K. Shung | University of Southern California (original) (raw)

Papers by K. Shung

Biomedical Optics and 3-D Imaging, 2012

ABSTRACT Photoacoustic endoscopy provides unique functional information through its broad spectro... more ABSTRACT Photoacoustic endoscopy provides unique functional information through its broad spectroscopic imaging capability. The imaging results presented here suggest its potential for use as a comprehensive endoscopic tool in various medical applications.

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

Alumina colloidal/polymer composite films on silicon substrates have been successfully fabricated... more Alumina colloidal/polymer composite films on silicon substrates have been successfully fabricated using the sol-gel method, in which the crystallite sizes of alumina are between 20 and 50 nm. The density and ultrasonic phase velocities in these films with different alumina ratios from 14% to 32% were measured at the desired operating frequency. We have proved that the density, acoustic phase velocities, and hence the acoustic impedance of the nanocomposite films increase with the alumina content, which gives us another option of tailoring the acoustic impedance of the nano-composite film for making the matching layer of high-frequency medical ultrasonic transducers.

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

Concentric annular type dual element transducers for second harmonic imaging at 20 MHz / 40 MHz w... more Concentric annular type dual element transducers for second harmonic imaging at 20 MHz / 40 MHz were designed and fabricated to improve spatial resolution and depth of penetration for ophthalmic imaging applications. The outer ring element was designed to transmit the 20 MHz signal and the inner circular element was designed to receive the 40 MHz second harmonic signal. Lithium niobate (LiNbO(3)), with its low dielectric constant, was used as the piezoelectric material to achieve good electrical impedance matching. Double matching layers and conductive backing were used and optimized by KLM modeling to achieve high sensitivity and wide bandwidth for harmonic imaging and superior time-domain characteristics. Prototype transducers were fabricated and evaluated quantitatively and clinically. The average measured center frequency for the transmit ring element was 21 MHz and the one-way --3 dB bandwidth was greater than 50%. The 40 MHz receive element functioned at 31 MHz center frequency with acceptable bandwidth to receive attenuated and frequency downshifted harmonic signal. The lateral beam profile for the 20 MHz ring elements at the focus matched the Field II simulated results well, and the effect of outer ring diameter was also examined. Images of a posterior segment of an excised pig eye and a choroidal nevus of human eye were obtained both for single element and dual element transducers and compared to demonstrate the advantages of dual element harmonic imaging.

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

Lead-free K 0.5 Na 0.5 NbO 3 /Bi 0.5 Na 0.5 TiO 3 (KNN/ BNT) films have been fabricated by a comp... more Lead-free K 0.5 Na 0.5 NbO 3 /Bi 0.5 Na 0.5 TiO 3 (KNN/ BNT) films have been fabricated by a composite sol-gel technique. Crystalline KNN fine powder was dispersed in the BNT precursor solution to form a composite slurry which was then spin-coated onto a platinum-buffered Si substrate. Repeated layering and vacuum infiltration were applied to produce 5-µm-thick dense composite film. By optimizing the sintering temperature, the films exhibited good dielectric and ferroelectric properties comparable to PZT films. A 193-MHz high-frequency ultrasonic transducer fabricated from this composite film showed a −6-dB bandwidth of approximately 34%. A tungsten wire phantom was imaged to demonstrate the capability of the transducer. reagent-grade raw materials of K 2 co 3 (99%), na 2 co 3 (99.8%) and nb 2 o 5 (99.5%) were used to prepare the Manuscript

