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Sample records for photoacoustic piezoelectric technique

  1. 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

    2015-06-01

    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 , which is at a medium level among the ordinary steel materials ( to 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.

  2. A piezoelectric cell for simultaneous photoacoustic and fluorescence measurements

    SciTech Connect

    Williamson, C.K.; Coleman, G.N.

    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.

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

    SciTech Connect

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

    1987-10-01

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

  4. 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.

  5. Normalized photoacoustic techniques for thermal diffusivity measurements of buried layers in multilayered systems

    E-print Network

    Mandelis, Andreas

    Normalized photoacoustic techniques for thermal diffusivity measurements of buried layers for the implementation of normalized depth-profilometric photoacoustic methodologies involving the open photoacoustic the theoretical photoacoustic signal from the three layers with the corresponding signal from the uppermost two

  6. Photoacoustic technique applied to the study of skin and leather

    NASA Astrophysics Data System (ADS)

    Vargas, M.; Varela, J.; Hernández, L.; González, A.

    1998-08-01

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

  7. Photoacoustic technique applied to the study of skin and leather

    SciTech Connect

    Vargas, M.; Varela, J.; Hernandez, L.; Gonzalez, A.

    1998-08-28

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

  8. 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.

  9. Dual-pulse nonlinear photoacoustic technique: a practical investigation.

    PubMed

    Tian, Chao; Xie, Zhixing; Fabiilli, Mario L; Liu, Shengchun; Wang, Cheng; Cheng, Qian; Wang, Xueding

    2015-08-01

    The dual-pulse nonlinear photoacoustic technique is a recently developed technology based on temperature dependence of the Grüneisen parameter and involves consecutive excitations of biological tissue using two laser pulses with a short time delay. Here we review the principle of the technique and give a discussion about its technical aspects, including selection and combination of excitation laser wavelengths, determination of laser fluence, estimation of thermal relaxation function and probability of photoablation or cavitation. Comparisons between the dual-pulse technique and conventional photoacoustics as well as thermal photoacoustics are also presented. These investigations are supported by experimental results and will give a practical reference and guide for further developments of the technique. PMID:26309756

  10. Dual-pulse nonlinear photoacoustic technique: a practical investigation

    PubMed Central

    Tian, Chao; Xie, Zhixing; Fabiilli, Mario L.; Liu, Shengchun; Wang, Cheng; Cheng, Qian; Wang, Xueding

    2015-01-01

    The dual-pulse nonlinear photoacoustic technique is a recently developed technology based on temperature dependence of the Grüneisen parameter and involves consecutive excitations of biological tissue using two laser pulses with a short time delay. Here we review the principle of the technique and give a discussion about its technical aspects, including selection and combination of excitation laser wavelengths, determination of laser fluence, estimation of thermal relaxation function and probability of photoablation or cavitation. Comparisons between the dual-pulse technique and conventional photoacoustics as well as thermal photoacoustics are also presented. These investigations are supported by experimental results and will give a practical reference and guide for further developments of the technique. PMID:26309756

  11. Numerical homogenization techniques applied to piezoelectric composites.

    PubMed

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

    2003-02-01

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

  12. Laser Photoacoustic Technique Detects Photo-Oxidation

    NASA Technical Reports Server (NTRS)

    Liange, R. H.; Coulter, D. R.; Gupta, A.

    1986-01-01

    Laser photoacoustic instrument detects small amounts of oxidation in polymers. Instrument used to evaluate resistance to oxidation in Sunlight of polymer encapsulants for solar-cell arrays. With instrument, researchers monitor samples for early stages of photooxidation and study primary mechanisms of oxidation and degradation. Effects of these mechanisms masked during later stages.

  13. Glucose concentration measurement using photoacoustic technique

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    In this paper, a noninvasive photoacoustic measurement setup was established to simple simulate the glucose concentration measurement. The PPA signal excited by a pulsed tunable wavelength laser can be used to determine the glucose concentration in solution. By building the multiple linear regression (MLR) model for the peak valves of the PPA signal at five characteristic absorption wavelengths, the relative error of prediction is less than 20% and the absolute error is less than 33mg/dL.

  14. Piezoelectric photoacoustic spectra in CuGaSe{sub 2} thin films grown by molecular beam epitaxy

    SciTech Connect

    Yoshino, Kenji; Maruoka, Daisuke; Kawahara, Masakazu; Fukuyama, Atsuhiko; Maeda, Kouji; Ikari, Tetsuo; Fons, P.J.; Niki, Shigeru

    1998-12-31

    The piezoelectric photoacoustic (PPA) spectra for Cu-rich CuGaSe{sub 2} (CGS)/GaAs epitaxial layers were successfully observed between liquid nitrogen and room temperatures for the first time. Bandgap energy of CGS (A band) is estimated to be 1.72 eV at liquid nitrogen temperature. The activation energies of three possible intrinsic defect levels are estimated to be about 80, 130 and 190 meV.

  15. Technique development for photoacoustic imaging guided interventions

    NASA Astrophysics Data System (ADS)

    Cheng, Qian; Zhang, Haonan; Yuan, Jie; Feng, Ting; Xu, Guan; Wang, Xueding

    2015-03-01

    Laser-induced thermotherapy (LITT), i.e. tissue destruction induced by a local increase of temperature by means of laser light energy transmission, has been frequently used for minimally invasive treatments of various diseases such as benign thyroid nodules and liver cancer. The emerging photoacoustic (PA) imaging, when integrated with ultrasound (US), could contribute to LITT procedure. PA can enable a good visualization of percutaneous apparatus deep inside tissue and, therefore, can offer accurate guidance of the optical fibers to the target tissue. Our initial experiment demonstrated that, by picking the strong photoacoustic signals generated at the tips of optical fibers as a needle, the trajectory and position of the fibers could be visualized clearly using a commercial available US unit. When working the conventional US Bscan mode, the fibers disappeared when the angle between the fibers and the probe surface was larger than 60 degree; while working on the new PA mode, the fibers could be visualized without any problem even when the angle between the fibers and the probe surface was larger than 75 degree. Moreover, with PA imaging function integrated, the optical fibers positioned into the target tissue, besides delivering optical energy for thermotherapy, can also be used to generate PA signals for on-line evaluation of LITT. Powered by our recently developed PA physio-chemical analysis, PA measurements from the tissue can provide a direct and accurate feedback of the tissue responses to laser ablation, including the changes in not only chemical compositions but also histological microstructures. The initial experiment on the rat liver model has demonstrated the excellent sensitivity of PA imaging to the changes in tissue temperature rise and tissue status (from native to coagulated) when the tissue is treated in vivo with LITT.

  16. Monitoring the concentration and oxygen saturation of hemoglobin using photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Su, Yi-Xiong; Wang, Ruikang K.; Lu, Tao; Song, Zhi-Yuan

    2007-02-01

    Time-resolved photoacoustic spectroscopy is a novel and potential tool for the noninvasive measurements of chromophore concentrations in vivo. In this study, noninvasive measurement of concentration and oxygen saturation of hemoglobin has been investigated by using photoacoustic method. We detailedly report a home-made photoacoustic experiment system for this study. In our system, a Q-switched ND: YAG pulse laser operating at 1064nm with a 10ns pulse width has been employed to generate photoacoustic signals. The photoacoustic signals, generated by varying the hemoglobin concentration or oxygenation saturation in blood experimentally, were picked up and analyzed. The results show that the photoacoustic technique is a useful and helpful tool for noninvasive monitoring of the total hemoglobin concentration and the oxygen saturation, for it can accurately detect the variation of the total hemoglobin concentration and oxygen saturation of hemoglobin, even when the blood vessel is deep in high scattering medium for 1cm.

  17. Determination of glucose concentration based on pulsed laser induced photoacoustic technique and least square fitting algorithm

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Liu, Guodong; Huang, Zhen

    2015-08-01

    In this paper, a noninvasive glucose concentration monitoring setup based on the photoacoustic technique was established. In this setup, a 532nm pumped Q switched Nd: YAG tunable pulsed laser with repetition rate of 20Hz was used as the photoacoustic excitation light source, and a ultrasonic transducer with central response frequency of 9.55MHz was used as the detector of the photoacoustic signal of glucose. As the preliminary exploration of the blood glucose concentration, a series of in vitro photoacoustic monitoring of glucose aqueous solutions by using the established photoacoustic setup were performed. The photoacoustic peak-to-peak values of different concentrations of glucose aqueous solutions induced by the pulsed laser with output wavelength of 1300nm to 2300nm in interval of 10nm were obtained with the average times of 512. The differential spectral and the first order derivative spectral method were used to get the characteristic wavelengths. For the characteristic wavelengths of glucose, the least square fitting algorithm was used to establish the relationship between the glucose concentrations and photoacoustic peak-to-peak values. The characteristic wavelengths and the predicted concentrations of glucose solution were obtained. Experimental results demonstrated that the prediction effect of characteristic wavelengths of 1410nm and 1510nm were better than others, and this photoacoustic setup and analysis method had a certain potential value in the monitoring of the blood glucose concentration.

  18. A circular array transducer for photoacoustic imaging by using piezoelectric single crystal lead magnesium niobate-lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Cao, Yonggang; Ha, Kanglyeol; Kim, Moojoon; Kang, Hyunwook; Oh, Jung-Hwan; Kim, Jungsoon

    2015-07-01

    The ultrasound transducers of which center frequencies are lower than 10 MHz are commonly used in low frequency photoacoustic (PA) imaging systems. However, the improvement of their sensitivity is still needed to detect weak PA signals. In this study, a circular array transducer was constructed by using 120 needle hydrophones made of piezoelectric single crystal lead magnesium niobate-lead zirconate titanate (PMN-PZT). The needle hydrophone was designed to have high sensitivity and wide bandwidth through the Krimtholz-Leedom-Matthaei (KLM) simulation of receiving impulse response. The sensitivity of the fabricated PMN-PZT hydrophone was compared with a commercial poly(vinylidene fluoride) (PVDF) needle hydrophone. The usefulness of the circular array transducer was demonstrated by applying it to a PA system for obtaining images.

  19. Photoacoustic spectroscopy of photoactive matter — Applications to photographic emulsions

    NASA Astrophysics Data System (ADS)

    Bohá?, L.; Fiala, J.; Pelant, I.; Sladký, P.; Vacek, K.

    1982-01-01

    A new technique — the photoacoustic spectroscopy with microphone detection has been successfully applied to the studies of spectral sensitivity of silver halide emulsions. Regardless of the fact that the sensitivity of photographic emulsions is greater or comparable with the detectivity of real photoacoustic transducers (i.e. the photoacoustic cell with microphone or piezoelectric transducer), absorption-like spectra of strongly diffusive and nontransparent silver halide emulsions can be readily recorded. Applications of this new technique for the studies of silver halide emulsions bears full potential advantages of photoacoustic spectroscopy. Particularly we demonstrate priority of the new technique over the conventional photographic sensitometry or reflectance spectroscopy both in qualitative and quantitative manner. Photoacoustic measurements of photochemical decomposition rates are shown and suggestions for the measurements of excitation energy transfer efficiencies are given. The results clearly show a unique applicability of the technique in fundamental as well as industrial research and process control of the photographic emulsion production.

  20. 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.

  1. Effect of shunted piezoelectric control for tuning piezoelectric power harvesting system responses—analytical techniques

    NASA Astrophysics Data System (ADS)

    Lumentut, M. F.; Howard, I. M.

    2015-10-01

    This paper presents new analytical modelling of shunt circuit control responses for tuning electromechanical piezoelectric vibration power harvesting structures with proof mass offset. For this combination, the dynamic closed-form boundary value equations reduced from strong form variational principles were developed using the extended Hamiltonian principle to formulate the new coupled orthonormalized electromechanical power harvesting equations showing combinations of the mechanical system (dynamical behaviour of piezoelectric structure), electromechanical system (electrical piezoelectric response) and electrical system (tuning and harvesting circuits). The reduced equations can be further formulated to give the complete forms of new electromechanical multi-mode frequency response functions and the time waveform of the standard AC-DC circuit interface. The proposed technique can demonstrate self-adaptive harvesting response capabilities for tuning the frequency band and the power amplitude of the harvesting devices. The self-adaptive tuning strategies are demonstrated by modelling the shunt circuit behaviour of the piezoelectric control layer in order to optimize the harvesting piezoelectric layer during operation under input base excitation. In such situations, with proper tuning parameters the system performance can be substantially improved. Moreover, the validation of the closed-form technique is also provided by developing the Ritz method-based weak form analytical approach giving similar results. Finally, the parametric analytical studies have been explored to identify direct and relevant contributions for vibration power harvesting behaviours.

  2. PHOTOACOUSTIC DETECTION OF PARTICULATE CARBON

    EPA Science Inventory

    A photoacoustic technique for the mass monitoring of carbonaceous aerosols deposited on filter substrates has been developed. The technique involves the use of a specially designed photoacoustic cell. Photoacoustic response is calibrated as a function of elemental carbon loading ...

  3. Piezoelectric cantilevers energy harvesting in MEMS technique

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  4. Piezoelectric cantilevers energy harvesting in MEMS technique

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  5. Photoacoustic Imaging

    PubMed Central

    Zhang, Yin; Hong, Hao; Cai, Weibo

    2014-01-01

    Photoacoustic imaging, based on the photoacoustic effect, has come a long way over the last decade. Possessing many attractive characteristics such as the use of non-ionizing electromagnetic waves, good resolution/contrast, portable instrumention, as well as the ability to quantitate the signal to a certain extent, photoacoustic techniques have been applied for the imaging of cancer, wound healing, disorders in the brain, gene expression, among others. As a promising structural, functional and molecular imaging modality for a wide range of biomedical applications, photoacoustic imaging systems can be briefly categorized into two types: photoacoustic tomography (PAT, the focus of this chapter) and photoacoustic microscopy (PAM). We will first briefly describe the endogenous (e.g. hemoglobin and melanin) and exogenous contrast agents (e.g. indocyanine green, various gold nanoparticles, single-walled carbon nanotubes, quantum dots, and fluorescent proteins) for photoacoustic imaging. Next, we will discuss in detail the applications of non-targeted photoacoustic imaging. Recently, molecular photoacoustic (MPA) imaging has gained significant interest and a few proof-of-principle studies have been reported. We will summarize the current state-of-the-art of MPA imaging, including the imaging of gene expression and combination of photoacoustic imaging with other imaging modalities. Lastly, we will point out the obstacles facing photoacoustic imaging. Although photoacoustic imaging will likely continue to be a highly vibrant research field for the years to come, the key question of whether MPA imaging could provide significant advantages over non-targeted photoacoustic imaging remains to be demonstrated in the future. PMID:21880823

  6. Applications of photoacoustic techniques to the study of jet fuel residue

    NASA Technical Reports Server (NTRS)

    Claspy, P. C.

    1983-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Ji, X.; Yang, S.

    2010-12-01

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

  8. Thermal Diffusivity Measurement for p-Si and Ag/p-Si by Photoacoustic Technique

    NASA Astrophysics Data System (ADS)

    Hussein, Mohammed Jabbar; Yunus, W. Mahmood Mat; Kamari, Halimah Mohamed; Zakaria, Azmi

    2015-10-01

    Thermal diffusivity (TD) of p-Si and Ag/p-Si samples were measured by photoacoustic technique using open photoacoustic cell (OPC). The samples were annealed by heating them at 960, 1050, 1200, and 1300 °C for 3 h in air. The thermal diffusivity of Ag-coated samples was obtained by fitting the photoacoustic experimental data to the thermally thick equation for Rosencwaig and Gersho (RG) theory. For the single layer samples, the thermal diffusivity can be obtained by fitting as well as by obtaining the critical frequency f c . In this study, the thermal diffusivity of the p-Si samples increased with increasing the annealing temperature. The thermal diffusivity of the Ag/p-Si samples, after reaching the maximum value of about 2.73 cm2/s at a temperature of 1200 °C, decreased due to the silver complete melt in the surface of the silicon.

  9. 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.

  10. 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.

  11. Investigation of diseases through red blood cells' shape using photoacoustic response technique

    NASA Astrophysics Data System (ADS)

    Biswas, Deblina; Gorey, Abhijeet; Chen, Goerge C. K.; Sharma, Norman; Vasudevan, Srivathsan

    2015-03-01

    Photoacoustic (PA) imaging is a non-invasive real-time technique, widely applied to many biomedical imaging studies in the recent years. While most of these studies have been focussed on obtaining an image after reconstruction, various features of time domain signal (e.g. amplitude, width, rise and relaxation time) would provide very high sensitivity in detecting morphological changes in cells during a biological study. Different haematological disorders (e.g., sickle cell anaemia, thalassemia) exhibit significant morphological cellular changes. In this context, this study explores the possibility of utilizing the developed photoacoustic response technique to apply onto blood samples. Results of our preliminary study demonstrate that there is a significant change in signal amplitude due to change in concentration of the blood. Thus it shows the sensitivity of the developed photoacoustic technique towards red blood cell count (related to haematological disease like anaemia). Subsequently, morphological changes in RBC (i.e. swollen and shrunk compared to normal RBC) induced by hypotonic and hypertonic solutions respectively were also experimented. The result shows a distinct change in PA signal amplitude. This would serve as a diagnostic signature for many future studies on cellular morphological disorders.

  12. Jitter reduction technique for acoustic radiation force impulse microscopy via photoacoustic detection.

    PubMed

    Kang, Bong Jin; Yoon, Changhan; Park, Jin Man; Hwang, Jae Youn; Shung, K Kirk

    2015-07-27

    We demonstrate a jitter noise reduction technique for acoustic radiation force impulse microscopy via photoacoustic detection (PA-ARFI), which promises to be capable of measuring cell mechanics. To reduce the jitter noise induced by Q-switched pulsed laser operated at high repetition frequency, photoacoustic signals from the surface of an ultrasound transducer are aligned by cross-correlation and peak-to-peak detection, respectively. Each method is then employed to measure the displacements of a target sample in an agar phantom and a breast cancer cell due to ARFI application, followed by the quantitative comparison between their performances. The suggested methods for PA-ARFI significantly reduce jitter noises, thus allowing us to measure displacements of a target cell due to ARFI application by less than 3 ?m. PMID:26367579

  13. Efficient Driving of Piezoelectric Transducers Using a Biaxial Driving Technique

    PubMed Central

    2015-01-01

    Efficient driving of piezoelectric materials is desirable when operating transducers for biomedical applications such as high intensity focused ultrasound (HIFU) or ultrasound imaging. More efficient operation reduces the electric power required to produce the desired bioeffect or contrast. Our preliminary work [Cole et al. Journal of Physics: Condensed Matter. 2014;26(13):135901.] suggested that driving transducers by applying orthogonal electric fields can significantly reduce the coercivity that opposes ferroelectric switching. We present here the experimental validation of this biaxial driving technique using piezoelectric ceramics typically used in HIFU. A set of narrow-band transducers was fabricated with two sets of electrodes placed in an orthogonal configuration (following the propagation and the lateral mode). The geometry of the ceramic was chosen to have a resonance frequency similar for the propagation and the lateral mode. The average (± s.d.) resonance frequency of the samples was 465.1 (± 1.5) kHz. Experiments were conducted in which each pair of electrodes was driven independently and measurements of effective acoustic power were obtained using the radiation force method. The efficiency (acoustic/electric power) of the biaxial driving method was compared to the results obtained when driving the ceramic using electrodes placed only in the pole direction. Our results indicate that the biaxial method increases efficiency from 50% to 125% relative to the using a single electric field. PMID:26418550

  14. 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.

  15. Monitoring the effect of dextran on blood sedimentation using a pulsed photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Kinnunen, Matti

    2012-03-01

    The capabilities of a pulsed photoacoustic technique for monitoring blood sedimentation and red blood cell (RBC) aggregation were tested in a cuvette in vitro. Diluted blood samples with concentrations of 40% and 60% were used. In addition, the effect of dextran (T500) was investigated with blood concentrations of 40% and 60%. Optical coherence tomography was used in parallel to visualize the sedimentation process. The results show that a 1 MHz acoustic transducer can be used to detect PA signals from blood in vitro during sedimentation, and the acoustic pulse delay is a good indicator for following the sedimentation process. Dextran greatly accelerated the sedimentation process.

  16. 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.

  17. Non Linear Techniques for Increasing Harvesting Energy from Piezoelectric and Electromagnetic Micro-Power-Generators

    E-print Network

    Ammar, Yasser

    2007-01-01

    Non-linear techniques are used to optimize the harvested energy from piezoelectric and electromagnetic generators. This paper introduces an analytical study for the voltage amplification obtained from these techniques. The analytical study is experimentally validated using a macro model of piezoelectric generator. Moreover, the integration influences on these techniques is studied. Through all the obtained results, a suitable structure for autonomous microsystems is proposed.

  18. Measurement of the Auger lifetime in GaInAsSb/GaSb heterostructures using the photoacoustic technique

    SciTech Connect

    Riech, I.; Gomez-Herrera, M. L.; Diaz, P.; Mendoza-Alvarez, J. G.; Herrera-Perez, J. L.; Marin, E.

    2001-08-13

    We have studied Ga{sub x}In{sub 1-x}As{sub y}Sb{sub 1-y}/GaSb heterostructures for x=0.84 and y=0.14 using the photoacoustic technique with the heat transmission configuration. A theoretical model, which includes all the possible nonradiative recombination mechanisms that contribute to heat generation, was developed to calculate the photoacoustic signal for this type of heterostructure. The Auger recombination lifetime {tau}{sub Auger} was determined by fitting our experimental results to the calculated frequency dependence of the theoretical photoacoustic signal. The obtained value for {tau}{sub Auger} is compatible with those reported in the literature for semiconductors with band-gap energies below and above 0.5 eV, the energy region where there is a lack of experimental {tau}{sub Auger} values. {copyright} 2001 American Institute of Physics.

  19. Photoacoustic effect and its applications

    NASA Astrophysics Data System (ADS)

    Wei, M.; Qian, M.

    1985-03-01

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

  20. Photoacoustic method for measuring concentration of chemical species

    DOEpatents

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

    2001-01-01

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

  1. Piezoelectric Versus Conventional Rotary Techniques for Impacted Third Molar Extraction

    PubMed Central

    Jiang, Qian; Qiu, Yating; Yang, Chi; Yang, Jingyun; Chen, Minjie; Zhang, Zhiyuan

    2015-01-01

    Abstract Impacted third molars are frequently encountered in clinical work. Surgical removal of impacted third molars is often required to prevent clinical symptoms. Traditional rotary cutting instruments are potentially injurious, and piezosurgery, as a new osteotomy technique, has been introduced in oral and maxillofacial surgery. No consistent conclusion has been reached regarding whether this new technique is associated with fewer or less severe postoperative sequelae after third molar extraction. The aim of this study was to compare piezosurgery with rotary osteotomy techniques, with regard to surgery time and the severity of postoperative sequelae, including pain, swelling, and trismus. We conducted a systematic literature search in the Cochrane Library, PubMed, Embase, and Google Scholar. The eligibility criteria of this study included the following: the patients were clearly diagnosed as having impacted mandibular third molars; the patients underwent piezosurgery osteotomy, and in the control group rotary osteotomy techniques, for removing impacted third molars; the outcomes of interest include surgery time, trismus, swelling or pain; the studies are randomized controlled trials. We used random-effects models to calculate the difference in the outcomes, and the corresponding 95% confidence interval. We calculated the weighted mean difference if the trials used the same measurement, and a standardized mean difference if otherwise. A total of seven studies met the eligibility criteria and were included in our analysis. Compared with rotary osteotomy, patients undergoing piezosurgery experienced longer surgery time (mean difference 4.13 minutes, 95% confidence interval 2.75–5.52, P?piezoelectric technique had less swelling at postoperative days 1, 3, 5, and 7 (all Ps ?0.023). Additionally, there was a trend of less postoperative pain and trismus in the piezosurgery groups. The number of included randomized controlled trials and the sample size of each trial were relatively small, double blinding was not possible, and cost analysis was unavailable due to a lack of data. Our meta-analysis indicates that although patients undergoing piezosurgery experienced longer surgery time, they had less postoperative swelling, indicating that piezosurgery is a promising alternative technique for extraction of impacted third molars. PMID:26469902

  2. 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.

  3. 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.

  4. 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.).

  5. 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

  6. Photoacoustic characterization of carbon nanotube array thermal interfaces

    E-print Network

    Xu, Xianfan

    Photoacoustic characterization of carbon nanotube array thermal interfaces Baratunde A. Cola, Jun a photoacoustic technique PA . Well-anchored, dense, and vertically oriented multiwalled CNT arrays have been

  7. 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

  8. Study of thermal decomposition mechanisms and low-level detection of explosives using pulsed photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Yehya, F.; Chaudhary, A. K.; Srinivas, D.; Muralidharan, K.

    2015-11-01

    We report a novel time-resolved photoacoustic-based technique for studying the thermal decomposition mechanisms of some secondary explosives such as RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), picric acid, 4,6-dinitro-5-(4-nitro-1 H-imidazol-1-yl)-1 H-benzo[ d] [1-3] triazole, and 5-chloro-1-(4-nitrophenyl)-1 H-tetrazole. A comparison of the thermal decomposition mechanisms of these secondary explosives was made by detecting NO2 molecules released under controlled pyrolysis between 25 and 350 °C. The results show excellent agreement with the thermogravimetric and differential thermal analysis (TGA-DTA) results. A specially designed PA cell made of stainless steel was filled with explosive vapor and pumped using second harmonic, i.e., ? = 532 nm, pulses of duration 7 ns at a 10 Hz repetition rate, obtained using a Q-switched Nd:YAG laser. The use of a combination of PA and TGA-DTA techniques enables the study of NO2 generation, and this method can be used to scale the performance of these explosives as rocket fuels. The minimum detection limits of the four explosives were 38 ppmv to 69 ppbv, depending on their respective vapor pressures.

  9. Study of thermal decomposition mechanisms and low-level detection of explosives using pulsed photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Yehya, F.; Chaudhary, A. K.; Srinivas, D.; Muralidharan, K.

    2015-09-01

    We report a novel time-resolved photoacoustic-based technique for studying the thermal decomposition mechanisms of some secondary explosives such as RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), picric acid, 4,6-dinitro-5-(4-nitro-1H-imidazol-1-yl)-1H-benzo[d] [1-3] triazole, and 5-chloro-1-(4-nitrophenyl)-1H-tetrazole. A comparison of the thermal decomposition mechanisms of these secondary explosives was made by detecting NO2 molecules released under controlled pyrolysis between 25 and 350 °C. The results show excellent agreement with the thermogravimetric and differential thermal analysis (TGA-DTA) results. A specially designed PA cell made of stainless steel was filled with explosive vapor and pumped using second harmonic, i.e., ? = 532 nm, pulses of duration 7 ns at a 10 Hz repetition rate, obtained using a Q-switched Nd:YAG laser. The use of a combination of PA and TGA-DTA techniques enables the study of NO2 generation, and this method can be used to scale the performance of these explosives as rocket fuels. The minimum detection limits of the four explosives were 38 ppmv to 69 ppbv, depending on their respective vapor pressures.

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

    PubMed

    Yehya, Fahem; Chaudhary, A K

    2013-11-01

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

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

    NASA Astrophysics Data System (ADS)

    Yehya, Fahem; Chaudhary, A. K.

    2013-11-01

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

  12. Photoacoustic Measurements in Brain Tissue

    SciTech Connect

    Kasili, P.M.; Mobley, J.; Vo-Dinh, T.

    1999-09-19

    In this work, we develop and evaluate the photoacoustic technique for recording spectra of white and gray mammalian brain tissues. In addition to the experimental work, we also discuss the geometric aspects of photoacoustic signal generation using collimated light. Spectra constructed from the peak-to-peak amplitude of the photoacoustic waveforms indicate differences in the two tissue types at wavelengths between 620 and 695 nm. The potential of the technique for non-invasive diagnosis is discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

  14. Photoacoustic Effect and the Physics of Waves.

    ERIC Educational Resources Information Center

    McDonald, F. Alan

    1980-01-01

    Discussions are presented for implementing photoacoustic spectroscopy as a technique for describing the photoacoustic effect. This technique makes it possible to study optical absorption in samples which are usually difficult to study. It is suggested that this approach makes understanding of the photoacoustic effect accessible even at the…

  15. 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.

  16. Reconstruction Formulas for Photoacoustic Sectional Imaging

    E-print Network

    Peter Elbau; Otmar Scherzer; Rainer Schulze

    2011-09-05

    The literature on reconstruction formulas for photoacoustic tomography (PAT) is vast. The various reconstruction formulas differ by used measurement devices and geometry on which the data are sampled. In standard photoacoustic imaging (PAI), the object under investigation is illuminated uniformly. Recently, sectional photoacoustic imaging techniques, using focusing techniques for initializing and measuring the pressure along a plane, appeared in the literature. This paper surveys existing and provides novel exact reconstruction formulas for sectional photoacoustic imaging.

  17. Reconstruction Formulas for Photoacoustic Sectional Imaging

    E-print Network

    Elbau, Peter; Schulze, Rainer

    2011-01-01

    The literature on reconstruction formulas for photoacoustic tomography (PAT) is vast. The various reconstruction formulas differ by used measurement devices and geometry on which the data are sampled. In standard photoacoustic imaging (PAI), the object under investigation is illuminated uniformly. Recently, sectional photoacoustic imaging techniques, using focusing techniques for initializing and measuring the pressure along a plane, appeared in the literature. This paper surveys existing and provides novel exact reconstruction formulas for sectional photoacoustic imaging.

