Zhongping Chen

Oregon Health and Science University, Portland, Oregon, United States

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Publications (385)715.81 Total impact

  • No preview · Article · Feb 2016 · Biomedical Optics Express
  • Shenghai Huang · Meixiao Shen · Dexi Zhu · Qi Chen · Ce Shi · Zhongping Chen · Fan Lu

    No preview · Article · Feb 2016 · Biomedical Optics Express
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    ABSTRACT: Biofilm formation has been linked to ventilator-associated pneumonia, which is a prevalent infection in hospital intensive care units. Currently, there is no rapid diagnostic tool to assess the degree of biofilm formation or cellular biofilm composition. Optical coherence tomography (OCT) is a minimally invasive, nonionizing imaging modality that can be used to provide high-resolution cross-sectional images. Biofilm deposited in critical care patients' endotracheal tubes was analyzed in vitro. This study demonstrates that OCT could potentially be used as a diagnostic tool to analyze and assess the degree of biofilm formation and extent of airway obstruction caused by biofilm in endotracheal tubes. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE).
    No preview · Article · Dec 2015 · Journal of Biomedical Optics

  • No preview · Article · Dec 2015 · Optics Express
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    ABSTRACT: Objectives/hypothesis: To evaluate for the first time the feasibility and methodology of long-range Fourier domain optical coherence tomography (LR-OCT) imaging of the internal nasal valve (INV) area in healthy individuals. Study design: Prospective individual cohort study. Methods: For 16 individuals, OCT was performed in each nare. The angle and the cross-sectional area of the INV were measured. OCT images were compared to corresponding digital pictures recorded with a flexible endoscope. Results: INV angle measured by OCT was found to be 18.3° ± 3.1° (mean ± standard deviation). The cross-sectional area was 0.65 ± 0.23 cm(2) . The INV angle measured by endoscopy was 18.8° ± 6.9°. There was no statistically significant difference between endoscopy and OCT concerning the mean INV angle (P = .778), but there was a significant difference in test precision (coefficient of variance 50% vs. 15%; P < .001). Conclusions: LR-OCT proved to be a fast and easily performed method. OCT could accurately quantify the INV area. The values of the angle and the cross-sectional area of the INV were reproducible and correlated well with the data seen with other methods. Changes in size could be reliably delineated. Endoscopy showed similar values but was significantly less precise. Level of evidence: 2b. Laryngoscope, 2015.
    No preview · Article · Nov 2015 · The Laryngoscope
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    ABSTRACT: We have developed laser-diode-based optical-resolution photoacoustic microscopy (LD-OR-PAM) of superficial microvasculature which has the desirable properties of being compact, low-cost, and label-free. A 300-mW visible pulsed laser diode was operated at 405 ± 5 nm wavelength with a pulse energy as low as 52 nJ. By using a 3.6 MHz ultrasound transducer, the system was tested on carbon fibers with a lateral resolution of 0.95 µm and an SNR of 38 dB. The subcutaneous microvasculature on a mouse back was imaged without an exogenous contrast agent which demonstrates the potential of the proposed prototype for skin chromophores. Our eventual goal is to offer a practical and affordable multi-wavelength functional LD-OR-PAM instrument suitable for clinical applications.
    Full-text · Article · Nov 2015 · Optics Express
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    ABSTRACT: Lipid deposition inside the arterial wall is a hallmark of plaque vulnerability. Based on overtone absorption of C-H bonds, intravascular photoacoustic (IVPA) catheter is a promising technology for quantifying the amount of lipid and its spatial distribution inside the arterial wall. Thus far, the clinical translation of IVPA technology is limited by its slow imaging speed due to lack of a high-pulse-energy high-repetition-rate laser source for lipid-specific first overtone excitation at 1.7 μm. Here, we demonstrate a potassium titanyl phosphate (KTP)-based optical parametric oscillator with output pulse energy up to 2 mJ at a wavelength of 1724 nm and with a repetition rate of 500 Hz. Using this laser and a ring-shape transducer, IVPA imaging at speed of 1 frame per sec was demonstrated. Performance of the IVPA imaging system's resolution, sensitivity, and specificity were characterized by carbon fiber and a lipid-mimicking phantom. The clinical utility of this technology was further evaluated ex vivo in an excised atherosclerotic human femoral artery with comparison to histology.
    Full-text · Article · Nov 2015 · Biomedical Optics Express
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    ABSTRACT: Intravascular photoacoustic imaging at 1.7 μm spectral band has shown promising capabilities for lipid-rich vulnerable atherosclerotic plaque detection. In this work, we report a high speed catheter-based integrated intravascular photoacoustic/intravascular ultrasound (IVPA/IVUS) imaging system with a 500 Hz optical parametric oscillator laser at 1725 nm. A lipid-mimicking phantom and atherosclerotic rabbit abdominal aorta were imaged at 1 frame per second, which is two orders of magnitude faster than previously reported in IVPA imaging with the same wavelength. Clear photoacoustic signals by the absorption of lipid rich deposition demonstrated the ability of the system for high speed vulnerable atherosclerotic plaques detection.
