1. Articles from John S. Oghalai

    1-19 of 19
    1. Noise and sensitivity in optical coherence tomography based vibrometry

      Noise and sensitivity in optical coherence tomography based vibrometry

      There is growing interest in using the exquisite phase sensitivity of optical coherence tomography (OCT) to measure the vibratory response in organ systems such as the middle and inner ear. Using frequency domain analysis, it is possible to achieve picometer sensitivity to vibration over a wide frequency band. Here we explore the limits of the frequency domain vibratory sensitivity due to additive noise and consider the implication of phase noise statistics on the estimation of vibratory amplitude and phase. Noise statistics are derived in both the Rayleigh ( s/n = 0 ) and Normal distribution ( s/n > 3 ) limits. These theoretical findings ...

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    2. Picometer scale vibrometry in the human middle ear using a surgical microscope based optical coherence tomography and vibrometry system

      Picometer scale vibrometry in the human middle ear using a surgical microscope based optical coherence tomography and vibrometry system

      We have developed a highly phase stable optical coherence tomography and vibrometry system that attaches directly to the accessory area of a surgical microscope common to both the otology clinic and operating room. Careful attention to minimizing sources of phase noise has enabled a system capable of measuring vibrations of the middle ear with a sensitivity of < 5 pm in an awake human patient. The system is shown to be capable of collecting a wide range of information on the morphology and function of the ear in live subjects, including frequency tuning curves below the hearing threshold, maps of tympanic ...

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    3. Organ of Corti vibration within the intact gerbil cochlea measured by volumetric optical coherence tomography and vibrometry

      Organ of Corti vibration within the intact gerbil cochlea measured by volumetric optical coherence tomography and vibrometry

      There is indirect evidence that the mammalian cochlea in the low-frequency apical and the more commonly-studied high-frequency basal regions function in fundamentally different ways. Here, we directly tested this hypothesis by measuring sound-induced vibrations of the organ of Corti (OoC) at three turns of the gerbil cochlea using volumetric optical coherence tomography vibrometry (VOCTV), an approach that permits non-invasive imaging through the bone. In the apical turn, there was little frequency selectivity and the displacement-versus-frequency curves had low-pass filter characteristics with a corner frequency of ~0.5-0.9 kHz. The vibratory magnitudes increased compressively with increasing stimulus intensity at all ...

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    4. Osmotic stabilization prevents cochlear synaptopathy after blast trauma

      Osmotic stabilization prevents cochlear synaptopathy after blast trauma

      Traumatic noise causes hearing loss by damaging sensory hair cells and their auditory synapses. There are no treatments. Here, we investigated mice exposed to a blast wave approximating a roadside bomb. In vivo cochlear imaging revealed an increase in the volume of endolymph, the fluid within scala media, termed endolymphatic hydrops. Endolymphatic hydrops, hair cell loss, and cochlear synaptopathy were initiated by trauma to the mechanosensitive hair cell stereocilia and were K + -dependent. Increasing the osmolality of the adjacent perilymph treated endolymphatic hydrops and prevented synaptopathy, but did not prevent hair cell loss. Conversely, inducing endolymphatic hydrops in control mice ...

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    5. Endoscopic optical coherence tomography enables morphological and subnanometer vibratory imaging of the porcine cochlea through the round window

      Endoscopic optical coherence tomography enables morphological and subnanometer vibratory imaging of the porcine cochlea through the round window

      A highly phase stable hand-held (HH) endoscopic system has been developed for optical coherence tomography and vibrometry. Designed to transit the ear canal to the middle ear space and peer through the round window (RW), it is capable of imaging the vibratory function of the cochlear soft tissues with subnanometer scale sensitivity. A side-looking, 9 cm long rigid endoscope with a distal diameter of 1.2 mm, was able to fit within the RW niche and provide imaging access. The phase stability was achieved in part by fully integrating a Michelson interferometer into the HH device. Ex vivo imaging of ...

