1. Articles from Niloy Choudhury

    1-14 of 14
    1. Feature Of The Week 3/17/13: Using Optical Coherence Tomography to Study Mechanisms of Hearing

      Feature Of The Week 3/17/13: Using Optical Coherence Tomography to Study Mechanisms of Hearing

      The Oregon Hearing Research Centre (OHRC) at the Oregon Health and Science University (OHSU), Portland, Oregon is one of the strongest hearing research groups in the world, and one of the early adopters of optical coherence tomography technology in the field of hearing research. Researchers at OHRC have developed a couple of novel OCT based imaging technologies for functional imaging of middle and inner ear. This includes high-speed OCT system for in vivo imaging of microstructural morphology and micvascular perfusion within the cochlea [1,2], phase-sensitive time-domain and Fourier domain OCT for studying cochlear micromechanics [3,4] and middle ear ...

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    2. Measurement of in vivo basal-turn vibrations of the organ of Corti using phase-sensitive Fourier domain optical coherence tomography

      Measurement of in vivo basal-turn vibrations of the organ of Corti using phase-sensitive Fourier domain optical coherence tomography

      A major reason we can perceive faint sounds and communicate in noisy environments is that the outer hair cells of the organ of Corti enhance the sound-evoked motions inside the cochlea. To understand how the organ of Corti works, we have built and tested the phase-sensitive Fourier domain optical coherence tomography (PSFDOCT) system. This system has key advantages over our previous time domain OCT system [1]. The PSFDOCT system has better signal to noise and simultaneously acquires vibration data from all points along the optical-axis [2]. Feasibility of this system to measure in vitro cochlear vibrations in the apex was ...

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    3. Depth-resolved dual-beamlet vibrometry based on Fourier domain low coherence interferometry

      Depth-resolved dual-beamlet vibrometry based on Fourier domain low coherence interferometry

      We present an optical vibrometer based on delay-encoded, dual-beamlet phase-sensitive Fourier domain interferometric system to provide depth-resolved subnanometer scale vibration information from scattering biological specimens. System characterization, calibration, and preliminary vibrometry with biological specimens were performed. The proposed system has the potential to provide both amplitude and direction of vibration of tissue microstructures on a single two-dimensional plane.

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    4. Feasibility of spectral-domain phase-sensitive optical coherence tomography for middle ear vibrometry

      Feasibility of spectral-domain phase-sensitive optical coherence tomography for middle ear vibrometry

      We describe a novel application of spectral-domain phase-sensitive optical coherence tomography (SD PS-OCT) to detect the tiny motions of the middle ear structures, such as the tympanic membrane and ossicular chain, and their morphological features for differential diagnosis of CHL. This technique has the potential to provide meaningful vibration of ossicles with a vibration sensitivity of ∼ 0.5  nm at 1 kHz of acoustic stimulation. To the best of our knowledge, this is the first demonstration of depth-resolved vibration imaging of ossicles with a PS-OCT system at a nanometer scale.

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    5. Feature Of The Week 5/27/11: Researchers Utilize Optical Coherence Tomography to Perform in vivo Investigation into the Process of Hearing

      Feature Of The Week 5/27/11: Researchers Utilize Optical Coherence Tomography to Perform in vivo Investigation into the Process of Hearing

      A multidisciplinary research groups spanning several countries (USA, China, Sweden) are using optical coherence tomography (OCT) to investigate minute changes in hair cells within the cochlea - the auditory portion of the inner ear. Below is a summary of their work. Mammalian hearing is refined by amplification of the sound-evoked vibration of the cochlear partition. This amplification is at least partly due to forces produced by protein motors residing in the cylindrical body of the outer hair cell. To transmit power to the cochlear partition, it is required that the outer hair cells dynamically change their length, in addition to generating ...

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    6. In Vivo Outer Hair Cell Length Changes Expose the Active Process in the Cochlea

      In Vivo Outer Hair Cell Length Changes Expose the Active Process in the Cochlea

      Background Mammalian hearing is refined by amplification of the sound-evoked vibration of the cochlear partition. This amplification is at least partly due to forces produced by protein motors residing in the cylindrical body of the outer hair cell. To transmit power to the cochlear partition, it is required that the outer hair cells dynamically change their length, in addition to generating force. These length changes, which have not previously been measured in vivo, must be correctly timed with the acoustic stimulus to produce amplification. Methodology/Principal Findings Using in vivo optical coherence tomography, we demonstrate that outer hair cells in ...

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    7. Absolute measurement of subnanometer scale vibration of cochlear partition of an excised guinea pig cochlea using spectral-domain phase-sensitive optical coherence tomography

      Absolute measurement of subnanometer scale vibration of cochlear partition of an excised guinea pig cochlea using spectral-domain phase-sensitive optical coherence tomography

      Direct measurement of absolute vibration parameters from different locations within the mammalian organ of Corti is crucial for understanding the hearing mechanics such as how sound propagates through the cochlea and how sound stimulates the vibration of various structures of the cochlea, namely, basilar membrane (BM), recticular lamina, outer hair cells and tectorial membrane (TM). In this study we demonstrate the feasibility a modified phase-sensitive spectral domain optical coherence tomography system to provide subnanometer scale vibration information from multiple angles within the imaging beam. The system has the potential to provide depth resolved absolute vibration measurement of tissue microstructures from ...

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    8. Imaging Organ of Corti Vibration Using Fourier-Domain OCT

      Imaging Organ of Corti Vibration Using Fourier-Domain OCT

      Measuring the sound stimulated vibration from various structures in the organ of Corti is important in understanding how the small vibrations are amplified and detected. In this study we examine the feasibility of using phase-sensitive Fourier domain optical coherence tomography (PSFD-OCT) to measure vibration of the cellular structures of the organ of Corti. PSFD-OCT is a low coherence interferrometry system where the interferrogram is detected as a function of wavelength. The phase of the Fourier transformation of the detected spectra contains path deference (between the sample arm and the reference arm) information of the interferometer. In PSFD-OCT this phase is ...

