K. Kirk Shung

Daegu Gyeongbuk Institute of Science and Technology, Daikyū, Daegu, South Korea

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Publications (349)557.52 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Inadequate replacement of lost ventricular myocardium from myocardial infarction leads to heart failure. Investigating the regenerative capacity of mammalian hearts represents an emerging direction for tissue engineering and cellbased therapy. Recent advances in stem cells hold promise to restore cardiac functions. However, embryonic or induced pluripotent stem cell-derived cardiomyocytes lack functional phenotypes of the native myocardium, and transplanted tissues are not fully integrated for synchronized electrical and mechanical coupling with the host. In this context, this review highlights the mechanical and electrical strategies to promote cardiomyocyte maturation and integration, and to assess the functional phenotypes of regenerating myocardium. Simultaneous microelectrocardiogram and high-frequency ultrasound techniques will also be introduced to assess electrical and mechanical coupling for small animal models of heart regeneration.
    05/2015; DOI:10.1109/RBME.2015.2431681
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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.
    Optics Letters 05/2015; 40(9):2099-102. DOI:10.1364/OL.40.002099 · 3.18 Impact Factor
  • Journal of Biomedical Optics 05/2015; 20(5):56005. DOI:10.1117/1.JBO.20.5.056005 · 2.75 Impact Factor
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    ABSTRACT: Using tape-casting technology, 35 μm free-standing (100)-textured Li doped KNN (KNLN) thick film was prepared by employing NaNbO3 (NN) as template. It exhibited similar piezoelectric behavior to lead containing materials: a longitudinal piezoelectric coefficient (d33) of ∼150 pm/V and an electromechanical coupling coefficient (kt ) of 0.44. Based on this thick film, a 52 MHz side-looking miniature transducer with a bandwidth of 61.5% at −6 dB was built for Intravascular ultrasound (IVUS) imaging. In comparison with 40 MHz PMN-PT single crystal transducer, the rabbit aorta image had better resolution and higher noise-to-signal ratio, indicating that lead-free (100)-textured KNLN thick film may be suitable for IVUS (>50 MHz) imaging.
    Applied Physics Letters 04/2015; 106(17):173504. DOI:10.1063/1.4919387 · 3.52 Impact Factor
  • PLoS ONE 04/2015; 10(4):e0120269. DOI:10.1371/journal.pone.0120269 · 3.53 Impact Factor
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    ABSTRACT: Imaging of coronary vasa vasorum may lead to assessment of the vulnerable plaque development in diagnosis of atherosclerosis diseases. Dual frequency transducers capable of detection of microbubble super-harmonics have shown promise as a new contrast-enhanced intravascular ultrasound (CE-IVUS) platform with the capability of vasa vasorum imaging. Contrast-to-tissue ratio (CTR) in CE-IVUS imaging can be closely associated with low frequency transmitter performance. In this paper, transducer designs encompassing different transducer layouts, transmitting frequencies, and transducer materials are compared for optimization of imaging performance. In the layout selection, the stacked configuration showed superior super-harmonic imaging compared with the interleaved configuration. In the transmitter frequency selection, a decrease in frequency from 6.5 MHz to 5 MHz resulted in an increase of CTR from 15 dB to 22 dB when receiving frequency was kept constant at 30 MHz. In the material selection, the dual frequency transducer with the lead magnesium niobate-lead titanate (PMN-PT) 1-3 composite transmitter yielded higher axial resolution compared to single crystal transmitters (70 μm compared to 150 μm pulse length). These comparisons provide guidelines for the design of intravascular acoustic angiography transducers.
