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

    2014-07-01

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

  2. High-frequency differential piezoelectric photoacoustic investigation of ion-implanted (100) silicon wafers via laser beam position modulation.

    PubMed

    Zuccon, J F; Mandelis, A

    1988-01-01

    An exploratory application of position-modulation photoacoustic imaging of ion-implanted (100)-oriented Si wafers was undertaken to assess its potential as a diagnostic probe in semiconductor processing. Wafer scans were performed using acoustooptic modulation of a 1.06-mum Nd(3+):YAG laser beam up to 0.2 MHz with piezoelectric photoacoustic detection. Sensitivity ranges to ion-implanted parameters (ionic species and fluences) were studied and the capability of the technique to monitor processing-induced damage was established. Results indicate that position-modulated photoacoustic detection offers higher sensitivity than single-beam photothermal imaging and has distinct advantages over other analytical techniques. PMID:18290123

  3. The features of photoacoustic spectra of Cds and GaAs under piezoelectric detection

    NASA Astrophysics Data System (ADS)

    Bulakh, G. I.; Volchanski, O. V.; Kucherov, I. Ya.

    1992-03-01

    To study the influence of unmodulated additional illumination on photoacoustic spectra of piezosemiconductor compounds, the photoacoustic spectroscopy using piezoelectric and gas-microphone detections has been applied in this work to CdS and GaAs crystals. The dependence of photoacoustic signal have been investigated both on modulated radiation wavelength and additional illumination wavelength (so called secondary photoacoustic spectrum). It is shown that the features of photoacoustic spectra of piezosemiconductor compounds arise due to additional non-thermoelastic component of photoacoustic signal. The latter is generated by alternating photovoltage via inverse piezoeffect in the samples under study and can be suppressed by additional illumination.

  4. Non-destructive Imaging of Standard Cracks of Railway by Photoacoustic Piezoelectric Technology

    NASA Astrophysics Data System (ADS)

    Yan, Laijun; Gao, Chunming; Zhao, Binxing; Ma, Xingchen; Zhuang, Nan; Duan, Haiyang

    2012-11-01

    The photoacoustic piezoelectric (PAPE) technique is an effective non-destructive testing technique for detecting defects in materials. In this paper, Chinese national standard railway cracks have been detected by thermal wave imaging based on the PAPE technique. First, the theory of the PAPE technique has been introduced and the corresponding imaging principle has been analyzed. Second, the corresponding experimental system has been setup, and the imaging tests have been carried out. Third, two kinds of standard cracks have been examined by the imaging system. The results show that thermal wave imaging based on the PAPE technique can effectively image and identify the cracks at different depths, which lays a foundation for practical application to the detection of rail cracks.

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

    Microsoft Academic Search

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

    2010-01-01

    We built a photoacoustic tomographic (PAT) imaging system by scanning a single detector (phi 3.5 mm) made of piezoelectric copolymer poly(vinylidene difluoride-trifluoroethylene), P(VDF-TrFE), which had been fabricated for diagnostic photoacoustic measurement of cartilage tissues in our group. The PAT images of a phantom were obtained at two excitation wavelength of 687.5 nm and 795 nm. The phantom was made of

  6. 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.

  7. Thermal Effusivity Measurement of Virgin Coconut Oil-Methanol Mixtures using Photoacoustic Technique

    Microsoft Academic Search

    Firas Kamel; Mohamad Al-asfoor; W. Mahmood; Mat Yunus; Azmi Zakaria

    2008-01-01

    Thermal effusivity of virgin coconut oil-methanol mixtures were measured using open photoacoustic cell technique. The samples were prepared by simply mixing virgin coconut oil and methanol using similar procedure applied for preparation of biodisel. Thermal effusivity of the sample was obtained by fitting the experimental data of photoacoustic amplitude signal to the expression of photoacoustic signal as a function of

  8. 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.

  9. Simultaneous photoacoustic imaging technique using an acoustic imaging lens

    Microsoft Academic Search

    Xian Chen; Zhilie Tang; Yongheng He; Haifeng Liu; Yadong Wei; Yongbo Wu

    2009-01-01

    A simultaneous photoacoustic (PA) tomography imaging technique in multilayer samples was developed. Instead of using the PA image reconstruction methods on the basis of complex algorithms, obtaining a two-dimensional PA image in real time is available by using an acoustic lens that has the ability of parallel imaging. The imaging system can acquire the complete PA signals of high signal-to-noise

  10. Photoacoustic microscopy achieved by microcavity synchronous parallel acquisition technique.

    PubMed

    Tan, Zhiliang; Liao, Yanfei; Wu, Yongbo; Tang, Zhilie; Wang, Ruikang K

    2012-02-27

    We report on a sub-cellular resolution photoacoustic microscopy (PAM) system that employs microcavity synchronous parallel acquisition technique for detecting the weak photoacoustic (PA) signal excited by a modulated continuous wave (CW) laser source. The gas microcavity transducer is developed based on the fact that the bulk modulus of the gas is far less than the solid and the change of the air-gas pressure is inversely proportional to the gas volume, making it extremely sensitive to the tiny PA pressure wave. Besides, considering PA wave expends in various directions, detecting PA signals from different position and adding them together can increase the detecting sensitivity and the signal to noise ratio(SNR), then we employs two microphone to acquire PA wave synchronously and parallelly. We show that the developed PAM system is capable of label-free imaging and differentiating of the hemoglobin distribution within single red blood cells under normal and anemia conditions. PMID:22418386

  11. The piezoelectric sorption technique: a practical method

    E-print Network

    Flipse, Eugene Charles

    1983-01-01

    THE PIEZOELECTRIC SORPTION TECHNIQUE, A PRACTICAL METHOD A Thesis by EUGENE CHARLES FLIPSE Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 1983... Major Subject: Chemical Engineering THE PI E ZOELECTRI C SORPTI ON TECHNI QUE, A PRACTICAL METHOD A Thesis by EUGENE CHARLES FLIPSE Approved as to style and content by: J. C. Holste (Chairman of Committee) C. J. Glover (Member) K. Lou (Member...

  12. Simultaneous photoacoustic imaging technique using an acoustic imaging lens.

    PubMed

    Chen, Xian; Tang, Zhilie; He, Yongheng; Liu, Haifeng; Wei, Yadong; Wu, Yongbo

    2009-01-01

    A simultaneous photoacoustic (PA) tomography imaging technique in multilayer samples was developed. Instead of using the PA image reconstruction methods on the basis of complex algorithms, obtaining a two-dimensional PA image in real time is available by using an acoustic lens that has the ability of parallel imaging. The imaging system can acquire the complete PA signals of high signal-to-noise ratio from all the object planes by utilizing the advantages of the acoustic lens with long focal depth and a fast data acquisition system with a high sampling rate. With the time-resolved technique, the PA signals from different object planes can be distinguished and then the high optical contrast multilayer PA images can be reconstructed simultaneously without any algorithms. The experimental results show that the reconstructed sections agree well with the original samples. PMID:19566292

  13. 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.

  14. Piezoelectric Energy Harvesting using a Synchronized Switch Technique

    Microsoft Academic Search

    Adrien Badel; Daniel Guyomar; Elie Lefeuvre; Claude Richard

    2006-01-01

    This article describes a new approach to harvest electrical energy from a mechanically excited structure equipped with piezoelectric elements. Standard harvesting circuits using piezoelectric elements as an electric generator consist of an AC-DC converter coupled to a load. The technique proposed herein is fully compatible with the standard approach. The difference consists in adding up an electrical switching device connected

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  16. 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.

  17. 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

  18. 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.

  19. The thermoelastic bending and thermal diffusion processes influence on photoacoustic signal generation using open photoacoustic cell technique

    NASA Astrophysics Data System (ADS)

    Somer, A.; Camilotti, F.; Costa, G. F.; Bonardi, C.; Novatski, A.; Andrade, A. V. C.; Kozlowski, V. A.; Cruz, G. K.

    2013-08-01

    Thermal diffusion and thermoelastic bending are two consequences of heating generated on the sample surface. Both are employed in Open Photoacoustic Cell (OPC) technique to measure the thermal diffusivity of the sample. In this work, we explore the potential use of the OPC technique to study the effectiveness of thermoelastic bending process and thermal diffusion process on photoacoustic signal (S) generation in solids. More specifically, it is observed that if the thermoelastic bending process becomes more effective while the sample thickness is decreased, this information can be used to obtain a method to self-check the value of the thermal diffusivity parameter measured. The method is based on the measurement of the thermoelastic bending parameter as a function of the sample thickness (ls). The expected dependence of the thermoelastic bending parameter (C2) with the sample thickness, according to the theoretical model, is C2 ? ls-3. Our results for aluminum metallic samples give a C2 ? ls-2.8 dependence. Also, a thermal diffusivity value of ?exp = (8.4 ± 0.3) × 10-5 m2/s was measured for metallic aluminum. This value is in good agreement when compared with the theoretical value ?Al = 8.6 × 10-5 m2/s.

  20. Experimental study of rotational relaxation processes by pulsed photoacoustic technique

    Microsoft Academic Search

    M. Terzic; J. Jovanovic-Kurepa; D. D. Markusev

    1999-01-01

    The IR pulsed photoacoustic method was used to investigate rotational relaxation processes in MPA. We have examined the bulk rotational relaxation times 0953-4075\\/32\\/5\\/012\\/img4 and the bulk rotational relaxation cross sections 0953-4075\\/32\\/5\\/012\\/img5, related to R-R and R-T relaxation mechanisms. The saturation intensities for 0953-4075\\/32\\/5\\/012\\/img6 gas molecules have been measured in the gas mixtures with 0953-4075\\/32\\/5\\/012\\/img7 (buffer) molecules, at constant 0953-4075\\/32\\/5\\/012\\/img6 gas

  1. 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.

  2. The application of the photoacoustic technique to the measurement of the thermal effusivity of liquids

    NASA Astrophysics Data System (ADS)

    Delgado-Vasallo, O.; Marín, E.

    1999-03-01

    We describe the application of the photoacoustic technique to the thermal characterization of liquids. An experimental method which allows the experimental determination of the thermal effusivity in transparent as well as in light absorbing samples is proposed. The method is tested by measurements in water, ethanol, diffusion-pump oil, glycerol and petroleum. Our results agree quite well with the literature reported values for these samples.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  5. Photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Williams, C. C.; Quate, C. F.

    1984-10-01

    This is the final report on the work done in the area of high resolution photoacoustic and photothermal imaging. It contains recent advances in photoacoustic and photothermal theory and the experimental demonstration of new techiques. Photoacoustic and photothermal theories have been extended to include the effects of the highly focused optical power sources necessary for high resolution imaging and three high frequency techniques (1 GHz) have been demonstrated and used to characterize the material properties of solids. The formalism behind photothermal characterization of solids is established under general focusing conditions. The three dimensional thermoacoustic field equation is derived and discussed. Two high resolution photoacoustic techniques have been demonstrated. These techniques involve the use of an acoustic lens for collection for the acoustic power generated by a highly focused optical beam modulated at 1 GHz frequency. Images of gold and laser recrystallized silicon films are presented demonstrating the high resolution and sensitivity of these techniques. A high resolution photothermal probe has been demonstrated. This optical technique provides a means of photothermal characterization with submicrometer resolution and high sensitivity. The theory behind the probe is presented along with the experimental verification. Images of boron implanted silicon are included which demonstrate the resolution and sensitivity of this technique.

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

    PubMed

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

    2012-03-26

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

  7. 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.

  8. Assessment of speciation techniques including the application of photoacoustic spectroscopy

    SciTech Connect

    Bucher, J.; Gehmecker, H.; Edelstein, N.

    1985-08-01

    This document describes laboratory experiments that compare chromatographic and spectroscopic methods for rapidly characterizing ionic species in detail. These techniques were tested on various radioactive ion systems to develop a rapid, accurate approach to site characterization for use with Remedial Action Programs. Promising techniques were evaluated. 9 refs., 16 figs., 2 tabs.

  9. A novel photoacoustic tomography based on a time-resolved technique and an acoustic lens imaging system

    Microsoft Academic Search

    Yongheng He; Zhilie Tang; Zhanxu Chen; Wei Wan; Jianghua Li

    2006-01-01

    A novel photoacoustic (PA) tomographic method, which is based on a time-resolved technique and an acoustic lens imaging system, is presented in this paper. A YAG laser operating at 532 nm with a 7 ns pulse width and 10 mJ optical pulse is employed as the excitation source to irradiate the tissue. PA signals generated from the tissue are imaged

  10. 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.

  11. 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.

  12. Consideration of Impedance Matching Techniques for Efficient Piezoelectric Energy Harvesting

    Microsoft Academic Search

    Hyeoungwoo Kim; Shashank Priya; Harry Stephanou; Kenji Uchino

    2007-01-01

    This study investigates multiple levels of impedance-matching methods for piezoelectric energy harvesting in order to enhance the conversion of mechanical to electrical energy. First, the transduction rate was improved by using a high piezoelectric voltage constant (g) ceramic material having a magnitude of g33 = 40 times 10-3 V m\\/N. Second, a transducer structure, cymbal, was optimized and fabricated to

  13. 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.

  14. 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

  15. Development of novel piezoelectric composites by solid freeform fabrication techniques

    NASA Astrophysics Data System (ADS)

    Panda, Rajesh Kumar

    Piezoelectric ceramic/polymer composites have been widely used for ultrasonic transducers because of their superior properties as compared to bulk piezoceramics or polymers. The electromechanical Properties of the composites can be tailored for various applications by changing the design and connectivity of the piezoceramic skeleton. The goal of this project was to utilize the design flexibility provided by solid freeform fabrication (SFF) techniques to manufacture complex PZT composite transducers for ultrasonic medical imaging applications. The ceramic element shape, size and spatial arrangement could be varied easily; by changing the parameters in the input computer aided design file. Many SFF techniques, including fused deposition modeling (FDM), fused deposition of ceramics (FDC), and Sanders prototyping (SP) were used to fabricate a variety of novel PZT structures. The composites were processed either by a direct, indirect or multiple mold route. In the direct route (FDC), green ceramic preforms were produced from 52 vol.% PZT-5H ceramic loaded polymer filaments. A lost mold technique was used for the indirect and multiple mold routes (SP, FDM). After heat treatment, the sintered PZT skeletons were backfilled with epoxy, polished, electroded and corona poled. A variety of novel and complex designs such as 3-D Honeycomb, 3-D Mesh, ladder, oriented fibers, 1-3 regular and staggered rods, and other composites including concentric polygon, hexagonal patterns, and 2-2 sheets with and without volume fraction gradient (VFG) were fabricated. The 3-D Honeycomb structures with a 3-3 connectivity showed d33 coefficients as high as 340 pC/N. The ladder structure exhibited distinctly different properties when poled along different directions. One of them, i.e. the oriented 3-3 fiber structure was believed to utilize the d33, d31 and d15 coefficients to show an effective d33 of 510 pC/N. VFG composites were fabricated to achieve a reduction the side and grating lobe intensities in medical imaging transducers, by decreasing the pressure output of the edges. A variety of mathematical distributions including gaussian, linear, and exponential were produced. Using them it was possible to precisely control the vibration amplitude according to the defined gradient. Finite element simulations predicted a linear gradient to show reduced (-42 dB as compared to -30 dB for regular) side lobes intensities.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    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.

  17. 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

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

    Microsoft Academic Search

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

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

  19. Comparative study of optical coherence tomography, photoacoustic technique, and time-of-flight technique in phantom measurements

    NASA Astrophysics Data System (ADS)

    Kinnunen, Matti; Myllylä, Risto

    2006-08-01

    of biomedical imaging techniques, the optical coherence tomography (OCT), photoacoustic (PA) and time-of-flight (TOF) techniques are among the most researched and, consequently, increasingly broadly applied. This article reviews their basic principles, compares their technical aspects and discusses their ability to determine optical parameters. Also studied is their applicability to non-invasive glucose monitoring in Intralipid TM phantom measurements, followed by a discussion of some detected problems. Although suffering from a limited probing depth, OCT was found to have the best capacity for detecting changes in the light scattering properties of Intralipid TM. Photon migration studies with the TOF technique showed changes in pulse amplitude, pulse width and arrival time of the pulse maximum as a function of changes in Intralipid TM concentration, whereas the sensitivity of the PA technique for detecting changes in scattering was less pronounced. However, each technique showed changes in the registered signals when measuring large glucose concentrations in Intralipid TM phantoms. Measurement results were also affected by the varying measurement geometries and the photon energies of the light sources.

  20. Multi-contrast Photoacoustic Microscopy

    NASA Astrophysics Data System (ADS)

    Yao, Junjie

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

  1. In vivo measurement of human skin absorption of topically applied substances by a photoacoustic technique.

    PubMed

    Gutiérrez-Juárez, G; Vargas-Luna, M; Córdova, T; Varela, J B; Bernal-Alvarado, J J; Sosa, M

    2002-08-01

    A photoacoustic technique is used for studying topically applied substance absorption in human skin. The proposed method utilizes a double-chamber PA cell. The absorption determination was obtained through the measurement of the thermal effusivity of the binary system substance-skin. The theoretical model assumes that the effective thermal effusivity of the binary system corresponds to that of a two-phase system. Experimental applications of the method employed different substances of topical application in different parts of the body of a volunteer. The method is demonstrated to be an easily used non-invasive technique for dermatology research. The relative concentrations as a function of time of substances such as ketoconazol and sunscreen were determined by fitting a sigmoidal function to the data, while an exponential function corresponds to the best fit for the set of data for nitrofurazona, vaseline and vaporub. The time constants associated with the rates of absorption, were found to vary in the range between 10 and 58 min, depending on the substance and the part of the body. PMID:12214760

  2. A new fabrication method for microactuators with piezoelectric thin film using precision cutting technique

    Microsoft Academic Search

    Y. Yamagata; S. Mihara; N. Nishioki; T. Higuchi

    1996-01-01

    A new fabrication method for microactuators and microstructures is presented. It is based on a precision cutting technique and hydrothermal method to make piezoelectric thin film. It is generally considered that the cutting technique is not suitable for microparts fabrication because the cutting force is too large compared to the size of the structure. The authors have used a four

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

    PubMed

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

    2010-01-01

    A photoacoustic imaging system that incorporates a commercial ultrasonic camera for real-time imaging of two-dimensional (2-D) projection planes in tissue at video rate (30 Hz) is presented. The system uses a Q-switched frequency-doubled Nd:YAG pulsed laser for photoacoustic generation. The ultrasonic camera consists of a 2-D 12 x 12 mm CCD chip with 120 x 120 piezoelectric sensing elements used for detecting the photoacoustic pressure distribution radiated from the target. An ultrasonic lens system is placed in front of the chip to collect the incoming photoacoustic waves, providing the ability for focusing and imaging at different depths. Compared with other existing photoacoustic imaging techniques, the camera-based system is attractive because it is relatively inexpensive and compact, and it can be tailored for real-time clinical imaging applications. Experimental results detailing the real-time photoacoustic imaging of rubber strings and buried absorbing targets in chicken breast tissue are presented, and the spatial resolution of the system is quantified. PMID:20459240

  4. Photoacoustic imaging

    Microsoft Academic Search

    C. C. Williams; C. F. Quate

    1984-01-01

    This is the final report on the work done in the area of high resolution photoacoustic and photothermal imaging. It contains recent advances in photoacoustic and photothermal theory and the experimental demonstration of new techiques. Photoacoustic and photothermal theories have been extended to include the effects of the highly focused optical power sources necessary for high resolution imaging and three

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  7. 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

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

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  9. 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

  10. 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

  11. A novel photoacoustic tomography based on a time-resolved technique and an acoustic lens imaging system.

    PubMed

    He, Yongheng; Tang, Zhilie; Chen, Zhanxu; Wan, Wei; Li, Jianghua

    2006-05-21

    A novel photoacoustic (PA) tomographic method, which is based on a time-resolved technique and an acoustic lens imaging system, is presented in this paper. A YAG laser operating at 532 nm with a 7 ns pulse width and 10 mJ optical pulse is employed as the excitation source to irradiate the tissue. PA signals generated from the tissue are imaged onto a multi-element linear array transducer with an acoustic lens. A 64 electronic switch is efficiently used for changing the parallel PA signals into a series. The proposed method directly provides PA images without any complex reconstruction algorithms. With the time-resolved technique, tomographic imaging can be achieved successfully. The results show that the images agree well with the original samples. PMID:16675875

  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.

    PubMed

    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. PMID:25933886

  14. 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.

  15. Grueneisen relaxation photoacoustic microscopy

    PubMed Central

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

    2014-01-01

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

  16. 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

  17. 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.

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

    SciTech Connect

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

    2010-05-15

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

  19. 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

  20. Photoacoustic effect induced by negative luminescence device

    NASA Astrophysics Data System (ADS)

    Kuusela, T.; Peura, J.; Matveev, B. A.; Remennyy, M. A.; Stus', N. M.

    2010-07-01

    The cantilever enhanced photoacoustic trace gas detection technique has been combined with mid-infrared light emitting diodes (LEDs) producing significant negative luminescence at a reverse bias. In contrast to normal positive photoacoustic phenomenon the negative luminescence of the LED creates wavelength specific cooling of the gas under study and pressure drop in the photoacoustic sample cell, which can be detected by a cantilever microphone. In experiments a LED operating at 5.5 ?m wavelength range was used to detect acetone vapor.

  1. 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

  2. Optical-resolution photoacoustic endomicroscopy in vivo.

    PubMed

    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

    2015-03-01

    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

  3. 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

  4. 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.

  5. Photoacoustic imaging with integrating line detectors

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

    Photoacoustic Tomography is an emerging imaging technology mainly for medical and biological applications. A sample is illuminated by a short laser pulse. Depending on the optical properties the electromagnetic radiation is distributed and absorbed. Thereby local temperature increase generates thermal expansion and broadband ultrasonic signals, also called photoacoustic signals. Unlike conventional ultrasound in photoacoustic imaging the contrast depends on the optical properties of the sample which provides not only morphologic information but also functional information. This way photoacoustic imaging combines the advantages of optical imaging (high contrast) and ultrasonic imaging (high spatial resolution) and is particularly suited for medical applications like mammography or skin cancer detection. Our group uses integrating line detectors instead of ultrasonic point receivers. Line detectors integrate the pressure along one dimension whereby the 3D problem is reduced to a 2D problem and enables a tomography setup that requires only a single axis of rotation. Implementations of line detectors use optical interferometers, e.g. a Fabry-Perot interferometer or a Mach-Zehnder interferometer. We use free-beam interferometers as well as fiber-based interferometers for collecting photoacoustic signals. The latter are somewhat easier to handle because they require fewer optical components. Finally, the advantages of optical detection methods over piezoelectric detection methods are the better frequency response and the resistance against electrical interference from the environment. First measurements on phantoms and image reconstruction using a time reversal method demonstrated the capability of integrating line detectors for collecting broadband ultrasonic signals for photoacoustic tomography.

  6. Miniaturization and integration of photoacoustic detection

    NASA Astrophysics Data System (ADS)

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

    2002-08-01

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

  7. Photoacoustic computed microscopy

    PubMed Central

    Yao, Lei; Xi, Lei; Jiang, Huabei

    2014-01-01

    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. PMID:24828539

  8. 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.

  9. 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.

  10. 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

  11. Photoacoustic cystography.

    PubMed

    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/cm(2) (1/20 of the safety limit), our current imaging system could map the methylene-blue-filled-rat-bladder at the depth of beyond 1 cm in biological tissues in vivo. Both in vivo and ex vivo PA imaging results validate that the contrast agents were naturally excreted via urination. Thus, there is no concern regarding long-term toxic agent accumulation, which will facilitate clinical translation. PMID:23792925

  12. Pure optical photoacoustic microscopy

    PubMed Central

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

    2011-01-01

    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 3.0×105 was achieved which provided high sensitivity with a noise equivalent detectable pressure(NEDP) value of 29Pa. This NEDP is much lower than the hundreds of Pascals achieved with existing optical resonant structures such as etalons, fiber gratings and dielectric multilayer interference filters available for acoustic measurement. The featured high sensitivity allowed the microring resonator to detect the weak photoacoustic signals from micro- or submicroscale objects. The inherent superbroad bandwidth of the optical microring resonator combined with an optically focused scanning beam provided POPAM 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

  13. 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.

  14. Photoacoustic Tomography of the Brain

    NASA Astrophysics Data System (ADS)

    Xia, Jun; Wang, Lihong V.

    Photoacoustic tomography (PAT) is an emerging hybrid imaging technique with great potential for a wide range of brain imaging applications. A unique feature of PAT is the capability of sensing optical contrasts ultrasonically. Because of the low ultrasonic scattering in tissue, PAT generates high resolution images in both the ballistic and diffusive regimes. With a rich choice of endogenous and exogenous optical contrasts, PAT can provide neurovascular, structural, functional, and molecular brain images at multiple spatial scales. In this chapter, we review the principles and imaging capability of various photoacoustic brain tomography systems and highlight studies published in the past few years.

  15. 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.

