1. Articles from Chunhui Li

    1-18 of 18
    1. Spatial resolution in dynamic optical coherence elastography

      Spatial resolution in dynamic optical coherence elastography

      Dynamic optical coherence elastography (OCE) tracks elastic wave propagation speed within tissue, enabling quantitative three-dimensional imaging of the elastic modulus. We show that propagating mechanical waves are mode converted at interfaces, creating a finite region on the order of an acoustic wavelength where there is not a simple one-to-one correspondence between wave speed and elastic modulus. Depending on the details of a boundary’s geometry and elasticity contrast, highly complex propagating fields produced near the boundary can substantially affect both the spatial resolution and contrast of the elasticity image. We demonstrate boundary effects on Rayleigh waves incident on a vertical ...

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    2. Feasibility study of using the dispersion of surface acoustic wave (SAW) impulse for viscoelasticity characterization in tissue mimicking phantoms

      Feasibility study of using the dispersion of surface acoustic wave (SAW) impulse for viscoelasticity characterization in tissue mimicking phantoms

      The aim of this study was to investigate the feasibility of utilizing the phase velocity dispersion of impulse surface acoustic wave (SAW) for viscoelasticity characterization of soft materials. The focused ultrasound transducer and the phase sensitive optical coherence tomography (PhS‐OCT) were applied as the impulse SAW inducer and tracker respectively. Three types of liquid‐paraffin‐based cream‐in‐agar phantoms were tested. Phase velocity dispersion curve was extracted using a Fourier transform based phase velocity analysis algorithm. Viscoelastic parameters were obtained by fitting the dispersion curve of SAW into Rayleigh wave dispersion equation. The estimated viscoelasticity was compared with ...

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    3. The potential of high intensity focused ultrasound (HIFU) combine phase-sensitive optical coherence tomography (PhS-OCT) for diseases diagnosis, treatment and monitoring

      The potential of high intensity focused ultrasound (HIFU) combine phase-sensitive optical coherence tomography (PhS-OCT) for diseases diagnosis, treatment and monitoring

      HIFU is a truly noninvasive, acoustic therapeutic technique that utilizes high intensity acoustic field in the focus to kill the targeted tissue for disease treatment purpose. The mechanical properties of targeted tissue changes before and after treatment, and this change can be accurately detected by shear wave elastography. Hence, shear wave elastography is usually used for monitoring HIFU treatment asynchronously. To improve the low spatial resolution in ultrasound shear wave elastography, and to perform diseases diagnosis, treatment and monitoring in the same system, a new setup that combines HIFU and PhS-OCT system was proposed in this study. This proposed setup ...

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    4. Structural characterization on in vitro porcine skin treated by ablative fractional laser using optical coherence tomography

      Structural characterization on in vitro porcine skin treated by ablative fractional laser using optical coherence tomography

      Ablative fractional skin laser is widely applied for various skin conditions, especially for cosmetic repairing and promoting the located drug delivery. Although the influence of laser treatment over the skin has been explored before in means of excision and biopsy with microscopy, these approaches are invasive, only morphological and capable of distorting the skin. In this paper the authors use fresh porcine skin samples irradiated by the lasers, followed by detected by using Optical Coherence Tomography (OCT). This advanced optical technique has the ability to present the high resolution structure image of treated sample. The results shows that laser beams ...

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    5. Quantitative assessment of the mechanical properties of prostate tissue with optical coherence elastography

      Quantitative assessment of the mechanical properties of prostate tissue with optical coherence elastography

      Prostate cancer (PCa) is a heterogeneous disease with multifocal origin. In current clinical care, the Gleason scoring system is the well-established diagnosis by microscopic evaluation of the tissue from trans-rectal ultrasound (TRUS) guided biopsies. Nevertheless, the sensitivity and specificity in detecting PCa can range from 40 to 50% for conventional TRUS B-mode imaging. Tissue elasticity is associated with the disease progression and elastography technique has recently shown promise in aiding PCa diagnosis. However, many cancer foci in the prostate gland has very small size less than 1 mm and those detected by medical elastography were larger than 2 mm. Hereby ...

