Sample records for photoacoustic piezoelectric technique

  1. Piezoelectric detection of photoacoustic signals

    Microsoft Academic Search

    M. M. Farrow; R. K. Burnham; M. Auzanneau; S. L. Olsen; N. Purdie

    1977-01-01

    Piezoelectric detection of photoacoustic signals offers a number of advantages over the better known microphonic technique for condensed phase samples. Experimental techniques are greatly simplified by taking advantage of the acoustic impedence match offered by solid state detectors with solid or liquid samples. Such piezoelectric detectors prove suitable for a.c. steady state measurements as well as impulse-transient response detectors. Several

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  3. A piezoelectric cell for simultaneous photoacoustic and fluorescence measurements

    SciTech Connect

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

    1994-12-31

    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.

  4. Piezoelectric annular array for large depth of field photoacoustic imaging

    PubMed Central

    Passler, K.; Nuster, R.; Gratt, S.; Burgholzer, P.; Paltauf, G.

    2011-01-01

    A piezoelectric detection system consisting of an annular array is investigated for large depth of field photoacoustic imaging. In comparison to a single ring detection system, X-shaped imaging artifacts are suppressed. Sensitivity and image resolution studies are performed in simulations and in experiments and compared to a simulated spherical detector. In experiment an eight ring detection systems offers an extended depth of field over a range of 16 mm with almost constant lateral resolution. PMID:21991555

  5. Photoacoustic Signal Formation in Heterogeneous Multilayer Systems with Piezoelectric Detection

    NASA Astrophysics Data System (ADS)

    Isaiev, Mykola; Andrusenko, Dmytro; Tytarenko, Alona; Kuzmich, Andrey; Lysenko, Vladimir; Burbelo, Roman

    2014-12-01

    A new efficient model describing photoacoustic (PA) signal formation with piezoelectric detection is reported. Multilayer sandwich-like systems: heterogeneous studied structure—buffer layer—piezoelectric transducers are considered. In these systems, the buffer layer is used for spatial redistribution of thermoelastic force moments generated in the investigated structure. Thus, mechanical properties of this layer play a crucial role to ensure perfect control of the detected voltage formed on a piezoelectric transducer by contribution of different regions of the studied structure. In particular, formation of the voltage signal strongly depends on the point at which the thermoelastic source is applied. Therefore, use of relatively simple linear Green's functions introduced in frames of the Kirchhoff-Love theory is chosen as an efficient approach for the PA signal description. Moreover, excellent agreement between the theoretical model and measured results obtained on a heterogeneous "porous silicon-bulk Si substrate" structure is stated. Furthermore, resolving of the inverse problem with fitting of the experimental curves by the developed model allows reliable evaluation of the thermal conductivity of the nanostructured porous silicon layer.

  6. Recent Progress on Infrared Photoacoustic Spectroscopy Techniques

    Microsoft Academic Search

    Jingsong Li; Weidong Chen; Benli Yu

    2011-01-01

    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

  7. Effects of repetitive irradiation in laser ablation of aluminum in gases observed by photoacoustic and imaging techniques

    Microsoft Academic Search

    Yoshiro Ito; Isamu Oguro; Susumu Nakamura

    2000-01-01

    Effects of irradiating number of pulses of Nd:YAG laser in laser ablation of metals in air have been studied by both photoacoustic and fast-imaging techniques. Photacoustic detection technique using piezoelectric polymer film revealed the change of coupling among laser radiation, ablated matter, plasma and the target as a function of the laser fluence. Nanosecond imaging technique, where the second harmonic

  8. Piezoelectric photoacoustic spectra of Cu-In-Se crystals grown by the traveling heater method

    NASA Astrophysics Data System (ADS)

    Yoshino, K.; Kawahara, M.; Fukuyama, A.; Yokoyama, H.; Maeda, K.; Miyake, H.; Sugiyama, K.; Ikari, T.

    1999-03-01

    The piezoelectric photoacoustic spectra of bulk CIS, CuIn3Se5 and Cu2In4Se7 crystals grown by a traveling heater method were successively observed at 20, 80 and 300 K. The bandgap energy of bulk Cu2In4Se7 crystal are larger than that of CuIn3Se5 crystal. Two activation energies of 120 and 260 meV for CuIn3Se5 crystals and the four energies of 110, 230, 340 and 470 meV for Cu2In4Se7 crystals are obtained as nonradiative recombination centers for the first time.

  9. A photoacoustic technique to measure the properties of single cells

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  10. The piezoelectric sorption technique: a practical method

    E-print Network

    Flipse, Eugene Charles

    1983-01-01

    THE PIEZOELECTRIC SORPTION TECHNIQUE, A PRACTICAL METHOD A Thesis by EUGENE CHARLES FLIPSE Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 1983...) D. Holland (Head of Department) August 1983 ABSTRACT The Piezoelectric Sorption Technique, A Practical Method. (August 1983) Eugene Charles Flipse, B. A. , Virginia Polytechnic Institute and State University Chairman of Advisory Committee: Dr...

  11. Surface investigations of ZnBeMnSe mixed crystals by means of the piezoelectric spectroscopy and the AFM technique

    NASA Astrophysics Data System (ADS)

    Strza?kowski, K.; Kulesza, S.; Zakrzewski, J.; Mali?ski, M.

    2014-01-01

    Piezoelectric photoacoustic spectroscopy with a piezoelectric detection has been used for measurements of the amplitude and phase spectra of Zn1-x-yBexMnySe mixed semiconductors. The investigated crystals were grown from the melt by the modified high pressure Bridgman method under the argon overpressure. The preliminary study of the sample's surface of the investigated crystals was carried out using the AFM technique. The influence of a different surface treatment on the amplitude and phase piezoelectric spectra as well as on AFM images is presented and analyzed. The correlations between these two techniques have been found and are discussed. Piezoelectric (PZE) spectra were analyzed using an extended and modified Jackson-Amer theory.

  12. Piezoelectric Surgery -A Novel Technique for Laminectomy.

    PubMed

    Duerr, Felix M; Seim, Howard B; Bascuñán, Ana L; Palmer, Ross H; Easley, Jeremiah

    2014-12-01

    ABSTRACT Objective: Piezoelectric surgery is a novel technology that allows for the osteotomy of mineralized tissue with less risk of damaging underlying soft tissue structures. This selective cutting increases the safety of osteotomies performed in close vicinity to delicate structures such as dura mater, blood vessels, and neural tissue. This study aimed to develop and describe the technique of piezoelectric surgery for dorsal laminectomy and to assess its clinical safety in normal sheep. Methods: A piezoelectric, dorsal laminectomy technique was developed using ovine cadavers. Following technique development, six live sheep underwent a piezoelectric (n = 6) two-level dorsal laminectomy at L2-L3 and L4-L5 (PiezoL2-3,4-5), and another 30 live sheep underwent a three-level laminectomy at L1, L3, and L5 (PiezoL1,3,5) for a total of 102 laminectomy sites. Surgery time and postoperative complications were recorded. Results: Dorsal laminectomy was safely and accurately performed in 35/36 study sheep using a Piezoelectric surgical instrument. No dural tears were noted in any animal. Non-ambulatory paraparesis in one study sheep (PiezoL1,3,5) led to euthanasia at 48 hr and only mild epidural hematoma was noted on necropsy. No other major postoperative complications were observed in any of the animals. Subjectively, PiezoL was easy to perform and with a rapid learning curve. Mean surgery time was 105 min (range: 75-165 min; median: 97.5) for PiezoL2-3,4-5 and 93 minutes (range 55-100 min; median: 67.5) for PiezoL1,3,5. Conclusions: Based on our study, PiezoL is considered a safe and viable technique for performing ovine dorsal laminectomy in the preclinical research setting. PMID:25438097

  13. Force control in piezoelectric microactuators using self scheduled H technique

    E-print Network

    Boyer, Edmond

    Force control in piezoelectric microactuators using self scheduled H technique Micky Rakotondrabe-scheduled controller, H, force, piezoactuators, micromanipulation and microasembly 1. INTRODUCTION Piezoelectric to control the manipulation force. In fact, the force control allows keeping the manipulated object inside

  14. Percutaneous permeation measurement of topical phthalocyanine by photoacoustic technique

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    PubMed

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

    2014-01-13

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

  17. Noninvasive detection of glucose level based on tunable pulsed laser induced photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Liu, Guodong; Huang, Zhen

    2014-12-01

    This paper presents the preliminary investigation of glucose measurement based on tunable pulsed laser induced photoacoustic technique. A photoacoustic glucose detection set-up with forward mode was established. Meanwhile, a 532nm pumped Nd:YAG optical parametric oscillator(OPO) pulsed laser was employed as the photoacoustic signal excitation light source and a confocal PZT transducer was used as photoacoustic signal detector. In experiments, glucose aqueous solutions with several different concentrations were loaded in quartz cuvette in turn and irradiated by focused laser beam, the time-resolved photoacoustic signals were gotten with average of 512 times, the photoacoustic peak-to-peak(PP) value of all concentrations were gotten from 1300nm to 2300nm with interval of 10nm, the characteristic wavelengths of glucose were found via the difference and one order derivative spectral technique. Two optimum characteristic wavelengths were preliminarily chosen via the least square fitting algorithm, their predicted concentration errors were all less than 0.62mmol/dl.

  18. Photoacoustic radio-frequency spectroscopy (PA-RFS): A technique for monitoring absorber size and concentration

    NASA Astrophysics Data System (ADS)

    Hysi, Eno; Dopsa, Dustin; Kolios, Michael C.

    2013-03-01

    A photoacoustic technique for monitoring absorber size and concentration is presented. The technique relies on analyzing the power spectra of the radio-frequency signals and taking into account the receiving transducer response in order to remove system dependencies. By normalizing the power spectra, parameters derived from ultrasound tissue characterization (spectral slope and midband fit) can be obtained. Tissue mimicking phantoms were constructed using black polystyrene beads of various sizes and concentrations as absorbers. The spectral slope decreased by 0.63 dB/MHz when the size of the particle increased from 1 ?m to 10 ?m at every bead concentration. The midband fit was ~4 dB higher for the 10 ?m particle and increased linearly with concentration. These results suggest that photoacoustic radiofrequency spectroscopy (PA-RFS) can potentially monitor changes in absorber size and concentration thus improving the ability of photoacoustic imaging to distinguish structural tissue variations.

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

    NASA Astrophysics Data System (ADS)

    Wadamori, Naoki

    2014-09-01

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

  20. Piezoelectric energy harvesting using a series synchronized switch technique

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  1. Resonance frequencies and Young's modulus determination of magnetorheological elastomers using the photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Daniel Macias, J.; Ordonez-Miranda, J.; Alvarado-Gil, J. J.

    2012-12-01

    A simple and reliable methodology for determining the Young's modulus of magnetorheological elastomers is proposed based on the resonance frequencies of the amplitude of the photoacoustic signal. An explicit expression for the pressure changes within a photoacoustic cell, due to the thermal expansion of the air and the elastic bending of a clamped circular elastic membrane, is derived and analyzed. It is found that the resonance behavior of the amplitude of the photoacoustic signal is due to the contribution of the axial bending of its thickness. It is also shown that the Young's modulus of the membrane is proportional to its density, the square of its resonance frequencies and the fourth power of its radius, and inversely proportional to the square of its thickness. The application of the proposed approach to membranes made up of spherical microparticles of carbonyl iron powder embedded in a matrix of silicone rubber with weight concentrations of 0%, 5.2%, and 13.7% yields accurate and reproducible results, which are in good agreement with reported data in the literature. The highest accuracy on the measurement of the resonance frequencies and therefore on the Young's modulus is found for the first resonance peak. When a magnetic field is applied to the samples to modify their stiffness, it is observed that the Young's modulus increases with the magnetic field. This novel application of the photoacoustic technique opens the possibility of performing mechanical characterization of a broad diversity of magnetorheological membranes.

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

    NASA Astrophysics Data System (ADS)

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

    2005-06-01

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

  3. Phase transition of TiO2 thin films detected by the pulsed laser photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Pérez-Pacheco, A.; Castañeda-Guzmán, R.; Oliva Montes de Oca, C.; Esparza-García, A.; Pérez Ruiz, S. J.

    2011-03-01

    In this work, we present characterization of titanium oxide thin films by photoacoustic measurements to determine the ablation threshold and phase transitions from amorphous to crystalline states. The important advantages of this method are that it does not require amplification at the detection stage and that it is a non-destructive technique. The correlation analysis of the photoacoustic signals allows us to visualize the ablation threshold and the phase transitions with enhanced sensitivity. This correlation analysis clearly exhibits the changes in the thin-film morphology due to controlled variations of the fluence (energy/area) and the temperature of the surrounding medium. This is particularly important for those cases where the crystalline changes caused by temperature variations need to be monitored. The thin-film samples were prepared by the sputtering technique at room temperature in the amorphous state. The phase transformations were induced by controlled temperature scanning and then corroborated with Raman spectroscopy measurements.

  4. Applying laser pulse stretching technique on photoacoustic imaging for efficiently delivering laser energy

    NASA Astrophysics Data System (ADS)

    Wang, Tianheng; Kumavor, Patrick D.; Zhu, Quing

    2012-02-01

    High-energy and short-duration outputs from lasers are desirable to improve the photoacoustic image quality when imaging deeply-seated lesions. In many clinical applications, optical fibers are used to couple the high-energy laser pulse to tissue. These high peak intensity pulses can damage an optical fiber input face if the damage threshold is exceeded. It is necessary to reduce the peak intensity to minimize the fiber damage and to delivery sufficient light for imaging. In this paper, a laser-pulse-stretching technique is introduced to reduce the peak intensity of laser pulses. To demonstrate the technique, an initial 17ns pulse was stretched to 37ns by a ring-cavity laser-pulse-stretching system, and the laser peak power reduced to 42%. The stretched pulse increased the fiber damage threshold by 1.5-fold. Three ultrasound transducers centered at 1.3MHz, 3.5MHz, 6MHz frequencies were simulated and the results showed that the photoacoustic signal of 0.5mm-diameter target obtained with 37ns pulse was about 98%, 91% and 80% respectively using the same energy as with the 17ns pulse. Simulations were validated using a broadband hydrophone. Quantitative comparisons of photoacoustic images obtained with three corresponding ultrasound transducers showed that the image quality was not affected by stretching the pulse.

  5. Diffusion of Methylene Blue in Phantoms of Agar Using a Photoacoustic Technique

    NASA Astrophysics Data System (ADS)

    Vilca-Quispe, L.; Alvarado-Gil, J. J.; Quintana, P.; Ordonez-Miranda, J.

    2010-05-01

    In this work, the kinetics of diffusion of methylene blue in agar aqueous solution is studied using a photoacoustic technique. Two agar phantoms solutions in water with a relation of mass/volume of 0.01% and 0.05% were analyzed. The study was performed using a modified Rosencwaig photoacoustic cell that is enclosed by transparent windows, on both sides. The sample is deposited directly on top of the upper window. A red light beam, at a fixed modulation frequency, is sent through the lower window illuminating the sample and inducing the photoacoustic effect inside the closed chamber of the cell. At the beginning of the experiment, a droplet of 100?L of agar solution is deposited; afterwards, the signal stabilizes, and 10?L of methylene blue aqueous solution (0.0125 g · mL-1) is added to the surface of the agar. During the first seconds of the experiment, the photoacoustic signal amplitude increases followed by a gradual and long decay. Results for modulation frequencies in the range from 10Hz to 80Hz for both agar concentrations are presented. A simple theoretical approach is presented to analyze the experimental data. It is demonstrated that the kinetics of the process can be parameterized as a function of the changes of an effective optical absorption coefficient. From these results, the characteristic time, in which the dye diffusion process stabilizes, is obtained. It is found that this time is larger for samples with a higher agar concentration. These differences provide important results for biomedical sciences in which agar gels are used as phantoms resembling some of the properties of living organs and tissues.

  6. Improved piezoelectric switch shunt damping technique using negative capacitance

    NASA Astrophysics Data System (ADS)

    Han, Xu; Neubauer, Marcus; Wallaschek, Jörg

    2013-01-01

    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.

  7. Identification of Plant Growth-Promoting Bacteria Using Titanium Dioxide Photocatalysis-Assisted Photoacoustic Technique

    NASA Astrophysics Data System (ADS)

    Gordillo-Delgado, F.; Marín, E.; Calderón, A.

    2013-09-01

    The effect of titanium dioxide photocatalysis against bacteria that are dangerous for human health has been investigated in the past, suggesting the possibility of using a specific behavior for each microorganism during this process for its discrimination. In this study, the behavior of some plants’ growth promoting bacteria ( Burkholderia unamae (Strain MTI 641), Acetobacter diazotrophicus (Strain PAl 5T), A. diazotrophicus (Strain CFN-Cf 52), and B. unamae (Strain TATl-371)) interacting with light and bactericidal titanium dioxide films have been analyzed using the photoacoustic technique. The monitoring of these interactions shows particular characteristics that could serve for identifying these species.

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

    NASA Astrophysics Data System (ADS)

    Mateu, Loreto; Zessin, Henrik; Spies, Peter

    2013-12-01

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

  9. Early detection of dental caries using photoacoustics

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

    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 relatively easily and accurately detected at ultrasound resolution. In this paper, a pulsed laser (Nd:YAG, Quanta-Ray) was used to probe extracted human molars at different disease stages determined from periapical radiographs. Both fundamental (1064nm) and first harmonic (532nm) pulses (15ns pulse length, 100mJ at fundamental and 9mJ at first harmonic , 10Hz pulse repetition rate) were used to illuminate the occlusal surface of tooth samples placed in a water tank. The photoacoustic signal was recorded with an unfocused wideband single-element piezoelectric transducer (centered at 12 MHz, bandwidth 15 MHz) positioned at small angle (less than 30 degrees) to the laser beam close to the occlusal surface. At the fundamental wavelength, total photoacoustic energy increases from normal to incipient stage disease by as much as a factor of 10. Differences between photoacoustic energy at the fundamental and first harmonic wavelength further indicate spectral absorption changes of the underlying structure with disease progression. Using a focused laser beam, an extracted molar with suspected incipient caries was scanned along the occulusal surface to help localize the caries inside enamel and dentin. The significantly increasing photoacoustic signal at a specific scan line both at fundamental and first harmonic indicates the local development of the incipient caries. The photoacoustic results compare well with visual inspection after layer by layer dissection. Preliminary results demonstrate the feasibility of detecting incipient occlusal and proximal caries. This technique may ultimately allow for continuous monitoring of caries before and during treatment.

  10. Benefits of the Mycorrhizal Fungi in Tomato Leaves Measured by Open Photoacoustic Cell Technique: Interpretation of the Diffusion Parameters

    NASA Astrophysics Data System (ADS)

    Sánchez-Rocha, S.; Vargas-Luna, M.; Gutiérrez-Juárez, G.; Huerta-Franco, R.; Olalde-Portugal, V.

    2008-12-01

    The open photoacoustic cell technique was used to measure tomato leaves from plants with and without mycorrhizal fungi ( Glomus fasciculatum). Based on measurement of the photobaric contribution of the photoacoustic signal, the exponential parameter of the diffusion behavior for this contribution was calculated. From this value, the oxygen diffusion coefficient was derived. The changes in the oxygen- diffusion-coefficient-dependent exponential parameter are statistically significant ( p < 0.05) and are consistent with the expected benefits of mycorrhizal symbiosis. Potentially similar results obtained from the photothermal contribution are discussed.

  11. Study on Photoacoustic Measurement Technique of Thermophysical Properties of Thick Solid Material and Human Skin

    NASA Astrophysics Data System (ADS)

    Yoshida, Atsumasa; Imuta, Azusa; Yamada, Tetsuya; Kagata, Kakeru

    2014-12-01

    The thermal effusivity and thermal diffusivity of thick solid materials were measured to validate a developed technique using a photoacoustic method. First, the thermal effusivity was determined by making close contact between an optically opaque sheet and the material. A titanium plate was used as the sheet with known thermophysical properties. Second, using the thermal effusivity as a known value, the thermal diffusivity was also determined by making close contact between an optically semitransparent sheet and the material. A rigid polyvinyl chloride plate was used as the thin sheet with known thermophysical and radiative properties, and a natural rubber block and an epoxy resin block were adopted as samples. The results indicated that the present technique was sufficiently accurate. The thermal effusivity and then the thermal diffusivity of human skin in vivo were measured noninvasively in the same way instead of the solid materials. The results also indicated that the present technique was sufficiently accurate for human skin.

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

    E-print Network

    Paris-Sud XI, Université de

    EARLY-AGE CONCRETE STRENGTH ESTIMATION TECHNIQUE USING EMBEDDED PIEZOELECTRIC SELF strength concrete (HSC) has been increased. However, HSC might be susceptible to brittle fracture) measurements using an embedded piezoelectric sensor is proposed. The EMI of NPP concrete specimen was tracked

  13. Evaluation of Her2 status using photoacoustic spectroscopic CT techniques

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

    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.

  14. Techniques and Considerations for Driving Piezoelectric Actuators at High-speed

    E-print Network

    Fleming, Andrew J.

    Techniques and Considerations for Driving Piezoelectric Actuators at High-speed Andrew J. Fleming inductance respectively. E-mail: andrew.fleming@newcastle.edu.au Modeling, Signal Processing, and Control

  15. Analysis of Maize Seed Germs by Photoacoustic Microscopy and Photopyroelectric Technique

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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.

  16. Investigation of Thermal Transport Properties of Porous Silicon by Photoacoustic Technique

    NASA Astrophysics Data System (ADS)

    Lishchuk, Pavlo; Andrusenko, Dmytro; Isaiev, Mykola; Lysenko, Vladimir; Burbelo, Roman

    2015-02-01

    In this paper the results of an experimental study of heat transport peculiarities in a composite system "porous matrix - liquid" are presented where porous silicon with different values of porosity was used as the matrix. For evaluation of the thermal conductivity, a photoacoustic technique in a classical configuration with a gas-microphone registration was used. As a result of the experimental research, the increase of the thermal conductivity (up to two times) of the composite system "porous silicon - viscous liquid" in comparison with porous silicon has been determined. It was shown that such an increase is caused mainly by improved thermal contact between nanocrystallites of the PSi matrix as the result of the filling of second-order pores.

  17. Techniques and considerations for driving piezoelectric actuators at high speed

    Microsoft Academic Search

    Andrew J. Fleming

    2008-01-01

    Due to their high stiffness, small dimensions and low mass, piezoelectric stack actuators are capable of developing large displacements with bandwidths of greater than 100 kHz. However, due to their large electrical capacitance, the associated driving amplifier is usually limited in bandwidth to a few kHz. In this paper the limiting characteristics of piezoelectric drives are identified as the signal-bandwidth,

  18. Photoacoustic Microscopy

    PubMed Central

    Yao, Junjie; Wang, Lihong V.

    2012-01-01

    Photoacoustic microscopy (PAM) is a hybrid in vivo imaging technique that acoustically detects optical contrast via the photoacoustic effect. Unlike pure optical microscopic techniques, PAM takes advantage of the weak acoustic scattering in tissue and thus breaks through the optical diffusion limit (~1 mm in soft tissue). With its excellent scalability, PAM can provide high-resolution images at desired maximum imaging depths up to a few millimeters. Compared with backscattering-based confocal microscopy and optical coherence tomography, PAM provides absorption contrast instead of scattering contrast. Furthermore, PAM can image more molecules, endogenous or exogenous, at their absorbing wavelengths than fluorescence-based methods, such as wide-field, confocal, and multi-photon microscopy. Most importantly, PAM can simultaneously image anatomical, functional, molecular, flow dynamic and metabolic contrasts in vivo. Focusing on state-of-the-art developments in PAM, this Review discusses the key features of PAM implementations and their applications in biomedical studies. PMID:24416085

  19. Photoacoustic Microscopy.

    PubMed

    Yao, Junjie; Wang, Lihong V

    2013-09-01

    Photoacoustic microscopy (PAM) is a hybrid in vivo imaging technique that acoustically detects optical contrast via the photoacoustic effect. Unlike pure optical microscopic techniques, PAM takes advantage of the weak acoustic scattering in tissue and thus breaks through the optical diffusion limit (~1 mm in soft tissue). With its excellent scalability, PAM can provide high-resolution images at desired maximum imaging depths up to a few millimeters. Compared with backscattering-based confocal microscopy and optical coherence tomography, PAM provides absorption contrast instead of scattering contrast. Furthermore, PAM can image more molecules, endogenous or exogenous, at their absorbing wavelengths than fluorescence-based methods, such as wide-field, confocal, and multi-photon microscopy. Most importantly, PAM can simultaneously image anatomical, functional, molecular, flow dynamic and metabolic contrasts in vivo. Focusing on state-of-the-art developments in PAM, this Review discusses the key features of PAM implementations and their applications in biomedical studies. PMID:24416085

  20. Analysis of Piezoelectric Structural Sensors with Emergent Computing Techniques

    NASA Technical Reports Server (NTRS)

    Ramers, Douglas L.

    2005-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

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

    Microsoft Academic Search

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

    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

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

    PubMed Central

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

    2013-01-01

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

  4. Consideration of impedance matching techniques for efficient piezoelectric energy harvesting.

    PubMed

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

    2007-09-01

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

  5. Multi-contrast Photoacoustic Microscopy

    NASA Astrophysics Data System (ADS)

    Yao, Junjie

    Photoacoustic microscopy is a hybrid imaging modality with high spatial resolution, moderate imaging depth, excellent imaging contrast and functional imaging capability. Taking full advantage of this powerful weapon, we have investigated different anatomical, functional, flow dynamic and metabolic parameter measurements using photoacoustic microscopy. Specifically, Evans-blue dye was used to enhance photoacoustic microscopy of capillaries; label-free transverse and axial blood flow was measured based on bandwidth broadening and time shift of the photoacoustic signals; metabolic rate of oxygen was quantified in vivo from all the five parameters measured by photoacoustic microcopy; whole cross-sectional imaging of small intestine was achieved on a double-illumination photoacoustic microscopy with extended depth of focus and imaging depth; hemodynamic imaging was performed on a MEMS-mirror enhanced photoacoustic microscopy with a cross-sectional imaging rate of 400 Hz. As a maturing imaging technique, PAM is expected to find new applications in both fundamental life science and clinical practice.

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

    NASA Astrophysics Data System (ADS)

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

    2002-05-01

    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 offset was applied on the piezoelectric actuator to drive the crack growth in the thin metallic layer while the sample was imaged in TEM. The technique was demonstrated on solder thin films where cavitation was found to be the dominant fatigue damage mechanism.

  7. Diagnostic of human teeth using photoacoustic response

    NASA Astrophysics Data System (ADS)

    El-Sharkawy, Yasser H.; Badr, Y.; Gadallah, M.; El-Sherif, Ashraf F.

    2006-02-01

    Laser-induced photoacoustic spectroscopy (LIPS) can be used to measure trace-element concentration in materials, down to parts-per-million. In this paper we investigate the use of laser-induced photoacoustic response in carious teeth detection. First, we found the Q-switched Nd:YAG laser of a wavelength of 1064 nm to produce detectable response in teeth. Then, we implemented two detection techniques using a piezoelectric transducer and Michelson Interferometer. The accurately detected response of a tooth sample by the piezoelectric transducer was analyzed using spectral analysis. However, in dentistry we do not necessarily mead an exact quantitative measurement; thus we designed a more physically realizable system that measures the acoustically-induced surface displacement using Michelson Interferometer. Monitoring this surface displacement we were able to determine the physical and optical properties of the tooth sample which could be used as a basis in diagnostics. The responses obtained by both detectors were equally confined to the categorization of a carious tooth from a normal one.

  8. Adsorption and desorption kinetics in ZrO2 TiO2 by photoacoustic techniques

    NASA Astrophysics Data System (ADS)

    Pinto Neto, A.; Moura, D.; Kuranaga, C.; Silva, M. D.; Miranda, L. C. M.

    2005-06-01

    In this paper we report on the photoacoustic (PA) characterization of ZrO2-TiO2 ceramic wafers as a sensing element for solvent adulteration evaluation. The experiments consisted of photoacoustic time dependent monitoring of the sorption and desorption of a droplet of a solvent deposited on the outer face of a ceramic wafer. The used solvents were isopropanol and chloroform. For the polar isopropanol molecule the results shown diffusion into the sample, with a characteristic diffusion time ?_1, accompanied by the evaporation at a rate with a time constant ?_2. Indeed, for the non polar chloroform, wetting-drying kinetics is adequately described by a simple diffusion-evaporation.

  9. Carbon nanotubes as photoacoustic molecular imaging agents in living mice

    Microsoft Academic Search

    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

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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.

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

    PubMed Central

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

    2011-01-01

    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. PMID:21520862

  12. Identification of possible factors influencing temperatures elevation during implant site preparation with piezoelectric technique

    PubMed Central

    Lamazza, Luca; Laurito, Domenica; Lollobrigida, Marco; Brugnoletti, Orlando; Garreffa, Girolamo; De Biase, Alberto

    2014-01-01

    Summary Background Overheating during implant site preparation negatively affects the osseointegration process as well the final outcome of implant rehabilitations. Piezoelectric techniques seem to provide to a gentle implant preparation although few scientific reports have investigated the heat generation and its underlying factors. Purpose To investigate, through a proper methodological approach, the main factors influencing temperature rise during piezoelectric implant site preparation. Materials and methods Different piezoelectric tips (IM1s, IM2, P2-3, IM3, Mectron Medical Technology, Carasco, Italy) have been tested. The experimental set-up consisted in a mechanical positioning device equipped with a load cell and a fluoroptic thermometer. Results The first tip of the sequence (IM1s) generated the highest temperature increasing (?T). The diamond tips (IM1s and P2-3) determined higher ?T values than the smooth tips (IM2 and IM3). Further tests with IM1s suggested that the temperature elevation during the first thirty seconds may be predictive of the maximal temperature as well as of the overall thermal impact. Conclusions Working load, working movements management and bone features resulted to be the main factors influencing temperature rise during piezoelectric implant site preparation. Irrigant temperature and clogging effect may also synergically contribute to the heat generation. PMID:25774245

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

    PubMed Central

    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

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

  14. Influence of Te doping in InGaAsSb epilayers on the non-radiative recombination time studied by the photoacoustic technique

    Microsoft Academic Search

    M. L. Gomez-Herrera; I. Reich; P. Rodríguez-Fragoso; A. Cruz-Orea; F. Sanchez-Sinencio; J. L. Herrera-Perez; J. Diaz-Reyes; J. G. Mendoza-Alvarez

    2005-01-01

    In this work we present results on the study of the influence of Te doping of InGaAsSb epitaxial layers, grown by the liquid phase epitaxy technique, on the non-radiative recombination times of the epilayers. In the photoacoustic (PA) technique, we use a recently developed model for two-layer semiconductor heterostructures where, taking into account all the possible contributions to the heat

  15. Grueneisen relaxation photoacoustic microscopy

    PubMed Central

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

    2014-01-01

    The temperature-dependent property of the Grueneisen parameter has been employed in photoacoustic imaging mainly to measure tissue temperature. Here we explore this property using a different approach and develop Grueneisen-relaxation photoacoustic microscopy (GR-PAM), a technique that images non-radiative absorption with confocal optical resolution. GR-PAM sequentially delivers two identical laser pulses with a micro-second-scale time delay. The first laser pulse generates a photoacoustic signal and thermally tags the in-focus absorbers. Owing to the temperature dependence of the Grueneisen parameter, when the second laser pulse excites the tagged absorbers within the thermal relaxation time, a photoacoustic signal stronger than the first one is produced. GR-PAM detects the amplitude difference between the two co-located photoacoustic signals, confocally imaging the non-radiative absorption. We greatly improved axial resolution from 45 µm to 2.3 µm and at the same time slightly improved lateral resolution from 0.63 µm to 0.41 µm. In addition, the optical sectioning capability facilitates the measurement of the absolute absorption coefficient without fluence calibration. PMID:25379919

  16. Spontaneous high piezoelectricity in poly(vinylidene fluoride) nanoribbons produced by iterative thermal size reduction technique.

    PubMed

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

    2014-09-23

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

  17. Micromachining techniques in developing high-frequency piezoelectric composite ultrasonic array transducers.

    PubMed

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

    2013-12-01

    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 mm(2) 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. PMID:24297027

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

    NASA Astrophysics Data System (ADS)

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

    2005-06-01

    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.

  19. 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

    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

    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.

  20. Cavity-enhanced resonant photoacoustic spectroscopy with optical feedback cw diode lasers: A novel technique for ultratrace gas analysis and high-resolution spectroscopy

    Microsoft Academic Search

    Michael Hippler; Christian Mohr; Katherine A. Keen; Edward D. McNaghten

    2010-01-01

    Cavity-enhanced resonant photoacoustic spectroscopy with optical feedback cw diode lasers (OF-CERPAS) is introduced as a novel technique for ultratrace gas analysis and high-resolution spectroscopy. In the scheme, a single-mode cw diode laser (3 mW, 635 nm) is coupled into a high-finesse linear cavity and stabilized to the cavity by optical feedback. Inside the cavity, a build-up of laser power to

  1. Quantitative spectroscopic photoacoustic imaging: a review.

    PubMed

    Cox, Ben; Laufer, Jan G; Arridge, Simon R; Beard, Paul C

    2012-06-01

    Obtaining absolute chromophore concentrations from photoacoustic images obtained at multiple wavelengths is a nontrivial aspect of photoacoustic imaging but is essential for accurate functional and molecular imaging. This topic, known as quantitative photoacoustic imaging, is reviewed here. The inverse problems involved are described, their nature (nonlinear and ill-posed) is discussed, proposed solution techniques and their limitations are explained, and the remaining unsolved challenges are introduced. PMID:22734732

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  3. Optical-resolution photoacoustic endomicroscopy in vivo

    PubMed Central

    Yang, Joon-Mo; Li, Chiye; Chen, Ruimin; Rao, Bin; Yao, Junjie; Yeh, Cheng-Hung; Danielli, Amos; Maslov, Konstantin; Zhou, Qifa; Shung, K. Kirk; Wang, Lihong V.

    2015-01-01

    Optical-resolution photoacoustic microscopy (OR-PAM) has become a major experimental tool of photoacoustic tomography, with unique imaging capabilities for various biological applications. However, conventional imaging systems are all table-top embodiments, which preclude their use in internal organs. In this study, by applying the OR-PAM concept to our recently developed endoscopic technique, called photoacoustic endoscopy (PAE), we created an optical-resolution photoacoustic endomicroscopy (OR-PAEM) system, which enables internal organ imaging with a much finer resolution than conventional acoustic-resolution PAE systems. OR-PAEM has potential preclinical and clinical applications using either endogenous or exogenous contrast agents. PMID:25798315

  4. Photoacoustic determination of glucose concentration in whole blood by a near-infrared laser diode

    NASA Astrophysics Data System (ADS)

    Zhao, Zuomin; Myllylae, Risto A.

    2001-06-01

    The near-infrared photoacoustic technique is recognized as a potential method for the non-invasive determination of human glucose, because near-infrared light can incident a few millimeters into human tissue, where it produces an acoustic wave capable of carrying information about the composition of the tissue. This paper demonstrates a photoacoustic glucose measurement in a blood sample as a step toward a non-invasive measurement. The experimental apparatus consists of a near-infrared laser diode operating with 4 micro joules pulse energy at 905 nm, a roller pump connected to a silicon plastic tube and a cuvette for circulating the blood sample. In addition, the apparatus comprises a PZT piezoelectric transducer integrated with a battery-powered preamplifier to receive the photoacoustic signal. During the experiment, a glucose solution is mixed into a human blood sample to change its concentration. Although the absorption coefficient of glucose is much smaller than that of blood in the near-infrared region, the osmotic and hydrophilic properties of glucose decrease the reduced scattering coefficient of blood caused by the dissolved glucose surrounding the blood cells. This changes the distribution of the absorbed optical energy in blood, which, in turn, produces a change in the photoacoustic signal. Our experiment demonstrates that signal amplitudes in fresh and stored blood samples in crease about 7% and 10%, respectively, when the glucose concentration reaches the upper limit of the physiological region (500 mg/dl).

  5. Photoacoustic molecular imaging

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

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

  6. 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)

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

    2014-06-01

    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.

  7. Photoacoustic computed microscopy

    NASA Astrophysics Data System (ADS)

    Yao, Lei; Xi, Lei; Jiang, Huabei

    2014-05-01

    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.

  8. Photoacoustics meets ultrasound: micro-Doppler photoacoustic effect and detection by ultrasound

    E-print Network

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

    2014-01-01

    In recent years, photoacoustics has attracted intensive research for both anatomical and functional biomedical imaging. However, the physical interaction between photoacoustic generated endogenous waves and an exogenous ultrasound wave is a largely unexplored area. Here, we report the initial results about the interaction of photoacoustic and external ultrasound waves leading to a micro-Doppler photoacoustic (mDPA) effect, which is experimentally observed and consistently modelled. It is based on a simultaneous excitation on the target with a pulsed laser and continuous wave (CW) ultrasound. The thermoelastically induced expansion will modulate the CW ultrasound and leads to transient Doppler frequency shift. The reported mDPA effect can be described as frequency modulation of the intense CW ultrasound carrier through photoacoustic vibrations. This technique may open the possibility to sensitively detect the photoacoustic vibration in deep optically and acoustically scattering medium, avoiding acoustic distor...

