Dual Energy를 이용한 Liver Volumetry CT의 Non-Enhanced Phase와 Arterial Phase에서 Fat CT Number의 차이에 대한 비교 연구

김세환(Se Hwan Kim),이기백(Ki Baek Lee) 대한전산화단층기술학회 2017 대한CT영상기술학회지 Vol.19 No.1

목적 : liver donor의 liver function을 평가 할 때, 이식할 liver 실질에 liver의 function을 저해하는 fat의 양을 측정하는 것은 중요하다. 본 연구는 Non-enhanced phase에서의 3-material decomposition(fat-water-iodine)을 이용하여 측정한 fat값과 Arterial phase에서 3-material decomposition(fat-water-iodine)을 이용하여 얻은 fat값을 비교하여 3-material decomposition의 유용성을 평가하는 것이다. 대상 및 방법 : 2015년 2월부터 2016년 4월 까지, Liver transplantation을 위한 donor 환자들 29명을 대상으로 하였다. 장비는 GE사의 GSI 기능이 탑재된 discovery CT750HD(GE Healthcare, Wisconsin, USA)를 사용하였고, Non-enhanced phase와 Arterial phase에 GSI-44 protocol: Large, 0.7 s, 40mm, 275mA, 10.68mGy, and GSI assist off 조건으로 GSI 기능을 사용하였다. 획득된 thin data를 GE사에서 제공하는 workstation으로 각각 3-material decomposition(fat-water-iodine)을 시행하여 fat image를 획득하였고, liver가 가장 크게 보이는 level에서 segment5, segment8 부위에 혈관을 벗어난 간의 실질에 ROl(Region of Interest)를 연속하는 세 개의 slice에 그리고 측정하였다. 결과 : Non-enhanced phase와 Arterial phase에서 측정된 fat value(HU)의 차이는 axial에서 0부터 2까지 평균 0.49이었고, coronal은 0.03부터 1.63까지 평균 0.51, sagittal은 0부터 1.97까지 평균 0.44였다. 전체적인 차이는 최소 0부터 2까지 평균 0.48이었다. SD값의 차이는 axial에서 0부터 1.97까지 평균 0.48이었고, coronal은 0.07부터 1.33까지 평균 0.61, sagittal은 0부터 1.37까지 평균 0.45 이었다. 이러한 차이는 통계적으로 유의성을 보이지 않았다.(p〉0.05) 결론 : 결과적으로 Non-enhanced phase와 Arterial phase의 3-material decomposition에서 측정되는 fat값의 양은 큰 차이가 없으며, Non-enhanced phase의 3-material decomposition 없이 Arterial phase의 3-material decomposition으로도 충분한 fat값의 quantification이 가능하다고 생각된다. 이는 선량적인 측면에서 볼 때, liver volumetry CT를 간 이식 전 환자의 liver fat값 측정을 목적으로 시행한다면 Arterial phase의 3-material decomposition 만으로도 충분히 유용한 fat값을 획득할 수 있기 때문에 Non-enhanced phase가 없는 protocol 사용으로 환자에 대한 선량을 줄일 수 있을 것으로 사료된다. Purpose : It is important to measure the amount of fat in liver parenchyma which hinders function of the liver in order to evaluate liver function of liver donor. The purpose of this study was to evaluate the usability of 3-material decomposition by comparing measured fat values between non-enhanced phase and arterial phase in dual-energy Computed Tomography (DECT). Materials and Methods: Between February, 2015 and April, 2016, 29 liver donors who undeiwent DECT for liver transplantation enrolled in this study. Non-contrast phase and arterial phase were performed on a fast kilovoltage-switching DECT scanner (Discovery 750HD scanner, GE Healthcare, Milwaukee, Wis, USA) and thin data of Gemstone Spectral Imaging (GSI) was obtained with the GSl-44 protocol: Large, 0.7 s, 40 mm, 275 mA, 10.68 mGy, and GSI assist off. Fat images were acquired by using 3-material decomposition (fat-water-iodine) on workstation. In 3 consecutive images which show the largest boundary of the liver, The values of Hounsfield Unit(HU) and Standard Deviation(SD) about fat were measured on the same Region of Interest (ROI): segment 5 or segment 8 of liver parenchyma. Results : The differences of HU Values on fat between non-enhanced phase and arterial phase in axial was average 0.49 (range: 0 to 2), coronal was average 0.51 (range : 0.03 to 1.63), sagittal was average 0.44(range: 0 to 1.97). Total difference was 0.48 (range: 0 to 2). The differences of SD on fat between non-enhanced phase and arterial phase in axial was average 0.48(range: 0 to 1.97), coronal was average 0.61 (range: 0.07 to 1.33), sagittal was 0.45(range: 0 to 1.37). That differences were not statistically significant (p〉0.05). Conclusion : There were no big differences of measured fat amount between non-contrast and arterial phasic 3-material decomposition imaging. It was enough to quantify fat only with arterial phasic 3-material decomposition imaging. When performing liver volumetry CT for liver fat measurement in liver donor before liver transplantation, we can reduce radiation dose by skipping non-contrast phase.

