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1

Thermal diffusivity of light-emitting material determination by photoacoustic piezoelectric technique  

NASA Astrophysics Data System (ADS)

The theory of Photoacoustic Piezoelectric (PAPE) technique has been developed for two-layered model. An analytical expression for the phase of output voltage versus modulation frequency has been obtained. The thermal diffusivity of Phosphor/PVA light-emitting composite material has been studied. PAPE technique has been employed successfully for investigating the thermal diffusivity of two-layered materials.

Sun, Qiming; Gao, Chunming; Zhao, Binxing; Rao, Haibo

2008-12-01

2

Thermal diffusivity of light-emitting diode packaging material determined by photoacoustic piezoelectric technique  

NASA Astrophysics Data System (ADS)

Thermal property is one of the most important properties of light-emitting diode (LED). Thermal property of LED packaging material determines the heat dissipations of the phosphor and the chip surface, accordingly having an influence on the light-emitting efficiency and the life-span of the device. In this paper, photoacoustic piezoelectric (PAPE) technique has been employed to investigate the thermal properties of polyvinyl alcohol (PVA) and silicon dioxide, which are the new and the traditional packaging materials in white LED, respectively. Firstly, the theory of PAPE technique has been developed for two-layer model in order to investigate soft materials; secondly, the experimental system has been set up and adjusted by measuring the reference sample; thirdly, the thermal diffusivities of PVA and silicon dioxide are measured and analysed. The experimental results show that PVA has a higher thermal diffusivity than silicon dioxide and is a better packaging material in the sense of thermal diffusivity for white LED.

Sun, Qi-Ming; Gao, Chun-Ming; Zhao, Bin-Xing; Rao, Hai-Bo

2010-11-01

3

A Modified Photoacoustic Piezoelectric Model for Thermal Diffusivity Determination of Solids  

NASA Astrophysics Data System (ADS)

The conventional photoacoustic piezoelectric (PAPE) model did not take into account the influence of the piezoelectric transducer (PZT) on the vibrations of the sample, and this approximation brought certain error. In this article, a simple method has been proposed to investigate the vibrations of the sample-PZT combination, and the theory of the PAPE technique has been modified. By introducing an equivalent thickness parameter, the two-layered model has been simplified and an analytical expression for the phase of the PAPE output signal has been obtained. The experimental system has been set up, and the thermal diffusivities of several metal samples have been measured. The experimental results show that the modified model has a higher accuracy than the conventional model.

Sun, Qiming; Gao, Chunming; Zhao, Binxing; Bi, Yanfang

2010-06-01

4

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

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

5

AlN-based piezoelectric micromachined ultrasonic transducer for photoacoustic imaging  

NASA Astrophysics Data System (ADS)

We report on the fabrication of a piezoelectric micromachined ultrasonic transducer (pMUT) and its application to photoacoustic imaging. With c-axis orientation, AlN was grown on a 300 nm-thick SiO2 film and a 200 nm-thick bottom electrode at room temperature. The device consists of SiO2, bottom electrode, AlN films, upper electrode, and polyimide protective layer. An area ratio of 0.45 was used between the upper electrode and the vibration area of the pMUT to provide an optimal sensitivity of transducer. Its resonant frequency was measured to be 2.885 MHz, and the coupling coefficient in the range of 2.38%-3.71%. The fabricated pMUT was integrated with a photoacoustic imaging system and photoacoustic image of a phantom was obtained. The resolution of the system was measured to be about 240 ?m.

Chen, Bingzhang; Chu, Futong; Liu, Xingzhao; Li, Yanrong; Rong, Jian; Jiang, Huabei

2013-07-01

6

Photoacoustic technique applied to the study of skin and leather  

SciTech Connect

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

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

1998-08-28

7

Photoacoustic technique applied to the study of skin and leather  

NASA Astrophysics Data System (ADS)

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

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

1998-08-01

8

A photoacoustic technique to measure the properties of single cells  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

9

Numerical homogenization techniques applied to piezoelectric composites.  

PubMed

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

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

2003-02-01

10

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

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

11

Photoacoustic Techniques for Trace Gas Sensing Based on Semiconductor Laser Sources  

PubMed Central

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

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

2009-01-01

12

Photoacoustic technique to measure beam profile of pulsed laser systems  

PubMed Central

The beam profiles of pulsed lasers are currently measured using either complementary metal oxide semiconductor (CMOS) or charge coupled device (CCD) cameras. Despite providing high-resolution beam profiles, these devices cannot work with high power lasers. If additional optical attenuators are used, beam distortions may occur. In this paper we demonstrate a high-resolution photoacoustic technique capable of measuring the beam profile of pulsed lasers. The beam profiles of a pulsed neodymium-doped yttrium aluminium garnet (Nd:YAG) laser and a pulsed optical parametric oscillator (OPO) laser system were measured using a polydimethylsiloxane film and a single element high-frequency ultrasonic transducer. The advantages and limitations of the developed photoacoustic technique are discussed.

Mallidi, Srivalleesha; Emelianov, Stanislav

2009-01-01

13

Photoacoustic correlation technique for low-speed flow measurement.  

PubMed

A photoacoustic correlation spectroscopy (PACS) technique was proposed for the first time. This technique is inspired by its optical counterpart-the fluorescence correlation spectroscopy (FCS), which is widely used in the characterization of the dynamics of fluorescent species. The fluorescence intensity is measured in FCS while the acoustic signals are detected in PACS. To proof of concept, we demonstrated the flow measurement of light-absorbing beads probed by a pulsed laser. A PACS system with temporal resolution of 0.8 sec was built. Polymer microring resonators were used to detect the photoacoustic signals, which were then signal processed and used to obtain the autocorrelation curves. Flow speeds ranging from 249 to 15.1 ?m/s with corresponding flow time from 4.42 to 72.5 sec were measured. The capability of low-speed flow measurement can potentially be used for detecting blood flow in relatively deep capillaries in biological tissues. Moreover, similar to FCS, PACS may have many potential applications in studying the dynamics of photoacoustic beads. PMID:20689645

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

2010-02-11

14

Photoacoustic correlation technique for low-speed flow measurement  

PubMed Central

A photoacoustic correlation spectroscopy (PACS) technique was proposed for the first time. This technique is inspired by its optical counterpart—the fluorescence correlation spectroscopy (FCS), which is widely used in the characterization of the dynamics of fluorescent species. The fluorescence intensity is measured in FCS while the acoustic signals are detected in PACS. To proof of concept, we demonstrated the flow measurement of light-absorbing beads probed by a pulsed laser. A PACS system with temporal resolution of 0.8 sec was built. Polymer microring resonators were used to detect the photoacoustic signals, which were then signal processed and used to obtain the autocorrelation curves. Flow speeds ranging from 249 to 15.1 ?m/s with corresponding flow time from 4.42 to 72.5 sec were measured. The capability of low-speed flow measurement can potentially be used for detecting blood flow in relatively deep capillaries in biological tissues. Moreover, similar to FCS, PACS may have many potential applications in studying the dynamics of photoacoustic beads.

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

2010-01-01

15

Thermal NDE techniques-from photoacoustics to thermosonics  

NASA Astrophysics Data System (ADS)

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

Thomas, Robert L.

2002-05-01

16

Advancement of a MEMS photoacoustic chemical sensor  

NASA Astrophysics Data System (ADS)

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

Pellegrino, Paul M.; Polcawich, Ronald G.

2003-08-01

17

Accurate Method for the Determination of Phase Transitions in Liquid Crystals with Photoacoustic Technique  

Microsoft Academic Search

A compact Photoacoustic spectrometer (PAS) was fabricated, for the determination of phase transitions in liquid crystals (LCs). Photoacoustic (PA) technique is a powerful tool for the determination of phase transitions in solids, liquids and gasses compared to other techniques like Raman spectroscopy, Newton scattering, NMR & ultrasound studies and DSC. PA signal information is used to investigate the variations in

S. Lakshminarayana; K. Gouthami; V. G. K. M. Pisipati; N. V. S. Rao; G. Venkata Rao

2009-01-01

18

Advancement of a MEMS photoacoustic chemical sensor  

Microsoft Academic Search

Photoacoustic spectroscopy is a useful monitoring technique that is well suited for trace gas detection. The technique also possesses favorable detection characteristics when the system dimensions are scaled to a micro-system design. The objective of present work is to incorporate two strengths of the Army Research Laboratory (ARL), piezoelectric microelectromechanical systems (MEMS) and chemical and biological sensing into a monolithic

Paul M. Pellegrino; Ronald G. Polcawich

2003-01-01

19

Studies on selected polymeric materials using the photoacoustic spectroscopic technique  

NASA Astrophysics Data System (ADS)

Polymethylmethacrylate—graft—polybisphenol—A-carbonate (PMMA-G-PC) with 50% grafting is synthesized. The graft co-polymerization of methylmethacrylate (0.036 mol · lit-1) onto polybisphenol—A-carbonate (0.5 g) in the presence of a redox couple formed from potassium persulphate (40 mol · lit-1) and thio-urea (30 mmol · lit-1) in aqueous nitric acid (0.18 M, 100 ml) in air at (45±2) °C for 3.0 h. Condensation of (PMMA-G-PC) with N- [p-(carboxyl phenyl amino acetic acid)] hydrazide (PCPH) affords polybisphenol-A-carbonate-graft-polymethylmethacrylate hydrazide (PCGH). The photoacoustic (PA) spectra of (PCGH) are recorded in a wavelength range from 200 nm to 800 nm at a modulation frequency of 22 Hz, and compared with those of pure polybisphenol-A-carbonate (PC), (PMMA-G-PC) and (PCPH). In the present work, a non-destructive and non-contact analytical method, namely the photoacoustic technique, is successfully implemented for optical and thermal characterization of selected polymeric materials. The indigenous PA spectrometer used in the present study consists of a 300-W xenon arc lamp, a lock-in amplifier, a chopper, a (1/8)-m monochromator controlled by computer and a home-made PA cell.

Hukum, Singh

2011-06-01

20

Annealing behavior of damage in Si-implanted InP studied by piezoelectric detection of photoacoustic signal  

NASA Astrophysics Data System (ADS)

The recovery process of damage in Si+ (1012-1016 cm-2)-implanted InP with furnace annealing has been investigated by photoacoustic spectroscopy (PAS) using a piezoelectric transducer. All the photoacoustic (PA) spectra for the implanted samples were found to have a long decreasing tail towards the shorter wavelength side in the upper band-edge region. From the ion-dose dependence of the tail intensities the state of disorder produced in the samples was estimated. The isochronal furnace annealing behavior of the damage was also investigated and the removal of the damage and the recrystallization were found to be achieved via at least four temperature regions; region I <= 200°C, regionII 200-400°C, region III 400-650°C and region IV >= 650°C. The results of Raman spectrometry verified that the state of the implanted layers was amorphous for the samples implanted with >= 1014 ions cm-2 and that in the temperature region II it changed to a polycrystalline state which remained till a 700°C anneal.

Yoshinaga, Hiroshi; Kawai, Jun; Agui, Takaaki; Uehara, Fumiya; Matsumori, Tokue

1993-06-01

21

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

Microsoft Academic Search

In this work, the kinetics of diffusion of methylene blue in agar aqueous solution is studied using a photoacoustic technique.\\u000a Two agar phantoms solutions in water with a relation of mass\\/volume of 0.01% and 0.05% were analyzed. The study was performed\\u000a using a modified Rosencwaig photoacoustic cell that is enclosed by transparent windows, on both sides. The sample is deposited

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

2010-01-01

22

PHOTOACOUSTIC DETECTION OF PARTICULATE CARBON  

EPA Science Inventory

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

23

Application of photothermal and photoacoustic deflection techniques to sooting flames; velocity, temperature, and concentration measurements  

Microsoft Academic Search

Photothermal and photoacoustic deflection techniques have been applied for the first time to sooting flames. The values of these techniques for combustion diagnosis is demonstrated by measurements of velocity, temperature, and soot concentration profiles in a C2H2\\/O2 flame.

A. Rose; R. Gupta

1986-01-01

24

Mode Shape Measurement of Piezoelectric Resonators Using Image Processing Technique  

Microsoft Academic Search

An image processing technique for measuring the mode shapes of piezoelectric resonators is described. Laser speckle interference, a periodic resonator excitation and charge coupled device (CCD) image captures are effectively combined in this method. The experimental results for three kinds of AT-cut quartz resonators demonstrate the applicability of the proposed method.

Yasuaki Watanabe; Yuji Shikama; Shigeyoshi Goka; Takayuki Sato; Hitoshi Sekimoto

2001-01-01

25

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

NASA Astrophysics Data System (ADS)

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

Kislyakov, Ivan M.; Yelleswarapu, Chandra S.

2013-10-01

26

New Developments in Photoacoustics.  

National Technical Information Service (NTIS)

There have been several important new developments in the fields of photoacoustics and photoacoustic spectroscopy. Photoactoustic techniques are now being used in ferromagnetic and electron spin resonance experiments, and there have been rapid advances in...

A. Rosencwaig

1981-01-01

27

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

NASA Astrophysics Data System (ADS)

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.

Delgado-Vasallo, O.; Marín, E.

1999-03-01

28

Investigating the Energy Band Gap of Fe2O3 Doped with Cr: Using the Photoacoustic Technique  

Microsoft Academic Search

In the present paper, we report the observations made on the electronic properties of Fe2O3 thin films formed on a glass substrate, with different doping concentrations of chromium, using a photoacoustic spectroscopic (PAS) technique. Photoacoustic (PA) spectra of Fe2O3 thin films, with different doping concentrations of Cr, were recorded in the wavelength range of 300–700 nm at a modulation frequency of

H. Singh; A. K. Rai; V. R. Satsangi

2005-01-01

29

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

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

30

Two-photon photoacoustics ultrasound measurement by a loss modulation technique  

NASA Astrophysics Data System (ADS)

In this work, we investigated the principle of the two-photon absorption (TPA) detection with a loss modulation technique, and first demonstrated the existence of two-photon photoacoustics ultrasound excited by a femtosecond high repetition rate laser. By using the AO modulation with different modulation frequencies, we successfully create the beating of the light signal when the two arms of the beams are both spatial and temporal overlapping. The pulse train of the femtosecond laser causes the narrow band excitation, providing the frequency selectivity and sensitivity. Moreover, the pulse energy is no more than 15nJ/pulse, which is at least 3 orders of magnitude smaller than that of the nanosecond laser, and therefore prevents the thermal damage of the sample. With the help of lock-in detection and a low noise amplifier, we can separate the signal of two-photon absorption from one-photon absorption. We used an ultrasonic transducer to detect the response of the sample, and verified the existence of the two-photon photoacoustics ultrasound generating by the femtosecond laser. Several contrast agents, such as the black carbon solution, the fluorescence dye and the nano-particles, were used in the experiment. In the end, we demonstrated the application, two photo-acoustic imaging, which provides the high spatial resolution (<10?m) and large penetration depth (~1mm), to the simulated biological tissue. This is a milestone to develop the two-photon photoacoustics microscopy, which, in principle, has the great potential to achieve the in vitro and in vivo high resolution deep tissue imaging.

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

2013-03-01

31

Application of design optimization techniques for vibration control of structures using piezoelectric devices  

NASA Astrophysics Data System (ADS)

Active vibration control of structures using piezoelectric materials is a new approach for damping unwanted vibrations in structures lacking sufficient stiffness or passive damping. The finite elements method is used to model active damping elements which are piezoelectric actuators bonded to a box beam. Efficient implementation of these actuators requires that their optimal locations on the structure be determined and that the structure be designed to best utilize the properties of the piezoelectrics. A formal optimization procedure has been developed to address both of these issues. Multiobjective optimization techniques are used to minimize multiple and conflicting design objectives such as mass and energy dissipated by the piezoelectric actuators.

Chattopadhyay, Aditi; Seeley, Charles E.

1993-09-01

32

Standoff detection of ozone in an open environment using photoacoustic spectroscopy technique  

NASA Astrophysics Data System (ADS)

The current work reports a practical photoacoustic spectroscopy (PAS) technique that can be applied for the standoff detection of ozone in an open environment. The developed PAS detection system consists of a laser, a parabolic acoustic reflector, and an acoustic resonator that acts as a lock-in amplifier to extract only the signals resonating with the laser chopping frequency. The design of the acoustic resonator is described, and a detection capability of 700 ppb ozone at 2 m distance in the ambient air is demonstrated. The system would have broad applications for open-air detection of chemicals in various forms.

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

2012-03-01

33

Evaluation of coupled piezoelectric and electromagnetic technique for vibration energy harvesting  

Microsoft Academic Search

Vibration energy harvesting is an attractive technique for potential powering of wireless sensors and other low power micro devices. In order for the device to have maximum power output, it is necessary to match electrical and mechanical damping. In this work a coupled piezoelectric and electromagnetic energy harvesting device is evaluated for its efficiency and compared with optimized standalone piezoelectric

Vinod R. Challa; M. G. Prasad; Frank T. Fisher

2008-01-01

34

Early detection of dental caries using photoacoustics  

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

35

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

36

Consideration of Impedance Matching Techniques for Efficient Piezoelectric Energy Harvesting  

Microsoft Academic Search

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

Hyeoungwoo Kim; Shashank Priya; Harry Stephanou; Kenji Uchino

2007-01-01

37

Study of the compact fiber optic photoacoustic ultrasonic transducer  

NASA Astrophysics Data System (ADS)

Recently, many studies have been exerted on developing ultrasonic transducers that can feature high frequencies for better resolutions and compact sizes for the limit space nondestructive testing applications. Conventional ultrasonic transducers, which are made by piezoelectric materials, suffer from issues such as low frequencies and bulky sizes due to the difficulty of dicing piezoelectric materials into smaller pieces. On the other hand, generating ultrasonic signals by photoacoustic principle is a promising way to generate a high frequency ultrasonic pulse. Optical fiber is a very compact material that can carry the light energy. By combining the photoacoustic principle and the optical fiber together, a novel ultrasonic transducer that features a high frequency and a compact size could be achieved. In this paper, an ultrasonic transducer using gold nanoparticles as the photoacoustic generation material is described. Gold nanoparticles are deposited on the end surface of an optical fiber acting as the ultrasonic generator. A cavity and a diaphragm are fabricated in the center of the fiber using as the ultrasonic receiver. A phase array technique is applied to the transducer to steer the direction of the acoustic beam. Simulation results demonstrated that the photoacoustic ultrasonic transducer is feasible.

Wu, Nan; Tian, Ye; Zou, Xiaotian; Wang, Xingwei

2012-03-01

38

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

39

Consideration of impedance matching techniques for efficient piezoelectric energy harvesting.  

PubMed

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

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

2007-09-01

40

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

NASA Astrophysics Data System (ADS)

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

Yehya, Fahem; Chaudhary, A. K.

2013-11-01

41

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

42

Photoacoustic Effect and the Physics of Waves.  

ERIC Educational Resources Information Center

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

McDonald, F. Alan

1980-01-01

43

Adsorption and desorption kinetics in ZrO2 TiO2 by photoacoustic techniques  

NASA Astrophysics Data System (ADS)

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.

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

2005-06-01

44

Monitoring of HIFU thermal damage using integrated photoacoustic imaging and high intensity focused ultrasound technique  

NASA Astrophysics Data System (ADS)

In this study, we applied an integrated photoacoustic imaging (PAI) and high intensity focused ultrasound (HIFU) system to noninvasively monitor the thermal damage due to HIFU ablation in vivo. A single-element, spherically focused ultrasonic transducer, with a central frequency of 5MHz, was used to generate a HIFU area in soft tissue. Photoacoustic signals were detected by the same ultrasonic transducer before and after HIFU treatments using different wavelengths. The feasibility of combined contrast imaging and treatment of solid tumor in vivo by the integrated PAI and HIFU system was also studied. Gold nanorods were used to enhance PAI during the imaging of a CT26 tumor, which was subcutaneously inoculated on the hip of a BALB/c mouse. Subsequently, the CT26 tumor was ablated by HIFU with the guidance of photoacoustic images. Our results suggested that the tumor was clearly visible on photoacoustic images after the injection of gold nanorods and was ablated by HIFU. In conclusion, PAI may potentially be used for monitoring HIFU thermal lesions with possible diagnosis and treatment of solid tumors.

Cui, Huizhong; Yang, Xinmai

2011-02-01

45

Thermal intravascular photoacoustic imaging  

PubMed Central

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

Wang, Bo; Emelianov, Stanislav

2011-01-01

46

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

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

47

Subsurface imaging with photoacoustics  

NASA Astrophysics Data System (ADS)

The use of piezoelectric detection for photoacoustic thermal-wave imaging of substrate features is investigated experimentally. In the experiment, a 4-W CO2 laser beam is scanned over the surface of an aluminum sample which has a piezoceramic disk of lead zirconate titanate bonded with cement to its rear side. The periodic stress-strain fluctuations induced in the sample by the laser beam produce a periodic electrical output from the piezoceramic transducer that is monitored with a lock-in amplifier. The lock-in output is combined with the outputs of the beam deflectors to provide a three-dimensional projection of the signal surface on the recorder. The z axis gives either the photoacoustic signal magnitude or its phase. Both magnitude and phase images show an increased resolution with increasing frequency. It is found that depth sensitivity for phase imaging is more than twice as great as that for magnitude imaging.

Busse, G.; Rosencwaig, A.

1980-05-01

48

High-resolution photoacoustic thermal-wave microscopy  

NASA Astrophysics Data System (ADS)

Experiments on photoacoustic thermal-wave microscopy are presented, for the first time, at high resolution. Using piezoelectric detection and a modulation frequency of 185 kHz, a thermal-wave resolution of approximately 7 microns is obtained. It is shown that the photoacoustic phase signal provides true thermal-wave imaging even in the presence of surface features with strong optical contrast.

Rosencwaig, A.; Busse, G.

1980-05-01

49

High-resolution photoacoustic thermal-wave microscopy  

Microsoft Academic Search

Experiments on photoacoustic thermal-wave microscopy are presented, for the first time, at high resolution. Using piezoelectric detection and a modulation frequency of 185 kHz, a thermal-wave resolution of approximately 7 microns is obtained. It is shown that the photoacoustic phase signal provides true thermal-wave imaging even in the presence of surface features with strong optical contrast.

Allan Rosencwaig; G. Busse

1980-01-01

50

Photoacoustic measurement of epidermal melanin  

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

51

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

52

PHOTOACOUSTIC TECHNIQUE FOR MEASURING BANDGAP ENERGY OF POROUS SILICON LAYER ON n-Si SUBSTRATE  

Microsoft Academic Search

The porous silicon layer was prepared on n-type Si wafers using electrochemical- etching method. The current density was varied from 16 mA\\/cm2 to 40 mA\\/cm2. The surface morphology measured using SEM confirms the formation of porous layer on the silicon substrate. The photoacoustic (PA) absorption band and optical band gap energy were determined from PA signal intensity spectra measured at

Chan Kok Sheng; W. Mahmood; Mat Yunus; Wan Yunus; Zainal Abidin Talib; Anuar Kassim

53

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

PubMed

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

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

2013-08-26

54

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

PubMed Central

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

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

2013-01-01

55

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

NASA Astrophysics Data System (ADS)

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

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

2005-06-01

56

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

PubMed Central

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

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

2009-01-01

57

Piezoelectric active sensing techniques for damage detection on wind turbine blades  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

59

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

PubMed

Acetaldehyde (AA), ethanol, and CO2 production in red bell pepper (Capsicum annum L.) fruit has been measured in a continuous flow system as the fruit was switched between 20% O2 and anaerobic conditions. Minimum gas phase concentrations of 0.5 nL L-1, 10 nL L-1, and 1 mL L-1, respectively, can be detected employing a laser-based photoacoustic technique. This technique allows monitoring of low production rates and transient features in real time. At the start of anaerobic treatment respiration decreases by 60% within 0.5 h, whereas AA and ethanol production is delayed by 1 to 3 h. This suggests a direct slow-down of the tricarboxylic acid cycle and a delayed onset of alcoholic fermentation. Reexposure of the fruit to oxygen results in a 2- to 10-fold upsurge in AA production. A short anoxic period leads to a sharp transient peak lasting about 40 min, whereas after numerous and longer anoxic periods, post-anoxic AA production stays high for several hours. High sensitivity of the fruit tissue to oxygen is further evidenced by a sharp decrease in post-anoxic AA production upon an early return to anaerobic conditions. Ethanol oxidation by the "peroxidatic" action of catalase is proposed to account for the immediate post-anoxic AA upsurge. PMID:12223654

Zuckermann, H.; Harren, FJM.; Reuss, J.; Parker, D. H.

