, leading to a red shift in their plasmon resonance frequency. Capitalizing on this effect, we demonstrate the efficacy of the molecular specific photoacoustic imaging technique using subcutaneous tumor-mimicking gelatin implants in ex-vivo mouse tissue. The results of our study suggest that highly selective and sensitive detection of cancer cells is possible using multiwavelength photoacoustic imaging and molecular specific gold nanoparticles.

Mallidi, Srivalleesha; Larson, Timothy; Tam, Justina; Joshi, Pratixa P.; Karpiouk, Andrei; Sokolov, Konstantin; Emelianov, Stanislav

2010-01-01

308

Effect of cement-polymer ratio on 1-3 piezoelectric composites  

NASA Astrophysics Data System (ADS)

A 1-3 type piezoelectric composite was fabricated by cut-filling technique. The effects of cement-polymer ratio on piezoelectric and dielectric properties of the composites were analyzed. The results show that piezoelectric strain factor d33 and piezoelectric voltage factor g33 exhibit the trend of decrease initially and then increase with increasing cement-polymer ratio. With the increase of cement-polymer ratio, the dielectric factor ?r and dielectric loss tan? of the composites increase initially and then decrease. Comparing with pure piezoelectric ceramic, the mechanical quality factor Qm decreases obviously. Acoustic impedance Z is about 9 M raly, which is matching with concrete.

Guo, Lili; Xu, Dongyu; Huang, Shifeng

2009-07-01

309

Photoacoustic phasoscopy super-contrast imaging  

NASA Astrophysics Data System (ADS)

Phasoscopy is a recently proposed concept correlating electromagnetic (EM) absorption and scattering properties based on energy conservation. Phase information can be extracted from EM absorption induced acoustic wave and scattered EM wave for biological tissue characterization. In this paper, an imaging modality, termed photoacoustic phasoscopy imaging (PAPS), is proposed and verified experimentally based on phasoscopy concept with laser illumination. Both endogenous photoacoustic wave and scattered photons are collected simultaneously to extract the phase information. The PAPS images are then reconstructed on vessel-mimicking phantom and ex vivo porcine tissues to show significantly improved contrast than conventional photoacoustic imaging.

Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin

2014-05-01

310

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

311

In-situ measurement of sensitivity for a piezoelectric sensor  

NASA Technical Reports Server (NTRS)

The paper presents a technique for the in situ and real-time measurement of sensitivity change in a piezoelectric accelerometer. This technique involves the electrical stimulation of the accelerometer's piezoelectric element in a 'diagnostic' frequency band and the measurement of the frequency response of the sensor's electromechanical properties. It is found that changes in the piezomechanical properties of a compression-mode accelerator, as measured by the autocalibration function, detected a relative change in sensitivity.

Flanagan, Patrick M.

1991-01-01

312

Thermal-Diffusivity Measurements of Mexican Citrus Essential Oils Using Photoacoustic Methodology in the Transmission Configuration  

Microsoft Academic Search

Photoacoustic methodology in the transmission configuration (PMTC) was used to study the thermophysical properties and their relation with the composition in Mexican citrus essential oils providing the viability of using photothermal techniques for quality control and for authentication of oils and their adulteration. Linear relations for the amplitude (on a semi-log scale) and phase, as functions of the sample's thickness,

G. A. López Muńoz; R. F. López González; J. A. Balderas López; L. Martínez-Pérez

2011-01-01

313

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

314

New Piezoelectric Polymers  

NASA Astrophysics Data System (ADS)

Four kinds of piezoelectric polymers are introduced. Submicron thin films of polyurea are prepared by vapor deposition polymerization. Poled films of aromatic polyurea exhibit the piezoelectric constant d31=20 pC/N, which is almost independent of temperature in the range of 100 to 200°C. Aliphatic polyureas show a ferroelectric hysteresis with a coercive field of about 100 MV/m. Single crystalline films of a copolymer of vinylidene fluoride and trifluoroethylene were prepared by annealing elongated films at a paraelectric temperature range avoiding the side surface contacts. No lamella structures were present and the crystallinity was near 100%. The large electromechanical coupling factors k33=0.3 and k31=0.1 were observed. A large electrostrictive constant R=2.6×10-17 m2/V2 was observed for polyurethane. With a dc bias field of 15 MV/m, a piezoelectric constant of d33=600 pC/N was obtained, which was larger than that of PZT. A shear piezoelectric constant d14=-10 pC/N was obtained for oriented films of poly-L-lactic acid, which were optically active and biodegradable. After poling, this polymer showed the tensile piezoelectricity and pyroelectricity.

Fukada, Eiichi

1998-05-01

315

New method for multiple-mode shunt damping of structural vibration using a single piezoelectric transducer  

Microsoft Academic Search

A new multi-mode semi-active shunt technique for controlling vibration in piezoelectric laminated structures is proposed in this paper. The effect of the ``negative capacitor'' controller is studied theoretically and then validated experimentally on a piezoelectric laminated simply-supported beam. The negative capacitor controller is similar in nature to passive shunt damping techniques, as a single piezoelectric transducer is used to dampen

Sam Behrens; Andrew J. Fleming; S. O. Reza Moheimani

2001-01-01

316

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.

2011-02-01

317

Phase reference materials for photoacoustic spectroscopy  

SciTech Connect

Interest in the phase of photoacoustic signals has increased greatly since the advent of phase modulation in FTIR spectroscopy. The photoacoustic phase provides information on the depth of the light-absorbing species within a solid sample. A spectroscopist needs data from a phase-reference material for standardizing phase measurements and for correcting the instrumental effects on the observed phase. Unfortunately, there is no universally accepted phase-reference material. The authors have studied the photoacoustic-signal phase and magnitude behavior for several potential phase-reference materials as a function of experimental parameters, such as beam modulation frequency, sample position in the photoacoustic cell, and cell purge gas. Theoretically, an ideal surface-absorbing material would have a photoacoustic phase that trails the phase of the excitation light by 90{degree}. They have found no material with this behavior, although some come close under a limited range of conditions. The three samples were separately sealed in the photoacoustic detector and illuminated by a red LED that was modulated at selected frequencies. The phases of the samples vary rapidly at very low frequencies because of the response of the cell microphone. Above that range, all three are within 10{degree} of the ideal 90{degree}, but each varies linearly with frequency with a different slope. The behaviors of these and other samples will be discussed in detail.

Jones, R.; Bajic, S. [Ames Lab., IA (United States); McClelland, J. [Ames Lab., IA (United States)]|[MTEC Photoacoustics, Ames, IA (United States)

1999-06-01

318

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

319

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

320

Active Piezoelectric Diaphragms  

NASA Technical Reports Server (NTRS)

Several active piezoelectric diaphragms were fabricated by placing unelectroded piezoelectric disks between copper clad films patterned with Inter-Circulating Electrodes "ICE". When a voltage potential is applied to the electrodes, the result is radially distributed electric field that mechanically strains the piezo-ceramic along the Z-axis (perpendicular to the applied electric field), rather than the expected in-plane (XY-axis) direction. Unlike other out of plane piezoelectric actuators, which are benders, these Radial Field Diaphragms (RFDs) strain concentrically yet afford high displacements while maintaining a constant circumference. This paper covers the fabrication and characterization of these diaphragms as a function of poling field strength, ceramic diameter and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage ranging from DC to 10 Hz.

Bryant, Robert G.; Effinger, Robert T., IV; Aranda, Isaiah, Jr.; Copeland, Ben M.; Covington, Ed W., III

2002-01-01

321

Piezoelectric hydraulic pump  

NASA Astrophysics Data System (ADS)

A hybrid piezohydraulic pump is under development for smart structures applications. Structural control applications often require large force be delivered over a large displacement. Piezoelectric actuators produce a large force over a small displacement. This can be repeated many times per second. Step and repeat piezoelectric devices, such as inchworm motors, increase the power output of the actuators and have the potential to produce large forces and large displacements simultaneously. The piezohydraulic pump makes use of the step and repeat capability. The pump utilizes a piezoelectric stack actuator to drive a piston in a cylinder. The forward stroke pressurizes the hydraulic fluid in the cylinder and forces it out through a check valve. The reverse stroke draws fluid into the cylinder through a second check valve. The prototype pump has produced a working pressure of 6.9 MPa (1000 psi) and a flow rate of 45 ccm.

Mauck, Lisa D.; Lynch, Christopher S.

1999-06-01

322

Piezoelectric hydraulic pump performance  

NASA Astrophysics Data System (ADS)

A piezohydraulic pump making use of the step and repeat capability of piezoelectric actuators has been developed for actuation of aircraft control surfaces. The piezohydraulic pump utilizes a piezoelectric stack actuator to drive a piston in a cylinder. The cylinder is fitted with two check valves. On the compression stroke, oil is forced out of the cylinder. On the intake stroke, oil is drawn into the cylinder. The oil is used to drive a linear actuator. The actuator was driven at 7cm/sec with a 271N (61lb) blocking force. To achieve this, the piezoelectric stack actuator was driven at 60Hz with a switching power supply. The system utilizes an accumulator to eliminate cavitation. This work discusses piezohydraulic pumping theory, pump design, and pump performance. Consideration of pump performance includes the effects of varying accumulator pressure, hydraulic oil viscosity, and load imposed on the linear actuator.

Mauck, Lisa D.; Oates, William S.; Lynch, Christopher S.

2001-06-01

323

Active piezoelectric diaphragms  

NASA Astrophysics Data System (ADS)

Several active piezoelectric diaphragms were fabricated by placing unelectroded piezoelectric disks between copper clad films patterned with Inter-Circulating Electrodes (ICE). When a voltage potential is applied to the electrodes, the result is radially distributed electric field that mechanically strains the piezo-ceramic along the Z-axis, rather than the expected in-plane direction. Unlike other out of plane piezoelectric actuators, which are benders, these Radial Field Diaphragms strain concentrically yet afford high displacements while maintaining a constant circumference. This paper covers the fabrication and characterization of these diaphragms as a function of poling field strength, ceramic diameter and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage ranging from DC to 10 Hz.

Bryant, Robert G.; Effinger, Robert T., IV; Aranda, Isaiah, Jr.; Copeland, Ben M., Jr.; Covington, Ed W., III

2002-07-01

324

Ultrasound and photoacoustic imaging to monitor vascular growth in tissue engineered constructs  

NASA Astrophysics Data System (ADS)

Quantitative and qualitative monitoring of neovascular growth is required in many vascular tissue engineering applications. For example, the contribution of progenitor cells in growing microvasculature has been demonstrated; however, the process of vascularization from progenitor cells is not well understood. Therefore, there is a need for an imaging technique that is consistent, easy to use, and can quantitatively assess the dynamics of vascular growth or regression in a three-dimensional environment. In this study, we evaluate the ability of combined ultrasound and photoacoustic imaging to assess the dynamics of vascular growth. The experiments were performed using hydrogels that spontaneously promote tube formation from implanted mesenchymal stem cells (MSCs). Specifically, PEGylated fibrin gels, supporting the development of capillary growth were implanted in a Lewis rat. After one week, the rat was euthanized and the gel implants were excised and positioned in water cuvettes for imaging. Simultaneous ultrasound and photoacoustic images were obtained using single-element, focused ultrasound transducers interfaced with a nanosecond pulsed laser source. To image samples, ultrasound transducers operating at either 25 MHz or 48 MHz and interfaced with laser sources operating at either 532 nm or within 680-800 nm wavelengths were used. The 3-D ultrasound and photoacoustic images were acquired by mechanically scanning the transducer over the region of interest and capturing spatially co-registered and temporally consecutive photoacoustic transients and ultrasound pulse-echo signals. The ultrasound and photoacoustic images agree well with the overall anatomy and vascular structure in the gel samples. The results suggest that the photoacoustic and ultrasound imaging could be used to sequentially monitor the growth of neovasculature in-vivo.

