화합물의 물리적 밀도와 유효원자번호에 대한 CT수 측정

김종언(Jong Eon Kim) 한국방사선학회 2021 한국방사선학회 논문지 Vol.15 No.2

AAPM CT 성능 팬텀에서 CT수 교정 삽입부의 각 핀과 물에 대응하는 유효원자번호 및 물리적 밀도에 대한 CT수에 관한 자료가 거의 없다. 따라서 자료화의 필요성이 제기되었다. 이 연구의 목적은 AAPM CT 성능 팬텀에서 CT수 교정 삽입부의 각 핀 및 물에 대하여 유효원자번호를 산출하고, 산출된 유효원자번호 및 물리적 밀도에 대한 CT수를 측정하여 비교분석하는데 있다. AAPM CT 성능 팬텀의 CT수 교정 삽입부에서 각 핀과 물의 유효원자번호 및 물리적 밀도에 관한 CT수의 자료를 획득하기 위하여, 먼저 각 핀과 물에 대한 유효원자번호를 산출하였다. 그리고 CT스캐너로 CT수 교정 삽입부를 스캔하여 CT슬라이스들을 획득하였다. 중심 CT슬라이스에서 각 핀과 물에 대하여 CT수들을 측정하였다. 결과로서, 유효원자번호에 대한 CT수들은 유효원자번호가 증가할수록 비선형적으로 증가와 감소를 반복하는 양상을 나타내었다. 그리고 물리적 밀도에 대한 CT수들도 물리적 밀도가 증가할수록 비선형적으로 증가와 감소를 반복하는 양상을 나타내었다. In the AAPM CT performance phantom, there is little data on the CT number of the effective atomic number and physical density corresponding to each peg and water of the CT number calibration insert. Therefore, the necessity of documentation was raised.The purpose of this study is to calculate the effective atomic number for each peg and water of the CT number calibration insert in the AAPM CT performance phantom, and to measure the CT number for the calculated effective atomic number and physical density for comparative analysis.In order to obtain CT number data on the effective atomic number and physical density of each peg and water from the CT number calibration insert of the AAPM CT performance phantom, the effective atomic number for each peg and water was first calculated. Then, CT slices were obtained by scanning the CT number calibration with a CT scanner. CT numbers were measured for each peg and water in the central CT slice. As a result, the CT numbers for the effective atomic number showed a nonlinear pattern of repeating the increase and decrease as the effective atomic number increased. In addition, the CT numbers for physical density showed a nonlinear pattern of repeating the increase and decrease as the physical density increased.

이중에너지 CT와 같은 시뮬레이션을 이용한 유효원자번호 추출을 통한 췌장 검출 가능성 연구

손기홍,이수열,정명애,김대홍 한국방사선학회 2022 한국방사선학회 논문지 Vol.16 No.5

The purpose of this simulation study was to evaluate the possibility of pancreas detection through effective atomic number information using dual-energy computed tomography(CT). The effective atomic number of 10 tissue-equivalent materials were estimated through stoichiometric calibration. For stoichiometric calibration, HU values at low-energy (80 kV) and high-energy (140 kV) for 10 tissue-equivalent materials were used. Based on this method, the effective atomic number image of the tissue-equivalent material was extracted through an iterative algorithm. According to the results, the attenuation ratio in accordance with the effective atomic number was estimated to have an R2 value of 0.9999, and the effective atomic number of Pancreas, Water, Liver, Blood, Spongiosa, and Cortical bone was overall within 1% accuracy compared to the theoretical value. Conventional pancreatic cancer examination uses a contrast medium, so there is a possibility of potential side effects of the contrast medium. In order to solve this problem, it is thought that it will be possible to contribute to an accurate and safe examination by extracting the effective atomic number using dual-energy CT without contrast enhancement. Based on this study, future research will be conducted on the detection of pancreatic cancer using the HU value of pancreatic cancer based on clinical images. 본 연구의 목적은 이중에너지 CT를 이용한 유효원자번호 정보를 통한 췌장 검출 가능성 연구이다. 10개의 다양한 인체 등가 물질의 유효원자번호를 Stoichiometric calibration을 통해 추정하였다. Stoichiometric calibration을 위해 저에너지와 고에너지에 해당하는 10개 인체 등가 물질에 대한 HU값을 이용하였다. 이를 바탕으로 반복 알고리즘을 통해 인체 등가 물질에 대한 유효원자번호 영상을 추출하였다. 연구결과에 따르면, 유효원자번호에 따른 감약의 비는 R2값이 0.9999로 추정되었고, Pancreas, water, Liver, Blood, Spongiosa, Cortical bone의 유효원자번호는 이론값과 비교하여 전체적으로 1% 이내의 정확도를 보였다. 췌장암 검사는 조영제를 사용하므로 잠재적인 조영제 부작용 가능성이 있다. 이를 해결하기 위해 조영 증강 없는 이중에너지를 이용한 유효원자번호 추출을 통해 정확하고 안전한 검사에 기여할 수 있을 것으로 사료된다. 본 연구를 바탕으로 향후 연구에서는 임상 영상을 바탕으로 췌장암의 HU값을 이용하여 췌장암 검출에 대한 연구를 수행할 것이다.

