1. Articles from Tyler S. Ralston

    1-12 of 12
    1. Inverse scattering for frequency-scanned full-field optical coherence tomography

      Inverse scattering for frequency-scanned full-field optical coherence tomography

      Full-field optical coherence tomography (OCT) is able to image an entire en face plane of scatterers simultaneously, but typically the focus is scanned through the volume to acquire three-dimensional structure. By solving the inverse scattering problem for full-field OCT, we show it is possible to computationally reconstruct a three-dimensional volume while the focus is fixed at one plane inside the sample. While a low-numerical-aperture (NA) OCT system can tolerate defocus because the depth of field is large, for high NA it is critical to correct for defocus. By deriving a solution to the inverse scattering problem for full-field OCT, we ...

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    2. Interferometric Synthetic Aperture Microscopy: Microscopic Laser Radar

      Interferometric Synthetic Aperture Microscopy: Microscopic Laser Radar
      Combining optical coherence tomography instrumentation and the principles of synthetic aperture radar, researchers have developed a new method for reconstructing 3-D optical images—even in regions that are out of focus in the raw data. Doctors may soon be able to use this approach as a noninvasive diagnostic tool in clinical settings. Microscopic 3-D optical imaging provides guidance to tomorrow’s doctors during surgical interventions. In many clinical scenarios, doctors require high-resolution visualization of tissues and their underlying cellular structures. Perhaps the most common example is for the identification, diagnosis and treatment of cancer. In such cases, clinicians typically take ...
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    3. Cross-validation of interferometric synthetic aperture microscopy and optical coherence tomography

      Cross-validation of interferometric synthetic aperture microscopy and optical coherence tomography
      Computationally reconstructed interferometric synthetic aperture microscopy is coregistered with optical coherence tomography (OCT) focal plane data to provide quantitative cross validation with OCT. This is accomplished through a qualitative comparison of images and a quantitative analysis of the width of the point-spread function in simulation and experiment. The width of the ISAM point-spread function is seen to be independent of depth, in contrast to OCT.
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    4. Magnetomotive nanoparticle transducers for optical rheology of viscoelastic materials

      Magnetomotive nanoparticle transducers for optical rheology of viscoelastic materials
      The availability of a real-time non-destructive modality to interrogate the mechanical properties of viscoelastic materials would facilitate many new investigations. We introduce a new optical method for measuring elastic properties of samples which employs magnetite nanoparticles as perturbative agents. Magnetic nanoparticles distributed in silicone-based samples are displaced upon probing with a small external magnetic field gradient and depth-resolved optical coherence phase shifts allow for the tracking of scatterers in the sample with nanometer-scale sensitivity. The scatterers undergo underdamped oscillations when the magnetic field is applied step-wise, allowing for the measurement of the natural frequencies of oscillation of the samples. Validation ...
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    5. Interferometric synthetic aperture microscopy

      Methods and apparatus for three-dimensional imaging of a sample. A source is provided of a beam of substantially collimated light characterized by a temporally dependent spectrum. The beam is focused in a plane characterized by a fixed displacement along the propagation axis of the beam, and scattered light from the sample is superposed with a reference beam derived from the substantially collimated source onto a focal plane detector array to provide an interference signal. A forward scattering model is derived relating measured data to structure of an object to allow solution of an inverse scattering problem based upon the interference ...
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    6. Detecting intrinsic scattering changes correlated to neuron action potentials using optical coherence imaging

      Detecting intrinsic scattering changes correlated to neuron action potentials using optical coherence imaging
      We demonstrate how optical coherence imaging techniques can detect intrinsic scattering changes that occur during action potentials in single neurons. Using optical coherence tomography (OCT), an increase in scattering intensity from neurons in the abdominal ganglion of Aplysia californica is observed following electrical stimulation of the connective nerve. In addition, optical coherence microscopy (OCM), with its superior transverse spatial resolution, is used to demonstrate a direct correlation between scattering intensity changes and membrane voltage in single cultured Aplysia bag cell neurons during evoked action potentials. While intrinsic scattering changes are small, OCT and OCM have potential use as tools in ...
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    7. Imaging gold nanorods in excised human breast carcinoma by spectroscopic optical coherence tomography

      Imaging gold nanorods in excised human breast carcinoma by spectroscopic optical coherence tomography
      Plasmon-resonant gold nanorods (GNRs) can serve as imaging agents for spectroscopic optical coherence tomography (SOCT). The aspect ratio of the GNRs is adjusted for maximum absorption in the far red to create a partial spectral overlap with the short-wavelength edge of the near-infrared SOCT imaging band. The spectroscopic absorption profile of the GNRs is incorporated into a depth-resolved algorithm for mapping the relative GNR density within OCT images. This technique enables us to image GNR distributions in excised human breast carcinomas, demonstrating their potential as OCT contrast agents in heterogeneous, highly scattering tissues.
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    8. Interferometric Synthetic Aperture Microscopy: Physics-Based Image Reconstruction from Optical Coherence Tomography Data

