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Jeeun Kang,Changhan Yoon,Jaejin Lee,Sang-Bum Kye,Yongbae Lee,Jin Ho Chang,Gi-Duck Kim,Yangmo Yoo,Tai-kyong Song IEEE 2016 IEEE transactions on biomedical circuits and syste Vol.10 No.2
<P>In this paper, we present a novel system-on-chip (SOC) solution for a portable ultrasound imaging system (PUS) for point-of-care applications. The PUS-SOC includes all of the signal processing modules (i.e., the transmit and dynamic receive beamformer modules, mid- and back-end processors, and color Doppler processors) as well as an efficient architecture for hardware-based imaging methods (e.g., dynamic delay calculation, multi-beamforming, and coded excitation and compression). The PUS-SOC was fabricated using a UMC 130-nm NAND process and has 16.8 GFLOPS of computing power with a total equivalent gate count of 12.1 million, which is comparable to a Pentium-4 CPU. The size and power consumption of the PUS-SOC are 27 x 27 mm(2) and 1.2 W, respectively. Based on the PUS-SOC, a prototype hand-held US imaging system was implemented. Phantom experiments demonstrated that the PUS-SOC can provide appropriate image quality for point-of-care applications with a compact PDA size (200 x 120 x 45 mm(3)) and 3 hours of battery life.</P>
Kang, Jeeun,Kim, Eun-Kyung,Kim, Ga Ram,Yoon, Changhan,Song, Tai-Kyong,Chang, Jin Ho Wiley 2015 Journal of biophotonics Vol.8 No.1
<P>This paper investigates whether photoacoustic imaging (PAI) can provide the visualization of microcalcifications in breast tissue. For this, the geometrical correlation between the 3-D PA images of breast microcalcifications within ex vivo specimens and the corresponding mammograms was ascertained. Also, the optical absorbance of the calcification compositions (i.e., hydroxyapatite and calcium oxalate) was measured and compared with the PA responses of the microcalcifications. The experimental results demonstrated that the PA images discriminated between the microcalcifications and the surrounding tissue, and their locations in PA images reasonably meshed with those of the microcalcifications appeared in the mammograms. Also, the change in PA signal amplitude along the laser wavelength agreed with the absorbance of hydroxyapatite associated with the relatively high potential of malignant cancers, but not calcium oxalate with only benign cases.</P>
Kang, Jeeun,Chang, Jin Ho,Wilson, Brian C.,Veilleux, Israel,Bai, Yanhui,DaCosta, Ralph,Kim, Kang,Ha, Seunghan,Lee, Jong Gun,Kim, Jeong Seok,Lee, Sang-Goo,Kim, Sun Mi,Lee, Hak Jong,Ahn, Young Bok,Han, American Institute of Physics 2015 Review of scientific instruments Vol.86 No.3
<P>Multi-modality imaging is beneficial for both preclinical and clinical applications as it enables complementary information from each modality to be obtained in a single procedure. In this paper, we report the design, fabrication, and testing of a novel tri-modal in vivo imaging system to exploit molecular/functional information from fluorescence (FL) and photoacoustic (PA) imaging as well as anatomical information from ultrasound (US) imaging. The same ultrasound transducer was used for both US and PA imaging, bringing the pulsed laser light into a compact probe by fiberoptic bundles. The FL subsystem is independent of the acoustic components but the front end that delivers and collects the light is physically integrated into the same probe. The tri-modal imaging system was implemented to provide each modality image in real time as well as co-registration of the images. The performance of the system was evaluated through phantom and in vivo animal experiments. The results demonstrate that combining the modalities does not significantly compromise the performance of each of the separate US, PA, and FL imaging techniques, while enabling multi-modality registration. The potential applications of this novel approach to multi-modality imaging range from preclinical research to clinical diagnosis, especially in detection/localization and surgical guidance of accessible solid tumors.</P>
Generalised dynamic decimation method using polyphase MACs for ultrasound imaging
Hyungil Kang,Jeeun Kang,Tai-Kyong Song IET 2015 Electronics letters Vol.51 No.6
<P>In medical ultrasound imaging, the focused echo signal is decimated with a finite impulse response filter by a rational factor <I>M</I>/<I>L</I>, the frequency response of which dynamically changes over time. Presented is, an efficient structure for dynamic decimation by a programmable rational factor that use a fixed number of polyphase multiplier-accumulators (MACs) regardless of the values of <I>M</I> and <I>L</I>. The proposed structure uses the minimum number of MAC units operating at the input data rate to minimise both power consumption and hardware complexity.</P>
Enhancement of photoacoustic image quality by sound speed correction: ex vivo evaluation.
