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Sample records for array photoacoustic tomographic

  1. Array-based photoacoustic spectroscopy

    Science.gov (United States)

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

    2005-03-22

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

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

    Science.gov (United States)

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

    2006-02-14

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

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

    Science.gov (United States)

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

    2005-03-29

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

  4. Motion Estimation and Correction in Photoacoustic Tomographic Reconstruction

    CERN Document Server

    Chung, Julianne

    2016-01-01

    Motion, e.g., due to patient movement or improper device calibration, is inevitable in many imaging modalities such as photoacoustic tomography (PAT) by a rotating system and can lead to undesirable motion artifacts in image reconstructions, if ignored. In this paper, we establish a hybrid-type model for PAT that incorporates motion in the model. We first introduce an approximate continuous model and establish two uniqueness results for simple parameterized motion models. Then we formulate the discrete problem of simultaneous motion estimation and image reconstruction as a separable nonlinear least squares problem and describe an automatic approach to detect and eliminate motion artifacts during the reconstruction process. Numerical examples validate our methods.

  5. Small-animal whole-body imaging using a photoacoustic full ring array system

    Science.gov (United States)

    Xia, Jun; Guo, Zijian; Aguirre, Andres; Zhu, Quing; Wang, Lihong V.

    2011-03-01

    In this report, we present a novel 3D photoacoustic computed tomography (PACT) system for small-animal whole-body imaging. The PACT system, based on a 512-element full-ring transducer array, received photoacoustic signals primarily from a 2-mm-thick slice. The light was generated by a pulse laser, and can either illuminate from the top or be reshaped to illuminate the sample from the side, using a conical lens and an optical condenser. The PACT system was capable of acquiring an in-plane image in 1.6 s; by scanning the sample in the elevational direction, a 3D tomographic image could be constructed. We tested the system by imaging a cylindrical phantom made of human hairs immersed in a scattering medium. The reconstructed image achieved an in-plane resolution of 0.1 mm and an elevational resolution of 1 mm. After deconvolution in the elevational direction, the 3D image was found to match well with the phantom. The system was also used to image a baby mouse in situ; the spinal cord and ribs can be seen easily in the reconstructed image. Our results demonstrate that the PACT system has the potential to be used for fast small-animal whole-body tomographic imaging.

  6. Light Focusing and Two-Dimensional Imaging Through Scattering Media using the Photoacoustic Transmission-Matrix with an Ultrasound Array

    CERN Document Server

    Chaigne, Thomas; Katz, Ori; Bossy, Emmanuel; Gigan, Sylvain

    2014-01-01

    We implement the photoacoustic transmission-matrix approach on a two-dimensional photoacoustic imaging system, using a 15 MHz linear ultrasound array. Using a black leaf skeleton as a complex absorbing structure, we demonstrate that the photoacoustic transmission-matrix approach allows to reveal structural features that are invisible in conventional photoacoustic images, as well as to selectively control light focusing on absorbing targets, leading to a local enhancement of the photoacoustic signal.

  7. Guided Wave Annular Array Sensor Design for Improved Tomographic Imaging

    Science.gov (United States)

    Koduru, Jaya Prakash; Rose, Joseph L.

    2009-03-01

    Guided wave tomography for structural health monitoring is fast emerging as a reliable tool for the detection and monitoring of hotspots in a structure, for any defects arising from corrosion, crack growth etc. To date guided wave tomography has been successfully tested on aircraft wings, pipes, pipe elbows, and weld joints. Structures practically deployed are subjected to harsh environments like exposure to rain, changes in temperature and humidity. A reliable tomography system should take into account these environmental factors to avoid false alarms. The lack of mode control with piezoceramic disk sensors makes it very sensitive to traces of water leading to false alarms. In this study we explore the design of annular array sensors to provide mode control for improved structural tomography, in particular, addressing the false alarm potential of water loading. Clearly defined actuation lines in the phase velocity dispersion curve space are calculated. A dominant in-plane displacement point is found to provide a solution to the water loading problem. The improvement in the tomographic images with the annular array sensors in the presence of water traces is clearly illustrated with a series of experiments. An annular array design philosophy for other problems in NDE/SHM is also discussed.

  8. In vivo three-dimensional photoacoustic imaging based on a clinical matrix array ultrasound probe

    Science.gov (United States)

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

    2012-06-01

    We present an integrated photoacoustic and ultrasonic three-dimensional (3-D) volumetric imaging system based on a two-dimensional (2-D) matrix array ultrasound probe. A wavelength-tunable dye laser pumped by a Q-switched Nd:YAG laser serves as the light source and a modified commercial ultrasound imaging system (iU22, Philips Healthcare) with a 2-D array transducer (X7-2, Philips Healthcare) detects both the pulse-echo ultrasound and photoacoustic signals. A multichannel data acquisition system acquires the RF channel data. The imaging system enables rendering of co-registered 3-D ultrasound and photoacoustic images without mechanical scanning. The resolution along the azimuth, elevation, and axial direction are measured to be 0.69, 0.90 and 0.84 mm for photoacoustic imaging. In vivo 3-D photoacoustic mapping of the sentinel lymph node was demonstrated in a rat model using methylene blue dye. These results highlight the clinical potential of 3-D PA imaging for identification of sentinel lymph nodes for cancer staging in humans.

  9. I vivo three-dimensional photoacoustic imaging based on a clinicall matrix array ultrasound probe

    NARCIS (Netherlands)

    Wang, Y.; Erpelding, T.N.; Jankovic, L.; Guo, Z.; Robert, J.L.; David, G.; Wang, L.V.

    2011-01-01

    We present an integrated photoacoustic and ultrasonic three-dimensional (3D) volumetric imaging system based on a two-dimensional (2D) matrix array ultrasound probe. A wavelength-tunable dye laser pumpedby a Q-switched Nd:YAG laser serves as the light source and a modified commercial ultrasound imag

  10. Single-side access, isotropic resolution and multispectral 3D photoacoustic imaging with rotate-translate scanning of ultrasonic detector array

    CERN Document Server

    Gateau, Jérôme; Chassot, Jean-Marie; Bossy, Emmanuel

    2015-01-01

    Photoacoustic imaging can achieve high-resolution three-dimensional visualization of optical absorbers at penetration depths ~ 1 cm in biological tissues by detecting optically-induced high ultrasound frequencies. Tomographic acquisition with ultrasound linear arrays offers an easy implementation of single-side access, parallelized and high-frequency detection, but usually comes with an image quality impaired by the directionality of the detectors. Indeed, a simple translation of the array perpendicularly to its median imaging plane is often used, but results both in a poor resolution in the translation direction and in strong limited view artifacts. To improve the spatial resolution and the visibility of complex structures while keeping a planar detection geometry, we introduce, in this paper, a novel rotate-translate scanning scheme, and investigate the performance of a scanner implemented at 15 MHz center frequency. The developed system achieved a quasi-isotropic uniform 3D resolution of ~170 um over a cub...

  11. Realtime photoacoustic microscopy in vivo with a 30-MHz ultrasound array transducer

    OpenAIRE

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

    2008-01-01

    We present a novel high-frequency photoacoustic microscopy system capable of imaging the microvasculature of living subjects in realtime to depths of a few mm. The system consists of a high-repetition-rate Q-switched pump laser, a tunable dye laser, a 30-MHz linear ultrasound array transducer, a multichannel high-frequency data acquisition system, and a shared-RAM multi-core-processor computer. Data acquisition, beamforming, scan conversion, and display are implemented in realtime at 50 frame...

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

    Science.gov (United States)

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

    2014-10-20

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

  13. Interventional multispectral photoacoustic imaging with a clinical linear array ultrasound probe for guiding nerve blocks

    Science.gov (United States)

    Xia, Wenfeng; West, Simeon J.; Nikitichev, Daniil I.; Ourselin, Sebastien; Beard, Paul C.; Desjardins, Adrien E.

    2016-03-01

    Accurate identification of tissue structures such as nerves and blood vessels is critically important for interventional procedures such as nerve blocks. Ultrasound imaging is widely used as a guidance modality to visualize anatomical structures in real-time. However, identification of nerves and small blood vessels can be very challenging, and accidental intra-neural or intra-vascular injections can result in significant complications. Multi-spectral photoacoustic imaging can provide high sensitivity and specificity for discriminating hemoglobin- and lipid-rich tissues. However, conventional surface-illumination-based photoacoustic systems suffer from limited sensitivity at large depths. In this study, for the first time, an interventional multispectral photoacoustic imaging (IMPA) system was used to image nerves in a swine model in vivo. Pulsed excitation light with wavelengths in the ranges of 750 - 900 nm and 1150 - 1300 nm was delivered inside the body through an optical fiber positioned within the cannula of an injection needle. Ultrasound waves were received at the tissue surface using a clinical linear array imaging probe. Co-registered B-mode ultrasound images were acquired using the same imaging probe. Nerve identification was performed using a combination of B-mode ultrasound imaging and electrical stimulation. Using a linear model, spectral-unmixing of the photoacoustic data was performed to provide image contrast for oxygenated and de-oxygenated hemoglobin, water and lipids. Good correspondence between a known nerve location and a lipid-rich region in the photoacoustic images was observed. The results indicate that IMPA is a promising modality for guiding nerve blocks and other interventional procedures. Challenges involved with clinical translation are discussed.

  14. Photoacoustic and Doppler ultrasound for oxygen consumption estimation: implementation on a clinical array system

    Science.gov (United States)

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

    2011-03-01

    Recently, we have developed a combined photoacoustic and high-frequency Doppler ultrasound system with a single element transducer to estimate the metabolic rate of oxygen consumption in small animal models. However, the long scanning time due to mechanical motion may be a limitation of our swept-scan system. In this work, the single element transducer was replaced by a clinical array transducer which may provide more accurate flow velocity estimations, higher frame rates, improved penetration depth, and improved depth-of-field due to dynamic focusing capabilities. We used an array system from Verasonics Inc. which enables flexible pulse-sequence programming and parallel channel data acquisition, along with a pulsed laser and optical parametric oscillator. For flow estimation, we implemented a flash- Doppler sequence which transmits ensembles of plane-wave excitations. Echo signals are beamformed and subjected to wall-filtering and Kasai flow estimation algorithms. High frame rates over a wide region can be achieved. Combined interlaced photoacoustic and Doppler imaging on flow phantoms has been performed on this system. We demonstrate the ability to image animal blood to depths of 1.5-cm with high signal-to-noise with both modalities. The light penetration is 2-cm. We discuss the performance of Doppler flow estimation and photoacoustic oxygen saturation estimation and their role in future work of estimating oxygen consumption.

  15. 3D electrical tomographic imaging using vertical arrays of electrodes

    Science.gov (United States)

    Murphy, S. C.; Stanley, S. J.; Rhodes, D.; York, T. A.

    2006-11-01

    Linear arrays of electrodes in conjunction with electrical impedance tomography have been used to spatially interrogate industrial processes that have only limited access for sensor placement. This paper explores the compromises that are to be expected when using a small number of vertically positioned linear arrays to facilitate 3D imaging using electrical tomography. A configuration with three arrays is found to give reasonable results when compared with a 'conventional' arrangement of circumferential electrodes. A single array yields highly localized sensitivity that struggles to image the whole space. Strategies have been tested on a small-scale version of a sludge settling application that is of relevance to the industrial sponsor. A new electrode excitation strategy, referred to here as 'planar cross drive', is found to give superior results to an extended version of the adjacent electrodes technique due to the improved uniformity of the sensitivity across the domain. Recommendations are suggested for parameters to inform the scale-up to industrial vessels.

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

    NARCIS (Netherlands)

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

    2014-01-01

    Ultrasound and photoacoustics can be utilized as complementary imaging techniques to improve clinical diagnoses. Photoacoustics provides optical contrast and functional information while ultrasound provides structural and anatomical information. As of yet, photoacoustic imaging uses large and expens

  17. Standoff photoacoustic detections with high-sensitivity microphones and acoustic arrays

    Science.gov (United States)

    Choa, Fow-Sen; Wang, Chen-Chia; Khurgin, Jacob; Samuels, Alan; Trivedi, Sudhir; Gupta, Deepa

    2016-05-01

    Standoff detection of dangerous chemicals like explosives, nerve gases, and harmful aerosols has continuously been an important subject due to the serious concern about terrorist threats to both overseas and homeland lives and facility. Compared with other currently available standoff optical detection techniques, like Raman, photo-thermal, laser induced breakdown spectroscopy,...etc., photoacoustic (PA) sensing has the advantages of background free and very high detection sensitivity, no need of back reflection surfaces, and 1/R instead of 1/R2 signal decay distance dependence. Furthermore, there is still a great room for PA sensitivity improvement by using different PA techniques, including lockin amplifier, employing new microphones, and microphone array techniques. Recently, we have demonstrated standoff PA detection of isopropanol vapor, solid phase TNT and RDX at a standoff distance. To further calibrate the detection sensitivity, we use nerve gas simulants that were generated and calibrated by a commercial vapor generator. For field operations, array of microphones and microphone-reflector pairs can be utilized to achieve noise rejection and signal enhancement. We have experimentally demonstrated signal enhancement and noise reduction using an array of 4 microphone/4 reflector system as well as an array of 16-microphone/1 reflector. In this work we will review and compare different standoff techniques and discuss the advantages of using different photoacoustic techniques. We will also discuss new advancement of using new types of microphone and the performance comparison of using different structure of microphone arrays and combining lock-in amplifier with acoustic arrays. Demonstration of out-door real-time operations with high power mid-IR laser and microphone array will be presented.

  18. Continuous, high-speed, volumetric photoacoustic microscopy via a field programmable gate array

    Science.gov (United States)

    Mattison, Scott P.; Shelton, Ryan L.; Maxson, Ryan T.; Applegate, Brian E.

    2013-03-01

    The ability to collect data in real time is important in all biological imaging modalities that aim to image dynamic processes. Photoacoustic Microscopy (PAM) is a rapidly growing biomedical imaging technique that is often used to image microvasculature and melanoma, and is capable of fully rendering three-dimensional images. However, due to the bi-polar nature of the PAM signal, post processing through demodulation is required to accurately display morphological data. Typically, demodulation requires post processing of the data, limiting its use in real-time applications. This results in many PAM systems displaying data through maximum amplitude projection (MAP) images, completely ignoring the axial dimension of their scans and throwing away useful data. We overcome this processing limit by utilizing a configurable integrated circuit known as a Field Programmable Gate Array (FPGA). The FPGA allows us to perform quadrature demodulation of the photoacoustic signal as it is being collected. The result is a PAM system capable of producing continuous, morphologically accurate B-scans and volumes at a rate limited only by the repetition rate of the laser. This allows us to generate accurately rendered volumes at the same speed as MAP images. With a 100 KHz actively q-switched laser we are able to generate 200 by 200 pixel b-scans at a rate of 500 Hz. The imaging potential of the system has been demonstrated in volumes of human hair phantoms and chick embryo vasculature. This system is capable of 50 x 50 x 50 volume stacks processed and displayed at better than video rate.

  19. High-speed dynamic 3D photoacoustic imaging of sentinel lymph node in a murine model using an ultrasound array.

    Science.gov (United States)

    Song, Liang; Kim, Chulhong; Maslov, Konstantin; Shung, K Kirk; Wang, Lihong V

    2009-08-01

    Noninvasive photoacoustic sentinel lymph node (SLN) mapping with high spatial resolution has the potential to improve the false negative rate and eliminate the use of radioactive tracers in SLN identification. In addition, the demonstrated high spatial resolution may enable physicians to replace SLN biopsy with fine needle aspiration biopsy, and thus reduce the risk of associated morbidity. The primary goal of this study is to demonstrate the feasibility of high-speed 3D photoacoustic imaging of the uptake and clearance dynamics of Evans blue dye in SLNs. The photoacoustic imaging system was developed with a 30 MHz ultrasound array and a kHz repetition rate laser system. It acquires one 3D photoacoustic image of 166 B-scan frames in 1 s, with axial, lateral, and elevational resolutions of 25, 70, and 200 microm, respectively. With optic-fiber based light delivery, the entire system is compact and is convenient to use. Upon injection of Evans blue, a blue dye currently used in clinical SLN biopsy, SLNs in mice and rats were accurately and noninvasively mapped in vivo using our imaging system. In our experiments, the SLNs were found to be located at approximately 0.65 mm below the skin surface in mice and approximately 1.2 mm in rats. In some cases, lymph vessels and lymphatic valves were also imaged. The dye dynamics--accumulation and clearance--in SLNs were quantitatively monitored by sequential 3D imaging with temporal resolution of as high as approximately 6 s. The demonstrated capability suggests that high-speed 3D photoacoustic imaging should facilitate the understanding of the dynamics of various dyes in SLNs and potentially help identify SLNs with high accuracy. PMID:19746805

  20. High-frequency annular array with coaxial illumination for dual-modality ultrasonic and photoacoustic imaging

    Science.gov (United States)

    Filoux, Erwan; Sampathkumar, Ashwin; Chitnis, Parag V.; Aristizábal, Orlando; Ketterling, Jeffrey A.

    2013-05-01

    This paper presents a combined ultrasound and photoacoustic (PA) imaging (PAI) system used to obtain high-quality, co-registered images of mouse-embryo anatomy and vasculature. High-frequency ultrasound (HFU, >20 MHz) is utilized to obtain high-resolution anatomical images of small animals while PAI provides high-contrast images of the vascular network. The imaging system is based on a 40 MHz, 5-element, 6 mm aperture annular-array transducer with a 800 μm diameter hole through its central element. The transducer was integrated in a cage-plate assembly allowing for a collimated laser beam to pass through the hole so that the optical and acoustic beams were collinear. The assembly was mounted on a two-axis, motorized stage to enable the simultaneous acquisition of co-registered HFU and PA volumetric data. Data were collected from all five elements in receive and a synthetic-focusing algorithm was applied in post-processing to beamform the data and increase the spatial resolution and depth-of-field (DOF) of the HFU and PA images. Phantom measurements showed that the system could achieve high-resolution images (down to 90 μm for HFU and 150 μm for PAI) and a large DOF of >8 mm. Volume renderings of a mouse embryo showed that the scanner allowed for visualizing morphologically precise anatomy of the entire embryo along with corresponding co-registered vasculature. Major head vessels, such as the superior sagittal sinus or rostral vein, were clearly identified as well as limb bud vasculature.

  1. Multi-view Hilbert transformation in full-ring-transducer-array based photoacoustic computed tomography (Conference Presentation)

    Science.gov (United States)

    Li, Lei; Li, Guo; Zhu, Liren; Xia, Jun; Wang, Lihong V.

    2016-03-01

    Photoacoustic tomography (PAT) exploits optical contrast and ultrasonic detection principles to form images of absorbed optical energy density within tissue. Based on the photoacoustic effect, PAT directly and quantitatively measures specific optical absorption. A full-ring ultrasonic transducer array based photoacoustic computed tomography (PACT) system was recently developed for small animal whole-body imaging with a full-view detection angle and high in-plane resolution (100 µm). However, due to the band-pass frequency response of the piezoelectric transducer elements, the reconstructed images present bipolar (both positive and negative) pixel values, which is artificial and counterintuitive for physicians and biologists seeking to interpret the image. Moreover, bipolar pixel values hinder quantification of physiological parameters, such as oxygen saturation and blood flow speed. Unipolar images can be obtained by deconvolving the raw channel data with the transducer's electrical impulse response and applying non-negativity during iteration, but this process requires complex transducer modeling and time-consuming computation. Here, we present a multi-view Hilbert transformation method to recover the unipolar initial pressure for full-ring PACT. Multi-view Hilbert transformation along the acoustic wave propagation direction minimizes reconstruction artifacts during envelope extraction and maintains the signal-to-noise ratio of the reconstructed images. The in-plane isotropic spatial resolution of this method was quantified to 168 μm within a 20 × 20 mm2 field of view. The effectiveness of the proposed algorithm was first validated by numerical simulations and then demonstrated with ex-vivo mouse brain structural imaging and in-vivo mouse wholebody imaging.

  2. Objective assessment and design improvement of a staring, sparse transducer array by the spatial crosstalk matrix for 3D photoacoustic tomography.

    Directory of Open Access Journals (Sweden)

    Philip Wong

    Full Text Available Accurate reconstruction of 3D photoacoustic (PA images requires detection of photoacoustic signals from many angles. Several groups have adopted staring ultrasound arrays, but assessment of array performance has been limited. We previously reported on a method to calibrate a 3D PA tomography (PAT staring array system and analyze system performance using singular value decomposition (SVD. The developed SVD metric, however, was impractical for large system matrices, which are typical of 3D PAT problems. The present study consisted of two main objectives. The first objective aimed to introduce the crosstalk matrix concept to the field of PAT for system design. Figures-of-merit utilized in this study were root mean square error, peak signal-to-noise ratio, mean absolute error, and a three dimensional structural similarity index, which were derived between the normalized spatial crosstalk matrix and the identity matrix. The applicability of this approach for 3D PAT was validated by observing the response of the figures-of-merit in relation to well-understood PAT sampling characteristics (i.e. spatial and temporal sampling rate. The second objective aimed to utilize the figures-of-merit to characterize and improve the performance of a near-spherical staring array design. Transducer arrangement, array radius, and array angular coverage were the design parameters examined. We observed that the performance of a 129-element staring transducer array for 3D PAT could be improved by selection of optimal values of the design parameters. The results suggested that this formulation could be used to objectively characterize 3D PAT system performance and would enable the development of efficient strategies for system design optimization.

  3. Multiple-illumination photoacoustic tomography

    Science.gov (United States)

    Barber, Quinn M.; Zemp, Roger J.

    2016-03-01

    Previously we described the potential for multiple illumination photoacoustic tomography to provide quantitative reconstructions, however this work used only simulated data. We have developed a custom photoacoustic-ultrasound tomography system capable of multiple illuminations and parallel acquisition from a 256 element 5 MHz transducer ring array with 8-cm diameter. The multiple illumination scheme uses a free-space light delivery geometry where a rotational stage scans a pulsed laser beam onto different incident locations around the sample. For each illumination location a photoacoustic image is reconstructed using a modified backprojection algorithm. Images from different source locations have the potential to be combined to form an improved deep-tissue image using our previously developed iterative algorithms. We complement the photoacoustic imaging data with unique ultrasound imaging data. Most previous ultrasound tomography methods have used migration algorithms, iterative ray-based analysis, wave-equation modeling, or frequency-based algorithms that all demand large amounts of data and computational power. We propose a new UST method that offers isotropic resolution, provides scattering contrast, as well as the potential for measuring ultrasound scattering anisotropy and decoupling density and compressibility contributions. The imaging system is driven by a Verasonics scan engine and programmed for both ultrasound and photoacoustic imaging modes. Resolution has been measured to be 150 μm for ultrasound and 200 μm for photoacoustic images. Imaging capabilities are demonstrated on phantoms with custom-tailored ultrasound scattering and optical properties, as well as in murine models.

  4. Assessment of neurovascular dynamics during transient ischemic attack by the novel integration of micro-electrocorticography electrode array with functional photoacoustic microscopy.

    Science.gov (United States)

    Liu, Yu-Hang; Liao, Lun-De; Tan, Stacey Sze Hui; Kwon, Ki Yong; Ling, Ji Min; Bandla, Aishwarya; Shih, Yen-Yu Ian; Tan, Eddie Tung Wee; Li, Wen; Ng, Wai Hoe; Lai, Hsin-Yi; Chen, You-Yin; Thakor, Nitish V

    2015-10-01

    This study developed a novel system combining a 16-channel micro-electrocorticography (μECoG) electrode array and functional photoacoustic microscopy (fPAM) to examine changes in neurovascular functions following transient ischemic attack (TIA) in rats. To mimic the pathophysiology of TIA, a modified photothrombotic ischemic model was developed by using 3 min illumination of 5 mW continuous-wave (CW) green laser light focusing on a distal branch of the middle cerebral artery (MCA). Cerebral blood volume (CBV), hemoglobin oxygen saturation (SO2), somatosensory evoked potentials (SSEPs) and alpha-to-delta ratio (ADR) were measured pre- and post-ischemia over a focal cortical region (i.e., 1.5×1.5 mm(2)). Unexpectedly, the SO2, peak-to-peak amplitude (PPA) of SSEPs and ADR recovered and achieved levels greater than the baseline values at the 4th hour post-ischemia induction without any intervention, whereas the CBV value only partially recovered. In other words, transient ischemia led to increased neural activity when the relative CBV was reduced, which may further compromise neural integrity or lead to subsequent vascular disease. This novel μECoG-fPAM system complements currently available imaging techniques and represents a promising technology for studying neurovascular coupling in animal models. PMID:26149348

  5. Assessment of neurovascular dynamics during transient ischemic attack by the novel integration of micro-electrocorticography electrode array with functional photoacoustic microscopy.

    Science.gov (United States)

    Liu, Yu-Hang; Liao, Lun-De; Tan, Stacey Sze Hui; Kwon, Ki Yong; Ling, Ji Min; Bandla, Aishwarya; Shih, Yen-Yu Ian; Tan, Eddie Tung Wee; Li, Wen; Ng, Wai Hoe; Lai, Hsin-Yi; Chen, You-Yin; Thakor, Nitish V

    2015-10-01

    This study developed a novel system combining a 16-channel micro-electrocorticography (μECoG) electrode array and functional photoacoustic microscopy (fPAM) to examine changes in neurovascular functions following transient ischemic attack (TIA) in rats. To mimic the pathophysiology of TIA, a modified photothrombotic ischemic model was developed by using 3 min illumination of 5 mW continuous-wave (CW) green laser light focusing on a distal branch of the middle cerebral artery (MCA). Cerebral blood volume (CBV), hemoglobin oxygen saturation (SO2), somatosensory evoked potentials (SSEPs) and alpha-to-delta ratio (ADR) were measured pre- and post-ischemia over a focal cortical region (i.e., 1.5×1.5 mm(2)). Unexpectedly, the SO2, peak-to-peak amplitude (PPA) of SSEPs and ADR recovered and achieved levels greater than the baseline values at the 4th hour post-ischemia induction without any intervention, whereas the CBV value only partially recovered. In other words, transient ischemia led to increased neural activity when the relative CBV was reduced, which may further compromise neural integrity or lead to subsequent vascular disease. This novel μECoG-fPAM system complements currently available imaging techniques and represents a promising technology for studying neurovascular coupling in animal models.

  6. Positron tomographs

    International Nuclear Information System (INIS)

    Specifications of position emission tomographs used for examination of brain and internal organs of human beings are presented. The tomograph comprises a detecting system, devices for detector displacement, sighting, calibration, electronics units (discriminators-formers, coincidence circuits, coders, buffer memory), detectors for detecting system position, bed for patient. Spatial resolution of the tomograph is determined by sizes of the detectors and their dispositin relatively to the object of examination. Besides, it depends on positron path in the investigated medium, deflections of the angle of scatter of annihilation quanta from 180 deg, distribution of points of gamma-quantum interaction by depth of the detector, filter and algorithm of image reconstruction, motion of organs of a patient, motion of labelled pharm-preparation in the organism. Such factors as absorption of annihilation radiation by substance of an object, radiation scattering and registration of random coincidences essentially affect the quality of tomographic image. It is shown that use of asseblies of microchannel plates and a scintillator on the base of barium fluoride permits to produce a coordinate-sensitive detector for a tomograph complying with highest requirements

  7. A Portable Laser Photoacoustic Methane Sensor Based on FPGA

    Science.gov (United States)

    Wang, Jianwei; Wang, Huili; Liu, Xianyong

    2016-01-01

    A portable laser photoacoustic sensor for methane (CH4) detection based on a field-programmable gate array (FPGA) is reported. A tunable distributed feedback (DFB) diode laser in the 1654 nm wavelength range is used as an excitation source. The photoacoustic signal processing was implemented by a FPGA device. A small resonant photoacoustic cell is designed. The minimum detection limit (1σ) of 10 ppm for methane is demonstrated. PMID:27657079

  8. Multiple-bandwidth photoacoustic tomography

    International Nuclear Information System (INIS)

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

  9. Tomographic Imaging of the Magmatic System at Mount St. Helens with the iMUSH Broadband Array

    Science.gov (United States)

    Ulberg, C. W.; Creager, K. C.; Levander, A.; Kiser, E.; Moran, S. C.; Abers, G. A.; Schmandt, B.; Vidale, J. E.; Houston, H.; Denlinger, R. P.; Williams, M. C. B.

    2015-12-01

    We deployed 70 broadband seismometers in the summer of 2014 to image the velocity structure beneath Mount St. Helens (MSH), Washington, USA as part of a collaborative project called imaging Magma Under St. Helens (iMUSH). Our goal is to illuminate the MSH magmatic system, using active- and passive-source seismology, magnetotellurics and petrology. Details of the velocity structure, coupled with other geophysical and geologic data, can help constrain the geometry and physical state of any bodies of melt beneath the volcano. The broadband array has a diameter of ~100 km centered on MSH with an average station spacing of 10 km, and will remain deployed through summer 2016. It is augmented by dozens of permanent stations in the area. We determine P-wave arrival times using Antelope software and incorporate permanent network picks for the region. We use the program struct3DP to invert travel times to obtain a 3-D seismic velocity model and relocate hypocenters, computing travel times using a 3-D eikonal-equation solver. There were more than 500 useable local events during the first year of iMUSH broadband recording, which to date have provided 5000 arrival times, with the number growing rapidly. The local events include 23 active shots that were set off in the summer of 2014 as part of the iMUSH experiment, which recorded with good signal-to-noise ratios across the entire array. The absolute P times will be augmented by differential times calculated by cross-correlation between observations at the same station for nearby event pairs. These will be incorporated into our model using double-difference tomography. We anticipate that our 3D velocity model will provide the highest resolution image of volcanic plumbing at MSH thus far. Our model interpretation will incorporate results from active-source and ambient noise tomography, receiver functions, magnetotellurics, and petrology.

  10. Photoacoustic microcantilevers

    Science.gov (United States)

    Thundat, Thomas G.; Van Neste, Charles W.; Brown, Gilbert M.; Senesac, Lawrence R.

    2012-06-05

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

  11. Photoacoustic Tomography System

    Directory of Open Access Journals (Sweden)

    J. D. Martínez-Ramírez

    2012-03-01

    Full Text Available Based on the pulsed photoacoustic effect, we set up an experimental system to obtain bi-dimensional images of optically-opaque samples embedded within the bulk of turbid medium. The turbid medium was made of agar gel mixed with single-sized nanoparticles; with these materials we induce an optical absorption and an optical scattering like that appearing in human tissues. The PA signals are generated from the absorption processes in the buried target, and then traveling through the bulk of scatter medium. The optical absorption properties and the shape of target, defines the amplitude and shape of the PA signals. This time the laser pulses are set from a pulsed Nd: YAG laser, with pulse width of 10 ns, at rate repetition of 10 Hz and wavelength set at 1064 nm. The signals generated in this way are registered by means of an ultrasonic transducer with resonance cut at 10 MHz. The sample was rotated to obtain as many as 36 projections which are used to feed an image reconstruction forward-projection algorithm based on the Radon Transform. As result we obtain 2D tomographic slices of three different samples.

  12. Towards photoacoustic mammography

    NARCIS (Netherlands)

    Kharin, Aleksey Anatolievich

    2005-01-01

    This research deals with developing the photoacoustic imaging technique for breast cancer detection. Photoacoustics brings together the strong aspects of ultrasound and optical imaging. Medical imaging with photoacoustics is relatively new, and promising for a lot of applications, one of which is br

  13. 4-D Photoacoustic Tomography

    Science.gov (United States)

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

    2013-01-01

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

  14. Reflection-artifact-free photoacoustic imaging using PAFUSion (photoacoustic-guided focused ultrasound)

    Science.gov (United States)

    Kuniyil Ajith Singh, Mithun; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2016-03-01

    Reflection artifacts caused by acoustic inhomogeneities are a main challenge to deep-tissue photoacoustic imaging. Photoacoustic transients generated by the skin surface and superficial vasculature will propagate into the tissue and reflect back from echogenic structures to generate reflection artifacts. These artifacts can cause problems in image interpretation and limit imaging depth. In its basic version, PAFUSion mimics the inward travelling wave-field from blood vessel-like PA sources by applying focused ultrasound pulses, and thus provides a way to identify reflection artifacts. In this work, we demonstrate reflection artifact correction in addition to identification, towards obtaining an artifact-free photoacoustic image. In view of clinical applications, we implemented an improved version of PAFUSion in which photoacoustic data is backpropagated to imitate the inward travelling wave-field and thus the reflection artifacts of a more arbitrary distribution of PA sources that also includes the skin melanin layer. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. We present a phantom experiment and initial in vivo measurements on human volunteers where we demonstrate significant reflection artifact reduction using our technique. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can reduce these artifacts significantly to improve the deep-tissue photoacoustic imaging.

  15. Photoacoustic imaging of carotid artery atherosclerosis

    Science.gov (United States)

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

    2014-11-01

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

  16. Miniaturized photoacoustic spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Okandan, Murat; Robinson, Alex; Nielson, Gregory N.; Resnick, Paul J.

    2016-08-09

    A low-power miniaturized photoacoustic sensor uses an optical microphone made by semiconductor fabrication techniques, and optionally allows for all-optical communication to and from the sensor. This allows integration of the photoacoustic sensor into systems with special requirements, such as those that would be reactive in an electrical discharge condition. The photoacoustic sensor can also be operated in various other modes with wide application flexibility.

  17. Improving visibility in photoacoustic imaging using dynamic speckle illumination

    CERN Document Server

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

    2013-01-01

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

  18. Gynecologic electrical impedance tomograph

    Science.gov (United States)

    Korjenevsky, A.; Cherepenin, V.; Trokhanova, O.; Tuykin, T.

    2010-04-01

    Electrical impedance tomography extends to the new and new areas of the medical diagnostics: lungs, breast, prostate, etc. The feedback from the doctors who use our breast EIT diagnostic system has induced us to develop the 3D electrical impedance imaging device for diagnostics of the cervix of the uterus - gynecologic impedance tomograph (GIT). The device uses the same measuring approach as the breast imaging system: 2D flat array of the electrodes arranged on the probe with handle is placed against the body. Each of the 32 electrodes of the array is connected in turn to the current source while the rest electrodes acquire the potentials on the surface. The current flows through the electrode of the array and returns through the remote electrode placed on the patient's limb. The voltages are measured relative to another remote electrode. The 3D backprojection along equipotential surfaces is used to reconstruct conductivity distribution up to approximately 1 cm in depth. Small number of electrodes enables us to implement real time imaging with a few frames per sec. rate. The device is under initial testing and evaluation of the imaging capabilities and suitability of usage.

  19. Taking advantage of acoustic inhomogeneities in photoacoustic measurements

    Science.gov (United States)

    Da Silva, Anabela; Handschin, Charles; Riedinger, Christophe; Piasecki, Julien; Mensah, Serge; Litman, Amélie; Akhouayri, Hassan

    2016-03-01

    Photoacoustic offers promising perspectives in probing and imaging subsurface optically absorbing structures in biological tissues. The optical uence absorbed is partly dissipated into heat accompanied with microdilatations that generate acoustic pressure waves, the intensity which is related to the amount of fluuence absorbed. Hence the photoacoustic signal measured offers access, at least potentially, to a local monitoring of the absorption coefficient, in 3D if tomographic measurements are considered. However, due to both the diffusing and absorbing nature of the surrounding tissues, the major part of the uence is deposited locally at the periphery of the tissue, generating an intense acoustic pressure wave that may hide relevant photoacoustic signals. Experimental strategies have been developed in order to measure exclusively the photoacoustic waves generated by the structure of interest (orthogonal illumination and detection). Temporal or more sophisticated filters (wavelets) can also be applied. However, the measurement of this primary acoustic wave carries a lot of information about the acoustically inhomogeneous nature of the medium. We propose a protocol that includes the processing of this primary intense acoustic wave, leading to the quantification of the surrounding medium sound speed, and, if appropriate to an acoustical parametric image of the heterogeneities. This information is then included as prior knowledge in the photoacoustic reconstruction scheme to improve the localization and quantification.

  20. In vivo demonstration of reflection artifact reduction in photoacoustic imaging using synthetic aperture photoacoustic-guided focused ultrasound (PAFUSion).

    Science.gov (United States)

    Singh, Mithun Kuniyil Ajith; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2016-08-01

    Reflection artifacts caused by acoustic inhomogeneities are a critical problem in epi-mode biomedical photoacoustic imaging. High light fluence beneath the probe results in photoacoustic transients, which propagate into the tissue and reflect back from echogenic structures. These reflection artifacts cause problems in image interpretation and significantly impact the contrast and imaging depth. We recently proposed a method called PAFUSion (Photoacoustic-guided focused ultrasound) to identify such reflection artifacts in photoacoustic imaging. In its initial version, PAFUSion mimics the inward-travelling wavefield from small blood vessel-like PA sources by applying ultrasound pulses focused towards these sources, and thus provides a way to identify the resulting reflection artifacts. In this work, we demonstrate reduction of reflection artifacts in phantoms and in vivo measurements on human volunteers. In view of the spatially distributed PA sources that are found in clinical applications, we implemented an improved version of PAFUSion where photoacoustic signals are backpropagated to imitate the inward travelling wavefield and thus the reflection artifacts. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can strongly reduce these artifacts to improve deep-tissue photoacoustic imaging. PMID:27570690

  1. In vivo demonstration of reflection artifact reduction in photoacoustic imaging using synthetic aperture photoacoustic-guided focused ultrasound (PAFUSion).

    Science.gov (United States)

    Singh, Mithun Kuniyil Ajith; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2016-08-01

    Reflection artifacts caused by acoustic inhomogeneities are a critical problem in epi-mode biomedical photoacoustic imaging. High light fluence beneath the probe results in photoacoustic transients, which propagate into the tissue and reflect back from echogenic structures. These reflection artifacts cause problems in image interpretation and significantly impact the contrast and imaging depth. We recently proposed a method called PAFUSion (Photoacoustic-guided focused ultrasound) to identify such reflection artifacts in photoacoustic imaging. In its initial version, PAFUSion mimics the inward-travelling wavefield from small blood vessel-like PA sources by applying ultrasound pulses focused towards these sources, and thus provides a way to identify the resulting reflection artifacts. In this work, we demonstrate reduction of reflection artifacts in phantoms and in vivo measurements on human volunteers. In view of the spatially distributed PA sources that are found in clinical applications, we implemented an improved version of PAFUSion where photoacoustic signals are backpropagated to imitate the inward travelling wavefield and thus the reflection artifacts. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can strongly reduce these artifacts to improve deep-tissue photoacoustic imaging.

  2. Photoacoustic clutter reduction by inversion of a linear scatter model using plane wave ultrasound measurements

    Science.gov (United States)

    Schwab, Hans-Martin; Beckmann, Martin F.; Schmitz, Georg

    2016-01-01

    Photoacoustic imaging aims to visualize light absorption properties of biological tissue by receiving a sound wave that is generated inside the observed object as a result of the photoacoustic effect. In clinical applications, the strong light absorption in human skin is a major problem. When high amplitude photoacoustic waves that originate from skin absorption propagate into the tissue, they are reflected back by acoustical scatterers and the reflections contribute to the received signal. The artifacts associated with these reflected waves are referred to as clutter or skin echo and limit the applicability of photoacoustic imaging for medical applications severely. This study seeks to exploit the acoustic tissue information gained by plane wave ultrasound measurements with a linear array in order to correct for reflections in the photoacoustic image. By deriving a theory for clutter waves in k-space and a matching inversion approach, photoacoustic measurements compensated for clutter are shown to be recovered. PMID:27446669

  3. Photoacoustic clutter reduction by inversion of a linear scatter model using plane wave ultrasound measurements.

    Science.gov (United States)

    Schwab, Hans-Martin; Beckmann, Martin F; Schmitz, Georg

    2016-04-01

    Photoacoustic imaging aims to visualize light absorption properties of biological tissue by receiving a sound wave that is generated inside the observed object as a result of the photoacoustic effect. In clinical applications, the strong light absorption in human skin is a major problem. When high amplitude photoacoustic waves that originate from skin absorption propagate into the tissue, they are reflected back by acoustical scatterers and the reflections contribute to the received signal. The artifacts associated with these reflected waves are referred to as clutter or skin echo and limit the applicability of photoacoustic imaging for medical applications severely. This study seeks to exploit the acoustic tissue information gained by plane wave ultrasound measurements with a linear array in order to correct for reflections in the photoacoustic image. By deriving a theory for clutter waves in k-space and a matching inversion approach, photoacoustic measurements compensated for clutter are shown to be recovered.

  4. Photoacoustic imaging and spectroscopy

    CERN Document Server

    Wang, Lihong

    2009-01-01

    Photoacoustics promises to revolutionize medical imaging and may well make as dramatic a contribution to modern medicine as the discovery of the x-ray itself once did. Combining electromagnetic and ultrasonic waves synergistically, photoacoustics can provide deep speckle-free imaging with high electromagnetic contrast at high ultrasonic resolution and without any health risk. While photoacoustic imaging is probably the fastest growing biomedical imaging technology, this book is the first comprehensive volume in this emerging field covering both the physics and the remarkable noninvasive applic

  5. Advances in tomographic PIV

    NARCIS (Netherlands)

    Novara, M.

    2013-01-01

    This research deals with advanced developments in 3D particle image velocimetry based on the tomographic PIV technique (Tomo-PIV). The latter is a relatively recent measurement technique introduced by Elsinga et al. in 2005, which is based on the tomographic reconstruction of particle tracers in thr

  6. Photoacoustic determination of blood vessel diameter

    Science.gov (United States)

    Kolkman, Roy G. M.; Klaessens, John H. G. M.; Hondebrink, Erwin; Hopman, Jeroen C. W.; de Mul, Frits F. M.; Steenbergen, Wiendelt; Thijssen, Johan M.; van Leeuwen, Ton G.

    2004-10-01

    A double-ring sensor was applied in photoacoustic tomographic imaging of artificial blood vessels as well as blood vessels in a rabbit ear. The peak-to-peak time (tgrpp) of the laser (1064 nm) induced pressure transient was used to estimate the axial vessel diameter. Comparison with the actual vessel diameter showed that the diameter could be approximated by 2ctgrpp, with c the speed of sound in blood. Using this relation, the lateral diameter could also precisely be determined. In vivo imaging and monitoring of changes in vessel diameters was feasible. Finally, acoustic time traces were recorded while flushing a vessel in the rabbit ear with saline, which proved that the main contribution to the laser-induced pressure transient is caused by blood inside the vessel and that the vessel wall gives only a minor contribution.

  7. Photoacoustic determination of blood vessel diameter

    International Nuclear Information System (INIS)

    A double-ring sensor was applied in photoacoustic tomographic imaging of artificial blood vessels as well as blood vessels in a rabbit ear. The peak-to-peak time (τpp) of the laser (1064 nm) induced pressure transient was used to estimate the axial vessel diameter. Comparison with the actual vessel diameter showed that the diameter could be approximated by 2cτpp, with c the speed of sound in blood. Using this relation, the lateral diameter could also precisely be determined. In vivo imaging and monitoring of changes in vessel diameters was feasible. Finally, acoustic time traces were recorded while flushing a vessel in the rabbit ear with saline, which proved that the main contribution to the laser-induced pressure transient is caused by blood inside the vessel and that the vessel wall gives only a minor contribution

  8. Computationally intelligent pulsed photoacoustics

    International Nuclear Information System (INIS)

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

  9. Photoacoustic Tomography using a Michelson Interferometer with Quadrature Phase Detection

    CERN Document Server

    Speirs, Rory W

    2013-01-01

    We present a pressure sensor based on a Michelson interferometer, for use in photoacoustic tomography. Quadrature phase detection is employed allowing measurement at any point on the mirror surface without having to retune the interferometer, as is typically required by Fabry-Perot type detectors. This opens the door to rapid full surface detection, which is necessary for clinical applications. Theory relating acoustic pressure to detected acoustic particle displacements is used to calculate the detector sensitivity, which is validated with measurement. Proof-of-concept tomographic images of blood vessel phantoms have been taken with sub-millimeter resolution at depths of several millimeters.

  10. Photoacoustic elastic oscillation and characterization

    CERN Document Server

    Gao, Fei; Zheng, Yuanjin

    2014-01-01

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

  11. Pulsed photoacoustic flow imaging with a handheld system.

    Science.gov (United States)

    van den Berg, Pim J; Daoudi, Khalid; Steenbergen, Wiendelt

    2016-02-01

    Flow imaging is an important technique in a range of disease areas, but estimating low flow speeds, especially near the walls of blood vessels, remains challenging. Pulsed photoacoustic flow imaging can be an alternative since there is little signal contamination from background tissue with photoacoustic imaging. We propose flow imaging using a clinical photoacoustic system that is both handheld and portable. The system integrates a linear array with 7.5 MHz central frequency in combination with a high-repetition-rate diode laser to allow high-speed photoacoustic imaging--ideal for this application. This work shows the flow imaging performance of the system in vitro using microparticles. Both two-dimensional (2-D) flow images and quantitative flow velocities from 12 to 75  mm/s were obtained. In a transparent bulk medium, flow estimation showed standard errors of ∼7% the estimated speed; in the presence of tissue-realistic optical scattering, the error increased to 40% due to limited signal-to-noise ratio. In the future, photoacoustic flow imaging can potentially be performed in vivo using fluorophore-filled vesicles or with an improved setup on whole blood.

  12. Tutorial on photoacoustic tomography.

    Science.gov (United States)

    Zhou, Yong; Yao, Junjie; Wang, Lihong V

    2016-06-01

    Photoacoustic tomography (PAT) has become one of the fastest growing fields in biomedical optics. Unlike pure optical imaging, such as confocal microscopy and two-photon microscopy, PAT employs acoustic detection to image optical absorption contrast with high-resolution deep into scattering tissue. So far, PAT has been widely used for multiscale anatomical, functional, and molecular imaging of biological tissues. We focus on PAT’s basic principles, major implementations, imaging contrasts, and recent applications. PMID:27086868

  13. Organosilicon phantom for photoacoustic imaging.

    Science.gov (United States)

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

    2015-04-01

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

  14. Clinical photoacoustic imaging of cancer

    Science.gov (United States)

    2016-01-01

    Photoacoustic imaging is a hybrid technique that shines laser light on tissue and measures optically induced ultrasound signal. There is growing interest in the clinical community over this new technique and its possible clinical applications. One of the most prominent features of photoacoustic imaging is its ability to characterize tissue, leveraging differences in the optical absorption of underlying tissue components such as hemoglobin, lipids, melanin, collagen and water among many others. In this review, the state-of-the-art photoacoustic imaging techniques and some of the key outcomes pertaining to different cancer applications in the clinic are presented. PMID:27669961

  15. Combined ultrasonic and photoacoustic system for deep tissue imaging

    Science.gov (United States)

    Kim, Chulhong; Erpelding, Todd N.; Jankovic, Ladislav; Wang, Lihong V.

    2011-03-01

    A combined ultrasonic and photoacoustic imaging system is presented that is capable of deep tissue imaging. The system consists of a modified clinical ultrasound array system and tunable dye laser pumped by a Nd:YAG laser. The system is designed for noninvasive detection of sentinel lymph nodes and guidance of needle biopsies for axillary lymph node staging in breast cancer patients. Using a fraction of the American National Standards Institute (ANSI) safety limit, photoacoustic imaging of methylene blue achieved penetration depths of greater than 5 cm in chicken breast tissue. Photoacoustic imaging sensitivity was measured by varying the concentration of methylene blue dye placed at a depth of 3 cm within surrounding chicken breast tissue. Signal-to-noise ratio, noise equivalent sensitivity, and axial spatial resolution were quantified versus depth based on in vivo and chicken breast tissue experiments. The system has been demonstrated in vivo for detecting sentinel lymph nodes in rats following intradermal injection of methylene blue. These results highlight the clinical potential of photoacoustic image-guided identification and needle biopsy of sentinel lymph nodes for axillary staging in breast cancer patients.

  16. Nonlinear photoacoustic spectroscopy of hemoglobin

    Energy Technology Data Exchange (ETDEWEB)

    Danielli, Amos; Maslov, Konstantin; Favazza, Christopher P.; Xia, Jun; Wang, Lihong V., E-mail: LHWANG@WUSTL.EDU [Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130 (United States)

    2015-05-18

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

  17. All-optical photoacoustic microscopy

    Directory of Open Access Journals (Sweden)

    Sung-Liang Chen

    2015-12-01

    Full Text Available Three-dimensional photoacoustic microscopy (PAM has gained considerable attention within the biomedical imaging community during the past decade. Detecting laser-induced photoacoustic waves by optical sensing techniques facilitates the idea of all-optical PAM (AOPAM, which is of particular interest as it provides unique advantages for achieving high spatial resolution using miniaturized embodiments of the imaging system. The review presents the technology aspects of optical-sensing techniques for ultrasound detection, such as those based on optical resonators, as well as system developments of all-optical photoacoustic systems including PAM, photoacoustic endoscopy, and multi-modality microscopy. The progress of different AOPAM systems and their representative applications are summarized.

  18. Photoacoustic tomography of vascular compliance in humans

    Science.gov (United States)

    Hai, Pengfei; Zhou, Yong; Liang, Jinyang; Li, Chiye; Wang, Lihong V.

    2015-12-01

    Characterization of blood vessel elastic properties can help in detecting thrombosis and preventing life-threatening conditions such as acute myocardial infarction or stroke. Vascular elastic photoacoustic tomography (VE-PAT) is proposed to measure blood vessel compliance in humans. Implemented on a linear-array-based photoacoustic computed tomography system, VE-PAT can quantify blood vessel compliance changes due to simulated thrombosis and occlusion. The feasibility of the VE-PAT system was first demonstrated by measuring the strains under uniaxial loading in perfused blood vessel phantoms and quantifying their compliance changes due to the simulated thrombosis. The VE-PAT system detected a decrease in the compliances of blood vessel phantoms with simulated thrombosis, which was validated by a standard compression test. The VE-PAT system was then applied to assess blood vessel compliance in a human subject. Experimental results showed a decrease in compliance when an occlusion occurred downstream from the measurement point in the blood vessels, demonstrating VE-PAT's potential for clinical thrombosis detection.

  19. Medical imaging with a microwave tomographic scanner.

    Science.gov (United States)

    Jofre, L; Hawley, M S; Broquetas, A; de los Reyes, E; Ferrando, M; Elias-Fusté, A R

    1990-03-01

    A microwave tomographic scanner for biomedical applications is presented. The scanner consists of a 64 element circular array with a useful diameter of 20 cm. Electronically scanning the transmitting and receiving antennas allows multiview measurements with no mechanical movement. Imaging parameters are appropriate for medical use: a spatial resolution of 7 mm and a contrast resolution of 1% for a measurement time of 3 s. Measurements on tissue-simulating phantoms and volunteers, together with numerical simulations, are presented to assess the system for absolute imaging of tissue distribution and for differential imaging of physiological, pathological, and induced changes in tissues. PMID:2329003

  20. Photoacoustic measurement of epidermal melanin

    Science.gov (United States)

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

    2003-06-01

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

  1. Reconstruction Formulas for Photoacoustic Sectional Imaging

    CERN Document Server

    Elbau, Peter; Schulze, Rainer

    2011-01-01

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

  2. Photoacoustic Effect and the Physics of Waves.

    Science.gov (United States)

    McDonald, F. Alan

    1980-01-01

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

  3. A novel fiber laser development for photoacoustic microscopy

    Science.gov (United States)

    Yavas, Seydi; Aytac-Kipergil, Esra; Arabul, Mustafa U.; Erkol, Hakan; Akcaalan, Onder; Eldeniz, Y. Burak; Ilday, F. Omer; Unlu, Mehmet B.

    2013-03-01

    Photoacoustic microscopy, as an imaging modality, has shown promising results in imaging angiogenesis and cutaneous malignancies like melanoma, revealing systemic diseases including diabetes, hypertension, tracing drug efficiency and assessment of therapy, monitoring healing processes such as wound cicatrization, brain imaging and mapping. Clinically, photoacoustic microscopy is emerging as a capable diagnostic tool. Parameters of lasers used in photoacoustic microscopy, particularly, pulse duration, energy, pulse repetition frequency, and pulse-to-pulse stability affect signal amplitude and quality, data acquisition speed and indirectly, spatial resolution. Lasers used in photoacoustic microscopy are typically Q-switched lasers, low-power laser diodes, and recently, fiber lasers. Significantly, the key parameters cannot be adjusted independently of each other, whereas microvasculature and cellular imaging, e.g., have different requirements. Here, we report an integrated fiber laser system producing nanosecond pulses, covering the spectrum from 600 nm to 1100 nm, developed specifically for photoacoustic excitation. The system comprises of Yb-doped fiber oscillator and amplifier, an acousto-optic modulator and a photonic-crystal fiber to generate supercontinuum. Complete control over the pulse train, including generation of non-uniform pulse trains, is achieved via the AOM through custom-developed field-programmable gate-array electronics. The system is unique in that all the important parameters are adjustable: pulse duration in the range of 1-3 ns, pulse energy up to 10 μJ, repetition rate from 50 kHz to 3 MHz. Different photocoustic imaging probes can be excited with the ultrabroad spectrum. The entire system is fiber-integrated; guided-beam-propagation rendersit misalignment free and largely immune to mechanical perturbations. The laser is robust, low-cost and built using readily available components.

  4. Integrated transrectal probe for translational ultrasound-photoacoustic imaging

    Science.gov (United States)

    Bell, Kevan L.; Harrison, Tyler; Usmani, Nawaid; Zemp, Roger J.

    2016-03-01

    A compact photoacoustic transrectal probe is constructed for improved imaging in brachytherapy treatment. A 192 element 5 MHz linear transducer array is mounted inside a small 3D printed casing along with an array of optical fibers. The device is fed by a pump laser and tunable NIR-optical parametric oscillator with data collected by a Verasonics ultrasound platform. This assembly demonstrates improved imaging of brachytherapy seeds in phantoms with depths up to 5 cm. The tuneable excitation in combination with standard US integration provides adjustable contrast between the brachytherapy seeds, blood filled tubes and background tissue.

  5. Photoacoustic imaging: current status and future development

    Science.gov (United States)

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

    2006-09-01

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

  6. Neurovascular photoacoustic tomography

    Directory of Open Access Journals (Sweden)

    Song Hu

    2010-06-01

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

  7. Reverse photoacoustic standoff spectroscopy

    Science.gov (United States)

    Van Neste, Charles W.; Senesac, Lawrence R.; Thundat, Thomas G.

    2011-04-12

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

  8. Photoacoustic point spectroscopy

    Science.gov (United States)

    Van Neste, Charles W.; Senesac, Lawrence R.; Thundat, Thomas G.