  18. Photoacoustic detection of particulate carbon

    SciTech Connect

    Bennett, C.A.; Patty, R.R.

    1981-08-01

    A photoacoustic technique for the mass monitoring of carbonaceous aerosols deposited on filter substrates has been developed. The technique involves the use of a specially designed photoacoustic cell. Photoacoustic response is calibrated as a function of elemental carbon loading using laboratory-generated elemental carbon standards. The nature of the photoacoustic response is examined at several chopping frequencies using these calibration standards, and the physical principles necessary for an adequate interpretation of the experimental results is presented in detail. Practical considerations concerning ambient carbon monitoring are outlined; in particular, the perturbation due to the presence of scattering particulates is examined and limited experimental quantification of this perturbation is reported.

  19. Open Photoacoustic Cell Technique as a Tool for Thermal and Thermo-Mechanical Characterization of Teeth and Their Restorative Materials

    NASA Astrophysics Data System (ADS)

    Pichardo-Molina, J. L.; Gutiérrez-Juárez, G.; Huerta-Franco, R.; Vargas-Luna, M.; Cholico, P.; Alvarado-Gil, J. J.

    2005-01-01

    The thermal diffusivity and thermal expansion coefficient of teeth and three of their most common restorative materials (Amalgam Phase Alloy, Ionomer Fuji II LC, and Resin 3MFPITEK Lutine TMZ250) were studied by means of the open photoacoustic technique. These results were then used as a basis for the theoretical simulation of the photothermal process taking place as a consequence of modulated illumination of a two-layer system formed by the tooth and the restorative material. The model accounts for the coupling of thermal waves and thermoelastic vibration in the two-layer system.

  20. Internal Water Vapor Photoacoustic Calibration

    NASA Technical Reports Server (NTRS)

    Pilgrim, Jeffrey S.

    2009-01-01

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

  1. Quantitative fluorescence photoacoustic tomography Hongkai Zhao

    E-print Network

    Ren, Kui

    Quantitative fluorescence photoacoustic tomography Kui Ren Hongkai Zhao Abstract Fluorescence photoacoustic tomography (fPAT) is a multi-modality biomedical imaging technique that combines the high utilizes the photoacoustic effect to recover the total absorbed energy map inside the media with ultrasound

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

    E-print Network

    Aguilar, Guillermo

    A Comparative Study of Photoacoustic and Reflectance Methods for Determination of Epidermal Melanin. We have developed a photoacoustic probe that uses a Q-switched, frequency-doubled Nd:YAG (neodymium. The probe contained a piezoelectric element that detected photoacoustic waves that were then analyzed

  3. 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

  4. Measurements of dynamic Young's modulus in short specimens with the PUCOT. [Piezoelectric Ultrasonic Composite Oscillator Technique

    NASA Technical Reports Server (NTRS)

    Wickstrom, S. N.; Wolfenden, A.

    1990-01-01

    The piezoelectric ultrasonic composite oscillator technique (PUCOT) was used at frequencies in the range 40 to 150 kHz to measure dynamic Young's modulus for short-length single crystals of copper at temperatures in the range 25 to 650 C and for polycrystalline copper at room temperature. Corrections to the modulus for variations in length/diameter resulted in no loss of precision due to wave velocity dispersion.

  5. 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

  6. Study of the lime influence on the thermal and optical properties of pericarp films of nixtamalized corn by means of the photoacoustic techniques

    SciTech Connect

    Cruz-Orea, A.; Sinencio, F. Sanchez; Falcony, C.; Hernandez, R. A. Munoz; Calderon, A.; Tomas, S. A.; Mendoza-Barrera, C.

    1999-03-15

    We present a study of the influence of Ca(OH){sub 2} in the thermal and optical properties on pericarp films obtained from nixtamalized corn grains. The nixtamalization process was performed using alkaline solutions with different Ca(OH){sub 2} concentrations. For this study we have used Photoacoustic techniques and complementary analysis of optical microscopy and x-ray diffraction.

  7. Photoacoustic measurement of epidermal melanin

    NASA Astrophysics Data System (ADS)

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

    2003-06-01

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

  8. Relaxation time measurements in frequency and time-domain photoacoustic spectroscopy of condensed phases

    E-print Network

    Mandelis, Andreas

    Relaxation time measurements in frequency and time-domain photoacoustic spectroscopy of condensed08544 (Received 8 August 1979) The use of the photoacoustic spectroscopy (PAS) technique to measure velocity in the transducer gas. INTRODUCTION Photoacoustic spectroscopy (PAS) provides a method

  9. Combined photothermal and photoacoustic characterization of siliconepoxy composites and the existence of a particle thermal

    E-print Network

    Mandelis, Andreas

    Combined photothermal and photoacoustic characterization of silicon±epoxy composites Received 9 February 2001; received in revised form 21 May 2001 Abstract Photoacoustic (PA) and photothermal (PTR) and other photoacoustic (PA) techniques are widely used in the investigation of material

  10. Photoacoustic angiography of the breast

    PubMed Central

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

    2010-01-01

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

  11. 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

  12. Rapid and noncontact photoacoustic tomography imaging system using an interferometer with high-speed phase modulation technique

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    We designed, fabricated, and tested a rapid and noncontact photoacoustic tomography (PAT) imaging system using a low-coherence interferometer with high-speed phase modulation technique. Such a rapid and noncontact probing system can greatly decrease the time of imaging. The proposed PAT imaging system is experimentally verified by capturing images of a simulated tissue sample and the blood vessels within the ear flap of a mouse (pinna) in vivo. The axial and lateral resolutions of the system are evaluated at 45 and ˜15 ?m, respectively. The imaging depth of the system is 1 mm in a special phantom. Our results show that the proposed system opens a promising way to realize noncontact, real-time PAT.

  13. Rapid and noncontact photoacoustic tomography imaging system using an interferometer with high-speed phase modulation technique

    SciTech Connect

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

    2015-04-15

    We designed, fabricated, and tested a rapid and noncontact photoacoustic tomography (PAT) imaging system using a low-coherence interferometer with high-speed phase modulation technique. Such a rapid and noncontact probing system can greatly decrease the time of imaging. The proposed PAT imaging system is experimentally verified by capturing images of a simulated tissue sample and the blood vessels within the ear flap of a mouse (pinna) in vivo. The axial and lateral resolutions of the system are evaluated at 45 and ?15 ?m, respectively. The imaging depth of the system is 1 mm in a special phantom. Our results show that the proposed system opens a promising way to realize noncontact, real-time PAT.

  14. 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

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

    PubMed Central

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

    2014-01-01

    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 mm2 with a 16-?m kerf between elements. The active piezoelectric material is (1 ? x) Pb(Mg1/3Nb2/3)O3?xPbTiO3 (PMN-PT)/epoxy 1–3 composite with a PMN-PT pillar lateral dimension of 8 ?m and an average gap width of ~4 ?m, which was produced by deep reactive ion etching (DRIE) dry etching techniques. A novel electric interconnection strategy for high-density, small-size array elements was proposed. After assembly, the array transducer was tested and characterized. The capacitance, pulse–echo responses, and crosstalk were measured for each array element. The desired center frequency of ~60 MHz was achieved and the ?6-dB bandwidth of the received signal was ~50%. At the center frequency, the crosstalk between adjacent 2-D array elements was about ?33 dB. The techniques described herein can be used to build larger arrays containing smaller elements. PMID:24297027

  16. Multi-mode vibration suppression in 2-DOF piezoelectric systems using zero placement input shaping technique

    NASA Astrophysics Data System (ADS)

    Al Hamidi, Yasser; Rakotondrabe, Micky

    2015-06-01

    This paper deals with the feedforward control of the vibrations of a 2-DOF piezoelectric micropositioner in order to damp the vibrations in the direct axes and in the cross-couplings. The actuator exhibit badly damped vibrations in its direct transfers as well as in the cross-couplings transfers. We therefore propose a bivariable control which does not require sensors to reduce the vibrations in the different axes. The proposed scheme reduces all modes of vibrations for both outputs through extending the monovariable zero placement input shaping technique into bivariable. Experimental tests have been carried out and demonstrate the efficiency of the proposed method.

  17. Picosecond measurements using photoacoustic detection

    NASA Technical Reports Server (NTRS)

    Heritier, J.-M.; Siegman, A. E.

    1983-01-01

    A report is presented of experimental results on picosecond time-resolved photoacoustic measurements of excited-state lifetimes, cross sections, and polarization properties for organic dye molecules in solution, using a new technique in which the total photoacoustic impulse produced by two ultrashort optical pulses with variable time delay between them is detected. The picosecond photoacoustic detection technique reported here appears to be a promising new way to observe weak excited-state cross sections and to perform picosecond lifetime measurements in a large variety of weakly absorbing and/or nonfluorescing atomic and molecular systems.

  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. Photoacoustic imaging in biomedicine

    NASA Astrophysics Data System (ADS)

    Xu, Minghua; Wang, Lihong V.

    2006-04-01

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

  20. 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

  1. Grueneisen Relaxation Photoacoustic Microscopy

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  2. Grueneisen relaxation photoacoustic microscopy.

    PubMed

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

    2014-10-24

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

  3. 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.; Aldama-Reyna, W.; Lara-Rodriguez, A.G.; Garcia-Fernandez, T.; Pulos, G.; Trivi, M.; Villagran-Muniz, M.

    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.

  4. Photoacoustic detection of intracavity absorption

    SciTech Connect

    Kelly, R.A.; Nogar, N.S.; Bomse, D.S.

    1983-11-01

    It is demonstrated that the photoacoustic effect in an external cell is a sensitive resonant detector of inracavity absorption. The detection limits for I/sub 2/ and Br/sub 2/ ng/cm/sup 3/ and 48 ng/cm/sup 3/, respectively. For the case of I/sub 2/ the detection limit using the photoacoustic detector is essentially the same as the detection limit using a fluorescence detector. The sensitive response of photoacoustic detection to IR absorption makes this technique particularly attractive as a potential resonance detector for intracavity absorption with IR lasers.

  5. Organosilicon phantom for photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Avigo, Cinzia; Di Lascio, Nicole; Armanetti, Paolo; Kusmic, Claudia; Cavigli, Lucia; Ratto, Fulvio; Meucci, Sandro; Masciullo, Cecilia; Cecchini, Marco; Pini, Roberto; Faita, Francesco; Menichetti, Luca

    2015-04-01

    Photoacoustic imaging is an emerging technique. Although commercially available photoacoustic imaging systems currently exist, the technology is still in its infancy. Therefore, the design of stable phantoms is essential to achieve semiquantitative evaluation of the performance of a photoacoustic system and can help optimize the properties of contrast agents. We designed and developed a polydimethylsiloxane (PDMS) phantom with exceptionally fine geometry; the phantom was tested using photoacoustic experiments loaded with the standard indocyanine green dye and compared to an agar phantom pattern through polyethylene glycol-gold nanorods. The linearity of the photoacoustic signal with the nanoparticle number was assessed. The signal-to-noise ratio and contrast were employed as image quality parameters, and enhancements of up to 50 and up to 300%, respectively, were measured with the PDMS phantom with respect to the agar one. A tissue-mimicking (TM)-PDMS was prepared by adding TiO2 and India ink; photoacoustic tests were performed in order to compare the signal generated by the TM-PDMS and the biological tissue. The PDMS phantom can become a particularly promising tool in the field of photoacoustics for the evaluation of the performance of a PA system and as a model of the structure of vascularized soft tissues.

  6. Organosilicon phantom for photoacoustic imaging.

    PubMed

    Avigo, Cinzia; Di Lascio, Nicole; Armanetti, Paolo; Kusmic, Claudia; Cavigli, Lucia; Ratto, Fulvio; Meucci, Sandro; Masciullo, Cecilia; Cecchini, Marco; Pini, Roberto; Faita, Francesco; Menichetti, Luca

    2015-04-01

    Photoacoustic imaging is an emerging technique. Although commercially available photoacoustic imaging systems currently exist, the technology is still in its infancy. Therefore, the design of stable phantoms is essential to achieve semiquantitative evaluation of the performance of a photoacoustic system and can help optimize the properties of contrast agents. We designed and developed a polydimethylsiloxane (PDMS) phantom with exceptionally fine geometry; the phantom was tested using photoacoustic experiments loaded with the standard indocyanine green dye and compared to an agar phantom pattern through polyethylene glycol-gold nanorods. The linearity of the photoacoustic signal with the nanoparticle number was assessed. The signal-tonoiseratio and contrast were employed as image quality parameters, and enhancements of up to 50 and up to 300%, respectively, were measured with the PDMS phantom with respect to the agar one. A tissue-mimicking (TM)-PDMS was prepared by adding TiO2 and India ink; photoacoustic tests were performed in order to compare the signal generated by the TM-PDMS and the biological tissue. The PDMS phantom can become a particularly promising tool in the field of photoacoustics for the evaluation of the performance of a PA system and as a model of the structure of vascularized soft tissues. PMID:25894254

  7. Study of acoustic fingerprinting of nitromethane and some triazole derivatives using UV 266 nm pulsed photoacoustic pyrolysis technique.

    PubMed

    Rao, K S; Chaudhary, A K; Yehya, F; Kumar, A Sudheer

    2015-08-01

    We report a comparative study of acoustic fingerprints of nitromethane, nitrobenzene and some nitro rich triazole derivatives using pulsed photoacoustic technique. UV 266 nm wavelength i.e. Fourth harmonic of Q-switched Nd: YAG laser having pulse duration 7 ns and 10 Hz repetition rate is employed to record the time resolved PA spectrum. The PA fingerprint is produced due to absorption of incident UV light by molecule itself and photo dissociation of nitromethane and nitrobenzene at room temperature while in case of triazole it is attributed to the combination of thermal and photo-dissociation process. The entire dissociation process follows the root of cleavage of C-NO? bond to produce free NO, NO? and other by product gases due to ?(?)?n excitation. In addition, we have studied the thermal stability criteria of nitro rich triazoles based on the quality factor of acoustic resonance frequencies of the PA cavity. We have also studied the effect of data acquisition time to ascertain the decay behavior of HEMs samples. PMID:25854611

  8. Study of acoustic fingerprinting of nitromethane and some triazole derivatives using UV 266 nm pulsed photoacoustic pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Rao, K. S.; Chaudhary, A. K.; Yehya, F.; Kumar, A. Sudheer

    2015-08-01

    We report a comparative study of acoustic fingerprints of nitromethane, nitrobenzene and some nitro rich triazole derivatives using pulsed photoacoustic technique. UV 266 nm wavelength i.e. Fourth harmonic of Q-switched Nd: YAG laser having pulse duration 7 ns and 10 Hz repetition rate is employed to record the time resolved PA spectrum. The PA fingerprint is produced due to absorption of incident UV light by molecule itself and photo dissociation of nitromethane and nitrobenzene at room temperature while in case of triazole it is attributed to the combination of thermal and photo-dissociation process. The entire dissociation process follows the root of cleavage of C-NO2 bond to produce free NO, NO2 and other by product gases due to ?? ? n excitation. In addition, we have studied the thermal stability criteria of nitro rich triazoles based on the quality factor of acoustic resonance frequencies of the PA cavity. We have also studied the effect of data acquisition time to ascertain the decay behavior of HEMs samples.

  9. Investigation of thermal stability and fingerprint spectra of energetic 1,2,3-triazole using pulsed photoacoustic pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Rao, K. S.; Chaudhary, A. K.; Yehya, F.

    2015-10-01

    This paper reports on a comparative study of UV and visible radiation-based pulsed photoacoustic (PA) pyrolysis technique examining thermal stability and acoustic fingerprint spectra of a newly synthesized high-energy molecule named 1-(2,4-dinitrobenzyl)-4-nitro-1H-1,2,3-triazole (S 6). The thermal PA spectra of S 6 were recorded in temperatures ranging between 30 and 350 °C using second and fourth harmonic wavelengths (i.e., 532 and 266 nm), obtained from Q-switched Nd:YAG laser pulses of duration 7 ns at 10 Hz repetition rate. The PA results are further compared with TG-DTA data to understand the release mechanism of NO2 along with other gaseous by-products. The difference in thermal PA spectra of S 6 which follows two different mechanisms, such as vibronic transition V-V and V-T relaxation in NO2 functional group, while electronic ?* ? n transition in the entire molecule, is due to selection of visible and UV wavelengths. In addition, the effect of data acquisition time and incident laser energy has been examined in order to understand the behavior of acoustic modes of a PA cavity at the desired vapor temperature. The stability of the compound is also evaluated on the basis of thermal quality factor (Q), of PA cavity.

  10. Photoacoustic imaging: current status and future development

    NASA Astrophysics Data System (ADS)

    Lu, Tao; Jiang, Jingying; Su, Yixiong; Wang, Ruikang K.; Zhang, Fan; Yao, Jianquan

    2006-09-01

    Photo-acoustic tomography(PAT) is a new ultrasound-mediated biomedical imaging technology which combines the advantages of high optical contrast and high ultrasonic resolution. In theory, PAT can image object embedded several centimeters under the surface of sample with the resolution of tens of microns. In this paper, several representative image reconstruction algorithms are discussed. Because the PA signal is wide band signal, it is hard to get the whole frequency spectrum due to the tremendous calculation needed. Therefore, the most applicable reconstruction algorithms are all performed in time domain such as "delay-and-sum" and "back projection". The current research methods have been focused on optical detecting and piezoelectric detecting. The optical method has the advantage of high spatial sensitivity due to the short wavelength of the probe laser beam. PA signal detecting using piezoelectric sensor has two main modes i.e. using unfocused transducer or transducer array or using focused transducer array or linear transducer array. When a focused transducer array is used, the "delay-and-sum" method is often used for image reconstruction. The advantage of the method is that its data acquisition time can be reduced to several minutes or even several seconds by employing the phase control linear scan technique. The future development in PAT research and its potential clinic application is also presented.

  11. Multiple-source quantitative photoacoustic tomography Guillaume Bal

    E-print Network

    Biasutti, Michela

    Multiple-source quantitative photoacoustic tomography Guillaume Bal Kui Ren November 6, 2010 Abstract Photoacoustic tomography (PAT) is a novel hybrid medical imaging technique that aims to combine measurement, is done. We focus on quantitative photoacoustic tomography (QPAT), which aims at quantitatively

  12. Multicontrast photoacoustic in vivo imaging using near-infrared fluorescent

    E-print Network

    Verkhusha, Vladislav V.

    Multicontrast photoacoustic in vivo imaging using near-infrared fluorescent proteins Arie Krumholz1 is invaluable in advancing biology. Photoacoustic tomography is a scalable imaging technique that provides from bacterial phytochromes, as photoacoustic contrast agents. iRFPs provide tissue-specific contrast

  13. Photoacoustic Tomography

    NASA Astrophysics Data System (ADS)

    Wang, Lihong V.

    Photoacoustic tomography (PAT) refers to imaging that is based on the photoacoustic effect. Although the photoacoustic effect as a physical phenomenon was first reported on by Alexander Graham Bell in 1880 [1], PAT as an imaging technology was developed only after the advent of ultrasonic transducers, computers, and lasers [2-31]. A review on biomedical photoacoustics is available [32]. The motivation for PAT is to combine optical-absorption contrast with ultrasonic spatial resolution for deep imaging in the optical quasi-diffusive or diffusive regime. In PAT, the tissue is irradiated by usually a short-pulsed laser beam to achieve a thermal and acoustic impulse response (Fig. 19.1). Locally absorbed light is converted into heat, which is further converted to a pressure rise via thermo-elastic expansion. The initial pressure rise - determined by the local optical absorption coefficient (? â ), fluence (?) and other thermal and mechanical properties - propagates as an ultrasonic wave, which is referred to as a photoacoustic wave.

  14. 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

  15. Mathematics of Photoacoustic and

    E-print Network

    Kunyansky, Leonid

    Mathematics of Photoacoustic and Thermoacoustic Tomography Peter Kuchment Leonid Kunyansky of Photoacoustic and Thermoacoustic Tomography .. Partial (Incomplete) Data of Photoacoustic and Thermoacoustic Tomography Abstract: The chapter surveys the mathematical models, problems

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

    SciTech Connect

    Felmetsger, V. V.; Laptev, P. N.; Tanner, S. M.

    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.

  17. A low-loss hybrid rectification technique for piezoelectric energy harvesting

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  18. 3D photoacoustic imaging

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    Our group has concentrated on development of a 3D photoacoustic imaging system for biomedical imaging research. The technology employs a sparse parallel detection scheme and specialized reconstruction software to obtain 3D optical images using a single laser pulse. With the technology we have been able to capture 3D movies of translating point targets and rotating line targets. The current limitation of our 3D photoacoustic imaging approach is its inability ability to reconstruct complex objects in the field of view. This is primarily due to the relatively small number of projections used to reconstruct objects. However, in many photoacoustic imaging situations, only a few objects may be present in the field of view and these objects may have very high contrast compared to background. That is, the objects have sparse properties. Therefore, our work had two objectives: (i) to utilize mathematical tools to evaluate 3D photoacoustic imaging performance, and (ii) to test image reconstruction algorithms that prefer sparseness in the reconstructed images. Our approach was to utilize singular value decomposition techniques to study the imaging operator of the system and evaluate the complexity of objects that could potentially be reconstructed. We also compared the performance of two image reconstruction algorithms (algebraic reconstruction and l1-norm techniques) at reconstructing objects of increasing sparseness. We observed that for a 15-element detection scheme, the number of measureable singular vectors representative of the imaging operator was consistent with the demonstrated ability to reconstruct point and line targets in the field of view. We also observed that the l1-norm reconstruction technique, which is known to prefer sparseness in reconstructed images, was superior to the algebraic reconstruction technique. Based on these findings, we concluded (i) that singular value decomposition of the imaging operator provides valuable insight into the capabilities of a 3D photoacoustic imaging system, and (ii) that reconstruction algorithms which favor sparseness can significantly improve imaging performance. These methodologies should provide a means to optimize detector count and geometry for a multitude of 3D photoacoustic imaging applications.

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

    PubMed

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

    2013-07-14

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

  20. Photopyroelectric versus photoacoustic characterization of photovoltaic cells

    SciTech Connect

    Faria I.F. Jr.; Ghizoni, C.C.; Miranda, L.C.M.; Vargas, H.

    1986-05-01

    The photothermal pyroelectric technique is applied to the characterization of photovoltaic cells and a comparison with the photoacoustic detection is presented. The difference between the photoacoustic and the pyroelectric data is interpreted in terms of a simple model for a junction-type solar cell.

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  2. 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.

  3. Quantitative Photoacoustic Image Reconstruction using Fluence Dependent Chromophores

    PubMed Central

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

    2010-01-01

    In biomedical photoacoustic imaging the images are proportional to the absorbed optical energy density, and not the optical absorption, which makes it difficult to obtain a quantitatively accurate image showing the concentration of a particular absorbing chromophore from photoacoustic measurements alone. Here it is shown that the spatially varying concentration of a chromophore whose absorption becomes zero above a threshold light fluence can be estimated from photoacoustic images obtained at increasing illumination strengths. This technique provides an alternative to model-based multiwavelength approaches to quantitative photoacoustic imaging, and a new approach to photoacoustic molecular and functional imaging. PMID:21258458

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

    SciTech Connect

    Alvisi, M.; Vasanelli, L.; De Nunzio, G.; Diso, D.; Perrone, M. R.; Protopapa, L.; Rizzo, A.; Scaglione, S.

    1999-03-15

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

  5. 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.

  6. Photoacoustic spectroscopy of condensed matter

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.

    1978-01-01

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

  7. Photoacoustic Cystography

    PubMed Central

    Jeon, Mansik; Kim, Jeehyun; Kim, Chulhong

    2013-01-01

    Conventional pediatric cystography, which is based on diagnostic X-ray using a radio-opaque dye, suffers from the use of harmful ionizing radiation. The risk of bladder cancers in children due to radiation exposure is more significant than many other cancers. Here we demonstrate the feasibility of nonionizing and noninvasive photoacoustic (PA) imaging of urinary bladders, referred to as photoacoustic cystography (PAC), using near-infrared (NIR) optical absorbents (i.e. methylene blue, plasmonic gold nanostructures, or single walled carbon nanotubes) as an optical-turbid tracer. We have successfully imaged a rat bladder filled with the optical absorbing agents using a dark-field confocal PAC system. After transurethral injection of the contrast agents, the rat's bladders were photoacoustically visualized by achieving significant PA signal enhancement. The accumulation was validated by spectroscopic PA imaging. Further, by using only a laser pulse energy of less than 1 mJ/cm2 (1/20 of the safety limit), our current imaging system could map the methylene-blue-filled-rat-bladder at the depth of beyond 1 cm in biological tissues in vivo. Both in vivo and ex vivo PA imaging results validate that the contrast agents were naturally excreted via urination. Thus, there is no concern regarding long-term toxic agent accumulation, which will facilitate clinical translation. PMID:23792925

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

    SciTech Connect

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

    1993-11-01

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

  9. Pure optical photoacoustic microscopy.

    PubMed

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

    2011-05-01

    The concept of pure optical photoacoustic microscopy(POPAM) was proposed based on optical rastering of a focused excitation beam and optically sensing the photoacoustic signal using a microring resonator fabricated by a nanoimprinting technique. After the refinements of the microring's working wavelength and in the resonator structure and mold fabrication, an ultrahigh Q factor of 3.0×10(5) was achieved which provided high sensitivity with a noise equivalent detectable pressure(NEDP) value of 29 Pa. This NEDP is much lower than the hundreds of Pascals achieved with existing optical resonant structures such as etalons, fiber gratings and dielectric multilayer interference filters available for acoustic measurement. The featured high sensitivity allowed the microring resonator to detect the weak photoacoustic signals from micro- or submicroscale objects. The inherent superbroad bandwidth of the optical microring resonator combined with an optically focused scanning beam provided POPAM with high resolution in the axial as well as both lateral directions while the axial resolution of conventional photoacoustic microscopy (PAM) suffers from the limited bandwidth of PZT detectors. Furthermore, the broadband microring resonator showed similar sensitivity to that of our most sensitive PZT detector. The current POPAM system provides a lateral resolution of 5 ?m and an axial resolution of 8 ?m, comparable to that achieved by optical microscopy while presenting the unique contrast of optical absorption and functional information complementing other optical modalities. The 3D structure of microvasculature, including capillary networks, and even individual red blood cells have been discerned successfully in the proof-of-concept experiments on mouse bladders ex vivo and mouse ears in vivo. The potential of approximately GHz bandwidth of the microring resonator also might allow much higher resolution than shown here in microscopy of optical absorption and acoustic propagation properties at depths in unfrozen tissue specimens or thicker tissue sections, which is not now imageable with current optical or acoustic microscopes of comparable resolution. PMID:21643156

  10. 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.

  11. 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.

  12. Prospects of photoacoustic tomography

    PubMed Central

    Wang, Lihong V.

    2008-01-01

    Commercially available high-resolution three-dimensional optical imaging modalities—including confocal microscopy, two-photon microscopy, and optical coherence tomography—have fundamentally impacted biomedicine. Unfortunately, such tools cannot penetrate biological tissue deeper than the optical transport mean free path (?1 mm in the skin). Photoacoustic tomography, which combines strong optical contrast and high ultrasonic resolution in a single modality, has broken through this fundamental depth limitation and achieved superdepth high-resolution optical imaging. In parallel, radio frequency-or microwave-induced thermoacoustic tomography is being actively developed to combine radio frequency or microwave contrast with ultrasonic resolution. In this Vision 20?20 article, the prospects of photoacoustic tomography are envisaged in the following aspects: (1) photoacoustic microscopy of optical absorption emerging as a mainstream technology, (2) melanoma detection using photoacoustic microscopy, (3) photoacoustic endoscopy, (4) simultaneous functional and molecular photoacoustic tomography, (5) photoacoustic tomography of gene expression, (6) Doppler photoacoustic tomography for flow measurement, (7) photoacoustic tomography of metabolic rate of oxygen, (8) photoacoustic mapping of sentinel lymph nodes, (9) multiscale photoacoustic imaging in vivo with common signal origins, (10) simultaneous photoacoustic and thermoacoustic tomography of the breast, (11) photoacoustic and thermoacoustic tomography of the brain, and (12) low-background thermoacoustic molecular imaging. PMID:19175133

  13. 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.

  14. High-sensitivity photoacoustic leak testing.

    PubMed

    Huang, Eric; Dowling, David R; Whelan, Timothy; Spiesberger, John L

    2003-10-01

    The photoacoustic effect may be exploited for the detection and localization of gas leaks from otherwise sealed components. The technique involves filling the test component with a tracer gas, and radiating the component to produce photoacoustic sound from any leak site where tracer gas is present. This paper describes demonstration experiments utilizing 10.6-micro radiation from a carbon-dioxide laser and sulfur hexafluoride as a tracer gas for photoacoustic leak testing at leak rates between 6 x 10(-5) cm3/s (1 cm3 in 4.6 h) and 5 x 10(-9) cm3/s (1 cm3 in 6.3 years). The technique may reach or exceed the capabilities of the most sensitive commercial leak test systems using helium mass-spectrometers. In addition, comparison of the measured results to a simple scaling law suggests that tracer gas cloud geometry influences the photoacoustic signal amplitude. PMID:14587593

  15. Temperature mapping using photoacoustic and thermoacoustic tomography

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Trindade, M. A.; Benjeddou, A.