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    9. A differentially amplified motion in the ear for near-threshold sound detection

      A differentially amplified motion in the ear for near-threshold sound detection

      The ear is a remarkably sensitive pressure fluctuation detector. In guinea pigs, behavioral measurements indicate a minimum detectable sound pressure of ~20 μPa at 16 kHz. Such faint sounds produce 0.1-nm basilar membrane displacements, a distance smaller than conformational transitions in ion channels. It seems that noise within the auditory system would swamp such tiny motions, making weak sounds imperceptible. Here we propose a new mechanism contributing to a resolution of this problem and validate it through direct measurement. We hypothesized that vibration at the apical side of hair cells is enhanced compared with that at the commonly measured ...

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    10. Dermal reflectivity determined by optical coherence tomography is an indicator of epidermal hyperplasia and dermal edema within inflamed skin

      Dermal reflectivity determined by optical coherence tomography is an indicator of epidermal hyperplasia and dermal edema within inflamed skin
      Psoriasis is a common inflammatory skin disease resulting from genetic and environmental alterations of cutaneous immune responses. While numerous therapeutic targets involved in the immunopathogenesis of psoriasis have been identified, the in vivo dynamics of inflammation in psoriasis remain unclear. We undertook in vivo time course focus-tracked optical coherence tomography (OCT) imaging to noninvasively document cutaneous alterations in mouse skin treated topically with Imiquimod (IMQ), an established model of a psoriasis-like disease. Quantitative appraisal of dermal architectural changes was achieved through a two parameter fit of OCT axial scans in the dermis of the form A(x, y, z) = ρ ...
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    11. Quantitative characterization of developing collagen gels using optical coherence tomography

      Quantitative characterization of developing collagen gels using optical coherence tomography
      Nondestructive optical imaging methods such as optical coherence tomography (OCT) have been proposed for characterizing engineered tissues such as collagen gels. In our study, OCT was used to image collagen gels with different seeding densities of smooth muscle cells (SMCs), including acellular gels, over a five-day period during which the gels contracted and became turbid with increased optical scattering. The gels were characterized quantitatively by their optical properties, specified by analysis of OCT data using a theoretical model. At 6 h, seeded cell density and scattering coefficient (µs) were correlated, with µs equal to 10.8 cm−1/(106 cells ...
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    12. Optically characterizing collagen gels made with different cell types

      Optically characterizing collagen gels made with different cell types
      The ability of optical imaging techniques such as optical coherence tomography (OCT) to non-destructively characterize tissue-engineered constructs has generated enormous interest recently. Collagen gels are 3D structures that represent a simple common model of many engineered tissues that contain 2 primary scatterers: collagen and cells. We are testing the ability of OCT data to characterize the remodeling of such collagen-based constructs by 3 different types of cells: vascular smooth muscle cells (SMCs), endothelial cells (ECs), and osteoblasts (OBs). Collagen gels were prepared with SMCs, ECs, and OBs with a seeding density of 1×106 cells/ml; additionally, acellular controls were ...
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    13. The effect of wavelength on optical properties extracted from images of engineered tissue

      The effect of wavelength on optical properties extracted from images of engineered tissue
      Optical imaging modalities such as confocal microscopy and optical coherence tomography (OCT) are emerging as appealing methods for non-destructive evaluation of engineered tissues. The information offered by such optical imaging methods depends on the wavelength vis-á-vis the optical scattering properties of the sample. These properties affect many factors critical to image analysis in a nonlinear and nontrivial manner. Thus, we sought to characterize the effect wavelength has on the optical properties collagen remodeled by cells at 3 common imaging wavelengths: 488, 633, and 1310 nm. To do this, we seeded smooth muscle cells (SMCs) in soluble collagen gels at a ...
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    14. Measuring tissue optical properties in vivo using reflectance-mode confocal microscopy and OCT

      The ability to separately measure the scattering coefficient ([mu] [cm]) and the anisotropy (g) is difficult, especially when measuring an in vivo site that can not be excised for bench-top measurements. The scattering properties ([mu] and g) can characterize the ultrastructure of a biological tissu ... [Proc. SPIE Int. Soc. Opt. Eng. 6864, 68640B (2008)] published Fri Feb 15, 2008.
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    1-14 of 14
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    The effect of wavelength on optical properties extracted from images of engineered tissue Optically characterizing collagen gels made with different cell types Quantitative characterization of developing collagen gels using optical coherence tomography Dermal reflectivity determined by optical coherence tomography is an indicator of epidermal hyperplasia and dermal edema within inflamed skin A differentially amplified motion in the ear for near-threshold sound detection Absolute measurement of subnanometer scale vibration of cochlear partition of an excised guinea pig cochlea using spectral-domain phase-sensitive optical coherence tomography In Vivo Outer Hair Cell Length Changes Expose the Active Process in the Cochlea Feature Of The Week 5/27/11: Researchers Utilize Optical Coherence Tomography to Perform in vivo Investigation into the Process of Hearing Feature Of The Week 3/17/13: Using Optical Coherence Tomography to Study Mechanisms of Hearing Fantom Encore Sirolimus-eluting Bioresorbable Scaffold for Treatment of De-novo CAD: the ENCORE-I Study Assessment of Microcirculatory Dysfunction in Septic Shock Patients by OCTA OCT system used at home demonstrates potential for daily monitoring of AMD