Science.gov

Sample records for potential swept source

  1. Experimental confirmation of potential swept source optical coherence tomography performance limitations

    PubMed Central

    Zheng, Kathy; Liu, Bin; Huang, Chuanyong; Brezinski, Mark E.

    2009-01-01

    Optical coherence tomography (OCT) has demonstrated considerable potential for a wide range of medical applications. Initial work was done in the time domain OCT (TD-OCT) approach, but recent interest has been generated with spectral domain OCT (SD-OCT) approaches. While SD-OCT offers higher data acquisition rates and no movable parts, we recently pointed out theoretical inferior aspects to its performance relative to TD-OCT. In this paper we focus on specific limitations of swept source OCT (SS-OCT), as this is the more versatile of the two SD-OCT embodiments. We present experimental evidence of reduced imaging penetration, increased low frequency noise, higher multiple scattering (which can be worsened still via aliasing), increased need to control the distance from the sample, and saturation of central bandwidth frequencies. We conclude that for scenarios where the dynamic range is relatively low (e.g., retina), the distance from the sample is relatively constant, or high acquisition rates are needed, SS-OCT has a role. However, when penetration remains important in the setting of a relatively high dynamic range, acquisition rates above video rate are not needed, or the distance to the tissue is not constant, TD-OCT may be the superior approach. PMID:19023378

  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. Fiber-based swept-source terahertz radar.

    PubMed

    Huang, Yu-Wei; Tseng, Tzu-Fang; Kuo, Chung-Chiu; Hwang, Yuh-Jing; Sun, Chi-Kuang

    2010-05-01

    We demonstrate an all-terahertz swept-source imaging radar operated at room temperature by using terahertz fibers for radiation delivery and with a terahertz-fiber directional coupler acting as a Michelson interferometer. By taking advantage of the high water reflection contrast in the low terahertz regime and by electrically sweeping at a high speed a terahertz source combined with a fast rotating mirror, we obtained the living object's distance information with a high image frame rate. Our experiment showed that this fiber-based swept-source terahertz radar could be used in real time to locate concealed moving live objects with high stability.

  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. Frequency multiplexed long range swept source optical coherence tomography

    PubMed Central

    Zurauskas, Mantas; Bradu, Adrian; Podoleanu, Adrian Gh.

    2013-01-01

    We present a novel swept source optical coherence tomography configuration, equipped with acousto-optic deflectors that can be used to simultaneously acquire multiple B-scans originating from different depths. The sensitivity range of the configuration is evaluated while acquiring five simultaneous B-scans. Then the configuration is employed to demonstrate long range B-scan imaging by combining two simultaneous B-scans from a mouse head sample. PMID:23760762

  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. Swept laser source based on acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Chen, Minghui; Li, Hao; Chen, Rong

    2014-12-01

    The design and development of the swept laser for optical coherence tomography is presented. It is manifested by a semiconductor optical amplifier, a fiber coupler, two fiber isolators, a semiconductor optical amplifier (SOA) and an acousto-optic tunable filter (AOTF) for frequency tuning within a unidirectional all-fiber ring cavity. Light output from the coupler is further amplified and spectral shaped by a booster SOA terminated at both ends with two isolators. The total loss in ring cavity is 8.2 dB. The gain SOA provides fiber-to-fiber small signal gain of 22.2 dB with saturation output power of 9.0 dBm. The developed laser source provides up to 100 kHz over a full-width wavelength tuning range of 140 nm at center wavelength of 1308 nm with an average power of 8 mW, yielding an axial resolution of 5.4 μm in air for OCT imaging. Theoretically, the measurement principle and the feasibility of the system are analyzed. Implementing the laser source in swept source based OCT (SS-OCT) system, real-time structural imaging of biological tissue is realized.

  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. Swept Source OCT Angiography of Neovascular Macular Telangiectasia Type 2

    PubMed Central

    Zhang, Qinqin; Wang, Ruikang K.; Chen, Chieh-Li; Legarreta, Andrew D.; Durbin, Mary K.; An, Lin; Sharma, Utkarsh; Stetson, Paul F.; Legarreta, John E.; Roisman, Luiz; Gregori, Giovanni; Rosenfeld, Philip J.

    2015-01-01

    Objective To image subretinal neovascularization in proliferative macular telangiectasia type 2 (MacTel2) using swept source optical coherence tomography based microangiography (OMAG). Study Design Patients with MacTel2 were enrolled in a prospective, observational study known as the MacTel Project and evaluated using a high-speed 1050nm swept-source OCT (SS-OCT) prototype system. The OMAG algorithm generated en face flow images from three retinal layers, as well as the region bounded by the outer retina and Bruch’s membrane, the choriocapillaris, and the remaining choroidal vasculature. The en face OMAG images were compared to images from fluorescein angiography (FA) and indocyanine green angiography (ICGA). Results Three eyes with neovascular MacTel2 were imaged. The neovascularization was best identified from the en face OMAG images that included a layer between the outer retinal boundary and Bruch’s membrane. OMAG images identified these abnormal vessels better than FA and were comparable to the images obtained using ICGA. In all three cases, OMAG identified choroidal vessels communicating with the neovascularization, and these choroidal vessels were evident in the two cases with ICGA imaging. In one case, monthly injections of bevacizumab reduced the microvascular complexity of the neovascularization, as well as the telangiectatic changes within the retinal microvasculature. In another case, less frequent bevacizumab therapy was associated with growth of the subretinal neovascular complex. Conclusions OMAG imaging provided detailed, depth-resolved information about subretinal neovascularization in MacTel2 eyes demonstrating superiority to FA imaging and similarities to ICGA imaging for documenting the retinal microvascular changes, the size and extent of the neovascular complex, the communications between the neovascular complex and the choroidal circulation, and the response to monthly bevacizumab therapy. PMID:26457402

  11. 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

  12. Modeling and interpreting speckle pattern formation in swept-source optical coherence tomography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Demidov, Valentin; Vitkin, I. Alex; Doronin, Alexander; Meglinski, Igor

    2017-03-01

    We report on the development of a unified Monte-Carlo based computational model for exploring speckle pattern formation in swept-source optical coherence tomography (OCT). OCT is a well-established optical imaging modality capable of acquiring cross-sectional images of turbid media, including biological tissues, utilizing back scattered low coherence light. The obtained OCT images include characteristic features known as speckles. Currently, there is a growing interest to the OCT speckle patterns due to their potential application for quantitative analysis of medium's optical properties. Here we consider the mechanisms of OCT speckle patterns formation for swept-source OCT approaches and introduce further developments of a Monte-Carlo based model for simulation of OCT signals and images. The model takes into account polarization and coherent properties of light, mutual interference of back-scattering waves, and their interference with the reference waves. We present a corresponding detailed description of the algorithm for modeling these light-medium interactions. The developed model is employed for generation of swept-source OCT images, analysis of OCT speckle formation and interpretation of the experimental results. The obtained simulation results are compared with selected analytical solutions and experimental studies utilizing various sizes / concentrations of scattering microspheres.

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

    PubMed

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

    2011-12-15

    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 µm in 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.

  14. Quantitative evaluation of dental abfraction and attrition using a swept-source optical coherence tomography system.

    PubMed

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

    2014-02-01

    A fast swept-source optical coherence tomography (SS-OCT) system is employed to acquire volumes of dental tissue, in order to monitor the temporal evolution of dental wear. An imaging method is developed to evaluate the volume of tissue lost in ex vivo artificially induced abfractions and attritions. The minimal volume (measured in air) that our system could measure is 2352 μm3. A volume of 25,000 A-scans is collected in 2.5 s. All these recommend the SS-OCT method as a valuable tool for dynamic evaluation of the abfraction and attrition with remarkable potential for clinical use.

  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. Swept source OCT imaging of human anterior segment at 200 kHz

    NASA Astrophysics Data System (ADS)

    Karnowski, Karol; Gora, Michalina; Kaluzny, Bartlomiej; Huber, Robert; Szkulmowski, Maciej; Kowalczyk, Andrzej; Wojtkowski, Maciej

    2009-02-01

    We present applicability of the high speed swept-source optical coherence tomography for in vivo imaging of the anterior segment of the human eye. Three dimensional imaging of the cornea with reduced motion artifacts is possible by using swept source with Fourier domain mode locking operating at 200kHz with 1300nm central wavelength. High imaging speeds allow for assessment of anterior and posterior corneal topography and generation of thickness and elevation maps.

  17. Spectro-refractometry of individual microscopic objects using swept-source quantitative phase imaging.

    PubMed

    Jung, Jae-Hwang; Jang, Jaeduck; Park, Yongkeun

    2013-11-05

    We present a novel spectroscopic quantitative phase imaging technique with a wavelength swept-source, referred to as swept-source diffraction phase microscopy (ssDPM), for quantifying the optical dispersion of microscopic individual samples. Employing the swept-source and the principle of common-path interferometry, ssDPM measures the multispectral full-field quantitative phase imaging and spectroscopic microrefractometry of transparent microscopic samples in the visible spectrum with a wavelength range of 450-750 nm and a spectral resolution of less than 8 nm. With unprecedented precision and sensitivity, we demonstrate the quantitative spectroscopic microrefractometry of individual polystyrene beads, 30% bovine serum albumin solution, and healthy human red blood cells.

  18. 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.

  19. 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.

  20. 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

  1. Ultra-compact silicon photonic integrated interferometer for swept-source optical coherence tomography.

    PubMed

    Yurtsever, Günay; Weiss, Nicolás; Kalkman, Jeroen; van Leeuwen, Ton G; Baets, Roel

    2014-09-01

    We demonstrate an ultra-compact silicon integrated photonic interferometer for swept-source optical coherence tomography (SS-OCT). The footprint of the integrated interferometer is only 0.75×5  mm2. The design consists of three 2×2 splitters, a 13 cm physical length (50.4 cm optical length) reference arm, and grating couplers. The photonic integrated circuit was used as the interferometer of an SS-OCT system. The sensitivity of the system was measured to be -62  dB with 115 μW power delivered to the sample. Using the system, we demonstrate cross-sectional OCT imaging of a layered tissue phantom. We also discuss potential improvements in passive silicon photonic integrated circuit design and integration with active components.

  2. VCSEL-based swept source for low-cost optical coherence tomography

    PubMed Central

    Moon, Sucbei; Choi, Eun Seo

    2017-01-01

    We present a novel wavelength-swept laser source for optical coherence tomography (OCT) which is based on the conventional laser diode technology of the vertical-cavity surface-emitting laser (VCSEL). In our self-heating sweep VCSEL (SS-VCSEL), a VCSEL device is simply driven by ramped pulses of currents in direct intensity modulation. The intrinsic property of VCSEL produces a frequency-swept output through the self-heating effect. By the injected current, the temperature of the active region is gradually increased in this effect. Consequently, it changes the wavelength of the laser output by itself. In this study, various characteristics of our SS-VCSEL were experimentally investigated for low-cost instrumentation of a swept source OCT system. A low-cost SS-VCSEL-based OCT system was demonstrated in this research that provided an axial resolution of 135 μm in air, sensitivity of −91 dB and a maximum imaging range longer than 10 cm when our source was operated at a sweep repetition rate of 5 kHz with an output power of 0.41 mW. Based on the experimental observations, we believe that our SS-VCSEL swept source can be an economic alternative in some of low-cost or long-range applications of OCT. PMID:28271006

  3. 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.

  4. 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.

  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. [The new findings of high myopia by swept-source optical coherence tomography].

    PubMed

    Liu, Y Y; Han, Q H

    2016-07-01

    The fundus disease of high myopia, one of the main reasons leading to visual impairment, includes different types of the retinal, choroidal and scleral changes, and in particular the macular and optic disc lesions. Due to technical limitations, it is relatively difficult to study the characteristics of the sclera and the choroid in humans in vivo. The swept-source optical coherence tomography, with the long wave swept laser as a light source, has less sensitivity roll-off with the tissue depth, which makes it possible to check the choroid and the sclera. The recent studies of the characteristics of the choroid and the sclera in high myopia, and new findings of spinal and vascular systems posterior to the sclera in humans are mainly reviewed in this article. (Chin J Ophthalmol, 2016, 52: 547-550).

  7. Assessment of Optic Nerve Head Drusen Using Enhanced Depth Imaging and Swept Source Optical Coherence Tomography

    PubMed Central

    Silverman, Anna L.; Tatham, Andrew J.; Medeiros, Felipe A.; Weinreb, Robert N.

    2015-01-01

    Background Optic nerve head drusen (ONHD) are calcific deposits buried or at the surface of the optic disc. Although ONHD may be associated with progressive visual field defects, the mechanism of drusen-related field loss is poorly understood. Methods for detecting and imaging disc drusen include B-scan ultrasonography, fundus autofluorescence, and optical coherence tomography (OCT). These modalities are useful for drusen detection but are limited by low resolution or poor penetration of deep structures. This review was designed to assess the potential role of new OCT technologies in imaging ONHD. Evidence Acquisition Critical appraisal of published literature and comparison of new imaging devices to established technology. Results The new imaging modalities of enhanced depth imaging optical coherence tomography (EDI-OCT) and swept source optical coherence tomography (SS-OCT) are able to provide unprecedented in vivo detail of ONHD. Using these devices it is now possible to quantify optic disc drusen dimensions and assess integrity of neighboring retinal structures, including the retinal nerve fiber layer. Conclusions EDI-OCT and SS-OCT have the potential to allow better detection of longitudinal changes in drusen and neural retina and improve our understanding of drusen-related visual field loss. PMID:24662838

  8. 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

  9. 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

    2015-03-09

    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.

  10. 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

  11. Corneal topography with high-speed swept source OCT in clinical examination

    PubMed Central

    Karnowski, Karol; Kaluzny, Bartlomiej J.; Szkulmowski, Maciej; Gora, Michalina; Wojtkowski, Maciej

    2011-01-01

    We present the applicability of high-speed swept source (SS) optical coherence tomography (OCT) for quantitative evaluation of the corneal topography. A high-speed OCT device of 108,000 lines/s permits dense 3D imaging of the anterior segment within a time period of less than one fourth of second, minimizing the influence of motion artifacts on final images and topographic analysis. The swept laser performance was specially adapted to meet imaging depth requirements. For the first time to our knowledge the results of a quantitative corneal analysis based on SS OCT for clinical pathologies such as keratoconus, a cornea with superficial postinfectious scar, and a cornea 5 months after penetrating keratoplasty are presented. Additionally, a comparison with widely used commercial systems, a Placido-based topographer and a Scheimpflug imaging-based topographer, is demonstrated. PMID:21991558

  12. 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.

  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. Swept-source OCT Angiography of the Retinal Vasculature using Intensity Differentiation Based OMAG Algorithms

    PubMed Central

    Huang, Yanping; Zhang, Qinqin; Thorell, Mariana Rossi; An, Lin; Durbin, Mary; Laron, Michal; Sharma, Utkarsh; Gregori, Giovanni; Rosenfeld, Philip J.; Wang, Ruikang K

    2014-01-01

    Background and Objective To demonstrate the feasibility of using a 1050 nm swept-source OCT (SS-OCT) system to achieve noninvasive retinal vasculature imaging in human eyes. Materials and Methods Volumetric datasets were acquired using a ZEISS 1 µm SS-OCT prototype that operated at an A-line rate of 100 kHz. A scanning protocol designed to allow for motion contrast processing, referred to as OCT angiography or optical microangiography (OMAG), was used to scan ~3 mm × 3 mm area in the central macular region of the retina within ~4.5 seconds. Intensity differentiation based OMAG algorithm was used to extract 3-D retinal functional microvasculature information. Results Intensity signal differentiation generated capillary-level resolution en face OMAG images of the retina. The parafoveal capillaries were clearly visible, thereby allowing visualization of the foveal avascular zone (FAZ) in normal subjects. Conclusion The capability of OMAG to produce retinal vascular images was demonstrated using the ZEISS 1 µm SS-OCT prototype. This technique can potentially have clinical value for studying retinal vasculature abnormalities. PMID:25230403

  15. 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.

  16. In vivo imaging of the rodent eye with swept source/Fourier domain OCT

    PubMed Central

    Liu, Jonathan J.; Grulkowski, Ireneusz; Kraus, Martin F.; Potsaid, Benjamin; Lu, Chen D.; Baumann, Bernhard; Duker, Jay S.; Hornegger, Joachim; Fujimoto, James G.

    2013-01-01

    Swept source/Fourier domain OCT is demonstrated for in vivo imaging of the rodent eye. Using commercial swept laser technology, we developed a prototype OCT imaging system for small animal ocular imaging operating in the 1050 nm wavelength range at an axial scan rate of 100 kHz with ~6 µm axial resolution. The high imaging speed enables volumetric imaging with high axial scan densities, measuring high flow velocities in vessels, and repeated volumetric imaging over time. The 1050 nm wavelength light provides increased penetration into tissue compared to standard commercial OCT systems at 850 nm. The long imaging range enables multiple operating modes for imaging the retina, posterior eye, as well as anterior eye and full eye length. A registration algorithm using orthogonally scanned OCT volumetric data sets which can correct motion on a per A-scan basis is applied to compensate motion and merge motion corrected volumetric data for enhanced OCT image quality. Ultrahigh speed swept source OCT is a promising technique for imaging the rodent eye, proving comprehensive information on the cornea, anterior segment, lens, vitreous, posterior segment, retina and choroid. PMID:23412778

  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 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

  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. Swept source optical coherence microscopy using a Fourier domain mode-locked laser

    NASA Astrophysics Data System (ADS)

    Huang, Shu-Wei; Aguirre, Aaron D.; Huber, Robert A.; Adler, Desmond C.; Fujimoto, James G.

    2007-05-01

    Swept source optical coherence microscopy (OCM) enables cellular resolution en face imaging as well as integration with optical coherence tomography (OCT) cross sectional imaging. A buffered Fourier domain mode-locked (FDML) laser light source provides high speed, three dimensional imaging. Image resolutions of 1.6 µm × 8 µm (transverse × axial) with a 220 µm × 220 µm field of view and sensitivity higher than 98 dB are achieved. Three dimensional cellular imaging is demonstrated in vivo in the Xenopus laevis tadpole and ex vivo in the rat kidney and human colon.

  1. Comparison of dual rotating Scheimpflug-Placido, swept-source optical coherence tomography, and Placido-scanning-slit systems.

    PubMed

    Lee, Yong Woo; Choi, Chul Young; Yoon, Geun Young

    2015-05-01

    To compare measurements of corneal indices using dual rotating Scheimpflug-Placido, swept-source optical coherence tomography (OCT), and Placido-scanning-slit systems. Kangbuk Samsung Hospital, Seoul, South Korea. Prospective evaluation of diagnostic tests. Corneal topography measurements were performed using dual rotating Scheimpflug-Placido (Galilei G2), swept-source OCT (Casia SS-1000), and Placido-scanning-slit (Orbscan IIz) systems. The intraclass correlation coefficients (ICCs) and Bland-Altman plots were used to evaluate the agreement between measurements. Fifty post-refractive surgery eyes and 50 normal eyes were evaluated. The agreement in anterior keratometry and pachymetry between the 3 devices was high in both groups (ICC > 0.9). In both groups, the ICC values for posterior keratometry and eccentricity were high between the dual rotating Scheimpflug-Placido and swept-source OCT systems (ICC > 0.9) but not between the Placido-scanning-slit system and the other 2 systems. The Placido-scanning-slit system yielded much steeper values for posterior keratometry in both groups (P < .05). The ICC values for posterior corneal elevation were lower than 0.9 between all 3 devices. The dual rotating Scheimpflug-Placido and swept-source OCT systems showed relatively higher ICC values than the Placido-scanning-slit system in both groups. Maximum posterior elevations were highest with the Placido-scanning-slit system followed by the swept-source OCT system and then the dual rotating Scheimpflug-Placido system. Anterior keratometry obtained using 3 devices showed high degrees of agreement. Posterior keratometry and eccentricity showed greater agreement between the dual rotating Scheimpflug-Placido and swept-source OCT systems than with the Placido-scanning-slit system. The dual rotating Scheimpflug-Placido and swept-source OCT systems were equivalent in detecting the shape of the cornea and could be considered interchangeable. Copyright © 2015. Published by Elsevier

  2. DETECTION OF TREATMENT-NAIVE CHOROIDAL NEOVASCULARIZATION IN AGE-RELATED MACULAR DEGENERATION BY SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY.

    PubMed

    Ahmed, Daniel; Stattin, Martin; Graf, Alexandra; Forster, Julia; Glittenberg, Carl; Krebs, Ilse; Ansari-Shahrezaei, Siamak

    2017-09-04

    To compare the detection rate of choroidal neovascularization (CNV) in treatment-naive neovascular age-related macular degeneration by swept source optical coherence tomography angiography (SS-OCTA, Topcon's DRI Triton) working at 1,050 nm wavelength versus fluorescence angiography. Cross-sectional analysis of 156 eyes (107 neovascular age-related macular degeneration and 49 dry AMD) in 98 patients, previously diagnosed by multimodal imaging using fluorescein (FA) and indocyanine green angiography (Heidelberg's Spectralis) in a tertiary retina center, evaluated by SS-OCTA 4.5 mm × 4.5 mm and 6 mm × 6 mm macular cubes. Main outcome measures were sensitivity and specificity of SS-OCTA in AMD. Potential factors influencing CNV detection rate were analyzed. Swept source optical coherence tomography angiography detected CNV in 81 of 107 eyes, resulting in a sensitivity of 75.7%. In 49 eyes with dry AMD, no CNV could be identified (specificity 100%). A statistical significance was calculated for nondetection of treatment-naive CNV by SS-OCTA in pigment epithelial detachment over 400 μm (P = 0.0238). Topcon's SS-OCTA was not able to detect all CNV lesions. Large pigment epithelial detachments were associated with signal loss. Fluorescence angiography still remains the gold standard, but the tested SS-OCTA device can be considered as a feasible additional diagnostic tool in AMD.

  3. 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.

  4. 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.

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

    PubMed

    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.

  6. Swept-Source OCT Angiography Shows Sparing of the Choriocapillaris in Multiple Evanescent White Dot Syndrome.

    PubMed

    Yannuzzi, Nicolas A; Swaminathan, Swarup S; Zheng, Fang; Miller, Andrew; Gregori, Giovanni; Davis, Janet L; Rosenfeld, Philip J

    2017-01-01

    Two women with unilateral vision loss from multiple evanescent white dot syndrome were imaged serially with swept-source optical coherence tomography (SS-OCT). En face wide-field structural images revealed peripapillary outer photoreceptor disruption better than conventional fundus autofluorescence imaging. OCT angiography (OCTA) imaging showed preservation of flow within the retinal vasculature and choriocapillaris. As OCTA imaging of the choriocapillaris continues to evolve, these images may lay the groundwork for future investigation. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:69-74.].

  7. Phase and frequency dynamics of a short cavity swept-source OCT laser

    NASA Astrophysics Data System (ADS)

    Butler, T.; Goulding, D.; Slepneva, S.; O'Shaughnessy, B.; Kelleher, B.; Lyu, H.-C.; Hegarty, S. P.; Vladimirov, A. G.; Karnowski, K.; Wojtkowski, M.; Huyet, G.

    2015-03-01

    We analyse the dynamical behaviour of a short cavity OCT swept-source laser experimentally and theoretically. Mode-hopping, sliding frequency mode-locking and chaos are all observed during the laser sweep period. Hetero- dyne measurements of laser dynamics allows some insight into the behaviour of the laser, while interferometric techniques allow the full phase reconstruction of the laser electric field. A delay differential equation enables modelling of the laser output, and laser parameters can be altered to provide optimisation conditions for future laser designs.

  8. 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.

  9. High-speed swept source optical coherence Doppler tomography for deep brain microvascular imaging

    NASA Astrophysics Data System (ADS)

    Chen, Wei; You, Jiang; Gu, Xiaochun; Du, Congwu; Pan, Yingtian

    2016-12-01

    Noninvasive microvascular imaging using optical coherence Doppler tomography (ODT) has shown great promise in brain studies; however, high-speed microcirculatory imaging in deep brain remains an open quest. A high-speed 1.3 μm swept-source ODT (SS-ODT) system is reported which was based on a 200 kHz vertical-cavity-surface-emitting laser. Phase errors induced by sweep-trigger desynchronization were effectively reduced by spectral phase encoding and instantaneous correlation among the A-scans. Phantom studies have revealed a significant reduction in phase noise, thus an enhancement of minimally detectable flow down to 268.2 μm/s. Further in vivo validation was performed, in which 3D cerebral-blood-flow (CBF) networks in mouse brain over a large field-of-view (FOV: 8.5 × 5 × 3.2 mm3) was scanned through thinned skull. Results showed that fast flows up to 3 cm/s in pial vessels and minute flows down to 0.3 mm/s in arterioles or venules were readily detectable at depths down to 3.2 mm. Moreover, the dynamic changes of the CBF networks elicited by acute cocaine such as heterogeneous responses in various vessel compartments and at different cortical layers as well as transient ischemic events were tracked, suggesting the potential of SS-ODT for brain functional imaging that requires high flow sensitivity and dynamic range, fast frame rate and a large FOV to cover different brain regions.

  10. High-speed swept source optical coherence Doppler tomography for deep brain microvascular imaging

    PubMed Central

    Chen, Wei; You, Jiang; Gu, Xiaochun; Du, Congwu; Pan, Yingtian

    2016-01-01

    Noninvasive microvascular imaging using optical coherence Doppler tomography (ODT) has shown great promise in brain studies; however, high-speed microcirculatory imaging in deep brain remains an open quest. A high-speed 1.3 μm swept-source ODT (SS-ODT) system is reported which was based on a 200 kHz vertical-cavity-surface-emitting laser. Phase errors induced by sweep-trigger desynchronization were effectively reduced by spectral phase encoding and instantaneous correlation among the A-scans. Phantom studies have revealed a significant reduction in phase noise, thus an enhancement of minimally detectable flow down to 268.2 μm/s. Further in vivo validation was performed, in which 3D cerebral-blood-flow (CBF) networks in mouse brain over a large field-of-view (FOV: 8.5 × 5 × 3.2 mm3) was scanned through thinned skull. Results showed that fast flows up to 3 cm/s in pial vessels and minute flows down to 0.3 mm/s in arterioles or venules were readily detectable at depths down to 3.2 mm. Moreover, the dynamic changes of the CBF networks elicited by acute cocaine such as heterogeneous responses in various vessel compartments and at different cortical layers as well as transient ischemic events were tracked, suggesting the potential of SS-ODT for brain functional imaging that requires high flow sensitivity and dynamic range, fast frame rate and a large FOV to cover different brain regions. PMID:27934907

  11. Assessment of Choroidal Thickness in Healthy and Glaucomatous Eyes Using Swept Source Optical Coherence Tomography

    PubMed Central

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

    2014-01-01

    Purpose To evaluate choroidal thickness (CT) in healthy and glaucomatous eyes using Swept Source Optical Coherence Tomography (SS-OCT). Methods A cross-sectional observational study of 216 eyes of 140 subjects with glaucoma and 106 eyes of 67 healthy subjects enrolled in the Diagnostic Innovations in Glaucoma Study. CT was assessed from wide-field (12×9 mm) SS-OCT scans. The association between CT and potential confounding variables including age, gender, axial length, intraocular pressure, central corneal thickness and ocular perfusion pressure was examined using univariable and multivariable regression analyses. Results Overall CT was thinner in glaucomatous eyes with a mean (± standard deviation) of 157.7±48.5 µm in glaucoma compared to 179.9±36.1 µm in healthy eyes (P<0.001). The choroid was thinner in both the peripapillary and macular regions in glaucoma compared to controls. Mean peripapillary CT was 154.1±44.1 µm and 134.0±56.9 µm (P<0.001) and macular CT 199.3±46.1 µm and 176.2±57.5 µm (P<0.001) for healthy and glaucomatous eyes respectively. However, older age (P<0.001) and longer axial length (P<0.001) were also associated with thinner choroid and when differences in age and axial length between glaucomatous and healthy subjects were accounted for, glaucoma was not significantly associated with CT. There was also no association between glaucoma severity and CT. Conclusions Glaucoma was not associated with CT measured using SS-OCT; however, older age and longer axial length were associated with thinner choroid so should be considered when interpreting CT measurements. PMID:25295876

  12. 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.

  13. 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.

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

    PubMed Central

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

    2009-01-01

    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. PMID:19895102

  15. Detection of Apical Root Cracks Using Spectral Domain and Swept-source Optical Coherence Tomography.

    PubMed

    de Oliveira, Bruna Paloma; Câmara, Andréa Cruz; Duarte, Daniel Amancio; Gomes, Anderson Stevens Leonidas; Heck, Richard John; Antonino, Antonio Celso Dantas; Aguiar, Carlos Menezes

    2017-07-01

    This study aimed to evaluate the ability of 2 optical coherence tomographic (OCT) systems to detect apical dentinal microcracks. Twenty extracted human single-rooted mandibular incisors were selected. After root canal preparation with an R40 Reciproc file (VDW, Munich, Germany), the specimens presenting apical microcracks were identified using micro-computed tomographic (micro-CT) scanning as the gold standard. Then, the apical portions of the roots were imaged with spectral domain OCT (SD-OCT) and swept-source OCT systems, and the resulting images were blindly evaluated by 3 independent examiners to detect microcracks. The diagnostic performance of each OCT device was calculated, and statistical analysis was performed. Based on the micro-CT images, 12 (60%) roots presented dentinal microcracks in the apical region. The images generated by the OCT systems were able to show microcrack lines at the same location as the corresponding micro-CT cross sections. Although the diagnostic performance of the SD-OCT device was superior, there were no statistically significant differences between the 2 OCT devices (P > .05). Interexaminer agreement was substantial to almost perfect for the SD-OCT system and moderate to almost perfect for the swept-source OCT system, whereas intraexaminer agreement was substantial to almost perfect for both OCT devices. The detection ability verified for both OCT systems renders them promising tools for the diagnosis of apical microcracks. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  16. 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

  17. 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.

  18. 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

  19. Efficient sweep buffering in swept source optical coherence tomography using a fast optical switch

    PubMed Central

    Dhalla, Al-Hafeez; Shia, Kevin; Izatt, Joseph A.

    2012-01-01

    We describe a novel buffering technique for increasing the A-scan rate of swept source optical coherence tomography (SSOCT) systems employing low duty cycle swept source lasers. This technique differs from previously reported buffering techniques in that it employs a fast optical switch, capable of switching in 60 ns, instead of a fused fiber coupler at the end of the buffering stage, and is therefore appreciably more power efficient. The use of the switch also eliminates patient exposure to light that is not used for imaging that occurs at the end of the laser sweep, thereby increasing the system sensitivity. We also describe how careful management of polarization can remove undesirable artifacts due to polarization mode dispersion. In addition, we demonstrate how numerical compensation techniques can be used to modify the signal from a Mach-Zehnder interferometer (MZI) clock obtained from the original sweep to recalibrate the buffered sweep, thereby reducing the complexity of systems employing lasers with integrated MZI clocks. Combining these methods, we constructed an SSOCT system employing an Axsun technologies laser with a sweep rate of 100kHz and 6dB imaging range of 5.5mm. The sweep rate was doubled with sweep buffering to 200 kHz, and the imaging depth was extended to 9 mm using coherence revival. We demonstrated the feasibility of this system by acquiring images of the anterior segments and retinas of healthy human volunteers. PMID:23243559

  20. Full range line-field parallel swept source imaging utilizing digital refocusing

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    We present geometric optics-based refocusing applied to a novel off-axis line-field parallel swept source imaging (LPSI) system. LPSI is an imaging modality based on line-field swept source optical coherence tomography, which permits 3-D imaging at acquisition speeds of up to 1 MHz. The digital refocusing algorithm applies a defocus-correcting phase term to the Fourier representation of complex-valued interferometric image data, which is based on the geometrical optics information of the LPSI system. We introduce the off-axis LPSI system configuration, the digital refocusing algorithm and demonstrate the effectiveness of our method for refocusing volumetric images of technical and biological samples. An increase of effective in-focus depth range from 255 μm to 4.7 mm is achieved. The recovery of the full in-focus depth range might be especially valuable for future high-speed and high-resolution diagnostic applications of LPSI in ophthalmology.

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

    PubMed

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

    2012-03-01

    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.

  2. 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.

  3. Wide field and highly sensitive angiography based on optical coherence tomography with akinetic swept source

    PubMed Central

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

    2016-01-01

    Wide-field vascular visualization in bulk tissue that is of uneven surface is challenging due to the relatively short ranging distance and significant sensitivity fall-off for most current optical coherence tomography angiography (OCTA) systems. We report a long ranging and ultra-wide-field OCTA (UW-OCTA) system based on an akinetic swept laser. The narrow instantaneous linewidth of the swept source with its high phase stability, combined with high-speed detection in the system enable us to achieve long ranging (up to 46 mm) and almost negligible system sensitivity fall-off. To illustrate these advantages, we compare the basic system performances between conventional spectral domain OCTA and UW-OCTA systems and their functional imaging of microvascular networks in living tissues. In addition, we show that the UW-OCTA is capable of different depth-ranging of cerebral blood flow within entire brain in mice, and providing unprecedented blood perfusion map of human finger in vivo. We believe that the UW-OCTA system has promises to augment the existing clinical practice and explore new biomedical applications for OCT imaging. PMID:28101428

  4. 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

  5. Demonstration of depth-resolved wavefront sensing using a swept-source coherence-gated Shack-Hartmann wavefront sensor

    NASA Astrophysics Data System (ADS)

    Wang, Jingyu; Podoleanu, Adrian G.

    2015-03-01

    In this report we demonstrate results of measuring wavefront aberrations from different depths in a fabricated phantom using a coherence-gated Shack-Hartman wavefront sensing technique (CG-SH/WFS). The SH/WFS is equipped with a Mach-Zehnder interferometer and the coherence gate operates on principles of swept source (SS) interferometry. The CG-SH/WFS is able to differentiate wavefront signals from different depths separated by a depth resolution of 7.1 micron. The CG-SH/WFS delivers a similar SH spot pattern as that provided by a conventional SH/WFS. Due to the coherence gate, the sensor is capable of eliminating stray reflections. Hereby we present the results of measuring depth-resolved wavefront aberrations. The method is robust and all depth-resolved aberrations are recorded simultaneously without any mechanical movement. This technique has the potential of providing depth resolved correction in adaptive optics assisted ophthalmology imaging and in nonlinear microscopy.

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

    PubMed

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

    2015-06-01

    We present nnnnnin 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, 10(5) 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.

  7. 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.

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

    PubMed Central

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

    2015-01-01

    We present nnnnnin 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. PMID:25984290

  9. 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.

  10. A mechanical-free 150-kHz repetition swept light source incorporated a KTN electro-optic deflector

    NASA Astrophysics Data System (ADS)

    Yagi, Shogo; Naganuma, Kazunori; Imai, Tadayuki; Shibata, Yasuo; Ishibashi, Shigeo; Sasaki, Yuzo; Sasaura, Masahiro; Fujiura, Kazuo; Kato, Kazutoshi

    2011-03-01

    We present a new light source for the swept-source OCT, that is, an external-cavity LD incorporating an electro-optic deflector. We use a KTN deflector that is unique in being very fast and simultaneously providing an appreciable deflection caused by injected carriers. Particularly, high-speed and nearly linear to the applied voltage operation is attained when KTN crystal is pre-charged. Our 1.3-μm Littman-Metcalf external-cavity laser exhibits static linewidth < 0.1 nm, and a 110-nm scanning range up to 150-kHz under a +/-200 V sinusoidal driving voltage to the deflector. Being free of mechanical resonance, the laser would hopefully realize a faster (in a separate study, deflector itself worked up to 400 kHz) and wavenumber-linear scan that is ideal for the swept-source OCT by designing the waveform of driving voltage. And as for the resolving power of deflector, while our KTN deflector has only 35 spatial resolvable points, the number of wavelength points for the swept source clearly exceeds to this limit, which we attribute to line narrowing effect accompanied by the laser operation. Preliminary OCT images taken using the swept source are also presented.

  11. Scattering optical coherence angiography with 1-μm swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yasuno, Yoshiaki; Hong, Youngjoo; Makita, Shuichi; Akiba, Masahiro; Miura, Masahiro; Yatagai, Toyohiko

    2007-07-01

    Retinal and choroidal imaging by using swept-source optical coherence tomography (SS-OCT) with a 1-μm band probe light, and high-contrast and three-dimensional (3D) imaging of choroidal vasculature are presented. This SS-OCT has a measurement speed of 28,000 A-lines/s, a depth resolution of 10.4 μm in tissue, and a sensitivity of 99.3 dB. A software-based algorithm for scattering optical coherence angiography (S-OCA) is developed for the high-contrast and 3D imaging of the choroidal vessels. This OCT is employed for the investigation of age related macular degeneration and visualizes structures beneath the retinal pigment epithelial detachment.

  12. 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.

  13. 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.

  14. 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

  15. 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

  16. Quantitative optical inspection of contact lenses immersed in wet cell using swept source OCT.

    PubMed

    Karnowski, Karol; Grulkowski, Ireneusz; Mohan, Nishant; Cox, Ian; Wojtkowski, Maciej

    2014-08-15

    We demonstrate swept source optical coherence tomography (OCT) imaging of contact lenses (CLs) in a wet cell and comprehensive quantitative characterization of CLs from volumetric OCT datasets. The approach is based on a technique developed for lens autopositioning and autoleveling enabled by lateral capillary interactions between the wet cell wall and the lens floating on the liquid surface. The demonstrated OCT imaging has enhanced contrast due to the application of a scattering medium and it improves visualization of both CL interfaces and edges. We also present precise and accurate three-dimensional metrology of soft and rigid CLs based on the OCT data. The accuracy and precision of the extracted lens parameters are compared with the manufacturer's specifications. The presented methodology facilitates industrial inspection methods of the CLs.

  17. Endoscopic swept-source optical coherence tomography based on a two-axis microelectromechanical system mirror

    NASA Astrophysics Data System (ADS)

    Wang, Donglin; Fu, Linlai; Wang, Xin; Gong, Zhongjian; Samuelson, Sean; Duan, Can; Jia, Hongzhi; Ma, Jun Shan; Xie, Huikai

    2013-08-01

    A microelectromechanical system (MEMS) mirror based endoscopic swept-source optical coherence tomography (SS-OCT) system that can perform three-dimensional (3-D) imaging at high speed is reported. The key component enabling 3-D endoscopic imaging is a two-axis MEMS scanning mirror which has a 0.8×0.8 mm2 mirror plate and a 1.6×1.4 mm2 device footprint. The diameter of the endoscopic probe is only 3.5 mm. The imaging rate of the SS-OCT system is 50 frames/s. OCT images of both human suspicious oral leukoplakia tissue and normal buccal mucosa were taken in vivo and compared. The OCT imaging result agrees well with the histopathological analysis.

  18. 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.

  19. 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.

  20. Numerical correction of coherence gate in full-field swept-source interference microscopy.

    PubMed

    Grebenyuk, Anton A; Ryabukho, Vladimir P

    2012-07-01

    A big problem in low-coherence interference microscopy is the degradation of the coherence signal caused by shift of the angular and temporal spectrum gates. It limits the depth of field in confocal optical coherence microscopy and degrades images of sample inner structure in most interference microscopy techniques. To overcome this problem we propose numerical correction of the coherence gate in application to full-field swept-source interference microscopy. The proposed technique allows three-dimensional sample imaging without mechanical movement of the microscope components and is also capable of determining separately the geometrical thickness and the refractive index of the sample layers, when the sample contains a transversal pattern. The applicability of the proposed technique is verified with numerical simulation.

  1. 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.

  2. 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.

  3. CHOROIDAL STRUCTURAL CHANGES AND VASCULARITY INDEX IN STARGARDT DISEASE ON SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY.

    PubMed

    Ratra, Dhanashree; Tan, Roy; Jaishankar, Durgasri; Khandelwal, Neha; Gupta, Arushi; Chhablani, Jay; Agrawal, Rupesh

    2017-10-06

    To evaluate structural changes in the choroid of patients with Stargardt disease using swept source optical coherence tomography scans. A retrospective comparison cohort study was conducted on 39 patients with Stargardt disease, and on 25 age and gender matched-healthy controls. Subfoveal choroidal thickness (SFCT) was computed from the swept source optical coherence tomography machine, and the scans were binarized into luminal area and stromal areas, which were then used to derive choroidal vascularity index (CVI). Choroidal vascularity index and SFCT were analyzed independently using linear mixed effects model. There was no significant difference in SFCT between the 2 groups (347.20 ± 13.61 μm in Stargardt disease vs. 333.09 ± 18.96 μm in the control group, P = 0.548). There was a significant decrease in the CVI among eyes with Stargardt disease as compared with the normal eyes (62.51 ± 0.25% vs. 65.45 ± 0.29%, P < 0.001). There was a negative association between visual acuity and CVI (correlation coefficient = -0.75, P < 0.001) and a positive association between visual acuity and SFCT (correlation coefficient = 0.21, P = 0.035). Choroidal vascularity index appears to be a more robust tool compared with SFCT for choroidal changes in Stargardt disease. Choroidal vascularity index can possibly be used as a surrogate marker for disease monitoring. A decrease in CVI was associated with a decrease in visual function in eyes with Stargardt disease.

  4. Spectral phase-based automatic calibration scheme for swept source-based optical coherence tomography systems

    NASA Astrophysics Data System (ADS)

    Ratheesh, K. M.; Seah, L. K.; Murukeshan, V. M.

    2016-11-01

    The automatic calibration in Fourier-domain optical coherence tomography (FD-OCT) systems allows for high resolution imaging with precise depth ranging functionality in many complex imaging scenarios, such as microsurgery. However, the accuracy and speed of the existing automatic schemes are limited due to the functional approximations and iterative operations used in their procedures. In this paper, we present a new real-time automatic calibration scheme for swept source-based optical coherence tomography (SS-OCT) systems. The proposed automatic calibration can be performed during scanning operation and does not require an auxiliary interferometer for calibration signal generation and an additional channel for its acquisition. The proposed method makes use of the spectral component corresponding to the sample surface reflection as the calibration signal. The spectral phase function representing the non-linear sweeping characteristic of the frequency-swept laser source is determined from the calibration signal. The phase linearization with improved accuracy is achieved by normalization and rescaling of the obtained phase function. The fractional-time indices corresponding to the equidistantly spaced phase intervals are estimated directly from the resampling function and are used to resample the OCT signals. The proposed approach allows for precise calibration irrespective of the path length variation induced by the non-planar topography of the sample or galvo scanning. The conceived idea was illustrated using an in-house-developed SS-OCT system by considering the specular reflection from a mirror and other test samples. It was shown that the proposed method provides high-performance calibration in terms of axial resolution and sensitivity without increasing computational and hardware complexity.

  5. Demonstration of Shot-noise-limited Swept Source OCT Without Balanced Detection.

    PubMed

    Fathipour, Vala; Schmoll, Tilman; Bonakdar, Alireza; Wheaton, Skylar; Mohseni, Hooman

    2017-04-26

    Optical coherence tomography (OCT) has been utilized in a rapidly growing number of clinical and scientific applications. In particular, swept source OCT (SS-OCT) has attracted many attentions due to its excellent performance. So far however, the limitations of existing photon detectors have prevented achieving shot-noise-limited sensitivity without using balanced-detection scheme in SS-OCT, even when superconducting single-photon detectors were used. Unfortunately, balanced-detection increases OCT system size and cost, as it requires many additional components to boost the laser power and maintain near ideal balanced performance across the whole optical bandwidth. Here we show for the first time that a photon detector is capable of achieving shot noise limited performance without using the balanced-detection technique in SS-OCT. We built a system using a so-called electron-injection photodetector, with a cutoff-wavelength of 1700 nm. Our system achieves a shot-noise-limited sensitivity of about -105 dB at a reference laser power of ~350 nW, which is more than 30 times lower laser power compared with the best-reported results. The high sensitivity of the electron-injection detector allows utilization of micron-scale tunable laser sources (e.g. VCSEL) and eliminates the need for fiber amplifiers and highly precise couplers, which are an essential part of the conventional SS-OCT systems.

  6. 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

  7. Imaging of the Lamina Cribrosa using Swept-Source Optical Coherence Tomography.

    PubMed

    Nuyen, Brenda; Mansouri, Kaweh; N Weinreb, Robert

    2012-01-01

    The lamina cribrosa (LC) is the presumed site of axonal injury in glaucoma. Its deformation has been suggested to contribute to optic neuropathy by impeding axoplasmic flow within the optic nerve fibers, leading to apoptosis of retinal ganglion cells. To visualize the LC in vivo, optical coherence tomography (OCT) has been applied. Spectral domain (SD)-OCT, used in conjunction with recently introduced enhanced depth imaging (EDI)-OCT, has improved visualization of deeper ocular layers, but in many individuals it is still limited by inadequate resolution, poor image contrast and insufficient depth penetrance. The posterior laminar surface especially is not viewed clearly using these methods. New generation high-penetration (HP)-OCTs, also known as swept-source (SS)-OCT, are capable to evaluate the choroid in vivo to a remarkable level of detail. SS-OCTs use a longer wavelength (1,050 nm instead of 840 nm) compared to the conventional techniques. We review current knowledge of the LC, findings from trials that use SD-OCT and EDI-OCT, and our experience with a prototype SS-OCT to visualize the LC in its entirety. Key Points What is known? •     The LC is the presumed site of axonal injury in glaucoma •     Compared to spectral domain-OCT, enhanced depth imaging-OCT improves imaging of the LC •     Even so, currently used SD-OCT techniques are restricted by poor wavelength penetrance of the deeper ocular layers What our findings add? •    SS-OCT may be a superior imaging modality for deep ocular structures •    Prior studies used SS-OCT to evaluate choroidal thickness in both healthy and 'normal tension glaucoma' eyes •    SS-OCT enables good evaluation of three-dimension (3D) lamina cribrosa morphology. How to cite this article: Nuyen B, Mansouri K, Weinreb RN. Imaging of the Lamina Cribrosa using Swept-Source Optical Coherence Tomography. J Current Glau Prac 2012;6(3): 113-119.

  8. Corneal thickness and elevation measurements using swept-source optical coherence tomography and slit scanning topography in normal and keratoconic eyes.

    PubMed

    Jhanji, Vishal; Yang, Bingzhi; Yu, Marco; Ye, Cong; Leung, Christopher K S

    2013-11-01

    To compare corneal thickness and corneal elevation using swept source optical coherence tomography and slit scanning topography. Prospective study. 41 normal and 46 keratoconus subjects. All eyes were imaged using swept source optical coherence tomography and slit scanning tomography during the same visit. Mean corneal thickness and best-fit sphere measurements were compared between the instruments. Agreement of measurements between swept source optical coherence tomography and scanning slit topography was analyzed. Intra-rater reproducibility coefficient and intraclass correlation coefficient were evaluated. In normal eyes, central corneal thickness measured by swept source optical coherence tomography was thinner compared with slit scanning topography (p < 0.0001) and ultrasound pachymetry (p = < .0001). Ultrasound pachymetry readings had better 95% limits of agreement with swept source optical coherence tomography than slit scanning topography. In keratoconus eyes, central corneal thickness was thinner on swept source optical coherence tomography than slit scanning topography (p = 0.081) and ultrasound pachymetry (p = 0.001). There were significant differences between thinnest corneal thickness, and, anterior and posterior best-fit sphere measurements between both instruments (p < 0.05 for all). Overall, reproducibility coefficients and intraclass correlation coefficients were significantly better with swept source optical coherence tomography for measurement of central corneal thickness, anterior best-fit sphere and, posterior best-fit sphere (all p < 0.001). Corneal thickness and elevation measurements were significantly different between swept source optical coherence tomography and slit scanning topography. With better reproducibility coefficients and intraclass correlation coefficients, swept source optical coherence tomography may provide a reliable alternative for measurement of corneal parameters. © 2013 The Authors. Clinical

  9. 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

  10. A viscous/potential flow interaction analysis method for multi-element infinite swept wings, volume 1

    NASA Technical Reports Server (NTRS)

    Dvorak, F. A.; Woodward, F. A.

    1974-01-01

    An analysis method and computer program have been developed for the calculation of the viscosity dependent aerodynamic characteristics of multi-element infinite swept wings in incompressible flow. The wing configuration consisting at the most of a slat, a main element and double slotted flap is represented in the method by a large number of panels. The inviscid pressure distribution about a given configuration in the normal chord direction is determined using a two dimensional potential flow program employing a vortex lattice technique. The boundary layer development over each individual element of the high lift configuration is determined using either integral or finite difference boundary layer techniques. A source distribution is then determined as a function of the calculated boundary layer displacement thickness and pressure distributions. This source distribution is included in the second calculation of the potential flow about the configuration. Once the solution has converged (usually after 2-5 iterations between the potential flow and boundary layer calculations) lift, drag, and pitching moments can be determined as functions of Reynolds number.

  11. 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.

  12. Development of phase-stabilized swept-source OCT for the ultrasensitive quantification of microbubbles

    NASA Astrophysics Data System (ADS)

    Manapuram, R. K.; Manne, V. G. R.; Larin, K. V.