    2011-07-01

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

  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. 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

  20. 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

  1. 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

  2. BODIPY derivatives as molecular photoacoustic contrast agents

    NASA Astrophysics Data System (ADS)

    Laoui, Samir; Bag, Seema; Dantiste, Olivier; Frenette, Mathieu; Hatamimoslehabadi, Maryam; Bellinger-Buckley, Stephanie; Tseng, Jen-Chieh; Rochford, Jonathan; Yelleswarapu, Chandra

    2014-03-01

    Photoacoustic imaging (PAI) is emerging as a key in vivo imaging technique. Endogenous contrast agents alone are insufficient to obtain high contrast images necessitating a need for synthetic exogenous contrast agents. In recent years a great deal of research has been devoted to the development of nanoparticle based contrast agents with little effort on molecular systems. Here we report on the design and evaluation of BODIPY inspired molecular photoacoustic contrast agents (MPACs). Through chemical modification of the established BODIPY fluorophore, increasing its vibrational freedom and appending with non-emissive functionalities, it is demonstrated that the S0-S1 absorbed excitation energy is redirected towards a nonradiative excited-state decay pathway. Optical and photoacoustic characterization of the modified BODIPY MPACs demonstrates a stronger photoacoustic signal compared to the corresponding fluorescent BODIPY probes.

  3. 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.

  4. 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.

  5. 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

  6. 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

  7. Photoacoustic Point Source

    SciTech Connect

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

    2001-04-16

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

  8. Determination of formation constants at elevated temperatures by laser-induced photoacoustic spectroscopy

    SciTech Connect

    Wruck, D.A.; Kadkhodayan, B.; Russo, R.E.

    1994-12-31

    A photoacoustic spectrometer has been developed for high-sensitivity optical absorption measurements of aqueous solutions at temperatures from ambient to 90 C. The light source is a Nd:YAG-pumped dye laser, and the photoacoustic signal is detected with a piezoelectric transducer coupled to a thermostatted quartz cell. The temperature dependence of the observed photoacoustic signal is compared to a theoretical model, and the application of the instrument to the determination of formation constants of metal-ligand complexes at elevated temperatures is discussed. Measurements of the temperature dependence of the formation constant for AmCO{sub 3}{sup +} are reported.

  9. 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.

  10. Emissions monitoring by infrared photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Jalenak, Wayne

    1991-04-01

    The pollution of the atmosphere and the air we breathe is of major concern today. In order to protect the health and welfare of people and to understand how pollutants affect our atmosphere, monitoring of the air for various pollutants is needed. There are numerous ways to do this monitoring, and a variety of analytical techniques to accomplish it. One of these techniques is infrared photoacoustic spectroscopy. Photoacoustic spectroscopy is based upon the detection of acoustic waves which are generated when a substance absorbs radiant energy. It has been used in many different fields of research including trace gas analysis. The first part of this paper reviews the principles and characteristics of infrared photoacoustic spectroscopy. The second part will describe the development of a portable instrument based upon this technique. The application of this instrument to some problems in industrial hygiene and emissions monitoring will also be discussed.

  11. Lifetime-weighted photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Forbrich, A.; Shao, P.; Shi, Wei; Zemp, Roger J.

    2015-03-01

    It has previously been shown that photoacoustic imaging can interrogate lifetimes of exogenous agents by a sequence of pulses with varying pump-probe delay intervals. Rather than attempt to unmix molecules based on their composite lifetime profile, we introduce a technique called lifetime weighted imaging, which preferentially weights signals from chromophores with long lifetimes (including exogenous contrast agents such as methylene blue and porphyrins with microsecond-scale lifetimes) while nulling chromophores with short lifetimes (including hemoglobin with ps-ns-scale lifetimes). A probe beam is used to interrogate samples with or without a pump beam. By subtracting probe-beam photoacoustic signals with pump- from those without a pump excitation, we effectively eliminate probe signals from chromophores with short lifetimes while preserving excited-state photoacoustic signals from long-lifetimes. This differential signal will be weighted by a decaying exponential function of the pump-probe delay divided by the exogenous agent lifetime. This technique enabled the imaging of both triplet excited state lifetime and ground-state recovery lifetime. We demonstrate the oxygen-dependent lifetime of both methylene blue and porphyrins. Lifetimeweighted imaging could be used for photodynamic therapy dosimetry guidance, oxygen sensing, or other molecular imaging applications.

  12. 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.

  13. 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.

  14. Thermoacoustic and photoacoustic sensing of temperature

    PubMed Central

    Pramanik, Manojit; Wang, Lihong V.

    2009-01-01

    We present a novel temperature-sensing technique using thermoacoustic and photoacoustic measurements. This noninvasive method has been demonstrated using a tissue phantom to have high temporal resolution and temperature sensitivity. Because both photoacoustic and thermoacoustic signal amplitudes depend on the temperature of the source object, the signal amplitudes can be used to monitor the temperature. A temperature sensitivity of 0.15°C was obtained at a temporal resolution as short as 2 s, taking the average of 20 signals. The deep-tissue imaging capability of this technique can potentially lead us to in vivo temperature monitoring in thermal or cryogenic applications. PMID:19895126

  15. Quantitative photoacoustic imaging in radiative transport regime

    E-print Network

    Ren, Kui

    Quantitative photoacoustic imaging in radiative transport regime Alexander V. Mamonov Kui Ren July 6, 2012 Abstract The objective of quantitative photoacoustic tomography (QPAT) is to reconstruct. Key words. Quantitative photoacoustic tomography (QPAT), sectional photoacoustic tomogra- phy

  16. 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.

  17. Theoretical and experimental investigation of the photoacoustic effect in solids with residual stresses

    NASA Astrophysics Data System (ADS)

    Muratikov, K.; Glazov, A.

    2003-09-01

    Modern experiment and theory in the field of residual stress detection by the photoacoustic method are summarized and analyzed. A multimode approach based on the simultaneous application of several photothermal and photoacoustic methods is proposed for the study of thermal and thermoelastic effects in solids with residual stress. Some experimental results obtained within the framework of this approach for Vickers indentation zones in ceramics are presented. The effect of annealing on the photoacoustic, piezoelectric signal for ceramics and the influence of the given external loading on the behavior of the photoacoustic signal near the radial crack tips is investigated. It is experimentally shown that both compressive and shear stresses contribute to the photoacoustic signal near the radial crack tips. The model of the photoacoustic, thermoelastic effect in solids with residual stress is proposed. It is based on the modified Murnaghan model of non-linear elastic bodies, which takes into account a possible dependence of the thermoelastic constant on stress. This model is further developed to explain the photoacoustic signal behavior near the radial crack tips. It is demonstrated that this model of the photoacoustic effect agrees qualitatively with the available experimental data.

  18. Hadamard transform photoacoustic spectrometry and depth profiling

    SciTech Connect

    Wright, S.L.; Hammaker, R.M.; Fateley, W.G. )

    1993-03-01

    The Hadamard transform technique has been extended to include photoacoustic detection. The feasibility of Hadamard transform photoacoustic spectrometry in the visible spectral region has been demonstrated. Depth profiling has been illustrated in a layered sample consisting of a thin (20 [mu]m) surface layer of neodymium oxide dispersed in a polystyrene matrix on a thick (2.5 mm) interior layer of holmium oxide dispersed in a polystyrene matrix. Depth profiling may be accomplished by varying the modulation frequency or by phase-sensitive detection at the appropriate modulation frequency. 9 refs., 6 figs.

  19. Enhanced photoacoustic detection using photonic crystal substrate

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  20. Enhanced photoacoustic detection using photonic crystal substrate

    SciTech Connect

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

    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.

  1. Piezoelectric Versus Conventional Rotary Techniques for Impacted Third Molar Extraction: A Meta-analysis of Randomized Controlled Trials.

    PubMed

    Jiang, Qian; Qiu, Yating; Yang, Chi; Yang, Jingyun; Chen, Minjie; Zhang, Zhiyuan

    2015-10-01

    Impacted third molars are frequently encountered in clinical work. Surgical removal of impacted third molars is often required to prevent clinical symptoms. Traditional rotary cutting instruments are potentially injurious, and piezosurgery, as a new osteotomy technique, has been introduced in oral and maxillofacial surgery. No consistent conclusion has been reached regarding whether this new technique is associated with fewer or less severe postoperative sequelae after third molar extraction.The aim of this study was to compare piezosurgery with rotary osteotomy techniques, with regard to surgery time and the severity of postoperative sequelae, including pain, swelling, and trismus.We conducted a systematic literature search in the Cochrane Library, PubMed, Embase, and Google Scholar.The eligibility criteria of this study included the following: the patients were clearly diagnosed as having impacted mandibular third molars; the patients underwent piezosurgery osteotomy, and in the control group rotary osteotomy techniques, for removing impacted third molars; the outcomes of interest include surgery time, trismus, swelling or pain; the studies are randomized controlled trials.We used random-effects models to calculate the difference in the outcomes, and the corresponding 95% confidence interval. We calculated the weighted mean difference if the trials used the same measurement, and a standardized mean difference if otherwise.A total of seven studies met the eligibility criteria and were included in our analysis. Compared with rotary osteotomy, patients undergoing piezosurgery experienced longer surgery time (mean difference 4.13 minutes, 95% confidence interval 2.75-5.52, P?piezoelectric technique had less swelling at postoperative days 1, 3, 5, and 7 (all Ps ?0.023). Additionally, there was a trend of less postoperative pain and trismus in the piezosurgery groups.The number of included randomized controlled trials and the sample size of each trial were relatively small, double blinding was not possible, and cost analysis was unavailable due to a lack of data.Our meta-analysis indicates that although patients undergoing piezosurgery experienced longer surgery time, they had less postoperative swelling, indicating that piezosurgery is a promising alternative technique for extraction of impacted third molars. PMID:26469902

  2. 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.

  3. 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.

  4. 1902 OPTICS LETTERS / Vol. 27, No. 21 / November 1, 2002 Quartz-enhanced photoacoustic spectroscopy

    E-print Network

    1902 OPTICS LETTERS / Vol. 27, No. 21 / November 1, 2002 Quartz-enhanced photoacoustic spectroscopy is accumulated in a high-Q crystal element. Feasibility experi- ments utilizing a quartz-watch tuning fork- phone). A well-suited material for a resonant high-Q microphone is piezoelectric crystal quartz

  5. Functional photoacoustic microscopy 

    E-print Network

    Zhang, Hao

    2009-06-02

    with the high-contrast advantage of optical imaging. It detects the short-pulsed laser-induced photoacoustic waves, whose amplitudes reflect the localized laser energy absorption, to image the internal optical absorption distributions. The spatial resolution...

  6. Photoacoustic spectroscopy of ?-hematin

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    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 hemin. 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.

  7. Optical properties of albino rat skin heated in vitro: comparison of photoacoustic and integrating sphere measurement techniques

    NASA Astrophysics Data System (ADS)

    Thomsen, Sharon L.; Vijverberg, Helene; Jacques, Steven L.; Oraevsky, Alexander A.

    1994-08-01

    The optical properties represented by the absorption coefficient ((mu) a) and reduced scattering coefficient [(mu) s(1-g) or (mu) 's] at (lambda) equals 355 nm of thermally altered albino rat skin were measured in vitro by two methods: (1) a time-resolved stress detection (TRSD) technique which directly measured the effective attenuation coefficient ((mu) eff) and the absorption coefficient ((mu) a), and (2) the well-known integrating sphere technique which measured total transmittance (Tt) nd total diffuse reflectance (Rd). The skin pieces were wrapped in water-tight packets and heated for 20 minutes in a calibrated water bath (temperature range: 20 degree(s) - 90 degree(s)C) and the same skin samples were used for both measurement methods. The experimental data were analyzed to specify the absorption and the scattering properties. The results, which were in general agreement for both methods, indicated that denaturation of the rat skin caused a decrease in scattering due to melting of the collagen fibers. The decrease began at 55 degree(s)C and plateaued at 65 degree(s) - 70 degree(s)C and was essentially unchanged at higher temperatures. Absorption was not significantly affected by denaturation except for a transient rise at 50 degree(s) - 60 degree(s)C.

  8. Piezoelectric single crystals for ultrasonic transducers in biomedical applications

    PubMed Central

    Zhou, Qifa; Lam, Kwok Ho; Zheng, Hairong; Qiu, Weibao; Shung, K. Kirk

    2014-01-01

    Piezoelectric single crystals, which have excellent piezoelectric properties, have extensively been employed for various sensors and actuators applications. In this paper, the state–of–art in piezoelectric single crystals for ultrasonic transducer applications is reviewed. Firstly, the basic principles and design considerations of piezoelectric ultrasonic transducers will be addressed. Then, the popular piezoelectric single crystals used for ultrasonic transducer applications, including LiNbO3 (LN), PMN–PT and PIN–PMN–PT, will be introduced. After describing the preparation and performance of the single crystals, the recent development of both the single–element and array transducers fabricated using the single crystals will be presented. Finally, various biomedical applications including eye imaging, intravascular imaging, blood flow measurement, photoacoustic imaging, and microbeam applications of the single crystal transducers will be discussed. PMID:25386032

  9. 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

  10. Fine-resolution photoacoustic imaging of the eye

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

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

  11. Intravascular ultrasound and photoacoustic imaging.

    PubMed

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

    2008-01-01

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

  12. k-Wave simulation to understand the photoacoustic signal characteristics from various shapes of nanoparticles

    NASA Astrophysics Data System (ADS)

    Verawaty; Pramanik, Manojit

    2015-07-01

    Current attempts in understanding the photoacoustic signal characteristic of various shapes of nanoparticles is mostly performed through numerical simulations. However these computational methods are very time consuming, costly and complicated. Thus there is a need for an easy and fast simulation technique to understand the photoacoustic signal generated from various shapes of nanoparticles. k-Wave is a MATLAB based simulation toolbox to simulate photoacoustic signal given the initial pressure distribution of the target object. In this work, we used k-Wave simulation to understand the photoacoustic signal generated from various shapes of nanoparticles. Seven shapes of nanoparticles are created mainly sphere, cylinder, hollow cylinder, cube, hollow cube, triangle, and star. A point sensor (ultrasound detector) is used to detect the photoacoustic waves generated from different shapes of nanoparticles. The photoacoustic signal generated by different shapes of nanoparticles is captured and processed for further analysis to see their frequency content.

  13. 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

  14. Texture generation in compressional photoacoustic elastography

    NASA Astrophysics Data System (ADS)

    Schmid, J. W.; Zabihian, B.; Widlak, T.; Glatz, T.; Liu, M.; Drexler, W.; Scherzer, O.

    2015-03-01

    Elastography is implemented by applying a mechanical force to a specimen and visualizing the resulting displacement. As a basis of elastographic imaging typically ultrasound, optical coherence tomography or magnetic resonance imaging are used. Photoacoustics has not been viewed as a primary imaging modality for elastography, but only as a complementary method to enhance the contrast in ultrasound elastography. The reason is that photoacoustics is considered speckle free [3], which hinders application of speckle tracking algorithms. However, while conventional ultrasound only uses a single frequency, photoacoustics utilizes a broad frequency spectrum. We are therefore able to generate artificial texture by using a frequency band limited part of the recorded data. In this work we try to assess the applicability of this technique to photoacoustic tomography. We use Agar phantoms with predefined Young's moduli and laterally apply a 50?m static compression. Pre- and post compression data are recorded via a Fabry Pérot interferometer planar sensor setup and reconstructed via a non-uniform-FFT reconstruction algorithm. A displacement vector field, between pre- and post compressed data is then determined via optical flow algorithms. While the implementation of texture generation during post processing reduces image quality overall, it turns out that it improves the detection of moving patterns and is therefore better suited for elastography.

  15. Piezoelectric and pyroelectric polymers

    SciTech Connect

    Davis, G.T.

    1995-12-01

    Many polar polymers can be made to exhibit piezoelectric and pyroelectric properties by permanently aligning their dipoles in an electric field. The largest response is found in semi-crystalline polymers which exhibit a polar crystal phase which is amenable to reorientation in an applied electric field. The properties of poly(vinylidenefluoride), copolymers of vinyl idenefluoride and trifluoroethylene, nylon 7 and nylon 11 are compared. Polarization distribution across the thickness of such polymer films are discussed and novel techniques for the construction of piezoelectric bimorphs from the above copolymers are presented.

  16. FULL ARTICLE Photoacoustic and photothermal cytometry using

    E-print Network

    Verkhusha, Vladislav V.

    FULL ARTICLE Photoacoustic and photothermal cytometry using photoswitchable proteins: photoswitchable fluorescent proteins, photothermal and photoacoustic spectroscopy, photothermal switching. As an alternative, photothermal (PT) and photoacoustic (PA) spectroscopy have demon- strated a tremendous potential

  17. Synchrotron infrared photoacoustic spectroscopy Kirk H. Michaeliana)

    E-print Network

    Johnson, Peter D.

    Synchrotron infrared photoacoustic spectroscopy Kirk H. Michaeliana) Natural Resources Canada-infrared source in the measurement of photoacoustic Fourier transform infrared spectra of solids is demonstrated Light Source, Brookhaven National Laboratory. For synchrotron photoacoustic spectroscopy to be feasible

  18. Human teeth model using photoacoustic frequency response

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  19. 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.

  20. 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

  1. Photoacoustic imaging platforms for multimodal imaging.

    PubMed

    Kim, Jeesu; Lee, Donghyun; Jung, Unsang; Kim, Chulhong

    2015-04-01

    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

  2. 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

  3. Photoacoustic microscopy of ceramic turbine blades

    NASA Technical Reports Server (NTRS)

    Khandelwal, P. K.; Kinnick, R. R.; Heitman, P. W.

    1985-01-01

    Scanning photoacoustic microscopy (SPAM) is evaluated as a nondestructive technique for the detection of both surface and subsurface flaws in polycrystalline ceramics, such as those currently under consideration for the high temperature components of small vehicular and industrial gas turbine engines; the fracture strength of these brittle materials is controlled by small, 25-200 micron flaws. Attention is given to the correlation of SPAM-detected flaws with actual, fracture-controlling flaws in ceramic turbine blades.

  4. Photoacoustic elastic oscillation and characterization

    E-print Network

    Gao, Fei; Zheng, Yuanjin

    2014-01-01

    Photoacoustic imaging and sensing have been studied extensively to probe the optical absorption of biological tissue in multiple scales ranging from large organs to small molecules. However, its elastic oscillation characterization is rarely studied and has been an untapped area to be explored. In literature, photoacoustic signal induced by pulsed laser is commonly modelled as a bipolar "N-shape" pulse from an optical absorber. In this paper, the photoacoustic damped oscillation is predicted and modelled by an equivalent mass-spring system by treating the optical absorber as an elastic oscillator. The photoacoustic simulation incorporating the proposed oscillation model shows better agreement with the measured signal from an elastic phantom, than conventional photoacoustic simulation model. More interestingly, the photoacoustic damping oscillation effect could potentially be a useful characterization approach to evaluate biological tissue's mechanical properties in terms of relaxation time, peak number and ra...

  5. Photoacoustic elastic oscillation and characterization.

    PubMed

    Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin

    2015-08-10

    Photoacoustic imaging and sensing have been studied extensively to probe the optical absorption of biological tissue in multiple scales ranging from large organs to small molecules. However, its elastic oscillation characterization is rarely studied and has been an untapped area to be explored. In literature, photoacoustic signal induced by pulsed laser is commonly modelled as a bipolar "N-shape" pulse from an optical absorber. In this paper, the photoacoustic damped oscillation is predicted and modelled by an equivalent mass-spring system by treating the optical absorber as an elastic oscillator. The photoacoustic simulation incorporating the proposed oscillation model shows better agreement with the measured signal from an elastic phantom, than conventional photoacoustic simulation model. More interestingly, the photoacoustic damping oscillation effect could potentially be a useful characterization approach to evaluate biological tissue's mechanical properties in terms of relaxation time, peak number and ratio beyond optical absorption only, which is experimentally demonstrated in this paper. PMID:26367914

  6. Array-based photoacoustic spectroscopy

    DOEpatents

    Autrey, S. Thomas; Posakony, Gerald J.; Chen, Yu

    2005-03-22

    Methods and apparatus for simultaneous or sequential, rapid analysis of multiple samples by photoacoustic spectroscopy are disclosed. A photoacoustic spectroscopy sample array including a body having at least three recesses or affinity masses connected thereto is used in conjunction with a photoacoustic spectroscopy system. At least one acoustic detector is positioned near the recesses or affinity masses for detection of acoustic waves emitted from species of interest within the recesses or affinity masses.

  7. Photoacoustic microscopy of coal macerals

    SciTech Connect

    Ahmed, T.; Biswas, A.; Telschow, K.L.; Johnson, K.W.; Crelling, J.C.; Meyer, J.

    1983-09-01

    The application of photoacoustic microscopy to characterizing coal macerals will be presented. Photoacoustic microscopy can be used as an analytical tool that is responsive to the thermal-elastic properties of individual macerals. It is known that the photoacoustic signal is a function of the absorbing maceral's density, specific heat, and coefficient of linear expansion. The unique ability to probe the thermal-elastic properties of macerals is a principal advantage of photoacoustic microscopy when applied to the study of coal macerals. A standard reflectance microscope is modified to measure both the reflectance and photoacoustic data from the same macerals. Since reflectance depends on the optical parameters of the maceral, and the photoacoustic signal depends on the thermal-elastic properties of the maceral, the two measurements are complementary. Macerals which differ in density, specific heat, or linear expansion exhibit different photoacoustic responses, even though they may display the same optical properties. In this respect, photoacoustic microscopy offers a potentially valuable way of differentiating between macerals which have identical optical properties but different thermal-elastic properties. Data will be presented showing both the photoacoustic and reflectance measurments from different vitrinite macerals of the same sample, as well as from samples of different rank.

  8. Photoacoustic endoscopy probe using a coherent fibre optic bundle

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Zhang, E.; Mathews, S.; Desjardins, A. E.; Beard, P. C.

    2015-07-01

    There is considerable interest in the development of photoacoustic endoscopy probes (PAE) for applications in foetal medicine, interventional surgery and gastroenterology. However, most previous PAE probes employ a combination of mechanical scanning and piezoelectric transducers at the distal end which can be technically complex and pose challenges in achieving the required level of miniaturisation and acoustic performance. To overcome these limitations, we present two novel all-optical forward-viewing endoscopic probes that use coherent fibre bundles to address a Fabry-Perot polymer film ultrasound sensor.

  9. Catheter-based photoacoustic endoscope

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

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

  12. 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.

  13. Photoacoustic thermal characterization of lime-partially stabilized zirconia

    SciTech Connect

    Contreras, M.E.; Serrato, J.; Zarate, J.; Pacheco, C.; Villasenor, L.

    1997-01-01

    Photoacoustic and photothermal techniques are used to investigate the room-temperature thermophysical properties of 9.4 mol% lime-partially stabilized zirconia (C-PSZ) samples in the density range of 5.12 {times} 10{sup 3}--5.58 {times} 10{sup 3}kg/m{sup 3}. The open-photoacoustic-cell approach is used to measure thermal diffusivity, and the photothermal technique of continuous illumination of the sample in vacuum is used to measure the product of density and specific heat capacity. Thermal conductivity is shown to be the thermophysical parameter most sensitive to changes in porosity.

  14. Towards nonionizing photoacoustic cystography

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  15. 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

  16. Nondestructive evaluation of structural ceramics by photoacoustic microscopy. Final report

    SciTech Connect

    Khandelwal, P.K.

    1987-06-01

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

  17. Nondestructive evaluation of structural ceramics by photoacoustic microscopy

    NASA Technical Reports Server (NTRS)

    Khandelwal, Pramod K.

    1987-01-01

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

  18. Photoacoustic Fourier Transform Infrared (FTIR) Spectroscopy Of Solids

    NASA Astrophysics Data System (ADS)

    Vidrine, D. Warren

    1981-10-01

    After discovering the photoacoustic effect, Alexander Graham Bell predicted its use in spectrometers, and that it would find its greatest utility "in the ultra-red." More than ninety years were required to fulfil his first prediction, and the second is still a prophecy. There is no record whether he ever imagined that an invention being developed that same winter by a young protege of his named Albert Michelson would ever be combined with his photoacoustic effect. A century later, the combination was made by Farrow Burnham, and Eyring, using a visible-range interferometer spectrometer of their own design. Soon afterwards, Rockley and myself, working independently, applied the technique to infrared measurements of solid samples. Photoacoustic cells are now commercially available as FT-IR accessories, and the technique is in use in the field.

  19. Multimodal non-contact photoacoustic and OCT imaging with galvanometer scanning

    NASA Astrophysics Data System (ADS)

    Berer, Thomas; Hochreiner, Armin; Leiss-Holzinger, Elisabeth; Bauer-Marschallinger, Johannes; Buchsbaum, Andreas

    2015-03-01

    In this paper we present multimodal non-contact photoacoustic and optical coherence tomography (OCT) imaging using a galvanometer scanner. Photoacoustic signals are acquired without contact on the surface of a specimen using an interferometric technique. The interferometer is realized in a fiber-optic network using a fiber laser at 1550 nm as source. In the same fiber-optic network a spectral-domain OCT system is realized, using a broadband light source at 1300 nm. Light from the fiber laser and the OCT source are multiplexed into the same fiber and the same objective is used for both imaging modalities. Fast non-contact photoacoustic and OCT imaging is demonstrated by scanning the detection spot utilizing a galvanometer scanner. Multimodal photoacoustic and OCT imaging is shown on agarose phantoms. As the same fiber network and optical components are used for non-contact photoacoustic and OCT imaging the obtained images are co-registered intrinsically.

  20. Photoacoustic imaging: a potential new platform for assessment of bone health

    NASA Astrophysics Data System (ADS)

    Feng, Ting; Kozloff, Kenneth M.; Hsiao, Yi-Sing; Xu, Guan; Du, Sidan; Yuan, Jie; Deng, Cheri X.; Wang, Xueding

    2015-02-01

    The ultimate goal of this work is to develop a novel photoacoustic (QPA) platform for highly-sensitive and quantitative assessment of bone health. First, the feasibility to perform 3D photoacoustic imaging (PAI) of bone was investigated. Then another two techniques, including thermal photoacoustic measurement (TPAM) and photoacoustic spectral analysis (PASA), both being able to achieve quantitative results were investigated for bone characterization. TPAM, by evaluating the dependence of photoacoustic signal amplitude on the sample temperature, is sensitive to the chemical constituents in tissue and holds promise for assessment of bone mineral density (BMD). PASA characterizes micron size physical features in tissue, and has shown feasibility for objective assessment of bone microarchitecture (BMA). This integrated QPA platform can assess both bone mass and microstructure simultaneously without involving invasive biopsy or ionizing radiation. Since QPA is non-ionizing, non-invasive, and has sufficient penetration in both soft tissue and bone, it has unique advantages for clinical translation.

  1. 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.

  2. Virus-based piezoelectric energy generation.

    PubMed

    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. PMID:22581406

  3. Experiments of glucose solution measurement based on the tunable pulsed laser induced photoacoustic spectroscopy method

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Liu, Guodong; Xiong, Zhihua; Huang, Zhen

    2015-07-01

    Photoacoustic spectroscopy (PAS) is a hybrid, well-established and promising detection technique that has widely applied into a lot of fields such as bio-medical, material and environment monitoring etc. PAS has high contrast and resolution because of combining the advantages of the pure-optical and the pure-acoustic. In this paper, a photoacoustic experiment of glucose solution induced by 532nm pumped Nd:YAG tunable pulsed laser with repetition rate of 20Hz and pulse width of 10ns is performed. The time-resolved photoacoustic signals of glucose solution induced by pulsed laser in the average time of 512 are obtained. And the photoacoustic experiments of different concentrations of glucose solutions and different wavelengths of pulsed laser are carried out in this paper. Experimental results demonstrate that the bipolar sine-wave profiles for the time-resolved photoacoustic signal of glucose solution are in good agreement with the past reported literatures. And the different absorbing coefficients of glucose solution can be gotten according to the slope of the first part of the time-resolved photoacoustic signals. In addition, the different acoustic velocities of glucose solution can also be gotten according to the shift change of the time-resolved photoacoustic peak values. Research results illustrate that the characteristic wavelengths, different optical and acoustic properties of glucose solution can be interpreted by the time-resolved and peak-to-peak photoacoustic signals induced by the pulsed laser.

  4. 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.

  5. Photoacoustic and Colorimetric Visualization of Latent Fingerprints.

    PubMed

    Song, Kai; Huang, Peng; Yi, Chenglin; Ning, Bo; Hu, Song; Nie, Liming; Chen, Xiaoyuan; Nie, Zhihong

    2015-12-22

    There is a high demand on a simple, rapid, accurate, user-friendly, cost-effective, and nondestructive universal method for latent fingerprint (LFP) detection. Herein, we describe a combination imaging strategy for LFP visualization with high resolution using poly(styrene-alt-maleic anhydride)-b-polystyrene (PSMA-b-PS) functionalized gold nanoparticles (GNPs). This general approach integrates the merits of both colorimetric imaging and photoacoustic imaging. In comparison with the previous methods, our strategy is single-step and does not require the signal amplification by silver staining. The PSMA-b-PS functionalized GNPs have good stability, tunable color, and high affinity for universal secretions (proteins/polypeptides/amino acids), which makes our approach general and flexible for visualizing LFPs on different substrates (presumably with different colors) and from different people. Moreover, the unique optical property of GNPs enables the photoacoustic imaging of GNPs-deposited LFPs with high resolution. This allows observation of level 3 hyperfine features of LFPs such as the pores and ridge contours by photoacoustic imaging. This technique can potentially be used to identify chemicals within LFP residues. We believe that this dual-modality imaging of LFPs will find widespread use in forensic investigations and medical diagnostics. PMID:26528550

  6. 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

  7. 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 ...