Nam, Seung Yun; Mallidi, Srivalleesha; Zhang, Ge; Suggs, Laura J.; Emelianov, Stanislav

2009-02-01

325

Vibration of beams with embedded piezoelectric sensors and actuators  

NASA Astrophysics Data System (ADS)

This paper presents a micromechanics approach to the study of the vibration of beams with embedded piezoelectric sensors and actuators. The natural frequency of the beam is determined from the variational principle in Rayleigh quotient form. The piezoelectric sensors and actuators embedded in the beam are analysed using Eshelby's equivalent inclusion method. In addition, the Euler-Bernoulli beam theory and Rayleigh-Ritz approximation technique are used in the analysis. Results show that the size, volume fraction and location of the piezoelectric inclusions significantly influence the natural frequency of the beam. The results of the present model agree well with the theoretical results presented in the literature.

Della, Christian N.; Shu, Dongwei

2006-04-01

326

On the spectral response of thick piezoelectric capacitive sensors for arrays in imagenology applications  

NASA Astrophysics Data System (ADS)

We investigate the spectral response of capacitive sensors with 28 ?m thick Polyvinylidene Fluoride (PVDF) films operating in the piezoelectric mode. We present spectra of signals obtained from laser-induced photoacoustic emissions in several materials. We examine the sensor response to direct laser pulses and to ultrasonic signals generated by laser pulses interacting with polyvinyl alcohol (PVA) phantoms, neoprene slabs and a composite of PVA phantom with a hidden slab of neoprene. We exhibit the sensor's sensitivity to the phantom thickness, affecting the amplitude and bandwidth of the ultrasonic output signal. The sensors fabricated and tested under water achieved an operational frequency bandwidth ranging from 1 to 50 MHz.

Reyes-Ramírez, B.; Garcia-Segundo, C.; García-Valenzuela, A.

2014-03-01

327

Photoacoustic tomography with integrating fiber-based annular detectors  

Microsoft Academic Search

Photoacoustic tomography is an emerging technology combining the advantages of optical imaging (high contrast) and ultrasonic imaging (high spatial resolution). Applications for photoacoustic tomography are mainly in imaging soft tissue. For photoacoustic imaging the sample is illuminated by a short pulse of electromagnetic energy. Depending on the specific absorption rate (SAR) the electromagnetic radiation is absorbed and the subsequent thermoelastic

H. Grün; H. Altmisdört; T. Berer; G. Paltauf; G. Zangerl; M. Haltmeier; P. Burgholzer

2011-01-01

328

Photoacoustic Doppler flow measurement in optically scattering media  

Microsoft Academic Search

We recently observed the photoacoustic Doppler effect from flowing small light-absorbing particles. Here, we apply the effect to measure blood-mimicking fluid flow in an optically scattering medium. The light scattering in the medium decreases the amplitude of the photoacoustic Doppler signal but does not affect either the magnitude or the directional discrimination of the photoacoustic Doppler shift. This technology may

Hui Fang; Konstantin Maslov; Lihong V. Wang

2007-01-01

329

Depth-Resolved Analysis of Biofilms by Photoacoustic Spectroscopy  

Microsoft Academic Search

A photoacoustic sensor system is presented for depth-resolved analysis of biofilms. The investigation of biofilm growth on the surface of the sensor head showed the potential of Photoacoustic Spectroscopy (PAS) in this area. The increase of biomass was monitored by analysis of the photoacoustic signal amplitudes (wavelength ? = 550 nm). The distribution of the organic mass inside the biofilm

Thomas Schmid; Larissa Kazarian; Ulrich Panne; Reinhard Niessner

330

Pulsed photoacoustic Doppler flow measurements in blood-mimicking phantoms  

NASA Astrophysics Data System (ADS)

The feasibility of making spatially resolved measurements of blood flow using pulsed photoacoustic Doppler techniques has been explored. Doppler time shifts were quantified via cross-correlation of pairs of photoacoustic waveforms generated within a blood-simulating phantom using pairs of laser light pulses. The photoacoustic waves were detected using a focussed or planar PZT ultrasound transducer. For each flow measurement, a series of 100 waveform pairs was collected. Previous data processing methods involved rejection of poorly correlated waveform pairs; the modal velocity value and standard deviation were then extracted from the selected distribution of velocity measurements. However, the data selection criteria used in this approach is to some extent arbitrary. A new data analysis protocol, which involves averaging the 100 cross-correlation functions and thus uses all of the measured data, has been designed in order to prevent exclusion of outliers. This more rigorous approach has proved effective for quantifying the linear motion of micron-scale absorbers imprinted on an acetate sheet moving with velocities in the range 0.14 to 1.25 ms-1. Experimental parameters, such as the time separation between the laser pulses and the transducer frequency response, were evaluated in terms of their effect on the accuracy, resolution and range of measurable velocities. The technique was subsequently applied to fluid phantoms flowing at rates less than 5 mms-1 along an optically transparent tube. Preliminary results are described for three different suspensions of phenolic resin microspheres, and also for whole blood. Velocity information was obtained even under non-optimal conditions using a low frequency transducer and a low pulse repetition frequency. The distinguishing advantage of pulsed rather than continuous-wave excitation is that spatially resolved velocity measurements can be made. This offers the prospect of mapping flow within the microcirculation and thus providing insights into the perfusion of tumours and other pathologies characterised by abnormalities in flow status.

Brunker, J.; Beard, P.

2011-02-01

331

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

2011-02-01

332

Monitoring of acoustic emission activity using thin wafer piezoelectric sensors  

NASA Astrophysics Data System (ADS)

Acoustic emission (AE) is a well-known technique for monitoring onset and propagation of material damage. The technique has demonstrated utility in assessment of metallic and composite materials in applications ranging from civil structures to aerospace vehicles. While over the course of few decades AE hardware has changed dramatically with the sensors experiencing little changes. A traditional acoustic emission sensor solution utilizes a thickness resonance of the internal piezoelectric element which, coupled with internal amplification circuit, results in relatively large sensor footprint. Thin wafer piezoelectric sensors are small and unobtrusive, but they have seen limited AE applications due to low signal-to-noise ratio and other operation difficulties. In this contribution, issues and possible solutions pertaining to the utility of thin wafer piezoelectrics as AE sensors are discussed. Results of AE monitoring of fatigue damage using thin wafer piezoelectric and conventional AE sensors are presented.

Trujillo, Blaine; Zagrai, Andrei; Meisner, Daniel; Momeni, Sepand

2014-03-01

333

Detection of Delaminations in Composite Beams Using Piezoelectric Sensors  

NASA Technical Reports Server (NTRS)

This paper investigates the feasibility of a proposed technique for detecting delamination using piezoelectric layers or patches embedded or bonded to a composite structure. Variations in the voltage generated in the piezoelectric layers indicates the presence and location of delamination, when the structure is excited either externally or via actuators. The theoretical foundations of a method for predicting the dynamic response of delaminated composite beams with piezoelectric layers are described. The governing equations are presented for the case of external vibroacoustic excitation, as well as, for the case of locally induced vibrations by some of the embedded piezoelectric elements. An exact solution is developed within the limits of linear laminate theory. Applications illustrate the feasibility of delamination detection in cantilever beams. The results illustrate that the proposed technique may provide accurate detection of the presence, size, and location of a delamination.

Saravanos, Dimitris A.; Birman, Victor; Hopkins, Dale A.

1994-01-01

334

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

335

Characterization of human skin through photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

The photoacoustic (PA) technique is based on the absorption of modulated or pulsed light by a sample with subsequent heat generation, generating thermal waves that propagate in the surrounding media. Such waves produce the pressure oscillation detected as the PA signal. In this work, PA spectroscopy was used to characterize different human skin samples with respect to their response to ultraviolet radiation (UVA and UVB, 240nm < ? < 400nm). Measurements were performed at 70Hz and 17Hz, using a 1000W Xe arc lamp as the light source. Skin samples were about 0,5cm diameter. It was possible to obtain the absorption spectra of the stratum corneum and of a deeper layer of epidermis; when the lower modulation frequency is utilized, PA spectroscopy characterizes the absorption of the whole epidermis, because in this case the thermal diffusion length is thicker than that of the stratum corneum. PA spectroscopy was also employed to monitor the drying kinetics of the skin. Pre-treatment of the samples included different periods in a drying chamber. Measurements show that the PA spectra changes according to the humidity of the skin. Future work includes detailed monitoring of skin hydration.

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

2005-06-01

336

Computational Modeling of Piezoelectric Foams  

NASA Astrophysics Data System (ADS)

Piezoelectric materials, by virtue of their unique electromechanical characteristics, have been recognized for their potential utility in many applications as sensors and actuators. However, the sensing or actuating functionality of monolithic piezoelectric materials is generally limited. The composite approach to piezoelectric materials provides a unique opportunity to access a new design space with optimal mechanical and coupled characteristics. The properties of monolithic piezoelectric materials can be enhanced via the additive approach by adding two or more constituents to create several types of piezoelectric composites or via the subtractive approach by introducing controlled porosity in the matrix materials to create porous piezoelectric materials. Such porous piezoelectrics can be tailored to demonstrate improved signal-to-noise ratio, impedance matching, and sensitivity, and thus, they can be optimized for applications such as hydrophone devices. This article captures key results from the recent developments in the field of computational modeling of novel piezoelectric foam structures. It is demonstrated that the fundamental elastic, dielectric, and piezoelectric properties of piezoelectric foam are strongly dependent on the internal structure of the foams and the material volume fraction. The highest piezoelectric coupling constants and the highest acoustic impedance are obtained in the [3-3] interconnect-free piezoelectric foam structures, while the corresponding figures of merit for the [3-1] type long-porous structure are marginally higher. Among the [3-3] type foam structures, the sparsely-packed foam structures (with longer and thicker interconnects) display higher coupling constants and acoustic impedance as compared to closepacked foam structures (with shorter and thinner interconnects). The piezoelectric charge coefficients ( d h), the hydrostatic voltage coefficients ( g h), and the hydrostatic figures of merit ( d hgh) are observed to be significantly higher for the [3-3] type piezoelectric foam structures as compared to the [3-1] type long-porous materials, and these can be enhanced significantly by modifying the aspect ratio of the porosity in the foam structures as well.

Challagulla, K. S.; Venkatesh, T. A.

2013-02-01

337

Piezoelectric ultrasonic motors: overview  

Microsoft Academic Search

This paper reviews recent developments of ultrasonic motors using piezoelectric resonant vibrations. Following the historical background, ultrasonic motors using standing and traveling waves are introduced. Driving principles and motor characteristics are explained in comparison with conventional electromagnetic motors. After a brief discussion on speed and thrust calculation, finally, reliability issues of ultrasonic motors are described.

Kenji Uchino

1998-01-01

338

UHV piezoelectric translator  

SciTech Connect

A UHV compatible piezoelectric translator has been developed to correct for angular misalignments in the crysals of a UHV x-ray monochromator. The unit is small, bakeable to 150/sup 0/C, and uses only ceramic materials for insulation. We report on the construction details, vacuum compatibility, mechanical properties, and uses of the device.

Oversluizen, T.; Watson, G.

1985-01-01

339

Properties of Piezoelectric Materials.  

National Technical Information Service (NTIS)

The purpose of this monograph is to provide a source of data on a wide variety of piezoelectric materials which will be useful to those conducting research in this area as well as to the engineer designing ultrasonic transducers, filters, and other piezoe...

B. D. Wedlock

1964-01-01

340

PVDF piezoelectric polymer  

Microsoft Academic Search

PVDF piezo polymers are new, valuable materials for sensing and actuating applications. These materials are strong candidates for new sensors that cannot be realised with piezoceramics or single crystals. The combination of the mechanical properties of a plastic material with those of a piezoelectric material led to new sensors and transducers whose design is not easy. For this reason, the

Pierre Ueberschlag

2001-01-01

341

Piezoelectric Q switching of a CO2 laser  

NASA Astrophysics Data System (ADS)

Reactive Q-switching of a CO2 laser by means of a piezoelectrically actuated end reflector is reported. The high-frequency response of the piezoelectric transducer was maintained by optically polishing the transducer's surface directly instead of employing a separate mirror. Submicrosecond pulses at rates in excess of 100 kHz were obtained. This technique is especially appropriate for generating high pulse rates in low-power lasers, as no lossy intracavity elements are required.

