1. Articles from adrian bradu

    1-24 of 102 1 2 3 4 5 »
    1. Direct en-face, speckle-reduced images using angular-compounded Master-Slave optical coherence tomography

      Direct en-face, speckle-reduced images using angular-compounded Master-Slave optical coherence tomography

      In this paper, an angular compounding method to achieve speckle contrast reduction in optical coherence tomography (OCT) imaging is explored in detail. The angular compounding approach involves collecting multiple images at different angles of incidence, registering the images to correct for induced distortions, and then incoherently summing the images to reduce speckle. The method was experimentally demonstrated with a spectrometer-based Master-Slave enhanced OCT instrument capable of directly generating en-face images. We have investigated the impact of the angular range and number of averaged frames on the degree of speckle artefact reduction, as well as the effect on image resolution and ...

      Read Full Article
    2. En-face optical coherence tomography/fluorescence endomicroscopy for minimally invasive imaging using a robotic scanner

      En-face optical coherence tomography/fluorescence endomicroscopy for minimally invasive imaging using a robotic scanner

      We report a compact rigid instrument capable of delivering en-face optical coherence tomography (OCT) images alongside (epi)-fluorescence endomicroscopy (FEM) images by means of a robotic scanning device. Two working imaging channels are included: one for a one-dimensional scanning, forward-viewing OCT probe and another for a fiber bundle used for the FEM system. The robotic scanning system provides the second axis of scanning for the OCT channel while allowing the field of view (FoV) of the FEM channel to be increased by mosaicking. The OCT channel has resolutions of 25  /  60  μm (axial/lateral) and can provide en-face images with ...

      Read Full Article
    3. Quantitative assessment of rat bone regeneration using complex master-slave optical coherence tomography

      Quantitative assessment of rat bone regeneration using complex master-slave optical coherence tomography

      ackground: The need for hard and soft tissues in oral implantology determined the development of methods and techniques to increase bone volume and their quality with different alternative materials used as substituents of patient’s natural bone. In addition, laser radiation can be used to accelerate the repair of fractures and to produce an increased volume of formed callus, as well as an increased bone mineral density. Methods: The aim of this work is to evaluate the capability of an in-house developed multimodal complex master slave (CMS) enhanced swept source (SS) optical coherence tomography (OCT) imaging instrument to analyze the ...

      Read Full Article
    4. Optical Coherence Tomography Investigations and Modeling of the Sintering of Ceramic Crowns

      Optical Coherence Tomography Investigations and Modeling of the Sintering of Ceramic Crowns

      Dental prostheses are sintered in ovens that sometimes suffer from a loss of calibration. This can lead to variations of the sintering temperature outside the range recommended by the manufacturer. Stress and even fractures in dental ceramics may occur, and this leads to the necessity to rebuild the dental construct. The aim of this work is to monitor the quality of sintering processes using an established biomedical imaging technique—optical coherence tomography (OCT). Conventional current procedures imply the fabrication of supplemental samples that add to the expenses and are only evaluated visually. To our knowledge, we were the first to ...

      Read Full Article
    5. Down-conversion en-face optical coherence tomography

      Down-conversion en-face optical coherence tomography

      We present an optical coherence tomography (OCT) method that can deliver an en-face OCT image from a sample in real-time, irrespective of the tuning speed of the swept source. The method, based on the master slave interferometry technique, implements a coherence gate principle by requiring that the optical path difference (OPD) between the arms of an imaging interferometer is the same with the OPD in an interrogating interferometer. In this way, a real-time en-face OCT image can originate from a depth in the sample placed in the imaging interferometer, selected by actuating on the OPD in the interrogating interferometer, while ...