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

This paper reports the design, fabrication, and characterization of a 1-3 composite annular-array... more This paper reports the design, fabrication, and characterization of a 1-3 composite annular-array transducer. An interdigital bonded (IB) 1-3 composite was prepared using two IB operations on a fine-grain piezoelectric ceramic. The final composite had 19-μm-wide posts separated by 6-μmwide polymer kerfs. A novel method to remove metal electrodes from polymer portions of the 1-3 composite was established to eliminate the need for patterning and aligning the electrode on the composite to the electrodes on a flexible circuit. Unloaded epoxy was used for both the matching and backing layers and a flexible circuit was used for interconnect. A prototype array was successfully fabricated and tested. The results were in reasonable agreement with those predicted by a circuit-analogous model. The average center frequency estimated from the measured pulseecho responses of array elements was 33.5 MHz and the −6-dB fractional bandwidth was 57%. The average insertion loss recorded was 14.3 dB, and the maximum crosstalk between the nearestneighbor elements was less than −37 dB. Images of a wire phantom and excised porcine eye were obtained to show the capabilities of the array for high-frequency ultrasound imaging.

... NDI technique development for new technologies. Author(s): Susan Ruth. In the aerospace indus... more ... NDI technique development for new technologies. Author(s): Susan Ruth. In the aerospace industry, the space industry in particular, there is a ... A key feature of SHIELD is the implementation of a wireless ZIGBEE (802.15.4) network for implementing large numbers of small, low ...

Quantitative imaging in medicine and surgery, 2015

Elastography, capable of mapping the biomechanical properties of biological tissues, serves as a ... more Elastography, capable of mapping the biomechanical properties of biological tissues, serves as a useful technique for clinicians to perform disease diagnosis and determine stages of many diseases. Many acoustic radiation force (ARF) based elastography, including acoustic radiation force impulse (ARFI) imaging and harmonic motion imaging (HMI), have been developed to remotely assess the elastic properties of tissues. However, due to the lower operating frequencies of these approaches, their spatial resolutions are insufficient for revealing stiffness distribution on small scale applications, such as cancerous tumor margin detection, atherosclerotic plaque composition analysis and ophthalmologic tissue characterization. Though recently developed ARF-based optical coherence elastography (OCE) methods open a new window for the high resolution elastography, shallow imaging depths significantly limit their usefulness in clinics. The aim of this study is to develop a high-resolution HMI me...

Biomedical Optics and 3-D Imaging, 2012

ABSTRACT Photoacoustic endoscopy provides unique functional information through its broad spectro... more ABSTRACT Photoacoustic endoscopy provides unique functional information through its broad spectroscopic imaging capability. The imaging results presented here suggest its potential for use as a comprehensive endoscopic tool in various medical applications.

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

Alumina colloidal/polymer composite films on silicon substrates have been successfully fabricated... more Alumina colloidal/polymer composite films on silicon substrates have been successfully fabricated using the sol-gel method, in which the crystallite sizes of alumina are between 20 and 50 nm. The density and ultrasonic phase velocities in these films with different alumina ratios from 14% to 32% were measured at the desired operating frequency. We have proved that the density, acoustic phase velocities, and hence the acoustic impedance of the nanocomposite films increase with the alumina content, which gives us another option of tailoring the acoustic impedance of the nano-composite film for making the matching layer of high-frequency medical ultrasonic transducers.

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

Concentric annular type dual element transducers for second harmonic imaging at 20 MHz / 40 MHz w... more Concentric annular type dual element transducers for second harmonic imaging at 20 MHz / 40 MHz were designed and fabricated to improve spatial resolution and depth of penetration for ophthalmic imaging applications. The outer ring element was designed to transmit the 20 MHz signal and the inner circular element was designed to receive the 40 MHz second harmonic signal. Lithium niobate (LiNbO(3)), with its low dielectric constant, was used as the piezoelectric material to achieve good electrical impedance matching. Double matching layers and conductive backing were used and optimized by KLM modeling to achieve high sensitivity and wide bandwidth for harmonic imaging and superior time-domain characteristics. Prototype transducers were fabricated and evaluated quantitatively and clinically. The average measured center frequency for the transmit ring element was 21 MHz and the one-way --3 dB bandwidth was greater than 50%. The 40 MHz receive element functioned at 31 MHz center frequency with acceptable bandwidth to receive attenuated and frequency downshifted harmonic signal. The lateral beam profile for the 20 MHz ring elements at the focus matched the Field II simulated results well, and the effect of outer ring diameter was also examined. Images of a posterior segment of an excised pig eye and a choroidal nevus of human eye were obtained both for single element and dual element transducers and compared to demonstrate the advantages of dual element harmonic imaging.

