• Title/Summary/Keyword: X-ray 시스템

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The Necessity of Resetting the Filter Criteria for the Minimization of Dose Creep in Digital Imaging Systems (디지털 영상 시스템에서 선량 크리프 최소화를 위한 부가 필터 두께 권고 기준의 재설정에 대한 연구)

  • Kim, Kyo Tae;Kim, Kum Bae;Kang, Sang Sik;Park, Ji Koon
    • Journal of the Korean Society of Radiology
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    • v.13 no.5
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    • pp.757-763
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    • 2019
  • Recently, Following the recent development of flat panel detector with wide dynamic ranges, increasing numbers of healthcare providers have begun to use digital radiography. As a result, filter thickness standards should be reestablished, as current clinical practice requires the use of thicknesses recommended by the National Council on Radiation Protection and Measurements, which are based on information, acquired using conventional analog systems. Here we investigated the possibility of minimizing dose creep and optimizing patient dose using Al filters in digital radiography. The use of thicker Al filters resulted in a maximum 19.3% reduction in the entrance skin exposure dose when medical images with similar sharpness values were compared. However, resolution, which is a critical factor in imaging, had a significant change of 1.01 lp/mm. This change in resolution is thought to be due to the increased amount of scattered rays generated from the object due to the X-ray beam hardening effect. The increase in the number of scattered rays was verified using the scattering degradation factor. However, the FPD, which has recently been developed and is widely used in various areas, has greater response to radiation than analog devices and has a wide dynamic range. Therefore, the FPD is expected to maintain an appropriate level of resolution corresponding to the increase in the scattered-ray content ratio, which depends on filter thickness. Use of the FPD is also expected to minimize dose creep by reducing the exposure dose.

Evaluation of Image Quality for Various Electronic Portal Imaging Devices in Radiation Therapy (방사선치료의 다양한 EPID 영상 질평가)

  • Son, Soon-Yong;Choi, Kwan-Woo;Kim, Jung-Min;Jeong, Hoi-Woun;Kwon, Kyung-Tae;Cho, Jeong-Hee;Lee, Jea-Hee;Jung, Jae-Yong;Kim, Ki-Won;Lee, Young-Ah;Son, Jin-Hyun;Min, Jung-Whan
    • Journal of radiological science and technology
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    • v.38 no.4
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    • pp.451-461
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    • 2015
  • In megavoltage (MV) radiotherapy, delivering the dose to the target volume is important while protecting the surrounding normal tissue. The purpose of this study was to evaluate the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE) using an edge block in megavoltage X-ray imaging (MVI). We used an edge block, which consists of tungsten with dimensions of 19 (thickness) ${\times}$ 10 (length) ${\times}$ 1 (width) $cm^3$ and measured the pre-sampling MTF at 6 MV energy. Various radiation therapy (RT) devices such as TrueBeam$^{TM}$ (Varian), BEAMVIEW$^{PLUS}$ (Siemens), iViewGT (Elekta) and Clinac$^{(R)}$iX (Varian) were used. As for MTF results, TrueBeam$^{TM}$(Varian) flattening filter free(FFF) showed the highest values of $0.46mm^{-1}$ and $1.40mm^{-1}$ for MTF 0.5 and 0.1. In NPS, iViewGT (Elekta) showed the lowest noise distribution. In DQE, iViewGT (Elekta) showed the best efficiency at a peak DQE and $1mm^{-1}DQE$ of 0.0026 and 0.00014, respectively. This study could be used not only for traditional QA imaging but also for quantitative MTF, NPS, and DQE measurement for development of an electronic portal imaging device (EPID).

Development of the Algorithm for On-line Dosimetry System for High Energy Radiation Treatment (고에너지 방사선치료용 on-line 선량측정시스템을 위한 알고리즘의 개발)

  • Wu, Hong-Hyun;Ha, Sung-Whan
    • Journal of Radiation Protection and Research
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    • v.22 no.3
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    • pp.207-218
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    • 1997
  • Purpose: The objective of this study is to develop an algorithm for estimation of tumor dose using measured transmission dose as a part of the development of on-line dosimetry system. Materials and Methods: Data of transmission dose were measured under various FS, Tp and PCD with a special water phantom for 6 MV and 10 MV X-ray. SCD (source-chamber distance) was set to 150 cm. Measurements were conducted with a 0.125 cc ion chamber. Results: Using measured data and regression analysis, two algorithms were developed for estimation of expected reading for measured data. Algorithm 1 consisted of the quadratic function of PCD and the tertiary function of AlP (area-perimeter ratio). Algorithm 2 consisted of the tertiary function of log(A/P)and the tertiary function of PCD. Algorithm 2 required less data set and was more accurate in comparing expected and observed dose. Conclusion: Using the algorithm developed, transmission dose can be estimated for any exposure condition, i.e. any given Tp, PCD and FS with high accuracy. To complete this algorithm, further developments are needed regarding the beam modifying device, the tissue inhomogeneity and the irregular body surface.

