Science.gov

Sample records for potential swept source

  1. VCSEL Swept Light Sources

    NASA Astrophysics Data System (ADS)

    Jayaraman, Vijaysekhar; Jiang, James; Potsaid, Benjamin; Robertson, Martin; Heim, Peter J. S.; Burgner, Christopher; John, Demis; Cole, Garrett D.; Grulkowski, Ireneusz; Fujimoto, James G.; Davis, Anjul M.; Cable, Alex E.

    Wavelength-swept light sources are widely recognized as a critical enabling technology for swept source optical coherence tomography (SS-OCT). In recent years, amplified micro-electromechanical systems tunable vertical cavity surface-emitting lasers (MEMS-VCSELs) have emerged as a high performance swept source, providing a unique combination of of wide tuning range, high maximum sweep rate, variable sweep rate, long dynamic coherence length enabled by dynamic mode-hop-free single mode operation, high optical power, and excellent imaging quality. Other important parameters provided by these devices include operation in a stable polarization state, low output power ripple, and linearized wavelength sweeping. This work describes MEMS-VCSEL device design, fabrication, and performance for devices in the 1050nm band relevant to ophthalmic imaging, and the 1310nm band relevant to vascular, skin, and anatomic imaging. Tuning ranges achieved include 100 nm at 1050nm and 150nm at 1310, with the latter result representing the widest tuning range of any MEMS-VCSEL at any wavelength. Both 1050 and 1310nm devices have enabled record imaging speed, record imaging range, and enhanced SS-OCT imaging.

  2. Swept Light Sources

    NASA Astrophysics Data System (ADS)

    Johnson, Bart; Atia, Walid; Kuznetsov, Mark; Cook, Christopher; Goldberg, Brian; Wells, Bill; Larson, Noble; McKenzie, Eric; Melendez, Carlos; Mallon, Ed; Woo, Seungbum; Murdza, Randal; Whitney, Peter; Flanders, Dale

    A 1060 nm OEM laser "engine", manufactured by Axsun Technologies, is described. It consists of a swept laser and control electronics coupled with a balanced receiver, k-clock, and a 550 MS/s data acquisition board. The laser's passive mode-locking behavior induced by the rapid wavelength sweep is discussed. As they pass though the gain medium, each pulse is shifted to longer wavelength due to the rise in refractive index associated with gain depletion. New, longer wavelengths, are thus created by nonlinear means rather than by building up anew from spontaneous emission. This nonlinear mechanism enables low noise operation and fast sweep rates. The so-called "coherence revival" phenomenon associated with interference between neighboring mode-locked pulses, is discussed. Typical laser and system data is shown, including k-clock frequency, trigger waveform, pulsed and average output powers and RIN. Receiver and DAQ board noise performance is quantified. The laser RIN is estimated to be lower than -150 dB/Hz. A typical shot-noise-limited sensitivity of 103 dB is achieved for 1.9 mW sample power. The engine is designed for ophthalmic imaging and retinal images from prototype commercial systems are presented.

  3. Dual mode-locked swept sources for SS-OCT

    NASA Astrophysics Data System (ADS)

    Stancu, Radu F.; Podoleanu, Adrian G.

    2016-03-01

    A novel dual-mode-locking mechanism was developed in order to tune an akinetic swept source (AKSS) based on dispersive cavity at a repetition rate close to, but slightly different from the inverse of the cavity roundtrip. Several optical source configurations emitting in the 1060 nm or 1550 nm wavelength region were developed, characterized and tested in OCT applications. For the 1550 nm swept source employing a Faraday rotating mirror in a dispersive cavity, sweeping rates in the range of MHz were achieved, from 782 kHz to up to 5 times this value, with proportional decrease in the tuning bandwidth. Linewidths smaller than 60 pm and output powers exceeding a few mW were measured. The 1060 nm swept source implemented was used to generate OCT images of a pressure sensitive adhesive.

  4. SLEDs and Swept Source Laser Technology for OCT

    NASA Astrophysics Data System (ADS)

    Duelk, Marcus; Hsu, Kevin

    EXALOS offers broadband and high-power superluminescent light-emitting diodes (SLEDs) and high-speed wavelength-swept lasers, covering various visible and near-infrared wavelength regions (390-1,700 nm). These diverse wavelengths are realized in different semiconductor material systems such as GaN, GaAs, or InP. Those light sources are used in various fields such as navigation, optical coherence tomography (OCT), metrology, sensing, and microscopy. Detailed discussions on SLED characteristics and key swept-source OCT system design parameters are presented.

  5. Simultaneous 1310/1550 dual-band swept laser source and fiber-based dual-band common-path swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Mao, Youxin; Chang, Shoude; Murdock, Erroll; Flueraru, Costel

    2011-08-01

    A simultaneous two wavelength band swept laser source and a fiber-based dual-band common-path swept source optical coherence tomography is reported. Simultaneous 1310/1550 dual-wavelength tuning is performed by using two fiber-ring cavities with corresponding optical semiconductor amplifier as their gain mediums and two narrowband optical filters with a single dual-window polygonal scanner. Measured average output powers of 60 mW and 27 mW have been achieved for 1310 and 1550 nm bands, respectively, while the two wavelengths were swept simultaneously from 1227 nm to 1387 nm for 1310 nm band and from 1519 nm to 1581 nm for 1550 nm band at an A-scan rate of 65 kHz. A broadband 1310/1550 wavelength-division multiplexing is used for coupling two wavelengths into a common-path single-mode GRIN-lensed fiber probe to form a dual-band common-path swept-source optical coherence tomography. Simultaneous OCT imaging at 1310 and 1550 nm is achieved by using a depth ratio correction method. This technique allows potentially for in vivo endoscopic high-speed functional OCT imaging with high quality spectroscopic contrast with low computational costs. On the other hand, the common path configuration is able to reject common mode noise and potentially implement high stability quantitative phase measurements.

  6. Phase-sensitive swept source OCT imaging of the human retina with a VCSEL light source

    PubMed Central

    Choi, WooJhon; Potsaid, Benjamin; Jayaraman, Vijaysekhar; Baumann, Bernhard; Grulkowski, Ireneusz; Liu, Jonathan J.; Lu, Chen D.; Cable, Alex E.; Huang, David; Duker, Jay S.; Fujimoto, James G.

    2013-01-01

    Despite the challenges in achieving high phase stability, Doppler swept source / Fourier domain OCT has advantages of less fringe washout and faster imaging speeds compared to spectral / Fourier domain detection. This manuscript demonstrates swept source OCT with a VCSEL light source at 400kHz sweep rate for phase-sensitive Doppler imaging, measuring pulsatile total retinal blood flow with high sensitivity and phase stability. A robust, simple, and computationally efficient phase stabilization approach for phase-sensitive swept source imaging is also presented. PMID:23381430

  7. Swept-source anatomic optical coherence elastography of porcine trachea

    NASA Astrophysics Data System (ADS)

    Bu, Ruofei; Price, Hillel; Mitran, Sorin; Zdanski, Carlton; Oldenburg, Amy L.

    2016-02-01

    Quantitative endoscopic imaging is at the vanguard of novel techniques in the assessment upper airway obstruction. Anatomic optical coherence tomography (aOCT) has the potential to provide the geometry of the airway lumen with high-resolution and in 4 dimensions. By coupling aOCT with measurements of pressure, optical coherence elastography (OCE) can be performed to characterize airway wall stiffness. This can aid in identifying regions of dynamic collapse as well as informing computational fluid dynamics modeling to aid in surgical decision-making. Toward this end, here we report on an anatomic optical coherence tomography (aOCT) system powered by a wavelength-swept laser source. The system employs a fiber-optic catheter with outer diameter of 0.82 mm deployed via the bore of a commercial, flexible bronchoscope. Helical scans are performed to measure the airway geometry and to quantify the cross-sectional-area (CSA) of the airway. We report on a preliminary validation of aOCT for elastography, in which aOCT-derived CSA was obtained as a function of pressure to estimate airway wall compliance. Experiments performed on a Latex rubber tube resulted in a compliance measurement of 0.68+/-0.02 mm2/cmH2O, with R2=0.98 over the pressure range from 10 to 40 cmH2O. Next, ex vivo porcine trachea was studied, resulting in a measured compliance from 1.06+/-0.12 to 3.34+/-0.44 mm2/cmH2O, (R2>0.81). The linearity of the data confirms the elastic nature of the airway. The compliance values are within the same order-of-magnitude as previous measurements of human upper airways, suggesting that this system is capable of assessing airway wall compliance in future human studies.

  8. In vivo estimation of elastic wave parameters using phase-stabilized swept source optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Manapuram, Ravi Kiran; Aglyamov, Salavat R.; Monediado, Floredes M.; Mashiatulla, Maleeha; Li, Jiasong; Emelianov, Stanislav Y.; Larin, Kirill V.

    2012-10-01

    We report a highly sensitive method based on phase-stabilized swept source optical coherence elastography (PhS-SSOCE) to measure elastic wave propagation in soft tissues in vivo. The waves were introduced using a mechanical stimulus and were assessed using the phase response of the swept source optical coherence tomography signal. The technique was utilized to measure age-related changes in elastic flexural wave velocity and attenuation in mice cornea in vivo. Results demonstrate that the wave velocity increases with animal age, supporting previous observations that stiffness of mice cornea gradually increases with age. Our studies suggest that the PhS-SSOCE technique could potentially be used to obtain biomechanical properties of ocular tissues in vivo.

  9. Ultrahigh-Speed Swept-Source OCT Angiography in Exudative AMD

    PubMed Central

    Moult, Eric; Choi, WooJhon; Waheed, Nadia K.; Adhi, Mehreen; Lee, ByungKun; Lu, Chen D.; Jayaraman, Vijaysekhar; Potsaid, Benjamin; Rosenfeld, Philip J.; Duker, Jay S.; Fujimoto, James G.

    2016-01-01

    Background and Objective To investigate the potential of ultrahigh-speed swept-source optical coherence tomography angiography (OCTA) to visualize retinal and choroidal vascular changes in patients with exudative age-related macular degeneration (AMD). Patients and Methods Observational, prospective cross-sectional study. An ultrahigh-speed swept-source prototype was used to perform OCTA of the retinal and choriocapillaris microvasculature in 63 eyes of 32 healthy controls and 19 eyes of 15 patients with exudative AMD. Main outcome measure: qualitative comparison of the retinal and choriocapillaris microvasculature in the two groups. Results Choroidal neovascularization (CNV) was clearly visualized in 16 of the 19 eyes with exudative AMD, located above regions of severe choriocapillaris alteration. In 14 of these eyes, the CNV lesions were surrounded by regions of choriocapillaris alteration. Conclusion OCTA may offer noninvasive monitoring of the retinal and choriocapillaris microvasculature in patients with CNV, which may assist in diagnosis and monitoring. PMID:25423628

  10. Spectral delay line for display control in swept source OCT

    NASA Astrophysics Data System (ADS)

    Toadere, Florin; Bradu, Adrian; Poon, Wallace; Schultz, David; Podoleanu, Adrian

    2015-02-01

    A modality of controlling the unbalanced dispersion in an optical coherence tomography (OCT) set-up is presented, together with image processing techniques that improve the quality of the interferogram image by reducing its noise and dispersion. The ultimate goal of the study is to obtain dispersion free and enhanced signal to noise ratio OCT images of the human retina. The OCT set-up incorporates a spectral delay line, which is used to compensate for the dispersion in the system. The configuration is driven by a swept optical source. The interferometric signal is digitized by a fast acquisition board, then processed and rendered as images on a computer display. Preliminary results are presented showing images of a multilayer structure obtained using different filtering techniques that were tested for their effects on the noise reduction and image sharpness.

  11. Images of arterial tissues using catheter swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Mao, Youxin; Flueraru, Costel; Chang, Shoude; Popescu, Dan P.; Sowa, M. G.

    2010-06-01

    Optical coherence tomography images of arterial samples harvested from asymptomatic pigs and from lipid-rich Watanabe heritable hyperlipidemic rabbits were acquired using a fiber catheter-based swept-source optical coherence tomography system (OCT). A quadrature Mach-Zehnder interferometer based on multi-port fiber couplers and a semiconductor optical amplifier (SOA) were employed in the swept-source optical coherence tomography system. The improvement of signal to noise ratio as a result of incorporating the SOA into the configuration translated in an increase of the penetration depth. A fiber probe ending in a fiber ball lens was developed for the arterial imaging. The images acquired by this system offer the possibility to investigate anatomical details located under the surface of the artery such as the intima, media, and adventitia layers (from lumen side) of the blood vessel wall , as well as morphological features specific to artherosclerotic plaques such as lipid pools, fibrous caps, macrophage accumulations and calcified. This report indicates that our improved catheter-based swept source OCT is a potential tool for in vivo intravascular imaging.

  12. 28 MHz swept source at 1.0 μm for ultrafast quantitative phase imaging.

    PubMed

    Wei, Xiaoming; Lau, Andy K S; Xu, Yiqing; Tsia, Kevin K; Wong, Kenneth K Y

    2015-10-01

    Emerging high-throughput optical imaging modalities, in particular those providing phase information, necessitate a demanding speed regime (e.g. megahertz sweep rate) for those conventional swept sources; while an effective solution is yet to be demonstrated. We demonstrate a stable breathing laser as inertia-free swept source (BLISS) operating at a wavelength sweep rate of 28 MHz, particularly for the ultrafast interferometric imaging modality at 1.0 μm. Leveraging a tunable dispersion compensation element inside the laser cavity, the wavelength sweep range of BLISS can be tuned from ~10 nm to ~63 nm. It exhibits a good intensity stability, which is quantified by the ratio of standard deviation to the mean of the pulse intensity, i.e. 1.6%. Its excellent wavelength repeatability, <0.05% per sweep, enables the single-shot imaging at an ultrafast line-scan rate without averaging. To showcase its potential applications, it is applied to the ultrafast (28-MHz line-scan rate) interferometric time-stretch (iTS) microscope to provide quantitative morphological information on a biological specimen at a lateral resolution of 1.2 μm. This fiber-based inertia-free swept source is demonstrated to be robust and broadband, and can be applied to other established imaging modalities, such as optical coherence tomography (OCT), of which an axial resolution better than 12 μm can be achieved. PMID:26504636

  13. 28 MHz swept source at 1.0 μm for ultrafast quantitative phase imaging

    PubMed Central

    Wei, Xiaoming; Lau, Andy K. S.; Xu, Yiqing; Tsia, Kevin K.; Wong, Kenneth K. Y.

    2015-01-01

    Emerging high-throughput optical imaging modalities, in particular those providing phase information, necessitate a demanding speed regime (e.g. megahertz sweep rate) for those conventional swept sources; while an effective solution is yet to be demonstrated. We demonstrate a stable breathing laser as inertia-free swept source (BLISS) operating at a wavelength sweep rate of 28 MHz, particularly for the ultrafast interferometric imaging modality at 1.0 μm. Leveraging a tunable dispersion compensation element inside the laser cavity, the wavelength sweep range of BLISS can be tuned from ~10 nm to ~63 nm. It exhibits a good intensity stability, which is quantified by the ratio of standard deviation to the mean of the pulse intensity, i.e. 1.6%. Its excellent wavelength repeatability, <0.05% per sweep, enables the single-shot imaging at an ultrafast line-scan rate without averaging. To showcase its potential applications, it is applied to the ultrafast (28-MHz line-scan rate) interferometric time-stretch (iTS) microscope to provide quantitative morphological information on a biological specimen at a lateral resolution of 1.2 μm. This fiber-based inertia-free swept source is demonstrated to be robust and broadband, and can be applied to other established imaging modalities, such as optical coherence tomography (OCT), of which an axial resolution better than 12 μm can be achieved. PMID:26504636

  14. Polarization-maintaining buffered Fourier domain mode-locked swept source for optical coherence tomography

    PubMed Central

    Zhang, Jun; Jing, Joe; Wang, Pinghe; Chen, Zhongping

    2012-01-01

    A polarization-maintaining buffered Fourier domain mode-locked (FDML) swept source with a center wavelength of 1300 nm is demonstrated. The scanning rate of the buffered FDML swept source is doubled without sacrificing the output power of the swept source by combining two orthogonally polarized outputs with a polarization beam combiner. The stability of the swept source is improved because the polarization state of the laser beam inside the laser cavity is maintained without the use of any polarization controllers. The swept source is capable of an edge-to-edge tuning range of more than 150 nm and a FWHM range of 95 nm at a 102 kHz sweeping rate and with an average power of 12 mW. A swept source optical coherence tomography (SSOCT) system is developed utilizing this buffered FDML swept source. The axial resolution of the SSOCT system is measured to be 9.4 μmin air. The sensitivity of the SSOCT system is 107.5 dB at a depth of 0.25 mm with a 6 dB roll-off at a depth of 2.25 mm. PMID:22179884

  15. Colorectal neoplasm characterization based on swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lu, Chih-Wei; Chiu, Han-Mo; Sun, Chia-Wei

    2009-07-01

    Most of the colorectal cancer has grown from the adenomatous polyp. Adenomatous lesions have a well-documented relationship to colorectal cancer in previous studies. Thus, to detect the morphological changes between polyp and tumor can allow early diagnosis of colorectal cancer and simultaneous removal of lesions. In this paper, the various adenoma/carcinoma in-vitro samples are monitored by our swept-source optical coherence tomography (SS-OCT) system. The significant results indicate a great potential for early detection of colorectal adenomas based on the SS-OCT imaging.

  16. Breathing laser as an inertia-free swept source for high-quality ultrafast optical bioimaging.

    PubMed

    Wei, Xiaoming; Xu, Jingjiang; Xu, Yiqing; Yu, Luoqin; Xu, Jianbing; Li, Bowen; Lau, Andy K S; Wang, Xie; Zhang, Chi; Tsia, Kevin K; Wong, Kenneth K Y

    2014-12-01

    We demonstrate an all-fiber breathing laser as inertia-free swept source (BLISS), with an ultra-compact design, for the emerging ultrafast bioimaging modalities. The unique feature of BLISS is its broadband wavelength-swept operation (∼60  nm) with superior temporal stability in terms of both long term (0.08 dB over 27 h) and shot-to-shot power variations (2.1%). More importantly, it enables a wavelength sweep rate of >10  MHz (∼7×10⁸  nm/s)—orders-of-magnitude faster than the existing swept sources based on mechanical or electrical tuning techniques. BLISS thus represents a practical and new generation of swept source operating in the unmet megahertz swept-rate regime that aligns with the pressing need for scaling the optical bioimaging speed in ultrafast phenomena study or high-throughput screening applications. To showcase its utility in high-speed optical bioimaging, we here employ BLISS for ultrafast time-stretch microscopy and multi-MHz optical coherence tomography of the biological specimen at a single-shot line-scan rate or A-scan rate of 11.5 MHz. PMID:25490629

  17. The advantages of a swept source optical coherence tomography system in the evaluation of occlusal disorders

    NASA Astrophysics Data System (ADS)

    Marcauteanu, Corina; Bradu, Adrian; Sinescu, Cosmin; Topala, Florin Ionel; Negrutiu, Meda Lavinia; Duma, Virgil Florin; Podoleanu, Adrian Gh.

    2014-01-01

    Occlusal disorders are characterized by multiple dental and periodontal signs. Some of these are reversible (such as excessive tooth mobility, fremitus, tooth pain, migration of teeth in the absence of periodontitis), some are not (pathological occlusal/incisal wear, abfractions, enamel cracks, tooth fractures, gingival recessions). In this paper we prove the advantages of a fast swept source OCT system in the diagnosis of pathological incisal wear, a key sign of the occlusal disorders. On 15 extracted frontal teeth four levels of pathological incisal wear facets were artificially created. After every level of induced defect, OCT scanning was performed. B scans were acquired and 3D reconstructions were generated. A swept source OCT instrument is used in this study. The swept source is has a central wavelength of 1050 nm and a sweeping rate of 100 kHz. A depth resolution determined by the swept source of 12 μm in air was experimentally measured. The pathological incisal wear is qualitatively observed on the B-scans as 2D images and 3D reconstructions (volumes). For quantitative evaluations of volumes, we used the Image J software. Our swept source OCT system has several advantages, including the ability to measure (in air) a minimal volume of 2352 μm3 and to collect high resolution volumetric images in 2.5 s. By calculating the areas of the amount of lost tissue corresponding to each difference of B-scans, the final volumes of incisal wear were obtained. This swept source OCT method is very useful for the dynamic evaluation of pathological incisal wear.

  18. Estimation of elastic parameters of ovarian tissue using phase stabilized swept source optical-coherence tomography

    NASA Astrophysics Data System (ADS)

    Nandy, Sreyankar; Wang, Tianheng; Salehi, Hassan; Sanders, Melinda; Brewer, Molly; Zhu, Quing

    2015-03-01

    We have estimated the micro-mechanical properties of ovarian tissue using phase-sensitive swept source optical coherence tomography. Ovary samples were mechanically excited by periodical vibration of an ultrasound transducer. The displacement and strain of the tissues were calculated during loading. Significant difference in strain was observed between the normal and malignant ovary groups, which indicates much softer and heterogeneous tissue structure for malignant ovaries. The initial results show that the phase sensitive swept source optical coherence elastography (OCE) can be an effective tool for characterization of stiffness and other micro-mechanical properties of normal and malignant ovarian tissue.

  19. Phase-stable swept source OCT angiography in human skin using an akinetic source

    PubMed Central

    Chen, Zhe; Liu, Mengyang; Minneman, Michael; Ginner, Laurin; Hoover, Erich; Sattmann, Harald; Bonesi, Marco; Drexler, Wolfgang; Leitgeb, Rainer A.

    2016-01-01

    We demonstrate noninvasive structural and microvascular contrast imaging of human skin in vivo, using phase difference swept source OCT angiography (pOCTA). The pOCTA system employs an akinetic, all-semiconductor, highly phase-stable swept laser source which operates at 1340 nm central wavelength, with 37 nm bandwidth (at 0 dB region) and 200 kHz A-scan rate. The phase sensitive detection does not need any external phase stabilizing implementations, due to the outstanding high phase linearity and sweep phase repeatability within 2 mrad. We compare the performance of phase based OCTA to speckle based OCTA for visualizing human vascular networks. pOCTA shows better contrast especially for deeper vascular details as compared to speckle based OCTA. The phase stability of the akinetic source allows the OCTA system to show decent vascular contrast only with 2 B-scans. We compare the performance of using 2 versus 4 B-scans for calculating the vascular contrast. Finally, the performance of a 100 nm bandwidth akinetic laser at 1310 nm is investigated for both OCT and OCTA. PMID:27570695

  20. Phase-stable swept source OCT angiography in human skin using an akinetic source.

    PubMed

    Chen, Zhe; Liu, Mengyang; Minneman, Michael; Ginner, Laurin; Hoover, Erich; Sattmann, Harald; Bonesi, Marco; Drexler, Wolfgang; Leitgeb, Rainer A

    2016-08-01

    We demonstrate noninvasive structural and microvascular contrast imaging of human skin in vivo, using phase difference swept source OCT angiography (pOCTA). The pOCTA system employs an akinetic, all-semiconductor, highly phase-stable swept laser source which operates at 1340 nm central wavelength, with 37 nm bandwidth (at 0 dB region) and 200 kHz A-scan rate. The phase sensitive detection does not need any external phase stabilizing implementations, due to the outstanding high phase linearity and sweep phase repeatability within 2 mrad. We compare the performance of phase based OCTA to speckle based OCTA for visualizing human vascular networks. pOCTA shows better contrast especially for deeper vascular details as compared to speckle based OCTA. The phase stability of the akinetic source allows the OCTA system to show decent vascular contrast only with 2 B-scans. We compare the performance of using 2 versus 4 B-scans for calculating the vascular contrast. Finally, the performance of a 100 nm bandwidth akinetic laser at 1310 nm is investigated for both OCT and OCTA. PMID:27570695

  1. 23 kHz MEMS based swept source for optical coherence tomography imaging.

    PubMed

    Vuong, Barry; Sun, Cuiru; Harduar, Mark K; Mariampillai, Adrian; Isamoto, Keiji; Chong, Changho; Standish, Beau A; Yang, Victor X D

    2011-01-01

    The transition from benchtop to clinical system often requires the medical technology to be robust, portable and accurate. This poses a challenge to current swept source optical coherence tomography imaging systems, as the bulk of the systems footprint is due to laser components. With the recent advancement of micromachining technology, we demonstrate the characterization of a microelectromechanical system (MEMS) swept source laser for optical coherence tomography imaging (OCT). This laser utilizes a 2 degree of freedom MEMS scanning mirror and a diffraction grating, which are arranged in a Littrow configuration. This resulted in a swept source laser that was capable of scanning at 23.165 kHz (bidirectional) or 11.582 kHz (unidirectional). The free spectral range of the laser was ≈ 100 nm with a central wavelength of ≈ 1330 nm. The 6 dB roll off depth was measured to be at 2.5 mm. Furthermore, the structural morphology of a human finger and tadpole (Xenopus laevis) were evaluated. The overall volumetric footprint of the laser source was measured to be 70 times less than non-MEMS swept sources. Continued work on the miniaturization of OCT system is on going. It is hypothesized that the overall laser size can be reduced for suitable OCT imaging for a point of care application. PMID:22255739

  2. Imaging of noncarious cervical lesions by means of a fast swept source optical coherence tomography system

    NASA Astrophysics Data System (ADS)

    Stoica, Eniko T.; Marcauteanu, Corina; Bradu, Adrian; Sinescu, Cosmin; Topala, Florin Ionel; Negrutiu, Meda Lavinia; Duma, Virgil Florin; Podoleanu, Adrian Gh.

    2014-01-01

    Non-carious cervical lesions (NCCL) are defined as the loss of tooth substance at the cemento-enamel junction and are caused by abrasion, erosion and/or occlusal overload. In this paper we proved that our fast swept source OCT system is a valuable tool to track the evolution of NCCL lesions in time. On several extracted bicuspids, four levels of NCCL were artificially created. After every level of induced lesion, OCT scanning was performed. B scans were acquired and 3D reconstructions were generated. The swept source OCT instrument used in this study has a central wavelength of 1050 nm, a sweeping range of 106 nm (measured at 10 dB), an average output power of 16 mW and a sweeping rate of 100 kHz. A depth resolution determined by the swept source of 12 μm in air was experimentally obtained. NCCL were measured on the B-scans as 2D images and 3D reconstructions (volumes). For quantitative evaluations of volumes, the Image J software was used. By calculating the areas of the amount of lost tissue corresponding to each difference of Bscans, the final volumes of NCCL were obtained. This swept source OCT method allows the dynamic diagnosis of NCCL in time.

  3. Simple and versatile long range swept source for optical coherence tomography applications

    NASA Astrophysics Data System (ADS)

    Bräuer, Bastian; Lippok, Norman; Murdoch, Stuart G.; Vanholsbeeck, Frédérique

    2015-12-01

    We present a versatile long coherence length swept-source laser design for optical coherence tomography applications. This design consists of a polygonal spinning mirror and an optical gain chip in a modified Littman-Metcalf cavity. A narrowband intra-cavity filter is implemented through multiple passes off a diffraction grating set at grazing incidence. The key advantage of this design is that it can be readily adapted to any wavelength regions for which broadband gain chips are available. We demonstrate this by implementing sources at 1650 nm, 1550 nm, 1310 nm and 1050 nm. In particular, we present a 1310 nm swept source laser with 24 mm coherence length, 95 nm optical bandwidth, 2 kHz maximum sweep frequency and 7.5 mW average output power. These parameters make it a suitable source for the imaging of biological samples.

  4. High-speed miniaturized swept sources based on resonant MEMS mirrors and diffraction gratings

    NASA Astrophysics Data System (ADS)

    Gloor, S.; Bachmann, A. H.; Epitaux, M.; von Niederhäusern, T.; Vorreau, P.; Matuschek, N.; Hsu, K.; Duelk, M.; Vélez, C.

    2013-03-01

    We show a broad range of swept source performances based on a highly-flexible external cavity laser architecture. Specifically, we demonstrate a 40-kHz 1300-nm swept source with 10 mm coherence length realized in a compact butterfly package. Fast wavelength sweeping is achieved through a 1D 20-kHz MEMS mirror in combination with an advanced diffraction grating. The MEMS mirror is a resonant electrostatic mirror that performs harmonic oscillation only within a narrow frequency range, resulting in low-jitter and long-term phase-stable sinusoidal bidirectional sweep operation with an A-scan rate of 40 kHz. The source achieves a coherence length of 10 mm for both the up- and downsweep and an OCT sensitivity of 105 dB.

  5. Clinical utility of anterior segment swept-source optical coherence tomography in glaucoma

    PubMed Central

    Angmo, Dewang; Nongpiur, Monisha E.; Sharma, Reetika; Sidhu, Talvir; Sihota, Ramanjit; Dada, Tanuj

    2016-01-01

    Optical coherence tomography (OCT), a noninvasive imaging modality that uses low-coherence light to obtain a high-resolution cross-section of biological structures, has evolved dramatically over the years. The Swept-source OCT (SS-OCT) makes use of a single detector with a rapidly tunable laser as a light source. The Casia SS-1000 OCT is a Fourier-domain, SS-OCT designed specifically for imaging the anterior segment. This system achieves high resolution imaging of 10΅m (Axial) and 30΅m (Transverse) and high speed scanning of 30,000 A-scans per second. With a substantial improvement in scan speed, the anterior chamber angles can be imaged 360 degrees in 128 cross sections (each with 512 A-scans) in about 2.4 seconds. We summarize the clinical applications of anterior segment SS-OCT in Glaucoma. Literature search: We searched PubMed and included Medline using the phrases anterior segment optical coherence tomography in ophthalmology, swept-source OCT, use of AS-OCT in glaucoma, use of swept-source AS-OCT in glaucoma, quantitative assessment of angle, filtering bleb in AS-OCT, comparison of AS-OCT with gonioscopy and comparison of AS-OCT with UBM. Search was made for articles dating 1990 to August 2015. PMID:27013821

  6. Fiber Bragg grating sensor system using single-mode wavelength swept light source

    NASA Astrophysics Data System (ADS)

    Saitoh, Takanori; Nakamura, Kenichi; Furukawa, Hiroshi; Koshihara, Masaru

    2011-05-01

    This paper reports a high-performance FBG sensor system using a novel single-mode wavelength swept light source that can sweep wavelengths with a spectrum line width of 1 pm, a sweep range of 135 nm, and a sweep frequency of 160 Hz. This system can measure an FBG spectrum with 1-pm resolution and an FBG wavelength with 0.2-pm repeatability with a measurement frequency of 160 Hz.

  7. Swept source optical coherence tomography with external clocking using voltage controlled oscillator

    NASA Astrophysics Data System (ADS)

    Lee, Eung Je; Kim, Yong Pyung

    2011-05-01

    In this study, a beat signal recalibration method was developed for optical coherence tomography (OCT) with a high-speed wavelength-swept source. By adopting a voltage-controlled oscillator (VCO) modulated by a sinusoidal waveform as a trigger for the OCT system, the broadening of the beat frequency due to laser tuning rate variations was recalibrated. For this study, OCT based on a Fourier domain mode-locked (FDML) laser at a sweep rate of 60.9 kHz was demonstrated. OCT images of 1500×409 pixels were obtained with the sensitivity of 100 dB. Temporal frequency variations in the FDML laser and OCT images obtained with the proposed technique were also described. When compared to a conventional recalibration method using optical components, swept source optical coherence tomography operated with a VCO clock exhibited superior performance and high stability. From the experimental results, it was demonstrated that the proposed method is sufficient to recalibrate the time-frequency variations in interferometry with a high-speed wavelength-swept source.

  8. Swept-Source Optical Coherence Tomography Angio™ (Topcon Corp, Japan): Technology Review.

    PubMed

    Stanga, Paulo E; Tsamis, Emmanouil; Papayannis, Alessandro; Stringa, Francesco; Cole, Tim; Jalil, Assad

    2016-01-01

    Optical coherence tomography (OCT) angiography (OCTA) is a novel, noninvasive, three-dimensional imaging technique that allows for the visualization of intravascular flow in the microvasculature. Swept-source OCT technology utilizes longer-wavelength infrared light than conventional spectral-domain OCT. This enables improved penetration into tissue and imaging through optical opacities and is invisible to the subject. Topcon has recently developed an innovative OCTA algorithm, OCTARA (OCTA Ratio Analysis), which benefits from being paired with swept-source OCT. OCTARA aims to provide improved detection sensitivity of low blood flow and reduced motion artifacts without compromising axial resolution. In this chapter, we describe the implementation of OCTARA with swept-source OCT technology, the technical specifications of acquisition (e.g. the number of scans, area of examination field, etc.) along with the algorithm's function and principles for analysis of B-scan data to achieve angiographic visualization. Examples of OCTA scans performed using the OCTARA algorithm and a comparison of these scans with images obtained using other technologies are also presented. PMID:27023108

  9. Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation

    PubMed Central

    Siddiqui, Meena; Tozburun, Serhat; Zhang, Ellen Ziyi; Vakoc, Benjamin J.

    2015-01-01

    We provide a framework for compensating errors within passive optical quadrature demodulation circuits used in swept-source optical coherence tomography (OCT). Quadrature demodulation allows for detection of both the real and imaginary components of an interference fringe, and this information separates signals from positive and negative depth spaces. To achieve a high extinction (∼60 dB) between these positive and negative signals, the demodulation error must be less than 0.1% in amplitude and phase. It is difficult to construct a system that achieves this low error across the wide spectral and RF bandwidths of high-speed swept-source systems. In a prior work, post-processing methods for removing residual spectral errors were described. Here, we identify the importance of a second class of errors originating in the RF domain, and present a comprehensive framework for compensating both spectral and RF errors. Using this framework, extinctions >60 dB are demonstrated. A stability analysis shows that calibration parameters associated with RF errors are accurate for many days, while those associated with spectral errors must be updated prior to each imaging session. Empirical procedures to derive both RF and spectral calibration parameters simultaneously and to update spectral calibration parameters are presented. These algorithms provide the basis for using passive optical quadrature demodulation circuits with high speed and wide-bandwidth swept-source OCT systems. PMID:25836784

  10. Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation.

    PubMed

    Siddiqui, Meena; Tozburun, Serhat; Zhang, Ellen Ziyi; Vakoc, Benjamin J

    2015-03-01

    We provide a framework for compensating errors within passive optical quadrature demodulation circuits used in swept-source optical coherence tomography (OCT). Quadrature demodulation allows for detection of both the real and imaginary components of an interference fringe, and this information separates signals from positive and negative depth spaces. To achieve a high extinction (∼60 dB) between these positive and negative signals, the demodulation error must be less than 0.1% in amplitude and phase. It is difficult to construct a system that achieves this low error across the wide spectral and RF bandwidths of high-speed swept-source systems. In a prior work, post-processing methods for removing residual spectral errors were described. Here, we identify the importance of a second class of errors originating in the RF domain, and present a comprehensive framework for compensating both spectral and RF errors. Using this framework, extinctions >60 dB are demonstrated. A stability analysis shows that calibration parameters associated with RF errors are accurate for many days, while those associated with spectral errors must be updated prior to each imaging session. Empirical procedures to derive both RF and spectral calibration parameters simultaneously and to update spectral calibration parameters are presented. These algorithms provide the basis for using passive optical quadrature demodulation circuits with high speed and wide-bandwidth swept-source OCT systems. PMID:25836784

  11. Detection of occlusal caries in primary teeth using swept source optical coherence tomography.

    PubMed

    Nakajima, Yukie; Shimada, Yasushi; Sadr, Alireza; Wada, Ikumi; Miyashin, Michiyo; Takagi, Yuzo; Tagami, Junji; Sumi, Yasunori

    2014-01-01

    This study aimed to investigate swept source optical coherence tomography (SS-OCT) as a detecting tool for occlusal caries in primary teeth. At the in vitro part of the study, 38 investigation sites of occlusal fissures (noncavitated and cavitated) were selected from 26 extracted primary teeth and inspected visually using conventional dental equipment by six examiners without any magnification. SS-OCT cross-sectional images at 1330-nm center wavelength were acquired on the same locations. The teeth were then sectioned at the investigation site and directly viewed under a confocal laser scanning microscope (CLSM) by two experienced examiners. The presence and extent of caries were scored in each observation. The results obtained from SS-OCT and conventional visual inspections were compared with those of CLSM. Consequently, SS-OCT could successfully detect both cavitated and noncavitated lesions. The magnitude of sensitivity for SS-OCT was higher than those for visual inspection (sensitivity of visual inspection and SS-OCT, 0.70 versus 0.93 for enamel demineralization, 0.49 versus 0.89 for enamel cavitated caries, and 0.36 versus 0.75 for dentin caries). Additionally, occlusal caries of a few clinical cases were observed using SS-OCT in vivo. The results indicate that SS-OCT has a great detecting potential for occlusal caries in primary teeth. PMID:24474506

  12. Adaptive optics OCT using 1060nm swept source and dual deformable lenses for human retinal imaging

    NASA Astrophysics Data System (ADS)

    Jian, Yifan; Lee, Sujin; Cua, Michelle; Miao, Dongkai; Bonora, Stefano; Zawadzki, Robert J.; Sarunic, Marinko V.

    2016-03-01

    Adaptive optics concepts have been applied to the advancement of biological imaging and microscopy. In particular, AO has also been very successfully applied to cellular resolution imaging of the retina, enabling visualization of the characteristic mosaic patterns of the outer retinal layers using flood illumination fundus photography, Scanning Laser Ophthalmoscopy (SLO), and Optical Coherence Tomography (OCT). Despite the high quality of the in vivo images, there has been a limited uptake of AO imaging into the clinical environment. The high resolution afforded by AO comes at the price of limited field of view and specialized equipment. The implementation of a typical adaptive optics imaging system results in a relatively large and complex optical setup. The wavefront measurement is commonly performed using a Hartmann-Shack Wavefront Sensor (HS-WFS) placed at an image plane that is optically conjugated to the eye's pupil. The deformable mirror is also placed at a conjugate plane, relaying the wavefront corrections to the pupil. Due to the sensitivity of the HS-WFS to back-reflections, the imaging system is commonly constructed from spherical mirrors. In this project, we present a novel adaptive optics OCT retinal imaging system with significant potential to overcome many of the barriers to integration with a clinical environment. We describe in detail the implementation of a compact lens based wavefront sensorless adaptive optics (WSAO) 1060nm swept source OCT human retinal imaging system with dual deformable lenses, and present retinal images acquired in vivo from research volunteers.

