The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Yoshiaki Yasuno - One of the best experts on this subject based on the ideXlab platform.
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Birefringence measurement of cornea and anterior segment by office based polarization sensitive optical coherence tomography
Biomedical Optics Express, 2011Co-Authors: Masahiro Yamanari, Shinichi Fukuda, Yuichi Kaji, Takahiro Kiuchi, Masahiro Miura, Tetsuro Oshika, Yoshiaki YasunoAbstract:We present a case series of cornea and anterior segment disorders investigated by an office-based polarization-sensitive optical coherence tomography (PS-OCT). Blebs of glaucoma patients treated by trabeculectomy, and corneas of keratoconus and keratoplasty patients were measured by PS-OCT. Birefringence formations in trabeculectomy bleb were measured in 1 control eye and 3 eyes of trabeculectomy model rabbits. Polarization insensitive scattering OCT and the depth-resolved Birefringence were measured simultaneously by PS-OCT. Abnormal Birefringence was observed in keratoconus cases with advanced thinning and with a rupture of Descemet’s membrane. The graft-host interface of the keratoplasty case showed abnormal Birefringence. The appearance of abnormal Birefringence in the cornea was likely to be an indication of cross-linking of collagen fibrils. The measurement of rabbit showed abnormal Birefringence in the scarring eyes. Wide regions of strong Birefringence were observed in the eyes of trabeculectomy patients who had high intraocular pressure. Visualization of scarring in bleb by PS-OCT may be useful for the planning of secondary surgery. PS-OCT showed promising for the study and diagnosis diseases related to abnormal fibrous tissues of the cornea and anterior eye segment.
Johannes F De Boer - One of the best experts on this subject based on the ideXlab platform.
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thickness and Birefringence of healthy retinal nerve fiber layer tissue measured with polarization sensitive optical coherence tomography
Investigative Ophthalmology & Visual Science, 2004Co-Authors: Barry Cense, Teresa C Chen, Hyle B Park, Mark C Pierce, Johannes F De BoerAbstract:PURPOSE: Thinning of the retinal nerve fiber layer and changes in retinal nerve fiber layer (RNFL) Birefringence may both precede clinically detectable glaucomatous vision loss. Early detection of RNFL changes may enable treatment to prevent permanent loss of vision. Polarization-sensitive optical coherence tomography (PS-OCT) can provide objective information on RNFL thickness and Birefringence. METHODS: PS-OCT scans around the optic nerve head (ONH) of two healthy young volunteers were made using 10 concentric circles of increasing radius. Both the mean RNFL thickness and mean retinal nerve fiber Birefringence for each of 48 sectors on a circle were determined with data analysis. RESULTS: Both the RNFL thickness and Birefringence varied as a function of sector around the ONH. The RNFL became thinner with increasing distance from the ONH. In contrast, the Birefringence did not vary significantly as a function of radius. CONCLUSIONS: Birefringence of healthy RNFL is constant as a function of scan radius but varies as a function of position around the ONH, with higher thickness values occurring superior and inferior to the ONH. Measured double-pass phase retardation per unit depth around the ONH ranged between 0.10 and 0.35 deg/microm, equivalent to Birefringences of 1.2 x 10(-4) and 4.1 x 10(-4) respectively, measured at a wavelength of 840 nm. Consequently, when a spatially constant Birefringence around the ONH is assumed, the conversion of scanning laser polarimetry (SLP) phase-retardation measurements to RNFL thickness may yield incorrect values. The data do not invalidate the clinical value of a phase-retardation measurement, but affect the conversion of phase retardation to RNFL thickness.
Matthew E. Reid - One of the best experts on this subject based on the ideXlab platform.
