1. Articles from Ernest W. Chang

    1-14 of 14
    1. Investigation of middle ear anatomy and function with combined video otoscopy-phase sensitive OCT

      Investigation of middle ear anatomy and function with combined video otoscopy-phase sensitive OCT

      We report the development of a novel otoscopy probe for assessing middle ear anatomy and function. Video imaging and phase-sensitive optical coherence tomography are combined within the same optical path. A sound stimuli channel is incorporated as well to study middle ear function. Thus, besides visualizing the morphology of the middle ear, the vibration amplitude and frequency of the eardrum and ossicles are retrieved as well. Preliminary testing on cadaveric human temporal bone models has demonstrated the capability of this instrument for retrieving middle ear anatomy with micron scale resolution, as well as the vibration of the tympanic membrane and ...

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    2. Combined reflectance confocal microscopy-optical coherence tomography for delineation of basal cell carcinoma margins: an ex vivo study

      Combined reflectance confocal microscopy-optical coherence tomography for delineation of basal cell carcinoma margins: an ex vivo study

      We present a combined reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) approach, integrated within a single optical layout, for diagnosis of basal cell carcinomas (BCCs) and delineation of margins. While RCM imaging detects BCC presence (diagnoses) and its lateral spreading (margins) with measured resolution of ∼ 1    μ m ∼1  μm , OCT imaging delineates BCC depth spreading (margins) with resolution of ∼ 7    μ m ∼7  μm . When delineating margins in 20 specimens of superficial and nodular BCCs, depth could be reliably determined down to ∼600    μ m ∼600  μm , and agreement with histology was within about ±50    μ m ±50  μm .

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    3. Observation of sound-induced corneal vibrational modes by optical coherence tomography

      Observation of sound-induced corneal vibrational modes by optical coherence tomography

      The mechanical stability of the cornea is critical for maintaining its normal shape and refractive function. Here, we report an observation of the mechanical resonance modes of the cornea excited by sound waves and detected by using phase-sensitive optical coherence tomography. The cornea in bovine eye globes exhibited three resonance modes in a frequency range of 50-400 Hz. The vibration amplitude of the fundamental mode at 80-120 Hz was ~8 µm at a sound pressure level of 100 dB (2 Pa). Vibrography allows the visualization of the radially symmetric profiles of the resonance modes. A dynamic finite-element analysis supports our ...

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    4. Hand scanning optical coherence tomography imaging using encoder feedback

      Hand scanning optical coherence tomography imaging using encoder feedback

      We present a new method for generating micron-scale OCT images of interstitial tissue with a hand scanning probe and a linear optical encoder that senses probe movement relative to a fixed reference point, i.e., tissue surface. Based on this approach, we demonstrate high resolution optical imaging of biological tissues through a very long biopsy needle. Minor artifacts caused by tissue noncompliance are corrected using a software algorithm which detects the simple repetition of the adjacent A-scans. This hand-scanning OCT imaging approach offers the physician the freedom to access imaging sites of interest repeatedly.

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    5. Low coherence interferometry approach for aiding fine needle aspiration biopsie

      Low coherence interferometry approach for aiding fine needle aspiration biopsie

      We present portable preclinical low-coherence interference (LCI) instrumentation for aiding fine needle aspiration biopsies featuring the second-generation LCI-based biopsy probe and an improved scoring algorithm for tissue differentiation. Our instrument and algorithm were tested on 38 mice with cultured tumor mass and we show the specificity, sensitivity, and positive predictive value of tumor detection of over 0.89, 0.88, and 0.96, respectively.

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    6. Numerical model of optical coherence tomographic vibrography imaging to estimate corneal biomechanical properties

      Numerical model of optical coherence tomographic vibrography imaging to estimate corneal biomechanical properties

      Most techniques measuring corneal biomechanics in vivo are biased by side factors. We demonstrate the ability of optical coherence tomographic (OCT) vibrography to determine corneal material parameters, while reducing current prevalent restrictions of other techniques (such as intraocular pressure (IOP) and thickness dependency). Modal analysis was performed in a finite-element (FE) model to study the oscillation response in isolated thin corneal flaps/eye globes and to analyse the dependency of the frequency response function on: corneal elasticity, viscoelasticity, geometry (thickness and curvature), IOP and density. The model was verified experimentally in flaps from three bovine corneas and in two enucleated ...

