1. Articles from Austin B. McElroy

    1-14 of 14
    1. Laser brain cancer surgery in a xenograft model guided by optical coherence tomography

      Laser brain cancer surgery in a xenograft model guided by optical coherence tomography

      Higher precision surgical devices are needed for tumor resections near critical brain structures. The goal of this study is to demonstrate feasibility of a system capable of precise and bloodless tumor ablation. An image-guided laser surgical system is presented for excision of brain tumors in vivo in a murine xenograft model. The system combines optical coherence tomography (OCT) guidance with surgical lasers for high-precision tumor ablation (Er:YAG) and microcirculation coagulation (Thulium (Tm) fiber laser). Methods: A fluorescent human glioblastoma cell line was injected into mice and allowed to grow four weeks. Craniotomies were performed and tumors were imaged with ...

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    2. Understanding and improving optical coherence tomography imaging depth in selective laser sintering nylon 12 parts and powder

      Understanding and improving optical coherence tomography imaging depth in selective laser sintering nylon 12 parts and powder

      Optical coherence tomography (OCT) has shown promise as a process sensor in selective laser sintering (SLS) due to its ability to yield depth-resolved data not attainable with conventional sensors. However, OCT images of nylon 12 powder and nylon 12 components fabricated via SLS contain artifacts that have not been previously investigated in the literature. A better understanding of light interactions with SLS powder and components is foundational for further research expanding the utility of OCT imaging in SLS and other additive manufacturing (AM) sensing applications. Specifically, in this work, nylon powder and sintered parts were imaged in air and in ...

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    3. In situ process monitoring in selective laser sintering using optical coherence tomography

      In situ process monitoring in selective laser sintering using optical coherence tomography

      Selective laser sintering (SLS) is an efficient process in additive manufacturing that enables rapid part production from computer-based designs. However, SLS is limited by its notable lack of in situ process monitoring when compared with other manufacturing processes. We report the incorporation of optical coherence tomography (OCT) into an SLS system in detail and demonstrate access to surface and subsurface features. Video frame rate cross-sectional imaging reveals areas of sintering uniformity and areas of excessive heat error with high temporal resolution. We propose a set of image processing techniques for SLS process monitoring with OCT and report the limitations and ...

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    4. Optical coherence tomography image-guided smart laser knife for surgery

      Optical coherence tomography image-guided smart laser knife for surgery

      Background and Objective Surgical oncology can benefit from specialized tools that enhance imaging and enable precise cutting and removal of tissue without damage to adjacent structures. The combination of high-resolution, fast optical coherence tomography (OCT) co-aligned with a nanosecond pulsed thulium (Tm) laser offers advantages over conventional surgical laser systems. Tm lasers provide superior beam quality, high volumetric tissue removal rates with minimal residual thermal footprint in tissue, enabling a reduction in unwanted damage to delicate adjacent sub-surface structures such as nerves or micro-vessels. We investigated such a combined Tm/OCT system with co-aligned imaging and cutting beams—a configuration ...

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    5. Feature Of The Week 5/26/2013: University of Texas at Austin Investigates Dual-Wavelength Photothermal OCT for Imaging Microvasculature Blood Oxygen Saturation

      Feature Of The Week 5/26/2013: University of Texas at Austin Investigates Dual-Wavelength Photothermal OCT for Imaging Microvasculature Blood Oxygen Saturation

      A swept-source dual-wavelength photothermal optical coherence tomography (DWP-OCT) is demonstrated for imaging and measurement of microvasculature oxygen saturation (SO2). DWP-OCT is capable of recording three-dimensional images of tissue and depth-resolved phase variation in response to photothermal excitations in two different wavelengths (770 and 800 nm). Two phantom microvessels with different inner-diameter size (50 and 300 μm) were constructed, porcine blood with various SO2 levels were prepared for the experiment. Phantom microvessels were imaged and blood SO2 levels measured using DWP-OCT are compared with values provided by a commercial oximeter. Propagation error analysis suggests DWP-OCT is feasible for measurement of blood ...

