1. Articles from Adrian Gh. Podoleanu

    1-24 of 57 1 2 3 »
    1. 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 ...

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    2. Assessment of dental plaque by optoelectronic methods

      Assessment of dental plaque by optoelectronic methods

      The formation of dental biofilm follows specific mechanisms of initial colonization on the surface, microcolony formation, development of organized three dimensional community structures, and detachment from the surface. The structure of the plaque biofilm might restrict the penetration of antimicrobial agents, while bacteria on a surface grow slowly and display a novel phenotype; the consequence of the latter is a reduced sensitivity to inhibitors. The aim of this study was to evaluate with different optoelectronic methods the morphological characteristics of the dental biofilm. The study was performed on samples from 25 patients aged between 18 and 35 years. The methods ...

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    3. Demonstration of tolerance to dispersion of master/slave interferometry

      Demonstration of tolerance to dispersion of master/slave interferometry

      A theoretical model is developed for the Master/Slave interferometry (MSI) that is used to demonstrate its tolerance to dispersion left uncompensated in the interferometer when evaluating distances and thicknesses. In order to prove experimentally its tolerance to dispersion, different lengths of optical fiber are inserted into the interferometer to introduce dispersion. It is demonstrated that the sensitivity profile versus optical path difference is not affected by the length of fiber left uncompensated. It is also demonstrated that the axial resolution is constant within the axial range, close to the expected theoretical resolution determined by the optical source bandwidth. Then ...

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    4. Noninvasive Quantitative Evaluation of the Dentin Layer during Dental Procedures Using Optical Coherence Tomography

      Noninvasive Quantitative Evaluation of the Dentin Layer during Dental Procedures Using Optical Coherence Tomography

      A routine cavity preparation of a tooth may lead to opening the pulp chamber. The present study evaluates quantitatively, in real time, for the first time to the best of our knowledge, the drilled cavities during dental procedures. An established noninvasive imaging technique, Optical Coherence Tomography (OCT), is used. The main scope is to prevent accidental openings of the dental pulp chamber. Six teeth with dental cavities have been used in this ex vivo study. The real time assessment of the distances between the bottom of the drilled cavities and the top of the pulp chamber was performed using an ...

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    5. Optical Coherence Tomography for Non-Invasive ex vivo Investigations in Dental Medicine — a Joint Group Experience (Review)

      Optical Coherence Tomography for Non-Invasive ex vivo Investigations in Dental Medicine — a Joint Group Experience (Review)

      This review emphasizes the current knowledge related to optical coherence tomography (OCT) as a non-invasive diagnostic tool to perform ex vivo and showing great potential for in vivo structural imaging of features in the oral cavity. OCT technology can generate high-resolution cross-sectional and en-face images of the internal architecture of the investigated sample (2–3 mm in depth). To this goal, en-face time domain OCT (TD-OCT) and spectral domain OCT (SD-OCT) were employed. Topics included in this review refer to OCT non-destructive evaluations of: dental abfraction and attrition, material defects and micro-leakages at the tooth-filling interface, temporal-mandibular joint disc, quality ...

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    6. Assessment of the sealant/tooth interface using optical coherence tomography

      Assessment of the sealant/tooth interface using optical coherence tomography

      Sealant materials are typically employed in dentistry in order to prevent the development of cavities on the teeth. They prevent bacterial adhesion to enamel, thus arresting the development of demineralization and of caries. In this study, the critical zone of the interface between different sealant materials and the results of the dental work for the teeth processed were investigated ex vivo using swept source (SS) optical coherence tomography (OCT). Optical inspection and X-ray investigation revealed no defects, while SS-OCT proved capable to asses exactly the position, the nature, and the dimensions of each type of these defects. Specifically, different failures ...

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    7. Surface imaging of metallic material fractures using optical coherence tomography

      Surface imaging of metallic material fractures using optical coherence tomography

      We demonstrate the capability of optical coherence tomography (OCT) to perform topography of metallic surfaces after being subjected to ductile or brittle fracturing. Two steel samples, OL 37 and OL 52, and an antifriction Sn–Sb–Cu alloy were analyzed. Using an in-house-built swept source OCT system, height profiles were generated for the surfaces of the two samples. Based on such profiles, it can be concluded that the first two samples were subjected to ductile fracture, while the third one was subjected to brittle fracture. The OCT potential for assessing the surface state of materials after fracture was evaluated by ...

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    8. Versatile Swept Source With Adjustable Coherence Length

      Versatile Swept Source With Adjustable Coherence Length

      An electronically controlled optical swept source at 1550 nm using mode locking in a dispersive ring cavity is described. Active mode-locking was achieved by directly modulating the current of a semiconductor optical amplifier (SOA) used as a gain medium. In the static regime, parameters such as linewidth, tuning bandwidth, and contrast were measured, whereas the axial range was determined dynamically. Two types of fiber, dispersion compensation and single mode, are employed in the laser ring cavity. It is demonstrated that the relative lengths of the two types of fiber have little effect on the linewidth, whereas more control on the ...