    2011-06-14

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

  9. Photoacoustic-guided focused ultrasound (PAFUSion for identifying reflection artifacts in photoacoustic imaging

    Directory of Open Access Journals (Sweden)

    Mithun Kuniyil Ajith Singh

    2015-12-01

    Full Text Available Influence of acoustic inhomogeneities and resulting reflection artifacts is an important problem in reflection-mode photoacoustic imaging. Absorption of light by skin and superficial optical absorbers will generate photoacoustic transients, which traverse into the tissue and get reflected from structures having different acoustic impedance. These reflected photoacoustic signals, when reconstructed, may appear in the region of interest, which causes difficulties in image interpretation. We propose a novel method to identify and potentially eliminate reflection artifacts in photoacoustic images using photoacoustic-guided focused ultrasound [PAFUSion]. Our method uses focused ultrasound pulses to mimic the wave field produced by photoacoustic sources and thus provides a way to identify reflection artifacts in clinical combined photoacoustic and pulse-echo ultrasound. Simulation and phantom results are presented to demonstrate the validity and impact of this method. Results show that PAFUSion can identify reflections in photoacoustic images and thus envisages potential for improving photoacoustic imaging of acoustically inhomogeneous tissue.

  10. The derivative-free Fourier shell identity for photoacoustics.

    Science.gov (United States)

    Baddour, Natalie

    2016-01-01

    In X-ray tomography, the Fourier slice theorem provides a relationship between the Fourier components of the object being imaged and the measured projection data. The Fourier slice theorem is the basis for X-ray Fourier-based tomographic inversion techniques. A similar relationship, referred to as the 'Fourier shell identity' has been previously derived for photoacoustic applications. However, this identity relates the pressure wavefield data function and its normal derivative measured on an arbitrary enclosing aperture to the three-dimensional Fourier transform of the enclosed object evaluated on a sphere. Since the normal derivative of pressure is not normally measured, the applicability of the formulation is limited in this form. In this paper, alternative derivations of the Fourier shell identity in 1D, 2D polar and 3D spherical polar coordinates are presented. The presented formulations do not require the normal derivative of pressure, thereby lending the formulas directly adaptable for Fourier based absorber reconstructions.

  11. Photoacoustic imaging: a potential new tool for arthritis

    Science.gov (United States)

    Wang, Xueding

    2012-12-01

    The potential application of photoacoustic imaging (PAI) technology to diagnostic imaging and therapeutic monitoring of inflammatory arthritis has been explored. The feasibility of our bench-top joint imaging systems in delineating soft articular tissue structures in a noninvasive manner was validated first on rat models and then on human peripheral joints. Based on the study on commonly used arthritis rat models, the capability of PAI to differentiate arthritic joints from the normal was also examined. With sufficient imaging depth, PAI can realize tomographic imaging of a human peripheral joint or a small-animal joint as a whole organ noninvasively. By presenting additional optical contrast and tissue functional information such as blood volume and blood oxygen saturation, PAI may provide an opportunity for early diagnosis of inflammatory joint disorders, e.g. rheumatoid arthritis, and for monitoring of therapeutic outcomes with improved sensitivity and accuracy.

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

    OpenAIRE

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

    2014-01-01

    In recent years, photoacoustics has attracted intensive research for both anatomical and functional biomedical imaging. However, the physical interaction between photoacoustic generated endogenous waves and an exogenous ultrasound wave is a largely unexplored area. Here, we report the initial results about the interaction of photoacoustic and external ultrasound waves leading to a micro-Doppler photoacoustic (mDPA) effect, which is experimentally observed and consistently modelled. It is base...

  13. Photoacoustic characterization of radiofrequency ablation lesions

    Science.gov (United States)

    Bouchard, Richard; Dana, Nicholas; Di Biase, Luigi; Natale, Andrea; Emelianov, Stanislav

    2012-02-01

    Radiofrequency ablation (RFA) procedures are used to destroy abnormal electrical pathways in the heart that can cause cardiac arrhythmias. Current methods relying on fluoroscopy, echocardiography and electrical conduction mapping are unable to accurately assess ablation lesion size. In an effort to better visualize RFA lesions, photoacoustic (PA) and ultrasonic (US) imaging were utilized to obtain co-registered images of ablated porcine cardiac tissue. The left ventricular free wall of fresh (i.e., never frozen) porcine hearts was harvested within 24 hours of the animals' sacrifice. A THERMOCOOLR Ablation System (Biosense Webster, Inc.) operating at 40 W for 30-60 s was used to induce lesions through the endocardial and epicardial walls of the cardiac samples. Following lesion creation, the ablated tissue samples were placed in 25 °C saline to allow for multi-wavelength PA imaging. Samples were imaged with a VevoR 2100 ultrasound system (VisualSonics, Inc.) using a modified 20-MHz array that could provide laser irradiation to the sample from a pulsed tunable laser (Newport Corp.) to allow for co-registered photoacoustic-ultrasound (PAUS) imaging. PA imaging was conducted from 750-1064 nm, with a surface fluence of approximately 15 mJ/cm2 maintained during imaging. In this preliminary study with PA imaging, the ablated region could be well visualized on the surface of the sample, with contrasts of 6-10 dB achieved at 750 nm. Although imaging penetration depth is a concern, PA imaging shows promise in being able to reliably visualize RF ablation lesions.

  14. Dynamic contrast-enhanced 3D photoacoustic imaging

    Science.gov (United States)

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

    2013-03-01

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

  15. Photoacoustic analysis of dental resin polymerization

    Science.gov (United States)

    Coloiano, E. C. R.; Rocha, R.; Martin, A. A.; da Silva, M. D.; Acosta-Avalos, D.; Barja, P. R.

    2005-06-01

    In this work, we use the photoacoustic technique to monitor the curing process of diverse dental materials, as the resins chemically activated (RCA). The results obtained reveal that the composition of a determined RCA significantly alters its activation kinetics. Photoacoustic data also show that temperature is a significant parameter in the activation kinetics of resins. The photoacoustic technique was also applied to evaluate the polymerization kinetics of photoactivated resins. Such resins are photoactivated by incidence of continuous light from a photodiode. This leads to the polymerization of the resin, modifying its thermal properties and, consequently, the level of the photoacoustic signal. Measurements show that the polymerization of the resin changes the photoacoustic signal amplitude, indicating that photoacoustic measurements can be utilized to monitor the polymerization kinetic and the degree of polymerization of photoactivated dental resins.

  16. One laser pulse generates two photoacoustic signals

    CERN Document Server

    Gao, Fei; Zheng, Yuanjin

    2016-01-01

    Photoacoustic sensing and imaging techniques have been studied widely to explore optical absorption contrast based on nanosecond laser illumination. In this paper, we report a long laser pulse induced dual photoacoustic (LDPA) nonlinear effect, which originates from unsatisfied stress and thermal confinements. Being different from conventional short laser pulse illumination, the proposed method utilizes a long square-profile laser pulse to induce dual photoacoustic signals. Without satisfying the stress confinement, the dual photoacoustic signals are generated following the positive and negative edges of the long laser pulse. More interestingly, the first expansion-induced photoacoustic signal exhibits positive waveform due to the initial sharp rising of temperature. On the contrary, the second contraction-induced photoacoustic signal exhibits exactly negative waveform due to the falling of temperature, as well as pulse-width-dependent, signal amplitude which is caused by the concurrent heat accumulation and ...

  17. Time-resolved tomographic images of a relativistic electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Koehler, H.A.; Jacoby, B.A.; Nelson, M.

    1984-07-01

    We obtained a sequential series of time-resolved tomographic two-dimensional images of a 4.5-MeV, 6-kA, 30-ns electron beam. Three linear fiber-optic arrays of 30 or 60 fibers each were positioned around the beam axis at 0/sup 0/, 61/sup 0/, and 117/sup 0/. The beam interacting with nitrogen at 20 Torr emitted light that was focused onto the fiber arrays and transmitted to a streak camera where the data were recorded on film. The film was digitized, and two-dimensional images were reconstructed using the maximum-entropy tomographic technique. These images were then combined to produce an ultra-high-speed movie of the electron-beam pulse.

  18. Acoustic resonance phase locked photoacoustic spectrometer

    Science.gov (United States)

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

    2003-08-19

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

  19. Forward-viewing photoacoustic imaging probe with bundled ultra-thin hollow optical fibers

    Science.gov (United States)

    Seki, A.; Iwai, K.; Katagiri, T.; Matsuura, Y.

    2016-07-01

    A photoacoustic imaging system composed of a flexible bundle of thin hollow-optical fibers is proposed for endoscopic diagnosis. In this system, a bundle of 127 hollow-optical fibers with an inner diameter of 100 μm was fabricated. The total diameter of the bundle was 2.1 mm, and the minimum bending radius was around 10 mm. Owing to the small numerical aperture of hollow optical fibers, a high resolution image was obtained without using a lens array at the distal end. In the imaging system, the hollow fibers in the bundle were aligned at the input end, so the hollow fibers were sequentially excited by linearly scanning the laser beam at the input end. Photoacoustic imaging systems consisting of the bundled fibers for excitation of acoustic wave and piezoelectric probes for detection of photoacoustic signals were built. By using the systems, photoacoustic images of blood vessels in the ovarian membrane of fish were taken to test the feasibility of the system. As a result, photoacoustic images of the vessel were successfully obtained with a laser fluence of around 6.6 mJ cm‑2.

  20. Multi-acoustic lens design methodology for a low cost C-scan photoacoustic imaging camera

    Science.gov (United States)

    Chinni, Bhargava; Han, Zichao; Brown, Nicholas; Vallejo, Pedro; Jacobs, Tess; Knox, Wayne; Dogra, Vikram; Rao, Navalgund

    2016-03-01

    We have designed and implemented a novel acoustic lens based focusing technology into a prototype photoacoustic imaging camera. All photoacoustically generated waves from laser exposed absorbers within a small volume get focused simultaneously by the lens onto an image plane. We use a multi-element ultrasound transducer array to capture the focused photoacoustic signals. Acoustic lens eliminates the need for expensive data acquisition hardware systems, is faster compared to electronic focusing and enables real-time image reconstruction. Using this photoacoustic imaging camera, we have imaged more than 150 several centimeter size ex-vivo human prostate, kidney and thyroid specimens with a millimeter resolution for cancer detection. In this paper, we share our lens design strategy and how we evaluate the resulting quality metrics (on and off axis point spread function, depth of field and modulation transfer function) through simulation. An advanced toolbox in MATLAB was adapted and used for simulating a two-dimensional gridded model that incorporates realistic photoacoustic signal generation and acoustic wave propagation through the lens with medium properties defined on each grid point. Two dimensional point spread functions have been generated and compared with experiments to demonstrate the utility of our design strategy. Finally we present results from work in progress on the use of two lens system aimed at further improving some of the quality metrics of our system.

  1. Photoacoustic microscopy in tissue engineering

    Directory of Open Access Journals (Sweden)

    Xin Cai

    2013-03-01

    Full Text Available 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 an imaging depth of 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.

  2. Inverse Transport Theory of Photoacoustics

    CERN Document Server

    Bal, Guillaume; Jugnon, Vincent

    2009-01-01

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

  3. Multimodal photoacoustic ophthalmoscopy in mouse

    OpenAIRE

    Song, Wei; Wei, Qing; Feng, Liang; Sarthy, Vijay; Jiao, Shuliang; LIU, XIAORONG; Zhang, Hao F.

    2012-01-01

    Photoacoustic ophthalmoscopy (PAOM) is a novel imaging technology that measures optical absorption in the retina. The capability of PAOM can be further enhanced if it could image mouse eyes, because mouse models are widely used for various retinal diseases. The challenges in achieving high-quality imaging of mouse retina, however, come from the much smaller eyeball size. Here, we report an optimized imaging system, which integrates PAOM, spectral-domain optical coherence tomography (SD-OCT), ...

  4. Tomographic characteristics of spin states

    NARCIS (Netherlands)

    Chernega, VN; Man'ko, OV; Man'ko, [No Value; Pilyavets, OV; Zborovskii, VG

    2006-01-01

    Spin states are studied in the tomographic-probability representation. The standard probability distribution of spin projection onto a direction in space is used instead of the spinor or the density matrix to identify the quantum state. The Shannon entropy and information are associated with the spi

  5. On the tomographic description of classical fields

    International Nuclear Information System (INIS)

    After a general description of the tomographic picture for classical systems, a tomographic description of free classical scalar fields is proposed both in a finite cavity and the continuum. The tomographic description is constructed in analogy with the classical tomographic picture of an ensemble of harmonic oscillators. The tomograms of a number of relevant states such as the canonical distribution, the classical counterpart of quantum coherent states and a new family of so-called Gauss–Laguerre states, are discussed. Finally the Liouville equation for field states is described in the tomographic picture offering an alternative description of the dynamics of the system that can be extended naturally to other fields.

  6. On the tomographic description of classical fields

    Energy Technology Data Exchange (ETDEWEB)

    Ibort, A., E-mail: albertoi@math.uc3m.es [Departamento de Matemáticas, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganés, Madrid (Spain); López-Yela, A., E-mail: alyela@math.uc3m.es [Departamento de Matemáticas, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganés, Madrid (Spain); Man' ko, V.I., E-mail: manko@na.infn.it [P.N. Lebedev Physical Institute, Leninskii Prospect 53, Moscow 119991 (Russian Federation); Marmo, G., E-mail: marmo@na.infn.it [Dipartimento di Scienze Fisiche dell' Università “Federico II” e Sezione INFN di Napoli, Complesso Universitario di Monte S. Angelo, via Cintia, 80126 Naples (Italy); Simoni, A., E-mail: simoni@na.infn.it [Dipartimento di Scienze Fisiche dell' Università “Federico II” e Sezione INFN di Napoli, Complesso Universitario di Monte S. Angelo, via Cintia, 80126 Naples (Italy); Sudarshan, E.C.G., E-mail: bhamathig@gmail.com [Physics Department, Center for Particle Physics, University of Texas, Austin, TX 78712 (United States); Ventriglia, F., E-mail: ventriglia@na.infn.it [Dipartimento di Scienze Fisiche dell' Università “Federico II” e Sezione INFN di Napoli, Complesso Universitario di Monte S. Angelo, via Cintia, 80126 Naples (Italy)

    2012-03-26

    After a general description of the tomographic picture for classical systems, a tomographic description of free classical scalar fields is proposed both in a finite cavity and the continuum. The tomographic description is constructed in analogy with the classical tomographic picture of an ensemble of harmonic oscillators. The tomograms of a number of relevant states such as the canonical distribution, the classical counterpart of quantum coherent states and a new family of so-called Gauss–Laguerre states, are discussed. Finally the Liouville equation for field states is described in the tomographic picture offering an alternative description of the dynamics of the system that can be extended naturally to other fields.

  7. On the tomographic description of classical fields

    CERN Document Server

    Ibort, A; Man'ko, V I; Marmo, G; Simoni, A; Sudarshan, E C G; Ventriglia, F

    2012-01-01

    After a general description of the tomographic picture for classical systems, a tomographic description of free classical scalar fields is proposed both in a finite cavity and the continuum. The tomographic description is constructed in analogy with the classical tomographic picture of an ensemble of harmonic oscillators. The tomograms of a number of relevant states such as the canonical distribution, the classical counterpart of quantum coherent states and a new family of so called Gauss--Laguerre states, are discussed. Finally the Liouville equation for field states is described in the tomographic picture offering an alternative description of the dynamics of the system that can be extended naturally to other fields.

  8. Novel Ultrasound Tomograph for Anatomical Inspection

    Science.gov (United States)

    Rouyer, Julien; Lasaygues, Philippe; Mensah, Serge

    A device for ultrasound computed tomography (UCT) is introduced here. An half-ring transducer array was designed in conformity with the breast anatomy and the cancer growth region to perform an early detection. The array comprises 1,024 elements set in a 190-degree circular arc with a radius of 100 mm. The nominal frequency is 3 MHz with a 79% -6 dB bandwidth. The front-end electronics incorporate 32 independent transmit/receive parallel channels and a 32-to-1,024 multiplexer unit. The acquisition circuitries have a variable sampling frequency of up to 80 MHz and a precision of 12 bits. Arbitrary waveforms are synthesized to improve the signal-to-noise ratio and to increase the in-depth resolution. Tomographic acquisitions were realized in diffraction mode using a restricted aperture. The backscattered field was recorded in the case of a string phantom (0.08-mm diameter steel threads) and a breast-shaped phantom containing inclusions. Data were processed with dedicated correction tools processes such as pulse compression. Objects were reconstructed with the ellipsoidal back-projection method.

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

    CERN Document Server

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

    2014-01-01

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

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

    DEFF Research Database (Denmark)

    Duggen, Lars; Lopes, Natasha; Willatzen, Morten;

    2011-01-01

    The finite-element method (FEM) is used to simulate the photoacoustic signal in a cylindrical resonant photoacoustic cell. Simulations include loss effects near the cell walls that appear in the boundary conditions for the inhomogeneous Helmholtz equation governing the acoustic pressure. Reasonably...... the photoacoustic signal was demonstrated and good agreement with experiments for the actual resonance frequency and the quality factor of the cell was obtained despite its complicated geometry....

  11. Wavelength-modulated differential photoacoustic radar imager (WM-DPARI): accurate monitoring of absolute hemoglobin oxygen saturation

    Science.gov (United States)

    Choi, Sung Soo Sean; Lashkari, Bahman; Dovlo, Edem; Mandelis, Andreas

    2016-01-01

    Accurate monitoring of blood oxy-saturation level (SO2) in human breast tissues is clinically important for predicting and evaluating possible tumor growth at the site. In this work, four different non-invasive frequency-domain photoacoustic (PA) imaging modalities were compared for their absolute SO2 characterization capability using an in-vitro sheep blood circulation system. Among different PA modes, a new WM-DPAR imaging modality could estimate the SO2 with great accuracy when compared to a commercial blood gas analyzer. The developed WM-DPARI theory was further validated by constructing SO2 tomographic images of a blood-containing plastisol phantom.

  12. Photoacoustic phasoscopy super-contrast imaging

    International Nuclear Information System (INIS)

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

  13. Photoacoustic phasoscopy super-contrast imaging

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-05-26

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

  14. Development of MEMS photoacoustic spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-01-01

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

  15. Detector Based Radio Tomographic Imaging

    OpenAIRE

    Yiğitler, Hüseyin; Jäntti, Riku; Kaltiokallio, Ossi; Patwari, Neal

    2016-01-01

    Received signal strength based radio tomographic imaging is a popular device-free indoor localization method which reconstructs the spatial loss field of the environment using measurements from a dense wireless network. Existing methods solve an associated inverse problem using algebraic or compressed sensing reconstruction algorithms. We propose an alternative imaging method that reconstructs spatial field of occupancy using a back-projection based reconstruction algorithm. The introduced sy...

  16. Computer tomographic findings in neurosyphilis

    OpenAIRE

    Pavithran K

    1993-01-01

    Computer tomographic features of the brain in 2 cases of neurosyphilis are described. Less prominence of the cortical sulci suggesting cortical atrophy was the predominant feature in a case of general paralysis of insane. Diffuse, irregular, non-enhancing, low-attenuated area in the cortical and subcortical region of the right temporoparietal lobe of a patient with vascular syphilis, suggested infarction of the brain.

  17. Computer tomographic findings in neurosyphilis

    Directory of Open Access Journals (Sweden)

    Pavithran K

    1993-01-01

    Full Text Available Computer tomographic features of the brain in 2 cases of neurosyphilis are described. Less prominence of the cortical sulci suggesting cortical atrophy was the predominant feature in a case of general paralysis of insane. Diffuse, irregular, non-enhancing, low-attenuated area in the cortical and subcortical region of the right temporoparietal lobe of a patient with vascular syphilis, suggested infarction of the brain.

  18. Photoacoustic tomography imaging of biological tissues

    Science.gov (United States)

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

    2005-01-01

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

  19. Photoacoustic Multicomponent Analyzer for Atmospheric Compounds Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to build a compact, rugged field-deployable laser photoacoustic spectrometric (LPAS) sensor for continuous, real-time measurements of multiple chemical...

  20. Photoacoustic spectroscopy of Entamoeba histolytica strains

    Science.gov (United States)

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

    2005-06-01

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

  1. Photoacoustic spectroscopy of β-hematin

    International Nuclear Information System (INIS)

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

  2. Photoacoustic spectroscopy of β-hematin

    Science.gov (United States)

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

    2012-06-01

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

  3. Multi-spectral photoacoustic elasticity tomography

    Science.gov (United States)

    Liu, Yubin; Yuan, Zhen

    2016-01-01

    The goal of this work was to develop and validate a spectrally resolved photoacoustic imaging method, namely multi-spectral photoacoustic elasticity tomography (PAET) for quantifying the physiological parameters and elastic modulus of biological tissues. We theoretically and experimentally examined the PAET imaging method using simulations and in vitro experimental tests. Our simulation and in vitro experimental results indicated that the reconstructions were quantitatively accurate in terms of sizes, the physiological and elastic properties of the targets. PMID:27699101

  4. Photo-acoustic tomography in a rotating measurement setting

    Science.gov (United States)

    Bal, Guillaume; Moradifam, Amir

    2016-10-01

    Photo-acoustic tomography (PAT) aims to leverage the photo-acoustic coupling between optical absorption of light sources and ultrasound (US) emission to obtain high contrast reconstructions of optical parameters with the high resolution of sonic waves. Quantitative PAT often involves a two-step procedure: first the map of sonic emission is reconstructed from US boundary measurements; and second optical properties of biological tissues are evaluated. We consider here a practical measurement setting in which such a separation does not apply. We assume that the optical source and an array of ultrasonic transducers are mounted on a rotating frame (in two or three dimensions) so that the light source rotates at the same time as the US measurements are acquired. As a consequence, we no longer have the option to reconstruct a map of sonic emission corresponding to a given optical illumination. We propose here a framework where the two steps are combined into one and an absorption map is directly reconstructed from the available US measurements.

  5. An adaptive filtered back-projection for photoacoustic image reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Huang, He; Bustamante, Gilbert; Peterson, Ralph; Ye, Jing Yong, E-mail: jingyong.ye@utsa.edu [Department of Biomedical Engineering, University of Texas at San Antonio, San Antonio, Texas 78249 (United States)

    2015-05-15

    Purpose: The purpose of this study is to develop an improved filtered-back-projection (FBP) algorithm for photoacoustic tomography (PAT), which allows image reconstruction with higher quality compared to images reconstructed through traditional algorithms. Methods: A rigorous expression of a weighting function has been derived directly from a photoacoustic wave equation and used as a ramp filter in Fourier domain. The authors’ new algorithm utilizes this weighting function to precisely calculate each photoacoustic signal’s contribution and then reconstructs the image based on the retarded potential generated from the photoacoustic sources. In addition, an adaptive criterion has been derived for selecting the cutoff frequency of a low pass filter. Two computational phantoms were created to test the algorithm. The first phantom contained five spheres with each sphere having different absorbances. The phantom was used to test the capability for correctly representing both the geometry and the relative absorbed energy in a planar measurement system. The authors also used another phantom containing absorbers of different sizes with overlapping geometry to evaluate the performance of the new method for complicated geometry. In addition, random noise background was added to the simulated data, which were obtained by using an arc-shaped array of 50 evenly distributed transducers that spanned 160° over a circle with a radius of 65 mm. A normalized factor between the neighbored transducers was applied for correcting measurement signals in PAT simulations. The authors assumed that the scanned object was mounted on a holder that rotated over the full 360° and the scans were set to a sampling rate of 20.48 MHz. Results: The authors have obtained reconstructed images of the computerized phantoms by utilizing the new FBP algorithm. From the reconstructed image of the first phantom, one can see that this new approach allows not only obtaining a sharp image but also showing

  6. Tomographic PIV: principles and practice

    Science.gov (United States)

    Scarano, F.

    2013-01-01

    A survey is given of the major developments in three-dimensional velocity field measurements using the tomographic particle image velocimetry (PIV) technique. The appearance of tomo-PIV dates back seven years from the present review (Elsinga et al 2005a 6th Int. Symp. PIV (Pasadena, CA)) and this approach has rapidly spread as a versatile, robust and accurate technique to investigate three-dimensional flows (Arroyo and Hinsch 2008 Topics in Applied Physics vol 112 ed A Schröder and C E Willert (Berlin: Springer) pp 127-54) and turbulence physics in particular. A considerable number of applications have been achieved over a wide range of flow problems, which requires the current status and capabilities of tomographic PIV to be reviewed. The fundamental aspects of the technique are discussed beginning from hardware considerations for volume illumination, imaging systems, their configurations and system calibration. The data processing aspects are of uppermost importance: image pre-processing, 3D object reconstruction and particle motion analysis are presented with their fundamental aspects along with the most advanced approaches. Reconstruction and cross-correlation algorithms, attaining higher measurement precision, spatial resolution or higher computational efficiency, are also discussed. The exploitation of 3D and time-resolved (4D) tomographic PIV data includes the evaluation of flow field pressure on the basis of the flow governing equation. The discussion also covers a-posteriori error analysis techniques. The most relevant applications of tomo-PIV in fluid mechanics are surveyed, covering experiments in air and water flows. In measurements in flow regimes from low-speed to supersonic, most emphasis is given to the complex 3D organization of turbulent coherent structures.

  7. Computed tomographic findings of trichuriasis

    Institute of Scientific and Technical Information of China (English)

    Naime Tokmak; Zafer Koc; Serife Ulusan; Ismail Soner Koltas; Nebil Bal

    2006-01-01

    In this report, we present computed tomographic findings of colonic trichuriasis. The patient was a 75-year-old man who complained of abdominal pain, and weight loss.Diagnosis was achieved by colonoscopic biopsy. Abdominal computed tomography showed irregular and nodular thickening of the wall of the cecum and ascending colon.Although these findings are nonspecific, they may be one of the findings of trichuriasis. These findings, confirmed by pathologic analysis of the biopsied tissue and KatoKatz parasitological stool flotation technique, revealed adult Trichuris. To our knowledge, this is the first report of colonic trichuriasis indicated by computed tomography.

  8. X-ray tomographic apparatus

    International Nuclear Information System (INIS)

    An x-ray tomographic system consists of a radiation source such as gamma or x radiation which produces a fan-shaped beam. The fan is wide enough to encompass the patient circle. The system further includes means for rotating the radiation source about the patient for less than a full rotation, and detectors for detecting the radiation at positions that surround the patient by 1800 plus the angle of the fan beam plus the angle between adjacent fan detectors. Attenuation data from the detectors is sorted into detector fans of attenuation data, then processed. The convolved data is back-projected into an image memory and displayed on a video monitor

  9. Detecting both melanoma depth and volume in vivo with a handheld photoacoustic probe

    Science.gov (United States)

    Zhou, Yong; Li, Guo; Zhu, Liren; Li, Chiye; Cornelius, Lynn A.; Wang, Lihong V.

    2016-03-01

    We applied a linear-array-based photoacoustic probe to detect the tumor depth and volume of melanin-containing melanoma in nude mice in vivo. We demonstrated the ability of this linear-array-based system to measure both the depth and volume of melanoma through phantom, ex vivo, and in vivo experiments. The volume detection ability also enables us to accurately calculate the rate of growth of the tumor, which is important in quantifying tumor activity. Our results show that this system can be used for clinical melanoma diagnosis and treatment at the bedside.

  10. Quantitative photoacoustic elastography in humans

    Science.gov (United States)

    Hai, Pengfei; Zhou, Yong; Gong, Lei; Wang, Lihong V.

    2016-06-01

    We report quantitative photoacoustic elastography (QPAE) capable of measuring Young's modulus of biological tissue in vivo in humans. By combining conventional PAE with a stress sensor having known stress-strain behavior, QPAE can simultaneously measure strain and stress, from which Young's modulus is calculated. We first demonstrate the feasibility of QPAE in agar phantoms with different concentrations. The measured Young's modulus values fit well with both the empirical expectation based on the agar concentrations and those measured in an independent standard compression test. Next, QPAE was applied to quantify the Young's modulus of skeletal muscle in vivo in humans, showing a linear relationship between muscle stiffness and loading. The results demonstrated the capability of QPAE to assess the absolute elasticity of biological tissue noninvasively in vivo in humans, indicating its potential for tissue biomechanics studies and clinical applications.

  11. Catheter-based photoacoustic endoscope

    Science.gov (United States)

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

    2014-06-01

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

  12. Inverse Diffusion Theory of Photoacoustics

    CERN Document Server

    Bal, Guillaume

    2009-01-01

    This paper analyzes the reconstruction of diffusion and absorption parameters in an elliptic equation from knowledge of internal data. In the application of photo-acoustics, the internal data are the amount of thermal energy deposited by high frequency radiation propagating inside a domain of interest. These data are obtained by solving an inverse wave equation, which is well-studied in the literature. We show that knowledge of two internal data based on well-chosen boundary conditions uniquely determines two constitutive parameters in diffusion and Schroedinger equations. Stability of the reconstruction is guaranteed under additional geometric constraints of strict convexity. No geometric constraints are necessary when $2n$ internal data for well-chosen boundary conditions are available, where $n$ is spatial dimension. The set of well-chosen boundary conditions is characterized in terms of appropriate complex geometrical optics (CGO) solutions.

  13. Improving limited-view reconstruction in photoacoustic tomography by incorporating a priori boundary information

    Science.gov (United States)

    Anastasio, Mark A.; Wang, Kun; Zhang, Jin; Kruger, Gabe A.; Reinecke, Daniel; Kruger, Robert A.

    2008-02-01

    Photoacoustic tomography (PAT) is an emerging ultrasound-mediated biophotonic imaging modality that has great potential for many biomedical imaging applications. In many practical implementations of PAT, the photoacoustic signals are recorded over an aperture that does not enclose the object, which results in a limitedview tomographic reconstruction problem. When conventional reconstruction algorithms are applied to limitedview measurement data, the resulting images can contain severe image artifacts and distortions. To circumvent such artifacts, we exploit a priori information about the locations of boundaries within the object (optical absorption function) to improve the fidelity of the reconstructed images. Such boundary information can be inferred, for example, from a co-registered B-mode ultrasound image or other adjunct imaging study. We develop and implement an iterative reconstruction algorithm that exploits a priori object information in the form of support constraints. We demonstrate that the developed iterative reconstruction algorithm produces images with reduced artifact levels as compared to those produced by a conventional PAT reconstruction algorithm.

  14. High resolution tomographic instrument development

    International Nuclear Information System (INIS)

    Our recent work has concentrated on the development of high-resolution PET instrumentation reflecting in part the growing importance of PET in nuclear medicine imaging. We have developed a number of positron imaging instruments and have the distinction that every instrument has been placed in operation and has had an extensive history of application for basic research and clinical study. The present program is a logical continuation of these earlier successes. PCR-I, a single ring positron tomograph was the first demonstration of analog coding using BGO. It employed 4 mm detectors and is currently being used for a wide range of biological studies. These are of immense importance in guiding the direction for future instruments. In particular, PCR-II, a volume sensitive positron tomograph with 3 mm spatial resolution has benefited greatly from the studies using PCR-I. PCR-II is currently in the final stages of assembly and testing and will shortly be placed in operation for imaging phantoms, animals and ultimately humans. Perhaps the most important finding resulting from our previous study is that resolution and sensitivity must be carefully balanced to achieve a practical high resolution system. PCR-II has been designed to have the detection characteristics required to achieve 3 mm resolution in human brain under practical imaging situations. The development of algorithms by the group headed by Dr. Chesler is based on a long history of prior study including his joint work with Drs. Pelc and Reiderer and Stearns. This body of expertise will be applied to the processing of data from PCR-II when it becomes operational

  15. Tomographic anthropomorphic models. Pt. 1

    International Nuclear Information System (INIS)

    The first generation of heterogenoeous anthropomorphic mathematical models to be used in dose calculations was the MIRD-5 adult phantom, followed by the pediatric MIRD-type phantoms and by the GSF sex-specific phantoms ADAM and EVA. A new generation of realistic anthropomorphic models is now introduced. The organs and tissues of these models consist of a well defined number of volume elements (voxels), derived from computer tomographic (CT) data; consequently, these models were named voxel or tomographic models. So far two voxel models of real patients are available: one of an 8 week old baby and of a 7 year old child. For simplicity, the model of the baby will be referred to as BABY and that of the child as CHILD. In chapter 1 a brief literature review is given on the existing mathematical models and their applications. The reasons that lead to the construction of the new CT models is discussed. In chapter 2 the technique is described which allows to convert any physical object into computer files to be used for dose calculations. The technique which produces three dimensional reconstructions of high resolution is discussed. In chapter 3 the main characteristics of the models of the baby and child are given. Tables of organ masses and volumes are presented together with three dimensional images of some organs and tissues. A special mention is given to the assessment of bone marrow distribution. Chapter 4 gives a short description of the Monte Carlo code used in conjunction with the models to calculate organ and tissue doses resulting from photon exposures. Some technical details concerning the computer files which describe the models are also given. (orig./HP)

  16. High resolution tomographic instrument development

    Energy Technology Data Exchange (ETDEWEB)

    1992-08-01

    Our recent work has concentrated on the development of high-resolution PET instrumentation reflecting in part the growing importance of PET in nuclear medicine imaging. We have developed a number of positron imaging instruments and have the distinction that every instrument has been placed in operation and has had an extensive history of application for basic research and clinical study. The present program is a logical continuation of these earlier successes. PCR-I, a single ring positron tomograph was the first demonstration of analog coding using BGO. It employed 4 mm detectors and is currently being used for a wide range of biological studies. These are of immense importance in guiding the direction for future instruments. In particular, PCR-II, a volume sensitive positron tomograph with 3 mm spatial resolution has benefited greatly from the studies using PCR-I. PCR-II is currently in the final stages of assembly and testing and will shortly be placed in operation for imaging phantoms, animals and ultimately humans. Perhaps the most important finding resulting from our previous study is that resolution and sensitivity must be carefully balanced to achieve a practical high resolution system. PCR-II has been designed to have the detection characteristics required to achieve 3 mm resolution in human brain under practical imaging situations. The development of algorithms by the group headed by Dr. Chesler is based on a long history of prior study including his joint work with Drs. Pelc and Reiderer and Stearns. This body of expertise will be applied to the processing of data from PCR-II when it becomes operational.

  17. High resolution tomographic instrument development

    Energy Technology Data Exchange (ETDEWEB)

    1992-01-01

    Our recent work has concentrated on the development of high-resolution PET instrumentation reflecting in part the growing importance of PET in nuclear medicine imaging. We have developed a number of positron imaging instruments and have the distinction that every instrument has been placed in operation and has had an extensive history of application for basic research and clinical study. The present program is a logical continuation of these earlier successes. PCR-I, a single ring positron tomograph was the first demonstration of analog coding using BGO. It employed 4 mm detectors and is currently being used for a wide range of biological studies. These are of immense importance in guiding the direction for future instruments. In particular, PCR-II, a volume sensitive positron tomograph with 3 mm spatial resolution has benefited greatly from the studies using PCR-I. PCR-II is currently in the final stages of assembly and testing and will shortly be placed in operation for imaging phantoms, animals and ultimately humans. Perhaps the most important finding resulting from our previous study is that resolution and sensitivity must be carefully balanced to achieve a practical high resolution system. PCR-II has been designed to have the detection characteristics required to achieve 3 mm resolution in human brain under practical imaging situations. The development of algorithms by the group headed by Dr. Chesler is based on a long history of prior study including his joint work with Drs. Pelc and Reiderer and Stearns. This body of expertise will be applied to the processing of data from PCR-II when it becomes operational.

  18. Enhanced photoacoustic detection using photonic crystal substrate

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-04-21

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

  19. Molecular photoacoustic imaging of follicular thyroid carcinoma

    DEFF Research Database (Denmark)

    Levi, Jelena; Kothapalli, Sri-Rajashekar; Bohndiek, Sarah;

    2013-01-01

    Purpose To evaluate the potential of targeted photoacoustic imaging as a non-invasive method for detection of follicular thyroid carcinoma. Experimental Design We determined the presence and activity of two members of matrix metalloproteinase family (MMP), MMP-2 and MMP-9, suggested as biomarkers...... for malignant thyroid lesions, in FTC133 thyroid tumors subcutaneously implanted in nude mice. The imaging agent used to visualize tumors was MMP activatable photoacoustic probe, Alexa750-CXeeeeXPLGLAGrrrrrXK-BHQ3. Cleavage of the MMP activatable agent was imaged after intratumoral and intravenous injections...... in living mice optically, observing the increase in Alexa750 fluorescence, and photoacoustically, using a dual wavelength imaging method. Results Active forms of both MMP2 and MMP-9 enzymes were found in FTC133 tumor homogenates, with MMP-9 detected in greater amounts. The molecular imaging agent...

  20. Feasibility of photoacoustic tomography for ophthalmology

    Institute of Scientific and Technical Information of China (English)

    Tao Lu; Zhiyuan Song; Yixiong Su; Fan Zhang; Jianquan Yao

    2007-01-01

    For the eyeball composed of membrane and liquid, the contrast of ultrasound imaging is not high due to its small variance in acoustic impedance. As a new imaging modality, photoacoustic tomography combines the advantages of pure optical and ultrasonic imaging together and can provide high resolution, high contrast images. In this paper, the feasibility of photoacoustic tomography for ophthalmology is studied experimentally. A Q-switched Nd:YAG pulsed laser with 7-ns pulse width is used to generate photoacoustic signal of a porcine eyeball in vitro. The two-dimensional (2D) optical absorption image of the entire eyeball is reconstructed by time-domain spherical back projection algorithm. The imaging results agree well with the histological structure of the eyeball and show a high imaging contrast.

  1. Early detection of dental caries using photoacoustics

    Science.gov (United States)

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

    2006-02-01

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

  2. Determination of Tequila Quality by Photoacoustic Analysis

    Science.gov (United States)

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

    2013-09-01

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

  3. Photoacoustic tomography of water in biological tissue

    Science.gov (United States)

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

    2011-03-01

    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.

  4. Compressed sensing and sparsity in photoacoustic tomography

    CERN Document Server

    Haltmeier, Markus; Moon, Sunghwan; Burgholzer, Peter

    2016-01-01

    Increasing the imaging speed is a central aim in photoacoustic tomography. In this work we address this issue using techniques of compressed sensing. We demonstrate that the number of measurements can significantly be reduced by allowing general linear measurements instead of point wise pressure values. A main requirement in compressed sensing is the sparsity of the unknowns to be recovered. For that purpose we develop the concept of sparsifying temporal transforms for three dimensional photoacoustic tomography. Reconstruction results for simulated and for experimental data verify that the proposed compressed sensing scheme allows to significantly reducing the number of spatial measurements without reducing the spatial resolution.

  5. In vivo virtual intraoperative surgical photoacoustic microscopy

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-11-11

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

  6. Photoacoustic lifetime imaging and its biomedical applications

    Science.gov (United States)

    Shao, Qi

    Even though oxygen plays a crucial role in body function and cancer biology, methods of measuring oxygen level in tissue are all limited. The current gold standard relies on an invasive electrode for only single-point reading at a time. The photoacoustic lifetime imaging (PALI) approach overcomes these major limitations by applying photoacoustic probing to oxygen-sensitive optical transient absorption. The capability of assessing oxygen distribution is demonstrated by imaging tumor hypoxia in a small animal model, and monitoring changes of tissue oxygen induced by external modulations. Proposed applications of this imaging technique includes imaging-guided photodynamic therapy (PDT) and activatable probes for molecular imaging.

  7. Method of tomographic examination of objects

    International Nuclear Information System (INIS)

    The method for tomographic examination of objects is suggested to increase informative investigation. The point of the method is to obtain transemission and emission tomographic images inside an investigating cycle and bring them into coincidence with each other so, that the resulting image gave information on tissue density distribution in the body region studied and on isotope distribution in the given tissues of the same region

  8. Precision tomographic analysis of reactor fuels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yong Deok; Lee, Chang Hee; Kim, Jong Soo; Jeong, Jwong Hwan; Nam, Ki Yong

    2001-03-01

    For the tomographical assay, search of current status, analysis of neutron beam characteristics, MCNP code simulation, sim-fuel fabrication, neutron experiment for sim-fuel, multiaxes operation system design were done. In sensitivity simulation, the reconstruction results showed the good agreement. Also, the scoping test at ANL was very helpful for actual assay. Therefore, the results are applied for HANARO tomographical system setup and consecutive next research.

  9. 光声成像技术在生物医学中的研究进展%Development of Photoacoustic Imaging Technology in Biomedical Applications

    Institute of Scientific and Technical Information of China (English)

    常金凤; 李成; 李荧

    2014-01-01

    As a kind of nondestructive testing technology, photoacoustic imaging technology, which is characterized by high resolution and high contrast, has been one of the development directions in the field of biomedical technologies. From the view of photoacoustic imaging systems, photoacoustic detec-tors and image reconstruction algorithms, the photoacoustic imaging technology is analyzed in this paper. Then the current photoacoustic imaging systems are illustrated in accordance with photoacoustic com-puted tomography, photoacoustic microscopy and photoacoustic endoscopy. The research advance of pho-toacoustic detectors, relating to multi-elememnt probes, array probes, MEMS probes and diaphragm-type Fabry-Perot probes, is discussed. Also, the application characteristics of typical image reconstruction algorithms are compared. As a result, the major research orientations of the photoacoustic imaging tech-nology, including higher resolution, greater detective depth, hard real-time, miniaturization technology and low-cost design, are demonstrated in consideration of potential future applications.%光声成像是近年来发展较快的无损检测技术,其高分辨率、高对比度的特点使其成为生物医学检测技术的主要发展方向之一。文中从光声成像系统、光声探测器和图像重建算法的角度,对光声成像技术进行了分析。在此基础上,分别结合光声计算层析成像、光声显微成像和光声内窥成像对光声成像系统进行了阐述,探讨了光声探测器在多探头、阵列式、MEMS微型化和光纤F-P腔等方面的研究进展,比较了典型图像重建算法的应用特点,并指出了基于光声技术的生物医学无损成像系统的高分辨率、大探测深度、实时性强、小型化、低成本的研究方向。

  10. Texture generation in compressional photoacoustic elastography

    Science.gov (United States)

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

    2015-03-01

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

  11. Photoacoustic tomography: applications for atherosclerosis imaging

    Science.gov (United States)

    Sangha, Gurneet S.; Goergen, Craig J.

    2016-08-01

    Atherosclerosis is a debilitating condition that increases a patient’s risk for intermittent claudication, limb amputation, myocardial infarction, and stroke, thereby causing approximately 50% of deaths in the western world. Current diagnostic imaging techniques, such as ultrasound, digital subtraction angiography, computed tomography angiography, magnetic resonance angiography, and optical imaging remain suboptimal for detecting development of early stage plaques. This is largely due to the lack of compositional information, penetration depth, and/or clinical efficiency of these traditional imaging techniques. Photoacoustic imaging has emerged as a promising modality that could address some of these limitations to improve the diagnosis and characterization of atherosclerosis-related diseases. Photoacoustic imaging uses near-infrared light to induce acoustic waves, which can be used to recreate compositional images of tissue. Recent developments in photoacoustic techniques show its potential in noninvasively characterizing atherosclerotic plaques deeper than traditional optical imaging approaches. In this review, we discuss the significance and development of atherosclerosis, current and novel clinical diagnostic methods, and recent works that highlight the potential of photoacoustic imaging for both experimental and clinical studies of atherosclerosis.

  12. Photoacoustic imaging of port-wine stains

    NARCIS (Netherlands)

    Kolkman, Roy G.M.; Mulder, Miranda J.; Glade, Conrad P.; Steenbergen, Wiendelt; Leeuwen, van Ton G.

    2008-01-01

    Background and Objective: To optimize laser therapy of port-wine stains (PWSs), information about the vasculature as well as lesion depth is valuable. In this study we investigated the use of photoacoustic imaging (PAI) to obtain this information. - Study Design/Materials and Methods: PAI uses puls

  13. Tomographic PIV: particles versus blobs

    Science.gov (United States)

    Champagnat, Frédéric; Cornic, Philippe; Cheminet, Adam; Leclaire, Benjamin; Le Besnerais, Guy; Plyer, Aurélien

    2014-08-01

    We present an alternative approach to tomographic particle image velocimetry (tomo-PIV) that seeks to recover nearly single voxel particles rather than blobs of extended size. The baseline of our approach is a particle-based representation of image data. An appropriate discretization of this representation yields an original linear forward model with a weight matrix built with specific samples of the system’s point spread function (PSF). Such an approach requires only a few voxels to explain the image appearance, therefore it favors much more sparsely reconstructed volumes than classic tomo-PIV. The proposed forward model is general and flexible and can be embedded in a classical multiplicative algebraic reconstruction technique (MART) or a simultaneous multiplicative algebraic reconstruction technique (SMART) inversion procedure. We show, using synthetic PIV images and by way of a large exploration of the generating conditions and a variety of performance metrics, that the model leads to better results than the classical tomo-PIV approach, in particular in the case of seeding densities greater than 0.06 particles per pixel and of PSFs characterized by a standard deviation larger than 0.8 pixels.

  14. Photoacoustic Doppler flow measurement in optically scattering media

    OpenAIRE

    Fang, Hui; Maslov, Konstantin; Wang, Lihong V.

    2007-01-01

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

  15. Photoacoustic sample vessel and method of elevated pressure operation

    Science.gov (United States)

    Autrey, Tom; Yonker, Clement R.

    2004-05-04

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

  16. Nonlinear frequency-mixing photoacoustic imaging of a crack

    Science.gov (United States)

    Chigarev, N.; Zakrzewski, J.; Tournat, V.; Gusev, V.

    2009-08-01

    We present a technique for nonlinear photoacoustic imaging of cracks by laser excitation with intensity modulation at two fundamental frequencies combined with detection at mixed frequencies. By exploiting the strong dependence of the photoacoustic emission efficiency on the state—open or closed—of the contacts between the crack faces, remarkably enhanced image contrast is observed, ˜20 times higher than in linear photoacoustic images at the highest of the fundamental frequencies.

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

    CERN Document Server

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2013-07-01

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

  19. Model-based tomographic reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, David H.; Lehman, Sean K.; Goodman, Dennis M.

    2012-06-26

    A model-based approach to estimating wall positions for a building is developed and tested using simulated data. It borrows two techniques from geophysical inversion problems, layer stripping and stacking, and combines them with a model-based estimation algorithm that minimizes the mean-square error between the predicted signal and the data. The technique is designed to process multiple looks from an ultra wideband radar array. The processed signal is time-gated and each section processed to detect the presence of a wall and estimate its position, thickness, and material parameters. The floor plan of a building is determined by moving the array around the outside of the building. In this paper we describe how the stacking and layer stripping algorithms are combined and show the results from a simple numerical example of three parallel walls.

  20. Introduction to curved rotary tomographic apparatus 'TOMOREX'

    International Nuclear Information System (INIS)

    In recent years, panorama X-ray photographic method is widely used for the X-ray diagnosis of teeth, jawbones and faces. One type based on the principle of tomography is curved surface rotary tomographic method utilizing fine-gap X-ray beam. With the synchronous rotation of an X-ray tube and a photographic film around a face, describing a U-shaped tomographic plane along a dental arch, an upper or lower jawbone is photographed. In the ''TOMOREX'' belonging to this type, is different tomographic planes are available, so that by selecting any position in advance, the part can be photographed. Furthermore, patients can be subjected to examination as laid on a stretcher. The mechanism and equipment, and the photographic method for eye sockets, cheekbones, upper jaw cavities and stereoscopic images are described. (J.P.N.)

  1. Microcantilever Actuation by Laser Induced Photoacoustic Waves

    Science.gov (United States)

    Gao, Naikun; Zhao, Dongfang; Jia, Ran; Liu, Duo

    2016-01-01

    We present here a combined theoretical and experimental investigation on effective excitation of microcantilever by using photoacoustic waves. The photoacoustic waves arose from a vibrating Al foil induced by an intensity-modulated laser. We demonstrate that, superior to photothermal excitation, this new configuration avoids direct heating of the microcantilever, thus minimizing undesired thermal effects on the vibration of microcantilever, while still keeps the advantage of being a remote, non-contact excitation method. We also measured the vibration amplitude of the microcantilever as a function of distance between the microcantilever and the Al foil and found that the amplitudes decay gradually according to the inverse distance law. This method is universal and can be adopted in bio-microelectromechanical systems (BioMEMs) for the detection of small signals where detrimental thermal effects must be avoided.

  2. Photoacoustic and Photothermal Effects in Particulate Suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Diebold, Gerald, J.

    2009-04-30

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

  3. Quartz-Enhanced Photoacoustic Spectroscopy: A Review

    Directory of Open Access Journals (Sweden)

    Pietro Patimisco

    2014-03-01

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

  4. Steering in spin tomographic probability representation

    Science.gov (United States)

    Man'ko, V. I.; Markovich, L. A.

    2016-09-01

    The steering property known for two-qubit state in terms of specific inequalities for the correlation function is translated for the state of qudit with the spin j = 3 / 2. Since most steering detection inequalities are based on the correlation functions we introduce analogs of such functions for the single qudit systems. The tomographic probability representation for the qudit states is applied. The connection between the correlation function in the two-qubit system and the single qudit is presented in an integral form with an intertwining kernel calculated explicitly in tomographic probability terms.

  5. Tomographic causal analysis of two-qubit states and tomographic discord

    International Nuclear Information System (INIS)

    We study a behavior of two-qubit states subject to tomographic measurement. In this Letter we propose a novel approach to definition of asymmetry in quantum bipartite state based on its tomographic Shannon entropies. We consider two types of measurement bases: the first is one that diagonalizes density matrices of subsystems and is used in a definition of tomographic discord, and the second is one that maximizes Shannon mutual information and relates to symmetrical form quantum discord. We show how these approaches relate to each other and then implement them to the different classes of two-qubit states. Consequently, new subclasses of X-states are revealed.

  6. Photoacoustic imaging of prostate brachytherapy seeds

    OpenAIRE

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

    2011-01-01

    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...

  7. Photoacoustics of disperse systems: Below cavitation threshold

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-05-24

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

  8. Mathematics of Photoacoustic and Thermoacoustic Tomography

    KAUST Repository

    Kuchment, Peter

    2011-01-01

    The chapter surveys the mathematical models, problems, and algorithms of the thermoacoustic tomography (TAT) and photoacoustic tomography (PAT). TAT and PAT represent probably the most developed of the several novel “hybrid” methods of medical imaging. These new modalities combine different physical types of waves (electromagnetic and acoustic in case of TAT and PAT) in such a way that the resolution and contrast of the resulting method are much higher than those achievable using only acoustic or electromagnetic measurements.

  9. Acoustic resonance frequency locked photoacoustic spectrometer

    Science.gov (United States)

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

    2003-09-09

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

  10. Hands-on resonance-enhanced photoacoustic detection

    Science.gov (United States)

    Euler, Manfred

    2001-10-01

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

  11. Phase transition in L-alaninium oxalate by photoacoustics

    Indian Academy of Sciences (India)

    M Sivabarathy; S Natarajan; S K Ramakrishnan; K Ramachandran

    2004-10-01

    Phase transition in L-alaninium oxalate is studied by using TG, DTA and photoacoustic spectroscopy. A sharp transition at 378 K by photoacoustics is observed whereas at the same temperature the endothermic energy change observed by TG and DTA is not very sharp. This is discussed in detail with reference to the other known data for the organic crystals.

  12. Multifunctional Photosensitizer-Based Contrast Agents for Photoacoustic Imaging

    Science.gov (United States)

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

    2014-06-01

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

  13. Near Infrared Photoacoustic Detection of Heptane in Synthetic Air

    DEFF Research Database (Denmark)

    Duggen, Lars; Albu, Mihaela; Willatzen, Morten;

    2013-01-01

    Trace contaminations of n-heptane in synthetic air is measured in the parts-per-billion (ppb) range using near infrared photoacoustic detection. We describe the fundamental theory used in the design of the photoacoustic cell for trace gas analysis and determine the detection limit of the cell...

  14. Multi-scale molecular photoacoustic tomography of gene expression

    NARCIS (Netherlands)

    Li, L.; Cai, X.; Krumholz, A.; Guo, Z.; Erpelding, T.N.; Zhang, Y.; Xia, Y.; Wang, L.V.

    2012-01-01

    Photoacoustic tomography (PAT) is a molecular imaging technology. Unlike conventional reporter gene imaging, which is based on fluorescent proteins, photoacoustic reporter gene imaging is based on opticalabsorption. Using lacZ, one of the most widely used reporter genesin biology, this work demonstr

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

    Science.gov (United States)

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

    2014-06-18

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

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

    Science.gov (United States)

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

    1998-08-01

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

  17. In vivo photoacoustic imaging of mouse embryos

    Science.gov (United States)

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

    2012-06-01

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

  18. Photoacoustic and Colorimetric Visualization of Latent Fingerprints.

    Science.gov (United States)

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

    2015-12-22

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

  19. Photoacoustic imaging of voltage signals (Conference Presentation)

    Science.gov (United States)

    Rao, Bin; Zhang, Ruiying; Wang, Lihong V.

    2016-03-01

    Optical imaging of brain voltage signals is significantly limited in depth due to optical scattering and the absorptive property of brain tissue. Photoacoustic (PA) imaging promises to break this hard limit by utilizing both ballistic and diffused photons. To demonstrate the feasibility of PA, we used an in vivo mouse model. The brain cortex tissue was stained with dipicrylamine dye, electrically stimulated, and imaged with a customized dual-isosbestic-wavelength PA microscope (DIW-PAM). DIW-PAM separates voltage-induced PA signals from blood-induced PA signals and thereby allows recording the voltage response of mouse cortex tissue without interference from hemoglobin responses. The resting state PA voltage response signal exhibited a noise-like signal in the frequency domain. Upon 3 Hz electrical stimulation, the PA voltage response signal showed frequency peaks of 3.2 Hz and 6.3 Hz (Fig. 1). Although dipicrylamine dye is not fast enough for recording neuron action potentials, it served well for the purpose of this feasibility study. In conclusion, we successfully demonstrated in vivo photoacoustic imaging of mouse brain voltage signals for the first time. If a fast voltage-sensitive dye is available, using photoacoustic computed tomography (PACT) instead of PA microscopy could allow acquiring full-field PA action potential images at a speed limited only by the laser pulse repetition rate.

  20. Functional photoacoustic microscopy of pH

    Science.gov (United States)

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

    2012-02-01

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

  1. An optimized ultrasound detector for photoacoustic breast tomography

    CERN Document Server

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

    2012-01-01

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

  2. High resolution ultrasound and photoacoustic imaging of single cells.

    Science.gov (United States)

    Strohm, Eric M; Moore, Michael J; Kolios, Michael C

    2016-03-01

    High resolution ultrasound and photoacoustic images of stained neutrophils, lymphocytes and monocytes from a blood smear were acquired using a combined acoustic/photoacoustic microscope. Photoacoustic images were created using a pulsed 532 nm laser that was coupled to a single mode fiber to produce output wavelengths from 532 nm to 620 nm via stimulated Raman scattering. The excitation wavelength was selected using optical filters and focused onto the sample using a 20× objective. A 1000 MHz transducer was co-aligned with the laser spot and used for ultrasound and photoacoustic images, enabling micrometer resolution with both modalities. The different cell types could be easily identified due to variations in contrast within the acoustic and photoacoustic images. This technique provides a new way of probing leukocyte structure with potential applications towards detecting cellular abnormalities and diseased cells at the single cell level.