Improvement with the Multi-material Decomposition Framework in Dual-energy Computed Tomography: A Phantom Study

Haenghwa Lee,Hee-Joung Kim,Donghoon Lee,Dohyeon Kim,Seungyeon Choi,Minjae Lee 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.6

Dual energy computed tomography (DECT) enhances tissue characterization by obtaining two or three material images from two measurements with different X-ray spectra. Recently, multi-material decomposition (MMD) in DECT has been studied to obtain decomposed material images for more than three basis materials. However, the MMD method is highly sensitive to noise fluctuation due to the direct inversion and the material triplet selection for each pixel. Although several studies have reported to reduce the noise resulting from direct inversion, no studies have researched reduction in the image quality degradation caused by material triplet selection. We proposed a MMD framework for DECT that includes pre-decomposition and post-decomposition stages to reduce image quality degradation due to material triplet selection and direct inversion. The total variation denoising method was applied to the pre-decomposition and the post-decomposition stages as a noise suppression algorithm. The digital phantom, tissue characterization phantom, and Catphan phantom were employed as test objects in this study. The volume fraction accuracy (VFA) and the standard deviation (STD) were quantitatively calculated to evaluate the quality of the decomposed images. The results of the proposed method were compared to those of the direct MMD (DMMD) and the MMD with total variation denoising (MMD-TVD) methods. Compared to the DMMD method, the proposed method improved average the VFA value by 11.40%, 17.31%, and 19.13% in the digital phantom, the tissue characterization phantom, and the Catphan phantom studies, respectively. The STD values for the proposed method are better than those of the DMMD method, and are similar to those of the MMD-TVD method. Our method successfully improved quantification accuracy and suppressed noise. In conclusion, the proposed method resulted in quantitatively better multi-material images for DECT.

분해기술에 의한 자연재료의 물성변화와 표면디자인 표현방법

이정원(Lee, Jeong-Won),서지은(Seo, Ji-Eun) 대한건축학회 2015 대한건축학회논문집 Vol.31 No.2

This study was to grasp the change of materiality of natural material through decomposition techniques after the raw material are extracted from natural material. In addition, it is to analyze examples to achieve the purpose that is to apply expressive possibility of new material into the space design. The results of the research are as in the following. First, the development of technology could allow use in various directions on nature material which has not been applied on architectural and spatial until now. In particular, material properties and surface design are shown differently by "decomposition techniques". Second, decomposition techniques fall into two categories. One can be subdivided into "thermal decomposition, catalytic decomposition and electrolysis’ that is the technology to decompose nature material with the chemical combination. Other is ‘cutting, grinding, crushing and pressing’ that is to dissolve nature material with physical power. Third, ‘thermal decomposition’ and ‘catalytic decomposition’ technology changed into natural ingredients which are to complement properties than raw material by removing harmful or unnecessary ingredients of nature material and ‘cutting’ technology changed color, form, and patterns etc hidden in natural material into the ways to express outwards. In addition, ‘grinding’ and ‘crushing’ technology confirm characteristics that are unlike earlier by vanishing most of existing properties. Forth, surface design is appeared as realistically, metaphorically, concretely, timely and autonomically. Therefore, decomposition techniques expand the area of expression by leading (inducing) differences between the change of materiality and surface design. Also it will serve as a foundation that excellent properties of natural resources appear in a positive qualities and will have a great influence on various use as an advanced material.

교류 유전체 방전 공정에 의한 휘발성유기화합물 분해 및 전력공급에 관한 연구

목영선,이호원,현영진 제주대학교 해양과환경연구소 2001 해양과환경연구소 연구논문집 Vol.25 No.-

Dielectric barrier discharge reactor packed with glass beads or scoria was utilized for decomposition of volatile organic compounds including benzene, toluene, trichloroethylene, n-butanol and chloroform. Glass beads of 4 to 6 mm in diameter and scoria of 4.75-6.7 mm were used as the dielectric packing materials. The effects of the dielectric packing materials, the gas composition, the applied voltage, and the polarity of the voltage on the decomposition and the power delivery were examined. Filling of the dielectric materials such as glass beads and scoria in the reactor gave rise to the increase in the decomposition of the organic compounds and the discharge power. In spite of the adsorption capability, the scoria showed similar decomposition performance to the glass beads, which indicates that the adsorption capability does not significantly affect the decomposition in steady state condition. In the absence of the dielectric packing material, higher voltage was required to decompose the organic compounds. The gas composition did not largely influence the decomposition efficiency of the organic compounds. When the AC voltage was rectified to positive or negative half-wave, the discharge power and the decomposition efficiency greatly decreased. The power transfer efficiency from the wall plug to the reactor was found to be a strong function of the applied voltage, and a weak function of the gas composition.