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    6. High intensity focused ultrasound (HIFU) and phase-sensitive optical coherence tomography (PhS-OCT) for high resolution surface acoustic wave (SAW) elastography

      High intensity focused ultrasound (HIFU) and phase-sensitive optical coherence tomography (PhS-OCT) for high resolution surface acoustic wave (SAW) elastography

      Elastography has the ability of quantitatively evaluating the mechanical properties of soft tissue, thus is helpful for diagnosis and treatment monitoring for many diseases, e.g. skin diseases. Surface acoustic waves (SAWs) have been proven to be a non-invasive, non-destructive method for accurate characterization of tissue elastic properties. Current surface acoustic wave elastography using high energy laser pulse or mechanical shaker still have some problems. In order to improve SAW elastography in medical application, a new technique was proposed in this paper, which combines high intensity focused ultrasound (HIFU) as a SAWs impulse inducer and PhS-OCT as a SAWs detector ...

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    7. Effects of fixation and preservation on tissue elastic properties measured by quantitative optical coherence elastography (OCE)

      Effects of fixation and preservation on tissue elastic properties measured by quantitative optical coherence elastography (OCE)

      Fixed and preserved tissues have been massively used in the development of biomedical equipment and instrumentation. Not only the tissue morphology, but also its mechanical properties need to be considered in the fixation and preservation procedures since mechanical properties have significant influence on the design and performance of such instruments. Understanding the effects of storage and preservation conditions on the mechanical properties of soft tissue has both clinical and experimental significance. To this end, we aimed to study the effects of tissue preservation (by 10% formalin and Thiel fluids) on the elastic properties of five different kinds of fresh tissues ...

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    8. Feature Of The Week 01/25/15: Detection and characterisation of biopsy tissue using quantitative optical coherence elastogaphy (OCE) in men with suspected prostate cancer.

      Feature Of The Week 01/25/15: Detection and characterisation of biopsy tissue using quantitative optical coherence elastogaphy (OCE) in men with suspected prostate cancer.

      Prostate cancer (PCa) is the most common non-cutaneous malignancy in men. Men suspected with PCa are then offered transrectal ultrasound (TRUS) guided prostate biopsies to confirm the diagnosis, which falls short of making a reliable differentiation between cancer and benign hyperplasia of the gland. Suspected cancerous lesions tend to be stiffer (or harder to feel) than benign tissue. Various elastography modalities such as Ultrasound elastography and MRI elastography are known to have poor spatial resolution, which limits their ability to differentiate small lesions and in identifying early and subtle changes. OCT is an optical imaging technique that enables high-resolution, cross-sectional ...

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    9. Detection and characterisation of biopsy tissue using quantitative optical coherence elastography (OCE) in men with suspected prostate cancer

      Detection and characterisation of biopsy tissue using quantitative optical coherence elastography (OCE) in men with suspected prostate cancer

      We present first quantitative three-dimensional (3D) data sets recorded using optical coherence elastography (OCE) for the diagnosis and detection of prostate cancer (PCa). 120 transrectal ultrasound guided prostate biopsy specimens from 10 men suspected with prostate cancer were imaged using OCE. 3D quantitative mechanical assessment of biopsy specimens obtained in kilopascals (kPa) at an interval of 40 µm was compared with histopathology. Sensitivity, specificity, and positive and negative predictive values were calculated for OCE in comparison to histopathology. The results show OCE imaging could reliably differentiate between benign prostate tissue, acinar atypical hyperplasia, prostatic intraepithelial neoplasia and malignant PCa. The ...

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    10. Quantitative elasticity measurement of urinary bladder wall using laser-induced surface acoustic waves

      Quantitative elasticity measurement of urinary bladder wall using laser-induced surface acoustic waves

      The maintenance of urinary bladder elasticity is essential to its functions, including the storage and voiding phases of the micturition cycle. The bladder stiffness can be changed by various pathophysiological conditions. Quantitative measurement of bladder elasticity is an essential step toward understanding various urinary bladder disease processes and improving patient care. As a nondestructive, and noncontact method, laser-induced surface acoustic waves (SAWs) can accurately characterize the elastic properties of different layers of organs such as the urinary bladder. This initial investigation evaluates the feasibility of a noncontact, all-optical method of generating and measuring the elasticity of the urinary bladder. Quantitative ...