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

    SciTech Connect

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

    2009-05-15

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    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 d33 piezoelectric coefficient and the stiffness variation induced by the bias in AlN are measured.

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

  12. Photoacoustic spectroscopy for chemical detection

    NASA Astrophysics Data System (ADS)

    Holthoff, Ellen L.; Pellegrino, Paul M.

    2012-06-01

    The Global War on Terror has made rapid detection and identification of chemical and biological agents a priority for Military and Homeland Defense applications. Reliable real-time detection of these threats is complicated by our enemy's use of a diverse range of materials. Therefore, an adaptable platform is necessary. Photoacoustic spectroscopy (PAS) is a useful monitoring technique that is well suited for trace detection of gaseous media. This method routinely exhibits detection limits at the parts-per-billion (ppb) or sub-ppb range. The versatility of PAS also allows for the investigation of solid and liquid analytes. Current research utilizes quantum cascade lasers (QCLs) in combination with an air-coupled solid-phase photoacoustic cell design for the detection of condensed phase material films deposited on a surface. Furthermore, variation of the QCL pulse repetition rate allows for identification and molecular discrimination of analytes based solely on photoacoustic spectra collected at different film depths.

  13. Photoacoustic microcantilevers

    DOEpatents

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

    2012-06-05

    A system generates a photoacoustic spectrum in an open or closed environment with reduced noise. A source focuses a beam on a target substance disposed on a base. The base supports a cantilever that measures acoustic waves generated as light is absorbed by the target substance. By focusing a chopped/pulsed light beam on the target substance, a range of optical absorbance may be measured as the wavelength of light changes. An identifying spectrum of the target may detected by monitoring the vibration intensity variation of the cantilever as a function of illuminating wavelength or color.

  14. High-speed laser photoacoustic imaging system combined with a digital ultrasonic imaging platform

    NASA Astrophysics Data System (ADS)

    Zeng, Lvming; Liu, Guodong; Ji, Xuanrong; Ren, Zhong; Huang, Zhen

    2009-07-01

    As a new field of combined ultrasound/photoacoustic imaging in biomedical photonics research, we present and demonstrate a high-speed laser photoacoustic imaging system combined with digital ultrasound imaging platform. In the prototype system, a new B-mode digital ultrasonic imaging system is modified as the hardware platform with 384 vertical transducer elements. The centre resonance frequency of the piezoelectric transducer is 5.0 MHz with greater than 70% pulse-echo -6dB fractional bandwidth. The modular instrument of PCI-6541 is used as the hardware control centre of the testing system, which features 32 high-speed channels to build low-skew and multi-channel system. The digital photoacoustic data is transported into computer for subsequent reconstruction at 25 MHz clock frequency. Meantime, the software system for controlling and analyzing is correspondingly explored with LabVIEW language on virtual instrument platform. In the breast tissue experiment, the reconstructed image agrees well with the original sample, and the spatial resolution of the system can reach 0.2 mm with multi-element synthetic aperture focusing technique. Therefore, the system and method may have a significant value in improving early detecting level of cancer in the breast and other organs.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Wang, Jianhua; Xiao, Zexin

    2011-11-01

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

  17. Improved Photoacoustic Generator

    NASA Astrophysics Data System (ADS)

    Borowski, T.; Burd, A.; Suchenek, M.; Starecki, T.

    2014-12-01

    In conventional photoacoustic setups, the photoacoustic signal results from stimulation of a sample placed in the photoacoustic cell by the light modulated at a selected frequency. The signal can be amplified in a resonance photoacoustic cell. For this purpose, different types of acoustic resonators are used. Acoustic resonators are passive, frequency selective elements. An acoustic resonator used in a photoacoustic cell offers the opportunity to design a system working on a basis similar to that of a self-oscillating generator. The geometrical dimensions of an acoustic resonator, and the temperature, composition, and concentration of substances in the gas filling its interior determine the resonance frequency. In conventional photoacoustic setups, in which the resonance method is used, the variability of parameters requires continuous adjusting of or searching for the actual resonance frequency. Use of a fixed and arbitrary selected modulation frequency of the light beam can cause considerable errors in detection of substances in the sample or in determination of their concentration. Unlike conventional photoacoustic methods, the frequency of a photoacoustic signal in an improved photoacoustic generator is self-tuned to the actual resonant frequency of the photoacoustic cell. The improved photoacoustic generator operates without an external circuit that controls the optical modulator. The improved photoacoustic generator has been tested in different measurements of the concentration of methane in air. The automatic gain control signal can be used for determination of the absorption by the sample.

  18. Photoacoustic spectroscopy of Entamoeba histolytica strains

    NASA Astrophysics Data System (ADS)

    Acosta-Avalos, D.; Alvarado-Gil, J. J.; Silva, E. F.; Orozco, E.; de Menezes, L. F.; Vargas, H.

    2005-06-01

    Pathogenic and non-pathogenic strains of E. histolytica are studied using photoacoustic spectroscopy. It is shown that the pathogenic strain presents a spectrum similar to that of iron sulfur proteins. The non-pathogenic strain does not show any relevant absorption at the studied wavelength range. The differences observed between the optical absorption spectra of both strains opens the possibility of using photoacoustic spectroscopy as a reliable and simple technique to identify different types of E. histolytica strains.

  19. Biomedical photoacoustics in China?

    PubMed Central

    Meng, Jing; Song, Liang

    2013-01-01

    During the last decade, along with its explosive growth globally, biomedical photoacoustics has become a rapidly growing research field in China as well. In particular, photoacoustic tomography (PAT), capable of imaging intact biological tissue in vivo at great depths, has generated intense interest among Chinese researchers. This review briefly summarizes the current status and recent progress of the research in PAT in China. The focus is on the technology development and biomedical applications of three representative embodiments of PAT: photoacoustic microscopy, photoacoustic computed tomography, and photoacoustic endoscopy. In addition, recent development and studies in other related areas are also reviewed shortly. PMID:25300898

  20. Photoacoustic tomography imaging of biological tissues

    NASA Astrophysics Data System (ADS)

    Su, Yixiong; Wang, Ruikang K.; Xu, Kexin; Zhang, Fan; Yao, Jianquan

    2005-01-01

    Non-invasive laser-induced photoacoustic tomography is attracting more and more attentions in the biomedical optical imaging field. This imaging modality takes the advantages in that the tomography image has the optical contrast similar to the optical techniques while enjoying the high spatial resolution comparable to the ultrasound. Currently, its biomedical applications are mainly focused on breast cancer diagnosis and small animal imaging. In this paper, we report in detail a photoacoustic tomography experiment system constructed in our laboratory. In our system, a Q-switched ND:YAG pulse laser operated at 532nm with a 10ns pulse width is employed to generate photoacoustic signal. A tissue-mimicking phantom was built to test the system. When imaged, the phantom and detectors were immersed in a water tank to facilitate the acoustic detection. Based on filtered back-projection process of photoacoustic imaging, the two-dimension distribution of optical absorption in tissue phantom was reconstructed.

  1. Photoacoustic radiation force on a microbubble

    NASA Astrophysics Data System (ADS)

    Erkol, Hakan; Aytac-Kipergil, Esra; Unlu, Mehmet Burcin

    2014-08-01

    We investigate the radiation force on a microbubble due to the photoacoustic wave which is generated by using a pulsed laser. In particular, we focus on the dependence of pulsed laser parameters on the radiation force. In order to do so, we first obtain a new and comprehensive analytical solution to the photoacoustic wave equation based on the Fourier transform for various absorption profiles. Then, we write an expression of the radiation force containing explicit laser parameters, pulse duration, and beamwidth of the laser. Furthermore, we calculate the primary radiation force acting on a microbubble. We show that laser parameters and the position of the microbubble relative to a photoacoustic source have a considerable effect on the primary radiation force. By means of recent developments in laser technologies that render tunability of pulse duration and repetition frequency possible, an adjustable radiation force can be applied to microbubbles. High spatial control of applied force is ensured on account of smaller focal spots achievable by focused optics. In this context, conventional piezoelectric acoustic source applications could be surpassed. In addition, it is possible to increase the radiation force by making source wavelength with the absorption peak of absorber concurrent. The application of photoacoustic radiation force can open a cache of opportunities such as manipulation of microbubbles used as contrast agents and as carrier vehicles for drugs and genes with a desired force along with in vivo applications.

  2. 4-D Photoacoustic Tomography

    PubMed Central

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

    2013-01-01

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

  3. 4-D Photoacoustic Tomography

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    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.

  4. Robust passive piezoelectric shunt dampener

    Microsoft Academic Search

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

    2003-01-01

    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.

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

    PubMed Central

    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

    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. PMID:22163900

  6. Photoacoustic thermal diffusion flowmetry

    PubMed Central

    Sheinfeld, Adi; Eyal, Avishay

    2012-01-01

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

  7. Advances in Clinical and Biomedical Applications of Photoacoustic Imaging

    PubMed Central

    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

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

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

    SciTech Connect

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

    2004-06-01

    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.

  9. Photoacoustic signal generation based on self-oscillation method

    NASA Astrophysics Data System (ADS)

    Borowski, T.; Starecki, T.

    2008-01-01

    In conventional photoacoustic experiments a signal generated by photoacoustic phenomenon is produced by a forced stimulation of the investigated sample by electromagnetic radiation energy (light) which intensity is modulated at a user selected frequency. Resultant photoacoustic signal has the same frequency as the light modulation frequency. The paper presents a new technique of photoacoustic signal generation, based on self-oscillations resulting from a loopback in the signal path consisting of a modulated light source, a photoacoustic chamber, a microphone, and an amplifier. Signal from the amplifier output was used to drive the light source. Gain of the amplifier was chosen in order to obtain total loop gain of the signal path greater than one and positive feedback operation. On contrary to conventional photoacoustic methods, frequency of the photoacoustic signal in the presented self-oscillation method is determined mainly by acoustic properties of the photoacoustic cell, which in the experiments was corresponding to the resonance frequency of the cell. Taking into consideration that resonance frequency of a photoacoustic cell depends on the speed of sound, which is affected by properties of the fluid filling the cell, the method based on self-oscillations can be applied e.g. to quantitative analysis of the investigated substance.

  10. Tuning fork enhanced interferometric photoacoustic spectroscopy: a new method for trace gas analysis

    NASA Astrophysics Data System (ADS)

    Köhring, M.; Pohlkötter, A.; Willer, U.; Angelmahr, M.; Schade, W.

    2011-01-01

    A photoacoustic trace gas sensor based on an optical read-out method of a quartz tuning fork is shown. Instead of conventional piezoelectric signal read-out, as applied in well-known quartz-enhanced photoacoustic spectroscopy (QEPAS), an interferometric read-out method for measurement of the tuning fork's oscillation is presented. To demonstrate the potential of the optical read-out of tuning forks in photoacoustics, a comparison between the performances of a sensor with interferometric read-out and conventional QEPAS with piezoelectric read-out is reported. The two sensors show similar characteristics. The detection limit (L) for the optical read-out is determined to be L opt=(2598±84) ppm (1 ?) compared to L elec=(2579±78) ppm (1 ?) for piezoelectric read-out. In both cases the detection limit is defined by the thermal noise of the tuning fork.

  11. Photoacoustic tomography: principles and advances

    PubMed Central

    Xia, Jun; Yao, Junjie; Wang, Lihong V.

    2014-01-01

    Photoacoustic tomography (PAT) is an emerging imaging modality that shows great potential for preclinical research and clinical practice. As a hybrid technique, PAT is based on the acoustic detection of optical absorption from either endogenous chromophores, such as oxy-hemoglobin and deoxy-hemoglobin, or exogenous contrast agents, such as organic dyes and nanoparticles. Because ultrasound scatters much less than light in tissue, PAT generates high-resolution images in both the optical ballistic and diffusive regimes. Over the past decade, the photoacoustic technique has been evolving rapidly, leading to a variety of exciting discoveries and applications. This review covers the basic principles of PAT and its different implementations. Strengths of PAT are highlighted, along with the most recent imaging results. PMID:25642127

  12. Photoacoustic characterization of ovarian tissue

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

    Ovarian cancer has the highest mortality of all gynecologic cancers with a five-year survival rate of only 30%. Because current imaging techniques (ultrasound, CT, MRI, PET) are not capable of detecting ovarian cancer early, most diagnoses occur in later stages (III/IV). Thus many women are not correctly diagnosed until the cancer becomes widely metastatic. On the other hand, while the majority of women with a detectable ultrasound abnormality do not harbor a cancer, they all undergo unnecessary oophorectomy. Hence, new imaging techniques that can provide functional and molecular contrasts are needed for improving the specificity of ovarian cancer detection and characterization. One such technique is photoacoustic imaging, which has great potential to reveal early tumor angiogenesis through intrinsic optical absorption contrast from hemoglobin or extrinsic contrast from conjugated agents binding to appropriate molecular receptors. To better understand the cancer disease process of ovarian tissue using photoacoustic imaging, it is necessary to first characterize the properties of normal ovarian tissue. We have imaged ex-vivo ovarian tissue using a 3D co-registered ultrasound and photoacoustic imaging system. The system is capable of volumetric imaging by means of electronic focusing. Detecting and visualizing small features from multiple viewing angles is possible without the need for any mechanical movement. The results show strong optical absorption from vasculature, especially highly vascularized corpora lutea, and low absorption from follicles. We will present correlation of photoacoustic images from animals with histology. Potential application of this technology would be the noninvasive imaging of the ovaries for screening or diagnostic purposes.

  13. The elimination of the temperature effect on a piezoelectric transformer in a backlight inverter based on the phase-locked loop technique

    Microsoft Academic Search

    Chang-Hua Lin; Ying-Chi Chen; John Yanhao Chen; Fuh-Liang Wen

    2005-01-01

    A new method is proposed in this paper to eliminate the temperature effect on a piezoelectric transformer (PT) residing inside a half-bridge backlight module which utilizes the phase-locked loop (PLL) technique. The PT is adopted to drive a cold cathode fluorescent lamp (CCFL) to eliminate the downside of a conventional transformer and to reduce the dimension, particularly the thickness, of

  14. Identification of combustible material with piezoelectric crystal sensor array using pattern-recognition techniques.

    PubMed

    He, X W; Xing, W L; Fang, Y H

    1997-11-01

    A promising way of increasing the selectivity and sensitivity of gas sensors is to treat the signals from a number of different gas sensors with pattern recognition (PR) method. A gas sensor array with seven piezoelectric crystals each coated with a different partially selective coating material was constructed to identify four kinds of combustible materials which generate smoke containing different components. The signals from the sensors were analyzed with both conventional multivariate analysis, stepwise discriminant analysis (SDA), and artificial neural networks (ANN) models. The results show that the predictions were even better with ANN models. In our experiment, we have reported a new method for training data selection, 'training set stepwise expending method' to solve the problem that the network can not converge at the beginning of the training. We also discussed how the parameters of neural networks, learning rate eta, momentum term alpha and few bad training data affect the performance of neural networks. PMID:18966950

  15. Determination of Tequila Quality by Photoacoustic Analysis

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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.

  16. Photoacoustic chemical sensing: ultracompact sources and standoff detection

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  17. Combined photoacoustic and fluorescent quenching studies on organic dyes

    NASA Astrophysics Data System (ADS)

    Viappiani, Cristiano; Small, Jeanne R.

    1992-04-01

    The development of deconvolution techniques in pulsed-laser, time-resolved photoacoustics has opened the possibility of accurately distinguishing between processes occurring on different time scales, and has given photoacoustics better resolution in determining reaction enthalpies and quantum yields. While fluorescent signals are usually generated by a single de- excitation pathway in the fluorophore, photoacoustic signals usually arise from different sources, such as excited singlet and triplet deactivation, occurring on well-distinguished time scales. The understanding of the effect of quenching on photoacoustic signals therefore requires careful analysis of the data. In this work, a model is developed to describe the effect of fluorescence quenching on photoacoustic signals. The model takes advantage of the time resolution in pulsed-laser photoacoustics. Both static and dynamic quenching are taken into account. Important photophysical parameters (fluorescence and intersystem crossing quantum yields, the bimolecular quenching rate constant, and the volume of the sphere of action) appear in the expressions describing the dependence of photoacoustic signal on quencher concentration. Data from both steady-state fluorescence and time-resolved photoacoustic quenching measurements are analyzed simultaneously using a set of equations containing common parameters. Experimental data on the quenching of organic dyes are presented which support the validity of the model.

  18. Design considerations for ultrasound detectors in photoacoustic breast imaging

    NASA Astrophysics Data System (ADS)

    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

    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.

  19. Piezoelectric Polymers

    NASA Technical Reports Server (NTRS)

    Harrison, J. S.; Ounaies, Z.; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    The purpose of this review is to detail the current theoretical understanding of the origin of piezoelectric and ferroelectric phenomena in polymers; to present the state-of-the-art in piezoelectric polymers and emerging material systems that exhibit promising properties; and to discuss key characterization methods, fundamental modeling approaches, and applications of piezoelectric polymers. Piezoelectric polymers have been known to exist for more than forty years, but in recent years they have gained notoriety as a valuable class of smart materials.

  20. Photoacoustic cell for ultrasound contrast agent characterization

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  1. Photoacoustic cell for ultrasound contrast agent characterization.

    PubMed

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

    2010-10-01

    Photoacoustics has emerged as a tool for the study of liquid gel suspension behavior and has been recently employed in a number of new biomedical applications. In this paper, a photoacoustic sensor is presented which was designed and realized for analyzing photothermal signals from solutions filled with microbubbles, commonly used as ultrasound contrast agents in echographic imaging techniques. It is a closed cell device, where photothermal volume variation of an aqueous solution produces the periodic deflection of a thin membrane closing the cell at the end of a short pipe. The cell then acts as a Helmholtz resonator, where the displacement of the membrane is measured through a laser probe interferometer, whereas photoacoustic signal is generated by a laser chopped light beam impinging onto the solution through a glass window. Particularly, the microbubble shell has been modeled through an effective surface tension parameter, which has been then evaluated from experimental data through the shift of the resonance frequencies of the photoacoustic sensor. This shift of the resonance frequencies of the photoacoustic sensor caused by microbubble solutions is high enough for making such a cell a reliable tool for testing ultrasound contrast agent, particularly for bubble shell characterization. PMID:21034110

  2. Biomechanical characterization of tissue-engineered cartilages by photoacoustic measurement

    NASA Astrophysics Data System (ADS)

    Ishihara, Miya; Sato, Masato; Sato, Shunichi; Kikuchi, Toshiyuki; Fujikawa, Kyosuke; Kikuchi, Makoto

    2003-07-01

    We have demonstrated a capability of biomechanical characterization by photoacoustic measurement using various concentraiton gelatins as tissue pahntom. We have also evaluated the viscoelasticity of the cartilages tissue-engineered under the different culture conditions. Structural tissues, such as cartilage, bone, tendon, and muscle require time-dependent mechanical responses (viscoelastic properties) to describe their mechanical behavior. However, non-invasive measurement of tissue viscoelastic has not been developed; such measurement is necessary for tissue engineering applications on weight-bearing tissues. As tissue viscoelasticity affects the propagation and attenuation of the stress waves generated in the tissue, their relaxation times which are defined as the time for the stress wave amplitude to decrease by a factor of 1/e, give the viscosity-elasticity ratio of the tissue. In this study, stress waves (photoacoustic waves) which were induced by 250-nm, 6-ns, light pulses from an OPO were detected by a piezoelectric transducer. The relaxation time of the photoacoustic wave was measured for various concentrations of gelatins which had been measured their viscoelastic properties by a conventional method. Consequently, the relaxation time corresponded to the known viscosity-elasticity ratio of the gelatins. For the tissue-engineered cartileges, photoacoustic measurements were performed under the different cultured conditions. The relaxation time of the cartilages closely correlated with the viscosity-elasticity ratio measured by a convetional method. Therefore, the photoacoustic measurement is one of the qualified candidates for a non-invasive viscoelastic measurement of tissue.

  3. Piezoelectric valve

    DOEpatents

    Petrenko, Serhiy Fedorovich

    2013-01-15

    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.

  4. Enhanced photoacoustic detection using photonic crystal substrate

    SciTech Connect

    Zhao, Yunfei; Liu, Kaiyang [Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011 (United States); McClelland, John [Ames Laboratory-USDOE, Ames, Iowa 50011 (United States); Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States); Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011 (United States); Lu, Meng, E-mail: menglu@iastate.edu [Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011 (United States); Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States)

    2014-04-21

    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.

  5. Measurements of thermal effusivity of liquids using a conventional photoacoustic cell

    Microsoft Academic Search

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

    1999-01-01

    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:

  6. Investigation of photoacoustic spectroscopy for biomolecular detection

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

    We are developing a non- or minimally-invasive method for detecting and measuring specific drugs and biomolecules in vivo using photoacoustic spectroscopy (PAS). This pilot study investigated the feasibility of detecting the concentration of certain drugs in the vitreous or aqueous of the eye. As a prototype for using PAS for molecular detection in vivo, the technique was applied to the detection in a surrogate eye, of drugs with known optical spectrum such as Trypan Blue, Rose Bengal, and Amphotericin B (AB), at concentrations as low as 1 ?g/ml. Chopped CW, or short pulse, Q-switch lasers, were used as pumping sources to generate ultrasonic photoacoustic signals in an ocular phantom containing the drug solutions. In addition to an ultrasonic hydrophone, the photothermal deflection technique (PhDT), a non-contact optical method with high sensitivity and fast response, were used to record the photoacoustic signals. The data from both detectors were compared over a range of drug concentrations. The photoacoustic signal generated from the retina was used as a reference, to measure the attenuation of light through drug solutions of different concentrations in the ocular phantom. The results indicated that photoacoustic spectroscopy is feasible in ocular phantoms incorporating ex vivo ocular tissue. The signals recorded using PAS were to be found to be linearly dependent on drug concentration, as predicted by theory. The photoacoustic method was found to be sensitive to drug concentrations as low as 1 ?g/ml, a clinically relevant concentration for many drugs. Future work will be directed at adapting this method for in vivo measurement, and enhancing its sensitivity by using a tunable laser as the pump source.

  7. Sound Wave Transmission Reduction through a Plate using Piezoelectric Synchronized Switch Damping Technique

    Microsoft Academic Search

    Daniel Guyomar; Thibaut Richard; Claude Richard

    2008-01-01

    Wave control and development of anechoic systems in air are of major interest to improve acoustic comfort. Currently, passive control techniques, which consist in using absorbing materials are effective at high frequency, but the principal limitation of this approach is mass and volume, particularly in the low-frequency range. Active control techniques (like the use of antinoise, which uses interference of

  8. Piezoelectrically Enhanced Photocathodes

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  9. Photoacoustic spectroscopy of ?-hematin

    PubMed Central

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

    2012-01-01

    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. PMID:22844576

  10. Piezoelectric spectroscopy

    Microsoft Academic Search

    Jie Fang Li; Paul Moses; Dwight Viehland

    1994-01-01

    In this paper, we report the development of a piezoelectric spectrometer using a Michelson-Morely interferometer. The measurement system has been developed to study the frequency and temperature dependence of the complex piezoelectric and electrostriction coefficients of ferroelectric materials. The system is controlled by computer and has very significantly wider frequency range and lower noise than previously developed systems. Results are

  11. Piezoelectricity Demo

    NSDL National Science Digital Library

    This lesson plan from the Oregon Museum of Science and Industry explores the history of piezoelectricity, with hands-on examples of how itâ??s used, models of why it happens, and how it is applied in nanotechnology. Pressing on the piezoelectric buzzer in the background causes a current to flow and the neon bulb in the foreground to glow.

  12. Piezoelectric films

    NASA Astrophysics Data System (ADS)

    Shermergor, Timofei Dmitrievich; Strel'Tsova, Natalia Nikolaevna

    The physical properties of piezoelectric materials for use in microelectronics are described with particular emphasis on SAW propagation. Piezoelectric-film (PF) fabrication processes are discussed, with consideration given to sputtering and chemical vapor deposition. The properties (acoustic, optical, and mechanical) of PFs are examined along with their applications (e.g., in BAW and SAW devices).

  13. Mechanistic aspects of peptide-membrane interactions determined by optical, dielectric and piezoelectric techniques: an overview.

    PubMed

    Oliveira, Maria D L; Franco, Octavio L; Nascimento, Jessica M; de Melo, Celso P; Andrade, Cesar A S

    2013-11-01

    Antimicrobial peptides (AMPs) have been isolated from a wide variety of organisms that include microorganisms, plants, insects, frogs and mammals. As part of the innate immune system expressed in many tissues, AMPs are able to provide protection against invasion of foreign microorganisms and exhibit a broad spectrum of activity against bacteria, fungi and/or virus. Non-AMPs cell-penetrating peptides have been used as carriers for overcoming the membrane barrier and helping in the delivery of various molecules into the cell. Physicochemical peptide-lipid interactions studies can provide us with reliable molecular information about microbe defense response, including the elucidation of the prevailing mechanisms of its action, such as the barrel-stave, toroidal pore, carpet and detergent-like models. In this paper, we present an overview of the peptide-lipid mechanisms of interaction as well as discuss alternative techniques that could help to elucidate the peptides functionality. Quartz crystal microbalance (QCM), surface plasmon resonance (SPR) spectroscopy and electrochemical impedance spectroscopy (EIS) are useful techniques to investigate in details of the peptide-membrane interaction. The techniques here discussed could also offer specific and low-cost methods that can to shed some light over the different modes of action of AMPs, contributing to the development of drugs against infectious diseases. PMID:23968347

  14. High-Temperature Piezoelectric Sensing

    PubMed Central

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

    2014-01-01

    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. PMID:24361928

  15. Photoacoustic-based nanomedicine for cancer diagnosis and therapy.

    PubMed

    Sim, Changbeom; Kim, Haemin; Moon, Hyungwon; Lee, Hohyeon; Chang, Jin Ho; Kim, Hyuncheol

    2015-04-10

    Photoacoustic imaging is the latest promising diagnostic modality that has various advantages such as high spatial resolution, deep penetration depth, and use of non-ionizing radiation. It also employs a non-invasive imaging technique and optically functionalized imaging. The goal of this study was to develop a nanomedicine for simultaneous cancer therapy and diagnosis based on photoacoustic imaging. Human serum albumin nanoparticles loaded with melanin and paclitaxel (HMP-NPs) were developed using the desolvation technique. The photoacoustic-based diagnostic and chemotherapeutic properties of HMP-NPs were evaluated through in vitro and in vivo experiments. The size and zeta potential of the HMP-NPs were found to be 192.8±21.11nm and -22.2±4.39mV, respectively. In in vitro experiments, HMP-NPs produced increased photoacoustic signal intensity because of the loaded melanin and decreased cellular viability because of the encapsulated paclitaxel, compared to the free human serum albumin nanoparticles (the control). In vivo experiments showed that the HMP-NPs efficiently accumulated inside the tumor, resulting in the enhanced photoacoustic signal intensity in the tumor site, compared to the normal tissues. The in vivo chemotherapy study demonstrated that HMP-NPs had the capability to treat cancer for an extended period. In conclusion, HMP-NPs were simultaneously capable of photoacoustic diagnostic and chemotherapy against cancer. PMID:25701310

  16. Photoacoustic correlation spectroscopy for in vivo blood flow speed measurement

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  17. Development of a Multiphoton Photoacoustic Microscope

    E-print Network

    Shelton, Ryan 1983-

    2012-08-15

    of which exhibit very strong photoacoustic signals. Regarding spatial resolution, one of the primary benefits that photoacoustic imaging boasts in tomographic implementations becomes the primary drawback in microscopic implementations. Photoacoustic...

  18. Biomedical photoacoustic imaging

    PubMed Central

    Beard, Paul

    2011-01-01

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

  19. Stimulated Raman photoacoustic imaging

    PubMed Central

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

    2010-01-01

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

  20. Computationally intelligent pulsed photoacoustics

    NASA Astrophysics Data System (ADS)

    Luki?, Mladena; ?ojbaši?, Žarko; Rabasovi?, Mihailo D.; Markushev, Dragan D.

    2014-12-01

    In this paper, the application of computational intelligence in pulsed photoacoustics is discussed. Feedforward multilayer perception networks are applied for real-time simultaneous determination of the laser beam spatial profile and vibrational-to-translational relaxation time of the polyatomic molecules in gases. Networks are trained and tested with theoretical data adjusted for a given experimental set-up. Genetic optimization has been used for calculation of the same parameters, fitting the photoacoustic signals with a different number of generations. Observed benefits from the application of computational intelligence in pulsed photoacoustics and advantages over previously developed methods are discussed, such as real-time operation, high precision and the possibility of finding solutions in a wide range of parameters, similar to in experimental conditions. In addition, the applicability for practical uses, such as the real-time in situ measurements of atmospheric pollutants, along with possible further developments of obtained results, is argued.

  1. Photoacoustic imaging using a conical axicon detector

    NASA Astrophysics Data System (ADS)

    Gratt, S.; Passler, K.; Nuster, R.; Paltauf, G.

    2009-07-01

    Photoacoustic imaging with a scanning, fixed focus receiver gives images with high resolution, without the need for image reconstruction. For achieving high depth of field, a conically shaped piezoelectric ultrasound detector, the so called axicon-detector, is investigated. It is characterized by a sustained line of focus with a length that depends only on the geometry of the detector but not on the wavelength. Simulated and experimentally taken images of various objects reveal X-shaped artifacts due to the conical surface of the detector. To improve the image quality a frequency domain deconvolution can be applied, as the point spread function (PSF) of the detector is spatially invariant over the depth of field. The reduction of the artifacts works well for simulated images but is not functional for experimental data yet. Nevertheless, the detector gives images with precise shape and position of the investigated samples.

  2. Urogenital photoacoustic endoscope

    PubMed Central

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

    2014-01-01

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

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

    Microsoft Academic Search

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

    2003-01-01

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

  4. Application of pulsed laser photoacoustic sensors in monitoring oil contamination in water

    Microsoft Academic Search

    P. Hodgson; K. M. Quan; H. A. MacKenzie; S. S. Freeborn; J. Hannigan; E. M. Johnston; F. Greig; T. D. Binnie

    1995-01-01

    A pulsed laser photoacoustic measurement technique, utilising laser diode sources, has been developed for the detection of oil contamination in water. The measurement of oil-contaminated water samples of oil concentration ranging from 0 to 900 mg 1?1 is presented. Also reported are results from a theoretical modelling, which includes several experimental factors important to the photoacoustic sensor design for this

  5. Photoacoustic Doppler flowmetry of carbon particles flow using an autocorrelation method

    NASA Astrophysics Data System (ADS)

    Lu, Tao

    2014-11-01

    In order to measure the axial flowing velocity of carbon particle suspension with particle diameter of tens of micrometers, the photoacoustic Doppler (PAD) frequency shift is calculated based on a series of individual A scans using an autocorrelation method. A 532 nm pulsed laser with repetition rate of 20 Hz is used as a pumping source to generate photoacoustic signal. The photoacoustic signals are detected using a focused piezoelectric (PZT) ultrasound transducer with central frequency of 5 MHz. The suspension of carbon particles is driven by a syringe pump. The complex photoacoustic signal is calculated by the Hilbert transformation from time-domain photoacoustic signal, and then it is autocorrelated to calculate the Doppler frequency shift. The photoacoustic Doppler frequency shift is calculated by averaging the autocorrelation results of some individual A scans. The advantage of the autocorrelation method is that the time delay in autocorrelation can be defined by user, and the requirement of high pulse repetition rate is avoided. The feasibility of the proposed autocorrelation method is preliminarily demonstrated by quantifying the motion of a carbon particle suspension with flow velocity from 5 mm/s to 60 mm/s. The experimental results show that there is an approximately linear relation between the autocorrelation result and the setting velocity.

  6. REVIEW OF SCIENTIFIC INSTRUMENTS 81, 124901 (2010) Signal-to-noise analysis of biomedical photoacoustic measurements in

    E-print Network

    Mandelis, Andreas

    to the sensitivity of ultrasonic transducers, noise level in the system, and the signal processing algorithm, which with a modu- lated optical source. The feasibility of high-SNR continuous wave depth-resolved photoacoustics of piezoelectric transducers and optical properties of tissue. © 2010 American Institute of Physics. [doi:10

  7. Prototyping of radially oriented piezoelectric ceramic-polymer tube composites using fused deposition and lost mold processing techniques

    NASA Astrophysics Data System (ADS)

    McNulty, Thomas Francis

    Piezoelectric tube composite hydrophones of 3-1, 3-2, and 2-2 connectivity were developed using Fused Deposition (FD) and lost mold processing (LMP). In this work, a new series of thermoplastic binder formulations, named the ECG series, were developed for the FD process. The ECG-9 formulation exhibits mechanical, thermal, and rheological properties suitable for the Fused Deposition of functional lead zirconate titanate ceramic devices. This binder consists of 100 parts (by weight) Vestoplast 408, 20 parts Escorez 2520, 15 parts Vestowax A-227, and 5 parts Indopol H-1500. Oleic acid, oleyl alcohol, stearic acid, and stearyl alcohol (in toluene) were tested for use as a dispersant in the PZT/ECG-9 system. It was found that stearic acid adsorbs the most onto PZT powder, adsorbing 8.1 mg/m2. Using stearic acid, solutions of increasing concentration (5.0--50.0 g/l) were measured for adsorption. It was found that 30.0 g/l is the minimum concentration necessary for optimum surface coverage. The surfactant-coated powder was compounded with ECG-9 binder to create a 54 vol.% mix. The mix was extruded using a single screw extrusion apparatus into continuous lengths (>30 m) of 1.78 mm diameter filament. Fused Deposition was used to create composite designs of 3-1, 3-2, and 2-2 connectivity. After sintering, samples exhibit a sintered density greater than 97%. Sanders Prototyping (SPI) was used to manufacture molds for use with LMP techniques. Molds of 3-1, 3-2, and 2-2 connectivity were developed. The molds were infiltrated with a 55 vol.% aqueous based PZT slurry. The parts were subjected to a binder decomposition cycle, followed by sintering. Resultant samples were highly variable due to random macro-pores present in the samples after sintering. The resultant preforms were embedded in epoxy, and polished to dimensions of 8.0 mm inside diameter (ID), 14.0 mm outside diameter (OD), and 10.0 mm length (l) the OD and l dimensions are accurate to +/--2%, while the ID is accurate to +/--5%. Samples were corona poled, and the electromechanical properties were evaluated. Dielectric constant (K), hydrostatic charge coefficients (dh), and radial displacements (ur) were measured. Of the seven composite types studied, the FD-based composites with 3-2 connectivity exhibited the highest average dh of 42.4 pCN. The same 3-2 composites exhibited the highest dhgh (FOM) of 140 fm2/N.

  8. Photoacoustic imaging platforms for multimodal imaging

    PubMed Central

    2015-01-01

    Photoacoustic (PA) imaging is a hybrid biomedical imaging method that exploits both acoustical Epub ahead of print and optical properties and can provide both functional and structural information. Therefore, PA imaging can complement other imaging methods, such as ultrasound imaging, fluorescence imaging, optical coherence tomography, and multi-photon microscopy. This article reviews techniques that integrate PA with the above imaging methods and describes their applications. PMID:25754364

  9. Thermal Diffusivity of Sandstone Using Photoacoustics

    NASA Astrophysics Data System (ADS)

    Guimarães, A. O.; de Souza, C. G.; da Silva, E. C.; Soffner, M. E.; Mansanares, A. M.; Ribeiro, H. J. P. S.; Carrasquilla, A. A. G.; Vargas, H.

    2015-02-01

    An open photoacoustic cell was used to investigate the thermal diffusivity of sandstone taken from the Paraná Basin, in Brazil. Although the organic-rich sedimentary rocks represent an important energy source in the Paraná Basin, only limited data are reported concerning their thermophysical properties. A sandstone rock sample, from the Botucatu Formation, was investigated. The thermal diffusivity values were determined with uncertainties around 12 %, comparable to other methods. These values consider not only the experimental errors but also take into account the heterogeneity of the materials. It was possible to verify the behavior of the thermal diffusivity of the sandstone under heat treatment. The variation of the thermal diffusivity followed an expected trend, based on the possible variation of porosity which is related to the decomposition of some constituents. The results presented in this work identify the photoacoustic technique as a useful tool for thermal characterization of sedimentary rocks.

  10. Quartz-Enhanced Photoacoustic Spectroscopy: A Review

    PubMed Central

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

    2014-01-01

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

  11. Photoacoustic spectroscopy of Baru Dipteryx alata Vog

    NASA Astrophysics Data System (ADS)

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

    2008-01-01

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

  12. Quartz-enhanced photoacoustic spectroscopy: a review.

    PubMed

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

    2014-01-01

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

  13. Quantitative photoacoustic image reconstruction for molecular imaging

    NASA Astrophysics Data System (ADS)

    Cox, B. T.; Arridge, S. R.; Beard, P. C.

