• Journal of the Korean Society of Radiology
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• v.14 no.7
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• pp.1003-1011
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• 2020

This study aims to compare and evaluate the image differences between single and dual sources in applying a technique to reduce metal artifacts using dual energy CT. Discovery CT 256 (GE, USA) as a single source device and Somatom Definition Flash (Siemens Health Care, Forchheim, Germany) as a dual source device. The self-made phantom (pigs with medical titanium screws inserted) was quantitative and qualitatively evaluated under the same conditions by varying the dose under the same conditions using a dual energy CT. The evaluation method was compared by measuring SNR for metal artifacts (scattering, stripe) generated by metal inserts, divided around bones and around tissues. There was a difference in images in the method of reducing metal artifacts between single-source and dual-source devices. In a single source device, the linearized prosthesis by metal implantation showed a greater decrease than the image obtained from a double source device, and the surrounding tissue was well observed without interference from the artifact. In dual-source devices, scattering and stripe artifacts caused by metal inserts decreased more than on a single source device, and signals from adjacent tissues surrounding the metal implant were well observed without diminishing. If the examination is conducted separately between single source and dual source devices depending on whether the area to which the patient is intended to be viewed during the examination is adjacent to the metal insert or the total tissue surrounding the metal insert, it is believed that diagnostic helpful images can be obtained.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.1
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• pp.1-7
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• 1999

This study deals with linear flow pattern in steady-state or transient dual-porosity media with a vertical geologic structure such as fault, fracture zone, etc. A pumping well is located in the vertical structure of infinitesimal or finite width with high hydraulic conductivity and negligible specific storage. Selected type curves on a pumping well and observation wells in the fractured system and the matrix block are provided. The type curves on the pumping well considers both wellhole and well-loss effects.

• Journal of Radiation Protection and Research
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• v.37 no.4
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• pp.191-196
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• 2012

A double-scattering type Compton camera which is appropriate to imaging a high-energy gamma source has been developed for nuclear material surveillance at Hanyang University. The double-scattering type Compton camera can provide high imaging resolution; however, it has disadvantage of relatively low imaging sensitivity than existing single-scattering type Compton camera. In this study, we introduce a novel concept of a dual-mode Compton camera which incorporates two different types of Compton camera, i.e., single- and double-scattering type. The dual-mode Compton camera can operate high-resolution mode and high-sensitivity mode in a single system. To maximize its performance, the geometrical configuration was optimized by using Geant4 Monte Carlo simulation toolkit. In terms of imaging sensitivity, high-sensitivity mode had higher sensitivity than high-resolution mode up to 100 times while high imaging resolution of the double-scattering Compton camera was maintained.

• Journal of the Korean Society of Radiology
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• v.6 no.2
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• pp.129-136
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• 2012

The purpose of this study was to estimate radiation doses from 64-slice single source Computed Tomography(SSCT) coronary angiography(CA) and 128-slice dual source Computed Tomography(DSCT). With SSCT CA, the effective dose averaged approximately 13.86 mSv when two dose modulation was not. The mean effective dose for DSCT CA with retrospectively gated helical(RGH) technique was 11.87 mSv, when prospective ECG gating transverse(PGT) without dose modulation technique was 5.61 mSv. The one with dose modulation in PGT technique and flash mode were 3.04 mSv and flash mode was 0.98 mSv respectively. The lifetime attributable risk(LAR) of cancer incidence from SSCT RGH mode averaged approximately 1 for 1,176, and DSCT averaged 1 for 1,960(RGH mode), 1 for 3,030(PGT without modulation), 1 for 5,882(PGT with modulation). Because of CTCA is associated with non-negligible risk of cancer. Doses can be reduced by application PGT, FLASH than RGH using DSCT.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.109-109
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• 2013

고주파 가속기의 전자선원의 설계 및 제작검증을 위한 hot-firing station을 설계하였다. 본 장치는 전자총의 빔 사이즈, 빔 전류 등을 측정할 수 있는 기기로 전원장치부, 고진공 챔버, 측정장치부 등 크게 세 부분으로 이루어져 있다. 특히 전원장치는 이중에너지 모드를 구현할 수 있도록 에너지의 크기가 다른 두개의 전자총 펄스를 생산해 낼 수 있도록 설계되었다. 고진공 챔버는 고전압 절연체를 이용하여 제작되었으며, 스크롤(건식) 펌프 와 터보 분자펌프를 이용하여 $10^{-7}$ torr 저/고진공 배기를 수행한 뒤, 이온 펌프를 이용하여 $10^{-8}$ torr까지 초고진공 배기를 수행할 수 있도록 설계하였다. 전자총으로 부터 나오는 전자들의 특성을 분석하기 위하여 패러데이 컵과 YAG 스크린을 설치하였다. 패러데이 컵은 전자빔의 인출 파형및 빔 전류를 측정하고, YAG 스크린은 CCD 카메라와 컴퓨터를 이용하여 전자빔의 균일도를 측정하여 정보를 얻도록 한다. 진공 쳄버의 최대 진공배기는 $10^{-9}$ torr이다.