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    7. Perspectives of mid-infrared optical coherence tomography for inspection and micrometrology of industrial ceramics

      Perspectives of mid-infrared optical coherence tomography for inspection and micrometrology of industrial ceramics

      Optical coherence tomography (OCT) is a promising tool for detecting micro channels, metal prints, defects and delaminations embedded in alumina and zirconia ceramic layers at hundreds of micrometers beneath surfaces. The effect of surface roughness and scattering of probing radiation within sample on OCT inspection is analyzed from the experimental and simulated OCT images of the ceramic samples with varying surface roughnesses and operating wavelengths. By Monte Carlo simulations of the OCT images in the mid-IR the optimal operating wavelength is found to be 4 µm for the alumina samples and 2 µm for the zirconia samples for achieving sufficient ...

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    8. Detection of breast surgical margins with optical coherence tomography imaging: a concept evaluation study

      Detection of breast surgical margins with optical coherence tomography imaging: a concept evaluation study

      This study aimed to evaluate the concept of using high-resolution optical coherence tomography (OCT) imaging to rapidly assess surgical specimens and determine if cancer positive margins were left behind in the surgical bed. A mouse model of breast cancer was used in this study. Surgical specimens from 30 animals were investigated with OCT and automated interpretation of the OCT images was performed and tested against histopathology findings. Specimens from 10 animals were used to build a training set of OCT images, while the remaining 20 specimens were used for a validation set of images. The validation study showed that automated ...

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    9. Fast and accurate metrology of multi-layered ceramic materials by an automated boundary detection algorithm developed for optical coherence tomography data

      Fast and accurate metrology of multi-layered ceramic materials by an automated boundary detection algorithm developed for optical coherence tomography data

      Optical coherence tomography (OCT) is useful for materials defect analysis and inspection with the additional possibility of quantitative dimensional metrology. Here, we present an automated image-processing algorithm for OCT analysis of roll-to-roll multilayers in 3D manufacturing of advanced ceramics. It has the advantage of avoiding filtering and preset modeling, and will, thus, introduce a simplification. The algorithm is validated for its capability of measuring the thickness of ceramic layers, extracting the boundaries of embedded features with irregular shapes, and detecting the geometric deformations. The accuracy of the algorithm is very high, and the reliability is better than 1 μm when ...

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    10. Simultaneous 3D imaging of sound-induced motions of the tympanic membrane and middle ear ossicles

      Simultaneous 3D imaging of sound-induced motions of the tympanic membrane and middle ear ossicles

      Efficient transfer of sound by the middle ear ossicles is essential for hearing. Various pathologies can impede the transmission of sound and thereby cause conductive hearing loss. Differential diagnosis of ossicular disorders can be challenging since the ossicles are normally hidden behind the tympanic membrane (TM). Here we describe the use of a technique termed optical coherence tomography (OCT) vibrography to view the sound-induced motion of the TM and ossicles simultaneously. With this method, we were able to capture three-dimensional motion of the intact TM and ossicles of the chinchilla ear with nanometer-scale sensitivity at sound frequencies from 0.5 ...

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    11. Subnanometer optical coherence tomographic vibrography

      Subnanometer optical coherence tomographic vibrography

      The ability to quantify and visualize submicrometer-scale oscillatory motions of objects in three dimensions has a wide range of application in acoustics, materials sciences, and medical imaging. Here we demonstrate that volumetric snapshots of rapid periodic motion can be captured using optical coherence tomography (OCT) with subnanometer-scale motion sensitivity and microsecond-scale temporal resolution. This technique, termed OCT vibrography, was applied to generate time-resolved volumetric vibrographs of a miniature drum driven acoustically at several kilohertz.