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    9. Imaging the eye fundus with real-time en-face spectral domain optical coherence tomography

      Imaging the eye fundus with real-time en-face spectral domain optical coherence tomography

      Real-time display of processed en-face spectral domain optical coherence tomography (SD-OCT) images is important for diagnosis. However, due to many steps of data processing requirements, such as Fast Fourier transformation (FFT), data re-sampling, spectral shaping, apodization, zero padding, followed by software cut of the 3D volume acquired to produce an en-face slice, conventional high-speed SD-OCT cannot render an en-face OCT image in real time. Recently we demonstrated a Master/Slave (MS)-OCT method that is highly parallelizable, as it provides reflectivity values of points at depth within an A-scan in parallel. This allows direct production of en-face images. In addition ...

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    10. Towards simultaneous Talbot bands based optical coherence tomography and scanning laser ophthalmoscopy imaging

      Towards simultaneous Talbot bands based optical coherence tomography and scanning laser ophthalmoscopy imaging

      We report a Talbot bands-based optical coherence tomography (OCT) system capable of producing longitudinal B-scan OCT images and en-face scanning laser ophthalmoscopy (SLO) images of the human retina in-vivo . The OCT channel employs a broadband optical source and a spectrometer. A gap is created between the sample and reference beams while on their way towards the spectrometer’s dispersive element to create Talbot bands. The spatial separation of the two beams facilitates collection by an SLO channel of optical power originating exclusively from the retina, deprived from any contribution from the reference beam. Three different modes of operation are presented ...

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    11. Zirconia enriched dental adhesive: A solution for OCT contrast enhancement. Demonstrative study by synchrotron radiation microtomography

      Zirconia enriched dental adhesive: A solution for OCT contrast enhancement. Demonstrative study by synchrotron radiation microtomography

      Objective The major aim of this study was to prove the capability of the optical coherence tomography (OCT) method in visualizing the integrity of the adhesive fillings and of the interfaces between the adhesive, tooth structures and composite resin. As zirconium dioxide was added to the composition of the adhesive layer in order to strengthen the backscattered light in the OCT investigation, for a better visualization of the interfaces, the determination of a proper zirconia concentration was another aim of our study. Method Several class II cavities were prepared in human premolars and were filled with dental adhesive containing different ...

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    12. Calibration-free B-scan images produced by master/slave optical coherence tomography

      Calibration-free B-scan images produced by master/slave optical coherence tomography

      We report on a novel method to produce B-scan images in spectral domain optical coherence tomography (SD-OCT). The method proceeds in two steps. In the first step, using a mirror in the sample arm of the interferometer, channelled spectra are acquired for different values of the optical path difference (OPD) and stored as masks. In the second step, the mirror is replaced with an object and the captured channelled spectrum is correlated with each mask, providing the interference strength from the OPD value used to collect the respective mask. Such a procedure does not require data organized in equal frequency ...

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

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

      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 ...

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

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

      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 ...

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    15. Optical Imaging of Oral Squamous Cell Carcinoma Using Optical Coherence Tomography and Micro CT

      Optical Imaging of Oral Squamous Cell Carcinoma Using Optical Coherence Tomography and Micro CT

      Oral squamous cell carcinoma (OSCC) constitutes 90% of oral cancer. Early detection is a cornerstone to improve survival and to reduce diagnostic delay. We propose optical coherence tomography (OCT), as a non-invasive diagnosis method. OCT represents a new high-resolution optical technique that permits 3D, real-time imaging of near surface abnormalities in complex tissues. In the present study half of the excisional biopsy was directed to the pathologist and the other half was assigned for OCT and Micro-CT investigation. For the OCT imaging it was used an OCT prototype (1300 nm), Synchrotron Radiation Micro-CT and histopathology validated the results. Areas of ...

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    16. Tuning a fast linear camera used within a Talbot bands spectrometer-based optical coherence tomography set-up

      Tuning a fast linear camera used within a Talbot bands spectrometer-based optical coherence tomography set-up

      Spectrometer-based Optical Coherence Tomography (Sp-OCT) introduced a number of improvements in terms of imaging speed and overall sensitivity over the existing OCT methods. This variant uses a spectrometer to acquire channelled spectra resulting from white light interferometry, which are then processed to yield the depth profiles for each transverse position. A spectrometer can be constructed using a dispersive medium such as a diffraction grating, focusing optics and a linear camera, which allows for a certain degree of control over the spectrometer parameters (exposure time, wavelength range and resolution). The recent advances in line camera technology also allow for fast camera ...