    2008-09-01

    This paper describes the development of a novel-phase resolved system based on swept-source optical-coherence tomography (SSOCT) for the ultrasensitive imaging and monitoring of gas microbubbles in aqueous media. The developed phase-stabilized SSOCT (PhS-SSOCT) system has an axial resolution of 10 μm, a phase sensitivity of 0.03 rad, an imaging depth of up to 6 mm in air, and a scanning speed of 20 kHz for a single A line. The performance of the sensing system was evaluated in water-containing gas microbubbles with a different diameter. The obtained results demonstrate that bubbles with a diameter greater than 10 μm could be detected by both structural imaging and phase response, whereas bubbles with diameters of less than 10 μm could be detected by the phase response of the SSOCT with a high sensitivity. The accuracy for the measurement of the diameter of gas microbubbles is limited to 10 μm in structural imaging and 0.01 μm in phase-sensitive monitoring. The results from this study indicate that PhS-SSOCT could be used to detect fast-moving microbubbles in aqueous solutions and ultimately could be applied for rapid assessment in biofluids (e.g., blood) and tissues (e.g., skin) in vivo.

  13. 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

  14. 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)

  15. 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".

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

    PubMed Central

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

    2015-01-01

    Abstract. 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. PMID:26662065

  17. Volumetric Measurement of Optic Nerve Head Drusen Using Swept-Source Optical Coherence Tomography.

    PubMed

    Tsikata, Edem; Vercellin Verticchio, Alice C; Falkenstein, Iryna; Poon, Linda Yi-Chieh; Brauner, Stacey; Khoueir, Ziad; Miller, John B; Chen, Teresa C

    2017-09-01

    To describe new software tools for quantifying optic nerve head drusen volume using 3-dimensional (3D) swept-source optical coherence tomography (SS-OCT) volumetric scans. SS-OCT was used to acquire raster volume scans of 8 eyes of 4 patients with bilateral optic nerve head drusen. The scans were manually segmented by 3 graders to identify the drusen borders, and thereafter total drusen volumes were calculated. Linear regression was performed to study the relationships between drusen volume, retinal nerve fiber layer thickness, and Humphrey visual field mean deviation. In the 8 study eyes, drusen volumes ranged between 0.24 to 1.05 mm. Visual field mean deviation decreased by ∼20 dB per cubic millimeter increase in drusen volume, and the coefficient of correlation of the linear regression was 0.92. In this small patient series, visual field defects were detected when drusen volume was larger than about 0.2 mm. Software tools have been developed to quantify the size of OHND using SS-OCT volume scans.

  18. All-semiconductor high-speed akinetic swept-source for OCT

    NASA Astrophysics Data System (ADS)

    Minneman, Michael P.; Ensher, Jason; Crawford, Michael; Derickson, Dennis

    2011-12-01

    A novel swept-wavelength laser for optical coherence tomography (OCT) using a monolithic semiconductor device with no moving parts is presented. The laser is a Vernier-Tuned Distributed Bragg Reflector (VT-DBR) structure exhibiting a single longitudinal mode. All-electronic wavelength tuning is achieved at a 200 kHz sweep repetition rate, 20 mW output power, over 100 nm sweep width and coherence length longer than 40 mm. OCT point-spread functions with 45- 55 dB dynamic range are demonstrated; lasers at 1550 nm, and now 1310 nm, have been developed. Because the laser's long-term tuning stability allows for electronic sample trigger generation at equal k-space intervals (electronic k-clock), the laser does not need an external optical k-clock for measurement interferometer sampling. The non-resonant, allelectronic tuning allows for continuously adjustable sweep repetition rates from mHz to 100s of kHz. Repetition rate duty cycles are continuously adjustable from single-trigger sweeps to over 99% duty cycle. The source includes a monolithically integrated power leveling feature allowing flat or Gaussian power vs. wavelength profiles. Laser fabrication is based on reliable semiconductor wafer-scale processes, leading to low and rapidly decreasing cost of manufacture.

  19. All fiber optics circular-state swept source polarization-sensitive optical coherence tomography.

    PubMed

    Lin, Hermann; Kao, Meng-Chun; Lai, Chih-Ming; Huang, Jyun-Cin; Kuo, Wen-Chuan

    2014-02-01

    A swept source (SS)-based circular-state (CS) polarization-sensitive optical coherence tomography (PS-OCT) constructed entirely with polarization-maintaining fiber optics components is proposed with the experimental verification. By means of the proposed calibration scheme, bulk quarter-wave plates can be replaced by fiber optics polarization controllers to, therefore, realize an all-fiber optics CS SSPS-OCT. We also present a numerical dispersion compensation method, which can not only enhance the axial resolution, but also improve the signal-to-noise ratio of the images. We demonstrate that this compact and portable CS SSPS-OCT system with an accuracy comparable to bulk optics systems requires less stringent lens alignment and can possibly serve as a technology to realize PS-OCT instrument for clinical applications (e.g., endoscopy). The largest deviations in the phase retardation (PR) and fast-axis (FA) angle due to sample probe in the linear scanning and a rotation angle smaller than 65 deg were of the same order as those in stationary probe setups. The influence of fiber bending on the measured PR and FA is also investigated. The largest deviations of the PR were 3.5 deg and the measured FA change by ~12 to 21 deg. Finally, in vivo imaging of the human fingertip and nail was successfully demonstrated with a linear scanning probe.

  20. Extended focus high-speed swept source OCT with self-reconstructive illumination.

    PubMed

    Blatter, Cedric; Grajciar, Branislav; Eigenwillig, Christoph M; Wieser, Wolfgang; Biedermann, Benjamin R; Huber, Robert; Leitgeb, Rainer A

    2011-06-20

    We present a Bessel beam illumination FDOCT setup using a FDML Swept Source at 1300 nm with up to 440 kHz A-scan rate, and discuss its advantages for structural and functional imaging of highly scattering samples. An extended focus is achieved due to the Bessel beam that preserves its lateral extend over a large depth range. Furthermore, Bessel beams exhibit a self-reconstruction property that allows imaging even behind obstacles such as hairs on skin. Decoupling the illumination from the gaussian detection increases the global sensitivity and enables dark field imaging. Dark field imaging is useful to avoid strong reflexes from the sample surface that adversely affect the sensitivity due to the limited dynamic range of high speed 8 bit acquisition cards. In addition the possibility of contrasting capillaries with high sensitivity is shown, using inter-B-scan speckle variance analysis. We demonstrate intrinsic advantages of the extended focus configuration, in particular the reduction of the phase decorrelation effect below vessels leading to improved axial vessel definition.

  1. 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

  2. Using swept source optical coherence tomography to monitor wound healing in tissue engineered skin

    NASA Astrophysics Data System (ADS)

    Smith, L. E.; Lu, Z.; Bonesi, M.; Smallwood, R.; Matcher, S. J.; MacNeil, S.

    2010-02-01

    There is an increasing need for a robust simple to use non-invasive imaging technology for monitoring tissue engineered constructs as they develop. We have applied optical coherence tomography (OCT), a relatively new optical technique, to image tissue engineered constructs. Our aim was to evaluate the use of swept-source optical coherence tomography (SSOCT) to non-invasively image reconstructed skin as it developed over several weeks. The epidermis of the reconstructed skin was readily distinguished from the neodermis when examined with standard histology - a destructive imaging technique - of samples. The development of reconstructed skin based on deepithelialised acellular dermis (DED) was accurately monitored with SS-OCT over three weeks and confirmed with conventional histology. It was also possible to image changes in the epidermis due to the presence of melanoma and the healing of these 3D models after wounding with a scalpel, with or without the addition of a fibrin clot. SS-OCT is proving to be a valuable tool in tissue engineering, showing great promise for the non-invasive imaging of optically turbid tissue engineered constructs, including tissue engineered skin.

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

    PubMed Central

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

    2016-01-01

    Abstract. 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 (p<0.05). 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

  4. Robust numerical phase stabilization for long-range swept-source optical coherence tomography.

    PubMed

    Song, Shaozhen; Xu, Jingjiang; Men, Shaojie; Shen, Tueng T; Wang, Ruikang K

    2017-05-09

    A novel phase stabilization technique is demonstrated with significant improvement in the phase stability of a micro-electromechanical (MEMS) vertical cavity surface-emitting laser (VCSEL) based swept-source optical coherence tomography (SS-OCT) system. Without any requirements of hardware modifications, the new fully numerical phase stabilization technique features high tolerance to acquisition jitter, and significantly reduced budget in computational effort. We demonstrate that when measured with biological tissue, this technique enables a phase sensitivity of 89 mrad in highly scattering tissue, with image ranging distance of up to 12.5 mm at A-line scan rate of 100.3 kHz. We further compare the performances delivered by the phase-stabilization approach with conventional numerical approach for accuracy and computational efficiency. Imaging result of complex signal-based optical coherence tomography angiography (OCTA) and Doppler OCTA indicate that the proposed phase stabilization technique is robust, and efficient in improving the image contrast-to-noise ratio and extending OCTA depth range. The proposed technique can be universally applied to improve phase-stability in generic SS-OCT with different scale of scan rates without a need for special treatment. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. 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.

  6. Wide field OCT angiography by using swept source OCT in living human eye

    NASA Astrophysics Data System (ADS)

    Zhang, Qinqin; Chen, Chieh-Li; Chu, Zhongdi; Wang, Ruikang K.

    2017-02-01

    To investigate the application of wide field OCT angiography (OCTA) in living human eye. Normal and pathologic eyes were recruited and imaged by a 1060 nm swept source OCTA system with A-line speed of 100 kHz provided by Carl Zeiss Meditec. Inc.. Wide field OCTA images were generated in a single scan within 5 seconds based on the tracking capability installed in the system with 9 x 9 mm2 and 12 x 12 mm2 field of view and sampled by 500 A-lines x 500 Bframes with 2 repetitions in the same location for one 3D data. Complex optical microangiography (OMAG) algorithm was used to extract the blood flow information. The en face maximum projection provided by the device was used to generate 2-dimensional angiograms of different layers and color-code images. Wide field en face OCTA images of different macular diseases showed a great agreement with fluorescein angiography (FA). Meanwhile, OCTA provides depth-resolved information and detailed vascular images of venous occlusion and DR patients in far peripheral region, and choroidal vessels imaging in serpiginous choroidopathy patient, providing a better visualization of vascular network compared to FA.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Non-contact investigation of the corneal biomechanics with air-puff swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Maczynska, Ewa; Karnowski, Karol; Kaluzny, Bartlomiej; Grulkowski, Ireneusz; Wojtkowski, Maciej

    2016-08-01

    In this paper, we use swept source optical coherence tomography combined with air-puff module (air-puff SS-OCT) to investigate the properties of the cornea. During OCT measurement the cornea was stimulated by short, air pulse, and corneal response was recorded. In this preliminary study, the air-puff SS-OCT instrument was applied to measure behavior of the porcine corneas under varied, well-controlled intraocular pressure conditions. Additionally, the biomechanical response of the corneal tissue before, during and after crosslinking procedure (CXL) was assessed. Air-puff swept source OCT is a promising tool to extract information about corneal behavior as well as to monitor and assess the effect of CXL.

  16. In vivo imaging of cortical vitreous using 1050-nm swept-source deep range imaging optical coherence tomography.

    PubMed

    Stanga, Paulo E; Sala-Puigdollers, Anna; Caputo, Silvestro; Jaberansari, Hojr; Cien, Monica; Gray, Jane; D'Souza, Yvonne; Charles, Stephen J; Biswas, Susmito; Henson, David B; McLeod, David

    2014-02-01

    To image the cortical vitreous, determine the prevalence of the bursa premacularis and space of Martegiani, and measure the dimensions of the bursa using the new 1050-nm swept-source deep range imaging optical coherence tomography (DRI OCT-1 Atlantis). Retrospective cross-sectional study. One hundred and nineteen consecutive patients (5-100 years) underwent an OCT scan using 1050-nm swept-source deep range imaging optical coherence tomography. Prevalence of the bursa premacularis and space of Martegiani and the stage of posterior vitreous detachment (PVD) were determined. The horizontal (width) and anteroposterior (depth) dimensions of the bursa were recorded along with the patient's age. A bursa was detected in 57.1% (136/238) of eyes. The bursa and space of Martegiani coexisted in 97.8% of eyes. Prevalence of detected bursa was 84.5% in eyes with either no PVD or perifoveal PVD only; the prevalence fell with further increases in the extent of PVD. Prevalence of detected bursa was 75.4% in patient group aged 0-60 years and 38% in the group aged 60-100 years. Mean width was 7001 μm (range: 3354-10 316 μm, SD: 1412 μm). Mean depth was 416 μm (range: 31-1189 μm, SD: 187 μm). Width and depth of the bursa did not correlate with age (R(2) width = 0.0316; R(2) depth = 0.0108). Bilateral bursa tended to be symmetrical in width but less so in depth (R(2) width = 0.63, P < .001; R(2) depth = 0.33, P < .001). Swept-source OCT has allowed us to demonstrate the almost invariable coexistence of the bursa premacularis and space of Martegiani. Swept-source OCT can image both in patients from as early as the first to as late as the tenth decade of life. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Asymmetry Analysis of Macular Inner Retinal Layers for Glaucoma Diagnosis: Swept-Source Optical Coherence Tomography Study

    PubMed Central

    Lee, Sang-Yoon; Lee, Eun Kyoung; Park, Ki Ho; Kim, Dong Myung

    2016-01-01

    Purpose To report an asymmetry analysis of macular inner retinal layers using swept-source optical coherence tomography (OCT) and to evaluate the utility for glaucoma diagnosis. Design Observational, cross-sectional study. Participants Seventy normal healthy subjects and 62 glaucoma patients. Methods Three-dimensional scans were acquired from 70 normal subjects and 62 open angle glaucoma patients by swept-source OCT. The thickness of the retinal nerve fiber layer, ganglion cell-inner plexiform layer (GCIPL), ganglion cell complex, and total retina were calculated within a 6.2×6.2 mm macular area divided into a 31×31 grid of 200×200 μm superpixels. For each of the corresponding superpixels, the thickness differences between the subject eyes and contra-lateral eyes and between the upper and lower macula halves of the subject eyes were determined. The negative differences were displayed on a gray-scale asymmetry map. Black superpixels were defined as thickness decreases over the cut-off values. Results The negative inter-ocular and inter-hemisphere differences in GCIPL thickness (mean ± standard deviation) were -2.78 ± 0.97 μm and -3.43 ± 0.71 μm in the normal group and -4.26 ± 2.23 μm and -4.88 ± 1.46 μm in the glaucoma group. The overall extent of the four layers’ thickness decrease was larger in the glaucoma group than in the normal group (all Ps<0.05). The numbers of black superpixels on all of the asymmetry maps were larger in the glaucoma group than in the normal group (all Ps<0.05). The area under receiver operating characteristic curves of average negative thickness differences in macular inner layers for glaucoma diagnosis ranged from 0.748 to 0.894. Conclusions The asymmetry analysis of macular inner retinal layers showed significant differences between the normal and glaucoma groups. The diagnostic performance of the asymmetry analysis was comparable to that of previous methods. These findings suggest that the asymmetry analysis can be a

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  2. Estimation of lesion progress in artificial root caries by swept source optical coherence tomography in comparison to transverse microradiography

    NASA Astrophysics Data System (ADS)

    Natsume, Yuko; Nakashima, Syozi; Sadr, Alireza; Shimada, Yasushi; Tagami, Junji; Sumi, Yasunori

    2011-07-01

    This study aimed to investigate whether swept source optical coherence tomography (SS-OCT) could estimate the lesion depth and mineral loss quantitatively without the use of polarization sensitivity, and to examine a relationship between OCT data and transverse microradiography (TMR) lesion parameters. Twenty-four bovine root dentin specimens were allocated to three groups of 4-, 7-, and 14-day demineralization. Cross-sectional images of the specimens before and after the demineralization were captured by OCT at 1319 nm center wavelength. Following the demineralization, these specimens were cut into sections for TMR analysis. Correlations between the OCT data and TMR lesion parameters were examined. TMR images of the specimens showed cavitated lesions (lesion depth or LDTMR: 200 to 500 μm, ΔZ or mineral loss: 10,000 to 30,000 vol % μm). The OCT images showed ``boundaries,'' suggesting the lesion front. Integrated dB values before and after the demineralization and their difference (RD, RS, and ΔR, respectively) were calculated from the lesion surface to the corrected depth of boundary (LDOCT). A statistically significant correlation was found between LDOCT and LDTMR (p < 0.05, r = 0.68). Similarly, statistically significant correlations were found between ΔZ and RD or ΔR. The OCT showed a potential for quantitative estimation of lesion depth and mineral loss with cavitated dentin lesions in vitro.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. In Vivo Identification of the Posttrabecular Aqueous Outflow Pathway Using Swept-Source Optical Coherence Tomography.

    PubMed

    Uji, Akihito; Muraoka, Yuki; Yoshimura, Nagahisa

    2016-08-01

    The purpose of this study was to investigate a novel imaging technique to identify the continuous posttrabecular aqueous outflow pathway from a single B-scan, using swept-source optical coherence tomography (SS-OCT). Three-dimensional volume scans of the temporal or nasal side of the anterior segment area at the limbus were acquired from 11 eyes of 11 healthy subjects, using SS-OCT. The aqueous outflow pathway was identified using an en face OCT image and reconstructed images of the vasculature (vasculature map). Delineation of the whole aqueous outflow pathway in a single B-scan was accomplished by reslicing the volume scan. The posttrabecular aqueous outflow pathway was successfully identified in 10 eyes (90.9%). Combined with a flattening technique, the en face video and vasculature map showed a clear blood stream that could not be observed on a sequential stack of B-scans. In the en face images, the vessels were widely branched in the episclera venous plexus, perpendicularly penetrating the scleral stroma. Vessels running parallel to Schlemm's canal and the collector channels were observed in the deeper region of the sclera. The average longitudinal diameter of the vessel was 29.7 ± 6.6 μm at the episcleral venous plexus, and it was significantly larger than that in the deep scleral aqueous plexus (22.0 ± 4.8 μm; P = 0.0002). The continuous posttrabecular aqueous outflow pathway could be identified from a single B-scan and quantitatively analyzed using SS-OCT with en face imaging and volume scan reslicing.

  10. En face mode of swept-source optical coherence tomography in circumscribed choroidal haemangioma.

    PubMed

    Flores-Moreno, Ignacio; Caminal, Josep M; Arias-Barquet, Luis; Rubio-Caso, Marcos J; Catala-Mora, Jaume; Vidal-Martí, María; Muñoz-Blanco, Alex; Filloy, Alejandro; Ruiz-Moreno, José M; Duker, Jay S; Arruga, Jorge

    2016-03-01

    To describe the findings in circumscribed choroidal haemangioma (CCH) using en face swept-source optical coherence tomography (SS-OCT). En face images were obtained employing DRI-1 Atlantis OCT (Topcon, Tokyo, Japan), using a three-dimensional volumetric scan of 12×9 mm. Images were obtained from the retinal pigment epithelium to 1000 μm in depth of the tumour. Twenty-two eyes from 22 patients with the clinical diagnosis of CCH were included. In 20 eyes (90.9%), a characteristic pattern was visualised in the en face image across the vascular tumour. A multilobular pattern, similar to a honeycomb, with hyporeflective, confluent, oval or round areas corresponding with the lumen of the tumour vascular spaces, and hyper-reflective zones, which may represent the vessels walls and connective tissue of the tumour. Ten eyes (45.4%) showed a hyper-reflective halo surrounding the tumour. Seventeen tumours (77.2%) showed small diameter vessels at the inner zone and larger vessels in the outer area. Twelve patients (54.5%) had previously received treatment (photodynamic therapy, transpupillary thermotherapy, dexamethasone intravitreal implant or brachytherapy with ruthenium-106). No differences were found between treated and untreated patients in any of the measured parameters. En face SS-OCT is a rapid, non-invasive, high-resolution, technology, which allows a complementary study to cross-sectional scans in CCH. A characteristic multilobular pattern, with a hyper-reflective halo surrounding the tumour, was found in en face SS-OCT images. No morphological differences were found between naïve patients and patients who received previous treatment. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  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. 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.

  13. Choroidal Thickness in 3001 Chinese Children Aged 6 to 19 Years Using Swept-Source OCT

    PubMed Central

    Xiong, Shuyu; He, Xiangui; Deng, Junjie; Lv, Minzhi; Jin, Jiali; Sun, Sifei; Yao, Chunxia; Zhu, Jianfeng; Zou, Haidong; Xu, Xun

    2017-01-01

    The purpose of the cross-sectional study is to describe the values and distribution of choroidal thickness and to explore its related factors, especially age, in Chinese children. A total of 3001 Chinese school children aged 6 to 19 years underwent comprehensive ophthalmic examinations, including axial length and cycloplegic refraction. Choroidal thickness was measured by swept-source optical coherence tomography (SS-OCT). There was a greater difference in the more central regions between the myopes and emmetropes. Multiple regression analysis was performed to determine the associated factors of choroidal thickness. The results demonstrated that age was independently positively related to choroidal thickness for emmetropes (β = 3.859, p < 0.001), and mild myopes with spherical equivalent greater than −2.00 D (−1.25 D < spherical equivalent ≤ −0.50 D: β = 3.476, p = 0.006; −2.00 D < spherical equivalent ≤ −1.25 D: β = 3.232, p = 0.020). However, no significant relationship between age and choroidal thickness was found in children with spherical equivalent ≤ −2.00 D, suggesting that the protective effect of physiologic choroidal growth with age against rapid axial elongation disappeared while axial elongation becomes the dominant determinant of choroidal thickness among children with myopia worse than −2.00 D. PMID:28327553

  14. 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.

  15. Single-mode 140 nm swept light source realized by using SSG-DBR lasers

    NASA Astrophysics Data System (ADS)

    Fujiwara, N.; Yoshimura, R.; Kato, K.; Ishii, H.; Kano, F.; Kawaguchi, Y.; Kondo, Y.; Ohbayashi, K.; Oohashi, H.

    2008-02-01

    We demonstrate a single-mode and fast wavelength swept light source by using Superestrucuture grating distributed Bragg reflector (SSG-DBR) lasers for use in optical frequency-domain reflectometry optical coherence tomography. The SSG-DBR lasers provide single-mode operation resulting in high coherency. Response of the wavelength tuning is very fast; several nanoseconds, but there was an unintentional wavelength drift resulting from a thermal drift due to injecting tuning current. The dri1ft unfortunately requires long time to converge; more than a few milliseconds. For suppressing the wavelength drift, we introduced Thermal Drift Compensation mesa (TDC) parallel to the laser mesa with the spacing of 20 μm. By controlling TDC current to satisfy the total electric power injected into both the laser mesa and the TDC mesa, the thermal drift can be suppressed. In the present work, we fabricated 4 wavelength's kinds of SSG-DBR laser, which covers respective wavelength band; S-band (1496-1529 nm), C-band (1529-1564 nm), L --band (1564-1601 nm), and L +-band (1601-1639). We set the frequency channel of each laser with the spacing 6.25 GHz and 700 channels. The total frequency channel number is 2800 channels (700 ch × 4 lasers). We simultaneously operated the 4 lasers with a time interval of 500 ns/channel. A wavelength tuning range of more than 140 nm was achieved within 350 μs. The output power was controlled to be 10 mW for all channels. A single-mode, accurate, wide, and fast wavelength sweep was demonstrated with the SSG-DBR lasers having TDC mesa structure for the first time.

  16. 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

  17. Evaluation of Anterior Chamber Volume in Cataract Patients with Swept-Source Optical Coherence Tomography

    PubMed Central

    He, Wenwen; Zhu, Xiangjia; Wolff, Don; Sun, Xinghuai

    2016-01-01

    Purpose. To evaluate the anterior chamber volume in cataract patients with Swept-Source Optical Coherence Tomography (SS-OCT) and its influencing factors. Methods. Anterior chamber volume of 92 cataract patients was evaluated with SS-OCT in this cross-sectional study. Univariate analyses and multiple linear regression were used to investigate gender, age, operated eye, posterior vitreous detachment, lens opacity grading, and axial length (AXL) related variables capable of influencing the ACV. Results. The average ACV was 139.80 ± 38.21 mm3 (range 59.41 to 254.09 mm3). The average ACV was significantly larger in male patients than in female patients (P = 0.001). ACV was negatively correlated with age and LOCS III cortical (C) grading of the lens (Pearson's correlation analysis, r = −0.443, P < 0.001, and Spearman's correlation analysis, ρ = −0.450, P < 0.001). ACV was also increased with AXL (Pearson's correlation analysis, r = 0.552, P < 0.001). Multiple linear regression showed that, with all of the covariates entered into the model, gender (P = 0.002), age (P = 0.015), LOCS III C grade (P = 0.043), and AXL (P = 0.001) were still associated with ACV (F = 10.252  P < 0.001  R2 = 0.498). Conclusion. With SS-OCT, we found that, in healthy cataract patients, ACV varied significantly among different subjects. Influencing factors that contribute to reduced ACV were female gender, increased age, LOCS III C grade, and shorter AXL. PMID:27688910

  18. Evaluation of Anterior Chamber Volume in Cataract Patients with Swept-Source Optical Coherence Tomography.

    PubMed

    He, Wenwen; Zhu, Xiangjia; Wolff, Don; Zhao, Zhennan; Sun, Xinghuai; Lu, Yi

    2016-01-01

    Purpose. To evaluate the anterior chamber volume in cataract patients with Swept-Source Optical Coherence Tomography (SS-OCT) and its influencing factors. Methods. Anterior chamber volume of 92 cataract patients was evaluated with SS-OCT in this cross-sectional study. Univariate analyses and multiple linear regression were used to investigate gender, age, operated eye, posterior vitreous detachment, lens opacity grading, and axial length (AXL) related variables capable of influencing the ACV. Results. The average ACV was 139.80 ± 38.21 mm(3) (range 59.41 to 254.09 mm(3)). The average ACV was significantly larger in male patients than in female patients (P = 0.001). ACV was negatively correlated with age and LOCS III cortical (C) grading of the lens (Pearson's correlation analysis, r = -0.443, P < 0.001, and Spearman's correlation analysis, ρ = -0.450, P < 0.001). ACV was also increased with AXL (Pearson's correlation analysis, r = 0.552, P < 0.001). Multiple linear regression showed that, with all of the covariates entered into the model, gender (P = 0.002), age (P = 0.015), LOCS III C grade (P = 0.043), and AXL (P = 0.001) were still associated with ACV (F = 10.252  P < 0.001  R (2) = 0.498). Conclusion. With SS-OCT, we found that, in healthy cataract patients, ACV varied significantly among different subjects. Influencing factors that contribute to reduced ACV were female gender, increased age, LOCS III C grade, and shorter AXL.

  19. 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.

  20. 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.

  1. Assessment of choroidal topographic changes by swept source optical coherence tomography after photodynamic therapy for central serous chorioretinopathy.

    PubMed

    Razavi, Sam; Souied, Eric H; Cavallero, Edoardo; Weber, Michel; Querques, Giuseppe

    2014-04-01

    To investigate the relationship between choroidal thickness and angiographic abnormalities in central serous chorioretinopathy (CSC) eyes by swept-source optical coherence tomography (swept-OCT), before and after half-fluence photodynamic therapy (PDT). Prospective interventional case series. Consecutive patients presenting with treatment-naive active CSC underwent a complete ophthalmologic examination, including swept-OCT at study entry and at 7 days and 30 days after treatment with half-fluence PDT. The main outcome measures were changes in choroidal maps after PDT (mean ± SD) and the relationship between choroidal thickness and angiographic abnormalities. Of 12 patients (2 females, 10 males; mean age, 55.6 ± 14.0 years), 12 eyes were included. At study entry, mean choroidal thickness measured in the center of the fovea was significantly thicker in the study eyes as compared to the fellow eyes (420.7 ± 107.5 μm vs 349.2 ± 109.7 μm, respectively; P = 0.016). Mean choroidal thickness in the center of the fovea significantly decreased in the study eyes at both 7 days (380.2 ± 113 μm; P = 0.005) and 30 days after PDT (362.3 ± 111 μm; P = 0.002). A similar significant choroidal thinning was recorded in each early treatment of diabetic retinopathy study (ETDRS) applied to 3D swept-OCT maps. At each time point, mean choroidal thickness was significantly thicker in sectors with than in sectors without angiographic abnormalities (421 ± 102.4 μm vs 397.6 ± 96.5 μm, P = 0.002 at study entry; 381.2 ± 106.6 μm vs 364 ± 101.2 μm, P = 0.01 at day 7; 366.3 ± 103.2 μm vs 347.2 ± 99.6 μm at day 30). Using swept-OCT, we demonstrated that in active CSC, choroidal thickness is increased to a greater extent in areas characterized by angiographic abnormalities. This increased choroidal thickness may persist even after PDT. Copyright © 2014 Elsevier Inc. All rights reserved.

  2. Correlation of choroidal thickness and volume measurements with axial length and age using swept source optical coherence tomography and optical low-coherence reflectometry.

    PubMed

    Michalewski, Janusz; Michalewska, Zofia; Nawrocka, Zofia; Bednarski, Maciej; Nawrocki, Jerzy

    2014-01-01

    To report choroidal thickness and volume in healthy eyes using swept source optical coherence tomography (SS-OCT). A prospective observational study of 122 patients examined with swept source OCT (DRI-OCT, Topcon, Japan). In each eye, we performed 256 horizontal scans, 12 mm in length and centered on the fovea. We calculated choroidal thickness manually with a built-in caliper and automatically using DRI-OCT mapping software. Choroidal volume was also automatically calculated. We measured axial length with optical low-coherence reflectometry (Lenstar LS 900, Haag-Streit, Switzerland). The choroid has focally increased thickness under the fovea. Choroid was thinnest in the outer nasal quadrant. In stepwise regression analysis, age was estimated as the most significant factor correlating with decreased choroidal thickness (F=23.146, P<0.001) followed by axial length (F=4.902, P=0.03). Refractive error was not statistically significant (F=1.16, P=0.28). SS-OCT is the first commercially available system that can automatically create choroidal thickness and volume maps. Choroidal thickness is increased at the fovea and is thinnest nasally. Age and axial length are critical for the estimation of choroidal thickness and volume. Choroidal measurements derived from SS-OCT images have potential value for objectively documenting disease-related choroidal thickness abnormalities and monitoring progressive changes over time.

  3. 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.

  4. Assessment of Anterior Segment Measurements with Swept Source Optical Coherence Tomography before and after Ab Interno Trabeculotomy (Trabectome) Surgery

    PubMed Central

    Huang, Ping

    2016-01-01

    Purpose. To compare the changes of anterior segment parameters, assessed by swept source anterior segment optical coherence tomography (AS-OCT) after combined Trabectome-cataract surgery and Trabectome-only surgery in open angle glaucoma patients. Methods. Thirty-eight eyes of 24 patients with open angle glaucoma were scanned with swept source AS-OCT before and 4 weeks after combined Trabectome-cataract or Trabectome-only surgery. Intraocular pressure, number of medications, and AS-OCT parameters, such as angle opening distance at 500 and 750 μm from the scleral spur (AOD500 and AOD750), trabecular-iris space area at 500 and 750 mm2 (TISA500, TISA750), angle recess area at 500 and 750 mm2 (ARA500, ARA750), trabecular iris angle (TIA), anterior chamber depth (ACD), anterior chamber width (ACW), and anterior chamber volume (ACV), were obtained before the surgery. These parameters were compared to evaluate whether the outcome of the surgery differed among the patients after the surgery. The width of the trabecular cleft was also measured for both groups. Results. The reduction of IOP and number of medications was found to be statistically significant in both groups (p < 0.001). ACD, ACV, and angle parameters such as AOD 500/750, TISA 500/750, ARA 500/750, and TIA500 showed significantly greater changes from the preoperative values to postoperative 1st month values in combined Trabectome-cataract surgery group (p < 0.05), whereas Trabectome-only group did not show statistically significant difference (p > 0.05). There was no statistically significant difference between two groups for the width of the trabecular cleft (p = 0.7). Conclusion. Anterior chamber angle parameters measured with swept source AS-OCT may be useful for evaluating glaucoma patients before and after Trabectome surgery with or without cataract surgery. PMID:27795855

  5. Assessment of choroidal thickness before and after steep Trendelenburg position using swept-source optical coherence tomography.

    PubMed

    Rim, Tyler Hyungtaek; Lee, Christopher Seungkyu; Kim, Kangyoon; Kim, Sung Soo

    2015-04-01

    To evaluate changes in choroidal thickness before and after steep Trendelenburg position (STP, 40° head-down) using automated segmentation software to analyse swept-source optical coherence tomography (SS-OCT) data. The eyes of 20 healthy volunteers underwent a three-dimensional wide scanning protocol with SS-OCT (Topcon, Tokyo, Japan) at baseline, immediately after STP was initiated, and 5, 10 and 15 min after STP; blood pressure and heart rate were measured concurrently. The predictive mean difference was calculated using a generalised linear mixed model that adjusted for potential confounders. Mean choroidal thickness significantly and transiently increased immediately (268.18±9.24 μm, p<0.01) and 5 min (264.25±9.30 μm, p=0.03) after STP, relative to baseline (256.51±9.20 μm). However, choroidal thickness decreased by 10 min (262.51±9.34 μm, p=0.15) and 15 min (261.38±9.40 μm, p=0.37) after STP. Mean arterial pressure also transiently increased from baseline (78.2±1.2 mm Hg) immediately after STP (79.9±1.1 mm Hg, p=0.01), but normalised by 5 min after STP (p>0.05 for all comparisons ≥5 min). Choroidal thickness significantly but transiently increases after adopting STP, as evaluated by automated layer segmentation analysis of SS-OCT data. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  6. Wide-field human photoreceptor morphological analysis using phase-resolved sensorless adaptive optics swept-source OCT (Conference Presentation)

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

    Adaptive optics optical coherence tomography (AO-OCT) systems capable of 3D high resolution imaging have been applied to posterior eye imaging in order to resolve the fine morphological features in the retina. Human cone photoreceptors have been extensively imaged and studied for the investigation of retinal degeneration resulting in photoreceptor cell death. However, there are still limitations of conventional approaches to AO in the clinic, such as relatively small field-of-view (FOV) and the complexities in system design and operation. In this research, a recently developed phase-resolved Sensorless AO Swept Source based OCT (SAO-SS-OCT) system which is compact in size and easy to operate is presented. Owing to its lens-based system design, wide-field imaging can be performed up to 6° on the retina. A phase stabilization unit was integrated with the OCT system. With the phase stabilized OCT signal, we constructed retinal micro-vasculature image using a phase variance technique. The retinal vasculature image was used to align and average multiple OCT volumes acquired sequentially. The contrast-enhanced photoreceptor projection image was then extracted from the averaged volume, and analyzed based on its morphological features through a novel photoreceptor structure evaluation algorithm. The retinas of twelve human research subjects (10 normal and 2 pathological cases) were measured in vivo. Quantitative parameters used for evaluating the cone photoreceptor mosaic such as cell density, cell area, and mosaic regularity are presented and discussed. The SAO-SS-OCT system and the proposed photoreceptor evaluation method has significant potential to reveal early stage retinal diseases associated with retinal degeneration.

  7. Imaging collector channel entrance with a new intraocular micro-probe swept-source optical coherence tomography.

    PubMed

    Xin, Chen; Chen, Xiaoya; Li, Meng; Shi, Yan; Wang, Huaizhou; Wang, Ruikang; Wang, Ningli

    2017-09-01

    To describe the use of a newly developed side-viewing catheter probe to provide the cross-sectional images of collector channel entrance (CCE), achieved by swept-source optical coherence tomography (SS-OCT). A side-viewing SS-OCT catheter probe was developed that has a core probe diameter of 0.15 mm and an outer diameter of 0.25 mm, for the purpose of imaging CCEs within eye globe. Cadaver eyes harvested from swine and human were used to demonstrate its feasibility. For porcine eyes, the probe imaged the CCE by accessing the region of the aqueous plexus (AP) as well as along the inner wall (IW) of the trabecular meshwork (TM). For human eyes, the CCE images were captured by placing the probe within the lumen of the Schlemm's canal (SC) and along its IW. With the optical coherence tomography (OCT) catheter probe, the CCE is well delineated as optically empty areas within the highly scattering sclera. In porcine eyes, images captured in the region of the AP demonstrate a large cavity with delicate tissue strands around the probe. The CCE can be identified at the outer margin of the AP. When imaged along the IW, the TM is discernable but difficult to be distinguished from the AP. In the human limbal regions, when placed within the lumen of the SC, the catheter probe fully occupies the potential space. TM is highly compact. The CCE can be identified at the outer wall of the SC. When imaged along the IW of TM, the SC and CCE can be identified. The intraocular SS-OCT catheter probe is feasible to provide the CCE images, indicating useful clinical applications to assist glaucoma surgery. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  8. Fiber-needle swept-source optical coherence tomography system for the identification of the epidural space in piglets.

    PubMed

    Kuo, Wen-Chuan; Kao, Meng-Chun; Chang, Kuang-Yi; Teng, Wei-Nung; Tsou, Mei-Yung; Chang, Yin; Ting, Chien-Kun

    2015-03-01

    Epidural needle insertion is traditionally a blind technique whose success depends on the experience of the operator. The authors describe a novel method using a fiber-needle-based swept-source optical coherence tomography (SSOCT) to identify epidural space. An optical fiber probe was placed into a hollow 18-gauge Tuohy needle. It was then inserted by an experienced anesthesiologist to continuously construct a series of two-dimensional SSOCT images by mechanically rotating the optical probe. To quantify this observation, both the average SSOCT signal intensities and their diagnostic potentials were assessed. The insertions were performed three times into both the lumbar and thoracic regions of five pigs using a paramedian approach. A side-looking SSOCT is constructed to create a visual image of the underlying structures. The image criteria for the identification of the epidural space from the outside region were generated by the analysis of a training set (n = 100) of ex vivo data. The SSOCT image criteria for in vivo epidural space identification are high sensitivity (0.867 to 0.965) and high specificity (0.838 to 0.935). The mean value of the average signal intensities exhibits statistically significant differences (P < 0.01) and a high discriminatory capacity (area under curve = 0.88) between the epidural space and the outside tissues. This is the first study to introduce a SSOCT fiber probe embedded in a standard epidural needle. The authors anticipate that this technique will reduce the occurrence of failed epidural blocks and other complications such as dural punctures.

  9. Multi-volumetric registration and mosaicking using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Bozic, Ivan; El-Haddad, Mohamed T.; Malone, Joseph D.; Joos, Karen M.; Patel, Shriji N.; Tao, Yuankai K.

    2017-02-01

    Ophthalmic diagnostic imaging using optical coherence tomography (OCT) is limited by bulk eye motions and a fundamental trade-off between field-of-view (FOV) and sampling density. Here, we introduced a novel multi-volumetric registration and mosaicking method using our previously described multimodal swept-source spectrally encoded scanning laser ophthalmoscopy and OCT (SS-SESLO-OCT) system. Our SS-SESLO-OCT acquires an entire en face fundus SESLO image simultaneously with every OCT cross-section at 200 frames-per-second. In vivo human retinal imaging was performed in a healthy volunteer, and three volumetric datasets were acquired with the volunteer moving freely and refixating between each acquisition. In post-processing, SESLO frames were used to estimate en face rotational and translational motions by registering every frame in all three volumetric datasets to the first frame in the first volume. OCT cross-sections were contrast-normalized and registered axially and rotationally across all volumes. Rotational and translational motions calculated from SESLO frames were applied to corresponding OCT B-scans to compensate for interand intra-B-scan bulk motions, and the three registered volumes were combined into a single interpolated multi-volumetric mosaic. Using complementary information from SESLO and OCT over serially acquired volumes, we demonstrated multivolumetric registration and mosaicking to recover regions of missing data resulting from blinks, saccades, and ocular drifts. We believe our registration method can be directly applied for multi-volumetric motion compensation, averaging, widefield mosaicking, and vascular mapping with potential applications in ophthalmic clinical diagnostics, handheld imaging, and intraoperative guidance.

  10. Simultaneous multimodal ophthalmic imaging using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

    PubMed Central

    Malone, Joseph D.; El-Haddad, Mohamed T.; Bozic, Ivan; Tye, Logan A.; Majeau, Lucas; Godbout, Nicolas; Rollins, Andrew M.; Boudoux, Caroline; Joos, Karen M.; Patel, Shriji N.; Tao, Yuankai K.

    2016-01-01

    Scanning laser ophthalmoscopy (SLO) benefits diagnostic imaging and therapeutic guidance by allowing for high-speed en face imaging of retinal structures. When combined with optical coherence tomography (OCT), SLO enables real-time aiming and retinal tracking and provides complementary information for post-acquisition volumetric co-registration, bulk motion compensation, and averaging. However, multimodality SLO-OCT systems generally require dedicated light sources, scanners, relay optics, detectors, and additional digitization and synchronization electronics, which increase system complexity. Here, we present a multimodal ophthalmic imaging system using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography (SS-SESLO-OCT) for in vivo human retinal imaging. SESLO reduces the complexity of en face imaging systems by multiplexing spatial positions as a function of wavelength. SESLO image quality benefited from single-mode illumination and multimode collection through a prototype double-clad fiber coupler, which optimized scattered light throughput and reduce speckle contrast while maintaining lateral resolution. Using a shared 1060 nm swept-source, shared scanner and imaging optics, and a shared dual-channel high-speed digitizer, we acquired inherently co-registered en face retinal images and OCT cross-sections simultaneously at 200 frames-per-second. PMID:28101411

  11. Simultaneous multimodal ophthalmic imaging using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography.

    PubMed

    Malone, Joseph D; El-Haddad, Mohamed T; Bozic, Ivan; Tye, Logan A; Majeau, Lucas; Godbout, Nicolas; Rollins, Andrew M; Boudoux, Caroline; Joos, Karen M; Patel, Shriji N; Tao, Yuankai K

    2017-01-01

    Scanning laser ophthalmoscopy (SLO) benefits diagnostic imaging and therapeutic guidance by allowing for high-speed en face imaging of retinal structures. When combined with optical coherence tomography (OCT), SLO enables real-time aiming and retinal tracking and provides complementary information for post-acquisition volumetric co-registration, bulk motion compensation, and averaging. However, multimodality SLO-OCT systems generally require dedicated light sources, scanners, relay optics, detectors, and additional digitization and synchronization electronics, which increase system complexity. Here, we present a multimodal ophthalmic imaging system using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography (SS-SESLO-OCT) for in vivo human retinal imaging. SESLO reduces the complexity of en face imaging systems by multiplexing spatial positions as a function of wavelength. SESLO image quality benefited from single-mode illumination and multimode collection through a prototype double-clad fiber coupler, which optimized scattered light throughput and reduce speckle contrast while maintaining lateral resolution. Using a shared 1060 nm swept-source, shared scanner and imaging optics, and a shared dual-channel high-speed digitizer, we acquired inherently co-registered en face retinal images and OCT cross-sections simultaneously at 200 frames-per-second.

  12. Application of a long-range swept source optical coherence tomography-based scheme for dimensional characterization of multilayer transparent objects

    NASA Astrophysics Data System (ADS)

    Morel, Eneas N.; Russo, Nélida A.; Torga, Jorge R.; Duchowicz, Ricardo

    2017-08-01

    This work presents the use of a recently developed interferometric system based on the swept source optical coherence tomography (SS-OCT) technique, which allows the characterization of transparent and semitransparent multilayer systems employing a tunable fiber-optic laser with a coherence length suitable for achieving long-deep range imaging (>10 cm). The inclusion of fiber Bragg gratings in the system allows it to perform a self-calibration in each sweep of the light source. Measurements carried out on cuvettes, ampoules, small bottles, and glass containers used in the pharmaceutical industry are presented. The thicknesses of the walls and the distance between them were determined. Transparent and semitransparent objects of a multilayer type of different thicknesses were also measured. The configuration presented allows extension of the measurement range obtainable with the usual OCT systems, demonstrating the potentiality of the proposed scheme to carry out quality control in industrial applications.

  13. 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

  14. A study on optical coherence tomography using high frequency swept source

    NASA Astrophysics Data System (ADS)

    Ding, Lei; Tong, Xinglin; Chen, Liang; Hu, Pan; Huang, Di; Zhao, Minli; Wen, Hongqiao

    2016-05-01

    Optical coherence tomography based on ultra technology is used for the assessment of subcutaneous tissue. Using high swept laser technology based on Fourier domain mode locking (FDML), the system operated in the 1300 nm wavelength range with axial scan rate of 150 kHz. Imaging at this wavelength range reduces optical scattering and improves imaging penetration depths in the tissues. The laser consists of a semiconductor amplifier as the gain medium, a tunable Fabry-Perot filter to change the wavelengthcand a long fiber ring cavity. The tuning range of laser is 102 nm. A balanced detector is used for spectra collection instead of the expensive CCD.

  15. 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. (c) 2010 Optical Society of America.

  16. External amplification of OCT swept-sources for challenging applications: from 10 mW to more than 120 mW

    NASA Astrophysics Data System (ADS)

    Rivard, Maxime; Villeneuve, Alain; Lamouche, Guy

    2017-02-01

    For bioimaging applications, commercial swept-sources currently provide enough power (tens of milliwatts) insuring good imaging condition without damaging the tissues. For industrial applications, more power is needed since the amount of light collected can be very low due to challenging measurement conditions or due to poor sample reflectivity. To address this challenge, we explore three different setups to externally amplify the output of a commercial swept-source: a booster semiconductor optical amplifier (BOA), an erbium-doped fiber amplifier (EDFA) and a combination of both. These external amplification setups allow the exploration of emerging OCT applications without the need to develop new hardware.

  17. 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.

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

    PubMed

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

    2016-02-01

    To evaluate the thickness and volume of the choroid in healthy Korean children using swept-source optical coherence tomography. 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. 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). 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.

  19. 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

  20. Multimodal swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography at 400 kHz

    NASA Astrophysics Data System (ADS)

    El-Haddad, Mohamed T.; Joos, Karen M.; Patel, Shriji N.; Tao, Yuankai K.

    2017-02-01

    Multimodal imaging systems that combine scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) have demonstrated the utility of concurrent en face and volumetric imaging for aiming, eye tracking, bulk motion compensation, mosaicking, and contrast enhancement. However, this additional functionality trades off with increased system complexity and cost because both SLO and OCT generally require dedicated light sources, galvanometer scanners, relay and imaging optics, detectors, and control and digitization electronics. We previously demonstrated multimodal ophthalmic imaging using swept-source spectrally encoded SLO and OCT (SS-SESLO-OCT). Here, we present system enhancements and a new optical design that increase our SS-SESLO-OCT data throughput by >7x and field-of-view (FOV) by >4x. A 200 kHz 1060 nm Axsun swept-source was optically buffered to 400 kHz sweep-rate, and SESLO and OCT were simultaneously digitized on dual input channels of a 4 GS/s digitizer at 1.2 GS/s per channel using a custom k-clock. We show in vivo human imaging of the anterior segment out to the limbus and retinal fundus over a >40° FOV. In addition, nine overlapping volumetric SS-SESLO-OCT volumes were acquired under video-rate SESLO preview and guidance. In post-processing, all nine SESLO images and en face projections of the corresponding OCT volumes were mosaicked to show widefield multimodal fundus imaging with a >80° FOV. Concurrent multimodal SS-SESLO-OCT may have applications in clinical diagnostic imaging by enabling aiming, image registration, and multi-field mosaicking and benefit intraoperative imaging by allowing for real-time surgical feedback, instrument tracking, and overlays of computationally extracted image-based surrogate biomarkers of disease.

  1. Frequency comb swept lasers.

    PubMed

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C; Fujimoto, James G

    2009-11-09

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a approximately -1.2dB sensitivity roll off over approximately 3mm range, compared to conventional swept source and FDML lasers which have -10dB and -5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0-3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed.

  2. Frequency comb swept lasers

    PubMed Central

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C.; Fujimoto, James G.

    2010-01-01

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a ~−1.2dB sensitivity roll off over ~3mm range, compared to conventional swept source and FDML lasers which have −10dB and −5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0–3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed. PMID:19997365

  3. Select Features of Diabetic Retinopathy on Swept-Source Optical Coherence Tomographic Angiography Compared With Fluorescein Angiography and Normal Eyes

    PubMed Central

    Salz, David A.; de Carlo, Talisa E.; Adhi, Mehreen; Moult, Eric; Choi, WhooJhon; Baumal, Caroline R.; Witkin, Andre J.; Duker, Jay S.; Fujimoto, James G.; Waheed, Nadia K.

    2017-01-01

    IMPORTANCE Optical coherence tomographic angiography (OCTA) is a recently developed noninvasive imaging technique that can visualize the retinal and choroidal microvasculature without the injection of exogenous dyes. OBJECTIVE To evaluate the potential clinical utility of OCTA using a prototype swept-source OCT (SS-OCT) device and compare it with fluorescein angiography (FA) for analysis of the retinal microvasculature in diabetic retinopathy. DESIGN, SETTING, AND PARTICIPANTS Prospective, observational cross-sectional study conducted at a tertiary care academic retina practice from November 2013 through November 2014. A cohort of diabetic and normal control eyes were imaged with a prototype SS-OCT system. The stage of diabetic retinopathy was determined by clinical examination. Imaging was performed using angiographic 3 × 3-mm and 6 × 6-mm SS-OCT scans to generate 3-dimensional en-face OCT angiograms for each eye. Two trained Boston Image Reading Center readers reviewed and graded FA and OCTA images independently. MAIN OUTCOMES AND MEASURES The size of the foveal nonflowzone and the perifoveal intercapillary area on OCTA were measured in both normal and diabetic eyes using Boston Image Reading Center image analysis software. RESULTS The study included 30 patients with diabetes (mean [SD] age, 55.7 [10] years) and 6 control individuals (mean [SD] age, 55.1 [6.4] years). A total of 43 diabetic and 11 normal control eyes were evaluated with OCTA. Fluorescein angiography was performed in 17 of 43 diabetic eyes within 8 weeks of the OCTA. Optical coherence tomographic angiography was able to identify a mean (SD) of 6.4 (4.0) microaneurysms (95% CI, 4.4–8.5), while FA identified a mean (SD) of 10 (6.9) microaneurysms (95% CI, 6.4–13.5). The exact intraretinal depth of microaneurysms on OCTA was localized in all cases (100%). The sensitivity of OCTA in detecting microaneuryms when compared with FA was 85% (95% CI, 53–97), while the specificity was 75% (95% CI, 21

  4. 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.