      Optical coherence tomography (OCT) is an optical ranging technique analogous to radar - detection of back-scattered light produces a signal that is temporally localized at times-of-flight corresponding to the location of scatterers in the object. However the interferometric collection technique used in OCT allows, in principle, the coherent collection of data, i.e. amplitude and phase information can be extracted. Interferometric synthetic aperture microscopy (ISAM) adds phase-stable data collection to OCT instrumentation and employs physics-based processing analogous to that used in synthetic aperture radar (SAR). That is, the complex nature of the coherent data is exploited to give gains in image ...
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    9. High-speed processing architecture for spectral-domain optical coherence microscopy

      Robin G. Chelliyil, Tyler S. Ralston, Daniel L. Marks et al. Optical coherence microscopy (OCM) is an interferometric technique that combines principles of confocal microscopy and optical coherence tomography (OCT) to obtain high-resolution en face images. Axial and lateral resolutions of several microns can be achieved using OCM depending on the numerical ap ... [J. Biomed. Opt. 13, 044013 (2008)] published Fri Aug 8, 2008.
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    10. Interferometric synthetic aperture microscopy: tissue structure inferred by computed imaging techniques

      Interferometric synthetic aperture microscopy: tissue structure inferred by computed imaging techniques
      Daniel L. Marks, Tyler S. Ralston, Brynmor J. Davis et al. Interferometric Synthetic Aperture Microscopy (ISAM) is an optical microscopy computed-imaging technique for measuring the optical properties of three-dimensional structures and biological tissues. In this work, the principle of ISAM is reviewed, and its application to imaging tissue properties in v ... [Proc. SPIE Int. Soc. Opt. Eng. 6864, 686407 (2008)] published Fri Feb 15, 2008.
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    11. Real-time interferometric synthetic aperture microscopy

      Tyler S. Ralston, Daniel L. Marks, P. S. Carney, Stephen A. Boppart. An interferometric synthetic aperture microscopy (ISAM) system design with real-time 2D cross-sectional processing is described in detail. The system can acquire, process, and display the ISAM reconstructed images at frame rates of 2.25 frames per second for 512 X 1024 pixel images. This system ... [Opt. Express 16, 2555-2569 (2008)]
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    12. Interferometric synthetic aperture microscopy

      Interferometric synthetic aperture microscopy
      State-of-the-art methods in high-resolution three-dimensional optical microscopy require that the focus be scanned through the entire region of interest. However, an analysis of the physics of the light–sample interaction reveals that the Fourier-space coverage is independent of depth. Here we show that, by solving the inverse scattering problem for interference microscopy, computed reconstruction yields volumes with a resolution in all planes that is equivalent to the resolution achieved only at the focal plane for conventional high-resolution microscopy. In short, the entire illuminated volume has spatially invariant resolution, thus eliminating the compromise between resolution and depth of field. We describe ...
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    1-12 of 12
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  2. Topics in the News

    1. (12 articles) University of Illinois at Urbana-Champaign
    2. (12 articles) Tyler S. Ralston
    3. (12 articles) Stephen A. Boppart
    4. (8 articles) P. Scott Carney
    5. (8 articles) Daniel L. Marks
    6. (2 articles) Amy L. Oldenburg
    7. (2 articles) Steven G. Adie
    8. (1 articles) Purdue University
    9. (1 articles) Vasilica Crecea
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    11. (1 articles) Xincheng Yao
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    Interferometric synthetic aperture microscopy: tissue structure inferred by computed imaging techniques Imaging gold nanorods in excised human breast carcinoma by spectroscopic optical coherence tomography Magnetomotive nanoparticle transducers for optical rheology of viscoelastic materials Interferometric synthetic aperture microscopy Cross-validation of interferometric synthetic aperture microscopy and optical coherence tomography Interferometric Synthetic Aperture Microscopy: Microscopic Laser Radar Postdoctoral Openings in Biomedical Optics and Retinal Imaging Laboratory at University of Illinois at Chicago Integrated Multifunctional Laryngoscope for Medical Diagnosis and Treatment Devices and arrangements for performing coherence range imaging using a common path interferometer Scan error correction in low coherence scanning interferometry Optical imaging techniques could offer non-invasive method to measure swelling within the brain, new study finds Using Optical Coherence Tomography as a Surrogate of Measurements of Intracranial Pressure in Idiopathic Intracranial Hypertension