Marcus, S.; Stein, D. T.

1987-01-01

342

Strain dependence of piezoelectric coefficients for pseudomorphically grown semiconductors  

Microsoft Academic Search

Advances in nanofabrication techniques have opened a plethora of opportunities to exploit the electrical and optical properties of exotic nanostructures such as Quantum Dots. Internal strain in such nanostructures facilitates band engineering. In this work we focus on III-As materials (GaAs\\/InAs) to study the strain dependence on the piezoelectric coefficients. The piezoelectric effect in quantum dots is one of the

R. Garg; M. Migliorato; V. Haxha; A. Hue; G. P. Srivastava; T. Hammerschmidt

2008-01-01

343

Theoretical studies of wave propagation in multilayered piezoelectric media  

SciTech Connect

The purpose of this paper is to extend the analysis of a single plate or substrate to the case of a multilayered medium. Due to the requiring of higher operating frequency, lower attenuation, and stronger piezoelectricity, layered structure becomes necessary. This technique is rapidly applied in the field of nondestructive evaluation and testing (NDE/T). Recently, a new feature of applying the piezoelectric effect for remote sensing, actuating, and vibration controlling came under study and development in aerospace and automative industries.

Chien, Hual-Te; Sheen, Shuh-Haw; Raptis, A.C.

1993-08-01

344

Piezoelectric properties of micro-machined cantilever PLZT thin films  

Microsoft Academic Search

A cantilever actuator of piezoelectric thin films was fabricated on Si wafer for micro-electro-mechanical-system (MEMS) devices such as micro mirror array and accelerometer. The piezoelectric thin films, La doped lead zirconate titanate. (PLZT) were prepared on Pt\\/Ti\\/SiO2\\/Si-wafer by the sol-gel technique. Geometrically flat cantilevers were obtained using a stress balance layer. Electrical properties, dielectric constants and breakdown fields, of PLZT

Chih-Hsing Cheng; Yuhuan Xu; Hilary B. Cherry; Justine Tseng; Greg Um; Weijia Wen; John D. Mackenzie

1999-01-01

345

Efficiency Enhancement of a Piezoelectric Energy Harvesting Device in Pulsed Operation by Synchronous Charge Inversion  

Microsoft Academic Search

This paper presents a new application of the ‘Synchronized Switch Harvesting on Inductor’ (SSHI). This nonlinear technique results in a significant increase of the electromechanical conversion capability of piezoelectric materials. Previous studies have shown the interest of this technique on steady state excited structures equipped with piezoelectric elements where the harvested power may be increased nearly tenfold compared to the

A. Badel; D. Guyomar; E. Lefeuvre; C. Richard

2005-01-01

346

Piezoelectric Smart Panels for Broadband Noise Reduction  

Microsoft Academic Search

This article presents the noise reduction performance of piezoelectric smart panels featuring piezoelectric shunt damping. A piezoelectric smart panel is a plate structure on which a piezoelectric patch with an electrical shunt circuit is attached. When an incidence sound is impinged on the panel structure, the structure vibrates and the attached piezoelectric patch produces electrical energy, which is effectively dissipated

Jaehwan Kim; Young-Chae Jung

2006-01-01

347

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.

2011-02-01

348

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

349

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.

Jiao, Shuliang; Zhang, Hao F.

2013-01-01

350

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

351

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.

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

352

Integrating bulk piezoelectric materials into MEMS for high authority actuators  

Microsoft Academic Search

A new technique was developed under the European Aeromems II project to produce integrated, thin (<100 µm) piezoelectric bimorph structures to be used in MEMS applications requiring large forces and displacements. The process employs machining, low-temperature bonding and standard microfabrication techniques to build up a laminated actuator structure. The process is believed to be a major improvement over existing techniques

M. J. Hucker; C. Warsop

2007-01-01

353

Structural health monitoring using piezoelectric impedance measurements.  

PubMed

This paper presents an overview and recent advances in impedance-based structural health monitoring. The basic principle behind this technique is to apply high-frequency structural excitations (typically greater than 30kHz) through surface-bonded piezoelectric transducers, and measure the impedance of structures by monitoring the current and voltage applied to the piezoelectric transducers. Changes in impedance indicate changes in the structure, which in turn can indicate that damage has occurred. An experimental study is presented to demonstrate how this technique can be used to detect structural damage in real time. Signal processing methods that address damage classifications and data compression issues associated with the use of the impedance methods are also summarized. Finally, a modified frequency-domain autoregressive model with exogenous inputs (ARX) is described. The frequency-domain ARX model, constructed by measured impedance data, is used to diagnose structural damage with levels of statistical confidence. PMID:17255044

Park, Gyuhae; Inman, Daniel J

2007-02-15

354

Observation of FT-IR\\/photoacoustic and FT-IR\\/photoacoustic reflection-absorption spectra of Langmuir-Blodgett films on a metal substrate  

Microsoft Academic Search

Fourier transform infrared photoacoustic (FT-IR\\/PA) spectroscopy combined with the reflection-absorption (RA) technique is demonstrated for Langmuir-Blodgett (LB) films deposited on metal substrate FT-IR\\/PA and FT-IR\\/PA\\/RA spectra can be taken on the same LB film. By the use of FT-IR\\/PA and FT-IR\\/PA\\/RA methods. Spectra corresponding to transmission and RA spectra can bee identified for the same LB film on a metal

S. Ochiai; J. F. McClelland; K. Kobayashi; K. Takaoka

1994-01-01

355

Penetration of compounds through human stratum corneum as studied by Fourier transform infrared photoacoustic spectroscopy  

Microsoft Academic Search

The penetration of the lipophilic model permeant, 1-cyanodecane, into isolated human stratum corneum (SC) was followed nondestructively by step-scan Fourier transform infrared (FTIR) photoacoustic spectroscopy (PAS) with phase modulation technique. The uptake of the compound in the SC was quantified by monitoring the alterations in the spectra in the course of the penetration using multivariate analysis. Step-scan technique in conjunction

Bui D. Hanh; Reinhard H. H. Neubert; Siegfried Wartewig; Jürgen Lasch

2001-01-01

356

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.

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

357

Molecular photoacoustic tomography of breast cancer using receptor targeted magnetic iron oxide nanoparticles as contrast agents.  

PubMed

In this report, we present a breast imaging technique combining high-resolution near-infrared (NIR) light induced photoacoustic tomography (PAT) with NIR dye-labeled amino-terminal fragments of urokinase plasminogen activator receptor (uPAR) targeted magnetic iron oxide nanoparticles (NIR830-ATF-IONP) for breast cancer imaging using an orthotopic mouse mammary tumor model. We show that accumulation of the targeted nanoparticles in the tumor led to photoacoustic contrast enhancement due to the high absorption of iron oxide nanoparticles (IONP). NIR fluorescence images were used to validate specific delivery of NIR830-ATF-IONP to mouse mammary tumors. We found that systemic delivery of the targeted IONP produced 4- and 10-fold enhancement in photoacoustic signals in the tumor, compared to the tumor of the mice that received non-targeted IONP or control mice. The use of targeted nanoparticles allowed imaging of tumors located as deep as 3.1 cm beneath the normal tissues. Our study indicates the potential of the combination of photoacoustic tomography and receptor-targeted NIR830-ATF-IONP as a clinical tool that can provide improved specificity and sensitivity for breast cancer detection. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim). PMID:23125139

Xi, Lei; Grobmyer, Stephen R; Zhou, Guangyin; Qian, Weiping; Yang, Lily; Jiang, Huabei

2014-06-01

358

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.

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

2014-01-01

359

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

360

A new biophysics approach using photoacoustic spectroscopy to study the DNA-ethidium bromide interaction.  

PubMed

We have examined the binding processes of ethidium bromide interacting with calf thymus DNA using photoacoustic spectroscopy. These binding processes are generally investigated by a combination of absorption or fluorescence spectroscopies with hydrodynamic techniques. The employment of photoacoustic spectroscopy for the DNA-ethidium bromide system identified two binding manners for the dye. The presence of two isosbestic points (522 and 498 nm) during DNA titration was evidence of these binding modes. Analysis of the photoacoustic amplitude signal data was performed using the McGhee-von Hippel excluded site model. The binding constant obtained was 3.4 x 10(8) M(bp)(-1), and the number of base pairs excluded to another dye molecule by each bound dye molecule (n) was 2. A DNA drug dissociation process was applied using sodium dodecyl sulfate to elucidate the existence of a second and weaker binding mode. The dissociation constant determined was 0.43 mM, whose inverse value was less than the previously obtained binding constant, demonstrating the existence of the weaker binding mode. The calculated binding constant was adjusted by considering the dissociation constant and its new value was 1.2 x 10(9) M(bp)(-1) and the number of excluded sites was 2.6. Using the photoacoustic technique it is also possible to obtain results regarding the dependence of the quantum yield of the dye on its binding mode. While intercalated between two adjacent base pairs the quantum yield found was 0.87 and when associated with an external site it was 0.04. These results reinforce the presence of these two binding processes and show that photoacoustic spectroscopy is more extensive than commonly applied spectroscopies. PMID:12029336

Bugs, Roque; Cornélio, Marinônio Lopes

2002-06-01

361

Design, Manufacturing and Characterization of Functionally Graded Flextensional Piezoelectric Actuators  

NASA Astrophysics Data System (ADS)

Previous works have been shown several advantages in using Functionally Graded Materials (FGMs) for the performance of flextensional devices, such as reduction of stress concentrations and gains in reliability. In this work, the FGM concept is explored in the design of graded devices by using the Topology Optimization Method (TOM), in order to determine optimal topologies and gradations of the coupled structures of piezoactuators. The graded pieces are manufactured by using the Spark Plasma Sintering (SPS) technique and are bonded to piezoelectric ceramics. The graded actuators are then tested by using a modular vibrometer system for measuring output displacements, in order to validate the numerical simulations. The technological path developed here represents the initial step toward the manufacturing of an integral piezoelectric device, constituted by piezoelectric and non-piezoelectric materials without bonding layers.

Amigo, R. C. R.; Vatanabe, S. L.; Silva, E. C. N.

2013-03-01

362

Piezoelectric step-motion actuator  

DOEpatents

A step-motion actuator using piezoelectric material to launch a flight mass which, in turn, actuates a drive pawl to progressively engage and drive a toothed wheel or rod to accomplish stepped motion. Thus, the piezoelectric material converts electrical energy into kinetic energy of the mass, and the drive pawl and toothed wheel or rod convert the kinetic energy of the mass into the desired rotary or linear stepped motion. A compression frame may be secured about the piezoelectric element and adapted to pre-compress the piezoelectric material so as to reduce tensile loads thereon. A return spring may be used to return the mass to its resting position against the compression frame or piezoelectric material following launch. Alternative embodiment are possible, including an alternative first embodiment wherein two masses are launched in substantially different directions, and an alternative second embodiment wherein the mass is eliminated in favor of the piezoelectric material launching itself.

Mentesana; Charles P. (Leawood, KS)

2006-10-10

363

Thermophysical investigation of Gafchromic EBT2 films using photoacoustic spectroscopy.  