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    11. Laser induced surface acoustic wave combined with phase sensitive optical coherence tomography for superficial tissue characterization: a solution for practical application

      Laser induced surface acoustic wave combined with phase sensitive optical coherence tomography for superficial tissue characterization: a solution for practical application

      Mechanical properties are important parameters that can be used to assess the physiologic conditions of biologic tissue. Measurements and mapping of tissue mechanical properties can aid in the diagnosis, characterisation and treatment of diseases. As a non-invasive, non-destructive and non-contact method, laser induced surface acoustic waves (SAWs) have potential to accurately characterise tissue elastic properties. However, challenge still exists when the laser is directly applied to the tissue because of potential heat generation due to laser energy deposition. This paper focuses on the thermal effect of the laser induced SAW on the tissue target and provides an alternate solution to ...

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    12. Quantitative evaluation of degenerated tendon model using combined optical coherence elastography and acoustic radiation force method

      Quantitative evaluation of degenerated tendon model using combined optical coherence elastography and acoustic radiation force method

      Damage of collagen fibers in tendons is often directly related to changes in a tendon’s mechanical properties. Direct quantitative elasticity measurement of tendons will provide important information in tendon dysfunction diagnosis and treatment assessment. A feasibility study of quantifying the mechanical properties of a degenerated tendon model by a nondestructive imaging modality, which combines optical coherence elastography and acoustic radiation force (ARF) method, is presented. The degenerated tendon model was produced by the partial degradation of chicken tendons through incubation with collagenase at different concentrations and incubation times. A 30-kHz longitudinal ultrasound transducer was used to provide an ARF ...

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    13. Noncontact all-optical measurement of corneal elasticity

      Noncontact all-optical measurement of corneal elasticity

      We report on a noninvasive and noncontact all-optical method to measure the elasticity of the cornea. We use a pulsed laser to excite surface acoustic waves (SAW) that propagate on the corneal surface, then use a phase-sensitive optical coherence tomography system to remotely record the SAWs from which the corneal elasticity is estimated. In addition, the system is able to provide real-time tomographic images of the cornea being examined, an important consideration for clinical studies. While precisely maintaining a range of intraocular pressures (IOP), a series of measurements is performed on ex vivo intact primate eyes. The measurement results not ...

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    14. Evaluating elastic properties of heterogeneous soft tissue by surface acoustic waves detected by phase-sensitive optical coherence tomography

      Evaluating elastic properties of heterogeneous soft tissue by surface acoustic waves detected by phase-sensitive optical coherence tomography

      The combined use of surface acoustic wave (SAW) and phase-sensitive optical coherence tomography (PhS-OCT) is useful to evaluate the elasticity of layered biological tissues, such as normal skin. However, the pathological tissue is often originated locally, leading to the alternation of mechanical properties along both axial and lateral directions. We present a feasibility study on whether the SAW technique is sensitive to detect the alternation of mechanical property along the lateral direction within tissue, which is important for clinical utility of this technique to localize diseased tissue. Experiments are carried out on purposely designed tissue phantoms and ex vivo chicken ...

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    15. Quantitative elastography provided by surface acoustic waves measured by phase-sensitive optical coherence tomography

      Quantitative elastography provided by surface acoustic waves measured by phase-sensitive optical coherence tomography

      We report on a quantitative elastography technique achieved by combining phase-sensitive optical coherence tomography (PhS-OCT) with the surface acoustic wave (SAW) method. Different from traditional optical coherence elastography, the elastography is achieved by impulse-stimulated SAW, rather than by shear waves. PhS-OCT serves not only as a detector to measure SAW signals but also as a means to provide a cross-sectional image of the sample. The experimental results indicate that the combination of PhS-OCT with SAW is feasible to provide quantitative elastography of heterogeneous tissue samples

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    16. Determining elastic properties of skin by measuring surface waves from an impulse mechanical stimulus using phase-sensitive optical coherence tomography

