1. Articles from adrian podoleanu

    1-24 of 80 1 2 3 4 »
    1. Endoscopic en-face optical coherence tomography and fluorescence imaging using correlation-based probe tracking

      Endoscopic en-face optical coherence tomography and fluorescence imaging using correlation-based probe tracking

      Forward-viewing endoscopic optical coherence tomography (OCT) provides 3D imaging in vivo, and can be combined with widefield fluorescence imaging by use of a double-clad fiber. However, it is technically challenging to build a high-performance miniaturized 2D scanning system with a large field-of-view. In this paper we demonstrate how a 1D scanning probe, which produces cross-sectional OCT images (B-scans) and 1D fluorescence T-scans, can be transformed into a 2D scanning probe by manual scanning along the second axis. OCT volumes are assembled from the B-scans using speckle decorrelation measurements to estimate the out-of-plane motion along the manual scan direction. Motion within ...

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    2. A novel 3D printed hollow microneedle microelectromechanical system for controlled, personalized transdermal drug delivery

      A novel 3D printed hollow microneedle microelectromechanical system for controlled, personalized transdermal drug delivery

      The advancement of drug delivery devices is critical for the individualization of patient treatment and the improvement of healthcare. Here, we introduce the 3DMNMEMS, a novel device that combines 3D printing, microneedles (MNs) and Microelectromechanical Systems (MEMS), allowing versatile and controllable by the user transdermal drug delivery. Hollow MNs were designed and 3D printed using Stereolithography, followed by integrating into a MEMS. By employing advanced imaging techniques, we monitored the distribution of liquid delivered by the device within skin tissue in real time. In vivo testing revealed that the delivery of insulin using the 3DMNMEMS achieved improved glycemic control to ...

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    3. Optimization of X-ray Investigations in Dentistry Using Optical Coherence Tomography

      Optimization of X-ray Investigations in Dentistry Using Optical Coherence Tomography

      The most common imaging technique for dental diagnoses and treatment monitoring is X-ray imaging, which evolved from the first intraoral radiographs to high-quality three-dimensional (3D) Cone Beam Computed Tomography (CBCT). Other imaging techniques have shown potential, such as Optical Coherence Tomography (OCT). We have recently reported on the boundaries of these two types of techniques, regarding. the dental fields where each one is more appropriate or where they should be both used. The aim of the present study is to explore the unique capabilities of the OCT technique to optimize X-ray units imaging (i.e., in terms of image resolution ...

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    4. Akinetic Swept-Source Master–Slave-Enhanced Optical Coherence Tomography

      Akinetic Swept-Source Master–Slave-Enhanced Optical Coherence Tomography

      This paper presents a different approach for processing the signal from interferometers driven by swept sources that exhibit non-linear tuning during stable time intervals. Such sources are, for example, those commercialised by Insight, which are electrically tunable and akinetic. These Insight sources use a calibration procedure to skip frequencies already included in a spectral sweep, i.e., a process of “clearing the spectrum”. For the first time, the suitability of the Master–Slave (MS) procedure is evaluated as an alternative to the conventional calibration procedure for such sources. Here, the MS process is applied to the intact, raw interferogram spectrum ...

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    5. Sub-surface characterisation of latest-generation identification documents using optical coherence tomography

      Sub-surface characterisation of latest-generation identification documents using optical coherence tomography

      The identification of individuals, particularly at international border crossings, coupled with the evolving sophistication of identity documents are issues that authorities must contend with. Particularly, the ability to distinguish legitimate from counterfeit documents, with high throughput, sensitivity, and selectivity is an ever-evolving challenge. Over the last decade, an increasing number of security features have been introduced by authorities in identification documents. The latest generation of travel documents (such as passports and national ID cards) forego paper substrates for several layers of polycarbonate, allowing security features to be embedded within the documents. These security features may contain information at either the ...

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    6. Dental Diagnosis and Treatment Assessments: Between X-rays Radiography and Optical Coherence Tomography

      Dental Diagnosis and Treatment Assessments: Between X-rays Radiography and Optical Coherence Tomography

      A correct diagnosis in dental medicine is typically provided only after clinical and radiological evaluations. They are also required for treatment assessments. The aim of this study is to establish the boundaries from which a modern, although established, imaging technique, Optical Coherence Tomography (OCT), is more suitable than the common X-ray radiography to assess dental issues and treatments. The most common methods for daily-basis clinical imaging are utilized in this study for extracted teeth (but also for other dental samples and materials), i.e., panoramic, intraoral radiography, and three-dimensional (3D) cone beam computed tomography (CBCT). The advantages of using OCT ...

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    7. Apparatus and method for processing the signal in master slave interferometry and apparatus and method for master slave optical coherence tomography with any number of sampled depths

      Apparatus and method for processing the signal in master slave interferometry and apparatus and method for master slave optical coherence tomography with any number of sampled depths

      The present invention related to an apparatus and method for master slave interferometry, referred to as Complex Master Slave (CMS). The method and apparatus can be used to provide complex-valued measurements of a signal reflected from an axial position inside an object or of signals reflected from points at several axial positions inside an object.

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    8. 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 ...

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    9. 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 ...

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    10. 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 ...