    2006-02-01

    Biomedical photoacoustic imaging produces a map of the initial acoustic pressure distribution, or absorbed energy density, in tissue following a short laser pulse. Quantitative photoacoustic imaging (QPI) takes the reconstruction process one stage further to produce a map of the tissue optical coefficients. This has two important advantages. Firstly, it removes the distorting effect of the internal light distribution on image contrast. Secondly, by obtaining images at multiple wavelengths, it enables standard spectroscopic techniques to be used to quantify the concentrations of specific chromophores, for instance, oxy and deoxy haemoglobin for the measurement of blood oxygenation - applying such techniques directly to "conventionally" reconstructed absorbed energy maps is problematic due to the spectroscopic 'spatial crosstalk' effects between different tissue chromophores. As well as naturally-occurring chromophores, dye-labelled molecular markers can be used to tag specific molecules, such as cell surface receptors, enzymes or pharmaceutical agents. In QPI, a diffusion-based finite element model of light transport in scattering media, with ?-Eddington scattering coefficients, is fitted to the absorbed energy distribution to estimate the optical coefficient maps. The approach described here uses a recursive algorithm and converges quickly on the absorption coefficient distribution, when the scattering is known. By adding an area of known absorption, an unknown constant scattering coefficient may also be recovered. With optical coefficient maps estimated in this way, QPI has the potential to be a powerful tool for quantifying the concentration of molecular markers in photoacoustic molecular imaging.

  14. Towards single molecule detection using photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  15. Photoacoustic probe for spectroscopic measurements in condensed matter: convenient and corosion-resistant

    SciTech Connect

    Lai, E.P.C.; Voigtman, E.; Winefordner, J.D.

    1982-09-01

    A simple effective photoacoustic probe employing the acoustic waveguide effect in quartz substrate is described. The photoacoustic probe consists of a quartz rod to the upper end of which PZT-5A piezoelectric ceramic disk is attached. The probe was used in the acquisition of a dye-laser-excited photoacoustic spectrum of 10-..mu..g/ml 9,10-dimethylanthracene in ethanol at room temperature. With the probe system, the spectrum was found to be essentially identical with the corresponding spectra obtained with a standard cuvette cell/attached PZT disk and a cylindrical cell/attached PZT tube detection systems; the observed relative sensitivities were 1.6:1.0:4.4, respectively.

  16. An equivalent network representation of a clamped bimorph piezoelectric micromachined ultrasonic transducer with circular and annular electrodes using matrix manipulation techniques.

    PubMed

    Sammoura, Firas; Smyth, Katherine; Kim, Sang-Gook

    2013-09-01

    An electric circuit model for a clamped circular bimorph piezoelectric micromachined ultrasonic transducer (pMUT) was developed for the first time. The pMUT consisted of two piezoelectric layers sandwiched between three thin electrodes. The top and bottom electrodes were separated into central and annular electrodes by a small gap. While the middle electrode was grounded, the central and annular electrodes were biased with two independent voltage sources. The strain mismatch between the piezoelectric layers caused the plate to vibrate and transmit a pressure wave, whereas the received echo generated electric charges resulting from plate deformation. The clamped pMUT plate was separated into a circular and an annular plate, and the respective electromechanical transformation matrices were derived. The force and velocity vectors were properly selected using Hamilton's principle and the necessary boundary conditions were invoked. The electromechanical transformation matrix for the clamped circular pMUT was deduced using simple matrix manipulation techniques. The pMUT performance under three biasing schemes was elaborated: 1) central electrode only, 2) central and annular electrodes with voltages of the same magnitude and polarity, and 3) central and annular electrodes with voltages of the same magnitude and opposite polarity. The circuit parameters of the pMUT were extracted for each biasing scheme, including the transformer ratio, the clamped electric impedance, and the open-circuit mechanical impedance. Each pMUT scheme was characterized under different acoustic loadings using the theoretically developed model, which was verified with finite element modeling (FEM) simulation. The electrode size was optimized to maximize the electromechanical transformer ratio. As such, the developed model could provide more insight into the design, optimization, and characterization of pMUTs and allow for performance comparison with their cMUT counterparts. PMID:24658730

  17. Combined photoacoustic and high-frequency power Doppler ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Jiang, Yan; Harrison, Tyler; Ranasinghesagara, Janaka; Zemp, Roger J.

    2010-02-01

    Photoacoustic imaging has emerged as a promising technique for visualizing optically absorbing structures with ultrasonic spatial resolution. Since it relies on optical absorption of tissues, photoacoustic imaging is particularly sensitive to vascular structures even at the micro-scale. Power Doppler ultrasound can be used to detect moving blood irrespective of Doppler angles. However, the sensitivity may be inadequate to detect very small vessels with slow flow velocities. In this work, we merge these two synergistic modalities and compare power Doppler ultrasound images with high-contrast photoacoustic images. We would like to understand the advantages and disadvantages of each technique for assessing microvascular density, an important indicator of disease status. A combined photoacoustic and highfrequency ultrasound system has been developed. The system uses a swept-scan 25 MHz ultrasound transducer with confocal dark-field laser illumination optics. A pulse-sequencer enables ultrasonic and laser pulses to be interlaced so that photoacoustic and Doppler ultrasound images are co-registered. Experiments have been performed on flow phantoms to test the capability of our system and signal processing methods. Work in progress includes in vivo color flow mapping. This combined system will be used to perform blood oxygen saturation and flow estimations, which will provide us with the parameters to estimate the local rate of metabolic oxygen consumption, an important indicator for many diseases.

  18. Sensitivity of photoacoustic microscopy

    PubMed Central

    Yao, Junjie; Wang, Lihong V.

    2014-01-01

    Building on its high spatial resolution, deep penetration depth and excellent image contrast, 3D photoacoustic microscopy (PAM) has grown tremendously since its first publication in 2005. Integrating optical excitation and acoustic detection, PAM has broken through both the optical diffusion and optical diffraction limits. PAM has 100% relative sensitivity to optical absorption (i.e., a given percentage change in the optical absorption coefficient yields the same percentage change in the photoacoustic amplitude), and its ultimate detection sensitivity is limited only by thermal noise. Focusing on the engineering aspects of PAM, this Review discusses the detection sensitivity of PAM, compares the detection efficiency of different PAM designs, and summarizes the imaging performance of various endogenous and exogenous contrast agents. It then describes representative PAM applications with high detection sensitivity, and outlines paths to further improvement. PMID:25302158

  19. Thermally Induced Photoacoustic Transients Produced by Laser-Irradiated Fluid Spheres

    NASA Astrophysics Data System (ADS)

    Frez, Clifford; Diebold, Gerald J.

    2014-12-01

    Pulsed laser irradiation of a weakly absorbing fluid sphere in a transparent medium results in the production of a large thermal gradient at the surface of the sphere. The rapid transfer of heat from the sphere to the surrounding fluid as a result of the thermal gradient generates high frequency photoacoustic transients which affect the leading edge of a photoacoustic wave. Here, the character of the photoacoustic wave is determined by solving a modified wave equation for the photoacoustic effect. A solution to the heat diffusion equation is determined, which, together with the heating function for the optical source, provides the source term for the wave equation for pressure. The wave equation is then solved with appropriate boundary conditions using Laplace transform techniques to give the photoacoustic waveform. The relative magnitude of the transient to the N-shaped wave is shown to be determined, in part, by the laser pulse length.

  20. Multiplex photoacoustic molecular imaging using targeted silica-coated gold nanorods

    PubMed Central

    Bayer, Carolyn L.; Chen, Yun-Sheng; Kim, Seungsoo; Mallidi, Srivalleesha; Sokolov, Konstantin; Emelianov, Stanislav

    2011-01-01

    The establishment of multiplex photoacoustic molecular imaging to characterize heterogeneous tissues requires the use of a tunable, thermally stable contrast agent targeted to specific cell types. We have developed a multiplex photoacoustic imaging technique which uses targeted silica-coated gold nanorods to distinguish cell inclusions in vitro. This paper describes the use of tunable targeted silica-coated gold nanorods (SiO2-AuNRs) as contrast agents for photoacoustic molecular imaging. SiO2-AuNRs with peak absorption wavelengths of 780 nm and 830 nm were targeted to cells expressing different cell receptors. Cells were incubated with the targeted SiO2-AuNRs, incorporated in a tissue phantom, and imaged using multiwavelength photoacoustic imaging. We used photoacoustic imaging and statistical correlation analysis to distinguish between the unique cell inclusions within the tissue phantom. PMID:21750761

  1. Integrated system for ultrasonic, photoacoustic and elasticity imaging

    NASA Astrophysics Data System (ADS)

    Park, S.; Shah, J.; Aglyamov, S. R.; Karpiouk, A. B.; Mallidi, S.; Gopal, A.; Moon, H.; Zhang, X. J.; Scott, W. G.; Emelianov, S. Y.

    2006-03-01

    A hybrid imaging system is proposed for cancer detection, diagnosis and therapy monitoring by integrating three complementary imaging techniques - ultrasound, photoacoustic and elasticity imaging. Indeed, simultaneous imaging of the anatomy (ultrasound imaging), cancer-induced angiogenesis (photoacoustic imaging) and changes in biomechanical properties (elasticity imaging) of tissue is based on many synergistic features of these modalities and may result in a unique and important imaging tool. To facilitate the design and development of a real-time imaging system for clinical applications, we have investigated the core components of the imaging system using numerical simulations. Differences and similarities between each imaging technique were considered and contrasted. The results of our study suggest that the integration of ultrasound, photoacoustic and elasticity imaging is possible using a custom designed imaging system.

  2. Functional photoacoustic microscopy of pH

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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.

  3. Photoacoustic detection of breast cancer cells in human blood

    NASA Astrophysics Data System (ADS)

    Thomas, T. S.; Dale, P. S.; Weight, R. M.; Atasoy, Ulus; Magee, J.; Viator, J. A.

    2008-02-01

    Detection of breast cancer cells in human blood may provide early determination of metastasis, enabling aggressive treatment prior to detection by conventional radiographic methods. We developed a photoacoustic flowmetry system in which we irradiated breast cancer cells in suspension to simulate metastatic breast cancer cells derived from human blood. In order to provide optical discrimination between the breast cancer cells and lymphocytes, we attached antibody labeled latex microspheres and gold nanoparticles to breast cancer cells. The breast cancer cells were derived from an estrogen receptor (ER) positive cell line, MCF-7. The particles were conjugated to ER antibodies. We irradiated the cell suspension using the photoacoustic flowmeter consisting of a glass flow chamber with a piezoelectric sensor. We irradiated the suspension at 422 and 530nm and solved a linear system of equations in two variables to separate the contribution of the photoacoustic wave from the breast cancer cells and possible erythrocytes that may be present in a patient blood draw. We found a detection threshold of 10 breast cancer cells using this flowmeter. Future optimization of the system may decrease the detection threshold to single breast cancer cells.

  4. Piezoelectrically actuated tunable capacitor

    Microsoft Academic Search

    Chuang-Yuan Lee; Eun Sok Kim

    2006-01-01

    This paper describes the design, fabrication, and characterization of the first MEMS piezoelectric tunable capacitors employing zinc oxide (ZnO) actuation. Relatively simple design rules for the device-structure optimization for largest deflection are shown from simulation results based on theoretical equations. The ZnO-actuated tunable capacitors are accordingly designed and fabricated with both surface and bulk micromachining techniques. Through the surface micromachining

  5. High-sensitivity detection of trace gases using dynamic photoacoustic spectroscopy

    E-print Network

    Wynn, Charles M.

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

  6. Optical-absorptioncoefficient measurements in solids and liquids using correlation photoacoustic spectroscopy

    E-print Network

    Mandelis, Andreas

    -correlation photoacoustic spectroscopy (CPAS), has been investigated. Powders of holmium oxide and aqueous solutions technique de spectroscopie photo-acoustique a corrtlation croiste (CPAS). Des poudres d'oxyde de holmium et

  7. High finesse optical cavity coupled with a quartz-enhanced photoacoustic spectroscopic sensor.

    PubMed

    Patimisco, Pietro; Borri, Simone; Galli, Iacopo; Mazzotti, Davide; Giusfredi, Giovanni; Akikusa, Naota; Yamanishi, Masamichi; Scamarcio, Gaetano; De Natale, Paolo; Spagnolo, Vincenzo

    2015-02-01

    An ultra-sensitive and selective quartz-enhanced photoacoustic spectroscopy (QEPAS) combined with a high-finesse cavity sensor platform is proposed as a novel method for trace gas sensing. We call this technique Intra-cavity QEPAS (I-QEPAS). In the proposed scheme, a single-mode continuous wave quantum cascade laser (QCL) is coupled into a bow-tie optical cavity. The cavity is locked to the QCL emission frequency by means of a feedback-locking loop that acts directly on a piezoelectric actuator mounted behind one of the cavity mirrors. A power enhancement factor of ?240 was achieved, corresponding to an intracavity power of ?0.72 W. CO2 was selected as the target gas to validate our sensor. For the P(42) CO2 absorption line, located at 2311.105 cm(-1), a minimum detection limit of 300 parts per trillion by volume at a total gas pressure of 50 mbar was achieved with a 20 s integration time. This corresponds to a normalized noise equivalent absorption of 3.2 × 10(-10) W cm(-1) Hz(-1/2), comparable with the best results reported for the QEPAS technique on much faster relaxing gases. A comparison with standard QEPAS performed under the same experimental conditions confirms that the I-QEPAS sensitivity scales with the intracavity laser power enhancement factor. PMID:25465410

  8. Three-dimensional photoacoustic imaging using a two-dimensional CMUT array.

    PubMed

    Vaithilingam, Srikant; Ma, Te-Jen; Furukawa, Yukio; Wygant, Ira O; Zhuang, Xuefeng; De La Zerda, Adam; Oralkan, Omer; Kamaya, Aya; Gambhir, Sanjiv S; Jeffrey, R Brooke; Khuri-Yakub, Butrus T

    2009-11-01

    In this paper, we describe using a 2-D array of capacitive micromachined ultrasonic transducers (CMUTs) to perform 3-D photoacoustic and acoustic imaging. A tunable optical parametric oscillator laser system that generates nanosecond laser pulses was used to induce the photoacoustic signals. To demonstrate the feasibility of the system, 2 different phantoms were imaged. The first phantom consisted of alternating black and transparent fishing lines of 180 mum and 150 mum diameter, respectively. The second phantom comprised polyethylene tubes, embedded in chicken breast tissue, filled with liquids such as the dye indocyanine green, pig blood, and a mixture of the 2. The tubes were embedded at a depth of 0.8 cm inside the tissue and were at an overall distance of 1.8 cm from the CMUT array. Two-dimensional cross-sectional slices and 3-D volume rendered images of pulse-echo data as well as photoacoustic data are presented. The profile and beamwidths of the fishing line are analyzed and compared with a numerical simulation carried out using the Field II ultrasound simulation software. We investigated using a large aperture (64 x 64 element array) to perform photoacoustic and acoustic imaging by mechanically scanning a smaller CMUT array (16 x 16 elements). Two-dimensional transducer arrays overcome many of the limitations of a mechanically scanned system and enable volumetric imaging. Advantages of CMUT technology for photoacoustic imaging include the ease of integration with electronics, ability to fabricate large, fully populated 2-D arrays with arbitrary geometries, wide-bandwidth arrays and high-frequency arrays. A CMUT based photoacoustic system is proposed as a viable alternative to a piezoelectric transducer based photoacoustic systems. PMID:19942528

  9. Virus-based piezoelectric energy generation

    NASA Astrophysics Data System (ADS)

    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

    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.

  10. Photoacoustic spectroscopic differences between normal and malignant thyroid tissues

    NASA Astrophysics Data System (ADS)

    Li, Li; Xie, Wengming; Li, Hui

    2012-12-01

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

  11. Functional photoacoustic microscopy

    E-print Network

    Zhang, Hao

    2009-06-02

    in various biomedical applications. Nowadays, the major focus of PAI is on the photoacoustic tomography (PAT), 1,5,6,18,20-23 in which a non-focused ultrasonic detector is used to collect the time-resolved short- pulsed laser induced PA pulses and a... in the field of computer graphics, such as closest-intensity-projection,48 surface rendering, and cross-sectional image along arbitrary plane, 50 which are also applicable to PAM. 2. Imaging of subcutaneous microvasculature in rats In biological tissue...

  12. Quantitative photoacoustic tomography

    PubMed Central

    Yuan, Zhen; Jiang, Huabei

    2009-01-01

    In this paper, several algorithms that allow for quantitative photoacoustic reconstruction of tissue optical, acoustic and physiological properties are described in a finite-element method based framework. These quantitative reconstruction algorithms are compared, and the merits and limitations associated with these methods are discussed. In addition, a multispectral approach is presented for concurrent reconstructions of multiple parameters including deoxyhaemoglobin, oxyhaemoglobin and water concentrations as well as acoustic speed. Simulation and in vivo experiments are used to demonstrate the effectiveness of the reconstruction algorithms presented. PMID:19581254

  13. Series-parallel impedance structure for piezoelectric vibration damping

    Microsoft Academic Search

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

    2002-01-01

    This paper introduces a passive piezoelectric shunt controller, for damping multiple modes of a flexible structure using one piezoelectric transducer. The series-parallel impedance structure has a number of advantages over to previous techniques; it is simpler to implement, requires less passive elements and contains smaller inductors values. The vibration control strategy is validated through experimental work on a piezoelectric laminated

  14. An autonomous piezoelectric shunt damping system

    Microsoft Academic Search

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

    2003-01-01

    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

  15. Optimal impedance design for piezoelectric vibration control

    Microsoft Academic Search

    Andrew J. Fleming; S. O. Reza Moheimani

    2004-01-01

    Piezoelectric transducers are commonly used as strain actuators in the control of mechanical vibration. One control strategy, termed piezoelectric shunt damping, involves the connection of an electrical impedance to the terminals of a structurally bonded transducer. Many passive, nonlinear, and semi-active impedance designs have been proposed that reduce structural vibration. The paper introduces a new technique for the design and

  16. Energy Harvesting From Low Frequency Applications Using Piezoelectric Materials

    SciTech Connect

    Li, Huidong; Tian, Chuan; Deng, Zhiqun

    2014-11-06

    This paper reviewed the state of research on piezoelectric energy harvesters. Various types of harvester configurations, piezoelectric materials, and techniques used to improve the mechanical-to-electrical energy conversion efficiency were discussed. Most of the piezoelectric energy harvesters studied today have focused on scavenging mechanical energy from vibration sources due to their abundance in both natural and industrial environments. Cantilever beams have been the most studied structure for piezoelectric energy harvester to date because of the high responsiveness to small vibrations.

  17. Functional photoacoustic tomography of animal brains

    E-print Network

    Wang, Xueding

    2005-11-01

    This research is primarily focused on laser-based non-invasive photoacoustic tomography of small animal brains. Photoacoustic tomography, a novel imaging modality, was applied to visualize the distribution of optical absorptions in small...

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  19. A method for reducing piezoelectric non-linearity in scanning probe microscope images

    Microsoft Academic Search

    Andrew J. Fleming

    2011-01-01

    This paper describes a new technique for reducing the piezoelectric hysteresis in SPM images. Imaging modes such as constant-force AFM require a piezoelectric actuator to vary the probe-sample distance. In such modes, the topography of the sample is reconstructed from the voltage applied to the vertical piezoelectric actuator. However, piezoelectric actuators exhibit significant hysteresis which can produce up to 14%

  20. Light In and Sound Out: Emerging Translational Strategies for Photoacoustic Imaging

    PubMed Central

    Gambhir, S.S.

    2014-01-01

    Photoacoustic imaging has the potential for real-time molecular imaging at high resolution and deep inside the tissue, using non-ionizing radiation and not necessarily depending on exogenous imaging agents, making this technique very promising for a range of clinical applications. The fact that photoacoustic imaging systems can be made portable and compatible with existing imaging technologies favors clinical translation even more. The breadth of clinical applications in which photoacoustics could play a valuable role include: noninvasive imaging of the breast, sentinel lymph nodes, skin, thyroid, eye, prostate (transrectal), and ovaries (transvaginal); minimally invasive endoscopic imaging of gastrointestinal tract, bladder, and circulating tumor cells (in vivo flow cytometry); and intraoperative imaging for assessment of tumor margins and (lymph node) metastases. In this review we describe the basics of photoacoustic imaging and its recent advances in biomedical research, followed by a discussion of strategies for clinical translation of the technique. PMID:24514041

  1. Near-infrared resonant photoacoustic gas measurement using simultaneous dual-frequency excitation

    NASA Astrophysics Data System (ADS)

    Rey, J. M.; Romer, C.; Gianella, M.; Sigrist, M. W.

    2010-07-01

    The simultaneous dual-frequency operation of a resonant photoacoustic gas sensor based on the differential mode excitation photoacoustic (DME-PA) technique is presented. The DME-PA method uses the excitation of two different modes in a resonant photoacoustic cell and the gas concentration is derived from the amplitude ratio of these acoustic modes. With the simultaneous dual-frequency excitation, the amplitude ratio needed by the DME-PA technique is obtained instantaneously, in contrast to the sequential modulation scheme where additional time delays are introduced by changing the modulation frequency. For a given excitation power reaching the photoacoustic cell, and a total acquisition time longer than 7 s, the simultaneous modulation scheme provides an improved measurement uncertainty compared to the sequential scheme. The proposed sensor allows measuring water vapour with a ±150 ppmV uncertainty using current-modulated near-infrared LEDs and a 15 s total acquisition time.

  2. Prospects of photoacoustic tomography Lihong V. Wanga

    E-print Network

    Wang, Lihong

    than the optical transport mean free path 1 mm in the skin . Photoacoustic tomography, which com- bines tomography of gene expression, 6 Doppler photoacoustic tomography for flow measurement, 7 photoacoustic tomog gene imaging, Doppler effect, metabolic rate of oxygen, sentinel lymph nodes, multiscale imaging

  3. Photoacoustic lifetime imaging of dissolved oxygen using methylene blue

    NASA Astrophysics Data System (ADS)

    Ashkenazi, Shai

    2010-07-01

    Measuring distribution of dissolved oxygen in biological tissue is of prime interest for cancer diagnosis, prognosis, and therapy optimization. Tumor hypoxia indicates poor prognosis and resistance to radiotherapy. Despite its major clinical significance, no current imaging modality provides direct imaging of tissue oxygen. We present preliminary results demonstrating the potential of photoacoustic lifetime imaging (PALI) for noninvasive, 3-D imaging of tissue oxygen. The technique is based on photoacoustic probing of the excited state lifetime of methylene blue (MB) dye. MB is an FDA-approved water soluble dye with a peak absorption at 660 nm. A double pulse laser system (pump probe) is used to excite the dye and probe its transient absorption by detecting photoacoustic emission. The relaxation rate of MB depends linearly on oxygen concentration. Our measurements show high photoacoustic signal contrast at a probe wavelength of 810 nm, where the excited state absorption is more than four times higher than the ground state absorption. Imaging of a simple phantom is demonstrated. We conclude by discussing possible implementations of the technique in clinical settings and combining it with photodynamic therapy (PDT) for real-time therapy monitoring.

  4. Photoacoustic lifetime imaging of dissolved oxygen using methylene blue.

    PubMed

    Ashkenazi, Shai

    2010-01-01

    Measuring distribution of dissolved oxygen in biological tissue is of prime interest for cancer diagnosis, prognosis, and therapy optimization. Tumor hypoxia indicates poor prognosis and resistance to radiotherapy. Despite its major clinical significance, no current imaging modality provides direct imaging of tissue oxygen. We present preliminary results demonstrating the potential of photoacoustic lifetime imaging (PALI) for noninvasive, 3-D imaging of tissue oxygen. The technique is based on photoacoustic probing of the excited state lifetime of methylene blue (MB) dye. MB is an FDA-approved water soluble dye with a peak absorption at 660 nm. A double pulse laser system (pump probe) is used to excite the dye and probe its transient absorption by detecting photoacoustic emission. The relaxation rate of MB depends linearly on oxygen concentration. Our measurements show high photoacoustic signal contrast at a probe wavelength of 810 nm, where the excited state absorption is more than four times higher than the ground state absorption. Imaging of a simple phantom is demonstrated. We conclude by discussing possible implementations of the technique in clinical settings and combining it with photodynamic therapy (PDT) for real-time therapy monitoring. PMID:20799768

  5. Photoacoustic sensor for medical diagnostics

    NASA Astrophysics Data System (ADS)

    Wolff, Marcus; Groninga, Hinrich G.; Harde, Hermann

    2004-03-01

    The development of new optical sensor technologies has a major impact on the progress of diagnostic methods. Of the permanently increasing number of non-invasive breath tests, the 13C-Urea Breath Test (UBT) for the detection of Helicobacter pylori is the most prominent. However, many recent developments, like the detection of cancer by breath test, go beyond gastroenterological applications. We present a new detection scheme for breath analysis that employs an especially compact and simple set-up. Photoacoustic Spectroscopy (PAS) represents an offset-free technique that allows for short absorption paths and small sample cells. Using a single-frequency diode laser and taking advantage of acoustical resonances of the sample cell, we performed extremely sensitive and selective measurements. The smart data processing method contributes to the extraordinary sensitivity and selectivity as well. Also, the reasonable acquisition cost and low operational cost make this detection scheme attractive for many biomedical applications. The experimental set-up and data processing method, together with exemplary isotope-selective measurements on carbon dioxide, are presented.

  6. Photoacoustic imaging with limited diffraction beam transducers

    NASA Astrophysics Data System (ADS)

    Paltauf, Günther; Gratt, Sibylle; Passler, Klaus; Nuster, Robert; Burgholzer, Peter

    2009-02-01

    Photoacoustic imaging with a scanning, fixed focus receiver gives images with high resolution, without the need for reconstruction algorithms. However, the usually employed spherical ultrasound lenses have a limited focal depth that decreases with increasing lateral resolution due to the inverse relation between numerical aperture and Rayleigh length. In this study the use of an axicon detector is proposed, consisting of a conical surface onto which a piezoelectric polymer film is attached. The detector is characterized in simulations and in experiments, demonstrating the expected high resolution over an extended depth of focus. Simulated and experimental images reveal X-shaped artifacts that are due to the conical detector surface. Since the point spread function (PSF) of the detector is spatially invariant over the depth of field, a frequency domain deconvolution can be applied to the images. Although this clearly improves the image quality in simulations, the reduction of artifacts was not so efficient in experiments. However, the detector is able to produce images with accurate position and shape of objects. Moreover, the axicon transducer rejects signals from planar surfaces (e.g. the skin surface) and favors signals from small, isolated sources.

  7. Reverse photoacoustic standoff spectroscopy

    DOEpatents

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

    2011-04-12

    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.

  8. Photoacoustic point spectroscopy

    DOEpatents

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

    2011-06-14

    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.

  9. Photoacoustic tomography and sensing in biomedicine

    PubMed Central

    Li, Changhui; Wang, Lihong V.

    2010-01-01

    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. PMID:19724102

  10. 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)

    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

    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.

  11. Variational Asymptotic Micromechanics Modeling of Heterogeneous Piezoelectric

    E-print Network

    Yu, Wenbin

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

  12. Using Diffusion Bonding in Making Piezoelectric Actuators

    NASA Technical Reports Server (NTRS)

    Sager, Frank E.

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

    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.

  14. Recent advances in photoacoustic endoscopy

    PubMed Central

    Yoon, Tae-Jong; Cho, Young-Seok

    2013-01-01

    Imaging based on photoacoustic effect relies on illuminating with short light pulses absorbed by tissue absorbers, resulting in thermoelastic expansion, giving rise to ultrasonic waves. The ultrasonic waves are then detected by detectors placed around the sample. Photoacoustic endoscopy (PAE) is one of four major implementations of photoacoustic tomography that have been developed recently. The prototype PAE was based on scanning mirror system that deflected both the light and the ultrasound. A recently developed mini-probe was further miniaturized, and enabled simultaneous photoacoustic and ultrasound imaging. This PAE-endoscopic ultrasound (EUS) system can offer high-resolution vasculature information in the gastrointestinal (GI) tract and display differences between optical and mechanical contrast compared with single-mode EUS. However, PAE for endoscopic GI imaging is still at the preclinical stage. In this commentary, we describe the technological improvements in PAE for possible clinical application in endoscopic GI imaging. In addition, we discuss the technical details of the ultrasonic transducer incorporated into the photoacoustic endoscopic probe. PMID:24255745

  15. Contrast Agents for Photoacoustic and Thermoacoustic Imaging: A Review

    PubMed Central

    Wu, Dan; Huang, Lin; Jiang, Max S.; Jiang, Huabei

    2014-01-01

    Photoacoustic imaging (PAI) and thermoacoustic imaging (TAI) are two emerging biomedical imaging techniques that both utilize ultrasonic signals as an information carrier. Unique advantages of PAI and TAI are their abilities to provide high resolution functional information such as hemoglobin and blood oxygenation and tissue dielectric properties relevant to physiology and pathology. These two methods, however, may have a limited detection depth and lack of endogenous contrast. An exogenous contrast agent is often needed to effectively resolve these problems. Such agents are able to greatly enhance the imaging contrast and potentially break through the imaging depth limit. Furthermore, a receptor-targeted contrast agent could trace the molecular and cellular biological processes in tissues. Thus, photoacoustic and thermoacoustic molecular imaging can be outstanding tools for early diagnosis, precise lesion localization, and molecular typing of various diseases. The agents also could be used for therapy in conjugation with drugs or in photothermal therapy, where it functions as an enhancer for the integration of diagnosis and therapy. In this article, we present a detailed review about various exogenous contrast agents for photoacoustic and thermoacoustic molecular imaging. In addition, challenges and future directions of photoacoustic and thermoacoustic molecular imaging in the field of translational medicine are also discussed. PMID:25530615

  16. Application of time-resolved glucose concentration photoacoustic signals based on an improved wavelet denoising

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Liu, Guodong; Huang, Zhen

    2014-10-01

    Real-time monitoring of blood glucose concentration (BGC) is a great important procedure in controlling diabetes mellitus and preventing the complication for diabetic patients. Noninvasive measurement of BGC has already become a research hotspot because it can overcome the physical and psychological harm. Photoacoustic spectroscopy is a well-established, hybrid and alternative technique used to determine the BGC. According to the theory of photoacoustic technique, the blood is irradiated by plused laser with nano-second repeation time and micro-joule power, the photoacoustic singals contained the information of BGC are generated due to the thermal-elastic mechanism, then the BGC level can be interpreted from photoacoustic signal via the data analysis. But in practice, the time-resolved photoacoustic signals of BGC are polluted by the varities of noises, e.g., the interference of background sounds and multi-component of blood. The quality of photoacoustic signal of BGC directly impacts the precision of BGC measurement. So, an improved wavelet denoising method was proposed to eliminate the noises contained in BGC photoacoustic signals. To overcome the shortcoming of traditional wavelet threshold denoising, an improved dual-threshold wavelet function was proposed in this paper. Simulation experimental results illustrated that the denoising result of this improved wavelet method was better than that of traditional soft and hard threshold function. To varify the feasibility of this improved function, the actual photoacoustic BGC signals were test, the test reslut demonstrated that the signal-to-noises ratio(SNR) of the improved function increases about 40-80%, and its root-mean-square error (RMSE) decreases about 38.7-52.8%.

  17. Improved Open Photoacoustic Helmholtz Cell

    NASA Astrophysics Data System (ADS)

    Starecki, Tomasz; Geras, Antonina

    2014-11-01

    This paper presents the design of an open photoacoustic Helmholtz cell in which high acoustic volumes with quarter-wave ducts act as high-impedance separators between the main Helmholtz cell structure and the exterior. As a result, penetration of the external acoustic noise into the cell was substantially reduced in comparison to earlier open Helmholtz cell designs. Although the presented cell is not windowless, the photoacoustic background signal resulting from the absorption of the light by the windows is significantly lower in comparison to standard Helmholtz cells. Such an effect was obtained by locating the windows not at the relatively small sample cavity, but at the acoustic buffers, for which the volumes are two orders of magnitude higher. The proposed cell is dedicated for gas or liquid measurements, and its design allows for constant flow of the fluid. Hence, it can be used in continuous, real-time photoacoustic measurements.

  18. Photoacoustic tomography with integrating fiber-based annular detectors

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    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 expansion launches broadband ultrasonic waves. Usually point like piezo-electric detectors are used. Our group introduced integrating detectors a few years ago. This type of detector integrates the pressure at least along one dimension. Integrating line detectors, which integrate the pressure along one dimension, can be realized by using either free-beam or fiber-based interferometers. The latter approach also allows other detector shapes than a line. In this paper we use a fiber-based annular detector for tomography. Thereby the sample is rotated inside the annular detector on a position different from the symmetry axis of the annular detector. Hence the sample is enclosed by the detector and all data from one plane are collected at once. By moving the detector parallel to the symmetrie axis of the ring one can acquire data for a 3D image reconstruction. Therfore, tomography can be performed with only one rotation axis and one translation axis. For image reconstruction a novel algorithm is necessary which was tested on simulated data. Here we present an imaging setup using such a fiber-based annular detector. First measurements of simple structures and subsequent image reconstruction from these real data are shown in this paper.

  19. Photoacoustic spectroscopy application in diffusion examinations

    NASA Astrophysics Data System (ADS)

    Bodzenta, Jerzy; Hanh, Bui Duc; Kazmierczak, Anna; Neubert, Reinhard H. H.; Wartewig, Siegfrid

    2005-09-01

    Based on Fick's second law the problem of drug diffusion into a membrane was solved. Spatial and time dependent distribution of the drug in the membrane was described analytically. Comparison of obtained solution with experimental results from infrared attenuated total reflectance studies of dithranol diffusion into the dodecanol-collodion membrane confirmed correctness of the theory. Based on a model describing the concentration of diffusing matter it was possible to calculate numerically the photoacoustic signal arising when the membrane was illuminated by modulated light. Detailed numerical analysis showed that photoacoustic spectroscopy (PAS) can be used in experimental investigation of diffusion, but some limitations connected with optical parameters of diffusing matter and the membrane must be taken into account. Proposed mathematical model was used for interpretation of experimental data from "classical" PAS measurement in UV range and step-scan Fourier-transform infrared PAS. Experiments were carried out for diffusion of: dithranol, ketoconazole and methoxalen. Using a multiparameter fitting procedure one has determined diffusion coefficient of enumerated drugs in dodecanol-collodion membrane. Obtained results confirmed usability of PAS technique for studies of diffusion processes.

  20. Label-free photoacoustic microscopy of cytochromes

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

  1. Piezoelectric Ultrasonic Micromotors

    E-print Network

    Flynn, Anita M.

    1995-06-01

    This report describes development of micro-fabricated piezoelectric ultrasonic motors and bulk-ceramic piezoelectric ultrasonic motors. Ultrasonic motors offer the advantage of low speed, high torque operation without ...

  2. In-situ determination of concentration and degree of oxygenation of hemoglobin in neural tissue by pulsed photoacoustic spectroscopy

    Microsoft Academic Search

    Raul Fainchtein; Basil J. Stoyanov; John C. Murphy; David A. Wilson; Daniel F. Hanley

    1997-01-01

    Pulsed-photoacoustic spectroscopy (PPAS) is an in-situ technique used for quantitative monitoring of brain-tissue hemoglobin concentration and its oxygenation state. In contrast to most spectroscopic techniques that measure infrared absorption PPAS does not require knowledge of the pathlength of light traveling through tissues in order to determine the absorption coefficient and hence the concentration of absorbing species. The photoacoustic response (PAR)

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

    PubMed Central

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

    2014-01-01

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

  4. Photoacoustic probe for spectroscopic measurements in condensed matter: convenient and corrosion-resistant.

    PubMed

    Lai, E P; Voigtman, E; Winefordner, J D

    1982-09-01

    A simple effective photoacoutic probe employing the acoustic waveguide effect in quartz substrate is described. The photoacoustic probe consists of a quartz rod to the upper end of which a PZT-5A piezoelectric ceramic disk is attached. The probe was used in the acquisition of a dye-laser-excited photoacoustic spectrum of 10-microg/ml 9,10-dimethylanthracene in ethanol at room temperature. With the probe system, the spectrum was found to be essentially identical with the corresponding spectra obtained with a standard cuvette cell/attached PZT disk and a cylindrical cell/attached PZT tube detection systems; the observed relative sensitivities were 1.6:1.0:4.4, respectively. PMID:20396188

  5. Piezoelectric drive circuit

    DOEpatents

    Treu, C.A. Jr.

    1999-08-31

    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.

  6. Piezoelectric drive circuit

    DOEpatents

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

    1999-08-31

    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. "Mighty Worm" Piezoelectric Actuator

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    "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.

  8. Researchers at the Texas A&M University have developed a new method for using the photoacoustic effect to create images. The technique allows for functional imaging of oxy and

    E-print Network

    Wang, Lihong

    Laboratory in College Station, Tex. The photoacoustic effect is an ultrasonic wave created when tissue the tissue as a sound wave that can be detected by ultrasonic transducers. "Since ultrasonic waves are much light on the tissue. Then, they listen to the ultrasonic wave and use that to create an image

  9. Multi-contrast photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Hu, S.; Sohn, R.; Lu, Z.-H.; Soetikno, B.; Zhong, Q.; Yao, J.; Maslov, K.; Arbeit, J. M.; Wang, L. V.