  3. High resolution ultrasound and photoacoustic imaging of single cells

    Directory of Open Access Journals (Sweden)

    Eric M. Strohm

    2016-03-01

    Full Text Available High resolution ultrasound and photoacoustic images of stained neutrophils, lymphocytes and monocytes from a blood smear were acquired using a combined acoustic/photoacoustic microscope. Photoacoustic images were created using a pulsed 532 nm laser that was coupled to a single mode fiber to produce output wavelengths from 532 nm to 620 nm via stimulated Raman scattering. The excitation wavelength was selected using optical filters and focused onto the sample using a 20× objective. A 1000 MHz transducer was co-aligned with the laser spot and used for ultrasound and photoacoustic images, enabling micrometer resolution with both modalities. The different cell types could be easily identified due to variations in contrast within the acoustic and photoacoustic images. This technique provides a new way of probing leukocyte structure with potential applications towards detecting cellular abnormalities and diseased cells at the single cell level.

  4. In vivo demonstration of reflection artifact reduction in photoacoustic imaging using synthetic aperture photoacoustic-guided focused ultrasound (PAFUSion)

    NARCIS (Netherlands)

    Singh, M.K.A.; Jaeger, M.; Frenz, M.; Steenbergen, W.

    2016-01-01

    Reflection artifacts caused by acoustic inhomogeneities are a critical problem in epi-mode biomedical photoacoustic imaging. High light fluence beneath the probe results in photoacoustic transients, which propagate into the tissue and reflect back from echogenic structures. These reflection artifact

  5. Computed tomographic angiography in tetralogy of Fallot.

    Science.gov (United States)

    Kasar, Pankajkumar Ashok; Ravikumar, Radhakrishnan; Varghese, Roy; Kotecha, Monika; Vimala, Jesudian; Kumar, Raghavan Nair Suresh

    2011-10-01

    Echocardiography is often inadequate for imaging tetralogy of Fallot, prompting cineangiography. This study prospectively evaluated multidetector computed tomographic angiography for preoperative evaluation of tetralogy of Fallot in 112 consecutive patients. Forty-eight had nonconfluent or hypoplastic pulmonary arteries (mean z-score, -2; range, -11.1-0.13) permitting only palliative or no surgery; 64 had adequate pulmonary artery anatomy (mean z-score, 0.59; range, -2.53-3.4) allowing total repair. The surgical data of 50 patients who underwent total correction were compared with transthoracic echocardiography and multidetector computed tomographic angiography findings. Multidetector computed tomographic angiography tended to reveal unsuspected collaterals and coronary abnormalities besides outlining the right ventricular outflow tract and pulmonary artery branches. The branch pulmonary artery diameter z-score was the most important determinant of surgical strategy, with the worst figures being associated with no surgical options or palliative surgery, and the best figures leading to corrective surgery. The mean radiation dose was 3.45 mSv. Multidetector computed tomographic angiography is a powerful supplement to echocardiography in the preoperative evaluation of tetralogy of Fallot.

  6. Computed Tomographic Scan Evaluation of Pulmonary Blastomycosis

    Directory of Open Access Journals (Sweden)

    Suzanne Ronald

    2009-01-01

    Full Text Available BACKGROUND: Blastomycosis is an uncommon granulomatous pulmonary and extrapulmonary infectious disease caused by the thermally dimorphic fungus Blastomyces dermatitidis. Diagnosis may be delayed or difficult because of varied presentation. The characteristics of blastomycosis on computed tomographic (CT scan of the chest are not well characterized.

  7. Computed tomographic imaging of pulmonary alveolar proteinosis

    International Nuclear Information System (INIS)

    Pulmonary alveolar proteinosis is a rare disease of uncertain etiology. The computed tomographic image is characterized by geographically sharply delineated alveolar infiltrates, faint, ground-glass-like parenchymal turbidity, with well bordered interstitial structures and recesses in the subpleural space. (orig.)

  8. Decomposition of time-resolved tomographic PIV

    NARCIS (Netherlands)

    Schmid, P.J.; Violato, D.; Scarano, F.

    2012-01-01

    An experimental study has been conducted on a transitional water jet at a Reynolds number of Re = 5,000. Flow fields have been obtained by means of time-resolved tomographic particle image velocimetry capturing all relevant spatial and temporal scales. The measured threedimensional flow fields have

  9. Tomographic Heating Holder for In Situ TEM

    DEFF Research Database (Denmark)

    Gontard, Lionel C.; Dunin-Borkowski, Rafal E.; Fernández, Asunción;

    2014-01-01

    A tomographic heating holder for transmission electron microscopy that can be used to study supported catalysts at temperatures of up to ~1,500°C is described. The specimen is placed in direct thermal contact with a tungsten filament that is oriented perpendicular to the axis of the holder withou...

  10. Theranostic probe for simultaneous in vivo photoacoustic imaging and confined photothermolysis by pulsed laser at 1064 nm in 4T1 breast cancer model

    Science.gov (United States)

    Zhou, Min; Ku, Geng; Pageon, Laura; Li, Chun

    2014-11-01

    Here, we report that polyethylene glycol (PEG)-coated copper(ii) sulfide nanoparticles (PEG-CuS NPs) with their peak absorption tuned to 1064 nm could be used both as a contrast agent for photoacoustic tomographic imaging of mouse tumor vasculature and as a mediator for confined photothermolysis of tumor cells in an orthotopic syngeneic 4T1 breast tumor model. PEG-CuS NPs showed stronger photoacoustic signal than hollow gold nanospheres and single-wall carbon nanotubes at 1064 nm. MicroPET imaging of 4T1 tumor-bearing mice showed a gradual accumulation of the NPs in the tumor over time. About 6.5% of injected dose were taken up in each gram of tumor tissue at 24 h after intravenous injection of 64Cu-labeled PEG-CuS NPs. For both photoacoustic imaging and therapeutic studies, nanosecond (ns)-pulsed laser was delivered with Q-switched Nd:YAG at a wavelength of 1064 nm. Unlike conventional photothermal ablation therapy mediated by continuous wave laser with which heat could spread to the surrounding normal tissue, interaction of CuS NPs with short pulsed laser deliver heat rapidly to the treatment volume keeping the thermal damage confined to the target tissues. Our data demonstrated that it is possible to use a single-compartment nanoplatform to achieve both photoacoustic tomography and highly selective tumor destruction at 1064 nm in small animals.Here, we report that polyethylene glycol (PEG)-coated copper(ii) sulfide nanoparticles (PEG-CuS NPs) with their peak absorption tuned to 1064 nm could be used both as a contrast agent for photoacoustic tomographic imaging of mouse tumor vasculature and as a mediator for confined photothermolysis of tumor cells in an orthotopic syngeneic 4T1 breast tumor model. PEG-CuS NPs showed stronger photoacoustic signal than hollow gold nanospheres and single-wall carbon nanotubes at 1064 nm. MicroPET imaging of 4T1 tumor-bearing mice showed a gradual accumulation of the NPs in the tumor over time. About 6.5% of injected dose were

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

    CERN Document Server

    Simandoux, Oliver; Gâteau, Jérôme; Bossy, Emmanuel

    2013-01-01

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

  12. Photoacoustic Imaging of the Breast Using the Twente Photoacoustic Mammoscope: Present Status and Future Perspectives

    NARCIS (Netherlands)

    D. Piras; W. Xia; W. Steenbergen; T.G. van Leeuwen; S. Manohar

    2010-01-01

    The Twente photoacoustic mammoscope (PAM) uses pulsed light at 1064 nm to excite PA signals. Detection is using a planar 590-element ultrasound (US) sensor matrix. Image reconstruction uses a delay-and-sum beamforming algorithm. Measurements are performed in the forward mode, with mild compression o

  13. Photoacoustic Imaging: Semiconducting Oligomer Nanoparticles as an Activatable Photoacoustic Probe with Amplified Brightness for In Vivo Imaging of pH (Adv. Mater. 19/2016).

    Science.gov (United States)

    Miao, Qingqing; Lyu, Yan; Ding, Dan; Pu, Kanyi

    2016-05-01

    Despite the great potential of photoacoustic imaging in the life sciences, the development of smart activatable photoacoustic probes remains elusive. On page 3662, K. Pu and co-workers report a facile nanoengineering approach based on semiconducting oligomer nano-particles to develop ratiometric photoacoustic probes with amplified brightness and enhanced sensing capability for accurate photoacoustic mapping of pH in the tumors of living mice.

  14. Visualization of microcalcifications using photoacoustic imaging: feasibility study

    Science.gov (United States)

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

    2011-03-01

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

  15. Combined Photoacoustic-Acoustic Technique for Crack Imaging

    Science.gov (United States)

    Zakrzewski, J.; Chigarev, N.; Tournat, V.; Gusev, V.

    2010-01-01

    Nonlinear imaging of a crack by combination of a common photoacoustic imaging technique with additional acoustic loading has been performed. Acoustic signals at two different fundamental frequencies were launched in the sample, one photoacoustically through heating of the sample surface by the intensity-modulated scanning laser beam and another by a piezoelectrical transducer. The acoustic signal at mixed frequencies, generated due to system nonlinearity, has been detected by an accelerometer. Different physical mechanisms of the nonlinearity contributing to the contrast in linear and nonlinear photoacoustic imaging of the crack are discussed.

  16. Photoacoustic Soot Spectrometer (PASS) Instrument Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Dubey, M [Los Alamos National Laboratory; Springston, S [Brookhaven National Laboratory; Koontz, A [Pacific Northwest National Laboratory; Aiken, A [Los Alamos National Laboratory

    2013-01-17

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

  17. Mathematics of Photoacoustic and Thermoacoustic Tomography

    CERN Document Server

    Kuchment, Peter

    2009-01-01

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

  18. Micro-optical-mechanical system photoacoustic spectrometer

    Science.gov (United States)

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

    2013-01-01

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

  19. FPGA-based reconfigurable processor for ultrafast interlaced ultrasound and photoacoustic imaging.

    Science.gov (United States)

    Alqasemi, Umar; Li, Hai; Aguirre, Andrés; Zhu, Quing

    2012-07-01

    In this paper, we report, to the best of our knowledge, a unique field-programmable gate array (FPGA)-based reconfigurable processor for real-time interlaced co-registered ultrasound and photoacoustic imaging and its application in imaging tumor dynamic response. The FPGA is used to control, acquire, store, delay-and-sum, and transfer the data for real-time co-registered imaging. The FPGA controls the ultrasound transmission and ultrasound and photoacoustic data acquisition process of a customized 16-channel module that contains all of the necessary analog and digital circuits. The 16-channel module is one of multiple modules plugged into a motherboard; their beamformed outputs are made available for a digital signal processor (DSP) to access using an external memory interface (EMIF). The FPGA performs a key role through ultrafast reconfiguration and adaptation of its structure to allow real-time switching between the two imaging modes, including transmission control, laser synchronization, internal memory structure, beamforming, and EMIF structure and memory size. It performs another role by parallel accessing of internal memories and multi-thread processing to reduce the transfer of data and the processing load on the DSP. Furthermore, because the laser will be pulsing even during ultrasound pulse-echo acquisition, the FPGA ensures that the laser pulses are far enough from the pulse-echo acquisitions by appropriate time-division multiplexing (TDM). A co-registered ultrasound and photoacoustic imaging system consisting of four FPGA modules (64-channels) is constructed, and its performance is demonstrated using phantom targets and in vivo mouse tumor models. PMID:22828830

  20. In-vivo continuous monitoring of mixed venous oxygen saturation by photoacoustic transesophageal echocardiography (Conference Presentation)

    Science.gov (United States)

    Li, Li; Subramaniam, Balachundhar; Aguirre, Aaron D.; Andrawes, Michael N.; Tearney, Guillermo J.

    2016-02-01

    Mixed venous oxygen saturation (SvO2), measured from pulmonary arteries, is a gold-standard measure of the dynamic balance between the oxygen supply and demand in the body. In critical care, continuous monitoring of SvO2 plays a vital role in early detection of circulatory shock and guiding goal-oriented resuscitation. In current clinical practice, SvO2 is measured by invasive pulmonary artery catheters (PAC), which are associated with a 10% risk of severe complications. To address the unmet clinical need for a non-invasive SvO2 monitor, we are developing a new technology termed photoacoustic transesophageal echocardiography (PA-TEE). PA-TEE integrates transesophageal echocardiography with photoacoustic oximetry, and enables continuous assessment of SvO2 through an esophageal probe that can be inserted into the body in a minimally invasive manner. We have constructed a clinically translatable PA-TEE prototype, which features a mobile OPO laser, a modified ultrasonography console and a dual-modality esophageal probe. Comprised of a rotatable acoustic array detector, a flexible optical fiber bundle and a light-integrating acoustic lens, the oximetric probe has an outer diameter smaller than 15 mm and will be tolerable for most patients. Through custom-made C++/Qt software, our device acquires and displays ultrasonic and photoacoustic images in real time to guide the deployment of the probe. SvO2 is calculated on-line and updated every second. PA-TEE has now been used to evaluate SvO2 in living swine. Our findings show that changing the fraction of oxygen in the inspired gas modulates SvO2 measured by PA-TEE. Statistic comparison between SvO2 measurements from PA-TEE in vivo the gold-standard laboratorial analysis on blood samples drawn from PACs will be presented.

  1. FPGA-Based Reconfigurable Processor for Ultrafast Interlaced Ultrasound and Photoacoustic Imaging

    Science.gov (United States)

    Alqasemi, Umar; Li, Hai; Aguirre, Andrés; Zhu, Quing

    2016-01-01

    In this paper, we report, to the best of our knowledge, a unique field-programmable gate array (FPGA)-based reconfigurable processor for real-time interlaced co-registered ultrasound and photoacoustic imaging and its application in imaging tumor dynamic response. The FPGA is used to control, acquire, store, delay-and-sum, and transfer the data for real-time co-registered imaging. The FPGA controls the ultrasound transmission and ultrasound and photoacoustic data acquisition process of a customized 16-channel module that contains all of the necessary analog and digital circuits. The 16-channel module is one of multiple modules plugged into a motherboard; their beamformed outputs are made available for a digital signal processor (DSP) to access using an external memory interface (EMIF). The FPGA performs a key role through ultrafast reconfiguration and adaptation of its structure to allow real-time switching between the two imaging modes, including transmission control, laser synchronization, internal memory structure, beamforming, and EMIF structure and memory size. It performs another role by parallel accessing of internal memories and multi-thread processing to reduce the transfer of data and the processing load on the DSP. Furthermore, because the laser will be pulsing even during ultrasound pulse-echo acquisition, the FPGA ensures that the laser pulses are far enough from the pulse-echo acquisitions by appropriate time-division multiplexing (TDM). A co-registered ultrasound and photoacoustic imaging system consisting of four FPGA modules (64-channels) is constructed, and its performance is demonstrated using phantom targets and in vivo mouse tumor models. PMID:22828830

  2. Addition of Tomographic Capabilities to NMIS

    CERN Document Server

    Mullens, J A

    2003-01-01

    This paper describes tomographic capabilities for the Nuclear Materials Identification System (NMIS). The tomographic capabilities add weapons component spatial and material properties information that result in a more detailed item signature (template) and provide more information for physical attributes analyses. The Nuclear Materials Identification System (NMIS) is used routinely to confirm the identity of HEU components in sealed containers. It does this through a radiation signature acquired by shining a sup 2 sup 5 sup 2 Cf source through the container and measuring the radiation at four detectors stacked vertically on the other side. This measurement gives a gamma and neutron radiation transmission profile of the weapons component, mixed with the radiation production due to the induced fissions in the fissile materials. This information is sufficient to match an ''unknown'' weapons component signature to a template signature from a reference item when measuring under controlled conditions. Tomography m...

  3. Tomographic Techniques for Radar Ice Sounding

    DEFF Research Database (Denmark)

    Nielsen, Ulrik

    challenge. This dissertation deals with tomographic techniques based on multiphase-center radars that represent state-of-the-art technology within thefield of ice sounding. The use of advanced tomographic processing forclutter suppression is investigated, which up to this point has beenlargely unexplored...... in the literature. The investigation also includes atheoretical study of beamforming and direction-of-arrival (DOA) estimationtechniques. In addition to the primary treatment of clutter suppression,additional novel applications of tomography are also explored. Based on an experimental multi-phase-center dataset...... discrimination of the desired bed return from strong surface clutter ispresented. The technique is applied to data from the channel of the challengingJakobshavn Glacier acquired with the Multi-channel CoherentiiiRadar Depth Sounder/Imager (MCoRDS/I), where it is shown how thetechnique can be used to close some...

  4. On the tomographic picture of quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Ibort, A., E-mail: albertoi@math.uc3m.e [Departamento de Matematicas, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganes, Madrid (Spain); Man' ko, V.I., E-mail: manko@na.infn.i [P.N. Lebedev Physical Institute, Leninskii Prospect 53, Moscow 119991 (Russian Federation); Marmo, G., E-mail: marmo@na.infn.i [Dipartimento di Scienze Fisiche dell' Universita ' Federico II' e Sezione INFN di Napoli, Complesso Universitario di Monte S. Angelo, via Cintia, 80126 Naples (Italy); Simoni, A., E-mail: simoni@na.infn.i [Dipartimento di Scienze Fisiche dell' Universita ' Federico II' e Sezione INFN di Napoli, Complesso Universitario di Monte S. Angelo, via Cintia, 80126 Naples (Italy); Ventriglia, F., E-mail: ventriglia@na.infn.i [Dipartimento di Scienze Fisiche dell' Universita ' Federico II' e Sezione INFN di Napoli, Complesso Universitario di Monte S. Angelo, via Cintia, 80126 Naples (Italy)

    2010-06-07

    We formulate necessary and sufficient conditions for a symplectic tomogram of a quantum state to determine the density state. We establish a connection between the (re)construction by means of symplectic tomograms with the construction by means of Naimark positive definite functions on the Weyl-Heisenberg group. This connection is used to formulate properties which guarantee that tomographic probabilities describe quantum states in the probability representation of quantum mechanics.

  5. On the Tomographic Picture of Quantum Mechanics

    CERN Document Server

    Ibort, A; Marmo, G; Simoni, A; Ventriglia, F

    2010-01-01

    We formulate necessary and sufficient conditions for a symplectic tomogram of a quantum state to determine the density state. We establish a connection between the (re)construction by means of symplectic tomograms with the construction by means of Naimark positive-definite functions on the Weyl-Heisenberg group. This connection is used to formulate properties which guarantee that tomographic probabilities describe quantum states in the probability representation of quantum mechanics.

  6. On the tomographic picture of quantum mechanics

    Science.gov (United States)

    Ibort, A.; Man'ko, V. I.; Marmo, G.; Simoni, A.; Ventriglia, F.

    2010-06-01

    We formulate necessary and sufficient conditions for a symplectic tomogram of a quantum state to determine the density state. We establish a connection between the (re)construction by means of symplectic tomograms with the construction by means of Naimark positive definite functions on the Weyl-Heisenberg group. This connection is used to formulate properties which guarantee that tomographic probabilities describe quantum states in the probability representation of quantum mechanics.

  7. On the tomographic picture of quantum mechanics

    International Nuclear Information System (INIS)

    We formulate necessary and sufficient conditions for a symplectic tomogram of a quantum state to determine the density state. We establish a connection between the (re)construction by means of symplectic tomograms with the construction by means of Naimark positive definite functions on the Weyl-Heisenberg group. This connection is used to formulate properties which guarantee that tomographic probabilities describe quantum states in the probability representation of quantum mechanics.

  8. Computed tomographic colonography:Hope or hype?

    Institute of Scientific and Technical Information of China (English)

    Otto; Schiueh-Tzang; Lin

    2010-01-01

    Computed tomographic colonography (CTC) is a promising emerging technology for imaging of the colon. This concise review discusses the currently available data on CTC technique,test characteristics,acceptance,safety,cost-effectiveness,follow-up strategy,and extracolonic findings. In summary,CTC technique is still evolving,and further research is needed to clarify the role of automated colonic insufflation,smooth-muscle relaxants,intravenous and oral contrast,soft-ware rendering,and patient positioning. Curr...

  9. Computed tomographic findings of benign retroperitoneal tumors

    Energy Technology Data Exchange (ETDEWEB)

    Matsuura, Takashi; Nakata, Hajime; Nakayama, Chikashi (Univ. of Occupational and Environmental Health School of Medicine, Kitakyushu, Fukuoka (Japan)); Nishitani, Hiroshi; Matsuura, Keiichi

    1983-07-01

    We have reviewed the computed tomographic (CT) findings of 8 cases of benign retroperitoneal tumors with histological proof. Two teratomas, two schwannomas, and one each of epidermoid cyst, simple cyst, bronchogenic cyst, and cystic lymphangioma were included. The most common CT appearance of these tumors was the solitary, round, well-demarcated, relatively low density mass. Capsule or calcification was demonstrated in some. CT is a highly valuable non-invasive examination method for a diagnosis of a benign retroperitoneal tumor.

  10. Cosmological dynamics in tomographic probability representation

    OpenAIRE

    Man'ko, V. I.; G. Marmo(Università di Napoli and INFN, Napoli, Italy); Stornaiolo, C.

    2004-01-01

    The probability representation for quantum states of the universe in which the states are described by a fair probability distribution instead of wave function (or density matrix) is developed to consider cosmological dynamics. The evolution of the universe state is described by standard positive transition probability (tomographic transition probability) instead of the complex transition probability amplitude (Feynman path integral) of the standard approach. The latter one is expressed in te...

  11. Fast integrated intravascular photoacoustic/ultrasound catheter

    Science.gov (United States)

    Choi, Changhoon; Cho, Seunghee; Kim, Taehoon; Park, Sungjo; Park, Hyoeun; Kim, Jinmoo; Lee, Seunghoon; Kang, Yeonsu; Jang, Kiyuk; Kim, Chulhong

    2016-03-01

    In cardiology, a vulnerable plaque is considered to be a key subject because it is strongly related to atherosclerosis and acute myocardial infarction. Because conventional intravascular imaging devices exhibit several limitations with regard to vulnerable plaque detection, the need for an effective lipid imaging modality has been continuously suggested. Photoacoustic (PA) imaging is a medical imaging technique with a high level of ultrasound (US) resolution and strong optical contrast. In this study, we successfully developed an integrated intravascular photoacoustic/ultrasound (IV-PAUS) imaging system with a catheter diameter of 1.2 mm for lipid-rich atherosclerosis imaging. An Nd:YAG pulsed laser with an excitation wavelength of 1064 nm was utilized. IV-PAUS offers 5-mm depth penetration and axial and lateral PA imaging resolutions of 94 μm and 203 μm, respectively, as determined by imaging a 6-μm carbon fiber. We initially obtained 3-dimensional (3D) co-registered PA/US images of metal stents. Subsequently, we successfully obtained 3D coregistered PA/US ex vivo images using an iliac artery from a rabbit atherosclerosis model. Accordingly, lipid-rich plaques were sufficiently differentiated from normal tissue in the ex vivo experiment. We validated these findings histologically to confirm the lipid content.

  12. Spatial Angular Compounding of Photoacoustic Images.

    Science.gov (United States)

    Kang, Hyun Jae; Bell, Muyinatu A Lediju; Guo, Xiaoyu; Boctor, Emad M

    2016-08-01

    Photoacoustic (PA) images utilize pulsed lasers and ultrasound transducers to visualize targets with higher optical absorption than the surrounding medium. However, they are susceptible to acoustic clutter and background noise artifacts that obfuscate biomedical structures of interest. We investigated three spatial-angular compounding methods to improve PA image quality for biomedical applications, implemented by combining multiple images acquired as an ultrasound probe was rotated about the elevational axis with the laser beam and target fixed. Compounding with conventional averaging was based on the pose information of each PA image, while compounding with weighted and selective averaging utilized both the pose and image content information. Weighted-average compounding enhanced PA images with the least distortion of signal size, particularly when there were large (i.e., 2.5 mm and 7 (°)) perturbations from the initial probe position. Selective-average compounding offered the best improvement in image quality with up 181, 1665, and 1568 times higher contrast, CNR, and SNR, respectively, compared to the mean values of individual PA images. The three presented spatial compounding methods have promising potential to enhance image quality in multiple photoacoustic applications. PMID:26890642

  13. Functional photoacoustic microscopy of diabetic vasculature

    Science.gov (United States)

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

    2012-06-01

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

  14. Standoff photoacoustic sensing of trace chemicals by laser Doppler vibrometer

    Science.gov (United States)

    Fu, Y.; Hu, Q.; Liu, H.

    2016-05-01

    Photoacoustic spectroscopy (PAS) is a useful technique that suitable for trace detection of chemicals and explosives. Normally a high-sensitive microphone or a quartz tuning fork is used to detect the signal in photoacoustic cell. In recent years, laser Doppler vibrometer (LDV) is proposed to remote-sense photoacoustic signal on various substrates. It is a high-sensitivity sensor with a displacement resolution of effect of various chemicals is excited by a quantum cascade laser (QCL) with a scanning wavelength range of 6.89μm to 8.5 μm. A home-developed LDV at 1550nm wavelength is applied to detect the vibration signal. After normalize the vibration amplitude with QCL power, the photoacoustic spectrum of various chemicals can be obtained. Different factors that affect the detection accuracy and sensitivity have also been discussed. The results show the potential of the proposed technique for standoff detection of trace chemicals and explosives.

  15. Photoacoustic Imaging in Oncology: Translational Preclinical and Early Clinical Experience.

    Science.gov (United States)

    Valluru, Keerthi S; Wilson, Katheryne E; Willmann, Jürgen K

    2016-08-01

    Photoacoustic imaging has evolved into a clinically translatable platform with the potential to complement existing imaging techniques for the management of cancer, including detection, characterization, prognosis, and treatment monitoring. In photoacoustic imaging, tissue is optically excited to produce ultrasonographic images that represent a spatial map of optical absorption of endogenous constituents such as hemoglobin, fat, melanin, and water or exogenous contrast agents such as dyes and nanoparticles. It can therefore provide functional and molecular information that allows noninvasive soft-tissue characterization. Photoacoustic imaging has matured over the years and is currently being translated into the clinic with various clinical studies underway. In this review, the current state of photoacoustic imaging is presented, including techniques and instrumentation, followed by a discussion of potential clinical applications of this technique for the detection and management of cancer. (©) RSNA, 2016. PMID:27429141

  16. Photoacoustic microscopy by photodeformation applied to thermal diffusivity determination

    OpenAIRE

    Balageas, Daniel; Boscher, Daniel; Déom, Alain; Enguehard, Franck

    1991-01-01

    International audience In this paper, an original technique is proposed to measure the thermal diffusivity at local scale using a photoacoustic microscopy set-up. Several experimental results collected on thin metallic layers are presented.

  17. Dual Modality Noncontact Photoacoustic and Spectral Domain OCT Imaging

    OpenAIRE

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

    2016-01-01

    We developed a multimodal imaging system, combining noncontact photoacoustic imaging and optical coherence tomography (OCT). Photoacoustic signals are recorded without contact to the specimens’ surface by using an interferometric technique. The interferometer is realized within a fiber-optic network using a fiber laser at 1550 nm as source. The fiber-optic network allows the integration of a fiber-based OCT system operating at a wavelength region around 1310 nm. Light from the fiber laser and...

  18. Photoacoustic microscopy of tyrosinase reporter gene in vivo

    OpenAIRE

    Krumholz, Arie; VanVickle-Chavez, Sarah J.; Yao, Junjie; Fleming, Timothy P.; Gillanders, William E.; Wang, Lihong V.

    2011-01-01

    Photoacoustic tomography is a hybrid modality based on optical absorption excitation and ultrasonic detection. It is sensitive to melanin, one of the primary absorbers in skin. For cells that do not naturally contain melanin, melanin production can be induced by introducing the gene for tyrosinase, the primary enzyme responsible for expression of melanin in melanogenic cells. Optical resolution photoacoustic microscopy was used in the ex vivo study reported here, where the signal from transfe...

  19. Photoacoustic Doppler effect from flowing small light-absorbing particles.

    Science.gov (United States)

    Fang, Hui; Maslov, Konstantin; Wang, Lihong V

    2007-11-01

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

  20. Photoacoustic method for measuring concentration of chemical species

    Science.gov (United States)

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

    2001-01-01

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

  1. Comparison of transrectal photoacoustic, Doppler, and magnetic resonance imaging for prostate cancer detection

    Science.gov (United States)

    Ishihara, Miya; Horiguchi, Akio; Shinmoto, Hiroshi; Tsuda, Hitoshi; Irisawa, Kaku; Wada, Takatsugu; Asano, Tomohiko

    2016-03-01

    Transrectal ultrasonography (TRUS) is the most popular imaging modality for diagnosing and treating prostate cancer. TRUS-guided prostate biopsy is mandatory for the histological diagnosis of patients with elevated serum prostatespecific antigen (PSA), but its diagnostic accuracy is not satisfactory due to TRUS's low resolution. As a result, a considerable number of patients are required to undergo an unnecessary repeated biopsy. Photoacoustic imaging (PAI) can be used to provide microvascular network imaging using hemoglobin as an intrinsic, optical absorption molecule. We developed an original TRUS-type PAI probe consisting of a micro-convex array transducer with an optical illumination system to provide superimposed PAI and ultrasound images. TRUS-type PAI has the advantage of having much higher resolution and greater contrast than does Doppler TRUS. The purpose of this study was to demonstrate the clinical feasibility of the transrectal PAI system. We performed a clinical trial to compare the image of the cancerous area obtained by transrectal PAI with that obtained by TRUS Doppler during prostate biopsy. The obtained prostate biopsy cores were stained with anti-CD34 antibodies to provide a microvascular distribution map. We also confirmed its consistency with PAI and pre-biopsy MRI findings. Our study demonstrated that transrectal identification of tumor angiogenesis under superimposed photoacoustic and ultrasound images was easier than that under TRUS alone. We recognized a consistent relationship between PAI and MRI findings in most cases. However, there were no correspondences in some cases.

  2. Three-dimensional photoacoustic endoscopic imaging of the rabbit esophagus.

    Directory of Open Access Journals (Sweden)

    Joon Mo Yang

    Full Text Available We report photoacoustic and ultrasonic endoscopic images of two intact rabbit esophagi. To investigate the esophageal lumen structure and microvasculature, we performed in vivo and ex vivo imaging studies using a 3.8-mm diameter photoacoustic endoscope and correlated the images with histology. Several interesting anatomic structures were newly found in both the in vivo and ex vivo images, which demonstrates the potential clinical utility of this endoscopic imaging modality. In the ex vivo imaging experiment, we acquired high-resolution motion-artifact-free three-dimensional photoacoustic images of the vasculatures distributed in the walls of the esophagi and extending to the neighboring mediastinal regions. Blood vessels with apparent diameters as small as 190 μm were resolved. Moreover, by taking advantage of the dual-mode high-resolution photoacoustic and ultrasound endoscopy, we could better identify and characterize the anatomic structures of the esophageal lumen, such as the mucosal and submucosal layers in the esophageal wall, and an esophageal branch of the thoracic aorta. In this paper, we present the first photoacoustic images showing the vasculature of a vertebrate esophagus and discuss the potential clinical applications and future development of photoacoustic endoscopy.

  3. Photoacoustic image reconstruction based on Bayesian compressive sensing algorithm

    Institute of Scientific and Technical Information of China (English)

    Mingjian Sun; Naizhang Feng; Yi Shen; Jiangang Li; Liyong Ma; Zhenghua Wu

    2011-01-01

    The photoacoustic tomography (PAT) method, based on compressive sensing (CS) theory, requires that,for the CS reconstruction, the desired image should have a sparse representation in a known transform domain. However, the sparsity of photoacoustic signals is destroyed because noises always exist. Therefore,the original sparse signal cannot be effectively recovered using the general reconstruction algorithm. In this study, Bayesian compressive sensing (BCS) is employed to obtain highly sparse representations of photoacoustic images based on a set of noisy CS measurements. Results of simulation demonstrate that the BCS-reconstructed image can achieve superior performance than other state-of-the-art CS-reconstruction algorithms.%@@ The photoacoustic tomography (PAT) method, based on compressive sensing (CS) theory, requires that,for the CS reconstruction, the desired image should have a sparse representation in a known transform domain.However, the sparsity of photoacoustic signals is destroyed because noises always exist.Therefore,the original sparse signal cannot be effectively recovered using the general reconstruction algorithm.In this study, Bayesian compressive sensing (BCS) is employed to obtain highly sparse representations of photoacoustic inages based on a set of noisy CS measurements.Results of simulation demonstrate that the BCS-reconstructed image can achieve superior performance than other state-of-the-art CS-reconstruction algorithms.

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

    Science.gov (United States)

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

    2015-04-10

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

  5. Three-dimensional photoacoustic endoscopic imaging of the rabbit esophagus.

    Science.gov (United States)

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

    2015-01-01

    We report photoacoustic and ultrasonic endoscopic images of two intact rabbit esophagi. To investigate the esophageal lumen structure and microvasculature, we performed in vivo and ex vivo imaging studies using a 3.8-mm diameter photoacoustic endoscope and correlated the images with histology. Several interesting anatomic structures were newly found in both the in vivo and ex vivo images, which demonstrates the potential clinical utility of this endoscopic imaging modality. In the ex vivo imaging experiment, we acquired high-resolution motion-artifact-free three-dimensional photoacoustic images of the vasculatures distributed in the walls of the esophagi and extending to the neighboring mediastinal regions. Blood vessels with apparent diameters as small as 190 μm were resolved. Moreover, by taking advantage of the dual-mode high-resolution photoacoustic and ultrasound endoscopy, we could better identify and characterize the anatomic structures of the esophageal lumen, such as the mucosal and submucosal layers in the esophageal wall, and an esophageal branch of the thoracic aorta. In this paper, we present the first photoacoustic images showing the vasculature of a vertebrate esophagus and discuss the potential clinical applications and future development of photoacoustic endoscopy.

  6. High frame rate photoacoustic imaging using clinical ultrasound system

    Science.gov (United States)

    Sivasubramanian, Kathyayini; Pramanik, Manojit

    2016-03-01

    Photoacoustic tomography (PAT) is a potential hybrid imaging modality which is gaining attention in the field of medical imaging. Typically a Q-switched Nd:YAG laser is used to excite the tissue and generate photoacoustic signals. But, they are not suitable for clinical applications owing to their high cost, large size. Also, their low pulse repetition rate (PRR) of few tens of hertz prevents them from being used in real-time PAT. So, there is a growing need for an imaging system capable of real-time imaging for various clinical applications. In this work, we are using a nanosecond pulsed laser diode as an excitation source and a clinical ultrasound imaging system to obtain the photoacoustic imaging. The excitation laser is ~803 nm in wavelength with energy of ~1.4 mJ per pulse. So far, the reported frame rate for photoacoustic imaging is only a few hundred Hertz. We have demonstrated up to 7000 frames per second framerate in photoacoustic imaging (B-mode) and measured the flow rate of fast moving obje ct. Phantom experiments were performed to test the fast imaging capability and measure the flow rate of ink solution inside a tube. This fast photoacoustic imaging can be used for various clinical applications including cardiac related problems, where the blood flow rate is quite high, or other dynamic studies.

  7. Photoacoustic Techniques for Trace Gas Sensing Based on Semiconductor Laser Sources

    Directory of Open Access Journals (Sweden)

    Vincenzo Spagnolo

    2009-12-01

    Full Text Available 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.

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

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new highly sensitive spectroscopy technique- differential photoacoustic spectroscopy (PAS) is presented in this paper. The blood samples from 3 healthy persons, patients with leukemia, patients with pregnancy-induced hypertension (PIH), and 40 patients with nasopharyngeal carcinoma were measured by the PAS technique. The normalized, the first order, and the second order differential photoacoustic spectroscopy of the blood were gained. The results show that (ⅰ) weak absorption peaks or shoulder peaks, which could not be found using conventional photoacoustic spectroscopy, were determined by the first order and the second order differential photoacoustic spectroscopy which significantly improve the sensitivity of detection; and (ii) that two characteristic absorption peaks were found at the wavelength of 637 and 664 nm in all persons' blood samples by the differential photoacoustic spectroscopy technique. This experiment concludes that the differential photoacoustic spectroscopy technique is superior to the conventional photoacoustic spectroscopy technique in detecting photoacoustic spectroscopy of biological samples.

  9. Tomographic apparatus for reconstructing planar slices from non-absorbed and non-scattered radiation

    International Nuclear Information System (INIS)

    After briefly reviewing the history of computerised tomography, the deficiencies inherent in the various methods that have been adopted are discussed, e.g. slow data collection time, blurring of images and poor spatial resolution. Tomographic apparatus and processing methods are then described which can overcome these problems. The apparatus consists of a fan-shaped source of X-rays and a detector array which both rotate around the patient being examined. The data reduction process is derived in great detail; it is claimed that digital processing using convolution techniques is much faster than conventional methods. (U.K.)

  10. 3D Reconstruction Technique for Tomographic PIV

    Institute of Scientific and Technical Information of China (English)

    姜楠; 包全; 杨绍琼

    2015-01-01

    Tomographic particle image velocimetry(Tomo-PIV) is a state-of-the-art experimental technique based on a method of optical tomography to achieve the three-dimensional(3D) reconstruction for three-dimensional three-component(3D-3C) flow velocity measurements. 3D reconstruction for Tomo-PIV is carried out herein. Meanwhile, a 3D simplified tomographic reconstruction model reduced from a 3D volume light inten-sity field with 2D projection images into a 2D Tomo-slice plane with 1D projecting lines, i.e., simplifying this 3D reconstruction into a problem of 2D Tomo-slice plane reconstruction, is applied thereafter. Two kinds of the most well-known algebraic reconstruction techniques, algebraic reconstruction technique(ART) and multiple algebraic reconstruction technique(MART), are compared as well. The principles of the two reconstruction algorithms are discussed in detail, which has been performed by a series of simulation images, yielding the corresponding recon-struction images that show different features between the ART and MART algorithm, and then their advantages and disadvantages are discussed. Further discussions are made for the standard particle image reconstruction when the background noise of the pre-initial particle image has been removed. Results show that the particle image recon-struction has been greatly improved. The MART algorithm is much better than the ART. Furthermore, the computa-tional analyses of two parameters(the particle density and the number of cameras), are performed to study their effects on the reconstruction. Lastly, the 3D volume particle field is reconstructed by using the improved algorithm based on the simplified 3D tomographic reconstruction model, which proves that the algorithm simplification is feasible and it can be applied to the reconstruction of 3D volume particle field in a Tomo-PIV system.

  11. Health risks from computed tomographic screening.

    Science.gov (United States)

    Krantz, Seth B; Meyers, Bryan F

    2015-05-01

    Results of the recent National Lung Cancer Screening Trial show a significant survival benefit for annual screening with a low-dose computed tomographic (CT) scan in high-risk individuals. This result has led the US Preventive Services Task Force to recommend annual low-dose CT scans for this at-risk population. Less well characterized are the risks from screening. The primary risks from screening are radiation exposure, false-positive results and unnecessary diagnostic and therapeutic procedures, overdiagnosis and overtreatment, and increased psychological distress. This article reviews these risks, which must be considered and weighed against the benefits when discussing enrollment with patients. PMID:25901559

  12. Total Variation and Tomographic Imaging from Projections

    DEFF Research Database (Denmark)

    Hansen, Per Christian; Jørgensen, Jakob Heide

    2011-01-01

    Total Variation (TV) regularization is a powerful technique for image reconstruction tasks such as denoising, in-painting, and deblurring, because of its ability to produce sharp edges in the images. In this talk we discuss the use of TV regularization for tomographic imaging, where we compute a 2D...... or 3D reconstruction from noisy projections. We demonstrate that for a small signal-to-noise ratio, this new approach allows us to compute better (i.e., more reliable) reconstructions than those obtained by classical methods. This is possible due to the use of the TV reconstruction model, which...

  13. Computed tomographic analysis of urinary calculi

    Energy Technology Data Exchange (ETDEWEB)

    Newhouse, J.H.; Prien, E.L.; Amis, E.S. Jr.; Dretler, S.P.; Pfister, R.C.

    1984-03-01

    Excised urinary calculi were subjected to computed tomographic (CT) scanning in an attempt to determine whether CT attenuation values would allow accurate analysis of stone composition. The mean, maximum, and modal pixel densities of the calculi were recorded and compared; the resulting values reflected considerable heterogeneity in stone density. Although uric acid and cystine calculi could be identified by their discrete ranges on one or more of these criteria, calcium-containing stones of various compositions, including struvite, could not be distinguished reliably. CT analysis of stone density is not likely to be more accurate than standard radiography in characterizing stone composition in vivo.

  14. Improving analytical tomographic reconstructions through consistency conditions

    CERN Document Server

    Arcadu, Filippo; Stampanoni, Marco; Marone, Federica

    2016-01-01

    This work introduces and characterizes a fast parameterless filter based on the Helgason-Ludwig consistency conditions, used to improve the accuracy of analytical reconstructions of tomographic undersampled datasets. The filter, acting in the Radon domain, extrapolates intermediate projections between those existing. The resulting sinogram, doubled in views, is then reconstructed by a standard analytical method. Experiments with simulated data prove that the peak-signal-to-noise ratio of the results computed by filtered backprojection is improved up to 5-6 dB, if the filter is used prior to reconstruction.

  15. Photoacoustic tomography to identify inflammatory arthritis

    Science.gov (United States)

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

    2012-09-01

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

  16. Absolute photoacoustic thermometry in deep tissue.

    Science.gov (United States)

    Yao, Junjie; Ke, Haixin; Tai, Stephen; Zhou, Yong; Wang, Lihong V

    2013-12-15

    Photoacoustic thermography is a promising tool for temperature measurement in deep tissue. Here we propose an absolute temperature measurement method based on the dual temperature dependences of the Grüneisen parameter and the speed of sound in tissue. By taking ratiometric measurements at two adjacent temperatures, we can eliminate the factors that are temperature irrelevant but difficult to correct for in deep tissue. To validate our method, absolute temperatures of blood-filled tubes embedded ~9 mm deep in chicken tissue were measured in a biologically relevant range from 28°C to 46°C. The temperature measurement accuracy was ~0.6°C. The results suggest that our method can be potentially used for absolute temperature monitoring in deep tissue during thermotherapy.

  17. Resolution enhancement in nonlinear photoacoustic imaging

    Energy Technology Data Exchange (ETDEWEB)

    Goy, Alexandre S.; Fleischer, Jason W. [Department of Electrical Engineering, Princeton University, Olden St., Princeton, New Jersey 08544 (United States)

    2015-11-23

    Nonlinear processes can be exploited to gain access to more information than is possible in the linear regime. Nonlinearity modifies the spectra of the excitation signals through harmonic generation, frequency mixing, and spectral shifting, so that features originally outside the detector range can be detected. Here, we present an experimental study of resolution enhancement for photoacoustic imaging of thin metal layers immersed in water. In this case, there is a threshold in the excitation below which no acoustic signal is detected. Above threshold, the nonlinearity reduces the width of the active area of the excitation beam, resulting in a narrower absorption region and thus improved spatial resolution. This gain is limited only by noise, as the active area of the excitation can be arbitrarily reduced when the fluence becomes closer to the threshold. Here, we demonstrate a two-fold improvement in resolution and quantify the image quality as the excitation fluence goes through threshold.

  18. Grueneisen relaxation photoacoustic microscopy in vivo

    Science.gov (United States)

    Ma, Jun; Shi, Junhui; Hai, Pengfei; Zhou, Yong; Wang, Lihong V.

    2016-06-01

    Grueneisen relaxation photoacoustic microscopy (GR-PAM) can achieve optically defined axial resolution, but it has been limited to ex vivo demonstrations so far. Here, we present the first in vivo image of a mouse brain acquired with GR-PAM. To induce the GR effect, an intensity-modulated continuous-wave laser was employed to heat absorbing objects. In phantom experiments, an axial resolution of 12.5 μm was achieved, which is sixfold better than the value achieved by conventional optical-resolution PAM. This axial-resolution improvement was further demonstrated by imaging a mouse brain in vivo, where significantly narrower axial profiles of blood vessels were observed. The in vivo demonstration of GR-PAM shows the potential of this modality for label-free and high-resolution anatomical and functional imaging of biological tissues.

  19. Multi-quartz-enhanced photoacoustic spectroscopy

    Science.gov (United States)

    Ma, Yufei; Yu, Xin; Yu, Guang; Li, Xudong; Zhang, Jingbo; Chen, Deying; Sun, Rui; Tittel, Frank K.

    2015-07-01

    A multi-quartz-enhanced photoacoustic spectroscopy (M-QEPAS) sensor system for trace gas detection is reported. Instead of a single quartz tuning fork (QTF) as used in QEPAS technique, a dual QTF sensor platform was adopted in M-QEPAS to increase the signal strength by the addition of the detected QEPAS signals. Water vapor was selected as the target analyte. M-QEPAS realized a 1.7 times signal enhancement as compared to the QEPAS method for the same operating conditions. A minimum detection limit of 23.9 ppmv was achieved for the M-QEPAS sensor, with a calculated normalized noise equivalent absorption coefficient of 5.95 × 10-8 cm-1W/√Hz. The M-QEPAS sensor performance can be further improved when more QTFs are employed or an acoustic micro-resonator architecture is used.

  20. Technique development for photoacoustic imaging guided interventions

    Science.gov (United States)

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

    2015-03-01

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

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

    Science.gov (United States)

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

    2014-03-01

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

  2. Tomographs based on non-conventional radiation sources and methods

    International Nuclear Information System (INIS)

    Computer techniques for tomographic reconstruction of objects X-rayed with a compact plasma focus (PF) are presented. The implemented reconstruction algorithms are based on stochastic searching of solutions of Radon equation, using Genetic Algorithms and Monte Carlo methods. Numerical experiments using actual projections were performed concluding the feasibility of the application of both methods in tomographic reconstruction problem. (author)

  3. Advances in Time-Resolved Tomographic Particle Image Velocimetry

    NARCIS (Netherlands)

    Lynch, K.P.

    2015-01-01

    This thesis details advanced developments in 3-D particle image velocimetry (PIV) based on the tomographic PIV technique, with an emphasis on time-resolved experiments. Tomographic PIV is a technique introduced in 2006 to measure the flow velocity in a three-dimensional volume. When measurements are

  4. Complete removal of ghost particles in Tomographic-PIV

    NARCIS (Netherlands)

    Elsinga, G.E.

    2013-01-01

    This paper discusses and compares several methods, which aim to remove spurious peaks, i.e. ghost particles, from the volume intensity reconstruction in Tomographic-PIV. The assessment is based on numerical simulations of timeresolved tomographic-PIV experiments in linear shear flows. Within the r

  5. Terahertz wave tomographic imaging with a Fresnel lens

    Institute of Scientific and Technical Information of China (English)

    S. Wang; X.-C. Zhang

    2003-01-01

    We demonstrate three-dimensional tomographic imaging using a Fresnel lens with broadband terahertz pulses. Objects at various locations along the beam propagation path are uniquely imaged on the same imaging plane using a Fresnel lens with different frequencies of the imaging beam. This procedure allows the reconstruction of an object's tomographic contrast image by assembling the frequency-dependent images.

  6. Computed tomographic features of cerebellar hemangioblastoma

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yong Lan; Ko, Young Tae; Kim, Ho Kyun [Kyung Hee University Hospital, Seoul (Korea, Republic of)

    1980-06-15

    Computed tomographic and angiographic findings of 6 proven cerebellar Hemangiotoma seen in this hospital during last 2 years were analyzed. The results were as follows: 1. Except one 14 years old female, all of them wee 37 to 48 years old males. 2. The operative findings of the tumors were 3 cystic tumors with mural nodules and 3 solid tumors. Computed tomographic findings were: 3. Of three cases of cystic cerebellar hemangiotomas, 2 cases revealed characteristic CT findings such as; a. In precontrast study, a well defined round lower density containing one isodense nodule in its periphery was seen in each case. The absorption coefficiency of each lower density was around 5 EMI unit. b. In post contrast study, the nodules were enhanced densely and homogeneously white the lower densities remain unchanged. 4. Of three cases of solid cerebella hemangiotoma, 2 cases revealed isodense mass suggested by mass effect such as displaced 4th ventricle and peripheral edema in precontrast study, while the remaining case revealed ill defined slightly high density with peripheral edema. In postcontrast study, the 2 isodense masses showed well circumscribed homogenous enhancement with central slight lower density in one of them, while high density mass revealed no enhancement at all. 5. The vertebral angiography performed in 5 cases revealed high vascular tumors with feeding arteries, draining veins and increased circulation time. 6. The tumor blushing seen in vertebral angiography was correlated to the postcontrast enhancement of solid tumors and mural nodules in cystic hemangioblastoma.

  7. Single photon tomographic imaging of the heart

    International Nuclear Information System (INIS)

    Tomographic imaging of the heart, utilizing gamma-emitting radionuclides, a rotating camera and computer reconstruction (SPECT), represents an important advance in cardiac nuclear imaging over standard 2-dimensional planar techniques. In addition to more precise 3-dimensional localization of cardiac lesions, tomography provides improved resistivity for lesion detection, improved lesion contrast, and enhanced ability to accurately quantify lesion severity and extent. The authors determined that tomographic imaging of exercise induced pefusion defects, using the flow tracer thallium-201, is superior to conventional planar imaging. By random selection, first one technique and then the other was performed in 3 groups of subjects: 54 patients with cardiac catheterization-proven coronary artery disease (CAD) defined as >50% stenosis of one or more major coronary arteries; 13 patients with no significant CAD at catheterization, and 20 normal volunteers, age 30-51. For SPECT imaging, 60 acquisitions were performed over 1800, transaxial images were reconstructed with a Hanning filter (cut-off 0.30), and data was reoriented to display short and long axis slices. Equal numbers of studies or normal volunteers and catheterization patients were interpreted without knowledge of patient identity using a five point scale. Receiver operating characteristic (ROC) analysis, in which false positives were plotted against true positives, was used to determine the full sensitivity-specificity relationships for both imaging modalities. The SPECT ROC curve was higher and to the left, indicating improved performance

  8. Computerized tomographic in non-destructive testing

    International Nuclear Information System (INIS)

    The process of computerized tomography has been developed for medical imaging purposes using tomographs with X-ray, and little attention has been given to others possibles applications of technique, because of its cost. As an alternative for the problem, we constructed a Tomographic System (STAC-1), using gamma-rays, for nonmedical applications. In this work we summarize the basic theory of reconstructing images using computerized tomography and we describe the considerations leading to the development of the experimental system. The method of reconstruction image implanted in the system is the filtered backprojection or convolution, with a digital filters system to carried on a pre-filtering in the projections. The experimental system is described, with details of control and the data processing. An alternative and a complementary system, using film as a detector is shown in preliminary form . This thesis discuss and shows the theorical and practical aspects, considered in the construction of the STAC-1, and also its limitations and apllications

  9. Super-resolution photoacoustic imaging of single gold nanoparticles

    Science.gov (United States)

    Lee, Seunghyun; Kwon, Owoong; Jeon, Mansik; Song, Jaejung; Jo, Minguk; Kim, Sungjee; Son, Junwoo; Kim, Yunseok; Kim, Chulhong

    2016-03-01

    Photoacoustic imaging (PAI) is an emerging hybrid imaging modality that can provide a strong optical absorption contrast using the photoacoustic (PA) effect, and breaks through the fundamental imaging depth limit of existing optical microscopy such as optical coherence tomography (OCT), confocal or two-photon microscopy. In PAI, a short-pulsed laser is illuminated to the tissue, and the PA waves are generated by thermoelastic expansion. Despite the high lateral resolution of optical-resolution photoacoustic microscopy (OR-PAM) thanks to the tight optical focus, the lateral resolution of OR-PAM is limited to the optical diffraction limit, which is approximately a half of the excitation wavelength. Here, we demonstrate a new super-resolution photoacoustic microscopy (SR-PAM) system by breaking the optical diffraction limit. The conventional microscopes with nanoscale resolutions such as a scanning electron microscope (SEM) and transmission electron microscope (TEM) are typically used to image the structures of nanomaterials, but these systems should work in a high vacuum environment and cannot provide the optical properties of the materials. Our newly developed SR-PAM system provides the optical properties with a nanoscale resolution in a normal atmosphere. We have photoacoustically imaged single gold nanoparticles with an average size of 80 nm in diameter and shown their PA expansion properties individually. The lateral resolution of this system was approximately 20 nm. Therefore, this tool will provide an unprecedented optical absorption property with an accurate nanoscale resolution and greatly impact on materials science and nanotechnology field.

  10. Initial studies using the RatCAP conscious animal PET tomograph

    Energy Technology Data Exchange (ETDEWEB)

    Woody, C. [Brookhaven National Laboratory, Upton, NY (United States)]. E-mail: woody@bnl.gov; Vaska, P. [Brookhaven National Laboratory, Upton, NY (United States); Schlyer, D. [Brookhaven National Laboratory, Upton, NY (United States); Pratte, J.-F. [Brookhaven National Laboratory, Upton, NY (United States); Junnarkar, S. [Brookhaven National Laboratory, Upton, NY (United States); Park, S.-J. [Brookhaven National Laboratory, Upton, NY (United States); Stoll, S. [Brookhaven National Laboratory, Upton, NY (United States); Purschke, M. [Brookhaven National Laboratory, Upton, NY (United States); Southekal, S. [Stony Brook University, Stony Brook, NY (United States); Kriplani, A. [Stony Brook University, Stony Brook, NY (United States); Krishnamoorthy, S. [Stony Brook University, Stony Brook, NY (United States); Maramraju, S. [Stony Brook University, Stony Brook, NY (United States); Lee, D. [Brookhaven National Laboratory, Upton, NY (United States); Schiffer, W. [Brookhaven National Laboratory, Upton, NY (United States); Dewey, S. [Brookhaven National Laboratory, Upton, NY (United States); Neill, J. [Long Island University, Brookville, NY (United States); Kandasamy, A. [Brookhaven National Laboratory, Upton, NY (United States); O' Connor, P. [Brookhaven National Laboratory, Upton, NY (United States); Radeka, V. [Brookhaven National Laboratory, Upton, NY (United States); Fontaine, R. [Sherbrooke University, Sherbrooke, Que. (Canada); Lecomte, R. [Sherbrooke University, Sherbrooke, Que. (Canada)

    2007-02-01

    The RatCAP is a small, head-mounted PET tomograph designed to image the brain of a conscious rat without the use of anesthesia. The detector is a complete, high-performance 3D tomograph consisting of a 3.8 cm inside-diameter ring containing 12 block detectors, each of which is comprised of a 4x8 array of 2.2x2.2x5 mm{sup 3} LSO crystals readout with a matching APD array and custom ASIC, and has a 1.8 cm axial field of view. Construction of the first working prototype detector has been completed and its performance characteristics have been measured. The results show an intrinsic spatial resolution of 2.1 mm, a time resolution of {approx}14 ns FWHM, and a sensitivity of 0.7% at an energy threshold of 150 keV. First preliminary images have been obtained using {sup 18}F-FDG and {sup 11}C-methamphetamine, which show comparable image quality to those obtained from a commercial MicroPET R4 scanner. Initial studies have also been carried out to study stress levels in rats wearing the RatCAP.