      Read Full Article
    6. Complex master-slave for long axial range swept-source optical coherence tomography

      Complex master-slave for long axial range swept-source optical coherence tomography

      Using complex master-slave interferometry, we demonstrate extended axial range optical coherence tomography for two commercially available swept sources, well beyond the limit imposed by their k -clocks. This is achieved without k -domain re-sampling and without engaging any additional Mach-Zehnder interferometer providing a k -clock signal to the digitizer. An axial imaging range exceeding 17 mm with an attenuation of less than 30 dB is reported using two commercially available swept sources operating at 1050 nm and a 100 kHz repetition rate. This procedure has more than trebled the range achievable using the k -clock signal provided by the manufacturers ...

      Read Full Article
    7. Recovering distance information in spectral domain interferometry

      Recovering distance information in spectral domain interferometry

      This work evaluates the performance of the Complex Master Slave (CMS) method, that processes the spectra at the interferometer output of a spectral domain interferometry device without involving Fourier transforms (FT) after data acquisition. Reliability and performance of CMS are compared side by side with the conventional method based on FT, phase calibration with dispersion compensation (PCDC). We demonstrate that both methods provide similar results in terms of resolution and sensitivity drop-off. The mathematical operations required to produce CMS results are highly parallelizable, allowing real-time, simultaneous delivery of data from several points of different optical path differences in the interferometer ...

      Read Full Article
    8. Group refractive index and group velocity dispersion measurement by complex master slave interferometry

      Group refractive index and group velocity dispersion measurement by complex master slave interferometry

      This paper demonstrates that the complex master slave interferometry ( CMSI ) method used in spectral domain interferometry ( SDI ) can efficiently be used for accurate refractive index and group velocity dispersion measurements of optically transparent samples. For the first time, we demonstrate the relevance of the phase information delivered by CMSI for dispersion evaluations with no need to linearize data. The technique proposed here has been used to accurately measure the group refractive index and the group velocity dispersion of a strong dispersive sample (SF6 glass), and a weak dispersive one (distilled water). The robustness of the technique is demonstrated through the ...

      Read Full Article
    9. Assessment of Ductile, Brittle, and Fatigue Fractures of Metals Using Optical Coherence Tomography

      Assessment of Ductile, Brittle, and Fatigue Fractures of Metals Using Optical Coherence Tomography

      ome forensic in situ investigations, such as those needed in transportation (for aviation, maritime, road, or rail accidents) or for parts working under harsh conditions (e.g., pipes or turbines) would benefit from a method/technique that distinguishes ductile from brittle fractures of metals—as material defects are one of the potential causes of incidents. Nowadays, the gold standard in material studies is represented by scanning electron microscopy (SEM). However, SEM instruments are large, expensive, time-consuming, and lab-based; hence, in situ measurements are impossible. To tackle these issues, we propose as an alternative, lower-cost, sufficiently high-resolution technique, Optical Coherence Tomography ...

      Read Full Article
    10. PhD Scholarship in Multi-Spectral Photo-Acoustic Imaging University of Kent

      PhD Scholarship in Multi-Spectral Photo-Acoustic Imaging University of Kent

      School of Physical Sciences, Applied Optics Group Qualification type: PhD Location: Kent Funding for: UK Students, EU Students Funding amount: Standard UK Research Councils' rate (currently £14,296; to cover living costs) + tuition fees at the Home/EU rate (currently £4,121 per annum). Hours: Full Time Placed on: 19th December 2017 Closes: 6th February 2018 Supervisor: Adrian Bradu A funded PhD position is available in the field of Biomedical Imaging. Photo-acoustic (PA) imaging is a hot topic in the biomedical imaging field. It can offer not only structural but also functional information of biological tissues with excellent resolution and ...

      Read Full Article
    11. Passive optical module for polarization-sensitive optical coherence tomography systems

      Passive optical module for polarization-sensitive optical coherence tomography systems

      The paper presents a proof-of-concept polarization-sensitive swept source optical coherence tomography (OCT) system that performs measurements of the retardance as well as of the axis orientation of a linear birefringent sample. The system performs single input state polarization-sensitive OCT and employs an optical module based on optically passive elements such as two beam displacers and a Faraday rotator. Our implementation of the PS-OCT system does not need any calibration step to compensate for the polarimetric effect of the fibers, and its operation does not require a balanced polarization-diversity detector. The optical module allows measurement of the two polarization properties of ...

