Papers by Keyword: Optical Coherence Tomography

Abstract: Bone graft substitute materials play an important role in oral rehabilitation and understanding the biological effects of these materials is important for an optimum use. Many bone graft substitutes have been approved for clinical use but this large variability make it hard to select a graft materials. The present study aimed to evaluate the methods that we can today use to assess the degree of osseointegration of the synthetic bone augmentation materials.For this study we made three study groups, each of them consisting of six laboratory rats. On the maxilla of this animals 3-mm diameter experimental cavities were carried out. For the first study group the cavities were augmented with the collagen fleece Alveoprotect, for the second group with the synthetic bone graft Ossceram nano, and in the third group the experimental cavities were left unaugmented. The obtained samples were subjected to three examination methods: clinical and radiological examination, Optical Coherence Tomography (OCT), and a histological study.The evaluation methods of bone graft materials may be divided in two categories: in vivo and in vitro methods. In vivo methods include clinical evaluation and imagistic such as radiological or computer tomography (CT) evaluation. Even a minimal but careful direct clinical observation allows observing the appearance of the bone defect healing at its different stages. CBCT scan is the imaging method of choice in the graft materials repairment of the osseous defects because provides 3D volumetric measurements of newly formed hard tissues.Optical Coherence Tomography (OCT) is a constantly growing imaging method characterized by high spatial resolution and noninvasive subsurface detection. The OCT allowed us to evaluate the surface and subsurface of the ongoing healing bone defects in a non-destructive manner.For the in vitro methods histological methods represents the classical evaluation of the bone graft materials biological integration. On the histological samples we generally noticed the experimental defects filling with connective tissue with various bone ingrowths from the surrounding bone tissue.However new emerging methods give new opportunities to a more accurate research of this materials. The microcomputed tomography analysis may determine the relationships and differences in three-dimensional bone mineral density and microtrabecular structures between bone grafts and their adjacent native boneTo design and produce an efficient bone graft, the researchers and clinicians should have sufficient knowledge of the characteristics of grafts such as osteogenesis, osteoinductivity, and osteoconductivity, and their other advantages and disadvantages.

Abstract: In this paper, we investigated a high lateral resolution common-path Fourier domain OCT system with the use of a chemically etched single mode fiber. In our experiments, single mode optical fiber for 840nm was used for preparing the tapered tips. Our system used a conical microlens that was chemically etched by selective chemical etching technique using an etching solution of buffered hydrofluoric acid (BHF). From experimental results, we verified that our proposed optical coherence tomography system could operate as a common-path Fourier domain OCT (FD-OCT) system. Furthermore, we experimentally investigated the chemical etching process of silica-based optical fiber probes by controlling the etching time when applying chemical etching techniques using hydrofluoric acid. We evaluated the beam profile from fiber probe. From these investigations, it was found that etching time was important parameter for sensor probe of optical coherence tomography.

Abstract: Full ceramic crowns are considered revolutionary in developing the concept of aesthetic dentistry. Appreciate their aesthetic appearance particularly raise the cost prices, they do not ensure the risk of fractures and cracks which sometimes face the clinician after their insertion directly into the mouth. As a result of the fracture may occur between disputes team dentist-dental technician. The purpose of this study was to identify flaws of material included in the pottery table analyzing the full ceramic crowns using non-invasive technologies. As materials we use 25 full ceramic crowns (e. max, IVOCLAR) obtained through the technology of pressing were used for this study. Non-invasive methods used for this study were OCT and Micro CT. The OCT technology works in Time Domain, at 1300 nm and scan angle at 18 degrees, and for each sample scans were carried out in areas of maximum voltage. After the scans, we have been obtained through the stack of 500 slicers at a distance of 10 microns each other. A number of 17 samples of the total samples obtained exhibited defects in areas of major stress corresponding to the crown considered. As a result of defects discovered using the technology OCT it has considered necessary for validation them by employing the Micro CT technology. In conclusion, we consider that OCT technology can be considered an early diagnosis method of faults contained in the table structure of the ceramic crowns before inserting them in the oral cavity, by reducing the risks of a prosthetic treatment.

Abstract: 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 OSCC of the buccal mucosa were identified in the OCT images by the disruption of the basement membrane, an epithelial layer that was highly variable in thickness, with areas of erosion, extensive epithelial down-growth and invasion into the sub-epithelial layers. In this respect, OCT seems to be a highly promising imaging modality.

Abstract: This paper proposed a fast algorithm to detect anterior chamber angle points and measure central corneal thickness for anterior chamber optical coherence tomography (OCT) images automatically. This algorithm uses biggest connected regions method to get the anterior chamber region, and detects the anterior chamber angle points (ACAPs) in this region firstly. Secondly, the algorithm uses ACAPs to obtain the real position of central cornea then measures the central corneal thickness of anterior chamber. The proposed algorithm was tested on 74 anterior chamber OCT images and provided accurate measurements in about 90 milliseconds.

Abstract: The objective of this research was to investigate a new detection method for testing a MEMS V-shaped groove in silicon using spectral domain optical coherence tomography (SDOCT) technique with a thermal light source where the V-groove depth, width and bottom width were measured. The SD-OCT technique with non-contact operation and acquisition rate advantage made it suitable for on-line precision measurement of V-shaped grooves in silicon.

Abstract: In order to measure the optical parameters of biological tissue accurately and non-invasive, the measurement system based on optical coherence tomography was analyzed and designed from two aspects of hardware and software. The refractive index was calibrated by standard refractive index solutions, experiments were preformed to obtain refractive index of tissue samples and scattering coefficient of Intralipid^TM solution with different concentrations. Results show that the experimental values of refractive index agree with the standard values roughly and scattering coefficient linear relate with concentration in Intralipid^TM solution. The measurement system designed in our experiment is accurate and reliable, simple and feasible.

Abstract: In orthodontics, the scientific interest regarding adhesion is focused on optimizing adherents: metallic or aesthetic bracket base conditioning, creating aesthetic brackets with improved mechanical properties, enamel conditioning and artificial surface conditioning (aesthetic veneers and crowns). In order to investigate the interfaces between adherents there are several invasive (destructive) methods such as tensile bond strength tests, shear bond strength tests and microleakage tests.

Abstract: We demonstrate a swept-source OCT system based on a polorization-dependent semiconductor optical amplifier (SOA)-enabled Fourier Domain Mode Locked laser (FDML). The broad bandwidth and high saturation power of the semiconductor optical amplifier enables single semiconductor optical amplifier operation with enough bandwidth and output power. The FDML generates ~32mW output power at 45kHz sweep rates, with a tuning range of 115 nm centered at 1326 nm. Using the SOA-enabled FDML laser, ~12.9μm axial resolution,9μm transverse spot size and 105dB sensitivity are achieved. OCT imaging of biological sample is also demonstrated.

Abstract: Glucose-concentration of turbid media is measured based on optical coherence tomography (OCT) . The effects of scattering coefficient and anisotropic factor on heterodyne efficiency factor were analyzed by the Monte Carlo simulation and analog calculation. A new method was developed to extract the optical properties using Extended Huygens-Fresnel principle for the case of the specular reflection. The scattering and absorption properties were obtained by measuring the Intralipid^TM solution of the different concentration. And the relationship between scattering coefficient and the concentration of glucose in IntralipidTM were studied.