  11. Initial studies using the RatCAP conscious animal PET tomograph

    Science.gov (United States)

    Woody, C.; Vaska, P.; Schlyer, D.; Pratte, J.-F.; Junnarkar, S.; Park, S.-J.; Stoll, S.; Purschke, M.; Southekal, S.; Kriplani, A.; Krishnamoorthy, S.; Maramraju, S.; Lee, D.; Schiffer, W.; Dewey, S.; Neill, J.; Kandasamy, A.; O'Connor, P.; Radeka, V.; Fontaine, R.; Lecomte, R.

    2007-02-01

    The RatCAP is a small, head-mounted PET tomograph designed to image the brain of a conscious rat without the use of anesthesia. The detector is a complete, high-performance 3D tomograph consisting of a 3.8 cm inside-diameter ring containing 12 block detectors, each of which is comprised of a 4×8 array of 2.2×2.2×5 mm 3 LSO crystals readout with a matching APD array and custom ASIC, and has a 1.8 cm axial field of view. Construction of the first working prototype detector has been completed and its performance characteristics have been measured. The results show an intrinsic spatial resolution of 2.1 mm, a time resolution of ˜14 ns FWHM, and a sensitivity of 0.7% at an energy threshold of 150 keV. First preliminary images have been obtained using 18F-FDG and 11C-methamphetamine, which show comparable image quality to those obtained from a commercial MicroPET R4 scanner. Initial studies have also been carried out to study stress levels in rats wearing the RatCAP.

  12. Tomographic 3D-radiometry for the visualisation and measurement of the defects of girth seams

    International Nuclear Information System (INIS)

    Tomographic Computer Aided Radiology (TomoCAR) is based on the mechanical position control of an X-ray tube in front of a weld seam and the application of a Dgital Detector Array (DDA) behind it. Several hundred radiometric projections in small angle steps are acquired. The tomographical reconstruction allows the three-dimensional (3D) representation of the defects. A new radiometric detector array with small internal unsharpness and high image contrast was used for the 2- and 3-dimensional visualization and sizing of planar defects with a defect opening of less than 100 μm. This detector is based on a CMOS-flat panel with a direct converting CdTe-single crystal layer. The small design allows the application of the mobile testing equipment for mechanized X-ray inspection in industrial plants. The physical pixel size of the detector amounts to 0,1 x 0,1 mm2. Nevertheless, this system yields a better spatial resolution than indirect converting detectors (e.g. cameras with fluorescence layers of Gd2O2S). It allows the reliable detection of planar defects with openings far below the detector pixel size by subpixel resolution. A German pilot study was successfully carried out on the basis of the ENIQ guidelines. In this context 'TomoCAR' was qualified for application in the nuclear power industry. (orig.)

  13. Tomographic Diffuse Fluorescence Flow Cytometry for Enumeration of Rare Circulating Cells in Vitro and in Vivo

    Science.gov (United States)

    Zettergren, Eric William

    2011-12-01

    Accurate quantification of circulating cell populations is important in many areas of preclinical and clinical biomedical research including the study of metastasized cancers, T-Lymphotocyes and hematopoietic stem cells. Normally this is done either by extraction and analysis of small blood samples or more recently using microscopy-based in vivo fluorescence flow cytometry. In this thesis, a new technological approach to this problem is described using detection of diffuse fluorescent light from relatively large blood vessels in vivo. The 'tomographic diffuse fluorescence flow cytometer' (TDFFC) uses modulated lasers to illuminate a mouse limb and an array of optical fibers coupled to a high-sensitivity photomultiplier tube array operating in photon counting mode to detect weak fluorescence signals from cells. It is first demonstrated that the TDFFC instrument is capable of detecting fluorescent microspheres and Vybrant-DiD labeled cells with excellent accuracy in an optical flow phantom with similar size, optical properties, linear flow rates and autofluorescence as a mouse limb. Preliminary data demonstrating that the TDFFC is capable of detecting circulating cells in nude mice in vivo is also shown. Finally, a number of methods for performing coarse tomographic localization of fluorescent cells within the cross-section of a mouse limb using TDFFC data sets are described, and the feasibility of this approach is demonstrated using in vitro data sets. In principle, this device would allow interrogation of the whole blood volume of a mouse in minutes, with several orders of magnitude sensitivity improvement compared with current approaches.

  14. Photoacoustic detection of blood in dental pulp by using short-time Fourier transform

    Science.gov (United States)

    Yamada, Azusa; Kakino, Satoko; Matsuura, Yuji

    2016-03-01

    A method based on photoacoustic analysis is proposed to diagnose dental pulp vitality. Photoacoustic analysis enables to get signal from deeper tissues than other optical analyses and therefore, signal detection from root canal of thick dental tissues such as molar teeth is expected. As a light source for excitation of photoacoustic waves, a microchip Q-switched YAG laser with a wavelength of 1064 nm was used and owing to large penetration depth of the near infrared laser, photoacoustic signals from dental root were successfully obtained. It was found that the photoacoustic signals from the teeth containing hemoglobin solution in the pulp cavity provide vibration in high frequency region. It was also shown that the intensities of the high frequency component have correlation with the hemoglobin concentration of solution. We applied short-time Fourier transform for evaluation of photoacoustic signals and this analysis clearly showed photoacoustic signals from dental root.

  15. SPICE benchmark for global tomographic methods

    Science.gov (United States)

    Qin, Yilong; Capdeville, Yann; Maupin, Valerie; Montagner, Jean-Paul; Lebedev, Sergei; Beucler, Eric

    2008-11-01

    The existing global tomographic methods result in different models due to different parametrization, scale resolution and theoretical approach. To test how current imaging techniques are limited by approximations in theory and by the inadequacy of data quality and coverage, it is necessary to perform a global-scale benchmark to understand the resolving properties of each specific imaging algorithm. In the framework of the Seismic wave Propagation and Imaging in Complex media: a European network (SPICE) project, it was decided to perform a benchmark experiment of global inversion algorithms. First, a preliminary benchmark with a simple isotropic model is carried out to check the feasibility in terms of acquisition geometry and numerical accuracy. Then, to fully validate tomographic schemes with a challenging synthetic data set, we constructed one complex anisotropic global model, which is characterized by 21 elastic constants and includes 3-D heterogeneities in velocity, anisotropy (radial and azimuthal anisotropy), attenuation, density, as well as surface topography and bathymetry. The intermediate-period (>32 s), high fidelity anisotropic modelling was performed by using state-of-the-art anisotropic anelastic modelling code, that is, coupled spectral element method (CSEM), on modern massively parallel computing resources. The benchmark data set consists of 29 events and three-component seismograms are recorded by 256 stations. Because of the limitation of the available computing power, synthetic seismograms have a minimum period of 32 s and a length of 10 500 s. The inversion of the benchmark data set demonstrates several well-known problems of classical surface wave tomography, such as the importance of crustal correction to recover the shallow structures, the loss of resolution with depth, the smearing effect, both horizontal and vertical, the inaccuracy of amplitude of isotropic S-wave velocity variation, the difficulty of retrieving the magnitude of azimuthal

  16. E-learn Computed Tomographic Angiography

    DEFF Research Database (Denmark)

    Havsteen, Inger; Christensen, Anders; Nielsen, Jens K;

    2012-01-01

    BACKGROUND: Computed tomographic angiography (CTA) is widely available in emergency rooms to assess acute stroke patients. To standardize readings and educate new readers, we developed a 3-step e-learning tool based on the test-teach-retest methodology in 2 acute stroke scenarios: vascular...... occlusion and "spot sign" in acute intracerebral hemorrhage. We hypothesized that an e-learning program enhances reading skills in physicians of varying experience. METHODS: We developed an HTML-based program with a teaching segment and 2 matching test segments. Tests were taken before and after...... sign correctly 69% before versus 92% after teaching (P = .009) and reported a median self-perceived diagnostic certainty of 50% versus 75% (P = .030). Self-perceived diagnostic certainty revealed no significant increase for vascular occlusion. CONCLUSIONS: The e-learning program is a useful educational...

  17. Tomographic phase microscopy and its biological applications

    Science.gov (United States)

    Choi, Wonshik

    2012-12-01

    Conventional interferometric microscopy techniques such as digital holographic microscopy and quantitative phase microscopy are often classified as 3D imaging techniques because a recorded complex field image can be numerically propagated to a different depth. In a strict sense, however, a single complex field image contains only 2D information on a specimen. The measured 2D image is only a subset of the 3D structure. For the 3D mapping of an object, multiple independent 2D images are to be taken, for example at multiple incident angles or wavelengths, and then combined by the so-called optical diffraction tomography (ODT). In this Letter, tomographic phase microscopy (TPM) is reviewed that experimentally realizes the concept of the ODT for the 3D mapping of biological cells in their native state, and some of its interesting biological and biomedical applications are introduced. [Figure not available: see fulltext.

  18. Computed tomographic investigations on intraventricular hematomas

    International Nuclear Information System (INIS)

    This work investigated in 106 patients with intraventricular hematomas all the known factors which can have an influence on prognosis: age, sex, anamnesis of the patients, size, extent and localization of the intracranial bleeding, underlying angiopathy and differences between arterial and venous and spontaneous and traumatic bleedings. It was shown that the state of mind was the deciding prognostic factor, whereby viligance was the cumulative expression of all other investigated influences. A computed tomography (CT) examination is deciding in the question of operative hydrocephalus care. In 13 patients it was further shown, how clearly CT results and brain dissection allowed themselves to be compared. The computed tomographic examination method is best suited to achieve even physiological and more extensive prognostic possibilities. (orig.)

  19. Collimated trans-axial tomographic scintillation camera

    International Nuclear Information System (INIS)

    The objects of this invention are first to reduce the time required to obtain statistically significant data in trans-axial tomographic radioisotope scanning using a scintillation camera. Secondly, to provide a scintillation camera system to increase the rate of acceptance of radioactive events to contribute to the positional information obtainable from a known radiation source without sacrificing spatial resolution. Thirdly to reduce the scanning time without loss of image clarity. The system described comprises a scintillation camera detector, means for moving this in orbit about a cranial-caudal axis relative to a patient and a collimator having septa defining apertures such that gamma rays perpendicular to the axis are admitted with high spatial resolution, parallel to the axis with low resolution. The septa may be made of strips of lead. Detailed descriptions are given. (U.K.)

  20. Collimated trans-axial tomographic scintillation camera

    International Nuclear Information System (INIS)

    The principal problem in trans-axial tomographic radioisotope scanning is the length of time required to obtain meaningful data. Patient movement and radioisotope migration during the scanning period can cause distortion of the image. The object of this invention is to reduce the scanning time without degrading the images obtained. A system is described in which a scintillation camera detector is moved to an orbit about the cranial-caudal axis relative to the patient. A collimator is used in which lead septa are arranged so as to admit gamma rays travelling perpendicular to this axis with high spatial resolution and those travelling in the direction of the axis with low spatial resolution, thus increasing the rate of acceptance of radioactive events to contribute to the positional information obtainable without sacrificing spatial resolution. (author)

  1. Bessel beam Grueneisen photoacoustic microscopy with extended depth of field

    Science.gov (United States)

    Shi, Junhui; Wang, Lidai; Noordam, Cedric; Wang, Lihong V.

    2016-03-01

    The short focal depth of a Gaussian beam limits the volumetric imaging speed of optical resolution photoacoustic microscopy (OR-PAM). A Bessel beam, which is diffraction-free, provides a long focal depth, but its side-lobes may deteriorate image quality when the Bessel beam is directly employed to excite photoacoustic signals in ORPAM. Here, we present a nonlinear approach based on the Grueneisen relaxation effect to suppress the side-lobe artifacts in photoacoustic imaging. This method extends the focal depth of OR-PAM and speeds up volumetric imaging. We experimentally demonstrated a 1-mm focal depth with a 7-μm lateral resolution and volumetrically imaged a carbon fiber and red blood cell samples.

  2. Reconstructing absorption and scattering distributions in quantitative photoacoustic tomography

    International Nuclear Information System (INIS)

    Quantitative photoacoustic tomography is a novel hybrid imaging technique aiming at estimating optical parameters inside tissues. The method combines (functional) optical information and accurate anatomical information obtained using ultrasound techniques. The optical inverse problem of quantitative photoacoustic tomography is to estimate the optical parameters within tissue when absorbed optical energy density is given. In this paper we consider reconstruction of absorption and scattering distributions in quantitative photoacoustic tomography. The radiative transport equation and diffusion approximation are used as light transport models and solutions in different size domains are investigated. The simulations show that scaling of the data, for example by using logarithmic data, can be expected to significantly improve the convergence of the minimization algorithm. Furthermore, both the radiative transport equation and diffusion approximation can give good estimates for absorption. However, depending on the optical properties and the size of the domain, the diffusion approximation may not produce as good estimates for scattering as the radiative transport equation. (paper)

  3. Multiple stimulated emission fluorescence photoacoustic sensing and spectroscopy

    Science.gov (United States)

    Li, Gaoming; Gao, Fei; Qiu, Yishen; Feng, Xiaohua; Zheng, Yuanjin

    2016-07-01

    Multiple stimulated emission fluorescence photoacoustic (MSEF-PA) phenomenon is demonstrated in this letter. Under simultaneous illumination of pumping light and stimulated emission light, the fluorescence emission process is speeded up by the stimulated emission effect. This leads to nonlinear enhancement of photoacoustic signal while the quantity of absorbed photons is more than that of fluorescent molecules illuminated by pumping light. The electronic states' specificity of fluorescent molecular can also be labelled by the MSEF-PA signals, which can potentially be used to obtain fluorescence excitation spectrum in deep scattering tissue with nonlinearly enhanced photoacoustic detection. In this preliminary study, the fluorescence excitation spectrum is reconstructed by MSEF-PA signals through sweeping the wavelength of exciting light, which confirms the theoretical derivation well.

  4. SNR and Contrast Enhancement Techniques for the Photoacoustic Radar Imaging

    Science.gov (United States)

    Wang, Wei; Mandelis, Andreas

    2016-07-01

    This paper presents two methods for photoacoustic signal enhancement in biological tissues. One such method is based on the fact that temperature can affect the signals of the photoacoustic radar. Therefore, thermally assisted methods have been used for photoacoustic imaging contrast improvement. Another method is based on harmonic wavelength modulation which results in a differential PA radar signal to strengthen early cancer detection. Two chirped waveforms modulated out-of-phase between 680 nm and 800 nm can effectively suppress the background noise, greatly enhance the SNR and detect small variations in hemoglobin oxygenation levels, thereby distinguishing pre-malignant tumors. Experimental results demonstrate the accuracy of the frequency-modulated differential measurement with sheep blood at different hemoglobin oxygenation (S_tO2) levels.

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

    Science.gov (United States)

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

    2009-10-01

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

  6. Fabrication of a Resonant Photoacoustic Cell for Samples Study

    Directory of Open Access Journals (Sweden)

    J.C. Kapil

    2004-04-01

    Full Text Available Nondestructive treatment of a sample in photoacoustic spectroscopy is helpful in the study of thermal and optical properties of ice and snow. In the present study, a  low-temperature resonant photoacoustic cell, based on Helmholtz resonator model, has been designed and fabricated for the study of samples like ice or snow. Its performance has also been studied using carbon black as a standard sample and various other samples like water, ice, glass, plexi-glass, polycarbonate, etc. Thermal diffusivity of ice, water, and many other transparent materials has been determined by varying chopping frequency and recording corresponding phase changes in the photoacoustic signal. The results obtained are in good agreement with those predicted by Rosencwaig-Gersho (R-G' theory.

  7. Photoacoustic Imaging: Opening New Frontiers in Medical Imaging

    Directory of Open Access Journals (Sweden)

    Keerthi S Valluru

    2011-01-01

    Full Text Available In today′s world, technology is advancing at an exponential rate and medical imaging is no exception. During the last hundred years, the field of medical imaging has seen a tremendous technological growth with the invention of imaging modalities including but not limited to X-ray, ultrasound, computed tomography, magnetic resonance imaging, positron emission tomography, and single-photon emission computed tomography. These tools have led to better diagnosis and improved patient care. However, each of these modalities has its advantages as well as disadvantages and none of them can reveal all the information a physician would like to have. In the last decade, a new diagnostic technology called photoacoustic imaging has evolved which is moving rapidly from the research phase to the clinical trial phase. This article outlines the basics of photoacoustic imaging and describes our hands-on experience in developing a comprehensive photoacoustic imaging system to detect tissue abnormalities.

  8. Modeling photoacoustic spectral features of micron-sized particles.

    Science.gov (United States)

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

    2014-10-01

    The photoacoustic signal generated from particles when irradiated by light is determined by attributes of the particle such as the size, speed of sound, morphology and the optical absorption coefficient. Unique features such as periodically varying minima and maxima are observed throughout the photoacoustic signal power spectrum, where the periodicity depends on these physical attributes. The frequency content of the photoacoustic signals can be used to obtain the physical attributes of unknown particles by comparison to analytical solutions of homogeneous symmetric geometric structures, such as spheres. However, analytical solutions do not exist for irregularly shaped particles, inhomogeneous particles or particles near structures. A finite element model (FEM) was used to simulate photoacoustic wave propagation from four different particle configurations: a homogeneous particle suspended in water, a homogeneous particle on a reflecting boundary, an inhomogeneous particle with an absorbing shell and non-absorbing core, and an irregularly shaped particle such as a red blood cell. Biocompatible perfluorocarbon droplets, 3-5 μm in diameter containing optically absorbing nanoparticles were used as the representative ideal particles, as they are spherical, homogeneous, optically translucent, and have known physical properties. The photoacoustic spectrum of micron-sized single droplets in suspension and on a reflecting boundary were measured over the frequency range of 100-500 MHz and compared directly to analytical models and the FEM. Good agreement between the analytical model, FEM and measured values were observed for a droplet in suspension, where the spectral minima agreed to within a 3.3 MHz standard deviation. For a droplet on a reflecting boundary, spectral features were correctly reproduced using the FEM but not the analytical model. The photoacoustic spectra from other common particle configurations such as particle with an absorbing shell and a

  9. Ring artifacts correction in compressed sensing tomographic reconstruction

    CERN Document Server

    Paleo, Pierre

    2015-01-01

    We present a novel approach to handle ring artifacts correction in compressed sensing tomographic reconstruction. The correction is part of the reconstruction process, which differs from classical sinogram pre-processing and image post-processing techniques. The principle of compressed sensing tomographic reconstruction is presented. Then, we show that the ring artifacts correction can be integrated in the reconstruction problem formalism. We provide numerical results for both simulated and real data. This technique is included in the PyHST2 code which is used at the European Synchrotron Radiation Facility for tomographic reconstruction.

  10. Optimal laser wavelength for photoacoustic imaging of breast microcalcifications

    Science.gov (United States)

    Kang, Jeeun; Kim, Eun-Kyung; Young Kwak, Jin; Yoo, Yangmo; Song, Tai-Kyong; Ho Chang, Jin

    2011-10-01

    This paper presents photoacoustic imaging (PAI) for real-time detection of micro-scale calcifications (e.g., <1 mm) in the breast, which are an indicator of the cancer occurrence. Optimal wavelength of incident laser for the microcalcification imaging was ascertained through ex vivo experiments with seven breast specimens of volunteers. In the ex vivo experiments, the maximum amplitude of photoacoustic signals from the microcalcifications occurred when the laser wavelength ranged from 690 to 700 nm. This result demonstrated that PAI can serve as a real-time imaging and guidance tool for diagnosis and biopsy of the breast microcalcifications.

  11. In vivo photoacoustic tomography of myoglobin oxygen saturation

    Science.gov (United States)

    Lin, Li; Yao, Junjie; Li, Lei; Wang, Lihong V.

    2016-06-01

    Myoglobin is an essential oxygen-binding hemoprotein in skeletal and cardiac muscles that buffers intracellular oxygen (O2) concentration in response to hypoxia or elevated muscle activities. We present a method that uses photoacoustic computed tomography to measure the distribution of myoglobin in tissue and the oxygen saturation of myoglobin (sO2-Mb). From photoacoustic measurements of mice in different oxygenation states, we performed calibration-free quantification of the sO2-Mb change in the backbone muscle in vivo.

  12. An algorithm for total variation regularized photoacoustic imaging

    DEFF Research Database (Denmark)

    Dong, Yiqiu; Görner, Torsten; Kunis, Stefan

    2014-01-01

    Recovery of image data from photoacoustic measurements asks for the inversion of the spherical mean value operator. In contrast to direct inversion methods for specific geometries, we consider a semismooth Newton scheme to solve a total variation regularized least squares problem. During the iter......Recovery of image data from photoacoustic measurements asks for the inversion of the spherical mean value operator. In contrast to direct inversion methods for specific geometries, we consider a semismooth Newton scheme to solve a total variation regularized least squares problem. During...

  13. Cellulose nanoparticles: photoacoustic contrast agents that biodegrade to simple sugars

    Science.gov (United States)

    Jokerst, Jesse V.; Bohndiek, Sarah E.; Gambhir, Sanjiv S.

    2014-03-01

    In photoacoustic imaging, nanoparticle contrast agents offer strong signal intensity and long-term stability, but are limited by poor biodistribution and clearance profiles. Conversely, small molecules offer renal clearance, but relatively low photoacoustic signal. Here we describe a cellulose-based nanoparticle with photoacoustic signal superior to gold nanorods, but that undergoes enzymatic cleavage into constituent glucose molecules for renal clearance. Cellulose nanoparticles (CNPs) were synthesized through acidic cleavage of cellulose linters and purified with centrifugation. TEM indicated that the nanoparticles were 132 +/- 46 nm; the polydispersity index was 0.138. Ex vivo characterization showed a photoacoustic limit of detection of 0.02 mg/mL CNPs, and the photoacoustic signal of CNPs was 1.5- to 3.0-fold higher than gold nanorods (also at 700 nm resonance) on a particle-to-particle basis. Cell toxicity assays suggested that overnight doses below 0.31 mg/mL CNPs produced no significant (p>0.05) impact on cell metabolism. Intravenous doses up to 0.24 mg were tolerated well in nude mice. Subcutaneous and orthotopic tumor xenografts of the OV2008 ovarian cancer cell line were then created in nude mice. Data was collected with a Nexus128 scanner from Endra LifeSciences. Spectral data used a LAZR system from Visualsonics both at 700 nm excitation. We injected CNPs (0.024 mg, 0.048 mg, and 0.80 mg) via tail vein and showed that the tumor photoacoustic signal reached maximum increase between 10 and 20 minutes. All injected concentrations were statistically (p0.96 suggesting quantitative signal. CNP biodegradation was demonstrated ex vivo with a glucose assay. CNPs in the presence of cellulase were reduced to free glucose in under than four hours. The glucose concentration before addition of cellulase was not detectable, but increased to 92.1 μg/mL in four hours. CNPs in the absence of cellulase did not produce glucose. Small fragments of nanoparticle in the

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

    DEFF Research Database (Denmark)

    Hansen, René Skov

    The preliminary result of using a high-power light emitting diode, LED, for photoacoustic imaging is presented. The pulsed light source is created by a 1Watt red Luxeon LED. The LED delivers light pulses with 25W peak power when supplied by 40A peak, 60ns wide current pulses. The phantom used...... for the experiment consists of a 3mm high x 5mm wide slice of green colored gelatine overlaid by a 3cm layer of colorless gelatine. The light pulses from the LED is focused on the green gelatine. The photoacoustic response from the green gelatine is detected by a single transducer on the opposite (top) surface...

  15. Microwave-heating-coupled photoacoustic radar for tissue diagnostic imaging

    Science.gov (United States)

    Wang, Wei; Mandelis, Andreas

    2016-06-01

    An investigation of microwave (MW) heating effects on biotissue for enhancing photoacoustic radar (PAR) signals was conducted. Localized tissue heating generated by MWs was used to improve PAR imaging depth and signal-to-noise ratio (SNR). Elevated temperatures were measured with thermocouples in ex vivo bovine muscle. The measured temperature rise on the heated spot surface by MWs was in agreement with theoretical predictions. The study showed localized MW heating can increase the photoacoustic imaging depth by 11%, and the SNR by 5% in ex vivo bovine muscle.

  16. Photoacoustic spectroscopy of surface defects states of semiconductor samples

    Science.gov (United States)

    Maliński, M.; Zakrzewski, J.; Firszt, F.

    2008-01-01

    This paper presents both theoretical and experimental issues connected with measurements and numerical analysis of the microphone amplitude and phase photoacoustic spectra of semiconductor samples exhibiting surface absorption connected with defects states located on their surfaces. The analytical model of surface absorption in semiconductors is described and the results of computations are compared with experimental amplitude and phase spectra for Zn{0.965}Be{0.035}Se crystal samples. This paper shows the importance of the phase spectra for the proper interpretation of the PA (photoacoustic) results.

  17. Self-assembled nanomaterials for photoacoustic imaging

    Science.gov (United States)

    Wang, Lei; Yang, Pei-Pei; Zhao, Xiao-Xiao; Wang, Hao

    2016-01-01

    In recent years, extensive endeavors have been paid to construct functional self-assembled nanomaterials for various applications such as catalysis, separation, energy and biomedicines. To date, different strategies have been developed for preparing nanomaterials with diversified structures and functionalities via fine tuning of self-assembled building blocks. In terms of biomedical applications, bioimaging technologies are urgently calling for high-efficient probes/contrast agents for high-performance bioimaging. Photoacoustic (PA) imaging is an emerging whole-body imaging modality offering high spatial resolution, deep penetration and high contrast in vivo. The self-assembled nanomaterials show high stability in vivo, specific tolerance to sterilization and prolonged half-life stability and desirable targeting properties, which is a kind of promising PA contrast agents for biomedical imaging. Herein, we focus on summarizing recent advances in smart self-assembled nanomaterials with NIR absorption as PA contrast agents for biomedical imaging. According to the preparation strategy of the contrast agents, the self-assembled nanomaterials are categorized into two groups, i.e., the ex situ and in situ self-assembled nanomaterials. The driving forces, assembly modes and regulation of PA properties of self-assembled nanomaterials and their applications for long-term imaging, enzyme activity detection and aggregation-induced retention (AIR) effect for diagnosis and therapy are emphasized. Finally, we conclude with an outlook towards future developments of self-assembled nanomaterials for PA imaging.

  18. Intracavity quartz-enhanced photoacoustic sensor

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-03-03

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

  19. A photoacoustic immunoassay for biomarker detection.

    Science.gov (United States)

    Zhao, Yunfei; Cao, Mingfeng; McClelland, John F; Shao, Zengyi; Lu, Meng

    2016-11-15

    Challenges in protein biomarker analysis include insufficient sensitivity for detecting low-abundance biomarkers, poor measurement reproducibility, and the high costs and large footprints of detection systems. To address these issues, a new detection modality was developed for analyzing protein biomarkers based on the plasmon-enhanced photoacoustic (PA) effect. The detection modality employed a heterogeneous immunoassay scheme and used gold nanoparticles (AuNPs) as the signal reporter. Due to their localized plasmon resonance, AuNPs can strongly interact with intensity-modulated laser excitation and generate strong PA signals, which are subsequently sensed and quantified using a microphone. As an example, the performance of the PA immunoassay was evaluated by detecting the human interleukin 8 chemokine. The PA immunoassay provided approximately 143× lower limit of detection (LOD) than observed with the gold standard enzyme-linked immunosorbent assay - a decrease from 23pg/mL to 0.16pg/mL. In addition to the significant performance improvement in terms of the LOD, the PA immunoassay also offers advantages in terms of compatibility with low-cost instruments and the long-term stability of assay results. PMID:27183276

  20. Computer simulations of a low energy proton beam tomograph

    Energy Technology Data Exchange (ETDEWEB)

    Milhoretto, E.; Schelin, H.R.; Setti, J.A.P.; Denyak, V.; Paschuk, S.A.; Basilio, A.C.; Rocha, R.; Ribeiro Junior, S. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil). Curso de Pos-Graduacao em Engenharia Eletrica e Informatica Industrial (CPGEI)]. E-mails: sergei@utfpr.edu.br; edneymilhoretto@yahoo.com; schelin@cpgei.cefetpr.br; Evseev, I.; Yevseyeva, O. [Universidade Estadual do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil)]. E-mail: evseev@iprj.uerj.br; Lopes, R.T. [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graducao em Engenharia (COPPE). Lab. de Instrumentacao Nuclear]. E-mail: ricardo@lin.ufrj.br; Vinagre Filho, U.M. [Instituto de Energia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2007-07-01

    This work presents the recent development of a low energy proton beam tomograph. The proton tomograph prototype (involving UTFPR, UERJ, UFRJ and IEN/CNEN) has been installed and tested at the cyclotron CV-28 of IEN/CNEN. New computer simulations were performed in order to optimize the performance of the scattered proton beam and its aluminum collimator energy losses. The computer code simulates the tomographic measurements with two aluminum collimators (variable aperture from 0.2 mm to 0.4 mm in diameter and variable thickness from 4 mm to 8 mm), a water phantom and a Si(Li) detector. The analysis of the exit beam energy spectra in comparison with a perfectly collimated proton beam made it possible to achieve the best quality of reconstructed tomographic images of water phantom. (author)

  1. 21 CFR 892.1740 - Tomographic x-ray system.

    Science.gov (United States)

    2010-04-01

    ...) Identification. A tomographic x-ray system is an x-ray device intended to be used to produce radiologic images of a specific cross-sectional plane of the body by blurring or eliminating detail from other...

  2. Wavelength-Modulated Differential Photoacoustic (WM-DPA) imaging: a high dynamic range modality towards noninvasive diagnosis of cancer

    Science.gov (United States)

    Dovlo, Edem; Lashkari, Bahman; Choi, Sung soo Sean; Mandelis, Andreas

    2016-03-01

    This study explores wavelength-modulated differential photo-acoustic (WM-DPA) imaging for non-invasive early cancer detection via sensitive characterization of functional information such as hemoglobin oxygenation (sO2) levels. Well-known benchmarks of tumor formation such as angiogenesis and hypoxia can be addressed this way. While most conventional photo-acoustic imaging has almost entirely employed high-power pulsed lasers, frequency-domain photo-acoustic radar (FD-PAR) has seen significant development as an alternative technique. It employs a continuous wave laser source intensity-modulated and driven by frequency-swept waveforms. WM-DPA imaging utilizes chirp modulated laser beams at two distinct wavelengths for which absorption differences between oxy- and deoxygenated hemoglobin are minimum (isosbestic point, 805 nm) and maximum (680 nm) to simultaneously generate two signals detected using a standard commercial array transducer as well as a single-element transducer that scans the sample. Signal processing is performed using Lab View and Matlab software developed in-house. Minute changes in total hemoglobin concentration (tHb) and oxygenation levels are detectable using this method since background absorption is suppressed due to the out-of-phase modulation of the laser sources while the difference between the two signals is amplified, thus allowing pre-malignant tumors to become identifiable. By regulating the signal amplitude ratio and phase shift the system can be tuned to applications like cancer screening, sO2 quantification and hypoxia monitoring in stroke patients. Experimental results presented demonstrate WM-DPA imaging of sheep blood phantoms in comparison to single-wavelength FD-PAR imaging. Future work includes the functional PA imaging of small animals in vivo.

  3. A tomographic setting for quasi-distribution functions

    CERN Document Server

    Man'ko, V I; Simoni, A; Sudarshan, E C G; Ventriglia, F

    2006-01-01

    The method of constructing the tomographic probability distributions describing quantum states in parallel with density operators is presented. Known examples of Husimi-Kano quasi-distribution and photon number tomography are reconsidered in the new setting. New tomographic schemes based on coherent states and nonlinear coherent states of deformed oscillators, including q-oscillators, are suggested. The associated identity decompositions providing Gram-Schmidt operators are explicitly given

  4. Image interface in Java for tomographic reconstruction in nuclear medicine

    International Nuclear Information System (INIS)

    The aim of this study is to implement a software for tomographic reconstruction of SPECT data from Nuclear Medicine with a flexible interface design, cross-platform, written in Java. Validation tests were performed based on SPECT simulated data. The results showed that the implemented algorithms and filters agree with the theoretical context. We intend to extend the system by implementing additional tomographic reconstruction techniques and Java threads, in order to provide simultaneously image processing. (author)

  5. From tomographic images to fault heterogeneities

    Directory of Open Access Journals (Sweden)

    A. Amato

    1994-06-01

    Full Text Available Local Earthquake Tomography (LET is a useful tool for imaging lateral heterogeneities in the upper crust. The pattern of P- and S-wave velocity anomalies, in relation to the seismicity distribution along active fault zones. can shed light on the existence of discrete seismogenic patches. Recent tomographic studies in well monitored seismic areas have shown that the regions with large seismic moment release generally correspond to high velocity zones (HVZ's. In this paper, we discuss the relationship between the seismogenic behavior of faults and the velocity structure of fault zones as inferred from seismic tomography. First, we review some recent tomographic studies in active strike-slip faults. We show examples from different segments of the San Andreas fault system (Parkfield, Loma Prieta, where detailed studies have been carried out in recent years. We also show two applications of LET to thrust faults (Coalinga, Friuli. Then, we focus on the Irpinia normal fault zone (South-Central Italy, where a Ms = 6.9 earthquake occurred in 1980 and many thousands of attershock travel time data are available. We find that earthquake hypocenters concentrate in HVZ's, whereas low velocity zones (LVZ’ s appear to be relatively aseismic. The main HVZ's along which the mainshock rupture bas propagated may correspond to velocity weakening fault regions, whereas the LVZ's are probably related to weak materials undergoing stable slip (velocity strengthening. A correlation exists between this HVZ and the area with larger coseismic slip along the fault, according to both surface evidence (a fault scarp as high as 1 m and strong ground motion waveform modeling. Smaller wave-length, low-velocity anomalies detected along the fault may be the expression of velocity strengthening sections, where aseismic slip occurs. According to our results, the rupture at the nucleation depth (~ 10-12 km is continuous for the whole fault lenoth (~ 30 km, whereas at shallow depth

  6. Reflection mode photoacoustic measurement of speed of sound

    NARCIS (Netherlands)

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

    2007-01-01

    We present a method to determine the speed of sound in tissue using a double-ring photoacoustic sensor working in reflection mode. This method uses the cross-correlation between the laser-induced ultrasound waves detected by two concentric ring shaped sensors, while a priori information about the de

  7. Photoacoustic trace gas sensing : application to fruit and insects

    NARCIS (Netherlands)

    Persijn, Stefan Timotheüs

    2001-01-01

    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

  8. Transurethral Photoacoustic Endoscopy for Prostate Cancer: A Simulation Study.

    Science.gov (United States)

    Tang, Shanshan; Chen, Jian; Samant, Pratik; Stratton, Kelly; Xiang, Liangzhong

    2016-07-01

    The purpose of this study was to optimize the configuration of a photoacoustic endoscope (PAE) for prostate cancer detection and therapy monitoring. The placement of optical fiber bundles and ultrasound detectors was chosen to maximize the photoacoustic imaging penetration depth. We performed both theoretical calculations and simulations of this optimized PAE configuration on a prostate-sized phantom containing tumor and various photosensitizer concentrations. The optimized configuration of PAE with transurethral light delivery simultaneously increases the imaging penetration depth and improves image quality. Thermal safety, investigated via COMSOL Multiphysics, shows that there is only a 4 mK temperature rise in the urethra during photoacoustic imaging, which will cause no thermal damage. One application of this PAE has been demonstrated for quasi-quantifying photosensitizer concentrations during photodynamic therapy. The sensitivity of the photoacoustic detection for TOOKAD was 0.18 ng/mg at a 763 nm laser wavelength. Results of this study will greatly enhance the potential of prostate PAE for in vivo monitoring of drug delivery and guidance of the laser-induced therapy for future clinical use. PMID:26886974

  9. Engineering Dark Chromoprotein Reporters for Photoacoustic Microscopy and FRET Imaging

    Science.gov (United States)

    Li, Yan; Forbrich, Alex; Wu, Jiahui; Shao, Peng; Campbell, Robert E.; Zemp, Roger

    2016-03-01

    A subset of the family of fluorescent proteins are the non-fluorescent chromoproteins which are promising probe molecules for use in photoacoustic imaging and as acceptor chromophores in Förster resonance energy transfer (FRET)-based biosensors. Typical approaches for fluorescent protein optimization by screening of large libraries of variants cannot be effectively applied to chromoproteins due to their characteristic lack of fluorescence. To address this challenge, we have developed a directed evolution method to iteratively screen large libraries of protein variants on the basis of their photoacoustic signal levels. By applying this procedure to the promising Ultramarine and cjBlue chromoprotein templates, we were able to identify improved variants with a 02-04 fold increase in photoacoustic signal-to-noise ratio after only a few evolutionary steps. These improved variants enable more accurate spectral de-mixing and localization of protein-producing bacteria in vivo and serve as effective FRET acceptors for both fluorescence- and photoacoustic-based detection of protease activity.

  10. Introduction: Advances in Optical Coherence Tomography, Photoacoustic Imaging, and Microscopy

    OpenAIRE

    Li, X; Beard, P.C.; Georgakoudi, I.

    2010-01-01

    The editors introduce the Biomedical Optics Express feature issue, “Advances in Optical Coherence Tomography, Photoacoustic Imaging, and Microscopy,” which combines three technical areas from the 2010 Optical Society of America (OSA), Biomedical Optics (BIOMED) Topical Meeting held on 11–14 April in Miami, Florida, and includes contributions from conference attendees.

  11. Integrated diffuse optical tomography and photoacoustic tomography: phantom validations

    OpenAIRE

    Li, Xiaoqi; Xi, Lei; Jiang, Ruixin; Yao, Lei; Jiang, Huabei

    2011-01-01

    We designed, fabricated and tested a novel imaging system that fuses diffuse optical tomography (DOT) and photoacoustic tomography (PAT) in a single platform. This platform takes advantages of both DOT and PAT, and can potentially provide dual-modality two dimensional functional and cellular images of the breast quantitatively. Here we describe this integrated platform along with initial tissue phantom validations.

  12. Photoacoustic lifetime imaging of dissolved oxygen using methylene blue

    Science.gov (United States)

    Ashkenazi, Shai

    2010-07-01

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

  13. Simple Model of a Photoacoustic System as a CR Circuit

    Science.gov (United States)

    Fukuhara, Akiko; Kaneko, Fumitoshi; Ogawa, Naohisa

    2012-01-01

    We introduce the photoacoustic educational system (PAES), by which we can identify which gas causes the greenhouse effect in a classroom (Kaneko "et al" 2010 "J. Chem. Educ." 87 202-4). PAES is an experimental system in which a pulse of infrared (IR) is absorbed into gas as internal energy, an oscillation of pressure (sound) appears, and then we…

  14. Photoacoustic elastic bending in thin film—Substrate system

    Energy Technology Data Exchange (ETDEWEB)

    Todorović, D. M., E-mail: dmtodor@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, P.O. Box 33, 11030 Belgrade (Serbia); Rabasović, M. D.; Markushev, D. D. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade-Zemun (Serbia)

    2013-12-07

    Theoretical model for optically excited two-layer elastic plate, which includes plasmaelastic, thermoelastic, and thermodiffusion mechanisms, is given in order to study the dependence of the photoacoustic (PA) elastic bending signal on the optical, thermal, and elastic properties of thin film—substrate system. Thin film-semiconductor sample (in our case Silicon) is modeled by simultaneous analysis of the plasma, thermal, and elastic wave equations. Multireflection effects in thin film are included in theoretical model and analyzed. Relations for the amplitude and phase of electronic and thermal elastic bending in the optically excited two-layer mechanically-supported circular plate are derived. Theoretical analysis of the thermodiffusion, plasmaelastic, and thermoelastic effects in a sample-gas-microphone photoacoustic detection configuration is given. Two normalization procedures of the photoacoustic elastic bending signal in function of the modulation frequency of the optical excitation are established. Given theoretical model can be used for various photoacoustic detection configurations, for example, in the study of optical, thermal, and elastic properties of the dielectric-semiconductor or metal-semiconductor structure, etc., Theoretical analysis shows that it is possible to develop new noncontact and nondestructive experimental method—PA elastic bending method for thin film study, with possibility to obtain the optical, thermal, and elastic parameters of the film thinner than 1 μm.

  15. Photoacoustic study of nanocrystalline silicon produced by mechanical grinding

    Energy Technology Data Exchange (ETDEWEB)

    Poffo, C.M. [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Lima, J.C. de, E-mail: fsc1jcd@fisica.ufsc.b [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Souza, S.M.; Triches, D.M. [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Grandi, T.A. [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Biasi, R.S. de [Secao de Engenharia Mecanica e de Materiais, Instituto Militar de Engenharia, 22290-270 Rio de Janeiro, RJ (Brazil)

    2011-04-01

    Mechanical grinding (MG) was used to produce nanocrystalline silicon and its thermal and transport properties were investigated by photoacoustic absorption spectroscopy (PAS). The experimental results suggest that in as-milled nanocrystalline silicon for 10 h the heat transfer through the crystalline and interfacial components is similar, and after annealed at 470 {sup o}C the heat transfer is controlled by crystalline component.

  16. Photoacoustic monitoring of life cycles of Leishmania Mexicana

    Science.gov (United States)

    Arguello, C.; Acosta-Avalos, D.; Alvarado-Gil, J. J.; Vargas, H.

    1999-03-01

    Photoacoustic spectroscopy is used to monitor in situ, the difference between the two forms of the protozoan Leishmania Mexicana. Differences are the result of changes in the respiratory chain and could be attributed, according to our results, to the presence of cytochrome b in promastigotes and cytochrome c in amastigotes.

  17. Lensfree on-chip tomographic microscopy employing multi-angle illumination and pixel super-resolution.

    Science.gov (United States)

    Isikman, Serhan O; Bishara, Waheb; Ozcan, Aydogan

    2012-01-01

    Tomographic imaging has been a widely used tool in medicine as it can provide three-dimensional (3D) structural information regarding objects of different size scales. In micrometer and millimeter scales, optical microscopy modalities find increasing use owing to the non-ionizing nature of visible light, and the availability of a rich set of illumination sources (such as lasers and light-emitting-diodes) and detection elements (such as large format CCD and CMOS detector-arrays). Among the recently developed optical tomographic microscopy modalities, one can include optical coherence tomography, optical diffraction tomography, optical projection tomography and light-sheet microscopy. These platforms provide sectional imaging of cells, microorganisms and model animals such as C. elegans, zebrafish and mouse embryos. Existing 3D optical imagers generally have relatively bulky and complex architectures, limiting the availability of these equipments to advanced laboratories, and impeding their integration with lab-on-a-chip platforms and microfluidic chips. To provide an alternative tomographic microscope, we recently developed lensfree optical tomography (LOT) as a high-throughput, compact and cost-effective optical tomography modality. LOT discards the use of lenses and bulky optical components, and instead relies on multi-angle illumination and digital computation to achieve depth-resolved imaging of micro-objects over a large imaging volume. LOT can image biological specimen at a spatial resolution of <1 μm x <1 μm x <3 μm in the x, y and z dimensions, respectively, over a large imaging volume of 15-100 mm(3), and can be particularly useful for lab-on-a-chip platforms.

  18. Computed tomographic findings of cerebral paragonimiasis

    Energy Technology Data Exchange (ETDEWEB)

    Sung, Nak Kwan; Nam, Kyung Jin; Park, Churl Min; Eun, Chung Kie; Lee, Sun Wha [Kyung Hee Unversity Hospital, Seoul (Korea, Republic of)

    1983-03-15

    Paragonimiasis is widely distributed in Far East and Southeast Asia, particularly in Korea. The central nervous system is the most frequent location for paragonimiasis outside the lungs. We analyzed the computed tomographic findings of 17 cases which were diagnosed pathologically and clinically as cerebral paragonimiasis. The results were as follows: 1. The ratio of male to female was 10 : 7 and about 88% of cases were under the age of 40 years. 2. The common locations of cerebral paragonimiasis were the occipital (12 cases) and temporal (11 cases) lobes. 3. Precontrast CT findings of cerebral paragonimiasis were low density with calcifications in 6 cases, low and isodensities in 4 cases, mixed densities in 3 cases, only low density in 2 cases and only calcification in 2 cases. Hydrocephalus (7 cases), mass effect (6 cases), atrophic change (6 cases) and cyst formation (3 cases) were associated. 4. The shape of calcifications in CT scan were soap-bubble or ring in 6 cases, nodular or oval in 6 cases, stipple in 4 cases and amorphous conglomerated in 2 cases. 5. The contrast -enhanced 8 cases were 5 ring or rim like, 2 nodular and 1 irregular enhancements, while 9 cases were not enhanced.

  19. Computerized tomographic studies in cerebral palsy

    International Nuclear Information System (INIS)

    Computed tomographic (CT) findings in 200 children with cerebral palsy (CP) were analysed from the viewpoint of clinical manifestations, disease complications and etiological factors. CT scans of 135 cases (67.5%) were found to be abnormal and there were 14 (7%) borderline cases. The major abnormality found on CT scans was cerebral atrophy. Other important changes included focal or diffuse low density area in the brain tissue, congenital malformation, and cerebellar atrophy. From the clinical point of view, a large number of patients with spastic tetraplegia and spastic diplegia showed highly abnormal CT scans. On the other hand, in patients with spastic monoplegia, spastic paraplegia, and athetotic type, CT findings were normal or revealed only minor cerebral atrophy. Most children showing asymmetric clinical symptoms had corresponding asymmetric CT abnormalities which included ventricular enlargement, low density area in the brain tissue, and hemispherical volume. There was a significant correlation between the severity of physical impairment and the extent of CT abnormalities. Severely affected children had grossly abnormal CT scans such as hydranencephaly, polycystic change, and extensive cerebral atrophy. In the patients complicated with epilepsy, the incidence and severity of abnormal CT were higher than those of non-epileptic patients. Mentally retarded patients had variable enlargement of the subarachnoidal space depending on the severity of their mental retardation. Patients with suspected postnatal etiology also had high incidence of severe CT abnormality. CT scan is a valuable tool for evaluating patients with CP and in some cases, possible etiology of the disease may be discovered. (author)

  20. Tomographic display of ventilation-perfusion ratio

    International Nuclear Information System (INIS)

    Tomographic displays of the distribution of ventilation-perfusion ratio in six subjects with a single photon radionuclide computed tomography (RCT) were obtained. The distribution of ventilation (V) and perfusion (Q) were measured separately with continuous breathing of Kr-81m and with intravenous administration of Tc-99m labelled macroaggregates of human serum albumin (MAA). V/Q was calculated pixel-by-pixel and the distributions of V/Q were displayed in a logarithmic scale with the surrounding thoracic cage obtained from transmission CT. The number of voxel, ventilation and perfusion were plotted against log(V/Q). They had almost log normal distributions with smaller variances in healthy subjects than those with emphysema or bronchitis. In the former, much coincidence between V and Q was observed, whereas in the latter, dissociation was seen between them. This noninvasive technique provided not only the visualization of the distribution of V/Q in a transaxial images, but also the quantifications of the V-Q mismatch

  1. Computed tomographic findings of intracerebral cysticercosis

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Jin Kyo; Lee, Sun Wha; Kim, Ho Kyun; Ahn, Chi Yul [School of Medicine, Kyung-Hee University, Seoul (Korea, Republic of)

    1980-12-15

    Cysticercosis is a parasitic disease in which man serves as the intermediate host of Taenia Solium, the pork tapeworm. The computed tomographic findings of 25 cases of intracerebral cysticercosis proven by pathologic and/or clinical findings during past 2 years were analysed. The results were as follows; 1. The sex was 19 males and 6 females, and 56 percent of the patients were seen in fourth and fifth decades. The most common symptom was epilepsy (72%). 2. The C. T. findings in precontrast study were varied; such as ill defined low density (48%), cystic low density (20%), dilated ventricles (20%), ill defined low density with isodense nodule (18%), cystic low density with isodense mural nodule (12%) and calcification (8%). 3. The areas of involvement were 20 cases (80%) of parenchymal form, 3 cases (12%) of ventricular form and 2 cases (8%) of mixed form. 4. The contrast-enhanced 13 cases were 5 nodular, 5 ring or rim-like and 3 mixed type enhancements, while 12 cases were not enhanced. 5. C.T. scan demonstrated more precise location and extents of cerebral cysticercosis, especially in parenchymal form. It was considered to be important in determination of surgical feasibility and its approach.

  2. Computed tomographic anatomy of the equine foot.

    Science.gov (United States)

    Claerhoudt, S; Bergman, E H J; Saunders, J H

    2014-10-01

    This study describes a detailed computed tomographic reference of the normal equine foot. Ten forefeet of five adult cadavers, without evidence of orthopaedic disease, were used. Computed tomography (CT) was performed on all feet. Two-millimetre thick transverse slices were obtained, and sagittal and dorsal planes were reformatted. The CT images were matched with the corresponding anatomic slices. The phalanges and the distal sesamoid bone showed excellent detail. The extensor and flexor tendons (including their attachments) could be clearly evaluated. The collateral (sesamoidean) ligaments could be readily located, but were difficult to delineate at their proximal attachment. The distal digital annular ligament could only be distinguished from the deep digital flexor tendon proximal to the distal sesamoid bone, and its proximal attachment could be identified, but not its distal insertion. Small ligaments (impar ligament, chondrosesamoidean, chondrocoronal and chondrocompedal ligaments, axial and abaxial palmar ligaments of the proximal inter-phalangeal joint) were seen with difficulty and not at all slices. The joint capsules could not be delineated from the surrounding soft tissue structures. The lateral and medial proprius palmar digital artery and vein could be visualized occasionally on some slices. The ungular cartilages, corium and hoof wall layering were seen. The nerves, the articular and fibrocartilage of the distal sesamoid bone and the chondroungular ligament could not be assessed. Computed tomography of the equine foot can be of great value when results of radiography and ultrasonography are inconclusive. Images obtained in this study may serve as reference for CT of the equine foot.

  3. Computed tomographic findings of intracerebral cysticercosis

    International Nuclear Information System (INIS)

    Cysticercosis is a parasitic disease in which man serves as the intermediate host of Taenia Solium, the pork tapeworm. The computed tomographic findings of 25 cases of intracerebral cysticercosis proven by pathologic and/or clinical findings during past 2 years were analysed. The results were as follows; 1. The sex was 19 males and 6 females, and 56 percent of the patients were seen in fourth and fifth decades. The most common symptom was epilepsy (72%). 2. The C. T. findings in precontrast study were varied; such as ill defined low density (48%), cystic low density (20%), dilated ventricles (20%), ill defined low density with isodense nodule (18%), cystic low density with isodense mural nodule (12%) and calcification (8%). 3. The areas of involvement were 20 cases (80%) of parenchymal form, 3 cases (12%) of ventricular form and 2 cases (8%) of mixed form. 4. The contrast-enhanced 13 cases were 5 nodular, 5 ring or rim-like and 3 mixed type enhancements, while 12 cases were not enhanced. 5. C.T. scan demonstrated more precise location and extents of cerebral cysticercosis, especially in parenchymal form. It was considered to be important in determination of surgical feasibility and its approach

  4. Computer tomographic imaging of rabbit bulbourethral glands

    International Nuclear Information System (INIS)

    The aim of the study was to utilize the obtained data for differentiation of normal and pathologically altered bulbourethral glands in rabbits with regard to using this animal species as a model for studying diseases in this organ in humans. MATERIAL AND METHODS: Ten sexually mature healthy male white New Zealand rabbits, 12 months old, weighed 2.8−3.2 kg were investigated. The animals were anesthetized. Scans were done at 2 mm intervals and the image reconstruction was three-dimensional. RESULTS: Rabbit bulbourethral glands were observed as a transversely oval homogeneous, relatively hyperdense structure against the surrounding soft tissues. They are visualized in the transverse cut of the pelvic outlet in the plane through the cranial part of cg2, the body of ischium, cranially to tuber ischiadicum and dorsally to the caudal part of symphysis pubis –sciatic arch. The glandular margins are adequately distinguished from the adjacent soft tissue structures. The density of the rabbit bulbourethral glands was similar to this of the soft tissues. CONCLUSION: The data obtained by the computed tomographic imaging of the rabbit bulbourethral glands could be used as an anatomical reference in the diagnosis and interpretation of imaging findings of various pathological states of the gland in this species, as well as in utilization of the rabbit as an animal model for studying diseases of this organ in humans, particularly diverticula, stenosis, lithiasis and valves

  5. Photoacoustic and ultrasound imaging using dual contrast perfluorocarbon nanodroplets triggered by laser pulses at 1064 nm.

    Science.gov (United States)

    Hannah, Alexander S; VanderLaan, Donald; Chen, Yun-Sheng; Emelianov, Stanislav Y

    2014-09-01

    Recently, a dual photoacoustic and ultrasound contrast agent-named photoacoustic nanodroplet-has been introduced. Photoacoustic nanodroplets consist of a perfluorocarbon core, surfactant shell, and encapsulated photoabsorber. Upon pulsed laser irradiation the perfluorocarbon converts to gas, inducing a photoacoustic signal from vaporization and subsequent ultrasound contrast from the resulting gas microbubbles. In this work we synthesize nanodroplets which encapsulate gold nanorods with a peak absorption near 1064 nm. Such nanodroplets are optimal for extended photoacoustic imaging depth and contrast, safety and system cost. We characterized the nanodroplets for optical absorption, image contrast and vaporization threshold. We then imaged the particles in an ex vivo porcine tissue sample, reporting contrast enhancement in a biological environment. These 1064 nm triggerable photoacoustic nanodroplets are a robust biomedical tool to enhance image contrast at clinically relevant depths.

  6. Characterizing intraocular tumors with photoacoustic imaging

    Science.gov (United States)

    Xu, Guan; Xue, Yafang; Gursel, Zeynep; Slimani, Naziha; Wang, Xueding; Demirci, Hakan

    2016-03-01

    Intraocular tumors are life-threatening conditions. Long-term mortality from uveal melanoma, which accounts for 80% of primary intraocular tumors, could be as high as 25% depending on the size, ciliary body involvement and extraocular extension. The treatments of intraocular tumors include eye-sparing approaches such as radiotherapy and thermotherapy, and the more aggressive enucleation. The accurate diagnosis of intraocular tumors is thereby critical in the management and follow-up of the patients. The diagnosis of intraocular tumors is usually based on clinical examination with acoustic backscattering based ultrasonography. By analyzing the high frequency fluctuations within the ultrasound (US) signals, microarchitecture information inside the tumor can be characterized. However, US cannot interrogate the histochemical components formulating the microarchitecture. One representative example is the inability of US imaging (and other contemporary imaging modalities as well) in differentiating nevoid and melanoma cells as the two types of cells possesses similar acoustic backscattering properties. Combining optical and US imaging, photoacoustic (PA) measurements encode both the microarchitecture and histochemical component information in biological tissue. This study attempts to characterize ocular tumors by analyzing the high frequency signal components in the multispectral PA images. Ex vivo human eye globes with melanoma and retinoblastoma tumors were scanned using less than 6 mJ per square centimeters laser energy with tunable range of 600-1700 nm. A PA-US parallel imaging system with US probes CL15-7 and L22-14 were used to acquire the high frequency PA signals in real time. Preliminary results show that the proposed method can identify uveal melanoma against retinoblastoma tumors.

