1. Articles from Guangying Guan

    1-17 of 17
    1. 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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    2. Loose powder detection and surface characterization in selective laser sintering via optical coherence tomography

      Loose powder detection and surface characterization in selective laser sintering via optical coherence tomography

      Defects produced during selective laser sintering (SLS) are difficult to non-destructively detect after build completion without the use of X-ray-based methods. Overcoming this issue by assessing integrity on a layer-by-layer basis has become an area of significant interest for users of SLS apparatus. Optical coherence tomography (OCT) is used in this study to detect surface texture and sub-surface powder, which is un-melted/insufficiently sintered, is known to be a common cause of poor part integrity and would prevent the use of SLS where applications dictate assurance of defect-free parts. To demonstrate the capability of the instrument and associated data-processing algorithms ...

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    3. Towards in-situ process monitoring in selective laser sintering using optical coherence tomography

      Towards in-situ process monitoring in selective laser sintering using optical coherence tomography

      Selective laser sintering (SLS) enables fast, flexible and cost-efficient production of parts directly from 3D CAD data. However, compared with more established machine tools, there is a marked lack of process monitoring and feedback control of key process variables to optimize production parameters in-situ. We apply optical coherence tomography (OCT) to evaluate components produced by SLS and suggest a route for its application in in-situ process monitoring within the SLS tool for real-time monitoring of the SLS process for assurance, or even dynamic correction of defects during the build. OCT is shown to be a viable technique for evaluation of ...

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    4. Evaluation of selective laser sintering processes by optical coherence tomography

      Evaluation of selective laser sintering processes by optical coherence tomography

      Selective laser sintering (SLS) enables the fast, flexible and cost-efficient production of parts directly from 3D CAD data. Unlike more established machine tools, there is a marked lack of process monitoring and feedback control of key process variables. In-situ analysis techniques permit the emergence of repair techniques, in-process optimization of production parameters, and will also serve to save time and material. In this study, optical coherence tomography (OCT) is used for the first time to evaluate components produced by SLS. Using a Polyamide-PA2200, surface defects are analyzed and the limiting factors associated with the measurement technique are quantified. OCT is ...

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    5. Micro-motion detection by optical coherence tomography (OCT) and its clinical applications (Thesis)

      Micro-motion detection by optical coherence tomography (OCT) and its clinical applications (Thesis)

      Detection of micro-motion on biological tissues has various applications such as ultrasound elastography and magnetic resonance elastography (MRE). Ultrasound transducers, the most commonly used tool to detect endogenous and exogenous micro-motions, have a number of drawbacks: including the requirements of the physical contact with the sample and limited spatial resolution (millimetre scale). The aim of this thesis is to develop a non-contact phase-sensitive imaging technique which is suitable for functional imaging in the micron range which also has the potential for quantitative analysis of relative properties resulting from an appropriate image processing. Concerning imaging techniques, this thesis focused on optical ...

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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    11. 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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    12. 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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    13. 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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    14. Depth profile absorber concentration reconstruction using photothermal optical coherence tomography

      Depth profile absorber concentration reconstruction using photothermal optical coherence tomography

      The concentration of photothermal (light-to-heat converters) compounds as a function of depth is determined in solid agar gel phantoms. The system contains an 808nm pump laser, which excites the photothermal compound, and a phase sensitive spectral domain optical coherence tomography system, which detects the changes in the optical pathlength of the sample induced by the temperature increase. The derivation of the model is described, and its parameters are empirically determined. The concentration of photothermal compounds are observed from double layer agar gel phantoms.

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    15. Depth profiling of photothermal compound concentrations using phase sensitive optical coherence tomography

      Depth profiling of photothermal compound concentrations using phase sensitive optical coherence tomography
      A model that describes the concentration of photothermal (light-to-heat converters) compounds as a function of depth in a turbid medium is developed. The system consists of a pump laser (808 nm modulated at 400 Hz), which heats a photothermal compound, and a phase sensitive spectral domain optical coherence tomography system, which detects the changes in the optical path length of the sample induced by the temperature increase. The model is theoretically derived and the coefficients are empirically determined using solid homogeneous gel phantoms. The model is validated by reconstructing the concentration of a photothermal compound in thick single and double ...
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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. High-speed 1310 nm-band spectral domain optical coherence tomography at 184,000 lines per second

      High-speed 1310 nm-band spectral domain optical coherence tomography at 184,000 lines per second
      We propose a useful method to boost the imaging speed for spectral domain optical coherence tomography (SDOCT) by multiplying a number of high-speed spectrometers used in the system with selective precise control of data-recording and data-reading phases for spectral cameras employed in each spectrometer. To demonstrate the proposed method, we use two spectrometers built in a 1310 nm-band SDOCT system, each equipped with a high-speed InGaAs line-scan camera capable of 92-kHz line-scan rate, to achieve an unprecedented imaging speed at 184,000 lines/s. We validate the multiplied imaging speed by measuring Doppler-induced phase shift in the spectrograms using a ...
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    1-17 of 17
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    High-speed 1310 nm-band spectral domain optical coherence tomography at 184,000 lines per second Determining elastic properties of skin by measuring surface waves from an impulse mechanical stimulus using phase-sensitive optical coherence tomography Depth profiling of photothermal compound concentrations using phase sensitive optical coherence tomography Quantitative elastography provided by surface acoustic waves measured by phase-sensitive optical coherence tomography Depth profile absorber concentration reconstruction using photothermal optical coherence tomography Multifunctional nanoprobe to enhance the utility of optical based imaging techniques Evaluating elastic properties of heterogeneous soft tissue by surface acoustic waves detected by phase-sensitive optical coherence tomography 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 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. Long-Term Arterial Remodeling After Bioresorbable Scaffold Implantation 4-Year Follow-up of Quantitative Coronary Angiography, Histology and Optical Coherence Tomography Visualization of Bacterial Colonization and Cellular Layers in a Gut-on-a-Chip System Using Optical Coherence Tomography