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    6. Dual-wavelength photothermal optical coherence tomography for imaging microvasculature blood oxygen saturation

      Dual-wavelength photothermal optical coherence tomography for imaging microvasculature blood oxygen saturation

      A swept-source dual-wavelength photothermal (DWP) optical coherence tomography (OCT) system is demonstrated for quantitative imaging of microvasculature oxygen saturation. DWP-OCT is capable of recording three-dimensional images of tissue and depth-resolved phase variation in response to photothermal excitation. A 1,064-nm OCT probe and 770-nm and 800-nm photothermal excitation beams are combined in a single-mode optical fiber to measure microvasculature hemoglobin oxygen saturation ( SO 2 ) levels in phantom blood vessels with a range of blood flow speeds (0 to 17     mm / s ). A 50- μ m-diameter blood vessel phantom is imaged, and SO 2 levels are measured using DWP-OCT and compared with ...

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    7. Dual-wavelength photothermal optical coherence tomography for blood oxygen saturation measurement

      Dual-wavelength photothermal optical coherence tomography for blood oxygen saturation measurement

      We report design and demonstration of a dual wavelength photothermal (DWP) optical coherence tomography (OCT) system for imaging of a phantom microvessel and measurement of hemoglobin oxygen saturation (SO 2 ) level. The DWP-OCT system contains a swept-source (SS) two-beam phase-sensitive (PhS) OCT system (1060 nm) and two intensity modulated photothermal excitation lasers (770 nm and 800 nm). The PhS-OCT probe beam (1060 nm) and photothermal excitation beams are combined into one single-mode optical fiber. A galvanometer based two-dimensional achromatic scanning system is designed to provide 14 μm lateral resolution for the PhS-OCT probe beam (1060 nm) and 13 μm lateral ...

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    8. Feature Of The Week 1/22/12: In vivo depth-resolved oxygen saturation by dual-wavelength photothermal (DWP) OCT.

      Feature Of The Week 1/22/12: In vivo depth-resolved oxygen saturation by dual-wavelength photothermal (DWP) OCT.
      All mammalian tissues need oxygen for survival. The human body has a delicately organized vascular network that supplies our tissue with oxygen and other nutrients as well as removing waist products. Not surprisingly, aberrations in vascular oxygen supply are implicated in at least 70 diseases and that number continues to grow. The oxygen distribution from vascular hemoglobin to the parenchymal cells begins with oxygen diffusion first from arterioles with diameters less than 50 µm, and second from capillaries, with deoxygenated blood draining back to venules where the blood is redirected to the lungs for re-oxygenation. The earliest abnormalities in oxygen ...
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    9. In vivo depth-resolved oxygen saturation by dual-wavelength photothermal (DWP) OCT

      In vivo depth-resolved oxygen saturation by dual-wavelength photothermal (DWP) OCT
      Microvasculature hemoglobin oxygen saturation (SaO2) is important in the progression of various pathologies. Non-invasive depth-resolved measurement of SaO2 levels in tissue microvasculature has the potential to provide early biomarkers and a better understanding of the pathophysiological processes allowing improved diagnostics and prediction of disease progression. We report proof-of-concept in vivo depth-resolved measurement of SaO2 levels in selected 30 µm diameter arterioles in the murine brain using Dual-Wavelength Photothermal (DWP) Optical Coherence Tomography (OCT) with 800 nm and 770 nm photothermal excitation wavelengths. Depth location of back-reflected light from a target arteriole was confirmed using Doppler and speckle contrast OCT images ...
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    10. Birefringence measurement of the retinal nerve fiber layer by swept source polarization sensitive optical coherence tomography