  7. Array processors: an introduction to their architecture, software, and applications in nuclear medicine

    International Nuclear Information System (INIS)

    Array processors are ''number crunchers'' that dramatically enhance the processing power of nuclear medicine computer systems for applicatons dealing with the repetitive operations involved in digital image processing of large segments of data. The general architecture and the programming of array processors are introduced, along with some applications of array processors to the reconstruction of emission tomographic images, digital image enhancement, and functional image formation

  8. Design and evaluation of a laboratory prototype system for 3D photoacoustic full breast tomography

    OpenAIRE

    Xia, W; Piras, D; Singh, M. K. A.; van Hespen, J. C. G.; Van Leeuwen, T. G.; Steenbergen, W Van; Manohar, S.

    2013-01-01

    Photoacoustic imaging can visualize vascularization-driven optical absorption contrast with great potential for breast cancer detection and diagnosis. State-of-the-art photoacoustic breast imaging systems are promising but are limited either by only a 2D imaging capability or by an insufficient imaging field-of-view (FOV). We present a laboratory prototype system designed for 3D photoacoustic full breast tomography, and comprehensively characterize it and evaluate its performance in imaging p...

  9. Pharmacokinetic Monitoring of Indocyanine Green for Tumor Detection Using Photoacoustic Imaging

    Institute of Scientific and Technical Information of China (English)

    YANG Si-Hua; YIN Guang-Zhi; XING Da

    2010-01-01

    @@ 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).

  10. High frame rate photoacoustic imaging at 7000 frames per second using clinical ultrasound system.

    Science.gov (United States)

    Sivasubramanian, Kathyayini; Pramanik, Manojit

    2016-02-01

    Photoacoustic tomography, a hybrid imaging modality combining optical and ultrasound imaging, is gaining attention in the field of medical imaging. Typically, a Q-switched Nd:YAG laser is used to excite the tissue and generate photoacoustic signals. But, such photoacoustic imaging systems are difficult to translate into clinical applications owing to their high cost, bulky size often requiring an optical table to house such lasers. Moreover, the low pulse repetition rate of few tens of hertz prevents them from being used in high frame rate photoacoustic imaging. In this work, we have demonstrated up to 7000 Hz photoacoustic imaging (B-mode) and measured the flow rate of a fast moving object. We used a ~140 nanosecond pulsed laser diode as an excitation source and a clinical ultrasound imaging system to capture and display the photoacoustic images. The excitation laser is ~803 nm in wavelength with ~1.4 mJ energy per pulse. So far, the reported 2-dimensional photoacoustic B-scan imaging is only a few tens of frames per second using a clinical ultrasound system. Therefore, this is the first report on 2-dimensional photoacoustic B-scan imaging with 7000 frames per second. We have demonstrated phantom imaging to view and measure the flow rate of ink solution inside a tube. This fast photoacoustic imaging can be useful for various clinical applications including cardiac related problems, where the blood flow rate is quite high, or other dynamic studies.

  11. Improving Photoacoustic-guided Focusing in Scattering Media by Spectrally Filtered Detection

    CERN Document Server

    Chaigne, Thomas; Gateau, Jérôme; Boccara, Claude; Gigan, Sylvain; Bossy, Emmanuel

    2013-01-01

    We experimentally and numerically study the potential of photoacoustic-guiding for light focusing through scattering samples via wavefront-shaping and iterative optimization. We experimentally demonstrate that the focusing efficiency on an extended absorber can be improved by iterative optimization of the high frequency components of the broadband photoacoustic signal detected with a spherically focused transducer. We demonstrate more than 8-fold increase in the photoacoustic signal generated by a 30 microns wire using a narrow frequency band around 60MHz. We numerically confirm that such optimization leads to a smaller optical focus than using the low frequency content of the photoacoustic feedback.

  12. Computed tomographic findings of cerebral paragonimiasis

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Weon Tae; Jung, Min Ki; Kang, Heoung Keun; Chung, Hyon De [Chonnam University Medicine School, Gwangju (Korea, Republic of)

    1988-10-15

    Authors analyzed the computed tomographic (CT) findings of 19 cases pathologically and clinically proven cerebral paragonimiasis that were performed at Chonnam University Hospital from April 1983 through March 1987. The results were as follows: 1. Male to female ratio was 15:4 and the most prevalent age group was 3rd decade (7 cases). The common symptoms were epileptic seizure (16 cases) and headache (12 cases). 2. The multiplicity of cerebral paragonimiasis was 7 of 19 cases and the distributions of lesion were occipital (11 cases), temporal (6 cases), frontal (5 cases) and parietal (5 cases) lobe. 3. The calcification on CT scan were single (7 cases) or multiple (7 cases) and the shape of calcification were nodular (10 cases), soap babble of ring (8 cases), and stippled (6 cases). The pattern of contrast enhancement were ring (5 cases) or nodular (1 case), and along the basal cistern (1 case with arachnoiditis). 4. 12 out of 13 cases, had long clinical symptoms over 3 years with calcifications, could be analyzed according to Valentine's vascular territory; 6 cases in PCA territory, 3 in MCA and 3 in ACA. 5. CT findings were noted according to the duration of symptoms; 5 cases, had symptoms less than 1 year, showed abscess (5 cases) and arachnoiditis (1 case) with brain edema, mass effect, hydrocephalus and contrast enhancement but no calcification in all. One case, had symptom of 1 year and 2 months, showed partially calcified granulomatous lesion with perifocal edema and contrast enhancement, 13 cases, had symptoms over 3 years, showed multiple calcification with brain atrophy (10 cases), but no contrast enhancement in all cases.

  13. Tomographic velocity model for the aftershock region of the 2001 Gujarat, India earthquake

    Science.gov (United States)

    Negishi, H.; Kumar, S.; Mori, J. J.; Sato, T.; Bodin, P.; Rastogi, B.

    2002-12-01

    A tomographic inversion was applied to the aftershock data collected after the January 26, 2001 Bhuj earthquake (Ms 7.9, Mw 7.7), which occurred on a south dipping (~50 degrees) reverse fault in the state of Gujarat in western India. We used high quality arrivals from 8,374 P and 7,994 S waves of 1404 aftershocks recorded on 27 digital stations from temporary seismic arrays setup by the India-Japan team; NGRI, India; and CERI, Memphis Univ., USA, following the Bhuj main shock. First, we used the Joint Hypocenters Determination Method for obtaining relocated hypocenters and a one-dimensional Vp and Vs velocity model, and then the resultant hypocenters and 1-D velocity model were used as the initial parameters for a 3-D tomographic inversion. The tomography technique is based on a grid-modeling method by Zhao et al. . Vp, Vs and hypocenters are determined simultaneously. We tried to use the Cross-Validation Technique for determining an optimum model in the seismic tomography. This approach has been applied to other tomographic studies to investigate the quantitative fluctuation range of velocity perturbations . Significant variations in the velocity (up to 6%) and Poisson's ratio (up to 8%) are revealed in the aftershock area. It seems that the aftershock distribution corresponds to the boundary between high and low velocity heterogeneities. Small values of Vp/Vs are generally found at depths of 10 to 35 km, i.e. the depth range of aftershock distribution. However, the deeper region below the hypocenter of the mainshock, at depths of 35 to 45 km, is characterized by relatively high values of Vp/Vs and low values of Vs. This anomaly may be due to a weak fractured and fluid filled rock matrix, which might have contributed to triggering this earthquake. This earthquake occurred on a relatively deep and steeply dipping fault with a large stress drop . Theoretically it is difficult to slip steep faults, especially in the lower crust. Our tomographic investigation provides

  14. Energy efficiency of near infrared cobalt luminscence in ZnSe:Co determined by a photoacoustic method

    Science.gov (United States)

    Chrobak, Ł.; Maliński, M.; Strzałkowski, K.; Zakrzewski, J.

    2012-03-01

    The paper presents results of computations of the energy efficiency of the cobalt luminescence in ZnSe:Co determined by the photoacoustic method. The transmission spectra, photoacoustic experimental and theoretical spectra, and the frequency dependence on the photoacoustic amplitude characteristics are presented. From them, the energy efficiency of Co2+ the near infrared luminescence (3200 nm) was computed in the frame of new proposed photoacoustic model of computations of the luminescence energy efficiency.

  15. Combining ART and FBP for improved fidelity of tomographic BOS

    Science.gov (United States)

    Hartmann, Ulrich; Seume, Joerg R.

    2016-09-01

    Engine component defects along the hot-gas path (HGP) of jet engines influence the density distribution of the flow, and thus result in characteristic patterns in the exhaust jet. These characteristic patterns can be reconstructed with the optical background-oriented schlieren (BOS) method in a tomographic set-up, which in turn allows the identification of defects inside the engine through an exhaust jet analysis. The quality of the tomographic reconstruction strongly influences how easily defects can be detected inside the jet engine. In particular, the presence of high gradients in the reconstruction area has a strong impact on the reconstruction quality. An algebraic reconstruction algorithm (ART) is implemented and compared to a filtered-back projection (FBP) algorithm in terms of the capability of performing high-gradient tomographic BOS reconstructions. A combination of both algorithms is presented which significantly improves the reconstruction quality of high-gradient tomographic BOS in terms of artifact reduction. The combination of both algorithms is applied to both synthetic and real measurement data in this paper, in order to show possible applications and the achievable improvement of high-gradient tomographic BOS reconstructions.

  16. Tomographic techniques for safeguards measurements of nuclear fuel assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Lundqvist Saleh, Tobias

    2007-10-15

    Nuclear power is currently experiencing increased interest over the world. New nuclear reactors are being built and techniques for taking care of the nuclear waste are being developed. This development puts new demands and standards to safeguards, i.e. the international efforts for ensuring the non-proliferation of nuclear weapons. New measuring techniques and devices are continuously being developed for enhancing the ability to detect diversion of fissile material. In this thesis, tomographic techniques for application in safeguards are presented. Tomographic techniques can non-destructively provide information of the inner parts of an object and may thus be used to control that no material is missing from a nuclear fuel assembly. When using the tomographic technique described in this thesis, the radiation field around a fuel assembly is first recorded. In a second step, the internal source distribution is mathematically reconstructed based on the recorded data. In this work, a procedure for tomographic safeguards measurements is suggested and the design of a tomographic measuring device is presented. Two reconstruction algorithms have been specially developed and evaluated for the application on nuclear fuel; one algorithm for image reconstruction and one for reconstructing conclusive data on the individual fuel rod level. The combined use of the two algorithms is suggested. The applicability for detecting individual removed or replaced rods has been demonstrated, based on experimental data

  17. Tomographic techniques for safeguards measurements of nuclear fuel assemblies

    International Nuclear Information System (INIS)

    Nuclear power is currently experiencing increased interest over the world. New nuclear reactors are being built and techniques for taking care of the nuclear waste are being developed. This development puts new demands and standards to safeguards, i.e. the international efforts for ensuring the non-proliferation of nuclear weapons. New measuring techniques and devices are continuously being developed for enhancing the ability to detect diversion of fissile material. In this thesis, tomographic techniques for application in safeguards are presented. Tomographic techniques can non-destructively provide information of the inner parts of an object and may thus be used to control that no material is missing from a nuclear fuel assembly. When using the tomographic technique described in this thesis, the radiation field around a fuel assembly is first recorded. In a second step, the internal source distribution is mathematically reconstructed based on the recorded data. In this work, a procedure for tomographic safeguards measurements is suggested and the design of a tomographic measuring device is presented. Two reconstruction algorithms have been specially developed and evaluated for the application on nuclear fuel; one algorithm for image reconstruction and one for reconstructing conclusive data on the individual fuel rod level. The combined use of the two algorithms is suggested. The applicability for detecting individual removed or replaced rods has been demonstrated, based on experimental data

  18. Comparison of Deconvolution Filters for Photoacoustic Tomography.

    Directory of Open Access Journals (Sweden)

    Dominique Van de Sompel

    Full Text Available In this work, we compare the merits of three temporal data deconvolution methods for use in the filtered backprojection algorithm for photoacoustic tomography (PAT. We evaluate the standard Fourier division technique, the Wiener deconvolution filter, and a Tikhonov L-2 norm regularized matrix inversion method. Our experiments were carried out on subjects of various appearances, namely a pencil lead, two man-made phantoms, an in vivo subcutaneous mouse tumor model, and a perfused and excised mouse brain. All subjects were scanned using an imaging system with a rotatable hemispherical bowl, into which 128 ultrasound transducer elements were embedded in a spiral pattern. We characterized the frequency response of each deconvolution method, compared the final image quality achieved by each deconvolution technique, and evaluated each method's robustness to noise. The frequency response was quantified by measuring the accuracy with which each filter recovered the ideal flat frequency spectrum of an experimentally measured impulse response. Image quality under the various scenarios was quantified by computing noise versus resolution curves for a point source phantom, as well as the full width at half maximum (FWHM and contrast-to-noise ratio (CNR of selected image features such as dots and linear structures in additional imaging subjects. It was found that the Tikhonov filter yielded the most accurate balance of lower and higher frequency content (as measured by comparing the spectra of deconvolved impulse response signals to the ideal flat frequency spectrum, achieved a competitive image resolution and contrast-to-noise ratio, and yielded the greatest robustness to noise. While the Wiener filter achieved a similar image resolution, it tended to underrepresent the lower frequency content of the deconvolved signals, and hence of the reconstructed images after backprojection. In addition, its robustness to noise was poorer than that of the Tikhonov

  19. Evaluation of multislice computed tomographic perfusion imaging and computed tomographic angiography on traumatic cerebral infarction

    Institute of Scientific and Technical Information of China (English)

    XU Fang-hong; CHEN Wei-jian; YANG Yun-jun; DUAN Yu-xia; FU Feng-li

    2008-01-01

    Objective: To evaluate the application value of multislice computed tomographic perfusion imaging (MSCTPI) and multislice computed tomographic angiography (MSCTA) on traumatic cerebral infarction. Methods: MSCTA was performed on 10 patients who were initiailly diagnosed as traumatic cerebral infarction by normal conventional computed tomography (NCCT), among whom, 3 patients were examined by MSCTPI simultaneously. Reconstructed images of the intracranial artery were made with techniques of maximum intensity projection (MIP) and volume rendering (VR) from MSCTA scanning data. Then the graph of function of four parameters, regional cerebral blood flow (Rcbf), regional cerebral blood volume (Rcbv), mean transit time (MTT), and time to peak (TTP), acquired by the perfusing analysis software was obtained. Results: Among the 10 patients with traumatic cerebral infarction, 6 showed complex type on NCCT, which depicted abnormality on MSCTA, and 4 showed simple type on NCCT, which had negative results on MSCTA. Among the 4 patients with abnormal great vessels, 2 suffered from steno sis or occlusion of the middle cerebral artery, 1 from spasm of the anterior cerebral artery, and 1 from spasm of the vertebral-basal artery. The image of MSCTPI of 1 patient with massive cerebral infarction on the right cerebral hemisphere confirmed by CT was smaller than those of the other patients, which showed occlusion of the ipsilateral middle cerebral artery on MSCTA. Among the 6 patients whose MSCTA showed no abnormality, 4 showed simple infarction and 2 showed complex infarction. The infarction focus of 5 patients occurred in the basal ganglia and 1 in the splenium of corpus callosum. Among the 2 cases of small cerebral infarction volume on NCCT, one was normal, the other showed hypoperfusion on MSCTPI and was normal on MSCTA. Conclusion: The combination of MSCTPI and MSCTA is very useful for evaluating the change of intracranial artery in ischemic regions and assessing the cerebral

  20. Generalized Row-Action Methods for Tomographic Imaging

    DEFF Research Database (Denmark)

    Andersen, Martin Skovgaard; Hansen, Per Christian

    2014-01-01

    Row-action methods play an important role in tomographic image reconstruction. Many such methods can be viewed as incremental gradient methods for minimizing a sum of a large number of convex functions, and despite their relatively poor global rate of convergence, these methods often exhibit fast...... initial convergence which is desirable in applications where a low-accuracy solution is acceptable. In this paper, we propose relaxed variants of a class of incremental proximal gradient methods, and these variants generalize many existing row-action methods for tomographic imaging. Moreover, they allow...... us to derive new incremental algorithms for tomographic imaging that incorporate different types of prior information via regularization. We demonstrate the efficacy of the approach with some numerical examples....

  1. In vivo acoustic and photoacoustic focusing of circulating cells

    Science.gov (United States)

    Galanzha, Ekaterina I.; Viegas, Mark G.; Malinsky, Taras I.; Melerzanov, Alexander V.; Juratli, Mazen A.; Sarimollaoglu, Mustafa; Nedosekin, Dmitry A.; Zharov, Vladimir P.

    2016-03-01

    In vivo flow cytometry using vessels as natural tubes with native cell flows has revolutionized the study of rare circulating tumor cells in a complex blood background. However, the presence of many blood cells in the detection volume makes it difficult to count each cell in this volume. We introduce method for manipulation of circulating cells in vivo with the use of gradient acoustic forces induced by ultrasound and photoacoustic waves. In a murine model, we demonstrated cell trapping, redirecting and focusing in blood and lymph flow into a tight stream, noninvasive wall-free transportation of blood, and the potential for photoacoustic detection of sickle cells without labeling and of leukocytes targeted by functionalized nanoparticles. Integration of cell focusing with intravital imaging methods may provide a versatile biological tool for single-cell analysis in circulation, with a focus on in vivo needleless blood tests, and preclinical studies of human diseases in animal models.

  2. Photoacoustic imaging using an 8-beam Fabry-Perot scanner

    Science.gov (United States)

    Huynh, Nam; Ogunlade, Olumide; Zhang, Edward; Cox, Ben; Beard, Paul

    2016-03-01

    The planar Fabry Perot (FP) photoacoustic scanner has been shown to provide exquisite high resolution 3D images of soft tissue structures in vivo to depths up to approximately 10mm. However a significant limitation of current embodiments of the concept is low image acquisition speed. To increase acquisition speed, a novel multi-beam scanner architecture has been developed. This enables a line of equally spaced 8 interrogation beams to be scanned simultaneously across the FP sensor and the photoacoustic signals detected in parallel. In addition, an excitation laser operating at 200Hz was used. The combination of parallelising the detection and the high pulse repetition frequency (PRF) of the excitation laser has enabled dramatic reductions in image acquisition time to be achieved. A 3D image can now be acquired in 10 seconds and 2D images at video rates are now possible.

  3. Optical pyrometer based on the gas phase photoacoustic effect.

    Science.gov (United States)

    Meng, Xiangling; Diebold, Gerald J

    2016-05-15

    A photoacoustic cell containing an infrared active gas and equipped with a pair of infrared transmitting windows that alternately views two bodies at different temperatures through a pair of chopping wheels acts as a differential detector of the radiation emitted by the two bodies. A theory for the photoacoustic signal shows that the device acts to monitor the difference in the incidances between the two bodies integrated over the absorptions of the gas in the cell. Experiments are reported showing that the response of the pyrometer depends on the relative temperatures of heated bodies, the absorption coefficient of the gas in the cell, and the modulation frequency of the chopping wheels. The instrument is shown to be a sensitive detector of a null in the integrated incidance of the two bodies. PMID:27176967

  4. Photoacoustic imaging of blood perfusion in tissue and phantoms

    Science.gov (United States)

    Pilatou, Magdalena C.; Kolkman, Roy G. M.; Hondebrink, Erwin; Bolt, Rene A.; de Mul, Frits F. M.

    2001-06-01

    To localize and monitor the blood content in tissue we developed a very sensitive photo-acoustical detector. PVDF has been used as piezo-electric material. In this detector also fibers for the illumination of the sample are integrated. Resolution is about 20 (m in depth and about 50-100 m laterally). We use 532 nm light. We will show how photoacoustics can be used for measuring the thickness of tissue above bone. We will also report measurements on tissue phantoms: e.g. a vessel delta from the epigastric artery branching of a Wistar rat, filled with an artificial blood-resembling absorber. The measurements have been carried out on phantoms containing vessels at several depths. Signal processing was enhanced by Fourier processing of the data.

  5. Spectroscopic intravascular photoacoustic imaging of neovasculature: phantom studies

    Science.gov (United States)

    Su, Jimmy L.; Wang, Bo; Emelianov, Stanislav Y.

    2009-02-01

    An acceleration of angiogenesis in the adventitial vasa-vasorum is usually associated with vulnerable, thin-cap fibroatheroma in atherosclerotic plaques. Angiogenesis creates microvasculature too small to be detected and differentiated using conventional imaging techniques. However, by using spectroscopic photoacoustic imaging, we take advantage of the wavelength-dependent optical absorption properties of blood. We used a vessel-mimicking phantom with micro blood vessels. The phantom was imaged with intravascular photoacoustic imaging across a range of wavelengths. The image intensities were cross-correlated with the known absorption spectra of blood. The resulting cross-correlation image was able to reveal the location of the artificial blood vessels differentiated from non-blood vessel components.

  6. Miniature fibre optic probe for minimally invasive photoacoustic sensing

    Science.gov (United States)

    Mathews, Sunish J.; Zhang, Edward Z.; Desjardins, Adrien E.; Beard, Paul C.

    2016-03-01

    A miniature (175 μm) all-optical photoacoustic probe has been developed for minimally invasive sensing and imaging applications. The probe comprises a single optical fibre which delivers the excitation light and a broadband 50 MHz Fabry-Pérot (F-P) ultrasound sensor at the distal end for detecting the photoacoustic waves. A graded index lens proximal to the F-P sensor is used to reduce beam walk-off and thus increase sensitivity as well as confine the excitation beam in order to increase lateral spatial resolution. The probe was evaluated in non-scattering media and found to provide lateral and axial resolutions of blood vessel mimicking phantom at distances up to 7 mm from the tip was demonstrated in order to illustrate its potential suitability for needle guidance applications.

  7. Photoacoustic molecular imaging for in vivo liver iron quantitation

    Science.gov (United States)

    Maccarinelli, Federica; Carmona, Fernando; Regoni, Maria; Arosio, Paolo

    2016-05-01

    A recent study showed that ferritin is a suitable endogenous contrast agent for photoacoustic molecular imaging in cultured mammalian cells. We have therefore tested whether this imaging technique can be used for in vivo quantification of iron in mouse livers. To verify this hypothesis, we used multispectral optoacoustic tomography (MSOT) to image albino CD1 mice before and after experimental iron loading. Postmortem assays showed that the iron treatment caused a 15-fold increase in liver iron and a 40-fold increase in liver ferritin levels, while in vivo longitudinal analysis using MSOT revealed just a 1.6-fold increase in the ferritin/iron photoacoustic signal in the same animals. We conclude that MSOT can monitor changes in ferritin/iron levels in vivo, but its sensitivity is much lower than that of ex vivo iron assays.

  8. Thermal property of biological tissues characterized by piezoelectric photoacoustic technique

    Institute of Scientific and Technical Information of China (English)

    GAO Chunming; ZHANG Shuyi; CHEN Yan; SHUI Xiuji; YANG Yuetao

    2004-01-01

    A photoacoustic piezoelectric method based on a simplified thermoelastic theory is employed to determine thermal diffusivities of biological tissues. The thermal diffusivities of porcine tissues with different preparation conditions, including fresh, dry and specially prepared conditions, are characterized. Comparing the experimental evaluated diffusivities of the tissues in three conditions with each other, it can be seen that the diffusivities of the fresh tissues are the biggest and the diffusivities of the specially prepared tissues are bigger than that of the dry ones generally. The results show that the piezoelectric photoacoustic method is especially effective for determining macro-effective (average) thermal diffusivities of biological materials with micro- inhomogeneity and easy to be performed, which can provide useful information for researching thermal characters of biological tissues.

  9. Detection of cocaine induced rat brain activation by photoacoustic tomography

    Science.gov (United States)

    Jo, Janggun; Yang, Xinmai

    2011-01-01

    Photoacoustic tomography (PAT) was used to detect the progressive changes on the cerebral cortex of Sprague Dawley rats after the administration of cocaine hydrochloride. Different concentrations (0, 2.5, and 5.0 mg per kg body) of cocaine hydrochloride in saline solution were injected into Sprague Dawley rats through tail veins. Cerebral cortex images of the animals were continuously acquired by PAT. For continuous observation, PAT system used multi-transducers to reduce the scanning time and maintain a good signal-to-noise ratio (SNR). The obtained photoacoustic images were compared with each other and confirmed that changes in blood volume were induced by cocaine hydrochloride injection. The results demonstrate that PAT may be used to detect the effects of drug abuse-induced brain activation. PMID:21163301

  10. Laser Illumination Modality of Photoacoustic Imaging Technique for Prostate Cancer

    Science.gov (United States)

    Peng, Dong-qing; Peng, Yuan-yuan; Guo, Jian; Li, Hui

    2016-02-01

    Photoacoustic imaging (PAI) has recently emerged as a promising imaging technique for prostate cancer. But there was still a lot of challenge in the PAI for prostate cancer detection, such as laser illumination modality. Knowledge of absorbed light distribution in prostate tissue was essential since the distribution characteristic of absorbed light energy would influence the imaging depth and range of PAI. In order to make a comparison of different laser illumination modality of photoacoustic imaging technique for prostate cancer, optical model of human prostate was established and combined with Monte Carlo simulation method to calculate the light absorption distribution in the prostate tissue. Characteristic of light absorption distribution of transurethral and trans-rectal illumination case, and of tumor at different location was compared with each other.The relevant conclusions would be significant for optimizing the light illumination in a PAI system for prostate cancer detection.

  11. Polyacrylamide based ICG nanocarriers for enhanced fluorescence and photoacoustic imaging

    Science.gov (United States)

    Ray, Aniruddha; Yoon, Hyung Ki; Ryu, HeeJu; Koo Lee, Yong-Eun; Kim, Gwangseong; Wang, Xueding; Kopelman, Raoul

    2013-02-01

    Indocyanine green (ICG) is an FDA approved tricarbocyanine dye. This dye, with a strong absorbance in the near infrared (NIR) region, has been extensively used for fluorescence and photoacoustic imaging in vivo. ICG in its free form, however, has a few drawbacks that limit its in vivo applications, such as non-targetability, tendency to form aggregates which changes its optical properties, fast degradation, short plasma lifetime and reduced fluorescence at body temperature. In order to bypass these inherent drawbacks, we demonstrate a polyacrylamide based nanocarrier that was particularly designed to carry the negatively charged ICG molecules. These nanocarriers are biodegradable, biocompatible and can be specifically targeted to any cell or tissue. Using these nanocarriers we avoid all the problems associated with free ICG, such as degradation, aggregation and short plasma lifetime, and also enhance demonstrate its ability towards photoacoustics and fluorescence imaging.

  12. Investigation of zinc stannate synthesis using photoacoustic spectroscopy

    Directory of Open Access Journals (Sweden)

    Ivetić T.

    2007-01-01

    Full Text Available Mixtures of ZnO and SnO2 powders, with molar ratio of 2:1, were mechanically activated for 40, 80 and 160 minutes in a planetary ball mill. The resulting powders were compacted into pellets and non-isothermally sintered up to 1200°C with a heating rate of 5°C/min. X-ray diffraction analysis of obtained powders and sintered samples was performed in order to investigate changes of the phase composition. The microstructure of sintered samples was examined by scanning electron microscopy. The photoacoustic phase and amplitude spectra of sintered samples were measured as a function of the laser beam modulating frequency using a transmission detection configuration. Fitting of experimental data enabled determination of photoacoustic properties including thermal diffusivity. Based on the results obtained a correlation between thermal diffusivity and experimental conditions as well the samples microstructure characteristics was discussed. .

  13. Initial results of finger imaging using Photoacoustic Computed Tomography

    CERN Document Server

    van Es, Peter; Moens, Hein J Bernelot; Steenbergen, Wiendelt; Manohar, Srirang

    2014-01-01

    We present a photoacoustic computed tomography investigation on a healthy human finger, to image blood vessels with a focus on vascularity across the interphalangeal joints. The cross-sectional images were acquired using an imager specifically developed for this purpose. The images show rich detail of the digital blood vessels with diameters between 100 $\\mu$m and 1.5 mm in various orientations and at various depths. Different vascular layers in the skin including the subpapillary plexus could also be visualized. Acoustic reflections on the finger bone of photoacoustic signals from skin were visible in sequential slice images along the finger except at the location of the joint gaps. Not unexpectedly, the healthy synovial membrane at the joint gaps was not detected due to its small size and normal vascularization. Future research will concentrate on studying digits afflicted with rheumatoid arthritis to detect the inflamed synovium with its heightened vascularization, whose characteristics are potential marke...

  14. Nonlinear quantitative photoacoustic tomography with two-photon absorption

    CERN Document Server

    Ren, Kui

    2016-01-01

    Two-photon photoacoustic tomography (TP-PAT) is a non-invasive optical molecular imaging modality that aims at inferring two-photon absorption property of heterogeneous media from photoacoustic measurements. In this work, we analyze an inverse problem in quantitative TP-PAT where we intend to reconstruct optical coefficients in a semilinear elliptic PDE, the mathematical model for the propagation of near infra-red photons in tissue-like optical media with two-photon absorption, from the internal absorbed energy data. We derive uniqueness and stability results on the reconstructions of single and multiple optical coefficients, and present some numerical reconstruction results based on synthetic data to complement the theoretical analysis.

  15. Accelerated High-Resolution Photoacoustic Tomography via Compressed Sensing

    CERN Document Server

    Arridge, Simon; Betcke, Marta; Cox, Ben; Huynh, Nam; Lucka, Felix; Ogunlade, Olumide; Zhang, Edward

    2016-01-01

    Current 3D photoacoustic tomography (PAT) systems offer either high image quality or high frame rates but are not able to deliver high spatial and temporal resolution simultaneously, which limits their ability to image dynamic processes in living tissue. A particular example is the planar Fabry-Perot (FP) scanner, which yields high-resolution images but takes several minutes to sequentially map the photoacoustic field on the sensor plane, point-by-point. However, as the spatio-temporal complexity of many absorbing tissue structures is rather low, the data recorded in such a conventional, regularly sampled fashion is often highly redundant. We demonstrate that combining variational image reconstruction methods using spatial sparsity constraints with the development of novel PAT acquisition systems capable of sub-sampling the acoustic wave field can dramatically increase the acquisition speed while maintaining a good spatial resolution: First, we describe and model two general spatial sub-sampling schemes. Then...

  16. Percutaneous permeation measurement of topical phthalocyanine by photoacoustic technique

    Science.gov (United States)

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

    2012-11-01

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

  17. Measurement of Environmental NO2 by Photoacoustic Spectroscopy

    Science.gov (United States)

    Wang, Gaoxuan; Yi, Hongming; Fertein, Eric; Sigrist, Markus W.; Chen, Weidong

    2016-04-01

    The most widely used technique for the measurements of nitrogen dioxide (NO2) is the chemiluminescence technique. However this indirect NO2 measurement method is affected by positive or negative interferences due to the use of non selective catalyzer molybdenum or photolytic converter [1]. Photoacoustic spectroscopy (PAS) offers the capability of interference-free direct NO2 measurement without any sample preparation or/and chemical conversion [2,3]. In this paper, we report on the development and applications of a photoacoustic spectroscopy-based NO2 sensor for continuous measurement of NO2 in air with a sensitivity of about 0.5 ppb (SNR=1) and 1 min time resolution. Time series measurements of environmental NO2 concentrations were carried out and compared with side-by-side measurements by a NOx analyzer (AC-31 M). Good agreement has been observed. Experimental detail and preliminary results will be presented. Acknowledgements The authors acknowledge financial supports from the CaPPA project (ANR-10-LABX-005) and the CPER CLIMIBIO program. G. W. thanks the "Pôle Métropolitain de la Côte d'Opale" (PMCO) and the Région Nord Pas de Calais for the PhD fellowship support. References [1] G. Villena, I. Bejan, R. Kurtenbach, P. Wiesen, J. Kleffmann, "Interferences of Commercial NO2 instruments in the urban atmosphere and in a smog chamber", Atmos. Meas. Tech. 5 (2012) 149. [2] M. Lassen, D. B. Clsusen, A. Brusch, J. C. Petersen, "A versatil integrating sphere based photoacoustic sensor for trace gas monitoring", Opt. Express 22 (2014) 11660. [3] C. Haisch, R. Niessner, "Photoacoustic analyzer for the artifact-free parallel detection of soot and NO2 in engin exhaut", Anal. Chem. 84 (2012) 7292.

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

    OpenAIRE

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

    2011-01-01

    Almost all diseases, especially cancer and diabetes, manifest abnormal oxygen metabolism. Accurately measuring the metabolic rate of oxygen (MRO2) can be helpful for fundamental pathophysiological studies, and even early diagnosis and treatment of disease. Current techniques either lack high resolution or rely on exogenous contrast. Here, we propose label-free metabolic photoacoustic microscopy (mPAM) with small vessel resolution to noninvasively quantify MRO2in vivo in absolute units. mPAM i...

  19. Groupoids and the tomographic picture of quantum mechanics

    International Nuclear Information System (INIS)

    The existing relation between the tomographic description of quantum states and the convolution algebra of certain discrete groupoids represented on Hilbert spaces will be discussed. The realizations of groupoid algebras based on qudit, photon-number (Fock) states and symplectic tomography quantizers and dequantizers will be constructed. Conditions for identifying the convolution product of groupoid functions and the star product arising from a quantization–dequantization scheme will be given. A tomographic approach to construct quasi-distributions out of suitable immersions of groupoids into Hilbert spaces will be formulated and, finally, intertwining kernels for such generalized symplectic tomograms will be evaluated explicitly. (paper)

  20. Quantumness tests and witnesses in the tomographic-probability representation

    Energy Technology Data Exchange (ETDEWEB)

    Filippov, S N [Moscow Institute of Physics and Technology, Moscow (Russian Federation); Man' ko, V I [P N Lebedev Physical Institute, Moscow (Russian Federation)], E-mail: filippovsn@gmail.com, E-mail: manko@sci.lebedev.ru

    2009-05-15

    In view of the tomographic-probability representation of quantum states, we reconsider the approach to quantumness tests of a single system developed by Alicki and Van Ryn (2008 J. Phys. A: Math. Theor. 41 062001). For qubits we introduce a general family of quantumness witnesses, which are operators depending on an extra parameter. Spin tomogram and dual-spin tomographic symbols are used to study qubit examples and the test inequalities which are shown to satisfy simple relations within the framework of the standard probability theory.

  1. Correction of ring artifacts in X-ray tomographic images

    DEFF Research Database (Denmark)

    Lyckegaard, Allan; Johnson, G.; Tafforeau, P.

    2011-01-01

    the same intensity level as the grain boundaries and thus make it impossible to perform grain segmentation. This paper describes an implementation of a method for correcting the ring artifacts in tomographic X-ray images of simple objects such as metal samples where the object and the background......Ring artifacts are systematic intensity distortions located on concentric circles in reconstructed tomographic X-ray images. When using X-ray tomography to study for instance low-contrast grain boundaries in metals it is crucial to correct for the ring artifacts in the images as they may have...

  2. Oxidative stress and pathogenic attack in plants, studied by laser based photoacoustic trace gas detection

    NARCIS (Netherlands)

    Santosa, Ignatius Edi

    2002-01-01

    Photoacoustic detection has proven to be a sensitive method, which is suitable for trace gas measurement. In this thesis, we improved the photoacoustic detection system to measure new biologically interesting gases, ethane (C2H6) and nitric oxide (NO). A new design of grating holder is incorporated

  3. In vitro characterization of genetically expressed absorbing proteins using photoacoustic spectroscopy.

    Science.gov (United States)

    Laufer, Jan; Jathoul, Amit; Pule, Martin; Beard, Paul

    2013-01-01

    Genetically expressed fluorescent proteins have been shown to provide photoacoustic contrast. However, they can be limited by low photoacoustic generation efficiency and low optical absorption at red and near infrared wavelengths, thus limiting their usefulness in mammalian small animal models. In addition, many fluorescent proteins exhibit low photostability due to photobleaching and transient absorption effects. In this study, we explore these issues by synthesizing and characterizing a range of commonly used fluorescent proteins (dsRed, mCherry, mNeptune, mRaspberry, AQ143, E2 Crimson) and novel non-fluorescent chromoproteins (aeCP597 and cjBlue and a non-fluorescent mutant of E2 Crimson). The photoacoustic spectra, photoacoustic generation efficiency and photostability of each fluorescent protein and chromoprotein were measured. Compared to the fluorescent proteins, the chromoproteins were found to exhibit higher photoacoustic generation efficiency due to the absence of radiative relaxation and ground state depopulation, and significantly higher photostability. The feasibility of converting an existing fluorescent protein into a non-fluorescent chromoprotein via mutagenesis was also demonstrated. The chromoprotein mutant exhibited greater photoacoustic signal generation efficiency and better agreement between the photoacoustic and the specific extinction coefficient spectra than the original fluorescent protein. Lastly, the genetic expression of a chromoprotein in mammalian cells was demonstrated. This study suggests that chromoproteins may have potential for providing genetically encoded photoacoustic contrast.

  4. Simultaneous Reconstructions of Absorption Density and Wave Speed with Photoacoustic Measurements

    CERN Document Server

    Kirsch, Andreas

    2011-01-01

    In this paper we propose an approach for \\emph{simultaneous} identification of the \\emph{absorption density} and the \\emph{speed of sound} by photoacoustic measurements. Experimentally our approach can be realized with sliced photoacoustic experiments. The mathematical model for such an experiment is developed and exact reconstruction formulas for both parameters are presented.

  5. Dual Modality Noncontact Photoacoustic and Spectral Domain OCT Imaging

    Science.gov (United States)

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

    2016-01-01

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

  6. Novel organosilicon phantoms as testing material for photoacoustic imaging

    Science.gov (United States)

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

    2016-03-01

    The contrast in photoacoustic (PA) imaging depends on the mechanical and elastic properties of the tissue, as well as on his optical absorption and scatter properties. Thanks to these futures, this novel modality could offer additional specificity compared to conventional ultrasound techniques, being able to reveal the signal of absorbing materials and chomophores, e.g. endogenous molecules like haemoglobin or specific near infrared dyes or plasmonic contrast agents. The development of semi-quantitative protocols for the assessment of the contrast enhancement, is one of the key aspect of the ongoing research, that could open new routes to the use of PA imaging for a variety of applications in preclinical research of cancer and cardiovascular diseases. In this work, we designed and tested a tissue mimicking polydimethylsiloxane (PDMS) phantom for photoacoustic applications, with tailored biomechanical/optical and geometrical properties. In order to modulate the light fluence and penetration, that remains one of the major challenge for this technique, we added titanium dioxide and black ink, rendering the optical absorption and scattering coefficients similar to those of biological tissues. The PDMS phantom can become a particularly promising tool in the field of photoacoustics for the evaluation of the performance of a PA system and as a model of the structure of vascularized soft tissues.

  7. Photoacoustic spectroscopy based evaluation of breast cancer condition

    Science.gov (United States)

    Priya, Mallika; Chandra, Subhas; Rao, Bola Sadashiva S.; Ray, Satadru; Shetty, Prashanth; Mathew, Stanley; Mahato, Krishna Kishore

    2015-02-01

    Photoacoustic spectroscopy, a hybrid of optics and acoustics has been gaining popularity in the biomedical field very fast. The main aim in the present study was to apply this technique to detect and distinguish breast tumor tissues from normal and hence develop a tool for clinical applications. There were 224 photoacoustic spectra recorded from 28 normal and 28 breast tumor tissues using PZT detector at 281nm pulsed laser excitations from Nd-YAG laser pumped frequency doubled dye laser system. The recorded time domain photoacoustic spectra were fast Fourier transformed into frequency domain patterns in the frequency region 0-1250kHz and from each pattern, 7 features (mean, median, mode, variance, standard deviation, area under the curve & spectral residual after fitting with 10th degree polynomial) were extracted using MATLAB algorithms. These features were then tested for their significance between normal and malignant conditions using Student T-test and two of them (variance, std. deviation) showing significant variation were selected for further discrimination analysis using supervised quadratic discriminate analysis (QDA). In QDA, 60 spectra from each of the normal and malignant were used for making the respective calibration sets and the remaining 52 spectra from each were used for the validation. The performance of the analysis tested for the frequency region 406.25 - 625.31 kHz, showed specificity and sensitivity values of 100% and 88.46% respectively suggesting possible application of the technique in breast tumor detection.

  8. Acoustic and photoacoustic microscopy imaging of single leukocytes

    Science.gov (United States)

    Strohm, Eric M.; Moore, Michael J.; Kolios, Michael C.

    2016-03-01

    An acoustic/photoacoustic microscope was used to create micrometer resolution images of stained cells from a blood smear. Pulse echo ultrasound images were made using a 1000 MHz transducer with 1 μm resolution. Photoacoustic images were made using a fiber coupled 532 nm laser, where energy losses through stimulated Raman scattering enabled output wavelengths from 532 nm to 620 nm. The laser was focused onto the sample using a 20x objective, and the laser spot co-aligned with the 1000 MHz transducer opposite the laser. The blood smear was stained with Wright-Giemsa, a common metachromatic dye that differentially stains the cellular components for visual identification. A neutrophil, lymphocyte and a monocyte were imaged using acoustic and photoacoustic microscopy at two different wavelengths, 532 nm and 600 nm. Unique features in each imaging modality enabled identification of the different cell types. This imaging method provides a new way of imaging stained leukocytes, with applications towards identifying and differentiating cell types, and detecting disease at the single cell level.

  9. Repositioning Clofazimine as a Macrophage-Targeting Photoacoustic Contrast Agent.

    Science.gov (United States)

    Keswani, Rahul K; Tian, Chao; Peryea, Tyler; Girish, Gandikota; Wang, Xueding; Rosania, Gus R

    2016-01-01

    Photoacoustic Tomography (PAT) is a deep-tissue imaging modality, with potential clinical applications in the diagnosis of arthritis, cancer and other disease conditions. Here, we identified Clofazimine (CFZ), a red-pigmented dye and anti-inflammatory FDA-approved drug, as a macrophage-targeting photoacoustic (PA) imaging agent. Spectroscopic experiments revealed that CFZ and its various protonated forms yielded optimal PAT signals at wavelengths -450 to 540 nm. CFZ's macrophage-targeting chemical and structural forms were detected with PA microscopy at a high contrast-to-noise ratio (CNR > 22 dB) as well as with macroscopic imaging using synthetic gelatin phantoms. In vivo, natural and synthetic CFZ formulations also demonstrated significant anti-inflammatory activity. Finally, the injection of CFZ was monitored via a real-time ultrasound-photoacoustic (US-PA) dual imaging system in a live animal and clinically relevant human hand model. These results demonstrate an anti-inflammatory drug repurposing strategy, while identifying a new PA contrast agent with potential applications in the diagnosis and treatment of arthritis. PMID:27000434

  10. Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection

    Directory of Open Access Journals (Sweden)

    Gaetano Scamarcio

    2006-10-01

    Full Text Available Various applications, such as pollution monitoring, toxic-gas detection, noninvasive medical diagnostics and industrial process control, require sensitive and selectivedetection of gas traces with concentrations in the parts in 109 (ppb and sub-ppb range.The recent development of quantum-cascade lasers (QCLs has given a new aspect toinfrared laser-based trace gas sensors. In particular, single mode distributed feedback QCLsare attractive spectroscopic sources because of their excellent properties in terms of narrowlinewidth, average power and room temperature operation. In combination with these lasersources, photoacoustic spectroscopy offers the advantage of high sensitivity and selectivity,compact sensor platform, fast time-response and user friendly operation. This paper reportsrecent developments on quantum cascade laser-based photoacoustic spectroscopy for tracegas detection. In particular, different applications of a photoacoustic trace gas sensoremploying a longitudinal resonant cell with a detection limit on the order of hundred ppb ofozone and ammonia are discussed. We also report two QC laser-based photoacousticsensors for the detection of nitric oxide, for environmental pollution monitoring andmedical diagnostics, and hexamethyldisilazane, for applications in semiconductormanufacturing process.

  11. An automated breast ultrasound scanner with integrated photoacoustic tomography

    Science.gov (United States)

    Kelly, Corey J.; Moradi, Hamid; Salcudean, Septimiu E.

    2016-03-01

    We have integrated photo-acoustic imaging into an automated breast ultrasound scanner (ABUS) with the goal of simultaneously performing ultrasound (US) and multi-spectral photo-acoustic tomography (PAT). This was accomplished with minimal change to the existing automated scanner by coupling laser light into an optical fiber for flexible and robust light delivery. We present preliminary tomography data acquired with this setup, including a simple resolution-testing geometry and a tissue phantom. Integrating PAT into the ABUS such that breast imaging is possible will require illumination from below the transducer dome. To that end, we are moving towards a fiber-based, localized illumination geometry which is fixed relative to the transducer. By illuminating locally (only near the current acquisition slice), this approach reduces overall light exposure at the tissue surface, allowing higher light intensity per acquisition (which translates to higher absorber contrast), while remaining below safe exposure thresholds. We present time-domain simulations of photo-acoustic imaging under non-uniform illumination conditions, and test one potential weighting scheme which can be used to extract absorber locations.

  12. Nanosensor aided photoacoustic measurement of pH in vivo

    Science.gov (United States)

    Ray, Aniruddha; Yoon, Hyung Ki; Kopelman, Raoul; Wang, Xueding

    2013-03-01

    pH plays a critical role in many aspects of cell and tissues physiology. Lower pH is also a typical characteristic of arthritic joints and tumor tissues. These pH anomalies are also exploited in different drug delivery mechanisms. Here we present, a new method of pH sensing in vivo using spectroscopic photoacoustic measurements facilitated by pH sensitive nanosensors. The nanosensors consist of Seminaphtharhodafluor (SNARF), a pH sensitive dye, encapsulated in a specially designed polyacrylamide hydrogel matrix with a hydrophobic core. The photoacoustic intensity ratio between the excitation wavelengths of 585nm and 565nm increases in the pH range from 6.0 to 8.0 and is used to determine the pH of the local environment. These nanosensors are biodegradable, biocompatible, have a long plasma lifetime and can be targeted to any type of cells or tissues by surface modification using proper targeting moieties. The encapsulation of the dye prevents the interaction of the dye with proteins in plasma and also reduces the dye degradation. The SNARF dye in its free form loses 90% of its absorbance in presence of albumin, a protein found in abundance in plasma, and this has severely limited its adaptation to in vivo environments. In comparison, the SNARF nanosensors lose only 16% of their absorbance in the same environment. We employ these nanosensors to demonstrate the feasibility of pH sensing in vivo through photoacoustic measurements on a rat joint model.

  13. Characterization of an intraluminal differential frequency-domain photoacoustics system

    Science.gov (United States)

    Lashkari, Bahman; Son, Jungik; Liang, Simon; Castelino, Robin; Foster, F. Stuart; Courtney, Brian; Mandelis, Andreas

    2016-03-01

    Cardiovascular related diseases are ranked as the second highest cause of death in Canada. Among the most important cardiovascular diseases is atherosclerosis. Current methods of diagnosis of atherosclerosis consist of angiography, intravascular ultrasound (IVUS) and optical coherence tomography (OCT). None of these methods possesses adequate sensitivity, as the ideal technique should be capable of both depth profiling, as well as functional imaging. An alternative technique is photoacoustics (PA) which can perform deep imaging and spectroscopy. The presented study explores the application of wavelength-modulated differential photoacoustic radar (WM-DPAR) for characterizing arterial vessels. The wavelength-modulated differential photoacoustic technique was shown to be able to substantially increase the dynamic range and sensitivity of hemoglobin oxygenation level detection. In this work the differential PA technique was used with a very high frequency modulation range. To perform spectroscopic PA imaging, at least two wavelengths are required. The selected wavelengths for this work are 1210 nm and 980 nm. 1210 nm corresponds to the maximum optical absorption coefficient of cholesterol and cholesteryl esters which are the main constituents of plaques. Since water, elastin and collagen also have high absorption coefficients at 1210 nm, this wavelength alone cannot provide very high sensitivity and specificity. The additional wavelength, 980 nm corresponds to high absorption coefficient of those constituents of healthy artery tissue. The simultaneous application of the abovementioned wavelengths can provide higher sensitivity and improved specificity in detecting lipids in the arterial vessels.

  14. Photoacoustic imaging of inflammatory arthritis in human joints

    Science.gov (United States)

    Jo, Janggun; Xu, Guan; Marquardt, April; Francis, Sheeja; Yuan, Jie; Girish, Dhanuj; Girish, Gandikota; Wang, Xueding

    2016-02-01

    The ducal imaging with photoacoustic imaging (PAI) that is an emerging technology and clinical ultrasound imaging that is an established modality is developed for the imaging of early inflammatory arthritis. PAI is sensitive to blood volume, not limited by flow like ultrasound, holding great promise for the earliest detection of increase in blood volume and angiogenesis - a key early finding inflammation PAI has the capability of assessing inflammation in superficial human soft tissues, offering potential benefits in diagnosis, treatment and monitoring of inflammatory arthritis. PAI combined with ultrasonography (US), is a real time dual-modality system developed and tested to identify active synovitis in metacarpophalangeal (MCP) joints of 10 arthritis patients and 10 normal volunteers. Photoacoustic images of the joints were acquired at 580-nm laser wavelength, which provided the desired balance between the optical contrast of hemoglobin over bone cortex and the imaging depth. Confirmed by US Doppler imaging, the results from ten patients and ten normal volunteers demonstrated satisfactory sensitivity of PAI in assessing enhanced blood flow due to active synovitis. This preliminary study suggests that photoacoustic imaging, by identifying early increase in blood volume, related to increased vascularity, a hallmark of joint inflammation, could be a valuable supplement to musculoskeletal US.

  15. A direct method for photoacoustic tomography with inhomogeneous sound speed

    Science.gov (United States)

    Belhachmi, Zakaria; Glatz, Thomas; Scherzer, Otmar

    2016-04-01

    The standard approach for photoacoustic imaging with variable speed of sound is time reversal, which consists of solving a well-posed final-boundary value problem for the wave equation backwards in time. This paper investigates the iterative Landweber regularization algorithm, where convergence is guaranteed by standard regularization theory, notably also in cases of trapping sound speed or for short measurement times. We formulate and solve the direct and inverse problem on the whole Euclidean space, which is common in standard photoacoustic imaging, but not for time reversal algorithms, where the problems are considered on a domain enclosed by the measurement devices. We formulate both the direct and adjoint photoacoustic operator as the solution of an interior and an exterior differential equation which are coupled by transmission conditions. The former is solved numerically using a Galerkin scheme in space and finite difference discretization in time, while the latter consists of solving a boundary integral equation. We therefore use a boundary element method/finite element method approach for numerical solution of the forward operators. We analyze this method, prove convergence, and provide numerical tests. Moreover, we compare the approach to time reversal.

  16. In vivo switchable optical- and acoustic-resolution photoacoustic microscopy

    Science.gov (United States)

    Jeon, Seungwan; Kim, Jaewoo; Kim, Chulhong

    2016-03-01

    Photoacoustic microscopy (PAM) provides high resolution and large penetration depth by utilizing the high optical sensitivity and low scattering of ultrasound. Hybrid PAM systems can be classified into two categories: opticalresolution photoacoustic microscopy (OR-PAM) and acoustic-resolution photoacoustic microscopy (AR-PAM). ORPAM provides a very high lateral resolution with a strong optical focus, but the penetration depth is limited to one optical transport mean free path. AR-PAM provides a relatively greater penetration depth using diffused light in biological tissues. The resolution of AR-PAM is determined by its ultrasonic parameters. In this study, we performed an in vivo testing of a switchable OR-/AR-PAM system. In this system, two modes can be switched by changing its collimator lens and optical fiber. The lateral resolution of OR-PAM was measured using a resolution test target, and the full width at half maximum (FWHM) of the edge spread function was 2.5 μm. To calculate the lateral resolution of ARPAM, a 6-μm-diameter carbon fiber was used, and the FWHM of the line spread function was 80.2 μm. We successfully demonstrated the multiscale imaging capability of the switchable OR-/AR-PAM system by visualizing microvascular networks in mouse ears, brain, legs, skin, and eyes.

  17. Photoacoustic generation by a gold nanosphere: from the linear to the nonlinear thermoelastic regime

    CERN Document Server

    Prost, Amaury

    2015-01-01

    We theoretically investigate the photoacoustic generation by a gold nanosphere in water in the thermoelastic regime. Photoacoustic signals are predicted numerically based on the successive resolution of a thermal diffusion problem and a thermoelastic problem, taking into account the finite size of the gold nanosphere, thermoelastic and elastic properties of both water and gold, and the temperature-dependence of the thermal expansion coefficient of water. For sufficiently high illumination fluences, this temperature dependence yields a nonlinear relationship between the photoacoustic amplitude and the fluence. For nanosecond pulses in the linear regime, we show that more than $90\\ \\%$ of the emitted photoacoustic energy is generated in water, and the thickness of the generating layer around the particle scales close to the square root of the pulse duration. The amplitude of the photoacoustic waves in the linear regime are accurately predicted by the point-absorber model introduced by Calasso and Diebold, but o...

  18. Spiral computed tomographic imaging related to computerized ultrasonographic images of carotid plaque morphology and histology

    DEFF Research Database (Denmark)

    Grønholdt, Marie-Louise; Wagner, A; Wiebe, B M;

    2001-01-01

    Echolucency of carotid atherosclerotic plaques, as evaluated by computerized B-mode ultrasonographic images, has been associated with an increased incidence of brain infarcts on cerebral computed tomographic scans. We tested the hypotheses that characterization of carotid plaques on spiral computed...... tomographic images correlates with that on computerized B-mode ultrasonographic images and that spiral computed tomographic imaging predicts the histomorphometric plaque content....

  19. Amplified photoacoustic performance and enhanced photothermal stability of reduced graphene oxide coated gold nanorods for sensitive photoacoustic imaging.

    Science.gov (United States)

    Moon, Hyungwon; Kumar, Dinesh; Kim, Haemin; Sim, Changbeom; Chang, Jin-Ho; Kim, Jung-Mu; Kim, Hyuncheol; Lim, Dong-Kwon

    2015-03-24

    We report a strongly amplified photoacoustic (PA) performance of the new functional hybrid material composed of reduced graphene oxide and gold nanorods. Due to the excellent NIR light absorption properties of the reduced graphene oxide coated gold nanorods (r-GO-AuNRs) and highly efficient heat transfer process through the reduced graphene oxide layer, r-GO-AuNRs exhibit excellent photothermal stability and significantly higher photoacoustic amplitudes than those of bare-AuNRs, nonreduced graphene oxide coated AuNRs (GO-AuNRs), or silica-coated AuNR, as demonstrated in both in vitro and in vivo systems. The linear response of PA amplitude from reduced state controlled GO on AuNR indicates the critical role of GO for a strong photothermal effect of r-GO-AuNRs. Theoretical studies with finite-element-method lab-based simulation reveal that a 4 times higher magnitude of the enhanced electromagnetic field around r-GO-AuNRs can be generated compared with bare AuNRs or GO-AuNRs. Furthermore, the r-GO-AuNRs are expected to be a promising deep-tissue imaging probe because of extraordinarily high PA amplitudes in the 4-11 MHz operating frequency of an ultrasound transducer. Therefore, the r-GO-AuNRs can be a useful imaging probe for highly sensitive photoacoustic images and NIR sensitive therapeutics based on a strong photothermal effect.

