Science.gov

Sample records for full-field laser-doppler imaging

  1. Real-time full field laser Doppler imaging

    NASA Astrophysics Data System (ADS)

    Leutenegger, Marcel; Harbi, Pascal; Thacher, Tyler; Raffoul, Wassim; Lasser, Theo

    2012-06-01

    We present a full field laser Doppler imaging instrument that enables real-time in vivo assessment of blood flow in dermal tissue and skin. The instrument monitors the blood perfusion in an area of about 50cm2 with 480 × 480 pixels per frame at a rate of 12-14 frames per second. Smaller frames can be monitored at much higher frame rates. We recorded the microcirculation in healthy skin before, during and after arterial occlusion. In initial clinical case studies, we imaged the microcirculation in burned skin and monitored the recovery of blood flow in a skin flap during reconstructive surgery indicating the high potential of LDI for clinical applications.

  2. Full-field high-speed laser Doppler imaging system for blood-flow measurements

    NASA Astrophysics Data System (ADS)

    Serov, Alexandre; Lasser, Theo

    2006-02-01

    We describe the design and performance of a new full-field high-speed laser Doppler imaging system developed for mapping and monitoring of blood flow in biological tissue. The total imaging time for 256x256 pixels region of interest is 1.2 seconds. An integrating CMOS image sensor is utilized to detect Doppler signal in a plurality of points simultaneously on the sample illuminated by a divergent laser beam of a uniform intensity profile. The integrating property of the detector improves the signal-to-noise ratio of the measurement, which results in high-quality flow-images provided by the system. The new technique is real-time, non-invasive and the instrument is easy to use. The wide range of applications is one of the major challenges for a future application of the imager. High-resolution high-speed laser Doppler perfusion imaging is a promising optical technique for diagnostic and assessing the treatment effect of the diseases such as e.g. atherosclerosis, psoriasis, diabetes, skin cancer, allergies, peripheral vascular diseases, skin irritancy and wound healing. We present some biological applications of the new imager and discuss the perspectives for the future implementations of the imager for clinical and physiological applications.

  3. Experimental comparison of perfusion imaging systems using multi-exposure laser speckle, single-exposure laser speckle, and full-field laser Doppler

    NASA Astrophysics Data System (ADS)

    Thompson, Oliver; Bakker, Jimmy; Kloeze, Carla; Hondebrink, Erwin; Steenbergen, Wiendelt

    2012-03-01

    A variety of laser Doppler and laser speckle contrast systems have been constructed by various groups and companies, for commercial sale and for research. All rely on the same physical phenomenon - the dynamic laser speckle pattern generated by illuminating tissue with coherent light - but differ in details of system design, operation and analysis. We present a comparison between measurements made with three systems: a multi-exposure laser speckle contrast system built at Industrial Research Ltd, a commercial single-exposure laser speckle contrast system developed by Perimed AB (PSI NR) and the full-field laser Doppler camera built by the University of Twente (TOPCam). We compare the response to changing flows of all three systems. The systems are found to produce similar results for a variety of in-vivo and in-vitro measurements. Multi-exposure speckle contrast shows some advantages in information gained and insensitivity to static speckle, at the cost of increased complexity and measurement time.

  4. Full-field linear and nonlinear measurements using Continuous-Scan Laser Doppler Vibrometry and high speed Three-Dimensional Digital Image Correlation

    NASA Astrophysics Data System (ADS)

    Ehrhardt, David A.; Allen, Matthew S.; Yang, Shifei; Beberniss, Timothy J.

    2017-03-01

    Spatially detailed dynamic measurements of thin, lightweight structures can be difficult to obtain due to the structure's low mass and complicated deformations under certain loading conditions. If traditional contacting sensors, such as accelerometers, strain gauges, displacement transducers, etc., are used, the total number of measurement locations available is limited by the weight added and the effect each sensor has on the local stiffness of the contact area. Other non-contacting sensors, such as Laser Doppler Vibrometers (LDV), laser triangulation sensors, proximity sensors, etc., do not affect the dynamics of a structure, but are limited to single point measurements. In contrast, a few recently developed non-contacting measurement techniques have been shown to be capable of simultaneously measuring the response over a wide measurement field. Two techniques are considered here: Continuous-Scan Laser Doppler Vibrometry (CSLDV) and high speed Three-Dimensional Digital Image Correlation (3D DIC). With the use of these techniques, unprecedented measurement resolution can be achieved. In this work, the linear and nonlinear deformations of a clamped, nominally flat beam and plate under steady state sinusoidal loading will be measured using both techniques. In order to assess their relative merits, the linear natural frequencies, mode shapes, and nonlinear deformation shapes measured with each method are compared. Both measurement systems give comparable results in many cases, although 3D DIC is more accurate for spatially complex deformations at large amplitudes and CSLDV is more accurate at low amplitudes and when the spatial deformation pattern is simpler.

  5. Laser Doppler Velocimetry and full-field soot volume fraction

    NASA Technical Reports Server (NTRS)

    Greenberg, Paul S.

    1995-01-01

    Since its introduction in the mid-sixties, Laser Doppler Velocimetry (LDV) has become one of the most widely used methods for the measurement of flows. Its remote and essentially non-intrusive nature provides an invaluable tool for a variety of difficult measurement situations which would be otherwise inaccessible. The high spatial resolution and rapid temporal response afforded by this technique are well suited to the determination of spatial and temporal details of flow fields, as well as characterization of turbulence. Advances in the understanding of the properties of LDV signals, accompanied by technological advances in coherent laser sources, detectors of high sensitivity and low noise, optical fabrication techniques and high-speed digital signal processing architectures have resulted in systems of increased accuracy and flexibility. As will be shown, recent progress in solid-state lasers and photo-detectors has been beneficial insofar as the compatibility of this method with the unique and severe constraints inherent in microgravity combustion science experiments.

  6. Influence of tissue movements on laser Doppler perfusion imaging

    NASA Astrophysics Data System (ADS)

    Karlsson, Daniel M.; Larsson, Marcus; Stroemberg, Tomas; Wardell, Karin

    2002-05-01

    The microvascular perfusion can be measured using laser Doppler blood flowmetry (LDF), a technique sensitive to the concentration of moving blood cells and their velocity. However, movements of the tissue itself can cause artifacts in the perfusion readings. In a clinical situation, these movement induced artifacts may arise from patient movements or from movements of internal organs e.g. the intestines or the beating heart. Therefore, we have studied how a well-controlled tissue movement affects the LDF signals during different flow conditions and for different surface structures. Tissue perfusion was recorded non-touch in one point using a laser Doppler perfusion imager. During the measurements the object was placed on a shaker that generated the movement (both horizontal and vertical). Measurements were carried out both on DELRIN (polyacetal plastic) and the fingertip, for a wide range of velocities (0-3 cm/s). The influence of the microvascular perfusion was evaluated by occluding the brachial artery as well as blood emptying the finger and by using a flow model. The LDF signals were correlated to the movement. In vivo measurements showed that velocities above 0.8 cm/s gave a significant contribution to the perfusion signal. Corresponding velocities for the DELRIN piece were higher (1.4 - 2.6 cm/s), and dependent on the surface structures and reflecting properties. By reducing the amount of specular reflection the movement influence was substantially lowered.

  7. Comparison of laser Doppler and laser speckle contrast imaging using a concurrent processing system

    NASA Astrophysics Data System (ADS)

    Sun, Shen; Hayes-Gill, Barrie R.; He, Diwei; Zhu, Yiqun; Huynh, Nam T.; Morgan, Stephen P.

    2016-08-01

    Full field laser Doppler imaging (LDI) and single exposure laser speckle contrast imaging (LSCI) are directly compared using a novel instrument which can concurrently image blood flow using both LDI and LSCI signal processing. Incorporating a commercial CMOS camera chip and a field programmable gate array (FPGA) the flow images of LDI and the contrast maps of LSCI are simultaneously processed by utilizing the same detected optical signals. The comparison was carried out by imaging a rotating diffuser. LDI has a linear response to the velocity. In contrast, LSCI is exposure time dependent and does not provide a linear response in the presence of static speckle. It is also demonstrated that the relationship between LDI and LSCI can be related through a power law which depends on the exposure time of LSCI.

  8. Full-field, nonscanning, optical imaging for perfusion indication

    NASA Astrophysics Data System (ADS)

    Chou, Nee-Yin; Winchester, L. W., Jr.; Naramore, W. J.; Alley, M. S.; Lesnick, A. J.

    2010-04-01

    Laser speckle imaging (LSI) has been gaining popularity for the past few years. Like other optical imaging modalities such as optical coherence tomography (OCT), orthogonal polarization spectroscopy (OPS), and laser Doppler imaging (LDI), LSI utilizes nonionizing radiation. In LSI, blood flow velocity is obtained by analyzing, temporally or spatially, laser speckle (LS) patterns generated when an expanded laser beam illuminates the tissue. The advantages of LSI are that it is fast, does not require scanning, and provides full-field LS images to extract realtime, quantitative hemodynamic information of subtle changes in the tissue vasculature. For medical applications, LSI has been used for obtaining blood velocities in human retina, skin flaps, wounds, and cerebral and sublingual areas. When coupled with optical fibers, LSI can be used for endoscopic measurements for a variety of applications. This paper describes the application of LSI in retinal, sublingual, and skin flap measurements. Evaluation of retinal hemodynamics provides very important diagnostic information, since the human retina offers direct optical access to both the central nervous system (CNS) and afferent and efferent CNS vasculature. The performance of an LSI-based fundus imager for measuring retinal hemodynamics is presented. Sublingual microcirculation may have utility for sepsis indication, since inherent in organ injury caused by sepsis is a profound change in microvascular hemodynamics. Sublingual measurement results using an LSI scope are reported. A wound imager for imaging LS patterns of wounds and skin flaps is described, and results are presented.

  9. Novel Applications of Laser Doppler Vibration Measurements to Medical Imaging

    NASA Astrophysics Data System (ADS)

    Tabatabai, Habib; Oliver, David E.; Rohrbaugh, John W.; Papadopoulos, Christopher

    2013-06-01

    Laser Doppler Vibrometry (LDV) has been widely used in engineering applications involving non-contact vibration and sound measurements. This technique has also been used in some biomedical applications including hearing research. The detectable frequencies are in the range of near-DC to 1 GHz or higher. This paper reviews applications of LDV in biomedical engineering and proposes new medical imaging applications based on measuring surface vibrations of tissues and organs. Tests were conducted on human skin using single point and scanning laser vibrometers. These tests suggest that skin vibrations due to the forcing excitation from the heart can be used in imaging of blood flow. The results of these tests illustrate the potential of such vibration measurements in a variety of diagnostic medical imaging applications including blood flow/restrictions, real-time monitoring of blood pressure variations, wound healing, muscle movements, etc. The fact that the measurements can be conducted remotely (non-contact) is an important benefit that adds to the promise of this approach.

  10. Novel Applications of Laser Doppler Vibration Measurements to Medical Imaging.

    PubMed

    Tabatabai, Habib; Oliver, David E; Rohrbaugh, John W; Papadopoulos, Christopher

    2013-01-01

    Laser Doppler Vibrometry (LDV) has been widely used in engineering applications involving non-contact vibration and sound measurements. This technique has also been used in some biomedical applications including hearing research. The detectable frequencies are in the range of near-DC to 1 GHz or higher. This paper reviews applications of LDV in biomedical engineering and proposes new medical imaging applications based on measuring surface vibrations of tissues and organs. Tests were conducted on human skin using single point and scanning laser vibrometers. These tests suggest that skin vibrations due to the forcing excitation from the heart can be used in imaging of blood flow. The results of these tests illustrate the potential of such vibration measurements in a variety of diagnostic medical imaging applications including blood flow/restrictions, real-time monitoring of blood pressure variations, wound healing, muscle movements, etc. The fact that the measurements can be conducted remotely (non-contact) is an important benefit that adds to the promise of this approach.

  11. Laser-Doppler Imaging in the Detection of Peripheral Neuropathy

    PubMed Central

    Illigens, Ben M.W.; Siepmann, Timo; Roofeh, Joe; Gibbons, Christopher H.

    2013-01-01

    Small fiber neuropathy is common in a number of systemic diseases and is often challenging to diagnose. Laser-Doppler Imaging (LDI) is a test of small fiber neurovascular function that can quantify the integrity of the vasomotor C-fiber mediated axon-reflex, but no standardized method of analysis exists. We developed a novel LDI analysis technique and tested it in a human model of small fiber neuropathy. Eighteen healthy subjects (age 24±3 years) underwent LDI testing to assess the axon-mediated flare area in response to 10% acetylcholine iontophoresis. LDI measurements were taken before and longitudinally after a 48-hour application of 0.1% capsaicin (to cause a transient small fiber neuropathy) on the skin of the thigh; placebo cream was placed on the contralateral thigh as a control. We compared our new LDI image analysis technique to two previously published methods. The new LDI analysis technique was the only method to show a consistent difference in axon-reflex area between capsaicin treated and placebo treated skin on all testing days (p<0.05) with maximum attenuation of the flare area immediately post-application (438 ±298 mm2 vs. 824 ±375 mm2, p<0.05). In conclusion, this study demonstrates that our novel flare area method for LDI analysis can detect neurovascular dysfunction in a model of small fiber neuropathy, is an improvement over existing methods, and may supplement clinical assessment of small fiber neuropathy. PMID:23850386

  12. Laser Doppler imaging in the detection of peripheral neuropathy.

    PubMed

    Illigens, Ben M W; Siepmann, Timo; Roofeh, Joseph; Gibbons, Christopher H

    2013-10-01

    Small fiber neuropathy is common in a number of systemic diseases and is often challenging to diagnose. Laser Doppler imaging (LDI) is a test of small fiber neurovascular function that can quantify the integrity of the vasomotor C-fiber mediated axon-reflex, but no standardized method of analysis exists. We developed a novel LDI analysis technique and tested it in a human model of small fiber neuropathy. Eighteen healthy subjects (age 24 ± 3 years) underwent LDI testing to assess the axon-mediated flare area in response to 10% acetylcholine iontophoresis. LDI measurements were taken before and longitudinally after a 48-hour application of 0.1% capsaicin (to cause a transient small fiber neuropathy) on the skin of the thigh; placebo cream was placed on the contralateral thigh as a control. We compared our new LDI image analysis technique to two previously published methods. The new LDI analysis technique was the only method to show a consistent difference in axon-reflex area between capsaicin treated and placebo treated skin on all testing days (p<0.05) with maximum attenuation of the flare area immediately post-application (438 ± 298 mm(2) vs. 824 ± 375 mm(2), p<0.05). In conclusion, this study demonstrates that our novel flare area method for LDI analysis can detect neurovascular dysfunction in a model of small fiber neuropathy, is an improvement over existing methods, and may supplement clinical assessment of small fiber neuropathy.

  13. Seismic imaging in laboratory trough laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Brito, Daniel; Poydenot, Valier; Garambois, Stéphane; Diaz, Julien; Bordes, Clarisse; Rolando, Jean-Paul

    2016-04-01

    Mimic near-surface seismic field measurements at a small scale, in the laboratory, under a well-controlled environment, may lead to a better understanding of wave propagation in complex media such as in geological materials. Laboratory experiments can help in particular to constrain and refine theoretical and numerical modelling of physical phenomena occurring during seismic propagation, in order to make a better use of the complete set of measurements recorded in the field. We have developed a laser Doppler vibrometer (laser interferometry) platform designed to measure non-contact seismic displacements (or velocities) of a surface. This technology enables to measure displacements as small as a tenth of a nanometer on a wide range of frequencies, from a few tenths to a few megahertz. Our experimental set-up is particularly suited to provide high-density spatial and temporal records of displacements on the edge of any vibrating material. We will show in particular a study of MHz wave propagation (excited by piezoelectric transducers) in cylindrical cores of typical diameter size around 10 cm. The laser vibrometer measurements will be first validated in homogeneous materials cylinders by comparing the measurements to a direct numerical simulation. Special attention will be given to the comparison of experimental versus numerical amplitudes of displacements. In a second step, we will conduct the same type of study through heterogeneous carbonate cores, possibly fractured. Tomographic images of velocity in 2D slices of the carbonate core will be derived based upon on the time of first arrival. Preliminary attempts of tomographic attenuation maps will also be presented based on the amplitudes of first arrivals. Experimental records will be confronted to direct numerical simulations and tomographic images will be compared to x-ray scanner imaging of the cylindrical cores.

  14. Burn imaging with a whole field laser Doppler perfusion imager based on a CMOS imaging array.

    PubMed

    van Herpt, Heleen; Draijer, Matthijs; Hondebrink, Erwin; Nieuwenhuis, Marianne; Beerthuizen, Gerard; van Leeuwen, Ton; Steenbergen, Wiendelt

    2010-05-01

    Laser Doppler perfusion imaging (LDPI) has been proven to be a useful tool in predicting the burn wound outcome in an early stage. A major disadvantage of scanning beam LDPI devices is their slow scanning speed, leading to patient discomfort and imaging artifacts. We have developed the Twente Optical Perfusion Camera (TOPCam), a whole field laser Doppler perfusion imager based on a CMOS imaging array, which is two orders of magnitude faster than scanning beam LDPI systems. In this paper the first clinical results of the TOPCam in the setting of a burn centre are presented. The paper shows perfusion images of burns of various degrees. While our system encounters problems caused by blisters, tissue necrosis, surface reflection and curvature in a manner similar to scanning beam imagers, it poses a clear advantage in terms of procedure time. Image quality in terms of dynamic range and resolution appears to be sufficient for burn diagnosis. Hence, we made important steps in overcoming the limitations of LDPI in burn diagnosis imposed by the measurement speed. Copyright 2009 Elsevier Ltd and ISBI. All rights reserved.

  15. Characteristics of laser Doppler perfusion imaging in vitro and in vivo.

    PubMed

    Kernick, D P; Shore, A C

    2000-05-01

    Traditional laser Doppler flowmetry (LDF) employs continuous recording of perfusion at one point with time. In order to eliminate the large spatial and temporal fluctuations that occur in the microcirculation, laser Doppler perfusion imaging (LDI) integrates flow readings over a large area. This paper describes a number of experiments to identify some of the characteristics of the LDI, its relationship to flow and no-flow conditions and to compare it with LDF. We undertook experiments to establish the effect of scanner head height, avascular skin thickness and haematocrit on LDI output. We also investigated the contribution of the biological zero signal (the signal obtained from skin when flow is arrested) to the LDI output. LDI output increased with scanner height in vitro and in vivo. Increasing avascular skin thickness reduced the LDI output although linear output characteristics with flow were maintained over the flow range studied. Increasing the haematocrit resulted in a loss of linearity of output with flow at lower velocities. The biological zero signal contributes a similar proportion of the output signal in LDF and LDI. We have presented a series of experiments that will contribute to the understanding of the characteristics of laser Doppler perfusion imaging, its comparison to laser Doppler flowmetry and its relationship to flow and no flow situations. However, our experiments were restricted to one machine, and may not necessarily be applicable to other instruments.

  16. Monitoring microcirculatory changes in the deep inferior epigastric artery perforator flap with laser Doppler perfusion imaging.

    PubMed

    Tindholdt, Tyge Tind; Saidian, Said; Pripp, Are Hugo; Tønseth, Kim Alexander

    2011-08-01

    Microcirculatory changes were monitored in 20 deep inferior epigastric artery perforator (DIEAP) flaps during unilateral breast reconstruction until the seventh postoperative day using laser Doppler perfusion imaging. Measurements were recorded according to the zonal classification by Scheflan and Dinner. The cutaneous territory zone IV was discarded during insetting due to marginal circulation. The highest perfusion levels were found the first postoperative day for both zones I and III. Postoperative perfusion values were significantly higher for these zones compared with zone II. Immediately after revascularization, zone I was significantly better perfused than both II and III. However, the perfusion in zone III stabilized at the level of zone I in the postoperative phase. Evaluating microcirculatory changes in the DIEAP flap with laser Doppler perfusion imaging showed that zones I and III have higher perfusion levels than zone II in the postoperative phase.

  17. High-speed laser Doppler perfusion imaging using an integrating CMOS image sensor.

    PubMed

    Serov, Alexandre; Lasser, Theo

    2005-08-22

    This paper describes the design and the performance of a new high-speed laser Doppler imaging system for monitoring blood flow over an area of tissue. The new imager delivers high-resolution flow images (256x256 pixels) every 2 to 10 seconds, depending on the number of points in the acquired time-domain signal (32-512 points). This new imaging modality utilizes a digital integrating CMOS image sensor to detect Doppler signals in a plurality of points over the area illuminated by a divergent laser beam of a uniform intensity profile. The integrating property of the detector improves the signal-to-noise ratio of the measurements, which results in high-quality flow images. We made a series of measurements in vitro to test the performance of the system in terms of bandwidth, SNR, etc. Subsequently we give some examples of flow-related images measured on human skin, thus demonstrating the performance of the imager in vivo. The perspectives for future implementations of the imager for clinical and physiological applications are discussed.

  18. Laser Doppler perfusion imaging of skin blood flow using red and near-infrared sources.

    PubMed

    Abbot, N C; Ferrell, W R; Lockhart, J C; Lowe, J G

    1996-12-01

    At present, scanning laser Doppler imaging uses a 633-nm helium-neon laser (RED) as the only light source, but this restricts its ability to measure blood flow (i) at darkly pigmented skin and (ii) from deeper or subdermal structures. Because near-infrared (NIR) light is known to penetrate deeper into tissue and to be less absorbed than RED, two imagers were adapted to include a NIR laser diode source (one of 830 nm for UK studies; one of 780 nm for leprosy field trials) in parallel with the existing RED source. In human hands representing a range of skin pigmentations, RED scans were unobtainable at the darkest areas of skin, but intact NIR scans could be collected in all cases. In experiments at the rat knee and the dorsal human hand, NIR and RED values were similar on normal skin. Over underlying vessels, however, NIR values greatly exceeded RED values, an effect abolished by occlusion. Similarly, in patients with leprosy and in healthy controls in Spain, fingerpulp NIR values exceeded RED values to the greatest degree when thermoregulatory flow was highest, i.e., when the deeper-lying arteriovenous anastomoses were open. Over areas of experimental inflammation, NIR gave higher values and also exhibited a greater degree of spatial heterogeneity than RED. We conclude that some current limitations of laser Doppler imaging technology can be overcome by the use of NIR laser diode sources.

  19. Laser Doppler blood flow complementary metal oxide semiconductor imaging sensor with analog on-chip processing

    SciTech Connect

    Gu Quan; Hayes-Gill, Barrie R.; Morgan, Stephen P

    2008-04-20

    A 4x4 pixel array with analog on-chip processing has been fabricated within a 0.35 {mu}m complementary metal oxide semiconductor process as a prototype sensor for laser Doppler blood flow imaging. At each pixel the bandpass and frequency weighted filters necessary for processing laser Doppler blood flow signals have been designed and fabricated. Because of the space constraints of implementing an accurate {omega}{sup 0.5} filter at the pixel level, this has been approximated using the ''roll off'' of a high-pass filter with a cutoff frequency set at 10 kHz. The sensor has been characterized using a modulated laser source. Fixed pattern noise is present that is demonstrated to be repeatable across the array and can be calibrated. Preliminary blood flow results on a finger before and after occlusion demonstrate that the sensor array provides the potential for a system that can be scaled to a larger number of pixels for blood flow imaging.

  20. Laser Doppler blood flow complementary metal oxide semiconductor imaging sensor with analog on-chip processing.

    PubMed

    Gu, Quan; Hayes-Gill, Barrie R; Morgan, Stephen P

    2008-04-20

    A 4 x 4 pixel array with analog on-chip processing has been fabricated within a 0.35 mum complementary metal oxide semiconductor process as a prototype sensor for laser Doppler blood flow imaging. At each pixel the bandpass and frequency weighted filters necessary for processing laser Doppler blood flow signals have been designed and fabricated. Because of the space constraints of implementing an accurate omega(0.5) filter at the pixel level, this has been approximated using the "roll off" of a high-pass filter with a cutoff frequency set at 10 kHz. The sensor has been characterized using a modulated laser source. Fixed pattern noise is present that is demonstrated to be repeatable across the array and can be calibrated. Preliminary blood flow results on a finger before and after occlusion demonstrate that the sensor array provides the potential for a system that can be scaled to a larger number of pixels for blood flow imaging.

  1. Laser Doppler Blood Flow Imaging Using a CMOS Imaging Sensor with On-Chip Signal Processing

    PubMed Central

    He, Diwei; Nguyen, Hoang C.; Hayes-Gill, Barrie R.; Zhu, Yiqun; Crowe, John A.; Gill, Cally; Clough, Geraldine F.; Morgan, Stephen P.

    2013-01-01

    The first fully integrated 2D CMOS imaging sensor with on-chip signal processing for applications in laser Doppler blood flow (LDBF) imaging has been designed and tested. To obtain a space efficient design over 64 × 64 pixels means that standard processing electronics used off-chip cannot be implemented. Therefore the analog signal processing at each pixel is a tailored design for LDBF signals with balanced optimization for signal-to-noise ratio and silicon area. This custom made sensor offers key advantages over conventional sensors, viz. the analog signal processing at the pixel level carries out signal normalization; the AC amplification in combination with an anti-aliasing filter allows analog-to-digital conversion with a low number of bits; low resource implementation of the digital processor enables on-chip processing and the data bottleneck that exists between the detector and processing electronics has been overcome. The sensor demonstrates good agreement with simulation at each design stage. The measured optical performance of the sensor is demonstrated using modulated light signals and in vivo blood flow experiments. Images showing blood flow changes with arterial occlusion and an inflammatory response to a histamine skin-prick demonstrate that the sensor array is capable of detecting blood flow signals from tissue. PMID:24051525

  2. Laser doppler blood flow imaging using a CMOS imaging sensor with on-chip signal processing.

    PubMed

    He, Diwei; Nguyen, Hoang C; Hayes-Gill, Barrie R; Zhu, Yiqun; Crowe, John A; Gill, Cally; Clough, Geraldine F; Morgan, Stephen P

    2013-09-18

    The first fully integrated 2D CMOS imaging sensor with on-chip signal processing for applications in laser Doppler blood flow (LDBF) imaging has been designed and tested. To obtain a space efficient design over 64 × 64 pixels means that standard processing electronics used off-chip cannot be implemented. Therefore the analog signal processing at each pixel is a tailored design for LDBF signals with balanced optimization for signal-to-noise ratio and silicon area. This custom made sensor offers key advantages over conventional sensors, viz. the analog signal processing at the pixel level carries out signal normalization; the AC amplification in combination with an anti-aliasing filter allows analog-to-digital conversion with a low number of bits; low resource implementation of the digital processor enables on-chip processing and the data bottleneck that exists between the detector and processing electronics has been overcome. The sensor demonstrates good agreement with simulation at each design stage. The measured optical performance of the sensor is demonstrated using modulated light signals and in vivo blood flow experiments. Images showing blood flow changes with arterial occlusion and an inflammatory response to a histamine skin-prick demonstrate that the sensor array is capable of detecting blood flow signals from tissue.

  3. Comparison of scanning beam and whole field laser Doppler perfusion imaging

    NASA Astrophysics Data System (ADS)

    Steenbergen, Wiendelt; Hondebrink, Erwin; Van Leeuwen, Ton G.; Draijer, Matthijs J.

    2010-02-01

    Currently, laser perfusion imaging (LDPI) is undergoing a technology shift from scanning beam perfusion imagers to whole field systems. The latter can be subdivided in laser Doppler methods systems based on high speed CMOS cameras, and laser speckle contrast analysis (LASCA) technologies using slow imaging arrays, mostly CCD-based. In scanning beam systems, a collimated laser beam scans the tissue with diffusely back reflected light being captured with a single detector. In whole field systems a large tissue area is illuminated, and the reflected light is imaged onto an array and captured at once. Unlike scanning beam systems, both whole field methods enable perfusion imaging at video rate. In this study we experimentally compare the scanning beam LDPI principle with whole field LDPI, using Intralipid phantoms. For the tissue phantoms, the Monte Carlo simulation technique will be used as a reference. From measurements on Intralipid phantoms compared to Monte Carlo, we conclude that in whole field LDPI the flux image, representing the first order moment of the power spectrum of photocurrent fluctuations is much closer related to real perfusion than for scanning beam systems. This difference can be explained in terms of the different behaviour of dynamic speckle patterns generated in both methods, in response to varying tissue optical properties.

  4. [Meta-analysis on the diagnostic value of laser Doppler imaging for burn depth].

    PubMed

    Huang, Y; Qiu, L; Mei, A L; Li, J X

    2017-05-20

    Objective: To evaluate the value of laser Doppler imaging (LDI) in diagnosing deep or superficial partial-thickness burn wound with meta-analysis. Methods: Databases including PubMed, Cochrane Library were searched using key words " burn, burns, burn depth, laser Doppler imaging, laser Doppler perfusion imaging, LDI, LDPI" , and Chinese Journals Full-text Database, Wanfang Database, VIP Database were searched using Chinese key words ",,,," to obtain the published trials of LDI in diagnosing deep or superficial partial-thickness burn wound from the establishment of each database to October 2015. The risk of bias and applicability concerns of the included studies were evaluated by Quality Assessment of Diagnostic Accuracy Studies-2. Data were processed with Meta-DiSc 1.4 statistical software. The heterogeneity among the included studies was evaluated. The pooled estimates of LDI in diagnosing deep or superficial partial-thickness burn wound in the included studies, including sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, as well as the area under the curve of summary receiver operating characteristic and index of Q(*) were calculated. The stability of results of the overall pooled estimates of the included studies was validated by sensitivity analysis. The sources of heterogeneity among the included studies were sought through subgroup analysis. The publication bias caused by the results of the included studies was evaluated by drawing the Deek's funnel plot. Results: A total of 5 articles conforming to the inclusion criteria, involving 138 patients and 179 burn wounds, were included. One of the included studies had low risk of bias, while the other 4 studies had high/unclear risk of bias. In applicability concern aspect, one of the included studies had high/unclear concerns regarding applicability, while the other 4 studies had low concerns regarding applicability. There was no heterogeneity caused by threshold

  5. Application of a new laser Doppler imaging system in planning and monitoring of surgical flaps

    NASA Astrophysics Data System (ADS)

    Schlosser, Stefan; Wirth, Raphael; Plock, Jan A.; Serov, Alexandre; Banic, Andrej; Erni, Dominique

    2010-05-01

    There is a demand for technologies able to assess the perfusion of surgical flaps quantitatively and reliably to avoid ischemic complications. The aim of this study is to test a new high-speed high-definition laser Doppler imaging (LDI) system (FluxEXPLORER, Microvascular Imaging, Lausanne, Switzerland) in terms of preoperative mapping of the vascular supply (perforator vessels) and postoperative flow monitoring. The FluxEXPLORER performs perfusion mapping of an area 9×9 cm with a resolution of 256×256 pixels within 6 s in high-definition imaging mode. The sensitivity and predictability to localize perforators is expressed by the coincidence of preoperatively assessed LDI high flow spots with intraoperatively verified perforators in nine patients. 18 free flaps are monitored before, during, and after total ischemia. 63% of all verified perforators correspond to a high flow spot, and 38% of all high flow spots correspond to a verified perforator (positive predictive value). All perfused flaps reveal a value of above 221 perfusion units (PUs), and all values obtained in the ischemic flaps are beneath 187 PU. In summary, we conclude that the present LDI system can serve as a reliable, fast, and easy-to-handle tool to detect ischemia in free flaps, whereas perforator vessels cannot be detected appropriately.

  6. Application of a new laser Doppler imaging system in planning and monitoring of surgical flaps.

    PubMed

    Schlosser, Stefan; Wirth, Raphael; Plock, Jan A; Serov, Alexandre; Banic, Andrej; Erni, Dominique

    2010-01-01

    There is a demand for technologies able to assess the perfusion of surgical flaps quantitatively and reliably to avoid ischemic complications. The aim of this study is to test a new high-speed high-definition laser Doppler imaging (LDI) system (FluxEXPLORER, Microvascular Imaging, Lausanne, Switzerland) in terms of preoperative mapping of the vascular supply (perforator vessels) and postoperative flow monitoring. The FluxEXPLORER performs perfusion mapping of an area 9 x 9 cm with a resolution of 256 x 256 pixels within 6 s in high-definition imaging mode. The sensitivity and predictability to localize perforators is expressed by the coincidence of preoperatively assessed LDI high flow spots with intraoperatively verified perforators in nine patients. 18 free flaps are monitored before, during, and after total ischemia. 63% of all verified perforators correspond to a high flow spot, and 38% of all high flow spots correspond to a verified perforator (positive predictive value). All perfused flaps reveal a value of above 221 perfusion units (PUs), and all values obtained in the ischemic flaps are beneath 187 PU. In summary, we conclude that the present LDI system can serve as a reliable, fast, and easy-to-handle tool to detect ischemia in free flaps, whereas perforator vessels cannot be detected appropriately.

  7. The influence of burn wound dressings on laser Doppler imaging assessment of a standardized cutaneous injury model.

    PubMed

    Holland, Andrew J A; Ward, Diane; Farrell, Bree

    2007-01-01

    The objective of this study was to determine the impact of burn wound dressings on Laser Doppler imaging assessment of a cutaneous injury model. A healthy volunteer was subjected to a standardized mechanical stimulus to produce a triple response. This was scanned under ideal conditions using the moor LDI2 before and after application of the following dressings: GLAD Wrap , Bactigras, Hypafix, Omiderm, DuoDERM, Acticoat, and Avance. The triple response was readily and consistently detected on the LDI blood flow image. Glad Wrap, Bactigras, Hypafix, Omiderm, and DuoDERM all had minimal adverse impact on the Laser Doppler blood flow image. Acticoat and Avance prevented detection of the triple response. In addition, there was a false-positive blood flow image with the Acticoat dressing positioned with the silver colored surface uppermost. Dressings transparent to the near infrared spectrum allowed detection of a standardized cutaneous injury model under ideal conditions. Laser Doppler imaging might therefore be used to assess a burn wound without removal of such a dressing. This would have implications for the selection and use of dressings in the treatment of burn patients, especially in an ambulatory care setting.

  8. Full-field digital image correlation with Kriging regression

    NASA Astrophysics Data System (ADS)

    Wang, Dezhi; DiazDelaO, F. A.; Wang, Weizhuo; Mottershead, John E.

    2015-04-01

    A full-field Digital Image Correlation (DIC) method with integrated Kriging regression is presented in this article. The displacement field is formulated as a best linear unbiased model that includes the correlations between all the locations in the Region of Interest (RoI). A global error factor is employed to extend conventional Kriging interpolation to quantify displacement errors of the control points. An updating strategy for the self-adaptive control grid is developed on the basis of the Mean Squared Error (MSE) determined from the Kriging model. Kriging DIC is shown to outperform several other full-field DIC methods when using open-access experimental data. Numerical examples are used to demonstrate the robustness of Kriging DIC to different choices of initial control points and to speckle pattern variability. Finally Kriging DIC is tested on an experimental example.

  9. 32×32 pixel array complementary metal-oxide semiconductor imaging sensor for laser Doppler blood-flow measurement

    NASA Astrophysics Data System (ADS)

    He, Diwei; Kongsavatsak, Chayut; Hayes-Gill, Barrie R.; Crowe, John A.; Morgan, Stephen P.

    2011-05-01

    A 32×32 pixel array has been fabricated in a 0.35-μm complementary metal-oxide semiconductor process with the aim of producing two-dimensional laser Doppler blood-flow images. In the design, each pixel contains five basic elements: a photodiode, a front-end consisting of a current to voltage converter, voltage amplifier, antialiasing filter, and buffer. The analog design is optimized for the detection of laser Doppler blood-flow signals and thus offers advantages over conventional sensors. The analog outputs are passed through an on-chip multiplexer and digitized by an external analog-to-digital converter. The sensor has been fully characterized electrically and optically using modulated electrical and optical signals. A calibration process for fixed pattern noise reduces the standard deviation of the ac gain by a factor of 2. The imaging response is tested by imaging a vibrating test structure and a rotating diffuser. Blood-flow measurements on a finger before and after occlusion demonstrate that the sensor array is capable of detecting blood-flow signals from tissue. The knowledge gained from the characterization of the design can be used to develop a fully integrated laser Doppler blood-flow sensors with a higher number of pixels.

  10. Diagnostic accuracy of laser Doppler imaging in burn depth assessment: Systematic review and meta-analysis.

    PubMed

    Shin, Jin Yong; Yi, Hyung Suk

    2016-11-01

    Accurate assessment of burn depth is important for determination of treatment modality. Laser Doppler imaging (LDI) is known to be an objective and effective measurement tool in burn depth assessment. Our study evaluated the diagnostic accuracy of LDI across enrolled studies and subgroups. A systematic literature review and meta-analysis were performed using MEDLINE, EMBASE, and Cochrane databases. Data from LDI cases were extracted from all primary studies and categorized into four cell values (true positives, false positives, true negatives, and false negatives). Subgroup analyses were performed according to perfusion units of LDI, clinical criteria of superficial and deep burns during the treatment period, and publication date of enrolled studies. The search strategy identified 321 publications. After screening, 10 articles were selected for review. The pooled sensitivity and specificity of LDI in all enrolled studies and subgroups were found to be similarly high. However, the sensitivity of LDI in our meta-analysis was not as high as that identified in previous studies. Although LDI in burn depth assessment was identified as an accurate measurement tool in this meta-analysis, careful clinical assessment should be performed along with LDI in patients with deep burns. Copyright © 2016 Elsevier Ltd and ISBI. All rights reserved.

  11. Scanning laser Doppler imaging may predict disease progression of localized scleroderma in children and young adults.

    PubMed

    Shaw, L J; Shipley, J; Newell, E L; Harris, N; Clinch, J G; Lovell, C R

    2013-07-01

    Localized scleroderma is a rare but potentially disfiguring and disabling condition. Systemic treatment should be started early in those with active disease in key functional and cosmetic sites, but disease activity is difficult to determine clinically. Superficial blood flow has been shown to correlate with disease activity in localized scleroderma. To examine whether superficial blood flow measured by laser Doppler imaging (LDI) has the potential to predict disease progression and therefore select patients for early systemic treatment. A group of 20 individuals had clinical assessment and scanning LDI blood-flow measurements of 32 affected body sites. After a mean follow-up of 8.7 months their clinical outcome was compared with the results of the initial LDI assessment. Eleven out of 15 patients with an assessment of active LDI had progressed clinically, and 16 out of the 17 scans with inactive LDI assessment had not progressed, giving a positive predictive value of 73% and a negative predictive value of 94%. We believe that LDI can be a useful tool in predicting disease progression in localized scleroderma, and it may help clinicians to decide which patients to treat early. © 2013 The Authors BJD © 2013 British Association of Dermatologists.

  12. Power spectrum and blood flow velocity images obtained by dual-beam backscatter laser Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Ishida, Hiroki; Yasue, Youichi; Hachiga, Tadashi; Andoh, Tsugunobu; Akiguchi, Shunsuke; Kuraishi, Yasushi; Shimizu, Tadamichi

    2014-07-01

    We developed a micro multipoint laser Doppler velocimeter (μ-MLDV) for noninvasive in-vivo measurements of blood flow and we presented the results of demonstrations performed on experimental animals. In this paper, we investigate the validity of power spectrum analysis for determining the flow velocity and the minimum power of the semiconductor laser in the μ-MLDV. Although average velocity is generally estimated from a peak position ( f peak) in the power spectrum, the power spectrum of blood flow included an additional component in the high-frequency region. The conventional method for determining the average velocity of flows of transparent artificial fluids, which involves determining the average velocity from f peak, is unsuitable for in-vivo measurements of blood flow. The laser power was reduced from 140 to 30mW since 30mW was the minimum power at which images of blood flow velocity in microvessels could be obtained. About 30mW (power density of 15mW/mm2) is the maximum power which can be irradiated to humans. Further reduction in the laser power is necessary before this technique can be applied to humans.

  13. Full-Field Indentation Damage Measurement Using Digital Image Correlation.

    PubMed

    López-Alba, Elías; Díaz-Garrido, Francisco A

    2017-07-10

    A novel approach based on full-field indentation measurements to characterize and quantify the effect of contact in thin plates is presented. The proposed method has been employed to evaluate the indentation damage generated in the presence of bending deformation, resulting from the contact between a thin plate and a rigid sphere. For this purpose, the 3D Digital Image Correlation (3D-DIC) technique has been adopted to quantify the out of plane displacements at the back face of the plate. Tests were conducted using aluminum thin plates and a rigid bearing sphere to evaluate the influence of the thickness and the material behavior during contact. Information provided by the 3D-DIC technique has been employed to perform an indirect measurement of the contact area during the loading and unloading path of the test. A symmetrical distribution in the contact damage region due to the symmetry of the indenter was always observed. In the case of aluminum plates, the presence of a high level of plasticity caused shearing deformation as the load increased. Results show the full-field contact damage area for different plates' thicknesses at different loads. The contact damage region was bigger when the thickness of the specimen increased, and therefore, bending deformation was reduced. With the proposed approach, the elastic recovery at the contact location was quantified during the unloading, as well as the remaining permanent indentation damage after releasing the load. Results show the information obtained by full-field measurements at the contact location during the test, which implies a substantial improvement compared with pointwise techniques.

  14. Accuracy of early burn depth assessment by laser Doppler imaging on different days post burn.

    PubMed

    Hoeksema, Henk; Van de Sijpe, Karlien; Tondu, Thiery; Hamdi, Moustapha; Van Landuyt, Koenraad; Blondeel, Phillip; Monstrey, Stan

    2009-02-01

    Accurate diagnosis of burn depth is essential in selecting the most appropriate treatment. Early assessment of burn depth by clinical means only has been shown to be inaccurate, resulting in unnecessary operations or delay of grafting procedures. Laser Doppler imaging (LDI) was reported as an objective technique to determine the depth of a burn wound, but the accuracy on very early days post burn has never been investigated yet. In 40 patients with intermediate depth burns, we prospectively evaluated and compared the accuracy of the LDI measurements with the clinical assessments on days 0, 1, 3, 5, 8. Clinical evaluation of the depth of the burn was performed by two observers blinded to the LDI images. Accuracies were assessed by comparison with outcome: healing times longer than 21 days were considered to be equivalent to a biopsy finding of a deep dermal wound. Obviously superficial and full thickness wounds were excluded. LDI flux level was used for LDI prediction of outcome: less than 220PU to predict non-healing at day 21. The accuracies of burn depth assessments on the day of burn and post burn days 0, 1, 3, 5 and 8 using LDI were 54%, 79.5%, 95%, 97% and 100% compared with clinical assessment accuracies of 40.6%, 61.5%, 52.5%, 71.4% and 100%, respectively. LDI accuracy was significantly higher than clinical accuracy on day 3 (p<0.001) and day 5 (p=0.005). Burn depth conversion was also considered. This is the first study to quantify the advantage of LDI scanning over clinical assessments during these important early after burn days.

  15. Dynamic full-field infrared imaging with multiple synchrotron beams

    PubMed Central

    Stavitski, Eli; Smith, Randy J.; Bourassa, Megan W.; Acerbo, Alvin S.; Carr, G. L.; Miller, Lisa M.

    2013-01-01

    Microspectroscopic imaging in the infrared (IR) spectral region allows for the examination of spatially resolved chemical composition on the microscale. More than a decade ago, it was demonstrated that diffraction limited spatial resolution can be achieved when an apertured, single pixel IR microscope is coupled to the high brightness of a synchrotron light source. Nowadays, many IR microscopes are equipped with multi-pixel Focal Plane Array (FPA) detectors, which dramatically improve data acquisition times for imaging large areas. Recently, progress been made toward efficiently coupling synchrotron IR beamlines to multi-pixel detectors, but they utilize expensive and highly customized optical schemes. Here we demonstrate the development and application of a simple optical configuration that can be implemented on most existing synchrotron IR beamlines in order to achieve full-field IR imaging with diffraction-limited spatial resolution. Specifically, the synchrotron radiation fan is extracted from the bending magnet and split into four beams that are combined on the sample, allowing it to fill a large section of the FPA. With this optical configuration, we are able to oversample an image by more than a factor of two, even at the shortest wavelengths, making image restoration through deconvolution algorithms possible. High chemical sensitivity, rapid acquisition times, and superior signal-to-noise characteristics of the instrument are demonstrated. The unique characteristics of this setup enabled the real time study of heterogeneous chemical dynamics with diffraction-limited spatial resolution for the first time. PMID:23458231

  16. Full field imaging based instantaneous hyperspectral absolute refractive index measurement

    SciTech Connect

    Baba, Justin S; Boudreaux, Philip R

    2012-01-01

    Multispectral refractometers typically measure refractive index (RI) at discrete monochromatic wavelengths via a serial process. We report on the demonstration of a white light full field imaging based refractometer capable of instantaneous multispectral measurement of absolute RI of clear liquid/gel samples across the entire visible light spectrum. The broad optical bandwidth refractometer is capable of hyperspectral measurement of RI in the range 1.30 1.70 between 400nm 700nm with a maximum error of 0.0036 units (0.24% of actual) at 414nm for a = 1.50 sample. We present system design and calibration method details as well as results from a system validation sample.

  17. Laser Doppler imaging of genital blood flow: a direct measure of female sexual arousal.

    PubMed

    Waxman, Samantha E; Pukall, Caroline F

    2009-08-01

    Female sexual arousal is a challenging construct to measure, partly because of the subtle nature of its indicators, vaginal lubrication and genital swelling. As a result, many instruments have been used in an attempt to accurately measure it; however, problems are associated with each. Furthermore, the relationship between subjective and physiological indicators of arousal appears to be influenced by the instrument used to measure physiological arousal. Specifically, instruments measuring physiological arousal internally yield lower correlations between measures of physiological and subjective arousal than instruments examining the external genitals. Laser Doppler imaging (LDI) is a direct measure of external genital blood flow. The purpose of this study was to investigate the usefulness of LDI for measuring genital blood flow in women in response to erotic visual stimuli, and to explore the relationship between physiological and subjective sexual arousal. Sixty-five participants watched three 15-minute films during LDI scanning. Two nature films (measuring acclimatization and baseline blood flow levels) and one randomly assigned experimental film (erotic, anxiety, humor, or neutral) were used. Participants rated their level of subjective arousal following the third film. Results indicated a significant effect of film condition on genital blood flow, P < 0.001, with the erotic condition differing significantly from the other three conditions. In terms of the relationship between physiological and subjective sexual arousal, physiological arousal was significantly predicted by subjective ratings of sexual arousal (P < 0.001). LDI appears to be able to differentiate blood flow during erotic and nonerotic conditions. In addition, physiological sexual arousal was significantly predicted by women's reported subjective sexual arousal. These findings suggest that LDI is a useful instrument for measuring female sexual arousal, and that women may be more aware of their level

  18. Local Changes in Microcirculation and the Analgesic Effects of Acupuncture: A Laser Doppler Perfusion Imaging Study

    PubMed Central

    Min, Seorim; Lee, Hyangsook; Kim, Song-Yi; Park, Ji-Yeun; Chae, Younbyoung; Lee, Hyejung

    2015-01-01

    Abstract Objectives Although the local response induced by acupuncture manipulation has been considered to be among the important factors that induce the effects of acupuncture, this connection has not yet been properly studied with standardized tools. The aims of this study are to examine the local changes in microcirculation that occur at different manipulation intensities and explore any associations of these changes with the analgesic effects of acupuncture. Participants/Interventions Twelve healthy volunteers received three acupuncture interventions (insertion only, a single manipulation, and repeated manipulations) at the right LI4 (Hegu or Hapgok) in random order. Outcome measures Skin blood perfusion was measured in a 100-mm2 area ellipse centered on LI4 by using laser Doppler perfusion imaging (LDPI) before, during, and after acupuncture stimulation. Pressure pain thresholds (PPTs) were measured at ipsilateral areas, including acupoints ST25 (abdomen), LI5 (hand), LI10 (arm), and SP9 (leg). Results Repeated acupuncture manipulations enhanced microcirculatory perfusion compared with the insertion-only (p<0.01) and the single-manipulation (p<0.05) conditions. The repeated acupuncture manipulations significantly decreased the pressure pain at ST25 compared with the other groups (each p<0.05). Of note, Spearman correlation analysis revealed significant correlation between changes of local perfusion and PPTs (r=0.393; p=0.018). Conclusions These results suggested that repeated manipulation induced higher local microcirculatory changes that were correlated with the analgesic effects at the relevant sites. The findings suggest that a proper dose of acupuncture stimulation might be essential to elicit the acupuncture effects. PMID:25354241

  19. ECG-triggering of the laser Doppler signal: an approach for perfusion imaging on the beating calf heart

    NASA Astrophysics Data System (ADS)

    Wardell, Karin; Karlsson, Daniel M.; Loenn, Urban; Traff, Stefan; Casimir-Ahn, Henrik

    2001-06-01

    Laser Doppler perfusion imaging (LDPI) has successfully been used to map the myocardial perfusion on patients undergoing coronary bypass surgery on the arrested heart. The need for intra-operative evaluation of graft function is obvious in routine surgery but even more imperative when adapting new surgical techniques where the procedure is performed on the beating heart. When using LDPI on the beating heart, artifacts originating from the movement of the heart are superimposed on the Doppler signal. We have investigated a method to reduce these artifacts by controlling the sampling sequence with ECG-triggering. The method has been assessed in an animal model on the beating calf heart. After sternotomy, an area covering 1 cm2 was imaged at the anterior wall of the left ventricle. In this area, six perfusion images were captured each of them recorded at fixed, but different time intervals in the cardiac cycle. In addition continuous measurements at one spot was done during 1 - 2 minutes. The signal recorded during pumping action was high compared to measurements performed in the same muscle area during infusion of blood with a syringe pump. Repeated measurements captured at a fixed delay time from the R-peak in the same areas at the same heart frequency showed reproducibility. ECG-triggering of the laser Doppler signal is the first step in our attempts to adapt LDPI to enabling assessment of myocardial perfusion on the beating heart. Further technical achievements and in-vivo investigations are, however, needed and will be performed by our research team in future studies.

  20. Blood perfusion values of laser speckle contrast imaging and laser Doppler flowmetry: is a direct comparison possible?

    PubMed

    Binzoni, Tiziano; Humeau-Heurtier, Anne; Abraham, Pierre; Mahe, Guillaume

    2013-05-01

    Laser Doppler flowmetry (LDF) and laser speckle contrast imaging (LSCI) allow the monitoring of microvascular blood perfusion. The relationship between the measurements obtained by these two techniques remains unclear. In the present contribution, we demonstrate, experimentally and theoretically, that skin blood flow measurements obtained by LDF and LSCI techniques cannot be compared directly even after "classical" normalization procedure. This technical problem is generated by the nonlinear relationship existing between LDF and LSCI flow data. The experiments have been performed on five healthy voluntary subjects (forearm) by using repeated ischemia/reperfusion cycles to induce the necessary skin blood flow changes. LDF and LSCI data were simultaneously acquired on the same region of interest. Considering the importance of this problem from the clinical point of view, it is concluded that the definition of new corrected algorithms for LSCI is probably a mandatory step that must be taken into account if LDF and LSCI blood flow have to be compared.

  1. Retinal imaging with adaptive optics full-field OCT

    NASA Astrophysics Data System (ADS)

    Xiao, Peng; Fink, Mathias; Boccara, A. Claude

    2017-02-01

    Adaptive optics full-filed OCT (FFOCT) with a transmissive liquid crystal spatial light modulator (LCSLM) as wavefront corrector is used without strict plane conjugation for low order aberrations corrections. We validated experimentally that FFOCT resolution is independent of aberrations and only reduce the signal level. A signal based sensorless algorithm was thus applied for wavefront distortion compensation. Image quality improvements by the wavefront sensorless control of the LCSLM were evaluated on in vitro samples. By replacing the FFOCT sample arm objective with an artificial eye used to train ophthalmologists, adaptive optics retinal imaging was achieved. In vivo experiments using a liquid lens to correct focus and astigmatism are underway.

  2. Effects of permanent magnets on resting skin blood perfusion in healthy persons assessed by laser Doppler flowmetry and imaging.

    PubMed

    Mayrovitz, H N; Groseclose, E E; Markov, M; Pilla, A A

    2001-10-01

    Effects on skin blood perfusion of permanent ceramic magnets [0.1 T (1000 G) surface field], individually (disk shaped, 4 cm diameter x 1 cm thick) or in the form of a 11 x 7 in pad ( approximately 28 x 17.8 cm) with an array of 16 rectangular magnets (4.5 x 2.2 cm), were investigated in 16 female volunteers (27.4 +/- 1.7 years, range 21-48 years) using three separate protocols. In protocol A, a disk magnet was placed on the palmar surface of the hand in contact with the thenar eminence (n = 5). In protocol B, the magnet was placed on the hand dorsum overlying the thenar eminence (n = 5). In protocol C, the entire palm and fingers rested on the magnetic pad (n = 6). Magnets were in place for 36 min on one hand, and a sham was in place on the other hand. Blood perfusion was measured on the middle finger dorsum by laser Doppler flowmetry (LDF) and on the index finger by laser Doppler imaging (LDI). Perfusion measurements were simultaneously taken in sham and magnet exposed hands, before and during the entire magnet exposure interval. Magnetic field effects were tested by comparing skin blood perfusion sequences in magnet and sham exposed regions. Results showed no significant changes in either LDF or LDI perfusion at magnet or sham sites during exposure, nor were there any significant differences between sham and magnet sites for any protocol. Measurements of skin temperature at the LDF measurement sites also showed no significant change. It is concluded that in the healthy subjects studied with normal, unstressed circulation, magnets of the type and for the duration used, showed no detectible effect on skin blood perfusion in the anatomical area studied.

  3. Automated registration of laser Doppler perfusion images by an adaptive correlation approach: application to focal cerebral ischemia in the rat.

    PubMed

    Riyamongkol, Panomkhawn; Zhao, Weizhao; Liu, Yitao; Belayev, Ludmila; Busto, Raul; Ginsberg, Myron D

    2002-12-31

    Hemodynamic changes are extremely important in analyzing responses from a brain subjected to a stimulus or treatment. The Laser Doppler technique has emerged as an important tool in neuroscience research. This non-invasive method scans a low-power laser beam in a raster pattern over a tissue surface to generate the time course of images in unit of relative flux changes. Laser Doppler imager (LDI) records cerebral perfusion not only in the temporal but also in the spatial domain. The traditional analysis of LD images has been focused on the region-of-interest (ROI) approach, in which the analytical accuracy in an experiment that necessitates a relative repositioning between the LDI and the scanned tissue area will be weakened due to the operator's subjective decision in data collecting. This report describes a robust image registration method designed to obviate this problem, which is based on the adaptive correlation approach. The assumption in mapping corresponding pixels in two images is to correlate the regions in which these pixels are centered. Based on this assumption, correlation coefficients are calculated between two regions by a method in which one region is moved around over the other in all possible combinations. To avoid ambiguity in distinguishing maximum correlation coefficients, an adaptive algorithm is adopted. Correspondences are then used to estimate the transformation by linear regression. We used a pair of phantom LD images to test this algorithm. A reliability test was also performed on each of the 15 sequential LD images derived from an actual experiment by imposing rotation and translation. The result shows that the calculated transformation parameters (rotation: theta =7.7+/-0.5 degrees; translation: Delta x =2.8+/-0.3, Deltaŷ=4.7+/-0.4) are very close to the prior-set parameters (rotation: theta=8 degrees; translation: Delta x=3, Delta y=5). This result indicates that this approach is a valuable adjunct to LD perfusion monitoring. An

  4. Laser Doppler imaging of cutaneous blood flow through transparent face masks: a necessary preamble to computer-controlled rapid prototyping fabrication with submillimeter precision.

    PubMed

    Allely, Rebekah R; Van-Buendia, Lan B; Jeng, James C; White, Patricia; Wu, Jingshu; Niszczak, Jonathan; Jordan, Marion H

    2008-01-01

    A paradigm shift in management of postburn facial scarring is lurking "just beneath the waves" with the widespread availability of two recent technologies: precise three-dimensional scanning/digitizing of complex surfaces and computer-controlled rapid prototyping three-dimensional "printers". Laser Doppler imaging may be the sensible method to track the scar hyperemia that should form the basis of assessing progress and directing incremental changes in the digitized topographical face mask "prescription". The purpose of this study was to establish feasibility of detecting perfusion through transparent face masks using the Laser Doppler Imaging scanner. Laser Doppler images of perfusion were obtained at multiple facial regions on five uninjured staff members. Images were obtained without a mask, followed by images with a loose fitting mask with and without a silicone liner, and then with a tight fitting mask with and without a silicone liner. Right and left oblique images, in addition to the frontal images, were used to overcome unobtainable measurements at the extremes of face mask curvature. General linear model, mixed model, and t tests were used for data analysis. Three hundred seventy-five measurements were used for analysis, with a mean perfusion unit of 299 and pixel validity of 97%. The effect of face mask pressure with and without the silicone liner was readily quantified with significant changes in mean cutaneous blood flow (P < .5). High valid pixel rate laser Doppler imager flow data can be obtained through transparent face masks. Perfusion decreases with the application of pressure and with silicone. Every participant measured differently in perfusion units; however, consistent perfusion patterns in the face were observed.

  5. Concurrent Reflectance Confocal Microscopy and Laser Doppler Flowmetry to Improve Skin Cancer Imaging: A Monte Carlo Model and Experimental Validation

    PubMed Central

    Mowla, Alireza; Taimre, Thomas; Lim, Yah Leng; Bertling, Karl; Wilson, Stephen J.; Prow, Tarl W.; Soyer, H. Peter; Rakić, Aleksandar D.

    2016-01-01

    Optical interrogation of suspicious skin lesions is standard care in the management of skin cancer worldwide. Morphological and functional markers of malignancy are often combined to improve expert human diagnostic power. We propose the evaluation of the combination of two independent optical biomarkers of skin tumours concurrently. The morphological modality of reflectance confocal microscopy (RCM) is combined with the functional modality of laser Doppler flowmetry, which is capable of quantifying tissue perfusion. To realize the idea, we propose laser feedback interferometry as an implementation of RCM, which is able to detect the Doppler signal in addition to the confocal reflectance signal. Based on the proposed technique, we study numerical models of skin tissue incorporating two optical biomarkers of malignancy: (i) abnormal red blood cell velocities and concentrations and (ii) anomalous optical properties manifested through tissue confocal reflectance, using Monte Carlo simulation. We also conduct a laboratory experiment on a microfluidic channel containing a dynamic turbid medium, to validate the efficacy of the technique. We quantify the performance of the technique by examining a signal to background ratio (SBR) in both the numerical and experimental models, and it is shown that both simulated and experimental SBRs improve consistently using this technique. This work indicates the feasibility of an optical instrument, which may have a role in enhanced imaging of skin malignancies. PMID:27598157

  6. Can blood flow in separate small tubes be quantitatively assessed by high-resolution laser Doppler imaging?

    PubMed

    Lindén, M

    1997-11-01

    A method is suggested for quantitative flow assessment of whole-blood perfusing tubes with diameters in the range from 500 microns to 1.5 mm, for velocities below 9 mm s-1. The algorithm is based both on the Doppler broadening of backscattered laser light and the magnitude of the diameter of the perfused tube. A bandwidth-modified high-resolution laser Doppler perfusion imaging system is used to record the Doppler broadening. A flow model, consisting of a linearly narrowing tube (inner diameter 620-1330 microns), is connected to a precision infusion pump and perfused by human whole blood of volume flows ranging from 0 to 6.6 mm3 s-1. Empirical data are fitted into a regression model, and the parameters of the algorithm can be determined, resulting in a correlation coefficient of 0.975 between the predicted and true volume flows. Using this algorithm, volume flows in tubes of inner diameters of 500 microns, 750 microns and 1.4 mm are predicted, with accuracies corresponding to correlation coefficients of 0.994, 0.993 and 0.996.

  7. Concurrent Reflectance Confocal Microscopy and Laser Doppler Flowmetry to Improve Skin Cancer Imaging: A Monte Carlo Model and Experimental Validation.

    PubMed

    Mowla, Alireza; Taimre, Thomas; Lim, Yah Leng; Bertling, Karl; Wilson, Stephen J; Prow, Tarl W; Soyer, H Peter; Rakić, Aleksandar D

    2016-09-01

    Optical interrogation of suspicious skin lesions is standard care in the management of skin cancer worldwide. Morphological and functional markers of malignancy are often combined to improve expert human diagnostic power. We propose the evaluation of the combination of two independent optical biomarkers of skin tumours concurrently. The morphological modality of reflectance confocal microscopy (RCM) is combined with the functional modality of laser Doppler flowmetry, which is capable of quantifying tissue perfusion. To realize the idea, we propose laser feedback interferometry as an implementation of RCM, which is able to detect the Doppler signal in addition to the confocal reflectance signal. Based on the proposed technique, we study numerical models of skin tissue incorporating two optical biomarkers of malignancy: (i) abnormal red blood cell velocities and concentrations and (ii) anomalous optical properties manifested through tissue confocal reflectance, using Monte Carlo simulation. We also conduct a laboratory experiment on a microfluidic channel containing a dynamic turbid medium, to validate the efficacy of the technique. We quantify the performance of the technique by examining a signal to background ratio (SBR) in both the numerical and experimental models, and it is shown that both simulated and experimental SBRs improve consistently using this technique. This work indicates the feasibility of an optical instrument, which may have a role in enhanced imaging of skin malignancies.

  8. Study on Water Distribution Imaging in the Sand Using Propagation Velocity of Sound with Scanning Laser Doppler Vibrometer

    NASA Astrophysics Data System (ADS)

    Sugimoto, Tsuneyoshi; Nakagawa, Yutaka; Shirakawa, Takashi; Sano, Motoaki; Ohaba, Motoyoshi; Shibusawa, Sakae

    2013-07-01

    We propose a method for the monitoring and imaging of the water distribution in the rooting zone of plants using sound vibration. In this study, the water distribution measurement in the horizontal and vertical directions in the soil layer was examined to confirm whether a temporal change in the volume water content of the soil could be estimated from a temporal changes in propagation velocity. A scanning laser Doppler vibrometer (SLDV) is used for measurement of the vibration velocity of the soil surface, because the highly precise vibration velocity measurement of several many points can be carried out automatically. Sand with a uniform particle size distribution is used for the soil, as it has high plasticity; that is, the sand can return to a dry state easily even if it is soaked with water. A giant magnetostriction vibrator or a flat speaker is used as a sound source. Also, a soil moisture sensor, which measures the water content of the soil using the electric permittivity, is installed in the sand. From the experimental results of the vibration measurement and soil moisture sensors, we can confirm that the temporal changes of the water distribution in sand using the negative pressure irrigation system in both the horizontal and vertical directions can be estimated using the propagation velocity of sound. Therefore, in the future, we plan to develop an insertion-type sound source and receiver using the acceleration sensors, and we intend to examine whether our method can be applied even in commercial soil with growing plants.

  9. What's behind the mask? A look at blood flow changes with prolonged facial pressure and expression using laser Doppler imaging.

    PubMed

    Van-Buendia, Lan B; Allely, Rebekah R; Lassiter, Ronald; Weinand, Christian; Jordan, Marion H; Jeng, James C

    2010-01-01

    Clinically, the initial blanching in burn scar seen on transparent plastic face mask application seems to diminish with time and movement requiring mask alteration. To date, studies quantifying perfusion with prolonged mask use do not exist. This study used laser Doppler imaging (LDI) to assess perfusion through the transparent face mask and movement in subjects with and without burn over time. Five subjects fitted with transparent face masks were scanned with the LDI on four occasions. The four subjects without burn were scanned in the following manner: 1) no mask, 2) mask on while at rest, 3) mask on with alternating intervals of sustained facial expression and rest, and 4) after mask removal. Images were acquired every 3 minutes throughout the 85-minute study period. The subject with burn underwent a shortened scanning protocol to increase comfort. Each face was divided into five regions of interest for analysis. Compared with baseline, mask application decreased perfusion significantly in all subjects (P < .0001). Perfusion did not change during the rest period. There were no significant differences with changing facial expression in any of the regions of interest. On mask removal, all regions of the face demonstrated a hyperemic effect with the chin (P = .05) and each cheek (P < .0001) reaching statistical significance. Perfusion levels did not return to baseline in the chin and cheeks after 30 minutes of mask removal. Perfusions remain constantly low while wearing the face mask, despite changing facial expressions. Changing facial expressions with the mask on did not alter perfusion. Hyperemic response occurs on removal of the mask. This study exposed methodology and statistical issues worth considering when conducting future research with the face, pressure therapy, and with LDI technology.

  10. Prostaglandin E1 Increases Microcirculation in Random Pattern Flaps on Rats Measured with Laser Doppler Perfusion Imaging

    PubMed Central

    Sneistrup, Christian; Berg, Thomas Moe

    2017-01-01

    Background: Reconstructive procedures with pedicled and free flaps are associated with a risk of ischemia. Prostaglandin E1 (PGE1) is a hormone-like substance with known antiischemic and tissue-protective effects. The aim of this study was to evaluate the effect of PGE1 on the microcirculation in random pattern skin flaps on rats. Methods: Twenty-four rats were divided into 2 groups: an intervention group given PGE1 for 6 hours and a control group given saline. The flap (2 × 10 cm) was created on the back of the rats, and the microcirculation was monitored with laser Doppler perfusion imaging in 5 different zones (1, proximal; 5, distal) before surgery and after 60, 180, and 360 minutes postoperatively. Results: Before surgery, there was no difference in the perfusion in any zones between the intervention group and the control group. The mean perfusion values in zone 1 in the intervention group were significantly higher than those in the control group at 60, 180, and 360 minutes postoperatively (P = 0.02, P = 0.05, and P = 0.04, respectively). At 360 minutes, we also found significantly higher levels of perfusion in the intervention group in zones 4 and 5 (P = 0.05 and P = 0.03, respectively) compared with the controls. Comparing the perfusion at 360 to 60 minutes in the intervention group, we found a significant increase in microcirculation in all zones, which were not seen in the control group. Conclusion: PGE1 increased perfusion in the dermal random pattern flaps on rats. PMID:28203503

  11. Reproducibility of Non-Invasive Assessment of Skin Endothelial Function Using Laser Doppler Flowmetry and Laser Speckle Contrast Imaging

    PubMed Central

    Puissant, Cyril; Abraham, Pierre; Durand, Sylvain; Humeau-Heurtier, Anne; Faure, Sébastien; Lefthériotis, Georges; Rousseau, Pascal; Mahé, Guillaume

    2013-01-01

    Background Endothelial dysfunction precedes atherosclerosis. Vasodilation induced by acetylcholine (ACh) is a specific test of endothelial function. Reproducibility of laser techniques such as laser-Doppler-flowmetry (LDF) and Laser-speckle-contrast-imaging (LSCI) to detect ACh vasodilation is debated and results expressions lack standardization. We aimed to study at a 7-day interval (i) the inter-subject reproducibility, (ii) the intra-subjects reproducibility, and (iii) the effect of the results expressions over variability. Methods and Results Using LDF and LSCI simultaneously, we performed two different ACh-iontophoresis protocols. The maximal ACh vasodilation (peak-ACh) was expressed as absolute or normalized flow or conductance values. Inter-subject reproducibility was expressed as coefficient of variation (inter-CV,%). Intra-subject reproducibility was expressed as within subject coefficients of variation (intra-CV,%), and intra-class correlation coefficients (ICC). Fifteen healthy subjects were included. The inter-subject reproducibility of peak-ACh depended upon the expression of the results and ranged from 55% to 162% for LDF and from 17% to 83% for LSCI. The intra-subject reproducibility (intra-CV/ICC) of peak-ACh was reduced when assessed with LSCI compared to LDF no matter how the results were expressed and whatever the protocol used. The highest intra-subject reproducibility was found using LSCI. It was 18.7%/0.87 for a single current stimulation (expressed as cutaneous vascular conductance) and 11.4%/0.61 for multiple current stimulations (expressed as absolute value). Conclusion ACh-iontophoresis coupled with LSCI is a promising test to assess endothelial function because it is reproducible, safe, and non-invasive. N°: NCT01664572. PMID:23620742

  12. Comparison of Laser Doppler Imaging (LDI) and clinical assessment in differentiating between superficial and deep partial thickness burn wounds.

    PubMed

    Jan, Saadia Nosheen; Khan, Farid Ahmed; Bashir, Muhammad Mustehsan; Nasir, Muneeb; Ansari, Hamid Hussain; Shami, Hussan Birkhez; Nazir, Umer; Hanif, Asif; Sohail, Muhammad

    2017-09-14

    To compare the accuracy of Laser Doppler Imaging (LDI) and clinical assessment in differentiating between superficial and deep partial thickness burns to decide whether early tangential excision and grafting or conservative management should be employed to optimize burn and patient management. March 2015 to November 2016. Ninety two wounds in 34 patients reporting within 5days of less than 40% burn surface area were included. Unstable patients, pregnant females and those who expired were excluded. The wounds were clinically assessed and LDI done concomitantly Plastic Surgeons blinded to each other's findings. Wound appearance, color, blanching, pain, hair follicle dislodgement were the clinical parameters that distinguished between superficial and deep partial thickness burns. On day 21, the wounds were again assessed for the presence of healing by the same plastic surgeons. The findings were correlated with the initial findings on LDI and clinical assessment and the results statistically analyzed. The data of 92 burn wounds was analyzed using SPSS (ver. 17). Clinical assessment correctly identified the depth of 75 and LDI 83 wounds, giving diagnostic accuracies of 81.52% and 90.21% respectively. The sensitivity of clinical assessment was 81% and of LDI 92.75%, whereas the specificity was 82% for both. The positive predictive value was 93% for clinical assessment and 94% for LDI while the negative predictive value was 59% and 79% respectively. Predictive accuracy of LDI was found to be better than clinical assessment in the prediction of wound healing, the gold standard for wound healing being 21 days. As such it can prove to be a reliable and viable cost effective alternative per se to clinical assessment. Copyright © 2017 Elsevier Ltd and ISBI. All rights reserved.

  13. Ultrasound assessed thickness of burn scars in association with laser Doppler imaging determined depth of burns in paediatric patients.

    PubMed

    Wang, Xue-Qing; Mill, Julie; Kravchuk, Olena; Kimble, Roy M

    2010-12-01

    This study describes the ultrasound assessment of burn scars in paediatric patients and the association of these scar thickness with laser Doppler imaging (LDI) determined burn depth. A total of 60 ultrasound scar assessments were conducted on 33 scars from 21 paediatric burn patients at 3, 6 and 9 months after-burn. The mean of peak scar thickness was 0.39±0.032 cm, with the thickest at 6 months (0.40±0.036 cm). There were 17 scald burn scars (0.34±0.045 cm), 4 contact burn scars (0.61±0.092 cm), and 10 flame burn scars (0.42±0.058 cm). Each group of scars followed normal distributions. Twenty-three scars had original burns successfully scanned by LDI and various depths of burns were presented by different colours according to blood perfusion units (PU), with dark blue <125, light blue 125-250, and green 250-440 PU. The thickness of these scars was significantly different between the predominant colours of burns, with the thinnest scars for green coloured burns and the thickest for dark blue coloured burns. Within light blue burns, grafted burns healed with significantly thinner scars than non-grafted burns. This study indicates that LDI can be used for predicting the risk of hypertrophic scarring and for guiding burn care. To our knowledge, this is the first study to correlate the thickness of burns scars by ultrasound scan with burn depth determined by LDI. Copyright © 2010 Elsevier Ltd and ISBI. All rights reserved.