    Physics in Medicine and Biology 04/2015; 60(9):3441-3457. DOI:10.1088/0031-9155/60/9/3441 · 2.92 Impact Factor
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    ABSTRACT: Intravascular ultrasound (IVUS) has been used for diagnosis of coronary diseases. According to the outstanding transducer performance, Ba0.5Na0.5TiO3 (BNT)-based piezoelectric materials are good candidates for the IVUS applications. In this paper, lead-free BNT piezoelectric thick film has been used to fabricate a linear array transducer. The BNT based transducer array has a 2×16-element pattern. In the fabrication process of transducers, micro-machining technologies have been adopted. Wet etching was used to pattern the silicon substrate. The thin layers of Si3N4 and SiO2, are used as etching masks, and patterned by reactive etching and buffered oxide etch (BOE), respectively. After that, the part of Si not covered by the patterned masks is etched by 30% KOH solution. BNT slurry prepared by mixing BNT solution and BNT powder has been deposited on the substrate by spin coating and then thermally treated to obtain the thick film. The PiezoCAD software has been employed to analyze the performance of the array, and the simulation results show that the BNT film array has a center frequency of 82.84 MHz and a −6 dB bandwidth of 46.77%.
    Ceramics International 04/2015; DOI:10.1016/j.ceramint.2015.03.256 · 2.09 Impact Factor
  • Hojong Choi, Hayong Jung, K. Kirk Shung
    Journal of Medical and Biological Engineering 04/2015; 35(2):226-235. DOI:10.1007/s40846-015-0026-7 · 1.08 Impact Factor
  • 04/2015; 2(2):027001. DOI:10.1117/1.JMI.2.2.027001
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    ABSTRACT: Capitalizing on the optical absorption of hemoglobin, photoacoustic microscopy (PAM) is uniquely capable of anatomical and functional characterization of the intact microcirculation in vivo. However, PAM of the metabolic rate of oxygen (MRO2) at the microscopic level remains an unmet challenge, mainly due to the inability to simultaneously quantify microvascular diameter, oxygen saturation of hemoglobin (sO2), and blood flow at the same spatial scale. To fill this technical gap, we have developed a multi-parametric PAM platform. By analyzing both the sO2-encoded spectral dependence and the flow-induced temporal decorrelation of photoacoustic signals generated by the raster-scanned mouse ear vasculature, we demonstrated—for the first time—simultaneous wide-field PAM of all three parameters down to the capillary level in vivo.
    Optics Letters 03/2015; 40(6). DOI:10.1364/OL.40.000910 · 3.18 Impact Factor
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    ABSTRACT: A transducer with an angled and focused aperture for intravascular ultrasound imaging has been developed. The acoustic stack for the angled-focused transducer was made of PMN-PT single crystal with one matching layer, one protective coating layer, and a highly damped backing layer. It was then press-focused to a desired focal length and inserted into a thin needle housing with an angled tip. A transducer with an angled and unfocused aperture was also made, following the same fabrication procedure, to compare the performance of the two transducers. The focused and unfocused transducers were tested to measure their center frequencies, bandwidths, and spatial resolutions. Lateral resolution of the angled-focused transducer (AFT) improved more than two times compared to that of the angled-unfocused transducer (AUT). A tissue-mimicking phantom in water and a rabbit aorta tissue sample in rabbit blood were scanned using AFT and AUT. Imaging with AFT offered improved contrast, over imaging with AUT, of the tissue-mimicking phantom and the rabbit aorta tissue sample by 23 dB and 8 dB, respectively. The results show that AFT has strong potential to provide morphological and pathological information of coronary arteries with high resolution and high contrast.
    Sensors and Actuators A Physical 03/2015; 228. DOI:10.1016/j.sna.2015.02.037 · 1.94 Impact Factor
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    ABSTRACT: Porous Lead zirconate titanate (PZT) films may have promising applications in high frequency ultrasonic transducers for their capability to modify electrical properties for better electrical and acoustic matching. In this work, porous PZT films in range of several micrometers were fabricated using a chemical solution deposition (CSD) method modified with polyvinylpyrrolidone (PVP) as a pore-foaming agent. The crystalline phase, microstructure and electrical properties of the porous films were investigated as a function of PVP contents, molecular weights and annealing temperatures. It was found that the electrical properties were closely associated with the porosity.