  20. Methylene blue microbubbles as a model dual-modality contrast agent for ultrasound and activatable photoacoustic imaging.

    Science.gov (United States)

    Jeon, Mansik; Song, Wentao; Huynh, Elizabeth; Kim, Jungho; Kim, Jeesu; Helfield, Brandon L; Leung, Ben Y C; Goertz, David E; Zheng, Gang; Oh, Jungtaek; Lovell, Jonathan F; Kim, Chulhong

    2014-01-01

    Ultrasound and photoacoustic imaging are highly complementary modalities since both use ultrasonic detection for operation. Increasingly, photoacoustic and ultrasound have been integrated in terms of hardware instrumentation. To generate a broadly accessible dual-modality contrast agent, we generated microbubbles (a standard ultrasound contrast agent) in a solution of methylene blue (a standard photoacoustic dye). This MB2 solution was formed effectively and was optimized as a dual-modality contrast solution. As microbubble concentration increased (with methylene blue concentration constant), photoacoustic signal was attenuated in the MB2 solution. When methylene blue concentration increased (with microbubble concentration held constant), no ultrasonic interference was observed. Using an MB2 solution that strongly attenuated all photoacoustic signal, high powered ultrasound could be used to burst the microbubbles and dramatically enhance photoacoustic contrast (>800-fold increase), providing a new method for spatiotemporal control of photoacoustic signal generation.

  1. 2-D soft x-ray arrays in the EAST

    Science.gov (United States)

    Chen, Kaiyun; Xu, Liqing; Hu, Liqun; Duan, Yanmin; Li, Xueqin; Yuan, Yi; Mao, Songtao; Sheng, Xiuli; Zhao, Jinlong

    2016-06-01

    A high spatial and temporal resolution soft x-ray (SXR) imaging diagnostic has been installed in EAST for the study of magnetohydrodynamics activities and core high-Z impurity transport. Up to 122 lines of sight view the poloidal plasma from three directions (two up-down symmetrical horizontal arrays and one vertical array), which renders the diagnostic able to provide detailed tomographic reconstructions under various conditions. Fourier-Bessel method based on flux coordinates was employed for 2-D SXR tomographic reconstruction. Examples of several events measured by SXR diagnostic in EAST are shown, namely the crash patterns of sawtooth, periodical burst of edge localized modes, and the transport of high-Z intrinsic impurities.

  2. Classical and quantum free motions in the tomographic probability representation

    CERN Document Server

    Man'ko, Vladimir I

    2011-01-01

    Based on a geometric picture, the example of free particle motion for both classical and quantum domains is considered in the tomographic probability representation. Wave functions and density operators as well as optical and symplectic tomograms are obtained as solutions of kinetic classical and quantum equations for the state tomograms. The difference of tomograms of free particle for classical and quantum states is discussed.

  3. Propagators in the moyal and tomographic representations of states

    NARCIS (Netherlands)

    Bazrafkan, MR; Man'ko, [No Value

    2004-01-01

    The tomographic map and density operator description of quantum states are reviewed. The connection between the tomogram and the probability distribution function is discussed. The relation of the Green function of the Moyal equation for the Wigner function to the Green function of the Schrodinger (

  4. Tomographic Approach in Three-Orthogonal-Basis Quantum Key Distribution

    Science.gov (United States)

    Liang, Wen-Ye; Wen, Hao; Yin, Zhen-Qiang; Chen, Hua; Li, Hong-Wei; Chen, Wei; Han, Zheng-Fu

    2015-09-01

    At present, there is an increasing awareness of some three-orthogonal-basis quantum key distribution protocols, such as, the reference-frame-independent (RFI) protocol and the six-state protocol. For secure key rate estimations of these protocols, there are two methods: one is the conventional approach, and another is the tomographic approach. However, a comparison between these two methods has not been given yet. In this work, with the general model of rotation channel, we estimate the key rate using conventional and tomographic methods respectively. Results show that conventional estimation approach in RFI protocol is equivalent to tomographic approach only in the case of that one of three orthogonal bases is always aligned. In other cases, tomographic approach performs much better than the respective conventional approaches of the RFI protocol and the six-state protocol. Furthermore, based on the experimental data, we illustrate the deep connections between tomography and conventional RFI approach representations. Supported by the National Basic Research Program of China under Grant Nos. 2011CBA00200 and 2011CB921200 and the National Natural Science Foundation of China under Grant Nos. 60921091, 61475148, and 61201239 and Zhejiang Natural Science Foundation under Grant No. LQ13F050005

  5. Microstructural and Tomographic Analyses in Geotechnical Assessment of Soil Media

    Directory of Open Access Journals (Sweden)

    Kumor Maciej Kordian

    2015-02-01

    Full Text Available This paper discusses two different approaches to microanalysis of the soil medium. It presents testing results collected by electromicroscopy, which requires special sample preparation, and a non-destructive method, requiring no sample preparation and using a computer-assisted tomograph. The paper presents:

  6. Combined photoacoustic and ultrasound imaging of human breast in vivo in the mammographic geometry

    Science.gov (United States)

    Xie, Zhixing; Lee, Won-Mean; Hooi, Fong Ming; Fowlkes, J. Brian; Pinsky, Renee W.; Mueller, Dean; Wang, Xueding; Carson, Paul L.

    2013-03-01

    This photoacoustic volume imaging (PAVI) system is designed to study breast cancer detection and diagnosis in the mammographic geometry in combination with automated 3D ultrasound (AUS). The good penetration of near-infrared (NIR) light and high receiving sensitivity of a broad bandwidth, 572 element, 2D PVDF array at a low center-frequency of 1MHz were utilized with 20 channel simultaneous acquisition. The feasibility of this system in imaging optically absorbing objects in deep breast tissues was assessed first through experiments on ex vivo whole breasts. The blood filled pseudo lesions were imaged at depths up to 49 mm in the specimens. In vivo imaging of human breasts has been conducted. 3D PAVI image stacks of human breasts were coregistered and compared with 3D ultrasound image stacks of the same breasts. Using the designed system, PAVI shows satisfactory imaging depth and sensitivity for coverage of the entire breast when imaged from both sides with mild compression in the mammographic geometry. With its unique soft tissue contrast and excellent sensitivity to the tissue hemodynamic properties of fractional blood volume and blood oxygenation, PAVI, as a complement to 3D ultrasound and digital tomosynthesis mammography, might well contribute to detection, diagnosis and prognosis for breast cancer.

  7. Nanoparticle-enhanced spectral photoacoustic tomography: effect of oxygen saturation and tissue heterogeneity

    Science.gov (United States)

    Vogt, William C.; Jia, Congxian; Wear, Keith A.; Garra, Brian S.; Pfefer, T. Joshua

    2016-03-01

    Molecular imaging for breast cancer detection, infectious disease diagnostics and preclinical animal research may be achievable through combined use of targeted exogenous agents - such as nanoparticles - and spectral Photoacoustic Tomography (PAT). However, tissue heterogeneity can alter fluence distributions and acoustic propagation, corrupting measured PAT absorption spectra and complicating in vivo nanoparticle detection and quantitation. Highly absorptive vascular structures represent a common confounding factor, and variations in vessel hemoglobin saturation (SO2) may alter spectral content of signals from adjacent/deeper regions. To evaluate the impact of this effect on PAT nanoparticle detectability, we constructed heterogeneous phantoms with well-characterized channel-inclusion geometries and biologically relevant optical and acoustic properties. Phantoms contained an array of tubes at several depths filled with hemoglobin solutions doped with varying concentrations of gold nanorods with an absorption peak at 780 nm. Both overlying and target network SO2 was tuned using sodium dithionite. Phantoms were imaged from 700 to 900 nm using a custom PAT system comprised of a tunable pulsed laser and a research-grade ultrasound system. Recovered nanoparticle spectra were analyzed and compared with results from both spectrophotometry and PAT data from waterimmersed tubes containing blood and nanoparticle solutions. Results suggested that nanoparticle selection for a given PAT application should take into account expected oxygenation states of both target blood vessel and background tissue oxygenation to achieve optimal performance.

  8. Biologically relevant photoacoustic imaging phantoms with tunable optical and acoustic properties.

    Science.gov (United States)

    Vogt, William C; Jia, Congxian; Wear, Keith A; Garra, Brian S; Joshua Pfefer, T

    2016-10-01

    Established medical imaging technologies such as magnetic resonance imaging and computed tomography rely on well-validated tissue-simulating phantoms for standardized testing of device image quality. The availability of high-quality phantoms for optical-acoustic diagnostics such as photoacoustic tomography (PAT) will facilitate standardization and clinical translation of these emerging approaches. Materials used in prior PAT phantoms do not provide a suitable combination of long-term stability and realistic acoustic and optical properties. Therefore, we have investigated the use of custom polyvinyl chloride plastisol (PVCP) formulations for imaging phantoms and identified a dual-plasticizer approach that provides biologically relevant ranges of relevant properties. Speed of sound and acoustic attenuation were determined over a frequency range of 4 to 9 MHz and optical absorption and scattering over a wavelength range of 400 to 1100 nm. We present characterization of several PVCP formulations, including one designed to mimic breast tissue. This material is used to construct a phantom comprised of an array of cylindrical, hemoglobin-filled inclusions for evaluation of penetration depth. Measurements with a custom near-infrared PAT imager provide quantitative and qualitative comparisons of phantom and tissue images. Results indicate that our PVCP material is uniquely suitable for PAT system image quality evaluation and may provide a practical tool for device validation and intercomparison. PMID:26886681

  9. India ink incorporated multifunctional phase-transition nanodroplets for photoacoustic/ultrasound dual-modality imaging and photoacoustic effect based tumor therapy.

    Science.gov (United States)

    Jian, Jia; Liu, Chengbo; Gong, Yuping; Su, Lei; Zhang, Bin; Wang, Zhigang; Wang, Dong; Zhou, Yu; Xu, Fenfen; Li, Pan; Zheng, Yuanyi; Song, Liang; Zhou, Xiyuan

    2014-01-01

    The in vivo applications of gas-core microbubbles have been limited by gas diffusion, rapid body clearance, and poor vascular permeability. To overcome these limitations, using a modified three-step emulsion process, we have developed a first-of-its-kind India ink incorporated optically-triggerable phase-transition perfluorocarbon nanodroplets (INDs) that can provide not only three types of contrast mechanisms-conventional/thermoelastic photoacoustic, phase-transition/nonlinear photoacoustic, and ultrasound imaging contrasts, but also a new avenue for photoacoustic effect mediated tumor therapy. Upon pulsed laser illumination above a relatively low energy threshold, liquid-gas phase transition of the INDs has been demonstrated both in vitro and in vivo, offering excellent contrasts for photoacoustic and ultrasound dual-modality imaging. With further increased laser energy, the nanodroplets have been shown to be capable of destructing cancer cells in vivo, presumably due to the photoacoustic effect induced shock-wave generation from the carbon particles of the incorporated India ink. The demonstrated results suggest that the developed multifunctional phase-transition nanodroplets have a great potential for many theranostic biomedical applications, including photoacoustic/ultrasound dual-modality molecular imaging and targeted, localized cancer therapy.

  10. Array tomography: imaging stained arrays.

    Science.gov (United States)

    Micheva, Kristina D; O'Rourke, Nancy; Busse, Brad; Smith, Stephen J

    2010-11-01

    Array tomography is a volumetric microscopy method based on physical serial sectioning. Ultrathin sections of a plastic-embedded tissue are cut using an ultramicrotome, bonded in an ordered array to a glass coverslip, stained as desired, and imaged. The resulting two-dimensional image tiles can then be reconstructed computationally into three-dimensional volume images for visualization and quantitative analysis. The minimal thickness of individual sections permits high-quality rapid staining and imaging, whereas the array format allows reliable and convenient section handling, staining, and automated imaging. Also, the physical stability of the arrays permits images to be acquired and registered from repeated cycles of staining, imaging, and stain elution, as well as from imaging using multiple modalities (e.g., fluorescence and electron microscopy). Array tomography makes it possible to visualize and quantify previously inaccessible features of tissue structure and molecular architecture. However, careful preparation of the tissue is essential for successful array tomography; these steps can be time-consuming and require some practice to perfect. In this protocol, tissue arrays are imaged using conventional wide-field fluorescence microscopy. Images can be captured manually or, with the appropriate software and hardware, the process can be automated. PMID:21041399

  11. Array tomography: production of arrays.

    Science.gov (United States)

    Micheva, Kristina D; O'Rourke, Nancy; Busse, Brad; Smith, Stephen J

    2010-11-01

    Array tomography is a volumetric microscopy method based on physical serial sectioning. Ultrathin sections of a plastic-embedded tissue are cut using an ultramicrotome, bonded in an ordered array to a glass coverslip, stained as desired, and imaged. The resulting two-dimensional image tiles can then be reconstructed computationally into three-dimensional volume images for visualization and quantitative analysis. The minimal thickness of individual sections permits high-quality rapid staining and imaging, whereas the array format allows reliable and convenient section handling, staining, and automated imaging. Also, the physical stability of the arrays permits images to be acquired and registered from repeated cycles of staining, imaging, and stain elution, as well as from imaging using multiple modalities (e.g., fluorescence and electron microscopy). Array tomography makes it possible to visualize and quantify previously inaccessible features of tissue structure and molecular architecture. However, careful preparation of the tissue is essential for successful array tomography; these steps can be time consuming and require some practice to perfect. This protocol describes the sectioning of embedded tissues and the mounting of the serial arrays. The procedures require some familiarity with the techniques used for ultramicrotome sectioning for electron microscopy. PMID:21041397

  12. Tomographic Reconstruction of Electron Density from Visible Light Emission Diagnostics on a Translated FRC Plasma

    Science.gov (United States)

    Votroubek, George R.; Slough, John; Crawford, Edward

    1999-11-01

    Visible light emission detector arrays have been set up on the TCS and STX experiments at RPPL. Light collected by the system is filtered through a pair of Kodak\\copyright Wratten^TM gel filters in order to look at time resolved Bremsstrahlung radiation emitted at wavelengths between 500-600 nm and attenuate line emission from D_α and D_β. The emission data ( ~ int n^2\\:dl) will be correlated with a 10.6 μm CO2 interferometer ( ~ int n\\:dl) to relate the emission to calibrated units of electron density. The array of chordal information is then processed through a method of tomographic inversion in order to get radial profile information of the translated FRC, and will eventually be used to examine RMF sustained FRCs. This data can then be compared to MOQUI , a full 2D MHD code, results. Experimental setup, hardware, and data will be presented. Supported by USDOE. www.aa.washington.edu/AERP/RPPL.

  13. Near-Infrared Squaraine Dye Encapsulated Micelles for in Vivo Fluorescence and Photoacoustic Bimodal Imaging.

    Science.gov (United States)

    Sreejith, Sivaramapanicker; Joseph, James; Lin, Manjing; Menon, Nishanth Venugopal; Borah, Parijat; Ng, Hao Jun; Loong, Yun Xian; Kang, Yuejun; Yu, Sidney Wing-Kwong; Zhao, Yanli

    2015-06-23

    Combined near-infrared (NIR) fluorescence and photoacoustic imaging techniques present promising capabilities for noninvasive visualization of biological structures. Development of bimodal noninvasive optical imaging approaches by combining NIR fluorescence and photoacoustic tomography demands suitable NIR-active exogenous contrast agents. If the aggregation and photobleaching are prevented, squaraine dyes are ideal candidates for fluorescence and photoacoustic imaging. Herein, we report rational selection, preparation, and micelle encapsulation of an NIR-absorbing squaraine dye (D1) for in vivo fluorescence and photoacoustic bimodal imaging. D1 was encapsulated inside micelles constructed from a biocompatible nonionic surfactant (Pluoronic F-127) to obtain D1-encapsulated micelles (D1(micelle)) in aqueous conditions. The micelle encapsulation retains both the photophysical features and chemical stability of D1. D1(micelle) exhibits high photostability and low cytotoxicity in biological conditions. Unique properties of D1(micelle) in the NIR window of 800-900 nm enable the development of a squaraine-based exogenous contrast agent for fluorescence and photoacoustic bimodal imaging above 820 nm. In vivo imaging using D1(micelle), as demonstrated by fluorescence and photoacoustic tomography experiments in live mice, shows contrast-enhanced deep tissue imaging capability. The usage of D1(micelle) proven by preclinical experiments in rodents reveals its excellent applicability for NIR fluorescence and photoacoustic bimodal imaging.

  14. Oscillatory Dynamics and In Vivo Photoacoustic Imaging Performance of Plasmonic Nanoparticle-Coated Microbubbles.

    Science.gov (United States)

    Dixon, Adam J; Hu, Song; Klibanov, Alexander L; Hossack, John A

    2015-07-01

    Microbubbles bearing plasmonic nanoparticles on their surface provide contrast enhancement for both photoacoustic and ultrasound imaging. In this work, the responses of microbubbles with surface-bound gold nanorods-termed AuMBs-to nanosecond pulsed laser excitation are studied using high-speed microscopy, photoacoustic imaging, and numerical modeling. In response to laser fluences below 5 mJ cm(-2) , AuMBs produce weak photoacoustic emissions and exhibit negligible microbubble wall motion. However, in reponse to fluences above 5 mJ cm(-2) , AuMBs undergo dramatically increased thermal expansion and emit nonlinear photoacoustic waves of over 10-fold greater amplitude than would be expected from freely dispersed gold nanorods. Numerical modeling suggests that AuMB photoacoustic responses to low laser fluences result from conductive heat transfer from the surface-bound nanorods to the microbubble gas core, whereas at higher fluences, explosive boiling may occur at the nanorod surface, producing vapor nanobubbles that contribute to rapid AuMB expansion. The results of this study indicate that AuMBs are capable of producing acoustic emissions of significantly higher amplitude than those produced by conventional sources of photoacoustic contrast. In vivo imaging performance of AuMBs in a murine kidney model suggests that AuMBs may be an effective alternative to existing contrast agents for noninvasive photoacoustic and ultrasound imaging applications.

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

    Directory of Open Access Journals (Sweden)

    Rafael Pérez Solano

    2012-03-01

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

  16. Detection of Melanoma Metastases in Resected Human Lymph Nodes by Noninvasive Multispectral Photoacoustic Imaging

    Directory of Open Access Journals (Sweden)

    Gerrit Cornelis Langhout

    2014-01-01

    Full Text Available Objective. Sentinel node biopsy in patients with cutaneous melanoma improves staging, provides prognostic information, and leads to an increased survival in node-positive patients. However, frozen section analysis of the sentinel node is not reliable and definitive histopathology evaluation requires days, preventing intraoperative decision-making and immediate therapy. Photoacoustic imaging can evaluate intact lymph nodes, but specificity can be hampered by other absorbers such as hemoglobin. Near infrared multispectral photoacoustic imaging is a new approach that has the potential to selectively detect melanin. The purpose of the present study is to examine the potential of multispectral photoacoustic imaging to identify melanoma metastasis in human lymph nodes. Methods. Three metastatic and nine benign lymph nodes from eight melanoma patients were scanned ex vivo using a Vevo LAZR© multispectral photoacoustic imager and were spectrally analyzed per pixel. The results were compared to histopathology as gold standard. Results. The nodal volume could be scanned within 20 minutes. An unmixing procedure was proposed to identify melanoma metastases with multispectral photoacoustic imaging. Ultrasound overlay enabled anatomical correlation. The penetration depth of the photoacoustic signal was up to 2 cm. Conclusion. Multispectral three-dimensional photoacoustic imaging allowed for selective identification of melanoma metastases in human lymph nodes.

  17. Improvements in seismic event locations in a deep western U.S. coal mine using tomographic velocity models and an evolutionary search algorithm

    Institute of Scientific and Technical Information of China (English)

    LURKA Adam; SWANSON Peter

    2009-01-01

    Methods of improving seismic event locations were investigated as part of a research study aimed at reducing ground control safety hazards. Seismic event waveforms collected with a 23-station three-dimensional sensor array during longwall coal mining provide the data set used in the analyses. A spatially variable seismic velocity model is constructed using seismic event sources in a passive tomographic method. The resulting three-dimensional velocity model is used to relocate seismic event positions. An evolutionary optimization algorithm is implemented and used in both the velocity model development and in seeking improved event location solutions. Results obtained using the different velocity models are compared. The combination of the tomographic velocity model development and evolutionary search algorithm provides improvement to the event locations.

  18. Photoacoustic removal of occlusions from blood vessels

    Science.gov (United States)

    Visuri, Steven R.; Da Silva, Luiz B.; Celliers, Peter M.; London, Richard A.; Maitland, IV, Duncan J.; Esch, Victor C.

    2002-01-01

    Partial or total occlusions of fluid passages within the human body are removed by positioning an array of optical fibers in the passage and directing treatment radiation pulses along the fibers, one at a time, to generate a shock wave and hydrodynamics flows that strike and emulsify the occlusions. A preferred application is the removal of blood clots (thrombin and embolic) from small cerebral vessels to reverse the effects of an ischemic stroke. The operating parameters and techniques are chosen to minimize the amount of heating of the fragile cerebral vessel walls occurring during this photo acoustic treatment. One such technique is the optical monitoring of the existence of hydrodynamics flow generating vapor bubbles when they are expected to occur and stopping the heat generating pulses propagated along an optical fiber that is not generating such bubbles.

  19. Photoacoustic tomography of human hepatic malignancies using intraoperative indocyanine green fluorescence imaging.

    Science.gov (United States)

    Miyata, Akinori; Ishizawa, Takeaki; Kamiya, Mako; Shimizu, Atsushi; Kaneko, Junichi; Ijichi, Hideaki; Shibahara, Junji; Fukayama, Masashi; Midorikawa, Yutaka; Urano, Yasuteru; Kokudo, Norihiro

    2014-01-01

    Recently, fluorescence imaging following the preoperative intravenous injection of indocyanine green has been used in clinical settings to identify hepatic malignancies during surgery. The aim of this study was to evaluate the ability of photoacoustic tomography using indocyanine green as a contrast agent to produce representative fluorescence images of hepatic tumors by visualizing the spatial distribution of indocyanine green on ultrasonographic images. Indocyanine green (0.5 mg/kg, intravenous) was preoperatively administered to 9 patients undergoing hepatectomy. Intraoperatively, photoacoustic tomography was performed on the surface of the resected hepatic specimens (n = 10) under excitation with an 800 nm pulse laser. In 4 hepatocellular carcinoma nodules, photoacoustic imaging identified indocyanine green accumulation in the cancerous tissue. In contrast, in one hepatocellular carcinoma nodule and five adenocarcinoma foci (one intrahepatic cholangiocarcinoma and 4 colorectal liver metastases), photoacoustic imaging delineated indocyanine green accumulation not in the cancerous tissue but rather in the peri-cancerous hepatic parenchyma. Although photoacoustic tomography enabled to visualize spatial distribution of ICG on ultrasonographic images, which was consistent with fluorescence images on cut surfaces of the resected specimens, photoacoustic signals of ICG-containing tissues decreased approximately by 40% even at 4 mm depth from liver surfaces. Photoacoustic tomography using indocyanine green also failed to identify any hepatocellular carcinoma nodules from the body surface of model mice with non-alcoholic steatohepatitis. In conclusion, photoacoustic tomography has a potential to enhance cancer detectability and differential diagnosis by ultrasonographic examinations and intraoperative fluorescence imaging through visualization of stasis of bile-excreting imaging agents in and/or around hepatic tumors. However, further technical advances are needed

  20. Photoacoustic tomography of human hepatic malignancies using intraoperative indocyanine green fluorescence imaging.

    Directory of Open Access Journals (Sweden)

    Akinori Miyata

    Full Text Available Recently, fluorescence imaging following the preoperative intravenous injection of indocyanine green has been used in clinical settings to identify hepatic malignancies during surgery. The aim of this study was to evaluate the ability of photoacoustic tomography using indocyanine green as a contrast agent to produce representative fluorescence images of hepatic tumors by visualizing the spatial distribution of indocyanine green on ultrasonographic images. Indocyanine green (0.5 mg/kg, intravenous was preoperatively administered to 9 patients undergoing hepatectomy. Intraoperatively, photoacoustic tomography was performed on the surface of the resected hepatic specimens (n = 10 under excitation with an 800 nm pulse laser. In 4 hepatocellular carcinoma nodules, photoacoustic imaging identified indocyanine green accumulation in the cancerous tissue. In contrast, in one hepatocellular carcinoma nodule and five adenocarcinoma foci (one intrahepatic cholangiocarcinoma and 4 colorectal liver metastases, photoacoustic imaging delineated indocyanine green accumulation not in the cancerous tissue but rather in the peri-cancerous hepatic parenchyma. Although photoacoustic tomography enabled to visualize spatial distribution of ICG on ultrasonographic images, which was consistent with fluorescence images on cut surfaces of the resected specimens, photoacoustic signals of ICG-containing tissues decreased approximately by 40% even at 4 mm depth from liver surfaces. Photoacoustic tomography using indocyanine green also failed to identify any hepatocellular carcinoma nodules from the body surface of model mice with non-alcoholic steatohepatitis. In conclusion, photoacoustic tomography has a potential to enhance cancer detectability and differential diagnosis by ultrasonographic examinations and intraoperative fluorescence imaging through visualization of stasis of bile-excreting imaging agents in and/or around hepatic tumors. However, further technical

  1. Downscaling Smooth Tomographic Models: Separating Intrinsic and Apparent Anisotropy

    Science.gov (United States)

    Bodin, Thomas; Capdeville, Yann; Romanowicz, Barbara

    2016-04-01

    In recent years, a number of tomographic models based on full waveform inversion have been published. Due to computational constraints, the fitted waveforms are low pass filtered, which results in an inability to map features smaller than half the shortest wavelength. However, these tomographic images are not a simple spatial average of the true model, but rather an effective, apparent, or equivalent model that provides a similar 'long-wave' data fit. For example, it can be shown that a series of horizontal isotropic layers will be seen by a 'long wave' as a smooth anisotropic medium. In this way, the observed anisotropy in tomographic models is a combination of intrinsic anisotropy produced by lattice-preferred orientation (LPO) of minerals, and apparent anisotropy resulting from the incapacity of mapping discontinuities. Interpretations of observed anisotropy (e.g. in terms of mantle flow) requires therefore the separation of its intrinsic and apparent components. The "up-scaling" relations that link elastic properties of a rapidly varying medium to elastic properties of the effective medium as seen by long waves are strongly non-linear and their inverse highly non-unique. That is, a smooth homogenized effective model is equivalent to a large number of models with discontinuities. In the 1D case, Capdeville et al (GJI, 2013) recently showed that a tomographic model which results from the inversion of low pass filtered waveforms is an homogenized model, i.e. the same as the model computed by upscaling the true model. Here we propose a stochastic method to sample the ensemble of layered models equivalent to a given tomographic profile. We use a transdimensional formulation where the number of layers is variable. Furthermore, each layer may be either isotropic (1 parameter) or intrinsically anisotropic (2 parameters). The parsimonious character of the Bayesian inversion gives preference to models with the least number of parameters (i.e. least number of layers, and

  2. Noninvasive photoacoustic computed tomography of mouse brain metabolism in vivo

    Science.gov (United States)

    Yao, Junjie; Xia, Jun; Maslov, Konstantin; Avanaki, Mohammadreza R. N.; Tsytsarev, Vassiliy; Demchenko, Alexei V.; Wang, Lihong V.

    2013-03-01

    To control the overall action of the body, brain consumes a large amount of energy in proportion to its volume. In humans and many other species, the brain gets most of its energy from oxygen-dependent metabolism of glucose. An abnormal metabolic rate of glucose and/or oxygen usually reflects a diseased status of brain, such as cancer or Alzheimer's disease. We have demonstrated the feasibility of imaging mouse brain metabolism using photoacoustic computed tomography (PACT), a fast, noninvasive and functional imaging modality with optical contrast and acoustic resolution. Brain responses to forepaw stimulations were imaged transdermally and transcranially. 2-NBDG, which diffuses well across the blood-brain-barrier, provided exogenous contrast for photoacoustic imaging of glucose response. Concurrently, hemoglobin provided endogenous contrast for photoacoustic imaging of hemodynamic response. Glucose and hemodynamic responses were quantitatively unmixed by using two-wavelength measurements. We found that glucose uptake and blood perfusion around the somatosensory region of the contralateral hemisphere were both increased by stimulations, indicating elevated neuron activity. The glucose response amplitude was about half that of the hemodynamic response. While the glucose response area was more homogenous and confined within the somatosensory region, the hemodynamic response area showed a clear vascular pattern and spread about twice as wide as that of the glucose response. The PACT of mouse brain metabolism was validated by high-resolution open-scalp OR-PAM and fluorescence imaging. Our results demonstrate that 2-NBDG-enhanced PACT is a promising tool for noninvasive studies of brain metabolism.

  3. Molecular application of spectral photoacoustic imaging in pancreatic cancer pathology

    Science.gov (United States)

    Lakshman, Minalini; Hupple, Clinton; Lohse, Ines; Hedley, David; Needles, Andrew; Theodoropoulos, Catherine

    2012-12-01

    Spectral imaging is an advanced photo-acoustic (PA) mode that can discern optical absorption of contrast agent(s) in the tissue micro-environment. This advancement is made possible by precise control of optical wavelength using a tunable pulsed laser, ranging from 680-970 nm. Differential optical absorption of blood oxygenation states makes spectral imaging of hemoglobin ideal to investigate remodeling of the tumor microenvironment- a molecular change that renders resistance to standard cancer treatment. Approach: Photo-acoustic imaging was performed on the Vevo® LAZR system (VisualSonics) at 5-20 Hz. Deep abdominal imaging was accomplished with a LZ250D probe at a center frequency of 21MHz and an axial resolution of 75 μm. The tumor model was generated in an immune compromised mouse by surgical implantation of primary patient derived tumors, in the pancreas. Results: Spectral imaging for oxygen saturation at 750 nm and 850 nm characterized this tumor with a poorly oxygenated core surrounded by a well oxygenated periphery. Multispectral imaging identified a sub region in the core with a four-fold signal exclusively at 750 and 800 nm. A co-registered 2D image of this region was shown to be echogenic and calcification was suspected. Perfusion imaging with contrast enhanced ultrasound using microbubbles (Vevo MicroMarker® contrast agents, VisualSonics) identified functional vessels towards this sub region. Histology confirmed calcification and vascularization in the tumor core. Taken together, non-invasive characterization of the tumor microenvironment using photo-acoustics rendered spectral imaging a sensitive tool to monitor molecular changes representative of progression of pancreatic cancer that kills within 6 months of diagnosis.

  4. Detection and isolation of circulating melanoma cells using photoacoustic flowmetry.

    Science.gov (United States)

    O'Brien, Christine M; Rood, Kyle; Sengupta, Shramik; Gupta, Sagar K; DeSouza, Thiago; Cook, Aaron; Viator, John A

    2011-01-01

    Circulating tumor cells (CTCs) are those cells that have separated from a macroscopic tumor and spread through the blood and lymph systems to seed secondary tumors(1,2,3). CTCs are indicators of metastatic disease and their detection in blood samples may be used to diagnose cancer and monitor a patient's response to therapy. Since CTCs are rare, comprising about one tumor cell among billions of normal blood cells in advanced cancer patients, their detection and enumeration is a difficult task. We exploit the presence of pigment in most melanoma cells to generate photoacoustic, or laser induced ultrasonic waves in a custom flow cytometer for detection of circulating melanoma cells (CMCs)(4,5). This process entails separating a whole blood sample using centrifugation and obtaining the white blood cell layer. If present in whole blood, CMCs will separate with the white blood cells due to similar density. These cells are resuspended in phosphate buffered saline (PBS) and introduced into the flowmeter. Rather than a continuous flow of the blood cell suspension, we induced two phase flow in order to capture these cells for further study. In two phase flow, two immiscible liquids in a microfluidic system meet at a junction and form alternating slugs of liquid(6,7). PBS suspended white blood cells and air form microliter slugs that are sequentially irradiated with laser light. The addition of a surfactant to the liquid phase allows uniform slug formation and the user can create different sized slugs by altering the flow rates of the two phases. Slugs of air and slugs of PBS with white blood cells contain no light absorbers and hence, do not produce photoacoustic waves. However, slugs of white blood cells that contain even single CMCs absorb laser light and produce high frequency acoustic waves. These slugs that generate photoacoustic waves are sequestered and collected for cytochemical staining for verification of CMCs. PMID:22143421

  5. Photoacoustic endoscopy probe using a coherent fibre-optic bundle and Fabry-Pérot ultrasound sensor (Conference Presentation)

    Science.gov (United States)

    Ansari, Rehman; Beard, Paul C.; Zhang, Edward Z.; Desjardins, Adrien E.

    2016-03-01

    There is considerable interest in the development of photoacoustic endoscopy (PAE) probes for the clinical assessment of pathologies in the gastrointestinal (GI) tract, guiding minimally invasive laparoscopic surgeries and applications in foetal medicine. However, most previous PAE probes integrate mechanical scanners and piezoelectric transducers at the distal end which can be technically complex, expensive and pose challenges in achieving the necessary level of miniaturisation. We present two novel all-optical forward-viewing endoscopic probes operating in widefield tomography mode that have the potential to overcome these limitations. In one configuration, the probe comprises a transparent 40 MHz Fabry-Pérot ultrasound sensor deposited at the tip of a rigid, 3 mm diameter coherent fibre-optic bundle. In this way, the distal end of coherent fibre bundle acts as a 2D array of wideband ultrasound detectors. In another configuration, an optical relay is used between the distal end face of flexible fibre bundle and the Fabry-Pérot sensor to enlarge the lateral field of view to 6 mm x 6 mm. In both configurations, the pulsed excitation laser beam is full-field coupled into the fibre bundle at the proximal end for uniform backward-mode illumination of the tissue at the probe tip. In order to record the photoacoustic waves arriving at the probe tip, the proximal end of the fibre bundle is optically scanned in 2D with a CW wavelength-tunable interrogation laser beam thereby interrogating different spatial points on the sensor. A time-reversal image reconstruction algorithm was used to reconstruct a 3D image from the detected signals. The 3D field of view of the flexible PAE probe is 6 mm x 6 mm x 6 mm and the axial and lateral spatial resolution is 30 µm and 90 µm, respectively. 3D imaging capability is demonstrated using tissue phantoms, ex vivo tissues and in vivo. To the best of our knowledge, this is the first forward-viewing implementation of a photoacoustic

  6. Laser photoacoustic detection of the essential oil vapors of thyme, mint, and anise

    Science.gov (United States)

    El-Kahlout, A. M.; Al-Jourani, M. M.; Abu-Taha, M. I.; Laine, Derek C.

    1998-07-01

    Photoacoustic studies of the vapors of the essential oils of thyme, mint and anise have been made using a line-tunable waveguide CO2 laser in conjunction with a heat-pipe type of photoacoustic vapor sample cell operated over the temperature range 20 - 180 degree(s)C. Identifying spectral fingerprint features are found in the 9 - 10 micrometers spectral region for each of the three essential oils investigated. The principal features of the photoacoustic spectrum of each essential oil are associated with the dominant chemicals present i.e. thymol in thyme oil, menthol in mint and anethole in anise.

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

    Directory of Open Access Journals (Sweden)

    Firas K.M. Al-asfoor

    2008-01-01

    Full Text Available Thermal effusivity of virgin coconut oil-methanol mixtures were measured using open photoacoustic cell technique. The samples were prepared by simply mixing virgin coconut oil and methanol using similar procedure applied for preparation of biodisel. Thermal effusivity of the sample was obtained by fitting the experimental data of photoacoustic amplitude signal to the expression of photoacoustic signal as a function of chopping frequency. Thermal effusivity of mixtures decrease between 0.0851 W s1/2 K-1 cm-2 (pure virgin coconut oil and 0.0644 W s1/2 K-1 cm-2 (pure methanol with the increasing of methanol in the mixture.

  8. Application of laser-induced photoacoustic spectroscopy for determination of plutonium concentration in nuclear waste solutions.

    Science.gov (United States)

    Surugaya, Naoki; Sato, Soichi; Jitsukata, Syu; Watahiki, Masaru

    2008-04-01

    Laser-induced photoacoustic spectroscopy was used in a quantitative analysis of Pu in HNO3 medium. Plutonium was quantitatively oxidized to Pu(VI) using Ce(IV). The photoacoustic measurement of Pu(VI) with maximum absorption at 830.5 nm was subsequently performed to determine the concentration. The photoacoustic signal was linearly proportional to the Pu(VI) ion concentration. The detection limit of Pu(VI) was estimated to be 0.5 microg mL(-1) (3sigma) in 3 M HNO3. By the proposed method, Pu concentration was successfully determined in a nuclear waste solution for use in nuclear materials management.

  9. Quartz enhanced photoacoustic leak sensor for mechatronic components

    Science.gov (United States)

    Sampaolo, A.; Patimisco, P.; Giglio, M.; Calabrese, P. P.; Chieco, L.; Scamarcio, G.; Tittel, F. K.; Spagnolo, V.

    2016-02-01

    We report the first demonstration of a leak sensor based on a mid-IR quartz-enhanced photoacoustic (QEPAS) spectroscopic technique. A QEPAS sensor was integrated in a vacuum seal test station for mechatronic components. The laser source is a quantum cascade laser emitting at 10.56 μm, resonant with a strong absorption band of sulfur hexafluoride (SF6), which was selected as target gas for leak detection. The minimum detectable concentration of the QEPAS sensor is 6.9 ppb with an integration time of 1 s. This detection sensitivity allowed to measure SF6 leak flows as low as 3x10-5 standard cm3.

  10. Photoacoustic monitoring and imaging of blood vessels in tissue

    Science.gov (United States)

    Kolkman, Roy G. M.; Pilatou, Magdalena C.; Steenbergen, Wiendelt; de Mul, Frits F. M.

    2002-06-01

    Using very sensitive photoacoustical detectors we localized and monitored the blood content in tissue. In these detectors a PVdF-layer has been used as piezo-electric material and also fibers for the illumination of the sample are integrated. The resolution is about 20micrometers in depth and about 50-100micrometers laterally. The wavelengths of the laser light were 532 and 1064 nm. With these colors we can measure at different depths in tissue. The measurements concerned blood perfusion in real tissue: vessels in chicken breast, in test animals at various positions and in the human arm.

  11. Photoacoustic cavitation for theranostics: mechanism, current progress and applications

    Science.gov (United States)

    Feng, Y.; Qin, D.; Wan, M.

    2015-12-01

    As an emerging cavitation technology, photoacoustic cavitation (PAC) means the formation of bubbles in liquids using focused laser and pre-established ultrasound synchronously. Its significant advantages include the decreased threshold of each modality and the precise location of cavitation determined by the focused laser. In this paper, a brief review of PAC is presented, including the physical mechanism description, the classic experimental technology, the representative results in variety of media, and its applications in biomedical imaging and therapy. Moreover, some preliminary results of PAC in perfluoropentane (PFP) liquid and PFP droplets investigated by passive cavitation detection (PCD) in our group are also presented.

  12. Quartz-Enhanced Photoacoustic Spectroscopy with Right-Angle Prism

    OpenAIRE

    Yongning Liu; Jun Chang; Jie Lian; Zhaojun Liu; Qiang Wang; Zengguang Qin

    2016-01-01

    A right-angle prism was used to enhance the acoustic signal of a quartz-enhanced photoacoustic spectroscopy (QEPAS) system. The incident laser beam was parallelly inverted by the right-angle prism and passed through the gap between two tuning fork prongs again to produce another acoustic excitation. Correspondingly, two pairs of rigid metal tubes were used as acoustic resonators with resonance enhancement factors of 16 and 12, respectively. The QEPAS signal was enhanced by a factor of 22.4 co...

  13. Photoacoustic spectroscopy for fast and sensitive ammonia detection

    Institute of Scientific and Technical Information of China (English)

    Wang Zhang; Zhiying Wu; Qingxu Yu

    2007-01-01

    A photoacoustic (PA) spectrometer with H-type first longitudinal resonant cells for ammonia detection is developed. A new PA cell structure is designed to accelerate the drift velocity of the sample gas near the cell surface, so that the short response time at the flow rate of 100 sccm (standard cubic centimeter per minute) is achieved. The response time of 5 min and detection limit of 0.86 ppbv is reached for ammonia concentration measurement with a Teflon polytetrafluoroethylene (PTFE) cell. Further improvement could be expected when using a brass cell with a high quality Teflon fluorinated ethylene propylene (FEP) coating.

  14. Photoacoustic and transmission studies of SiC polytypes

    Directory of Open Access Journals (Sweden)

    A.C. de Oliveira

    2003-01-01

    Full Text Available The optical bandgap energies (OBGE of 3C, 15R, 6H and 4H-SiC have been investigate experimentally by transmission and photoacoustic spectroscopies. The measurements were performed on 470 mum thick wafers. The OBGE obtained from both spectroscopies for different polytypes show very good agreement. In order to have a better understanding of these materials calculations of eletronic band structure were performed by the full-potential linearized augmented plane wave (FPLAPW method. For the OBGE the results are compared to the measurements agreeing closely over the energies of those polytypes.

  15. Tomographic diagnosis of defects in hydraulic concrete structure

    Institute of Scientific and Technical Information of China (English)

    Mingjie ZHAO; Xibin XU

    2008-01-01

    The ultrasonic tomographic technology is applied to diagnose the defects in hydraulic concrete structure. In order to improve the precision of diagnoses, the wavelet transformation is used in the processing of ultrasonic signals. The influences of water, scale and ori-entation of defect, processing methods and theoretical model on image resolution are investigated. The experi-mental results indicate that the result of the tomographic diagnosis of a single defect is sensitive and the boundary can be clearly determined. However, the image resolution of multiple defects is not satisfactory. The water content and scale of a defect may significantly affect the imaging resolution. Defects with the orientation perpendicular to the direction of the diagnosis may have higher precision in diagnosing. The wavelet transformation technology can elevate the imaging resolution. The applied calculation model plays a very important role in improving the accu-racy of detection.

  16. Progress Update on Iterative Reconstruction of Neutron Tomographic Images

    Energy Technology Data Exchange (ETDEWEB)

    Hausladen, Paul [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gregor, Jens [Univ. of Tennessee, Knoxville, TN (United States)

    2016-09-15

    This report satisfies the fiscal year 2016 technical deliverable to report on progress in development of fast iterative reconstruction algorithms for project OR16-3DTomography-PD2Jb, "3D Tomography and Image Processing Using Fast Neutrons." This project has two overall goals. The first of these goals is to extend associated-particle fast neutron transmission and, particularly, induced-reaction tomographic imaging algorithms to three dimensions. The second of these goals is to automatically segment the resultant tomographic images into constituent parts, and then extract information about the parts, such as the class of shape and potentially shape parameters. This report addresses of the component of the project concerned with three-dimensional (3D) image reconstruction.

  17. Terahertz Imaging for Biomedical Applications Pattern Recognition and Tomographic Reconstruction

    CERN Document Server

    Yin, Xiaoxia; Abbott, Derek

    2012-01-01

    Terahertz Imaging for Biomedical Applications: Pattern Recognition and Tomographic Reconstruction presents the necessary algorithms needed to assist screening, diagnosis, and treatment, and these algorithms will play a critical role in the accurate detection of abnormalities present in biomedical imaging. Terahertz biomedical imaging has become an area of interest due to its ability to simultaneously acquire both image and spectral information. Terahertz imaging systems are being commercialized with an increasing number of trials performed in a biomedical setting. Terahertz tomographic imaging and detection technology contributes to the ability to identify opaque objects with clear boundaries,and would be useful to both in vivo and ex vivo environments. This book also: Introduces terahertz radiation techniques and provides a number of topical examples of signal and image processing, as well as machine learning Presents the most recent developments in an emerging field, terahertz radiation Utilizes new methods...

  18. Analysis of the Spectral Resolving Power in Tomographic Imaging Spectrometry

    Institute of Scientific and Technical Information of China (English)

    方俊永; 赵达尊; 蒋月娟

    2004-01-01

    From the point of view of design requirements, influence of the width of the output image of an imaging subsystem in a tomographic imaging spectrometer, namely width of the slit, the grating and the size of the CCD pixel are analyzed. For the tomographic imaging spectrometry, if the amplification ratio of the imaging subsystem is not high enough to make the whole object to be compressed within the slit, then either the slit width should be increased or the slit width kept unchanged but scanned to receive information of the object. While the width-increase method reduces the spectral resolving power and the SNR; the scanning method reduces the SNR. Analysis of the two cases and computer simulation results are given.

  19. Computer Aided Interpretation Approach for Optical Tomographic Images

    CERN Document Server

    Klose, Christian D; Netz, Uwe; Beuthan, Juergen; Hielscher, Andreas H

    2010-01-01

    A computer-aided interpretation approach is proposed to detect rheumatic arthritis (RA) of human finger joints in optical tomographic images. The image interpretation method employs a multi-variate signal detection analysis aided by a machine learning classification algorithm, called Self-Organizing Mapping (SOM). Unlike in previous studies, this allows for combining multiple physical image parameters, such as minimum and maximum values of the absorption coefficient for identifying affected and not affected joints. Classification performances obtained by the proposed method were evaluated in terms of sensitivity, specificity, Youden index, and mutual information. Different methods (i.e., clinical diagnostics, ultrasound imaging, magnet resonance imaging and inspection of optical tomographic images), were used as "ground truth"-benchmarks to determine the performance of image interpretations. Using data from 100 finger joints, findings suggest that some parameter combinations lead to higher sensitivities while...

  20. Dynamic computed tomographic scans in experimental brain abscess

    International Nuclear Information System (INIS)

    Dynamic computed tomographic scans were performed in an experimental brain abscess model to establish criteria that could be utilized in abscess staging. The vascular phase of the time-density curves did not differentiate cerebritis and capsule stages. The amount of residual enhancement after the first pass of an intra-arterial contrast bolus differed between major abscess stages, the greater residual enhancement being noted in the capsule stage. (orig.)

  1. Dynamic computed tomographic scans in experimental brain abscess

    Energy Technology Data Exchange (ETDEWEB)

    Enzmann, D.R.; Britt, R.H.; Placone, R.C.

    1984-07-01

    Dynamic computed tomographic scans were performed in an experimental brain abscess model to establish criteria that could be utilized in abscess staging. The vascular phase of the time-density curves did not differentiate cerebritis and capsule stages. The amount of residual enhancement after the first pass of an intra-arterial contrast bolus differed between major abscess stages, the greater residual enhancement being noted in the capsule stage.

  2. Tomographic analysis of reflectometry data II: the phase derivative

    CERN Document Server

    Briolle, F; Mendes, R Vilela

    2008-01-01

    A tomographic technique has been used in the past to decompose complex signals in its components. The technique is based on spectral decomposition and projection on the eigenvectors of a family of unitary operators. Here this technique is also shown to be appropriate to obtain the instantaneous phase derivative of the signal components. The method is illustrated on simulated data and on data obtained from plasma reflectometry experiments in the Tore Supra.

  3. Optimization of tomographic reconstruction workflows on geographically distributed resources.

    Science.gov (United States)

    Bicer, Tekin; Gürsoy, Dogˇa; Kettimuthu, Rajkumar; De Carlo, Francesco; Foster, Ian T

    2016-07-01

    New technological advancements in synchrotron light sources enable data acquisitions at unprecedented levels. This emergent trend affects not only the size of the generated data but also the need for larger computational resources. Although beamline scientists and users have access to local computational resources, these are typically limited and can result in extended execution times. Applications that are based on iterative processing as in tomographic reconstruction methods require high-performance compute clusters for timely analysis of data. Here, time-sensitive analysis and processing of Advanced Photon Source data on geographically distributed resources are focused on. Two main challenges are considered: (i) modeling of the performance of tomographic reconstruction workflows and (ii) transparent execution of these workflows on distributed resources. For the former, three main stages are considered: (i) data transfer between storage and computational resources, (i) wait/queue time of reconstruction jobs at compute resources, and (iii) computation of reconstruction tasks. These performance models allow evaluation and estimation of the execution time of any given iterative tomographic reconstruction workflow that runs on geographically distributed resources. For the latter challenge, a workflow management system is built, which can automate the execution of workflows and minimize the user interaction with the underlying infrastructure. The system utilizes Globus to perform secure and efficient data transfer operations. The proposed models and the workflow management system are evaluated by using three high-performance computing and two storage resources, all of which are geographically distributed. Workflows were created with different computational requirements using two compute-intensive tomographic reconstruction algorithms. Experimental evaluation shows that the proposed models and system can be used for selecting the optimum resources, which in turn can

  4. Optimization of tomographic reconstruction workflows on geographically distributed resources.

    Science.gov (United States)

    Bicer, Tekin; Gürsoy, Dogˇa; Kettimuthu, Rajkumar; De Carlo, Francesco; Foster, Ian T

    2016-07-01

    New technological advancements in synchrotron light sources enable data acquisitions at unprecedented levels. This emergent trend affects not only the size of the generated data but also the need for larger computational resources. Although beamline scientists and users have access to local computational resources, these are typically limited and can result in extended execution times. Applications that are based on iterative processing as in tomographic reconstruction methods require high-performance compute clusters for timely analysis of data. Here, time-sensitive analysis and processing of Advanced Photon Source data on geographically distributed resources are focused on. Two main challenges are considered: (i) modeling of the performance of tomographic reconstruction workflows and (ii) transparent execution of these workflows on distributed resources. For the former, three main stages are considered: (i) data transfer between storage and computational resources, (i) wait/queue time of reconstruction jobs at compute resources, and (iii) computation of reconstruction tasks. These performance models allow evaluation and estimation of the execution time of any given iterative tomographic reconstruction workflow that runs on geographically distributed resources. For the latter challenge, a workflow management system is built, which can automate the execution of workflows and minimize the user interaction with the underlying infrastructure. The system utilizes Globus to perform secure and efficient data transfer operations. The proposed models and the workflow management system are evaluated by using three high-performance computing and two storage resources, all of which are geographically distributed. Workflows were created with different computational requirements using two compute-intensive tomographic reconstruction algorithms. Experimental evaluation shows that the proposed models and system can be used for selecting the optimum resources, which in turn can

  5. Development of an advanced 3D cone beam tomographic system

    Science.gov (United States)

    Sire, Pascal; Rizo, Philippe; Martin, M.; Grangeat, Pierre; Morisseau, P.

    Due to its high spatial resolution, the 3D X-ray cone-beam tomograph (CT) maximizes understanding of test object microstructure. In order for the present X-ray CT NDT system to control ceramics and ceramic-matrix composites, its spatial resolution must exceed 50 microns. Attention is given to two experimental data reconstructions that have been conducted to illustrate system capabilities.

  6. An introduction to the tomographic picture of quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Ibort, A [Departamento de Matematicas, Universidad Carlos III de Madrid, Avda de la Universidad 30, 28911 Leganes, Madrid (Spain); Man' ko, V I [P N Lebedev Physical Institute, Leninskii Prospect 53, Moscow 119991 (Russian Federation); Marmo, G; Simoni, A; Ventriglia, F [Dipartimento di Scienze Fisiche dell' Universita ' Federico II' e Sezione INFN di Napoli, Complesso Universitario di Monte S Angelo, via Cintia, 80126 Naples (Italy)], E-mail: albertoi@math.uc3m.es, E-mail: manko@na.infn.it, E-mail: marmo@na.infn.it, E-mail: simoni@na.infn.it, E-mail: ventriglia@na.infn.it

    2009-06-15

    Starting from the famous Pauli problem on the possibility of associating quantum states with probabilities, the formulation of quantum mechanics in which quantum states are described by fair probability distributions (tomograms, i.e. tomographic probabilities) is reviewed in a pedagogical style. The relation between the quantum state description and the classical state description is elucidated. The difference between those sets of tomograms is described by inequalities equivalent to a complete set of uncertainty relations for the quantum domain and to non-negativity of probability density on phase space in the classical domain. The intersection of such sets is studied. The mathematical mechanism that allows us to construct different kinds of tomographic probabilities like symplectic tomograms, spin tomograms, photon number tomograms, etc is clarified and a connection with abstract Hilbert space properties is established. The superposition rule and uncertainty relations in terms of probabilities as well as quantum basic equations like quantum evolution and energy spectra equations are given in an explicit form. A method to check experimentally the uncertainty relations is suggested using optical tomograms. Entanglement phenomena and the connection with semigroups acting on simplexes are studied in detail for spin states in the case of two-qubits. The star-product formalism is associated with the tomographic probability formulation of quantum mechanics.

  7. An introduction to the tomographic picture of quantum mechanics

    International Nuclear Information System (INIS)

    Starting from the famous Pauli problem on the possibility of associating quantum states with probabilities, the formulation of quantum mechanics in which quantum states are described by fair probability distributions (tomograms, i.e. tomographic probabilities) is reviewed in a pedagogical style. The relation between the quantum state description and the classical state description is elucidated. The difference between those sets of tomograms is described by inequalities equivalent to a complete set of uncertainty relations for the quantum domain and to non-negativity of probability density on phase space in the classical domain. The intersection of such sets is studied. The mathematical mechanism that allows us to construct different kinds of tomographic probabilities like symplectic tomograms, spin tomograms, photon number tomograms, etc is clarified and a connection with abstract Hilbert space properties is established. The superposition rule and uncertainty relations in terms of probabilities as well as quantum basic equations like quantum evolution and energy spectra equations are given in an explicit form. A method to check experimentally the uncertainty relations is suggested using optical tomograms. Entanglement phenomena and the connection with semigroups acting on simplexes are studied in detail for spin states in the case of two-qubits. The star-product formalism is associated with the tomographic probability formulation of quantum mechanics.

  8. Information fusion in regularized inversion of tomographic pumping tests

    Science.gov (United States)

    Bohling, G.C.; ,

    2008-01-01

    In this chapter we investigate a simple approach to incorporating geophysical information into the analysis of tomographic pumping tests for characterization of the hydraulic conductivity (K) field in an aquifer. A number of authors have suggested a tomographic approach to the analysis of hydraulic tests in aquifers - essentially simultaneous analysis of multiple tests or stresses on the flow system - in order to improve the resolution of the estimated parameter fields. However, even with a large amount of hydraulic data in hand, the inverse problem is still plagued by non-uniqueness and ill-conditioning and the parameter space for the inversion needs to be constrained in some sensible fashion in order to obtain plausible estimates of aquifer properties. For seismic and radar tomography problems, the parameter space is often constrained through the application of regularization terms that impose penalties on deviations of the estimated parameters from a prior or background model, with the tradeoff between data fit and model norm explored through systematic analysis of results for different levels of weighting on the regularization terms. In this study we apply systematic regularized inversion to analysis of tomographic pumping tests in an alluvial aquifer, taking advantage of the steady-shape flow regime exhibited in these tests to expedite the inversion process. In addition, we explore the possibility of incorporating geophysical information into the inversion through a regularization term relating the estimated K distribution to ground penetrating radar velocity and attenuation distributions through a smoothing spline model. ?? 2008 Springer-Verlag Berlin Heidelberg.

  9. Tomographic Particle Image Velocimetry Using Colored Shadow Imaging

    KAUST Repository

    Alarfaj, Meshal K.

