• Title/Summary/Keyword: X-ray imager

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Development of an Automatic Seed Marker Registration Algorithm Using CT and kV X-ray Images (CT 영상 및 kV X선 영상을 이용한 자동 표지 맞춤 알고리듬 개발)

  • Cheong, Kwang-Ho;Cho, Byung-Chul;Kang, Sei-Kwon;Kim, Kyoung-Joo;Bae, Hoon-Sik;Suh, Tae-Suk
    • Radiation Oncology Journal
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    • v.25 no.1
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    • pp.54-61
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    • 2007
  • [ $\underline{Purpose}$ ]: The purpose of this study is to develop a practical method for determining accurate marker positions for prostate cancer radiotherapy using CT images and kV x-ray images obtained from the use of the on- board imager (OBI). $\underline{Materials\;and\;Methods}$: Three gold seed markers were implanted into the reference position inside a prostate gland by a urologist. Multiple digital image processing techniques were used to determine seed marker position and the center-of-mass (COM) technique was employed to determine a representative reference seed marker position. A setup discrepancy can be estimated by comparing a computed $COM_{OBI}$ with the reference $COM_{CT}$. A proposed algorithm was applied to a seed phantom and to four prostate cancer patients with seed implants treated in our clinic. $\underline{Results}$: In the phantom study, the calculated $COM_{CT}$ and $COM_{OBI}$ agreed with $COM_{actual}$ within a millimeter. The algorithm also could localize each seed marker correctly and calculated $COM_{CT}$ and $COM_{OBI}$ for all CT and kV x-ray image sets, respectively. Discrepancies of setup errors between 2D-2D matching results using the OBI application and results using the proposed algorithm were less than one millimeter for each axis. The setup error of each patient was in the range of $0.1{\pm}2.7{\sim}1.8{\pm}6.6\;mm$ in the AP direction, $0.8{\pm}1.6{\sim}2.0{\pm}2.7\;mm$ in the SI direction and $-0.9{\pm}1.5{\sim}2.8{\pm}3.0\;mm$ in the lateral direction, even though the setup error was quite patient dependent. $\underline{Conclusion}$: As it took less than 10 seconds to evaluate a setup discrepancy, it can be helpful to reduce the setup correction time while minimizing subjective factors that may be user dependent. However, the on-line correction process should be integrated into the treatment machine control system for a more reliable procedure.

Visual Explanation of a Deep Learning Solar Flare Forecast Model and Its Relationship to Physical Parameters

  • Yi, Kangwoo;Moon, Yong-Jae;Lim, Daye;Park, Eunsu;Lee, Harim
    • The Bulletin of The Korean Astronomical Society
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    • v.46 no.1
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    • pp.42.1-42.1
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    • 2021
  • In this study, we present a visual explanation of a deep learning solar flare forecast model and its relationship to physical parameters of solar active regions (ARs). For this, we use full-disk magnetograms at 00:00 UT from the Solar and Heliospheric Observatory/Michelson Doppler Imager and the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, physical parameters from the Space-weather HMI Active Region Patch (SHARP), and Geostationary Operational Environmental Satellite X-ray flare data. Our deep learning flare forecast model based on the Convolutional Neural Network (CNN) predicts "Yes" or "No" for the daily occurrence of C-, M-, and X-class flares. We interpret the model using two CNN attribution methods (guided backpropagation and Gradient-weighted Class Activation Mapping [Grad-CAM]) that provide quantitative information on explaining the model. We find that our deep learning flare forecasting model is intimately related to AR physical properties that have also been distinguished in previous studies as holding significant predictive ability. Major results of this study are as follows. First, we successfully apply our deep learning models to the forecast of daily solar flare occurrence with TSS = 0.65, without any preprocessing to extract features from data. Second, using the attribution methods, we find that the polarity inversion line is an important feature for the deep learning flare forecasting model. Third, the ARs with high Grad-CAM values produce more flares than those with low Grad-CAM values. Fourth, nine SHARP parameters such as total unsigned vertical current, total unsigned current helicity, total unsigned flux, and total photospheric magnetic free energy density are well correlated with Grad-CAM values.

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Development of Friction Welding Process of Zr-based Bulk Metallic Glasses (Zr-기 벌크 금속 유리의 마찰 접합 공정 개발)

  • Shin, Hyung-Seop;Jeong, Young-Jin;Kim, Ki-Hyun
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.337-341
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    • 2004
  • Bulk metallic glasses(BMG) with good mechanical properties have problems that engineering application fields have been limited because of limitation of the alloy size. In order to solving this problem, the friction welding of BMG has been tried using the superplastic-like deformation behavior under the supercooled liquid region. The apparatus for friction welding test was designed and constructed using pneumatic cylinder and gripper based on a conventional lathe. Friction welding have been tried to combination of same BMG alloy and crystalline alloys. The results of welding test were evaluated by X-ray diffraction, measurement of hardness and mechanical properties test. In order to obtain the optimized welding test conditions the temperature of friction interface was measured using Infrared thermal imager.