    2012-02-01

    We developed multi-contrast photoacoustic microscopy (PAM) for in vivo anatomical, functional, metabolic, and molecular imaging. This technical innovation enables comprehensive understanding of the tumor microenvironment. With multi-contrast PAM, we longitudinally determined tumor vascular anatomy, blood flow, oxygen saturation of hemoglobin, and oxygen extraction fraction.

  10. Time reversal in photoacoustic tomography and levitation in a cavity

    NASA Astrophysics Data System (ADS)

    Palamodov, V. P.

    2014-12-01

    A class of photoacoustic acquisition geometries in {{{R}}n} is considered such that the spherical mean transform admits an exact filtered back projection reconstruction formula. The reconstruction is interpreted as a time reversion mirror that reproduces exactly an arbitrary source distribution in the cavity. A series of examples of non-uniqueness of the inverse potential problem is constructed based on the same geometrical technique.

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

    PubMed Central

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

    2009-01-01

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

  12. Acoustic resonance phase locked photoacoustic spectrometer

    DOEpatents

    Pilgrim, Jeffrey S.; Bomse, David S.; Silver, Joel A.

    2003-08-19

    A photoacoustic spectroscopy method and apparatus for maintaining an acoustic source frequency on a sample cell resonance frequency comprising: providing an acoustic source to the sample cell to generate a photoacoustic signal, the acoustic source having a source frequency; continuously measuring detection phase of the photoacoustic signal with respect to source frequency or a harmonic thereof; and employing the measured detection phase to provide magnitude and direction for correcting the source frequency to the resonance frequency.

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

    E-print Network

    Ramadass, Yogesh Kumar

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

  14. High Power Piezoelectric Characterization for Piezoelectric Transformer Development

    NASA Astrophysics Data System (ADS)

    Ural, Seyit O.

    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

  15. Photoacoustic tomography of a rat cerebral cortex

    E-print Network

    Wang, Lihong

    detector; ring detector; photoacoustic imaging; small animal imaging; aperture effect; resolution; signal depth because the pure optical imaging methods are limited by the extinction coefficient of light

  16. Photoacoustic signal amplification through plasmonic nanoparticle aggregation

    PubMed Central

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

    2013-01-01

    Abstract. Photoacoustic imaging, using targeted plasmonic metallic nanoparticles, is a promising noninvasive molecular imaging method. Analysis of the photoacoustic signal generated by plasmonic metallic nanoparticles is complex because of the dependence upon physical properties of both the nanoparticle and the surrounding environment. We studied the effect of the aggregation of gold nanoparticles on the photoacoustic signal amplitude. We found that the photoacoustic signal from aggregated silica-coated gold nanoparticles is greatly enhanced in comparison to disperse silica-coated gold nanoparticles. Because cellular uptake and endocytosis of nanoparticles results in their aggregation, these results have important implications for the application of plasmonic metallic nanoparticles towards quantitative molecular imaging. PMID:23288414

  17. Fluoropolymer and aluminum piezoelectric reactives

    NASA Astrophysics Data System (ADS)

    Janesheski, Robert S.; Groven, Lori J.; Son, Steven

    2012-03-01

    The ability to sensitize a nanoaluminum/piezoelectric polymer composite has been studied using two fluoropolymer systems (THV220A and FC-2175). Reactive composite samples of the nanoaluminum/polymer were made into thin sheets and their ability to store energy and exhibit piezoelectric properties was measured. Also, initial drop weight impact tests were performed on the samples and results showed the piezoelectric energetic composites failed to ignite at a given impact energy unless sensitized. When a DC voltage was applied to the sample, the materials ignited at the same impact energy where previous ignition failed. Results indicate that the reactive composites may have been sensitized by storing the applied charge. The application of a DC voltage may also have an effect on the piezoelectric properties of the energetic composites similar to the way poling techniques work. Further work is planned to investigate what parameters are inducing the sensitization of the material. A better understanding could lead to applications where switching or tuning the sensitization of an energetic material is beneficial.

  18. Intracavity quartz-enhanced photoacoustic sensor

    SciTech Connect

    Borri, S., E-mail: simone.borri@ino.it; Galli, I.; Mazzotti, D.; Giusfredi, G.; De Natale, P. [CNR-INO UOS Sesto Fiorentino and LENS, via Carrara 1, 50019 Sesto Fiorentino FI (Italy); Patimisco, P.; Scamarcio, G.; Spagnolo, V. [CNR-IFN UOS Bari and Dipartimento Interateneo di Fisica, Università degli Studi di Bari e Politecnico di Bari, via Amendola 173, 70126 Bari BA (Italy); Akikusa, N. [Development Bureau Laser Device R and D Group, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan); Yamanishi, M. [Central Research Laboratories, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan)

    2014-03-03

    We report on a spectroscopic technique named intracavity quartz-enhanced photoacoustic spectroscopy (I-QEPAS) employed for sensitive trace-gas detection in the mid-infrared spectral region. It is based on a combination of QEPAS with a buildup optical cavity. The sensor includes a distributed feedback quantum cascade laser emitting at 4.33??m. We achieved a laser optical power buildup factor of ?500, which corresponds to an intracavity laser power of ?0.75?W. CO{sub 2} has been selected as the target molecule for the I-QEPAS demonstration. We achieved a detection sensitivity of 300 parts per trillion for 4?s integration time, corresponding to a noise equivalent absorption coefficient of 1.4?×?10{sup ?8}?cm{sup ?1} and a normalized noise-equivalent absorption of 3.2?×?10{sup ?10} W cm{sup ?1}?Hz{sup ?1/2}.

  19. Photoacoustic spectroscopy of standard explosives in the MIR region

    NASA Astrophysics Data System (ADS)

    Giubileo, Gianfranco; Puiu, Adriana

    2010-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

    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.

  1. Amplitude-masked photoacoustic wavefront shaping and application in flowmetry

    PubMed Central

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

    2014-01-01

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

  2. Multi-spectral photoacoustic mapping of bacteriochlorins diffusing through the skin: exploring a new PAT contrast agent

    NASA Astrophysics Data System (ADS)

    Schaberle, Fábio A.; Reis, Luis A. F.; Sá, Gonçalo F. F.; Serpa, Carlos; Abreu, Artur R.; Pereira, Mariette M.; Arnaut, Luis G.

    2011-07-01

    A skin depth map was built reconstructing photoacoustic signals at several wavelengths of visible and infrared light. The mapping technique was used to follow the diffusion through the skin of near-infrared absorbing dyes. Such dyes can be useful for photodynamic therapy (PDT) of skin lesions and are investigated as contrast agents for photoacoustic tomography (PAT), because they strongly absorb light at wavelengths where the skin is more transparent.

  3. Combined photoacoustic and magneto-motive ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Qu, Min; Kim, Seungsoo; Mehrmohammadi, Mohammad; Mallidi, Srivalleesha; Joshi, Pratixa; Homan, Kimberly; Chen, Yun-Sheng; Emelianov, Stanislav

    2010-02-01

    Ultrasound imaging can provide excellent resolution at reasonable depths while retaining the advantages of being nonionizing, cost-effective and portable. However, the contrast in ultrasound imaging is limited, and various ultrasoundbased techniques such as photoacoustic (PA) and magneto-motive ultrasound (MMUS) imaging have been developed to augment ultrasound imaging. Photoacoustic imaging enhances imaging contrast by visualizing the optical absorption of either tissue or injected contrast agents (e.g., gold or silver nanoparticles). MMUS imaging enhances the sensitivity and specificity of ultrasound based on the detection of magnetic nanoparticles perturbed by an external magnetic field. This paper presents integrated magneto-photo-acoustic (MPA) imaging - a fusion of complementary ultrasound-based imaging techniques. To demonstrate the feasibility of MPA imaging, porcine ex-vivo tissue experiments were performed using a dual contrast (magnetic/plasmonic) agent. Spatially co-registered and temporally consecutive ultrasound, photoacoustic, and magneto-motive ultrasound images of the same cross-section of tissue were obtained. Our ex-vivo results indicate that magneto-photo-acoustic imaging can be used to detect magnetic/plasmonic nanoparticles with high resolution, sensitivity and contrast. Therefore, our study suggests that magneto-photo-acoustic images can identify the morphological properties, molecular information and complementary functional information of the tissue.

  4. Imaging of gene expression in vivo with photoacoustic tomography

    NASA Astrophysics Data System (ADS)

    Li, Li; Zemp, Roger J.; Lungu, Gina; Stoica, George; Wang, Lihong V.

    2006-02-01

    In the post-genomic era, there is an increasing interest in visualizing the expression of functional genes in vivo. With the assistance of the reporter gene technique, various imaging modalities have been adopted for this purpose. In vivo gene expression imaging promises to provide biologists with a powerful tool for deepening our understanding of developmental biology, expanding our knowledge of the genetic basis of disease, and advancing the development of medicine. In this paper, we demonstrate the feasibility of imaging gene expression with photoacoustic imaging, which offers unique absorption contrast with ultrasonic resolution in vivo. We mark tumors in rats with the lacZ reporter gene. The lacZ gene encodes an enzyme ?-galactosidase, which yields a dark blue product when acting on a colorimetric assay called X-gal. Photoacoustic tomography at 650nm clearly visualizes the presence of this blue product. The spectroscopic method can also potentially improve specificity. Considering how many staining methods are used in traditional biology, we believe that photoacoustic techniques will revolutionize the field of molecular imaging. The further development of reporter gene systems with high absorbing products in the NIR region is needed.

  5. Piezoelectric immunosensors -- Theory and applications

    SciTech Connect

    O`Sullivan, C.K.; Vaughan, R.; Guilbault, G.G. [Univ. Coll. Cork (Ireland). Dept. of Chemistry

    1999-09-01

    A Mini Review of recent advances in piezoelectric immunobiosensors is presented. First a review of the theory and history of the technique is given, followed by a critical survey of the use of this method in various fields of analysis. A biosensor can be defined as a device incorporating biological material connected to or integrated within a transducer. The specificity and sensitivity is complemented by the transducer, which electronically measures and computes the signal.

  6. Harvesting Raindrop Energy with Piezoelectrics: a Review

    NASA Astrophysics Data System (ADS)

    Wong, Chin-Hong; Dahari, Zuraini; Abd Manaf, Asrulnizam; Miskam, Muhammad Azman

    2015-01-01

    Harvesting vibration energy from piezoelectric material impacted by raindrops has proved to be a promising approach for future applications. A piezoelectric harvester has interesting advantages such as simple structure, easy fabrication, reduced number of components, and direct conversion of vibrations to electrical charge. Extensive research has been carried out and is still underway to explore this technique for practical applications. This review provides a comprehensive picture of global research and development of raindrop energy harvesting using piezoelectric material to enable researchers to determine the direction of further investigation. The work published so far in this area is reviewed and summarized with relevant suggestions for future work. In addition, a brief experiment was carried out to investigate the suitable piezoelectric structure for raindrop energy harvesting. Results showed that the bridge structure generated a higher voltage compared with the cantilever structure.

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

    PubMed Central

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

    2013-01-01

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

  8. A piezoelectric transformer

    NASA Technical Reports Server (NTRS)

    Won, C. C.

    1993-01-01

    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.

  9. Determination of dynamic young's modulus, shear modulus, and poisson's ratio as a function of temperature for depleted Uranium-0.75 wt% Titanium using the piezoelectric ultrasonic composite oscillator technique

    NASA Astrophysics Data System (ADS)

    Keene, K. H.; Hartman, J. T.; Wolfenden, A.; Ludtka, G. M.

    1987-07-01

    Dynamic Young's modulus ( E) and shear modulus ( G) measurements were performed for three microstructures (gamma, alpha + delta, and alpha prime) of a depleted uranium-0.75 wt% titanium alloy. Measurements were made from 298 to 1123 K. From the measured values of E and G, values were obtained for Poisson's ratio (PR). The experimental apparatus was the piezoelectric ultrasonic composite oscillator technique (PUCOT) at 40 or 80 kHz. The ranges of values for E, G, and PR were 193 to 99 GPa, 81 to 35 GPa, and 0.17 to 0.56, respectively. Correlations for E, G, and PR as functions of temperature are presented.

  10. Sono-photoacoustic imaging of gold nanoemulsions: Part I. Exposure thresholds

    PubMed Central

    Arnal, Bastien; Perez, Camilo; Wei, Chen-Wei; Xia, Jinjun; Lombardo, Michael; Pelivanov, Ivan; Matula, Thomas J.; Pozzo, Lilo D.; O’Donnell, Matthew

    2015-01-01

    Integrating high contrast bubbles from ultrasound imaging with plasmonic absorbers from photoacoustic imaging is investigated. Nanoemulsion beads coated with gold nanopsheres (NEB-GNS) are excited with simultaneous light (transient heat at the GNS's) and ultrasound (rarefactional pressure) resulting in a phase transition achievable under different scenarios, enhancing laser-induced acoustic signals and enabling specific detection of nanoprobes at lower concentration. An automated platform allowed dual parameter scans of both pressure and laser fluence while recording broadband acoustic signals. Two types of NEB-GNS and individual GNS were investigated and showed the great potential of this technique to enhance photoacoustic/acoustic signals. The NEB-GNS size distribution influences vaporization thresholds which can be reached at both permissible ultrasound and light exposures at deep penetration and at low concentrations of targets. This technique, called sono-photoacoustics, has great potential for targeted molecular imaging and therapy using compact nanoprobes with potentially high-penetrability into tissue.

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

    PubMed Central

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

    2013-01-01

    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. PMID:24298407

  12. A photoacoustic study of adsorption

    NASA Astrophysics Data System (ADS)

    Melander, N.; Henningsen, J.

    1999-03-01

    Adsorption is a serious source of systematic error in trace gas monitoring at low concentrations. We present the results of a photoacoustic study of the adsorption of ammonia on a number of materials such as pyrex, quartz, stainless steel, teflon PTFE and teflon PFA. The results are interpreted in terms of the Langmuir model, and conclusions are validated by thermal desorption experiments. Pyrex shows the lowest adsorption whereas stainless steel has extremely undesirable properties.

  13. Coherent photoacoustic-ultrasound correlation and imaging.

    PubMed

    Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin

    2014-09-01

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

  14. Photoacoustic Spectroscopy Analysis of Traditional Chinese Medicine

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  15. Characterization of novel molecular photoacoustic contrast agents for in vivo photoacoustic tomography

    NASA Astrophysics Data System (ADS)

    Laoui, Samir

    Photoacoustic tomography is a hybrid imaging modality that takes advantage of the high contrast of pure optical imaging and the high intrinsic resolution of ultrasound without the necessity of ionizing radiation. Photoacoustic imaging (PM) is neither purely optical nor purely acoustical in nature, but a combination of the two. It is fundamentally based on light excitation and ultrasonic detection. Photoacoustic imaging has been successful without the introduction of exogenous contrast agents; however, to image deeper regions of biological tissue, a contrast agent is necessary. Several types of photoacoustic contrast agents have been made available for diagnostic purposes; however, the majority of literature has focused on gold nanoparticle systems for which the surface-plasmon resonance effect is important. The only option currently available for molecular PM contrast agents is to choose an existing near infrared absorbing fluorescent probes with the hope that they may generate a substantial photoacoustic (PA) response. However, these dyes have been designed with an optimized fluorescence emission response and are not anticipated to generate an adequate photoacoustic response. This dissertation addresses this lack of precedence in the literature for understanding the mechanism of a photoacoustic signal generation from strongly absorbing dye molecules including BODIPY, cyanine and curcumin systems. This work represents preliminary efforts in bringing novel molecular photoacoustic contrast agents (MPACs) into the photoacoustic imaging arena. To this end, photoacoustic and optical Z-scan experiments, and quenching studies were employed to demonstrate correlation of photoacoustic emission enhancement with excited state absorption mechanisms. To investigate further the photoacoustic emission in a practical imaging setting, MPACs were imaged using a recently developed photoacoustic imaging tomography system which was constructed exclusively for the purpose of this study.

  16. Potential for photoacoustic imaging of the neonatal brain

    NASA Astrophysics Data System (ADS)

    Tavakolian, Pantea; Kosik, Ivan; Chamson-Reig, Astrid; St. Lawrence, Keith; Carson, Jeffrey J. L.

    2013-03-01

    Photoacoustic imaging (PAI) has been proposed as a non-invasive technique for imaging neonatal brain injury. Since PAI combines many of the merits of both optical and ultrasound imaging, images with high contrast, high resolution, and a greater penetration depth can be obtained when compared to more traditional optical methods. However, due to the strong attenuation and reflection of photoacoustic pressure waves at the skull bone, PAI of the brain is much more challenging than traditional methods (e.g. near infrared spectroscopy) for optical interrogation of the neonatal brain. To evaluate the potential limits the skull places on 3D PAI of the neonatal brain, we constructed a neonatal skull phantom (1.4-mm thick) with a mixture of epoxy and titanium dioxide powder that provided acoustic insertion loss (1-5MHz) similar to human infant skull bone. The phantom was molded into a realistic infant skull shape by means of a CNCmachined mold that was based upon a 3D CAD model. To evaluate the effect of the skull bone on PAI, a photoacoustic point source was raster scanned within the phantom brain cavity to capture the imaging operator of the 3D PAI system (128 ultrasound transducers in a hemispherical arrangement) with and without the intervening skull phantom. The resultant imaging operators were compared to determine the effect of the skull layer on the PA signals in terms of amplitude loss and time delay.

  17. Characterization of seeds with different moisture content by photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Domínguez Pacheco, Arturo; Hernández Aguilar, Claudia; Cruz-Orea, Alfredo; Martínez Ortiz, Efraín; Ayala-Maycotte, Esther

    2010-03-01

    Photoacoustic (PA) technique has important applications for material characterization and nondestructive evaluation of opaque solid materials. PA microscopy allows the acquisition of information of samples with inhomogeneous structures as agricultural seeds. A determining factor for seed safe storage is their moisture content. Seeds stored at high moisture content exhibit increased respiration, heating, and fungal invasion resulting in poor seed vigor and viability. Low moisture content, in the seed to be stored, is the best prevention for these problems. In this study, Photoacoustic Microscopy (PAM) was used to characterize seeds with different moisture content. In the PAM experimental setup the photoacoustic cell and its sensor, an electret microphone, are mounted on an x-y stage of mobile axes, with spatial resolution of 70 ?m. The excitation light source is a fiber coupled laser diode, at 650 nm wavelength, modulated in intensity at 1 Hz of frequency, by the reference oscillator of a lock-in amplifier. By using a microscope objective the laser beam was focused on the seed surface. The resolution was enough to obtain differences in the obtained images, which are dependent on the moisture content. This method, to study differences in the seed moisture content, is nondestructive and could be useful for a sustainable Agriculture.

  18. Photoacoustic tomography of ex vivo mouse hearts with myocardial infarction

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    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.

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

    PubMed

    Wagner, Maximilian E H; Rana, Majeed; Traenkenschuh, Wolfgang; Kokemueller, Horst; Eckardt, André M; Gellrich, Nils-Claudius

    2011-01-01

    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. PMID:22040611

  20. High-Performance Control of Piezoelectric Tube Scanners

    Microsoft Academic Search

    B.. Bhikkaji; M.. Ratnam; Andrew J. Fleming; S. O. Reza Moheimani

    2007-01-01

    In this paper, a piezoelectric tube of the type typically used in scanning tunneling microscopes (STMs) and atomic force microscopes (AFMs) is considered. Actuation of this piezoelectric tube is hampered by the presence of a lightly damped low-frequency resonant mode. The resonant mode is identified and damped using a positive velocity and position feedback (PVPF) controller, a control technique proposed

  1. Synthesis of optimal piezoelectric shunt impedances for structural vibration control

    Microsoft Academic Search

    Andrew J. Fleming; S. O. Reza Moheimani

    2004-01-01

    Piezoelectric transducers are commonly used as strain actuators in the control of mechanical vibration. One control strategy, termed piezoelectric shunt damping, involves the connection of an electrical impedance to the terminals of a structurally bonded transducer. Many passive, non-linear, and semi-active impedance designs have been proposed that reduce structural vibration. This paper introduces a new technique for the design and

  2. Synthesis of optimal piezoelectric shunt impedances for structural vibration control

    Microsoft Academic Search

    Andrew J. Fleming; S. O. Reza Moheimani

    Piezoelectric transducers are commonly used as strain actuators in the control of mechanical vibration. One control strategy, termed piezoelectric shunt damping, involves the connection of an electrical impedance to the terminals of a structurally bonded transducer. Many passive, non-linear, and semi-active impedance designs have been proposed that reduce structural vibration. This paper introduces a new technique for the design and

  3. Sensorless vibration suppression and scan compensation for piezoelectric tube nanopositioners

    Microsoft Academic Search

    Andrew J. Fleming; S. O. Reza Moheimani

    2006-01-01

    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

  4. Structural multi-modal damping by optimizing shunted piezoelectric transducers

    Microsoft Academic Search

    Stéphanie Livet; Manuel Collet; Marc Berthillier; Pierrick Jean; Jean-Marc Cote

    2011-01-01

    The capacity of different auto-supplied devices using shunted piezoelectric circuits are studied here to improve structural damping by avoiding implementation of complex and heavy control devices. The presented technique uses a dedicated numerical piezo-mechanical model combining both mechanical and electrical coupling parameters. An original methodology are also introduced for optimizing the parameters of electrical shunt circuits connected to piezoelectric elements

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

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Liu, Guodong; Huang, Zhen

    2014-09-01

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

  6. Gold nano-rods as a targeting contrast agent for photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Agarwal, A.; Huang, S.-W.; Day, K. C.; O'Donnell, M.; Day, M.; Kotov, N.; Ashkenazi, S.

    2007-02-01

    We have studied the potential of gold nanorods to target cancer cells and provide contrast for photoacoustic imaging. The elongated "rod" shape of these nanoparticles provides a mechanism to tune their plasmon peak absorption wavelength. The absorption peak is shifted to longer wavelengths by increasing the aspect ratio of the rods. Particles 15 nm in diameter and 45 nm long were prepared using a seed mediated growth method. Their plasmon absorption peak was designed to be at 800 nm for increased penetration depth into biological tissue. They were conjugated with a specific antibody to target prostate cancer cells. We have applied photoacoustics to image a prostate cell culture targeted by conjugated gold particles. Images confirm the efficiency of conjugated particle binding to the targeted cell membranes. Photoacoustic detection of a single cell layer is demonstrated. To evaluate the applicability of the technique to clinical prostate cancer detection, we have imaged phantom objects mimicking a real tissue with small (2 mm size) inclusions of nanoparticle gel solution. Our photoacoustic imaging setup is based on a modified commercial ultrasonic scanner which makes it attractive for fast implementation in cancer diagnosis in clinical application. In addition, the setup allows for dual mode operation where a photoacoustic image is superimposed on a conventional B-mode ultrasound image. Dual mode operation is demonstrated by imaging a mouse with gold nanorod gel solution implanted in its hind limb.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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.

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

    PubMed Central

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

    2014-01-01

    Abstract. 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. PMID:24395586

  10. Adaptive piezoelectric shunt damping

    Microsoft Academic Search

    Andrew J. Fleming; S. O. Reza Moheimani

    2002-01-01

    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

  11. Active piezoelectric damping composites

    Microsoft Academic Search

    A. Baz; A. Tempia

    2004-01-01

    Patches of active piezoelectric damping composites (APDC) consisting of piezoelectric rods, which are obliquely embedded across the thickness of viscoelastic damping matrix, are presented as a viable candidate for smart actuation. In this configuration, activation of the piezo-rods simultaneously enhances both the shear and compression damping characteristics of the smart composite actuator. With such active\\/passive capabilities, the APDC presents an

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

    PubMed Central

    Yao, Lei; Jiang, Huabei

    2011-01-01

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

  13. Photoacoustic measurements of the thermal conductivity of some bulk polymer samples

    NASA Astrophysics Data System (ADS)

    Madhusoodanan, K. N.; Thomas, Mini R.; Philip, Jacob

    1987-08-01

    Thermal parameters such as thermal diffusivity and thermal conductivity of the polymers nylon 66, cellulose acetate, polyacetal, Teflon, and polystyrene have been determined using the photoacoustic technique. Samples having thickness of the order of 25-50 ?m have been specially prepared from bulk solid samples for measurements. The experimental method involves the determination of the characteristic frequency fc by measuring the variation of the amplitude and phase of the photoacoustic signal as a function of the chopping frequency for a monochromatic incident beam. Front surface illumination geometry has been used in the measurements. The measured thermal properties agree with the existing values in literature.

  14. Image reconstruction in quantitative photoacoustic tomography using the radiative transfer equation and the diffusion approximation

    NASA Astrophysics Data System (ADS)

    Tarvainen, Tanja; Pulkkinen, Aki; Cox, Ben T.; Kaipio, Jari P.; Arridge, Simon R.

    2013-06-01

    Quantitative photoacoustic tomography is an emerging imaging technique aiming at estimating the distribution of optical parameters inside tissue from photoacoustic image which is formed by combining optical information and ultrasound propagation. In this paper reconstruction of absorption and scattering distributions using the radiative transfer equation and the diffusion approximation as forward models for light propagation is investigated. Data is simulated using Monte Carlo method and different size target domains are considered. The results show that the radiative transfer equation can estimate both absorption and scattering distributions with good accuracy. Furthermore, in the simulated test cases, the diffusion approximation can produce as good estimates for absorption as the radiative transfer equation.

  15. Quartz enhanced photoacoustic spectroscopy with a 3.38 ?m antimonide distributed feedback laser.

    PubMed

    Jahjah, Mohammad; Belahsene, Sofiane; Nähle, Lars; Fischer, Marc; Koeth, Johannes; Rouillard, Yves; Vicet, Aurore

    2012-07-01

    A system for gas sensing based on the quartz-enhanced photoacoustic spectroscopy technique has been developed. It makes use of a quantum well distributed feedback (DFB) laser diode emitting at 3.38 ?m. This laser emits near room temperature in the continuous wave regime. A spectrophone, consisting of a quartz tuning fork and two steel microresonators were used. Second derivative wavelength modulation detection is used to perform low concentration measurements. The sensitivity and the linearity of the Quartz enhanced photoacoustic spectroscopy (QEPAS) sensor were studied. A normalized noise equivalent absorption coefficient of 4.06×10(-9) cm(-1)·W/Hz(1/2) was achieved. PMID:22743435

  16. Structural, optical and photoacoustic study of milled and melted Bi2Se3

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  17. Intravascular photoacoustic imaging of exogenously labeled atherosclerotic plaque through luminal blood

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  18. Realtime photoacoustic microscopy of murine cardiovascular and respiratory dynamics in vivo

    NASA Astrophysics Data System (ADS)

    Zemp, Roger J.; Song, Liang; Bitton, Rachel; Shung, K. Kirk; Wang, Lihong V.

    2008-02-01

    While photoacoustic imaging has emerged as a promising modality in recent years, a key drawback of practical and widespread use of the technique has been slow imaging rates. We present a 30-MHz array-based photoacoustic imaging system that can acquire and display photoacoustic images in realtime. Realtime display is very helpful and provides the system operator the ability to better navigate and position the probe for selecting a desired anatomical field of view. The system is capable of imaging at 50 frames per second to depths of a few mm in tissue. We used this system to successfully image the beating hearts of young athymic nude mice in vivo. Also of interest was the ability to visualize microvascular changes during respiration.

  19. Photoacoustic signal measurement for burned skins in the spectral range of 500-650 nm: experiment with rat burn models

    NASA Astrophysics Data System (ADS)

    Yamazaki, Mutsuo; Sato, Shunichi; Saito, Daizo; Fujita, Masanori; Okada, Yoshiaki; Kikuchi, Makoto; Ashida, Hiroshi; Obara, Minoru

    2002-06-01

    This paper reports the burn diagnosis that is based on the measurement of photoacoustic waves from skin, where the acoustic waves originate from the absorption of light by blood. For this purpose, a transducer composed of a ring-shaped piezoelectric film and a quartz fiber was made. An optical parametric oscillator (500 - 650 nm) was used as a light source and its output pulses were coupled to the quartz fiber. To investigate the optimum light wavelength, we conducted experiments using rat burn models. We demonstrated that the superficial dermal burn (SDB), deep dermal burn (DDB), deep burn (DB), and control (healthy skin) could be clearly differentiated based on the photoacoustic signals induced by the light of 532 - 580nm.

  20. Energy harvesting from low frequency applications using piezoelectric materials

    NASA Astrophysics Data System (ADS)

    Li, Huidong; Tian, Chuan; Deng, Z. Daniel

    2014-12-01

    In an effort to eliminate the replacement of the batteries of electronic devices that are difficult or impractical to service once deployed, harvesting energy from mechanical vibrations or impacts using piezoelectric materials has been researched over the last several decades. However, a majority of these applications have very low input frequencies. This presents a challenge for the researchers to optimize the energy output of piezoelectric energy harvesters, due to the relatively high elastic moduli of piezoelectric materials used to date. This paper reviews the current state of research on piezoelectric energy harvesting devices for low frequency (0-100 Hz) applications and the methods that have been developed to improve the power outputs of the piezoelectric energy harvesters. Various key aspects that contribute to the overall performance of a piezoelectric energy harvester are discussed, including geometries of the piezoelectric element, types of piezoelectric material used, techniques employed to match the resonance frequency of the piezoelectric element to input frequency of the host structure, and electronic circuits specifically designed for energy harvesters.

  1. Photoacoustic phasoscopy super-contrast imaging

    SciTech Connect

    Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin, E-mail: yjzheng@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2014-05-26

    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.

  2. Photoacoustic phasoscopy super-contrast imaging

    NASA Astrophysics Data System (ADS)

    Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin

    2014-05-01

    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.

  3. Photoacoustic resonance spectroscopy for biological tissue characterization

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  4. Magnetocaloric piezoelectric composites for energy harvesting

    NASA Astrophysics Data System (ADS)

    Cleveland, Michael; Liang, Hong

    2012-04-01

    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).

  5. Investigational detection of pharmacological agents in the eye using photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

    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 to scan through different wavelengths with 0.1nm wavelength resolution to determine spectra of different drug solutions in an ocular phantom. The short pulse duration (5-10ns) of the OPO laser has significantly increased the photoacoustic efficiency conversion, and the ability to tune its output from 210nm to1800nm has provided a wide selection range that is useful for optimizing spectroscopic studies. PAS spectra of different solutions of molecules, such as Trypan Blue, Rose Bengal, Indocyanine Green (ICG), and Amphotericin B (AB), at concentrations as low as 1 ?g/ml, were constructed and compared to their actual optical absorption spectra. Ultrasonic hydrophone and photothermal deflection technique (PhDT), a noncontact optical method, were both used to record the photoacoustic signals, and compared in terms of sensitivity and applicability to record signals from the ocular tissue-bearing phantom. The results show good agreement between the optical and photoacoustic spectra, which supports moving to an in vivo application of recording the PAS responses from the eye. Future work will be directed at adapting this method for in vivo measurements, as well as improve the data acquisition system for faster PAS signal analysis.

  6. Characterization of Greenhouse Soil Properties Using Mid-infrared Photoacoustic Spectroscopy

    Microsoft Academic Search

    Du Changwen; Deng Jing; Zhou Jianmin; Wang Huoyan; Chen Xiaoqin

    2011-01-01

    Evaluation of soil fertility is required for the sustainable production in greenhouses; however, routine agrochemical analytical methods are not practical since most of them are too time consuming and costly. In this study, Fourier transform midinfrared photoacoustic spectroscopy (FTIR-PAS) was applied as an alternative technique in the fast characterization of greenhouse soils. Nine source clays and 235 soil samples were

  7. Monitoring the photobleaching of cresyl violet in polyvinyl alcohol using the photoacoustic effect

    NASA Astrophysics Data System (ADS)

    Philip, Annieta; Radhakrishnan, P.; Nampoori, V. P.; Vallabhan, C. P.

    1994-06-01

    Bleaching of cresyl violet in polyvinyl alcohol due to irradiation by a laser beam at three chopping frequencies is investigated using the photoacoustic technique. The results indicate that the bleaching rate decreases with increase in chopping frequency. This can be used as a potential medium for holographic recording and information storage.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  9. d Original Contribution HIGH-RESOLUTION PHOTOACOUSTIC IMAGING OF OCULAR TISSUES

    E-print Network

    d Original Contribution HIGH-RESOLUTION PHOTOACOUSTIC IMAGING OF OCULAR TISSUES RONALD H. SILVERMAN) and ultrasound (US) are methods widely used for diagnostic imaging of the eye. These techniques detect by OCTor US. Our aim was to demonstrate the application of PAI in ocular tissues and to do so with lateral

  10. A photoacoustic study of phase transition in modified strontium barium niobate ceramics

    Microsoft Academic Search

    S. I. Lee; W. K. Choo

    1990-01-01

    Strontium barium niobate (SBN) of the tetragonal tungsten bronze structure is a well known dielectric relaxor. In the present paper, the relaxor behavior which is a manifestation of the diffuse phase transition (DPT) characteristics is further pursued in a La-substituted SBN ceramics by the photoacoustic (PA) technique. An abrupt change of the PA signal of the pure and modified specimens

  11. DEVELOPMENT OF A BREADBOARD CO2 LASER PHOTOACOUSTIC TOXIC VAPOR MONITOR

    EPA Science Inventory

    The report describes the development of a breadboard version of a CO2 laser photoacoustic (LPA) detector. The CO2 LPA technique has been demonstrated to be capable of detecting, with high specificity, a variety of toxic compounds at low parts-per-billion (ppb) levels in multicomp...

  12. Developing photoacoustic ocular imaging system

    NASA Astrophysics Data System (ADS)

    Ye, Shuoqi; Wu, Ning; Ren, Qiushi; Li, Changhui

    2013-03-01

    Ocular imaging plays a key role for the diagnosis of various ocular diseases. In this work, we have developed an ocular imaging system based on the photoacoustic tomography. This system has successfully imaged the entire eye of a mouse, from its iris to the retina region, and the imaging is label-free and non-invasively. The resolution of this system reaches several micron meters, allowing the study of microstructures in various ocular tissues. Our system has the potential to be a powerful non-invasive imaging method for the ophthalmology.

  13. Piezoelectric cantilever sensors

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

  14. Photoacoustic, Photothermal, and Diffusion-Wave Sciences in the Twenty-First Century: Triumphs of the Past Set the Trends for the Future

    NASA Astrophysics Data System (ADS)

    Mandelis, Andreas

    2012-11-01

    A handful of early breakthroughs in photoacoustic science and engineering since its modern-day (scientific) renaissance in the 1970s has defined directions in the development of the photoacoustic, photothermal, and diffusion-wave fields in the past 40 years that have shaped modern day developments and have led to an impressive range of vibrant and unique technologies in the third millennium (technological renaissance). A power-point presentation on the ICPPP-16 opening plenary talk focuses on the historical roots of what I perceive to be some of today's most successful and unique technologies, while readily acknowledging the impossibility to be all inclusive. It can be found under the url: http://cadift.mie.utoronto.ca/History_of_Photoacoustics-Photothermics.ppt. The thematic areas in question include historical reviews selected among the following topics: Piezoelectric photoacoustic microscopy (PAM) which, along with early gas-phase PA spectroscopic studies of biomaterials such as blood haemoglobin and progress in the physics of photon diffusion waves, has led to the modern-day explosion in biomedical photoacoustic imaging technologies with future trends for photoacoustic and ultrasound co-registered imagers; Thermoreflectance, piezoelectric, and gas-phase PA imaging of semiconductors which, along with developments in photocarrier diffusion wave physics, led to photocarrier radiometry, nanolayer diagnostics, carrierographic imaging of optoelectronic materials, and devices with industrial trends in solar cell inspection and control; Photoacoustic gas-phase and infrared radiometric probing and scanning imaging NDE which led to lock-in thermography and have spawned industrial and biomedical technologies; Thermal-wave interferometry and the quest for thermal coherence which led to thermal-wave cavities, the thermal-wave radar, and derivative depth profiling technologies, and, very recently, thermal coherence tomography. This review is meant to be a growing public record of work in progress, with new materials in the given thematic areas and other thematic areas being added as more information on the rich history of the field becomes available. Direct inputs to the author by the broader photoacoustic, photothermal, and diffusion-wave community are solicited and strongly encouraged to ensure that all landmark and seminal work that shaped the state of the science and art in the field receives fair and deserving exposure and the historical review becomes truly representative and comprehensive.

  15. Piezoelectric composite materials

    NASA Technical Reports Server (NTRS)

    Kiraly, L. J. (inventor)

    1983-01-01

    A laminated structural devices has the ability to change shape, position and resonant frequency without using discrete motive components. The laminate may be a combination of layers of a piezoelectrically active, nonconductive matrix material. A power source selectively places various levels of charge in electrically conductive filaments imbedded in the respective layers to produce various configurations in a predetermined manner. The layers may be electrically conductive having imbedded piezoelectrically active filaments. A combination of layers of electrically conductive material may be laminated to layers of piezoelectrically active material.