  5. 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.

  6. 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).

  7. In vivo early detection of smoke-induced airway injury using three-dimensional swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yin, Jiechen; Liu, Gangjun; Zhang, Jun; Yu, Lingfeng; Mahon, Sari; Mukai, David; Brenner, Matthew; Chen, Zhongping

    2009-11-01

    We report on the feasibility of rapid, high-resolution, 3-D swept-source optical coherence tomography (SSOCT) to detect early airway injury changes following smoke inhalation exposure in a rabbit model. The SSOCT system obtains 3-D helical scanning using a microelectromechanical system motor-based endoscope. Real-time 2-D data processing and image display at the speed of 20 frames/s are achieved by adopting the technique of parallel computing. Longitudinal images are reconstructed via an image processing algorithm to remove motion artifacts caused by ventilation and pulse. Quantitative analyses of tracheal airway thickness as well as thickness distribution along tracheal circumference are also performed based on the comprehensive 3-D volumetric data.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Full-range swept source optical coherence tomography based on carrier frequency by transmissive dispersive optical delay line

    NASA Astrophysics Data System (ADS)

    Wu, Tong; Ding, Zhihua; Wang, Chuan; Chen, Minghui

    2011-12-01

    A high speed swept source optical coherence tomography (SS-OCT) system capable of full-range imaging is presented. Wave-number carrier frequency is introduced into the spectral interference signal by a transmissive dispersive optical delay line (TDODL). High carrier frequency in the spectral interference signal corresponding to an equivalent distance-shift is exploited to obtain full-range OCT imaging. Theoretical development is conducted with the instantaneous coherence function introduced for a complete description of a spectral interference signal. Performance advantage of the TDODL-based method over the conventional approach where only one side (positive or negative path length difference) is used for imaging to avoid overlaying mirror artifacts is confirmed by the measured envelopes of spectral interference signal. Feasibility of the proposed method for full-range imaging is validated in a custom-built SS-OCT system by in vivo imaging of a biological sample.

  13. Dual-core ytterbium fiber amplifier for high-power 1060 nm swept source multichannel optical coherence tomography imaging.

    PubMed

    Harduar, Mark K; Mariampillai, Adrian; Vuong, Barry; Gu, Xijia; Standish, Beau A; Yang, Victor X D

    2011-08-01

    A novel (to our knowledge) dual-core ytterbium (Yb(3+)) doped fiber, as an optically pumped amplifier, boosts the output power from a 1060 nm swept source laser beyond 250 mW, while providing a wavelength tuning range of 93 nm, for optical coherence tomography (OCT) imaging. The design of the dual-core Yb-doped fiber amplifier and its multiple wavelength optical pumping scheme to optimize output bandwidth are discussed. Use of the dual-core fiber amplifier showed no appreciable degradation to the coherence length of the seed laser. The signal intensity improvement of this amplifier is demonstrated on a multichannel in vivo OCT imaging system at 1060 nm.

  14. Ultrahigh Speed Swept Source OCT Angiography in Non-Exudative Age-Related Macular Degeneration with Geographic Atrophy

    PubMed Central

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

    2015-01-01

    PURPOSE To investigate ultrahigh speed, swept source optical coherence tomography (SSOCT) angiography for visualizing vascular changes in eyes with non-exudative age-related macular degeneration (AMD) with geographic atrophy (GA). DESIGN Observational, prospective, cross-sectional study. PARTICIPANTS A total of 63 eyes from 32 normal subjects and 12 eyes from 7 patients with non-exudative AMD with GA. METHODS A 1050 nm, 400 kHz A-scan rate SSOCT system was used to perform volumetric optical coherence tomography angiography (OCTA) of the retinal and choriocapillaris (CC) vasculatures in normal subjects and patients with non-exudative AMD with GA. OCTA using variable interscan time analysis (VISTA) was performed to assess CC alteration and differentiate varying degrees of CC flow impairment. MAIN OUTCOME MEASURES Qualitative comparison of retinal and CC vasculatures in normal subjects versus those in patients with a clinical diagnosis of non-exudative AMD with GA. RESULTS In all 12 eyes with GA, OCTA showed pronounced CC flow impairment within the region of GA. In 10 of the 12 eyes with GA, OCTA with VISTA showed milder CC flow impairment extending beyond the margin of GA. Of the 5 eyes exhibiting foveal sparing GA, OCTA showed CC flow within the region of foveal sparing in 4 of the eyes. CONCLUSIONS The ability of ultrahigh speed, swept source OCTA to visualize alterations in the retinal and CC vasculatures noninvasively makes it a promising tool for assessing non-exudative AMD with GA. OCTA using VISTA can distinguish varying degrees of CC alteration and flow impairment and may be useful for elucidating disease pathogenesis, progression, and response to therapy. PMID:26481819

  15. Choroidal and Retinal Thickness in Children With Different Refractive Status Measured by Swept-Source Optical Coherence Tomography.

    PubMed

    Jin, Peiyao; Zou, Haidong; Zhu, Jianfeng; Xu, Xun; Jin, Jiali; Chang, Ta Chen; Lu, Lina; Yuan, Hong; Sun, Sifei; Yan, Bo; He, Jiangnan; Wang, Mingjin; He, Xiangui

    2016-08-01

    To investigate the choroidal and retinal thickness in myopic, emmetropic, and hyperopic Chinese children by swept-source longer-wavelength optical coherence tomography. Cross-sectional study. Two-hundred and seventy-six schoolchildren aged 7-13 years underwent comprehensive ophthalmic examinations, including cycloplegic refraction, and swept-source optical coherence tomography measurements. The thickness of the choroid, retina, ganglion cell layer, and nerve fiber layer were compared among children of different refractive status. The topographic variation and factors related to the thickness of the choroid and retinal layers were analyzed. Compared to emmetropic subjects, those with myopia had a significantly thinner choroid in all regions (P < .01), and hyperopic subjects had a thicker choroid in most regions (P < .05). The myopic retinas were thinner than those of emmetropic or hyperopic subjects in the superior parafoveal and all 4 perifoveal subfields (P < .05), but no other subfields differed significantly among different refractive groups (P > .05). The axial length and refractive diopters were independently related to central foveal choroidal thickness (R(2) = 0.17, P < .01), while age and intraocular pressure were independently associated with central fovea retinal (R(2) = 0.15, P < .01) and ganglion cell layer thicknesses (R(2) = 0.10, P < .01) after adjustment for other systematic and ocular factors. Central foveal choroidal and retinal thickness were unrelated in children of different refractive status (P > .05). Choroidal thickness, but not retinal thickness, correlated closely with axial length and refractive diopters in Chinese children. Choroid thinning occurs before retina thinning early in myopic progression. Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.

  16. Fast 3D in vivo swept-source optical coherence tomography using a two-axis MEMS scanning micromirror

    NASA Astrophysics Data System (ADS)

    Kumar, Karthik; Condit, Jonathan C.; McElroy, Austin; Kemp, Nate J.; Hoshino, Kazunori; Milner, Thomas E.; Zhang, Xiaojing

    2008-04-01

    We report on a fibre-based forward-imaging swept-source optical coherence tomography system using a high-reflectivity two-axis microelectromechanical scanning mirror for high-speed 3D in vivo visualization of cellular-scale architecture of biological specimens. The scanning micromirrors, based on electrostatic staggered vertical comb drive actuators, can provide ± 9° of optical deflection on both rotation axes and uniform reflectivity of greater than 90% over the range of imaging wavelengths (1260-1360 nm), allowing for imaging turbid samples with good signal-to-noise ratio. The wavelength-swept laser, scanning over 100 nm spectrum at 20 kHz rate, enables fast image acquisition at 10.2 million voxels s-1 (for 3D imaging) or 40 frames s-1 (for 2D imaging with 500 transverse pixels per image) with 8.6 µm axial resolution. Lateral resolution of 12.5 µm over 3 mm field of view in each lateral direction is obtained using ZEMAX optical simulations for the lateral beam scanning system across the scanning angle range of the 500 µm × 700 µm micromirror. We successfully acquired en face and tomographic images of rigid structures (scanning micromirror), in vitro biological samples (onion peels and pickle slices) and in vivo images of human epidermis over 2 × 1 × 4 mm3 imaging volume in real time at faster-than-video 2D frame rates. The results indicate that our system framework may be suitable for image-guided minimally invasive examination of various diseased tissues.

  17. Observations of vascular structures within and posterior to sclera in eyes with pathologic myopia by swept-source optical coherence tomography.

    PubMed

    Ohno-Matsui, Kyoko; Akiba, Masahiro; Ishibashi, Tatsuro; Moriyama, Muka

    2012-10-19

    We examined the intrascleral and retrobulbar blood vessels in highly myopic eyes by swept-source optical coherence tomography (swept-source OCT). We included in the study 662 of 357 patients with pathologic myopia (spherical equivalent of myopic refractive error ≥ 8.00 diopters or axial length > 26.5 mm). A swept-source OCT system that uses a wavelength sweeping laser with A-scan repetition rate of 100,000 Hz and 1 μm wavelength was used. Radial scans along 12 meridians of 12 mm scan length centered on the fovea were made. Indocyanine green angiography (ICGA) also was performed to identify the intrascleral and retrobulbar vessels that were observed by swept-source OCT. Intrascleral and retrobulbar blood vessels were observed in the macular area of the highly myopic eyes. Linear hyporeflective structures running in the sclera were observed in 474 of the 662 myopic eyes, and ICGA confirmed that these structures were the long posterior ciliary arteries (LPCAs) or the short posterior ciliary arteries (SPCAs) whose entry sites into the eye were displaced toward the temporal edge of the posterior staphyloma in 50 eyes. In 36 of the 662 eyes (5.4%), cross sections of the blood vessels were seen coursing through the scleral layer. In 177 of these 443 eyes, the retrobulbar posterior ciliary arteries (PCAs) also were observed as a cluster of circular or curved hyporeflectant structures just posterior to the sclera. Swept-source OCT is a high-quality method to detect intrascleral and retroscleral blood vessels in the eyes with pathologic myopia. These findings and longitudinal studies of these vessels will help in investigating how they are altered in pathologic myopia, and how such alterations are related to the complications in the retina-choroid and optic nerve.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

    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 2×5.0 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 μm) that is insensitive to eye motion sufficient for long-term monitoring.

  20. Natural History of Subclinical Neovascularization in Nonexudative Age-Related Macular Degeneration Using Swept-Source OCT Angiography.

    PubMed

    de Oliveira Dias, João R; Zhang, Qinqin; Garcia, José M B; Zheng, Fang; Motulsky, Elie H; Roisman, Luiz; Miller, Andrew; Chen, Chieh-Li; Kubach, Sophie; de Sisternes, Luis; Durbin, Mary K; Feuer, William; Wang, Ruikang K; Gregori, Giovanni; Rosenfeld, Philip J

    2017-09-27

    Swept-source (SS) OCT angiography (OCTA) was used to determine the prevalence, incidence, and natural history of subclinical macular neovascularization (MNV) in eyes with nonexudative age-related macular degeneration (AMD). Prospective, observational, consecutive case series. Patients with intermediate AMD (iAMD) or geographic atrophy (GA) secondary to nonexudative AMD in 1 eye and exudative AMD in the fellow eye. All patients were imaged using both the 3×3 mm and 6×6 mm SS OCTA fields of view (PLEX Elite 9000; Carl Zeiss Meditec, Inc, Dublin, CA). The en face slab used to detect the MNV extended from the outer retina to the choriocapillaris, and projection artifacts were removed using a proprietary algorithm. Prevalence of subclinical MNV and time to exudation with Kaplan-Meier cumulative estimates of exudation at 1 year. From August 2014 through March 2017, 160 patients underwent SS OCTA (110 eyes with iAMD and 50 eyes with GA). Swept-source OCTA identified subclinical MNV at the time of first imaging in 23 of 160 eyes, for a prevalence of 14.4%. Six eyes demonstrated subclinical MNV during the follow-up. Of 134 eyes with follow-up visits, a total of 13 eyes demonstrated exudation, and of these 13 eyes, 10 eyes were found to have pre-existing subclinical MNV. By 12 months, the Kaplan-Meier cumulative incidence of exudation for all 134 eyes was 6.8%. For eyes with subclinical MNV at the time of first SS OCTA imaging, the incidence was 21.1%, and for eyes without subclinical MNV, the incidence was 3.6%. There was no difference in the cumulative incidence of exudation from pre-existing MNV in eyes with iAMD or GA (P = 0.847, log-rank test). After the detection of subclinical MNV, the risk of exudation was 15.2 times (95% confidence interval, 4.2-55.4) greater compared with eyes without subclinical MNV. By 12 months, the risk of exudation was greater for eyes with documented subclinical MNV compared with eyes without detectable MNV. For eyes with subclinical MNV

  1. 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.

  2. In-vivo imaging of keratoconic corneas using high-speed high-resolution swept-source OCT

    NASA Astrophysics Data System (ADS)

    Marschall, S.; Gawish, A.; Feng, Y.; Sorbara, L.; Fieguth, P.; Bizheva, K.

    2013-06-01

    Keratoconus (KC) is a progressive degenerative corneal disease that can lead to a strong deformation of the cornea and loss of clarity, causing distorted or blurred vision. Surgical treatment for severe cases requires precise evaluation of the corneal curvature, thickness, layer structure, and clarity. Current clinical instruments for assessing the corneal shape cannot resolve the internal structure, and high-resolution microscopy techniques are limited to a small field of view. We have implemented a swept-source OCT (SS-OCT) system that enables high-speed imaging (100 kA-scans/s) of the entire cornea and provides ~5.1μm axial resolution in corneal tissue. With an imaging range of 5.6 mm (in air), we can cover the full length from the cornea's apex to the anterior surface of the lens. We have acquired volumetric corneal images from human subjects with different stages of KC and from subjects who underwent surgery or cross-linking therapy. We developed an automatic algorithm for segmenting the outer and inner surfaces of the cornea in the images which will enable precise measurement of the corneal curvature and thickness. This makes SS-OCT an ideal instrument for comprehensive examination of keratoconic corneas.

  3. Comparison of time-domain, spectral-domain and swept-source OCT in evaluating aqueous cells in vitro.

    PubMed

    Li, Meng; Wang, Huaizhou; Liu, Yue; Zhang, Xifang; Wang, Ningli

    2016-12-01

    Different optical coherence tomography (OCT), both time-domain OCT and spectral-domain OCT, has been used to evaluate anterior chamber cells in previous studies. Recently, commercial swept-source OCT was available. The comparison among three kinds of OCTs have not been done before. Here, we compared their feasibility in discerning aqueous cells in vitro. The peripheral blood was diluted to eight different cell concentrations and was packed into plastic-film bag. Each sample was tested using different scan modes of three OCTs. It was easy to discern aqueous cells from background noise in both Visante AS-OCT and RTVue XR Avanti OCT, but difficult in Casia SS-1000 OCT. The measured blood cell densities in high-resolution corneal cross-sectional scan of Visante AS-OCT, cornea line scan and 3D cornea scan of RTVue XR Avanti OCT were highly correlated with the actual blood cell concentration (Pearson correlation=0.991, 0.989, and 0.993 respectively). The mean adjusted cell densities of cornea line scan (10.46±2.87 spots mm(-2)) and 3D cornea scan (11.01±2.47 spots mm(-2)) of RTVue XR Avanti OCT were significantly larger than that of Visante AS-OCT (1.55±1.75 spots mm(-2)) (P<0.01). Our study demonstrated that RTVue XR Avanti OCT, a spectral-domain OCT, is superior to other two OCTs in evaluating aqueous cells.

  4. 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

  5. Associated factors for visibility and width of retrobulbar subarachnoid space on swept-source optical coherence tomography in high myopia

    PubMed Central

    Fan, Hua; Ma, Hongjie; Gao, Rulong; Ng, Danny Siu-Chun; Cheung, Carol Y.; Li, Shuangnong; Wu, Dezheng; Tang, Shibo

    2016-01-01

    Subarachnoid space (SAS) around optic nerve can be visible with swept-source optical coherence tomography (SS-OCT). However, the relevant factors for its visibility and width have not been reported. In this prospective study, 193 eyes with high myopia were evaluated by SS-OCT. The relationship between age, gender, axial length, optic disc area, parapapillary atrophy (PPA) area, peripapillary choroidal thickness with the visibility and width of SAS were assessed. The results showed that SAS was observed in 125 (64.8%) and not observed in 68 (35.2%) eyes. Visibility of SAS is associated with long axial length, high myopia, thin choroid, large PPA and large optic disc areas. Among these associations, PPA area was the only independent factor (b = 0.177, p < 0.001). The width of SAS was associated with thin choroid, long axial length, large optic disc area and large PPA area. Multivariant analysis showed that optic disc area and PPA area were independent factors for the width of SAS (b = 30.8, p = 0.016 and 16.2, p < 0.001 respectively). These results suggested that SAS was extended into the peripapillary region possibly due to extension of posterior sclera in high myopia. PMID:27827444

  6. Ultra-compact swept-source optical coherence tomography handheld probe with motorized focus adjustment (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    LaRocca, Francesco; Nankivil, Derek; Keller, Brenton; Farsiu, Sina; Izatt, Joseph A.

    2017-02-01

    Handheld optical coherence tomography (OCT) systems facilitate imaging of young children, bedridden subjects, and those with less stable fixation. Smaller and lighter OCT probes allow for more efficient imaging and reduced operator fatigue, which is critical for prolonged use in either the operating room or neonatal intensive care unit. In addition to size and weight, the imaging speed, image quality, field of view, resolution, and focus correction capability are critical parameters that determine the clinical utility of a handheld probe. Here, we describe an ultra-compact swept source (SS) OCT handheld probe weighing only 211 g (half the weight of the next lightest handheld SSOCT probe in the literature) with 20.1 µm lateral resolution, 7 µm axial resolution, 102 dB peak sensitivity, a 27° x 23° field of view, and motorized focus adjustment for refraction correction between -10 to +16 D. A 2D microelectromechanical systems (MEMS) scanner, a converging beam-at-scanner telescope configuration, and an optical design employing 6 different custom optics were used to minimize device size and weight while achieving diffraction limited performance throughout the system's field of view. Custom graphics processing unit (GPU)-accelerated software was used to provide real-time display of OCT B-scans and volumes. Retinal images were acquired from adult volunteers to demonstrate imaging performance.

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

    PubMed

    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.

  8. Long-range and wide field of view optical coherence tomography for in vivo 3D imaging of large volume object based on akinetic programmable swept source.

    PubMed

    Song, Shaozhen; Xu, Jingjiang; Wang, Ruikang K

    2016-11-01

    Current optical coherence tomography (OCT) imaging suffers from short ranging distance and narrow imaging field of view (FOV). There is growing interest in searching for solutions to these limitations in order to expand further in vivo OCT applications. This paper describes a solution where we utilize an akinetic swept source for OCT implementation to enable ~10 cm ranging distance, associated with the use of a wide-angle camera lens in the sample arm to provide a FOV of ~20 x 20 cm(2). The akinetic swept source operates at 1300 nm central wavelength with a bandwidth of 100 nm. We propose an adaptive calibration procedure to the programmable akinetic light source so that the sensitivity of the OCT system over ~10 cm ranging distance is substantially improved for imaging of large volume samples. We demonstrate the proposed swept source OCT system for in vivo imaging of entire human hands and faces with an unprecedented FOV (up to 400 cm(2)). The capability of large-volume OCT imaging with ultra-long ranging and ultra-wide FOV is expected to bring new opportunities for in vivo biomedical applications.

  9. Long-range and wide field of view optical coherence tomography for in vivo 3D imaging of large volume object based on akinetic programmable swept source

    PubMed Central

    Song, Shaozhen; Xu, Jingjiang; Wang, Ruikang K.

    2016-01-01

    Current optical coherence tomography (OCT) imaging suffers from short ranging distance and narrow imaging field of view (FOV). There is growing interest in searching for solutions to these limitations in order to expand further in vivo OCT applications. This paper describes a solution where we utilize an akinetic swept source for OCT implementation to enable ~10 cm ranging distance, associated with the use of a wide-angle camera lens in the sample arm to provide a FOV of ~20 x 20 cm2. The akinetic swept source operates at 1300 nm central wavelength with a bandwidth of 100 nm. We propose an adaptive calibration procedure to the programmable akinetic light source so that the sensitivity of the OCT system over ~10 cm ranging distance is substantially improved for imaging of large volume samples. We demonstrate the proposed swept source OCT system for in vivo imaging of entire human hands and faces with an unprecedented FOV (up to 400 cm2). The capability of large-volume OCT imaging with ultra-long ranging and ultra-wide FOV is expected to bring new opportunities for in vivo biomedical applications. PMID:27896012

  10. Miniaturized silicon photonic integrated swept source OCT receiver with dual polarization, dual balanced, in-phase and quadrature detection (Conference Presentation)

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Miniaturization and cost reduction of OCT systems are important for enabling many new clinical applications as well as accelerating the development of existing applications. Silicon photonics is an important low-cost, high-volume, multi-functional platform for integrated optics because it can benefit from existing semiconductor fabrication techniques to integrate many advanced optical functions onto a single microchip. We present a miniaturized silicon photonic integrated swept source OCT receiver, measuring 3×4mm2, with advanced functionalities including dual polarization, dual balanced, in-phase and quadrature detection, essentially enabling the detection of the full vector field (amplitude, phase, and polarization) of the optical signal. With this integrated receiver, we demonstrate full-range OCT for complex conjugate artifact suppression, polarization diversity detection for removing polarization fading artifact, and polarization sensitive OCT for tissue birefringence imaging. The silicon photonic integrated receiver is a key advance towards developing a miniaturized, multi-functional swept source OCT system.

  11. Application of full range swept source optical coherence tomography for imaging of the anterior eye segment in patients with type I Boston Keratoprosthesis

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    We present a high-speed complex conjugate resolved 1 μm swept source optical coherence tomography [SS-OCT] system using coherence revival of the light source for clinical imaging of the anterior segment of the eye. High-speed of 100,000 A-scans/sec and 1 μm imaging window of OCT permits dense 3D imaging of the anterior segment, minimizing the influence of motion artifacts and deep penetration of images for topographic analysis. The swept laser performance with internal clocking was adapted to achieve extended imaging depth requirements. The feasibility of our instrument for visualization of the anterior segment of patients with the Boston Keratoprosthesis (KPro) was discussed. The relations between of the KPro and the surrounding tissue were also demonstrated.

  12. 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.

  13. 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.

  14. Diabetic Choroidopathy: Choroidal Vascular Density and Volume in Diabetic Retinopathy with Swept-Source Optical Coherence Tomography.

    PubMed

    Wang, Jay C; Laíns, Inês; Providência, Joana; Armstrong, Grayson W; Santos, Ana R; Gil, Pedro; Gil, João; Talcott, Katherine E; Marques, João H; Figueira, João; Vavvas, Demetrios G; Kim, Ivana K; Miller, Joan W; Husain, Deeba; Silva, Rufino; Miller, John B

    2017-10-05

    To compare choroidal vascular density (CVD) and volume (CVV) in diabetic eyes and controls, using en face swept-source optical coherence tomography (SS-OCT). Prospective cross-sectional study. ▪▪▪ SETTING: Multicenter PATIENT POPULATION: 143 diabetic eyes - 27 with no diabetic retinopathy (DR), 47 with nonproliferative DR (NPDR), 51 with NPDR and diabetic macular edema (DME), and 18 with proliferative DR (PDR), and 64 age-matched non-diabetic control eyes. Complete ophthalmologic examination and SS-OCT imaging. En face SS-OCT images of the choroidal vasculature were binarized. CVD, calculated as the percent area occupied by choroidal vessels in the central macular region (6-mm diameter circle centered on the fovea), and throughout the posterior pole (12 x 9 mm). The central macular CVV was calculated by multiplying the average CVD by macular area and choroidal thickness (obtained with SS-OCT automated software). Multilevel mixed linear models were performed for analyses. Compared to controls (0.31 ± 0.07), central macular CVD was significantly decreased by 9% in eyes with NPDR + DME (0.28 ± 0.06; ß=-0.03, p=0.02) and by 15% in PDR (0.26 ± 0.05; ß= -0.04, p=0.01). The central macular CVV was significantly decreased by 19% in eyes with PDR (0.020 mm(3) ± 0.005 mm(3), ß = -0.01, p=0.01) compared to controls (0.025 mm(3) ± 0.01 mm(3)). Choroidal vascular density and volume are significantly reduced in more advanced stages of diabetic retinopathy. New imaging modalities should allow further exploration of the contributions of choroidal vessel disease to diabetic eye disease pathogenesis, prognosis, and treatment response. Copyright © 2017. Published by Elsevier Inc.

  15. 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

  16. Repeatability of swept-source optical coherence tomography retinal and choroidal thickness measurements in neovascular age-related macular degeneration.

    PubMed

    Hanumunthadu, Daren; Ilginis, Tomas; Restori, Marie; Sagoo, Mandeep S; Tufail, Adnan; Balaggan, Kamaljit S; Patel, Praveen J

    2017-05-01

    The aim was to determine the intrasession repeatability of swept-source optical coherence tomography (SS-OCT)-derived retinal and choroidal thickness measurements in eyes with neovascular age-related macular degeneration (nAMD). A prospective study consisting of patients with active nAMD enrolled in the Distance of Choroid Study at Moorfields Eye Hospital, London. Patients underwent three 12×9 mm macular raster scans using the deep range imaging (DRI) OCT-1 SS-OCT (Topcon) device in a single imaging session. Retinal and choroidal thicknesses were calculated for the ETDRS macular subfields. Repeatability was calculated according to methods described by Bland and Altman. 39 eyes of 39 patients with nAMD were included with a mean (±SD) age of 73.9 (±7.2) years. The mean (±SD) retinal thickness of the central macular subfield was 225.7 μm (±12.4 μm). The repeatability this subfield, expressed as a percentage of the mean central macular subfield thickness, was 23.2%. The percentage repeatability of the other macular subfields ranged from 13.2% to 28.7%. The intrasession coefficient of repeatability of choroidal thickness of the central macular subfield was 57.2 μm with a mean choroidal thickness (±SD) of 181 μm (±15.8 μm). This study suggests that a change >23.2% of retinal thickness and 57.2 μm choroidal thickness in the central macular subfield is required to distinguish true clinical change from measurement variability when using the DRI OCT-1 device to manage patients with nAMD. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  17. Choroidal thickness maps from spectral domain and swept source optical coherence tomography: algorithmic versus ground truth annotation.

    PubMed

    Philip, Ana-Maria; Gerendas, Bianca S; Zhang, Li; Faatz, Henrik; Podkowinski, Dominika; Bogunovic, Hrvoje; Abramoff, Michael D; Hagmann, Michael; Leitner, Roland; Simader, Christian; Sonka, Milan; Waldstein, Sebastian M; Schmidt-Erfurth, Ursula

    2016-10-01

    The purpose of the study was to create a standardised protocol for choroidal thickness measurements and to determine whether choroidal thickness measurements made on images obtained by spectral domain optical coherence tomography (SD-OCT) and swept source (SS-) OCT from patients with healthy retina are interchangeable when performed manually or with an automatic algorithm. 36 grid cell measurements for choroidal thickness for each volumetric scan were obtained, which were measured for SD-OCT and SS-OCT with two methods on 18 eyes of healthy volunteers. Manual segmentation by experienced retinal graders from the Vienna Reading Center and automated segmentation on >6300 images of the choroid from both devices were statistically compared. Model-based comparison between SD-OCT/SS-OCT showed a systematic difference in choroidal thickness of 16.26±0.725 μm (p<0.001) for manual segmentation and 21.55±0.725 μm (p<0.001) for automated segmentation. Comparison of automated with manual segmentations revealed small differences in thickness of -0.68±0.513 μm (p=0.1833). The correlation coefficients for SD-OCT and SS-OCT measures within eyes were 0.975 for manual segmentation and 0.955 for automatic segmentation. Choroidal thickness measurements of SD-OCT and SS-OCT indicate that these two devices are interchangeable with a trend of choroidal thickness measurements being slightly thicker on SD-OCT with limited clinical relevance. Use of an automated algorithm to segment choroidal thickness was validated in healthy volunteers. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

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

    PubMed

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

    2015-01-01

    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. 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. 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). 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.

  19. Choroidal Imaging with Swept-Source Optical Coherence Tomography in Patients with Birdshot Chorioretinopathy: Choroidal Reflectivity and Thickness.

    PubMed

    Dastiridou, Anna I; Bousquet, Elodie; Kuehlewein, Laura; Tepelus, Tudor; Monnet, Dominique; Salah, Sawsen; Brezin, Antoine; Sadda, Srinivas R

    2017-08-01

    To characterize choroidal thickness and choroidal reflectivity in the eyes of patients with birdshot chorioretinopathy (BSCR). Cross-sectional observational study. Two hundred twenty BSCR patients and 59 healthy controls. Patients with BSCR and healthy controls underwent imaging of the macula in both eyes with a swept-source optical coherence tomography device (DRI-OCT1 Atlantis; Topcon). Images were exported from the device, and analysis was performed by 2 graders in the Doheny Image Reading Center using Image J software. The choroidal thickness at the foveal center was measured. In addition, the inner and outer boundaries of the choroid and retinal pigment epithelium (RPE) as well as the inner retinal surface all were segmented to allow the brightness and reflectivity of the pixels in the choroid, RPE band, and overlying vitreous to be quantified. An adjusted or normalized choroidal reflectivity, with the RPE as the bright reference standard and the vitreous as the dark reference standard, was computed using the formula: normalized choroidal reflectivity = (choroidal reflectivity-vitreous reflectivity)/RPE reflectivity. Choroidal reflectivity and choroidal thickness. Three hundred eighty-six eyes in the BSCR group and 59 eyes in the control group were included in this analysis. Higher choroidal reflectivity and lower choroidal thickness were documented in inactive BSCR patients compared with active BSCR and controls (P < 0.01). Active BSCR patients showed lower choroidal thickness compared with controls (P < 0.01). There was a negative correlation between choroidal reflectivity and choroidal thickness (r = -0.793; P < 0.001). On multiple regression analysis, choroidal thickness, age, and disease duration (all P < 0.01) all were significant predictors of choroidal reflectivity. Choroidal reflectivity and choroidal thickness changes are evident in active and inactive BSCR patients. Novel choroidal parameters such as choroidal reflectivity may warrant further

  20. Complete complex conjugate resolved heterodyne swept-source optical coherence tomography using a dispersive optical delay line

    PubMed Central

    Dhalla, Al-Hafeez; Izatt, Joseph A.

    2011-01-01

    Swept-source optical coherence tomography (SSOCT) provides a substantial sensitivity advantage over its time-domain counterpart, but suffers from a reduced imaging depth range due to sensitivity falloff and complex conjugate ambiguity. Heterodyne complex conjugate-resolved SSOCT (HCCR-SSOCT) has been previously demonstrated as a technique to completely resolve the complex conjugate ambiguity, effectively doubling the falloff limited imaging depth, without the reduction in imaging speed associated with other CCR techniques. However, previous implementations of this technique have employed expensive and lossy optical modulators to provide the required differential phase modulation. In this paper, we demonstrate the use of a dispersive optical delay line (D-ODL) as the reference arm of an OCT system to realize HCCR-SSOCT. This technique maintains the existing advantages of HCCR-SSOCT in that it completely resolves the complex conjugate artifact and does not reduce imaging speed, while conferring the additional advantages of being low cost, maintaining system sensitivity and resolution, not requiring any additional signal processing, and working at all wavelengths and imaging speeds. The D-ODL also allows for hardware correction of unbalanced dispersion in the reference and sample arm, adding further flexibility to system design. We demonstrate the technique using an SSOCT system operating at 100kHz with a central wavelength of 1040nm. Falloff measurements performed using a standard OCT configuration and the proposed D-ODL demonstrate a doubling of the effective imaging range with no sensitivity or resolution penalty. Feasibility of the technique for in vivo imaging was demonstrated by imaging the ocular anterior segments of healthy human volunteers. PMID:21559133

  1. 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

  2. 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.

  3. Choroidal Line Scan Measurements in Swept-Source Optical Coherence Tomography as Surrogates for Volumetric Thickness Assessment.

    PubMed

    Gerendas, Bianca S; Hecht, Alexander; Kundi, Michael; Waldstein, Sebastian M; Deak, Gabor; Simader, Christian; Montuoro, Alessio; Schmidt-Erfurth, Ursula; Funk, Marion

    2016-02-01

    To compare choroidal thickness of different areas on swept-source optical coherence tomography (SSOCT) line and cube scans for their interchangeable use. Validity analysis. SSOCT line and cube scans were obtained from 21 patients with various choroidal thicknesses. Subfoveal center point choroidal thickness, mean central millimeter choroidal thickness, and mean 6-mm-area choroidal thicknesses were obtained from both eyes by 2 independent graders in a reading center setting. Cross-correlations were performed using Passing and Bablok regression models. A 95% confidence interval of slope that included 1 was considered to indicate no significant difference. Average choroidal thickness of center point, Early Treatment Diabetic Retinopathy Study grid subfields, and total grid area of 6 mm on both scans and the correlation between different areas served as main outcome measures. No significant difference between line scans/corresponding subfields of cube scans (outer nasal 0.92-1.11, inner nasal 0.88-1.06, central 0.94-1.11, inner temporal 0.95-1.12, outer temporal 0.93-1.17). No significant difference between subfoveal center point measurement/mean of choroidal thickness in the central millimeter of cube scans (0.89-1.08). Significant difference of subfoveal center point measurement or mean of central millimeter area of cube scans to entire 6-mm area of cube scans (1.01-1.53 and 1.03-1.38). Measurements on a single SSOCT horizontal line scan can represent the entire choroid but subfoveal center point measurements are only indicative for the central millimeter area. There is a consistent overestimation of choroidal thickness when trying to estimate overall choroidal thickness from any central measurement. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. 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.

  5. 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

  6. Comparison of choroidal thickness measurements between spectral-domain OCT and swept-source OCT in normal and diseased eyes

    PubMed Central

    Zafar, Sidra; Siddiqui, MA Rehman; Shahzad, Rida

    2016-01-01

    Purpose Sub-foveal choroidal thickness (SFCT) is affected in many ocular diseases. The aim of this study was to compare SFCT measurements between Topcon 3D 2000 spectral-domain optical coherence tomography (SD-OCT) and Topcon swept-source OCT (SS-OCT), with different laser wavelengths, in normal and diseased populations. Materials and methods This was a prospective, cross-sectional, noninterventional study including 27 normal volunteers and 27 participants with retinal disease. OCT scans were performed sequentially and under standardized conditions using both SD-OCT and SS-OCT. The OCT scans were evaluated by two independent graders. Paired t-tests and intraclass correlation coefficients (ICCs) were used to assess the statistically significant difference between SFCT measurements as measured by the two devices. Results Mean SFCT measurements for all 54 participants were 264.9±103.1 μm using SD-OCT (range: 47–470 μm) and 278.5±110.5 μm using SS-OCT (range: 56–502 μm), with an inter-device ICC of 0.850. Greater variability was noted in the diseased eyes. Inter-device ICCs were 0.870 (95% CI; 0.760–0.924) and 0.840 (95% CI; 0.654–0.930) for normal and diseased eyes, respectively. However, the difference was not statistically significant (P=0.132). Conclusion Both machines reliably measure SFCT. Larger studies are needed to confirm these findings. PMID:27881909

  7. Assessment of Choroidal Thickness and Volume During the Water Drinking Test By Swept-Source Optical Coherence Tomography

    PubMed Central

    Mansouri, Kaweh; Medeiros, Felipe A.; Marchase, Nicholas; Tatham, Andrew J.; Auerbach, Daniel; Weinreb, Robert N.

    2013-01-01

    Objective To evaluate changes in peripapillary and macular choroidal thickness and volume after the water-drinking test (WDT) using swept-source optical coherence tomography (SS-OCT). Design Prospective, cross-sectional observational study. Participants Fifty-six eyes of 28 healthy volunteers. Methods Participants underwent a 3-dimensional optic disc and macula scanning protocol with a prototype SS-OCT (Topcon Inc., Tokyo, Japan) at baseline and 15, 30, 45, and 120 minutes after the start of the WDT. The WDT consisted of drinking 1000mL of water within five minutes. Objective measurements of the choroid were obtained with automated segmentation of the choroidal boundaries. Main Outcome Measures Choroidal thickness and volume. Results Mean (standard deviation) age of participants was 35.6 ± 9.1 years. Intraocular pressure (IOP) increased from 14.9 ± 2.7 mmHg at baseline to a peak of 16.8 ± 3.0 mmHg at 15 minutes after the WDT (p<0.001). Mean baseline choroidal thickness and volume were 181.3 ± 50.8 μm and 6.19 ± 1.80 mm3 at the optic disc and 217.4 ± 43.6 μm and 7.83 ± 1.55 mm3 at the macula. Following the WDT, peripapillary and macular choroidal thickness increased by a maximum of 5.7% (P < 0.001) and 4.3% (P < 0.001) respectively. Choroidal volumes increased by 6.4% (P < 0.001) and 3.9% (P < 0.001), respectively. There was no association between change in IOP and peripapillary (P = 0.27) or macular (P = 0.09) choroidal thickness. Conclusions Using automated segmentation of SS-OCT measurements, significant increases in choroidal thickness and volume are observed after the WDT in healthy subjects. PMID:24021895

  8. 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.

  9. 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

  10. Improvement of Coherence Length in a 200 kHz Swept Light Source with a KTa1-xNbxO3 Deflector Using an Etalon

    NASA Astrophysics Data System (ADS)

    Ueno, Masahiro; Okabe, Yuichi; Toyoda, Seiji; Sakamoto, Takashi; Sasaki, Yuzo; Kobayashi, Junya; Naganuma, Kazunori; Yagi, Shogo

    2013-12-01

    For swept-source optical tomography, we demonstrate that the coherence length of a light source comprising a Littman-Metcalf external cavity with a KTa1-xNbxO3 (KTN) electrooptic deflector is increased by inserting an etalon into the cavity. Experimental results confirm that inserting the etalon into the laser cavity can significantly improve the coherence length of the laser output from 3.5 to around 23 mm at a 200 kHz repetition rate and 20 mW average output power in a 100 nm scanning range centered at 1.31 µm.

  11. 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

  12. Modular multimodal swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography scan-head for surgical microscope-integrated and slit-lamp imaging

    NASA Astrophysics Data System (ADS)

    Malone, Joseph D.; Li, Jianwei D.; El-Haddad, Mohamed T.; Joos, Karen M.; Patel, Shriji N.; Tao, Yuankai K.

    2017-02-01

    Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) enable noninvasive in vivo diagnostic imaging and provide complementary en face and depth-resolved visualization of ophthalmic structures, respectively. We previously demonstrated concurrent multimodal swept-source spectrally encoded scanning laser ophthalmoscopy and OCT (SS-SESLO-OCT) at 1060 nm using a swept-source and double clad fiber coupler. Here, we present system enhancements and novel designs for a modular SS-SESLO-OCT scan-head that can be coupled to ophthalmic surgical microscope-integrated and slit-lamp imaging optics. Multimodal SS-SESLO-OCT was demonstrated using a custom-built swept-source OCT engine with a 200 kHz 1060 nm source that was optically buffered for concurrent SESLO and OCT imaging at 100% duty cycle and 400 kHz sweep-rate. A shared optical relay and fast-axis galvanometer ensured inherent co-registration between SESLO and OCT field-of-views and concurrent acquisition of an en face SESLO image with each OCT cross-section. SESLO and OCT frames were acquired at 200 fps with 2560 x 2000 pix. (spectral x lateral). We show in vivo human ophthalmic imaging data using surgical microscope-integrated and slit-lamp imaging relays to demonstrate the utility of our SS-SESLO-OCT design. Our self-contained modular scan-head can be used for either intraoperative guidance or clinical diagnostics and reduces the complexity, cost, and maintenance required for clinical translation of these technologies. We believe concurrent multimodal SS-SESLO-OCT may benefit 1) intraoperative imaging by allowing for real-time surgical feedback, instrument tracking, and overlays of computationally extracted image-based surrogate biomarkers of disease, and 2) slit-lamp imaging by enabling aiming, image registration, and multi-field mosaicking.

  13. En face enhanced-depth swept-source optical coherence tomography features of chronic central serous chorioretinopathy.

    PubMed

    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

    2014-03-01

    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. Consecutive patients with chronic CSCR were prospectively examined with SS-OCT. Fifteen eyes of 13 patients. Three-dimensional 6×6 mm macular cube raster scans were obtained with SS-OCT operating at 1050 nm wavelength and 100000 A-lines/sec with 6 μm 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, fluorescein angiography, and indocyanine-green angiography (ICGA). En face SS-OCT morphology of the RPE and individual choroidal layers. En face SS-OCT imaging at the RPE level revealed absence of signal corresponding to RPE detachment or RPE loss in 15 of 15 (100%) eyes. 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 (CNV), distinct en face SS-OCT features corresponded to the neovascular lesions. High-speed, enhanced-depth SS-OCT at 1050 nm wavelength enables the visualization of pathologic features of the RPE and choroid in eyes with chronic CSCR not usually appreciated with standard spectral domain (SD) OCT. En face SS-OCT imaging seems to be a useful tool in

  14. Automated Quantitation of Choroidal Neovascularization: A Comparison Study Between Spectral-Domain and Swept-Source OCT Angiograms

    PubMed Central

    Zhang, Qinqin; Chen, Chieh-Li; Chu, Zhongdi; Zheng, Fang; Miller, Andrew; Roisman, Luiz; Rafael de Oliveira Dias, Joao; Yehoshua, Zohar; Schaal, Karen B.; Feuer, William; Gregori, Giovanni; Kubach, Sophie; An, Lin; Stetson, Paul F.; Durbin, Mary K.; Rosenfeld, Philip J.; Wang, Ruikang K.

    2017-01-01

    Purpose To compare the lesion sizes of choroidal neovascularization (CNV) imaged with spectral-domain (SD) and swept-source (SS) optical coherence tomography angiography (OCTA) and measured using an automated detection algorithm. Methods Patients diagnosed with CNV were imaged by SD-OCTA and SS-OCTA systems using 3 × 3-mm and 6 × 6-mm scans. The complex optical microangiography (OMAGC) algorithm was used to generate the OCTA images. Optical coherence tomography A datasets for imaging CNV were derived by segmenting from the outer retina to 8 μm below Bruch's membrane. An artifact removal algorithm was used to generate angiograms free of retinal vessel projection artifacts. An automated detection algorithm was developed to quantify the size of the CNV. Automated measurements were compared with manual measurements. Measurements from SD-OCTA and SS-OCTA instruments were compared as well. Results Twenty-seven eyes from 23 subjects diagnosed with CNV were analyzed. No significant differences were detected between manual and automatic measurements: SD-OCTA 3 × 3-mm (P = 0.61, paired t-test) and 6 × 6-mm (P = 0.09, paired t-test) scans and the SS-OCTA 3 × 3-mm (P = 0.41, paired t-test) and 6 × 6-mm (P = 0.16, paired t-test) scans. Bland-Altman analyses were performed to confirm the agreement between automatic and manual measurements. Mean lesion sizes were significantly larger for the SS-OCTA images compared with the SD-OCTA images: 3 × 3-mm scans (P = 0.011, paired sample t-test) and the 6 × 6-mm scans (P = 0.021, paired t-test). Conclusions The automated algorithm measurements of CNV were in agreement with the hand-drawn measurements. On average, automated SS-OCTA measurements were larger than SD-OCTA measurements and consistent with the results from using hand-drawn measurements. PMID:28273317

  15. Comparison Between Spectral-Domain and Swept-Source Optical Coherence Tomography Angiographic Imaging of Choroidal Neovascularization

    PubMed Central

    Miller, Andrew R.; Roisman, Luiz; Zhang, Qinqin; Zheng, Fang; Rafael de Oliveira Dias, Joao; Yehoshua, Zohar; Schaal, Karen B.; Feuer, William; Gregori, Giovanni; Chu, Zhongdi; Chen, Chieh-Li; Kubach, Sophie; An, Lin; Stetson, Paul F.; Durbin, Mary K.; Wang, Ruikang K.; Rosenfeld, Philip J.

    2017-01-01

    Purpose The purpose of this study was to compare imaging of choroidal neovascularization (CNV) using swept-source (SS) and spectral-domain (SD) optical coherence tomography angiography (OCTA). Methods Optical coherence tomography angiography was performed using a 100-kHz SS-OCT instrument and a 68-kHz SD-OCTA instrument (Carl Zeiss Meditec, Inc.). Both 3 × 3- and 6 × 6-mm2 scans were obtained on both instruments. The 3 × 3-mm2 SS-OCTA scans consisted of 300 A-scans per B-scan at 300 B-scan positions, and the SD-OCTA scans consisted of 245 A-scans at 245 B-scan positions. The 6 × 6-mm2 SS-OCTA scans consisted of 420 A-scans per B-scan at 420 B-scan positions, and the SD-OCTA scans consisted of 350 A-scans and 350 B-scan positions. B-scans were repeated four times at each position in the 3 × 3-mm2 scans and twice in the 6 × 6-mm2 scans. Choroidal neovascularization was excluded if not fully contained within the 3 × 3-mm2 scans. The same algorithm was used to detect CNV on both instruments. Two graders outlined the CNV, and the lesion areas were compared between instruments. Results Twenty-seven consecutive eyes from 23 patients were analyzed. For the 3 × 3-mm2 scans, the mean lesion areas for the SS-OCTA and SD-OCTA instruments were 1.17 and 1.01 mm2, respectively (P = 0.047). For the 6 × 6-mm2 scans, the mean lesion areas for the SS-OCTA and SD-OCTA instruments were 1.24 and 0.74 mm2 (P = 0.003). Conclusions The areas of CNV tended to be larger when imaged with SS-OCTA than with SD-OCTA, and this difference was greater for the 6 × 6-mm2 scans. PMID:28273316

  16. A pilot study to image the vascular network of small melanocytic choroidal tumors with speckle noise-free 1050-nm swept source optical coherence tomography (OCT choroidal angiography).

    PubMed

    Maloca, Peter; Gyger, Cyrill; Hasler, Pascal W

    2016-06-01

    To visualize and measure the vascular network of melanocytic choroidal tumors with speckle noise-free swept source optical coherence tomography (SS-OCT choroidal angiography). Melanocytic choroidal tumors from 24 eyes were imaged with 1050-nm optical coherence tomography (Topcon DRI OCT-1 Atlantis). A semi-automated algorithm was developed to remove speckle noise and to extract and measure the volume of the choroidal vessels from the obtained OCT data. In all cases, analysis of the choroidal vessels could be performed with SS-OCT without the need for pupillary dilation. The proposed method allows speckle noise-free, structure-guided visualization and measurement of the larger choroidal vessels in three dimensions. The obtained data suggest that speckle noise-free OCT may be more effective at identifying choroidal structures than traditional OCT methods. The measured volume of the extracted choroidal vessels of Haller's layer and Sattler's layer in the examined tumorous eyes was on average 0.982463955 mm(3) /982463956 μm(3) (range of 0.209764406 mm(3) /209764405.9 μm(3)to 1.78105544 mm(3) /1781055440 μm(3)). Full thickness obstruction of the choroidal vasculature by the tumor was found in 18 cases (72 %). In seven cases (18 %), choroidal vessel architecture did not show pronounced morphological abnormalities (18 %). Speckle noise-free OCT may serve as a new illustrative imaging technology and enhance visualization of the choroidal vessels without the need for dye injection. OCT can be used to identify and evaluate the choroidal vessels of melanocytic choroidal tumors, and may represent a potentially useful tool for imaging and monitoring of choroidal nevi and melanoma.

  17. Ultrahigh speed 1050nm swept source/Fourier domain OCT retinal and anterior segment imaging at 100,000 to 400,000 axial scans per second.