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

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

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

  9. 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.

  10. Structural Origins of Silk Piezoelectricity

    PubMed Central

    Yucel, Tuna; Cebe, Peggy

    2012-01-01

    Uniaxially oriented, piezoelectric silk films were prepared by a two-step method that involved: (1) air drying aqueous, regenerated silk fibroin solutions into films, and (2) drawing the silk films to a desired draw ratio. The utility of two different drawing techniques, zone drawing and water immersion drawing were investigated for processing the silk for piezoelectric studies. Silk films zone drawn to a ratio of ?= 2.7 displayed relatively high dynamic shear piezoelectric coefficients of d14 = ?1.5 pC/N, corresponding to over two orders of magnitude increase in d14 due to film drawing. A strong correlation was observed between the increase in the silk II, ?-sheet content with increasing draw ratio measured by FTIR spectroscopy (C?? e2.5 ?), the concomitant increasing degree of orientation of ?-sheet crystals detected via WAXD (FWHM = 0.22° for ?= 2.7), and the improvement in silk piezoelectricity (d14? e2.4 ?). Water immersion drawing led to a predominantly silk I structure with a low degree of orientation (FWHM = 75°) and a much weaker piezoelectric response compared to zone drawing. Similarly, increasing the ?-sheet crystallinity without inducing crystal alignment, e.g. by methanol treatment, did not result in a significant enhancement of silk piezoelectricity. Overall, a combination of a high degree of silk II, ?-sheet crystallinity and crystalline orientation are prerequisites for a strong piezoelectric effect in silk. Further understanding of the structural origins of silk piezoelectricity will provide important options for future biotechnological and biomedical applications of this protein. PMID:23335872

  11. Label-free optical-resolution photoacoustic endomicroscopy in vivo

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    Intravital microscopy techniques have become increasingly important in biomedical research because they can provide unique microscopic views of various biological or disease developmental processes in situ. Here we present an optical-resolution photoacoustic endomicroscopy (OR-PAEM) system that visualizes internal organs with a much finer resolution than conventional acoustic-resolution photoacoustic endoscopy systems. By combining gradient index (GRIN) lens-based optical focusing and ultrasonic ring transducer-based acoustic focusing, we achieved a transverse resolution as fine as ~10 ?m at an optical working distance of 6.5 mm. The OR-PAEM system's high-resolution intravital imaging capability is demonstrated through animal experiments.

  12. Sensitivity enhanced nanothermal sensors for photoacoustic temperature mapping.

    PubMed

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

    2013-06-01

    Photoacoustic imaging can be used to guide and validate the therapeutic outcome of nanoparticle-mediated photothermal therapy through its ability to visualize the delivery of nanoparticle contrast agents, image the temperature distribution inside living tissue, and confirm tissue coagulation. In this image-guided process, temperature mapping plays a critical role for thermal dosage control. Therefore, developing a sensitive and accurate photoacoustic technique to quantitatively measure the temperature distribution during thermal therapy is essential. In this study, we investigated and demonstrated that silica-coated gold nanorods, can provide a multi-fold improvement in sensitivity of the photoacoustic temperature mapping compared to gold nanorods without silica coating, and serve as a nanothermal sensor to accurately and quantitatively visualize temperature distributions during photothermal therapy. PMID:23450812

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

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

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

  14. 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.

  15. Characterization and matched-field processing localization of photoacoustic signals

    NASA Astrophysics Data System (ADS)

    Yonak, Serdar Hakki

    2000-09-01

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

  16. 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

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

    SciTech Connect

    Isak, S.J.

    1992-06-01

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

  18. Piezoelectric diaphragm for vibration energy harvesting.

    PubMed

    Minazara, E; Vasic, D; Costa, F; Poulin, G

    2006-12-22

    This paper presents a technique of electric energy generation using a mechanically excited unimorph piezoelectric membrane transducer. The electrical characteristics of the piezoelectric power generator are investigated under dynamic conditions. The electromechanical model of the generator is presented and used to predict its electrical performances. The experiments was performed with a piezoelectric actuator (shaker) moving a macroscopic 25 mm diameter piezoelectric membrane. A power of 0.65 mW was generated at the resonance frequency (1.71 kHz) across a 5.6 kOmega optimal resistor and for a 80 N force. A special electronic circuit has been conceived in order to increase the power harvested by the piezoelectric transducer. This electrical converter applies the SSHI (synchronized switch harvesting on inductor) technique, and leads to remarkable results: under the same actuation conditions the generated power reaches 1.7 mW, which is sufficient to supply a large range of low consumption sensors. PMID:16814837

  19. Nonlinear photoacoustic spectroscopy of hemoglobin

    SciTech Connect

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

    2015-05-18

    As light intensity increases in photoacoustic imaging, the saturation of optical absorption and the temperature dependence of the thermal expansion coefficient result in a measurable nonlinear dependence of the photoacoustic (PA) signal on the excitation pulse fluence. Here, under controlled conditions, we investigate the intensity-dependent photoacoustic signals from oxygenated and deoxygenated hemoglobin at varied optical wavelengths and molecular concentrations. The wavelength and concentration dependencies of the nonlinear PA spectrum are found to be significantly greater in oxygenated hemoglobin than in deoxygenated hemoglobin. These effects are further influenced by the hemoglobin concentration. These nonlinear phenomena provide insights into applications of photoacoustics, such as measurements of average inter-molecular distances on a nm scale or with a tuned selection of wavelengths, a more accurate quantitative PA tomography.

  20. Nonlinear photoacoustic spectroscopy of hemoglobin

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    As light intensity increases in photoacoustic imaging, the saturation of optical absorption and the temperature dependence of the thermal expansion coefficient result in a measurable nonlinear dependence of the photoacoustic (PA) signal on the excitation pulse fluence. Here, under controlled conditions, we investigate the intensity-dependent photoacoustic signals from oxygenated and deoxygenated hemoglobin at varied optical wavelengths and molecular concentrations. The wavelength and concentration dependencies of the nonlinear PA spectrum are found to be significantly greater in oxygenated hemoglobin than in deoxygenated hemoglobin. These effects are further influenced by the hemoglobin concentration. These nonlinear phenomena provide insights into applications of photoacoustics, such as measurements of average inter-molecular distances on a nm scale or with a tuned selection of wavelengths, a more accurate quantitative PA tomography.

  1. Thermal Images of Seeds Obtained at Different Depths by Photoacoustic Microscopy (PAM)

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    The objective of the present study was to obtain thermal images of a broccoli seed ( Brassica oleracea) by photoacoustic microscopy, at different modulation frequencies of the incident light beam ((0.5, 1, 5, and 20) Hz). The thermal images obtained in the amplitude of the photoacoustic signal vary with each applied frequency. In the lowest light frequency modulation, there is greater thermal wave penetration in the sample. Likewise, the photoacoustic signal is modified according to the structural characteristics of the sample and the modulation frequency of the incident light. Different structural components could be seen by photothermal techniques, as shown in the present study.

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

    PubMed Central

    Kang, Dongyel; Huang, Qiaojian; Li, Youzhi

    2014-01-01

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

  3. Trace-Gas Detection with Off-Beam Quartz Enhanced Photoacoustic Spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Kun; Wang, Lei; Tan, Tu; Zhang, Weijun; Chen, Weidong; Gao, Xiaoming

    2015-06-01

    Trace-gas sensors have a wide range of potential applications such as environmental monitoring, climate research, agriculture, workplace safety, medical diagnostics, and industrial process control. A recently introduced technique called quartz-enhanced photoacoustic spectroscopy (QEPAS) is described. QEPAS use a quartz tuning fork as an acoustic transducer for a photoacoustic signal induced in an absorbing gas by modulated optical radiation. Advantages of the QEPAS compared to conventional photoacoustic spectroscopy include immunity to environmental acoustic noise and ultra-small sample volume. Trace gases of , and were monitored with a novel off-beam QEPAS approach and are described in detail.

  4. PHOTOACOUSTIC SPECTROSCOPY USING A SYNCHROTRON LIGHT SOURCE.

    SciTech Connect

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

    2001-02-05

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

  5. 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

  6. 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.

  7. Bone Assessment via Thermal Photoacoustic Measurements

    PubMed Central

    Feng, Ting; Kozloff, Kenneth M.; Tian, Chao; Perosky, Joseph E.; Hsiao, Yi-Sing; Du, Sidan

    2015-01-01

    The feasibility of an innovative biomedical diagnostic technique, thermal photoacoustic (TPA) measurement, for non-ionizing and non-invasive assessment of bone health is investigated. Unlike conventional photoacoustic PA methods which 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 which 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

  8. Bone assessment via thermal photoacoustic measurements

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    The feasibility of an innovative biomedical diagnostic technique, thermal photoacoustic (TPA) measurement, for nonionizing and non-invasive assessment of bone health is investigated. Unlike conventional photoacoustic PA methods which 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 which is closely relevant to the chemical and molecular properties in the sample. Based on the differentiation measurement, the results from TPA technique is 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 370 C to 440 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.

  9. 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.

  10. Quantitative Photoacoustic Tomography , Hongkai Zhao2

    E-print Network

    Ferguson, Thomas S.

    Quantitative Photoacoustic Tomography Hao Gao1 , Hongkai Zhao2 , and Stanley Osher3 1 Department on quantitative photoacoustic tomography to recover optical maps from the deposited optical energy. After a brief-called gradient-based bound-constrained split Bregman method (GBSB). 1 Introduction Photoacoustic tomography (PAT

  11. Coherent Interferometry Algorithms for Photoacoustic Habib Ammari

    E-print Network

    Garnier, Josselin

    Coherent Interferometry Algorithms for Photoacoustic Imaging Habib Ammari Elie Bretin Josselin around a known constant) on photoacoustic images. By back-projecting the correla- tions between the pre-processed pressure measurements, we show that we are able to provide statistically stable photo-acoustic images

  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. 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.

  14. 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.

  15. Intravascular Photoacoustic Imaging

    PubMed Central

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

    2011-01-01

    Intravascular photoacoustic (IVPA) imaging is a catheter-based, minimally invasive, imaging modality capable of providing high-resolution optical absorption map of the arterial wall. Integrated with intravascular ultrasound (IVUS) imaging, combined IVPA and IVUS imaging can be used to detect and characterize atherosclerotic plaques building up in the inner lining of an artery. In this paper, we present and discuss various representative applications of combined IVPA/IVUS imaging of atherosclerosis, including assessment of the composition of atherosclerotic plaques, imaging of macrophages within the plaques, and molecular imaging of biomarkers associated with formation and development of plaques. In addition, imaging of coronary artery stents using IVPA and IVUS imaging is demonstrated. Furthermore, the design of an integrated IVUS/IVPA imaging catheter needed for in vivo clinical applications is discussed. PMID:21359138

  16. Note: Direct piezoelectric effect microscopy.

    PubMed

    Mori, T J A; Stamenov, P; Dorneles, L S

    2015-07-01

    An alternative method for investigating piezoelectric surfaces is suggested, exploiting the direct piezoeffect. The technique relies on acoustic (ultrasonic) excitation of the imaged surface and mapping of the resulting oscillatory electric potential. The main advantages arise from the spatial resolution of the conductive scanning probe microscopy in combination with the relatively large magnitude of the forward piezo signal Upf, which can be of the order of tens of mV even for non-ferroelectric piezoelectric materials. The potency of this experimental strategy is illustrated with measurements on well-crystallized quartz surfaces, where Upf ? 50 mV, for a piezoelectric coefficient of d33 = - 2.27? × ?10(-12) m/V, and applied stress of about T3 ? 5.7 kPa. PMID:26233416

  17. Note: Direct piezoelectric effect microscopy

    NASA Astrophysics Data System (ADS)

    Mori, T. J. A.; Stamenov, P.; Dorneles, L. S.

    2015-07-01

    An alternative method for investigating piezoelectric surfaces is suggested, exploiting the direct piezoeffect. The technique relies on acoustic (ultrasonic) excitation of the imaged surface and mapping of the resulting oscillatory electric potential. The main advantages arise from the spatial resolution of the conductive scanning probe microscopy in combination with the relatively large magnitude of the forward piezo signal Upf, which can be of the order of tens of mV even for non-ferroelectric piezoelectric materials. The potency of this experimental strategy is illustrated with measurements on well-crystallized quartz surfaces, where Upf ˜ 50 mV, for a piezoelectric coefficient of d33 = - 2.27 × 10-12 m/V, and applied stress of about T3 ˜ 5.7 kPa.

  18. 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

  19. 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

  20. 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.

  1. Mapping lipid and collagen by multispectral photoacoustic imaging of chemical bond vibration

    NASA Astrophysics Data System (ADS)

    Wang, Pu; Wang, Ping; Wang, Han-Wei; Cheng, Ji-Xin

    2012-09-01

    Photoacoustic microscopy using vibrational overtone absorption as a contrast mechanism allows bond-selective imaging of deep tissues. Due to the spectral similarity of molecules in the region of overtone vibration, it is difficult to interrogate chemical components using photoacoustic signal at single excitation wavelength. Here we demonstrate that lipids and collagen, two critical markers for many kinds of diseases, can be distinguished by multispectral photoacoustic imaging of the first overtone of C-H bond. A phantom consisting of rat-tail tendon and fat was constructed to demonstrate this technique. Wavelengths between 1650 and 1850 nm were scanned to excite both the first overtone and combination bands of C-H bonds. B-scan multispectral photoacoustic images, in which each pixel contains a spectrum, were analyzed by a multivariate curve resolution-alternating least squares algorithm to recover the spatial distribution of collagen and lipids in the phantom.

  2. Photoacoustic investigation of the specific heat of high T sub c superconductors

    SciTech Connect

    Song, Y.S.; Chung, N.S. )

    1990-01-15

    Photoacoustic measurements for the polycrystalline samples of orthorhombic GdBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} and DyBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} have been carried out in the temperature region around the superconducting transition. The relative values of the specific heat for the superconducting samples are obtained from the photoacoustic signal by using the thermal conductivity data measured by the longitudinal heat flow method and show a good agreement with the specific heat data measured using a calorimetric method by others. The usefulness of the photoacoustic technique for the specific heat measurement is confirmed by the photoacoustic measurement of KDP(KH{sub 2}PO{sub 4}) sample near the phase transition.

  3. 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

  4. Piezoelectric wind generator

    SciTech Connect

    Schmidt, V. H.

    1985-08-20

    An electric power generator used a piezoelectric transducer mounted on a resilient blade which in turn is mounted on an independently flexible support member. Fluid flow against the blade causes bending stresses in the piezoelectric polymer which produces electric power.

  5. 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 ...

  6. Remote photoacoustic detection of liquid contamination of a surface

    NASA Astrophysics Data System (ADS)

    Perrett, Brian; Harris, Michael; Pearson, Guy N.; Willetts, David V.; Pitter, Mark C.

    2003-08-01

    A method for the remote detection and identification of liquid chemicals at ranges of tens of meters is presented. The technique uses pulsed indirect photoacoustic spectroscopy in the 10-?m wavelength region. Enhanced sensitivity is brought about by three main system developments: (1) increased laser-pulse energy (150 ?J/pulse), leading to increased strength of the generated photoacoustic signal; (2) increased microphone sensitivity and improved directionality by the use of a 60-cm-diameter parabolic dish; and (3) signal processing that allows improved discrimination of the signal from noise levels through prior knowledge of the pulse shape and pulse-repetition frequency. The practical aspects of applying the technique in a field environment are briefly examined, and possible applications of this technique are discussed.

  7. FULL ARTICLE Synergy of photoacoustic and fluorescence flow

    E-print Network

    Verkhusha, Vladislav V.

    FULL ARTICLE Synergy of photoacoustic and fluorescence flow cytometry of circulating cells, photoacoustics, fluorescence detection, negative contrast, circulating tumor cells, liposomes, nanoparticles In vivo photoacoustic (PA) and fluorescence flow cyto- metry were previously applied separately using

  8. Photoacoustic lifetime contrast between methylene blue monomers and self-

    E-print Network

    Thomas, David D.

    Photoacoustic lifetime contrast between methylene blue monomers and self- quenched dimers/03/2013 Terms of Use: http://spiedl.org/terms #12;Photoacoustic lifetime contrast between methylene blue Church Street SE, Minneapolis, Minnesota 55455 Abstract. Activatable photoacoustic probes efficiently

  9. 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%.

  10. Sub-ppm multi-gas photoacoustic sensor.

    PubMed

    Besson, Jean-Philippe; Schilt, Stéphane; Thévenaz, Luc

    2006-04-01

    A photoacoustic multi-gas sensor using tuneable laser diodes in the near-infrared region is reported. An optimized resonant configuration based on an acoustic longitudinal mode is described. Automatic tracking of the acoustic resonance frequency using a piezo-electric transducer and a servo electronics is demonstrated. Water vapour, methane and hydrogen chloride have been measured at sub-ppm level in different buffer gas mixtures. The importance of the system calibration in presence of several diluting gases is discussed. Finally, trace gas measurements have been assessed and detection limits (signal-to-noise ratio=3) of 80 ppb at 1651.0 nm for CH(4), 24 ppb at 1368.6 nm for H(2)O and 30 ppb at 1737.9 for HCl have been demonstrated. PMID:16495131

  11. 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.

  12. 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.

  13. "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.

  14. Photoacoustic microscopy of coal macerals

    SciTech Connect

    Johnson, K.W.; Telschow, K.L.; Biswas, A.; Ahmed, T.; Crelling, J.C.

    1984-03-01

    The reactivity of a coal of a given rank under the thermal processing conditions of pyrolysis or gasification can vary greatly depending on the relative abundance of the coal's chemically different organic components - the macerals. The chemical composition of a maceral is the dominant factor responsible for its thermochemical behavior. Since distinctly different photoacoustic responses are obtained from different coal macerals, considerable potential may exist to use these differences as aids in understanding and predicting the thermochemical behavior of coal. This paper reviews the results and theory behind photoacoustic microscopy performed by the Southern Illinois University at Carbondale.

  15. COMPAS: Compositional mineralogy with a photoacoustic spectrometer

    NASA Technical Reports Server (NTRS)

    Smith, W. Hayden

    1992-01-01

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

  16. 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.

  17. A constrained variable projection reconstruction method for photoacoustic computed tomography without accurate knowledge of transducer responses

    E-print Network

    Sheng, Qiwei; Matthews, Thomas P; Xia, Jun; Zhu, Liren; Wang, Lihong V; Anastasio, Mark A

    2015-01-01

    Photoacoustic computed tomography (PACT) is an emerging computed imaging modality that exploits optical contrast and ultrasonic detection principles to form images of the absorbed optical energy density within tissue. When the imaging system employs conventional piezoelectric ultrasonic transducers, the ideal photoacoustic (PA) signals are degraded by the transducers' acousto-electric impulse responses (EIRs) during the measurement process. If unaccounted for, this can degrade the accuracy of the reconstructed image. In principle, the effect of the EIRs on the measured PA signals can be ameliorated via deconvolution; images can be reconstructed subsequently by application of a reconstruction method that assumes an idealized EIR. Alternatively, the effect of the EIR can be incorporated into an imaging model and implicitly compensated for during reconstruction. In either case, the efficacy of the correction can be limited by errors in the assumed EIRs. In this work, a joint optimization approach to PACT image r...

  18. 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

  19. Photoacoustic spectroscopy sample array vessels and photoacoustic spectroscopy methods for using the same

    DOEpatents

    Amonette, James E.; Autrey, S. Thomas; Foster-Mills, Nancy S.

    2006-02-14

    Methods and apparatus for simultaneous or sequential, rapid analysis of multiple samples by photoacoustic spectroscopy are disclosed. Particularly, a photoacoustic spectroscopy sample array vessel including a vessel body having multiple sample cells connected thereto is disclosed. At least one acoustic detector is acoustically positioned near the sample cells. Methods for analyzing the multiple samples in the sample array vessels using photoacoustic spectroscopy are provided.

  20. Photoacoustic spectroscopy sample array vessel and photoacoustic spectroscopy method for using the same

    DOEpatents

    Amonette, James E.; Autrey, S. Thomas; Foster-Mills, Nancy S.; Green, David

    2005-03-29

    Methods and apparatus for analysis of multiple samples by photoacoustic spectroscopy are disclosed. Particularly, a photoacoustic spectroscopy sample array vessel including a vessel body having multiple sample cells connected thereto is disclosed. At least one acoustic detector is acoustically coupled with the vessel body. Methods for analyzing the multiple samples in the sample array vessels using photoacoustic spectroscopy are provided.

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

    E-print Network

    Victor Palamodov

    2014-05-24

    A class of photoacoustic acquisition geometries in n-space 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 basing on the same geometrical technique.

  2. 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

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

    NASA Astrophysics Data System (ADS)

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

    1999-04-01

    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: distilled water, ethanol, methanol, chloroform, glycerol, and car oil. The comparison with literature values shows a remarkable agreement. Also, we show measurements of the thermal effusivity of acetone in distilled water mixtures, showing the graphical dependence of this thermal property with the concentration of one of the components.

  4. 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.

  5. 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.

  6. 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

  7. Micromachined Piezoelectric Microspeaker

    NASA Astrophysics Data System (ADS)

    Yi, Seung Hwan; Kim, Eun Sok

    2005-06-01

    A diaphragm-based piezoelectric microspeaker is fabricated on a heavily compressive silicon-nitride film, and is compared to commercial speakers. The largest sound pressure level (SPL) produced by the fabricated microspeaker is 92 dB (when measured 2 mm away from the microspeaker in open field) at around 3 kHz for 6 Vpeak-to-peak input. The microspeaker produces a comparable sound output as a commercial piezo-ceramic and electro-dynamic speaker used in current cellular phones. The keys to this success are as follows: (1) the usage of a diaphragm that has a very high compressive residual stress, high enough to cause the diaphragm to be wrinkled and (2) the usage of high quality ZnO film deposited by two-step deposition technique.

  8. Intracavity quartz-enhanced photoacoustic sensor

    SciTech Connect

    Borri, S. Galli, I.; Mazzotti, D.; Giusfredi, G.; De Natale, P.; Patimisco, P.; Scamarcio, G.; Spagnolo, V.; Akikusa, N.; Yamanishi, M.

    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}.

  9. 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.

  10. Photoacoustic imaging in both soft and hard biological tissue

    NASA Astrophysics Data System (ADS)

    Li, T.; Dewhurst, R. J.

    2010-03-01

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

  11. 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

  12. Super-resolution photoacoustic imaging through a scattering wall

    NASA Astrophysics Data System (ADS)

    Conkey, Donald B.; Caravaca-Aguirre, Antonio M.; Dove, Jake D.; Ju, Hengyi; Murray, Todd W.; Piestun, Rafael

    2015-08-01

    The use of wavefront shaping to compensate for scattering has brought a renewed interest as a potential solution to imaging through scattering walls. A key to the practicality of any imaging through scattering technique is the capability to focus light without direct access behind the scattering wall. Here we address this problem using photoacoustic feedback for wavefront optimization. By combining the spatially non-uniform sensitivity of the ultrasound transducer to the generated photoacoustic waves with an evolutionary competition among optical modes, the speckle field develops a single, high intensity focus significantly smaller than the acoustic focus used for feedback. Notably, this method is not limited by the size of the absorber to form a sub-acoustic optical focus. We demonstrate imaging behind a scattering medium using two different imaging modalities with up to ten times improvement in signal-to-noise ratio and five to six times sub-acoustic resolution.

  13. Electrospinning of continuous piezoelectric yarns for composite application

    NASA Astrophysics Data System (ADS)

    Lagoudas, Natasha C.; Ounaies, Zoubeida

    2008-03-01

    The focus of this research is to electrospin continuous yarns of piezoelectric nanofibers. Incorporating piezoelectric polymer fibers in traditional composites can add sensing and actuation capabilities, which creates a wide array of potential applications. To process nanofibers with piezoelectric properties, we are pursuing the electrospinning of poly (vinylidene fluoride) (PVDF) in DMAc. A method of electrospinning on water is used to form the continuous fibers, which are then tested using DSC, XRD, and microscopy. Through this technique, we see evidence that the non-polar ?-phase of PVDF is converted to the polar ?-phase, which is responsible for its piezoelectric behavior.

  14. Bregman methods in quantitative photoacoustic tomography , Hongkai Zhao2

    E-print Network

    Ferguson, Thomas S.

    Bregman methods in quantitative photoacoustic tomography Hao Gao1 , Hongkai Zhao2 and Stanley Osher Jacobian-based and gradient-based methods in quantitative photoacoustic tomography with multiple optical after numerous scattering events. 1.1. Quantitative photoacoustic tomography Photoacoustic tomography

  15. Development of a combined intravascular ultrasound and photoacoustic imaging system

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

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

  16. Error estimates for universal back-projection-based photoacoustic tomography

    NASA Astrophysics Data System (ADS)

    Pandey, Prabodh K.; Naik, Naren; Munshi, Prabhat; Pradhan, Asima

    2015-07-01

    Photo-acoustic tomography is a hybrid imaging modality that combines the advantages of optical as well as ultrasound imaging techniques to produce images with high resolution and good contrast at high penetration depths. Choice of reconstruction algorithm as well as experimental and computational parameters plays a major role in governing the accuracy of a tomographic technique. Therefore error estimates with the variation of these parameters have extreme importance. Due to the finite support, that photo-acoustic source has, the pressure signals are not band-limited, but in practice, our detection system is. Hence the reconstructed image from ideal, noiseless band-limited forward data (for future references we will call this band-limited reconstruction) is the best approximation that we have for the unknown object. In the present study, we report the error that arises in the universal back-projection (UBP) based photo-acoustic reconstruction for planer detection geometry due to sampling and filtering of forward data (pressure signals).Computational validation of the error estimates have been carried out for synthetic phantoms. Validation with noisy forward data has also been carried out, to study the effect of noise on the error estimates derived in our work. Although here we have derived the estimates for planar detection geometry, the derivations for spherical and cylindrical geometries follow accordingly.

  17. Development and characterization of non-resonant multiphoton photoacoustic spectroscopy (NMPPAS) for brain tumor margining

    NASA Astrophysics Data System (ADS)

    Dahal, Sudhir

    During tumor removal surgery, due to the problems associated with obtaining high-resolution, real-time chemical images of where exactly the tumor ends and healthy tissue begins (tumor margining), it is often necessary to remove a much larger volume of tissue than the tumor itself. In the case of brain tumor surgery, however, it is extremely unsafe to remove excess tissue. Therefore, without an accurate image of the tumor margins, some of the tumor's finger-like projections are inevitably left behind in the surrounding parenchyma to grow again. For this reason, the development of techniques capable of providing high-resolution real-time images of tumor margins up to centimeters below the surface of a tissue is ideal for the diagnosis and treatment of tumors, as well as surgical guidance during brain tumor excision. A novel spectroscopic technique, non-resonant multiphoton photoacoustic spectroscopy (NMPPAS), is being developed with the capabilities of obtaining high-resolution subsurface chemical-based images of underlying tumors. This novel technique combines the strengths of multiphoton tissue spectroscopy and photoacoustic spectroscopy into a diagnostic methodology that will, ultimately, provide unparalleled chemical information and images to provide the state of sub-surface tissues. The NMPPAS technique employs near-infrared light (in the diagnostic window) to excite ultraviolet and/or visible light absorbing species deep below the tissue's surface. Once a multiphoton absorption event occurs, non-radiative relaxation processes generates a localized thermal expansion and subsequent acoustic wave that can be detected using a piezoelectric transducer. Since NMPPAS employs an acoustic detection modality, much deeper diagnoses can be performed than that is possible using current state of the art high-resolution chemical imaging techniques such as multiphoton fluorescence spectroscopy. NMPPAS was employed to differentiate between excised brain tumors (astrocytoma III) and healthy tissue with over 99% accuracy. NMPPAS spectral features showed evident differences between tumor and healthy tissues, and ratiometric analysis ensured that only a few wavelengths could be used for excitation instead of using numerous wavelength excitations to create spectra. This process would significantly reduce the analysis time while maintaining the same degree of accuracy. Tissue phantoms were fabricated in order to characterize the properties of NMPPAS. Scattering particles were doped into the phantoms to simulate their light scattering properties to real tissues. This allowed for better control over shape, size, reproducibility and doping in the sample while maintaining the light-tissue interaction properties of real tissue. To make NMPPAS viable for clinical applications, the technique was characterized to determine the spatial (lateral and longitudinal) resolution, depth of penetration and its ability to image in three-dimension through layers of tissue. Both resolutions were determined to be near-cellular level resolution (50-70 microm), obtained initially with the aid of the technique of multiphoton fluorescence, and later verified using NMPPAS imaging. Additionally, the maximum depth of penetration and detection was determined to be about 1.4cm, making the technique extremely suitable to margin tumors from underlying tissues in the brain. The capability of NMPPAS to detect and image layers that lie beneath other structures and blood vessels was also investigated. Three-dimensional images were obtained for the first time using NMPPAS. The images were obtained from different depths and structures were imaged through other layers of existing structures in the sample. This verified that NMPPAS was capable of detecting and imaging structures that lie embedded within the tissues. NMPPAS images of embedded structures were also obtained with the presence of hemoglobin, which is potentially the largest source of background in blood-perfused tissues, thus showing that the technique is capable of detecting and differentiating in blood-perfused sam

  18. Quantum tunneling photoacoustic spectroscopy for the characterization of thin films

    NASA Astrophysics Data System (ADS)

    Goldschmidt, Benjamin S.; Rudy, Anna M.; Mandal, Swarnasri; Nowak, Charissa A.; Viator, John A.; Hunt, Heather K.