1997-03-01

60

Enhanced sensitivity carbon nanotubes as targeted photoacoustic molecular imaging agents  

Microsoft Academic Search

Photoacoustic imaging of living subjects offers high spatial resolution at increased tissue depths compared to purely optical imaging techniques. We have recently shown that intravenously injected single walled carbon nanotubes (SWNTs) can be used as targeted photoacoustic imaging agents in living mice using RGD peptides to target alphavbeta3 integrins. We have now developed a new targeted photoacoustic imaging agent based

Adam de La Zerda; Zhuang Liu; Cristina Zavaleta; Sunil Bodapati; Robert Teed; Srikant Vaithilingam; Te-Jen Ma; Omer Oralkan; Xiaoyuan Chen; Butrus T. Khuri-Yakub; Hongjie Dai; Sanjiv S. Gambhir

2009-01-01

61

Characterization of human skin through photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

The photoacoustic technique is based on the absorption of modulated light by a sample and subsequent heat generation. This generates thermal waves that propagate in the surrounding media. According to the Rosencwaig-Gersho Model, such waves produce the pressure oscillation detected as the photoacoustic signal. This technique allows the spectroscopic characterization of multilayer systems: as the thermal diffusion length varies with the modulation frequency of the absorbed light, the depth profile of a sample can be studied by the analysis of the photoacoustic signal at different modulation frequencies. In this work, photoacoustic spectroscopy was used to characterize different human skin samples. Measurements were performed at 70Hz and 17Hz, using a 1000W Xe arc lamp as the light source, for wavelengths between 240nm and 700nm. Skin samples were about 0,5cm diameter. It was possible to obtain the photoacoustic absorption spectra of the stratum corneum and of a deeper layer of epidermis; when the lower modulation frequency is utilized, photoacoustic spectroscopy characterizes the absorption of the whole epidermis, because in this case the thermal diffusion length is thicker than that of the stratum corneum. Photoacoustic spectroscopy was also employed to monitor the drying kinetics of the skin. This was done by analyzing the time evolution of the photoacoustic spectra of skin samples. Pre-treatment of the samples included different periods in a drying chamber. Measurements show that the photoacoustic spectra changes according to the humidity of the skin. Future work includes detailed monitoring of skin hydration.

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

2004-06-01

62

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

Microsoft Academic Search

A simple effective photoacoustic probe employing the acoustic waveguide effect in quartz substrate is described. The photoacoustic probe consists of a quartz rod to the upper end of which PZT-5A piezoelectric ceramic disk is attached. The probe was used in the acquisition of a dye-laser-excited photoacoustic spectrum of 10-..mu..g\\/ml 9,10-dimethylanthracene in ethanol at room temperature. With the probe system, the

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

1982-01-01

63

Photoacoustic imaging with integrating line detectors  

NASA Astrophysics Data System (ADS)

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.

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

2009-02-01

64

Photopyroelectric versus photoacoustic characterization of photovoltaic cells  

Microsoft Academic Search

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

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

1986-01-01

65

Photoacoustic Endoscopy  

PubMed Central

We have developed novel photoacoustic endoscopy with a miniaturized imaging probe. A light guiding optical fiber, an ultrasonic sensor, and a mechanical scanning unit are integrated to enable circumferential sector scanning, which produces B-scan images. Biological tissues, including the gastrointestinal tract of a rat, have been imaged ex vivo or in situ.

Yang, Joon-Mo; Maslov, Konstantin; Yang, Hao-Chung; Zhou, Qifa; Shung, K. Kirk; Wang, Lihong V.

2009-01-01

66

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

SciTech Connect

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

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

2009-05-15

67

Evolution of a MEMS Photoacoustic Chemical Sensor.  

National Technical Information Service (NTIS)

Photoacoustic spectroscopy is a useful monitoring technique that is well suited for trace gas detection. The technique also possesses favorable detection characteristics when the system dimensions are scaled to a micro- system design. The objective of pre...

P. M. Pellegrino R. G. Polcawich

2003-01-01

68

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

PubMed

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

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

2013-01-01

69

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

Microsoft Academic Search

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

Yeolho Lee; Geunbae Lim; Wonkyu Moon

2005-01-01

70

Carbon nanotubes as photoacoustic molecular imaging agents in living mice  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging of living subjects offers higher spatial resolution and allows deeper tissues to be imaged compared with most optical imaging techniques. As many diseases do not exhibit a natural photoacoustic contrast, especially in their early stages, it is necessary to administer a photoacoustic contrast agent. A number of contrast agents for photoacoustic imaging have been suggested previously, but most were not shown to target a diseased site in living subjects. Here we show that single-walled carbon nanotubes conjugated with cyclic Arg-Gly-Asp (RGD) peptides can be used as a contrast agent for photoacoustic imaging of tumours. Intravenous administration of these targeted nanotubes to mice bearing tumours showed eight times greater photoacoustic signal in the tumour than mice injected with non-targeted nanotubes. These results were verified ex vivo using Raman microscopy. Photoacoustic imaging of targeted single-walled carbon nanotubes may contribute to non-invasive cancer imaging and monitoring of nanotherapeutics in living subjects.

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

2008-09-01

71

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

NASA Astrophysics Data System (ADS)

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

Wang, Jianhua; Xiao, Zexin

2011-11-01

72

Photoacoustic Tomography of the Brain  

NASA Astrophysics Data System (ADS)

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.

Xia, Jun; Wang, Lihong V.

73

Nondestructive photoacoustic subsurface tissue imaging: a feasibility study  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) techniques may be used for imaging of absorbing structures within a light scattering medium. By use of an array of detectors, the macroscopic structure of the absorbers in the medium may be determined, based on differences in light absorption. A physical explanation of the spherical PA profile is presented, from which the signals generated by other source geometries can be derived. The potentialities of PA imaging of blood perfused tissue have been investigated. Experiments were performed with a pulsed frequency-doubled Nd:YAG laser which delivered 10 ns pulses at 532 nm wavelength. Dilutions of India ink, dyed epoxy strands and dyed polystyrene spheres acted as PA sources. Characteristic source dimensions varied between ca. 10 and 250 micrometer. The PA signals were detected with wide band piezoelectric transducers made of 9 and 28 micrometer thick PVdF film with mm and sub-mm lateral dimensions. Detection distances were between 1 and 50 mm. Nonlinear effects have been observed for higher levels of absorbed energy. Dilutions of Liposyn were used as optically scattering media. The calculations suggest the applicability of the method. For imaging of dermal blood vessels up to a depth of 1 mm, piezoelectric signals in the (mu) V range may be expected. The experimental PA signals contain significant frequency components up to 75 MHz, depending on the source characteristics. In principle from such signals the detection distance can be determined with micrometer resolution. The detectors show a forward directivity caused by acoustic interference on the detector surface which depends on the lateral dimensions and the acoustic pulse shape and pulse duration. Optical attenuation coefficients of the Liposyn dilutions have been determined photoacoustically. A spatial resolution of ca. 5-50 micrometer was achieved in the reconstruction of the PA source locations.

Hoelen, Christoph; de Mul, Frits F.; Greve, Jan

1996-01-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

75

Förster resonance energy transfer photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

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

Wang, Yu; Wang, Lihong V.

2013-03-01

76

Dual-modality thermoacoustic and photoacoustic imaging  

Microsoft Academic Search

Diagnosis of early breast cancer is the key to survival. The combined contrasts from thermoacoustic and photoacoustic tomography (TAT and PAT) can potentially predict early stage breast cancer. We have designed and engineered a breast imaging system integrating both thermoacoustic and photoacoustic imaging techniques to achieve dual-contrast (microwave and light absorption), non-ionizing, low-cost, high-resolution, three-dimensional breast imaging. We have also

Manojit Pramanik

2010-01-01

77

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

Microsoft Academic Search

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

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

2010-01-01

78

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

Microsoft Academic Search

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

Samara L. Firebaugh; Martin A. Schmidt

2001-01-01

79

4-D photoacoustic tomography.  

PubMed

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

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

2013-01-23

80

4-D Photoacoustic Tomography  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

81

FT-IR-cPAS--new photoacoustic measurement technique for analysis of hot gases: a case study on VOCs.  

PubMed

This article describes a new photoacoustic FT-IR system capable of operating at elevated temperatures. The key hardware component is an optical-readout cantilever microphone that can work up to 200 °C. All parts in contact with the sample gas were put into a heated oven, incl. the photoacoustic cell. The sensitivity of the built photoacoustic system was tested by measuring 18 different VOCs. At 100 ppm gas concentration, the univariate signal to noise ratios (1?, measurement time 25.5 min, at highest peak, optical resolution 8 cm(-1)) of the spectra varied from minimally 19 for o-xylene up to 329 for butyl acetate. The sensitivity can be improved by multivariate analyses over broad wavelength ranges, which effectively co-adds the univariate sensitivities achievable at individual wavelengths. The multivariate limit of detection (3?, 8.5 min, full useful wavelength range), i.e., the best possible inverse analytical sensitivity achievable at optimum calibration, was calculated using the SBC method and varied from 2.60 ppm for dichloromethane to 0.33 ppm for butyl acetate. Depending on the shape of the spectra, which often only contain a few sharp peaks, the multivariate analysis improved the analytical sensitivity by 2.2 to 9.2 times compared to the univariate case. Selectivity and multi component ability were tested by a SBC calibration including 5 VOCs and water. The average cross selectivities turned out to be less than 2% and the resulting inverse analytical sensitivities of the 5 interfering VOCs was increased by maximum factor of 2.2 compared to the single component sensitivities. Water subtraction using SBC gave the true analyte concentration with a variation coefficient of 3%, although the sample spectra (methyl ethyl ketone, 200 ppm) contained water from 1,400 to 100k ppm and for subtraction only one water spectra (10k ppm) was used. The developed device shows significant improvement to the current state-of-the-art measurement methods used in industrial VOC measurements. PMID:22163900

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

2011-05-16

82

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

PubMed Central

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

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

2011-01-01

83

Photoacoustic thermal diffusion flowmetry  

PubMed Central

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

Sheinfeld, Adi; Eyal, Avishay

2012-01-01

84

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

NASA Astrophysics Data System (ADS)

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

Sivadas, Vishak; Wickenheiser, Adam M.

2011-03-01

85

Piezoelectric Polymers.  

National Technical Information Service (NTIS)

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 prom...

J. S. Harrison Z. Ounaies

2001-01-01

86

Quartz-enhanced photoacoustic spectroscopy.  

PubMed

A new approach to detecting a weak photoacoustic signal in a gas medium is described. Instead of a gas-filled resonant acoustic cavity, the sound energy is accumulated in a high- Q crystal element. Feasibility experiments utilizing a quartz-watch tuning fork demonstrate a sensitivity of 1.2x10(-7) cm(-1) W/ radicalHz . Potential further developments and applications of this technique are discussed. PMID:18033396

Kosterev, A A; Bakhirkin, Yu A; Curl, R F; Tittel, F K

2002-11-01

87

Quartz-enhanced photoacoustic spectroscopy  

Microsoft Academic Search

A new approach to detecting a weak photoacoustic signal in a gas medium is described. Instead of a gas-filled resonant acoustic cavity, the sound energy is accumulated in a high-Q crystal element. Feasibility experiments utilizing a quartz-watch tuning fork demonstrate a sensitivity of 1.2 × 10-7 cm-1 W\\/Hz. Potential further developments and applications of this technique are discussed.

A. A. Kosterev; Yu. A. Bakhirkin; R. F. Curl; F. K. Tittel

2002-01-01

88

Quartz-enhanced photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

A new approach to detecting a weak photoacoustic signal in a gas medium is described. Instead of a gas-filled resonant acoustic cavity, the sound energy is accumulated in a high-Q crystal element. Feasibility experiments utilizing a quartz-watch tuning fork demonstrate a sensitivity of 1.2 × 10-7 cm-1 W/Hz. Potential further developments and applications of this technique are discussed.

Kosterev, A. A.; Bakhirkin, Yu. A.; Curl, R. F.; Tittel, F. K.

2002-11-01

89

Photoacoustic characterization of ovarian tissue  

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

90

Operating point stabilization of fiber-based line detectors for photoacoustic imaging  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging is an upcoming technique in the field of biomedical imaging. Our group introduced fiber-based line detectors, which are used to acquire broad-band ultrasonic signals, several years ago. Up to now operating point stabilization of fiber-based line detectors was realized by tuning the wavelength of the detection laser. This is, because of the high costs, not applicable for parallel detection. An alternative stabilization method, the change of the optical path length, is presented in this paper. Changing of the optical path length is realized by stretching the fiber with piezoelectric tubes. Fringe patterns and operation point stabilization of both stabilization schemes are compared. Next, signal detection utilizing a polymer optical fiber in a Mach-Zehnder and Fabry-Perot interferometer is demonstrated, and the influence of the detection wavelength (633nm and 1550nm) is examined. Finally, two-dimensional imaging by utilizing a perfluorinated polymer fiber is demonstrated.

Felbermayer, Karoline; Grün, Hubert; Berer, Thomas; Burgholzer, Peter

2011-06-01

91

Determination of Tequila Quality by Photoacoustic Analysis  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

92

Acoustic property measurements in a photoacoustic imager  

NASA Astrophysics Data System (ADS)

Photoacoustics is a hybrid imaging technique that combines the contrast available to optical imaging with the resolution that is possessed by ultrasound imaging. The technique is based on generating ultrasound from absorbing structures in tissue using pulsed light. In photoacoustic (PA) computerized tomography (CT) imaging, reconstruction of the optical absorption in a subject, is performed for example by filtered backprojection. The backprojection is performed along circular paths in image space instead of along straight lines as in X-ray CT imaging. To achieve this, the speed-of-sound through the subject is usually assumed constant. An unsuitable speed-of-sound can degrade resolution and contrast. We discuss here a method of actually measuring the speed-of- sound distribution using ultrasound transmission through the subject under photoacoustic investigation. This is achieved in a simple approach that does not require any additional ultrasound transmitter. The method uses a passive element (carbon fiber) that is placed in the imager in the path of the illumination which generates ultrasound by the photoacoustic effect and behaves as an ultrasound source. Measuring the time-of-flight of this ultrasound transient by the same detector used for conventional photoacoustics, allows a speed-of-sound image to be reconstructed. This concept is validated on phantoms.

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

2007-07-01

93

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

PubMed

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

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

2012-06-01

94

A photoacoustic and ultrasonic study on jatropha oil  

NASA Astrophysics Data System (ADS)

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

Krishna Bama, G.; Ramachandran, K.

2010-03-01

95

Piezoelectric moduli of piezoelectric ceramics  

SciTech Connect

The effective piezoelectric moduli of polycrystalline piezoelectric ceramics are calculated using a straightforward averaging method (a Voigt average) and a more rigorous effective-medium theory recently developed for piezocomposites. The effects of polarization orientation within each crystallographic domain and the shape of the domain on the effective piezoelectric moduli are presented. The effective-medium theory, which includes full coupling of the elastic and dielectric interactions, gives results in reasonable agreement with experimental ones.

Nan, C.W.; Clarke, D.R. [Univ. of California, Santa Barbara, CA (United States). Coll. of Engineering

1996-10-01

96

Photoacoustic tomography of water in biological tissue  

NASA Astrophysics Data System (ADS)

As an emerging imaging technique that combines high optical contrast and ultrasonic detection, photoacoustic tomography (PAT) has been widely used to image optically absorptive objects in both human and animal tissues. PAT overcomes the depth limitation of other high-resolution optical imaging methods, and it is also free from speckle artifacts. To our knowledge, water has never been imaged by PAT in biological tissue. Here, for the first time, we experimentally imaged water in both tissue phantoms and biological tissues using a near infrared (NIR) light source. The differences among photoacoustic images of water with different concentrations indicate that laser-based PAT can usefully detect and image water content in tissue.

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

2011-02-01

97

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 itâÂÂs 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.

2012-03-13

98

Gas phase photoacoustic Raman spectroscopy using pulsed laser excitation  

NASA Astrophysics Data System (ADS)

The sensitivity of a new spectroscopic technique, photoacoustic Raman spectroscopy (PARS), has been improved substantially by the use of high-peak-power pulsed lasers. The theory for generation of photoacoustic signals from stimulated Raman scattering is outlined, and vibration-rotation Raman spectra for CO2 and CH4 are presented. Applications of PARS are discussed, and a comparison is made with other Raman techniques.

West, Gary A.; Siebert, Donald R.; Barrett, Joseph J.

1980-05-01

99

Standoff chemical detection using quantum cascade lasers and photoacoustic sensing  

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

100

A comparative study of photoacoustic and reflectance methods for determination of epidermal melanin content.  

PubMed

Although epidermal melanin content has been quantified non-invasively using visible reflectance spectroscopy (VRS), there is currently no way to determine melanin distribution in the epidermis. We have developed a photoacoustic probe that uses a Q-switched, frequency-doubled Nd:YAG (neodymium, yttrium, aluminum, garnet) laser operating at 532 nm to generate acoustic pulses in skin in vivo. The probe contained a piezoelectric element that detected photoacoustic waves that were then analyzed for epidermal melanin content using a photoacoustic melanin index (PAMI). Melanin content was compared between results of photoacoustics and VRS. Spectra from human skin were fitted to a model based on diffusion theory that included parameters for epidermal thickness, melanin content, hair color and density, and dermal blood content. Ten human subjects with skin phototypes I-VI were tested using the photoacoustic probe and VRS. A plot of PAMI v. VRS showed a good linear fit with r2=0.85. Photoacoustic and VRS measurements are shown for a human subject with vitiligo, indicating that melanin was almost completely absent. We present preliminary modeling for photoacoustic probe design and analysis necessary for depth profiling of epidermal melanin. PMID:15175034

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

2004-06-01

101

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

Microsoft Academic Search

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

Vinod R Challa; M G Prasad; Frank T Fisher

2009-01-01

102

Nonlinear photoacoustics for measuring the nonlinear optical absorption coefficient.  

PubMed

We report a novel photoacoustic Z-scan (PAZ-scan) technique that combines the advantages offered by the conventional Z-scan method and the sensitivity of the photoacoustic detection. The sample is scanned through the focused laser beam and the generated photoacoustic signal is recorded using a 10 MHz focused ultrasound transducer. Since the signal strength is directly proportional to the optical absorption, PAZ-scan displays nonlinear behavior depicting the nonlinear optical absorption of the material. Among many advantages, our experiments on mouse blood show that PAZ-scan can potentially be used as a standard technique to calibrate contrast agents used in theranostics in general and photoacoustics in particular. PMID:20588748

Yelleswarapu, Chandra S; Kothapalli, Sri-Rajasekhar

2010-04-26

103

Combined photoacoustic and magneto-acoustic imaging.  

PubMed

Ultrasound is a widely used modality with excellent spatial resolution, low cost, portability, reliability and safety. In clinical practice and in the biomedical field, molecular ultrasound-based imaging techniques are desired to visualize tissue pathologies, such as cancer. In this paper, we present an advanced imaging technique - combined photoacoustic and magneto-acoustic imaging - capable of visualizing the anatomical, functional and biomechanical properties of tissues or organs. The experiments to test the combined imaging technique were performed using dual, nanoparticle-based contrast agents that exhibit the desired optical and magnetic properties. The results of our study demonstrate the feasibility of the combined photoacoustic and magneto-acoustic imaging that takes the advantages of each imaging techniques and provides high sensitivity, reliable contrast and good penetrating depth. Therefore, the developed imaging technique can be used in wide range of biomedical and clinical application. PMID:19964846

Qu, Min; Mallidi, Srivalleesha; Mehrmohammadi, Mohammad; Ma, Li Leo; Johnston, Keith P; Sokolov, Konstantin; Emelianov, Stanislav

2009-01-01

104

Piezoelectric Film.  

ERIC Educational Resources Information Center

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

Garrison, Steve

1992-01-01

105

Simultaneous optical and photoacoustic measurement of nonlinear absorption  

NASA Astrophysics Data System (ADS)

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

Chantharasupawong, Panit; Philip, Reji; Thomas, Jayan

2013-01-01

106

Optical detection of photoacoustic waves using phase sensitive low-coherence interferometry  

NASA Astrophysics Data System (ADS)

Detection of acoustic waves is the cornerstone of photoacoustic tomography (PAT). Detection has conventionally been performed mechanically using ultrasonic transducers, or optically by interferometric techniques. We propose an interferometric detection scheme using low coherence interferometry (LCI) and discuss the challenges, advantages and limitations of applying this technique to photoacoustics.

Hermann, B.; Gabriele-Sandrian, M.; Hofer, B.; Povazay, B.; Drexler, W.

2012-02-01

107

Piezoelectric quartz crystal biosensors  

Microsoft Academic Search

Biosensing methods utilize the intrinsic selectivity of a biorecognition process to create relatively simple, low cost, analytical alternatives for a variety of research investigations. Here, biosensor applications of the piezoelectric quartz crystal (PQC) are reviewed. The discussion is divided into sections focusing on the development of PQC based analytical techniques, applications in solution phase sensing pertaining to PQC biosensors, and

Renee L. Bunde; Eric J. Jarvi; Jeffrey J. Rosentreter

1998-01-01

108

Design of piezoelectric motor systems  

NASA Astrophysics Data System (ADS)

Designing, building, and testing piezoelectric motor systems are fundamental to the successful development and application of these relatively new components in practical devices. This dissertation describes the design, development, building, and testing of several unique motor systems along with the equipment and techniques for doing so. Designing original piezoelectric motors requires a fresh look at the existing selection of successful and unsuccessful motor systems. An extensive literature survey of piezoelectric motor systems over the past thirty years is provided as the first section of this work. Examining the construction geometry, the vibration and piezoelectric material orientation, and the output motion of these designs, new ideas as either variations on old designs or completely new and untested designs can be created. These ideas can be refined with analysis to develop a set of prototypes, which may be tested to compare their performance to the current art of piezoelectric motors. The design and testing of two new motor systems are described in detail in this work. Other problems associated with piezoelectric motor systems, including the measurement and calculation of the properties of piezoelectric materials; the calculation of their vibration characteristics, and problems with the analysis of piezoelectric motors form the final sections of this document.

Friend, James Robert

1998-12-01

109

Pharmacokinetic Monitoring of Indocyanine Green for Tumor Detection Using Photoacoustic Imaging  

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

110

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

PubMed Central

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.

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

2010-01-01

111

Biomedical photoacoustic imaging.  

PubMed

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

Beard, Paul

2011-06-22

112

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

NASA Astrophysics Data System (ADS)

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.