  13. Detection of occlusal caries in primary teeth using swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Nakajima, Yukie; Shimada, Yasushi; Sadr, Alireza; Wada, Ikumi; Miyashin, Michiyo; Takagi, Yuzo; Tagami, Junji; Sumi, Yasunori

    2014-01-01

    This study aimed to investigate swept source optical coherence tomography (SS-OCT) as a detecting tool for occlusal caries in primary teeth. At the in vitro part of the study, 38 investigation sites of occlusal fissures (noncavitated and cavitated) were selected from 26 extracted primary teeth and inspected visually using conventional dental equipment by six examiners without any magnification. SS-OCT cross-sectional images at 1330-nm center wavelength were acquired on the same locations. The teeth were then sectioned at the investigation site and directly viewed under a confocal laser scanning microscope (CLSM) by two experienced examiners. The presence and extent of caries were scored in each observation. The results obtained from SS-OCT and conventional visual inspections were compared with those of CLSM. Consequently, SS-OCT could successfully detect both cavitated and noncavitated lesions. The magnitude of sensitivity for SS-OCT was higher than those for visual inspection (sensitivity of visual inspection and SS-OCT, 0.70 versus 0.93 for enamel demineralization, 0.49 versus 0.89 for enamel cavitated caries, and 0.36 versus 0.75 for dentin caries). Additionally, occlusal caries of a few clinical cases were observed using SS-OCT in vivo. The results indicate that SS-OCT has a great detecting potential for occlusal caries in primary teeth.

  14. Doppler velocity detection limitations in spectrometer-based versus swept-source optical coherence tomography

    PubMed Central

    Hendargo, Hansford C.; McNabb, Ryan P.; Dhalla, Al-Hafeez; Shepherd, Neal; Izatt, Joseph A.

    2011-01-01

    Recent advances in Doppler techniques have enabled high sensitivity imaging of biological flow to measure blood velocities and vascular perfusion. Here we compare spectrometer-based and wavelength-swept Doppler OCT implementations theoretically and experimentally, characterizing the lower and upper observable velocity limits in each configuration. We specifically characterize the washout limit for Doppler OCT, the velocity at which signal degradation results in loss of flow information, which is valid for both quantitative and qualitative flow imaging techniques. We also clearly differentiate the washout effect from the separate phenomenon of phase wrapping. We demonstrate that the maximum detectable Doppler velocity is determined by the fringe washout limit and not phase wrapping. Both theory and experimental results from phantom flow data and retinal blood flow data demonstrate the superiority of the swept-source technique for imaging vessels with high flow rates. PMID:21833356

  15. Miniature swept source for point of care Optical Frequency Domain Imaging

    PubMed Central

    Goldberg, Brian D.; Nezam, S.M. Reza Motaghian; Jillella, Priyanka; Bouma, Brett E.; Tearney, Guillermo J.

    2009-01-01

    Point of care (POC) medical technologies require portable, small, robust instrumentation for practical implementation. In their current embodiment, optical frequency domain imaging (OFDI) systems employ large form-factor wavelength-swept lasers, making them impractical in the POC environment. Here, we describe a first step toward a POC OFDI system by demonstrating a miniaturized swept-wavelength source. The laser is based on a tunable optical filter using a reflection grating and a miniature resonant scanning mirror. The laser achieves 75 nm of bandwidth centered at 1340 nm, a 0.24 nm instantaneous line width, a 15.3 kHz repetition rate with 12 mW peak output power, and a 30.4 kHz A-line rate when utilizing forward and backward sweeps. The entire laser system is approximately the size of a deck of cards and can operate on battery power for at least one hour. PMID:19259202

  16. Lens-based wavefront sensorless adaptive optics swept source OCT

    PubMed Central

    Jian, Yifan; Lee, Sujin; Ju, Myeong Jin; Heisler, Morgan; Ding, Weiguang; Zawadzki, Robert J.; Bonora, Stefano; Sarunic, Marinko V.

    2016-01-01

    Optical coherence tomography (OCT) has revolutionized modern ophthalmology, providing depth resolved images of the retinal layers in a system that is suited to a clinical environment. Although the axial resolution of OCT system, which is a function of the light source bandwidth, is sufficient to resolve retinal features at a micrometer scale, the lateral resolution is dependent on the delivery optics and is limited by ocular aberrations. Through the combination of wavefront sensorless adaptive optics and the use of dual deformable transmissive optical elements, we present a compact lens-based OCT system at an imaging wavelength of 1060 nm for high resolution retinal imaging. We utilized a commercially available variable focal length lens to correct for a wide range of defocus commonly found in patient’s eyes, and a novel multi-actuator adaptive lens for aberration correction to achieve near diffraction limited imaging performance at the retina. With a parallel processing computational platform, high resolution cross-sectional and en face retinal image acquisition and display was performed in real time. In order to demonstrate the system functionality and clinical utility, we present images of the photoreceptor cone mosaic and other retinal layers acquired in vivo from research subjects. PMID:27278853

  17. Lens-based wavefront sensorless adaptive optics swept source OCT

    NASA Astrophysics Data System (ADS)

    Jian, Yifan; Lee, Sujin; Ju, Myeong Jin; Heisler, Morgan; Ding, Weiguang; Zawadzki, Robert J.; Bonora, Stefano; Sarunic, Marinko V.

    2016-06-01

    Optical coherence tomography (OCT) has revolutionized modern ophthalmology, providing depth resolved images of the retinal layers in a system that is suited to a clinical environment. Although the axial resolution of OCT system, which is a function of the light source bandwidth, is sufficient to resolve retinal features at a micrometer scale, the lateral resolution is dependent on the delivery optics and is limited by ocular aberrations. Through the combination of wavefront sensorless adaptive optics and the use of dual deformable transmissive optical elements, we present a compact lens-based OCT system at an imaging wavelength of 1060 nm for high resolution retinal imaging. We utilized a commercially available variable focal length lens to correct for a wide range of defocus commonly found in patient’s eyes, and a novel multi-actuator adaptive lens for aberration correction to achieve near diffraction limited imaging performance at the retina. With a parallel processing computational platform, high resolution cross-sectional and en face retinal image acquisition and display was performed in real time. In order to demonstrate the system functionality and clinical utility, we present images of the photoreceptor cone mosaic and other retinal layers acquired in vivo from research subjects.

  18. Lens-based wavefront sensorless adaptive optics swept source OCT.

    PubMed

    Jian, Yifan; Lee, Sujin; Ju, Myeong Jin; Heisler, Morgan; Ding, Weiguang; Zawadzki, Robert J; Bonora, Stefano; Sarunic, Marinko V

    2016-01-01

    Optical coherence tomography (OCT) has revolutionized modern ophthalmology, providing depth resolved images of the retinal layers in a system that is suited to a clinical environment. Although the axial resolution of OCT system, which is a function of the light source bandwidth, is sufficient to resolve retinal features at a micrometer scale, the lateral resolution is dependent on the delivery optics and is limited by ocular aberrations. Through the combination of wavefront sensorless adaptive optics and the use of dual deformable transmissive optical elements, we present a compact lens-based OCT system at an imaging wavelength of 1060 nm for high resolution retinal imaging. We utilized a commercially available variable focal length lens to correct for a wide range of defocus commonly found in patient's eyes, and a novel multi-actuator adaptive lens for aberration correction to achieve near diffraction limited imaging performance at the retina. With a parallel processing computational platform, high resolution cross-sectional and en face retinal image acquisition and display was performed in real time. In order to demonstrate the system functionality and clinical utility, we present images of the photoreceptor cone mosaic and other retinal layers acquired in vivo from research subjects. PMID:27278853

  19. Ultrahigh speed endoscopic swept source optical coherence tomography using a VCSEL light source and micromotor catheter

    NASA Astrophysics Data System (ADS)

    Tsai, Tsung-Han; Ahsen, Osman O.; Lee, Hsiang-Chieh; Liang, Kaicheng; Giacomelli, Michael G.; Potsaid, Benjamin M.; Tao, Yuankai K.; Jayaraman, Vijaysekhar; Kraus, Martin F.; Hornegger, Joachim; Figueiredo, Marisa; Huang, Qin; Mashimo, Hiroshi; Cable, Alex E.; Fujimoto, James G.

    2014-03-01

    We developed an ultrahigh speed endoscopic swept source optical coherence tomography (OCT) system for clinical gastroenterology using a vertical-cavity surface-emitting laser (VCSEL) and micromotor based imaging catheter, which provided an imaging speed of 600 kHz axial scan rate and 8 μm axial resolution in tissue. The micromotor catheter was 3.2 mm in diameter and could be introduced through the 3.7 mm accessory port of an endoscope. Imaging was performed at 400 frames per second with an 8 μm spot size using a pullback to generate volumetric data over 16 mm with a pixel spacing of 5 μm in the longitudinal direction. Three-dimensional OCT (3D-OCT) imaging was performed in patients with a cross section of pathologies undergoing standard upper and lower endoscopy at the Veterans Affairs Boston Healthcare System (VABHS). Patients with Barrett's esophagus, dysplasia, and inflammatory bowel disease were imaged. The use of distally actuated imaging catheters allowed OCT imaging with more flexibility such as volumetric imaging in the terminal ileum and the assessment of the hiatal hernia using retroflex imaging. The high rotational stability of the micromotor enabled 3D volumetric imaging with micron scale volumetric accuracy for both en face and cross-sectional imaging. The ability to perform 3D OCT imaging in the GI tract with microscopic accuracy should enable a wide range of studies to investigate the ability of OCT to detect pathology as well as assess treatment response.

  20. Combined tunable filters based swept laser source for optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Chen, Minghui; Ding, Zhihua; Wang, Cheng; Huang, Yimei; Chen, Rong; Song, Chengli

    2013-03-01

    We demonstrate a novel ultra-broad tunable bandwidth and narrow instantaneous line-width swept laser source using combined tunable filters working at 1290 nm center wavelength for application in optical coherence tomography. The combined filters consist of a fiber Fabry-Perot tunable filter (FFP-TF) and a polygon mirror with scanning grating based filter. The FFP-TF has the narrow free spectral range (FSR) but ultra-high spectral resolution (narrow instantaneous bandwidth) driven at high frequency far from resonant frequency. The polygon filter in the Littrow configuration is composed of fiber collimator, polygon mirror driven by function generator, and diffractive grating with low groove. Polygon filter coarsely tunes with wide turning range and then FFP-TF finely tunes with narrow band-pass filtering. In contrast to traditional method using single tunable filter, the trade-off between bandwidth and instantaneous line-width is alleviated. The combined filters can realize ultra wide scan range and fairly narrow instantaneous bandwidth simultaneously. Two semiconductor optical amplifiers (SOA) in the parallel manner are used as the gain medium. The wide bandwidth could be obtained by these parallel SOAs to be suitable for sufficient wide range of the polygon filter's FSR because each SOA generates its own spectrum independently. The proposed swept laser source provides an edge-to-edge scanning range of 180 nm covering 1220 to 1400 nm with instantaneous line-width of about 0.03 nm at sweeping rate of 23.3 kHz. The swept laser source with combined filters offers broadband tunable range with narrow instantaneous line-width, which especially benefits for high resolution and deep imaging depth optical frequency domain imaging.

  1. Fourier domain mode-locked swept source at 1050 nm based on a tapered amplifier.

    PubMed

    Marschall, Sebastian; Klein, Thomas; Wieser, Wolfgang; Biedermann, Benjamin R; Hsu, Kevin; Hansen, Kim P; Sumpf, Bernd; Hasler, Karl-Heinz; Erbert, Götz; Jensen, Ole B; Pedersen, Christian; Huber, Robert; Andersen, Peter E

    2010-07-19

    While swept source optical coherence tomography (OCT) in the 1050 nm range is promising for retinal imaging, there are certain challenges. Conventional semiconductor gain media have limited output power, and the performance of high-speed Fourier domain mode-locked (FDML) lasers suffers from chromatic dispersion in standard optical fiber. We developed a novel light source with a tapered amplifier as gain medium, and investigated the FDML performance comparing two fiber delay lines with different dispersion properties. We introduced an additional gain element into the resonator, and thereby achieved stable FDML operation, exploiting the full bandwidth of the tapered amplifier despite high dispersion. The light source operates at a repetition rate of 116 kHz with an effective average output power in excess of 30 mW. With a total sweep range of 70 nm, we achieved an axial resolution of 15 microm in air (approximately 11 microm in tissue) in OCT measurements. As our work shows, tapered amplifiers are suitable gain media for swept sources at 1050 nm with increased output power, while high gain counteracts dispersion effects in an FDML laser. PMID:20720964

  2. Spectral-domain and swept-source OCT imaging of asteroid hyalosis: a case report.

    PubMed

    Alasil, Tarek; Adhi, Mehreen; Liu, Jonathan J; Fujimoto, James G; Duker, Jay S; Baumal, Caroline R

    2014-01-01

    A 72-year-old man with diabetes was referred to the retina clinic for diabetic retinopathy. Detailed funduscopic examination of the left eye was limited by prominent asteroid hyalosis. Spectral-domain (SD) and swept-source (SS) optical coherence tomography (OCT) were utilized to examine the vitreous, vitreoretinal interface, and the morphology of the retina. Asteroid hyalosis induced artifacts of the OCT images, which resolved when the appropriate imaging protocols were applied. SS-OCT may show superior diagnostic and preoperative capabilities when compared to SD-OCT in the settings of asteroid hyalosis-induced media opacity. PMID:25230400

  3. Subgingival calculus imaging based on swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Hsieh, Yao-Sheng; Ho, Yi-Ching; Lee, Shyh-Yuan; Lu, Chih-Wei; Jiang, Cho-Pei; Chuang, Ching-Cheng; Wang, Chun-Yang; Sun, Chia-Wei

    2011-07-01

    We characterized and imaged dental calculus using swept-source optical coherence tomography (SS-OCT). The refractive indices of enamel, dentin, cementum, and calculus were measured as 1.625 +/- 0.024, 1.534 +/- 0.029, 1.570 +/- 0.021, and 2.097 +/- 0.094, respectively. Dental calculus leads strong scattering properties, and thus, the region can be identified from enamel with SS-OCT imaging. An extracted human tooth with calculus is covered with gingiva tissue as an in vitro sample for tomographic imaging.

  4. Office-based laryngeal imaging in awake patients with swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yu, Lingfeng; Liu, Gangjun; Guo, Shuguang; Wong, Brian J. F.; Chen, Zhongping

    2009-02-01

    Optical coherence tomography (OCT) is an evolving noninvasive imaging modality and has been used to image the human larynx during surgical endoscopy. The design of a long GRIN lens based probe capable of capturing images of the human larynx by use of a swept-source OCT during a typical office-based laryngoscopy examination is presented. An optical-ballast-based 4F optical relay system is proposed to realize variable working distance with a constant optical delay. In vivo OCT imaging of the human larynx is demonstrated with 40 fame/second. Office-based OCT is a promising imaging modality to study the larynx.

  5. Design of a swept-source, anatomical OCT system for pediatric bronchoscopy

    NASA Astrophysics Data System (ADS)

    Wijesundara, Kushal C.; Iftimia, Nicusor V.; Oldenburg, Amy L.

    2013-03-01

    We describe the design and performance of a long coherence length, swept-source anatomical OCT (aOCT) system for pediatric airway imaging. A fiber-optic catheter is designed to be accommodated by a small-bore bronchoscope, and is scanned distally in a helical scan pattern to provide aOCT during bronchoscopy. We discuss particular challenges associated with the need for large imaging range, low SNR roll-off, and small catheter diameter. We present 3-D visualizations of airway phantoms and discuss optimization of the airway surface geometry obtained by aOCT. Accurate reconstruction of airway geometry will enable predictive modeling of patients suffering from airway obstruction.

  6. Passive component based multifunctional Jones matrix swept source optical coherence tomography for Doppler and polarization imaging.

    PubMed

    Lim, Yiheng; Hong, Young-Joo; Duan, Lian; Yamanari, Masahiro; Yasuno, Yoshiaki

    2012-06-01

    We present a fiber based multifunctional Jones matrix swept source optical coherence tomography (SS-OCT) system for Doppler and polarization imaging. Jones matrix measurement without using active components such as electro-optic modulators is realized by incident polarization multiplexing based on independent delay of two orthogonal polarization states and polarization diversity detection. In addition to polarization sensitivity, this system measures Doppler flow without extra hardware for phase stabilized SS-OCT detection. An eighth-wave plate was measured to demonstrate the polarization detection accuracy. The optic nerve head of a retina was measured in vivo. Detailed vasculature and birefringent structures were investigated simultaneously. PMID:22660086

  7. Diagnosis of Dry Eye by Tear Meniscus Measurements Using Anterior Segment Swept Source Optical Coherence Tomography.

    PubMed

    Akiyama, Reina; Usui, Tomohiko; Yamagami, Satoru

    2015-11-01

    To evaluate the diagnostic power of tear meniscus measurements using anterior segment swept source optical coherence tomography (SS-OCT) for dry eye and suspected dry eye. Fifty subjects (27 men and 23 women; mean age 43.3 ± 13.7 years), comprising 26 eyes of 26 healthy subjects and 24 eyes of 24 patients with dry eye or suspected dry eye according to Japanese diagnostic criteria, were enrolled at The University of Tokyo Graduate School of Medicine. Subjects underwent SS-OCT, and the central upper and lower tear meniscus heights (TMHs) and areas (TMAs) and the lower tear meniscus volume (TMV) were examined. Intergrader variability and interimage variability, calculated using the pooled coefficient of variation and intraclass correlation coefficient, were used to assess repeatability of measurements in the dry eye group. To diagnose dry eye using tear meniscus measurements by SS-OCT, sensitivity, specificity, and cutoff values of optical coherence tomography (OCT) measurements were determined using receiver operating characteristic analysis. The TMH, TMA, and TMV measured by OCT were significantly lower in the dry eye group than in the control group (P < 0.001). Cutoff values of the lower TMH, TMA, and TMV were 191 μm, 12,360 μm, and 0.0473 mm, respectively. Intergrader repeatability and interimage repeatability, measured as the intraclass correlation coefficient, were >80% for all tear meniscus parameters, with acceptable repeatability. Significant correlations between tear meniscus measurements by OCT and vital staining scores, Schirmer test values, and tear film breakup time were observed (P < 0.05). SS-OCT is a noninvasive and practical method for quantitative evaluation of tear fluid and has the potential for detecting dry eye and suspected dry eye. PMID:26448168

  8. Real-time speckle variance swept-source optical coherence tomography using a graphics processing unit

    PubMed Central

    Lee, Kenneth K. C.; Mariampillai, Adrian; Yu, Joe X. Z.; Cadotte, David W.; Wilson, Brian C.; Standish, Beau A.; Yang, Victor X. D.

    2012-01-01

    Abstract: Advances in swept source laser technology continues to increase the imaging speed of swept-source optical coherence tomography (SS-OCT) systems. These fast imaging speeds are ideal for microvascular detection schemes, such as speckle variance (SV), where interframe motion can cause severe imaging artifacts and loss of vascular contrast. However, full utilization of the laser scan speed has been hindered by the computationally intensive signal processing required by SS-OCT and SV calculations. Using a commercial graphics processing unit that has been optimized for parallel data processing, we report a complete high-speed SS-OCT platform capable of real-time data acquisition, processing, display, and saving at 108,000 lines per second. Subpixel image registration of structural images was performed in real-time prior to SV calculations in order to reduce decorrelation from stationary structures induced by the bulk tissue motion. The viability of the system was successfully demonstrated in a high bulk tissue motion scenario of human fingernail root imaging where SV images (512 × 512 pixels, n = 4) were displayed at 54 frames per second. PMID:22808428

  9. Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

    PubMed Central

    Choi, Woo June; Wang, Ruikang K.

    2015-01-01

    Three-dimensional (3D) assessment of cutaneous microcirculation in human skin is essential in the identification of disease states in skin or other organs. Few 3D imaging techniques have revealed the skin micro-vasculatures non-invasively and with sufficient imaging depth. Here, we demonstrate volumetric cutaneous microangiography of the human skin in vivo that utilizes a 1.3 µm high-speed swept-source optical coherence tomography (SS-OCT). The swept source is based on a MEMS tunable vertical cavity surface emission laser (VCSEL) that is advantageous in terms of long coherence length over 50 mm and 100 nm spectral bandwidth that enables the visualization of microstructures within a few mm from the skin surface. We show that skin microvasculature can be delineated in 3D SS-OCT images using ultrahigh-sensitive optical microangiography (UHS-OMAG) with a correlation mapping mask, providing a contrast enhanced blood perfusion map with capillary flow sensitivity. 3D microangiograms of a healthy human finger are shown with distinct cutaneous vessel architectures from different dermal layers and even within hypodermis. These findings suggest that the OCT microangiography could be a beneficial biomedical assay to assess cutaneous vascular functions in clinic. PMID:25635163

  10. Live imaging of rat embryos with Doppler swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Larina, Irina V.; Furushima, Kenryo; Dickinson, Mary E.; Behringer, Richard R.; Larin, Kirill V.

    2009-09-01

    The rat has long been considered an excellent system to study mammalian embryonic cardiovascular physiology, but has lacked the extensive genetic tools available in the mouse to be able to create single gene mutations. However, the recent establishment of rat embryonic stem cell lines facilitates the generation of new models in the rat embryo to link changes in physiology with altered gene function to define the underlying mechanisms behind congenital cardiovascular birth defects. Along with the ability to create new rat genotypes there is a strong need for tools to analyze phenotypes with high spatial and temporal resolution. Doppler OCT has been previously used for 3-D structural analysis and blood flow imaging in other model species. We use Doppler swept-source OCT for live imaging of early postimplantation rat embryos. Structural imaging is used for 3-D reconstruction of embryo morphology and dynamic imaging of the beating heart and vessels, while Doppler-mode imaging is used to visualize blood flow. We demonstrate that Doppler swept-source OCT can provide essential information about the dynamics of early rat embryos and serve as a basis for a wide range of studies on functional evaluation of rat embryo physiology.

  11. Complex conjugate resolved heterodyne swept source optical coherence tomography using coherence revival

    PubMed Central

    Dhalla, Al-Hafeez; Nankivil, Derek; Izatt, Joseph A.

    2012-01-01

    We describe a simple and low-cost technique for resolving the complex conjugate ambiguity in Fourier domain optical coherence tomography (OCT) that is applicable to many swept source OCT (SSOCT) systems. First, we review the principles of coherence revival, wherein an interferometer illuminated by an external cavity tunable laser (ECTL) exhibits interference fringes when the two arms of the interferometer are mismatched by an integer multiple of the laser cavity length. Second, we report observations that the spectral interferogram obtained from SSOCT systems employing certain ECTLs are automatically phase modulated when the arm lengths are mismatched this way. This phase modulation results in a frequency-shifted interferogram, effectively creating an extended-depth heterodyne SSOCT system without the use of acousto-optic or electro-optic modulators. We suggest that this phase modulation may be caused by the ECTL cavity optical pathlength varying slightly over the laser sweep, and support this hypothesis with numerical simulations. We also report on the successful implementation of this technique with two commercial swept source lasers operating at 840nm and 1040nm, with sweep rates of 8kHz and 100kHz respectively. The extended imaging depth afforded by this technique was demonstrated by measuring the sensitivity fall-off profiles of each laser with matched and mismatched interferometer arms. The feasibility of this technique for clinical systems is demonstrated by imaging the ocular anterior segments of healthy human volunteers. PMID:22435108

  12. Swept-source optical coherence tomography of lower limb wound healing with histopathological correlation

    NASA Astrophysics Data System (ADS)

    Barui, Ananya; Banerjee, Provas; Patra, Rusha; Das, Raunak Kumar; Dhara, Santanu; Dutta, Pranab K.; Chatterjee, Jyotirmoy

    2011-02-01

    Direct noninvasive visualization of wound bed with depth information is important to understand the tissue repair. We correlate skin swept-source-optical coherence tomography (OCT) with histopathological and immunohistochemical evaluation on traumatic lower limb wounds under honey dressing to compare and assess the tissue repair features acquired noninvasively and invasively. Analysis of optical biopsy identifies an uppermost brighter band for stratum corneum with region specific thickness (p < 0.0001) and gray-level intensity (p < 0.0001) variation. Below the stratum corneum, variation in optical intensities is remarkable in different regions of the wound bed. Correlation between OCT and microscopic observations are explored especially in respect to progressive growth and maturation of the epithelial and subepithelial components. Characteristic transition of uniform hypolucid band in OCT image for depigmented zone to wavy highly lucid band in the pigmented zone could be directly correlated with the microscopic findings. The transformation of prematured epithelium of depigmented area, with low expression of E-cadherin, to matured epithelium with higher E-cadherin expression in pigmented zone, implicated plausible change in their optical properties as depicted in OCT. This correlated evaluation of multimodal images demonstrates applicability of swept-source-OCT in wound research and importance of integrated approach in validation of new technology.

  13. Wide-angle KTa1‑ x Nb x O3 deflector for swept light source using DC charge technique

    NASA Astrophysics Data System (ADS)

    Akiyama, Tatsuhiro; Shinagawa, Mitsuru; Ueno, Masahiro; Sasaki, Yuzo; Toyoda, Seiji; Sakamoto, Tadashi

    2016-09-01

    A 5-pass KTa1‑ x Nb x O3 (KTN) deflector based on a DC charge technique for the swept light source of an optical coherence tomography system is proposed. The DC charge technique used in a 3-pass KTN deflector enables us to obtain the long-term stability of the optical power without any degradation of the important features of the swept light source. Experimental results confirm that the coherence length of a swept light source with the 5-pass KTN deflector using the DC charge technique is almost equal to that using a precharge technique reported previously. This means that the DC charge technique does not degrade the coherence length. There are limitation values for applied voltage, the KTN electrode gap, relative dielectric constant, and sweep frequency of the KTN deflector in terms of obtaining long coherence length. We believe that a 7-pass KTN deflector is effective for obtaining a longer coherence length.

  14. Longitudinal Evaluation of Cornea With Swept-Source Optical Coherence Tomography and Scheimpflug Imaging Before and After Lasik.

    PubMed

    Chan, Tommy C Y; Biswas, Sayantan; Yu, Marco; Jhanji, Vishal

    2015-07-01

    Swept-source optical coherence tomography (OCT) is the latest advancement in anterior segment imaging. There are limited data regarding its performance after laser in situ keratomileusis (LASIK). We compared the reliability of swept-source OCT and Scheimpflug imaging for evaluation of corneal parameters in refractive surgery candidates with myopia or myopic astigmatism. Three consecutive measurements were obtained preoperatively and 1 year postoperatively using swept-source OCT and Scheimpflug imaging. The study parameters included central corneal thickness (CCT), thinnest corneal thickness (TCT), keratometry at steep (Ks) and flat (Kf) axes, mean keratometry (Km), and, anterior and posterior best fit spheres (Ant and Post BFS). The main outcome measures included reliability of measurements before and after LASIK was evaluated using intraclass correlation coefficient (ICC) and reproducibility coefficients (RC). Association between the mean value of corneal parameters with age, spherical equivalent (SEQ), and residual bed thickness (RBT) and association of variance heterogeneity of corneal parameters and these covariates were analyzed. Twenty-six right eyes of 26 participants (mean age, 32.7 ± 6.9 yrs; mean SEQ, -6.27 ± 1.67 D) were included. Preoperatively, swept-source OCT demonstrated significantly higher ICC for Ks, CCT, TCT, and Post BFS (P ≤ 0.016), compared with Scheimpflug imaging. Swept-source OCT demonstrated significantly smaller RC values for CCT, TCT, and Post BFS (P ≤ 0.001). After LASIK, both devices had significant differences in measurements for all corneal parameters (P ≤ 0.015). Swept-source OCT demonstrated a significantly higher ICC and smaller RC for all measurements, compared with Scheimpflug imaging (P ≤ 0.001). Association of variance heterogeneity was only found in pre-LASIK Ant BFS and post-LASIK Post BFS for swept-source OCT, whereas significant association of variance heterogeneity was noted for all measurements except Ks and

  15. Active tremor cancellation by a “Smart” handheld vitreoretinal microsurgical tool using swept source optical coherence tomography

    PubMed Central

    Song, Cheol; Gehlbach, Peter L.; Kang, Jin U.

    2012-01-01

    Abstract: Microsurgeons require dexterity to make precise and stable maneuvers to achieve surgical objectives and to minimize surgical risks during freehand procedures. This work presents a novel, common path, swept source optical coherence tomography-based “smart” micromanipulation aided robotic-surgical tool (SMART) that actively suppresses surgeon hand tremor. The tool allows enhanced tool tip stabilization, more accurate targeting and the potential to lower surgical risk. Freehand performance is compared to smart tool-assisted performance and includes assessment of the one-dimensional motion tremor in an active microsurgeon’s hand. Surgeon hand tremor—the ability to accurately locate a surgical target and maintain tool tip offset distances—were all improved by smart tool assistance. PMID:23188305

  16. In vivo volumetric depth-resolved vasculature imaging of human limbus and sclera with 1 μm swept source phase-variance optical coherence angiography

    NASA Astrophysics Data System (ADS)

    Poddar, Raju; Zawadzki, Robert J.; Cortés, Dennis E.; Mannis, Mark J.; Werner, John S.

    2015-06-01

    We present in vivo volumetric depth-resolved vasculature images of the anterior segment of the human eye acquired with phase-variance based motion contrast using a high-speed (100 kHz, 105 A-scans/s) swept source optical coherence tomography system (SSOCT). High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. The human corneo-scleral junction and sclera were imaged with swept source phase-variance optical coherence angiography and compared with slit lamp images from the same eyes of normal subjects. Different features of the rich vascular system in the conjunctiva and episclera were visualized and described. This system can be used as a potential tool for ophthalmological research to determine changes in the outflow system, which may be helpful for identification of abnormalities that lead to glaucoma.

  17. Multimodal ophthalmic imaging using swept source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Malone, Joseph D.; El-Haddad, Mohamed T.; Tye, Logan A.; Majeau, Lucas; Godbout, Nicolas; Rollins, Andrew M.; Boudoux, Caroline; Tao, Yuankai K.

    2016-03-01

    Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) benefit clinical diagnostic imaging in ophthalmology by enabling in vivo noninvasive en face and volumetric visualization of retinal structures, respectively. Spectrally encoding methods enable confocal imaging through fiber optics and reduces system complexity. Previous applications in ophthalmic imaging include spectrally encoded confocal scanning laser ophthalmoscopy (SECSLO) and a combined SECSLO-OCT system for image guidance, tracking, and registration. However, spectrally encoded imaging suffers from speckle noise because each spectrally encoded channel is effectively monochromatic. Here, we demonstrate in vivo human retinal imaging using a swept source spectrally encoded scanning laser ophthalmoscope and OCT (SSSESLO- OCT) at 1060 nm. SS-SESLO-OCT uses a shared 100 kHz Axsun swept source, shared scanner and imaging optics, and are detected simultaneously on a shared, dual channel high-speed digitizer. SESLO illumination and detection was performed using the single mode core and multimode inner cladding of a double clad fiber coupler, respectively, to preserve lateral resolution while improving collection efficiency and reducing speckle contrast at the expense of confocality. Concurrent en face SESLO and cross-sectional OCT images were acquired with 1376 x 500 pixels at 200 frames-per-second. Our system design is compact and uses a shared light source, imaging optics, and digitizer, which reduces overall system complexity and ensures inherent co-registration between SESLO and OCT FOVs. En face SESLO images acquired concurrent with OCT cross-sections enables lateral motion tracking and three-dimensional volume registration with broad applications in multivolume OCT averaging, image mosaicking, and intraoperative instrument tracking.

  18. 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.

  19. Line-field parallel swept source MHz OCT for structural and functional retinal imaging

    PubMed Central

    Fechtig, Daniel J.; Grajciar, Branislav; Schmoll, Tilman; Blatter, Cedric; Werkmeister, Rene M.; Drexler, Wolfgang; Leitgeb, Rainer A.

    2015-01-01

    We demonstrate three-dimensional structural and functional retinal imaging with line-field parallel swept source imaging (LPSI) at acquisition speeds of up to 1 MHz equivalent A-scan rate with sensitivity better than 93.5 dB at a central wavelength of 840 nm. The results demonstrate competitive sensitivity, speed, image contrast and penetration depth when compared to conventional point scanning OCT. LPSI allows high-speed retinal imaging of function and morphology with commercially available components. We further demonstrate a method that mitigates the effect of the lateral Gaussian intensity distribution across the line focus and demonstrate and discuss the feasibility of high-speed optical angiography for visualization of the retinal microcirculation. PMID:25798298

  20. Method to calibrate phase fluctuation in polarization-sensitive swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

    2011-07-01

    We present a phase fluctuation calibration method for polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) using continuous polarization modulation. The method uses a low-voltage broadband polarization modulator driven by a synchronized sinusoidal burst waveform rather than an asynchronous waveform, together with the removal of the global phases of the measured Jones matrices by the use of matrix normalization. This makes it possible to average the measured Jones matrices to remove the artifact due to the speckle noise of the signal in the sample without introducing auxiliary optical components into the sample arm. This method was validated on measurements of an equine tendon sample by the PS-SS-OCT system.

  1. A method to calibrate phase fluctuation in polarization-sensitive swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

    2011-06-01

    A phase fluctuation calibration method is presented for polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) using continuous polarization modulation. The method consists of the generation of a continuous triggered tone-burst waveform rather than an asynchronous waveform by use of a function generator and the removal of the global phases of the measured Jones matrices by use of matrix normalization. This could remove the use of auxiliary optical components for the phase fluctuation compensation in the system, which reduces the system complexity. Phase fluctuation calibration is necessary to obtain the reference Jones matrix by averaging the measured Jones matrices at sample surfaces. Measurements on an equine tendon sample were made by the PS-SS-OCT system to validate the proposed method.

  2. Full-field swept-source optical coherence tomography with Gaussian spectral shaping

    NASA Astrophysics Data System (ADS)

    Dubey, Satish Kumar; Sheoran, Gyanendra; Anna, Tulsi; Anand, Arun; Mehta, Dalip Singh; Shakher, Chandra

    2008-09-01

    A swept source system was realized in the wavelength range of 810-875 nm with the combination of a broad-band superluminescent diode (SLD) and an acousto-optic tunable filter (AOTF) as a frequency-tuning device. SLD has two spectral centers at 820 nm and 845 nm with spectral bandwidth (FWHM) of around 40 nm. Gaussian spectral shaping was performed onto the original SLD spectrum while reconstructing OCT images for various test samples such as onion slice and fingerprint impression taken on a glass substrate. As a pulse can be considered a Gaussian distribution of frequencies, spectral shaping yields sharper Fourier peaks. Application of Gaussian spectrum facilitates in precisely locating the reflective boundaries within the sample that results in improved OCT images.

  3. High-speed MEMS swept-wavelength light source for FBG sensor system

    NASA Astrophysics Data System (ADS)

    Saitoh, Takanori; Nakamura, Kenichi; Takahashi, Yoshifumi; Miyagi, Koichiro

    2005-05-01

    A high-speed MEMS swept-wavelength light source (SLS) for an FBG sensor system is proposed and demonstrated. It is basically a multi-mode external-cavity laser diode (LD), and consists mainly of an LD head, diffraction grating, and electromagnetically actuated MEMS scanning mirror. It has a linewidth of 0.03 nm, scan range from 1508 to 1582 nm, scan rate of 0.57 ms and output power of 10 mW. The heart of the MEMS SLS is the MEMS scanning mirror (8 x 6 mm) that changes the oscillation wavelength continuously and rapidly. The scanning mirror is actuated by electromagnetic force derived from a permalloy piece glued on the back of the mirror and a C-shape electromagnet. The MEMS SLS allows construction of a low-cost, simple and high-speed FBG interrogator system.

  4. Suppression of saturation artifacts in swept source optical coherence tomography using dual channel detection

    NASA Astrophysics Data System (ADS)

    Li, Xinyu; Liang, Shanshan; Zhang, Jun

    2016-03-01

    A technique to suppress saturation artifacts in swept source optical coherence tomography (SSOCT) system was presented. The detected signal was split into two channels of a high speed data acquisition card with two levels by a power divider. The signal in one channel with higher level was used to reconstruct OCT images and the signal in the other channel with lower level was used to compensate the saturated signal in the first channel by calibrating the splitting ratio between the two channels. Based on dual channel detection, this technique can enhance the dynamic range of SSOCT system and remove saturation artifacts in OCT imaging with simple and cost effective design. Imaging of human finger with the system demonstrated that this method can achieve high dynamic range without saturation artifacts in SSOCT.

  5. Swept source OCT with air puff chamber for corneal dynamics measurements

    NASA Astrophysics Data System (ADS)

    Karnowski, Karol; Alonso-Caneiro, David; Kaluzny, Bartlomiej; Kowalczyk, Andrzej; Wojtkowski, Maciej

    2012-03-01

    None of currently used tonometers produce estimated IOP values that are free of errors. Measurement incredibility arises from indirect measurement of corneal deformation and the fact that pressure calculations are based on population averaged parameters of anterior segment. Reliable IOP values are crucial for understanding and monitoring of number of eye pathologies e.g. glaucoma. We have combined high speed swept source OCT with air-puff chamber. System provides direct measurement of deformation of cornea and anterior surface of the lens. This paper describes in details the performance of air-puff ssOCT instrument. We present different approaches of data presentation and analysis. Changes in deformation amplitude appears to be good indicator of IOP changes. However, it seems that in order to provide accurate intraocular pressure values an additional information on corneal biomechanics is necessary. We believe that such information could be extracted from data provided by air-puff ssOCT.