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

    E-print Network

    Wang, Lihong

    an optical fiber to the scanning head and uses a photodiode to calibrate the laser energy. The laser beam, although the optical focus is wider. The ring shaped pattern is intended to reduce the photoacoustic effect technique measures optical contrast based on physiological parameters, such as the total hemoglobin

  17. A fiber optic optoacoustic ultrasound sensor for photoacoustic endoscopy

    Microsoft Academic Search

    Clay Sheaff; Shai Ashkenazi

    2010-01-01

    Photoacoustic Endoscopy (PE) is a new imaging modality that can provide high-resolution vascular imaging in vivo. Optoacoustic sensing (optical detection of ultrasound) is a good candidate for PE due to its enhanced sensitivity, wide bandwidth, and miniaturizability in comparison to piezoelectric, PVDF, and capacitive transducers. In this work we present the fabrication and testing of a fiber optic optoacoustic ultrasound

  18. Features of photoacoustic transformation in microporous nanocrystalline silicon

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  19. Prospects of photoacoustic tomography.

    PubMed

    Wang, Lihong V

    2008-12-01

    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 (approximately 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

  20. Piezoelectric BNT-BT 0.11 thin films processed by sol–gel technique

    Microsoft Academic Search

    Marin CerneaAurelian; Aurelian Catalin Galca; Marius Cristian Cioangher; Cristina Dragoi; Gelu Ioncea

    2011-01-01

    0.89(Na0.5Bi0.5)TiO3–0.11BaTiO3, (BNT-BT0.11) thin film was fabricated by sol–gel\\/spin coating process, on platinized silicon wafer. Perovskite structure with random\\u000a orientation of crystallites has been obtained at 700 °C. Piezoelectric activity of BNT-BT0.11 thin film was detected using piezoresponse force microscopy (PFM). Effective piezoelectric coefficient d\\u000a 33eff of such film, recorded at 5 V applied dc voltage, was ~29 pm\\/V, which is similar to other

  1. 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

  2. Photoacoustic thermography of tissue

    PubMed Central

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

    2014-01-01

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

  3. Transient response optimization of piezoelectric disc transducers by time domain techniques

    Microsoft Academic Search

    H. A. Wolf

    1979-01-01

    Design procedures for reducing the mechanical ringing of piezoelectric disc transducers under impulsive electrical excitation are examined. The transducer was treated as a three port device: the two mechanical ports and one electrical port. Improvements to the transient response were sought through the determination of appropriate matching networks at the ports. The optimization of specified time domain characteristics was accomplished

  4. Photoacoustic imaging of living mouse brain vasculature using hollow gold nanospheres

    E-print Network

    Wang, Lihong

    Toxicity a b s t r a c t Photoacoustic tomography (PAT) also referred to as optoacoustic tomography (OAT than most optical imaging techniques [1­8]. Photoacoustic tomography (PAT) referred to as optoacoustic and ultrasonic imaging methods [6]. PAT detects absorbed photons ultrasonically through the photoacoustic effect

  5. Near infrared photoacoustic detection of sentinel lymph nodes with gold nanobeacons

    Microsoft Academic Search

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

    2010-01-01

    Detection of sentinel lymph node (SLN) using photoacoustic imaging is an emerging technique for noninvasive axillary staging of breast cancer. Due to the absence of intrinsic contrast inside the lymph nodes, exogenous contrast agents are used for photoacoustic detection. In this work, we have demonstrated near infrared detection of SLN with gold nanobeacons (GNBs) providing the photoacoustic contrast in a

  6. 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

  7. 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

  8. 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.

  9. 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

  10. Photo-acoustic devices using (Pb,La)(Zr,Ti)O3 ceramics

    Microsoft Academic Search

    Sheng-Yuan Chu; K. Uchino

    1994-01-01

    Photostriction in ferroelectrics arises from a superposition of photovoltaic and inverse piezoelectric effects. This phenomenon provides promise for photo-acoustic devices, when the response has been sufficiently improved. In this paper, B-site donor doping was investigated in (Pb,La)(Zr,Ti)O3 based ceramics with the aim of improving the response speed. Using a PLZT bimorph configuration, a photoacoustic device was fabricated, and the fundamental

  11. Advances in Clinical and Biomedical Applications of Photoacoustic Imaging

    PubMed Central

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

    2010-01-01

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

  12. Photoacoustic imaging in cancer detection, diagnosis, and treatment guidance

    PubMed Central

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

    2011-01-01

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

  13. 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.

  14. A monitoring technique of piezoelectric impedance analysis used in tea polyphenols (TP) antimutagenic characteristics.

    PubMed

    Tang, Biyu; Wei, Wanzhi; Yin, Jian; Liu, Xiaoyin; Xiang, Hongxia; Kong, Bo

    2007-09-01

    A new method was proposed for studying antimutagenic characteristics of tea polyphenols (TP) using piezoelectric impedance analysis during the Salmonella typhimurium strain TA100 growth process in the presence of mutagen 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (abbreviated NNK). Compared with the general method of antimutagenic investigation, the proposed method provided real-time, multidimensional response information about the antimutagenic characteristics during the bacterial growth process. The results showed that TP was allowed to be antimutagenic at the lowest concentration of 0.25 microg/ml, and the inhibitory effect of TP presented a linear relationship with its dosage in the range of 0.25-2.5 microg/ml. And the relationship between the bacterial growth kinetic parameters and the TP dosage was also obtained. The present method provided a new approach for studying microbial antimutagenic characteristics. PMID:17688962

  15. Thermoacoustic and photoacoustic sensing of temperature.

    PubMed

    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 degrees 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

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. Enhanced photoacoustic detection using photonic crystal substrate

    SciTech Connect

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

    2014-04-21

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

  1. Photoacoustic spectroscopy of ?-hematin

    PubMed Central

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

    2012-01-01

    Malaria affects over 200 million individuals annually, resulting in 800,000 fatalities. Current tests use blood smears and can only detect the disease when 0.1–1% of blood cells are infected. We are investigating the use of photoacoustic flowmetry to sense as few as one infected cell among 10 million or more normal blood cells, thus diagnosing infection before patients become symptomatic. Photoacoustic flowmetry is similar to conventional flow cytometry, except that rare cells are targeted by nanosecond laser pulses to induce ultrasonic responses. This system has been used to detect single melanoma cells in 10 ml of blood. Our objective is to apply photoacoustic flowmetry to detection of the malaria pigment hemozoin, which is a byproduct of parasite-digested hemoglobin in the blood. However, hemozoin is difficult to purify in quantities greater than a milligram, so a synthetic analog, known as ?-hematin was derived from porcine haemin. The specific purpose of this study is to establish the efficacy of using ?-hematin, rather than hemozoin, for photoacoustic measurements. We characterized ?-hematin using UV-vis spectroscopy, TEM, and FTIR, then tested the effects of laser irradiation on the synthetic product. We finally determined its absorption spectrum using photoacoustic excitation. UV-vis spectroscopy verified that ?-hematin was distinctly different from its precursor. TEM analysis confirmed its previously established nanorod shape, and comparison of the FTIR results with published spectroscopy data showed that our product had the distinctive absorbance peaks at 1661 and 1206 cm?1. Also, our research indicated that prolonged irradiation dramatically alters the physical and optical properties of the ?-hematin, resulting in increased absorption at shorter wavelengths. Nevertheless, the photoacoustic absorption spectrum mimicked that generated by UV-vis spectroscopy, which confirms the accuracy of the photoacoustic method and strongly suggests that photoacoustic flowmetry may be used as a tool for diagnosis of malaria infection. PMID:22844576

  2. POWER HARVESTING PIEZOELECTRIC SHUNT DAMPING 1

    E-print Network

    Fleming, Andrew J.

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

  3. Determination of the thermophysical properties of polymers (PET) using photoacoustic spectroscopy

    Microsoft Academic Search

    J. P. Valcárcel M; J. A. Palacios; J. J. Alvarado-Gil

    1999-01-01

    Using photothermal techniques and the Open Photoacoustic Cell (OPC) we measure thermophysical properties, such as thermal diffusivity, thermal conductivity, and heat capacity per unit volume of 5 polymer foils, poly(ethylene terephthalate) PET, of different molecular weights. It is shown that the physical properties influence strongly the thermal ones, and that photoacoustics can be used as a monitoring technique in the

  4. A coupled piezoelectric–electromagnetic energy harvesting technique for achieving increased power output through damping matching

    Microsoft Academic Search

    Vinod R Challa; M G Prasad; Frank T Fisher

    2009-01-01

    Vibration energy harvesting is being pursued as a means to power wireless sensors and ultra-low power autonomous devices. From a design standpoint, matching the electrical damping induced by the energy harvesting mechanism to the mechanical damping in the system is necessary for maximum efficiency. In this work two independent energy harvesting techniques are coupled to provide higher electrical damping within

  5. Simultaneous optical and photoacoustic measurement of nonlinear absorption

    NASA Astrophysics Data System (ADS)

    Chantharasupawong, Panit; Philip, Reji; Thomas, Jayan

    2013-01-01

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

  6. Piezoelectricity Demo

    NSDL National Science Digital Library

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

  7. Photoacoustic active ultrasound element for catheter tracking

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  8. CO2 laser photoacoustic detection of hydrazine based rocket fuels

    NASA Astrophysics Data System (ADS)

    Loper, G. L.; Calloway, A. R.; Stamps, M. A.; Gelbwachs, J. A.

    1982-03-01

    This report describes recent work performed at The Aerospace Corporation to determine the capability of the CO2 laser photoacoustic technique to detect the rocket fuels hydrazine, monomethylhydrazine (MMH), and unsymmetrical dimethylhydrazine (UDMH) at low parts-per-billion (ppb) levels in the ambient air in real time. These compounds are highly toxic and recent studies indicate that they may also be carcinogens. Estimates made from CO2 laser absorption cross section data determined for the hydrazines in a previous Aerospace study indicate that the hydrazines should be detectable by the CO2 laser photoacoustic technique at the desired low ppb levels even in the presence of the ambient levels of pollutants and water vapor found in urban atmospheres. To assess the validity of these hydrazine-fuel detection estimates by the CO2 laser photoacoustic technique, various laboratory photoacoustic detection systems were assembled and their minimum detectable absorptivity values were determined during the present study. The photoacoustic detection system that provided the best performance in this study possessed optically tandem sample and reference cells connected to a differential capacitance manometer. This system was designed to minimize the effects of spurious absorption at the photoacoustic cell windows.

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

    PubMed

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

    2002-10-01

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

  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. Design and evaluation of a novel breast cancer detection system combining both thermoacoustic ,,TA... and photoacoustic ,,PA... tomography

    E-print Network

    Wang, Lihong

    Design and evaluation of a novel breast cancer detection system combining both thermoacoustic ,,TA thermoacoustic and photoacoustic techniques to achieve dual contrast microwave and light absorption imaging

  13. 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.

  14. Biomedical photoacoustic imaging.

    PubMed

    Beard, Paul

    2011-08-01

    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

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

    PubMed

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

    2015-04-10

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

  16. Urogenital photoacoustic endoscope

    PubMed Central

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

    2014-01-01

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

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

    Microsoft Academic Search

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

    1995-01-01

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

  18. Inverse Transport Theory of Photoacoustics Guillaume Bal

    E-print Network

    Bal, Guillaume

    estimates for the reconstructions. Keywords. Photoacoustics, Optoacoustics, transport equation, inverse of detectors (ultrasound transducers). The photoacoustic effect is now being actively investigated for its

  19. Catheter-based photoacoustic endoscope

    PubMed Central

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

    2014-01-01

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

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    McNulty, Thomas Francis

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

  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. 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.

  4. Photoacoustic section imaging with an integrating cylindrical detector

    PubMed Central

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

    2011-01-01

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

  5. 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.

  6. A comparison between several approaches of piezoelectric energy harvesting

    Microsoft Academic Search

    E. Lefeuvre; A. Badel; A. Benayad; L. Lebrun; C. Richard; D. Guyomar

    2005-01-01

    This paper compares the performances of vibration-powered electrical generators using a piezoelectric ceramic and a piezoelectric single crystal associated to several power conditioning interfaces. A new approach of the piezoelectric power conversion based on a non linear voltage processing is presented, leading to three novel high-performance techniques. Theoretical predictions and experimental results show that the novel techniques may increase the

  7. Development of real-time photoacoustic microscopy

    Microsoft Academic Search

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

    2011-01-01

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

  8. High resolution photoacoustic and photothermal imaging

    NASA Astrophysics Data System (ADS)

    Williams, C. C.

    High resolution photoacoustic and photothermal imaging advances are described. Photoacoustic and photothermal theories were extended to include the effects of the highly focused optical power sources necessary for high resolution imaging. Three high frequency techniques (1 GHz) were demonstrated and used to characterize the material properties of solids. The formalism behind photothermal characterization of solids is established under general focusing conditions. An analysis of the frequency dependence of the photothermal response demonstrates that very high frequencies may be employed without loss of sensitivity if highly focused optical beams are used. Photothermal signal can be used to directly measure the thermal conductivity of solids on a microscopic scale. The three dimensional thermoacoustic field equation is derived and discussed. This equation is used to obtain the one dimensional thermoacoustic wave equation.

  9. 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

  10. Quartz-enhanced photoacoustic spectroscopy: a review.

    PubMed

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

    2014-01-01

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

  11. Photoacoustic characterization of carbon nanotube array thermal interfaces

    E-print Network

    Xu, Xianfan

    carbon nanotube CNT array interfaces, one sided Si-CNT-Ag and two sided Si-CNT-CNT-Cu , using a photoacoustic technique PA . Well-anchored, dense, and vertically oriented multiwalled CNT arrays have been. With the PA technique, the small interface resistances of the highly conductive CNT interfaces can be measured

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

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

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

  13. Piezoelectric transducer

    NASA Technical Reports Server (NTRS)

    Conragan, J.; Muller, R. S.

    1970-01-01

    Transducer consists of a hybrid thin film and a piezoelectric transistor that acts as a stress-sensitive device with built-in gain. It provides a stress/strain transducer that incorporates a signal amplification stage and sensor in a single package.

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

    NASA Astrophysics Data System (ADS)

    Frez, Clifford; Diebold, Gerald J.

    2014-12-01

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

  15. 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.

  16. Ultrasound-heated photoacoustic flowmetry

    PubMed Central

    Wang, Lidai; Yao, Junjie; Maslov, Konstantin I.; Xing, Wenxin; Wang, Lihong V.

    2013-01-01

    Abstract. We report the development of photoacoustic flowmetry assisted by high-intensity focused ultrasound (HIFU). This novel method employs HIFU to generate a heating impulse in the flow medium, followed by photoacoustic monitoring of the thermal decay process. Photoacoustic flowmetry in a continuous medium remains a challenge in the optical diffusive regime. Here, both the HIFU heating and photoacoustic detection can focus at depths beyond the optical diffusion limit (?1??mm in soft tissue). This method can be applied to a continuous medium, i.e., a medium without discrete scatterers or absorbers resolvable by photoacoustic imaging. Flow speeds up to 41??mm·s?1 have been experimentally measured in a blood phantom covered by 1.5-mm-thick tissue. PMID:24194064

  17. Piezoelectrically actuated tunable capacitor

    Microsoft Academic Search

    Chuang-Yuan Lee; Eun Sok Kim

    2006-01-01

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

  18. 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

  19. 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 ...

  20. Sunscreen effects in skin analyzed by photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2004-06-01

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

  1. Four-dimensional photoacoustic imaging of moving targets.

    PubMed

    Ephrat, Pinhas; Roumeliotis, Michael; Prato, Frank S; Carson, Jeffrey J L

    2008-12-22

    Photoacoustic imaging provides optical contrast with improved tissue penetration and spatial resolution compared to pure optical techniques. Three-dimensional photoacoustic imaging is particularly advantageous for visualizing non-planar light absorbing structures, such as blood vessels, internal organs or tumours. We have developed a fast 3-D photoacoustic imaging system for small animal research based on a sparse array of ultrasonic detectors and iterative image reconstruction. The system can acquire 3-D images with a single laser-shot at a frame rate of 10 Hz. To demonstrate the imaging capabilities we have constructed phantoms made of a scanning point source and a rotating line object and imaged them at a rate of 10 frames per second. The resulting 4-D photoacoustic images depicted well the motion of each target. Comparison of the perceived motion in the images with the known velocity of the target showed good agreement. To our knowledge, this is the first report of single-shot high frame-rate 3-D photoacoustic imaging system. With further developments, this system could bring to bear its inherent speed for applications in small animal research, such as motion tracking of tumour outline during respiration, and rapid monitoring of contrast agent kinetics. PMID:19104588

  2. 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.

  3. Photoacoustic spectroscopy for trace vapor detection and molecular discrimination

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

  4. ADAPTIVE ANTENNA SHAPE CONTROL USING PIEZOELECTRIC ACTUATORS?

    Microsoft Academic Search

    BRIJ N. AGRAWALt; M. ADNAN ELSHAFEI; GANGBING SONG

    1997-01-01

    This paper presents improved techniques for the shape control of composite material plates using piezoelectric actuators. The application of this work is for the shape control of spacecraft antenna to correct surface errors introduced by manufacturing, in-orbit thermal distortion, and moisture. A finite element model has been developed for a composite plate with distributed piezoelectric actuators and sensors. To improve

  5. Adaptive antenna shape control using piezoelectric actuators

    Microsoft Academic Search

    Brij N. Agrawal; M. Adnan Elshafei; Gangbing Song

    1997-01-01

    This paper presents improved techniques for the shape control of composite material plates using piezoelectric actuators. The application of this work is for the shape control of spacecraft antenna to correct surface errors introduced by manufacturing, in-orbit thermal distortion, and moisture. A finite element model has been developed for a composite plate with distributed piezoelectric actuators and sensors. To improve

  6. 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.

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

    Microsoft Academic Search

    S. Sethuraman; S. r. Aglyamov; J. h. Amirian; R. w. Smalling; S. y. Emelianov

    ABSTRACT 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

  8. 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

  9. 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.

  10. Potential clinical applications of photoacoustics.

    PubMed

    Rosencwaig, A

    1982-09-01

    Photoacoustic spectroscopy offers the opportunity for extending the exact science of noninvasive spectral analysis to intact medical substances such as tissues. Thermal-wave imaging offers the potential for microscopic imaging of thermal features in biological matter. PMID:7127803

  11. Adaptive optics photoacoustic microscopy.

    PubMed

    Jiang, Minshan; Zhang, Xiangyang; Puliafito, Carmen A; Zhang, Hao F; Jiao, Shuliang

    2010-10-11

    We have developed an adaptive optics photoacoustic microscope (AO-PAM) for high-resolution imaging of biological tissues, especially the retina. To demonstrate the feasibility of AO-PAM we first designed the AO system to correct the wavefront errors of the illuminating light of PAM. The aberrations of the optical system delivering the illuminating light to the sample in PAM was corrected with a close-loop AO system consisting of a 141-element MEMS-based deformable mirror (DM) and a Shack-Hartmann (SH) wavefront sensor operating at 15 Hz. The photoacoustic signal induced by the illuminating laser beam was detected by a custom-built needle ultrasonic transducer. When the wavefront errors were corrected by the AO system, the lateral resolution of PAM was measured to be better than 2.5 µm using a low NA objective lens. We tested the system on imaging ex vivo ocular samples, e.g., the ciliary body and retinal pigment epithelium (RPE) of a pig eye. The AO-PAM images showed significant quality improvement. For the first time we were able to resolve single RPE cells with PAM. PMID:20941077

  12. Adaptive optics photoacoustic microscopy

    PubMed Central

    Jiang, Minshan; Zhang, Xiangyang; Puliafito, Carmen A.; Zhang, Hao F.; Jiao, Shuliang

    2010-01-01

    We have developed an adaptive optics photoacoustic microscope (AO-PAM) for high-resolution imaging of biological tissues, especially the retina. To demonstrate the feasibility of AO-PAM we first designed the AO system to correct the wavefront errors of the illuminating light of PAM. The aberrations of the optical system delivering the illuminating light to the sample in PAM was corrected with a close-loop AO system consisting of a 141-element MEMS-based deformable mirror (DM) and a Shack-Hartmann (SH) wavefront sensor operating at 15 Hz. The photoacoustic signal induced by the illuminating laser beam was detected by a custom-built needle ultrasonic transducer. When the wavefront errors were corrected by the AO system, the lateral resolution of PAM was measured to be better than 2.5 µm using a low NA objective lens. We tested the system on imaging ex vivo ocular samples, e.g., the ciliary body and retinal pigment epithelium (RPE) of a pig eye. The AO-PAM images showed significant quality improvement. For the first time we were able to resolve single RPE cells with PAM. PMID:20941077

  13. Piezoelectric Effect

    NSDL National Science Digital Library

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

  14. Inverse Diffusion Theory of Photoacoustics Guillaume Bal

    E-print Network

    Bal, Guillaume

    . Keywords. Photoacoustics, Optoacoustics, diffusion equation, inverse problems, internal data, stability; this is the photoacoustic effect. Such an expansion is sufficient to emit acoustic pulses, which travel back to the boundary

  15. 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

  16. Remote Temperature Estimation in Intravascular Photoacoustic Imaging

    PubMed Central

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

    2008-01-01

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

  17. 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.

  18. 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

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

    Microsoft Academic Search

    Ellen L. Holthoff; Paul M. Pellegrino

    2009-01-01

    Photoacoustic spectroscopy (PAS) is a useful monitoring technique that is well suited for trace gas detection. This method routinely exhibits detection limits at the parts-per-million (ppm) or parts-per-billion (ppb) level for gaseous samples. PAS also possesses favorable detection characteristics when the system dimensions are scaled to a microsystem design. Micro-electromechanical systems (MEMS)-scale designs offer the possibility to develop photoacoustic sensors

  20. Photoacoustic characterization and FTIR spectroscopic studies on conducting polyaniline doped with different sulphonic acids

    Microsoft Academic Search

    W. M. M. Yunus; C. Y. J. Fanny; M. Z. Ab Rahman

    2001-01-01

    The open photoacoustic cell technique is used to measure the thermal diffusivity value of conducting polyaniline doped with different sulphonic acids. It is based on the measuring of the photoacoustic signal as a,function of modulation frequency. In the present work the measured thermal diffusivity and electrical conductivity values were (4.55-6.02)×10-2 cm2\\/s. and of (4.48×10-3-3.22) S cm-1 respectively. The IR absorbance

  1. 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.

  2. 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.

  3. Novel photoacoustic Stark cell

    NASA Astrophysics Data System (ADS)

    Thöny, A.; Sigrist, M. W.

    1995-01-01

    In order to further enhance the detection selectivity of a mobile CO2-laser photoacoustic (PA) system for air monitoring we have developed a novel type of Stark cell and an appropriate power supply that provides variable dc and ac high voltages. The special design of the electrode profile enables the operation of the cell with electric field strengths of up to 16.7 kV/cm at atmospheric pressure without any appearance of arcing. The Stark PA cell is of special interest for the detection of compounds exhibiting a permanent electric dipole moment such as ammonia. We present results on the absorption of ammonia, ethene, and nonabsorbing synthetic air derived from PA measurements with variable dc and/or ac electric field applied. Good agreement with theoretical predictions is obtained.

  4. 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.

  5. 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.

  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. Photoacoustic characterization of carbon nanotube array thermal interfaces

    Microsoft Academic Search

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

    2007-01-01

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

  8. Photoacoustic correlation spectroscopy and its application to low-speed flow measurement

    PubMed Central

    Chen, Sung-Liang; Ling, Tao; Huang, Sheng-Wen; Baac, Hyoung Won; Guo, L. Jay

    2010-01-01

    A photoacoustic correlation technique, inspired by its optical counterpart—the fluorescence correlation spectroscopy (FCS), was tested for the first time to demonstrate the feasibility of low-speed flow measurement based on photoacoustic signal detection. A pulsed laser was used to probe the flow of light-absorbing beads. A photoacoustic correlation system of 0.8 sec temporal resolution was built and flow speeds ranging from 249 to 14.9 µm/s with corresponding flow time from 4.42 to 74.1 sec were measured. The experiment serves as a proof of concept for photoacoustic correlation spectroscopy, which may have many potential applications similar to FCS. PMID:20410966

  9. 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

  10. Contrast agents for photoacoustic and thermoacoustic imaging: a review.

    PubMed

    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

  11. Photoacoustic imaging and temperature measurement for photothermal cancer therapy

    PubMed Central

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

    2009-01-01

    Photothermal therapy is a noninvasive, targeted, laser-based technique for cancer treatment. During photothermal therapy, light energy is converted to heat by tumor-specific photoabsorbers. The corresponding temperature rise causes localized cancer destruction. For effective treatment, however, the presence of photoabsorbers in the tumor must be ascertained before therapy and thermal imaging must be performed during therapy. This study investigates the feasibility of guiding photothermal therapy by using photoacoustic imaging to detect photoabsorbers and to monitor temperature elevation. Photothermal therapy is carried out by utilizing a continuous wave laser and metal nanocomposites broadly absorbing in the near-infrared optical range. A linear array-based ultrasound imaging system is interfaced with a nanosecond pulsed laser to image tissue-mimicking phantoms and ex-vivo animal tissue before and during photothermal therapy. Before commencing therapy, photoacoustic imaging identifies the presence and spatial location of nanoparticles. Thermal maps are computed by monitoring temperature-induced changes in the photoacoustic signal during the therapeutic procedure and are compared with temperature estimates obtained from ultrasound imaging. The results of our study suggest that photoacoustic imaging, augmented by ultrasound imaging, is a viable candidate to guide photoabsorber-enhanced photothermal therapy. PMID:18601569

  12. 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

  13. Remote photoacoustic detection of liquid contamination of a surface.

    PubMed

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

    2003-08-20

    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-microm wavelength region. Enhanced sensitivity is brought about by three main system developments: (1) increased laser-pulse energy (150 microJ/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. PMID:12952337

  14. 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%.