    PubMed

    Potsaid, Benjamin; Baumann, Bernhard; Huang, David; Barry, Scott; Cable, Alex E; Schuman, Joel S; Duker, Jay S; Fujimoto, James G

    2010-09-13

    We demonstrate ultrahigh speed swept source/Fourier domain ophthalmic OCT imaging using a short cavity swept laser at 100,000 - 400,000 axial scan rates. Several design configurations illustrate tradeoffs in imaging speed, sensitivity, axial resolution, and imaging depth. Variable rate A/D optical clocking is used to acquire linear-in-k OCT fringe data at 100 kHz axial scan rate with 5.3 um axial resolution in tissue. Fixed rate sampling at 1 GSPS achieves a 7.5mm imaging range in tissue with 6.0 um axial resolution at 100 kHz axial scan rate. A 200 kHz axial scan rate with 5.3 um axial resolution over 4mm imaging range is achieved by buffering the laser sweep. Dual spot OCT using two parallel interferometers achieves 400 kHz axial scan rate, almost 2X faster than previous 1050 nm ophthalmic results and 20X faster than current commercial instruments. Superior sensitivity roll-off performance is shown. Imaging is demonstrated in the human retina and anterior segment. Wide field 12x12 mm data sets include the macula and optic nerve head. Small area, high density imaging shows individual cone photoreceptors. The 7.5 mm imaging range configuration can show the cornea, iris, and anterior lens in a single image. These improvements in imaging speed and depth range provide important advantages for ophthalmic imaging. The ability to rapidly acquire 3D-OCT data over a wide field of view promises to simplify examination protocols. The ability to image fine structures can provide detailed information on focal pathologies. The large imaging range and improved image penetration at 1050 m wavelengths promises to improve performance for instrumentation which images both the retina and anterior eye. These advantages suggest that swept source OCT at 1050 nm wavelengths will play an important role in future ophthalmic instrumentation.

  18. 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.

  19. Geometric & radiometric vignetting associated with a 72-facet, off-axis, polygon mirror for swept source optical coherence tomography (SS-OCT)

    NASA Astrophysics Data System (ADS)

    Everson, Michael; Duma, Virgil-Florin; Dobre, George

    2017-01-01

    Optical Coherence Tomography (OCT) has a broad range of applications in 2D and volumetric imaging of micron scale structures typically used on inaccessible objects such as the retina of the eye. This report focuses on Swept Source OCT (SS-OCT), favoured for its faster scanning speeds and therefore faster data acquisition (highly favourable when imaging live patients). SS-OCT relies on the scanning of a narrow laser line at speeds typically in excess of 100 kHz. We have employed ZemaxTM ray tracing software to simulate one method of splitting the spectrum of a broadband, near-infrared source, into its component wavelengths by reflecting the spectrum from an off-axis, 72-facet polygon mirror at a frequency of 48 kHz. We specifically addressed the geometric and radiometric vignetting associated with the reflected spectrum off an individual mirrored facet and how this may impose limitations to the incident beam size and hence lead to a loss in the power available from the source. It was found that for certain configurations up to 44% of the light was lost at the edges of the spectrum due to both radiometric and geometric vignetting, which may result in an effective swept range of <50 nm from an initial bandwidth of 100 nm. Our simulations account for real refractive errors and losses in the beam caused by lens aberrations, and produce a model of the sampling function of wavelength against time.

  20. 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

  1. 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.

  2. Quantitative assessment of oral mucosa and labial minor salivary glands in patients with Sjögren’s syndrome using swept source OCT

    PubMed Central

    Grulkowski, Ireneusz; Nowak, Jan K.; Karnowski, Karol; Zebryk, Paweł; Puszczewicz, Mariusz; Walkowiak, Jaroslaw; Wojtkowski, Maciej

    2013-01-01

    Three-dimensional imaging of the mucosa of the lower lip and labial minor salivary glands is demonstrated in vivo using swept source optical coherence tomography (OCT) system at 1310 nm with modified interface. Volumetric data sets of the inner surface of the lower lip covering ~230 mm2 field are obtained from patients with Sjögren’s syndrome and a control group. OCT enables high-resolution visualization of mucosal architecture using cross-sectional images as well as en-face projection images. Comprehensive morphometry of the labial minor salivary glands is performed, and statistical significance is assessed. Statistically significant differences in morphometric parameters are found when subgroups of patients with Sjögren’s syndrome are analyzed. PMID:24466492

  3. 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

  4. 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.

  5. Image-guided feedback for ophthalmic microsurgery using multimodal intraoperative swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Li, Jianwei D.; Malone, Joseph D.; El-Haddad, Mohamed T.; Arquitola, Amber M.; Joos, Karen M.; Patel, Shriji N.; Tao, Yuankai K.

    2017-02-01

    Surgical interventions for ocular diseases involve manipulations of semi-transparent structures in the eye, but limited visualization of these tissue layers remains a critical barrier to developing novel surgical techniques and improving clinical outcomes. We addressed limitations in image-guided ophthalmic microsurgery by using microscope-integrated multimodal intraoperative swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography (iSS-SESLO-OCT). We previously demonstrated in vivo human ophthalmic imaging using SS-SESLO-OCT, which enabled simultaneous acquisition of en face SESLO images with every OCT cross-section. Here, we integrated our new 400 kHz iSS-SESLO-OCT, which used a buffered Axsun 1060 nm swept-source, with a surgical microscope and TrueVision stereoscopic viewing system to provide image-based feedback. In vivo human imaging performance was demonstrated on a healthy volunteer, and simulated surgical maneuvers were performed in ex vivo porcine eyes. Denselysampled static volumes and volumes subsampled at 10 volumes-per-second were used to visualize tissue deformations and surgical dynamics during corneal sweeps, compressions, and dissections, and retinal sweeps, compressions, and elevations. En face SESLO images enabled orientation and co-registration with the widefield surgical microscope view while OCT imaging enabled depth-resolved visualization of surgical instrument positions relative to anatomic structures-of-interest. TrueVision heads-up display allowed for side-by-side viewing of the surgical field with SESLO and OCT previews for real-time feedback, and we demonstrated novel integrated segmentation overlays for augmented-reality surgical guidance. Integration of these complementary imaging modalities may benefit surgical outcomes by enabling real-time intraoperative visualization of surgical plans, instrument positions, tissue deformations, and image-based surrogate biomarkers correlated with completion of

  6. 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

  7. 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.

  8. 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.

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

    PubMed

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

    2015-07-01

    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.

  10. Dynamics of macular hole closure in gas-filled eyes within 24 h of surgery observed with swept source optical coherence tomography.

    PubMed

    Kikushima, Wataru; Imai, Akira; Toriyama, Yuichi; Hirano, Takao; Murata, Toshinori; Ishibashi, Tatsuro

    2015-01-01

    To investigate the dynamics of macular hole (MH) closure in gas-filled eyes starting 20 min after vitrectomy using swept source optical coherence tomography (SS-OCT). Twenty consecutive eyes with MH underwent vitrectomy with internal limiting membrane peeling and gas tamponade. SS-OCT imaging was performed approximately 20 min after the operation, and then once a day, until MH closure was confirmed. The correlation between the base, top and minimum hole diameters and the duration required for MH closure was investigated. MH closure in gas-filled eyes was confirmed in 1 eye on day 0, 10 eyes on day 1, 2 eyes on day 2, and 3 eyes on day 3, at which times face-down posturing was discontinued without MH recurrence. SS-OCT revealed a distinct closure pattern within the first 24 h postoperatively. MHs closing by day 1 had a significantly smaller minimum diameter (312.5 ± 105.2 µm) than holes closing on day 2 or later (510.8 ± 153.5 µm; p = 0.019). SS-OCT enables tomographic images of MH in gas-filled eyes immediately postoperatively, thus permitting early discontinuation of, or no necessity for, face-down positioning upon confirmation of MH closure. © 2014 S. Karger AG, Basel.

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. Lower Tear Meniscus Measurements Using a New Anterior Segment Swept-Source Optical Coherence Tomography and Agreement With Fourier-Domain Optical Coherence Tomography.

    PubMed

    Arriola-Villalobos, Pedro; Fernández-Vigo, José Ignacio; Díaz-Valle, David; Almendral-Gómez, Jaime; Fernández-Pérez, Cristina; Benítez-Del-Castillo, José M

    2017-02-01

    To assess intraobserver repeatability and interobserver and intersession reproducibility of lower tear meniscus height (LTMH) measurements obtained using a new anterior segment swept-source optical coherence tomography (SS-OCT) device. Agreement with Fourier-domain (FD) OCT (Spectralis) was also examined. In an observational cross-sectional study, one eye of 29 healthy subjects was randomly imaged with both devices at our center. Two examiners then randomly measured the LTMH using the software's calipers. To assess intraobserver repeatability and interobserver and intersession reproducibility, within-subject standard deviation (Sw), test-retest repeatability, coefficients of variation (CoV), and intraclass correlation coefficients (ICCs) were calculated. Agreement between both devices was also determined in Bland-Altman plots. Mean LTMHs for SS-OCT and FD-OCT were 276.6 ± 87.6 and 280.3 ± 80 μm, respectively. Using the SS-OCT device, intraobserver CoV, interobserver CoV, and intersession CoV were found to be ≥16.9%, ≤7.2%, and ≤11.5%, respectively. ICCs for these parameters were ≤88%, ≥97%, and ≥94%, respectively. Bland-Altman analysis indicated poor agreement between SS-OCT and FD-OCT, and the correlation was low (CoV 34.5%, ICC 0.36). SS-OCT LTMH measurements showed excellent interobserver and intersession repeatability along with good intraobserver reproducibility. Agreement between the devices was poor.

  16. Lower Tear Meniscus Measurements Using a New Anterior Segment Swept-Source Optical Coherence Tomography and Agreement With Fourier-Domain Optical Coherence Tomography.

    PubMed

    Arriola-Villalobos, Pedro; Fernández-Vigo, José Ignacio; Díaz-Valle, David; Almendral-Gómez, Jaime; Fernández-Pérez, Cristina; Benítez-Del-Castillo, José M

    2016-11-23

    To assess intraobserver repeatability and interobserver and intersession reproducibility of lower tear meniscus height (LTMH) measurements obtained using a new anterior segment swept-source optical coherence tomography (SS-OCT) device. Agreement with Fourier-domain (FD) OCT (Spectralis) was also examined. In an observational cross-sectional study, one eye of 29 healthy subjects was randomly imaged with both devices at our center. Two examiners then randomly measured the LTMH using the software's calipers. To assess intraobserver repeatability and interobserver and intersession reproducibility, within-subject standard deviation (Sw), test-retest repeatability, coefficients of variation (CoV), and intraclass correlation coefficients (ICCs) were calculated. Agreement between both devices was also determined in Bland-Altman plots. Mean LTMHs for SS-OCT and FD-OCT were 276.6 ± 87.6 and 280.3 ± 80 μm, respectively. Using the SS-OCT device, intraobserver CoV, interobserver CoV, and intersession CoV were found to be ≥16.9%, ≤7.2%, and ≤11.5%, respectively. ICCs for these parameters were ≤88%, ≥97%, and ≥94%, respectively. Bland-Altman analysis indicated poor agreement between SS-OCT and FD-OCT, and the correlation was low (CoV 34.5%, ICC 0.36). SS-OCT LTMH measurements showed excellent interobserver and intersession repeatability along with good intraobserver reproducibility. Agreement between the devices was poor.

  17. In vivo high-contrast imaging of deep posterior eye by 1-um swept source optical coherence tomography and scattering optical coherence angiography

    NASA Astrophysics Data System (ADS)

    Yasuno, Yoshiaki; Hong, Youngjoo; Makita, Shuichi; Yamanari, Masahiro; Akiba, Masahiro; Miura, Masahiro; Yatagai, Toyohiko

    2007-05-01

    Retinal, choroidal and scleral imaging by using swept-source optical coherence tomography (SS-OCT) with a 1-μm band probe light, and high-contrast and three-dimensional (3D) imaging of the choroidal vasculature are presented. This SS-OCT has a measurement speed of 28,000 A-lines/s, a depth resolution of 10.4 μm in tissue, and a sensitivity of 99.3 dB. Owing to the high penetration of the 1-μm probe light and the high sensitivity of the system, the in vivo sclera of a healthy volunteer can be observed. A software-based algorithm of scattering optical coherence angiography (S-OCA) is developed for the high-contrast and 3D imaging of the choroidal vessels. The S-OCA is used to visualize the 3D choroidal vasculature of the in vivo human macula and the optic nerve head. Comparisons of S-OCA with several other angiography techniques including Doppler OCA, Doppler OCT, fluorescein angiography, and indocyanine green angiography are also presented.

  18. 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.

  19. Visualizing the Choriocapillaris Under Drusen: Comparing 1050-nm Swept-Source Versus 840-nm Spectral-Domain Optical Coherence Tomography Angiography

    PubMed Central

    Lane, Mark; Moult, Eric M.; Novais, Eduardo A.; Louzada, Ricardo N.; Cole, Emily D.; Lee, ByungKun; Husvogt, Lennart; Keane, Pearse A.; Denniston, Alastair K.; Witkin, André J.; Baumal, Caroline R.; Fujimoto, James G.; Duker, Jay S.; Waheed, Nadia K.

    2016-01-01

    Purpose To investigate the appearance of choriocapillaris (CC) flow under drusen by comparing long-wavelength (1050 nm) swept-source optical coherence tomography (SS-OCT) angiography with shorter-wavelength (840 nm) spectral-domain (SD) OCT angiography. Methods Patients with drusen imaged on both devices on the same day were selected and graded. Ambiguous OCT angiography (OCTA) signal loss was defined as low OCTA signal on the en face OCTA CC image that also had low OCT signal in the corresponding area on the en face OCT CC image and OCT B-scans. Unambiguous OCTA signal loss was defined as low OCTA signal on the en face OCTA CC image that did not have low OCT signal in the corresponding area on the en face OCT CC image and OCT B-scans. False-positive flow impairment on SS-OCTA was defined as ambiguous OCTA signal loss on SS-OCTA but no OCTA signal loss on SD-OCTA. False-positive flow impairment on SD-OCTA was defined as ambiguous OCTA signal loss on SD-OCTA but no OCTA signal loss on SS-OCTA. Results Nine eyes from seven patients were enrolled, 23 drusen were analyzed. On 840-nm SD-OCTA, 17 drusen (73.9%) exhibited OCTA signal loss. Fourteen (82.4%) were classified as ambiguous, and three (17.6%) were classified as unambiguous; 10 (58.8%) were classified as having false-positive flow impairment. On 1050-nm SS-OCTA, seven drusen (30.4%) exhibited OCTA signal loss and were classified as unambiguous; none were classified as having false-positive flow impairment. Conclusions Results showed that 1050-nm SS-OCTA appears less prone to producing areas of false-positive flow impairment under drusen. PMID:27547891

  20. Choroidal Thickness and Choroidal Vessel Density in Nonexudative Age-Related Macular Degeneration Using Swept-Source Optical Coherence Tomography Imaging.

    PubMed

    Zheng, Fang; Gregori, Giovanni; Schaal, Karen B; Legarreta, Andrew D; Miller, Andrew R; Roisman, Luiz; Feuer, William J; Rosenfeld, Philip J

    2016-11-01

    To analyze the relationship between choroidal thickness and the distribution of choroidal blood vessels in eyes with nonexudative AMD. Eyes with a diagnosis of nonexudative AMD were imaged using a prototype 100-kHz swept-source (SS) optical coherence tomography (OCT) instrument (Carl Zeiss Meditec, Dublin, CA, USA) with a central wavelength of 1050 nm. We used an OCT cube scan pattern consisting of 512 × 512 A-scans over a 12 × 12 mm retinal area. The eyes were partitioned into two groups based on the presence or absence of reticular pseudodrusen (RPD). All scans were segmented using an automated algorithm. In addition, five eyes from each of the two groups were randomly chosen for manual segmentation. Binary choroidal vessels maps were generated from suitable OCT choroidal slabs, and the relationship between the density of large choroidal vessels and choroidal thickness was analyzed using an Early Treatment Diabetic Retinopathy Study-like target centered on the fovea. Twenty-five eyes were enrolled in each group. The automated algorithm produced accurate choroidal thickness maps with an average difference between the manual and automated segmentations of 13.7 μm. There was a significant and stable correlation between choroidal thickness and choroidal vessel density across the two groups. Both average choroidal thickness and vessel density were significantly lower in eyes with RPD. Our fully automated choroidal segmentation algorithm was able to capture the different patterns of choroidal thickness over a wide area. Choroidal thickness has a clear relationship with the density of large choroid vessels in our sample, irrespective of the presence or absence of RPD.

  1. Visualizing the Choriocapillaris Under Drusen: Comparing 1050-nm Swept-Source Versus 840-nm Spectral-Domain Optical Coherence Tomography Angiography.

    PubMed

    Lane, Mark; Moult, Eric M; Novais, Eduardo A; Louzada, Ricardo N; Cole, Emily D; Lee, ByungKun; Husvogt, Lennart; Keane, Pearse A; Denniston, Alastair K; Witkin, André J; Baumal, Caroline R; Fujimoto, James G; Duker, Jay S; Waheed, Nadia K

    2016-07-01

    To investigate the appearance of choriocapillaris (CC) flow under drusen by comparing long-wavelength (1050 nm) swept-source optical coherence tomography (SS-OCT) angiography with shorter-wavelength (840 nm) spectral-domain (SD) OCT angiography. Patients with drusen imaged on both devices on the same day were selected and graded. Ambiguous OCT angiography (OCTA) signal loss was defined as low OCTA signal on the en face OCTA CC image that also had low OCT signal in the corresponding area on the en face OCT CC image and OCT B-scans. Unambiguous OCTA signal loss was defined as low OCTA signal on the en face OCTA CC image that did not have low OCT signal in the corresponding area on the en face OCT CC image and OCT B-scans. False-positive flow impairment on SS-OCTA was defined as ambiguous OCTA signal loss on SS-OCTA but no OCTA signal loss on SD-OCTA. False-positive flow impairment on SD-OCTA was defined as ambiguous OCTA signal loss on SD-OCTA but no OCTA signal loss on SS-OCTA. Nine eyes from seven patients were enrolled, 23 drusen were analyzed. On 840-nm SD-OCTA, 17 drusen (73.9%) exhibited OCTA signal loss. Fourteen (82.4%) were classified as ambiguous, and three (17.6%) were classified as unambiguous; 10 (58.8%) were classified as having false-positive flow impairment. On 1050-nm SS-OCTA, seven drusen (30.4%) exhibited OCTA signal loss and were classified as unambiguous; none were classified as having false-positive flow impairment. Results showed that 1050-nm SS-OCTA appears less prone to producing areas of false-positive flow impairment under drusen.

  2. Axial length measurements: Comparison of a new swept-source optical coherence tomography-based biometer and partial coherence interferometry in myopia.

    PubMed

    Yang, Jong Yun; Kim, Hong Kyu; Kim, Sung Soo

    2017-03-01

    To compare axial length (AL) measurements between a swept-source optical coherence tomography (SS-OCT) biometer (IOLMaster 700) and a partial coherence interferometry (PCI) biometer (IOLMaster, version 5.4) in myopic eyes. Severance Hospital, Yonsei University, Seoul, South Korea. Prospective evaluation of a diagnostic test. This study enrolled patients with a diagnosis of myopia in their medical records. Two consecutive AL measurements were performed in each eye in random order using the 2 biometers. Subanalysis was performed according to lens status, fixation status, degree of myopia, and the presence of posterior staphyloma. The interdevice agreement was evaluated with Bland-Altman analyses and paired t tests. This study comprised 219 eyes of 117 patients. During a fixation check using SS-OCT, 19.6% of eyes showed fixation loss. Overall, the SS-OCT biometer showed a longer AL than the PCI biometer. (P < .001) In a subanalysis that categorized eyes according to lens status, fixation status, degree of myopia, and the presence of posterior staphyloma, the SS-OCT biometer also showed longer ALs than the PCI biometer. Of eyes with good fixation, significant differences in AL measurements between devices were detected for those with posterior staphyloma (P < .001) but not for those without posterior staphyloma (P = .104). The 2 devices showed differences in AL measurements in myopic eyes. Fixation status and the presence of posterior staphyloma were important factors in these differences. For myopic eyes with posterior staphyloma, the SS-OCT biometer is expected to produce more precise AL measurements because it allows evaluation of the fixation status. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  3. Choroidal Thickness and Choroidal Vessel Density in Nonexudative Age-Related Macular Degeneration Using Swept-Source Optical Coherence Tomography Imaging

    PubMed Central

    Zheng, Fang; Gregori, Giovanni; Schaal, Karen B.; Legarreta, Andrew D.; Miller, Andrew R.; Roisman, Luiz; Feuer, William J.; Rosenfeld, Philip J.

    2016-01-01

    Purpose To analyze the relationship between choroidal thickness and the distribution of choroidal blood vessels in eyes with nonexudative AMD. Methods Eyes with a diagnosis of nonexudative AMD were imaged using a prototype 100-kHz swept-source (SS) optical coherence tomography (OCT) instrument (Carl Zeiss Meditec, Dublin, CA, USA) with a central wavelength of 1050 nm. We used an OCT cube scan pattern consisting of 512 × 512 A-scans over a 12 × 12 mm retinal area. The eyes were partitioned into two groups based on the presence or absence of reticular pseudodrusen (RPD). All scans were segmented using an automated algorithm. In addition, five eyes from each of the two groups were randomly chosen for manual segmentation. Binary choroidal vessels maps were generated from suitable OCT choroidal slabs, and the relationship between the density of large choroidal vessels and choroidal thickness was analyzed using an Early Treatment Diabetic Retinopathy Study–like target centered on the fovea. Results Twenty-five eyes were enrolled in each group. The automated algorithm produced accurate choroidal thickness maps with an average difference between the manual and automated segmentations of 13.7 μm. There was a significant and stable correlation between choroidal thickness and choroidal vessel density across the two groups. Both average choroidal thickness and vessel density were significantly lower in eyes with RPD. Conclusions Our fully automated choroidal segmentation algorithm was able to capture the different patterns of choroidal thickness over a wide area. Choroidal thickness has a clear relationship with the density of large choroid vessels in our sample, irrespective of the presence or absence of RPD. PMID:27849311

  4. Comparison of Neovascular Lesion Area Measurements From Different Swept-Source OCT Angiographic Scan Patterns in Age-Related Macular Degeneration.

    PubMed

    Zheng, Fang; Zhang, Qinqin; Motulsky, Elie H; de Oliveira Dias, João Rafael; Chen, Chieh-Li; Chu, Zhongdi; Miller, Andrew R; Feuer, William; Gregori, Giovanni; Kubach, Sophie; Durbin, Mary K; Wang, Ruikang K; Rosenfeld, Philip J

    2017-10-01

    We compared area measurements for the same neovascular lesions imaged using swept source optical coherence tomography angiography (SS-OCTA) and enlarging scan patterns. Patients with neovascular age-related macular degeneration were imaged using a 100-kHz SS-OCTA instrument (PLEX Elite 9000). The scanning protocols included the 3 × 3, 6 × 6, 9 × 9, and 12 × 12 mm fields of view. Two groups were studied. Group 1 included small lesions contained within the 3 \\( \\times \\) 3 mm scan, and Group 2 included larger lesions that were fully contained within the 6 \\( \\times \\) 6 mm scan. A total of 30 eyes of 26 patients were enrolled in Group 1 and 30 eyes of 25 patients were enrolled in Group 2. In Group 1, the automated mean lesion area measurements were 1.11 (SD = 0.78), 1.14 (SD = 0.80), and 1.27 (SD = 0.82) mm2 for the 3 \\( \\times \\) 3, 6 \\( \\times \\) 6, and 12 \\( \\times \\) 12 mm scans, respectively (ANOVA P < 0.001; post hoc comparisons, P = 0.184, 3 \\( \\times \\) 3 vs. 6 \\( \\times \\) 6 mm; P < 0.001 for the other two pairs). In Group 2, the automated mean lesion area measurements were 5.43 (SD = 2.56), 5.53 (SD = 2.48), and 5.49 (SD = 2.65) mm2 for the 6 \\( \\times \\) 6, 9 \\( \\times \\) 9, and 12 \\( \\times \\) 12 mm scans, respectively (ANOVA P = 0.435; post-hoc comparisons, P = 0.062, 6 \\( \\times \\) 6 vs. 9 \\( \\times \\) 9 mm; P = 0.553, 6 \\( \\times \\) 6 vs. 12 \\( \\times \\) 12 mm; P = 0.654, 9 \\( \\times \\) 9 vs. 12 \\( \\times \\) 12 mm). The similarity in lesion area measurements across different scan patterns suggests that SS-OCTA imaging can be used to follow quantitatively the enlargement of choroidal neovascularization as the disease progresses.

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

    PubMed

    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

    2015-10-01

    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. 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. 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. 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.

  6. Axial Length Measurement Failure Rates With Biometers Using Swept-Source Optical Coherence Tomography Compared to Partial-Coherence Interferometry and Optical Low-Coherence Interferometry.

    PubMed

    McAlinden, Colm; Wang, Qinmei; Gao, Rongrong; Zhao, Weiqi; Yu, Ayong; Li, Yu; Guo, Yan; Huang, Jinhai

    2017-01-01

    To compare a new swept-source optical coherence tomography (SSOCT)-based biometer (OA-2000) with the IOLMaster v5.4 (partial-coherence interferometry) and Aladdin (optical low-coherence interferometry) biometers in terms of axial length measurement and failure rate in eyes with cataract. Reliability study. A total of 377 eyes of 210 patients were scanned with the 3 biometers in a random order. For each biometer, the number of unobtainable axial length measurements was recorded and grouped as per the type and severity of cataract based on the Lens Opacities Classification System III by the same experienced ophthalmologist. The Bland-Altman limits-of-agreement (LoA) method was used to assess the agreement in axial length measurements between the 3 biometers. The failure rate was 0 eyes (0%) with the OA-2000, 136 eyes (36.07%) with the IOLMaster, and 51 eyes (13.53%) with the Aladdin. χ(2) analyses indicated a significant difference in failure rate between all 3 devices (P < .001). Logistic regression analysis highlighted a statistically significant trend of higher failure rates with increasing severity of nuclear, cortical, and posterior subcapsular cataracts. Bland-Altman statistics indicated small mean differences and narrow LoA (OA-2000 vs IOLMaster -0.09 to 0.08 mm; OA-2000 vs Aladdin -0.10 to 0.07 mm; IOLMaster vs Aladdin -0.05 to 0.04 mm). The OA-2000, a new SSOCT-based biometer, outperformed both the IOLMaster and Aladdin biometers in very advanced cataracts of various morphologies. The use of SSOCT technology may be the reason for the improved performance of the OA-2000 and may lead to this technology becoming the gold standard for the measurement of axial length. Copyright © 2016 Elsevier Inc. All rights reserved.

  7. 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

  8. Non-destructive evaluation of an internal adaptation of resin composite restoration with swept-source optical coherence tomography and micro-CT.

    PubMed

    Han, Seung-Hoon; Sadr, Alireza; Tagami, Junji; Park, Sung-Ho

    2016-01-01

    Swept-source optical coherence tomography (SS-OCT) and micro-CT can be useful non-destructive methods for evaluating internal adaptation. There is no comparative study evaluating the two methods in the assessment of internal adaptation in composite restoration. The purpose of this study was to compare internal adaptation measurements of SS-OCT and micro-CT. Two cylindrical cavities were created on the labial surface of twelve bovine incisors. The 24 cavities were randomly assigned to four groups of dentin adhesives: (1) three-step etch-and-rinse adhesive, (2) two-step etch-and-rinse adhesive, (3) two-step self-etch adhesive, and (4) one-step self-etch adhesive. After application, the cavities were filled with resin composite. All restorations underwent a thermocycling challenge, and then, eight SS-OCT images were taken using a Santec OCT-2000™ (Santec Co., Komaki, Japan). The internal adaptation was also evaluated using micro-CT (Skyscan, Aartselaar, Belgium). The image analysis was used to calculate the percentage of defective spot (%DS) and compare the results. The groups were compared using one-way ANOVA with Duncan analysis at the 95% significance level. The SS-OCT and micro-CT measurements were compared with a paired t-test, and the relationship was analyzed using a Pearson correlation test at the 95% significance level. The %DS results showed that Group 3≤Group 4

  9. Effects of Diabetic Macular Edema on Repeatability of Retinal Nerve Fiber Layer Thickness Measurements at the Macular and Peripapillary Area Using Swept-Source Optical Coherence Tomography.

    PubMed

    Min, Jung Kee; Lee, Seunghwan; Kim, Ju Sung; Woo, Je Moon; Yang, Hyun Seung

    2017-02-01

    To investigate the repeatability of macular and peripapillary retinal nerve fiber layer (RNFL) thickness measurements made using swept-source optical coherence tomography (SS-OCT) and automated segmentation. Measurements were made in non-diabetic controls and in patients with diabetic retinopathy (DR) with or without diabetic macular edema (DME). A total of 131 eyes of 131 participants were included. Fifty-one eyes with DR had no DME (DME[-]), 45 eyes with DR had DME (DME[+]), and 35 eyes were healthy. Measurements of RNFL and full retinal thickness were simultaneously obtained with SS-OCT in the peripapillary area and in the nine Early Treatment Diabetic Retinopathy Study (ETDRS) subfields using the wide three-dimensional mode. All measurements were made twice on the same day by a single examiner to test intra-observer repeatability. Intraclass correlation coefficients (ICCs) and coefficients of repeatability were examined to evaluate repeatability. Average macular and temporal peripapillary RNFL thickness values were greater in the DME[+] group (36.4 ± 13.2 and 83.8 ± 19.4 µm, respectively) than in the control (27.4 ± 3.5 and 73.5 ± 11.4 µm, respectively) and DME[-] (27.9 ± 3.4 µm and 70.3 ± 11.3 µm, respectively) groups (both P < 0.001). The ICCs of average macular (control: 0.982, DME[-]: 0.913, and DME[+]: 0.970) and peripapillary (control: 0.972, DME[-]: 0.973, and DME[+]: 0.958) RNFL thickness measurements indicated good repeatability in all three study groups. Although the ICCs of average RNFL thickness measurements were relatively lower in eyes with DR than in healthy controls, the intra-observer repeatability of SS-OCT RNFL and full retinal thickness measurements is sufficiently reliable for them to be clinically useful.

  10. 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

  11. High-speed polarization-sensitive OCT at 1060 nm using a Fourier domain mode-locked swept source

    NASA Astrophysics Data System (ADS)

    Marschall, Sebastian; Torzicky, Teresa; Klein, Thomas; Wieser, Wolfgang; Pircher, Michael; Götzinger, Erich; Zotter, Stefan; Bonesi, Marco; Biedermann, Benjamin; Pedersen, Christian; Huber, Robert; Hitzenberger, Christoph; Andersen, Peter

    2012-06-01

    Optical coherence tomography (OCT) in the 1060nm range is interesting for in vivo imaging of the human posterior eye segment (retina, choroid, sclera), as it permits a long penetration depth. Complementary to structural images, polarization-sensitive OCT (PS-OCT) images visualize birefringent, polarization-maintaining or depolarizing areas within the sample. This information can be used to distinguish retinal layers and structures with different polarization properties. High imaging speed is crucial for imaging ocular structures in vivo in order to minimize motion artifacts while acquiring sufficiently large datasets. Here, we demonstrate PS-OCT imaging at 350 kHz A-scan rate using a two-channel PS-OCT system in conjunction with a Fourier domain mode-locked laser. The light source spectrum spans up to 100nm around the water absorption minimum at 1060 nm. By modulating the laser pump current, we can optimize the spectrum and achieve a depth resolution of 9 μm in air (6.5 μm in tissue). We acquired retinal images in vivo with high resolution and deep penetration into choroid and sclera, and features like the depolarizing RPE or an increasing phase retardation at the chorio-scleral interface are clearly visualized.

  12. Real-time full-depth visualization of posterior ocular structures: comparison between Full Depth Imaging Spectral Domain OCT and Swept Source OCT

    PubMed Central

    Barteselli, Giulio; Bartsch, Dirk-Uwe; Weinreb, Robert N; Camacho, Natalia; Nezgoda, Joseph T; Marvasti, Amir H; Freeman, William R

    2015-01-01

    Purpose To compare the real-time visualization of vitreoretino-choroidal structures using Full Depth Imaging (FDI) spectral domain optical coherence tomography (SD-OCT) and swept source (SS)-OCT. Methods Foveal scans using both FDI SD-OCT (Heidelberg Spectralis) and SS-OCT (Topcon DRI OCT-1) were obtained in 40 normal eyes, 40 eyes with macular pathologies, and 40 eyes with glaucoma. FDI SD-OCT images were obtained by manually enhancing the vitreoretinal interface first and then the choroid, while averaging each OCT B-scan 100 times. SS-OCT images were obtained by averaging each B-scan 96 times. After masking and randomly mixing the original OCT images, two independent physicians graded visualization of the premacular bursa, interdigitation zone line, and chorio-scleral boundary, as well as sharpness of choroidal structures. Results A real-time full-depth image of vitreoretino-choroidal structures was successfully achieved with FDI SD-OCT in 118 cases (98.3%) and with SS-OCT in 45 cases (37.5%, p<0.001). FDI SD-OCT imaging was superior to SS-OCT imaging in visualizing the anterior border of the premacular bursa in 109 eyes (90.8%), with average grading of 1.63 ± 0.53 for the FDI SD-OCT and 0.39 ± 0.52 for the SS-OCT (p<0.001). SS-OCT was similar to FDI SD-OCT in visualizing the chorio-scleral boundary in 108 eyes (90.0%), with average grading of 1.81 ± 0.39 for the SS-OCT and 1.78 ± 0.38 for the FDI-OCT (p=0.566). The visualization of the interdigitation zone line was identical in the two imaging instruments (p=1.000). The sharpness of the choroidal structures was greater with SS-OCT than with FDI-OCT (p<0.001). Conclusion Manual double-enhancing FDI technique using SD-OCT provided a good compromise between vitreous and retino-choroidal structures visualization in real time during scanning procedure. In contrast, SS-OCT imaged well fine choroidal details. Appropriate OCT technology and software should be selected according to its application in clinical

  13. 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

  14. Choroidal neovascularization analyzed on ultra-high speed swept source optical coherence tomography angiography compared to spectral domain optical coherence tomography angiography

    PubMed Central

    Novais, Eduardo A.; Adhi, Mehreen; Moult, Eric M.; Louzada, Ricardo N.; Cole, Emily D.; Husvogt, Lennart; Lee, ByungKun; Dang, Sabin; Regatieri, Caio V. S.; Witkin, André J.; Baumal, Caroline R.; Hornegger, Joachim; Jayaraman, Vijaysekhar; Fujimoto, James G; Duker, Jay S.; Waheed, Nadia K.

    2016-01-01

    Purpose To compare visualization of choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) using an ultra-high speed swept-source (SS)-optical coherence tomography angiography (OCTA) prototype versus a spectral-domain (SD)-OCTA device. Design Comparative analysis of diagnostic instruments. Methods Patients were prospectively recruited to be imaged on SD-OCT and SS-OCT devices on the same day. The SD-OCT device employed is the RTVue Avanti that operates at ~840nm wavelength and 70,000 A-scans/second. The SS-OCT device used is an ultra-high speed long-wavelength prototype that operates at ~1050nm wavelength and 400,000 A-scans/second. Two observers independently measured the CNV area on OCTA en face images from the two devices using ImageJ. The non-parametric Wilcoxon signed-rank test was used to compare area measurements and p-values of <0.05 were considered statistically significant. Results Fourteen eyes from 13 patients were enrolled. The CNV in 11 eyes (78.6%) were classified as type-1, 2 eyes (14.3%) as type-2, and 1 eye (7.1%) as mixed type. Total CNV area measured using SS-OCT and SD-OCT 3mm × 3mm OCTA were 0.949 ± 1.168mm2 and 0.340 ± 0.301mm2, respectively (p=0.001). For the 6mm × 6mm OCTA the total CNV area using SS-OCT and SD-OCT were 1.218 ± 1.284mm2 and 0.604 ± 0.597mm2, respectively (p=0.0019). The field of view did not significantly affect the measured CNV area (p=0.19 and p=0.18 for SS-OCT and SD-OCT respectively). Conclusion SS-OCTA yielded significantly larger CNV areas than SD-OCTA. It is possible that SS-OCTA is better able to demarcate the full extent of CNV vasculature. PMID:26851725

  15. Real-time swept source optical coherence tomography imaging of the human airway using a microelectromechanical system endoscope and digital signal processor

    PubMed Central

    Su, Jianping; Zhang, Jun; Yu, Lingfeng; Colt, Henri G; Brenner, Matthew; Chen, Zhongping

    2009-01-01

    A fast-scan-rate swept laser for optical coherence tomography (OCT) is suitable to record and analyze a 3-D image volume. However, the whole OCT system speed is limited by data streaming, processing, and storage. In this case, postprocessing is a common technique. Endoscopic clinical applications prefer onsite diagnosis, which requires a real-time technique. Parallel digital signal processors were applied to stream and process data directly from a data digitizer. A real-time system with 20-kHz axial line speed, which was limited only by our swept laser scan rate, was implemented. To couple with the system speed, an endoscope based on an improved 3-D microelectromechanical motor (diameter 1.5 mm, length 9.4 mm) was developed. In vivo 3-D imaging of the human airway was demonstrated. PMID:18601523

  16. Real-time swept source optical coherence tomography imaging of the human airway using a microelectromechanical system endoscope and digital signal processor.

    PubMed

    Su, Jianping; Zhang, Jun; Yu, Lingfeng; G Colt, Henri; Brenner, Matthew; Chen, Zhongping

    2008-01-01

    A fast-scan-rate swept laser for optical coherence tomography (OCT) is suitable to record and analyze a 3-D image volume. However, the whole OCT system speed is limited by data streaming, processing, and storage. In this case, postprocessing is a common technique. Endoscopic clinical applications prefer onsite diagnosis, which requires a real-time technique. Parallel digital signal processors were applied to stream and process data directly from a data digitizer. A real-time system with 20-kHz axial line speed, which was limited only by our swept laser scan rate, was implemented. To couple with the system speed, an endoscope based on an improved 3-D microelectromechanical motor (diameter 1.5 mm, length 9.4 mm) was developed. In vivo 3-D imaging of the human airway was demonstrated.

  17. Photodynamic therapy in VEGF inhibition non-responders-Pharmacogenetic study in age-related macular degeneration assessed with swept-source optical coherence tomography.

    PubMed

    Teper, Slawomir J; Nowinska, Anna; Pilat, Jaroslaw; Wylegala, Edward

    2016-03-01

    Treatment of neovascular age-related macular degeneration (nAMD) remains a major challenge in ophthalmology. It is essential to determine which of VEGF inhibition non-responders can benefit from photodynamic therapy (PDT). As AMD is strongly related to gene polymorphisms, genetic factors can modify efficacy of treatment. Swept-source optical coherence tomography (SS-OCT) gives exceptional insight into the retina and choroid. SS-OCT usefulness needs to be evaluated in nAMD patients. Prospective 6-month study included consecutive 110 patients (110 eyes) with predominantly classic neovascular AMD treated with photodynamic therapy. Only non-responders to anti-VEGF were included in the study. Greatest linear dimension (GLD) of the lesion, best corrected visual acuity (BCVA), central subfield macular thickness (CSMT) and central choroidal thickness were assessed and compared between CFH and ARMS2 genotype groups. Success rate was the main endpoint. It was defined as not active CNV in the center of the fovea and no worsening in BCVA. Multiple regression was used to assess gene polymorphisms influence on PDT results. Wilcoxon tests were performed to determine significance of changes from baseline values. Following genotype frequencies were obtained-CFH CC 35 patients (31.8%), CT 52 (47.3%), TT 23 (20.9%); ARMS2 TT 28 patients (25.4%), GT 43 (39.1%), GG 39 (35.4%) success rate in CC/CT/TT CFH and TT/GT/GG ARMS2 groups were as follows respectively: 22.9%, 28.8%, 30.4% and 28.6%, 25.6%, 28.2%. The differences were not significant with highest odds ratio TT vs. CC CFH 1.57 (95% CI 0.48-5.2, p=0.4). Significant increase in GLD was observed only in CC CFH group. Overall mean following measured parameters were obtained at baseline/day 7/month 3/month 6 (significant changes from baseline are marked with asterisk): GLD-3825±1301μm/3901±1579μm/3861±1463μm/3925±1523μm; CSMT-405±203μm/434±257μm*/321±163μm*/295±157*μm; CCT-235±103μm/278±157*μm/211±113μm*/201±107

  18. High-speed high-sensitivity infrared spectroscopy using mid-infrared swept lasers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Childs, David T. D.; Groom, Kristian M.; Hogg, Richard A.; Revin, Dmitry G.; Cockburn, John W.; Rehman, Ihtesham U.; Matcher, Stephen J.

    2016-03-01

    Infrared spectroscopy is a highly attractive read-out technology for compositional analysis of biomedical specimens because of its unique combination of high molecular sensitivity without the need for exogenous labels. Traditional techniques such as FTIR and Raman have suffered from comparatively low speed and sensitivity however recent innovations are challenging this situation. Direct mid-IR spectroscopy is being speeded up by innovations such as MEMS-based FTIR instruments with very high mirror speeds and supercontinuum sources producing very high sample irradiation levels. Here we explore another possible method - external cavity quantum cascade lasers (EC-QCL's) with high cavity tuning speeds (mid-IR swept lasers). Swept lasers have been heavily developed in the near-infrared where they are used for non-destructive low-coherence imaging (OCT). We adapt these concepts in two ways. Firstly by combining mid-IR quantum cascade gain chips with external cavity designs adapted from OCT we achieve spectral acquisition rates approaching 1 kHz and demonstrate potential to reach 100 kHz. Secondly we show that mid-IR swept lasers share a fundamental sensitivity advantage with near-IR OCT swept lasers. This makes them potentially able to achieve the same spectral SNR as an FTIR instrument in a time x N shorter (N being the number of spectral points) under otherwise matched conditions. This effect is demonstrated using measurements of a PDMS sample. The combination of potentially very high spectral acquisition rates, fundamental SNR advantage and the use of low-cost detector systems could make mid-IR swept lasers a powerful technology for high-throughput biomedical spectroscopy.

  19. 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.

  20. Swept Impact Seismic Technique (SIST)

    USGS Publications Warehouse

    Park, C.B.; Miller, R.D.; Steeples, D.W.; Black, R.A.

    1996-01-01

    A coded seismic technique is developed that can result in a higher signal-to-noise ratio than a conventional single-pulse method does. The technique is cost-effective and time-efficient and therefore well suited for shallow-reflection surveys where high resolution and cost-effectiveness are critical. A low-power impact source transmits a few to several hundred high-frequency broad-band seismic pulses during several seconds of recording time according to a deterministic coding scheme. The coding scheme consists of a time-encoded impact sequence in which the rate of impact (cycles/s) changes linearly with time providing a broad range of impact rates. Impact times used during the decoding process are recorded on one channel of the seismograph. The coding concept combines the vibroseis swept-frequency and the Mini-Sosie random impact concepts. The swept-frequency concept greatly improves the suppression of correlation noise with much fewer impacts than normally used in the Mini-Sosie technique. The impact concept makes the technique simple and efficient in generating high-resolution seismic data especially in the presence of noise. The transfer function of the impact sequence simulates a low-cut filter with the cutoff frequency the same as the lowest impact rate. This property can be used to attenuate low-frequency ground-roll noise without using an analog low-cut filter or a spatial source (or receiver) array as is necessary with a conventional single-pulse method. Because of the discontinuous coding scheme, the decoding process is accomplished by a "shift-and-stacking" method that is much simpler and quicker than cross-correlation. The simplicity of the coding allows the mechanical design of the source to remain simple. Several different types of mechanical systems could be adapted to generate a linear impact sweep. In addition, the simplicity of the coding also allows the technique to be used with conventional acquisition systems, with only minor modifications.

  1. Doppler optical cardiogram gated 2D color flow imaging at 1000 fps and 4D in vivo visualization of embryonic heart at 45 fps on a swept source OCT system

    NASA Astrophysics Data System (ADS)

    Mariampillai, Adrian; Standish, Beau A.; Munce, Nigel R.; Randall, Cristina; Liu, George; Jiang, James Y.; Cable, Alex E.; Vitkin, I. A.; Yang, Victor X. D.

    2007-02-01

    We report a Doppler optical cardiogram gating technique for increasing the effective frame rate of Doppler optical coherence tomography (DOCT) when imaging periodic motion as found in the cardiovascular system of embryos. This was accomplished with a Thorlabs swept-source DOCT system that simultaneously acquired and displayed structural and Doppler images at 12 frames per second (fps). The gating technique allowed for ultra-high speed visualization of the blood flow pattern in the developing hearts of African clawed frog embryos (Xenopus laevis) at up to 1000 fps. In addition, four-dimensional (three spatial dimensions + temporal) Doppler imaging at 45 fps was demonstrated using this gating technique, producing detailed visualization of the complex cardiac motion and hemodynamics in a beating heart.

  2. Long-range, wide-field swept-source optical coherence tomography with GPU accelerated digital lock-in Doppler vibrography for real-time, in vivo middle ear diagnostics

    PubMed Central

    MacDougall, Dan; Farrell, Joshua; Brown, Jeremy; Bance, Manohar; Adamson, Robert

    2016-01-01

    We present the design, implementation and validation of a swept-source optical coherence tomography (OCT) system for real-time imaging of the human middle ear in live patients. Our system consists of a highly phase-stable Vernier-tuned distributed Bragg-reflector laser along with a real-time processing engine implemented on a graphics processing unit. We use the system to demonstrate, for the first time in live subjects, real-time Doppler measurements of middle ear vibration in response to sound, video rate 2D B-mode imaging of the middle ear and 3D volumetric B-mode imaging. All measurements were performed non-invasively through the intact tympanic membrane demonstrating that the technology is readily translatable to the clinic. PMID:27896001

  3. 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.

  4. Doppler optical cardiogram gated 2D color flow imaging at 1000 fps and 4D in vivo visualization of embryonic heart at 45 fps on a swept source OCT system.

    PubMed

    Mariampillai, Adrian; Standish, Beau A; Munce, Nigel R; Randall, Cristina; Liu, George; Jiang, James Y; Cable, Alex E; Vitkin, I A; Yang, Victor X D

    2007-02-19

    We report a Doppler optical cardiogram gating technique for increasing the effective frame rate of Doppler optical coherence tomography (DOCT) when imaging periodic motion as found in the cardiovascular system of embryos. This was accomplished with a Thorlabs swept-source DOCT system that simultaneously acquired and displayed structural and Doppler images at 12 frames per second (fps). The gating technique allowed for ultra-high speed visualization of the blood flow pattern in the developing hearts of African clawed frog embryos (Xenopus laevis) at up to 1000 fps. In addition, four-dimensional (three spatial dimensions + temporal) Doppler imaging at 45 fps was demonstrated using this gating technique, producing detailed visualization of the complex cardiac motion and hemodynamics in a beating heart.

  5. 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

    PubMed Central

    Choi, Woo June; Wang, Ruikang K.

    2015-01-01

    Abstract. 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. PMID:26447860

  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

    SciTech Connect

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

    2016-05-09

    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. 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…

  8. Economic analysis of potential fuelwood sources

    Treesearch

    W.F. Watson; J.R. Ragan; T.J. Straka; B.J. Stokes

    1987-01-01

    Fuelwood can be producsd from mill residues, logging residues, or energy plantations. This paper will compare the last two sources on the basis of potential for productlon and expected costs at the various levels of productfon. Prospects for improving the production of fuelwood frw each source will also be examined.

  9. 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…

  10. Confirmed and Potential Sources of Legionella Reviewed.

    PubMed

    van Heijnsbergen, Eri; Schalk, Johanna A C; Euser, Sjoerd M; Brandsema, Petra S; den Boer, Jeroen W; de Roda Husman, Ana Maria

    2015-04-21

    Legionella bacteria are ubiquitous in natural matrices and man-made systems. However, it is not always clear if these reservoirs can act as source of infection resulting in cases of Legionnaires' disease. This review provides an overview of reservoirs of Legionella reported in the literature, other than drinking water distribution systems. Levels of evidence were developed to discriminate between potential and confirmed sources of Legionella. A total of 17 systems and matrices could be classified as confirmed sources of Legionella. Many other man-made systems or natural matrices were not classified as a confirmed source, since either no patients were linked to these reservoirs or the supporting evidence was weak. However, these systems or matrices could play an important role in the transmission of infectious Legionella bacteria; they might not yet be considered in source investigations, resulting in an underestimation of their importance. To optimize source investigations it is important to have knowledge about all the (potential) sources of Legionella. Further research is needed to unravel what the contribution is of each confirmed source, and possibly also potential sources, to the LD disease burden.

  11. 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.

  12. 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)

  13. 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)

  14. A pilot study to compartmentalize small melanocytic choroidal tumors and choroidal vessels with speckle-noise free 1050 nm swept source optical coherence tomography (OCT choroidal "tumoropsy").