  6. Short ring cavity swept source based on a highly reflective chirped FBG

    NASA Astrophysics Data System (ADS)

    Stancu, Radu-Florin; Podoleanu, Adrian

    2015-09-01

    An optical akinetic swept source (AKSS) at 1060 nm, comprising a 5 m length fiber ring cavity, a semiconductor optical amplifier (SOA) as gain medium, and a 98% reflective chirped fiber Bragg grating as a dispersive element, is described. Active mode-locking was achieved by directly modulating the current of the SOA with sinusoidal signal of frequency equal to 10 times and 20 times the cavity resonance frequency. In the static regime, linewidths as narrow as 60 pm and a tuning bandwidth of 30 nm were achieved, while a 2 mW output power, without any optical booster, was measured dynamically at a sweep speed of 100 kHz. The axial range of the AKSS was evaluated by scanning through the channeled spectrum of a Mach-Zehnder interferometer.

  7. 4D in vivo imaging of subpleural lung parenchyma by swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Meissner, S.; Tabuchi, A.; Mertens, M.; Homann, H.; Walther, J.; Kuebler, W. M.; Koch, E.

    2009-07-01

    In this feasibility study we present a method for 4D imaging of healthy and injured subpleural lung tissue in a mouse model. We used triggered swept source optical coherence tomography with an A-scan frequency of 20 kHz to image murine subpleural alveoli during the ventilation cycle. The data acquisition was gated to the pulmonary airway pressure to take one B-scan in each ventilation cycle for different pressure levels. The acquired B-scans were combined offline to one C-scan for each pressure level. Due to the high acquisition rate of the used optical coherence tomography system, we are also able to perform OCT Doppler imaging of the alveolar arterioles. We demonstrated that OCT is a useful tool to investigate the alveolar dynamics in spatial dimensions and to analyze the alveolar blood flow by using Doppler OCT.

  8. Design of a Swept-Source, Anatomical OCT System for Pediatric Bronchoscopy

    PubMed Central

    Wijesundara, Kushal C.; Iftimia, Nicusor V.; Oldenburg, Amy L.

    2013-01-01

    We describe the design and performance of a long coherence length, swept-source anatomical OCT (aOCT) system for pediatric airway imaging. A fiber-optic catheter is designed to be accommodated by a small-bore bronchoscope, and is scanned distally in a helical scan pattern to provide aOCT during bronchoscopy. We discuss particular challenges associated with the need for large imaging range, low SNR roll-off, and small catheter diameter. We present 3-D visualizations of airway phantoms and discuss optimization of the airway surface geometry obtained by aOCT. Accurate reconstruction of airway geometry will enable predictive modeling of patients suffering from airway obstruction. PMID:24357912

  9. Master/slave interferometry - ideal tool for coherence revival swept source optical coherence tomography.

    PubMed

    Bradu, Adrian; Rivet, Sylvain; Podoleanu, Adrian

    2016-07-01

    In this paper, we demonstrate that the master slave (MS) interferometry method can significantly simplify the practice of coherence revival swept source optical coherence tomography (OCT) technique. Previous implementations of the coherence revival technique required considerable resources on dispersion compensation and data resampling. The total tolerance of the MS method to nonlinear tuning, to dispersion in the interferometer and to dispersion due to the laser cavity, makes the MS ideally suited to the practice of coherence revival. In addition, enhanced versatility is allowed by the MS method in displaying shorter axial range images than that determined by the digital sampling of the data. This brings an immediate improvement in the speed of displaying cross-sectional images at high rates without the need of extra hardware such as graphics processing units or field programmable gate arrays. The long axial range of the coherence revival regime is proven with images of the anterior segment of healthy human volunteers. PMID:27446682

  10. 4D Optical Coherence Tomography based Microangiography achieved by 1.6 MHz FDML Swept source

    PubMed Central

    Zhi, Zhongwei; Qin, Wan; Wang, Jingang; Wei, Wei; Wang, Ruikang K.

    2015-01-01

    We demonstrate the use of an ultra-high speed swept-source optical coherence tomography (OCT) to achieve optical microangiography (OMAG) of microcirculatory tissue beds in vivo. The system is based on a 1310 nm Fourier domain mode locking (FDML) laser with 1.6MHz A-line rate, providing a frame rate of 3.415 KHz, an axial resolution of ~10 µm and signal to noise ratio of 102 dB. Motion from blood flow causes change in OCT signals between consecutive B-frames acquired at the same location. Intensity based inter-frame subtraction algorithm is applied to extract blood flow from tissue background without any motion correction. We demonstrate the capability of this 1.6 MHz OCT system for 4D optical microangiography of in vivo tissue at a volume rate of 4.7 volumes/s (volume size: 512×200×720 voxels). PMID:25872072

  11. Master/slave interferometry – ideal tool for coherence revival swept source optical coherence tomography

    PubMed Central

    Bradu, Adrian; Rivet, Sylvain; Podoleanu, Adrian

    2016-01-01

    In this paper, we demonstrate that the master slave (MS) interferometry method can significantly simplify the practice of coherence revival swept source optical coherence tomography (OCT) technique. Previous implementations of the coherence revival technique required considerable resources on dispersion compensation and data resampling. The total tolerance of the MS method to nonlinear tuning, to dispersion in the interferometer and to dispersion due to the laser cavity, makes the MS ideally suited to the practice of coherence revival. In addition, enhanced versatility is allowed by the MS method in displaying shorter axial range images than that determined by the digital sampling of the data. This brings an immediate improvement in the speed of displaying cross-sectional images at high rates without the need of extra hardware such as graphics processing units or field programmable gate arrays. The long axial range of the coherence revival regime is proven with images of the anterior segment of healthy human volunteers. PMID:27446682

  12. Line-field parallel swept source MHz OCT for structural and functional retinal imaging.

    PubMed

    Fechtig, Daniel J; Grajciar, Branislav; Schmoll, Tilman; Blatter, Cedric; Werkmeister, Rene M; Drexler, Wolfgang; Leitgeb, Rainer A

    2015-03-01

    We demonstrate three-dimensional structural and functional retinal imaging with line-field parallel swept source imaging (LPSI) at acquisition speeds of up to 1 MHz equivalent A-scan rate with sensitivity better than 93.5 dB at a central wavelength of 840 nm. The results demonstrate competitive sensitivity, speed, image contrast and penetration depth when compared to conventional point scanning OCT. LPSI allows high-speed retinal imaging of function and morphology with commercially available components. We further demonstrate a method that mitigates the effect of the lateral Gaussian intensity distribution across the line focus and demonstrate and discuss the feasibility of high-speed optical angiography for visualization of the retinal microcirculation. PMID:25798298

  13. Differential intensity contrast swept source optical coherence tomography for human retinal vasculature visualization

    NASA Astrophysics Data System (ADS)

    Motaghiannezam, Reza; Fraser, Scott

    2012-03-01

    We demonstrate an intensity-based motion sensitive method, called differential logarithmic intensity variance (DLOGIV), for 3D microvasculature imaging and foveal avascular zone (FAZ) visualization in the in vivo human retina using swept source optical coherence tomography (SS-OCT) at 1060 nm. A motion sensitive SS-OCT system was developed operating at 50,000 A-lines/s with 5.9 μm axial resolution, and used to collect 3D images over 4 mm2 in a normal subject eye. Multiple B-scans were acquired at each individual slice through the retina and the variance of differences of logarithmic intensities as well as the differential phase variances (DPV) was calculated to identify regions of motion (microvasculature). En face DLOGIV image were capable of capturing the microvasculature through depth with an equal performance compared to the DPV.

  14. Akinetic swept source with adjustable coherence length for SS-OCT

    NASA Astrophysics Data System (ADS)

    Stancu, Radu F.; Jackson, David A.; Podoleanu, Adrian G.

    2015-03-01

    An electronically controlled optical swept source (SS) at 1550 nm using mode locking in a dispersive ring cavity is described. Active mode-locking was achieved by directly modulating the current of a semiconductor optical amplifier (SOA) used as a gain medium. In the static regime, parameters such as linewidth, tuning bandwidth and contrast were measured, while the axial range was determined dynamically. Two types of fiber, dispersion compensation and single mode, are employed in the laser ring cavity. It is demonstrated that the relative lengths of the two types of fiber have little effect on the linewidth, while more control on the linewidth is obtained via the frequency of the signal driving the SOA. Linewidths less than 60 pm and over 1 nm were measured in the static regime while driving the SOA at 50 - 500 MHz. The narrowest linewidths were achieved where the proportion of dispersion compensation fiber in the cavity is 80- 90% of the total length. The optical source is developed to respond to the demands of OCT applications in general as well as address the need for low cost tunable lasers for configurations where a large tuning bandwidths and long coherence length might not be necessary.

  15. Depth encoded three-beam swept source Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wartak, Andreas; Haindl, Richard; Trasischker, Wolfgang; Baumann, Bernhard; Pircher, Michael; Hitzenberger, Christoph K.

    2016-03-01

    A novel approach for investigation of human retinal and choroidal blood flow by the means of multi-channel swept source Doppler optical coherence tomography (SS-D-OCT) system is being developed. We present preliminary in vitro measurement results for quantification of the 3D velocity vector of scatterers in a flow phantom. The absolute flow velocity of moving scatterers can be obtained without prior knowledge of flow orientation. In contrast to previous spectral domain (SD-) D-OCT investigations, that already proved the three-channel D-OCT approach to be suitable for in vivo retinal blood flow evaluation, this current work aims for a similar functional approach by means of a differing technique. To the best of our knowledge, this is the first three-channel D-OCT setup featuring a wavelength tunable laser source. Furthermore, we present a modification of our setup allowing a reduction of the former three active illumination channels to one active illumination channel and two passive channels, which only probe the illuminated sample. This joint aperture (JA) approach provides the advantage of not having to divide beam power among three beams to meet corresponding laser safety limits. The in vitro measurement results regarding the flow phantom show good agreement between theoretically calculated and experimentally obtained flow velocity values.

  16. Depth-encoded all-fiber swept source polarization sensitive OCT

    PubMed Central

    Wang, Zhao; Lee, Hsiang-Chieh; Ahsen, Osman Oguz; Lee, ByungKun; Choi, WooJhon; Potsaid, Benjamin; Liu, Jonathan; Jayaraman, Vijaysekhar; Cable, Alex; Kraus, Martin F.; Liang, Kaicheng; Hornegger, Joachim; Fujimoto, James G.

    2014-01-01

    Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of conventional OCT and can assess depth-resolved tissue birefringence in addition to intensity. Most existing PS-OCT systems are relatively complex and their clinical translation remains difficult. We present a simple and robust all-fiber PS-OCT system based on swept source technology and polarization depth-encoding. Polarization multiplexing was achieved using a polarization maintaining fiber. Polarization sensitive signals were detected using fiber based polarization beam splitters and polarization controllers were used to remove the polarization ambiguity. A simplified post-processing algorithm was proposed for speckle noise reduction relaxing the demand for phase stability. We demonstrated systems design for both ophthalmic and catheter-based PS-OCT. For ophthalmic imaging, we used an optical clock frequency doubling method to extend the imaging range of a commercially available short cavity light source to improve polarization depth-encoding. For catheter based imaging, we demonstrated 200 kHz PS-OCT imaging using a MEMS-tunable vertical cavity surface emitting laser (VCSEL) and a high speed micromotor imaging catheter. The system was demonstrated in human retina, finger and lip imaging, as well as ex vivo swine esophagus and cardiovascular imaging. The all-fiber PS-OCT is easier to implement and maintain compared to previous PS-OCT systems and can be more easily translated to clinical applications due to its robust design. PMID:25401008

  17. Characterization of Choroidal Layers in Normal Aging Eyes Using Enface Swept-Source Optical Coherence Tomography

    PubMed Central

    Mullins, Robert F.; Baumal, Caroline R.; Mohler, Kathrin J.; Kraus, Martin F.; Liu, Jonathan; Badaro, Emmerson; Alasil, Tarek; Hornegger, Joachim; Fujimoto, James G.; Duker, Jay S.; Waheed, Nadia K.

    2015-01-01

    Purpose To characterize qualitative and quantitative features of the choroid in normal eyes using enface swept-source optical coherence tomography (SS-OCT). Methods Fifty-two eyes of 26 consecutive normal subjects were prospectively recruited to obtain multiple three-dimensional 12x12mm volumetric scans using a long-wavelength high-speed SS-OCT prototype. A motion-correction algorithm merged multiple SS-OCT volumes to improve signal. Retinal pigment epithelium (RPE) was segmented as the reference and enface images were extracted at varying depths every 4.13μm intervals. Systematic analysis of the choroid at different depths was performed to qualitatively assess the morphology of the choroid and quantify the absolute thicknesses as well as the relative thicknesses of the choroidal vascular layers including the choroidal microvasculature (choriocapillaris, terminal arterioles and venules; CC) and choroidal vessels (CV) with respect to the subfoveal total choroidal thickness (TC). Subjects were divided into two age groups: younger (<40 years) and older (≥40 years). Results Mean age of subjects was 41.92 (24-66) years. Enface images at the level of the RPE, CC, CV, and choroidal-scleral interface were used to assess specific qualitative features. In the younger age group, the mean absolute thicknesses were: TC 379.4μm (SD±75.7μm), CC 81.3μm (SD±21.2μm) and CV 298.1μm (SD±63.7μm). In the older group, the mean absolute thicknesses were: TC 305.0μm (SD±50.9μm), CC 56.4μm (SD±12.1μm) and CV 248.6μm (SD±49.7μm). In the younger group, the relative thicknesses of the individual choroidal layers were: CC 21.5% (SD±4.0%) and CV 78.4% (SD±4.0%). In the older group, the relative thicknesses were: CC 18.9% (SD±4.5%) and CV 81.1% (SD±4.5%). The absolute thicknesses were smaller in the older age group for all choroidal layers (TC p=0.006, CC p=0.0003, CV p=0.03) while the relative thickness was smaller only for the CC (p=0.04). Conclusions Enface SS-OCT at

  18. Sensitivity enhancement in swept-source optical coherence tomography by parametric balanced detector and amplifier.

    PubMed

    Kang, Jiqiang; Wei, Xiaoming; Li, Bowen; Wang, Xie; Yu, Luoqin; Tan, Sisi; Jinata, Chandra; Wong, Kenneth K Y

    2016-04-01

    We proposed a sensitivity enhancement method of the interference-based signal detection approach and applied it on a swept-source optical coherence tomography (SS-OCT) system through all-fiber optical parametric amplifier (FOPA) and parametric balanced detector (BD). The parametric BD was realized by combining the signal and phase conjugated idler band that was newly-generated through FOPA, and specifically by superimposing these two bands at a photodetector. The sensitivity enhancement by FOPA and parametric BD in SS-OCT were demonstrated experimentally. The results show that SS-OCT with FOPA and SS-OCT with parametric BD can provide more than 9 dB and 12 dB sensitivity improvement, respectively, when compared with the conventional SS-OCT in a spectral bandwidth spanning over 76 nm. To further verify and elaborate their sensitivity enhancement, a bio-sample imaging experiment was conducted on loach eyes by conventional SS-OCT setup, SS-OCT with FOPA and parametric BD at different illumination power levels. All these results proved that using FOPA and parametric BD could improve the sensitivity significantly in SS-OCT systems. PMID:27446655

  19. Assessment of cervical demineralization induced by Streptococcus mutans using swept-source optical coherence tomography.

    PubMed

    Tezuka, Hiroki; Shimada, Yasushi; Matin, Khairul; Ikeda, Masaomi; Sadr, Alireza; Sumi, Yasunori; Tagami, Junji

    2016-01-01

    Exposed root surfaces due to gingival recession are subject to biofilm stagnation that can result in caries formation. Cervical enamel and dentin demineralization induced by a cariogenic biofilm was evaluated using swept-source optical coherence tomography (SS-OCT). The cementoenamel junction (CEJ) sections of extracted human teeth were subjected to demineralization for 1, 2, or 3 weeks. A suspension of Streptococcus mutans was applied to form a cariogenic biofilm using an oral biofilm reactor. After incubation, demineralization was observed by SS-OCT. For the analysis of SS-OCT signal, the value of the area under the curve (AUC) of the signal profile was measured. Statistical analyses were performed with 95% level of confidence. Cervical demineralization was displayed as a bright zone in SS-OCT. The demineralization depth of dentin was significantly deeper than that of enamel ([Formula: see text]). Enamel near the CEJ demonstrated a significant increase of AUC over the other enamel region after the demineralization. The gaps along the dentinoenamel junction were additionally observed in SS-OCT. SS-OCT was capable of monitoring the cervical demineralization induced by a cariogenic biofilm and is considered to be a promising modality for the diagnosis of cervical demineralization. PMID:27014718

  20. Imaging of cardiovascular dynamics in early mouse embryos with swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Larina, Irina V.; Liebling, Michael; Dickinson, Mary E.; Larin, Kirill V.

    2009-02-01

    Congenital cardiovascular defects are very common, occurring in 1% of live births, and cardiovascular failures are the leading cause of birth defect-related deaths in infants. To improve diagnostics, prevention and treatment of cardiovascular abnormalities, we need to understand not only how cells form the heart and vessels but also how physical factors such as heart contraction and blood flow influence heart development and changes in the circulatory network. Mouse models are an excellent resource for studying cardiovascular development and disease because of the resemblance to humans, rapid generation time, and availability of mutants with cardiovascular defects linked to human diseases. In this work, we present results on development and application of Doppler Swept Source Optical Coherence Tomography (DSS-OCT) for imaging of cardiovascular dynamics and blood flow in the mouse embryonic heart and vessels. Our studies demonstrated that the spatial and temporal resolution of the DSS-OCT makes it possible to perform sensitive measurements of heart and vessel wall movements and to investigate how contractile waves facilitate the movement of blood through the circulatory system.

  1. Longitudinal study of arteriogenesis with swept source optical coherence tomography and hyperspectral imaging

    NASA Astrophysics Data System (ADS)

    Poole, Kristin M.; Patil, Chetan A.; Nelson, Christopher E.; McCormack, Devin R.; Madonna, Megan C.; Duvall, Craig L.; Skala, Melissa C.

    2014-03-01

    Peripheral arterial disease (PAD) is an atherosclerotic disease of the extremities that leads to high rates of myocardial infarction and stroke, increased mortality, and reduced quality of life. PAD is especially prevalent in diabetic patients, and is commonly modeled by hind limb ischemia in mice to study collateral vessel development and test novel therapies. Current techniques used to assess recovery cannot obtain quantitative, physiological data non-invasively. Here, we have applied hyperspectral imaging and swept source optical coherence tomography (OCT) to study longitudinal changes in blood oxygenation and vascular morphology, respectively, intravitally in the diabetic mouse hind limb ischemia model. Additionally, recommended ranges for controlling physiological variability in blood oxygenation with respect to respiration rate and body core temperature were determined from a control animal experiment. In the longitudinal study with diabetic mice, hyperspectral imaging data revealed the dynamics of blood oxygenation recovery distally in the ischemic footpad. In diabetic mice, there is an early increase in oxygenation that is not sustained in the long term. Quantitative analysis of vascular morphology obtained from Hessian-filtered speckle variance OCT volumes revealed temporal dynamics in vascular density, total vessel length, and vessel diameter distribution in the adductor muscle of the ischemic limb. The combination of hyperspectral imaging and speckle variance OCT enabled acquisition of novel functional and morphological endpoints from individual animals, and provides a more robust platform for future preclinical evaluations of novel therapies for PAD.

  2. Labview programming for swept-source full-field optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Chang, Shoude; Mao, Youxin; Flueraru, Costel

    2011-08-01

    Full-field optical coherence tomography (FFOCT) acquires image data in parallel. It has a big advantage in high-speed imaging because 2-dimensional mechanical raster scanning in the sample arm, which is essentially needed in a common fiber-based OCT system, does not exist anymore. Swept-source FFOCT (SSFFOCT) further makes the system free of depth scanning that significantly increases the operation speed. National Instrument's LabVIEW is a powerful tool to fast develop optical-electronic systems which have motion/vision units, signal processing functions and easy-to-generate Graphic User Interface (GUI). In this paper, we describe the design and implementation of Labview program prepared for an SSFFOCT system. Basically, there are four modules of Labview programming in such a system: 1. Wavelength sweeping control; 2. Synchronized image grabbing; 3. SSFFOCT signal processing; 4. 3-dimensional tomogram displaying mode selection. A general graphic user interface is used to input the parameters and monitor all necessary data and curves. The tomographic images can be displayed at any given cutting direction. More details and examples are provided and discussed.

  3. Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

    SciTech Connect

    Woo June Choi; Wang, R K

    2014-08-31

    We demonstrate volumetric cutaneous microangiography of the human skin in vivo that utilises 1.3-μm high-speed sweptsource optical coherence tomography (SS-OCT). The swept source is based on a micro-electro-mechanical (MEMS)-tunable vertical cavity surface emission laser (VCSEL) that is advantageous in terms of long coherence length over 50 mm and 100 nm spectral bandwidth, which enables the visualisation of microstructures within a few mm from the skin surface. We show that the skin microvasculature can be delineated in 3D SS-OCT images using ultrahigh-sensitive optical microangiography (UHS-OMAG) with a correlation mapping mask, providing a contrast enhanced blood perfusion map with capillary flow sensitivity. 3D microangiograms of a healthy human finger are shown with distinct cutaneous vessel architectures from different dermal layers and even within hypodermis. These findings suggest that the OCT microangiography could be a beneficial biomedical assay to assess cutaneous vascular functions in clinic. (laser biophotonics)

  4. Optic axis determination by fibre-based polarization-sensitive swept-source optical coherence tomography.

    PubMed

    Lu, Zenghai; Kasaragod, Deepa K; Matcher, Stephen J

    2011-02-21

    We describe a fibre-based variable-incidence angle (VIA) polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) system to determine the 3D optical axis of birefringent biological tissues. Single-plane VIA-PS-OCT is also explored which requires measurement of the absolute fast-axis orientation. A state-of-the-art PS-SS-OCT system with some improvements both in hardware and software was used to determine the apparent optical birefringence of equine tendon for a number of different illumination directions. Polar and azimuthal angles of cut equine tendon were produced by the VIA method and compared with the nominal values. A quarter waveplate (QWP) and equine tendon were used as test targets to validate the fast-axis measurements using the system. Polar and azimuthal angles of cut equine tendon broadly agreed with the expected values within about 8% of the nominal values. A theoretical and experimental analysis of the effect of the sample arm fibre on determination of optical axis orientation using a proposed definition based on the orientation of the eigenpolarization ellipse experimentally confirms that this algorithm only works correctly for special settings of the sample arm fibre. A proposed algorithm based on the angle between Stokes vectors on the Poincaré sphere is confirmed to work for all settings of the sample arm fibre. A calibration procedure is proposed to remove the sign ambiguity of the measured orientation and was confirmed experimentally by using the QWP. PMID:21263175

  5. Imaging pulse wave velocity in mouse retina using swept-source OCT (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Song, Shaozhen; Wei, Wei; Wang, Ruikang K.

    2016-03-01

    Blood vessel dynamics has been a significant subject in cardiology and internal medicine, and pulse wave velocity (PWV) on artery vessels is a classic evaluation of arterial distensibility, and has never been ascertained as a cardiovascular risk marker. The aim of this study is to develop a high speed imaging technique to capture the pulsatile motion on mouse retina arteries with the ability to quantify PWV on any arterial vessels. We demonstrate a new non-invasive method to assess the vessel dynamics on mouse retina. A Swept-source optical coherence tomography (SS-OCT) system is used for imaging micro-scale blood vessel motion. The phase-stabilized SS-OCT provides a typical displacement sensitivity of 20 nm. The frame rate of imaging is ~16 kHz, at A-line rate of ~1.62 MHz, which allows the detection of transient pulse waves with adequate temporal resolution. Imaging volumes with repeated B-scans are obtained on mouse retina capillary bed, and the mouse oxymeter signal is recorded simultaneously. The pulse wave on artery and vein are resolved, and with the synchronized heart beat signal, the temporal delay on different vessel locations is determined. The vessel specific measurement of PWV is achieved for the first time with SS-OCT, for pulse waves propagating more than 100 cm/s. Using the novel methodology of retinal PWV assessment, it is hoped that the clinical OCT scans can provide extended diagnostic information of cardiology functionalities.

  6. Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Choi, Woo June; Wang, R. K.

    2014-08-01

    We demonstrate volumetric cutaneous microangiography of the human skin in vivo that utilises 1.3-μm high-speed sweptsource optical coherence tomography (SS-OCT). The swept source is based on a micro-electro-mechanical (MEMS)-tunable vertical cavity surface emission laser (VCSEL) that is advantageous in terms of long coherence length over 50 mm and 100 nm spectral bandwidth, which enables the visualisation of microstructures within a few mm from the skin surface. We show that the skin microvasculature can be delineated in 3D SS-OCT images using ultrahigh-sensitive optical microangiography (UHS-OMAG) with a correlation mapping mask, providing a contrast enhanced blood perfusion map with capillary flow sensitivity. 3D microangiograms of a healthy human finger are shown with distinct cutaneous vessel architectures from different dermal layers and even within hypodermis. These findings suggest that the OCT microangiography could be a beneficial biomedical assay to assess cutaneous vascular functions in clinic.

  7. Quantitative upper airway endoscopy with swept-source anatomical optical coherence tomography

    PubMed Central

    Wijesundara, Kushal; Zdanski, Carlton; Kimbell, Julia; Price, Hillel; Iftimia, Nicusor; Oldenburg, Amy L.

    2014-01-01

    Minimally invasive imaging of upper airway obstructions in children and adults is needed to improve clinical decision-making. Toward this goal, we demonstrate an anatomical optical coherence tomography (aOCT) system delivered via a small-bore, flexible endoscope to quantify the upper airway lumen geometry. Helical scans were obtained from a proximally-scanned fiber-optic catheter of 820 μm outer diameter and >2 mm focal length. Coupled with a long coherence length wavelength-swept light source, the system exhibited an SNR roll-off of < 10 dB over a 10 mm range. Operating at 10 rotations/s, the average accuracy of segmented cross-sectional areas was found to be −1.4 ± 1.0%. To demonstrate the capability of this system, aOCT was performed on a pediatric airway phantom and on ex vivo swine trachea. The ability for quantitative endoscopy afforded by this system can aid in diagnosis, medical and surgical decision making, and predictive modeling of upper airway obstructive disorders. PMID:24688814

  8. Imaging the anterior eye with dynamic-focus swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Su, Johnny P.; Li, Yan; Tang, Maolong; Liu, Liang; Pechauer, Alex D.; Huang, David; Liu, Gangjun

    2015-12-01

    A custom-built dynamic-focus swept-source optical coherence tomography (SS-OCT) system with a central wavelength of 1310 nm was used to image the anterior eye from the cornea to the lens. An electrically tunable lens was utilized to dynamically control the positions of focusing planes over the imaging range of 10 mm. The B-scan images were acquired consecutively at the same position but with different focus settings. The B-scan images were then registered and averaged after filtering the out-of-focus regions using a Gaussian window. By fusing images obtained at different depth focus locations, high-resolution and high signal-strength images were obtained over the entire imaging depth. In vivo imaging of human anterior segment was demonstrated. The performance of the system was compared with two commercial OCT systems. The human eye ciliary body was better visualized with the dynamic-focusing SS-OCT system than using the commercial 840 and 1310 nm OCT systems. The sulcus-to-sulcus distance was measured, and the result agreed with that acquired with ultrasound biomicroscopy.

  9. Sensitivity enhancement in swept-source optical coherence tomography by parametric balanced detector and amplifier

    PubMed Central

    Kang, Jiqiang; Wei, Xiaoming; Li, Bowen; Wang, Xie; Yu, Luoqin; Tan, Sisi; Jinata, Chandra; Wong, Kenneth K. Y.

    2016-01-01

    We proposed a sensitivity enhancement method of the interference-based signal detection approach and applied it on a swept-source optical coherence tomography (SS-OCT) system through all-fiber optical parametric amplifier (FOPA) and parametric balanced detector (BD). The parametric BD was realized by combining the signal and phase conjugated idler band that was newly-generated through FOPA, and specifically by superimposing these two bands at a photodetector. The sensitivity enhancement by FOPA and parametric BD in SS-OCT were demonstrated experimentally. The results show that SS-OCT with FOPA and SS-OCT with parametric BD can provide more than 9 dB and 12 dB sensitivity improvement, respectively, when compared with the conventional SS-OCT in a spectral bandwidth spanning over 76 nm. To further verify and elaborate their sensitivity enhancement, a bio-sample imaging experiment was conducted on loach eyes by conventional SS-OCT setup, SS-OCT with FOPA and parametric BD at different illumination power levels. All these results proved that using FOPA and parametric BD could improve the sensitivity significantly in SS-OCT systems. PMID:27446655

  10. Effects of fiber bundle on the performance of full-field swept source OCT

    NASA Astrophysics Data System (ADS)

    Zhou, Xiang; Wang, Jingyu; Selvon, Kieran; Matela, Milan; Dobre, G. M.; Podoleanu, Adrian G.

    2013-08-01

    This paper investigates the effects of fiber bundle on the performance of Full-field swept source OCT (FFSS-OCT) in terms of depth range, depth resolution and transversal resolution. A superfast CMOS camera with full sensor resolution 1024 x 1024 pixels and 60 kHz in maximum frame rate is employed in the testing system. A fiber bundle which contains 18000 single fibers is used to transmit images from interference beam to the camera. Depth range and resolution are assessed by varying optical path difference (OPD) between object arm and reference arm. The operation is repeated under a set of frame rates from 1 kHz to 3 kHz. In addition, an USAF plate is used as a planar object to test transversal resolution. For comparison, above parameters are tested as well with a bulk-optic setup which is built under the same system configuration but without bundle. The results show that the difference between performances of bundle and Bulkoptic setups is not remarkable. As a practical example, 3D profile of a coin is measured using two setups. In sum, this investigation shows that the performance of bundle setup can compete with that of bulk-optic setup in implementing FFSS-OCT. The quantitative results are helpful for researchers to incorporate bundles to FFSS-OCT systems in future.

  11. Optic axis determination by fibre-based polarization-sensitive swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

    2011-02-01

    We describe a fibre-based variable-incidence angle (VIA) polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) system to determine the 3D optical axis of birefringent biological tissues. Single-plane VIA-PS-OCT is also explored which requires measurement of the absolute fast-axis orientation. A state-of-the-art PS-SS-OCT system with some improvements both in hardware and software was used to determine the apparent optical birefringence of equine tendon for a number of different illumination directions. Polar and azimuthal angles of cut equine tendon were produced by the VIA method and compared with the nominal values. A quarter waveplate (QWP) and equine tendon were used as test targets to validate the fast-axis measurements using the system. Polar and azimuthal angles of cut equine tendon broadly agreed with the expected values within about 8% of the nominal values. A theoretical and experimental analysis of the effect of the sample arm fibre on determination of optical axis orientation using a proposed definition based on the orientation of the eigenpolarization ellipse experimentally confirms that this algorithm only works correctly for special settings of the sample arm fibre. A proposed algorithm based on the angle between Stokes vectors on the Poincaré sphere is confirmed to work for all settings of the sample arm fibre. A calibration procedure is proposed to remove the sign ambiguity of the measured orientation and was confirmed experimentally by using the QWP.

  12. Optic axis determination by fiber-based polarization-sensitive swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

    2011-03-01

    We describe a fiber-based variable-incidence-angle (VIA) polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) system to determine the 3-D optical axis of birefringent biological tissues. Single-plane VIAPS- OCT is also explored which requires measurement of the absolute fast-axis orientation. A state-of-the-art PS-SS-OCT system with some improvements both in hardware and software was used to determine the apparent optical birefringence of equine tendon for a number of different illumination directions. Polar and azimuthal angles of cut equine tendon were produced by VIA method and compared with the nominal values. A quarter waveplate (QWP) and equine tendon were used as test targets to validate the fast-axis measurements using the system. Polar and azimuthal angles of cut equine tendon broadly agreed with the expected values within about 8% of the nominal values. A theoretical and experimental analysis of the effect of the sample arm fiber on determination of optical axis orientation using a proposed definition based on the orientation of the eigenpolarization ellipse experimentally confirms that this algorithm only works correctly for special settings of the sample arm fiber. A proposed algorithm based on the angle between Stokes vectors on the Poincaré sphere is confirmed to work for all settings of the sample arm fiber. A calibration procedure is proposed to remove the sign ambiguity of the measured orientation and was confirmed experimentally by using the QWP.

  13. Swept-source common-path optical coherence tomography with a MEMS endoscopic imaging probe

    NASA Astrophysics Data System (ADS)

    Duan, Can; Wang, Donglin; Zhou, Zhengwei; Liang, Peng; Samuelson, Sean; Pozzi, Antonio; Xie, Huikai

    2014-03-01

    A MEMS-based common-path endoscopic imaging probe for 3D swept-source optical coherence tomography (SSOCT) has been developed. The common path is achieved by setting the reference plane at the rear surface of the GRIN lens inside the probe. MEMS devices have the advantages of low cost, small size and fast speed, which are suitable for miniaturizing endoscopic probes. The aperture size of the two-axis MEMS mirror employed in this endoscopic probe is 1 mm by 1 mm and the footprint of the MEMS chip is 1.55 mm by 1.7 mm. The MEMS mirror achieves large two dimensional optical scan angles up to 34° at 4.0 V. The endoscopic probe using the MEMS mirror as the scan engine is only 4.0 mm in diameter. Additionally, an optimum length of the GRIN lens is established to remove the artifacts in the SSOCT images generated from the multiple interfaces inside the endoscopic imaging probe. The MEMS based commonpath probe demonstrates real time 3D OCT images of human finger with 10.6 μm axial resolution, 17.5 μm lateral resolution and 1.0 mm depth range at a frame rate of 50 frames per second.

  14. Speckle reduction in swept source optical coherence tomography images with slow-axis averaging

    NASA Astrophysics Data System (ADS)

    Tan, Ou; Li, Yan; Wang, Yimin; Kraus, Martin F.; Liu, Jonathan J.; Potsaid, Benjamin; Baumann, Bernhard; Fujimoto, James G.; Huang, David

    2012-01-01

    The effectiveness of speckle reduction using traditional frame averaging technique was limited in ultrahigh speed optical coherence tomography (OCT). As the motion between repeated frames was very small, the speckle pattern of the frames might be identical. This problem could be solved by averaging frames acquired at slightly different locations. The optimized scan range depended on the spot size of the laser beam, the smoothness of the boundary, and the homogeneity of the tissue. In this study we presented a method to average frames obtained within a narrow range along the slow-axis. A swept-source OCT with 100,000 Hz axial scan rate was used to scan the retina in vivo. A series of narrow raster scans (0-50 micron along the slow axis) were evaluated. Each scan contained 20 image frames evenly distributed in the scan range. The imaging frame rate was 417 HZ. Only frames with high correlation after rigid registration were used in averaging. The result showed that the contrast-to-noise ratio (CNR) increased with the scan range. But the best edge reservation was obtained with 15 micron scan range. Thus, for ultrahigh speed OCT systems, averaging frames from a narrow band along the slow-axis could achieve better speckle reduction than traditional frame averaging techniques.

  15. Swept source optical coherence tomography for quantitative and qualitative assessment of dental composite restorations

    NASA Astrophysics Data System (ADS)

    Sadr, Alireza; Shimada, Yasushi; Mayoral, Juan Ricardo; Hariri, Ilnaz; Bakhsh, Turki A.; Sumi, Yasunori; Tagami, Junji

    2011-03-01

    The aim of this work was to explore the utility of swept-source optical coherence tomography (SS-OCT) for quantitative evaluation of dental composite restorations. The system (Santec, Japan) with a center wavelength of around 1300 nm and axial resolution of 12 μm was used to record data during and after placement of light-cured composites. The Fresnel phenomenon at the interfacial defects resulted in brighter areas indicating gaps as small as a few micrometers. The gap extension at the interface was quantified and compared to the observation by confocal laser scanning microscope after trimming the specimen to the same cross-section. Also, video imaging of the composite during polymerization could provide information about real-time kinetics of contraction stress and resulting gaps, distinguishing them from those gaps resulting from poor adaptation of composite to the cavity prior to polymerization. Some samples were also subjected to a high resolution microfocus X-ray computed tomography (μCT) assessment; it was found that differentiation of smaller gaps from the radiolucent bonding layer was difficult with 3D μCT. Finally, a clinical imaging example using a newly developed dental SS-OCT system with an intra-oral scanning probe (Panasonic Healthcare, Japan) is presented. SS-OCT is a unique tool for clinical assessment and laboratory research on resin-based dental restorations. Supported by GCOE at TMDU and NCGG.

  16. All ceramic table tops analyzed using swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Stoica, Eniko Tunde; Marcauteanu, Corina; Sinescu, Cosmin; Negrutiu, Meda Lavinia; Topala, Florin; Duma, Virgil Florin; Bradu, Adrian; Podoleanu, Adrian Gh.

    2016-03-01

    Erosion is the progressive loss of tooth substance by chemical processes that do not involve bacterial action. The affected teeth can be restored by using IPS e.max Press "table tops", which replace the occlusal surfaces. In this study we applied a fast in-house Swept Source Optical Coherence Tomography (SS OCT) system to analyze IPS e.max Press "table tops". 12 maxillary first premolars have been extracted and prepared for "table tops". These restorations were subjected to 3000 alternating cycles of thermo-cycling in a range from -10°C to +50°C mechanical occlusal loads of 200 N were also applied. Using SS OCT we analyze the marginal seal of these restorations, before and after applying the mechanical and thermal strain. The characteristics of the SS OCT system utilized are presented. Its depth resolution, measured in air is 10 μm. The system is able to acquire entire volumetric reconstructions in 2.5 s. From the dataset acquired high resolution en-face projections were also produced. Thus, the interfaces between all ceramic "table tops" and natural teeth were analyzed on the cross-sections (i.e., the B-scans) produced and also on the volumetric (tri-dimensional (3D)) reconstructions, several open interfaces being detected. The study therefore demonstrates the utility of SS OCT for the analysis of lithium disilicate glass ceramic "table tops".