    2015-03-01

    Thin films continue to show great promise for improving a wide variety of devices in applications such as medical instrumentation, material processing, and astronomical instrumentation. While ellipsometry and reflectometry are standard characterization techniques for determining thickness and refractive index, these techniques tend to require highly reflective or polished films and rely on empirical equations. We have created Quantum Tunneling Photoacoustic Spectroscopy (QTPAS) that uses light induced ultrasound to obtain thickness and refractive index estimates of transparent films. We present QTPAS to be used for the estimation of properties of single layer films as an alternative to ellipsometry and give qualitative sample measurements of the technique's estimated parameters.

  19. Thermally nonlinear laser photoacoustic tomography

    SciTech Connect

    Oshurko, Vadim B

    2005-02-28

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

  20. 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

  1. Modelling, verification, and calibration of a photoacoustics based continuous non-invasive blood glucose monitoring system

    NASA Astrophysics Data System (ADS)

    Pai, Praful P.; Sanki, Pradyut K.; Sarangi, Satyabrata; Banerjee, Swapna

    2015-06-01

    This paper examines the use of photoacoustic spectroscopy (PAS) at an excitation wavelength of 905 nm for making continuous non-invasive blood glucose measurements. The theoretical background of the measurement technique is verified through simulation. An apparatus is fabricated for performing photoacoustic measurements in vitro on glucose solutions and in vivo on human subjects. The amplitude of the photoacoustic signals measured from glucose solutions is observed to increase with the solution concentration, while photoacoustic amplitude obtained from in vivo measurements follows the blood glucose concentration of the subjects, indicating a direct proportionality between the two quantities. A linear calibration method is applied separately on measurements obtained from each individual in order to estimate the blood glucose concentration. The estimated glucose values are compared to reference glucose concentrations measured using a standard glucose meter. A plot of 196 measurement pairs taken over 30 normal subjects on a Clarke error grid gives a point distribution of 82.65% and 17.35% over zones A and B of the grid with a mean absolute relative deviation (MARD) of 11.78% and a mean absolute difference (MAD) of 15.27 mg/dl (0.85 mmol/l). The results obtained are better than or comparable to those obtained using photoacoustic spectroscopy based methods or other non-invasive measurement techniques available. The accuracy levels obtained are also comparable to commercially available continuous glucose monitoring systems.

  2. Photoacoustic spectroscopy at electrode-solution interface

    SciTech Connect

    Vallet, C.E.; Brown, G.M.

    1984-01-01

    Photoacoustic spectroscopy, coupled with electrochemical measurements, can be used to monitor film formation and breakdown during corrosion passivation. A two-beam photoacoustic-electrochemical spectrometer was built. The spectrometer was tested using holmium oxide and titanium oxide, and then it was used to study the passivation of titanium in sulfuric acid solutions. 8 figures.

  3. Virtual intraoperative surgical photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Lee, Changho; Lee, Donghyun; Zhou, Qifa; Kim, Jeehyun; Kim, Chulhong

    2015-07-01

    A virtual intraoperative surgical photoacoustic microscopy at 1064 nm wavelength (VISPAM) system was designed and fabricated by integrating a commercial type surgical microscope and laser scanning photoacoustic microscopy (PAM) with a 1064 nm pulsed laser. Based on simple augmented reality device, VISPAM could simultaneously provide 2D depth-resolved photoacoustic and magnified microscope images of surgery regions on the same vision of surgeon via an eyepiece of the microscope. The invisible 1064 nm laser removed the interruption of surgical sight due to visible laser scanning of previous report, and decreased the danger of tissue damage caused by over irradiated laser. In addition, to approach the real practical surgery application, a needle-type transducer was utilized without a water bath for PA signal coupling. In order to verify our system's performance, we conducted needle guiding as ex vivo phantom study and needle guiding and injection of carbon particles mixtures into a melanoma tumor region as in vivo study. We expect that VISPAM can be essential tool of brain and ophthalmic microsurgery.

  4. Ultrahigh Sensitivity Carbon Nanotube Agents for Photoacoustic Molecular Imaging in Living

    E-print Network

    Khuri-Yakub, Butrus T. "Pierre"

    Ultrahigh Sensitivity Carbon Nanotube Agents for Photoacoustic Molecular Imaging in Living Mice), National Institutes of Health (NIH), Bethesda, Maryland 20892, USA ABSTRACT Photoacoustic imaging photoacoustic contrast, it is essential to develop exogenous photoacoustic contrast agents that can target

  5. 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. PMID:25893169

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

    PubMed

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

    2015-03-01

    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. PMID:25893169

  7. 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.

  8. 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.

  9. In vitro and ex vivo evaluation of silica-coated super paramagnetic iron oxide nanoparticles (SPION) as biomedical photoacoustic contrast agent

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    The employment of contrast agents in photoacoustic imaging has gained significant attention within the past few years for their biomedical applications. In this study, the use of silica-coated superparamagnetic iron oxide (Fe3O4) nanoparticles (SPION) was investigated as a contrast agent in biomedical photoacoustic imaging. SPIONs have been widely used as Food-and-Drug-Administration (FDA)-approved contrast agents for magnetic resonance imaging (MRI) and are known to have an excellent safety profile. Using our frequency-domain photoacoustic correlation technique ("the photoacoustic radar") with modulated laser excitation, we examined the effects of nanoparticle size, concentration and biological medium (e.g. serum, sheep blood) on its photoacoustic response in turbid media (intralipid solution). Maximum detection depth and minimum measurable SPION concentration were determined experimentally. The detection was performed using a single element transducer. The nanoparticle-induced optical contrast ex vivo in dense muscular tissues (avian pectus) was evaluated using a phased array photoacoustic probe and the strong potential of silicacoated SPION as a possible photoacoustic contrast agent was demonstrated. This study opens the way for future clinical applications of nanoparticle-enhanced photoacoustic imaging in cancer therapy.

  10. Novel applications of photoacoustic spectroscopy in life sciences

    NASA Astrophysics Data System (ADS)

    Stolik, S.

    2004-10-01

    The Photoacoustic Spectroscopy, based on the generation of acoustic waves following the absorption of the modulated light by an enclosed material, was discovered in 1880 by Alexander Graham Bell. There are a lot of remarkable achievements in this topic since those days. It has been intended to present a relatively new tool to the researchers in biological areas and, simultaneously, to propose new fields of investigation to those who have been attracted by physics. The application of Photoacoustic trace gas detection to the determination of ethylene content in mice exhalation is described as a biomarker of free radicals production. It has been demonstrated the feasibility of studying the lipid peroxidation in vivo by this technique. Specifically, the results of ?-aminolevulinic acid administration in mice are presented. This drug has been used to induce Protoporphyrin IX production and ultimately to apply the Photodynamic Therapy, a recent method in cancer treatment. A kinetic study of Protoporphyrin IX production in mice skin and blood after ?-aminolevulinic acid administration in different doses is also shown. This study was performed using Photoacoustic Spectroscopy in solids.

  11. Dual Modality Noncontact Photoacoustic and Spectral Domain OCT Imaging.

    PubMed

    Leiss-Holzinger, Elisabeth; Bauer-Marschallinger, Johannes; Hochreiner, Armin; Hollinger, Philipp; Berer, Thomas

    2016-01-01

    We developed a multimodal imaging system, combining noncontact photoacoustic imaging and optical coherence tomography (OCT). Photoacoustic signals are recorded without contact to the specimens' surface by using an interferometric technique. The interferometer is realized within a fiber-optic network using a fiber laser at 1550 nm as source. The fiber-optic network allows the integration of a fiber-based OCT system operating at a wavelength region around 1310 nm. Light from the fiber laser and the OCT source are multiplexed into one fiber using wavelength-division multiplexing. The same focusing optics is used for both modalities. Back-reflected light from the sample is demultiplexed and guided to the respective imaging systems. As the same optical components are used for OCT and photoacoustic imaging, the obtained images are co-registered intrinsically in lateral direction. Three-dimensional imaging is implemented by hybrid galvanometer and mechanical scanning. To allow fast B-scan measurements, scanning of the interrogation beam along one dimension is executed by a galvanometer scanner. Slow-axis scanning, perpendicular to the fast axis, is performed utilizing a linear translational stage. We demonstrate two-dimensional and three-dimensional imaging on agarose phantoms. PMID:25900968

  12. 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.

  13. Photoacoustic Imaging with a Commercial Ultrasound System and a Custom Probe

    PubMed Central

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

    2010-01-01

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

  14. Energy harvesting from low frequency applications using piezoelectric materials

    SciTech Connect

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

    2014-12-15

    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.

  15. Characterization of piezoelectric materials for simultaneous strain and temperature sensing for ultra-low frequency applications

    NASA Astrophysics Data System (ADS)

    Nouroz Islam, Mohammad; Seethaler, Rudolf; Shahria Alam, M.

    2015-08-01

    Piezoelectric materials are used extensively in a number of sensing applications ranging from aerospace industries to medical diagnostics. Piezoelectric materials generate charge when they are subjected to strain. However, since measuring charge is difficult at low frequencies, traditional piezoelectric sensors are limited to dynamic applications. In this research an alternative technique is proposed to determine static strain that relies upon the measurement of piezoelectric capacitance and resistance using piezoelectric sensors. To demonstrate the validity of this approach, the capacitance and resistance of a piezoelectric patch sensor was characterized for a wide range of strain and temperature. The study shows that the piezoelectric capacitance is sensitive to both strain and temperature while the resistance is mostly dependent on the temperature variation. The findings can be implemented to obtain thermally compensated static strain from piezoelectric sensors, which does not require an additional temperature sensor.

  16. 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.

  17. 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.

  18. Remote mid-infrared photoacoustic spectroscopy with a quantum cascade laser.

    PubMed

    Berer, Thomas; Brandstetter, Markus; Hochreiner, Armin; Langer, Gregor; Märzinger, Wolfgang; Burgholzer, Peter; Lendl, Bernhard

    2015-08-01

    We demonstrate non-contact remote photoacoustic spectroscopy in the mid-infrared region. A room-temperature-operated pulsed external-cavity quantum cascade laser is used to excite photoacoustic waves within a semitransparent sample. The ultrasonic waves are detected remotely on the opposite side of the sample using a fiber-optic Mach-Zehnder interferometer, thereby avoiding problems associated with acoustic attenuation in air. We present the theoretical background of the proposed technique and demonstrate measurements on a thin polystyrene film. The obtained absorption spectrum in the region of 1030-1230??cm(-1) is compared to a spectrum obtained by attenuated total reflection, showing reasonable agreement. PMID:26258336

  19. 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.

  20. 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.

  1. Three-dimensional photoacoustic and ultrasonic endoscopic imaging of two rabbit esophagi

    NASA Astrophysics Data System (ADS)

    Yang, Joon-Mo; Favazza, Christopher P.; Yao, Junjie; Chen, Ruimin; Zhou, Qifa; Shung, K. K.; Wang, Lihong V.

    2015-03-01

    The addition of photoacoustic endoscopy to conventional endoscopic ultrasound offers imaging capabilities that may improve diagnosis and clinical care of gastrointestinal tract diseases. In this study, using a 3.8-mm diameter dual-mode photoacoustic and ultrasonic endoscopic probe, we investigated photoacoustic and ultrasonic image features of rabbit esophagi. Specifically, we performed ex vivo imaging of intact rabbit esophagi and correlated the acquired images with histology. Without motion artifact-based limitations, we were able to utilize the full resolving power of the endoscopic device and acquire the first three-dimensional vasculature map of the esophagus and mediastinum, along with coregistered tissue density information. Here, we present the experimental results and discuss potential clinical applications of the technique.

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

    PubMed Central

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

    2012-01-01

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

  3. A numerical model for the study of photoacoustic imaging of brain tumours

    E-print Network

    Firouzi, Kamyar

    2015-01-01

    Photoacoustic imaging has shown great promise for medical imaging, where optical energy absorption by blood haemoglobin is used as the contrast mechanism. A numerical method was developed for the in-silico assessment of the photoacoustic image reconstruction of the brain. Image segmentation techniques were used to prepare a digital phantom from MR images. Light transport through brain tissue was modelled using a Finite Element approach. The resulting acoustic pressure was then estimated by pulsed photoacoustics considerations. The forward acoustic wave propagation was modelled by the linearized coupled first order wave equations and solved by an acoustic k-space method. Since skull bone is an elastic solid and strongly attenuates ultrasound (due to both scattering and absorption), a k-space method was developed for elastic media. To model scattering effects, a new approach was applied based on propagation in random media. In addition, absorption effects were incorporated using a power law. Finally, the acoust...

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

    NASA Astrophysics Data System (ADS)

    Zhao, Zuomin; Myllylä, Risto

    2001-12-01

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

  5. 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.

  6. 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.

  7. Photoacoustic resonance spectroscopy for biological tissue characterization.

    PubMed

    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. PMID:24928154

  8. In vivo optically encoded photoacoustic flowgraphy

    PubMed Central

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

    2014-01-01

    We present an optically encoded photoacoustic flow imaging method based on optical-resolution photoacoustic microscopy. An intensity-modulated continuous-wave laser photothermally encodes the flowing medium, and a pulsed laser generates photoacoustic 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 mm/s to 11 mm/s. Venous blood flow speed in a mouse ear was also measured. PMID:24978744

  9. Photoacoustic phasoscopy super-contrast imaging

    SciTech Connect

    Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin

    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.

  10. Photoacoustic shock generation in carbon suspensions

    SciTech Connect

    Beveridge, Andrew C.; McGrath, Thomas E.; Diebold, Gerald J.; Karabutov, Alexander A.

    1999-12-27

    This letter discusses photoacoustic shock wave generation and the origin of nonlinear sound wave generation in carbon suspensions. The Burgers equation for an inviscid fluid is solved for an exponential acoustic wave. The solution shows an increasingly steep wave form that gradually coalesces into a shock front. Large dynamic range measurements of photoacoustic waves generated by a pulsed-laser beam in carbon suspensions show the pressure in the wave to depart significantly from the predictions of linear response theory. Acoustic sound speed and amplitude measurements indicate that weak shocks are produced from the photoacoustic sound generation process rather than from nonlinear propagational effects. (c) 1999 American Institute of Physics.

  11. Photoacoustic Cell with Digital Differential Detection

    NASA Astrophysics Data System (ADS)

    Suchenek, Mariusz

    2015-01-01

    Solutions which reduce the impact of the external acoustic noise on the photoacoustic signal rely often on the appropriate modification of the photoacoustic cell structure. The goal is to obtain a frequency response of the cell which suppresses the external noise as much as possible. Another approach is differential detection, in which two microphones are used, and assuming that the external noise signal components from both microphones are identical, their subtraction should result in canceling the external noise. The main difficulty of that solution is that both microphone signal paths should be calibrated to have virtually identical characteristics. The paper presents a differential photoacoustic cell with digital differential detection.

  12. 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.

  13. Development of MEMS photoacoustic spectroscopy

    SciTech Connect

    Robinson, Alex Lockwood; Eichenfield, Matthew S.; Griffin, Benjamin; Harvey, Heidi Alyssa; Nielson, Gregory N.; Okandan, Murat; Langlois, Eric; Resnick, Paul James; Shaw, Michael J.; Young, Ian; Givler, Richard C.; Reinke, Charles M.

    2014-01-01

    After years in the field, many materials suffer degradation, off-gassing, and chemical changes causing build-up of measurable chemical atmospheres. Stand-alone embedded chemical sensors are typically limited in specificity, require electrical lines, and/or calibration drift makes data reliability questionable. Along with size, these "Achilles' heels" have prevented incorporation of gas sensing into sealed, hazardous locations which would highly benefit from in-situ analysis. We report on development of an all-optical, mid-IR, fiber-optic based MEMS Photoacoustic Spectroscopy solution to address these limitations. Concurrent modeling and computational simulation are used to guide hardware design and implementation.

  14. Photoacoustic imaging of salivary glands.

    PubMed

    Rich, Laurie J; Seshadri, Mukund

    2015-09-01

    In this work, we utilized photoacoustic imaging (PAI) with co-registered ultrasound (US) to non-invasively assess salivary gland function in vivo. A significant increase in salivary gland oxygen saturation was observed on PAI within minutes after gustatory stimulation of healthy mice reflective of the hyperemic response associated with secretion of saliva. Good correlation was seen between PAI and Doppler sonography. Salivary adenoid cystic carcinomas showed higher oxygen saturation compared to surrounding salivary gland tissue. Our results demonstrate the potential clinical utility of PAI for visualization of salivary gland physiology and pathology. PMID:26417488

  15. Photoacoustic imaging of salivary glands

    PubMed Central

    Rich, Laurie J.; Seshadri, Mukund

    2015-01-01

    In this work, we utilized photoacoustic imaging (PAI) with co-registered ultrasound (US) to non-invasively assess salivary gland function in vivo. A significant increase in salivary gland oxygen saturation was observed on PAI within minutes after gustatory stimulation of healthy mice reflective of the hyperemic response associated with secretion of saliva. Good correlation was seen between PAI and Doppler sonography. Salivary adenoid cystic carcinomas showed higher oxygen saturation compared to surrounding salivary gland tissue. Our results demonstrate the potential clinical utility of PAI for visualization of salivary gland physiology and pathology. PMID:26417488

  16. Photoacoustic study of layered samples

    NASA Astrophysics Data System (ADS)

    Helander, Per; Lundström, Ingemar; McQueen, Douglas

    1981-03-01

    The application of photoacoustic spectroscopy to the spectroscopy of layered samples with thicknesses of tens of microns is demonstrated both theoretically and experimentally. Theoretical expressions for the signal damping and phase delay are developed in terms of the thermal diffusion length, which is determined by the chopper frequency and the thermal properties of the sample. The theory is supported by measurements of both amplitude and phase on a color photographic film containing three light absorbing layers. The application of the method is further illustrated by a simple study of fading leaves.

  17. Uniqueness of reconstruction and an inversion procedure for thermoacoustic and photoacoustic tomography

    E-print Network

    Agranovsky, Mark

    2007-01-01

    The paper contains a simple approach to reconstruction in Thermoacoustic and Photoacoustic Tomography. The technique works for any geometry of point detectors placement and for variable sound speed satisfying a non-trapping condition. A uniqueness of reconstruction result is also obtained.

  18. Uniqueness of reconstruction and an inversion procedure for thermoacoustic and photoacoustic tomography

    E-print Network

    Mark Agranovsky; Peter Kuchment

    2007-06-05

    The paper contains a simple approach to reconstruction in Thermoacoustic and Photoacoustic Tomography. The technique works for any geometry of point detectors placement and for variable sound speed satisfying a non-trapping condition. A uniqueness of reconstruction result is also obtained.

  19. 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...

  20. High-resolution photoacoustic imaging with focused laser and ultrasonic beams

    E-print Network

    High-resolution photoacoustic imaging with focused laser and ultrasonic beams Fanting Kong,1 Y. C is based on a ring transducer that combines ultrasonic and laser beams collinearly and confocally improvement in lateral and axial resolutions compared to the pulse-echo ultrasonic imaging technique

  1. 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.

  2. Energy harvesting wireless piezoelectric resonant force sensor

    NASA Astrophysics Data System (ADS)

    Ahmadi, Mehdi

    The piezoelectric energy harvester has become a new powering option for some low-power electronic devices such as MEMS (Micro Electrical Mechanical System) sensors. Piezoelectric materials can collect the ambient vibrations energy and convert it to electrical energy. This thesis is intended to demonstrate the behavior of a piezoelectric energy harvester system at elevated temperature from room temperature up to 82°C, and compares the system's performance using different piezoelectric materials. The systems are structured with a Lead Magnesium Niobate-Lead Titanate (PMN-PT) single crystal patch bonded to an aluminum cantilever beam, Lead Indium Niobate-Lead Magnesium Niobate-Lead Titanate (PIN-PMN-PT) single crystal patch bonded to an aluminum cantilever beam and a bimorph cantilever beam which is made of Lead Zirconate Titanate (PZT). The results of this experimental study show the effects of the temperature on the operation frequency and output power of the piezoelectric energy harvesting system. The harvested electrical energy has been stored in storage circuits including a battery. Then, the stored energy has been used to power up the other part of the system, a wireless resonator force sensor, which uses frequency conversion techniques to convert the sensor's ultrasonic signal to a microwave signal in order to transmit the signal wirelessly.

  3. 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.

  4. Piezoelectric energy harvesting solutions.

    PubMed

    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

  5. 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.

  6. 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

  7. Monkey brain cortex imaging by photoacoustic tomography

    E-print Network

    Yang, Xinmai; Wang, Lihong V.

    2008-08-20

    Photoacoustic tomography (PAT) is applied to image the brain cortex of a monkey through the intact scalp and skull ex vivo. The reconstructed PAT image shows the major blood vessels on the monkey brain cortex. For comparison, the brain cortex...

  8. 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

  9. 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

  10. 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, ...

  11. Coherent Interferometry Algorithms for Photoacoustic Imaging

    E-print Network

    Ammari, Habib

    The aim of this paper is to develop new coherent interferometry (CINT) algorithms to correct the effect of an unknown cluttered sound speed (random fluctuations around a known constant) on photoacoustic images. By ...

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  13. Photoacoustic cell using elliptical acoustic focusing

    NASA Technical Reports Server (NTRS)

    Heritier, J.-M.; Fouquet, J. E.; Siegman, A. E.

    1982-01-01

    A photoacoustic cell has been developed in the form of an elliptical cylinder in which essentially all the acoustic energy generated by a laser beam passing down one axis is focused onto a cylindrical acoustic tranducer located along the other axis. Preliminary measurements on a liquid-filled cell of this design show high sensitivity and a notably clean impulse response. A similar design may be useful for photoacoustic measurements in vapors as well.

  14. Phase reference materials for photoacoustic spectroscopy

    SciTech Connect

    Jones, R.; Bajic, S.; McClelland, J. |

    1999-06-01

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

  15. In vivo blood oxygenation level measurements using photoacoustic microscopy 

    E-print Network

    Sivaramakrishnan, Mathangi

    2007-09-17

    We investigate the possibility of extracting accurate functional information such as local blood oxygenation level using multi-wavelength photoacoustic measurements. Photoacoustic microscope is utilized to acquire images of microvasculature...

  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. Photo-acoustic measurement of thermal conductivity of thin films and bulk materials

    SciTech Connect

    Wang, X.; Hu, H.; Xu, X.

    1999-07-01

    Thermal property data are important for every material that is exposed to thermal loading. Due to the microstructures of thin films such as grain size, amorphousness, and concentration of foreign atoms and defects, and also due to the physical dimensions of thin films, thermal conductivity of thin films may differ significantly from the bulk value. Because of the complexity of the thin film microstructure, experiments are often needed to determine thermal conductivity of thin films. The photoacoustic technique is one of the many techniques for measuring thermal conductivity of thin films. Compared with other techniques for thermal conductivity measurement, the photoacoustic method is relatively simple, yet is able to provide accurate thermal conductivity data for many types of thin films and bulk materials. In this work, a general analytical expression is developed, which relates the photoacoustic signal with the thermal properties, optical properties, and thermal contact resistance of a multi-layer system. Thermal conductivity of SiO{sub 2} with thicknesses from 0.05 to 0.5 {micro}m on Si wafer, e-beam evaporated thin nickel film on Si wafer and thermal barrier coatings on alloys is measured using the photoacoustic method up to a frequency of 20 kHz. In addition to the commonly used phase shift fitting method, an amplitude fitting method is also employed. Using amplitude fitting, thermal conductivity for both thin films and bulk materials with smooth or rough surface are obtained, while phase shift fitting can only be used for films which are not thermally thick. Applications of the photoacoustic technique are discussed based on the experimental results.

  18. 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.

  19. Variable pulse width piezoelectric ultrasonic transducer driver

    NASA Astrophysics Data System (ADS)

    Martin, R.

    1983-11-01

    Requirements of ceramic piezoelectric ultrasonic transducer drive circuits are discussed in the light of today's advanced nondestructive testing techniques. A new drive circuit based upon power MOSFET devices, which overcomes many of the shortcomings of capacitor discharge circuits, is described. This new driving technique enables transducers of a wide range of resonant frequencies to be driven from a simple drive unit. It also enables transducer characteristics to be optimized for particular applications by control of the drive pulse shape.

  20. Photoacoustic measurement of methane concentrations with a compact pulsed

    E-print Network

    Kung, Andy

    Photoacoustic measurement of methane concentrations with a compact pulsed optical parametric of trace quan- tities of methane in nitrogen by photoacoustic spectroscopy with a novel differential photoacoustic detector. A sensitivity of 1.2 parts in 109 by volume of methane was obtained in direct

  1. Photoacoustic-guided convergence of light through optically diffusive media

    E-print Network

    Photoacoustic-guided convergence of light through optically diffusive media Fanting Kong,1 Ronald H-absorbing target through optically diffusive media by using photoacoustic-guided interferometric focusing to maximize the photoacoustic signal, which is propor- tional to the scattered light intensity at the light

  2. Mapping lipid and collagen by multispectral photoacoustic imaging of

    E-print Network

    Cheng, Ji-Xin

    Mapping lipid and collagen by multispectral photoacoustic imaging of chemical bond vibration Pu Wang Ping Wang Han-Wei Wang Ji-Xin Cheng #12;Mapping lipid and collagen by multispectral photoacoustic, Department of Chemistry, West Lafayette, Indiana 47907 Abstract. Photoacoustic microscopy using vibrational

  3. Photoacoustic Imaging of the Bladder A Pilot Study

    E-print Network

    Khuri-Yakub, Butrus T. "Pierre"

    Photoacoustic Imaging of the Bladder A Pilot Study ladder cancer is the second most common cancer:1245­1250 | 0278-4297 | www.aium.org TECHNICAL INNOVATION Photoacoustic imaging is a promising new technology pulse-echo sonography and photoacoustic imaging. Isoechoic biomaterials

  4. 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 intensity, the photoacoustic system was able to visualize the blood distribution of an enucleated pig's eye

  5. Design, Synthesis, and Imaging of an Activatable Photoacoustic Probe

    E-print Network

    Khuri-Yakub, Butrus T. "Pierre"

    Design, Synthesis, and Imaging of an Activatable Photoacoustic Probe Jelena Levi, Sri Rajasekhar Received May 10, 2010; E-mail: sgambhir@stanford.edu Abstract: Photoacoustic tomography is a rapidly with two chromophores, BHQ3 and Alexa750, shows photoacoustic signals of similar intensity at the two

  6. Piezotransistive transduction of femtoscale displacement for photoacoustic spectroscopy.

    PubMed

    Talukdar, Abdul; Faheem Khan, M; Lee, Dongkyu; Kim, Seonghwan; Thundat, Thomas; Koley, Goutam

    2015-01-01

    Measurement of femtoscale displacements in the ultrasonic frequency range is attractive for advanced material characterization and sensing, yet major challenges remain in their reliable transduction using non-optical modalities, which can dramatically reduce the size and complexity of the transducer assembly. Here we demonstrate femtoscale displacement transduction using an AlGaN/GaN heterojunction field effect transistor-integrated GaN microcantilever that utilizes piezoelectric polarization-induced changes in two-dimensional electron gas to transduce displacement with very high sensitivity. The piezotransistor demonstrated an ultra-high gauge factor of 8,700 while consuming an extremely low power of 1.36?nW, and transduced external excitation with a superior noise-limited resolution of 12.43?fm?Hz(-1/2) and an outstanding responsivity of 170?nV?fm(-1), which is comparable to the optical transduction limits. These extraordinary characteristics, which enabled unique detection of nanogram quantity of analytes using photoacoustic spectroscopy, can be readily exploited in realizing a multitude of novel sensing paradigms. PMID:26258983

  7. Piezotransistive transduction of femtoscale displacement for photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Talukdar, Abdul; Faheem Khan, M.; Lee, Dongkyu; Kim, Seonghwan; Thundat, Thomas; Koley, Goutam

    2015-08-01

    Measurement of femtoscale displacements in the ultrasonic frequency range is attractive for advanced material characterization and sensing, yet major challenges remain in their reliable transduction using non-optical modalities, which can dramatically reduce the size and complexity of the transducer assembly. Here we demonstrate femtoscale displacement transduction using an AlGaN/GaN heterojunction field effect transistor-integrated GaN microcantilever that utilizes piezoelectric polarization-induced changes in two-dimensional electron gas to transduce displacement with very high sensitivity. The piezotransistor demonstrated an ultra-high gauge factor of 8,700 while consuming an extremely low power of 1.36 nW, and transduced external excitation with a superior noise-limited resolution of 12.43 fm Hz-1/2 and an outstanding responsivity of 170 nV fm-1, which is comparable to the optical transduction limits. These extraordinary characteristics, which enabled unique detection of nanogram quantity of analytes using photoacoustic spectroscopy, can be readily exploited in realizing a multitude of novel sensing paradigms.