  14. Laser Doppler anemometry

    NASA Technical Reports Server (NTRS)

    Johnson, Dennis A.

    1988-01-01

    The material in this NASA TM is to appear as a chapter on Laser Doppler Anemometry (LDA) in the AGARDograph entitled, A Survey of Measurements and Measuring Techniques in Rapidly Distorted Compressible Turbulent Boundary Layers. The application of LDA (specifically, the dual-beam, burst-counter approach) to compressible flows is discussed. Subjects treated include signal processing, particle light scattering and tracking, data reduction and sampling bias, and three-dimensional measurements.

  15. Different imaging methods in the comparative assessment of vascular lesions: color-coded duplex sonography, laser Doppler perfusion imaging, and infrared thermography

    NASA Astrophysics Data System (ADS)

    Urban, Peter; Philipp, Carsten M.; Weinberg, Lutz; Berlien, Hans-Peter

    1997-12-01

    Aim of the study was the comparative investigation of cutaneous and subcutaneous vascular lesions. By means of color coded duplex sonography (CCDS), laser doppler perfusion imaging (LDPI) and infrared thermography (IT) we examined hemangiomas, vascular malformations and portwine stains to get some evidence about depth, perfusion and vascularity. LDI is a helpful method to get an impression of the capillary part of vascular lesions and the course of superficial vessels. CCDS has disadvantages in the superficial perfusion's detection but connections to deeper vascularizations can be examined precisely, in some cases it is the only method for visualizing vascular malformations. IT gives additive hints on low blood flow areas or indicates arterial-venous-shunts. Only the combination of all imaging methods allows a complete assessment, not only for planning but also for controlling the laser treatment of vascular lesions.

  16. Comparison of laser Doppler imaging, fingertip lacticemy test, and nailfold capillaroscopy for assessment of digital microcirculation in systemic sclerosis.

    PubMed

    Correa, Marcelo Ju; Andrade, Luis Ec; Kayser, Cristiane

    2010-01-01

    Laser Doppler imaging (LDI) is a relatively new method for assessing the functional aspect of superficial skin blood flow in systemic sclerosis (SSc) and Raynaud's phenomenon. The present study investigated the dynamic behavior of digital skin microvascular blood flow before and after cold stimulus (CS) in SSc patients and in healthy controls by means of a comprehensive approach of the functional (LDI), morphological (nailfold capillaroscopy (NFC)), and biochemical (fingertip lacticemy (FTL)) microcirculation components. Forty-four SSc patients and 40 healthy controls were included. After acclimatization, all subjects underwent NFC followed by LDI and FTL measurement. NFC was performed with a stereomicroscope under 10× to 20× magnification in the 10 digits of the hands. Skin blood flow of the dorsum of four fingertips (excluding the thumb) of the left hand was measured using LDI at baseline and for 30 minutes after CS. The mean finger blood flow (FBF) of the four fingertips was expressed as arbitrary perfusion units. FTL was determined on the fourth left finger before (pre-CS-FTL) and 10 minutes after CS. LDI showed significantly lower mean baseline FBF in SSc patients as compared with controls (296.9 ± 208.8 vs. 503.6 ± 146.4 perfusion units; P < 0.001) and also at all time points after CS (P < 0.001). There was a significant decrease in mean FBF after CS as compared with baseline in SSc patients and in controls, followed by recovery of the blood flow 27 minutes after CS in healthy controls, but not in SSc patients. FBF tended to be lower in patients with digital scars and previous ulceration/amputation (P = 0.06). There was no correlation between mean baseline FBF and NFC parameters. Interestingly, there was a negative correlation between FTL and FBF measured by LDI in basal conditions and 10 minutes after CS in SSc patients. LDI showed lower digital blood flow in SSc patients when compared with healthy controls and correlated well with FTL both at baseline

  17. Comparison of laser Doppler imaging, fingertip lacticemy test, and nailfold capillaroscopy for assessment of digital microcirculation in systemic sclerosis

    PubMed Central

    2010-01-01

    Introduction Laser Doppler imaging (LDI) is a relatively new method for assessing the functional aspect of superficial skin blood flow in systemic sclerosis (SSc) and Raynaud's phenomenon. The present study investigated the dynamic behavior of digital skin microvascular blood flow before and after cold stimulus (CS) in SSc patients and in healthy controls by means of a comprehensive approach of the functional (LDI), morphological (nailfold capillaroscopy (NFC)), and biochemical (fingertip lacticemy (FTL)) microcirculation components. Methods Forty-four SSc patients and 40 healthy controls were included. After acclimatization, all subjects underwent NFC followed by LDI and FTL measurement. NFC was performed with a stereomicroscope under 10× to 20× magnification in the 10 digits of the hands. Skin blood flow of the dorsum of four fingertips (excluding the thumb) of the left hand was measured using LDI at baseline and for 30 minutes after CS. The mean finger blood flow (FBF) of the four fingertips was expressed as arbitrary perfusion units. FTL was determined on the fourth left finger before (pre-CS-FTL) and 10 minutes after CS. Results LDI showed significantly lower mean baseline FBF in SSc patients as compared with controls (296.9 ± 208.8 vs. 503.6 ± 146.4 perfusion units; P < 0.001) and also at all time points after CS (P < 0.001). There was a significant decrease in mean FBF after CS as compared with baseline in SSc patients and in controls, followed by recovery of the blood flow 27 minutes after CS in healthy controls, but not in SSc patients. FBF tended to be lower in patients with digital scars and previous ulceration/amputation (P = 0.06). There was no correlation between mean baseline FBF and NFC parameters. Interestingly, there was a negative correlation between FTL and FBF measured by LDI in basal conditions and 10 minutes after CS in SSc patients. Conclusions LDI showed lower digital blood flow in SSc patients when compared with healthy controls and

  18. Laser-Doppler imaging assessment of skin hyperemia as an indicator of trauma after adhesive strip removal.

    PubMed

    Mayrovitz, H N; Carta, S G

    1996-01-01

    The effect of adhesive tape and dressing removal on skin integrity is particularly important for patients who have increased risk for skin damage or impaired physiological responses to skin trauma. Visual observation of skin erythema does not always provide an adequate assessment of acute injury; detection of trauma is limited by the naturally occurring wide range of skin color and tones. This study had two purposes: (1) to assess the sensitivity and objectivity of laser-Doppler perfusion imaging (LDI) in measuring skin blood perfusion in forearm skin before and after removal of adhesive strips and (2) to determine the relationship between skin perfusion levels after adhesive-strip removal and the peel force required to remove the strips. Variations in peel-force levels were obtained in two ways: first, from naturally occurring skin differences; and second, by using an adhesive remover product (ARP) developed to reduce skin trauma. In 10 subjects, acrylic adhesive strips (13 x 70 mm) were placed in pairs on standardized sites on both volar forearms and peeled off 24 hours later at a constant velocity of 5 mm/sec while the peel force was recorded. During peeling, an ARP was used with one strip; nothing was used on the adjacent paired strip (CONTROL). Skin blood perfusion was measured at 5 and 20 minutes after strip removal by non-contact LDI under the ARP and CONTROL conditions simultaneously. Results show that (1) hyperemia after strip removal is linearly related to peel force (r2 = 0.55, p < .01): (2) use of an ARP, as indexed by the hyperemic response, significantly reduces skin trauma (1.02 [SD = 0.11] versus 1.47 [SD = 0.11], p < .01) with a mean CONTROL/ARP ratio of 1.56; and (3) the peel force required is reduced by using an ARP. These findings indicate that LDI is a useful, sensitive tool for assessment of skin trauma and that reducing peel forces has a positive effect.

  19. A study of vascular response to thermal injury on hairless mice by fibre optic confocal imaging, laser doppler flowmetry and conventional histology.

    PubMed

    Vo, L T; Papworth, G D; Delaney, P M; Barkla, D H; King, R G

    1998-06-01

    Burn injury causes vascular thrombosis and occlusion by thermal damage to the vascular network in the dermis. In this study, fibre optic confocal imaging (FOCI) and laser doppler flowmetry were used to detect changes in vascular morphology and local dermal blood flux over 4 h, in three defined zones after a thermal burn (50 degrees C, 20 s duration, 3 mm in diameter) was induced on fully anaesthetised hairless mice. FITC-dextran (i.v.) was used to enable FOCI of vascular morphology including three-dimensional imaging of the burn site and its surrounding areas. Samples of the affected areas were collected for conventional histology, including Masson's trichrome. There was vascular damage in the zone of coagulation which showed no change during the 4 h period. The zone of stasis showed an initial reduction in blood flux and confocal imaging of the area indicated significant vessel leakage during the first 2 h which later improved. The zone of hyperaemia showed an initial increase in total blood flux and confocal imaging of the area showed initial blood vessel dilatation. This study demonstrates that FOCI is a useful non-invasive tool in the assessment of vascular changes in thermal burns in vivo, and compares the findings of FOCI with those from laser doppler flowmetry and histology.

  20. Speckle-suppressed full-field imaging through a scattering medium using a supercontinuum.

    PubMed

    Zheng, Yipeng; Si, Jinhai; Tan, Wenjiang; Ren, Yu Hu; Tong, Junyi; Hou, Xun

    2016-11-14

    We demonstrate speckle-suppressed full-field imaging through a scattering medium using incoherent supercontinuum (SC) illumination. The patterns in images obtained using SC illumination were found to be more easily identifiable than those in images acquired using coherent direct laser illumination due to the speckle suppression. Even when the optical depth reached 12.3, the patterns remained identifiable. As one of the potential applications, we also demonstrated the imaging for a high-pressure diesel spray using SC illumination.

  1. Image analysis for denoising full-field frequency-domain fluorescence lifetime images.

    PubMed

    Spring, B Q; Clegg, R M

    2009-08-01

    Video-rate fluorescence lifetime-resolved imaging microscopy (FLIM) is a quantitative imaging technique for measuring dynamic processes in biological specimens. FLIM offers valuable information in addition to simple fluorescence intensity imaging; for instance, the fluorescence lifetime is sensitive to the microenvironment of the fluorophore allowing reliable differentiation between concentration differences and dynamic quenching. Homodyne FLIM is a full-field frequency-domain technique for imaging fluorescence lifetimes at every pixel of a fluorescence image simultaneously. If a single modulation frequency is used, video-rate image acquisition is possible. Homodyne FLIM uses a gain-modulated image intensified charge-coupled device (ICCD) detector, which unfortunately is a major contribution to the noise of the measurement. Here we introduce image analysis for denoising homodyne FLIM data. The denoising routine is fast, improves the extraction of the fluorescence lifetime value(s) and increases the sensitivity and fluorescence lifetime resolving power of the FLIM instrument. The spatial resolution (especially the high spatial frequencies not related to noise) of the FLIM image is preserved, because the denoising routine does not blur or smooth the image. By eliminating the random noise known to be specific to photon noise and from the intensifier amplification, the fidelity of the spatial resolution is improved. The polar plot projection, a rapid FLIM analysis method, is used to demonstrate the effectiveness of the denoising routine with exemplary data from both physical and complex biological samples. We also suggest broader impacts of the image analysis for other fluorescence microscopy techniques (e.g. super-resolution imaging).

  2. Composite NDE using full-field pulse-echo ultrasonic propagation imaging system

    NASA Astrophysics Data System (ADS)

    Hong, Seung-Chan; Lee, Jung-Ryul; Park, Jongwoon

    2016-04-01

    In this paper, a novel ultrasonic propagation imaging system, called a full-field pulse-echo ultrasonic propagation imaging (FF PE UPI) system is presented. The coincided laser beams for ultrasonic sensing and generation are scanned and pulse-echo mode laser ultrasounds are captured. This procedure makes it possible to generate full-field ultrasound in through-the-thickness direction as large as the scan area. The system nondestructively inspected targets with two-axis translation stages. Various structural inspection results in the form of full-field ultrasonic wave propagation videos are introduced, which are an aluminum honeycomb sandwich, ailerons and carbon fiber reinforced plastic (CFRP) honeycomb sandwich structures including various defects.

  3. Laser Doppler velocimetry primer

    NASA Technical Reports Server (NTRS)

    Bachalo, William D.

    1985-01-01

    Advanced research in experimental fluid dynamics required a familiarity with sophisticated measurement techniques. In some cases, the development and application of new techniques is required for difficult measurements. Optical methods and in particular, the laser Doppler velocimeter (LDV) are now recognized as the most reliable means for performing measurements in complex turbulent flows. And such, the experimental fluid dynamicist should be familiar with the principles of operation of the method and the details associated with its application. Thus, the goals of this primer are to efficiently transmit the basic concepts of the LDV method to potential users and to provide references that describe the specific areas in greater detail.

  4. Fingerprint imaging from the inside of a finger with full-field optical coherence tomography

    PubMed Central

    Auksorius, Egidijus; Boccara, A. Claude

    2015-01-01

    Imaging below fingertip surface might be a useful alternative to the traditional fingerprint sensing since the internal finger features are more reliable than the external ones. One of the most promising subsurface imaging technique is optical coherence tomography (OCT), which, however, has to acquire 3-D data even when a single en face image is required. This makes OCT inherently slow for en face imaging and produce unnecessary large data sets. Here we demonstrate that full-field optical coherence tomography (FF-OCT) can be used to produce en face images of sweat pores and internal fingerprints, which can be used for the identification purposes. PMID:26601009

  5. Full-field OCT: ex vivo and in vivo biological imaging applications

    NASA Astrophysics Data System (ADS)

    Grieve, Katharine; Dubois, Arnaud; Moneron, Gael; Guyot, Elvire; Boccara, Albert C.

    2005-04-01

    We present results of studies in embryology and ophthalmology performed using our ultrahigh-resolution full-field OCT system. We also discuss recent developments to our ultrashort acquisition time full-field optical coherence tomography system designed to allow in vivo biological imaging. Preliminary results of high-speed imaging in biological samples are presented. The core of the experimental setup is the Linnik interferometer, illuminated by a white light source. En face tomographic images are obtained in real-time without scanning by computing the difference of two phase-opposed interferometric images recorded by high-resolution CCD cameras. An isotropic spatial resolution of ~1 μm is achieved thanks to the short source coherence length and the use of high numerical aperture microscope objectives. A detection sensitivity of ~90 dB is obtained by means of image averaging and pixel binning. In ophthalmology, reconstructed xz images from rat ocular tissue are presented, where cellular-level structures in the retina are revealed, demonstrating the unprecedented resolution of our instrument. Three-dimensional reconstructions of the mouse embryo allowing the study of the establishment of the anterior-posterior axis are shown. Finally we present the first results of embryonic imaging using the new rapid acquisition full-field OCT system, which offers an acquisition time of 10 μs per frame.

  6. Transmission X-ray microscopy for full-field nano-imaging of biomaterials

    PubMed Central

    ANDREWS, JOY C; MEIRER, FLORIAN; LIU, YIJIN; MESTER, ZOLTAN; PIANETTA, PIERO

    2010-01-01

    Imaging of cellular structure and extended tissue in biological materials requires nanometer resolution and good sample penetration, which can be provided by current full-field transmission X-ray microscopic techniques in the soft and hard X-ray regions. The various capabilities of full-field transmission X-ray microscopy (TXM) include 3D tomography, Zernike phase contrast, quantification of absorption, and chemical identification via X-ray fluorescence and X-ray absorption near edge structure (XANES) imaging. These techniques are discussed and compared in light of results from imaging of biological materials including microorganisms, bone and mineralized tissue and plants, with a focus on hard X-ray TXM at ≤ 40 nm resolution. PMID:20734414

  7. Imaging of transient surface acoustic waves by full-field photorefractive interferometry.

    PubMed

    Xiong, Jichuan; Xu, Xiaodong; Glorieux, Christ; Matsuda, Osamu; Cheng, Liping

    2015-05-01

    A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz.

  8. Imaging-AOTF-based full-field spectral-domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Machikhin, Alexander; Viskovatykh, Alexander; Pozhar, Vitold; Burmak, Ludmila

    2015-03-01

    A technique for spectral filtration of interference images in full-field optical coherence tomography is proposed, implemented and tested. It is based on the spectral selection of light in the registration channel of the interferometer by imaging acousto-optic tunable filter. It is demonstrated that the diffraction of two interfering optical beams via the same ultrasound wave does not destruct the coherence. This new technique, which can be named tunable-imaging-filter-based full-field spectral-domain optical coherence tomography (TIF FF SD OCT), is applicable for 3D surface and inner structure visualization of optically inhomogeneous biomedical objects with moderate spectral, lateral and axial resolution, however with rather high speed.

  9. Imaging of transient surface acoustic waves by full-field photorefractive interferometry

    NASA Astrophysics Data System (ADS)

    Xiong, Jichuan; Xu, Xiaodong; Glorieux, Christ; Matsuda, Osamu; Cheng, Liping

    2015-05-01

    A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz.

  10. Imaging of transient surface acoustic waves by full-field photorefractive interferometry

    SciTech Connect

    Xiong, Jichuan; Xu, Xiaodong E-mail: christ.glorieux@fys.kuleuven.be; Glorieux, Christ E-mail: christ.glorieux@fys.kuleuven.be; Matsuda, Osamu; Cheng, Liping

    2015-05-15

    A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz.

  11. Rat brain imaging using full field optical coherence microscopy with short multimode fiber probe

    NASA Astrophysics Data System (ADS)

    Sato, Manabu; Saito, Daisuke; Kurotani, Reiko; Abe, Hiroyuki; Kawauchi, Satoko; Sato, Shunichi; Nishidate, Izumi

    2017-02-01

    We demonstrated FF OCM(full field optical coherence microscopy) using an ultrathin forward-imaging SMMF (short multimode fiber) probe of 50 μm core diameter, 125 μm diameter, and 7.4 mm length, which is a typical graded-index multimode fiber for optical communications. The axial resolution was measured to be 2.20 μm, which is close to the calculated axial resolution of 2.06 μm. The lateral resolution was evaluated to be 4.38 μm using a test pattern. Assuming that the FWHM of the contrast is the DOF (depth of focus), the DOF of the signal is obtained at 36 μm and that of the OCM is 66 μm. The contrast of the OCT images was 6.1 times higher than that of the signal images due to the coherence gate. After an euthanasia the rat brain was resected and cut at 2.6mm tail from Bregma. Contacting SMMF to the primary somatosensory cortex and the agranular insular cortex of ex vivo brain, OCM images of the brain were measured 100 times with 2μm step. 3D OCM images of the brain were measured, and internal structure information was obtained. The feasibility of an SMMF as an ultrathin forward-imaging probe in full-field OCM has been demonstrated.

  12. High-resolution imaging of biological tissue with full-field optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Zhu, Yue; Gao, Wanrong

    2015-03-01

    A new full-field optical coherence tomography system with high-resolution has been developed for imaging of cells and tissues. Compared with other FF-OCT (Full-field optical coherence tomography, FF-OCT) systems illuminated with optical fiber bundle, the improved Köhler illumination arrangement with a halogen lamp was used in the proposed FF-OCT system. High numerical aperture microscopic objectives were used for imaging and a piezoelectric ceramic transducer (PZT) was used for phase-shifting. En-face tomographic images can be obtained by applying the five-step phase-shifting algorithm to a series of interferometric images which are recorded by a smart camera. Three-dimensional images can be generated from these tomographic images. Imaging of the chip of Intel Pentium 4 processor demonstrated the ultrahigh resolution of the system (lateral resolution is 0.8μm ), which approaches the theoretical resolution 0.7 μm× 0.5 μm (lateral × axial). En-face images of cells of onion show an excellent performance of the system in generating en-face images of biological tissues. Then, unstained pig stomach was imaged as a tissue and gastric pits could be easily recognized using FF-OCT system. Our study provides evidence for the potential ability of FFOCT in identifying gastric pits from pig stomach tissue. Finally, label-free and unstained ex vivo human liver tissues from both normal and tumor were imaged with this FFOCT system. The results show that the setup has the potential for medical diagnosis applications such liver cancer diagnosis.

  13. Full-field digital mammography image data storage reduction using a crop tool.

    PubMed

    Kang, Bong Joo; Kim, Sung Hun; An, Yeong Yi; Choi, Byung Gil

    2015-05-01

    The storage requirements for full-field digital mammography (FFDM) in a picture archiving and communication system are significant, so methods to reduce the data set size are needed. A FFDM crop tool for this purpose was designed, implemented, and tested. A total of 1,651 screening mammography cases with bilateral FFDMs were included in this study. The images were cropped using a DICOM editor while maintaining image quality. The cases were evaluated according to the breast volume (1/4, 2/4, 3/4, and 4/4) in the craniocaudal view. The image sizes between the cropped image group and the uncropped image group were compared. The overall image quality and reader's preference were independently evaluated by the consensus of two radiologists. Digital storage requirements for sets of four uncropped to cropped FFDM images were reduced by 3.8 to 82.9 %. The mean reduction rates according to the 1/4-4/4 breast volumes were 74.7, 61.1, 38, and 24 %, indicating that the lower the breast volume, the smaller the size of the cropped data set. The total image data set size was reduced from 87 to 36.7 GB, or a 57.7 % reduction. The overall image quality and the reader's preference for the cropped images were higher than those of the uncropped images. FFDM mammography data storage requirements can be significantly reduced using a crop tool.

  14. Application of GEM-based detectors in full-field XRF imaging

    NASA Astrophysics Data System (ADS)

    Dąbrowski, W.; Fiutowski, T.; Frączek, P.; Koperny, S.; Lankosz, M.; Mendys, A.; Mindur, B.; Świentek, K.; Wiącek, P.; Wróbel, P. M.

    2016-12-01

    X-ray fluorescence spectroscopy (XRF) is a commonly used technique for non-destructive elemental analysis of cultural heritage objects. It can be applied to investigations of provenance of historical objects as well as to studies of art techniques. While the XRF analysis can be easily performed locally using standard available equipment there is a growing interest in imaging of spatial distribution of specific elements. Spatial imaging of elemental distrbutions is usually realised by scanning an object with a narrow focused X-ray excitation beam and measuring characteristic fluorescence radiation using a high energy resolution detector, usually a silicon drift detector. Such a technique, called macro-XRF imaging, is suitable for investigation of flat surfaces but it is time consuming because the spatial resolution is basically determined by the spot size of the beam. Another approach is the full-field XRF, which is based on simultaneous irradiation and imaging of large area of an object. The image of the investigated area is projected by a pinhole camera on a position-sensitive and energy dispersive detector. The infinite depth of field of the pinhole camera allows one, in principle, investigation of non-flat surfaces. One of possible detectors to be employed in full-field XRF imaging is a GEM based detector with 2-dimensional readout. In the paper we report on development of an imaging system equipped with a standard 3-stage GEM detector of 10 × 10 cm2 equipped with readout electronics based on dedicated full-custom ASICs and DAQ system. With a demonstrator system we have obtained 2-D spatial resolution of the order of 100 μm and energy resolution at a level of 20% FWHM for 5.9 keV . Limitations of such a detector due to copper fluorescence radiation excited in the copper-clad drift electrode and GEM foils is discussed and performance of the detector using chromium-clad electrodes is reported.

  15. Development of achromatic full-field hard x-ray microscopy with two monolithic imaging mirrors

    NASA Astrophysics Data System (ADS)

    Matsuyama, S.; Kino, H.; Yasuda, S.; Kohmura, Y.; Okada, H.; Ishikawa, T.; Yamauchi, K.

    2015-09-01

    Advanced Kirkpatrick-Baez mirror optics using two monolithic imaging mirrors was developed to realize an achromatic, high-resolution, and a high-stability full-field X-ray microscope. The mirror consists of an elliptical section and a hyperbolic section on a quartz glass substrate, in which the geometry follows the Wolter (type I) optics rules. A preliminary test was performed at SPring-8 using X-rays monochromatized to 9.881 keV. A 100-nm feature on a Siemens star chart could be clearly observed.

  16. Reconstructing material properties by deconvolution of full-field measurement images: The conductivity case

    NASA Astrophysics Data System (ADS)

    Bellis, Cédric; Trabelsi, Manel; Frémy, Flavien

    2017-03-01

    This study concerns the reconstruction of material parameters from full-field measurements. In this context the typical available data is a set of digital images that is seldom handled as such when solving the inverse problem. Therefore, this work investigates a direct method to compute constitutive parameter maps from full-field measurement images. Within the prototypical framework of the periodic conductivity model, the starting point for the proposed approach is the Lippmann–Schwinger equation, which is satisfied by the fields measured internally. This integral equation is reinterpreted as a linear convolution model for the sought conductivity field. Considering that multiple experiments might be available and then combined, this problem is solved in the least-square sense. To do so, the Krylov subspace-based LSQR algorithm is employed. Full advantage is taken of the convenient expression of the featured Green’s function in Fourier space and of the intensive use of the fast Fourier transform (FFT). Moreover, a spectral-based filtering regularization scheme is implemented to tackle noisy data. Overall, the proposed reconstruction algorithm only handles image-like quantities in an efficient mesh-free approach. The performance of the method is assessed on a set of synthetic 2D numerical examples both for isotropic and anisotropic material configurations.

  17. Low spatial coherence electrically pumped semiconductor laser for speckle-free full-field imaging.

    PubMed

    Redding, Brandon; Cerjan, Alexander; Huang, Xue; Lee, Minjoo Larry; Stone, A Douglas; Choma, Michael A; Cao, Hui

    2015-02-03

    The spatial coherence of laser sources has limited their application to parallel imaging and projection due to coherent artifacts, such as speckle. In contrast, traditional incoherent light sources, such as thermal sources or light emitting diodes (LEDs), provide relatively low power per independent spatial mode. Here, we present a chip-scale, electrically pumped semiconductor laser based on a novel design, demonstrating high power per mode with much lower spatial coherence than conventional laser sources. The laser resonator was fabricated with a chaotic, D-shaped cavity optimized to achieve highly multimode lasing. Lasing occurs simultaneously and independently in ∼1,000 modes, and hence the total emission exhibits very low spatial coherence. Speckle-free full-field imaging is demonstrated using the chaotic cavity laser as the illumination source. The power per mode of the sample illumination is several orders of magnitude higher than that of a LED or thermal light source. Such a compact, low-cost source, which combines the low spatial coherence of a LED with the high spectral radiance of a laser, could enable a wide range of high-speed, full-field imaging and projection applications.

  18. Low spatial coherence electrically pumped semiconductor laser for speckle-free full-field imaging

    PubMed Central

    Redding, Brandon; Cerjan, Alexander; Huang, Xue; Lee, Minjoo Larry; Stone, A. Douglas; Choma, Michael A.; Cao, Hui

    2015-01-01

    The spatial coherence of laser sources has limited their application to parallel imaging and projection due to coherent artifacts, such as speckle. In contrast, traditional incoherent light sources, such as thermal sources or light emitting diodes (LEDs), provide relatively low power per independent spatial mode. Here, we present a chip-scale, electrically pumped semiconductor laser based on a novel design, demonstrating high power per mode with much lower spatial coherence than conventional laser sources. The laser resonator was fabricated with a chaotic, D-shaped cavity optimized to achieve highly multimode lasing. Lasing occurs simultaneously and independently in ∼1,000 modes, and hence the total emission exhibits very low spatial coherence. Speckle-free full-field imaging is demonstrated using the chaotic cavity laser as the illumination source. The power per mode of the sample illumination is several orders of magnitude higher than that of a LED or thermal light source. Such a compact, low-cost source, which combines the low spatial coherence of a LED with the high spectral radiance of a laser, could enable a wide range of high-speed, full-field imaging and projection applications. PMID:25605946

  19. Numerical correction of distorted images in full-field optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Min, Gihyeon; Kim, Ju Wan; Choi, Woo June; Lee, Byeong Ha

    2012-03-01

    We propose a numerical method which can numerically correct the distorted en face images obtained with a full field optical coherence tomography (FF-OCT) system. It is shown that the FF-OCT image of the deep region of a biological sample is easily blurred or degraded because the sample has a refractive index (RI) much higher than its surrounding medium in general. It is analyzed that the focal plane of the imaging system is segregated from the imaging plane of the coherence-gated system due to the RI mismatch. This image-blurring phenomenon is experimentally confirmed by imaging the chrome pattern of a resolution test target through its glass substrate in water. Moreover, we demonstrate that the blurred image can be appreciably corrected by using the numerical correction process based on the Fresnel-Kirchhoff diffraction theory. The proposed correction method is applied to enhance the image of a human hair, which permits the distinct identification of the melanin granules inside the cortex layer of the hair shaft.

  20. Laser Doppler velocimeter measurements and laser sheet imaging in an annular combustor model. M.S. Thesis, Final Report

    NASA Technical Reports Server (NTRS)

    Dwenger, Richard Dale

    1995-01-01

    An experimental study was conducted in annular combustor model to provide a better understanding of the flowfield. Combustor model configurations consisting of primary jets only, annular jets only, and a combination of annular and primary jets were investigated. The purpose of this research was to provide a better understanding of combustor flows and to provide a data base for comparison with computational models. The first part of this research used a laser Doppler velocimeter to measure mean velocity and statistically calculate root-mean-square velocity in two coordinate directions. From this data, one Reynolds shear stress component and a two-dimensional turbulent kinetic energy term was determined. Major features of the flowfield included recirculating flow, primary and annular jet interaction, and high turbulence. The most pronounced result from this data was the effect the primary jets had on the flowfield. The primary jets were seen to reduce flow asymmetries, create larger recirculation zones, and higher turbulence levels. The second part of this research used a technique called marker nephelometry to provide mean concentration values in the combustor. Results showed the flow to be very turbulent and unsteady. All configurations investigated were highly sensitive to alignment of the primary and annular jets in the model and inlet conditions. Any imbalance between primary jets or misalignment of the annular jets caused severe flow asymmetries.

  1. A method for non-invasive full-field imaging and quantification of chemical species.

    PubMed

    Shkolnikov, Viktor; Santiago, Juan G

    2013-04-21

    We present a novel method for full-field scalar visualization and quantification of species concentration fields. We term this method species-altered fluorescence imaging (SAFI). The method employs electrically neutral fluorescent dyes whose quantum yields are selectively quenched or enhanced by species of interest. SAFI enables simultaneous imaging of material interfaces and provides non-invasive, scalar-field quantitation of two-dimensional species concentration fields. We describe criteria for choosing SAFI dyes and tabulate 35 promising SAFI dyes and their relevant properties. Next, we describe species concentration quantification with SAFI via Stern-Volmer quenching and discuss the sensitivity and resolution of our method. We demonstrate this method with two dyes, 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ) and 10-(3-sulfopropyl)acridinium betaine (SAB). We demonstrate our method in full-field visualization of several challenging electrokinetic flows: isotachophoresis (ITP) in both cationic and anionic modes, and in a convective electrokinetic instability (EKI) flow. Through these experiments we collectively quantify ion concentration shock velocities, simultaneously measure concentrations of five species, and quantify the development of an unsteady, chaotic, 2D flow.

  2. Ultrahigh-resolution full-field optical coherence tomography for imaging of a developing embryo

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Zheng, Jinggao; Wang, Rui; Chen, Dieyan; Xue, Ping

    2009-07-01

    Optical coherence tomography (OCT) is a new emerging technique for cross-sectional imaging with high spatial resolution of micrometer scale. It enables in vivo and non-invasive imaging with no need to contact the sample and is widely used in biological and clinic application. In this paper a white-light interference microscope is developed for ultrahigh-resolution full-field optical coherence tomography (Full-Field OCT) to implement 3D imaging of biological tissue. The experimental setup is based on a Linnik-type interferometer illuminated by a tungsten halogen lamp via a bundle of fiber. En-face tomographic images are obtained by demodulation of a combination of interferometric images recorded by a CCD camera. We use a PZT synchronized with the CCD in the reference arm to get the modulated interferometric image and use a programmed precisely controlled electric lift stage in the sample arm to get a 3D image. To fulfill the requirement of in vivo measurement and better match the index of bio-tissue, a pair of high numerical-aperture water immersion microscope objectives is used. Spatial resolution of 1.8μm×1.12μm (transverse×axial) is achieved owing to the extremely short coherence length of the light source and optimized compensation of dispersion mismatch. A shot-noise limited detection sensitivity of 80 dB is obtained at an acquisition time of 5 seconds per image. The development of a mouse embryo is studied layer by layer with our ultrahigh-resolution full-filed OCT. 3D imaging of the embryo can be reconstructed by the OCT images. Information of cell shape, centroid, reflectivity, mitosis period in the development process can be obtained. The variance of the relative reflectivity of an oocyte with time is calculated as well. It is found that the reflectivity of a living oocyte is much lower than that of a dead. Therefore the reflectivity of the cytoplasm can be a signal of the cell activity. In fact, all these parameters above could be very useful for

  3. Full-field velocity imaging of red blood cells in capillaries with spatiotemporal demodulation autocorrelation.

    PubMed

    Wang, Mingyi; Zeng, Yaguang; Dong, Nannan; Liao, Riwei; Yang, Guojian

    2016-03-01

    We propose a full-field optical method for the label-free and quantitative mapping of the velocities of red blood cells (RBCs) in capillaries. It integrates spatiotemporal demodulation and an autocorrelation algorithm, and measures RBC velocity according to the ratio of RBC length to lag time. Conventionally, RBC length is assumed to be a constant and lag time is taken as a variable, while our method treats both of them as variables. We use temporal demodulation and the Butterworth spatial filter to separate RBC signal from background signal, based on which we obtain the RBC length by image segmentation and lag time by autocorrelation analysis. The RBC velocity calculated now is more accurate. The validity of our method is verified by an in vivo experiment on a mouse ear. Owing to its higher image signal-to-noise ratio, our method can be used for mapping RBC velocity in the turbid tissue case.

  4. In vitro retinal imaging with full field swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Fergusson, James; Považay, Boris; Hofer, Bernd; Drexler, Wolfgang

    2010-02-01

    Weakly scattering tree shrew retina has been imaged in vitro with full field swept source optical coherence tomography, visualising multiple intraretinal layers. The system utilises a 50nm bandwidth Superlum SLD, to acheive ~8μm of axial resolution and 4μm of transversal resolution. Volumetric images of retinal tissue with dimensions of 1248x936x678μm (horizontal by vertical by axial) were recorded in two second (equivalent of 153,600 A-scans per second) with a measured signal to noise ratio of 75dB. From the 5mW of SLD optical power available, 720μW illuminates the sample, giving a power per pixel of 4.6nW, ten times less power per pixel then standard FDOCT systems. After upgrading the camera and redesigning the optical beam path, 82dB of SNR was realised.

  5. Full-field velocity imaging of red blood cells in capillaries with spatiotemporal demodulation autocorrelation

    NASA Astrophysics Data System (ADS)

    Wang, Mingyi; Zeng, Yaguang; Dong, Nannan; Liao, Riwei; Yang, Guojian

    2016-03-01

    We propose a full-field optical method for the label-free and quantitative mapping of the velocities of red blood cells (RBCs) in capillaries. It integrates spatiotemporal demodulation and an autocorrelation algorithm, and measures RBC velocity according to the ratio of RBC length to lag time. Conventionally, RBC length is assumed to be a constant and lag time is taken as a variable, while our method treats both of them as variables. We use temporal demodulation and the Butterworth spatial filter to separate RBC signal from background signal, based on which we obtain the RBC length by image segmentation and lag time by autocorrelation analysis. The RBC velocity calculated now is more accurate. The validity of our method is verified by an in vivo experiment on a mouse ear. Owing to its higher image signal-to-noise ratio, our method can be used for mapping RBC velocity in the turbid tissue case.

  6. Image restoration method based on Hilbert transform for full-field optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Na, Jihoon; Choi, Woo June; Choi, Eun Seo; Ryu, Seon Young; Lee, Byeong Ha

    2008-01-01

    A full-field optical coherence tomography (FF-OCT) system utilizing a simple but novel image restoration method suitable for a high-speed system is demonstrated. An en-face image is retrieved from only two phase-shifted interference fringe images through using the mathematical Hilbert transform. With a thermal light source, a high-resolution FF-OCT system having axial and transverse resolutions of 1 and 2.2 μm, respectively, was implemented. The feasibility of the proposed scheme is confirmed by presenting the obtained en-face images of biological samples such as a piece of garlic and a gold beetle. The proposed method is robust to the error in the amount of the phase shift and does not leave residual fringes. The use of just two interference images and the strong immunity to phase errors provide great advantages in the imaging speed and the system design flexibility of a high-speed high-resolution FF-OCT system.

  7. High-resolution full-field optical coherence tomography using high dynamic range image processing

    NASA Astrophysics Data System (ADS)

    Leong-Hoï, A.; Claveau, R.; Montgomery, P. C.; Serio, B.; Uhring, W.; Anstotz, F.; Flury, M.

    2016-04-01

    Full-field optical coherence tomography (FF-OCT) based on white-light interference microscopy, is an emerging noninvasive imaging technique for characterizing biological tissue or optical scattering media with micrometer resolution. Tomographic images can be obtained by analyzing a sequence of interferograms acquired with a camera. This is achieved by scanning an interferometric microscope objectives along the optical axis and performing appropriate signal processing for fringe envelope extraction, leading to three-dimensional imaging over depth. However, noise contained in the images can hide some important details or induce errors in the size of these details. To firstly reduce temporal and spatial noise from the camera, it is possible to apply basic image post processing methods such as image averaging, dark frame subtraction or flat field division. It has been demonstrate that this can improve the quality of microscopy images by enhancing the signal to noise ratio. In addition, the dynamic range of images can be enhanced to improve the contrast by combining images acquired with different exposure times or light intensity. This can be made possible by applying a hybrid high dynamic range (HDR) technique, which is proposed in this paper. High resolution tomographic analysis is thus performed using a combination of the above-mentioned image processing techniques. As a result, the lateral resolution of the system can be improved so as to approach the diffraction limit of the microscope as well as to increase the power of detection, thus enabling new sub-diffraction sized structures contained in a transparent layer, initially hidden by the noise, to be detected.

  8. Actinic imaging of native and programmed defects on a full-field mask

    SciTech Connect

    Mochi, I.; Goldberg, K. A.; Fontaine, B. La; Tchikoulaeva, A.; Holfeld, C.

    2010-03-12

    We describe the imaging and characterization of native defects on a full field extreme ultraviolet (EUV) mask, using several reticle and wafer inspection modes. Mask defect images recorded with the SEMA TECH Berkeley Actinic Inspection Tool (AIT), an EUV-wavelength (13.4 nm) actinic microscope, are compared with mask and printed-wafer images collected with scanning electron microscopy (SEM) and deep ultraviolet (DUV) inspection tools. We observed that defects that appear to be opaque in the SEM can be highly transparent to EUV light, and inversely, defects that are mostly transparent to the SEM can be highly opaque to EUV. The nature and composition of these defects, whether they appear on the top surface, within the multilayer coating, or on the substrate as buried bumps or pits, influences both their significance when printed, and their detectability with the available techniques. Actinic inspection quantitatively predicts the characteristics of printed defect images in ways that may not be possible with non-EUV techniques. As a quantitative example, we investigate the main structural characteristics of a buried pit defect based on EUV through-focus imaging.

  9. Applications of Full-Field X-ray Microscopy for High Spatial Resolution Magnetic Imaging

    NASA Astrophysics Data System (ADS)

    Denbeaux, Gregory; Chao, Weilun; Fischer, Peter; Kusinski, Greg; Le Gros, Mark; Pearson, Angelic; Schneider, Gerd

    2001-03-01

    The XM-1 soft x-ray microscope, located at the Advanced Light Source at Lawrence Berkeley National Laboratory has recently been established as a tool for high-resolution imaging of magnetic domains. It is a "conventional" full-field transmission microscope which is able to achieve a resolution of 25 nm by using high-precision zone plates. It uses off-axis bend magnet radiation to illuminate samples with elliptically polarized light. When the illumination energy is tuned to absorption edges of specific elements, it can be used as an element-specific probe of magnetism on a 25 nm scale with a contrast provided by magnetic circular dichroism. The illumination energy can be tuned between 250-850 eV. This allows imaging of specific elements including chromium, iron and cobalt. The spectral resolution has been shown to be E/DE = 500-700. This spectral resolution allows a high sensitivity so that magnetization has been imaged within layers as thin as 3 nm. Since this is a photon based magnetic microscopy, fields can be applied to the sample even during imaging without affect ng the spatial resolution. Recent magnetic imaging results will be shown.

  10. High resolution in-vivo imaging of skin with full field optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Dalimier, E.; Bruhat, Alexis; Grieve, K.; Harms, F.; Martins, F.; Boccara, C.

    2014-03-01

    Full-field OCT (FFOCT) has the ability to provide en-face images with a very good axial sectioning as well as a very high transverse resolution (about 1 microns in all directions). Therefore it offers the possibility to visualize biological tissues with very high resolution both on the axial native view, and on vertical reconstructed sections. Here we investigated the potential dermatological applications of in-vivo skin imaging with FFOCT. A commercial FFOCT device was adapted for the in-vivo acquisition of stacks of images on the arm, hand and finger. Several subjects of different benign and pathological skin conditions were tested. The images allowed measurement of the stratum corneum and epidermis thicknesses, measurement of the stratum corneum refractive index, size measurement and count of the keratinocytes, visualization of the dermal-epidermal junction, and visualization of the melanin granules and of the melanocytes. Skins with different pigmentations could be discriminated and skin pathologies such as eczema could be identified. The very high resolution offered by FFOCT both on axial native images and vertical reconstructed sections allows for the visualization and measurement of a set of parameters useful for cosmetology and dermatology. In particular, FFOCT is a potential tool for the understanding and monitoring of skin hydration and pigmentation, as well as skin inflammation.

  11. Full-Field Imaging of Acoustic Motion at Nanosecond Time and Micron Length Scales

    SciTech Connect

    Telschow, Kenneth Louis; Deason, Vance Albert; Cottle, David Lynn; Larson III, John D.

    2002-10-01

    A full-field view laser ultrasonic imaging method has been developed that measures acoustic motion at a surface without scanning. Images are recorded at normal video frame rates by employing dynamic holography using photorefractive interferometric detection. By extending the approach to ultra high frequencies, an acoustic microscope has been developed capable of operation on the nanosecond time and micron length scales. Both acoustic amplitude and phase are recorded allowing full calibration and determination of phases to within a single arbitrary constant. Results are presented of measurements at frequencies at 800-900 MHz illustrating a multitude of normal mode behavior in electrically driven thin film acoustic resonators. Coupled with microwave electrical impedance measurements, this imaging mode provides an exceptionally fast method for evaluation of electric to acoustic coupling and performance of these devices. Images of 256x240 pixels are recorded at 18Hz rates synchronized to obtain both in-phase and quadrature detection of the acoustic motion. Simple averaging provides sensitivity to the subnanometer level calibrated over the image using interferometry. Identification of specific acoustic modes and their relationship to electrical impedance characteristics show the advantages and overall high speed of the technique.

  12. Robust full-field measurement considering rotation using digital image correlation

    NASA Astrophysics Data System (ADS)

    Wu, Rong; Qian, Hao; Zhang, Dongsheng

    2016-10-01

    Digital image correlation (DIC) has been widely accepted as a method for displacement and strain measurement and is applied in a variety of engineering fields. Most DIC algorithms encounter errors in measuring the deformation in conditions that involve rotation since they are designed without considering rotation of the deformed object. In this paper, a robust and automated DIC method capable of determining full-field displacement and strain components with random rotations has been presented. The algorithm starts with the determination of the initial position of the seed point in the integer-pixel domain. An approximate rotational angle between the reference and the deformed subset is estimated using an automated feature matching technology. A two-step Newton-Raphson algorithm has been developed for optimizing a suite of variables including displacement, strain and the rotational angle to achieve subpixel accuracy. A reliable propagation scheme, which enables rapid determination of the initial guess for full-field analysis is also proposed. Results from numerical simulations are used to validate the feasibility of the proposed DIC method. An application to 3-point bending with large deflection shows that the algorithm can be employed to measure displacement or strain parameters of the deformed object with arbitrary angles of rotation.

  13. Digital image correlation for full-field time-resolved assessment of arterial stiffness

    NASA Astrophysics Data System (ADS)

    Campo, Adriaan; Soons, Joris; Heuten, Hilde; Ennekens, Guy; Goovaerts, Inge; Vrints, Christiaan; Lava, Pascal; Dirckx, Joris

    2014-01-01

    Pulse wave velocity (PWV) of the arterial system is a very important parameter to evaluate cardiovascular health. Currently, however, there is no golden standard for PWV measurement. Digital image correlation (DIC) was used for full-field time-resolved assessment of displacement, velocity, acceleration, and strains of the skin in the neck directly above the common carotid artery. By assessing these parameters, propagation of the pulse wave could be tracked, leading to a new method for PWV detection based on DIC. The method was tested on five healthy subjects. As a means of validation, PWV was measured with ultrasound (US) as well. Measured PWV values were between 3.68 and 5.19 m/s as measured with DIC and between 5.14 and 6.58 m/s as measured with US, with a maximum absolute difference of 2.78 m/s between the two methods. DIC measurements of the neck region can serve as a test base for determining a robust strategy for PWV detection, they can serve as reference for three-dimensional fluid-structure interaction models, or they may even evolve into a screening method of their own. Moreover, full-field, time-resolved DIC can be adapted for other applications in biomechanics.

  14. Extracting relevant information for cancer diagnosis from dynamic full field OCT through image processing and learning

    NASA Astrophysics Data System (ADS)

    Apelian, Clément; Gastaud, Clément; Boccara, A. Claude

    2017-02-01

    For a large number of cancer surgeries, the lack of reliable intraoperative diagnosis leads to reoperations or bad outcomes for the patients. To deliver better diagnosis, we developed Dynamic Full Field OCT (D-FFOCT) as a complement to FFOCT. FFOCT already presents interesting results for cancer diagnosis e.g. Mohs surgery and reaching 96% accuracy on prostate cancer. D-FFOCT accesses the dynamic processes of metabolism and gives new tools to diagnose the state of a tissue at the cellular level to complement FFOCT contrast. We developed a processing framework that intends to maximize the information provided by the FFOCT technology as well as D-FFOCT and synthetize this as a meaningful image. We use different time processing to generate metrics (standard deviation of time signals, decorrelation times and more) and spatial processing to sort out structures and the corresponding imaging modality, which is the most appropriate. Sorting was achieved through quadratic discriminant analysis in a N-dimension parametric space corresponding to our metrics. Combining the best imaging modalities for each structure leads to a rich morphology image. This image displaying the morphology is then colored to represent the dynamic behavior of these structures (slow or fast) and to be quickly analyzed by doctors. Therefore, we achieved a micron resolved image, rich of both FFOCT ability of imaging fixed and highly backscattering structures as well as D-FFOCT ability of imaging low level scattering cellular level details. We believe that this morphological contrast close to histology and the dynamic behavior contrast will push forward the limits of intraoperative diagnosis further on.

  15. A comparison of image interpretation times in full field digital mammography and digital breast tomosynthesis

    NASA Astrophysics Data System (ADS)

    Astley, Susan; Connor, Sophie; Lim, Yit; Tate, Catriona; Entwistle, Helen; Morris, Julie; Whiteside, Sigrid; Sergeant, Jamie; Wilson, Mary; Beetles, Ursula; Boggis, Caroline; Gilbert, Fiona

    2013-03-01

    Digital Breast Tomosynthesis (DBT) provides three-dimensional images of the breast that enable radiologists to discern whether densities are due to overlapping structures or lesions. To aid assessment of the cost-effectiveness of DBT for screening, we have compared the time taken to interpret DBT images and the corresponding two-dimensional Full Field Digital Mammography (FFDM) images. Four Consultant Radiologists experienced in reading FFDM images (4 years 8 months to 8 years) with training in DBT interpretation but more limited experience (137-407 cases in the past 6 months) were timed reading between 24 and 32 two view FFDM and DBT cases. The images were of women recalled from screening for further assessment and women under surveillance because of a family history of breast cancer. FFDM images were read before DBT, according to local practice. The median time for readers to interpret FFDM images was 17.0 seconds, with an interquartile range of 12.3-23.6 seconds. For DBT, the median time was 66.0 seconds, and the interquartile range was 51.1-80.5 seconds. The difference was statistically significant (p<0.001). Reading times were significantly longer in family history clinics (p<0.01). Although it took approximately four times as long to interpret DBT than FFDM images, the cases were more complex than would be expected for routine screening, and with higher mammographic density. The readers were relatively inexperienced in DBT interpretation and may increase their speed over time. The difference in times between clinics may be due to increased throughput at assessment, or decreased density.

  16. Full-field AO-assisted OCT for high-resolution tomographic imaging of the retina

    NASA Astrophysics Data System (ADS)

    Glanc, M.; Lafaille, D.; Puget, P.; Lacombe, F.; Vabre, L.; Levecq, X.; Chateau, N.

    2006-02-01

    Since the advent of Adaptive Optics in ophthalmic instrumentation, several attempts for improving the performances of the existing observing techniques, either in imaging or tomography, have been made. For long, Adaptive Optics have proven its ability to restore high lateral resolution with the SLO or flood imaging, or more recently to enhance the interferometric contrast and hence, the sensitivity, of OCT. Nevertheless, the direct acquisition of en face tomographic images equivalent to horizontal optical sections of the retinal tissue is still the objective of intensive developments. We report here a new instrumental approach where a time domain full field OCT setup has been coupled with a double pass adaptive optics system, providing 300 x 300 x 4 m instantaneous optical sections of biological tissues. We will describe how the interferometric contrast is derived without any modulation of the optical path, thus giving access to targets as critical, because unstable, as the retinal tissue during in vivo ophthalmic examinations. The advantages of this new design, which benefits from the implementation of very recent deformable mirrors, featuring simultaneously a higher actuators density and a much larger stroke, will be discussed, and the ability of the system to accommodate for variable pupil sizes, thanks to wavefront sensing techniques optimized for ophthalmology, are commented. The performances of the system, in terms of X,Y,Z resolution, sensitivity, registration capability and / or image stabilisation are discussed and illustrated with results obtained in the laboratory and in clinical environment.

  17. A comparison of non-invasive imaging modalities: Infrared thermography, spectrophotometric intracutaneous analysis and laser Doppler imaging for the assessment of adult burns.

    PubMed

    Burke-Smith, Alexandra; Collier, Jonathan; Jones, Isabel

    2015-12-01

    Currently, the only evidence-based adjunct to clinical evaluation of burn depth is laser Doppler imaging (LDI), although preliminary studies of alternative imaging modalities with instant image acquisition are promising. This is a study to investigate the accuracy of infrared thermography (IRT) and spectrophotometric intracutaneous analysis (SIA) for burn depth assessment, and compare this to the current gold standard: LDI. We include a comparison of the three modalities in terms of cost, reliability and usability. We recruited 20 patients with burns presenting to the Chelsea and Westminster Adult Burns Service. Between 48h and 5 days afterburn we recorded imaging using moorLDI2-BI-VR (LDI), FLIR E60 (IRT) and Scanoskin™ (SIA). Subsequent clinical management and outcome was as normal, and not affected by the extra images taken. 24 burn regions were grouped according to burn wound healing: group A healed within 14 days, group B within 14-21 days, and group C took more than 21 days or underwent grafting. Both LDI and IRT accurately determined healing potential in groups A and C, but failed to distinguish between groups B and C (p>0.05). Scanoskin™ interpretation of SIA was 100% consistent with clinical outcome. FLIR E60 and Scanoskin™ both present advantages to moorLDI2-BI-VR in terms of cost, ease-of-use and acceptability to patients. IRT is unlikely to challenge LDI as the gold standard as it is subject to the systematic bias of evaporative cooling. At present, the LDI colour-coded palette is the easiest method for image interpretation, whereas Scanoskin™ monochrome colour-palettes are more difficult to interpret. However the additional analyses of pigment available using SIA may help more accurately indicate the depth of burn compared with perfusion alone. We suggest development of Scanoskin™ software to include a simplified colour-palette similar to LDI and additional work to further investigate the potential of SIA as an alternative to the current gold

  18. From supersonic shear wave imaging to full-field optical coherence shear wave elastography

    NASA Astrophysics Data System (ADS)

    Nahas, Amir; Tanter, Mickaël; Nguyen, Thu-Mai; Chassot, Jean-Marie; Fink, Mathias; Claude Boccara, A.

    2013-12-01

    Elasticity maps of tissue have proved to be particularly useful in providing complementary contrast to ultrasonic imaging, e.g., for cancer diagnosis at the millimeter scale. Optical coherence tomography (OCT) offers an endogenous contrast based on singly backscattered optical waves. Adding complementary contrast to OCT images by recording elasticity maps could also be valuable in improving OCT-based diagnosis at the microscopic scale. Static elastography has been successfully coupled with full-field OCT (FF-OCT) in order to realize both micrometer-scale sectioning and elasticity maps. Nevertheless, static elastography presents a number of drawbacks, mainly when stiffness quantification is required. Here, we describe the combination of two methods: transient elastography, based on speed measurements of shear waves induced by ultrasonic radiation forces, and FF-OCT, an en face OCT approach using an incoherent light source. The use of an ultrafast ultrasonic scanner and an ultrafast camera working at 10,000 to 30,000 images/s made it possible to follow shear wave propagation with both modalities. As expected, FF-OCT is found to be much more sensitive than ultrafast ultrasound to tiny shear vibrations (a few nanometers and micrometers, respectively). Stiffness assessed in gel phantoms and an ex vivo rat brain by FF-OCT is found to be in good agreement with ultrasound shear wave elastography.

  19. From supersonic shear wave imaging to full-field optical coherence shear wave elastography.

    PubMed

    Nahas, Amir; Tanter, Mickaël; Nguyen, Thu-Mai; Chassot, Jean-Marie; Fink, Mathias; Claude Boccara, A

    2013-12-01

    Elasticity maps of tissue have proved to be particularly useful in providing complementary contrast to ultrasonic imaging, e.g., for cancer diagnosis at the millimeter scale. Optical coherence tomography (OCT) offers an endogenous contrast based on singly backscattered optical waves. Adding complementary contrast to OCT images by recording elasticity maps could also be valuable in improving OCT-based diagnosis at the microscopic scale. Static elastography has been successfully coupled with full-field OCT (FF-OCT) in order to realize both micrometer-scale sectioning and elasticity maps. Nevertheless, static elastography presents a number of drawbacks, mainly when stiffness quantification is required. Here, we describe the combination of two methods: transient elastography, based on speed measurements of shear waves induced by ultrasonic radiation forces, and FF-OCT, an en face OCT approach using an incoherent light source. The use of an ultrafast ultrasonic scanner and an ultrafast camera working at 10,000 to 30,000 images/s made it possible to follow shear wave propagation with both modalities. As expected, FF-OCT is found to be much more sensitive than ultrafast ultrasound to tiny shear vibrations (a few nanometers and micrometers, respectively). Stiffness assessed in gel phantoms and an ex vivo rat brain by FF-OCT is found to be in good agreement with ultrasound shear wave elastography.

  20. Full-field inspection of a wind turbine blade using three-dimensional digital image correlation

    NASA Astrophysics Data System (ADS)

    LeBlanc, Bruce; Niezrecki, Christopher; Avitabile, Peter; Chen, Julie; Sherwood, James; Hughes, Scott

    2011-04-01

    Increasing demand and deployment of wind power has led to a significant increase in the number of wind-turbine blades manufactured globally. As the physical size and number of turbines deployed grows, the probability of manufacturing defects being present in composite turbine blade fleets also increases. As both capital blade costs, and operational and maintenance costs, increase for larger turbine systems the need for large-scale inspection and monitoring of the state of structural health of turbine blades during manufacturing and operation critically increase. One method for locating and quantifying manufacturing defects, while also allowing for the in-situ measurement of the structural health of blades, is through the observation of the full-field state of deformation and strain of the blade. Static tests were performed on a nine-meter CX-100 composite turbine blade to extract full-field displacement and strain measurements using threedimensional digital image correlation (3D DIC). Measurements were taken at several angles near the blade root, including along the high-pressure surface, low-pressure surface, and along the trailing edge of the blade. The overall results indicate that the measurement approach can clearly identify failure locations and discontinuities in the blade curvature under load. Post-processing of the data using a stitching technique enables the shape and curvature of the entire blade to be observed for a large-scale wind turbine blade for the first time. The experiment demonstrates the feasibility of the approach and reveals that the technique readily can be scaled up to accommodate utility-scale blades. As long as a trackable pattern is applied to the surface of the blade, measurements can be made in-situ when a blade is on a manufacturing floor, installed in a test fixture, or installed on a rotating turbine. The results demonstrate the great potential of the optical measurement technique and its capability for use in the wind industry for

  1. Hard X-ray Full Field Nano-imaging of Bone and Nanowires at SSRL

    SciTech Connect

    Andrews, Joy C.; Pianetta, Piero; Meirer, Florian; Chen Jie; Almeida, Eduardo; Meulen, Marjolein C. H. van der; Alwood, Joshua S.; Lee, Cathy; Zhu Jia; Cui Yi

    2010-06-23

    A hard X-ray full field microscope from Xradia Inc. has been installed at SSRL on a 54-pole wiggler end station at beam line 6-2. It has been optimized to operate from 5-14 keV with resolution as high as 30 nm. High quality images are achieved using a vertical beam stabilizer and condenser scanner with high efficiency zone plates with 30 nm outermost zone width. The microscope has been used in Zernike phase contrast, available at 5.4 keV and 8 keV, as well as absorption contrast to image a variety of biological, environmental and materials samples. Calibration of the X-ray attenuation with crystalline apatite enabled quantification of bone density of plate-like and rod-like regions of mouse bone trabecula. 3D tomography of individual lacuna revealed the surrounding cell canaliculi and processes. 3D tomography of chiral branched PbSe nanowires showed orthogonal branches around a central nanowire.

  2. Hard X-ray Full Field Nano-imaging of Bone and Nanowires at SSRL

    NASA Astrophysics Data System (ADS)

    Andrews, Joy C.; Pianetta, Piero; Meirer, Florian; Chen, Jie; Almeida, Eduardo; van der Meulen, Marjolein C. H.; Alwood, Joshua S.; Lee, Cathy; Zhu, Jia; Cui, Yi

    2010-06-01

    A hard X-ray full field microscope from Xradia Inc. has been installed at SSRL on a 54-pole wiggler end station at beam line 6-2. It has been optimized to operate from 5-14 keV with resolution as high as 30 nm. High quality images are achieved using a vertical beam stabilizer and condenser scanner with high efficiency zone plates with 30 nm outermost zone width. The microscope has been used in Zernike phase contrast, available at 5.4 keV and 8 keV, as well as absorption contrast to image a variety of biological, environmental and materials samples. Calibration of the X-ray attenuation with crystalline apatite enabled quantification of bone density of plate-like and rod-like regions of mouse bone trabecula. 3D tomography of individual lacuna revealed the surrounding cell canaliculi and processes. 3D tomography of chiral branched PbSe nanowires showed orthogonal branches around a central nanowire.

  3. Full Field X-Ray Fluorescence Imaging Using Micro Pore Optics for Planetary Surface Exploration

    NASA Technical Reports Server (NTRS)

    Sarrazin, P.; Blake, D. F.; Gailhanou, M.; Walter, P.; Schyns, E.; Marchis, F.; Thompson, K.; Bristow, T.

    2016-01-01

    Many planetary surface processes leave evidence as small features in the sub-millimetre scale. Current planetary X-ray fluorescence spectrometers lack the spatial resolution to analyse such small features as they only provide global analyses of areas greater than 100 mm(exp 2). A micro-XRF spectrometer will be deployed on the NASA Mars 2020 rover to analyse spots as small as 120m. When using its line-scanning capacity combined to perpendicular scanning by the rover arm, elemental maps can be generated. We present a new instrument that provides full-field XRF imaging, alleviating the need for precise positioning and scanning mechanisms. The Mapping X-ray Fluorescence Spectrometer - "Map-X" - will allow elemental imaging with approximately 100µm spatial resolution and simultaneously provide elemental chemistry at the scale where many relict physical, chemical and biological features can be imaged in ancient rocks. The arm-mounted Map-X instrument is placed directly on the surface of an object and held in a fixed position during measurements. A 25x25 mm(exp 2) surface area is uniformly illuminated with X-rays or alpha-particles and gamma-rays. A novel Micro Pore Optic focusses a fraction of the emitted X-ray fluorescence onto a CCD operated at a few frames per second. On board processing allows measuring the energy and coordinates of each X-ray photon collected. Large sets of frames are reduced into 2d histograms used to compute higher level data products such as elemental maps and XRF spectra from selected regions of interest. XRF spectra are processed on the ground to further determine quantitative elemental compositions. The instrument development will be presented with an emphasis on the characterization and modelling of the X-ray focussing Micro Pore Optic. An outlook on possible alternative XRF imaging applications will be discussed.

  4. Correlative analysis of breast lesions on full-field digital mammography and magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Yuan, Yading

    Multi-modality imaging techniques are increasingly being applied in clinical practice to improve the accuracy with which breast cancer can be diagnosed. However, interpreting images from different modalities is not trivial as different images of the same lesion may exhibit different physical lesion attributes, and currently the various image modality acquisitions are performed under different breast positioning protocols. The general objective of this research is to investigate computerized correlative feature analysis (CFA) methods for integrating information from full-field digital mammographic (FFDM) images and dynamic contrast-enhanced magnetic resonance (DCE-MR) images by taking advantage of the information from different imaging modalities, and thus improving the diagnostic ability of computer-aided diagnosis (CADx) in breast cancer workup. The main hypothesis to be tested is that by incorporating correlative feature analysis in CADx, one can achieve an accurate and efficient discrimination between corresponding and non-corresponding lesion pairs, and subsequently improve performance in the estimation of computer-estimated probabilities of malignancy. The main contributions of this research work are summarized as follows. (1) A novel active-contour model based algorithm was developed for lesion segmentation on mammograms. This new algorithm yielded a statistically improved segmentation performance as compared to previously developed methods: a region-growing method and a radial gradient index (RGI) based method. (2) A computerized feature-based, supervised-learning driven CFA method was investigated to identify corresponding lesions in different mammographic views. The performance obtained by combining multiple features was found to be statistically better than the use of a distance feature alone, and robust across different mammographic view combinations. (3) A multi-modality CADx method that automatically selects and combines discriminative information from

  5. [Blood perfusion in different facial acupoint areas and its changes after acupuncture stimulation of Hegu (LI 4) displayed by laser Doppler imager in healthy volunteers].

    PubMed

    Wang, Shu-You; Qu, Xiao-Xiao; Song, Xiao-Jing; Li, Shun-Yue; Ma, Hui-Min; Zhang, Dong

    2012-12-01

    To observe the blood perfusion levels in different facial acupoint regions and changes after acupuncture stimulation of Hegu (LI 4). Thirty healthy volunteer subjects were equally divided into control group and acupuncture group. Blood perfusion levels of different facial acupoint areas were detected using a Laser Doppler Imager. Acupuncture stimulation was applied to bilateral Hegu (LI 4) by using two filiform needles which were manipulated for a while till "Deqi", followed by keeping them in position for 30 min. The needles were then manipulated once again every 10 min. The blood perfusion levels of facial acupoint regions were from 0.73 to 1.17 PU in healthy volunteers, with relatively higher levels being in Juliao (ST 3), Kouheliao (LI 19), Sibai (ST 2) and Chengqi (ST 1) regions and relatively lower levels in Xiaguan (ST 7), Qianzheng (Ex-HN) and Sizhukong (TE 23) regions, but without significant difference between the isonym acupoint areas of the bilateral face in the control group. Following acupuncture stimulation of bilateral Hegu (LI 4), the blood perfusion volumes were remarkably increased in the acupoint regions on bilateral sides of the face (P < 0.05, P < 0.01). Acupuncture of Hegu (LI 4) can effectively increase blood perfusion volume of the acupoint areas of the bilateral face in healthy volunteers.

  6. The impact of laser Doppler imaging on the early decision-making process for surgical intervention in adults with indeterminate burns.

    PubMed

    Park, Yoo Seok; Choi, Young Hwan; Lee, Hye Sun; Moon, Duk Ju; Kim, Seon Gyu; Lee, Jong Ho; Cho, Jin Kyung; Yoon, Cheon Jae

    2013-06-01

    We aimed to analyze whether laser Doppler imaging (LDI) can lead to earlier decision-making regarding the need for surgery in adults with indeterminate burns. In a retrospective cohort study, we developed a prediction model for surgery in adults with indeterminate burns. Patient data (n=101) from January 2007 to December 2009 were used for model development, and those (n=40) from January 2010 to October 2010 for external validation. Between non-surgical and surgical groups, there were significant differences for mean age (p=0.009), % total body surface area burn (p=0.016), site of burn wound (p=0.033), and mean perfusion units (PU) (p<0.001). Multiple logistic regression showed that only the mean PU differed significantly between the groups. The area under the curve (AUC) of the equation derived from multiple logistic regression was 0.938, which did not differ from that of the mean PU alone (0.931; p=0.453). Using a cut-off point of 154.7PU, the sensitivity of LDI was 78.3% and the specificity was 92.7%. This cut-off point also yielded a sensitivity of 77.8% and specificity of 95.5% in the external validation dataset. LDI can help make a decision for surgery in the early stages of care for adults with indeterminate burns. Copyright © 2012 Elsevier Ltd and ISBI. All rights reserved.

  7. Insights into the use of thermography to assess burn wound healing potential: a reliable and valid technique when compared to laser Doppler imaging.

    PubMed

    Jaspers, Mariëlle E H; Maltha, Ilse; Klaessens, John H G M; de Vet, Henrica C W; Verdaasdonk, Rudolf M; van Zuijlen, Paul P M

    2016-09-01

    Adequate assessment of burn wounds is crucial in the management of burn patients. Thermography, as a noninvasive measurement tool, can be utilized to detect the remaining perfusion over large burn wound areas by measuring temperature, thereby reflecting the healing potential (HP) (i.e., number of days that burns require to heal). The objective of this study was to evaluate the clinimetric properties (i.e., reliability and validity) of thermography for measuring burn wound HP. To evaluate reliability, two independent observers performed a thermography measurement of 50 burns. The intraclass correlation coefficient (ICC), the standard error of measurement (SEM), and the limits of agreement (LoA) were calculated. To assess validity, temperature differences between burned and nonburned skin (?T) were compared to the HP found by laser Doppler imaging (serving as the reference standard). By applying a visual method, one ?T cutoff point was identified to differentiate between burns requiring conservative versus surgical treatment. The ICC was 0.99, expressing an excellent correlation between two measurements. The SEM was calculated at 0.22°C, the LoA at ?0.58°C and 0.64°C. The ?T cutoff point was ?0.07°C (sensitivity 80%; specificity 80%). These results show that thermography is a reliable and valid technique in the assessment of burn wound HP.

  8. Insights into the use of thermography to assess burn wound healing potential: a reliable and valid technique when compared to laser Doppler imaging

    NASA Astrophysics Data System (ADS)

    Jaspers, Mariëlle E. H.; Maltha, Ilse; Klaessens, John H. G. M.; de Vet, Henrica C. W.; Verdaasdonk, Rudolf M.; van Zuijlen, Paul P. M.

    2016-09-01

    Adequate assessment of burn wounds is crucial in the management of burn patients. Thermography, as a noninvasive measurement tool, can be utilized to detect the remaining perfusion over large burn wound areas by measuring temperature, thereby reflecting the healing potential (HP) (i.e., number of days that burns require to heal). The objective of this study was to evaluate the clinimetric properties (i.e., reliability and validity) of thermography for measuring burn wound HP. To evaluate reliability, two independent observers performed a thermography measurement of 50 burns. The intraclass correlation coefficient (ICC), the standard error of measurement (SEM), and the limits of agreement (LoA) were calculated. To assess validity, temperature differences between burned and nonburned skin (ΔT) were compared to the HP found by laser Doppler imaging (serving as the reference standard). By applying a visual method, one ΔT cutoff point was identified to differentiate between burns requiring conservative versus surgical treatment. The ICC was 0.99, expressing an excellent correlation between two measurements. The SEM was calculated at 0.22°C, the LoA at -0.58°C and 0.64°C. The ΔT cutoff point was -0.07°C (sensitivity 80% specificity 80%). These results show that thermography is a reliable and valid technique in the assessment of burn wound HP.

  9. Spatially resolved diffuse reflectance with laser Doppler imaging for the simultaneous in-vivo measurement of tissue perfusion and metabolic state

    NASA Astrophysics Data System (ADS)

    Forrester, Kevin R.; Shymkiw, Roxane; Tulip, John; Sutherland, Craig; Hart, David; Bray, Robert C.

    2000-06-01

    Laser Doppler Imaging (LDI) has become an established technique for the two dimensional measurement of tissue perfusion but the uncertainty of photon penetration depth leads to ambiguous interpretation of what fraction of the tissue microcirculation is being sampled. This study investigates a diffuse reflectance technique for measuring tissue optical properties during LDI perfusion measurement for the simultaneous determination of photon penetration depth and tissue metabolic state. LDI and diffuse reflectance spectroscopy measurements were made on surgically exposed ligaments in pregnant and non-pregnant rabbits. Photon penetration depths are reported. It was observed that anisotropic scattering occurs due to the ordered alignment of collagen fibers within ligament. Tissue perfusion in the ligaments of pregnant animals was significantly lower than in non-pregnant animals. Tissue hemoglobin concentration and oxygenation, and percent vascularization are also reported showing no statistical difference between the ligaments in pregnant and non-pregnant rabbits. A significant difference was observed in the photon scattering coefficient between the pregnant and non-pregnant groups suggesting a change in fibril spacing and/or orientation, most likely caused by an increased laxity in the ligaments of the pregnant animals. These investigations compare well with previous biochemical and biomechanical information obtained on ligaments.

  10. A comparison between objective and subjective image quality measurements for a full field digital mammography system.

    PubMed

    Marshall, N W

    2006-05-21

    This paper presents pre-sampling modulation transfer function (MTF), normalized noise power spectrum (NNPS) and detective quantum efficiency (DQE) results for an amorphous selenium (a-Se) full field digital mammography system. MTF was calculated from the image of an angled 0.5 mm thick Cu edge, acquired without additional beam filtration. NNPS data were acquired at detector air-kerma levels ranging from 9.1 microGy to 331 microGy, using a standard mammography x-ray spectrum of 28 kV, Mo/Mo target/filter combination and 4 cm of PMMA additional filtration. Prior to NNPS estimation, the image statistics were assessed using a variance image. This method was able to easily identify a detector artefact and should prove useful in routine quality assurance (QA) measurements. Detector DQE, calculated from the NNPS and MTF data, dropped to 0.3 for low detector air-kerma settings but reached an approximately constant value of 0.6 above 50 microGy at the detector. Subjective image quality data were also obtained at these detector air-kerma settings using the CDMAM contrast-detail (c-d) test object. The c-d data reflected the trend seen in DQE, with threshold contrast increasing at low detector air-kerma values. The c-d data were then compared against predictions made using two established models, the Rose model and a standard signal detection theory model. Using DQE(0), the Rose model gave results within approximately 15% on average for all the detector air-kerma values studied and for detail diameters down to 0.2 mm. Similar agreement was also found between the measured c-d data and the signal detection theory results, which were calculated using an ideal human visual response function and a system magnification of unity. The use of full spatial frequency DQE improved the agreement between the calculated and observer results for detail sizes below 0.13 mm.