Improvement of three-material decomposition in spectral mammography with a photon-counting detector

Lee Minjae,Kim Hyemi 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.2

The accurate analysis of breast imaging is important because it has been reported that an increase in breast density of only 1% results in a 2% increase in the relative risk of breast cancer. The proteins, water, and lipids that determine breast density are important biomarkers in the diagnosis of breast cancer. In mammography, photon-counting detectors (PCDs) with energy-discrimination capabilities can cause errors in the measurement of chemical composition when the attenuation coefcient is small. This is typically the case with proteins, water, and lipids because of the low photon efciency in each bin. In this study, a dual-energy technique for PCDs was developed based on a non-local means denoising technique for accurate material decomposition and the quantifcation of protein, water, and lipid content. To evaluate the proposed material decomposition algorithm, spectral images were acquired with a modeled PCD using the Geant4 Application for Tomographic Emission (GATE) version 6.0. Linear, quadratic, and rational models were used for three-material decomposition based on the spectral images acquired using the PCD. The proposed algorithm yielded the best results for the estimation of breast density, composed of three materials. It was determined that the developed approach improved the accuracy of three-material decomposition using a PCD with energy-discrimination capabilities. The presented material decomposition algorithm has the potential to improve the diagnostic accuracy of breast cancer detection based on the quantitative measurement of breast density using PCDs.

Absolute Measurement of the Effective Atomic Number and the Electron Density by Using Dual-energy CT images

김대홍,김희중,이원형,전성수 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.12

Material decomposition using dual-energy and material-selective techniques was performed using computed-tomography (CT)-generated reconstructed images. Previous work using the dual-energy method focused on extracting the effective atomic number and the electron density of materials to confirm the dosimetric accuracy in radiation therapy. Dual-energy methods mostly depend on the device generating the X-rays, such as a synchrotron, and on dose verification for radiation treatment planning. Information obtained from CT imaging is important both in diagnosis and in planning radiation therapy. In a clinical setting, CT images are usually displayed as Houndsfield units (HU), which are extracted from the attenuation coefficient of a material. The attenuation coefficient is calculated using the effective atomic number and the electron density of a material; thus, information expressed in HU can be converted into the effective atomic number and the electron density by using the dual-energy equation. This study was performed using realistic Xray spectra to differentiate between the contrast media and plaque in vascular images. Our results suggest that the effective atomic number and electron density are useful in distinguishing between two adjacent materials with similar HUs.

몬테카를로 시뮬레이션을 이용한 광자계수검출기 기반 이중에너지 스펙트럼 유방촬영에서 가중 영상 감산법을 통한 물질분리

엄지수(Eom Jisoo),강순철(Kang Sooncheol),이승완(Lee Seungwan) 대한방사선과학회(구 대한방사선기술학회) 2017 방사선기술과학 Vol.40 No.3

유방촬영술은 유방암의 조기검진을 위해 시행되는 대표적인 검사이다. 하지만 유방 구성물질의 물리적 특성에 의존하는 유방촬영상은 병변의 악성 또는 양성 여부에 대한 정보 제공이 불가능하다. 이중에너지 영상 감산법을 시행하는 경우 유방촬영상에서 특정 물질에 대한 정보를 추출할 수 있지만 피폭선량을 증가시킬 뿐만 아니라 물질 분리의 정확도를 감소시키는 단점이 있다. 본 연구에서는 물질의 선감약계수를 적용한 유방팬텀을 모사하여 광자 계수검출기 기반 이중에너지 유방촬영에서 특정 물질에 대한 가중함수를 적용하여 분리의 정확도를 향상시킬 수 있는 기술을 제안하였다. 그리고 유방팬텀영상으로부터 물질분리의 정확도를 평가하기 위해 대조도 및 잡음 특성을 분석하였다. 분석 결과 이중에너지 가중 영상 감산법의 악성종양에 대한 대조도는 일반적인 유방촬영과 이중에너지 영상 감산법에 비해 각각 0.98, 1.06배로 큰 차이가 없다. 그렇지만 이중에너지 가중 영상 감산법 적용 시 양성종양에 대한 대조도가 0에 근사하기 때문에 양성종양에 대한 악성종양의 상대적인 대조도가 13.54배로 크게 향상된 것으로 확인되었다. 따라서 본 연구에서 제안하는 이중에너지 가중 영상 감산법은 유방촬영 진단의 정확도 향상에 기여할 수 있을 것이다. Mammography is commonly used for screening early breast cancer. However, mammographic images, which depend on the physical properties of breast components, are limited to provide information about whether a lesion is malignant or benign. Although a dual-energy subtraction technique decomposes a cer-tain material from a mixture, it increases radiation dose and degrades the accuracy of material decomposition. In this study, we simulated a breast phantom using attenuation characteristics, and we pro-posed a technique to enable the accurate material decomposition by applying weighting factors for the du-al-energy mammography based on a photon-counting detector using a Monte Carlo simulation tool. We al-so evaluated the contrast and noise of simulated breast images for validating the proposed technique. As a result, the contrast for a malignant tumor in the dual-energy weighted subtraction technique was 0.98 and 1.06 times similar than those in the general mammography and dual-energy subtraction techniques, respectively. However the contrast between malignant and benign tumors dramatically increased 13.54 times due to the low contrast of a benign tumor. Therefore, the proposed technique can increase the ma-terial decomposition accuracy for malignant tumor and improve the diagnostic accuracy of mammography.