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    6. ELHnet: a convolutional neural network for classifying cochlear endolymphatic hydrops imaged with optical coherence tomography

      ELHnet: a convolutional neural network for classifying cochlear endolymphatic hydrops imaged with optical coherence tomography

      Detection of endolymphatic hydrops is important for diagnosing Meniere’s disease, and can be performed non-invasively using optical coherence tomography (OCT) in animal models as well as potentially in the clinic. Here, we developed ELHnet, a convolutional neural network to classify endolymphatic hydrops in a mouse model using learned features from OCT images of mice cochleae. We trained ELHnet on 2159 training and validation images from 17 mice, using only the image pixels and observer-determined labels of endolymphatic hydrops as the inputs. We tested ELHnet on 37 images from 37 mice that were previously not used, and found that the ...

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    7. Computer-aided detection and quantification of endolymphatic hydrops within the mouse cochlea in vivo using optical coherence tomography

      Computer-aided detection and quantification of endolymphatic hydrops within the mouse cochlea in vivo using optical coherence tomography

      Diseases that cause hearing loss and/or vertigo in humans such as Meniere’s disease are often studied using animal models. The volume of endolymph within the inner ear varies with these diseases. Here, we used a mouse model of increased endolymph volume, endolymphatic hydrops, to develop a computer-aided objective approach to measure endolymph volume from images collected in vivo using optical coherence tomography. The displacement of Reissner’s membrane from its normal position was measured in cochlear cross sections. We validated our computer-aided measurements with manual measurements and with trained observer labels. This approach allows for computer-aided detection of ...

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    8. High-speed spectral calibration by complex FIR filter in phase-sensitive optical coherence tomography

      High-speed spectral calibration by complex FIR filter in phase-sensitive optical coherence tomography

      Swept-laser sources offer a number of advantages for Phase-sensitive Optical Coherence Tomography (PhOCT). However, inter- and intra-sweep variability leads to calibration errors that adversely affect phase sensitivity. While there are several approaches to overcoming this problem, our preferred method is to simply calibrate every sweep of the laser. This approach offers high accuracy and phase stability at the expense of a substantial processing burden. In this approach, the Hilbert phase of the interferogram from a reference interferometer provides the instantaneous wavenumber of the laser, but is computationally expensive. Fortunately, the Hilbert transform may be approximated by a Finite Impulse-Response (FIR ...

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    9. Phase-sensitive optical coherence tomography-based vibrometry using a highly phase-stable akinetic swept laser source

      Phase-sensitive optical coherence tomography-based vibrometry using a highly phase-stable akinetic swept laser source

      Phase-sensitive Optical Coherence Tomography (PhOCT) is an emerging tool for in vivo investigation of the vibratory function of the intact middle and inner ear. PhOCT is able to resolve micron scale tissue morphology in three dimensions as well as measure picometer scale motion at each spatial position. Most PhOCT systems to date have relied upon the phase stability offered by spectrometer detection. On the other hand swept laser source based PhOCT offers a number of advantages including balanced detection, long imaging depths, and high imaging speeds. Unfortunately the inherent phase instability of traditional swept laser sources has necessitated complex user ...

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    10. Miniature, minimally invasive, tunable endoscope for investigation of the middle ear

      Miniature, minimally invasive, tunable endoscope for investigation of the middle ear

      We demonstrate a miniature, tunable, minimally invasive endoscope for diagnosis of the auditory system. The probe is designed to sharply image anatomical details of the middle ear without the need for physically adjusting the position of the distal end of the endoscope. This is achieved through the addition of an electrowetted, tunable, electronically-controlled lens to the optical train. Morphological imaging is enabled by scanning light emanating from an optical coherence tomography system. System performance was demonstrated by imaging part of the ossicular chain and wall of the middle ear cavity of a normal mouse. During the experiment, we electronically moved ...