  8. Off-axis photoacoustic microscopy.

    PubMed

    Shelton, Ryan L; Applegate, Brian E

    2010-08-01

    Photoacoustic microscopy (PAM) is a high-contrast, high-resolution imaging modality, used primarily for imaging hemoglobin and melanin. Important applications include mapping of the microvasculature and melanoma tumor margins. We demonstrate a novel PAM design that markedly simplifies the implementation by separating the optical illumination from the acoustic detection path. This modification enables the use of high-quality commercial optics and transducers, and may be readily adapted to commercial light microscopes. The designed PAM system is only sensitive to signals generated in the overlap of the illumination and detection solid angles, providing the additional benefit of quasi-dark-field detection. An off-axis PAM system with a lateral resolution of 26 microm and a modest axial resolution of 410 microm has been assembled and characterized using tissue samples. The axial resolution is readily scaled down to tens of micrometers within the same design, by utilizing commercially available high-frequency acoustic transducers. PMID:20176531

  9. Photoacoustic biopsy: a feasibility study

    NASA Astrophysics Data System (ADS)

    Xu, Guan; Tomlins, Scott A.; Siddiqui, Javed; Davis, Mandy A.; Kunju, Lakshmi P.; Wei, John T.; Wang, Xueding

    2015-03-01

    Photoacoustic (PA) measurements encode the information associated with both physical microstructures and chemical contents in biological tissues. A two-dimensional physio-chemical spectrogram (PCS) can be formulated by combining the power spectra of PA signals acquired at a series of optical wavelengths. The analysis of PCS, or namely PA physio-chemical analysis (PAPCA), enables the quantification of the concentrations and the spatial distributions of a variety of chemical components in the tissue. The chemical components and their distribution are the two major features observed in the biopsy procedures which have been regarded as the gold standard of the diagnosis of many diseases. Taking non-alcoholic fatty liver disease and prostate cancer for example, this study investigates the feasibility of PAPCA in characterizing the histopathological changes in the diseased conditions in biological tissue. A catheter based setup facilitating measurement in deep tissues was also proposed and tested.

  10. Gold nanoparticles for photoacoustic imaging

    PubMed Central

    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

  11. High Temperature Piezoelectric Drill

    NASA Technical Reports Server (NTRS)

    Bao, Xiaoqi; Scott, James; Boudreau, Kate; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom; Zhang, Shujun

    2009-01-01

    The current NASA Decadal mission planning effort has identified Venus as a significant scientific target for a surface in-situ sampling/analyzing mission. The Venus environment represents several extremes including high temperature (460 deg C), high pressure (9 MPa), and potentially corrosive (condensed sulfuric acid droplets that adhere to surfaces during entry) environments. This technology challenge requires new rock sampling tools for these extreme conditions. Piezoelectric materials can potentially operate over a wide temperature range. Single crystals, like LiNbO3, have a Curie temperature that is higher than 1000 deg C and the piezoelectric ceramics Bismuth Titanate higher than 600 deg C. A study of the feasibility of producing piezoelectric drills that can operate in the temperature range up to 500 deg C was conducted. The study includes the high temperature properties investigations of engineering materials and piezoelectric ceramics with different formulas and doping. The drilling performances of a prototype Ultrasonic/Sonic Drill/Corer (USDC) using high temperate piezoelectric ceramics and single crystal were tested at temperature up to 500 deg C. The detailed results of our study and a discussion of the future work on performance improvements are presented in this paper.

  12. High temperature piezoelectric drill

    NASA Astrophysics Data System (ADS)

    Bao, Xiaoqi; Scott, James; Boudreau, Kate; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom; Zhang, Shujun

    2009-03-01

    The current NASA Decadal mission planning effort has identified Venus as a significant scientific target for a surface in-situ sampling/analyzing mission. The Venus environment represents several extremes including high temperature (460°C), high pressure (~9 MPa), and potentially corrosive (condensed sulfuric acid droplets that adhere to surfaces during entry) environments. This technology challenge requires new rock sampling tools for these extreme conditions. Piezoelectric materials can potentially operate over a wide temperature range. Single crystals, like LiNbO3, have a Curie temperature that is higher than 1000°C and the piezoelectric ceramics Bismuth Titanate higher than 600°C. A study of the feasibility of producing piezoelectric drills that can operate in the temperature range up to 500°C was conducted. The study includes the high temperature properties investigations of engineering materials and piezoelectric ceramics with different formulas and doping. The drilling performances of a prototype Ultrasonic/Sonic Drill/Corer (USDC) using high temperate piezoelectric ceramics and single crystal were tested at temperature up to 500°C. The detailed results of our study and a discussion of the future work on performance improvements are presented in this paper.

  13. 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.

  14. 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. PMID:25893171

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

    PubMed

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

    2015-03-01

    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. PMID:25893171

  16. 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

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

  19. Photochromism-induced photoacoustic spectrometry for the determination of trace mercury(II) as its dithizonate in the solid state

    SciTech Connect

    Chen, N.; Guo, R.; Lai, E.P.C.

    1988-11-01

    A new technique, photochromism-induced photoacoustic spectrometry, has been developed for the determination of mercury(II) as mercury(II) dithizonate in the solid state. A special photoacoustic cell was designed for inducing a photochromic reaction in mercury(II) dithizonate and detecting the resultant photoacoustic signal from its excited state. Interferences from all other metal ions are absent because only mercury(II) dithizonate can exhibit photochromism in the solid state. A linear standard calibration graph for Hg(II) was obtained in the quantity range from 1.5 to 450 pmol. The relative standard deviations determined at 15 and 150 pmol were 6% and 3%, respectively. When the technique is applied to water analysis with dithizone extraction, a detection limit of 3 pptr (parts per trillion) Hg(II) is easily achievable.

  20. Photoacoustic Characterization of Randomly Oriented Silver Nanowire Films

    NASA Astrophysics Data System (ADS)

    Li Voti, R.; Leahu, G.; Larciprete, M. C.; Sibilia, C.; Bertolotti, M.; Nefedov, I.; Anoshkin, I. V.

    2015-06-01

    In this work, the photoacoustic characterization in the UV/Vis range of randomly oriented silver nanowire films deposited onto either a quartz or polymeric substrate is presented. This study was performed for a set of films differing in both metallic nanowire dimensions, as well as metal content. Samples were prepared starting from suspensions of Ag nanowires in isopropanol (IPA) , differing in both the length and diameter of the nanowires. The obtained films were characterized by scanning electron micrography (SEM) images; thus, the metal filling factor was retrieved with MATLAB software based on a visual method. Following the morphological characterization, both spectrophotometry and the photoacoustic spectroscopy (PAS) technique were employed to investigate in detail the absorbance spectra of silver nanowire films, in order to evidence their peculiar properties in the UV/Vis spectral range. Specifically, this photothermal technique is particularly useful to investigate a film that may exhibit relevant scattering phenomena, as for metallic nanowire films. The obtained experimental results show that the choice of the metal filling factor may affect the absorbance spectra of the resulting mesh.

  1. Tissue type characterization using photoacoustic power spectrum, a feasibility study

    NASA Astrophysics Data System (ADS)

    Tavakoli, Behnoosh; Goldstein, Seth D.; Kang, Jin U.; Choti, Michaal; Boctor, Emad M.

    2015-03-01

    The development of technologies capable of non-invasive characterization of tissue has the potential to significantly improve diagnostic and therapeutic medical interventions. In this study we investigated the feasibility of a noninvasive photoacoustic (PA) approach for characterizing biological tissues. The measurement was performed in the transmission mode with a wideband hydrophone while a tunable Q-switched Nd:YAG pulsed laser was used for illumination. The power spectrum of photoacoustic signal induced by a pulsed laser light from tissue was analyzed and features were extracted to study their correlation with tissue biomechanical properties. For a controlled study, tissue mimicking gelatin phantoms with different densities and equivalent optical absorptions were used as targets. The correlation between gelatin concentration of such phantoms and their mechanical properties were validated independently with a dynamic mechanical analyzer capable of calculating complex loss and storage moduli between two compression plates. It was shown that PA spectrums were shifted towards higher frequencies by increasing gelatin concentration. In order to quantify this effect, signal energy in two intervals of low and high frequency ranges were calculated. Gelatin concentration was correlated with PA energy in high frequency range with R2=0.94. Subsequently, PA signals generated from freshly resected human thyroid specimens were measured and analyzed in a similar fashion. We found that in aggregate, malignant thyroid tissue contains approximately 1.6 times lower energy in the high frequency range in comparison to normal thyroid tissue (p<0.01). This ratio increased with increasing illumination wavelength from 700 nm to 900nm. In summary, this study demonstrated the feasibility of using photoacoustic technique for characterizing tissue on the basis of viscoelastic properties of the tissue.

  2. 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.

  3. Photoacoustic brain imaging: from microscopic to macroscopic scales

    PubMed Central

    Yao, Junjie; Wang, Lihong V.

    2014-01-01

    Abstract. Human brain mapping has become one of the most exciting contemporary research areas, with major breakthroughs expected in the coming 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

  4. 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.

  5. 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.

  6. Development Of A Supercontinuum Based Photoacoustic Aerosol Light Absorption And Albedo Spectrometer (PALAAS)

    NASA Astrophysics Data System (ADS)

    Arnold, Ian J.

    Aerosols are a major contributor to the global radiation budget because they modify the planetary albedo with their optical properties. These optical properties need to be measured and understood, ideally at multiple wavelengths. This thesis describes the ongoing development of a supercontinuum based multi-wavelength photoacoustic instrument to measure the light absorption and scattering coefficients of aerosols. Collimation techniques for supercontinuum sources using lens-based and off-axis parabolic mirror-based collimators were evaluated and it was determined that the off-axis mirror had superior collimation abilities for multi-spectral beams. A proof of concept supercontinuum-based photoacoustic instrument was developed using sequential measurements at multiple wavelengths. The instrument data were in good agreement with those from a commercial 3-wavelength photoacoustic instrument and the novel instrument had minimum detectable absorption and scattering coefficients of better than 4 Mm-1 and 21 Mm-1, respectively. The instrument however suffered from poor temporal resolution due to the sequential measurement and required the development of an aerosol delivery system to deliver a slowly varying aerosol concentration. In response, a spectral modulator has been developed to frequency encode different wavelength bands for simultaneous measurement with a photoacoustic instrumen.

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

    PubMed Central

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

    2014-01-01

    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. PMID:24487319

  8. 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.

  9. Piezoelectric Nanoparticle-Polymer Composite Materials

    NASA Astrophysics Data System (ADS)

    McCall, William Ray

    Herein we demonstrate that efficient piezoelectric nanoparticle-polymer composite materials can be synthesized and fabricated into complex microstructures using sugar-templating methods or optical printing techniques. Stretchable foams with excellent tunable piezoelectric properties are created by incorporating sugar grains directly into polydimethylsiloxane (PDMS) mixtures containing barium titanate (BaTiO3 -- BTO) nanoparticles and carbon nanotubes (CNTs), followed by removal of the sugar after polymer curing. Porosities and elasticity are tuned by simply adjusting the sugar/polymer mass ratio and the electrical performance of the foams showed a direct relationship between porosity and the piezoelectric outputs. User defined 2D and 3D optically printed piezoelectric microstructures are also fabricated by incorporating BTO nanoparticles into photoliable polymer solutions such as polyethylene glycol diacrylate (PEGDA) and exposing to digital optical masks that can be dynamically altered. Mechanical-to-electrical conversion efficiency of the optically printed composite is enhanced by chemically altering the surface of the BTO nanoparticles with acrylate groups which form direct covalent linkages with the polymer matrix under light exposure. Both of these novel materials should find exciting uses in a variety of applications including energy scavenging platforms, nano- and microelectromechanical systems (NEMS/MEMS), sensors, and acoustic actuators.

  10. Ultrasonically encoded photoacoustic flowgraphy in biological tissue.

    PubMed

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

    2013-11-15

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

  11. 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.

  12. 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.

  13. Photoacoustic frequency-domain depth profiling of contintiouslly inhomogeneous condensed phases: Theory and simulations

    E-print Network

    Mandelis, Andreas

    Photoacoustic frequency-domain depth profiling of contintiouslly inhomogeneous condensed phases: Theory and simulations for the inverse problem Andreas Mandelisa) and Samuel B. Peralta Photoacoustic- nal inversion basedon the spatial Laplace transform of the photoacoustic frequency responseof

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

    E-print Network

    Mandelis, Andreas

    Optical-absorptioncoefficient measurements in solids and liquids using correlation photoacoustic spectroscopy JAMEST. DODGSON,ANDREASMANDELIS,AND CLAUDIOANDREETTA Photoacoustic and Photothermal Sciences-correlation photoacoustic spectroscopy (CPAS), has been investigated. Powders of holmium oxide and aqueous solutions

  15. Photoacoustic frequency-domain depth profilometry of surface-layer inhomogeneities: Application to laser processed steels

    E-print Network

    Mandelis, Andreas

    Photoacoustic frequency-domain depth profilometry of surface-layer inhomogeneities: Application change in the photoacoustic signal frequency response of laser processed stainless-steel and carbon steel examination and microhardness testing. I. INTRODUCTION Photoacoustic and photothermal detection methods have

  16. 40 CFR 1065.269 - Photoacoustic analyzer for ethanol and methanol.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 2014-07-01 false Photoacoustic analyzer for ethanol and methanol...Measurements § 1065.269 Photoacoustic analyzer for ethanol and methanol...Application. You may use a photoacoustic analyzer to measure...

  17. Piezoelectric actuation of a compliant semi-infinite beam

    NASA Astrophysics Data System (ADS)

    Austin, Eric M.; Ananthasayanam, Balajee

    2004-07-01

    Piezoelectric materials (PZT) are commonly used as actuators and sensors for vibration suppression in flexible metal or composite substrates. There are well-established techniques for modeling the actuation of PZTs when they are bonded to these structures. However, if the substrate material is much softer than the piezoelectric actuator/sensor, a higher level of modeling is needed to predict the local deformations at the interface. In this research, a finite-length piezoelectric element bonded perfectly to an infinite elastic strip is modeled. The specific goal was to quantify the actuation and sensing mechanics of piezoelectric devices on substrates potentially much softer than the piezoelectric element. Previous works have addressed membranes or plates bonded to an elastic half-space subjected to mechanical or thermal loads. Euler-Bernoulli beam theory is used to derive equations of equilibrium for the piezoelectric beam. These equations are then recast as integral equations for the interface displacement gradients and equated to the equivalent quantities for an elastic layer subject to distributed shear and normal tractions. The resulting singular integral equations are solved by expanding the interface tractions using a series of Chebyshev polynomials. First, certain sanity checks are performed to confirm the validity of the model by choosing a stiff substrate for which Euler-Bernoulli beam-assumptions holds good. For certain combinations of geometrical and material parameters, the substrate has a positive curvature, whereas the piezoelectric has a negative curvature and vice versa. After analyzing the forces acting on both piezoelectric and the substrate, the reasons for this behavior in soft substrates are justified here. Finally, the range of geometric parameters where the reversal of bending occurs in the piezoelectric is given.

  18. Study on an improved wavelet shift-invariant threshold denoising for pulsed laser induced glucose photoacoustic signals

    NASA Astrophysics Data System (ADS)

    Wang, Zhengzi; Ren, Zhong; Liu, Guodong

    2015-10-01

    Noninvasive measurement of blood glucose concentration has become a hotspot research in the world due to its characteristic of convenient, rapid and non-destructive etc. The blood glucose concentration monitoring based on photoacoustic technique has attracted many attentions because the detected signal is ultrasonic signals rather than the photo signals. But during the acquisition of the photoacoustic signals of glucose, the photoacoustic signals are not avoid to be polluted by some factors, such as the pulsed laser, electronic noises and circumstance noises etc. These disturbances will impact the measurement accuracy of the glucose concentration, So, the denoising of the glucose photoacoustic signals is a key work. In this paper, a wavelet shift-invariant threshold denoising method is improved, and a novel wavelet threshold function is proposed. For the novel wavelet threshold function, two threshold values and two different factors are set, and the novel function is high order derivative and continuous, which can be looked as the compromise between the wavelet soft threshold denoising and hard threshold denoising. Simulation experimental results illustrate that, compared with other wavelet threshold denoising, this improved wavelet shift-invariant threshold denoising has higher signal-to-noise ratio(SNR) and smaller root mean-square error (RMSE) value. And this improved denoising also has better denoising effect than others. Therefore, this improved denoising has a certain of potential value in the denoising of glucose photoacoustic signals.

  19. Multichannel Detection of Photoacoustic Signals: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Zbysi?ski, Piotr; Starecki, Tomasz

    2015-07-01

    In a typical photoacoustic measurement system, signal detection is usually implemented with a single microphone or another pressure sensor. A solution presented in this paper consists of an array of 14 MEMS microphones equipped with dedicated and individually controllable signal paths, based on programmable gain amplifiers and analog-to-digital converters. Further, digital signal processing and recording are implemented in an FPGA-based hardware system. Use of multiple microphones increases the signal amplitude and the signal-to-noise ratio and allows for measurements of pressure-field distribution inside the photoacoustic cell.

  20. Photoacoustic imaging based on MEMS mirror scanning.

    PubMed

    Xi, Lei; Sun, Jingjing; Zhu, Yiping; Wu, Lei; Xie, Huikai; Jiang, Huabei

    2010-01-01

    A microelectromechanical systems (MEMS)-based photoacoustic imaging system is reported for the first time. In this system, the MEMS-based light scanning subsystem and a ring-shaped polyvinylidene fluoride (PVDF) transducer are integrated into a miniaturized probe that is capable of three-dimensional (3D) photoacoustic imaging. It is demonstrated that the imaging system is able to image small objects embedded in phantom materials and in chicken and to in vivo visualize blood vessels under the skin of a human hand. PMID:21258548

  1. In vivo virtual intraoperative surgical photoacoustic microscopy

    SciTech Connect

    Han, Seunghoon Kim, Sehui Kim, Jeehyun E-mail: chulhong@postech.edu; Lee, Changho Jeon, Mansik; Kim, Chulhong E-mail: chulhong@postech.edu; Department of Biomedical Engineering, The State University of New York at Buffalo, Buffalo, New York 14221

    2013-11-11

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

  2. Photoacoustic lifetime imaging for direct in vivo tissue oxygen monitoring

    NASA Astrophysics Data System (ADS)

    Shao, Qi; Ashkenazi, Shai

    2015-03-01

    Measuring the partial pressure of oxygen (pO2) in tissue may provide physicians with essential information about the physiological state of tissue. However, currently available methods for measuring or imaging tissue pO2 have significant limitations, preventing them from being widely used in clinics. Recently, we have reported a direct and noninvasive in vivo imaging modality based on the photoacoustic lifetime which overcomes certain drawbacks of the existing methods. The technique maps the excited triplet state of oxygen-sensitive dye, thus reflecting the spatial and temporal distributions of tissue oxygen. Here, we present two studies which apply photoacoustic lifetime imaging (PALI) to monitor changes of tissue oxygen induced by external modulations. The first study modulates tissue oxygen by controlling the percentage of oxygen a normal mouse inhales. We demonstrate that PALI is able to reflect the change in oxygen level with respect to normal, oxygen-rich, and oxygen-poor breathing conditions. The second study involves an acute ischemia model using a thin thread tied around the hindlimb of a normal mouse to reduce the blood flow. PALI images were acquired before, during, and after the restriction. The drop of tissue pO2 and recovery from hypoxia due to reperfusion were tracked and observed by PALI.

  3. Photoacoustic Spectroscopy of the Oxygen A-Band

    NASA Astrophysics Data System (ADS)

    Lunny, Elizabeth M.; Bui, Thinh Quoc; Bray, Caitlin; Rupasinghe, Priyanka; Okumura, Mitchio

    2015-06-01

    The oxygen A-band (760 nm) is used in a number of remote sensing applications due to the precisely known, uniform distribution of molecular oxygen throughout the atmosphere and the spectral isolation of the band. The A-band is used to determine the pathlength of solar radiation for OCO-2, a current NASA mission which seeks to measure the global sources and sinks of carbon dioxide at unprecedented spatial and temporal resolution. The goal of measuring atmospheric carbon dioxide concentrations with a precision of 0.25% requires a precise knowledge of line shape parameters. Currently, the most significant uncertainties in A-band spectroscopy result from line mixing and collision induced absorption, which become more prominent at elevated pressures. Photoacoustic spectroscopy is ideal to observe these phenomena due to the large dynamic range and zero-background advantages of the technique. Photoacoustic spectra of the oxygen A-band over a range of pressures will be presented in addition to line shape parameters extracted from multispectrum fits of the data.

  4. Super-resolution photoacoustic imaging through a scattering wall

    E-print Network

    Conkey, Donald B; Dove, Jacob D; Ju, Hengyi; Murray, Todd W; Piestun, Rafael

    2013-01-01

    Imaging through opaque, highly scattering walls is a long sought after capability with potential applications in a variety of fields. The use of wavefront shaping to compensate for scattering has brought a renewed interest as a potential solution to this problem. A key to the practicality of any imaging technique is the capability to focus light without direct access behind the scattering wall. Here, we address this problem using photoacoustic feedback for wavefront optimization. By combining the spatially non-uniform sensitivity of the ultrasound transducer to the generated photoacoustic waves with an evolutionary competition among optical modes, the speckle field develops a single, high intensity focus significantly smaller than the acoustic focus used for feedback. Notably, this method is not limited by the size of the absorber to form a sub-acoustic optical focus. We demonstrate imaging behind a scattering medium with up to ten times improvement in signal-to-noise ratio (SNR) and five to six times sub-aco...

  5. Photoacoustic imaging of single circulating melanoma cells in vivo

    NASA Astrophysics Data System (ADS)

    Wang, Lidai; Yao, Junjie; Zhang, Ruiying; Xu, Song; Li, Guo; Zou, Jun; Wang, Lihong V.

    2015-03-01

    Melanoma, one of the most common types of skin cancer, has a high mortality rate, mainly due to a high propensity for tumor metastasis. The presence of circulating tumor cells (CTCs) is a potential predictor for metastasis. Label-free imaging of single circulating melanoma cells in vivo provides rich information on tumor progress. Here we present photoacoustic microscopy of single melanoma cells in living animals. We used a fast-scanning optical-resolution photoacoustic microscope to image the microvasculature in mouse ears. The imaging system has sub-cellular spatial resolution and works in reflection mode. A fast-scanning mirror allows the system to acquire fast volumetric images over a large field of view. A 500-kHz pulsed laser was used to image blood and CTCs. Single circulating melanoma cells were imaged in both capillaries and trunk vessels in living animals. These high-resolution images may be used in early detection of CTCs with potentially high sensitivity. In addition, this technique enables in vivo study of tumor cell extravasation from a primary tumor, which addresses an urgent pre-clinical need.

  6. A Constrained Variable Projection Reconstruction Method for Photoacoustic Computed Tomography Without Accurate Knowledge of Transducer Responses.

    PubMed

    Sheng, Qiwei; Wang, Kun; Matthews, Thomas P; Xia, Jun; Zhu, Liren; Wang, Lihong V; Anastasio, Mark A

    2015-12-01

    Photoacoustic computed tomography (PACT) is an emerging computed imaging modality that exploits optical contrast and ultrasonic detection principles to form images of the absorbed optical energy density within tissue. When the imaging system employs conventional piezoelectric ultrasonic transducers, the ideal photoacoustic (PA) signals are degraded by the transducers' acousto-electric impulse responses (EIRs) during the measurement process. If unaccounted for, this can degrade the accuracy of the reconstructed image. In principle, the effect of the EIRs on the measured PA signals can be ameliorated via deconvolution; images can be reconstructed subsequently by application of a reconstruction method that assumes an idealized EIR. Alternatively, the effect of the EIR can be incorporated into an imaging model and implicitly compensated for during reconstruction. In either case, the efficacy of the correction can be limited by errors in the assumed EIRs. In this work, a joint optimization approach to PACT image reconstruction is proposed for mitigating errors in reconstructed images that are caused by use of an inaccurate EIR. The method exploits the bi-linear nature of the imaging model and seeks to refine the measured EIR during the process of reconstructing the sought-after absorbed optical energy density. Computer-simulation and experimental studies are conducted to investigate the numerical properties of the method and demonstrate its value for mitigating image distortions and enhancing the visibility of fine structures. PMID:26641726

  7. Deblurring algorithms accounting for the finite detector size in photoacoustic tomography.

    PubMed

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

    2014-05-01

    Most reconstruction algorithms for photoacoustic tomography, like back projection or time reversal, work ideally for point-like detectors. For real detectors, which integrate the pressure over their finite size, images reconstructed by these algorithms show some blurring. Iterative reconstruction algorithms using an imaging matrix can take the finite size of real detectors directly into account, but the numerical effort is significantly higher compared to the use of direct algorithms. For spherical or cylindrical detection surfaces, the blurring caused by a finite detector size is proportional to the distance from the rotation center (spin blur) and is equal to the detector size at the detection surface. In this work, we apply deconvolution algorithms to reduce this type of blurring on simulated and on experimental data. Two particular deconvolution methods are compared, which both utilize the fact that a representation of the blurred image in polar coordinates decouples pixels at different radii from the rotation center. Experimental data have been obtained with a flat, rectangular piezoelectric detector measuring signals around a plastisol cylinder containing various small photoacoustic sources with variable distance from the center. Both simulated and experimental results demonstrate a nearly complete elimination of spin blur. PMID:24853146

  8. 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.

  9. Formation constants of neodymium acetate complexes at elevated temperatures by laser-induced photoacoustic spectroscopy

    SciTech Connect

    Wruck, D.A.; Kadkhodayan, B.; Palmer, C.E.A.; Silva, R.J.

    1995-12-01

    Chemical thermodynamic data on the formation of solution complexes by radionuclides as a function of temperature are needed for performance assessment studies of proposed radioactive waste repositories. Optical absorption spectroscopy is a preferred method for the measurement of complexation constants in aqueous solutions. Because many of radionuclides of interest, e.g., actinides, must be studied at very low solution concentrations, a system of high sensitivity is required. Therefore, a photoacoustic spectrometer has been developed for high sensitivity optical absorption measurements of aqueous solutions at elevated temperatures. The light source is a Nd: YAG-pumped dye laser system. The photoacoustic signal generated in the sample solution is detected with a piezoelectric transducer coupled to the thermostatted sample cell. The spectrometer has been tested by applying it to the determination of the formation constants of Nd(III) acetate complexes. The formation constants are reported for the temperature range 20 to 70{degrees}C; and are compared to measurements by spectrophotometry and calorimetry.

  10. Piezoelectric Energy Harvesting From Flutter

    NASA Astrophysics Data System (ADS)

    Norouzi, Soroush

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

  11. Photoacoustic microscopy of human teeth

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

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

    SciTech Connect

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

    2015-03-15

    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.

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

    NASA Astrophysics Data System (ADS)

    LeBoulluec, Peter; Liu, Hanli; Yuan, Baohong

    2013-09-01

    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.

  14. 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

  15. 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

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

    PubMed

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

    2012-02-01

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

  17. Optimization of Piezoelectric Electrical Generators Powered by Random Vibrations

    E-print Network

    Lefeuvre, E; Richard, C; Petit, L; Guyomar, D

    2007-01-01

    This paper compares the performances of a vibrationpowered electrical generators using PZT piezoelectric ceramic associated to two different power conditioning circuits. A new approach of the piezoelectric power conversion based on a nonlinear voltage processing is presented and implemented with a particular power conditioning circuit topology. Theoretical predictions and experimental results show that the nonlinear processing technique may increase the power harvested by a factor up to 4 compared to the Standard optimization technique. Properties of this new technique are analyzed in particular in the case of broadband, random vibrations, and compared to those of the Standard interface.

  18. Rapid analysis of wood using transient infrared spectroscopy and photoacoustic spectroscopy with PLS regression

    SciTech Connect

    Bajic, Stanley J.; Jones, Roger W.; McClelland, John F.; Meglen, Robert R.

    1998-06-01

    In the forest products industry, improved methods are needed for rapid analysis of wood and paper products. Currently, the best methods for determining chemical and physical properties of wood-based materials require considerable sample preparation and analysis time. Consequently, quantitative information is often not obtained on a time scale suitable for process monitoring, control, and quality assurance. The primary barriers to practical utilization of conventional infrared methods are the opaqueness and poor reflection properties of the wood-based materials. This paper demonstrates how photoacoustic and transient infrared spectroscopies have been combined with chemometric techniques to overcome the limitations of conventional infrared spectroscopies and to permit rapid chemical and physical characterization of wood chips. Both photoacoustic and transient infrared spectroscopic methods are examined as rapid at- and on-line techniques for feedstock identification and chemical composition analysis prior to processing. {copyright} {ital 1998 American Institute of Physics.}

  19. Piezoelectric Resonator with Two Layers

    NASA Technical Reports Server (NTRS)

    Stephanou, Philip J. (Inventor); Black, Justin P. (Inventor)

    2013-01-01

    A piezoelectric resonator device includes: a top electrode layer with a patterned structure, a top piezoelectric layer adjacent to the top layer, a middle metal layer adjacent to the top piezoelectric layer opposite the top layer, a bottom piezoelectric layer adjacent to the middle layer opposite the top piezoelectric layer, and a bottom electrode layer with a patterned structure and adjacent to the bottom piezoelectric layer opposite the middle layer. The top layer includes a first plurality of electrodes inter-digitated with a second plurality of electrodes. A first one of the electrodes in the top layer and a first one of the electrodes in the bottom layer are coupled to a first contact, and a second one of the electrodes in the top layer and a second one of the electrodes in the bottom layer are coupled to a second contact.

  20. 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.

  1. Nonresonant photoacoustic monitoring of atmospheric methane

    NASA Astrophysics Data System (ADS)

    Fiedler, Michael; Goelz, C.; Platt, Ulrich

    1993-02-01

    The resonant and non-resonant photoacoustic (PA) detection of atmospheric trace gases is discussed with special respect to field measurements. Continuous in-situ methane measurements in a cow shed by a non-resonant PA detector applying an HeNe laser are reported, which allow the model based determination of the methane production rate of cows.

