1. Articles from Matthew O’Donnell

    1-10 of 10
    1. Acoustic micro-tapping for non-contact 4D imaging of tissue elasticity

      Acoustic micro-tapping for non-contact 4D imaging of tissue elasticity

      Elastography plays a key role in characterizing soft media such as biological tissue. Although this technology has found widespread use in both clinical diagnostics and basic science research, nearly all methods require direct physical contact with the object of interest and can even be invasive. For a number of applications, such as diagnostic measurements on the anterior segment of the eye, physical contact is not desired and may even be prohibited. Here we present a fundamentally new approach to dynamic elastography using non-contact mechanical stimulation of soft media with precise spatial and temporal shaping. We call it acoustic micro-tapping (A ...

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    2. Elasticity imaging of speckle-free tissue regions with moving acoustic radiation force and phase-sensitive optical coherence tomography

      Elasticity imaging of speckle-free tissue regions with moving acoustic radiation force and phase-sensitive optical coherence tomography

      Phase-sensitive optical coherence tomography (PhS-OCT) can be utilized for quantitative shear-wave elastography using speckle tracking. However, current approaches cannot directly reconstruct elastic properties in speckle-less or speckle-free regions, for example within the crystalline lens in ophthalmology. Investigating the elasticity of the crystalline lens could improve understanding and help manage presbyopia-related pathologies that change biomechanical properties. We propose to reconstruct the elastic properties in speckle-less regions by sequentially launching shear waves with moving acoustic radiation force (mARF), and then detecting the displacement at a specific speckle-generating position, or limited set of positions, with PhS-OCT. A linear ultrasound array (with a center ...

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    3. Moving beam shear wave reconstruction for both ultrasound and optical coherence tomography applications

      Moving beam shear wave reconstruction for both ultrasound and optical coherence tomography applications

      Shear wave elasticity imaging can quantitatively estimate a stiffness map of biological tissues based on speckle-tracking shear wave propagation. However, current approaches cannot directly reconstruct elasticity properties in speckle-less or speckle-free regions, for example within the crystalline lens in ophthalmology. We propose an imaging sequence to reconstruct the elastic properties in speckle-free regions by sequentially launching shear waves with a laterally moving acoustic radiation force, and then detecting the displacement at a specific speckle-generating position. The imaging sequence was tested for both ultrasound and phase-sensitive optical coherence tomography imaging. Tissue-mimicking phantom studies were performed and results demonstrate that elastic properties ...

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    4. Shear wave elastography using amplitude-modulated acoustic radiation force and phase-sensitive optical coherence tomography

      Shear wave elastography using amplitude-modulated acoustic radiation force and phase-sensitive optical coherence tomography

      Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the understanding and management of pathologies related to biomechanical deficiency. In previous studies, we introduced a setup based on optical coherence tomography for shear wave elastography (SWE) with high resolution and high sensitivity. SWE determines tissue stiffness from the propagation speed of shear waves launched within tissue. We proposed acoustic radiation force to remotely induce shear waves by focusing an ultrasound (US) beam in tissue, similar to several elastography techniques. Minimizing the maximum US pressure is essential in ophthalmology for safety reasons. For this purpose, we propose a ...

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    5. Shear wave elastography method combining phase-sensitive optical coherence tomography and coded acoustic radiation force

      Shear wave elastography method combining phase-sensitive optical coherence tomography and coded acoustic radiation force

      We combined phase-sensitive optical coherence tomography (PhS-OCT) and acoustic radiation force (ARF) to develop a shear wave elastography (SWE) method that could be used for ophthalmic applications. SWE measures tissue stiffness from the speed of shear waves propagating through tissue. Assessing the elastic properties of the cornea and the intraocular lens can, for example, help the management of refractive surgeries (myopia or presbyopia correction). OCT is a non-contact imaging method easily applicable in vivo that provides micron-scale resolution particularly suitable for characterizing ocular tissues. ARF is commonly used to remotely induce shear waves in tissue by emitting short (∼100 µs ...

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    6. Shear wave elastography of ex vivo human corneas using phase-sensitive optical coherence tomography

      Shear wave elastography of ex vivo human corneas using phase-sensitive optical coherence tomography

      Assessing the biomechanical properties of the cornea can provide clinically valuable information in addition to structural images for better management of pathologies (e.g. glaucoma) or refractive surgeries. OCT provides a micron scale and high sensitivity that are ideal for ophthalmic applications. We propose a shear wave elastography (SWE) method for the cornea based on phase-sensitive optical coherence tomography (PhS-OCT). SWE consists in launching a propagating shear wave in tissues and retrieving tissue elasticity from the shear wave speed. We used a piezo-electric actuator in contact with the cornea to induce shear waves that were then tracked using a PhSOCT ...