    PubMed

    Maloca, Peter; Gyger, Cyrill; Hasler, Pascal Willy

    2016-06-01

    The purpose was to illustrate small melanocytic choroidal tumors with speckle-noise free swept-source optical coherence tomography (SSOCT). Twenty-five small melanocytic choroidal tumors in 24 eyes underwent 1050 nm OCT. All tumors were measured manually with the built-in caliper tool and compared to data derived from a semiautomated algorithm that removed speckle noise but preserved the structure of the tumors from the SSOCT data. The average manual measurements for the horizontal, vertical, and axial diameters were 1535.28 μm (range, 547-2807 μm), 1713.8 μm (range, 574-3921 μm), and 227.28 μm (range, 115-489 μm), respectively. The measured average volumes of the tumors were 835,248,212 μm(3) (range, 48,818,700 to 4,567,401,810 μm(3)) and 228,588,535 μm(3) (range, 22,879,641 to 787,668,886 μm(3)) for caliper measurements, respectively, for the extracted volumes. The average volume variation between the two methods was 66.16 % (range, 46.5 % to 82.75 %). The average ratio between the caliper and extracted volumes was 3.402 (range, 1.346-8.198, SD 1.681), 2.367 (range, 1.346-3.258, SD 0.618), 2.321 (range, 1.346-3.258, SD 0.611), 2.402 (range, 1.518-3.258, SD 0.591), and 1.749 (range, 1.518-1.733, SD 0.239) for all tumors, all tumors with the exclusion of extreme parameters, tumor <3 mm, tumor <2 mm, and tumor <1 mm, respectively. The average ratio (tumor index) between the tumor volume and the choroidal vessel volume was 12.539 (range, 0.489-73.701). Speckle-noise free swept-source OCT may be an illustrative OCT imaging technology. OCT may be useful for describing and monitoring small melanocytic choroidal tumors and the choroidal vessels.

  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. The mid-infrared swept laser: life beyond OCT?

    NASA Astrophysics Data System (ADS)

    Childs, D. T. D.; Hogg, R. A.; Revin, D. G.; Rehman, I. U.; Cockburn, J. W.; Matcher, S. J.

    2015-03-01

    Near-infrared external cavity lasers with high tuning rates ("swept lasers") have come to dominate the field of nearinfrared low-coherence imaging of biological tissues. Compared with time-domain OCT, swept-source OCT a) replaces slow mechanical scanning of a bulky reference mirror with much faster tuning of a laser cavity filter element and b) provides a ×N (N being the number of axial pixels per A-scan) speed advantage with no loss of SNR. We will argue that this striking speed advantage has not yet been fully exploited within biophotonics but will next make its effects felt in the mid-infrared. This transformation is likely to be driven by recent advances in external cavity quantum cascade lasers, which are the mid-IR counterpart to the OCT swept-source. These mid-IR sources are rapidly emerging in the area of infrared spectroscopy. By noting a direct analogy between time-domain OCT and Fourier Transform Infrared (FTIR) spectroscopy we show analytically and via simulations that the mid-IR swept laser can acquire an infrared spectrum ×N (N being the number of spectral data points) faster than an FTIR instrument, using identical detected flux levels and identical receiver noise. A prototype external cavity mid-IR swept laser is demonstrated, offering a comparatively low sweep rate of 400 Hz over 60 cm-1 with 2 cm-1 linewidth, but which provides evidence that sweep rates of over a 100 kHz should be readily achievable simply by speeding up the cavity tuning element. Translating the knowledge and experience gained in near-IR OCT into mid-IR source development may result in sources offering significant benefits in certain spectroscopic applications.

  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. Hydrocarbon source potential in Brazilian margin basins

    SciTech Connect

    Mello, M.R.; Estrella, G.D.O.; Gaglianone, P.C.

    1984-04-01

    Twenty thousand samples from the Brazilian continental shelf basins were analyzed to characterize and evaluate the hydrocarbon source potential of the areas. The geochemical evaluation of the rock and oil samples was performed by organic carbon determinations, Rock-Eval pyrolysis, vitrinite reflectance, thermal alteration index, liquid and gas chromatographies, gas chromatography-mass spectrometry, and carbon isotope analyses. Three source rock systems have been identified: lower Neocomian shales deposited in a continental environment, upper Neocomian shales grading from continental to lagoonal environment, and Aptian shales related to evaporitic and lacustrine sequences. Upper Cretaceous and Tertiary open marine slope sediments are not considered as source rocks. Locally, these sediments present high organic carbon content but show an extremely poor hydrocarbon yield. Anoxic depositional conditions, nevertheless, can be traced locally along some levels of the Santonian to Cenomanian shales and marls. These sediments are generally immature in the Brazilian margin basins and no oil was generated from this section. Three oil families were distinguished through oil-to-oil and oil-to-source rock correlations: the lower Neocomian continental type, the upper Neocomian continental to lagoonal type, and the Aptian evaporitic to lacustrine related sequences. The geochemical studies, together with geologic and geophysical data, provided the basis to display some models for the migration pathways and habitat of oils in the Brazilian margin basins.

  20. 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.

  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. 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.

  3. Positional and Curvature Difference of Lamina Cribrosa According to the Baseline Intraocular Pressure in Primary Open-Angle Glaucoma: A Swept-Source Optical Coherence Tomography (SS-OCT) Study

    PubMed Central

    Kim, Yong Woo; Jeoung, Jin Wook; Girard, Michael J. A.; Mari, Jean Martial; Park, Ki Ho

    2016-01-01

    Purpose To investigate the variation of lamina cribrosa (LC) structure based on the baseline intraocular pressure (IOP) in eyes with primary open-angle glaucoma (POAG) and healthy individuals using swept-source optical coherence tomography. Methods A total of 108 eyes with POAG and 61 healthy eyes were recruited. Based on the baseline IOP, the POAG eyes were divided into higher-baseline IOP (HTG; baseline IOP > 21 mmHg, n = 38 eyes) and lower-baseline IOP (NTG; baseline IOP ≤ 21 mmHg, n = 70 eyes). The anterior laminar insertion depth (ALID), mean LC depth (mLCD), and the LC curvature index (mLCD–ALID) were measured, and compared among the three groups. The regional variation of LC structure was evaluated by vertical-horizontal ALID difference. Results The mLCD and LC curvature index were greatest in HTG eyes (520.3 ± 123.0 and 80.9 ± 30.7 μm), followed by NTG (463.2 ± 110.5 and 64.5 ± 30.7 μm) and healthy eyes (382.9 ± 107.6 and 47.6 ± 25.7 μm, all P < 0.001). However, there were no significant difference in ALID between HTG and NTG eyes. The vertical-horizontal ALID difference was larger in NTG eyes (72.8 ± 56.2 μm) than in HTG (32.7 ± 61.4 μm, P = 0.004) and healthy eyes (25.5 ± 34.8 μm, P < 0.001). Conclusions Lamina cribrosa position and curvature differed in POAG eyes with low and high IOP. This would support the theory that IOP induced biomechanical effects on the optic play a role on glaucoma. PMID:27611970

  4. Surgical site markers: potential source of infection.

    PubMed

    Driessche, Ann Marie

    2012-01-01

    Observing licensed independent practitioners mark surgical sites with all types of marking pens is a concern related to the potential spread of infections from patient to patient. The practice of using the same marking pen to mark a surgical site has been questioned as a source of cross contamination. A literature review was done on recent studies and best practice recommendations to determine whether marking pens can act as fomites for nosocomial infections. The review indicated that surgical site markers, ink pens, and aging permanent marking pens can be a source for cross-infection with methicillin-resistant Staphylococcus aureus, other bacteria, fungus, or virus. The type of marking pens used and the act of using the same marking pen from patient to patient could contribute to nosocomial infections. The literature reviewed recommends a single time use of a surgical marking pen. Interventions to prevent cross contamination and postoperative surgical site infections are a major concern in the care of the orthopaedic patient.

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

    PubMed

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

    2004-01-01

    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.

  6. 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

  7. Flutter of swept fan blades

    NASA Technical Reports Server (NTRS)

    Kielb, R. E.; Kaza, K. R. V.

    1984-01-01

    The effect of sweep on fan blade flutter is studied by applying the analytical methods developed for aeroelastic analysis of advance turboprops. Two methods are used. The first method utilizes an approximate structural model in which the blade is represented by a swept, nonuniform beam. The second method utilizes a finite element technique to conduct modal flutter analysis. For both methods the unsteady aerodynamic loads are calculated using two dimensional cascade theories which are modified to account for sweep. An advanced fan stage is analyzed with 0, 15 and 30 degrees of sweep. It is shown that sweep has a beneficial effect on predominantly torsional flutter and a detrimental effect on predominantly bending flutter. This detrimental effect is shown to be significantly destabilizing for 30 degrees of sweep.

  8. Swept wing ice accretion modeling

    NASA Technical Reports Server (NTRS)

    Potapczuk, M. G.; Bidwell, C. S.

    1990-01-01

    An effort to develop a three-dimensional ice accretion modeling method is initiated. This first step toward creation of a complete aircraft icing simulation code builds on previously developed methods for calculating three-dimensional flowfields and particle trajectories combined with a two-dimensional ice accretion calculation along coordinate locations corresponding to streamlines. This work is intended as a demonstration of the types of calculations necessary to predict a three-dimensional ice accretion. Results of calculations using the 3D method for a MS-317 swept wing geometry are projected onto a 2D plane normal to the wing leading edge and compared to 2D results for the same geometry. These results indicate that the flowfield 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 3D calculation.

  9. Computation of the transonic flow about a swept wing in the presence of an engine nacelle

    SciTech Connect

    Ross, D.

    1985-12-01

    We have developed a method to model the effects of an engine nacelle on the transonic flow about a swept wing. The nacelle is modelled by adding an inhomogeneous term, which represents a source distribution, to the potential equation, which is solved by relaxation. Our method is an extension of the design code FL22INV of Bauer, Garabedian, and McFadden, which was based on Caughy and Jameson's FLO22 and on the oblique wing code FLO16. In order to obtain a sharply defined obstacle using a source distribution on a finite difference grid, we must use a small grid size near the source. We accomplish this through a mapping of the flow domain to the computational domain. We thus obtain a concentrated source distribution which, for transonic Mach numbers, will cause high speeds and cavitation. To overcome this problem we use a constant coefficient equation for the velocity potential near the source. Once the flow has been computed, the size and position of the nacelle are found by tracing streamlines. We have used our code to study the effect of the presence of an engine nacelle on the shock waves which form above a swept wing in transonic flight. It was found that sizeable shocks appear on wings that were previously nearly shockless. By applying the free boundary redesign technique of FL22INV we were able to minimize the wave drag due to these shocks. The results of these studies are included along with a listing of our new FORTRAN code NACROSS, in which an effort has been made to improve the implementation. 26 refs., 14 figs.

  10. 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.

  11. 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.

  12. Coherence properties of short cavity swept lasers

    PubMed Central

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

    2017-01-01

    It has been shown theoretically and experimentally that short cavity swept lasers are passively mode locked. We develop a mathematical model of these lasers and the light field solutions are used to predict the coherence length and coherence revival behavior. The calculations compare favorably with data from a 990–1100 nm laser swept at 100 kHz suitable for optical coherence tomography applications. PMID:28271002

  13. 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

  14. Potential sources of methylmercury in tree foliage.

    PubMed

    Tabatchnick, Melissa D; Nogaro, Géraldine; Hammerschmidt, Chad R

    2012-01-01

    Litterfall is a major source of mercury (Hg) and toxic methylmercury (MeHg) to forest soils and influences exposures of wildlife in terrestrial and aquatic ecosystems. However, the origin of MeHg associated with tree foliage is largely unknown. We tested the hypothesis that leaf MeHg is influenced by root uptake and thereby related to MeHg levels in soils. Concentrations of MeHg and total Hg in deciduous and coniferous foliage were unrelated to those in soil at 30 urban and rural forested locations in southwest Ohio. In contrast, tree genera and trunk diameter were significant variables influencing Hg in leaves. The fraction of total Hg as MeHg averaged 0.4% and did not differ among tree genera. Given that uptake of atmospheric Hg(0) appears to be the dominant source of total Hg in foliage, we infer that MeHg is formed by in vivo transformation of Hg in proportion to the amount accumulated. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. Chromatic polarization effects of swept waveforms in FDML lasers and fiber spools.

    PubMed

    Wieser, Wolfgang; Palte, Gesa; Eigenwillig, Christoph M; Biedermann, Benjamin R; Pfeiffer, Tom; Huber, Robert

    2012-04-23

    We present detailed investigations of chromatic polarization effects, caused by fiber spools used in FDML lasers and buffering spools for rapidly wavelength swept lasers. We introduce a novel wavelength swept FDML laser source, specially tailored for polarization sensitive optical coherence tomography (OCT) which switches between two different linear polarization states separated by 45°, i.e. 90° on the Poincaré sphere. The polarization maintaining laser cavity itself generates a stable linear polarization state and uses an external buffering technique in order to provide alternating polarization states for successive wavelength sweeps. The design of the setup is based on a comprehensive analysis of the polarization output from FDML lasers, using a novel 150 MHz polarization analyzer. We investigate the fiber polarization properties related to swept source OCT for different fiber delay topologies and analyze the polarization state of different FDML laser sources.

  16. Extremozymes: A Potential Source for Industrial Applications.

    PubMed

    Dumorné, Kelly; Córdova, David Camacho; Astorga-Eló, Marcia; Renganathan, Prabhaharan

    2017-01-20

    Extremophilic microorganisms have established a diversity of molecular strategies in order to survive in extreme conditions. Biocatalysts isolated by these organisms are termed extremozymes, possess extraordinary properties are salt allowance thermostability and cold adaptivity. Extremozymes are very resistant in extreme conditions due to their great solidity and they propose new opportunities for biocatalysis and biotransformations, also for the development of the economy and new line of research through their application. Thermophilic proteins, piezophilic proteins, acidophilic proteins and halophilic proteins have been studied during the last years. Amylases, proteases lipases pullulanases, cellulases, chitinases, xylanases, pectinases isomerases, esterases, dehydrogenases have great potential application for biotechnology such as agricultural, chemical, biomedical and biotechnological processes. The study of extremozymes and their main applications have emerged during the last years.

  17. 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

  18. Discretely swept optical coherence tomography system using super-structure grating distributed Bragg reflector lasers at 1561-1639nm

    NASA Astrophysics Data System (ADS)

    Choi, D.; Yoshimura, R.; Hiro-Oka, H.; Furukawa, H.; Goto, A.; Satoh, N.; Igarashi, A.; Nakanishi, M.; Shimizu, K.; Ohbayashi, K.

    2012-01-01

    We have developed swept source optical coherence tomography (OCT) system with an optical comb swept source system. The swept source system comprised of two super-structured grating distributed Bragg reflector lasers covering a wavelength range from 1561-1693 nm. A method to scan these lasers to obtain an interference signal without stitching noises, which are inherent in these lasers, and to connect two lasers without concatenation noise is explained. Method to reduce optical aliasing noises in this optical comb swept laser OCT is explained and demonstrated based on the characteristic of the optical aliasing noises in this particular OCT system. By reduction of those noises, a sensitivity of 124 dB was realized. The A-scan rate, resolution and depth range were 3.1 kHz, 16 μm (in air) and 12 mm, respectively. Deep imaging penetration into tissue is demonstrated for two selected samples.

  19. Amplified, frequency swept lasers for frequency domain reflectometry and OCT imaging: design and scaling principles.

    PubMed

    Huber, R; Wojtkowski, M; Taira, K; Fujimoto, J; Hsu, K

    2005-05-02

    We demonstrate a high-speed, frequency swept, 1300 nm laser source for frequency domain reflectometry and OCT with Fourier domain/swept-source detection. The laser uses a fiber coupled, semiconductor amplifier and a tunable fiber Fabry-Perot filter. We present scaling principles which predict the maximum frequency sweep speed and trade offs in output power, noise and instantaneous linewidth performance. The use of an amplification stage for increasing output power and for spectral shaping is discussed in detail. The laser generates ~45 mW instantaneous peak power at 20 kHz sweep rates with a tuning range of ~120 nm full width. In frequency domain reflectometry and OCT applications the frequency swept laser achieves 108 dB sensitivity and ~10 mum axial resolution in tissue. We also present a fast algorithm for real time calibration of the fringe signal to equally spaced sampling in frequency for high speed OCT image preview.

  20. Full-Field Optical Coherence Tomography Using Galvo Filter-Based Wavelength Swept Laser

    PubMed Central

    Shirazi, Muhammad Faizan; Kim, Pilun; Jeon, Mansik; Kim, Jeehyun

    2016-01-01

    We report a wavelength swept laser-based full-field optical coherence tomography for measuring the surfaces and thicknesses of refractive and reflective samples. The system consists of a galvo filter–based wavelength swept laser and a simple Michelson interferometer. Combinations of the reflective and refractive samples are used to demonstrate the performance of the system. By synchronizing the camera with the source, the cross-sectional information of the samples can be seen after each sweep of the swept source. This system can be effective for the thickness measurement of optical thin films as well as for the depth investigation of samples in industrial applications. A resolution target with a glass cover slip and a step height standard target are imaged, showing the cross-sectional and topographical information of the samples. PMID:27869659

  1. 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.

  2. Acousto-Optic–Based Wavelength-Comb-Swept Laser for Extended Displacement Measurements

    PubMed Central

    Park, Nam Su; Chun, Soo Kyung; Han, Ga-Hee; Kim, Chang-Seok

    2017-01-01

    We demonstrate a novel wavelength-comb-swept laser based on two intra-cavity filters: an acousto-optic tunable filter (AOTF) and a Fabry-Pérot etalon filter. The AOTF is used for the tunable selection of the output wavelength with time and the etalon filter for the narrowing of the spectral linewidth to extend the coherence length. Compared to the conventional wavelength-swept laser, the acousto-optic–based wavelength-comb-swept laser (WCSL) can extend the measureable range of displacement measurements by decreasing the sensitivity roll-off of the point spread function. Because the AOTF contains no mechanical moving parts to select the output wavelength acousto-optically, the WCSL source has a high wavenumber (k) linearity of R2 = 0.9999 to ensure equally spaced wavelength combs in the wavenumber domain. PMID:28362318

  3. Acousto-Optic-Based Wavelength-Comb-Swept Laser for Extended Displacement Measurements.

    PubMed

    Park, Nam Su; Chun, Soo Kyung; Han, Ga-Hee; Kim, Chang-Seok

    2017-03-31

    We demonstrate a novel wavelength-comb-swept laser based on two intra-cavity filters: an acousto-optic tunable filter (AOTF) and a Fabry-Pérot etalon filter. The AOTF is used for the tunable selection of the output wavelength with time and the etalon filter for the narrowing of the spectral linewidth to extend the coherence length. Compared to the conventional wavelength-swept laser, the acousto-optic-based wavelength-comb-swept laser (WCSL) can extend the measureable range of displacement measurements by decreasing the sensitivity roll-off of the point spread function. Because the AOTF contains no mechanical moving parts to select the output wavelength acousto-optically, the WCSL source has a high wavenumber (k) linearity of R² = 0.9999 to ensure equally spaced wavelength combs in the wavenumber domain.

  4. Constrained blind source extraction of readiness potentials from EEG.

    PubMed

    Ahmadian, Pouya; Sanei, Saeid; Ascari, Luca; González-Villanueva, Lara; Alessandra Umiltà, Maria

    2013-07-01

    One of the changes seen in electroencephalography (EEG) data preceding human voluntary movement is a cortical potential called readiness potential (RP). Detection of this potential can benefit researchers in clinical neurosciences for rehabilitation of malfunctioning brain and those working on brain-computer interfacing to develop a suitable mechanism to detect the intention of movement. Here, a constrained blind source extraction (CBSE) is attempted for detection of RP. A suitable constraint is defined and applied. The results are also compared with those of the traditional blind source separation in terms of true positive rate, false positive rate, and computation time. The results show that the CBSE approach in overall has superior performance.

  5. 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

  6. Source inversion of self-potential data with compactness constraints

    NASA Astrophysics Data System (ADS)

    Minsley, B.; Sogade, J.; Morgan, F. D.

    2005-12-01

    Self-potential (SP) measurements sample the electric field that results from a source term in Poisson's equation together with the earth resistivity structure and appropriate boundary conditions. These sources can be generated by various subsurface flows, typically due to hydraulic, thermal, or chemical gradients. We utilize forward and inverse modeling using the transmission network analogy to determine the 3D self-potential source distribution from measured SP and resistivity data. Self-potential source inversion is a linear problem, though it is complicated by ill-conditioning and non-uniqueness common to potential field problems. The linear operator is composed of the Green's functions defined by the survey geometry and estimated resistivity structure. Inversion stability often relies on regularization that imposes a flatness or smoothness constraint on the model that is sometimes physically inappropriate. Our approach utilizes a minimum support regularization operator that favors a class of solutions that fit the SP data with sources that are spatially compact. This iterative method produces multiple source models with increasing compactness but similar data misfit, and is an effective way to examine the non-uniqueness in this type of problem where there is an inherent tradeoff between the source shape, magnitude, and location. Prior knowledge of the expected compactness of the source can then be used to select a physically appropriate model. Similar forms of regularization have proven successful in other potential field problems such as gravity and magnetics, as well as electroencephalographic (EEG) imaging in the medical community. A significant benefit of these methods is the resolution of targets at depth from surface measurements alone. We also discuss the incorporation of sensitivity information in the inversion, imperfect knowledge of the resistivity structure, and the effect of noisy data using synthetic and field examples.

  7. Determination of sources using brain-evoked potential maps

    NASA Astrophysics Data System (ADS)

    Amir, Avner; Jewett, Don L.

    1993-08-01

    Methods to localize the sources of Brain Evoked Potential Maps based on modeling of the sources as point dipoles have been widely used for more than twenty years. Such methods still lack a basic theory which can answer questions regarding the resolution and uniqueness of the results in the context of a realistic head model, with no a prior restrictions on the sources. In the first part of the paper we present simple physical models for the origin of far-field potentials associated with the auditory and somatosensory systems. An action potential travels along a straight axon can only produce a quadrupole field at far distances. We show that the far field potentials must originate when the action potential passes through a bent axon or through changes in the conductivities or in the external boundaries of the volume conductor surrounding the axon. We discuss the question of uniqueness of the solution for the 'inverse problem' of evoked potentials. This problem involved the reconstruction of the location and pattern of activity of the neuronal generators in the brain, given the map of the scalp electric potentials. We show that in a head shape with a realistic geometry spatially distinct points, line or open surface generators cannot create the same scalp potential map. The same applies to two non-overlapping generators occupying finite volumes.

  8. 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.

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

    PubMed

    Singh, A K; Singh, M P

    2014-12-24

    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.

  10. Potential Sources of Polarized Light from a Plant Canopy

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

    2016-01-01

    Field measurements have demonstrated that sunlight polarized during a first surface reflection by shiny leaves dominates the optical polarization of the light reflected by shiny-leafed plant canopies having approximately spherical leaf angle probability density functions ("Leaf Angle Distributions" - LAD). Yet for other canopies - specifically those without shiny leaves and/or spherical LADs - potential sources of optically polarized light may not always be obvious. Here we identify possible sources of polarized light within those other canopies and speculate on the ecologically important information polarization measurements of those sources might contain.

  11. 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.

  12. Model-based source localization of extracellular action potentials.

    PubMed

    Somogyvári, Zoltán; Zalányi, László; Ulbert, István; Erdi, Péter

    2005-09-30

    A new model-based analysis method was set up for revealing information encrypted in extracellular spatial potential patterns of neocortical action potentials. Spikes were measured by extracellular linear multiple microelectrode in vivo cat's primary auditory cortex and were analyzed based on current source density (CSD) distribution models. Validity of the monopole and other point source approximations were tested on the measured potential patterns by numerical fitting. We have found, that point source models could not provide accurate description of the measured patterns. We introduced a new model of the CSD distribution on a spiking cell, called counter-current model (CCM). This new model was shown to provide better description of the spatial current distribution of the cell during the initial negative deflection of the extracellular action potential, from the onset of the spike to the negative peak. The new model was tested on simulated extracellular potentials. We proved numerically, that all the parameters of the model could be determined accurately based on measurements. Thus, fitting of the CCM allowed extraction of these parameters from the measurements. Due to model fitting, CSD could be calculated with much higher accuracy as done with the traditional method because distance dependence of the spatial potential patterns was explicitly taken into consideration in our method. Average CSD distribution of the neocortical action potentials was calculated and spatial decay constant of the dendritic trees was determined by applying our new method.

  13. High Resolution Frequency Swept Imaging.

    DTIC Science & Technology

    1983-09-30

    elements can be em- ployed to cut cost. However a systematic study of ordered and random aperture thinning [1], [21 Indicates rapid deterioration in...yield 3-D image information. Impulse illumination is desirable incertain instances of rapid target motion but may be more difficlt to implement than...various slices are seen in depth * at different VFT planes that are determined by the positions of the axially incremented point source. Repeated rapid

  14. Precipitation measurements on wind-swept slopes

    Treesearch

    Austin E. Helmers

    1954-01-01

    Precipitation catch for three calendar years is compared for four types of gage installation on a wind-swept south-facing slope with a 22° gradient at elevation 5500 ft. The 1950 precipitation catch by (1) weighing-recording gage with the orifice and an Alter type wind shield sloped parallel to the ground surface, (2) unshielded nonrecording gage with orifice sloped...

  15. Impact Crater Environments as Potential Sources of Hadean Detrital Zircons

    NASA Astrophysics Data System (ADS)

    Kenny, G. G.; Whitehouse, M. J.; Kamber, B. S.

    2016-08-01

    Here we show that contrary to previous suggestions, there is no reason to rule out impact melt sheets as major sources of Hadean detrital zircons. We then explore the potential of other impact crater-related environments in which zircons crystallise.

  16. Potential Sources of Bias in Dual Language Achievement Tests.

    ERIC Educational Resources Information Center

    Cabello, Beverly

    Potential sources of bias in dual language achievement tests were identified and examined. Content, concepts, and vocabulary presented in monolingual English curricula may differ drastically from those presented in bilingual curricula. The Spanish or English versions of the Comprehensive Tests of Basic Skills (CTBS) were administered to 1259…

  17. CLASSIFICATION OF MATERIALS AS POTENTIAL SOURCES OF INDOOR AIR POLLUTION

    EPA Science Inventory

    The report gives a complete classification of all materials used in the construction of, or brought inside, homes and office buildings. n the classification tables Presented in the report, shaded entries are potential Sources of indoor air emissions. he classification system is b...

  18. Utilization of leaf litter as a potential feed source

    USDA-ARS?s Scientific Manuscript database

    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 ...

  19. 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.

  20. Diabatic sources of potential vorticity in the general circulation

    SciTech Connect

    Hoerling, M.P. )

    1992-12-01

    A form of the potential vorticity (PV) budget is proposed that facilitates analysis on the role of global heat sources and sinks in the general circulation. A local diabatic source of PV occurs due to vertical variations of heating. Additionally, since the irrotational mass circulation in isentropic coordinates is uniquely linked to diabatic heating, the associated horizontal advection of PV may be viewed as a diabatic source. The sum of these processes constitutes an effective [open quotes]baroclinic wave source[close quotes] due to diabatic processes, and is analogous to the effective barotropic Rossby wave source due to divergence as discussed by Sardeshmukh and Hoskins. Diagnostic results are presented for the upper-tropospheric PV balance at 350 K during northern winter. When the PV budget is diagnosed in its conventional form, the midlatitude flow appears insulated from the influence of tropical heating in the sense that diabatic sources and sinks are mainly due to vertical variations of extratropical heat sources and sinks. In the NH, these sources/sinks are balanced by the mean horizontal advection of PV by the total flow, which acts to transport PV from reservoirs of large values over eastern Asia and Canada to small values over the central North Pacific and western North Atlantic oceans. Analysis of the effective baroclinic wave source reveals that the midlatitude PV balance depends strongly on the distribution of tropical heating, a result that agrees more favorably with empirical and numerical studies on tropical-extratropical interactions. Sinks due to horizontal PV advection by the irrotational flow occur throughout the eastern hemisphere along 30[degrees] latitude, and exceed the local sources associated with in situ diabatic cooling. The implied poleward transport of low PV air from the tropics occurs in the outflow branch of the regional Hadley circulation, revealing the large influence of the Australasian monsoon.

  1. Measurement and determination of radon source potential: A literature review

    SciTech Connect

    Tanner, A.B.

    1994-04-01

    Radon source potential may be estimated for areas of a nation, state, county, housing development, or building lot. The critical characteristics of the soil are its radium concentration, emanation coefficient, permeability to gas, and diffusion coefficient for radon under typical conditions. This report summarizes and evaluates available information on radon potential mapping and site-specific characterization. More than 100 reports have been found that bear on radon potential mapping, and indicate fair to good agreement with indoor radon results where correlations have been possible.

  2. Marine Microbes as a Potential Source of Cellulolytic Enzymes.

    PubMed

    Trivedi, N; Reddy, C R K; Lali, A M

    Marine environment hosts the wide range of habitats with remarkably high and diverse microbial populations. The ability of marine microorganisms to survive in extreme temperature, salinity, and pressure depends on the function of multivarious enzyme systems that in turn provide vast potential for biotechnological exploration studies. Therefore, the enzymes from marine microorganism represent novel bio catalytic potential with stable and reliable properties. Microbial cellulases constitute a major group of industrial enzymes that find applications in various industries. Majority of cellulases are of terrestrial origin, and very limited research has been carried out to explore marine microbes as a source of cellulases. This chapter presents an overview about the types of marine polysaccharases, classification and potential applications of cellulases, different sources of marine cellulases, and their future perspectives. © 2016 Elsevier Inc. All rights reserved.

  3. Phosphine production potential of various wastewater and sewage sludge sources

    SciTech Connect

    Devai, I.; DeLaune, R.D.; Patrick, W.H. Jr.; Devai, G.; Czegeny, I.

    1999-05-01

    A laboratory incubation procedure followed by gas chromatographic detection was used to measure phosphine production potential in representative wastewater and sewage sludge sources. Phosphine production potential was determined by measuring the rate of phosphine formation in samples incubated under laboratory conditions over a seven day period when both electron donors and the targeted electron acceptor were not limiting factors. Results of their experiments showed that except the primary effluent and secondary effluent wastewater samples all other samples studied (influent wastewater, various type of sludge and sediment sources) produced phosphine. The minimum phosphine production potential value (0.39 pg/ml wastewater/day) was measured in composite influent wastewater samples while the maximum (268 pg/g wet sludge/day) was measured in sediment samples collected from an open-air sewage treatment plant.

  4. 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

    2015-10-30

    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.

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. Improved computational treatment of transonic flow about swept wings

    NASA Technical Reports Server (NTRS)

    Ballhaus, W. F.; Bailey, F. R.; Frick, J.

    1976-01-01

    Relaxation solutions to classical three-dimensional small-disturbance (CSD) theory for transonic flow about lifting swept wings are reported. For such wings, the CSD theory was found to be a poor approximation to the full potential equation in regions of the flow field that are essentially two-dimensional in a plane normal to the sweep direction. The effect of this deficiency on the capture of embedded shock waves in terms of (1) the conditions under which shock waves can exist and (2) the relations they must satisfy when they do exist is emphasized. A modified small-disturbance (MSD) equation, derived by retaining two previously neglected terms, was proposed and shown to be a consistent approximation to the full potential equation over a wider range of sweep angles. The effect of these extra terms is demonstrated by comparing CSD, MSD, and experimental wing surface pressures.

  10. Distinguishing potential sources of genotoxic exposure via HPRT mutations.

    PubMed

    Molholt, B; Finette, B A

    2000-01-01

    We utilize T-cell HPRT mutations to monitor exposure to environmental mutagens in siblings of children who have developed cancer at a persistently high rate in Toms River, New Jersey, U.S.A. A preliminary epidemiological study has found a statistically-significant association between drinking public water (by pregnant mother or infant) and subsequent risk for childhood cancer. Three potential sources of mutagenic exposures in Toms River may have increased the rate of carcinogenic initiation significantly in children: 1. Benzidine-based, other azo dye and anthraquinone dye wastes released by Ciba-Geigy, 2. Styrene-acrylonitrile (SAN) trimer and other plastic wastes of Union Carbide, and 3. Radium-224, present in unusually high concentrations in the Cohansey aquifer. Specific patterns of HPRT mutations are utilized to distinguish these various potential sources of carcinogenic exposures in the drinking water of families with childhood cancer and to differentiate chemically or radiologically induced cancers from those which occur spontaneously.

  11. Interaction of a swept shock wave and a supersonic wake

    NASA Astrophysics Data System (ADS)

    He, G.; Zhao, Y. X.; Zhou, J.

    2017-09-01

    The interaction of a swept shock wave and a supersonic wake has been studied. The swept shock wave is generated by a swept compression sidewall, and the supersonic wake is generated by a wake generator. The flow field is visualized with the nanoparticle-based planar laser scattering method, and a supplementary numerical simulation is conducted by solving the Reynolds-averaged Navier-Stokes equations. The results show that the pressure rise induced by the swept shock wave can propagate upstream in the wake, which makes the location where vortices are generated move upstream, thickens the laminar section of the wake, and enlarges the generated vortices. The wake is swept away from the swept compression sidewall by the pressure gradient of the swept shock wave. This pressure gradient is not aligned with the density gradient of the supersonic wake, so the baroclinic torque generates streamwise vorticity and changes the distribution of the spanwise vorticity. The wake shock is curved, so the flow downstream of it is non-uniform, leaving the swept shock wave being distorted. A three-dimensional Mach disk structure is generated when the wake shock interacts with the swept shock wave.

  12. Interaction of a swept shock wave and a supersonic wake

    NASA Astrophysics Data System (ADS)

    He, G.; Zhao, Y. X.; Zhou, J.

    2017-03-01

    The interaction of a swept shock wave and a supersonic wake has been studied. The swept shock wave is generated by a swept compression sidewall, and the supersonic wake is generated by a wake generator. The flow field is visualized with the nanoparticle-based planar laser scattering method, and a supplementary numerical simulation is conducted by solving the Reynolds-averaged Navier-Stokes equations. The results show that the pressure rise induced by the swept shock wave can propagate upstream in the wake, which makes the location where vortices are generated move upstream, thickens the laminar section of the wake, and enlarges the generated vortices. The wake is swept away from the swept compression sidewall by the pressure gradient of the swept shock wave. This pressure gradient is not aligned with the density gradient of the supersonic wake, so the baroclinic torque generates streamwise vorticity and changes the distribution of the spanwise vorticity. The wake shock is curved, so the flow downstream of it is non-uniform, leaving the swept shock wave being distorted. A three-dimensional Mach disk structure is generated when the wake shock interacts with the swept shock wave.

  13. Annona species (Annonaceae): a rich source of potential antitumor agents?

    PubMed

    Tundis, Rosa; Xiao, Jianbo; Loizzo, Monica R

    2017-06-01

    Plants have provided the basis of traditional medicine systems throughout the world for thousands of years and continue to yield molecules for new remedies. We analyzed studies published from 2009 to 2016 on the Annona species (Annonaceae), including A. coriacea, A. crassifolia, A. hypoglauca, A. muricata, A. squamosa, A. sylvatica, and A. vepretorum, as sources of potential antitumor agents. Here, we report and discuss the mechanisms of action and structure-activity relationships of the most active Annona constituents. Annonaceous acetogenins are one of the most promising classes of natural products, owing to their potential antitumor activity. However, their neurotoxicity should not be underestimated. © 2017 New York Academy of Sciences.

  14. On the uniqueness of the surface sources of evoked potentials.

    PubMed

    Cabo, A; Handy, C; Bessis, D

    2001-10-01

    The uniqueness of a surface density of sources localized inside a spatial region R and producing a given electric potential distribution in its boundary B0 is revisited. The situation in which R is filled with various subregions, each one having a definite constant value for the electric conductivity is considered. It is argued that the knowledge of the potential in all B0 fully determines the surface-located sources for a general class of surfaces supporting them and also a wide type of those sources. The class of surfaces can be defined as a union of an arbitrary but finite number of open or closed surfaces. The only restriction upon them is that no one of the closed surfaces contains inside it another (nesting) of the closed or open ones. The types of sources are surface charge densities and double layer (dipolar) densities for the open surfaces and more restrictively, only surface charge densities for the closed ones. A two-dimensional analytically solvable example illustrating the drastic appearance of uniqueness after arbitrarily small holes are opened in nested surfaces is discussed.

  15. Wavelength-swept fiber laser based on acousto-optic tuning method

    NASA Astrophysics Data System (ADS)

    Chen, Ming-hui; Fan, Yun-ping; Zhang, Hao; Tao, Jian-feng; Zheng, Gang

    2016-10-01

    In this study, we have demonstrated a wavelength-swept fiber laser based on an acousto-optic tunable filter(AOTF) as a selective element and a semiconductor optical amplifier(SOA) as a gain medium in an internal fiber ring cavity. The light deriving from one port of the SOA goes through an optical isolator, the AOTF, a fiber coupler and a polarized controller successively, then it goes back to the other port of the SOA to form a ring cavity. The laser output is from another port of the fiber coupler. The laser made by this method is mainly used for swept-source optical coherence tomography(SS-OCT). The application of the SOA provides a sufficiently broad range and can ensure an increased axial resolution of SS-OCT. AOTF offers a wide tuning range, high switching speed and stable operation against vibration for the non-mechanical structure. The proposed wavelength-swept fiber laser ensures a high axial resolution of tomographic images and has a stable laser output. We have discussed the influence of the SOA injection current to the tuning range of the laser. In the SOA injection current of 280 mA, a continuous wavelength tuning range from 1295 to 1370 nm centered at a wavelength of 1330nm is obtained at the sweep rate of 1.06 kHz, and the power of the swept source was 1.14 mW. In addition, for quantitative characterization of the wavelength-swept performance with a AOTF, we have theoretically and experimentally analyzed the influence of the following controllable parameters: injection current, output power and sweeping frequency.

  16. 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.

  17. 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.

  18. 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.

  19. Analytical study of vortex flaps on highly swept delta wings

    NASA Technical Reports Server (NTRS)

    Frink, N. T.

    1982-01-01

    This paper highlights some current results from ongoing analytical studies of vortex flaps on highly swept delta wings. A brief discussion of the vortex flow analysis tools is given along with comparisons of the theories to vortex flap force and pressure data. Theoretical trends in surface pressure distribution for both angle-of-attack variation and flap deflection are correctly predicted by Free Vortex Sheet theory. Also shown are some interesting calculations for attached-flow and vortex-flow flap hinge moments that indicate flaps utilizing vortex flow may generate less hinge moment than attached flow flaps. Finally, trailing-edge flap effects on leading-edge flap thrust potential are investigated and theory-experiment comparisons made.

  20. Water as a source of potentially pathogenic mycobacteria.

    PubMed

    Goslee, S; Wolinsky, E

    1976-03-01

    The mycobacterial flora of 321 water samples was explored to evaluate the role of this part of the environment as a possible source of human mycobacterial disease. The samples included natural waters, waters treated to make them suitable for drinking, and waters in contact with animals. Water from the city aquarium contained the greatest abundance of mycobacteria, with an average of 3.5 strains per sample. The highest yield of positive cultures came from samples in contact with zoo animals and with fish. The majority of the isolated strains were slowly growing mycobacteria; 80 were Mycobacterium gordonae, and 34 of thse belong to a new serotype. Forty-seven cultures were members of the M. avian-intracellulare-scrofulaceum complex, of which 11 were typable by agglutination. From this study and from the work of others, it is concluded that water may be contaminated with potentially pathogenic mycobacteria and thus may serve as a source of human disease.

  1. 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.

  2. 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.

  3. The potential distribution in the Radial Plasma Source

    NASA Astrophysics Data System (ADS)

    Fruchtman, Amnon; Makrinich, Gennady

    2011-10-01

    The Radial Plasma Source (RPS) is based on plasma acceleration by an applied voltage across a magnetic field. Here we report the recent progress in understanding the mechanism of plasma acceleration in the RPS. The RPS has a cylindrical symmetry. The accelerating electric field is radial and the magnetic field is axial. Most of the potential drop between the inner anode and the outer cathode is expected to be located where the magnetic field intensity is large. We employ an emissive probe and a Langmuir probe in order to evaluate the radial dependence of the potential. For inferring the plasma potential from the measured emissive probe potential, we employ our recently developed theory for a cylindrical emissive probe. Using the theory and the probe measurements, we plot the radial profiles in the RPS of the plasma potential as well as of the electron density and temperature. The possible modification of the geometry for propulsion applications will be discussed. Partially supported by the Israel Science Foundation, Grant 864/07.

  4. Aeroelastic Tailoring with Composites Applied to Forward Swept Wings

    DTIC Science & Technology

    1981-11-01

    wings a viable configo.-tion option for high perfotmance aircraft. Forward swept wings have an inherent -.endency to encounter a static aeroelastic...configuration option for high performance aircraft. Forward swept wings have an inherent tendency to encounter a static aeroelastic instability ialled divergence...conventional and super- critical airfoils. ....... ..................... 19 12 Static methods for subcritical divergence dynamic pressure projection. (a

  5. Flaxseed: a potential source of food, feed and fiber.

    PubMed

    Singh, K K; Mridula, D; Rehal, Jagbir; Barnwal, P

    2011-03-01

    Flaxseed is one of the most important oilseed crops for industrial as well as food, feed, and fiber purposes. Almost every part of the flaxseed plant is utilized commercially, either directly or after processing. The stem yields good quality fiber having high strength and durability. The seed provides oil rich in omega-3, digestible proteins, and lignans. In addition to being one of the richest sources of α-linolenic acid oil and lignans, flaxseed is an essential source of high quality protein and soluble fiber and has considerable potential as a source of phenolic compounds. Flaxseed is emerging as an important functional food ingredient because of its rich contents of α-linolenic acid (ALA), lignans, and fiber. Lignans appear to be anti-carcinogenic compounds. The omega-3s and lignan phytoestrogens of flaxseed are in focus for their benefits for a wide range of health conditions and may possess chemo-protective properties in animals and humans. This paper presents a review of literature on the nutritional composition of flaxseed, its health benefits, and disease-prevention qualities, utilization of flaxseed for food, feed, and fiber, and processing of flaxseed.

  6. Potential Field Source Surface Model and Solar Wind Prediction

    NASA Astrophysics Data System (ADS)

    Poduval, B.; Zhao, X.; Hoeksema, T.

    2005-05-01

    Various magnetic activities of the Sun causes disturbances in the near-Earth enviornment as well as on the weather and technology on Earth. "Addressing these disturbances and predicting them well in advance are the main task of Space Weather research. Much of the solar side of Space Weather is concerned with the accurate prediction of solar wind and its properties which are closely related to the coronal magnetic field. Since a direct measurement of the coronal magnetic field is still limited to strong field regions, solar wind predictions are based on theoretical models of the corona. The primary prediction scheme of the solar wind speed currently used at SEC is based on the empirical relationship between the flux tube expansion (FTE) factor obtained using Potential Field Source Surface (PFSS) model of the corona and the solar wind speed near the Earth. Though successful, this scheme has significant discrepancies. We have studied, using the near-Earth saltellites data as well as near--Sun Helios data, the possible causes of these discrepancies. In our study, FTE at the source surface were obtained using two different coronal models: PFSS model and the Current--Sheet Source Surface (CSSS) model. We present the results of this investigation and a comparison of the two models.

  7. Prospecting for potentially new pharmaceuticals from natural sources.

    PubMed

    Pandey, R C

    1998-09-01

    Many new natural product-derived pharmaceutically active compounds and compositions, each effective in treating an array of diseases and maladies including various tumors and HIV, have been reportedly isolated from different sources of vegetation, including the bark of yew trees, needles, leaves, fungi, and cell culture of many different species; vegetables such as West African yams; and Chinese and Indian herbs. Other sources include vegetation from South American rainforests. Many of the sources of such natural products are historical in nature and/or are known from folklore. Recent studies have provided potentially new biodiverse pharmaceutical compounds such as paclitaxel, which is obtainable from several species, including various portions of T. brevifolia, the Western yew tree, and other yew species such as T. baccata, T. cuspidata, T. wallichiana, T. media, T. canadensis, T. chinensis and T. yunnanensis as well as from T. wardii, T. capitata, T. brownii, T. gem, T. globosa, T. floridana, T. hicksii, T. densiformis, and T. darkgreen spreader, in addition to cultured plant cells and fungi. The novel compounds and their semisynthetic brominated and chlorinated analogs prepared from T. yunnanensis extract show strong activity against several types of tumors.

  8. Modeling and numerical investigation of the inlet circumferential fluctuations of swept and bowed blades

    NASA Astrophysics Data System (ADS)

    Tang, Mingzhi; Jin, Donghai; Gui, Xingmin

    2017-02-01

    The circumferential fluctuation (CF) source terms induced by the inviscid blade force can affect the inlet distribution of flow parameters and radial equilibrium of swept and bowed blades. However, these phenomena cannot be adequately described by throughflow methods based on the axisymmetric assumption. A transport model for the CF stresses is proposed and correlated to the distribution of circulation to reflect the effect of the inviscid blade force. To investigate the effect of the inlet CFs on swept and bowed blades, the model is integrated into a throughflow model and applied to a series of cascades with different sweep and bow angles. For swept cascades, the CF source terms change the distributions of incidence angles, as well as the radial equilibrium at the inlet of the blade passage. And the influence is enhanced as the absolute value of the sweep angle increases. For bowed cascades, the distributions of incidence angles are also altered. For both cases, the model can offer a good prediction of the inlet CF source terms, and prove to exert a better prediction of blade design key parameters such as flow angles.

  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. Source rock potential of middle cretaceous rocks in Southwestern Montana

    USGS Publications Warehouse

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

    1996-01-01

    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 (S1+S2) 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% Ro. Maturity is high in the Pioneer Mountains, where vitrinite reflectance averages 3.4% Ro, and at Big Sky Montana, where vitrinite reflectance averages 2.5% Ro. At both localities, high Ro values are due to local heat sources, such as the Pioneer batholith in the Pioneer Mountains.

  11. 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.

  12. Frequency-Swept Integrated Solid Effect.

    PubMed

    Can, Thach V; Weber, Ralph T; Walish, Joseph J; Swager, Timothy M; Griffin, Robert G

    2017-06-06

    The efficiency of continuous wave dynamic nuclear polarization (DNP) experiments decreases at the high magnetic fields used in contemporary high-resolution NMR applications. To recover the expected signal enhancements from DNP, we explored time domain experiments such as NOVEL which matches the electron Rabi frequency to the nuclear Larmor frequency to mediate polarization transfer. However, satisfying this matching condition at high frequencies is technically demanding. As an alternative we report here frequency-swept integrated solid effect (FS-ISE) experiments that allow low power sweeps of the exciting microwave frequencies to constructively integrate the negative and positive polarizations of the solid effect, thereby producing a polarization efficiency comparable to (±10 % difference) NOVEL. Finally, the microwave frequency modulation results in field profiles that exhibit new features that we coin the "stretched" solid effect. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. W-Band Frequency-Swept EPR

    PubMed Central

    Hyde, James S.; Strangeway, Robert A.; Camenisch, Theodore G.; Ratke, Joseph J.; Froncisz, Wojciech

    2010-01-01

    This paper describes a novel experiment on nitroxide radical spin labels using a multiarm EPR W-band bridge with a loop-gap resonator (LGR). We demonstrate EPR spectroscopy of spin labels by linear sweep of the microwave frequency across the spectrum. The high bandwidth of the LGR, about 1 GHz between 3 dB points of the microwave resonance, makes this new experiment possible. A frequency-tunable yttrium iron garnet (YIG) oscillator provides sweep rates as high as 1.8 × 105 GHz/s, which corresponds to 6.3 kT/s in magnetic field-sweep units over a 44 MHz range. Two experimental domains were identified. In the first, linear frequency sweep rates were relatively slow, and pure absorption and pure dispersion spectra were obtained. This appears to be a practical mode of operation at the present level of technological development. The main advantage is the elimination of sinusoidal magnetic field modulation. In the second mode, the frequency is swept rapidly across a portion of the spectrum, and then the frequency sweep is stopped for a readout period; FID signals from a swept line oscillate at a frequency that is the difference between the spectral position of the line in frequency units and the readout position. If there is more than one line, oscillations are superimposed. The sweep rates using the YIG oscillator were too slow, and the portion of the spectrum too narrow to achieve the full EPR equivalent of Fourier transform (FT) NMR. The paper discusses technical advances required to reach this goal. The hypothesis that trapezoidal frequency sweep is an enabling technology for FT EPR is supported by this study. PMID:20462775

  14. The Potential of Renewable Energy Sources in Latvia

    NASA Astrophysics Data System (ADS)

    Sakipova, S.; Jakovics, A.; Gendelis, S.

    2016-02-01

    The article discusses some aspects of the use of renewable energy sources in the climatic conditions prevailing in most of the territory of Latvia, with relatively low wind speeds and a small number of sunny days a year. The paper gives a brief description of the measurement equipment and technology to determine the parameters of the outer air; the results of the measurements are also analysed. On the basis of the data obtained during the last two years at the meteorological station at the Botanical Garden of the University of Latvia, the energy potential of solar radiation and wind was estimated. The values of the possible and the actual amount of produced energy were determined.

  15. Bioactivities of alternative protein sources and their potential health benefits.

    PubMed

    Pihlanto, A; Mattila, P; Mäkinen, S; Pajari, A-M

    2017-08-14

    Increasing the utilisation of plant proteins is needed to support the production of protein-rich foods that could replace animal proteins in the human diet so as to reduce the strain that intensive animal husbandry poses to the environment. Lupins, quinoa and hempseed are significant sources of energy, high quality proteins, fibre, vitamins and minerals. In addition, they contain compounds such as polyphenols and bioactive peptides that can increase the nutritional value of these plants. From the nutritional standpoint, the right combination of plant proteins can supply sufficient amounts of essential amino acids for human requirements. This review aims at providing an overview of the current knowledge of the nutritional properties, beneficial and non-nutritive compounds, storage proteins, and potential health benefits of lupins, quinoa and hempseed.