McNulty, Thomas Francis

113

Piezoelectric sound generation and detection at 70 GHz using the technique of linear frequency modulation of a continuous wave  

Microsoft Academic Search

The method of linear frequency modulation of a continuous wave (FM-CW) in sound-echo experiments is demonstrated at a sound frequency of 70 GHz. A reflex klystron with a cw power of only 300 mW and a planar Hertzian resonator are used for the piezoelectric sound excitation. Applying homodyne detection, spectral echo signals are detected in the kHz range by means

B. Scheffold; O. Weis

1995-01-01

114

Photoacoustic spectroscopy of ?-hematin  

Microsoft Academic Search

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

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

2012-01-01

115

Ultrafast photoacoustic imaging with improved elevational focusing  

NASA Astrophysics Data System (ADS)

Conventional photoacoustic imaging system has limited temporal resolution and hence prohibits the applications in areas such as real-time 3D imaging. In this study, an ultrafast photoacoustic imaging system with its frame rate up to 2,000Hz is demonstrated. An ultrasound transducer with plane wave excitation and a high pulse repetition rate laser are utilized to acquire the data in parallel. Additionally, the 3D data acquisition which approaches the video rate is achieved when the volume data are collected by swept scanning of a motor. The synthetic aperture focusing technique (SAFT) based on the concept of the virtual source in the elevation plane is applied to improve the imaging quality. The 3D imaging has a frame rate of 12Hz to cover a square region of 19.2mm × 19.2mm.

Wang, Yu-Hsin; Li, Pai-Chi

2011-02-01

116

Towards single molecule detection using photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

117

Quantitative photoacoustic image reconstruction for molecular imaging  

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

118

Towards nonionizing photoacoustic cystography  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

119

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

Microsoft Academic Search

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

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

2004-01-01

120

Lifetime-based photoacoustic oxygen sensing in vivo  

PubMed Central

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

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

2012-01-01

121

Photoacoustic detection and monitoring of pollutant gases from urban public transport  

NASA Astrophysics Data System (ADS)

Nowadays, air pollution is presented as a serious threat to the planet. The concentration of gases from anthropogenic activities, such as transport, cause consequences ranging from local to global scale, affecting the climate, the environment and the human health. It is necessary to detect and monitor of a large number of gas species emitted by these sources of pollutants. The photothermal techniques, specially photoacoustic spectroscopy, allow the detection of many gaseous species. In this work, it is presented a new detection limit for a photoacoustic spectrometer composed of a CO2 Laser and a Photoacoustic Resonant Cell. Analyses of many gas samples collected in the exhaust of urban buses in the city were performed. Ethylene was detected with the help of the CO2 Laser photoacoustic spectroscopy and concentrations of CO, CO2 and NO were obtained through a commercial infrared photoacoustic analyzer called URAS.

Teodoro, C. G.; Schramm, D. U. S.; Sthel, M. S.; Lima, G. R.; Rocha, M. V.; Tavares, J. R.; Vargas, H.

2010-03-01

122

Multiplex photoacoustic molecular imaging using targeted silica-coated gold nanorods  

PubMed Central

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

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

2011-01-01

123

Structural Origins of Silk Piezoelectricity  

PubMed Central

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

Yucel, Tuna; Cebe, Peggy

2012-01-01

124

Structural Origins of Silk Piezoelectricity.  

PubMed

Uniaxially oriented, piezoelectric silk films were prepared by a two-step method that involved: (1) air drying aqueous, regenerated silk fibroin solutions into films, and (2) drawing the silk films to a desired draw ratio. The utility of two different drawing techniques, zone drawing and water immersion drawing were investigated for processing the silk for piezoelectric studies. Silk films zone drawn to a ratio of ?= 2.7 displayed relatively high dynamic shear piezoelectric coefficients of d(14) = -1.5 pC/N, corresponding to over two orders of magnitude increase in d(14) due to film drawing. A strong correlation was observed between the increase in the silk II, ?-sheet content with increasing draw ratio measured by FTIR spectroscopy (C(?)? e(2.5) (?)), the concomitant increasing degree of orientation of ?-sheet crystals detected via WAXD (FWHM = 0.22° for ?= 2.7), and the improvement in silk piezoelectricity (d(14)? e(2.4) (?)). Water immersion drawing led to a predominantly silk I structure with a low degree of orientation (FWHM = 75°) and a much weaker piezoelectric response compared to zone drawing. Similarly, increasing the ?-sheet crystallinity without inducing crystal alignment, e.g. by methanol treatment, did not result in a significant enhancement of silk piezoelectricity. Overall, a combination of a high degree of silk II, ?-sheet crystallinity and crystalline orientation are prerequisites for a strong piezoelectric effect in silk. Further understanding of the structural origins of silk piezoelectricity will provide important options for future biotechnological and biomedical applications of this protein. PMID:23335872

Yucel, Tuna; Cebe, Peggy; Kaplan, David L

2011-01-13

125

Frequency-domain analysis of photoacoustic imaging data from prostate adenocarcinoma tumors in a murine model  

PubMed Central

Photoacoustic imaging is an emerging technique for anatomical and functional sub-surface imaging, but previous studies have predominantly focused on time-domain analysis. In this study, frequency-domain analysis of the radio-frequency signals from photoacoustic imaging was performed to generate quantitative parameters for tissue characterization. To account for the response of the imaging system, the photoacoustic spectra were calibrated by dividing the photoacoustic spectra (radio-frequency ultrasound spectra resulting from laser excitation) from tissue by the photoacoustic spectrum of a point absorber excited under the same conditions. The resulting quasi-linear photoacoustic spectra were fit by linear regression, and midband fit, slope, and intercept were computed from the best-fit line. These photoacoustic spectral parameters were compared between the region-of-interests (ROIs) representing prostate adenocarcinoma tumors and adjacent normal flank tissue in a murine model. The mean midband fit and intercept in the ROIs showed significant differences between cancerous and non-cancerous regions. These initial results suggest that such frequency-domain analysis can provide a quantitative method for tumor tissue characterization using photoacoustic imaging in vivo.

Kumon, Ronald E.; Deng, Cheri X.; Wang, Xueding

2011-01-01

126

Polyimides: Piezoelectric properties and interfacial imidization  

Microsoft Academic Search

This work presents novel computational methodologies to bridge computational and experimental time scales and to incorporate chemical reactions into classical simulations. Specifically, the mechanisms underlying both the piezoelectric properties and interfacial imidization of polyimides are examined. The dielectric relaxation strength, Deltaepsilon, is directly proportional to the piezoelectric response in amorphous polymers. A simulation technique is presented which allows the calculation

Jennifer Ann Young

1999-01-01

127

Functional photoacoustic microscopy of pH  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

128

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

129

Piezoelectric Effect  

NSDL National Science Digital Library

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

2008-10-23

130

Enhanced sensitivity carbon nanotubes as targeted photoacoustic molecular imaging agents  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging of living subjects offers high spatial resolution at increased tissue depths compared to purely optical imaging techniques. We have recently shown that intravenously injected single walled carbon nanotubes (SWNTs) can be used as targeted photoacoustic imaging agents in living mice using RGD peptides to target ?v?3 integrins. We have now developed a new targeted photoacoustic imaging agent based on SWNTs and Indocyanine Green (SWNT-ICG) with absorption peak at 780nm. The photoacoustic signal of the new imaging agent is enhanced by ~20 times as compared to plain SWNTs. The particles are synthesized from SWNT-RGD that noncovalently attach to multiple ICG molecules through pi-pi stacking interactions. Negative control particles had RAD peptide instead of RGD. We measured the serum stability of the particles and verified that the RGD/RAD conjugation did not alter the particle's absorbance spectrum. Finally, through cell uptake studies with U87MG cells we verified that the particles bind selectively to ?v?3 integrin. In conclusion, the extremely high absorption of the SWNT-ICG particles shows great promise for high sensitivity photoacoustic imaging of molecular targets in-vivo. This work lays the foundations for future in-vivo studies that will use the SWNT-ICG particles as imaging agents administered systemically.

de La Zerda, Adam; Liu, Zhuang; Zavaleta, Cristina; Bodapati, Sunil; Teed, Robert; Vaithilingam, Srikant; Ma, Te-Jen; Oralkan, Omer; Chen, Xiaoyuan; Khuri-Yakub, Butrus T.; Dai, Hongjie; Gambhir, Sanjiv S.

2009-02-01

131

Four-dimensional photoacoustic imaging of moving targets.  

PubMed

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

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

2008-12-22

132

Photoacoustic spectroscopic differences between normal and malignant thyroid tissues  

NASA Astrophysics Data System (ADS)

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

Li, Li; Xie, Wengming; Li, Hui

2012-12-01

133

Photoacoustic spectroscopy for trace vapor detection and molecular discrimination  

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

134

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

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

135

Characterization and matched-field processing localization of photoacoustic signals  

NASA Astrophysics Data System (ADS)

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

Yonak, Serdar Hakki

2000-09-01

136

Standoff photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

2008-06-01

137

CO2 laser photoacoustic detection of hydrazine based rocket fuels  

Microsoft Academic Search

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

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

1982-01-01

138

Combined Photoacoustic and Molecular Fluorescence Imaging In Vivo  

Microsoft Academic Search

Because of the overwhelming scattering of light in biological tissues, the spatial resolution and imaging depth of conventional fluorescent imaging is unsatisfactory. Therefore, we present a dual modality imaging technique by combining fluorescence imaging with high-resolution noninvasive photoacoustic tomography (PAT) for the study of an animal tumor model. PAT provides high-resolution structural images of tumor angiogenesis, and fluorescence imaging offers

Lihong V. Wang; Xueyi Xie; Jung-Taek Oh; Meng-Lin Li; Geng Ku; Shi Ke; Sergiu Similache; Chun Li; George Stoica

2005-01-01

139

Application of Infrared Photoacoustic Spectroscopy in Soil Analysis  

Microsoft Academic Search

Soil analysis has become routine work for soil management and crop production. However, laboratory analysis–based determination of soil properties is expensive and time consuming, which is not suitable for precision agriculture. Infrared spectroscopy (IR) appears as an alternative and fast technique to measure soil properties and has had wide application; in particular, a new method called infrared photoacoustic spectroscopy (FTIR-PAS)

Changwen Du; Jianmin Zhou

2011-01-01

140

THERMAL WAVE IMAGING USING HARMONIC DETECTION OF THE PHOTOACOUSTIC SIGNAL  

Microsoft Academic Search

We describe a thermal wave imaging system based on gas-microphone detection of the harmonic component of the photoacoustic (PA) signal. In this system the sample is excited by a laser beam modulated at a frequency ƒ and the detection of the associated thermal wave field is carried out at a frequency 2ƒ. The technique demonstrates lateral resolution comparable to conventional

S. B. PERALTA; H. H. AL-KHAFAJI; A. W. WILLIAMS

1991-01-01

141

Adaptive optics photoacoustic microscopy  

PubMed Central

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.

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

2010-01-01

142

Photoacoustic spectrometer for ozone detection  

Microsoft Academic Search

A high-resolution external laser photoacoustic spectrometer has been developed. The spectrometer was used to analyze the absorption transitions of the ozone in coincidence with the CO2 laser emission and to evaluate its limit of sensitivity. A CO2 laser and a photoacoustic resonant cell, totally built in project, formed the spectrometer. The CO2 laser operates in 80 CW transitions distributed in

Edjar M. Telles; Edson Bezerra; Artemio Scalabrin

2001-01-01

143

Photoacoustics of the Stressed State in Solids.  

National Technical Information Service (NTIS)

The modern experimental and theoretical states of the problem of residual stress detection by the photoacoustic method are analyzed. Some experimental results obtained by the photoacoustic method for Vickers indentation zones in silicon nitride and Al2O3-...

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

2003-01-01

144

Remote Temperature Estimation in Intravascular Photoacoustic Imaging  

PubMed Central

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

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

2008-01-01

145

Photoacoustic sensor for medical diagnostics  

NASA Astrophysics Data System (ADS)

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.

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

2004-03-01

146

Photoacoustic lifetime imaging of dissolved oxygen using methylene blue  

NASA Astrophysics Data System (ADS)

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

Ashkenazi, Shai

2010-07-01

147

Photoacoustic point spectroscopy  

SciTech Connect

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

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

2011-06-14

148

Reverse photoacoustic standoff spectroscopy  

DOEpatents

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

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

2011-04-12

149

Photosynthetic Induction in Eucalyptus Urograndis Seedlings and Cuttings Measured by an Open Photoacoustic Cell  

Microsoft Academic Search

Photosynthetic induction in leaves of four-month-old Eucalyptus urograndis seedlings and of cuttings obtained from adult trees that were previously dark-adapted was studied by the in vivo and in situ Open Photoacoustic Cell Technique. Results for the gas exchange component of the photoacoustic (PA) signal were interpreted considering that the gas uptake component would have a phase angle nearly opposite to

P. R. Barja; A. M. Mansanares; E. C. Da Silva; A. C. N. Magalhães; P. L. C. A. Alves

2001-01-01

150

In vivo flow speed measurement of capillaries by photoacoustic correlation spectroscopy  

PubMed Central

We recently proposed the photoacoustic correlation spectroscopy (PACS) and demonstrated a proof-of-concept experiment. Here, we use the technique for in vivo flow speed measurement in capillaries in a chick embryo model. The photoacoustic microscopy system is used to render high spatial resolution and high sensitivity, enabling sufficient signals from single red blood cells. The probe beam size is calibrated by a blood-mimicking phantom. The results indicate that the feasibility of using PACS to study flow speeds in capillaries.

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

2012-01-01

151

Piezoelectric drive circuit  

DOEpatents

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

Treu, C.A. Jr.

1999-08-31

152

Photoacoustic tomography and sensing in biomedicine.  

PubMed

Photoacoustics has been broadly studied in biomedicine, for both human and small animal tissues. Photoacoustics uniquely combines the absorption contrast of light or radio frequency waves with ultrasound resolution. Moreover, it is non-ionizing and non-invasive, and is the fastest growing new biomedical method, with clinical applications on the way. This review provides a brief recap of recent developments in photoacoustics in biomedicine, from basic principles to applications. The emphasized areas include the new imaging modalities, hybrid detection methods, photoacoustic contrast agents and the photoacoustic Doppler effect, as well as translational research topics. PMID:19724102

Li, Changhui; Wang, Lihong V

2009-09-01

153

Engineered piezoelectricity in graphene.  

PubMed

We discover that piezoelectric effects can be engineered into nonpiezoelectric graphene through the selective surface adsorption of atoms. Our calculations show that doping a single sheet of graphene with atoms on one side results in the generation of piezoelectricity by breaking inversion symmetry. Despite their 2D nature, piezoelectric magnitudes are found to be comparable to those in 3D piezoelectric materials. Our results elucidate a designer piezoelectric phenomenon, unique to the nanoscale, that has potential to bring dynamical control to nanoscale electromechanical devices. PMID:22196055

Ong, Mitchell T; Reed, Evan J

2012-01-06

154

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

155

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

PubMed Central

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

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

2012-01-01

156

Photoacoustic imaging and temperature measurement for photothermal cancer therapy  

PubMed Central

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

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

2009-01-01

157

Photoacoustic section imaging with an integrating cylindrical detector  

NASA Astrophysics Data System (ADS)

A piezoelectric detector with cylindrical shape for photoacoustic section imaging is characterized. This detector is larger than the imaging object in direction of the cylinder axis, giving rise to its integrating properties. Its focal volume has the shape of a slice and the acquisition of signals for one section image requires rotation of an object about an axis perpendicular to this slice. Image reconstruction from the signals requires the application of the inverse Radon transform. It is shown that implementing the Abel transform is a suitable step in data processing, allowing speeding up the data acquisition since the scanning angle can be reduced. The resolution of the detector was estimated in directions perpendicular and parallel to the detection plane. An upper limit for the out of plane resolution is given and section images of a zebra fish are shown.

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

2011-06-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2007-10-01

159

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

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is a useful monitoring technique that is well suited for trace gas detection applications. A sensitive and compact differential photoacoustic method for trace gas measurements is proposed. The technique possesses favorable detection characteristics that suggest the system dimensions may scale to a micro-system design. The objective of present work is to incorporate two strengths of the Army Research Laboratory (ARL); Interband Quantum Cascade Laser (ICL) source development and Chemical and Biological Sensing; we then applied them into a monolithic micro-electromechanical systems (MEMS) photoacoustic trace gas sensor. Previous data has shown that reducing the size of the photoacoustic cell can produce a very sensitive sensor using a CO2 laser. Recent work has shown that with further reduction in the size of the photoacoustic cell in combination with an ICL as the source, produces favorable detection limits for Dimethyl Methyl Phosphonate (DMMP) a precursor to a nerve agent. These studies involve the incorporation of an ICL source operating at ~3.45 ?m. This experimentation is expected to culminate in the creation of an extremely versatile MEMS photoacoustic sensor.

Heaps, David A.; Pellegrino, Paul M.

2007-05-01

160

Power enhancement of piezoelectric transformers by adding thermal pad  

NASA Astrophysics Data System (ADS)

It is well known that power density of piezoelectric transformers is limited by mechanical stress. The power density of piezoelectric transformers calculated by the stress boundary can reach 330 W/cm3. However, no piezoelectric transformer has ever reached such a high power density in practice. The power density of the piezoelectric transformer is limited to 33 W/cm3 typically. This fact implies that there is another physical limitation in piezoelectric transformer. In fact, it is also known that piezoelectric material is constrained by vibration velocity. Once the vibration velocity is too large, the piezoelectric transformer generates heat until it cracks. To explain the instability of piezoelectric transformer, we will first model the relationship between vibration velocity and resulting heat by a physical feedback loop. It will be shown that the vibration velocity as well as the heat generation determines the loop gain. A large vibration velocity and heat may cause the feedback loop to enter into an unstable state. Therefore, to enhance the power capacity of piezoelectric transformer, the heat needs to be dissipated. In this paper, we used commercial thermal pads on the surface of the piezoelectric transformer to dissipate the heat. The mechanical current of piezoelectric transformers can move from 0.382A/2W to 0.972A/9W at a temperature of 55°C experimentally. It implies that the power capacity possibly increases 3 times in the piezoelectric material. Moreover, piezoelectric transformers that are well suited in applications of high voltage/low current becomes also well suited for low voltage/high current power supplies that are widely spread. This technique not only increases the power capacity of the piezoelectric transformer but also allows it to be used in enlarged practical applications. In this paper, the theoretical modeling will be detailed and verified by experiments.

Su, Y. H.; Liu, Y. P.; Vasic, D.; Costa, F.

2012-03-01

161

Slow-sound photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

162

Single-cell photoacoustic thermometry  

NASA Astrophysics Data System (ADS)

A novel photoacoustic thermometric method is presented for simultaneously imaging cells and sensing their temperature. With 3 seconds per frame imaging speed, a temperature resolution of 0.2 °C was achieved in a photo-thermal cell heating experiment. Compared to other approaches, the photoacoustic thermometric method has the advantage of not requiring custom-developed temperature-sensitive biosensors. This feature should facilitate the conversion of single-cell thermometry into a routine lab tool and make it accessible to a much broader biological research community.

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

2013-03-01

163

Photoacoustic spectroscopy application in diffusion examinations  

NASA Astrophysics Data System (ADS)

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

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

2005-09-01

164

Label-free photoacoustic microscopy of cytochromes  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

165

a Novel Piezoelectric Device  

NASA Astrophysics Data System (ADS)

This paper introduces a new based-on ultrasonic wave micro-fluid driving technique that is different from the present principle. The standing wave is generated by ultrasonic vibration in the device, and acoustic field is generated simultaneously. The particles in fluid medium of the device move towards the node of the standing waves caused by the effect of acoustic radiation pressure. A new device structure has been designed based on piezoelectric drive principle. The vibration modes and response has been obtained by FEA. The simulation results also indicate the feasibility of movements. Considering the influence of vibrator dimension, the dimension of the vibrator has been optimized. The experiment has been accomplished in the device with polystyrene spheres and achieves the enrichment of the particles.

Yuan, Song-Mei; Tang, Zhuang-Yun

166

Piezoelectric immunosensors -- Theory and applications  

SciTech Connect

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

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

1999-09-01

167

Multi-contrast photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

168

Saturation effect in functional photoacoustic imaging  

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

169

Lead Free Piezoelectric Materials  

Microsoft Academic Search

Lead oxide based ferroelectrics, represented by lead zirconate titanate (Pb(Zr, Ti)O3) or PZT) are the most widely used materials for piezoelectric actuators, sensors and transducers due to their excellent piezoelectric properties. Considering lead toxicity, there is interest in developing piezoelectric materials that are biocompatible and environmentally friendlier. The low density of non-lead based materials can also be an advantage in

M. Demartin Maeder; D. Damjanovic; N. Setter

2004-01-01

170

Numerical shape optimization of photoacoustic resonators  

Microsoft Academic Search

The sensitivity of photoacoustic sensors strongly depends on the shape of the acoustical resonator. Up to now, mainly photoacoustic\\u000a sensors consisting of a number of cylindrical parts have been investigated (cylinder cells, H cells, T cells etc.). In this\\u000a paper, a numerical shape optimization of the resonator cell of photoacoustic sensors is described. The approach considers\\u000a all shapes that can be represented by

B. Kost; B. Baumann; M. Germer; M. Wolff; M. Rosenkranz

2011-01-01

171

Photoacoustic determination of energy band gap of semiconductors  

Microsoft Academic Search

Semiconducting materials are employed in the fabrication of a number of semiconductor devices and opto-electronic detectors\\u000a etc depending on their properties, state of purity and perfection and energy band gap values. In the present study, a latest\\u000a and novel photoacoustic spectroscopic technique has been employed for the determination of energy band gap of some semiconductors\\u000a namely CdS, CdSe, CdTe, ZnS,

R S Ram; O M Prakash; A N Pandey

1987-01-01

172

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

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

173

Coulomb-damped resonant generators using piezoelectric transduction  

NASA Astrophysics Data System (ADS)

Switching interface circuits employed with piezoelectric energy harvesters can increase the electrical damping considerably over that achievable with passive rectifiers. We show that a piezoelectric harvester coupled to certain types of switching circuits becomes a Coulomb-damped resonant generator. This allows analysis of such harvester systems within a well-known framework and, subject to practical constraints, allows the optimal electrical damping to be achieved. In the piezoelectric pre-biasing technique, the Coulomb damping is set by a pre-bias voltage whose optimal value is derived as a function of piezoelectric harvester parameters.

Miller, L. M.; Mitcheson, P. D.; Halvorsen, E.; Wright, P. K.

2012-06-01

174

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

175

Photoacoustic signal amplification through plasmonic nanoparticle aggregation  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

176

Photoacoustic signal amplification through plasmonic nanoparticle aggregation.  

PubMed

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

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

2013-01-01

177

Surface cracking of a piezoelectric strip bonded to an elastic substrate (Mode I crack problem)  

Microsoft Academic Search

Summary A piezoelectric material layer bonded to an elastic substrate is investigated. The piezoelectric layer contains an edge crack that is perpendicular to the surface of medium. The poling axis of the piezoelectric layer is parallel to its edge. The elastic layer can be an ideal insulator or an ideal conductor. The Fourier transform technique is used to reduce the

B. L. Wang; Y. W. Mai; Y. G. Sun

2003-01-01

178

Application of Photoacoustic Effect to Chemical Kinetics in Solution.  