    Ceramics International 03/2015; DOI:10.1016/j.ceramint.2015.03.202 · 2.09 Impact Factor
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    ABSTRACT: Optical-resolution photoacoustic microscopy (OR-PAM) has become a major experimental tool of photoacoustic tomography, with unique imaging capabilities for various biological applications. However, conventional imaging systems are all table-top embodiments, which preclude their use in internal organs. In this study, by applying the OR-PAM concept to our recently developed endoscopic technique, called photoacoustic endoscopy (PAE), we created an optical-resolution photoacoustic endomicroscopy (OR-PAEM) system, which enables internal organ imaging with a much finer resolution than conventional acoustic-resolution PAE systems. OR-PAEM has potential preclinical and clinical applications using either endogenous or exogenous contrast agents.
    Biomedical Optics Express 03/2015; 6(3). DOI:10.1364/BOE.6.000918 · 3.50 Impact Factor
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    ABSTRACT: Acute coronary syndrome (ACS) is frequently associated with the sudden rupture of a vulnerable atherosclerotic plaque within the coronary artery. Several unique physiological features, including a thin fibrous cap accompanied by a necrotic lipid core, are the targeted indicators for identifying the vulnerable plaques. Intravascular ultrasound (IVUS), a catheter-based imaging technology, has been routinely performed in clinics for more than 20 years to describe the morphology of the coronary artery and guide percutaneous coronary interventions. However, conventional IVUS cannot facilitate the risk assessment of ACS because of its intrinsic limitations, such as insufficient resolution. Renovation of the IVUS technology is essentially needed to overcome the limitations and enhance the coronary artery characterization. In this paper, a multi-frequency intravascular ultrasound (IVUS) imaging system was developed by incorporating a higher frequency IVUS transducer (80 to 150 MHz) with the conventional IVUS (30-50 MHz) system. The newly developed system maintains the advantage of deeply penetrating imaging with the conventional IVUS, while offering an improved higher resolution image with IVUS at a higher frequency. The prototyped multifrequency catheter has a clinically compatible size of 0.95 mm and a favorable capability of automated image co-registration. In vitro human coronary artery imaging has demonstrated the feasibility and superiority of the multi-frequency IVUS imaging system to deliver a more comprehensive visualization of the coronary artery. This ultrasonic-only intravascular imaging technique, based on a moderate refinement of the conventional IVUS system, is not only cost-effective from the perspective of manufacturing and clinical practice, but also holds the promise of future translation into clinical benefits.
    IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 03/2015; 62(1):97-107. DOI:10.1109/TUFFC.2014.006679 · 1.50 Impact Factor
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    ABSTRACT: Adult zebrafish is a well-known small animal model for studying heart regeneration. Although the regeneration of scars made by resecting the ventricular apex has been visualized with histological methods, there is no adequate imaging tool for tracking the functional recovery of the damaged heart. For this reason, high-frequency Doppler echocardiography using dual mode pulsed wave Doppler, which provides both tissue Doppler (TD) and Doppler flow in a same cardiac cycle, is developed with a 30 MHz high-frequency array ultrasound imaging system. Phantom studies show that the Doppler flow mode of the dual mode is capable of measuring the flow velocity from 0.1 to 15 cm s(-1) with high accuracy (p-value = 0.974 > 0.05). In the in vivo study of zebrafish, both TD and Doppler flow signals were simultaneously obtained from the zebrafish heart for the first time, and the synchronized valve motions with the blood flow signals were identified. In the longitudinal study on the zebrafish heart regeneration, the parameters for diagnosing the diastolic dysfunction, for example, E/Em < 10, E/A < 0.14 for wild-type zebrafish, were measured, and the type of diastolic dysfunction caused by the amputation was found to be similar to the restrictive filling. The diastolic function was fully recovered within four weeks post-amputation. © 2014 The Author(s) Published by the Royal Society. All rights reserved.