Material Decomposition with the Multi-Energy Attenuation Coefficient Ratio by Using a Multiple Discriminant Analysis

Woojin Lee,Se-Ryong Kang,Soon-Chul Choi,Sam-Sun Lee,Min-Suk Heo,Kyung-Hoe Huh,Won Jin Yi 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.2

The objective of this study was to develop a spectral CT system using a photon counting detector and to decompose materials by applying a multiple discriminant analysis (MDA) to the energy-dependent attenuation coefficient ratios. We imaged cylindrical phantoms of Polymethyl methacrylate (PMMA) with four holes filled with calcium chloride, iodine, and gold nanoparticle contrast agents. The attenuation coefficients were measured via reconstructed multi-energy images, and the linear attenuation ratio was used for material identification. The MDA projection matrix, determined from training phantoms, was used to identify the four materials in the testing phantoms. For quantification purposes, the relationships between the attenuation coefficients at multiple energy bins and the concentrations were characterized by using the least-squares method for each material. The mean identification accuracy for each of the three materials were 0.94 ± 0.09 for iodine, 0.96 ± 0.07 for gold nanoparticles, and 0.92 ± 0.05 for calcium chloride. The mean quantification errors were 1.90 ± 1.58% for iodine, 3.85 ± 3.13% for gold nanoparticle, and 3.40 ± 2.62% for calcium chloride. The developed multi-energy CT system based on the photon-counting detector with MDA can precisely decompose the four materials.

소형 시험모터의 노즐 열전달 및 삭마 통합해석

배지열,김태환,김지혁,함희철,조형희 한국전산구조공학회 2017 한국전산구조공학회논문집 Vol.30 No.2

Ablative material in a rocket nozzle is exposed to high temperature combustion gas, thus undergoes complicated thermal/chemical change in terms of chemical destruction of surface and thermal decomposition of inner material. Therefore, method for conjugate analysis of thermal response inside carbon/phenolic material including rocket nozzle flow, surface chemical reaction and thermal decomposition is developed in this research. CFD is used to simulate flow field inside nozzle and conduction in the ablative material. A change in material density and a heat absorption caused by the thermal decomposition is considered in solid energy equation. And algebraic equation under boundary layer assumption is used to deduce reaction rate on the surface and resulting destruction of the surface. In order to test the developed method, small rocket nozzle is solved numerically. Although the ablation of nozzle throat is deduced to be higher than the experiment, shape change and temperature distribution inside material is well predicted. Error in temperature with experimental results in rapid heating region is found to be within 100 K.

Influence Regularity of Aluminum, Copper and Stainless-steel on SF₆ PD Decomposition Characteristics Components

Zeng, Fuping,Luo, Jing,Tang, Ju,Zhou, Qian,Yao, Qiang The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.1

$SF_6$ decomposition products can be used to detect partial discharge (PD), but the metal materials in a PD area can significantly affect $SF_6$ decomposition characteristics. Disregarding the effect of metal materials on such characteristics inevitably result in certain errors when using them to diagnose the internal insulation faults of gas-insulated switchgears. This paper investigates the influence regularity on the main stable decomposition components of $SF_6$ (namely $SO_2F_2$ and $SOF_2$) of the commonly metal materials uesd in GIS, such as aluminum (Al), copper (Cu) and stainless steel (SS). Firstly, an experimental platform is constructed to simulate $SF_6$ decomposition under a PD area, and the influence regularities of Al, Cu and SS on the concentration, formation rate and saturation time of $SO_2F_2$ and $SOF_2$ are obtained. Secondly, the influence mechanism of Al, Cu and SS are preliminary explored combined with the chemical activity of the metal materials.