NASA Astrophysics Data System (ADS)

The application of the pulsed photoacoustic technique (PA) to the study of chemical kinetics in very dilute solutions is demonstrated with three different reactions: A bidental ligand substitution of 1,2-bi(diphenylphosphino) ethane on the five-coordinate cobalt dithiolene complex, a nucleophilic addition of tributyl phosphite to (p-(dimethylamino)triphenyl)methyl cation, and an enzyme catalyzed reduction of nicotinamide adenine dinucleotide by glucose-6-phosphate. Photoacoustic detection is shown to be 100 times more sensitive than spectrophotometric detection. As a consequence, it allows one to use lower reactant concentrations so that the time scale for the corresponding fast reactions can be lengthened. The pulsed PA technique also provides an alternative method for the direct determination of reverse rate constants and equilibrium constants of reactions. Moreover, Michaelis constants of biochemical reactions, especially for enzymes whose K_{rm m} values is below 1.0 muM, can be measured more accurately using photoacoustic detection than using spectrophotometric detection. Additionally, the pulsed PA method can be very valuable for the study of reactions that are restricted by the low solubility, availability, or high cost of reactants. The sensitivity of the PA method is found to be limited by the background signal resulting from solvents. Photoacoustic signals generated in strongly absorbing media are also studied and results are in agreement with the theory developed by G. J. Diebold. From the time profile of the acoustic signal, the absorption coefficient of strongly absorbing medium can be determined provided the sound speed is known. Since the pulse shape of the acoustic transient depends upon the relative density and the acoustic velocity of the transparent and the strongly absorbing media, the physical properties of the transparent medium can also be determined with the use of the PA technique.

Cheng, Huy-Zu.

179

3K-1 Integrated and Flexible Piezoelectric Ultrasonic Transducers  

Microsoft Academic Search

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

M. Kobayashi; C.-K. Jen

2006-01-01

180

I Situ Investigation of Linear Viscoelastic Media Using Piezoelectric Resonators  

Microsoft Academic Search

Our effort has been directed towards developing an in-situ technique, the piezoelectric quartz crystal microbalance (QCM), as a probe for viscoelastic fluid property investigation. Specifically, this effort was undertaken to study the effect of liquid elasticity on the response of liquid-contacted quartz crystal resonators. We have modelled the signal response of an externally damped piezoelectric resonator by two different but

Chukuemeka Obioma Nwankwo

1996-01-01

181

Fourier deconvolution of photoacoustic FTIR spectra  

NASA Astrophysics Data System (ADS)

Fourier self-deconvolution is a fairly routine numerical method for increasing the apparent resolution of spectra in which the intrinsic bandwidths are much greater than the instrumental resolution. The present work demonstrates that a photoacoustic (PA) interferogram obtained with a Fourier transform spectrometer can be used directly in this calculation, without the usual intermediate computation of a spectrum. Phase errors in the interferogram must be eliminated as a first step in this procedure. The technique has been applied to PA IR interferograms acquired for an Alberta coal and for kaolinite, a common layer silicate. Several new bands were identified in the coal spectrum and assigned utilizing previously published results for coal. Results for kaolinite illustrate a behaviour characteristic of deconvolution of single bands; in addition, an OH-stretching band usually not detectable in IR spectra of kaolinite was observed and verified by comparison with Raman data.

Friesen, W. I.; Michaelian, K. H.

1986-07-01

182

Piezoelectric Ultrasonic Motors  

Microsoft Academic Search

Piezoelectric ultrasonic motors are a new type of actuator. They are characterized by high torque at low rotational speed, simple mechanical design and good controllability. They also provide a high holding torque even if no power is applied. Compared to electromagnetic actuators the torque per volume ratio of piezoelectric ultrasonic motors can be higher by an order of magnitude. Recently

Jorg Wallaschek

1995-01-01

183

IPP: Piezoelectric Energy Harvesters  

NASA Video Gallery

Piezoelectric devices can convert mechanical energy -- like ambient vibrations -- into electrical energy that can power small devices.A group of NASA engineers is developing a way to amplify the forces being put into piezoelectric devices so we can harvest more energy from them.

Robert Allen

2010-12-15

184

Piezoelectric hydraulic pump performance  

Microsoft Academic Search

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

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

2001-01-01

185

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

NASA Astrophysics Data System (ADS)

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

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

186

Characterization of soils using photoacoustic mid-infrared spectroscopy.  

PubMed

This study investigates the use of photoacoustic spectroscopy (PAS) for rapid soil analysis. Photoacoustic spectroscopy requires very minimal sample preparation (air-drying), which is a major advantage compared to the more traditional transmittance technique, which requires time-consuming preparation of pellets. The amount of information contained in the PAS spectra appears to be similar to that contained in transmittance spectra, and the PAS spectra exhibit a large number of bands that can be associated with various soil constituents such as quartz, calcium carbonate, and various types of clay. Comparison with attenuated total reflection (ATR) spectra of saturated soil pastes shows that the PAS spectra provide much more information than the ATR spectra due to the strong water bands present in the latter. PAS quantitative analysis of clay, calcium carbonate, and organic matter is presented, with respective determination errors of approximately 12% clay, approximately 5% CaCO(3), and approximately 0.2% organic matter. PMID:17958956

Changwen, Du; Linker, Raphael; Shaviv, Avi

2007-10-01

187

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

PubMed

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. PMID:22867562

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

2012-07-20

188

Imaging of gene expression in vivo with photoacoustic tomography  

NASA Astrophysics Data System (ADS)

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.

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

2006-03-01

189

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

PubMed Central

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

2011-01-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

191

Photoacoustic spectrometer for ozone detection  

NASA Astrophysics Data System (ADS)

A high-resolution external laser photoacoustic spectrometer has been developed. The spectrometer was used to analyze the absorption transitions of the ozone in coincidence with the CO2 laser emission and to evaluate its limit of sensitivity. A CO2 laser and a photoacoustic resonant cell, totally built in project, formed the spectrometer. The CO2 laser operates in 80 CW transitions distributed in the regular bands with power of up to 15W, tuned by a diffraction grating. The cell has frequency resonance of longitudinal mode close to 1600 Hz. The cell is equipped with two small electret microphones and ZnSe windows in Brewster angle. The quality factor of the cell was measured about 30 through the ozone absorption in resonance with the 9P14 line of CO2 laser. The spectrometer sensitivity limit was preliminary evaluated for ozone detection around 100 ppb.

Telles, Edjar M.; Bezerra, Edson; Scalabrin, Artemio

2001-08-01

192

Photoacoustic Microscopy in Tissue Engineering  

PubMed Central

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

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

2013-01-01

193

Pattern Recognition in Photoacoustic Dataset  

NASA Astrophysics Data System (ADS)

In photoacoustic imaging, optical absorption properties of matter are imaged by detecting the ultrasound that is produced when the material is illuminated by a laser. For medical imaging, photoacoustics is a useful tool since matter in the human body has different optical absorption properties. In this study, pattern recognition systems are used to study a set of medical images for tumor identification and extraction—to detect the specific area in which the tumor is present. The objective is to incorporate this information into real-time image acquisition systems to improve medical diagnosis. Preliminary results obtained by studying the image dataset demonstrated the interchangeability of the proposed system. A system of automatic classification was constructed, using a set of images with and without cancerous tumors to evaluate the proposed method. The training set used was manually labeled, and the test set was never seen by the training set. The results helped us determine the feasibility of the proposed system.

Guzmán-Cabrera, R.; Guzmán-Sepúlveda, J. R.; Torres-Cisneros, M.; May-Arrioja, D. A.; Ruiz-Pinales, J.; Ibarra-Manzano, O. G.; Aviña-Cervantes, G.

2013-05-01

194

Dichroism optical-resolution photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

We have developed dichroism optical-resolution photoacoustic microscopy, capable of imaging polarization-dependent optical absorption (i.e., dichroism) with excellent specificity. This technical innovation enriches molecular photoacoustic contrasts and holds particular potential for detecting amyloid-associated neurodegenerative and cardiovascular diseases.

Hu, S.; Maslov, K.; Yan, Ping; Lee, Jin-Moo; Wang, L. V.

2012-02-01

195

A photoacoustic study of water infiltrated leaves  

Microsoft Academic Search

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

Shmuel Malkin; Marc Charland; Roger M. Leblanc

1992-01-01

196

Photoacoustic diffraction studies of planar tissue phantoms  

Microsoft Academic Search

Precise knowledge of the acoustic field in biological tissue after pulsed laser irradiation is necessary in order to perform medical imaging. Often, the photoacoustic pulse is delivered as a circular, stress confined laser spot incident upon a planar surface, such as skin. The resulting photoacoustic wave propagates in the tissue and may be detected by a detector or array of

Jason Komadina; John A. Viator; J. Stuart Nelson

2003-01-01

197

Gaseous trace analysis using pulsed photoacoustic Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The paper describes a method for the trace analysis of gases, based on the pulsed photoacoustic Raman spectroscopy (PARS) technique. It is reported that the method has been applied to the analysis of mixtures of CH4 in N2, CO2 in N2, and N2O in N2 at concentrations near 1 ppm. Attention is given to the apparatus used and means of improving the method's sensitivity as well as sensitivity-limiting processes are evaluated. Finally, the analytical capabilities of this technique are compared with both direct (IR) absorption and other Raman techniques such as CARS and stimulated Raman gain spectroscopy (SRGS).

Siebert, D. R.; West, G. A.; Barrett, J. J.

1980-01-01

198

Development and application of stable phantoms for the evaluation of photoacoustic imaging instruments.  

PubMed

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

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

2013-09-25

199

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

PubMed Central

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.

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

2010-01-01

200

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

PubMed Central

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

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

2013-01-01

201

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

202

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

NASA Astrophysics Data System (ADS)

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

Heaps, David A.; Pellegrino, Paul M.

2006-06-01

203

Photoacoustic Spectroscopy Analysis of Traditional Chinese Medicine  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

204

Photoacoustic Imaging with a Commercial Ultrasound System and a Custom Probe  

PubMed Central

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.

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

2010-01-01

205

Optical piezoelectric transducer for nano-ultrasonics.  

PubMed

Piezoelectric semiconductor strained layers can be treated as piezoelectric transducers to generate nanometer-wavelength and THz-frequency acoustic waves. The mechanism of nano-acoustic wave (NAW) generation in strained piezoelectric layers, induced by femtosecond optical pulses, can be modeled by a macroscopic elastic continuum theory. The optical absorption change of the strained layers modulated by NAW through quantum-confined Franz-Keldysh (QCFK) effects allows optical detection of the propagating NAW. Based on these piezoelectric-based optical principles, we have designed an optical piezoelectric transducer (OPT) to generate NAW. The optically generated NAW is then applied to one-dimensional (1-D) ultrasonic scan for thickness measurement, which is the first step toward multidimensional nano-ultrasonic imaging. By launching a NAW pulse and resolving the returned acoustic echo signal with femtosecond optical pulses, the thickness of the studied layer can be measured with <1 nm resolution. This nano-structured OPT technique will provide the key toward the realization of nano-ultrasonics, which is analogous to the typical ultrasonic techniques but in a nanometer scale. PMID:16245610

Lin, Kung-Hsuan; Chern, Gia-Wei; Yu, Cheng-Ta; Liu, Tzu-Ming; Pan, Chang-Chi; Chen, Guan-Ting; Chyi, Jen-Inn; Huang, Sheng-Wen; Li, Pai-Chi; Sun, Chi-Kuang

2005-08-01

206

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

207

Piezoelectricity of biopolymers.  

PubMed

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

Fukada, E

208

Quantum cascade laser based standoff photoacoustic detection of explosives using ultra-sensitive microphone and sound reflector  

NASA Astrophysics Data System (ADS)

We report standoff detection of explosives using quantum cascade laser (QCL) and photoacoustic technique. In our experiment, a QCL with emission wavelength near 7.35 ?m was used and operated at pulsed mode. The output light was focused on Trinitrotoluene (TNT) sample in its powder form. Photoacoustic signals were generated and detected by an ultra-sensitive low-noise microphone with one inch diameter. A detection distance up to 8 inches was obtained using the microphone alone. With the increasing detection distance the measured photoacoustic signal not only decayed in amplitude but also delayed in phase, which clearly verified the source location. To further increase the detection distance, a parabolic sound reflector was used for effective sound collection. With the help of the sound reflector, standoff photoacoustic detection of TNT with distance of 8 feet was demonstrated.

Chen, Xing; Guo, Dingkai; Choa, Fow-Sen; Wang, Chen-Chia; Trivedi, Sudhir; Fan, Jenyu

2013-01-01

209

Pulsed photoacoustic Doppler flowmetry using a cross correlation method  

NASA Astrophysics Data System (ADS)

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

Brunker, J.; Beard, P.

2010-02-01

210

Photoacoustic tomography of ex vivo mouse hearts with myocardial infarction  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

211

3D high resolution pure optical photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

212

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

213

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

NASA Astrophysics Data System (ADS)

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

Holthoff, Ellen L.; Pellegrino, Paul M.

2009-05-01

214

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

215

Piezoelectric Volumetric Array.  

National Technical Information Service (NTIS)

A three-dimensional array of acoustic sensors. The array can be used for both the transmission and reception of acoustic signals. The array comprises electroplated piezoelectric polymer layers that are laminated with a non- conductive epoxy to form indivi...

K. C. Benjamin

2002-01-01

216

Micro Piezoelectric Ultrasonic Motors.  

National Technical Information Service (NTIS)

This paper reviews recent developments of micro ultrasonic rotary motors using piezoelectric resonant vibrations. Following the historical background, four ultrasonic motors recently developed at Penn State University are introduced: windmill, PZT tube, m...

K. Uchino S. Cagatay B. Koc S. Dong P. Bouchilloux

2003-01-01

217

Piezoelectric transducers, state of research  

NASA Astrophysics Data System (ADS)

Methods for preparing, treating and sintering powders to be used in the production of ceramic elements (coprecipitation, isostatic compression, sintering under shock loading) are reviewed. Faults inherent in a piezoelectric ceramic element are outlined. Perovskite type compounds, analogous to PbTiO3, which are strongly anisotropic and have a very low k31 coupling factor; lead compounds which are strongly anisotropic and give strongly attenuated ceramic elements; PVDF type polymers; electrostrictive materials; composite materials; and polar glass materials and electrets are described. Techniques for metallizing elements to improve the adhesive power of the electrodes and contacts; and adhesives and glues used for manufacturing transducers and composites are considered.

Eyraud, L.; Eyraud, P.; Bauer, F.

1984-06-01

218

Molecular Modeling: An Approach for the Study of Piezoelectric Polymers.  

National Technical Information Service (NTIS)

This report describes the use of molecular modeling and computational chemistry techniques to investigate and tailor the piezoelectric properties of polyvinylidene fluoride (PVDF) and its copolymer with trifluoroethylene (PVDF-TrFE) for underwater hydroph...

G. J. Kavarnos

1994-01-01

219

Remote photoacoustic imaging on non-flat surfaces and appropriate reconstruction algorithms  

NASA Astrophysics Data System (ADS)

The recently introduced remote photoacoustic imaging technique allows measurement of photoacoustic signals on nonplanar surfaces without the need for a water bath or coupling agent. Hereby, photoacoustically generated ultrasonic displacements are detected without physical contact to the sample by utilizing laser interferometric techniques. In this work we adapted different algorithms to allow reconstruction on non-planar surfaces and evaluate them on experimental and simulated data. Experimental data were obtained using a remote photoacoustic setup based on two-wave mixing in a photorefractive crystal. Ultrasonic displacements were acquired on flat and non-flat surfaces. Three-dimensional reconstruction of simulated and real measurement data is shown with synthetic aperture focusing technique, Fourier domain synthetic aperture focusing technique, and spectral-domain time reversal algorithms. For the synthetic aperture focusing technique and the time reversal algorithm the surface morphology is taken into account. It is demonstrated that artifacts can occur if the surface is not considered. For the experimental data the shape of the surface is obtained from optical coherence tomography or by a priori knowledge.

Berer, T.; Hochreiner, A.; Roitner, H.; Grün, H.; Burgholzer, P.

2013-03-01

220

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

221

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

PubMed

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. PMID:12974585

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

2003-08-21

222

Monte Carlo modeling for photoacoustic-based transport-regime optical property estimation  

NASA Astrophysics Data System (ADS)

We developed a unique reflection-mode photoacoustic technique sensitive to optical scattering in turbid media. We focused a small laser spot on to the surface of a turbid medium and captured the photoacoustic signal by a focused ultrasound transducer. The amplitude of the photoacoustic signal for different surface illumination spot locations is an effective estimate of the Green's function of light transport in turbid media. Our results for different concentrations of Intralipid indicate that this method is capable of distinguishing small changes in the reduced scattering coefficient. In this work, we present experimental measurements for an Intralipid phantom with reduced scattering coefficients of 3, 4, and 5 cm-1, and show that Monte Carlo simulations of light transport accurately reproduce experimental curves. This means that we can estimate transport-regime optical properties of the media given a suitable fitting algorithm.

Ranasinghesagara, Janaka C.; Zemp, Roger J.

2010-02-01

223

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

224

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

PubMed Central

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

Yao, Lei; Jiang, Huabei

2011-01-01

225

Diode laser-based photoacoustic spectroscopy with interferometrically-enhanced cantilever detection.  

PubMed

A novel sensitive approach to detect weak pressure variations has been applied to tunable diode laser-based photoacoustic spectroscopy. The sensing device consists of a miniature silicon cantilever, the deflection of which is detected with a compact Michelson-type interferometer. The photoacoustic system has been applied to the detection of carbon dioxide (CO2) at 1572 nm with a distributed feedback diode laser. A noise equivalent sensitivity of 2.8 x 10-10 cm-1WHz-1/2 was demonstrated. Potential improvements of the technique are discussed. PMID:19495137

Laurila, Toni; Cattaneo, Heidi; Koskinen, Vesa; Kauppinen, Jyrki; Hernberg, Rolf

2005-04-01

226

Diode laser-based photoacoustic spectroscopy with interferometrically-enhanced cantilever detection  

NASA Astrophysics Data System (ADS)

A novel sensitive approach to detect weak pressure variations has been applied to tunable diode laser-based photoacoustic spectroscopy. The sensing device consists of a miniature silicon cantilever, the deflection of which is detected with a compact Michelson-type interferometer. The photoacoustic system has been applied to the detection of carbon dioxide (CO2) at 1572 nm with a distributed feedback diode laser. A noise equivalent sensitivity of 2.8 × 10­10 cm-1WHz-1/2 was demonstrated. Potential improvements of the technique are discussed.

Laurila, Toni; Cattaneo, Heidi; Koskinen, Vesa; Kauppinen, Jyrki; Hernberg, Rolf

2005-04-01

227

Nondestructive Evaluation of Weld Defect by Photoacoustic Microscopy and Its Destructive Inspection Using Replica  

NASA Astrophysics Data System (ADS)

The nondestructive evaluation (NDE) of a surface crack and an internal defect introduced in the welded region of an aluminum plate has been demonstrated by photoacoustic microscopy. The surface crack and internal defect are a blowhole and an incomplete fusion, which were formed in the weld metal during welding. Experiments were carried out at different modulation frequencies. Furthermore, to gather information on the internal defect, the measurement of the size and shape of the weld defect was carried out by the replica technique. A stereoscopic image of the replica specimen was compared with a photoacoustic (PA) amplitude image.

Kato, Ryosuke; Endoh, Haruo; Hoshimiya, Tsutomu

2011-07-01

228

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

PubMed Central

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

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

2010-01-01

229

Multiple-illumination photoacoustic tomography: reconstructing absorption, scattering, and Grüeneisen coefficient distributions  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging is a promising technique combining high ultrasonic resolution and high optical contrast. However, quantification has proved rather challenging. In this paper, we present a non-iterative reconstruction strategy with multiple-optical-sources for reconstruction of absorption, scattering perturbations as well as the spatially varying Grüeneisen parameter from a known turbid background. We term this method the multiple-illumination photoacoustic tomography (MI-PAT). While numerical challenges still exist, we demonstrated that the linearized MI-PAT framework we propose has orders of magnitude improved condition number compared with Continuous-Wave Diffuse Optical Tomography (CW-DOT).

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

2011-02-01

230

Photoacoustic analysis of bone osteogenesis to different doses of laser irradiation  

NASA Astrophysics Data System (ADS)

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.

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

2005-07-01

231

Integrated Photoacoustic and Fluorescence Confocal Microscopy  

PubMed Central

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.

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

2010-01-01

232

Developing photoacoustic ocular imaging system  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

233

Micromachined piezoelectric acoustic transducers  

NASA Astrophysics Data System (ADS)

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

Han, Cheol-Hyun

234

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

Microsoft Academic Search

Photoacoustic imaging technique, which provided high ultrasonic resolution and high optical contrast tissue images, can overcome the disadvantages of pure optical imaging by measurement of laser-induced sound waves. The waves produced by tissue are high-frequency ultrasounds, meaning that they cannot be heard by human ear. However, it can be picked up with ultrasonic transducer and analyze them with a computer.

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

2007-01-01

235

Fiber-amplifier-enhanced photoacoustic spectroscopy with near-infrared tunable diode lasers  

Microsoft Academic Search

A new approach to wavelength-modulation photoacoustic spectroscopy is reported, which incorporates diode lasers in the near infrared and optical fiber amplifiers to enhance sensitivity. We demonstrate the technique with ammonia detection, yielding a sensitivity limit less than 6 parts in 109, by interrogating a transition near 1532 nm with 500 mW of output power from the fiber amplifier, an optical

Michael E. Webber; Michael Pushkarsky; C. Kumar N. Patel

2003-01-01

236

Fiber-Amplifier-Enhanced Photoacoustic Spectroscopy with Near-Infrared Tunable Diode Lasers  

Microsoft Academic Search

A new approach to wavelength-modulation photoacoustic spectroscopy is reported, which incorporates diode lasers in the near infrared and optical fiber amplifiers to enhance sensitivity. We demonstrate the technique with ammonia detection, yielding a sensitivity limit less than 6 parts in 109, by interrogating a transition near 1532 nm with 500 mW of output power from the fiber amplifier, an optical

Michael E. Webber; Michael Pushkarsky; C. Kumar

2003-01-01

237

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

Microsoft Academic Search

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

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

2009-01-01

238

Optical fundamental band-gap energy of semiconductors by photoacoustic spectroscopy  

Microsoft Academic Search

The optical band-gap energy of the semiconductors GaAs, CdSe, Cds, ZnSe and Si doped with P at a concentration of 4 x 10~~cm-~, are obtained by photoacoustic spectroscopy technique. Excellent agreements are found with the values recorded in the literature.

J. Caetano de Souza; A. Ferreira da Silva; H. Vargas

1994-01-01

239

Photoacoustic infrared spectra (IR-PAS) of aged and fresh-cleaved coal surfaces  

Microsoft Academic Search

The application of the newly developed technique of photoacoustic infrared spectroscopy, using a Fourier transform infrared spectrometer, to the measurement of the infrared spectra of single slabs of various coal types is described. The effects of aging of coal surfaces, which include both oxidation and abrasion, are clearly apparent in a comparison of the spectra of freshly cleaved and aged

Mark G. Rockley; J. Paul Devlin

1980-01-01

240

Piezoelectric Ceramics and Their Applications  

ERIC Educational Resources Information Center

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

Flinn, I.

1975-01-01

241

CMOS-Compatible Piezoelectric Microphone.  

National Technical Information Service (NTIS)

Piezoelectric Microphone: advantageous over condenser microphone except sensitivity; Major Sensitivity-Limiting Factor in Piezoelectric Microphone: residual stress in the diaphragm; Modeled and demonstrated stress releasing effect of corrugations; Fabrica...