      Read Full Article
    12. Effects of Temperature Variations during Sintering of Metal Ceramic Tooth Prostheses Investigated Non-Destructively with Optical Coherence Tomography

      Effects of Temperature Variations during Sintering of Metal Ceramic Tooth Prostheses Investigated Non-Destructively with Optical Coherence Tomography

      Calibration loss of ovens used in sintering metal ceramic prostheses leads to stress and cracks in the material of the prostheses fabricated, and ultimately to failure of the dental treatment. Periodic calibration may not be sufficient to prevent such consequences. Evaluation methods based on firing supplemental control samples are subjective, time-consuming, and rely entirely on the technician’s skills. The aim of this study was to propose an alternative procedure for such evaluations. Fifty prostheses were sintered in a ceramic oven at a temperature lower, equal to or larger than the temperature prescribed by the manufacturer. A non-destructive imaging method ...

      Read Full Article
    13. Polarization-sensitive plug-in optical module for a Fourier-domain optical coherence tomography system

      Polarization-sensitive plug-in optical module for a Fourier-domain optical coherence tomography system

      In this manuscript we communicate a theoretical study on a plug-in optical module to be used within a Fourier-domain optical coherence tomography system (FD-OCT). The module can be inserted between the object under investigation and any single-mode fiber based FD-OCT imaging instrument, enabling the latter to carry out polarization measurements on the former. Similarly to our previous communication1 this is an active module which requires two sequential steps to perform a polarization measurement. Alternating between the two steps is achieved by changing the value of the retardance produced by two electro-optic polarization modulators, which together behave as a polarization state ...

      Read Full Article
    14. Master/slave: the ideal tool for coherence revival based optical coherence tomography imaging instruments

      Master/slave: the ideal tool for coherence revival based optical coherence tomography imaging instruments

      In this communication, we present the utility of the Master/Slave (MS) method in combination with the coherence revival technique to obtain full axial range Optical Coherence Tomography (OCT) cross-section images. The MS method eliminates two major drawbacks of the conventional Fourier Transformed (FT) based OCT technology when applied to the coherence revival technique: the need of data re-sampling as well as the need to compensate for unbalanced dispersion in the interferometer.

      Read Full Article
    15. Master/slave based optical coherence tomography for in-vivo, real-time, long axial imaging range of the anterior segment

      Master/slave based optical coherence tomography for in-vivo, real-time, long axial imaging range of the anterior segment

      In this report, we demonstrate that in a coherence revival (CR) based swept source optical coherence tomography (SSOCT) set-up, real-time cross-sectional long-range images can be produced via the Master Slave (MS) method. 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 ...

      Read Full Article
    16. Gabor fusion master slave optical coherence tomography

      Gabor fusion master slave optical coherence tomography

      This paper describes the application of the Gabor filtering protocol to a Master/Slave (MS) swept source optical coherence tomography (SS)-OCT system at 1300 nm. The MS-OCT system delivers information from selected depths, a property that allows operation similar to that of a time domain OCT system, where dynamic focusing is possible. The Gabor filtering processing following collection of multiple data from different focus positions is different from that utilized by a conventional swept source OCT system using a Fast Fourier transform (FFT) to produce an A-scan. Instead of selecting the bright parts of A-scans for each focus position ...

      Read Full Article
    17. Master/slave optical coherence tomography imaging of eyelid basal cell carcinoma

      Master/slave optical coherence tomography imaging of eyelid basal cell carcinoma

      Optical coherence tomography (OCT) is fast emerging as an additional non-interventional modality for skin tumor detection and diagnosis. A master/slave flying spot OCT configuration was assembled to detect periocular basal cell carcinomas (BCC). A swept source at 1300 nm and sweeping speed of 50 kHz were used. A three-step process was involved. First, 384 channeled spectra using a mirror were stored for 384 optical path differences at the master stage. Then, the stored channeled spectra (masks) were correlated with the channeled spectrum from the BCC tissue to produce 384 en face OCT images ( 200 × 200 pixels) for the optical ...