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    11. Feature Of The Week 04/05/15: Noninvasive in vivo Imaging Reveals Differences Between Tectorial Membrane and Basilar Membrane Traveling Waves in the Mouse Cochlea

      Feature Of The Week 04/05/15: Noninvasive in vivo Imaging Reveals Differences Between Tectorial Membrane and Basilar Membrane Traveling Waves in the Mouse Cochlea

      Sound is encoded within the auditory portion of the inner ear, the cochlea, after propagating down its length as a traveling wave. For over half a century, vibratory measurements to study cochlear traveling waves have been made using invasive approaches such as laser Doppler vibrometry. While these studies have provided critical information regarding the non-linear processes within the living cochlea that increase the amplitude of vibration and sharpen frequency tuning, the data have typically been limited to point measurements of basilar membrane vibration. In addition, opening the cochlea may alter its function and affect the findings. Here we describe volumetric ...

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    12. Noninvasive in vivo imaging reveals differences between tectorial membrane and basilar membrane traveling waves in the mouse cochlea

      Noninvasive in vivo imaging reveals differences between tectorial membrane and basilar membrane traveling waves in the mouse cochlea

      Sound is encoded within the auditory portion of the inner ear, the cochlea, after propagating down its length as a traveling wave. For over half a century, vibratory measurements to study cochlear traveling waves have been made using invasive approaches such as laser Doppler vibrometry. Although these studies have provided critical information regarding the nonlinear processes within the living cochlea that increase the amplitude of vibration and sharpen frequency tuning, the data have typically been limited to point measurements of basilar membrane vibration. In addition, opening the cochlea may alter its function and affect the findings. Here we describe volumetric ...

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    13. Phase-sensitive optical coherence tomography using an Vernier-tuned distributed Bragg reflector swept laser in the mouse middle ear

      Phase-sensitive optical coherence tomography using an Vernier-tuned distributed Bragg reflector swept laser in the mouse middle ear

      Phase-sensitive optical coherence tomography (PhOCT) offers exquisite sensitivity to mechanical vibration in biological tissues. There is growing interest in using PhOCT for imaging the nanometer scale vibrations of the ear in animal models of hearing disorders. Swept-source-based systems offer fast acquisition speeds, suppression of common mode noise via balanced detection, and good signal roll-off. However, achieving high phase stability is difficult due to nonlinear laser sweeps and trigger jitter in a typical swept laser source. Here, we report on the initial application of a Vernier-tuned distributed Bragg reflector (VT-DBR) swept laser as the source for a fiber-based PhOCT system. The ...

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    14. Method And Apparatus For Examining Inner Ear

      Method And Apparatus For Examining Inner Ear

      An apparatus, for examining an inner ear is provided. An endoscope is provided, comprising a wave guide and an end piece comprising an end window to be placed a first distance from an inner ear, wherein the waveguide focuses light to create a focal plane the first distance from the end window. An optical coherence tomography (OCT) system is connected to a second end of the wave guide and comprises an imaging system connected to the OCT system for generating an image of the inner ear.

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    15. In vivo vibrometry inside the apex of the mouse cochlea using spectral domain optical coherence tomography

      In vivo vibrometry inside the apex of the mouse cochlea using spectral domain optical coherence tomography

      Sound transduction within the auditory portion of the inner ear, the cochlea, is a complex nonlinear process. The study of cochlear mechanics in large rodents has provided important insights into cochlear function. However, technological and experimental limitations have restricted studies in mice due to their smaller cochlea. These challenges are important to overcome because of the wide variety of transgenic mouse strains with hearing loss mutations that are available for study. To accomplish this goal, we used spectral domain optical coherence tomography to visualize and measure sound-induced vibrations of intracochlear tissues. We present, to our knowledge, the first vibration measurements ...

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    16. Methodology for assessment of structural vibrations by spectral domain optical coherence tomography

      Methodology for assessment of structural vibrations by spectral domain optical coherence tomography

      Clinical diagnosis of cochlear dysfunction typically remains incomplete due to a lack of proper diagnostic methods. Medical imaging modalities can only detect gross changes in the cochlea, and non-invasive in vivo cochlear measurements are scarce. As a result, extensive efforts have been made to adapt optical coherence tomography (OCT) techniques to analyze and study the cochlea. Herein, we detail the methods for measuring vibration using OCT. We used spectral domain OCT with ~950 nm as the center wavelength and a bandwidth of ~80 nm. The custom spectrometer used was based on a high speed line scan camera which is capable ...