  15. Photoacoustic imaging of tumor angiogenesis

    NASA Astrophysics Data System (ADS)

    Kolkman, Roy G. M.; Thumma, Kiran K.; ten Brinke, Gerbert A.; Siphanto, Ronald I.; van Neck, Han; Steenbergen, Wiendelt; van Leeuwen, Ton G.

    2008-02-01

    Photoacoustic imaging is a hybrid imaging modality that is based on the detection of acoustic waves generated by absorption of pulsed light by tissue chromophores such as hemoglobin in blood. Serial photoacoustic imaging has been performed over a 10-day period after subcutaneous inoculation of pancreatic tumor cells in a rat. The images were obtained from ultrasound generated by absorption in hemoglobin of short laser pulses at a wavelength of 1064 nm. The ultrasound signals were measured in reflection mode using a double-ring photoacoustic detector. A correction algorithm has been developed to correct for scanning and movement artifacts during the measurements. Three-dimensional data visualize the development and quantify the extent of individual blood vessels around the growing tumor, blood concentration changes inside the tumor and growth in depth of the neovascularized region.

  16. Sub-ppm multi-gas photoacoustic sensor

    NASA Astrophysics Data System (ADS)

    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 2O and 30 ppb at 1737.9 for HCl have been demonstrated.

  17. Slow-sound photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Zhou, Yong; Li, Chiye; Wang, Lihong V.

    2013-04-01

    We propose to enhance the axial resolution of photoacoustic microscopy (PAM) by reducing the speed of sound within the imaging region of interest. With silicone oil immersion, we have achieved a finest axial resolution of 5.8 ?m for PAM, as validated by phantom experiments. The axial resolution was also enhanced in vivo when mouse ears injected with silicone oil were imaged. When tissue-compatible low-speed liquid becomes available, this approach may find broad applications in PAM as well as in other imaging modalities, such as photoacoustic computed tomography and ultrasound imaging.

  18. Single-cell photoacoustic thermometry

    PubMed Central

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

    2013-01-01

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

  19. SPICE model for lossy piezoelectric polymers.

    PubMed

    Dahiya, Ravinder S; Valle, Maurizio; Lorenzelli, Leandro

    2009-02-01

    This work presents the transmission line equivalent model for lossy piezoelectric polymers and its SPICE implementation. The model includes the mechanical/viscoelastic, dielectric/electrical, and piezoelectric/electromechanical losses in a novel way by using complex elastic, dielectric, and piezoelectric constants obtained from the measured impedances of PVDF and PVDF-TrFE samples by nonlinear regression technique. The equivalent circuit parameters are derived from analogies between a lossy electrical transmission line and acoustic wave propagation. The simulated impedance and phase plots of various samples, working in thickness mode, have been shown to agree well with the measured data. PMID:19251526

  20. 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

  1. 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...

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

    E-print Network

    Ramadass, Yogesh Kumar

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

  3. A simple photoacoustic method for the in situ study of soot distribution in flames

    NASA Astrophysics Data System (ADS)

    Humphries, G. S.; Dunn, J.; Hossain, M. M.; Lengden, M.; Burns, I. S.; Black, J. D.

    2015-05-01

    This paper presents a simple photoacoustic technique capable of quantifying soot volume fraction across a range of flame conditions. The output of a high-power (30 W) 808-nm cw-diode laser was modulated in order to generate an acoustic pressure wave via laser heating of soot within the flame. The generated pressure wave was detected using a micro-electro-mechanical microphone mounted close to a porous-plug flat-flame burner. Measurements were taken using the photoacoustic technique in flames of three different equivalence ratios and were compared to laser-induced incandescence. The results presented here show good agreement between the two techniques and show the potential of the photoacoustic method as a way to measure soot volume fraction profiles in this type of flame. We discuss the potential to implement this technique with much lower laser power than was used in the experiments presented here.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Palamodov, V. P.

    2014-12-01

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

  7. 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

  8. Fabrication of piezoelectric MEMS devices-from thin film to bulk PZT wafer

    Microsoft Academic Search

    Zhihong Wang; Jianmin Miao; Chee Wee Tan; Ting Xu

    2010-01-01

    Integrating patterned functional piezoelectric layer onto silicon substrate is a key technique challenge in fabrication of\\u000a piezoelectric Micro Electro Mechanical System (pMEMS) devices. Different device applications have different requirements on\\u000a the thickness and in-plane geometry of the piezoelectric layers and thus have their own processing difficulties. In this paper,\\u000a the techniques of integrating piezoelectric function into pMEMS has been discussed

  9. Fluoropolymer and aluminum piezoelectric reactives

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  10. 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.

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

    PubMed

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

    2010-01-01

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

  12. 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

  13. Photoacoustic tomography in a rectangular reflecting cavity

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

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

  16. 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

  17. PIEZOELECTRIC POWER SCAVENGING OF MECHANICAL VIBRATION ENERGY

    E-print Network

    Ervin, Elizabeth K.

    with other smart materials for power harvesting #12;Piezoelectric MaterialsPiezoelectric MaterialsPIEZOELECTRIC POWER SCAVENGING OF MECHANICAL VIBRATION ENERGY PIEZOELECTRIC POWER SCAVENGING and magneticand magnetic field.field. Piezoelectric Materials as Smart Material- Among the all smart materials

  18. Imaging of gene expression in vivo with photoacoustic tomography

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

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

  19. Measurement of thermal properties of gases using an open photoacoustic cell as a sensor

    Microsoft Academic Search

    B. Bonno; J. L. Laporte; R. Tascon D'Leon

    2005-01-01

    An alternative photothermal technique for the measurement of thermal properties of gases is described. The proposed technique uses the open photoacoustic cell as a sensor. The gas sample is confined between two thin aluminum foils. One of these acts as the absorber of modulated light while the other, coupled with an electret microphone, is used for sensing the temperature fluctuations

  20. 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.

  1. 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

  2. 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.

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

    PubMed

    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. PMID:26133859

  4. Analysis of a photoacoustic imaging system by the crosstalk matrix and singular value decomposition.

    PubMed

    Roumeliotis, Michael; Stodilka, Robert Z; Anastasio, Mark A; Chaudhary, Govind; Al-Aabed, Hazem; Ng, Eldon; Immucci, Andrea; Carson, Jeffrey J L

    2010-05-24

    Photoacoustic imaging is a hybrid imaging modality capable of producing contrast similar to optical imaging techniques but with increased penetration depth and resolution in turbid media by encoding the information as acoustic waves. In general, it is important to characterize the performance of a photoacoustic imaging system by parameters such as sensitivity, resolution, and contrast. However, system characterization can extend beyond these metrics by implementing advanced analysis via the crosstalk matrix and singular value decomposition. A method was developed to experimentally measure a matrix that represented the imaging operator for a photoacoustic imaging system. Computations to produce the crosstalk matrix were completed to provide insight into the spatially dependent sensitivity and aliasing for the photoacoustic imaging system. Further analysis of the imaging operator was done via singular value decomposition to estimate the capability of the imaging system to reconstruct objects and the inherent sensitivity to those objects. The results provided by singular value decomposition were compared to SVD results from a de-noised imaging operator to estimate the number of measurable singular vectors for the system. These characterization techniques can be broadly applied to any photoacoustic system and, with regards to the studied system, could be used as a basis for improvements to future iterations. PMID:20589001

  5. Thermally nonlinear laser photoacoustic tomography

    SciTech Connect

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

    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)

  6. Photoacoustic Microscopy in Tissue Engineering

    PubMed Central

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

    2013-01-01

    Photoacoustic tomography (PAT) is an attractive modality for noninvasive, volumetric imaging of scattering media such as biological tissues. By choosing the ultrasonic detection frequency, PAT enables scalable spatial resolution with desired imaging depth up to ~7 cm while maintaining a high depth-to-resolution ratio of ~200 and consistent optical absorption contrasts. Photoacoustic microscopy (PAM), the microscopic embodiment of PAT, aims to image at millimeter depth and micrometer-scale resolution. PAM is well-suited for characterizing three-dimensional scaffold-based samples, including scaffolds themselves, cells, and blood vessels, both qualitatively and quantitatively. Here we review our previous work on applications of PAM in tissue engineering and then discuss its future developments. PMID:23766667

  7. Nonionizing photoacoustic cystography in vivo.

    PubMed

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

    2011-09-15

    We demonstrate the feasibility of a novel and nonionizing process for bladder imaging in vivo, called photoacoustic cystography (PAC). Using a photoacoustic imaging system, we have successfully imaged a rat bladder filled with clinically used Methylene Blue (MB) dye. An image contrast of ~8 was achieved. Further, spectroscopic PAC confirmed the accumulation of MB in the bladder. Using a laser pulse energy of less than 1 mJ/cm² (1/20 of the ANSI safety limit), a deeply (1.2 cm) positioned bladder in biological tissues was clearly visible in the PA image. Our results suggest that PAC can potentially provide a nonionizing, relatively cheap, and portable tool for bladder mapping. Among our clinical interests, nonionizing PAC with an injection of MB can potentially monitor vesicoureteral reflux in children. PMID:21931403

  8. Kelvin and piezoelectricity

    NASA Astrophysics Data System (ADS)

    Trainer, Matthew

    2003-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Wynn, Charles M.; Palmacci, Stephen; Clark, Michelle L.; Kunz, Roderick R.

    2014-02-01

    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 system. A fielded DPAS system has the potential to enable rapid, early warning of airborne chemical threats. DPAS is a new form of photoacoustic spectroscopy that relies on a laser beam swept at the speed of sound to amplify an otherwise weak photoacoustic signal. We experimentally determine the sensitivity of this technique using trace quantities of SF6 gas. A clutter-limited sensitivity of ˜100 ppt is estimated for an integration path of 0.43 m. Additionally, detection at ranges over 5 m using two different detection modalities is demonstrated: a parabolic microphone and a laser vibrometer. Its utility in detecting ammonia emanating from solid samples in an ambient environment is also demonstrated.

  10. 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

  11. Sensor-less Vibration Suppression and Scan Compensation for Piezoelectric Tube Nanopositioners

    E-print Network

    Fleming, Andrew J.

    Sensor-less Vibration Suppression and Scan Compensation for Piezoelectric Tube Nanopositioners (Invited Paper) Andrew J. Fleming and S. O. Reza Moheimani Abstract-- Piezoelectric tube scanners associated with piezoelectric tube scanners. In this paper, two simple techniques are proposed for simultane

  12. Photoacoustic characterization of different food samples.

    PubMed

    Favier, J P; Buijs, J; Miklós, A; Lörincz, A; Bicanic, D

    1994-07-01

    Photoacoustic spectroscopy in the 350-700 nm range proved a useful tool for discriminating between a variety of opaque, light-scattering samples. Spectral features originating from powdered food specimens of different colour and grain size were observed. These results suggest the feasibility of photoacoustics for quality control in the food-processing industry. PMID:8067061

  13. Thermoacoustic and photoacoustic sensing of temperature

    E-print Network

    Wang, Lihong

    Thermoacoustic and photoacoustic sensing of temperature Manojit Pramanik Lihong V. Wang Washington thermoacoustic and photoacoustic measurements. This noninvasive method has been demonstrated using a tissue and thermoacoustic signal amplitudes depend on the tempera- ture of the source object, the signal amplitudes can

  14. Mathematics of thermoacoustic and photoacoustic tomography

    E-print Network

    Mathematics of thermoacoustic and photoacoustic tomography Peter Kuchment and Leonid Kunyansky in the Thermoacoustic and Photoacoustic To- mography. 1 Introduction Medical tomography has had a huge impact on medical succesfull example of such a combination is the Thermoacoustic Tomography (TAT) (also abbreviated as TCT) [50

  15. Multiple-bandwidth photoacoustic tomography.

    PubMed

    Ku, Geng; Wang, Xueding; Stoica, George; Wang, Lihong V

    2004-04-01

    Photoacoustic tomography, also referred to as optoacoustic tomography, employs short laser pulses to generate ultrasonic waves in biological tissues. The reconstructed images can be characterized by the convolution of the structure of samples, the laser pulse and the impulse response of the ultrasonic transducer used for detection. Although the laser-induced ultrasonic waves cover a wide spectral range, a single transducer can receive only part of the spectrum because of its limited bandwidth. To systematically analyse this problem, we constructed a photoacoustic tomographic system that uses multiple ultrasonic transducers simultaneously, each at a different central frequency. The photoacoustic images associated with the different transducers were compared and analysed. The system was tested by imaging both mouse brains and phantom samples. The vascular vessels in the brain were revealed by all of the transducers, but the image resolutions differed. The higher frequency detectors provided better image resolution while the lower frequency detectors delineated the major structural traits with a higher signal-noise ratio. PMID:15128208

  16. 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.

  17. 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.

  18. Quantitative photoacoustic tomography using illuminations from a single direction

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    Quantitative photoacoustic tomography is an emerging imaging technique aimed at estimating optical parameters inside tissues from photoacoustic images, which are formed by combining optical information and ultrasonic propagation. This optical parameter estimation problem is ill-posed and needs to be approached within the framework of inverse problems. It has been shown that, in general, estimating the spatial distribution of more than one optical parameter is a nonunique problem unless more than one illumination pattern is used. Generally, this is overcome by illuminating the target from various directions. However, in some cases, for example when thick samples are investigated, illuminating the target from different directions may not be possible. In this work, the use of spatially modulated illumination patterns at one side of the target is investigated with simulations. The results show that the spatially modulated illumination patterns from a single direction could be used to provide multiple illuminations for quantitative photoacoustic tomography. Furthermore, the results show that the approach can be used to distinguish absorption and scattering inclusions located near the surface of the target. However, when compared to a full multidirection illumination setup, the approach cannot be used to image as deep inside tissues.

  19. 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.

  20. 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

  1. Nonplanar piezoelectric film structures

    Microsoft Academic Search

    Seppo Leppävuori; Arvi Kruusing; Antti Uusimäki

    1999-01-01

    Microengineered, non-planar piezoelectric structures can offer solutions to a variety of challenging problems arising in the microsystem technologies. Besides the piezoelectric polymers, which can easily be shaped, there has also been significant progress in developing fabrication technologies based on thin layers of the lead – zirconate – titanate family of piezoceramics. The processing methods include dip-casting, printing, cathodic electrosynthesis, electrolytic

  2. Piezoelectric energy harvesting

    Microsoft Academic Search

    Christopher A Howells

    2009-01-01

    Piezoelectric materials can be used to convert oscillatory mechanical energy into electrical energy. This technology, together with innovative mechanical coupling designs, can form the basis for harvesting energy from mechanical motion. Piezoelectric energy can be harvested to convert walking motion from the human body into electrical power. Recently four proof-of-concept Heel Strike Units were developed where each unit is essentially

  3. Light Controlled Piezoelectric Transformer

    Microsoft Academic Search

    Lucjan Kozielski

    2011-01-01

    The author designed ``smart material'' device allow to control an output voltage level by change of incident light intensity. New functions of piezoelectric transformer (PT) was realized by superimposing piezoelectricity with photostriction. The effect of a light influence on the PT voltage gain was proved experimentally, consequently these ``smart'' transformers with its new functionality can be utilized as a promising

  4. 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.

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

    PubMed Central

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

    2014-01-01

    Abstract. Photoacoustic tomography (PAT) is an emerging technique that has a great potential for preclinical whole-body imaging. To date, most whole-body PAT systems require multiple laser shots to generate one cross-sectional image, yielding a frame rate of <1??Hz. Because a mouse breathes at up to 3 Hz, without proper gating mechanisms, acquired images are susceptible to motion artifacts. Here, we introduce, for the first time to our knowledge, retrospective respiratory gating for whole-body photoacoustic computed tomography. This new method involves simultaneous capturing of the animal’s respiratory waveform during photoacoustic data acquisition. The recorded photoacoustic signals are sorted and clustered according to the respiratory phase, and an image of the animal at each respiratory phase is reconstructed subsequently from the corresponding cluster. The new method was tested in a ring-shaped confocal photoacoustic computed tomography system with a hardware-limited frame rate of 0.625 Hz. After respiratory gating, we observed sharper vascular and anatomical images at different positions of the animal body. The entire breathing cycle can also be visualized at 20??frames/cycle. PMID:24395586

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Holthoff, Ellen L.; Pellegrino, Paul M.

    2009-05-01

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

  8. Magnetocaloric piezoelectric composites for energy harvesting

    NASA Astrophysics Data System (ADS)

    Cleveland, Michael; Liang, Hong

    2012-04-01

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

  9. Photoacoustic analysis of bone osteogenesis to different doses of laser irradiation

    NASA Astrophysics Data System (ADS)

    Mejia, P. A. Lomelí; Jiménez Pérez, J. L.; Orea, A. Cruz; Castrejón, H. Villegas; Butron, H. Lecona; Lira, M. Meléndez

    2005-07-01

    The photoacoustic analysis of fractured bone callus to different consolidation times in the presence of laser irradiation was performed. In this study we take into account the fractured tibias of sacrified Wistar rats. By using the photoacoustic spectroscopy technique it was possible to determine, for different doses of laser irradiation (doses of 25 J cm-2) the presence of characteristic absorption band of p-Nitrophenylphosphatase (p-Npp) in the fractured bone callus. The evolution of bone consolidation was accelerated by laser radiation when compared with nonirradiated fractured bones.

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

    PubMed Central

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-08-01

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

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  14. Dielectric and piezoelectric studies of perovskite-tungsten bronze structured (1 ?  x )[0.5PMN0.5PZT]- x PBBiN nanoceramic composites by high-energy mechanical activation technique

    Microsoft Academic Search

    Ramam Koduri; Marta Lopez; K. Chandramouli

    2010-01-01

    In this paper, phase development, dielectric and piezoelectric properties of nanocomposites consisting of perovskite structured\\u000a PMN-PZT and tungsten bronze structured PBBiN synthesized via high energy mechanical activation technique were examined as\\u000a a function of x in (1 ? x)(0.5PMN-0.5PZT)-xPBBiN with a stoichiometric formula as (1 ? x)[0.5Pb(Mg0.33Nb0.67)O3-0.5Pb(Zr0.53Ti0.47)O3]-x[Pb0.59Ba0.38Bi0.02Nb2O6]. It was observed that the high-energy mechanical activation technique has greatly improved the reactivity of the precursors

  15. Integrated photoacoustic and fluorescence confocal microscopy.

    PubMed

    Wang, Yu; Maslov, Konstantin; Kim, Chulhong; Hu, Song; Wang, Lihong V

    2010-10-01

    We have developed a dual-modality imaging system by integrating optical-resolution photoacoustic microscopy and fluorescence confocal microscopy to provide optical absorption and fluorescence contrasts simultaneously. By sharing the same laser source and objective lens, intrinsically registered photoacoustic and fluorescence images are acquired in a single scan. The micrometer resolution allows imaging of both blood and lymphatic vessels down to the capillary level. Simultaneous photoacoustic angiography and fluorescence lymphangiography were demonstrated, presenting more information to study tumor angiogenesis, vasculature, and microenvironments in vivo. PMID:20639165

  16. Photoacoustic shock generation in carbon suspensions

    SciTech Connect

    Beveridge, Andrew C. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)] [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); McGrath, Thomas E. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)] [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Diebold, Gerald J. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)] [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Karabutov, Alexander A. [International Laser Center, Moscow State University, Moscow, Russia (Russian Federation)] [International Laser Center, Moscow State University, Moscow, Russia (Russian Federation)

    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.

  17. Integrated Photoacoustic and Fluorescence Confocal Microscopy

    PubMed Central

    Wang, Yu; Maslov, Konstantin; Kim, Chulhong; Hu, Song

    2010-01-01

    We have developed a dual-modality imaging system by integrating optical-resolution photoacoustic microscopy and fluorescence confocal microscopy to provide optical absorption and fluorescence contrasts simultaneously. By sharing the same laser source and objective lens, intrinsically registered photoacoustic and fluorescence images are acquired in a single scan. The micrometer resolution allows imaging of both blood and lymphatic vessels down to the capillary level. Simultaneous photoacoustic angiography and fluorescence lymphangiography were demonstrated, presenting more information about tumor angiogenesis, vasculature, and microenvironments in vivo. PMID:20639165

  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. 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.

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

    Microsoft Academic Search

    Tasdiq Ahmed

    1987-01-01

    Transmission photoacoustic microscopy (TPAM) was developed as an analytical technique for the in-situ measurement of the thermal properties of heterogeneous materials. In TPAM, a modulated light is focused on a polished surface of a heterogeneous material using the objective lens of an optical reflectance microscope. The heat generated at the front or illuminated surface of the sample diffuses to the

  1. Photoacoustically Measured Speeds of Sound of Liquid HBO2: On Unlocking the Fuel Potential of Boron

    Microsoft Academic Search

    S Bastea; J Crowhurst; M Armstrong

    2010-01-01

    Elucidation of geodynamic, geochemical, and shock induced processes is often limited by challenges to accurately determine molecular fluid equations of state (EOS). High pressure liquid state reactions of carbon species underlie physiochemical mechanisms such as differentiation of planetary interiors, deep carbon sequestration, propellant deflagration, and shock chemistry. Here we introduce a versatile photoacoustic technique developed to measure accurate and precise

  2. 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 focusing transducer to obtain micron-resolution tissue images over a long working distance. The imager improvement in lateral and axial resolutions compared to the pulse-echo ultrasonic imaging technique

  3. 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...

  4. Double-illumination photoacoustic microscopy

    PubMed Central

    Yao, Junjie; Maslov, Konstantin I.; Puckett, Ernest R.; Rowland, Kathryn J.; Warner, Brad W.; Wang, Lihong V.

    2012-01-01

    Recent developments of optical-resolution photoacoustic microscopy (OR-PAM) have improved its spatial resolution and imaging speed. However, the penetration depth of OR-PAM is still limited to ~1 mm in tissue due to the strong tissue scattering. Here, we have developed double-illumination PAM (DI-PAM), which illuminates the sample from both top and bottom sides simultaneously. Through phantom and in vivo experiments, we have demonstrated for thin targets that DI-PAM has a penetration depth of ~2 mm in tissue at 532 nm and a focal zone of 260 µm, both significant improvements over traditional reflection or transmission mode OR-PAM. PMID:22344139

  5. Broadband pulsed flow using piezoelectric microjets

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

  6. 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

  7. 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

  8. Photoacoustic excitation profiles of gold nanoparticles?

    PubMed Central

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

    2014-01-01

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

  9. Coherent Interferometry Algorithms for Photoacoustic Habib Ammari

    E-print Network

    Ammari, Habib

    In photoacoustic imaging, optical energy absorption causes thermo-elastic expansion of the tissue, which leads absorption) with the resolution of ultrasound [28]. Potential applications include breast cancer and vascular

  10. 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 reconstruction algorithms for multi- source QPAT in the radiative transport regime with energy data collected, radiative transport equation, inverse transport problem, interior data, Born approximation, iterative

  11. 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, ...

  12. Evaluation of arsenazo III as a contrast agent for photoacoustic detection of micromolar calcium transients

    NASA Astrophysics Data System (ADS)

    Cooley, Erika J.; Kruizinga, Pieter; Branch, Darren W.; Emelianov, Stanislav

    2010-02-01

    Elucidating the role of calcium fluctuations at the cellular level is essential to gain insight into more complex signaling and metabolic activity within tissues. Recent developments in optical monitoring of calcium transients suggest that cells integrate and transmit information through large networks. Thus, monitoring calcium transients in these populations is important for identifying normal and pathological states of a variety of systems. Though optical techniques can be used to image calcium fluxes using fluorescent probes, depth penetration limits the information that can be acquired from tissues in vivo. Alternatively, the calcium-sensitive dye arsenazo III is useful for optical techniques that rely on absorption of light rather than fluorescence for image contrast. We report on the use of arsenazo III for detection of calcium using photoacoustics, a deeply penetrating imaging technique in which an ultrasound signal is generated following localized absorption of light. The absorbance properties of the dye in the presence of calcium were measured directly using UV-Vis spectrophotometry. For photoacoustic studies, a phantom was constructed to monitor the change in absorbance of 25 ?M arsenazo III at 680 nm in the presence of calcium. Subsequent results demonstrated a linear increase in photoacoustic signal as calcium in the range of 1 - 20 ?M complexed with the dye, followed by saturation of the signal as increasing amounts of calcium were added. For delivery of the dye to tissue preparations, a liposomal carrier was fabricated and characterized. This work demonstrates the feasibility of using arsenazo III for photoacoustic monitoring of calcium transients in vivo.