Yoon, Changhan,Kang, Jeeun,Han, Seunghee,Yoo, Yangmo,Song, Tai-Kyong,Chang, Jin Ho Optical Society of America 2012 Optics express Vol.20 No.3
<P>Real-time photoacoustic (PA) imaging involves beamforming methods using an assumed fixed sound speed, typically 1540 m/s in soft tissue. This leads to degradation of PA image quality because the true sound speed changes as PA signal propagates through different types of soft tissues: the range from 1450 m/s to 1600 m/s. This paper proposes a new method for estimating an optimal sound speed to enhance the cross-sectional PA image quality. The optimal sound speed is determined when coherent factor with the sound speed is maximized. The proposed method was validated through simulation and ex vivo experiments with microcalcification-contained breast cancer specimen. The experimental results demonstrated that the best lateral resolution of PA images of microcalcifications can be achieved when the optimal sound speed is utilized.</P>
Kim, Haemin,Kang, Jeeun,Chang, Jin Ho Optical Society of America 2014 Optics letters Vol.39 No.9
<P>Photothermal therapy is performed by delivering laser radiation into the target lesion containing tissue chromophores so as to induce localized heating. For high treatment efficacy, the laser wavelength should be selected to maximize the absorption of incident laser radiation in the tissue chromophores. However, even with the optimal laser wavelength, both the absorption and the scattering of laser energy in tissue openly hamper treatment efficacy in deep-lying lesions. To overcome the limitation, we propose a dual thermal therapeutic method in which both laser and acoustic energies are transmitted to increase therapeutic depth while maintaining high target selectivity of photothermal therapy. Through skin-mimicking phantom experiments, it was verified that the two different energies are complementary in elevation of tissue temperature, and the treatment depth using laser radiation is increased along with acoustic energy.</P>
Moon, Hyungwon,Kang, Jeeun,Lee, Hohyeon,Lee, Minji,Chang, Jin Ho,Lee, Hak Jong,Kim, Hyuncheol American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.11
<P>Theragnostic contrast agents are among the newest tools for simultaneous diagnosis and therapy, but still have limitations in terms of their contrast enhancement capabilities and, consequently, their effectiveness. Among the various biomedical imaging modalities, photoacoustic (PA) imaging is a technology that can enhance diagnostic capacity by use of contrast agents; however, the traditional mechanism for generating PA signals by inducing thermal expansion is limited by low efficiency and sensitivity. To address these issues, we have developed an Indocyanine Green (ICG)loaded perfluoropentane (Pen) nanodroplet for vaporization-induced amplification of PA signals, and enhancement of ultrasound echogenicity by a vaporization mechanism. We found that vaporization was a more effective mechanism for signal enhancement than thermal expansion. Under laser irradiation, vaporization of ICG nanodroplets encapsulating perfluoropentane by a graded temperature increase enabled the visualization of a PA image. The gas phase of perfluoropentane present after evaporation-induced acoustic impedance mismatch relative to the surroundings, causing echogenic signals to be effectively propagated for ultrasonographic detection. The nanodroplet also demonstrated therapeutic efficacy through optically triggered release of paclitaxel via vaporization, which reduced the viability of breast cancer cells. These findings suggest that the ICG-Pen nanodroplet is a promising theragnostic contrast agent that can both amplify photoacoustic and echogenic signals and target local delivery of chemotherapeutic drugs in cancer treatment.</P>
Ju, Kuk-Youn,Kang, Jeeun,Chang, Jin Ho,Lee, Jin-Kyu AMERICAN CHEMICAL SOCIETY 2016 Biomacromolecules Vol. No.
<P>The contradictory biological function of eumelanin (photoprotection vs photosensitization) has long been a topic of debate in a wide range of disciplines such as chemistry, physics and biology. For understanding full spectrum of eumelanin's photobiological aspect, revealing how eumelanin's complex structural organization dictates its photophysical properties is critical step. Here, we report a practical approach to controlling the hierarchically assembled structure of natural eumelanin, which leads to disassembly of its structure into subunits and oxidized subunits, respectively. Based on the well-characterized model system, it was possible to systematically determine how the photophysical properties of eumelanin are ruled by its hierarchical assembly organization. Particularly, our experiments reveal that the chemical oxidation of eumelanin's subunits, which leads to delamination of their stacked layer structure, is critical to significantly increase their photochemical reactivity to generate ROS under UV irradiation. This result provides clear experimental evidence that oxidative degradation of eumelanin, which might be induced by phagosomal enzymatic activity in the process of melanomagenesis, is responsible for triggering the negative photobiological role of eumelanin such as ROS source needed for development of malignant melanoma.</P>