E. S. Kim

1999-01-01

242

Noise-equivalent sensitivity of photoacoustics.  

PubMed

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

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

2013-09-01

243

Adaptive optics photoacoustic spectroscopic imaging  

NASA Astrophysics Data System (ADS)

For decreasing wavefront error and obtaining higher resolution image of biological tissues, an adaptive optics photoacoustic spectroscopic imaging (AOPSI) system is proposed in this paper. In this system, an adaptive optics (AO) sub-system consisting of a Shack-Hartmann wavefront sensor (SHWS) and a liquid crystal on silicon (LCOS) is designed to correct the wavefront aberration of the illuminating light for getting high resolution image. The photoacoustic (PA) signals of AOPSI generated by irradiating the sample with a tunable optical parametric oscillator (OPO) lasers emitting light at 680-950 nm are received by a broadband ultrasound transducer. The received data are rearranged according to the wavelength sequences and decoded for image reconstruction. Moreover, the PA spectroscopy is used to obtain different wavelength PA images, with which one can accurately distinguish organization structures and identify organizational components, etc. The final simulation results demonstrated that when the wavefront errors were corrected by the AO system, the AOPSI images showed significant quality improvement which will be helpful to enhance the ability and application of PA imaging.

Jian, Xiaohua; Cui, Yaoyao; Xiang, Yongjia; Han, Zhile; Gu, Tianming; Lv, Tiejun

2013-01-01

244

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)

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.

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

245

Fracture mechanics of piezoelectric materials  

Microsoft Academic Search

This paper presents an analysis of crack problems in homogeneous piezoelectrics or on the interfaces between two dissimilar\\u000a piezoelectric materials based on the continuity of normal electric displacement and electric potential across the crack faces.\\u000a The explicit analytic solutions are obtained for a single crack in an infinite piezoelectric or on the interface of piezoelectric\\u000a bimaterials. For homogeneous materials it

T. C. Wang; X. L. Han

1999-01-01

246

Photopyroelectric versus photoacoustic characterization of photovoltaic cells  

Microsoft Academic Search

The use of photopyroelectric spectroscopy (PPS) to characterize photovoltaic cells is reported. Photopyroelectric and photoacoustic conversion efficiencies are presented as a function of load resistance for a 500 micron thick p-n solar cell at 18 Hz under about 5.2 mW He-Ne laser illumination. At 350 ohms, the photoacoustic-determined conversion efficiency is about 12 percent, whereas the photopyroelectric-determined optimal conversion efficiency

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

1986-01-01

247

New Piezoelectric Polymers  

NASA Astrophysics Data System (ADS)

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

Fukada, Eiichi

1998-05-01

248

High temperature piezoelectric drill  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

249

Nondestructive Evaluation of Structural Ceramics by Photoacoustic Microscopy.  

National Technical Information Service (NTIS)

A photoacoustic microscopy (PAM) digital imaging system was developed and utilized to characterize silicon nitride material at the various stages of the ceramic fabrication process. Correlation studies revealed that photoacoustic microscopy detected failu...

P. K. Khandelwal

1987-01-01

250

Phase reference materials for photoacoustic spectroscopy  

SciTech Connect

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

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

1999-06-01

251

Development of real-time photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

252

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

253

Piezoelectric actuation of helicopter rotor blades  

NASA Astrophysics Data System (ADS)

The work presented in this paper is concerned with the application of embedded piezo-electric actuators in model helicopter rotor blades. The paper outlines techniques to define the optimal location of actuators to excite particular modes of vibration whilst the blade is rotating. Using composite blades the distribution of strain energy is defined using a Finite Element model with imposed rotor-dynamic and aerodynamics loads. The loads are specified through strip theory to determine the position of maximum bending moment and thus the optimal location of the embedded actuators. The effectiveness of the technique is demonstrated on a 1/4 scale fixed cyclic pitch rotor head. Measurement of the blade displacement is achieved by using strain gauges. In addition a redundant piezo-electric actuator is used to measure the blades' response characteristics. The addition of piezo-electric devices in this application has been shown to exhibit adverse aeroelastic effects, such as counter mass balancing and increased drag. Methods to minimise these effects are suggested. The outcome of the paper is a method for defining the location and orientation of piezo-electric devices in rotor-dynamic applications.

Lieven, Nicholas A.

2001-07-01

254

Piezoelectric\\/electrostrictive multimaterial PMN-PT monomorph actuators  

Microsoft Academic Search

Fused deposition of multimaterials (FDMM), a CAD-based layered manufacturing technique, was utilized to fabricate monolithic piezoelectric\\/electrostrictive multimaterial monomorphs. The samples, comprised of piezoelectric 0.65Pb(Mg1\\/3Nb2\\/3)O3-0.35PbTiO3 and electrostrictive 0.90Pb(Mg1\\/3Nb2\\/3)O3-0.1PbTiO3, have been successfully prototyped and co-sintered. Bimorphs, that are isometric with the co-fired samples, have also been prepared by attaching individual piezoelectric and electrostrictive layers with conductive epoxy, and were used as a

A. Hall; M. Allahverdi; E. K. Akdogan; A. Safari

2005-01-01

255

Broadening the potential bandwidth of piezoelectric transducers by partial depolarization  

SciTech Connect

Elastic waves are used more and more in a nondestructive way to probe the physical properties of materials. The resolution of the images or the accuracy of the measurements is directly associated with the ultrasonic signal bandwidth and amplitude a system can generate or detect. The authors propose a technique to broaden the potential bandwidth of piezoelectric generators and sensors, which is based on utilizing a nonuniformly-polarized piezoelectric material. Both simulated and experimental responses are shown. They are in good agreement and exhibit a useful bandwidth over several natural harmonics of the piezoelectric transducer. {copyright} 2001 American Institute of Physics.

Hariti, Sid Ahmed; Hole, Stephane; Lewiner, Jacques

2001-06-18

256

Piezoelectric wave motor  

DOEpatents

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

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

2003-02-11

257

Piezoelectric wave motor  

DOEpatents

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

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

2001-07-17

258

Optical and piezoelectric biosensors  

SciTech Connect

One of the most significant applications of analytical chemistry involves its use in the determination of biologically important analytes. In recent years, considerable research in analytical biochemistry has centered on the development of small, portable, and (in some cases) disposable monitoring devices that are collectively referred to as biosensors. Biosensors are based on a number of different operating principles, including amperometric and potentiometric electrochemistry, fiber optics, and piezoelectricity or microacoustics. In this second of a two-part FOCUS, optical and piezoelectric sensors are discussed.

Borman, S.

1987-10-01

259

Development of a neonatal skull phantom for photoacoustic imaging  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

260

Induced piezoelectricity in isotropic biomaterial.  

PubMed Central

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

Zimmerman, R L

1976-01-01

261

Induced piezoelectricity in isotropic biomaterial.  

PubMed

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

Zimmerman, R L

1976-12-01

262

Characterization of human skin through photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

2005-06-01

263

Photoacoustics of individual live cells and particles  

NASA Astrophysics Data System (ADS)

The photoacoustic (PA) technique has been employed to a number of new biomedical applications based of highly sensitive detection of laser-induced acoustic waves from individual live cells and single absorbing micro-particles or clusters of nanoparticles. These applications involve both linear and non-linear thermoacoustic phenomena initiated by focused nanosecond single laser pulse and detected with a fast PZT-ceramic acoustic transducer. Particularly, we present the following experimental results: 1) monitoring of linear and non-linear PA responses from red blood cells in suspensions in vitro; 2) detection of PA responses from breast cancer cell targeted with gold nanoparticles; 3) PA study of linear and non-linear interaction of laser with colored polystyrene micro-particles as model single absorbers; 4) monitoring of PA responses from moving absorbers in flow in vitro (PA flow cytometry in vitro); 5) recording of PA responses from blood flow in vivo on rat mesentery as animal model (PA flow cytometery in vivo); and 6) monitoring of sedimentation kinetics of particles and cells. The obtained results demonstrate the high sensitivity, low background, simple detection principle, easy data acquisition, and straightforward interpretation of the PA data.

Kudryashov, Sergey I.; Allen, Susan D.; Galanzha, Ekaterina I.; Galitovskaya, E.; Zharov, Vladimir P.

2006-03-01

264

Finite element analysis of piezoelectric underwater transducers for acoustic characteristics  

Microsoft Academic Search

This paper presents a simulation technique for analyzing acoustic characteristics of piezoelectric underwater transducers.\\u000a A finite element method is adopted for modeling piezoelectric coupled problems including material damping and fluid-structure\\u000a interaction problems by taking system matrices in complex form. For the finite element modeling of unbounded acoustic fluid,\\u000a infinite wave envelope element (IWEE) is adopted to take into account the

Jaehwan Kim; Heung Soo Kim

2009-01-01

265

Off-axis photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

Photoacoustic microscopy (PAM) is a high-contrast, high-resolution imaging modality used primarily for imaging hemoglobin and melanin. Important applications include mapping of the microvasculature and melanoma tumor margins. We have developed a novel photoacoustic microscope design, which substantially simplifies construction by enabling the use of unmodified commercial optics and ultrasonic transducers. Moreover, the simple design may be readily incorporated into a standard light microscope, thus providing a familiar imaging platform for clinical researchers. A proof-of-concept Off-Axis PAM system with a lateral resolution of 26 ?m and a modest axial resolution of 410 ?m has been assembled and characterized using tissue samples. We have derived the appropriate equations to describe the relevant design parameters and verified the equations via measurements made on our prototype Off-Axis PAM system. A consequence of the simple design is a reduction in axial resolution compared to coaxial designs. The reduction is inversely proportional to the cosine of the angle between excitation and detection and equal to 15% and 41% for angles of 30° and 45°, respectively. While resolution is negatively affected by off-axis detection, the ability to measure weak signals at depth is enhanced. Off-axis detection has an inherent dark-field quality; chromophores excited outside the numerical aperture of the ultrasonic detector will not be detected. The physical geometry of Off-Axis PAM enables the placement of the ultrasonic transducer at the minimum distance from the sample with no obstructions between the sample and transducer. This may prove to be an additional advantage of Off-Axis PAM over designs that incorporate long working distance ultrasonic transducers and/or require the propagation of the acoustic wave through the laser excitation optics to achieve co-axial detection.

Shelton, Ryan; Applegate, Brian E.

2010-02-01

266

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

Microsoft Academic Search

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

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

2005-01-01

267

Piezoelectric direct drive servovalve  

NASA Astrophysics Data System (ADS)

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

Lindler, Jason E.; Anderson, Eric H.

2002-07-01

268

Piezoelectric deicing device  

Microsoft Academic Search

A fast voltage pulse is applied to a transducer which comprises a composite of multiple layers of alternately polarized piezoelectric material. These layers are bonded together and positioned over the curved leading edge of an aircraft wing structure. Each layer is relatively thin and metallized on both sides. The strain produced in the transducer causes the composite to push forward

R. C. Finke; B. A. Banks

1985-01-01

269

Piezoelectric ultrasonic motors: overview  

Microsoft Academic Search

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

Kenji Uchino

1998-01-01

270

Compact piezoelectric ultrasonic motors  

Microsoft Academic Search

This paper reviews recent developments of compact ultrasonic motors using piezoelectric resonant vibrations. Following the historical background, ultrasonic motors using the standing and traveling waves are introduced. Driving principles and motor characteristics are explained in comparison with the conventional electromagnetic motors.

Kenji Uchino; Burhanettin Koc

1999-01-01

271

Boundary conditions for axisymmetric piezoelectric cylinder  

NASA Astrophysics Data System (ADS)

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

Zhao, Baosheng; Wu, Di; Chen, Xi

2013-09-01

272

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

273

Integrated photoacoustic ophthalmoscopy and spectral-domain optical coherence tomography.  

PubMed

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 photography, confocal scanning laser ophthalmoscopy (cSLO), and optical coherence tomography (OCT), 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 sensitivity. 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. More importantly, based on the well-developed spectroscopic photoacoustic imaging, 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 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 contrasts. 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

Song, Wei; Wei, Qing; Jiao, Shuliang; Zhang, Hao F

2013-01-15

274

Piezoelectric actuation of a compliant semi-infinite beam  

NASA Astrophysics Data System (ADS)

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

Austin, Eric M.; Ananthasayanam, Balajee

2004-07-01

275

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

Microsoft Academic Search

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

Yogesh K. Ramadass; Anantha P. Chandrakasan

2010-01-01

276

Depth profile study of large-sized coal samples by Fourier transform infrared photoacoustic spectroscopy  

Microsoft Academic Search

A multidisciplinary approach is demonstrated to elucidate coal weathering at a molecular level. Fourier Transform Infrared Photoacoustic Spectroscopy (FT-IR\\/PAS) provides a technique for a compositional depth profile of coal by simply varying the modulation frequency (mirror velocity) of the light impinging upon the solid surface. In order that the potential of this technique in this field could be evaluated, large-sized

Tiziana Zerlia

1986-01-01

277

Photoacoustic and thermoacoustic imaging application in cancer early detection and treatment monitoring  

NASA Astrophysics Data System (ADS)

Laser-based photoacoustic imaging and microwave-based thermoacoustic imaging, combining the advantages of both the high image contrast that results from electromagnetic absorption and the high resolution of ultrasound imaging, could be the next successful generation imaging techniques in biomedical application. It can provide an effective approach of tissue structure and functional images to study the architectures, physiological and pathological properties and metabolisms of biological tissues. This paper is focused on photoacoustic and thermoacoustic imaging application in cancer early detection and treatment monitoring. A unique photoacoustic imaging system was used to detect tumors neovascularization associated with angiogenesis in a rat animal model. We also developed the imaging system to monitor the vascular damage during photodynamic therapy treatment. This method could be potentially used to guide PDT and other phototherapies using vascular changes during treatment to optimize treatment protocols, by choosing appropriate types and doses of photosensitizers, and doses of light. Potentially development of photoacoustic imaging and thermoacoustic imaging to employing in functional and molecular imaging also has been discussed. Especially, these imaging modalities can be further developed by using the contrast agents which modified with tumor-targeting antibodies to realize cancer early detection and cancer target treatment monitoring.

Xing, Da; Xiang, Liangzhong

2007-10-01

278

Photoacoustic detection of CO2 based on LABVIEW at 10.303 ?m  

NASA Astrophysics Data System (ADS)

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).

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

2011-04-01

279

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

280

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

PubMed

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 CO(2) concentration was measured with the non-resonant photoacoustic cell technique through measuring the photoacoustic signal caused by the CO(2). 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 CO(2) conducted at 100 Hz demonstrated large signals (15.89 mV) for CO(2) concentrations at 600 ppm and high signal-to-noise values (?85:1). PMID:21529032

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

2011-04-01

281

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

PubMed

In this report, we present a breast imaging technique combining high-resolution near-infrared (NIR) light induced photoacoustic tomography (PAT) with NIR dye-labeled amino-terminal fragments of urokinase plasminogen activator receptor (uPAR) targeted magnetic iron oxide nanoparticles (NIR830-ATF-IONP) for breast cancer imaging using an orthotopic mouse mammary tumor model. We show that accumulation of the targeted nanoparticles in the tumor led to photoacoustic contrast enhancement due to the high absorption of iron oxide nanoparticles (IONP). NIR fluorescence images were used to validate specific delivery of NIR830-ATF-IONP to mouse mammary tumors. We found that systemic delivery of the targeted IONP produced 4- and 10-fold enhancement in photoacoustic signals in the tumor, compared to the tumor of the mice that received non-targeted IONP or control mice. The use of targeted nanoparticles allowed imaging of tumors located as deep as 3.1 cm beneath the normal tissues. Our study indicates the potential of the combination of photoacoustic tomography and receptor-targeted NIR830-ATF-IONP as a clinical tool that can provide improved specificity and sensitivity for breast cancer detection. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim). PMID:23125139

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

2012-11-01

282

Method of Fabricating a Piezoelectric Composite Apparatus.  

National Technical Information Service (NTIS)

A method for fabricating a piezoelectric macro-fiber composite actuator comprises providing a piezoelectric material that has two sides and attaching one side upon an adhesive backing sheet. The method further comprises slicing the piezoelectric material ...

A. Jalink B. D. Little J. W. High P. H. Mirick R. Bryant R. F. Hellbaum R. L. Fox W. K. Wilkie

2003-01-01

283

Multilayer piezoelectric devices based on PZT  

Microsoft Academic Search

A PZT 53\\/47 was obtained by a modified chemical route. Small-particle-size powders were allowed to obtain high solid content, non-aqueous slips with Newtonian behaviour. The use of both the tape-casting technique and the common multilayer ceramic fabrication process led to a high-density multilayer ceramic body without cracks or delaminations, and a homogeneous microstructure. The architecture of multilayer piezoelectrics has an

E. Nieto; J. F. Fernandez; C. Moure; P. Duran

1996-01-01

284

Quantitative Photoacoustic Spectroscopy in the Frequency Domain  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

285

Intravascular photoacoustic imaging of human coronary atherosclerosis  

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

286

Parallel acoustic delay lines for photoacoustic tomography  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

287

Parallel acoustic delay lines for photoacoustic tomography  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

288

Piezoelectric step-motion actuator  

SciTech Connect

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

Mentesana; Charles P. (Leawood, KS)

2006-10-10

289

Continuous Poling Technique for PZT Fibers.  

National Technical Information Service (NTIS)

A continuous electrically poling technique for piezoelectric materials is described wherein the piezoelectric elements or rods are gradually advanced through a region of electric field with two metallic plates with flexible contacts used as electrodes. (A...

T. R. Guraraja L. E. Cross R. E. Newnham L. J. Bowen

1982-01-01

290

Photoacoustic array imaging of calcifications: phantom study  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

291

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

NASA Astrophysics Data System (ADS)

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.

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

2009-02-01

292

Intravascular photoacoustic imaging of human coronary atherosclerosis.  

PubMed

We demonstrate intravascular photoacoustic imaging of human coronary atherosclerotic plaque. The data was obtained from two fresh human coronary arteries ex vivo, showing different stages of disease. A 1.25?mm diameter intravascular imaging catheter was built, comprising an angle-polished optical fiber adjacent to a 30?MHz ultrasound transducer. Specific photoacoustic imaging of lipid content, a key factor in vulnerable plaques that may lead to myocardial infarction, is achieved by spectroscopic imaging at different wavelengths between 1180 and 1230?nm. Simultaneous imaging with intravascular ultrasound was performed. PMID:21368919

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

2011-03-01

293

Raman spectroscopy of piezoelectrics  

NASA Astrophysics Data System (ADS)

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

Pezzotti, Giuseppe

2013-06-01

294

Piezoelectric deicing device  

NASA Astrophysics Data System (ADS)

A fast voltage pulse is applied to a transducer which comprises a composite of multiple layers of alternately polarized piezoelectric material. These layers are bonded together and positioned over the curved leading edge of an aircraft wing structure. Each layer is relatively thin and metallized on both sides. The strain produced in the transducer causes the composite to push forward resulting in detachment and breakup of ice on the leading edge of the aircraft wing.

Finke, R. C.; Banks, B. A.

1985-10-01

295

Multi-source quantitative photoacoustic tomography in a diffusive regime  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography (PAT) is a novel hybrid medical imaging technique that aims to combine the large contrast of optical coefficients with the high-resolution capabilities of ultrasound. We assume that the first step of PAT, namely the reconstruction of a map of absorbed radiation from ultrasound boundary measurement, has been done. We focus on quantitative photoacoustic tomography, which aims at quantitatively reconstructing the optical coefficients from knowledge of the absorbed radiation map. We present a non-iterative procedure to reconstruct such optical coefficients, namely the diffusion and absorption coefficients, and the Grüneisen coefficient when the propagation of radiation is modeled by a second-order elliptic equation. We show that PAT measurements allow us to uniquely reconstruct only two out of the above three coefficients, even when data are collected using an arbitrary number of radiation illuminations. We present uniqueness and stability results for the reconstructions of two such parameters and demonstrate the accuracy of the reconstruction algorithm with numerical reconstructions from two-dimensional synthetic data.

Bal, Guillaume; Ren, Kui

2011-07-01

296

Multimaterial piezoelectric fibres.  

PubMed

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

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

2010-07-11

297

Multimaterial piezoelectric fibres  

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

298

Photoacoustic generation using coded excitation  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) imaging has been used to image soft tissue due to its high contrast and high spatial resolution. The generation of PA signal is based on the object's absorption characteristic to the emitted electromagnetic energy. Typically, a Q-switched Nd:YAG laser providing mJ pulse energy is suitable for biomedical PA applications. However, such laser is relatively bulky and expensive. An alternative way is to use a diode laser. A diode laser can generate laser pulse at much higher pulse repetition frequency (PRF). However, the output power of the diode laser is too low for effective PA generation. One method to overcome this problem is to increase the transmission energy using coded excitation. The coded laser signals can be transmitted by a diode laser with high PRF and the signal intensity of the received signal can be enhanced using pulse compression. In this study, we proposed a chirp coded excitation algorithm for a diode laser. Compared to Golay coded excitation seen in the literature, the proposed chirp coded excitation requires only a single transmission. Chirp-coded PA signal was generated by tuning the pulse duration of individual laser pulses in time domain. Result shows that the PA signal intensity can be enhanced after matched filtering. However, high range side-lobes are still present. The compression filter is an important tool to reduce the range side-lobes, which is subject to further investigation.

Su, Shin-Yuan; Li, Pai-Chi

2011-02-01

299

Fundus camera guided photoacoustic ophthalmoscopy.  

PubMed

Abstract 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

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

2013-07-25

300

Measuring non-radiative relaxation time of fluorophores with biomedical applications by intensity-modulated laser-induced photoacoustic effect  

PubMed Central

Modulated tone-burst light was employed to measure non-radiative relaxation time of fluorophores with biomedical importance through photoacoustic effect. Non-radiative relaxation time was estimated through the frequency dependence of photoacoustic signal amplitude. Experiments were performed on solutions of new indocyanine green (IR-820), which is a near infrared dye and has biomedical applications, in two different solvents (water and dimethyl sulfoxide (DMSO)). A 1.5 times slower non-radiative relaxation for the solution of dye in DMSO was observed comparing with the aqueous solution. This result agrees well with general finding that non-radiative relaxation of molecules in triplet state depends on viscosity of solvents in which they are dissolved. Measurements of the non-radiative relaxation time can be used as a new source of contrast mechanism in photoacoustic imaging technique. The proposed method has potential applications such as imaging tissue oxygenation and mapping of other chemophysical differences in microenvironment of exogenous biomarkers.

Soroushian, Behrouz; Yang, Xinmai

2011-01-01

301

Photoacoustic sonar: principles of operation, imaging, and signal-to-noise analysis in time and frequency domains  

NASA Astrophysics Data System (ADS)

A photoacoustic (PA) imaging methodology utilizing coded optical excitation and correlation signal processing has been described. The basic principles of using relatively long coded waveforms and a matched filter signal compression to increase signal-to-noise ratio (SNR) and axial resolution are common in conventional radar and sonar systems. To emphasize these similarities, the proposed technique is called the photoacoustic sonar (or radar). We describe the implementation of the PA sonar using a near-IR intensity modulated continuous wave laser source and frequency-domain correlation processing of the acoustic response. Application of the PA sonar for imaging of biological materials with discrete chromophores was studied using tissue mimicking phantoms. The SNR gain achieved with linear chirps is analyzed and compared with conventional time-domain photoacoustics.

