1. Articles from Ashley J. Welch

    1-8 of 8
    1. Changes in morphology and optical properties of sclera and choroidal layers due to hyperosmotic agent

      Changes in morphology and optical properties of sclera and choroidal layers due to hyperosmotic agent

      Light scattering in the normally white sclera prevents diagnostic imaging or delivery of a focused laser beam to a target in the underlying choroid layer. In this study, we examine optical clearing of the sclera and changes in blood flow resulting from the application of glycerol to the sclera of rabbits. Recovery dynamics are monitored after the application of saline. The speed of clearing for injection delivery is compared to the direct application of glycerol through an incision in the conjunctiva. Although, the same volume of glycerol was applied, the sclera cleared much faster (5 to 10 s) with the ...

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    2. Overview of Optical and Thermal Laser-Tissue Interaction and Nomenclature

      Overview of Optical and Thermal Laser-Tissue Interaction and Nomenclature
      The development of a unified theory for the optical and thermal response of tissue to laser radiation is no longer in its infancy, though it is still not fully developed. This book describes our current understanding of the physical events that can occur when light interacts with tissue, particularly the sequence of formulations that estimate the optical and thermal responses of tissue to laser radiation. This overview is followed by an important chapter that describes the basic interactions of light with tissue. Part I considers basic tissue optics. Tissue is treated as an absorbing and scattering medium and methods are ...
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    3. Investigations on laser hard tissue ablation under various environments.

      Investigations on laser hard tissue ablation under various environments. Phys Med Biol. 2008 Jun 3;53(12):3381-3390 Authors: Kang HW, Oh J, Welch AJ The purpose of this study was to investigate the effect of liquid environments upon laser bone ablation. A long-pulsed Er,Cr:YSGG laser was employed to ablate bovine bone tibia at various radiant exposures under dry, wet (using water or perfluorocarbon) and spray environmental conditions. Energy loss by the application of liquid during laser irradiation was evaluated, and ablation performance for all conditions was quantitatively measured by optical coherence tomography (OCT). Microscope images were also ...
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    4. Investigations on laser hard tissue ablation under various environments

      The purpose of this study was to investigate the effect of liquid environments upon laser bone ablation. A long-pulsed Er,Cr:YSGG laser was employed to ablate bovine bone tibia at various radiant exposures under dry, wet (using water or perfluorocarbon) and spray environmental conditions. Energy loss by the application of liquid during laser irradiation was evaluated, and ablation performance for all conditions was quantitatively measured by optical coherence tomography (OCT). Microscope images were also used to estimate thermal side effects in tissue after multiple-pulse ablation. Wet using water and spray conditions equally attenuated the 2.79 µm wavelength laser ...
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    5. Enhancement of light in tissue using hyper-osmotic agents

      Raiyan T. Zaman, Bo Chen, Ashwin B. Parthasarathy et al. Optical changes in skin blood flow due to the presence of glycerol were measured from a two-dimensional map of blood flow in skin blood vessels with a dynamic imaging technique using laser speckle. In this study a dorsal skin-flap window was implanted on the hamster skin with and without a hyper-osm ... [Proc. SPIE Int. Soc. Opt. Eng. 6854, 68541F (2008)] published Tue Feb 12, 2008.
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    6. Laser treatment of cutaneous vascular lesions

      Methods for treating maladies such as cutaneous vascular lesions. A patient in need of vascular lesion treatment is identified. A hyperosmotic agent is administered to a region adjacent the lesion. Blood flow velocity is slowed within the region using the hyperosmotic agent, and the lesion is exposed to laser radiation.
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    7. Methods of enhanced light transmission through turbid biological media

      A new process to increase light transmission in biological tissue has been developed. The technique involves temporarily replacing tissue water with a fluid that has a refractive index closer to that of inter/intra cellular components. Subsequently, the amount of index mis-match between these components and the fluid environment is temporarily decreased. This lowers the amount of random reflection and refraction which also reduces light scattering. In addition, the infrared absorption is reduced when the fluid has a lower absorption coefficient than water. Furthermore, this process is reversible; thus creating a transient window to enhance light transmission for therapeutic and ...
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    8. In vivo bidirectional color Doppler flow imaging of picoliter blood volumes using optical coherence tomography

      In vivo bidirectional color Doppler flow imaging of picoliter blood volumes using optical coherence tomography
      We describe a novel optical system for bidirectional color Doppler imaging of flow in biological tissues with micrometer-scale resolution and demonstrate its use for in vivo imaging of blood flow in an animal model. Our technique, color Doppler optical coherence tomography (CDOCT), performs spatially localized optical Doppler velocimetry by use of scanning low-coherence interferometry. CDOCT is an extension of optical coherence tomography (OCT), employing coherent signal-acquisition electronics and joint time-frequency analysis algorithms to perform flow imaging simultaneous with conventional OCT imaging. Cross-sectional maps of blood flow velocity with <50-µm spatial resolution and <0.6-mm/s velocity precision were obtained through ...
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    1-8 of 8
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  2. Topics in the News

    1. (7 articles) University of Texas at Austin
    2. (1 articles) Academic Medical Center at the University of Amsterdam
    3. (1 articles) Case Western Reserve University
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    In vivo bidirectional color Doppler flow imaging of picoliter blood volumes using optical coherence tomography Overview of Optical and Thermal Laser-Tissue Interaction and Nomenclature Changes in morphology and optical properties of sclera and choroidal layers due to hyperosmotic agent Association of retinal thickness and microvasculature with cognitive performance and brain volumes in elderly adults A Deep Learning Framework for the Detection and Quantification of Reticular Pseudodrusen and Drusen on Optical Coherence Tomography Quantitative assessment of textural features in the early detection of diabetic retinopathy with optical coherence tomography angiography Line-field confocal optical coherence tomography of fibroepithelioma of Pinkus Assessment of demineralized tooth lesions using optical coherence tomography and other state-of-the-art technologies: a review Optic disc and retinal vessel densities assessment by optical coherence tomography angiography in patients with keratoconus Optical coherence tomography angiography in Bietti crystalline dystrophy Choroidal vascularity profile in diabetic eyes using wide field optical coherence tomography Diagnostic accuracy of OCTA and OCT for myopic choroidal neovascularisation: a systematic review and meta-analysis