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Anisotropic Compression Behavior and Phase Transition of Sepiolite Under Moderate Pressure Conditions (천부지권 압력 하 해포석의 비등방적 압축 특성 및 상전이 연구)

  • Seohee, Yun;Yongjae, Lee
    • Korean Journal of Mineralogy and Petrology
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    • v.35 no.4
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    • pp.423-430
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    • 2022
  • Pressure-dependent elastic behavior and chemical reaction of natural sepiolite (Mg8Si12O30(OH)4·12H2O) was studied under two different pressure-transmitting medium (PTM) conditions using synchrotron X-ray powder diffraction. Under non pore-penetrating silicone oil PTM, we observed that the b-axis length increases up to ca. 3.6 GPa, marking an anisotropic compression region with negative linear compressibility of βb= -0.0012 GPa-1, which then decreases at 7.7 GPa. Under pore-penetrating water PTM, the anisotropic compression behavior is enhanced with doubled negative linear compressibility of βb= -0.0025 GPa-1 up to 3.2 GPa, where transformation into stevensite is observed upon ex-situ temperature treatment at 280 ℃ as confirmed via XRD and SEM. Derived bulk moduli (K0) and linear compressibilities (β) were compared to other structurally and chemically related minerals.

Analysis of Tissue Equivalent Characteristics of Agar Phantom for Hyperthermia Therapy (온열종양치료 한천 팬텀의 조직등가 특성 분석)

  • Jeong-Geun Park;Kyeong-Hwan Jeong;Jeong-Min Seo
    • Journal of the Korean Society of Radiology
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    • v.17 no.6
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    • pp.985-991
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    • 2023
  • A tissue-equivalent phantom is necessary for quality control of hyperthermia therapy. However, since there is no phantom for this purpose, phantoms made from agar are being used in various studies. The tissue-equivalent properties of the agar phantom were confirmed by comparison with the tissue-equivalent material bolus in this study. CT images of the agar phantom and bolus were acquired, and tissue equivalent characteristics were analyzed with image analysis and dose calculation using a computerized radiation therapy planning system. The average pixel value was 96.960±10.999 in bolus, 108.559±8.233 in 3% agar phantom, and 111.844±8.651 in 4% agar phantom. Using the SSD technique, 100 cGy was prescribed at a depth of 1.5 cm and 6 MV X -ray was set to irradiated to 10x10 cm2, and the absorbed dose according to depth was calculated from the central axis of the beam. The intraclass correlation coefficient of dose distribution of bolus, 3% agar phantom, and 4% agar phantom was 0.979 (p<.001, 95%CI .957-.991). The density (g/cm3) at the point where the absorbed dose was calculated was 0.990±0.020 at the bolus, 1.018±0.020 at the 3% agar phantom, and 1.035±0.024 at the 4% agar phantom. In this study, the internal density distribution and uniformity of the agar phantom were confirmed to be appropriate as a tissue equivalent material by analysis of CT images and a computerized radiation therapy planning system.

High Yield Bacterial Expression and Purification of Active Cytochrome P450 p-coumarate-3-hydroxylase (C3H), the Arabidopsis Membrane Protein (대장균 시스템을 이용한 Arabidopsis 막 단백질 cytochrome P450 p-coumarate-3hydroxylase (C3H) 활성형의 과발현 및 분리정제)