  11. Widefield laser doppler velocimeter: development and theory.

    SciTech Connect

    Hansche, Bruce David; Reu, Phillip L.; Massad, Jordan Elias

    2007-03-01

    The widefield laser Doppler velocimeter is a new measurement technique that significantly expands the functionality of a traditional scanning system. This new technique allows full-field velocity measurements without scanning, a drawback of traditional measurement techniques. This is particularly important for tests in which the sample is destroyed or the motion of the sample is non-repetitive. The goal of creating ''velocity movies'' was accomplished during the research, and this report describes the current functionality and operation of the system. The mathematical underpinnings and system setup are thoroughly described. Two prototype experiments are then presented to show the practical use of the current system. Details of the corresponding hardware used to collect the data and the associated software to analyze the data are presented.

  12. Concurrent optical imaging spectroscopy and laser-Doppler flowmetry: the relationship between blood flow, oxygenation, and volume in rodent barrel cortex.

    PubMed

    Jones, M; Berwick, J; Johnston, D; Mayhew, J

    2001-06-01

    Functional magnetic resonance imaging (fMRI) is based on the coupling between neural activity and changes in the concentration of the endogenous paramagnetic contrast agent deoxygenated hemoglobin. Changes in the blood oxygen level-dependent (BOLD) signal result from a complex interplay of blood volume, flow, and oxygen consumption. Optical imaging spectroscopy (OIS) has been used to measure changes in blood volume and saturation in response to increased neural activity, while laser Doppler Flowmetry (LDF) can be used to measure flow changes and is now commonplace in neurovascular research. Here, we use concurrent OIS and LDF to examine the hemodynamic response in rodent barrel cortex using electrical stimulation of the whisker pad at varying intensities. Spectroscopic analysis showed that stimulation produced a biphasic early increase in deoxygenated hemoglobin (Hbr), followed by a decrease below baseline, reaching minima at approximately 3.7 s. There was no evidence for a corresponding early decrease in oxygenated hemoglobin (HbO(2)), which simply increased after stimulation, reaching maximum at approximately 3.2 s. The time courses of changes in blood volume (CBV) and blood flow (CBF) were similar. Both increased within a second of stimulation onset and peaked at approximately 2.7 s, after which CBV returned to baseline at a slower rate than CBF. The changes in Hbr, Hbt, and CBF were used to estimate changes in oxygen consumption (CMRO(2)), which increased within a second of stimulation and peaked approximately 2.2 s after stimulus onset. Analysis of the relative magnitudes of CBV and CBF indicates that the fractional changes of CBV could be simply scaled to match those of CBF. We found the relationship to be well approximated by CBV = CBF(0.29). A similar relationship was found using the response to elevated fraction of inspired carbon dioxide (FICO(2)). Copyright 2001 Academic Press.

  13. Novel instantaneous laser Doppler velocimeter.

    PubMed

    Avidor, J M

    1974-02-01

    A laser Doppler velocimeter capable of directly measuring instantaneous velocities is described. The new LDV uses a novel detection technique based on the utilization of a static slightly defocused spherical Fabry-Perot interferometer used in conjunction with a special mask for the detection of instantaneous Doppler frequency shifts. The essential characteristics of this LDV are discussed, and such a system recently developed is described. Results of turbulent flow measurements show good agreement with data obtained using hot wire anemometry.

  14. Nickel-Related Intestinal Mucositis in IBS-Like Patients: Laser Doppler Perfusion Imaging and Oral Mucosa Patch Test in Use.

    PubMed

    Borghini, Raffaele; Puzzono, Marta; Rosato, Edoardo; Di Tola, Marco; Marino, Mariacatia; Greco, Francesca; Picarelli, Antonio

    2016-09-01

    Nickel (Ni) is often the trigger of irritable bowel syndrome (IBS)-like gastrointestinal disorders: its ingestion may cause allergic contact mucositis, identifiable by means of oral mucosa patch test (omPT). OmPT effectiveness has been proven, but it is still an operator-dependent method. Laser Doppler perfusion imaging (LDPI) was tested to support omPT in Ni allergic contact mucositis diagnosis. Group A: 22 patients with intestinal/systemic symptoms related to the ingestion of Ni-containing foods. Group B: 12 asymptomatic volunteers. Ni-related symptoms and their severity were tested by a questionnaire. All patients underwent Ni omPT with clinical evaluation at baseline (T0), after 30 min (T1), after 2 h (T2), and after 24-48 h (T3). LDPI was performed to evaluate the mean mucosal perfusion at T0, T1, and T2. Statistical analysis was performed by ANOVA test and Bonferroni multiple-comparison test. All 22 Ni-sensitive patients (group A) presented oral mucosa hyperemia and/or edema at T2. Eight out of the same 22 patients presented a local delayed vesicular reaction at T3 (group A1), unlike the remaining 14 out of 22 patients (group A2). All 12 patients belonging to control group B did not show any alteration. The mean mucosal perfusion calculated with LDPI showed an increase in both subgroups A1 and A2. In group B, no significant perfusion variations were observed. LDPI may support omPT for diagnostic purposes in Ni allergic contact mucositis. This also applies to symptomatic Ni-sensitive patients without aphthous stomatitis after 24-48 h from omPT and that could risk to miss the diagnosis.

  15. Functional and morphological evaluation of hand microcirculation with nailfold capillaroscopy and laser Doppler imaging in Raynaud's and Sjögren's syndrome and poly/dermatomyositis.

    PubMed

    Szabo, N; Csiki, Z; Szanto, A; Danko, K; Szodoray, P; Zeher, M

    2008-01-01

    Nailfold capillaroscopy is widely used in autoimmune patients to determine capillary morphology. Laser Doppler imaging (LDI) is a relatively new method for measuring the microcirculation of cutaneous perfusion. The aim of this study was to investigate the capillary morphology and microcirculation among patients with Sjögren's syndrome (SS) and poly/dermatomyositis (PM/DM) with these two non-invasive methods and to detect secondary Raynaud's syndrome (SRS) in these autoimmune diseases. Thirty patients with primary SS, 30 patients with PM/DM, 30 patients with primary Raynaud's syndrome (PRS), and 30 healthy volunteers were included in the study. Nailfold capillaroscopy and LDI were performed on each patient. A comprehensive analysis was performed among the patients and healthy individuals. Among SS patients avascularity and among PM/DM patients avascularity and capillary morphology changes were most often detected by capillaroscopy. With LDI the mean steady-state cutaneous perfusion was 1.25 perfusion units (PU) in region of interest 1 (ROI1), 1.22 in ROI2, and 1.49 at the fingertips in PRS patients; the corresponding values were 1.2, 1.03, and 1.48 PU in SS, 0.91, 0.76, and 1.19 PU in PM/DM, and 1.79, 1.62, and 2.2 PU in the controls. The differences were significant between each autoimmune group compared to the control group (p<0.02, p<0.001, and p<0.001, respectively). By using nailfold capillaroscopy, abnormalities in capillary morphology can be detected, and by using LDI, the reduced blood flow in the capillaries can be detected. These investigations can be useful in the detection of SRS, or in distinguishing whether the reduced blood flow is due to primary/systemic autoimmune diseases.

  16. Relative indexes of cutaneous blood perfusion measured by real-time laser Doppler imaging (LDI) in healthy volunteers.

    PubMed

    Seyed Jafari, S Morteza; Schawkat, Megir; Van De Ville, Dimitri; Shafighi, Maziar

    2014-07-01

    We used real-time LDI to study regional variations in microcirculatory perfusion in healthy candidates to establish a new methodology for global perfusion body mapping that is based on intra-individual perfusion index ratios. Our study included 74 (37 female) healthy volunteers aged between 22 and 30 years (mean 24.49). Imaging was performed using a recent microcirculation-imaging camera (EasyLDI) for different body regions of each volunteer. The perfusion values were reported in Arbitrary Perfusion Units (APU). The relative perfusion indexes for each candidate's body region were then obtained by normalization with the perfusion value of the forehead. Basic parameters such as weight, height, and blood pressure were also measured and analyzed. The highest mean perfusion value was reported in the forehead area (259.21APU). Mean perfusion in the measured parts of the body correlated positively with mean forehead value, while there was no significant correlation between forehead blood perfusion values and room temperature, BMI, systolic blood pressure and diastolic blood pressure (p=0.420, 0.623, 0.488, 0.099, respectively). Analysis of the data showed that perfusion indexes were not significantly different between male and female volunteers except for the ventral upper arm area (p=.001). LDI is a non-invasive, fast technique that opens several avenues for clinical applications. The mean perfusion indexes are useful in clinical practice for monitoring patients before and after surgical interventions. Perfusion values can be predicted for different body parts for patients only by taking the forehead perfusion value and using the perfusion index ratios to obtain expected normative perfusion values. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. First steps toward 3D high resolution imaging using adaptive optics and full-field optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Blanco, Leonardo; Blavier, Marie; Glanc, Marie; Pouplard, Florence; Tick, Sarah; Maksimovic, Ivan; Chenegros, Guillaume; Mugnier, Laurent; Lacombe, Francois; Rousset, Gérard; Paques, Michel; Le Gargasson, Jean-François; Sahel, Jose-Alain

    2008-09-01

    We describe here two parts of our future 3D fundus camera coupling Adaptive Optics and full-field Optical Coherence Tomography. The first part is an Adaptive Optics flood imager installed at the Quinze-Vingts Hospital, regularly used on healthy and pathological eyes. A posteriori image reconstruction is performed, increasing the final image quality and field of view. The instrument lateral resolution is better than 2 microns. The second part is a full-field Optical Coherence Tomograph, which has demonstrated capability of performing a simple kind of "4 phases" image reconstruction of non biological samples and ex situ retinas. Final aim is to couple both parts in order to achieve 3D high resolution mapping of in vivo retinas.

  18. [Full-field digital mammography with amorphous silicon-based flat- panel detector: physical imaging characteristics and signal detection].

    PubMed

    Ideguchi, Tadamitsu; Higashida, Yoshiharu; Himuro, Kazuhiko; Ohki, Masafumi; Nakamura, Satoru; Yoshida, Akira; Takagi, Rie; Hatano, Hirohide; Kuwahara, Rie; Toyonaga, Makiko; Tanaka, Isamu; Toyofuku, Fukai

    2004-03-01

    The physical characteristics of a clinical amorphous silicon-based flat-panel imager for full-field digital mammography were investigated. Pre-sampled modulation transfer functions (MTF) were measured by using a slit method. Noise power spectra were determined for different input exposures by fast Fourier transform. The MTFs of full-field digital mammography systems showed significantly higher values than those of the computed radiography (CR) system. The full-field digital mammography system showed a lower noise level than that of the CR system under the same exposure conditions. Contrast detail analysis has been performed to compare the detectability of the full-field digital mammography system with that of the screen-film (Min-R 2000/Min-R 2000) system. The average contrast-detail curves of digital and film images were obtained from the results of observation. Image quality figures (IQF) were also calculated from the individual observer performance tests. The results indicated that the digital contrast-detail curves and IQF, on average, are superior to those of the screen-film system.

  19. Dynamic measurements of flowing cells labeled by gold nanoparticles using full-field photothermal interferometric imaging

    NASA Astrophysics Data System (ADS)

    Turko, Nir A.; Roitshtain, Darina; Blum, Omry; Kemper, Björn; Shaked, Natan T.

    2017-06-01

    We present highly dynamic photothermal interferometric phase microscopy for quantitative, selective contrast imaging of live cells during flow. Gold nanoparticles can be biofunctionalized to bind to specific cells, and stimulated for local temperature increase due to plasmon resonance, causing a rapid change of the optical phase. These phase changes can be recorded by interferometric phase microscopy and analyzed to form an image of the binding sites of the nanoparticles in the cells, gaining molecular specificity. Since the nanoparticle excitation frequency might overlap with the sample dynamics frequencies, photothermal phase imaging was performed on stationary or slowly dynamic samples. Furthermore, the computational analysis of the photothermal signals is time consuming. This makes photothermal imaging unsuitable for applications requiring dynamic imaging or real-time analysis, such as analyzing and sorting cells during fast flow. To overcome these drawbacks, we utilized an external interferometric module and developed new algorithms, based on discrete Fourier transform variants, enabling fast analysis of photothermal signals in highly dynamic live cells. Due to the self-interference module, the cells are imaged with and without excitation in video-rate, effectively increasing signal-to-noise ratio. Our approach holds potential for using photothermal cell imaging and depletion in flow cytometry.

  20. Dynamic measurements of flowing cells labeled by gold nanoparticles using full-field photothermal interferometric imaging.

    PubMed

    Turko, Nir A; Roitshtain, Darina; Blum, Omry; Kemper, Björn; Shaked, Natan T

    2017-06-01

    We present highly dynamic photothermal interferometric phase microscopy for quantitative, selective contrast imaging of live cells during flow. Gold nanoparticles can be biofunctionalized to bind to specific cells, and stimulated for local temperature increase due to plasmon resonance, causing a rapid change of the optical phase. These phase changes can be recorded by interferometric phase microscopy and analyzed to form an image of the binding sites of the nanoparticles in the cells, gaining molecular specificity. Since the nanoparticle excitation frequency might overlap with the sample dynamics frequencies, photothermal phase imaging was performed on stationary or slowly dynamic samples. Furthermore, the computational analysis of the photothermal signals is time consuming. This makes photothermal imaging unsuitable for applications requiring dynamic imaging or real-time analysis, such as analyzing and sorting cells during fast flow. To overcome these drawbacks, we utilized an external interferometric module and developed new algorithms, based on discrete Fourier transform variants, enabling fast analysis of photothermal signals in highly dynamic live cells. Due to the self-interference module, the cells are imaged with and without excitation in video-rate, effectively increasing signal-to-noise ratio. Our approach holds potential for using photothermal cell imaging and depletion in flow cytometry.

  1. Development of achromatic full-field x-ray microscopy with compact imaging mirror system

    NASA Astrophysics Data System (ADS)

    Matsuyama, S.; Emi, Y.; Kino, H.; Sano, Y.; Kohmura, Y.; Tamasaku, K.; Yabashi, M.; Ishikawa, T.; Yamauchi, K.

    2013-09-01

    Compact advanced Kirkpatrick-Baez optics are used to construct a microscope that is easy to align and robust against vibrations and thermal drifts. The entire length of the imaging mirror system is 286 mm, which is 34% shorter than the previous model. A spatial resolution test is performed in which magnified bright-field images of a pattern are taken with an X-ray camera at an energy of 10 keV at the BL29XUL beamline of SPring-8. A line-and-space pattern having a 50- nm width could be resolved, although the image contrast is low.

  2. Periodic artifact reduction in Fourier transforms of full field atomic resolution images.

    PubMed

    Hovden, Robert; Jiang, Yi; Xin, Huolin L; Kourkoutis, Lena F

    2015-04-01

    The discrete Fourier transform is among the most routine tools used in high-resolution scanning/transmission electron microscopy (S/TEM). However, when calculating a Fourier transform, periodic boundary conditions are imposed and sharp discontinuities between the edges of an image cause a cross patterned artifact along the reciprocal space axes. This artifact can interfere with the analysis of reciprocal lattice peaks of an atomic resolution image. Here we demonstrate that the recently developed Periodic Plus Smooth Decomposition technique provides a simple, efficient method for reliable removal of artifacts caused by edge discontinuities. In this method, edge artifacts are reduced by subtracting a smooth background that solves Poisson's equation with boundary conditions set by the image's edges. Unlike the traditional windowed Fourier transforms, Periodic Plus Smooth Decomposition maintains sharp reciprocal lattice peaks from the image's entire field of view.

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

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  4. 3D fingerprint imaging system based on full-field fringe projection profilometry

    NASA Astrophysics Data System (ADS)

    Huang, Shujun; Zhang, Zonghua; Zhao, Yan; Dai, Jie; Chen, Chao; Xu, Yongjia; Zhang, E.; Xie, Lili

    2014-01-01

    As an unique, unchangeable and easily acquired biometrics, fingerprint has been widely studied in academics and applied in many fields over the years. The traditional fingerprint recognition methods are based on the obtained 2D feature of fingerprint. However, fingerprint is a 3D biological characteristic. The mapping from 3D to 2D loses 1D information and causes nonlinear distortion of the captured fingerprint. Therefore, it is becoming more and more important to obtain 3D fingerprint information for recognition. In this paper, a novel 3D fingerprint imaging system is presented based on fringe projection technique to obtain 3D features and the corresponding color texture information. A series of color sinusoidal fringe patterns with optimum three-fringe numbers are projected onto a finger surface. From another viewpoint, the fringe patterns are deformed by the finger surface and captured by a CCD camera. 3D shape data of the finger can be obtained from the captured fringe pattern images. This paper studies the prototype of the 3D fingerprint imaging system, including principle of 3D fingerprint acquisition, hardware design of the 3D imaging system, 3D calibration of the system, and software development. Some experiments are carried out by acquiring several 3D fingerprint data. The experimental results demonstrate the feasibility of the proposed 3D fingerprint imaging system.

  5. Ultrathin forward-imaging short multimode fiber probe for full-field optical coherence microscopy

    NASA Astrophysics Data System (ADS)

    Sato, Manabu; Saito, Daisuke; Shouji, Kou; Kurotani, Reiko; Abe, Hiroyuki; Nishidate, Izumi

    2016-12-01

    To extend the applications of optical coherence tomography (OCT) to the fields of physiology and clinical medicine, less invasive, robust, and reliable optical probes are required. Thus, we demonstrate an ultrathin forward-imaging short multimode fiber (SMMF) optical coherence microscopy (OCM) probe with a 50 μm core diameter, 125 μm total diameter, and 5.12 mm length. Imaging conditions and magnification were analyzed, and they correspond closely to the measured results. The dispersion of the SMMF was investigated, and the modal dispersion coefficient was found to be 2.3% of the material dispersion coefficient. The axial resolution was minimized at 2.15 μm using a 0.885-mm-thick dispersion compensator. The lateral resolution was evaluated to be 4.38 μm using a test pattern. The contrast of the OCM images was 5.7 times higher than that of the signal images owing to the coherence gate. The depth of focus and diameter of the field of view were measured to be 60 μm and 40-50 μm, respectively. OCM images of the dried fins of small fish (Medaka) were measured and internal structures could be recognized.

  6. The influence of ocular pulsatility on scanning laser Doppler flowmetry.

    PubMed

    Sullivan, P; Cioffi, G A; Wang, L; Johnson, C A; Van Buskirk, E M; Sherman, K R; Bacon, D R

    1999-07-01

    To determine the effect of the cardiac cycle on scanning laser Doppler flowmeter measurements of retinal capillary blood flow in rhesus monkeys and humans. Multiple scanning laser Doppler flowmetry images of rhesus monkey and human retinal capillary blood flow over a range of heart rates were obtained. Average flow values were determined for the 64 scan lines that compose the two-dimensional flow map. Cutaneous blood flow was measured simultaneously with a laser Doppler flowmeter. The temporal relationships between retinal capillary blood flow, peripheral arterial pulse, and cutaneous blood flow were determined. In addition, human retinal capillary blood flow in a 10 x 10-pixel area during different phases of the cardiac cycle was compared. Regular oscillations in human and rhesus monkey retinal capillary blood flow are evident as alternating bright and dark horizontal bands in scanning laser Doppler flowmetry images. These fluctuations are temporally correlated with cutaneous blood flow. Linear regression of actual vs predicted heart rate based on peaks in retinal capillary flow yielded r = 0.999 in a rhesus monkey and 0.938 in a human. Retinal capillary blood flow in a 10 x 10-pixel area fluctuated as much as 50% depending on the phase of the cardiac cycle. The alternating bright and dark banding pattern observed in scanning laser Doppler flowmetry scans of retinal capillary blood flow is related to the cardiac pulse. The errors introduced by pulse-related fluctuations in retinal capillary blood flow are significant and must be minimized or corrected for accurate and reproducible measurements of ocular hemodynamics.

  7. Full field spatially-variant image-based resolution modelling reconstruction for the HRRT.

    PubMed

    Angelis, Georgios I; Kotasidis, Fotis A; Matthews, Julian C; Markiewicz, Pawel J; Lionheart, William R; Reader, Andrew J

    2015-03-01

    Accurate characterisation of the scanner's point spread function across the entire field of view (FOV) is crucial in order to account for spatially dependent factors that degrade the resolution of the reconstructed images. The HRRT users' community resolution modelling reconstruction software includes a shift-invariant resolution kernel, which leads to transaxially non-uniform resolution in the reconstructed images. Unlike previous work to date in this field, this work is the first to model the spatially variant resolution across the entire FOV of the HRRT, which is the highest resolution human brain PET scanner in the world. In this paper we developed a spatially variant image-based resolution modelling reconstruction dedicated to the HRRT, using an experimentally measured shift-variant resolution kernel. Previously, the system response was measured and characterised in detail across the entire FOV of the HRRT, using a printed point source array. The newly developed resolution modelling reconstruction was applied on measured phantom, as well as clinical data and was compared against the HRRT users' community resolution modelling reconstruction, which is currently in use. Results demonstrated improvements both in contrast and resolution recovery, particularly for regions close to the edges of the FOV, with almost uniform resolution recovery across the entire transverse FOV. In addition, because the newly measured resolution kernel is slightly broader with wider tails, compared to the deliberately conservative kernel employed in the HRRT users' community software, the reconstructed images appear to have not only improved contrast recovery (up to 20% for small regions), but also better noise characteristics.

  8. Improving chemical mapping algorithm and visualization in full-field hard x-ray spectroscopic imaging

    NASA Astrophysics Data System (ADS)

    Chang, Cheng; Xu, Wei; Chen-Wiegart, Yu-chen Karen; Wang, Jun; Yu, Dantong

    2013-12-01

    X-ray Absorption Near Edge Structure (XANES) imaging, an advanced absorption spectroscopy technique, at the Transmission X-ray Microscopy (TXM) Beamline X8C of NSLS enables high-resolution chemical mapping (a.k.a. chemical composition identification or chemical spectra fitting). Two-Dimensional (2D) chemical mapping has been successfully applied to study many functional materials to decide the percentages of chemical components at each pixel position of the material images. In chemical mapping, the attenuation coefficient spectrum of the material (sample) can be fitted with the weighted sum of standard spectra of individual chemical compositions, where the weights are the percentages to be calculated. In this paper, we first implemented and compared two fitting approaches: (i) a brute force enumeration method, and (ii) a constrained least square minimization algorithm proposed by us. Next, as 2D spectra fitting can be conducted pixel by pixel, so theoretically, both methods can be implemented in parallel. In order to demonstrate the feasibility of parallel computing in the chemical mapping problem and investigate how much efficiency improvement can be achieved, we used the second approach as an example and implemented a parallel version for a multi-core computer cluster. Finally we used a novel way to visualize the calculated chemical compositions, by which domain scientists could grasp the percentage difference easily without looking into the real data.

  9. Laser Doppler dust devil measurements

    NASA Technical Reports Server (NTRS)

    Bilbro, J. W.; Jeffreys, H. B.; Kaufman, J. W.; Weaver, E. A.

    1977-01-01

    A scanning laser doppler velocimeter (SLDV) system was used to detect, track, and measure the velocity flow field of naturally occurring tornado-like flows (dust devils) in the atmosphere. A general description of the dust devil phenomenon is given along with a description of the test program, measurement system, and data processing techniques used to collect information on the dust devil flow field. The general meteorological conditions occurring during the test program are also described, and the information collected on two selected dust devils are discussed in detail to show the type of information which can be obtained with a SLDV system. The results from these measurements agree well with those of other investigators and illustrate the potential for the SLDV in future endeavors.

  10. Improved Newton-Raphson digital image correlation method for full-field displacement and strain calculation.

    PubMed

    Cofaru, Corneliu; Philips, Wilfried; Van Paepegem, Wim

    2010-11-20

    The two-dimensional in-plane displacement and strain calculation problem through digital image processing methods has been studied extensively in the past three decades. Out of the various algorithms developed, the Newton-Raphson partial differential correction method performs the best quality wise and is the most widely used in practical applications despite its higher computational cost. The work presented in this paper improves the original algorithm by including adaptive spatial regularization in the minimization process used to obtain the motion data. Results indicate improvements in the strain accuracy for both small and large strains. The improvements become even more significant when employing small displacement and strain window sizes, making the new method highly suitable for situations where the underlying strain data presents both slow and fast spatial variations or contains highly localized discontinuities.

  11. Applying RGB LED in full-field optical coherence tomography for real-time full-color tissue imaging.

    PubMed

    Yang, Bor-Wen; Wang, Yu-Yen; Lin, Yu-Min; Juan, Yu-Shan; Chen, Hung-Te; Ying, Shang-Ping

    2014-08-01

    A conventional handheld skin camera is suitable for 2D inspection of shallow skin. Due to its high resolution and noninvasiveness, optical coherence tomography (OCT) has become a popular medical-imaging technology. Among OCT schemes, full-field optical coherence tomography (FF-OCT) is suitable for rapid en face imaging, as it uses a 2D imaging device for pixel processing of a sample plane. Because of its wide bandwidth and long lifetime, an RGB LED was chosen in an FF-OCT system among three source candidates in this study. A full-color tissue image and real-time video were obtained from the system to demonstrate the potential of the RGB LED FF-OCT system in medical imaging. All devices used here can be integrated by micro-optoelectromechanical technology into a handheld model. Noninvasive, real-time, full-color handheld imaging capability contributes to advance dermatology and cosmetology.

  12. Caffeine consumption does not have an effect on digital microvascular perfusion assessed by laser Doppler imaging on healthy volunteers: a pilot study.

    PubMed

    Knight, R; Pagkalos, J; Timmons, C; Jose, R

    2015-05-01

    Caffeine is one of the most commonly consumed pharmacologically active ingredients in the Western world. It is postulated to cause peripheral vasoconstriction and decreased digital blood flow. As a result, many hand surgeons forbid caffeine consumption post-operatively by patients undergoing replantation surgery for fear of compromising healing. We hypothesized that caffeine has no effect on digital microvascular perfusion. Healthy volunteers were recruited and digital microperfusion was assessed using laser Doppler probes attached to the finger pulp, both before and after ingestion of 100 mg of caffeine. A total of 34 patients were included in the final study. The mean flow before the consumption of caffeine was 226.15 PU. The mean flow following the consumption of caffeine was 197.7 PU. This decrease was not statistically significant. This study revealed no decrease in digital blood flow following the ingestion of 100 mg of caffeine by healthy volunteers, as measured by laser Doppler flow monitoring. 3. © The Author(s) 2014.

  13. Image stack alignment in full-field X-ray absorption spectroscopy using SIFT_PyOCL.

    PubMed

    Paleo, Pierre; Pouyet, Emeline; Kieffer, Jérôme

    2014-03-01

    Full-field X-ray absorption spectroscopy experiments allow the acquisition of millions of spectra within minutes. However, the construction of the hyperspectral image requires an image alignment procedure with sub-pixel precision. While the image correlation algorithm has originally been used for image re-alignment using translations, the Scale Invariant Feature Transform (SIFT) algorithm (which is by design robust versus rotation, illumination change, translation and scaling) presents an additional advantage: the alignment can be limited to a region of interest of any arbitrary shape. In this context, a Python module, named SIFT_PyOCL, has been developed. It implements a parallel version of the SIFT algorithm in OpenCL, providing high-speed image registration and alignment both on processors and graphics cards. The performance of the algorithm allows online processing of large datasets.

  14. Anterior segment imaging in vivo in rats and ex vivo in mice using full-field optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Grieve, Kate; Kuchynka, Petr; Simonutti, Manuel; Dubois, Arnaud; Le Gargasson, Jean-François; Boccara, Albert Claude

    2006-02-01

    We present results of ex vivo imaging of the mouse cornea following photorefractive keratectomy and in vivo imaging in the anterior segment of the rat eye using full-field optical coherence tomography. The instrument is based on the Linnik interferometer, illuminated by a white light source: a tungsten halogen lamp for ex vivo imaging and a fibered Xenon arc lamp for in vivo imaging. En face tomographic images are obtained in real-time without scanning by calculating the difference of two phase-opposed interferometric images recorded by a CCD or CMOS camera. Spatial resolution of ~1 μm in both axial and lateral directions is achieved thanks to the short coherence length of the illumination source and the use of relatively high numerical aperture microscope objectives. A detection sensitivity of up to 90 dB is reached by means of pixel binning and image averaging. Photorefractive keratectomy was performed on mice and the excised eyes were examined under immersion 21 days after surgery. Rats were anesthetized and their anterior segments imaged under immersion. The high resolution of our instrument gives cellular-level resolution in the cornea, allowing visualization of individual stromal keratocytes and collagen fibers, and cells in the endothelium. The basal and Descemet's membranes are well defined. Quantitative measurement of scattering in each layer is possible. Penetration to the level of the lens surface is achieved. Acquisition of stacks of en face images permits three-dimensional navigation through the cornea. Development of image treatment algorithms to allow three-dimensional reconstruction is discussed. The full-field optical coherence tomography technique could be useful in monitoring corneal scattering following refractive surgery.

  15. Redox and speciation mapping of rock thin sections using high spatial resolution full-field imaging technique

    NASA Astrophysics Data System (ADS)

    de Andrade, V.; Susini, J.; Salomé, M.; Beraldin, O.; Heymes, T.; Lewin, E.

    2009-04-01

    Because of their complex genesis, natural rocks are the most often heterogeneous systems, with various scale-level heterogeneities for both chemistry and structure. In the last decade, the dramatic improvements of hyperspectral imaging techniques provided new tools for accurate material characterisation. Most of these micro- and nano- analytical techniques rely on scanning instruments, which offer high spatial resolution but suffer from long acquisition times imposing practical limits on the field of view. Conversely, full-field imaging techniques rely on a fast parallel acquisition but have limited resolution. Although soft X-ray full-field microscopes based on Fresnel zone plates are commonly used for high resolution imaging, its combination with spectroscopy is challenging and 2D chemical mapping still difficult. For harder X-rays, lensless X-ray microscope based on simple propagation geometry is easier and can be readily used for 2D spectro-microscopy. A full-field experimental setup was optimized at the ESRF-ID21 beamline to image iron redox and speciation distributions in rocks thin sections. The setup comprises a Si111 or Si220 (E = 0.4 eV) monochromator, a special sample stage and a sensitive camera associated with a brand new GGG:Eu light conversion scintillator and high magnification visible light optics. The pixel size ranges from 1.6 to 0.16 m according to the optic used. This instrument was used to analyse phyllosilicates and oxides of metamorphic sediments coming from the Aspromonte nappes-pile in Calabria. Iron chemical state distributions were derived - from images of 1000 Ã- 2000 Ã- 30 m3 rock thin sections - by subtraction of absorption images above and below the Fe K-edge. Using an automatic stitching reconstruction, a wide field image (4Ã-3 mm2 with a 1 m2 resolution for a total of about 12 millions pixels) of Fetotal elemental distribution was produced. Moreover, -XANES analyses (more than 1 million individual -XANES spectra) were performed

  16. Compact LED-based full-field optical coherence microscopy for high-resolution high-speed in vivo imaging

    NASA Astrophysics Data System (ADS)

    Ogien, Jonas; Dubois, Arnaud

    2017-02-01

    This work reports on a compact full-field optical coherence microscopy (FF-OCM) setup specifically designed to meet the needs for in vivo imaging, illuminated by a high-brightness broadband light emitting diode (LED). Broadband LEDs have spectra potentially large enough to provide imaging spatial resolutions similar to those reached using conventional halogen lamps, but their radiance can be much higher, which leads to high speed acquisition and makes in vivo imaging possible. We introduce a FF-OCM setup using a 2.3 W broadband LED, with an interferometer designed to be as compact as possible in order to provide the basis for a portable system that will make it possible to fully benefit from the capacity for in vivo imaging by providing the ability to image any region of interest in real-time. The interferometer part of the compact FF-OCM setup weighs 210 g for a size of 11x11x5 cm3. Using this setup, a sub-micron axial resolution was reached, with a detection sensitivity of 68 dB at an imaging rate of 250 Hz. Due to the high imaging rate, the sensitivity could be improved by accumulation while maintaining an acquisition time short enough for in vivo imaging. It was possible to reach a sensitivity of 75 dB at a 50 Hz imaging rate. High resolution in vivo human skin images were obtained with this setup and compared with images of excised human skin, showing high similarity.

  17. Single-camera high-speed stereo-digital image correlation for full-field vibration measurement

    NASA Astrophysics Data System (ADS)

    Yu, Liping; Pan, Bing

    2017-09-01

    A low-cost, easy-to-implement single-camera high-speed stereo-digital image correlation (SCHS stereo-DIC) method using a four-mirror adapter is proposed for full-field 3D vibration measurement. With the aid of the four-mirror adapter, surface images of calibration target and test objects can be separately imaged onto two halves of the camera sensor through two different optical paths. These images can be further processed to retrieve the vibration responses on the specimen surface. To validate the effectiveness and accuracy of the proposed approach, dynamic parameters including natural frequencies, damping ratios and mode shapes of a rectangular cantilever plate were extracted from the directly measured vibration responses using the established system. The results reveal that the SCHS stereo-DIC is a simple, practical and effective technique for vibration measurements and dynamic parameters identification.

  18. First results with real-time selenium-based full-field digital mammography three-dimensional imaging system

    NASA Astrophysics Data System (ADS)

    Lehtimaki, Mari; Pamilo, Martti; Raulisto, Leena; Kalke, Martti

    2004-05-01

    Our goal in this paper is to evaluate the capability of real-time selenium-technology-based full-field digital mammography (FFDM) system in breast tomosynthesis. The objective of this study is to find out the present status of amorphous selenium technology in the sense of advanced applications in clinical use. We were using tuned aperture computed tomography (TACT+) 3-dimensional (3D) technology for reconstruction. Under evaluation were amorphous selenium signal-to-noise-ratio, flat panel image artefacts and acquisition time to perform full-field digital mammography 3D examination. To be able to validate the system we used a special breast phantom. We found out that 3D imaging technology provides diagnostic value and benefits over 2-dimensional (2D) imaging. 3D TACT advantages are to define if mammography finding is caused by a real abnormal lesion or by superposition of normal parenchymal structures, to be able to diagnose and analyze the findings properly, to detect changes in breast tissue which would otherwise be missed, to verify the possible multifocality of the breast cancers, to verify the correct target for biopsies and to reduce number of biopsies performed. Slice visualization and 3D volume model provide greater diagnostic information compared to 2D projection screening and diagnostic imaging.

  19. Laser Doppler Measurement of Atmopsheric Wind Velocity

    NASA Technical Reports Server (NTRS)

    Schwiesow, R. L.; Abshire, N. L.; Derr, V. E.

    1973-01-01

    Our presentation consists of two parts: (1) a summary review of laser Doppler principles and applications, and (2) operational design and preliminary laboratory tests of a CO2 laser system for NOAA applications.

  20. Enhancement of the resolution of full-field optical coherence tomography by using a colour image sensor

    SciTech Connect

    Kalyanov, A L; Lychagov, V V; Smirnov, I V; Ryabukho, V P

    2013-08-31

    The influence of white balance in a colour image detector on the resolution of a full-field optical coherence tomograph (FFOCT) is studied. The change in the interference pulse width depending on the white balance tuning is estimated in the cases of a thermal radiation source (incandescent lamp) and a white light emitting diode. It is shown that by tuning white balance of the detector in a certain range, the FFOCT resolution can be increased by 20 % as compared to the resolution, attained with the use of a monochrome detector. (optical coherence tomography)

  1. Full-field dynamic displacement and strain measurement using pulsed and high-speed 3D image correlation photogrammetry

    NASA Astrophysics Data System (ADS)

    Schmidt, Timothy; Tyson, John; Galanulis, Konstantin

    2004-02-01

    3D image correlation is a robust method for measuring full-field displacements and strains using a calibrated pair of video cameras. Underlying principles and benefits are reviewed, and the method is compared to both 3D ESPI and 2D image correlation. Several applications combining image correlation photogrammetry with stroboscopic illumination and/or high-speed video cameras are presented. Operational strains in ionic polymeric muscle samples and electro-restrictive actuators are determined. The use of short-duration white light pulses to study automobile tires on road wheels at speeds up to 150 miles per hour is demonstrated. Initial work measuring strains on an 18" flywheel in a spin pit at up to 35,000 rpm is described. A notched rubber dogbone sample is pulled to failure at 125% strain in 38 milliseconds, and hundreds of full-field strain maps are captured. This paper includes discussion of sample preparation methods and special lighting systems, including pulsed arc lamps and pulsed lasers. A matrix of capability using available high speed cameras is included.

  2. Defect visualization of aircraft UHF antenna radome using full-field pulse-echo ultrasonic propagation imaging system

    NASA Astrophysics Data System (ADS)

    Shin, H. J.; Hong, S. C.; Lee, J. R.; Kim, J. H.

    2016-10-01

    Most of aircraft antennas usually have various types of radome made of composite materials for protecting antenna structures. However, these antenna radome structures, which are installed on the outside of airplane, are easy to be damaged by external forces such as drag, foreign object, bird strike and others. In this study, full-field pulse-echo ultrasonic propagation imaging (PE UPI) system is proposed as the non-destructive inspection technique to visualize manufacturing defects in composite antenna radome. Based on the results of the sample case study, it is shown that the ultrasonic wave propagation imaging (UWPI) that is generated by the proposed full-field PE UPI system is able to highlight the intact internal condition of antenna structure and its defect area. Additional damage visualization techniques like ultrasonic energy mapping (UEM), variable time window amplitude map (VTWAM) and also ultrasonic spectral imaging (USI) algorithms are applied to improve the reliability of the damage visualization. It can be concluded that the proposed PE UPI system is an effective non-destructive inspection technique for the composite radome structures.

  3. High-resolution full-field optical coherence microscopy using a Mirau interferometer for the quantitative imaging of biological cells.

    PubMed

    Anna, Tulsi; Srivastava, Vishal; Mehta, Dalip Singh; Shakher, Chandra

    2011-12-01

    In this paper quantitative imaging of biological cells using high-resolution full-field optical coherence microscopy (FF-OCM) is reported. The FF-OCM was realized using a swept-source system, a Mirau interferometer, and a CCD camera (a two-dimensional detection unit). A Mirau-interferometric objective lens was used to generate the interferometric signal. The signal was analyzed by a Fourier analysis technique. Optically sectioned amplitude images and a quantitative phase map of biological cells such as onion skin and red blood cells (RBCs) are demonstrated. Further, the refractive index profile of the RBCs is also presented. For the 50× Mirau objective, the experimentally achieved axial and transverse resolution of the present system are 3.8 and 1.2 μm, respectively. The CCD provides parallel detection and measures enface images without X, Y, Z mechanical scanning.

  4. High-dynamic-range microscope imaging based on exposure bracketing in full-field optical coherence tomography.

    PubMed

    Leong-Hoi, Audrey; Montgomery, Paul C; Serio, Bruno; Twardowski, Patrice; Uhring, Wilfried

    2016-04-01

    By applying the proposed high-dynamic-range (HDR) technique based on exposure bracketing, we demonstrate a meaningful reduction in the spatial noise in image frames acquired with a CCD camera so as to improve the fringe contrast in full-field optical coherence tomography (FF-OCT). This new signal processing method thus allows improved probing within transparent or semitransparent samples. The proposed method is demonstrated on 3 μm thick transparent polymer films of Mylar, which, due to their transparency, produce low contrast fringe patterns in white-light interference microscopy. High-resolution tomographic analysis is performed using the technique. After performing appropriate signal processing, resulting XZ sections are observed. Submicrometer-sized defects can be lost in the noise that is present in the CCD images. With the proposed method, we show that by increasing the signal-to-noise ratio of the images, submicrometer-sized defect structures can thus be detected.

  5. Fast subsurface fingerprint imaging with full-field optical coherence tomography system equipped with a silicon camera.

    PubMed

    Auksorius, Egidijus; Boccara, A Claude

    2017-09-01

    Images recorded below the surface of a finger can have more details and be of higher quality than the conventional surface fingerprint images. This is particularly true when the quality of the surface fingerprints is compromised by, for example, moisture or surface damage. However, there is an unmet need for an inexpensive fingerprint sensor that is able to acquire high-quality images deep below the surface in short time. To this end, we report on a cost-effective full-field optical coherent tomography system comprised of a silicon camera and a powerful near-infrared LED light source. The system, for example, is able to record 1.7  cm×1.7  cmen face images in 0.12 s with the spatial sampling rate of 2116 dots per inch and the sensitivity of 93 dB. We show that the system can be used to image internal fingerprints and sweat ducts with good contrast. Finally, to demonstrate its biometric performance, we acquired subsurface fingerprint images from 240 individual fingers and estimated the equal-error-rate to be ∼0.8%. The developed instrument could also be used in other en face deep-tissue imaging applications because of its high sensitivity, such as in vivo skin imaging. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

  6. Full-field modal analysis during base motion excitation using high-speed 3D digital image correlation

    NASA Astrophysics Data System (ADS)

    Molina-Viedma, Ángel J.; López-Alba, Elías; Felipe-Sesé, Luis; Díaz, Francisco A.

    2017-10-01

    In recent years, many efforts have been made to exploit full-field measurement optical techniques for modal identification. Three-dimensional digital image correlation using high-speed cameras has been extensively employed for this purpose. Modal identification algorithms are applied to process the frequency response functions (FRF), which relate the displacement response of the structure to the excitation force. However, one of the most common tests for modal analysis involves the base motion excitation of a structural element instead of force excitation. In this case, the relationship between response and excitation is typically based on displacements, which are known as transmissibility functions. In this study, a methodology for experimental modal analysis using high-speed 3D digital image correlation and base motion excitation tests is proposed. In particular, a cantilever beam was excited from its base with a random signal, using a clamped edge join. Full-field transmissibility functions were obtained through the beam and converted into FRF for proper identification, considering a single degree-of-freedom theoretical conversion. Subsequently, modal identification was performed using a circle-fit approach. The proposed methodology facilitates the management of the typically large amounts of data points involved in the DIC measurement during modal identification. Moreover, it was possible to determine the natural frequencies, damping ratios and full-field mode shapes without requiring any additional tests. Finally, the results were experimentally validated by comparing them with those obtained by employing traditional accelerometers, analytical models and finite element method analyses. The comparison was performed by using the quantitative indicator modal assurance criterion. The results showed a high level of correspondence, consolidating the proposed experimental methodology.

  7. Laser Doppler velocimeter system simulation for sensing aircraft wake vortices

    NASA Technical Reports Server (NTRS)

    Thomson, J. A. L.; Meng, J. C. S.

    1974-01-01

    A hydrodynamic model of aircraft vortex wakes in an irregular wind shear field near the ground is developed and used as a basis for modeling the characteristics of a laser Doppler detection and vortex location system. The trailing vortex sheet and the wind shear are represented by discrete free vortices distributed over a two-dimensional grid. The time dependent hydrodynamic equations are solved by direct numerical integration in the Boussinesq approximation. The ground boundary is simulated by images, and fast Fourier Transform techniques are used to evaluate the vorticity stream function. The atmospheric turbulence was simulated by constructing specific realizations at time equal to zero, assuming that Kolmogoroff's law applies, and that the dissipation rate is constant throughout the flow field. The response of a simulated laser Doppler velocimeter is analyzed by simulating the signal return from the flow field as sensed by a simulation of the optical/electronic system.

  8. 3D Imaging of Nickel Oxidation States using Full Field X-ray Absorption Near Edge Structure Nanotomography

    SciTech Connect

    Nelson, George; Harris, William; Izzo, John; Grew, Kyle N.

    2012-01-20

    Reduction-oxidation (redox) cycling of the nickel electrocatalyst phase in the solid oxide fuel cell (SOFC) anode can lead to performance degradation and cell failure. A greater understanding of nickel redox mechanisms at the microstructural level is vital to future SOFC development. Transmission x-ray microscopy (TXM) provides several key techniques for exploring oxidation states within SOFC electrode microstructure. Specifically, x-ray nanotomography and x-ray absorption near edge structure (XANES) spectroscopy have been applied to study samples of varying nickel (Ni) and nickel oxide (NiO) compositions. The imaged samples are treated as mock SOFC anodes containing distinct regions of the materials in question. XANES spectra presented for the individual materials provide a basis for the further processing and analysis of mixed samples. Images of composite samples obtained are segmented, and the distinct nickel and nickel oxide phases are uniquely identified using full field XANES spectroscopy. Applications to SOFC analysis are discussed.

  9. Time-Lapse Observation of Electrolysis of Copper Sulfate with a Full-Field X-ray Fluorescence Imaging Microscope

    NASA Astrophysics Data System (ADS)

    Ohigashi, Takuji; Aota, Tatsuya; Watanabe, Norio; Takano, Hidekazu; Yokosuka, Hiroki; Aoki, Sadao

    2008-06-01

    The time-lapse observation of the electrodeposition of copper in copper sulfate solution was performed by imaging X-ray fluorescence from the copper deposition. The X-ray fluorescence was directly imaged with a full-field Wolter mirror microscope, which was constructed at the Photon Factory. Controlling the electric current in the solution from 0 to 71.7 µA, the deposition of copper on a Pt cathode was directly observed by imaging its X-ray fluorescence. One exposure time for obtaining an X-ray fluorescence image was 80 s. Then, it was 17 min later from the beginning of the electrolysis when the X-ray fluorescence image of the electrodeposition is observed for the first time. At this exposure time, the detection limit of the mass of copper was estimated to be 0.60 pg/image, which was calculated using test samples of 1.00×10-3-1.00 mol/l copper sulfate solutions.

  10. Tissue perfusion measurements: multiple-exposure laser speckle analysis generates laser Doppler-like spectra.

    PubMed

    Thompson, Oliver B; Andrews, Michael K

    2010-01-01

    Variations in skin perfusion are easily detected by laser speckle contrast maps, but a robust interpretation of the information has been lacking. We show that multiple-exposure laser speckle methods produce the same spectral information as laser Doppler methods when applied to targets with embedded moving scatterers. This enables laser speckle measurements to be interpreted more quantitatively. We do this by using computer simulation of speckle data, and by experimental measurements on Brownian motion and skin perfusion using a laser Doppler system and a multiple-exposure laser speckle system. The power spectral density measurements of the light fluctuations derived using both techniques are exactly equivalent. Dermal perfusion can therefore be measured by laser Doppler or laser speckle contrast methods. In particular, multiexposure laser speckle can be rapidly processed to generate a full-field map of the perfusion index proportional to the concentration and mean velocity of red blood cells.

  11. Label-free subcellular 3D live imaging of preimplantation mouse embryos with full-field optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Zheng, Jing-gao; Lu, Danyu; Chen, Tianyuan; Wang, Chengming; Tian, Ning; Zhao, Fengying; Huo, Tiancheng; Zhang, Ning; Chen, Dieyan; Ma, Wanyun; Sun, Jia-lin; Xue, Ping

    2012-07-01

    Early patterning and polarity is of fundamental interest in preimplantation embryonic development. Label-free subcellular 3D live imaging is very helpful to its related studies. We have developed a novel system of full-field optical coherence tomography (FF-OCT) for noninvasive 3D subcellular live imaging of preimplantation mouse embryos with no need of dye labeling. 3D digitized embryos can be obtained by image processing. Label-free 3D live imaging is demonstrated for the mouse embryos at various typical preimplantation stages with a spatial resolution of 0.7 μm and imaging rate of 24 fps. Factors that relate to early patterning and polarity, such as pronuclei in zygote, shapes of zona pellucida, location of second polar body, cleavage planes, and the blastocyst axis, can be quantitatively measured. The angle between the two second cleavage planes is accurately measured to be 87 deg. It is shown that FF-OCT provides a potential breakthrough for early patterning, polarity formation, and many other preimplantation-related studies in mammalian developmental biology.

  12. Super-resolved image acquisition with full-field localization-based microscopy: theoretical analysis and evaluation

    NASA Astrophysics Data System (ADS)

    Son, Taehwang; Lee, Wonju; Kim, Donghyun

    2016-02-01

    We analyze and evaluate super-resolved image acquisition with full-field localization microscopy in which an individual signal sampled by localization may or may not be switched. For the analysis, Nyquist-Shannon sampling theorem based on ideal delta function was extended to sampling with unit pulse comb and surface-enhanced localized near-field that was numerically calculated with finite difference time domain. Sampling with unit pulse was investigated in Fourier domain where magnitude of baseband becomes larger than that of adjacent subband, i.e. aliasing effect is reduced owing to pulse width. Standard Lena image was employed as imaging target and a diffraction-limited optical system is assumed. A peak signal-to-noise ratio (PSNR) was introduced to evaluate the efficiency of image reconstruction quantitatively. When the target was sampled without switching by unit pulse as the sampling width and period are varied, PSNR increased eventually to 18.1 dB, which is the PSNR of a conventional diffraction-limited image. PSNR was found to increase with a longer pulse width due to reduced aliasing effect. When switching of individual sampling pulses was applied, blurry artifact outside the excited field is removed for each pulse and PSNR soars to 25.6 dB with a shortened pulse period, i.e. effective resolution of 72 nm is obtained, which can further be decreased.

  13. Measurement of high temperature full-field strain up to 2000 °C using digital image correlation

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Xu, Chenghai; Jin, Hua; Meng, Songhe; Zhang, Yumin; Xie, Weihua

    2017-03-01

    Understanding the deformation and strain at elevated temperature is a critical factor for the stability of aerodynamic shape, and an important consideration for the thermal protection system design. However, accurate measurement of deformation and strain at high temperatures is a challenge. Here, we present a measurement study for full-field strain mapping up to 2000 °C using digital image correlation (DIC) method, which mainly depends on the quality of speckle patterns on the specimen surface. In our study, the strain values are analyzed by DIC method while specimens are heated using a large electric current. Improvements in filtering and speckling allow the measured temperatures using this method to reach 2000 °C. We confirmed the validity of this method by comparison of measured Young’s modulus values with reference data for Inconel 718 Ni-based superalloy and graphite at different temperatures. Additionally, the full-field strain and Young’s modulus were demonstrated for a carbon fiber-reinforced carbon (C/C) composite uniaxial tensile specimen at 2000 °C.

  14. Full-field wing deformation measurement scheme for in-flight cantilever monoplane based on 3D digital image correlation

    NASA Astrophysics Data System (ADS)

    Li, Lei-Gang; Liang, Jin; Guo, Xiang; Guo, Cheng; Hu, Hao; Tang, Zheng-Zong

    2014-06-01

    In this paper, a new non-contact scheme, based on 3D digital image correlation technology, is presented to measure the full-field wing deformation of in-flight cantilever monoplanes. Because of the special structure of the cantilever wing, two conjugated camera groups, which are rigidly connected and calibrated to an ensemble respectively, are installed onto the vertical fin of the aircraft and record the whole measurement. First, a type of pre-stretched target and speckle pattern are designed to adapt the oblique camera view for accurate detection and correlation. Then, because the measurement cameras are swinging with the aircraft vertical trail all the time, a camera position self-correction method (using control targets sprayed on the back of the aircraft), is designed to orientate all the cameras’ exterior parameters to a unified coordinate system in real time. Besides, for the excessively inclined camera axis and the vertical camera arrangement, a weak correlation between the high position image and low position image occurs. In this paper, a new dual-temporal efficient matching method, combining the principle of seed point spreading, is proposed to achieve the matching of weak correlated images. A novel system is developed and a simulation test in the laboratory was carried out to verify the proposed scheme.

  15. Imaging vascular dynamics in human retina using full-field swept-source optical coherence tomography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Spahr, Hendrik; Hillmann, Dierck; Hain, Carola; Pfäffle, Clara; Sudkamp, Helge; Franke, Gesa; Hüttmann, Gereon

    2016-03-01

    We demonstrate a new non-invasive method to assess the functional condition of the retinal vascular system. Phase-sensitive full-field swept-source optical coherence tomography (PhS-FF-SS-OCT) is used to investigate retinal vascular dynamics at unprecedented temporal resolution. Motion of retinal tissue, that is induced by expansion of the vessels therein, is measured with an accuracy of about 10 nm. The pulse shape of arterial and venous pulsation, their temporal delay as well as the frequency dependent pulse propagation through the capillary bed are determined. For the first time, imaging speed and motion sensitivity are sufficient for a direct measurement of pulse waves propagating with more than 600 mm/s in retinal vessels of a healthy young subject.

  16. A Full-Field KB-FZP Microscope for Hard X-Ray Imaging with Sub 100 nm Resolution

    SciTech Connect

    Rau, C.; Crecea, V.; Peterson, K.M.; Jemian, P.R.; Richter, C.-P.; Neuhausler, U.; Schmeider, G.; Yu, X.; Braun, P.V.; Robinson, I.K.

    2007-06-28

    A full-field hard X-ray microscope has been built at the UNICAT/APS beamline 34ID-C. A Kirkpatrick-Baez mirror is used for the condenser and a micro-Fresnel Zone Plate (FZP) as the objective lens. The zone plates available give access to 50-85 nm spatial resolution operating the microscope between 6-12keV photon energy. The first tomography experiments have been performed with this device. A KB-FZP microscope has been built for sub-100 nm imaging and tomography. Features of 50 nm have been visualized at 9 keV photon energy. A 40 x 20 microns field of view of can be imaged in a minute. The first tomography experiments have been performed with this device. Further, it is planned to apply phase contrast techniques, such as the Zernike method. Both the efficiency and the resolution of the instrument can be further improved. A more efficient zone plate and an improved detector will reduce the exposure times and the use of the 50x100 times more intense so called 'pink-beam' is possible. To improve the resolution, the zone plates deliver in their third order a resolution of 15 nm. A KB-FZP microscope has been built for sub-100 nm imaging and tomography. Features of 50 nm have been visualized at 9 keV photon energy. A 40 x 20 microns field of view of can be imaged in seconds. Tomography experiments have been performed with this device. Phase objects have been visualized taking image series. Phase contrast techniques, such as the Zernike method will be tested in the future. Both the efficiency and the resolution of the instrument can be further improved. Together with the instrument for In-line phase contrast imaging the nano- and micrometer lenghtscale is covered.

  17. Three-dimensional imaging of chemical phase transformations at the nanoscale with full-field transmission X-ray microscopy

    PubMed Central

    Meirer, Florian; Cabana, Jordi; Liu, Yijin; Mehta, Apurva; Andrews, Joy C.; Pianetta, Piero

    2011-01-01

    The ability to probe morphology and phase distribution in complex systems at multiple length scales unravels the interplay of nano- and micrometer-scale factors at the origin of macroscopic behavior. While different electron- and X-ray-based imaging techniques can be combined with spectroscopy at high resolutions, owing to experimental time limitations the resulting fields of view are too small to be representative of a composite sample. Here a new X-ray imaging set-up is proposed, combining full-field transmission X-ray microscopy (TXM) with X-ray absorption near-edge structure (XANES) spectroscopy to follow two-dimensional and three-dimensional morphological and chemical changes in large volumes at high resolution (tens of nanometers). TXM XANES imaging offers chemical speciation at the nanoscale in thick samples (>20 µm) with minimal preparation requirements. Further, its high throughput allows the analysis of large areas (up to millimeters) in minutes to a few hours. Proof of concept is provided using battery electrodes, although its versatility will lead to impact in a number of diverse research fields. PMID:21862859

  18. Imaging of physiological responses to photostimulation in human photoreceptors with full-field swept-source OCT (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hillmann, Dierck; Spahr, Hendrik; Pfäffle, Clara; Sudkamp, Helge M.; Franke, Gesa L.; Hüttmann, Gereon

    2017-02-01

    The non-invasive measurement of cellular physiological responses to photostimulation in living retina may have significant clinical value and give new insight into the vision process. Optical coherence tomography (OCT) has been reported to detect suitable intrinsic optical signals (IOS) in retinal photoreceptor layers upon their stimulation. Commonly, changes in backscattering intensity were observed ex vivo and immobilized animals in vivo. However, in humans measurements were time-consuming and cumbersome. Promising results were achieved when observing phase signals to detect intrinsic optical signals. But to achieve sufficient phase stability to image an entire area of photoreceptors turned out to be challenging. Here, we report full-field swept-source OCT to be sufficiently stable to detect the phase signals after projecting a stimulation image onto the living human retina. We extracted time-courses and signal dependencies from the measured datasets. For long stimuli, we were even able to assign responses to single cones. This functional imaging of photoreceptor activity could potentially be used to detect loss of photoreceptor function prior to visible morphological changes, which is associated with numerous retinal diseases.

  19. 50-nm-resolution full-field X-ray microscope without chromatic aberration using total-reflection imaging mirrors

    PubMed Central

    Matsuyama, Satoshi; Yasuda, Shuhei; Yamada, Jumpei; Okada, Hiromi; Kohmura, Yoshiki; Yabashi, Makina; Ishikawa, Tetsuya; Yamauchi, Kazuto

    2017-01-01

    X-ray spectromicroscopy with a full-field imaging technique is a powerful method for chemical analysis of heterogeneous complex materials with a nano-scale spatial resolution. For imaging optics, an X-ray reflective optical system has excellent capabilities with highly efficient, achromatic, and long-working-distance properties. An advanced Kirkpatrick–Baez geometry that combines four independent mirrors with elliptic and hyperbolic shapes in both horizontal and vertical directions was developed for this purpose, although the complexity of the system has a limited applicable range. Here, we present an optical system consisting of two monolithic imaging mirrors. Elliptic and hyperbolic shapes were formed on a single substrate to achieve both high resolution and sufficient stability. The mirrors were finished with a ~1-nm shape accuracy using elastic emission machining. The performance was tested at SPring-8 with a photon energy of approximately 10 keV. We could clearly resolve 50-nm features in a Siemens star without chromatic aberration and with high stability over 20 h. We applied this system to X-ray absorption fine structure spectromicroscopy and identified elements and chemical states in specimens of zinc and tungsten micron-size particles. PMID:28406227

  20. 50-nm-resolution full-field X-ray microscope without chromatic aberration using total-reflection imaging mirrors.

    PubMed

    Matsuyama, Satoshi; Yasuda, Shuhei; Yamada, Jumpei; Okada, Hiromi; Kohmura, Yoshiki; Yabashi, Makina; Ishikawa, Tetsuya; Yamauchi, Kazuto

    2017-04-13

    X-ray spectromicroscopy with a full-field imaging technique is a powerful method for chemical analysis of heterogeneous complex materials with a nano-scale spatial resolution. For imaging optics, an X-ray reflective optical system has excellent capabilities with highly efficient, achromatic, and long-working-distance properties. An advanced Kirkpatrick-Baez geometry that combines four independent mirrors with elliptic and hyperbolic shapes in both horizontal and vertical directions was developed for this purpose, although the complexity of the system has a limited applicable range. Here, we present an optical system consisting of two monolithic imaging mirrors. Elliptic and hyperbolic shapes were formed on a single substrate to achieve both high resolution and sufficient stability. The mirrors were finished with a ~1-nm shape accuracy using elastic emission machining. The performance was tested at SPring-8 with a photon energy of approximately 10 keV. We could clearly resolve 50-nm features in a Siemens star without chromatic aberration and with high stability over 20 h. We applied this system to X-ray absorption fine structure spectromicroscopy and identified elements and chemical states in specimens of zinc and tungsten micron-size particles.

  1. 50-nm-resolution full-field X-ray microscope without chromatic aberration using total-reflection imaging mirrors

    NASA Astrophysics Data System (ADS)

    Matsuyama, Satoshi; Yasuda, Shuhei; Yamada, Jumpei; Okada, Hiromi; Kohmura, Yoshiki; Yabashi, Makina; Ishikawa, Tetsuya; Yamauchi, Kazuto

    2017-04-01

    X-ray spectromicroscopy with a full-field imaging technique is a powerful method for chemical analysis of heterogeneous complex materials with a nano-scale spatial resolution. For imaging optics, an X-ray reflective optical system has excellent capabilities with highly efficient, achromatic, and long-working-distance properties. An advanced Kirkpatrick-Baez geometry that combines four independent mirrors with elliptic and hyperbolic shapes in both horizontal and vertical directions was developed for this purpose, although the complexity of the system has a limited applicable range. Here, we present an optical system consisting of two monolithic imaging mirrors. Elliptic and hyperbolic shapes were formed on a single substrate to achieve both high resolution and sufficient stability. The mirrors were finished with a ~1-nm shape accuracy using elastic emission machining. The performance was tested at SPring-8 with a photon energy of approximately 10 keV. We could clearly resolve 50-nm features in a Siemens star without chromatic aberration and with high stability over 20 h. We applied this system to X-ray absorption fine structure spectromicroscopy and identified elements and chemical states in specimens of zinc and tungsten micron-size particles.

  2. Rapid and high-resolution imaging of human liver specimens by full-field optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Zhu, Yue; Gao, Wanrong; Zhou, Yuan; Guo, Yingcheng; Guo, Feng; He, Yong

    2015-11-01

    We report rapid and high-resolution tomographic en face imaging of human liver specimens by full-field optical coherence tomography (FF-OCT). First, the arrangement of the FF-OCT system was described and the performance of the system was measured. The measured axial and lateral resolutions of the system are 0.8 and 0.9 μm, respectively. The system has a sensitivity of ˜60 dB and can achieve an imaging rate of 7 fps and a penetration depth of ˜80 μm. The histological structures of normal liver can be seen clearly in the en face tomographic images, including central veins, cords of hepatocytes separated by sinusoidal spaces, and portal area (portal vein, the hepatic arteriole, and the bile duct). A wide variety of histological subtypes of hepatocellular carcinoma was observed in en face tomographic images, revealing notable cancerous features, including the nuclear atypia (enlarged convoluted nuclei), the polygonal tumor cells with obvious resemblance to hepatocytes with enlarged nuclei. In addition, thicker fibrous bands, which make the cytoplasmic plump vesicular nuclei indistinct, were also seen in the images. Finally, comparison between the portal vein in a normal specimen versus that seen in the rare type of cholangiocarcinoma was made. The results show that the cholangiocarcinoma presents with a blurred pattern of portal vein in the lateral direction and an aggregated distribution in the axial direction; the surrounding sinusoidal spaces and nuclei of cholangiocarcinoma are absent. The findings in this work may be used as additional signs of liver cancer or cholangiocarcinoma, demonstrating capacity of FF-OCT device for early cancer diagnosis and many other tumor-related studies in biopsy.

  3. Laser Doppler distance sensor using phase evaluation.

    PubMed

    Günther, P; Pfister, T; Büttner, L; Czarske, J

    2009-02-16

    This paper presents a novel optical sensor which allows simultaneous measurements of axial position and tangential velocity of moving solid state objects. An extended laser Doppler velocimeter setup is used with two slightly tilted interference fringe systems. The distance to a solid state surface can be determined via a phase evaluation. The phase laser Doppler distance sensor offers a distance resolution of 150 nm and a total position uncertainty below 1 microm. Compared to conventional measurement techniques, such as triangulation, the distance resolution is independent of the lateral surface velocity. This advantage enables precise distance and shape measurements of fast rotating surfaces.

  4. Laser Doppler velocimeter aerial spray measurements

    NASA Technical Reports Server (NTRS)

    Zalay, A. D.; Eberle, W. R.; Howle, R. E.; Shrider, K. R.

    1978-01-01

    An experimental research program for measuring the location, spatial extent, and relative concentration of airborne spray clouds generated by agricultural aircraft is described. The measurements were conducted with a ground-based laser Doppler velocimeter. The remote sensing instrumentation, experimental tests, and the results of the flight tests are discussed. The cross section of the aerial spray cloud and the observed location, extent, and relative concentration of the airborne particulates are presented. It is feasible to use a mobile laser Doppler velocimeter to track and monitor the transport and dispersion of aerial spray generated by an agricultural aircraft.

  5. Micro X-ray Fluorescence Imaging in a Tabletop Full Field-X-ray Fluorescence Instrument and in a Full Field-Particle Induced X-ray Emission End Station.

    PubMed

    Romano, Francesco Paolo; Caliri, Claudia; Cosentino, Luigi; Gammino, Santo; Mascali, David; Pappalardo, Lighea; Rizzo, Francesca; Scharf, Oliver; Santos, Hellen Cristine

    2016-10-08

    A full field-X-ray camera (FF-XRC) was developed for performing the simultaneous mapping of chemical elements with a high lateral resolution. The device is based on a conventional CCD detector coupled to a straight shaped polycapillary. Samples are illuminated at once with a broad primary beam that can consist of X-rays or charged particles in two different analytical setups. The characteristic photons induced in the samples are guided by the polycapillary to the detector allowing the elemental imaging without the need for scanning. A single photon counting detection operated in a multiframe acquisition mode and a processing algorithm developed for event hitting reconstruction have enabled one to use the CCD as a high energy resolution X-ray detector. A novel software with a graphical user interface (GUI) programmed in Matlab allows full control of the device and the real-time imaging with a region-of-interest (ROI) method. At the end of the measurement, the software produces spectra for each of the pixels in the detector allowing the application of a least-squares fitting with external analytical tools. The FF-XRC is very compact and can be installed in different experimental setups. This work shows the potentialities of the instrument in both a full field-micro X-ray fluorescence (FF-MXRF) tabletop device and in a full field-micro particle induced X-ray emission (FF-MPIXE) end-station operated with an external proton beam. Some examples of applications are given as well.

  6. A full-field transmission x-ray microscope for time-resolved imaging of magnetic nanostructures

    SciTech Connect

    Ewald, J.; Nisius, T.; Abbati, G.; Baumbach, S.; Overbuschmann, J.; Wilhein, T.; Wessels, P.; Wieland, M.; Drescher, M.; Vogel, A.; Viefhaus, J.; Meier, G.

    2016-01-28

    Sub-nanosecond magnetization dynamics of small permalloy (Ni{sub 80}Fe{sub 20}) elements has been investigated with a new full-field transmission microscope at the soft X-ray beamline P04 of the high brilliance synchrotron radiation source PETRA III. The soft X-ray microscope generates a flat-top illumination field of 20 μm diameter using a grating condenser. A tilted nanostructured magnetic sample can be excited by a picosecond electric current pulse via a coplanar waveguide. The transmitted light of the sample plane is directly imaged by a micro zone plate with < 65 nm resolution onto a 2D gateable X-ray detector to select one particular bunch in the storage ring that probes the time evolution of the dynamic information successively via XMCD spectromicroscopy in a pump-probe scheme. In the experiments it was possible to generate a homogeneously magnetized state in patterned magnetic layers by a strong magnetic Oersted field pulse of 200 ps duration and directly observe the recovery to the initial flux-closure vortex patterns.

  7. A full-field transmission x-ray microscope for time-resolved imaging of magnetic nanostructures

    NASA Astrophysics Data System (ADS)

    Ewald, J.; Wessels, P.; Wieland, M.; Nisius, T.; Vogel, A.; Abbati, G.; Baumbach, S.; Overbuschmann, J.; Viefhaus, J.; Meier, G.; Wilhein, T.; Drescher, M.

    2016-01-01

    Sub-nanosecond magnetization dynamics of small permalloy (Ni80Fe20) elements has been investigated with a new full-field transmission microscope at the soft X-ray beamline P04 of the high brilliance synchrotron radiation source PETRA III. The soft X-ray microscope generates a flat-top illumination field of 20 μm diameter using a grating condenser. A tilted nanostructured magnetic sample can be excited by a picosecond electric current pulse via a coplanar waveguide. The transmitted light of the sample plane is directly imaged by a micro zone plate with < 65 nm resolution onto a 2D gateable X-ray detector to select one particular bunch in the storage ring that probes the time evolution of the dynamic information successively via XMCD spectromicroscopy in a pump-probe scheme. In the experiments it was possible to generate a homogeneously magnetized state in patterned magnetic layers by a strong magnetic Oersted field pulse of 200 ps duration and directly observe the recovery to the initial flux-closure vortex patterns.

  8. Atmospheric laser Doppler velocimetry - An overview

    NASA Technical Reports Server (NTRS)

    Bilbro, J. W.

    1980-01-01

    Research, development, and application of atmospheric laser Doppler velocimetry are overviewed. Consideration is given to operation principles of CO2 heterodyne systems. Global wind, pollution, V/STOL flow, and true airspeed measurements are outlined. Wind energy, dust devils, water spouts, tornadoes, and aircraft wake vortices are covered.

  9. High resolution imaging of intracellular dynamics in explanted retinas with dynamic full-field OCT (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Thouvenin, Olivier; Boccara, A. Claude; Paques, Michel; Sahel, José-Alain; Fink, Mathias; Grieve, Kate F.

    2017-02-01

    Full-Field Optical Coherence Tomography (FF-OCT) reveals submicrometric morphological details in retinal explants without the use of contrast agents. Notably, in the nerve fiber and ganglion cell layers, FF-OCT images reveal nerve fibers bundles, single axons, capillaries and even some ganglion cell bodies. Dynamic FF-OCT (D-FF-OCT) takes advantage of the temporal evolution of the local FF-OCT signal to reveal a movement-dependent contrast inside tissues. Notably, the D-FF-OCT signal depends on cellular motility and membrane fluctuations. Compared to regular FF-OCT images, the signal from stationary structures such as nerve fibers is reduced, and contrast inside cells is enhanced, revealing many more cells, as well as the position of nuclei, and cell metabolism. We used a multimodal D-FF-OCT and fluorescence microscope to compare and identify the structures observed in both FF-OCT and D-FF-OCT. In the ganglion cell and inner nuclear layers in both macaque and mouse, two different cell sizes could be measured, which correlated well with ganglion and amacrine cell diameters found in the literature for these two species. We could also detect cell bodies of the photoreceptors in the outer nuclear layer. To our knowledge, this is the first time that an OCT technique can reveal these cell bodies. Finally, to investigate post-mortem tissue changes, time series were acquired over periods of 24 hours and cell contrast was plotted in time to monitor the decrease in intracellular activity over time. It is anticipated that dynamic FF-OCT may be used to non-invasively monitor viability and functional changes in the retina.

  10. Breast Imaging Reporting and Data System (BI-RADS) breast composition descriptors: Automated measurement development for full field digital mammography

    SciTech Connect

    Fowler, E. E.; Sellers, T. A.; Lu, B.; Heine, J. J.