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.

Experimental investigation of effective atomic numbers for some binary alloys

Renu Sharma,J.K. Sharma,Taranjot Kaur,Tejbir Singh,Jeewan Sharma,Parjit S. Singh 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.7

In the present work, the gamma ray backscattering technique was used to determine the effective atomic numbers for certain binary alloys. With the help of a muffle furnace, the binary alloys were synthesized using the melt quenching technique with different compositions of 82Pb, 50Sn, and 30Zn. The intensity distribution of backscattered photons from radioactive isotope 22Na (511 keV) was recorded with the help of GAMMARAD5 [76 mm × 76 mm NaI(Tl) scintillator detector] and analyzed as a function of both atomic number and thickness of the target material. The effective atomic numbers for the same binary alloys were also computed theoretically using the atomic to electronic cross-section method with the help of the mass attenuation coefficient database of WinXCom (2001). Good agreement was observed between theoretical and experimental results for the effective atomic numbers of all the selected alloys.

이중 에너지 CT 영상에서 다항식 기반 교정에 의해 추출된 유효원자번호 및 상대전자밀도의 정확도 향상 효과

김대홍,조일훈,이미조 한국방사선학회 2023 한국방사선학회 논문지 Vol.17 No.7

본 연구의 목적은 이중 에너지 CT 영상을 이용하여 다항식 기반 calibration 방법을 통해 유효원자번호(Effective atomic number, EAN)과 상대전자밀도 (Relative electron density, RED)의 정확도를 향상시키는 것이다.11개의 조직 등가 물질로 구성된 팬텀을 이중 에너지로 촬영하여 고에너지와 저에너지 영상을 획득하였다. 획득된 영상을 이용하여 Stoichiometric, 2차, 3차, 4차 다항식을 기반으로 EAN에 대한 저에너지와 고에너지 영상의 감약의 비율을 calibration 하였다. 각 calibration 방법으로 EAN과 RED를 추출하였다. 실험 결과 3차 다항식 기반 calibration에 의한 EAN의 평균 오차가 가장 작았다. EAN을 이용하여 추출한 RED 영상에서도 3차 다항식 기반 RED의 오차가 가장 작았다. 3차 다항식 기반 calibration은 EAN과 RED의 정확성 향상에 기여하며, 이를 통해 CT 검사에서 병변의 정확한 진단 또는 인체의 다양한 물질의 정량화에 기여할 것으로 사료된다. The purpose of this study was to improve the accuracy of effective atomic number (EAN) and relative electron density (RED) using a polynomial-based calibration method using dual-energy CT images. A phantom composed of 11 tissue-equivalent materials was acquired with dual-energy CT to obtain low- and high-energy images. Using the acquired dual-energy images, the ratio of attenuation of low- and high-energy images for EAN was calibrated based on Stoichiometric, Quadratic, Cubic, Quartic polynomials. EAN and RED were extracted using each calibration method. As a result of the experiment, the average error of EAN using Cubic polynomial-based calibration was minimum. Even in the RED image extracted using EAN, the error of the Cubic polynomial-based RED was minimum. Cubic polynomial-based calibration contributes to improving the accuracy of EAN and RED, and would like to contribute to accurate diagnosis of lesions in CT examinations or quantification of various materials in the human body.

Deriving Effective Atomic Number based on Dual-Energy Image sets with Big bore CT Simulator

Seongmoon Jung,Bitbyeol Kim,Jung-in Kim,Jong Min Park,Chang Heon Choi 대한방사선방어학회 2020 대한방사선방어학회 학술발표회 논문요약집 Vol.2020 No.11

Effect of Total Collimation Width on Relative Electron Density, Effective Atomic Number, and Stopping Power Ratio Acquired by Dual-Layer Dual-Energy Computed Tomography