  17. Phase-sensitive optical coherence tomography-based vibrometry using a highly phase-stable akinetic swept laser source

    SciTech Connect

    Applegate, Brian E.; Park, Jesung; Carbajal, Esteban; Oghalai, John S.

    2015-12-31

    Phase-sensitive Optical Coherence Tomography (PhOCT) is an emerging tool for in vivo investigation of the vibratory function of the intact middle and inner ear. PhOCT is able to resolve micron scale tissue morphology in three dimensions as well as measure picometer scale motion at each spatial position. Most PhOCT systems to date have relied upon the phase stability offered by spectrometer detection. On the other hand swept laser source based PhOCT offers a number of advantages including balanced detection, long imaging depths, and high imaging speeds. Unfortunately the inherent phase instability of traditional swept laser sources has necessitated complex user developed hardware/software solutions to restore phase sensitivity. Here we present recent results using a prototype swept laser that overcomes these issues. The akinetic swept laser is electronically tuned and precisely controls sweeps without any mechanical movement, which results in high phase stability. We have developed an optical fiber based PhOCT system around the akinetic laser source that had a 1550 nm center wavelength and a sweep rate of 140 kHz. The stability of the system was measured to be 4.4 pm with a calibrated reflector, thus demonstrating near shot noise limited performance. Using this PhOCT system, we have acquired structural and vibratory measurements of the middle ear in a mouse model, post mortem. The quality of the results suggest that the akinetic laser source is a superior laser source for PhOCT with many advantages that greatly reduces the required complexity of the imaging system.

  18. Phase-sensitive optical coherence tomography-based vibrometry using a highly phase-stable akinetic swept laser source

    NASA Astrophysics Data System (ADS)

    Applegate, Brian E.; Park, Jesung; Carbajal, Esteban; Oghalai, John S.

    2015-12-01

    Phase-sensitive Optical Coherence Tomography (PhOCT) is an emerging tool for in vivo investigation of the vibratory function of the intact middle and inner ear. PhOCT is able to resolve micron scale tissue morphology in three dimensions as well as measure picometer scale motion at each spatial position. Most PhOCT systems to date have relied upon the phase stability offered by spectrometer detection. On the other hand swept laser source based PhOCT offers a number of advantages including balanced detection, long imaging depths, and high imaging speeds. Unfortunately the inherent phase instability of traditional swept laser sources has necessitated complex user developed hardware/software solutions to restore phase sensitivity. Here we present recent results using a prototype swept laser that overcomes these issues. The akinetic swept laser is electronically tuned and precisely controls sweeps without any mechanical movement, which results in high phase stability. We have developed an optical fiber based PhOCT system around the akinetic laser source that had a 1550 nm center wavelength and a sweep rate of 140 kHz. The stability of the system was measured to be 4.4 pm with a calibrated reflector, thus demonstrating near shot noise limited performance. Using this PhOCT system, we have acquired structural and vibratory measurements of the middle ear in a mouse model, post mortem. The quality of the results suggest that the akinetic laser source is a superior laser source for PhOCT with many advantages that greatly reduces the required complexity of the imaging system.

  19. Performance analysis of a full-field and full-range swept-source OCT system

    NASA Astrophysics Data System (ADS)

    Krauter, J.; Boettcher, T.; Körner, K.; Gronle, M.; Osten, W.; Passilly, N.; Froehly, L.; Perrin, S.; Gorecki, C.

    2015-09-01

    In recent years, optical coherence tomography (OCT) became gained importance in medical disciplines like ophthalmology, due to its noninvasive optical imaging technique with micrometer resolution and short measurement time. It enables e. g. the measurement and visualization of the depth structure of the retina. In other medical disciplines like dermatology, histopathological analysis is still the gold standard for skin cancer diagnosis. The EU-funded project VIAMOS (Vertically Integrated Array-type Mirau-based OCT System) proposes a new type of OCT system combined with micro-technologies to provide a hand-held, low-cost and miniaturized OCT system. The concept is a combination of full-field and full-range swept-source OCT (SS-OCT) detection in a multi-channel sensor based on a micro-optical Mirau-interferometer array, which is fabricated by means of wafer fabrication. This paper presents the study of an experimental proof-of-concept OCT system as a one-channel sensor with bulk optics. This sensor is a Linnik-interferometer type with similar optical parameters as the Mirau-interferometer array. A commercial wavelength tunable light source with a center wavelength at 845nm and 50nm spectral bandwidth is used with a camera for parallel OCT A-Scan detection. In addition, the reference microscope objective lens of the Linnik-interferometer is mounted on a piezo-actuated phase-shifter. Phase-shifting interferometry (PSI) techniques are applied for resolving the conjugate complex artifact and consequently contribute to an increase of image quality and depth range. A suppression ratio of the complex conjugate term of 36 dB is shown and a system sensitivity greater than 96 dB could be measured.

  20. Swept source optical coherence tomography for in vivo imaging and vibrometry in the apex of the mouse cochlea

    NASA Astrophysics Data System (ADS)

    Lee, Hee Yoon; Raphael, Patrick D.; Ellerbee, Audrey K.; Applegate, Brian E.; Oghalai, John S.

    2015-12-01

    Cochlear amplification has been most commonly investigated by measuring the vibrations of the basilar membrane in animal models. Several different techniques have been used for measuring these vibrations such as laser Doppler vibrometry, miniature pressure sensors, low coherence interferometry, and spectral-domain optical coherence tomography (SD-OCT). We have built a swept-source OCT (SS-OCT) system, which is similar to SD-OCT in that it is capable of performing both imaging and vibration measurements within the mouse cochlea in vivo without having to open the bone. In vivo 3D images of a mouse cochlea were obtained, and the basilar membrane, tectorial membrane, Reissner's membrane, tunnel of Corti, and reticular lamina could all be resolved. We measured vibrations of multiple structures within the mouse cochlea to sound stimuli. As well, we measured the radial deflections of the reticular lamina and tectorial membrane to estimate the displacement of the outer hair cell stereocilia. These measurements have the potential to more clearly define the mechanisms underlying the linear and non-linear processes within the mammalian cochlea.

  1. Swept source optical coherence tomography for in vivo imaging and vibrometry in the apex of the mouse cochlea

    SciTech Connect

    Lee, Hee Yoon; Raphael, Patrick D.; Oghalai, John S.; Ellerbee, Audrey K.; Applegate, Brian E.

    2015-12-31

    Cochlear amplification has been most commonly investigated by measuring the vibrations of the basilar membrane in animal models. Several different techniques have been used for measuring these vibrations such as laser Doppler vibrometry, miniature pressure sensors, low coherence interferometry, and spectral-domain optical coherence tomography (SD-OCT). We have built a swept-source OCT (SS-OCT) system, which is similar to SD-OCT in that it is capable of performing both imaging and vibration measurements within the mouse cochlea in vivo without having to open the bone. In vivo 3D images of a mouse cochlea were obtained, and the basilar membrane, tectorial membrane, Reissner’s membrane, tunnel of Corti, and reticular lamina could all be resolved. We measured vibrations of multiple structures within the mouse cochlea to sound stimuli. As well, we measured the radial deflections of the reticular lamina and tectorial membrane to estimate the displacement of the outer hair cell stereocilia. These measurements have the potential to more clearly define the mechanisms underlying the linear and non-linear processes within the mammalian cochlea.

  2. Handheld, rapidly switchable, anterior/posterior segment swept source optical coherence tomography probe.

    PubMed

    Nankivil, Derek; Waterman, Gar; LaRocca, Francesco; Keller, Brenton; Kuo, Anthony N; Izatt, Joseph A

    2015-11-01

    We describe the first handheld, swept source optical coherence tomography (SSOCT) system capable of imaging both the anterior and posterior segments of the eye in rapid succession. A single 2D microelectromechanical systems (MEMS) scanner was utilized for both imaging modes, and the optical paths for each imaging mode were optimized for their respective application using a combination of commercial and custom optics. The system has a working distance of 26.1 mm and a measured axial resolution of 8 μm (in air). In posterior segment mode, the design has a lateral resolution of 9 μm, 7.4 mm imaging depth range (in air), 4.9 mm 6dB fall-off range (in air), and peak sensitivity of 103 dB over a 22° field of view (FOV). In anterior segment mode, the design has a lateral resolution of 24 μm, imaging depth range of 7.4 mm (in air), 6dB fall-off range of 4.5 mm (in air), depth-of-focus of 3.6 mm, and a peak sensitivity of 99 dB over a 17.5 mm FOV. In addition, the probe includes a wide-field iris imaging system to simplify alignment. A fold mirror assembly actuated by a bi-stable rotary solenoid was used to switch between anterior and posterior segment imaging modes, and a miniature motorized translation stage was used to adjust the objective lens position to correct for patient refraction between -12.6 and + 9.9 D. The entire probe weighs less than 630 g with a form factor of 20.3 x 9.5 x 8.8 cm. Healthy volunteers were imaged to illustrate imaging performance. PMID:26601014

  3. Observation of the pulp horn by swept source optical coherence tomography and cone beam computed tomography

    NASA Astrophysics Data System (ADS)

    Iino, Yoshiko; Yoshioka, Toshihiko; Hanada, Takahiro; Ebihara, Arata; Sunakawa, Mitsuhiro; Sumi, Yasunori; Suda, Hideaki

    2015-02-01

    Cone-beam computed tomography (CBCT) is one of the most useful diagnostic techniques in dentistry but it involves ionizing radiation, while swept source optical coherence tomography (SS-OCT) has been introduced recently as a nondestructive, real-time, high resolution imaging technique using low-coherence interferometry, which involves no ionizing radiation. The purpose of this study was to evaluate the ability of SS-OCT to detect the pulp horn (PH) in comparison with that of CBCT. Ten extracted human mandibular molars were used. After horizontally removing a half of the tooth crown, the distance from the cut dentin surface to PH was measured using microfocus computed tomography (Micro CT) (SL) as the gold standard, by CBCT (CL) and by SS-OCT (OL). In the SS-OCT images, only when PH was observed beneath the overlying dentin, the distance from the cut dentin surface to PH was recorded. If the pulp was exposed, it was defined as pulp exposure (PE). The results obtained by the above three methods were statistically analyzed by Spearman's rank correlation coefficient at a significance level of p < 0.01. SS-OCT detected the presence of PH when the distance from the cut dentin surface to PH determined by SL was 2.33 mm or less. Strong correlations of the measured values were found between SL and CL (r=0.87), SL and OL (r=0.96), and CL and OL (r=0.86). The results showed that SS-OCT images correlated closely with CBCT images, suggesting that SS-OCT can be a useful tool for the detection of PH.

  4. Handheld, rapidly switchable, anterior/posterior segment swept source optical coherence tomography probe

    PubMed Central

    Nankivil, Derek; Waterman, Gar; LaRocca, Francesco; Keller, Brenton; Kuo, Anthony N.; Izatt, Joseph A.

    2015-01-01

    We describe the first handheld, swept source optical coherence tomography (SSOCT) system capable of imaging both the anterior and posterior segments of the eye in rapid succession. A single 2D microelectromechanical systems (MEMS) scanner was utilized for both imaging modes, and the optical paths for each imaging mode were optimized for their respective application using a combination of commercial and custom optics. The system has a working distance of 26.1 mm and a measured axial resolution of 8 μm (in air). In posterior segment mode, the design has a lateral resolution of 9 μm, 7.4 mm imaging depth range (in air), 4.9 mm 6dB fall-off range (in air), and peak sensitivity of 103 dB over a 22° field of view (FOV). In anterior segment mode, the design has a lateral resolution of 24 μm, imaging depth range of 7.4 mm (in air), 6dB fall-off range of 4.5 mm (in air), depth-of-focus of 3.6 mm, and a peak sensitivity of 99 dB over a 17.5 mm FOV. In addition, the probe includes a wide-field iris imaging system to simplify alignment. A fold mirror assembly actuated by a bi-stable rotary solenoid was used to switch between anterior and posterior segment imaging modes, and a miniature motorized translation stage was used to adjust the objective lens position to correct for patient refraction between −12.6 and + 9.9 D. The entire probe weighs less than 630 g with a form factor of 20.3 x 9.5 x 8.8 cm. Healthy volunteers were imaged to illustrate imaging performance. PMID:26601014

  5. Handheld ultrahigh speed swept source optical coherence tomography instrument using a MEMS scanning mirror

    PubMed Central

    Lu, Chen D.; Kraus, Martin F.; Potsaid, Benjamin; Liu, Jonathan J.; Choi, WooJhon; Jayaraman, Vijaysekhar; Cable, Alex E.; Hornegger, Joachim; Duker, Jay S.; Fujimoto, James G.

    2013-01-01

    We developed an ultrahigh speed, handheld swept source optical coherence tomography (SS-OCT) ophthalmic instrument using a 2D MEMS mirror. A vertical cavity surface-emitting laser (VCSEL) operating at 1060 nm center wavelength yielded a 350 kHz axial scan rate and 10 µm axial resolution in tissue. The long coherence length of the VCSEL enabled a 3.08 mm imaging range with minimal sensitivity roll-off in tissue. Two different designs with identical optical components were tested to evaluate handheld OCT ergonomics. An iris camera aided in alignment of the OCT beam through the pupil and a manual fixation light selected the imaging region on the retina. Volumetric and high definition scans were obtained from 5 undilated normal subjects. Volumetric OCT data was acquired by scanning the 2.4 mm diameter 2D MEMS mirror sinusoidally in the fast direction and linearly in the orthogonal slow direction. A second volumetric sinusoidal scan was obtained in the orthogonal direction and the two volumes were processed with a software algorithm to generate a merged motion-corrected volume. Motion-corrected standard 6 x 6 mm2 and wide field 10 x 10 mm2 volumetric OCT data were generated using two volumetric scans, each obtained in 1.4 seconds. High definition 10 mm and 6 mm B-scans were obtained by averaging and registering 25 B-scans obtained over the same position in 0.57 seconds. One of the advantages of volumetric OCT data is the generation of en face OCT images with arbitrary cross sectional B-scans registered to fundus features. This technology should enable screening applications to identify early retinal disease, before irreversible vision impairment or loss occurs. Handheld OCT technology also promises to enable applications in a wide range of settings outside of the traditional ophthalmology or optometry clinics including pediatrics, intraoperative, primary care, developing countries, and military medicine. PMID:24466495

  6. In Vivo Choroidal Vascular Lesions in Diabetes on Swept-Source Optical Coherence Tomography

    PubMed Central

    Murakami, Tomoaki; Uji, Akihito; Suzuma, Kiyoshi; Dodo, Yoko; Yoshitake, Shin; Ghashut, Rima; Yoza, Rina; Fujimoto, Masahiro; Yoshimura, Nagahisa

    2016-01-01

    Diabetes induces microvascular diseases including diabetic retinopathy and choroidopathy which reciprocally promote the pathogenesis, although optical coherence tomography images of diabetic choroidopathy remains to be documented. Here we evaluated the qualitative characteristics of choroidal vascular lesions in patients with diabetes and their association with diabetic retinopathy on swept-source optical coherence tomography (SS-OCT) images. We retrospectively reviewed 110 consecutive eyes of 110 patients with diabetes and 35 eyes of 35 healthy subjects for whom SS-OCT images (6x6-mm scans centered on the fovea) of sufficient quality were acquired. The curve of chorioretinal sections was flattened using Bruch’s membrane as a reference surface, followed by generation of en-face images. We characterized choroidal vascular lesions and evaluated their association with the logarithm of the minimum angle of resolution visual acuity (logMAR VA), retinal and choroidal thicknesses, and diabetic retinopathy severity. En-face SS-OCT images showed unvisualized vessels in Sattler’s layer in 33 eyes (30.0%). Focal narrowing was seen in choroidal vessels in Haller’s layer in 56 eyes (50.9%). The choroidal vessels ended in the superficial or middle portion of Haller’s layer, referred to as vascular stumps, in 20 eyes (18.2%). Diabetic eyes had these findings more frequently than nondiabetic eyes. The subfoveal choroid was thicker in eyes with focal vascular narrowing and vascular stumps than in eyes without such lesions. Vascular stumps in Haller’s layer were significantly related to diabetic retinopathy severity, logMAR VA, and central retinal and choroidal thicknesses. These novel findings on SS-OCT images would promote the better understanding of complicated pathogenesis in diabetic retinopathy and choroidopathy. PMID:27479070

  7. High-speed, digitally refocused retinal imaging with line-field parallel swept source OCT

    NASA Astrophysics Data System (ADS)

    Fechtig, Daniel J.; Kumar, Abhishek; Ginner, Laurin; Drexler, Wolfgang; Leitgeb, Rainer A.

    2015-03-01

    MHz OCT allows mitigating undesired influence of motion artifacts during retinal assessment, but comes in state-of-the-art point scanning OCT at the price of increased system complexity. By changing the paradigm from scanning to parallel OCT for in vivo retinal imaging the three-dimensional (3D) acquisition time is reduced without a trade-off between speed, sensitivity and technological requirements. Furthermore, the intrinsic phase stability allows for applying digital refocusing methods increasing the in-focus imaging depth range. Line field parallel interferometric imaging (LPSI) is utilizing a commercially available swept source, a single-axis galvo-scanner and a line scan camera for recording 3D data with up to 1MHz A-scan rate. Besides line-focus illumination and parallel detection, we mitigate the necessity for high-speed sensor and laser technology by holographic full-range imaging, which allows for increasing the imaging speed by low sampling of the optical spectrum. High B-scan rates up to 1kHz further allow for implementation of lable-free optical angiography in 3D by calculating the inter B-scan speckle variance. We achieve a detection sensitivity of 93.5 (96.5) dB at an equivalent A-scan rate of 1 (0.6) MHz and present 3D in vivo retinal structural and functional imaging utilizing digital refocusing. Our results demonstrate for the first time competitive imaging sensitivity, resolution and speed with a parallel OCT modality. LPSI is in fact currently the fastest OCT device applied to retinal imaging and operating at a central wavelength window around 800 nm with a detection sensitivity of higher than 93.5 dB.

  8. In Vivo Choroidal Vascular Lesions in Diabetes on Swept-Source Optical Coherence Tomography.

    PubMed

    Murakami, Tomoaki; Uji, Akihito; Suzuma, Kiyoshi; Dodo, Yoko; Yoshitake, Shin; Ghashut, Rima; Yoza, Rina; Fujimoto, Masahiro; Yoshimura, Nagahisa

    2016-01-01

    Diabetes induces microvascular diseases including diabetic retinopathy and choroidopathy which reciprocally promote the pathogenesis, although optical coherence tomography images of diabetic choroidopathy remains to be documented. Here we evaluated the qualitative characteristics of choroidal vascular lesions in patients with diabetes and their association with diabetic retinopathy on swept-source optical coherence tomography (SS-OCT) images. We retrospectively reviewed 110 consecutive eyes of 110 patients with diabetes and 35 eyes of 35 healthy subjects for whom SS-OCT images (6x6-mm scans centered on the fovea) of sufficient quality were acquired. The curve of chorioretinal sections was flattened using Bruch's membrane as a reference surface, followed by generation of en-face images. We characterized choroidal vascular lesions and evaluated their association with the logarithm of the minimum angle of resolution visual acuity (logMAR VA), retinal and choroidal thicknesses, and diabetic retinopathy severity. En-face SS-OCT images showed unvisualized vessels in Sattler's layer in 33 eyes (30.0%). Focal narrowing was seen in choroidal vessels in Haller's layer in 56 eyes (50.9%). The choroidal vessels ended in the superficial or middle portion of Haller's layer, referred to as vascular stumps, in 20 eyes (18.2%). Diabetic eyes had these findings more frequently than nondiabetic eyes. The subfoveal choroid was thicker in eyes with focal vascular narrowing and vascular stumps than in eyes without such lesions. Vascular stumps in Haller's layer were significantly related to diabetic retinopathy severity, logMAR VA, and central retinal and choroidal thicknesses. These novel findings on SS-OCT images would promote the better understanding of complicated pathogenesis in diabetic retinopathy and choroidopathy. PMID:27479070

  9. Defense of fake fingerprint attacks using a swept source laser optical coherence tomography setup

    NASA Astrophysics Data System (ADS)

    Meissner, Sven; Breithaupt, Ralph; Koch, Edmund

    2013-03-01

    The most established technique for the identification at biometric access control systems is the human fingerprint. While every human fingerprint is unique, fingerprints can be faked very easily by using thin layer fakes. Because commercial fingerprint scanners use only a two-dimensional image acquisition of the finger surface, they can only hardly differentiate between real fingerprints and fingerprint fakes applied on thin layer materials. A Swept Source OCT system with an A-line rate of 20 kHz and a lateral and axial resolution of approximately 13 μm, a centre wavelength of 1320 nm and a band width of 120 nm (FWHM) was used to acquire fingerprints and finger tips with overlying fakes. Three-dimensional volume stacks with dimensions of 4.5 mm x 4 mm x 2 mm were acquired. The layering arrangement of the imaged finger tips and faked finger tips was analyzed and subsequently classified into real and faked fingerprints. Additionally, sweat gland ducts were detected and consulted for the classification. The manual classification between real fingerprints and faked fingerprints results in almost 100 % correctness. The outer as well as the internal fingerprint can be recognized in all real human fingers, whereby this was not possible in the image stacks of the faked fingerprints. Furthermore, in all image stacks of real human fingers the sweat gland ducts were detected. The number of sweat gland ducts differs between the test persons. The typical helix shape of the ducts was observed. In contrast, in images of faked fingerprints we observe abnormal layer arrangements and no sweat gland ducts connecting the papillae of the outer fingerprint and the internal fingerprint. We demonstrated that OCT is a very useful tool to enhance the performance of biometric control systems concerning attacks by thin layer fingerprint fakes.

  10. Evaluation of Tizian overlays by means of a swept source optical coherence tomography system

    NASA Astrophysics Data System (ADS)

    Marcauteanu, Corina; Sinescu, Cosmin; Negrutiu, Meda Lavinia; Stoica, Eniko Tunde; Topala, Florin; Duma, Virgil Florin; Bradu, Adrian; Podoleanu, Adrian Gh.

    2016-03-01

    The teeth affected by pathologic attrition can be restored by a minimally invasive approach, using Tizian overlays. In this study we prove the advantages of a fast swept source (SS) OCT system in the evaluation of Tizian overlays placed in an environment characterized by high occlusal forces. 12 maxillary first premolars were extracted and prepared for overlays. The Tizian overlays were subjected to 3000 alternating cycles of thermo-cycling (from -10°C to +50°C) and to mechanical occlusal overloads (at 800 N). A fast SS OCT system was used to evaluate the Tizian overlays before and after the mechanical and thermal straining. The SS (Axsun Technologies, Billerica, MA) has a central wavelength of 1060 nm, sweeping range of 106 nm (quoted at 10 dB) and a 100 kHz line rate. The depth resolution of the system, measured experimentally in air was 10 μm. The imaging system used for this study offers high spatial resolutions in both directions, transversal and longitudinal of around 10 μm, a high sensitivity, and it is also able to acquire entire tridimensional (3D)/volume reconstructions as fast as 2.5 s. Once the full dataset was acquired, rendered high resolutions en-face projections could be produced. Using them, the overlay (i.e., cement) abutment tooth interfaces were remarked both on B-scans/two-dimensional (2D) sections and in the 3D reconstructions. Using the system several open interfaces were possible to detect. The fast SS OCT system thus proves useful in the evaluation of zirconia reinforced composite overlays, placed in an environment characterized by high occlusal forces.

  11. Dynamic imaging of accommodation by swept-source anterior-segment optical coherence tomography

    PubMed Central

    Neri, Alberto; Ruggeri, Marco; Protti, Alessandra; Leaci, Rosachiara; Gandolfi, Stefano A.; Macaluso, Claudio

    2015-01-01

    Purpose To study the accommodation process in normal eyes using a commercially available clinical system based on swept-source anterior-segment optical coherence tomography (SS-AS-OCT). Setting Ophthalmology, University of Parma, Parma, Italy. Design Experimental study. Methods The right eye of 14 healthy volunteers (18–46 years) was analyzed with SS-AS-OCT. The optical vergence of the coaxial fixation target integrated in the OCT device was adjusted during imaging to obtain monocular accommodation stimuli with different amplitudes (ASA: 0, 3, 6 and 9 Diopters). Overlapping of real and conjugate OCT images enabled imaging of all the anterior segment optical surfaces in a single frame. Intraocular distances including central corneal thickness (CCT), anterior chamber depth (ACD) and lens thickness (LT) were extracted from the OCT scans acquired at different static ASA. Dynamic analysis of the crystalline lens was also performed during accommodation and disaccommodation by sequentially acquiring OCT images of the anterior segment at a rate of 8 frames per second. LT was extracted from the temporal sequence of OCT images and plotted as a function of time. Results With accommodation ACD decreased significantly (p<0.05), LT increased (p<0.001) and lens central point moved slightly forward (p<0.01). CCT and ACW measurements did not change significantly with accommodation, which in turn confirmed that centering of the eye in the OCT images was maintained through ASA. LT at 0D was positively correlated with age (range: 3.131–4.088mm, r=0.772, p<0.01). Conclusions High-resolution real-time imaging and biometry of the accommodating anterior segment can be effectively performed with a commercial SS-AS-OCT clinical device. PMID:25704218

  12. Apices of maxillary premolars observed by swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Ebihara, Arata; Iino, Yoshiko; Yoshioka, Toshihiko; Hanada, Takahiro; Sunakawa, Mitsuhiro; Sumi, Yasunori; Suda, Hideaki

    2015-02-01

    Apicoectomy is performed for the management of apical periodontitis when orthograde root canal treatment is not possible or is ineffective. Prior to the surgery, cone beam computed tomography (CBCT) examination is often performed to evaluate the lesion and the adjacent tissues. During the surgical procedure, the root apex is resected and the resected surface is usually observed under dental operating microscope (DOM). However, it is difficult to evaluate the details and the subsurface structure of the root using CBCT and DOM. A new diagnostic system, swept source optical coherence tomography (SS-OCT), has been developed to observe the subsurface anatomical structure. The aim of this study was to observe resected apical root canals of human maxillary premolars using SS-OCT and compare the findings with those observed using CBCT and DOM. Six extracted human maxillary premolars were used. After microfocus computed tomography (Micro CT; for gold standard) and CBCT scanning of the root, 1 mm of the apex was cut perpendicular to the long axis of the tooth. Each resected surface was treated with EDTA, irrigated with saline solution, and stained with methylene blue dye. The resected surface was observed with DOM and SS-OCT. This sequence was repeated three times. The number of root canals was counted and statistically evaluated. There was no significant difference in the accuracy of detecting root canals among CBCT, DOM and SS-OCT (p > 0.05, Wilcoxon test). Because SS-OCT can be used in real time during surgery, it would be a useful tool for observing resected apical root canals.

  13. Handheld ultrahigh speed swept source optical coherence tomography instrument using a MEMS scanning mirror.

    PubMed

    Lu, Chen D; Kraus, Martin F; Potsaid, Benjamin; Liu, Jonathan J; Choi, Woojhon; Jayaraman, Vijaysekhar; Cable, Alex E; Hornegger, Joachim; Duker, Jay S; Fujimoto, James G

    2013-12-20

    We developed an ultrahigh speed, handheld swept source optical coherence tomography (SS-OCT) ophthalmic instrument using a 2D MEMS mirror. A vertical cavity surface-emitting laser (VCSEL) operating at 1060 nm center wavelength yielded a 350 kHz axial scan rate and 10 µm axial resolution in tissue. The long coherence length of the VCSEL enabled a 3.08 mm imaging range with minimal sensitivity roll-off in tissue. Two different designs with identical optical components were tested to evaluate handheld OCT ergonomics. An iris camera aided in alignment of the OCT beam through the pupil and a manual fixation light selected the imaging region on the retina. Volumetric and high definition scans were obtained from 5 undilated normal subjects. Volumetric OCT data was acquired by scanning the 2.4 mm diameter 2D MEMS mirror sinusoidally in the fast direction and linearly in the orthogonal slow direction. A second volumetric sinusoidal scan was obtained in the orthogonal direction and the two volumes were processed with a software algorithm to generate a merged motion-corrected volume. Motion-corrected standard 6 x 6 mm(2) and wide field 10 x 10 mm(2) volumetric OCT data were generated using two volumetric scans, each obtained in 1.4 seconds. High definition 10 mm and 6 mm B-scans were obtained by averaging and registering 25 B-scans obtained over the same position in 0.57 seconds. One of the advantages of volumetric OCT data is the generation of en face OCT images with arbitrary cross sectional B-scans registered to fundus features. This technology should enable screening applications to identify early retinal disease, before irreversible vision impairment or loss occurs. Handheld OCT technology also promises to enable applications in a wide range of settings outside of the traditional ophthalmology or optometry clinics including pediatrics, intraoperative, primary care, developing countries, and military medicine. PMID:24466495

  14. Detection of Root Surface Fractures with Swept-Source Optical Coherence Tomography (SS-OCT)

    PubMed Central

    Yoshioka, Toshihiko; Sakaue, Hitoshi; Ishimura, Hitomi; Suda, Hideaki; Sumi, Yasunori

    2013-01-01

    Abstract Objective: The purpose of this study was to compare optical coherence tomography (OCT) with the existing technologies, to assess its accuracy and utility in detecting vertical root fractures of extracted human teeth. Background data: The detection of root fractures in teeth that have undergone root canal treatment is challenging because of the great difficulty in differentiating these fractures from morphologic or radiographic anomalies. OCT methods are based on depth-resolved optical reflectivity and have been developed to reduce the invasiveness and radiation exposure inherent to other techniques. Methods: Twelve extracted human mandibular teeth (totaling 25 roots) that were free of caries, calculus, and root treatment were used, and assessed by microfocus computed tomography, the current gold standard for fracture detection. The ability of appropriately trained observers to detect root fractures using visual, microscopic, and swept-source OCT (SS-OCT) techniques were compared. micro-CT and SS-OCT produce three-dimensional images of the tooth from which to diagnose fractures, but CT scanning involves radiation exposure that is not required in SS-OCT. Results: Seventeen of the 25 roots were found to have fractures by microfocus CT. These findings were replicated by SS-OCT, which revealed fractures exhibiting identical origin, size, and angulation within the root. We found that SS-OCT gave results compatible to the gold standard technique, and that SS-OCT and microscopy were more effective for identifying root fractures than was visual observation alone. Conclusions: SS-OCT may represent a novel, noninvasive, noncontact and nonexposure alternative to the conventional methods used for assessing root fractures in teeth. PMID:23240873

  15. Viscous/potential flow about multi-element two-dimensional and infinite-span swept wings - Theory and experiment

    NASA Technical Reports Server (NTRS)

    Olson, L. E.; Dvorak, F. A.

    1976-01-01

    The viscous subsonic flow past two-dimensional and infinite-span swept multi-component airfoils is studied theoretically and experimentally. The computerized analysis is based on iteratively coupled boundary-layer and potential-flow analysis. The method, which is restricted to flows with only slight separation, gives surface pressure distribution, chordwise and spanwise boundary-layer characteristics, lift, drag, and pitching moment for airfoil configurations with up to four elements. Merging confluent boundary layers are treated. Theoretical predictions are compared with an exact theoretical potential flow solution and with experimental measures made in the Ames 40- by 80-Foot Wind Tunnel for both two-dimensional and infinite-span swept wing configurations. Section lift characteristics are accurately predicted for zero and moderate sweep angles where flow separation effects are negligible.

  16. Viscous/potential flow about multi-element two-dimensional and infinite-span swept wings: Theory and experiment

    NASA Technical Reports Server (NTRS)

    Olson, L. E.; Dvorak, F. A.

    1975-01-01

    The viscous subsonic flow past two-dimensional and infinite-span swept multi-component airfoils is studied theoretically and experimentally. The computerized analysis is based on iteratively coupled boundary layer and potential flow analysis. The method, which is restricted to flows with only slight separation, gives surface pressure distribution, chordwise and spanwise boundary layer characteristics, lift, drag, and pitching moment for airfoil configurations with up to four elements. Merging confluent boundary layers are treated. Theoretical predictions are compared with an exact theoretical potential flow solution and with experimental measures made in the Ames 40- by 80-Foot Wind Tunnel for both two-dimensional and infinite-span swept wing configurations. Section lift characteristics are accurately predicted for zero and moderate sweep angles where flow separation effects are negligible.

  17. Retinal Nerve Fiber Layer Thickness Measurement Comparison Using Spectral Domain and Swept Source Optical Coherence Tomography

    PubMed Central

    Ha, Ahnul; Lee, Seung Hyen; Lee, Eun Ji

    2016-01-01

    Purpose To investigate the retinal nerve fiber layer (RNFL) thickness concordance when measured by spectral domain (SD) and swept source (SS) optical coherence tomography (OCT), and to compare glaucoma-discriminating capability. Methods RNFL thicknesses were measured with the scan circle, centered on the optic nerve head, in 55 healthy, 41 glaucoma suspected, and 87 glaucomatous eyes. The RNFL thickness measured by the SD-OCT (sdRNFL thickness) and SS-OCT (ssRNFL thickness) were compared using the t-test. Bland-Altman analysis was performed to examine their agreement. We compared areas under the receiver operating characteristics curve and examined sdRNFL and ssRNFL thickness for discriminating glaucomatous eyes from healthy eyes, and from glaucoma suspect eyes. Results The average ssRNFL thickness was significantly greater than sdRNFL thickness in healthy (110.0 ± 7.9 vs. 100.1 ± 6.8 µm, p < 0.001), glaucoma suspect (96.8 ± 9.3 vs. 89.6 ± 7.9 µm, p < 0.001), and glaucomatous eyes (74.3 ± 14.2 vs. 69.1 ± 12.4 µm, p = 0.011). Bland-Altman analysis showed that there was a tendency for the difference between ssRNFL and sdRNFL to increase in eyes with thicker RNFL. The area under the curves of the average sdRNFL and ssRNFL thickness for discriminating glaucomatous eyes from healthy eyes (0.984 vs. 0.986, p = 0.491) and glaucoma suspect eyes (0.936 vs. 0.918, p = 0.132) were comparable. Conclusions There was a tendency for ssRNFL thickness to increase, compared with sdRNFL thickness, in eyes with thicker RNFL. The ssRNFL thickness had comparable diagnostic capability compared with sdRNFL thickness for discriminating glaucomatous eyes from healthy eyes and glaucoma suspect eyes. PMID:27051263

  18. Enhanced Vitreous Imaging in Healthy Eyes Using Swept Source Optical Coherence Tomography

    PubMed Central

    Liu, Jonathan J.; Witkin, Andre J.; Adhi, Mehreen; Grulkowski, Ireneusz; Kraus, Martin F.; Dhalla, Al-Hafeez; Lu, Chen D.; Hornegger, Joachim; Duker, Jay S.; Fujimoto, James G.

    2014-01-01

    Purpose To describe enhanced vitreous imaging for visualization of anatomic features and microstructures within the posterior vitreous and vitreoretinal interface in healthy eyes using swept-source optical coherence tomography (SS-OCT). The study hypothesis was that long-wavelength, high-speed, volumetric SS-OCT with software registration motion correction and vitreous window display or high-dynamic-range (HDR) display improves detection sensitivity of posterior vitreous and vitreoretinal features compared to standard OCT logarithmic scale display. Design Observational prospective cross-sectional study. Methods Multiple wide-field three-dimensional SS-OCT scans (500×500A-scans over 12×12 mm2) were obtained using a prototype instrument in 22 eyes of 22 healthy volunteers. A registration motion-correction algorithm was applied to compensate motion and generate a single volumetric dataset. Each volumetric dataset was displayed in three forms: (1) standard logarithmic scale display, enhanced vitreous imaging using (2) vitreous window display and (3) HDR display. Each dataset was reviewed independently by three readers to identify features of the posterior vitreous and vitreoretinal interface. Detection sensitivities for these features were measured for each display method. Results Features observed included the bursa premacularis (BPM), area of Martegiani, Cloquet's/BPM septum, Bergmeister papilla, posterior cortical vitreous (hyaloid) detachment, papillomacular hyaloid detachment, hyaloid attachment to retinal vessel(s), and granular opacities within vitreous cortex, Cloquet's canal, and BPM. The detection sensitivity for these features was 75.0% (95%CI: 67.8%–81.1%) using standard logarithmic scale display, 80.6% (95%CI: 73.8%–86.0%) using HDR display, and 91.9% (95%CI: 86.6%–95.2%) using vitreous window display. Conclusions SS-OCT provides non-invasive, volumetric and measurable in vivo visualization of the anatomic microstructural features of the posterior

  19. Ultrahigh phase-stable swept-source optical coherence tomography as a cardiac imaging platform (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Ling, Yuye; Hendon, Christine P.

    2016-02-01

    Functional extensions to optical coherence tomography (OCT) provide useful imaging contrasts that are complementary to conventional OCT. Our goal is to characterize tissue types within the myocardial due to remodeling and therapy. High-speed imaging is necessary to extract mechanical properties and dynamics of fiber orientation changes in a beating heart. Functional extensions of OCT such as polarization sensitive and optical coherence elastography (OCE) require high phase stability of the system, which is a drawback of current mechanically tuned swept source OCT systems. Here we present a high-speed functional imaging platform, which includes an ultrahigh-phase-stable swept source equipped with KTN deflector from NTT-AT. The swept source does not require mechanical movements during the wavelength sweeping; it is electrically tuned. The inter-sweep phase variance of the system was measured to be less than 300 ps at a path length difference of ~2 mm. The axial resolution of the system is 20 µm and the -10 dB fall-off depth is about 3.2 mm. The sample arm has an 8 mmx8 mm field of view with a lateral resolution of approximately 18 µm. The sample arm uses a two-axis MEMS mirror, which is programmable and capable of scanning arbitrary patterns at a sampling rate of 50 kHz. Preliminary imaging results showed differences in polarization properties and image penetration in ablated and normal myocardium. In the future, we will conduct dynamic stretching experiments with strips of human myocardial tissue to characterize mechanical properties using OCE. With high speed imaging of 200 kHz and an all-fiber design, we will work towards catheter-based functional imaging.