    2013-11-15

    Purpose: The Breast Imaging Reporting and Data System (BI-RADS) breast composition descriptors are used for standardized mammographic reporting and are assessed visually. This reporting is clinically relevant because breast composition can impact mammographic sensitivity and is a breast cancer risk factor. New techniques are presented and evaluated for generating automated BI-RADS breast composition descriptors using both raw and calibrated full field digital mammography (FFDM) image data.Methods: A matched case-control dataset with FFDM images was used to develop three automated measures for the BI-RADS breast composition descriptors. Histograms of each calibrated mammogram in the percent glandular (pg) representation were processed to create the new BR{sub pg} measure. Two previously validated measures of breast density derived from calibrated and raw mammograms were converted to the new BR{sub vc} and BR{sub vr} measures, respectively. These three measures were compared with the radiologist-reported BI-RADS compositions assessments from the patient records. The authors used two optimization strategies with differential evolution to create these measures: method-1 used breast cancer status; and method-2 matched the reported BI-RADS descriptors. Weighted kappa (κ) analysis was used to assess the agreement between the new measures and the reported measures. Each measure's association with breast cancer was evaluated with odds ratios (ORs) adjusted for body mass index, breast area, and menopausal status. ORs were estimated as per unit increase with 95% confidence intervals.Results: The three BI-RADS measures generated by method-1 had κ between 0.25–0.34. These measures were significantly associated with breast cancer status in the adjusted models: (a) OR = 1.87 (1.34, 2.59) for BR{sub pg}; (b) OR = 1.93 (1.36, 2.74) for BR{sub vc}; and (c) OR = 1.37 (1.05, 1.80) for BR{sub vr}. The measures generated by method-2 had κ between 0.42–0.45. Two of these measures

  11. Sub miniaturized laser doppler velocimeter sensor

    NASA Technical Reports Server (NTRS)

    Gharib, Morteza (Inventor); Modaress, Darius (Inventor); Taugwalder, Frederic (Inventor)

    2003-01-01

    A miniaturized laser Doppler velocimeter is formed in a housing that is preferably 3 mm in diameter or less. A laser couples light to a first diffractive optical element that is formed on the fiber end. The light is coupled to a lens that also includes a diffractive optical element. The same lens is also used to collect receive light, and receives includes another diffractive optical element to collect that received light.

  12. Full-field point-by-point direct design method of off-axis aspheric imaging systems.

    PubMed

    Gong, Tongtong; Jin, Guofan; Zhu, Jun

    2016-12-26

    It is of urgent need to develop a point-by-point design method for off-axis aspheric systems in full field and full aperture. So a general full-field point-by-point method for off-axis aspheric systems is presented in this paper, in which light rays from different field angles and aperture coordinates are considered. Surface fitting is included during the point calculations, rather than after all the points are calculated. Data point calculations and aspheric surface fitting are repeated continuously to calculate an unknown aspheric surface. Both coordinate and surface normal deviations are considered. As an example, an aspheric off-axis three-mirror reflective system is designed to operate at F/2.4 with a 100-mm entrance pupil diameter and a 3° × 6° off-axis field of view. This method can also be used to design co-axial aspheric systems and novel systems with new structures.

  13. 3D camera assisted fully automated calibration of scanning laser Doppler vibrometers

    SciTech Connect

    Sels, Seppe Ribbens, Bart; Mertens, Luc; Vanlanduit, Steve

    2016-06-28

    Scanning laser Doppler vibrometers (LDV) are used to measure full-field vibration shapes of products and structures. In most commercially available scanning laser Doppler vibrometer systems the user manually draws a grid of measurement locations on a 2D camera image of the product. The determination of the correct physical measurement locations can be a time consuming and diffcult task. In this paper we present a new methodology for product testing and quality control that integrates 3D imaging techniques with vibration measurements. This procedure allows to test prototypes in a shorter period because physical measurements locations will be located automatically. The proposed methodology uses a 3D time-of-flight camera to measure the location and orientation of the test-object. The 3D image of the time-of-flight camera is then matched with the 3D-CAD model of the object in which measurement locations are pre-defined. A time of flight camera operates strictly in the near infrared spectrum. To improve the signal to noise ratio in the time-of-flight measurement, a time-of-flight camera uses a band filter. As a result of this filter, the laser spot of most laser vibrometers is invisible in the time-of-flight image. Therefore a 2D RGB-camera is used to find the laser-spot of the vibrometer. The laser spot is matched to the 3D image obtained by the time-of-flight camera. Next an automatic calibration procedure is used to aim the laser at the (pre)defined locations. Another benefit from this methodology is that it incorporates automatic mapping between a CAD model and the vibration measurements. This mapping can be used to visualize measurements directly on a 3D CAD model. Secondly the orientation of the CAD model is known with respect to the laser beam. This information can be used to find the direction of the measured vibration relatively to the surface of the object. With this direction, the vibration measurements can be compared more precisely with numerical

  14. Anti-Stokes effect CCD camera and SLD based optical coherence tomography for full-field imaging in the 1550nm region

    NASA Astrophysics Data System (ADS)

    Kredzinski, Lukasz; Connelly, Michael J.

    2012-06-01

    Full-field Optical coherence tomography is an en-face interferometric imaging technology capable of carrying out high resolution cross-sectional imaging of the internal microstructure of an examined specimen in a non-invasive manner. The presented system is based on competitively priced optical components available at the main optical communications band located in the 1550 nm region. It consists of a superluminescent diode and an anti-stokes imaging device. The single mode fibre coupled SLD was connected to a multi-mode fibre inserted into a mode scrambler to obtain spatially incoherent illumination, suitable for OCT wide-field modality in terms of crosstalk suppression and image enhancement. This relatively inexpensive system with moderate resolution of approximately 24um x 12um (axial x lateral) was constructed to perform a 3D cross sectional imaging of a human tooth. To our knowledge this is the first 1550 nm full-field OCT system reported.

  15. Mobile fiber-optic laser Doppler anemometer.

    PubMed

    Stieglmeier, M; Tropea, C

    1992-07-20

    A laser Doppler anemometer (LDA) has been developed that combines the compactness and low power consumption of laser diodes and avalanche photodiodes with the flexibility and possibility of miniaturization by using fiber-optic probes. The system has been named DFLDA for laser diode fiber LDA and is especially suited for mobile applications, for example, in trains, airplanes, or automobiles. Optimization considerations of fiber-optic probes are put forward and several probe examples are described in detail. Measurement results from three typical applications are given to illustrate the use of the DFLDA. Finally, a number of future configurations of the DFLDA concept are discussed.

  16. Signal broadening in the laser Doppler velocimeter.

    NASA Technical Reports Server (NTRS)

    Angus, J. C.; Edwards, R. V.; Dunning, J. W., Jr.

    1971-01-01

    Critical review of a recent paper in which Denison, Stevenson, and Fox (1971) discussed the sources of spectral broadening in the laser Doppler velocimeter. It is pointed out that, in their discussion, the above-mentioned authors indicated that the spread in wave vectors of the incident and detected fields and the finite length of time a scattering center stayed in the sample volume each contributed separately and independently to the observed spectral width of the scattered radiation. This statement is termed incorrect, and it is shown that the two effects are one and the same.

  17. Laser Doppler Velocimeter particle velocity measurement system

    SciTech Connect

    Wilson, W.W.; Srikantaiah, D.V.; Philip, T.; George, A.

    1993-10-01

    This report gives a detailed description of the operation of the Laser Doppler Velocimeter (LDV) system maintained by DIAL at MSU. LDV is used for the measurement of flow velocities and turbulence levels in various fluid flow settings. Ills report details the operation and maintenance of the LDV system and provides a first-time user with pertinent information regarding the system`s setup for a particular application. Particular attention has been given to the use of the Doppler signal analyzer (DSA) and the burst spectrum analyzer (BSA) signal processors and data analysis.

  18. Catadioptric optics for laser Doppler velocimeter applications

    NASA Technical Reports Server (NTRS)

    Dunagan, Stephen E.

    1989-01-01

    This paper examines the adaptation of low-cost Schmidt-Cassegrain astronomical telescopes to perform the laser-beam-focusing and scattered-light collection tasks associated with dual-beam laser Doppler velocimetry. A generic telescope design is analyzed using ray-tracing methods and Gaussian beam-propagation theory. A straightforward modification procedure to convert from infinite to near unity conjugate-ratio operation with very low residual aberration is identified and tested with a 200-mm-aperture telescope modified for f/10 operation. Performance data for this modified telescope configuration are near the diffraction limit and agree well with predictions.

  19. Catadioptric optics for laser Doppler velocimeter applications

    NASA Technical Reports Server (NTRS)

    Dunagan, Stephen E.

    1989-01-01

    This paper examines the adaptation of low-cost Schmidt-Cassegrain astronomical telescopes to perform the laser-beam-focusing and scattered-light collection tasks associated with dual-beam laser Doppler velocimetry. A generic telescope design is analyzed using ray-tracing methods and Gaussian beam-propagation theory. A straightforward modification procedure to convert from infinite to near unity conjugate-ratio operation with very low residual aberration is identified and tested with a 200-mm-aperture telescope modified for f/10 operation. Performance data for this modified telescope configuration are near the diffraction limit and agree well with predictions.

  20. Velocity precision measurements using laser Doppler anemometry

    NASA Astrophysics Data System (ADS)

    Dopheide, D.; Taux, G.; Narjes, L.

    1985-07-01

    A Laser Doppler Anemometer (LDA) was calibrated to determine its applicability to high pressure measurements (up to 10 bars) for industrial purposes. The measurement procedure with LDA and the experimental computerized layouts are presented. The calibration procedure is based on absolute accuracy of Doppler frequency and calibration of interference strip intervals. A four-quadrant detector allows comparison of the interference strip distance measurements and computer profiles. Further development of LDA is recommended to increase accuracy (0.1% inaccuracy) and to apply the method industrially.

  1. Imaging performance of a clinical selenium flat-panel detector for advanced applications in full-field digital mammography

    NASA Astrophysics Data System (ADS)

    Loustauneau, Vincent; Bissonnette, Michel; Cadieux, Sebastien; Hansroul, Marc; Masson, E.; Savard, Serge; Polischuk, Brad T.; Lehtimauki, Mari J.

    2003-06-01

    The advent of digital detectors will enable several advanced imaging applications to be used in the fight against breast cancer. For example, dynamic imaging applications such as tomosynthesis, contrast enhanced and dual energy mammography have demonstrated promising results. In this paper, we will assess the suitability of this detector for these advanced applications. MTF and DQE measurements were performed on a selenium FFDM detector to assess image quality. Ghosting properties of a digital detector are also an important factor, since it can strongly degrade image quality. In this paper, we will also report on the ghosting characteristics of the selenium detector, using typical exposures envisioned to be used in tomosynthesis exams. The physical mechanisms that create ghost images will be discussed and will be quantified.

  2. Evaluation of low-energy contrast-enhanced spectral mammography images by comparing them to full-field digital mammography using EUREF image quality criteria.

    PubMed

    Lalji, U C; Jeukens, C R L P N; Houben, I; Nelemans, P J; van Engen, R E; van Wylick, E; Beets-Tan, R G H; Wildberger, J E; Paulis, L E; Lobbes, M B I

    2015-10-01

    Contrast-enhanced spectral mammography (CESM) examination results in a low-energy (LE) and contrast-enhanced image. The LE appears similar to a full-field digital mammogram (FFDM). Our aim was to evaluate LE CESM image quality by comparing it to FFDM using criteria defined by the European Reference Organization for Quality Assured Breast Screening and Diagnostic Services (EUREF). A total of 147 cases with both FFDM and LE images were independently scored by two experienced radiologists using these (20) EUREF criteria. Contrast detail measurements were performed using a dedicated phantom. Differences in image quality scores, average glandular dose, and contrast detail measurements between LE and FFDM were tested for statistical significance. No significant differences in image quality scores were observed between LE and FFDM images for 17 out of 20 criteria. LE scored significantly lower on one criterion regarding the sharpness of the pectoral muscle (p < 0.001), and significantly better on two criteria on the visualization of micro-calcifications (p = 0.02 and p = 0.034). Dose and contrast detail measurements did not reveal any physical explanation for these observed differences. Low-energy CESM images are non-inferior to FFDM images. From this perspective FFDM can be omitted in patients with an indication for CESM. • Low-energy CESM images are non-inferior to FFDM images. • Micro-calcifications are significantly more visible on LE CESM than on FFDM. • There is no physical explanation for this improved visibility of micro-calcifications. • There is no need for an extra FFDM when CESM is indicated.

  3. Traceable technique for an in situ full field in-plane measurement validation of digital image correlation

    NASA Astrophysics Data System (ADS)

    Szigeti, Eszter; Loparco, Matthew; Todorov, Evgeni; Wheatley, Shelby; Greene, Richard J.

    2017-03-01

    For digital image correlation to be firmly accepted as a validated displacement measurement system in the industrial arena, a measurement must be captured by the analysis system at time of test which confirms that the image correlation hardware and software system is performing as expected. To this end, a method for validating stereo digital image correlation optical test setups is presented, which is traceable to the length standard. The method employs a screen, on which is displayed a randomized speckle pattern of appropriate pitch for the test in question. This speckle pattern is then artificially translated by a known number of pixels on the screen, and image pairs captured of the original and translated speckles. Processing of these data image pairs with image correlation, and calibration of the pixel pitch of the display screen using a traceable measurement system, allows the image correlation test setup to be traceably calibrated in terms of in-plane displacement. The method is shown to be sufficiently sensitive and repeatable to provide a reasonably accurate, traceable validation in a practical environment.

  4. High-Power Terahertz Source Opens the Door for Full-Field Video-Rate Terahertz Imaging

    SciTech Connect

    Klopf, John; Coppinger, Matthew; Sustersic, Nathan; Kolodzey, James; Williams, Gwyn

    2008-07-01

    Terahertz (THz) light, at wavelengths between electronics and photonics, promises novel imaging applications such as revealing epithelial carcinomas 1 or identifying objects hidden in clothing and packages 2. But THz imaging has been little exploited because generating source power high enough for adequate signal detection is difficult -- and because even more power is needed for most applications that require detecting scattered light rather than light transmitted straight through the target 3. The ability to image movement in real time would aid medicine by allowing the rapid viewing of multiple perspectives and larger areas for detecting skin cancer. Real-time imaging is also essential for the efficient detection, with sufficient resolution, of hidden, and possibly moving, objects. Here, in work building on our earlier demonstration that relativistic electrons can yield tens of watts of broadband THz light 4, 5, we report the first video-rate THz movies of objects observed in real t

  5. Laser Doppler systems in pollution monitoring

    NASA Technical Reports Server (NTRS)

    Miller, C. R.; Sonnenschein, C. M.; Herget, W. F.; Huffaker, R. M.

    1976-01-01

    The paper reports on a program undertaken to determine the feasibility of using a laser Doppler velocimeter (LDV) to measure smoke-stack gas exit velocity, particulate concentration, and mass flow. Measurements made with a CO2 laser Doppler radar system at a coal-burning power plant are compared with in-stack measurements made by a pitot tube. The operational principles of a LDV are briefly described along with the system employed in the present study. Data discussed include typical Doppler spectra from smoke-stack effluents at various laser elevation angles, the measured velocity profile across the stack exit, and the LDV-measured exit velocity as a function of the exit velocity measured by the in-stack instrument. The in-stack velocity is found to be about 14% higher than the LDV velocity, but this discrepancy is regarded as a systematic error. In general, linear relationships are observed between the laser data, the exit velocity, and the particulate concentration. It is concluded that an LDV has the capability of determining both the mass concentration and the mass flow from a power-plant smoke stack.

  6. Large-area full field x-ray differential phase-contrast imaging using 2D tiled gratings

    NASA Astrophysics Data System (ADS)

    Schröter, Tobias J.; Koch, Frieder J.; Kunka, Danays; Meyer, Pascal; Tietze, Sabrina; Engelhardt, Sabine; Zuber, Marcus; Baumbach, Tilo; Willer, Konstantin; Birnbacher, Lorenz; Prade, Friedrich; Pfeiffer, Franz; Reichert, Klaus-Martin; Hofmann, Andreas; Mohr, Jürgen

    2017-06-01

    Grating-based x-ray differential phase-contrast imaging (DPCI) is capable of acquiring information based on phase-shift and dark-field signal, in addition to conventional x-ray absorption-contrast. Thus DPCI gives an advantage to investigate composite materials with component wise similar absorption properties like soft tissues. Due to technological challenges in fabricating high quality gratings over a large extent, the field of view (FoV) of the imaging systems is limited to a grating area of a couple of square centimeters. For many imaging applications (e.g. in medicine), however, a FoV that ranges over several ten centimeters is needed. In this manuscript we propose to create large area gratings of theoretically any extent by assembling a number of individual grating tiles. We discuss the precision needed for alignment of each microstructure tile in order to reduce image artifacts and to preserve minimum 90% of the sensitivity obtainable with a monolithic grating. To achieve a reliable high precision alignment a semiautomatic assembly system consisting of a laser autocollimator, a digital microscope and a force sensor together with positioning devices was built. The setup was used to tile a first four times four analyzer grating with a size of 200 mm  ×  200 mm together with a two times two phase grating. First imaging results prove the applicability and quality of the tiling concept.

  7. Optimizing Digital Mammographic Image Quality for Full-Field Digital Detectors: Artifacts Encountered during the QC Process.

    PubMed

    Jayadevan, Rashmi; Armada, M Julie; Shaheen, Rola; Mulcahy, Constance; Slanetz, Priscilla J

    2015-01-01

    Early detection of breast cancer through routine mammographic screening has been shown to reduce mortality from breast cancer by up to 30% in multiple studies. However, this reduction of mortality is possible only with careful attention to image quality by the medical physicist, radiologic technologist, and interpreting radiologist. The accepted quality control (QC) processes for analog mammography are well established. However, now that use of digital units is widespread in both the United States and internationally, information regarding the necessary steps and the inherent challenges that might be encountered at each step needs to be elucidated. In this review, the essential steps of the QC process for digital mammography are reviewed, with special attention to the possible problems that can occur during the QC process, many of which can lead to image artifacts. For each of the daily, weekly, monthly, and semiannual QC tests, we review the steps and expected performance and provide examples of some of the common artifacts that may be encountered. Understanding the components of the QC process and recognizing problems that may result in a suboptimal image is critical to ensure optimal image quality in an effort to maximize early detection of breast cancer. (©)RSNA, 2015.

  8. Should processed or raw image data be used in mammographic image quality analyses? A comparative study of three full-field digital mammography systems.

    PubMed

    Borg, Mark; Badr, Ishmail; Royle, Gary

    2015-01-01

    The purpose of this study is to compare a number of measured image quality parameters using processed and unprocessed or raw images in two full-field direct digital units and one computed radiography mammography system. This study shows that the difference between raw and processed image data is system specific. The results have shown that there are no significant differences between raw and processed data in the mean threshold contrast values using the contrast-detail mammography phantom in all the systems investigated; however, these results cannot be generalised to all available systems. Notable differences were noted in contrast-to-noise ratios and in other tests including: response function, modulation transfer function , noise equivalent quanta, normalised noise power spectra and detective quantum efficiency as specified in IEC 62220-1-2. Consequently, the authors strongly recommend the use of raw data for all image quality analyses in digital mammography. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  9. Assessment of the metrological performance of an in situ storage image sensor ultra-high speed camera for full-field deformation measurements

    NASA Astrophysics Data System (ADS)

    Rossi, Marco; Pierron, Fabrice; Forquin, Pascal

    2014-02-01

    Ultra-high speed (UHS) cameras allow us to acquire images typically up to about 1 million frames s-1 for a full spatial resolution of the order of 1 Mpixel. Different technologies are available nowadays to achieve these performances, an interesting one is the so-called in situ storage image sensor architecture where the image storage is incorporated into the sensor chip. Such an architecture is all solid state and does not contain movable devices as occurs, for instance, in the rotating mirror UHS cameras. One of the disadvantages of this system is the low fill factor (around 76% in the vertical direction and 14% in the horizontal direction) since most of the space in the sensor is occupied by memory. This peculiarity introduces a series of systematic errors when the camera is used to perform full-field strain measurements. The aim of this paper is to develop an experimental procedure to thoroughly characterize the performance of such kinds of cameras in full-field deformation measurement and identify the best operative conditions which minimize the measurement errors. A series of tests was performed on a Shimadzu HPV-1 UHS camera first using uniform scenes and then grids under rigid movements. The grid method was used as full-field measurement optical technique here. From these tests, it has been possible to appropriately identify the camera behaviour and utilize this information to improve actual measurements.

  10. Full Field Digital Mammography (FFDM) versus CMOS Technology versus Tomosynthesis (DBT) - Which System Increases the Quality of Intraoperative Imaging?

    PubMed

    Schulz-Wendtland, R; Dilbat, G; Bani, M; Fasching, P A; Lux, M P; Wenkel, E; Schwab, S; Loehberg, C R; Jud, S M; Rauh, C; Bayer, C M; Beckmann, M W; Uder, M; Meier-Meitinger, M

    2012-06-01

    Aim: The aim of this prospective clinical study was to assess whether it would be possible to reduce the rate of re-excisions and improve the quality using CMOS technology or digital breast tomosynthesis (DBT) compared to a conventional FFDM system. Material and Methods: An invasive breast cancer (BI-RADS 5) was diagnosed in 200 patients in the period from 5/2011 to 1/2012. After histological verification, a breast-conserving therapy was performed with intraoperative imaging. Three different imaging systems were used: 1) Inspiration™ (Siemens, Erlangen, Germany), amorphous selenium, tungsten source, focus 0.1 mm, resolution 85 µm pixel pitch, 8 l/mm as the standard; 2) BioVision™ (Bioptics, Tucson, USA), flat panel photodiode array, tungsten source, focus 0.05, resolution 50 µm pixel pitch, 12 l/mm; 3) Tomosynthesis (Siemens, Erlangen, Germany), amorphous selenium, tungsten source, focus 0.1 mm, resolution 85 µm pixel pitch, 8 l/mm, range: 50°, 25 projections, scan time > 20 s, geometry: uniform scanning, reconstruction: filtered back projection. The 600 radiograms were prospectively shown to 3 radiologists. Results: Out of a total of 200 patients with histologically confirmed breast cancer (BI-RADS 6) 156 patients required no further operative therapy (re-excision) after breast-conserving therapy. A retrospective analysis (n = 44) showed an increase in sensitivity with tomosynthesis compared to the BioVision™ (CMOS technology) and the Inspiration™ at a magnification of 1.0 : 1.0 of 8 % (p < 0.05), i.e. re-excision would not have been necessary in 16 patients with tomosynthesis. Conclusions: The sensitivity of tomosynthesis for intraoperative radiography is significantly (p < 0.05) higher compared to both CMOS technology and an FFDM system with a conventional detector. Additional studies using higher magnification, e.g. 2.0 : 1.0, but no zooming will be necessary to evaluate the method further.

  11. Full Field Digital Mammography (FFDM) versus CMOS Technology versus Tomosynthesis (DBT) – Which System Increases the Quality of Intraoperative Imaging?

    PubMed Central

    Schulz-Wendtland, R.; Dilbat, G.; Bani, M.; Fasching, P. A.; Lux, M. P.; Wenkel, E.; Schwab, S.; Loehberg, C. R.; Jud, S. M.; Rauh, C.; Bayer, C. M.; Beckmann, M. W.; Uder, M.; Meier-Meitinger, M.

    2012-01-01

    Aim: The aim of this prospective clinical study was to assess whether it would be possible to reduce the rate of re-excisions and improve the quality using CMOS technology or digital breast tomosynthesis (DBT) compared to a conventional FFDM system. Material and Methods: An invasive breast cancer (BI-RADS 5) was diagnosed in 200 patients in the period from 5/2011 to 1/2012. After histological verification, a breast-conserving therapy was performed with intraoperative imaging. Three different imaging systems were used: 1) Inspiration™ (Siemens, Erlangen, Germany), amorphous selenium, tungsten source, focus 0.1 mm, resolution 85 µm pixel pitch, 8 l/mm as the standard; 2) BioVision™ (Bioptics, Tucson, USA), flat panel photodiode array, tungsten source, focus 0.05, resolution 50 µm pixel pitch, 12 l/mm; 3) Tomosynthesis (Siemens, Erlangen, Germany), amorphous selenium, tungsten source, focus 0.1 mm, resolution 85 µm pixel pitch, 8 l/mm, range: 50°, 25 projections, scan time > 20 s, geometry: uniform scanning, reconstruction: filtered back projection. The 600 radiograms were prospectively shown to 3 radiologists. Results: Out of a total of 200 patients with histologically confirmed breast cancer (BI-RADS 6) 156 patients required no further operative therapy (re-excision) after breast-conserving therapy. A retrospective analysis (n = 44) showed an increase in sensitivity with tomosynthesis compared to the BioVision™ (CMOS technology) and the Inspiration™ at a magnification of 1.0 : 1.0 of 8 % (p < 0.05), i.e. re-excision would not have been necessary in 16 patients with tomosynthesis. Conclusions: The sensitivity of tomosynthesis for intraoperative radiography is significantly (p < 0.05) higher compared to both CMOS technology and an FFDM system with a conventional detector. Additional studies using higher magnification, e.g. 2.0 : 1.0, but no zooming will be necessary to evaluate the method further. PMID:26640287

  12. Laser Doppler systems in atmospheric turbulence

    NASA Technical Reports Server (NTRS)

    Murty, S. S. R.

    1976-01-01

    The loss of heterodyne signal power for the Marshall Space Flight Center laser Doppler system due to the random changes in the atmospheric index of refraction is investigated. The current status in the physics of low energy laser propagation through turbulent atmosphere is presented. The analysis and approximate evaluation of the loss of the heterodyne signal power due to the atmospheric absorption, scattering, and turbulence are estimated for the conditions of the January 1973 flight tests. Theoretical and experimental signal to noise values are compared. Maximum and minimum values of the atmospheric attenuation over a two way path of 20 km range are calculated as a function of altitude using models of atmosphere, aerosol concentration, and turbulence.

  13. Laser Doppler vibrometry: new ENT applications

    NASA Astrophysics Data System (ADS)

    Stasche, Norbert; Baermann, M.; Kempe, C.; Hoermann, Karl; Foth, Hans-Jochen

    1996-12-01

    Common audiometry often does not really allow a reliable and objective differential diagnosis of hearing disorders such as otosclerosis, adhesive otitis, ossicular interruption or tinnitus, even though several methods might be used complementarily. In recent years, some experimental studies on middle ear mechanics established laser Doppler vibrometry (LDV) as a useful method allowing objective measurement of human tympanic membrane displacement. The present study on LDV investigated the clinical use of this new method under physiological conditions. LDV proved to be a fast, reproducible, non-invasive and very sensitive instrument to characterize ear-drum vibrations in various middle ear dysfunctions, except in tinnitus patients. For future applications, improved optical characteristics of the vibrometer might result in a better differential diagnosis of subjective and objective tinnitus, otoacoustic emissions or Morbus Meniere.

  14. [Use of laser Doppler flowmetry in dentistry].

    PubMed

    Roeykens, H; Nammour, S; De Moor, R

    2009-01-01

    An early determination of pulpal vitality is crucial with respect to a correct differential diagnosis of revascularisation or necrosis and its treatment. The use of sensibility tests (cold, heat, electrical pulp test) in combination with X-ray are commonly promoted. However these tests are arbitrary, based on sensations and therefore not always reliable. In such situation the registration of 'real' pulpal blood flow and hence pulp vitality will be more than an added value. The most studied and well documented method is laser Doppler flowmetry (LDF) as it is non invasive, direct and objective. In this article we describe blood flow, LDF and its characteristics, advantages and disadvantages of this method and the newest developments regarding LDF. Despite a low implementation of LDF in Belgium, this technique proved to belong indisputable to the basic assets of a dental clinic. A number of cases are described to demonstrate the efficacy and added value of LDF in assessing tooth vitality.

  15. Processing of the laser Doppler velocimeter signals

    NASA Technical Reports Server (NTRS)

    Meyers, J. F.; Feller, W. V.

    1973-01-01

    The laser Doppler velocimeter (LDV) is a probeless technique that provides a remote measurement of mean and fluctuating velocities. The measurement is actually obtained from small particles embedded in the flow which scatter light from an illuminating laser beam interference pattern. A portion of this scattered light is collected by a photomultiplier which yields an electronic signal whose frequency is directly proportional to the velocity of the small particles. The purpose of this paper is to describe and critically compare three techniques most used to process this electronic signal. These techniques are: (1) spectrum analyzer - a frequency scanning filter (frequency domain instrument), (2) wide-band frequency tracker - a frequency lock loop (frequency domain instrument), and (3) high-speed frequency counter - an interval timer (time domain instrument). The study determines the ability of each technique to process the LDV signal and yield velocity data to be used in determining the flow characteristics.

  16. A laboratory 8 keV transmission full-field x-ray microscope with a polycapillary as condenser for bright and dark field imaging

    SciTech Connect

    Baumbach, S. Wilhein, T.; Kanngießer, B.; Malzer, W.; Stiel, H.

    2015-08-15

    This article introduces a laboratory setup of a transmission full-field x-ray microscope at 8 keV photon energy. The microscope operates in bright and dark field imaging mode with a maximum field of view of 50 μm. Since the illumination geometry determines whether the sample is illuminated homogeneously and moreover, if different imaging methods can be applied, the condenser optic is one of the most significant parts. With a new type of x-ray condenser, a polycapillary optic, we realized bright field imaging and for the first time dark field imaging at 8 keV photon energy in a laboratory setup. A detector limited spatial resolution of 210 nm is measured on x-ray images of Siemens star test patterns.

  17. A laboratory 8 keV transmission full-field x-ray microscope with a polycapillary as condenser for bright and dark field imaging

    NASA Astrophysics Data System (ADS)

    Baumbach, S.; Kanngießer, B.; Malzer, W.; Stiel, H.; Wilhein, T.

    2015-08-01

    This article introduces a laboratory setup of a transmission full-field x-ray microscope at 8 keV photon energy. The microscope operates in bright and dark field imaging mode with a maximum field of view of 50 μm. Since the illumination geometry determines whether the sample is illuminated homogeneously and moreover, if different imaging methods can be applied, the condenser optic is one of the most significant parts. With a new type of x-ray condenser, a polycapillary optic, we realized bright field imaging and for the first time dark field imaging at 8 keV photon energy in a laboratory setup. A detector limited spatial resolution of 210 nm is measured on x-ray images of Siemens star test patterns.

  18. Simulation of concave-convex imaging mirror system for development of a compact and achromatic full-field x-ray microscope.

    PubMed

    Yamada, Jumpei; Matsuyama, Satoshi; Sano, Yasuhisa; Yamauchi, Kazuto

    2017-02-01

    We propose the use of two pairs of concave-convex mirrors as imaging optics for the compact full-field x-ray microscope with high resolution and magnification factors. The optics consists of two pairs of hyperbolic convex and elliptical concave mirrors with the principal surface near the object, consequently enabling the focal length to be 10 times shorter than conventional advanced Kirkpatrick-Baez mirror optics. This paper describes characteristics of the optics calculated by ray-tracing and wave-optical simulators. The expected spatial resolution is approximately 40 nm with a wide field of view of more than 10 μm and a total length of about 2 m, which may lead to the possibility of laboratory-sized, achromatic, and high-resolution full-field x-ray microscopes.

  19. Laser Doppler anemometer signal processing for blood flow velocity measurements

    SciTech Connect

    Borozdova, M A; Fedosov, I V; Tuchin, V V

    2015-03-31

    A new method for analysing the signal in a laser Doppler anemometer based on the differential scheme is proposed, which provides the flow velocity measurement in strongly scattering liquids, particularly, blood. A laser Doppler anemometer intended for measuring the absolute blood flow velocity in animal and human near-surface arterioles and venules is developed. The laser Doppler anemometer signal structure is experimentally studied for measuring the flow velocity in optically inhomogeneous media, such as blood and suspensions of scattering particles. The results of measuring the whole and diluted blood flow velocity in channels with a rectangular cross section are presented. (laser applications and other topics in quantum electronics)

  20. Non-contact full-field optical coherence tomography: a novel tool for in vivo imaging of the human cornea (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Mazlin, Viacheslav; Dalimier, Eugénie; Grieve, Katharine F.; Irsch, Kristina; Sahel, José-Alain; Fink, Mathias; Boccara, A. Claude

    2017-02-01

    According to the World Health Organization (WHO), corneal diseases alongside with cataract and retinal diseases are major causes of blindness worldwide. For the 95.5% of corneal blindness cases, prevention or rehabilitation could have been possible without negative consequences for vision, provided that disease is diagnosed early. However, diagnostics at the early stage requires cellular-level resolution, which is not achieved with routinely used Slit-lamp and OCT instruments. Confocal microscopy allows examination of the cornea at a resolution approaching histological detail, however requires contact with a patient's eye. The recently developed full-field OCT technique, in which 2D en face tangential optical slices are directly recorded on a camera, was successfully applied for ex vivo eye imaging. However, in vivo human eye imaging has not been demonstrated yet. Here we present a novel non-contact full-field OCT system, which is capable of imaging in air and, therefore, shows potential for in vivo cornea imaging in patients. The first cellular-level resolution ex vivo images of cornea, obtained in a completely non-contact way, were demonstrated. We were able to scan through the entire cornea (400 µm) and resolve epithelium, Bowman's layer, stroma and endothelium. FFOCT images of the human cornea in vivo were obtained for the first time. The epithelium structures and stromal keratocyte cells were distinguishable. Both ex vivo and in vivo images were acquired with a large (1.26 mm x 1.26 mm) field of view. Cellular details in obtained images make this device a promising candidate for realization of high-resolution in vivo cornea imaging.

  1. Using digital image correlation and three dimensional point tracking in conjunction with real time operating data expansion techniques to predict full-field dynamic strain

    NASA Astrophysics Data System (ADS)

    Avitabile, Peter; Baqersad, Javad; Niezrecki, Christopher

    2014-05-01

    Large structures pose unique difficulties in the acquisition of measured dynamic data with conventional techniques that are further complicated when the structure also has rotating members such as wind turbine blades and helicopter blades. Optical techniques (digital image correlation and dynamic point tracking) are used to measure line of sight data without the need to contact the structure, eliminating cumbersome cabling issues. The data acquired from these optical approaches are used in conjunction with a unique real time operating data expansion process to obtain full-field dynamic displacement and dynamic strain. The measurement approaches are described in this paper along with the expansion procedures. The data is collected for a single blade from a wind turbine and also for a three bladed assembled wind turbine configuration. Measured strains are compared to results from a limited set of optical measurements used to perform the expansion to obtain full-field strain results including locations that are not available from the line of sight measurements acquired. The success of the approach clearly shows that there are some very extraordinary possibilities that exist to provide very desperately needed full field displacement and strain information that can be used to help identify the structural health of structures.

  2. Micrometer scale resolution images of human corneal graft using full-field optical coherence tomography (FF-OCT)-link to polarimetric study of scattered field

    NASA Astrophysics Data System (ADS)

    Georges, Ga"lle; Siozade-Lamoine, Laure; Casadessus, Olivier; Deumié, Carole; Hoffart, Louis; Conrath, John

    2011-10-01

    The suitability of a corneal graft for transplant surgery is based on different criteria. It may be rejected in particular due to a loss of transparency, directly linked to its scattering properties. Then, these become an important parameter. The aim of this paper is to quantify the influence of the cornea thickness and of the epithelial layer on scattering properties. The origin of scattering is discussed based on polarimetric analysis of scattered field (surface and/or bulk) and on full-field optical coherence tomography imaging (structural information).

  3. Three-Dimensional Rapidly Scanning Laser Doppler Velocimeter with Low SNR Signal Processing

    DTIC Science & Technology

    1990-11-30

    Three-Dimensional Rapidly Scanning Laser Doppler Velocimeter with Low SNR Signal Processing 12. PERSONAL AUTHOR(S) Kevin A. Shinpaugh and Rog er L...curvature for concave mirror or lens surface s .................... object distance from lens s.. ................. image distance from lens SNR ...where the signal-to-noise ratio ( SNR ) of the PMT signal is 20 dB and signal processing is performed via the fast Fourier trasnform (FFT) with zero

  4. Signature stability in laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Iverson, Thomas Z.; Watson, Edward A.

    2017-05-01

    Speckle can complicate signal acquisition in coherent laser systems such as Laser Doppler Vibrometry (LDV). Variations in the speckle pattern at the reliever due to fluctuations in the system such as beam pointing can lead to impulsive events in the signature. The beam size at the object has a direct influence on the size of the speckle at the receiving aperture. Increasing the beam spot size reduces the average speckle size, but also decreases the strength of the signal coupled with the local oscillator in the LDV. In this paper, we derive the relationship between scattering spot size at the object and average speckle size at the receiver. Theory is presented on how increasing the beam diameter at the object can reduce the fluctuations of the heterodyned signal coupled with the Local Oscillator (LO). The Antenna theorem is presented to show the tradeoff between angular field of view and capture area. We show experimental results on the effects of speckle size and decreasing signal strength have on the stability of an LDV signature. We use a kurtosis metric previously reported in the literature to assess the stability and quality of the return signature.

  5. Muscle activity characterization by laser Doppler Myography

    NASA Astrophysics Data System (ADS)

    Scalise, Lorenzo; Casaccia, Sara; Marchionni, Paolo; Ercoli, Ilaria; Primo Tomasini, Enrico

    2013-09-01

    Electromiography (EMG) is the gold-standard technique used for the evaluation of muscle activity. This technique is used in biomechanics, sport medicine, neurology and rehabilitation therapy and it provides the electrical activity produced by skeletal muscles. Among the parameters measured with EMG, two very important quantities are: signal amplitude and duration of muscle contraction, muscle fatigue and maximum muscle power. Recently, a new measurement procedure, named Laser Doppler Myography (LDMi), for the non contact assessment of muscle activity has been proposed to measure the vibro-mechanical behaviour of the muscle. The aim of this study is to present the LDMi technique and to evaluate its capacity to measure some characteristic features proper of the muscle. In this paper LDMi is compared with standard superficial EMG (sEMG) requiring the application of sensors on the skin of each patient. sEMG and LDMi signals have been simultaneously acquired and processed to test correlations. Three parameters has been analyzed to compare these techniques: Muscle activation timing, signal amplitude and muscle fatigue. LDMi appears to be a reliable and promising measurement technique allowing the measurements without contact with the patient skin.

  6. Effect of the Availability of Prior Full-Field Digital Mammography and Digital Breast Tomosynthesis Images on the Interpretation of Mammograms

    PubMed Central

    Catullo, Victor J.; Chough, Denise M.; Ganott, Marie A.; Kelly, Amy E.; Shinde, Dilip D.; Sumkin, Jules H.; Wallace, Luisa P.; Bandos, Andriy I.; Gur, David

    2015-01-01

    Purpose To assess the effect of and interaction between the availability of prior images and digital breast tomosynthesis (DBT) images in decisions to recall women during mammogram interpretation. Materials and Methods Verbal informed consent was obtained for this HIPAA-compliant institutional review board–approved protocol. Eight radiologists independently interpreted twice deidentified mammograms obtained in 153 women (age range, 37–83 years; mean age, 53.7 years ± 9.3 [standard deviation]) in a mode by reader by case-balanced fully crossed study. Each study consisted of current and prior full-field digital mammography (FFDM) images and DBT images that were acquired in our facility between June 2009 and January 2013. For one reading, sequential ratings were provided by using (a) current FFDM images only, (b) current FFDM and DBT images, and (c) current FFDM, DBT, and prior FFDM images. The other reading consisted of (a) current FFDM images only, (b) current and prior FFDM images, and (c) current FFDM, prior FFDM, and DBT images. Fifty verified cancer cases, 60 negative and benign cases (clinically not recalled), and 43 benign cases (clinically recalled) were included. Recall recommendations and interaction between the effect of prior FFDM and DBT images were assessed by using a generalized linear model accounting for case and reader variability. Results Average recall rates in noncancer cases were significantly reduced with the addition of prior FFDM images by 34% (145 of 421) and 32% (106 of 333) without and with DBT images, respectively (P < .001). However, this recall reduction was achieved at the cost of a corresponding 7% (23 of 345) and 4% (14 of 353) reduction in sensitivity (P = .006). In contrast, availability of DBT images resulted in a smaller reduction in recall rates (false-positive interpretations) of 19% (76 of 409) and 26% (71 of 276) without and with prior FFDM images, respectively (P = .001). Availability of DBT images resulted in 4% (15 of

  7. Effect of the Availability of Prior Full-Field Digital Mammography and Digital Breast Tomosynthesis Images on the Interpretation of Mammograms.

    PubMed

    Hakim, Christiane M; Catullo, Victor J; Chough, Denise M; Ganott, Marie A; Kelly, Amy E; Shinde, Dilip D; Sumkin, Jules H; Wallace, Luisa P; Bandos, Andriy I; Gur, David

    2015-07-01

    To assess the effect of and interaction between the availability of prior images and digital breast tomosynthesis (DBT) images in decisions to recall women during mammogram interpretation. Verbal informed consent was obtained for this HIPAA-compliant institutional review board-approved protocol. Eight radiologists independently interpreted twice deidentified mammograms obtained in 153 women (age range, 37-83 years; mean age, 53.7 years ± 9.3 [standard deviation]) in a mode by reader by case-balanced fully crossed study. Each study consisted of current and prior full-field digital mammography (FFDM) images and DBT images that were acquired in our facility between June 2009 and January 2013. For one reading, sequential ratings were provided by using (a) current FFDM images only, (b) current FFDM and DBT images, and (c) current FFDM, DBT, and prior FFDM images. The other reading consisted of (a) current FFDM images only, (b) current and prior FFDM images, and (c) current FFDM, prior FFDM, and DBT images. Fifty verified cancer cases, 60 negative and benign cases (clinically not recalled), and 43 benign cases (clinically recalled) were included. Recall recommendations and interaction between the effect of prior FFDM and DBT images were assessed by using a generalized linear model accounting for case and reader variability. Average recall rates in noncancer cases were significantly reduced with the addition of prior FFDM images by 34% (145 of 421) and 32% (106 of 333) without and with DBT images, respectively (P < .001). However, this recall reduction was achieved at the cost of a corresponding 7% (23 of 345) and 4% (14 of 353) reduction in sensitivity (P = .006). In contrast, availability of DBT images resulted in a smaller reduction in recall rates (false-positive interpretations) of 19% (76 of 409) and 26% (71 of 276) without and with prior FFDM images, respectively (P = .001). Availability of DBT images resulted in 4% (15 of 338) and 8% (25 of 322) increases in

  8. A study of radial-flow turbomachinery blade vibration measurements using Eulerian laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Oberholster, A. J.; Heyns, P. S.

    2014-05-01

    The structural integrity of blades is critical to the health of turbomachinery. Since operational failure of these blades can possibly lead to catastrophic failure of the machine, it is important to have knowledge of blade conditions in an online fashion. Due to several practical implications, it is desired to measure blade vibration with a non-contact technique. The application of laser Doppler vibrometry towards the vibration based condition monitoring of axial-flow turbomachinery blades has been successfully demonstrated in previous work. In this paper the feasibility of using laser Doppler vibrometry to measure radial-flow turbomachinery blade vibrations is investigated with the aid of digital image correlation and strain gauge telemetry.

  9. Continuous monitoring of cortical perfusion by laser Doppler flowmetry in ventilated patients with head injury.

    PubMed Central

    Kirkpatrick, P J; Smielewski, P; Czosnyka, M; Pickard, J D

    1994-01-01

    A method for monitoring cortical perfusion by laser Doppler flowmetry (LDF) in the neurointensive care unit is described. Out of 22 patients with head injuries, reliable and long term recordings were obtained in 16. Laser Doppler flowmetry registered changes in cortical microcirculatory flow in response to spontaneous waves of raised intracranial pressure, and to therapeutic manoeuvres that altered the cerebral perfusion pressure. Comparisons of variations in flux signal with cerebral perfusion pressure provided an indication of the autoregulatory state of the cortical microcirculation, and analysis of raw LDF data demonstrated an autoregulatory breakpoint of cerebral perfusion pressure of 58 mm Hg, below which cortical perfusion failed. Although middle cerebral artery flow velocities were generally tightly coupled with LDF signal changes, episodes of uncoupling were seen. The potential uses and limitations of LDF in the neurointensive care setting are discussed. Images PMID:7964816

  10. A new full-field digital mammography system with and without the use of an advanced post-processing algorithm: comparison of image quality and diagnostic performance.

    PubMed

    Ahn, Hye Shin; Kim, Sun Mi; Jang, Mijung; Yun, Bo La; Kim, Bohyoung; Ko, Eun Sook; Han, Boo-Kyung; Chang, Jung Min; Yi, Ann; Cho, Nariya; Moon, Woo Kyung; Choi, Hye Young

    2014-01-01

    To compare new full-field digital mammography (FFDM) with and without use of an advanced post-processing algorithm to improve image quality, lesion detection, diagnostic performance, and priority rank. During a 22-month period, we prospectively enrolled 100 cases of specimen FFDM mammography (Brestige®), which was performed alone or in combination with a post-processing algorithm developed by the manufacturer: group A (SMA), specimen mammography without application of "Mammogram enhancement ver. 2.0"; group B (SMB), specimen mammography with application of "Mammogram enhancement ver. 2.0". Two sets of specimen mammographies were randomly reviewed by five experienced radiologists. Image quality, lesion detection, diagnostic performance, and priority rank with regard to image preference were evaluated. Three aspects of image quality (overall quality, contrast, and noise) of the SMB were significantly superior to those of SMA (p < 0.05). SMB was significantly superior to SMA for visualizing calcifications (p < 0.05). Diagnostic performance, as evaluated by cancer score, was similar between SMA and SMB. SMB was preferred to SMA by four of the five reviewers. The post-processing algorithm may improve image quality with better image preference in FFDM than without use of the software.

  11. A New Full-Field Digital Mammography System with and without the Use of an Advanced Post-Processing Algorithm: Comparison of Image Quality and Diagnostic Performance

    PubMed Central

    Ahn, Hye Shin; Jang, Mijung; Yun, Bo La; Kim, Bohyoung; Ko, Eun Sook; Han, Boo-Kyung; Chang, Jung Min; Yi, Ann; Cho, Nariya; Moon, Woo Kyung; Choi, Hye Young

    2014-01-01

    Objective To compare new full-field digital mammography (FFDM) with and without use of an advanced post-processing algorithm to improve image quality, lesion detection, diagnostic performance, and priority rank. Materials and Methods During a 22-month period, we prospectively enrolled 100 cases of specimen FFDM mammography (Brestige®), which was performed alone or in combination with a post-processing algorithm developed by the manufacturer: group A (SMA), specimen mammography without application of "Mammogram enhancement ver. 2.0"; group B (SMB), specimen mammography with application of "Mammogram enhancement ver. 2.0". Two sets of specimen mammographies were randomly reviewed by five experienced radiologists. Image quality, lesion detection, diagnostic performance, and priority rank with regard to image preference were evaluated. Results Three aspects of image quality (overall quality, contrast, and noise) of the SMB were significantly superior to those of SMA (p < 0.05). SMB was significantly superior to SMA for visualizing calcifications (p < 0.05). Diagnostic performance, as evaluated by cancer score, was similar between SMA and SMB. SMB was preferred to SMA by four of the five reviewers. Conclusion The post-processing algorithm may improve image quality with better image preference in FFDM than without use of the software. PMID:24843234

  12. A full-field and real-time 3D surface imaging augmented DOT system for in-vivo small animal studies

    NASA Astrophysics Data System (ADS)

    Yi, Steven X.; Yang, Bingcheng; Yin, Gongjie

    2010-02-01

    A crucial parameter in Diffuse Optical Tomography (DOT) is the construction of an accurate forward model, which greatly depends on tissue boundary. Since photon propagation is a three-dimensional volumetric problem, extraction and subsequent modeling of three-dimensional boundaries is essential. Original experimental demonstration of the feasibility of DOT to reconstruct absorbers, scatterers and fluorochromes used phantoms or tissues confined appropriately to conform to easily modeled geometries such as a slab or a cylinder. In later years several methods have been developed to model photon propagation through diffuse media with complex boundaries using numerical solutions of the diffusion or transport equation (finite elements or differences) or more recently analytical methods based on the tangent-plane method . While optical examinations performed simultaneously with anatomical imaging modalities such as MRI provide well-defined boundaries, very limited progress has been done so far in extracting full-field (360 degree) boundaries for in-vivo three-dimensional DOT stand-alone imaging. In this paper, we present a desktop multi-spectrum in-vivo 3D DOT system for small animal imaging. This system is augmented with Technest's full-field 3D cameras. The built system has the capability of acquiring 3D object surface profiles in real time and registering 3D boundary with diffuse tomography. Extensive experiments are performed on phantoms and small animals by our collaborators at the Center for Molecular Imaging Research (CMIR) at Massachusetts General Hospital (MGH) and Harvard Medical School. Data has shown successful reconstructed DOT data with improved accuracy.

  13. A Systematic Review of the Evolution of Laser Doppler Techniques in Burn Depth Assessment

    PubMed Central

    Fitzgerald O'Connor, Edmund; Philp, Bruce

    2014-01-01

    Aims. The introduction of laser Doppler (LD) techniques to assess burn depth has revolutionized the treatment of burns of indeterminate depth. This paper will systematically review studies related to these two techniques and trace their evolution. At the same time we hope to highlight current controversies and areas where further research is necessary with regard to LD imaging (LDI) techniques. Methods. A systematic search for relevant literature was carried out on PubMed, Medline, EMBASE, and Google Scholar. Key search terms included the following: “Laser Doppler imaging,” “laser Doppler flow,” and “burn depth.” Results. A total of 53 studies were identified. Twenty-six studies which met the inclusion/exclusion criteria were included in the review. Conclusions. The numerous advantages of LDI over those of LD flowmetry have resulted in the former technique superseding the latter one. Despite the presence of alternative burn depth assessment techniques, LDI remains the most favoured. Various newer LDI machines with increasingly sophisticated methods of assessing burn depth have been introduced throughout the years. However, factors such as cost effectiveness, scanning of topographically inconsistent areas of the body, and skewing of results due to tattoos, peripheral vascular disease, and anaemia continue to be sighted as obstacles to LDI which require further research. PMID:25180087

  14. Laser Doppler flowmetry in endodontics: a review.

    PubMed

    Jafarzadeh, H

    2009-06-01

    Vascular supply is the most accurate marker of pulp vitality. Tests for assessing vascular supply that rely on the passage of light through a tooth have been considered as possible methods for detecting pulp vitality. Laser Doppler flowmetry (LDF), which is a noninvasive, objective, painless, semi-quantitative method, has been shown to be reliable for measuring pulpal blood flow. The relevant literature on LDF in the context of endodontics up to March 2008 was reviewed using PubMed and MEDLINE database searches. This search identified papers published between June 1983 and March 2008. Laser light is transmitted to the pulp by means of a fibre optic probe. Scattered light from moving red blood cells will be frequency-shifted whilst that from the static tissue remains unshifted. The reflected light, composed of Doppler-shifted and unshifted light, is returned by afferent fibres and a signal is produced. This technique has been successfully employed for estimating pulpal vitality in adults and children, differential diagnosis of apical radiolucencies (on the basis of pulp vitality), examining the reactions to pharmacological agents or electrical and thermal stimulation, and monitoring of pulpal responses to orthodontic procedures and traumatic injuries. Assessments may be highly susceptible to environmental and technique-related factors. Nonpulpal signals, principally from periodontal blood flow, may contaminate the signal. Because this test produces no noxious stimuli, apprehensive or distressed patients accept it more readily than current methods of pulp vitality assessment. A review of the literature and a discussion of the application of this system in endodontics are presented.

  15. X-ray absorption spectroscopy by full-field X-ray microscopy of a thin graphite flake: Imaging and electronic structure via the carbon K-edge

    PubMed Central

    Hitchock, Adam P; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Ewels, Chris P; Guttmann, Peter

    2012-01-01

    Summary We demonstrate that near-edge X-ray-absorption fine-structure spectra combined with full-field transmission X-ray microscopy can be used to study the electronic structure of graphite flakes consisting of a few graphene layers. The flake was produced by exfoliation using sodium cholate and then isolated by means of density-gradient ultracentrifugation. An image sequence around the carbon K-edge, analyzed by using reference spectra for the in-plane and out-of-plane regions of the sample, is used to map and spectrally characterize the flat and folded regions of the flake. Additional spectral features in both π and σ regions are observed, which may be related to the presence of topological defects. Doping by metal impurities that were present in the original exfoliated graphite is indicated by the presence of a pre-edge signal at 284.2 eV. PMID:23016137

  16. Which phantom is better for assessing the image quality in full-field digital mammography?: American College of Radiology Accreditation phantom versus digital mammography accreditation phantom.

    PubMed

    Song, Sung Eun; Seo, Bo Kyoung; Yie, An; Ku, Bon Kyung; Kim, Hee-Young; Cho, Kyu Ran; Chung, Hwan Hoon; Lee, Seung Hwa; Hwang, Kyu-Won

    2012-01-01

    To compare between the American College of Radiology (ACR) accreditation phantom and digital mammography accreditation phantom in assessing the image quality in full-field digital mammography (FFDM). In each week throughout the 42-week study, we obtained phantom images using both the ACR accreditation phantom and the digital mammography accreditation phantom, and a total of 42 pairs of images were included in this study. We assessed the signal-to-noise ratio (SNR) in each phantom image. A radiologist drew a square-shaped region of interest on the phantom and then the mean value of the SNR and the standard deviation were automatically provided on a monitor. SNR was calculated by an equation, measured mean value of SNR-constant coefficient of FFDM/standard deviation. Two breast radiologists scored visible objects (fibers, specks, and masses) with soft-copy images and calculated the visible rate (number of visible objects/total number of objects). We compared SNR and the visible rate of objects between the two phantoms and calculated the k-coefficient for interobserver agreement. The SNR of the ACR accreditation phantom ranged from 42.0 to 52.9 (Mean, 47.3 ± 2.79) and that of Digital Phantom ranged from 24.8 to 54.0 (Mean, 44.1 ± 9.93) (p = 0.028). The visible rates of all three types of objects were much higher in the ACR accreditation phantom than those in the digital mammography accreditation phantom (p < 0.05). Interobserver agreement for visible rates of objects on phantom images was fair to moderate agreement (k-coefficients: 0.34-0.57). The ACR accreditation phantom is superior to the digital mammography accreditation phantom in terms of SNR and visibility of phantom objects. Thus, ACR accreditation phantom appears to be satisfactory for assessing the image quality in FFDM.

  17. Impact of type of full-field digital image on mammographic density assessment and breast cancer risk estimation: a case-control study.

    PubMed

    Busana, Marta Cecilia; Eng, Amanda; Denholm, Rachel; Dowsett, Mitch; Vinnicombe, Sarah; Allen, Steve; Dos-Santos-Silva, Isabel

    2016-09-26

    Full-field digital mammography, which is gradually being introduced in most clinical and screening settings, produces two types of images: raw and processed. However, the extent to which mammographic density measurements, and their ability to predict breast cancer risk, vary according to type of image is not fully known. We compared the performance of the semi-automated Cumulus method on digital raw, "analogue-like" raw and processed images, and the performance of a recently developed method - Laboratory for Breast Radiodensity Assessment (LIBRA) - on digital raw and processed images, in a case-control study (414 patients (cases) and 684 controls) by evaluating the extent to which their measurements were associated with breast cancer risk factors, and by comparing their ability to predict breast cancer risk. Valid Cumulus and LIBRA measurements were obtained from all available images, but the resulting distributions differed according to the method and type of image used. Both Cumulus and LIBRA percent density were inversely associated with age, body mass index (BMI), parity and postmenopausal status, regardless of type of image used. Cumulus percent density was strongly associated with breast cancer risk, but with the magnitude of the association slightly stronger for processed (risk increase per one SD increase in percent density (95 % CI): 1.55 (1.29, 1.85)) and "analogue-like" raw (1.52 (1.28, 1.80)) than for raw (1.35 (1.14, 1.60)) images. LIBRA percent density produced weaker associations with risk, albeit stronger for processed (1.32 (1.08, 1.61)) than raw images (1.17 (0.99, 1.37)). The percent density values yielded by the various density assessment/type of image combinations had similar ability to discriminate between patients and controls (area under the receiving operating curve values for percent density, age, BMI, parity and menopausal status combined ranged from 0.61 and 0.64). The findings showed that Cumulus can be used to measure density on all

  18. En-face sectional imaging using single-shot full-field optical coherence tomography (SS-FF-OCT) based on white light emitting diode (WLED)

    NASA Astrophysics Data System (ADS)

    Anna, Tulsi; Lai, Chih-Ming; Chiou, Arthur; Kuo, Wen-Chuan

    2016-10-01

    This work reports a Linnik type single shot full-field optical coherence tomography (SS-FF-OCT), which uses a fast generalized analytic signal based complex Riesz transform scheme to reconstruct wide area en-face OCT images. The OCT interferometer is illuminated using a single broad band white light emitting diode (WLED) (wavelength range 470- 850nm, central wavelength 650nm) and detection unit is a two-dimensional (2D) charge complementary metal oxide semiconductor (CMOS) camera. The measured axial and lateral resolution (using 4x, NA=0.1 microscope objective) of the present system is 0.9μm and 3.9μm, very close to theoretical values. The measured imaging area using CMOS camera is 2150 x 2150μm2. The feasibility of the system is demonstrated by imaging scattering samples such as onion bulk and plant leaf. The present SS-FF-OCT is compact, fast (Riesz transform based scheme), stable, cost-effective, and provides comparable axial resolution.

  19. Modeling and processing of laser Doppler reactive hyperaemia signals

    NASA Astrophysics Data System (ADS)

    Humeau, Anne; Saumet, Jean-Louis; L'Huiller, Jean-Pierre

    2003-07-01

    Laser Doppler flowmetry is a non-invasive method used in the medical domain to monitor the microvascular blood cell perfusion through tissue. Most commercial laser Doppler flowmeters use an algorithm calculating the first moment of the power spectral density to give the perfusion value. Many clinical applications measure the perfusion after a vascular provocation such as a vascular occlusion. The response obtained is then called reactive hyperaemia. Target pathologies include diabetes, hypertension and peripheral arterial occlusive diseases. In order to have a deeper knowledge on reactive hyperaemia acquired by the laser Doppler technique, the present work first proposes two models (one analytical and one numerical) of the observed phenomenon. Then, a study on the multiple scattering between photons and red blood cells occurring during reactive hyperaemia is carried out. Finally, a signal processing that improves the diagnosis of peripheral arterial occlusive diseases is presented.

  20. Laser Doppler technology applied to atmospheric environmental operating problems

    NASA Technical Reports Server (NTRS)

    Weaver, E. A.; Bilbro, J. W.; Dunkin, J. A.; Jeffreys, H. B.

    1976-01-01

    Carbon dioxide laser Doppler ground wind data were very favorably compared with data from standard anemometers. As a result of these measurements, two breadboard systems were developed for taking research data: a continuous wave velocimeter and a pulsed Doppler system. The scanning continuous wave laser Doppler velocimeter developed for detecting, tracking and measuring aircraft wake vortices was successfully tested at an airport where it located vortices to an accuracy of 3 meters at a range of 150 meters. The airborne pulsed laser Doppler system was developed to detect and measure clear air turbulence (CAT). This system was tested aboard an aircraft, but jet stream CAT was not encountered. However, low altitude turbulence in cumulus clouds near a mountain range was detected by the system and encountered by the aircraft at the predicted time.

  1. MO-A-BRD-01: An Investigation of the Dynamic Response of a Novel Acousto-Optic Liquid Crystal Detector for Full-Field Transmission Ultrasound Breast Imaging

    SciTech Connect

    Rosenfield, J.R.; La Riviere, P.J.; Sandhu, J.S.

    2014-06-15

    Purpose: To characterize the dynamic response of a novel acousto-optic (AO) liquid crystal detector for high-resolution transmission ultrasound breast imaging. Transient and steady-state lesion contrast were investigated to identify optimal transducer settings for our prototype imaging system consistent with the FDA limits of 1 W/cm{sup 2} and 50 J/cm{sup 2} on the incident acoustic intensity and the transmitted acoustic energy flux density. Methods: We have developed a full-field transmission ultrasound breast imaging system that uses monochromatic plane-wave illumination to acquire projection images of the compressed breast. The acoustic intensity transmitted through the breast is converted into a visual image by a proprietary liquid crystal detector operating on the basis of the AO effect. The dynamic response of the AO detector in the absence of an imaged breast was recorded by a CCD camera as a function of the acoustic field intensity and the detector exposure time. Additionally, a stereotactic needle biopsy breast phantom was used to investigate the change in opaque lesion contrast with increasing exposure time for a range of incident acoustic field intensities. Results: Using transducer voltages between 0.3 V and 0.8 V and exposure times of 3 minutes, a unique one-to-one mapping of incident acoustic intensity to steady-state optical brightness in the AO detector was observed. A transfer curve mapping acoustic intensity to steady-state optical brightness shows a high-contrast region analogous to the linear portion of the Hurter-Driffield curves of radiography. Using transducer voltages between 1 V and 1.75 V and exposure times of 90 s, the lesion contrast study demonstrated increasing lesion contrast with increasing breast exposure time and acoustic field intensity. Lesion-to-background contrast on the order of 0.80 was observed. Conclusion: Maximal lesion contrast in our prototype system can be obtained using the highest acoustic field intensity and the

  2. Miniature Laser Doppler Velocimeter for Measuring Wall Shear

    NASA Technical Reports Server (NTRS)

    Gharib, Morteza; Modarress, Darius; Forouhar, Siamak; Fourguette, Dominique; Taugwalder, Federic; Wilson, Daniel

    2005-01-01

    A miniature optoelectronic instrument has been invented as a nonintrusive means of measuring a velocity gradient proportional to a shear stress in a flow near a wall. The instrument, which can be mounted flush with the wall, is a variant of a basic laser Doppler velocimeter. The laser Doppler probe volume can be located close enough to the wall (as little as 100 micron from the surface) to lie within the viscosity-dominated sublayer of a turbulent boundary layer. The instrument includes a diode laser, the output of which is shaped by a diffractive optical element (DOE) into two beams that have elliptical cross sections with very high aspect ratios.

  3. Modular high accuracy tracker for dual channel laser Doppler velocimeter

    NASA Technical Reports Server (NTRS)

    Fridman, J. D.; Young, R. M.; Seavey, R. E.; Orloff, K. L.

    1976-01-01

    In the study described, a scanning dual-channel cross-beam laser Doppler velocimeter (developed for measuring simultaneously the two orthogonal components of flow velocity and turbulence intensity) was used to measure the instantaneous velocity characteristics of a model helicopter rotor and in a vortex wake survey experiment on a Boeing 747 aircraft model. Particular attention is given to a special purpose dual-loop frequency tracker developed to track and demodulate 10 microsecond wide pulse burst Doppler signals with a study cycle of 25% (or narrower signals at a higher duty cycle) generated by the laser Doppler velocimeter.

  4. Non-contact photoacoustic tomography with a laser Doppler vibrometer

    NASA Astrophysics Data System (ADS)

    Xu, Guan; Wang, Cheng; Feng, Ting; Oliver, David E.; Wang, Xueding

    2014-03-01

    Most concurrent photoacoustic tomography systems are based on traditional ultrasound measurement regime, which requires the contact or acoustic coupling material between the biological tissue and the ultrasound transducer. This study investigates the feasibility of non-contact measurement of photacoustic signals generated inside biomedical tissues by observing the vibrations at the surface of the tissues with a commercial laser Doppler vibrometer. The vibrometer with 0- 2MHz measurement bandwidth and 5 MHz sampling frequency was integrated to a conventional rotational PAT data acquisition system. The data acquisition of the vibrometer was synchronized to the laser illumination from an Nd:YAG laser with output at 532nm. The laser energy was tuned to 17.5mJ per square centimeter. The PA signals were acquired at 120 angular locations uniformly distributed around the scanned objects. The frequency response of the measurement system was first calibrated. 2-inch-diamater cylindrical phantoms containing small rubber plates and biological tissues were afterwards imaged. The phantoms were made from 5% intralipid solution in 10% porcine gelatin to simulate the light scattering in biological tissue and to backscatter the measurement laser from the vibrometer. Time-domain backprojection method was used for the image reconstruction. Experiments with real-tissue phantoms show that with laser illumination of 17.5 mJ/cm2 at 532 nm, the non-contact photoacoustic (PA) imaging system with 15dB detection bandwidth of 2.5 MHz can resolve spherical optical inclusions with dimension of 500μm and multi-layered structure with optical contrast in strongly scattering medium. The experiment results prompt the potential implementation of the non-contact PAT to achieve "photoacoustic camera".

  5. Dual beam translator for use in Laser Doppler anemometry

    DOEpatents

    Brudnoy, D.M.

    1984-04-12

    A method and apparatus for selectively translating the path of at least one pair of light beams in a Laser Doppler anemometry device whereby the light paths are translated in a direction parallel to the original beam paths so as to enable attainment of spacial coincidence of the two intersection volumes and permit accurate measurements of Reynolds shear stress.

  6. Wing tip vortex measurements with laser Doppler systems

    NASA Technical Reports Server (NTRS)

    Fuller, C. E., III

    1973-01-01

    The vortex velocity field produced by a rectangular wing in a subsonic wind tunnel was measured using two laser Doppler velocimeter systems. One system made three dimensional mean velocity measurements and the other made one dimensional turbulence measurements. The systems and test procedures are described and comparisons of the measurements are made. The data defined a strong spiral motion in the vortex formation process.

  7. Anomaly Detection In Additively Manufactured Parts Using Laser Doppler Vibrometery

    SciTech Connect

    Hernandez, Carlos A.

    2015-09-29

    Additively manufactured parts are susceptible to non-uniform structure caused by the unique manufacturing process. This can lead to structural weakness or catastrophic failure. Using laser Doppler vibrometry and frequency response analysis, non-contact detection of anomalies in additively manufactured parts may be possible. Preliminary tests show promise for small scale detection, but more future work is necessary.

  8. Three-dimensional shear wave imaging based on full-field laser speckle contrast imaging with one-dimensional mechanical scanning.

    PubMed

    Chao, Pei-Yu; Li, Pai-Chi

    2016-08-22

    The high imaging resolution and motion sensitivity of optical-based shear wave detection has made it an attractive technique in biomechanics studies with potential for improving the capabilities of shear wave elasticity imaging. In this study we implemented laser speckle contrast imaging for two-dimensional (X-Z) tracking of transient shear wave propagation in agarose phantoms. The mechanical disturbances induced by the propagation of the shear wave caused temporal and spatial fluctuations in the local speckle pattern, which manifested as local blurring. By mechanically moving the sample in the third dimension (Y), and performing two-dimensional shear wave imaging at every scan position, the three-dimensional shear wave velocity distribution of the phantom could be reconstructed. Based on comparisons with the reference shear wave velocity measurements obtained using a commercial ultrasound shear wave imaging system, the developed system can estimate the shear wave velocity with an error of less than 6% for homogeneous phantoms with shear moduli ranging from 1.52 kPa to 7.99 kPa. The imaging sensitivity of our system makes it capable of measuring small variations in shear modulus; the estimated standard deviation of the shear modulus was found to be less than 0.07 kPa. A submillimeter spatial resolution for three-dimensional shear wave imaging has been achieved, as demonstrated by the ability to detect a 1-mm-thick stiff plate embedded inside heterogeneous agarose phantoms.

  9. Elemental mapping in a contemporary miniature by full-field X-ray fluorescence imaging with gaseous detector vs. scanning X-ray fluorescence imaging with polycapillary optics

    NASA Astrophysics Data System (ADS)

    Silva, A. L. M.; Cirino, S.; Carvalho, M. L.; Manso, M.; Pessanha, S.; Azevedo, C. D. R.; Carramate, L. F. N. D.; Santos, J. P.; Guerra, M.; Veloso, J. F. C. A.

    2017-03-01

    Energy dispersive X-ray imaging can be used in several research fields and industrial applications. Elemental mapping through energy dispersive X-ray imaging technique has become a promising method to obtain positional distribution of specific elements in a non-destructive way. To obtain the elemental distribution of a sample it is necessary to use instruments capable of providing a precise positioning together with a good energy resolution. Polycapillary beams together with silicon drift chamber detectors are used in several commercial systems and are considered state-of-the-art spectrometers, however they are usually very costly. A new concept of large energy dispersive X-ray imaging systems based on gaseous radiation detectors emerged in the last years enabling a promising 2D elemental detection at a very reduced price. The main goal of this work is to analyze a contemporary Indian miniature with both X-ray fluorescence imaging systems, the one based on a gaseous detector 2D-THCOBRA and the state-of-the-art spectrometer M4 Tornado, from Bruker. The performance of both systems is compared and evaluated in the context of the sample's analysis.

  10. Two-view and single-view tomosynthesis versus full-field digital mammography: high-resolution X-ray imaging observer study.

    PubMed

    Wallis, Matthew G; Moa, Elin; Zanca, Federica; Leifland, Karin; Danielsson, Mats

    2012-03-01

    To compare the diagnostic accuracy of two-dimensional (2D) full-field digital mammography with that of two-view (mediolateral and craniocaudal) and single-view (mediolateral oblique) tomosynthesis in an observer study involving two institutions. Ethical committee approval was obtained. All participating women gave informed consent. Two hundred twenty women (mean age, 56.3; range, 40-80 years) with breast density of 2-4 according to American College of Radiology criteria were recruited between November 2008 and September 2009 and underwent standard treatment plus tomosynthesis with a prototype photon-counting machine. After exclusion criteria were met, this resulted in a final test set of 130 women. Ten accredited readers classified the 130 cases (40 cancers, 24 benign lesions, and 66 normal images) using 2D mammography and two-view tomosynthesis. Another 10 readers reviewed the same cases using 2D mammography but single-view tomosynthesis. The multireader, multicase receiver operating characteristic (ROC) method was applied. The significance of the observed difference in accuracy between 2D mammography and tomosynthesis was calculated. For diagnostic accuracy, 2D mammography performed significantly worse than two-view tomosynthesis (average area under ROC curve [AUC] = 0.772 for 2D, AUC = 0.851 for tomosynthesis, P = .021). Significant differences were found for both masses and microcalcification (P = .037 and .049). The difference in AUC between the two modalities of -0.110 was significant (P = .03) only for the five readers with the least experience (<10 years of reading); with AUC of -0.047 for the five readers with 10 years or more experience (P = .25). No significant difference (P = .79) in reader performance was seen when 2D mammography (average AUC = 0.774) was compared with single-view tomosynthesis (average AUC = 0.775). Two-view tomosynthesis outperforms 2D mammography but only for readers with the least experience. The benefits were seen for both masses

  11. Laser Doppler anemometer studies in unsteady ventricular flows.

    PubMed

    Phillips, W M; Furkay, S S; Pierce, W S

    1979-01-01

    The laser Doppler technique was employed to obtain intraventricular velocity distributions on the basis of in vivo confirmation of previous in vitro flow visualization predictions. The quasi-steady assumption required for quantification of flow visualization results is unsatisfactory in regions of high acceleration and fluctuating velocities are unavailable via such techniques. Mean and fluctuating velocity profiles were obtained in a pneumatically driven prosthetic ventricle with the laser Doppler anemometer and stress levels estimated. The preliminary data presented here illustrates that the technique can be applied to such flows. The measurement and data reduction schemes are applicable to a wide range of simulated cardiovascular flows. The particular application to prosthetic ventricle design should minimize the number of in vivo experiments required to develop a satisfactory blood pump and aid in tailoring pump actuation protocols for minimum thromboembolic complications.