정성문,김빛별,윤은택,김정인,박종민,최창헌 한국의학물리학회 2021 의학물리 Vol.32 No.4

Purpose: This study aimed to evaluate the effect of collimator width on effective atomic number (EAN), relative electron density (RED), and stopping power ratio (SPR) measured by dual-layer dual-energy computed tomography (DL-DECT). Methods: CIRS electron density calibration phantoms with two different arrangements of material plugs were scanned by DL-DECT with two different collimator widths. The first phantom included two dense bone plugs, while the second excluded dense bone plugs. The collimator widths selected were 64 mm×0.625 mm for wider collimators and 16 mm×0.625 mm for narrow collimators. The scanning parameters were 120 kVp, 0.33 second gantry rotation, 3 mm slice thickness, B reconstruction filter, and spectral level 4. An image analysis portal system provided by a computed tomography (CT) manufacturer was used to derive the EAN and RED of the phantoms from the combination of low energy and high energy CT images. The EAN and RED were compared between the images scanned using the two different collimation widths. Results: The CT images with the wider collimation width generated more severe artifacts, particularly with high-density material (i.e., dense bone). RED and EAN for tissues (excluding lung and bones) with the wider collimation width showed significant relative differences compared to the theoretical value (4.5% for RED and 20.6% for EAN), while those with the narrow collimation width were closer to the theoretical value of each material (2.2% for EAN and 2.3% for RED). Scanning with narrow collimation width increased the accuracy of SPR estimation even with high- density bone plugs in the phantom. Conclusions: The effect of CT collimation width on EAN, RED, and SPR measured by DL-DECT was evaluated. In order to improve the accuracy of the measured EAN, RED, and SPR by DL-DECT, CT scanning should be performed using narrow collimation widths.

Investigation on radiation shielding parameters of cerrobend alloys

Borhan Tellili,Youssef Elmahroug,Chedly Souga 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.8

In this study, to determine the most effective alloy for shielding against gamma-rays, the gamma-rayshielding parameters of six types of cerrobend alloys have been investigated. Gamma-ray interactionwith the cerrobend alloys has been discussed mainly in terms of total mass attenuation coefficient (mt),half value layer (HVL), tenth value layer (TVL), effective atomic number (Zeff), and effective electrondensity (Neff). These parameters have been calculated by theoretical approach using the ParShield programin a photon energy range between 0.1 MeV and 100 GeV. The dependence of these parameters onthe incident photon energy and chemical composition of the cerrobend alloys has been studied.

Application of Effective Atomic Number for Contrast Agent Imaging using Dual-energy Computed Tomography: A Simulation Study

Kihong Son,Seunghyung Lee,Hyobin Lee,Yejin Lee,Dongwook Son,Seunghyeon Myeong,Minjoo Chang,Daehong Kim,Myung-Ae Chung 한국자기학회 2023 Journal of Magnetics Vol.28 No.4

This simulation study aims to differentiate between contrast media and calcification in blood vessel using the effective atomic number (EAN) extraction method in electromagnetic X-ray computed tomography (CT) imaging. Calibration was performed on six tissue-equivalent materials, three contrast medium, and one calcium solution. The Hounsfield unit (HU) values at 80 kV and 140 ㎸ with electromagnetic spectrum using dualenergy computed tomography (DECT) facilitated this calibration. EAN from the polynomial method was then compared with that from the Stoichiometric method. In 120 ㎸ vascular imaging, when the HU of calcium and iodine contrast media were alike, EAN provided a more pronounced contrast than HU. The iodine contrast agent’s enhancement in EAN was approximately 30.0 %, and in HU, it was 13.0 % relative to calcium. This indicates EAN’s potential to better differentiate contrast media from calcification in clinical contexts.

A comparative study of gadolinium based oxide and oxyfluoride glasses as low energy radiation shielding materials

Shamshad, L.,Rooh, G.,Limkitjaroenporn, P.,Srisittipokakun, N.,Chaiphaksa, W.,Kim, H.J.,Kaewkhao, J. Elsevier 2017 Progress in nuclear energy Vol.97 No.-

<P><B>Abstract</B></P> <P>The Gadolinium based oxide and oxyfluoride glass systems were prepared using conventional melt quenching method and studied for their radiation shielding properties. The mass attenuation coefficients (μ<SUB>m</SUB>), effective atomic numbers (Z<SUB>eff</SUB>) and effective electron densities (N<SUB>e</SUB>) of the glasses at different photon energies were calculated theoretically by WinXcom program and experimentally determined by the transmission method. Moreover, the mass attenuation coefficient was investigated using Geant4 Monte Carlo code and compared with each other. The gamma ray energies were varied by Compton scattering technique. The values of attenuation parameters of both the glass systems have been found to be decrease with the increase in gamma ray photon energy. The results show that, the experimental values of mass attenuation coefficients, effective atomic numbers and effective electron densities are in good agreement with the theoretical values. It seems that Geant4 values are systematically lower than WinXCom. It could be caused by the simplification of geometry in Geant4. Although, the oxide glass system have superior shielding properties than oxyfluoride glass system, but, still, it has better shielding properties than commercial window glass and some existing concretes indicating the potential of this glass to be used as gamma ray shielding material. Moreover, there is no effect of fluoride component on the optical spectra. The optical absorption spectra of the glass systems under investigation have been shown with light transparency which is an edge to be used as radiation shielding material.</P>