  16. Adaptive piezoelectric sensoriactuator

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

  17. Photoacoustic Imaging for Cancer Detection and Staging

    PubMed Central

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

    2013-01-01

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

  18. Noise-equivalent sensitivity of photoacoustics

    PubMed Central

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

    2013-01-01

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

  19. Photoacoustic photonic crystal fiber gas sensor

    E-print Network

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

    2007-01-01

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

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

    PubMed Central

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

    2013-01-01

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

  1. Photoacoustic spectroscopy of Baru Dipteryx alata Vog

    Microsoft Academic Search

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

    2008-01-01

    Photoacoustic spectroscopy (PAS) was used to investigate samples produced from Baru (Dipteryx alata Vog.), a typical fruit from the Brazilian Cerrado, which is considered as a good source of nutrients. The photoacoustic (PA) spectra of samples prepared from Baru seeds present three different absorption bands in the wavelength range 0.3 1.0 mum, named Band-C, Band-S, and Band-L. We found that

  2. Trace aerosol detection and identification by dynamic photoacoustic spectroscopy.

    PubMed

    Sullenberger, R M; Clark, M L; Kunz, R R; Samuels, A C; Emge, D K; Ellzy, M W; Wynn, C M

    2014-12-15

    Dynamic photoacoustic spectroscopy (DPAS) is a high sensitivity technique for standoff detection of trace vapors. A field-portable DPAS system has potential as an early warning provider for gaseous-based chemical threats. For the first time, we utilize DPAS to successfully detect the presence of trace aerosols. Aerosol identification via long-wavelength infrared (LWIR) spectra is demonstrated. We estimate the sensitivity of our DPAS system to aerosols comprised of silica particles is comparable to that of SF(6) gas based on a signal level per absorbance unit metric for the two materials. The implications of these measurements are discussed. PMID:25607495

  3. An Autonomous Piezoelectric Shunt Damping System

    Microsoft Academic Search

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

    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

  4. Piezoelectric actuation of helicopter rotor blades

    Microsoft Academic Search

    Nicholas A. Lieven

    2001-01-01

    The work presented in this paper is concerned with the application of embedded piezo-electric actuators in model helicopter rotor blades. The paper outlines techniques to define the optimal location of actuators to excite particular modes of vibration whilst the blade is rotating. Using composite blades the distribution of strain energy is defined using a Finite Element model with imposed rotor-dynamic

  5. Multilayer electromechanical composites with controlled piezoelectric coefficient distribution

    E-print Network

    Aksay, Ilhan A.

    . This technique is an extremely versatile method to fabricate displacement actuators to fabricate monolithic ceramic parts with controlled material property gradients. To obtain a quantifiable method to optimize-2875 ABSTRACT We have fabricated multilayer electromechanical composites with controlled piezoelectric

  6. Piezoelectric Polymer Shock Gauges

    NASA Astrophysics Data System (ADS)

    Bauer, F.

    2006-07-01

    The science and technology of piezoelectric materials has long been dominated by the availability of specific materials with particular properties. Piezoelectric PVDF (Poly(vinylidene fluoride) polymer and copolymers of PVDF with trifluoroethylene have shown to have the potential for new shock-wave sensors. Since 1981 through 1995, the piezoelectric response of PVDF was studied in a cooperative effort with François Bauer of ISL, France, R.A. Graham of Sandia National Laboratories and L.M. Lee of Ktech Corporation, Albuquerque. Among the known piezoelectric polymers, the PVDF plays an important role in measuring mechanical and physical state of matter under shock loading. The present paper presents the history of the development of the PVDF gauge. After 24 years of research in this area, main relevant results and data obtained are summarized as well as some original applications of the PVDF gauges.

  7. Piezoelectric Polymer Shock Gauges

    NASA Astrophysics Data System (ADS)

    Bauer, François

    2005-07-01

    The science and technology of piezoelectric materials has long been dominated by the availability of specific materials with particular properties. Piezoelectric PVDF (Poly(vinylidene fluoride)) polymer and copolymers of PVDF with trifluoroethylene have shown that they have the potential for new shock-wave sensors. Since 1981 and until 1995, the piezoelectric response of PVDF has been studied in a cooperative effort with Francois Bauer of ISL, France, R.A. Graham of Sandia National Laboratories and L.M. Lee of the Ktech Corporation of Albuquerque. Among the known piezoelectric polymers, the PVDF plays an important role in measuring mechanical and physical state of matter under shock loading. The present paper presents the history of the development of the PVDF shock gauge. After 24 years of research in this area, main relevant results and data obtained are summarized as well as some of original applications of the PVDF gauges.

  8. Piezoactuator design considering the optimum placement of FGM piezoelectric material

    NASA Astrophysics Data System (ADS)

    Carbonari, Ronny C.; Nishiwaki, Shinji; Paulino, Glaucio H.; Nelli Silva, Emílio C.

    2007-04-01

    Functionally Graded Materials (FGMs) possess continuous variation of material properties and are characterized by spatially varying microstructures. Recently, the FGM concept has been explored in piezoelectric materials to improve properties and to increase the lifetime of piezoelectric actuators. Elastic, piezoelectric, and dielectric properties are graded along the thickness of a piezoceramic FGM. Thus, the gradation of piezoceramic properties can influence the performance of piezoactuators, and an optimum gradation can be sought through optimization techniques. However, the design of these FGM piezoceramics are usually limited to simple shapes. An interesting approach to be investigated is the design of FGM piezoelectric mechanisms which essentially can be defined as a FGM structure with complex topology made of piezoelectric and non-piezoelectric material that must generate output displacement and force at a certain specified point of the domain and direction. This can be achieved by using topology optimization method. Thus, in this work, a topology optimization formulation that allows the simultaneous distribution of void and FGM piezoelectric material (made of piezoelectric and non-piezoelectric material) in the design domain, to achieve certain specified actuation movements, will be presented. The method is implemented based on the SIMP material model where fictitious densities are interpolated in each finite element, providing a continuum material distribution in the domain. The optimization algorithm employed is based on sequential linear programming (SLP) and the finite element method is based on the graded finite element concept where the properties change smoothly inside the element. This approach provides a continuum approximation of material distribution, which is appropriate to model FGMs. Some FGM piezoelectric mechanisms were designed to demonstrate the usefulness of the proposed method. Examples are limited to two-dimensional models, due to FGM manufacturing constraints and the fact that most of the applications for such FGM piezoelectric mechanisms are planar devices. An one-dimensional constraint of the material gradation is imposed to provide more realistic designs.

  9. Photoacoustic signal simulation and detection optimization based on laser-scanning optical-resolution photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Li, Lin; Du, Yi; Zhao, Qingliang; Li, Qian; Chai, Xinyu; Zhou, Chuanqing

    2014-11-01

    Laser-scanning optical-resolution photoacoustic microscopy (LSOR-PAM) has a high application potential in ophthalmology and other clinical fields because of its high resolution and imaging speed. The stationary unfocused ultrasonic transducer of this system decides the efficiency and field of view (FOV) of photoacoustic signal detection, but the refraction and attenuation of laser generated photoacoustic signal in different tissue mediums will cause signal strength and direction distribution uneven. In this study, we simulated the photoacoustic signal propagation and detection in compound medium models with different tissue parameters using k-space method based on LSOR-PAM imaging principle. The results show a distance related signal strength attenuation and FOV changes related to transducer angle. Our study provides a method for photoacoustic signal detection optimization for different complex tissue structure with LSOR-PAM.

  10. Laminated piezoelectric transformer

    NASA Technical Reports Server (NTRS)

    Vazquez Carazo, Alfredo (Inventor)

    2006-01-01

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

  11. Porous Piezoelectric Ceramic Transducer

    Microsoft Academic Search

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

    1991-01-01

    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

  12. Piezoelectric direct drive servovalve

    Microsoft Academic Search

    Jason E. Lindler; Eric H. Anderson

    2002-01-01

    A single-stage servovalve using direct piezoelectric actuator drive is described. The single-stage servovalve design offers higher bandwidth than conventional two-stage valves. It takes advantage of the high energy density in piezoelectric materials while addressing the need for internal amplification of stroke. When used alone, the valve can regulate pressure, and when used in combination with a hydraulic output device it

  13. Piezoelectric Energy Harvesting Solutions

    PubMed Central

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

    2014-01-01

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

  14. Piezoelectricity in PANI filled Nylon 11

    NASA Astrophysics Data System (ADS)

    Pande, S. A.; Kelkar, D. S.; Peshwe, D. R.

    2007-07-01

    The piezoelectric response of pure Nylon 11 and conducting Polyaniline (PANI) filled Nylon 11 is presented. Nylon 11 samples were filled with PANI fillers of two different concentrations (1% and 5% w/w) each. The samples were poled using Corona discharge technique with poling field of 200 kV/cm and 350 kV/cm. The piezoelectric strain constant d 31, stress constant e 31 and electromechanical coupling coefficient k 31 of pure and PANI filled samples were measured up to 100°C. The study suggests that the piezoelectric coefficient (d 31) of the PANI filled Nylon 11 shows considerable decline with respect to its individual component. The thermal stability of the PANI filled samples improved and is almost stable at comparatively low temperature than pure Nylon 11.

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

    NASA Astrophysics Data System (ADS)

    Guo, Lili; Xu, Dongyu; Huang, Shifeng

    2009-07-01

    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.

  16. Development of a neonatal skull phantom for photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Tavakolian, Pantea; Todd, Rhiannon; Kosik, Ivan; Chamson-Reig, Astrid; Vasefi, Fartash; St. Lawrence, Keith; Carson, Jeffrey J. L.

    2013-03-01

    Photoacoustic imaging (PAI) has been proposed as a non-invasive technique for the diagnosis and monitoring of disorders in the neonatal brain. However, PAI of the brain through the intact skull is challenging due to reflection and attenuation of photoacoustic pressure waves by the skull bone. The objective of this work was to develop a phantom for testing the potential limits the skull bone places on PAI of the neonatal brain. Our approach was to make acoustic measurements on materials designed to mimic the neonatal skull bone and construct a semi-realistic phantom. A water tank and two ultrasound transducers were utilized to measure the ultrasound insertion loss (100 kHz to 5MHz) of several materials. Cured mixtures of epoxy and titanium dioxide powder provided the closest acoustic match to neonatal skull bone. Specifically, a 1.4-mm thick sample composed of 50% (by mass) titanium dioxide powder and 50% epoxy was closest to neonatal skull bone in terms of acoustic insertion loss. A hemispherical skull phantom (1.4 mm skull thickness) was made by curing the epoxy/titanium dioxide powder mixture inside a mold. The mold was constructed using 3D prototyping techniques and was based on the hairless head of a realistic infant doll. The head was scanned to generate a 3D model, which in turn was used to build a 3D CAD version of the mold. The mold was CNC machined from two solid blocks of Teflon®. The neonatal skull phantom will enable the study of the propagation of photoacoustic pressure waves under a variety of experimental conditions.

  17. Theoretical and experimental investigation of multispectral photoacoustic osteoporosis detection method

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  18. Bone assessment via thermal photo-acoustic measurements.

    PubMed

    Feng, Ting; Kozloff, Kenneth M; Tian, Chao; Perosky, Joseph E; Hsiao, Yi-Sing; Du, Sidan; Yuan, Jie; Deng, Cheri X; Wang, Xueding

    2015-04-15

    The feasibility of an innovative biomedical diagnostic technique, thermal photo-acoustic (TPA) measurement, for non-ionizing and non-invasive assessment of bone health is investigated. Unlike conventional photo-acoustic PA methods that are mostly focused on the measurement of absolute signal intensity, TPA targets the change in PA signal intensity as a function of the sample temperature, i.e., the temperature-dependent Grueneisen parameter that is closely relevant to the chemical and molecular properties in the sample. Based on the differentiation measurement, the results from TPA technique are less susceptible to the variations associated with sample and system, and could be quantified with improved accurately. Due to the fact that the PA signal intensity from organic components such as blood changes faster than that from non-organic mineral under the same modulation of temperature, TPA measurement is able to objectively evaluate bone mineral density (BMD) and its loss as a result of osteoporosis. In an experiment on well-established rat models of bone loss and preservation, PA measurements of rat tibia bones were conducted over a temperature range from 37°C to 44°C. The slope of PA signal intensity verses temperature was quantified for each specimen. The comparison among three groups of specimens with different BMD shows that bones with lower BMD have higher slopes, demonstrating the potential of the proposed TPA technique in future clinical management of osteoporosis. PMID:25872057

  19. Characterization of human skin through photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2005-06-01

    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.

  20. Ultrasonic attenuation of biomaterials for compensation in photoacoustic imaging

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Harrison, Tyler; Zemp, Roger J.

    2011-03-01

    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.

  2. Gold nanoparticles for photoacoustic imaging.

    PubMed

    Li, Wanwan; Chen, Xiaoyuan

    2015-01-01

    Photoacoustic (PA) imaging is a biomedical imaging modality that provides functional information regarding the cellular and molecular signatures of tissue by using endogenous and exogenous contrast agents. There has been tremendous effort devoted to the development of PA imaging agents, and gold nanoparticles as exogenous contrast agents have great potential for PA imaging due to their inherent and geometrically induced optical properties. The gold-based nanoparticles that are most commonly employed for PA imaging include spheres, rods, shells, prisms, cages, stars and vesicles. This article provides an overview of the current state of research in utilizing these gold nanomaterials for PA imaging of cancer, atherosclerotic plaques, brain function and image-guided therapy. PMID:25600972

  3. Visualization of molecular composition and functionality of cancer cells using nanoparticle-augmented ultrasound-guided photoacoustics

    PubMed Central

    Mallidi, Srivalleesha; Kim, Seungsoo; Karpiouk, Andrei; Joshi, Pratixa P.; Sokolov, Konstantin; Emelianov, Stanislav

    2015-01-01

    Assessment of molecular signatures of tumors in addition to their anatomy and morphology is desired for effective diagnostic and therapeutic procedures. Development of in vivo imaging techniques that can identify and monitor molecular composition of tumors remains an important challenge in pre-clinical research and medical practice. Here we present a molecular photoacoustic imaging technique that can visualize the presence and activity of an important cancer biomarker – epidermal growth factor receptor (EGFR), utilizing the effect of plasmon resonance coupling between molecular targeted gold nanoparticles. Specifically, spectral analysis of photoacoustic images revealed profound changes in the optical absorption of systemically delivered EGFR-targeted gold nanospheres due to their molecular interactions with tumor cells overexpressing EGFR. In contrast, no changes in optical properties and, therefore, photoacoustic signal, were observed after systemic delivery of non-targeted gold nanoparticles to the tumors. The results indicate that multi-wavelength photoacoustic imaging augmented with molecularly targeted gold nanoparticles has the ability to monitor molecular specific interactions between nanoparticles and cell-surface receptors, allowing visualization of the presence and functional activity of tumor cells. Furthermore, the approach can be used for other cancer cell-surface receptors such as human epidermal growth factor receptor 2 (HER2). Therefore, ultrasound-guided molecular photoacoustic imaging can potentially aid in tumor diagnosis, selection of customized patient-specific treatment, and monitor the therapeutic progression and outcome in vivo.

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

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

    Microsoft Academic Search

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

    2001-01-01

    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

  6. Dynamics of Linear Piezoelectric Rods

    Microsoft Academic Search

    F. DavÍ

    1997-01-01

    A one-dimensional model of a linear piezoelectric thin rod is deduced from three-dimensional piezoelectricity by introducing suitable internal constraints and appropriate hypotheses on the electric displacement field.

  7. Piezoelectric Ceramics and Their Applications

    ERIC Educational Resources Information Center

    Flinn, I.

    1975-01-01

    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)

  8. Photoacoustic Imaging of Animals with an Annular Transducer Array

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  9. Using high-power light emitting diodes for photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Skov Hansen, René

    2011-03-01

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

  10. Multicontrast photoacoustic in vivo imaging using near-infrared fluorescent proteins

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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.

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

    PubMed Central

    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

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

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

    PubMed

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

    2014-10-20

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

  13. Handheld probe for portable high frame photoacoustic/ultrasound imaging system

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    Photoacoustics is a hybrid imaging modality that is based on the detection of acoustic waves generated by absorption of pulsed light by tissue chromophors. In current research, this technique uses large and costly photoacoustic systems with a low frame rate imaging. To open the door for widespread clinical use, a compact, cost effective and fast system is required. In this paper we report on the development of a small compact handset pulsed laser probe which will be connected to a portable ultrasound system for real-time photoacoustic imaging and ultrasound imaging. The probe integrates diode lasers driven by an electrical driver developed for very short high power pulses. It uses specifically developed highly efficient diode stacks with high frequency repetition rate up to 10 kHz, emitting at 800nm wavelength. The emitted beam is collimated and shaped with compact micro optics beam shaping system delivering a homogenized rectangular laser beam intensity distribution. The laser block is integrated with an ultrasound transducer in an ergonomically designed handset probe. This handset is a building block enabling for a low cost high frame rate photoacoustic and ultrasound imaging system. The probe was used with a modified ultrasound scanner and was tested by imaging a tissue mimicking phantom.

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  15. A gradient-based method for quantitative photoacoustic tomography using the radiative transfer equation

    NASA Astrophysics Data System (ADS)

    Saratoon, T.; Tarvainen, T.; Cox, B. T.; Arridge, S. R.

    2013-07-01

    Quantitative photoacoustic tomography (QPAT) offers the possibility of high-resolution molecular imaging by quantifying molecular concentrations in biological tissue. QPAT comprises two inverse problems: (1) the construction of a photoacoustic image from surface measurements of photoacoustic wave pulses over time, and (2) the determination of the optical properties of the imaged region. The first is a well-studied area for which a number of solution methods are available, while the second is, in general, a nonlinear, ill-posed inverse problem. Model-based inversion techniques to solve (2) are usually based on the diffusion approximation to the radiative transfer equation (RTE) and typically assume the acoustic inversion step has been solved exactly. Here, neither simplification is made: the full RTE is used to model the light propagation, and the acoustic propagation and image reconstruction are included in the simulations of measured data. Since Hessian- and Jacobian-based minimizations are computationally expensive for the large data sets typically encountered in QPAT, gradient-based minimization schemes provide a practical alternative. The acoustic pressure time series were simulated using a k-space, pseudo-spectral time domain model, and a time-reversal reconstruction algorithm was used to form a set of photoacoustic images corresponding to four illumination positions. A regularized, adjoint-assisted gradient inversion using a finite element model of the RTE was then used to determine the optical absorption and scattering coefficients.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    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.

  17. Thermophysical investigation of Gafchromic EBT2 films using photoacoustic spectroscopy.

    PubMed

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

    2014-07-01

    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

  18. Thermophysical investigation of Gafchromic EBT2 films using photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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%.

  19. Photoacoustic Brain Imaging: from Microscopic to Macroscopic Scales

    PubMed Central

    Yao, Junjie; Wang, Lihong V.

    2014-01-01

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

  20. Piezoelectric wave motor

    DOEpatents

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

    2001-07-17

    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.

  1. Piezoelectric wave motor

    DOEpatents

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

    2003-02-11

    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.

  2. Active Piezoelectric Diaphragms

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

  3. 40 CFR 1065.269 - Photoacoustic analyzer for ethanol and methanol.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...Photoacoustic analyzer for ethanol and methanol. 1065.269 Section 1065.269...Photoacoustic analyzer for ethanol and methanol. (a) Application. You may use...photoacoustic analyzer to measure ethanol and/or methanol concentrations in diluted exhaust...

  4. Detection of Delaminations in Composite Beams Using Piezoelectric Sensors

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  5. Parallel acoustic delay lines for photoacoustic tomography

    PubMed Central

    Yapici, Murat Kaya; Kim, Chulhong; Chang, Cheng-Chung; Jeon, Mansik; Guo, Zijian; Cai, Xin; Wang, Lihong V.

    2012-01-01

    Abstract. Achieving real-time photoacoustic (PA) tomography typically requires multi-element ultrasound transducer arrays and their associated multiple data acquisition (DAQ) electronics to receive PA waves simultaneously. We report the first demonstration of a photoacoustic tomography (PAT) system using optical fiber-based parallel acoustic delay lines (PADLs). By employing PADLs to introduce specific time delays, the PA signals (on the order of a few micro seconds) can be forced to arrive at the ultrasonic transducers at different times. As a result, time-delayed PA signals in multiple channels can be ultimately received and processed in a serial manner with a single-element transducer, followed by single-channel DAQ electronics. Our results show that an optically absorbing target in an optically scattering medium can be photoacoustically imaged using the newly developed PADL-based PAT system. Potentially, this approach could be adopted to significantly reduce the complexity and cost of ultrasonic array receiver systems. PMID:23139043

  6. Photoacoustic imaging of carotid artery atherosclerosis

    NASA Astrophysics Data System (ADS)

    Kruizinga, Pieter; van der Steen, Antonius F. W.; de Jong, Nico; Springeling, Geert; Robertus, Jan Lukas; van der Lugt, Aad; van Soest, Gijs

    2014-11-01

    We introduce a method for photoacoustic imaging of the carotid artery, tailored toward detection of lipid-rich atherosclerotic lesions. A common human carotid artery was obtained at autopsy, embedded in a neck mimicking phantom and imaged with a multimodality imaging system using interstitial illumination. Light was delivered through a 1.25-mm-diameter optical probe that can be placed in the pharynx, allowing the carotid artery to be illuminated from within the body. Ultrasound imaging and photoacoustic signal detection is achieved by an external 8-MHz linear array coupled to an ultrasound imaging system. Spectroscopic analysis of photoacoustic images obtained in the wavelength range from 1130 to 1250 nm revealed plaque-specific lipid accumulation in the collagen structure of the artery wall. These spectroscopic findings were confirmed by histology.

  7. Photoacoustic imaging of carotid artery atherosclerosis.

    PubMed

    Kruizinga, Pieter; van der Steen, Antonius F W; de Jong, Nico; Springeling, Geert; Robertus, Jan Lukas; van der Lugt, Aad; van Soest, Gijs

    2014-11-01

    We introduce a method for photoacoustic imaging of the carotid artery, tailored toward detection of lipid-rich atherosclerotic lesions. A common human carotid artery was obtained at autopsy, embedded in a neck mimicking phantom and imaged with a multimodality imaging system using interstitial illumination. Light was delivered through a 1.25-mm-diameter optical probe that can be placed in the pharynx, allowing the carotid artery to be illuminated from within the body. Ultrasound imaging and photoacoustic signal detection is achieved by an external 8-MHz linear array coupled to an ultrasound imaging system. Spectroscopic analysis of photoacoustic images obtained in the wavelength range from 1130 to 1250 nm revealed plaque-specific lipid accumulation in the collagen structure of the artery wall. These spectroscopic findings were confirmed by histology. PMID:25411898

  8. Ultrasonically Encoded Photoacoustic Flowgraphy in Biological Tissue

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  9. Intravascular photoacoustic imaging of human coronary atherosclerosis

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    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.

  10. Quantitative Photoacoustic Spectroscopy in the Frequency Domain

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  11. Dynamics of nonlinear thin piezoelectric rods with domain switching

    Microsoft Academic Search

    Fabrizio Davi

    1998-01-01

    We obtain a model for the non-linear electromechanical motion of piezoelectric rod with domain switching. We assume the piezoelectric body as a continuum with a microstructure given by the effective number of switchable aligned dipoles. As in previous related works, by using suitable mechanical internal constraints and electrical semi-inverse hypotheses, we arrive at a 1D functional. With standard variational techniques

  12. Photoacoustic generation of focused ultrasonic pulses with predefined temporal profiles including quasi-unipolar pressure pulses

    NASA Astrophysics Data System (ADS)

    Maslov, Konstantin; Zhang, Hao F.; Wang, Lihong V.

    2008-02-01

    One of the applications of the photoacoustic effect in biomedical research is generation of ultra-short acoustic pressure pulses in tissue. An acoustic wave is generated directly in tissue or in an acoustically well coupled immersion liquid, thus avoiding mechanical resonances of the piezoelectric ultrasonic transducer. Although laser generation of the unipolar pressure pulses has been proposed and used before, little attention was paid to the change of the temporal shape of the pulse when it propagates from a transducer. Here we derive simple mathematical solution which helps to predict the pulse shape in the focal region of the transducer and to experimentally verify theoretical calculations showing generation of short quasi-unipolar pressure pulses.

  13. Photoacoustic spectroscopy of Baru – Dipteryx alata Vog

    Microsoft Academic Search

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

    2008-01-01

    .  Photoacoustic spectroscopy (PAS) was used to investigate \\u000a samples produced from Baru (Dipteryx alata Vog.), a typical fruit from the Brazilian \\u000a Cerrado, which is considered as a good source of nutrients. The \\u000a photoacoustic (PA) spectra of samples prepared from Baru seeds present three \\u000a different absorption bands in the wavelength range 0.3–1.0??m, named \\u000a Band-C, Band-S, and Band-L. We found that PAS can

  14. Photoacoustic tomography of pathological tissue in ex vivo mouse hearts

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

    In the present study, we evaluate the applicability of ex-vivo photoacoustic imaging (PAI) in organs of small animals. We used photoacoustic tomography (PAT) to visualize infarcted areas within mouse hearts and compared it to other imaging techniques (MRI and ?CT). In order to induce ischemia an in-vivo ligation of the Ramus interventricularis anterior (RIVA, left anterior descending, LAD) was performed on nine wild type C41 mice. After varying survival periods the mice were sacrificed. The hearts were excised and immediately transferred into a formaldehyde solution for conservation. Various wavelengths in the visible and near infrared region (500 nm - 1000 nm) had been tested to find the best representation of the ischemic regions. Samples were illuminated with nanosecond laser pulses delivered by an Nd:YAG pumped optical parametric oscillator. Ultrasound detection was achieved by an optical Mach-Zehnder interferometer working as an integrating line detector. For acoustic coupling the samples were located inside a water tank. The voxel data are computed from the measurement data by a Fourier-domain based reconstruction algorithm, followed by a sequence of inverse Radon transforms. Results clearly show the capability of PAI to detect pathological tissue and the possibility to produce three-dimensional images with resolutions well below 100 ?m. Different wavelengths allow the representation of structure inside an organ or on the surface even without contrast enhancing tracers.

  15. Investigation of Micromechanical Structures by Photoacoustic Elastic Bending Method

    NASA Astrophysics Data System (ADS)

    Todorovi?, D. M.; Rabasovi?, M. D.; Markushev, D. D.; Jovi?, V.; Radulovi?, K. T.

    2012-11-01

    Photoacoustic (PA) and photothermal (PT) science and technology extensively developed new methods for the investigation of micro (nano)-mechanical structures. PA and PT effects can be important also as driven mechanisms for optically excited micromechanical structures. The photoacoustic elastic bending method (PA-EBM) is based on the optical excitation of the micromechanical structure and detection of the acoustic response (PA signal) with a very sensitive PA detection system. The experimental PA elastic bending signals of the whole micromechanical structure were measured by using a special constructed PA cell (the gas-microphone detection technique with transmission configuration). The PA amplitude and phase spectra were measured, as a function of the modulation frequency in a frequency range from 20 Hz to 20 000 Hz, for different samples (Si chip with square membrane). The electronic and thermal elastic PA effects (electronic deformation and thermoelastic mechanisms of elastic wave generation) in a Si simply supported rectangular plate (3D geometry), photogenerated by a uniform and intensity-modulated optical beam, were studied. The theoretical model for the PA elastic bending frequency distribution by using the Green function method was given. The amplitude and phase PA signals were calculated and analyzed, including the thermalization and surface and volume recombination heat sources. The theoretical results were compared with experimental data.

  16. Mapping tissue oxygen in vivo by photoacoustic lifetime imaging

    NASA Astrophysics Data System (ADS)

    Shao, Qi; Morgounova, Ekaterina; Choi, Jeung-Hwan; Jiang, Chunlan; Bischof, John; Ashkenazi, Shai

    2013-03-01

    Oxygen plays a key role in the energy metabolism of living organisms. Any imbalance in the oxygen levels will affect the metabolic homeostasis and lead to pathophysiological diseases. Hypoxia, a status of low tissue oxygen, is a key factor in tumor biology as it is highly prominent in tumor tissues. However, clinical tools for assessing tissue oxygenation are limited. The gold standard is polarographic needle electrode which is invasive and not capable of mapping (imaging) the oxygen content in tissue. We applied the method of photoacoustic lifetime imaging (PALI) of oxygen-sensitive dye to small animal tissue hypoxia research. PALI is new technology for direct, non-invasive imaging of oxygen. The technique is based on mapping the oxygen-dependent transient optical absorption of Methylene Blue (MB) by pump-probe photoacoustic imaging. Our studies show the feasibility of imaging of dissolved oxygen distribution in phantoms. In vivo experiments demonstrate that the hypoxia region is consistent with the site of subcutaneously xenografted prostate tumor in mice with adequate spatial resolution and penetration depth.

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

    NASA Astrophysics Data System (ADS)

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

    2005-06-01

    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 those characteristic for the mid-day sunlight. The OPC was found capable of discriminating between the two contributions to photoacoustic signal. The experimental evidence was collected for statistically significant differences between photobaric signals from plants with and without mycorrhiza.

  18. Human hair in the identification of cocaine abuse with cantilever-enhanced photoacoustic spectroscopy and principal component analysis.

    PubMed

    Lehtinen, Jaakko; Hirschmann, Christian Bernd; Keiski, Riitta Liisa; Kuusela, Tom

    2013-08-01

    In this study, a novel approach combining different techniques, including Fourier transform infrared (FT-IR) spectroscopy, photoacoustic spectroscopy (PAS) with an interferometric cantilever microphone, and principal component analysis (PCA) along with a proper data preprocessing procedure, have been used in the investigation of hair samples for cocaine abuse. Hair fibers from cocaine-overdose patients have been measured using a simple procedure involving cantilever-enhanced photoacoustic Fourier transform infrared spectroscopy. In addition, a reference group of hair samples from subjects with no cocaine abuse has been measured. We present a first approach to discriminate the cocaine users from the reference group with the photoacoustic method and PCA. With proper data preprocessing methods, the two groups were successfully separated according to their spectra. The results were confirmed with two different classification methods independent of the principal component data analysis. PMID:23876723

  19. In vivo high-resolution 3D photoacoustic imaging of superficial vascular anatomy

    NASA Astrophysics Data System (ADS)

    Zhang, E. Z.; Laufer, J. G.; Pedley, R. B.; Beard, P. C.

    2009-02-01

    The application of a photoacoustic imaging instrument based upon a Fabry-Perot polymer film ultrasound sensor to imaging the superficial vasculature is described. This approach provides a backward mode-sensing configuration that has the potential to overcome the limitations of current piezoelectric based detection systems used in superficial photoacoustic imaging. The system has been evaluated by obtaining non-invasive images of the vasculature in human and mouse skin as well as mouse models of human colorectal tumours. These studies showed that the system can provide high-resolution 3D images of vascular structures to depths of up to 5 mm. It is considered that this type of instrument may find a role in the clinical assessment of conditions characterized by changes in the vasculature such as skin tumours and superficial soft tissue damage due to burns, wounds or ulceration. It may also find application in the characterization of small animal cancer models where it is important to follow the tumour vasculature over time in order to study its development and/or response to therapy.

  20. Computational Modeling of Piezoelectric Foams

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Glorieux, Christ; Thoen, Jan

    2010-01-01

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

  2. NOTE: Automated wavelet denoising of photoacoustic signals for circulating melanoma cell detection and burn image reconstruction

    NASA Astrophysics Data System (ADS)

    Holan, Scott H.; Viator, John A.

    2008-06-01

    Photoacoustic image reconstruction may involve hundreds of point measurements, each of which contributes unique information about the subsurface absorbing structures under study. For backprojection imaging, two or more point measurements of photoacoustic waves induced by irradiating a biological sample with laser light are used to produce an image of the acoustic source. Each of these measurements must undergo some signal processing, such as denoising or system deconvolution. In order to process the numerous signals, we have developed an automated wavelet algorithm for denoising signals. We appeal to the discrete wavelet transform for denoising photoacoustic signals generated in a dilute melanoma cell suspension and in thermally coagulated blood. We used 5, 9, 45 and 270 melanoma cells in the laser beam path as test concentrations. For the burn phantom, we used coagulated blood in 1.6 mm silicon tube submerged in Intralipid. Although these two targets were chosen as typical applications for photoacoustic detection and imaging, they are of independent interest. The denoising employs level-independent universal thresholding. In order to accommodate nonradix-2 signals, we considered a maximal overlap discrete wavelet transform (MODWT). For the lower melanoma cell concentrations, as the signal-to-noise ratio approached 1, denoising allowed better peak finding. For coagulated blood, the signals were denoised to yield a clean photoacoustic resulting in an improvement of 22% in the reconstructed image. The entire signal processing technique was automated so that minimal user intervention was needed to reconstruct the images. Such an algorithm may be used for image reconstruction and signal extraction for applications such as burn depth imaging, depth profiling of vascular lesions in skin and the detection of single cancer cells in blood samples.

  3. Automated wavelet denoising of photoacoustic signals for circulating melanoma cell detection and burn image reconstruction.

    PubMed

    Holan, Scott H; Viator, John A

    2008-06-21

    Photoacoustic image reconstruction may involve hundreds of point measurements, each of which contributes unique information about the subsurface absorbing structures under study. For backprojection imaging, two or more point measurements of photoacoustic waves induced by irradiating a biological sample with laser light are used to produce an image of the acoustic source. Each of these measurements must undergo some signal processing, such as denoising or system deconvolution. In order to process the numerous signals, we have developed an automated wavelet algorithm for denoising signals. We appeal to the discrete wavelet transform for denoising photoacoustic signals generated in a dilute melanoma cell suspension and in thermally coagulated blood. We used 5, 9, 45 and 270 melanoma cells in the laser beam path as test concentrations. For the burn phantom, we used coagulated blood in 1.6 mm silicon tube submerged in Intralipid. Although these two targets were chosen as typical applications for photoacoustic detection and imaging, they are of independent interest. The denoising employs level-independent universal thresholding. In order to accommodate nonradix-2 signals, we considered a maximal overlap discrete wavelet transform (MODWT). For the lower melanoma cell concentrations, as the signal-to-noise ratio approached 1, denoising allowed better peak finding. For coagulated blood, the signals were denoised to yield a clean photoacoustic resulting in an improvement of 22% in the reconstructed image. The entire signal processing technique was automated so that minimal user intervention was needed to reconstruct the images. Such an algorithm may be used for image reconstruction and signal extraction for applications such as burn depth imaging, depth profiling of vascular lesions in skin and the detection of single cancer cells in blood samples. PMID:18495977

  4. Piezoelectric ultrasonic motors: overview

    Microsoft Academic Search

    Kenji Uchino

    1998-01-01

    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.

  5. UHV piezoelectric translator

    SciTech Connect

    Oversluizen, T.; Watson, G.

    1985-01-01

    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.

  6. Piezoelectric direct drive servovalve

    NASA Astrophysics Data System (ADS)

    Lindler, Jason E.; Anderson, Eric H.

    2002-07-01

    A single-stage servovalve using direct piezoelectric actuator drive is described. The single-stage servovalve design offers higher bandwidth than conventional two-stage valves. It takes advantage of the high energy density in piezoelectric materials while addressing the need for internal amplification of stroke. When used alone, the valve can regulate pressure, and when used in combination with a hydraulic output device it forms part of an effective servohydraulic actuator. Development of a direct drive prototype valve is described. Discussion includes design issues related to low stroke smart material actuators such as piezoelectrics. Component and subsystem testing and results are reviewed. Electronic drive and control of the piezoelectric and overall device along with performance in the control of fluid flow is discussed. The value of the new servovalve is shown in the combination of the valve with a hydraulic output device. Data are supplied for this servohydraulic actuator. The new actuator shows promise for a motion simulator application and more generally for motion control at higher bandwidth than is possible with currently available servohydraulics.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  8. A cost-efficient frequency-domain photoacoustic imaging system

    PubMed Central

    LeBoulluec, Peter; Liu, Hanli; Yuan, Baohong

    2013-01-01

    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. PMID:24659823

  9. Contributed Review: Quantum cascade laser based photoacoustic detection of explosives.

    PubMed

    Li, J S; Yu, B; Fischer, H; Chen, W; Yalin, A P

    2015-03-01

    Detecting trace explosives and explosive-related compounds has recently become a topic of utmost importance for increasing public security around the world. A wide variety of detection methods and an even wider range of physical chemistry issues are involved in this very challenging area. Optical sensing methods, in particular mid-infrared spectrometry techniques, have a great potential to become a more desirable tools for the detection of explosives. The small size, simplicity, high output power, long-term reliability make external cavity quantum cascade lasers (EC-QCLs) the promising spectroscopic sources for developing analytical instrumentation. This work reviews the current technical progress in EC-QCL-based photoacoustic spectroscopy for explosives detection. The potential for both close-contact and standoff configurations using this technique is completely presented over the course of approximately the last one decade. PMID:25832204

  10. Smart photoacoustics: a pulsed-laser system for analysis of rapid volume changes due to heat release, molecular conformational change, and charge solvation

    NASA Astrophysics Data System (ADS)

    Small, Jeanne R.; Libertini, Louis J.; Heissenbuttel, James F.; Daniels, Summer T.; Eide, Mark; Tillman, Bryan; Mrakovcich, Karina L.; Small, Enoch W.; Smith, Richard D.