      Read Full Article
    18. Acousto-optic tunable filter for dispersion characterization of time-domain optical coherence tomography systems

      Acousto-optic tunable filter for dispersion characterization of time-domain optical coherence tomography systems

      A broadband supercontinuum light source with an acousto-optic tunable filter (AOTF) are used to characterize dispersion in two time-domain OCT systems, at 850 and 1300 nm. The filter is designed to sweep across two spectral ranges, which are restricted here from 800 to 900 nm and from 1200 to 1500 nm, respectively. Dispersion compensation for 850 nm was achieved with a spectral delay line. Dispersion compensation for 1300 nm was achieved using BK 7 rod glasses in the reference arm. The AOTF allows evaluation of dispersion in under as well as overcompensated systems. The AOTF method is based on wavelength ...

      Read Full Article
    19. Method and apparatus for processing the signal in spectral domain interferometry and method and apparatus for spectral domain optical coherence tomography

      Method and apparatus for processing the signal in spectral domain interferometry and method and apparatus for spectral domain optical coherence tomography

      Real-time depth measurements in sensing in spectral domain interferometry and for en-face and cross section image production in optical coherence tomography can operate without any need to linearize the data to maximize the output signal and achieve the theoretical depth resolution. Novel interferometry is disclosed, where parameters of a master interferometer dictate the results in a slave interferometer. The master interferometer can be the same measuring interferometer used in two stages. The master interferometer parameters are at least optical path difference (OPD) or the speed of variation of the OPD in the master interferometer. Coherence gated data are produced from ...

      Read Full Article
    20. Master/slave interferometry – ideal tool for coherence revival swept source optical coherence tomography

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

      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 ...

      Read Full Article
    21. Optical module to extend any Fourier-domain optical coherence tomography system into a polarisation-sensitive system

      Optical module to extend any Fourier-domain optical coherence tomography system into a polarisation-sensitive system

      This article presents a theoretical study on an optical module (OM) that can be inserted between an object under investigation and a Fourier-domain optical coherence tomography system, transforming the latter into a polarisation-sensitive optical coherence tomography optical coherence tomography (OCT) system. The module consists of two electro-optic modulators, a Faraday rotator, a linear polariser and a quarter-wave plate. A detailed description on how the module can be used to extract both the net retardance and the fast axis orientation of a linear birefringent sample is presented. This is achieved by taking two sequential measurements for different values of retardance produced ...

      Read Full Article
    22. Feature of the Week 05/08/2016: Complex Master Slave Interferometry

      Feature of the Week 05/08/2016: Complex Master Slave Interferometry

      A general theoretical model is developed to improve the novel Spectral Domain Interferometry method denoted as Master/Slave (MS) Interferometry. In this model, two functions, g and h are introduced to describe the modulation chirp of the channeled spectrum signal due to nonlinearities in the decoding process from wavenumber to time and due to dispersion in the interferometer. The utilization of these two functions brings two major improvements to previous implementations of the MS method. A first improvement consists in reducing the number of channeled spectra necessary to be collected at Master stage. In previous MSI implementation, the number of ...

      Read Full Article
    23. Feature of the Week 03/20/2016: Closed Loop Tracked Doppler OCT Based Heart Monitor for the Drosophila Melanogaster Larvae

      Feature of the Week 03/20/2016: Closed Loop Tracked Doppler OCT Based Heart Monitor for the Drosophila Melanogaster Larvae

      A fruit fly larva (top) was continuously tracked for continuous remote monitoring. A heartbeat trace of freely moving larva (bottom) was obtained by a low coherence interferometry based doppler sensing technique. This paper presents a novel instrument for biosciences, useful for studies of moving embryos. A dual sequential imaging/measurement channel is assembled via a closed-loop tracking architecture. The dual channel system can operate in two regimes: (i) single-point Doppler signal monitoring or (ii) fast 3-D swept source OCT imaging. The system is demonstrated for characterizing cardiac dynamics in Drosophila melanogaster larva. Closed loop tracking enables long term in vivo ...