      Determining elastic properties of skin by measuring surface waves from an impulse mechanical stimulus using phase-sensitive optical coherence tomography

      The mechanical properties of skin are important tissue parameters that are useful for understanding skin patho-physiology, which can aid disease diagnosis and treatment. This paper presents an innovative method that employs phase-sensitive spectral-domain optical coherence tomography (PhS-OCT) to characterize the biomechanical properties of skin by measuring surface waves induced by short impulses from a home-made shaker. Experiments are carried out on single and double-layer agar–agar phantoms, of different concentrations and thickness, and on in vivo human skin, at the forearm and the palm. For each experiment, the surface wave phase-velocity dispersion curves were calculated, from which the elasticity of ...

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    17. Noncontact photoacoustic imaging achieved by using a low-coherence interferometer as the acoustic detector

      Noncontact photoacoustic imaging achieved by using a low-coherence interferometer as the acoustic detector

      We report on a noncontact photoacoustic imaging (PAI) technique in which a low-coherence interferometer [(LCI), optical coherence tomography (OCT) hardware] is utilized as the acoustic detector. A synchronization approach is used to lock the LCI system at its highly sensitive region for photoacoustic detection. The technique is experimentally verified by the imaging of a scattering phantom embedded with hairs and the blood vessels within a mouse ear in vitro. The system’s axial and lateral resolutions are evaluated at 60 and 30 μm, respectively. The experimental results indicate that PAI in a noncontact detection mode is possible with high resolution ...

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    18. Elastic properties of soft tissue-mimicking phantoms assessed by combined use of laser ultrasonics and low coherence interferometry

      Elastic properties of soft tissue-mimicking phantoms assessed by combined use of laser ultrasonics and low coherence interferometry
      Advances in the field of laser ultrasonics have opened up new possibilities in medical applications. This paper evaluates this technique as a method that would allow for rapid characterization of the elastic properties of soft biological tissue. In doing so, we propose a novel approach that utilizes a low coherence interferometer to detect the laser-induced surface acoustic waves (SAW) from the tissue-mimicking phantoms. A Nd:YAG focused laser line-source is applied to one- and two-layer tissue-mimicking agar-agar phantoms, and the generated SAW signals are detected by a time domain low coherence interferometry system. SAW phase velocity dispersion curves are calculated ...
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    1-18 of 18
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  2. Topics in the News

    1. (18 articles) Chunhui Li
    2. (12 articles) University of Washington
    3. (12 articles) University of Dundee
    4. (12 articles) Ruikang K. Wang
    5. (7 articles) Ghulam Nabi
    6. (1 articles) Ying Yang
    7. (1 articles) Yan Wang
    8. (1 articles) Yi Wang
    9. (1 articles) Tueng T. Shen
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    Elastic properties of soft tissue-mimicking phantoms assessed by combined use of laser ultrasonics and low coherence interferometry Noncontact photoacoustic imaging achieved by using a low-coherence interferometer as the acoustic detector Determining elastic properties of skin by measuring surface waves from an impulse mechanical stimulus using phase-sensitive optical coherence tomography Quantitative elastography provided by surface acoustic waves measured by phase-sensitive optical coherence tomography Evaluating elastic properties of heterogeneous soft tissue by surface acoustic waves detected by phase-sensitive optical coherence tomography Noncontact all-optical measurement of corneal elasticity Quantitative evaluation of degenerated tendon model using combined optical coherence elastography and acoustic radiation force method Laser induced surface acoustic wave combined with phase sensitive optical coherence tomography for superficial tissue characterization: a solution for practical application Quantitative elasticity measurement of urinary bladder wall using laser-induced surface acoustic waves Feature Of The Week 01/25/15: Detection and characterisation of biopsy tissue using quantitative optical coherence elastogaphy (OCE) in men with suspected prostate cancer. Full-field optical coherence tomography: novel imaging technique for extemporaneous high-resolution analysis of mucosal architecture in human gut biopsies Simon Poole, Cylite co-founder, elected as Fellow of Australian Academy of Science