    No preview · Article · Aug 2015 · Applied Physics Letters
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    ABSTRACT: The upper airway is a complex and intricate system responsible for respiration, phonation, and deglutition. Obstruction of the upper airways afflicts an estimated 12–18 million Americans. Pharyngeal size and shape are important factors in the pathogenesis of airway obstructions. In addition, nocturnal loss in pharyngeal muscular tone combined with high pharyngeal resistance can lead to collapse of the airway and periodic partial or complete upper airway obstruction. Anatomical optical coherence tomography (OCT) has the potential to provide high-speed three-dimensional tomographic images of the airway lumen without the use of ionizing radiation. In this chapter we describe the methods behind endoscopic OCT imaging and processing to generate full three dimensional anatomical models of the human airway which can be used in conjunction with numerical simulation methods to assess areas of airway obstruction. Combining this structural information with flow dynamic simulations, we can better estimate the site and causes of airway obstruction and better select and design surgery for patients with obstructive sleep apnea. © Springer-Verlag Berlin Heidelberg 2008 and Springer International Publishing Switzerland 2015.
    No preview · Chapter · Aug 2015
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    ABSTRACT: Subglottic edema and acquired subglottic stenosis are potentially airway-compromising sequelae in neonates following endotracheal intubation. At present, no imaging modality is capable of in vivo diagnosis of subepithelial airway wall pathology as signs of intubation-related injury. To use Fourier domain long-range optical coherence tomography (LR-OCT) to acquire micrometer-resolution images of the airway wall of intubated neonates in a neonatal intensive care unit (NICU) setting and to analyze images for histopathology and airway wall thickness. LR-OCT of the neonatal laryngotracheal airway was performed a total of 94 times on 72 subjects (age 1-175 days, total intubation 1-104 days). LR-OCT images of the airway wall were analyzed in MATLAB. Medical records were reviewed retrospectively for extubation outcome. Backwards stepwise regression analysis demonstrated a statistically significant association between log(duration of intubation) and both laryngeal (p<0.001; multiple r2=0.44) and subglottic (p<0.001; multiple r2=0.55) airway wall thickness. Subjects with positive histopathology on LR-OCT images had a higher likelihood of extubation failure (odds ratio 5.9, p=0.007). Longer intubation time was found to be significantly associated with extubation failure. LR-OCT allows for high-resolution evaluation and measurement of the airway wall in intubated neonates. Our data demonstrate a positive correlation between laryngeal and subglottic wall thickness and duration of intubation, suggestive of progressive soft tissue injury. LR-OCT may ultimately aid in the early diagnosis of post-intubation subglottic injury and help reduce the incidences of failed extubation due to subglottic edema or acquired subglottic stenosis in neonates. Clinical trial registration available at www.clinicaltrials.gov, ID NCT00544427.
    No preview · Article · Jul 2015 · American Journal of Respiratory and Critical Care Medicine
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    ABSTRACT: Measuring ciliary beat frequency (CBF) is a technical challenge and difficult to perform in vivo. Doppler optical coherence tomography (D-OCT) is a mesoscopic noncontact imaging modality that provides high-resolution tomographic images and detects micromotion simultaneously in living tissues. In this work we used D-OCT to measure CBF in ex vivo tissue as the first step toward translating this technology to clinical use. Fresh ex vivo samples of rabbit tracheal mucosa were imaged using both D-OCT and phase-contrast microscopy (n = 5). The D-OCT system was designed and built to specification in our lab (1310-nm swept source vertical-cavity surface-emitting laser [VCSEL], 6-μm axial resolution). The samples were placed in culture and incubated at 37°C. A fast Fourier transform was performed on the D-OCT signal recorded on the surface of the samples to gauge CBF. High-speed digital video of the epithelium recorded via phase-contrast microscopy was analyzed to confirm the CBF measurements. The D-OCT system detected Doppler signal at the epithelial layer of ex vivo rabbit tracheal samples suggestive of ciliary motion. CBF was measured at 9.36 ± 1.22 Hz using D-OCT and 9.08 ± 0.48 Hz using phase-contrast microscopy. No significant differences were found between the 2 methods (p > 0.05). D-OCT allows for the quantitative measurement of CBF without the need to resolve individual cilia. Furthermore, D-OCT technology can be incorporated into endoscopic platforms that allow clinicians to readily measure CBF in the office and provide a direct measurement of mucosal health. © 2015 ARS-AAOA, LLC.
    No preview · Article · Jul 2015 · International Forum of Allergy and Rhinology