PubMed

The thermophysical properties of EBT2 films exposed to different doses of x-ray were investigated. The doses ranged from 2 to 818 cGy. The films were irradiated by a Varian linear accelerator using a 6 MV photon beam. The thermal conductivity (k) was obtained by measuring the thermal diffusivity (?) and thermal effusivity (e) using the photoacoustic (PA) technique. The ?, e, and k values clearly indicated their dependence on the dose from 0 to 818 cGy. The results demonstrate that the PA technique can detect variations in the thermal diffusivity at doses as low as approximately 3 cGy. The thermal conductivity for the film exposed to 818 cGy of radiation increased by a factor of approximately 3.70 compared to the non-exposed film. The PA spectroscopic technique displayed good reproducibility, with a relative standard deviation of less than 5%. PMID:24874301

Aydarous, A; Abdallah, S; Towairqi, M Al

2014-07-01

364

Thermophysical investigation of Gafchromic EBT2 films using photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

The thermophysical properties of EBT2 films exposed to different doses of x-ray were investigated. The doses ranged from 2 to 818 cGy. The films were irradiated by a Varian linear accelerator using a 6 MV photon beam. The thermal conductivity (k) was obtained by measuring the thermal diffusivity (?) and thermal effusivity (e) using the photoacoustic (PA) technique. The ?, e, and k values clearly indicated their dependence on the dose from 0 to 818 cGy. The results demonstrate that the PA technique can detect variations in the thermal diffusivity at doses as low as approximately 3 cGy. The thermal conductivity for the film exposed to 818 cGy of radiation increased by a factor of approximately 3.70 compared to the non-exposed film. The PA spectroscopic technique displayed good reproducibility, with a relative standard deviation of less than 5%.

Aydarous, A.; Abdallah, S.; Towairqi, M. Al

2014-07-01

365

Systematic study of high-frequency ultrasonic transducer design for laser-scanning photoacoustic ophthalmoscopy  

NASA Astrophysics Data System (ADS)

Photoacoustic ophthalmoscopy (PAOM) is a high-resolution in vivo imaging modality that is capable of providing specific optical absorption information for the retina. A high-frequency ultrasonic transducer is one of the key components in PAOM, which is in contact with the eyelid through coupling gel during imaging. The ultrasonic transducer plays a crucial role in determining the image quality affected by parameters such as spatial resolution, signal-to-noise ratio, and field of view. In this paper, we present the results of a systematic study on a high-frequency ultrasonic transducer design for PAOM. The design includes piezoelectric material selection, frequency selection, and the fabrication process. Transducers of various designs were successfully applied for capturing images of biological samples in vivo. The performances of these designs are compared and evaluated.

Ma, Teng; Zhang, Xiangyang; Chiu, Chi Tat; Chen, Ruimin; Kirk Shung, K.; Zhou, Qifa; Jiao, Shuliang

2014-01-01

366

All-optical scanhead for ultrasound and photoacoustic dual-modality imaging.  

PubMed

We propose a new scanhead design for combined ultrasound (US)/photoacoustic (PA) imaging that can be applied to dual-modality microscopy and biomedical imaging. Both imaging modalities employ the optical generation and detection of acoustic waves. The scanhead consists of an optical fiber with an axicon tip for excitation, and a microring for acoustic detection. No conventional piezoelectric device is needed, and the cost of the design makes it suitable for one-time, disposable use. Furthermore, a single laser pulse is employed to generate both US and PA signals. A subband imaging method can be applied to the receiver to enhance the contrast between the US and PA signals. Phantom data demonstrate the feasibility of this approach. PMID:22274501

Hsieh, Bao-Yu; Chen, Sung-Liang; Ling, Tao; Guo, L Jay; Li, Pai-Chi

2012-01-16

367

Ultrasonically encoded photoacoustic flowgraphy in biological tissue.  

PubMed

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

2013-11-15

368

Infrared photoacoustic spectroscopy of adsorption on powders  

NASA Astrophysics Data System (ADS)

A photoacoustic cell for adsorption spectroscopy on powders is described. The cell permits spectra to be obtained, with a flowing gas and temperatures up to 400°C. Experiments were performed examining methanol adsorption on silica and Na-Y zeolites. On the silica, methoxy groups quantitatively displaced surface hydroxyl groups at elevated temperatures. On the Na zeolite, methanol seemed to associate with cation centers. The photoacoustic spectra were able to clearly display the entire spectrum from 4000-400 cm -1, and the methoxy C-O stretching band was clearly visible superimposed on the Si-O bands. Adsorption studies of CO on Pt/Al 2O 3 and Pt-black showed that photoacoustic spectra could be obtained for supported metal catalysts, but not for massive metal catalysts. Criteria are presented that relate the applicability of PAS to the physical properties of the powder.

McGovern, S. J.; Royce, B. S. H.; Benziger, J. B.

1984-09-01

369

A theoretical investigation of photoacoustic contrast agents.  

PubMed

Photoacoustic imaging offers significant potential as a biomedical imaging modality. For some applications, however, there is a need for contrast enhancement. In this paper, a theoretical comparison is presented of the efficacy of three different designs for photoacoustic contrast agents (PACAs), specifically, a droplet of dye, a bubble filled with gas coated by a dye loaded shell, and a droplet of volatile dye. For each case, the governing equations describing the dynamics of a single PACA in a homogenous incompressible fluid are derived. The coupled sets of equations describing the bubble oscillation and resulting radiated pressure, the photo-acoustic energy equation, and the equation of state are then solved numerically. The numerical results predict a stronger radiated acoustic signal for the same optical source energy density in the case of the volatile dye droplet by a factor of up to two orders of magnitude compared with the other two types of agent. PMID:23742340

Firouzi, K; Stride, E; Saffari, N

2013-06-01

370

Integrative System of Fast Photoacoustic Imaging  

NASA Astrophysics Data System (ADS)

An integrative fast (Photoacoustic) PA imaging system based on multi-element linear ultrasonic transducer array was developed, which integrates laser delivery, photoacoustic excitation and photoacoustic detection into a portable system. It collects PA signals by a multi-element linear transducer array in a reflection mode. The PA images with high spatial resolution and high contrast were obtained. Compared to other existing PA imaging methods, the integrative PA imaging system is characterized by rapidness, convenience and high practicality. The integrative system is mobile and portable, and it is suitable for imaging samples in natural condition with various different shapes. It will provide a novel and effective PA imaging approach for clinic diagnosis of neoplasm and tissue functional imaging in vivo, and has potential to be developed into a practical apparatus used in the early non-invasive detection of breast-cancer.

Yi, Tan

371

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.

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

2014-01-01

372

Photoacoustic tomography with a virtual point detector  

NASA Astrophysics Data System (ADS)

We devise and explore a ring-shaped acoustic detector associated with a virtual point detector concept for photoacoustic tomography. The center of the ring transducer scans a circle around the object to be imaged and then is treated as an omni-directional virtual point detector in photoacoustic image reconstruction. The virtual point detector introduces a space-invariant point spread function in photoacoustic image reconstruction and thus improves the tangential resolution, which is due to the finite aperture. Compared with a real point detector, the virtual point detector can provide similar spatial resolution but better SNR. Compared with a real finite-aperture detector, the virtual point detector can provide similar SNR but better spatial resolution. In addition, because of its virtual feature, the virtual point detector can be placed very close to and even inside of a tissue sample to locally scan a region of interest, which yields good SNR and spatial resolution.

Yang, Xinmai; Li, Meng-Lin; Wang, Lihong V.

2007-03-01

373

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

2011-02-01

374

Piezoelectricity in protein amino acids  

NASA Astrophysics Data System (ADS)

The piezoelectric activity of protein amino acids and their compounds has been measured using the pulse method at a frequency of 10 MHz. It has been established that, at room temperature, the piezoelectric effect is not observed in ?-glycine (achiral amino acid) and protein amino acids of the L modification, namely, methionine, phenylalanine, and tryptophan. An assumption has been made that this phenomenon is associated with the enhanced damping of elastic vibrations excited in samples due to the piezoelectric effect.

Lemanov, V. V.; Popov, S. N.; Pankova, G. A.

2011-06-01

375

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

376

Multilayered Unipoled Piezoelectric Transformers  

Microsoft Academic Search

This study describes a multi-layer piezoelectric voltage and power transformer which has one direction poling, operates in a wide-frequency range and delivers both step-up and step-down voltages by inverting the electrical connections. In this design, the input and output electrodes are on the same side of the disk and are isolated from each other by a fixed gap. Investigations were

Shashank Priya; Seyit Ural; Hyeoung Woo Kim; Kenji Uchino; Toru Ezaki

2004-01-01

377

Raman spectroscopy of piezoelectrics  

NASA Astrophysics Data System (ADS)

Raman spectroscopy represents an insightful characterization tool in electronics, which comprehensively suits the technological needs for locally and quantitatively assessing crystal structures, domain textures, crystallographic misalignments, and residual stresses in piezoelectric materials and related devices. Recent improvements in data processing and instrumental screening of large sampling areas have provided Raman spectroscopic evaluations with rejuvenating effectiveness and presently give spin to increasingly wider and more sophisticated experimental explorations. However, the physics underlying the Raman effect represents an issue of deep complexity and its applicative development to non-cubic crystallographic structures can yet be considered in its infancy. This review paper revisits some applicative aspects of the physics governing Raman emission from crystalline matter, exploring the possibility of disentangling the convoluted dependences of the Raman spectrum on crystal orientation and mechanical stress. Attention is paid to the technologically important class of piezoelectric materials, for which working algorithms are explicitly worked out in order to quantitatively extract both structural and mechanical information from polarized Raman spectra. Systematic characterizations of piezoelectric materials and devices are successively presented as applications of the developed equations. The Raman response of complex crystal structures, described here according to a unified formalism, is interpreted as a means for assessing both crystallographic textures and stress-related issues in the three-dimensional space (thus preserving their vectorial and tensorial nature, respectively). Statistical descriptions of domain textures based on orientation distribution functions are also developed in order to provide a link between intrinsic single-crystal data and data collected on polycrystalline (partly textured) structures. This paper aims at providing rigorous spectroscopic foundations to Raman approaches dealing with the analyses of functional behavior and structural reliability of piezoelectric devices.

Pezzotti, Giuseppe

2013-06-01

378

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

379

Deblurring algorithms accounting for the finite detector size in photoacoustic tomography  

NASA Astrophysics Data System (ADS)

Most reconstruction algorithms for photoacoustic tomography, like back projection or time reversal, work ideally for point-like detectors. For real detectors, which integrate the pressure over their finite size, images reconstructed by these algorithms show some blurring. Iterative reconstruction algorithms using an imaging matrix can take the finite size of real detectors directly into account, but the numerical effort is significantly higher compared to the use of direct algorithms. For spherical or cylindrical detection surfaces, the blurring caused by a finite detector size is proportional to the distance from the rotation center (spin blur) and is equal to the detector size at the detection surface. In this work, we apply deconvolution algorithms to reduce this type of blurring on simulated and on experimental data. Two particular deconvolution methods are compared, which both utilize the fact that a representation of the blurred image in polar coordinates decouples pixels at different radii from the rotation center. Experimental data have been obtained with a flat, rectangular piezoelectric detector measuring signals around a plastisol cylinder containing various small photoacoustic sources with variable distance from the center. Both simulated and experimental results demonstrate a nearly complete elimination of spin blur.

Roitner, Heinz; Haltmeier, Markus; Nuster, Robert; O'Leary, Dianne P.; Berer, Thomas; Paltauf, Guenther; Grün, Hubert; Burgholzer, Peter

2014-05-01

380

64-line-sensor array: fast imaging system for photoacoustic tomography  

NASA Astrophysics Data System (ADS)

Three-dimensional photoacoustic tomography with line sensors, which integrate the pressure along their length, has shown to produce accurate images of small animals. To reduce the scanning time and to enable in vivo applications, a detection array is built consisting of 64 piezoelectric line sensors which are arranged on a semi-cylinder. When measuring line integrated pressure signals 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. The shape and size of the array were adapted to the given problem of biomedical imaging and small animal imaging in particular. The length and width of individual line elements had to be chosen in order to take advantage of the favorable line integrating properties, maintaining the requested resolution of the image. For data acquisition the signals from the 64 elements are amplified and multiplexed into a 32 channel digitizer. Single projection images are recorded with two laser pulses within 0.2 seconds, as determined by the laser pulse repetition rate of 10 Hz. Phantom experiments are used for characterization of the line-array. Compared to previous implementations with a single line sensor scanning around an object, with the developed array the data acquisition time can be reduced from about one hour to about one minute.