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

Lead-free K 0.5 Na 0.5 NbO 3 /Bi 0.5 Na 0.5 TiO 3 (KNN/ BNT) films have been fabricated by a comp... more Lead-free K 0.5 Na 0.5 NbO 3 /Bi 0.5 Na 0.5 TiO 3 (KNN/ BNT) films have been fabricated by a composite sol-gel technique. Crystalline KNN fine powder was dispersed in the BNT precursor solution to form a composite slurry which was then spin-coated onto a platinum-buffered Si substrate. Repeated layering and vacuum infiltration were applied to produce 5-µm-thick dense composite film. By optimizing the sintering temperature, the films exhibited good dielectric and ferroelectric properties comparable to PZT films. A 193-MHz high-frequency ultrasonic transducer fabricated from this composite film showed a −6-dB bandwidth of approximately 34%. A tungsten wire phantom was imaged to demonstrate the capability of the transducer. reagent-grade raw materials of K 2 co 3 (99%), na 2 co 3 (99.8%) and nb 2 o 5 (99.5%) were used to prepare the Manuscript

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

This paper reports the design, fabrication, and characterization of a 1-3 composite annular-array... more This paper reports the design, fabrication, and characterization of a 1-3 composite annular-array transducer. An interdigital bonded (IB) 1-3 composite was prepared using two IB operations on a fine-grain piezoelectric ceramic. The final composite had 19-μm-wide posts separated by 6-μmwide polymer kerfs. A novel method to remove metal electrodes from polymer portions of the 1-3 composite was established to eliminate the need for patterning and aligning the electrode on the composite to the electrodes on a flexible circuit. Unloaded epoxy was used for both the matching and backing layers and a flexible circuit was used for interconnect. A prototype array was successfully fabricated and tested. The results were in reasonable agreement with those predicted by a circuit-analogous model. The average center frequency estimated from the measured pulseecho responses of array elements was 33.5 MHz and the −6-dB fractional bandwidth was 57%. The average insertion loss recorded was 14.3 dB, and the maximum crosstalk between the nearestneighbor elements was less than −37 dB. Images of a wire phantom and excised porcine eye were obtained to show the capabilities of the array for high-frequency ultrasound imaging.

... NDI technique development for new technologies. Author(s): Susan Ruth. In the aerospace indus... more ... NDI technique development for new technologies. Author(s): Susan Ruth. In the aerospace industry, the space industry in particular, there is a ... A key feature of SHIELD is the implementation of a wireless ZIGBEE (802.15.4) network for implementing large numbers of small, low ...

Quantitative imaging in medicine and surgery, 2015

Elastography, capable of mapping the biomechanical properties of biological tissues, serves as a ... more Elastography, capable of mapping the biomechanical properties of biological tissues, serves as a useful technique for clinicians to perform disease diagnosis and determine stages of many diseases. Many acoustic radiation force (ARF) based elastography, including acoustic radiation force impulse (ARFI) imaging and harmonic motion imaging (HMI), have been developed to remotely assess the elastic properties of tissues. However, due to the lower operating frequencies of these approaches, their spatial resolutions are insufficient for revealing stiffness distribution on small scale applications, such as cancerous tumor margin detection, atherosclerotic plaque composition analysis and ophthalmologic tissue characterization. Though recently developed ARF-based optical coherence elastography (OCE) methods open a new window for the high resolution elastography, shallow imaging depths significantly limit their usefulness in clinics. The aim of this study is to develop a high-resolution HMI me...