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    ABSTRACT: Detection of an early stage of subglottic edema is vital for airway management and prevention of stenosis, a life-threatening condition in critically ill neonates. As an observer for the task of diagnosing edema in vivo, we investigated spatiotemporal correlation (STC) of full-range optical coherence tomography (OCT) images acquired in the rabbit airway with experimentally simulated edema. Operating the STC observer on OCT images generates STC coefficients as test statistics for the statistical decision task. Resulting from this, the receiver operating characteristic (ROC) curves for the diagnosis of airway edema with full-range OCT in-vivo images were extracted and areas under ROC curves were calculated. These statistically quantified results demonstrated the potential clinical feasibility of the STC method as a means to identify early airway edema. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
    No preview · Article · Jul 2015 · Journal of Biomedical Optics
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    Shenghai Huang · Zhonglie Piao · Jiang Zhu · Fan Lu · Zhongping Chen
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    ABSTRACT: Microvascular network of the retina plays an important role in diagnosis and monitoring of various retinal diseases. We propose a three-dimensional (3-D) segmentation method with intensity-based Doppler variance (IBDV) based on swept-source optical coherence tomography. The automatic 3-D segmentation method is used to obtain seven surfaces of intraretinal layers. The microvascular network of the retina, which is acquired by the IBDV method, can be divided into six layers. The microvascular network of the six individual layers is visualized, and the morphology and contrast images can be improved by using the segmentation method. This method has potential for earlier diagnosis and precise monitoring in retinal vascular diseases.
    Full-text · Article · Jul 2015 · Journal of Biomedical Optics
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    ABSTRACT: We report on a novel acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) technique for imaging shear wave and quantifying shear modulus under orthogonal acoustic radiation force (ARF) excitation using the optical coherence tomography (OCT) Doppler variance method. The ARF perpendicular to the OCT beam is produced by a remote ultrasonic transducer. A shear wave induced by ARF excitation propagates parallel to the OCT beam. The OCT Doppler variance method, which is sensitive to the transverse vibration, is used to measure the ARF-induced vibration. For analysis of the shear modulus, the Doppler variance method is utilized to visualize shear wave propagation instead of Doppler OCT method, and the propagation velocity of the shear wave is measured at different depths of one location with the M scan. In order to quantify shear modulus beyond the OCT imaging depth, we move ARF to a deeper layer at a known step and measure the time delay of the shear wave propagating to the same OCT imaging depth. We also quantitatively map the shear modulus of a cross-section in a tissue-equivalent phantom after employing the B scan.
    Full-text · Article · May 2015 · Optics Letters
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    ABSTRACT: An increasing number of integrated optical and acoustic intravascular imaging systems have been developed and hold great promise for accurately diagnosing vulnerable plaques and guiding atherosclerosis treatment. However, in any intravascular environment, the vascular lumen is filled with blood, a high-scattering source for optical and high-frequency ultrasound signals. Blood must be flushed away to provide clearer images. To our knowledge, no research has been performed to find the ideal flushing agent for combined optical and acoustic imaging techniques. We selected three solutions as potential flushing agents for their image-enhancing effects: mannitol, dextran, and iohexol. Testing of these flushing agents was performed in a closed-loop circulation model and in vivo on rabbits. We found that a high concentration of dextran was the most useful for simultaneous intravascular ultrasound and optical coherence tomography imaging.
    No preview · Article · May 2015 · Journal of Biomedical Optics
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    ABSTRACT: High-resolution elasticity mapping of tissue biomechanical properties is crucial in early detection of many diseases. We report a method of acoustic radiation force optical coherence elastography (ARF-OCE) based on the methods of vibro-acoustography, which uses a dual-ring ultrasonic transducer in order to excite a highly localized 3-D field. The single element transducer introduced previously in our ARF imaging has low depth resolution because the ARF is difficult to discriminate along the entire ultrasound propagation path. The novel dual-ring approach takes advantage of two overlapping acoustic fields and a few-hundred-Hertz difference in the signal frequencies of the two unmodulated confocal ring transducers in order to confine the acoustic stress field within a smaller volume. This frequency difference is the resulting "beating" frequency of the system. The frequency modulation of the transducers has been validated by comparing the dual ring ARF-OCE measurement to that of the single ring using a homogeneous silicone phantom. We have compared and analyzed the phantom resonance frequency to show the feasibility of our approach. We also show phantom images of the ARF-OCE based vibro-acoustography method and map out its acoustic stress region. We concluded that the dual-ring transducer is able to better localize the excitation to a smaller region to induce a focused force, which allows for highly selective excitation of small regions. The beat-frequency elastography method has great potential to achieve high-resolution elastography for ophthalmology and cardiovascular applications.
    No preview · Article · Mar 2015