Gratt, Sibylle; Nuster, Robert; Wurzinger, Gerhild; Bugl, Markus; Paltauf, Guenther

2014-03-01

381

Hybrid piezoelectric energy harvesting transducer system  

NASA Technical Reports Server (NTRS)

A hybrid piezoelectric energy harvesting transducer system includes: (a) first and second symmetric, pre-curved piezoelectric elements mounted separately on a frame so that their concave major surfaces are positioned opposite to each other; and (b) a linear piezoelectric element mounted separately on the frame and positioned between the pre-curved piezoelectric elements. The pre-curved piezoelectric elements and the linear piezoelectric element are spaced from one another and communicate with energy harvesting circuitry having contact points on the frame. The hybrid piezoelectric energy harvesting transducer system has a higher electromechanical energy conversion efficiency than any known piezoelectric transducer.

Xu, Tian-Bing (Inventor); Jiang, Xiaoning (Inventor); Su, Ji (Inventor); Rehrig, Paul W. (Inventor); Hackenberger, Wesley S. (Inventor)

2008-01-01

382

Source-receiver photoacoustic wave interferometry  

NASA Astrophysics Data System (ADS)

The representation theorems of the convolution type and the correlation type are used to obtain the superposition of the Green's function and its time reversal counterpart for the photoacoustic wave equation. Based on the representation theorems, an interferometry relation providing the Green's function between sources and receivers is obtained. The reciprocity theorems for a spherical geometrical system consisting of sources located on the boundary of the inner spherical region and transducers located on the outer boundary are utilized. Therefore, the measurement would be observed at one of the detectors if there were a photoacoustic point source at the other one.

Erkol, Hakan; Demirkiran, Aytac; Aytac-Kipergil, Esra; Uluc, Nasire; Unlu, Mehmet B.

2014-03-01

383

Realtime photoacoustic microscopy of murine cardiovascular dynamics.  

PubMed

Non-invasive visualization of cardiovascular dynamics in small animals is challenging due to their rapid heart-rates. We present a realtime photoacoustic imaging system consisting of a 30-MHz ultrasound array transducer, receive electronics, a high-repetition-rate laser, and a multicore-computer, and demonstrate its ability to image optically-absorbing structures of the beating hearts of young athymic nude mice at rates of approximately 50 frames per second with 100 microm x 25 microm spatial resolution. To our knowledge this is the first report of realtime photoacoustic imaging of physiological dynamics. PMID:18958134

Zemp, R J; Song, L; Bitton, R; Shung, K K; Wang, L V

2008-10-27

384

Combined optical resolution photoacoustic and fluorescence micro-endoscopy  

NASA Astrophysics Data System (ADS)

We present a new micro-endoscopy system combining real-time C-scan optical-resolution photoacoustic micro-endoscopy (OR-PAME), and a high-resolution fluorescence micro-endoscopy system for visualizing fluorescently labeled cellular components and optically absorbing microvasculature simultaneously. With a diode-pumped 532-nm fiber laser, the OR-PAM sub-system is capable of imaging with a resolution of ~ 7?m. The fluorescence sub-system consists of a diode laser with 445 nm-centered emissions as the light source, an objective lens and a CCD camera. Proflavine, a FDA approved drug for human use, is used as the fluorescent contrast agent by topical application. The fluorescence system does not require any mechanical scanning. The scanning laser and the diode laser light source share the same light path within an optical fiber bundle containing 30,000 individual single mode fibers. The absorption of Proflavine at 532 nm is low, which mitigates absorption bleaching of the contrast agent by the photoacoustic excitation source. We demonstrate imaging in live murine models. The system is able to provide cellular morphology with cellular resolution co-registered with the structural and functional information given by OR-PAM. Therefore, the system has the potential to serve as a virtual biopsy technique, helping researchers and clinicians visualize angiogenesis, effects of anti-cancer drugs on both cells and the microcirculation, as well as aid in the study of other diseases.

Shao, Peng; Shi, Wei; Hajireza, Parsin; Zemp, Roger J.

2012-02-01

385

Using a phase contrast imaging method in photoacoustic tomography  

NASA Astrophysics Data System (ADS)

To speed up the data acquisition in photoacoustic tomography full field detection can be used to avoid the time consuming scanning around the object. The full field detection is realized using a phase contrast method like commonly used in optical microscopy. An expanded light beam considerably larger than the object size illuminates the sample placed in the middle of the propagating light beam. Images obtained with a CCD-camera at a certain time show a projection of the instantaneous pressure field (phase object) in a given direction. The reconstruction method is related to imaging with integrating line detectors, but has to be matched to the specific information in the recorded images, which is now purely spatially resolved as opposed to spatiotemporally for a single scanning detector. The reconstruction of the projection images of the initial pressure distribution is done by back propagating the observed wave pattern in Radon space. Numerical simulations and experiments are performed to show the overall adaptability of this technique in photoacoustic tomography.

Nuster, R.; Zangerl, G.; Haltmeier, M.; Scherzer, O.; Paltauf, G.

2010-02-01

386

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; Hćggström, Edward; Timonen, Jussi; Myllylä, Risto

2012-12-01

387

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.

Soroushian, Behrouz; Yang, Xinmai

2011-01-01

388

[Evaluation of nutrient release profiles from polymer coated fertilizers using Fourier transform mid-infrared photoacoustic spectroscopy].  

PubMed

The acrylate-like materials were used to develop the polymer coated controlled release fertilizer, the nutrients release profiles were determined, meanwhile the Fourier transform mid-infrared photoacoustic spectra of the coatings were recorded and characterized; GRNN model was used to predict the nutrients release profiles using the principal components of the mid-infrared photoacoustic spectra as input. Results showed that the GRNN model could fast and effectively predict the nutrient release profiles, and the predicted calibration coefficients were more than 0.93; on the whole, the prediction errors (RMSE) were influenced by the profiling depth of the spectra, the average prediction error was 10.28%, and the spectra from the surface depth resulted in a lowest prediction error with 7.14%. Therefore, coupled with GRNN modeling, Fourier transform mid-infrared photoacoustic spectroscopy can be used as an alternative new technique in the fast and accurate prediction of nutrient release from polymer coated fertilizer. PMID:22512162

Shen, Ya-zhen; Du, Chang-wen; Zhou, Jian-min; Wang, Huo-yan; Chen, Xiao-qin

2012-02-01

389

Multimodal photoacoustic ophthalmoscopy in mouse  

PubMed Central

Photoacoustic ophthalmoscopy (PAOM) is a novel imaging technology that measures optical absorption in the retina. The capability of PAOM can be further enhanced if it could image mouse eyes, because mouse models are widely used for various retinal diseases. The challenges in achieving high-quality imaging of mouse retina, however, come from the much smaller eyeball size. Here, we report an optimized imaging system, which integrates PAOM, spectral-domain optical coherence tomography (SD-OCT), and autofluorescence-scanning laser ophthalmoscopy (AF-SLO), for mouse eyes. Its multimodal capability was demonstrated by imaging transgenic Nrl-GFP mice that express green fluorescent protein (GFP) in photoreceptors. SD-OCT provided guidance of optical alignment for PAOM and AF-SLO, and complementary contrast with high depth-resolution retinal cross sections. PAOM visualized the retinal vasculature and retinal pigment epithelium melanin, and AF-SLO measured GFP-expressing in retinal photoreceptors. The in vivo imaging results were verified by histology and confocal microscopy.

Feng, Liang; Sarthy, Vijay; Jiao, Shuliang; Liu, Xiaorong; Zhang, Hao F.

2014-01-01

390

Multimodal photoacoustic ophthalmoscopy in mouse.  

PubMed

Photoacoustic ophthalmoscopy (PAOM) is a novel imaging technology that measures optical absorption in the retina. The capability of PAOM can be further enhanced if it could image mouse eyes, because mouse models are widely used for various retinal diseases. The challenges in achieving high-quality imaging of mouse retina, however, come from the much smaller eyeball size. Here, we report an optimized imaging system, which integrates PAOM, spectral-domain optical coherence tomography (SD-OCT), and autofluorescence-scanning laser ophthalmoscopy (AF-SLO), for mouse eyes. Its multimodal capability was demonstrated by imaging transgenic Nrl-GFP mice that express green fluorescent protein (GFP) in photoreceptors. SD-OCT provided guidance of optical alignment for PAOM and AF-SLO, and complementary contrast with high depth-resolution retinal cross sections. PAOM visualized the retinal vasculature and retinal pigment epithelium melanin, and AF-SLO measured GFP-expressing in retinal photoreceptors. The in vivo imaging results were verified by histology and confocal microscopy. PMID:22649053

Song, Wei; Wei, Qing; Feng, Liang; Sarthy, Vijay; Jiao, Shuliang; Liu, Xiaorong; Zhang, Hao F

2013-06-01

391

Piezoelectrically actuated flextensional micromachined ultrasound droplet ejectors.  

PubMed

This paper reports a variation on the design of the flextensional transducer for use in ejecting liquids. The transducer is constructed by depositing a piezoelectric thin film to a thin, edge-clamped, circular annular plate. By placing a fluid behind one face of a vibrating compound plate that has an orifice at its center, we achieve continuous or drop-on-demand ejection of the fluid. We present results of ejection of water and isopropanol. The ejector is harmless to sensitive fluids and can be used to eject fuels as well as chemical and biological samples. Micromachined two-dimensional array piezoelectrically actuated flextensional droplet ejectors were realized using planar silicon micromachining techniques. Typical resonant frequency of the micromachined device ranges from 400 kHz to 4.5 MHz. The ejection of water thru a 5-microm diameter orifice at 3.5 MHz was demonstrated by using the developed micromachined two-dimensional array ejectors. PMID:12075968

Perçin, Gökhan; Khuri-Yakub, Butrus T

2002-06-01

392

A cost-efficient frequency-domain photoacoustic imaging system  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) imaging techniques have recently attracted much attention and can be used for noninvasive imaging of biological tissues. Most PA imaging systems in research laboratories use the time domain method with expensive nanosecond pulsed lasers that are not affordable for most educational laboratories. Using an intensity modulated light source to excite PA signals is an alternative technique, known as the frequency domain method, with a much lower cost. In this paper, we describe a simple frequency domain PA system and demonstrate its imaging capability. The system provides opportunities not only to observe PA signals in tissue phantoms but also to acquire hands-on skills in PA signal detection. It also provides opportunities to explore the underlying mechanisms of the PA effect.

LeBoulluec, Peter; Liu, Hanli; Yuan, Baohong

2013-09-01

393

Photoacoustic imaging using an adaptive interferometer with a photorefractive crystal.  

PubMed

In this paper we report on remote three-dimensional photoacoustic imaging without the need for a coupling agent or other aids (e.g. detector foils) by utilizing a two-wave mixing interferometer (TWMI). In this technique the beams coming from sample and reference are brought to interfere in a Bi??SiO?? photorefractive crystal (PRC). Such a setup allows the measurement of ultrasonic displacements on rough sample surfaces. After data acquisition the initial pressure distribution is reconstructed by a Fourier domain synthetic aperture focusing technique (FSAFT). We present three-dimensional imaging of a hair ribbon phantom, on biological samples with embedded artificial blood vessels or pig bristles, and measurements on a human forearm in-vivo. PMID:22354686

Hochreiner, Armin; Berer, Thomas; Grün, Hubert; Leitner, Michael; Burgholzer, Peter

2012-07-01

394

Photoacoustic tweezers with a pulsed laser: theory and experiments  

NASA Astrophysics Data System (ADS)

A novel noninvasive optical technique for manipulating particles and cells is presented that utilizes laser-generated forces in an absorbing medium surrounding the particles or cells. In this technique, a laser pulse creates near-object acoustic waves, which during interaction with the objects lead to then being moved or trapped. The main optical schemes are considered, and a theory is presented for this new optical tool, namely photoacoustic (PA) tweezer with pulsed laser. The magnitudes of forces acting on polystyrene particles suspended in water were estimated as a function of the particles' properties for circular and ring geometries of the laser beam. Results of our preliminary experiments demonstrated proof that the manipulation, trapping and even rotation of cells is possible with PA tweezers.

Zharov, V. P.; Malinsky, T. V.; Kurten, R. C.

2005-08-01

395

Photoacoustic Doppler measurement of flow using tone burst excitation.  