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Time-Phased Implementation of a Large-Scale PACS at Samsung Medical Center

  • Ro, Duk-Woo;Choi, Hyung-Sik;Lim, Jae-Hoon;Kim, Won-Ki
    • Proceedings of the KOSOMBE Conference
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    • v.1994 no.12
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    • pp.26-27
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    • 1994
  • The first step implementation of a hospital-wide Picture Archiving Communications System (PACS) at a newly built hospital Samsung Medical Center (SMC), is described. Current clinical operation encompasses the fiber optics delivery of direct-interfaced magnetic resonance imager (LRI), X-ray computed tomography (CT). digital subtraction angiography (DSA) and computed radiography (CR) digital images via high performance file server to the departments of radiology, neurosurgery, orthopedics surgery, neurology, emergency room and the surgical intensive care unit.

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A study on electrical response property of photoconductor film for x-ray imaging sensor (X선 영상센서 적용을 위한 광도전체 필름의 전기적 응답특성 연구)

  • Kang, Sang-Sik;Kim, Chan-Wook;Lee, Mi-Hyun;Lee, Kwang-Ok;Moon, Yong-Soo;An, Sung-A;No, Ci-Chul;Park, Ji-Koon
    • Journal of the Korean Society of Radiology
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    • v.3 no.4
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    • pp.29-33
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    • 2009
  • Recently, the compound materials(a-Se, $HgI_2$, PbO, CdTe, $PbI_2$, etc.) that are used in flat panel x-ray imager have been studied for digital x-ray imaging. In this paper, the signal detection properties of $HgI_2$ and a-Se conversion layer, are compared. The thick $HgI_2$ film is fabricated by special particle-in-binder method and the conventional vacuum thermal evaporation is used for a deposition of a-Se film. And an electrical characteristic measurements were investigated about leakage current, signal response property and x-ray sensitivity. From the experimental results show that the $HgI_2$ film has a low operation voltage and high signal generation than that of a-Se.

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Evaluation of Geometric Correspondence of kV X-ray Images, Electric Portal Images and Digitally Reconstructed Radiographic Images (kV X선 영상, 전자조사문 영상, 디지털화재구성 영상 간 기하학적 일치성 평가)

  • Cheong, Kwang-Ho;Kim, Kyoung-Joo;Cho, Byung-Chul;Kang, Sei-Kwon;Juh, Ra-Hyeong;Bae, Hoon-Sik;Suh, Tae-Suk
    • Progress in Medical Physics
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    • v.18 no.3
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    • pp.118-125
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    • 2007
  • In this study we estimated a geometric correlation among digitally reconstructed radiographic image (DRRI), kV x-ray image (kVXI) from the On-Board Imager (OBI) and electric portal image (EPI). To verify geometric correspondence of DRRI, kVXI and EPI, specially designed phantom with indexed 6 ball bearings (BBs) were employed. After accurate setup of the phantom on a treatment couch using orthogonal EPIs, we acquired set of orthogonal kVXIs and EPIs then compared the absolute positions of the center of the BBs calculated at each phantom plane for kVXI and EPI respectively. We also checked matching result for obliquely incident beam (gantry angle of $315^{\circ}$) after 2D-2D matching provided by OBI application. A reference EPI obtained after initial setup of the phantom was compared with 10 series of EPIs acquired after each 2D-2D matching. Imaginary setup errors were generated from -5 mm to 5 mm at each couch motion direction. Calculated positions of all center positions of the BBs at three different images were agreed with the actual points within a millimeter and each other. Calculated center positions of the BBs from the reference and obtained EPIs after 2D-2D matching agreed within a millimeter. We could tentatively conclude that the OBI system was mechanically quite reliable for image guided radiation therapy (IGRT) purpose.

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Fast Dimming Associated with a Coronal Jet Seen in Multi-Wavelength and Stereoscopic Observations

  • Lee, K.S.;Innes, D.E.;Moon, Y.J.;Shibata, K.;Lee, Jin-Yi
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.1
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    • pp.89.1-89.1
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    • 2012
  • We have investigated a coronal jet observed near the limb on 2010 June 27 by the Hinode/X-Ray Telescope (XRT), EUV Imaging Spectrograph (EIS), and Solar Optical Telescope (SOT), and the SDO/Atmospheric Imaging Assembly (AIA), Helioseismic and Magnetic Imager (HMI), and on the disk by STEREO-A/EUVI. From EUV (AIA and EIS) and soft X-ray (XRT) images we have identified both cool and hot jets. There was a small loop eruption in Ca II images of the SOT before the jet eruption. Using high temporal and multi wavelength AIA images, we found that the hot jet preceded its associated cool jet by about 2 minutes. The cool jet showed helical-like structures during the rising period. According to the spectroscopic analysis, the jet's emission changed from blue to red shift with time, implying helical motions in the jet. The STEREO observation, which enabled us to observe the jet projected against the disk, showed that there was a dim loop associated with the jet. We have measured a propagation speed of ~800 km/s for the dimming front. This is comparable to the Alfven speed in the loop computed from a magnetic field extrapolation of the HMI photospheric field measured 5 days earlier and the loop densities obtained from EIS Fe XIV line ratios. We interpret the dimming as indicating the presence of Alfvenic waves initiated by reconnection in the upper chromosphere.