Telenkov, Sergey; Mandelis, Andreas

2011-02-01

302

A high frame rate photoacoustic imaging system and its applications to perfusion measurements  

NASA Astrophysics Data System (ADS)

A high frame rate photoacoustic imaging system is described. Applications of this system to perfusion measurements are also presented as a demonstration of its potential usage. The system consists of an ultrasound front-end sub-system for acquisition of acoustic array data. The ultrasound front-end sub-system is also known as the DiPhAS (digital phased array system) which is capable of simultaneously acquiring radio frequency data from 64 transducer channels at a rate up to 40 MSamples/sec per channel. In this study, an ultrasonic linear array with a 5 MHz center frequency was employed as part of the integrated photoacoustic probe. The photoacoustic probe also had two linear light guides mounted on the sides of the ultrasonic array for broad laser irradiation from a Q-switched Nd:YAG pulsed laser. After the acquired ultrasound array data were transferred to a personal computer via a high speed digital I/Q card, dynamic focusing and image reconstruction were done off-line. The 64-channel array data can be acquired and transferred every 4 milliseconds, thus making the frame rate of the system up to 250 Hz. The actual frame rate of the current system is limited by the pulse repetition frequency of the laser at 15 Hz. To demonstrate capabilities of the system, photoacoustic perfusion measurements with gold nanorods were performed. A previously proposed time-intensity based flow estimation technique utilizing the shape transitions of gold nanorods under laser irradiation was employed. Good estimation results were achieved and potential of this high frame rate photoacoustic imaging system is clearly demonstrated.

Liao, Chao-Kang; Huang, Sheng-Wen; Wei, Chen-Wei; Li, Pai-Chi

2006-03-01

303

Photoacoustic imaging of prostate brachytherapy seeds  

PubMed Central

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

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

2011-01-01

304

Piezoelectric dispenser based on a piezoelectric-metal-cavity actuator  

NASA Astrophysics Data System (ADS)

A piezoelectric dispenser has been fabricated based on the idea of a piezoelectric-metal-cavity (PMC) actuator. The PMC actuator consists of a metal ring sandwiched between two identical piezoelectric unimorphs. The radial contraction of the piezoelectric ceramic is converted into a flextensional motion of the unimorph, causing a large flexural displacement in the center part of the actuator. With the PMC actuator as a fluid chamber, the large flexural actuation can be used to produce the displacement needed to eject fluid. By applying an appropriate voltage to the piezoelectric unimorphs, a drop-on-demand ejection of ink or water can be achieved. The efficiency of fluid ejection can be enhanced after installing a valve in the fluid chamber. With the simple PMC structure, the dispenser can be operated with a low driving voltage of 12-15 V.

Lam, K. H.; Sun, C. L.; Kwok, K. W.; Chan, H. L. W.

2009-07-01

305

Photoacoustic imaging using an adaptive interferometer with a photorefractive crystal.  

PubMed

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

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

2012-02-21

306

A cost-efficient frequency-domain photoacoustic imaging system  

NASA Astrophysics Data System (ADS)

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

LeBoulluec, Peter; Liu, Hanli; Yuan, Baohong

2013-09-01

307

Piezoelectrically actuated flextensional micromachined ultrasound droplet ejectors.  

PubMed

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

Perçin, Gökhan; Khuri-Yakub, Butrus T

2002-06-01

308

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

Microsoft Academic Search

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

BIAO WANG

309

Piezoelectric MEMS energy harvesting systems driven by harmonic and random vibrations  

Microsoft Academic Search

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

Lars-Cyril Blystad; Einar Halvorsen; Svein Husa

2010-01-01

310

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

NASA Astrophysics Data System (ADS)

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

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

1994-08-01

311

Imagining the Future of Photoacoustic Mammography  

Microsoft Academic Search

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 devel- opment of photoacoustic mammography, which is intended for the non-invasive detection of breast cancer. Imagination in this context already informs the

Simone van der Burg

2009-01-01

312

Quantitative photoacoustic spectroscopy of cataractous human lenses.  

PubMed

Quantitative photoacoustic spectra of the nuclei of cataractous human lenses with various degrees of colouration and opacification were measured in the spectral range 250-600 nm. The lens nuclei were obtained from 20 cataractous patients through extracapsular cataract extraction. These measurements yield the light loss per unit path length in the nucleus of cataractous lenses. PMID:2111385

Bernini, U; Reccia, R; Russo, P; Scala, A

1990-03-01

313

Improving photoacoustic imaging contrast of brachytherapy seeds  

NASA Astrophysics Data System (ADS)

Prostate brachytherapy is a form of radiotherapy for treating prostate cancer where the radiation sources are seeds inserted into the prostate. Accurate localization of seeds during prostate brachytherapy is essential to the success of intraoperative treatment planning. The current standard modality used in intraoperative seeds localization is transrectal ultrasound. Transrectal ultrasound, however, suffers in image quality due to several factors such speckle, shadowing, and off-axis seed orientation. Photoacoustic imaging, based on the photoacoustic phenomenon, is an emerging imaging modality. The contrast generating mechanism in photoacoustic imaging is optical absorption that is fundamentally different from conventional B-mode ultrasound which depicts changes in acoustic impedance. A photoacoustic imaging system is developed using a commercial ultrasound system. To improve imaging contrast and depth penetration, absorption enhancing coating is applied to the seeds. In comparison to bare seeds, approximately 18.5 dB increase in signal-to-noise ratio as well as a doubling of imaging depth are achieved. Our results demonstrate that the coating of the seeds can further improve the discernibility of the seeds.

Pan, Leo; Baghani, Ali; Rohling, Robert; Abolmaesumi, Purang; Salcudean, Septimiu; Tang, Shuo

2013-03-01

314

Photoacoustic FTIR spectroscopic study of undisturbed human cortical bone  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

315

Photoacoustic FTIR spectroscopic study of undisturbed human cortical bone.  

PubMed

Chemical pretreatment has been the prevailing sample preparation procedure for infrared (IR) spectroscopic studies on bone. However, experiments have indicated that chemical pretreatment can potentially affect the interactions between the components. Typically the IR techniques have involved transmission experiments. Here we report experimental studies using photoacoustic Fourier transform infrared spectroscopy (PA-FTIR). As a nondestructive technique, PA-FTIR can detect absorbance spectrum from a sample at controllable sampling depth and with little or no sample preparation. Additionally, the coupling inert gas, helium, which is utilized in the PA-FTIR system, can inhibit bacteria growth of bone by displacing oxygen. Therefore, we used this technique to study the undisturbed human cortical bone. It is found that photoacoustic mode (linear-scan, LS-PA-FTIR) can obtain basically similar spectra of bone as compared to the traditional transmission mode, but it seems more sensitive to amide III and ?(2) carbonate bands. The ?(3) phosphate band is indicative of detailed mineral structure and symmetry of native bone. The PA-FTIR depth profiling experiments on human cortical bone also indicate the influence of water on OH band and the cutting effects on amide I and mineral bands. Our results indicate that phosphate ion geometry appears less symmetric in its undisturbed state as detected by the PA-FTIR as compared to higher symmetry observed using transmission techniques on disturbed samples. Moreover, the PA-FTIR spectra indicate a band at 1747 cm(-1) possibly resulting from CO stretching of lipids, cholesterol esters, and triglycerides from the arteries. Comparison of the spectra in transverse and longitudinal cross-sections demonstrates that, the surface area of the longitudinal section bone appears to have more organic matrix exposed and with higher mineral stoichiometry. PMID:23257327

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

2012-11-23

316

Piezoelectric Vibration Energy Harvesting Device.  

National Technical Information Service (NTIS)

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

K. Andic K. K. Deng

2005-01-01

317

Optical piezoelectric transducer based nanoultrasonics  

Microsoft Academic Search

In this work, we review our recent development on nanoultrasonics based on an optical piezoelectric transducer. By embedding strain patterns in piezoelectric nano-layers and by manipulating optical field intensity in temporal and spatial domains, THz nanoacoustic waves with an acoustic wavelength on the order of or shorter than 10 nm can be generated with a nanometer-scaled lateral spot size, much

Chi-Kuang Sun; Kung-Hsuan Lin; Yu-Chieh Wen; Tzu-Ming Liu; Pai-Chi Li; Jen-Inn Chyi

2007-01-01

318

V-Stack piezoelectric actuator  

Microsoft Academic Search

Aeroelastic control of wings by means of a distributed, trailing-edge control surface is of interest with regards to maneuvers, gust alleviation, and flutter suppression. The use of high energy density, piezoelectric materials as motors provides an appealing solution to this problem. A comparative analysis of the state of the art actuators is currently being conducted. A new piezoelectric actuator design

Emil V. Ardelean; Robert L. Clark

2001-01-01

319

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

NASA Astrophysics Data System (ADS)

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

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

1998-06-01

320

Noncontact photoacoustic imaging achieved by using a low-coherence interferometer as the acoustic detector.  

PubMed

We report on a noncontact photoacoustic imaging (PAI) technique in which a low-coherence interferometer [(LCI), optical coherence tomography (OCT) hardware] is utilized as the acoustic detector. A synchronization approach is used to lock the LCI system at its highly sensitive region for photoacoustic detection. The technique is experimentally verified by the imaging of a scattering phantom embedded with hairs and the blood vessels within a mouse ear in vitro. The system's axial and lateral resolutions are evaluated at 60 and 30??m, respectively. The experimental results indicate that PAI in a noncontact detection mode is possible with high resolution and high bandwidth. The proposed approach lends itself to a natural integration of PAI with OCT, rather than a combination of two separate and independent systems. PMID:22002357

Wang, Yi; Li, Chunhui; Wang, Ruikang K

2011-10-15

321

Ultrasharp nonlinear photothermal and photoacoustic resonances and holes beyond the spectral limit  

NASA Astrophysics Data System (ADS)

High-resolution nonlinear laser spectroscopy based on absorption saturation, Lamb-dip and spectral hole-burning phenomena has contributed much to basic and applied photonics. Here, a laser spectroscopy based on nonlinear nanobubble-related photothermal and photoacoustic phenomena is presented. It shows ultrasharp resonances and dips up to a few nanometres wide in broad plasmonic spectra of nanoparticles. It also demonstrates narrowing of absorption spectra of dyes and cellular chromophores, as well as an increase in the sensitivity and resolution of the spectral hole-burning technique. This approach can permits the study of nonlinear plasmonics at a level of resolution beyond the spectral limits, the identification of weakly absorbing spectral holes, spectral optimization of photothermal nanotherapy, measurements of tiny red and blue resonance shifts in nanoplasmonic sensors, the use of negative contrast in photoacoustic technique, multispectral imaging and multicolour cytometry.

Zharov, Vladimir P.

2011-02-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

323

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

324

Practical implementation of piezoelectric energy harvesting synchronized switching schemes  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

325

Photoacoustic spectral characterization of perfluorocarbon droplets  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

326

X-ray diffraction, Raman, and photoacoustic studies of ZnTe nanocrystals  

Microsoft Academic Search

Nanocrystalline ZnTe was prepared by mechanical alloying. X-ray diffraction (XRD), energy dispersive spectroscopy, Raman spectroscopy, and photoacoustic absorption spectroscopy techniques were used to study the structural, chemical, optical, and thermal properties of the as-milled powder. An annealing of the mechanical alloyed sample at 590 °C for 6 h was done to investigate the optical properties in a defect-free sample (close

K. Ersching; C. E. M. Campos; J. C. de Lima; T. A. Grandi; S. M. Souza; D. L. da Silva; P. S. Pizani

2009-01-01

327

On-line monitoring of biogenic isoprene emissions using photoacoustic spectroscopy  

Microsoft Academic Search

.   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

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

2000-01-01

328

Photoacoustic tomography and molecular fluorescence imaging: dual modality imaging of small animal brains in vivo  

Microsoft Academic Search

We present a dual modality imaging technique by combining photoacoustic tomography (PAT) and near-infrared (NIR) fluorescence imaging for the study of animal model tumors. PAT provides high-resolution structural images of tumor angiogenesis, and fluorescence imaging offers high sensitivity to molecular probes for tumor detection. Coregistration of the PAT and fluorescence images was performed on nude mice with M21 human melanoma

Xueyi Xie; Jung-Taek Oh; Meng-Lin Li; Geng Ku; Xueding Wang; Shi Ke; Chun Li; Sergiu Similache; George Stoica; Lihong V. Wang

2005-01-01

329

Undersurface photoacoustic imaging of plane solid specimens by the use of a line laser beam  

Microsoft Academic Search

A line laser beam focused on a solid plane specimen was used to image undersurface defect by photoacoustic microscope (PAM). A CT (computed tomography) technique was applied to the imaging of a line-shape undersurface defect fabricated at the welded region of two steel plates by drilling. The diameter of welded region is about 8mm and the steel thickness is 1.5mm

Tsutomu Hoshimiya; Manabu Suzuki

2005-01-01

330

Time-Resolved Photoacoustic Calorimetry: Probing the Energetics and Dynamics of Fast Chemical and Biochemical Reactions  

NASA Astrophysics Data System (ADS)

Time-resolved photoacoustic calorimetry is a new experimental technique that measures the dynamics of enthalpy changes on the time scale of nanoseconds to microseconds for reactions initiated by absorption of light. When the reaction is carried out in water, it is also possible to obtain the dynamics of the corresponding volume changes. This method has been applied to a variety of biochemical, organic, and organometallic reactions.

Peters, Kevin S.; Snyder, Gary J.

1988-08-01

331

Ultrasonic Linear Motor Using Multilayer Piezoelectric Actuators  

Microsoft Academic Search

In order to lower operating voltage and improve the lifetime of an ultrasonic linear motor, we have developed an ultrasonic oscillator with multilayer piezoelectric actuators. Multilayer piezoelectric actuators are operable at low voltage. However, the tensile strength of the multilayer piezoelectric actuator is small. Therefore, the multilayer piezoelectric actuators are build within an elastic body to lower the tensile stress

Tomoki Funakubo; Toshiharu Tsubata; Yoshihisa Taniguchi; Kazuhiro Kumei; Takanao Fujimura; Chikara Abe

1995-01-01

332

Multifunctional microbubbles and nanobubbles for photoacoustic and ultrasound imaging.  

PubMed

We develop a novel dual-modal contrast agent-encapsulated-ink poly(lactic-co-glycolic acid) (PLGA) microbubbles and nanobubbles-for photoacoustic and ultrasound imaging. Soft gelatin phantoms with embedded tumor simulators of encapsulated-ink PLGA microbubbles and nanobubbles in various concentrations are clearly shown in both photoacoustic and ultrasound images. In addition, using photoacoustic imaging, we successfully image the samples positioned below 1.8-cm-thick chicken breast tissues. Potentially, simultaneous photoacoustic and ultrasound imaging enhanced by encapsulated-dye PLGA microbubbles or nanobubbles can be a valuable tool for intraoperative assessment of tumor boundaries and therapeutic margins. PMID:20210423

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

333

Piezoelectric Volumetric Array  

NASA Astrophysics Data System (ADS)

A three-dimensional array of acoustic sensors. The array can be used for both the transmission and reception of acoustic signals. The array comprises electroplated piezoelectric polymer layers that are laminated with a non-conductive epoxy to form individual multi-layer array transducer elements. Circuit support layer layers are incorporated between the multi-layer array transducer elements. Because of the three-dimensional configuration of the array, logical transducers can be created from multiple transducer elements, and transmission and reception of acoustic signals in any direction can be realized.

Benjamin, Kim C.

2002-09-01

334

Design of optimized piezoelectric HDD-sliders  

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

335

Shear piezoelectricity in bone at the nanoscale  

NASA Astrophysics Data System (ADS)

Recent demonstration of shear piezoelectricity in an isolated collagen fibril, which is the origin of piezoelectricity in bone, necessitates investigation of shear piezoelectric behavior in bone at the nanoscale. Using high resolution lateral piezoresponse force microcopy (PFM), shear piezoelectricity in a cortical bone sample was studied at the nanoscale. Subfibrillar structure of individual collagen fibrils with a periodicity of 60-70 nm were revealed in PFM map, indicating the direct contribution of collagen fibrils to the shear piezoelectricity of bone.

Minary-Jolandan, Majid; Yu, Min-Feng

2010-10-01

336

Laser photoacoustic spectrometer for remote monitoring of atmospheric pollutants.  

PubMed

An acoustically resonant CO(2) laser photoacoustic (PA) spectrometer for remote or in situ monitoring of air pollutants has been designed. The salient features of this PA system, along with the optimization tests of various operating parameters that affect the PA signal (buffer-gas pressure, type of buffer gas, laser power, gas concentration, and acoustic modes), are described. The system has been applied for the detection of pollutants emitted from the exhaust of a car located at a remote distance. Also, an alarm system based on the PA detection technique has been built for leak detection of toxic gases at industrial complexes. The minimum detectable concentration of C(2) H(4) and SO(2) with this system is 50 parts in 10(12) by volume and 50 parts in 10(9) by volume, respectively. PMID:18253326

Gondal, M A

1997-05-20

337

Characterization of reconstructed human skin using Photoacoustic Spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

2008-01-01

338

Label-free oxygen-metabolic photoacoustic microscopy in vivo  

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

339

Fast measurements with a slow detector: photoacoustic investigations of "steam" laser cleaning  

NASA Astrophysics Data System (ADS)

The dynamics of explosive boiling of a 2-propanol layer of variable thickness on a Si substrate heated by a nanosecond KrF excimer laser was studied using a contact photoacoustic technique. The transition from acoustic generation at a free Si boundary to that at a rigid alcohol/Si boundary accompanied by a sharp increase of acoustic generation efficiency was found above a laser fluence threshold of 0.17 J/cm2 and a liquid layer thickness greater than 0.25 ?m due to subnanosecond near-critical explosive boiling of the superheated liquid layer near the hot absorbing Si substrate. The gradual increase of the photoacoustic response of the superheated alcohol with increasing thickness of the liquid film at fluences above the explosive boiling threshold was attributed to the fluence- and time-dependent increase of the area undergoing explosive boiling.

Kudryashov, Sergei I.; Allen, Susan D.; Shukla, Shishir

2004-07-01

340

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

PubMed

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

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

2013-06-17

341

Photoacoustic monitoring of sedimentation of micro-particles in low viscosity fluids  

NASA Astrophysics Data System (ADS)

In this work, the potential of photoacoustic technique in the study of the sedimentation process of particles in liquids is explored. Experiments were performed using zirconia particles of 50 and 100 ?m in three different low viscosity liquids, water, citronella, and ethylene glycol. It is shown that the evolution of the PA signal depends not only on the kind of liquids used but also on the size of the particles. An effective thermal model is developed in order to study the process and to infer the evolution of the thermal conductivity of the sedimented layer when it behaves as thermally thin, or the thermal effusivity if it behaves as thermally thick. It is shown that based on these results, the time evolution of the volume fraction of particles, in the region in which the sediment is deposited, can be obtained. These results can be useful in establishing a methodology for the photoacoustic monitoring of the process of sedimentation in more complex systems.

Pech-May, Nelson W.; Alvarado-Gil, Juan J.

2013-08-01

342

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

PubMed Central

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

Jo, Janggun; Yang, Xinmai

2011-01-01

343

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

PubMed Central

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

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

2012-01-01

344

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

345

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

NASA Astrophysics Data System (ADS)

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.

Spradling, Emily M.; Viator, John A.

2009-02-01

346

A photoacoustic spectrometer for trace gas detection  

NASA Astrophysics Data System (ADS)

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.

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

2005-06-01

347

Photoacoustic and Photothermal Effects in Particulate Suspensions  

SciTech Connect

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

Diebold, Gerald, J.

2009-04-30

348

Photoacoustic investigation of maghemite-based nanocomposite.  

PubMed

Photoacoustic spectroscopy was used to investigate magnetic nanocomposites incorporating nanosized maghemite particles into styrene-divinylbenzene copolymer template. Typical photoacoustic features were observed in bands C, S and L in the wavelength region of 300-1000 nm. The relative intensity of band-C scaled with the nominal concentration of nanosized maghemite incorporated into the polymeric template whereas the lowest relative intensity of band-S was found in the sample in which the template polymerization took place in the presence of the highest polar-like reaction medium. X-ray diffraction and transmission electron microscopy were used to characterize the magnetic nanosized phase as maghemite, with average particle diameter of 6.9 nm (sample Est34), 7.0 nm (sample H30), and 7.9 nm (sample Em15). PMID:22483383

Rodriguez, A F R; Gilhermitti, M F S; Faria, F S E D V; Cunha, R M; Santos, J G; Oliveira, A C; Morales, M A; Rabelo, D; Azevedo, R B; Morais, P C

2012-03-22

349

Photoacoustic ophthalmoscopy for in vivo retinal imaging  

PubMed Central

We have developed a non-invasive photoacoustic ophthalmoscopy (PAOM) for in vivo retinal imaging. PAOM detects the photoacoustic signal induced by pulsed laser light shined onto the retina. By using a stationary ultrasonic transducer in contact with the eyelids and scanning only the laser light across the retina, PAOM provides volumetric imaging of the retinal micro-vasculature and retinal pigment epithelium at a high speed. For B-scan frames containing 256 A-lines, the current PAOM has a frame rate of 93 Hz, which is comparable with state-of-the-art commercial spectral-domain optical coherence tomography (SD-OCT). By integrating PAOM with SD-OCT, we further achieved OCT-guided PAOM, which can provide multi-modal retinal imaging simultaneously. The capabilities of this novel technology were demonstrated by imaging both the microanatomy and microvasculature of the rat retina in vivo.

Jiao, Shuliang; Jiang, Minshan; Hu, Jianming; Fawzi, Amani; Zhou, Qifa; Shung, K. Kirk; Puliafito, Carmen A.; Zhang, Hao F.

2010-01-01

350

Scattered light: improving photoacoustic spectral measurement with a drug tablet  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy (PAS) is a powerful tool for the study of the absorption spectra of solid samples. Scattered light, which used to be a main error source in conventional absorption spectroscopy, is not a problem for PAS, and furthermore, in this paper it is helpful for photoacoustic spectroscopy measurement. In this work, the photoacoustic spectra of an olanzapine tablet and its powder have been investigated. Differential analysis was used to eliminate the background signal generated by the photoacoustic cell. It is found that the photoacoustic spectrum of olanzapine in the powdered olanzapine tablet has the same spectral features as that of the pure olanzapine powder, while the photoacoustic spectrum of the olanzapine tablet does not have, although the ingredients in both are completely the same. This phenomenon can be interpreted as the light scattering effects in the powdered olanzapine tablet. The light scattering effects in a solid mixture amplify the photoacoustic spectral features of the main light-absorbing ingredient in the mixture, rather than enhance the measured photoacoustic signal over the whole measured wavelength range, which is different from the influence of light scattering effects on a single-ingredient solid powder. Based on this work, a method is proposed to preliminarily fast identify the light-absorbing ingredient in a solid mixture. Using the method, a drug tablet can be measured directly in solid state and hardly need sample preprocessing, and thus the time for composition analyses will be reduced significantly.

Yu, Rong; Jiang, Yue-song; Yu, Lan; Wen, Dong-hai; Hua, Hou-qiang; Wu, Xiao-fang

2013-08-01

351

Simulation study of photoacoustic coded excitation using Golay Codes  

Microsoft Academic Search

Photoacoustics (PA) is a new imaging modality based on the generation of ultrasound due to laser irradiation. Instead of commonly used Q-switched Nd:YAG lasers the application of pulsed laser diodes as light sources for photoacoustic imaging is proposed. The high pulse repetition frequency of laser diodes enables the usage of coded excitation schemes for SNR improvement. Therefore, the performance of

Martin P. Mienkina; Annika Eder; Georg Schmitz; Claus-Stefan Friedrich; Nils C. Gerhardt; Martin R. Hofmann

2008-01-01

352

CO2-laser photoacoustic detection of gaseous n-pentylacetate  

NASA Astrophysics Data System (ADS)

The absorption spectra of gaseous n-pentylacetate were investigated by FT IR spectroscopy as well as CO2-laser photoacoustic spectroscopy for simulation of the dispersion of a nerve agent (sarin) within a modeled atmospheric boundary layer. Three CO2-laser emission lines were used for photoacoustic detection of n-pentylacetate with detection limit in the range of 1-3 ppm.