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    17. Multiplexing-based polarization sensitive en-face optical coherence tomography

      Multiplexing-based polarization sensitive en-face optical coherence tomography

      We present a time-domain polarization-sensitive (PS) optical coherence tomography configuration operating at 830 nm, equipped with multichannel acousto-optic deflectors and single photodetectors. The system is used to simultaneously acquire interference information from multiple PS channels and to enable measurement and imaging of backscattered intensity to create both PS and polarization insensitive images. Our approach enables multiple channel imaging without need to divide the object signal. Here, we employ our system in order to demonstrate PS imaging of a thermally damaged muscle tissue.

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    18. Two applications of solid phantoms in performance assessment of optical coherence tomography systems

      Two applications of solid phantoms in performance assessment of optical coherence tomography systems

      Virtual tissues (phantoms) are widely used for performance evaluation of imaging systems. Specific design of the phantom is necessary for the correct assessment of a system’s parameters. In an effort to reduce the amount of time and energy spent making application-oriented phantoms, we describe procedures to make epoxy-resin solid phantoms based on Mie scattering theory, with two different scatterers: polystyrene and gold microspheres. The phantoms are specifically designed to be used in two applications: (a) the gold microspheres solid phantoms are used to estimate the point-spread function (PSF) of an optical coherence tomography (OCT) system, and (b) the polystyrene ...

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

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

      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     μ m 3 . 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.

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    20. Master–slave interferometry for parallel spectral domain interferometry sensing and versatile 3D optical coherence tomography

      Master–slave interferometry for parallel spectral domain interferometry sensing and versatile 3D optical coherence tomography

      Conventional spectral domain interferometry (SDI) methods suffer from the need of data linearization. When applied to optical coherence tomography (OCT), conventional SDI methods are limited in their 3D capability, as they cannot deliver direct en-face cuts. Here we introduce a novel SDI method, which eliminates these disadvantages. We denote this method as Master - Slave Interferometry (MSI), because a signal is acquired by a slave interferometer for an optical path difference (OPD) value determined by a master interferometer. The MSI method radically changes the main building block of an SDI sensor and of a spectral domain OCT set-up. The serially provided ...

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    21. Spatial Compounding Algorithm for Speckle Reduction of Dynamic Focus OCT Images

      Spatial Compounding Algorithm for Speckle Reduction of Dynamic Focus OCT Images

      Optical coherence tomography is capable of imaging the microstructures within tissues. To preserve the transverse resolution at all imaging depths, we implement a dynamic focusing scheme. To improve the quality of images further, a simple speckle reduction scheme is employed which uses the vibration introduced by the translation stage used for axial scanning. A spatial compounding technique is developed based on co-registration followed by an averaging algorithm. We conclude that the degree of speckle reduction achieved is worth the expense of more complicated processing required.

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    22. Optical imaging of oral pathological tissue using optical coherence tomography and synchrotron radiation computed microtomography

      Optical imaging of oral pathological tissue using optical coherence tomography and synchrotron radiation computed microtomography

      The efforts aimed at early diagnosis of oral cancer should be prioritized towards developing a new screening instrument, based on optical coherence tomography (OCT), to be used directly intraorally, able to perform a fast, real time, 3D and non-invasive diagnosis of oral malignancies. The first step in this direction would be to optimize the OCT image interpretation of oral tissues. Therefore we propose plastination as a tissue preparation method that better preserves three-dimensional structure for study by new optical imaging techniques. The OCT and the synchrotron radiation computed microtomography (micro-CT) were employed for tissue sample analyze. For validating the OCT ...

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    23. Full-Field Thickness Distribution of Human Tympanic Membrane Obtained with Optical Coherence Tomography

      Full-Field Thickness Distribution of Human Tympanic Membrane Obtained with Optical Coherence Tomography

      The full-field thickness distribution, three-dimensional surface model and general morphological data of six human tympanic membranes are presented. Cross-sectional images were taken perpendicular through the membranes using a high-resolution optical coherence tomography setup. Five normal membranes and one membrane containing a pathological site are included in this study. The thickness varies strongly across each membrane, and a great deal of inter-specimen variability can be seen in the measurement results, though all membranes show similar features in their respective relative thickness distributions. Mean thickness values across the pars tensa ranged between 79 and 97 μm; all membranes were thinnest in the ...

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    24. Frequency multiplexed long range swept source optical coherence tomography

      Frequency multiplexed long range swept source optical coherence tomography

      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

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    1-24 of 57 1 2 3 »
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    1. (57 articles) Adrian G. Podoleanu
    2. (54 articles) University of Kent
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