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    7. Visualizing ultrasonically induced shear wave propagation using phase-sensitive optical coherence tomography for dynamic elastography

      Visualizing ultrasonically induced shear wave propagation using phase-sensitive optical coherence tomography for dynamic elastography

      We report on the use of phase-sensitive optical coherence tomography (PhS-OCT) to detect and track temporal and spatial shear wave propagation within tissue, induced by ultrasound radiation force. Kilohertz-range shear waves are remotely generated in samples using focused ultrasound emission and their propagation is tracked using PhS-OCT. Cross-sectional maps of the local shear modulus are reconstructed from local estimates of shear wave speed in tissue-mimicking phantoms. We demonstrate the feasibility of combining ultrasound radiation force and PhS-OCT to perform high-resolution mapping of the shear modulus.

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    8. Shear wave pulse compression for dynamic elastography using phase-sensitive optical coherence tomography

      Shear wave pulse compression for dynamic elastography using phase-sensitive optical coherence tomography

      Assessing the biomechanical properties of soft tissue provides clinically valuable information to supplement conventional structural imaging. In the previous studies, we introduced a dynamic elastography technique based on phase-sensitive optical coherence tomography (PhS-OCT) to characterize submillimetric structures such as skin layers or ocular tissues. Here, we propose to implement a pulse compression technique for shear wave elastography. We performed shear wave pulse compression in tissue-mimicking phantoms. Using a mechanical actuator to generate broadband frequency-modulated vibrations (1 to 5 kHz), induced displacements were detected at an equivalent frame rate of 47 kHz using a PhS-OCT. The recorded signal was digitally compressed ...

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    9. Shear modulus imaging by direct visualization of propagating shear waves with phase-sensitive optical coherence tomography

      Shear modulus imaging by direct visualization of propagating shear waves with phase-sensitive optical coherence tomography

      We propose an integrated method combining low-frequency mechanics with optical imaging to map the shear modulus within the biological tissue. Induced shear wave propagating in tissue is tracked in space and time using phase-sensitive optical coherence tomography (PhS-OCT). Local estimates of the shear-wave speed obtained from tracking results can image the local shear modulus. A PhS-OCT system remotely records depth-resolved, dynamic mechanical waves at an equivalent frame rate of ∼ 47     kHz with the high spatial resolution. The proposed method was validated by examining tissue-mimicking phantoms made of agar and light scattering material. Results demonstrate that the shear wave imaging can ...

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    10. Multifunctional nanoprobe to enhance the utility of optical based imaging techniques

      Multifunctional nanoprobe to enhance the utility of optical based imaging techniques

      Several imaging modalities such as optical coherence tomography, photothermal, photoacoustic and magnetic resonance imaging, are sensitive to different physical properties (i.e. scattering, absorption and magnetic) that can provide contrast within biological tissues. Usually exogenous agents are designed with specific properties to provide contrast for these imaging methods. In nano-biotechnology there is a need to combine several of these properties into a single contrast agent. This multifunctional contrast agent can then be used by various imaging techniques simultaneously or can be used to develop new imaging modalities. We reported and characterized a multifunctional nanoparticle, made from gold nanoshells, which exhibits ...

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    1-10 of 10
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  2. Topics in the News

    1. (10 articles) University of Washington
    2. (10 articles) Ruikang K. Wang
    3. (8 articles) Thu-Mai Nguyen
    4. (2 articles) University of Dundee
    5. (2 articles) Tueng T. Shen
    6. (1 articles) Roberto Reif
    7. (1 articles) British Columbia Cancer Agency
    8. (1 articles) Shanghai Jiao Tong University
    9. (1 articles) Singapore Eye Research Institute
    10. (1 articles) Simon Fraser University
    11. (1 articles) Columbia University
    12. (1 articles) Stephen Lam
    13. (1 articles) Pierre M. Lane
    14. (1 articles) Tien Yin Wong
    15. (1 articles) Giuseppe Querques
    16. (1 articles) Francesco Bandello
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    Multifunctional nanoprobe to enhance the utility of optical based imaging techniques Shear modulus imaging by direct visualization of propagating shear waves with phase-sensitive optical coherence tomography Shear wave pulse compression for dynamic elastography using phase-sensitive optical coherence tomography Visualizing ultrasonically induced shear wave propagation using phase-sensitive optical coherence tomography for dynamic elastography Shear wave elastography of ex vivo human corneas using phase-sensitive optical coherence tomography Shear wave elastography method combining phase-sensitive optical coherence tomography and coded acoustic radiation force Shear wave elastography using amplitude-modulated acoustic radiation force and phase-sensitive optical coherence tomography Moving beam shear wave reconstruction for both ultrasound and optical coherence tomography applications Elasticity imaging of speckle-free tissue regions with moving acoustic radiation force and phase-sensitive optical coherence tomography Acoustic micro-tapping for non-contact 4D imaging of tissue elasticity Line-field confocal optical coherence tomography-Practical applications in dermatology and comparison with established imaging methods Optical coherence tomography detection of changes in inner retinal and choroidal thicknesses in patients with early retinitis pigmentosa