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Formations of Coronal Hole Associated with Halo CME

  • Kim, Su-Jin;Lee, Sung-Eun;Marubashi, Katsuhide;Cho, Kyung-Suk;Bong, Su-Chan;Moon, Yong-Jae
    • The Bulletin of The Korean Astronomical Society
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    • v.35 no.1
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    • pp.27.2-27.2
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    • 2010
  • We have studied the formation of coronal holes (CHs) associated with halo CMEs. For this study, we used multi-wavelength data from Yohkoh Soft X-ray Telescope (SXT), GOES Soft X-ray Imager (SXI), SOHO EIT 195 ${\AA}$, SOHO MDI magnetogram, MLSO He I 10830 ${\AA}$, and BBSO H-alpha. The CHs are characterized by open magentic field regions with low emission, density, and temperature and their open fields drive high speed solar winds which cause geomagnetic storms. So far, the formation and the evolution of CHs are not well understood. The formation of the dark region associated with the eruption of a CME is well known as "coronal dimming" which may be caused by the mass depletion near the CME footpoint. It is different from a typical CH since it persists for only one or two days. In this study, we present three cases that show the formation of coronal holes which are associated with three halo CMEs: 1) 2000 Jul 14, 2) 2003 Oct 28, 3) 2005 May 13. In the first case, hot plasma was ejected during a weak eruption and then filled out the pre-existing CH. After the halo CME occurred, the hot plasma region becomes a CH again. In the second and the third cases, we found newly formed CHs just after their associated CMEs. All three coronal holes are associated with strong flares and persist over 3 days until they disappeared by the solar rotation. Examining the MDI magnetograms, we found that the magnetic polarity of each CH region has one polarity. Based on these results, we suggest that the coronal holes can be formed by the CMEs and they should be distinguished from the coronal dimming.

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Characteristics of Friction Welding of Bulk Metallic Glass Rods and Tubes (벌크 비정질 금속 봉재 및 튜브재의 마찰접합 특성)

  • Shin, Hyung-Seop;Park, Jung-Soo;Jung, Yoon-Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.7
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    • pp.687-692
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    • 2009
  • The friction welding of Zr-based bulk metallic glass (BMG) rods and tubes to similar BMGs, and to crystalline metals were performed. An infrared thermal imager (FLIR-Thermal Cam SC-2000) was used to measure the temperature distribution at joining interface of the specimens during friction welding. All BMGs adopted in this study showed a successful friction joining to similar BMG. The shape of the protrusion formed at the weld interface were examined. In order to characterize the friction weld interface, the micrographic observation and the X-ray diffraction analysis on the weld cross-section were carried out. The obtained results were discussed based on the temperature distribution measured at the weld interface A successful joining of the BMGs to crystalline metals could be obtained for certain pairs of the material combination through the precise control of the friction condition. The residual strength after dissimilar friction welding of BMG was evaluated by the four-point bending test and compared with the cases of friction welding to similar materials.

Integrated Ray Tracing Model for In-Orbit Optical Performance Simulation for GOCI (통합적 광추적 모델에 의한 해양탑재체 GOCI의 궤도 상 광학 성능 검증)

  • Ham, Seon-Jeong;Lee, Jae-Min;Kim, Seong-Hui;Yun, Hyeong-Sik;Gang, Geum-Sil;Myeong, Hwan-Chun;Kim, Seok-Hwan
    • Journal of Satellite, Information and Communications
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    • v.1 no.2
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    • pp.1-7
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    • 2006
  • GOCi (Geostationary Ocean Color Imager) is one of the COMS payloads that KARI is currently developing and scheduled to be in operation from around 2008. Its primary objective is to monitor the Korean coastal water environmental condition. We report the current progress in development of the integrated optical model as one of the key analysis tools for the GOCI in-orbit performance verification. The model includes the Sun as the emitting light source. The curved Earth surface section of 2500 km x 2500 km includingthe Korean peninsular os defined as a Lambertian scattering surface consisted of land and sea surface. From its geostationary orbit, the GOCI optical system observes the reflected light from the surfaces with varying reflectance representing the changes in its environmental conditions. The optical ray tracing technique was used to demonstrate the GOCI in-orbit performances such as red tide detection. The computational concept, simulation results and its implications to the on-going development of GOCI are presented.

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