PubMed

In this paper a novel technique for flow measurement which is based on the photoacoustic (PA) Doppler effect is described. A significant feature of the proposed approach is that it can be implemented using tone burst optical excitation thus enabling simultaneous measurement of both velocity and position. The technique, which is based on external modulation and heterodyne detection, was experimentally demonstrated by measurement of the flow of a suspension of carbon particles in a silicon tube and successfully determined the particles mean velocity up to values of 130 mm/sec, which is about 10 times higher than previously reported PA Doppler set-ups. In the theoretical part a rigorous derivation of the PA response of a flowing medium is described and some important simplifying approximations are highlighted. PMID:20389434

Sheinfeld, Adi; Gilead, Sharon; Eyal, Avishay

2010-03-01

396

Piezoelectric energy conversion in windmills  

Microsoft Academic Search

Theory and practice for wind generators based on piezoelectric polymers are reviewed. The basic piezoelectric equations are applied to bimorphs set into mechanical oscillation by the wind. The importance of incorporating mechanical and electrical resonance into the design is emphasized. The design and performance of two rotating generators are described, and performance is compared with theory. Design improvements are proposed,

V. H. Schmidt

1992-01-01

397

Piezoelectric Vibration Energy Harvesting Device.  

National Technical Information Service (NTIS)

A piezoelectric vibration energy harvesting device which is made up of a first mass, a second, a first spring coupled to the first mass, and a second spring coupled to the second mass. A piezoelectric element is bonded between the first mass and the secon...

K. Andic K. K. Deng

2005-01-01

398

Removing effects of temperature changes from piezoelectric impedance-based qualitative health monitoring  

Microsoft Academic Search

A high frequency NDE technique has been under investigation at the Center for Intelligent Material Systems and Structures. Physical changes in the structure cause changes in the mechanical impedance. Due to the electromechanical coupling in piezoelectric materials, this change in structural mechanical impedance cause a change in the electrical impedance of the piezoelectric sensor. Hence, by monitoring the electrical impedance

Kazuhisa Kabeya; Harley H. Cudney; Daniel J. Inman

1998-01-01

399

The analysis of a piezoelectric bimorph beam with two input base motions for power harvesting  

Microsoft Academic Search

The exploitation of usable power from vibration environments shows potential benefit for recharging batteries and powering wireless transmission. In this paper, we present a novel technique for simulating the electromechanical cantilevered piezoelectric bimorph beam system with two input base transverse and longitudinal motions for predicting power harvesting. The piezoelectric bimorph beam with tip mass was modelled using the Euler-Bernoulli beam

M F Lumentut; I M Howard

2010-01-01

400

Oxygen evolution from tomato (C3) plants with and without mycorrhiza: Open photoacoustic cell measurement and statistical analysis  

Microsoft Academic Search

Mycorrhiza, a common association between root plants and mycorrhizic fungus provides some benefits to the plant, improving its nutrient uptake and increasing the drought resistance as well as the photosynthetic rate. Open photoacoustic (OPC) cell technique was used here to study oxygen evolution from C3 plants (tomato) with and with mycorrhizic fungus (Glomus Fasciculatum) under the lighting conditions similar to

S. Sanchez-Rocha; M. Vargas-Luna; G. Gutiérrez-Juárez; R. Huerta Franco; L. Madueńo; V. Olalde-Portugal

2005-01-01

401

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

402

Thermal decomposition study of nitropyrazoles based on time-resolved pulsed photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

The paper reports the study of thermal decomposition of 3(5)-nitropyrozole, 4-nitropyrazole and 1-nitropyrazole using time-resolved pulsed photoacoustic spectroscopy technique for the first time. The second harmonic, i.e., ? = 532 nm, 7 ns pulse width at 10 Hz repetition rate, obtained from Q-switched Nd: YAG laser has been employed. In addition, we have studied the effect of pressure, temperature and incident laser energy on the thermal decomposition mechanism of nitropyrazoles. The strength of photoacoustic signal provides significant information about the multistep thermal decomposition mechanism of 3(5)-nitropyrazole and 4-nitropyrazole, while 1-nitropyrazole follows the path of direct decomposition based on single reaction, which is also verified by the thermal gravimetric-differential thermal analysis (TG-DTA) technique. We have also experimentally demonstrated the presence of free NO2 before the melting point, which is due to the thermal dissociation of solid nitropyrazole compounds.

Yehya, F.; Chaudhary, A. K.

2013-01-01

403

Thermal Images of Small Agricultural Seeds Obtained by Photoacoustic and Photopyroelectric Microscopies  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) and photopyroelectric microscopies were used to obtain photothermal images of small agricultural seeds. In the photoacoustic microscopy (PAM) technique, a tightly closed PA cell was used with an electret microphone as the sensor. In photopyroelectric microscopy (PPEM), the seeds were placed in contact with a pyroelectric (PE) sensor. From the experimental data, it was possible to obtain thermal images of the scanned samples from the amplitude and phase signals. In the present research, thermal images of small agricultural seeds were obtained by both techniques and compared. The experimental results show that the photothermal images obtained by PAM have better resolution than those obtained by PPEM. PAM images using the amplitude signal appear to be more sensitive to detect seed structures as was observed in the seed thermal images obtained in this study.

Domínguez Pacheco, A.; Hernández Aguilar, C.; Cruz-Orea, A.

2013-05-01

404

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; Muńoz Hernández, R A

2014-01-01

405

Gold nanorods: contrast agents for photoacoustic imaging?  

Microsoft Academic Search

Gold nanorods are seen as possible contrast agents for photoacoustic imaging since they have strong absorption peaks at near-infrared wavelengths. Also they are easy to conjugate with various proteins. If these particles can be conjugated with cancer affinity proteins then these particles can accumulate specifically at a tumor site. By detecting the presence of accumulation of gold nanorods inside the

C. Ungureanu; R. Raja Gopal; T. G. van Leeuwen; S. Manohar

2007-01-01

406

Tutorial on Photoacoustic Microscopy and Computed Tomography  

Microsoft Academic Search

The field of photoacoustic tomography has experienced considerable growth in the past few years. Although several commercially available pure optical imaging modalities, including confocal microscopy, two-photon microscopy, and optical coherence tomography, have been highly successful, none of these technologies can provide penetration beyond ~1 mm into scattering biological tissues, because they are based on ballistic and quasi-ballistic photons. Heretofore, there

Lihong V. Wang

2008-01-01

407

Molecular Photoacoustic Tomography with Colloidal Nanobeacons**  

PubMed Central

Vascularly constrained, “soft” colloidal gold nanobeacons (GNB) demonstrate for the first time that GNBs can be characterized as exogenous photoacoustic contrast agents for targeted detection of fibrin, a major biochemical feature of thrombus. Fibrin-targeted GNBs provide a more than tenfold signal enhancement in photo acoustic tomography (PAT) in the NIR wavelength window, indicating their potential for diagnostic imaging with PAT.

Pramanik, Manojit; Senpan, Angana; Yang, Xinmai; Song, Kwang H.; Scott, Mike J.; Zhang, Huiying; Gaffney, Patrick J.; Wickline, Samuel A.; Lanza, Gregory M.

2010-01-01

408

Piezoelectric Pushers Suppress Vibrations  

NASA Technical Reports Server (NTRS)

Vibration-suppressing control systems including piezoelectric actuators undergoing development. Small, lightweight, and rugged. Requires simpler electronic control subsystems and does not require large electromagnet coils. Continues to provide support and some passive damping even when electronic control subsystems or power supplies fail. Intended primarily to enhance safety and prevent damage in rotating machinery by sensing and counteracting vibrations. Useful in suppressing unpredictable vibrations caused by changes in loads, losses of rotating components and consequent imbalances in rotors, and ingestion of foreign objects into turbines.

Kascak, Albert F.

1990-01-01

409

Piezoelectric slotted ring transducer.  

PubMed

Analytical treatment of a slotted piezoelectric ceramic ring transducer vibrating in flexure is presented. The mode shape of the slotted ring vibration is determined, and parameters of the equivalent electromechanical circuit of the transducer are calculated. Possibilities to optimize the effective electromechanical coupling coefficient of the transducer by combining active and passive materials are considered. Acoustic loading for typical projectors made from slotted rings is estimated. Challenges in implementing the slotted ring transducers in terms of depth limitation and radiated power are discussed. PMID:23742342

Aronov, Boris S

2013-06-01

410

Thermal-Diffusivity Measurements of Mexican Citrus Essential Oils Using Photoacoustic Methodology in the Transmission Configuration  

Microsoft Academic Search

Photoacoustic methodology in the transmission configuration (PMTC) was used to study the thermophysical properties and their\\u000a relation with the composition in Mexican citrus essential oils providing the viability of using photothermal techniques for\\u000a quality control and for authentication of oils and their adulteration. Linear relations for the amplitude (on a semi-log scale)\\u000a and phase, as functions of the sample’s thickness,

G. A. López Muńoz; R. F. López González; J. A. Balderas López; L. Martínez-Pérez

2011-01-01

411

Photoacoustic and optothermal studies of tomato ketchup adulterated by the red beet (Beta vulgaris)  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) spectroscopy and optothermal window (OW) technique were used to explore their potential to detect red beet added as a colorant to tomato ketchup. The associated changes of colour resulting in the changes of absorbance (and hence of PA and OT signals) were monitored in the 500 nm region corresponding to the absorption maximum of lycopene. Both methods were shown capable of quantifying about 1% of red beet (by mass) in the mixture of ketchup and red beet.

Bicanic, D.; Westra, E.; Seters, J.; van Houten, S.; Huberts, D.; Coli?-Bari?, I.; Cozijnsen, J.; Boshoven, H.

2005-06-01

412

Multifunctional microbubbles and nanobubbles for photoacoustic and ultrasound imaging  

Microsoft Academic Search

We develop a novel dual-modal contrast agent-encapsulated-ink poly(lactic-co-glycolic acid) (PLGA) microbubbles and nanobubbles-for photoacoustic and ultrasound imaging. Soft gelatin phantoms with embedded tumor simulators of encapsulated-ink PLGA microbubbles and nanobubbles in various concentrations are clearly shown in both photoacoustic and ultrasound images. In addition, using photoacoustic imaging, we successfully image the samples positioned below 1.8-cm-thick chicken breast tissues. Potentially, simultaneous

Chulhong Kim; Ruogu Qin; Jeff S. Xu; Lihong V. Wang; Ronald Xu

2010-01-01

413

New applications of photoacoustics to the study of photosynthesis  

Microsoft Academic Search

Photoacoustic methods offer unique capabilities for photosynthesis research. Phenomena that are readily observed by photoacoustics\\u000a include the storage of energy by electron transport, oxygen evolution by leaf tissue at microsecond time resolution, and the\\u000a conformational changes of photosystems caused by charge separation. Despite these capabilities, photoacoustic methods have\\u000a not been widely exploited in photosynthesis research. One factor that has contributed

Stephen K. Herbert; Tao Han; Thomas C. Vogelmann

2000-01-01

414

Piezoelectric materials used in underwater acoustic transducers  

Microsoft Academic Search

Piezoelectric materials have been used in underwater acoustic transducers for nearly a century. In this paper, we reviewed four different types of piezoelectric materials: piezoelectric ceramics, single crystals, composites, and polymers, which are widely used in underwater acoustic transducers nowadays. Piezoelectric ceramics are the most dominant material type and are used as a single-phase material or one of the end

Huidong Li; Zhiqun Deng; Thomas J. Carlson

2012-01-01

415

Derivation of Piezoelectric Losses from Admittance Spectra  

Microsoft Academic Search

High power density piezoelectrics are required to miniaturize devices such as ultrasonic motors, transformers, and sound projectors. The power density is limited by the heat generation in piezoelectrics, therefore, clarification of the loss mechanisms is necessary. This paper provides a methodology to determine the electromechanical losses, i.e., dielectric, elastic and piezoelectric loss factors in piezoelectrics by means of a detailed

Yuan Zhuang; Seyit O. Ural; Aditya Rajapurkar; Safakcan Tuncdemir; Ahmed Amin; Kenji Uchino

2009-01-01

416

Nonlinear behavior in piezoelectric ceramic transducers  

Microsoft Academic Search

In recent years intensive development efforts have been devoted to new piezoelectric high-power devices, such as ultrasonic motors, piezoelectric actuators, and piezoelectric transformers. Piezoelectric ceramic transducers used in these devices are usually driven at a high level of vibration stress in a resonant mode. To optimize the performance of such devices, it is essential to understand the nonlinear behavior which

S. Takahashi; Y. Sasaki; M. Umeda; K. Nakamura; S. Ueha

2000-01-01

417

Experiments to demonstrate piezoelectric and pyroelectric effects  

NASA Astrophysics Data System (ADS)

Piezoelectric and pyroelectric materials are used in many current applications. The purpose of this paper is to explain the basic properties of pyroelectric and piezoelectric effects and demonstrate them in simple experiments. Pyroelectricity is presented on lead zirconium titanate (PZT) ceramics as an electric charge generated by the temperature change. The direct piezoelectric effect is demonstrated by the electric charge generated from the bending of the piezoelectric ceramic membrane or from the gas igniter. The converse piezoelectric effect is presented in the experiments by the deflection of the bending piezoelectric element (piezoelectric bimorph).

