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Erbium-Doped Fibre Lasers
Published in Shyamal Bhadra, Ajoy Ghatak, Guided Wave Optics and Photonic Devices, 2017
Aditi Ghosh, Deepa Venkitesh, R. Vijaya
The prominent medical application of broadband sources is in optical coherence tomography (OCT). OCT is an imaging technique that utilizes interferometry with a low-coherence light to perform micrometre-scale resolution imaging, in situ on an inhomogeneous biological tissue [65]. The choice of the centre wavelength of the source depends on the type of tissue imaged and the penetration depth required. For nontransparent tissue, where the scattering should be minimal, the use of longer wavelengths is suitable, thereby allowing a greater penetration depth. OCT imaging performed on human aortas with 1550 nm EDFs shows that this spectral range is well suited for such types of biological tissue [66]. The axial resolution achievable with OCT is inversely proportional to the spectral width of the source, and several types of broadband sources have been experimented with for this purpose [67].
in vitro Conditioning of Engineered Tissues
Published in Claudio Migliaresi, Antonella Motta, Scaffolds for Tissue Engineering, 2014
Aaron S. Goldstein, Patrick Thayer
This technique can be used to form micrometer resolution, three-dimensional images through a fiberoptic cable from an optically scattering medium. OCT is essentially an optical ultrasound technique, recording the light reflections within a tissue to reconstruct cross-sectional images of the medium. It has several advantages such as real-time imaging, minimal sample preparation required, and no ionizing radiation. Although the resolution of the resulting images can be less than a micron, the depth of penetration is limited to approximately 2 mm. Nevertheless, OCT can be applied to thin tissues such as skin. In one particular study, Smith et al.83 used OCT to visualize the development of the epidermis and dermis over time. They subsequently validated this technique by comparing their OCT cross sections with traditional histological sections.
Optical coherence tomography in medicine
Published in P. Dakin John, G. W. Brown Robert, Handbook of Optoelectronics, 2017
OCT is based on low-coherence interferometry (LCI), typically using a near-infrared light source, allowing it to penetrate better into a scattering medium. The data obtained from OCT are, in many ways, similar to those obtained from ultrasound “B-mode” imaging, another method that allows cross-sectional imaging of the tissue microstructure as a function of depth. However, instead of acoustic waves, OCT uses light and performs imaging by measuring the backscattered intensity of light from structures in tissues. In contrast to ultrasound, which utilizes intensity versus echo time delay, coherent (interferometric) detection techniques are employed. Since the wavelength of light is so much shorter, the depth resolution is much better than is possible with ultrasound.
A deep separable neural network for human tissue identification in three-dimensional optical coherence tomography images
Published in IISE Transactions on Healthcare Systems Engineering, 2019
Haifeng Wang, Daehan Won, Sang Won Yoon
OCT is an interferometric imaging modality that can visualize tissue microstructures via near-infrared light interferometry by providing cross-sectional images (Olsen, Themstrup, and Jemec, 2015). OCT can produce around 15,000–40,000 A-line scans (depth) per second, which enables the acquisition of 3D data sets in a short period of time (Vermeer, Schoot, Van der, Lemij, and De Boer, 2011). Figure 1 shows the scanning process in a typical OCT imaging system. In practical application, noninvasive real-time imaging is still not available. OCT is a potential technique for such a modality (Lenz, Krug, Welp, Schmieder, and Hofmann, 2016), as it can be used as an optical biopsy (Tearney, Brezinski, Bouma, et al., 1997). OCT has a penetration depth of 1–2 mm and a resolution of 1–15 μm. Studies have shown that OCT technology is sufficient to identify structural differences between healthy tissue and pathological tissue (Lenz et al., 2016). Compared with MRI, CT, and PET technologies, OCT can provide depth-resolved, high-resolution images of biological tissue in real time (Leggett, Chan, and Wang, 2016).
Artificial neural network (ANN) for dispersion compensation of spectral domain – optical coherence tomography (SD-OCT)
Published in Instrumentation Science & Technology, 2022
Dan Yang, Wenxin Guo, Tonglei Cheng, Zhulin Wei, Bin Xu
Optical coherence tomography (OCT) is an imaging technique that uses low-coherence light to achieve micrometer-resolution of two- and three-dimensional images through the optical scattering media (e.g., biological tissue).[1,2] In OCT, the broad-bandwidth light source is split into a sample beam (incorporating the item of interest) and a reference beam (generally a mirror). The interference pattern is produced by the combination of the reflected light of the sample beam and the reference light of the reference beam.[3] Because of its noninvasive and non-contact characteristics,[4] OCT has been clinically used in ophthalmology,[5] cardiology,[6] endoscopy,[7] dermatology,[8] and oncology.[9] Initially, OCT depth scans were performed via scanning the reference beam of the Michelson interferometer, which called time-domain OCT (TD-OCT). Today, compared with the time domain methods, the development of spectral-domain OCT (SD-OCT) enables increased imaging speed and sensitivity. For both TD-OCT and SD-OCT, OCT images are more sensitive to dispersion. The influence of the different optical path lengths in reference and sample beams for different wavelengths causes dispersion mismatch, which enlarges the axial point spread function (PSF) and causes a loss of resolution. Therefore, the cancelation of the dispersion mismatch for high quality images is a significant issue for OCT development.
Automated identification of SD-optical coherence tomography derived macular diseases by combining 3D-block-matching and deep learning techniques
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2021
Ilhem Mezni, Amine Ben Slama, Zouhair Mbarki, Hassen Seddik, Hedi Trabelsi
Optical Coherence Tomography (OCT) is a recently established imaging technique to describe different information about the internal structures of an object and to image various aspects of biological tissues, such as structural information, blood flow, elastic parameters, change of polarisation states, and molecular content (Leitgeb 2019). The OCT is widely used in ophthalmology for viewing the morphology of the retina, which is important for disease detection and assessing the response to treatment (Kawasaki et al. 2010; Lanzillo et al. 2018; Ji et al. 2018; Leal et al. 2019).