  • No preview · Article · Mar 2015 · Lasers in Surgery and Medicine

  • No preview · Article · Jan 2015 · IEEE Journal of Selected Topics in Quantum Electronics
  • Article: Dental OCT
    Petra Wilder-Smith · Linda Otis · Jun Zhang · Zhongping Chen
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    ABSTRACT: The oral cavity is a diverse environment that includes oral mucosa, gingival tissues, teeth and their supporting structures. Oral health is currently evaluated through three main avenues: visual/tactile examination, periodontal probing, and radiographic imaging. After the surfaces are dried with a gentle stream of air, visual examination of the teeth and surrounding soft tissue is completed. Clinicians tactically explore the surface hardness of the teeth to detect dental caries while early demineralization of the enamel and soft tissue inflammation are characterized by changes in visual characteristics. Probes are also placed between the soft tissue and tooth to assess periodontal health. Radiographs are used to determine the internal structural integrity of the teeth and alveolar bone. Although radiographs are highly sensitive for detecting regions of carious demineralization and alveolar bone loss, they have several limitations. Since radiographs are two-dimensional, precisely locating the position of a carious lesion or osseous defect is impossible. Radiographs cannot distinguish active from inactive disease and cannot identify periodontal disease until after bone loss has occurred. Finally, radiography uses harmful ionizing radiation and provides no information on soft tissue status. This section will address all the anatomical structures within the oral cavity that are listed above. A brief review of normal oral structures will be followed by a summary of the pathologies affecting each structure, a discussion of existing diagnostic tools, and an overview of diagnostic usage of OCT in each structure to date. In the final section the authors present their views on the potential uses of OCT in Dentistry in the future.
    No preview · Article · Jan 2015
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    ABSTRACT: In this Letter, we present a trimodality imaging system and an intravascular endoscopic probe for the detection of early-stage atherosclerotic plaques. The integrated system is able to acquire optical coherence tomography (OCT), fluorescence, and ultrasound images and simultaneously display them in real time. A trimodality intravascular endoscopic probe of 1.2 mm in diameter and 7 mm in length was fabricated based on a dual-modality optical probe that integrates OCT and fluorescence imaging functions and a miniature ultrasound transducer. The probe is capable of rotating at up to 600 rpm. Ex vivo images from rabbit aorta and human coronary arteries showed that this combined system is capable of providing high resolution, deep penetration depth and specific molecular fluorescence contrast simultaneously.
    No preview · Article · Dec 2014 · Optics Letters

Publication Stats

6k Citations
715.81 Total Impact Points


  • 2015
    • Oregon Health and Science University
      Portland, Oregon, United States
  • 2002-2015
    • Beckman Research Institute
      Дуарте, California, United States
  • 1996-2015
    • University of California, Irvine
      • • Department of Biomedical Engineering
      • • Beckman Laser Institute
      • • Department of Electrical Engineering and Computer Science
      Irvine, California, United States
    • US Army Armament Research, Development and Engineering Center
      Rockaway, New Jersey, United States
  • 2014
    • University of California, Los Angeles
      • Department of Bioengineering
      Los Ángeles, California, United States
  • 2008-2014
    • Pusan National University
      • Department of Cogno-Mechatronics Engineering
      Tsau-liang-hai, Busan, South Korea
  • 2012
    • Ulsan National Institute of Science and Technology
      Ulsan, Ulsan, South Korea
  • 1999-2012
    • University of Illinois, Urbana-Champaign
      Urbana, Illinois, United States
  • 2005
    • University of California, Berkeley
      • Department of Electrical Engineering and Computer Sciences
      Berkeley, California, United States
  • 2004
    • Johns Hopkins University
      Baltimore, Maryland, United States
    • California State University
      • Department of Biomedical Engineering
      Long Beach, California, United States
  • 2003
    • Zhejiang University
      • State Key Lab of Modern Optical Instrumentation
      Hang-hsien, Zhejiang Sheng, China
  • 1994-1995
    • University of Massachusetts Lowell
      • Department of Chemistry
      Lowell, Massachusetts, United States