    2016-02-01

    Tomographic Particle Image Velocimetry Using Colored Shadow Imaging by Meshal K Alarfaj, Master of Science King Abdullah University of Science & Technology, 2015 Tomographic Particle image velocimetry (PIV) is a recent PIV method capable of reconstructing the full 3D velocity field of complex flows, within a 3-D volume. For nearly the last decade, it has become the most powerful tool for study of turbulent velocity fields and promises great advancements in the study of fluid mechanics. Among the early published studies, a good number of researches have suggested enhancements and optimizations of different aspects of this technique to improve the effectiveness. One major aspect, which is the core of the present work, is related to reducing the cost of the Tomographic PIV setup. In this thesis, we attempt to reduce this cost by using an experimental setup exploiting 4 commercial digital still cameras in combination with low-cost Light emitting diodes (LEDs). We use two different colors to distinguish the two light pulses. By using colored shadows with red and green LEDs, we can identify the particle locations within the measurement volume, at the two different times, thereby allowing calculation of the velocities. The present work tests this technique on the flows patterns of a jet ejected from a tube in a water tank. Results from the images processing are presented and challenges discussed.

  10. Tomographic findings of lobar consolidation in primary pulmonary tuberculosis

    International Nuclear Information System (INIS)

    Objective: To describe tomographic findings of lobar consolidation as early manifestation of primary pulmonary tuberculosis. Materials and methods: The present study was developed at Hospital Municipal Jesus, Rio de Janeiro, RJ, Brazil, in the period between 2002 and 2006, retrospectively evaluating tomographic findings in four children aged from 3 to 14 months with lobar consolidation as an early manifestation of primary pulmonary tuberculosis. Results: The most frequently found radiological pattern was lobar consolidation with calcifications, cavitation and intermingle necrotic areas, associated with bulging fissure. Signs of bronchogenic dissemination and lymph node enlargement were observed in all of the four children. Consolidation with a pseudotumor aspect and masslike effect was observed in one case. Conclusion: The cases included in the present study have demonstrated that primary pulmonary tuberculosis manifested as lobar consolidation presents typical tomographic images such as cavitation, hypodense areas and calcifications intermingled with consolidation. The association with lymph node enlargement with central necrosis and signs of bronchogenic dissemination reinforce the diagnosis of tuberculosis. (author)

  11. Voids in Ly{\\alpha} Forest Tomographic Maps

    CERN Document Server

    Stark, Casey W; White, Martin; Lee, Khee-Gan

    2015-01-01

    We present a new method of finding cosmic voids using tomographic maps of Ly{\\alpha} forest flux. We identify cosmological voids with radii of 2 - 12 $h^{-1}$Mpc in a large N-body simulation at $z = 2.5$, and characterize the signal of the high-redshift voids in density and Ly{\\alpha} forest flux. The void properties are similar to what has been found at lower redshifts, but they are smaller and have steeper radial density profiles. Similarly to what has been found for low-redshift voids, the radial velocity profiles have little scatter and agree very well with the linear theory prediction. We run the same void finder on an ideal Ly{\\alpha} flux field and tomographic reconstructions at various spatial samplings. We compare the tomographic map void catalogs to the density void catalog and find good agreement even with modest-sized voids ($r > 6 \\, h^{-1}$Mpc). Using our simple void-finding method, the configuration of the ongoing CLAMATO survey covering 1 deg$^2$ would provide a sample of about 100 high-redshi...

  12. STATISTICAL ANALYSIS OF TOMOGRAPHIC RECONSTRUCTION ALGORITHMS BY MORPHOLOGICAL IMAGE CHARACTERISTICS

    Directory of Open Access Journals (Sweden)

    Sebastian Lǖck

    2011-05-01

    Full Text Available We suggest a procedure for quantitative quality control of tomographic reconstruction algorithms. Our task-oriented evaluation focuses on the correct reproduction of phase boundary length and has thus a clear implication for morphological image analysis of tomographic data. Indirectly the method monitors accurate reproduction of a variety of locally defined critical image features within tomograms such as interface positions and microstructures, debonding, cracks and pores. Tomographic errors of such local nature are neglected if only global integral characteristics such as mean squared deviation are considered for the evaluation of an algorithm. The significance of differences in reconstruction quality between algorithms is assessed using a sample of independent random scenes to be reconstructed. These are generated by a Boolean model and thus exhibit a substantial stochastic variability with respect to image morphology. It is demonstrated that phase boundaries in standard reconstructions by filtered backprojection exhibit substantial errors. In the setting of our simulations, these could be significantly reduced by the use of the innovative reconstruction algorithm DIRECTT.

  13. Multimodality tomographic scintimammography with PET, PECI, and SPECT: initial evaluation

    Science.gov (United States)

    Krol, Andrzej; Feiglin, David H.; Thomas, Frank D.; Hellwig, Bradford J.; Gagne, George M.

    2002-04-01

    We compared tomographic scintimammography performed using single photon emission computed tomography (SPECT), positron emission coincidence imaging (PECI) and positron emission tomography (PET). A female thorax phantom was used. Activities of the myocardium, thorax and breasts were adjusted to emulate the count rate observed with patients. Hollow plastic spheres, imitating hot lesions (1.5-20ml), filled with radioactive saline were inserted in the center of each breast. Specific activities of internal organs were adjusted to emulate the count rate observed with patients. SPECT data were acquired with Tc-99m using gamma cameras with NaI(Tl) detectors. A modified FBP (CODE) reconstruction algorithm was used to render SPECT tomographic images. PECI (Siemens E.CAM with NaI(Tl)) and PET (GE Advance with BGO) data were acquired using F-18 FDG. Vendor supplied reconstruction algorithms were used. The reconstructed hot lesions contrast and resolution were investigated. Image quality obtained can be ranked as follows: (1) PET(BGO), (2) PECI(NaI), (3) SPECT(NaI) In conclusion, assuming comparable uptake values of Tc-99m-sestamibi and F-18 FDG, PET seems to be a superior methodology in visualization of breast lesion as compared to SPECT and PECI. All these tomographic methods appear to be promising adjunct to x-ray mammography in difficult to interpret cases.

  14. Application of tomographic imaging to photodiode arrays in large helical device

    Science.gov (United States)

    Liu, Y.; Tamura, N.; Peterson, B. J.; Iwama, N.; LHD Experimental Group

    2006-10-01

    Two 20-channel absolute x-ray ultraviolet photodiode (AXUVD) cameras are being used on the large helical device for measuring the two-dimensional radiation distribution. The local radiation emissivity is obtained by inverting the measured brightnesses with linear (Tikhonov-Phillips) or nonlinear (maximum entropy) regularization methods. The most important features of these improved methods are the capability of reconstructing radiation distributions without any symmetry assumptions, built-in smoothing, and useful reconstructions with relatively few detector channels. Together with improvements in the analysis method, the current AXUVD system makes it possible to obtain radiation emissivity images of various localized radiative phenomena, such as radiation collapse or transport of impurities injected into the plasma.

  15. High speed intravascular photoacoustic imaging of atherosclerotic arteries (Conference Presentation)

    Science.gov (United States)

    Piao, Zhonglie; Ma, Teng; Qu, Yueqiao; Li, Jiawen; Yu, Mingyue; He, Youmin; Shung, K. Kirk; Zhou, Qifa; Kim, Chang-Seok; Chen, Zhongping

    2016-02-01

    Cardiovascular disease is the leading cause of death in the industrialized nations. Accurate quantification of both the morphology and composition of lipid-rich vulnerable atherosclerotic plaque are essential for early detection and optimal treatment in clinics. In previous works, intravascular photoacoustic (IVPA) imaging for detection of lipid-rich plaque within coronary artery walls has been demonstrated in ex vivo, but the imaging speed is still limited. In order to increase the imaging speed, a high repetition rate laser is needed. In this work, we present a high speed integrated IVPA/US imaging system with a 500 Hz optical parametric oscillator laser at 1725 nm. A miniature catheter with 1.0 mm outer diameter was designed with a 200 μm multimode fiber and an ultrasound transducer with 45 MHz center frequency. The fiber was polished at 38 degree and enclosed in a glass capillary for total internal reflection. An optical/electrical rotary junction and pull-back mechanism was applied for rotating and linearly scanning the catheter to obtain three-dimensional imaging. Atherosclerotic rabbit abdominal aorta was imaged as two frame/second at 1725 nm. Furthermore, by wide tuning range of the laser wavelength from 1680 nm to 1770 nm, spectroscopic photoacoustic analysis of lipid-mimicking phantom and an human atherosclerotic artery was performed ex vivo. The results demonstrated that the developed IVPA/US imaging system is capable for high speed intravascular imaging for plaque detection.

  16. Photoacoustic tomography in absorbing acoustic media using time reversal

    International Nuclear Information System (INIS)

    The reconstruction of photoacoustic images typically neglects the effect of acoustic absorption on the measured time domain signals. Here, a method to compensate for acoustic absorption in photoacoustic tomography is described. The approach is based on time-reversal image reconstruction and an absorbing equation of state which separately accounts for acoustic absorption and dispersion following a frequency power law. Absorption compensation in the inverse problem is achieved by reversing the absorption proportionality coefficient in sign but leaving the equivalent dispersion parameter unchanged. The reconstruction is regularized by filtering the absorption and dispersion terms in the spatial frequency domain using a Tukey window. This maintains the correct frequency dependence of these parameters within the filter pass band. The method is valid in one, two and three dimensions, and for arbitrary power law absorption parameters. The approach is verified through several numerical experiments. The reconstruction of a carbon fibre phantom and the vasculature in the abdomen of a mouse are also presented. When absorption compensation is included, a general improvement in the image magnitude and resolution is seen, particularly for deeper features

  17. Interventional multi-spectral photoacoustic imaging in laparoscopic surgery

    Science.gov (United States)

    Hill, Emma R.; Xia, Wenfeng; Nikitichev, Daniil I.; Gurusamy, Kurinchi; Beard, Paul C.; Hawkes, David J.; Davidson, Brian R.; Desjardins, Adrien E.

    2016-03-01

    Laparoscopic procedures can be an attractive treatment option for liver resection, with a shortened hospital stay and reduced morbidity compared to open surgery. One of the central challenges of this technique is visualisation of concealed structures within the liver, particularly the vasculature and tumourous tissue. As photoacoustic (PA) imaging can provide contrast for haemoglobin in real time, it may be well suited to guiding laparoscopic procedures in order to avoid inadvertent trauma to vascular structures. In this study, a clinical laparoscopic ultrasound probe was used to receive ultrasound for PA imaging and to obtain co-registered B-mode ultrasound (US) images. Pulsed excitation light was delivered to the tissue via a fibre bundle in dark-field mode. Monte Carlo simulations were performed to optimise the light delivery geometry for imaging targets at depths of 1 cm, 2 cm and 3 cm, and 3D-printed mounts were used to position the fibre bundle relative to the transducer according to the simulation results. The performance of the photoacoustic laparoscope system was evaluated with phantoms and tissue models. The clinical potential of hybrid PA/US imaging to improve the guidance of laparoscopic surgery is discussed.

  18. Fibre lasers for photo-acoustic gas spectroscopy

    Science.gov (United States)

    Arsad, Norhana; Stewart, George

    2011-05-01

    We report here on the use of fiber lasers for recovery of gas absorption line shapes by photo-acoustic spectroscopy. We demonstrate the principle of operation using an erbium-doped fiber, stabilized using a length of un-pumped doped fibre as a saturable absorber. Intensity modulation of the laser output for phase sensitive detection is performed by modulation of the pump current while the wavelength is scanned through the absorption line by a PZT on a fibre Bragg grating. This avoids the distortions that arise in recovered signals due to simultaneous wavelength and intensity modulation, as is the case with conventional DFB diode lasers. Furthermore, the near zero off-line signals with photo-acoustic spectroscopy means that high modulation indices can be used with simple intensity modulation of the fiber laser output. The modulation frequency is set to the acoustic resonance frequency of the gas cell and measurements are made on the P17 absorption line of acetylene at 1535.39nm showing good agreement with the theoretical line-shape profile.

  19. Deconvolution based photoacoustic reconstruction for directional transducer with sparsity regularization

    Science.gov (United States)

    Moradi, Hamid; Tang, Shuo; Salcudean, Septimiu E.

    2016-03-01

    We define a deconvolution based photoacoustic reconstruction with sparsity regularization (DPARS) algorithm for image restoration from projections. The proposed method is capable of visualizing tissue in the presence of constraints such as the specific directivity of sensors and limited-view Photoacoustic Tomography (PAT). The directivity effect means that our algorithm treats the optically-generated ultrasonic waves based on which direction they arrive at the transducer. Most PA image reconstruction methods assume that sensors have omni-directional response; however, in practice, the sensors show higher sensitivity to the ultrasonic waves coming from one specific direction. In DPARS, the sensitivity of the transducer to incoming waves from different directions are considered. Thus, the DPARS algorithm takes into account the relative location of the absorbers with respect to the transducers, and generates a linear system of equations to solve for the distribution of absorbers. The numerical conditioning and computing times are improved by the use of a sparse Discrete Fourier Transform (DCT) representation of the distribution of absorption coefficients. Our simulation results show that DPARS outperforms the conventional Delay-and-Sum reconstruction method in terms of CNR and RMS errors. Experimental results confirm that DPARS provides images with higher resolution than DAS.

  20. A Bayesian approach to spectral quantitative photoacoustic tomography

    International Nuclear Information System (INIS)

    A Bayesian approach to the optical reconstruction problem associated with spectral quantitative photoacoustic tomography is presented. The approach is derived for commonly used spectral tissue models of optical absorption and scattering: the absorption is described as a weighted sum of absorption spectra of known chromophores (spatially dependent chromophore concentrations), while the scattering is described using Mie scattering theory, with the proportionality constant and spectral power law parameter both spatially-dependent. It is validated using two-dimensional test problems composed of three biologically relevant chromophores: fat, oxygenated blood and deoxygenated blood. Using this approach it is possible to estimate the Grüneisen parameter, the absolute chromophore concentrations, and the Mie scattering parameters associated with spectral photoacoustic tomography problems. In addition, the direct estimation of the spectral parameters is compared to estimates obtained by fitting the spectral parameters to estimates of absorption, scattering and Grüneisen parameter at the investigated wavelengths. It is shown with numerical examples that the direct estimation results in better accuracy of the estimated parameters. (papers)

  1. Portable multiwavelength laser diode source for handheld photoacoustic devices

    Science.gov (United States)

    Canal, Celine; Laugustin, Arnaud; Kohl, Andreas; Rabot, Olivier

    2016-04-01

    The ageing population faces today an increase of chronic diseases such as rheumatism/arthritis, cancer and cardio vascular diseases for which appropriate treatments based on a diagnosis at an early-stage of the disease are required. Some imaging techniques are already available in order to get structural information. Within the non-invasive group, ultrasound images are common in these fields of medicine. However, there is a need for a point-of-care device for imaging smaller structures such as blood vessels that cannot be observed with purely ultrasound based devices. Photoacoustics proved to be an attractive candidate. This novel imaging technique combines pulsed laser light for excitation of tissues and an ultrasound transducer as a receptor. Introduction of this technique into the clinic requires to drastically shrink the size and cost of the expensive and bulky nanosecond lasers generally used for light emission. In that context, demonstration of ultra-short pulse emission with highly efficient laser diodes in the near-infrared range has been performed by Quantel, France. A multi-wavelength laser source as small as a hand emitted more than 1 mJ per wavelength with four different wavelengths available in pulses of about 90 ns. Such a laser source can be integrated into high sensitivity photoacoustic handheld systems due to their outstanding electrical-to-optical efficiency of about 25 %. Further work continues to decrease the pulse length as low as 40 ns while increasing the pulse energy to 2 mJ.

  2. Stable phantoms for characterization of photoacoustic tomography (PAT) systems

    Science.gov (United States)

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

    2013-02-01

    Photoacoustic tomography (PAT) is an emerging modality that combines the high contrast of optical imaging, with the spatial resolution and penetration depth of ultrasound, by exploiting the photoacoustic effect. As with any new imaging modality, reliable physical phantoms are needed to: calibrate instruments; validate performance; optimize signal-to-noise; perform routine quality control; and compare systems. Phantom materials for testing small animal PAT systems should also mimic both the optical and acoustic properties of soft tissue, while for calibration purposes should be resistant to degradation over long time periods. We show here that polyvinyl chloride plastisol (PVCP) phantoms enable calibration and performance validation using two PAT systems with distinct designs (Visualsonics Vevo LAZR and Endra Nexus 128) across a wavelength range of 680 nm - 950 nm. Inclusions between 2 and 3.2 mm in diameter were fabricated from PVCP using a range of dye concentrations (0 % to 0.256 % Black Plastic Color, BPC) in a custom mold. A calibration phantom was imaged repeatedly on both systems, over time scales of minutes, hours and days, to assess system stability. Both systems demonstrated good reproducibility over time, with the coefficient of variation in the measured signal-to-noise ratio (SNR) being less than 15% over the course of 30 days. Imaging performance was optimized by plotting SNR as a function of different system parameters. The visualization of objects embedded in optically absorbing and scattering backgrounds was also assessed. PVCP is easy to work with and provides stable phantoms for assessing PAT system performance.

  3. Compensation for air voids in photoacoustic computed tomography image reconstruction

    Science.gov (United States)

    Matthews, Thomas P.; Li, Lei; Wang, Lihong V.; Anastasio, Mark A.

    2016-03-01

    Most image reconstruction methods in photoacoustic computed tomography (PACT) assume that the acoustic properties of the object and the surrounding medium are homogeneous. This can lead to strong artifacts in the reconstructed images when there are significant variations in sound speed or density. Air voids represent a particular challenge due to the severity of the differences between the acoustic properties of air and water. In whole-body small animal imaging, the presence of air voids in the lungs, stomach, and gastrointestinal system can limit image quality over large regions of the object. Iterative reconstruction methods based on the photoacoustic wave equation can account for these acoustic variations, leading to improved resolution, improved contrast, and a reduction in the number of imaging artifacts. However, the strong acoustic heterogeneities can lead to instability or errors in the numerical wave solver. Here, the impact of air voids on PACT image reconstruction is investigated, and procedures for their compensation are proposed. The contributions of sound speed and density variations to the numerical stability of the wave solver are considered, and a novel approach for mitigating the impact of air voids while reducing the computational burden of image reconstruction is identified. These results are verified by application to an experimental phantom.

  4. In vivo visualization of prostate brachytherapy seeds with photoacoustic imaging

    Science.gov (United States)

    Lediju Bell, Muyinatu A.; Kuo, Nathanael P.; Song, Danny Y.; Kang, Jin U.; Boctor, Emad M.

    2014-12-01

    We conducted a canine study to investigate the in vivo feasibility of photoacoustic imaging for intraoperative updates to brachytherapy treatment plans. A fiber coupled to a 1064-nm Nd:YAG laser was inserted into high-dose-rate brachytherapy needles, which diffused light spherically. These needles were inserted through the perineum into the prostate for interstitial light delivery and the resulting acoustic waves were detected with a transrectal ultrasound probe. Postoperative computed tomography images and ex vivo photoacoustic images confirmed seed locations. Limitations with insufficient light delivery were mitigated with short-lag spatial coherence (SLSC) beamforming, providing a 10-20 dB contrast improvement over delay-and-sum (DAS) beamforming for pulse energies ranging from 6.8 to 10.5 mJ with a fiber-seed distance as large as 9.5 mm. For the same distance and the same range of energy densities, signal-to-noise ratios (SNRs) were similar while the contrast-to-noise ratio (CNR) was higher in SLSC compared to DAS images. Challenges included visualization of signals associated with the interstitial fiber tip and acoustic reverberations between seeds separated by ≤2 mm. Results provide insights into the potential for clinical translation to humans.

  5. Photoacoustic Characterization of Randomly Oriented Silver Nanowire Films

    Science.gov (United States)

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

    2015-06-01

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

  6. Super-resolution photoacoustic imaging through a scattering wall

    CERN Document Server

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

    2013-01-01

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

  7. Studies on selected polymeric materials using the photoacoustic spectroscopic technique

    Institute of Scientific and Technical Information of China (English)

    Hukum Singh

    2011-01-01

    Polymethylmethacrylate-graft-polybisphenol-A-carbonate (PMMA-G-PC) with 50% grafting is synthesized. The acid (0.18 M, 100 ml) in air at (45±12) ℃ 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.

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

    Science.gov (United States)

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

    2014-03-01

    Osteoporosis is a widespread disorder, which has a catastrophic impact on patients lives and overwhelming related to healthcare costs. Recently, we proposed a multispectral photoacoustic technique for early detection of osteoporosis. Such technique has great advantages over pure ultrasonic or optical methods as it allows the deduction of both bone functionality from the bone absorption spectrum and bone resistance to fracture from the characteristics of the ultrasound propagation. We demonstrated the propagation of multiple acoustic modes in animal bones in-vitro. To further investigate the effects of multiple wavelength excitations and of induced osteoporosis on the PA signal a multispectral photoacoustic system is presented. The experimental investigation is based on measuring the interference of multiple acoustic modes. The performance of the system is evaluated and a simple two mode theoretical model is fitted to the measured phase signals. The results show that such PA technique is accurate and repeatable. Then a multiple wavelength excitation is tested. It is shown that the PA response due to different excitation wavelengths revels that absorption by the different bone constitutes has a profound effect on the mode generation. The PA response is measured in single wavelength before and after induced osteoporosis. Results show that induced osteoporosis alters the measured amplitude and phase in a consistent manner which allows the detection of the onset of osteoporosis. These results suggest that a complete characterization of the bone over a region of both acoustic and optical frequencies might be used as a powerful tool for in-vivo bone evaluation.

  9. Predicting photodynamic therapy efficacy with photoacoustic imaging (Conference Presentation)

    Science.gov (United States)

    Mallidi, Srivalleesha; Mai, Zhiming; Khan, Amjad P.; Hasan, Tayyaba

    2016-03-01

    Photodynamic therapy (PDT) is a photochemistry based cytotoxic technique that imparts cellular damage via excitation of a photosensitizer with drug-specific wavelength of light. The dose at the treatment site for type II PDT is determined by three factors: photosensitizer (PS) concentration, oxygenation status and delivered light irradiance. Most of the FDA approved photosensitizers in their triplet-excited state generate cytotoxic species by reacting with the ground state oxygen that is available in the surrounding environment. Given the inter- and intra-subject variability in the uptake of the photosensitizer and the distribution of oxygen in the tumor, understanding the interplay between these dose parameters could aid in determining photodynamic therapy efficacy. Previously several studies have discussed the interplay between the dose parameters using shown point measurements and 2D imaging systems. Using various subcutaneous and orthotopic mouse models we will demonstrate the utility of a non-invasive non-ionizing photoacoustic imaging modality to determine efficacy and predict treatment response in Benzoporphyrin derivative (BPD) or Aminolevulinic acid (ALA) based PDT. We further compare the predictive capability of photoacoustic imaging with the more predominantly used fluorescence imaging and immunohistochemistry techniques.

  10. Dual plasmonic gold nanoparticles for multispectral photoacoustic imaging application

    Science.gov (United States)

    Raghavan, Vijay; Subhash, Hrebesh; Breathnach, Aedán.; Leahy, Martin; Dockery, Peter; Olivo, Malini

    2014-03-01

    Nanoparticle contrast agents for molecular targeted imaging have widespread interest in diagnostic applications with cellular resolution, specificity and selectivity for visualization and assessment of various disease processes. Of particular interest is gold nanoparticle owing to its tunability of the surface plasmon resonance (SPR) and its relative inertness. Here we present the synthesis of anisotropic multi-branched star shaped gold nanoparticles exhibiting dual-band plasmon absorption peaks and its application as a contrast agent for multispectral photoacoustic imaging. The transverse plasmon absorption peak of the synthesised dual plasmonic gold nanostar (DPGNS) was around 700 nm and that of longitudinal plasmon absorption in the longer wavelength region around 1050-1150 nm. Unlike most reported PA contrast agent with surface plasmon absorption in the range of 700 to 800 nm showing moderate tissue penetration, 1050-1200 nm range lies in the farther region of the optical window of biological tissue where scattering and the intrinsic optical extinction of endogenous chromophores is at its minimum. We also present a proof of principle demonstration of DPGNS as contrast agent for multispectral photoacoustic animal imaging. Our results show that DPGNS are promising for PA imaging with extended-depth imaging applications.

  11. Imaging of turbulent structures and tomographic reconstruction of TORPEX plasma emissivity

    International Nuclear Information System (INIS)

    In the TORPEX [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)], a simple magnetized plasma device, low frequency electrostatic fluctuations associated with interchange waves, are routinely measured by means of extensive sets of Langmuir probes. To complement the electrostatic probe measurements of plasma turbulence and study of plasma structures smaller than the spatial resolution of probes array, a nonperturbative direct imaging system has been developed on TORPEX, including a fast framing Photron-APX-RS camera and an image intensifier unit. From the line-integrated camera images, we compute the poloidal emissivity profile of the plasma by applying a tomographic reconstruction technique using a pixel method and solving an overdetermined set of equations by singular value decomposition. This allows comparing statistical, spectral, and spatial properties of visible light radiation with electrostatic fluctuations. The shape and position of the time-averaged reconstructed plasma emissivity are observed to be similar to those of the ion saturation current profile. In the core plasma, excluding the electron cyclotron and upper hybrid resonant layers, the mean value of the plasma emissivity is observed to vary with (Te)α(ne)β, in which α=0.25-0.7 and β=0.8-1.4, in agreement with collisional radiative model. The tomographic reconstruction is applied to the fast camera movie acquired with 50 kframes/s rate and 2 μs of exposure time to obtain the temporal evolutions of the emissivity fluctuations. Conditional average sampling is also applied to visualize and measure sizes of structures associated with the interchange mode. The ω-time and the two-dimensional k-space Fourier analysis of the reconstructed emissivity fluctuations show the same interchange mode that is detected in the ω and k spectra of the ion saturation current fluctuations measured by probes. Small scale turbulent plasma structures can be detected and tracked in the reconstructed emissivity movies

  12. Methodology of Pulsed Photoacoustics and Its Application to Probe Photosystems and Receptors

    Directory of Open Access Journals (Sweden)

    Harvey J.M. Hou

    2010-06-01

    Full Text Available We review recent advances in the methodology of pulsed time-resolved photoacoustics and its application to studies of photosynthetic reaction centers and membrane receptors such as the G protein-coupled receptor rhodopsin. The experimental parameters accessible to photoacoustics include molecular volume change and photoreaction enthalpy change. Light-driven volume change secondary to protein conformational changes or electrostriction is directly related to the photoreaction and thus can be a useful measurement of activity and function. The enthalpy changes of the photochemical reactions observed can be measured directly by photoacoustics. With the measurement of enthalpy change, the reaction entropy can also be calculated when free energy is known. Dissecting the free energy of a photoreaction into enthalpic and entropic components may provide critical information about photoactivation mechanisms of photosystems and photoreceptors. The potential limitations and future applications of time-resolved photoacoustics are also discussed.

  13. Quantum Cascade Laser-Based Photoacoustic Spectroscopy for Trace Vapor Detection and Molecular Discrimination

    Directory of Open Access Journals (Sweden)

    Almon Fisher

    2010-03-01

    Full Text Available We report on the development of a microelectromechanical systems (MEMS-scale photoacoustic sensor for the detection of trace gases. A mid-infrared quantum cascade laser (QCL was used to determine detection limits for acetic acid, acetone, 1,4-dioxane, and vinyl acetate. The source was continuously tunable from 1015 cm-1 to 1240 cm-1, allowing for the collection of photoacoustic vibrational spectra for these gases. Exceptional agreement between the measured photoacoustic spectra and the infrared spectra for acetic acid, acetone, 1,4-dioxane, and vinyl acetate was observed. Partial least-squares (PLS regression was used to develop an algorithm for classification of these compounds based solely on photoacoustic spectra.

  14. Nonlinear photoacoustic response of opaque media in gas microphone signal detection

    Science.gov (United States)

    Madvaliev, U.; Salikhov, T. Kh.; Sharifov, D. M.; Khan, N. A.

    2006-03-01

    We have theoretically studied the effect of thermal nonlinearity, due to the temperature dependence of the thermophysical and optical parameters for thermally thick opaque media, on the characteristics of the fundamental photoacoustic signal when the signal is detected by a gas microphone. We have shown that the dependence of the amplitude of the nonlinear component of the signal on the intensity of the incident radiation I0 is expressed by means of the dependence of the temperature rise for the irradiated sample surface Θ0 on I0, and the thermal nonlinearity does not affect the phase of the photoacoustic signal. We propose a theory for generation of the second harmonic of the photoacoustic signal. We have established that the phase shift of the photoacoustic signal is equal to 3π/4, while its amplitude depends on the frequency (˜ω-3/2) and the intensity (˜ I{0/2}).

  15. Photoacoustic imaging to detect rat brain activation after cocaine hydrochloride injection

    Science.gov (United States)

    Jo, Janggun; Yang, Xinmai

    2011-03-01

    Photoacoustic imaging (PAI) was employed to detect small animal brain activation after the administration of cocaine hydrochloride. Sprague Dawley rats were injected with different concentrations (2.5, 3.0, and 5.0 mg per kg body) of cocaine hydrochloride in saline solution through tail veins. The brain functional response to the injection was monitored by photoacoustic tomography (PAT) system with horizontal scanning of cerebral cortex of rat brain. Photoacoustic microscopy (PAM) was also used for coronal view images. The modified PAT system used multiple ultrasonic detectors to reduce the scanning time and maintain a good signal-to-noise ratio (SNR). The measured photoacoustic signal changes confirmed that cocaine hydrochloride injection excited high blood volume in brain. This result shows PAI can be used to monitor drug abuse-induced brain activation.

  16. Photo-acoustic imaging of coronary arteries with polymer optical fibers

    DEFF Research Database (Denmark)

    Woyessa, Getinet; Broadway, Christian; Lamela, Horacio;

    2014-01-01

    less blood to flow through the arteries hence the heart muscle can't get the blood or oxygen it needs. Worse, a plaque can suddenly rupture. As a result, blood clot over the rapture and suddenly cut off the hearts’ blood supply, causing permanent heart dama ge or stroke [1]. Photo-acoustic imaging...... is useful for detection of plaques for prevention of rupture of vulnerable plaques. These vulnerable plaques in the arteries can be distinguished using photo-acoustic imaging based on lipid accumulation with different characteristics of optical absorption. The basic principle of this imaging technique...... relies on exposing lipids to a laser capable of inducing photo-acoustic effect and a sensor affected by the induced pressure. Polymer optical fibre Bragg grating and Fabry-Perot sensors will be developed for detection of photo-acoustic signal in collaboration of Optoelectronics and Laser technology group...

  17. Spectral power density of the random excitation for the photoacoustic wave equation

    Directory of Open Access Journals (Sweden)

    Hakan Erkol

    2014-09-01

    Full Text Available The superposition of the Green's function and its time reversal can be extracted from the photoacoustic point sources applying the representation theorems of the convolution and correlation type. It is shown that photoacoustic pressure waves at locations of random point sources can be calculated with the solution of the photoacoustic wave equation and utilization of the continuity and the discontinuity conditions of the pressure waves in the frequency domain although the pressure waves cannot be measured at these locations directly. Therefore, with the calculated pressure waves at the positions of the sources, the spectral power density can be obtained for any system consisting of two random point sources. The methodology presented here can also be generalized to any finite number of point like sources. The physical application of this study includes the utilization of the cross-correlation of photoacoustic waves to extract functional information associated with the flow dynamics inside the tissue.

  18. Multifunctional polyelectrolyte microcapsules as a contrast agent for photoacoustic imaging in blood.

    Science.gov (United States)

    Yashchenok, Alexey M; Jose, Jithin; Trochet, Philippe; Sukhorukov, Gleb B; Gorin, Dmitry A

    2016-08-01

    The polyelectrolyte microcapsules that can be accurate either visualized in biological media or in tissue would enhance their further in vivo application both as a carrier of active payloads and as a specific sensor. The immobilization of active species, for instance fluorescent dyes, quantum dots, metal nanoparticles, in polymeric shell enables visualization of capsules by optical imaging techniques in aqueous solution. However, for visualization of capsules in complex media an instrument with high contrast modality requires. Herein, we show for the first time photoacoustic imaging (PAI) of multifunctional microcapsules in water and in blood. The microcapsules exhibit greater photoacoustic intensity compare to microparticles with the same composition of polymeric shell presumably their higher thermal expansion. Photoacoustic intensity form microcapsules dispersed in blood displays an enhancement (2-fold) of signal compare to blood. Photoacoustic imaging of microcapsules might contribute to non-invasive carrier visualization and further their in vivo distribution.

  19. Identification and measurement of intermolecular interaction in polyester/polystyrene blends by FTIR-photoacoustic spectrometry

    Science.gov (United States)

    Fourier transform infrared photoacoustic spectrometry was used to reveal and identify n-p type intermolecular interaction formed in plastic comprising binary blends of polystyrene and a biodegradable polymer, either polylactic acid, polycaprolactone or poly(tetramethyleneadipate-co-terephthalate)....

  20. Feasibility of noncontact piezoelectric detection of photoacoustic signals in tissue-mimicking phantoms

    Science.gov (United States)

    Kolkman, Roy G. M.; Blomme, Erik; Cool, Tijl; Bilcke, Mattias; van Leeuwen, Ton G.; Steenbergen, Wiendelt; Grimbergen, Kees A.; den Heeten, Gerard J.

    2010-09-01

    The feasibility of air-coupled ultrasound transducers to detect laser-induced ultrasound from artificial blood vessels embedded in an optically scattering phantom is demonstrated. These air-coupled transducers allow new applications in biomedical photoacoustic imaging where contact with tissue is not preferred. One promising application of such transducers is the addition of photoacoustic imaging to the regular x-ray mammographic screening procedure.

  1. Feasibility of noncontact piezoelectric detection of photoacoustic signals in tissue-mimicking phantoms

    OpenAIRE

    Kolkman, Roy G.M.; Blomme, Erik; Cool, Tijl; Bilcke, Mattias; Leeuwen, van, P.W.; Steenbergen, Wiendelt; Grimbergen, Kees A.; Heeten, den, G.J.

    2010-01-01

    The feasibility of air-coupled ultrasound transducers to detect laser-induced ultrasound from artificial blood vessels embedded in an optically scattering phantom is demonstrated. These air-coupled transducers allow new applications in biomedical photoacoustic imaging where contact with tissue is not preferred. One promising application of such transducers is the addition of photoacoustic imaging to the regular x-ray mammographic screening procedure. (C) 2010 Society of Photo-Optical Instrume...

  2. Exact solution for a photoacoustic wave from a finite-length cylindrical source.

    Science.gov (United States)

    Zalev, Jason; Kolios, Michael C

    2015-04-01

    In wide-field pulsed photoacoustics, a nearly instantaneous source of electromagnetic energy is applied uniformly to an absorbing medium to create an acoustic wave. In this work, an exact solution is derived for the photoacoustic wave originating from a finite-length solid cylindrical source in terms of known analytic functions involving elliptic integrals of canonical form. The solution is compared with the output of a finite-element simulation. PMID:25920820

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

    OpenAIRE

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

    2009-01-01

    Noninvasive, high resolution imaging of mouse brain activity is poised to provide clinically translatable insights into human neurological disease progression. Toward noninvasive imaging of brain activity through the hemodynamic response, the dark-field photoacoustic microscopy (PAM) technique was enhanced to image the cortex vasculature of the mouse brain in vivo using endogenous hemoglobin contrast. Specifically, the PAM system was redesigned to efficiently collect photoacoustic waves origi...

  4. Pulsed photoacoustic techniques and glucose determination in human blood and tissue

    OpenAIRE

    Zhao, Z.

    2002-01-01

    Abstract Determination of blood glucose level is a frequently occurring procedure in diabetes care. As the most common method involves collecting blood drops for chemical analysis, it is invasive and liable to afflict a degree of pain and cause a skin injury. To eliminate these disadvantages, this thesis focuses on pulsed photoacoustic techniques, which have potential ability in non-invasive blood glucose measurement. The fundamental theory of photoacoustics in liquid and soft tissue ...

  5. Patterned thin metal film for the lateral resolution measurement of photoacoustic tomography

    Directory of Open Access Journals (Sweden)

    Kim Do-Hyun

    2012-07-01

    Full Text Available Abstract Background Image quality assessment method of photoacoustic tomography has not been completely standardized yet. Due to the combined nature of photonic signal generation and ultrasonic signal transmission in biological tissue, neither optical nor ultrasonic traditional methods can be used without modification. An optical resolution measurement technique was investigated for its feasibility for resolution measurement of photoacoustic tomography. Methods A patterned thin metal film deposited on silica glass provides high contrast in optical imaging due to high reflectivity from the metal film and high transmission from the glass. It provides high contrast when it is used for photoacoustic tomography because thin metal film can absorb pulsed laser energy. An US Air Force 1951 resolution target was used to generate patterned photoacoustic signal to measure the lateral resolution. Transducer with 2.25 MHz bandwidth and a sample submerged in water and gelatinous block were tested for lateral resolution measurement. Results Photoacoustic signal generated from a thin metal film deposited on a glass can propagate along the surface or through the surrounding medium. First, a series of experiments with tilted sample confirmed that the measured photoacoustic signal is what is propagating through the medium. Lateral resolution of the photoacoustic tomography system was successfully measured for water and gelatinous block as media: 0.33 mm and 0.35 mm in water and gelatinous material, respectively, when 2.25 MHz transducer was used. Chicken embryo was tested for biomedical applications. Conclusions A patterned thin metal film sample was tested for its feasibility of measuring lateral resolution of a photoacoustic tomography system. Lateral resolutions in water and gelatinous material were successfully measured using the proposed method. Measured resolutions agreed well with theoretical values.

  6. Photoacoustic investigation of Cd1-xMnxTe mixed crystals

    Science.gov (United States)

    Zakrzewski, J.; Firszt, F.; ŁÈ©gowski, S.; MÈ©czyńska, H.; Marasek, A.; Pawlak, M.

    2003-01-01

    Ternary diluted magnetic semiconductors Cd1-xMnxTe obtained by Bridgman method in the range of composition 0⩽x⩽0.7 were investigated. The photoacoustic spectroscopy with a piezoelectric transducer was employed to evaluate the energy gaps of Cd1-xMnxTe bulk mixed crystals at room temperature. A linear increase of energy gap with increasing x value has been observed. Photoacoustic data were correlated with ellipsometric measurements.

  7. Photoacoustic study of Cd{1-x-y}BexMnyTe mixed crystals

    Science.gov (United States)

    Zakrzewski, J.; Firszt, F.; Legowski, S.; Męczyńska, H.; Marasek, A.; Pawlak, M.

    2003-06-01

    Quaternary diluted niagnetic semiconductors Cd{1-x-y}BexMnyTe obtained by Bridgman method for x=0.01 and 0leq yleq 0.15 were investigated. The photoacoustic spectroscopy with a piezoelectric transducer was employed to evaluate the energy gaps of Cd{1-x-y}BexMnyTe bulk mixed crystals at room temperature. The increase of the energy gap with increasing x value has been observed. Characteristic features of amplitude and phase photoacoustic spectra were discussed.

  8. Photoacoustic image patterns of breast carcinoma and comparisons with Magnetic Resonance Imaging and vascular stained histopathology

    Science.gov (United States)

    Heijblom, M.; Piras, D.; Brinkhuis, M.; van Hespen, J. C. G.; van den Engh, F. M.; van der Schaaf, M.; Klaase, J. M.; van Leeuwen, T. G.; Steenbergen, W.; Manohar, S.

    2015-07-01

    Photoacoustic (optoacoustic) imaging can visualize vasculature deep in tissue using the high contrast of hemoglobin to light, with the high-resolution possible with ultrasound detection. Since angiogenesis, one of the hallmarks of cancer, leads to increased vascularity, photoacoustics holds promise in imaging breast cancer as shown in proof-of-principle studies. Here for the first time, we investigate if there are specific photoacoustic appearances of breast malignancies which can be related to the tumor vascularity, using an upgraded research imaging system, the Twente Photoacoustic Mammoscope. In addition to comparisons with x-ray and ultrasound images, in subsets of cases the photoacoustic images were compared with MR images, and with vascular staining in histopathology. We were able to identify lesions in suspect breasts at the expected locations in 28 of 29 cases. We discovered generally three types of photoacoustic appearances reminiscent of contrast enhancement types reported in MR imaging of breast malignancies, and first insights were gained into the relationship with tumor vascularity.

  9. In vivo photoacoustic molecular imaging of breast carcinoma with folate receptor-targeted indocyanine green nanoprobes

    Science.gov (United States)

    Wang, Huina; Liu, Chengbo; Gong, Xiaojing; Hu, Dehong; Lin, Riqiang; Sheng, Zonghai; Zheng, Cuifang; Yan, Meng; Chen, Jingqin; Cai, Lintao; Song, Liang

    2014-11-01

    As an optical-acoustic hybrid imaging technology, photoacoustic imaging uniquely combines the advantages of rich optical contrast with high ultrasonic resolution in depth, opening up many new possibilities not attainable with conventional pure optical imaging technologies. To perform photoacoustic molecular imaging, optically absorbing exogenous contrast agents are needed to enhance the signals from specifically targeted disease activity. In this work, we designed and developed folate receptor targeted, indocyanine green dye doped poly(d,l-lactide-co-glycolide) lipid nanoparticles (FA-ICG-PLGA-lipid NPs) for molecular photoacoustic imaging of tumor. The fabricated FA-ICG-PLGA-lipid NPs exhibited good aqueous stability, a high folate-receptor targeting efficiency, and remarkable optical absorption in near-infrared wavelengths, providing excellent photoacoustic signals in vitro. Furthermore, after intravenous administration of FA-ICG-PLGA-lipid NPs, mice bearing MCF-7 breast carcinomas showed significantly enhanced photoacoustic signals in vivo in the tumor regions, compared with those using non-targeted ICG-PLGA-lipid NPs. Given the existing wide clinical use of ICG and PLGA, the developed FA-ICG-PLGA-lipid NPs, in conjunction with photoacoustic imaging technology, offer a great potential to be translated into the clinic for non-ionizing molecular imaging of breast cancer in vivo.

  10. Comparison of Photoacoustic Signals in Photosynthetic and Nonphotosynthetic Leaf Tissues of Variegated Pelargonium zonale

    Science.gov (United States)

    Veljović-Jovanović, S.; Vidović, M.; Morina, F.; Prokić, Lj.; Todorović, D. M.

    2016-09-01

    Green-white variegated leaves of Pelargonium zonale were studied using the photoacoustic method. Our aim was to characterize photosynthetically active green tissue and nonphotosynthetically active white tissue by the photoacoustic amplitude signals. We observed lower stomatal conductance and higher leaf temperature in white tissue than in green tissue. Besides these thermal differences, significantly higher absorbance in green tissue was based on chlorophyll and carotenoids which were absent in white tissue. However, optical properties of epidermal layers of both tissues were equal. The photoacoustic amplitude of white tissue was over four times higher compared to green tissue, which was correlated with lower stomatal conductance. In addition, at frequencies >700 Hz, the significant differences between the photoacoustic signals of green and white tissue were obtained. We identified the photoacoustic signal deriving from photosynthetic oxygen evolution in green tissue, using high intensity of red light modulated at 10 Hz. Moreover, the photoacoustic amplitude of green tissue increased progressively with time which corresponded to the period of induction of photosynthetic oxygen evolution. For the first time, very high frequencies (1 kHz to 5 kHz) were applied on leaf material.

  11. In vivo photoacoustic molecular imaging of breast carcinoma with folate receptor-targeted indocyanine green nanoprobes.

    Science.gov (United States)

    Wang, Huina; Liu, Chengbo; Gong, Xiaojing; Hu, Dehong; Lin, Riqiang; Sheng, Zonghai; Zheng, Cuifang; Yan, Meng; Chen, Jingqin; Cai, Lintao; Song, Liang

    2014-11-01

    As an optical-acoustic hybrid imaging technology, photoacoustic imaging uniquely combines the advantages of rich optical contrast with high ultrasonic resolution in depth, opening up many new possibilities not attainable with conventional pure optical imaging technologies. To perform photoacoustic molecular imaging, optically absorbing exogenous contrast agents are needed to enhance the signals from specifically targeted disease activity. In this work, we designed and developed folate receptor targeted, indocyanine green dye doped poly(d,l-lactide-co-glycolide) lipid nanoparticles (FA-ICG-PLGA-lipid NPs) for molecular photoacoustic imaging of tumor. The fabricated FA-ICG-PLGA-lipid NPs exhibited good aqueous stability, a high folate-receptor targeting efficiency, and remarkable optical absorption in near-infrared wavelengths, providing excellent photoacoustic signals in vitro. Furthermore, after intravenous administration of FA-ICG-PLGA-lipid NPs, mice bearing MCF-7 breast carcinomas showed significantly enhanced photoacoustic signals in vivo in the tumor regions, compared with those using non-targeted ICG-PLGA-lipid NPs. Given the existing wide clinical use of ICG and PLGA, the developed FA-ICG-PLGA-lipid NPs, in conjunction with photoacoustic imaging technology, offer a great potential to be translated into the clinic for non-ionizing molecular imaging of breast cancer in vivo.

  12. Theoretical and experimental study of spectral characteristics of the photoacoustic signal from stochastically distributed particles.

    Science.gov (United States)

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

    2015-07-01

    Photoacoustic imaging is an emerging technique which inherits the merits of optical imaging and ultrasonic imaging. However, classical photoacoustic imaging mainly makes use of the time-domain parameters of signals. In contrast to previous studies, we theoretically investigate the spectral characteristics of the photoacoustic signal from stochastic distributed particles. The spectral slope is extracted and used for describing the spectral characteristics of the photoacoustic signal. Both Gaussian and spherical distributions of optical absorption in particles are considered. For both situations, the spectral slope is monotonically decreased with the increase of particle size. In addition, the quantitative relationship between the spectral slope and the imaging system factors, including the laser pulse envelope, directivity of ultrasound transducer, and signal bandwidth, are theoretically analyzed. Finally, an idealized phantom experiment is performed to validate the analyses and examine the instrument independent of the spectral slope. This work provides a theoretical framework and new experimental evidence for spectrum analysis of the photoacoustic signal. This could be helpful for quantitative tissue evaluation and imaging based on the spectral parameters of the photoacoustic signal.

  13. Dense velocity reconstruction from tomographic PTV with material derivatives

    Science.gov (United States)

    Schneiders, Jan F. G.; Scarano, Fulvio

    2016-09-01

    A method is proposed to reconstruct the instantaneous velocity field from time-resolved volumetric particle tracking velocimetry (PTV, e.g., 3D-PTV, tomographic PTV and Shake-the-Box), employing both the instantaneous velocity and the velocity material derivative of the sparse tracer particles. The constraint to the measured temporal derivative of the PTV particle tracks improves the consistency of the reconstructed velocity field. The method is christened as pouring time into space, as it leverages temporal information to increase the spatial resolution of volumetric PTV measurements. This approach becomes relevant in cases where the spatial resolution is limited by the seeding concentration. The method solves an optimization problem to find the vorticity and velocity fields that minimize a cost function, which includes next to instantaneous velocity, also the velocity material derivative. The velocity and its material derivative are related through the vorticity transport equation, and the cost function is minimized using the limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm. The procedure is assessed numerically with a simulated PTV experiment in a turbulent boundary layer from a direct numerical simulation (DNS). The experimental validation considers a tomographic particle image velocimetry (PIV) experiment in a similar turbulent boundary layer and the additional case of a jet flow. The proposed technique (`vortex-in-cell plus', VIC+) is compared to tomographic PIV analysis (3D iterative cross-correlation), PTV interpolation methods (linear and adaptive Gaussian windowing) and to vortex-in-cell (VIC) interpolation without the material derivative. A visible increase in resolved details in the turbulent structures is obtained with the VIC+ approach, both in numerical simulations and experiments. This results in a more accurate determination of the turbulent stresses distribution in turbulent boundary layer investigations. Data from a jet

  14. Towards a micrometer resolution x-ray tomographic microscope

    International Nuclear Information System (INIS)

    Near-micrometer resolution, three-dimensional computed tomographic images were made of a test object using the hard x-ray microscope developed by the National Institute of Standards and Technology (NIST). The microscope uses a cooled CCD camera with direct conversion of the incident x rays by a 512 x 512 chip with 19 microm by 19microm cells. Magnification by a factor of 20 is achieved using asymmetric Bragg diffraction from a pair of silicon crystals. The imaging system is designed for samples of the order of 0.50 mm diameter by 0.50 mm height. 8.17 keV x-rays were used from beamline X23A3 at the National Synchrotron Light Source (NSLS) Brookhaven National Laboratory (BNL). Two hundred, 512 x 512 two-dimensional projections were collected every 0.9 degree about the test object using the NIST microscope. The projections were digitized and sent to a computer for volume tomographic reconstruction by a parallel-beam, convolution-backprojection algorithm into a 5123 image with (1 microm)3 voxels. The test object consisted of glass and nickel microspheres with distributions from about 4 to 40 microm (glass) or to 24 microm (nickel) diameters suspended in epoxy in order to demonstrate near one micrometer resolution in all three dimensions and probe contrast sensitivity. The effect and interplay of photon statistics and energy, and sample composition, density and size on tomographic performance are discussed as are resolution limitations and image artifacts from Fresnel diffraction

  15. Diffuse reflection model and noise stabilization for tangential image tomographic reconstruction (TITR) code

    International Nuclear Information System (INIS)

    A tomographic reconstruction code had been reported by us for inferring the poloidal emissivity of tokamak plasma from tangentially acquired images. Here we present modifications to the code that account for any diffuse reflections from the surfaces of walls enclosing the plasma. It is generally recognized that such reconstruction codes are highly susceptible to noise in the data. In this work we have analysed the sensitivity to noise for varying degrees of over-determinism in the set of equations; over-determinism is defined as the ratio of the number of detector signals available to the grid resolution of reconstruction. A tractable scheme for dividing the poloidal cross section into a finite number of unknown sub-tori and voids, while still keeping the over-determinism high, is incorporated. Finally it is shown that noise level >20% can be handled with over-determinism achievable from present day detector array/cameras. The singular value decomposition of the matrix, as used here, can be expected to converge even if any ill-conditioned matrix is encountered due to computational round-off errors in the estimation of chord lengths through sub-tori and voids.

  16. Pineal region tumors: computed tomographic-pathologic spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Futrell, N.N.; Osborn, A.G.; Cheson. B.D.

    1981-11-01

    While several computed tomographic (CT) studies of posterior third ventricular neoplasms have included descriptions of pineal tumors, few reports have concentrated on these uncommon lesions. Some authors have asserted that the CT appearance of many pineal tumors is virtually pathognomonic. A series of nine biopsy-proved pineal gland and eight other presumed tumors is presented that illustrates their remarkable heterogeneity in both histopathologic and CT appearance. These tumors included germinomas, teratocarcinomas, hamartomas, and other varieties. They had variable margination, attentuation, calcification, and suprasellar extension. Germinomas have the best response to radiation therapy. Biopsy of pineal region tumors is now feasible and is recommended for treatment planning.

  17. Computed tomographical imaging of the brain in post hypoglycemic coma

    Energy Technology Data Exchange (ETDEWEB)

    Iwai, A.; Sakamoto, T.; Kinoshita, Y.; Yokota, J.I.; Yoshioka, T.; Sugimoto, T.

    1987-07-01

    A case of post severe hypoglycemic coma was studied by sequential Computed Tomographic Imaging (CT) of the brain. The CT 1) was normal in the early stage, 2) subsequently showed a low density area, which was enhanced by the contrast medium, in the cerebral cortex and the boundary zone between the major cerebral arteries, and 3) revealed marked enhancement in the entire cortical region and hypodensity in the periventricular region in the late stage. These CT findings, representing the course of neural cell damage by severe hypoglycemia, are discussed from the pathophysiological viewpoint.

  18. Acquisition of the EELS data cube by tomographic reconstruction

    International Nuclear Information System (INIS)

    Energy filtered TEM, EFTEM, provides three-dimensional data, two spatial and one spectral dimension. We propose to acquire these data by measuring a series of images with a defocused energy filter. It will be shown that each image is a projection of the data on the detector and that reconstruction of the data out of a sufficient number of such projections using a tomographic reconstruction algorithm is possible. This technique uses only a fraction of the electron dose an energy filtered series (EFS) needs for the same spectral and spatial resolution and the same mean signal-to-noise ratio

  19. Electromagnetic Hydrophone with Tomographic System for Absolute Velocity Field Mapping

    CERN Document Server

    Grasland-Mongrain, Pol; Mari, Jean-Martial; Chapelon, Jean-Yves; Lafon, Cyril; 10.1063/1.4726178

    2012-01-01

    The velocity and pressure of an ultrasonic wave can be measured by an electromagnetic hydrophone made of a thin wire and a magnet. The ultrasonic wave vibrates the wire inside a magnetic field, inducing an electrical current. Previous articles reported poor spatial resolution of comparable hydrophones along the axis of the wire. In this study, submillimetric spatial resolution has been achieved by using a tomographic method. Moreover, a physical model is presented for obtaining absolute measurements. A pressure differential of 8% has been found between piezoelectric and electromagnetic hydrophone measurements. These characteristics show this technique as an alternative to standard hydrophones.

  20. Computed tomographical imaging of the brain in post hypoglycemic coma

    International Nuclear Information System (INIS)

    A case of post severe hypoglycemic coma was studied by sequential Computed Tomographic Imaging (CT) of the brain. The CT 1) was normal in the early stage, 2) subsequently showed a low density area, which was enhanced by the contrast medium, in the cerebral cortex and the boundary zone between the major cerebral arteries, and 3) revealed marked enhancement in the entire cortical region and hypodensity in the periventricular region in the late stage. These CT findings, representing the course of neural cell damage by severe hypoglycemia, are discussed from the pathophysiological viewpoint. (orig.)

  1. Tomographic diffractive microscopy and multiview profilometry with flexible aberration correction.

    Science.gov (United States)

    Liu, H; Bailleul, J; Simon, B; Debailleul, M; Colicchio, B; Haeberlé, O

    2014-02-01

    We have developed a tomographic diffractive microscope in reflection, which permits observation of sample surfaces with an improved lateral resolution, compared to a conventional holographic microscope. From the same set of data, high-precision measurements can be performed on the shape of the reflective surface by reconstructing the phase of the diffracted field. Doing so allows for several advantages compared to classical holographic interferometric measurements: improvement in lateral resolution, easier phase unwrapping, reduction of the coherent noise, combined with the high-longitudinal precision provided by interferometric phase measurements. We demonstrate these capabilities by imaging various test samples. PMID:24514193

  2. ULTRASOUND AND COMPUTED TOMOGRAPHIC DIAGNOSIS OF OPTIC NERVE TUMORS

    Directory of Open Access Journals (Sweden)

    S. V. Saakyan

    2012-01-01

    Full Text Available A comprehensive examination was made in 93 patients, including 18 children, with tumors of the optic nerve (ON. Duplex ultrasound scanning was performed in 39 patients, of them there were 11 patients with ON gliomas and 28 with ON meningiomas. The specific computed tomographic and echographic signs of ON glioma and meningiomas were detected. The studies have shown that duplex ultrasound scanning and structural computed tomography of orbital sockets are highly informative complementary imaging procedures for ON tumors, which permits one to make their correct diagnosis, to specify surgical volume, and to plan adequate treatment.