  20. Retinal, anterior segment and full eye imaging using ultrahigh speed swept source OCT with vertical-cavity surface emitting lasers

    PubMed Central

    Grulkowski, Ireneusz; Liu, Jonathan J.; Potsaid, Benjamin; Jayaraman, Vijaysekhar; Lu, Chen D.; Jiang, James; Cable, Alex E.; Duker, Jay S.; Fujimoto, James G.

    2012-01-01

    We demonstrate swept source OCT utilizing vertical-cavity surface emitting laser (VCSEL) technology for in vivo high speed retinal, anterior segment and full eye imaging. The MEMS tunable VCSEL enables long coherence length, adjustable spectral sweep range and adjustable high sweeping rate (50–580 kHz axial scan rate). These features enable integration of multiple ophthalmic applications into one instrument. The operating modes of the device include: ultrahigh speed, high resolution retinal imaging (up to 580 kHz); high speed, long depth range anterior segment imaging (100 kHz) and ultralong range full eye imaging (50 kHz). High speed imaging enables wide-field retinal scanning, while increased light penetration at 1060 nm enables visualization of choroidal vasculature. Comprehensive volumetric data sets of the anterior segment from the cornea to posterior crystalline lens surface are also shown. The adjustable VCSEL sweep range and rate make it possible to achieve an extremely long imaging depth range of ~50 mm, and to demonstrate the first in vivo 3D OCT imaging spanning the entire eye for non-contact measurement of intraocular distances including axial eye length. Swept source OCT with VCSEL technology may be attractive for next generation integrated ophthalmic OCT instruments. PMID:23162712

  1. Age-Dependent Morphologic Alterations in the Outer Retinal and Choroidal Thicknesses Using Swept Source Optical Coherence Tomography

    PubMed Central

    2016-01-01

    Purpose To evaluate the age-dependent morphologic alterations in the outer retina and choroid at the macula using swept-source optical coherence tomography (OCT). Methods Thirty eyes (30 normal subjects; average age, 49 years) were examined; five (age range, third-eighth decades of life) had refractive errors of ±2 diopters or less and no fundus abnormalities. An Early Treatment Diabetic Retinopathy Study (ETDRS) map of the outer retinal and choroidal thickness was constructed using swept-source OCT. The outer retinal and choroidal segmentation lines were drawn automatically, partially manually, within 6 millimeters of the macula. Results The mean outer retinal and choroidal thicknesses in the 6-millimeter-diameter circle were 145±13 and 236±68 microns, respectively. The choroidal thickness and age were negatively (r = -0.66, P<0.01) correlated; the outer retinal thickness and age were not correlated (r = -0.16, P = 0.39). The outer retinal and choroidal thicknesses in the ETDRS map were not correlated (r = -0.13, P = 0.49) within 1 millimeter but correlated (r = 0.32, P<0.01) within 6 millimeters. Conclusions The choroid thins with aging. The outer retina remains stable. Outer retina and choroid are correlated in the entire macula except for the center. ETDRS map can be useful for evaluation of the morphologic relationship between the outer retina and choroid. PMID:27467879

  2. Experimental validation of an optimized signal processing method to handle non-linearity in swept-source optical coherence tomography.

    PubMed

    Vergnole, Sébastien; Lévesque, Daniel; Lamouche, Guy

    2010-05-10

    We evaluate various signal processing methods to handle the non-linearity in wavenumber space exhibited by most laser sources for swept-source optical coherence tomography. The following methods are compared for the same set of experimental data: non-uniform discrete Fourier transforms with Vandermonde matrix or with Lomb periodogram, resampling with linear interpolation or spline interpolation prior to fast-Fourier transform (FFT), and resampling with convolution prior to FFT. By selecting an optimized Kaiser-Bessel window to perform the convolution, we show that convolution followed by FFT is the most efficient method. It allows small fractional oversampling factor between 1 and 2, thus a minimal computational time, while retaining an excellent image quality. PMID:20588899

  3. Automated detection of inflammatory cells in whole anterior chamber of a uveitis mouse from swept-source optical coherence tomography images

    NASA Astrophysics Data System (ADS)

    Choi, Woo June; Pepple, Kathryn L.; Wang, Ruikang K.

    2016-03-01

    Cell grading in a rodent anterior chamber is essential for anterior inflammation evaluation in preclinical vision research. This paper describes a computerized method for detection and counting of the anterior chamber cells from swept-source optical coherence tomography (SS-OCT) images of a experimental rodent model of uveitis. The volumetric anterior segment OCT data is obtained from 100 kHz SS-OCT imaging of mouse eye in vivo. For the OCT cross-sections, each OCT structural image is de-speckled and binarized. After removal of cornea, iris, and crystalline lens structures connected to the binary image border, an area thresholding is then employed for each labeled region to isolate only celllike objects in the anterior chamber, followed by roundness estimation of the objects to identify potential cell candidates in the data. Eventually, the cell candidates are counted and graded as total number of cells in the anterior chamber.

  4. Macular Choroidal Thickness and Volume Measured by Swept-source Optical Coherence Tomography in Healthy Korean Children

    PubMed Central

    Lee, Jung Wook; Song, In Seok; Lee, Ju-hyang; Shin, Yong Un; Lim, Han Woong; Lee, Won June

    2016-01-01

    Purpose To evaluate the thickness and volume of the choroid in healthy Korean children using swept-source optical coherence tomography. Methods We examined 80 eyes of 40 healthy children and teenagers (<18 years) using swept-source optical coherence tomography with a tunable long-wavelength laser source. A volumetric macular scan protocol using the Early Treatment Diabetic Retinopathy Study grid was used to construct a choroidal thickness map. We also examined 44 eyes of 35 healthy adult volunteers (≥18 years) and compared adult measurements with the findings in children. Results The mean age of the children and teenagers was 9.47 ± 3.80 (4 to 17) vs. 55.04 ± 12.63 years (36 to 70 years) in the adult group (p < 0.001, Student's t-test). Regarding the Early Treatment Diabetic Retinopathy Study subfields, the inner temporal subfield was the thickest (247.96 µm). The inner and outer nasal choroid were thinner (p = 0.004, p = 0.002, respectively) than the surrounding areas. The mean choroidal volumes of the inner and outer nasal areas were smaller (p = 0.004, p = 0.003, respectively) than those of all the other areas in each circle. Among the nine subfields, all areas in the children, except the outer nasal subfield, were thicker than those in adults (p < 0.05). Regression analysis showed that age, axial length, and refractive error correlated with subfoveal choroidal thickness (p < 0.05). Conclusions Overall macular choroidal thickness and volume in children and teenagers were significantly greater than in adults. The nasal choroid was significantly thinner than the surrounding areas. The pediatric subfoveal choroid is prone to thinning with increasing age, axial length, and refractive error. These differences should be considered when choroidal thickness is evaluated in children with chorioretinal diseases. PMID:26865801

  5. Reproducibility of a Long-Range Swept Source Optical Coherence Tomography Ocular Biometry System and Comparison with Clinical Biometers

    PubMed Central

    Grulkowski, Ireneusz; Liu, Jonathan J.; Zhang, Jason Y.; Potsaid, Benjamin; Jayaraman, Vijaysekhar; Cable, Alex E.; Duker, Jay S.

    2013-01-01

    Purpose To demonstrate a novel swept source optical coherence tomography (SS-OCT) imaging device employing a vertical cavity surface-emitting laser (VCSEL) capable of imaging the full eye length and to introduce a method employing this device for non-contact optical ocular biometry. To compare the measurements of intraocular distances using this SS-OCT instrument with commercially available optical and ultrasound biometers. To evaluate the intersession reproducibility of measurements of intraocular distances using SS-OCT. Design Evaluation of technology Participants Twenty eyes of 10 healthy subjects imaged at the New England Eye Center at Tufts Medical Center and Massachusetts Institute of Technology between May and September 2012. Methods Averaged central depth profiles were extracted from volumetric SS-OCT datasets. The intraocular distances such as central corneal thickness (CCT), aqueous depth (AD), anterior chamber depth (ACD), crystalline lens thickness (LT), vitreous depth (VD), and axial eye length (AL) were measured and compared with a partial coherence interferometry (PCI) device (IOL Master; Carl Zeiss Meditec, Inc.), as well as an immersion ultrasound (IUS) A-scan biometer (Axis-II PR; Quantel Medical, Inc.). Main Outcome Measures Reproducibility of the measurements of intraocular distances, correlation coefficients, intraclass correlation coefficients Results The standard deviations of the repeated measurements of intraocular distances using SS-OCT were: 6 μm (CCT), 16 μm (ACD), 14 μm (AD), 13 μm (LT), 14 μm (VD) and 16 μm (AL). Strong correlations between all three biometric instruments were found for AL (r > 0.98). AL measurement using SS-OCT correlates better with IOL Master (r = 0.998) than with immersion ultrasound (r = 0.984). SS-OCT and IOL Master measured higher AL values than ultrasound (175 μm and 139 μm). No statistically significant difference of ACD between optical (SS-OCT or IOL Master) and ultrasound method was detected. High

  6. EN FACE ENHANCED-DEPTH SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY FEATURES OF CHRONIC CENTRAL SEROUS CHORIORETINOPATHY

    PubMed Central

    Ferrara, Daniela; Mohler, Kathrin J.; Waheed, Nadia; Adhi, Mehreen; Liu, Jonathan J.; Grulkowski, Ireneusz; Kraus, Martin F.; Baumal, Caroline; Hornegger, Joachim; Fujimoto, James G.; Duker, Jay S.

    2013-01-01

    Purpose To characterize en face features of the retinal pigment epithelium (RPE) and choroid in eyes with chronic central serous chorioretinopathy (CSCR) using a high-speed, enhanced-depth swept-source optical coherence tomography (SS-OCT) prototype. Design Consecutive patients with chronic CSCR were prospectively examined with SS-OCT. Participants Fifteen eyes of 13 patients. Methods Three-dimensional 6×6mm macular cube raster scans were obtained with SS-OCT operating at 1050nm wavelength and 100,000 A-lines/sec with 6μm axial resolution. Segmentation of the RPE generated a reference surface; en face SS-OCT images of the RPE and choroid were extracted at varying depths every 3.5 μm (1 pixel). Abnormal features were characterized by systematic analysis of multimodal fundus imaging including color photographs, fundus autofluorescence, and fluorescein and indocyanine-green angiography (ICGA). Main Outcome Measures En face SS-OCT morphology of the RPE and individual choroidal layers. Results In all eyes, 15/15 (100%) en face SS-OCT imaging at the RPE level revealed absence of signal corresponding to RPE detachment and/or RPE loss. En face SS-OCT imaging at the choriocapillaris level showed focally enlarged vessels in 8 of 15 eyes (53%). At the level of Sattler’s layer, en face SS-OCT documented focal choroidal dilation in 8 of 15 eyes (53%) and diffuse choroidal dilation in 7 of 15 eyes (47%). At the level of Haller’s layer, these same features were observed in 3 of 15 eyes (20%) and 12 of 15 eyes (80%) respectively. In all affected eyes, these choroidal vascular abnormalities were seen just below areas of RPE abnormalities. In 2 eyes with secondary choroidal neovascularization, distinct en face SS-OCT features corresponded to the neovascular lesions. Conclusions High-speed, enhanced-depth SS-OCT at 1050 nm wavelength enables the visualization of pathological features of the RPE and choroid in eyes with chronic CSCR not usually appreciated with standard

  7. Real-time and high-performance calibration method for high-speed swept-source optical coherence tomography

    PubMed Central

    Azimi, Ehsan; Liu, Bin; Brezinski, Mark E.

    2010-01-01

    For high-speed swept-source optical coherence tomography (SS-OCT), the real-time calibration process to convert the OCT signal to wave number space is highly essential. A novel calibration process∕algorithm using a genetic algorithm and precise interpolation is developed. This algorithm is embedded and validated in a SS-OCT system with 16-kHz A-scan rate. The performance of the new algorithm is evaluated by measuring point spread functions at two distinct locations in the entire imaging range. The data is compared to the same system but embedded with a regular calibration algorithm, which demonstrates about 20% improvement in the axial resolution. The steady improvement at different locations of the range suggests the strong robustness of the algorithm, which will ultimately optimize the operation performance of this SS-OCT system in terms of resolution and dynamic range and improves details in biological tissues. PMID:20210451

  8. Assessment of Schlemm’s canal in a normal human eye by swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Shi, G. H.; Wang, F.; Li, X. Q.; Lu, J.; Sun, X. H.; Jiang, C. H.; Zhang, Y. D.

    2013-07-01

    We have applied custom-built anterior segment optical coherence tomography based on a 1310 nm center wavelength swept laser source to measure Schlemm’s canal (SC) area in the living human eye. A total of 50 healthy volunteers with 100 normal eyes have been measured on the nasal and temporal sides successfully. The statistical results show that there are no significant differences between females and males in respect of SC area (female: 8062.24 μm2 ± 1492.304 μm2 male: 7714.52 μm2 ± 1439.034 μm2 p = 0.095), and also no significant differences of SC area are found between the five age groups (Sig=0.253). Therefore, it would be reasonable to assume that, in normal human eyes, the SC possibly maintains the same impact on the gender- and age-related aqueous outflow facility.

  9. 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.

  10. Swept-Source Optical Coherence Tomography and OCT Angiography of Minocycline-Induced Retinal and Systemic Hyperpigmentation.

    PubMed

    Jung, Jesse J; Chen, Michael H; Sorenson, Andrew L; Rofagha, Soraya

    2016-04-01

    This is a report of an 80-year-old man with a history of rosacea and rhinophyma treated for 15 years with oral minocycline who developed significant minocycline-induced hyperpigmentation. He also had a history of Fuchs' endothelial dystrophy and had undergone penetrating keratoplasty in the right eye. Best-corrected visual acuity was 20/60 in both eyes. Examination revealed slate-grey hyperpigmentation of his body, face, and sclera and black, confluent pigmentation in the central maculae of both eyes. Green wavelength fundus autofluorescence demonstrated speckled hyperautofluorescence in the right eye, and swept-source OCT and OCTA demonstrated pigmented epithelial detachments and significant signal blocking without choroidal neovascularization. PMID:27065376

  11. En face projection imaging of the human choroidal layers with tracking SLO and swept source OCT angiography methods

    NASA Astrophysics Data System (ADS)

    Gorczynska, Iwona; Migacz, Justin; Zawadzki, Robert J.; Sudheendran, Narendran; Jian, Yifan; Tiruveedhula, Pavan K.; Roorda, Austin; Werner, John S.

    2015-07-01

    We tested and compared the capability of multiple optical coherence tomography (OCT) angiography methods: phase variance, amplitude decorrelation and speckle variance, with application of the split spectrum technique, to image the choroiretinal complex of the human eye. To test the possibility of OCT imaging stability improvement we utilized a real-time tracking scanning laser ophthalmoscopy (TSLO) system combined with a swept source OCT setup. In addition, we implemented a post- processing volume averaging method for improved angiographic image quality and reduction of motion artifacts. The OCT system operated at the central wavelength of 1040nm to enable sufficient depth penetration into the choroid. Imaging was performed in the eyes of healthy volunteers and patients diagnosed with age-related macular degeneration.

  12. Swept source optical coherence tomography Gabor fusion splicing technique for microscopy of thick samples using a deformable mirror.

    PubMed

    Costa, Christopher; Bradu, Adrian; Rogers, John; Phelan, Pauline; Podoleanu, Adrian

    2015-01-01

    We present a swept source optical coherence tomography (OCT) system at 1060 nm equipped with a wavefront sensor at 830 nm and a deformable mirror in a closed-loop adaptive optics (AO) system. Due to the AO correction, the confocal profile of the interface optics becomes narrower than the OCT axial range, restricting the part of the B-scan (cross section) with good contrast. By actuating on the deformable mirror, the depth of the focus is changed and the system is used to demonstrate Gabor filtering in order to produce B-scan OCT images with enhanced sensitivity throughout the axial range from a Drosophila larvae. The focus adjustment is achieved by manipulating the curvature of the deformable mirror between two user-defined limits. Particularities of controlling the focus for Gabor filtering using the deformable mirror are presented. PMID:25588163

  13. In vivo office-based dynamic imaging of vocal cords in awake patients with swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yu, Lingfeng; Liu, Gangjun; Rubinstein, Marc; Saidi, Arya; Guo, Shuguang; Wong, Brian J. F.; Chen, Zhongping

    2009-02-01

    Optical coherence tomography (OCT) is an evolving noninvasive imaging modality and has been used to image the human larynx during surgical endoscopy. The design of a long GRIN lens based probe capable of capturing images of the human larynx by use of swept-source OCT during a typical office-based laryngoscopy examination is presented. In vivo OCT imaging of the human larynx is demonstrated with 40 fame/second. Dynamic vibration of the vocal folds is recorded to provide not only high-resolution cross-sectional tissue structures but also vibration parameters, such as the vibration frequency and magnitude of the vocal cord, which provide important information for clinical diagnosis and treatment, as well as in fundamental research of the voice. Office-based OCT is a promising imaging modality to study the larynx.

  14. Office-based dynamic imaging of vocal cords in awake patients with swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yu, Lingfeng; Liu, Gangjun; Rubinstein, Marc; Saidi, Arya; Wong, Brian J. F.; Chen, Zhongping

    2009-11-01

    Optical coherence tomography (OCT) is an evolving noninvasive imaging modality that has been used to image the human larynx during surgical endoscopy. The design of a long gradient index (GRIN) lens-based probe capable of capturing images of the human larynx by use of swept-source OCT during a typical office-based laryngoscopy examination is presented. In vivo OCT imaging of the human larynx is demonstrated with a rate of 40 frames per second. Dynamic vibration of the vocal folds is recorded to provide not only high-resolution cross-sectional tissue structures but also vibration parameters, such as the vibration frequency and magnitude of the vocal cords, which provides important information for clinical diagnosis and treatment, as well as fundamental research of the voice itself. Office-based OCT is a promising imaging modality to study the larynx for physicians in otolaryngology.

  15. Swept source optical coherence tomography Gabor fusion splicing technique for microscopy of thick samples using a deformable mirror

    NASA Astrophysics Data System (ADS)

    Costa, Christopher; Bradu, Adrian; Rogers, John; Phelan, Pauline; Podoleanu, Adrian

    2015-01-01

    We present a swept source optical coherence tomography (OCT) system at 1060 nm equipped with a wavefront sensor at 830 nm and a deformable mirror in a closed-loop adaptive optics (AO) system. Due to the AO correction, the confocal profile of the interface optics becomes narrower than the OCT axial range, restricting the part of the B-scan (cross section) with good contrast. By actuating on the deformable mirror, the depth of the focus is changed and the system is used to demonstrate Gabor filtering in order to produce B-scan OCT images with enhanced sensitivity throughout the axial range from a Drosophila larvae. The focus adjustment is achieved by manipulating the curvature of the deformable mirror between two user-defined limits. Particularities of controlling the focus for Gabor filtering using the deformable mirror are presented.

  16. Office-based dynamic imaging of vocal cords in awake patients with swept-source optical coherence tomography

    PubMed Central

    Yu, Lingfeng; Liu, Gangjun; Rubinstein, Marc; Saidi, Arya; Wong, Brian J.F.; Chen, Zhongping

    2009-01-01

    Optical coherence tomography (OCT) is an evolving noninvasive imaging modality that has been used to image the human larynx during surgical endoscopy. The design of a long gradient index (GRIN) lens–based probe capable of capturing images of the human larynx by use of swept-source OCT during a typical office-based laryngoscopy examination is presented. In vivo OCT imaging of the human larynx is demonstrated with a rate of 40 frames per second. Dynamic vibration of the vocal folds is recorded to provide not only high-resolution cross-sectional tissue structures but also vibration parameters, such as the vibration frequency and magnitude of the vocal cords, which provides important information for clinical diagnosis and treatment, as well as fundamental research of the voice itself. Office-based OCT is a promising imaging modality to study the larynx for physicians in otolaryngology. PMID:20059258

  17. Morphometric measurement of Schlemm's canal in normal human eye using anterior segment swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Shi, Guohua; Wang, Fei; Li, Xiqi; Lu, Jing; Ding, Zhihua; Sun, Xinghuai; Jiang, Chunhui; Zhang, Yudong

    2012-01-01

    We have used anterior segment swept source optical coherence tomography to measure Schlemm's canal (SC) morphometric values in the living human eye. Fifty healthy volunteers with 100 normal eyes were measured in the nasal and temporal side. Comparison with the published SC morphometric values of histologic sections proves the reliability of our results. The statistical results show that there are no significant differences between nasal and temporal SC with respect to their diameter, perimeter, and area in our study (diameter: t=0.122, p=0.903; perimeter: t=-0.003, p=0.998; area: t=-1.169, p=0.244); further, no significant differences in SC morphometric values are found between oculus sinister and oculus dexter (diameter: t=0.943, p=0.35; perimeter: t=1.346, p=0.18; area: t=1.501, p=0.135).

  18. Highly reproducible swept-source, dispersion-encoded full-range biometry and imaging of the mouse eye.

    PubMed

    Wang, Ling; Hofer, Bernd; Chen, Yen-Po; Guggenheim, Jeremy A; Drexler, Wolfgang; Povazay, Boris

    2010-01-01

    We report a high-speed, dispersion-encoded, full-range (DEFR) swept-source optical coherence tomography system for in vivo ocular imaging and biometry of small animals. The fast DEFR algorithm removes the depth ambiguity, gives access to objects located at the zero delay position, and doubles the sampling depth to 2x5.0 mm (at -101 to -71 dB sensitivity) in a single scan using 2048 samples/depth scan 0.43 nm line width of a light source operating at 1056 nm with 70 nm tuning range. The acquisition speed (frames of 512 depth scans in 18.3 ms) permits precise on-line monitoring during positioning and provides cross-sectional views of the mouse eye. Preliminary studies demonstrate high-throughput, reproducible assessment of multiple biometric features (e.g., day-to-day reproducibility of axial length measurement +/-5.3 microm) that is insensitive to eye motion sufficient for long-term monitoring. PMID:20799806

  19. Full-field swept-source optical coherence tomography with phase-shifting techniques for skin cancer detection

    NASA Astrophysics Data System (ADS)

    Krauter, J.; Boettcher, T.; Körner, K.; Gronle, M.; Osten, W.; Passilly, N.; Froehly, L.; Perrin, S.; Gorecki, C.

    2015-05-01

    The EU-funded project VIAMOS1 proposes an optical coherence tomography system (OCT) for skin cancer detection, which combines full-field and full-range swept-source OCT in a multi-channel sensor for parallel detection. One of the project objectives is the development of new fabrication technologies for micro-optics, which makes it compatible to Micro-Opto-Electromechanical System technology (MOEMS). The basic system concept is a wafer-based Mirau interferometer array with an actuated reference mirror, which enables phase shifted interferogram detection and therefore reconstruction of the complex phase information, resulting in a higher measurement range with reduced image artifacts. This paper presents an experimental one-channel on-bench OCT system with bulk optics, which serves as a proof-of-concept setup for the final VIAMOS micro-system. It is based on a Linnik interferometer with a wavelength tuning light source and a camera for parallel A-Scan detection. Phase shifting interferometry techniques (PSI) are used for the suppression of the complex conjugate artifact, whose suppression reaches 36 dB. The sensitivity of the system is constant over the full-field with a mean value of 97 dB. OCT images are presented of a thin membrane microlens and a biological tissue (onion) as a preliminary demonstration.

  20. Non-destructive assessment of cavity wall adaptation of class V composite restoration using swept-source optical coherence tomography.

    PubMed

    Senawongse, Pisol; Pongprueksa, Pong; Harnirattisai, Choltacha; Sumi, Yasunori; Otsuki, Masayuki; Shimada, Yasushi; Tagami, Junji

    2011-01-01

    The purpose of this study was to evaluate gap formations under class V restoration using swept-source optical coherence tomography (SS-OCT). Wedge-shaped cavities were prepared on the buccal surface of 40 extracted premolar teeth at 2 locations; 1) cemento-enamel junction (CEJ) with enamel and cementum margin and 2) root surfaces with cementum margin. The cavity was treated with Clearfil S(3) Bond, restored with Clearfil Majesty and polished with abrasive disks. The specimens were kept in water at 37°C for 24 hours and subjected to a thermocycling procedure. Gap formations at the tooth-restoration interface were measured with SS-OCT image and conventional dye leakage under a microscope. There was no effect of the locations of the cavity and the margins of the cavity on the gap formation. Therefore, a significant effect of the observational methods was observed. The gap formation was 0.89±0.48 mm with the SS-OCT, and the gap formation was 0.34±0.41 mm with the dye leakage. The observation with SS-OCT demonstrated a greater degree of gap formation than the observation with dye leakage. PMID:21778598

  1. Common approach for compensation of axial motion artifacts in swept-source OCT and dispersion in Fourier-domain OCT.

    PubMed

    Hillmann, Dierck; Bonin, Tim; Lührs, Christian; Franke, Gesa; Hagen-Eggert, Martin; Koch, Peter; Hüttmann, Gereon

    2012-03-12

    Swept-source optical coherence tomography (SS-OCT) is sensitive to sample motion during the wavelength sweep, which leads to image blurring and image artifacts. In line-field and full-field SS-OCT parallelization is achieved by using a line or area detector, respectively. Thus, approximately 1000 lines or images at different wavenumbers are acquired. The sweep duration is identically with the acquisition time of a complete B-scan or volume, rendering parallel SS-OCT more sensitive to motion artifacts than scanning OCT. The effect of axial motion on the measured spectra is similar to the effect of non-balanced group velocity dispersion (GVD) in the interferometer arms. It causes the apparent optical path lengths in the sample arm to vary with the wavenumber. Here we propose the cross-correlation of sub-bandwidth reconstructions (CCSBR) as a new algorithm that is capable of detecting and correcting the artifacts induced by axial motion in line-field or full-field SS-OCT as well as GVD mismatch in any Fourier-domain OCT (FD-OCT) setup. By cross-correlating images which were reconstructed from a limited spectral range of the interference signal, a phase error is determined which is used to correct the spectral modulation prior to the calculation of the A-scans. Performance of the algorithm is demonstrated on in vivo full-field SS-OCT images of skin and scanning FD-OCT of skin and retina. PMID:22418560

  2. Two configurations of miniature Mirau interferometry for swept-source OCT imaging: applications in dermatology and gastroendoscopy

    NASA Astrophysics Data System (ADS)

    Gorecki, Christophe

    2015-08-01

    The early diagnosis of cancer is essential since it can be treated more effectively when detected earlier. Visual inspection followed by histological examination is, still today, the gold standard for clinicians. However, a large number of unnecessary surgical procedures are still performed. New diagnostics aids are emerging including the recent techniques of optical coherence tomography (OCT) which permits non-invasive 3D optical biopsies of biological tissues, improving patient's quality of life. Nevertheless, the existing bulk or fiber optics systems are expensive, only affordable at the hospital and thus, not sufficiently used by physicians or cancer's specialists as an early diagnosis tool. We developed two different microsystems based on Mirau interferometry and applied for swept source OCT imaging: one for dermatology and second for gastroenterology. In both cases the architecture is based tem based on spectrally tuned Mirau interferometry. The first configuration, developed in the frame of the European project VIAMOS, includes an active array of 4x4 Mirau interferometers. The matrix of Mirau reference mirrors is integrated on top of an electrostatic vertical comb-drive actuator. In second configuration, developed in the frame of Labex ACTION, we adapted VIAMOS technology to develop an OCT endomicroscope with a single-channel passive Mirau interferometer.

  3. Comparison of Schlemm's canal's biological parameters in primary open-angle glaucoma and normal human eyes with swept source optical

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Shi, Guohua; Li, Xiqi; Lu, Jing; Ding, Zhihua; Sun, Xinghuai; Jiang, Chunhui; Zhang, Yudong

    2012-11-01

    Thirty-seven normal and primary open angle glaucoma (POAG) subjects were noninvasively imaged by a tailor-made real-time anterior segment swept source optical coherence tomography (SS-OCT) to demonstrate the differences of the Schlemm's canal (SC) between POAG and normal eyes. After the cross-section images of the anterior chamber angle were acquired by SS-OCT, SC was confirmed by two independent masked observers and the average area, long diameter, and perimeter of the SC were measured. In normal subjects the circumference, area, and long diameter is 580.34±87.81 μm, 8023.89±1486.10 μ, and 272.83±49.39 μm, respectively, and these parameters were 393.25±98.04 μm, 3941.50±1210.69 μ, and 190.91±46.47 μm in the POAG subjects. The area of SC in the normal ones was significantly larger than that in POAG eyes (p<0.001), so as the long diameter and the perimeter (p<0.001 p<0.001).

  4. Postprocessing algorithms to minimize fixed-pattern artifact and reduce trigger jitter in swept source optical coherence tomography

    PubMed Central

    Liu, Gangjun; Tan, Ou; Gao, Simon S.; Pechauer, Alex D.; Lee, ByungKun; Lu, Chen D.; Fujimoto, James G.; Huang, David

    2015-01-01

    We propose methods to align interferograms affected by trigger jitter to a reference interferogram based on the information (amplitude/phase) at a fixed-pattern noise location to reduce residual fixed-pattern noise and improve the phase stability of swept source optical coherence tomography (SS-OCT) systems. One proposed method achieved this by introducing a wavenumber shift (k-shift) in the interferograms of interest and searching for the k-shift that minimized the fixed-pattern noise amplitude. The other method calculated the relative k-shift using the phase information at the residual fixed-pattern noise location. Repeating this wavenumber alignment procedure for all A-lines of interest produced fixed-pattern noise free and phase stable OCT images. A system incorporating these correction routines was used for human retina OCT and Doppler OCT imaging. The results from the two methods were compared, and it was found that the intensity-based method provided better results. PMID:25969023

  5. Logarithmic intensity and speckle-based motion contrast methods for human retinal vasculature visualization using swept source optical coherence tomography

    PubMed Central

    Motaghiannezam, Reza; Fraser, Scott

    2012-01-01

    We formulate a theory to show that the statistics of OCT signal amplitude and intensity are highly dependent on the sample reflectivity strength, motion, and noise power. Our theoretical and experimental results depict the lack of speckle amplitude and intensity contrasts to differentiate regions of motion from static areas. Two logarithmic intensity-based contrasts, logarithmic intensity variance (LOGIV) and differential logarithmic intensity variance (DLOGIV), are proposed for serving as surrogate markers for motion with enhanced sensitivity. Our findings demonstrate a good agreement between the theoretical and experimental results for logarithmic intensity-based contrasts. Logarithmic intensity-based motion and speckle-based contrast methods are validated and compared for in vivo human retinal vasculature visualization using high-speed swept-source optical coherence tomography (SS-OCT) at 1060 nm. The vasculature was identified as regions of motion by creating LOGIV and DLOGIV tomograms: multiple B-scans were collected of individual slices through the retina and the variance of logarithmic intensities and differences of logarithmic intensities were calculated. Both methods captured the small vessels and the meshwork of capillaries associated with the inner retina in en face images over 4 mm2 in a normal subject. PMID:22435098

  6. Differential phase-contrast, swept-source optical coherence tomography at 1060 nm for in vivo human retinal and choroidal vasculature visualization

    NASA Astrophysics Data System (ADS)

    Motaghiannezam, S. M. Reza; Koos, David; Fraser, Scott E.

    2012-02-01

    Human retinal and choroidal vasculature was visualized by a differential phase-contrast (DPC) method using high-speed, swept-source optical coherence tomography (SS-OCT) at 1060 nm. The vasculature was recognized as regions of motion by creating differential phase-variance (DPV) tomograms: multiple B-scans of individual slices through the retina were collected and the variance of the phase differences was calculated. DPV captured the small vessels and the meshwork of capillaries associated with the inner retina in en-face images over 4 mm2. The swept-source laser at 1060 nm offered the needed phase sensitivity to perform DPV and generated en-face images that capture motion in the inner choroidal layer exceeding the capabilities of previous spectrometer-based instruments. In comparison with the power Doppler phase-shift method, DPV provided better visualization of the foveal avascular zone in en-face images.

  7. Robot-assisted three-dimensional registration for cochlear implant surgery using a common-path swept-source optical coherence tomography probe.

    PubMed

    Gurbani, Saumya S; Wilkening, Paul; Zhao, Mingtao; Gonenc, Berk; Cheon, Gyeong Woo; Iordachita, Iulian I; Chien, Wade; Taylor, Russell H; Niparko, John K; Kang, Jin U

    2014-05-01

    Cochlear implantation offers the potential to restore sensitive hearing in patients with severe to profound deafness. However, surgical placement of the electrode array within the cochlea can produce trauma to sensorineural components, particularly if the initial turn of the cochlea is not successfully navigated as the array is advanced. In this work, we present a robot-mounted common-path swept-source optical coherence tomography endoscopic platform for three-dimensional (3-D) optical coherence tomography (OCT) registration and preoperative surgical planning for cochlear implant surgery. The platform is composed of a common-path 600-μm diameter fiber optic rotary probe attached to a five degrees of freedom robot capable of 1 μm precision movement. The system is tested on a dry fixed ex vivo human temporal bone, and we demonstrate the feasibility of a 3-D OCT registration of the cochlea to accurately describe the spatial and angular profiles of the canal formed by the scala tympani into the first cochlear turn. PMID:24805810

  8. Robot-assisted three-dimensional registration for cochlear implant surgery using a common-path swept-source optical coherence tomography probe

    NASA Astrophysics Data System (ADS)

    Gurbani, Saumya S.; Wilkening, Paul; Zhao, Mingtao; Gonenc, Berk; Cheon, Gyeong Woo; Iordachita, Iulian I.; Chien, Wade; Taylor, Russell H.; Niparko, John K.; Kang, Jin U.

    2014-05-01

    Cochlear implantation offers the potential to restore sensitive hearing in patients with severe to profound deafness. However, surgical placement of the electrode array within the cochlea can produce trauma to sensorineural components, particularly if the initial turn of the cochlea is not successfully navigated as the array is advanced. In this work, we present a robot-mounted common-path swept-source optical coherence tomography endoscopic platform for three-dimensional (3-D) optical coherence tomography (OCT) registration and preoperative surgical planning for cochlear implant surgery. The platform is composed of a common-path 600-μm diameter fiber optic rotary probe attached to a five degrees of freedom robot capable of 1 μm precision movement. The system is tested on a dry fixed ex vivo human temporal bone, and we demonstrate the feasibility of a 3-D OCT registration of the cochlea to accurately describe the spatial and angular profiles of the canal formed by the scala tympani into the first cochlear turn.

  9. Human cervical carcinoma detection and glucose monitoring in blood micro vasculatures with swept source OCT

    NASA Astrophysics Data System (ADS)

    Ullah, H.; Ahmed, E.; Ikram, M.

    2013-08-01

    We report a pilot method, i.e., speckle variance (SV) and structured optical coherence tomography to visualize normal and malignant blood microvasculature in three and two dimensions and to monitor the glucose levels in blood by analyzing the Brownian motion of the red blood cells. The technique was applied on nude live mouse's skin and the obtained images depict the enhanced intravasculature network forum up to the depth of ˜2 mm with axial resolution of ˜8 μm. Microscopic images have also been obtained for both types of blood vessels to observe the tumor spatially. Our SV-OCT methodologies and results give satisfactory techniques in real time imaging and can potentially be applied during therapeutic techniques such as photodynamic therapy as well as to quantify the higher glucose levels injected intravenously to animal by determining the translation diffusion coefficient.

  10. Enhanced volumetric visualization for real time 4D intraoperative ophthalmic swept-source OCT.

    PubMed

    Viehland, Christian; Keller, Brenton; Carrasco-Zevallos, Oscar M; Nankivil, Derek; Shen, Liangbo; Mangalesh, Shwetha; Viet, Du Tran; Kuo, Anthony N; Toth, Cynthia A; Izatt, Joseph A

    2016-05-01

    Current-generation software for rendering volumetric OCT data sets based on ray casting results in volume visualizations with indistinct tissue features and sub-optimal depth perception. Recent developments in hand-held and microscope-integrated intrasurgical OCT designed for real-time volumetric imaging motivate development of rendering algorithms which are both visually appealing and fast enough to support real time rendering, potentially from multiple viewpoints for stereoscopic visualization. We report on an enhanced, real time, integrated volumetric rendering pipeline which incorporates high performance volumetric median and Gaussian filtering, boundary and feature enhancement, depth encoding, and lighting into a ray casting volume rendering model. We demonstrate this improved model implemented on graphics processing unit (GPU) hardware for real-time volumetric rendering of OCT data during tissue phantom and live human surgical imaging. We show that this rendering produces enhanced 3D visualizations of pathology and intraoperative maneuvers compared to standard ray casting. PMID:27231623

  11. Enhanced volumetric visualization for real time 4D intraoperative ophthalmic swept-source OCT

    PubMed Central

    Viehland, Christian; Keller, Brenton; Carrasco-Zevallos, Oscar M.; Nankivil, Derek; Shen, Liangbo; Mangalesh, Shwetha; Viet, Du Tran; Kuo, Anthony N.; Toth, Cynthia A.; Izatt, Joseph A.

    2016-01-01

    Current-generation software for rendering volumetric OCT data sets based on ray casting results in volume visualizations with indistinct tissue features and sub-optimal depth perception. Recent developments in hand-held and microscope-integrated intrasurgical OCT designed for real-time volumetric imaging motivate development of rendering algorithms which are both visually appealing and fast enough to support real time rendering, potentially from multiple viewpoints for stereoscopic visualization. We report on an enhanced, real time, integrated volumetric rendering pipeline which incorporates high performance volumetric median and Gaussian filtering, boundary and feature enhancement, depth encoding, and lighting into a ray casting volume rendering model. We demonstrate this improved model implemented on graphics processing unit (GPU) hardware for real-time volumetric rendering of OCT data during tissue phantom and live human surgical imaging. We show that this rendering produces enhanced 3D visualizations of pathology and intraoperative maneuvers compared to standard ray casting. PMID:27231623

  12. Performance comparison between 8- and 14-bit-depth imaging in polarization-sensitive swept-source optical coherence tomography.