    Journal of The Royal Society Interface 02/2015; 12(103). DOI:10.1098/rsif.2014.1154 · 3.86 Impact Factor
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    ABSTRACT: This brief presents a monolithically integrated fully differential linear HV amplifier as the driver of an ultrasonic transducer. The linear amplifier is capable of transmitting HV arbitrary signals with a very low harmonic distortion, which is suitable for tissue harmonic imaging and other ultrasonic modes for enhanced imaging quality. The amplifier is designed and implemented using the 0.7- μm CMOS silicon-on-insulator process with 120-V devices. The amplifier, when driving a load of 300 pF in parallel with 100 Ω, is capable of transmitting a sine-wave signal with a frequency of up to 4.4 MHz, a maximum signal swing of 180 Vpp, and a second-order harmonic distortion (HD2) of -56 dBc but only dissipating an average power of 62 mW with a 0.1% duty cycle.
    Circuits and Systems II: Express Briefs, IEEE Transactions on 02/2015; 62(2):149-153. DOI:10.1109/TCSII.2014.2387687 · 1.19 Impact Factor
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    ABSTRACT: We demonstrate a novel non-contact method: acoustic radiation force impulse microscopy via photoacoustic detection (PA-ARFI), capable of probing cell mechanics. A 30 MHz lithium niobate ultrasound transducer is utilized for both detection of phatoacoustic signals and generation of acoustic radiation force. To track cell membrane displacements by acoustic radiation force, functionalized single-walled carbon nanotubes are attached to cell membrane. Using the developed microscopy evaluated with agar phantoms, the mechanics of highly- and weakly-metastatic breast cancer cells are quantified. These results clearly show that the PA-ARFI microscopy may serve as a novel tool to probe mechanics of single breast cancer cells.
    Biomedical Optics Express 01/2015; 6(1). DOI:10.1364/BOE.6.000011 · 3.50 Impact Factor
  • IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 01/2015; 62(1):c1-c1. DOI:10.1109/TUFFC.2015.620101 · 1.50 Impact Factor
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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.
    Optics Letters 12/2014; 39(23):6652-5. DOI:10.1364/OL.39.006652 · 3.18 Impact Factor
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    ABSTRACT: We report the multiple micro-particle trapping and manipulation by a single-beam acoustic tweezer using a high-frequency array transducer. A single acoustic beam generated by a 30 MHz ultrasonic linear array transducer can entrap and transport multiple micro-particles located at the main lobe and the grating lobes. The distance between trapped particles can be adjusted by changing the transmit arrangement of array-based acoustic tweezers and subsequently the location of grating lobes. The experiment results showed that the proposed method can trap and manipulate multiple particles within a range of hundreds of micrometers. Due to its simplicity and low acoustic power, which is critical to protect cells from any thermal and mechanical damages, the technique may be used for transportation of cells in cell biology, biosensors, and tissue engineering.
    Applied Physics Letters 11/2014; 105(21):214103. DOI:10.1063/1.4902923 · 3.52 Impact Factor

Publication Stats

3k Citations
557.52 Total Impact Points


  • 2015
    • Daegu Gyeongbuk Institute of Science and Technology
      • Department of Information and Communication Engineering
      Daikyū, Daegu, South Korea
  • 2003–2015
    • University of California, Los Angeles
      • Department of Bioengineering
      Los Ángeles, California, United States
    • University of Southern California
      • • Department of Biomedical Engineering
      • • Department of Ophthalmology
      Los Ángeles, California, United States
  • 2007–2012
    • Washington University in St. Louis
      • Department of Biomedical Engineering
      Saint Louis, MO, United States
    • National Taiwan University
      • Institute of Applied Mechanics
      T’ai-pei, Taipei, Taiwan
    • Oregon Health and Science University
      Portland, Oregon, United States
    • Institute of Electrical and Electronics Engineers
      Washington, Washington, D.C., United States
  • 2011
    • The University of Hong Kong
      Hong Kong, Hong Kong
  • 2010–2011
    • Taipei Veterans General Hospital
      T’ai-pei, Taipei, Taiwan
    • Sogang University
      Sŏul, Seoul, South Korea
  • 2009–2010
    • Jeju National University
      • Department of Ocean System Engineering
      Cheju, Jeju, South Korea
  • 1992–2003
    • Pennsylvania State University
      • Department of Bioengineering
      University Park, Maryland, United States
  • 2000–2002
    • William Penn University
      Worcester, Massachusetts, United States