  13. Inverse Transport Theory of Photoacoustics

    E-print Network

    Guillaume Bal; Alexandre Jollivet; Vincent Jugnon

    2009-08-27

    We consider the reconstruction of optical parameters in a domain of interest from photoacoustic data. Photoacoustic tomography (PAT) radiates high frequency electromagnetic waves into the domain and measures acoustic signals emitted by the resulting thermal expansion. Acoustic signals are then used to construct the deposited thermal energy map. The latter depends on the constitutive optical parameters in a nontrivial manner. In this paper, we develop and use an inverse transport theory with internal measurements to extract information on the optical coefficients from knowledge of the deposited thermal energy map. We consider the multi-measurement setting in which many electromagnetic radiation patterns are used to probe the domain of interest. By developing an expansion of the measurement operator into singular components, we show that the spatial variations of the intrinsic attenuation and the scattering coefficients may be reconstructed. We also reconstruct coefficients describing anisotropic scattering of photons, such as the anisotropy coefficient $g(x)$ in a Henyey-Greenstein phase function model. Finally, we derive stability estimates for the reconstructions.

  14. Characterization of a Piezoelectric Buzzer Using a Michelson Interferometer

    NASA Astrophysics Data System (ADS)

    Lloyd, S.; Paetkau, M.

    2010-12-01

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

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

    PubMed

    Chang, Kuo-Tsai; Lee, Chun-Wei

    2008-04-01

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

  16. 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.

  17. Photoacoustic microscopy with 2-microm transverse resolution.

    PubMed

    Ku, Geng; Maslov, Konstantin; Li, Li; Wang, Lihong V

    2010-01-01

    We present a new-generation optical-resolution confocal photoacoustic microscope, consisting of a 0.25-numerical aperture optical microscope objective and a 75-MHz center-frequency spherically focused ultrasonic transducer. Experiments verified that this microscope has a transverse resolution of 2 microm, which is the highest to our knowledge among all photoacoustic imaging systems. In situ imaging of mouse ears shows the feasibility of resolving individual red blood cells in microvessels using the current system. PMID:20459224

  18. Gas cell photoacoustic detection of ultrasound absorption

    NASA Astrophysics Data System (ADS)

    Netzelmann, U.

    2010-03-01

    The photoacoustic signal generated by a 2 MHz ultrasound transducer has been detected at 500 Hz modulation frequency by an attached photoacoustic cell. A dominant mechanism for signal generation is the ultrasound absorption in the gas of the cell, where strong acoustic resonances are excited. The periodic heating by ultrasound absorption in the transducer buffer rod and subsequent thermal diffusion into the gas is a second mechanism. Experiment and theory are in reasonable accordance.

  19. Functional photoacoustic microscopy 

    E-print Network

    Zhang, Hao

    2009-06-02

    with physiological changes in biological tissues, which gives optical techniques high sensitivity in functional imaging. As a result, optical imaging has the potential in detecting abnormality and physiological changes in tissues, for example cancer in early...-related metabolic processes, such as changes of total hemoglobin concentration and hemoglobin oxygen saturation (SO 2 ), 7,8 to image tumor angiogenesis. It can also be applied to detect melanin-related skin melanoma cancers. Furthermore, by employing exogenous...

  20. Piezoelectric cantilever acoustic transducer

    Microsoft Academic Search

    Seung S. Lee; Richard M. White

    1998-01-01

    We present a piezoelectric acoustic transducer fabricated on a bulk-micromachined cantilever diaphragm. Use of the cantilever as a supporting diaphragm produces a highly sensitive microphone. In addition, when the device is driven electrically as an output transducer, a microspeaker, the relatively large deflections produce significant acoustic output. A voltage-to-frequency converter has also been demonstrated with piezoelectric cantilever transducers. The 0960-1317\\/8\\/3\\/009\\/img5

  1. Piezoelectric cantilever acoustic transducer

    Microsoft Academic Search

    Seung S Leey; Richard M White

    1998-01-01

    We present a piezoelectric acoustic transducer fabricated on a bulk-micromachined cantilever diaphragm. Use of the cantilever as a supporting diaphragm produces a highly sensitive microphone. In addition, when the device is driven electrically as an output transducer, a microspeaker, the relatively large deflections produce significant acoustic output. A voltage-to-frequency converter has also been demonstrated with piezoelectric cantilever transducers. The 2

  2. 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.

  3. In vivo blood oxygenation level measurements using photoacoustic microscopy 

    E-print Network

    Sivaramakrishnan, Mathangi

    2007-09-17

    in smallanimal skin. Owing to endogenous optical contrast, optical spectral information obtained from spectral photoacoustic measurements are successfully inverted to yield oxygenation level in blood. Analysis of error propagation from photoacoustic measurements...

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

    PubMed Central

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

    2013-01-01

    In this report, we present a breast imaging technique combining high-resolution near-infrared (NIR) light induced photoacoustic tomography (PAT) with NIR dyelabeled amino-terminal fragments of urokinase plasminogen activator receptor (uPAR) targeted magnetic iron oxide nanoparticles (NIR830-ATF-IONP) for breast cancer imaging using an orthotopic mouse mammary tumor model. We show that accumulation of the targeted nanoparticles in the tumor led to photoacoustic contrast enhancement due to the high absorption of iron oxide nanoparticles (IONP). NIR fluorescence images were used to validate specific delivery of NIR830-ATF-IONP to mouse mammary tumors. We found that systemic delivery of the targeted IONP produced 4- and 10-fold enhancement in photoacoustic signals in the tumor, compared to the tumor of the mice that received non-targeted IONP or control mice. The use of targeted nanoparticles allowed imaging of tumors located as deep as 3.1 cm beneath the normal tissues. Our study indicates the potential of the combination of photoacoustic tomography and receptor-targeted NIR830-ATF-IONP as a clinical tool that can provide improved specificity and sensitivity for breast cancer detection. In vivo photoacoustic MAP and fluorescence images before and after injection. Micrographs were merged with fluorescence images taken 24 hours post injection with indicated agent (a, e, i). Panels b thru 1. Photoacoustic MAP images were merged with images of blood vessels before injection (b, f, j), and at 5 hours (c, g, k) and 24 hours (d, h, l) post injection. PMID:23125139

  5. In-situ post-annealing technique for improving piezoelectricity and ferroelectricity of Li-doped ZnO thin films prepared by radio frequency magnetron sputtering system

    NASA Astrophysics Data System (ADS)

    Lin, Chun-Cheng; Chang, Chia-Chiang; Wu, Chin-Jyi; Tseng, Zong-Liang; Tang, Jian-Fu; Chu, Sheng-Yuan; Chen, Yi-Chun; Qi, Xiaoding

    2013-03-01

    Li-doped zinc oxide (L0.03Z0.97O) thin films are deposited onto Pt/Ti/SiO2/Si substrates via the radio frequency magnetron sputtering method. The structure evolution with annealing temperature of the predominantly (002)-oriented Li-doped ZnO (LZO) films after in-situ post-annealing process is determined. The largest values of the piezoelectric coefficient (d33) and the remnant polarization (Pr) (22.85 pm/V and 0.655 ?C/cm2, respectively) are obtained for LZO films post-annealed at 600 °C, which can be attributed to the predominant (002)-oriented crystalline structure, the release of intrinsic residual compressive stress, and less non-lattice oxygen.

  6. Piezoelectric dilatometric analysis using homodyne and heterodyne laser interferometry

    NASA Astrophysics Data System (ADS)

    Delahoussaye, Keith

    The electromechanical coupling of piezoelectric materials has been widely studied since such property is found to be a key element of enhanced sensitivity in piezoelectric sensors or actuators. However a unified view of this coupling as function of frequencies verified using multiple measurement techniques has not previously been available. This study examines and compares multiple optical based homodyne and heterodyne interferometry techniques for piezoelectric displacement measurement, over a wide range of frequencies from DC to 20 MHz. A custom configured homodyne optical interferometer and a commercial heterodyne Laser Doppler Vibrometer are used in the study. Because the frequency ranges used by these devices overlap, it is possible to compare the results. Ferroelectric lead titanate PbTiO3 (PT) ceramic sample with high ferroelectric strain is studied in this work. Frequency dependence of the electromechanical displacement is obtained using multiple techniques and the emphasis of the interrogations is given to frequencies near piezoelectric resonances.

  7. Photoacoustic spectroscopy of chemically modified surfaces. Doctoral thesis

    Microsoft Academic Search

    Burggraf

    1981-01-01

    The ultimate goal of this research was to apply photoacoustic spectroscopy to the study of surface species on chemically modified surfaces. The study begins with a review of the theory of photoacoustic spectroscopy developed by Rosencwaig and Gersho. The theory for thermally thick samples is cast into a form more suitable for quantification. The photoacoustic magnitude and phase information are

  8. Ultrasonic attenuation of biomaterials for compensation in photoacoustic imaging

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  9. Magnetocaloric piezoelectric composites for energy harvesting

    Microsoft Academic Search

    Michael Cleveland; Hong Liang

    2012-01-01

    Magnetocaloric alloy, Gd5Si2Ge2, was developed into a composite with the poly(vinylidene fluoride) (PVDF) piezoelectric polymer. This multifunctional material possesses unique properties that are suitable for energy conversion and harvesting. Experimental approaches include using an arc melting technique to synthesize the Gd5Si2Ge2 (GSG) alloy and the spinning casting method to fabricate the composite. The materials were characterized using various techniques at

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

    NASA Astrophysics Data System (ADS)

    Harrison, Tyler; Zemp, Roger J.

    2011-03-01

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

  11. 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  14. 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.

  15. 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.

  16. 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.

  17. Piezoelectric hydraulic pump performance

    NASA Astrophysics Data System (ADS)

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

    2001-06-01

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

  18. Piezoelectric wave motor

    DOEpatents

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

    2003-02-11

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

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

    Microsoft Academic Search

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

    2005-01-01

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

  20. Photoacoustic Brain Imaging: from Microscopic to Macroscopic Scales

    PubMed Central

    Yao, Junjie; Wang, Lihong V.

    2014-01-01

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

  1. Automated wavelet denoising of photoacoustic signals for burn-depth image reconstruction

    NASA Astrophysics Data System (ADS)

    Holan, Scott H.; Viator, John A.

    2007-02-01

    Photoacoustic image reconstruction involves dozens or perhaps hundreds of point measurements, each of which contributes unique information about the subsurface absorbing structures under study. For backprojection imaging, two or more point measurements of photoacoustic waves induced by irradiating a sample with laser light are used to produce an image of the acoustic source. Each of these point measurements must undergo some signal processing, such as denoising and system deconvolution. In order to efficiently process the numerous signals acquired for photoacoustic imaging, we have developed an automated wavelet algorithm for processing signals generated in a burn injury phantom. We used the discrete wavelet transform to denoise photoacoustic signals generated in an optically turbid phantom containing whole blood. The denoising used universal level independent thresholding, as developed by Donoho and Johnstone. The entire signal processing technique was automated so that no user intervention was needed to reconstruct the images. The signals were backprojected using the automated wavelet processing software and showed reconstruction using denoised signals improved image quality by 21%, using a relative 2-norm difference scheme.

  2. 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

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

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

    PubMed

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

    2014-10-20

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

  5. 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.

  6. Photoacoustic detection of CO2 based on LABVIEW at 10.303 ?m

    NASA Astrophysics Data System (ADS)

    Zhao, Junjuan; Zhao, Zhan; Du, Lidong; Geng, Daoqu; Wu, Shaohua

    2011-04-01

    A detailed study on a photoacoustic carbon dioxide detection system, through sound card based on virtual instrument, is presented in this paper. In this system, the CO2 concentration was measured with the non-resonant photoacoustic cell technique through measuring the photoacoustic signal caused by the CO2. In order to obtain small photoacoustic signals buried in noise, a measurement software was designed with LABVIEW. It has functions of Lock-in Amplifier, digital filter, and signal generator; can also be used to achieve spectrum analysis and signal recovery; has been provided with powerful function for data processing and communication with other measuring instrument. The test results show that the entire system has an outstanding measuring performance with the sensitivity of 10?v between 10-44 KHz. The non-resonance test of the trace gas analyte CO2 conducted at 100 Hz demonstrated large signals (15.89 mV) for CO2 concentrations at 600 ppm and high signal-to-noise values (˜ 85:1).

  7. Theoretical studies of wave propagation in multilayered piezoelectric media

    SciTech Connect

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

    1993-08-01

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

  8. An Efficient Neumann-Series Based Algorithm for Thermoacoustic and Photoacoustic Tomography with Variable Sound Speed

    E-print Network

    Stefanov, Plamen

    An Efficient Neumann-Series Based Algorithm for Thermoacoustic and Photoacoustic Tomography present an efficient algorithm for reconstructing an unknown source in Thermoacoustic and Photoacoustic of the Neumann-series based algorithm. 1 Introduction Thermoacoustic (TAT) and Photoacoustic (PAT) Tomography

  9. A New Numerical Algorithm for Thermoacoustic and Photoacoustic Tomography with Variable Sound Speed

    E-print Network

    Uhlmann, Gunther

    A New Numerical Algorithm for Thermoacoustic and Photoacoustic Tomography with Variable Sound Speed algorithm for reconstructing an unknown source in Thermoacoustic and Photoacoustic Tomography based Thermoacoustic (TAT) and Photoacoustic (PAT) Tomography are emerging medical imaging modal- ities [32, 30

  10. 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. 1065.269 Section...1065.269 Photoacoustic analyzer for ethanol and methanol. (a) Application...use a photoacoustic analyzer to measure ethanol and/or methanol concentrations in...

  11. Ultrasonically encoded photoacoustic flowgraphy in biological tissue

    PubMed Central

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

    2014-01-01

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

  12. Ultrasonically Encoded Photoacoustic Flowgraphy in Biological Tissue

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

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

    PubMed Central

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

    2014-01-01

    Abstract. Photoacoustic ophthalmoscopy (PAOM) is a high-resolution in vivo imaging modality that is capable of providing specific optical absorption information for the retina. A high-frequency ultrasonic transducer is one of the key components in PAOM, which is in contact with the eyelid through coupling gel during imaging. The ultrasonic transducer plays a crucial role in determining the image quality affected by parameters such as spatial resolution, signal-to-noise ratio, and field of view. In this paper, we present the results of a systematic study on a high-frequency ultrasonic transducer design for PAOM. The design includes piezoelectric material selection, frequency selection, and the fabrication process. Transducers of various designs were successfully applied for capturing images of biological samples in vivo. The performances of these designs are compared and evaluated. PMID:24441942

  16. 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.

  17. Ultrahigh resolution photoacoustic microscopy via transient absorption

    NASA Astrophysics Data System (ADS)

    Shelton, Ryan; Applegate, Brian E.

    2011-03-01

    We have developed a novel, hybrid imaging modality, Transient Absorption Ultrasonic Microscopy (TAUM), which fuses photoacoustic microscopy with non-linear microscopy. Photoacoustic microscopy is well known for its ability to image chromophores deep (> 1 mm) in scattering media with spatial resolutions in the 10s of microns. Non-linear microscopy is well known for its exquisite spatial resolution in three dimensions. This superior spatial resolution is attributed to the fact that the collected signal has a non-linear dependence on the light intensity. This dependence confines the signal to a very small focal volume, producing optically resolved voxels. Transient absorption is a non-linear process often used to map the excited state lifetimes of molecules exhibiting low fluorescence quantum efficiency. This sensitivity to non-radiative transitions makes transient absorption an attractive process to combine with photoacoustic imaging. We have built a prototype transient absorption ultrasonic microscope, implementing off-axis photoacoustic detection to allow the use of a high-quality, high numerical aperture objective. This high-quality, commercial lens is required to provide the tight focusing needed to optimize non-linear effects. We have demonstrated the increased spatial resolution of TAUM by imaging Rhodamine 6G in a capillary tube. The capillary cross-section is fully resolved, suggesting an axial resolution of < 10 microns. A 6 MHz transducer was used in this experiment, which results in an axial resolution of ~ 400 microns when used in a traditional photoacoustic microscope. Boasting the superior penetration depth and absorption contrast offered by photoacoustic emission and complemented by spatial resolutions comparable to confocal microscopy, we believe that Transient Absorption Ultrasonic Microscopy has excellent potential for producing volumetric images with cellular/subcellular resolution in three dimensions deep inside living tissue.

  18. 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.

  19. Combined optical resolution photoacoustic and fluorescence micro-endoscopy

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  20. 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...

  1. 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.

  2. Muscular PiezoElectricity?

    Microsoft Academic Search

    F. Buchanan

    1921-01-01

    THE well-known ``action current'' of muscle can have nothing to do with piezo-electricity, since it may reach its maximum before any mechanical change begins. Nor do I see anything to suggest the occurrence of such electricity in other animal tissues or organs. Mr. Wriothesley Russell (NATURE, October 27, p. 275) might, however, find plants worth investigating for evidence of it.

  3. In vivo virtual intraoperative surgical photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Han, Seunghoon; Lee, Changho; Kim, Sehui; Jeon, Mansik; Kim, Jeehyun; Kim, Chulhong

    2013-11-01

    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.

  4. In vivo virtual intraoperative surgical photoacoustic microscopy

    SciTech Connect

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

    2013-11-11

    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.

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

    Microsoft Academic Search

    Yogesh K. Ramadass; Anantha P. Chandrakasan

    2010-01-01

    Harvesting ambient vibration energy through piezoelectric means is a popular energy harvesting technique which can potentially supply 10-100's of ¿W of available power. One of the main limitations of existing piezoelectric harvesters is in their interface circuitry. In this paper, a bias-flip rectifier circuit that can improve the power extraction capability from piezoelectric harvesters over conventional full-bridge rectifiers and voltage

  6. 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

  7. Pulsed photoacoustic measurements of suspensions: in case study of mitochnodrial NADH and its phantom

    NASA Astrophysics Data System (ADS)

    Zhao, Zuomin; Hast, Jukka; Myllylä, Risto; Känsäkoski, Markku

    2008-09-01

    The laser photoacoustic spectroscopy (LPAS) can be applied analytically to determine the concentration of an analyte in samples and its absorption variation as a function of time. The LPAS has advantages of higher detection sensitivity, pure absorption measurement and much less interference by background scattering in comparison with traditional optical spectroscopy. On the other hand, the apparatus is simpler and more generally useful than that of fluorescent spectroscopy. In this study, we built a photoacoustic setup of a Q-switched Nd:YAG laser excited at the third harmonic wavelength and a wideband piezoelectric transducer clamped to the side of a cuvette. The samples included NADH solutions, mitochondrial suspensions and Intralipid-ink mixtures. The experiment results show that the lowest detectable absorption of the setup is in the order of 10-5 cm-1; the detectable concentration of NADH in a buffer is as low as 1.67 ?M. When monitoring mitochondrial suspensions, the minimal concentration that can be detected is lower than 0.1 mg/mL and the absorption variation caused by full reduction of NAD+ to NADH in mitochondria can be detected.

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

    NASA Astrophysics Data System (ADS)

    Glorieux, Christ; Thoen, Jan

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Holan, Scott H.; Viator, John A.

    2008-06-01

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

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

    PubMed

    Holan, Scott H; Viator, John A

    2008-06-21

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

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

    E-print Network

    Ramadass, Yogesh Kumar

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

  13. 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

  14. 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.

  15. 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

  16. Fundus Camera Guided Photoacoustic Ophthalmoscopy

    PubMed Central

    Liu, Tan; Li, Hao; Song, Wei; Jiao, Shuliang; Zhang, Hao F.

    2014-01-01

    Purpose To demonstrate the feasibility of fundus camera guided photoacoustic ophthalmoscopy (PAOM) system and its multimodal imaging capabilities. Methods We integrated PAOM and a fundus camera consisting of a white-light illuminator and a high-sensitivity, high-speed CCD. The fundus camera captures both retinal anatomy and PAOM illumination at the same time to provide a real-time feedback when we position the PAOM illuminating light. We applied the integrated system to image rat eyes in vivo and used full-spectrum, visible (VIS), and near infrared (NIR) illuminations in fundus photography. Results Both albino and pigmented rat eyes were imaged in vivo. During alignment, different trajectories of PAOM laser scanning were successfully visualized by the fundus camera, which reduced the PAOM alignment time from several minutes to 30 s. In albino eyes, in addition to retinal vessels, main choroidal vessels were observed using VIS-illumination, which is similar to PAOM images. In pigmented eyes, the radial striations of retinal nerve fiber layer were visualized by fundus photography using full-spectrum illumination; meanwhile, PAOM imaged both retinal vessels and the retinal pigmented epithelium melanin distribution. Conclusions The results demonstrated that PAOM can be well-integrated with fundus camera without affecting its functionality. The fundus camera guidance is faster and easier comparing with our previous work. The integrated system also set the stage for the next-step verification between oximetry methods based on PAOM and fundus photography. PMID:24131226

  17. The cyclic electron pathways around photosystem I in Chlamydomonas reinhardtii as determined in vivo by photoacoustic measurements of energy storage

    Microsoft Academic Search

    Jacques Ravenel; Gilles Peltier; Michel Havaux

    1994-01-01

    The photoacoustic technique was used to measure energy storage by cyclic electron transfer around photosystem I in intact Chlamydomonas reinhardtii cells illuminated with far-red light (>715 nm). The in-vivo cyclic pathway was characterized by investigating the effects of various chemicals on energy storage. Participation of plastoquinone and ferredoxin in the cyclic electron flow was confirmed by the complete suppression of

  18. Photoacoustically Measured Speeds of Sound and the Equation of State of HBO2: On Understanding Detonation with Boron Fuel

    Microsoft Academic Search

    J M Zaug; S Bastea; J Crowhurst; M Armstrong; L Fried; N Teslich

    2010-01-01

    Elucidation of geodynamic, geochemical, and shock induced processes is limited by challenges to accurately determine molecular fluid equations of state (EOS). High pressure liquid state reactions of carbon species underlie physiochemical mechanisms such as differentiation of planetary interiors, deep carbon sequestration, propellant deflagration, and shock chemistry. In this proceedings paper we introduce a versatile photoacoustic technique developed to measure accurate

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  20. Photoacoustic tomography imaging based on a 4f acoustic lens imaging system.

    PubMed

    Chen, Zhanxu; Tang, Zhilie; Wan, Wei

    2007-04-16

    The theory of photoacoustic tomography (PAT) imaging using a 4f acoustic lens imaging system has been investigated, and the theoretical results show that a 4f acoustic lens has the ability of imaging and guarantees axial and lateral unit magnification of image. A system, a 4f acoustic lens imaging system combining with time-resolved technique, is developed to acquire PAT images. The 4f acoustic lens is able to image initial photoacoustic (PA) pressure distribution, which exactly resembles the absorption distribution, onto an imaging plane. Combining with time-resolved technique, the linear transducer array is adopted to acquire the PA pressure distribution to reconstruct the PAT images. Experimental results demonstrate that the system is able to obtain PAT images and the images contrast sharply with their backgrounds. PMID:19532746

  1. Photoacoustic tomography using integrating line detectors

    NASA Astrophysics Data System (ADS)

    Burgholzer, P.; Berer, T.; Gruen, H.; Roitner, H.; Bauer-Marschallinger, J.; Nuster, R.; Paltauf, G.

    2010-03-01

    Photoacoustic Imaging (also known as thermoacoustic or optoacoustic imaging) is a novel imaging method which combines the advantages of Diffuse Optical Imaging (high contrast) and Ultrasonic Imaging (high spatial resolution). In photoacoustic imaging, a short laser pulse excites the sample. The absorbed energy causes a thermoelastic expansion and thereby launches a broadband ultrasonic wave (photoacoustic signal). This way one can measure the optical contrast of a sample with ultrasonic resolution. For collecting photoacoustic signals our group introduced so called integrating detectors a few years ago. Such integrating detectors integrate the pressure in one or two dimensions (line or plane detectors). Thereby the three dimensional imaging problem is reduced to a two or a one dimensional problem for the pressure projections for line or plane detectors, respectively. Several reconstruction methods like Fourier or F-SAFT reconstruction or back projection are used for the two dimensional first step, but the model-based time reversal method shows a significant advantage: acoustical heterogeneity and attenuation, which both cause blurring of reconstructions, can be directly implemented in the reconstruction method. The integrating detectors are mainly optical detectors and thus can provide a high bandwidth up to several 100 MHz. Using these detectors the resolution is often limited by the acoustic attenuation in the sample itself, because attenuation increases with higher frequencies. For thin layers, small cylinders, and small spherical inclusions the effect of attenuation in human fat is simulated and the influence of dispersion on image reconstruction is shown.

  2. Photoacoustic microscopy of blood pulse Chenghung Yeh

    E-print Network

    Wang, Lihong

    coaxially and confocally. The generated photoacoustic wave was focused by an acoustic lens, detected, Thorlabs; aper- ture size: 2 mm), focused by a condenser lens (LA1131, Thor- labs) through a 50-m-limited optical focusing (focal diameter: 2.6 m). A home-made acoustic-optical beam combiner, containing an oil

  3. Noninvasive Photoacoustic and Fluorescence Sentinel Lymph Node

    E-print Network

    Wang, Lihong

    nodes and the blood- stream, leading to a wider spread of the cancer. The closest lymph node that drainsNoninvasive Photoacoustic and Fluorescence Sentinel Lymph Node Identification using Dye the lymphatic system. Cancer cells that migrate from the primary tumor may become lodged in the first lymph

  4. 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 ...