    1994-08-01

    The goal of `smart photoacoustics' is to rapidly analyze the rate and amplitude of photoinduced volume changes (ns to microsecond(s) time window), as well as to diagnose the source of the measured volume change: heat release, molecular conformational change and/or electrostriction (solvation or desolvation of charged groups). In contrast, the older technique of `photoacoustic calorimetry' tacitly assumes that only heat release from photoexcited molecules contributed to signals. Smart photoacoustics uses hardware, software, and chemical protocols to distinguish the different contributors to the observed signals. The method is demonstrated using two systems: the proton reactions of photoexcited pyranine (8-hydroxpyrene-1,3,6-trisulfonic acid) and the conformational changes in sperm whale carboxymyoglobin upon cleavage of the Fe-CO bond. Smart photoacoustics is the basis for the pulsed-laser photoacoustic instrument we are developing, which includes a sample chamber having thermoelectric control of temperature, magnetic stirring, control of transducer mounting tension, nitrogen flush of cuvette surfaces to eliminate condensation, argon degassing of samples, and two ports for monitoring optical properties of the sample. Central to the instrument is a Windows-based instrument control program which uses a script language to completely automate the operation of the instrument, the collection of data, and the analysis of the photoacoustic waveforms.

  11. Photoacoustic Spectroscopy for Identification and Differential Diagnosis of T. Indica with Other Seed-Borne Pathogens of Wheat and Rice

    Microsoft Academic Search

    Vikrant Gupta; Anil Kumar; G. K. Garg; A. K. Rai

    2001-01-01

    The photoacoustic study of dry spores (PAS) described in the present paper proved to be a suitable technique (when compared with other conventional methods) for the identification of Karnal bunt (KB) amongst other seed borne pathogens. Spores of six pathogens, i.e., Tilletia. indica, T. barclayana, Ustilago tritici, Ustilaginoidea virens, Helminthosporium sativum, and Alternaria triticina were isolated and their PA spectra

  12. Electrooptic and piezoelectric measurements in photorefractive barium titanate and strontium barium niobate

    Microsoft Academic Search

    Stephen Ducharme; Jack Feinberg; Ratnaker R. Neurgaonkar

    1987-01-01

    Interferometric techniques are used to measure the low-frequency electrooptic and piezoelectric coefficients in undoped BaTiO3 and Sr(x)Ba(1-x)Nb2O6 (x = 0.61) crystals. Consideration is given to the contribution of the piezoelectric effect to the Pockels measurements. For an applied ac electric field in the range of 0.1-200 V\\/cm, the electrooptic and piezoelectric effects are linear in the magnitude of the applied

  13. Photoacoustic FTIR spectroscopic study of undisturbed human cortical bone

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  15. Functional photoacoustic microscopy of diabetic vasculature

    E-print Network

    Wang, Lihong

    and adults with diabetes living in the United States, with 1.9 million new cases diagnosed annually in people fraction, and oxygen consumption rate were also measured, but showed no significant change. © 2012 Society; photoacoustic microscopy; metabolism; streptozo- tocin; glucose. Paper 12166L received Mar. 8, 2012; revised

  16. Photoacoustic Analysis of pigments from archeological ceramics

    Microsoft Academic Search

    J. L. Jiménez; A. Cruz; J. G. Mendoza

    Photoacoustic spectroscopy (PAS) is widely used nowadays for diverse applications in different areas. These include studies in material, environmental and life sciences. In the present work we report the study of pigments from potteries surface and volume of Mexican (Aztec) and Poblana cultures which were developed in central Mexico from 1325-1521 AD and 1521-1800 respectively. It was obtained the optical

  17. Photoacoustic Analysis of Pigments from Archeological Ceramics

    Microsoft Academic Search

    J. Jiménez-Pérez; A. Brancamontes Cruz; A. Cruz-Orea; J. G. Mendoza-Alvarez

    2004-01-01

    Photoacoustic spectroscopy (PAS) is widely used for diverse applications in different areas. These include studies in material, environmental, and life sciences. In the present work the study of pigments from pottery surfaces and volumes of Mexican (Aztec) and Poblana cultures that were developed in central Mexico from 1325 to 1521 and 1521 to 1800, respectively, is reported. The optical absorption

  18. Design, Manufacturing and Characterization of Functionally Graded Flextensional Piezoelectric Actuators

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  19. Quantitative photoacoustic measurement of blood oxygen saturation in vivo aided by an optical contrast agent

    NASA Astrophysics Data System (ADS)

    Rajian, Justin Rajesh; Carson, Paul L.; Fowlkes, J. Brian; Wang, Xueding

    2010-02-01

    The characteristic absorption spectrum of hemoglobin depends upon the amount of oxygen the hemoglobin carries. This property of the hemoglobin enables one to image blood oxygen saturation distribution in biological tissues by using spectroscopic photoacoustic tomography. In photoacoustic imaging, the amplitude of photoacoustic signal induced by optical absorption is proportional to light energy deposition which is the product of the optical absorption coefficient and local light fluence at the imaging target. Since the attenuation of light in biological tissues are wavelength dependent, the spectrum of local light fluence at a target tissue beneath the sample surface is different from the spectrum of the incident light fluence above the surface. An unknown spectrum of the light fluence in the sample prevents us from obtaining quantitative functional images such as oxygen saturation and hemoglobin concentration in the sample by photoacoustic tomography. We developed a new technique of using an optical contrast agent with known optical absorption spectrum to obtain the accurate spectrum of light fluence at a subsurface target tissue such as a blood vessel beneath the sample surface. The technique has been validated by obtaining an accurate absorption spectrum of a micro-flow vessel buried in strong optical scattering media including diluted whole milk and chicken breast tissue. In this work, we further explored the capability of this technique through the experiments on tissue mimicking phantoms and living animals. By using this technique we were able to obtain accurate blood oxygen saturation in vessels buried at different depths in an optical scattering medium. Also, the oxygenation levels in main arteries in rat tails have been quantified more accurately in a noninvasive manner.

  20. Photoacoustic sample vessel and method of elevated pressure operation

    DOEpatents

    Autrey, Tom; Yonker, Clement R.

    2004-05-04

    An improved photoacoustic vessel and method of photoacoustic analysis. The photoacoustic sample vessel comprises an acoustic detector, an acoustic couplant, and an acoustic coupler having a chamber for holding the acoustic couplant and a sample. The acoustic couplant is selected from the group consisting of liquid, solid, and combinations thereof. Passing electromagnetic energy through the sample generates an acoustic signal within the sample, whereby the acoustic signal propagates through the sample to and through the acoustic couplant to the acoustic detector.

  1. Piezoelectric step-motion actuator

    DOEpatents

    Mentesana; Charles P. (Leawood, KS)

    2006-10-10

    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.

  2. In vivo optical resolution photoacoustic microscopy using glancing angle-deposited nanostructured Fabry-Perot etalons.

    PubMed

    Hajireza, Parsin; Sorge, Jason; Brett, Michael; Zemp, Roger

    2015-04-01

    In this Letter, reflection-mode optical resolution photoacoustic microscopy (OR-PAM) using glancing angle-deposited (GLAD) nanostructured Fabry-Perot interferometers (FPI) for in vivo applications is reported. GLAD is a single-step physical vapor deposition (PVD) technique used to fabricate porous nanostructured thin films. Using titanium dioxide, a transparent semiconductor with a high refractive index (n=2.4), the GLAD technique can be employed to fabricate samples with tailored nano-porosity, refractive index periodicities, and high Q-factor reflectance spectra. The OR-PAM in vivo images of chorioallantoic membrane (CAM) of 5-day chicken embryo model are demonstrated. The phantom study shows lateral resolution and signal-to-noise ratio better than 7 ?m and 35 dB, respectively. The sensitive GLAD FPI allows photoacoustic imaging down to a few-nJ pulse energy. To the best of our knowledge, this is the first time that a FPI-based reflection mode optical resolution photoacoustic imaging technique is demonstrated for in vivo applications. PMID:25831330

  3. Measurement of Grüneisen parameter of tissue by photoacoustic spectrometry

    NASA Astrophysics Data System (ADS)

    Yao, Da-Kang; Wang, Lihong V.

    2013-03-01

    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).

  4. Multifunctional microbubbles and nanobubbles for photoacoustic and ultrasound imaging

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

    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 photoacoustic and ultrasound imaging enhanced by encapsulated-dye PLGA microbubbles or nanobubbles can be a valuable tool for intraoperative assessment of tumor boundaries and therapeutic margins.

  5. Improved Piezoelectric Loudspeakers And Transducers

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  6. High Temperature Piezoelectric Drill

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  7. Piezoelectrically enhanced photocathode

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  8. Modeling piezoelectric actuators

    Microsoft Academic Search

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

    2000-01-01

    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

  9. Raman spectroscopy of piezoelectrics

    NASA Astrophysics Data System (ADS)

    Pezzotti, Giuseppe

    2013-06-01

    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.

  10. PIEZOELECTRIC POWER SCAVENGING OF MECHANICAL VIBRATION ENERGY

    E-print Network

    Ervin, Elizabeth K.

    PIEZOELECTRIC POWER SCAVENGING OF MECHANICAL VIBRATION ENERGY PIEZOELECTRIC POWER SCAVENGING OFPIEZOELECTRIC POWER SCAVENGING OF MECHANICAL VIBRATION ENERGYMECHANICAL VIBRATION ENERGY CE 511- Structural

  11. Hybrid piezoelectric energy harvesting transducer system

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

  12. Multimaterial piezoelectric fibres.

    PubMed

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

    2010-08-01

    Fibre materials span a broad range of applications ranging from simple textile yarns to complex modern fibre-optic communication systems. Throughout their history, a key premise has remained essentially unchanged: fibres are static devices, incapable of controllably changing their properties over a wide range of frequencies. A number of approaches to realizing time-dependent variations in fibres have emerged, including refractive index modulation, nonlinear optical mechanisms in silica glass fibres and electroactively modulated polymer fibres. These approaches have been limited primarily because of the inert nature of traditional glassy fibre materials. Here we report the composition of a phase internal to a composite fibre structure that is simultaneously crystalline and non-centrosymmetric. A ferroelectric polymer layer of 30 mum thickness is spatially confined and electrically contacted by internal viscous electrodes and encapsulated in an insulating polymer cladding hundreds of micrometres in diameter. The structure is thermally drawn in its entirety from a macroscopic preform, yielding tens of metres of piezoelectric fibre. The fibres show a piezoelectric response and acoustic transduction from kilohertz to megahertz frequencies. A single-fibre electrically driven device containing a high-quality-factor Fabry-Perot optical resonator and a piezoelectric transducer is fabricated and measured. PMID:20622864

  13. Piezoelectric wind turbine

    NASA Astrophysics Data System (ADS)

    Kishore, Ravi Anant; Priya, Shashank

    2013-03-01

    In past few years, there has been significant focus towards developing small scale renewable energy based power sources for powering wireless sensor nodes in remote locations such as highways and bridges to conduct continuous health monitoring. These prior efforts have led to the development of micro-scale solar modules, hydrogen fuel cells and various vibration based energy harvesters. However, the cost effectiveness, reliability, and practicality of these solutions remain a concern. Harvesting the wind energy using micro-to-small scale wind turbines can be an excellent solution in variety of outdoor scenarios provided they can operate at few miles per hour of wind speed. The conventional electromagnetic generator used in the wind mills always has some cogging torque which restricts their operation above certain cut-in wind speed. This study aims to develop a novel piezoelectric wind turbine that utilizes bimorph actuators for electro-mechanical energy conversion. This device utilizes a Savonius rotor that is connected to a disk having magnets at the periphery. The piezoelectric actuators arranged circumferentially around the disk also have magnets at the tip which interacts with the magnetic field of the rotating disk and produces cyclical deflection. The wind tunnel experiments were conducted between 2-12 mph of wind speeds to characterize and optimize the power output of the wind turbine. Further, testing was conducted in the open environment to quantify the response to random wind gusts. An attempt was made towards integration of the piezoelectric wind turbine with the wireless sensor node.

  14. Quantum cascade laser based standoff photoacoustic chemical detection.

    PubMed

    Chen, Xing; Cheng, Liwei; Guo, Dingkai; Kostov, Yordan; Choa, Fow-Sen

    2011-10-10

    Standoff chemical detection with a distance of more than 41 feet using photoacoustic effect and quantum cascade laser (QCL) operated at relatively low power, less than 40 mW, is demonstrated for the first time. The option of using QCL provides the advantages of easy tuning and modulation besides the benefit of compact size, light weight and low power consumption. The standoff detection signal can be calibrated as a function of different parameters such as laser pulse energy, gas vapor concentration and detection distance. The results yield good agreements with theoretical model. Techniques to obtain even longer detection distance and achieve outdoor operations are in the process of implementation and their projection is discussed. PMID:21997036

  15. Characterization of reconstructed human skin using Photoacoustic Spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2008-01-01

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

  16. Label-free oxygen-metabolic photoacoustic microscopy in vivo

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    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.

  17. Intracellular temperature mapping with fluorescence-assisted photoacoustic thermometry

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  18. Investigation of standoff explosives detection via photothermal/photoacoustic interferometry

    NASA Astrophysics Data System (ADS)

    Cho, Pak S.; Jones, Robert M.; Shuman, Timothy; Scoglietti, Daniel; Harston, Geof

    2011-05-01

    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 probe laser system positioned 5 meters away from the explosives targets. In addition, PTI measurements of the stimulated Raman (SR) spectra of ammonium nitrate and 2,4,6-trinitrotoluene obtained using a near-IR OPO laser are described. We believe this is the first-ever application of photothermal techniques to the measurement of the SR effect on solid explosive materials at meaningful standoff distances.

  19. Energy Harvesting Using PVDF Piezoelectric Nanofabric

    NASA Astrophysics Data System (ADS)

    Shafii, Chakameh Shafii

    Energy harvesting using piezoelectric nanomaterial provides an opportunity for advancement towards self-powered electronics. The fabrication complexities and limited power output of these nano/micro generators have hindered these advancements thus far. This thesis presents a fabrication technique with electrospinning using a grounded cylinder as the collector. This method addresses the difficulties with the production and scalability of the nanogenerators. The non-aligned nanofibers are woven into a textile form onto the cylindrical drum that can be easily removed. The electrical poling and mechanical stretching induced by the electric field and the drum rotation increase the concentration of the piezoelectric beta phase in the PVDF nanofabric. The nanofabric is placed between two layers of polyethylene terephthalate (PET) that have interdigitated electrodes painted on them with silver paint. Applying continuous load onto the flexible PVDF nanofabric at 35Hz produces a peak voltage of 320 mV and maximum power of 2200 pW/(cm2) .

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  1. Characterizing phantom arteries with multi-channel laser ultrasonics and photo-acoustics.

    PubMed

    Johnson, Jami L; van Wijk, Kasper; Sabick, Michelle

    2014-03-01

    Multi-channel photo-acoustic and laser ultrasonic waves are used to sense the characteristics of proxies for healthy and diseased vessels. The acquisition system is non-contacting and non-invasive with a pulsed laser source and a laser vibrometer detector. As the wave signatures of our targets are typically low in amplitude, we exploit multi-channel acquisition and processing techniques. These are commonly used in seismology to improve the signal-to-noise ratio of data. We identify vessel proxies with a diameter on the order of 1 mm, at a depth of 18 mm. Variations in scattered and photo-acoustic signatures are related to differences in vessel wall properties and content. The methods described have the potential to improve imaging and better inform interventions for atherosclerotic vessels, such as the carotid artery. PMID:24412169

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

    NASA Astrophysics Data System (ADS)

    Jo, Janggun; Yang, Xinmai

    2011-09-01

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

  3. High frequency photoacoustic imaging for in vivo visualizing blood flow of zebrafish heart.

    PubMed

    Park, Jinhyoung; Cummins, Thomas M; Harrison, Michael; Lee, Jungwoo; Zhou, Qifa; Lien, Ching-Ling; Shung, K Kirk

    2013-06-17

    A technique on high frame rate(28fps), high frequency co-registered ultrasound and photoacoustic imaging for visualizing zebrafish heart blood flow was demonstrated. This approach was achieved with a 40MHz light weight(0.38g) ring-type transducer, serving as the ultrasound transmitter and receiver, to allow an optic fiber, coupled with a 532nm laser, to be inserted into the hole. From the wire target study, axial resolutions of 38µm and 42µm were obtained for ultrasound and photoacoustic imaging, respectively. Carbon nanotubes were utilized as contrast agents to increase the flow signal level by 20dB in phantom studies, and zebrafish heart blood flow was successfully observed. PMID:23787651

  4. Noninvasive, in vivo imaging of the mouse brain using photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Stein, Erich W.; Maslov, Konstantin; Wang, Lihong V.

    2009-05-01

    Noninvasive, high resolution imaging of mouse brain activity is poised to provide clinically translatable insights into human neurological disease progression. Toward noninvasive imaging of brain activity through the hemodynamic response, the dark-field photoacoustic microscopy (PAM) technique was enhanced to image the cortex vasculature of the mouse brain in vivo using endogenous hemoglobin contrast. Specifically, the PAM system was redesigned to efficiently collect photoacoustic waves originating from cortical vessels, providing high (70 ?m lateral and 54 ?m axial) resolution images of the mouse brain vasculature with a contrast-to-noise ratio of 25 dB. These findings confirm the efficacy of PAM to noninvasively image vascular structures in the mouse brain and the potential to image mouse brain function by tracking the hemodynamic response.

  5. Sono-photoacoustic imaging of gold nanoemulsions: Part II. Real time imaging

    PubMed Central

    Arnal, Bastien; Wei, Chen-Wei; Perez, Camilo; Nguyen, Thu-Mai; Lombardo, Michael; Pelivanov, Ivan; Pozzo, Lilo D.; O’Donnell, Matthew

    2015-01-01

    Photoacoustic (PA) imaging using exogenous agents can be limited by degraded specificity due to strong background signals. This paper introduces a technique called sono-photoacoustics (SPA) applied to perfluorohexane nanodroplets coated with gold nanospheres. Pulsed laser and ultrasound (US) excitations are applied simultaneously to the contrast agent to induce a phase-transition ultimately creating a transient microbubble. The US field present during the phase transition combined with the large thermal expansion of the bubble leads to 20–30 dB signal enhancement. Aqueous solutions and phantoms with very low concentrations of this agent were probed using pulsed laser radiation at diagnostic exposures and a conventional US array used both for excitation and imaging. Contrast specificity of the agent was demonstrated with a coherent differential scheme to suppress US and linear PA background signals. SPA shows great potential for molecular imaging with ultrasensitive detection of targeted gold coated nanoemulsions and cavitation-assisted theranostic approaches. PMID:25893170

  6. Spectroscopic Studies of Human Hair, Nail, and Saliva Samples Using a Cantilever-Based Photoacoustic Detection

    NASA Astrophysics Data System (ADS)

    Lehtinen, Jaakko

    2013-09-01

    In infrared spectroscopy human hair has normally been studied using attenuated total reflectance or diffuse reflectance infrared Fourier transform spectroscopy, for which the sample preparation methods can lead to problems of reproducibility. Definite information could be obtained by studying intact individual hair fibers, but the small diameter of hair fibers and the lack of sensitivity make such measurement difficult. A highly detailed infrared spectrum of human hair has been measured using a cantilever-based photoacoustic detection. The spectrum can be obtained even if a piece of hair as small as 1 cm is used as a sample. Photoacoustic spectroscopy (PAS) is a well-established technique in many areas, but very little has been published in the research of proteins. Two simple applications of PAS for human hair, as well as measurements with different types of proteins, are presented in this paper.

  7. Photoacoustic imaging of functional domains in primary motor cortex in rhesus macaques

    NASA Astrophysics Data System (ADS)

    Jo, Janggun; Zhang, Hongyu; Cheney, Paul; Yang, Xinmai

    2012-02-01

    Functional detection in primate brains has particular advantages because of the similarity between non-human primate brain and human brain and the potential for relevance to a wide range of conditions such as stroke and Parkinson's disease. In this research, we used photoacoustic imaging (PAI) technique to detect functional changes in primary motor cortex of awake rhesus monkeys. We observed strong increases in photoacoustic signal amplitude during both passive and active forelimb movement, which indicates an increase in total hemoglobin concentration resulting from activation of primary motor cortex. Further, with PAI approach, we were able to obtain depthresolved functional information from primary motor cortex. The results show that PAI can reliably detect primary motor cortex activation associated with forelimb movement in rhesus macaques with a minimal-invasive approach.

  8. Evaluation of tissue microstructure with a narrowband and low frequency photoacoustic tomography system

    NASA Astrophysics Data System (ADS)

    Yang, Yiqun; Wang, Shaohua; Tao, Chao; Wang, Xueding; Liu, Xiaojun

    2013-03-01

    The characteristic microstructures in biological tissues could be used to differentiate tissue types, such as tumor vs. normal tissue. The spatial resolution of classical photoacoustic tomography (PAT) mainly depends on the wavelengths of the detected ultrasonic signals. In order to present the very detailed microstructures in a biological sample, the receiving bandwidth of the PAT system needs to be extremely wide. Another challenge in detecting the high frequency signals associated with microstructures is the strong acoustic attenuation which increases quadratically with ultrasound frequency. In this study, we propose a novel photoacoustic spectral analysis (PSA) technique which evaluates the microstructures in tissues by analyzing the spectral parameters of detected photoacoustic signals. Experimental result verified that, using a limited 1-5 MHz working bandwidth, PSA could effectively differentiate two melanoma-mimicking phantoms containing different microstructures (49 ?m and 199 ?m absorber sizes respectively). In comparison, since the physical scales of the microstructures are too small and beyond the spatial resolution of the PAT system, classical tomographic imaging could not differentiate the two phantoms. The findings from this study suggest that the proposed PSA technique could help distinguish different tissue types, by evaluating the characteristic microstructures in tissues, without relying on the detection of high frequency signals which is extremely challenging when the target object is deep.

  9. Detection of melanoma cells suspended in mononuclear cells and blood plasma using photoacoustic generation

    NASA Astrophysics Data System (ADS)

    Spradling, Emily M.; Viator, John A.

    2009-02-01

    Melanoma is the deadliest form of skin cancer. Although the initial malignant cells are removed, it is impossible to determine whether or not the cancer has metastasized until a secondary tumor forms that is large enough to detect with conventional imaging. Photoacoustic detection of circulating melanoma cells in the bloodstream has shown promise for early detection of metastasis that may aid in treatment of this aggressive cancer. When blood is irradiated with energy from an Nd:YAG laser at 532 nm, photoacoustic signals are created and melanoma cells can be differentiated from the surrounding cells based on waveforms produced by an oscilloscope. Before this can be used as a diagnostic technique, however, we needed to investigate several parameters. Specifically, the current technique involves the in vitro separation of blood through centrifugation to isolate and test only the white blood cell layer. Using this method, we have detected a single cultured melanoma cell among a suspension of white blood cells. However, the process could be made simpler if the plasma layer were used for detection instead of the white blood cell layer. This layer is easier to obtain after blood separation, the optical difference between plasma and melanoma cells is more pronounced in this layer than in the white blood cell layer, and the possibility that any stray red blood cells could distort the results is eliminated. Using the photoacoustic apparatus, we detected no melanoma cells within the plasma of whole blood samples spiked with cultured melanoma cells.

  10. Indocyanine Green-Loaded Photoacoustic Nanodroplets – Dual Contrast Nanoconstructs for Enhanced Photoacoustic and Ultrasound Imaging

    PubMed Central

    Hannah, Alexander; Luke, Geoffrey; Wilson, Katheryne; Homan, Kimberly Ann; Emelianov, Stanislav

    2014-01-01

    Recently, perfluorocarbon (PFC) nanodroplets were introduced as contrast agents for imaging and image-guided therapy. For example, in sonography, high-intensity ultrasound pulses were used to phase-transition liquid perfluorocarbon to produce gas microbubbles. More recently, perfluorocarbon nanodroplets with encapsulated gold nanorods were used as dual ultrasound/photoacoustic contrast agents. To expedite clinical translation, we synthesized and characterized ICG-loaded perfluorocarbon nanodroplets, i.e. constructs comprising biocompatible, non-toxic and biologically safe materials. We then demonstrated enhanced photoacoustic contrast through optically triggered phase transition of PFC nanodroplets and ultrasound contrast from the resulting PFC bubbles. We assessed the quality enhancement of photoacoustic and ultrasound images through analysis of contrast and contrast-to-noise ratio. We further investigated the changes in image contrast due to increased ambient temperature. Our studies suggest that ICG-loaded perfluorocarbon nanodroplets may become a valuable tool for various imaging modalities, and have promising therapeutic applications. PMID:24303934

  11. Practical implementation of piezoelectric energy harvesting synchronized switching schemes

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  12. A Piezoelectric-Piezomagnetic Gyrator

    Microsoft Academic Search

    M. Onoe; M. Sawabe

    1962-01-01

    A linear passive unilateral element, which has a high forward\\/backward transmission ratio at all frequencies, is realized by combining two resistances and an electromechanical gyrator according to Gamo's theory. The gyrator consists of three mechanically coupled ceramic elements, two of which may be piezomagnetic and the third piezoelectric, or two of which may be piezoelectric and the third piezomagnetic. In

  13. Photoacoustic and Photothermal Effects in Particulate Suspensions

    SciTech Connect

    Diebold, Gerald, J.

    2009-04-30

    A summary of the research areas investigated by the author during the grant period is given. Experiments and theory have been carried out on the photoacoustic effect arising from a number of physical and chemical processes. A number of studies of the photoacoustic effect as it occurs in transient grating experiments have been completed. The research done with the Ludwig-Soret effect on the generation of shock waves is reported. Other research, such as that carried out on interferometric and beam deflection microphones, the use of microphones in vacuum as momentum flux detectors, and chemical generation of sonoluminescence is listed. A list of published research including selected publications, a complete list of journal articles, books, review articles, and reviews are given.

  14. High-Temperature Piezoelectrics with Large Piezoelectric Coefficients

    NASA Astrophysics Data System (ADS)

    Shinekumar, K.; Dutta, Soma

    2015-02-01

    High-temperature piezoelectric materials are of interest for sensors and actuators in various industrial applications in which the devices are exposed to high temperature. A lot of research has been conducted in this area to bring forth a suitable piezoelectric material having a high Curie temperature for suitable usage at a high temperature with good piezoelectric properties. This report is an attempt to review the state of the art in high-temperature piezoelectric materials, covering their issues and concerns at elevated temperatures. Among the non-ferroelectric crystal classes, langasite and oxyborate crystals retain their piezoelectricity up to a very high temperature, but their piezoelectric coefficient is much smaller compared to a standard piezoelectric material such as lead zirconate titanate. A similar trend has also been observed in ferroelectric crystal class which shows poor piezoelectricity but retains it until a high temperature. Recent studies on solid solutions of bismuth-based oxides and lead titanate with the chemical formulae Bi(Me3+) O3-PbTiO3 and Bi(Me1Me2)O3-PbTiO3 (Me3+ represents a trivalent cation and Me1 and Me2 are cations having a combined valency of 3) show a much application potential of these materials due to improved piezoelectric property and high Curie temperature. BiScO3-PbTiO3, Bi(Mg0.5Ti0.5)O3-PbTiO3, (Bi(Ni0.5Ti0.5)O3-PbTiO3 and Bi(Zn0.5T0.5)O3-PbTiO3 are some interesting high-temperature piezoelectrics from the group of Bi(Me3+)O3-PbTiO3 and Bi(Me1Me2) O3-PbTiO3 which shows superior piezoelectric properties at high temperatures. Among the lead-free piezoelectrics, (K0.5Na0.5)NbO3 demands a special interest for further studies due to its plausible good piezoelectric property at elevated temperature.

  15. Multifunctional Photosensitizer-Based Contrast Agents for Photoacoustic Imaging

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  16. In vivo photoacoustic tomography of mouse cerebral edema induced

    E-print Network

    Wang, Lihong

    In vivo photoacoustic tomography of mouse cerebral edema induced by cold injury Zhun Xu Quing Zhu cerebral edema induced by cold injury Zhun Xu,a Quing Zhu,b and Lihong V. Wanga aWashington University. For the first time, we have implemented photoacoustic tomography (PAT) to image the water content of an edema

  17. Photoacoustic ocular imaging Adam de la Zerda,1,2

    E-print Network

    Khuri-Yakub, Butrus T. "Pierre"

    Photoacoustic ocular imaging Adam de la Zerda,1,2 Yannis M. Paulus,3 Robert Teed,1 Sunil Bodapati,1); published January 20, 2010 We developed a photoacoustic ocular imaging device and demonstrated its utility in imaging the deeper lay- ers of the eye including the retina, choroid, and optic nerve. Using safe laser

  18. Silica-coated gold nanorods as photoacoustic signal nanoamplifiers.

    PubMed

    Chen, Yun-Sheng; Frey, Wolfgang; Kim, Seungsoo; Kruizinga, Pieter; Homan, Kimberly; Emelianov, Stanislav

    2011-02-01

    Photoacoustic signal generation by metal nanoparticles relies on the efficient conversion of light to heat, its transfer to the environment, and the production of pressure transients. In this study we demonstrate that a dielectric shell has a strong influence on the amplitude of the generated photoacoustic signal and that silica-coated gold nanorods of the same optical density are capable of producing about 3-fold higher photoacoustic signals than nanorods without silica coating. Spectrophotometry measurements and finite difference time domain (FDTD) analysis of gold nanorods before and after silica coating showed only an insignificant change of the extinction and absorption cross sections, hence indicating that the enhancement is not attributable to changes in absorption cross section resulting from the silica coating. Several factors including the silica thickness, the gold/silica interface, and the surrounding solvent were varied to investigate their effect on the photoacoustic signal produced from silica-coated gold nanorods. The results suggest that the enhancement is caused by the reduction of the gold interfacial thermal resistance with the solvent due to the silica coating. The strong contrast enhancement in photoacoustic imaging, demonstrated using phantoms with silica-coated nanorods, shows that these hybrid particles acting as "photoacoustic nanoamplifiers" are high efficiency contrast agents for photoacoustic imaging or photoacoustic image-guided therapy. PMID:21244082

  19. Multifunctional Photosensitizer-Based Contrast Agents for Photoacoustic Imaging

    PubMed Central

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

    2014-01-01

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

  20. Multifunctional photosensitizer-based contrast agents for photoacoustic imaging.

    PubMed

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

    2014-01-01

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

  1. Photoacoustic Doppler Effect from Flowing Small Light-Absorbing Particles

    Microsoft Academic Search

    Hui Fang; Konstantin Maslov; Lihong V. Wang

    2007-01-01

    From the flow of a suspension of micrometer-scale carbon particles, the photoacoustic Doppler shift is observed. As predicted theoretically, the observed Doppler shift equals half of that in Doppler ultrasound and does not depend on the direction of laser illumination. This new physical phenomenon provides a basis for developing photoacoustic Doppler flowmetry, which can potentially be used for detecting fluid

  2. Thickness dependence of hydrostatic piezoelectric properties of 1–3 piezoelectric composites

    Microsoft Academic Search

    Li Denghua; Yao Xi

    1999-01-01

    Thickness dependence of hydrostatic piezoelectric properties of 1–3 piezoelectric composites was studied. PZT rods with square cross section were used as piezoelectric active components. Epoxy resin was used as matrix. The volume fraction of piezoelectric ceramic was about 25%. The hydrostatic piezoelectric properties dh, gh and hydrostatic figure of merit dh gh are all dependent on the ratio of width

  3. Acoustic resonance frequency locked photoacoustic spectrometer

    DOEpatents

    Pilgrim, Jeffrey S.; Bomse, David S.; Silver, Joel A.

    2003-09-09

    A photoacoustic spectroscopy method and apparatus for maintaining an acoustic source frequency on a sample cell resonance frequency comprising: providing an acoustic source to the sample cell, the acoustic source having a source frequency; repeatedly and continuously sweeping the source frequency across the resonance frequency at a sweep rate; and employing an odd-harmonic of the source frequency sweep rate to maintain the source frequency sweep centered on the resonance frequency.

  4. Evaluation of Dry Chemicals by Photoacoustic Imaging

    NASA Astrophysics Data System (ADS)

    Hoshimiya, Tsutomu

    1992-10-01

    In this study, an apparatus suitable to photoacoustic (PA) imaging to measure blood-analysis and urinalysis is fabricated and its measurement scheme has been established for the first time. The PA imaging of urinalysis test strip, blood sugar test strip, and cholesterol test strip is performed. A calibration curve of PA measurement is obtained for a urine test strip. The detectivity is better than that obtained by an eye-measurement.

  5. In vivo optically encoded photoacoustic flowgraphy.

    PubMed

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

    2014-07-01

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

  6. Quantitative imaging of bilirubin by photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  7. Dual-modal whole eye photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Wu, Ning; Ren, Qiushi; Li, Changhui

    2014-09-01

    We developed a prototype dual-modal ocular imaging system integrating optical-resolution photoacoustic microscopy and high-frequency ultrasound imaging modalities. This system can perform high-resolution ocular imaging from the anterior region down to the fundus area. The novel system successfully imaged the murine eyes in vivo, including iris, lens, retina, and retinal pigment epithelium. Our results demonstrated that this system has a great potential in the diagnosis of ophthalmic diseases.

  8. Photoacoustics of disperse systems: Below cavitation threshold

    SciTech Connect

    Egerev, Sergey; Ovchinnikov, Oleg [Andreyev Acoustics Institute, Moscow, 117036 (Russian Federation)

    2012-05-24

    The paper considers photoacoustic (PA) conversion while irradiating suspensions in extra-small volume probes with laser pulses having small fluence values. Only linear and nonlinear thermooptical laser sound generation regimes were observed. Thus, good repeatability of acoustic signal parameters informative about probe content was achieved. The experiment conducted has shown how one can avoid the decrease of particles detection sensitivity for the thermooptical mode.

  9. In vivo photoacoustic imaging of mouse embryos

    NASA Astrophysics Data System (ADS)

    Laufer, Jan; Norris, Francesca; Cleary, Jon; Zhang, Edward; Treeby, Bradley; Cox, Ben; Johnson, Peter; Scambler, Pete; Lythgoe, Mark; Beard, Paul

    2012-06-01

    The ability to noninvasively image embryonic vascular anatomy in mouse models is an important requirement for characterizing the development of the normal cardiovascular system and malformations in the heart and vascular supply. Photoacoustic imaging, which can provide high resolution non invasive images of the vasculature based upon optical absorption by endogenous hemoglobin, is well suited to this application. In this study, photoacoustic images of mouse embryos were obtained ex vivo and in vivo. The images show intricate details of the embryonic vascular system to depths of up to 10 mm, which allowed whole embryos to be imaged in situ. To achieve this, an all-optical photoacoustic scanner and a novel time reversal image reconstruction algorithm, which provide deep tissue imaging capability while maintaining high spatial resolution and contrast were employed. This technology may find application as an imaging tool for preclinical embryo studies in developmental biology as well as more generally in preclinical and clinical medicine for studying pathologies characterized by changes in the vasculature.

  10. Acoustic and Photoacoustic Molecular Imaging of Cancer

    PubMed Central

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

    2014-01-01

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

  11. Imaging hypoxia using 3D photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Stantz, Keith M.

    2010-02-01

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

  12. Photoacoustic cavitation in spherical and cylindrical absorbers

    NASA Astrophysics Data System (ADS)

    Paltauf, G.; Schmidt-Kloiber, H.

    Photomechanical damage in absorbing regions or particles surrounded by a non-absorbing medium is investigated experimentally and theoretically. The damage mechanism is based on the generation of thermoelastic pressure by absorption of pulsed laser radiation under conditions of stress confinement. Principles of photoacoustic sound generation predict that the acoustic wave generated in a finite-size absorbing region must contain both compressive and tensile stresses. Time-resolved imaging experiments were performed to examine whether the tensile stress causes cavitation in absorbers of spherical or cylindrical shape. The samples were absorbing water droplets and gelatin cylinders suspended in oil. They were irradiated with 6-ns-long pulses from an optical parametric oscillator. Photoacoustic cavitation was observed near the center of the absorbers, even if the estimated temperature caused by absorption of the laser pulse did not exceed the boiling point. The experimental findings are supported by theoretical simulations that reveal strong tensile stress in the interior of the absorbers, near the center of symmetry. Tensile stress amplitudes depend on the shape of the absorber, the laser pulse duration, and the ratio of absorber size to optical absorption length. The photoacoustic damage mechanism has implications for the interaction of ns and sub-nslaser pulses with pigmented structures in biological tissue.

  13. Photoacoustic imaging and characterization of the microvasculature

    PubMed Central

    Hu, Song; Wang, Lihong V.

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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.

  15. An optimized ultrasound detector for photoacoustic breast tomography

    E-print Network

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

    2012-01-01

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

  16. Numerical characterization of soft piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

  17. Narcotics detection using piezoelectric ringing

    NASA Astrophysics Data System (ADS)

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

    1997-02-01

    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.

  18. Spectroscopic photoacoustic imaging of lipid-rich plaques in the human aorta in the 740 to 1400 nm wavelength range

    NASA Astrophysics Data System (ADS)

    Allen, Thomas J.; Hall, Andrew; Dhillon, Amar P.; Owen, James S.; Beard, Paul C.