  16. Motherhood: a potential source of bias in employment decisions.

    PubMed

    Heilman, Madeline E; Okimoto, Tyler G

    2008-01-01

    Results of 2 experimental studies in which job incumbents were said to be applying for promotions to traditionally male positions demonstrated bias against mothers in competence expectations and in screening recommendations. This bias occurred regardless of whether the research participants were students (Study 1) or working people (Study 2). Although anticipated job commitment, achievement striving, and dependability were rated as generally lower for parents than for nonparents, anticipated competence was uniquely low for mothers. Mediational analyses indicated that, as predicted, negativity in competence expectations, not anticipated job commitment or achievement striving, promoted the motherhood bias in screening recommendations; expected deficits in agentic behaviors, not in dependability, were found to fuel these competence expectations. These findings suggest that motherhood can indeed hinder the career advancement of women and that it is the heightened association with gender stereotypes that occurs when women are mothers that is the source of motherhood's potentially adverse consequences. 2008 APA

  17. Source localization in electromyography using the inverse potential problem

    NASA Astrophysics Data System (ADS)

    van den Doel, Kees; Ascher, Uri M.; Pai, Dinesh K.

    2011-02-01

    We describe an efficient method for reconstructing the activity in human muscles from an array of voltage sensors on the skin surface. MRI is used to obtain morphometric data which are segmented into muscle tissue, fat, bone and skin, from which a finite element model for volume conduction is constructed. The inverse problem of finding the current sources in the muscles is solved using a careful regularization technique which adds a priori information, yielding physically reasonable solutions from among those that satisfy the basic potential problem. Several regularization functionals are considered and numerical experiments on a 2D test model are performed to determine which performs best. The resulting scheme leads to numerical difficulties when applied to large-scale 3D problems. We clarify the nature of these difficulties and provide a method to overcome them, which is shown to perform well in the large-scale problem setting.

  18. Perfluorochemicals: potential sources of and migration from food packaging.

    PubMed

    Begley, T H; White, K; Honigfort, P; Twaroski, M L; Neches, R; Walker, R A

    2005-10-01

    Perfluorochemicals are widely used in the manufacturing and processing of a vast array of consumer goods, including electrical wiring, clothing, household and automotive products. Furthermore, relatively small quantities of perfluorochemicals are also used in the manufacturing of food-contact substances that represent potential sources of oral exposure to these chemicals. The most recognizable products to consumers are the uses of perfluorochemicals in non-stick coatings (polytetrafluoroethylene (PTFE)) for cookware and also their use in paper coatings for oil and moisture resistance. Recent epidemiology studies have demonstrated the presence of two particular perfluorochemicals, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in human serum at very low part per billion levels. These perfluorochemicals are biopersistent and are the subject of numerous studies investigating the many possible sources of human exposure. Among the various uses of these two chemicals, PFOS is a residual impurity in some paper coatings used for food contact and PFOA is a processing aid in the manufacture of PTFE used for many purposes including non-stick cookware. Little information is available on the types of perfluorochemicals that have the potential to migrate from perfluoro coatings into food. One obstacle to studying migration is the difficulty in measuring perfluorochemicals by routine conventional analytical techniques such as GC/MS or LC-UV. Many perfluorochemicals used in food-contact substances are not detectable by these conventional methods. As liquid chromatography-mass spectrometry (LC/MS) develops into a routine analytical technique, potential migrants from perfluoro coatings can be more easily characterized. In this paper, data will be presented on the types of perfluoro chemicals that are used in food packaging and cookware. Additionally, research will be presented on the migration or potential for migration of these chemicals into foods or food

  19. Frequency swept microwaves for hyperfine decoupling and time domain dynamic nuclear polarization

    PubMed Central

    Hoff, Daniel E.M.; Albert, Brice J.; Saliba, Edward P.; Scott, Faith J.; Choi, Eric J.; Mardini, Michael; Barnes, Alexander B.

    2015-01-01

    Hyperfine decoupling and pulsed dynamic nuclear polarization (DNP) are promising techniques to improve high field DNP NMR. We explore experimental and theoretical considerations to implement them with magic angle spinning (MAS). Microwave field simulations using the high frequency structural simulator (HFSS) software suite are performed to characterize the inhomogeneous phase independent microwave field throughout a 198 GHz MAS DNP probe. Our calculations show that a microwave power input of 17 W is required to generate an average EPR nutation frequency of 0.84 MHz. We also present a detailed calculation of microwave heating from the HFSS parameters and find that 7.1% of the incident microwave power contributes to dielectric sample heating. Voltage tunable gyrotron oscillators are proposed as a class of frequency agile microwave sources to generate microwave frequency sweeps required for the frequency modulated cross effect, electron spin inversions, and hyperfine decoupling. Electron spin inversions of stable organic radicals are simulated with SPINEVOLUTION using the inhomogeneous microwave fields calculated by HFSS. We calculate an electron spin inversion efficiency of 56% at a spinning frequency of 5 kHz. Finally, we demonstrate gyrotron acceleration potentials required to generate swept microwave frequency profiles for the frequency modulated cross effect and electron spin inversions. PMID:26482131

  20. Frequency swept microwaves for hyperfine decoupling and time domain dynamic nuclear polarization.

    PubMed

    Hoff, Daniel E M; Albert, Brice J; Saliba, Edward P; Scott, Faith J; Choi, Eric J; Mardini, Michael; Barnes, Alexander B

    2015-11-01

    Hyperfine decoupling and pulsed dynamic nuclear polarization (DNP) are promising techniques to improve high field DNP NMR. We explore experimental and theoretical considerations to implement them with magic angle spinning (MAS). Microwave field simulations using the high frequency structural simulator (HFSS) software suite are performed to characterize the inhomogeneous phase independent microwave field throughout a 198GHz MAS DNP probe. Our calculations show that a microwave power input of 17W is required to generate an average EPR nutation frequency of 0.84MHz. We also present a detailed calculation of microwave heating from the HFSS parameters and find that 7.1% of the incident microwave power contributes to dielectric sample heating. Voltage tunable gyrotron oscillators are proposed as a class of frequency agile microwave sources to generate microwave frequency sweeps required for the frequency modulated cross effect, electron spin inversions, and hyperfine decoupling. Electron spin inversions of stable organic radicals are simulated with SPINEVOLUTION using the inhomogeneous microwave fields calculated by HFSS. We calculate an electron spin inversion efficiency of 56% at a spinning frequency of 5kHz. Finally, we demonstrate gyrotron acceleration potentials required to generate swept microwave frequency profiles for the frequency modulated cross effect and electron spin inversions. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. A Description of the Design of Highly Swept Propeller Blades

    NASA Technical Reports Server (NTRS)

    Whitcomb, Richard T

    1950-01-01

    A description of the two swept propellers investigated in the Langley 8-foot high-speed tunnel is presented, together with the discussions of the numerous assumptions and analyses on which the designs of these propellers are based. The blades are swept considerably along the entire blade radius and, in order to allow for reductions in the maximum stresses, are swept forward inboard and backward outboard. The blades have been designed on the basis of the blade-element method primarily to have subcritical efficiencies at the highest possible forward speed. The designs have been controlled primarily by the stresses in the blades. (author)

  2. Artocarpus plants as a potential source of skin whitening agents.

    PubMed

    Arung, Enos Tangke; Shimizu, Kuniyoshi; Kondo, Ryuichiro

    2011-09-01

    Artocarpus plants have been a focus of constant attention due to the potential for skin whitening agents. In the in vitro experiment, compounds from the Artocarpus plants, such as artocarpanone, norartocarpetin, artocarpesin, artogomezianol, andalasin, artocarbene, and chlorophorin showed tyrosinase inhibitory activity. Structure-activity investigations revealed that the 4-substituted resorcinol moiety in these compounds was responsible for their potent inhibitory activities on tyrosinase. In the in vitro assay, using B16 melanoma cells, the prenylated polyphenols isolated from Artocarpus plants, such as artocarpin, cudraflavone C, 6-prenylapigenin, kuwanon C, norartocarpin, albanin A, cudraflavone B, and brosimone I showed potent inhibitory activity on melanin formation. Structure-activity investigations revealed that the introduction of an isoprenoid moiety to a non-isoprenoid-substituted polyphenol enhanced the inhibitory activity of melanin production in B16 melanoma cells. In the in vivo investigation, the extract of the wood of Artocarpus incisus and a representative isolated compound from it, artocarpin had a lightening effect on the skin of guinea pigs' backs. Other in vivo experiments using human volunteers have shown that water extract of Artocarpus lakoocha reduced the melanin formation in the skin of volunteers. These results indicate that the extracts of Artocarpus plants are potential sources for skin whitening agents.

  3. On the linear stability of swept attachment-line boundary layer flow. Part 2. Non-modal effects and receptivity

    NASA Astrophysics Data System (ADS)

    Obrist, Dominik; Schmid, Peter J.

    2003-10-01

    Following the study of the spectral properties of linearized swept Hiemenz flow (see Part 1, Obrist & Schmid 2003) we investigate the potential of swept Hiemenz flow to support transiently growing perturbations owing to the non-normal nature of the underlying linear stability operator. Transient amplification of perturbation energy is found for polynomial orders higher than zero, and a catalytic role of the continuous modes in increasing transient growth is demonstrated. The adjoint stability equations are derived and used in a numerical receptivity experiment to illustrate the scattering of vortical free-stream disturbances into the least stable boundary layer mode.

  4. Potential sources of microbial contamination in unpasteurized apple cider.

    PubMed

    Garcia, Luis; Henderson, John; Fabri, Martha; Oke, Moustapha

    2006-01-01

    A study was conducted to identify possible sources of microbial contamination and to assess the effect of good cleaning and sanitation practices on the microbial quality and safety of unpasteurized apple cider. Raw unwashed apples, washed apples, cleaning water, fresh cider, and finished cider samples were collected from five Ontario producers over 4 months and microbiologically tested. Total coliforms were found in 31, 71 and 38% of the unwashed apple, water, and washed apple samples, respectively. Escherichia coli was found in 40% of the water samples from one producer alone. The washing step was identified as a potential source of contamination, possibly due to water in the dump tanks seldom being refreshed, and because scrubbers, spray nozzles, and conveyors were not properly cleaned and sanitized. Higher total coliform counts (P < 0.0001) and prevalence (P < 0.0001) in fresh cider compared with those in unwashed apples and washed apples indicated considerable microbial buildup along the process, possibly explained by the lack of appropriate equipment sanitation procedures. Results showed that producers who had better sanitary practices in place had lower (P < 0.001) total coliform prevalence than the rest of the producers. Overall results show that good sanitation procedures are associated with improved microbial quality of fresh cider in terms of total coliforms and that operators who pasteurize and/or UV treat their product should still be required to have a sound good manufacturing practices program in place to prevent recontamination. Cryptosporidium parvum, an important pathogen for this industry, was found in different sample types, including washed apples, water, and fresh and finished cider.

  5. A linearly frequency-swept high-speed-rate multi-wavelength laser for optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wang, Qiyu; Wang, Zhaoying; Yuan, Quan; Ma, Rui; Du, Tao; Yang, Tianxin

    2017-02-01

    We proposed and demonstrated a linearly frequency-swept multi-wavelength laser source for optical coherence tomography (OCT) eliminating the need of wavenumber space resampling in the postprocessing progress. The source consists of a multi-wavelength fiber laser source (MFS) and an optical sweeping loop. In this novel laser source, an equally spaced multi-wavelength laser is swept simultaneously by a certain step each time in the frequency domain in the optical sweeping loop. The sweeping step is determined by radio frequency (RF) signal which can be precisely controlled. Thus the sweeping behavior strictly maintains a linear relationship between time and frequency. We experimentally achieved linear time-frequency sweeping at a sweeping rate of 400 kHz with our laser source.

  6. Downstream influence of swept slot injection in hypersonic turbulent flow

    NASA Technical Reports Server (NTRS)

    Hefner, J. N.; Cary, A. M., Jr.; Bushnell, D. B.

    1977-01-01

    Results of an experimental and numerical investigation of tangential swept slot injection into a thick turbulent boundary layer at Mach 6 are presented. Film cooling effectiveness, skin friction, and flow structure downstream of the swept slot injection were investigated. The data were compared with that for unswept slots, and it was found that cooling effectiveness and skin friction reductions are not significantly affected by sweeping the slot.

  7. Wideband detection of middle ear muscle activation using swept-tone distortion product otoacoustic emissions.

    PubMed

    Henin, Simon; Long, Glenis R; Thompson, Suzanne

    2014-07-01

    The measurement of efferent-induced suppression of otoacoustic emissions (OAEs) using contralateral acoustic stimulation (CAS) is complicated by potential contamination by the middle ear muscle reflex (MEMR), particularly at moderate to high CAS levels. When logarithmically sweeping primaries are used to measure distortion product otoacoustic emissions, the level and phase of the primaries at the entrance of the ear canal may be monitored simultaneously along with the OAEs elicited by the swept-tones. A method of detecting MEMR activation using swept-tones is presented in which the differences in the primaries in the ear canal with and without CAS are examined, permitting evaluation of MEMR effects over a broad frequency range. A range of CAS levels above and below expected contralateral acoustic reflex thresholds permitted evaluation of conditions with and without MEMR activation.

  8. A swept frequency multiplication technique for air-coupled ultrasonic NDE.

    PubMed

    Gan, Tat Hean; Hutchins, David A; Green, Roger J

    2004-10-01

    A new technique has been investigated for improving the signals that can be obtained in air-coupled nondestruction evaluation (NDE). This relies on the wide bandwidth available from polymer-filmed capacitive transducers. The technique relies on a swept-frequency "chirp" signal, which is transmitted from a transducer in air. The new technique differs from existing time-domain correlation techniques, such as pulse compression, in that a single multiplication process is performed in the time domain to give a difference frequency signal. This then can be isolated easily in the frequency domain. It will be demonstrated that this new swept frequency multiplication (SFM) approach gives the potential for rapid air-coupled imaging.

  9. Oxidative Stress in COPD: Sources, Markers, and Potential Mechanisms

    PubMed Central

    McGuinness, Adam John Anthony; Sapey, Elizabeth

    2017-01-01

    Markers of oxidative stress are increased in chronic obstructive pulmonary disease (COPD) and reactive oxygen species (ROS) are able to alter biological molecules, signaling pathways and antioxidant molecule function, many of which have been implicated in the pathogenesis of COPD. However, the involvement of ROS in the development and progression of COPD is not proven. Here, we discuss the sources of ROS, and the defences that have evolved to protect against their harmful effects. We address the role that ROS may have in the development and progression of COPD, as well as current therapeutic attempts at limiting the damage they cause. Evidence has indicated that the function of several key cells appears altered in COPD patients, and expression levels of important oxidant and antioxidant molecules may be abnormal. Therapeutic trials attempting to restore equilibrium to these molecules have not impacted upon all facets of disease and whilst the theory behind ROS influence in COPD appears sound, current models testing relevant pathways to tissue damage are limited. The heterogeneity seen in COPD patients presents a challenge to our understanding, and further research is essential to identify potential targets and stratified COPD patient populations where ROS therapies may be maximally efficacious. PMID:28212273

  10. Geothermal source potential and utilization for alcohol production

    SciTech Connect

    Austin, J.C.

    1981-11-01

    A study was conducted to assess the technical and economic feasibility of using a potential geothermal source to drive a fuel grade alcohol plant. Test data from the well at the site indicated that the water temperature at approximately 8500 feet should approach 275/sup 0/F. However, no flow data was available, and so the volume of hot water that can be expected from a well at this site is unknown. Using the available data, numerous fuel alcohol production processes and various heat utilization schemes were investigated to determine the most cost effective system for using the geothermal resource. The study found the direct application of hot water for alcohol production based on atmospheric processes using low pressure steam to be most cost effective. The geothermal flow rates were determined for various sizes of alcohol production facility using 275/sup 0/F water, 235/sup 0/F maximum processing temperature, 31,000 and 53,000 Btu per gallon energy requirements, and appropriate process approach temperatures. It was determined that a 3 million gpy alcohol plant is the largest facility that can practically be powered by the flow from one large geothermal well. An order-of-magnitude cost estimate was prepared, operating costs were calculated, the economic feasibility of the propsed project was examined, and a sensitivity analysis was performed.

  11. Processed oat hulls as potential dietary fiber sources in rats.

    PubMed

    López-Guisa, J M; Harned, M C; Dubielzig, R; Rao, S C; Marlett, J A

    1988-08-01

    Processed oat hull products were evaluated as potential dietary fiber sources. Three levels, 5, 10 and 15%, of processed oat hulls, bleached oat hulls or oat hulls coated with starch, were added to purified diets and fed to groups of rats for 6 wk. Control diets consisted of 5, 10 or 15% alpha-cellulose or commercial nonpurified diet. None of the oat hull products at the three levels tested had any negative effect on rat growth. Fresh and dry fecal weights increased linearly as the concentration of dietary fiber increased and were highly correlated with fiber intake (r = 0.95). Apparent digestibility of neutral detergent fiber in all diets was low and apparent calcium absorption was not consistently affected by any diet. None of the oat hull test diets lowered plasma or hepatic cholesterol levels, a finding consistent with the failure to detect mixed-linkage beta-glucans in any of the processed oat hull products. Detailed analysis of the processed oat hull fibers also indicated that they were greater than 95% insoluble fiber and high in cellulose and xylans. Light-microscopy histology of kidney, spleen, pancreas, stomach, duodenum, ileum and colon was normal. The extent of hepatocellular destruction produced by the cholesterol (1%) and cholic acid (0.2%) added to the diet to induce hypocholesterolemia was independent of the kind and amount of dietary fiber.

  12. Middle Ordovician Kanosh Formation: Remaining source rock potential

    SciTech Connect

    McDowell, R.R. )

    1988-10-01

    The Kanosh Formation is an early Middle Ordovician, mixed clastic an carbonate sequence exposed in Basin and Range uplifts throughout the eastern Great Basin. The initiation of Kanosh deposition corresponds to shelf-wide change from shallow-water carbonate to relatively deeper, fine-grained siliciclastic sedimentation. Thickest accumulations of the Kanosh Formation lie within a northeast-southwest elongate, intrashelf basin that may represent a re-activated, Middle Cambrian, tectonic basin. Total organic carbon content (TOC) of the Kanosh ranges from 0.02 to 5.66% (mean 0.33%). Equivalent vitrinite reflectances (R{sub o}) for the unit indicate pervasive over-maturation with respect to oil throughout most of the eastern Great Basin; however, much of this area has remaining potential for gas and gas condensate. An east-west trending corridor in southwestern Utah and southeastern Nevada had R{sub o} valves ranging from I to 2, suggesting that gas and some oil could be preserved in this trend. This corridor also approximately corresponds to the areas of highest TOCs and thickest continuous shale; consequently, it is the most favorable petroleum source area.

  13. 46 CFR 112.30-10 - Restoration of normal source potential.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Systems Having an Automatically Connected Storage Battery as the Sole Emergency Power Source § 112.30-10 Restoration of normal source potential. When the potential...

  14. 46 CFR 112.30-10 - Restoration of normal source potential.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Systems Having an Automatically Connected Storage Battery as the Sole Emergency Power Source § 112.30-10 Restoration of normal source potential. When the potential...

  15. 46 CFR 112.30-10 - Restoration of normal source potential.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Systems Having an Automatically Connected Storage Battery as the Sole Emergency Power Source § 112.30-10 Restoration of normal source potential. When the potential...

  16. 46 CFR 112.30-10 - Restoration of normal source potential.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Systems Having an Automatically Connected Storage Battery as the Sole Emergency Power Source § 112.30-10 Restoration of normal source potential. When the potential...

  17. 46 CFR 112.30-10 - Restoration of normal source potential.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Systems Having an Automatically Connected Storage Battery as the Sole Emergency Power Source § 112.30-10 Restoration of normal source potential. When the potential...

  18. Comparison of Tone Mode Measurements for a Forward Swept and Baseline Rotor Fan

    NASA Technical Reports Server (NTRS)

    Heidelberg, Laurence J.

    2003-01-01

    A forward swept fan, designated the Quite High Speed Fan (QHSF), was tested in the NASA Glenn 9- by 15-foot Low Speed Wind Tunnel to investigate its noise reduction relative to a baseline fan of the same aerodynamic performance. The design objective of the QHSF was a 6 dB reduction in Effective Perceived Noise Level relative to the baseline fan at the takeoff condition. The design noise reduction was to be a result of lower levels of multiple pure tone noise due to the forward swept rotor, and lower rotor/stator interaction tone noise from a leaned stator. Although the design 6 dB reduction was observed in far-field measurements, the induct mode measurements revealed the reasons for goals. All of the noise reduction was from the blade passing tone and its harmonics and most of this was unexpectedly from rotor/strut interaction modes. The reason for large differences in rotor/strut noise sources could not be determined with certainty. The reductions in the multiple pure tone noise for the forward swept rotor were not observed. this reduction were not the ones related to the design

  19. Measurement of frequency swept linearly with Fabry-Perot fiber interferometer

    NASA Astrophysics Data System (ADS)

    Luan, Zhu; Xu, Nan; Liu, De'an; Zhou, Yu; Liu, Liren

    2009-08-01

    Synthetic aperture imaging ladar (SAIL) used a series of pulses in which the optical frequency was swept linearly in time over a bandwidth greater than several gigahertz. The linearity of such broadly tunable sources is often poor which is leading to phase errors. Many methods are adopted to correct for quadratic and higher-order phase errors such as the reference channel or algorithm for unmatched channel of Aerospace and the reference interferometer of Naval Research Laboratory. If the real value of frequency swept quasi-linearly is measured another direct way to mitigate the waveform linearity problem can be developed. At first the frequency curve is measured with Fabry Perot fiber interferometer. Experiment and results are explained in detail in this paper. The quadratic and higher-order terms of frequency swept are calculated. They may be used to deduce the phase errors directly later. At the same time the wavefront is also measured by a Jamin shearing interferometer through the fringe analysis.

  20. Multiplexing of fiber-optic ultrasound sensors via swept frequency interferometry.

    PubMed

    Gabai, Haniel; Steinberg, Idan; Eyal, Avishay

    2015-07-27

    The use of fiber-optic sensors for ultrasound (US) detection has many advantages over conventional piezoelectric detectors. However, the issue of multiplexing remains a major challenge. Here, a novel approach for multiplexing fiber-optic based US sensors using swept frequency interferometry is introduced. Light from a coherent swept source propagates in an all-fiber interferometric network made of a reference arm and a parallel connection of N sensing arms. Each sensing arm comprises a short polyimide coated sensing section (~4cm), which is exposed to the US excitation, preceded by a delay of different length. When the instantaneous frequency of the laser is linearly swept, the receiver output contains N harmonic beat components which correspond to the various optical paths. Exposing the sensing sections to US excitation introduces phase modulation of the harmonic components. The US-induced signals can be separated in the frequency domain and be extracted from their carriers by common demodulation techniques. The method was demonstrated by multiplexing 4 sensing fibers and detecting microsecond US pulses which were generated by a 2.25MHz ultrasound transducer. The pulses were successfully measured by all sensing fibers without noticeable cross-talk.

  1. A fiber-optic epoxy cure monitoring technique by using a wavelength-swept laser

    NASA Astrophysics Data System (ADS)

    Kim, Hyunjin; Kim, Dae-gil; Sampath, Umesh; Song, Minho

    2015-07-01

    An epoxy cure monitoring system has been constructed by combining fiber grating sensors and Fresnel reflection monitoring. The sensors measure strain and refractive index variations during the curing process, indicating the onset of gelification, the progress, and the end of curing. We used a wavelength-swept laser source to address both types of sensors. The signals from different sensors could be easily separated, resulting in simple optical setup and increased efficiency. The fiber grating sensors are demodulated by a spectrometer. The output fluctuation in the Fresnel reflection was compensated by referencing it with the tapped output of light source.

  2. Potential use of Cadmium Isotopes to Source Cadmium in Oysters

    NASA Astrophysics Data System (ADS)

    Shiel, A. E.; Barling, J.; Weis, D.; Orians, K. J.

    2005-12-01

    Cd concentrations are relatively high in oysters harvested from the Pacific Northwest (mean 2.63 ppm, wet weight) when compared with those from the east coast (0.33 ppm, wet weight). The cause of the concentration discrepancy between coasts is unknown and may result from natural sources such as local geology and upwelling along the coast, or from anthropogenic sources such as mining, forestry, and urban runoff. This study investigates Cd isotopic variations in the marine environment and the potential use of Cd isotopes as a Cd tracer. Cd isotopic composition is determined for BC oyster tissue samples previously measured and found to have relatively high and low Cd concentrations, from both the east and west coasts of Vancouver Island. The study of natural variations in Cd isotopic composition is allowed by the advent of MC-ICPMS. The capability of the MC-ICPMS to measure small variations in Cd isotopic composition in biological matrices will be discussed including matrix effects. Prior to analysis, samples are digested and Cd is isolated using anion exchange chromatography following the method of Mason (2003). Cd isotopes were measured by dynamic multi-collection using a Nu Plasma MC-ICPMS following the methods reported by Wombacher et al. (2003). Reproducibility is estimated from repeat analysis of an in-house gravimetric standard which is prepared to give a del value of -1‰ on 110/111Cd. Measurements of this standard give δ110/111Cd = -0.993 ± 0.066 (2SD, n=13). Sample data is reported in delta notation per atomic mass unit. Isotopic variations were measured between BC oyster tissues, with values between -0.096‰ and 0.104‰. Preliminary evidence suggests no significant difference in Cd isotopes between the digestive (0.046) and non-digestive (0.104) tissues of a BC oyster. Data will also be presented for the east coast oyster, lobster hepatopancreas (CRM TORT-2) and BC sediment.

  3. Impulse radar with swept range gate

    DOEpatents

    McEwan, T.E.

    1998-09-08

    A radar range finder and hidden object locator is based on ultra-wide band radar with a high resolution swept range gate. The device generates an equivalent time amplitude scan with a typical range of 4 inches to 20 feet, and an analog range resolution as limited by a jitter of on the order of 0.01 inches. A differential sampling receiver is employed to effectively eliminate ringing and other aberrations induced in the receiver by the near proximity of the transmit antenna, so a background subtraction is not needed, simplifying the circuitry while improving performance. Techniques are used to reduce clutter in the receive signal, such as decoupling the receive and transmit cavities by placing a space between them, using conductive or radiative damping elements on the cavities, and using terminating plates on the sides of the openings. The antennas can be arranged in a side-by-side parallel spaced apart configuration or in a coplanar opposed configuration which significantly reduces main bang coupling. 25 figs.

  4. Impulse radar with swept range gate

    DOEpatents

    McEwan, Thomas E.

    1998-09-08

    A radar range finder and hidden object locator is based on ultra-wide band radar with a high resolution swept range gate. The device generates an equivalent time amplitude scan with a typical range of 4 inches to 20 feet, and an analog range resolution as limited by a jitter of on the order of 0.01 inches. A differential sampling receiver is employed to effectively eliminate ringing and other aberrations induced in the receiver by the near proximity of the transmit antenna (10), so a background subtraction is not needed, simplifying the circuitry while improving performance. Techniques are used to reduce clutter in the receive signal, such as decoupling the receive (24) and transmit cavities (22) by placing a space between them, using conductive or radiative damping elements on the cavities, and using terminating plates on the sides of the openings. The antennas can be arranged in a side-by-side parallel spaced apart configuration or in a coplanar opposed configuration which significantly reduces main bang coupling.

  5. Swept frequency technique for dispersion measurement of microstrip lines

    NASA Technical Reports Server (NTRS)

    Lee, R. Q.

    1986-01-01

    Microstrip lines used in microwave integrated circuits are dispersive. Because a microstrip line is an open structure, the dispersion can not be derived with pure TEM, TE, or TM mode analysis. Dispersion analysis has commonly been done using a spectral domain approach, and dispersion measurement has been made with high Q microstrip ring resonators. Since the dispersion of a microstrip line is fully characterized by the frequency dependent phase velocity of the line, dispersion measurement of microstrip lines requires the measurement of the line wavelength as a function of frequency. In this paper, a swept frequency technique for dispersion measurement is described. The measurement was made using an automatic network analyzer with the microstrip line terminated in a short circuit. Experimental data for two microstrip lines on 10 and 30 mil Cuflon substrates were recorded over a frequency range of 2 to 20 GHz. Agreement with theoretical results computed by the spectral domain approach is good. Possible sources of error for the discrepancy are discussed.

  6. Arabian Red Sea coastal soils as potential mineral dust sources

    NASA Astrophysics Data System (ADS)

    Jish Prakash, P.; Stenchikov, Georgiy; Tao, Weichun; Yapici, Tahir; Warsama, Bashir; Engelbrecht, Johann P.

    2016-09-01

    Both Moderate Resolution Imaging Spectroradiometer (MODIS) and Spinning Enhanced Visible and InfraRed Imager (SEVIRI) satellite observations suggest that the narrow heterogeneous Red Sea coastal region is a frequent source of airborne dust that, because of its proximity, directly affects the Red Sea and coastal urban centers. The potential of soils to be suspended as airborne mineral dust depends largely on soil texture, moisture content and particle size distributions. Airborne dust inevitably carries the mineralogical and chemical signature of a parent soil. The existing soil databases are too coarse to resolve the small but important coastal region. The purpose of this study is to better characterize the mineralogical, chemical and physical properties of soils from the Arabian Red Sea coastal plain, which in turn will help to improve assessment of dust effects on the Red Sea, land environmental systems and urban centers. Thirteen surface soils from the hot-spot areas of windblown mineral dust along the Red Sea coastal plain were sampled for analysis. Analytical methods included optical microscopy, X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), ion chromatography (IC), scanning electron microscopy (SEM) and laser particle size analysis (LPSA). We found that the Red Sea coastal soils contain major components of quartz and feldspar, as well as lesser but variable amounts of amphibole, pyroxene, carbonate, clays and micas, with traces of gypsum, halite, chlorite, epidote and oxides. The range of minerals in the soil samples was ascribed to the variety of igneous and metamorphic provenance rocks of the Arabian Shield forming the escarpment to the east of the Red Sea coastal plain. The analysis revealed that the samples contain compounds of nitrogen, phosphorus and iron that are essential nutrients to marine life. The analytical results from this study will provide a valuable input into dust emission models used in climate

  7. Blade-to-Blade Variations in Shocks Upstream of Both a Forward-Swept and an Aft-Swept Fan

    NASA Technical Reports Server (NTRS)

    Podboy, Gary G.; Krupar, Martin J.

    2006-01-01

    Detailed laser Doppler velocimeter (LDV) flow field measurements were made upstream of 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 supersonic tip speeds. The blade-to-blade variations in the flows associated with these shocks are thought to be responsible for generating Multiple Pure Tone (MPT) noise. The measured blade-to-blade variations are documented in this report through a series of slideshows which show relative Mach number contours computed from the velocity measurements. Data are presented for the forward-swept fan operating at three speeds (corresponding to tip relative Mach numbers of 0.817, 1.074, and 1.189), and for the aft-swept fan operating at two (tip relative Mach numbers of 1.074 and 1.189). These LDV data illustrate how the perturbations in the upstream flow field created by the rotating blades vary with axial position, radial position and rotor speed. As expected, at the highest tested speed the forward-swept fan swallowed the shocks which occur in the tip region, whereas the aftswept fan did not. This resulted in a much smaller flow disturbance just upstream of the tip of the forward-swept fan. Nevertheless, further upstream the two fan flows were much more similar.

  8. Comparison of Potential ASKAP HI Survey Source Finders

    NASA Astrophysics Data System (ADS)

    Popping, A.; Jurek, R.; Westmeier, T.; Serra, P.; Flöer, L.; Meyer, M.; Koribalski, B.

    2012-02-01

    The large size of the ASKAP HI surveys DINGO and WALLABY necessitates automated 3D source finding. A performance difference of a few percent corresponds to a significant number of galaxies being detected or undetected. As such, the performance of the automated source finding is of paramount importance to both of these surveys. We have analysed the performance of various source finders to determine which will allow us to meet our survey goals during the DINGO and WALLABY design studies. Here we present a comparison of the performance of five different methods of automated source finding. These source finders are duchamp, gamma-finder, a CNHI finder, a 2d-1d wavelet reconstruction finder and a sigma clipping method (s+c finder). Each source finder was applied to the same three-dimensional data cubes containing (a) point sources with a Gaussian velocity profile and (b) spatially extended model-galaxies with inclinations and rotation profiles. We focus on the completeness and reliability of each algorithm when comparing the performance of the different source finders.

  9. Stimulus frequency otoacoustic emissions evoked by swept tones.

    PubMed

    Chen, Shixiong; Deng, Jun; Bian, Lin; Li, Guanglin

    2013-12-01

    Otoacoustic emissions (OAEs) are soft sounds generated by the cochlea and the measurements of OAEs are useful in detecting cochlear damages. Stimulus frequency otoacoustic emissions (SFOAEs) are evoked by one single tone and they are the most frequency specific in probing functional status of the cochlea than other types of OAEs. However, SFOAEs are currently restricted to research only because of the difficulty and low efficiency of their measurements. To solve these problems, an efficient method of using swept tones to measure SFOAEs was proposed in this study. The swept tones had time-varying frequencies and therefore could efficiently measure SFOAEs over a wide frequency range with a resolution dependent on the sweep rate. A three-interval paradigm and a tracking filter were used to separate the swept-tone SFOAEs from background noises. The reliability of the swept-tone SFOAEs was examined by a repeated-measure design, and the accuracy was evaluated by the comparison with a standard method using pure tones as the stimuli. The pilot results of this study showed that SFOAEs could be measured successfully using swept tones in human ears with normal hearing. The amplitude and phase of the swept-tone SFOAEs were highly reproducible in the repeated measures, and were nearly equivalent to SFOAEs evoked by pure tones under various signal conditions. These findings suggest that the proposed swept-tone SFOAEs could be a useful method in estimating the cochlear functions and developing an efficient approach of OAE measurements to help with accurate hearing diagnoses in the clinic.

  10. An Optical Survey of Potential Gamma-ray Sources

    NASA Astrophysics Data System (ADS)

    Carpenter, Lisa R.

    2006-12-01

    The EGRET instrument aboard the Compton Gamma-Ray Observatory detected 271 sources. Several objects were identified as "high-confidence" AGN, quasars, and low-confidence AGN. 170 sources remain unidentified (Hartman et al. 1999). Our project is to conduct an optical survey of unidentified sources, looking for evidence of blazar activity that may have been missed by the initial EGRET survey. The method of identifying sources used by the EGRET survey was to search for radio spectra peaking at 5 GHz. Such a spectrum is evidence of blazar-like activity. However, a study by Mattox et al. (1997); Mattox, Hartman & Reimer (2001) concluded that any gamma-ray source with a flux density less than 500 mJy at 5 GHz would be difficult to positively identify. The method described above neglects the possibility that blazar-like sources may be dim at such low frequencies and peak instead at higher frequencies (at least 200 Ghz). It has been hypothesized that sources that behave in this way could very well be counterparts to gamma-ray blazars (Tornikoski et al. 2002; Bloom et al. 1997, 2000). Our goal is to determine the magnitudes of objects in the optical wavelengths and check for evidence of blazar-like activity.

  11. A rapid, dispersion-based wavelength-stepped and wavelength-swept laser for optical coherence tomography

    PubMed Central

    Tozburun, Serhat; Siddiqui, Meena; Vakoc, Benjamin J.

    2014-01-01

    Abstract: Optical-domain subsampling enables Fourier-domain OCT imaging at high-speeds and extended depth ranges while limiting the required acquisition bandwidth. To perform optical-domain subsampling, a wavelength-stepped rather than a wavelength-swept source is required. This preliminary study introduces a novel design for a rapid wavelength-stepped laser source that uses dispersive fibers in combination with a fast lithium-niobate modulator to achieve wavelength selection. A laser with 200 GHz wavelength-stepping and a sweep rate of 9 MHz over a 94 nm range at a center wavelength of 1550 nm is demonstrated. A reconfiguration of this source design to a continuous wavelength-swept light for conventional Fourier-domain OCT is also demonstrated. PMID:24663631

  12. High-speed OCT light sources and systems [Invited

    PubMed Central

    Klein, Thomas; Huber, Robert

    2017-01-01

    Imaging speed is one of the most important parameters that define the performance of optical coherence tomography (OCT) systems. During the last two decades, OCT speed has increased by over three orders of magnitude. New developments in wavelength-swept lasers have repeatedly been crucial for this development. In this review, we discuss the historical evolution and current state of the art of high-speed OCT systems, with focus on wavelength swept light sources and swept source OCT systems. PMID:28270988

  13. Aerodynamic Classification of Swept-Wing Ice Accretion

    NASA Technical Reports Server (NTRS)

    Broeren, Andy; Diebold, Jeff; Bragg, Mike

    2013-01-01

    The continued design, certification and safe operation of swept-wing airplanes in icing conditions rely on the advancement of computational and experimental simulation methods for higher fidelity results over an increasing range of aircraft configurations and performance, and icing conditions. The current state-of-the-art in icing aerodynamics is mainly built upon a comprehensive understanding of two-dimensional geometries that does not currently exist for fundamentally three-dimensional geometries such as swept wings. The purpose of this report is to describe what is known of iced-swept-wing aerodynamics and to identify the type of research that is required to improve the current understanding. Following the method used in a previous review of iced-airfoil aerodynamics, this report proposes a classification of swept-wing ice accretion into four groups based upon unique flowfield attributes. These four groups are: ice roughness, horn ice, streamwise ice, and spanwise-ridge ice. For all of the proposed ice-shape classifications, relatively little is known about the three-dimensional flowfield and even less about the effect of Reynolds number and Mach number on these flowfields. The classifications and supporting data presented in this report can serve as a starting point as new research explores swept-wing aerodynamics with ice shapes. As further results are available, it is expected that these classifications will need to be updated and revised.

  14. Americium As A Potential Power Source For Space Missions

    NASA Astrophysics Data System (ADS)

    Cordingley, Leon; Rice, Tom; Sarsfield, Mark J.; Stephenson, Keith; Tinsley, Tim

    2011-10-01

    Electrical power sources used in outer planet missions are a key enabling technology for data acquisition and communications. Power sources generate electricity from the thermal energy from alpha decay of the radioisotope 238Pu via thermoelectric conversion. Production of 238Pu requires specialist facilities including a nuclear reactor and reprocessing plants that are expensive to build and operate, so naturally, a more economical alternative is attractive to the industry. Within Europe 241Am is a feasible alternative to 238Pu that can provide a heat source for radioisotope thermoelectric generators (RTGs) and radioisotope heating units (RHUs). Whilst there are implications associated with the differences between 238Pu and 241Am, these technological challenges are surmountable.

  15. Development of a spectrally resolved fluorescence tomography system using a NIR swept laser and a digital micromirror array based detection system

    NASA Astrophysics Data System (ADS)

    Cho, Jaedu; Jeon, Seung Woan; Zheng, Jie; Kim, Chang-Seok; Nalcioglu, Orhan; Gulsen, Gultekin

    2014-03-01

    We developed a spectrally-resolved fluorescence tomography (FT) system using a new source and detection unit. On the source side, we utilized a near-infrared (NIR) swept laser-based technology and on the detection side, we developed a digital micromirror device (DMD) based spectrally-resolved detection unit. We demonstrated the development of a NIR swept laser centered at 800 nm for FT, which covers the maximum absorption wavelength of a NIR fluorescence dye, indo-cyanine green (ICG) in plasma. Two different ICG samples whose absorption characteristics were slightly different were used to demonstrate the performance of the NIR swept laser-based FT system, and this FT system was able to show the difference of absorption between the ICG samples. In addition, we also developed a prototype spectrally-resolved detection unit based on the DMD. This detection system provided a spectral resolution of 15 nm and the possibility of simultaneous detection of multiple fluorescence spectra.

  16. Snow Harvesting: A Potential Water Source for Afghanistan

    DTIC Science & Technology

    2009-08-01

    storage capabilities, with many regions suffering recurring drought. A widespread drought occurred from 1997 to 2002, causing a significant decrease ...supply using snow fences depends not only upon the ability to capture the snow but also the effect that introducing a new water source has upon the...

  17. Antideuterons in cosmic rays: sources and discovery potential

    NASA Astrophysics Data System (ADS)

    Herms, Johannes; Ibarra, Alejandro; Vittino, Andrea; Wild, Sebastian

    2017-02-01

    Antibaryons are produced in our Galaxy in collisions of high energy cosmic rays with the interstellar medium and in old supernova remnants, and possibly, in exotic sources such as primordial black hole evaporation or dark matter annihilations and decays. The search for signals from exotic sources in antiproton data is hampered by large backgrounds from spallation which, within theoretical errors, can solely account for the current data. Due to the higher energy threshold for antideuteron production, which translates into a suppression of the low energy flux from spallations, antideuteron searches have been proposed as a probe for exotic sources. We perform in this paper a comprehensive analysis of the antideuteron fluxes at the Earth expected from known and hypothetical sources in our Galaxy, and we calculate their maximal values consistent with current antiproton data from AMS-02. We find that supernova remnants generate a negligible flux, whereas primordial black hole evaporation and dark matter annihilations or decays may dominate the total flux at low energies. On the other hand, we find that the {detection of cosmic antideuterons} would require, for the scenarios studied in this paper and assuming optimistic values of the coalescence momentum and solar modulation, an increase of the experimental sensitivity compared to ongoing and planned instruments by at least a factor of 2. Finally, we briefly comment on the prospects for antihelium-3 detection.

  18. The longitudinal stability of elastic swept wings at supersonic speed

    NASA Technical Reports Server (NTRS)

    Frick, C W; Chubb, R S

    1950-01-01

    The longitudinal stability characteristics of elastic swept wings of high aspect ratio experiencing bending and torsional deformations are calculated for supersonic speed by the application of linearized lifting-surface theory. A parabolic wing deflection curve is assumed and the analysis is simplified by a number of structural approximations. The method is thereby limited in application to wings of high aspect ratio for which the root effects are small. Expressions for the lift, pitching-moment, and span load distribution characteristics are derived in terms of the elastic properties of the wing; namely, the design stress, the modulus of elasticity, the shearing modulus, and the maximum design load factor. The analysis applies to wings with leading edges swept behind the Mach lines. In all cases, however, the trailing edge is sonic or supersonic. Application of the method of analysis to wings with leading edges swept ahead of the Mach lines is discussed.

  19. Fast swept-volume distance for robust collision detection

    SciTech Connect

    Xavier, P.G.

    1997-04-01

    The need for collision detection arises in several robotics areas, including motion-planning, online collision avoidance, and simulation. At the heart of most current methods are algorithms for interference detection and/or distance computation. A few recent algorithms and implementations are very fast, but to use them for accurate collision detection, very small step sizes can be necessary, reducing their effective efficiency. We present a fast, implemented technique for doing exact distance computation and interference detection for translationally-swept bodies. For rotationally swept bodies, we adapt this technique to improve accuracy, for any given step size, in distance computation and interference detection. We present preliminary experiments that show that the combination of basic and swept-body calculations holds much promise for faster accurate collision detection.

  20. Electrical potential source mechanisms in microbial induced sulfate reducing environments

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Slater, L.; Ntarlagiannis, D.; Singh, K.; Doherty, R.

    2007-12-01

    In order to compare self-potential (SP) signals resulting from possible 'geobattery' effects with electrodic potential signals based on a known galvanic cell (GC) effect in the presence of sulfide, we designed a column experiment using dual sensor Ag-AgCl electrodes. Water from the Langan River (Belfast, UK), known to contain a sulfate reducing microbial community, was obtained. Two experimental columns were packed with fine-grained glass beads. One column continuously circulated (closed loop) with autoclaved river water as a control, while the other retained biologically active natural river water. Six Ag-AgCl electrodes equally spaced along one side of each column, and three Ag-AgCl self potential electrodes (where the metal is in electrolytic contact with the column via a sterilized 1M KCl agar gel), were placed on the other side of each column. Electrical potential signals were continuously recorded with both sensor types. Induced polarization, electrical resistivity, temperature and aqueous geochemistry measurements (pH, Eh, and conductivity) were taken once daily. Over the 20 day experiment duration, darkening of the circulating fluid, biofilm formation and a sulfurous smell were observed in the biologically active column whereas no such color change (or smell) was observed for the control column. In the active column electrodic potential readings approached 570 mV whereas stable and small electrodic potential values (~8 mV) were detected in the control column.. Self potential signals were consistently only 1-8 mV in both columns. The experiment shows although electrodic potentials (at the electrode) are diagnostic of microbial driven sulfate reduction there is no measurable self potential (geobattery) effect associated with this microbial process.

  1. Swept-Wing Ice Accretion Characterization and Aerodynamics

    NASA Technical Reports Server (NTRS)

    Broeren, Andy P.; Potapczuk, Mark G.; Riley, James T.; Villedieu, Philippe; Moens, Frederic; Bragg, Michael B.

    2013-01-01

    NASA, FAA, ONERA, the University of Illinois and Boeing have embarked on a significant, collaborative research effort to address the technical challenges associated with icing on large-scale, three-dimensional swept wings. The overall goal is to improve the fidelity of experimental and computational simulation methods for swept-wing ice accretion formation and resulting aerodynamic effect. A seven-phase research effort has been designed that incorporates ice-accretion and aerodynamic experiments and computational simulations. As the baseline, full-scale, swept-wing-reference geometry, this research will utilize the 65 percent scale Common Research Model configuration. Ice-accretion testing will be conducted in the NASA Icing Research Tunnel for three hybrid swept-wing models representing the 20, 64 and 83 percent semispan stations of the baseline-reference wing. Threedimensional measurement techniques are being developed and validated to document the experimental ice-accretion geometries. Artificial ice shapes of varying geometric fidelity will be developed for aerodynamic testing over a large Reynolds number range in the ONERA F1 pressurized wind tunnel and in a smaller-scale atmospheric wind tunnel. Concurrent research will be conducted to explore and further develop the use of computational simulation tools for ice accretion and aerodynamics on swept wings. The combined results of this research effort will result in an improved understanding of the ice formation and aerodynamic effects on swept wings. The purpose of this paper is to describe this research effort in more detail and report on the current results and status to date.

  2. Swept-Wing Ice Accretion Characterization and Aerodynamics

    NASA Technical Reports Server (NTRS)

    Broeren, Andy P.; Potapczuk, Mark G.; Riley, James T.; Villedieu, Philippe; Moens, Frederic; Bragg, Michael B.

    2013-01-01

    NASA, FAA, ONERA, the University of Illinois and Boeing have embarked on a significant, collaborative research effort to address the technical challenges associated with icing on large-scale, three-dimensional swept wings. The overall goal is to improve the fidelity of experimental and computational simulation methods for swept-wing ice accretion formation and resulting aerodynamic effect. A seven-phase research effort has been designed that incorporates ice-accretion and aerodynamic experiments and computational simulations. As the baseline, full-scale, swept-wing-reference geometry, this research will utilize the 65% scale Common Research Model configuration. Ice-accretion testing will be conducted in the NASA Icing Research Tunnel for three hybrid swept-wing models representing the 20%, 64% and 83% semispan stations of the baseline-reference wing. Three-dimensional measurement techniques are being developed and validated to document the experimental ice-accretion geometries. Artificial ice shapes of varying geometric fidelity will be developed for aerodynamic testing over a large Reynolds number range in the ONERA F1 pressurized wind tunnel and in a smaller-scale atmospheric wind tunnel. Concurrent research will be conducted to explore and further develop the use of computational simulation tools for ice accretion and aerodynamics on swept wings. The combined results of this research effort will result in an improved understanding of the ice formation and aerodynamic effects on swept wings. The purpose of this paper is to describe this research effort in more detail and report on the current results and status to date. 1

  3. Sharks: a potential source of antiangiogenic factors and tumor treatments.

    PubMed

    Cho, Jung; Kim, Young

    2002-12-01

    Since angiogenesis is a key feature of tumor growth, inhibiting this process is one way to treat cancer. Cartilage is a natural source of material with strong antiangiogenic activity. This report reviews knowledge of the anticancer properties of shark cartilage and clinical information on drugs such as neovastat and squalamine. Because their entire endoskeleton is composed of cartilage, sharks are thought to be an ideal source of angiogenic and tumor growth inhibitors. Shark cartilage extract has shown antiangiogenic and antitumor activities in animals and humans. The oral administration of cartilage extract was efficacious in reducing angiogenesis. Purified antiangiogenic factors from shark cartilage, such as U-995 and neovastat (AE-941), also showed antiangiogenic and antitumor activity. AE-941 is under phase III clinical investigation. Squalamine, a low molecular weight aminosterol, showed strong antitumor activity when combined with chemotherapeutic materials. The angiogenic tissue inhibitor of metalloprotease 3 (TIMP-3) and tumor suppressor protein (snm23) genes from shark cartilage were cloned and characterized.