• Journal of Radiation Protection and Research
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• v.14 no.2
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• pp.23-29
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• 1989

A Lucas cell was established and calibrated by using the double layer tube standard radon source. The calibration factors were 0.031$\pm$0.002 (pCi/l)/(cph/Cell) at room temperature, and 0.029$\pm$0.001 (pCi/l)/(cph/Cell) at $50^{\circ}C$. Radon and its daughters concentrations were measured in a room air for the demonstrating purpose. The concentrations of 222 Rn, $^{218}Po,\;224\;Pb,\;and\;^{214}Bi$ were 0.87, 0.53, 0.35 and 0.26 pCi/l. The total eqilibrium factor was around 0.40 and the WL is $3.33{\times}10^{-3}$, resulting in 30 mrem/yr at this place.

• Progress in Medical Physics
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• v.27 no.1
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• pp.8-13
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• 2016

Dual energy cone-beam CT can distinguish two materials with different atomic compositions. The principle of dual energy cone-beam CT based on modulation layer is that higher energy spectrum can be acquired at blocked x-ray window. To evaluate the possibility of modulation layer based dual energy cone-beam CT, we analyzed x-ray spectrum for various thicknesses of modulation layers by Monte Carlo simulation. To compare with the results of simulation, the experiment was performed on prototype cone-beam CT for 50~100 kVp with CdTe XR-100T detector. As the result of comparing, the mean energy of energy spectrum for 80 kVp are well matched with that of simulation. The mean energy of energy spectrum for 80 and 120 kVp were increased as 1.67 and 1.52 times by 2.0 mm modulation layer, respectively. We realized that the virtual dual energy x-ray source can be generated by modulation layer.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.899-904
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• 1995

원자로 수명기간동안 압력용기의 중성자 조사량 계산은 사용된 핵단면적자료, 모델링시의 기하학적인 단순화 및 가정, 그리고 선원항 선정에 있어서의 가정 등에 의한 불확실성을 포함하고 있다. 이중 핵단면적자료는 이론 및 실험의 발전에 따라 계속 개선되고 있으며 Regulatory Guide(1)에서는 압력용기에서의 중성자 조사량 계산시 가장 최근의 핵자료를 적용할 것을 명시하고 있다. 특히 기존의 ENDF/B-IV나 ENDF/B-V에 포함된 철 핵단면적이 중성자 투과를 작게 평가하고 있음이 밝혀지면서[2] 새로운 핵단면적의 채택이 필요하게되었다. ENDF/B-Vl 핵자료는 개선된 철의 핵단면적을 포함하여 여러 가지 최근의 계산 및 실험치를 바탕으로 생산되었다. 따라서 ENDF/B-Vl를 근거로 하고 있는 BUGLE93[3]을 이용하여 원자로 내부구조물 및 압력용기에서의 고속중성자속 계산을 수행하였다. 그리고 기존의 핵자료를 근거로 예측한 울진 3,4호기 원자로의 수명기간 중 압력용기 중성자 조사량 계산의 타당성을 검토하였다.

• Progress in Medical Physics
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• v.27 no.1
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• pp.31-36
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• 2016

The paper discusses radiation dose of dual energy CT on which copper modulation layer, is mounted in order to improve diagnostic performance of the dual energy CT. The radiation dose is estimated using MCNPX and its results are compared with that of the conventional dual energy CT system. CT X-ray spectra of 80 and 120 kVp, which are usually used for thorax, abdominal, head, and neck CT scans, were generated by the SPEC78 code and were used for the source specification 'SDEF' card for MCNPX dose modeling. The copper modulation layer was located 20 cm away from a source covering half of the X-ray window. The radiation dose was measured as changing its thickness from 0.5 to 2.0 mm at intervals of 0.5 mm. Since the MCNPX tally provides only normalized values to a single particle, the dose conversion coefficients of F6 tally for the modulation layer-based dual energy CBCT should be calculated for matching the modeling results into the actual dose. The dose conversion coefficient is $7.2*10^4cGy/output$ that is obtained from dose calibration curve between F6 tally and experimental results in which GAFCHORMIC EBT3 films were exposed by an already known source. Consequently, the dose of the modulation layer-based dual energy cone beam CT is 33~40% less than that of the single energy CT system. On the basis of the results, it is considered that scattered dose produced by the copper modulation layer is very small. It shows that the modulation layer-based dual energy CBCT system can effectively reduce radiation dose, which is the major disadvantage of established dual energy CT.

• Journal of Conservation Science
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• v.37 no.3
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• pp.220-231
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• 2021

The use of digital copies of film-based analog images and the introduction of digital radiographic imaging systems using image plates gradually replace the non-destructive radiationirradiation method of Cultural Heritage. The quality of images obtained from this technique is affected by conditions such as tube voltage, tube current, and exposure time, type of image acquisition medium, distance of the artifacts from the image acquisition medium, and thickness of artifacts. In this study, we evaluated the grayscale image obtained using GE's Computed Radiograhpy (CR) imaging system, the transmission characteristics of the X-ray source for each tree type (pine, chestnut, sawtooth oak, ginkgo) used in wooden Cultural Heritage, and the signal-to-noise ratio (SNR) and contrast. The GE's CR imaging were analyzed using the Duplex wire image quality indicator, line-pair gauges.