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    12. Triggered optical coherence tomography for capturing rapid periodic motion

      Triggered optical coherence tomography for capturing rapid periodic motion
      Quantitative cross-sectional imaging of vocal folds during phonation is potentially useful for diagnosis and treatments of laryngeal disorders. Optical coherence tomography (OCT) is a powerful technique, but its relatively low frame rates makes it challenging to visualize rapidly vibrating tissues. Here, we demonstrate a novel method based on triggered laser scanning to capture 4-dimensional (4D) images of samples in motu at audio frequencies over 100 Hz. As proof-of-concept experiments, we applied this technique to imaging the oscillations of biopolymer gels on acoustic vibrators and aerodynamically driven vibrations of the vocal fold in an ex vivo calf larynx model. Our results ...
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    13. Dynamic imaging of vocal fold oscillation with four-dimensional optical coherence tomography

      Dynamic imaging of vocal fold oscillation with four-dimensional optical coherence tomography

      Optical coherence tomography (OCT) can provide high-resolution ([sim]10-15 [mu]m/pixel) images of vocal fold microanatomy, as demonstrated previously. We explored physiologically triggered Fourier-domain OCT for imaging vocal folds during phonation. The goal is to visualize dynamic histological cross sections and four-dimensional data sets where multiple planes are displayed in synchronized motion. If feasible, this approach could be a useful research tool and spur development of new clinical instrumentation.A Fourier-domain, triggered OCT system was created and tested in experiments on excised calf larynges to obtain preliminary observations and characterize important factors affecting image quality.Larynges were imaged during ...

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    14. Long-wavelength optical coherence tomography at 1.7 μm for enhanced imaging depth

      Long-wavelength optical coherence tomography at 1.7 μm for enhanced imaging depth

      Multiple scattering in a sample presents a significant limitation to achieve meaningful structural information at deeper penetration depths in optical coherence tomography (OCT). Previous studies suggest that the spectral region around 1.7 μm may exhibit reduced scattering coefficients in ... [Opt. Express 16, 19712-19723 (2008)]

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    1-14 of 14
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  2. Topics in the News

    1. (14 articles) Ernest W. Chang
    2. (13 articles) Harvard University
    3. (12 articles) Massachusetts General Hospital
    4. (9 articles) Seok-Hyun Yun
    5. (7 articles) Wei Chang
    6. (5 articles) Nicusor Iftimia
    7. (5 articles) Physical Sciences Incorporated
    8. (3 articles) Boston University
    9. (2 articles) Massachusetts Eye and Ear Infirmary
    10. (2 articles) B. Imran Akca
    11. (1 articles) UCLA
    12. (1 articles) University of Copenhagen
    13. (1 articles) Cornell University
    14. (1 articles) Gregor B. E. Jemec
    15. (1 articles) Steven G. Adie
    16. (1 articles) Jon Holmes
    17. (1 articles) Optovue
    18. (1 articles) Michelson Diagnostics
    19. (1 articles) Heidelberg Spectralis
    20. (1 articles) Zeiss Cirrus HD-OCT
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    Long-wavelength optical coherence tomography at 1.7 μm for enhanced imaging depth Dynamic imaging of vocal fold oscillation with four-dimensional optical coherence tomography Triggered optical coherence tomography for capturing rapid periodic motion Subnanometer optical coherence tomographic vibrography Simultaneous 3D imaging of sound-induced motions of the tympanic membrane and middle ear ossicles Fast and accurate metrology of multi-layered ceramic materials by an automated boundary detection algorithm developed for optical coherence tomography data Detection of breast surgical margins with optical coherence tomography imaging: a concept evaluation study Perspectives of mid-infrared optical coherence tomography for inspection and micrometrology of industrial ceramics Numerical model of optical coherence tomographic vibrography imaging to estimate corneal biomechanical properties Low coherence interferometry approach for aiding fine needle aspiration biopsie Alterations of Hyaluronan Metabolism in Acute Coronary Syndrome: Implications for Plaque Erosion The vascular morphology of melanoma is related to Breslow index: an in vivo study with dynamic optical coherence tomography