  12. All semiconductor laser Doppler anemometer at 1.55 microm.

    PubMed

    Hansen, René Skov; Pedersen, Christian

    2008-10-27

    We report to our best knowledge the first all semiconductor Laser Doppler Anemometer (LIDAR) for wind speed determination. We will present the design and first experimental results on a focusing coherent cw laser Doppler anemometer for measuring atmospheric wind velocities in the 10 meters to 300 meters distance range. Especially, we will demonstrate that both the output power as well as the demanding coherence properties required from the laser source can be accomplished by an all semiconductor laser. Preliminary tests at a distance of 40 meters indicate a typical signal to noise ratio of 9 dB. This result is obtained at a clear day with an up-date rate of 12 Hz.

  13. Phase relation recovery for scanning laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Alveringh, D.; Sanders, R. G. P.; Wiegerink, R. J.; Lötters, J. C.

    2017-02-01

    Laser Doppler vibrometers are able to measure the velocity of a single point compared to a reference point by analyzing the Doppler shift of the laser beams. In many commercially available laser Doppler vibrometers, the laser point can be scanned to obtain an out-of-plane velocity profile of a surface. It is essential that the phase information of the velocities between points is measured as well to be able to fully reproduce the velocity profile of the surface. If this cannot be done by triggering on the actuation signal, the proposed two stage method can be used. This method measures the surface in two stages: one scan with the reference beam at a fixed point and one scan with the reference beam on a moving point. The algorithm in this article calculates the phase and reconstructs the velocity of each point. This is experimentally verified on three different micro structures. The postprocessing algorithm is not intensive in computing power.

  14. Laser Doppler flowmetry in diagnoses of chronic tonsillitis

    NASA Astrophysics Data System (ADS)

    Mareew, Gleb O.; Mareew, Oleg V.; Maslyakova, Galina N.; Ivliev, Igor I.; Fedosov, Ivan V.; Lychagov, Vladislav V.; Tuchin, Valery V.

    2005-06-01

    Chronic tonsillitis is one of the most common diseases in ENT all over the world. There are two ways of treatment-surgical tonsillectomy and conservative therapeutically treatment. But still doctors have no possibility to make objective decisions for this painful and tonsil-destructive operation. In this article we try to research how the degree of sclerosis in tonsillar tissue affects the blood flow in tonsils, by using laser Doppler flowmetry.

  15. Laser Doppler interferometer for vibration of rotating curved surfaces

    NASA Astrophysics Data System (ADS)

    Wu, Giin-Yuan; Lee, Chih-Kung; Lin, San; Wakabayashi, Takenori; Ono, K.

    1999-10-01

    With the rapid advancement of today's ultra-high performance mechanical or mechatronic system such as magnetic or optical disk drives, improving metrology capabilities to examine the performance characteristics of these system are growing ever more important. The primary tested studied in this paper is an ultra-high precision ball-bearing spindle that possesses non-repeatable runout of less than 100nm. The metrology tool adopted is laser Doppler interferometer system that has Megahertz bandwidth and nanometer resolutions. Experimental data obtained clearly indicates that measuring vertical runout of a spindle motor is a straightforward process. However, a fundamental effect was identified, where the radial runout data was found to drift upward or downward with time, when using the laser Doppler system to measure the radial runout of ultra-high precision rotational systems whose surface profile is not flat. All of the underlying reasons that cause this undesirable effect were proposed and verified. Approaches that can be adopted to circumvent this apparent limitation on adopting the laser Doppler interferometer systems to measure rotational curved surface were implemented to further extend its application horizon. The experimental data realized and the application experience obtained were shown to further advance our measurement capabilities.

  16. New signal analysis methods for laser doppler flowmetric recordings

    NASA Astrophysics Data System (ADS)

    ǎgǎnescu, G. E., Dr; Todea, Carmen

    2014-01-01

    The laser Doppler flowmetry devices give a series of information like the blood flux and some statistical parameters, automatically estimated. There are also new important attempts based on the Fourier transform of the flow flux signal which gather more information from the laser Doppler flowmetry. The amplitude spectra estimated in these articles, exhibit a series of peaks corresponding to the cardiac variation of the blood flow and noise components of the flow flux signals, dependent on the state of the tooth. The aim of our investigations is to introduce new signal processing methods, based on wavelet continuous tranform, which express in a more sensitive manner the modifications of the flow flux signal with the state of the tooth, and to introduce new quantitative parameters, defined in a previous paper. These parameters express, in a more sensitive manner the modifications of the pulp flow flux signal in relation with the pulp tooth healt, and to introduce new quantitative parameters, defined in a previous paper. These parameters express, in a sensitive way the changes of the blood flux. For practical investigations we used a series of signals recorded with the aid of a Laser Doppler Blood Flow Monitoring device (Moor Instruments) and processed with the computer.

  17. Thermal tests for laser Doppler perfusion measurements in Raynaud's syndrome

    NASA Astrophysics Data System (ADS)

    Kacprzak, Michal; Skora, A.; Obidzinska, J.; Zbiec, A.; Maniewski, Roman; Staszkiewicz, W.

    2004-07-01

    The laser Doppler method offers a non-invasive, real time technique for monitoring of blood perfusion in microcirculation. In practical measurements the perfusion index is given only in relative values. Thus, accurate and reproducible results can be only obtained when using a well controlled stimulation test. The aim of this study was evaluation of the thermal stimulation test, which is frequently used to investigate microcirculation in patients with Raynaud's syndrome. Three types of thermal tests, in which air or water with temperature in range 5°C - 40°C were used. Ten normal volunteers and fifteen patients with clinical symptoms of the primary Raynaud's syndrome were enrolled in this study. To estimate skin microcirculation changes during the thermal test, the multichannel laser Doppler system and laser Doppler scanner were used. The obtained results were analyzed from the point of view of the efficiency of these methods and the thermal provocative tests in differentiation of normal subjects and patient with Raynaud's syndrome.

  18. Performance analysis of continuous tracking laser Doppler vibrometry applied to rotating structures in coast-down

    NASA Astrophysics Data System (ADS)

    Martarelli, M.; Castellini, P.

    2012-06-01

    In this paper a performance analysis of the so-called tracking continuous scanning laser Doppler vibrometry (TCSLDV) exploited in coast-down has been performed. This non-contact measurement system is able to scan continuously over a rotating surface during coast-down and to determine vibration operational deflection shapes (ODSs) and natural frequencies in short time, i.e. the temporal extent of the coast-down. The method is based on a laser Doppler vibrometer (LDV) whose laser beam is driven to scan continuously over the whole rotor surface synchronously with its rotation, so that the LDV output is modulated by the structure's ODSs. This technique has a full-field nature that enables it to measure simultaneously the time and spatial dependence of the vibration in a unique measurement. However, the TCSLDV presents some criticalities in practical applications, especially when applied to rotary transient and fast processes. In fact, if the vibration is transient and decays very fast, then the laser beam could not have had the time to scan the complete structure surface and the modulation of the ODS could be partial. An analytical model reproducing a representative experiment has been developed in order to evaluate the sensitivity of results to testing conditions. The laser beam trajectory in both the fixed and rotating reference systems has been synthesized showing its dependence on experimental parameters as the rotation speed variation during coast-down. It has been demonstrated the decrease in speed induces the deformation of the laser trajectory influencing the LDV output time history, spectrum and consequently the recovered ODS.

  19. Laser Doppler velocity measurement without directional ambiguity by using frequency shifted incident beams

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.

    1970-01-01

    Laser Doppler heterodyning system for velocity measurements without directional ambiguity, employing incident beams of different frequencies through rotating diffraction grating or Bragg cell application

  20. Perceived sufficiency of full-field digital mammograms with and without irreversible image data compression for comparison with next-year mammograms.

    PubMed

    Destounis, Stamatia; Somerville, Patricia; Murphy, Philip; Seifert, Posy

    2011-02-01

    Problems associated with the large file sizes of digital mammograms have impeded the integration of digital mammography with picture archiving and communications systems. Digital mammograms irreversibly compressed by the novel wavelet Access Over Network (AON) compression algorithm were compared with lossless-compressed digital mammograms in a blinded reader study to evaluate the perceived sufficiency of irreversibly compressed images for comparison with next-year mammograms. Fifteen radiologists compared the same 100 digital mammograms in three different comparison modes: lossless-compressed vs 20:1 irreversibly compressed images (mode 1), lossless-compressed vs 40:1 irreversibly compressed images (mode 2), and 20:1 irreversibly compressed images vs 40:1 irreversibly compressed images (mode 3). Compression levels were randomly assigned between monitors. For each mode, the less compressed of the two images was correctly identified no more frequently than would occur by chance if all images were identical in compression. Perceived sufficiency for comparison with next-year mammograms was achieved by 97.37% of the lossless-compressed images and 97.37% of the 20:1 irreversibly compressed images in mode 1, 97.67% of the lossless-compressed images and 97.67% of the 40:1 irreversibly compressed images in mode 2, and 99.33% of the 20:1 irreversibly compressed images and 99.19% of the 40:1 irreversibly compressed images in mode 3. In a random-effect analysis, the irreversibly compressed images were found to be noninferior to the lossless-compressed images. Digital mammograms irreversibly compressed by the wavelet AON compression algorithm were as frequently judged sufficient for comparison with next-year mammograms as lossless-compressed digital mammograms.

  1. Full-field OCT: applications in ophthalmology

    NASA Astrophysics Data System (ADS)

    Grieve, Kate; Dubois, Arnaud; Paques, Michel; Le Gargasson, Jean-Francois; Boccara, Albert C.

    2005-04-01

    We present images of ocular tissues obtained using ultrahigh resolution full-field OCT. The experimental setup is based on the Linnik interferometer, illuminated by a tungsten halogen lamp. En face tomographic images are obtained in real-time without scanning by computing the difference of two phase-opposed interferometric images recorded by a high-resolution CCD camera. A spatial resolution of 0.7 μm × 0.9 μm (axial × transverse) is achieved thanks to the short source coherence length and the use of high numerical aperture microscope objectives. A detection sensitivity of 90 dB is obtained by means of image averaging and pixel binning. Whole unfixed eyes and unstained tissue samples (cornea, lens, retina, choroid and sclera) of ex vivo rat, mouse, rabbit and porcine ocular tissues were examined. The unprecedented resolution of our instrument allows cellular-level resolution in the cornea and retina, and visualization of individual fibers in the lens. Transcorneal lens imaging was possible in all animals, and in albino animals, transscleral retinal imaging was achieved. We also introduce our rapid acquisition full-field optical coherence tomography system designed to accommodate in vivo ophthalmologic imaging. The variations on the original system technology include the introduction of a xenon arc lamp as source, and rapid image acquisition performed by a high-speed CMOS camera, reducing acquisition time to 5 ms per frame.

  2. Surface Charge Measurement of SonoVue, Definity and Optison: A Comparison of Laser Doppler Electrophoresis and Micro-Electrophoresis.

    PubMed

    Ja'afar, Fairuzeta; Leow, Chee Hau; Garbin, Valeria; Sennoga, Charles A; Tang, Meng-Xing; Seddon, John M

    2015-11-01

    Microbubble (MB) contrast-enhanced ultrasonography is a promising tool for targeted molecular imaging. It is important to determine the MB surface charge accurately as it affects the MB interactions with cell membranes. In this article, we report the surface charge measurement of SonoVue, Definity and Optison. We compare the performance of the widely used laser Doppler electrophoresis with an in-house micro-electrophoresis system. By optically tracking MB electrophoretic velocity in a microchannel, we determined the zeta potentials of MB samples. Using micro-electrophoresis, we obtained zeta potential values for SonoVue, Definity and Optison of -28.3, -4.2 and -9.5 mV, with relative standard deviations of 5%, 48% and 8%, respectively. In comparison, laser Doppler electrophoresis gave -8.7, +0.7 and +15.8 mV with relative standard deviations of 330%, 29,000% and 130%, respectively. We found that the reliability of laser Doppler electrophoresis is compromised by MB buoyancy. Micro-electrophoresis determined zeta potential values with a 10-fold improvement in relative standard deviation.

  3. Full-field direct digital telemammography: preliminary

    NASA Astrophysics Data System (ADS)

    Lou, Shyhliang A.; Sickles, Edward A.; Huang, H. K.; Cao, Fei; Hoogstrate, David R.; Jahangiri, Mohammad I.

    1997-05-01

    Full-field direct digital mammography has many advantages over the conventional film/screen imaging detector. Among these are larger dynamic range, lower scattering noise, and the possibility of using it for telemammography applications to alleviate the shortage of expert mammographers. We are in the process of developing a full-field direct digital telemammography imaging chain to investigate its usefulness for telediagnosis, teleconsultation, and telemanagement. This paper describes the first phase of a three-year research program to set up a full-field direct digital mammography (FFDDM) imaging chain at the Breast Imaging Section connecting the University of California, San Francisco Medical Center and the Mt. Zion Hospital in the San Francisco Bay area. The chain consists of two FFDDM system, and two 2,500 line two-monitor workstations. An OC-3 155 Mbits/sec asynchronous transfer mode (ATM) communication network is used to connect the FFDDM and the two workstations. The FFDDM is based on a slot scan CCD detector which can image a full breast with 3,100 X 3,870 pixels, and produce a direct digital image with 50 micron pixel size. Preliminary results of the FFDDM demonstrate that it has a greater dynamic range and lower detector noise than that of a film-screen detector, and that the scattered radiation is reduced without using a grid. However, the spatial resolution is less than that of the conventional screen/film system. The 2K workstation can display simultaneously any two or four full-view mammographic images by either scrolling or subsampling on the two monitors. Display of an image takes about 1.5 seconds from the RAID disks. The ATM can transmit a 32 Mbyte digital mammogram from the FFDDM to the workstation in 3-4 seconds.

  4. Catadioptric Optics for laser Doppler velocimeter applications

    NASA Technical Reports Server (NTRS)

    Dunagan, Stephen E.

    1989-01-01

    In the design of a laser velocimeter system, attention must be given to the performance of the optical elements in their two principal tasks: focusing laser radiation into the probe volume, and collecting the scattered light. For large aperture applications, custom lens design and fabrication costs, long optical path requirements, and chromatic aberration (for two color operation) can be problematic. The adaptation of low cost Schmidt-Cassegrain astronomical telescopes to perform these laser beam manipulation and scattered light collection tasks is examined. A generic telescope design is analyzed using ray tracing and Gaussian beam propagation theory, and a simple modification procedure for converting from infinite to near unity conjugate ratio operation with image quality near the diffraction limit was identified. Modification requirements and performance are predicted for a range of geometries. Finally, a 200-mm-aperture telescope was modified for f/10 operation; performance data for this modified optic for both laser beam focusing and scattered light collection tasks agree well with predictions.

  5. Compact laser Doppler flowmeter for application in dentistry

    NASA Astrophysics Data System (ADS)

    Fedosov, Ivan V.; Mareew, Gleb O.; Finokhina, Olga A.; Lepilin, Alexander V.; Tuchin, Valery V.

    2005-06-01

    Lightweight handheld laser Doppler instrument is designed for blood flow assessment in soft tissues of oral cavity. Laser light source, fiber optic probe detector and amplifier circuitry are mounted inside the compact hand held probe assembly to minimize noise and to exclude optical fiber motion artifacts. Both the instrument and data processing software are optimized for the using of the standard PC sound interface as the data acquisition device that provides low cost and effective solution for clinical use. The instrument is suitable for quantitative diagnostics of gingivitis and other disorders in dentistry.

  6. Structural damage assessment in composite material using laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Willemann, Daniel P.; Castellini, Paolo; Revel, Gian M.; Tomasini, Enrico P.

    2004-06-01

    In recent years, a great effort has been done to improve damage detection techniques in structures by using vibration measurements. This paper presents a case where a non-contact measurement system, a Scanning Laser Doppler Vibrometer, has been used to detect delaminations in a composite material plate. The diagnostic technique is the evolution of a methodology previously approached by the authors. An in-house made software has been produced for data acquisition and vibrometer control. The maps of the detected defects are presented, thus allowing the assessment of the performances of this methodology to detect damages. This analysis permitted to outline the main points to be improved in the future investigations.

  7. Quality assurance in laser-Doppler flowmetry applied to dentistry

    NASA Astrophysics Data System (ADS)

    Kaulich, Theodor W.; Koerber, Erich

    1996-12-01

    Laser-doppler flowmetry (LDF) is a diagnostic method for checking and judging vitality in tissues. In dentistry, with the help of LDF, there can be investigated short-term or long-term changes of the oral microcirculation. Defects in the LDF equipment which go undiscovered lead to changes in the quality of the biosignals and hamper diagnosis. Reliable and reproducible results are only obtained if the LDF equipment concerned there exists a standardized quality assurance program. There has been developed and tested a method for constancy checks in LDF measurements. The investigation shows that before each clinical application of an LDF equipment careful testing is necessary.

  8. Nonmechanical axial scanning laser Doppler velocimeter with directional discrimination.

    PubMed

    Maru, Koichi; Hata, Takahiro

    2012-07-10

    An axial scanning laser Doppler velocimeter (LDV) with directional discrimination not requiring any moving mechanism in its probe is proposed. The proposed LDV utilizes frequency shift induced by acousto-optic modulators (AOMs) for discriminating the direction of velocity. The measurement position is axially scanned by changing the wavelength of the light input to the probe. The experimental result reveals that both the axial scan and the directional discrimination can be realized by using the proposed method without any moving element in the probe.

  9. Dynamic characteristics of laser-Doppler flux data.

    PubMed

    Popivanov, D; Mineva, A; Dushanova, J

    1999-01-01

    Methods for tracking the dynamics of the blood flow microcirculation obtained by laser-Doppler flowmetry (LDF) technique are described. It was shown that LDF signals have complex dynamics. It was mainly characterized by fractal structures and chaos, though multiperiodic, trend-like and stochastic components were also established. Procedures for (i) describing the dynamic structure and (ii) tracking the dynamic changes in time of LDF data are proposed. Examples illustrating the efficiency of these procedures are given using both simulated and LDF data collected in experiments with reactive hyperemia. Irrespective of the universality of the methods, the procedures should be specified according to the problem-oriented clinical and experimental studies.

  10. Two-color dual-beam backscatter laser Doppler velocimeter

    NASA Technical Reports Server (NTRS)

    Grant, G. R.; Orloff, K. L.

    1973-01-01

    A laser Doppler velocimeter has been developed that uses two of the colors emitted from an argon-ion laser for the simultaneous measurement of orthogonal velocities. Designed for use in a 2.13- by 3.05-m wind tunnel, it is capable of traversing its focal volume across spatially unstable flows at scan speeds of up to 1.5 m/sec. Its optical layout and principles of operation are discussed, and the data from a typical traversal of a trailing wing-tip vortex are presented.

  11. A two color, dual beam backscattering laser Doppler velocimeter

    NASA Technical Reports Server (NTRS)

    Grant, G. R.; Orloff, K. L.

    1973-01-01

    A laser Doppler velocimeter has been developed which uses two of the colors emitted from an argon ion laser for the simultaneous measurement of orthogonal velocities. Designed for use in a 2.13 m by 3.05 m wind tunnel, it is capable of traversing its focal volume across spatially unstable flows at scan speeds of up to 1.15 m/sec. Its optical layout and principles of operation are discussed and the data from a typical traversal of a trailing wing tip vortex are presented.

  12. Laser Doppler Vibrometry measurement of the mechanical myogram

    NASA Astrophysics Data System (ADS)

    Rohrbaugh, John W.; Sirevaag, Erik J.; Richter, Edward J.

    2012-06-01

    Contracting muscles show complex dimensional changes that include lateral expansion. Because this expansion process is intrinsically vibrational, driven by repetitive actions of multiple motor units, it can be sensed and quantified using the method of Laser Doppler Vibrometry (LDV). LDV has a number of advantages over more traditional mechanical methods based on microphones and accelerometers. The LDV mechanical myogram from a small hand muscle was shown under conditions of elastic loading to be related systematically to the level of force production, and to compare favorably with conventional methods for sensing the mechanical and electrical aspects of muscle contraction.

  13. A relative performance analysis of atmospheric Laser Doppler Velocimeter methods.

    NASA Technical Reports Server (NTRS)

    Farmer, W. M.; Hornkohl, J. O.; Brayton, D. B.

    1971-01-01

    Evaluation of the effectiveness of atmospheric applications of a Laser Doppler Velocimeter (LDV) at a wavelength of about 0.5 micrometer in conjunction with dual scatter LDV illuminating techniques, or at a wavelength of 10.6 micrometer with local oscillator LDV illuminating techniques. Equations and examples are given to provide a quantitative basis for LDV system selection and performance criteria in atmospheric research. The comparative study shows that specific ranges and conditions exist where performance of one of the methods is superior to that of the other. It is also pointed out that great care must be exercised in choosing system parameters that optimize a particular LDV designed for atmospheric applications.

  14. Laser Doppler anemometer measurements using nonorthogonal velocity components: error estimates.

    PubMed

    Orloff, K L; Snyder, P K

    1982-01-15

    Laser Doppler anemometers (LDAs) that are arranged to measure nonorthogonal velocity components (from which orthogonal components are computed through transformation equations) are more susceptible to calibration and sampling errors than are systems with uncoupled channels. In this paper uncertainty methods and estimation theory are used to evaluate, respectively, the systematic and statistical errors that are present when such devices are applied to the measurement of mean velocities in turbulent flows. Statistical errors are estimated for two-channel LDA data that are either correlated or uncorrelated. For uncorrelated data the directional uncertainty of the measured velocity vector is considered for applications where mean streamline patterns are desired.

  15. Laser Doppler anemometer measurements using nonorthogonal velocity components - Error estimates

    NASA Technical Reports Server (NTRS)

    Orloff, K. L.; Snyder, P. K.

    1982-01-01

    Laser Doppler anemometers (LDAs) that are arranged to measure nonorthogonal velocity components (from which orthogonal components are computed through transformation equations) are more susceptible to calibration and sampling errors than are systems with uncoupled channels. In this paper uncertainty methods and estimation theory are used to evaluate, respectively, the systematic and statistical errors that are present when such devices are applied to the measurement of mean velocities in turbulent flows. Statistical errors are estimated for two-channel LDA data that are either correlated or uncorrelated. For uncorrelated data the directional uncertainty of the measured velocity vector is considered for applications where mean streamline patterns are desired.

  16. Fiber optic laser Doppler anemometry in swirling jets

    NASA Technical Reports Server (NTRS)

    Taghavi, R.; Rice, E. J.

    1991-01-01

    Time-averaged and fluctuating quantities are measured in a free turbulent swirling jet. Data from a two-component laser Doppler anemometry (LDA) are compared to the measurements via hot-wire and 5-hole pitot probes. To acquire the proper seeding density near the axis of a swirling jet for LDA measurements proved difficult. This is due to an imbalance of the centrifugal force and radial pressure gradient, which throws the seeding material off the axis. Despite this problem, close agreement between various measurement techniques is obtained.

  17. Spinning disk calibration method and apparatus for laser Doppler velocimeter

    NASA Technical Reports Server (NTRS)

    Snyder, P. K. (Inventor)

    1986-01-01

    A method and apparatus for calibrating laser Doppler velocimeters having one or more intersecting beam pairs are described. These velocimeters measure fluid velocity by observing the light scattered by particles in the fluid stream. Moving fluid particulates are simulated by fine taut wires that are radially mounted on a disk that is rotated at a known velocity. The laser beam intersection locus is first aimed at the very center of the disk and then the disk is translated so that the locus is swept by the rotating wires. The radial distance traversed is precisely measured so that the velocity of the wires (pseudo particles) may be calculated.

  18. Spark discharge particle generator for laser Doppler anemometry

    NASA Astrophysics Data System (ADS)

    Altgeld, H.; Schnettler, A.; Stehmeier, D.

    1980-04-01

    A spark-discharge aerosol generator for seeding of gases in laser Doppler measurements in turbulent flames has been developed in which solid particles are produced by the dispersal of particle powders. The operating principle, construction, and optimization of the generator are discussed together with the performance tests, conducted with different carrier gases and powders. Attention is given to the influence of gas type and electrode form on spark-discharge stability and of electrode distance and particle layer height on particle size, and also to the particle concentration and steadiness of aerosol generation. Tests have shown that the generator can meet all the requirements.

  19. Turbulent transport measurements with a laser Doppler velocimeter.

    NASA Technical Reports Server (NTRS)

    Edwards, R. V.; Angus, J. C.; Dunning, J. W., Jr.

    1972-01-01

    The power spectrum of phototube current from a laser Doppler velocimeter operating in the heterodyne mode has been computed. The spectral width and shape predicted by the theory are in agreement with experiment. For normal operating parameters the time-average spectrum contains information only for times shorter than the Lagrangian-integral time scale of the turbulence. To examine the long-time behavior, one must use either extremely small scattering angles, much-longer-wavelength radiation, or a different mode of signal analysis, e.g., FM detection.

  20. Turbulent transport measurements with a laser Doppler velocimeter

    NASA Technical Reports Server (NTRS)

    Edwards, R. V.; Angus, J. C.; Dunning, J. W., Jr.

    1972-01-01

    The power spectrum of phototube current from a laser Doppler velocimeter operating in the heterodyne mode has been computed. The spectrum is obtained in terms of the space time correlation function of the fluid. The spectral width and shape predicted by the theory are in agreement with experiment. For normal operating parameters the time average spectrum contains information only for times shorter than the Lagrangian integral time scale of the turbulence. To examine the long time behavior, one must use either extremely small scattering angles, much longer wavelength radiation or a different mode of signal analysis, e.g., FM detection.

  1. Radial pump impeller measurements using a laser Doppler velocimeter

    NASA Astrophysics Data System (ADS)

    Kannemans, H.

    1980-03-01

    A shrouded fully transparent radial pump impeller with thin backswept blades has been tested using a laser Doppler velocimeter. Two components of the velocity were measured relative to the laboratory reference frame in a plane perpendicular to the axis of rotation. The velocity distribution is presented relative to the blades at different radii and different flow rates over the whole blade passage. The results show that the flow is essentially unsteady and, at low flow rate, highly influenced by viscous effects. A comparison between the experimental data and a potential flow theory shows good agreement at high flow rates.

  2. Comparison of scatter rejection and low-contrast performance of scan equalization digital radiography (SEDR), slot-scan digital radiography, and full-field digital radiography systems for chest phantom imaging

    SciTech Connect

    Liu Xinming; Shaw, Chris C.; Lai, Chao-Jen; Wang Tianpeng

    2011-01-15

    Purpose: To investigate and compare the scatter rejection properties and low-contrast performance of the scan equalization digital radiography (SEDR) technique to the slot-scan and conventional full-field digital radiography techniques for chest imaging. Methods: A prototype SEDR system was designed and constructed with an a-Se flat-panel (FP) detector to improve image quality in heavily attenuating regions of an anthropomorphic chest phantom. Slot-scanning geometry was used to reject scattered radiation without attenuating primary x rays. The readout scheme of the FP was modified to erase accumulated scatter signals prior to image readout. A 24-segment beam width modulator was developed to regulate x-ray exposures regionally and compensate for the low x-ray flux in heavily attenuating regions. To measure the scatter-to-primary ratios (SPRs), a 2 mm thick lead plate with a 2-D array of aperture holes was used to measure the primary signals, which were then subtracted from those obtained without the lead plate to determine scatter components. A 2-D array of aluminum beads (3 mm in diameter) was used as the low-contrast objects to measure the contrast ratios (CRs) and contrast-to-noise ratios (CNRs) for evaluating the low-contrast performance in chest phantom images. A set of two images acquired with the same techniques were subtracted from each other to measure the noise levels. SPRs, CRs, and CNRs of the SEDR images were measured in four anatomical regions of chest phantom images and compared to those of slot-scan images and full-field images acquired with and without antiscatter grid. Results: The percentage reduction of SPR (percentage of SPRs reduced with scatter removal/rejection methods relative to that for nongrid full-field imaging) averaged over four anatomical regions was measured to be 80%, 83%, and 71% for SEDR, slot-scan, and full-field with grid, respectively. The average CR over four regions was found to improve over that for nongrid full-field

  3. Estimation of breast percent density in raw and processed full field digital mammography images via adaptive fuzzy c-means clustering and support vector machine segmentation.

    PubMed

    Keller, Brad M; Nathan, Diane L; Wang, Yan; Zheng, Yuanjie; Gee, James C; Conant, Emily F; Kontos, Despina

    2012-08-01

    The amount of fibroglandular tissue content in the breast as estimated mammographically, commonly referred to as breast percent density (PD%), is one of the most significant risk factors for developing breast cancer. Approaches to quantify breast density commonly focus on either semiautomated methods or visual assessment, both of which are highly subjective. Furthermore, most studies published to date investigating computer-aided assessment of breast PD% have been performed using digitized screen-film mammograms, while digital mammography is increasingly replacing screen-film mammography in breast cancer screening protocols. Digital mammography imaging generates two types of images for analysis, raw (i.e., "FOR PROCESSING") and vendor postprocessed (i.e., "FOR PRESENTATION"), of which postprocessed images are commonly used in clinical practice. Development of an algorithm which effectively estimates breast PD% in both raw and postprocessed digital mammography images would be beneficial in terms of direct clinical application and retrospective analysis. This work proposes a new algorithm for fully automated quantification of breast PD% based on adaptive multiclass fuzzy c-means (FCM) clustering and support vector machine (SVM) classification, optimized for the imaging characteristics of both raw and processed digital mammography images as well as for individual patient and image characteristics. Our algorithm first delineates the breast region within the mammogram via an automated thresholding scheme to identify background air followed by a straight line Hough transform to extract the pectoral muscle region. The algorithm then applies adaptive FCM clustering based on an optimal number of clusters derived from image properties of the specific mammogram to subdivide the breast into regions of similar gray-level intensity. Finally, a SVM classifier is trained to identify which clusters within the breast tissue are likely fibroglandular, which are then aggregated into a

  4. Estimation of breast percent density in raw and processed full field digital mammography images via adaptive fuzzy c-means clustering and support vector machine segmentation

    SciTech Connect

    Keller, Brad M.; Nathan, Diane L.; Wang Yan; Zheng Yuanjie; Gee, James C.; Conant, Emily F.; Kontos, Despina

    2012-08-15

    Purpose: The amount of fibroglandular tissue content in the breast as estimated mammographically, commonly referred to as breast percent density (PD%), is one of the most significant risk factors for developing breast cancer. Approaches to quantify breast density commonly focus on either semiautomated methods or visual assessment, both of which are highly subjective. Furthermore, most studies published to date investigating computer-aided assessment of breast PD% have been performed using digitized screen-film mammograms, while digital mammography is increasingly replacing screen-film mammography in breast cancer screening protocols. Digital mammography imaging generates two types of images for analysis, raw (i.e., 'FOR PROCESSING') and vendor postprocessed (i.e., 'FOR PRESENTATION'), of which postprocessed images are commonly used in clinical practice. Development of an algorithm which effectively estimates breast PD% in both raw and postprocessed digital mammography images would be beneficial in terms of direct clinical application and retrospective analysis. Methods: This work proposes a new algorithm for fully automated quantification of breast PD% based on adaptive multiclass fuzzy c-means (FCM) clustering and support vector machine (SVM) classification, optimized for the imaging characteristics of both raw and processed digital mammography images as well as for individual patient and image characteristics. Our algorithm first delineates the breast region within the mammogram via an automated thresholding scheme to identify background air followed by a straight line Hough transform to extract the pectoral muscle region. The algorithm then applies adaptive FCM clustering based on an optimal number of clusters derived from image properties of the specific mammogram to subdivide the breast into regions of similar gray-level intensity. Finally, a SVM classifier is trained to identify which clusters within the breast tissue are likely fibroglandular, which are then

  5. [Full-field digital mammography].

    PubMed

    Bick, U

    2000-12-01

    Due to the extremely high image quality requirements in mammography, there has for a long time been no adequate digital alternative to conventional film-screen mammography. The longest experience so far exists with digital mammography on the basis of storage phosphor (CR) systems. However, at normal dose this technique has a relatively poor signal-to-noise ratio and has not found general acceptance. Recently three novel systems for digital mammography by the companies Fischer (slot-scan detector), Trex (CCD-array), and GE (amorphous silicon detector) have been introduced and are currently under clinical investigation. The main advantage of digital mammography is the linear relationship between dose and detector signal with the possibility of a tailored optimization of image contrast. Other advantages include digital image storage, telemammography, and computer-assisted diagnosis.

  6. Development of in-situ full-field spectroscopic imaging analysis and application on Li-ion battery using transmission x-ray microscopy

    NASA Astrophysics Data System (ADS)

    Chen-Wiegart, Yu-chen K.; Wang, Jiajun; Wang, Jun

    2013-09-01

    This paper presents the advance in spectroscopic imaging technique and analysis method from the newly developed transmission x-ray microscopy (TXM) at the beamline X8C of National Synchrotron Light Source. Through leastsquares linear combination fitting we developed on the in situ spectroscopic images, a time-dependent and spatially resolved chemical composition mapping can be obtained and quantitatively analyzed undergone chemical/electrochemical reactions. A correlation of morphological evolution, chemical state distribution changes and reaction conditions can be revealed. We successfully applied this method to study the electrochemical evolution of CuO, an anode material of Li-ion battery, during the lithiation-delitiation cycling.

  7. Label-free characterization of living human induced pluripotent stem cells by subcellular topographic imaging technique using full-field quantitative phase microscopy coupled with interference reflection microscopy.

    PubMed

    Sugiyama, Norikazu; Asai, Yasuyuki; Yamauchi, Toyohiko; Kataoka, Takuji; Ikeda, Takahiro; Iwai, Hidenao; Sakurai, Takashi; Mizuguchi, Yoshinori

    2012-09-01

    There is a need for a noninvasive technique to monitor living pluripotent stem cell condition without any labeling. We present an optical imaging technique that is able to capture information about optical path difference through the cell and cell adhesion properties simultaneously using a combination of quantitative phase microscopy (QPM) and interference reflection microscopy (IRM) techniques. As a novel application of QPM and IRM, this multimodal imaging technique demonstrated its ability to distinguish the undifferentiated status of human induced pluripotent stem (hiPS) cells quantitatively based on the variation of optical path difference between the nucleus and cytoplasm as well as hiPS cell-specific cell adhesion properties.

  8. Label-free characterization of living human induced pluripotent stem cells by subcellular topographic imaging technique using full-field quantitative phase microscopy coupled with interference reflection microscopy

    PubMed Central

    Sugiyama, Norikazu; Asai, Yasuyuki; Yamauchi, Toyohiko; Kataoka, Takuji; Ikeda, Takahiro; Iwai, Hidenao; Sakurai, Takashi; Mizuguchi, Yoshinori

    2012-01-01

    There is a need for a noninvasive technique to monitor living pluripotent stem cell condition without any labeling. We present an optical imaging technique that is able to capture information about optical path difference through the cell and cell adhesion properties simultaneously using a combination of quantitative phase microscopy (QPM) and interference reflection microscopy (IRM) techniques. As a novel application of QPM and IRM, this multimodal imaging technique demonstrated its ability to distinguish the undifferentiated status of human induced pluripotent stem (hiPS) cells quantitatively based on the variation of optical path difference between the nucleus and cytoplasm as well as hiPS cell-specific cell adhesion properties. PMID:23024911

  9. Laser Doppler velocity measurements of swirling flows with upstream influence

    NASA Technical Reports Server (NTRS)

    Rloff, K. L.; Bossel, H. H.

    1973-01-01

    Swirling flow in a rotating tube is studied by flow visualization at a moderate Reynolds number, and its velocity field is measured by laser-Doppler anemometry. The tube has constant diameter, and approximately uniform initial rigid rotation of the flow is assured by passing the flow through a rotating plug of porous metal before it enters the test section. At moderate swirl values, an object mounted on the tube centerline causes a closed bubble to form upstream of the obstacle, with a clearly defined stagnation point on the axis, and recirculating flow inside the bubble. The bubble length grows upstream as the swirl is increased, until it breaks up into a Taylor column reaching all the way upstream and downstream at swirl values above a certain critical value. A vortex jump (in the sense of Benjamin) occurs downstream of the obstacle except when the Taylor column is present. Using a laser-Doppler anemometer, axial and swirl velocity profiles are obtained at several stations upstream and downstream of the bubble, and in and around the bubble.

  10. Mucosal blood flow measurements using laser Doppler perfusion monitoring

    PubMed Central

    Hoff, Dag Arne Lihaug; Gregersen, Hans; Hatlebakk, Jan Gunnar

    2009-01-01

    Perfusion of individual tissues is a basic physiological process that is necessary to sustain oxygenation and nutrition at a cellular level. Ischemia, or the insufficiency of perfusion, is a common mechanism for tissue death or degeneration, and at a lower threshold, a mechanism for the generation of sensory signalling including pain. It is of considerable interest to study perfusion of peripheral abdominal tissues in a variety of circumstances. Microvascular disease of the abdominal organs has been implicated in the pathogenesis of a variety of disorders, including peptic ulcer disease, inflammatory bowel disease and chest pain. The basic principle of laser Doppler perfusion monitoring (LDPM) is to analyze changes in the spectrum of light reflected from tissues as a response to a beam of monochromatic laser light emitted. It reflects the total local microcirculatory blood perfusion, including perfusion in capillaries, arterioles, venules and shunts. During the last 20-25 years, numerous studies have been performed in different parts of the gastrointestinal (GI) tract using LDPM. In recent years we have developed a multi-modal catheter device which includes a laser Doppler probe, with the intent primarily to investigate patients suffering from functional chest pain of presumed oesophageal origin. Preliminary studies show the feasibility of incorporating LDPM into such catheters for performing physiological studies in the GI tract. LDPM has emerged as a research and clinical tool in preference to other methods; but, it is important to be aware of its limitations and account for them when reporting results. PMID:19132770

  11. Evaluation of gingival vascularisation using laser Doppler flowmetry

    NASA Astrophysics Data System (ADS)

    Vitez, B.; Todea, C.; Velescu, A.; Şipoş, C.

    2016-03-01

    Aim: The present study aims to assess the level of vascularisation of the lower frontal gingiva of smoker patients, in comparison with non-smokers by using Laser Doppler Flowmetry (LDF), in order to determine the changes in gingival microcirculation. Material & methods: 16 volunteers were included in this study and separated into 2 equal groups: non-smoker subjects in Group I and smoker subjects in Group II. All patients were submitted to a visual examination and professional cleaning The gingival bloodflow of each patient was recorded in 5 zones using LDF, resulting in a total of 80 recordings. LDF was done with the Moor Instruments Ltd. "moorLAB" Laser Doppler. All data were collected as graphs, raw values and statistically analyzed. Results: After strict analysis results show that Group II presents a steady level of gingival microcirculation with even patterns in the graph, while Group I shows many signs of damage to it`s microvascular system through many irregularities in the microcirculation level and graph patterns. Conclusion: The results suggest that prolonged smoking has a definitive effect on the gingival vascularisation making it a key factor in periodontal pathology.

  12. Reader variability in breast density estimation from full-field digital mammograms: the effect of image postprocessing on relative and absolute measures.

    PubMed

    Keller, Brad M; Nathan, Diane L; Gavenonis, Sara C; Chen, Jinbo; Conant, Emily F; Kontos, Despina

    2013-05-01

    Mammographic breast density, a strong risk factor for breast cancer, may be measured as either a relative percentage of dense (ie, radiopaque) breast tissue or as an absolute area from either raw (ie, "for processing") or vendor postprocessed (ie, "for presentation") digital mammograms. Given the increasing interest in the incorporation of mammographic density in breast cancer risk assessment, the purpose of this study is to determine the inherent reader variability in breast density assessment from raw and vendor-processed digital mammograms, because inconsistent estimates could to lead to misclassification of an individual woman's risk for breast cancer. Bilateral, mediolateral-oblique view, raw, and processed digital mammograms of 81 women were retrospectively collected for this study (N = 324 images). Mammographic percent density and absolute dense tissue area estimates for each image were obtained from two radiologists using a validated, interactive software tool. The variability of interreader agreement was not found to be affected by the image presentation style (ie, raw or processed, F-test: P > .5). Interreader estimates of relative and absolute breast density are strongly correlated (Pearson r > 0.84, P < .001) but systematically different (t-test, P < .001) between the two readers. Our results show that mammographic density may be assessed with equal reliability from either raw or vendor postprocessed images. Furthermore, our results suggest that the primary source of density variability comes from the subjectivity of the individual reader in assessing the absolute amount of dense tissue present in the breast, indicating the need to use standardized tools to mitigate this effect. Copyright © 2013 AUR. Published by Elsevier Inc. All rights reserved.

  13. Full-field optical micro-angiography

    NASA Astrophysics Data System (ADS)

    Wang, Mingyi; Zeng, Yaguang; Liang, Xianjun; Lu, Xuanlong; Feng, Guanping; Han, Dingan; Yang, Guojian

    2014-02-01

    We present a detailed description of full-field optical micro-angiography on the basis of frequency-domain laser speckle imaging with intensity fluctuation modulation (LSI-IFM). The imaging approach works based on the instantaneous local intensity fluctuation realized via the combination of short exposure and low sampling rate of a camera and appropriate magnification of a microscope. In vivo experiments on mouse ear verify the theoretical description we made for the imaging mechanism and demonstrate the ability of LSI-IFM as optical micro-angiography. By introducing a fundus camera into LSI-IFM system, our approach has a potential application in label-free retina optical micro-angiography.

  14. Flow tracing fidelity of scattering aerosol in laser Doppler velocimetry

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Kirsch, K. J.

    1974-01-01

    An experimental method for determinating the flow tracing fidelity of a scattering aerosol used in laser Doppler velocimeters was developed with particular reference to the subsonic turbulence measurements. The method employs the measurement of the dynamic response of a flow seeding aerosol excited by acoustic waves. The amplitude and frequency of excitation were controlled to simulate the corresponding values of fluid turbulence components. Experimental results are presented on the dynamic response of aerosols over the size range from 0.1 to 2.0 microns in diameter and over the frequency range 100 Hz to 100 kHz. It was observed that unit density spherical scatterers with diameters of 0.2 microns followed subsonic air turbulence frequency components up to 100 kHz with 98 percent fidelity.

  15. Laser Doppler vibrometry measurement of the mechanical myogram

    NASA Astrophysics Data System (ADS)

    Rohrbaugh, John W.; Sirevaag, Erik J.; Richter, Edward J.

    2013-12-01

    Contracting muscles show complex dimensional changes that include lateral expansion. Because this expansion process is intrinsically vibrational, driven by repetitive actions of multiple motor units, it can be sensed and quantified using the method of Laser Doppler Vibrometry (LDV). LDV has a number of advantages over more traditional mechanical methods based on microphones and accelerometers. The LDV mechanical myogram from a small hand muscle (the first dorsal interosseous) was studied under conditions of elastic loading applied to the tip of the abducted index finger. The LDV signal was shown to be related systematically to the level of force production, and to compare favorably with conventional methods for sensing the mechanical and electrical aspects of muscle contraction.

  16. Holographic optical system for aberration corrections in laser Doppler velocimetry

    NASA Technical Reports Server (NTRS)

    Kim, R. C.; Case, S. K.; Schock, H. J.

    1985-01-01

    An optical system containing multifaceted holographic optical elements (HOEs) has been developed to correct for aberrations introduced by nonflat windows in laser Doppler velocimetry. The multifacet aberration correction approach makes it possible to record on one plate many sets of adjacent HOEs that address different measurement volume locations. By using 5-mm-diameter facets, it is practical to place 10-20 sets of holograms on one 10 x 12.5-cm plate, so that the procedure of moving the entire optical system to examine different locations may not be necessary. The holograms are recorded in dichromated gelatin and therefore are nonabsorptive and suitable for use with high-power argon laser beams. Low f-number optics coupled with a 90-percent efficient distortion-correcting hologram in the collection side of the system yield high optical efficiency.

  17. Application of laser Doppler velocimeter to chemical vapor laser system

    NASA Technical Reports Server (NTRS)

    Gartrell, Luther R.; Hunter, William W., Jr.; Lee, Ja H.; Fletcher, Mark T.; Tabibi, Bagher M.

    1993-01-01

    A laser Doppler velocimeter (LDV) system was used to measure iodide vapor flow fields inside two different-sized tubes. Typical velocity profiles across the laser tubes were obtained with an estimated +/-1 percent bias and +/-0.3 to 0.5 percent random uncertainty in the mean values and +/-2.5 percent random uncertainty in the turbulence-intensity values. Centerline velocities and turbulence intensities for various longitudinal locations ranged from 13 to 17.5 m/sec and 6 to 20 percent, respectively. In view of these findings, the effects of turbulence should be considered for flow field modeling. The LDV system provided calibration data for pressure and mass flow systems used routinely to monitor the research laser gas flow velocity.

  18. Measurements of enlarged blood pump models using Laser Doppler Anemometer.

    PubMed

    Chua, L P; Yu, S C; Leo, H L

    2000-01-01

    In an earlier study (Chua et al., 1998, 1999a), a 5:1 enlarged model of the Kyoto-NTN Magnetically Suspended Centrifugal Blood Pump (Akamatsu et al., 1995) with five different impeller blade profiles was designed and constructed. Their respective flow characteristics with respect to (1) the three different blade profile designs: forward, radial, and backward, (2) the number of blades used, and (3) the rotating speed were investigated. Among the five impeller designs, the results obtained suggested that impellers A and C designs should be adopted if higher head is required. Impellers A and C therefore were selected for the flow in between their blades to be measured using Laser Doppler Anemometer (LDA), so as to have a better understanding of the flow physics with respect to the design parameters.

  19. Fiber-optic laser Doppler turbine tip clearance probe.

    PubMed

    Büttner, Lars; Pfister, Thorsten; Czarske, Jürgen

    2006-05-01

    A laser Doppler based method for in situ single blade tip clearance measurements of turbomachines with high precision is presented for what we believe is the first time. The sensor is based on two superposed fanlike interference fringe systems generated by two laser wavelengths from a fiber-coupled, passive, and therefore compact measurement head employing diffractive optics. Tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm (833 Hz, 586 m/s tip speed) are reported. At these speeds the measured uncertainty of the tip position was less than 20 microm, a factor of 2 more accurate than that of capacitive probes. The sensor offers great potential for in situ and online high-precision tip clearance measurements of metallic and nonmetallic turbine blades.

  20. Laser Doppler velocimetry using a modified computer mouse

    NASA Astrophysics Data System (ADS)

    Zaron, Edward D.

    2016-10-01

    A computer mouse has been modified for use as a low-cost laser Doppler interferometer and used to measure the two-component fluid velocity of a flowing soap film. The mouse sensor contains two vertical cavity surface emitting lasers, photodiodes, and signal processing hardware integrated into a single package, approximately 1 cm2 in size, and interfaces to a host computer via a standard USB port. Using the principle of self-mixing interferometry, whereby laser light re-enters the laser cavity after being scattered from a moving target, the Doppler shift and velocity of scatterers dispersed in the flow are measured. Observations of the boundary layer in a turbulent soap film channel flow demonstrate the capabilities of the sensor.

  1. Flow tracing fidelity of scattering aerosol in laser Doppler velocimetry

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Kirsch, K. J.

    1975-01-01

    An experimental method for the determination of the flow-tracing fidelity of a scattering aerosol used in laser Doppler velocimeters was developed with particular reference to the subsonic turbulence measurements. The method employs the measurement of the dynamic response of a flow-seeding aerosol excited by acoustic waves. The amplitude and frequency of excitation were controlled in order to simulate the corresponding values of fluid turbulence components. Experimental results are presented on the dynamic response of aerosols over the size range from 0.1 to 2.0 microns in diam and over the frequency range 100 Hz to 100 kHz. It was observed that unit-density spherical scatterers with diameters of 0.2 micron followed subsonic air turbulence frequency components up to 100 kHz with 98% fidelity.

  2. Laser Doppler velocimeter measurements in a turbine stator cascade facility

    NASA Technical Reports Server (NTRS)

    Seasholtz, R. G.

    1974-01-01

    A laser Doppler velocimeter (LDV) developed for mapping the flow velocity downstream from a 32-inch diameter annular cascade of turbine stator vanes in described. The LDV measurements were taken in a plane located approximately 0.5 inch downstream of the trailing edges of the vanes. Two components of the mean velocity (axial and circumferential) were measured. The flow velocities were in the high subsonic range. The LDV optics are of the dual scatter type with off-axis collection of the scattered light. The electronics system is based on the measurement of the time interval corresponding to eight periods of the Doppler signal and has a range of 10 to 80 MHz. The LDV measurements are compared with previous measurements made with a pressure probe.

  3. Laser Doppler velocimeter measurements in a turbine stator cascade facility

    NASA Technical Reports Server (NTRS)

    Seasholtz, R. G.

    1974-01-01

    A laser Doppler velocimeter (LDV) developed for mapping the flow velocity downstream from a 32-inch diameter annular cascade of turbine stator vanes is described. The LDV measurements were taken in a plane located approximately 0.5 inch downstream of the trailing edges of the vanes. Two components of the mean velocity (axial and circumferential) were measured. The flow velocities were in the high subsonic range. The LDV optics are of the dual scatter type with off-axis collection of the scattered light. The electronics system is based on the measurement of the time interval corresponding to eight periods of the Doppler signal and has a range of 10 to 80 MHz. The LDV measurements are compared with previous measurements made with a pressure probe.

  4. Laser Doppler flowmetry to measure changes in cerebral blood flow.

    PubMed

    Sutherland, Brad A; Rabie, Tamer; Buchan, Alastair M

    2014-01-01

    Laser Doppler flowmetry (LDF) is a method by which relative cerebral blood flow (CBF) of the cortex can be measured. Although the method is easy to employ, LDF only measures relative CBF, while absolute CBF cannot be quantified. LDF is useful for investigating CBF changes in a number of different applications including neurovascular and stroke research. This chapter will prepare the reader for rodent experiments using LDF with two preparations. The closed skull preparation can be used to monitor CBF with an intact skull, but in adult rats, thinning of the skull is required to obtain an accurate cortical CBF signal. The open skull preparation requires a craniotomy to expose the surface of the brain and the LDF probe is held close to the surface to measure cerebral perfusion.

  5. Cantilever spring constant calibration using laser Doppler vibrometry

    SciTech Connect

    Ohler, Benjamin

    2007-06-15

    Uncertainty in cantilever spring constants is a critical issue in atomic force microscopy (AFM) force measurements. Though numerous methods exist for calibrating cantilever spring constants, the accuracy of these methods can be limited by both the physical models themselves as well as uncertainties in their experimental implementation. Here we report the results from two of the most common calibration methods, the thermal tune method and the Sader method. These were implemented on a standard AFM system as well as using laser Doppler vibrometry (LDV). Using LDV eliminates some uncertainties associated with optical lever detection on an AFM. It also offers considerably higher signal to noise deflection measurements. We find that AFM and LDV result in similar uncertainty in the calibrated spring constants, about 5%, using either the thermal tune or Sader methods provided that certain limitations of the methods and instrumentation are observed.

  6. Measuring with laser Doppler vibrometer on moving frame (LDVMF)

    NASA Astrophysics Data System (ADS)

    Rahimi, Siamand; Li, Zili; Dollevoet, Rolf

    2014-05-01

    Structural dynamic gives insight into structural properties such as mass, eigenfrequencies, eigenmodes, modal damping and strain distribution and can be utilized in structural health monitoring, dynamic sub-structuring, etc. In this context structural vibration is measured and used. The measurement is done by means of conventional sensors such as accelerometers or non destructively using Laser Doppler Vibrometer (LDV), for instance. The non-destructive, non-contact measurement techniques preserve the integrity of the structure and don't add mass and stiffness to the structure under test. When one deals with civil structures such as rail and road ways, pipelines and catenary the importance of these techniques becomes more evident as they allow standoff measurement on a moving frame. Nevertheless when LDV is employed due to the relative in-plane motion between the LDV and the target speckle noise is generated which degrades the signal quality and makes this application not very straightforward but challenging. One of the first Laser Doppler Vibrometer on moving frame is adopted to measure and monitor the ground vibration, aiming at detection of buried land mines. The major addressed difficulty in this application is the speckle noise present in the acquired signal. In general the signal quality and the Signal to Noise Ratio (SNR) are a function of the laser spot size and wave length, measurement distance, relative velocity and sampling frequency. A trade-off between these factors, which are not always intuitive would help to minimize the noise floor due to the speckle noise. In this paper a test rig is presented which allows to study the speckle noise at different measurement ranges, between 1.8 and 2.8 m, and different velocities, up to 150 km/h. The results might serve as a guideline to the design process of a LDVMF.

  7. Novel laser Doppler flowmeter for pulpal blood flow measurements

    NASA Astrophysics Data System (ADS)

    Zang, De Yu; Millerd, James E.; Wilder-Smith, Petra B. B.; Arrastia-Jitosho, Anna-Marie A.

    1996-04-01

    We have proposed and experimentally demonstrated a new configuration of laser Doppler flowmetry for dental pulpal blood flow measurements. To date, the vitality of a tooth can be determined only by subjective thermal or electric tests, which are of questionable reliability and may induced pain in patient. Non-invasive techniques for determining pulpal vascular reactions to injury, treatment, and medication are in great demand. The laser Doppler flowmetry technique is non-invasive; however, clinical studies have shown that when used to measure pulpal blood flow the conventional back-scattering Doppler method suffers from low signal-to-noise ratio (SNR) and unreliable flux readings rendering it impossible to calibrate. A simplified theoretical model indicates that by using a forward scattered geometry the detected signal has a much higher SNR and can be calibrated. The forward scattered signal is readily detectable due to the fact that teeth are relatively thin organs with moderate optical loss. A preliminary experiment comparing forward scattered detection with conventional back- scattered detection was carried out using an extracted human molar. The results validated the findings of the simple theoretical model and clearly showed the utility of the forward scattering geometry. The back-scattering method had readings that fluctuated by as much as 187% in response to small changes in sensor position relative to the tooth. The forward scattered method had consistent readings (within 10%) that were independent of the sensor position, a signal-to-noise ratio that was at least 5.6 times higher than the back-scattering method, and a linear response to flow rate.

  8. Full-field wafer warpage measurement technique

    NASA Astrophysics Data System (ADS)

    Hsieh, H. L.; Lee, J. Y.; Huang, Y. G.; Liang, A. J.; Sun, B. Y.

    2017-06-01

    An innovative moiré technique for full-field wafer warpage measurement is proposed in this study. The wafer warpage measurement technique is developed based on moiré method, Talbot effect, scanning profiling method, stroboscopic, instantaneous phase-shift method, as well as four-step phase shift method, high resolution, high stability and full-field measurement capabilities can be easily achieved. According to the proposed full-field optical configuration, a laser beam is expanded into a collimated beam with a 2-inch diameter and projected onto the wafer surface. The beam is reflected by the wafer surface and forms a moiré fringe image after passing two circular gratings, which is then focused and captured on a CCD camera for computation. The corresponding moiré fringes reflected from the wafer surface are obtained by overlapping the images of the measuring grating and the reference grating. The moiré fringes will shift when wafer warpage occurs. The phase of the moiré fringes will change proportionally to the degree of warpage in the wafer, which can be measured by detecting variations in the phase shift of the moiré fringes in each detection points on the surface of the entire wafer. The phase shift variations of each detection points can be calculated via the instantaneous phase-shift method and the four-step phase-shift method. By adding up the phase shift variations of each detection points along the radii of the circular gratings, the warpage value and surface topography of the wafer can be obtained. Experiments show that the proposed method is capable of obtaining test results similar to that of a commercial sensor, as well as performing accurate measurements under high speed rotation of 1500rpm. As compared to current warpage measurement methods such as the beam optical method, confocal microscopy, laser interferometry, shadow moiré method, and structured light method, this proposed technique has the advantage of full-field measurement, high

  9. Remote measurement utilizing NASA's scanning laser Doppler systems. Volume 1. Laser Doppler wake vortex tracking at Kennedy Airport

    NASA Technical Reports Server (NTRS)

    Krause, M. C.; Wilson, D. J.; Howle, R. E.; Edwards, B. B.; Craven, C. E.; Jetton, J. L.

    1976-01-01

    Test operations of the Scanning Laser Doppler System (SLDS) at Kennedy International Airport (KIA) during August 1974 through June 1975 are reported. A total of 1,619 data runs was recorded with a totally operational system during normal landing operations at KIA. In addition, 53 data runs were made during cooperative flybys with the C880 for a grand total of 1672 recorded vortex tracks. Test crews were in attendance at KIA for 31 weeks, of which 25 weeks were considered operational and the other six were packing, unpacking, setup and check out. Although average activity equates to 67 recorded landing operations per week, two periods of complete runway inactivity spanned 20 days and 13 days, respectively. The operation frequency therefore averaged about 88 operations per week.

  10. Data processing and display of laser Doppler experimental results, volume 1

    NASA Technical Reports Server (NTRS)

    Ashmore, B. R.; Kimura, A.; Skeith, R. W.

    1976-01-01

    Contract activities performed in developing a laser Doppler system for detecting, tracking, and measuring aircraft wake vortices are summarized. The computer program for processing and displaying the Dust Devil experimental data is presented. Program listings are included in the appendix.

  11. A comparison of a coaxial focused laser Doppler system in atmospheric measurements

    NASA Technical Reports Server (NTRS)

    Karaki, S.

    1973-01-01

    Measurements of atmospheric velocities and turbulence with the laser Doppler system were obtained, and the results compared with cup anemometer and hot-wire measurements in the same wind field. The laser Doppler velocimeter (LDV) is described along with the test procedures. It was found that mean values determined from the LDV data are within 5% of other anemometer data for long time periods, and the LDV measures higher velocities.

  12. Three dimensional laser Doppler velocimeter turbulence measurements in a pipe flow

    NASA Technical Reports Server (NTRS)

    Fuller, C. E., III; Cliff, W. C.; Huffaker, R. M.

    1973-01-01

    The mean and turbulent u, v, and w components of a gaseous fully developed turbulent pipe flow were measured with a laser Doppler velocimeter system. Measurements of important system parameters are presented and discussed in relation to the measurement accuracy. Simultaneous comparisons of the laser Doppler and hot wire anemometer measurements in the turbulent flow provided evidence that the two systems were responding to the same flow phenomena.

  13. Laser Doppler flowmetry of focal ischaemia and reperfusion in deep brain structures in rats.

    PubMed

    Reith, W; Forsting, M; Weber, J; Stingele, R; Hacke, W; Sartor, K

    1994-01-01

    Monitoring cerebral blood flow during focal ischaemia and reperfusion with established techniques such as hydrogen clearance and autoradiography is difficult. Laser Doppler flowmetry is a new technique, it allows one to continuously measure blood flow in small tissue samples. The objective of this study was to compare laser Doppler flowmetry with hydrogen clearance using a new single fiber probe to obtain measurements in deep brain structures and then to show the temporal profile of cerebral blood flow during focal ischaemia and after reperfusion. First, the single fiber laser Doppler method was compared with the hydrogen clearance method in ten Wistar rats. Second, focal cerebral ischaemia was induced in fifteen Wistar rats using a model of middle cerebral artery occlusion based on the intravascular insertion of a nylon suture; reperfusion occurred after withdrawal of the suture. The laser Doppler probe was placed in the lateral caudatoputamen, and local cerebral blood flow was measured continuously before and during occlusion as well as after reperfusion. The relative blood flow values obtained by the laser Doppler method and the hydrogen clearance method showed a good correlation (r = 0.76) and a linear relationship. A rapid decrease in laser Doppler flowmetry to 42 +/- 16% of former baseline values was seen with occlusion of the middle cerebral artery; during occlusion cerebral blood flow remained at this level. Reperfusion resulted in a heterogeneous pattern of cerebral blood flow as laser Doppler flowmetry values ranged from 25% to 134% of baseline values. The effects of middle cerebral artery occlusion and reperfusion on cerebral blood flow can be monitored on-line with laser Doppler flowmetry.(ABSTRACT TRUNCATED AT 250 WORDS)

  14. Laser Doppler phase shifting using a high-speed digital micromirror device

    NASA Astrophysics Data System (ADS)

    Kuo, D.; Sharpe, J. P.

    2015-03-01

    Here we demonstrate the use of a binary spatial light modulator (Texas Instruments Digital Micromirror Device) to impart a phase shift to the beams of a laser Doppler velocimeter. Advantages of this approach to laser Doppler phase shifting include low cost, low power consumption, a precisely known phase-stepping frequency and the capability of working with a broad range of optical wavelengths. In the implementation shown here velocities of order 1 cm/s are measured.

  15. Measurement by laser Doppler interferometry of intraocular distances in humans and chicks with a precision of better than [plusmn]20 mu m

    NASA Astrophysics Data System (ADS)

    Schmid, G. F.; Petrig, B. L.; Riva, C. E.; Shin, K. H.; Stone, R. A.; Mendel, M. J.; Laties, A. M.

    1996-07-01

    A laser Doppler interferometer was built for the precise measurement of intraocular optical distances in humans and chicks. A technique using Purkinje images was developed to position the chick's eye reproducibly. A computer algorithm for the objective analysis of the interference signal and determination of the optical distances is presented. The precision of this noncontact interferometric method for measuring the cornea-retina distance is better than +/-20 mu m.

  16. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Laser Doppler visualisation of the velocity field by excluding the influence of multiparticle scattering

    NASA Astrophysics Data System (ADS)

    Dubnishchev, Yu N.; Chugui, Yu V.; Kompenhans, J.

    2009-10-01

    The method of laser Doppler visualisation and measurement of the velocity field in gas and liquid flows by suppressing the influence of multiparticle scattering is discussed. The cross section of the flow under study is illuminated by a laser beam transformed by an anamorphic optical system into a laser sheet. The effect of multiparticle scattering is eliminated by obtaining differential combinations of frequency-demodulated images of the laser sheet in different regions of the angular spectrum of scattered light.

  17. Laser Doppler Vibrometry measurements of human cadaveric tympanic membrane vibration

    PubMed Central

    2013-01-01

    Objective To determine the feasibility of measuring tympanic membrane (TM) vibrations at multiple locations on the TM to differentiate normal eardrums from those with associated ossicular pathologies. Design Cadaveric human temporal bone study. Setting Basic science laboratory. Methods A mastoidectomy and facial recess approach was performed on four cadaveric temporal bones to obtain access to the ossicles without disrupting the TM. Ossicles were palpated to ensure normal mobility and an intact ossicular chain. Laser Doppler Vibrometry (LDV) measurements were then taken on all four TMs. LDV measurements were repeated on each TM following stapes footplate fixation, incudo-stapedial joint dislocation, and malleus head fixation. Main outcome measures LDV measurements of TM vibration at the umbo, the lateral process of the malleus, and in each of the four quadrants of the TM. Results The best signal-to-noise ratios were found between 2 and 4 kHz, at the umbo, the anterior superior quadrant, the anterior inferior quadrant, and the posterior inferior quadrant. Since our goal was to assess the ossicular chain, we selected the TM locations closest to the ossicular chain (the umbo and lateral process of the malleus) for further analysis. Differences could be seen between normals and the simulated ossicular pathologies, but values were not statistically significant. Conclusions LDV measurements are technically challenging and require optimization to obtain consistent measurements. This study demonstrates the potential of LDV to differentiate ossicular pathologies behind an intact tympanic membrane. Future studies will further characterize the clinical role of this diagnostic modality. PMID:23663748

  18. Arterial compliance measurement using a noninvasive laser Doppler measurement system

    NASA Astrophysics Data System (ADS)

    Hast, Jukka T.; Myllylae, Risto A.; Sorvoja, Hannu; Nissilae, Seppo M.

    2000-11-01

    The aim of this study was to study the elasticity of the arterial wall using a non-invasive laser Doppler measurement system. The elasticity of the arterial wall is described by its compliance factor, which can be determined when both blood pressure and the radial velocity of the arterial wall are known. To measure radical velocity we used a self- mixing interferometer. The compliance factors were measured from six healthy volunteers, whose ages were varied from 21 to 32. Although a single volunteer's compliance factor is presented as an example, this paper treated the volunteers as a group. First, the elastic modulus, which is inversely proportional to the compliance factor, was determined. Then, an exponential curve was fitted into the measured data and a characteristic equation for the elastic modulus of the arterial wall was determined. The elastic modulus was calculated at different pressures and the results were compared to the static incremental modulus of a dog's femoral artery. The results indicate that there is a correlation between human elastic and canine static incremental modulus for blood pressures varying from 60 to 110 mmHg.

  19. Model-based quantitative laser Doppler flowmetry in skin

    NASA Astrophysics Data System (ADS)

    Fredriksson, Ingemar; Larsson, Marcus; Strömberg, Tomas

    2010-09-01

    Laser Doppler flowmetry (LDF) can be used for assessing the microcirculatory perfusion. However, conventional LDF (cLDF) gives only a relative perfusion estimate for an unknown measurement volume, with no information about the blood flow speed distribution. To overcome these limitations, a model-based analysis method for quantitative LDF (qLDF) is proposed. The method uses inverse Monte Carlo technique with an adaptive three-layer skin model. By analyzing the optimal model where measured and simulated LDF spectra detected at two different source-detector separations match, the absolute microcirculatory perfusion for a specified speed region in a predefined volume is determined. qLDF displayed errors <12% when evaluated using simulations of physiologically relevant variations in the layer structure, in the optical properties of static tissue, and in blood absorption. Inhomogeneous models containing small blood vessels, hair, and sweat glands displayed errors <5%. Evaluation models containing single larger blood vessels displayed significant errors but could be dismissed by residual analysis. In vivo measurements using local heat provocation displayed a higher perfusion increase with qLDF than cLDF, due to nonlinear effects in the latter. The qLDF showed that the perfusion increase occurred due to an increased amount of red blood cells with a speed >1 mm/s.

  20. Self-mixing birefringent dual-frequency laser Doppler velocimeter.

    PubMed

    Chen, Junbao; Zhu, Hongbin; Xia, Wei; Guo, Dongmei; Hao, Hui; Wang, Ming

    2017-01-23

    A self-mixing birefringent dual-frequency laser Doppler velocimeter (SBD-LDV) for high-resolution velocity measurements is presented in this paper. The velocity information of the object can be accurately extracted from the self-mixing Doppler frequency shift of the birefringent light-carried microwave signal. We generate a virtual stable light-carried microwave by using a birefringent dual-frequency He-Ne laser which further simplifies the structure of the light source. Moreover, the optical configuration based on the laser self-mixing interference brings benefits of compact optical setup, self-alignment, and direction discriminability. Experimentally, we extracted the Doppler beat frequency signal by the low-frequency (millihertz) phase lock-in amplifier, measured the beat frequency precisely in time-domain with a low sampling rate and calculated the magnitude of velocity. Compared with the previous self-mixing LDV, the average velocity resolution of SBD-LDV is improved to 0.030 mm/s for a target with longitudinal velocity, benefiting from the high stability of light-carried microwave. It is of great meaning and necessity because it helps to provide an available velocimeter with high stability and an extremely compact configuration, making a potential contribution to the velocimetry in practical engineering application.

  1. Laser Doppler pulp vitality measurements: simulation and measurement

    NASA Astrophysics Data System (ADS)

    Ertl, T.

    2017-02-01

    Frequently pulp vitality measurement is done in a dental practice by pressing a frozen cotton pellet on the tooth. This method is subjective, as the patient's response is required, sometimes painful and has moderate sensitivity and specificity. Other methods, based on optical or electrical measurement have been published, but didńt find wide spread application in the dental offices. Laser Doppler measurement of the blood flow in the pulp could be an objective method to measure pulp vitality, but the influence of the gingival blood flow on the measurements is a concern. Therefore experiments and simulations were done to learn more about the gingival blood flow in relation to the pulpal blood flow and how to minimize the influence. First patient measurements were done to show the feasibility clinically. Results: Monte Carlo simulations and bench experiments simulating the blood flow in and around a tooth show that both basic configurations, transmission and reflection measurements are possible. Most favorable is a multi-point measurement with different distances from the gingiva. Preliminary sensitivity / specificity are promising and might allow an objective and painless measurement of tooth vitality.

  2. Novel measure for the calibration of laser Doppler flowmetry devices

    NASA Astrophysics Data System (ADS)

    Dunaev, Andrey V.; Zherebtsov, Evgeny A.; Rogatkin, Dmitrii A.; Stewart, Neil A.; Sokolovski, Sergei G.; Rafailov, Edik U.

    2014-03-01

    The metrological basis for optical non-invasive diagnostic devices is an unresolved issue. A major challenge for laser Doppler flowmetry (LDF) is the need to compare the outputs from individual devices and various manufacturers to identify variations useful in clinical diagnostics. The most common methods for instrument calibration are simulants or phantoms composed of colloids of light-scattering particles which simulate the motion of red blood cells based on Brownian motion. However, such systems have limited accuracy or stability and cannot calibrate for the known rhythmic components of perfusion (0.0095-1.6 Hz). To solve this problem, we propose the design of a novel technique based on the simulation of moving particles using an electromechanical transducer, in which a precision piezoelectric actuator is used (e.g., P-602.8SL with maximum movement less than 1 mm). In this system, Doppler shift is generated in the layered structure of different solid materials with different optical light diffusing properties. This comprises a fixed, light transparent upper plane-parallel plate and an oscillating fluoroplastic (PTFE) disk. Preliminary studies on this experimental setup using the LDF-channel of a "LAKK-M" system demonstrated the detection of the linear portion (0-10 Hz with a maximum signal corresponding to Doppler shift of about 20 kHz) of the LDF-signal from the oscillating frequency of the moving layer. The results suggest the possibility of applying this technique for the calibration of LDF devices.

  3. Multi-site laser Doppler flowmetry for assessing collateral flow in experimental ischemic stroke: Validation of outcome prediction with acute MRI.

    PubMed

    Cuccione, Elisa; Versace, Alessandro; Cho, Tae-Hee; Carone, Davide; Berner, Lise-Prune; Ong, Elodie; Rousseau, David; Cai, Ruiyao; Monza, Laura; Ferrarese, Carlo; Sganzerla, Erik P; Berthezène, Yves; Nighoghossian, Norbert; Wiart, Marlène; Beretta, Simone; Chauveau, Fabien

    2017-06-01

    High variability in infarct size is common in experimental stroke models and affects statistical power and validity of neuroprotection trials. The aim of this study was to explore cerebral collateral flow as a stratification factor for the prediction of ischemic outcome. Transient intraluminal occlusion of the middle cerebral artery was induced for 90 min in 18 Wistar rats. Cerebral collateral flow was assessed intra-procedurally using multi-site laser Doppler flowmetry monitoring in both the lateral middle cerebral artery territory and the borderzone territory between middle cerebral artery and anterior cerebral artery. Multi-modal magnetic resonance imaging was used to assess acute ischemic lesion (diffusion-weighted imaging, DWI), acute perfusion deficit (time-to-peak, TTP), and final ischemic lesion at 24 h. Infarct volumes and typology at 24 h (large hemispheric versus basal ganglia infarcts) were predicted by both intra-ischemic collateral perfusion and acute DWI lesion volume. Collateral flow assessed by multi-site laser Doppler flowmetry correlated with the corresponding acute perfusion deficit using TTP maps. Multi-site laser Doppler flowmetry monitoring was able to predict ischemic outcome and perfusion deficit in good agreement with acute MRI. Our results support the additional value of cerebral collateral flow monitoring for outcome prediction in experimental ischemic stroke, especially when acute MRI facilities are not available.