    PubMed

    Lu, Zenghai; Kasaragod, Deepa K; Matcher, Stephen J

    2011-01-01

    Recently the effects of reduced bit-depth acquisition on swept-source optical coherence tomography (SS-OCT) image quality have been evaluated by using simulations and empirical studies, showing that image acquisition at 8-bit depth allows high system sensitivity with only a minimal drop in the signal-to-noise ratio compared to higher bit-depth systems. However, in these studies the 8-bit data is actually 12- or 14-bit ADC data numerically truncated to 8 bits. In practice, a native 8-bit ADC could actually possess a true bit resolution lower than this due to the electronic jitter in the converter etc. We compare true 8- and 14-bit-depth imaging of SS-OCT and polarization-sensitive SS-OCT (PS-SS-OCT) by using two hardware-synchronized high-speed data acquisition (DAQ) boards. The two DAQ boards read exactly the same imaging data for comparison. The measured system sensitivity at 8-bit depth is comparable to that for 14-bit acquisition when using the more sensitive of the available full analog input voltage ranges of the ADC. Ex-vivo structural and birefringence images of equine tendon indicate no significant differences between images acquired by the two DAQ boards suggesting that 8-bit DAQ boards can be employed to increase imaging speeds and reduce storage in clinical SS-OCT/PS-SS-OCT systems. One possible disadvantage is a reduced imaging dynamic range which can manifest itself as an increase in image artifacts due to strong Fresnel reflection. PMID:21483604

  13. Noninvasive Characterisation of Foot Reflexology Areas by Swept Source-Optical Coherence Tomography in Patients with Low Back Pain

    PubMed Central

    Dalal, Krishna; Elanchezhiyan, D.; Das, Raunak; Dalal, Devjyoti; Pandey, Ravindra Mohan; Chatterjee, Subhamoy; Upadhyay, Ashish Datt; Maran, V. Bharathi; Chatterjee, Jyotirmoy

    2013-01-01

    Objective. When exploring the scientific basis of reflexology techniques, elucidation of the surface and subsurface features of reflexology areas (RAs) is crucial. In this study, the subcutaneous features of RAs related to the lumbar vertebrae were evaluated by swept source-optical coherence tomography (SS-OCT) in subjects with and without low back pain (LBP). Methods. Volunteers without LBP (n = 6 (male : female = 1 : 1)) and subjects with LBP (n = 15 (male : female = 2 : 3)) were clinically examined in terms of skin colour (visual perception), localised tenderness (visual analogue scale) and structural as well as optical attributes as per SS-OCT. From each subject, 6 optical tomograms were recorded from equidistant transverse planes along the longitudinal axis of the RAs, and from each tomogram, 25 different spatial locations were considered for recording SS-OCT image attributes. The images were analysed with respect to the optical intensity distributions and thicknesses of different skin layers by using AxioVision Rel. 4.8.2 software. The SS-OCT images could be categorised into 4 pathological grades (i.e., 0, 1, 2, and 3) according to distinctness in the visible skin layers. Results. Three specific grades for abnormalities in SS-OCT images were identified considering gradual loss of distinctness and increase in luminosity of skin layers. Almost 90.05% subjects were of mixed type having predominance in certain grades. Conclusion. The skin SS-OCT system demonstrated a definite association of the surface features of healthy/unhealthy RAs with cutaneous features and the clinical status of the lumbar vertebrae. PMID:23662156

  14. Noninvasive characterisation of foot reflexology areas by swept source-optical coherence tomography in patients with low back pain.

    PubMed

    Dalal, Krishna; Elanchezhiyan, D; Das, Raunak; Dalal, Devjyoti; Pandey, Ravindra Mohan; Chatterjee, Subhamoy; Upadhyay, Ashish Datt; Maran, V Bharathi; Chatterjee, Jyotirmoy

    2013-01-01

    Objective. When exploring the scientific basis of reflexology techniques, elucidation of the surface and subsurface features of reflexology areas (RAs) is crucial. In this study, the subcutaneous features of RAs related to the lumbar vertebrae were evaluated by swept source-optical coherence tomography (SS-OCT) in subjects with and without low back pain (LBP). Methods. Volunteers without LBP (n = 6 (male : female = 1 : 1)) and subjects with LBP (n = 15 (male : female = 2 : 3)) were clinically examined in terms of skin colour (visual perception), localised tenderness (visual analogue scale) and structural as well as optical attributes as per SS-OCT. From each subject, 6 optical tomograms were recorded from equidistant transverse planes along the longitudinal axis of the RAs, and from each tomogram, 25 different spatial locations were considered for recording SS-OCT image attributes. The images were analysed with respect to the optical intensity distributions and thicknesses of different skin layers by using AxioVision Rel. 4.8.2 software. The SS-OCT images could be categorised into 4 pathological grades (i.e., 0, 1, 2, and 3) according to distinctness in the visible skin layers. Results. Three specific grades for abnormalities in SS-OCT images were identified considering gradual loss of distinctness and increase in luminosity of skin layers. Almost 90.05% subjects were of mixed type having predominance in certain grades. Conclusion. The skin SS-OCT system demonstrated a definite association of the surface features of healthy/unhealthy RAs with cutaneous features and the clinical status of the lumbar vertebrae. PMID:23662156

  15. Freeform metrology using swept-source optical coherence tomography with custom pupil-relay precision scanning configuration

    NASA Astrophysics Data System (ADS)

    Yao, Jianing; Xu, Di; Zhao, Nan; Rolland, Jannick P.

    2015-10-01

    The recent advances in the optics manufacturing industry to achieve the capability of fabricating rotationally nonsymmetric optical quality surfaces have considerably stimulated the optical designs with freeform components. This opens up new horizons for novel optical systems with larger fields of view and higher performance, or significantly more compact in volume at equal performance compared to conventional systems. A bottleneck to the broad industrial applications of freeform optics remains the lack of a high performance optical metrology tool capable of measuring significant surface departures and slopes of the parts. To address this issue, we have developed a fiber-based swept-source optical coherence tomography (SS-OCT) system for point-cloud freeform metrology, where two-axis galvanometer scanners are leveraged for high-speed lateral scans. We specifically designed a custom all-reflective achromatic pupil relay system to achieve a diffraction-limited scanning configuration. Coupled with a large field-of-view (FOV) telecentric scan lens, the imaging covers 28.9 mm × 28.9 mm FOV with 35 μm lateral resolution and more than 600 μm depth of focus. Freeform metrology is demonstrated for an Alvarez surface of 400 μm surface sag. The high sensitivity of the SS-OCT system allows for capturing the slope variations of the part up to the maximum slope that is 5 degrees in this case. Specific surface reconstruction, rendering and fitting algorithms were developed to evaluate the metrology results and investigate the accuracy and precision of the measurements.

  16. Correlation of Aging and Segmental Choroidal Thickness Measurement using Swept Source Optical Coherence Tomography in Healthy Eyes

    PubMed Central

    Wakatsuki, Yu; Shinojima, Ari; Kawamura, Akiyuki; Yuzawa, Mitsuko

    2015-01-01

    Purpose To assess and compare choroidal thickness changes related to aging, we determined whether changes are due to thinning of the choriocapillaris plus Sattler's (CS) layer and/or the large vessel layer in healthy eyes using swept-source optical coherence tomography (SS-OCT) at a wavelength of 1,050-nm. Methods We studied 115 normal eyes of 115 healthy volunteers, all with refractive errors of less than -6 diopters. All 115 eyes underwent analysis of choroidal thickness at the fovea, the CS layer and the large choroidal vessel layer. In 68 of the 115 eyes, choroidal thickness was determined at five sites (the fovea, and superior, inferior, nasal, and temporal sites) using SS-OCT with an Early Treatment of Diabetic Retinopathy grid scan. Results Total choroidal thicknesses at each of the five sites were related to subject age (P<0.0001). The choroid was thinnest at the nasal site, followed by the temporal, inferior, superior and finally the subfoveal site itself. The total choroidal thickness at the nasal site was significantly less than those at the other four sites (p<0.05). The CS layer showed thinning which correlated with age (P<0.0001). The thickness of the choroidal large vessel layer also decreased with age (p = 0.02). Subfoveal choroidal thickness was calculated as follows: 443.89–2.98×age (μm) (P<0.0001). Conclusion Subfoveal choroidal thickness decreases by 2.98 μm each year. Total choroidal thickness diminishes with age. The CS and large vessel layers of the choroid at the subfovea showed significant decreases, though only the former correlated strongly with age. PMID:26632821

  17. EN FACE IMAGING OF THE CHOROID IN POLYPOIDAL CHOROIDAL VASCULOPATHY USING SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY

    PubMed Central

    Alasil, Tarek; Ferrara, Daniela; Adhi, Mehreen; Brewer, Erika; Kraus, Martin F; Baumal, Caroline R; Hornegger, Joachim; Fujimoto, James G; Witkin, Andre J; Reichel, Elias; Duker, Jay S; Waheed, Nadia K

    2014-01-01

    Objective To define morphological features of polypoidal choroidal vasculopathy (PCV) using en face images from swept source optical coherence tomography (SS-OCT). Design Prospective cross-sectional study. Methods Ten eyes from 6 patients with PCV and 10 eyes from 5 age-matched normal subjects. All subjects were prospectively scanned with a prototype SS-OCT system. A motion correction algorithm was applied to correct and merge scans into a single volumetric dataset. En face images were generated at intervals of 4.13 μm (1 pixel) relative to the Bruch’s membrane. Results Age ± standard deviation for the normal group was 62.4 (±12.1) years and for the PCV group was 68.3 (±5.2) years. En face SS-OCT imaging of PCV eyes demonstrated the relationship between larger pigment epithelial detachments (PEDs) and small adjoining PEDs which correlated with the polypoidal lesions seen on indocyanine green angiography in all PCV eyes. En face SS-OCT demonstrated choroidal vascular abnormalities in 7 out of 7 eyes with PCV, and in 2 out of 3 enrolled fellow eyes in patients with unilateral PCV. Out of 7 PCV eyes, focal choroidal vascular dilatation was noted in 3 eyes and diffuse choroidal vascular dilatation was noted in 1 eye. In addition, a branching vascular network was noted above Bruch’s membrane in 1 eye, below Bruch’s membrane within the choriocapillaris in 1 eye, and in the larger choroidal vascular layer in 1 eye. Conclusions En face SS-OCT provides an in vivo tool to visualize the pathological features and the choroidal vasculature in PCV. PMID:25528955

  18. Evaluation and comparison of the new swept source OCT-based IOLMaster 700 with the IOLMaster 500

    PubMed Central

    Akman, Ahmet; Asena, Leyla; Güngör, Sirel Gür

    2016-01-01

    Purpose To compare the measurements and failure rates obtained with a new swept source optical coherence tomography (OCT)-based biometry to IOLMaster 500. Setting Eye Clinic, Baskent University Faculty of Medicine, Ankara, Turkey. Design Observational cross-sectional study and evaluation of a new diagnostic technology. Methods 188 eyes of 101 subjects were included in the study. Measurements of axial length (AL), anterior chamber depth (ACD), corneal power (K1 and K2) and the measurement failure rate with the new Zeiss IOLMaster 700 were compared with those obtained with the IOLMaster 500. The results were evaluated using Bland–Altman analyses. The differences between both methods were assessed using the paired samples t test, and their correlation was evaluated by intraclass correlation coefficient (ICC). Results The mean age was 68.32±12.71 years and the male/female ratio was 29/72. The agreements between two devices were outstanding regarding AL (ICC=1.0), ACD (ICC=0.920), K1 (ICC=0.992) and K2 (ICC=0.989) values. IOLMaster 700 was able to measure ACD AL, K1 and K2 in all eyes within high-quality SD limits of the manufacturer. IOLMaster 500 was able to measure ACD in 175 eyes, whereas measurements were not possible in the remaining 13 eyes. AL measurements were not possible for 17 eyes with IOLMaster 500. Nine of these eyes had posterior subcapsular cataracts and eight had dense nuclear cataracts. Conclusions Although the agreement between the two devices was excellent, the IOLMaster 700 was more effective in obtaining biometric measurements in eyes with posterior subcapsular and dense nuclear cataracts. PMID:26674777

  19. Evaluation of two swept-infinite-wing potential/viscous-flow computer programs

    NASA Technical Reports Server (NTRS)

    Arimilli, R. V.

    1976-01-01

    Two computer programs capable of predicting the potential and viscous interacting flow around wings of infinite aspect ratio was evaluated. The programs are compared in terms of their capabilities, the approximations and the methods of solution used, and the input requirements. Six airfoils, each representative of a class of airfoils, are used as test airfoils. The results predicted by the programs are presented for each airfoil at sweep angles of 0, 20, and 40 degrees over a range of angles of attack. The results show that at zero sweep both programs predicted the aerodynamic coefficients well and generally in good agreement with measurements. At 20 and 40 degrees of sweep, as there are no experimental data available, definitive conclusions cannot be drawn about the accuracy of the predictions although the results are presented and discussed. The execution times are approximately the same for the two programs.

  20. Tuning of successively scanned two monolithic Vernier-tuned lasers and selective data sampling in optical comb swept source optical coherence tomography

    PubMed Central

    Choi, Dong-hak; Yoshimura, Reiko; Ohbayashi, Kohji

    2013-01-01

    Monolithic Vernier tuned super-structure grating distributed Bragg reflector (SSG-DBR) lasers are expected to become one of the most promising sources for swept source optical coherence tomography (SS-OCT) with a long coherence length, reduced sensitivity roll-off, and potential capability for a very fast A-scan rate. However, previous implementations of the lasers suffer from four main problems: 1) frequencies deviate from the targeted values when scanned, 2) large amounts of noise appear associated with abrupt changes in injection currents, 3) optically aliased noise appears due to a long coherence length, and 4) the narrow wavelength coverage of a single chip limits resolution. We have developed a method of dynamical frequency tuning, a method of selective data sampling to eliminate current switching noise, an interferometer to reduce aliased noise, and an excess-noise-free connection of two serially scanned lasers to enhance resolution to solve these problems. An optical frequency comb SS-OCT system was achieved with a sensitivity of 124 dB and a dynamic range of 55-72 dB that depended on the depth at an A-scan rate of 3.1 kHz with a resolution of 15 μm by discretely scanning two SSG-DBR lasers, i.e., L-band (1.560-1.599 μm) and UL-band (1.598-1.640 μm). A few OCT images with excellent image penetration depth were obtained. PMID:24409394

  1. Ultrahigh-phase-stable swept source based on KTN electro-optic deflector towards Doppler OCT and polarization-sensitive OCT

    NASA Astrophysics Data System (ADS)

    Sasaki, Yuzo; Fujimoto, Masatoshi; Yagi, Shogo; Yamagishi, Shogo; Toyoda, Seiji; Kobayashi, Junya

    2014-03-01

    We have developed a wavelength-swept laser source with ultrahigh phase stability. Potassium tantalate niobate (KTa1- xNbxO3, KTN) single crystal was employed as an electro-optic deflector for a high-speed wavelength sweep in the laser cavity. A 200-kHz sweep rate was obtained with an average output power of 20 mW and a coherence length of 8 mm at the wavelength range exceeding 100 nm. Since the electro-optic effect in KTN crystal has a fast response of more than 500 MHz, the deflection of a KTN deflector can follow the applied voltage precisely. Considering this advantage, we demonstrated a swept source with ultrahigh phase stability in the 1.3 μm wavelength range as a result of the low-jitter operation of the deflector. The standard deviation of measured timing jitters between adjacent A-lines was confirmed to be less than 78 ps, which corresponds to a phase difference of 0.017 radians at a path difference of 1.5 mm of a Michelson interferometer. The phase stability can be increased with an improved voltage source because the timing jitter is still mainly caused by the voltage applied to KTN. In addition to realizing the phase stability of neighboring A-lines, the long-term stable sweep was demonstrated by eliminating the refresh operation that was previously needed to prevent output power decay. The ultrahigh phase stability we achieved makes our swept source promising for Doppler OCT and polarization-sensitive OCT.

  2. High-penetration imaging of retinal and choroidal pathologies by 1 μm swept-source OCT and optical coherence angiography

    NASA Astrophysics Data System (ADS)

    Yasuno, Yoshiaki; Miura, Masahiro; Okamoto, Fumiki; Hong, Youngjoo

    2008-02-01

    Two pathologic cases are evaluated by high-penetration optical coherence tomography (HP-OCT) to demonstrate its clinical significance. The HP-OCT is based on a swept-source OCT (SS-OCT) technology with a probe wavelength of 1.06 μm. The depth resolution is 10.4 μm in tissue, and the measurement speed is 28,000 depth-scans/sec. A single case of age-related macular degeneration and a single case of Vogt-Koyanagi-Harada disease are examined by HP-OCT.

  3. Design and performance of broadly tunable, narrow line-width, high repetition rate 1310nm VCSELs for swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Jayaraman, V.; Jiang, J.; Potsaid, B.; Cole, G.; Fujimoto, J.; Cable, A.

    2012-03-01

    MEMS tunable vertical cavity surface emitting laser (MEMS-VCSEL) development, over the past two decades, has primarily focused on communications and spectroscopic applications. Because of the narrow line-width, single-mode operation, monolithic fabrication, and high-speed capability of these devices, MEMS-VCSELs also present an attractive optical source for emerging swept source optical coherence tomography (SSOCT) systems. In this paper, we describe the design and performance of broadly tunable MEMS-VCSELs targeted for SSOCT, emphasizing 1310nm operation for cancer and vascular imaging. We describe the VCSEL structure and fabrication, employing a fully oxidized GaAs/AlxOy mirrors in conjunction with dielectric mirrors and InP-based multi-quantum well active regions. We also describe the optimization of MEMs speed and frequency response for SSOCT. Key results include 1310 nm VCSELs with >120nm dynamic tuning range and imaging rates near 1MHz, representing the widest VCSEL tuning range and some of the fastest swept source imaging rates thus far obtained. We also describe how low-noise semiconductor optical amplification boosts average optical power to the required levels, while maintaining superior OCT imaging quality and state of the art system sensitivity. Finally, we present measured multi-centimeter dynamic coherence length, and discuss the implications of VCSELs for OCT.

  4. Clinical Factors Associated with Lamina Cribrosa Thickness in Patients with Glaucoma, as Measured with Swept Source Optical Coherence Tomography

    PubMed Central

    Omodaka, Kazuko; Takahashi, Seri; Matsumoto, Akiko; Maekawa, Shigeto; Kikawa, Tsutomu; Himori, Noriko; Takahashi, Hidetoshi; Maruyama, Kazuichi; Kunikata, Hiroshi; Akiba, Masahiro; Nakazawa, Toru

    2016-01-01

    Purpose To investigate the influence of various risk factors on thinning of the lamina cribrosa (LC), as measured with swept-source optical coherence tomography (SS-OCT; Topcon). Methods This retrospective study comprised 150 eyes of 150 patients: 22 normal subjects, 28 preperimetric glaucoma (PPG) patients, and 100 open-angle glaucoma patients. Average LC thickness was determined in a 3 x 3 mm cube scan of the optic disc, over which a 4 x 4 grid of 16 points was superimposed (interpoint distance: 175 μm), centered on the circular Bruch’s membrane opening. The borders of the LC were defined as the visible limits of the LC pores. The correlation of LC thickness with Humphrey field analyzer-measured mean deviation (MD; SITA standard 24–2), circumpapillary retinal nerve fiber layer thickness (cpRNFLT), the vertical cup-to-disc (C/D) ratio, and tissue mean blur rate (MBR) was determined with Spearman's rank correlation coefficient. The relationship of LC thickness with age, axial length, intraocular pressure (IOP), MD, the vertical C/D ratio, central corneal thickness (CCT), and tissue MBR was determined with multiple regression analysis. Average LC thickness and the correlation between LC thickness and MD were compared in patients with the glaucomatous enlargement (GE) optic disc type and those with non-GE disc types, as classified with Nicolela’s method. Results We found that average LC thickness in the 16 grid points was significantly associated with overall LC thickness (r = 0.77, P < 0.001). The measurement time for this area was 12.4 ± 2.4 minutes. Average LC thickness in this area had a correlation coefficient of 0.57 with cpRNFLT (P < 0.001) and 0.46 (P < 0.001) with MD. Average LC thickness differed significantly between the groups (normal: 268 ± 23 μm, PPG: 248 ± 13 μm, OAG: 233 ± 20 μm). Multiple regression analysis showed that MD (β = 0.29, P = 0.013), vertical C/D ratio (β = -0.25, P = 0.020) and tissue MBR (β = 0.20, P = 0.034) were

  5. SNR of swept SLEDs and swept lasers for OCT.

    PubMed

    Johnson, Bart; Atia, Walid; Flanders, Dale C; Kuznetsov, Mark; Goldberg, Brian D; Kemp, Nate; Whitney, Peter

    2016-05-16

    A back-to-back comparison of a tunable narrow-band-filtered SLED (TSLED) and a swept laser are made for OCT applications. The two sources are similar in terms of sweep speed, tuning range and coherence length. A fundamental issue with a TSLED is that the RIN is proportional to 1/linewidth, meaning that the longer the coherence length, the higher the RIN and clock jitter. We show that the TSLED has an SNR limit that causes noise streaks at points of high reflection in images. The laser, which is shot noise limited, does not exhibit this effect. We add noise terms proportional to the sample power times reference power to standard swept source SNR expressions to account for the SNR limit. PMID:27409939

  6. Strategies to improve phase-stability of ultrafast swept source optical coherence tomography for single shot imaging of transient mechanical waves at 16 kHz frame rate

    NASA Astrophysics Data System (ADS)

    Song, Shaozhen; Wei, Wei; Hsieh, Bao-Yu; Pelivanov, Ivan; Shen, Tueng T.; O'Donnell, Matthew; Wang, Ruikang K.

    2016-05-01

    We present single-shot phase-sensitive imaging of propagating mechanical waves within tissue, enabled by an ultrafast optical coherence tomography (OCT) system powered by a 1.628 MHz Fourier domain mode-locked (FDML) swept laser source. We propose a practical strategy for phase-sensitive measurement by comparing the phases between adjacent OCT B-scans, where the B-scan contains a number of A-scans equaling an integer number of FDML buffers. With this approach, we show that micro-strain fields can be mapped with ˜3.0 nm sensitivity at ˜16 000 fps. The system's capabilities are demonstrated on porcine cornea by imaging mechanical wave propagation launched by a pulsed UV laser beam, promising non-contact, real-time, and high-resolution optical coherence elastography.

  7. An experimental study of the sources of fluctuating pressure loads beneath swept shock/boundary-layer interactions

    NASA Technical Reports Server (NTRS)

    Settles, G. S.; Garg, S.

    1993-01-01

    An experimental research program providing basic knowledge and establishing a database on the fluctuating pressure loads produced on aerodynamic surfaces beneath three dimensional shock wave/boundary layer interactions is described. Such loads constitute a fundamental problem of critical concern to future supersonic and hypersonic flight vehicles. A turbulent boundary layer on a flat plate is subjected to interactions with swept planar shock waves generated by sharp fins at angle of attack. Fin angles from 10 to 20 deg at freestream Mach numbers of 3 and 4 produce a variety of interaction strengths from weak to very strong. Miniature Kulite pressure transducers flush-mounted in the flat plate are used to measure interaction-induced wall pressure fluctuations. The distributions of properties of the pressure fluctuations, such as their ring levels, amplitude distributions, and power spectra, are also determined. Measurements were made for the first time in the aft regions of these interactions, revealing fluctuating pressure levels as high as 160 dB. These fluctuations are dominated by low frequency (0-5 kHz) signals. The maximum ring levels in the interactions show an increasing trend with increasing interaction strength. On the other hand, the maximum ring levels in the forward portion of the interactions decrease linearly with increasing interaction sweep back. These ring pressure distributions and spectra are correlated with the features of the interaction flowfield. The unsteadiness of the off-surface flowfield is studied using a new, non-intrusive technique based on the shadow graph method. The results indicate that the entire lambda-shock structure generated by the interaction undergoes relatively low-frequency oscillations. Some regions where particularly strong fluctuations are generated were identified. Fluctuating pressure measurements are also made along the line of symmetry of an axisymmetric jet impinging upon a flat plate at an angle. This flow was

  8. Real-time calibration-free C-scan images of the eye fundus using Master Slave swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Bradu, Adrian; Kapinchev, Konstantin; Barnes, Fred; Garway-Heath, David F.; Rajendram, Ranjan; Keane, Pearce; Podoleanu, Adrian G.

    2015-03-01

    Recently, we introduced a novel Optical Coherence Tomography (OCT) method, termed as Master Slave OCT (MS-OCT), specialized for delivering en-face images. This method uses principles of spectral domain interfereometry in two stages. MS-OCT operates like a time domain OCT, selecting only signals from a chosen depth only while scanning the laser beam across the eye. Time domain OCT allows real time production of an en-face image, although relatively slowly. As a major advance, the Master Slave method allows collection of signals from any number of depths, as required by the user. The tremendous advantage in terms of parallel provision of data from numerous depths could not be fully employed by using multi core processors only. The data processing required to generate images at multiple depths simultaneously is not achievable with commodity multicore processors only. We compare here the major improvement in processing and display, brought about by using graphic cards. We demonstrate images obtained with a swept source at 100 kHz (which determines an acquisition time [Ta] for a frame of 200×200 pixels2 of Ta =1.6 s). By the end of the acquired frame being scanned, using our computing capacity, 4 simultaneous en-face images could be created in T = 0.8 s. We demonstrate that by using graphic cards, 32 en-face images can be displayed in Td 0.3 s. Other faster swept source engines can be used with no difference in terms of Td. With 32 images (or more), volumes can be created for 3D display, using en-face images, as opposed to the current technology where volumes are created using cross section OCT images.

  9. Three-dimensional anterior segment imaging in patients with type 1 Boston Keratoprosthesis with switchable full depth range swept source optical coherence tomography

    PubMed Central

    Poddar, Raju; Cortés, Dennis E.; Werner, John S.; Mannis, Mark J.

    2013-01-01

    Abstract. A high-speed (100 kHz A-scans/s) complex conjugate resolved 1 μm swept source optical coherence tomography (SS-OCT) system using coherence revival of the light source is suitable for dense three-dimensional (3-D) imaging of the anterior segment. The short acquisition time helps to minimize the influence of motion artifacts. The extended depth range of the SS-OCT system allows topographic analysis of clinically relevant images of the entire depth of the anterior segment of the eye. Patients with the type 1 Boston Keratoprosthesis (KPro) require evaluation of the full anterior segment depth. Current commercially available OCT systems are not suitable for this application due to limited acquisition speed, resolution, and axial imaging range. Moreover, most commonly used research grade and some clinical OCT systems implement a commercially available SS (Axsun) that offers only 3.7 mm imaging range (in air) in its standard configuration. We describe implementation of a common swept laser with built-in k-clock to allow phase stable imaging in both low range and high range, 3.7 and 11.5 mm in air, respectively, without the need to build an external MZI k-clock. As a result, 3-D morphology of the KPro position with respect to the surrounding tissue could be investigated in vivo both at high resolution and with large depth range to achieve noninvasive and precise evaluation of success of the surgical procedure. PMID:23912759

  10. Wavelength Swept Lasers

    NASA Astrophysics Data System (ADS)

    Yun, Seok Hyun; Bouma, Brett E.

    In optical interferometric metrology, the wavelength of light serves as a reference for length. At a given optical wavelength, an interference signal varies as a sinusoidal function of distance with a period equal to the wavelength. Although this approach offers unrivaled precision, the periodic signal results in a 2π ambiguity for measurement of lengths greater than one wavelength. In optical coherence tomography (OCT), one wishes to determine light scattering distances and distribution within a sample, but without the ambiguity. To accomplish this, OCT is based on interferometry using many optical wavelengths, each serving as a "ruler" with different periodicities. OCT traditionally has used broadband light sources providing a wide range of wavelengths, all simultaneously. Alternatively, a tunable light source emitting one wavelength at a time, rapidly swept over a broad spectral range, can also be used to achieve the absolute ranging capability in OCT. In this chapter, we describe a technical overview of these new emerging sources. We begin with a discussion general specifications of these light sources, the review basic fundamentals of laser and wavelength tuning. Finally, we discuss the principles of various techniques developed to date for high-speed and wide tuning range.

  11. Source rock potential in Pakistan

    SciTech Connect

    Raza, H.A. )

    1991-03-01

    Pakistan contains two sedimentary basins: Indus in the east and Balochistan in the west. The Indus basin has received sediments from precambrian until Recent, albeit with breaks. It has been producing hydrocarbons since 1914 from three main producing regions, namely, the Potwar, Sulaisman, and Kirthar. In the Potwar, oil has been discovered in Cambrian, Permian, Jurassic, and Tertiary rocks. Potential source rocks are identified in Infra-Cambrian, Permian, Paleocene, and Eocene successions, but Paleocene/Eocene Patala Formation seems to be the main source of most of the oil. In the Sulaiman, gas has been found in Cretaceous and Tertiary; condensate in Cretaceous rocks. Potential source rocks are indicated in Cretaceous, Paleocene, and Eocene successions. The Sembar Formation of Early Cretaceous age appears to be the source of gas. In the Kirthar, oil and gas have been discovered in Cretaceous and gas has been discovered in paleocene and Eocene rocks. Potential source rocks are identified in Kirthar and Ghazij formations of Eocene age in the western part. However, in the easter oil- and gas-producing Badin platform area, Union Texas has recognized the Sembar Formation of Early Cretaceous age as the only source of Cretaceous oil and gas. The Balochistan basin is part of an Early Tertiary arc-trench system. The basin is inadequately explored, and there is no oil or gas discovery so far. However, potential source rocks have been identified in Eocene, Oligocene, Miocene, and Pliocene successions based on geochemical analysis of surface samples. Mud volcanoes are present.

  12. Design of supercritical swept wings

    NASA Technical Reports Server (NTRS)

    Garabedian, P.; Mcfadden, G.

    1982-01-01

    Computational fluid dynamics are used to discuss problems inherent to transonic three-dimensional flow past supercritical swept wings. The formulation for a boundary value problem for the flow past the wing is provided, including consideration of weak shock waves and the use of parabolic coordinates. A swept wing code is developed which requires a mesh of 152 x 10 x 12 points and 200 time cycles. A formula for wave drag is calculated, based on the idea that the conservation form of the momentum equation becomes an entropy inequality measuring the drag, expressible in terms of a small-disturbance equation for a potential function in two dimensions. The entropy inequality has been incorporated in a two-dimensional code for the analysis of transonic flow over airfoils. A method of artificial viscosity is explored for optimum pressure distributions with design, and involves a free boundary problem considering speed over only a portion of the wing.

  13. Development of Extended-Depth Swept Source Optical Coherence Tomography for Applications in Ophthalmic Imaging of the Anterior and Posterior Eye

    NASA Astrophysics Data System (ADS)

    Dhalla, Al-Hafeez Zahir

    extending the imaging range of OCT systems are developed. These techniques include the use of a high spectral purity swept source laser in a full-field OCT system, as well as the use of a peculiar phenomenon known as coherence revival to resolve the complex conjugate ambiguity in swept source OCT. In addition, a technique for extending the depth of focus of OCT systems by using a polarization-encoded, dual-focus sample arm is demonstrated. Along the way, other related advances are also presented, including the development of techniques to reduce crosstalk and speckle artifacts in full-field OCT, and the use of fast optical switches to increase the imaging speed of certain low-duty cycle swept source OCT systems. Finally, the clinical utility of these techniques is demonstrated by combining them to demonstrate high-speed, high resolution, extended-depth imaging of both the anterior and posterior eye simultaneously and in vivo.

  14. In vivo microvascular imaging of human oral and nasal cavities using swept-source optical coherence tomography with a single forward/side viewing probe

    NASA Astrophysics Data System (ADS)

    Choi, Woo June; Wang, Ruikang K.

    2015-03-01

    We report three-dimensional (3D) imaging of microcirculation within human cavity tissues in vivo using a high-speed swept-source optical coherence tomography (SS-OCT) at 1.3 μm with a modified probe interface. Volumetric structural OCT images of the inner tissues of oral and nasal cavities are acquired with a field of view of 2 mm x 2 mm. Two types of disposable and detachable probe attachments are devised and applied to the port of the imaging probe of OCT system, enabling forward and side imaging scans for selective and easy access to specific cavity tissue sites. Blood perfusion is mapped with OCT-based microangiography from 3D structural OCT images, in which a novel vessel extraction algorithm is used to decouple dynamic light scattering signals, due to moving blood cells, from the background scattering signals due to static tissue elements. Characteristic tissue anatomy and microvessel architectures of various cavity tissue regions of a healthy human volunteer are identified with the 3D OCT images and the corresponding 3D vascular perfusion maps at a level approaching capillary resolution. The initial finding suggests that the proposed method may be engineered into a promising tool for evaluating and monitoring tissue microcirculation and its alteration within a wide-range of cavity tissues in the patients with various pathological conditions.

  15. Sensing and three-dimensional imaging of cochlea and surrounding temporal bone using swept source high-speed optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Zhao, Mingtao; Chien, Wade W.; Taylor, Russ; Iordachita, Iulian; Huang, Yong; Niparko, John; Kang, Jin U.

    2013-03-01

    We describe a novel dual-functional optical coherence tomography (OCT) system with both a fiber probe using a sapphire ball lens for cross-sectional imaging and sensing, and a 3-D bulk scanner for 3-D OCT imaging. A theoretical sensitivity model for Common Path (CP)-OCT was proposed to assess its optimal performance based on an unbalanced photodetector configuration. A probe design with working distances (WD) 415μm and lateral resolution 11 μm was implemented with sensitivity up to 88dB. To achieve high-speed data processing and real-time three-dimensional visualization, we use graphics processing unit (GPU) based real-time signal processing and visualization to boost the computing performance of swept source optical coherence tomography. Both the basal turn and facial nerve bundles inside the cadaveric human cochlea temporal bone can be clearly identified and 3D images can be rendered with the OCT system, which was integrated with a flexible robotic arm for robotically assisted microsurgery.

  16. The Repeatability Assessment of Three-Dimensional Capsule-Intraocular Lens Complex Measurements by Means of High-Speed Swept-Source Optical Coherence Tomography

    PubMed Central

    Chang, Pingjun; Li, Jin; Savini, Giacomo; Huang, Jinhai; Huang, Shenghai; Zhao, Yinying; Liao, Na; Lin, Lei; Yu, Xiaoyu; Zhao, Yun-e

    2015-01-01

    Purpose To rebuild the three-dimensional (3-D) model of the anterior segment by high-speed swept-source optical coherence tomography (SSOCT) and evaluate the repeatability of measurement for the parameters of capsule-intraocular lens (C-IOL) complex. Methods Twenty-two pseudophakic eyes from 22 patients were enrolled. Three continuous SSOCT measurements were performed in all eyes and the tomograms obtained were used for 3-D reconstruction. The output data were used to evaluate the measurement repeatability. The parameters included postoperative aqueous depth (PAD), the area and diameter of the anterior capsule opening (Area and D), IOL tilt (IOL-T), horizontal, vertical, and space decentration of the IOL, anterior capsule opening, and IOL-anterior capsule opening. Results PAD, IOL-T, Area, D, and all decentration measurements showed high repeatability. Repeated measure analysis showed there was no statistically significant difference among the three continuous measurements (all P > .05). Pearson correlation analysis showed high correlation between each pair of them (all r >0.90, P<0.001). ICCs were all more than 0.9 for all parameters. The 95% LoAs of all parameters were narrow for comparison of three measurements, which showed high repeatability for three measurements. Conclusion SSOCT is available to be a new method for the 3-D measurement of C-IOL complex after cataract surgery. This method presented high repeatability in measuring the parameters of the C-IOL complex. PMID:26600254

  17. FPGA-based real-time swept-source OCT systems for B-scan live-streaming or volumetric imaging

    NASA Astrophysics Data System (ADS)

    Bandi, Vinzenz; Goette, Josef; Jacomet, Marcel; von Niederhäusern, Tim; Bachmann, Adrian H.; Duelk, Marcus

    2013-03-01

    We have developed a Swept-Source Optical Coherence Tomography (Ss-OCT) system with high-speed, real-time signal processing on a commercially available Data-Acquisition (DAQ) board with a Field-Programmable Gate Array (FPGA). The Ss-OCT system simultaneously acquires OCT and k-clock reference signals at 500MS/s. From the k-clock signal of each A-scan we extract a remap vector for the k-space linearization of the OCT signal. The linear but oversampled interpolation is followed by a 2048-point FFT, additional auxiliary computations, and a data transfer to a host computer for real-time, live-streaming of B-scan or volumetric C-scan OCT visualization. We achieve a 100 kHz A-scan rate by parallelization of our hardware algorithms, which run on standard and affordable, commercially available DAQ boards. Our main development tool for signal analysis as well as for hardware synthesis is MATLAB® with add-on toolboxes and 3rd-party tools.

  18. Silicon photonic integrated circuit swept-source optical coherence tomography receiver with dual polarization, dual balanced, in-phase and quadrature detection

    PubMed Central

    Wang, Zhao; Lee, Hsiang-Chieh; Vermeulen, Diedrik; Chen, Long; Nielsen, Torben; Park, Seo Yeon; Ghaemi, Allan; Swanson, Eric; Doerr, Chris; Fujimoto, James

    2015-01-01

    Optical coherence tomography (OCT) is a widely used three-dimensional (3D) optical imaging method with many biomedical and non-medical applications. Miniaturization, cost reduction, and increased functionality of OCT systems will be critical for future emerging clinical applications. We present a silicon photonic integrated circuit swept-source OCT (SS-OCT) coherent receiver with dual polarization, dual balanced, in-phase and quadrature (IQ) detection. We demonstrate multiple functional capabilities of IQ polarization resolved detection including: complex-conjugate suppressed full-range OCT, polarization diversity detection, and polarization-sensitive OCT. To our knowledge, this is the first demonstration of a silicon photonic integrated receiver for OCT. The integrated coherent receiver provides a miniaturized, low-cost solution for SS-OCT, and is also a key step towards a fully integrated high speed SS-OCT system with good performance and multi-functional capabilities. With further performance improvement and cost reduction, photonic integrated technology promises to greatly increase penetration of OCT systems in existing applications and enable new applications. PMID:26203382

  19. In vivo imaging of functional microvasculature within tissue beds of oral and nasal cavities by swept-source optical coherence tomography with a forward/side-viewing probe

    PubMed Central

    Choi, Woo June; Wang, Ruikang K.