Erhart, Ji?í

2013-07-01

418

Single-wavelength functional photoacoustic microscopy in biological tissue  

PubMed Central

Recently, we developed a reflection-mode relaxation photoacoustic microscope, based on saturation intensity, to measure picosecond relaxation times using a nanosecond laser. Here, using the different relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, the oxygen saturation was quantified in vivo with single-wavelength photoacoustic microscopy. All previous functional photoacoustic microscopy measurements required imaging with multiple laser-wavelength measurements to quantify oxygen saturation. Eliminating the need for multi-wavelength measurements removes the influence of spectral properties on oxygenation calculations and improves the portability and cost-effectiveness of functional or molecular photoacoustic microscopy.

Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin; Wang, Lihong V.

2011-01-01

419

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

420

Photoacoustic imaging of the bladder: a pilot study.  

PubMed

Photoacoustic imaging is a promising new technology that combines tissue optical characteristics with ultrasound transmission and can potentially visualize tumor depth in bladder cancer. We imaged simulated tumors in 5 fresh porcine bladders with conventional pulse-echo sonography and photoacoustic imaging. Isoechoic biomaterials of different optical qualities were used. In all 5 of the bladder specimens, photoacoustic imaging showed injected biomaterials, containing varying degrees of pigment, better than control pulse-echo sonography. Photoacoustic imaging may be complementary to diagnostic information obtained by cystoscopy and urine cytologic analysis and could potentially obviate the need for biopsy in some tumors before definitive treatment. PMID:23804347

Kamaya, Aya; Vaithilingam, Srikant; Chung, Benjamin I; Oralkan, Omer; Khuri-Yakub, Butrus T

2013-07-01

421

Photoacoustic monitoring of the absorption of isotonic saline solution by human mucus.  

PubMed

Viscosity and elasticity are the fundamental rheologic properties of respiratory mucus, and are important determinants of transportability of mucus in the mucociliary system. One technique that permits to monitor indirectly the rheologic properties of any sample is the photoacoustic technique. Using that technique, the absorption of isotonic saline solution by human mucus was monitored. The mucus was obtained from 11 volunteers, divided into two groups: five volunteers presenting pneumology symptoms (group I) and six healthy volunteers (group II). The photoacoustic signal of the mucus absorbing the saline solution was monitored as function of time, with measurements being performed each 10 min, up to 120 min. The resulting curves were fitted to sigmoidal curves to simulate the evolution on time of the photoacoustic signal. A characteristic time for the half saturation of the absorption process was obtained. For group I the time obtained was 23.3+/-5.3 min and for group II the time obtained was 55.0+/-7.7 min, both means being significantly different (Student t-test, p<0.05). This result supports the empirical practice of treating individuals presenting symptoms of airway obstruction with about 30 min of inhalations of isotonic saline solution vapor for the clearance of the airways. PMID:17158085

Dumas, F L; Marciano, F R; Oliveira, L V F; Barja, P R; Acosta-Avalos, D

2007-11-01

422

Development of cantilevered energy harvesters coupled with a topologically optimized piezoelectric layer oscillating in vortex  

NASA Astrophysics Data System (ADS)

An efficient design analysis method for cantilevered beam-type piezoelectric energy harvesters was developed for the prediction of the electric power output, based on the finite element method and the design optimization of piezoelectric materials. The optimum topology of a piezoelectric material layer could be obtained by a newly developed topology optimization technique for piezoelectric materials which utilized the electromechanical coupling equations, MMA (method of moving asymptotes), and SIMP (solid isotropic material with penalization) interpolation. Using the design optimization tool, several cantilevered beam-type piezoelectric energy harvesters which fluctuated in the region of vortex shedding were developed, that consisted of two different material layers - piezoelectric and aluminum layers. In order to obtain maximum electric power, the exciting frequency of the cantilevered energy device must be tuned as close to the natural frequency of the beam as possible. Using the method, the effects of geometric parameters and several piezoelectric materials (PZT, PVDF, and PZT fiber composites) attached to the beam device on power generation were investigated and the electric characteristics were evaluated. The three kinds of material coefficients such as elasticity, capacitance, and piezoelectric coupling are interpolated by element density variables. Then, the shape and size design optimizations for the cantilevered beam geometries with an optimum piezoelectric topology have been performed for a base model.

Kim, Cheol; Shin, Jae-Uk; Kim, Ju-Young

2012-03-01

423

Design of optimized piezoelectric HDD-sliders  

NASA Astrophysics Data System (ADS)

As storage data density in hard-disk drives (HDDs) increases for constant or miniaturizing sizes, precision positioning of HDD heads becomes a more relevant issue to ensure enormous amounts of data to be properly written and read. Since the traditional single-stage voice coil motor (VCM) cannot satisfy the positioning requirement of high-density tracks per inch (TPI) HDDs, dual-stage servo systems have been proposed to overcome this matter, by using VCMs to coarsely move the HDD head while piezoelectric actuators provides fine and fast positioning. Thus, the aim of this work is to apply topology optimization method (TOM) to design novel piezoelectric HDD heads, by finding optimal placement of base-plate and piezoelectric material to high precision positioning HDD heads. Topology optimization method is a structural optimization technique that combines the finite element method (FEM) with optimization algorithms. The laminated finite element employs the MITC (mixed interpolation of tensorial components) formulation to provide accurate and reliable results. The topology optimization uses a rational approximation of material properties to vary the material properties between 'void' and 'filled' portions. The design problem consists in generating optimal structures that provide maximal displacements, appropriate structural stiffness and resonance phenomena avoidance. The requirements are achieved by applying formulations to maximize displacements, minimize structural compliance and maximize resonance frequencies. This paper presents the implementation of the algorithms and show results to confirm the feasibility of this approach.

Nakasone, Paulo H.; Yoo, Jeonghoon; Silva, Emilio C. N.

2010-03-01

424

Numerical characterization of soft piezoelectric ceramics  

NASA Astrophysics Data System (ADS)

Numerical simulations of piezoelectric ceramics can give detailed information about their static and dynamic behaviours. Resonance frequencies, mechanical displacements and other values of interest can be obtained using well known techniques, such as Finite Element Method (FEM). However, the predictions of such methods are strongly limited by the accuracy of the parameters in the piezoceramic model. Assuming a linear behaviour, five elastic constants, three piezoelectric constants, two dielectric constants and the mass density are needed to simulate piezoceramics belonging to the 6-mm symmetry class. In a recent work, our research group presents a novel methodology to obtain the parameters of piezoelectric ceramic disks based on FEM simulations in a set of ten hard PZT ceramics. In this work, the proposed methodology is applied for the characterization of two soft PZT ceramics (Pz27 from Ferroperm and APC850 from APC International) typically used in ultrasound applications. To provide the error bound two different thicknesses (frequencies of 1 MHz and 2 MHz) and three different diameters (10 mm, 20 mm and 30 mm) are used in the characterization, the mean value over this set is used to characterize the material itself. A set of ten samples belonging to a single fabrication batch is used to estimate the error bound for identical samples. The results adjust the impedance curves over a wide band of frequencies, including the radial modes, the thickness mode and other coupled modes.

Pérez, Nicolás; Buiochi, Flavio; Andrade, Marco A. B.; Adamowski, Julio C.

2012-05-01

425

In vivo multi-modality photoacoustic and pulse echo tracking of prostate tumor growth using a window chamber  

NASA Astrophysics Data System (ADS)

Understanding the tumor microenvironment is critical to characterizing how cancers operate and predicting how they will eventually respond to treatment. The mouse window chamber model is an excellent tool for cancer research, because it enables high resolution tumor imaging and cross-validation using multiple modalities. We describe a novel multimodality imaging system that incorporates three dimensional (3D) photoacoustics with pulse echo ultrasound for imaging the tumor microenvironment and tracking tissue growth in mice. Three mice were implanted with a dorsal skin flap window chamber. PC-3 prostate tumor cells, expressing green fluorescent protein (GFP), were injected into the skin. The ensuing tumor invasion was mapped using photoacoustic and pulse echo imaging, as well as optical and fluorescent imaging for comparison and cross validation. The photoacoustic imaging and spectroscopy system, consisting of a tunable (680-1000nm) pulsed laser and 25 MHz ultrasound transducer, revealed near infrared absorbing regions, primarily blood vessels. Pulse echo images, obtained simultaneously, provided details of the tumor microstructure and growth with 100-?m3 resolution. The tumor size in all three mice increased between three and five fold during 3+ weeks of imaging. Results were consistent with the optical and fluorescent images. Photoacoustic imaging revealed detailed maps of the tumor vasculature, whereas photoacoustic spectroscopy identified regions of oxygenated and deoxygenated blood vessels. The 3D photoacoustic and pulse echo imaging system provided complementary information to track the tumor microenvironment, evaluate new cancer therapies, and develop molecular imaging agents in vivo. Finally, these safe and noninvasive techniques are potentially applicable for human cancer imaging.

Bauer, Daniel R.; Olafsson, Ragnar; Montilla, Leonardo G.; Witte, Russell S.

2010-02-01

426

Piezoelectric trace vapor calibrator  

SciTech Connect

The design and performance of a vapor generator for calibration and testing of trace chemical sensors are described. The device utilizes piezoelectric ink-jet nozzles to dispense and vaporize precisely known amounts of analyte solutions as monodisperse droplets onto a hot ceramic surface, where the generated vapors are mixed with air before exiting the device. Injected droplets are monitored by microscope with strobed illumination, and the reproducibility of droplet volumes is optimized by adjustment of piezoelectric wave form parameters. Complete vaporization of the droplets occurs only across a 10 deg. C window within the transition boiling regime of the solvent, and the minimum and maximum rates of trace analyte that may be injected and evaporated are determined by thermodynamic principles and empirical observations of droplet formation and stability. By varying solution concentrations, droplet injection rates, air flow, and the number of active nozzles, the system is designed to deliver--on demand--continuous vapor concentrations across more than six orders of magnitude (nominally 290 fg/l to 1.05 {mu}g/l). Vapor pulses containing femtogram to microgram quantities of analyte may also be generated. Calibrated ranges of three explosive vapors at ng/l levels were generated by the device and directly measured by ion mobility spectrometry (IMS). These data demonstrate expected linear trends within the limited working range of the IMS detector and also exhibit subtle nonlinear behavior from the IMS measurement process.