    2012-06-01

    Spectroscopic photoacoustic imaging has the potential to discriminate between normal and lipid-rich atheromatous areas of arterial tissue by exploiting the differences in the absorption spectra of lipids and normal arterial tissue in the 740 to 1400 nm wavelength range. Identification of regions of high lipid concentration would be useful to identify plaques that are likely to rupture (vulnerable plaques). To demonstrate the feasibility of visualizing lipid-rich plaques, samples of human aortas were imaged in forward mode, at wavelengths of 970 and 1210 nm. It was shown that the structure of the arterial wall and the boundaries of lipid-rich plaques obtained from the photoacoustic images were in good agreement with histology. The presence of lipids was also confirmed by comparing the photoacoustic spectra (740 to 1400 nm) obtained in a region within the plaque to the spectral signature of lipids. Furthermore, a lipid-rich plaque was successfully imaged while illuminating the sample through 2.8 mm of blood demonstrating the possibility of implementing the photoacoustic technique in vivo.

  19. Combined acoustic-photoacoustic and fluorescence imaging catheter for the detection of the atherosclerotic plaque

    NASA Astrophysics Data System (ADS)

    Abran, Maxime; Matteau-Pelletier, Carl; Zerouali-Boukhal, Karim; Tardif, Jean-Claude; Lesage, Frédéric

    2011-03-01

    In industrialized countries, cardiovascular diseases remain the main cause of mortality. The detection of atherosclerosis and its associated plaque using imaging techniques allows studying the efficacy of new drugs in vivo. Intravascular ultrasound (IVUS) imaging has been demonstrated to be a powerful tool to uncover structural information of atherosclerotic plaques. Recently, intravascular photoacoustic (IVPA) has been combined with IVUS imaging to add functional and/or molecular information. The IVPA/IVUS combination has been demonstrated in phantoms and ex vivo tissues to provide relevant information about the composition of the plaque, as well as its vulnerability. In this work, we extend previous work by developing a combined IVPA/IVUS system using a rotating ultrasound transducer in a catheter to which an optical fiber is attached. In addition, a third modality was included through fluorescence detection in the same fiber at a distinct wavelength from PA, opening the door to complementary information using fluorescence activatable probes. Cylindrical silicon phantoms with inclusions containing fluorophores or ink were used to validate the system. Bleaching of the fluorophore by the pulsed laser used for photoacoustic was quantified. IVUS images were obtained continuously and used to co-register photoacoustic and fluorescence signals.

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

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

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

    PubMed

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

    2013-10-01

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

  3. Photoacoustic and nuclear imaging of [125I]-labeled gold nanorod contrast agent

    NASA Astrophysics Data System (ADS)

    Shao, Xia; Agarwal, Ashish; Rajian, Justin R.; Kotov, Nicholas A.; Wang, Xueding

    2011-03-01

    We have investigated the potential of emerging photoacoustic imaging and nuclear imaging in monitoring of drug delivery by using a newly developed dual-modality contrast agent. After the contrast agent composed of gold nanorods (GNRs) was produced, it was radiolabeled by [125I] with high yield and without disturbing the optical properties of the contrast agent. Photoacoustic and nuclear imaging were conducted to visualize the distribution of GNRs in articular tissues of rat tail joints in situ. Findings from the two modalities corresponded well with each other. Using the current imaging systems, GNRs down to a concentration of 10 pM in biological tissues and with a radioactive label of 5 ?Ci can be imaged. Moreover, by radiolabeling the GNRs, the in vivo behaviors of the contrast agent can be monitored conveniently using ?-camera, allowing validation of the findings from emerging photoacoustic technique. Enabled by the high sensitivity of nuclear imaging, whole-body and longitudinal studies of the biodistribution of GNRs contrast agent can be performed noninvasively and repeatedly in the same animal. The highly efficient method reported here provides an extensively useful tool for the guidance of design and development of new gold nanoparticles as target-specific agents for both diagnostics and therapy.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  5. Radial Field Piezoelectric Diaphragms

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

  6. Piezoelectric trace vapor calibrator

    NASA Astrophysics Data System (ADS)

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

    2006-08-01

    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 290fg/lto1.05?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.

  7. Design Requirements for Amorphous Piezoelectric Polymers

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  8. Comparison of photoacoustic radiometry to gas chromatography/mass spectrometry methods for monitoring chlorinated hydrocarbons

    SciTech Connect

    Sollid, J.E.; Trujillo, V.L.; Limback, S.P.; Woloshun, K.A.

    1996-03-01

    A comparison of two methods of gas chromatography mass spectrometry (GCMS) and a nondispersive infrared technique, photoacoustic radiometry (PAR), is presented in the context of field monitoring a disposal site. First is presented an historical account describing the site and early monitoring to provide an overview. The intent and nature of the monitoring program changed when it was proposed to expand the Radiological Waste Site close to the Hazardous Waste Site. Both the sampling methods and analysis techniques were refined in the course of this exercise.

  9. Precision piezoelectric stepping motor using piezoelectric torsional actuator

    NASA Astrophysics Data System (ADS)

    Kang, Byung-Woo; Kim, Jaehwan; Cheong, ChaeCheon; Yang, Bo-Won

    2001-03-01

    This paper deals with a newly developed piezoelectric motor that generates precise stepping motion using a piezoelectric torsional actuator and a pair of one-way clutch bearings. The torsional actuator consists of a piezoelectric cylinder that produces rotation motion invoking shear mode of piezoelectric materials and a torsion bar that magnifies the rotation angle produced from the piezoelectric cylinder. Inner one-way clutch bearing is fit on the torsion bar and outer bearing is mounted outside of the inner bearing such that when the torsion bar rotates in one direction, the inner bearing moves together while the outer one slips. When the torsion bar rotates in opposite direction, the inner bearing slips against the torsion bar while the outer bearing locks the inner bearing so as to accumulate the rotation angle. Because the elaborate piezoelectric torsional actuator functions as the driving source at high frequency, a precise step motion with high speed can be produced. The optimum condition for driving the motor is investigated in terms of excitation frequency, electrical impedance and the location of the bearing set. The rotation speed and torque of the motor is investigated, and 350 rpm and 0.19mNm torque are observed in maximum.

  10. A Resonant Damping Study Using Piezoelectric Materials

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  11. A mode III crack in functionally graded piezoelectric materials

    Microsoft Academic Search

    B. L. Wang

    2003-01-01

    This paper considers the mode III crack problem in functionally graded piezoelectric materials. The mechanical and the electrical properties of the medium are considered for a class of functional forms for which the equilibrium equations have an analytical solution. The problem is solved by means of singular integral equation technique. Both a single crack and a series of collinear cracks

  12. Aeroelastic tailoring using piezoelectric actuation and hybrid optimization

    Microsoft Academic Search

    Aditi Chattopadhyay; Charles E. Seeley; Ratneshwar Jha

    1998-01-01

    Active control of fixed wing aircraft using piezoelectric materials has the potential to improve its aeroelastic response while reducing weight penalties. However, the design of active aircraft wings is a complex optimization problem requiring the use of formal optimization techniques. In this paper, a hybrid optimization procedure is applied to the design of an airplane wing, represented by a flat

  13. Aeroelastic tailoring using piezoelectric actuation and hybrid optimization

    Microsoft Academic Search

    Aditi Chattopadhyay; Charles E. Seeley; Ratneshwar Jha

    1999-01-01

    Active control of fixed wing aircraft using piezoelectric materials has the potential to improve its aeroelastic response while reducing weight penalties. However, the design of active aircraft wings is a complex optimization problem requiring the use of formal optimization techniques. In this paper, a hybrid optimization procedure is applied to the design of a scaled airplane wing model, represented by

  14. AN EXPERIMENTAL STUDY OF SPHERICAL INDENTATION ON PIEZOELECTRIC MATERIALS

    E-print Network

    Suresh, Subra

    microindentation was investigated. Force vs penetration depth curves obtained from instrumented indenta- tion structures [2]. Most of the prior work on piezoelectric materials has focused on developing materials. Instrumented indentation techniques ®nd growing appeal for assessing the mechanical properties of small

  15. Piezoelectric microcantilever serum protein detector

    NASA Astrophysics Data System (ADS)

    Capobianco, Joseph A.

    The development of a serum protein detector will provide opportunities for better screening of at-risk cancer patients, tighter surveillance of disease recurrence and better monitoring of treatment. An integrated system that can process clinical samples for a number of different types of biomarkers would be a useful tool in the early detection of cancer. Also, screening biomarkers such as antibodies in serum would provide clinicians with information regarding the patient's response to treatment. Therefore, the goal of this study is to develop a sensor which can be used for rapid, all-electrical, real-time, label-fee, in-situ, specific quantification of cancer markers, e.g., human epidermal receptor 2 (Her2) or antibodies, in serum. To achieve this end, piezoelectric microcantilever sensors (PEMS) were constructed using an 8 mum thick lead magnesium niobate-lead titanate (PMN-PT) freestanding film as the piezoelectric layer. The desired limit of detection is on the order of pg/mL. In order to achieve this goal the higher frequency lateral extension modes were used. Also, as the driving and sensing of the PEMS is electrical, the PEMS must be insulated in a manner that allows it to function in aqueous solutions. The insulation layer must also be compatible with standardized bioconjugation techniques. Finally, detection of both cancer antigens and antibodies in serum was carried out, and the results were compared to a standard commercialized protocol. PEMS have demonstrated the capability of detecting Her2 at a concentration of 5 pg/mL in diluted human serum (1:40) in less than 1 hour. The approach can be easily translated into the clinical setting because the sensitivity is more than sufficient for monitoring prognosis of breast cancer patients. In addition to Her2 detection, antibodies in serum were assayed in order to demonstrate the feasibility of monitoring the immune response for antibody-dependent cellular cytotoxicity (ADCC) in patients on antibody therapies such as Herceptin and Cetuximab. The PEMS displayed a limit of detection of 100 fg/mL, which was 100 times lower than the current methods of protein detection in serum, such as ELISA. Furthermore, the sensitivity of the PEMS device allows it to be capable of determining the dissociation constant, K d, of selective receptors such as antibodies. Using the dose response trials of Her2, Kd has been deduced for H3 scFv, and Herceptin, a commercial antibody specific for Her2.

  16. Piezoelectric MEMS for energy harvesting

    E-print Network

    Kim, Sang-Gook

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

  17. Backward-mode multiwavelength photoacoustic scanner using a planar Fabry-Perot polymer film ultrasound sensor for high-resolution three-dimensional imaging of biological tissues.

    PubMed

    Zhang, Edward; Laufer, Jan; Beard, Paul

    2008-02-01

    A multiwavelength backward-mode planar photoacoustic scanner for 3D imaging of soft tissues to depths of several millimeters with a spatial resolution in the tens to hundreds of micrometers range is described. The system comprises a tunable optical parametric oscillator laser system that provides nanosecond laser pulses between 600 and 1200 nm for generating the photoacoustic signals and an optical ultrasound mapping system based upon a Fabry-Perot polymer film sensor for detecting them. The system enables photoacoustic signals to be mapped in 2D over a 50 mm diameter aperture in steps of 10 microm with an optically defined element size of 64 microm. Two sensors were used, one with a 22 microm thick polymer film spacer and the other with a 38 mum thick spacer providing -3 dB acoustic bandwidths of 39 and 22 MHz, respectively. The measured noise equivalent pressure of the 38 microm sensor was 0.21 kPa over a 20 MHz measurement bandwidth. The instrument line-spread function (LSF) was measured as a function of position and the minimum lateral and vertical LSFs found to be 38 and 15 microm, respectively. To demonstrate the ability of the system to provide high-resolution 3D images, a range of absorbing objects were imaged. Among these was a blood vessel phantom that comprised a network of blood filled tubes of diameters ranging from 62 to 300 microm immersed in an optically scattering liquid. In addition, to demonstrate the applicability of the system to spectroscopic imaging, a phantom comprising tubes filled with dyes of different spectral characteristics was imaged at a range of wavelengths. It is considered that this type of instrument may provide a practicable alternative to piezoelectric-based photoacoustic systems for high-resolution structural and functional imaging of the skin microvasculature and other superficial structures. PMID:18239717

  18. Backward-mode multiwavelength photoacoustic scanner using a planar Fabry-Perot polymer film ultrasound sensor for high-resolution three-dimensional imaging of biological tissues

    NASA Astrophysics Data System (ADS)

    Zhang, Edward; Laufer, Jan; Beard, Paul

    2008-02-01

    A multiwavelength backward-mode planar photoacoustic scanner for 3D imaging of soft tissues to depths of several millimeters with a spatial resolution in the tens to hundreds of micrometers range is described. The system comprises a tunable optical parametric oscillator laser system that provides nanosecond laser pulses between 600 and 1200 nm for generating the photoacoustic signals and an optical ultrasound mapping system based upon a Fabry-Perot polymer film sensor for detecting them. The system enables photoacoustic signals to be mapped in 2D over a 50 mm diameter aperture in steps of 10 ?m with an optically defined element size of 64 ?m. Two sensors were used, one with a 22 ?m thick polymer film spacer and the other with a 38 ?m thick spacer providing -3 dB acoustic bandwidths of 39 and 22 MHz, respectively. The measured noise equivalent pressure of the 38 ?m sensor was 0.21 kPa over a 20 MHz measurement bandwidth. The instrument line-spread function (LSF) was measured as a function of position and the minimum lateral and vertical LSFs found to be 38 and 15 ?m, respectively. To demonstrate the ability of the system to provide high-resolution 3D images, a range of absorbing objects were imaged. Among these was a blood vessel phantom that comprised a network of blood filled tubes of diameters ranging from 62 to 300 ?m immersed in an optically scattering liquid. In addition, to demonstrate the applicability of the system to spectroscopic imaging, a phantom comprising tubes filled with dyes of different spectral characteristics was imaged at a range of wavelengths. It is considered that this type of instrument may provide a practicable alternative to piezoelectric-based photoacoustic systems for high-resolution structural and functional imaging of the skin microvasculature and other superficial structures.

  19. Considering sources and detectors distributions for quantitative photoacoustic tomography

    PubMed Central

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

    2014-01-01

    Photoacoustic tomography (PAT) is a hybrid imaging modality that takes advantage of high optical contrast brought by optical imaging and high spatial resolution brought by ultrasound imaging. However, the quantification in photoacoustic imaging is challenging. Multiple optical illumination approach has proven to achieve uncoupling of diffusion and absorption effects. In this paper, this protocol is adopted and synthetic photoacoustic data, blurred with some noise, were generated. The influence of the distribution of optical sources and transducers on the reconstruction of the absorption and diffusion coefficients maps is studied. Specific situations with limited view angles were examined. The results show multiple illuminations with a wide field improve the reconstructions. PMID:25426322

  20. Concomitant speed-of-sound tomography in photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Manohar, Srirang; Willemink, René G. H.; van der Heijden, Ferdi; Slump, Cornelis H.; van Leeuwen, Ton G.

    2007-09-01

    We present a method to generate quantitative cross-sectional maps of acoustic propagation speed in tissue using the photoacoustic principle. The method is based on the interaction of laser-induced ultrasound from an extraneous absorber with the object under photoacoustic investigation. The propagation times of the ultrasound transients through the object at angles around 360° are measured using a multielement ultrasound detector. The geometry lends itself to fan-beam reconstruction allowing speed-of-sound tomograms to be generated. Simultaneously, conventional photoacoustic computed tomography can be performed as well. We demonstrate the concept showing results on phantoms carrying speed-of-sound distributions.

  1. Photoacoustic tomography: Ultrasonically beating optical diffusion and diffraction

    NASA Astrophysics Data System (ADS)

    Wang, Lihong

    2014-03-01

    A decade of research has pushed photoacoustic computed tomography to the forefront of molecular-level imaging, notes SPIE Fellow Lihong Wang (Washington University, St. Louis) in his plenary talk, "Photoacoustic Tomography: Ultrasonically Beating Optical Diffusion and Diffraction." Modern optical microscopy has resolution and diffraction limitations. But noninvasive functional photoacoustic computed tomography has overcome this limit, offering deep penetration with optical contrast and ultrasonic resolution of 1 cm depth or more -- up to 7 cm of penetration in some cases, such as evaluating sentinel lymph nodes for breast cancer staging. This opens up applications in whole body imaging, brain function, oxygen saturation, label-free cell analysis, and noninvasive cancer biopsies.

  2. Blood pulse wave velocity measured by photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  3. Considering sources and detectors distributions for quantitative photoacoustic tomography.

    PubMed

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

    2014-11-01

    Photoacoustic tomography (PAT) is a hybrid imaging modality that takes advantage of high optical contrast brought by optical imaging and high spatial resolution brought by ultrasound imaging. However, the quantification in photoacoustic imaging is challenging. Multiple optical illumination approach has proven to achieve uncoupling of diffusion and absorption effects. In this paper, this protocol is adopted and synthetic photoacoustic data, blurred with some noise, were generated. The influence of the distribution of optical sources and transducers on the reconstruction of the absorption and diffusion coefficients maps is studied. Specific situations with limited view angles were examined. The results show multiple illuminations with a wide field improve the reconstructions. PMID:25426322

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  5. Dedicated 3D photoacoustic breast imaging

    PubMed Central

    Kruger, Robert A.; Kuzmiak, Cherie M.; Lam, Richard B.; Reinecke, Daniel R.; Del Rio, Stephen P.; Steed, Doreen

    2013-01-01

    Purpose: To report the design and imaging methodology of a photoacoustic scanner dedicated to imaging hemoglobin distribution throughout a human breast. Methods: The authors developed a dedicated breast photoacoustic mammography (PAM) system using a spherical detector aperture based on our previous photoacoustic tomography scanner. The system uses 512 detectors with rectilinear scanning. The scan shape is a spiral pattern whose radius varies from 24 to 96 mm, thereby allowing a field of view that accommodates a wide range of breast sizes. The authors measured the contrast-to-noise ratio (CNR) using a target comprised of 1-mm dots printed on clear plastic. Each dot absorption coefficient was approximately the same as a 1-mm thickness of whole blood at 756 nm, the output wavelength of the Alexandrite laser used by this imaging system. The target was immersed in varying depths of an 8% solution of stock Liposyn II-20%, which mimics the attenuation of breast tissue (1.1 cm?1). The spatial resolution was measured using a 6 ?m-diameter carbon fiber embedded in agar. The breasts of four healthy female volunteers, spanning a range of breast size from a brassiere C cup to a DD cup, were imaged using a 96-mm spiral protocol. Results: The CNR target was clearly visualized to a depth of 53 mm. Spatial resolution, which was estimated from the full width at half-maximum of a profile across the PAM image of a carbon fiber, was 0.42 mm. In the four human volunteers, the vasculature was well visualized throughout the breast tissue, including to the chest wall. Conclusions: CNR, lateral field-of-view and penetration depth of our dedicated PAM scanning system is sufficient to image breasts as large as 1335 mL, which should accommodate up to 90% of the women in the United States. PMID:24320471

  6. Photoacoustic microscopy of the effect of mechanical processing on the martensite structure of near-surface layers in Cu-Al-Ni alloy single crystals

    Microsoft Academic Search

    A. L. Glazov; K. L. Muratikov; V. I. Nikolaev; S. A. Pul'Nev

    2010-01-01

    The near-surface layers in single crystals of copper-based alloys possessing shape memory and superelasticity have been studied using the photoacoustic microscopy (PAM) techniques. It is established that the PAM is advantageous to optical microscopy in studying the martensite structure, in particular, because this structure can be revealed without preliminary polishing of the sample surface. This circumstance allowed the effect of

  7. Testing fruit quality by photoacoustic spectroscopy assay

    NASA Astrophysics Data System (ADS)

    Popa, C.; Dumitras, D. C.; Patachia, M.; Banita, S.

    2014-10-01

    This study was conducted with the aim of testing the hypothesis that raspberry and strawberry fruits from nonorganic farming release more ethylene gas compounds compared to organic ones. At the same time, the experiments focused on evaluation of the potential and capabilities of the laser photoacoustic spectroscopy (LPAS) method in the assessment of fruit quality related to the effects of nitrogen. Ethylene gas can be harmful and carcinogenic, because it can accelerate the natural ripening process of physiologically mature fruits and makes the fruits more consistent in size. With the advantages of LPAS, we demonstrate that the concentration of ethylene from nonorganic raspberry and strawberry fruits is greater than from organic ones.

  8. Photoacoustic and thermoacoustic tomography of dog prostates

    NASA Astrophysics Data System (ADS)

    Ke, Haixin; Guo, Zijian; Erpelding, Todd N.; Jankovic, Ladislav; Grubb, Robert L., III; Wang, Lihong V.

    2011-03-01

    We developed a tri-modal system combining photoacoustic (PA) tomography, thermoacoustic (TA) tomography, and ultrasound (US) imaging. Acquired images of an excised dog prostate were compared to histology results. All three modalities can image distinct features. Features like the urethra were shown in both TA and US images, but TA gave a higher contrast-to-noise ratio. Fibrous tissue was more clearly imaged by TA, while the duct structure was better shown in PA images. These experimental results demonstrate the potential advantages of our tri-modal imaging system.

  9. Photoacoustic NO detection for asthma diagnostics

    NASA Astrophysics Data System (ADS)

    Germer, Markus; Wolff, Marcus; Harde, Hermann

    2009-07-01

    Exhaled nitric oxide was of high interest in breath analyses in the past few years. After its first detection in human breath in 1991, numerous publications uncovered the role of NO and its relation to different diseases. A strong relationship between an asthmatic eosinophilic airway inflammation and an increased NO level is medically confirmed. In this study a new photoacoustic detection system for nitric oxide based on a pulsed quantum cascade laser is introduced. The laser's single mode emission provides adequate selectivity to differentiate NO from other molecules in the sample. The demonstrated detection sensitivity allows in principle an application of the new system as diagnostic tool for asthma.

  10. Thermally Enhanced Photoacoustic Radar Imaging of Biotissues

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Mandelis, Andreas

    2015-02-01

    The signal-to-noise ratio (SNR) and imaging depth of photoacoustic (PA) imaging remain limited for clinical applications. The temperature can influence PA signals; the SNR of PA signals can be increased at higher temperatures. Therefore, the imaging quality and depth can be improved by the assistance of heating. Experimental results showed that the maximum imaging depth can be doubled by raising the temperature of the absorbers (ex-vivo beef muscle) uniformly from 20° C to 41° C, and the SNR can be increased 53 % from 20° C to 45° {C}.

  11. Piezoelectric activity in Perovskite ferroelectric crystals.

    PubMed

    Li, Fei; Wang, Linghang; Jin, Li; Lin, Dabin; Li, Jinglei; Li, Zhenrong; Xu, Zhuo; Zhang, Shujun

    2015-01-01

    Perovskite ferroelectrics (PFs) have been the dominant piezoelectric materials for various electromechanical applications, such as ultrasonic transducers, sensors, and actuators, to name a few. In this review article, the development of PF crystals is introduced, focusing on the crystal growth and piezoelectric activity. The critical factors responsible for the high piezoelectric activity of PFs (i.e., phase transition, monoclinic phase, domain size, relaxor component, dopants, and piezoelectric anisotropy) are surveyed and discussed. A general picture of the present understanding on the high piezoelectricity of PFs is described. At the end of this review, potential approaches to further improve the piezoelectricity of PFs are proposed. PMID:25585387

  12. Thermal Image of Coffee-Seed Germ Obtained by Photoacoustic Microscopy

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  13. Design and characterization of piezoelectric transformers for high power applications

    Microsoft Academic Search

    Pitak Laoratanakul

    2002-01-01

    A piezoelectric transformer (PT) is an electro-mechanical device that transfers electrical energy through a mechanical vibration at its resonance frequency. To improve the piezoelectric transformers in term of high density of transfer power, two types of piezoelectric transformers, a laminated piezoelectric transformer and an unipoled disk piezoelectric transformer, with radial extensional vibration mode were studied. For the laminated piezoelectric transformer,

  14. Photoacoustic and Photoelectrochemical Characterization of CdSe Quantum Dots Grafted onto Fluorine-Doped Tin Oxide (FTO) Substrate

    Microsoft Academic Search

    Taro Toyoda; Dai Arae; Qing Shen

    2005-01-01

    We report on the optical absorption properties, measured by the photoacoustic (PA) method, and photoelectrochemical current (PEC) characteristics (including transient measurements) of CdSe quantum dots (Q-dots) grafted onto a planar fluorine-doped SnO2 (FTO) substrate. CdSe Q-dots were fabricated by the chemical solution deposition (CD) technique. With increasing deposition time, the redshift of the PA spectra can be clearly observed and

  15. Non-contact photoacoustic tomography and ultrasonography for brain imaging

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  16. Photoacoustic measurement of the Grüneisen parameter of tissue.

    PubMed

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

    2014-01-01

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

  17. Water-soluble dopamine-based polymers for photoacoustic imaging.

    PubMed

    Repenko, Tatjana; Fokong, Stanley; De Laporte, Laura; Go, Dennis; Kiessling, Fabian; Lammers, Twan; Kuehne, Alexander J C

    2015-03-24

    Here we present a facile synthetic method yielding a linear form of polydopamine via Kumada-coupling, which can be converted into water-soluble melanin, generating high contrast in photoacoustic imaging. PMID:25670068

  18. Enhancement of photoacoustic emission from self-supported plasmonic multilayers

    NASA Astrophysics Data System (ADS)

    Namura, Kyoko; Nakajima, Kaoru; Kimura, Kenji; Suzuki, Motofumi

    2014-07-01

    In this paper, we demonstrate remarkable photoacoustic emission from self-supported Au nanoparticle/dielectric/Ag mirror structures. They were prepared by depositing thin films on both sides of a 50-nm-thick silicon nitride membrane. The photoacoustic emission generated by the self-supported sample is more than 2 orders of magnitude larger than that of a similar structure supported by a Si wafer at a laser modulation frequency of 1 kHz. In this frequency region, the thermal diffusion length becomes much greater than the thickness of the multilayers, so that the photoacoustic amplitude is determined mainly by the thermal conductivity of the substrate. Therefore, the large enhancement of the photoacoustic emission can be understood in terms of the reduced thermal conductivity of the substrate.

  19. Photoacoustic measurement of the Grüneisen parameter of tissue

    PubMed Central

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

    2014-01-01

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

  20. In vivo longitudinal photoacoustic imaging of subcutaneous tumours in mice

    NASA Astrophysics Data System (ADS)

    Laufer, Jan; Johnson, Peter; Zhang, Edward; Treeby, Bradley; Cox, Ben; Pedley, Barbara; Beard, Paul

    2011-03-01

    Photoacoustic tomography can provide high resolution 3D images of vascular networks, making it well suited to characterising the development of tumour vasculature and its response to treatment. In this study, photoacoustic images to depths of up to 9 mm were obtained using an all optical ultrasound detection scheme. Two type of colorectal tumours (LS174T and SW1222) implanted subcutaneously in a mouse were studied. 3D photoacoustic images were obtained in vivo revealing the different vascular architectures of each tumour type and their evolution over a period of several days. The results suggest that photoacoustic imaging could play a role in providing essential pre-clinical information on tumour pathophysiology and eliciting the biological mechanisms underlying anti-angiogenic therapies and other treatments.

  1. PHOTOACOUSTIC IMAGING AND HIGH INTENSITY FOCUSED ULTRASOUND IN BIOMEDICAL APPLICATIONS

    E-print Network

    Jo, Janggu

    2014-08-31

    . In this work, photoacoustic imaging that combines the advantages of optical and ultrasound imaging, and high intensity focused ultrasound (HIFU) treatment enhanced with laser were investigated to understand the application and feasibility of optics...

  2. Piezoelectrically Initiated Pyrotechnic Igniter

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  3. Self-powered discrete time piezoelectric vibration damper

    NASA Astrophysics Data System (ADS)

    Konak, Michael J.; Powlesland, Ian G.; van der Velden, Stephen P.; Galea, Stephen C.

    1997-11-01

    Structural vibration suppression is of great interest to the aircraft industry as it can reduce the amplitude of excessive vibration in lightly damped panels caused by conditions in their operational environment. One technique of suppressing vibration is to use passive damping techniques such as constrained layered damping incorporating viscoelastic materials. However these techniques may not be acceptable because of weight concerns or extreme temperature variations. Over the past decade much work has been done by researchers on the use of piezoelectric ceramic devices, using passive and active techniques, for structural vibration suppression. The passive piezoelectric damping devices consist of a piezoelectric element and either a resistive or resonant shunt. The resonant circuit shunt, which is analogous to a mechanical vibration absorber, gives better vibration reduction compared to the resistor shunt. This device requires a large value of inductance in order to be tuned to a particular structural vibration mode. A large value inductor can be made by a using a gyrator type circuit however the circuit needs external power. A method of vibration control using a discrete time controller and piezoelectric devices is presented. That is, this paper describes the concept of a self-powered discrete time piezoelectric vibration damper which does not need tuning to the structural resonant frequency and is powered by piezoelectric elements, i.e. does not need an external power supply. This device is referred to as a strain amplitude minimization patch (STAMP) damper. A brief description of the theory used and of the scheme is presented. Also the operation of this device is compared with other 'passive' techniques, involving piezoelectric elements, such as the resistive passive damper and the parallel resonant passive damper cases. Experimental results presented, on a cantilevered beam, demonstrate the concept and show that the device, even in its current underdeveloped form, has better damping than the simple resistor damper. Measurements taken indicate that the maximum RMS tip accelerations, at resonance, are reduced by 17.3%, 62.7% and 39.5% for the resistor, parallel resonant and STAMP damper devices, respectively, when compared to the short circuit reference condition. The performance of each device is observed when the resonant frequency of the system changes when a mass is added to the tip of the cantilever. This paper also discusses areas where improvements in the performance of the STAMP damper can be achieved.

  4. Photoacoustic study of the photostability of sunscreens

    NASA Astrophysics Data System (ADS)

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

    2008-01-01

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

  5. Functional photoacoustic microscopy of diabetic vasculature

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  6. Quantitative signal analysis in pulsed resonant photoacoustics

    NASA Astrophysics Data System (ADS)

    Schäfer, Stefan; Miklós, András; Hess, Peter

    1997-05-01

    The pulsed excitation of acoustic resonances was studied by means of a high- Q photoacoustic resonator with different types of microphone. The signal strength of the first radial mode was calculated by the basic theory as well as by a modeling program, which takes into account the acoustic impedances of the resonator, the acoustic filter system, and the influence of the microphone coupling on the photoacoustic cavity. When the calculated signal strength is used, the high- Q system can be calibrated for trace-gas analysis without a certified gas mixture. The theoretical results were compared with measurements and show good agreement for different microphone configurations. From the measured pressure signal (in pascals per joule), the absorption coefficient of ethylene was calculated; it agreed within 10 with literature values. In addition, a Helmholtz configuration with a highly sensitive 1-in. (2.54-cm) microphone was realized. Although the Q factor was reduced, the sensitivity could be increased by the Helmholtz resonator in the case of pulsed experiments. A maximum sensitivity of the coupled system of 341 mV Pa was achieved.

  7. A UV-Vis photoacoustic spectrophotometer.

    PubMed

    Wiegand, Joseph R; Mathews, L Dalila; Smith, Geoffrey D

    2014-06-17

    A novel photoacoustic spectrophotometer (PAS) for the measurement of gas-phase and aerosol absorption over the UV-visible region of the spectrum is described. Light from a broadband Hg arc lamp is filtered in eight separate bands from 300 to 700 nm using bandpass interference filters (centered at 301 nm, 314 nm, 364 nm, 405 nm, 436 nm, 546 nm, 578 and 687 nm) and modulated with an optical chopper before entering the photoacoustic cell. All wavelength bands feature a 20-s detection limit of better than 3.0 Mm(-1) with the exception of the lower-intensity 687 nm band for which it is 10.2 Mm(-1). Validation measurements of gas-phase acetone and nigrosin aerosol absorption cross sections at several wavelengths demonstrate agreement to within 10% with those measured previously (for acetone) and those predicted by Mie theory (for nigrosin). The PAS instrument is used to measure the UV-visible absorption spectrum of ambient aerosol demonstrating a dramatic increase in the UV region with absorption increasing by 300% from 405 to 301 nm. This type of measurement throughout the UV-visible region and free from artifacts associated with filter-based methods has not been possible previously, and we demonstrate its promise for classifying and quantifying different types of light-absorbing ambient particles. PMID:24905953

  8. Photoacoustic microtomography using optical interferometric detection

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  9. Fast-scanning ultrasonic-photoacoustic biomicroscope: in vivo performance

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

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

  10. Measuring droplet impact with piezoelectric film

    E-print Network

    Basahi, Jalal M. Al-Badry M.

    1993-01-01

    materials used in piezoelectric applications were barium titanate, rochelle salt and quartz (Klapholz, 1985). During World War H, researchers found that ceramics have high piezoelectric response. By 1960, researchers found that the polyvinylidene fluoride...

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  12. Tunable fiber laser based photoacoustic gas sensor for early fire detection

    NASA Astrophysics Data System (ADS)

    Wang, Jianwei; Wang, Huili

    2014-07-01

    A photoacoustic gas sensor using a near-infrared tunable fiber laser and based on wavelength modulation spectroscopy technique is developed. This sensor is capable of quasi-simultaneous quantification of water vapour, acetylene, carbon dioxide, and carbon monoxide (H2O, C2H2, CO and CO2) concentrations in the fire emulator. The feasibility of using this sensor as an early fire detector was demonstrated. The fire warning gases from smoldering paper were measured. The peak concentrations of gases from smoldering paper were 20,300 ppm H2O, 2.1 ppm C2H2, 756 ppm CO, and 1612 ppm CO2 after 400 s.

  13. Three-Dimensional Photoacoustic Endoscopic Imaging of the Rabbit Esophagus

    PubMed Central

    Yao, Junjie; Chen, Ruimin; Zhou, Qifa; Shung, K. Kirk; Wang, Lihong V.

    2015-01-01

    We report photoacoustic and ultrasonic endoscopic images of two intact rabbit esophagi. To investigate the esophageal lumen structure and microvasculature, we performed in vivo and ex vivo imaging studies using a 3.8-mm diameter photoacoustic endoscope and correlated the images with histology. Several interesting anatomic structures were newly found in both the in vivo and ex vivo images, which demonstrates the potential clinical utility of this endoscopic imaging modality. In the ex vivo imaging experiment, we acquired high-resolution motion-artifact-free three-dimensional photoacoustic images of the vasculatures distributed in the walls of the esophagi and extending to the neighboring mediastinal regions. Blood vessels with apparent diameters as small as 190 ?m were resolved. Moreover, by taking advantage of the dual-mode high-resolution photoacoustic and ultrasound endoscopy, we could better identify and characterize the anatomic structures of the esophageal lumen, such as the mucosal and submucosal layers in the esophageal wall, and an esophageal branch of the thoracic aorta. In this paper, we present the first photoacoustic images showing the vasculature of a vertebrate esophagus and discuss the potential clinical applications and future development of photoacoustic endoscopy. PMID:25874640

  14. Circulating tumor cell detection using photoacoustic spectral methods

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    A method to detect and differentiate circulating melanoma tumor cells (CTCs) from blood cells using ultrasound and photoacoustic signals with frequencies over 100 MHz is presented. At these frequencies, the acoustic wavelength is similar to the dimensions of a cell, which results in unique features in the signal; periodically varying minima and maxima occur throughout the power spectrum. The spacing between minima depends on the ratio of the size to sound speed of the cell. Using a 532 nm pulsed laser and a 375 MHz center frequency wide-bandwidth transducer, the ultrasound and photoacoustic signals were measured from single cells. A total of 80 cells were measured, 20 melanoma cells, 20 white blood cells (WBCs) and 40 red blood cells (RBCs). The photoacoustic spectral spacing ?f between minima was 95 +/- 15 MHz for melanoma cells and greater than 230 MHz for RBCs. No photoacoustic signal was detected from WBCs. The ultrasonic spectral spacing between minima was 46 +/- 9 MHz for melanoma cells and 98 +/- 11 for WBCs. Both photoacoustic and ultrasound signals were detected from melanoma cells, while only ultrasound signals were detected from WBCs. RBCs showed distinct photoacoustic spectral variations in comparison to any other type of cell. Using the spectral spacing and signal amplitudes, each cell type could be grouped together to aid in cell identification. This method could be used for label-free counting and classifying cells in a sample.

  15. Cryogenic Piezoelectric Actuator

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  16. Numerical Analysis of Piezoelectric Active Repair in the Presence of Frictional Contact Conditions

    PubMed Central

    Alaimo, Andrea; Milazzo, Alberto; Orlando, Calogero; Messineo, Antonio

    2013-01-01

    The increasing development of smart materials, such as piezoelectric and shape memory alloys, has opened new opportunities for improving repair techniques. Particularly, active repairs, based on the converse piezoelectric effect, can increase the life of a structure by reducing the crack opening. A deep characterization of the electromechanical behavior of delaminated composite structures, actively repaired by piezoelectric patches, can be achieved by considering the adhesive layer between the host structure and the repair and by taking into account the frictional contact between the crack surfaces. In this paper, Boundary Element (BE) analyses performed on delaminated composite structures repaired by active piezoelectric patches are presented. A two-dimensional boundary integral formulation for piezoelectric solids based on the multi-domain technique to model the composite host damaged structures and the bonded piezoelectric patches is employed. An interface spring model is also implemented to take into account the finite stiffness of the bonding layers and to model the frictional contact between the delamination surfaces, by means of an iterative procedure. The effect of the adhesive between the plies of piezoelectric bimorph devices on the electromechanical response is first pointed out for both sensing and actuating behavior. Then, the effect of the frictional contact condition on the fracture mechanics behavior of actively repaired delaminated composite structures is investigated. PMID:23549364

  17. Vertical comb drive actuator for the measurement of piezoelectric coefficients in small-scale systems

    NASA Astrophysics Data System (ADS)

    Wooldridge, J.; Muniz-Piniella, A.; Stewart, M.; Shean, T. A. V.; Weaver, P. M.; Cain, M. G.