    2014-01-01

    We report three-dimensional (3D) imaging of microcirculation within human cavity tissues in vivo using a high-speed swept-source optical coherence tomography (SS-OCT) at 1300 nm with a modified probe interface. Volumetric structural OCT images of the inner tissues of oral and nasal cavities are acquired with a field of view of 2 mm × 2 mm. Two types of disposable and detachable probe attachments are devised and applied to the port of the imaging probe of OCT system, enabling forward and side imaging scans for selective and easy access to specific cavity tissue sites. Blood perfusion is mapped with OCT-based microangiography from 3D structural OCT images, in which a novel vessel extraction algorithm is used to decouple dynamic light scattering signals, due to moving blood cells, from the background scattering signals due to static tissue elements. Characteristic tissue anatomy and microvessel architectures of various cavity tissue regions of a healthy human volunteer are identified with the 3D OCT images and the corresponding 3D vascular perfusion maps at a level approaching capillary resolution. The initial finding suggests that the proposed method may be engineered into a promising tool for evaluating and monitoring tissue microcirculation and its alteration within a wide-range of cavity tissues in the patients with various pathological conditions. PMID:25136490

  20. In vivo three-dimensional imaging of normal tissue and tumors in the rabbit pleural cavity using endoscopic swept source optical coherence tomography with thoracoscopic guidance

    NASA Astrophysics Data System (ADS)

    Xie, Tuqiang; Liu, Gangjun; Kreuter, Kelly; Mahon, Sari; Colt, Henri; Mukai, David; Peavy, George M.; Chen, Zhongping; Brenner, Matthew

    2009-11-01

    The purpose of this study was to develop a dynamic tunable focal distance graded-refractive-index lens rod-based high-speed 3-D swept-source (SS) optical coherence tomography (OCT) endoscopic system and demonstrate real-time in vivo, high-resolution (10-μm) imaging of pleural-based malignancies in an animal model. The GRIN lens-based 3-D SS OCT system, which images at 39 fps with 512 A-lines per frame, was able to capture images of and detect abnormalities during thoracoscopy in the thoracic cavity, including the pleura, chest wall, pericardium, and the lungs. The abnormalities were confirmed by histological evaluation and compared to OCT findings. The dynamic tunable focal distance range and rapid speed of the probe and SS prototype OCT system enabled this first-reported application of in vivo 3-D thoracoscopic imaging of pleural-based malignancies. The imaging probe of the system was found to be easily adaptable to various sites within the thoracic cavity and can be readily adapted to other sites, including rigid airway endoscopic examinations.

  1. In vivoimaging of human vasculature in the chorioretinal complex using phase-variance contrast method with phase-stabilized 1 - μ m swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Poddar, Raju; Kim, Dae Yu; Werner, John S.; Zawadzki, Robert J.

    2014-12-01

    We present a noninvasive phase-variance (pv)-based motion contrast method for depth-resolved imaging of the human chorioretinal complex microcirculation with a newly developed phase-stabilized high speed (100-kHz A-scans/s) 1-μm swept-source optical coherence tomography (SSOCT) system. Compared to our previous spectral-domain (spectrometer based) pv-spectral domain OCT (SDOCT) system, this system has the advantages of higher sensitivity, reduced fringe wash-out for high blood flow speeds and deeper penetration in choroid. High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. This process does not require additional calibration hardware and complex numerical procedures. Our phase stabilization method is simple and can be employed in a variety of SSOCT systems. Examples of vasculature in the chorioretinal complex imaged by pv-SSOCT from normal as well as diseased eyes are presented and compared to retinal images of the same subjects acquired with fluorescein angiography and indocyanine green angiography. Observations of morphology of vascular perfusion in chorioretinal complex visualized by our method are listed.

  2. Cardiac-Gated En Face Doppler Measurement of Retinal Blood Flow Using Swept-Source Optical Coherence Tomography at 100,000 Axial Scans per Second

    PubMed Central

    Lee, ByungKun; Choi, WooJhon; Liu, Jonathan J.; Lu, Chen D.; Schuman, Joel S.; Wollstein, Gadi; Duker, Jay S.; Waheed, Nadia K.; Fujimoto, James G.

    2015-01-01

    Purpose. To develop and demonstrate a cardiac gating method for repeatable in vivo measurement of total retinal blood flow (TRBF) in humans using en face Doppler optical coherence tomography (OCT) at commercially available imaging speeds. Methods. A prototype swept-source OCT system operating at 100-kHz axial scan rate was developed and interfaced with a pulse oximeter. Using the plethysmogram measured from the earlobe, Doppler OCT imaging of a 1.5- × 2-mm area at the optic disc at 1.8 volumes/s was synchronized to cardiac cycle to improve sampling of pulsatile blood flow. Postprocessing algorithms were developed to achieve fully automatic calculation of TRBF. We evaluated the repeatability of en face Doppler OCT measurement of TRBF in 10 healthy young subjects using three methods: measurement at 100 kHz with asynchronous acquisition, measurement at 100 kHz with cardiac-gated acquisition, and a control measurement using a 400-kHz instrument with asynchronous acquisition. Results. The median intrasubject coefficients of variation (COV) of the three methods were 8.0%, 4.9%, and 6.1%, respectively. All three methods correlated well, without a significant bias. Mean TRBF measured at 100 kHz with cardiac-gated acquisition was 40.5 ± 8.2 μL/min, and the range was from 26.6 to 55.8 μL/min. Conclusions. Cardiac-gated en face Doppler OCT can achieve smaller measurement variability than previously reported methods. Although further validation in older subjects and diseased subjects is required, precise measurement of TRBF using cardiac-gated en face Doppler OCT at commercially available imaging speeds should be feasible. PMID:25744974

  3. Combined 60° Wide-Field Choroidal Thickness Maps and High-Definition En Face Vasculature Visualization Using Swept-Source Megahertz OCT at 1050 nm

    PubMed Central

    Mohler, Kathrin J.; Draxinger, Wolfgang; Klein, Thomas; Kolb, Jan Philip; Wieser, Wolfgang; Haritoglou, Christos; Kampik, Anselm; Fujimoto, James G.; Neubauer, Aljoscha S.; Huber, Robert; Wolf, Armin

    2015-01-01

    Purpose To demonstrate ultrahigh-speed swept-source optical coherence tomography (SS-OCT) at 1.68 million A-scans/s for choroidal imaging in normal and diseased eyes over a ∼60° field of view. To investigate and correlate wide-field three-dimensional (3D) choroidal thickness (ChT) and vascular patterns using ChT maps and coregistered high-definition en face images extracted from a single densely sampled Megahertz-OCT (MHz-OCT) dataset. Methods High-definition, ∼60° wide-field 3D datasets consisting of 2088 × 1024 A-scans were acquired using a 1.68 MHz prototype SS-OCT system at 1050 nm based on a Fourier-domain mode-locked laser. Nine subjects (nine eyes) with various chorioretinal diseases or without ocular pathology are presented. Coregistered ChT maps, choroidal summation maps, and depth-resolved en face images referenced to either the retinal pigment epithelium or the choroidal–scleral interface were generated using manual segmentation. Results Wide-field ChT maps showed a large inter- and intraindividual variance in peripheral and central ChT. In only four of the nine eyes, the location with the largest ChT was coincident with the fovea. The anatomy of the large lumen vessels of the outer choroid seems to play a major role in determining the global ChT pattern. Focal ChT changes with large thickness gradients were observed in some eyes. Conclusions Different ChT and vascular patterns could be visualized over ∼60° in patients for the first time using OCT. Due to focal ChT changes, a high density of thickness measurements may be favorable. High-definition depth-resolved en face images are complementary to cross sections and thickness maps and enhance the interpretation of different ChT patterns. PMID:26431482

  4. Diagnostic Ability of Macular Ganglion Cell Inner Plexiform Layer Measurements in Glaucoma Using Swept Source and Spectral Domain Optical Coherence Tomography

    PubMed Central

    Yang, Zhiyong; Tatham, Andrew J.; Weinreb, Robert N.; Medeiros, Felipe A.; Liu, Ting; Zangwill, Linda M.

    2015-01-01

    Purpose To evaluate the diagnostic ability of macular ganglion cell and inner plexiform layer measurements in glaucoma, obtained using swept source (SS) and spectral domain (SD) optical coherence tomography (OCT) and to compare to circumpapillary retinal nerve fiber layer (cpRNFL) thickness measurements. Methods The study included 106 glaucomatous eyes of 80 subjects and 41 eyes of 22 healthy subjects from the Diagnostic Innovations in Glaucoma Study. Macular ganglion cell and inner plexiform layer (mGCIPL), macular ganglion cell complex (mGCC) and cpRNFL thickness were assessed using SS-OCT and SD-OCT, and area under the receiver operating characteristic curves (AUCs) were calculated to determine ability to differentiate glaucomatous and healthy eyes and between early glaucomatous and healthy eyes. Results Mean (± standard deviation) mGCIPL and mGCC thickness were thinner in both healthy and glaucomatous eyes using SS-OCT compared to using SD-OCT. Fixed and proportional biases were detected between SS-OCT and SD-OCT measures. Diagnostic accuracy (AUCs) for differentiating between healthy and glaucomatous eyes for average and sectoral mGCIPL was similar in SS-OCT (0.65 to 0.81) and SD-OCT (0.63 to 0.83). AUCs for average cpRNFL acquired using SS-OCT and SD-OCT tended to be higher (0.83 and 0.85, respectively) than for average mGCC (0.82 and 0.78, respectively), and mGCIPL (0.73 and 0.75, respectively) but these differences did not consistently reach statistical significance. Minimum SD-OCT mGCIPL and mGCC thickness (unavailable in SS-OCT) had the highest AUC (0.86) among macular measurements. Conclusion Assessment of mGCIPL thickness using SS-OCT or SD-OCT is useful for detecting glaucomatous damage, but measurements are not interchangeable for patient management decisions. Diagnostic accuracies of mGCIPL and mGCC from both SS-OCT and SD-OCT were similar to that of cpRNFL for glaucoma detection. PMID:25978420

  5. Forward Swept Compressor Testing

    NASA Technical Reports Server (NTRS)

    Miller, David P.

    1997-01-01

    A new forward-swept rotor designed by Allison Engine Company was tested in NASA Lewis Research Center's CE-18 facility. This testing was a follow-on project sponsored by NASA Lewis to study range enhancements in small turbomachinery. The test was conducted against a baseline rotor design that was also tested in CE-18. The design point for the rotor was a rotor pressure ratio of 2.69, a mass flow of 10.52 lbm/sec, and an adiabatic efficiency of 89.1 percent. Test data indicate that the rotor met the pressure ratio of 2.69 with a 10.77 lbm/sec flow rate, a 87.5-percent adiabatic efficiency, and a 19.5-percent stall margin. The baseline rotor achieved a pressure ratio of 2.69 at a 10.77 lbm/sec flow rate with a stall margin of only 9.2 percent and an adiabatic efficiency of 87.0 percent. The major differences are the significant stall margin increase and the substantially higher off-design peak efficiencies of the forward-swept rotor. The substantially higher performance over the baseline rotor design makes the new design a viable technology candidate for future products.

  6. Assessment of Open-Angle Glaucoma Peripapillary and Macular Choroidal Thickness Using Swept-Source Optical Coherence Tomography (SS-OCT)

    PubMed Central

    Song, Yong Ju; Kim, Young Kook; Jeoung, Jin Wook; Park, Ki Ho

    2016-01-01

    Objective To compare peripapillary and macular choroidal thickness (PCT and MCT) between open-angle glaucoma (OAG) and normal controls using swept-source optical coherence tomography (SS-OCT), and to evaluate global and localized relationships between choroidal thickness and various factors in OAG, also using SS-OCT. Methods In this cross-sectional comparative study, 134 OAG patients and 73 normal controls were examined. PCT (global, 12 clock-hour sectors), MCT (global, six sectors) were measured by SS-OCT. The difference in choroidal thickness between the OAG patients and the normal controls was analyzed. The relationships between choroidal thickness and various factors including age, sex, spherical equivalent (SE), axial length (AXL), central corneal thickness (CCT), intraocular pressure (IOP), peripapillary retinal nerve fiber layer thickness (pRNFLT), visual field mean deviation (MD), ganglion cell-inner plexiform layer thickness (GCIPLT), and disc area were analyzed by univariate and multivariate linear regression. Global and regional analyses were performed in 12 segments of the peripapillary circle and in six sectors of the macula. Results There were significant differences in global PCT and MCT between the OAG patients and the normal controls (115.22±41.17 vs. 138.89±44.70, P<0.001), (184.36±57.15 vs. 209.25±61.11, P = 0.004). The difference in global PCT remained, both after adjusting for age, AXL (117.08±3.45 vs. 135.47±4.70, P = 0.002) and also after adjusting for age, AXL, disc area (117.46±3.46 vs. 135.67±4.67, P = 0.002). But the difference in global MCT did not remain after adjusting for age, AXL, SE (188.18±4.46 vs. 202.25±6.08, P = 0.066). PCT showed significant differences between the groups in all of the 12 clock-hour sectors. These differences remained after adjusting for age, AXL and for age, AXL, disc area, with the exception of the 10 o’clock (o/c) sector. MCT in six sectors showed differences between the two groups, but they did

  7. Tank farm potential ignition sources

    SciTech Connect

    Scaief, C.C. III

    1996-01-01

    This document identifies equipment, instrumentation, and sensors that are located in-tank as well as ex-tank in areas that may have communication paths with the tank vapor space. For each item, and attempt is made to identify the potential for ignition of flammable vapors using a graded approach. The scope includes all 177 underground storage tanks.

  8. Potential of renewable and alternative energy sources

    NASA Astrophysics Data System (ADS)

    Konovalov, V.; Pogharnitskaya, O.; Rostovshchikova, A.; Matveenko, I.

    2015-11-01

    The article deals with application potential of clean alternative renewable energy sources. By means of system analysis the forecast for consumption of electrical energy in Tomsk Oblast as well as main energy sources of existing energy system have been studied up to 2018. Engineering potential of renewable and alternative energy sources is evaluated. Besides, ranking in the order of their efficiency descending is performed. It is concluded that Tomsk Oblast has high potential of alternative and renewable energy sources, among which the most promising development perspective is implementation of gasification stations to save fuel consumed by diesel power stations as well as building wind-power plants.

  9. Microwave generators simplify swept tests

    NASA Astrophysics Data System (ADS)

    Foster, C. E.; Hagins, M. R.

    1986-01-01

    The utilization of the swept-frequency capability makes it possible to conduct any number of microwave tests. It is pointed out that today's microwave sweepers make such tests simple and straightforward. A filter test involving a high-pass filter with a cutoff frequency of 14.0 GHz is discussed, taking into account the use of a microwave sweeper operating in the range from 12 to 18 GHz. Attention is also given to swept-frequency amplifier testing, antenna swept-gain testing, and microwave antenna testing. With a sweep generator, it is simple to assemble a setup for testing amplifier small-signal gain, flatness, and rolloff.

  10. The Power and Potential of Primary Sources

    ERIC Educational Resources Information Center

    Morgan, Denise N.; Rasinski, Timothy V.

    2012-01-01

    Using primary sources with students has untapped potential for expanding and deepening the reading experiences of elementary and middle grade students. Primary sources expands teachers' palette of reading materials, allows students to connect more closely to topics for learning, and deepens their understanding of the past. This article argues for…

  11. Swept-source optical coherence tomography powered by a 1.3-μm vertical cavity surface emitting laser enables 2.3-mm-deep brain imaging in mice in vivo

    NASA Astrophysics Data System (ADS)

    Choi, Woo June; Wang, Ruikang K.

    2015-10-01

    We report noninvasive, in vivo optical imaging deep within a mouse brain by swept-source optical coherence tomography (SS-OCT), enabled by a 1.3-μm vertical cavity surface emitting laser (VCSEL). VCSEL SS-OCT offers a constant signal sensitivity of 105 dB throughout an entire depth of 4.25 mm in air, ensuring an extended usable imaging depth range of more than 2 mm in turbid biological tissue. Using this approach, we show deep brain imaging in mice with an open-skull cranial window preparation, revealing intact mouse brain anatomy from the superficial cerebral cortex to the deep hippocampus. VCSEL SS-OCT would be applicable to small animal studies for the investigation of deep tissue compartments in living brains where diseases such as dementia and tumor can take their toll.

  12. Petroleum source rock potential on Jamaica

    SciTech Connect

    Rodrigues, K.

    1983-01-10

    By means of standard geochemical techniques, geologists evaluated the hydrocarbon source rock potential of Jamaican shales and mudstones in terms of the amount, type, and maturity of the organic matter preserved in these sediments. Samples taken from outcrops and well cores revealed that shales from the Chapelton and Windsor formations may have the best potential for hydrocarbon generation.

  13. Very high sensor-density multiplexing using a wavelength-to-time domain reflectometry approach based on a rapidly swept akinetic laser

    NASA Astrophysics Data System (ADS)

    Minneman, M. P.; Hoover, E.; Boschert, P.; Ensher, J.; Crawford, M.; Derrickson, D.; Kersey, A. D.

    2015-09-01

    We demonstrate a scheme for the interrogation of arrays of FBG sensors based on a Swept Laser Distributed Sensing system which can achieve 1000 sensors or more in a single fiber, while retaining the sensitivity and repeatability expected with FBG sensors of better than 0.5 μepsilon and 0.05 C. The system utilizes an `akinetic' wavelength swept source and an arrival time-dependent detection approach to allow potentially 1000s of very low reflectivity FBGs to be monitored via a form of Wavelength-to-Time Domain Reflectometry. We demonstrate the interrogation of 250 gratings in a system architecture designed to support 1000 gratings.

  14. Potential Energy Sources Pose Mining Problem

    ERIC Educational Resources Information Center

    Chemical and Engineering News, 1974

    1974-01-01

    Summarizes the discussions of a Division of Industrial and Engineering Chemistry symposium on solids handling for synthetic fuels production. Included is a description of technical difficulties with the use of coal seams and deposits of oil shale and oil sand as potential sources of fuel. (CC)

  15. Neutron sources: Present practice and future potential

    SciTech Connect

    Cierjacks, S.; Smith, A.B.

    1988-01-01

    The present capability and future potential of accelerator-based monoenergetic and white neutron sources are outlined in the context of fundamental and applied neutron-nuclear research. The neutron energy range extends from thermal to 500 MeV, and the time domain from steady-state to pico-second pulsed sources. Accelerator technology is summarized, including the production of intense light-ion, heavy-ion and electron beams. Target capabilities are discussed with attention to neutron-producing efficiency and power-handling capabilities. The status of underlying neutron-producing reactions is summarized. The present and future use of neutron sources in: fundamental neutron-nuclear research, nuclear data acquisition, materials damage studies, engineering tests, and biomedical applications are discussed. Emphasis is given to current status, near-term advances well within current technology, and to long-range projections. 90 refs., 4 figs.

  16. Neutron sources: present practice and future potential

    SciTech Connect

    Cierjacks, S.; Smith, A.B.

    1988-01-01

    The present capability and future potential of accelerator-based monoenergetic and white neutron sources are outlined in the context of fundamental and applied neutron-nuclear research. The neutron energy range extends from thermal to 500+ MeV, and the time domain from steady-state to pico-second pulsed sources. Accelerator technology is summarized, including the production of intense light-ion, heavy-ion and electron beams. Target capabilities are discussed with attention to neutron-production efficiency and power-handling capabilities. The status of underlying neutron-producing reactions is summarized. The present and future use of neutron sources in: (i) fundamental neutron-nuclear research, (ii) nuclear-data acquisition, (iii) materials-damage studies, (iv) engineering test, and (v) biomedical applications are discussed. Emphasis is given to current status, near-term advances well within current technology, and to long-range projections.

  17. k-domain linearization of wavelength-swept laser for optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lee, Byoung Chang; Jeon, Min Yong; Eom, Tae Joong

    2011-03-01

    We propose a new method for k-domain linearization using fiber Bragg gratings (FBGs) in a wavelength-swept source for optical coherence tomography (OCT). A wavelength-swept source with a scanning fiber Fabry-Perot tunable filter is constructed using a conventional ring laser cavity. Five FBGs are used to recalibrate the nonlinear response from the wavelength-swept source. We achieved good quality sample imaging using the k-domain linearization algorithm based on FBGs. The sensitivity at 2 mm is improved by more than 10 dB after k-domain linearization.

  18. Nanoparticles and cars - analysis of potential sources

    PubMed Central

    2012-01-01

    Urban health is potentially affected by particle emissions. The potential toxicity of nanoparticles is heavily debated and there is an enormous global increase in research activity in this field. In this respect, it is commonly accepted that nanoparticles may also be generated in processes occurring while driving vehicles. So far, a variety of studies addressed traffic-related particulate matter emissions, but only few studies focused on potential nanoparticles. Therefore, the present study analyzed the literature with regard to nanoparticles and cars. It can be stated that, to date, only a limited amount of research has been conducted in this area and more studies are needed to 1) address kind and sources of nanoparticles within automobiles and to 2) analyse whether there are health effects caused by these nanoparticles. PMID:22726351

  19. In vivo imaging of human vasculature in the chorioretinal complex using phase-variance contrast method with phase-stabilized 1-μm swept-source optical coherence tomography

    PubMed Central

    Poddar, Raju; Kim, Dae Yu; Werner, John S.; Zawadzki, Robert J.

    2014-01-01

    Abstract. We present a noninvasive phase-variance (pv)–based motion contrast method for depth-resolved imaging of the human chorioretinal complex microcirculation with a newly developed phase-stabilized high speed (100-kHz A-scans/s) 1-μm swept-source optical coherence tomography (SSOCT) system. Compared to our previous spectral-domain (spectrometer based) pv-spectral domain OCT (SDOCT) system, this system has the advantages of higher sensitivity, reduced fringe wash-out for high blood flow speeds and deeper penetration in choroid. High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. This process does not require additional calibration hardware and complex numerical procedures. Our phase stabilization method is simple and can be employed in a variety of SSOCT systems. Examples of vasculature in the chorioretinal complex imaged by pv-SSOCT from normal as well as diseased eyes are presented and compared to retinal images of the same subjects acquired with fluorescein angiography and indocyanine green angiography. Observations of morphology of vascular perfusion in chorioretinal complex visualized by our method are listed. PMID:25517255

  20. Control of a swept wing tailless aircraft through wing morphing

    NASA Astrophysics Data System (ADS)

    Guiler, Richard W.

    Inspired by flight in nature, work done by Lippisch, the Hortens, and Northrop offered insight to achieving the efficiency of bird flight with swept-wing tailless aircraft. Tailless designs must incorporate aerodynamic compromises for control, which have inhibited potential advantages. A morphing mechanism, capable of changing the twist of wing and that can also provide pitch, roll and yaw control for a tailless swept wing aircraft is the first step to a series of morphing techniques, which will lead to more fluid, bird-like flight. This research focuses on investigating the design of a morphing wing to improve the flight characteristics of swept wing Horten type tailless aircraft. Free flight demonstrators, wind tunnel flow visualization, wind-tunnel force and moment data along with CFD studies have been used to evaluate the stability, control and efficiency of a morphing swept wing tailless aircraft. A wing morphing mechanism for the control of a swept wing tailless aircraft has been developed. This new control technique was experimentally and numerically compared to an existing elevon equipped tailless aircraft and has shown the potential for significant improvement in efficiency. The feasibility of this mechanism was also validated through flight testing of a flight weight version. In the process of comparing the Horten type elevon equipped aircraft and the morphing model, formal wind tunnel verification of wingtip induced thrust, found in Horten (Bell Shaped Lift distribution) type swept wing tailless aircraft was documented. A more complete physical understanding of the highly complex flow generated in the control region of the morphing tailless aircraft has been developed. CFD models indicate the possibility of the presence of a Leading Edge Vortex (LEV) on the control section morphing wing when the tip is twisted between +3.5 degrees and +7 degrees. The presence of this LEV causes a reduction of drag while lift is increased. Similar LEVs have been

  1. Swept Frequency Laser Metrology System

    NASA Technical Reports Server (NTRS)

    Zhao, Feng (Inventor)

    2010-01-01

    A swept frequency laser ranging system having sub-micron accuracy that employs multiple common-path heterodyne interferometers, one coupled to a calibrated delay-line for use as an absolute reference for the ranging system. An exemplary embodiment uses two laser heterodyne interferometers to create two laser beams at two different frequencies to measure distance and motions of target(s). Heterodyne fringes generated from reflections off a reference fiducial X(sub R) and measurement (or target) fiducial X(sub M) are reflected back and are then detected by photodiodes. The measured phase changes Delta phi(sub R) and Delta phi (sub m) resulting from the laser frequency swept gives target position. The reference delay-line is the only absolute reference needed in the metrology system and this provides an ultra-stable reference and simple/economical system.

  2. Plasma source for spacecraft potential control

    NASA Technical Reports Server (NTRS)

    Olsen, R. C.

    1983-01-01

    A stable electrical ground which enables the particle spectrometers to measure the low energy particle populations was investigated and the current required to neutralize the spacecraft was measured. In addition, the plasma source for potential control (PSPO C) prevents high charging events which could affect the spacecraft electrical integrity. The plasma source must be able to emit a plasma current large enough to balance the sum of all other currents to the spacecraft. In ion thrusters, hollow cathodes provide several amperes of electron current to the discharge chamber. The PSPO C is capable of balancing the net negative currents found in eclipse charging events producing 10 to 100 microamps of electron current. The largest current required is the ion current necessary to balance the total photoelectric current.

  3. HELIOS dual swept frequency radiometer

    NASA Technical Reports Server (NTRS)

    White, J. R.

    1975-01-01

    The HELIOS dual swept frequency radiometer, used in conjunction with a dipole antenna, was designed to measure electromagnetic radiation in space. An engineering prototype was fabricated and tested on the HELIOS spacecraft. Two prototypes and two flight units were fabricated and three of the four units were integrated into the HELIOS spacecraft. Two sets of ground support equipment were provided for checkout of the radiometer.

  4. Characterization of FBG sensor interrogation based on a FDML wavelength swept laser

    PubMed Central

    Jung, Eun Joo; Kim, Chang-Seok; Jeong, Myung Yung; Kim, Moon Ki; Jeon, Min Yong; Jung, Woonggyu; Chen, Zhongping

    2012-01-01

    In this study, we develop an ultra-fast fiber Bragg grating sensor system that is based on the Fourier domain mode-locked (FDML) swept laser. A FDML wavelength swept laser has many advantages compared to the conventional wavelength swept laser source, such as high-speed interrogation, narrow spectral sensitivity, and high phase stability. The newly developed FDML wavelength swept laser shows a superior performance of a high scan rate of 31.3 kHz and a broad scan range of over 70 nm simultaneously. The performance of the grating sensor interrogating system using a FDML wavelength swept laser is characterized in both static and dynamic strain responses. PMID:18852764

  5. Wideband Raman-Pumped Wavelength-Swept Laser for Optical Coherence Tomography Application

    NASA Astrophysics Data System (ADS)

    Xu, Jianbing; Ou, Haiyan; Xu, Xing; Yang, Victor Xiao Dong; Chui, Po Ching; Kin-Yip Wong, Kenneth

    2013-06-01

    We demonstrate a new wavelength-swept laser based on fiber Raman amplification (FRA), achieved by multiplexing three different pump lasers at wavelengths of 1455, 1475, and 1509 nm. The obtained sweeping bandwidth was from 1526.1 to 1637.9 nm, which was as wide as 111.8 nm. It is the widest hitherto demonstrated based on FRA. We also present the use of this swept laser in the application scenario of optical coherence tomography (OCT). This scheme paves the way for fiber Raman amplification to be employed as a promising source for generating a wideband swept source for OCT application.

  6. FBG interrogation method based on wavelength-swept laser

    NASA Astrophysics Data System (ADS)

    Qin, Chuan; Zhao, Jianlin; Jiang, Biqiang; Rauf, Abdul; Wang, Donghui; Yang, Dexing

    2013-06-01

    Wavelength-swept laser technique is an active demodulation method which integrates laser source and detecting circuit together to achieve compact size. The method also has the advantages such as large demodulation range, high accuracy, and comparatively high speed. In this paper, we present a FBG interrogation method based on wavelength-swept Laser, in which an erbium-doped fiber is used as gain medium and connected by a WDM to form a ring cavity, a fiber FP tunable filter is inserted in the loop for choosing the laser frequency and a gas absorption cell is adopted as a frequency reference. The laser wavelength is swept by driving the FP filter. If the laser wavelength matches with that of FBG sensors, there will be some strong reflection peak signals. Detecting such signals with the transmittance signal after the gas absorption cell synchronously and analyzing them, the center wavelengths of the FBG sensors are calculated out at last. Here, we discuss the data processing method based on the frequency reference, and experimentally study the swept laser characteristics. Finally, we adopt this interrogator to demodulate FBG stress sensors. The results show that, the demodulation range almost covers C+L band, the resolution and accuracy can reach about 1pm or less and 5pm respectively. So it is very suitable for most FBG measurements.

  7. Multi-beam resolution video-rate swept-source optical coherence tomography (OCT) provides endogenous contrast for in vivo blood flow independent of flow direction

    NASA Astrophysics Data System (ADS)

    Bazant-Hegemark, F.; Woods, D.; Hattersley, S.; Holmes, J.

    2010-02-01

    Optical coherence tomography (OCT) allows non-invasive imaging of sub-surface structures in vivo, ideally without a need for target preparation. In conventional OCT, the contrast for blood vessels depends on a variety of factors and can be challenging. Speckle variance has been recognized as a method to enhance contrast for blood flow without the application of contrast agents in OCT images. Here, we demonstrate the possibility of extracting blood flow information from a volumetric OCT datasets that was obtained routinely from a human participant. We used a commercially available OCT system with a clinical CE-mark. The light source has a central wavelength of 1310 nm. Using Multi-Beam technology, the system achieves an isometric resolution of better than 7.5 μm in tissue over the entire imaging depth of around 1 mm. At 1 mm image width, 21 frames (B-scans) per second can be imaged. We used the speckle variance in order to enhance the contrast for blood vessels in vivo. This method allowed us determining the presence and depth of blood flow within the 1 mm penetration depth, without dependence on direction or orientation of the blood flow with respect to the scanning beam.

  8. Advances in Swept-Wavelength Interferometry for Precision Measurements

    NASA Astrophysics Data System (ADS)

    Moore, Eric D.

    2011-12-01

    Originally developed for radar applications in the 1950s, swept-wavelength interferometry (SWI) at optical wavelengths has been an active area of research for the past thirty years, with applications in fields ranging from fiber optic telecommunications to biomedical imaging. It now forms the basis of several measurement techniques, including optical frequency domain reflectometry (OFDR), swept-source optical coherence tomography (SS-OCT), and frequency-modulated continuous-wave (FMCW) lidar. In this thesis, I present several novel contributions to the field of SWI that include improvements and extensions to the state of the art in SWI for performing precision measurements. The first is a method for accurately monitoring the instantaneous frequency of the tunable source to accommodate nonlinearities in the source tuning characteristics. This work ex- tends the commonly used method incorporating an auxiliary interferometer to the increasingly relevant cases of long interferometer path mismatches and high-speed wavelength tuning. The second contribution enables precision absolute range measurements to within a small fraction of the transform-limited range resolution of the SWI system. This is accomplished through the use of digital filtering in the time domain and phase slope estimation in the frequency domain. Measurements of optical group delay with attosecond-level precision are experimentally demonstrated and applied to measurements of group refractive index and physical thickness. The accuracy of the group refractive index measurement is shown to be on the order of 10-6, while measurements of absolute thicknesses of macroscopic samples are accomplished with accuracy on the order of 10 nm. Furthermore, sub-nanometer uncertainty for relative thickness measurements can be achieved. For the case of crystalline silicon wafers, the achievable uncertainty is on the same order as the Si-Si bond length, opening the door to potential thickness profiling with single atomic

  9. Extended-Cavity Semiconductor Wavelength-Swept Laser for Biomedical Imaging

    PubMed Central

    Yun, S. H.; Boudoux, C.; Pierce, M. C.; de Boer, J. F.; Tearney, G. J.; Bouma, B. E.

    2010-01-01

    We demonstrate a compact high-power rapidly swept wavelength tunable laser source based on a semiconductor optical amplifier and an extended-cavity grating filter. The laser produces excellent output characteristics for biomedical imaging, exhibiting >4-mW average output power, <0.06-nm instantaneous linewidth, and >80-dB noise extinction with its center wavelength swept over 100 nm at 1310 nm at variable repetition rates up to 500 Hz. PMID:20640193

  10. SNR of swept SLEDs and swept lasers for OCT (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Johnson, Bart C.; Atia, Walid; Flanders, Dale; Kuznetsov, Mark; Goldberg, Brian; Kemp, Nate; Whitney, Peter

    2016-03-01

    A back-to-back comparison of a tunable narrow-band SLED (TSLED) and a swept laser are made for OCT applications. Both are 1310 nm sources sweeping at 50 kHz over a 100 nm tuning range and have similar coherence lengths. The TSLED consists of a seed SOA and two amplification SOAs. The ASE is filtered twice by a tunable MEMS Fabry Perot in a polarization multiplexed double-pass arrangement on either side of the middle SOA. This allows very long coherence lengths to be achieved. A fundamental issue with a SLED is that the RIN is proportional to 1/Linewidth, meaning that the longer the coherence length, the higher the RIN. High RIN also leads to increased clock jitter. Most swept source SNR calculations assume that the noise is independent of the amplitude of the signal light: The higher the signal, the higher the SNR. We show that in the case of the TSLED, that the high signal RIN and clock jitter give rise to additional noises that scale with signal power. This leads to an SNR limit in the case of the TSLED: The higher the signal, the higher the noise, so the SNR reaches a limit. While the TSLED has respectable sensitivity, the SNR limit causes noise streaks in an image where the A-line has a high reflectivity point. The laser, which is shot noise limited, does not exhibit this effect. This is illustrated with SNR data and side-by-side images taken with the two sources.

  11. Identifying Potential Noise Sources within Acoustic Signals

    NASA Astrophysics Data System (ADS)

    Holcomb, Victoria; Lewalle, Jacques

    2013-11-01

    We test a new algorithm for its ability to detect sources of noise within random background. The goal of these tests is to better understand how to identify sources within acoustic signals while simultaneously determining the strengths and weaknesses of the algorithm in question. Unlike previously published algorithms, the antenna method does not pinpoint events by looking for the most energetic portions of a signal. The algorithm searches for the ideal lag combinations between three signals by taking excerpts of possible events. The excerpt with the lowest calculated minimum distance between possible events is how the algorithm identifies sources. At the minimum distance, the events are close in time and frequency. This method can be compared to the cross correlation and denoising methods to better understand its effectiveness. This work is supported in part by Spectral Energies LLC, under an SBIR grant from AFRL, as well as the Syracuse University MAE department.

  12. Flying qualities of the X-29 forward swept wing aircraft

    NASA Technical Reports Server (NTRS)

    Walchli, Lawrence A.; Smith, Rogers E.

    1991-01-01

    An overview of the X-29 Forward Swept Wing Technology Demonstrator traces its development and test path during past years. Brief descriptions of the aircraft and its flight control system provide insight for evaluating this unique vehicle. The baseline flight control system provided a starting point for safe concept evaluation and envelope expansion for the aircraft. Subsequent up-dates resulted in performance levels favorably comparable to current fighter aircraft. Efforts are described for the current expansion of the X-29's capabilities into the high angle-of-attack (AOA) regime of flight. Control law changes have permitted all axis maneuvering to 40 deg AOA with pitch excursions to 66 deg, thereby exploiting the full potential of the X-29 forward swept wing configuration.

  13. Numerical simulation of swept-wing flows

    NASA Technical Reports Server (NTRS)

    Reed, Helen L.

    1991-01-01

    The transition process characteristics of flows over swept wings were computationally modelled. The crossflow instability and crossflow/T-S wave interaction are analyzed through the numerical solution of the full three dimensional Navier-Stokes equations including unsteadiness, curvature, and sweep. The leading-edge region of a swept wing is considered in a three-dimensional spatial simulation with random disturbances as the initial conditions.

  14. Swept wing ice accretion modeling

    NASA Technical Reports Server (NTRS)

    Potapczuk, Mark G.; Bidwell, Colin S.

    1990-01-01

    An effort to develop a three-dimensional modeling method was initiated. This first step towards creation of a complete aircraft icing simulation code builds on previously developed methods for calculating three-dimensional flow fields and particle trajectories combined with a two-dimensional ice accretion calculation along coordinate locations corresponding to streamlines. This work is a demonstration of the types of calculations necessary to predict a three-dimensional ice accretion. Results of calculations using the 3-D method for a MS-317 swept wing geometry are projected onto a 2-D plane normal to the wing leading edge and compared to 2-D results for the same geometry. It is anticipated that many modifications will be made to this approach, however, this effort will lay the groundwork for future modeling efforts. Results indicate that the flow field over the surface and the particle trajectories differed for the two calculations. This led to lower collection efficiencies, convective heat transfer coefficients, freezing fractions, and ultimately ice accumulation for the 3-D calculation.

  15. Dentin Biomodification Potential Depends on Polyphenol Source

    PubMed Central

    Aguiar, T.R.; Vidal, C.M.P.; Phansalkar, R.S.; Todorova, I.; Napolitano, J.G.; McAlpine, J.B.; Chen, S.N.; Pauli, G.F.; Bedran-Russo, A.K.