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    11. Progress in Multimodal En Face Imaging: feature introduction

      Progress in Multimodal En Face Imaging: feature introduction

      This feature issue contains papers that report on the most recent advances in the field of en face optical coherence tomography (OCT) and of combinations of modalities facilitated by the en face view. Hardware configurations for delivery of en face OCT images are described as well as specific signal and image processing techniques tailored to deliver relevant clinical diagnoses. The value of the en face perspective for enabling multimodality is illustrated by several combination modalities.

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    12. Feature Of The Week 04/28/2019: Real-Time High-Resolution Mid-Infrared OCT

      Feature Of The Week 04/28/2019: Real-Time High-ResolutionMid-Infrared OCT

      The potential for improving the penetration depth of optical coherence tomography systems by using light sources with longer wavelengths has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid-infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid-infrared spectral-domain optical coherence tomography system operating at a central wavelength of 4 µm and an axial resolution of 8.6 µm is demonstrated. The system produces two-dimensional cross-sectional images ...

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    13. 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 ...

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    14. Akinetic swept laser apparatus and method for fast sweeping of the same

      Akinetic swept laser apparatus and method for fast sweeping of the same

      A detuned resonant mechanism is employed in a laser cavity to modulate in frequency the mode-locking mechanism to achieve high frequency tuning rates, exceeding MHz. The configuration of the laser is compatible with working at sweeping rates close to multiples of the cavity resonance frequency as well as with buffering for increased tuning speeds.

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    15. 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 ...

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    16. Noise of supercontinuum sources in spectral domain optical coherence tomography

      Noise of supercontinuum sources in spectral domain optical coherence tomography

      In this paper, we investigate the effect of pulse-to-pulse fluctuations of supercontinuum sources on the noise in spectral domain optical coherence tomography (OCT) images. The commonly quoted theoretical expression for the OCT noise is derived for a thermal light source, which is not suitable if a supercontinuum light source is used. We therefore propose a new, measurement-based OCT noise model that predicts the noise without any assumptions on the type of light source. We show that the predicted noise values are in excellent agreement with the measured values. The spectral correlation evaluated for the photodetected signal when using a supercontinuum ...

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    17. Real-time high-resolution mid-infrared optical coherence tomography

      Real-time high-resolution mid-infrared optical coherence tomography

      The potential for improving the penetration depth of optical coherence tomography systems by using light sources with longer wavelengths has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid-infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid-infrared spectral-domain optical coherence tomography system operating at a central wavelength of 4 µm and an axial resolution of 8.6 µm is demonstrated. The system produces two-dimensional cross-sectional images ...

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    18. 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 ...

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    19. 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 ...

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    20. Real‐time High‐Resolution Mid‐infrared Optical Coherence Tomography

      Real‐time High‐Resolution Mid‐infrared Optical Coherence Tomography

      The potential for improving the penetration depth of optical coherence tomography systems by using increasingly longer wavelength light sources has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid‐infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid‐infrared spectral‐domain optical coherence tomography system operating at 4 µm central wavelength with an axial resolution of 8.6 µm is demonstrated. The system produces 2D cross ...

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    21. Feature Issue of Biomedical Optics Express: Progress in Multimodal En-Face Imaging Manuscript Deadline September 15, 2018

      Feature Issue of Biomedical Optics Express: Progress in Multimodal En-Face Imaging Manuscript Deadline September 15, 2018

      Biomedical Optics Express welcomes submissions to a feature issue on "Progress in Multimodal En-Face Imaging". Multimodal optical imaging certainly enriches the amount of information that can be retrieved from biological tissue. For this purpose, many different approaches have been combined, including optical coherence tomography (OCT), microscopy, scanning laser ophthalmoscopy (SLO), fluorescence imaging, multi-photon imaging, Raman spectroscopy, photoacoustics, and many more. This year marks 20 years from the publication of a first report on a combination of the old SLO, dating back from 1980, and of OCT, at that time a rather novel imaging technique as it was just invented in ...

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    22. 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 ...

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    23. Feature issue of Biomedical Optics Express: Progress in Multimodal En-Face Imaging

      Feature issue of Biomedical Optics Express: Progress in Multimodal En-Face Imaging

      Biomedical Optics Express welcomes submissions to a feature issue on "Progress in Multimodal En-Face Imaging". Multimodal optical imaging certainly enriches the amount of information that can be retrieved from biological tissue. For this purpose, many different approaches have been combined, including optical coherence tomography (OCT), microscopy, scanning laser ophthalmoscopy (SLO), fluorescence imaging, multi-photon imaging, Raman spectroscopy, photoacoustics, and many more. This year marks 20 years from the publication of a first report on a combination of the old SLO, dating back from 1980, and of OCT, at that time a rather novel imaging technique as it was just invented in ...

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    24. Q-switched based supercontinuum source towards low-cost ultra-high resolution optical coherence tomography

      Q-switched based supercontinuum source towards low-cost ultra-high resolution optical coherence tomography

      Supercontinuum (SC) light source is certainly one of the best option for ultra-high resolution optical coherence tomography (UHR-OCT). Over the last few years several demonstrations have been done for each commonly used wavelength range [1-2-3]. Nowadays, SC dedicated to UHR-OCT is a mature technology with turn-key commercially available system [4]. The new challenge to answer for SC source is the cost reduction one. In this study, we demonstrate that a Q-switched based SC (QS-SC) could be an alternative to the current state of the art SC based on a Mode-Locked laser (ML-SC). This QS-SC, whose cost is less than 15 ...

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    1-24 of 80 1 2 3 4 »
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