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

2009-07-01

353

Photoacoustic-guided convergence of light through optically diffusive media.  

PubMed

We demonstrate that laser beams can be converged toward a light-absorbing target through optically diffusive media by using photoacoustic-guided interferometric focusing. The convergence of light is achieved by shaping the wavefront of the incident light with a deformable mirror to maximize the photoacoustic signal, which is proportional to the scattered light intensity at the light absorber. PMID:21633446

Kong, Fanting; Silverman, Ronald H; Liu, Liping; Chitnis, Parag V; Lee, Kotik K; Chen, Y C

2011-06-01

354

Photoacoustic Doppler Effect from Flowing Small Light-Absorbing Particles  

Microsoft Academic Search

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

Hui Fang; Konstantin Maslov; Lihong V. Wang

2007-01-01

355

Signal analysis of transients in pulsed photoacoustic spectroscopy  

Microsoft Academic Search

A finite difference model was constructed to describe the origin of the complex transients in pulsed photoacoustic spectroscopy signals. With inclusion of boundary conditions and material interfaces, the model is shown to give qualitative agreement with experimental transients. The model provides insight into the results of varying the photoacoustic-cell materials and\\/or geometric configuration for cell optimization. The transients are found

D. A. Schurig; G. L. Klunder; M. A. Shannon; R. E. Russo; R. J. Silva

1993-01-01

356

Compressed sensing in photoacoustic tomography in vivo.  

PubMed

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

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

357

Compressed sensing in photoacoustic tomographyin vivo  

PubMed Central

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

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

2010-01-01

358

Quantitative imaging of bilirubin by photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

359

Second generation optical-resolution photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

We developed a second-generation optical-resolution photoacoustic microscope (OR-PAM) with a novel acoustic detection scheme, which improved upon the sensitivity of our first-generation system by 18 dB. Moreover, translating the imaging head instead of the living object improved the scanning speed by a factor of 5, widening the field of view within the same acquisition time. The anatomy and hemoglobin oxygen saturation of an entire mouse ear was imaged in vivo.

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

2011-02-01

360

Photoacoustics of disperse systems: Below cavitation threshold  

SciTech Connect

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.

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

2012-05-24

361

The Malaria Parasite Monitored by Photoacoustic Spectroscopy  

Microsoft Academic Search

Noninvasive photoacoustic spectroscopy was used to study the malaria parasites Plasmodium chabaudi and Plasmodium berghei, their pigment, and ferri-protoporphyrin IX, which is a by-product of the hemoglobin that the parasite ingests. The results indicate that the pigment consists of ferriprotophorphyrin self-aggregates and a noncovalent complex of ferriprotoporphyrin and protein. Spectra of chloroquine-treated parasites reveal in situ interaction between the drug

D. Balasubramanian; Ch. Mohan Rao; B. Panijpan

1984-01-01

362

Photoacoustic generation by multiple picosecond pulse excitation  

PubMed Central

Purpose: The purpose of this work is to demonstrate that higher amplitude of ultrashort laser induced photoacoustic signal can be achieved by multiple-pulse excitation when the temporal duration of the pulse train is less than the minimum of the medium’s thermal relaxation time and stress relaxation time. Thus, improved signal-to-noise ratio can thus be attained through multiple-pulse excitation while minimizing the energy of each pulse. Methods: The authors used a Michelson interferometer together with a picoseconds laser system to introduce two 6 ps pulses separated by a controllable delay by introducing a path length difference between the two arms of the interferometer. The authors then employed a series of three interferometers to create a pulse train consisting of eight pulses. The average pulse energy was 11 nJ and the temporal span of the pulse train was less than 1 ns. Results: The detected peak-to-peak amplitude of the multiple-pulse induced photoacoustic waves were linearly dependent on the number of pulses in the pulse train and such a linearity held for different optical absorption coefficients. The signal-to-noise ratio improved when the number of pulses increased. Moreover, nonlinear effects were not detected and no photoacoustic saturation effect was observed. Conclusions: The authors have shown that multiple-pulse excitation improves the signal-to-noise ratio through an accumulated energy deposition effect. This method is invaluable for photoacoustic measurements that require ultrashort laser pulses with minimized pulse energy to avoid laser damage.

Liu, Tan; Wang, Jing; Petrov, Georgi I.; Yakovlev, Vladislav V.; Zhang, Hao F.

2010-01-01

363

Photoacoustic speckles: boundary dependence and experimental validation  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography (PAT) suppresses speckles by prominent boundary buildups. We theoretically study the dependence of PAT speckles on the boundary roughness, which is quantified by the root-mean-squared (RMS) value and the correlation length of the height. The speckle visibility and the correlation coefficient between the reconstructed and actual boundaries are quantified as a function of the boundary roughness. The statistics of PAT speckles is studied experimentally.

Guo, Zijian; Xu, Zhun; Wang, Lihong V.

2012-02-01

364

Quantification and Reconstruction in Photoacoustic Tomography  

NASA Astrophysics Data System (ADS)

Optical absorption is closely associated with many physiological important parameters, such as the concentration and oxygen saturation of hemoglobin. Conventionally, accurate quantification in PAT requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. We demonstrate the method using the optical-resolution photoacoustic microscopy (OR-PAM) and the acoustical-resolution photoacoustic microscopy (AR-PAM) in the optical ballistic regime and in the optical diffusive regime, respectively. The data acquisition speed in photoacoustic computed tomography (PACT) is limited by the laser repetition rate and the number of parallel ultrasound detecting channels. Reconstructing an image with fewer measurements can effectively accelerate the data acquisition and reduce the system cost. We adapted Compressed Sensing (CS) for the reconstruction in PACT. CS-based PACT was implemented as a non-linear conjugate gradient descent algorithm and tested with both phantom and in vivo experiments. Speckles have been considered ubiquitous in all scattering-based coherent imaging technologies. As a coherent imaging modality based on optical absorption, photoacoustic (PA) tomography (PAT) is generally devoid of speckles. PAT suppresses speckles by building up prominent boundary signals, via a mechanism similar to that of specular reflection. When imaging smooth boundary absorbing targets, the speckle visibility in PAT, which is defined as the ratio of the square root of the average power of speckles to that of boundaries, is inversely proportional to the square root of the absorber density. If the surfaces of the absorbing targets have uncorrelated height fluctuations, however, the boundary features may become fully developed speckles. The findings were validated by simulations and experiments. The first- and second-order statistics of PAT speckles were also studied experimentally. While the amplitude of the speckles follows a Gaussian distribution, the autocorrelation of the speckle patterns tracks that of the system point spread function.

Guo, Zijian

365

Photoacoustic measurement of absolute overtone cross sections  

NASA Astrophysics Data System (ADS)

Using the photoacoustic effect, integrated absorption cross sections for the 5-0 and 6-0 C?H stretching overtones of ethane and ethylene were calibrated against the well-known cross sections for the 4-0 and 5-0 overtones of HD. The results of this calibration procedure agree well with FT-IR measurements by Quack and co-workers. Thus, these absorption cross sections would serve well as secondary reference standards in overtone measurements.

Gutow, J. H.; Davidsson, J.; Zare, R. N.

1991-10-01

366

New Pyroelectric Contributions to Piezoelectricity.  

National Technical Information Service (NTIS)

The authors show that the Voigt constitutive equations, the traditional algebraic proof of the equality of the direct and converse piezoelectric effects, and the usual neglect of the magnetic field are incorrect in pyroelectrics. A measurement of vector H...

D. F. Nelson M. Lax

1973-01-01

367

Conservation Laws in Linear Piezoelectricity.  

National Technical Information Service (NTIS)

We use Noether's theorem on variational principles invariant under a group of infinitesimal transformations to obtain a class of conservation laws for linear piezoelectric materials and linear elastic dielectrics.

J. S. Yang R. C. Batra

1995-01-01

368

Piezoelectricity: Venerable Effect, Modern Thrusts.  

National Technical Information Service (NTIS)

A synopsis of the piezoelectric effect is presented in the context of its history, traditional uses, and relation to crystal symmetry. Associated effects are briefly noted. Future prospects, particularly in the area of microelectromechanical systems/struc...

A. Ballato

1994-01-01

369

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

PubMed Central

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

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

2011-01-01

370

Imaging hypoxia using 3D photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

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

Stantz, Keith M.

2010-02-01

371

Ultrasonically Assisted and Piezoelectric Actuators Integrated Cutting Tool  

NASA Astrophysics Data System (ADS)

In this paper efforts are made to refine the current cutting tool system for active error compensation, with the aid of ultrasonic vibration cutting technique. Two piezoelectric actuators are integrated in the cutting tool, one of which is for active error compensation and the other for ultrasonic vibration cutting. Principles of the active compensation for cutting error and the ultrasonic vibration cutting are first described. The characteristics of the piezoelectric actuators are experimentally studied and finally the integrated cutting tool is developed. Experimental cutting results have shown that the cutting tool developed is satisfactory in terms of improved roundness and surface roughness of machined workpieces.

Han, Liang; Xu, Weiliang; Tso, Shiu

1998-08-01

372

Piezoelectric actuator based active error compensation of precision machining  

NASA Astrophysics Data System (ADS)

Efforts to refine a current cutting tool system for active error compensation with the aid of ultrasonic vibration cutting technique are described. Two piezoelectric actuators are integrated in the cutting tool, one of which is for active error compensation and the other for ultrasonic vibration cutting. The principles of active compensation for cutting error and ultrasonic vibration cutting are first explained. The experimentally studied characteristics of the piezoelectric actuators and the development of the integrated cutting tool are described. Experimental cutting results have shown that the cutting tool developed is satisfactory in terms of improved roundness and surface roughness of machined workpieces.

Xu, W. L.; Han, L.

1999-02-01

373

Gas Sensors Based on Piezoelectric Micro-Diaphragm Transducer  

Microsoft Academic Search

We have fabricated high sensitive gas sensor based on piezoelectrically driven micro-diaphragm transducers. The micro-diaphragm transducer was fabricated using micro-electro-mechanical-system (MEMS) technique. The diol based sol-gel derived Pb(Zr0.52,Ti0.48)O3(PZT) film was used as a piezoelectric actuating layer. We have used the resonant frequency change of micro-diaphragm transducer upon mass increase as a sensing signal. The resonant frequency values were measured by

Jaichan Lee; Sanghun Shin; Jun-Kyu Paik; Nae-Eung Lee; Hyo-Derk Park; Jun-Shik Park

2005-01-01

374

Piezoelectric ceramics with high dielectric constants for ultrasonic medical transducers  

Microsoft Academic Search

Complex system ceramics Pb(Sc12\\/Nb12\\/)O3-Pb(Mg13\\/Nb23\\/)O3-Pb(Ni12\\/Nb$ d12\\/)O3-(Pb0.965,Sr0.035) (Zr,Ti)O3 (PSN-PMN-PNN-PSZT abbreviated PSMNZT) have been synthesized by the conventional technique, and dielectric and piezoelectric properties of the ceramics have been investigated for ultrasonic medical transducers. High capacitances of the transducers are desired in order to match the electrical impedance between the transducers and the coaxial cable in array probes. Although piezoelectric ceramics that have

Yasuharu Hosono; Yohachi Yamashita

2005-01-01

375

Aeroelastic tailoring using piezoelectric actuation and hybrid optimization  

Microsoft Academic Search

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

Aditi Chattopadhyay; Charles E. Seeley; Ratneshwar Jha

1999-01-01

376

An active piezoelectric energy extraction method for pressure energy harvesting  

Microsoft Academic Search

This paper presents an energy harvesting technique to power autonomous systems and more particularly active implantable medical devices. We employ a piezoelectric diaphragm placed in a fluidic environment such as blood subjected to very low frequency (2 Hz) pressure variations that is deflected in a quasi-static manner and transduces mechanical energy into electrical energy. In order to maximize energy generation

M Deterre; E Lefeuvre; E Dufour-Gergam

2012-01-01

377

Development of novel piezoelectric ceramics and composites for transducer applications  

Microsoft Academic Search

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

Ahmad Safari; Stephen C. Danforth

1998-01-01

378

7D-4 Non Destructive Evaluation of Carbon Fiber Reinforced Plates Using Lamb Waves: A Comparison Between Pitch-Catch Air Coupled Techniques and Sector Images Obtained with Embedded Piezoelectric Linear Arrays  

Microsoft Academic Search

In this work, a carbon fiber composite plate with uniform thickness has been implemented with a flexible piezoelectric linear array bonded on it. A four cycles tone burst of 48 kHz has been used to excite an antisymmetric Lamb mode. Then, a 2D sector image of the plate with a delamination has been obtained using a synthetic aperture algorithm. Next,

Y. Gomez-Ullate; F. Montero de Espinosa

2007-01-01

379

Piezoelectric sensor based nondestructive active monitoring of strength gain in concrete  

Microsoft Academic Search

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

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

2008-01-01

380

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

381

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

382

Detection and capture of single circulating melanoma cells using photoacoustic flowmetry  

NASA Astrophysics Data System (ADS)

Photoacoustic flowmetry has been used to detect single circulating melanoma cells in vitro. Circulating melanoma cells are those cells that travel in the blood and lymph systems to create secondary tumors and are the hallmark of metastasis. This technique involves taking blood samples from patients, separating the white blood and melanoma cells from whole blood and irradiating them with a pulsed laser in a flowmetry set up. Rapid, visible wavelength laser pulses on the order of 5 ns can induce photoacoustic waves in melanoma cells due to their melanin content, while surrounding white blood cells remain acoustically passive. We have developed a system that identifies rare melanoma cells and captures them in 50 microliter volumes using suction applied near the photoacoustic detection chamber. The 50 microliter sample is then diluted and the experiment is repeated using the new sample until only a melanoma cell remains. We have tested this system on dyed microspheres ranging in size from 300 to 500 microns. Capture of circulating melanoma cells may provide the opportunity to study metastatic cells for basic understanding of the spread of cancer and to optimize patient specific therapies.

O'Brien, Christine; Mosley, Jeffrey; Goldschmidt, Benjamin S.; Viator, John A.

2010-02-01

383

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

384

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

NASA Astrophysics Data System (ADS)

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.

Brunker, J.; Beard, P.

2013-03-01

385

Identification of photoacoustic transients during pulsed laser ablation of the human temporal bone: an experimental model.  

PubMed

Laser ablation of hard tissues during neurotologic operations has been accomplished with continuous-wave (CW) lasers in the visible and midinfrared spectrum. The mechanism of ablation at these wavelengths is secondary to photothermal-induced tissue destruction. As a result, significant thermal damage to surrounding tissue may occur. Pulsed ultraviolet (UV) lasers have been suggested as an alternative to the argon, KTP-532, and CO2 lasers currently used in clinical practice. The pulse length of Excimer lasers are considerably shorter than the thermal diffusion time of bone tissue, and as a consequence thermal injury is minimal. This makes pulsed lasers an attractive tool for tissue ablation in the ear: in essence a "cold knife." However, the short pulse width of Excimer lasers (typically 10-150 ns) can create large thermoelastic stresses in the ablation specimen. This study identifies the presence of these photoacoustic waves during the Excimer laser treatment of the cadaveric human temporal bone. A XeCl (lambda = 308 nm, tau p = 12 ns) excimer laser was used to ablate hard tissue surrounding the oval window and facial ridge with energies of 75, 45, 25, and 12 mJ/pulse. Spot size was estimated to be 0.5 mm2. Custom high-frequency polyvinyldifluoride (PVDF) piezoelectric film transducers were fabricated and attached to the promontory, round window niche, and facial ridges. The signals were amplified using a low-noise preamplifier and recorded on a digitizing oscilloscope. Photoacoustic waves were clearly identified. Notably, large acoustic waves were measured on the promontory and on both sides of the facial ridge. The implications and clinical relevance of these findings is discussed and compared to findings obtained from a model system. PMID:9467330

Wong, B J; Dickinson, M R; Berns, M W; Neev, J

1996-12-01

386

Piezoelectric Film Load Cell Robot Collision Detector.  

National Technical Information Service (NTIS)

A piezoelectric load cell which can be utilized for detecting collisions and obstruction of a robot arm end effector includes a force sensing element of metallized polyvinylidene fluoride (PVDF) film. The piezoelectric film sensing element and a resilient...

J. R. Lembke

1988-01-01

387

Dynamic Analysis of Piezoelectric Strained Elements.  

National Technical Information Service (NTIS)

This report is addressed to the dynamic analysis of piezoelectric structural elements under a static mechanical bias. In the first part of the report, the current literature pertaining to the dynamic applications of piezoelectric crystals is reviewed; att...

M. C. Dokmeci

1992-01-01

388

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)

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.

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

2006-06-01

389

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

PubMed

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

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

2013-09-24

390

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

PubMed Central

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

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

2013-01-01

391

Simultaneous multimodal imaging with integrated photoacoustic microscopy and optical coherence tomography  

PubMed Central

We have developed a multimodal imaging technique by integrating photoacoustic microscopy and spectral-domain optical coherence tomography to provide simultaneous volumetric microscopic imaging of both optical absorption and scattering contrasts in biological tissues. In the integrated system, the two imaging modalities share the same optical scanning and delivery mechanisms after their probing and illumination light beams are combined. By further synchronizing the image acquisitions, the images from the two modalities are intrinsically registered. The capabilities of this novel technique were demonstrated by imaging both the microanatomy and microvasculature in mouse ears in vivo.

Jiao, Shuliang; Xie, Zhixing; Zhang, Hao F.; Puliafito, Carmen A.

2010-01-01

392

Flexural Analysis of Piezoelectric Coupled Structures  

Microsoft Academic Search

\\u000a The analysis of a coupled piezoelectric structure has recently been keenly researched because piezoelectric materials are\\u000a more extensively used either as actuators or sensors. The challenge of developing a basic mechanics model for the piezoelectric\\u000a coupled structure has been met by many researchers. (1987) developed a uniform strain model for a beam with surface bonded and embedded piezoelectric actuator patches

Q. Wang; S. T. Quek

393

Design and fabrication of ultrafine piezoelectric composites.  

PubMed

Making fine scale (< 20 microm) piezoelectric composites for high frequency (> 50 MHz) ultrasound transducers remains challenging. Interdigital phase bonding (IPhB), described in this paper, presents a new technique developed to make piezoelectric composites at the ultrafine scale using a conventional dicing saw. Using the IPhB technique, a composite structure with a pitch that is less than the dicing saw blade thickness can be created. The approach is flexible enough to make composites of different combination of pitch and volume ratio. Using a conventional dicing saw with a 50 microm thick blade, composite with a 25 microm pitch and a volume ratio of 61 percent are fabricated. Such a composite is suitable for fabrication of ultrasonic transducers and arrays with central frequencies of up to 85 MHz. Single element transducers working at central frequencies of 50-60 MHz were made of these composites as a mean to characterize the acoustic performance. Measurement results of the transducers show that the longitudinal electromechanical coupling coefficient is greater than 0.6 and that there are no noticeable lateral resonances in the frequency range of 55-150 MHz. Design criteria for fine scale elements are also discussed based on theoretical results from finite element analysis (FEA). PMID:16003926

Yin, J; Lukacs, M; Harasiewicz, K A; Foster, F S

2005-01-01

394

Piezoelectrically-driven Thermoacoustic Refrigerator  

NASA Astrophysics Data System (ADS)

Thermoacoustic refrigeration is an emerging refrigeration technology which does not require any moving parts or harmful refrigerants in its operation. This technology uses acoustic waves to pump heat across a temperature gradient. The vast majority of thermoacoustic refrigerators to date have used electromagnetic loudspeakers to generate the acoustic input. In this thesis, the design, construction, operation, and modeling of a piezoelectrically-driven thermoacoustic refrigerator are detailed. This refrigerator demonstrates the effectiveness of piezoelectric actuation in moving 0.3 W of heat across an 18 degree C temperature difference with an input power of 7.6 W. The performance characteristics of this class of thermoacoustic-piezoelectric refrigerators are modeled by using DeltaEC software and the predictions are experimentally validated. The obtained results confirm the validity of the developed model. Furthermore, the potential of piezoelectric actuation as effective means for driving thermoacoustic refrigerators is demonstrated as compared to the conventional electromagnetic loudspeakers which are heavy and require high actuation energy. The developed theoretical and experimental tools can serve as invaluable means for the design and testing of other piezoelectrically-driven thermoacoustic refrigerator configurations.

Chinn, Daniel George

395

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

PubMed

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

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

2013-04-02

396

Design, synthesis, and imaging of an activatable photoacoustic probe.  

PubMed

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

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

2010-08-18

397

Design, Synthesis and Imaging of an Activatable Photoacoustic Probe  

PubMed Central

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

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

2010-01-01

398

Recent developments of polar piezoelectric polymers  

Microsoft Academic Search

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

Eiichi Fukada

2006-01-01

399

Photoacoustic and filter measurements related to aerosol light absorption during the Northern Front Range Air Quality Study (Colorado 1996/1997)  

NASA Astrophysics Data System (ADS)

A new photoacoustic instrument for the measurement of aerosol light absorption was collocated with conventional aerosol instrumentation during the 1996-1997 winter intensive monitoring period of the Northern Front Range Air Quality Study. Measurements of the light absorption efficiency for black carbon were 5 m2/g at 685 nm and 10 m2/g at 532 nm, and for elemental carbon, they were 3.6 m2/g at 685 nm. We show that these values together with previous photoacoustic measurements of aerosol light absorption shed some light on the wavelength dependence of absorption efficiency for carbonaceous aerosol in the visible and near-visible region. Integrating plate type filter measurements of aerosol light absorption result in far larger values than those measured with the photoacoustic instrument. We demonstrate that a recently published correction technique [Horvath, 1997] can yield improved agreement.

Moosmüller, H.; Arnott, W. P.; Rogers, C. F.; Chow, J. C.; Frazier, C. A.; Sherman, L. E.; Dietrich, D. L.

1998-11-01

400

Photoacoustic tomography extracted from speckle noise in acoustically inhomogeneous tissue.  

PubMed

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

Wu, Dan; Tao, Chao; Liu, Xiaojun

2013-07-29

401

Photoacoustic emission from fluorescent nanodiamonds enhanced with gold nanoparticles  

PubMed Central

Fluorescent nanodiamonds (FNDs) have drawn much attention in recent years for biomedical imaging applications due to their desired physical properties including excellent photostability, high biocompatibility, extended far-red fluorescence emission, and ease of surface functionalization. Here we explore a new feature of FNDs, i.e. their photoacoustic emission capability, which may lead to potential applications of using FNDs as a dual imaging contrast agent for combined fluorescence and photoacoustic imaging modalities. We observed significant enhancement of photoacoustic emission from FNDs when they were conjugated with gold nanoparticles (GNPs).