  4. Car indoor air pollution - analysis of potential sources

    PubMed Central

    2011-01-01

    The population of industrialized countries such as the United States or of countries from the European Union spends approximately more than one hour each day in vehicles. In this respect, numerous studies have so far addressed outdoor air pollution that arises from traffic. By contrast, only little is known about indoor air quality in vehicles and influences by non-vehicle sources. Therefore the present article aims to summarize recent studies that address i.e. particulate matter exposure. It can be stated that although there is a large amount of data present for outdoor air pollution, research in the area of indoor air quality in vehicles is still limited. Especially, knowledge on non-vehicular sources is missing. In this respect, an understanding of the effects and interactions of i.e. tobacco smoke under realistic automobile conditions should be achieved in future. PMID:22177291

  5. Car indoor air pollution - analysis of potential sources.

    PubMed

    Müller, Daniel; Klingelhöfer, Doris; Uibel, Stefanie; Groneberg, David A

    2011-12-16

    The population of industrialized countries such as the United States or of countries from the European Union spends approximately more than one hour each day in vehicles. In this respect, numerous studies have so far addressed outdoor air pollution that arises from traffic. By contrast, only little is known about indoor air quality in vehicles and influences by non-vehicle sources.Therefore the present article aims to summarize recent studies that address i.e. particulate matter exposure. It can be stated that although there is a large amount of data present for outdoor air pollution, research in the area of indoor air quality in vehicles is still limited. Especially, knowledge on non-vehicular sources is missing. In this respect, an understanding of the effects and interactions of i.e. tobacco smoke under realistic automobile conditions should be achieved in future.

  6. The genus Rhodosporidium: a potential source of beta-carotene.

    PubMed

    de Miguel, T; Calo, P; Díaz, A; Villa, T G

    1997-03-01

    Four wild-type species of the genus Rhodosporidium have been studied as as possible sources for the industrial production of beta-carotene. HPLC-based studies showed that their carotenoid composition consisted of almost pure beta-carotene at concentrations ranging from 226 to 685 micrograms/g of dried yeast biomass. These results are consistent with those obtained by spectrophotometry at 480 nm.

  7. Source rock potential of shallow-water evaporitic settings

    SciTech Connect

    Warren, J.K.

    1986-05-01

    In the major evaporitic environments on the world's surface today, most organic matter accumulates in shallow subaqueous to seasonally subaerially exposed, algal-mat sediments. Given the present depositional setting, this organic matter probably could not be preserved to form source rocks. However, if the authors place such evaporite deposition into a geologic context, source rocks could have formed in shallow-water settings in the past. Such settings were characterized by hydrologic conditions that allowed the retention of hypersaline, anoxic pore water to depths where the organic material was buried deep enough to generate hydrocarbons. When deep-basin, shallow-water, evaporite successions were laid down in basins such as the Mediterranean during the late Miocene, the Michigan basin during the Silurian, and in other large saline giants, conditions were right for source rocks to form within shallow-water and salt-flat evaporitic environments. The evaporites in these saline giants were deposited under conditions of relatively shallow water (< 50 m); the basin never appears to have dried out, but water levels changed quickly (approx. 10,000 years) from shallow to deep. Continual water saturation coupled with saline pore fluids prevented the inflow of fresh, oxidizing ground water into the basin center of shallow-water organic-rich evaporites. Immature hydrocarbons derived from such rocks today drip from the 5.5-m.y. old evaporites of Sicily in active salt and sulfur mines. Organic-rich sediments could also be preserved to generate hydrocarbons in rapidly subsiding rift basins. In such basins, rapid burial has prevented the entrance of fresher oxygenated waters and the associated degradation and destruction of the organic matter. The early continental rift stage generates the source rocks; the ephemeral streams, wadis, and dune fields become the reservoirs, and the subsequent evaporite stage seals the reservoir.

  8. Potential application of microalga Spirulina platensis as a protein source.

    PubMed

    Lupatini, Anne Luize; Colla, Luciane Maria; Canan, Cristiane; Colla, Eliane

    2017-02-01

    The high protein level of various microalgal species is one of the main reasons to consider them an unconventional source of this compound. Spirulina platensis stands out for being one of the richest protein sources of microbial origin (460-630 g kg(-1) , dry matter basis), having similar protein levels when compared to meat and soybeans. The use of S. platensis in food can bring benefits to human health owing to its chemical composition, since it has high levels of vitamins, minerals, phenolics, essential fatty acids, amino acids and pigments. Furthermore, the development of new protein sources to supply the shortage of this nutrient is an urgent need, and protein from S. platensis plays an important role in this scenario. In this sense, extraction processes that allow maximum protein yield and total utilization of biomass is an urgent need, and ultrasonic waves have proven to be an effective extraction technique. The number of scientific papers related to protein fraction from S. platensis is still limited; thus further studies on its functional and technological properties are needed. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  9. Current Experimental Basis for Modeling Ice Accretions on Swept Wings

    NASA Technical Reports Server (NTRS)

    Vargas, Mario

    2005-01-01

    This work presents a review of the experimental basis for modeling ice accretions on swept wings. Experimental work related to ice accretion physics on swept wings conducted between 1954 and 2004 is reviewed. Proposed models or explanations of scallop formations are singled out and discussed. Special emphasis is placed on reviewing the work done to determine the basic macroscopic mechanisms of scallop formation. The role of feather growth and its connection to scallop growth is discussed. Conceptual steps in modeling scallop formations are presented. Research elements needed for modeling are discussed.

  10. Marine bacteria: potential sources for compounds to overcome antibiotic resistance.

    PubMed

    Eom, Sung-Hwan; Kim, Young-Mog; Kim, Se-Kwon

    2013-06-01

    Methicillin-resistant Staphylococcus aureus (MRSA) is the most problematic Gram-positive bacterium in the context of public health due to its resistance against almost all available antibiotics except vancomycin and teicoplanin. Moreover, glycopeptide-resistant S. aureus have been emerging with the increasing use of glycopeptides. Recently, resistant strains against linezolid and daptomycin, which are alternative drugs to treat MRSA infection, have also been reported. Thus, the development of new drugs or alternative therapies is clearly a matter of urgency. In response to the antibiotic resistance, many researchers have studied for alternative antibiotics and therapies. In this review, anti-MRSA substances isolated from marine bacteria, with their potential antibacterial effect against MRSA as potential anti-MRSA agents, are discussed and several strategies for overcoming the antibiotic resistance are also introduced. Our objective was to highlight marine bacteria that have potential to lead in developing novel antibiotics or clinically useful alternative therapeutic treatments.

  11. Active and retired public employees' health insurance: potential data sources.

    PubMed

    Morrill, Melinda Sandler

    2014-12-01

    Employer-provided health insurance for public sector workers is a significant public policy issue. Underfunding and the growing costs of benefits may hinder the fiscal solvency of state and local governments. Findings from the private sector may not be applicable because many public sector workers are covered by union contracts or salary schedules and often benefit modifications require changes in legislation. Research has been limited by the difficulty in obtaining sufficiently large and representative data on public sector employees. This article highlights data sources researchers might utilize to investigate topics concerning health insurance for active and retired public sector employees.

  12. Potential to Emit (PTE) Guidance for Specific Source Categories

    EPA Pesticide Factsheets

    This document may be of assistance in applying the New Source Review (NSR) air permitting regulations including the Prevention of Significant Deterioration (PSD) requirements. This document is part of the NSR Policy and Guidance Database. Some documents in the database are a scanned or retyped version of a paper photocopy of the original. Although we have taken considerable effort to quality assure the documents, some may contain typographical errors. Contact the office that issued the document if you need a copy of the original.

  13. Guidance on Limiting Potential to Emit in New Source Permitting

    EPA Pesticide Factsheets

    This document may be of assistance in applying the New Source Review (NSR) air permitting regulations including the Prevention of Significant Deterioration (PSD) requirements. This document is part of the NSR Policy and Guidance Database. Some documents in the database are a scanned or retyped version of a paper photocopy of the original. Although we have taken considerable effort to quality assure the documents, some may contain typographical errors. Contact the office that issued the document if you need a copy of the original.

  14. IDENTIFYING POTENTIAL SOURCES OF BACKGROUND CONTAMINATION IN RT-PCR

    EPA Science Inventory

    Extraction of nucleic acids from low biomass samples, such as drinking water, is particularly sensitive to potential background contamination because the contaminating material is minimally diluted by the sample. The presence of bacterial DNA in Taq DNA polymerase is wel...

  15. Potential of diesel engine, 1979 summary source document. Final report

    SciTech Connect

    Trella, T.

    1980-03-01

    This document assesses the fuel economy potential of diesel engines in future passenger cars and light trucks. The primary technologies evaluated include: (1) engine control strategy and implementation, (2) the engine design variables, (3) emissions and noise, (4) fuels, (5) lubricants, (6) vehicle-engine matching, and (7) the effects of vehicle characteristics. The major findings are summarized.

  16. IDENTIFYING POTENTIAL SOURCES OF BACKGROUND CONTAMINATION IN RT-PCR

    EPA Science Inventory

    Extraction of nucleic acids from low biomass samples, such as drinking water, is particularly sensitive to potential background contamination because the contaminating material is minimally diluted by the sample. The presence of bacterial DNA in Taq DNA polymerase is wel...

  17. Gravitational potential as a source of earthquake energy

    USGS Publications Warehouse

    Barrows, L.; Langer, C.J.

    1981-01-01

    Some degree of tectonic stress within the earth originates from gravity acting upon density structures. The work performed by this "gravitational tectonics stress" must have formerly existed as gravitational potential energy contained in the stress-causing density structure. According to the elastic rebound theory (Reid, 1910), the energy of earthquakes comes from an elastic strain field built up by fairly continuous elastic deformation in the period between events. For earthquakes resulting from gravitational tectonic stress, the elastic rebound theory requires the transfer of energy from the gravitational potential of the density structures into an elastic strain field prior to the event. An alternate theory involves partial gravitational collapse of the stress-causing density structures. The earthquake energy comes directly from a net decrease in gravitational potential energy. The gravitational potential energy released at the time of the earthquake is split between the energy released by the earthquake, including work done in the fault zone and an increase in stored elastic strain energy. The stress associated with this elastic strain field should oppose further fault slip. ?? 1981.

  18. Coal is a potential source of naphthenic acids in groundwater.

    PubMed

    Scott, Angela C; Whittal, Randy M; Fedorak, Phillip M

    2009-03-15

    Naphthenic acids, with the general formula C(n)H(2n+Z)O(2), are found in conventional petroleums and oil sands ores. These acids are toxic to aquatic life, so their discharge from petroleum processing into receiving waters must be avoided. In a previous study, naphthenic acids were putatively identified in groundwaters from two domestic wells that were distant from petroleum sources. However, coal deposits were near these wells. In this study, waters from the two wells were extracted and analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry to unequivocally confirm the presence of naphthenic acids and other organic acids. In addition, distilled water was percolated through three crushed coal samples and the leachates were shown to contain a variety of organic acids, including naphthenic acids. These results clearly demonstrate that coal is a source of naphthenic acids and that the naphthenic acids can leach into groundwaters. Thus, the presence of naphthenic acids in waters cannot be solely attributed to petroleum or petroleum industry activities.

  19. Factors limiting potential of evaporites as hydrocarbon source rocks

    SciTech Connect

    Katz, B.J.; Bissada, K.K.; Wood, J.W.

    1987-05-01

    It is well established that evaporite-bearing sequences account for a substantial proportion of petroleum occurrences. Examples can be cited from the Mesozoic of the Middle East, the Cretaceous of Latin America, and many others. An examination of effective source rocks within these provinces reveals that carbonate facies generate the bulk of the hydrocarbons. The higher evaporites (gypsum, anhydrate, halite, etc) seldom contribute to the resource base. Geochemical analyses of the higher evaporites reveal low organic carbon contents and imperceptible pyrolysis yields. These observations are not consistent with many of the current concepts of organic matter accumulation in evaporite environments, which suggests that hypersalinity should be especially favorable because abundant nutrient supply enhances primary productivity and elevated salt content enhances preservation efficiency. Their recent studies on oxidation of labile phytoplankton remains and relative sedimentation rates of organic and inorganic constituents in hypersaline brines suggest that three factors contribute to the observed low concentrations of hydrogen-enriched organic matter in the higher evaporites: (1) the density contrast between hypersaline brines and suspended organic matter retards the settling rate of the organic matter and prolongs its exposure to oxidative processes; (2) high concentrations of sulfates, and possibly nitrates, provide a secondary oxidizer for labile phytoplankton remains; and (3) high precipitation rates of the evaporite minerals dilute any organic matter which reaches the sediment-water interface. This paper will examine these factors in the modern and ancient record and discuss their influence on source-bed distribution through time and space.

  20. Pancreatic lipase inhibitors from natural sources: unexplored potential.

    PubMed

    Birari, Rahul B; Bhutani, Kamlesh K

    2007-10-01

    The prevalence of obesity is increasing at an alarming rate, but, unfortunately, only a few medications are currently on the market. Obesity is primarily regarded as a disorder of lipid metabolism and the enzymes involved in this process could be selectively targeted to develop antiobesity drugs. Recently, newer approaches for the treatment of obesity have involved inhibition of dietary triglyceride absorption via inhibition of pancreatic lipase (PL) as this is the major source of excess calories. Natural products provide a vast pool of PL inhibitors that can possibly be developed into clinical products. This article reviews various extracts and secondary metabolites from plants and microbial origin with PL inhibitory activity that can be focused for drug development programs.

  1. Flutter analysis of highly swept delta wings by conventional methods

    NASA Technical Reports Server (NTRS)

    Gibbons, M. D.; Soistmann, D. L.; Bennett, R. M.

    1988-01-01

    The flutter boundaries of six thin highly-swept delta-platform wings have been calculated. Comparisons are made between experimental data and results using several aerodynamic methods. The aerodynamic methods used include a subsonic and supersonic kernel function, second order piston theory, and a transonic small disturbance code. The dynamic equations of motion are solved using analytically calculated mode shapes and frequencies.

  2. Receptivity and Transition of Supersonic Boundary Layers Over Swept Wings

    NASA Technical Reports Server (NTRS)

    Balakumar, Ponnampalam; King, Rudolph A.

    2010-01-01

    The receptivity, stability, and transition of three-dimensional supersonic boundary layers over (1) a swept cylinder, (2) a swept wing with a sharp leading edge, and (3) a swept wing with a blunt leading edge are numerically investigated for a free-stream Mach number of 3. These computations are compared to an earlier experimental and computational study performed by Archambaud et al.1 The steady flow fields with and without roughness elements are obtained by solving the full Navier-Stokes equations. The N-factors computed in this study at the transition onset locations reported in Ref. 1 for flow over the swept cylinder are approximately 16.5 for traveling crossflow disturbances and 9 for stationary disturbances. The N-factors for the traveling crossflow are high based on our past experiences. However, they are comparatively smaller than those reported by Archambaud et al., who found N-factor values in the range of 20 to 25 for traveling disturbances and 13 to 20 for stationary disturbances. Similarly, the N-factors computed in this study for the traveling and stationary disturbances for the flow over the sharp wing are approximately 7 and 2.5, respectively, and for the flow over the blunt wing are 6.5 and 4.8, respectively. Using the envelope method, Archambaud et al. obtained values of approximately 8.0 and 4.0 for the sharp wing case and 16.0 and 12.0 for the blunt wing case.

  3. Plant Oils as Potential Sources of Vitamin D

    PubMed Central

    Baur, Anja C.; Brandsch, Corinna; König, Bettina; Hirche, Frank; Stangl, Gabriele I.

    2016-01-01

    To combat vitamin D insufficiency in a population, reliable diet sources of vitamin D are required. The recommendations to consume more oily fish and the use of UVB-treated yeast are already applied strategies to address vitamin D insufficiency. This study aimed to elucidate the suitability of plant oils as an alternative vitamin D source. Therefore, plant oils that are commonly used in human nutrition were first analyzed for their content of vitamin D precursors and metabolites. Second, selected oils were exposed to a short-term UVB irradiation to stimulate the synthesis of vitamin D. Finally, to elucidate the efficacy of plant-derived vitamin D to improve the vitamin D status, we fed UVB-exposed wheat germ oil (WGO) for 4 weeks to mice and compared them with mice that received non-exposed or vitamin D3 supplemented WGO. Sterol analysis revealed that the selected plant oils contained high amounts of not only ergosterol but also 7-dehydrocholesterol (7-DHC), with the highest concentrations found in WGO. Exposure to UVB irradiation resulted in a partial conversion of ergosterol and 7-DHC to vitamin D2 and D3 in these oils. Mice fed the UVB-exposed WGO were able to improve their vitamin D status as shown by the rise in the plasma concentration of 25-hydroxyvitamin D [25(OH)D] and the liver content of vitamin D compared with mice fed the non-exposed oil. However, the plasma concentration of 25(OH)D of mice fed the UVB-treated oil did not reach the values observed in the group fed the D3 supplemented oil. It was striking that the intake of the UVB-exposed oil resulted in distinct accumulation of vitamin D2 in the livers of these mice. In conclusion, plant oils, in particular WGO, contain considerable amounts of vitamin D precursors which can be converted to vitamin D via UVB exposure. However, the UVB-exposed WGO was less effective to improve the 25(OH)D plasma concentration than a supplementation with vitamin D3. PMID:27570765

  4. Theoretical and Experimental Investigation of the Subsonic-Flow Fields Beneath Swept and Unswept Wings with Tables or Vortex-induced Velocities

    NASA Technical Reports Server (NTRS)

    Alford, William J , Jr

    1957-01-01

    The flow-field characteristics beneath swept and unswept wings as determined by potential-flow theory are compared with the experimentally determined flow fields beneath swept and unswept wing-fuselage combinations. The potential-flow theory utilized considered both spanwise and chordwise distributions of vorticity as well as the wing-thickness effects. The perturbation velocities induced by a unit horseshoe vortex are included in tabular form. The theoretical predictions of the flow-field characteristics were qualitatively correct in all cases considered, although there were indications that the magnitudes of the downwash angles tended to be overpredicted as the tip of the swept wing was approached and that the sidewash angles ahead of the unswept wing were underpredicted. The calculated effects of compressibility indicated that significant increases in the chordwise variation of flow angles and dynamic-pressure ratios should be expected in going from low to high subsonic speeds.

  5. Lysobacter species: a potential source of novel antibiotics.

    PubMed

    Panthee, Suresh; Hamamoto, Hiroshi; Paudel, Atmika; Sekimizu, Kazuhisa

    2016-11-01

    Infectious diseases threaten global health due to the ability of microbes to acquire resistance against clinically used antibiotics. Continuous discovery of antibiotics with a novel mode of action is thus required. Actinomycetes and fungi are currently the major sources of antibiotics, but the decreasing rate of discovery of novel antibiotics suggests that the focus should be changed to previously untapped groups of microbes. Lysobacter species have a genome size of ~6 Mb with a relatively high G + C content of 61-70 % and are characterized by their ability to produce peptides that damage the cell walls or membranes of other microbes. Genome sequence analysis revealed that each Lysobacter species has gene clusters for the production of 12-16 secondary metabolites, most of which are peptides, thus making them 'peptide production specialists'. Given that the number of antibiotics isolated is much lower than the number of gene clusters harbored, further intensive studies of Lysobacter are likely to unearth novel antibiotics with profound biomedical applications. In this review, we summarize the structural diversity, activity and biosynthesis of lysobacterial antibiotics and highlight the importance of Lysobacter species for antibiotic production.

  6. Pueraria mirifica leaves, an alternative potential isoflavonoid source.

    PubMed

    Jungsukcharoen, Jutarmas; Dhiani, Binar Asrining; Cherdshewasart, Wichai; Vinayavekhin, Nawaporn; Sangvanich, Polkit; Boonchird, Chuenchit

    2014-01-01

    We investigated the major leaf isoflavonoid contents of Pueraria mirifica from three different cultivars (PM-III, PM-IV, and PM-V) using reverse RP-HPLC analysis. The proportions and net levels of puerarin, daidzin, genistin, and daidzein in P. mirifica leaves were found to depend on the plant cultivar and to correlate with cultivation temperature and rainfall amount. The crude leaf-extracts were tested using the Yeast Estrogen Screen (YES) assay with both human estrogen receptors (hERα and hERβ). Their estrogenic activity was higher when determined by the YES system containing hERβ than that with hERα and was also higher when the Δsnq2 than the wildtype yeast was employed. The results open the possibility of selecting and cultivating certain P. mirifica cultivars at a farm scale to produce a sufficient supply of leaf material to act as a starting source for the commercial scale extraction of these major isoflavonoids.

  7. Optical frequency-domain reflectometry using multiple wavelength-swept elements of a DFB laser array

    NASA Astrophysics Data System (ADS)

    DiLazaro, Tom; Nehmetallah, Georges

    2017-02-01

    Coherent optical frequency-domain reflectometry (C-OFDR) is a distance measurement technique with significant sensitivity and detector bandwidth advantages over normal time-of-flight methods. Although several swept-wavelength laser sources exist, many exhibit short coherence lengths, or require precision mechanical tuning components. Semiconductor distributed feedback lasers (DFBs) are advantageous as a mid-to-long range OFDR source because they exhibit a narrow linewidth and can be rapidly tuned simply via injection current. However, the sweep range of an individual DFB is thermally limited. Here, we present a novel high-resolution OFDR system that uses a compact, monolithic 12-element DFB array to create a continuous, gap-free sweep over a wide wavelength range. Wavelength registration is provided by the incorporation of a HCN gas cell and reference interferometer. The wavelength-swept spectra of the 12 DFBs are combined in post-processing to achieve a continuous total wavelength sweep of more than 40 nm (5.4 THz) in the telecommunications C-Band range.

  8. Alpinia calcarata Roscoe: A potential phytopharmacological source of natural medicine

    PubMed Central

    Rahman, Md Atiar; Islam, Md Shahidul

    2015-01-01

    Alpinia calcarata Roscoe (Family: Zingiberaceae), is a rhizomatous perennial herb, which is commonly used in the traditional medicinal systems in Sri Lanka. Alpinia calcarata is cultivated in tropical countries, including Sri Lanka, India, and Malaysia. Experimentally, rhizomes of Alpinia calcarata are shown to possess antibacterial, antifungal, anthelmintic, antinociceptive, anti-inflammatory, antioxidant, aphrodisiac, gastroprotective, and antidiabetic activities. Phytochemical screening revealed the presence of polyphenols, tannins, flavonoids, steroid glycosides and alkaloids in the extract and essential oil of this plant. Essential oil and extracts from this plant have been found to possess wide range of pharmacological and biological activities. This article provides a comprehensive review of its ethnomedical uses, chemical constituents and the pharmacological profile as a medicinal plant. Particular attention has been given to the pharmacological effects of the essential oil of Alpinia calcarata in this review so that the potential use of this plant either in pharmaceutics or as an agricultural resource can be evaluated. PMID:26009694

  9. Durian Husk as Potential Source for Particleboard Industry

    SciTech Connect

    Zddin, Z.; Risby, M. S.

    2010-03-11

    The main purpose of this study is to develop low cost particleboards using durian skin as its reinforcing materials. Mechanical characterizations such as tensile, compressive and flexural strength were investigated. The fibers were extracted through the traditional retting and also mechanized process to compare the fibers production output. Surface topology study using Scanning Electron Microscope was done to examine the surface texture of the produced fibers, as shown in Figure 1. The experimental investigation reveals that the addition of these fibers reduces the mechanical properties of the composite specimen. However it can be concluded that this composite satisfies the basic requirement of non-load bearing construction materials, and they could be used for partition walls and the like. Thus, the potential for development, therefore, seems to be very promising. Finally, apart from saving energy consumption for the building, the proposed materials offer an alternative option to dispose waste of fruit industry.

  10. Localizing Cortical Sources of Event-Related Potentials in Infants' Covert Orienting

    ERIC Educational Resources Information Center

    Richards, John E.

    2005-01-01

    This study used cortical source analysis to locate potential cortical sources of event-related potentials (ERPs) during covert orienting in infants aged 14 and 20 weeks. The infants were tested in a spatial cueing procedure. The reaction time to localize the target showed response facilitation for valid trials relative to invalid or neutral…

  11. Aerodynamic Classification of Swept-Wing Ice Accretion

    NASA Technical Reports Server (NTRS)

    Diebold, Jeff M.; Broeren, Andy P.; Bragg, Michael B.

    2013-01-01

    The continued design, certification and safe operation of swept-wing airplanes in icing conditions rely on the advancement of computational and experimental simulation methods for higher fidelity results over an increasing range of aircraft configurations and performance, and icing conditions. The current stateof- the-art in icing aerodynamics is mainly built upon a comprehensive understanding of two-dimensional geometries that does not currently exist for fundamentally three-dimensional geometries such as swept wings. The purpose of this report is to describe what is known of iced-swept-wing aerodynamics and to identify the type of research that is required to improve the current understanding. Following the method used in a previous review of iced-airfoil aerodynamics, this report proposes a classification of swept-wing ice accretion into four groups based upon unique flowfield attributes. These four groups are: ice roughness, horn ice, streamwise ice and spanwise-ridge ice. In the case of horn ice it is shown that a further subclassification of "nominally 3D" or "highly 3D" horn ice may be necessary. For all of the proposed ice-shape classifications, relatively little is known about the three-dimensional flowfield and even less about the effect of Reynolds number and Mach number on these flowfields. The classifications and supporting data presented in this report can serve as a starting point as new research explores swept-wing aerodynamics with ice shapes. As further results are available, it is expected that these classifications will need to be updated and revised.

  12. Aerodynamic Classification of Swept-Wing Ice Accretion

    NASA Technical Reports Server (NTRS)

    Diebold, Jeff M.; Broeren, Andy P.; Bragg, Michael B.

    2013-01-01

    The continued design, certification and safe operation of swept-wing airplanes in icing conditions rely on the advancement of computational and experimental simulation methods for higher fidelity results over an increasing range of aircraft configurations and performance, and icing conditions. The current state-of-the-art in icing aerodynamics is mainly built upon a comprehensive understanding of two-dimensional geometries that does not currently exist for fundamentally three-dimensional geometries such as swept wings. The purpose of this report is to describe what is known of iced-swept-wing aerodynamics and to identify the type of research that is required to improve the current understanding. Following the method used in a previous review of iced-airfoil aerodynamics, this report proposes a classification of swept-wing ice accretion into four groups based upon unique flowfield attributes. These four groups are: ice roughness, horn ice, streamwise ice and spanwise-ridge ice. In the case of horn ice it is shown that a further subclassification of nominally 3D or highly 3D horn ice may be necessary. For all of the proposed ice-shape classifications, relatively little is known about the three-dimensional flowfield and even less about the effect of Reynolds number and Mach number on these flowfields. The classifications and supporting data presented in this report can serve as a starting point as new research explores swept-wing aerodynamics with ice shapes. As further results are available, it is expected that these classifications will need to be updated and revised.

  13. Sediment sources in a small agricultural catchment: A composite fingerprinting approach based on the selection of potential sources

    NASA Astrophysics Data System (ADS)

    Zhou, Huiping; Chang, Weina; Zhang, Longjiang

    2016-08-01

    Fingerprinting techniques have been widely used as a reasonable and reliable means for investigating sediment sources, especially in relatively large catchments in which there are significant differences in surface materials. However, the discrimination power of fingerprint properties for small catchments, in which the surface materials are relatively homogeneous and human interference is marked, may be affected by fragmentary or confused source information. Using fingerprinting techniques can be difficult, and there is still a need for further studies to verify the effectiveness of such techniques in these small catchments. A composite fingerprinting approach was used in this study to investigate the main sources of sediment output, as well as their relative contributions, from a small catchment (30 km2) with high levels of farming and mining activities. The impact of the selection of different potential sediment sources on the derivation of composite fingerprints and its discrimination power were also investigated by comparing the results from different combinations of potential source types. The initial source types and several samples that could cause confusion were adjusted. These adjustments improved the discrimination power of the composite fingerprints. The results showed that the composite fingerprinting approach used in this study had a discriminatory efficiency of 89.2% for different sediment sources and that the model had a mean goodness of fit of 0.90. Cultivated lands were the main sediment source. The sediment contribution of the studied cultivated lands ranged from 39.9% to 87.8%, with a mean of 76.6%, for multiple deposited sediment samples. The mean contribution of woodlands was 21.7%. Overall, the sediment contribution from mining and road areas was relatively low. The selection of potential sources is an important factor in the application of fingerprinting techniques and warrants more attention in future studies, as is the case with other

  14. Gingiva as a source of stem cells with therapeutic potential.

    PubMed

    Fournier, Benjamin P J; Larjava, Hannu; Häkkinen, Lari

    2013-12-15

    Postnatal connective tissues contain phenotypically heterogeneous cells populations that include distinct fibroblast subpopulations, pericytes, myofibroblasts, fibrocytes, and tissue-specific mesenchymal stem cells (MSCs). These cells play key roles in tissue development, maintenance, and repair and contribute to various pathologies. Depending on the origin of tissue, connective tissue cells, including MSCs, have different phenotypes. Understanding the identity and specific functions of these distinct tissue-specific cell populations may allow researchers to develop better treatment modalities for tissue regeneration and find novel approaches to prevent pathological conditions. Interestingly, MSCs from adult oral mucosal gingiva possess distinct characteristics, including neural crest origin, multipotent differentiation capacity, fetal-like phenotype, and potent immunomodulatory properties. These characteristics and an easy, relatively noninvasive access to gingival tissue, and fast tissue regeneration after tissue biopsy make gingiva an attractive target for cell isolation for therapeutic purposes aiming to promote tissue regeneration and fast, scar-free wound healing. The purpose of this review is to discuss the identity, phenotypical heterogeneity, and function of gingival MSCs and summarize what is currently known about their properties, role in scar-free healing, and their future therapeutic potential.

  15. Microalga Scenedesmus obliquus as a potential source for biodiesel production.

    PubMed

    Mandal, Shovon; Mallick, Nirupama

    2009-08-01

    Biodiesel from microalgae seems to be the only renewable biofuel that has the potential to completely replace the petroleum-derived transport fuels. Therefore, improving lipid content of microalgal strains could be a cost-effective second generation feedstock for biodiesel production. Lipid accumulation in Scenedesmus obliquus was studied under various culture conditions. The most significant increase in lipid reached 43% of dry cell weight (dcw), which was recorded under N-deficiency (against 12.7% under control condition). Under P-deficiency and thiosulphate supplementation the lipid content also increased up to 30% (dcw). Application of response surface methodology in combination with central composite rotary design (CCRD) resulted in a lipid yield of 61.3% (against 58.3% obtained experimentally) at 0.04, 0.03, and 1.0 g l(-1) of nitrate, phosphate, and sodium thiosulphate, respectively for time culture of 8 days. Scenedesmus cells pre-grown in glucose (1.5%)-supplemented N 11 medium when subjected to the above optimized condition, the lipid accumulation was boosted up to 2.16 g l(-1), the value approximately 40-fold higher with respect to the control condition. The presence of palmitate and oleate as the major constituents makes S. obliquus biomass a suitable feedstock for biodiesel production.

  16. Potential source for crushed granite aggregate in Heard County, Georgia

    USGS Publications Warehouse

    Atkins, R.L.; Higgins, Michael W.; Dickerson, Robert P.

    1981-01-01

    The production of crushed stone suitable for highway and general construction is a major industry in Georgia. The state ranks eighth in the nation in overall crushed stone production, and first in crushed granite production. Crushed stone production in Georgia in 1979 was 40,902,000 short tons worth $154,021,000 (D.H. White, Jr., US Bureau of Mines, personal commun., Aug. 1980). More than 3,000 people were employed by the crushed stone industry in Georgia during that year.Presently, the only active quarry in Heard County is located in an amphibolite. Amphibolite is not a conventional aggregate. It has a high specific gravity, a tendency to make elongate fragments, and varies considerably in abrasion tests.Because the nearest approved aggregate quarry is more than 25 miles from Franklin, the county seat, the purpose of this brief report is to describe a body of granite gneiss that may provide suitable aggregate for the crushed stone industry, potential quarry operators and various agencies in Heard County. This report is part of a project to study the geology and mineral resources of the Piedmont south of the Brevard Zone, and is not intended to supplant detailed site investigations by industry or consultants. The report is a joint effort between the Georgia Geologic Survey and the Office of Materials and Research of the Georgia Department of Transportation.

  17. Medical literature as a potential source of new knowledge.

    PubMed Central

    Swanson, D R

    1990-01-01

    Specialized biomedical literatures have been found that are implicitly linked by arguments that they respectively contain, but which nonetheless do not cite or refer to each other. The combined arguments lead to new inferences and conclusions that cannot be drawn from the separate literatures. One such analysis identified one set of articles showing that dietary fish oils lead to certain blood and vascular changes, and a second set containing evidence that similar changes might benefit patients with Raynaud's syndrome. Yet these two literatures had no articles in common and had never before been cited together; neither literature mentioned the other or suggested that dietary fish oil might benefit Raynaud patients. Two years after publication of that analysis, the first clinical trial demonstrating such a beneficial effect was reported independently by others. A second example of literature synthesis, based on eleven indirect connections, led to an inference that magnesium deficiency might be a causal factor in migraine headache. A third example calls attention to implicit connections between arginine intake and blood levels of somatomedins, a potentially fruitful but neglected area of research with implications for the decline with age of thymic function and protein synthesis. A model and an online search strategy to aid in identifying other logically related noninteractive literatures is described. Such structures are probably not rare and may provide the foundation for a literature-based approach to scientific discovery. PMID:2403828

  18. Manilkara zapota (Linn.) Seeds: A Potential Source of Natural Gum

    PubMed Central

    Singh, Sudarshan; Bothara, Sunil B.

    2014-01-01

    Mucilage isolated from seeds of Manilkara zapota (Linn.) P. Royen syn. is a plant growing naturally in the forests of India. This mucilage is yet to be commercially exploited, and characterized as polymer. Various physicochemical methods like particle size analysis, scanning electron microscopy, thermal analysis, gel permeation chromatography, X-ray diffraction spectrometry, zeta potential, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy have been employed to characterize this gum in the present study. Particle size analyses suggest that mucilage has particle size in nanometer. Scanning electron microscopy analysis suggests that the mucilage has irregular particle size. The glass transition temperature of the gum was observed to be 138°C and 136°C by differential scanning calorimetry and differential thermal analysis, respectively. The thermogravimetric analysis suggested that mucilage had good thermal stability. The average molecular weight of mucilage was determined to be 379180, by gel permeation chromatography, while the viscosity of mucilage was observed to be 219.1 cP. The X-ray diffraction spectrometry pattern of the mucilage indicates a completely amorphous structure. Elemental analysis of the gum revealed the contents of carbon, hydrogen, nitrogen, and sulfur to be 80.9 (%), 10.1 (%), 1.58 (%), and 512 (mg/kg), respectively. Mucilage had specific content of calcium, magnesium, potassium, lower concentrations of aluminum, cadmium, cobalt, lead, and nickel. The major functional groups identified from FT-IR spectrum include 3441 cm−1 (–OH), 1660 cm−1 (Alkenyl C–H & C=C Stretch), 1632 cm−1 (–COO–), 1414 cm−1 (–COO–), and 1219 cm−1 (–CH3CO). Analysis of mucilage by paper chromatography and 1D NMR, indicated the presence of rhamnose, xylose, arabinose, mannose, and fructose. PMID:24729907

  19. Manilkara zapota (Linn.) Seeds: A Potential Source of Natural Gum.

    PubMed

    Singh, Sudarshan; Bothara, Sunil B

    2014-01-01

    Mucilage isolated from seeds of Manilkara zapota (Linn.) P. Royen syn. is a plant growing naturally in the forests of India. This mucilage is yet to be commercially exploited, and characterized as polymer. Various physicochemical methods like particle size analysis, scanning electron microscopy, thermal analysis, gel permeation chromatography, X-ray diffraction spectrometry, zeta potential, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy have been employed to characterize this gum in the present study. Particle size analyses suggest that mucilage has particle size in nanometer. Scanning electron microscopy analysis suggests that the mucilage has irregular particle size. The glass transition temperature of the gum was observed to be 138°C and 136°C by differential scanning calorimetry and differential thermal analysis, respectively. The thermogravimetric analysis suggested that mucilage had good thermal stability. The average molecular weight of mucilage was determined to be 379180, by gel permeation chromatography, while the viscosity of mucilage was observed to be 219.1 cP. The X-ray diffraction spectrometry pattern of the mucilage indicates a completely amorphous structure. Elemental analysis of the gum revealed the contents of carbon, hydrogen, nitrogen, and sulfur to be 80.9 (%), 10.1 (%), 1.58 (%), and 512 (mg/kg), respectively. Mucilage had specific content of calcium, magnesium, potassium, lower concentrations of aluminum, cadmium, cobalt, lead, and nickel. The major functional groups identified from FT-IR spectrum include 3441 cm(-1) (-OH), 1660 cm(-1) (Alkenyl C-H & C=C Stretch), 1632 cm(-1) (-COO-), 1414 cm(-1) (-COO-), and 1219 cm(-1) (-CH3CO). Analysis of mucilage by paper chromatography and 1D NMR, indicated the presence of rhamnose, xylose, arabinose, mannose, and fructose.

  20. Human skin flora as a potential source of epidural abscess.

    PubMed

    Sato, S; Sakuragi, T; Dan, K

    1996-12-01

    The mechanism of epidural infection associated with epidural block is not clearly understood. Resident organisms in skin specimens were studied after skin was prepared with disinfectants. Sixty-nine paired skin specimens were excised at incisional sites after skin disinfection with 10% povidone-iodine (10% PVP-I) or 0.5% chlorhexidine in 80% ethanol (0.5% CHE) from 60 patients having back surgery. One of the specimen pairs was placed in 10 ml brain-heart infusion broth and incubated in air at 37 degrees C for 96 h. The other specimen was sectioned at 3 microns and prepared with Gram's stain for examination with the microscope. Thirteen gram-positive staphylococcal species (Staphylococcus epidermidis, 69.2%; S. hyicus, 15.4%; and S. capitis, 15.4%) were isolated from cultures. The isolates were found in a significantly greater proportion of the skin specimens disinfected with 10% PVP-I than in those disinfected with 0.5% CHE (11 of 34 cultures [32.4%] vs. 2 of 35 cultures [5.7%]; P < 0.01). Many gram-positive cocci were observed with the microscope in 4 (11.8%) and 5 (14.3%) of 34 and 35 skin specimens disinfected with 10% PVP-I and 0.5% CHE, respectively. The cocci formed a dense colony in each follicle and in the stratum corneum. No organism was present in any of 17,584 sweat glands examined. In a large proportion of patients, isolation of viable organisms from excised skin specimens after disinfection with 10% PVP-I suggests that contamination of the epidural space by the skin flora may be a potential mechanism of epidural infection associated with epidural block.

  1. By-products: oil sorbents as a potential energy source.

    PubMed

    Karakasi, Olga K; Moutsatsou, Angeliki

    2013-04-01

    The present study investigated the utilization of an industrial by-product, lignite fly ash, in oil pollution treatment, with the further potential profit of energy production. The properties of lignite fly ash, such as fine particle size, porosity, hydrophobic character, combined with the properties, such as high porosity and low specific gravity, of an agricultural by-product, namely sawdust, resulted in an effective oil-sorbent material. The materials were mixed either in the dry state or in aqueous solution. The oil sorption behaviour of the fly ash-sawdust mixtures was investigated in both marine and dry environments. Mixtures containing fly ash and 15-25% w/w sawdust performed better than each material alone when added to oil spills in a marine environment, as they formed a cohesive semi-solid phase, adsorbing almost no water, floating on the water surface and allowing total oil removal. For the clean-up of an oil spill 0.5 mm thick with surface area 1000 m(2), 225-255 kg of lignite fly ash can be utilized with the addition of 15-25% w/w sawdust. Fly ash-sawdust mixtures have also proved efficient for oil spill clean-up on land, since their oil sorption capacity in dry conditions was at least 0.6-1.4 g oil g(-1) mixture. The higher calorific value of the resultant oil-fly ash-sawdust mixtures increased up to that of bituminous coal and oil and exceeded that of lignite, thereby encouraging their utilization as alternative fuels especially in the cement industry, suggesting that the remaining ash can contribute in clinker production.

  2. High-speed dispersion-tuned wavelength-swept fiber laser using a reflective SOA and a chirped FBG.

    PubMed

    Takubo, Yuya; Yamashita, Shinji

    2013-02-25

    We present a high-speed wavelength-swept fiber laser based on a dispersion tuning method using a reflective semiconductor optical amplifier (RSOA) and a chirped fiber Bragg grating (CFBG). By using these devices, the cavity length can be shortened drastically. The short cavity improves the laser performance at high sweep rates over 200 kHz. We achieve a sweep range of 60 nm and an output power of 8.4 mW at 100 kHz sweep. We applied the dispersion-tuned fiber laser to the swept-source OCT system and successfully obtained OCT images of an adhesive tape at up to 250 kHz sweep rate.

  3. Measuring of the pitch variation of cholesteric liquid crystals under electric field using wavelength-swept laser

    NASA Astrophysics Data System (ADS)

    Ko, Myeong Ock; Kim, Sung-Jo; Kim, Jong-Hyun; Jeon, Min Yong

    2017-04-01

    We measure the pitch variation of cholesteric liquid crystals (CLCs) according to the applied electric field using a wavelength-swept laser. While the electric field is applied to the CLC, the pitch of the CLC is elongated normal to the direction of electric field. Therefore, the reflection band is shifted to the longer wavelength. When the applied electric field to the CLC cell was over 1.52 V/μm, the reflection band was changed to the longer wavelength of about 75.1 nm. We believe that the dynamic behavior of the CLC can be analyzed if a high-speed wavelength-swept laser is used as an optical source.

  4. A Method for Determining Cloud-Droplet Impingement on Swept Wings

    NASA Technical Reports Server (NTRS)

    Dorsch, Robert G.; Brun, Rinaldo J.

    1953-01-01

    The general effect of wing sweep on cloud-droplet trajectories about swept wings of high aspect ratio moving at subsonic speeds is discussed. A method of computing droplet trajectories about yawed cylinders and swept wings is presented, and illustrative droplet trajectories are computed. A method of extending two-dimensional calculations of droplet impingement on nonswept wings to swept wings is presented. It is shown that the extent of impingement of cloud droplets on an airfoil surface, the total rate of collection of water, and the local rate of impingement per unit area of airfoil surface can be found for a swept wing from two-dimensional data for a nonswept wing. The impingement on a swept wing is obtained from impingement data for a nonswept airfoil section which is the same as the section in the normal plane of the swept wing by calculating all dimensionless parameters with respect to flow conditions in the normal plane of the swept wing.

  5. Phase-sensitive optical coherence tomography using an Vernier-tuned distributed Bragg reflector swept laser in the mouse middle ear.

    PubMed

    Park, Jesung; Carbajal, Esteban F; Chen, Xi; Oghalai, John S; Applegate, Brian E

    2014-11-01

    Phase-sensitive optical coherence tomography (PhOCT) offers exquisite sensitivity to mechanical vibration in biological tissues. There is growing interest in using PhOCT for imaging the nanometer scale vibrations of the ear in animal models of hearing disorders. Swept-source-based systems offer fast acquisition speeds, suppression of common mode noise via balanced detection, and good signal roll-off. However, achieving high phase stability is difficult due to nonlinear laser sweeps and trigger jitter in a typical swept laser source. Here, we report on the initial application of a Vernier-tuned distributed Bragg reflector (VT-DBR) swept laser as the source for a fiber-based PhOCT system. The VT-DBR swept laser is electronically tuned and precisely controls sweeps without mechanical movement, resulting in highly linear sweeps with high wavelength stability and repeatability. We experimentally measured a phase sensitivity of 0.4 pm standard deviation, within a factor of less than 2 of the computed shot-noise limit. We further demonstrated the system by making ex vivo measurements of the vibrations of the mouse middle ear structures.

  6. Phase-sensitive optical coherence tomography using an Vernier-tuned distributed Bragg reflector swept laser in the mouse middle ear

    PubMed Central

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

    2017-01-01

    Phase-sensitive optical coherence tomography (PhOCT) offers exquisite sensitivity to mechanical vibration in biological tissues. There is growing interest in using PhOCT for imaging the nanometer scale vibrations of the ear in animal models of hearing disorders. Swept-source-based systems offer fast acquisition speeds, suppression of common mode noise via balanced detection, and good signal roll-off. However, achieving high phase stability is difficult due to nonlinear laser sweeps and trigger jitter in a typical swept laser source. Here, we report on the initial application of a Vernier-tuned distributed Bragg reflector (VT-DBR) swept laser as the source for a fiber-based PhOCT system. The VT-DBR swept laser is electronically tuned and precisely controls sweeps without mechanical movement, resulting in highly linear sweeps with high wavelength stability and repeatability. We experimentally measured a phase sensitivity of 0.4 pm standard deviation, within a factor of less than 2 of the computed shot-noise limit. We further demonstrated the system by making ex vivo measurements of the vibrations of the mouse middle ear structures. PMID:25361322

  7. Fingerprinting surficial sediment sources: Exploring some potential problems associated with the spatial variability of source material properties.

    PubMed

    Du, Pengfei; Walling, Des E

    2016-07-20

    Recent advances in sediment source tracing or fingerprinting procedures have focussed primarily on the use of novel sediment properties that are either easier to measure or provide improved source discrimination, or on improved procedures for representing and estimating the uncertainty associated with the final source apportionment results. Spatial variability of source properties has long been recognised as a potential problem for the approach, but there have been few attempts to explore the nature and magnitude of such variability and its wider implications for source fingerprinting investigations. This contribution addresses this issue with particular reference to surficial sediment sources. It reports the results of an investigation aimed at documenting the magnitude and nature of the spatial variability of the geochemical properties of surface soils within a single 7 ha cultivated field and exploring the implications of the findings for sediment source fingerprinting procedures. Samples of surface soil were collected from 52 points located within the field. Particular attention is directed to the extent of the spatial variability of 53 geochemical properties of the surface soil which could potentially be used as fingerprints, the importance of the influence of soil redistribution rate on the properties of the surface soil, provision of guidelines for selecting sampling points and the degree of correlation between different soil properties and its implications for the numerical procedures employed in sediment source fingerprinting studies. A novel aspect of the study is that caesium-137 ((137)Cs) measurements were used to provide information on the magnitude and spatial pattern of the soil redistribution rate within the field, so that the influence of soil redistribution rate in causing systematic spatial variability of fingerprint properties could be further explored.

  8. Atmospheric aerosol over Finnish Arctic: source analysis by the multilinear engine and the potential source contribution function

    NASA Astrophysics Data System (ADS)

    Yli-Tuomi, Tarja; Hopke, Philip K.; Paatero, Pentti; Basunia, M. Shamsuzzoha; Landsberger, Sheldon; Viisanen, Yrjö; Paatero, Jussi

    Week-long samples of total suspended particles were collected between 1964 and 1978 from Kevo at the Finnish Arctic and analyzed for a number of chemical species. The chemical composition data was analyzed using a mixed 2-way/3-way model. The results of receptor modeling were connected with the back trajectory data in a Potential Source Contribution Function analysis to determine the likely source areas. Nine sources, namely silver emissions, coal/oil shale combustion, biomass burning, non-ferrous smelters (two sources), crustal elements from remote sources, excess silicon from local sources, sea salt particles and biogenic sulfur emissions from marine algae were found. Although the emissions from industrial areas in the Kola Peninsula had an effect on the concentration of anthropogenic pollutants at Kevo, the highest concentrations during winter were transported from the sources in the mid-latitudes. The yearly strength of the biogenic sulfur emissions showed no dependence on the Northern Hemisphere temperature anomaly and thus, a climatic feedback loop could not be confirmed.

  9. Excitation of Crossflow Instabilities in a Swept Wing Boundary Layer

    NASA Technical Reports Server (NTRS)

    Carpenter, Mark H.; Choudhari, Meelan; Li, Fei; Streett, Craig L.; Chang, Chau-Lyan

    2010-01-01

    The problem of crossflow receptivity is considered in the context of a canonical 3D boundary layer (viz., the swept Hiemenz boundary layer) and a swept airfoil used recently in the SWIFT flight experiment performed at Texas A&M University. First, Hiemenz flow is used to analyze localized receptivity due to a spanwise periodic array of small amplitude roughness elements, with the goal of quantifying the effects of array size and location. Excitation of crossflow modes via nonlocalized but deterministic distribution of surface nonuniformity is also considered and contrasted with roughness induced acoustic excitation of Tollmien-Schlichting waves. Finally, roughness measurements on the SWIFT model are used to model the effects of random, spatially distributed roughness of sufficiently small amplitude with the eventual goal of enabling predictions of initial crossflow disturbance amplitudes as functions of surface roughness parameters.

  10. Linear stability and control of swept Hiemenz flow

    NASA Astrophysics Data System (ADS)

    Guegan, Alan; Schmid, Peter; Huerre, Patrick

    2004-11-01

    Perturbations at the leading edge of swept wings may feed the downstream flow and trigger early boundary layer transition. Control strategies focusing on the leading edge boundary layer may provide significant improvement of flow stability over the wing surface. To this end, a gradient-based optimization algorithm is implemented to find the perturbations that experience the highest energy growth in swept Hiemenz flow over a finite time interval, under the Görtler-Hämmerlin assumption. A two-dimensional mechanism resembling the Orr-mechanism in the spanwise-wall-normal plane is shown to generate energy growth of up to three orders of magnitude for a Reynolds number Re=2000 and a spanwise wavenumber k=0.1. A similar algorithm is used to compute the wall-normal blowing/sucking sequence that most efficiently damps the energy amplification. The maximum energy is then found to decrease by more than 70%.

  11. Forward-Swept Fan Flutter Calculated Using TURBO Code

    NASA Technical Reports Server (NTRS)

    Srivastava, Rakesh; Bakhle, Milind A.; Stefko, George L.