  2. Extensions of quartz-enhanced photoacoustic spectroscopy

    E-print Network

    Masurkar, Amrita V

    2009-01-01

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

  3. Diode Pumped Solid State Laser Photoacoustic Spectrometer

    E-print Network

    to significantly long diode lifetimes. These types of pump lasers would be suitable for extended spaceborneDiode Pumped Solid State Laser Photoacoustic Spectrometer Jeffrey S. Pilgrim and David S. Bomse gas detection but has been hampered by the lack of a simple tunable infrared source. DPSS lasers offer

  4. 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

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

    NASA Astrophysics Data System (ADS)

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

    2005-06-01

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

  6. 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.

  7. Characteristic analysis of photoacoustic signal generated in biological tissue

    NASA Astrophysics Data System (ADS)

    Qian, Shengyou; Xing, Da

    2002-04-01

    The characteristics of photoacoustic signals generated in real biological tissues are analyzed in time domain and in frequency domain through experiments. It is found that the frequency ranges of photoacoustic signals generated in fresh porcine fat, muscle, liver and kidney are about 5.0 MHz, 1.5 MHz, 2.0 MHz and 2.0 MHz respectively, and their duration is about 1-4 microsecond(s) . A positive peak is very obvious in the photoacoustic waveform of porcine liver, and a negative peak is sharp in the photoacoustic waveform of porcine fat. The main frequencies of photoacoustic signal are relatively stable, which correspond to the properties of biological tissues. The results obtained here are significant for photoacoustic tomography of biological tissue.

  8. 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.

  9. Vibration and Tracking Control of a Flexure-Guided Nanopositioner Using a Piezoelectric Strain Sensor

    E-print Network

    Fleming, Andrew J.

    Vibration and Tracking Control of a Flexure-Guided Nanopositioner Using a Piezoelectric Strain Sensor Y. K. Yong, A. J. Fleming and S. O. R. Moheimani School of Electrical Engineering and Computer.yong@newcastle.edu.au Abstract--This paper presents a novel sensing technique which uses a piezoelectric strain sensor

  10. Feedforward Control of a Piezoelectric Flexure Stage for AFM Yang Li and John Bechhoefer

    E-print Network

    Bechhoefer, John

    Feedforward Control of a Piezoelectric Flexure Stage for AFM Yang Li and John Bechhoefer Abstract of the present generation of instruments, we have developed a simple feedforward technique that nonetheless of the physical parts and the electro- mechanical response of the piezoelectric actuators) consist of a number

  11. 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.

  12. 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) .

  13. Detection of Hepatic Fibrosis in Ex Vivo Liver Samples Using an Open-Photoacoustic-Cell Method: Feasibility Study

    NASA Astrophysics Data System (ADS)

    Stolik, S.; Fabila, D. A.; de la Rosa, J. M.; Escobedo, G.; Suárez-Álvarez, K.; Tomás, S. A.

    2015-04-01

    Design of non-invasive and accurate novel methods for liver fibrosis diagnosis has gained growing interest. Different stages of liver fibrosis were induced in Wistar rats by intraperitoneally administering different doses of carbon tetrachloride. The liver fibrosis degree was conventionally determined by means of histological examination. An open-photoacoustic-cell (OPC) technique for the assessment of liver fibrosis was developed and is reported here. The OPC technique is based on the fact that the thermal diffusivity can be accurately measured by photoacoustics taking into consideration the photoacoustic signal amplitude versus the modulation frequency. This technique measures directly the heat generated in a sample, due to non-radiative de-excitation processes, following the absorption of light. The thermal diffusivity was measured with a home-made open-photoacoustic-cell system that was specially designed to perform the measurement from ex vivo liver samples. The human liver tissue showed a significant increase in the thermal diffusivity depending on the fibrosis stage. Specifically, liver samples from rats exhibiting hepatic fibrosis showed a significantly higher value of the thermal diffusivity than for control animals.

  14. Photoacoustic effects in nanocomposite structure ‘porous silicon-liquid’

    PubMed Central

    2012-01-01

    Photoacoustic effect in nanocomposite structure ‘porous silicon-liquid’ has been investigated. Main mechanisms involved in the formation of photoacoustic signal in such structures have been experimentally studied. Liquids with different viscosity (ethanol and acetone) filling the nanopores have been used. A proposed mathematical model describing the photoacoustic signal formation was found to be in good agreement with the experimental results. The role of thermally induced pressures provoked by the liquids confined inside the nanopores in the photoacoustic process has been analyzed. PMID:22823996

  15. Plasmon enhanced photoacoustic generation from volumetric electromagnetic hotspots.

    PubMed

    Park, Sang-Gil; Yang, Seung-Bum; Ahn, Myeong-Su; Oh, Young-Jae; Kim, Yong Tae; Jeong, Ki-Hun

    2015-12-23

    This work reports plasmon enhanced photoacoustic generation by using a three dimensional plasmonic absorber. The 3D plasmonic absorber comprises a thin polymer film on glass nanopillar arrays with nanogap-rich silver nanoislands. The 3D plasmonic absorber clearly shows 24.6 times higher enhancement of photoacoustic signals at an excitation wavelength of 630 nm than a simple polymeric absorber. The photoacoustic enhancement results from the volumetric electromagnetic field enhancement on a light-absorbing polymer through 3D plasmonic nanostructures. This novel photoacoustic absorber provides a new direction for highly efficient ultrasonic generation. PMID:26659557

  16. Super-resolution photoacoustic fluctuation imaging with multiple speckle illumination

    E-print Network

    Chaigne, Thomas; Allain, Marc; Katz, Ori; Gigan, Sylvain; Sentenac, Anne; Bossy, Emmanuel

    2015-01-01

    In deep tissue photoacoustic imaging, the spatial resolution is inherently limited by acoustic diffraction. Moreover, as the ultrasound attenuation increases with frequency, resolution is often traded-off for penetration depth. Here we report on super-resolution photoacoustic imaging by use of multiple speckle illumination. Specifically, we show that the analysis of second-order fluctuations of the photoacoustic images combined with image deconvolution enables resolving optically absorbing structures beyond the acoustic diffraction limit. A resolution increase of almost a factor 2 is demonstrated experimentally. Our method introduces a new framework that could potentially lead to deep tissue photoacoustic imaging with sub-acoustic resolution.

  17. 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

  18. In vivo volumetric imaging of subcutaneous microvasculature by photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Hao F.; Maslov, Konstantin; Li, Meng-Lin; Stoica, George; Wang, Lihong V.

    2006-10-01

    Photoacoustic microscopy was developed to achieve volumetric imaging of the anatomy and functions of the subcutaneous microvasculature in both small animals and humans in vivo with high spatial resolution and high signal-to-background ratio. By following the skin contour in raster scanning, the ultrasonic transducer maintains focusing in the region of interest. Furthermore, off-focus lateral resolution is improved by using a synthetic-aperture focusing technique based on the virtual point detector concept. Structural images are acquired in both rats and humans, whereas functional images representing hemoglobin oxygen saturation are acquired in rats. After multiscale vesselness filtering, arterioles and venules in the image are separated based on the imaged oxygen saturation levels. Detailed structural information, such as vessel depth and spatial orientation, are revealed by volume rendering.

  19. 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.

  20. Photoacoustic imaging driven by an interstitial irradiation source

    PubMed Central

    Mitcham, Trevor; Dextraze, Katherine; Taghavi, Houra; Melancon, Marites; Bouchard, Richard

    2015-01-01

    Photoacoustic (PA) imaging has shown tremendous promise in providing valuable diagnostic and therapy-monitoring information in select clinical procedures. Many of these pursued applications, however, have been relatively superficial due to difficulties with delivering light deep into tissue. To address this limitation, this work investigates generating a PA image using an interstitial irradiation source with a clinical ultrasound (US) system, which was shown to yield improved PA signal quality at distances beyond 13 mm and to provide improved spectral fidelity. Additionally, interstitially driven multi-wavelength PA imaging was able to provide accurate spectra of gold nanoshells and deoxyhemoglobin in excised prostate and liver tissue, respectively, and allowed for clear visualization of a wire at 7 cm in excised liver. This work demonstrates the potential of using a local irradiation source to extend the depth capabilities of future PA imaging techniques for minimally invasive interventional radiology procedures. PMID:26236640

  1. Nanoparticle-targeted photoacoustic cavitation for tissue imaging

    NASA Astrophysics Data System (ADS)

    McLaughlan, James R.; Roy, Ronald A.; Ju, Hengyi; Murray, Todd W.

    2010-02-01

    Photoacoustic tomography is a non-invasive imaging technique based on the detection of broadband acoustic emissions generated by the absorption of light in tissue. This technique utilises the high contrast of optical imaging with high resolution from ultrasound imaging. However, the ability to detect these emissions above the noise level ultimately limits the depth to which imaging can be performed. Introduction of light-absorbing gold nanoparticles can improve the signal-to-noise ratio in tissue, through greater optical absorption and targeting specific cell populations, thereby enhancing contrast and the ability to delineate tissue types. For sufficiently high laser fluence incident on a nanoparticle, a transient vapour cavity is formed and undergoes inertial collapse, generating a broadband emission and possibly additional contrast. However, the laser fluence required to achieve this typically exceeds the maximum permissible exposure (MPE) for tissue. Through the combination of ultrasonic and optical pulses, the light and sound thresholds required to repeatedly generate inertial cavitation were reduced to 11.1 mJ/cm2 and 1.5 MPa respectively. Experiments employed a transparent acrylamide gel possessing a small (<600 ?m) spherical region doped with 80 nm diameter gold nanoparticles and simultaneously exposed to pulsed laser light (532 nm) and pulsed ultrasound (1.1 MHz). The amplitude of broadband emissions induced by both light and sound exceeded that produced by light alone by almost two orders of magnitude, thereby facilitating imaging a deeper depth within tissue. 2D images of doped regions generated from conventional photoacoustic and ultrasound-enhanced emissions are presented and compared.

  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. Review of photoacoustic flow imaging: its current state and its promises

    PubMed Central

    van den Berg, P.J.; Daoudi, K.; Steenbergen, W.

    2015-01-01

    Flow imaging is an important method for quantification in many medical imaging modalities, with applications ranging from estimating wall shear rate to detecting angiogenesis. Modalities like ultrasound and optical coherence tomography both offer flow imaging capabilities, but suffer from low contrast to red blood cells and are sensitive to clutter artefacts. Photoacoustic imaging (PAI) is a relatively new field, with a recent interest in flow imaging. The recent enthusiasm for PA flow imaging is due to its intrinsic contrast to haemoglobin, which offers a new spin on existing methods of flow imaging, and some unique approaches in addition. This review article will delve into the research on photoacoustic flow imaging, explain the principles behind the many techniques and comment on their individual advantages and disadvantages. PMID:26640771

  4. 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

  5. Intravascular photoacoustic detection of vulnerable plaque based on constituent selected imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Xing, Da

    2011-01-01

    Atherosclerosis, a disease of the large arteries, is the primary cause of heart disease and stroke. Over decades, atherosclerosis is characterized by thickening of the walls of the arteries, only advanced atherosclerotic disease could be observed. Photoacoustic imaging is a hybrid imaging technique that combines the advantages of high spatial resolution of ultrasound with contrast of optical absorption. In this paper, we present an intravascular photoacoustic (IVPA) imaging system to characterize vulnerable plaques by using the optical absorption contrast between different constituents. Epidemiological studies have revealed several important plaque constituents associated with early atherosclerosis, such as macrophage, cholesterol, lipid, calcification, and so on. We chose a section of lipid rich atherosclerosis artery and a section of normal artery as the phantom. Two IVPA images of them are given to show the difference between sick and normal. As a new method of detecting vulnerable plaque, IVPA constituents imaging will provide more details for diagnosis that offer an enticing prospect in early detecting of atherosclerosis.

  6. 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.

  7. 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.

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

    PubMed Central

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

    2013-01-01

    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

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

    PubMed Central

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

    2014-01-01

    Abstract. 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. PMID:25069009

  10. 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

  11. Can molecular imaging enable personalized diagnostics? An example using magnetomotive photoacoustic imaging

    PubMed Central

    O'Donnell, Matthew; Wei, Chen-wei; Xia, Jinjun; Pelivanov, Ivan; Jia, Congxian; Huang, Sheng-Wen; Hu, Xiaoge; Gao, Xiaohu

    2013-01-01

    The advantages of photoacoustic imaging, including low cost, non-ionizing operation, and sub-mm spatial resolution at centimeters depth, make it a promising modality to probe nanoparticle-targeted abnormalities in real time at cellular and molecular levels. However, detecting rare cell types in a heterogeneous background with strong optical scattering and absorption remains a big challenge. For example, differentiating circulating tumor cells in vivo (typically fewer than 10 cells/ml for an active tumor) among billions of erythrocytes in the blood is nearly impossible. In this paper, a newly developed technique, magnetomotive photoacoustic (mmPA) imaging, which can greatly increase the sensitivity and specificity of sensing targeted cells or molecular interactions, is reviewed. Its primary advantage is suppression of background signals through magnetic enrichment/manipulation with simultaneous photoacoustic detection of magnetic contrast agent targeted objects. Results from phantom and in vitro studies demonstrate the capability of mmPA imaging to differentiate regions targeted with magnetic nanoparticles from the background, and to trap and sensitively detect targeted cells at a concentration of a single cell per milliliter in a flow system mimicking a human peripheral artery. This technique provides an example of the ways in which molecular imaging can potentially enable robust molecular diagnosis and treatment, and accelerate the translation of molecular medicine into the clinic. PMID:23982280

  12. Comparison of photoacoustic spectroscopy, conventional absorption spectroscopy, and potentiometry as probes of lanthanide speciation

    SciTech Connect

    Torres, R.A.; Palmer, C.E.A.; Baisden, P.A.; Russo, R.E.; Silva, R.J. )

    1990-02-01

    The authors measured the stability constants of praseodymium acetate and oxydiacetate complexes by laser-induced photoacoustic spectroscopy, conventional UV-visible absorption spectroscopy, and pH titration. For the spectroscopic studies, changes in the free Pr absorption peaks at 468 and 481 nm were monitored at varying ligand concentrations. The total Pr concentration was 1 {times} 10{sup {minus}4} M in solutions used for the photoacoustic studies and 0.02 M for conventional spectroscopy. For the pH titrations, we used solutions whose Pr concentrations varied from 5 {times} 10{sup {minus}3} to 5 {times} 10{sup {minus}2} M, with total ligand-to-metal ratios ranging from 1 to 10. A comparison of the results obtained by the three techniques demonstrates that photoacoustic spectroscopy can give the same information about metal-ligand speciation as more conventional methods. It is particularly suited to those situations where the other techniques are insensitive because of limited metal concentrations.

  13. Acoustic Aspects of Photoacoustic Signal Generation and Detection in Gases

    NASA Astrophysics Data System (ADS)

    Miklós, A.

    2015-04-01

    In this paper photoacoustic signal generation and detection in gases is investigated and discussed from the standpoint of acoustics. Four topics are considered: the effect of the absorption-desorption process of modulated and pulsed light on the heat power density released in the gas; the generation of the primary sound by the released heat in an unbounded medium; the excitation of an acoustic resonator by the primary sound; and finally, the generation of the measurable PA signal by a microphone. When light is absorbed by a molecule and the excess energy is relaxed by collisions with the surrounding molecules, the average kinetic energy, thus also the temperature of an ensemble of molecules (called "particle" in acoustics) will increase. In other words heat energy is added to the energy of the particle. The rate of the energy transfer is characterized by the heat power density. A simple two-level model of absorption-desorption is applied for describing the heat power generation process for modulated and pulsed illumination. Sound generation by a laser beam in an unbounded medium is discussed by means of the Green's function technique. It is shown that the duration of the generated sound pulse depends mostly on beam geometry. A photoacoustic signal is mostly detected in a photoacoustic cell composed of acoustic resonators, buffers, filters, etc. It is not easy to interpret the measured PA signal in such a complicated acoustic system. The acoustic response of a PA detector to different kinds of excitations (modulated cw, pulsed, periodic pulse train) is discussed. It is shown that acoustic resonators respond very differently to modulated cw excitation and to excitation by a pulse train. The microphone for detecting the PA signal is also a part of the acoustic system; its properties have to be taken into account by the design of a PA detector. The moving membrane of the microphone absorbs acoustic energy; thus, it may influence the resonance frequency and amplification of the acoustic resonator. This property may be very important for PA cells equipped with several microphones. Furthermore, microphones have a mechanical resonance, which may influence the measurement of short sound pulses. Since the PA resonator and the microphone with its connecting tube form a coupled acoustic system, this system can be optimized for sensitivity.

  14. Finite Element Simulation of Photoacoustic Pressure in a Resonant Photoacoustic Cell Using Lossy Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Duggen, L.; Lopes, N.; Willatzen, M.; Rubahn, H.-G.

    2011-04-01

    The finite-element method (FEM) is used to simulate the photoacoustic signal in a cylindrical resonant photoacoustic cell. Simulations include loss effects near the cell walls that appear in the boundary conditions for the inhomogeneous Helmholtz equation governing the acoustic pressure. Reasonably good agreement is obtained between theoretical results and experimental data. However, it was anticipated that loss mechanisms other than viscous and thermal boundary losses occur and should be included. Nevertheless, the feasibility to use FEM together with the derived boundary conditions to simulate the photoacoustic signal was demonstrated and good agreement with experiments for the actual resonance frequency and the quality factor of the cell was obtained despite its complicated geometry.

  15. Design of optimized piezoelectric HDD-sliders

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

  16. 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.

  17. Ultrahigh resolution photoacoustic microscopy via transient absorption

    PubMed Central

    Shelton, Ryan L.; Applegate, Brian E.

    2010-01-01

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

  18. 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.

  19. Noninvasive photoacoustic microscopy of methemoglobin in vivo

    NASA Astrophysics Data System (ADS)

    Tang, Min; Zhou, Yong; Zhang, Ruiying; Wang, Lihong V.

    2015-03-01

    Various causes can lead to methemoglobinemia, and it has the potential to be confused with other diseases. In vivo measurements of methemoglobin have significant applications in the clinics. We quantified the average and the distributed percentage of methemoglobin both in vitro and in vivo using photoacoustic microscopy (PAM). Based on the absorption spectra of methemoglobin, oxyhemoglobin, and deoxyhemoglobin, three wavelengths were chosen to differentiate methemoglobin from the others. We imaged the methemoglobin percentage in microtubes that mimicked blood vessels as a phantom experiment. The methemoglobin concentrations calculated from the photoacoustic signals were in accordance with the preset concentrations. We also demonstrated the ability of PAM to quantitatively image methemoglobin distribution in vivo in a mouse ear.

  20. Singular value decomposition analysis of a photoacoustic imaging system and 3D imaging at 0.7 FPS

    PubMed Central

    Roumeliotis, Michael B.; Stodilka, Robert Z.; Anastasio, Mark. A.; Ng, Eldon; Carson, Jeffrey J. L.

    2011-01-01

    Photoacoustic imaging is a non-ionizing imaging modality that provides contrast consistent with optical imaging techniques while the resolution and penetration depth is similar to ultrasound techniques. In a previous publication [Opt. Express 18, 11406 (2010)], a technique was introduced to experimentally acquire the imaging operator for a photoacoustic imaging system. While this was an important foundation for future work, we have recently improved the experimental procedure allowing for a more densely populated imaging operator to be acquired. Subsets of the imaging operator were produced by varying the transducer count as well as the measurement space temporal sampling rate. Examination of the matrix rank and the effect of contributing object space singular vectors to image reconstruction were performed. For a PAI system collecting only limited data projections, matrix rank increased linearly with transducer count and measurement space temporal sampling rate. Image reconstruction using a regularized pseudoinverse of the imaging operator was performed on photoacoustic signals from a point source, line source, and an array of point sources derived from the imaging operator. As expected, image quality increased for each object with increasing transducer count and measurement space temporal sampling rate. Using the same approach, but on experimentally sampled photoacoustic signals from a moving point-like source, acquisition, data transfer, reconstruction and image display took 1.4 s using one laser pulse per 3D frame. With relatively simple hardware improvements to data transfer and computation speed, our current imaging results imply that acquisition and display of 3D photoacoustic images at laser repetition rates of 10Hz is easily achieved. PMID:21747496

  1. 2011201120112011 2011 Symposium on Piezoelectricity, Acoustic waves, and Device Application

    E-print Network

    Chen, Baoquan

    of Piezoelectric Devices; Oscillators and Filters; Ultrasound Imaging, drug delivery and Therapy; (, ) Kirk; MEMS/NEMS/Nano Piezoelectric Devices; Piezoelectric Materials; Ultrasonics; Manufacturing Technology

  2. Compressed sensing in photoacoustic tomographyin vivo

    PubMed Central

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

    2010-01-01

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

  3. 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.

  4. 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.

  5. Thermally Enhanced Photoacoustic Radar Imaging of Biotissues

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Mandelis, Andreas

    2015-06-01

    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 to , and the SNR can be increased.

  6. Photoacoustics of disperse systems: Below cavitation threshold

    SciTech Connect

    Egerev, Sergey; Ovchinnikov, Oleg

    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.

  7. Multiscale Functional and Molecular Photoacoustic Tomography.

    PubMed

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

    2016-01-01

    Photoacoustic tomography (PAT) combines rich optical absorption contrast with the high spatial resolution of ultrasound at depths in tissue. The high scalability of PAT has enabled anatomical imaging of biological structures ranging from organelles to organs. The inherent functional and molecular imaging capabilities of PAT have further allowed it to measure important physiological parameters and track critical cellular activities. Integration of PAT with other imaging technologies provides complementary capabilities and can potentially accelerate the clinical translation of PAT. PMID:25933617

  8. Photoacoustic imaging of human lymph nodes with endogenous lipid

    E-print Network

    Jones, Peter JS

    Photoacoustic imaging of human lymph nodes with endogenous lipid and hemoglobin contrast James A://spiedl.org/terms #12;Photoacoustic imaging of human lymph nodes with endogenous lipid and hemoglobin contrast James A, Gower Street, London WC1E 6BT, United Kingdom b University College London, Centre for Medical Imaging, 3

  9. 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

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

    E-print Network

    Khuri-Yakub, Butrus T. "Pierre"

    Carbon nanotubes as photoacoustic molecular imaging agents in living mice ADAM DE LA ZERDA1 not shown to target a diseased site in living subjects. Here we show that single-walled carbon nanotubes were verified ex vivo using Raman microscopy. Photoacoustic imaging of targeted single-walled carbon

  11. 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.

  12. Photoacoustic spectroscopy of short-period gyrotropic superlattices

    SciTech Connect

    Mityurich, G.S.; Starodubtsev, E.G.

    1994-12-31

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

  13. 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.

  14. 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.

  15. Piezoelectric axial flow microvalve

    DOEpatents

    Gemmen, Randall; Thornton, Jimmy; Vipperman, Jeffrey S.; Clark, William W.

    2007-01-09

    This invention is directed to a fuel cell operable with a quantity of fuel and a quantity of an oxidizer to produce electrical power, the fuel cell including a fuel cell body including a labyrinth system structured to permit the fuel and the oxidizer to flow therethrough; at least a first catalyst in fluid communication with the labyrinth; and at least a first microvalve operably disposed within at least a portion of the labyrinth. The microvalve utilizes a deflectable member operable upon the application of a voltage from a voltage source. The microvalve includes an elongated flow channel formed therein and extending substantially longitudinally between the first and second ends to permit substantially longitudinal flow of the fluid therethrough and between the first and second ends; and the deflectable member disposed on the valve body, the deflectable member including at least a first piezoelectric portion that is piezoelectrically operable to deflect the deflectable member between an open position and a closed position upon the application of a voltage, the deflectable member in the closed position being operable to resist the flow of the fluid through the flow channel.

  16. Piezoelectric trace vapor calibrator

    SciTech Connect

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

    2006-08-15

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

  17. 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.

  18. 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

  19. Real-time sono-photoacoustic imaging of gold nanoemulsions

    NASA Astrophysics Data System (ADS)

    Arnal, Bastien; Wei, Chen-Wei; Perez, Camilo; Lombardo, Michael; Pelivanov, Ivan M.; Pozzo, Danilo; O'Donnell, Matthew

    2015-03-01

    Phase transition contrast agents were first introduced in ultrasound (US) in the form of perfluorocarbon droplets. When their size is reduced to the nanoscale, surface tension dominates their stability and high pressure is required to vaporize them using long US emissions at high frequencies. Our group recently showed that nanoemulsion beads (100-300 nm) coated with gold nanopsheres could be used as non-linear contrast agents. Beads can be vaporized with light only, inducing stronger photoacoustic signals by increasing thermal expansion. A photoacoustic cavitation threshold study (US: 1.2 MHz, Laser 750 nm and 10-ns pulse) shows that the vaporization thresholds of NEB-GNS can be greatly reduced using simultaneous light and US excitations. The resulting signal is driven only by the pressure amplitude for a fluence higher than 2.4 mJ/cm2. At diagnostic exposures, it is possible to capture very high signals from the vaporized beads at concentrations reduced to 10 pM with optical absorption smaller than 0.01 cm-1. A real-time imaging mode selectively isolating vaporization signals was implemented on a Verasonics system. A linear US probe (L74, 3 MHz) launched short US bursts before light was emitted from the laser. Vaporization of NEB-GNS resulted in a persistent 30-dB signal enhancement compared to a dye with the same absorption. Specific vaporization signals were retrieved in phantom experiments with US scatterers. This technique, called sonophotoacoustics, has great potential for targeted molecular imaging and therapy using compact nanoprobes with potentially high-penetrability into tissue.

  20. Photoacoustic perfusion measurements: a comparison with power Doppler in phantoms

    NASA Astrophysics Data System (ADS)

    Heres, H. M.; Arabul, M. Ü.; Tchang, B. C.; van de Vosse, F. N.; Rutten, M. C.; Lopata, R. G.

    2015-03-01

    Ultrasound-based measurements using Doppler, contrast, and more recently photoacoustics (PA), have emerged as techniques for tissue perfusion measurements. In this study, the feasibility of in vitro perfusion measurements with a fully integrated, hand-held, photoacoustic probe was investigated and compared to Power Doppler (PD). Three cylindrical polyvinyl alcohol (PVA) phantoms were made (diameter = 15 mm) containing 100, 200 and 400 parallel polysulfone tubes (diameter = 0.2 mm), resulting in a perfused cross-sectional area of 1.8, 3.6 and 7.1% respectively. Each phantom was perfused with porcine blood (15 mL/min). Cross-sectional PA images (? = 805nm, frame rate = 10Hz) and PD images (PRF = 750Hz) were acquired with a MyLab One and MyLab 70 scanner (Esaote, NL), respectively. Data were averaged over 70 frames. The average PA signal intensity was calculated in a region-of-interest of 4 mm by 6 mm. The percentage of colored PD pixels was measured in the entire phantom region. The average signal intensity of the PA images increased linearly with perfusion density, being 0.54 (+/- 0.01), 0.56 (+/- 0.01), 0.58 (+/- 0.01) with an average background signal of 0.53 in the three phantoms, respectively. For PD, the percentage of colored pixels in the phantom area (1.5% (+/- 0.2%), 4.4% (+/- 0.2%), 13.7% (+/- 0.8%)) also increased linearly. The preliminary results suggest that PA, like PD, is capable of detecting an increase of blood volume in tissue. In the future, in vivo measurements will be explored, although validation will be more complex.

  1. 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...

  2. Dielectric Properties of Piezoelectric Polyimides

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  3. 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.

  4. All-Optical Cantilever-Enhanced Photoacoustic Spectroscopy in the Open Environment

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Zhu, Yong; Lin, Cheng; Tian, Li; Xu, Zhuwen; Nong, Jinpeng

    2015-06-01

    A novel all-optical cantilever-enhanced photoacoustic spectroscopy technique for trace gas detection in the open environment is proposed. A cantilever is set off-beam to "listen to" the photoacoustic signal, and an improved quadrature-point stabilization Fabry-Perot demodulation unit is used to pick up the vibration signal of the acoustic transducer instead of a complicated Michelson interferometer. The structure parameters of the cantilever are optimized to make the sensing system work more stably and reliably using a finite element method, which is then fabricated by surface micro-machining technology. Finally, related experiments are carried out to detect the absorption of water vapor at one atmosphere in the open environment. It was found that the normalized noise-equivalent absorption coefficient obtained by a traditional Fabry-Perot demodulation unit is , while that by a quadrature- point stabilization Fabry-Perot demodulation unit is , which indicates that the sensitivity is increased by a factor of 3.1 using improved cantilever-enhanced photoacoustic spectroscopy.

  5. 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%.

  6. 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.

  7. 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.

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

    PubMed Central

    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%. PMID:20210465

  9. Ultrasound and photoacoustic imaging to monitor mesenchymal stem cells labeled with gold nanoparticles

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    Mesenchymal stem cells (MSCs) are versatile in many tissue engineering applications and have the potential to be used for cellular therapies because they can differentiate into many cell types. Specifically, the use of MSCs for the treatment of ischemic disease is promising because MSCs can express characteristics of vascular cells. MSCs can promote vascular growth at the site of injury after delivery using a PEGylated fibrin gel. In order to quantitatively assess in vivo delivery and differentiation of MSCs, a non-invasive and high-resolution imaging technique is required. In this study, the combined ultrasound and photoacoustic imaging was demonstrated to monitor MSCs labeled with citrate-stabilized gold nanoparticles (Au NPs). It was observed that uptake of nanoparticles did not have a significant effect on cell viability and proliferation over a two-week period. Four different cell concentrations of either the non-labeled MSCs or the Au NP labeled MSCs were embedded in the tissue mimicking gelatin phantom. The ultrasound and photoacoustic signals were acquired and quantitatively analyzed to assess sensitivity and accuracy of the developed imaging approach. Furthermore, based on the results, the feasibility of in vivo ultrasound and photoacoustic imaging of MSCs was discussed.