      Read Full Article
    24. Coarse-grained and fine-grained parallel optimization for real-time en-face OCT imaging

      Coarse-grained and fine-grained parallel optimization for real-time en-face OCT imaging

      This paper presents parallel optimizations in the en-face (C-scan) optical coherence tomography (OCT) display. Compared with the cross-sectional (B-scan) imagery, the production of en-face images is more computationally demanding, due to the increased size of the data handled by the digital signal processing (DSP) algorithms. A sequential implementation of the DSP leads to a limited number of real-time generated en-face images. There are OCT applications, where simultaneous production of large number of en-face images from multiple depths is required, such as real-time diagnostics and monitoring of surgery and ablation. In sequential computing, this requirement leads to a significant increase of ...

      Read Full Article
    1-24 of 102 1 2 3 4 5 »
  1. Categories

    1. Applications:

      Art, Cardiology, Dentistry, Dermatology, Developmental Biology, Gastroenterology, Gynecology, Microscopy, NDE/NDT, Neurology, Oncology, Ophthalmology, Other Non-Medical, Otolaryngology, Pulmonology, Urology
    2. Business News:

      Acquisition, Clinical Trials, Funding, Other Business News, Partnership, Patents
    3. Technology:

      Broadband Sources, Probes, Tunable Sources
    4. Miscellaneous:

      Jobs & Studentships, Student Theses, Textbooks
  2. Topics in the News

    1. (102 articles) Adrian Bradu
    2. (101 articles) University of Kent
    3. (100 articles) Adrian G. Podoleanu
    4. (35 articles) Cosmin Sinescu
    5. (33 articles) Victor Babes University of Medicine and Pharmacy
    6. (16 articles) Meda-Lavinia Negrutiu
    7. (13 articles) Virgil-Florin Duma
    8. (13 articles) George M. Dobre
    9. (6 articles) State University of New York at Buffalo
    10. (5 articles) Ramona Cernat
    11. (5 articles) National Institutes of Health
    12. (1 articles) University of Houston
    13. (1 articles) University of Minnesota
    14. (1 articles) Indiana University
    15. (1 articles) Yale University
    16. (1 articles) Massachusetts Institute of Technology
    17. (1 articles) James G. Fujimoto
    18. (1 articles) Taner Akkin
    19. (1 articles) Donald T. Miller
  3. Popular Articles

  4. Picture Gallery

    Quality assessment of dental treatments using en-face optical coherence tomography Analysis of dental abfractions by optical coherence tomography Real-time resampling in Fourier domain optical coherence tomography using a graphics processing unit Extra long imaging range swept source optical coherence tomography using re-circulation loops Anti-Spoof Reliable Biometry of Fingerprints Using En-Face Optical Coherence Tomography Feature of the Week 03/20/2016: Closed Loop Tracked Doppler OCT Based Heart Monitor for the Drosophila Melanogaster Larvae Feature of the Week 05/08/2016: Complex Master Slave Interferometry Indiana University Receives NIH Grant for Imaging Spatial and Temporal Dynamics of Retinal Ganglion Cells University of Houston Receives NIH Grant for Structural and Molecular Phenotyping of Embryonic Development Through Multi-Modal Optical Imaging. Massachusetts Institute of Technology Receives NIH Grant for Novel Optical Diagnostics with Optical Coherence Tomography Yale University Receives a NIH Grant for Xenopus As A Model System for Hydrocephaly and Ependymal Ciliogenesis University of Minnesota Receives NIH Grant for Optical Imaging of Neural Activity Based on Lorentz Effect