  5. On-line monitoring of biogenic isoprene emissions using photoacoustic spectroscopy

    Microsoft Academic Search

    H. Dahnke; J. Kahl; G. Schüler; W. Boland; W. Urban; F. Kühnemann

    2000-01-01

    .   Isoprene (C5H8) is one of the most important biogenic volatile organic compounds (VOCs) in the atmosphere. To calculate the impact of isoprene\\u000a on atmospheric processes models have been developed that describe the isoprene release from plants. Measurements of this release\\u000a require techniques for a fast, sensitive, on-line isoprene detection.\\u000a \\u000a Photoacoustic (PA) spectroscopy is applied here for the first time

  6. Detection of Nonlinear Laser Absorption in Solids by Means of Photoacoustic Effect

    Microsoft Academic Search

    Youn Bae

    1981-01-01

    A photoacoustic detection technique was developed to measure nonlinear optical absorptions in oriented single crystals ZnS, ZnO, SrTiO(,3) and TiO(,2) over a wide frequency range from 3.6 to 5.6 eV. Nonlinear two photon absorption processes were extensively investigated by measuring the dependence of two photon absorption coefficient (beta) on the frequency as well as the polarization of the laser beam.

  7. Photoacoustic tomography imaging based on a 4f acoustic lens imaging system

    Microsoft Academic Search

    Zhanxu Chen; Zhilie Tang; Wei Wan

    2007-01-01

    The theory of photoacoustic tomography (PAT) imaging using a 4f acoustic lens imaging system has been investigated, and the theoretical results show that a 4f acoustic lens has the ability of imaging and guarantees axial and lateral unit magnification of image. A system, a 4f acoustic lens imaging system combining with time-resolved technique, is developed to acquire PAT images. The

  8. 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.

  9. In vivo photoacoustic imaging of blood vessels with a pulsed laser diode

    Microsoft Academic Search

    Roy G. M. Kolkman; Wiendelt Steenbergen; Ton G. van Leeuwen

    2006-01-01

    Photoacoustic imaging is a hybrid imaging modality that is based on the detection of acoustic waves generated by absorption of pulsed light by tissue chromophores such as hemoglobin in blood. For this technique, usually large and costly Q-switched Nd:YAG lasers are used. These lasers provide a pulse energy of at least several milliJoules. In search of alternative light sources, we

  10. 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.

  11. 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.

  12. Piezoelectricity in protein amino acids

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

  13. 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.

  14. Micromachined Piezoelectric Cantilever Transducers

    Microsoft Academic Search

    Seung Seob Lee

    1995-01-01

    In this thesis, we present a micromachined piezoelectric acoustic transducer fabricated on a cantilever. Use of the cantilever as a supporting diaphragm produces a highly sensitive microphone. In addition, when the device is driven electrically as an output transducer (microspeaker), the relatively large deflections produce significant acoustic output. A voltage-to-frequency converter and a self-excited oscillator have also been demonstrated with

  15. Piezoelectricity in indium nitride

    Microsoft Academic Search

    I. L Guy; Z Zheng; M Wintrebert-Fouquet; K. S. A Butcher; P Chen; T. L Tansley

    2004-01-01

    An interferometric method has been used to measure the piezoelectric coefficient d33 in thin, InN layers grown by remote plasma-enhanced chemical vapour deposition. The measured value of the coefficient varies from around 3.1 to 4.7pmV?1. Theoretical predictions for these coefficients are scarce, but these values are significantly lower than those which are available. The discrepancy arises largely from the clamping

  16. Piezoelectrically enhanced photocathode

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  17. Black branes as piezoelectrics.

    PubMed

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

    2012-12-14

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

  18. Size-dependent piezoelectricity

    E-print Network

    Ali R. Hadjesfandiari

    2012-06-28

    In this paper, a consistent theory is developed for size-dependent piezoelectricity in dielectric solids. This theory shows that electric polarization can be generated as the result of coupling to the mean curvature tensor, unlike previous flexoelectric theories that postulate such couplings with other forms of curvature and more general strain gradient terms ignoring the possible couple- stresses. The present formulation represents an extension of recent work that establishes a consistent size-dependent theory for solid mechanics. Here by including scale-dependent measures in the energy equation, the general expressions for force- and couple-stresses, as well as electric displacement, are obtained. Next, the constitutive relations, displacement formulations, the uniqueness theorem and the reciprocal theorem for the corresponding linear small deformation size-dependent piezoelectricity are developed. As with existing flexoelectric formulations, one finds that the piezoelectric effect can also exist in isotropic materials, although in the present theory the coupling is strictly through the skew-symmetric mean curvature tensor. In the last portion of the paper, this isotropic case is considered in detail by developing the corresponding boundary value problem for two dimensional analyses and obtaining a closed form solution for an isotropic dielectric cylinder.

  19. Collecting back-reflected photons in photoacoustic microscopy

    PubMed Central

    Zhang, Hao F.; Wang, Jing; Wei, Qing; Liu, Tan; Jiao, Shuliang; Puliafito, Carmen A.

    2010-01-01

    Since the photoacoustic effect relies only on the absorbed optical energy, the back-reflected photons from samples in optical-resolution photoacoustic microscopy are usually discarded. By employing a 2 × 2 single-mode fiber optical coupler in a laser-scanning optical-resolution photoacoustic microscope for delivering the illuminating laser light and collecting the back reflected photons, a fiber-optic confocal microscope is integrated with the photoacoustic microscope. Thus, simultaneous multimodal imaging can be achieved with a single light source and images from the two modalities are intrinsically registered. Such capabilities are demonstrated in imaging both phantoms and small animals in vivo. PMID:20173952

  20. Photoacoustic imaging of the bladder: a pilot study.

    PubMed

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

    2013-07-01

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

  1. Photoacoustic and thermoacoustic tomography: system development for biomedical applications 

    E-print Network

    Ku, Geng

    2006-04-12

    Photoacoustic tomography (PAT), as well as thermoacoustic tomography (TAT), utilize electromagnetic radiation in its visible, near infrared, microwave, and radiofrequency forms, respectively, to induce acoustic waves in ...

  2. Snap-through buckling behavior of piezoelectric bimorph beams: I. Analytical and numerical modeling

    Microsoft Academic Search

    Georgios Giannopoulos; Javier Monreal; John Vantomme

    2007-01-01

    Piezoelectric structures are used in a variety of applications where instant response, high energy conversion efficiency and accurate control are required. However, it is widely known that piezoelectric structures suffer from a series of drawbacks, among which the most important is the small displacement capacity. A number of techniques have been used in order to transform the micron-scale displacements of

  3. Active buckling control of beams using piezoelectric actuators and strain gauge sensors

    Microsoft Academic Search

    Q. S. Wang

    2010-01-01

    In this paper, a finite element model incorporating active control techniques has been developed to stabilize the first two buckling modes of both a simply supported and a cantilevered beam. The goal is to increase the corresponding beam buckling loads by using piezoelectric actuators along with optimal feedback control. The uniform beams are bonded with two pairs of segmented piezoelectric

  4. Piezoelectric MEMS energy harvesting systems driven by harmonic and random vibrations

    Microsoft Academic Search

    Lars-Cyril Blystad; Einar Halvorsen; Svein Husa

    2010-01-01

    Switching power conditioning techniques are known to greatly enhance the performance of linear piezoelectric energy harvesters subject to harmonic vibrations. With such circuits, little is known about the effect of mechanical stoppers that limit the motion or about waveforms other than harmonic vibrations. This work presents SPICE simulations of piezoelectric micro energy harvester systems that differ in choice of power

  5. A piezoelectric screw dislocation interacting with an interphase layer between a circular inclusion and the matrix

    Microsoft Academic Search

    Y. W. Liu; Q. H. Fang; C. P. Jiang

    2004-01-01

    The interaction of a piezoelectric screw dislocation with an interphase layer between the circular inclusion and the piezoelectric matrix is dealt with. An efficient method for multiplying connected region is developed by combining the sectional holomorphic function, Cauchy-type integral and Laurent series expansion techniques, in terms of which the relation among the complex potentials for the three material regions is

  6. Effect of electric cyclic loading on fatigue cracking of a bending piezoelectric hybrid composite actuator

    Microsoft Academic Search

    Sung-Choong Woo; Nam Seo Goo

    2009-01-01

    Fatigue damage development in bending piezoelectric hybrid composite actuators with different lay-up configurations under electrical loading cycles is addressed in this work with the aid of an acoustic emission (AE) technique. Electric cyclic fatigue tests have been performed up to 107cycles on the fabricated bending piezoelectric hybrid composite actuators. The applied electric loading range is from ?150 voltage to +150

  7. Image reconstruction in photoacoustic tomography involving layered acoustic media.

    PubMed

    Schoonover, Robert W; Anastasio, Mark A

    2011-06-01

    Photoacoustic tomography (PAT), also known as thermoacoustic or optoacoustic tomography, is a rapidly emerging biomedical imaging technique that combines optical image contrast with ultrasound detection principles. Most existing reconstruction algorithms for PAT assume the object of interest possesses homogeneous acoustic properties. The images produced by such algorithms can contain significant distortions and artifacts when the object's acoustic properties are spatially variant. In this work, we establish an image reconstruction formula for PAT applications in which a planar detection surface is employed and the to-be-imaged optical absorber is embedded in a known planar layered acoustic medium. The reconstruction formula is exact in a mathematical sense and accounts for multiple acoustic reflections between the layers of the medium. Computer-simulation studies are conducted to demonstrate and investigate the proposed method. PMID:21643397

  8. 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.

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

    PubMed

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

    2014-10-01

    Optical-resolution photoacoustic flowmetry (PAF) allows noninvasive 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 PAF beyond 1 mm in tissue. PMID:25360912

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

    Progress in standoff detection of surface-bound explosives residue using photothermal and photoacoustic (PT/PA) imaging and spectroscopy has been reported recently. Photothermal/photoacoustic interferometry (PTI), a variation of the aforementioned techniques, is a candidate for standoff detection as a result of its non-contact and non-destructive approach. In PTI, the transient PT/PA hydrodynamic response produced by impulsive infra-red laser excitation(s) are detected by an overlapping focused probe laser beam. The return back-scattered/reflected probe laser beam is collected and coupled into a single-mode optical fiber. The PT/PA-induced perturbation on the return probe laser, in the form of phase or amplitude modulation or both, is extracted interferometrically. The resulting quadrature signals are digitized and processed to recover the minute PT/PA dynamics above background noise. Characteristic spectra for materials can be obtained by quantifying the PT response as a function of excitation(s) wavelength. The CW probe laser, operating in the 1550 nm range, and the constituents of the coherent detection system are commercial off-the-shelf components. A commercially available and continuously tunable quantum cascade laser (QCL) with output pulse energies up to 50 nJ was employed to generate the PT/PA spectra in the 8.8-10.2 ?m range. PTI detected absorption spectra were collected for HMX, RDX, and PETN, with the probe laser system positioned 5 meters away from the explosives targets. In addition, PTI measurements of the stimulated Raman (SR) spectra of ammonium nitrate and 2,4,6-trinitrotoluene obtained using a near-IR OPO laser are described. We believe this is the first-ever application of photothermal techniques to the measurement of the SR effect on solid explosive materials at meaningful standoff distances.

  11. Thermal and optical properties of Cd2SnO4 thin films using photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Jeyadheepan, K.; Palanichamy, P.; Swaminathan, V.; Jayachandran, M.; Sanjeeviraja, C.

    2010-03-01

    Cadmium stannate (Cd2SnO4) thin films were prepared by the RF magnetron sputtering technique on glass substrates with substrate temperatures of room temperature (RT), 100°C, 200°C and 300°C. Photoacoustic analyses were made to obtain the thermal diffusivity and the optical bandgap values of the Cd2SnO4 thin films. The change in thermal diffusivity of the films with the substrate temperature was analyzed. The optical bandgap values obtained from the photoacoustic spectroscopy were compared with the values obtained from the optical transmittance spectra. X-ray photoelectron spectroscopic (XPS) studies confirm the formation of stoichiometric films. Surface morphological studies by atomic force microscopy (AFM) revealed the crystalline nature of the films deposited at 100°C.

  12. 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

  13. Born-ratio type data normalization improves quantitation in photoacoustic tomography

    NASA Astrophysics Data System (ADS)

    Singh, M. Suheshkumar; Yalavarthy, Phaneendra K.

    2014-03-01

    In this report, we present a Born-ratio type of data normalization for reconstruction of initial acoustic pressure distribution in photoacoustic tomography (PAT). The normalized Born-ratio type of data is obtained as a ratio of photoacoustic pressure obtained with tissue sample in a coupling medium to the one obtained using purely coupling medium. It is shown that this type of data normalization improves the quantitation (intrinsic contrast) of the reconstructed images in comparison to the traditional techniques (unnormalized) that are currently available in PAT. Studies are carried out using various tissue samples. The robustness of the proposed method is studied at various noise levels added to the collected data. The improvement in quantitation can enable accurate estimation of pathophysiological parameter (optical absorption coefficient, ?a) of tissue sample under investigation leading to better sensitivity in PAT.

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

    PubMed

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

    2015-03-01

    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

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Spradling, Emily M.; Viator, John A.

    2009-02-01

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

  17. Integrated Photoacoustic Ophthalmoscopy and Spectral-domain Optical Coherence Tomography

    PubMed Central

    Jiao, Shuliang; Zhang, Hao F.

    2013-01-01

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

  18. High-Temperature Piezoelectrics with Large Piezoelectric Coefficients

    NASA Astrophysics Data System (ADS)

    Shinekumar, K.; Dutta, Soma

    2015-02-01

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

  19. Structured Piezoelectric Composites: Materials and Applications

    Microsoft Academic Search

    D. A. Van den Ende

    2012-01-01

    The piezoelectric effect, which causes a material to generate a voltage when it deforms, is very suitable for making integrated sensors, and (micro-) generators. However, conventional piezoelectric materials are either brittle ceramics or certain polymers with a low thermal stability, which limits their practical application to certain specific fields. Piezoelectric composites, which contain an active piezoelectric (ceramic) phase in a

  20. Analytical Modelling of a Plucked Piezoelectric Bimorph for Energy Harvesting

    E-print Network

    Pozzi, Michele

    2012-01-01

    Energy harvesting (EH) is a multidisciplinary research area, involving physics, materials science and engineering, with the objective of providing renewable sources of sufficient power to operate targeted low-power applications. Piezoelectric transducers are often used for vibrational, inertial and direct movement EH. One problem is that, due to the stiffness of the most common material (PZT) and typically useful sizes, intrinsic resonant frequencies are normally high, whereas the available power is often concentrated at low frequencies. The aim of the plucking technique of frequency up-conversion, also known as "pizzicato" excitation, is to bridge this frequency gap. In this paper, the technique is modelled analytically. The analytical model is developed starting from the Euler-Bernoulli beam equations modified for piezoelectric coupling. A system of differential equations and associated initial conditions are derived which describe the free vibration of a piezoelectric bimorph in the last part of the plucki...

  1. A photoacoustic spectrometer for trace gas detection

    NASA Astrophysics Data System (ADS)

    Telles, E. M.; Bezerra, E.; Scalabrin, A.

    2005-06-01

    A high-resolution external laser photoacoustic spectrometer has been developed for trace gas detection with absorption transitions in coincidence with CO2 laser emission lines (9,2-10,9 ?m: 920-1086 cm-1). The CO2 laser operates in 90 CW lines with power of up to 15 W. A PC-controlled step motor can tune the laser lines. The resonance frequency of first longitudinal mode of the photoacoustic cell is at 1600 Hz. The cell Q-factor and cell constant are measured close to 50 and 28 mVcmW-1, respectively. The spectrometer has been tested in preliminary studies to analyze the absorption transitions of ozone (O_3). The ethylene (C_2H_4) from papaya fruit is also investigated using N2 as carrier gas at a constant flow rate.

  2. 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.

  3. Plucked piezoelectric bimorphs for energy harvesting applications

    NASA Astrophysics Data System (ADS)

    Pozzi, Michele; Zhu, Meiling

    2011-06-01

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

  4. PHOTOACOUSTIC AND THERMOACOUSTIC TOMOGRAPHY WITH AN UNCERTAIN WAVE SPEED

    E-print Network

    Uhlmann, Gunther

    PHOTOACOUSTIC AND THERMOACOUSTIC TOMOGRAPHY WITH AN UNCERTAIN WAVE SPEED LAURI OKSANEN AND GUNTHER UHLMANN Abstract. We consider the mathematical model of photoacoustic and thermoacoustic tomography. In Thermoacoustic tomography (TAT), see e.g. [8], low frequency microwaves, with wavelengths on the order of 1m

  5. Multifunctional Photosensitizer-Based Contrast Agents for Photoacoustic Imaging

    PubMed Central

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

    2014-01-01

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

  6. Negative lens concept for photoacoustic tomography Changhui Li,* Geng Ku,

    E-print Network

    Wang, Lihong

    lens. By analogy, an ultrasound wave can be di- verged by the acoustic counterpart--an acousticNegative lens concept for photoacoustic tomography Changhui Li,* Geng Ku, and Lihong V. Wang in reconstruction-based photoacoustic tomography PAT . Here, we propose a negative lens concept to increase

  7. CO 2-laser photoacoustic detection of gaseous n-pentylacetate

    NASA Astrophysics Data System (ADS)

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

    2009-07-01

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

  8. Hands-on resonance-enhanced photoacoustic detection

    NASA Astrophysics Data System (ADS)

    Euler, Manfred

    2001-10-01

    The design of an improved photoacoustic converter cell using kitchen equipment is described. It operates by changing manually the Helmholtz resonance frequency of bottles by adjusting the distance between the bottleneck and the outer ear. The experiment helps to gain insights in ear performance, in photoacoustic detection methods, in resonance phenomena and their role for detecting small periodic signals in the presence of noise.

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

    E-print Network

    Wang, Lihong

    tool for diagnosis and therapy of cancer and other diseases as well as for metabolismLabel-free oxygen-metabolic photoacoustic microscopy in vivo Junjie Yao Konstantin I. Maslov Yu-free oxygen-metabolic photoacoustic microscopy in vivo Junjie Yao, Konstantin I. Maslov, Yu Zhang, Younan Xia

  10. 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.

  11. Photoacoustic spectroscopy of gaseous biomarker in simulated breath

    NASA Astrophysics Data System (ADS)

    Le, Hanh N. D.; U-Thainual, Paweena; Kim, Do-Hyun

    2015-03-01

    In this study, a photoacoustic detector integrated with Fourier-transform infrared spectroscopy was used to measure biomarkers in gas samples independently. Simulated exhaled breath samples were created by mixing varying concentrations of acetone, ammonia and ethane. The results of these measurements demonstrate the potential of photoacoustic spectroscopy to detect biomarkers from human breath.

  12. In vivo photoacoustic tomography of mouse cerebral edema induced

    E-print Network

    Wang, Lihong

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

  13. Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Photoacoustic Imaging

    Microsoft Academic Search

    Srikant Vaithilingam; Ira O. Wygant; P Aulina S. Kuo; Xuefeng Zhuang; Omer Oralkan; Peter D. Olcott; Butrus T. Khuri-yakub

    ABSTRACT In photoacoustic (optoacoustic) medical imaging, short laser pulses irradiate absorbing structures found in tissue, such as blood vessels, causing brief thermal expansions that in turn generate ultrasound waves. These ultrasound waves which correspond to the optical absorption distribution were imaged using a two-dimensional array of capacitive micromachined ultrasonic transducers (CMUTs). Advantages of CMUT technology for photoacoustic imaging include the

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

    PubMed

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

    2011-02-01

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

  15. Adaptive beamforming for photoacoustic imaging using linear array transducer

    Microsoft Academic Search

    Andrei B. Karpiouk; Salavat R. Aglyamov; Stanislav Y. Emelianov

    2008-01-01

    Photoacoustic signals, detected by a transducer array, need to be beamformed for subsequent use in a limited view angle tomography such as B-scan imaging. In the presence of the light scattering or phase aberration, the spatial resolution and contrast in the photoacoustic images are degraded. Phase aberration due to tissues with inhomogeneous acoustic speeds is a major source for image

  16. Photoacoustic characterization of the mechanical properties of thin films

    Microsoft Academic Search

    Carmen M. Hernandez; Todd W. Murray; Sridhar Krishnaswamy

    Narrow band photoacoustics ~laser ultrasonics! are used to characterize the properties of free-standing nanometer-sized thin films. Photoacoustic generation is achieved by use of a microchip laser which deposits pulsed laser energy in the form of a spatially periodic source on the structure. The resulting narrow band ultrasonic modes are monitored using a Michelson interferometer. By varying the geometry of the

  17. Quantitative Photo-Acoustic Imaging of Small Absorbers Habib Ammari

    E-print Network

    Kang, Hyeonbae

    Quantitative Photo-Acoustic Imaging of Small Absorbers Habib Ammari Emmanuel Bossy Vincent Jugnon Hyeonbae Kang§ December 1, 2009 Abstract In photo-acoustic imaging, energy absorption causes thermo absorber from the absorbed density. AMS subject classifications. 31B20, 35B37,35L05 Key words. photo

  18. Experiments to demonstrate piezoelectric and pyroelectric effects

    NASA Astrophysics Data System (ADS)

    Erhart, Ji?í

    2013-07-01

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

  19. 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.

  20. 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.

  1. 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.

  2. Photoacoustics of disperse systems: Below cavitation threshold

    NASA Astrophysics Data System (ADS)

    Egerev, Sergey; Ovchinnikov, Oleg

    2012-05-01

    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.

  3. 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

  4. Imagining the future of photoacoustic mammography.

    PubMed

    van der Burg, Simone

    2009-03-01

    How can a realistic ethical imagination about the future of a technology take shape? This article contains a reflection which is based on the experiences of an embedded ethicist in the context of biophysical research conducive to the development of photoacoustic mammography, which is intended for the non-invasive detection of breast cancer. Imagination in this context already informs the activities of the biophysical researchers, but its role is limited: biophysical future scenarios concentrate on the technological advances that photoacoustics could bring about. In this article it is argued that it is advisable to also consider the medical practice and the ways in which this practice is likely to change as an effect of the introduction of photoacoustic mammography into it. On the basis of this more encompassing imaginative endeavor it is possible to get a clearer idea about how new technologies are able to contribute to human well being, which is informative for the setting of research-goals/priorities and a responsible implementation of new technologies into the world. PMID:18626790

  5. Photoacoustic imaging and characterization of the microvasculature

    NASA Astrophysics Data System (ADS)

    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.

  6. 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.

  7. Photoacoustic imaging and characterization of the microvasculature.

    PubMed

    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

  8. Acoustic and Photoacoustic Molecular Imaging of Cancer

    PubMed Central

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

    2014-01-01

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

  9. 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.

  10. 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.

  11. Simultaneous dual-frequency excitation of a resonant photoacoustic cell

    NASA Astrophysics Data System (ADS)

    Rey, Julien M.; Sigrist, Markus W.

    2008-10-01

    Simultaneous amplitude modulation of the exciting light beam with two different frequencies enables the excitation of two acoustic modes of a resonant photoacoustic cell. The photoacoustic amplitudes at both resonance frequencies and the corresponding photoacoustic amplitude ratio are obtained continuously without changing the modulation frequency. The photoacoustic mode amplitude ratio is affected neither by intensity fluctuations of the light source nor by microphone or electronics drifts and is a measure of the gas concentration. The simultaneous acquisition of signals at both resonance frequencies with the dual-modulation scheme reduces drifts on the timescale needed to obtain the PA amplitude ratio. As an example acetone measurements using this new dual-modulation photoacoustic scheme are presented. A detection limit of 90 ppm m -1 is reached with a simple heated black-body as infrared light source.

  12. 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...

  13. 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.

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

    PubMed

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

    2013-10-01

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

  15. 3-D photoacoustic and pulse echo imaging of prostate tumor progression in the mouse window chamber

    PubMed Central

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

    2011-01-01

    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. PMID:21361696

  16. 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.