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Origin of Birefringence in Wood at Terahertz Frequencies
IEEE Transactions on Terahertz Science and Technology, 2012Co-Authors: Tara M. Todoruk, Ian D. Hartley, Matthew E. ReidAbstract:In the wood products industry, terahertz (THz) radiation is showing promise for new types of sensing and imaging applications, which depend on the ability of THz radiation to probe the gross fiber structure of wood. The sensitivity to this gross fiber structure is a result of the strong Birefringence of wood at THz frequencies. Wood is a complex structure, and the large Birefringence observed may be due to either intrinsic or form Birefringence. In this paper, the origin of Birefringence in wood at THz frequencies is examined in detail. Although the source of Birefringence varies according to species, the trend shows contributions from both types of Birefringence. This has implications for application development in the wood products industry, where the possibility of probing both the gross physical structure of wood and wood products, and the intrinsic properties of wood such as crystallinity and microfibril angle, simultaneously may allow for nondestructive noncontact strength testing of wood and composite wood products.
Martin Villiger - One of the best experts on this subject based on the ideXlab platform.
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tissue like phantoms for quantitative Birefringence imaging
Biomedical Optics Express, 2017Co-Authors: Kathy Beaudette, Xianghong Wang, Brett E Bouma, Martin VilligerAbstract:Birefringence imaging, including polarization sensitive optical coherence tomography (PS-OCT), can provide valuable insight into the microscopic structure and organization of many biological tissues. In this paper, we report on a method to fabricate tissue-like Birefringence phantoms for such imaging modalities. We utilize the photo-elastic effect, wherein Birefringence is induced by stretching a polymer sample after heating it above its glass-transition temperature. The cooled samples stably exhibit homogeneous Birefringence, and were assembled into phantoms containing multiple well-defined regions of distinct Birefringence. We present planar slab phantoms for microscopy applications and cylindrical phantoms for catheter-based imaging and demonstrate quantitative analysis of the Birefringence within individual regions of interest. Birefringence phantoms enable testing, validating, calibrating, and improving PS-OCT acquisition systems and reconstruction strategies.
Tara M. Todoruk - One of the best experts on this subject based on the ideXlab platform.
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Origin of Birefringence in Wood at Terahertz Frequencies
IEEE Transactions on Terahertz Science and Technology, 2012Co-Authors: Tara M. Todoruk, Ian D. Hartley, Matthew E. ReidAbstract:In the wood products industry, terahertz (THz) radiation is showing promise for new types of sensing and imaging applications, which depend on the ability of THz radiation to probe the gross fiber structure of wood. The sensitivity to this gross fiber structure is a result of the strong Birefringence of wood at THz frequencies. Wood is a complex structure, and the large Birefringence observed may be due to either intrinsic or form Birefringence. In this paper, the origin of Birefringence in wood at THz frequencies is examined in detail. Although the source of Birefringence varies according to species, the trend shows contributions from both types of Birefringence. This has implications for application development in the wood products industry, where the possibility of probing both the gross physical structure of wood and wood products, and the intrinsic properties of wood such as crystallinity and microfibril angle, simultaneously may allow for nondestructive noncontact strength testing of wood and composite wood products.
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Birefringence of wood at terahertz frequencies
Photonics North 2008, 2008Co-Authors: Tara M. Todoruk, Ian D. Hartley, Jon Schneider, Matthew ReidAbstract:Fibre content of solid wood plays an important role in the wood products industry in terms of value. Additionally, fibre structure in composite wood products such as Oriented Strand Board (OSB) and paper products plays an important role in terms of strength properties. The effect of moisture content on wood properties is important in the manufacturing process and final product performance, and therefore its effect on the Birefringence is of considerable interest. Since solid wood exhibits strong Birefringence at terahertz frequencies, there may be potential applications of terahertz spectroscopy to fibre content and structure sensing. There are two potential sources for this strong Birefringence: (i) form Birefringence resulting from the porous structure of solid wood and (ii) intrinsic Birefringence resulting from the dielectric properties of the material itself. In this report, the variability of Birefringence within and between species, the dependence of the Birefringence on moisture content and the relative contributions from form and intrinsic Birefringence are examined. In order to clarify the role of these contributions to the measured Birefringence, polarized terahertz reflection spectroscopy is examined and compared to the results obtained in a transmission geometry. Comparison of the Birefringence measured in transmission and reflection geometries suggests that form Birefringence may dominate.