    2013-03-01

    A micro-electro-mechanical systems (MEMS) vertical levitation comb drive actuator has been created for the measurement of piezoelectric coefficients in thin/thick films or piezoelectrically active micro-scale components of other MEMS devices. The device exerts a dynamic force of 33 ?N at an applied voltage of 100 V. The charge developed on the piezoelectric test device is measured using a charge sensitive pre-amplifier and lock-in technique, enabling measurements down to 1×10-5 pC. The system was tested with ten different piezoelectric samples with coefficients in the range 70-1375 pC N-1 and showed a good correlation (r = 0.9997) to measurements performed with macroscopic applied stresses, and piezoelectric impedance resonance techniques. The measurement of the direct piezoelectric effect in micro- and nano-scale piezo-materials has been made possible using MEMS processing technology. This new application of a MEMS metrology device has been developed and fully characterized in order to accurately evaluate the functional properties of piezoelectric materials at the scale required in micro- to nano-scale applications.

  18. Radially sandwiched cylindrical piezoelectric transducer

    NASA Astrophysics Data System (ADS)

    Lin, Shuyu; Fu, Zhiqiang; Zhang, Xiaoli; Wang, Yong; Hu, Jing

    2013-01-01

    A new type of radially sandwiched piezoelectric short cylindrical transducer is developed and its radial vibration is studied. The transducer is composed of a solid metal disk, a radially polarized piezoelectric ceramic short tube and a metal tube. The radial vibrations of the solid metal disk, the radially polarized piezoelectric tube and the metal tube are analyzed and their electromechanical equivalent circuits are introduced. Based on the mechanical boundary conditions among the metal disk, the piezoelectric tube and the metal tube, a three-port electromechanical equivalent circuit for the radially sandwiched transducer is obtained and the frequency equation is given. The theoretical relationship of the resonance and anti-resonance frequencies and the effective electromechanical coupling coefficient with the geometrical dimensions is analyzed. The radial vibration of the sandwiched transducer is simulated by using two different numerical methods. It is shown that the analytical resonance and anti-resonance frequencies are in good agreement with the numerically simulated results. The transducer is expected to be used in piezoelectric resonators, actuators and ultrasonic radiators in ultrasonic and underwater sound applications.

  19. Fluoropolymer and Aluminum Piezoelectric Reactives

    NASA Astrophysics Data System (ADS)

    Janesheski, Robert; Son, Steven; Groven, Lori

    2011-06-01

    The ability to sensitize a nanoaluminum/piezoelectric polymer composite has been studied using two fluoropolymer systems (THV220A and FC-2175). Fluoropolymers were chosen based on the presence of vinylidene fluoride (VDF) that is known to exhibit piezoelectric properties in certain phases. Reactive composite samples of the nanoaluminum/polymer were made into thin sheets and their ability to store energy and exhibit piezoelectric properties was measured. Also, initial drop weight impact tests were performed on the samples and results showed the piezoelectric energetic composites failed to ignite at a given impact energy. However, when a DC voltage was applied to the sample, the materials ignited at the previous impact energy indicating that the reactive composites may have been sensitized by the stored charge. The application of a DC voltage may also have an effect on the piezoelectric properties of the inorganic energetic composites. Further work is planned to investigate what parameters are inducing the sensitization of the material. A better understanding could lead to applications where switching or changing the sensitization of an energetic material is beneficial.

  20. Photoacoustic diagnosis of burns in rats: two-dimensional photo-acoustic imaging of burned tissue

    NASA Astrophysics Data System (ADS)

    Yamazaki, Mutsuo; Sato, Shunichi; Saito, Daizo; Okada, Yoshiaki; Kurita, Akira; Kikuchi, Makoto; Ashida, Hiroshi; Obara, Minoru

    2003-06-01

    We previously reported that for rat burn models, deep dermal burns and deep burns can be well differentiated by measuring the propagation time of the photoacoustic signals originated from the blood in the healthy skin tissue under the damaged tissue layer. However, the diagnosis was based on point measurement in the wound, and therefore site-dependent information on the injuries was not obtained; such information is very important for diagnosis of extended burns. In the present study, we scanned a photoacoustic detector on the wound and constructed two-dimensional (2-D) images of the blood-originated photoacoustic signals for superficial dermal burns (SDB), deep dermal burns (DDB), deep burns (DB), and healthy skins (control) in rats. For each burn model, site-dependent variation of the signal was observed; the variation probably reflects the distribution of blood vessels in the skin tissue. In spite of the variation, clear differentiation was obtained between SDB, DDB, and DB from the 2D images. The images were constructed as a function of post burn time. Temporal signal variation will be also presented.

  1. Dynamic analysis of tubular piezoelectric gyroscopes

    Microsoft Academic Search

    Pavel S. Marinushkin

    2010-01-01

    The present article provides a theoretical and experimental research of piezoelectric gyroscopes based on the flexural vibrating modes of hollow piezoelectric cylinders. For different geometries, modal and harmonic analyses are conducted using ANSYS finite element software package. The sensitivity of piezoelectric gyroscopes and its correlation with geometrical and physical parameters of resonators are explored. The results obtained are compared with

  2. Whole-body ring-shaped confocal photoacoustic computed tomography of

    E-print Network

    Wang, Lihong

    Whole-body ring-shaped confocal photoacoustic computed tomography of small animals in vivo Jun Xia;Whole-body ring-shaped confocal photoacoustic computed tomography of small animals in vivo Jun Xia a novel small-animal whole-body imaging system called ring-shaped confocal photoacoustic computed

  3. Photoacoustic Doppler flow measurement in optically scattering media Konstantin Maslov, and Lihong V. Wangb

    E-print Network

    Wang, Lihong

    November 2007; published online 28 December 2007 We recently observed the photoacoustic Doppler effect from the photoacoustic Doppler PAD effect from flowing small light-absorbing particles.9 There, the experimentPhotoacoustic Doppler flow measurement in optically scattering media Hui Fang,a Konstantin Maslov

  4. Imaging and detection of early stage dental caries with an all-optical photoacoustic microscope

    NASA Astrophysics Data System (ADS)

    Hughes, D. A.; Sampathkumar, A.; Longbottom, C.; Kirk, K. J.

    2015-01-01

    Tooth decay, at its earliest stages, manifests itself as small, white, subsurface lesions in the enamel. Current methods for detection in the dental clinic are visual and tactile investigations, and bite-wing X-ray radiographs. These techniques suffer from poor sensitivity and specificity at the earliest (and reversible) stages of the disease due to the small size (<100?m) of the lesion. A fine-resolution (600 nm) ultra-broadband (200 MHz) all-optical photoacoustic microscopy system was is used to image the early signs of tooth decay. Ex-vivo tooth samples exhibiting white spot lesions were scanned and were found to generate a larger (one order of magnitude) photoacoustic (PA) signal in the lesion regions compared to healthy enamel. The high contrast in the PA images potentially allows lesions to be imaged and measured at a much earlier stage than current clinical techniques allow. PA images were cross referenced with histology photographs to validate our experimental results. Our PA system provides a noncontact method for early detection of white-spot lesions with a high detection bandwidth that offers advantages over previously demonstrated ultrasound methods. The technique provides the sensing depth of an ultrasound system, but with the spatial resolution of an optical system.

  5. Photoacoustically-guided photothermal killing of mosquitoes targeted by nanoparticles.

    PubMed

    Foster, Stephen R; Galanzha, Ekaterina I; Totten, Daniel C; Beneš, Helen; Shmookler Reis, Robert J; Zharov, Vladimir P

    2014-07-01

    In biomedical applications, nanoparticles have demonstrated the potential to eradicate abnormal cells in small localized pathological zones associated with cancer or infections. Here, we introduce a method for nanotechnology-based photothermal (PT) killing of whole organisms considered harmful to humans or the environment. We demonstrate that laser-induced thermal, and accompanying nano- and microbubble phenomena, can injure or kill C. elegans and mosquitoes fed carbon nanotubes, gold nanospheres, gold nanoshells, or magnetic nanoparticles at laser energies that are safe for humans. In addition, a photoacoustic (PA) effect was used to control nanoparticle delivery. Through the integration of this technique with molecular targeting, nanoparticle clustering, magnetic capturing and spectral sharpening of PA and PT plasmonic resonances, our laser-based PA-PT nano-theranostic platform can be applied to detection and the physical destruction of small organisms and carriers of pathogens, such as malaria vectors, spiders, bed bugs, fleas, ants, locusts, grasshoppers, phytophagous mites, or other arthropod pests, irrespective of their resistance to conventional treatments. PMID:23450780

  6. Non-contact photoacoustic tomography and ultrasonography for biomedical imaging

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    Photoacoustic tomography (PAT) and ultrasonography (US) of biological tissues usually rely on ultrasonic transducers for the detection of ultrasound. For an optimum sensitivity, transducers require a physical contact with the tissue using a coupling fluid (water or gel). Such a contact is a major drawback in important potential applications such as surgical procedures on human beings and small animal imaging in research laboratories. On the other hand, laser ultrasonics (LU) is a well established optical technique for the non-contact generation and detection of ultrasound in industrial materials. In this paper, the remote optical detection scheme used in industrial LU is adapted to allow the detection of ultrasound in biological tissues while remaining below laser exposure safety limits. Both non-contact PAT (NCPAT) and non-contact US (NCUS) are considered experimentally using a high-power single-frequency detection laser emitting suitably shaped pulses and a confocal Fabry-Perot interferometer in differential configuration. It is shown that an acceptable sensitivity is obtained while remaining below the maximum permissible exposure (MPE) of biological tissues. Results were obtained ex vivo on chicken breast specimens with embedded inclusions simulating blood vessels optical properties. Sub-mm inclusions are readily detected at depths approaching 1 cm. The method is expected to be applicable to living tissues.

  7. Optical-thermal light-tissue interactions during photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Gould, Taylor; Wang, Quanzeng; Pfefer, T. Joshua

    2014-03-01

    Photoacoustic imaging (PAI) has grown rapidly as a biomedical imaging technique in recent years, with key applications in cancer diagnosis and oximetry. In spite of these advances, the literature provides little insight into thermal tissue interactions involved in PAI. To elucidate these basic phenomena, we have developed, validated, and implemented a three-dimensional numerical model of tissue photothermal (PT) response to repetitive laser pulses. The model calculates energy deposition, fluence distributions, transient temperature and damage profiles in breast tissue with blood vessels and generalized perfusion. A parametric evaluation of these outputs vs. vessel diameter and depth, optical beam diameter, wavelength, and irradiance, was performed. For a constant radiant exposure level, increasing beam diameter led to a significant increase in subsurface heat generation rate. Increasing vessel diameter resulted in two competing effects - reduced mean energy deposition in the vessel due to light attenuation and greater thermal superpositioning due to reduced thermal relaxation. Maximum temperatures occurred either at the surface or in subsurface regions of the dermis, depending on vessel geometry and position. Results are discussed in terms of established exposure limits and levels used in prior studies. While additional experimental and numerical study is needed, numerical modeling represents a powerful tool for elucidating the effect of PA imaging devices on biological tissue.

  8. Nonlinear photoacoustic measurements of oxygen saturation levels in blood

    NASA Astrophysics Data System (ADS)

    Kamanzi, Albert

    Oxygen is necessary for metabolism. It is carried from lungs to the rest of the body by hemoglobin in blood. As each hemoglobin molecule can carry a maximum of four oxygen molecules, oxygen saturation (sO2) is the measure of percentage of oxygen content in blood. For a normal person sO2 is 95% - 100%. Point-of-care testing of sO2 in blood is important in medicine. It enables doctors and caregivers for monitoring a wide variety of chronic illnesses. On the other hand, mapping of sO2 values by performing a raster scan across the region of interest in vivo is also essential in clinical and research settings, such as to evaluate the therapeutic effects of a treatment, monitoring healing of wounds, etc. Several non-invasive methods have been developed for this purpose. In this thesis, I measured the nonlinear absorption coefficient (beta) of blood samples using photoacoustic Z-scan technique. Results depict linear dependency between beta and blood oxygenation levels.

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

    PubMed Central

    Xia, Jun; Wang, Lihong V.

    2014-01-01

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

  10. Photo-acoustic analysis of dental materials and tissue

    NASA Astrophysics Data System (ADS)

    Jeleva, Pavlina Jetchkova

    2005-11-01

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

  11. Photoacoustic Spectroscopy of Candida albicans Treated with Methylene Blue

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

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

    PubMed

    Xia, Jun; Wang, Lihong V

    2014-05-01

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

  13. Photoacoustic lymphatic imaging with high spatial-temporal resolution

    NASA Astrophysics Data System (ADS)

    Martel, Catherine; Yao, Junjie; Huang, Chih-Hsien; Zou, Jun; Randolph, Gwendalyn J.; Wang, Lihong V.

    2014-11-01

    Despite its critical function in coordinating the egress of inflammatory and immune cells out of tissues and maintaining fluid balance, the causative role of lymphatic network dysfunction in pathological settings is still understudied. Engineered-animal models and better noninvasive high spatial-temporal resolution imaging techniques in both preclinical and clinical studies will help to improve our understanding of different lymphatic-related pathologic disorders. Our aim was to take advantage of our newly optimized noninvasive wide-field fast-scanning photoacoustic (PA) microcopy system to coordinately image the lymphatic vasculature and its flow dynamics, while maintaining high resolution and detection sensitivity. Here, by combining the optical-resolution PA microscopy with a fast-scanning water-immersible microelectromechanical system scanning mirror, we have imaged the lymph dynamics over a large field-of-view, with high spatial resolution and advanced detection sensitivity. Depending on the application, lymphatic vessels (LV) were spectrally or temporally differentiated from blood vessels. Validation experiments were performed on phantoms and in vivo to identify the LV. Lymphatic flow dynamics in nonpathological and pathological conditions were also visualized. These results indicate that our newly developed PA microscopy is a promising tool for lymphatic-related biological research.

  14. Comparative analysis of the planar capacitor and IDT piezoelectric thin-film micro-actuator models

    NASA Astrophysics Data System (ADS)

    Myers, Oliver J.; Anjanappa, M.; Freidhoff, Carl B.

    2011-03-01

    A comparison of the analysis of similarly developed microactuators is presented. Accurate modeling and simulation techniques are vital for piezoelectrically actuated microactuators. Coupling analytical and numerical modeling techniques with variational design parameters, accurate performance predictions can be realized. Axi-symmetric two-dimensional and three-dimensional static deflection and harmonic models of a planar capacitor actuator are presented. Planar capacitor samples were modeled as unimorph diaphragms with sandwiched piezoelectric material. The harmonic frequencies were calculated numerically and compared well to predicted values and deformations. The finite element modeling reflects the impact of the d31 piezoelectric constant. Two-dimensional axi-symmetric models of circularly interdigitated piezoelectrically membranes are also presented. The models include the piezoelectric material and properties, the membrane materials and properties, and incorporates various design considerations of the model. These models also include the electro-mechanical coupling for piezoelectric actuation and highlight a novel approach to take advantage of the higher d33 piezoelectric coupling coefficient. Performance is evaluated for varying parameters such as electrode pitch, electrode width, and piezoelectric material thickness. The models also showed that several of the design parameters were naturally coupled. The static numerical models correlate well with the maximum static deflection of the experimental devices. Finally, this paper deals with the development of numerical harmonic models of piezoelectrically actuated planar capacitor and interdigitated diaphragms. The models were able to closely predict the first two harmonics, conservatively predict the third through sixth harmonics and predict the estimated values of center deflection using plate theory. Harmonic frequency and deflection simulations need further correlation by conducting extensive iterative harmonic simulations and experiments. The results, conclusions and potential improvements are discussed.

  15. Piezoelectricity and growth polarization in III-V nitrides

    NASA Astrophysics Data System (ADS)

    Tavernier, Philip Ross

    GaN, AlN and InN form a relatively new class of semiconductors being utilized for their direct wide bandgap and polarization effects. Novel transistors using only piezoelectric doping have already surpassed the power handling capabilities of traditional silicon transistors. GaN light emitting diodes and solid state lasers, sensitive to the effects of piezoelectric polarization, are rapidly proliferating for use in lighting and next generation optical storage devices. GaN and AIN sensors and MEMS devices using the strong piezoelectric coupling coefficients of these materials are slowly being introduced into communications and chemical sensing applications. Despite the importance of the piezoelectric effect in each of these devices, relatively little is known of the magnitude of the effect in GaN and AIN as measured experimentally. The present work seeks to develop an experimental method of measuring the piezoelectric effect in thin films of GaN and AIN. Using a stress pulse induced by the single shot of a Nd:YAG laser, substrates of polar GaAs and ZnO are subject to short duration loading which generates piezoelectric dipoles. The orientation and magnitude of these dipoles induces current flow in an external circuit which is measured as a function time. By comparing the magnitude of the current generated in this circuit and the applied stress, it is shown that the axial piezoelectric constant, e 33, can be determined. Extending the measurement technique to thin films of GaN and AIN on sapphire and silicon, we have observed the magnitude and orientation of the piezoelectric dipoles in these materials. A value of 0.45 C/m2 for e33 in GaN was determined. This work motivated a closer investigation of the polarity of GaN during crystal growth. The addition of Mg during MOCVD was found to cause a uniform inversion of the growth axis producing nitrogen terminated surfaces under certain growth conditions. Chemical-mechanical polishing of these surfaces with colloidal silica was found to produce smooth, damage free surfaces suitable for regrowth or additional processing. Growth of GaN and InGaN along the nitrogen polar direction was characterized by AFM, TEM, SIMS, x-ray, PL, and Hall measurements revealing surprisingly high quality material suitable for optical and electrical devices.

  16. Image reconstruction of the absorption coefficients with l1-norm minimization from photoacoustic measurements

    PubMed Central

    Hirasawa, Takeshi; Kushibiki, Toshihiro; Ishihara, Miya

    2015-01-01

    Background The photoacoustic (PA) imaging by considering light propagation into image reconstruction process can provide quantitative information of photon absorbers, such as hemoglobin and exogenous dyes, and to improve their imaging contrasts. Methods A 2D image reconstruction of the distribution of the light absorption coefficient from the PA measurements with light source and ultrasound transducer placed at the identical position was tested. The PA pressures were formulated with the PA wave equation and the photon diffusion equation. The relation between the PA pressure and the absorption coefficient was linearized. The image reconstruction was carried out by minimizing the squared error between the measured and calculated PA signals. The l1-norm of the reconstructed image was simultaneously minimized to improve the localization of the reconstructed target in the image. The image reconstruction with the l1-norm minimization was compared to that with the Tikhonov regularization by numerical simulation and phantom experiment. In phantom experiment, an aqueous solution of the intralipid and the indocyanine green was used as the measured object. The PA probe had optical fiber for illumination and piezoelectric film for detection placed at the identical position. Results The l1-norm minimization reconstructed more localized target than the Tikhonov regularization. Conclusions The l1-norm minimization is useful for the sparse PA image reconstruction. PMID:25694957

  17. A quartz-enhanced photoacoustic spectroscopy sensor for measurement of water vapor concentration in the air

    NASA Astrophysics Data System (ADS)

    Gong, Ping; Xie, Liang; Qi, Xiao-Qiong; Wang, Rui; Wang, Hui; Chang, Ming-Chao; Yang, Hui-Xia; Sun, Fei; Li, Guan-Peng

    2015-01-01

    A compact and highly linear quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor for the measurement of water vapor concentration in the air is demonstrated. A cost-effective quartz tuning fork (QTF) is used as the sharp transducer to convert light energy into an electrical signal based on the piezoelectric effect, thereby removing the need for a photodetector. The short optical path featured by the proposed sensing system leads to a decreased size. Furthermore, a pair of microresonators is applied in the absorbance detection module (ADM) for QTF signal enhancement. Compared with the system without microresonators, the detected QTF signal is increased to approximately 7-fold. Using this optimized QEPAS sensor with the proper modulation frequency and depth, we measure the water vapor concentration in the air at atmospheric pressure and room temperature. The experimental result shows that the sensor has a high sensitivity of 1.058 parts-per-million. Project supported by the National Natural Science Foundation of China (Grant Nos. 61107070, 61127018, and 61377071).

  18. Piezoelectric self sensing actuators for high voltage excitation

    NASA Astrophysics Data System (ADS)

    Grasso, E.; Totaro, N.; Janocha, H.; Naso, D.

    2013-06-01

    Self sensing techniques allow the use of a piezoelectric transducer simultaneously as an actuator and as a sensor. Such techniques are based on knowledge of the transducer behaviour and on measurements of electrical quantities, in particular voltage and charge. Past research work has mainly considered the linear behaviour of piezoelectric transducers, consequently restricting the operating driving voltages to low values. In this work a new self sensing technique is proposed which is able to perform self sensing reconstruction both at low and at high driving voltages. This technique, in fact, makes use of a hysteretic model to describe the nonlinear piezoelectric capacitance necessary for self sensing reconstruction. The capacitance can be measured and identified at the antiresonances of a vibrating structure with a good approximation. After providing a mathematical background to deal with the main aspects of self sensing, this technique is compared theoretically and experimentally to a typical linear one by using an aluminum plate with one bonded self sensing transducer and a positive position feedback (PPF) controller to verify the performance in self sensing based vibration control.

  19. Characterization of Piezoelectric Stack Actuators for Vibrothermography

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

  20. Piezoelectric ceramic assembly tubes for torsional actuators

    NASA Astrophysics Data System (ADS)

    Kim, Chulho; Glazounov, Alexandre E.; Flippen, Luther D.; Pattnaik, Amitav; Zhang, Qi Ming; Lewis, David, III

    1999-07-01

    The efforts described here are intended to provide a basis for the utilization of novel piezoelectric actuators in smart materials and structures. The actuator design developed in this study is a segmented, piezoelectric tube, with the individual segments driven in a d15 shear mode. The PZT-5A tubes were cut longitudinally in to an even number of equal slender segments. These slender segments were poled individually along their length using a continuous poling technique developed at NRL. The polarization of the poled segments alternates in direction between adjacent segments. The segments were reassembled with a conductive epoxy so that it serves as both joint and electrode. The assembled actuator tubes were evaluated by applying electric field normal to the polarization direction of the segments, demonstrating proof of concept. These solid state prototype devices were driven to precise angular displacement and torque output. Reliability test, including both fatigue and mechanical loading of the device, were conducted. In conjunction with this effort, numerical computation analyses were performed with respect to structural integrity versus segment joint thickness, and the relative effect of cylindrical versus polygonal configurations. These studies facilitated the successful production of prototypes. Projected actuator outputs based on electromechanical test results are also discussed in terms of requirements for noise and vibration control of helicopter rotor blades.

  1. Optical clearing in photoacoustic flow cytometry.

    PubMed

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

    2013-01-01

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

  2. Photoacoustic microscopy of bilirubin in tissue phantoms

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  3. Photoacoustic Raman spectroscopy in molecular gases

    NASA Astrophysics Data System (ADS)

    Brodnikovskii, A. M.; Zharov, V. P.; Koroteev, N. I.

    1985-12-01

    A novel method of nonlinear laser spectroscopy, photoacoustic Raman spectroscopy (PARS), is described. The differential equations governing the physical dimensions of the biharmonic light field in a PARS device are given, and an optimum geometry is found for the interaction of the light beams. A counterpropagating beam geometry is found to be the most practical scheme for increasing the strength of the recorded PARS signal. The increase in signal strength in comparison with unidirectional beam geometries is estimated near an order of magnitude. The effect of saturation due to two-frequency pumping in the Raman-active transition on the information content of PARS spectra is investigated, experimentally, using pure CO2 and other gas mixtures as laser active media. No significant decrease in the information content of the PARS spectra was observed.

  4. Photoacoustic tomography: fundamentals, advances and prospects

    PubMed Central

    Yao, Junjie; Wang, Lihong V.

    2011-01-01

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

  5. Multiscale photoacoustic microscopy and computed tomography

    PubMed Central

    Wang, Lihong V.

    2009-01-01

    Photoacoustic tomography (PAT) is probably the fastest growing biomedical imaging technology owing to its capability of high-resolution sensing of rich optical contrast in vivo at depths beyond the optical transport mean free path (~1 mm in the skin). Existing high-resolution optical imaging technologies, such as confocal microscopy and two-photon microscopy, have fundamentally impacted biomedicine but cannot reach such depths. Taking advantage of low ultrasonic scattering, PAT indirectly improves tissue transparency by 100 to 1000 fold and consequently enables deeply penetrating functional and molecular imaging at high spatial resolution. Further, PAT holds the promise of in vivo imaging at multiple length scales ranging from subcellular organelles to organs with the same contrast origin, an important application in multiscale systems biology research. PMID:20161535

  6. Optical clearing in photoacoustic flow cytometry

    PubMed Central

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

    2013-01-01

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

  7. Method of Fabricating a Piezoelectric Composite Apparatus

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  8. Piezoelectric materials used in underwater acoustic transducers

    SciTech Connect

    Li, Huidong; Deng, Zhiqun; Carlson, Thomas J.

    2012-07-07

    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 members in composites. Piezoelectric single crystals offer outstanding electromechanical response but are limited by their manufacturing cost. Piezoelectric polymers provide excellent acoustic impedance matching and transducer fabrication flexibility although their piezoelectric properties are not as good as ceramics and single crystals. Composites combined the merits of ceramics and polymers and are receiving increased attention. The typical structure and electromechanical properties of each type of materials are introduced and discussed with respect to underwater acoustic transducer applications. Their advantages and disadvantages are summarized. Some of the critical design considerations when developing underwater acoustic transducers with these materials are also touched upon.

  9. A Micro-Opto-Mechanical Photoacoustic Spectrometer

    SciTech Connect

    Kotovsky, J

    2008-10-17

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

  10. Doppler photoacoustic and Doppler ultrasound in blood with optical contrast agent

    NASA Astrophysics Data System (ADS)

    Sheinfeld, Adi; Eyal, Avishay

    2013-03-01

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

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

    PubMed Central

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

    2012-01-01

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

  12. Photoacoustic Imaging of Breast Microcalcifications: A Preliminary Study with 8-Gauge Core-Biopsied Breast Specimens

    PubMed Central

    Kim, Ga Ram; Kang, Jeeun; Kwak, Jin Young; Chang, Jin Ho; Kim, Seung Il; Youk, Ji Hyun; Moon, Hee Jung; Kim, Min Jung; Kim, Eun-Kyung

    2014-01-01

    Background We presented the photoacoustic imaging (PAI) tool and to evaluate whether microcalcifications in breast tissue can be detected on photoacoustic (PA) images. Methods We collected 21 cores containing microcalcifications (n?=?11, microcalcification group) and none (n?=?10, control group) in stereotactic or ultrasound (US) guided 8-gauge vacuum-assisted biopsies. Photoacoustic (PA) images were acquired through ex vivo experiments by transmitting laser pulses with two different wavelengths (700 nm and 800 nm). The presence of microcalcifications in PA images were blindly assessed by two radiologists and compared with specimen mammography. A ratio of the signal amplitude occurring at 700 nm to that occurring at 800 nm was calculated for each PA focus and was called the PAI ratio. Results Based on the change of PA signal amplitude between 700 nm and 800 nm, 10 out of 11 specimens containing microcalcifications and 8 out of 10 specimens without calcifications were correctly identified on blind review; the sensitivity, specificity, accuracy, positive predictive and negative predictive values of our blind review were 90.91%, 80.0%, 85.71%, 83.33% and 88.89%. The PAI ratio in the microcalcification group was significantly higher than that in the control group (the median PAI ratio, 2.46 versus 1.11, respectively, P?=?.001). On subgroup analysis in the microcalcification group, neither malignant diagnosis nor the number or size of calcification-foci was proven to contribute to PAI ratios. Conclusion Breast microcalcifications generated distinguishable PA signals unlike breast tissue without calcifications. So, PAI, a non-ionizing and non-invasive hybrid imaging technique, can be an alternative in overcoming the limitations of conventional US imaging. PMID:25153128

  13. Cylindrical Piezoelectric Fiber Composite Actuators

    NASA Technical Reports Server (NTRS)

    Allison, Sidney G.; Shams, Qamar A.; Fox, Robert L.

    2008-01-01

    The use of piezoelectric devices has become widespread since Pierre and Jacques Curie discovered the piezoelectric effect in 1880. Examples of current applications of piezoelectric devices include ultrasonic transducers, micro-positioning devices, buzzers, strain sensors, and clocks. The invention of such lightweight, relatively inexpensive piezoceramic-fiber-composite actuators as macro fiber composite (MFC) actuators has made it possible to obtain strains and displacements greater than those that could be generated by prior actuators based on monolithic piezoceramic sheet materials. MFC actuators are flat, flexible actuators designed for bonding to structures to apply or detect strains. Bonding multiple layers of MFC actuators together could increase force capability, but not strain or displacement capability. Cylindrical piezoelectric fiber composite (CPFC) actuators have been invented as alternatives to MFC actuators for applications in which greater forces and/or strains or displacements may be required. In essence, a CPFC actuator is an MFC or other piezoceramic fiber composite actuator fabricated in a cylindrical instead of its conventional flat shape. Cylindrical is used here in the general sense, encompassing shapes that can have circular, elliptical, rectangular or other cross-sectional shapes in the planes perpendicular to their longitudinal axes.

  14. Vacuum mounting for piezoelectric transducers

    NASA Technical Reports Server (NTRS)

    Tiede, D. A.

    1977-01-01

    Special housing couples piezoelectric transducers to nonporous surfaces for ultrasonic or acoustic-emission testing. Device, while providing sound isolation on flat or nonflat surfaces, can be attached and detached quickly. Vacuum sealing mechanism eliminates need for permanent or semipermanent bonds, viscous coupling liquids, weights, magnets, tape, or springs ordinarily used.

  15. Piezoelectric measurement of laser power

    DOEpatents

    Deason, Vance A. (Idaho Falls, ID); Johnson, John A. (Idaho Falls, ID); Telschow, Kenneth L. (Idaho Falls, ID)

    1991-01-01

    A method for measuring the energy of individual laser pulses or a series of laser pulses by reading the output of a piezoelectric (PZ) transducer which has received a known fraction of the total laser pulse beam. An apparatus is disclosed that reduces the incident energy on the PZ transducer by means of a beam splitter placed in the beam of the laser pulses.

  16. An investigation on 1 3 cement based piezoelectric composites

    NASA Astrophysics Data System (ADS)

    Li, Zongjin; Huang, Shifeng; Qin, Lei; Cheng, Xin

    2007-08-01

    1-3 cement based piezoelectric composites which had good compatibility with civil engineering structural materials were fabricated by the cut-fill technique. The piezoelectric, dielectric and ferroelectric properties of the composites were studied. The acoustic impedance of the composites was also investigated. The results show that the piezoelectric strain constant d33 and the dielectric constant ? of the composites increase linearly with the increase of PMN volume fraction, while the piezoelectric voltage constant g33 presents the opposite trend. The g33 values of the composites are much higher than those of pure PMN. The remnant polarization Pr and the coercive field Ec of the composite with 27.26% volume fraction of PMN are 4.12 µC cm-2 and 4.01 kV mm-1, respectively. By enhancing the PMN volume fraction, the acoustic impedance of the composites can be tailored to match that of the civil engineering structural material, i.e. concrete. Therefore, this new kind of composite has potential to be used in civil structure health monitoring.

  17. Feasibility of Piezoelectric Endoscopic Transsphenoidal Craniotomy: A Cadaveric Study

    PubMed Central

    Tomazic, Peter Valentin; Gellner, Verena; Koele, Wolfgang; Hammer, Georg Philipp; Braun, Eva Maria; Gerstenberger, Claus; Clarici, Georg; Holl, Etienne; Braun, Hannes; Stammberger, Heinz; Mokry, Michael

    2014-01-01

    Objective. Endoscopic transsphenoidal approach has become the gold standard for surgical treatment of treating pituitary adenomas or other lesions in that area. Opening of bony skull base has been performed with burrs, chisels, and hammers or standard instruments like punches and circular top knives. The creation of primary bone flaps—as in external craniotomies—is difficult.The piezoelectric osteotomes used in the present study allows creating a bone flap for endoscopic transnasal approaches in certain areas. The aim of this study was to prove the feasibility of piezoelectric endoscopic transnasal craniotomies. Study Design. Cadaveric study. Methods. On cadaveric specimens (N = 5), a piezoelectric system with specially designed hardware for endonasal application was applied and endoscopic transsphenoidal craniotomies at the sellar floor, tuberculum sellae, and planum sphenoidale were performed up to a size of 3–5?cm2. Results. Bone flaps could be created without fracturing with the piezoosteotome and could be reimplanted. Endoscopic handling was unproblematic and time required was not exceeding standard procedures. Conclusion. In a cadaveric model, the piezoelectric endoscopic transsphenoidal craniotomy (PETC) is technically feasible. This technique allows the surgeon to create a bone flap in endoscopic transnasal approaches similar to existing standard transcranial craniotomies. Future trials will focus on skull base reconstruction using this bone flap. PMID:24689037

  18. PHOTOACOUSTIC NON-DESTRUCTIVE EVALUATION AND IMAGING OF CARIES IN DENTAL SAMPLES

    SciTech Connect

    Li, T.; Dewhurst, R. J. [Photon Science Institute, University of Manchester, Alan Turing Building, Oxford Road, Manchester, M13 9PL (United Kingdom)

    2010-02-22

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

  19. Synergy of photoacoustic and fluorescence flow cytometry of circulating cells with negative and positive contrasts

    PubMed Central

    Nedosekin, Dmitry A.; Sarimollaoglu, Mustafa; Galanzha, Ekaterina I.; Sawant, Rupa; Torchilin, Vladimir P.; Verkhusha, Vladislav V.; Ma, Jie; Frank, Markus H.; Biris, Alexandru S.; Zharov, Vladimir P.

    2012-01-01

    In vivo photoacoustic (PA) and fluorescence flow cytometry were previously applied separately using pulsed and continuous wave lasers respectively, and positive contrast detection mode only. This paper introduces a real-time integration of both techniques with positive and negative contrast modes using only pulsed lasers. Various applications of this new tool are summarized, including detection of liposomes loaded with Alexa-660 dye, red blood cells labeled with Indocyanine Green, B16F10 melanoma cells co-expressing melanin and green fluorescent protein (GFP), C8161-GFP melanoma cells targeted by magnetic nanoparticles, MTLn3 adenocarcinoma cells expressing novel near-infrared iRFP protein, and quantum dot-carbon nanotube conjugates. Negative contrast flow cytometry provided label-free detection of low absorbing or weakly fluorescent cells in blood absorption and autofluorescence background, respectively. The use of pulsed laser for time-resolved discrimination of objects with long fluorescence lifetime (e.g., quantum dots) from shorter autofluorescence background (e.g., blood plasma) is also highlighted in this paper. The supplementary nature of PA and fluorescence detection increased the versatility of the integrated method for simultaneous detection of probes and cells having various absorbing and fluorescent properties, and provided verification of PA data using a more established fluorescence based technique. The principles of integrated photoacoustic and fluorescence flow cytometry using positive contrast for detection of strongly absorbing and fluorescent cells and negative contrast for detection of weakly absorbing and fluorescent cells in blood absorption and autofluorescence background, respectively. PMID:22903924

  20. Photoacoustic sensor for VOCs: first step towards a lung cancer breath test

    NASA Astrophysics Data System (ADS)

    Wolff, Marcus; Groninga, Hinrich G.; Dressler, Matthias; Harde, Hermann

    2005-08-01

    Development of new optical sensor technologies has a major impact on the progression of diagnostic methods. Specifically, the optical analysis of breath is an extraordinarily promising technique. Spectroscopic sensors for the non-invasive 13C-breath tests (the Urea Breath Test for detection of Helicobacter pylori is most prominent) are meanwhile well established. However, recent research and development go beyond gastroenterological applications. Sensitive and selective detection of certain volatile organic compounds (VOCs) in a patient's breath, could enable the diagnosis of diseases that are very difficult to diagnose with contemporary techniques. For instance, an appropriate VOC biomarker for early-stage bronchial carcinoma (lung cancer) is n-butane (C4H10). We present a new optical detection scheme for VOCs that employs an especially compact and simple set-up based on photoacoustic spectroscopy (PAS). This method makes use of the transformation of absorbed modulated radiation into a sound wave. Employing a wavelength-modulated distributed feedback (DFB) diode laser and taking advantage of acoustical resonances of the sample cell, we performed very sensitive and selective measurements on butane. A detection limit for butane in air in the ppb range was achieved. In subsequent research the sensitivity will be successively improved to match the requirements of the medical application. Upon optimization, our photoacoustic sensor has the potential to enable future breath tests for early-stage lung cancer diagnostics.