  17. Simplified method for ultra high-resolution photoacoustic microscopy via transient absorption.

    PubMed

    Mattison, Scott P; Applegate, Brian E

    2014-08-01

    Photoacoustic microscopy (PAM) is a hybrid imaging modality that combines optical illumination with ultrasonic detection to achieve absorption contrast imaging of endogenous and exogenous chromophores. Optical resolution PAM achieves high lateral-resolution by tightly focusing the excitation light; however the axial resolution is still dependent upon the bandwidth of the ultrasonic transducer. As a result, PAM images have highly asymmetric voxels with submicron lateral resolution and axial resolution typically limited to tens of microns. We have previously reported on a resonant multiphoton approach to PAM called transient absorption ultrasonic microscopy (TAUM), which enables high axial resolution by frequency encoding the photoacoustic signal at the overlap of a pump and a probe beam. This approach enables photoacoustic imaging with subcellular resolution on par with other multiphoton microscopy techniques. Here, we report on an innovation that enables TAUM imaging with a much less sophisticated optical system than previously reported. If we allow the time delay between the pump and probe to collapse to zero, the pump and probe optical paths can be combined. An amplitude modulator in the single beam path is sufficient to encode the TAUM signal at the second harmonic of the modulation frequency. The resulting system is essentially a standard optical resolution PAM system that incorporates an amplitude modulator and utilizes a Fourier post processing algorithm to improve the axial resolution by approximately an order of magnitude. A prototype system based on this approach has been assembled and tested on fixed bovine erythrocytes. PMID:25078206

  18. Direct measurement of aerosol absorption at elevated relative humidity using photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Langridge, J. M.; Lack, D. A.; Wagner, N.; Richardson, M.; Brock, C. A.; Law, D. C.; Murphy, D. M.

    2012-12-01

    The impacts of atmospheric aerosol on radiative forcing depend strongly on relative humidity (RH). As particles take up water at elevated humidity, both scattering and absorption properties can be modified. Experimental measurements to date have focused heavily on characterising the RH dependence of scattering. These efforts have yielded a large body of data, which has guided the construction of parameterisations needed for large-scale climate modelling. Similar measurements of the RH dependence of aerosol absorption are however limited, largely due to difficulties associated with making measurements using traditional methods. New approaches are needed. One technique that has shown promise is photoacoustic spectroscopy. In this presentation we will provide a comprehensive laboratory validation of the performance of the NOAA aerosol photoacoustic instrument at elevated RH. This section will highlight key factors that must be considered when operating photoacoustic instruments at elevated RH, such as variable microphone sensitivities, background corrections and evaporative heat transfer effects. We will also present measurements of absorption at elevated RH made in a dense forest fire smoke plume sampled aboard the NASA DC-8 aircraft during the recent Deep Convective Clouds and Chemistry (DC3) project. The significance of these measurements for understanding the impacts of this aerosol class on radiative forcing will be discussed.

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

    PubMed Central

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

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

    PubMed

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

    2013-12-15

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

  2. 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.

  3. 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%.

  4. 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.

  5. Acoustic resolution photoacoustic Doppler velocity measurements in fluids using time-domain cross-correlation

    NASA Astrophysics Data System (ADS)

    Brunker, J.; Beard, P.

    2013-03-01

    Blood flow measurements have been demonstrated using the acoustic resolution mode of photoacoustic sensing. This is unlike previous flowmetry methods using the optical resolution mode, which limits the maximum penetration depth to approximately 1mm. Here we describe a pulsed time correlation photoacoustic Doppler technique that is inherently flexible, lending itself to both resolution modes. Doppler time shifts are quantified via cross-correlation of pairs of photoacoustic waveforms generated in moving absorbers using pairs of laser light pulses, and the photoacoustic waves detected using an ultrasound transducer. The acoustic resolution mode is employed by using the transducer focal width, rather than the large illuminated volume, to define the lateral spatial resolution. The use of short laser pulses allows depth-resolved measurements to be obtained with high spatial resolution, offering the prospect of mapping flow within microcirculation. Whilst our previous work has been limited to a non-fluid phantom, we now demonstrate measurements in more realistic blood-mimicking phantoms incorporating fluid suspensions of microspheres flowing along an optically transparent tube. Velocities up to 110 mm/s were measured with accuracies approaching 1% of the known velocities, and resolutions of a few mm/s. The velocity range and resolution are scalable with excitation pulse separation, but the maximum measurable velocity was considerably smaller than the value expected from the detector focal beam width. Measurements were also made for blood flowing at velocities up to 13.5 mm/s. This was for a sample reduced to 5% of the normal haematocrit; increasing the red blood cell concentration limited the maximum measurable velocity so that no results were obtained for concentrations greater than 20% of a physiologically realistic haematocrit. There are several possible causes for this limitation; these include the detector bandwidth and irregularities in the flow pattern. Better results are obtained using a detector with a higher centre frequency and larger bandwidth and tubes with a narrower diameter.

  6. 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. (Ames Laboratory-USDOE, Iowa State University, Ames, Iowa 50011-3020 (United States)); Kobayashi, K.; Takaoka, K. (Department of Chemistry, Musashi Institute of Technology, Setagaya-ku, Tokyo 158 (Japan))

    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.

  7. 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

  8. A piezoelectric power harvester with adjustable frequency through axial preloads

    Microsoft Academic Search

    Yuantai Hu; Huan Xue; Hongping Hu

    2007-01-01

    We study the technique to adjust the performance of a piezoelectric bimorph vibrating in the flexural mode through axial preloads, which is useful for a power harvester to effectively scavenge energy from ambient mechanical vibrations\\/noise with varying-frequency spectra. The external circuit connected to the bimorph is simplified as an impedance in the analysis. Analytical solutions are derived. The analyses show

  9. Effect of thermal nonlinearity in high-absorption media on the parameters of the photoacoustic signal detected by the gas microphone method: The fundamental and second harmonics

    NASA Astrophysics Data System (ADS)

    Madvaliev, U.; Salikhov, T. Kh.; Sharifov, D. M.

    2006-06-01

    A perturbation theory is put forward that describes the effect of thermal nonlinearity due to the temperature dependence of the thermophysical parameters of high-absorption systems with a low thermal conductivity on the parameters of the photoacoustic signal detected by the gas microphone technique. It is found that the dependence of the photoacoustic signal amplitude on incident beam intensity I 0 stems from the dependence of the illuminated surface temperature on I 0. This dependence is a complicated function instead of being a simple quadratic function as was expected. In the limiting cases (?s? ? 1 and ?s? ? 1), this contribution to the photoacoustic signal amplitude is described by simple expressions, which are convenient for determining the thermal coefficients of the thermophysical parameters of the medium. It is found that the thermal nonlinearity significantly affects the photoacoustic signal phase in the frequency region meeting the condition ?s? ˜ 1. In the above limiting cases, its effect is insignificant. A theory of generation of the photoacoustic signal second harmonic is proposed. The second harmonic is related to the temperature dependence of the thermophysical parameters of the buffer gas and sample. It is shown that the amplitude of the signal is a quadratic function of the incident beam intensity and varies with its frequency as ?-3/2 for ?s? ? 1 and ?-5/2 for ?s? ? 1.

  10. Micromachined Piezoelectric Cantilever Transducers.

    NASA Astrophysics Data System (ADS)

    Lee, Seung Seob

    1995-05-01

    In this thesis, we present a micromachined piezoelectric acoustic transducer fabricated on a cantilever. Use of the cantilever as a supporting diaphragm produces a highly sensitive microphone. In addition, when the device is driven electrically as an output transducer (microspeaker), the relatively large deflections produce significant acoustic output. A voltage-to-frequency converter and a self-excited oscillator have also been demonstrated with piezoelectric cantilever transducers. The 2 x 2 x 0.0045 mm^3 micromachined transducers have a zinc oxide (ZnO) piezoelectric thin film on a 1.5 mum-thick bulk -micromachined cantilever diaphragm, made of low-pressure chemical-vapor-deposited (LPCVD) low-stress silicon nitride. The measured microphone sensitivity is fairly constant at 2 mV/mubar in the low -frequency range below the first resonant frequency, which occurs at 1.8 kHz. The microspeaker output is approximately 100 dB SPL at 4.8 kHz and 12 V_ {P-P} input drive. The voltage-to-frequency conversion is accomplished by the addition of a conducting plate and an aluminum (Al) sputtered layer on the underside of the cantilever. The resonant frequency of the microspeaker is changed by the potential applied between the top plate and the lower Al layer. As the potential is changed from 0 to 40 V _{P-P}, the resonant frequency shifts down from 14.5 kHz to 11.5 kHz while the amplitude of the output pressure is increased by 12.5 dB SPL. The multi-electrode cantilever transducer constitutes a self-excited oscillator with an amplifier that amplifies the feedback signal to drive the cantilever via drive electrode. If the gain of the amplifier is sufficient to overcome the loss of the transducer and the resonant frequency is in the amplifier passband, oscillation occurs and significant acoustic output is produced. The output pressure is higher than 90 dB SPL at 14.54 kHz at 0.5 cm from the transducer.

  11. Piezoelectric cantilever acoustic transducer

    NASA Astrophysics Data System (ADS)

    Lee, Seung S.; White, Richard M.

    1998-09-01

    We present a piezoelectric acoustic transducer fabricated on a bulk-micromachined cantilever diaphragm. Use of the cantilever as a supporting diaphragm produces a highly sensitive microphone. In addition, when the device is driven electrically as an output transducer, a microspeaker, the relatively large deflections produce significant acoustic output. A voltage-to-frequency converter has also been demonstrated with piezoelectric cantilever transducers. The 0960-1317/8/3/009/img5 micromachined transducer has a zinc oxide (ZnO) piezoelectric thin film on a 1.5 0960-1317/8/3/009/img6m thick cantilever diaphragm, made of LPCVD low-stress silicon nitride. The measured cantilever microphone sensitivity is fairly constant around 3 mV 0960-1317/8/3/009/img7 in the low-frequency range below the first resonant frequency, which occurs at 1.8 kHz. The microspeaker output is approximately 100 dB SPL at 4.8 kHz and 12 0960-1317/8/3/009/img8 (peak-peak) input drive. The voltage-to-frequency conversion is accomplished by the addition of a conducting plate and an aluminum (Al) sputtered layer on the underside of the cantilever. The resonant frequency of the microspeaker is changed by the potential applied between the top conducting plate and the lower Al layer. As the potential is changed from 0 to 40 0960-1317/8/3/009/img8, the resonant frequency shifts down from 14.5 kHz to 11.5 kHz while the amplitude of the output pressure is increased by 12.5 dB SPL. In the potential range of 15 to 25 0960-1317/8/3/009/img8, the frequency shift is fairly linear with the potential change and the sensitivity (frequency shift per unit applied potential change) is 200 Hz 0960-1317/8/3/009/img11 around 13 kHz.

  12. Modeling of Piezoelectric Tube Actuators

    E-print Network

    El Rifai, Osamah M.

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

  13. 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 ...

  14. 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.

  15. Visualization of microcalcifications using photoacoustic imaging: feasibility study

    NASA Astrophysics Data System (ADS)

    Hsiao, Tsai-Chu; Wang, Po-Hsun; Fan, Chih-Tai; Cheng, Yao-You; Li, Meng-Lin

    2011-03-01

    Recently, photoacoustic imaging has been intensively studied for blood vessel imaging, and shown its capability of revealing vascular features suggestive of malignancy of breast cancer. In this study, we explore the feasibility of visualization of micro-calcifications using photoacoustic imaging. Breast micro-calcification is also known as one of the most important indicators for early breast cancer detection. The non-ionizing radiation and speckle free nature of photoacoustic imaging overcomes the drawbacks of current diagnostic tools - X-ray mammography and ultrasound imaging, respectively. We employed a 10-MHz photoacoustic imaging system to verify our idea. A sliced chicken breast phantom with granulated calcium hydroxyapatite (HA) - major chemical composition of the breast calcification associated with malignant breast cancers - embedded was imaged. With the near infared (NIR) laser excitation, it is shown that the distribution of ~500 ?m HAs can be clearly imaged. In addition, photoacoustic signals from HAs rivals those of blood given an optimal NIR wavelength. In summary, photoacoustic imaging shows its promise for breast micro-calcification detection. Moreover, fusion of the photoacoustic and ultrasound images can reveal the location and distribution of micro-calcifications within anatomical landmarks of the breast tissue, which is clinically useful for biopsy and diagnosis of breast cancer staging.

  16. 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.

  17. 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.

  18. Photoacoustic tomography of water in phantoms and tissue

    PubMed Central

    Xu, Zhun; Li, Changhui; Wang, Lihong V.

    2010-01-01

    Photoacoustic tomography (PAT) has been widely used to image optically absorptive objects in both human and animal tissues. For the first time, we present imaging of water with laser-based PAT. We photoacoustically measure the absorption spectra of water-ethanol mixtures at various water concentrations, and then image water-ethanol and pure-water inclusions in gel and a water inclusion in fat tissue. The significant difference in photoacoustic signals between water and fat tissue indicates that the laser-based PAT has the potential to detect water content in tissue. PMID:20615021

  19. Vibrational Photoacoustic Tomography: Chemical Imaging beyond the Ballistic Regime

    PubMed Central

    Wang, Pu; Cheng, Ji-Xin

    2013-01-01

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

  20. DFB laser diodes for sensing applications using photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Koeth, J.; Fischer, M.; Legge, M.; Seufert, J.; Rössner, K.; Groninga, H.

    2010-03-01

    We present typical device characteristics of novel DFB laser diodes which are employed in various sensing applications including high resolution photoacoustic spectroscopy. The laser diodes discussed are based on a genuine fabrication technology which allows for the production of ultra stable devices within a broad spectral range from 760 nm up to 3000 nm wavelength. The devices exhibit narrow linewidths down to <1 MHz which makes them ideally suited for all photoacoustic sensing applications where a high spectral purity is required. As an example we will focus on a typical medical application where these diodes are used for breath analysis using photoacoustic spectroscopy.

  1. 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

  2. The piezoelectric sorption technique: a practical method 

    E-print Network

    Flipse, Eugene Charles

    1983-01-01

    commercially available QCM to measure the adsorption and desorption of water. Their results were consistent with existing theory. Mecca and Bucur (1980) used a QCMSD for dynamic sorption studies. They used a single crystal to determine mass changes. King... with the sample-coated crystal. Saeki and Bonner (1978) measured the sorption of benzene in poly-ethylene oxide. The apparatus used in the QCMSD included a single crystal driven by a hex inverter oscillator. Results agreed to within 3% of reported literature...

  3. 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.

  4. 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.

  5. Functional photoacoustic microscopy of pH

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    pH is a tightly regulated indicator of metabolic activity. In mammalian systems, an imbalance of pH regulation may result from or result in serious illness. In this paper, we report photoacoustic microscopy (PAM) of a commercially available pH-sensitive fluorescent dye (SNARF-5F carboxylic acid) in tissue phantoms. We demonstrated that PAM is capable of pH imaging in absolute values at tissue depths of up to 2.0 mm, greater than possible with other forms of optical microscopy.

  6. Liquid acoustic lens for photoacoustic tomography.

    PubMed

    Song, Chaolong; Xi, Lei; Jiang, Huabei

    2013-08-01

    Recently, intensive research has been conducted to accelerate the development of photoacoustic (PA) imaging modality for biomedical applications. The use of acoustic lenses to collect ultrasound signals is of great interest. This Letter presents the design and fabrication of a liquid acoustic diverging lens, which can enlarge the acceptance angle of an ultrasound transducer. This lens possesses an inherent advantage of low acoustic impedance and the convenience to be attached to or detached from a commercial flat transducer. Phantom experiments have been carried out to demonstrate the improvement of using such a liquid lens over using a bare transducer for PA tomography. PMID:23903182

  7. Testing fruit quality by photoacoustic spectroscopy assay

    NASA Astrophysics Data System (ADS)

    Popa, C.; Dumitras, D. C.; Patachia, M.; Banita, S.

    2014-10-01

    This study was conducted with the aim of testing the hypothesis that raspberry and strawberry fruits from nonorganic farming release more ethylene gas compounds compared to organic ones. At the same time, the experiments focused on evaluation of the potential and capabilities of the laser photoacoustic spectroscopy (LPAS) method in the assessment of fruit quality related to the effects of nitrogen. Ethylene gas can be harmful and carcinogenic, because it can accelerate the natural ripening process of physiologically mature fruits and makes the fruits more consistent in size. With the advantages of LPAS, we demonstrate that the concentration of ethylene from nonorganic raspberry and strawberry fruits is greater than from organic ones.

  8. Negative lens concept for photoacoustic tomography.

    PubMed

    Li, Changhui; Ku, Geng; Wang, Lihong V

    2008-08-01

    Although a small point ultrasound transducer has a wide acceptance angle, its small active area leads to a high thermal-noise-induced electric voltage in the transducer, thus the sensitivity is low. By contrast, a finite-size flat transducer has high sensitivity, but the acceptance angle is small, which limits its application in reconstruction-based photoacoustic tomography (PAT). Here, we propose a negative lens concept to increase the acceptance angle of a flat transducer without losing sensitivity. Phantom experiments demonstrate that use of this concept greatly increases the detection region for PAT with high sensitivity. PMID:18850859

  9. Self-powered discrete time piezoelectric vibration damper

    NASA Astrophysics Data System (ADS)

    Konak, Michael J.; Powlesland, Ian G.; van der Velden, Stephen P.; Galea, Stephen C.

    1997-11-01

    Structural vibration suppression is of great interest to the aircraft industry as it can reduce the amplitude of excessive vibration in lightly damped panels caused by conditions in their operational environment. One technique of suppressing vibration is to use passive damping techniques such as constrained layered damping incorporating viscoelastic materials. However these techniques may not be acceptable because of weight concerns or extreme temperature variations. Over the past decade much work has been done by researchers on the use of piezoelectric ceramic devices, using passive and active techniques, for structural vibration suppression. The passive piezoelectric damping devices consist of a piezoelectric element and either a resistive or resonant shunt. The resonant circuit shunt, which is analogous to a mechanical vibration absorber, gives better vibration reduction compared to the resistor shunt. This device requires a large value of inductance in order to be tuned to a particular structural vibration mode. A large value inductor can be made by a using a gyrator type circuit however the circuit needs external power. A method of vibration control using a discrete time controller and piezoelectric devices is presented. That is, this paper describes the concept of a self-powered discrete time piezoelectric vibration damper which does not need tuning to the structural resonant frequency and is powered by piezoelectric elements, i.e. does not need an external power supply. This device is referred to as a strain amplitude minimization patch (STAMP) damper. A brief description of the theory used and of the scheme is presented. Also the operation of this device is compared with other 'passive' techniques, involving piezoelectric elements, such as the resistive passive damper and the parallel resonant passive damper cases. Experimental results presented, on a cantilevered beam, demonstrate the concept and show that the device, even in its current underdeveloped form, has better damping than the simple resistor damper. Measurements taken indicate that the maximum RMS tip accelerations, at resonance, are reduced by 17.3%, 62.7% and 39.5% for the resistor, parallel resonant and STAMP damper devices, respectively, when compared to the short circuit reference condition. The performance of each device is observed when the resonant frequency of the system changes when a mass is added to the tip of the cantilever. This paper also discusses areas where improvements in the performance of the STAMP damper can be achieved.

  10. Experimental Evaluation of Adaptive and Variable Structure Control of Piezoelectric Actuation Systems for Micro\\/Nano Manipulation

    Microsoft Academic Search

    Hwee Choo Liaw; Bijan Shirinzadeh; Denny Oetomo; Gürsel Alici

    2006-01-01

    This paper proposes and evaluates an adaptive technique and a variable structure control approach for piezoelectric actuation systems to track specified motion trajectories. The proposed control methodologies are formulated to accommodate unknown or uncertain system parameters, nonlinearities including the hysteresis effect, and external disturbances in the piezoelectric actuation systems without any form of feed-forward compensation. In this study, both control

  11. Connected Vibrating Piezoelectric Bimorph Beams as a Wide-band Piezoelectric Power Harvester

    Microsoft Academic Search

    Zengtao Yang; Jiashi Yang

    2009-01-01

    We analyze coupled flexural vibration of two elastically and electrically connected piezoelectric beams near resonance for converting mechanical vibration energy to electrical energy. Each beam is a so-called piezoelectric bimorph with two layers of piezoelectrics. The 1D equations for bending of piezoelectric beams are used for a theoretical analysis. An exact analytical solution to the beam equations is obtained. Numerical

  12. Non destructive FTIR-photoacoustic spectroscopy studies on carbon fiber reinforced polyimide composite and water diffusion in epoxy resin

    Microsoft Academic Search

    Ravikumar Vijayaraghavan

    2008-01-01

    Photo-acoustic (PA) detection is a non-destructive, non-disruptive mode of sample analysis. The principle of PA detection is monitoring the change in thermal properties of the material as a result of optical absorption. The ability to use with any incident radiation source makes it an attractive technique to study molecular excitations, vibrations and defects in any sample. Given the need for

  13. Numerical analysis of piezoelectric active repair in the presence of frictional contact conditions.

    PubMed

    Alaimo, Andrea; Milazzo, Alberto; Orlando, Calogero; Messineo, Antonio

    2013-01-01

    The increasing development of smart materials, such as piezoelectric and shape memory alloys, has opened new opportunities for improving repair techniques. Particularly, active repairs, based on the converse piezoelectric effect, can increase the life of a structure by reducing the crack opening. A deep characterization of the electromechanical behavior of delaminated composite structures, actively repaired by piezoelectric patches, can be achieved by considering the adhesive layer between the host structure and the repair and by taking into account the frictional contact between the crack surfaces. In this paper, Boundary Element (BE) analyses performed on delaminated composite structures repaired by active piezoelectric patches are presented. A two-dimensional boundary integral formulation for piezoelectric solids based on the multi-domain technique to model the composite host damaged structures and the bonded piezoelectric patches is employed. An interface spring model is also implemented to take into account the finite stiffness of the bonding layers and to model the frictional contact between the delamination surfaces, by means of an iterative procedure. The effect of the adhesive between the plies of piezoelectric bimorph devices on the electromechanical response is first pointed out for both sensing and actuating behavior. Then, the effect of the frictional contact condition on the fracture mechanics behavior of actively repaired delaminated composite structures is investigated. PMID:23549364

  14. Experimental measurements and finite element analysis of the coupled vibrational characteristics of piezoelectric shells.

    PubMed

    Huang, Yu-Hsi; Ma, Chien-Ching

    2012-04-01

    Piezoelectric plates can provide low-frequency transverse vibrational displacements and high-frequency planar vibrational displacements, which are usually uncoupled. However, piezoelectric shells can induce three-dimensional coupled vibrational displacements over a large frequency range. In this study, three-dimensional coupled vibrational characteristics of piezoelectric shells with free boundary conditions are investigated using three different experimental methods and finite element numerical modeling. For the experimental measurements, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) is used to obtain resonant frequencies and radial, lateral, and angular mode shapes. This optical technique utilizes a real-time, full-field, non-contact optical system that measures both the natural frequency and corresponding vibration mode shape simultaneously. The second experimental technique used, laser Doppler vibrometry (LDV), is a pointwise displacement measurement method that determines the resonant frequencies of the piezoelectric shell. An impedance analyzer is also used to determine the resonant frequencies of the piezoelectric shell. The experimental results of the resonant frequencies and mode shapes for the piezoelectric shell are verified with a numerical finite element model. Excellent agreement between the experimental and numerical results is found for the three-dimensional coupled vibrational characteristics of the piezoelectric shell. It is noted in this study that there is no coupled phenomenon at low frequencies over which radial modes dominate. However, three-dimensional coupled vibrational modes do occur at high resonant frequencies over which lateral or angular modes dominate. PMID:22547289

  15. Optical wavelength selection for improved spectroscopic photoacoustic imaging?

    PubMed Central

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

    2013-01-01

    Spectroscopic photoacoustic imaging has the potential to become a powerful tool that can estimate distributions of optically absorbing chromophores in the body. We have developed an algorithm to select imaging wavelengths for spectroscopic photoacoustics given the spectra of expected chromophores. The algorithm uses the smallest singular value of a matrix constructed from the absorption spectra as a criterion to remove extraneous wavelengths. The method performed significantly better than an approach where evenly spaced wavelengths were used in the presence of noise and wavelength-dependent attenuation of light in tissue. Finally, the algorithm was applied to photoacoustic imaging of a phantom containing indocyanine green dye and silica-coated gold nanorods, demonstrating significant improvements in the ability to estimate relative contrast agent concentrations compared to the case where evenly spaced wavelengths were chosen. In summary, our work provides a versatile framework to select optical wavelengths and evaluate sets of absorbers for spectroscopic photoacoustic imaging. PMID:25302148

  16. Photoacoustic measurement of the Grüneisen parameter of tissue

    PubMed Central

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

    2014-01-01

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

  17. Video-rate photoacoustic microscopy of micro-vasculatures

    NASA Astrophysics Data System (ADS)

    Wang, Lidai; Maslov, Konstantin; Xing, Wenxin; Garcia-Uribe, Alejandro; Wang, Lihong V.

    2013-03-01

    We report the development of photoacoustic microscopy capable of video-rate high-resolution in-vivo imaging in deep tissue. A lightweight photoacoustic probe is made of a single-element broadband ultrasound transducer, a compact photoacoustic beam combiner, and a bright-field light delivery system. Focused broadband ultrasound detection provides a 44-?m lateral resolution and a 28-?m axial resolution. A multimode optical fiber is used to deliver laser pulses. The bright-field light delivery system can effectively improve the illumination efficiency. The photoacoustic probe weighs less than 40 grams and is mounted on a voice-coil scanner to acquire 40 cross-sectional images per second over several-mm range. The fast speed can effectively improve imaging throughput, reduce motion artifacts, and enable the visualization of highly dynamic biomedical processes. High-resolution micro-vascular imaging is successfully demonstrated.