  4. The effect of scatter and glare on image quality in contrast-enhanced breast imaging using an a-Si/CsI(TI) full-field flat panel detector.

    PubMed

    Carton, Ann-Katherine; Acciavatti, Raymond; Kuo, Johnny; Maidment, Andrew D A

    2009-03-01

    The purpose of this study is to evaluate the performance of an antiscatter grid and its potential benefit on image quality for a full-field digital mammography (FFDM) detector geometry at energies typical for temporal subtraction contrast-enhanced (CE) breast imaging. The signal intensities from primary, scatter, and glare were quantified in images acquired with an a-Si/CsI(T1) FFDM detector using a Rh target and a 0.27 mm Cu filter at tube voltages ranging from 35 to 49 kV. Measurements were obtained at the center of the irradiation region of 20-80 mm thick breast-equivalent phantoms. The phantoms were imaged with and without an antiscatter grid. Based on these data, the performance of the antiscatter grid was determined by calculating the primary and scatter transmission factors (T(P) and T(S)) and Bucky factors (Bf). In addition, glare-to-primary ratios (GPRs) and scatter-to-primary ratios (SPRs) were quantified. The effect of the antiscatter grid on the signal-difference-to-noise ratio (SDNR) was also assessed. It was found that T(P) increases with kV but does not depend on the phantom thickness; T(P) values between 0.81 and 0.84 were measured. T(S) increases with kV and phantom thickness; T(S) values between 0.13 and 0.21 were measured. Bf decreases with kV and increases with phantom thickness; Bf ranges from 1.4 to 2.1. GPR is nearly constant, varying from 0.10 to 0.11. SPR without an antiscatter grid (SPR-) ranges from 0.35 to 1.34. SPR- decreases by approximately 9% from 35 to 49 kV for a given phantom thickness and is 3.5 times larger for an 80 mm thick breast-equivalent phantom than for a 20 mm thick breast-equivalent phantom. SPR with an antiscatter grid (SPR+) ranges from 0.06 to 0.31. SPR+ increases by approximately 23% from 35 to 49 kV for a given phantom thickness; SPR+ is four times larger for an 80 mm breast-equivalent phantom than for a 20 mm breast-equivalent phantom. When imaging a 25 mm PMMA plate at the same mean glandular dose with and

  5. The anatomy of the human promontory for laser Doppler flowmetry.

    PubMed

    Laurikainen, E; Kanninen, P; Aho, H; Saukko, P

    1997-01-01

    Studies of the dynamic characteristics of cochlear blood flow (CBF) utilizing laser Doppler flowmetry (LDF) in laboratory animals have provided a new approach to the understanding of control mechanisms of CBF and the role of the CBF in cochlear disorders. However, few studies exist indicating that LDF of human CBF may be possible. Since bone thickness, density, structure characteristics, and blood flow all greatly affect LDF recording, we examined the anatomy of the human promontory for inter-individual variations in thickness, quality and vascularity of the bone and mucosa and recorded middle ear topographic relationships to the underlying cochlear lateral wall vasculature. Temporal bones from 21 cadavers without known premortem histories of ear disease were obtained. India ink was infused selectively via the vertebral or carotid system to study the origin of bone/ mucosa circulation to the otic capsule. Light microscopy revealed that the human promontory was characterized as cortical bone having few blood vessels. The thickness of the bone measured at four horizontal levels and mucosa at the top of promontory and anteriorly around the tympanic plexus varied from 1.67 +/- 0.64 to 1.13 +/- 0.26 mm for bone and 0.06-0.13 mm for mucosa. The thinnest bone was found around the tympanic plexus, where the bone thickness varied from 0.6 to 1.2 mm. Previous data indicate that current LDF instruments can provide a linear measure of blood flow through bone thicknesses of 1-3 mm or more (depending on the type of bone). Data from the current study indicate that direct valid dynamic measures of CBF are possible in humans. Since the optimal area available is small, the topography of the middle ear should be well known and the recording site well defined to obtain valid results.

  6. [Assessment of the microcirculation system by laser Doppler flowmetry].

    PubMed

    Barkhatov, I V

    2013-01-01

    Laser Doppler flowmetry (LDF) is extensively used to study microcirculatory disorders, a main problem facing modern medicine. A wealth of data have been obtained on microcirculation in diabetes mellitus, HD, venous insufficiency and other diseases. This review focuses on basic principles of the method for the assessment of microcirculatory disorders by LDF using the domestically produced equipment. The main elements of the microcirculation system, capillary hemodynamics, and mechanisms of its regulation are described. The main elements and terms of LDF are considered, such as microcirculation index, flux, and variation coefficient along with elements of analysis of the amplitude-frequency fluctuation spectrum and different types of tissue blood flow. Active factors of microcirculation control modulate the blood flow from the vascular wall; their action is mediated through its muscular component. Passive factors cause variations of blood flow outside the microcirculation system; they are the pulsed wave originating from arteries and the sucking action of the venous respiratory pump. Under normal conditions, the vasomotor rhythm driven by the pacemaker in the precapillary segment of the microcirculation bed predominates. The compensatory role of other regulatory mechanisms increases with decreasing contribution of vasomotion to the active modulation of microcirculation hemodynamics. A change in the low to high frequency rhythm ratio reflects the microcirculation index (MI). In case of well-balanced active vasomotor and passive compensatory modulations of tissue blood flow observed in normoemic type of microcirculation, MI amounts to 2.2 ± 0.05. Enhancement of high-frequency and pulsed fluctuation spectra results in a decrease of MI to 1.73 ± 0.04 (hyperemic type) and 1.86 ± 0.053 (hypoemic type).

  7. VCSEL-based miniature laser-Doppler interferometer

    NASA Astrophysics Data System (ADS)

    Pruijmboom, Armand; Schemmann, Marcel; Hellmig, Jochen; Schutte, Jeroen; Moench, Holger; Pankert, Joseph

    2008-02-01

    There are many applications for non-contact measurement of the displacement and velocity of moving objects, especially when achieved at low cost. An optical displacement sensor has been developed that can be compared to expensive laser-interferometry sensors, however at a cost compatible with requirements for consumer products. This miniature Laser-Doppler Interferometer works on all light scattering surfaces. The first large-scale application is in PC-mice. The measurement principle employs so-called "Laser Self Mixing", which occurs when laser light scattered on a surface, within the coherence length, is coupled back into the laser cavity. When the object is moving, the back-scattered light is continuously shifting in phase relative to the laser light at the laser mirror. This results in a periodic perturbation of the feedback into the laser cavity, which causes modulations of the light intensity in the cavity. The frequency of these modulations is proportional the speed of the object. A VCSEL, optimized for this application, is used as light source, a photo-diode in the sensor measures the intensity fluctuations and, finally, an integrated circuit transfers the photo-diode signal into velocity or displacement information. To determine the direction of the movement, a triangle modulation of the laser-current is used, which modulates the laser-temperature and hence the laser frequency. Next to the applications in PC-mice a much wider range of applications as input device in consumer products can be envisaged. For instance menu navigation by finger movement over a sensor in remote controls, mobile phones and lap tops. Furthermore a wide field of applications is envisaged in the manufacturing of industrial equipment, which requires non-contact measurement of the movement of materials. The small form factor of less than 0.2 cubic centimeters allows applications previously considered impossible.

  8. Exploiting Continuous Scanning Laser Doppler Vibrometry in timing belt dynamic characterisation

    NASA Astrophysics Data System (ADS)

    Chiariotti, P.; Martarelli, M.; Castellini, P.

    2017-03-01

    Dynamic behaviour of timing belts has always interested the engineering community over the years. Nowadays, there are several numerical methods to predict the dynamics of these systems. However, the tuning of such models by experimental approaches still represents an issue: an accurate characterisation does require a measurement in operating conditions since the belt mounting condition might severely affect its dynamic behaviour. Moreover, since the belt is constantly moving during running conditions, non-contact measurement methods are needed. Laser Doppler Vibrometry (LDV) and imaging techniques do represent valid candidates for this purpose. This paper aims at describing the use of Continuous Scanning LDV (CSLDV) as a tool for the dynamic characterisation of timing belts in IC (Internal Combustion) engines (cylinder head). The high-spatial resolution data that can be collected in short testing time makes CSLDV highly suitable for such application. The measurement on a moving surface, however, represents a challenge for CSLDV. The paper discusses how the belt in-plane speed influences CSLDV signal and how an order-based multi-harmonic excitation might affect the recovery of Operational Deflection Shapes in a CSLDV test. A comparison with a standard Discrete Scanning LDV measurement is also given in order to show that a CSLDV test, if well designed, can indeed provide the same amount of information in a drastically reduced amount of time.

  9. Full-field strain measurements on turbomachinery components using 3D SLDV technology

    NASA Astrophysics Data System (ADS)

    Maguire, Martyn; Sever, Ibrahim

    2016-06-01

    This paper focuses on measurements of 3D Operating Deflection Shapes (ODSs), and subsequently, construction of full-field surface strain maps of a number of turbomachinery components. For this purpose a 3D Scanning Laser Doppler Vibrometer (SLDV) is used. The ODS measurements are performed for a large number of modes and results obtained are compared with the 1-D shapes that are most commonly measured. It is demonstrated that the 3D measurements are a significant improvement over the 1-D case in terms of independent amount of extra information they provide. This is confirmed through comparisons with FE results. Special tests are carried out to recover the full-field strain on scanned faces of the components used. Visual comparison of these measurements with FE counterparts reveal that strain maps can be successfully measured, not only for low frequency modes but also for highly complex high frequency ones. These maps are measured with different levels of input force to assess the linearity of strain results to varying response amplitudes. Lessons learnt and observations made are summarised in concluding remarks and the scope of future work to take this study into the production environment is discussed. This study constitutes a unique comprehensive investigation into full-field strain measurements using real application hardware and a large frequency range.

  10. A laser Doppler study of gingival blood flow variations following periosteal stimulation.

    PubMed

    Ambrosini, Pascal; Cherene, Sabine; Miller, Neal; Weissenbach, Michel; Penaud, Jacques

    2002-02-01

    Evaluation of the modifications occurring in human gingival blood flow following periosteal stimulation. Laser Doppler was used to measure the gingival blood flow (GBF). The reproducibility of the technique was validated by comparing measures made at intervals of 1 week. Sensitivity was verified by recording GBF before and after injection of an anesthetic containing a vasoconstrictor. Finally, 12 patients were subjected to GBF measurements before and 8 days after periosteal stimulation prior to gingival grafting. The laser Doppler accurately measured GBF. Measurements made at day 0 and day 7 were not statistically different (p=0.60). After injection of an anesthesic solution containing vasoconstrictor, the laser Doppler recorded a sharp decrease of the GBF (p=0.04). The patient that underwent periosteal stimulation showed statistically significant increases (p=0.02) in GBF before and 1 week post-stimulation. Periosteal stimulation induces significant increases in the GBF after 1 week.

  11. Note: Laser Doppler velocimeter using a dual-longitudinal-mode laser source

    NASA Astrophysics Data System (ADS)

    Xiaoming, Nie; Jian, Zhou; Xingwu, Long

    2012-10-01

    This paper presents a new laser Doppler technique using a dual-longitudinal-mode He-Ne laser as the laser source. Theoretical analysis shows that the Doppler frequency is proportional with the frequency difference of the two modes. The Doppler frequency in this technique is very low compared with the one in the single-mode laser Doppler technique. The new laser Doppler technique can be used to measure high speed. Experiment results show that the Doppler frequency is only about 82 Hz while the measurement speed reaches 31.4 m/s. The signal-to-noise ratio of the Doppler signal is improved by the technique of digital filter and digital autocorrelation.

  12. Laser Doppler position sensor for position and shape measurements of fast rotating objects

    NASA Astrophysics Data System (ADS)

    Czarske, Jürgen; Pfister, Thorsten; Büttner, Lars

    2006-08-01

    We report about a novel optical method based on laser Doppler velocimetry for position and shape measurements of moved solid state surfaces with approximately one micrometer position resolution. 3D shape measurements of a rotating cylinder inside a turning machine as well as tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm and 586 m/s blade tip velocity are presented. All results are in good agreement with conventional reference probes. The measurement accuracy of the laser Doppler position sensor is investigated in dependence of the speckle pattern. Furthermore, it is shown that this sensor offers high temporal resolution and high position resolution simultaneously and that shading can be reduced compared to triangulation. Consequently, the presented laser Doppler position sensor opens up new perspectives in the field of real-time manufacturing metrology and process control, for example controlling the turning and the grinding process or for future developments of turbo machines.

  13. Intraoperative cavernous nerve stimulation and Laser-Doppler flowmetry during radical prostatectomy.

    PubMed

    Axelson, Hans W; Johansson, Eva; Bill-Axelson, Anna

    2013-11-01

    Erectile dysfunction is a common side effect following radical prostatectomy mainly due to damage of the pelvic autonomic nerve fibers (cavernous nerves). Intraoperative electrical stimulation of the cavernous nerves while measuring changes in penile girth has previously been shown to provide the surgeon with feedback of nerve integrity. To test the feasibility of recording changes in glans penis blood flow by Laser Doppler flowmetry from cavernous nerve stimulation. Fifteen patients with localized prostate cancer undergoing radical prostatectomy had electrical stimulation of the proximal and distal parts of the neurovascular bundles after prostate removal. The stimulation consisted of 30-40 seconds biphasic constant current (10-30 mA) with 0.5 millisecond pulse duration. Stimulus induced changes in penile blood flow was recorded from a Laser Doppler probe attached to the glans penis. Changes in penile girth were simultaneously recorded from a mercury-in rubber strain gauge. Erectile function was evaluated three months after surgery. Ten patients had stimulus induced increase in Laser Doppler flow unilaterally (N=7) or bilaterally (N=3). Out of 10 patients, 6 reported some preserved erectile function postoperatively at 3 months follow-up (indicating 6 true and 4 false positives). Three patients had no Doppler response from stimulation and had no postoperative erectile function postoperatively (indicating three true negatives). Two patients were excluded from the study due to bad signal quality in the Laser Doppler signal. In the majority of patients, stimulation produced increase in penile girth sensed by the strain gauge. This preliminary report provides evidence that Laser Doppler Flowmetry is able to detect increased penile blood flow from intraoperative electrical stimulation of the neurovascular bundles. However, further improvement in the recording technique is required. Laser Doppler Flowmetry may also be feasible to confirm autonomic nerve sparing in women

  14. Using ordinal logistic regression to evaluate the performance of laser-Doppler predictions of burn-healing time

    PubMed Central

    2009-01-01

    Background Laser-Doppler imaging (LDI) of cutaneous blood flow is beginning to be used by burn surgeons to predict the healing time of burn wounds; predicted healing time is used to determine wound treatment as either dressings or surgery. In this paper, we do a statistical analysis of the performance of the technique. Methods We used data from a study carried out by five burn centers: LDI was done once between days 2 to 5 post burn, and healing was assessed at both 14 days and 21 days post burn. Random-effects ordinal logistic regression and other models such as the continuation ratio model were used to model healing-time as a function of the LDI data, and of demographic and wound history variables. Statistical methods were also used to study the false-color palette, which enables the laser-Doppler imager to be used by clinicians as a decision-support tool. Results Overall performance is that diagnoses are over 90% correct. Related questions addressed were what was the best blood flow summary statistic and whether, given the blood flow measurements, demographic and observational variables had any additional predictive power (age, sex, race, % total body surface area burned (%TBSA), site and cause of burn, day of LDI scan, burn center). It was found that mean laser-Doppler flux over a wound area was the best statistic, and that, given the same mean flux, women recover slightly more slowly than men. Further, the likely degradation in predictive performance on moving to a patient group with larger %TBSA than those in the data sample was studied, and shown to be small. Conclusion Modeling healing time is a complex statistical problem, with random effects due to multiple burn areas per individual, and censoring caused by patients missing hospital visits and undergoing surgery. This analysis applies state-of-the art statistical methods such as the bootstrap and permutation tests to a medical problem of topical interest. New medical findings are that age and %TBSA are

  15. Pipe flow measurements of turbulence and ambiguity using laser-Doppler velocimetry

    NASA Technical Reports Server (NTRS)

    Berman, N. S.; Dunning, J. W.

    1973-01-01

    The laser-Doppler ambiguities predicted by George and Lumley (1973) have been verified experimentally for turbulent pipe flows. Experiments were performed at Reynolds numbers from 5000 to 15,000 at the center line and near the wall. Ambiguity levels were measured from power spectral densities of FM demodulated laser signals and were compared with calculations based on the theory. The turbulent spectra for these water flows after accounting for the ambiguity were equivalent to hot-film measurements at similar Reynolds numbers. The feasibility of laser-Doppler measurements very close to the wall in shear flows is demonstrated.

  16. Differential Laser Doppler based Non-Contact Sensor for Dimensional Inspection with Error Propagation Evaluation

    PubMed Central

    Mekid, Samir; Vacharanukul, Ketsaya

    2006-01-01

    To achieve dynamic error compensation in CNC machine tools, a non-contact laser probe capable of dimensional measurement of a workpiece while it is being machined has been developed and presented in this paper. The measurements are automatically fed back to the machine controller for intelligent error compensations. Based on a well resolved laser Doppler technique and real time data acquisition, the probe delivers a very promising dimensional accuracy at few microns over a range of 100 mm. The developed optical measuring apparatus employs a differential laser Doppler arrangement allowing acquisition of information from the workpiece surface. In addition, the measurements are traceable to standards of frequency allowing higher precision.

  17. WE-G-BRD-01: A Data-Driven 4D-MRI Motion Model to Estimate Full Field-Of-View Abdominal Motion From 2D Image Navigators During MR-Linac Treatment

    SciTech Connect

    Stemkens, B; Tijssen, RHN; Denis de Senneville, B Denis; Lagendijk, JJW; Berg, CAT van den

    2015-06-15

    Purpose: To estimate full field-of-view abdominal respiratory motion from fast 2D image navigators using a 4D-MRI based motion model. This will allow for radiation dose accumulation mapping during MR-Linac treatment. Methods: Experiments were conducted on a Philips Ingenia 1.5T MRI. First, a retrospectively ordered 4D-MRI was constructed using 3D transient-bSSFP with radial in-plane sampling. Motion fields were calculated through 3D non-rigid registration. From these motion fields a PCA-based abdominal motion model was constructed and used to warp a 3D reference volume to fast 2D cine-MR image navigators that can be used for real-time tracking. To test this procedure, a time-series consisting of two interleaved orthogonal slices (sagittal and coronal), positioned on the pancreas or kidneys, were acquired for 1m38s (dynamic scan-time=0.196ms), during normal, shallow, or deep breathing. The coronal slices were used to update the optimal weights for the first two PCA components, in order to warp the 3D reference image and construct a dynamic 4D-MRI time-series. The interleaved sagittal slices served as an independent measure to test the model’s accuracy and fit. Spatial maps of the root-mean-squared error (RMSE) and histograms of the motion differences within the pancreas and kidneys were used to evaluate the method. Results: Cranio-caudal motion was accurately calculated within the pancreas using the model for normal and shallow breathing with an RMSE of 1.6mm and 1.5mm and a histogram median and standard deviation below 0.2 and 1.7mm, respectively. For deep-breathing an underestimation of the inhale amplitude was observed (RMSE=4.1mm). Respiratory-induced antero-posterior and lateral motion were correctly mapped (RMSE=0.6/0.5mm). Kidney motion demonstrated good motion estimation with RMSE-values of 0.95 and 2.4mm for the right and left kidney, respectively. Conclusion: We have demonstrated a method that can calculate dynamic 3D abdominal motion in a large volume

  18. Three-dimensional gas turbulence measurement with a laser-Doppler velocimeter system

    NASA Technical Reports Server (NTRS)

    Fuller, C. E.

    1973-01-01

    Laser-Doppler system records gas-velocity data over wide dynamic range in three-dimensional space without physical probe. System detects shift in laser beam scattered by flowing particles and uses this frequency to calculate particle velocities. Technique is based on principle that laser beam scattered by flowing particles is shifted in frequency by amount proportional to laser frequency.

  19. A laser Doppler system for the remote sensing of boundary layer winds in clear air conditions

    NASA Technical Reports Server (NTRS)

    Lawrence, T. R.; Krause, M. C.; Craven, C. E.; Morrison, L. K.; Thomson, J. A. L.; Cliff, W. C.; Huffaker, R. M.

    1975-01-01

    The system discussed uses a laser Doppler radar in combination with a velocity azimuth display mode of scanning to determine the three-dimensional wind field in the atmospheric boundary layer. An attractive feature of this CW monostatic system is that the ambient aerosol provides a 'sufficient' scattering target to permit operation under clear air conditions. Spatial resolution is achieved by focusing.

  20. A laser Doppler system for the remote sensing of boundary layer winds in clear air conditions

    NASA Technical Reports Server (NTRS)

    Lawrence, T. R.; Krause, M. C.; Craven, C. E.; Morrison, L. K.; Thomson, J. A. L.; Cliff, W. C.; Huffaker, R. M.

    1975-01-01

    The system discussed uses a laser Doppler radar in combination with a velocity azimuth display mode of scanning to determine the three-dimensional wind field in the atmospheric boundary layer. An attractive feature of this CW monostatic system is that the ambient aerosol provides a 'sufficient' scattering target to permit operation under clear air conditions. Spatial resolution is achieved by focusing.

  1. Principal components analysis as a de-noising method applied to laser Doppler reactive hyperemia signals

    NASA Astrophysics Data System (ADS)

    Mansouri, C.; Humeau, A.; Abraham, P.; L'Huillier, J. P.

    2005-08-01

    Reactive hyperemia signals obtained with laser Doppler flowmetry are currently used to diagnose peripheral arterial occlusive diseases (PAOD). De-noising of such signals could lead to improved diagnoses. For this purpose, the principal components analysis is applied to signals acquired on PAOD and healthy subjects.

  2. Spectral analysis of the signal from the Laser Doppler Velocimeter - Turbulent flows.

    NASA Technical Reports Server (NTRS)

    Edwards, R. V.; Angus, J. C.; Dunning, J. W., Jr.

    1973-01-01

    A method for prediction and analysis of the spectrum of the signal from the Laser Doppler Velocimeter is presented. The results relate the heterodyne spectrum of the signal to the space-time correlation function for the turbulent transport of tracer particles in the fluid and to the characteristics of the optical system.

  3. Laser Doppler flowmetry in blood and lymph monitoring, technical aspects and analysis

    NASA Astrophysics Data System (ADS)

    Dremin, Victor V.; Zherebtsov, Evgeny A.; Makovik, Irina N.; Kozlov, Igor O.; Sidorov, Viktor V.; Krupatkin, Alexander I.; Dunaev, Andrey V.; Rafailov, Ilya E.; Litvinova, Karina S.; Sokolovski, Sergei G.; Rafailov, Edik U.

    2017-03-01

    The aim of this work was to study the possibilities of the laser Doppler flowmetry method for the joint study of microhaemo- and lymph circulation of human skin. Conducting a series of experimental studies allowed to trace the relationship of recorded signals of microcirculation of blood flow and lymph flow, as well as to study their oscillation nature by using wavelet analysis.

  4. Development of CO2 laser Doppler instrumentation for detection of clear air turbulence, volume 1

    NASA Technical Reports Server (NTRS)

    Harris, C. E.; Jelalian, A. V.

    1979-01-01

    Modification, construction, test and operation of an advanced airborne carbon dioxide laser Doppler system for detecting clear air turbulence are described. The second generation CAT program and those auxiliary activities required to support and verify such a first-of-a-kind system are detailed: aircraft interface; ground and flight verification tests; data analysis; and laboratory examinations.

  5. Laser Resurfacing: Full Field and Fractional.

    PubMed

    Pozner, Jason N; DiBernardo, Barry E

    2016-07-01

    Laser resurfacing is a very popular procedure worldwide. Full field and fractional lasers are used in many aesthetic practices. There have been significant advances in laser resurfacing in the past few years, which make patient treatments more efficacious and with less downtime. Erbium and carbon dioxide and ablative, nonablative, and hybrid fractional lasers are all extremely effective and popular tools that have a place in plastic surgery and dermatology offices.

  6. Analysis of Transitional and Turbulent Flow Through the FDA Benchmark Nozzle Model Using Laser Doppler Velocimetry.

    PubMed

    Taylor, Joshua O; Good, Bryan C; Paterno, Anthony V; Hariharan, Prasanna; Deutsch, Steven; Malinauskas, Richard A; Manning, Keefe B

    2016-09-01

    Transitional and turbulent flow through a simplified medical device model is analyzed as part of the FDA's Critical Path Initiative, designed to improve the process of bringing medical products to market. Computational predictions are often used in the development of devices and reliable in vitro data is needed to validate computational results, particularly estimations of the Reynolds stresses that could play a role in damaging blood elements. The high spatial resolution of laser Doppler velocimetry (LDV) is used to collect two component velocity data within the FDA benchmark nozzle model. Two flow conditions are used to produce flow encompassing laminar, transitional, and turbulent regimes, and viscous stresses, principal Reynolds stresses, and turbulence intensities are calculated from the measured LDV velocities. Axial velocities and viscous stresses are compared to data from a prior inter-laboratory study conducted with particle image velocimetry. Large velocity gradients are observed near the wall in the nozzle throat and in the jet shear layer located in the expansion downstream of the throat, with axial velocity changing as much as 4.5 m/s over 200 μm. Additionally, maximum Reynolds shear stresses of 1000-2000 Pa are calculated in the high shear regions, which are an order of magnitude higher than the peak viscous shear stresses (<100 Pa). It is important to consider the effects of both viscous and turbulent stresses when simulating flow through medical devices. Reynolds stresses above commonly accepted hemolysis thresholds are measured in the nozzle model, indicating that hemolysis may occur under certain flow conditions. As such, the presented turbulence quantities from LDV, which are also available for download at https://fdacfd.nci.nih.gov/ , provide an ideal validation test for computational simulations that seek to characterize the flow field and to predict hemolysis within the FDA nozzle geometry.

  7. Polarization-sensitive full-field optical coherence tomography.

    PubMed

    Moneron, Gael; Boccara, Albert-Claude; Dubois, Arnaud

    2007-07-15

    We present a polarization-sensitive full-field optical coherence tomography system that can produce high-resolution images of the linear retardance and reflectivity properties of biological media. En face images can be delivered at a frame rate of 3.5 Hz by combination of interferometric images acquired by two CCD cameras in an interference microscope illuminated with a tungsten halogen lamp. Isotropic spatial resolution of approximately 1.0 microm is achieved. The technique is demonstrated on ex vivo muscle tissues.

  8. Full field-of-view photoacoustic endoscopy in vivo

    NASA Astrophysics Data System (ADS)

    Lin, Riqiang; Li, Yan; Chen, Jianhua; Song, Liang

    2017-03-01

    We developed a miniaturized, simple and full field-of-view photoacoustic/ultrasonic endoscopy system, and used a flexible coil to transmit the rotational torque from the rotary stage, which enables a 360o field-of-view imaging in vivo. The developed imaging catheter was fully encapsulated by a single-use protective polyamide tube. A B-scan rate up to 5 Hz (200 A-lines/B-scan) was achieved. Three-dimensional photoacoustic and ultrasound images of the rectum from a SD rat were acquired in vivo. It suggests that this PAE system can be of great interest for clinical translation for a variety of endoscopic applications.

  9. Development and testing of laser Doppler system components for wake vortex monitoring. Volume 2: Scanner operations manual

    NASA Technical Reports Server (NTRS)

    Edwards, B. B.; Coffey, E. W.

    1974-01-01

    The theory and operation of the scanner portion of the laser Doppler system for detecting and monitoring aircraft trailing vortices in an airport environment are discussed. Schematics, wiring diagrams, component values, and operation and checkout procedures are included.

  10. Visual modeling of laser Doppler anemometer signals by moiré fringes.

    PubMed

    Durst, F; Stevenson, W H

    1976-01-01

    This report describes the employment of moiré patterns to model visually interference phenomena in general and laser Doppler anemometer signals in particular. The modeling includes signals created in dual beam and reference beam anemometers by both single particles and particle pairs. The considerations are extended to visual modeling of multiparticle signals and the decay of signal quality in the presence of many particles. The fringe model of the laser Doppler anemometer is also considered, and moiré patterns are employed to demonstrate the interference fringes in the crossover region of two intersecting laser beams. Gaussian beam properties are taken into account to allow the effects of improperly designed optical systems to be studied. Instructions for using computer generated transparencies to produce the different moiré patterns are provided to allow the reader to study in detail the various interference phenomena described.

  11. Laser Doppler velocimetry based on the photoacoustic effect in a CO{sub 2} laser

    SciTech Connect

    Choi, Jong-woon; Yu, Moon-jong; Kopica, Mirek; Woo, Sam-yong; Choi, Yong-Seok

    2005-02-01

    We report a simple laser Doppler velocimeter in which the photoacoustic effect was used to measure the rotation wheel speed. A Doppler signal, caused by mixing a returning wave with an originally existing wave inside the CO{sub 2} laser cavity, was detected using a microphone in the laser tube. Frequency of the microphone output was in proportion to the rotation speed of a wheel and is dependent on the cosine of the angle between the direction of the laser beam and tangent of wheel velocity. A Doppler-shifted frequency as high as 34 kHz was detected using this method. A frequency response of a few megahertz is expected from the laser Doppler velocimeter based on the photoacoustic effect in a CO{sub 2} laser by using a wider bandwidth microphone.

  12. Laser Doppler techniques for the combined measurement of inlet flow and valve motion in IC engines

    NASA Astrophysics Data System (ADS)

    Gasparetti, M.; Paone, N.; Tomasini, E. P.

    1996-04-01

    A measurement methodology and a test set-up for the experimental investigation of internal combustion engines are presented. This system is based on a laser Doppler anemometer and a laser Doppler vibrometer which measure in a co-ordinated or simultaneous mode both the velocity of the intake flow and the motion of the inlet poppet valve. A synchronized data acquisition procedure allows the use of two optical instruments to analyse the effects of valve jumps and bounces on the inlet flow field. At high rpm, anomalous valve behaviour may appear. Fluid velocity measurements are taken inside the cylinder and the manifold of a motored automotive engine head at different rpm, up to a speed at which anomalous valve behaviour regularly occurs. Velocity data are processed in both time and frequency domains. This measurement system also represents a valuable tool to study resonance phenomena in ducts.

  13. Exploiting continuous scanning laser Doppler vibrometry (CSLDV) in time domain correlation methods for noise source identification

    NASA Astrophysics Data System (ADS)

    Chiariotti, Paolo; Martarelli, Milena; Revel, Gian Marco

    2014-07-01

    This paper proposes the use of continuous scanning laser Doppler vibrometry (CSLDV) in time domain correlation techniques that aim at characterizing the structure-borne contributions of the noise emission of a mechanical system. The time domain correlation technique presented in this paper is based on the use of FIR (finite impulse response) filters obtained from the vibro-acoustic transfer matrix when vibration data are collected by laser Doppler vibrometry (LDV) exploited in continuous scan mode (CSLDV). The advantages, especially in terms of source decorrelation capabilities, related to the use of CSLDV for such purpose, with respect to standard discrete scan (SLDV), are discussed throughout the paper. To validate this approach, vibro-acoustic measurements were performed on a planetary gear motor for home appliances. The analysis of results is also supported by a simulation.

  14. [Laser Doppler vibrometry: a new tool for diagnosing hearing loss with an intact eardrum].

    PubMed

    Turcanu, Diana; Mârţu, D; Dalhoff, E; Gummer, A W

    2006-01-01

    The diagnosis of hearing loss with an intact eardrum frequently requires an entire battery of hearing tests, without the guarantee of an exact diagnosis. The techniques frequently provide only orientation for it, without establishing the site of the lesion and the etiology of the hearing loss. Laser Doppler vibrometry is a new technique, which has recently proved capable, of partially resolving this problem. The method is based on the study of the sound-induced vibration of the eardrum in humans in vivo, using a laser Doppler vibrometer. The method proved to be useful in the diagnosis of the pathology of the middle ear sound transmission system, avoiding the need for exploratory tympanotomy. Called "laser-audiometry", the method promises to become a new diagnostic tool for hearing impairment.

  15. Development of fiber optic laser Doppler velocimeter for measurement of local blood velocity

    NASA Astrophysics Data System (ADS)

    Ohba, Kenkich; Fujiwara, Noboru

    1993-08-01

    In order to measure the local velocity field in opaque fluid flows like blood flow, a new laser Doppler velocimeter having a pickup consisting of a small distributed index lens attached to the tips of two fibers which are joined side by side in parallel has been newly developed. The distributed index lens is the shape of a truncated cone. The flow field around this sensor has been measured very precisely by means of an ordinary LDV. The effect of turbidity of fluid on the quality of the laser Doppler signal from this sensor has been examined by experiments. As a result, it has been shown that this LDV sensor has a high signal-to-noise ratio, and that the disturbance against flow by the sensor is very small, and it is very promising as a velocity sensor for opaque or semi-opaque fluid flow like blood flow.

  16. Model studies of blood flow in basilar artery with 3D laser Doppler anemometer

    NASA Astrophysics Data System (ADS)

    Frolov, S. V.; Sindeev, S. V.; Liepsch, D.; Balasso, A.; Proskurin, S. G.; Potlov, A. Y.

    2015-03-01

    It is proposed an integrated approach to the study of basilar artery blood flow using 3D laser Doppler anemometer for identifying the causes of the formation and development of cerebral aneurysms. Feature of the work is the combined usage of both mathematical modeling and experimental methods. Described the experimental setup and the method of measurement of basilar artery blood flow, carried out in an interdisciplinary laboratory of Hospital Rechts der Isar of Technical University of Munich. The experimental setup used to simulate the blood flow in the basilar artery and to measure blood flow characteristics using 3D laser Doppler anemometer (3D LDA). Described a method of numerical studies carried out in Tambov State Technical University and the Bakoulev Center for Cardiovascular Surgery. Proposed an approach for sharing experimental and numerical methods of research to identify the causes of the basilar artery aneurysms.

  17. Directional acoustic measurements by laser Doppler velocimeters. [for jet aircraft noise

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Overbey, R. L.; Testerman, M. K.

    1976-01-01

    Laser Doppler velocimeters (LDVs) were used as velocity microphones to measure sound pressure level in the range of 90-130 db, spectral components, and two-point cross correlation functions for acoustic noise source identification. Close agreement between LDV and microphone data is observed. It was concluded that directional sensitivity and the ability to measure remotely make LDVs useful tools for acoustic measurement where placement of any physical probe is difficult or undesirable, as in the diagnosis of jet aircraft noise.

  18. Laser Doppler Velocimetry Measurements Across A Normal Shock In Transonic Flow

    DTIC Science & Technology

    1993-03-01

    15 A. SUPERSONIC WIND TUNNEL ..... ............. .. 15 B. LASER DOPPLER VELOCIMETRY SYSTEM ........... .. 20 1. Laser and Optics...of instability or high velocity gradients. Studies done on particle lag prediction, Chesnakas and Andrew [Ref. 15 ], and particle dynamics effects on...form the convergent-divergent nozzle and test 15 Figure 5. Supersonic Wind Tunnel CONVERGENT. D•VRGENT CONTROL VALVE SBLEtO TEST SECTION CONTROL VALVE

  19. Performance and analysis of a three-dimensional nonorthogonal laser Doppler anemometer

    NASA Technical Reports Server (NTRS)

    Snyder, P. K.; Orloff, K. L.; Aoyagi, K.

    1981-01-01

    A three dimensional laser Doppler anemometer with a nonorthogonal third axis coupled by 14 deg was designed and tested. A highly three dimensional flow field of a jet in a crossflow was surveyed to test the three dimensional capability of the instrument. Sample data are presented demonstrating the ability of the 3D LDA to resolve three orthogonal velocity components. Modifications to the optics, signal processing electronics, and data reduction methods are suggested.

  20. Laser Doppler flowmetry for measurement of laminar capillary blood flow in the horse

    NASA Astrophysics Data System (ADS)

    Adair, Henry S., III

    1998-07-01

    Current methods for in vivo evaluation of digital hemodynamics in the horse include angiography, scintigraphy, Doppler ultrasound, electromagnetic flow and isolated extracorporeal pump perfused digit preparations. These techniques are either non-quantifiable, do not allow for continuous measurement, require destruction of the horse orare invasive, inducing non- physiologic variables. In vitro techniques have also been reported for the evaluation of the effects of vasoactive agents on the digital vessels. The in vitro techniques are non-physiologic and have evaluated the vasculature proximal to the coronary band. Lastly, many of these techniques require general anesthesia or euthanasia of the animal. Laser Doppler flowmetry is a non-invasive, continuous measure of capillary blood flow. Laser Doppler flowmetry has been used to measure capillary blood flow in many tissues. The principle of this method is to measure the Doppler shift, that is, the frequency change that light undergoes when reflected by moving objects, such as red blood cells. Laser Doppler flowmetry records a continuous measurement of the red cell motion in the outer layer of the tissue under study, with little or no influence on physiologic blood flow. This output value constitutes the flux of red cells and is reported as capillary perfusion units. No direct information concerning oxygen, nutrient or waste metabolite exchange in the surrounding tissue is obtained. The relationship between the flowmeter output signal and the flux of red blood cells is linear. The principles of laser Doppler flowmetry will be discussed and the technique for laminar capillary blood flow measurements will be presented.

  1. Laser Doppler, velocimeter system for turbine stator cascade studies and analysis of statistical biasing errors

    NASA Technical Reports Server (NTRS)

    Seasholtz, R. G.

    1977-01-01

    A laser Doppler velocimeter (LDV) built for use in the Lewis Research Center's turbine stator cascade facilities is described. The signal processing and self contained data processing are based on a computing counter. A procedure is given for mode matching the laser to the probe volume. An analysis is presented of biasing errors that were observed in turbulent flow when the mean flow was not normal to the fringes.

  2. Spectroscopic polarization-sensitive full-field optical coherence tomography.

    PubMed

    Dubois, Arnaud

    2012-04-23

    Full-field optical coherence tomography (FF-OCT) is a recent optical imaging technology based on low-coherence interference microscopy for imaging of semi-transparent samples with ~1 µm spatial resolution. FF-OCT produces en-face tomographic images obtained by arithmetic combination of interferometric images acquired by an array camera. In this paper, we demonstrate a unique multimodal FF-OCT system, capable of measuring simultaneously the intensity, the power spectrum and the phase-retardation of light backscattered by the sample being imaged. Compared to conventional FF-OCT, this multimodal system provides enhanced imaging contrasts at the price of a moderate increase in experimental complexity and cost. © 2012 Optical Society of America

  3. Shape and vibration measurement of fast rotating objects employing novel laser Doppler techniques

    NASA Astrophysics Data System (ADS)

    Pfister, Thorsten; Günther, Philipp; Büttner, Lars; Czarske, Jürgen

    2007-06-01

    This contribution presents novel laser Doppler techniques, which allow simultaneous measurement of radial position and tangential velocity and, thus, determination of the shape of rotating objects with one single sensor. Conventional laser Doppler velocimeters measure only velocities. A concurrent position measurement can be realized by generating two fan-like interference fringe systems with contrary fringe spacing gradients and evaluating the quotient of the two resulting Doppler frequencies. Alternatively, two tilted fringe systems in combination with phase evaluation can be employed. It is shown that the position uncertainty of this sensor is not only independent of the surface roughness but, most notably, that it is in principle independent of the object velocity. Thus, in contrast to conventional distance sensors, the novel laser Doppler position sensor offers high temporal resolution below 3 μs and high position resolution in the micrometer range simultaneously. The sensor was applied to automatic 3D shape measurements of turning parts and to monitoring rotor unbalance and dynamic deformations. Furthermore, in situ measurements of tip clearance and rotor vibrations at turbo machines for up to 600 m/s blade tip velocity are reported. The results are in excellent agreement with those of triangulation and capacitive probes, respectively.

  4. Efficiency of use endobronchial laser doppler-flowmetry in patients with chronic leukemia

    NASA Astrophysics Data System (ADS)

    Vanina, E. A.; Voitsekhovskiy, V. V.; Landyshev, Y. S.; Tkacheva, S. I.

    2016-11-01

    In this work indicatorsendobronchial microcirculation were investigated in patients with chronic myeloid leukemia (CML), chronic lymphocytic leukemia (CLL), multiple myeloma (MM), polycythemia vera (PV), idiopathic myelofibrosis (IMF). A diagnostic bronchoscopy was performed using fibreoptic «Olympus» (Japan).Endobronchial laser Doppler flowmetry was carried out on the laser analyzer capillary blood LAK-02 (Russia). Laser Doppler flowmetry indicators such as parameter of microcirculation, the oscillation amplitude in the endothelial, neurogenic, myogenic, cardiac and respiratory ranges were calculated by continuous the Wavelet transforms. Reduced cardiac and respiratory amplitudes in CML and CLL are primarily due to the development leukostasis. If PV is the case, this is due to sludge syndrome. And when MM occurs, it is caused by protein stasis in the vessels of the bronchial tubes. Increased endothelial oscillation amplitudes in the range in CML, PV, IMF and their reduction in MM indicate the presence of endothelial dysfunction in these patients. Increasing the amplitude of oscillations in the range of neurogenic indicates the development of arteriolar vasodilation as a compensatory response to the violation of blood flow. Increasing the amplitude of oscillations of myogenic tone indicating decrease precapillaries as a compensatory reaction to improve blood flow. It is concluded that endobronchial laser Doppler flowmetry is an important method allowing diagnosing the pathology of the microvasculature of the bronchi in chronic leukemia.

  5. Laser-doppler sensor system for speed and length measurements at moving surfaces

    NASA Astrophysics Data System (ADS)

    Stork, Wilhelm; Wagner, Armin; Kunze, Carsten

    2001-10-01

    Laser-Doppler Velocimetry is a contact less method for measuring the speed and the path length of moving solid- state surfaces or of fluid streams. In the past the main application of this method was fluid mechanics. No other method was as suitable as Laser-Doppler Anemometry to measure the speed the streams at arbitrary positions. Therefore the market accepted the very high price of these systems. In the past for the measurement of solid-state surfaces mostly other methods with a more reasonable price were used. However from a pure technical point of view a contact less and precise method as Laser-Doppler Velocimetry is also very attractive for the measurement of solid-state surfaces. The method is suitable for nearly any type of technical surface. The measurement procedure does not damage the surfaces and no slippage occurs. These advantages will be become important also for standard applications, if the price of the LDV systems can compete with the price of other methods.

  6. UV laser-induced fluorescence spectroscopy and laser Doppler flowmetry in the diagnostics of alopecia

    NASA Astrophysics Data System (ADS)

    Skomorokha, Diana P.; Pigoreva, Yulia N.; Salmin, Vladimir V.

    2016-04-01

    Development of optical biopsy methods has a great interest for medical diagnostics. In clinical and experimental studies it is very important to analyze blood circulation quickly and accurately, thereby laser Doppler flowmetry (LDF) is widely used. UV laser-induced fluorescence spectroscopy (UV LIFS) is express highly sensitive and widely-spread method with no destructive impact, high excitation selectivity and the possibility to use in highly scattering media. The goal of this work was to assess a correlation of UV laser-induced fluorescence spectroscopy and laser Doppler flowmetry parameters, and a possibility to identify or to differentiate various types of pathological changes in tissues according to their autofluorescence spectra. Three groups of patients with diffuse (symptomatic) alopecia, androgenic alopecia, and focal alopecia have been tested. Each groups consisted of not less than 20 persons. The measurements have been done in the parietal and occipital regions of the sculls. We used the original automated spectrofluorimeter to record autofluorescence spectra, and standard laser Doppler flowmeter BLF-21 (Transonic Systems, Inc., USA) to analyze the basal levels of blood circulation. Our results show that UV LIFS accurately distinguishes the zones with different types of alopecia. We found high correlation of the basal levels of blood circulation and the integrated intensity of autofluorescence in the affected tissue.

  7. Relationship of oscillating and average components of laser Doppler flowmetry signal

    NASA Astrophysics Data System (ADS)

    Mizeva, Irina; Frick, Peter; Podtaev, Sergey

    2016-08-01

    Signals from laser Doppler flowmeters widely used in intravital studies of skin blood flow include, along with a slowly varying average component, an oscillating part. However, in most clinical studies, pulsations are usually smoothed by data preprocessing and only the mean blood flow is analyzed. To reveal the relationship between average and oscillating perfusion components measured by a laser Doppler flowmeter, we examined the microvascular response to the contralateral cold pressor test recorded at two different sites of the hand: dorsal part of the arm and finger pad. Such a protocol makes it possible to provide a wide range of perfusion. The average perfusion always decreases during cooling, while the oscillating component demonstrates a differently directed response. The wavelet analysis of laser Doppler flowmetry (LDF) signals shows that the pulsatile component is nonlinearly related to the average perfusion. Under low perfusion, the amplitude of pulsations is proportional to its mean value, but, as perfusion increases, the amplitude of pulsations becomes lower. The type of response is defined by the basal perfusion and the degree of vasoconstriction caused by cooling. Interpretation of the results is complicated by the nonlinear transfer function of the LDF device, the contribution of which is studied using artificial examples.

  8. Pancreatic cancer study based on full field OCT and dynamic full field OCT (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Apelian, Clement; Camus, Marine; Prat, Frederic; Boccara, A. Claude

    2017-02-01

    Pancreatic cancer is one of the most feared cancer types due to high death rates and the difficulty to perform surgery. This cancer outcome could benefit from recent technological developments for diagnosis. We used a combination of standard Full Field OCT and Dynamic Full Field OCT to capture both morphological features and metabolic functions of rodents pancreas in normal and cancerous conditions with and without chemotherapy. Results were compared to histology to evaluate the performances and the specificities of the method. The comparison highlighted the importance of a number of endogenous markers like immune cells, fibrous development, architecture and more.

  9. A full field, 3-D velocimeter for microgravity crystallization experiments

    NASA Technical Reports Server (NTRS)

    Brodkey, Robert S.; Russ, Keith M.

    1991-01-01

    The programming and algorithms needed for implementing a full-field, 3-D velocimeter for laminar flow systems and the appropriate hardware to fully implement this ultimate system are discussed. It appears that imaging using a synched pair of video cameras and digitizer boards with synched rails for camera motion will provide a viable solution to the laminar tracking problem. The algorithms given here are simple, which should speed processing. On a heavily loaded VAXstation 3100 the particle identification can take 15 to 30 seconds, with the tracking taking less than one second. It seeems reasonable to assume that four image pairs can thus be acquired and analyzed in under one minute.

  10. Ultrahigh-resolution full-field optical coherence tomography.

    PubMed

    Dubois, Arnaud; Grieve, Kate; Moneron, Gael; Lecaque, Romain; Vabre, Laurent; Boccara, Claude

    2004-05-10

    We have developed a white-light interference microscope for ultrahigh-resolution full-field optical coherence tomography of biological media. The experimental setup is based on a Linnik-type interferometer illuminated by a tungsten halogen lamp. En face tomographic images are calculated by a combination of interferometric images recorded by a high-speed CCD camera. Spatial resolution of 1.8 microm x 0.9 microm (transverse x axial) is achieved owing to the extremely short coherence length of the source, the compensation of dispersion mismatch in the interferometer arms, and the use of relatively high-numerical-aperture microscope objectives. A shot-noise-limited detection sensitivity of 90 dB is obtained in an acquisition time per image of 4 s. Subcellular-level images of plant, animal, and human tissues are presented.

  11. Time Domain Full Field Optical Coherence Tomography Microscopy

    NASA Astrophysics Data System (ADS)

    Harms, Fabrice; Latrive, Anne; Boccara, A. Claude

    This chapter mostly describes the main characteristics of the full field OCM (FFOCM) systems with an emphasis on the main differences with other systems described in this book: the use of spatially and temporally incoherent sources and large numerical aperture objectives that leads to a 3D ultra-high spatial resolution. We also show that FFOCM can be associated to other imaging modalities such as fluorescence and elasticity in order to increase its sensitivity and specificity when used as a diagnosis tool. Finally FFOCM is shown to successfully match the requirements of a rigid endoscopic system.

  12. Large Field, High Resolution Full-Field Optical Coherence Tomography

    PubMed Central

    Assayag, Osnath; Antoine, Martine; Sigal-Zafrani, Brigitte; Riben, Michael; Harms, Fabrice; Burcheri, Adriano; Grieve, Kate; Dalimier, Eugénie; Le Conte de Poly, Bertrand; Boccara, Claude

    2014-01-01

    We present a benchmark pilot study in which high-resolution Full-Field Optical Coherence Tomography (FF-OCT) was used to image human breast tissue and is evaluated to assess its ability to aid the pathologist’s management of intra-operative diagnoses. FF-OCT imaging safety was investigated and agreement between FF-OCT and routinely prepared histopathological images was evaluated. The compact setup used for this study provides 1 µm3 resolution and 200 µm imaging depth, and a 2.25 cm2 specimen is scanned in about 7 minutes. 75 breast specimens were imaged from 22 patients (21 women, 1 man) with a mean age of 58 (range: 25-83). Pathologists blind diagnosed normal/benign or malignant tissue based on FF-OCT images alone, diagnosis from histopathology followed for comparison. The contrast in the FF-OCT images is generated by intrinsic tissue scattering properties, meaning that no tissue staining or preparation is required. Major architectural features and tissue structures of benign breast tissue, including adipocytes, fibrous stroma, lobules and ducts were characterized. Subsequently, features resulting from pathological modification were characterized and a diagnosis decision tree was developed. Using FF-OCT images, two breast pathologists were able to distinguish normal/benign tissue from lesional with a sensitivity of 94% and 90%, and specificity of 75% and 79% respectively. PMID:24000981

  13. Comparison of blood flow measurements by hydrogen gas clearance and laser Doppler flowmetry in the rat duodenum.

    PubMed

    Leung, F W

    1990-05-01

    This report examines the relationship between hydrogen gas clearance and laser Doppler flowmetry measurements in the duodenum of fasted, anesthetized rats under conditions of 1) reduced perfusion due to graded levels of hemorrhagic hypotension or 2) hyperemia due to perfusion with step doses of acid. There was a significant correlation between hydrogen gas clearance and laser Doppler flowmetry measurements (r = 0.73, p less than 0.01; n = 32 data points in 16 rats). The change in laser Doppler flowmetry values from the period immediately before to the period during the 3 min of acid perfusion was significantly correlated with the dose of acid used (r = 0.51, p less than 0.01; n = 27 rats). The changes in hydrogen gas clearance and laser Doppler flowmetry values from the 30-min period before to the 30-min period after acid perfusion were not correlated with the dose of acid used (r = 0.30 and 0.33, respectively). We conclude that in the rat duodenum 1) the significant linear correlation between hydrogen gas clearance and laser Doppler flowmetry when blood flow is reduced suggests that the countercurrent exchange mechanism is unlikely to modulate significantly hydrogen gas clearance measurements, and 2) the dose-related acid-induced duodenal hyperemia is transient rather than persistent when the rat duodenum is exposed to hydrochloric acid (0.03 to 0.1 N) for 3 min.

  14. Simultaneous laser Doppler flowmetry and arterial spin labeling MRI for measurement of functional perfusion changes in the cortex.

    PubMed

    He, Jiabao; Devonshire, Ian M; Mayhew, John E W; Papadakis, Nikos G

    2007-02-15

    This study compares laser Doppler flowmetry (LDF) and arterial spin labeling (ASL) for the measurement of functional changes in cerebral blood flow (CBF). The two methods were applied concurrently in a paradigm of electrical whisker stimulation in the anaesthetised rat. Multi-channel LDF was used, with each channel corresponding to different fiber separation (and thus measurement depth). Continuous ASL was applied using separate imaging and labeling coils at 3 T. Careful experimental set up ensured that both techniques recorded from spatially concordant regions of the barrel cortex, where functional responses were maximal. Strong correlations were demonstrated between CBF changes measured by each LDF channel and ASL in terms of maximum response magnitude and response time-course within a 6-s-long temporal resolution imposed by ASL. Quantitatively, the measurements of the most superficial LDF channels agreed strongly with those of ASL, whereas the deeper LDF channels underestimated consistently the ASL measurement. It was thus confirmed that LDF quantifies CBF changes consistently at a superficial level, and for this case the two methods provided concordant measures of functional CBF changes, despite their essentially different physical principles and spatiotemporal characteristics.

  15. Multifractality in the peripheral cardiovascular system from pointwise holder exponents of laser Doppler flowmetry signals.

    PubMed

    Humeau, Anne; Chapeau-Blondeau, François; Rousseau, David; Tartas, Maylis; Fromy, Bérengère; Abraham, Pierre

    2007-12-15

    We study the dynamics of skin laser Doppler flowmetry signals giving a peripheral view of the cardiovascular system. The analysis of Hölder exponents reveals that the experimental signals are weakly multifractal for young healthy subjects at rest. We implement the same analysis on data generated by a standard theoretical model of the cardiovascular system based on nonlinear coupled oscillators with linear couplings and fluctuations. We show that the theoretical model, although it captures basic features of the dynamics, is not complex enough to reflect the multifractal irregularities of microvascular mechanisms.

  16. Acute radiation effects on cutaneous microvasculature: evaluation with a laser Doppler perfusion monitor

    SciTech Connect

    Amols, H.I.; Goffman, T.E.; Komaki, R.; Cox, J.D.

    1988-11-01

    Laser Doppler perfusion monitoring is a noninvasive technique for measuring blood flow in epidermal microvasculature that makes use of the frequency shift of light reflected from red blood cells. Measurements in patients undergoing radiation therapy show increases in blood flow of ten to 25 times baseline at doses above 50 Gy, and increases are observed with doses as low as 2 Gy. Follow-up measurements show rapid decreases in flow levels after completion of therapy, but levels remain elevated even at 1 year.

  17. The application of laser Doppler velocimetry to trailing vortex definition and alleviation

    NASA Technical Reports Server (NTRS)

    Orloff, K. L.; Grant, G. R.

    1973-01-01

    A laser Doppler velocimeter whose focal volume can be rapidly traversed through a flowfield has been used to overcome the problem introduced by excursions of the central vortex filament within a wind tunnel test section. The basic concepts of operation of the instrument are reviewed and data are presented which accurately define the trailing vortex from a square-tipped rectangular wing. Measured axial and tangential velocity distributions are given, both with and without a vortex dissipator panel installed at the wing tip. From the experimental data, circulation and vorticity distributions are obtained and the effect of turbulence injection into the vortex structure is discussed.

  18. Fiber-optic laser-Doppler anemometer microscope applied to the cerebral microcirculation in rats.

    PubMed

    Seki, J; Sasaki, Y; Oyama, T; Yamamoto, J

    1996-01-01

    We have applied our developed fiber-optic laser-Doppler anemometer microscope (FLDAM) for the study of the cerebral microcirculation in the rat. The red cell velocity in single pial microvessels was successfully measured through a closed cranial window for the vessel diameter range from 7.8 to 230 microns. The temporal resolution of the FLDAM was sufficiently high to detect the pulsation in the arterioles. Arterio-venous distributions of the temporal mean red cell velocity and wall shear rate are also described.

  19. Use of a laser doppler vibrometer for high frequency accelerometer characterizations

    SciTech Connect

    Bateman, V.I.; Hansche, B.D.; Solomon, O.M.

    1995-12-31

    A laser doppler vibrometer (LDV) is being used for high frequency characterizations of accelerometers at Sandia National Laboratories (SNL). A LDV with high frequency (up to 1.5 MHz) and high velocity (10 M/s) capability was purchased from a commercial source and has been certified by the Primary Electrical Standards Department at SNL. The method used for this certification and the certification results are presented. Use of the LDV for characterization of accelerometers at high frequencies and of accelerometer sensitivity to cross-axis shocks on a Hopkinson bar apparatus is discussed.

  20. Laser-Doppler vibrating tube densimeter for measurements at high temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Aida, Tsutomu; Yamazaki, Ai; Akutsu, Makoto; Ono, Takumi; Kanno, Akihiro; Hoshina, Taka-aki; Ota, Masaki; Watanabe, Masaru; Sato, Yoshiyuki; Smith, Richard L.; Inomata, Hiroshi

    2007-11-01

    A laser-Doppler vibrometer was used to measure the vibration of a vibrating tube densimeter for measuring P-V-T data at high temperatures and pressures. The apparatus developed allowed the control of the residence time of the sample so that decomposition at high temperatures could be minimized. A function generator and piezoelectric crystal was used to excite the U-shaped tube in one of its normal modes of vibration. Densities of methanol-water mixtures are reported for at 673K and 40MPa with an uncertainty of 0.009g /cm3.

  1. Modal analysis of rotating plate using tracking laser Doppler vibrometer: algorithm modification

    NASA Astrophysics Data System (ADS)

    Khalil, Hossam; Kim, Dongkyu; Nam, Joonsik; Park, Kyihwan

    2015-07-01

    A modified algorithm for tracking laser Doppler vibrometer (TLDV) is introduced to measure the vibration of rotating objects. The proposed algorithm unlike the old algorithm for TLDV can be used when the speed of the object to be tracked varies continuously or alternating in a small range. The proposed algorithm is to use encoder only as a position sensor. The position from the encoder is used to calculate the driving signals to the galvanometers. To verify the proposed method, experimental modal analysis of the circular plate in stationary and rotating cases are made.

  2. Influence of laser coherence on reference-matched laser Doppler velocimetry.

    PubMed

    Beuth, Thorsten; Fox, Maik; Stork, Wilhelm

    2016-03-10

    The probe length is investigated under the influence of the coherence length of Gaussian and Lorentzian spectra for the case that the focal point and the point of highest interference are matched in a strongly focused laser Doppler velocimetry setup (LDV). Isosurfaces of a -3  dB drop of the intensity maximum are estimated and suggested as an alternative, comprehensible way to define probe volumes. In the end, the equations are applied for an exemplary lidar setup to show the reduction of requirements for the coherence length of the laser source in comparison to unmatched cases.

  3. Adaptive Model-Based Mine Detection/Localization using Noisy Laser Doppler Vibration Measurements

    SciTech Connect

    Sullivan, E J; Xiang, N; Candy, J V

    2009-04-06

    The acoustic detection of buried mines is hampered by the fact that at the frequencies required for obtaining useful penetration, the energy is quickly absorbed by the ground. A recent approach which avoids this problem, is to excite the ground with a high-level low frequency sound, which excites low frequency resonances in the mine. These resonances cause a low-level vibration on the surface which can be detected by a Laser Doppler Vibrometer. This paper presents a method of quickly and efficiently detecting these vibrations by sensing a change in the statistics of the signal when the mine is present. Results based on real data are shown.

  4. Incident beam polarization for laser Doppler velocimetry employing a sapphire cylindrical window

    NASA Technical Reports Server (NTRS)

    Lock, J. A.; Schock, H. J.

    1985-01-01

    For laser Doppler velocimetry studies employing sapphire windows as optical access ports, the birefringency of sapphire produces an extra beam intersection volume which serves to effectively smear the acquired velocity flow field data. It is shown that for a cylindrical window geometry, the extra beam intersection volume may be eliminated with minimal decrease in the fringe visibility of the remaining intersection volume by suitably orienting the polarizations of the initial laser beams. For horizontally incident beams, these polarizations were measured at three intersection locations within the cylinder. It was found that the measured polarization angles agreed with the theoretical predictions.

  5. Investigations of fast-rotating bodies using an interferometric laser Doppler distance sensor system

    NASA Astrophysics Data System (ADS)

    Günther, P.; Dreier, F.; Pfister, T.; Czarske, J.; Haupt, T.; Gude, M.; Hufenbach, W.

    2010-05-01

    One challenge in micrometrology is to measure precisely the shape of fast moved objects with high temporal resolution. Deformation measurements of lightweight composite materials are of importance to guarantee its robustness e.g. against impacts. In a high-speed rotor test rig their elastic and plastic deformations due to centrifugal forces can be evaluated. Non-contact inspection techniques with micron resolution under vacuum conditions are necessary. For the first time, we present high-speed deformation measurements of a cylindrical rotor by a non-incremental laser Doppler distance sensor system using fiber and diffractive optics. Besides the determination of the radial enlargement also wobbling of the rotor was monitored.

  6. Frequency stabilisation of multimode helium-neon lasers in laser Doppler flowmetry.

    PubMed

    Deblén, H; Oberg, P A

    1991-09-01

    Low-frequency noise in laser Doppler recordings can be generated because of thermal instabilities in the gas laser cavity. Mode partition noise can be eliminated by thermal stabilisation of the laser cavity. The paper describes a method for closed loop temperature control of the laser cavity. The method uses orthogonal properties of longitudinal laser modes for the temperature control. The signal-to-noise ratio is considerably improved by the procedure. It is recommended that all gas laser equipped Doppler instruments used for precision blood flow studies should be equipped with stabilised laser sources.

  7. The remote measurement of tornado-like flows employing a scanning laser Doppler system

    NASA Technical Reports Server (NTRS)

    Jeffreys, H. B.; Bilbro, J. W.; Dimarzio, C.; Sonnenschein, C.; Toomey, D.

    1977-01-01

    The paper deals with a scanning laser Doppler velocimeter system employed in a test program for measuring naturally occurring tornado-like phenomena, known as dust devils. A description of the system and the test program is followed by a discussion of the data processing techniques and data analysis. The system uses a stable 15-W CO2 laser with the beam expanded and focused by a 12-inch telescope. Range resolution is obtained by focusing the optical system. The velocity of each volume of air (scanned in a horizontal plane) is determined from spectral analysis of the heterodyne signal. Results derived from the measurement program and data/system analyses are examined.

  8. The remote measurement of tornado-like flows employing a scanning laser Doppler system

    NASA Technical Reports Server (NTRS)

    Jeffreys, H. B.; Bilbro, J. W.; Dimarzio, C.; Sonnenschein, C.; Toomey, D.

    1977-01-01

    The paper deals with a scanning laser Doppler velocimeter system employed in a test program for measuring naturally occurring tornado-like phenomena, known as dust devils. A description of the system and the test program is followed by a discussion of the data processing techniques and data analysis. The system uses a stable 15-W CO2 laser with the beam expanded and focused by a 12-inch telescope. Range resolution is obtained by focusing the optical system. The velocity of each volume of air (scanned in a horizontal plane) is determined from spectral analysis of the heterodyne signal. Results derived from the measurement program and data/system analyses are examined.

  9. Geometric bias and time coincidence in 3-dimensional laser Doppler velocimeter systems

    NASA Technical Reports Server (NTRS)

    Brown, J. L.

    1989-01-01

    The measurement by a three-dimensional laser Doppler velocimeter of a turbulent flow has been numerically simulated. Errors associated with the probe volume geometry and the coincidence time window concept are revealed. One type of error occurs for high system data rates when multiple particles lead to system realizations. Another error occurs associated with a geometric bias discovered in the present study. This three-dimensional ldv geometric bias exists even for single-particle realizations and regardless of the system data rate. A technique for the elimination of the geometric bias is presented.

  10. The technology of grating laser Doppler velocimeter for measuring transverse velocity of objects

    NASA Astrophysics Data System (ADS)

    Zhang, Shu; Lu, Guangfeng; Fan, Zhenfang; Luo, Hui

    2014-12-01

    In order to lower production cost of Laser Doppler velocimeter (LDV) and simplify the system structure, a grating Doppler detection system has been designed. This LDV was carried out by differential measurement mode. Two beams of diffracted light from the grating are mixed, and the beat frequency will be detected by a detector when the grating is moving. Fundamentals also have been introduced and partial experiment results of this system are given out. The result indicates the experimental value is agreement with the theoretical value. Errors have been analyzed and the main factors affecting the accuracy were discussed. Upon inspection, the inexpensive and ease LDV is efficient to administer and feasible.

  11. Three interfering beams in laser Doppler velocimetry for particle position and microflow velocity profile measurements.

    PubMed

    Onofri, Fabrice

    2006-05-10

    It is proposed to use three interfering and coplanar laser beams to form the probe volume of laser Doppler systems. This allows us to obtain, for each particle crossing this probe volume, a Doppler signal whose frequency amplitude spectrum exhibits two characteristic peaks. Electromagnetic calculations and experimental validations clearly demonstrate that we can estimate simultaneously, from the analysis of these two frequency peaks, the particle position along the optical axis and one velocity component. This technique is expected to have great potentialities for velocity profile measurements in microfluidic or boundary layer flows, as well as for the sizing of spherical particles.

  12. Full field gas phase velocity measurements in microgravity

    NASA Technical Reports Server (NTRS)

    Griffin, Devon W.; Yanis, William

    1995-01-01

    Measurement of full-field velocities via Particle Imaging Velocimetry (PIV) is common in research efforts involving fluid motion. While such measurements have been successfully performed in the liquid phase in a microgravity environment, gas-phase measurements have been beset by difficulties with seeding and laser strength. A synthesis of techniques developed at NASA LeRC exhibits promise in overcoming these difficulties. Typical implementation of PIV involves forming the light from a pulsed laser into a sheet that is some fraction of a millimeter thick and 50 or more millimeters wide. When a particle enters this sheet during a pulse, light scattered from the particle is recorded by a detector, which may be a film plane or a CCD array. Assuming that the particle remains within the boundaries of the sheet for the second pulse and can be distinguished from neighboring particles, comparison of the two images produces an average velocity vector for the time between the pulses. If the concentration of particles in the sampling volume is sufficiently large but the particles remain discrete, a full field map may be generated.

  13. Full-field acoustomammography using an acousto-optic sensor

    PubMed Central

    Sandhu, J. S.; Schmidt, R. A.; La Rivière, P. J.

    2009-01-01

    In this Letter the authors introduce a wide-field transmission ultrasound approach to breast imaging based on the use of a large area acousto-optic (AO) sensor. Accompanied by a suitable acoustic source, such a detector could be mounted on a traditional mammography system and provide a mammographylike ultrasound projection image of the compressed breast in registration with the x-ray mammogram. The authors call the approach acoustography. The hope is that this additional information could improve the sensitivity and specificity of screening mammography. The AO sensor converts ultrasound directly into a visual image by virtue of the acousto-optic effect of the liquid crystal layer contained in the AO sensor. The image is captured with a digital video camera for processing, analysis, and storage. In this Letter, the authors perform a geometrical resolution analysis and also present images of a multimodality breast phantom imaged with both mammography and acoustography to demonstrate the feasibility of the approach. The geometric resolution analysis suggests that the technique could readily detect tumors of diameter of 3 mm using 8.5 MHz ultrasound, with smaller tumors detectable with higher frequency ultrasound, though depth penetration might then become a limiting factor. The preliminary phantom images show high contrast and compare favorably to digital mammograms of the same phantom. The authors have introduced and established, through phantom imaging, the feasibility of a full-field transmission ultrasound detector for breast imaging based on the use of a large area AO sensor. Of course variations in attenuation of connective, glandular, and fatty tissues will lead to images with more cluttered anatomical background than those of the phantom imaged here. Acoustic coupling to the mammographically compressed breast, particularly at the margins, will also have to be addressed. PMID:19610321

  14. Assesment of gingival microcirculation in anterior teeth using laser Doppler flowmetry

    NASA Astrophysics Data System (ADS)

    Canjau, Silvana; Miron, Mariana I.; Todea, Carmen D.

    2016-03-01

    Introduction: Evaluating the health status of the gingival tissue represents an important objective in the daily practice. Inflammation changes the microcirculatory and micromorphological dynamics of human gingiva. Aim: The purpose of this study was to evaluate the microcirculation in subjects with moderate gingivitis and healthy gingiva by using laser Doppler flowmetry (LDF). Material and Methods: Recordings of the gingival microcirculation (GM) were taken from 20 healthy gingival sites and from 20 sites with moderate gingivitis. The gingival blood flows in the gingivitis group before treatment was significantly different from those in the healthy gingiva group. Signals were recorded with the aid of a laser Doppler MoorLab instrument VMS-LDF2 probe VP3 10 mm S/N 2482. Three consecutive determinations of the GM were registered for each site, as follows: before the initial therapy, at 24 hours after the initial therapy and then, 7 days after the initial therapy. The data were processed using the statistical analysis software SPSS v16.0.1. Results: The results of this preliminary study showed statistically significant differences among the GM values recorded before and after the initial therapy. Conclusions: LDF could be a useful, noninvasive, sensitive, reproducible, and harmless method for measuring gingival blood flow (gingival microcirculation) in humans.

  15. Absolute and dynamic position and shape measurement of fast moving objects employing novel laser Doppler techniques

    NASA Astrophysics Data System (ADS)

    Pfister, Thorsten; Günther, Philipp; Büttner, Lars; Czarske, Jürgen

    2008-09-01

    In this contribution a novel laser Doppler distance (LDD) sensor is presented, which allows simultaneous measurement of axial position and tangential velocity and, thus, determination of the shape of moving and especially rotating objects with one single sensor. Conventional laser Doppler velocimeters measure only velocities. A concurrent position measurement can be realized by generating two fan-shaped interference fringe systems with contrary fringe spacing gradients and evaluating the quotient of the two resulting Doppler frequencies. Alternatively, two tilted fringe systems in combination with phase evaluation can be employed. It will be shown that, in contrast to conventional distance sensors, high temporal resolution below 3 μs and high position resolution of about 1 μm can be achieved simultaneously, because the position uncertainty of the LDD sensor is in principle independent of the object velocity. This is advantageous especially for monitoring highly dynamic processes e.g. at turbo machines, where in-process measurements of tip clearance and rotor vibrations are reported for up to 600 m/s blade tip velocity.

  16. A new single-fibre laser Doppler flowmeter based on digital signal processing.

    PubMed

    Cai, H; Pettersson, H; Rohman, H; Larsson, S E; Oberg, P A

    1996-10-01

    A new laser Doppler flowmeter, based on a personal computer with a digital signal processor for detecting the blood perfusion in skeletal muscle, was designed and evaluated. An infrared laser diode (750 nm) fed a single optical fibre, 400 microns in diameter, which was introduced into the muscle. A PC equipped with a digital processing unit was used for emulation of the laser Doppler algorithm and for presentation of the measurement results. The Doppler signal power spectral density and corresponding flow values were visualized on the computer screen continuously in real-time, and could also be saved on the hard disk for off-line analyses. The graphic-user interface supported by Labwindows software made the system easy to use. It is possible to alter in the software the signal processing and the ways in which the signals and results are presented. The new system was evaluated by using a flow model as well as a mechanical model. The model studies showed linear relationships between particle velocity and flow in the range of 0-5 mm s-1. The system was also tested in measurements of the blood flow in the brachioradial muscle, and was found to have advantages over our previously used systems.

  17. CO2 laser doppler systems for the measurement of atmospheric winds and turbulence

    NASA Technical Reports Server (NTRS)

    Huffaker, R. M.

    1975-01-01

    Two CO2 laser doppler systems developed by NASA and some results obtained with them are discussed. A continuous wave, monostatic system for short-range wind measurement is described, and direct comparisons between the data obtained with it and with a cup-anemometer/wind vane system and a hot-wire anemometer show excellent agreement between the systems. Improvements being made in three CW, CO2 laser doppler systems, including a filter bank for optimized signal processing and a versatile scanning system, are noted. A pulsed CO2 system for measuring clear air turbulence is described, and results of test performance on board a Convair 990 are presented. It is noted that while the system was able to measure air speed and turbulence, the range of its transmitter-atmosphere-receiver was lower than predicted, and a difference of about 20 to 30 dB existed between the actual and theoretical turbulence measurements. Factors that may account for this loss are listed.