  3. Characterizing intestinal strictures with acoustic resolution photoacoustic microscopy

    Science.gov (United States)

    Lei, Hao; Xu, Guan; Liu, Shengchun; Johnson, Laura A.; Moons, David S.; Higgins, Peter D. R.; Rice, Michael D.; Ni, Jun; Wang, Xueding

    2016-03-01

    Crohn's disease (CD) is an autoimmune disease, which may cause obstructing intestinal strictures due to inflammation, fibrosis (deposition of collagen), or a combination of both. Identifying the different stages of the disease progression is still challenging. In this work, we indicated the feasibility of non-invasively characterizing intestinal strictures using photoacoustic imaging (PAI), utilizing the uniquely optical absorption of hemoglobin and collagen. Surgically removed human intestinal stricture specimens were investigated with a prototype PAI system. 2D PA images with acoustic resolution at wavelength 532, 1210 and 1310 nm were formulated, and furthermore, the PA histochemical components images which show the microscopic distributions of histochemical components were solved. Imaging experiments on surgically removed human intestinal specimens has demonstrated the solved PA images were significantly different associated with the presence of fibrosis, which could be applied to characterize the intestinal strictures for given specimens.

  4. In vivo photoacoustic imaging of osteosarcoma on animal model

    Energy Technology Data Exchange (ETDEWEB)

    Yu Menglei; Hu Jun [Department of Orthopaedics, The First Affiliated Hospital, Shantou University Medical College, Shantou 515041 (China); Ye Fei, E-mail: hjzkm@yahoo.com.cn [MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631 (China)

    2011-01-01

    Osteosarcoma is the commonest primary malignant tumor of bone, and the second highest cause of cancer-related death in the paediatric age group. Although there are several methods for osteosarcoma detection, e.g. X-ray, CT, MRI and bone scan, they are not satisfied methods because they can hardly detect osteosarcoma in early stage. Photoacoustic imaging (PAI) is an emerging hybrid imaging modality that is noninvasive, nonionizing, with high sensitivity, satisfactory imaging depth and good temporal and spatial resolution. In order to explore this new method to detect osteosarcoma, we established SD rat models with osteosarcoma and utilized PAI to reconstruct the osteosarcoma image in vivo. This is the first time detecting osteosarcoma in vivo using PAI, and the results suggested that PAI has potential clinical application for detecting osteosarcoma in the early stage.

  5. Hybrid photoacoustic and optical imaging of pigments in vegetative tissues.

    Science.gov (United States)

    Tserevelakis, George J; Tsagkaraki, Margarita; Zacharakis, Giannis

    2016-09-01

    Pigments in vegetative tissues have been a subject of intense research during the previous decades, since they play an active role in several molecular mechanisms regarding plants' physiology and function. Towards this direction, the imaging modality that has been extensively employed and represents the state of the art for mapping pigments' distribution is confocal microscopy. Despite the advantage of a high spatial resolution however, confocal microscopy provides a rather limited imaging depth and requires necessarily strong fluorescence properties from the specimen under observation. To overcome such limitations, we propose a hybrid, photoacoustic and optical imaging methodology for the delineation of various vegetative pigments, such as chlorophylls, anthocyanins and betalains in different plant species. The superior sensitivity and the high contrast complementarity of the hybrid technique, render it a powerful alternative to the conventional fluorescence imaging modalities, significantly expanding the current state of the art. PMID:27019381

  6. Sub-ppm multi-gas photoacoustic sensor.

    Science.gov (United States)

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

    2006-04-01

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

  7. On multi-spectral quantitative photoacoustic tomography in diffusive regime

    International Nuclear Information System (INIS)

    The objective of quantitative photoacoustic tomography (qPAT) is to reconstruct the diffusion, absorption and Grüneisen thermodynamic coefficients of heterogeneous media from knowledge of the interior absorbed radiation. It has been shown in Bal and Ren (2011 Inverse Problems 27 075003), based on diffusion theory, that with data acquired at one given wavelength, all three coefficients cannot be reconstructed uniquely. In this work, we study the multi-spectral qPAT problem and show that when multiple wavelength data are available, all coefficients can be reconstructed simultaneously under minor prior assumptions. Moreover, the reconstructions are shown to be very stable. We present some numerical simulations that support the theoretical results. (paper)

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

    Science.gov (United States)

    LeBoulluec, Peter; Liu, Hanli; Yuan, Baohong

    2013-09-01

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

  9. Fabrication of indigenous computer controlled photoacoustic spectrometer for actinide spectroscopy

    International Nuclear Information System (INIS)

    The photoacoustic spectroscopy (PAS) monitoring the non-radiative de-excitation process is a powerful tool for investigating the absorption spectra of almost any type of samples like opaque solids, turbid solutions etc. Actinide compounds due to high probability of non-radiative relaxation process are good candidates for PAS investigations and also without any need for good optical quality crystals of these compounds. In addition, this technique is extremely useful for determination of thermal properties like thermal conductivity, diffusivity and related properties like phase transitions, thickness of thin film etc. In the present paper details of fabrication of indigenous PAS unit using low cost easily available components and interfacing this unit to a personal computer are given

  10. Simple model of a photoacoustic system as a CR circuit

    International Nuclear Information System (INIS)

    We introduce the photoacoustic educational system (PAES), by which we can identify which gas causes the greenhouse effect in a classroom (Kaneko et al 2010 J. Chem. Educ. 87 202-4). PAES is an experimental system in which a pulse of infrared (IR) is absorbed into gas as internal energy, an oscillation of pressure (sound) appears, and then we can measure the absorptance of IR by the strength of sound. In this paper, we construct a simple mathematical model for PAES which is equivalent to the CR circuit. The energy absorption of an IR pulse into gas corresponds to the charge of a condenser and the heat diffusion to the outside corresponds to the energy dissipation by electric resistance. We analyse the experimental results by using this simple model, and check its validity. Although the model is simple, it explains phenomena occurring in PAES and can be a good educational resource. (paper)

  11. In vitro photoacoustic sensing of calcium dynamics with arsenazo III

    Science.gov (United States)

    Dana, N.; Fowler, R. A.; Allen, A.; Zoldan, J.; Suggs, L.; Emelianov, S.

    2016-07-01

    Imaging of cellular electric potential via calcium-ion sensitive contrast agents is a useful tool, but current techniques lack sufficient depth penetration. We explore contrast-enhanced photoacoustic (PA) imaging, using Arsenazo III dye, to visualize cardiac myocyte depolarization in vitro. Phantom results show strong linearity of PA signal with dye concentration (R 2  >  0.95), and agree spectrally with extinction measurements with varying calcium concentration. Cell studies indicate a significant (>100-fold) increase in PA signal for dye-treated cells, as well as a 10-fold increase in peak-to-peak variation during a 30 s window. This suggests contrast-enhanced PA imaging may have sufficient sensitivity and specificity for depth-resolved visualization of tissue depolarization in real-time.

  12. Quartz crystal microbalance and photoacoustic measurements in dental photocuring

    Science.gov (United States)

    Lima, Marcenilda A.; Bastos, Ivan N.; Cella, Norberto

    2016-09-01

    Photocured dental resins are used extensively in restorative procedures in dentistry. Inadequate curing reduces the lifetime of the dental restoration, and consequently it is essential to precisely measure the polymerisation kinetics. In this study, two techniques, Quartz Crystal Microbalance (QCM) and Photoacoustic Spectroscopy (PAS), were used to monitor the real-time cure and to obtain the optical absorption spectra of resins, respectively. From the PAS measurements, the precise peaks of absorption were identified, and were used as the appropriate wavelength of the photocuring light in the QCM monitoring. The combined use of these techniques allows reliable determination of the duration of the phases of physical and chemical changes that occur during photocuring. Two commercial dental resins were tested, and the results confirmed the advantages of using PAS and QCM to study polymerisation kinetics.

  13. Integrated photoacoustic, confocal, and two-photon microscope

    Science.gov (United States)

    Rao, Bin; Soto, Florentina; Kerschensteiner, Daniel; Wang, Lihong V.

    2014-01-01

    Abstract. The invention of green fluorescent protein and other molecular fluorescent probes has promoted applications of confocal and two-photon fluorescence microscopy in biology and medicine. However, exogenous fluorescence contrast agents may affect cellular structure and function, and fluorescence microscopy cannot image nonfluorescent chromophores. We overcome this limitation by integrating optical-resolution photoacoustic microscopy into a modern Olympus IX81 confocal, two-photon, fluorescence microscope setup to provide complementary, label-free, optical absorption contrast. Automatically coregistered images can be generated from the same sample. Imaging applications in ophthalmology, developmental biology, and plant science are demonstrated. For the first time, in a familiar microscopic fluorescence imaging setting, this trimodality microscope provides a platform for future biological and medical discoveries. PMID:24589986

  14. Thermophysical investigation of Gafchromic EBT2 films using photoacoustic spectroscopy

    Science.gov (United States)

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

    2014-07-01

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

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

    Science.gov (United States)

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

    2011-07-01

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

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

    Science.gov (United States)

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

    2015-03-01

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

  17. Tunable light source for use in photoacoustic spectrometers

    Science.gov (United States)

    Bisson, Scott E.; Kulp, Thomas J.; Armstrong, Karla M.

    2005-12-13

    The present invention provides a photoacoustic spectrometer that is field portable and capable of speciating complex organic molecules in the gas phase. The spectrometer has a tunable light source that has the ability to resolve the fine structure of these molecules over a large wavelength range. The inventive light source includes an optical parametric oscillator (OPO) having combined fine and coarse tuning. By pumping the OPO with the output from a doped-fiber optical amplifier pumped by a diode seed laser, the inventive spectrometer is able to speciate mixtures having parts per billion of organic compounds, with a light source that has a high efficiency and small size, allowing for portability. In an alternative embodiment, the spectrometer is scanned by controlling the laser wavelength, thus resulting in an even more compact and efficient design.

  18. A Practical Guide to Photoacoustic Tomography in the Life Sciences

    Science.gov (United States)

    Wang, Lihong V.; Yao, Junjie

    2016-01-01

    The life sciences can benefit greatly from imaging technologies that connect microscopic discoveries with macroscopic observations. Photoacoustic tomography (PAT), a highly sensitive modality for imaging rich optical absorption contrast over a wide range of spatial scales at high speed, is uniquely positioned for this need. In PAT, endogenous contrast reveals tissue’s anatomical, functional, metabolic, and histologic properties, and exogenous contrast provides molecular and cellular specificity. The spatial scale of PAT covers organelles, cells, tissues, organs, and small-animal organisms. Consequently, PAT is complementary to other imaging modalities in contrast mechanism, penetration, spatial resolution, and temporal resolution. We review the fundamentals of PAT and provide practical guidelines to the broad life science community for matching PAT systems with research needs. We also summarize the most promising biomedical applications of PAT, discuss related challenges, and envision its potential to lead to further breakthroughs. PMID:27467726

  19. Speed-of-sound compensated photoacoustic tomography for accurate imaging

    CERN Document Server

    Jose, Jithin; Steenbergen, Wiendelt; Slump, Cornelis H; van Leeuwen, Ton G; Manohar, Srirang

    2012-01-01

    In most photoacoustic (PA) measurements, variations in speed-of-sound (SOS) of the subject are neglected under the assumption of acoustic homogeneity. Biological tissue with spatially heterogeneous SOS cannot be accurately reconstructed under this assumption. We present experimental and image reconstruction methods with which 2-D SOS distributions can be accurately acquired and reconstructed, and with which the SOS map can be used subsequently to reconstruct highly accurate PA tomograms. We begin with a 2-D iterative reconstruction approach in an ultrasound transmission tomography (UTT) setting, which uses ray refracted paths instead of straight ray paths to recover accurate SOS images of the subject. Subsequently, we use the SOS distribution in a new 2-D iterative approach, where refraction of rays originating from PA sources are accounted for in accurately retrieving the distribution of these sources. Both the SOS reconstruction and SOS-compensated PA reconstruction methods utilize the Eikonal equation to m...

  20. Enhancement of photoacoustic detection of inhomogeneities in polymers

    CERN Document Server

    Grondona, P; Iriarte, D I; Pomarico, J A; Ranea-Sandoval, Héctor F; Bilmes, G M

    2013-01-01

    We report a series of experiments on laser pulsed photoacoustic excitationin turbid polymer samples addressed to evaluate the sound speed in the samples and the presence of inhomogeneities in the bulk. We describe a system which allows the direct measurement of the speed of the detected waves by engraving the surface of the piece under study with a fiduciary pattern of black lines. We also describe how this pattern helps to enhance the sensitivity for the detection of an inhomogeneity in the bulk. These two facts are useful for studies in soft matter systems including, perhaps, biological samples. We have performed an experimental analysis on Grilon(R) samples in different situations and we show the limitations of the method.

  1. Photoacoustic transformation of Bessel light beams in magnetoactive superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Mityurich, G. S., E-mail: George-mityurich@mail.ru [Belarusian Trade and Economics University of Consumer Cooperatives (Belarus); Chernenok, E. V.; Sviridova, V. V.; Serdyukov, A. N. [Gomel State University (Belarus)

    2015-03-15

    Photoacoustic transformation of the TE mode of a Bessel light beam (BLB) has been studied for piezoelectric detection in short-period superlattices formed by magnetoactive crystals of bismuth germanate (Bi{sub 12}GeO{sub 20}) and bismuth silicate (Bi{sub 12}SiO{sub 20}) types. It is shown that the resulting signal amplitude can be controlled using optical schemes of BLB formation with a tunable cone angle. A resonant increase in the signal amplitude has been found in the megahertz range of modulation frequencies and its dependences on the BLB modulation frequency, geometric sizes of the two-layer structure and piezoelectric transducer, radial coordinate of the polarization BLB mode, and dissipative superlattice parameters are analyzed.

  2. Photoacoustic imaging driven by an interstitial irradiation source

    Directory of Open Access Journals (Sweden)

    Trevor Mitcham

    2015-06-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Li, J. S., E-mail: jingsong-li@ahu.edu.cn; Yu, B. [Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education, Anhui University, Hefei (China); Fischer, H. [Department of Atmospheric Chemistry, Max Planck Institute for Chemistry, Mainz (Germany); Chen, W. [Laboratoire de Physicochimie de l’Atmosphére, Université du Littoral Côte d’Opale, Dunkerque (France); Yalin, A. P. [Department of Mechanical Engineering, Colorado State University, Fort Collins, Colorado 80523-1374 (United States)

    2015-03-15

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

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

    Science.gov (United States)

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

    2015-03-01

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

  5. Characterisation of a phantom for multiwavelength quantitative photoacoustic imaging

    Science.gov (United States)

    Fonseca, M.; Zeqiri, B.; Beard, P. C.; Cox, B. T.

    2016-07-01

    Quantitative photoacoustic imaging (qPAI) has the potential to provide high- resolution in vivo images of chromophore concentration, which may be indicative of tissue function and pathology. Many strategies have been proposed recently for extracting quantitative information, but many have not been experimentally verified. Experimental phantom-based validation studies can be used to test the robustness and accuracy of such algorithms in order to ensure reliable in vivo application is possible. The phantoms used in such studies must have well-characterised optical and acoustic properties similar to tissue, and be versatile and stable. Polyvinyl chloride plastisol (PVCP) has been suggested as a phantom for quality control and system evaluation. By characterising its multiwavelength optical properties, broadband acoustic properties and thermoelastic behaviour, this paper examines its potential as a phantom for qPAI studies too. PVCP’s acoustic properties were assessed for various formulations, as well as its intrinsic optical absorption, and scattering with added TiO2, over a range of wavelengths from 400-2000 nm. To change the absorption coefficient, pigment-based chromophores that are stable during the phantom fabrication process, were used. These yielded unique spectra analogous to tissue chromophores and linear with concentration. At the high peak powers typically used in photoacoustic imaging, nonlinear optical absorption was observed. The Grüneisen parameter was measured to be Γ   =  1.01  ±  0.05, larger than typically found in tissue, though useful for increased PA signal. Single and multiwavelength 3D PA imaging of various fabricated PVCP phantoms were demonstrated.

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

    Science.gov (United States)

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

    2015-03-01

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

  7. Narrow Absorption NIR Wavelength Organic Nanoparticles Enable Multiplexed Photoacoustic Imaging.

    Science.gov (United States)

    Lu, Hoang D; Wilson, Brian K; Heinmiller, Andrew; Faenza, Bill; Hejazi, Shahram; Prud'homme, Robert K

    2016-06-15

    Photoacoustic (PA) imaging is an emerging hybrid optical-ultrasound based imaging technique that can be used to visualize optical absorbers in deep tissue. Free organic dyes can be used as PA contrast agents to concurrently provide additional physiological and molecular information during imaging, but their use in vivo is generally limited by rapid renal clearance for soluble dyes and by the difficulty of delivery for hydrophobic dyes. We here report the use of the block copolymer directed self-assembly process, Flash NanoPrecipitation (FNP), to form series of highly hydrophobic optical dyes into stable, biocompatible, and water-dispersible nanoparticles (NPs) with sizes from 38 to 88 nm and with polyethylene glycol (PEG) surface coatings suitable for in vivo use. The incorporation of dyes with absorption profiles within the infrared range, that is optimal for PA imaging, produces the PA activity of the particles. The hydrophobicity of the dyes allows their sequestration in the NP cores, so that they do not interfere with targeting, and high loadings of >75 wt % dye are achieved. The optical extinction coefficients (ε (mL mg(-1) cm(-1))) were essentially invariant to the loading of the dye in NP core. Co-encapsulation of dye with vitamin E or polystyrene demonstrates the ability to simultaneously image and deliver a second agent. The PEG chains on the NP surface were functionalized with folate to demonstrate folate-dependent targeting. The spectral separation of different dyes among different sets of particles enables multiplexed imaging, such as the simultaneous imaging of two sets of particles within the same animal. We provide the first demonstration of this capability with PA imaging, by simultaneously imaging nontargeted and folate-targeted nanoparticles within the same animal. These results highlight Flash NanoPrecipitation as a platform to develop photoacoustic tools with new diagnostic capabilities. PMID:27153806

  8. Characterisation of a phantom for multiwavelength quantitative photoacoustic imaging.

    Science.gov (United States)

    Fonseca, M; Zeqiri, B; Beard, P C; Cox, B T

    2016-07-01

    Quantitative photoacoustic imaging (qPAI) has the potential to provide high- resolution in vivo images of chromophore concentration, which may be indicative of tissue function and pathology. Many strategies have been proposed recently for extracting quantitative information, but many have not been experimentally verified. Experimental phantom-based validation studies can be used to test the robustness and accuracy of such algorithms in order to ensure reliable in vivo application is possible. The phantoms used in such studies must have well-characterised optical and acoustic properties similar to tissue, and be versatile and stable. Polyvinyl chloride plastisol (PVCP) has been suggested as a phantom for quality control and system evaluation. By characterising its multiwavelength optical properties, broadband acoustic properties and thermoelastic behaviour, this paper examines its potential as a phantom for qPAI studies too. PVCP's acoustic properties were assessed for various formulations, as well as its intrinsic optical absorption, and scattering with added TiO2, over a range of wavelengths from 400-2000 nm. To change the absorption coefficient, pigment-based chromophores that are stable during the phantom fabrication process, were used. These yielded unique spectra analogous to tissue chromophores and linear with concentration. At the high peak powers typically used in photoacoustic imaging, nonlinear optical absorption was observed. The Grüneisen parameter was measured to be [Formula: see text]  =  1.01  ±  0.05, larger than typically found in tissue, though useful for increased PA signal. Single and multiwavelength 3D PA imaging of various fabricated PVCP phantoms were demonstrated. PMID:27286411

  9. Validating tyrosinase homologue melA as a photoacoustic reporter gene for imaging Escherichia coli

    Science.gov (United States)

    Paproski, Robert J.; Li, Yan; Barber, Quinn; Lewis, John D.; Campbell, Robert E.; Zemp, Roger

    2015-10-01

    To understand the pathogenic processes for infectious bacteria, appropriate research tools are required for replicating and characterizing infections. Fluorescence and bioluminescence imaging have primarily been used to image infections in animal models, but optical scattering in tissue significantly limits imaging depth and resolution. Photoacoustic imaging, which has improved depth-to-resolution ratio compared to conventional optical imaging, could be useful for visualizing melA-expressing bacteria since melA is a bacterial tyrosinase homologue which produces melanin. Escherichia coli-expressing melA was visibly dark in liquid culture. When melA-expressing bacteria in tubes were imaged with a VisualSonics Vevo LAZR system, the signal-to-noise ratio of a 9× dilution sample was 55, suggesting that ˜20 bacteria cells could be detected with our system. Multispectral (680, 700, 750, 800, 850, and 900 nm) analysis of the photoacoustic signal allowed unmixing of melA-expressing bacteria from blood. To compare photoacoustic reporter gene melA (using Vevo system) with luminescent and fluorescent reporter gene Nano-lantern (using Bruker Xtreme In-Vivo system), tubes of bacteria expressing melA or Nano-lantern were submerged 10 mm in 1% Intralipid, spaced between bioluminescence and fluorescence imaging could not resolve the two tubes of Nano-lantern-expressing bacteria even when the tubes were spaced 10 mm from each other. After injecting 100-μL of melA-expressing bacteria in the back flank of a chicken embryo, photoacoustic imaging allowed visualization of melA-expressing bacteria up to 10-mm deep into the embryo. Photoacoustic signal from melA could also be separated from deoxy- and oxy-hemoglobin signal observed within the embryo and chorioallantoic membrane. Our results suggest that melA is a useful photoacoustic reporter gene for visualizing bacteria, and further work incorporating photoacoustic reporters into infectious bacterial strains is warranted.

  10. Influence of nanoscale temperature rises on photoacoustic generation: Discrimination between optical absorbers based on thermal nonlinearity at high frequency.

    Science.gov (United States)

    Simandoux, Olivier; Prost, Amaury; Gateau, Jérôme; Bossy, Emmanuel

    2015-03-01

    In this work, we experimentally investigate thermal-based nonlinear photoacoustic generation as a mean to discriminate between different types of absorbing particles. The photoacoustic generation from solutions of dye molecules and gold nanospheres (same optical densities) was detected using a high frequency ultrasound transducer (20 MHz). Photoacoustic emission was observed with gold nanospheres at low fluence for an equilibrium temperature around 4 °C, where the linear photoacoustic effect in water vanishes, highlighting the nonlinear emission from the solution of nanospheres. The photoacoustic amplitude was also studied as a function of the equilibrium temperature from 2 °C to 20 °C. While the photoacoustic amplitude from the dye molecules vanished around 4 °C, the photoacoustic amplitude from the gold nanospheres remained significant over the whole temperature range. Our preliminary results suggest that in the context of high frequency photoacoustic imaging, nanoparticles may be discriminated from molecular absorbers based on nanoscale temperature rises.

  11. Computed tomographic features of fibrous dysplasia of maxillofacial region

    Energy Technology Data Exchange (ETDEWEB)

    Sontakke, Subodh Arun; Karjodka, Freny R [Nair Hospital Dental College, Mumba (India); Umarji, Hemant R [Government Dental College and Hospital, Mumbai (India)

    2011-03-15

    This study was to find the computed tomographic features of fibrous dysplasia of the maxillofacial region. All eight cases included in the study reported either to Government Dental College and Hospital or Nair Hospital Dental College, Mumbai between 2003 and 2009. The patients were prescribed computed tomogram in addition to conventional radiographs of maxillofacial region which were studied for characteristic features of fibrous dysplasia. The diagnosis of fibrous dysplasia was confirmed by histopathological report. All cases showed the ill-defined margins of lesions except in the region where the lesions were extending to cortex of the involved bone. Internal structure of all cases showed ground glass appearance. Four cases of maxillary lesion showed the displacement of maxillary sinus maintaining the shape of maxillary sinus. Two cases showed complete obliteration of maxillary sinus. Displacement of inferior alveolar canal did not follow any typical pattern in any of the cases but was displaced in different directions. The craniofacial type of fibrous dysplasia is as common as fibrous dysplasia of jaw. The margins, extent, internal structure and effect on surrounding structure are well detected on computed tomographic images.

  12. Performance of analytical methods for tomographic gamma scanning

    International Nuclear Information System (INIS)

    The use of gamma-ray computerized tomography for nondestructive assay of radioactive materials has led to the development of specialized analytical methods. Over the past few years, Los Alamos has developed and implemented a computer code, called ARC-TGS, for the analysis of data obtained by tomographic gamma scanning (TGS). ARC-TGS reduces TGS transmission and emission tomographic data, providing the user with images of the sample contents, the activity or mass of selected radionuclides, and an estimate of the uncertainty in the measured quantities. The results provided by ARC-TGS can be corrected for self-attenuation when the isotope of interest emits more than one gamma-ray. In addition, ARC-TGS provides information needed to estimate TGS quantification limits and to estimate the scan time needed to screen for small amounts of radioactivity. In this report, an overview of the analytical methods used by ARC-TGS is presented along with an assessment of the performance of these methods for TGS

  13. A fast multi-resolution approach to tomographic PIV

    Energy Technology Data Exchange (ETDEWEB)

    Discetti, Stefano; Astarita, Tommaso [University of Naples Federico II, Department of Aerospace Engineering (DIAS), Naples (Italy)

    2012-03-15

    Tomographic particle image velocimetry (Tomo-PIV) is a recently developed three-component, three-dimensional anemometric non-intrusive measurement technique, based on an optical tomographic reconstruction applied to simultaneously recorded images of the distribution of light intensity scattered by seeding particles immersed into the flow. Nowadays, the reconstruction process is carried out mainly by iterative algebraic reconstruction techniques, well suited to handle the problem of limited number of views, but computationally intensive and memory demanding. The adoption of the multiplicative algebraic reconstruction technique (MART) has become more and more accepted. In the present work, a novel multi-resolution approach is proposed, relying on the adoption of a coarser grid in the first step of the reconstruction to obtain a fast estimation of a reliable and accurate first guess. A performance assessment, carried out on three-dimensional computer-generated distributions of particles, shows a substantial acceleration of the reconstruction process for all the tested seeding densities with respect to the standard method based on 5 MART iterations; a relevant reduction in the memory storage is also achieved. Furthermore, a slight accuracy improvement is noticed. A modified version, improved by a multiplicative line of sight estimation of the first guess on the compressed configuration, is also tested, exhibiting a further remarkable decrease in both memory storage and computational effort, mostly at the lowest tested seeding densities, while retaining the same performances in terms of accuracy. (orig.)

  14. Multi-modality systems for molecular tomographic imaging

    Science.gov (United States)

    Li, Mingze; Bai, Jing

    2009-11-01

    In vivo small animal imaging is a cornerstone in the study of human diseases by providing important clues on the pathogenesis, progression and treatment of many disorders. Molecular tomographic imaging can probe complex biologic interactions dynamically and to study diseases and treatment responses over time in the same animal. Current imaging technique including microCT, microMRI, microPET, microSPECT, microUS, BLT and FMT has its own advantages and applications, however, none of them can provide structural, functional and molecular information in one context. Multi-modality imaging, which utilizes the strengths of different modalities to provide a complete understanding of the object under investigation, emerges as an important alternative in small animal imaging. This article is to introduce the latest development of multimodality systems for small animal tomographic imaging. After a systematic review of imaging principles, systems and commerical products for each stand-alone method, we introduce some multimodality strategies in the latest years. In particular, two dual-modality systems, i.e. FMT-CT and FMT-PET are presented in detail. The end of this article concludes that though most multimodality systems are still in a laboratory research stage, they will surely undergo deep development and wide application in the near future.

  15. Clinical findings in 16 patients with tomographic diagnosis of schizencephaly

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Maria do Carmo de Souza [Universidade Federal do Espirito Santo, Vitoria, ES (Brazil). Hospital Universitario Cassiano Antonio Moraes]. E-mail: rodriguesmcs@yahoo.com.br; Monteiro, Alexandra Maria Vieira [Universidade do Estado do Rio de Janeiro, RJ (Brazil). Faculdade de Ciencias Medicas; Llerena Junior, Juan Clinton [Fundacao Oswaldo Cruz, Rio de Janeiro, RJ (Brazil). Instituto Fernandes Figueira. Centro de Genetica Medica; Fernandes, Alexandre Ribeiro [Universidade Gama Filho, Rio de Janeiro, RJ (Brazil). Dept. de Pediatria

    2006-09-15

    Objective: to establish a correlation between clinical features in a group of children with tomographic diagnosis of schizencephaly and clefts extent and localization. Materials and methods: retrospective study of dossiers from the archives of Neurology and Medical Genetics Services at Instituto Fernandes Figueira/FIOCRUZ and Hospital Municipal Jesus, Rio de Janeiro, RJ, Brazil, in the period between 2000 and 2003. The study included 16 patients, nine female and seven male, with tomographic diagnosis of schizencephaly investigated for clinical findings, psychomotor development, motor/cognitive deficits and epilepsy. Results: predominance of bilateral clefts in 10:16 patients, open-lip schizencephaly type in 23:27 patients, and small lips in 11:27 patients. As regards anomalies associated with schizencephaly, pellucid septum absence was the most frequent one (10:16 patients). As regards clinical findings, 15 patients presented with developmental delay and motor deficit, six patients with cognitive deficit and ten with epilepsy. In three patients, we observed discordant clinical findings and cleft sizes, although the clefts were small, the clinical features severity was high because of other cerebral anomalies. Conclusion: the clinical features of schizencephaly are related to the size of the clefts, regardless laterality, presenting higher severity when associated with other cerebral anomalies. (author)

  16. Evaluation of a multicore-optimized implementation for tomographic reconstruction.

    Directory of Open Access Journals (Sweden)

    Jose-Ignacio Agulleiro

    Full Text Available Tomography allows elucidation of the three-dimensional structure of an object from a set of projection images. In life sciences, electron microscope tomography is providing invaluable information about the cell structure at a resolution of a few nanometres. Here, large images are required to combine wide fields of view with high resolution requirements. The computational complexity of the algorithms along with the large image size then turns tomographic reconstruction into a computationally demanding problem. Traditionally, high-performance computing techniques have been applied to cope with such demands on supercomputers, distributed systems and computer clusters. In the last few years, the trend has turned towards graphics processing units (GPUs. Here we present a detailed description and a thorough evaluation of an alternative approach that relies on exploitation of the power available in modern multicore computers. The combination of single-core code optimization, vector processing, multithreading and efficient disk I/O operations succeeds in providing fast tomographic reconstructions on standard computers. The approach turns out to be competitive with the fastest GPU-based solutions thus far.

  17. Out-coupling of Longitudinal Photoacoustic Pulses by Mitigating the Phase Cancellation

    Science.gov (United States)

    Lee, Taehwa; Li, Qiaochu; Guo, L. Jay

    2016-02-01

    Waves of any kinds, including sound waves and light waves, can interfere constructively or destructively when they are overlapped, allowing for myriad applications. However, unlike continuous waves of a single frequency, interference of photoacoustic pulses is often overlooked because of their broadband characteristics and short pulse durations. Here, we study cancellation of two symmetric photoacoustic pulses radiated in the opposite direction from the same photoacoustic sources near a free surface. The cancellation occurs when one of the two pulses is reflected with polarity reversal from the free surface and catches up with the other. The cancellation effect, responsible for reduced signal amplitudes, is systematically examined by implementing a thin transparent matching medium of the same acoustic impedance. By changing the thickness of the transparent layer, the overlap of the two symmetric pulses is controlled. For optimized matching layers, the cancellation effect can be significantly reduced, while the resulting output waveform remains unchanged. Similar to the planar absorber, different dimensional absorbers including cylinders and spheres also exhibit the cancellation between the outward and inward waves. This work could provide further understanding of photoacoustic generation and a simple strategy for increasing photoacoustic signal amplitudes.

  18. Virus-mimicking nano-constructs as a contrast agent for near infrared photoacoustic imaging

    Science.gov (United States)

    Gupta, Sharad; Chatni, Muhammad R.; Rao, Ayala L. N.; Vullev, Valentine I.; Wang, Lihong V.; Anvari, Bahman

    2013-02-01

    We report the first proof-of-principle demonstration of photoacoustic imaging using a contrast agent composed of a plant virus protein shell, which encapsulates indocyanine green (ICG), the only FDA-approved near infrared chromophore. These nano-constructs can provide higher photoacoustic signals than blood in tissue phantoms, and display superior photostability compared to non-encapsulated ICG. Our preliminary results suggest that the constructs do not elicit an acute immunogenic response in healthy mice.We report the first proof-of-principle demonstration of photoacoustic imaging using a contrast agent composed of a plant virus protein shell, which encapsulates indocyanine green (ICG), the only FDA-approved near infrared chromophore. These nano-constructs can provide higher photoacoustic signals than blood in tissue phantoms, and display superior photostability compared to non-encapsulated ICG. Our preliminary results suggest that the constructs do not elicit an acute immunogenic response in healthy mice. Electronic supplemental information (ESI) available: Information on experimental procedure for fabrication of the nano-constructs, photoacoustic imaging, and immunogenic studies. See DOI: 10.1039/c3nr34124k

  19. Development of sensitive analytical technique by Laser-Induced Photoacoustic Spectroscopy

    International Nuclear Information System (INIS)

    A LIPAS (Laser-Induced Photoacoustic Spectroscopy) system has been developed for sensitive and remote analysis of neptunium which diffuse in low concentration range in reprocessing. The correction technique of background which disturbs sensitive analysis has been studied in visible to infrared range. And optical fiber system which is important for light operation has been also investigated for remote analysis in PUREX process. In visible range, the double-cell system, which has two photoacoustic cells in series, has been studied. The detection limit absorptivity was 4.47 x 10-5cm-1, this system has two orders higher sensitivity than that of absorption spectroscopy. This system was applied to measure photoacoustic spectrum of Pr(III), Nd(III), Er(III) and Np(V) in low concentration range in water. On photoacoustic spectrum of Np(V), the absorption peak at 614nm, which was not observed in low pH range, was identified. In near infrared range, analytical system which has parallel cells using alexandrite laser has been investigated. It was obtained that detection limit concentration of Np(V) is one order lower than that in visible range. The optical fiber system for application of LIPAS to reprocessing has been examined. The sensitivity of fiber-PAS is two times higher than that of absorption spectroscopy. However it is necessary to develop a beam operation system and a photoacoustic cell optimized for optical fiber system. (author)

  20. Photoacoustic imaging of breast tumor vascularization: a comparison with MRI and histopathology

    Science.gov (United States)

    Heijblom, Michelle; Piras, Daniele; van den Engh, Frank M.; Klaase, Joost M.; Brinkhuis, Mariël.; Steenbergen, Wiendelt; Manohar, Srirang

    2013-06-01

    Breast cancer is the most common form of cancer and the leading cause of cancer death among females. Early diagnosis improves the survival chances for the disease and that is why there is an ongoing search for improved methods for visualizing breast cancer. One of the hallmarks of breast cancer is the increase in tumor vascularization that is associated with angiogenesis: a crucial factor for survival of malignancies. Photoacoustic imaging can visualize the malignancyassociated increased hemoglobin concentration with optical contrast and ultrasound resolution, without the use of ionizing radiation or contrast agents and is therefore theoretically an ideal method for breast imaging. Previous clinical studies using the Twente Photoacoustic Mammoscope (PAM), which works in forward mode using a single wavelength (1064 nm), showed that malignancies can indeed be identified in the photoacoustic imaging volume as high contrast areas. However, the specific appearance of the malignancies led to questions about the contrast mechanism in relation to tumor vascularization. In this study, the photoacoustic lesion appearance obtained with an updated version of PAM is compared with the lesion appearance on Magnetic Resonance Imaging (MRI), both in general (19 patients) and on an individual basis (7 patients). Further, in 3 patients an extended histopathology protocol is being performed in which malignancies are stained for vascularity using an endothelial antibody: CD31. The correspondence between PAM and MRI and between PAM and histopathology makes it likely that the high photoacoustic contrast at 1064 nm is indeed largely the consequence of the increased tumor vascularization.

  1. [Quartz-enhanced photoacoustic spectroscopy trace gas detection system based on the Fabry-Perot demodulation].

    Science.gov (United States)

    Lin, Cheng; Zhu, Yong; Wei, Wei; Zhang, Jie; Tian, Li; Xu, Zu-Wen

    2013-05-01

    An all-optical quartz-enhanced photoacoustic spectroscopy system, based on the F-P demodulation, for trace gas detection in the open environment was proposed. In quartz-enhanced photoacoustic spectroscopy (QEPAS), an optical fiber Fabry-Perot method was used to replace the conventional electronic demodulation method. The photoacoustic signal was obtained by demodulating the variation of the Fabry-Perot cavity between the quartz tuning fork side and the fiber face. An experimental system was setup. The experiment for detection of water vapour in the open environment was carried on. A normalized noise equivalent absorption coefficient of 2.80 x 10(-7) cm(-1) x W x Hz(-1/2) was achieved. The result demonstrated that the sensitivity of the all-optical quartz-enhanced photoacoustic spectroscopy system is about 2.6 times higher than that of the conventional QEPAS system. The all-optical quartz-enhanced photoacoustic spectroscopy system is immune to electromagnetic interference, safe in flammable and explosive gas detection, suitable for high temperature and high humidity environments and realizable for long distance, multi-point and network sensing.

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

    Science.gov (United States)

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

    2011-03-01

    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.

  3. Effects of size and arrangement of virtual transducer on photoacoustic tomography

    Institute of Scientific and Technical Information of China (English)

    Wang Shao-Hua; Tao Chao; Liu Xiao-Jun

    2013-01-01

    In this paper,we investigate the effects of the relative size and arrangement of a virtual transducer on the image quality in limited-view photoacoustic tomography.A virtual transducer refers to the acoustic scatterers used to reflect photoacoustic waves and improve the images reconstructed from incomplete PA signal.Size and spatial arrangement determine the performance of the virtual transducer.In this study,the scatterers utilized as virtual transducers are arranged in different manners,such as on a straight line or on an arc line.We find that virtual transducers with a big distributing angle can provide more significant image improvement than with a small distributing angle,which is similar to the true transducers.We also change the size of virtual transducer and study its influence on image quality.It is found that the bigger scatterers provide better images than the smaller ones.Especially,when the size of scatterers is reduced to the wavelength of photoacoustic wave,the image quality observably decreases,owing to the strong diffraction effect.Thus,it is suggested that the size of the acoustical scatterers should be much larger than the photoacoustic wavelength.The simulations are conducted,and the results could be helpful for the application and further study of virtual transducer theory in limited-view photoacoustic tomography.

  4. Porphyrin Nanodroplets: Sub-micrometer Ultrasound and Photoacoustic Contrast Imaging Agents.

    Science.gov (United States)

    Paproski, Robert J; Forbrich, Alexander; Huynh, Elizabeth; Chen, Juan; Lewis, John D; Zheng, Gang; Zemp, Roger J

    2016-01-20

    A novel class of all-organic nanoscale porphyrin nanodroplet agents is presented which is suitable for multimodality ultrasound and photoacoustic molecular imaging. Previous multimodality photoacoustic-ultrasound agents are either not organic, or not yet demonstrated to exhibit enhanced accumulation in leaky tumor vasculature, perhaps because of large diameters. In the current study, porphyrin nanodroplets are created with a mean diameter of 185 nm which is small enough to exhibit the enhanced permeability and retention effect. Porphyrin within the nanodroplet shell has strong optical absorption at 705 nm with an estimated molar extinction coefficient >5 × 10(9) m(-1) cm(-1) , allowing both ultrasound and photoacoustic contrast in the same nanoparticle using all organic materials. The potential of nanodroplets is that they may be phase-changed into microbubbles using high pressure ultrasound, providing ultrasound contrast with single-bubble sensitivity. Multispectral photoacoustic imaging allows visualization of nanodroplets when injected intratumorally in an HT1080 tumor in the chorioallantoic membrane of a chicken embryo. Intravital microscopy imaging of Hep3-GFP and HT1080-GFP tumors in chicken embryos determines that nanodroplets accumulated throughout or at the periphery of tumors, suggesting that porphyrin nanodroplets may be useful for enhancing the visualization of tumors with ultrasound and/or photoacoustic imaging.

  5. Methodical study on plaque characterization using integrated vascular ultrasound, strain and spectroscopic photoacoustic imaging

    Science.gov (United States)

    Graf, Iulia M.; Su, Jimmy; Yeager, Doug; Amirian, James; Smalling, Richard; Emelianov, Stanislav

    2011-03-01

    Carotid atherosclerosis has been identified as a potential risk factor for cerebrovascular events, but information about its direct effect on the risk of recurrent stroke is limited due to incomplete diagnosis. The combination of vascular ultrasound, strain rate and spectroscopic photoacoustics could improve the timely diagnosis of plaque status and risk of rupturing. Current ultrasound techniques can noninvasively image the anatomy of carotid arteries. The spatio-temporal variation in displacement of different regions within the arterial wall can be derived from ultrasound radio frequency data; therefore an ultrasound based strain rate imaging modality can be used to reveal changes in arterial mechanical properties. Additionally, spectroscopic photoacoustic imaging can provide information on the optical absorption properties of arterial tissue and it can be used to identify the location of specific tissue components, such as lipid pools. An imaging technique combining ultrasound, strain rate and spectroscopic photoacoustics was tested on an excised atherosclerotic rabbit aorta. The ultrasound image illustrates inhomogeneities in arterial wall thickness, the strain rate indicates the arterial segment with reduced elasticity and the spectroscopic photoacoustic image illustrates the accumulation of lipids. The results demonstrated that ultrasound, strain rate and spectroscopic photoacoustic imaging are complementary. Thus the integration of the three imaging modalities advances the characterization of atherosclerotic plaques.

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

    Science.gov (United States)

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

    2013-12-01

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

  7. Trapping and dynamic manipulation of polystyrene beads mimicking circulating tumor cells using targeted magnetic/photoacoustic contrast agents

    Science.gov (United States)

    Wei, Chen-Wei; Xia, Jinjun; Hu, Xiaoge; Gao, Xiaohu; O’Donnell, Matthew

    2012-01-01

    Abstract. Results on magnetically trapping and manipulating micro-scale beads circulating in a flow field mimicking metastatic cancer cells in human peripheral vessels are presented. Composite contrast agents combining magneto-sensitive nanospheres and highly optical absorptive gold nanorods were conjugated to micro-scale polystyrene beads. To efficiently trap the targeted objects in a fast stream, a dual magnet system consisting of two flat magnets to magnetize (polarize) the contrast agent and an array of cone magnets producing a sharp gradient field to trap the magnetized contrast agent was designed and constructed. A water-ink solution with an optical absorption coefficient of 10  cm−1 was used to mimic the optical absorption of blood. Magnetomotive photoacoustic imaging helped visualize bead trapping, dynamic manipulation of trapped beads in a flow field, and the subtraction of stationary background signals insensitive to the magnetic field. The results show that trafficking micro-scale objects can be effectively trapped in a stream with a flow rate up to 12  ml/min and the background can be significantly (greater than 15 dB) suppressed. It makes the proposed method very promising for sensitive detection of rare circulating tumor cells within high flow vessels with a highly absorptive optical background. PMID:23223993

  8. Anatomical and metabolic small-animal whole-body imaging using ring-shaped confocal photoacoustic computed tomography

    Science.gov (United States)

    Xia, Jun; Chatni, Muhammad; Maslov, Konstantin; Wang, Lihong V.

    2013-03-01

    Due to the wide use of animals for human disease studies, small animal whole-body imaging plays an increasingly important role in biomedical research. Currently, none of the existing imaging modalities can provide both anatomical and glucose metabolic information, leading to higher costs of building dual-modality systems. Even with image coregistration, the spatial resolution of the metabolic imaging modality is not improved. We present a ring-shaped confocal photoacoustic computed tomography (RC-PACT) system that can provide both assessments in a single modality. Utilizing the novel design of confocal full-ring light delivery and ultrasound transducer array detection, RC-PACT provides full-view cross-sectional imaging with high spatial resolution. Scanning along the orthogonal direction provides three-dimensional imaging. While the mouse anatomy was imaged with endogenous hemoglobin contrast, the glucose metabolism was imaged with a near-infrared dye-labeled 2-deoxyglucose. Through mouse tumor models, we demonstrate that RC-PACT may be a paradigm shifting imaging method for preclinical research.

  9. Trapping and dynamic manipulation of polystyrene beads mimicking circulating tumor cells using targeted magnetic/photoacoustic contrast agents

    Science.gov (United States)

    Wei, Chen-Wei; Xia, Jinjun; Pelivanov, Ivan; Hu, Xiaoge; Gao, Xiaohu; O'Donnell, Matthew

    2012-10-01

    Results on magnetically trapping and manipulating micro-scale beads circulating in a flow field mimicking metastatic cancer cells in human peripheral vessels are presented. Composite contrast agents combining magneto-sensitive nanospheres and highly optical absorptive gold nanorods were conjugated to micro-scale polystyrene beads. To efficiently trap the targeted objects in a fast stream, a dual magnet system consisting of two flat magnets to magnetize (polarize) the contrast agent and an array of cone magnets producing a sharp gradient field to trap the magnetized contrast agent was designed and constructed. A water-ink solution with an optical absorption coefficient of 10 cm-1 was used to mimic the optical absorption of blood. Magnetomotive photoacoustic imaging helped visualize bead trapping, dynamic manipulation of trapped beads in a flow field, and the subtraction of stationary background signals insensitive to the magnetic field. The results show that trafficking micro-scale objects can be effectively trapped in a stream with a flow rate up to 12 ml/min and the background can be significantly (greater than 15 dB) suppressed. It makes the proposed method very promising for sensitive detection of rare circulating tumor cells within high flow vessels with a highly absorptive optical background.

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

    CERN Document Server

    Firouzi, Kamyar

    2015-01-01

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

  11. Nonlinear photoacoustic wavefront shaping (PAWS) for single speckle-grain optical focusing in scattering media

    CERN Document Server

    Lai, Puxiang; Tay, Jian Wei; Wang, Lihong V

    2014-01-01

    Non-invasively focusing light into strongly scattering media, such as biological tissue, is highly desirable but challenging. Recently, wavefront shaping technologies guided by ultrasonic encoding or photoacoustic sensing have been developed to address this limitation. So far, these methods provide only acoustic diffraction-limited optical focusing. Here, we introduce nonlinear photoacoustic wavefront shaping (PAWS), which achieves optical diffraction-limited (i.e. single-speckle-grain) focusing in scattering media. We develop an efficient dual-pulse excitation approach to generate strong nonlinear photoacoustic (PA) signals based on the Grueneisen memory effect. These nonlinear PA signals are used as feedback to guide iterative wavefront optimization. By maximizing the amplitude of the nonlinear PA signal, light is effectively focused to a single optical speckle grain. Experimental results demonstrate a clear optical focus on the scale of 5-7 micrometers, which is ~10 times smaller than the acoustic focus in...

  12. Self-normalized photoacoustic technique for thermo-optical characterization of samples mounted between transparent media

    Science.gov (United States)

    Balderas-López, J. A.; Díaz-Reyes, J.; Jaime-Fonseca, M. R.; Martínez-Pérez, L.; Pescador-Rojas, J. A.

    2016-03-01

    A self-normalized photoacoustic technique for thermo-optical characterization of materials, mounted between transparent media, is presented. It involves a complex ratio of photoacoustic signals in transmission and front configurations, taking the modulation frequency as the only variable. The analytical solutions for the corresponding 1D heat diffusion problems are analyzed to provide suitable methodologies for measuring the optical absorption coefficients and thermal diffusivity of such samples. This methodology was tested by measuring the optical absorption coefficient, at 660 nm, of methylene blue solutions at various concentrations and the thermal diffusivity of a black drawing ink sample. In addition, an approximated range of optical absorption coefficients, where this photoacoustic methodology is adequate, was established.

  13. Self-normalized photoacoustic technique for thermo-optical characterization of samples mounted between transparent media

    International Nuclear Information System (INIS)

    A self-normalized photoacoustic technique for thermo-optical characterization of materials, mounted between transparent media, is presented. It involves a complex ratio of photoacoustic signals in transmission and front configurations, taking the modulation frequency as the only variable. The analytical solutions for the corresponding 1D heat diffusion problems are analyzed to provide suitable methodologies for measuring the optical absorption coefficients and thermal diffusivity of such samples. This methodology was tested by measuring the optical absorption coefficient, at 660 nm, of methylene blue solutions at various concentrations and the thermal diffusivity of a black drawing ink sample. In addition, an approximated range of optical absorption coefficients, where this photoacoustic methodology is adequate, was established. (paper)

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

    Science.gov (United States)

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

    2015-03-01

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

  15. In vivo sub-femtoliter resolution photoacoustic microscopy with higher frame rates

    Science.gov (United States)

    Lee, Szu-Yu; Lai, Yu-Hung; Huang, Kai-Chih; Cheng, Yu-Hsiang; Tseng, Tzu-Fang; Sun, Chi-Kuang

    2015-10-01

    Microscopy based on non-fluorescent absorption dye staining is widely used in various fields of biomedicine for 400 years. Unlike its fluorescent counterpart, non-fluorescent absorption microscopy lacks proper methodologies to realize its in vivo applications with a sub-femtoliter 3D resolution. Regardless of the most advanced high-resolution photoacoustic microscopy, sub-femtoliter spatial resolution is still unattainable, and the imaging speed is relatively slow. In this paper, based on the two-photon photoacoustic mechanism, we demonstrated a in vivo label free laser-scanning photoacoustic imaging modality featuring high frame rates and sub-femtoliter 3D resolution simultaneously, which stands as a perfect solution to 3D high resolution non-fluorescent absorption microscopy. Furthermore, we first demonstrated in vivo label-free two-photon acoustic microscopy on the observation of non-fluorescent melanin distribution within mouse skin.

  16. Photoacoustic and spectroscopic characterization of the ablation process in orthogonal double-pulse configuration

    Energy Technology Data Exchange (ETDEWEB)

    Sobral, H; Sanchez-Ake, C; Sangines, R [Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-186, Mexico DF. 04360 (Mexico); Alvarez-Zauco, E [Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, (Mexico); Jimenez-Duran, K, E-mail: martin.sobral@ccadet.unam.mx [Unidad de Servicios de Apoyo a la Investigacion, Facultad de Quimica. Universidad Nacional Autonoma de Mexico (Mexico)

    2011-03-02

    A photoacoustic technique was used as an alternative method to monitor the crater volume and its role in the emission line intensification in double-pulse pre-ablation configuration. The crater volume was measured using confocal microscopy and correlated with the changes in the photoacoustic signal. Laser emission spectroscopy was used to characterize the emission enhancement as a function of the delay between lasers and the first pulse energy. Optimum delay was found to be in the microsecond timescale corresponding to the maximum of the crater volume and the largest change between the single- and the double-pulse photoacoustic signals. Only a slight intensification was detected with increasing first pulse energy above the first pulse ablation threshold; however, the crater volume did not significantly change and the possible involved mechanisms are discussed.

  17. Tumor homing indocyanine green encapsulated micelles for near infrared and photoacoustic imaging of tumors.

    Science.gov (United States)

    Uthaman, Saji; Bom, Joon-suk; Kim, Hyeon Sik; John, Johnson V; Bom, Hee-Seung; Kim, Seon-Jong; Min, Jung-Joon; Kim, Il; Park, In-Kyu

    2016-05-01

    Photoacoustic imaging (PAI) is an emerging analytical modality that is under intense preclinical development for the early diagnosis of various medical conditions, including cancer. However, the lack of specific tumor targeting by various contrast agents used in PAI obstructs its clinical applications. In this study, we developed indocyanine green (ICG)-encapsulated micelles specific for the CD 44 receptor and used in near infrared and photoacoustic imaging of tumors. ICG was hydrophobically modified prior to loading into hyaluronic acid (HA)-based micelles utilized for CD 44 based-targeting. We investigated the physicochemical characteristics of prepared HA only and ICG-encapsulated HA micelles (HA-ICG micelles). After intravenous injection of tumor-bearing mice, the bio-distribution and in vivo photoacoustic images of ICG-encapsulated HA micelles accumulating in tumors were also investigated. Our study further encourages the application of this HA-ICG-based nano-platform as a tumor-specific contrast agent for PAI.

  18. Bond-selective photoacoustic imaging by converting molecular vibration into acoustic waves.

    Science.gov (United States)

    Hui, Jie; Li, Rui; Phillips, Evan H; Goergen, Craig J; Sturek, Michael; Cheng, Ji-Xin

    2016-03-01

    The quantized vibration of chemical bonds provides a way of detecting specific molecules in a complex tissue environment. Unlike pure optical methods, for which imaging depth is limited to a few hundred micrometers by significant optical scattering, photoacoustic detection of vibrational absorption breaks through the optical diffusion limit by taking advantage of diffused photons and weak acoustic scattering. Key features of this method include both high scalability of imaging depth from a few millimeters to a few centimeters and chemical bond selectivity as a novel contrast mechanism for photoacoustic imaging. Its biomedical applications spans detection of white matter loss and regeneration, assessment of breast tumor margins, and diagnosis of vulnerable atherosclerotic plaques. This review provides an overview of the recent advances made in vibration-based photoacoustic imaging and various biomedical applications enabled by this new technology.

  19. Determination of Doping Density in GaAs Semiconductor by Wavelength-Dependent Photoacoustic Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Jongtae; Choi, Oklim; Boo, Doo Wan; Choi, Joonggill [Yonsei Univ., Seoul (Korea, Republic of)

    2014-03-15

    The wavelength dependence of the photoacoustic signal for n-type GaAs semiconductors in the region of the band-gap energies was investigated. The significant changes in the phase and amplitude of the photoacoustic signal near the band-gap absorption wavelengths were observed to occur when the Si-doping densities in GaAs were varied. Particularly, the first derivatives of the photoacoustic phase vs. wavelength graphs were evaluated and fitted with single Gaussian functions. The peak centers and the widths of the Gaussian curves clearly showed linear relationships with the log values of the Si-doping densities in n-type GaAs semiconductors. It is proposed that the wavelength-dependent PA spectroscopy can be used as a simple and nondestructive method for measuring the doping densities in bulk semiconductors.

  20. Optical-resolution photoacoustic microscopy by use of a multimode fiber

    CERN Document Server

    Papadopoulos, Ioannis N; Farahi, Salma; Huignard, Jean Pierre; Bossy, Emmanuel; Psaltis, Demetri; Moser, Christophe

    2013-01-01

    We demonstrate Optical-Resolution Photoacoustic Microscopy (OR-PAM), where the optical field is focused and scanned using Digital Phase Conjugation (DPC) through a multimode fiber. The focus is scanned across the field of view using digital means, and the acoustic signal induced is collected by a transducer. Optical-resolution photoacoustic images of a knot made by two absorptive wires are obtained and we report on resolution smaller than 1.5{\\mu}m across a 201{\\mu}m by 201{\\mu}m field of view. The use of a multimode optical fiber for the optical excitation part can pave the way for miniature endoscopes that can provide optical-resolution photoacoustic images at large optical depth.