  18. In vivo longitudinal photoacoustic imaging of subcutaneous tumours in mice

    NASA Astrophysics Data System (ADS)

    Laufer, Jan; Johnson, Peter; Zhang, Edward; Treeby, Bradley; Cox, Ben; Pedley, Barbara; Beard, Paul

    2011-03-01

    Photoacoustic tomography can provide high resolution 3D images of vascular networks, making it well suited to characterising the development of tumour vasculature and its response to treatment. In this study, photoacoustic images to depths of up to 9 mm were obtained using an all optical ultrasound detection scheme. Two type of colorectal tumours (LS174T and SW1222) implanted subcutaneously in a mouse were studied. 3D photoacoustic images were obtained in vivo revealing the different vascular architectures of each tumour type and their evolution over a period of several days. The results suggest that photoacoustic imaging could play a role in providing essential pre-clinical information on tumour pathophysiology and eliciting the biological mechanisms underlying anti-angiogenic therapies and other treatments.

  19. Application of the Pulsed Photoacoustic Spectroscopy in Biomedicine

    SciTech Connect

    Gutierrez-Juarez, G.; Sims, M. J.; Gupta, S. K.; Viator, J. A. [Department of Biological Engineering and Department of Dermatology University of Missouri, Columbia, Missouri 65211 (United States)

    2008-08-11

    The use of optical spectroscopy as a diagnostic tool in biomedical applications and research has grown considerably in the last two decades. One of them is the pulsed photoacoustic or optoacoustic, which promises to be one of the most important tools for disease diagnostic studies, because while most spectroscopies exploit the optical nature of the light-tissue interaction, this field of photoacoustics uses optical energy to generate an acoustic wave which propagates in the tissue environment. The acoustic wave propagation is fundamentally related to various tissue properties and an analysis of the wave dynamics can provide insights into these properties. This work presents a review on pulsed photoacoustic spectroscopy of several photoacoustic methods to derive information about tissue and tissue phantoms.

  20. Photoacoustic image-guided needle biopsy of sentinel lymph nodes

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  1. Photoacoustic imaging with rotational compounding for improved signal detection

    NASA Astrophysics Data System (ADS)

    Forbrich, A.; Heinmiller, A.; Jose, J.; Needles, A.; Hirson, D.

    2015-03-01

    Photoacoustic microscopy with linear array transducers enables fast two-dimensional, cross-sectional photoacoustic imaging. Unfortunately, most ultrasound transducers are only sensitive to a very narrow angular acceptance range and preferentially detect signals along the main axis of the transducer. This often limits photoacoustic microscopy from detecting blood vessels which can extend in any direction. Rotational compounded photoacoustic imaging is introduced to overcome the angular-dependency of detecting acoustic signals with linear array transducers. An integrate system is designed to control the image acquisition using a linear array transducer, a motorized rotational stage, and a motorized lateral stage. Images acquired at multiple angular positions are combined to form a rotational compounded image. We found that the signal-to-noise ratio improved, while the sidelobe and reverberation artifacts were substantially reduced. Furthermore, the rotational compounded images of excised kidneys and hindlimb tumors of mice showed more structural information compared with any single image collected.

  2. Enhancement of photoacoustic emission from self-supported plasmonic multilayers

    NASA Astrophysics Data System (ADS)

    Namura, Kyoko; Nakajima, Kaoru; Kimura, Kenji; Suzuki, Motofumi

    2014-07-01

    In this paper, we demonstrate remarkable photoacoustic emission from self-supported Au nanoparticle/dielectric/Ag mirror structures. They were prepared by depositing thin films on both sides of a 50-nm-thick silicon nitride membrane. The photoacoustic emission generated by the self-supported sample is more than 2 orders of magnitude larger than that of a similar structure supported by a Si wafer at a laser modulation frequency of 1 kHz. In this frequency region, the thermal diffusion length becomes much greater than the thickness of the multilayers, so that the photoacoustic amplitude is determined mainly by the thermal conductivity of the substrate. Therefore, the large enhancement of the photoacoustic emission can be understood in terms of the reduced thermal conductivity of the substrate.

  3. 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.

  4. Photoacoustic systems for NO2 traces detection

    NASA Astrophysics Data System (ADS)

    Slezak, V.; Peuriot, A.; Santiago, Guillermo D.; Codnia, J.

    2004-10-01

    Vast research work on visible-laser-based photoacoustic spectroscopy of NO2 in air has been performed at the CEILAP. The study of the mechanisms of acoustical energy losses in a cavity is carried out exciting with a pulsed visible laser. For precise measurements a processing method is developed which allows obtaining high resolution of the photoacoustic signal spectrum when the acquisition window is limited. Devices are shown, where the resonant excitation is obtained with either a mechanically amplitude-modulated or an acousto-optically Q-switched green laser. A simpler, more compact and cheaper acquisition system is obtained through digitizing the pre-amplified signal by the sound card of a PC. The detection limit of different setups and an application to the measurement of the NO2 content in car exhausts are presented. Moreover, a one-dimensional model for cell design and otimization of S/N ratio is developed. It is verified by measurements on NO2 mixtures in a specially built acoustic cavity with a detached Helmholtz resonator.

  5. 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.

  6. Photoacoustic microtomography using optical interferometric detection

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  7. Photoacoustic study of the photostability of sunscreens

    NASA Astrophysics Data System (ADS)

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

    2008-01-01

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

  8. 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.

  9. Carbon dioxide laser absorption spectra and low ppb photoacoustic detection of hydrazine fuels

    SciTech Connect

    Loper, G.L.; Calloway, A.R.; Stamps, M.A.; Gelbwachs, J.A.

    1980-08-15

    Absorption cross-section data are reported for the toxic rocket fuels hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine (UDMH), as well as for their selected air oxidation products dimethylamine, trimethylamine, and methanol at up to seventy-eight CO/sub 2/ laser wavelengths each. These data are important for the assessment of the capability of CO/sub 2/ laser-based spectroscopic techniques for monitoring low levels of hydrazine-fuel vapors in the ambient air. Interference-free detection sensitivities of <30 ppb have been demonstrated for UDMH using a laboratory photoacoustic detection system.

  10. Carbon dioxide laser absorption spectra and low ppb photoacoustic detection of hydrazine fuels.

    PubMed

    Loper, G L; Calloway, A R; Stamps, M A; Gelbwachs, J A

    1980-08-15

    Absorption cross-section data are reported for the toxic rocket fuels hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine (UDMH), as well as for their selected air oxidation products dimethylamine, trimethylamine, and methanol at up to seventy-eight CO(2) laser wavelengths each. These data are important for the assessment of the capability of CO(2) laser-based spectroscopic techniques for monitoring low levels of hydrazine-fuel vapors in the ambient air. Interference-free detection sensitivities of <30 ppb have been demonstrated for UDMH using a laboratory photoacoustic detection system. PMID:20234499

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

    NASA Astrophysics Data System (ADS)

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

    2008-01-01

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

  12. Direction Study of Multi-element Linear Transducer Array Based on Photoacoustic Imaging

    NASA Astrophysics Data System (ADS)

    Yi, Tan

    In order to approve the direction property of multi-element linear ultrasonic transducer array, the multi-element phase-controlled technique was adopted. Here we have explored the detected direction influence from dominant frequency, number of multi-element transducer and space between transducer on direction of multi-element linearultrasonic transducer array. These results show that large sub-array has good direction property when the main frequency of detector is low. However it is contrary for high frequency of ultrasonic detector. This will be significative in photoacoustic signal detection and image reconstruction.

  13. A Novel Method of Evaluating the Frequency Response of a Photoacoustic Cell

    NASA Astrophysics Data System (ADS)

    Suchenek, Mariusz

    2014-12-01

    The frequency response of a photoacoustic cell can be evaluated by measuring the output amplitudes point-by-point at different modulation frequencies, by measuring the pulse response, or by recording the cell response to a chirp stimulation, in which the light modulation signal sweeps within a given range of frequencies. This paper presents yet another method, in which the stimulation signal consists of a number of sine waves with different frequencies. A theoretical description is presented, and properties of the techniques are discussed and compared with the experimental results.

  14. 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.

  15. 3D photoacoustic imaging system with 4F acoustic lens

    Microsoft Academic Search

    En Jen; Hsintien Lin; Huihua Kenny Chiang

    2011-01-01

    Photoacoustic imaging (PAI) has several advantages in achieving high-contrast imaging of blood vessels or tumors over conventional ultrasound imaging. However, most PAI systems use conventional linear array transducers and need complex algorithms to reconstruct photoacoustic (PA) tomography or three-dimensional images. In this research, we successfully demonstrated the use of a 4F acoustic lens to realize 3D PAI system. The 3D

  16. Multigrid-based reconstruction algorithm for quantitative photoacoustic tomography

    PubMed Central

    Li, Shengfu; Montcel, Bruno; Yuan, Zhen; Liu, Wanyu; Vray, Didier

    2015-01-01

    This paper proposes a multigrid inversion framework for quantitative photoacoustic tomography reconstruction. The forward model of optical fluence distribution and the inverse problem are solved at multiple resolutions. A fixed-point iteration scheme is formulated for each resolution and used as a cost function. The simulated and experimental results for quantitative photoacoustic tomography reconstruction show that the proposed multigrid inversion can dramatically reduce the required number of iterations for the optimization process without loss of reliability in the results.

  17. 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.

  18. Piezoelectric Water Drop Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Al Ahmad, Mahmoud

    2014-02-01

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

  19. 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.

  20. PLZT-Based Light Controlled Piezoelectric Transformer

    Microsoft Academic Search

    Lucjan Kozielski; Ma?gorzata Adamczyk; Jiri Erhart; K. Rusek

    2011-01-01

    Novel functions of devices are sometimes realized by superimposing two different effects. The authors discovered light controlled Piezoelectric Transformers (PT), with light feedback on efficiency, taking advantage from sophistically coupled effects of piezoelectricity and photostriction. The PT is coupled with direct and converse piezoelectric effect, while the photostriction is associated with bulk photovoltaic effect. These “very smart” multifunctional transformers will

  1. Intravascular photoacoustic imaging of macrophages using molecularly targeted gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Joshi, Pratixa; Sapozhnikova, Veronika; Amirian, James; Litovsky, Silvio H.; Smalling, Richard; Sokolov, Konstantin; Emelianov, Stanislav

    2010-02-01

    Using contrast agents with desired targeting moiety and optical absorption, intravascular photoacoustic imaging may be used to identify various biomarkers expressed during the progression of atherosclerotic lesions. In this paper, we present intravascular photoacoustic imaging of macrophages in the atherosclerotic lesions using bio-conjugated gold nanoparticles as the contrast agent. Atherosclerotic lesions were created in the aorta of a New Zealand white rabbit subjected to a high cholesterol diet and balloon injury. The rabbit was injected with 20 nm spherical gold nanoparticles conjugated with antibodies. The macrophages with internalized gold nanoparticles were imaged by intravascular photoacoustic imaging in the near infrared range; this was possible because of plasmon resonance coupling between closely spaced gold nanoparticles internalized by macrophages. The multi-wavelength intravascular photoacoustic images of the diseased aorta were analyzed to identify the presence and location of macrophages labeled with gold nanoparticles. Spectroscopic intravascular photoacoustic image showing the distribution of gold nanoparticles was further confirmed by the gold-specific silver staining of the tissue crosssection. The results of our study suggest that molecular intravascular photoacoustic imaging can be used to image macrophages in atherosclerosis.

  2. Piezoelectricity and electrostriction in biocompatible (Na,K)NbO3 nanofiber scaffolds

    NASA Astrophysics Data System (ADS)

    Jalalian, A.; Grishin, A. M.

    2014-06-01

    Single phase and highly crystalline biocompatible ferroelectric (Na,K)NbO3 (NKN) nanofibers were synthesized by sol-gel assisted electrospinning technique. Low amplitude piezoelectric response as well as electrostriction effect in NKN fibers were examined using piezoelectric force microscopy technique. Piezoelectric coefficient d33 is strongly anisotropic varying from 75.8 to 18.3 pm/V for, respectively, out-of-axis and on-axis oriented ferroelectric domains in NKN fibers. Hysteresis P-E loop for individual nanofiber reconstructed from the bipolar E-field-induced butterfly strain curve yields: coercive field Ec = 31 kV/cm, remnant Pr = 6.2 ?C/cm2, and the maximum achieved polarization Pmax = 21.2 ?C/cm2. Enhanced piezoelectric effect and strong electrostriction promise NKN fibers as electrically polarizable scaffolds for tissue engineering and for energy harvesting biocompatible nanogenerators.

  3. Piezoelectric sensor based nondestructive active monitoring of strength gain in concrete

    NASA Astrophysics Data System (ADS)

    Shin, Sung Woo; Riaz Qureshi, Adeel; Lee, Jae-Yong; Bang Yun, Chung

    2008-10-01

    The recent advent of smart materials, such as piezoelectric materials, shape-memory alloys, and optical fibers, has added a new dimension to present structural health monitoring techniques. In particular, the electro-mechanical impedance (EMI) sensing technique utilizing piezoelectric materials has emerged as a potential tool for the implementation of a built-in monitoring system for damage detection of civil structures. However, there is little effort to apply this technique for concrete monitoring. In this study, an effort to extend the applicability of the EMI sensing technique is made for strength gain monitoring of early age concrete. PZT (piezoelectric lead zirconate titanate) patches are employed to sense the EMI signature of curing concrete. A series of experiments was conducted on concrete specimens to verify the applicability of the EMI sensing technique. The results show the excellent potential of the EMI sensing technique as a practical and reliable nondestructive method for strength gain monitoring.

  4. Acoustic resolution photoacoustic Doppler flowmetry: practical considerations for obtaining accurate measurements of blood flow

    NASA Astrophysics Data System (ADS)

    Brunker, J.; Beard, P.

    2014-03-01

    An assessment has been made of various experimental factors affecting the accuracy of flow velocities measured using a pulsed time correlation photoacoustic Doppler technique. In this method, Doppler time shifts are quantified via crosscorrelation of pairs of photoacoustic waveforms generated in moving absorbers using pairs of laser light pulses, and the photoacoustic waves are detected using an ultrasound transducer. The acoustic resolution mode is employed by using the transducer focal width, rather than the large illuminated volume, to define the lateral spatial resolution. This enables penetration depths of several millimetres or centimetres, unlike methods using the optical resolution mode, which limits the maximum penetration depth to approximately 1 mm. In the acoustic resolution mode, it is difficult to detect time shifts in highly concentrated suspensions of flowing absorbers, such as red blood cell suspensions and whole blood, and this challenge supposedly arises because of the lack of spatial heterogeneity. However, by assessing the effect of different absorption coefficients and tube diameters, we offer an alternative explanation relating to light attenuation and parabolic flow. We also demonstrate a new signal processing method that surmounts the previous problem of measurement under-reading. This method is a form of signal range gating and enables mapping of the flow velocity profile across the tube as well as measurement of the average flow velocity. We show that, using our signal processing scheme, it is possible to measure the flow of whole blood using a relatively low frequency detector. This important finding paves the way for application of the technique to measurements of blood flow several centimetres deep in living tissue.

  5. Piezoelectric Wafer Embedded Active Sensors for Aging Aircraft Structural Health Monitoring

    Microsoft Academic Search

    Victor Giurgiutiu; Andrei Zagrai; Jing Jing Bao

    2002-01-01

    Piezoelectric wafer active sensors may be applied on aging aircraft structures to monitor the onset and progress of structural damage such as fatigue cracks and corrosion. The state of the art in piezoelectric-wafer active sensors structural health monitoring and damage detection is reviewed. Methods based on (a) elastic wave propagation and (b) the Electro-Mechanical (E\\/M) impedance technique are cited and

  6. Fabrication and performance of MEMS-based piezoelectric power generator for vibration energy harvesting

    Microsoft Academic Search

    Hua-bin Fang; Jing-quan Liu; Zheng-yi Xu; Lu Dong; Li Wang; Di Chen; Bing-chu Cai; Yue Liu

    2006-01-01

    A MEMS-based energy harvesting device, micro piezoelectric power generator, is designed to convert ambient vibration energy to electrical power via piezoelectric effect. In this work, the generator structure of composite cantilever with nickel metal mass is devised. Micro-electronic-mechanical systems (MEMS) related techniques such as sol–gel, RIE dry etching, wet chemical etching, UV-LIGA are developed to fabricate the device and then

  7. Structural Health Monitoring of Composites Using Integrated and Flexible Piezoelectric Ultrasonic Transducers

    Microsoft Academic Search

    Makiko Kobayashi; Kuo-Ting Wu; Li Song; Cheng-Kuei Jen; Nezih Ad

    2009-01-01

    Two types of ultrasonic sensors are presented for structural health monitoring (SHM) and non-destructive testing (NDT) of graphite\\/epoxy (Gr\\/Ep) composites of thickness ranging from 1 mm to 12.7 mm. These piezoelectric film-based sensors are fabricated using a sol-gel spray technique. The center operation frequency of these sensors ranges from 1.3 MHz to 14.5 MHz. For the first sensor type, piezoelectric

  8. Improved in vivo photoacoustic microscopy based on a virtual-detector concept.

    PubMed

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

    2006-02-15

    Recently an in vivo high-resolution backward-mode photoacoustic microscope was developed that shows potential for applications in dermatology and related cancer research. However, the limited depth of focus of the large-numerical-aperture (NA) ultrasonic lens employed in this system causes the image quality to deteriorate significantly in the out-of-focus region. To solve this problem, we devised and explored, for the first time to our knowledge, a virtual-detector-based synthetic-aperture focusing technique, combined with coherence weighting, for photoacoustic microscopy with such a large-NA transducer. Images of phantoms show that the proposed technique improves the -6 dB lateral resolution from 49-379 to 46-53 microm and increases the signal-to-noise ratio by up to 29 dB, depending on the distance from the ultrasonic focal point. In vivo experiments show that the technique also provides a clearer representation of the vascular distribution in the rat's scalp. PMID:16496891

  9. In vivo dark-field reflection-mode photoacoustic Konstantin Maslov

    E-print Network

    Wang, Lihong

    In vivo dark-field reflection-mode photoacoustic microscopy Konstantin Maslov Optical Imaging Reflection-mode photoacoustic microscopy with dark-field laser pulse illumination and high in vivo. Dark-field optical illumination minimizes the interference caused by strong photoacoustic signals

  10. Using Monte Carlo simulations to understand the influence of photon propagation on photoacoustic spectroscopic imaging

    Microsoft Academic Search

    Keith M. Stantz; Bo Liu; Robert A. Kruger

    2007-01-01

    Purpose: The purpose of this study is to evaluate the influence of photon propagation on the NIR spectral features associated with photoacoustic imaging. Introduction: Photoacoustic CT spectroscopy (PCT-S) has the potential to identify molecular properties of tumors while overcoming the limited depth resolution associated with optical imaging modalities (e.g., OCT and DOT). Photoacoustics is based on the fact that biological

  11. Photoacoustic spectrometry for trace gas analysis and leak detection using different cell geometries

    Microsoft Academic Search

    M. A. Gondal; A. Dastageer; M. H. Shwehdi

    2004-01-01

    A photoacoustic (PA) spectrometer with high selectivity and sensitivity has been developed for trace gas analysis and for the detection of gas leak at part per trillion by volume (pptV) level. This PA system comprises of a resonant photoacoustic cell, a pulsed line tunable CO2 laser as an excitation source and a sensitive electret microphone as a photoacoustic detector with

  12. Evidence of the semiconductor-metal transition in V2O5 thin films by the pulsed laser photoacoustic method

    NASA Astrophysics Data System (ADS)

    Pérez-Pacheco, A.; Acosta-Najarro, D. R.; Castañeda-Guzmán, R.; Cruz-Manjarrez, H.; Rodriguez-Fernandez, L.; Pineda-Santamaría, J. C.; Aguilar-Franco, M.

    2013-05-01

    In this work, the pulsed photoacoustic technique was used to investigate the semiconductor-metal transition of thin vanadium pentoxide films (V2O5) under increasing temperature. The V2O5 thin films were simultaneously deposited by RF magnetron sputtering at room temperature, on corning glass and SnO2:F/glass substrates, in order to compare the photoacoustic response. The elemental and structural analysis of the V2O5 films was performed by Rutherford backscattering spectroscopy and X-ray diffraction. The optical transmission and band gap were determined using UV-Vis spectroscopy. The electrical properties were measured using four-point probe measurements with the Van der Pauw geometry.

  13. Sunscreen effects in skin analyzed by photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2005-06-01

    In this work, photoacoustic spectroscopy (PAS) was employed to characterize samples of commercially available sunscreen (SPF15) and the system formed by sunscreen plus skin (topically applied sunscreen). Measurements were performed at 70Hz, in the wavelength range that corresponds to most of the ultraviolet (UV) radiation that reaches Earth. The absorption spectrum of sunscreen was obtained in vitro and in situ., showing that the sunscreen analyzed presents an effective absorption of the UV radiation After that, the PAS technique was used to monitor the absorption kinetics of sunscreen applied to human skin (abdomen) samples, characterizing alterations in the human skin after application of sunscreen. This was done by applying the sunscreen in a skin sample and recording the absorption spectra in regular time intervals, up to 90 minutes after application. Measurements show that light absorption by the system sunscreen plus skin stabilizes between 25 and 45 minutes after sunscreen application. This agrees with the instructions given by the producers about the need of applying the sunscreen at least 30 minutes before sun exposition. The requirement to periodically reapply the sunscreen is confirmed by the progressive decrease in the level of UV absorption as a function of time.

  14. Nonlinear photoacoustic measurements of oxygen saturation levels in blood

    NASA Astrophysics Data System (ADS)

    Kamanzi, Albert

    Oxygen is necessary for metabolism. It is carried from lungs to the rest of the body by hemoglobin in blood. As each hemoglobin molecule can carry a maximum of four oxygen molecules, oxygen saturation (sO2) is the measure of percentage of oxygen content in blood. For a normal person sO2 is 95% - 100%. Point-of-care testing of sO2 in blood is important in medicine. It enables doctors and caregivers for monitoring a wide variety of chronic illnesses. On the other hand, mapping of sO2 values by performing a raster scan across the region of interest in vivo is also essential in clinical and research settings, such as to evaluate the therapeutic effects of a treatment, monitoring healing of wounds, etc. Several non-invasive methods have been developed for this purpose. In this thesis, I measured the nonlinear absorption coefficient (beta) of blood samples using photoacoustic Z-scan technique. Results depict linear dependency between beta and blood oxygenation levels.

  15. Photoacoustic lymphatic imaging with high spatial-temporal resolution

    NASA Astrophysics Data System (ADS)

    Martel, Catherine; Yao, Junjie; Huang, Chih-Hsien; Zou, Jun; Randolph, Gwendalyn J.; Wang, Lihong V.

    2014-11-01

    Despite its critical function in coordinating the egress of inflammatory and immune cells out of tissues and maintaining fluid balance, the causative role of lymphatic network dysfunction in pathological settings is still understudied. Engineered-animal models and better noninvasive high spatial-temporal resolution imaging techniques in both preclinical and clinical studies will help to improve our understanding of different lymphatic-related pathologic disorders. Our aim was to take advantage of our newly optimized noninvasive wide-field fast-scanning photoacoustic (PA) microcopy system to coordinately image the lymphatic vasculature and its flow dynamics, while maintaining high resolution and detection sensitivity. Here, by combining the optical-resolution PA microscopy with a fast-scanning water-immersible microelectromechanical system scanning mirror, we have imaged the lymph dynamics over a large field-of-view, with high spatial resolution and advanced detection sensitivity. Depending on the application, lymphatic vessels (LV) were spectrally or temporally differentiated from blood vessels. Validation experiments were performed on phantoms and in vivo to identify the LV. Lymphatic flow dynamics in nonpathological and pathological conditions were also visualized. These results indicate that our newly developed PA microscopy is a promising tool for lymphatic-related biological research.

  16. Improving the signal analysis for in vivo photoacoustic flow cytometry

    NASA Astrophysics Data System (ADS)

    Niu, Zhenyu; Yang, Ping; Wei, Dan; Tang, Shuo; Wei, Xunbin

    2015-03-01

    At early stage of cancer, a small number of circulating tumor cells (CTCs) appear in the blood circulation. Thus, early detection of malignant circulating tumor cells has great significance for timely treatment to reduce the cancer death rate. We have developed an in vivo photoacoustic flow cytometry (PAFC) to monitor the metastatic process of CTCs and record the signals from target cells. Information of target cells which is helpful to the early therapy would be obtained through analyzing and processing the signals. The raw signal detected from target cells often contains some noise caused by electronic devices, such as background noise and thermal noise. We choose the Wavelet denoising method to effectively distinguish the target signal from background noise. Processing in time domain and frequency domain would be combined to analyze the signal after denoising. This algorithm contains time domain filter and frequency transformation. The frequency spectrum image of the signal contains distinctive features that can be used to analyze the property of target cells or particles. The PAFC technique can detect signals from circulating tumor cells or other particles. The processing methods have a great potential for analyzing signals accurately and rapidly.