  18. Simultaneous measurement of respiration and cardiac period in preterm infants by laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Scalise, Lorenzo; Marchionni, Paolo; Ercoli, Ilaria; Tomasini, Enrico Primo

    2012-06-01

    The paper presents an optical non-contact method for simultaneous measurement of the heart beat and respiration period, based on the assessment of the chest wall movements induced by the pumping action of the heart, and by inspiration/expiration acts of the lungs. The measurement method is applied on 40 patients recovered in a Neonatal Intensive Care Unit (NICU), where the operating conditions are often critical and the contact with the patient's skin needs to be minimized. The method proposed is based on optical recording of the movements of chest wall by means of a laser Doppler vibrometer directly pointed onto the left, frontal part of the thoracic surface. Data measured were compared with reference instrumentation; to reach this goal, the ECG and Laser Doppler Vibrometer (LDV) signals were simultaneously acquired to monitor the heart period (HP), while to measure respiration period (RP) signals from a spirometer and a LDV were collected simultaneously. After LDV signals decomposition, heart and respiration acts were detected and compared in term of beat per minute (bpm). HPs measured by the proposed method showed an uncertainty <6% (respect to ECG), while for RPs data an uncertainty of 3% (respect to spirometer data) was estimated. The proposed method has the intrinsic advantage to be totally without contact and to allow the simultaneous measurement of heart and respiration rate also in critical, clinical environments such as the NICU.

  19. Noninvasive and nonocclusive determination of blood pressure using laser Doppler flowmetry

    NASA Astrophysics Data System (ADS)

    Elter, Peter; Stork, Wilhelm; Mueller-Glaser, Klaus-Dieter; Lutter, Norbert O.

    1999-04-01

    This report describes an approach determining blood pressure noninvasively without cuff. Regarding an elastic, fluid-filled tube as a model of an arterial segment, the solution of the Navier Stokes differential equations delivers a relation between the pressure and velocity pulse. There, simulations prove a minimal sensitivity of blood pressure concerning blood density, blood viscosity and damping. Hence, these parameters can be regarded interindividually as constants. Blood pressure is essentially sensitive on the pulse wave velocity, the velocity pulse, the arterial diameter and the reflection coefficient. To perform measurements, a system was built up comprising at least one laser Doppler blood flow sensor, a high performance DSP hardware and a PC. After individual initial Riva Rocci calibration, arterial diameter and reflection coefficient can be determined. Flow and pulse wave velocity and thus blood pressure can be calculated measuring continuously at least one velocity pulse with the laser Doppler flow sensor at a superficial artery like the a. radialis and simultaneously another cardiovascular signal like an ECG or another flow pulse at a different site of the artery. As a first result, high linear correlations between systolic blood pressure and pulse transit time were obtained.

  20. Evaluation of laser Doppler flowmetry system with fast signal processing using an autoregressive process model

    NASA Astrophysics Data System (ADS)

    Elter, Peter; Stork, Wilhelm; Mueller-Glaser, Klaus-Dieter; Lutter, Norbert O.

    1999-05-01

    This report describes the evaluation of a noninvasive laser Doppler system comprising a sensor, a digital signal processor (DSP) unit and a visualizing PC for continuous blood flow measurements. The first weighted moment of the power spectrum density of the laser Doppler sensor signal is a linear measure for blood flow. In order to estimate the power spectrum densities in real time, a first order autoregressive process model was developed. Due to this very fast signal processing, the system allows measurements both in microcirculation and of higher blood flows in larger vessels with a signal bandwidth of up to 200 kHz, e.g. in superficial arteries. Since the analytical dependency of blood flow and first spectral moment is only valid for tissue perfusion, Monte Carlo simulations were performed to evaluate this dependency also for higher blood flow velocities in larger vessels. A multilayered, semi- infinite tissue model essentially comprising epidermis, dermis and a blood vessel with a parabolic profile of constant blood flow was used varying different parameter like vessel diameter and skin thickness. Furthermore, model measurements were performed using a Delrine slab with a drilling through which constant flow of whole blood was provided. Both the Monte Carlo simulations and model measurements prove very high linear correlations between the calculated spectral moments and flow velocities.

  1. Determining radiated sound power of building structures by means of laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Roozen, N. B.; Labelle, L.; Rychtáriková, M.; Glorieux, C.

    2015-06-01

    This paper introduces a methodology that makes use of laser Doppler vibrometry to assess the acoustic insulation performance of a building element. The sound power radiated by the surface of the element is numerically determined from the vibrational pattern, offering an alternative for classical microphone measurements. Compared to the latter the proposed analysis is not sensitive to room acoustical effects. This allows the proposed methodology to be used at low frequencies, where the standardized microphone based approach suffers from a high uncertainty due to a low acoustic modal density. Standardized measurements as well as laser Doppler vibrometry measurements and computations have been performed on two test panels, a light-weight wall and a gypsum block wall and are compared and discussed in this paper. The proposed methodology offers an adequate solution for the assessment of the acoustic insulation of building elements at low frequencies. This is crucial in the framework of recent proposals of acoustic standards for measurement approaches and single number sound insulation performance ratings to take into account frequencies down to 50 Hz.

  2. Eulerian laser Doppler vibrometry: Online blade damage identification on a multi-blade test rotor

    NASA Astrophysics Data System (ADS)

    Oberholster, A. J.; Heyns, P. S.

    2011-01-01

    Laser Doppler vibrometry enables the telemetry-free measurement of online turbomachinery blade vibration. Specifically, the Eulerian or fixed reference frame implementation of laser vibrometry provides a practical solution to the condition monitoring of rotating blades. The short data samples that are characteristic of this measurement approach do however negate the use of traditional frequency domain signal processing techniques. It is therefore necessary to employ techniques such as time domain analysis and non-harmonic Fourier analysis to obtain useful information from the blade vibration signatures. The latter analysis technique allows the calculation of phase angle trends which can be used as indicators of blade health deterioration, as has been shown in previous work for a single-blade rotor. This article presents the results from tests conducted on a five-blade axial-flow test rotor at different rotor speeds and measurement positions. With the aid of artificial neural networks, it is demonstrated that the parameters obtained from non-harmonic Fourier analysis and time domain signal processing on Eulerian laser Doppler vibrometry signals can successfully be used to identify and quantify blade damage from among healthy blades. It is also shown that the natural frequencies of individual blades can be approximated from the Eulerian signatures recorded during rotor run-up and run-down.

  3. Pilot Study of Laser Doppler Measurement of Flow Variability in the Microcirculation of the Palatal Mucosa

    PubMed Central

    Le Bars, Pierre; Niagha, Gaston; Kouadio, Ayepa Alain; Demoersman, Julien; Roy, Elisabeth; Armengol, Valérie; Soueidan, Assem

    2016-01-01

    Background. Histopathological alterations can arise when the denture-supporting mucosa experiences microbial and mechanical stress through the denture base and diagnosis of these diseases usually follows microvascular changes. Microcirculation measurement could allow for detection of such dysfunction and aid in the early diagnosis of palatal mucosa pathologies. Materials and Methods. We tested the sensitivity of laser Doppler for measuring the microcirculation of the palatal mucosa, assessing the median raphe (MR), Schroeder area (SA), and retroincisive papilla (RP). A Doppler PeriFlux 5000 System, containing a laser diode, was used. 54 healthy participants were recruited. We compare the measurements of PU (perfusion unit) using ANOVA test. Results. The numerical values for palatal mucosa blood flow differed significantly among the anatomical areas (p = 0.0167). The mean value of Schroeder area was 92.6 (SD: 38.4) and was significantly higher than the retroincisive papilla (51.9) (SD: 20.2) (p < 0.05), which in turn was higher than that of median raphe (31.9) (SD: 24.2) (p < 0.0001). Conclusion. Schroeder area appeared to have the greatest sensitivity, and vascular flow variability among individuals was also greatest in this region. We suggest that analysis of blood stream modification with laser Doppler of the palatal mucosa can help to detect onset signs of pathological alterations. PMID:27340663

  4. Medical diagnosis of the cardiovascular system on the carotid artery with IR laser Doppler vibrometer

    NASA Astrophysics Data System (ADS)

    Mignanelli, Laura; Rembe, Christian; Kroschel, Kristian; Luik, Armin; Castellini, Paolo; Scalise, Lorenzo

    2014-05-01

    Laser Doppler Vibrometry (LDV) is known to be a possible diagnosis tool for many cardiac applications as the detection and monitoring of some important vital parameters (Heart Rate, Heart Rate Variability, Pulse Wave Velocity) in a non-contact and non-intrusive way. The technique has become known as Optical Vibrocardiography (VCG) i.e. by measuring the vibrations on the carotid artery or on the thorax [1-5]. The aim of the present study is to interpret the vibrational signal acquired from the carotid artery in relation to the electrocardiographic and hemodynamic aspects and to enable the extraction of further medical information relevant for diagnosis purpose. For the investigation an infrared (IR) Laser Doppler Vibrometer has been used. The acquired VCG signals have been processed and compared with the simultaneously acquired electrocardiogram and the color-coded Doppler sonogram. This has enabled a deeper understanding of the signature of the vibrational signal. Furthermore, in this paper, we also discuss the medical value of the VCG signal obtained from the carotid artery.

  5. New method of laser doppler flowmetry signal processing in pulp vitality evaluation after teeth cosmetic treatment

    NASA Astrophysics Data System (ADS)

    Todea, Carmen; Sarpe, Amalia; Vitez, Bogdan; Draganescu, Gheorghe

    2014-01-01

    The present study aims to assess the pulp vitality before and after different tooth bleaching procedures, in order to determine the changes in pulpal microcirculation and whether they are reversible or not. Twelve volunteers were included in this study. For each volunteer, the pulpal blood flow of maxillary teeth was assessed prior to treatment using Laser Doppler Flowmetry. The "in office" bleaching technique was used 6 anterior teeth, with two different gels, a conventional one chemically activated (Group I 3teeth) and another one activated using Nd:YAG laser (Group II-3 teeth). The bleaching agents were applied on counterpart teeth and, after obtaining a esthetic results for each tooth, the pulpal blood flow was assessed using Laser Doppler Flowmetry immediately after treatment and then after one day and one week. All data were collected and statistically analyzed. Immediately after treatment, the assessment showed an increase of pulpal blood flow, for both study groups, but higher in Group I as compared to Group II (p<0.005). The subsequent assessments showed a reduction of the pulpal blood flow with non - significant differences between the study groups (p<0.005).The results suggest that the tooth bleaching procedurere presents a safe treatment method, which does not lead to irreversible damage to the dental pulp, when used correctly.

  6. Local heating as a predilatation method for measurement of vasoconstrictor responses with laser-Doppler flowmetry.

    PubMed

    Henricson, Joakim; Tesselaar, Erik; Baiat, Yashma; Nilsson, Gert; Sjöberg, Folke

    2011-04-01

    Studying microvascular responses to iontophoresis of vasoconstricting drugs contributes to a better understanding of the regulatory mechanisms of cutaneous vessels, but measuring these responses with laser-Doppler flowmetry at basal blood flow conditions is technically challenging. This study aimed to investigate whether the measurement of cutaneous vasoconstrictor responses to noradrenaline (NA) and phenylephrine (PE), delivered by iontophoresis, is facilitated by predilatation of the microvascular bed using local heating. We used different drug delivery rates (100 s × 0.12 mA, 200 s × 0.06 mA, 300 s × 0.04 mA) to investigate whether predilatation affects the local drug dynamics by an increased removal of drugs from the skin. In a predilatated vascular bed, iontophoresis of NA and PE resulted in a significant decrease in perfusion from the thermal plateau (p < 0.001). The decrease was 25-33%, depending on drug delivery rate. In unheated skin, a significant vasoconstriction was observed (p < 0.001), with 17% and 14% decrease from baseline for NA and PE, respectively. These results indicate that predilatating the cutaneous vascular bed by local heating facilitates measurement of vasoconstriction with laser-Doppler flowmetry and does not seem to significantly affect the result by an increased removal of drugs from the skin.

  7. Fractal Dimension Characterization of in-vivo Laser Doppler Flowmetry signals

    NASA Astrophysics Data System (ADS)

    Srinivasan, Gayathri; Sujatha, N.

    Laser Doppler Blood Flow meter uses tissue backscattered light to non-invasively assess the blood flow rate. qualitatively. As there is large spatial variability and the temporal heterogeneity in tissue microvasculature, the measured blood flow rate is expressed in relative units. A non-linear approach in order to understand the dynamics of the microcirculation led to the fractal characterization of the blood flow signals. The study presented in the paper aims to analyze the fractal behavior of Laser Doppler Flow (LDF) signals and to quantitatively estimate the fractal dimension of waveforms using Box-Counting method. The measured Fractal dimension is an estimate of temporal variability of tissue perfusion. The rate at which fractal dimension varies as a function of location between individuals, exhibits a weak correlation with time. Further studies with a larger number of subjects are necessary to test the generality of the findings and if changes in dimension are reproducible in given individuals. In conclusion, the fractal dimension determined by Box-counting method may be useful for characterizing LDF time series signals. Future experiments evaluating whether the technique can be used to quantify microvascular dysfunction, as commonly occurring in conditions such as Diabetes, Raynaud's phenomenon, Erythromelalgia and Achenbach syndrome needs to be evaluated.

  8. A novel laser doppler linear encoder using multiple-reflection optical design for high-resolution linear actuator.

    SciTech Connect

    Shu, D.

    1998-07-16

    A novel laser Doppler linear encoder system (LDLE) has been developed at the Advanced Photon Source, Argonne National Laboratory. A self-aligning 3-D multiple-reflection optical design was used for the laser Doppler displacement meter (LDDM) to extend the encoder system resolution. The encoder is compact [about 70 mm(H) x 100 mm(W) x 250 mm(L)] and it has sub-Angstrom resolution, 100 mm/sec measuring speed, and 300 mm measuring range. Because the new device affords higher resolution, as compared with commercial laser interferometer systems, and yet cost less, it will have good potential for use in scientific and industrial applications.

  9. Coherent summation of spatially distorted laser Doppler signals by using a two-dimensional heterodyne detector array

    NASA Technical Reports Server (NTRS)

    Chan, Kin P.; Killinger, Dennis K.

    1992-01-01

    Phase-sensitive coherent summation of individual heterodyne detector array signals was demonstrated for the enhanced detection of spatially distorted laser Doppler returns. With the use of a 2 x 2 heterodyne detector array, the phase and amplitude of a time-varying speckle pattern was detected, and the signal-to-noise ratio of the Doppler shift estimate was shown to be improved by a factor of 2, depending on the extent of spatial coherence loss. These results are shown to agree with a first-order analysis and indicate the advantage of coherent summation for both short-range laser Doppler velocimetry and long-range atmospheric coherent lidar.

  10. Full-field optical coherence tomography apply in sphere measurements

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Li, Weiwei; li, Juncheng; Wang, Jingyu; Wang, Jianguo

    2016-10-01

    The geometry of a spherical surface, for example that of a precision optic, is completely determined by the radius -of-curvature at one point and the deviation from the perfect spherical form at all other points of the sphere. Full-field Optical Coherence Tomography (FF-OCT) is a parallel detection OCT technique that utilizes a 2D detector array. This technique avoids mechanical scanning in imaging optics, thereby speeding up the imaging process and enhancing the quality of images. The current paper presents an FF-OCT instrument that is designed to be used in sphere measurement with the principle of multiple delays (MD) OCT to evaluate the curvature and radius of curved objects in single-shot imaging. The optimum combination of the MD principle with the FF-OCT method was evaluated, and the radius of a metal ball was measured with this method. The generated 2n-1 contour lines were obtained by using an MDE with n delays in a single en-face OCT image. This method of measurement, it engaged in the measurement accuracy of spherical and enriches the means of measurement, to make a spherical scan techniques flexible application.

  11. Full-field inspection of three-dimensional structures using steady-state acoustic wavenumber spectroscopy

    NASA Astrophysics Data System (ADS)

    Koskelo, Elise Anne C.; Flynn, Eric B.

    2017-02-01

    Inspection of and around joints, beams, and other three-dimensional structures is integral to practical nondestructive evaluation of large structures. Non-contact, scanning laser ultrasound techniques offer an automated means of physically accessing these regions. However, to realize the benefits of laser-scanning techniques, simultaneous inspection of multiple surfaces at different orientations to the scanner must not significantly degrade the signal level nor diminish the ability to distinguish defects from healthy geometric features. In this study, we evaluated the implementation of acoustic wavenumber spectroscopy for inspecting metal joints and crossbeams from interior angles. With this technique, we used a single-tone, steady-state, ultrasonic excitation to excite the joints via a single transducer attached to one surface. We then measured the full-field velocity responses using a scanning Laser Doppler vibrometer and produced maps of local wavenumber estimates. With the high signal level associated with steady-state excitation, scans could be performed at surface orientations of up to 45 degrees. We applied camera perspective projection transformations to remove the distortion in the scans due to a known projection angle, leading to a significant improvement in the local estimates of wavenumber. Projection leads to asymmetrical distortion in the wavenumber in one direction, making it possible to estimate view angle even when neither it nor the nominal wavenumber is known. Since plate thinning produces a purely symmetric increase in wavenumber, it also possible to independently estimate the degree of hidden corrosion. With a two-surface joint, using the wavenumber estimate maps, we were able to automatically calculate the orthographic projection component of each angled surface in the scan area.

  12. Quantification of the Blood Platelet Reactivity in the ADP-Induced Model of Non-Lethal Pulmonary Thromboembolism in Mice with the Use of Laser Doppler Flowmetry

    PubMed Central

    Przygodzki, Tomasz; Talar, Marcin; Blazejczyk, Agnieszka; Kalchenko, Vyacheslav; Watala, Cezary

    2016-01-01

    Introduction The paper describes an alternative method for quantification of in vivo ADP-induced thromboembolism. The aim of the studies was to develop a method of quantification which would not require either extravasation or labelling of platelets. Our proposed approach is based on the monitoring of changes of blood flow with the use of laser Doppler flowmetry. Materials and Methods Mice of C57Bl strain were used in the study. ADP was injected to the vena cava and blood flow was monitored with the use of a laser Doppler flowmeter in the mesentery. Measurements in platelet-depleted mice, mice pretreated with cangrelor, an ADP receptor antagonist, and eptifibatide, a blocker of fibrinogen binding to GPIIbIIIa, were conducted as the proof-of-concept in the performed experiments. Intravital microscopy and ex vivo imaging of organs was performed to identify the sites of aggregate formation resulting from ADP injection. Results The injection of ADP resulted in a dose-dependent reduction of the blood flow in the mesentery. These responses were fully attributable to blood platelet aggregation, as shown by the lack of the effect in platelet-depleted mice, and significantly reduced responses in mice pretreated with cangrelor and eptifibatide. No platelet aggregate formation in mesenteric vessels was revealed by intravital microscopy, while ex vivo imaging showed accumulation of fluorescent labelled platelets in the lung. Conclusions Injection of ADP to the venous system results in the formation of platelet aggregates predominantly in the lung. This results in reversible blood flow cessation in peripheral blood vessels. The measurement of this blood flow cessation in the mesentery allows indirect measurement of ADP-induced pulmonary thromboembolism. We suggest that this approach can be useful for in vivo screening for antiplatelet drug candidates. PMID:26751810

  13. Advantages of gridless full-field digital mammography

    NASA Astrophysics Data System (ADS)

    Nykanen, Kirsi; Siltanen, Samuli

    2003-06-01

    The purpose of the study was to find out whether the image quality in full-field digital mammography can be improved while lowering the patient dose by removing the anti-scatter grid. Moreover, a fast approximate computational algorithm was developed for determining the scattered field in a real mammogram. The method is non-iterative, robust against noise, and works without modification for any scatter-to-primary ratio. Furthermore, it is computationally effective since it is based on fast Fourier transform (FFT). It was found out that the wide dynamic range of digital detectors leads to decrease in patient dose from 10.9% up to 46.6% at breast thickness of 2cm and from 0.8% up to 40.8% at breast thickness of 4cm depending on the efficiency of the removed grid. At constant patient dose the increase in contrast-to-noise ratio is 5.8% - 36.9% and 0.4%-30.0% accordingly at those two breast thickness. The convolution-based X-ray scatter model was considered. The developed scatter removal method was demonstrated with simulated mammograms and applied to clinical full-field digital mammograms acquired with a high-end digital flat panel detector based on amorphous selenium. Errors in reconstructed scattered fields were 0.3% in case of an ideal simulated mammogram and 7.4% in case of a real simulated mammogram (3cm breast). Applications where the scattered field needs to be determined include 3-D mammography and dual-energy breast imaging. In screening mammography gray-scale optimization eliminates the effect of scattering.

  14. Laser-Doppler flowmetry. A review of its application for measuring cerebral and spinal cord blood flow.

    PubMed

    Frerichs, K U; Feuerstein, G Z

    1990-01-01

    Laser-Doppler flowmetry is a new technique for noninvasive and continuous measurement of local microcirculatory cerebral and spinal-cord blood flow. The flow estimate by this technique is based on the assessment of the Doppler shift of low-power laser light, which is scattered by moving red blood cells. Laser-Doppler flowmetry has been validated for various organs, including the central nervous system. These studies revealed a linear relationship between relative changes of the Doppler signal and blood flow over a wide range of pharmacological as well as pathological flow alterations, including cerebral ischemia. The usefulness of laser-Doppler flowmetry in experimental as well as clinical applications has received growing attention. The superiority of the technique lies in its high spatial and temporal resolution. Disadvantages are the difficulty of obtaining absolute flow values and the sensitivity to artifacts. The versatility and on-line capacity of laser-Doppler flowmetry might allow new insights into the pathophysiology of alterations of the cerebral and spinal-cord microcirculation.

  15. Volumetric breast density estimation from full-field digital mammograms.

    PubMed

    van Engeland, Saskia; Snoeren, Peter R; Huisman, Henkjan; Boetes, Carla; Karssemeijer, Nico

    2006-03-01

    A method is presented for estimation of dense breast tissue volume from mammograms obtained with full-field digital mammography (FFDM). The thickness of dense tissue mapping to a pixel is determined by using a physical model of image acquisition. This model is based on the assumption that the breast is composed of two types of tissue, fat and parenchyma. Effective linear attenuation coefficients of these tissues are derived from empirical data as a function of tube voltage (kVp), anode material, filtration, and compressed breast thickness. By employing these, tissue composition at a given pixel is computed after performing breast thickness compensation, using a reference value for fatty tissue determined by the maximum pixel value in the breast tissue projection. Validation has been performed using 22 FFDM cases acquired with a GE Senographe 2000D by comparing the volume estimates with volumes obtained by semi-automatic segmentation of breast magnetic resonance imaging (MRI) data. The correlation between MRI and mammography volumes was 0.94 on a per image basis and 0.97 on a per patient basis. Using the dense tissue volumes from MRI data as the gold standard, the average relative error of the volume estimates was 13.6%.

  16. Technology evaluation center assessment synopsis: full-field digital mammography.

    PubMed

    Rothenberg, Barbara M; Ziegler, Kathleen M; Aronson, Naomi

    2006-08-01

    Full-field digital mammography (FFDM) is proposed as an alternative to screen-film mammography (SFM). The ability to separate and optimize the acquisition, storage, and display of images may allow greater visualization of breast cancers at equal or lower radiation doses, especially in younger women and those with denser breasts. This is a synopsis of a systematic review by the Blue Cross Blue Shield Association Technology Evaluation Center. This updated systematic review primarily incorporated the results of the ACR Imaging Network(R) Digital Mammographic Imaging Screening Trial (DMIST), which provided results on 42,760 asymptomatic women who underwent both FFDM and SFM and showed with reasonable certainty that there was no difference in the accuracy of the 2 modalities for asymptomatic women in general, with some advantages of FFDM in certain subgroups. There were no strong, new studies on the use of digital mammography compared with film mammography in a diagnostic population. However, the DMIST results indicated that tumors detected by FFDM, but not by SFM, were likely to be invasive carcinomas or medium-grade to high-grade ductal carcinoma in situ. On the basis of the suppositions that these are the cancers of greatest interest and the ones more likely to be found in a diagnostic population and that the diagnostic population may be younger on average than the screening population, it was concluded that there is sufficient evidence to support the use of FFDM for diagnostic purposes.

  17. An endoscopic laser Doppler flowmetry of a gastroduodenal mucosa at bleeding ulcer

    NASA Astrophysics Data System (ADS)

    Shapkin, U. G.; Kapralov, C. V.; Gogolev, A. A.; Lychagov, V. V.; Tuchin, V. V.

    2006-08-01

    One of the important problems of a bleeding gastroduodenal ulcer surgery is a prognosis of the recurrent hemorrhage and appraisal of endoscopic hemostasis quality. Endoscopic Laser Doppler Flowmetry of a mucous coat of stomach and a duodenum was made on 34 patients for the purpose of investigation of features of microcirculation. Analogous researches are made on 30 patients with a peptic ulcer and on 28 practically healthy people. Analysis of LDF-grams has shown certain differences in regional microcirculations in stomach and duodenal at normal and at a pathology. Increase of regional perfusion in periulcerose zone with its pathology disbalance can serve as a criterion for activities of an alteration processes in gastroduodenal ulcer defining the risk of possible hemorrhage.

  18. A 3-component laser-Doppler velocimeter data acquisition and reduction system

    NASA Technical Reports Server (NTRS)

    Rodman, L. C.; Bell, J. H.; Mehta, R. D.

    1985-01-01

    A laser doppler velocimeter capable of measuring all three components of velocity simultaneously in low-speed flows is described. All the mean velocities, Reynolds stresses, and higher-order products can be evaluated. The approach followed is to split one of the two colors used in a 2-D system, thus creating a third set of beams which is then focused in the flow from an off-axis direction. The third velocity component is computed from the known geometry of the system. The laser optical hardware and the data acquisition electronics are described in detail. In addition, full operating procedures and listings of the software (written in BASIC and ASSEMBLY languages) are also included. Some typical measurements obtained with this system in a vortex/mixing layer interaction are presented and compared directly to those obtained with a cross-wire system.

  19. A 3-component laser-Doppler velocimeter data acquisition and reduction system

    NASA Technical Reports Server (NTRS)

    Rodman, L. C.; Bell, J. H.; Mehta, R. D.

    1986-01-01

    This report describes a laser Doppler velocimeter capable of measuring all three components of velocity simultaneously in low-speed flows. All the mean velocities, Reynolds stresses, and higher-order products can then be evaluated. The approach followed is to split one of the colors used in a 2-D system, thus creating a third set of beams which is then focused in the flow from an off-axis direction. The third velocity component is computed from the known geometry of the system. In this report, the laser optical hardware and the data acquisition electronics are described in detail. In addition, full operating procedures and listings of the software (written in BASIC and assembly languages) are also included. Some typical measurements obtained with this system in a vortex/mixing layer interaction are presented and compared directly to those obtained with a cross-wire system.

  20. Nonmechanical scanning laser Doppler velocimeter for cross-sectional two-dimensional velocity measurement.

    PubMed

    Maru, Koichi; Hata, Takahiro

    2012-12-01

    We propose a two-dimensional scanning laser Doppler velocimeter (LDV) that does not require any moving mechanisms in its probe. In the proposed LDV, the measurement position can be scanned in two dimensions on a cross-sectional plane perpendicular to the direction of flow. The combination of the change in wavelength and change in port of the fiber array input to the probe is utilized for the scan. The experimental results using a sensor probe setup indicate that the measurement position can be scanned in two dimensions using the proposed method. The scanning range was estimated to be 39.7 mm in the axial direction over the wavelength range of 1536-1554 nm and 26.1 mm in the transverse direction for the use of 22 ports of the fiber array.

  1. Scanning laser Doppler Technique for velocity profile sensing on a moving surface.

    PubMed

    Sriram, P; Hanagud, S; Craig, J; Komerath, N M

    1990-06-01

    A scanning laser Doppler technique based on Chebyshev demodulation has been developed for the rapid measurement of spatially distributed velocity profiles. Scan frequencies up to 100 Hz can be used over scan lengths up to 270 mm. The Doppler signals are processed in the conventional manner using a frequency counter. The analog velocity output from the counter is post-processed to obtain the velocity profile. The Chebyshev demodulation post-processing technique for processing the velocity signals from solid surfaces has been introduced. The data processing technique directly yields the spatial velocity distribution in approximate functional form through frequency domain analysis of the scanning LDV velocity output. Results from a rotating disk setup are presented to illustrate the concept.

  2. Composite Characterization Using Laser Doppler Vibrometry and Multi-Frequency Wavenumber Analysis

    NASA Technical Reports Server (NTRS)

    Juarez, Peter; Leckey, Cara

    2015-01-01

    NASA has recognized the need for better characterization of composite materials to support advances in aeronautics and the next generation of space exploration vehicles. An area of related research is the evaluation of impact induced delaminations. Presented is a non-contact method of measuring the ply depth of impact delamination damage in a composite through use of a Scanning Laser Doppler Vibrometer (SLDV), multi-frequency wavenumber analysis, and a wavenumber-ply correlation algorithm. A single acquisition of a chirp excited lamb wavefield in an impacted composite is post-processed into a numerous single frequency excitation wavefields through a deconvolution process. A spatially windowed wavenumber analysis then extracts local wavenumbers from the wavefield, which are then correlated to theoretical dispersion curves for ply depth determination. SLDV based methods to characterize as-manufactured composite variation using wavefield analysis will also be discussed.

  3. Laser Doppler velocimeter measurement in the tip region of a compressor rotor

    NASA Technical Reports Server (NTRS)

    Murthy, K. N. S.; Lakshminarayana, B.

    1984-01-01

    The axial and tangential velocity components near the tip region of a compressor rotor were measured by a laser Doppler velocimeter. The measurements were taken at 25 radial locations in the outer twenty percent of the blade span and at 10 axial locations upstream, inside and at the exit of the rotor. The results are interpreted to derive the behavior of the leakage flow, annulus wall boundary layer growth, inviscid effects and the rotor wake decay characteristics in the tip region. The inviscid and annulus wall boundary layer effects dominate up to quarter chord, beyond which the leakage phenomena has a major influence in altering the flow characteristics in the outer ten percent of the blade span. The annulus wall boundary layer undergoes drastic change through the passage. The velocity field measured near the leading edge reveals the effects of rapid acceleration near the suction surface and the stagnation point on the pressure surface.

  4. Evaluation of blood microcirculation parameters by combined use of laser Doppler flowmetry and videocapillaroscopy methods

    NASA Astrophysics Data System (ADS)

    Volkov, M. V.; Kostrova, D. A.; Margaryants, N. B.; Gurov, I. P.; Erofeev, N. P.; Dremin, V. V.; Zharkikh, E. V.; Zherebtsov, E. A.; Kozlov, I. O.; Dunaev, A. V.

    2017-03-01

    Laser Doppler flowmetry (LDF) is widely used for diagnosing blood microcirculation diseases. It is well known that the Doppler shift of laser radiation scattered by moving red blood cells (RBC) can be assessed through analyzing photocurrent produced by a photodetector. LDF signal contains information about regulating blood flow rhythms: myogenic, cardiac, nervous and endothelial. The method of videocapillaroscopy (VCS) allows local capillary blood flow velocity evaluation and, using video data processing algorithms, is able to assess RBC velocity changes into capillary. We present the results of simultaneous investigations of changes in tissue perfusion of the distal phalanx of human finger by the LDF as well as changes in capillary blood flow velocity in the nail bed evaluated by the VCS method during arterial occlusion test. The experimental results confirmed the correspondence between blood perfusion and blood flow velocity.

  5. Laser Doppler velocimetry based on the optoacoustic effect in a RF-excited CO2 laser.

    PubMed

    Lee, Teaghee; Choi, Jong Woon; Kim, Yong Pyung

    2012-09-01

    We present a compact optoacoustic laser Doppler velocimetry method that utilizes the self-mixing effect in a RF-excited CO(2) laser. A portion of a Doppler-shifted laser beam, produced by irradiating a single wavelength laser beam on a moving object, is mixed with an originally existing laser beam inside a laser cavity. The fine change of pressure in the laser cavity modulated by the Doppler-shifted frequency is detected by a condenser microphone in the laser tube. In our studies, the frequency of the Doppler signal due to the optoacoustic effect was detected as high as 50 kHz. Our measurements also confirmed that the signal varied linearly with the velocity of the external scatterer (the moving object) and the cosine of the angle between the laser beam and the velocity vector of the object.

  6. An experimental study of a three-dimensional thrust augmenting ejector using laser Doppler velocimetry

    NASA Technical Reports Server (NTRS)

    Storms, Bruce Lowell

    1989-01-01

    Flow field measurements were obtained in a three-dimensional thrust augmenting ejector using laser Doppler velocimetry and hot wire anemometry. The primary nozzle, segmented into twelve slots of aspect ratio 3.0, was tested at a pressure ratio of 1.15. Results are presented on the mean velocity, turbulence intensity, and Reynolds stress progressions in the mixing chamber of the constant area ejector. The segmented nozzle was found to produce streamwise vortices that may increase the mixing efficiency of the ejector flow field. Compared to free jet results, the jet development is reduced by the presence of the ejector walls. The resulting thrust augmentation ratio of this ejector was also calculated to be 1.34.

  7. Application of a single laser Doppler system to the measurement of atmospheric winds

    NASA Technical Reports Server (NTRS)

    Cliff, W. C.; Huffaker, R. M.

    1974-01-01

    The feasibility of employing a single laser Doppler velocimeter (LDV) system to remotely measure one-, two-, and three-dimensional velocity components in atmospheric flow fields is presented. A focused continuous wave CO2 laser emitting at the 10.6 mu wavelength is used as the laser source. Scan configurations employed by the LDV system were single-point, two-point, conical, and spiral conical. Test results are presented, which include favorable comparisons of velocity components measured by conventional anemometry and the LDV system. The feasibility using a single-beam LDV employing a conical scan technique for measuring two- and three-dimensional mean winds. Measurements to 300 m in dense fogs showed the ability of the LDV system to operate in dense fogs.

  8. Quantitative measurement of blood flow dynamics in chorioallantoic membrane of chicken embryo using laser Doppler anemometry

    NASA Astrophysics Data System (ADS)

    Borozdova, M. A.; Stiukhina, E. S.; Sdobnov, A. A.; Fedosov, I. V.; Postnov, D. E.; Tuchin, V. V.

    2016-04-01

    We report the results on in ovo application of developed Laser Doppler Anemometer (LDA) device. The chorioallantoic membrane (CAM) of 9-13 days chicken embryos was used as a biological model that allows an easy access to both arterial and venous vessels of different size. The key point of our study was to find out how the periodic and aperiodic pulsations of blood flow (which are inevitable in living organism) will affect the LDA functions and measuring capability. Specifically, we (i) developed the technique to extract and refine the pulse rhythm from the signal received from a vessel, and (ii) analyzed the changes in power spectra of LDA signal that are caused by heart beating and considerably complicate the reliable measurement of Doppler shift. Our main conclusion is that the algorithm of LDA data processing need to be improved, and this possibly can be done by counting the information on current phase of cardiac cycle.

  9. Endoscopic laser Doppler flowmetry in the experiment and in the bleeding gastric and duodenal ulcer clinic

    NASA Astrophysics Data System (ADS)

    Kapralov, S. V.; Shapkin, Y. G.; Lychagov, V. V.; Tuchin, V. V.

    2007-05-01

    One of the most complex problems of emergency surgery is the choice of surgical tactics to deal with bleeding peptic ulcer. Endoscopic hemostasis is prescribed to patients with continuing bleedings and prerelapse syndrome. But till nowdays the objective verification of the prerelapse condition had not been worked out. What is more there are no objective criteria to judge the effectiveness of the carried endohemostasis. The aim of the study was to work out a new objective diagnostic method of pre-recurrence syndrome that can be able to make prognosis for possible gastroduodenal ulcer bleeding recurrence more precise. Laser Doppler flowmetry was the method of studies the regional perfusion. The device used in this work was made at the Optics and Biophysics Department of Saratov State University.

  10. Combined use of laser Doppler flowmetry and skin thermometry for functional diagnostics of intradermal finger vessels

    NASA Astrophysics Data System (ADS)

    Zherebtsov, Evgeny A.; Zherebtsova, Angelina I.; Doronin, Alexander; Dunaev, Andrey V.; Podmasteryev, Konstantin V.; Bykov, Alexander; Meglinski, Igor

    2017-04-01

    We introduce a noninvasive diagnostic approach for functional monitoring of blood microflows in capillaries and thermoregulatory vessels within the skin. The measuring system is based on the combined use of laser Doppler flowmetry and skin contact thermometry. The obtained results suggest that monitoring of blood microcirculation during the occlusion, performed in conjunction with the skin temperature measurements in the thermally stabilized medium, has a great potential for quantitative assessment of angiospatic dysfunctions of the peripheral blood vessels. The indices of blood flow reserve and temperature response were measured and used as the primarily parameters of the functional diagnostics of the peripheral vessels of skin. Utilizing these parameters, a simple phenomenological model has been suggested to identify patients with angiospastic violations in the vascular system.

  11. An experimental investigation of an axisymmetric jet in a coflowing airstream. [using laser Doppler velocimeter

    NASA Technical Reports Server (NTRS)

    Catalano, G. D.; Morton, J. B.; Humphris, R. R.

    1976-01-01

    The flow development of an axisymmetric jet exhausting into a moving airstream has been studied. The jet has a Reynolds number of 22,600, and the ratio of the jet velocity to the wind tunnel velocity is 5.1 to 1. The flow field of the axisymmetric jet was examined at locations varying from approximately zero to eight diameters downstream of the orifice. Of primary concern at each downstream location was the mapping of the one point statistical properties of the flow, including mean velocity, turbulent intensity, and intermittency. Autocorrelations and power spectral density curves were determined for both the fluctuating velocity field and the concentration signal at various distances from the jet's center line for different downstream locations. A laser Doppler velocimeter, using a phase locked loop processor, was used to make the desired velocity field measurements which were compared with hot wire anemometer and pressure probe data.

  12. Development of a new laser Doppler velocimeter for the Ames High Reynolds Channel No. 2

    NASA Technical Reports Server (NTRS)

    Seegmiller, H. L.; Bader, J. B.; Cooney, J. P.; Deyoung, A.; Donaldson, R. W., Jr.; Gunter, W. D., Jr.; Harrison, D. R.

    1985-01-01

    A new two-channel laser Doppler velocimeter developed for the Ames High Reynolds Channel No. 2 is described. Design features required for the satisfactory operation of the optical system in the channel environment are discussed. Fiber optics are used to transmit the megahertz Doppler signal to the photodetectors located outside the channel pressure vessel, and provision is made to isolate the optical system from pressure and thermal strain effects. Computer-controlled scanning mirrors are used to position the laser beams in the channel flow. Techniques used to seed the flow with 0.5-micron-diam polystyrene spheres avoiding deposition on the test-section windows and porous boundary-layer removal panels are described. Preliminary results are presented with a discussion of several of the factors affecting accuracy.

  13. Development of a new laser Doppler velocimeter for the Ames High Reynolds Channel No. II

    NASA Technical Reports Server (NTRS)

    Seegmiller, H. L.; Bader, J. B.; Cooney, J. P.; De Young, A.; Donaldson, R. W., Jr.

    1985-01-01

    A new two-channel laser Doppler velocimeter developed for the Ames High Reynolds Channel No. 2 is described. Design features required for the satisfactory operation of the optical system in the channel environment are discussed. Fiber optics are used to transmit the megahertz Doppler signal to the photodetectors located outside the channel pressure vessel, and provision is made to isolate the optical system from pressure and thermal strain effects. Computer-controlled scanning mirrors are used to position the laser beams in the channel flow. Techniques used to seed the flow with 0.5-micron-diam polystyrene spheres avoiding deposition on the test-section windows and porous boundary-layer removal panels are described. Preliminary results are presented with a discussion of several of the factors affecting accuracy.

  14. Laser Doppler velocimetry for continuous flow solar-pumped iodine laser system

    NASA Technical Reports Server (NTRS)

    Tabibi, Bagher M.; Lee, Ja H.

    1991-01-01

    A laser Doppler velocimetry (LDV) system was employed to measure the flow velocity profile of iodide vapor inside laser tubes of 36 mm ID and 20 mm ID. The LDV, which was operated in the forward scatter mode used a low power (15 mW) He-Ne laser beam. Velocity ranges from 1 m/s was measured to within one percent accuracy. The flow velocity profile across the laser tube was measured and the intensity of turbulence was determined. The flow of iodide inside the laser tube demonstrated a mixture of both turbulence and laminar flow. The flowmeter used for the laser system previously was calibrated with the LDV and found to be in good agreement.

  15. Pseudo-backscatter laser Doppler velocimeter employing antiparallel-reflector in the forward direction

    NASA Technical Reports Server (NTRS)

    Gunter, W. D., Jr. (Inventor)

    1977-01-01

    A laser Doppler velocimeter for measuring the velocity of a flowing fluid was discussed. It comprises laser means for providing first and second beams of collimated coherent monochromatic electromagnetic radiation which are focused to intersect at a predetermined location in a flowing fluid. The movement of the particles of the fluid serve to scatter radiation in substantially all directions. The scattered radiation is shifted in frequency from that of the first beam by an amount corresponding to the velocity of the fluid at the predetermined location. A corner cube is disposed generally forward of the predetermined location, the corner cube responding to a portion of the radiation scattered in the forward direction and being operative to reflect the portion in a direction substantially antiparallel to the forward direction.

  16. The Use of a Laser Doppler Velocimeter in a Standard Flammability Tube

    NASA Technical Reports Server (NTRS)

    Strehlow, R. A.; Flynn, E. M.

    1985-01-01

    The use of the Laser Doppler Velocimeter, (LDV), to measure the flow associated with the passage of a flame through a standard flammability limit tube (SFLT) was studied. Four major results are presented: (1) it is shown that by using standard ray tracing calculations, the displacement of the LDV volume and the fringe rotation within the experimental error of measurement can be predicted; (2) the flow velocity vector field associated with passage of an upward propagating flame in an SFLT is determined; (3) it is determined that the use of a light interruption technique to track particles is not feasible; and (4) it is shown that a 25 mW laser is adequate for LDV measurements in the Shuttle or Spacelab.

  17. Comparative analysis of the performance of laser Doppler systems using maximum likelihood and phase increment methods

    NASA Astrophysics Data System (ADS)

    Sobolev, V. S.; Zhuravel', F. A.; Kashcheeva, G. A.

    2016-11-01

    This paper presents a comparative analysis of the errors of two alternative methods of estimating the central frequency of signals of laser Doppler systems, one of which is based on the maximum likelihood criterion and the other on the so-called pulse-pair technique. Using computer simulation, the standard deviations of the Doppler signal frequency from its true values are determined for both methods and plots of the ratios of these deviations as a measure of the accuracy gain of one of them are constructed. The results can be used by developers of appropriate systems to choose an optimal algorithm of signal processing based on a compromise between the accuracy and speed of the systems as well as the labor intensity of calculations.

  18. A laser Doppler velocimeter approach for near-wall three-dimensional turbulence measurements

    NASA Technical Reports Server (NTRS)

    Johnson, D. A.; Brown, J. D.

    1990-01-01

    A near-wall laser Doppler velocimeter approach is described that relies on a beam-turning probe which makes possible the direct measurement of the crossflow velocity at a grazing incident and the placement of optical components close to the flow region of interest regardless of test facility size. Other important elements of the approach are the use of digital frequency processing, an optically smooth measurement surface, and observation of the sensing volume at 90 degrees. The combination was found to dramatically reduce noise-in-signal effects caused by surface light scattering. Turbulent boundary-layer data to within 20 microns (y(sup+) approximately equal to 1) of the surface are presented which illustrate the potential of the approach.

  19. Laser Doppler anemometry measurements in the near-wake of an isolated Formula One wheel

    NASA Astrophysics Data System (ADS)

    Saddington, A. J.; Knowles, R. D.; Knowles, K.

    2007-05-01

    An experimental investigation was conducted to identify the main structures in the near wake of an isolated Formula One wheel rotating in ground contact. A 50 percent-scale isolated wheel assembly, geometrically similar to the configuration mounted on a Formula One racing car, was tested in a closed-return three-quarter open-jet wind tunnel. The test Reynolds number, based on wheel diameter was 6.8 × 105. Using laser doppler anemometry, three velocity components were measured with a total of 1966 data points across four planes and within one diameter downstream of the wheel axis. Based on analysis of these data, the main characteristics of the near-wake of an isolated wheel rotating in ground contact are presented. A revised model of the trailing vortex system induced in the wake of such a wheel is proposed, which clarifies the contradictory ones published in the literature to date.

  20. Ambient cold air decreased nasal mucosa blood flow measured by laser Doppler flowmeter.

    PubMed

    Chu, Yueng-Hsiang; Lu, Da-Wen; Wang, Hsing-Won

    2010-06-01

    With its potentially conflicting physiological roles of both air-conditioning and body-heat recovery, the response of nasal mucosa blood flow (NMBF) to ambient cold air is not well understood. To evaluate the NMBF in response to cold ambient air. The NMBF was continuously measured by laser Doppler flowmetry in nine participants exposed to different air temperatures (24 degrees C and 4 degrees C). The NMBF significantly decreased at 4 degrees C compared with that at 24 degrees C (p < 0.01). The response to ambient cold air in the nasal microcirculation is similar to that of the body-surface blood vessels, suggesting that body-heat recovery rather than air-conditioning is the predominant function.

  1. Taking laser Doppler vibrometry off the tripod: correction of measurements affected by instrument vibration

    NASA Astrophysics Data System (ADS)

    Halkon, Ben J.; Rothberg, Steve J.

    2017-04-01

    Laser Doppler vibrometers (LDVs) are now well-established as an effective non-contact alternative to traditional contacting transducers. Despite 30 years of successful applications, however, very little attention has been given to sensitivity to vibration of the instrument itself. In this paper, the sensitivity to instrument vibration is confirmed before development theoretically and experimentally of a practical scheme to enable correction of measurements for arbitrary instrument vibration. The scheme requires a pair of correction sensors with appropriate orientation and relative location, while using frequency domain processing to accommodate inter-channel time delay and signal integrations. Error reductions in excess of 30 dB are delivered in laboratory tests with simultaneous instrument and target vibration over a broad frequency range. Ultimately, application to measurement on a vehicle simulator experiencing high levels of vibration demonstrates the practical nature of the correction technique and its robustness in a challenging measurement environment.

  2. Perfusion assessment in rat spinal cord tissue using photoplethysmography and laser Doppler flux measurements

    NASA Astrophysics Data System (ADS)

    Phillips, Justin P.; Cibert-Goton, Vincent; Langford, Richard M.; Shortland, Peter J.

    2013-03-01

    Animal models are widely used to investigate the pathological mechanisms of spinal cord injury (SCI), most commonly in rats. It is well known that compromised blood flow caused by mechanical disruption of the vasculature can produce irreversible damage and cell death in hypoperfused tissue regions and spinal cord tissue is particularly susceptible to such damage. A fiberoptic photoplethysmography (PPG) probe and instrumentation system were used to investigate the practical considerations of making measurements from rat spinal cord and to assess its suitability for use in SCI models. Experiments to assess the regional perfusion of exposed spinal cord in anesthetized adult rats using both PPG and laser Doppler flowmetry (LDF) were performed. It was found that signals could be obtained reliably from all subjects, although considerable intersite and intersubject variability was seen in the PPG signal amplitude compared to LDF. We present results from 30 measurements in five subjects, the two methods are compared, and practical application to SCI animal models is discussed.

  3. Laser-doppler examination shows high flow in some common telangiectasias of the lower limb.

    PubMed

    Bihari, Imre; Muranyi, Aniko; Bihari, Péter

    2005-04-01

    The accepted pathophysiology of telangiectasias is reflux from superficial or deep veins. There are physical signs and scientific findings that do not fit this theory but support the possibility of arteriovenous (AV) shunt origin. If there is a higher flow in spider veins than in the surrounding skin, it means that AV shunts participate in the circulation of the telangiectasia. On the other hand, slow flow indicates reflux as the etiologic factor. Telangiectasias and the surrounding skin of 22 legs of 19 patients were examined with laser-Doppler equipment. The probe over the spider vein found a higher flow value (average 28.2 perfusion units [PU]) than in the surrounding skin (15.6 PU) in 13 limbs, but it was significantly higher only in 5 cases. In 9 limbs, the flow was slower. We interpret the higher flow values as a consequence of open AV shunts. This means that AV shunt pathophysiology was present in some of our cases.

  4. Two-Dimensional Measurement of Rotational Speed of a Diffuse Object Based on Laser Doppler Anemometry

    NASA Astrophysics Data System (ADS)

    Omori, Ryota; Mita, Go; Kawasaki, Naoki; Suzuki, Atsuyuki

    1998-04-01

    A novel measurement method based on laser Doppler anemometry that determines the pure rotational speed of a diffuse object on the condition that its axis of rotation is in a plane perpendicular to the illuminating laser lights is described. The rotating object is illuminated by three parallel laser lights and its rotational speed is calculated from beat frequencies resulting from the mixing of their backscattered lights. To verify the principle, measurements of rotational speed of a brass cylinder were performed for rotational speeds in the range of 30 500 rpm. The measured values have a fairly good agreement with the preselected values over this range. The present method is useful for detection of rotational conditions of machinery components assembled in rotating or vibrating structures.

  5. Numerical solutions and laser-Doppler measurements of spin-up

    NASA Technical Reports Server (NTRS)

    Warn-Varnas, A.; Piacsek, S.; Fowlis, W. W.; Lee, S. M.

    1978-01-01

    The spin-up flow in a cylinder of homogeneous fluid has been examined both experimentally and numerically. A series of laser-Doppler measurements was made of the zonal flow over a range of Ekman numbers and Rossby numbers at various locations in the interior of the flow. These measurements exceed previous ones in accuracy. The weak inertial modes excited by the impulsive start are detectable. The numerical simulations used the primitive equations in axisymmetric form and employed finite-difference techniques on both constant and variable grids. The number of grid points necessary to resolve the Ekman layers was determined. A thorough comparison of the simulations and the experimental measurements is made which includes the details of the amplitude and frequency of the inertial modes. Agreement to within the experimental tolerance is achieved. Analytical results for conditions identical to those in the experiments are not available but some similar linear and nonlinear theories are also compared with the experiments.

  6. Velocity distribution measurements in a fishway like open channel by Laser Doppler Anemometry (LDA)

    NASA Astrophysics Data System (ADS)

    Sayeed-Bin-Asad, S. M.; Lundström, T. S.; Andersson, A. G.; Hellström, J. G. I.

    2016-03-01

    Experiments in an open channel flume with placing a vertical half cylinder barrier have been performed in order to investigate how the upstream velocity profiles are affected by a barrier. An experimental technique using Laser Doppler Velocimetry (LDV) was adopted to measure these velocity distributions in the channel for four different discharge rates. Velocity profiles were measured very close to wall and at 25, 50 and 100 mm upstream of the cylinder wall. For comparing these profiles with well-known logarithmic velocity profiles, velocity profiles were also measured in smooth open channel flow for all same four discharge rates. The results indicate that regaining the logarithmic velocity profiles upstream of the half cylindrical barrier occurs at 100 mm upstream of the cylinder wall.

  7. A microcomputer based frequency-domain processor for laser Doppler anemometry

    NASA Technical Reports Server (NTRS)

    Horne, W. Clifton; Adair, Desmond

    1988-01-01

    A prototype multi-channel laser Doppler anemometry (LDA) processor was assembled using a wideband transient recorder and a microcomputer with an array processor for fast Fourier transform (FFT) computations. The prototype instrument was used to acquire, process, and record signals from a three-component wind tunnel LDA system subject to various conditions of noise and flow turbulence. The recorded data was used to evaluate the effectiveness of burst acceptance criteria, processing algorithms, and selection of processing parameters such as record length. The recorded signals were also used to obtain comparative estimates of signal-to-noise ratio between time-domain and frequency-domain signal detection schemes. These comparisons show that the FFT processing scheme allows accurate processing of signals for which the signal-to-noise ratio is 10 to 15 dB less than is practical using counter processors.

  8. Laser Doppler vibrometer measurement on spiders in moving-coil loudspeakers

    NASA Astrophysics Data System (ADS)

    Kong, Xiaopeng; Zeng, Xinwu; Tian, Zhangfu

    2014-12-01

    The spider is the dominate stiffness to suspend the cone for a moving-coil loudspeaker unit, and is most commonly a concentrically corrugated fabric disk. A subwoofer closed box is designed to excite the tested spiders pneumatically, and the Laser Doppler Vibrometer (LDV) is used to measure the velocity of the moving spiders. The effective stiffness, loss factor and some viscoelastic behaviors such as level dependent stiffness have been investigated. The results find that, this pneumatic non-contact dynamic technique successfully measured the viscoelastic behaviors of spiders from extremely low frequency 5 Hz to 200 Hz, and the effective stiffness of spiders is dependent on the input voltage level, which is higher level with lower stiffness.

  9. Elasticity Evaluation of Regenerating Cartilage Sample Based on Laser Doppler Measurement of Ultrasonic Particle Velocity

    NASA Astrophysics Data System (ADS)

    Nitta, Naotaka; Misawa, Masaki; Homma, Kazuhiro; Shiina, Tsuyoshi

    2012-07-01

    It is important for regenerative medicine to evaluate the maturity of regenerating tissue. In the maturity evaluation of regenerating cartilage, it is useful to measure the temporal change of elasticity because the maturity of regenerating tissue is closely related to its elasticity. In this study, an elasticity evaluation method for the extracted regenerating cartilage sample, which is based on the laser Doppler measurement of ultrasonic particle velocity, was experimentally investigated using agar-based phantoms with different elastic moduli and the regenerating cartilage samples extracted from beagles in animal experiments. In addition, the experimentally-obtained elasticity was compared with the result of a static compression test. These results verified the feasibility of the proposed method in the elasticity evaluation of regenerating cartilage samples.

  10. A technique to measure the size of particles in laser Doppler velocimetry applications

    NASA Technical Reports Server (NTRS)

    Hess, C. F.

    1985-01-01

    A method to measure the size of particles in Laser Doppler Velocimeter (LDV) applications is discussed. Since in LDV the velocity of the flow is assocated with the velocity of particles to establish how well they follow the flow, in the present method the interferometric probe volume is surrounded by a larger beam of different polarization or wavelength. The particle size is then measured from the absolute intensity scattered from the large beam by particles crossing the fringes. Experiments using polystrene particles between 1.1 and 3.3 microns and larger glass beads are reported. It is shown that the method has an excellent size resolution and its accuracy is better than 10% for the particle size studied.

  11. Effect of timolol on sub-foveal choroidal blood flow using laser Doppler flowmetry

    NASA Astrophysics Data System (ADS)

    Palanisamy, Nithiyanantham; Rovati, Luigi; Cellini, Mauro; Gizzi, Corrado; Strobbe, Ernesto; Campos, Emilio; Riva, Charles E.

    2011-03-01

    Laser Doppler flowmetry (LDF) is a technique used to measure relative average velocity, number and flux (number times velocity) of red blood cells in vessels or capillaries. In this study, the effect of topical timolol on the choroidal circulation was investigated in 12 healthy subjects. Maximum velocity of red blood cells and volumetric blood flow rate in sub-foveal choroids are determined in each eye just before instillation of drops and then every 30 min upto 2 hours. Average intraocular pressure (IOP) decreased significantly in the timolol-treated eyes compared to that of placebo-treated eyes. Nevertheless no significant differences in choroidal blood hemodynamic between timolol and placebo-treated eyes were observed.

  12. Quantification of breast arterial calcification using full field digital mammography.

    PubMed

    Molloi, Sabee; Xu, Tong; Ducote, Justin; Iribarren, Carlos

    2008-04-01

    Breast arterial calcification is commonly detected on some mammograms. Previous studies indicate that breast arterial calcification is evidence of general atherosclerotic vascular disease and it may be a useful marker of coronary artery disease. It can potentially be a useful tool for assessment of coronary artery disease in women since mammography is widely used as a screening tool for early detection of breast cancer. However, there are currently no available techniques for quantification of calcium mass using mammography. The purpose of this study was to determine whether it is possible to quantify breast arterial calcium mass using standard digital mammography. An anthropomorphic breast phantom along with a vessel calcification phantom was imaged using a full field digital mammography system. Densitometry was used to quantify calcium mass. A calcium calibration measurement was performed at each phantom thickness and beam energy. The known (K) and measured (M) calcium mass on 5 and 9 cm thickness phantoms were related by M=0.964K -0.288 mg (r=0.997 and SEE=0.878 mg) and M=1.004K+0.324 mg (r=0.994 and SEE = 1.32 mg), respectively. The results indicate that accurate calcium mass measurements can be made without correction for scatter glare as long as careful calcium calibration is made for each breast thickness. The results also indicate that composition variations and differences of approximately 1 cm between calibration phantom and breast thickness introduce only minimal error in calcium measurement. The uncertainty in magnification is expected to cause up to 5% and 15% error in calcium mass for 5 and 9 cm breast thicknesses, respectively. In conclusion, a densitometry technique for quantification of breast arterial calcium mass was validated using standard full field digital mammography. The results demonstrated the feasibility and potential utility of the densitometry technique for accurate quantification of breast arterial calcium mass using standard digital

  13. Quantification of breast arterial calcification using full field digital mammography

    PubMed Central

    Molloi, Sabee; Xu, Tong; Ducote, Justin; Iribarren, Carlos

    2008-01-01

    Breast arterial calcification is commonly detected on some mammograms. Previous studies indicate that breast arterial calcification is evidence of general atherosclerotic vascular disease and it may be a useful marker of coronary artery disease. It can potentially be a useful tool for assessment of coronary artery disease in women since mammography is widely used as a screening tool for early detection of breast cancer. However, there are currently no available techniques for quantification of calcium mass using mammography. The purpose of this study was to determine whether it is possible to quantify breast arterial calcium mass using standard digital mammography. An anthropomorphic breast phantom along with a vessel calcification phantom was imaged using a full field digital mammography system. Densitometry was used to quantify calcium mass. A calcium calibration measurement was performed at each phantom thickness and beam energy. The known (K) and measured (M) calcium mass on 5 and 9 cm thickness phantoms were related by M=0.964K−0.288 mg (r=0.997 and SEE=0.878 mg) and M=1.004K+0.324 mg (r=0.994 and SEE=1.32 mg), respectively. The results indicate that accurate calcium mass measurements can be made without correction for scatter glare as long as careful calcium calibration is made for each breast thickness. The results also indicate that composition variations and differences of approximately 1 cm between calibration phantom and breast thickness introduce only minimal error in calcium measurement. The uncertainty in magnification is expected to cause up to 5% and 15% error in calcium mass for 5 and 9 cm breast thicknesses, respectively. In conclusion, a densitometry technique for quantification of breast arterial calcium mass was validated using standard full field digital mammography. The results demonstrated the feasibility and potential utility of the densitometry technique for accurate quantification of breast arterial calcium mass using standard digital

  14. Quantification of breast arterial calcification using full field digital mammography

    SciTech Connect

    Molloi, Sabee; Xu Tong; Ducote, Justin; Iribarren, Carlos

    2008-04-15

    Breast arterial calcification is commonly detected on some mammograms. Previous studies indicate that breast arterial calcification is evidence of general atherosclerotic vascular disease and it may be a useful marker of coronary artery disease. It can potentially be a useful tool for assessment of coronary artery disease in women since mammography is widely used as a screening tool for early detection of breast cancer. However, there are currently no available techniques for quantification of calcium mass using mammography. The purpose of this study was to determine whether it is possible to quantify breast arterial calcium mass using standard digital mammography. An anthropomorphic breast phantom along with a vessel calcification phantom was imaged using a full field digital mammography system. Densitometry was used to quantify calcium mass. A calcium calibration measurement was performed at each phantom thickness and beam energy. The known (K) and measured (M) calcium mass on 5 and 9 cm thickness phantoms were related by M=0.964K-0.288 mg (r=0.997 and SEE=0.878 mg) and M=1.004K+0.324 mg (r=0.994 and SEE=1.32 mg), respectively. The results indicate that accurate calcium mass measurements can be made without correction for scatter glare as long as careful calcium calibration is made for each breast thickness. The results also indicate that composition variations and differences of approximately 1 cm between calibration phantom and breast thickness introduce only minimal error in calcium measurement. The uncertainty in magnification is expected to cause up to 5% and 15% error in calcium mass for 5 and 9 cm breast thicknesses, respectively. In conclusion, a densitometry technique for quantification of breast arterial calcium mass was validated using standard full field digital mammography. The results demonstrated the feasibility and potential utility of the densitometry technique for accurate quantification of breast arterial calcium mass using standard digital

  15. Full-field imprinting of sub-40 nm patterns

    NASA Astrophysics Data System (ADS)

    Yeo, Jeongho; Kim, Hoyeon; Eynon, Ben

    2008-03-01

    Imprint lithography has been included on the ITRS Lithography Roadmap at the 32, 22 and 16 nm nodes. Step and Flash Imprint Lithography (S-FIL (R)) is a unique patterning method that has been designed from the beginning to enable precise overlay to enable multilevel device fabrication. A photocurable low viscosity resist is dispensed dropwise to match the pattern density requirements of the device, thus enabling patterning with a uniform residual layer thickness across a field and across multiple wafers. Further, S-FIL provides sub-50 nm feature resolution without the significant expense of multi-element projection optics or advanced illumination sources. However, since the technology is 1X, it is critical to address the infrastructure associated with the fabrication of imprint masks (templates). For sub-32 nm device manufacturing, one of the major technical challenges remains the fabrication of full-field 1x imprint masks with commercially viable write times. Recent progress in the writing of sub-40 nm patterns using commercial variable shape e-beam tools and non-chemically amplified resists has demonstrated a very promising route to realizing these objectives, and in doing so, has considerably strengthened imprint lithography as a competitive manufacturing technology for the sub-32nm node. Here we report the first imprinting results from sub-40 nm full-field patterns, using Samsung's current flash memory production device design. The fabrication of the imprint mask and the resulting critical dimension control and uniformity are discussed, along with image placement results. The imprinting results are described in terms of CD uniformity, etch results, and overlay.

  16. The sources of laser Doppler blood-flow signals recorded from human teeth.

    PubMed

    Soo-ampon, S; Vongsavan, N; Soo-ampon, M; Chuckpaiwong, S; Matthews, B

    2003-05-01

    Records of pulpal blood flow obtained from human teeth with a laser Doppler flowmeter include a very large component derived from periodontal and other tissues outside the pulp, but this contamination can be reduced by covering the surrounding tissues with opaque rubber dam. The present experiments were carried out to determine what proportion of the signal obtained with this dam in place is derived from non-pulpal tissues. Recordings were made from 22 healthy, intact upper incisors in 14 individuals (aged 22-40 years) with and without dam under the following conditions: from the intact teeth, after local anaesthesia (LA) and the preparation of a deep cavity in the incisal third of the labial surface of the tooth, and after removal of the pulp and arrest of bleeding. In some cases, a reading was also made after replacing the pulp in the pulp cavity. The rubber dam reduced significantly (P<0.05) the mean blood flow reading from the intact teeth by 73%, from 6.98 arbitrary perfusion units (PU) (+/-1.30 S.D., n=22) to 1.92+/-1.50 PU. After LA and cavity preparation, the mean signal with dam was 1.45+/-0.61 PU (n=16). This fell significantly by 76% to 0.35+/-0.19 PU (n=16) when the pulp was removed but not replaced, and by 43% to 0.98+/-0.36 PU (n=14) when the pulp was removed and replaced in the pulp cavity. The latter condition is thought to reproduce most closely the scattering of light in an intact tooth. The results confirm previous findings that up to 80% of the laser Doppler blood-flow signal recorded from an intact human tooth without rubber dam is of non-pulpal origin. They also show that only approximately 43% of the signal recorded with an opaque rubber dam is from pulp.

  17. Investigation of the acceleration of aluminum particles behind a shock wave using instantaneous Laser Doppler Velocimetry

    NASA Astrophysics Data System (ADS)

    Schlöffel, G.; Bastide, M.; Bachmann, S.; Mundt, Ch.; Seiler, F.

    2009-06-01

    The acceleration of aluminum particles with a 5μm diameter in the flow field behind an incident shock wave was investigated experimentally in a 10-m long and 70 mm inner diameter shock tube. By means of instantaneous Laser Doppler Velocimetry (LDV) the velocity of the particles was observed directly. The light scattered by the moving particles is Doppler shifted and sent to the laser Doppler velocimeter. The velocimeter essentially consists of a phase-stabilized Michelson interferometer used as a sensitive spectrometer. An electro-optical circuit ensures the phase stabilization that results in a voltage signal independent of the scattered light intensity and proportional to the mean velocity of the particles at the measurement point. Because of the very short response time (1μs) of the LDV system used here, the latter gives a continuous real-time signal of the particle acceleration. To avoid particle oxidation the particles were accelerated by a high-speed nitrogen gas flow. From the measured velocity the dimensionless drag coefficient was calculated. The drag coefficient is related to the fluid dynamic force exerted by the gas on the particles. The experimental data were compared to theoretical models from the literature. A significant deviation between the model and the experimental data was observed. This deviation is supposed to be induced by the shock wave, which hits the particles and breaks them into pieces of a smaller diameter. Further experiments will be carried out in the future to check the size distribution of the particles after the shock has gone past them.

  18. Laser Doppler vibrometry for assessment of arteriosclerosis: A first step towards validation

    NASA Astrophysics Data System (ADS)

    Campo, Adriaan; Dirckx, Joris

    2014-05-01

    It has been shown that in cardiovascular risk management, stiffness of large arteries has a very good predictive value for cardiovascular disease and mortality. This parameter can be estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) in the neck and femoral artery (FA) in the groin. However PWV can also be measured locally in the CCA, using non-invasive methods such as ultrasound (US) or laser Doppler vibrometry (LDV). Potential of the latter approach was already explored in previous research, and in this work a first step towards clinical validation is made. 50 hypertension II/III patients aged between 30 and 65 participate in the study. Patients were asked to remain sober for 4 hours prior to the measurements. The trajectory of the CCA in the neck was determined by a trained clinician guided by an US probe. 3 laser Doppler vibrometer (LDV) systems were aimed along the CCA. PWV was then calculated from the distance between beams and the time-shift between waveforms. Immediately after LDV measurements, PWV was measured with US. Additionally, carotid-femoral PWV was measured. As a validation, PWV results of the different techniques were compared with each other, and with medical background of the test subjects. Since data acquisition is still ongoing, data from only 20 patients will be discussed. No trends between measurement methods for PWV are apparent. However, a positive trend was detected between PWV as measured with LDV and blood pressure. More data, including additional experiments will be needed to verify this observation.

  19. Laser Doppler vibrometry for assessment of arteriosclerosis: A first step towards validation

    SciTech Connect

    Campo, Adriaan; Dirckx, Joris

    2014-05-27

    It has been shown that in cardiovascular risk management, stiffness of large arteries has a very good predictive value for cardiovascular disease and mortality. This parameter can be estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) in the neck and femoral artery (FA) in the groin. However PWV can also be measured locally in the CCA, using non-invasive methods such as ultrasound (US) or laser Doppler vibrometry (LDV). Potential of the latter approach was already explored in previous research, and in this work a first step towards clinical validation is made. 50 hypertension II/III patients aged between 30 and 65 participate in the study. Patients were asked to remain sober for 4 hours prior to the measurements. The trajectory of the CCA in the neck was determined by a trained clinician guided by an US probe. 3 laser Doppler vibrometer (LDV) systems were aimed along the CCA. PWV was then calculated from the distance between beams and the time-shift between waveforms. Immediately after LDV measurements, PWV was measured with US. Additionally, carotid-femoral PWV was measured. As a validation, PWV results of the different techniques were compared with each other, and with medical background of the test subjects. Since data acquisition is still ongoing, data from only 20 patients will be discussed. No trends between measurement methods for PWV are apparent. However, a positive trend was detected between PWV as measured with LDV and blood pressure. More data, including additional experiments will be needed to verify this observation.

  20. Rotating blade vibration analysis using photogrammetry and tracking laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Gwashavanhu, Benjamin; Oberholster, Abrie J.; Heyns, P. Stephan

    2016-08-01

    Online structural dynamic analysis of turbomachinery blades is conventionally done using contact techniques such as strain gauges for the collection of data. To transfer the captured data from the sensor to the data logging system, installation of telemetry systems is required. This is usually complicated, time consuming and may introduce electrical noise into the data. In addition, contact techniques are intrusive by definition and can introduce significant local mass loading. This affects the integrity of the captured measurements. Advances in technology now allow for the use of optical non-contact methods to analyse the dynamics of rotating structures. These include photogrammetry and tracking laser Doppler vibrometry (TLDV). Various investigations to establish the integrity of photogrammetry measurements for rotating structures involved a comparison to data captured using accelerometers. Discrepancies that were noticed were attributed to the intrusive nature of the contact measurement technique. As an extended investigation, the presented work focuses on the validation of photogrammetry applied to online turbomachinery blade measurements, using TLDV measurements. Through a frequency based characterisation approach of the dynamics of the two scanning mirrors inside the scanning head of a scanning laser Doppler vibrometer (SLDV), TLDV is employed in developing a system that can be used to achieve a perfect circular scan with a Polytec SLDV, (PSV 300). Photogrammetry out-of-plane displacements of a laser dot focused on a specific point on a rotating blade are compared to displacements captured by the laser scanning system. It is shown that there is good correlation between the two measurement techniques when applied to rotating structures, both in the time and frequency domains. The presence of slight discrepancies between the two techniques after elimination of accelerometer based errors illustrated that the optical system noise floor of photogrammetry does

  1. Setup and Test of a Laser Doppler Velocimeter for Investigations of Flow Behaviour of Polymer Melts

    NASA Astrophysics Data System (ADS)

    Schmidt, M.; Wassner, E.; Münstedt, H.

    1999-12-01

    The flow behaviour of a low-density polyethylene melt is investigated in a specifically developed flow channel by means of Laser Doppler Velocimetry (LDV). The used flow channel is a slit die with a planar contraction of 14:1. The investigation of the velocity fields was performed in the steady state of flow. The optics of the LDV system as well as the used frequency analyser proved to be reliable for measurements of velocities down to 250μm/s. By adding TiO2 tracer particles to the pellets the signal quality as well as the signal frequency were improved. It is demonstrated that the Laser Doppler Velocimeter is suited to detect velocities of polymer melts with an error of a few per cent by comparing the measured volume flow rate to the directly determined mass flow rate. Using simple fluid mechanics the viscosity function is obtained by measuring only one velocity profile within the fully developed flow in the slit die. Over a wide range of shear rates the viscosity function obtained via LDV measurement corresponds with the viscosity function which was determined by the classical mass-flow-rate method. Both resulting viscosity functions were additionally checked by performing measurements with a capillary rheometer. The LDV setup described in this paper is a powerful experimental tool to investigate the flow behaviour of polymer melts. Its accuracy and the high spatial and temporal resolution opens a way to get more quantitative insight into the flow of polymer melts and to check the validity of model calculations.