    2014-01-01

    Although proanthocyanidins (PACs) modify dentin, the effectiveness of different PAC sources and the correlation with their specific chemical composition are still unknown. This study describes the chemical profiling of natural PAC-rich extracts from 7 plants using ultra high pressure/performance liquid chromatography (UHPLC) to determine the overall composition of these extracts and, in parallel, comprehensively evaluate their effect on dentin properties. The total polyphenol content of the extracts was determined (as gallic acid equivalents) using Folin-Ciocalteau assays. Dentin biomodification was assessed by the modulus of elasticity, mass change, and resistance to enzymatic biodegradation. Extracts with a high polyphenol and PAC content from Vitis vinifera, Theobroma cacao, Camellia sinensis, and Pinus massoniana induced a significant increase in modulus of elasticity and mass. The UHPLC analysis showed the presence of multiple types of polyphenols, ranging from simple phenolic acids to oligomeric PACs and highly condensed tannins. Protective effect against enzymatic degradation was observed for all experimental groups; however, statistically significant differences were observed between plant extracts. The findings provide clear evidence that the dentin bioactivities of PACs are source dependent, resulting from a combination of concentration and specific chemical constitution of the complex PAC mixtures. PMID:24574140

  16. Dentin biomodification potential depends on polyphenol source.

    PubMed

    Aguiar, T R; Vidal, C M P; Phansalkar, R S; Todorova, I; Napolitano, J G; McAlpine, J B; Chen, S N; Pauli, G F; Bedran-Russo, A K

    2014-04-01

    Although proanthocyanidins (PACs) modify dentin, the effectiveness of different PAC sources and the correlation with their specific chemical composition are still unknown. This study describes the chemical profiling of natural PAC-rich extracts from 7 plants using ultra high pressure/performance liquid chromatography (UHPLC) to determine the overall composition of these extracts and, in parallel, comprehensively evaluate their effect on dentin properties. The total polyphenol content of the extracts was determined (as gallic acid equivalents) using Folin-Ciocalteau assays. Dentin biomodification was assessed by the modulus of elasticity, mass change, and resistance to enzymatic biodegradation. Extracts with a high polyphenol and PAC content from Vitis vinifera, Theobroma cacao, Camellia sinensis, and Pinus massoniana induced a significant increase in modulus of elasticity and mass. The UHPLC analysis showed the presence of multiple types of polyphenols, ranging from simple phenolic acids to oligomeric PACs and highly condensed tannins. Protective effect against enzymatic degradation was observed for all experimental groups; however, statistically significant differences were observed between plant extracts. The findings provide clear evidence that the dentin bioactivities of PACs are source dependent, resulting from a combination of concentration and specific chemical constitution of the complex PAC mixtures. PMID:24574140

  17. Sphygmomanometer cuffs: a potential source of infection!

    PubMed

    Zargaran, David; Hardwick, Sarah; Adel, Reeja; Hill, George; Stubbins, Daniel; Salmasi, Abdul Majeed

    2015-02-01

    We evaluated the potential pathogenic hazard of sphygmomanometer blood pressure cuffs (BPCs) in a hospital setting. Prospectively, the presence of bacterial organisms on 120 BPCs in 14 medical wards and outpatient clinics in a district general hospital in London was assessed. Swabs taken from the inner aspect of the cuffs were cultured using standard microbiological techniques. Bacterial organisms were found in 85% (102) of the 120 BPCs assessed. The highest rates of contamination were found in the outpatients department (90%). There were differences in the most common bacterial species isolated between the samples obtained from the outpatient clinics and the wards, with coagulase-negative Staphylococcus and diphtheroids being the most prevalent species in the wards and outpatient clinics, respectively. These findings highlight the necessity to eliminate this potential risk of infection. PMID:24569512

  18. New Potential Sources for Black Onaping Carbon

    NASA Technical Reports Server (NTRS)

    Bunch, T. E.; Becker, L.; Schultz, P. H.; Wolbach, W. S.

    1997-01-01

    One intriguing and important issue of the Sudbury Structure concerns the source of the relatively large amount of C in the Onaping Formation Black member. This dilemma was recently addressed, and the conclusion was reached that an impactor could not have delivered all of the requisite C. Becker et al. have suggested that much of the C came from the impactor and reported the presence of interstellar He "caged" inside some fullerenes that may have survived the impact. So, conceivably, the C inventory in the Sudbury Structure comes from both target and impactor materials, although the known target rocks have little C. We discuss here the possibility of two terrestrial sources for at least some of the C: (1) impact evaporation/dissociation of C from carbonate target rocks and (2) the presence of heretofore-unrecognized C-rich (up to 26 wt%) siliceous "shale," fragments, which are found in the upper, reworked Black member. Experimental: Hypervelocity impact of a 0.635-diameter Al projectile into dolomite at 5.03 km/s (performed at the Ames Research Center vertical gun range) produced a thin, black layer (= 0.05 mm thick) that partially lined the crater and coated impactor remnants. Scanning electronic microscope (SEM) imagery shows this layer to be spongelike on a submicron scale and Auger spectroscopic analyses yield: 33% C, 22% Mg, 19% 0, and 9% Al (from the projectile). Elemental mapping shows that all of the available 0 is combined with Ca and Mg, Al is not oxidized, and C is in elemental form. Dissociation efficiency of C from CO2 is estimated to be <10% of crater volume. Raman spectroscopy indicates that the C is highly disorganized graphite. Another impact experiment [4] also produced highly disordered graphite from a limestone target (reducing collector), in addition to small amounts of diamond/lonsdaleite/chaoite (oxidizing collector). These experiments confirm the reduction of C from carbonates in impact vapor plumes. Observational: SEM observations and

  19. New Potential Sources for Black Onaping Carbon

    NASA Technical Reports Server (NTRS)

    Bunch, T. E.; Becker, L.; Schultz, P. H.; Wolbach, W. S.

    1997-01-01

    One intriguing and important issue of the Sudbury Structure concerns the source of the relatively large amount of C in the Onaping Formation Black member. This dilemma was recently addressed, and the conclusion was reached that an impactor could not have delivered all of the requisite C. Becker et al. have suggested that much of the C came from the impactor and reported the presence of interstellar He "caged" inside some fullerenes that may have survived the impact. So, conceivably, the C inventory in the Sudbury Structure comes from both target and impactor materials, although the known target rocks have little C. We discuss here the possibility of two terrestrial sources for at least some of the C: (1) impact evaporation/dissociation of C from carbonate target rocks and (2) the presence of heretofore-unrecognized C-rich (up to 26 wt%) siliceous "shale," fragments, which are found in the upper, reworked Black member. Experimental: Hypervelocity impact of a 0.635-diameter Al projectile into dolomite at 5.03 km/s (performed at the Ames Research Center vertical gun range) produced a thin, black layer (= 0.05 mm thick) that partially lined the crater and coated impactor remnants. Scanning electronic microscope (SEM) imagery shows this layer to be spongelike on a submicron scale and Auger spectroscopic analyses yield: 33% C, 22% Mg, 19% 0, and 9% Al (from the projectile). Elemental mapping shows that all of the available 0 is combined with Ca and Mg, Al is not oxidized, and C is in elemental form. Dissociation efficiency of C from CO2 is estimated to be <10% of crater volume. Raman spectroscopy indicates that the C is highly disorganized graphite. Another impact experiment [4] also produced highly disordered graphite from a limestone target (reducing collector), in addition to small amounts of diamond/lonsdaleite/chaoite (oxidizing collector). These experiments confirm the reduction of C from carbonates in impact vapor plumes. Observational: SEM observations and

  20. Numerical simulation of swept-wing flows

    NASA Technical Reports Server (NTRS)

    Reed, Helen L.

    1991-01-01

    Efforts of the last six months to computationally model the transition process characteristics of flow over swept wings are described. Specifically, the crossflow instability and crossflow/Tollmien-Schlichting wave interactions are analyzed through the numerical solution of the full 3D Navier-Stokes equations including unsteadiness, curvature, and sweep. This approach is chosen because of the complexity of the problem and because it appears that linear stability theory is insufficient to explain the discrepancies between different experiments and between theory and experiment. The leading edge region of a swept wing is considered in a 3D spatial simulation with random disturbances as the initial conditions.

  1. THE SOURCE, POTENTIAL AND VULNERABILITY OF BYRD'S MILL SPRING

    EPA Science Inventory

    The presentation will cover topics including the potential recharge area for Byrd's Mill Spring, the variability in discharge rates and the susceptibility of the ground water to contamination by various sources.

  2. Inventory of Potential Funding Sources for Criminal Justice Education Programs.

    ERIC Educational Resources Information Center

    Positive Futures, Inc., Washington, DC.

    Potential funding sources for criminal justice education programs are listed and information on supplemental source materials and a brief outline of grant writing considerations are included. Sections on general foundation grants, state restricted grants, and government grants are provided. Included under state restricted grants are Alabama,…

  3. 24 mm depth range discretely swept optical frequency domain imaging in dentistry

    NASA Astrophysics Data System (ADS)

    Kakuma, Hideo; Choi, DongHak; Furukawa, Hiroyuki; Hiro-Oka, Hideaki; Ohbayashi, Kohji

    2009-02-01

    A large depth range is needed if optical coherence tomography (OCT) is to be used to observe multiple teeth simultaneously. A discretely swept optical frequency domain imaging system with a 24-mm depth range was made by using a superstructure-grating distributed Bragg reflector (SSG-DBR) laser as the light source and setting the frequencystep interval to be 3.13 GHz (λ ~ 0.026 nm). The swept wavelength range was 40 nm centered at 1580 nm, the resolution was 29 μm, and the A-scan rate was 1.3 kHz. Application of the OCT system to a dental phantom was demonstrated.

  4. Shock Characteristics Measured Upstream of Both a Forward-Swept and an Aft-Swept Fan

    NASA Technical Reports Server (NTRS)

    Podboy, Gary G.; Krupar, Martin J.; Sutliff, Daniel L.; Horvath, Csaba

    2007-01-01

    Three different types of diagnostic data-blade surface flow visualization, shroud unsteady pressure, and laser Doppler velocimeter (LDV)--were obtained on two fans, one forward-swept and one aft-swept, in order to learn more about the shocks which propagate upstream of these rotors when they are operated at transonic tip speeds. Flow visualization data are presented for the forward-swept fan operating at 13831 rpm(sub c), and for the aft-swept fan operating at 12500 and 13831 rpm(sub c) (corresponding to tip rotational Mach numbers of 1.07 and 1.19, respectively). The flow visualization data identify where the shocks occur on the suction side of the rotor blades. These data show that at the takeoff speed, 13831 rpm(sub c), the shocks occurring in the tip region of the forward-swept fan are further downstream in the blade passage than with the aft-swept fan. Shroud unsteady pressure measurements were acquired using a linear array of 15 equally-spaced pressure transducers extending from two tip axial chords upstream to 0.8 tip axial chords downstream of the static position of the tip leading edge of each rotor. Such data are presented for each fan operating at one subsonic and five transonic tip speeds. The unsteady pressure data show relatively strong detached shocks propagating upstream of the aft-swept rotor at the three lowest transonic tip speeds, and weak, oblique pressure disturbances attached to the tip of the aft-swept fan at the two highest transonic tip speeds. The unsteady pressure measurements made with the forward-swept fan do not show strong shocks propagating upstream of that rotor at any of the tested speeds. A comparison of the forward-swept and aft-swept shroud unsteady pressure measurements indicates that at any given transonic speed the pressure disturbance just upstream of the tip of the forward-swept fan is much weaker than that of the aft-swept fan. The LDV data suggest that at 12500 and 13831 rpm(sub c), the forward-swept fan swallowed the

  5. Wide and fast wavelength-swept fiber lasers based on dispersion tuning and their application to optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yamashita, Shinji; Takubo, Yuya

    2013-12-01

    We recently proposed a new class of wavelength-swept lasers for swept-source optical coherence tomography (SS-OCT). It uses the same gain medium with the conventional swept lasers, but does not require any tunable filters. It is based on a principle called "dispersion tuning", in which a highly dispersive medium is inserted in the laser cavity, and loss/gain modulation is applied to mode-lock the laser. Since the cavity contains no mechanical components, such as tunable filters, we could achieve the very high sweep rate. In this review paper, we describe the principle of the dispersion-tuned swept lasers in detail and present our recent work on the application to the SS-OCT system.

  6. Spatially Developing Secondary Instabilities in Compressible Swept Airfoil Boundary Layers

    NASA Technical Reports Server (NTRS)

    Li, Fei; Choudhari, Meelan M.

    2011-01-01

    Two-dimensional eigenvalue analysis is used on a massive scale to study spatial instabilities of compressible shear flows with two inhomogeneous directions. The main focus of the study is crossflow dominated swept-wing boundary layers although the methodology can also be applied to study other type of flows, such as the attachment-line flow. Certain unique aspects of formulating a spatial, two-dimensional eigenvalue problem for the secondary instability of finite amplitude crossflow vortices are discussed, namely, fixing the spatial growth direction unambiguously through a non-orthogonal formulation of the linearized disturbance equations. A primary test case used for parameter study corresponds to the low-speed, NLF-0415(b) airfoil configuration as tested in the ASU Unsteady Wind Tunnel, wherein a spanwise periodic array of roughness elements was placed near the leading edge in order to excite stationary crossflow modes with a specified fundamental wavelength. The two classes of flow conditions selected for this analysis include those for which the roughness array spacing corresponds to either the naturally dominant crossflow wavelength, or a subcritical wavelength that serves to reduce the growth of the naturally excited dominant crossflow modes. Numerical predictions are compared with the measured database, both as indirect validation for the spatial instability analysis and to provide a basis for comparison with a higher Reynolds number, supersonic swept-wing configuration. Application of the eigenvalue analysis to the supersonic configuration reveals that a broad spectrum of stationary crossflow modes can sustain sufficiently strong secondary instabilities as to potentially cause transition over this configuration. Implications of this finding for transition control in swept wing boundary layers are examined.

  7. Importance of algae as a potential source of biofuel.

    PubMed

    Singh, A K; Singh, M P

    2014-01-01

    Algae have a great potential source of biofuels and also have unique importance to reduce gaseous emissions, greenhouse gases, climatic changes, global warming receding of glaciers, rising sea levels and loss of biodiversity. The microalgae, like Scenedesmus obliquus, Neochloris oleabundans, Nannochloropsis sp., Chlorella emersonii, and Dunaliella tertiolecta have high oil content. Among the known algae, Scenedesmus obliquus is one of the most potential sources for biodiesel as it has adequate fatty acid (linolenic acid) and other polyunsaturated fatty acids. Bio—ethanol is already in the market of United States of America and Europe as an additive in gasoline. Bio—hydrogen is the cleanest biofuel and extensive efforts are going on to bring it to market at economical price. This review highlights recent development and progress in the field of algae as a potential source of biofuel. PMID:25535720

  8. In vivo imaging of human vasculature in the chorioretinal complex using phase-variance contrast method with phase-stabilized 1-μm swept-source optical coherence tomography.

    PubMed

    Poddar, Raju; Kim, Dae Yu; Werner, John S; Zawadzki, Robert J

    2014-12-01

    We present a noninvasive phase-variance (pv)–based motion contrast method for depth-resolved imaging of the human chorioretinal complex microcirculation with a newly developed phase-stabilized high speed (100-kHz A-scans/s) 1-μm swept- ource optical coherence tomography (SSOCT) system. Compared to our previous spectral-domain (spectrometer based) pv-spectral domain OCT (SDOCT) system, this system has the advantages of higher sensitivity, reduced fringe wash-out for high blood flow speeds and deeper penetration in choroid. High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. This process does not require additional calibration hardware and complex numerical procedures. Our phase stabilization method is simple and can be employed in a variety of SSOCT systems. Examples of vasculature in the chorioretinal complex imaged by pv-SSOCT from normal as well as diseased eyes are presented and compared to retinal images of the same subjects acquired with fluorescein angiography and indocyanine green angiography. Observations of morphology of vascular perfusion in chorioretinal complex visualized by our method are listed. PMID:25517255

  9. Potential applications of an electron cyclotron resonance multicusp plasma source

    SciTech Connect

    Tsai, C.C.; Berry, L.A.; Gorbatkin, S.M.; Haselton, H.H.; Roberto, J.B.; Stirling, W.L.

    1989-01-01

    An electron cyclotron resonance (ECR) multicusp plasmatron has been developed by feeding a multicusp bucket arc chamber with a compact ECR plasma source. This novel source produced large (about 25-cm-diam), uniform (to within {plus minus}10%), dense (>10{sup 11}-cm{sup -3}) plasmas of argon, helium, hydrogen, and oxygen. It has been operated to produce an oxygen plasma for etching 12.7-cm (5-in.) positive photoresist-coated silicon wafers with uniformity within {plus minus}8%. Results and potential applications of this new ECR plasma source for plasma processing of thin films are discussed. 21 refs., 10 figs.

  10. Implementation of swept synthetic aperture imaging

    NASA Astrophysics Data System (ADS)

    Bottenus, Nick; Jakovljevic, Marko; Boctor, Emad; Trahey, Gregg E.

    2015-03-01

    Ultrasound imaging of deep targets is limited by the resolution of current ultrasound systems based on the available aperture size. We propose a system to synthesize an extended effective aperture in order to improve resolution and target detectability at depth using a precisely-tracked transducer swept across the region of interest. A Field II simulation was performed to demonstrate the swept aperture approach in both the spatial and frequency domains. The adaptively beam-formed system was tested experimentally using a volumetric transducer and an ex vivo canine abdominal layer to evaluate the impact of clutter-generating tissue on the resulting point spread function. Resolution was improved by 73% using a 30.8 degree sweep despite the presence of varying aberration across the array with an amplitude on the order of 100 ns. Slight variations were observed in the magnitude and position of side lobes compared to the control case, but overall image quality was not significantly degraded as compared by a simulation based on the experimental point spread function. We conclude that the swept aperture imaging system may be a valuable tool for synthesizing large effective apertures using conventional ultrasound hardware.

  11. Utilization of leaf litter as a potential feed source

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Proximate analysis and In-situ nylon bag ruminal dry matter degradation of fall dropped Liriodendron tulipifera (tulip poplar) and Quercus alba (white oak) leaves were used to determine their potential use as a feed source for ruminant livestock animals. Ash content was 8.24 and 4.69 ...

  12. CATALOG OF MATERIALS AS POTENTIAL SOURCES OF INDOOR AIR POLLUTION

    EPA Science Inventory

    The paper discusses a series of documents being developed by the U.S. EPA, summarizing available information on building materials and products brought into homes and office buildings as potential sources of indoor air pollution. he documents will provide a complete list of mater...

  13. Potential GTCC LLW sealed radiation source recycle initiatives

    SciTech Connect

    Fischer, D

    1992-04-01

    This report suggests 11 actions that have the potential to facilitate the recycling (reuse or radionuclide) of surplus commercial sealed radiation sources that would otherwise be disposed of as greater-than-Class C low-level radioactive waste. The suggestions serve as a basis for further investigation and discussion between the Department of Energy, Nuclear Regulatory Commission, Agreement States, and the commercial sector. Information is also given that describes sealed sources, how they are used, and problems associated with recycling, including legal concerns. To illustrate the nationwide recycling potential, Appendix A gives the estimated quantity and application information for sealed sources that would qualify for disposal in commercial facilities if not recycle. The report recommends that the Department of Energy initiate the organization of a forum to explore the suggested actions and other recycling possibilities.

  14. Littoral lichens as a novel source of potentially bioactive Actinobacteria

    PubMed Central

    Parrot, Delphine; Antony-Babu, Sanjay; Intertaglia, Laurent; Grube, Martin; Tomasi, Sophie; Suzuki, Marcelino T.

    2015-01-01

    Cultivable Actinobacteria are the largest source of microbially derived bioactive molecules. The high demand for novel antibiotics highlights the need for exploring novel sources of these bacteria. Microbial symbioses with sessile macro-organisms, known to contain bioactive compounds likely of bacterial origin, represent an interesting and underexplored source of Actinobacteria. We studied the diversity and potential for bioactive-metabolite production of Actinobacteria associated with two marine lichens (Lichina confinis and L. pygmaea; from intertidal and subtidal zones) and one littoral lichen (Roccella fuciformis; from supratidal zone) from the Brittany coast (France), as well as the terrestrial lichen Collema auriforme (from a riparian zone, Austria). A total of 247 bacterial strains were isolated using two selective media. Isolates were identified and clustered into 101 OTUs (98% identity) including 51 actinobacterial OTUs. The actinobacterial families observed were: Brevibacteriaceae, Cellulomonadaceae, Gordoniaceae, Micrococcaceae, Mycobacteriaceae, Nocardioidaceae, Promicromonosporaceae, Pseudonocardiaceae, Sanguibacteraceae and Streptomycetaceae. Interestingly, the diversity was most influenced by the selective media rather than lichen species or the level of lichen thallus association. The potential for bioactive-metabolite biosynthesis of the isolates was confirmed by screening genes coding for polyketide synthases types I and II. These results show that littoral lichens are a source of diverse potentially bioactive Actinobacteria. PMID:26514347

  15. Littoral lichens as a novel source of potentially bioactive Actinobacteria.

    PubMed

    Parrot, Delphine; Antony-Babu, Sanjay; Intertaglia, Laurent; Grube, Martin; Tomasi, Sophie; Suzuki, Marcelino T

    2015-01-01

    Cultivable Actinobacteria are the largest source of microbially derived bioactive molecules. The high demand for novel antibiotics highlights the need for exploring novel sources of these bacteria. Microbial symbioses with sessile macro-organisms, known to contain bioactive compounds likely of bacterial origin, represent an interesting and underexplored source of Actinobacteria. We studied the diversity and potential for bioactive-metabolite production of Actinobacteria associated with two marine lichens (Lichina confinis and L. pygmaea; from intertidal and subtidal zones) and one littoral lichen (Roccella fuciformis; from supratidal zone) from the Brittany coast (France), as well as the terrestrial lichen Collema auriforme (from a riparian zone, Austria). A total of 247 bacterial strains were isolated using two selective media. Isolates were identified and clustered into 101 OTUs (98% identity) including 51 actinobacterial OTUs. The actinobacterial families observed were: Brevibacteriaceae, Cellulomonadaceae, Gordoniaceae, Micrococcaceae, Mycobacteriaceae, Nocardioidaceae, Promicromonosporaceae, Pseudonocardiaceae, Sanguibacteraceae and Streptomycetaceae. Interestingly, the diversity was most influenced by the selective media rather than lichen species or the level of lichen thallus association. The potential for bioactive-metabolite biosynthesis of the isolates was confirmed by screening genes coding for polyketide synthases types I and II. These results show that littoral lichens are a source of diverse potentially bioactive Actinobacteria. PMID:26514347

  16. Leptospirosis risk around a potential source of infection

    NASA Astrophysics Data System (ADS)

    Loaiza-Echeverry, Erica; Hincapié-Palacio, Doracelly; Ochoa Acosta, Jesús; Ospina Giraldo, Juan

    2015-05-01

    Leptospirosis is a bacterial zoonosis with world distribution and multiform clinical spectrum in men and animals. The etiology of this disease is the pathogenic species of Leptospira, which cause diverse manifestations of the disease, from mild to serious, such as the Weil disease and the lung hemorrhagic syndrome with lethal proportions of 10% - 50%. This is an emerging problem of urban health due to the growth of marginal neighborhoods without basic sanitary conditions and an increased number of rodents. The presence of rodents and the probability of having contact with their urine determine the likelihood for humans to get infected. In this paper, we simulate the spatial distribution of risk infection of human leptospirosis according to the proximity to rodent burrows considered as potential source of infection. The Bessel function K0 with an r distance from the potential point source, and the scale parameter α in meters was used. Simulation inputs were published data of leptospirosis incidence rate (range of 5 to 79 x 10 000), and a distance of 100 to 5000 meters from the source of infection. We obtained an adequate adjustment between the function and the simulated data. The risk of infection increases with the proximity of the potential source. This estimation can become a guide to propose effective measures of control and prevention.

  17. The bioelectrical source in computing single muscle fiber action potentials.

    PubMed Central

    van Veen, B K; Wolters, H; Wallinga, W; Rutten, W L; Boom, H B

    1993-01-01

    Generally, single muscle fiber action potentials (SFAPs) are modeled as a convolution of the bioelectrical source (being the transmembrane current) with a weighting or transfer function, representing the electrical volume conduction. In practice, the intracellular action potential (IAP) rather than the transmembrane current is often used as the source, because the IAP is relatively easy to obtain under experimental conditions. Using a core conductor assumption, the transmembrane current equals the second derivative of the IAP. In previous articles, discrepancies were found between experimental and simulated SFAPs. Adaptations in the volume conductor slightly altered the simulation results. Another origin of discrepancy might be an erroneous description of the source. Therefore, in the present article, different sources were studied. First, an analytical description of the IAP was used. Furthermore, an experimental IAP, a special experimental SFAP, and a measured transmembrane current scaled to our experimental situation were applied. The results for the experimental IAP were comparable to those with the analytical IAP. The best agreement between experimental and simulated data was found for a measured transmembrane current as source, but differences are still apparent. PMID:8324186

  18. Laser wakefield accelerator based light sources: potential applications and requirements

    SciTech Connect

    Albert, F.; Thomas, A. G.; Mangles, S. P.D.; Banerjee, S.; Corde, S.; Flacco, A.; Litos, M.; Neely, D.; Viera, J.; Najmudin, Z.; Bingham, R.; Joshi, C.; Katsouleas, T.

    2015-01-15

    In this article we review the prospects of laser wakefield accelerators as next generation light sources for applications. This work arose as a result of discussions held at the 2013 Laser Plasma Accelerators Workshop. X-ray phase contrast imaging, X-ray absorption spectroscopy, and nuclear resonance fluorescence are highlighted as potential applications for laser-plasma based light sources. We discuss ongoing and future efforts to improve the properties of radiation from plasma betatron emission and Compton scattering using laser wakefield accelerators for these specific applications.

  19. Numerical calculation of the transonic flow past a swept wing

    NASA Technical Reports Server (NTRS)

    Jameson, A.; Caughey, D. A.

    1977-01-01

    A numerical method is presented for analyzing the transonic potential flow past a lifting, swept wing. A finite difference approximation to the full potential equation is solved in a coordinate system which is nearly conformally mapped from the physical space in planes parallel to the symmetry plane, and reduces the wing surface to a portion of one boundary of the computational grid. A coordinate invariant, rotated difference scheme is used, and the difference equations are solved by relaxation. The method is capable of treating wings of arbitrary planform and dihedral, although approximations in treating the tips and vortex sheet make its accuracy suspect for wings of small aspect ratio. Comparisons of calculated results with experimental data are shown for examples of both conventional and supercritical transport wings. Agreement is good for both types, but it was found necessary to account for the displacement effect of the boundary layer for the supercritical wing, presumably because of its greater sensitivity to changes in effective geometry.

  20. Potential source regions of dust accumulated in northern Africa

    NASA Astrophysics Data System (ADS)

    Wasowska, S.; Woronko, B.

    2012-04-01

    Sahara is the largest source of the dust in the world. The material sampled from dust storms in Tunisia (Nefta Oasis, El Kantoui Harbor), north Egypt (Alexandria) and Morocco (Mhamid Oasis) (March 2001, March and April 2009) was taken to identify the potential sources of dust accumulation and transport paths in North Africa. The samples were analyzed on grain size, micromorphology of silt grain surfaces in Scanning Electron Microscope (SEM), elemental composition of grains and their surface crusts, loss on ignition, mineralogical composition of samples and carbonate content. Additionally the meteorological situation was analyzed during the dust storm occurrences and preceding periods. The results of grain size analyses show that all studied sediments belong to the small dust type, and dust accumulated in Mhamid is the clay mineral agglomerated (CMA) dust. The source of the CMA are the old dry lake beds. Dust particles are mobilized as aggregates of clay minerals, what is controlled by structure (particle packing) of the original lake sediment, and accumulation is dry and wet as well. The results of the analysis of the quartz grain surface micromorphology, the elemental composition and loss on ignition indicate that dust accumulated in Morocco originated from a relatively homogenous sediment source and, on the other hand, dust found in Alexandria comes from a diversified source. Dust sampled in Tunisia is characterized by the highest content of carbonates and organic matter which suggests the intensive dispelling acting on the weathered material from carbonate rocks and local Mediterranean soil covers rich in CaCO3. The analyses of meteorological conditions during the dust storms and the analyses of the textural characteristics of deposits show that it is highly probable that analysed aeolian dust was transported both for shorter and longer distances. Hypothetic source areas of dust accumulated in Mhamid could be the old ergs, some located 300-500 km away like

  1. Urban waste as a potential source for brick plants

    NASA Astrophysics Data System (ADS)

    Daugherty, K. E.; Eberendu, A.; Griffin, J.; Gegbe, H.; Ike, C.; Aboo, A.

    1982-02-01

    A joint government/industry/university project was formulated to address the technical feasibility of utilizing municipal solid waste (MSW) as a commercial fuel for the brick industry. Specifically, refuse derived fuel (RDF) from MSW was investigated for three potential applications in the brick industry: (1) rotary brick kilns; (2) tunnel brick kilns; and (3) moisture dryers. The successful development of such a procedure would be a dramatic achievement with widespread applicability, transferability, and commercial merit for energy displacement. The sampling, collection, and analysis of MSW, the analysis of RDF, and the potential utilization of RDF as an alternate source of fuel for the brick industry are described.

  2. Effect of electron temperature fluctuations on slowly swept Langmuir probe measurements

    SciTech Connect

    Rudakov, D.L.; Boedo, J.A.; Moyer, R.A.; Stangeby, P.C.; McLean, A.; Watkins, J.G.

    2004-10-01

    Swept Langmuir probes are widely used to measure electron temperature (T{sub e}) in laboratory plasmas by performing an exponential fit to the measured volt-ampere (I-V) characteristic. Often the probe voltage sweep frequency is much lower than the characteristic frequencies of the plasma fluctuations and a time-averaged I-V characteristic is used for the fit. We show by numerical modeling that in the presence of T{sub e} fluctuations with frequencies well above the voltage sweep frequency this standard technique applied to a swept single probe tends to read higher than the actual time-averaged T{sub e} provided no correlated plasma potential (V{sub p}) fluctuations are present. In the presence of coupled T{sub e} and V{sub p} fluctuations a slowly swept single probe may read either higher or lower than the average T{sub e}, depending on the relative amplitude and phase of the temperature and potential fluctuations. In contrast, swept double probe measurements of T{sub e} are virtually unaffected by either T{sub e} or V{sub p} fluctuations.

  3. Nonlinear wave interactions in swept wing flows

    NASA Technical Reports Server (NTRS)

    Elhady, Nabil M.

    1988-01-01

    An analysis is presented which examines the modulation of different instability modes satisfying the triad resonance condition in time and space in a three-dimensional boundary layer flow. Detuning parameters are used for the wave numbers and the frequencies. The nonparallelism of the mean flow is taken into account in the analysis. At the leading-edge region of an infinite swept wing, different resonant triads are investigated that are comprised of travelling crossflow, vertical vorticity and Tollmein-Schlichting modes. The spatial evolution of the resonating triad components are studied.

  4. The NYU inverse swept wing code

    NASA Technical Reports Server (NTRS)

    Bauer, F.; Garabedian, P.; Mcfadden, G.

    1983-01-01

    An inverse swept wing code is described that is based on the widely used transonic flow program FLO22. The new code incorporates a free boundary algorithm permitting the pressure distribution to be prescribed over a portion of the wing surface. A special routine is included to calculate the wave drag, which can be minimized in its dependence on the pressure distribution. An alternate formulation of the boundary condition at infinity was introduced to enhance the speed and accuracy of the code. A FORTRAN listing of the code and a listing of a sample run are presented. There is also a user's manual as well as glossaries of input and output parameters.

  5. High performance forward swept wing aircraft

    NASA Technical Reports Server (NTRS)

    Koenig, David G. (Inventor); Aoyagi, Kiyoshi (Inventor); Dudley, Michael R. (Inventor); Schmidt, Susan B. (Inventor)

    1988-01-01

    A high performance aircraft capable of subsonic, transonic and supersonic speeds employs a forward swept wing planform and at least one first and second solution ejector located on the inboard section of the wing. A high degree of flow control on the inboard sections of the wing is achieved along with improved maneuverability and control of pitch, roll and yaw. Lift loss is delayed to higher angles of attack than in conventional aircraft. In one embodiment the ejectors may be advantageously positioned spanwise on the wing while the ductwork is kept to a minimum.

  6. Optimal energy growth in swept Hiemenz flow

    NASA Astrophysics Data System (ADS)

    Guegan, Alan; Huerre, Patrick; Schmid, Peter

    2006-11-01

    It has been shown in Gu'egan, Schmid & Huerre 2006 that the kinetic energy of optimal G"ortler-H"ammerlin (GH) perturbations in swept Hiemenz flow can be transiently amplified by two orders of magnitude at Reynolds numbers ranging from 400 to 1000 and spanwise wavenumbers from 0.1 to 0.5. In this configuration an array of counter-rotating chordwise vortices is compressed by the spanwise shear, as in the well-known Orr mechanism. We show that stronger transient growth can be achieved when the GH assumption is relaxed. In this case the optimal initial perturbation consists in vorticity sheets stacked in the chordwise direction, at a small angle from the symmetry plane of the base flow. Although the spatial structure of the GH perturbations is lost, wall-normal-spanwise plane cuts show that the amplification mechanism is mostly unchanged. The GH assumption thus provides a reasonably good estimate for transient energy amplification levels in swept Hiemenz flow. Extension of this analysis to the spatial growth problem is under way and preliminary results will be shown.

  7. Source rock, maturity data indicate potential off Namibia

    SciTech Connect

    Bray, R.; Lawrence, S.; Swart, R.

    1998-08-10

    Namibia`s territorial waters occupy a large portion of West Africa`s continental shelf. The area to the 1,000 m isobath is comparable in size to the combined offshore areas of Gabon, Congo, Zaire, and Angola. Around half as much again lies in 1,000--2,500 m of water. The whole unlicensed part of this area will be open for bidding when the Third Licensing Round starts Oct. 1, 1998. Offshore Namibia is underexplored by drilling with only seven exploration wells drilled. Shell`s Kudu field represents a considerable gas resource with reserves of around 3 tcf and is presently the only commercial discovery.Namibia`s offshore area holds enormous exploration potential. Good quality sandstone reservoirs are likely to be distributed widely, and a number of prospective structural and stratigraphic traps have been identified. The recognition of Cretaceous marine oil-prone source rocks combined with the results of new thermal history reconstruction and maturity modeling studies are particularly significant in assessment of the oil potential. The paper discusses resource development and structures, oil source potential, maturity, and hydrocarbon generation.

  8. Subsonic roll damping of a model with swept-back and swept-forward wings

    NASA Technical Reports Server (NTRS)

    Boyden, R. P.

    1978-01-01

    The aerodynamic roll damping and the yawing moment due to roll rate characteristics were investigated at subsonic speeds for a model with either sweptback or swept forward wings. The tests were made in the Langley high speed 7 by 10 foot tunnel for Mach numbers between 0.3 and 0.7. The configuration with a 60 deg sweptback wing had positive damping in roll up to the maximum test angle of attack of almost 20 deg. The 32 deg swept forward wing configuration had positive damping in roll at the lower angles of attack, but there was a decrease in damping and negative damping in roll was measured at the highest angles of attack.

  9. Source rock potential of middle Cretaceous rocks in southwestern Montana

    SciTech Connect

    Dyman, T.S.; Palacas, J.G.; Tysdal, R.G.; Perry, W.J. Jr.; Pawlewicz, M.J.

    1996-08-01

    The middle Cretaceous in southwestern Montana is composed of a marine and nonmarine succession of predominantly clastic rocks that were deposited along the western margin of the Western Interior Seaway. In places, middle Cretaceous rocks contain appreciable total organic carbon (TOC), such as 5.59% for the Mowry Shale and 8.11% for the Frontier Formation in the Madison Range. Most samples, however, exhibit less than 1.0% TOC. The genetic or hydrocarbon potential (S{sub 1}+S{sub 2}) of all the samples analyzed, except one, yield less than 1 mg HC/g rock, strongly indicating poor potential for generating commercial amounts of hydrocarbons. Out of 51 samples analyzed, only one (a Thermopolis Shale sample from the Snowcrest Range) showed a moderate petroleum potential of 3.1 mg HC/g rock. Most of the middle Cretaceous samples are thermally immature to marginally mature, with vitrinite reflectance ranging from about 0.4 to 0.6% R{sub o}. Maturity is high in the Pioneer Mountains, where vitrinite reflectance averages 3.4% R{sub o}, and at Big Sky, Montana, where vitrinite reflectance averages 2.5% R{sub o}. At both localities, high R{sub o} values are due to local heat sources, such as the Pioneer batholith in the Pioneer Mountains.

  10. The water environment as a source of potentially pathogenic mycobacteria.

    PubMed

    Makovcova, Jitka; Slany, Michal; Babak, Vladimir; Slana, Iva; Kralik, Petr

    2014-06-01

    Nontuberculous mycobacteria (NTM) are ubiquitous organisms of a wide variety of environmental reservoirs, including natural and municipal water, soil, aerosols, protozoans, animals and humans. Several of these species are potential pathogens which affect human health. The aim of this study was to determine the occurrence of NTM in the water environment. Samples were taken from 13 water-related facilities including fish ponds, storage ponds, drinking water reservoirs and an experimental recirculation system. Altogether, 396 samples of water, sediment and aquatic plants were collected and analysed. All samples were examined using conventional culture methods. Suspected microbial isolates were subjected to polymerase chain reaction analysis and identified using partial sequence analysis of the 16S rDNA gene. The culture revealed 94/396 samples (23.7%) that contained mycobacteria. Among known NTM we identified potentially pathogenic mycobacteria isolated from the fresh water environment for the first time: Mycobacterium asiaticum, M. chimaera, M. interjectum, M. kumamotonense, M. lentiflavum, M. montefiorense, M. nebraskense, M. paraffinicum and M. simiae. Epidemiologic studies suggest that the natural water environment is the principal source of human exposure. Our results indicate that besides the well-known potentially pathogenic mycobacteria it is important to observe occurrence, proliferation and persistence of newly discovered mycobacterial species. PMID:24937219