  • Yang, Hee-Jung;Kim, Wan-Yeon;Yun, Young-Ju;Yoon, Ji-Won;Kwon, Tae-Woo;Youn, Hye-Sook;Youn, Bu-Hyun
    • Journal of Life Science
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    • v.19 no.8
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    • pp.1039-1046
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    • 2009
  • The cytochrome P450s (P450s) metabolizing natural products are among the most versatile biological catalysts known in plants, but knowledge of the structural basis for their broad substrate specificity has been limited. The activity of p-coumarate 3-hydroxylase (C3H) is thought to be essential for the biosynthesis of lignin and many other phenylpropanoid pathway products in plants however, all attempts to express and purify the protein corresponding C3H gene have failed. As a result, no conditions suitable for the unambiguous assay of the enzyme are known. The detailed understanding of the mechanism and substrate-specificity of C3Hdemands a method for the production of active protein on the milligram scale. We have developed a bacterial expression and purification system for the plant C3H, which allows for the quick expression and purification of active wild-type C3H via introduction of combinational mutagenesis. The modified cytochrome P450 C3H ($C3H_{mod}$) could be purified in the absence of detergent using immobilized metal affinity chromatography and size exclusion chromatography following extraction from isolated membranes in a high salt buffer and catalytically activated. This method makes the use of isotopic labeling of C3H for NMRstudies and X-ray crystallography practical, and is also applicable to other plant cytochrome P450 proteins.

Multi-classification of Osteoporosis Grading Stages Using Abdominal Computed Tomography with Clinical Variables : Application of Deep Learning with a Convolutional Neural Network (멀티 모달리티 데이터 활용을 통한 골다공증 단계 다중 분류 시스템 개발: 합성곱 신경망 기반의 딥러닝 적용)

  • Tae Jun Ha;Hee Sang Kim;Seong Uk Kang;DooHee Lee;Woo Jin Kim;Ki Won Moon;Hyun-Soo Choi;Jeong Hyun Kim;Yoon Kim;So Hyeon Bak;Sang Won Park
    • Journal of the Korean Society of Radiology
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    • v.18 no.3
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    • pp.187-201
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    • 2024
  • Osteoporosis is a major health issue globally, often remaining undetected until a fracture occurs. To facilitate early detection, deep learning (DL) models were developed to classify osteoporosis using abdominal computed tomography (CT) scans. This study was conducted using retrospectively collected data from 3,012 contrast-enhanced abdominal CT scans. The DL models developed in this study were constructed for using image data, demographic/clinical information, and multi-modality data, respectively. Patients were categorized into the normal, osteopenia, and osteoporosis groups based on their T-scores, obtained from dual-energy X-ray absorptiometry, into normal, osteopenia, and osteoporosis groups. The models showed high accuracy and effectiveness, with the combined data model performing the best, achieving an area under the receiver operating characteristic curve of 0.94 and an accuracy of 0.80. The image-based model also performed well, while the demographic data model had lower accuracy and effectiveness. In addition, the DL model was interpreted by gradient-weighted class activation mapping (Grad-CAM) to highlight clinically relevant features in the images, revealing the femoral neck as a common site for fractures. The study shows that DL can accurately identify osteoporosis stages from clinical data, indicating the potential of abdominal CT scans in early osteoporosis detection and reducing fracture risks with prompt treatment.

DEVELOPMENT OF KAO SPACE WEATHER MONITORING SYSTEM: II. NOWCAST, FORECAST AND DATABASE (한국천문연구원의 태양 및 우주환경 모니터링 시스템 개발: II. 실시간 진단, 예보, 데이터베이스)

  • Park, So-Young;Cho, Kyung-Seok;Moon, Yong-Jae;Park, Hyung-Min;Kim, Rok-Soon;Hwangbo, Jung-Eun;Park, Young-Deuk;Kim, Yeon-Han
    • Journal of Astronomy and Space Sciences
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    • v.21 no.4
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    • pp.441-452
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    • 2004
  • Nowcast and forecast based on realtime data are quite essential for space weather monitoring. We have developed the web pages (http://sun.kao.re.kr) of the KAO Space Weather Monitoring system by using ION (IDL on the Net). They display latest solar and geomagnetic data, and present their expected effects on satellite, communications and ground power system. In addition, daily NOAA/SEC prediction reports on the probability of solar X-ray flares, proton events and geomagnetic storms are provided. To predict the arrival times of interplanetary shocks and CMEs, two different types of prediction models are also implemented. A work is in progress to develop web-based database of several solar and geomagnetic activities. These data are automatically downloaded to our data server in every minute, or every day using IDL and FTP programs. In this paper, we will introduce more details on the development of the KAO Space Weather Monitoring system.