  2. Advanced materials characterization based on full field deformation measurements

    NASA Astrophysics Data System (ADS)

    Carpentier, A. Paige

    Accurate stress-strain constitutive properties are essential for understanding the complex deformation and failure mechanisms for materials with highly anisotropic mechanical properties. Among such materials, glass-fiber- and carbon-fiber-reinforced polymer--matrix composites play a critical role in advanced structural designs. The large number of different methods and specimen types currently required to generate three-dimensional allowables for structural design slows down the material characterization. Also, some of the material constitutive properties are never measured due to the prohibitive cost of the specimens needed. This work shows that simple short-beam shear (SBS) specimens are well-suited for measurement of multiple constitutive properties for composite materials and that can enable a major shift toward accurate material characterization. The material characterization is based on the digital image correlation (DIC) full-field deformation measurement. The full-field-deformation measurement enables additional flexibility for assessment of stress--strain relations, compared to the conventional strain gages. Complex strain distributions, including strong gradients, can be captured. Such flexibility enables simpler test-specimen design and reduces the number of different specimen types required for assessment of stress--strain constitutive behavior. Two key elements show advantage of using DIC in the SBS tests. First, tensile, compressive, and shear stress--strain relations are measured in a single experiment. Second, a counter-intuitive feasibility of closed-form stress and modulus models, normally applicable to long beams, is demonstrated for short-beam specimens. The modulus and stress--strain data are presented for glass/epoxy and carbon/epoxy material systems. The applicability of the developed method to static, fatigue, and impact load rates is also demonstrated. In a practical method to determine stress-strain constitutive relations, the stress

  3. Measurements in the Turbulent Boundary Layer at Constant Pressure in Subsonic and Supersonic Flow. Part 2: Laser-Doppler Velocity Measurements

    NASA Technical Reports Server (NTRS)

    Dimotakis, P. E.; Collins, D. J.; Lang, D. B.

    1979-01-01

    A description of both the mean and the fluctuating components of the flow, and of the Reynolds stress as observed using a dual forward scattering laser-Doppler velocimeter is presented. A detailed description of the instrument and of the data analysis techniques were included in order to fully document the data. A detailed comparison was made between the laser-Doppler results and those presented in Part 1, and an assessment was made of the ability of the laser-Doppler velocimeter to measure the details of the flows involved.

  4. Full-field transient vibrometry of the human tympanic membrane by local phase correlation and high-speed holography.

    PubMed

    Dobrev, Ivo; Furlong, Cosme; Cheng, Jeffrey T; Rosowski, John J

    2014-09-01

    Understanding the human hearing process would be helped by quantification of the transient mechanical response of the human ear, including the human tympanic membrane (TM or eardrum). We propose a new hybrid high-speed holographic system (HHS) for acquisition and quantification of the full-field nanometer transient (i.e., >10 kHz) displacement of the human TM. We have optimized and implemented a 2 þ 1 frame local correlation (LC) based phase sampling method in combination with a high-speed (i.e., >40 K fps) camera acquisition system. To our knowledge, there is currently no existing system that provides such capabilities for the study of the human TM. The LC sampling method has a displacement difference of <11 nm relative to measurements obtained by a four-phase step algorithm. Comparisons between our high-speed acquisition system and a laser Doppler vibrometer indicate differences of <10 μs. The high temporal (i.e., >40 kHz) and spatial (i.e., >100 k data points) resolution of our HHS enables parallel measurements of all points on the surface of the TM, which allows quantification of spatially dependent motion parameters, such as modal frequencies and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM.

  5. Full-field transient vibrometry of the human tympanic membrane by local phase correlation and high-speed holography

    NASA Astrophysics Data System (ADS)

    Dobrev, Ivo; Furlong, Cosme; Cheng, Jeffrey T.; Rosowski, John J.

    2014-09-01

    Understanding the human hearing process would be helped by quantification of the transient mechanical response of the human ear, including the human tympanic membrane (TM or eardrum). We propose a new hybrid high-speed holographic system (HHS) for acquisition and quantification of the full-field nanometer transient (i.e., >10 kHz) displacement of the human TM. We have optimized and implemented a 2+1 frame local correlation (LC) based phase sampling method in combination with a high-speed (i.e., >40 K fps) camera acquisition system. To our knowledge, there is currently no existing system that provides such capabilities for the study of the human TM. The LC sampling method has a displacement difference of <11 nm relative to measurements obtained by a four-phase step algorithm. Comparisons between our high-speed acquisition system and a laser Doppler vibrometer indicate differences of <10 μs. The high temporal (i.e., >40 kHz) and spatial (i.e., >100 k data points) resolution of our HHS enables parallel measurements of all points on the surface of the TM, which allows quantification of spatially dependent motion parameters, such as modal frequencies and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM.

  6. Full-field transient vibrometry of the human tympanic membrane by local phase correlation and high-speed holography

    PubMed Central

    Dobrev, Ivo; Furlong, Cosme; Cheng, Jeffrey T.; Rosowski, John J.

    2014-01-01

    Abstract. Understanding the human hearing process would be helped by quantification of the transient mechanical response of the human ear, including the human tympanic membrane (TM or eardrum). We propose a new hybrid high-speed holographic system (HHS) for acquisition and quantification of the full-field nanometer transient (i.e., >10  kHz) displacement of the human TM. We have optimized and implemented a 2+1 frame local correlation (LC) based phase sampling method in combination with a high-speed (i.e., >40  K fps) camera acquisition system. To our knowledge, there is currently no existing system that provides such capabilities for the study of the human TM. The LC sampling method has a displacement difference of <11  nm relative to measurements obtained by a four-phase step algorithm. Comparisons between our high-speed acquisition system and a laser Doppler vibrometer indicate differences of <10  μs. The high temporal (i.e., >40  kHz) and spatial (i.e., >100  k data points) resolution of our HHS enables parallel measurements of all points on the surface of the TM, which allows quantification of spatially dependent motion parameters, such as modal frequencies and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM. PMID:25191832

  7. FULL-FIELD DEFORMATION MEASUREMENT IN POLYMERIC FOAM SPECIMENS

    SciTech Connect

    C. LIU; ET AL

    2001-03-01

    In this investigation, a simple experimental technique, dot-matrix deposition and mapping, was developed to study the full-field deformation in a polymeric foam specimen. One of the advantages of using this technique is that it can be easily applied to situations where large deformations are involved. The spatial resolution of the current technique is not as high as the digital image correlation method and some other optical techniques. Nevertheless, because the largest cell diameter of the polyurethane foam studied in this investigation is about 1 mm, the smallest length scale over which the polymeric foam material can be treated as a homogeneous solid would be at least several millimeters. For the element size used in the present study in the range of 2.5 x 2.5 mm, the dot-matrix deposition and mapping technique would provide enough detail about the behavior of polymeric foam materials under complicated deformation states and under complicated loading conditions. It will also provide useful information to compare with numerical simulations so that the constitutive models can be validated.

  8. Physical characteristics of a full-field digital mammography system

    NASA Astrophysics Data System (ADS)

    Suryanarayanan, Sankararaman; Karellas, Andrew; Vedantham, Srinivasan

    2004-11-01

    The physical performance characteristics of a flat-panel clinical full-field digital mammography (FFDM) system were investigated for a variety of mammographic X-ray spectral conditions. The system was investigated using 26 kVp: Mo/Mo, 28 kVp: Mo/Rh, and 30 kVp: Rh/Rh, with polymethyl methacrylate (PMMA) "tissue equivalent material" of thickness 20, 45, and 60 mm for each of three X-ray spectra, resulting in nine different spectral conditions. The experimental results were compared with a theoretical cascaded linear systems-based model that has been developed independently by other investigators. The FFDM imager (Senographe 2000D, GE Medical Systems, Milwaukee, WI) uses an amorphous silicon (aSi:H) photodiode (100 μm pixel) array directly coupled to a cesium iodide (CsI) scintillator. The spatial resolution of the digital mammography system was determined by measuring the presampling modulation transfer function (MTF). The noise power spectra (NPS) of the system were measured under the different mammographic X-ray spectral conditions at an exposure of approximately 10 mR to the detector from which corresponding detective quantum efficiencies (DQE) were determined. The experimental results provide additional information on the performance of the mammographic system for a broader range of experimental conditions than have been reported in the past. The flat-panel imager exhibits favorable physical quality characteristics under the conditions investigated. The experimental results were compared with theoretical estimates under various spectral conditions and demonstrated good agreement.

  9. Assessment of Sentinel Node Biopsies With Full-Field Optical Coherence Tomography.

    PubMed

    Grieve, Kate; Mouslim, Karima; Assayag, Osnath; Dalimier, Eugénie; Harms, Fabrice; Bruhat, Alexis; Boccara, Claude; Antoine, Martine

    2016-04-01

    Current techniques for the intraoperative analysis of sentinel lymph nodes during breast cancer surgery present drawbacks such as time and tissue consumption. Full-field optical coherence tomography is a novel noninvasive, high-resolution, fast imaging technique. This study investigated the use of full-field optical coherence tomography as an alternative technique for the intraoperative analysis of sentinel lymph nodes. Seventy-one axillary lymph nodes from 38 patients at Tenon Hospital were imaged minutes after excision with full-field optical coherence tomography in the pathology laboratory, before being handled for histological analysis. A pathologist performed a blind diagnosis (benign/malignant), based on the full-field optical coherence tomography images alone, which resulted in a sensitivity of 92% and a specificity of 83% (n = 65 samples). Regular feedback was given during the blind diagnosis, with thorough analysis of the images, such that features of normal and suspect nodes were identified in the images and compared with histology. A nonmedically trained imaging expert also performed a blind diagnosis aided by the reading criteria defined by the pathologist, which resulted in 85% sensitivity and 90% specificity (n = 71 samples). The number of false positives of the pathologist was reduced by 3 in a second blind reading a few months later. These results indicate that following adequate training, full-field optical coherence tomography can be an effective noninvasive diagnostic tool for extemporaneous sentinel node biopsy qualification. © The Author(s) 2015.

  10. Monitoring perfusion changes in laser-treated tumors using laser doppler flowmetry

    NASA Astrophysics Data System (ADS)

    Deans, Abby; Hess, Linda; Koss, Michael; Liu, Hong; Chen, Wei R.

    2006-02-01

    Laser Doppler perfusion monitors are effect tools in understanding blood flow in many different types of biological studies. Because the low-intensity lasers used in Doppler perfusion measurements must interact with moving blood cells, the depth of probe-able tissue is limited to the volume of tissue within the hemisphere of radius ~1mm from the probe tip. In addition, heterogeneities in surface perfusion make precise probe placement very important if one is comparing successive measurements. Consequently, useful tissue perfusion measurements have been difficult to obtain, especially in deep tissues. In this study, a new method was developed for monitoring deep-tissue blood perfusion directionally with the Laserflo laser Doppler perfusion probe. The probe was inserted just under the skin superficially to a rat prostatic tumor through the shaft of a 16-gauge needle, which was modified to allow the probe to be exposed without extending beyond the beveled needle tip. Perfusion measurements of the tumor surface or the skin were made by rotating the bevel to face either inside or outside. Using this technique, tumor tissue can be differentiated from either skin or muscle. To study the responses of tumor to light stimulation, an 805nm biomedical treatment laser was used to irradiate the tumor. The perfusion of the tumor surface was shown to decrease slightly with short treatment laser applications (1W for 30 seconds or 1 minute). After a longer treatment session (5 minutes), the perfusion of the tumor tissue increased significantly. However, with an even longer (10 minutes) treatment, the perfusion of the tumor surface was shown to decrease once again. This trend indicates that before laser heating becomes significant, the perfusion decreases for as yet poorly understood reasons. When laser heating becomes significant, after the five-minute session, the perfusion increases dramatically, corresponding to the expected dilation of blood vessels during tissue heating. After

  11. Observation of a critically refracted converted SP wave using laser Doppler interferometer

    NASA Astrophysics Data System (ADS)

    Gurevich, Boris; Lebedev, Maxim; Madadi, Mahyar; Bona, Andrej; Pevzner, Roman

    2015-04-01

    Laboratory measurements of elastic properties of rocks are important for calibration of seismic data and for corroboration of theoretical models of rocks. The most common way of determining the elastic properties of rock samples in laboratory settings is to estimate the velocities of ultrasonic waves propagating in different directions. The wave velocities are usually obtained from the travel times of waves generated and recorded by ultrasonic piezoelectric transducers. This approach has a large uncertainty associated with shear-wave travel time estimation and separation of differently polarised shear waves, as well as uncertainty as to whether phase or group velocity is measured. The problems are caused by the relatively large size and small number of transducers. One way to address some of these issues is by using laser Doppler interferometer, which records a particle like movement that can serve to separate the waves and to pick the travel times from which the ray velocities cab be estimated reliably, and with a huge data redundancy. In this paper, laser Doppler interferometer is used to record wave propagation in an anisotropic rock sample by measuring three orthogonal components of particle velocity on the sample surface. These measurements allow a clear separation of different wave types. The travel time of these waves are used for estimation of anisotropy parameters of the sample. A key observation is the very strong wave which at small offsets has traveltimes equal to those of the S-wave, but at large offsets travels with a velocity close to that of the P-wave. We interpret this wave as a converted SP wave critically refracted at the free surface. The nature and characteristics of this wave are confirmed by numerical simulations in both isotropic and anisotropic media. These simulations show the same traveltimes as measured in the experiment, but the amplitude of the converted SP wave is much stronger in the measured data. Analysis of this inconsistency is

  12. Signal averaging and waveform analysis of laser Doppler flowmetry monitoring of porcine myocutaneous flaps: I. Acute assessment of flap viability.

    PubMed

    Stack, B C; Futran, N D; Ridley, M B; Schultz, S; Sillman, J S

    1995-11-01

    Postoperative monitoring of microvascular free-tissue transfer is essential to the early identification and correction of vascular compromise. Laser Doppler flowmetry is a noninvasive monitor of capillary bed perfusion. Its current clinical use requires continuous monitoring and trend analysis to detect changes in capillary perfusion. This study investigated the hypothesis that signal averaging of laser Doppler flowmetry output triggered by a fixed point in the cardiac cycle would provide accurate information about the microvascular flow patterns not dependent on trend analysis. These results indicate that averaged waveform analysis allowed for a rapid, objective, and statistically significant distinction between a viable myocutaneous flap and one with vascular compromise in a porcine model. Moreover, this technique allows for distinction between venous and arterial insufficiency.

  13. Experimental Validation of Simulations Using Full-field Measurement Techniques

    SciTech Connect

    Hack, Erwin

    2010-05-28

    The calibration by reference materials of dynamic full-field measurement systems is discussed together with their use to validate numerical simulations of structural mechanics. The discussion addresses three challenges that are faced in these processes, i.e. how to calibrate a measuring instrument that (i) provides full-field data, and (ii) is dynamic; (iii) how to compare data from simulation and experimentation.

  14. Investigation into the structure of a swirling flow in a model of a vortex combustion chamber by laser doppler anemometry

    NASA Astrophysics Data System (ADS)

    Anufriev, I. S.; Anikin, Yu. A.; Fil'kov, A. I.; Loboda, E. L.; Agafontseva, M. V.; Kasymov, D. P.; Tizilov, A. S.; Astanin, A. V.; Pesterev, A. V.; Evtyushkin, E. V.

    2013-01-01

    The structure of an isothermal swirling flow is investigated experimentally in a model of a vortex combustion chamber with a horizontal rotation axis and a distributed input of air-fuel jets. The averaged and pulsation characteristics of the velocity field in various sections of the model are measured using laser Doppler anemometry. The features of internal aerodynamics of a new design of a steam-generator firebox are analyzed.

  15. Laser-Doppler acoustic probing of granular media with in-depth property gradient and varying pore pressures

    SciTech Connect

    Bodet, L.; Dhemaied, A.; Mourgues, R.; Tournat, V.; Rejiba, F.

    2012-05-24

    Non-contacting ultrasonic techniques recently proved to be efficient in the physical modeling of seismic-wave propagation at various application scales, as for instance in the context of geological analogue and seismic modeling. An innovative experimental set-up is proposed here to perform laser-Doppler acoustic probing of unconsolidated granular media with varying pore pressures. The preliminary experiments presented here provide reproducible results and exploitable data, thus validating both the proposed medium preparation and pressure gradient generation procedure.

  16. Development of a laser-Doppler system for measurement of velocity fields in PVT crystal growth systems

    NASA Technical Reports Server (NTRS)

    Jones, O. C.; Glicksman, M. E.; Lin, J. T.; Kim, G. T.; Singh, N. B.

    1991-01-01

    A laser-Doppler velocimetry (LDV) system capable of measuring velocities as low as 10 exp -5 m/s is presented, and a calibration system for determining the accuracy of the LDV system at these velocities is described. The results obtained in mercurous chloride crystal grown in cylindrical ampoules at 300 C, using physical vapor transport (PVT) methods, are presented. It is concluded that the overall flow pattern observed is a unicellular, asymmetric pattern between Rayleigh number of 125 and 250.

  17. Effect of senescence on ocular blood flow in the retina, neuroretinal rim and lamina cribrosa, using scanning laser Doppler flowmetry.

    PubMed

    Embleton, S J; Hosking, S L; Roff Hilton, E J; Cunliffe, I A

    2002-03-01

    To determine the effects of age on blood flow measurements obtained using the scanning laser Doppler flowmeter (SLDF). Using SLDF (Heidelberg retina flowmeter, Heidelberg Engineering, Germany) three 10 degrees images were taken of the superior temporal retina and three further images of the superior temporal neuroretinal rim in 15 young, healthy subjects (mean age 27.9 years +/- 6.2 years) and 15 mature, healthy subjects (mean age 65.2 years +/- 13.7 years). In addition, measurements were taken of the lamina cribrosa in 12 of the volunteers from each subject group (mean age 27.1 +/- 6.3 years and 64.8 +/- 13.2 years respectively). Using a 10 x 10 pixel measurement frame, blood flow readings were obtained at a predetermined position on the retina, neuroretinal rim and lamina cribrosa. Student's two-tailed unpaired t-tests were used to compare measures of blood flow, volume and velocity between the two subject groups (P < 0.05). In addition, linear regression analysis was used to assess the relationship between age and blood flow, volume and velocity at the retina, neuroretinal rim and lamina cribrosa. Retinal blood volume measured at the retina was significantly lower in the mature compared with the young subject group (P = 0.01). Mature subjects also exhibited reduced blood flow and velocity at the neuroretinal rim (P = 0.01 for both parameters) and lamina cribrosa (P = 0.008 and P = 0.01 respectively). Regression analysis revealed negative trends for all blood flow parameters in each of the anatomical areas with advancing age. Significant negative correlations were obtained for retinal blood volume (r = -0.455, P < 0.05), neuroretinal rim blood velocity (r = -0.359, P < 0.05) and lamina cribrosa blood volume (r = -0.475, P < 0.05). Capillary blood flow in the retina, neuroretinal rim and lamina cribrosa decreases with advancing age. This may be of consequence in the progression of chronic ocular diseases such as glaucoma, and should be considered in the

  18. Dual-beam laser Doppler vibrometer for measurement of pulse wave velocity in elastic vessels

    NASA Astrophysics Data System (ADS)

    Campo, Adriaan; Dirckx, Joris

    2011-08-01

    When a fluid flowing through an elastic vessel is subjected to a sudden change in pressure gradient, pressure pulses will propagate through the fluid. Velocity of these pulse waves (PWV) can be determined by simultaneous detection of wall distension on two separate points on the vessel wall, along its trajectory. PWV depends on wall stiffness, and under certain circumstances, wall stiffness can be calculated from the propagation velocity. Optical interferometry is a noncontacting technique that allows measurement of wall distension on discrete locations. In this work we propose a miniaturized dual-beam laser Doppler vibrometer (LDV) to measure wall distension simultaneously at two locations. Our dual-beam LDV is based on a single laser source and one acousto-optic modulator with as much as possible of the interferometer optics shared among the different beams. The dual-beam LDV was used for simultaneous detection of wall distension of several elastic vessels of different stiffness. We found that PWV as measured in elastic vessels agrees well with theoretically expected values, and measurement precision is better than 5%. Moreover, the dual-beam LDV performs almost as good as commercial systems for detection of PWV. The dual-beam LDV can have applications in cardiovascular risk management. Stiffness of large arteries has a very good predictive value for cardiovascular disease and overall mortality. This parameter can be estimated from arterial PWV. Current methods to measure arterial PWV suffer from several shortcomings. A dual-beam LDV can offer substantial advantages over existing techniques.

  19. Photo-vibrational spectroscopy using quantum cascade laser and laser Doppler vibrometer

    NASA Astrophysics Data System (ADS)

    Liu, Huan; Hu, Qi; Xie, Jiecheng; Fu, Yu

    2017-06-01

    Photoacoustic/photothermal spectroscopy is an established technique for detection of chemicals and explosives. However, prior sample preparation is required and the analysis is conducted in a sealed space with a high-sensitivity sensor coupled with a lock-in amplifier, limiting the technique to applications in a controllable laboratory environment. Hence, this technique may not be suitable for defense and security applications where the detection of explosives or hazardous chemicals is required in an open environment at a safe standoff distance. In this study, chemicals in various forms were excited by an intensity-modulated quantum cascade laser (QCL), while a laser Doppler vibrometer (LDV) was applied to detect the vibration signal resulting from the photocoustic/photothermal effect. The photo-vibrational spectrum obtained by scanning the QCL's wavelength in MIR range, coincides well with the corresponding spectrum obtained using typical FTIR equipment. The experiment in short and long standoff distances demonstrated that the LDV is a capable sensor for chemical detection in an open environment.

  20. Particle flow within a transonic compressor rotor passage with application to laser-Doppler velocimetry

    NASA Technical Reports Server (NTRS)

    Maxwell, B. R.

    1975-01-01

    A theoretical analysis was conducted of the dynamic behavior of micron size particles moving in the three-dimensional flow field of a rotating transonic axial-flow air compressor rotor. The particle velocity lag and angular deviation relative to the gas were determined as functions of particle diameter, mass density and radial position. Particle size and density were varied over ranges selected to correspond to typical laser-Doppler velocimeter (LDV) flow field mapping applications. It was found that the particles move essentially on gas stream surfaces and that particle tracking is relatively insensitive to the rotor radial coordinate. Velocity lag and angular deviation increased whenever particle size or mass density increased, and particle tracking was more sensitive to a change in particle diameter than to a corresponding change in mass density. Results indicated that velocity and angular deviations generally less than 1 percent and 1 degree could be achieved with 1 gm/cc tracer particles with diameters of 1 micron or less.

  1. Axial scanning laser Doppler velocimeter using wavelength change without moving mechanism in sensor probe.

    PubMed

    Maru, Koichi

    2011-03-28

    A scanning laser Doppler velocimeter (LDV) without any moving mechanism in its sensor probe is proposed. In the proposed scanning LDV, the measurement position is axially scanned by change in the wavelength of the light input to the sensor probe, instead of using a moving mechanism in the sensor probe. For this purpose, a tunable laser and diffraction gratings are used, and the sensor probe including the gratings is separated from the main body including the tunable laser. To demonstrate the scanning function based on the proposed concept, an experiment was conducted using optical fibers, a commercial tunable laser and a setup of the sensor probe consisting of bulk optical components. As the experimental result, it is found that the measurement positions estimated from the measured beat frequencies are in good agreement with the theoretical values. The scan ranges over a wavelength range of 30 nm are estimated to be 29.3 mm when the beam angle to the measurement position at the wavelength of 1540 nm is 10° and 20.8 mm when the beam angle is 15°. The result indicates that the scanning function by means of changing the wavelength input to the sensor probe is successfully demonstrated for the first time. The proposed method has the potential for realizing a scanning LDV with a simple, compact and reliable sensor probe.

  2. Modal parameter determination of a lightweight aerospace panel using laser Doppler vibrometer measurements

    NASA Astrophysics Data System (ADS)

    de Sousa, Kleverson C.; Domingues, Allan C.; Pereira, Pedro P. de S.; Carneiro, Sergio H.; de Morais, Marcus V. G.; Fabro, Adriano T.

    2016-06-01

    The experimental determination of modal parameters, i.e. natural frequencies, mode shapes and damping ratio, are key in characterizing the dynamic behaviour of structures. Typically, such parameters are obtained from dynamic measurements using one or a set of accelerometers, for response measurements, along with force transducers from an impact hammer or an electrodynamic actuator, i.e. a shaker. However, lightweight structures, commonly applied in the aerospace industry, can be significantly affected by the added mass from accelerometers. Therefore, non-contact measurement techniques, like Laser Doppler Vibrometer (LDV), are a more suitable approach in determining the dynamic characteristics of such structures. In this article, the procedures and results of a modal test for a honeycomb sandwich panel for aerospace applications are presented and discussed. The main objectives of the test are the identification of natural frequencies and mode shapes in order to validate a numerical model, as well as the identification of the damping characteristics of the panel. A validated numerical model will be necessary for future detailed response analysis of the satellite, including vibroacoustic investigations to account for acoustic excitations encountered during launching. The numerical model using homogenised material properties is updated to fit the experimental results and very good agreement between experimental and numerically obtained natural frequencies and mode shapes.

  3. Atmospheric transmission of CO2 laser radiation with application to laser Doppler systems

    NASA Technical Reports Server (NTRS)

    Murty, S. S. R.

    1975-01-01

    The molecular absorption coefficients of carbon dioxide, water vapor, and nitrous oxide are calculated at the P16, P18, P20, P22, and P24 lines of the CO2 laser for temperatures from 200 to 300 K and for pressures from 100 to 1100 mb. The temperature variation of the continuum absorption coefficient of water vapor is taken into account semi-empirically from Burch's data. The total absorption coefficient from the present calculations falls within + or - 20 percent of the results of McClatchey and Selby. The transmission loss which the CO2 pulsed laser Doppler system experiences was calculated for flight test conditions for the five P-lines. The total transmission loss is approximately 7 percent higher at the P16 line and 10 percent lower at the P24 line compared to the P20 line. Comparison of the CO2 laser with HF and DF laser transmission reveals the P2(8) line at 3.8 micrometers of the DF laser is much better from the transmission point of view for altitudes below 10 km.

  4. Multipoint laser Doppler vibrometry with single detector: principles, implementations, and signal analyses.

    PubMed

    Fu, Y; Guo, M; Phua, P B

    2011-04-01

    A 20-point laser Doppler vibrometer with single photodetector is presented for noncontact dynamic measurement. A 5×4 beam array with various frequency shifts is generated by a 1.55 μm distributed feedback laser and four acousto-optic devices, and illuminating different points on vibrating objects. The reflected beams are coupled into a single-mode fiber by a pigtailed collimator and interfere with a reference beam. The signal output from a high-speed photodetector is amplified and then digitized by a high-speed analog-to-digital converter with a sampling rate of 1 gigasample per second (1 GS/s). Several methods are introduced to avoid the cross talk among different frequencies and extract the vibration information of 20 points from a one-dimensional signal. Two signal processing algorithms based on Fourier transform and windowed Fourier transform are illustrated to extract the vibration signals at different points. The experimental results are compared with that from a commercial single-point laser vibrometer. The results show simultaneous vibration measurement can be realized on multiple points using a single laser source and a single photodetector. © 2011 Optical Society of America

  5. Restoring high accuracy to laser Doppler vibrometry measurements affected by vibration of beam steering optics

    NASA Astrophysics Data System (ADS)

    Halkon, Ben J.; Rothberg, Steve J.

    2017-09-01

    Laser Doppler vibrometers are now well-established as an effective non-contact alternative to traditional contacting transducers. Wide-ranging applications include those where beam steering optics are required to reach locations that are difficult to access but no attention has yet been given to measurement sensitivity to the vibration of those optics. In this paper, a thorough mathematical treatment of this sensitivity to steering optic vibration and its correction is set out. A very practical scheme requiring a single correction measurement, from the back-surface of the mirror at the incidence point and aligned with the mirror normal, delivers an error reduction typically in excess of 30 dB. After validation in the laboratory, the scheme is then applied to a genuinely challenging measurement scenario on a single cylinder racing motorcycle. Correction is theoretically perfect for translational mirror vibrations but angular mirror vibrations require an adapted scheme using a triplet of accelerometers arranged around a circular path on the mirror back-surface and this is set out theoretically.

  6. Potential accuracy of methods of laser Doppler anemometry in the single-particle scattering mode

    NASA Astrophysics Data System (ADS)

    Sobolev, V. S.; Kashcheeva, G. A.

    2017-05-01

    Potential accuracy of methods of laser Doppler anemometry is determined for the singleparticle scattering mode where the only disturbing factor is shot noise generated by the optical signal itself. The problem is solved by means of computer simulations with the maximum likelihood method. The initial parameters of simulations are chosen to be the number of real or virtual interference fringes in the measurement volume of the anemometer, the signal discretization frequency, and some typical values of the signal/shot noise ratio. The parameters to be estimated are the Doppler frequency as the basic parameter carrying information about the process velocity, the signal amplitude containing information about the size and concentration of scattering particles, and the instant when the particles arrive at the center of the measurement volume of the anemometer, which is needed for reconstruction of the examined flow velocity as a function of time. The estimates obtained in this study show that shot noise produces a minor effect (0.004-0.04%) on the frequency determination accuracy in the entire range of chosen values of the initial parameters. For the signal amplitude and the instant when the particles arrive at the center of the measurement volume of the anemometer, the errors induced by shot noise are in the interval of 0.2-3.5%; if the number of interference fringes is sufficiently large (more than 20), the errors do not exceed 0.2% regardless of the shot noise level.

  7. Microcirculation in healing and healthy Achilles tendon assessed with invasive laser doppler flowmetry

    PubMed Central

    Arverud, Erica Domeij; Persson-Lindell, Olof; Sundquist, Fredrik; Labruto, Fausto; Edman, Gunnar; Ackermann, Paul W.

    2016-01-01

    Summary Introduction Achilles tendon (AT) rupture exhibits a prolonged healing process with varying clinical outcome. Reduced blood flow to the AT has been considered an underlying factor to AT rupture (ATR) and impaired healing. In vivo measurements using laser Doppler flowmetry (LDF) may be a viable method to assess blood flow in healthy and healing AT. Methods 29 persons were included in the study; 9 being ATR patients and 20 healthy subjects without any prior symptoms from the AT. Invasive LDF was used to determine the post-occlusive reactive hyperemia (PORH) in the paratenon after 15 minutes of occlusion of the lower extremities. ATR patients were examined two weeks post-operatively. Results LDF-assessments demonstrated a significantly different (p < 0.001) PORH response in the healing- versus intact- and control AT. In the healing AT, a slow, flattened PORH was observed compared to a fast, high peak PORH in intact, healthy AT. Conclusion in vivo LDF appears to be a feasible method to assess alterations in blood flow in healing and intact AT. The healing ATs capability to react to an ischemic period is clearly impaired, which may be due to the trauma at injury and/or surgery or degenerative changes in the tendon. PMID:27331035

  8. A multi-point laser Doppler vibrometer with fiber-based configuration

    SciTech Connect

    Yang, C.; Guo, M.; Liu, H.; Yan, K.; Xu, Y. J.; Fu, Y.; Miao, H.

    2013-12-15

    Laser Doppler vibrometer (LDV) is a non-contact optical interferometric system to measure vibrations of structures and machines with a high precision. Normal LDV can only offer a single-point measurement. Scanning LDV is usually impractical to do measurement on transient events. In this paper, a fiber-based self-synchronized multi-point LDV is proposed. The multiple laser beams with different frequency shifts are generated from one laser source. The beams are projected onto a vibrating object, reflected and interfered with a common reference beam. The signal including vibration information of multiple spatial points is captured by one single-pixel photodetector. The optical system is mainly integrated by fiber components for flexibility in measurement. Two experiments are conducted to measure a steady-state simple harmonic vibration of a cantilever beam and a transient vibration of a beam clamped at both ends. In the first measurement, a numerical interpolation is applied to reconstruct the mode shape with increased number of data points. The vibration mode obtained is compared with that from FEM simulation. In transient vibration measurement, the first five resonant frequencies are obtained. The results show the new-reported fiber-based multipoint LDV can offer a vibration measurement on various spatial points simultaneously. With the flexibility of fiber configuration, it becomes more practical for dynamic structural evaluation in industrial areas.

  9. Reproducibility of transcutaneous oximetry and laser Doppler flowmetry in facial skin and gingival tissue.

    PubMed

    Svalestad, J; Hellem, S; Vaagbø, G; Irgens, A; Thorsen, E

    2010-01-01

    Laser Doppler flowmetry (LDF) and transcutaneous oximetry (TcPO(2)) are non-invasive techniques, widely used in the clinical setting, for assessing microvascular blood flow and tissue oxygen tension, e.g. recording vascular changes after radiotherapy and hyperbaric oxygen therapy. With standardized procedures and improved reproducibility, these methods might also be applicable in longitudinal studies. The aim of this study was to evaluate the reproducibility of facial skin and gingival LDF and facial skin TcPO(2). The subjects comprised ten healthy volunteers, 5 men, aged 31-68 years. Gingival perfusion was recorded with the LDF probe fixed to a custom made, tooth-supported acrylic splint. Skin perfusion was recorded on the cheek. TcPO(2) was recorded on the forehead and cheek and in the second intercostal space. The reproducibility of LDF measurements taken after vasodilation by heat provocation was greater than for basal flow in both facial skin and mandibular gingiva. Pronounced intraday variations were observed. Interweek reproducibility assessed by intraclass correlation coefficient ranged from 0.74 to 0.96 for LDF and from 0.44 to 0.75 for TcPO(2). The results confirm acceptable reproducibility of LDF and TcPO(2) in longitudinal studies in a vascular laboratory where subjects serve as their own controls. The use of thermoprobes is recommended. Repeat measurements should be taken at the same time of day.

  10. Pulse transit times to the capillary bed evaluated by laser Doppler flowmetry.

    PubMed

    Bernjak, Alan; Stefanovska, Aneta

    2009-03-01

    The pulse transit time (PTT) of a wave over a specified distance along a blood vessel provides a simple non-invasive index that can be used for the evaluation of arterial distensibility. Current methods of measuring the PTT determine the propagation times of pulses only in the larger arteries. We have evaluated the pulse arrival time (PAT) to the capillary bed, through the microcirculation, and have investigated its relationship to the arterial PAT to a fingertip. To do so, we detected cardiac-induced pulse waves in skin microcirculation using laser Doppler flowmetry (LDF). Using the ECG as a reference, PATs to the microcirculation were measured on the four extremities of 108 healthy subjects. Simultaneously, PATs to the radial artery of the left index finger were obtained from blood pressure recordings using a piezoelectric sensor. Both PATs correlate in similar ways with heart rate and age. That to the microcirculation is shown to be sensitive to local changes in skin perfusion induced by cooling. We introduce a measure for the PTT through the microcirculation. We conclude that a combination of LDF and pressure measurements enables simultaneous characterization of the states of the macro and microvasculature. Information about the microcirculation, including an assessment of endothelial function, may be obtained from the responses to perturbations in skin perfusion, such as temperature stress or vasoactive substances.

  11. Multi-frequency, 3D ODS measurement by continuous scan laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Weekes, Ben; Ewins, David

    2015-06-01

    Continuous scan laser Doppler vibrometry (CSLDV) is a technique which has been described and explored in the literature for over two decades, but remains niche compared to SLDV inspection by a series of discrete-point measurements. This is in part because of the unavoidable phenomenon of laser speckle, which deteriorates signal quality when velocity data is captured from a moving spot measurement. Further, applicability of CSLDV has typically been limited to line scans and rectangular areas by the application of sine, step, or ramp functions to the scanning mirrors which control the location of the measurement laser spot. In this paper it is shown that arbitrary functions to scan any area can easily be derived from a basic calibration routine, equivalent to the calibration performed in conventional discrete-point laser vibrometry. This is extended by performing the same scan path upon a test surface from three independent locations of the laser head, and decomposing the three sets of one-dimensional deflection shapes into a single set of three-dimensional deflection shapes. The test was performed with multi-sine excitation, yielding 34 operating deflection shapes from each scan.

  12. Laser Doppler anemometer measurements of pulsatile flow in a model carotid bifurcation.

    PubMed

    Ku, D N; Giddens, D P

    1987-01-01

    Hemodynamics at the human carotid bifurcation is important to the understanding of atherosclerotic plaque initiation and progression as well as to the diagnosis of clinically important disease. Laser Doppler anemometry was performed in a large scale model of an average human carotid. Pulsatile waveforms and physiologic flow divisions were incorporated. Disturbance levels and shear stresses were computed from ensemble averages of the velocity waveform measurements. Flow in the common carotid was laminar and symmetric. Flow patterns in the sinus, however, were complex and varied considerably during the cycle. Strong helical patterns and outer wall flow separation waxed and waned during each systole. The changing flow patterns resulted in an oscillatory shear stress at the outer wall ranging from -13 to 9 dyn cm-2 during systole with a time-averaged mean of only -0.5 dyn cm-2. This contrasts markedly with an inner wall shear stress range of 17-50, (mean 26) dyn cm-2. The region of transient separation was confined to the carotid sinus outer wall with no reverse velocities detected in the distal internal carotid. Notable disturbance velocities were also time-dependent, occurring only during the deceleration phase of systole and the beginning of diastole. The present pulsatile flow studies have aided in identifying hemodynamic conditions which correlate with early intimal thickening and predict the physiologic level of flow disturbances in the bulb of undiseased internal carotid arteries.

  13. Fringe mode transmittance laser Doppler microscope anemometer: its adaptation for measurement in the microcirculation.

    PubMed

    Einav, S; Berman, H J

    1988-10-01

    Blood flow analysis in the microcirculation requires accurate measurement of velocity, volume flow and shear-rate versus shear-stress relationships. The resolution of most anemometers is too limited to obtain useful measurements, especially near the blood vessel wall and at branches and bifurcations. To make such measurements possible with a noninvasive, high resolution, accurate technique, we have developed a fringe mode, transmittance laser Doppler microscope anemometer (LDMA). This system has an intrinsically high spatial resolution (10 x 12 microns), and does not require a high concentration (10(6)/cm3) of scatters or red blood cells (RBC) as in our application. Preliminary measurements of water flow in a rectangular channel were conducted to ascertain the reliability and accuracy of velocity measurements using the LDMA. Velocity profiles were then measured by the LDMA system in arterioles 38-135 microns in diameter, in the transparent, everted cheek pouch of the anaesthetized hamster. The extremely high resolution of the optical system, and the ultra-fine traversing mechanism of the microscope stage, made velocity readings larger than 0.02 mm/s with accuracy and reproducibility better than 1%, possible near the wall to within 7-10 microns.

  14. Reference measurements on a Francis model turbine with 2D Laser-Doppler-Anemometry

    NASA Astrophysics Data System (ADS)

    Frey, A.; Kirschner, O.; Riedelbauch, S.; Jester-Zuerker, R.; Jung, A.

    2016-11-01

    To validate the investigations of a high-resolution CFD simulation of a Francis turbine, measurements with 2D Laser-Doppler-Anemometry are carried out. The turbine is operated in part load, where a rotating vortex rope occurs. To validate both, mean velocities and velocity fluctuations, the measurements are classified relative to the vortex rope position. Several acrylic glass windows are installed in the turbine walls such as upstream of the spiral case inlet, in the vaneless space and in the draft tube. The current investigation is focused on a measurement plane below the runner. 2D velocity components are measured on this whole plane by measuring several narrow spaced radial lines. To avoid optical refraction of the laser beam a plan parallel window is inserted in the cone wall. The laser probe is positioned with a 2D traverse system consisting of a circumferential rail and a radial aligned linear traverse. The velocity data are synchronized with the rotational frequency of the rotating vortex rope. The results of one measurement line show the dependency of the axial and circumferential velocities on the vortex rope position.

  15. Engine classification using vibrations measured by Laser Doppler Vibrometer on different surfaces

    NASA Astrophysics Data System (ADS)

    Wei, J.; Liu, Chi-Him; Zhu, Zhigang; Vongsy, Karmon; Mendoza-Schrock, Olga

    2015-05-01

    In our previous studies, vehicle surfaces' vibrations caused by operating engines measured by Laser Doppler Vibrometer (LDV) have been effectively exploited in order to classify vehicles of different types, e.g., vans, 2-door sedans, 4-door sedans, trucks, and buses, as well as different types of engines, such as Inline-four engines, V-6 engines, 1-axle diesel engines, and 2-axle diesel engines. The results are achieved by employing methods based on an array of machine learning classifiers such as AdaBoost, random forests, neural network, and support vector machines. To achieve effective classification performance, we seek to find a more reliable approach to pick authentic vibrations of vehicle engines from a trustworthy surface. Compared with vibrations directly taken from the uncooperative vehicle surfaces that are rigidly connected to the engines, these vibrations are much weaker in magnitudes. In this work we conducted a systematic study on different types of objects. We tested different types of engines ranging from electric shavers, electric fans, and coffee machines among different surfaces such as a white board, cement wall, and steel case to investigate the characteristics of the LDV signals of these surfaces, in both the time and spectral domains. Preliminary results in engine classification using several machine learning algorithms point to the right direction on the choice of type of object surfaces to be planted for LDV measurements.

  16. Particle flow in blade passages of turbomachinery with application to laser-Doppler velocimetry

    NASA Technical Reports Server (NTRS)

    Maxwell, B. R.

    1974-01-01

    A theoretical analysis was conducted of the dynamic behavior of micron size particles entrained in gas flow on the two-dimensional blade-to-blade surface of a circular stationary cascade of turbine stator blades. The particle velocity lag and angular deviation relative to the gas was determined as a function of particle diameter and mass density. Particles size and density were varied over ranges selected to correspond to typical laser-Doppler velocimeter (LDV) flow field mapping applications. It was found that velocity lag and angular deviation increased whenever particle size or mass density increased, and that particle tracking was more sensitive to a change in particle diameter than to a change in mass density. Results indicated that LDV applications employing 1 gm/cc tracer particles with diameters greater than approximately 1 micron, or 0.5 micron diameter particles with mass densities greater than 4 gm/cc would experience velocity and angular deviations generally greater than 2 percent and 1 degree, respectively.

  17. Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry

    NASA Astrophysics Data System (ADS)

    Strömberg, Tomas; Karlsson, Hanna; Fredriksson, Ingemar; Nyström, Fredrik H.; Larsson, Marcus

    2014-05-01

    Microvascular assessment would benefit from co-registration of blood flow and hemoglobin oxygenation dynamics during stimulus response tests. We used a fiber-optic probe for simultaneous recording of white light diffuse reflectance (DRS; 475-850 nm) and laser Doppler flowmetry (LDF; 780 nm) spectra at two source-detector distances (0.4 and 1.2 mm). An inverse Monte Carlo algorithm, based on a multiparameter three-layer adaptive skin model, was used for analyzing DRS data. LDF spectra were conventionally processed for perfusion. The system was evaluated on volar forearm recordings of 33 healthy subjects during a 5-min systolic occlusion protocol. The calibration scheme and the optimal adaptive skin model fitted DRS spectra at both distances within 10%. During occlusion, perfusion decreased within 5 s while oxygenation decreased slowly (mean time constant 61 s dissociation of oxygen from hemoglobin). After occlusion release, perfusion and oxygenation increased within 3 s (inflow of oxygenized blood). The increased perfusion was due to increased blood tissue fraction and speed. The supranormal hemoglobin oxygenation indicates a blood flow in excess of metabolic demands. In conclusion, by integrating DRS and LDF in a fiber-optic probe, a powerful tool for assessment of blood flow and oxygenation in the same microvascular bed has been presented.

  18. A preliminary report on the use of laser-Doppler flowmetry during tethered spinal cord release.

    PubMed

    Schneider, S J; Rosenthal, A D; Greenberg, B M; Danto, J

    1993-02-01

    Neurological deterioration in the tethered cord syndrome has been postulated to result from a compromise of blood flow in the distal spinal cord. In order to evaluate vascular perfusion in human subjects, a new technique of laser-Doppler flowmetry was used to monitor continuously the microcirculation of the distal spinal cord during surgery for tethered cord release in 10 children. For further comparison, five children undergoing selective dorsal rhizotomy were also monitored. In the tethered cord syndrome group, spinal cord blood flow before untethering was a mean of 12.6 ml/min per 100 g of tissue and increased in all cases after release to a mean of 29.4 ml/min per 100 g of tissue. All patients improved neurologically. The selective dorsal rhizotomy group had a preoperative mean spinal cord blood flow of 30.8 ml/min per 100 g of tissue, which was not altered by the operative procedure. Significant improvement occurs in distal spinal cord blood flow after tethered cord release, which may be representative of an important mechanism in the pathophysiology of the tethered cord syndrome.

  19. Agent-based station for on-line diagnostics by self-adaptive laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Serafini, S.; Paone, N.; Castellini, P.

    2013-12-01

    A self-adaptive diagnostic system based on laser vibrometry is proposed for quality control of mechanical defects by vibration testing; it is developed for appliances at the end of an assembly line, but its characteristics are generally suited for testing most types of electromechanical products. It consists of a laser Doppler vibrometer, equipped with scanning mirrors and a camera, which implements self-adaptive bahaviour for optimizing the measurement. The system is conceived as a Quality Control Agent (QCA) and it is part of a Multi Agent System that supervises all the production line. The QCA behaviour is defined so to minimize measurement uncertainty during the on-line tests and to compensate target mis-positioning under guidance of a vision system. Best measurement conditions are reached by maximizing the amplitude of the optical Doppler beat signal (signal quality) and consequently minimize uncertainty. In this paper, the optimization strategy for measurement enhancement achieved by the down-hill algorithm (Nelder-Mead algorithm) and its effect on signal quality improvement is discussed. Tests on a washing machine in controlled operating conditions allow to evaluate the efficacy of the method; significant reduction of noise on vibration velocity spectra is observed. Results from on-line tests are presented, which demonstrate the potential of the system for industrial quality control.

  20. Repeatability and reproducibility of characteristic features measured by laser Doppler vibrometry for on-line diagnostics

    NASA Astrophysics Data System (ADS)

    Agostinelli, G.; Paone, N.

    2008-06-01

    It is analyzed the statistical dispersion of characteristic features measured by Laser Doppler Vibrometry (LDV) in on-line diagnostic applications, with reference to on-line detection of mechanical defects of washing machines. The paper presents two complementary approaches: a) experimental evaluation of repeatability of measured features according to the Guide to the Expression of Uncertainty in Measurement-GUM; b) Montecarlo simulation of uncertainty propagation across the on-line test station. Experiments consist in a test bench which simulates the vibration of a washing machine, by playing back on a shaker a real signal acquired on-line and taking repeated measurements, so that a statistical analysis is performed about dispersion of diagnostic features. The analysis is repeated by varying the scattering characteristics of the vibrating surface, so to evaluate the effect of signal quality. The Montecarlo approach consists in modeling the propagation of uncertainty across the various elements of the measurement chain, up to the computation of features. The influence of LDV, Data Acquisition device (DAQ) and processing software have been taken into account. Results allow to estimate Repeatability and Reproducibility (R&R) of a typical set of characteristic features used in industrial diagnostics and to discuss uncertainty of similar diagnostic procedures.

  1. Non-contact measurement of facial surface vibration patterns during singing by scanning laser Doppler vibrometer

    PubMed Central

    Kitamura, Tatsuya; Ohtani, Keisuke

    2015-01-01

    This paper presents a method of measuring the vibration patterns on facial surfaces by using a scanning laser Doppler vibrometer (LDV). The surfaces of the face, neck, and body vibrate during phonation and, according to Titze (2001), these vibrations occur when aerodynamic energy is efficiently converted into acoustic energy at the glottis. A vocalist's vibration velocity patterns may therefore indicate his or her phonatory status or singing skills. LDVs enable laser-based non-contact measurement of the vibration velocity and displacement of a certain point on a vibrating object, and scanning LDVs permit multipoint measurements. The benefits of scanning LDVs originate from the facts that they do not affect the vibrations of measured objects and that they can rapidly measure the vibration patterns across planes. A case study is presented herein to demonstrate the method of measuring vibration velocity patterns with a scanning LDV. The objective of the experiment was to measure the vibration velocity differences between the modal and falsetto registers while three professional soprano singers sang sustained vowels at four pitch frequencies. The results suggest that there is a possibility that pitch frequency are correlated with vibration velocity. However, further investigations are necessary to clarify the relationships between vibration velocity patterns and phonation status and singing skills. PMID:26579054

  2. Beam pointing angle optimization and experiments for vehicle laser Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Fan, Zhe; Hu, Shuling; Zhang, Chunxi; Nie, Yanju; Li, Jun

    2015-10-01

    Beam pointing angle (BPA) is one of the key parameters that affects the operation performance of the laser Doppler velocimetry (LDV) system. By considering velocity sensitivity and echo power, for the first time, the optimized BPA of vehicle LDV is analyzed. Assuming mounting error is within ±1.0 deg, the reflectivity and roughness are variable for different scenarios, the optimized BPA is obtained in the range from 29 to 43 deg. Therefore, velocity sensitivity is in the range of 1.25 to 1.76 MHz/(m/s), and the percentage of normalized echo power at optimized BPA with respect to that at 0 deg is greater than 53.49%. Laboratory experiments with a rotating table are done with different BPAs of 10, 35, and 66 deg, and the results coincide with the theoretical analysis. Further, vehicle experiment with optimized BPA of 35 deg is conducted by comparison with microwave radar (accuracy of ±0.5% full scale output). The root-mean-square error of LDV's results is smaller than the Microstar II's, 0.0202 and 0.1495 m/s, corresponding to LDV and Microstar II, respectively, and the mean velocity discrepancy is 0.032 m/s. It is also proven that with the optimized BPA both high velocity sensitivity and acceptable echo power can simultaneously be guaranteed.

  3. Laser Doppler measurement of relative blood velocity in the human optic nerve head

    SciTech Connect

    Riva, C.E.; Grunwald, J.E.; Sinclair, S.H.

    1982-02-01

    The Doppler shift frequency spectrum (DSFS) of laser light scattered from red blood cells (RBCs) moving in the microcirculation of the optic nerve head has been recorded in normal volunteers by means of a fundus camera laser Doppler velocimeter. The width of the DSFS, which varies in proportion to the speed of the RBCs, has been characterized by a parameter alpha. With the use of a model for the scattering of light by tissue and RBCs and for the RBC velocity distribution, values of alpha recorded at normal intraocular pressure (IOP) suggest that the RBCs that contribute to the Doppler signal are flowing in capillaries. The parameter alpha was found to vary markedly with the IOP and with the phase of the ocular pressure pulse at elevated IOP. The return of the speed of RBCs toward normal, which is observed after a step increase of IOP above normal and after a step decrease below normal, has been attributed to an autoregulatory response of the optic nerve circulation.

  4. Photo-vibrational spectroscopy of solid and liquid chemicals using laser Doppler vibrometer.

    PubMed

    Hu, Qi; Lim, Jacob Song Kiat; Liu, Huan; Fu, Yu

    2016-08-22

    Photoacoustic/photothermal spectroscopy is an established technique for trace detection of chemicals and explosives. However, prior sample preparation is required and the analysis is conducted in a sealed space with a high-sensitivity microphone or a piezo sensor coupled with a lock-in amplifier, limiting the technique to applications in a laboratory environment. Due to the aforementioned requirements, traditionally this technique may not be suitable for defense and security applications where the detection of explosives or hazardous chemicals is required in an open environment at a safe standoff distance. In this study, chemicals in various forms (membrane, powder and liquid) were excited by an intensity-modulated quantum cascade laser (QCL), while a laser Doppler vibrometer (LDV) based on the Mach-Zehnder interferometer was applied to detect the vibration signal resulting from the photocoustic/photothermal effect. The photo-vibrational spectrum obtained by scanning the QCL's wavelength in MIR range, coincides well with the corresponding spectrum obtained using typical FTIR equipment. The experiment demonstrated that the LDV is a capable sensor for applications in photoacoustic/photothermal spectroscopy, with potential to enable the detection of chemicals in open environment at safe standoff distance.

  5. Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry.

    PubMed

    Strömberg, Tomas; Karlsson, Hanna; Fredriksson, Ingemar; Nyström, Fredrik H; Larsson, Marcus

    2014-05-01

    Microvascular assessment would benefit from co-registration of blood flow and hemoglobin oxygenation dynamics during stimulus response tests. We used a fiber-optic probe for simultaneous recording of white light diffuse reflectance (DRS; 475-850 nm) and laser Doppler flowmetry (LDF; 780 nm) spectra at two source-detector distances (0.4 and 1.2 mm). An inverse Monte Carlo algorithm, based on a multiparameter three-layer adaptive skin model, was used for analyzing DRS data. LDF spectra were conventionally processed for perfusion. The system was evaluated on volar forearm recordings of 33 healthy subjects during a 5-min systolic occlusion protocol. The calibration scheme and the optimal adaptive skin model fitted DRS spectra at both distances within 10%. During occlusion, perfusion decreased within 5 s while oxygenation decreased slowly (mean time constant 61 s; dissociation of oxygen from hemoglobin). After occlusion release, perfusion and oxygenation increased within 3 s (inflow of oxygenized blood). The increased perfusion was due to increased blood tissue fraction and speed. The supranormal hemoglobin oxygenation indicates a blood flow in excess of metabolic demands. In conclusion, by integrating DRS and LDF in a fiber-optic probe, a powerful tool for assessment of blood flow and oxygenation in the same microvascular bed has been presented.

  6. Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry.

    PubMed

    Fredriksson, Ingemar; Burdakov, Oleg; Larsson, Marcus; Strömberg, Tomas

    2013-12-01

    The tissue fraction of red blood cells (RBCs) and their oxygenation and speed-resolved perfusion are estimated in absolute units by combining diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF). The DRS spectra (450 to 850 nm) are assessed at two source-detector separations (0.4 and 1.2 mm), allowing for a relative calibration routine, whereas LDF spectra are assessed at 1.2 mm in the same fiber-optic probe. Data are analyzed using nonlinear optimization in an inverse Monte Carlo technique by applying an adaptive multilayered tissue model based on geometrical, scattering, and absorbing properties, as well as RBC flow-speed information. Simulations of 250 tissue-like models including up to 2000 individual blood vessels were used to evaluate the method. The absolute root mean square (RMS) deviation between estimated and true oxygenation was 4.1 percentage units, whereas the relative RMS deviations for the RBC tissue fraction and perfusion were 19% and 23%, respectively. Examples of in vivo measurements on forearm and foot during common provocations are presented. The method offers several advantages such as simultaneous quantification of RBC tissue fraction and oxygenation and perfusion from the same, predictable, sampling volume. The perfusion estimate is speed resolved, absolute (% RBC×mm/s), and more accurate due to the combination with DRS.

  7. Laser Doppler anemometry measurements of steady flow through two bi-leaflet prosthetic heart valves.

    PubMed

    Bazan, Ovandir; Ortiz, Jayme Pinto; Vieira, Francisco Ubaldo; Vieira, Reinaldo Wilson; Antunes, Nilson; Tabacow, Fabio Bittencourt Dutra; Costa, Eduardo Tavares; Petrucci, Orlando

    2013-01-01

    In vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hydrodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench. To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models) exposed to a steady flow regime, on four distinct sections, three downstream and one upstream. To provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min.) and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements. It was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found. Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM) is superior to the 21 AJ - 501 model (Master Series). Based on the results, future studies can choose to focus on specific regions of the these valves.

  8. Dynamic calibration technique for inertial navigation system based on one-dimensional laser Doppler velocimeter

    NASA Astrophysics Data System (ADS)

    Wang, Qun; Wei, Guo; Gao, Chunfeng; Wang, Qi; Long, Xingwu

    2016-10-01

    Taking the one-dimensional Laser Doppler Velocimeter (LDV) and a certain type of Laser Gyro Strapdown Inertial Navigation System (SINS) developed our staff room for object, the paper verifies that dynamic calibration technique can be achieved by SINS/LDV integrated system on the basis of the analysis of the software and hardware conditions. Extended Kalman filter states of SINS/LDV integrated system were chosen based on the error models of SINS and LDV. Using the difference of the output speed of the SINS and LDV as measurement, the error of bias and scale factor of the integrated navigation system are estimated effectively by setting up a reasonable calibration path. The effectiveness of the algorithm is further verified through the vehicular experiments. The results of experiments show that the dynamic calibration technique can be achieved through SINS/LDV integrated system and ensure the maneuverability of terrestrial inertial navigation system. The estimate of LDV scale factor is about 0.003%. The estimate error of accelerometer bias no more than 13μg. The estimate error of gyroscope drift no more than 1.7×10-3°/h. The yaw angle error is less than 0.19 ' within 20min.

  9. Dynamic Rotor Deformation and Vibration Monitoring Using a Non-Incremental Laser Doppler Distance Sensor

    SciTech Connect

    Pfister, Thorsten; Guenther, Philipp; Dreier, Florian; Czarske, Juergen

    2010-05-28

    Monitoring rotor deformations and vibrations dynamically is an important task for improving the safety and the lifetime as well as the energy efficiency of motors and turbo machines. However, due to the high rotor speed encountered in particular at turbo machines, this requires concurrently a high measurement rate and high accuracy, which can not be fulfilled by most commercially available sensors. To solve this problem, we developed a non-incremental laser Doppler distance sensor (LDDS), which is able to measure simultaneously the in-plane velocity and the out-of-plane position of moving rough solid objects with micrometer precision. In addition, this sensor concurrently offers a high temporal resolution in the microsecond range, because its position uncertainty is in principle independent of the object velocity in contrast to conventional distance sensors, which is a unique feature of the LDDS. Consequently, this novel sensor enables precise and dynamic in-process deformation and vibration measurements on rotating objects, such as turbo machine rotors, even at very high speed. In order to evidence the capability of the LDDS, measurements of rotor deformations (radial expansion), vibrations and wobbling motions are presented at up to 50,000 rpm rotor speed.

  10. Identification of pavement material properties using a scanning laser Doppler vibrometer

    NASA Astrophysics Data System (ADS)

    Hasheminejad, Navid; Vuye, Cedric; Van den Bergh, Wim; Dirckx, Joris; Leysen, Jari; Sels, Seppe; Vanlanduit, Steve

    2016-06-01

    This paper presents an inverse modeling approach to estimate mechanical properties of asphalt concrete (i.e. Young's modulus E, Poisson ratio ν and damping coefficients). Modal analysis was performed on an asphalt slab using a shaker to excite the specimen and an optical measurement system (a Scanning Laser Doppler Vibrometer or SLDV) to measure the velocity of a measurement grid on the surface of the slab. The SLDV has the ability to measure the vibration pattern of an object with high accuracy, short testing time and without making any contact. The measured data were used as inputs for a frequency domain model parameter estimation method (the Polymax estimator). Meanwhile, natural frequencies and damping ratios of the system were calculated using a Finite Element Modeling (FEM) method. Then, the Modal Assurance Criterion (MAC) was used to pair the mode shapes of the structure determined by measurements and estimated by FEM. By changing the inputs of the FEM analysis (E, ν and damping coefficients of the material) iteratively and minimizing the discrepancy between paired natural frequencies and damping ratios of the system estimated using the Polymax estimator and calculated by FEM, the Young's modulus, Poisson ratio and damping coefficients of the asphalt slab were estimated.

  11. Verification and validation of a patient simulator for test and evaluation of a laser doppler vibrometer

    NASA Astrophysics Data System (ADS)

    Byrd, Kenneth A.; Yauger, Sunny

    2012-06-01

    In the medical community, patient simulators are used to educate and train nurses, medics and doctors in rendering dierent levels of treatment and care to various patient populations. Students have the opportunity to perform real-world medical procedures without putting any patients at risk. A new thrust for the U.S. Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate (NVESD), is the use of remote sensing technologies to detect human vital signs at stando distances. This capability will provide medics with the ability to diagnose while under re in addition to helping them to prioritize the care and evacuation of battleeld casualties. A potential alternative (or precursor) to human subject testing is the use of patient simulators. This substitution (or augmenting) provides a safe and cost eective means to develop, test, and evaluate sensors without putting any human subjects at risk. In this paper, we present a generalized framework that can be used to accredit patient simulator technologies as human simulants for remote physiological monitoring (RPM). Results indicate that we were successful in using a commercial Laser Doppler Vibrometer (LDV) to exploit pulse and respiration signals from a SimMan 3G patient simulator at stando (8 meters).

  12. Sizing of irregular particles using a near backscattered laser Doppler system

    SciTech Connect

    Wu Xuecheng; Grehan, Gerard; Cen, Kefa; Ren, Kuan Fang; Wang Qinhui; Luo Zhongyang; Fang Mengxiang

    2007-12-20

    A near backscattered laser Doppler system was presented to carry out velocity and size distribution measurements for irregular particles in two-phase flows. The technique uses amplitudes of particles Doppler signals to estimate the particle size distribution in a statistical manner. Holve's numerical inversion scheme is employed to unfold the dependence of the scattered signals on both particle trajectory and orientation through the measurement volume. The performance and error level of the technique were simulated, and several parameters including the number of particle samples, the fluctuation of irregular particle response function, inversion algorithms, and types of particle size distribution were extensively investigated. The results show that the size distributions for those irregular particles even with strong fluctuations in response function can be successfully reconstructed with an acceptable error level using a Phillips-Twomey-non-negative least-squares algorithm instead of a non-negative least-squares one. The measurement system was then further experimentally verified with irregular quartz sands. Using inversion matrix obtained from the calibration experiment, the average measurement error for the mixing quartz sands with a size range of 200-560 {mu}m are found to be about 23.3%, which shows the reliability of the technique and the potential for it to be applied to industrial measurement.

  13. Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry

    NASA Astrophysics Data System (ADS)

    Fredriksson, Ingemar; Burdakov, Oleg; Larsson, Marcus; Strömberg, Tomas

    2013-12-01

    The tissue fraction of red blood cells (RBCs) and their oxygenation and speed-resolved perfusion are estimated in absolute units by combining diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF). The DRS spectra (450 to 850 nm) are assessed at two source-detector separations (0.4 and 1.2 mm), allowing for a relative calibration routine, whereas LDF spectra are assessed at 1.2 mm in the same fiber-optic probe. Data are analyzed using nonlinear optimization in an inverse Monte Carlo technique by applying an adaptive multilayered tissue model based on geometrical, scattering, and absorbing properties, as well as RBC flow-speed information. Simulations of 250 tissue-like models including up to 2000 individual blood vessels were used to evaluate the method. The absolute root mean square (RMS) deviation between estimated and true oxygenation was 4.1 percentage units, whereas the relative RMS deviations for the RBC tissue fraction and perfusion were 19% and 23%, respectively. Examples of in vivo measurements on forearm and foot during common provocations are presented. The method offers several advantages such as simultaneous quantification of RBC tissue fraction and oxygenation and perfusion from the same, predictable, sampling volume. The perfusion estimate is speed resolved, absolute (% RBC×mm/s), and more accurate due to the combination with DRS.

  14. Dual-frequency laser Doppler velocimeter for speckle noise reduction and coherence enhancement.

    PubMed

    Cheng, Chih-Hao; Lee, Chia-Wei; Lin, Tzu-Wei; Lin, Fan-Yi

    2012-08-27

    We study the characteristics of a dual-frequency laser Doppler velocimeter (DF-LDV) based on an optically injected semiconductor laser. The laser operated in a period-one (P1) dynamical state with two optical frequencies separated by 11.25 GHz is used as the dual-frequency light source. With a microwave beat signal carried by the light, the DF-LDV possesses both the advantages of good directionality, high intensity, and high spatial resolution from the light and low speckle noise and good coherence from the microwave, respectively. By phase-locking the two frequency components with a microwave signal, the coherence of the dual-frequency light source can be further improved and the detection range can be much extended. In this paper, velocity resolutions of the DF-LDV with different amounts of speckle noise and at different detection ranges are experimentally measured and analyzed. Compared with the conventional single-frequency LDV (SF-LDV), the velocity resolution of the DF-LDV is improved by 8 × 10(3) times from 2.5 m/s to 0.31 mm/s for a target with a longitudinal velocity vz = 4 cm/s, a transverse velocity vt = 5 m/s, and at a detection range of 108 m.

  15. Percutaneous penetration of methyl nicotinate from ointments using the laser Doppler technique: bioequivalence and enhancer effects.

    PubMed

    Remane, Yvonne; Leopold, Claudia S; Maibach, Howard I

    2006-12-01

    Laser Doppler flowmetry (LDF) may be used to quantify erythema response as a result of an increased cutaneous microcirculation induced by methyl nicotinate (MN). Bioequivalence of a test and a standard preparation (vehicles: light mineral oil and medium chain triglycerides, respectively) was confirmed according to the pilot study of the FDA Guidance for Industry "Topical dermatologic corticosteroids: In Vivo bioequivalence" applying the staggered application and synchronized removal method for one defined concentration. Furthermore, the influence of penetration enhancers (5% w/w Dimethylsulfoxide (DMSO) and 10% w/w diethylene glycol monoethyl ether) on MN penetration was investigated. It was shown that DMSO and diethylene glycol monoethyl ether altered cutaneous microcirculation and thus MN penetration in comparison to the standard formulation. However, true penetration enhancement could only be proved with diethylene glycol monoethyl ether resulting from an improved drug solubility in the skin which was confirmed by attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR). Increased MN penetration by DMSO was only caused by thermodynamic effects, i.e. a decreased drug solubility in the vehicle.

  16. Measurements of underwater acoustic pressure fields using a scanning laser Doppler vibrometer

    NASA Astrophysics Data System (ADS)

    Carroll, Gerard P.

    2004-05-01

    Laser Doppler vibrometers (LDV) are designed to measure structural vibration velocity by sensing the phase shift in the laser signal reflected from a vibrating source. It is known that index of refraction modulations resulting from acoustic pressure distributions along a laser light path will also cause a phase shift. Simpson et al. [J. Acoust. Soc. Am. 99(4), 2521(A) (1996)] have investigated this acousto-optic phase modulation as a possible contaminating effect for underwater LDV vibration measurements. This paper will investigate acousto-optic phase modulations measured by a scanning LDV as a method for measuring pressure radiating from underwater vibrating surfaces. This is done by passing the laser beam through the radiating pressure field and measuring the backscattered laser signal which is reflected off a rigid and retroreflective surface (outside the pressure field). It is shown experimentally, using the average pressure measured with an LDV over a plane in the vicinity of a vibrating structure, that the pressure at a far-field location normal to the plane can be determined.

  17. In-field use of laser Doppler vibrometer on a wind turbine blade

    SciTech Connect

    Rumsey, M.; Hurtado, J.; Hansche, B.

    1998-12-31

    One of our primary goals was to determine how well a laser Doppler vibrometer (LDV) could measure the structural dynamic response of a wind turbine that was parked in the field. We performed a series of preliminary tests in the lab to determine the basic limitations of the LDV for this application. We then instrumented an installed parked horizontal axis wind turbine with accelerometers to determine the natural frequencies, damping, and mode shapes of the wind turbine and rotor as a baseline for the LDV and our other tests. We also wanted to determine if LDV modal information could be obtained from a naturally (wind) excited wind turbine. We compared concurrently obtained accelerometer and LDV data in an attempt to assess the quality of the LDV data. Our test results indicate the LDV can be successfully used in the field environment of an installed wind turbine, but with a few restrictions. We were successful in obtaining modal information from a naturally (wind) excited wind turbine in the field, but the data analysis requires a large number of averaged data sets to obtain reasonable results. An ultimate goal of this continuing project is to develop a technique that will monitor the health of a structure, detect damage, and hopefully predict an impending component failure.

  18. Dynamic Rotor Deformation and Vibration Monitoring Using a Non-Incremental Laser Doppler Distance Sensor

    NASA Astrophysics Data System (ADS)

    Pfister, Thorsten; Günther, Philipp; Dreier, Florian; Czarske, Jürgen

    2010-05-01

    Monitoring rotor deformations and vibrations dynamically is an important task for improving the safety and the lifetime as well as the energy efficiency of motors and turbo machines. However, due to the high rotor speed encountered in particular at turbo machines, this requires concurrently a high measurement rate and high accuracy, which can not be fulfilled by most commercially available sensors. To solve this problem, we developed a non-incremental laser Doppler distance sensor (LDDS), which is able to measure simultaneously the in-plane velocity and the out-of-plane position of moving rough solid objects with micrometer precision. In addition, this sensor concurrently offers a high temporal resolution in the microsecond range, because its position uncertainty is in principle independent of the object velocity in contrast to conventional distance sensors, which is a unique feature of the LDDS. Consequently, this novel sensor enables precise and dynamic in-process deformation and vibration measurements on rotating objects, such as turbo machine rotors, even at very high speed. In order to evidence the capability of the LDDS, measurements of rotor deformations (radial expansion), vibrations and wobbling motions are presented at up to 50,000 rpm rotor speed.

  19. Accurate estimation of normal incidence absorption coefficients with confidence intervals using a scanning laser Doppler vibrometer

    NASA Astrophysics Data System (ADS)

    Vuye, Cedric; Vanlanduit, Steve; Guillaume, Patrick

    2009-06-01

    When using optical measurements of the sound fields inside a glass tube, near the material under test, to estimate the reflection and absorption coefficients, not only these acoustical parameters but also confidence intervals can be determined. The sound fields are visualized using a scanning laser Doppler vibrometer (SLDV). In this paper the influence of different test signals on the quality of the results, obtained with this technique, is examined. The amount of data gathered during one measurement scan makes a thorough statistical analysis possible leading to the knowledge of confidence intervals. The use of a multi-sine, constructed on the resonance frequencies of the test tube, shows to be a very good alternative for the traditional periodic chirp. This signal offers the ability to obtain data for multiple frequencies in one measurement, without the danger of a low signal-to-noise ratio. The variability analysis in this paper clearly shows the advantages of the proposed multi-sine compared to the periodic chirp. The measurement procedure and the statistical analysis are validated by measuring the reflection ratio at a closed end and comparing the results with the theoretical value. Results of the testing of two building materials (an acoustic ceiling tile and linoleum) are presented and compared to supplier data.

  20. Laser-tissue interaction with fs pulses: measurement of the recoil momentum by laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Mittnacht, Dirk, IV; Sessa, Gaetano; Travaglini, Michele; Foth, Hans-Jochen

    2003-10-01

    In the field of otolaryngology a precise contactless treatment of the bones in the middle ear is eligible. For this reason lasers are investigated for the use in this field. The main risk during laser surgery in the middle ear (e.g. stapedotomy) is the damage of hair cells in the inner ear due to heat diffusion or high pressure fluctuations. While the temperature problem has been resolved by shortening the pulse durations; the transfer of a recoil momentum due to the ablation process rises as another problem. To measure this momentum, special spring plates were designed as vibration disks for the mounting of the tissue. The probes were exposed to amplified Ti:Sapphire Laser pulses with a pulse length of 100fs and a power density up to 6,4*1013W/cm2. The beam of a Laser Doppler Vibrometer was focused on backside of the plate to monitor its motion. The results were compared to a damage threshold of hair cells in the inner ear calculated by a literature value for the Sound Pressure Level (SPL)-Threshold. The first results lead to SPL values below the critical value but measurements with a higher time resolution are necessary to verify this conclusion.