    2003-01-01

    Flutter, a self-excited dynamic instability arising because of fluid structure interaction, can be a significant design problem for rotor blades in gas turbines. Blade shapes influenced by noise-reduction requirements increase the likelihood of flutter in modern blade designs. Validated numerical methods provide designers an invaluable tool to calculate and avoid the flutter instability during the design phase. Toward this objective, a flutter analysis code, TURBO, was developed and validated by researchers from the NASA Glenn Research Center and other researchers working under grants and contracts with Glenn. The TURBO code, which is based on unsteady three-dimensional Reynolds-averaged Navier-Stokes equations was used to calculate the observed flutter of a forward-swept fan. The forward-swept experimental fan, designed to reduce noise, showed flutter at part-speed conditions during wind tunnel tests.

  12. Swept-Wing Receptivity Studies Using Distributed Roughness

    NASA Technical Reports Server (NTRS)

    Saric, William S.

    1998-01-01

    This paper reviews the important recent progress in three-dimensional boundary-layer transition research. The review focuses on the crossflow instability that leads to transition on swept wings with a favorable pressure gradient. Following a brief overview of swept-wing instability mechanisms and the crossflow problem, a summary of the important findings of the 1990s is given. The discussion is presented from the experimental viewpoint, highlighting the ITAM work of Kachanov and co-workers, the DLR experiments of Bippes and co-workers, and the Arizona State University (ASU) investigations of Saric and co-workers. Where appropriate, relevant comparisons with CFD are drawn. The recent (last 18 months) research conducted by the ASU team is described in more detail in order to underscore the latest developments concerning nonlinear effects and transition control.

  13. Widely tunable/wavelength-swept SLM fiber laser with ultra-narrow linewidth and ultra-high OSNR

    NASA Astrophysics Data System (ADS)

    Feng, Ting; Ding, Dong-liang; Liu, Peng; Su, Hong-xin; Yao, X. Steve

    2016-11-01

    We propose and demonstrate a novel single-longitudinal-mode (SLM) erbium-doped fiber laser (EDFL) capable of operating at fixed-wavelength lasing mode with a tunable range more than 54 nm, an ultra-narrow linewidth of 473 Hz and an ultra-high optical signal-to-noise ratio ( OSNR) more than 72 dB, or operating at wavelength-swept mode with tunable sweep rate of 10—200 Hz and a sweep range more than 50 nm. The excellent features mainly benefit from a triple-ring subring cavity constructed by three optical couplers nested one another and a fiber Fabry-Pérot tunable filter which can be driven by a constant voltage or a periodic sweep voltage for fixed or wavelength- swept operation, respectively. The proposed EDFL has potential applications in high-resolution spectroscopy and fiber optic sensing.

  14. Absolute Instability in Swept Leading-Edge Boundary Layers

    NASA Astrophysics Data System (ADS)

    Lin, R.-S.; Li, F.; Malik, M. R.

    1997-11-01

    Absolute instabilities in the swept Hiemenz flow and flows over Poll's swept cylinder are studied. It is assumed that the span is infinite and the laminar flow field is subjected to a line impulsive excitation so that the spanwise wavenumber (β) is taken to be real, which is akin to the rotating disk study made by Lingwood.footnote Lingwood, R. J., J. Fluid Mech., 299, 17, 1995. We found that these flows can be absolutely unstable in the chordwise (x) direction. The pinch-point singularities formed by the coalescence of two distinct spatial branches can lie either below or above the real α-axis. The pinch points with a positive αi imply the existence of an unstable disturbance propagating against the mainstream, which has never been observed before. It is found that singularities of pinch type occur in a region very close to the leading edge, therefore the attachment-line Reynolds number is used to correlate the onset of absolute instability. The critical Reynolds number for absolute instability is found to be about R=540 compared to 583 for the attachment-line instability. Provided the non-linear behavior of this absolute instability is sufficient to trigger the laminar to turbulent transition, then it would cause a complete loss of laminar flow on a swept wing as does the attachment-line instability.

  15. Evaluation of Icing Scaling on Swept NACA 0012 Airfoil Models

    NASA Technical Reports Server (NTRS)

    Tsao, Jen-Ching; Lee, Sam

    2012-01-01

    Icing scaling tests in the NASA Glenn Icing Research Tunnel (IRT) were performed on swept wing models using existing recommended scaling methods that were originally developed for straight wing. Some needed modifications on the stagnation-point local collection efficiency (i.e., beta(sub 0) calculation and the corresponding convective heat transfer coefficient for swept NACA 0012 airfoil models have been studied and reported in 2009, and the correlations will be used in the current study. The reference tests used a 91.4-cm chord, 152.4-cm span, adjustable sweep airfoil model of NACA 0012 profile at velocities of 100 and 150 knot and MVD of 44 and 93 mm. Scale-to-reference model size ratio was 1:2.4. All tests were conducted at 0deg angle of attack (AoA) and 45deg sweep angle. Ice shape comparison results were presented for stagnation-point freezing fractions in the range of 0.4 to 1.0. Preliminary results showed that good scaling was achieved for the conditions test by using the modified scaling methods developed for swept wing icing.

  16. Occurrence, Source, and Human Infection Potential of Cryptosporidium and Giardia spp. in Source and Tap Water in Shanghai, China▿

    PubMed Central

    Feng, Yaoyu; Zhao, Xukun; Chen, Jiaxu; Jin, Wei; Zhou, Xiaonong; Li, Na; Wang, Lin; Xiao, Lihua

    2011-01-01

    Genotyping studies on the source and human infection potential of Cryptosporidium oocysts in water have been almost exclusively conducted in industrialized nations. In this study, 50 source water samples and 30 tap water samples were collected in Shanghai, China, and analyzed by the U.S. Environmental Protection Agency (EPA) Method 1623. To find a cost-effective method to replace the filtration procedure, the water samples were also concentrated by calcium carbonate flocculation (CCF). Of the 50 source water samples, 32% were positive for Cryptosporidium and 18% for Giardia by Method 1623, whereas 22% were positive for Cryptosporidium and 10% for Giardia by microscopy of CCF concentrates. When CCF was combined with PCR for detection, the occurrence of Cryptosporidium (28%) was similar to that obtained by Method 1623. Genotyping of Cryptosporidium in 17 water samples identified the presence of C. andersoni in 14 water samples, C. suis in 7 water samples, C. baileyi in 2 water samples, C. meleagridis in 1 water sample, and C. hominis in 1 water sample. Therefore, farm animals, especially cattle and pigs, were the major sources of water contamination in Shanghai source water, and most oocysts found in source water in the area were not infectious to humans. Cryptosporidium oocysts were found in 2 of 30 tap water samples. The combined use of CCF for concentration and PCR for detection and genotyping provides a less expensive alternative to filtration and fluorescence microscopy for accurate assessment of Cryptosporidium contamination in water, although the results from this method are semiquantitative. PMID:21498768

  17. UNCERTAINTY IN LEACHING POTENTIAL OF NONPOINT SOURCE POLLUTANTS WITH APPLICATION TO A GIS

    EPA Science Inventory

    This paper presents a stochastic framework for the assessment of groundwater pollution potential of nonpoint source pesticides. A conceptual relationship is presented that relates seasonally averaged groundwater recharge to soil properties and depths to the water table. The analy...

  18. Petroleum potentialities of central Tunisia as deduced from identification and characterization of oil source rocks

    SciTech Connect

    Saidi, M.; Acheche, M.H.; Inoubli, H. ); Belayouni, H. )

    1991-08-01

    Many potential oil source rocks occur within the Tunisian stratigraphic column, including Silurian-Devonian shales, Albian and upper Albian-Vraconian carbonates, Cenomanian-Turonian black shales and lower Eocene carbonates. This focuses on the inventory of potential oil source rocks in central Tunisia ranging from middle Jurassic to Turonian. The emphasis is on determining their genetic potential and whether they could have generated oil and gas. Geochemical data obtained from the analysis of at least 2,147 samples show this region to be of significant interest as a petroleum prospective area. The main source rocks identified are Toarcian shales, upper Albian-Vraconian carbonates and Cenomanian-Turonian black shales. They contain predominantly type 2 organic matter (oil and gas prone) and are at the low maturity limit of the oil window. The occurrence of those source rocks close to numerous potential reservoir facies supports the conclusion that central Tunisia is a very interesting area for petroleum exploration.

  19. UNCERTAINTY IN LEACHING POTENTIAL OF NONPOINT SOURCE POLLUTANTS WITH APPLICATION TO A GIS

    EPA Science Inventory

    This paper presents a stochastic framework for the assessment of groundwater pollution potential of nonpoint source pesticides. A conceptual relationship is presented that relates seasonally averaged groundwater recharge to soil properties and depths to the water table. The analy...

  20. UNCERTAINTY IN LEACHING POTENTIAL OF NONPOINT SOURCE POLLUTANTS WITH APPLICATION TO GIS

    EPA Science Inventory

    This paper presents a stochastic framework for the assessment of groundwater pollution potential of nonpoint source pesticides. A conceptual relationship is presented that relates seasonally averaged groundwater recharge to soil properties and depths to the water table. The analy...

  1. UNCERTAINTY IN LEACHING POTENTIAL OF NONPOINT SOURCE POLLUTANTS WITH APPLICATION TO GIS

    EPA Science Inventory

    This paper presents a stochastic framework for the assessment of groundwater pollution potential of nonpoint source pesticides. A conceptual relationship is presented that relates seasonally averaged groundwater recharge to soil properties and depths to the water table. The analy...

  2. Observations of Traveling Crossflow Resonant Triad Interactions on a Swept Wing

    NASA Technical Reports Server (NTRS)

    Eppink, Jenna L.; Wlezien, Richard

    2012-01-01

    Experimental evidence indicates the presence of a triad resonance interaction between traveling crossflow modes in a swept wing flow. Results indicate that this interaction occurs when the stationary and traveling crossflow modes have similar and relatively low amplitudes (approx.1% to 6% of the total freestream velocity). The resonant interaction occurs at instability amplitudes well below those typically known to cause transition, yet transition is observed to occur just downstream of the resonance. In each case, two primary linearly unstable traveling crossflow modes are nonlinearly coupled to a higher frequency linearly stable mode at the sum of their frequencies. The higher-frequency mode is linearly stable and presumed to exist as a consequence of the interaction of the two primary modes. Autoand cross-bicoherence are used to determine the extent of phase-matching between the modes, and wavenumber matching confirms the triad resonant nature of the interaction. The bicoherence results indicate a spectral broadening mechanism and the potential path to early transition. The implications for laminar flow control in swept wing flows are significant. Even if stationary crossflow modes remain subcritical, traveling crossflow interactions can lead to early transition.

  3. Validation of a Residual Stress Measurement Method by Swept High-Frequency Eddy Currents

    NASA Astrophysics Data System (ADS)

    Lee, C.; Shen, Y.; Lo, C. C. H.; Nakagawa, N.

    2007-03-01

    This paper reports on a swept high-frequency eddy current (SHFEC) measurement method developed for electromagnetic nondestructive characterization of residual stresses in shot peened aerospace materials. In this approach, we regard shot-peened surfaces as modified surface layers of varying conductivity, and determine the conductivity deviation profile by inversion of the SHFEC data. The SHFEC measurement system consists of a pair of closely matched printed-circuit-board coils driven by laboratory instrument under software control. This provides improved sensitivity and high frequency performance compared to conventional coils, so that swept frequency EC measurements up to 50 MHz can be made to achieve the smallest skin depth of 80 μm for nickel-based superalloys. We devised a conductivity profile inversion procedure based on the laterally uniform multi-layer theory of Cheng, Dodd and Deeds. The main contribution of this paper is the methodology validation. Namely, the forward and inverse models were validated against measurements on artificial layer specimens consisting of metal films with different conductivities placed on a metallic substrate. The inversion determined the film conductivities which were found to agree with those measured using the direct current potential drop (DCPD) method.

  4. Event-related potential evidence of accessing gender stereotypes to aid source monitoring.

    PubMed

    Leynes, P Andrew; Crawford, Jarret T; Radebaugh, Anne M; Taranto, Elizabeth

    2013-01-23

    Source memory for the speaker's voice (male or female) was investigated when semantic knowledge (gender stereotypes) could and could not inform the episodic source judgment while event-related potentials (ERPs) were recorded. Source accuracy was greater and response times were faster when stereotypes could predict the speaker's voice at test. Recollection supported source judgments in both conditions as indicated by significant parietal "old/new" ERP effects (500-800ms). Prototypical late ERP effects (the right frontal "old/new" effect and the late posterior negativity, LPN) were evident when source judgment was based solely on episodic memory. However, these two late ERP effects were diminished and a novel, frontal-negative ERP with left-central topography was observed when stereotypes aided source judgments. This pattern of ERP activity likely reflects activation of left frontal or left temporal lobes when semantic knowledge, in the form of a gender stereotype, is accessed to inform the episodic source judgment.

  5. A Quantitative Evaluation of Potential Radio Identifications for 3EG EGRET Sources

    NASA Astrophysics Data System (ADS)

    Mattox, J. R.; Hartman, R. C.; Reimer, O.

    2001-08-01

    The method of Mattox et al. for identifying EGRET sources with 5 GHz radio sources has been applied to the 3EG EGRET catalog of Hartman et al. Complete results are tabulated. We tabulate separately 46 EGRET sources with radio identifications which we expect to have a high probability of being correct. We suggest that these sources are appropriate for most studies of the properties of γ-ray blazars as a class. All but one of these 46 sources were classified by Hartman et al. as high-confidence identifications; and the additional source was classified by Hartman et al. as a plausible identification. We also tabulate separately 37 additional ``plausible identifications of EGRET sources with radio sources.'' These less secure possibilities include the remaining 21 ``high-confidence identifications'' of Hartman et al., three of the 27 ``lower confidence potential blazar identifications'' of Hartman et al., and an additional 15 plausible identifications which have not been suggested previously. Many of these sources require new radio and optical observations to establish them as blazars. We suggest that the 23 ``lower-confidence potential blazar identifications'' of Hartman et al. which we do not find plausible should not be used in studies of the properties of the EGRET blazars. For this analysis, we have made elliptical fits to the 95% confidence contours of the position uncertainty regions of the 3EG sources which are tabulated in an Appendix.

  6. Oxidative potential and inflammatory impacts of source apportioned ambient air pollution in Beijing.

    PubMed

    Liu, Qingyang; Baumgartner, Jill; Zhang, Yuanxun; Liu, Yanju; Sun, Yongjun; Zhang, Meigen

    2014-11-04

    Air pollution exposure is associated with a range of adverse health impacts. Knowledge of the chemical components and sources of air pollution most responsible for these health effects could lead to an improved understanding of the mechanisms of such effects and more targeted risk reduction strategies. We measured daily ambient fine particulate matter (<2.5 μm in aerodynamic diameter; PM2.5) for 2 months in peri-urban and central Beijing, and assessed the contribution of its chemical components to the oxidative potential of ambient air pollution using the dithiothreitol (DTT) assay. The composition data were applied to a multivariate source apportionment model to determine the PM contributions of six sources or factors: a zinc factor, an aluminum factor, a lead point factor, a secondary source (e.g., SO4(2-), NO3(2-)), an iron source, and a soil dust source. Finally, we assessed the relationship between reactive oxygen species (ROS) activity-related PM sources and inflammatory responses in human bronchial epithelial cells. In peri-urban Beijing, the soil dust source accounted for the largest fraction (47%) of measured ROS variability. In central Beijing, a secondary source explained the greatest fraction (29%) of measured ROS variability. The ROS activities of PM collected in central Beijing were exponentially associated with in vivo inflammatory responses in epithelial cells (R2=0.65-0.89). We also observed a high correlation between three ROS-related PM sources (a lead point factor, a zinc factor, and a secondary source) and expression of an inflammatory marker (r=0.45-0.80). Our results suggest large differences in the contribution of different PM sources to ROS variability at the central versus peri-urban study sites in Beijing and that secondary sources may play an important role in PM2.5-related oxidative potential and inflammatory health impacts.

  7. Evaluation of agricultural nonpoint source pollution potential risk over China with a Transformed-Agricultural Nonpoint Pollution Potential Index method.

    PubMed

    Yang, Fei; Xu, Zhencheng; Zhu, Yunqiang; He, Chansheng; Wu, Genyi; Qiu, Jin Rong; Fu, Qiang; Liu, Qingsong

    2013-01-01

    Agricultural nonpoint source (NPS) pollution has been the most important threat to water environment quality. Understanding the spatial distribution of NPS pollution potential risk is important for taking effective measures to control and reduce NPS pollution. A Transformed-Agricultural Nonpoint Pollution Potential Index (T-APPI) model was constructed for evaluating the national NPS pollution potential risk in this study; it was also combined with remote sensing and geographic information system techniques for evaluation on the large scale and at 1 km2 spatial resolution. This model considers many factors contributing to the NPS pollution as the original APPI model, summarized as four indicators of the runoff, sediment production, chemical use and the people and animal load. These four indicators were analysed in detail at 1 km2 spatial resolution throughout China. The T-APPI model distinguished the four indicators into pollution source factors and transport process factors; it also took their relationship into consideration. The studied results showed that T-APPI is a credible and convenient method for NPS pollution potential risk evaluation. The results also indicated that the highest NPS pollution potential risk is distributed in the middle-southern Jiangsu province. Several other regions, including the North China Plain, Chengdu Basin Plain, Jianghan Plain, cultivated lands in Guangdong and Guangxi provinces, also showed serious NPS pollution potential. This study can provide a scientific reference for predicting the future NPS pollution risk throughout China and may be helpful for taking reasonable and effective measures for preventing and controlling NPS pollution.

  8. 48 CFR 317.7002 - Potential multi-agency and intra-agency sources.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Potential multi-agency and intra-agency sources. 317.7002 Section 317.7002 Federal Acquisition Regulations System HEALTH AND HUMAN SERVICES CONTRACTING METHODS AND CONTRACT TYPES SPECIAL CONTRACTING METHODS Multi-agency and Intra-agency Contracts 317.7002 Potential...

  9. Are research papers reporting results from nutrigenetics clinical research a potential source of biohype?

    PubMed

    Stenne, R; Hurlimann, T; Godard, Béatrice

    2012-01-01

    Nutrigenetics is a promising field, but the achievability of expected benefits is challenged by the methodological limitations that are associated with clinical research in that field. The mere existence of these limitations suggests that promises about potential outcomes may be premature. Thus, benefits claimed in scientific journal articles in which these limitations are not acknowledged might stimulate biohype. This article aims to examine whether nutrigenetics clinical research articles are a potential source of biohype. Of the 173 articles identified, 16 contained claims in which clinical applications were extrapolated from study results. The methodological limitations being incompletely acknowledged, these articles could potentially be a source of biohype.

  10. Potential sources of pesticides, PCBs, and PAHs to the atmosphere of the Great Lakes.

    PubMed

    Hafner, William D; Hites, Ronald A

    2003-09-01

    A probabilistic model called the potential source contribution function (PSCF) has been used to estimate atmospheric source regions of polycyclic aromatic hydrocarbons (PAHs), chlorinated pesticides, and polychlorinated biphenyls (PCBs) to the Great Lakes. This model allows us to map each compound's source region on a 0.5 degrees x 0.5 degrees latitude/longitude grid centered over the Great Lakes basin. PCBs primarily have urban sources, the strengths of which vary. Like PCBs, PAHs show a strong urban signature, but these compounds also seem to come from rural sites. The source regions of PAH become less distinct as the molecular weight of the compound increases. Since reactivity increases with PAH size, this diminishing trend may be an indication that atmospheric degradation plays a large role in PAH transport. The pesticides have the strongest source regions and are typically transported the farthest, often from areas distant from the Great Lakes basin.

  11. Understanding the electrical behavior of the action potential in terms of elementary electrical sources.

    PubMed

    Rodriguez-Falces, Javier

    2015-03-01

    A concept of major importance in human electrophysiology studies is the process by which activation of an excitable cell results in a rapid rise and fall of the electrical membrane potential, the so-called action potential. Hodgkin and Huxley proposed a model to explain the ionic mechanisms underlying the formation of action potentials. However, this model is unsuitably complex for teaching purposes. In addition, the Hodgkin and Huxley approach describes the shape of the action potential only in terms of ionic currents, i.e., it is unable to explain the electrical significance of the action potential or describe the electrical field arising from this source using basic concepts of electromagnetic theory. The goal of the present report was to propose a new model to describe the electrical behaviour of the action potential in terms of elementary electrical sources (in particular, dipoles). The efficacy of this model was tested through a closed-book written exam. The proposed model increased the ability of students to appreciate the distributed character of the action potential and also to recognize that this source spreads out along the fiber as function of space. In addition, the new approach allowed students to realize that the amplitude and sign of the extracellular electrical potential arising from the action potential are determined by the spatial derivative of this intracellular source. The proposed model, which incorporates intuitive graphical representations, has improved students' understanding of the electrical potentials generated by bioelectrical sources and has heightened their interest in bioelectricity. Copyright © 2015 The American Physiological Society.

  12. Optical frequency domain imaging with a rapidly swept laser in the 815-870 nm range

    NASA Astrophysics Data System (ADS)

    Lim, H.; de Boer, J. F.; Park, B. H.; Lee, E. C.; Yelin, R.; Yun, S. H.

    2006-06-01

    Optical frequency domain imaging (OFDI) in the 800-nm biological imaging window is demonstrated by using a novel wavelength-swept laser source. The laser output is tuned continuously from 815 to 870 nm at a 43.2-kHz repetition rate with 7-mW average power. Axial resolution of 10-μm in biological tissue and peak sensitivity of 96 dB are achieved. In vivo imaging of Xenopus laevis is demonstrated with an acquisition speed of 84 frames per second (512 axial lines per frame). This new imaging technique may prove useful in comprehensive retinal screening for medical diagnosis and contrast-agent-based imaging for biological investigations.

  13. Potential sources of atmospheric total gaseous mercury in the St. Lawrence River valley

    NASA Astrophysics Data System (ADS)

    Poissant, Laurier

    The potential source contribution function (PSCF) has been used to study the source-receptor relationships for total gaseous mercury (TGM) found in air collected at two sites along the St. Lawrence River valley, namely at St. Anicet and Mingan. TGM concentrations have been measured with high time-resolution analysers (Tekran instrument). The source-receptor analyses have been applied with regards to the seasonality of TGM. Median TGM concentrations are significantly less ( χ2: α=0.01) during the summertime than other periods at both sites. A total of 12 225 trajectory end-points for St. Anicet and 4480 trajectory end points for Mingan have been used to create potential source area maps. This study identifies preferred potential sources of TGM at St. Anicet during wintertime with strongest probability stretching from the Gulf of Mexico to the southern tip of Greenland. This pattern mimics, the North American anthropogenic Hg emission inventory. Furthermore, some Eurasian mercury air mass intrusions are suggested at Mingan during wintertime. The summertime period at Mingan points out some potential sources stretching from the american mid-west to the St. Lawrence River valley as well as areas around the southern tip of the Hudson Bay.

  14. Wide tuning range wavelength-swept laser with a single SOA at 1020 nm for ultrahigh resolution Fourier-domain optical coherence tomography.

    PubMed

    Lee, Sang-Won; Song, Hyun-Woo; Jung, Moon-Youn; Kim, Seung-Hwan

    2011-10-24

    In this study, we demonstrated a wide tuning range wavelength-swept laser with a single semiconductor optical amplifier (SOA) at 1020 nm for ultrahigh resolution, Fourier-domain optical coherence tomography (UHR, FD-OCT). The wavelength-swept laser was constructed with an external line-cavity based on a Littman configuration. An optical wavelength selection filter consisted of a grating, a telescope, and a polygon scanner. Before constructing the optical wavelength selection filter, we observed that the optical power, the spectrum bandwidth, and the center wavelength of the SOA were affected by the temperature of the thermoelectric (TE) cooler in the SOA mount as well as the applied current. Therefore, to obtain a wide wavelength tuning range, we adjusted the temperature of the TE cooler in the SOA mount. When the temperature in the TE cooler was 9 °C, our swept source had a tuning range of 142 nm and a full-width at half-maximum (FWHM) of 121.5 nm at 18 kHz. The measured instantaneous spectral bandwidth (δλ) is 0.085 nm, which was measured by an optical spectrum analyzer with a resolution bandwidth of 0.06 nm. This value corresponds to an imaging depth of 3.1 mm in air. Additionally, the averaged optical power of our swept source was 8.2 mW. In UHR, FD/SS-OCT using our swept laser, the measured axial resolution was 4.0 μm in air corresponding to 2.9 μm in tissue (n = 1.35). The sensitivity was measured to be 93.1 dB at a depth of 100 μm. Finally, we obtained retinal images (macular and optic disk) and a corneal image. © 2011 Optical Society of America

  15. Assessment of source probabilities for potential tsunamis affecting the U.S. Atlantic coast

    USGS Publications Warehouse

    Geist, E.L.; Parsons, T.

    2009-01-01

    Estimating the likelihood of tsunamis occurring along the U.S. Atlantic coast critically depends on knowledge of tsunami source probability. We review available information on both earthquake and landslide probabilities from potential sources that could generate local and transoceanic tsunamis. Estimating source probability includes defining both size and recurrence distributions for earthquakes and landslides. For the former distribution, source sizes are often distributed according to a truncated or tapered power-law relationship. For the latter distribution, sources are often assumed to occur in time according to a Poisson process, simplifying the way tsunami probabilities from individual sources can be aggregated. For the U.S. Atlantic coast, earthquake tsunami sources primarily occur at transoceanic distances along plate boundary faults. Probabilities for these sources are constrained from previous statistical studies of global seismicity for similar plate boundary types. In contrast, there is presently little information constraining landslide probabilities that may generate local tsunamis. Though there is significant uncertainty in tsunami source probabilities for the Atlantic, results from this study yield a comparative analysis of tsunami source recurrence rates that can form the basis for future probabilistic analyses.

  16. French Brittany macroalgae screening: composition and methane potential for potential alternative sources of energy and products.

    PubMed

    Jard, G; Marfaing, H; Carrère, H; Delgenes, J P; Steyer, J P; Dumas, C

    2013-09-01

    Macroalgae are biomass resources that represent a valuable feedstock to be used entirely for human consumption or for food additives after some extractions (mainly colloids) and/or for energy production. In order to better develop the algal sector, it is important to determine the capacity of macroalgae to produce these added-values molecules for food and/or for energy industries on the basis of their biochemical characteristics. In this study, ten macroalgae obtained from French Brittany coasts (France) were selected. The global biochemical composition (proteins, lipids, carbohydrates, fibers), the presence and characteristics of added-values molecules (alginates, polyphenols) and the biochemical methane potential of these algae were determined. Regarding its biochemical composition, Palmaria palmata is interesting for food (rich in nutrients) and for anaerobic digestion (0.279 LCH4/gVS). Saccharina latissima could be used for alginate extraction (242 g/kgTS, ratio between mannuronic and guluronic acid M/G=1.4) and Sargassum muticum for polyphenol extraction (19.8 g/kgTS). Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Demonstration of a rapidly-swept external cavity quantum cascade laser for atmospheric sensing applications

    SciTech Connect

    Brumfield, Brian E.; Taubman, Matthew S.; Phillips, Mark C.; Suter, Jonathan D.

    2016-07-01

    The application of quantum cascade lasers (QCLs) in atmospheric science for trace detection of gases has been demonstrated using sensors in point or remote sensing configurations. Many of these systems utilize single narrowly-tunable (~10 cm-1) distributed feedback (DFB-) QCLs that limit simultaneous detection to a restricted number of small chemical species like H2O or N2O. The narrow wavelength range of DFB-QCLs precludes accurate quantification of large chemical species with broad rotationally-unresolved vibrational spectra, such as volatile organic compounds, that play an important role in the chemistry of the atmosphere. External-cavity (EC-) QCL systems are available that offer tuning ranges >100 cm-1, making them excellent IR sources for measuring multiple small and large chemical species in the atmosphere. While the broad wavelength coverage afforded by an EC system enables measurements of large chemical species, most commercial systems can only be swept over their entire wavelength range at less than 10 Hz. This prohibits broadband simultaneous measurements of multiple chemicals in plumes from natural or industrial sources where turbulence and/or chemical reactivity are resulting in rapid changes in chemical composition on sub-1s timescales. At Pacific Northwest National Laboratory we have developed rapidly-swept EC-QCL technology that acquires broadband absorption spectra (~100 cm-1) on ms timescales. The spectral resolution of this system has enabled simultaneous measurement of narrow rotationally-resolved atmospherically-broadened lines from small chemical species, while offering the broad tuning range needed to measure broadband spectral features from multiple large chemical species. In this talk the application of this technology for open-path atmospheric measurements will be discussed based on results from laboratory measurements with simulated plumes of chemicals. The performance offered by the system for simultaneous detection of multiple chemical

  18. Transition Studies on a Swept-Wing Model

    NASA Technical Reports Server (NTRS)

    Saric, William S.

    1996-01-01

    The present investigation contributes to the understanding of boundary-layer stability and transition by providing detailed measurements of carefully-produced stationary crossflow vortices. It is clear that a successful prediction of transition in swept-wing flows must include an understanding of the detailed physics involved. Receptivity and nonlinear effects must not be ignored. Linear stability theory correctly predicts the expected wavelengths and mode shapes for stationary crossflow, but fails to predict the growth rates, even for low amplitudes. As new computational and analytical methods are developed to deal with three-dimensional boundary layers, the data provided by this experiment will serve as a useful benchmark for comparison.

  19. Fermions in Optical Lattices Swept across Feshbach Resonances

    SciTech Connect

    Diener, Roberto B.; Ho, T.-L.

    2006-01-13

    We point out that the recent experiments at ETH on fermions in optical lattices, where a band insulator evolves continuously into states occupying many bands as the system is swept adiabatically across Feshbach resonance, have implications on a wide range of fundamental issues in condensed matter. We derive the effective Hamiltonian of these systems, obtain expressions for their energies and band populations, and point out the increasing quantum entanglement of the ground state during the adiabatic sweep. Our results also explain why only specific regions in k space can be populated after the sweep as found at ETH.

  20. Swept frequency technique for dispersion measurement of microstrip lines

    NASA Technical Reports Server (NTRS)

    Lee, Richard Q.

    1987-01-01

    Microstrip lines used in microwave integrated circuits are dispersive. Because a microstrip line is an open structure, the dispersion can not be derived with pure TEM, TE, or TM mode analysis. Dispersion analysis has commonly been done using a spectral domain approach, and dispersion measurement has been made with high Q microstrip ring resonators. Since the dispersion of a microstrip line is fully characterized by the frequency dependent phase velocity of the line, dispersion measurement of microstrip lines requires the measurement of the line wavelength as a function of frequency. In this paper, a swept frequency technique for dispersion measurement is described.

  1. Swept-Wing Receptivity Studies Using Distributed Roughness

    NASA Technical Reports Server (NTRS)

    Saric, William S.

    1999-01-01

    Transition to turbulence in swept-wing flows has resisted correlation with linear theory because of its sensitivity to freestream conditions and 3-D roughness and because one of the principal instability modes quickly 'becomes nonlinear. In the face of such a formidable problem, two rather long-term fundamental efforts have been underway at DLR Gottinberg and Arizona State University that address swept-wing transition. These efforts have been recently reviewed by Bippes (1997) and Reibert and Saric (1997). Thus, the present work is a continuation of a series of studies on swept-wing boundary layers which have led to a better understanding of the transition process. In particular, we have taken advantage of the sensitivity to 3-D roughness and the modal nature of the instability in order to propose a particular control strategy. Complementing the two aforementioned reviews, general reviews of the swept-wing transition problem are found in Arnal (1997) and Kachanov (1996). Other recent reviews include Reshotko (t997), Crouch (1997), and Herbert (1997a,b). The failure of linear theory is discussed in Reed et al. (1996). The historical work is found in Reed and Sar-ic (1989). The basic idea is that the combination of sweep and chordwise pressure gradient within the boundary layer creates a velocity component perpendicular to the inviscid streamline. This crossflow profile is inflectional and exhibits both traveling and stationary unstable waves called crossflow vortices that are (approximately) aligned along the inviscid streamlines. Under conditions of low freestream turbulence levels, the dominant crossflow wave is stationary (Reibert and Saric t997) while moderate to high turbulence levels initiate dominant traveling waves (Dehle and Bippes 1996; Bippes 1997). 'Me mechanism is relatively insensitive to sound and 2-D surface roughness (Radeztsky et al. 1993) but very sensitive to 3-D roughness near the attachment line. We concentrate our work on low

  2. Suction laminarization of highly swept supersonic laminar flow control wings

    NASA Technical Reports Server (NTRS)

    Pfenninger, W.; Vemuru, C. S.

    1988-01-01

    An evaluation is made of a suction-based method for the laminarization of highly-swept supersonic wings at cruise Mach numbers in the 2.0-2.5 range, in the interest of the reduction of wave drag due to lift. The laminar boundary layer development, as well as Tollmien-Schlichting and crossflow instabilities, have been analyzed for the case of an X66 supercritical airfoil at 60 and 72 deg sweep, for Mach numbers of 1.56 and 2.52, respectively. Strong suction is found to be needed at the front part of the upper surface and both the upper and lower rear pressure-rise areas.

  3. Transition Flight Experiments on a Swept Wing with Suction

    NASA Technical Reports Server (NTRS)

    Maddalon, D. V.; Collier, F. S., Jr.; Montoya, L. C.; Putnam, R. J.

    1989-01-01

    Flight boundary-layer transition experiments were conducted on a 30 degree swept wing with a perforated leading-edge suction panel. The transition location on the panel was changed by systematically varying the location and amount of suction. Transition from laminar to turbulent flow was due to leading-edge turbulence contamination or crossflow disturbance growth and/or Tollmien-Schlichting disturbance growth, depending on flight condition and suction variation. Amplification factor correlations with transition location were made for various suction configurations using a state-of-the-art linear stability theory which accounts for body and streamline curvature and compressibility.

  4. Transition flight experiments on a swept wing with suction

    NASA Technical Reports Server (NTRS)

    Maddalon, D. V.; Collier, F. S., Jr.; Montoya, L. C.; Putnam, R. J.

    1989-01-01

    Flight boundary-layer transition experiments were conducted on a 30-degree swept wing with a perforated leading-edge suction panel. The transition location on the panel was changed by systematically varying the location and amount of suction. Transition from laminar to turbulent flow was due to leading-edge turbulence contamination or crossflow disturbance growth and/or Tollmien-Schlichting disturbance growth, depending on flight condition and suction variation. Amplification factor correlations with transition location were made for various suction configurations using a state-of-the-art linear stability theory which accounts for body and streamline curvature and compressibility.

  5. Transition flight experiments on a swept wing with suction

    NASA Technical Reports Server (NTRS)

    Maddalon, D. V.; Collier, F. S., Jr.; Montoya, L. C.; Putnam, R. J.

    1989-01-01

    Flight boundary-layer transition experiments were conducted on a 30-degree swept wing with a perforated leading-edge suction panel. The transition location on the panel was changed by systematically varying the location and amount of suction. Transition from laminar to turbulent flow was due to leading-edge turbulence contamination or crossflow disturbance growth and/or Tollmien-Schlichting disturbance growth, depending on flight condition and suction variation. Amplification factor correlations with transition location were made for various suction configurations using a state-of-the-art linear stability theory which accounts for body and streamline curvature and compressibility.

  6. Database of potential sources for earthquakes larger than magnitude 6 in Northern California

    USGS Publications Warehouse

    ,

    1996-01-01

    The Northern California Earthquake Potential (NCEP) working group, composed of many contributors and reviewers in industry, academia and government, has pooled its collective expertise and knowledge of regional tectonics to identify potential sources of large earthquakes in northern California. We have created a map and database of active faults, both surficial and buried, that forms the basis for the northern California portion of the national map of probabilistic seismic hazard. The database contains 62 potential sources, including fault segments and areally distributed zones. The working group has integrated constraints from broadly based plate tectonic and VLBI models with local geologic slip rates, geodetic strain rate, and microseismicity. Our earthquake source database derives from a scientific consensus that accounts for conflict in the diverse data. Our preliminary product, as described in this report brings to light many gaps in the data, including a need for better information on the proportion of deformation in fault systems that is aseismic.

  7. Dipole source analysis for readiness potential and field using simultaneously measured EEG and MEG signals.

    PubMed

    Mideksa, K G; Hellriegel, H; Hoogenboom, N; Krause, H; Schnitzler, A; Deuschl, G; Raethjen, J; Heute, U; Muthuraman, M

    2013-01-01

    Various source localization techniques have indicated the generators of each identifiable component of movement-related cortical potentials, since the discovery of the surface negative potential prior to self-paced movement by Kornhuber and Decke. Readiness potentials and fields preceding self-paced finger movements were recorded simultaneously using multichannel electroencephalography (EEG) and magnetoencephalography (MEG) from five healthy subjects. The cortical areas involved in this paradigm are the supplementary motor area (SMA) (bilateral), pre-SMA (bilateral), and contralateral motor area of the moving finger. This hypothesis is tested in this paper using the dipole source analysis independently for only EEG, only MEG, and both combined. To localize the sources, the forward problem is first solved by using the boundary-element method for realistic head models and by using a locally-fitted-sphere approach for spherical head models consisting of a set of connected volumes, typically representing the scalp, skull, and brain. In the source reconstruction it is to be expected that EEG predominantly localizes radially oriented sources while MEG localizes tangential sources at the desired region of the cortex. The effect of MEG on EEG is also observed when analyzing both combined data. When comparing the two head models, the spherical and the realistic head models showed similar results. The significant points for this study are comparing the source analysis between the two modalities (EEG and MEG) so as to assure that EEG is sensitive to mostly radially orientated sources while MEG is only sensitive to only tangential sources, and comparing the spherical and individual head models.

  8. Stem/progenitor cells: a potential source of retina-specific cells for retinal repair.

    PubMed

    Bi, Yong-Yan; Feng, Dong-Fu; Pan, Dong-Chao

    2009-11-01

    Retinal injury generally results in permanent visual disturbance or even blindness. Any effort to restore vision in such condition would require replacement of the highly specialized retinal cells. Stem/progenitor cells have been proposed as a potential source of new retina-specific cells to replace those lost due to retina injury. Evidence to date suggests that continued development of stem cell therapies may ultimately lead to viable treatment options for retina injury. A wide range of stem/progenitor cells from various sources is currently being investigated for the treatment of retinal injury. This article reviews the recent achievements about stem/progenitor cell source for retinal repair.

  9. Source depth estimation of self-potential anomalies by spectral methods

    NASA Astrophysics Data System (ADS)

    Di Maio, Rosa; Piegari, Ester; Rani, Payal

    2017-01-01

    Spectral analysis of the self-potential (SP) field for geometrically simple anomalous bodies is studied. In particular, three spectral techniques, i.e. Periodogram (PM), Multi Taper (MTM) and Maximum Entropy (MEM) methods, are proposed to derive the depth of the anomalous bodies. An extensive numerical analysis at varying the source parameters outlines that MEM is successful in determining the source depth with a percent error less than 5%. The application of the proposed spectral approach to the interpretation of field datasets has provided depth estimations of the SP anomaly sources in very good agreement with those obtained by other numerical methods.

  10. Non-Edible Plants as an Attractive Source of Compounds with Chemopreventive Potential

    PubMed Central

    Ji, Seungwon; Orlikova, Barbora; Diederich, Marc

    2014-01-01

    Cancer remains a lethal disease, and many scientists are currently trying to develop more effective therapies. Natural compounds are potential sources of anti-cancer therapies and are obtained from diverse sources including marine organisms, microorganisms and plants. In this paper, we evaluated natural compounds from non-edible plant sources, which is a neglected area of research despite the promising future of these compounds. In addition, we assessed the function and mechanism of action of these compounds in relation to cancer chemoprevention. PMID:25337566

  11. The versatile biopolymer chitosan: potential sources, evaluation of extraction methods and applications.

    PubMed

    Kaur, Surinder; Dhillon, Gurpreet Singh

    2014-05-01

    Among the biopolymers, chitin and its derivative chitosan (CTS) have been receiving increasing attention. Both are composed of randomly distributed β-(1-4)-linked d-glucosamine and N-acetyl glucosamine units. On commercial scale, CTS is mainly obtained from the crustacean shells. The chemical methods employed for extraction of CTS from crustacean shells are laden with many disadvantages. Waste fungal biomass represents a potential biological source of CTS, in fact with superior physico-chemical properties, such as high degree of deacetylation, low molecular weight, devoid of protein contamination and high bioactivity. Researchers around the globe are attempting to commercialize CTS production and extraction from fungal sources. Fungi are promising and environmentally benign source of CTS and they have the potential to completely replace crustacean-derived CTS. Waste fungal biomass resulting from various pharmaceutical and biotechnological industries is grown on inexpensive agro-industrial wastes and its by-products are a rich and inexpensive source of CTS. CTS is emerging as an important natural polymer having broad range of applications in different fields. In this context, the present review discusses the potential sources of CTS and their advantages and disadvantages. This review also deals with potential applications of CTS in different fields. Finally, the various attributes of CTS sought in different applications are discussed.

  12. Levels, seasonal patterns, and potential sources of organochlorine pesticides in the urban atmosphere of Beijing, China.

    PubMed

    Zhang, Lifei; Huang, Yeru; Dong, Liang; Shi, Shuangxin; Zhou, Li; Zhang, Ting; Mi, Fangzhuo; Zeng, Liangzi; Shao, Dingding

    2011-08-01

    Air samples collected monthly on the roof of a building in Beijing were analyzed for the levels, seasonal patterns, and potential sources of organochlorine pesticides (OCPs). A high-volume air sampler with polyurethane foam and quartz fiber filters was used to collect monthly samples from November 2005 to April 2009. Hexachlorobenzene (HCB) and DDT isomers were the most abundant organochlorinated pesticides in the Beijing atmosphere. Higher OCP concentrations were generally found in summer, except for HCB. Coal combustion, waste incineration, and fuel combustion were assumed to be the potential HCB emission sources. Significant input of either of these OCPs during our study period was considered very unlikely.

  13. Potential and challenges of upgrading the Advanced Photon Source to an Energy Recovery Linac.

    SciTech Connect

    Borland, M.; Decker, G.; Nassiri, A.; Sun, Y.-e; White, M.; Accelerator Systems Division

    2007-01-01

    The Advanced Photon Source (APS) is a third generation synchrotron radiation source operating at 7 GeV that has been in operation for over 10 years. In that time, the emittance has been improved from 8 nm to the present value of 3.1 nm, which is close to the practical minimum. Recently, APS undertook an intensive exploration of potential upgrades, including options for a replacement storage ring or Energy Recovery Linac (ERL) injector. Our conclusion was that only the ERL would provide a dramatically new capability. This paper discusses the potential performance available from an ERL upgrade to the APS and reviews the challenges of delivering this performance.

  14. Principles for transformation of scalp EEG from potential field into source distribution.

    PubMed

    Hjorth, B

    1991-10-01

    Tracings representing simultaneously recorded values of EEG potentials from different positions on the scalp surface describe how the instantaneous potential field over the scalp surface changes with time. Each instantaneous distribution of potential can be seen as resulting from spatial integration of primary components into the potential field. These components may be derived by means of the reverse procedure: subjecting the data from the potential field to spatial differentiation as provided by the Laplacian source operator. The result is a "deblurred," i.e., a more differentiated, distribution of source components hypothetically associated with the generators of the potential field. The Laplacian source operator can be implemented as a linear combination of the instantaneous potential values, either by means of very simple electronic circuitry or in a computer. The linear combination is a standard operation in matrix algebra and is widely applied in signal processing. The formalism of matrix algebra simplifies a precise evaluation of the method in relation to conventional derivation techniques and provides further methods for analysis of the EEG data.

  15. Effect of Substrate Potential on Plasma Parameters of Magnetic Multicusp Plasma Source

    NASA Astrophysics Data System (ADS)

    Ueda, Yoshio; Goto, Masahiro

    1998-06-01

    The effect of substrate potential on plasmas produced in a magnetic multicusp plasma source has been studied experimentally. Plasma parameters such as electron temperature and plasma potential are estimated from electron energy distribution function numerically calculated from probe current-voltage characteristics. For a substrate potential of -150 V with respect to the source chamber, which is much lower than substrate floating potentials, the plasma parameters are not affected by the application of the potential. However, for the case where the substrate is shorted with the source chamber, the high energy component of electrons significantly decreases in comparison with the floating case leading to the reduction of electron temperature. In this case, plasma potential is positive with respect to the substrate to suppress electron loss but its absolute value is only of the order of electron temperature in eV, which is much lower than the potential between the plasma and the substrate in the floating case. This discharge mode could be advantageous in significantly reducing the ion impact energy to the substrate plate.

  16. Discrete-Roughness-Element-Enhanced Swept-Wing Natural Laminar Flow at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Malik, Mujeeb; Liao, Wei; Li, Fei; Choudhari, Meelan

    2015-01-01

    Nonlinear parabolized stability equations and secondary-instability analyses are used to provide a computational assessment of the potential use of the discrete-roughness-element technology for extending swept-wing natural laminar flow at chord Reynolds numbers relevant to transport aircraft. Computations performed for the boundary layer on a natural-laminar-flow airfoil with a leading-edge sweep angle of 34.6 deg, freestream Mach number of 0.75, and chord Reynolds numbers of 17 × 10(exp 6), 24 × 10(exp 6), and 30 × 10(exp 6) suggest that discrete roughness elements could delay laminar-turbulent transition by about 20% when transition is caused by stationary crossflow disturbances. Computations show that the introduction of small-wavelength stationary crossflow disturbances (i.e., discrete roughness element) also suppresses the growth of most amplified traveling crossflow disturbances.

  17. DRE-Enhanced Swept-Wing Natural Laminar Flow at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Malik, Mujeeb; Liao, Wei; Li, Fe; Choudhari, Meelan

    2013-01-01

    Nonlinear parabolized stability equations and secondary instability analyses are used to provide a computational assessment of the potential use of the discrete roughness elements (DRE) technology for extending swept-wing natural laminar flow at chord Reynolds numbers relevant to transport aircraft. Computations performed for the boundary layer on a natural laminar flow airfoil with a leading-edge sweep angle of 34.6deg, free-stream Mach number of 0.75 and chord Reynolds numbers of 17 x 10(exp 6), 24 x 10(exp 6) and 30 x 10(exp 6) suggest that DRE could delay laminar-turbulent transition by about 20% when transition is caused by stationary crossflow disturbances. Computations show that the introduction of small wavelength stationary crossflow disturbances (i.e., DRE) also suppresses the growth of most amplified traveling crossflow disturbances.

  18. Applications of swept-frequency acoustic interferometer for nonintrusive detection and identification of chemical warfare compounds

    SciTech Connect

    Sinha, D.N.; Springer, K.; Han, W.; Lizon, D.; Kogan, S.

    1997-12-01

    Swept-Frequency Acoustic Interferometry (SFAI) is a nonintrusive liquid characterization technique developed specifically for detecting and identifying chemical warfare (CW) compounds inside sealed munitions. The SFAI technique can rapidly (less than 20 seconds) and accurately determine sound speed and sound attenuation of a liquid inside a container over a wide frequency range (1 kHz-15 MHz). From the frequency-dependent sound attenuation measurement, liquid density is determined. These three physical properties are used to uniquely identify the CW compounds. In addition, various chemical relaxation processes in liquids and particle size distribution in emulsions can also be determined from the frequency-dependent attenuation measurement. The SFAI instrument is battery-operated and highly portable (< 6 lb.). The instrument has many potential application in industry ranging from sensitive detection (ppm level) of contamination to process control. The theory of the technique will be described and examples of several chemical industry applications will be presented.

  19. An efficient method for computing unsteady transonic aerodynamics of swept wings with control surfaces

    NASA Technical Reports Server (NTRS)

    Liu, D. D.; Kao, Y. F.; Fung, K. Y.

    1989-01-01

    A transonic equivalent strip (TES) method was further developed for unsteady flow computations of arbitrary wing planforms. The TES method consists of two consecutive correction steps to a given nonlinear code such as LTRAN2; namely, the chordwise mean flow correction and the spanwise phase correction. The computation procedure requires direct pressure input from other computed or measured data. Otherwise, it does not require airfoil shape or grid generation for given planforms. To validate the computed results, four swept wings of various aspect ratios, including those with control surfaces, are selected as computational examples. Overall trends in unsteady pressures are established with those obtained by XTRAN3S codes, Isogai's full potential code and measured data by NLR and RAE. In comparison with these methods, the TES has achieved considerable saving in computer time and reasonable accuracy which suggests immediate industrial applications.

  20. Comparison of calculated and measured pressures on straight and swept-tip model rotor blades

    NASA Technical Reports Server (NTRS)

    Tauber, M. E.; Chang, I. C.; Caughey, D. A.; Phillipe, J. J.

    1983-01-01

    Using the quasi-steady, full potential code, ROT22, pressures were calculated on straight and swept tip model helicopter rotor blades at advance ratios of 0.40 and 0.45, and into the transonic tip speed range. The calculated pressures were compared with values measured in the tip regions of the model blades. Good agreement was found over a wide range of azimuth angles when the shocks on the blade were not too strong. However, strong shocks persisted longer than predicted by ROT22 when the blade was in the second quadrant. Since the unsteady flow effects present at high advance ratios primarily affect shock waves, the underprediction of shock strengths is attributed to the simplifying, quasi-steady, assumption made in ROT22.