Evaluation of Image Quality using Monte Carlo Simulation in Digital Mammography System (디지털유방영상시스템에서 몬테카를로 시뮬레이션을 이용한 영상평가)

  • Kim, Changsoo;Kang, Se-Sik;Kim, Jung-Hoon;Lee, Jin-Soo
    • The Journal of the Korea Contents Association
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    • v.14 no.6
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    • pp.247-254
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    • 2014
  • For the purpose of early diagnosis of the breast cancer, the attention on the screening mammography has been increasing-with supply of digital mammography day by day. Image quality is decided by target materials and filter combinations. Optimized selection by a glandular density and a thickness is needed, because these combinations change x-ray spectrum and effect to image quality. The purpose of this study is to find out optimized target and filter combinations through the evaluation of quantitative image quality and to suggest means which minimize patient dose through MCNPX. In results, spatial frequency resolution evaluation which is quantitative image quality evaluation method, MTF, NPS, DQE shows that we have to select Mo/Mo combinations or Mo/Rh combinations when compressed breast is thin. but in case of that when compressed breast is thick, we have to select Rh/Rh combinations or W /Rh combinations. In a comprehensive evaluation, W!Rh combinations which are not used in thin breasts in practice was superior to all image quality evaluation. This result is somewhat different-with clinical examination results. Secondary end point was organ dose evaluation, radiation dose of opposite breast was approximately 47 ~73% effectiveness when selecting standard breast. In conculsion, the most important point is that we have to select the optimal combinations-with considering dose evaluation and various thickness.

Characteristic of ITO-Ag-ITO multilayer thin films grown by linear facing target sputtering system (선형대향타겟 스퍼터로 성장시킨 ITO-Ag-ITO 다층박막의 특성 연구)

  • Jeong, Jin-A;Choi, Kwang-Hyuk;Lee, Jae-Young;Lee, Jung-Hwan;Bae, Hyo-Dae;Tak, Yoon-Heung;Ye, Min-Su;Kim, Han-Ki
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.11a
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    • pp.66-66
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    • 2008
  • 본 연구에서는 ITO/Ag/ITO 다층 박막을 유기발광소자와 플렉시블 광전소자의 전극으로 적용하기 위하여 선형 대항 타겟 스퍼터(Linear facing target sputter) 시스템을 이용하여 성막하였고, ITO/Ag/ITO 다층박막의 전기적, 광학적, 구조적 특성을 분석하였다. 선형 대항 타겟 스퍼터 시스템은 강한 일방항의 자계와 타겟에 걸린 음극에 의해 전자의 회전, 왕복 운동이 가능해 마주보는 두 ITO 타겟 사이에 고밀도의 플라즈마를 구속 시켜 플라즈마 데미지 없이 산화물 박막을 성막시킬 수 있는 장치이다. 대항 타겟 스퍼터 시스템을 이용하여 성막한 ITO 전극을 DC power, working pressure, Ar/O2 ratio 에 따른 특성을 각각 분석하였다. glass 기판위에 최적화된 ITO 전극을 bottom layer로 두고, bottom ITO layer 위에 thermal evaporation 을 이용하여 Ag 박막을 6~20nm의 조건에 따라 두께를 다르게 성막하고, Ag 박막을 성막한 후에 다시 bottom ITO 전극과 같은 조건으로 ITO 전극을 top layer로 성막 하였다. 두 비정질의 ITO 전극 사이에 매우 앓은 Ag 박막을 성막 함으로 해서 glass 기판위에 ITO/Ag/ITO 다층 박막전극은 매우 낮은 저항과 높은 투과도를 나타낸다. ITO/Ag/ITO 박막의 전기적 광학적 특성을 보기 위해 hall measurement와 UV/visible spectrometer 분석을 각각 진행하였다. ITO/Ag/ITO 다층 박막 전극이 매우 얇은 두께임에도 불구하고 $4\Omega$/sq.의 낮은 면저항과 85%의 높은 투과도를 나타내는 이유는 ITO/Ag/ITO 전극 사이에 있는 Ag층의 표면 플라즈몬 공명 (SPR) 현상으로 설명할 수 있다. ITO/Ag/ITO 전극의 Ag의 거동을 분석 하기위해 FESEM분석과 synchrotron x-ray scattering 분석을 하였다. ITO/Ag/ITO 전극의 Ag층이 islands의 모양에서 연속적으로 연결되는 변화과정 중에 SPR현상이 일어남을 알 수 있다. 여기서, 대항 타겟 스퍼터 시스템을 이용하여 성막한 ITO/Ag/ITO 다층박막을 OLED 또는 inverted OLEDs의 top 전극으로의 적용 가능성을 보이고 있다.

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