Verkouteren, R. Michael; Gillen, Greg; Taylor, David W. [Surface and Microanalysis Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); MicroFab Technologies, Inc., 1104 Summit Avenue, Suite 110, Plano, Texas 75074 (United States)

2006-08-15

427

Piezoelectric trace vapor calibrator  

NASA Astrophysics Data System (ADS)

The design and performance of a vapor generator for calibration and testing of trace chemical sensors are described. The device utilizes piezoelectric ink-jet nozzles to dispense and vaporize precisely known amounts of analyte solutions as monodisperse droplets onto a hot ceramic surface, where the generated vapors are mixed with air before exiting the device. Injected droplets are monitored by microscope with strobed illumination, and the reproducibility of droplet volumes is optimized by adjustment of piezoelectric wave form parameters. Complete vaporization of the droplets occurs only across a 10 °C window within the transition boiling regime of the solvent, and the minimum and maximum rates of trace analyte that may be injected and evaporated are determined by thermodynamic principles and empirical observations of droplet formation and stability. By varying solution concentrations, droplet injection rates, air flow, and the number of active nozzles, the system is designed to deliver-on demand-continuous vapor concentrations across more than six orders of magnitude (nominally 290 fg/l to 1.05 ?g/l). Vapor pulses containing femtogram to microgram quantities of analyte may also be generated. Calibrated ranges of three explosive vapors at ng/l levels were generated by the device and directly measured by ion mobility spectrometry (IMS). These data demonstrate expected linear trends within the limited working range of the IMS detector and also exhibit subtle nonlinear behavior from the IMS measurement process.

Verkouteren, R. Michael; Gillen, Greg; Taylor, David W.

2006-08-01

428

Radial Field Piezoelectric Diaphragms  

NASA Technical Reports Server (NTRS)

A series of active piezoelectric diaphragms were fabricated and patterned with several geometrically defined Inter-Circulating Electrodes "ICE" and Interdigitated Ring Electrodes "ICE". When a voltage potential is applied to the electrodes, the result is a radially distributed electric field that mechanically strains the piezoceramic along the Z-axis (perpendicular to the applied electric field). Unlike other piezoelectric bender actuators, these Radial Field Diaphragms (RFDs) strain concentrically yet afford high displacements (several times that of the equivalent Unimorph) while maintaining a constant circumference. One of the more intriguing aspects is that the radial strain field reverses itself along the radius of the RFD while the tangential strain remains relatively constant. The result is a Z-deflection that has a conical profile. This paper covers the fabrication and characterization of the 5 cm. (2 in.) diaphragms as a function of poling field strength, ceramic thickness, electrode type and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage at low frequencies. The unique features of these RFDs include the ability to be clamped about their perimeter with little or no change in displacement, the environmentally insulated packaging, and a highly repeatable fabrication process that uses commodity materials.

Bryant, R. G.; Effinger, R. T., IV; Copeland, B. M., Jr.

2002-01-01

429

Porous Piezoelectric Ceramic Transducer  

NASA Astrophysics Data System (ADS)

Porous piezoelectric ceramics of Pb(Zr, Ti)O3, (P-PZT), have been newly developed to apply to transducers in an echo sounder. The P-PZT was prepared from a mixture of PZT and poly-methyl-methacrylate (PMMA) powders. The piezoelectric characteristics of the P-PZT such as the dielectric constant (?), voltage output constant (g constant), acoustic impedance (Zc) and Q were evaluated. The P-PZT was employed in an echo sounder of 200 kHz, and its transmitting and receiving properties were measured in water. In these measurements, the P-PZT showed suitable characteristics for the echo sounder, which required high sensitivity, wide frequency bandwidth and high resolution. High sensitivity was realized by the large g constant and low Zc of P-PZT which made the impedance matching with water much easier. In the acoustic response to the burst wave, the rise and fall time were shortened to 1/3 that of the conventional PZT transducer.

Mizumura, Koichi; Kurihara, Yoshiaki; Ohashi, Hiroshi; Kumamoto, Susumu; Okuno, Kiyonori

1991-09-01

430

Narcotics detection using piezoelectric ringing  

NASA Astrophysics Data System (ADS)

Piezo-electric ringing (PER) has been demonstrated to be an effective means of scanning cargo for the presence of hidden narcotics. The PER signal is characteristic of certain types of crystallized material, such as cocaine hydrochloride. However, the PER signal cannot be used to conclusively identify all types of narcotic material, as the signal is not unique. For the purposes of cargo scanning, the PER technique is therefore most effective when used in combination with quadrupole resonance analysis (QRA). PER shares the same methodology as QRA technology, and can therefore be very easily and inexpensively integrated into existing QRA detectors. PER can be used as a pre-scanning technique before the QRA scan is applied and, because the PER scan is of a very short duration, can effectively offset some of the throughput limitations of standard QRA narcotics detectors. Following is a discussion of a PER detector developed by Quantum Manetics under contract to United States Customs. Design philosophy and performance are discussed, supported by results from recent tests conducted by the U.S. Drug Enforcement Agency and U.S. Customs.

Rayner, Timothy J.; Magnuson, Erik E.; West, Rebecca; Lyndquist, R.

1997-02-01

431

Design Requirements for Amorphous Piezoelectric Polymers  

NASA Technical Reports Server (NTRS)

An overview of the piezoelectric activity in amorphous piezoelectric polymers is presented. The criteria required to render a polymer piezoelectric are discussed. Although piezoelectricity is a coupling between mechanical and electrical properties, most research has concentrated on the electrical properties of potentially piezoelectric polymers. In this work, we present comparative mechanical data as a function of temperature and offer a summary of polarization and electromechanical properties for each of the polymers considered.

Ounaies, Z.; Young, J. A.; Harrison, J. S.

1999-01-01

432

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

433

Photoacoustic spectra of BaFBr:Eu 2+ phosphors  

NASA Astrophysics Data System (ADS)

The photoacoustic (PA) technique was used to study the properties of storage phosphors. The excited state energy levels of Eu 2+ in BaFBr crystal were studied and the structure of the excited energy levels was revealed in the PA spectra. With the phase shift of PA signal of this material, the de-excitation processes of Eu 2+ were also studied. By this, the relative emission efficiencies of different excited states were found in the order: 6P > 6I > 6D. The photostimulated luminescence (PSL) de-excitation process exist some fast non-radiation processes, which conform to the model of Von Seggern. The PA spectra of BaFBr:Eu phosphors synthesized in different conditions were studied and the best quality condition was sintered in 5% H 2-N 2 atmosphere.

Zhang, Yugen

1997-07-01

434

Diesel engines gas emissions monitored by photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

In Brazil, there has been an increasing demand for power generators, driven by diesel oil and other fossil fuels, because of the lack of rain and consequent decreased availability of hydroelectric energy, leading to the rationing of energy. It is known that the combustion of diesel oil in power generators is the main source of many contaminant gases such as nitrogen oxides, SO2, CO, and hydrocarbons. In this work, we carried out a thorough analysis, using the photoacoustic technique of gas samples collected in a closed room where a power generator was turned on for 60 min to saturate the ambient. Some substances such as SO2 and NO2 were detected in the parts per million range.

Schramm, D. U.; Sthel, M. S.; da Silva, M. G.; Carneiro, L. O.; Souza, A. P.; Vargas, H.

2003-01-01

435

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

436

Image reconstruction in photoacoustic tomography involving layered acoustic media  

PubMed Central

Photoacoustic tomography (PAT), also known as thermoacoustic or optoacoustic tomography, is a rapidly emerging biomedical imaging technique that combines optical image contrast with ultrasound detection principles. Most existing reconstruction algorithms for PAT assume the object of interest possesses homogeneous acoustic properties. The images produced by such algorithms can contain significant distortions and artifacts when the object’s acoustic properties are spatially variant. In this work, we establish an image reconstruction formula for PAT applications in which a planar detection surface is employed and the to-be-imaged optical absorber is embedded in a known planar layered acoustic medium. The reconstruction formula is exact in a mathematical sense and accounts for multiple acoustic reflections between the layers of the medium. Computer-simulation studies are conducted to demonstrate and investigate the proposed method.

Schoonover, Robert W.; Anastasio, Mark A.

2012-01-01

437

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.

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

2013-01-01

438

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

439

Dielectric Properties of Piezoelectric Polyimides  

NASA Technical Reports Server (NTRS)

Molecular modeling and dielectric measurements are being used to identify mechanisms governing piezoelectric behavior in polyimides such as dipole orientation during poling, as well as degree of piezoelectricity achievable. Molecular modeling on polyimides containing pendant, polar nitrile (CN) groups has been completed to determine their remanent polarization. Experimental investigation of their dielectric properties evaluated as a function of temperature and frequency has substantiated numerical predictions. With this information in hand, we are then able to suggest changes in the molecular structures, which will then improve upon the piezoelectric response.

Ounaies, Z.; Young, J. A.; Simpson, J. O.; Farmer, B. L.

1997-01-01

440

Fatigue crack monitoring with coupled piezoelectric film acoustic emission sensors  

NASA Astrophysics Data System (ADS)

Fatigue-induced cracking is a commonly seen problem in civil infrastructures reaching their original design life. A number of high-profile accidents have been reported in the past that involved fatigue damage in structures. Such incidences often happen without prior warnings due to lack of proper crack monitoring technique. In order to detect and monitor the fatigue crack, acoustic emission (AE) technique, has been receiving growing interests recently. AE can provide continuous and real-time monitoring data on damage progression in structures. Piezoelectric film AE sensor measures stress-wave induced strain in ultrasonic frequency range and its feasibility for AE signal monitoring has been demonstrated recently. However, extensive work in AE monitoring system development based on piezoelectric film AE sensor and sensor characterization on full-scale structures with fatigue cracks, have not been done. A lack of theoretical formulations for understanding the AE signals also hinders the use of piezoelectric film AE sensors. Additionally, crack detection and source localization with AE signals is a very important area yet to be explored for this new type of AE sensor. This dissertation presents the results of both analytical and experimental study on the signal characteristics of surface stress-wave induced AE strain signals measured by piezoelectric film AE sensors in near-field and an AE source localization method based on sensor couple theory. Based on moment tensor theory, generalized expression for AE strain signal is formulated. A special case involving the response of piezoelectric film AE sensor to surface load is also studied, which could potentially be used for sensor calibration of this type of sensor. A new concept of sensor couple theory based AE source localization technique is proposed and validated with both simulated and experimental data from fatigue test and field monitoring. Two series of fatigue tests were conducted to perform fatigue crack monitoring on large-scale steel test specimens using piezoelectric film AE sensors. Continuous monitoring of fatigue crack growth in steel structures is demonstrated in these fatigue test specimens. The use of piezoelectric film AE sensor for field monitoring of existing fatigue crack is also demonstrated in a real steel I-girder bridge located in Maryland. The sensor couple theory based AE source localization is validated using a limited number of piezoelectric film AE sensor data from both fatigue test specimens and field monitoring bridge. Through both laboratory fatigue test and field monitoring of steel structures with active fatigue cracks, the signal characteristics of piezoelectric film AE sensor have been studied in real-world environment.

Zhou, Changjiang

441

Investigation of standoff explosives detection via photothermal/photoacoustic interferometry  

NASA Astrophysics Data System (ADS)

Progress in standoff detection of surface-bound explosives residue using photothermal and photoacoustic (PT/PA) imaging and spectroscopy has been reported recently. Photothermal/photoacoustic interferometry (PTI), a variation of the aforementioned techniques, is a candidate for standoff detection as a result of its non-contact and non-destructive approach. In PTI, the transient PT/PA hydrodynamic response produced by impulsive infra-red laser excitation(s) are detected by an overlapping focused probe laser beam. The return back-scattered/reflected probe laser beam is collected and coupled into a single-mode optical fiber. The PT/PA-induced perturbation on the return probe laser, in the form of phase or amplitude modulation or both, is extracted interferometrically. The resulting quadrature signals are digitized and processed to recover the minute PT/PA dynamics above background noise. Characteristic spectra for materials can be obtained by quantifying the PT response as a function of excitation(s) wavelength. The CW probe laser, operating in the 1550 nm range, and the constituents of the coherent detection system are commercial off-the-shelf components. A commercially available and continuously tunable quantum cascade laser (QCL) with output pulse energies up to 50 nJ was employed to generate the PT/PA spectra in the 8.8-10.2 ?m range. PTI detected absorption spectra were collected for HMX, RDX, and PETN, with the pro