  17. Photoacoustically-guided photothermal killing of mosquitoes targeted by nanoparticles.

    PubMed

    Foster, Stephen R; Galanzha, Ekaterina I; Totten, Daniel C; Beneš, Helen; Shmookler Reis, Robert J; Zharov, Vladimir P

    2014-07-01

    In biomedical applications, nanoparticles have demonstrated the potential to eradicate abnormal cells in small localized pathological zones associated with cancer or infections. Here, we introduce a method for nanotechnology-based photothermal (PT) killing of whole organisms considered harmful to humans or the environment. We demonstrate that laser-induced thermal, and accompanying nano- and microbubble phenomena, can injure or kill C. elegans and mosquitoes fed carbon nanotubes, gold nanospheres, gold nanoshells, or magnetic nanoparticles at laser energies that are safe for humans. In addition, a photoacoustic (PA) effect was used to control nanoparticle delivery. Through the integration of this technique with molecular targeting, nanoparticle clustering, magnetic capturing and spectral sharpening of PA and PT plasmonic resonances, our laser-based PA-PT nano-theranostic platform can be applied to detection and the physical destruction of small organisms and carriers of pathogens, such as malaria vectors, spiders, bed bugs, fleas, ants, locusts, grasshoppers, phytophagous mites, or other arthropod pests, irrespective of their resistance to conventional treatments. PMID:23450780

  18. Photoacoustic lymphatic imaging with high spatial-temporal resolution.

    PubMed

    Martel, Catherine; Yao, Junjie; Huang, Chih-Hsien; Zou, Jun; Randolph, Gwendalyn J; Wang, Lihong V

    2014-11-01

    Despite its critical function in coordinating the egress of inflammatory and immune cells out of tissues and maintaining fluid balance, the causative role of lymphatic network dysfunction in pathological settings is still understudied. Engineered-animal models and better noninvasive high spatial-temporal resolution imaging techniques in both preclinical and clinical studies will help to improve our understanding of different lymphatic-related pathologic disorders. Our aim was to take advantage of our newly optimized noninvasive wide-field fast-scanning photoacoustic (PA) microcopy system to coordinately image the lymphatic vasculature and its flow dynamics, while maintaining high resolution and detection sensitivity. Here, by combining the optical-resolution PA microscopy with a fast-scanning water-immersible microelectromechanical system scanning mirror, we have imaged the lymph dynamics over a large field-of-view, with high spatial resolution and advanced detection sensitivity. Depending on the application, lymphatic vessels (LV) were spectrally or temporally differentiated from blood vessels. Validation experiments were performed on phantoms and in vivo to identify the LV. Lymphatic flow dynamics in nonpathological and pathological conditions were also visualized. These results indicate that our newly developed PA microscopy is a promising tool for lymphatic-related biological research. PMID:25408958

  19. Photothermal and photoacoustic Raman cytometry in vitro and in vivo

    PubMed Central

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

    2010-01-01

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

  20. Optical-thermal light-tissue interactions during photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Gould, Taylor; Wang, Quanzeng; Pfefer, T. Joshua

    2014-03-01

    Photoacoustic imaging (PAI) has grown rapidly as a biomedical imaging technique in recent years, with key applications in cancer diagnosis and oximetry. In spite of these advances, the literature provides little insight into thermal tissue interactions involved in PAI. To elucidate these basic phenomena, we have developed, validated, and implemented a three-dimensional numerical model of tissue photothermal (PT) response to repetitive laser pulses. The model calculates energy deposition, fluence distributions, transient temperature and damage profiles in breast tissue with blood vessels and generalized perfusion. A parametric evaluation of these outputs vs. vessel diameter and depth, optical beam diameter, wavelength, and irradiance, was performed. For a constant radiant exposure level, increasing beam diameter led to a significant increase in subsurface heat generation rate. Increasing vessel diameter resulted in two competing effects - reduced mean energy deposition in the vessel due to light attenuation and greater thermal superpositioning due to reduced thermal relaxation. Maximum temperatures occurred either at the surface or in subsurface regions of the dermis, depending on vessel geometry and position. Results are discussed in terms of established exposure limits and levels used in prior studies. While additional experimental and numerical study is needed, numerical modeling represents a powerful tool for elucidating the effect of PA imaging devices on biological tissue.

  1. Photoacoustic Spectroscopy of Candida albicans Treated with Methylene Blue

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  2. A review of piezoelectric polymers as functional materials for electromechanical transducers

    NASA Astrophysics Data System (ADS)

    Ramadan, Khaled S.; Sameoto, D.; Evoy, S.

    2014-03-01

    Polymer based MEMS and microfluidic devices have the advantages of mechanical flexibility, lower fabrication cost and faster processing over silicon based ones. Also, many polymer materials are considered biocompatible and can be used in biological applications. A valuable class of polymers for microfabricated devices is piezoelectric functional polymers. In addition to the normal advantages of polymers, piezoelectric polymers can be directly used as an active material in different transduction applications. This paper gives an overview of piezoelectric polymers based on their operating principle. This includes three main categories: bulk piezoelectric polymers, piezocomposites and voided charged polymers. State-of-the-art piezopolymers of each category are presented with a focus on fabrication techniques and material properties. A comparison between the different piezoelectric polymers and common inorganic piezoelectric materials (PZT, ZnO, AlN and PMN-PT) is also provided in terms of piezoelectric properties. The use of piezopolymers in different electromechanical devices is also presented. This includes tactile sensors, energy harvesters, acoustic transducers and inertial sensors.

  3. Improved Thermoelectric Performance via Piezoelectric Interaction

    NASA Astrophysics Data System (ADS)

    Montgomery, David

    2015-03-01

    Presented are the initial findings of enhanced voltage output in a hybrid thermoelectric piezoelectric generator (TPEG). We constructed TPEG by integrating insulating layers of polyvinylidene fluoride (PVDF) piezoelectric films between flexible thin film p-type and n-type thermoelectrics. The piezoelectric bound surface charge modifies the thermoelectric properties of the semiconductor electrodes which facilitates an increase in voltage. The TPEG voltage output has three contributions: traditional thermoelectric and piezoelectric terms, and a unique coupling term. A combined thermoelectric and piezoelectric model can be used to quantify the expected coupling voltage as a function of stress and thermal gradient. The fabrication, placement, and configuration of this interface allows for different device designs and affects overall performance. Under easily achievable stress and thermal gradient this new coupling effect can increase voltage output by 20%. Because of this piezoelectric modified thermoelectric effect these hybrid generators can out preform equivalent thermoelectric or piezoelectric generators.

  4. Hybrid ultrahigh resolution optical coherence / photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Hermann, B.; Liu, M.; Schmitner, N.; Maurer, B.; Meyer, D.; Weninger, W. J.; Drexler, W.

    2015-03-01

    We present an ultrahigh resolution dual modality optical resolution photoacoustic microsopy (OR-PAM) and spectral domain optical coherence microscopy (SD-OCM) system. The ultrahigh sub-micron lateral resolution is provided by the high numerical aperture of the objective lens used while the ultrahigh axial resolution is provided by the broadband OCT laser that covers 107 nm with a central wavelength of 840 nm. The synchronized simultaneous acquisition for the two modalities is achieved using a 40MHz FPGA. 2D-scanning is realized by two orthogonal translation stages (PI, 400 nm resolution). The transversal resolution of the system is 0.5 ?m, the axial resolutions are 30 ?m (PAM) and 4 ?m (OCM), respectively. The values have been determined experimentally using nanospheres (diameter 10-200nm). For a demonstration of the imaging capability we present images from thin slices of different biological samples as well as in vivo imaging in the zebrafish embryo.

  5. Photoacoustic tomography to identify inflammatory arthritis

    PubMed Central

    Rajian, Justin Rajesh; Girish, Gandikota; Wang, Xueding

    2012-01-01

    Abstract. Identifying neovascularity (angiogenesis) as an early feature of inflammatory arthritis can help in early accurate diagnosis and treatment monitoring of this disease. Photoacoustic tomography (PAT) is a hybrid imaging modality which relies on intrinsic differences in the optical absorption among the tissues being imaged. Since blood has highly absorbing chromophores including both oxygenated and deoxygenated hemoglobin, PAT holds potential in identifying early angiogenesis associated with inflammatory joint diseases. PAT is used to identify changes in the development of inflammatory arthritis in a rat model. Imaging at two different wavelengths, 1064 nm and 532 nm, on rats revealed that there is a significant signal enhancement in the ankle joints of the arthritis affected rats when compared to the normal control group. Histology images obtained from both the normal and the arthritis affected rats correlated well with the PAT findings. Results support the fact that the emerging PAT could become a new tool for clinical management of inflammatory arthritis. PMID:23085914

  6. Multiscale photoacoustic microscopy and computed tomography

    PubMed Central

    Wang, Lihong V.

    2009-01-01

    Photoacoustic tomography (PAT) is probably the fastest growing biomedical imaging technology owing to its capability of high-resolution sensing of rich optical contrast in vivo at depths beyond the optical transport mean free path (~1 mm in the skin). Existing high-resolution optical imaging technologies, such as confocal microscopy and two-photon microscopy, have fundamentally impacted biomedicine but cannot reach such depths. Taking advantage of low ultrasonic scattering, PAT indirectly improves tissue transparency by 100 to 1000 fold and consequently enables deeply penetrating functional and molecular imaging at high spatial resolution. Further, PAT holds the promise of in vivo imaging at multiple length scales ranging from subcellular organelles to organs with the same contrast origin, an important application in multiscale systems biology research. PMID:20161535

  7. Multiscale photoacoustic microscopy with continuously tunable resolution.

    PubMed

    Jiang, Bowen; Yang, Xiaoquan; Liu, Yanyan; Deng, Yong; Luo, Qingming

    2014-07-01

    A multiscale photoacoustic microscope with continuously tunable lateral resolution is developed. The tunable resolution is achieved by using an electrical varifocal lens and an optical fiber bundle. The varifocal lens is used to generate a size tunable focused laser spot on the tip of the fiber bundle. Laser beams emerging from the other end of the fiber bundle are imaged into the object as the excitation light spot for acoustic generation. The verified lateral resolution of the system can be tuned from ~1???m to more than 44.8 ?m, which span from optical resolution to acoustic resolution. Additionally, a mouse ear was imaged in vivo using three different resolutions to demonstrate the feasibility of the multiscale imaging capability of our system. PMID:24978776

  8. Near-infrared light photoacoustic ophthalmoscopy

    PubMed Central

    Liu, Tan; Wei, Qing; Song, Wei; Burke, Janice M.; Jiao, Shuliang; Zhang, Hao F.

    2012-01-01

    We achieved photoacoustic ophthalmoscopy (PAOM) imaging of the retina with near-infrared (NIR) light illumination. A PAOM imaging system with dual-wavelength illumination at 1064 nm and 532 nm was built. We compared in vivo imaging results of both albino and pigmented rat eyes at the two wavelengths. The results show that the bulk optical absorption of the retinal pigment epithelium (RPE) is only slightly higher than that of the retinal vessels at 532 nm while it becomes more than an order of magnitude higher than that of the retinal vessels at 1064 nm. These studies suggest that although visible light illumination is suitable for imaging both the retinal vessels and the RPE, NIR light illumination, being more comfortable to the eye, is better suited for RPE melanin related investigations and diagnoses. PMID:22574266

  9. Optical clearing in photoacoustic flow cytometry.

    PubMed

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

    2013-01-01

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

  10. Optical clearing in photoacoustic flow cytometry

    PubMed Central

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

    2013-01-01

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

  11. Inspection of functionally graded coating materials using frequency domain photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Steen, Thomas Lowell

    A frequency domain photoacoustic microscopy system has been developed for the inspection of functionally graded mullite coatings deposited on SiC substrates. Narrow-bandwidth surface acoustic waves (SAWs) are generated with an amplitude modulated laser source. A photorefractive crystal based interferometer coupled to a lock-in amplifier is used for the detection of the resulting surface displacements. The complex displacement field is mapped over a source-to-receiver distance of approximately 500mum in order to extract the wavelengths of SAWs at a given excitation frequency, from which the phase velocities are determined. SAW dispersion characteristics are sensitive to the elastic properties of the near surface region. The measured SAW dispersion is compared to a theoretical model in order to extract the elastic properties and thickness of the coatings. Frequency domain photoacoustic microscopy allows for the rapid, non-contact characterization of graded coatings and is potentially suitable for in-situ process control. The velocities of SAWs propagating in graded materials are found using the reflectance function technique combined with a transfer matrix approach. Theoretical results demonstrate that SAW dispersion in micron-scale functionally graded coatings over the 100-200 MHz frequency range is most sensitive to the mean elastic modulus of the coating and the coating thickness. In addition, the dispersion behavior is also influenced by the form of the elastic property variation through the coating thickness and can, in some cases, be used to determine the elastic property distribution. The photoacoustic microscopy technique was used to measure SAW dispersion on as-grown mullite coatings, and a simplex optimization algorithm was used to determine the mean elastic modulus and thickness through minimization of the error between measured and calculated SAW velocities. The results show agreement with independent measurements of the mean elastic modulus and thickness of the coating measured using nanoindentation and optical microscopy, respectively. It is found that SAW velocity measurement error caused by local porosity and spatial inhomogeneities can be reduced by spatial averaging over the measurement region. Experimental measurements also confirm that photoacoustic microscopy can be used to gain insight into the form of elastic modulus distribution through the coating thickness in micron scale graded coatings.

  12. Multispectral photoacoustic imaging of nerves with a clinical ultrasound system

    NASA Astrophysics Data System (ADS)

    Mari, Jean Martial; West, Simeon; Beard, Paul C.; Desjardins, Adrien E.

    2014-03-01

    Accurate and efficient identification of nerves is of great importance during many ultrasound-guided clinical procedures, including nerve blocks and prostate biopsies. It can be challenging to visualise nerves with conventional ultrasound imaging, however. One of the challenges is that nerves can have very similar appearances to nearby structures such as tendons. Several recent studies have highlighted the potential of near-infrared optical spectroscopy for differentiating nerves and adjacent tissues, as this modality can be sensitive to optical absorption of lipids that are present in intra- and extra-neural adipose tissue and in the myelin sheaths. These studies were limited to point measurements, however. In this pilot study, a custom photoacoustic system with a clinical ultrasound imaging probe was used to acquire multi-spectral photoacoustic images of nerves and tendons from swine ex vivo, across the wavelength range of 1100 to 1300 nm. Photoacoustic images were processed and overlaid in colour onto co-registered conventional ultrasound images that were acquired with the same imaging probe. A pronounced optical absorption peak centred at 1210 nm was observed in the photoacoustic signals obtained from nerves, and it was absent in those obtained from tendons. This absorption peak, which is consistent with the presence of lipids, provides a novel image contrast mechanism to significantly enhance the visualization of nerves. In particular, image contrast for nerves was up to 5.5 times greater with photoacoustic imaging (0.82 +/- 0.15) than with conventional ultrasound imaging (0.148 +/- 0.002), with a maximum contrast of 0.95 +/- 0.02 obtained in photoacoustic mode. This pilot study demonstrates the potential of photoacoustic imaging to improve clinical outcomes in ultrasound-guided interventions in regional anaesthesia and interventional oncology.

  13. Aerosol optical absorption measurements with photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Many parameters related to radiative forcing in climate research are known only with large uncertainties. And one of the largest uncertainties in global radiative forcing is the contribution from aerosols. Aerosols can scatter or absorb the electromagnetic radiation, thus may have negative or positive effects on the radiative forcing of the atmosphere, respectively [1]. And the magnitude of the effect is directly related to the quantity of light absorbed by aerosols [2,3]. Thus, sensitivity and precision measurement of aerosol optical absorption is crucial for climate research. Photoacoustic spectroscopy (PAS) is commonly recognized as one of the best candidates to measure the light absorption of aerosols [4]. A PAS based sensor for aerosol optical absorption measurement was developed. A 532 nm semiconductor laser with an effective power of 160 mW was used as a light source of the PAS sensor. The PAS sensor was calibrated by using known concentration NO2. The minimum detectable optical absorption coefficient (OAC) of aerosol was determined to be 1 Mm-1. 24 hours continues measurement of OAC of aerosol in the ambient air was carried out. And a novel three wavelength PAS aerosol OAC sensor is in development for analysis of aerosol wavelength-dependent absorption Angstrom coefficient. Reference [1] U. Lohmann and J. Feichter, Global indirect aerosol effects: a review, Atmos. Chem. Phys. 5, 715-737 (2005) [2] M. Z. Jacobson, Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols, Nature 409, 695-697 (2001) [3] V. Ramanathan and G. Carmichae, Global and regional climate changes due to black carbon, nature geoscience 1, 221-227 (2008) [4] W.P Arnott, H. Moosmuller, C. F. Rogers, T. Jin, and R. Bruch, Photoacoustic spectrometer for measuring light absorption by aerosol: instrument description. Atmos. Environ. 33, 2845-2852 (1999).

  14. Cylindrical Piezoelectric Fiber Composite Actuators

    NASA Technical Reports Server (NTRS)

    Allison, Sidney G.; Shams, Qamar A.; Fox, Robert L.

    2008-01-01

    The use of piezoelectric devices has become widespread since Pierre and Jacques Curie discovered the piezoelectric effect in 1880. Examples of current applications of piezoelectric devices include ultrasonic transducers, micro-positioning devices, buzzers, strain sensors, and clocks. The invention of such lightweight, relatively inexpensive piezoceramic-fiber-composite actuators as macro fiber composite (MFC) actuators has made it possible to obtain strains and displacements greater than those that could be generated by prior actuators based on monolithic piezoceramic sheet materials. MFC actuators are flat, flexible actuators designed for bonding to structures to apply or detect strains. Bonding multiple layers of MFC actuators together could increase force capability, but not strain or displacement capability. Cylindrical piezoelectric fiber composite (CPFC) actuators have been invented as alternatives to MFC actuators for applications in which greater forces and/or strains or displacements may be required. In essence, a CPFC actuator is an MFC or other piezoceramic fiber composite actuator fabricated in a cylindrical instead of its conventional flat shape. Cylindrical is used here in the general sense, encompassing shapes that can have circular, elliptical, rectangular or other cross-sectional shapes in the planes perpendicular to their longitudinal axes.

  15. Thin Film Piezoelectrics for MEMS

    Microsoft Academic Search

    S. Trolier-McKinstry; P. Muralt

    2004-01-01

    Thin film piezoelectric materials offer a number of advantages in microelectromechanical systems (MEMS), due to the large motions that can be generated, often with low hysteresis, the high available energy densities, as well as high sensitivity sensors with wide dynamic ranges, and low power requirements. This paper reviews the literature in this field, with an emphasis on the factors that

  16. Piezoelectric Responses of Highly-Oriented Tetragonal Pb(Zr 0.4 Ti 0.6 )O 3 Thin Films

    Microsoft Academic Search

    Desheng Fu; Kazumi Kato; Kenji Ishikawa; Yasutaka Yoshimi; Hisao Suzuki

    2003-01-01

    [111]-and[001]&[100]-highly-oriented Pb(Zr 0.4 Ti 0.6 )O 3 (PZT40\\/60) thin films were prepared by a chemical solution deposition on Si substrates. The influences of orientations on the piezoelectric responses of the thin films have been investigated by a charge integration technique based on the direct piezoelectric effect. A piezoelectric relaxation has been observed in the thin films. Contributions of relaxation have

  17. Circuit for Driving Piezoelectric Transducers

    NASA Technical Reports Server (NTRS)

    Randall, David P.; Chapsky, Jacob

    2009-01-01

    The figure schematically depicts an oscillator circuit for driving a piezoelectric transducer to excite vibrations in a mechanical structure. The circuit was designed and built to satisfy application-specific requirements to drive a selected one of 16 such transducers at a regulated amplitude and frequency chosen to optimize the amount of work performed by the transducer and to compensate for both (1) temporal variations of the resonance frequency and damping time of each transducer and (2) initially unknown differences among the resonance frequencies and damping times of different transducers. In other words, the circuit is designed to adjust itself to optimize the performance of whichever transducer is selected at any given time. The basic design concept may be adaptable to other applications that involve the use of piezoelectric transducers in ultrasonic cleaners and other apparatuses in which high-frequency mechanical drives are utilized. This circuit includes three resistor-capacitor networks that, together with the selected piezoelectric transducer, constitute a band-pass filter having a peak response at a frequency of about 2 kHz, which is approximately the resonance frequency of the piezoelectric transducers. Gain for generating oscillations is provided by a power hybrid operational amplifier (U1). A junction field-effect transistor (Q1) in combination with a resistor (R4) is used as a voltage-variable resistor to control the magnitude of the oscillation. The voltage-variable resistor is part of a feedback control loop: Part of the output of the oscillator is rectified and filtered for use as a slow negative feedback to the gate of Q1 to keep the output amplitude constant. The response of this control loop is much slower than 2 kHz and, therefore, does not introduce significant distortion of the oscillator output, which is a fairly clean sine wave. The positive AC feedback needed to sustain oscillations is derived from sampling the current through the piezoelectric transducer. This positive AC feedback, in combination with the slow feedback to the voltage-variable resistors, causes the overall loop gain to be just large enough to keep the oscillator running. The positive feedback loop includes two 16-channel multiplexers, which are not shown in the figure. One multiplexer is used to select the desired piezoelectric transducer. The other multiplexer, which is provided for use in the event that there are significant differences among the damping times of the 16 piezoelectric transducers, facilitates changing the value of one of the resistors in the positive-feedback loop to accommodate the damping time of the selected transducer.

  18. Photoacoustic Imaging of Breast Microcalcifications: A Preliminary Study with 8-Gauge Core-Biopsied Breast Specimens

    PubMed Central

    Kim, Ga Ram; Kang, Jeeun; Kwak, Jin Young; Chang, Jin Ho; Kim, Seung Il; Youk, Ji Hyun; Moon, Hee Jung; Kim, Min Jung; Kim, Eun-Kyung

    2014-01-01

    Background We presented the photoacoustic imaging (PAI) tool and to evaluate whether microcalcifications in breast tissue can be detected on photoacoustic (PA) images. Methods We collected 21 cores containing microcalcifications (n?=?11, microcalcification group) and none (n?=?10, control group) in stereotactic or ultrasound (US) guided 8-gauge vacuum-assisted biopsies. Photoacoustic (PA) images were acquired through ex vivo experiments by transmitting laser pulses with two different wavelengths (700 nm and 800 nm). The presence of microcalcifications in PA images were blindly assessed by two radiologists and compared with specimen mammography. A ratio of the signal amplitude occurring at 700 nm to that occurring at 800 nm was calculated for each PA focus and was called the PAI ratio. Results Based on the change of PA signal amplitude between 700 nm and 800 nm, 10 out of 11 specimens containing microcalcifications and 8 out of 10 specimens without calcifications were correctly identified on blind review; the sensitivity, specificity, accuracy, positive predictive and negative predictive values of our blind review were 90.91%, 80.0%, 85.71%, 83.33% and 88.89%. The PAI ratio in the microcalcification group was significantly higher than that in the control group (the median PAI ratio, 2.46 versus 1.11, respectively, P?=?.001). On subgroup analysis in the microcalcification group, neither malignant diagnosis nor the number or size of calcification-foci was proven to contribute to PAI ratios. Conclusion Breast microcalcifications generated distinguishable PA signals unlike breast tissue without calcifications. So, PAI, a non-ionizing and non-invasive hybrid imaging technique, can be an alternative in overcoming the limitations of conventional US imaging. PMID:25153128

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

    PubMed Central

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

    2012-01-01

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

  20. A handheld optical fiber parallel acoustic delay line (PADL) probe for photoacoustic tomography

    NASA Astrophysics Data System (ADS)

    Cho, Young; Chang, Cheung-Chung; Jeon, Mansik; Kim, Chulhong; Wang, Lihong V.; Zou, Jun

    2014-03-01

    In current photoacoustic tomography (PAT), l-D or 2-D ultrasound arrays and multi-channel data acquisition (DAQ) electronics are used to detect the photoacoustic signals simultaneously for "real-time" image construction. However, as the number of transducer elements and DAQ channels increase, the construction and operation of the ultrasound receiving system will become complex and costly. This situation can be addressed by using parallel acoustic delay lines (PADLs) to create true time delays in multiple PA signal channels. The time-delayed PA signals will reach the ultrasound transducer at different times and therefore can be received by one single-element transducer without mixing with each other. In this paper, we report the development of the first miniaturized PADL probe suitable for handheld operations. Fusedsilica optical fibers with low acoustic attenuation were used to construct the 16 PADLs with specific time delays. The handheld probe structure was fabricated using precision laser-micromachining process to provide robust mechanical support and accurate alignment of the PADLs with minimal acoustic distortion and inter-channel coupling. The 16 optical-fiber PADLs were arranged to form one input port and two output ports. Photoacoustic imaging of a black-ink target embedded in an optically-scattering phantom was successfully conducted using the handheld PADL probe with two single-element transducers and two DAQ channels (equal to a channel reduction ratio of 8:1). Our results show that the PADL technique and the handheld probe could provide a promising solution for real-time PAT with significantly reduced complexity and cost of the ultrasound receiver system.