Zhang, Bailin; Fang, Chia-Yi; Chang, Cheng-Chun; Peterson, Ralph; Maswadi, Saher; Glickman, Randolph D.; Chang, Huan-Cheng; Ye, Jing Yong

2012-01-01

402

Blood pulse wave velocity measured by photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

403

Photoacoustic thermal diffusion flowmetry in tissue-mimicking phantoms  

NASA Astrophysics Data System (ADS)

Photoacoustic Thermal Diffusion Flowmetry (PA-TDF) utilizes photothermal heating and photoacoustic temperature monitoring to measure the tissue heat clearance time constants from which blood velocity can be inferred. We extended our study of PA-TDF to tissue-mimicking phantoms with vessels at various diameters, configurations and depths and experimentally verified the relations between the estimated time constants and the vessels and the illuminating beam dimensions. We also demonstrated, for the first time, depth-resolved PA-TDF measurement using tone-burst photoacoustic excitation. The excitation utilized two fiber-coupled 830nm laser diodes, one induced slow temperature oscillations and the other induced the PA excitation.

Sheinfeld, Adi; Eyal, Avishay

2013-03-01

404

Multifocal optical-resolution photoacoustic microscopy in vivo.  

PubMed

Although ultrasound arrays have been exploited in photoacoustic imaging to improve imaging speed, ultrasound-array-based optical-resolution photoacoustic microscopy (OR-PAM) has never been achieved previously to our knowledge. Here we present our development of multifocal OR-PAM using a microlens array for optical illumination and an ultrasound array for photoacoustic detection. Our system is capable of imaging hemoglobin concentration and oxygenation in individual microvessels in vivo at high speed. Compared with a single focus, multiple foci reduce the scanning load and increase the imaging speed significantly. The current multifocal system can acquire 1000 × 500 × 200 voxels at ~10 ?m lateral resolution within 4 min. PMID:21479041

Song, Liang; Maslov, Konstantin; Wang, Lihong V

2011-04-01

405

Multi-focal optical-resolution photoacoustic microscopy in vivo  

PubMed Central

Although ultrasound arrays were exploited in photoacoustic imaging to improve imaging speed, ultrasound-array-based optical-resolution photoacoustic microscopy (OR-PAM) has never been achieved previously. Here we present our development of multi-focal OR-PAM using a microlens array for optical illumination and an ultrasound array for photoacoustic detection. Our system is capable of imaging hemoglobin concentration and oxygenation in individual microvessels in vivo at high speed. Compared with a single focus, multiple foci reduce the scanning load and increase the imaging speed significantly. The current multi-focal system can acquire 1000 × 500 × 200 voxels at ~10-?m lateral resolution within 4 min.

Song, Liang; Maslov, Konstantin; Wang, Lihong V.

2011-01-01

406

Shape modeling and validation of stress-biased piezoelectric actuators  

Microsoft Academic Search

Piezoelectric composites with a characteristic initial curvature and accompanying residual stresses are capable of enhanced performance, relative to flat actuators. This paper utilizes Rayleigh-Ritz techniques with revisions regarding the effective in-plane resultant force and the effective bending moment. The Rayleigh-Ritz technique is based on the assumption that the stable geometric configuration developed in the actuator after manufacturing is the configuration

K. Mossi; M. Mouhli; B. F. Smith; P. P. Mane; R. G. Bryant

2006-01-01

407

Hysteresis compensation for a piezoelectric fiber optic voltage sensor  

NASA Astrophysics Data System (ADS)

We present details of numerical techniques developed to compensate the effects of hysteresis experienced by a hybrid piezoelectric fiber optic voltage sensor. The techniques, implemented using a real-time signal processing system, are tested and their effectiveness evaluated experimentally. The best of the proposed algorithms provides phase error compensation from approximately 7 to nearly 0 deg, and allows us to perform sensor calibration to achieve accuracy better than 0.5% (full scale output).

Fusiek, G.; Niewczas, Pawel; Dziuda, L.; McDonald, James R.

2005-11-01

408

Monitoring stimulated Raman scattering with photoacoustic detection  

PubMed Central

A capability of high-frequency ultrasound detection to monitor the process of energy deposition into a molecular system via Raman excitation is experimentally demonstrated. It is shown that the generated ultrasound signal is directly proportional to the optical signal generated in stimulated Raman scattering. Ultrasound detection provides a simple way to discriminate against laser-induced breakdown and allows for the quantification of the stimulated Raman scattering process where direct optical detection is not available. Additionally, it can be used for stimulated Raman imaging in deep tissue, provided that the generated photoacoustic signal is sufficiently strong.

Yakovlev, Vladislav V.; Noojin, Gary D.; Denton, Michael L.; Rockwell, Benjamin A.; Thomas, Robert J.

2011-01-01

409

Monitoring stimulated Raman scattering with photoacoustic detection.  

PubMed

A capability of high-frequency ultrasound detection to monitor the process of energy deposition into a molecular system via Raman excitation is experimentally demonstrated. It is shown that the generated ultrasound signal is directly proportional to the optical signal generated in stimulated Raman scattering. Ultrasound detection provides a simple way to discriminate against laser-induced breakdown and allows for the quantification of the stimulated Raman scattering process where direct optical detection is not available. Additionally, it can be used for stimulated Raman imaging in deep tissue, provided that the generated photoacoustic signal is sufficiently strong. PMID:21479040

Yakovlev, Vladislav V; Noojin, Gary D; Denton, Michael L; Rockwell, Benjamin A; Thomas, Robert J

2011-04-01

410

Photoacoustic NO detection for asthma diagnostics  

NASA Astrophysics Data System (ADS)

Exhaled nitric oxide was of high interest in breath analyses in the past few years. After its first detection in human breath in 1991, numerous publications uncovered the role of NO and its relation to different diseases. A strong relationship between an asthmatic eosinophilic airway inflammation and an increased NO level is medically confirmed. In this study a new photoacoustic detection system for nitric oxide based on a pulsed quantum cascade laser is introduced. The laser's single mode emission provides adequate selectivity to differentiate NO from other molecules in the sample. The demonstrated detection sensitivity allows in principle an application of the new system as diagnostic tool for asthma.

Germer, Markus; Wolff, Marcus; Harde, Hermann

2009-07-01

411

Photoacoustic tomography in a reflecting cavity  

NASA Astrophysics Data System (ADS)

Almost all known photoacoustic image reconstruction algorithms are based on the assumption that the acoustic waves leave the object (the imaged region) after a finite time. This assumption is fulfilled if the measurements are made in free space and reflections from the detectors are negligible. However, when the object is surrounded by acoustically hard detectors arrays (and/or by additional acoustic mirrors), the acoustic waves will bounce around in such a reverberant cavity many times (in the absence of absorption, forever). This paper proposes fast reconstruction algorithms for the measurements made from the walls of a rectangular reverberant cavity. The algorithms are tested using numerical simulations.

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

2013-03-01

412

A Negative Lens Concept for Photoacoustic Tomography  

PubMed Central

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.

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

2008-01-01

413

Dynamic photoacoustic spectroscopy for trace gas detection  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

414

Micro-optical-mechanical system photoacoustic spectrometer  

DOEpatents

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

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

2013-01-01

415

Alternative Method to Characterize Corn Grain by Means of Photoacoustic Spectroscopy  

NASA Astrophysics Data System (ADS)

The application of photothermal (PT) techniques to obtain the optical and thermal properties of different materials has been widely reported in the literature. Among the PT techniques, photoacoustic spectroscopy stands out because this technique has been used to characterize different types of materials in solid, liquid, and gaseous phases, as well as homogeneous and inhomogeneous samples as biological materials which present great complexity in their structure. In particular, the seeds and corn kernels comprise different structural components such as endosperm, pericarp, embryo, and pedicel. The color attribute is very important in the grains because it gives information about the chemical composition and nutritional quality attributes which are important in consumer acceptance. In this investigation optical absorption spectra of corn grains were obtained by using photoacoustic spectroscopy in a wavelength range from 325 nm to 800 nm. Two varieties of corn grains were studied, establishing a complete block design at random for the measurements. From the obtained optical absorption spectra, the optical absorption coefficient (? ) was calculated as a function of the wavelength for each sample. A complementary study of the percentage of reflectance for these samples was carried out by using ultraviolet/visible spectrometry with an integrating sphere. The data were subjected to an analysis of the variance using software of the statistical analysis system. The results revealed significant differences (P? 0.05) between corn varieties in the range of 325 nm to 670 nm. The application of the photoacoustic spectroscopy technique as an alternative to conventional methods for the characterization of maize grain through an analysis of ? could be important for characterizing non-homogeneous materials like grains of corn, whose characterization is relevant in the food industry.

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

2013-03-01

416

A coherent photoacoustic approach to excited-state-excited-state absorption spectroscopy: application to the investigation of a near-resonant contribution to ultrasonic diffraction  

Microsoft Academic Search

The previously reported coherent photoacoustic method for measuring weak absorptions is extended to excited-state-excited-state spectroscopy for which conventional acoustic and thermal lensing techniques are greatly reduced in sensitivity. The method involves a picosecond pulse sequence with four pulses. The first pulse populates the excited state. Then, a pair of time coincident pulses cross in the sample, making an optical interference

R. J. Dwayne Miller; Marc Pierre; Todd S. Rose; M. D. Fayer

1984-01-01

417

Thermal Image of Coffee-Seed Germ Obtained by Photoacoustic Microscopy  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

418

Piezoelectric materials used in underwater acoustic transducers  

SciTech Connect

Piezoelectric materials have been used in underwater acoustic transducers for nearly a century. In this paper, we reviewed four different types of piezoelectric materials: piezoelectric ceramics, single crystals, composites, and polymers, which are widely used in underwater acoustic transducers nowadays. Piezoelectric ceramics are the most dominant material type and are used as a single-phase material or one of the end members in composites. Piezoelectric single crystals offer outstanding electromechanical response but are limited by their manufacturing cost. Piezoelectric polymers provide excellent acoustic impedance matching and transducer fabrication flexibility although their piezoelectric properties are not as good as ceramics and single crystals. Composites combined the merits of ceramics and polymers and are receiving increased attention. The typical structure and electromechanical properties of each type of materials are introduced and discussed with respect to underwater acoustic transducer applications. Their advantages and disadvantages are summarized. Some of the critical design considerations when developing underwater acoustic transducers with these materials are also touched upon.

Li, Huidong; Deng, Zhiqun; Carlson, Thomas J.

2012-07-07

419

Cylindrical mirror multipass Lissajous system for laser photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

A simple optical multiple reflection system is developed with two cylindrical concave mirrors at an appropriate spacing. The two cylindrical mirrors have different focal lengths and their principal sections are orthogonal. The alternate focusing of the two cylindrical mirrors at different direction keep the reflecting spots small. The reflecting spots fall on Lissajous patterns on the cylindrical mirrors. The mathematics for this optical system is described and the calculated coordinates of beam spots are very close matches of the experimental observations. The cylindrical mirror optical system is easy to construct and align, with a suitable method for obtaining long optical paths and a large number of passes in small volumes. In a photoacoustic spectrometer the beam family enhance the effective power in the photoacoustic cell and thus the signal-to-noise ratio of photoacoustic signal. An experimental result for photoacoustic spectrum of HDSe gas is given.

Hao, Lu-Yuan; Qiang, Shi; Wu, Guo-Rong; Qi, Li; Feng, Dang; Zhu, Qing-Shi; Hong, Zhang

2002-05-01

420

In-Situ Photoacoustic Spectrometry for Corrosion Studies.  

National Technical Information Service (NTIS)

These preliminary experiments showed that detectable acoustic signals can be obtained with an illumination intensity of the electrode which does not produce a significant photoelectrochemical effect. We therefore are confident that in-situ photoacoustic s...

C. E. Vallet G. M. Brown

1983-01-01

421

Thermal stability of biodegradable plasmonic nanoclusters in photoacoustic imaging.  

PubMed

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

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

2012-12-31

422

Photoacoustic image-guided needle biopsy of sentinel lymph nodes  

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

423

Diamond - Application to piezoelectric bimorph cantilever sensors  

NASA Astrophysics Data System (ADS)

Micro-cantilevers are excellent tools to measure tiny forces (from 1 nN up to 10 N) as shown by the development of atomic force microscopy (AFM) techniques. That is the reason why micro-cantilevers are also the most sensitive acoustic sensors. For instance, one can use the variation of the cantilever's resonant frequency to measure mass loading. In this work, we will show first why diamond is the most suitable material for a special type of cantilever sensors: piezoelectric bimorph cantilever sensors. In contrast to other cantilevers, it is possible to actuate piezoelectric bimorph cantilevers and to detect their resonance frequencies simultaneously. Then, we present one application of this type of cantilever: a diamond/AlN cantilever used as a high pressure sensor (up to 7 ar). The sensor operates by monitoring the frequency shift of the first resonant mode (f 1 36.5 kHz). We have measured a sensitivity of 0.155 Hz/mbar in pure nitrogen.

Mortet, V.; Haenen, K.; Potmesil, J.; Vanecek, M.; D'Olieslaeger, M.

2006-09-01

424

Functional photoacoustic microscopy of diabetic vasculature  

PubMed Central

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

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

2012-01-01

425

Functional photoacoustic microscopy of diabetic vasculature.  

PubMed

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

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

2012-06-01

426

Gold nanorods: contrast agents for photoacoustic imaging?  

NASA Astrophysics Data System (ADS)

Gold nanorods are seen as possible contrast agents for photoacoustic imaging since they have strong absorption peaks at near-infrared wavelengths. Also they are easy to conjugate with various proteins. If these particles can be conjugated with cancer affinity proteins then these particles can accumulate specifically at a tumor site. By detecting the presence of accumulation of gold nanorods inside the tissue the indirect detection of tumor can be realized. When these particles are irradiated with light pulses of appropriate temporal properties and energy the temperature around these particles can be high enough to induce apoptosis or necrosis in the surrounding cells. In order to use these particles at their full potential we must determine precisely their optical properties. We simulated the optical properties of gold nanorods synthesized by us using the DDSCAT code. The simulated spectra agree qualitatively with the spectra determined using spectrometry and also determined using photoacoustic spectroscopy. Further the values of molar extinction coefficient derived from the simulations were similar to the data measured experimentally by other groups. These results validated qualitatively the model used in the simulations. During simulations we found that the choice of the dielectric function used in simulations plays an important role in the results.

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

2007-07-01

427

Functional photoacoustic microscopy of diabetic vasculature  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

428

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

Microsoft Academic Search

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

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

2006-01-01

429

Piezoelectric bone surgery applied in alveolar distraction osteogenesis: a technical note.  

PubMed

Piezoelectric bone surgery is based on ultrasonic vibration of a device functioning as an osteotome. This device allows precise cuts to be made in bone structures without provoking lesions of adjacent soft tissues and at the same time offering excellent visibility within the surgical field. The use of this technique in alveolar distraction osteogenesis is described. Piezoelectric surgery appears to make the cutting of the transport segment easier and safer. PMID:18271385

González-García, Alberto; Diniz-Freitas, Márcio; Somoza-Martín, Manuel; García-García, Abel

430

Observation of Piezoelectric Relaxation in Ferroelectric Thin Films by Continuous Charge Integration  

Microsoft Academic Search

A continuous charge integration technique is used to measure the effective longitudinal piezoelectric coefficient (d33) of thin films. Measurements are performed by applying a static force normal to the films and recording the stress-induced polarization with a charge integrator. Measurements for the as-deposited PbZr0.53Ti0.47O3 (PZT) thin films show that the piezoelectric effect is strongly time-dependent and the relaxation is well

Desheng Fu; Kenji Ishikawa; Makoto Minakata; Hisao Suzuki

2001-01-01

431

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

Microsoft Academic Search

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

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

2006-01-01

432

TOPICAL REVIEW: Piezoelectric MEMS sensors: state-of-the-art and perspectives  

NASA Astrophysics Data System (ADS)

Over the past two decades, several advances have been made in micromachined sensors and actuators. As the field of microelectromechanical systems (MEMS) has advanced, a clear need for the integration of materials other than silicon and its compounds into micromachined transducers has emerged. Piezoelectric materials are high energy density materials that scale very favorably upon miniaturization and that has led to an ever-growing interest in piezoelectric films for MEMS applications. At this time, piezoelectric aluminum-nitride-based film bulk acoustic resonators (FBAR) have already been successfully commercialized. Future innovations and improvements in inertial sensors for navigation, high-frequency crystal oscillators and filters for wireless applications, microactuators for RF applications, chip-scale chemical analysis systems and countless other applications hinge upon the successful miniaturization of components and integration of piezoelectrics and metals into these systems. In this article, a comprehensive review of micromachined piezoelectric transducer technology will be presented. Piezoelectric materials in bulk and thin film forms will be reviewed and fabrication techniques for the integration of these materials for microsensor applications will be presented. Recent advances in various piezoelectric microsensors will be presented through specific examples. This review will conclude with a critical assessment of the future trends and promise of this technology.

Tadigadapa, S.; Mateti, K.

2009-09-01

433

Deep-penetration photoacoustic array imaging of calcifications  

NASA Astrophysics Data System (ADS)

Calcifications are one of the most important indicators for early breast cancer detection. We explore the feasibility of deep-penetration photoacoustic (PA) imaging of calcifications based on a medical ultrasound array imaging platform. Intralipid and chicken breast phantoms embedded with different-sized hydroxyapatite (HA) particles, which are the major components of calcifications, were imaged to verify the equipment's capability and penetration depth for the visualization of calcifications. An optimal near-infrared excitation wavelength was selected to maximize PA signals of HAs, resulting in a better HA signal-to-blood ratio. We demonstrated that PA imaging is capable of visualizing 0.5-mm HA particles at a depth of 3 cm in chicken breast phantoms. The noise-equivalent penetration depth of the system for visualizing 0.5-mm HA particles in the human breast was estimated to be about 2.9 to 3.5 cm, which is clinically relevant as calcifications are usually found at a depth of 0.6 to 3.0 cm. Moreover, the feasibility of differentiating HA from blood by the PA spectroscopic technique was presented and the mechanism of the HA signal generation was discussed. The results show that PA imaging is a promising technique for real-time visualization of breast calcifications.

Hsiao, Tsai-Chu; Cheng, Yao-Yu; Tein, Wan-Ting; Luo, Shih-Bin; Chiou, De-Yi; Chung, Ren-Jei; Li, Meng-Lin

2013-06-01

434

Deep-penetration photoacoustic array imaging of calcifications.  

PubMed

Calcifications are one of the most important indicators for early breast cancer detection. We explore the feasibility of deep-penetration photoacoustic (PA) imaging of calcifications based on a medical ultrasound array imaging platform. Intralipid and chicken breast phantoms embedded with different-sized hydroxyapatite (HA) particles, which are the major components of calcifications, were imaged to verify the equipment's capability and penetration depth for the visualization of calcifications. An optimal near-infrared excitation wavelength was selected to maximize PA signals of HAs, resulting in a better HA signal-to-blood ratio. We demonstrated that PA imaging is capable of visualizing 0.5-mm HA particles at a depth of 3 cm in chicken breast phantoms. The noise-equivalent penetration depth of the system for visualizing 0.5-mm HA particles in the human breast was estimated to be about 2.9 to 3.5 cm, which is clinically relevant as calcifications are usually found at a depth of 0.6 to 3.0 cm. Moreover, the feasibility of differentiating HA from blood by the PA spectroscopic technique was presented and the mechanism of the HA signal generation was discussed. The results show that PA imaging is a promising technique for real-time visualization of breast calcifications. PMID:23733018

Hsiao, Tsai-Chu; Cheng, Yao-Yu; Tein, Wan-Ting; Luo, Shih-Bin; Chiou, De-Yi; Chung, Ren-Jei; Li, Meng-Lin

2013-06-01

435

Non-contact photoacoustic tomography and ultrasonography for brain imaging  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

436

Contrast-enhanced photoacoustic imaging of live lobster nerve cord  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging provides optical contrast with good penetration and high spatial resolution, making it an attractive tool for noninvasive neural applications. We chose a commercial dye (NK2761) commonly used for optical imaging of membrane potential to enhance photoacoustic images of the live lobster nerve cord. The abdominal segment of the nerve cord was excised, stained and positioned in a custom neural recording system, enabling electrical stimulation and recording of compound action potentials. Photoacoustic and pulse echo images were also collected using a commercial ultrasound scanner and a 10-MHz linear probe. A wavelength-tunable pulsed laser source (SureliteTM, 5 ns, ~15 mJ, 30 mJ/cm2) operating at 20 Hz produced photoacoustic waves. Longitudinal photoacoustic scans of a 25-mm segment of the excised nerve cord, including ganglionic and axonal processes, were collected and displayed every 7 seconds. Without the contrast agent, an average of 10 scans produced a peak photoacoustic signal 6 dB over background noise. An additional 29 dB was obtained after the nerve was submerged in the dye for 20 minutes. The gain decreased to 23 dB and 14 dB at 810 nm and 910 nm, respectively - consistent with the dye's optical absorbance measured using a portable spectrometer. The contrast-enhanced photoacoustic signal had a broad spectrum peaking at 4 MHz, and, after high pass filtering, images approached 200-?m spatial resolution. The hybrid imaging system, which provided several hours of electrical stimulation and recording, represents a robust testbed to develop novel photoacoustic contrast for neural applications.

Witte, Russell S.; Huang, S.; Ashkenazi, S.; Kim, K.; O'Donnell, M.

2007-03-01

437

Photoacoustic trace gas sensing : application to fruit and insects  

Microsoft Academic Search

A novel photoacoustic spectrometer has been applied to study trace gas emissions by fruit and insects. The spectrometer is based on a newly designed CO laser that can operate on 400 laser lines between 5.1-8.0 and 2.8-4.1 micrometer (delta v=1 and 2 mode, respectively). The spectrometer is equipped with three intracavity photoacoustic cells which introduces additional losses in the laser

Stefan Timotheüs Persijn

2001-01-01

438

Fast-scanning ultrasonic-photoacoustic biomicroscope: in vivo performance  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

439

Photoacoustic Doppler Effect from Flowing Small Light-Absorbing Particles  

NASA Astrophysics Data System (ADS)

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

Fang, Hui; Maslov, Konstantin; Wang, Lihong V.

2007-11-01

440

Modification of a commercial spectrophotometer for photoacoustic measurement  

SciTech Connect

This note describes how a commercial UV-VIS-NIR spectrophotometer may be adapted to function as a double beam photoacoustic spectrophotometer operating at visible wavelengths. Modification of a Varian Cary 17 spectrophotometer was carried out first by dismounting the photomultiplier tube detector module and the cell compartment of the spectrophotometer. The sample and the reference beams were focused through two externally mounted quartz lenses onto the sample and reference photoacoustic cells, respectively.

Bandyopadhyay, S.; Harris, J.M.; Eyring, E.M.

1983-11-01

441

In vivo photoacoustic mapping of lymphatic systems with plasmon-resonant nanostars  

PubMed Central

Plasmon-resonant nanostars (NSTs) provide excellent contrast enhancement for photoacoustic tomography. The high photoacoustic sensitivity of NSTs at near-infrared wavelengths enable their in vivo detection in rat sentinel lymph nodes and vessels, with direct application toward lymphangiography.

Kim, Chulhong; Song, Hyon-Min; Cai, Xin; Yao, Junjie; Wei, Alexander; Wang, Lihong V.

2011-01-01

442

Piezoelectricity, ferroelectricity, and crystal structure  

Microsoft Academic Search

By visualizing polar crystals as a network of permanent dipole moments, the piezo- and ferroelectric properties of dielectrics may be derived from the standpoint of molecular symmetry. This approach is used to clarify the relation between the sphalerite and wurtzite structures, the ferroelectric feedback effect in barium titanate, aspects of domain formation, and the interrelationship between ferro and piezoelectricity.

A. von Hippel

1952-01-01