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    17. Imaging high-frequency periodic motion in the mouse ear with coherently interleaved optical coherence tomography

      Imaging high-frequency periodic motion in the mouse ear with coherently interleaved optical coherence tomography

      Vibratory measurements of the structures of the ear are key to understanding much of the pathology in mouse models of hearing loss. Unfortunately the high-speed sampling required to interrogate the high end of the mouse hearing spectrum is beyond the reach of most optical coherence tomography (OCT) systems. To address this issue, we have developed an algorithm that enables phase-sensitive OCT measurements over the full range of the mouse hearing spectrum (4–90 kHz). The algorithm phase-locks the line-trigger to the acoustic stimulation and then uses interleaved sampling to reconstruct the signal with higher temporal sampling. The algorithm was evaluated ...

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    18. Biophysical Mechanisms Underlying Hearing Loss Associated with a Shortened Tectorial Membrane

      Biophysical Mechanisms Underlying Hearing Loss Associated with a Shortened Tectorial Membrane

      The tectorial membrane (TM) connects to the stereociliary bundles of outer hair cells (OHCs). Herein, we summarize key experimental data and modeling analyses that describe how biophysical alterations to these connections underlie hearing loss. The heterozygous C1509G mutation in alpha tectorin produces partial congenital hearing loss that progresses in humans. We engineered this mutation in mice, and histology revealed that the TM was shortened. DIC imaging of freshly-dissected cochlea as well as imaging with optical coherence tomography indicated that the TM is malformed and only stimulates the first row of OHCs. Noise exposure produced acute threshold shifts that fully recovered ...

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    19. Quantitative imaging of cochlear soft tissues in wild-type and hearing-impaired transgenic mice by spectral domain optical coherence tomography

      Quantitative imaging of cochlear soft tissues in wild-type and hearing-impaired transgenic mice by spectral domain optical coherence tomography

      Human hearing loss often occurs as a result of damage or malformations to the functional soft tissues within the cochlea, but these changes are not appreciable with current medical imaging modalities. We sought to determine whether optical coherence tomography (OCT) could assess the soft tissue structures relevant to hearing using mouse models. We imaged excised cochleae with an altered tectorial membrane and during normal development. The soft tissue structures and expected anatomical variations were visible using OCT, and quantitative measurements confirmed the ability to detect critical changes relevant to hearing.

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    1-19 of 19
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    1. (19 articles) Brian E. Applegate
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    Quantitative imaging of cochlear soft tissues in wild-type and hearing-impaired transgenic mice by spectral domain optical coherence tomography Biophysical Mechanisms Underlying Hearing Loss Associated with a Shortened Tectorial Membrane Imaging high-frequency periodic motion in the mouse ear with coherently interleaved optical coherence tomography Methodology for assessment of structural vibrations by spectral domain optical coherence tomography In vivo vibrometry inside the apex of the mouse cochlea using spectral domain optical coherence tomography Method And Apparatus For Examining Inner Ear Noninvasive in vivo imaging reveals differences between tectorial membrane and basilar membrane traveling waves in the mouse cochlea Feature Of The Week 04/05/15: Noninvasive in vivo Imaging Reveals Differences Between Tectorial Membrane and Basilar Membrane Traveling Waves in the Mouse Cochlea Miniature, minimally invasive, tunable endoscope for investigation of the middle ear Osmotic stabilization prevents cochlear synaptopathy after blast trauma Conavi Medical and Japan Lifeline Announce MHLW Approval of Novasight Hybrid Intravascular Imaging System for Japanese Market Capsule Endomicroscopy for Visualization of the Small Intestine in EED Population in Pakistan