  10. 3-D photoacoustic and pulse echo imaging of prostate tumor progression in the mouse window chamber

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

    Understanding the tumor microenvironment is critical to characterizing how cancers operate and predicting their response to treatment. We describe a novel, high-resolution coregistered photoacoustic (PA) and pulse echo (PE) ultrasound system used to image the tumor microenvironment. Compared to traditional optical systems, the platform provides complementary contrast and important depth information. Three mice are implanted with a dorsal skin flap window chamber and injected with PC-3 prostate tumor cells transfected with green fluorescent protein. The ensuing tumor invasion is mapped during three weeks or more using simultaneous PA and PE imaging at 25 MHz, combined with optical and fluorescent techniques. Pulse echo imaging provides details of tumor structure and the surrounding environment with 100-?m3 resolution. Tumor size increases dramatically with an average volumetric growth rate of 5.35 mm3/day, correlating well with 2-D fluorescent imaging (R = 0.97, p < 0.01). Photoacoustic imaging is able to track the underlying vascular network and identify hemorrhaging, while PA spectroscopy helps classify blood vessels according to their optical absorption spectrum, suggesting variation in blood oxygen saturation. Photoacoustic and PE imaging are safe, translational modalities that provide enhanced depth resolution and complementary contrast to track the tumor microenvironment, evaluate new cancer therapies, and develop molecular contrast agents in vivo.

  11. 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.

  12. Tissue oxygen monitoring by photoacoustic lifetime imaging (PALI) and its application to image-guided photodynamic therapy (PDT)

    NASA Astrophysics Data System (ADS)

    Shao, Qi; Morgounova, Ekaterina; Ashkenazi, Shai

    2015-03-01

    The oxygen partial pressure (pO2), which results from the balance between oxygen delivery and its consumption, is a key component of the physiological state of a tissue. Images of oxygen distribution can provide essential information for identifying hypoxic tissue and optimizing cancer treatment. Previously, we have reported a noninvasive in vivo imaging modality based on photoacoustic lifetime. The technique maps the excited triplet state of oxygen-sensitive dye, thus reflects the spatial and temporal distribution of tissue oxygen. We have applied PALI on tumor on small animals to identify hypoxia area. We also showed that PALI is able monitor changes of tissue oxygen, in an acute ischemia and breathing modulation model. Here we present our work on developing a treatment/imaging modality (PDT-PALI) that integrates PDT and a combined ultrasound/photoacoustic imaging system. The system provides real-time feedback of three essential parameters namely: tissue oxygen, light penetration in tumor location, and distribution of photosensitizer. Tissue oxygen imaging is performed by applying PALI, which relies on photoacoustic probing of oxygen-dependent, excitation lifetime of Methylene Blue (MB) photosensitizer. Lifetime information can also be used to generate image showing the distribution of photosensitizer. The level and penetration depth of PDT illumination can be deduced from photoacoustic imaging at the same wavelength. All images will be combined with ultrasound B-mode images for anatomical reference.

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

    SciTech Connect

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

    1994-10-01

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

  14. Influence of nanoscale temperature rises on photoacoustic generation: discrimination between optical absorbers based on nonlinear photoacoustics at high frequency

    E-print Network

    Simandoux, Oliver; Gâteau, Jérôme; Bossy, Emmanuel

    2013-01-01

    In the thermoelastic regime, photoacoustic sensing of optical absorption relies on conversion from light to acoustic energy via the coefficient of thermal expansion \\beta. In this work, we confront confront experimental measurements to theoretical predictions of nonlinear photoacoustic generation based on the dynamic variation of \\beta(T) during the optical excitation of absorbers in aqueous solution. The photoacoustic generation from solutions of organic dye and gold nanospheres (with same optical densities), illuminated with 532 nm nanosecond pulses, was detected using a high frequency ultrasound transducer (center frequency 20 MHz). Photoacoustic emission was observed with gold nanospheres at low fluence (a few mJ/cm2) for an equilibrium temperature around 4{\\deg}C, where the linear photoacoustic effect in water vanishes, highlighting the nonlinear emission from the solution of nanospheres. Under the same condition, no emission was observed with the absorbing organic dye. At a fixed fluence of 5 mJ/cm2, th...

  15. High piezoelectric properties of cement piezoelectric composites containing kaolin

    NASA Astrophysics Data System (ADS)

    Pan, Huang Hsing; Yang, Ruei-Hao; Cheng, Yu-Chieh

    2015-04-01

    To obtain high piezoelectric properties, PZT/cement composites with kaolin were fabricated and polarized by 1.5kV/mm electric field for 40 min, where lead zirconate titanate (PZT) inclusion with 50% by volume was used. After the polarization, piezoelectric properties of the composite were measured daily till 100 days. Results indicated that relative dielectric constant (?r) and piezoelectric strain constant (d33) increase with aging day, and approach to asymptotic values after 70 days. Temperature treatment to the composite is a dominate factor to enhance piezoelectric properties. The d33 and ?r values of PZT/cement composites treated at the ambient temperature (23?) were 57pC/N and 275 at the 70th aging day respectively, and then reached 106pC/N and 455 in turn with 150? treatment. The composite contains 4% kaolin having the highest value of d33=111pC/N and ?r=500 at 90 days because the porosity is the less than the others. Cement piezoelectric composites containing kaolin own the higher d33 and ?r value, compared with the other reported composites with 50% PZT. The porosity, the electromechanical coupling factor and impedance-frequency spectra of the cement piezoelectric composites were also discussed.

  16. 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%.

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

    PubMed Central

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

    2013-01-01

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

  18. 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.

  19. Laser photoacoustic spectroscopy for trace level detection of actinides in groundwater

    SciTech Connect

    Doxtader, M.M.; Maroni, V.A.; Beitz, J.V.; Heaven, M.

    1986-01-01

    In this paper we examine the utility of the laser photoacoustic spectroscopy (LPAS) technique for elucidating the chemical behavior of species present in the near-field environment of the Basalt Waste Isolation Project (BWIP) repository. We briefly review the existing basis for interpreting actinide spectra at low concentrations, and describe our initial experiments. These experiments include development and demonstration of the methodology under optimum conditions, e.g., stable, well-characterized solutions of holmium; and application of the technique to conditions relevant to the repository, including studies performed with uranium in synthetic groundwater and at elevated temperatures.

  20. 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 ...

  1. Piezoelectric Vibration Damping Study for Rotating Composite Fan Blades

    NASA Technical Reports Server (NTRS)

    Min, James B.; Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Kray, Nicholas

    2012-01-01

    Resonant vibrations of aircraft engine blades cause blade fatigue problems in engines, which can lead to thicker and aerodynamically lower performing blade designs, increasing engine weight, fuel burn, and maintenance costs. In order to mitigate undesirable blade vibration levels, active piezoelectric vibration control has been investigated, potentially enabling thinner blade designs for higher performing blades and minimizing blade fatigue problems. While the piezoelectric damping idea has been investigated by other researchers over the years, very little study has been done including rotational effects. The present study attempts to fill this void. The particular objectives of this study were: (a) to develop and analyze a multiphysics piezoelectric finite element composite blade model for harmonic forced vibration response analysis coupled with a tuned RLC circuit for rotating engine blade conditions, (b) to validate a numerical model with experimental test data, and (c) to achieve a cost-effective numerical modeling capability which enables simulation of rotating blades within the NASA Glenn Research Center (GRC) Dynamic Spin Rig Facility. A numerical and experimental study for rotating piezoelectric composite subscale fan blades was performed. It was also proved that the proposed numerical method is feasible and effective when applied to the rotating blade base excitation model. The experimental test and multiphysics finite element modeling technique described in this paper show that piezoelectric vibration damping can significantly reduce vibrations of aircraft engine composite fan blades.

  2. Electrostrictive effect in ferroelectrics: An alternative approach to improve piezoelectricity

    NASA Astrophysics Data System (ADS)

    Li, Fei; Jin, Li; Xu, Zhuo; Zhang, Shujun

    2014-03-01

    Electrostriction plays an important role in the electromechanical behavior of ferroelectrics and describes a phenomenon in dielectrics where the strain varies proportional to the square of the electric field/polarization. Perovskite ferroelectrics demonstrating high piezoelectric performance, including BaTiO3, Pb(Zr1-xTix)O3, and relaxor-PbTiO3 materials, have been widely used in various electromechanical devices. To improve the piezoelectric activity of these materials, efforts have been focused on the ferroelectric phase transition regions, including shift the composition to the morphotropic phase boundary or shift polymorphic phase transition to room temperature. However, there is not much room left to further enhance the piezoelectric response in perovskite solid solutions using this approach. With the purpose of exploring alternative approaches, the electrostrictive effect is systematically surveyed in this paper. Initially, the techniques for measuring the electrostrictive effect are given and compared. Second, the origin of electrostriction is discussed. Then, the relationship between the electrostriction and the microstructure and macroscopic properties is surveyed. The electrostrictive properties of ferroelectric materials are investigated with respect to temperature, composition, phase, and orientation. The relationship between electrostriction and piezoelectric activity is discussed in detail for perovskite ferroelectrics to achieve new possibilities for piezoelectric enhancement. Finally, future perspectives for electrostriction studies are proposed.

  3. Piezoelectric Rotary Tube Motor

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  4. Enhanced piezoelectric response in the artificial ferroelectric polymer multilayers

    SciTech Connect

    Zhao, X. L.; Wang, J. L. E-mail: lin-tie@mail.sitp.ac.cn; Tian, B. B.; Liu, B. L.; Wang, X. D.; Sun, S.; Zou, Y. H.; Lin, T. E-mail: lin-tie@mail.sitp.ac.cn; Sun, J. L.; Meng, X. J.; Chu, J. H.

    2014-12-01

    An actuator with a high piezoelectric response, the ferroelectric polymer multilayer actuator, is described. The ferroelectric polymer multilayers consisting of alternative ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer and relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) (P(VDF-TrFE-CFE)) terpolymer with different periodicities and fixed total thickness are prepared by the Langmuir-Blodgett technique. Both X-ray diffraction and Raman spectroscopic measurements indicate that the structure of the multilayer with thin alternating layer is similar to that of the ferroelectric copolymer. Compared with that of the copolymer, it is found that the piezoelectric coefficient of the multilayer could be improved by 57%. We attributed the enhanced piezoelectric response of the multilayers to the internal electric fields that arises from the electrostatic couplings between different layers.

  5. Preloaded freeplay wide-bandwidth low-frequency piezoelectric harvesters

    NASA Astrophysics Data System (ADS)

    Sharpes, N.; Abdelkefi, A.; Hajj, M. R.; Heo, J.; Cho, K.-H.; Priya, S.

    2015-07-01

    We propose a technique for increasing the bandwidth of resonant low-frequency (<100 Hz) piezoelectric energy harvesters based on the modification of the clamped boundary condition of cantilevers, termed here as preloaded freeplay boundary condition. The effects of the preloaded freeplay boundary condition are quantified in terms of the fundamental frequency, frequency response, and power output for two beam configurations, namely, classical cantilevered bimorph piezoelectric energy harvester and zigzag unimorph piezoelectric energy harvester. A comparative analysis was performed between both the harvesters to empirically establish the advantages of the preloaded freeplay boundary condition. Using this approach, we demonstrate that the coupled degree-of-freedom dynamics results in an approximate 4-7 times increase in half-power bandwidth over the fixed boundary condition case.

  6. Semi-analytical modelling of piezoelectric excitation of guided waves

    NASA Astrophysics Data System (ADS)

    Kalkowski, Micha? K.; Rustighi, Emiliano; Waters, Timothy P.

    2015-03-01

    Piezoelectric elements are a key component of modern non-destructive testing (NDT) and structural health monitoring (SHM) systems and play a significant role in many other areas involving dynamic interaction with the structure such as energy harvesting, active control, power ultrasonics or removal of surface accretions using structural waves. In this paper we present a wave-based technique for modelling waveguides equipped with piezoelectric actuators in which there is no need for common simplifications regarding their dynamic behaviour or mutual interaction with the structure. The proposed approach is based on the semi-analytical finite element (SAFE) method. We developed a new piezoelectric semi-analytical element and employed the analytical wave approach to model the distributed electric excitation and scattering of the waves at discontinuities. The model is successfully validated against an experiment on a beam-like waveguide with emulated anechoic terminations.

  7. 40 CFR 1065.369 - H2O, CO, and CO2 interference verification for photoacoustic alcohol analyzers.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...and CO2 interference verification for photoacoustic alcohol analyzers. 1065.369 ...and CO2 interference verification for photoacoustic alcohol analyzers. (a) Scope and...measure ethanol or methanol using a photoacoustic analyzer, verify the amount of...

  8. Quantitative photoacoustic depth profilometry of magnetic field-induced thermal diffusivity inhomogeneity in the liquid crystal octylcyanobiphenyl

    E-print Network

    Mandelis, Andreas

    Quantitative photoacoustic depth profilometry of magnetic field-induced thermal diffusivity inhomogeneity in the liquid crystal octylcyanobiphenyl Andreas Mandelisa) Photoacoustic and Photothermal, Department of Physics, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium Samuel B. Paralta Photoacoustic

  9. Bulk-wave and guided-wave photoacoustic evaluation of the mechanical properties of aluminum/silicon nitride double-layer thin films.

    PubMed

    Zhang, Feifei; Krishnaswamy, Sridhar; Lilley, Carmen M

    2006-12-01

    The development of devices made of micro- and nano-structured thin film materials has resulted in the need for advanced measurement techniques to characterize their mechanical properties. Photoacoustic techniques, which use pulsed laser irradiation to nondestructively induce very high frequency ultrasound in a test object via rapid thermal expansion, are suitable for nondestructive and non-contact evaluation of thin films. In this paper, we compare two photoacoustic techniques to characterize the mechanical parameters of edge-supported aluminum and silicon nitride double-layer thin films. The elastic properties and residual stresses in such films affect their mechanical performance. In a first set of experiments, a femtosecond transient pump-probe technique is used to investigate the Young's moduli of the aluminum and silicon nitride layers by launching ultra-high frequency bulk acoustic waves in the films. The measured transient signals are compared with simulated transient thermoelastic signals in multi-layer structures, and the elastic moduli are determined. Independent pump-probe tests on silicon substrate-supported region and unsupported region are in good agreement. In a second set of experiments, dispersion curves of the A(0) mode of the Lamb waves that propagate along the unsupported films are measured using a broadband photoacoustic guided-wave method. The residual stresses and flexural rigidities for the same set of double-layer membranes are determined from these dispersion curves. Comparisons of the results obtained by the two photoacoustic techniques are made and discussed. PMID:16899268

  10. 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

  11. Shear piezoelectricity of optically active polysuccinimides

    NASA Astrophysics Data System (ADS)

    Tanimoto, Kazuhiro; Saihara, Shota; Adachi, Yu; Harada, Yuhei; Shiomi, Yuki; Tajitsu, Yoshiro

    2015-10-01

    Optically active crystalline polymers have shear piezoelectricity owing to their asymmetric crystal structure. In this study, to explore a novel shear piezoelectric polymer, we have focused on an imide ring structure and synthesized optically active polysuccinimides (PSIs), the minimum structure of optically active polyimides. As a result, optically active PSIs were obtained, and we observed that oriented optically active PSI films show shear piezoelectricity. Furthermore, both optical purity and molecular weight are significant factors in piezoelectric performance. This is the first report of the shear piezoelectricity of optically active polyimides, and we identify herein a novel category of a shear piezoelectric polymer.

  12. Report on a simultaneous ion viscosity, strain and impedance measurement technique using a novel integrated dielectric, optical fiber and piezoelectric sensing element for the online characterization of smart structures

    NASA Astrophysics Data System (ADS)

    Talaie, A.; Kosaka, T.; Oshima, N.; Osaka, K.; Asano, Y.; Fukuda, T.

    2001-04-01

    This paper reports on a simultaneous ion viscosity, strain and impedance (SISI) system in order to measure the physical and chemical properties of composites during their curing process. The SISI system uses an integrated multi-sensing element, entitled DOP, that is comprised of dielectric (D), optical fiber (O) and piezoelectric (P) sensors. This system was used to measure several data simultaneously in real time and in situ. The results clearly show that there is a direct relationship between the ion viscosity, impedance and strain changes during the curing process. It was found that dielectric sensor is very sensitive to physical and chemical changes of the composite both in the heating and cross-linking periods. The piezoelectric proved to be a useful element during the heating period with a very sensitive and surprising behavior during the cooling period. The optical fiber also demonstrated a very striking profile in strain variations during cooling.

  13. 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

  14. Alternative Method to Characterize Corn Grain by Means of Photoacoustic Spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  15. 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

  16. 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.

  17. Improving visibility in photoacoustic imaging using dynamic speckle illumination

    E-print Network

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

    2013-01-01

    In high-frequency photoacoustic imaging with uniform illumination, homogenous photo-absorbing structures may be invisible because of their large size or limited-view issues. Here we show that it is possible to reveal features, which are normally invisible with a photoacoustic system comprised of a 20MHz linear ultrasound array, by exploiting dynamic speckle illumination. We demonstrate imaging of a \\emptyset 5mm absorbing cylinder and a 30 \\mu m black thread arranged in a complex shape. The hidden structures are directly retrieved from photoacoustic images recorded for different random speckle illuminations of the phantoms by assessing the variation in the value of each pixel over the illumination patterns.

  18. Photon-phonon synergy: photoacoustic tomography and beyond (Presentation Video)

    NASA Astrophysics Data System (ADS)

    Wang, Lihong V.

    2015-03-01

    Photoacoustic tomography is expected to impact biology and medicine broadly by providing multiscale in vivo functional and molecular imaging of structures ranging from subcellular organelles to organs, enabling a noninvasive look at subcutaneous tissue at a deep level. Lihong Wang holds the Gene K. Beare Distinguished Professorship of Biomedical Engineering at Washington University in St. Louis, and is Editor-in-Chief of the Journal of Biomedical Optics. Wang was awarded the 2015 Britton Chance Biomedical Optics Award for his pioneering technical contributions and visionary leadership in the development and application of photoacoustic tomography, photoacoustic microscopy, and photon transport modeling.

  19. Photoacoustic Soot Spectrometer (PASS) Instrument Handbook

    SciTech Connect

    Dubey, M; Springston, S; Koontz, A; Aiken, A

    2013-01-17

    The photoacoustic soot spectrometer (PASS) measures light absorption by aerosol particles. As the particles pass through a laser beam, the absorbed energy heats the particles and in turn the surrounding air, which sets off a pressure wave that can be detected by a microphone. The PASS instruments deployed by ARM can also simultaneously measure the scattered laser light at three wavelengths and therefore provide a direct measure of the single-scattering albedo. The Operator Manual for the PASS-3100 is included here with the permission of Droplet Measurement Technologies, the instrument’s manufacturer.

  20. Micro-optical-mechanical system photoacoustic spectrometer

    DOEpatents

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

    2013-01-01

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

  1. Mathematics of Photoacoustic and Thermoacoustic Tomography

    E-print Network

    Kuchment, Peter

    2009-01-01

    This is the manuscript of the chapter for a planned Handbook of Mathematical Methods in Imaging that surveys the mathematical models, problems, and algorithms of the Thermoacoustic (TAT) and Photoacoustic (PAT) Tomography. TAT and PAT represent probably the most developed of the several novel ``hybrid'' methods of medical imaging. These new modalities combine different physical types of waves (electromagnetic and acoustic in case of TAT and PAT) in such a way that the resolution and contrast of the resulting method are much higher than those achievable using only acoustic or electromagnetic measurements.

  2. Mathematics of Photoacoustic and Thermoacoustic Tomography

    E-print Network

    Peter Kuchment; Leonid Kunyansky

    2009-12-10

    This is the manuscript of the chapter for a planned Handbook of Mathematical Methods in Imaging that surveys the mathematical models, problems, and algorithms of the Thermoacoustic (TAT) and Photoacoustic (PAT) Tomography. TAT and PAT represent probably the most developed of the several novel ``hybrid'' methods of medical imaging. These new modalities combine different physical types of waves (electromagnetic and acoustic in case of TAT and PAT) in such a way that the resolution and contrast of the resulting method are much higher than those achievable using only acoustic or electromagnetic measurements.

  3. 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.

  4. 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.

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

    E-print Network

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

    2011-10-27

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

  6. 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.

  7. An adaptive piezoelectric vibration absorber enhanced by a negative capacitance applied to a shell structure

    NASA Astrophysics Data System (ADS)

    Gripp, J. A. B.; Góes, L. C. S.; Heuss, O.; Scinocca, F.

    2015-12-01

    Piezoelectric shunt damping is a well-known technique to damp mechanical vibrations of a structure, using a piezoelectric transducer to convert mechanical vibration energy into electrical energy, which is dissipated in an electrical resistance. Resonant shunts consisting of a resistance and an inductance connected to a piezoelectric transducer are used to damp structural vibrations in narrow frequency bands, but their performance is very sensitive to variations in structural modal frequencies and transducer capacitance. In order to overcome this drawback, a piezoelectric shunt damping technique with improved performance and robustness is presented in this paper. The design of the adaptive circuit considers the variation of the host structure’s natural frequency as a project parameter. This paper describes an adaptive resonant piezoelectric vibration absorber enhanced by a synthetic negative capacitance applied to a shell structure. The resonant shunt circuit autonomously adapts its inductance value by comparing the phase difference of the vibration velocity and the current flowing through the shunt circuit. Moreover, a synthetic negative capacitance is added to the shunt circuit to enhance the vibration attenuation provided by the piezoelectric absorber. The circuitry is implemented using analog components. Validation of the proposed method is done by bonding the piezoelectric absorber on a free-formed metallic shell.

  8. Total internal reflection photoacoustic spectroscopy for the detection of ?-hematin

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    Evanescent field sensing methods are currently used to detect many different types of disease markers and biologically important chemicals such as the HER2 breast cancer receptor. Hinoue et al. used Total Internal Reflection Photoacoustic Spectroscopy (TIRPAS) as a method of using the evanescent field to detect an optically opaque dye at a sample interface. Although their methods were successful at detecting dyes, the results at that time did not show a very practical spectroscopic technique, which was due to the less than typical sensitivity of TIRPAS as a spectroscopy modality given the low power (~1 to 2 W) lasers being used. Contrarily, we have used an Nd:YAG laser with a five nanosecond pulse that gives peak power of 1 MW coupled with the TIRPAS system to increase the sensitivity of this technique for biological material sensing. All efforts were focused on the eventual detection of the optically absorbing material, hemozoin, which is created as a byproduct of a malarial infection in blood. We used an optically analogous material, ?-hematin, to determine the potential for detection in the TIRPAS system. In addition, four properties which control the sensitivity were investigated to increase understanding about the sensor's function as a biosensing method.

  9. Science to practice: photoacoustic imaging--can it let us see color and function deep inside the body?

    PubMed

    Mezrich, Reuben

    2010-07-01

    Photoacoustic imaging imparts the ability to distinguish materials according to their differences in optical absorption (ie, their colors) with the high spatial and temporal resolution of ultrasonography (US). Experiments in rats demonstrate the advantages this approach would have in the clinically important application of percutaneous sentinel node biopsy. The incorporation of the technique in a conventional US imaging system gives promise of rapid translation to clinical use. PMID:20574077

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  12. 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. This project was funded by the Department of the Air Force contract FA8651-10-M-0262 as a subcontract from Bennett Aerospace, Inc.

  13. Transurethral light delivery for prostate photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Lediju Bell, Muyinatu A.; Guo, Xiaoyu; Song, Danny Y.; Boctor, Emad M.

    2015-03-01

    Photoacoustic imaging has broad clinical potential to enhance prostate cancer detection and treatment, yet it is challenged by the lack of minimally invasive, deeply penetrating light delivery methods that provide sufficient visualization of targets (e.g., tumors, contrast agents, brachytherapy seeds). We constructed a side-firing fiber prototype for transurethral photoacoustic imaging of prostates with a dual-array (linear and curvilinear) transrectal ultrasound probe. A method to calculate the surface area and, thereby, estimate the laser fluence at this fiber tip was derived, validated, applied to various design parameters, and used as an input to three-dimensional Monte Carlo simulations. Brachytherapy seeds implanted in phantom, ex vivo, and in vivo canine prostates at radial distances of 5 to 30 mm from the urethra were imaged with the fiber prototype transmitting 1064 nm wavelength light with 2 to 8 mJ pulse energy. Prebeamformed images were displayed in real time at a rate of 3 to 5 frames per second to guide fiber placement and beamformed offline. A conventional delay-and-sum beamformer provided decreasing seed contrast (23 to 9 dB) with increasing urethra-to-target distance, while the short-lag spatial coherence beamformer provided improved and relatively constant seed contrast (28 to 32 dB) regardless of distance, thus improving multitarget visualization in single and combined curvilinear images acquired with the fiber rotating and the probe fixed. The proposed light delivery and beamforming methods promise to improve key prostate cancer detection and treatment strategies.

  14. Using phase in FTIR photoacoustic spectrometry

    SciTech Connect

    Jones, R.W.; McClelland, J.F.

    1994-12-31

    FTIR spectrometers with phase modulation capabilities make the phase of a photoacoustic signal much more accessible than previously, because all wavelengths are modulated synchronously. The commercial advent of such spectrometers has therefore heightened interest in using photoacoustic phase in depth profiling. The phase delay of the signal increases as the depth at which absorption occurs within a sample increases. The phase behavior in structured samples will be examined. In simple cases, the ordering, identity and thickness of layers in a discretely layered sample can be straightforwardly determined from the phase shifts among spectrum peaks. Complications arise in more complex cases, some of which will be discussed. In principle, the same approach may be used with rapid-scan FTIR spectrometers, but the application is much more difficult since modulation of different wavelengths is no longer synchronous. In addition, background signals interfere with determining phase at the higher rapid scan velocities. Nevertheless, when possible, using phase with rapid scan spectra can assist in depth profiling and reduce saturation in spectra. Examples will be discussed.

  15. Advanced laser systems for photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Klosner, Marc; Sampathkumar, Ashwin; Chan, Gary; Wu, Chunbai; Gross, Daniel; Heller, Donald F.

    2015-03-01

    We describe the ongoing development of laser systems for advanced photoacoustic imaging (PAI). We discuss the characteristics of these laser systems and their particular benefits for soft tissue imaging and next-generation breast cancer diagnostics. We provide an overview of laser performance and compare this with other laser systems that have been used for early-stage development of PAI. These advanced systems feature higher pulse energy output at clinically relevant repetition rates, as well as a novel wavelength-cycling output pulse format. Wavelength cycling provides pulse sequences for which the output repeatedly alternates between two wavelengths that provide differential imaging. This capability improves co-registration of captured differential images. We present imaging results of phantoms obtained with a commercial ultrasound detector system and a wavelength-cycling laser source providing ~500 mJ/pulse at 755 and 797 nm, operating at 25 Hz. The results include photoacoustic images and corresponding pulse-echo data from a tissue mimicking phantom containing inclusions, simulating tumors in the breast. We discuss the application of these systems to the contrast-enhanced detection of various tissue types and tumors.

  16. 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.

  17. Deep penetrating photoacoustic tomography in biological tissues

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

    Photoacoustic tomography (PAT) in a circular scanning configuration was developed to image the deeply embedded optical heterogeneity in biological tissues. Based on the intrinsic contrast between blood and chicken breast muscle, an embedded blood object that was 5 cm deep in the tissue was detected using pulsed laser light at a wavelength of 1064 nm. Compared with detectors for flat active surfaces, cylindrically focused ultrasonic transducers can reduce the interference generated from the off-plane photoacoustic sources and make the image in the scanning plane clearer. While the optical penetration was optimized with near-infrared laser pulses of 800 nm in wavelength, the optical contrast was enhanced by indocyanine green (ICG) whose absorption peak matched the laser wavelength. This optimized PAT was able to image fine objects embedded at a depth of up to 5.2-cm, which is 6.2 times the 1/e optical penetration depth, in chicken breast muscle, at a resolution of < ~750 microns with a sensitivity of <7 pmol of ICG in blood. The resolution was found to deteriorate slowly with increasing imaging depth.

  18. Polymer Piezoelectric Transducers for Ultrasonic NDE

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Xue, Tianji; Lih, Shyh-Shiuh

    1996-01-01

    Piezoelectric polymers are associated with a low noise and inherent damping that makes them very effective receivers as well as broadband transmitters for high frequencies tasks. This paper reviews polymer piezoelectric materials, the origin of their piezoelectric behavior and their applications to ultrasonic NDE.

  19. Modeling and Driving Piezoelectric Resonant Blade Elements

    E-print Network

    and in particular to the group that utilize the piezoelectric effect to generate motion such as motors and actuatorsModeling and Driving Piezoelectric Resonant Blade Elements Sam Ben-Yaakov* and Natan Krihely Power@ee.bgu.ac.il ; Website: http://www.ee.bgu.ac.il/~pel Abstract-- Piezoelectric Resonant Blade elements (PRB) are useful

  20. 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

    2015-04-11

    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