      Birefringence measurement of the retinal nerve fiber layer by swept source polarization sensitive optical coherence tomography
      A Swept Source Polarization-Sensitive Optical Coherence Tomography (SS-PS-OCT) instrument has been designed, constructed, and verified to provide high sensitivity depth-resolved birefringence and phase retardation measurements of the retinal nerve fiber layer. The swept-source laser had a center wavelength of 1059 nm, a full-width-half-max spectral bandwidth of 58 nm and an A-line scan rate of 34 KHz. Power incident on the cornea was 440 µW and measured axial resolution was 17 µm in air. A multiple polarization state nonlinear fitting algorithm was used to measure retinal birefringence with low uncertainty. Maps of RNFL phase retardation in a subject measured with SS-PS-OCT ...
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    11. Depth-resolved blood oxygen saturation measurement by dual-wavelength photothermal (DWP) optical coherence tomography

      Depth-resolved blood oxygen saturation measurement by dual-wavelength photothermal (DWP) optical coherence tomography
      Non-invasive depth-resolved measurement of hemoglobin oxygen saturation (SaO2) levels in discrete blood vessels may have implications for diagnosis and treatment of various pathologies. We introduce a novel Dual-Wavelength Photothermal (DWP) Optical Coherence Tomography (OCT) for non-invasive depth-resolved measurement of SaO2 levels in a blood vessel phantom. DWP OCT SaO2 is linearly correlated with blood-gas SaO2 measurements. We demonstrate 6.3% precision in SaO2 levels measured a phantom blood vessel using DWP-OCT with 800 and 765 nm excitation wavelengths. Sources of uncertainty in SaO2 levels measured with DWP-OCT are identified and characterized.
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    12. Gas-Cell Referenced Swept Source Phase Sensitive Optical Coherence Tomography

      Gas-Cell Referenced Swept Source Phase Sensitive Optical Coherence Tomography
      Distinct reference and signal interferometers in combination with a gas-cell spectral reference are employed to increase sensitivity and environmental stability of a swept source phase-sensitive optical coherence tomography. A displacement sensitivity (DS) of 65 pm at 280- $muhbox{m}$ depth and DS degradation with depth of 0.0015 rad/mm is achieved. Differential DS of 234 pm in a 127-$muhbox{m}$ -thick scattering phantom is six-fold superior to previously reported values. DS degradation with a depth of 0.026 rad/mm is reported for tissue-like scattering phantoms. Measured depth-dependent DS suggests that digitization time jitter noise contributes to degradation ...
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    13. Near infrared femtosecond laser ablation of urinary calculi in water

      Pulsed light emitted from a near infrared (=800nm) femtosecond laser is capable of plasma induced photodisruption of various materials. We used femtosecond laser pulses to ablate human urinary calculi. Femtosecond pulsed laser interaction with urinary calculi was investigated with various stone compositions, different incident fluences and number of applied pulses. Spectral-domain optical coherence tomography was used to image cross sections of ablation craters on the surface of urinary calculi. Our results indicate that femtosecond laser pulses can ablate various calculi compositions. Crater diameter and depth varies from tens of microns to several hundred microns when up to 1000 pulses were ...

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    1-14 of 14
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    1. (14 articles) University of Texas at Austin
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    Gas-Cell Referenced Swept Source Phase Sensitive Optical Coherence Tomography Depth-resolved blood oxygen saturation measurement by dual-wavelength photothermal (DWP) optical coherence tomography Birefringence measurement of the retinal nerve fiber layer by swept source polarization sensitive optical coherence tomography In vivo depth-resolved oxygen saturation by dual-wavelength photothermal (DWP) OCT Feature Of The Week 1/22/12: In vivo depth-resolved oxygen saturation by dual-wavelength photothermal (DWP) OCT. Dual-wavelength photothermal optical coherence tomography for blood oxygen saturation measurement Dual-wavelength photothermal optical coherence tomography for imaging microvasculature blood oxygen saturation Feature Of The Week 5/26/2013: University of Texas at Austin Investigates Dual-Wavelength Photothermal OCT for Imaging Microvasculature Blood Oxygen Saturation In situ process monitoring in selective laser sintering using optical coherence tomography Systems and methods for reflectance-based projection-resolved optical coherence tomography angiography Health collaborations forged at CIIE begin to bear fruit Method for determining the topography of the cornea of an eye