동적 심근관류 SPECT에서 심장의 위치 측정방법에 대한 고찰

성지혜,이동훈,김은혜,정우영,Seong, Ji Hye,Lee, Dong Hun,Kim, Eun Hye,Jung, Woo Young 대한핵의학기술학회 2019 핵의학 기술 Vol.23 No.1

Purpose Cadmium-zinc-telluride (CZT) camera with semiconductor detector is capable of dynamic myocardial perfusion SPECT for coronary flow reserve (CFR). Image acquisition with the heart positioned within 2 cm in the center of the quality field of view (QFOV) is recommended because the CZT detector based on focused multi-pinhole collimators and is stationary gantry without rotation. The aim of this study was to investigate the optimal method for measuring position of the heart within the center of the QFOV when performing dynamic myocardial perfusion SPECT with the Discovery NM 530c camera. Materials and Methods From June to September 2018, 45 patients were subject to dynamic myocardial perfusion SPECT with D530c. For accurate heart positioning, the patient's heart was scanned with a mobile ultrasound and marked at the top of the probe where the mitral valve (MV) was visible in the parasternal long-axis view (PLAX). And, the marked point on the patient's body matched with the reference point indicated CZT detector in dynamic stress. The heart was positioned to be in the center of the QFOV in rest. The coordinates of dynamic stress and rest were compared statistically. Results The coordinates of the dynamic stress using mobile ultrasound and those taken of the rest were recorded for comparative analysis with regard to the position of the couch and analyzed. There were no statistically significant differences in the coordinates of Table in & out, Table up & down, and Detector in & out (P > 0.05). The difference in distance between the 2 groups was measured at $0.25{\pm}1.00$, $0.24{\pm}0.96$ and $0.25{\pm}0.82cm$ respectively, with no difference greater than 2 cm in all categories. Conclusion The position of the heart taken using mobile ultrasound did not differ significantly from that of the center of the QFOV. Therefore, The use of mobile ultrasound in dynamic stress will help to select the correct position of the heart, which will be effective in clinical diagnosis by minimizing the image quality improvement and the patient's exposure to radiation.

CZT검출기를 이용한 CT/SPECT 조합영상시스템

권수일 한국의학물리학회 2002 의학물리 Vol.13 No.4

We have tested a combined CT/SPECT system with a single CZT detector for x-ray and gamma-ray medical imaging. The size of detector is 10$\times$10$\times$5 ㎣, and the anodes are pixellated as a 4$\times$4 array with a pixel dimension of $1.5\times$1.5 $\textrm{mm}^2$. The cathode was coated with a continuous Au-plated. We have characterized the system performance by scanning a radiographic resolution phantom and the Hoffman Brain phantom. Pulse counting electronics with very short shaping time (50 ㎱) are used to satisfy high photon rates in x-ray imaging, and response linearity up to 3$\times$10$^{5}$ counts per second per detector element is achieved. Energy resolution of 10.4% and 5.3% FWHM at Tc-99m 140 keV peak are obtained for the 50 ㎱ and 2 $mutextrm{s}$ shaping times, respectively. The spatial resolutions of CT and SPECT are about 1mm and 9mm, respectively. Photopeak efficiency of detector systems are 41.0% for 50㎱ and 72.5% for 2 $mutextrm{s}$ shaping time.

Monte Carlo Simulation for Designing a CZT-based Fork Detection System

Wooseong Hong,Geehyun Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

The detector response was simulated to design a fork detection system for verifying the characteristics of spent fuel. The fork detection system currently used consists of two fission chamber and an ion chamber, and it is nuclear safeguard equipment that measures the gross neutrons and gross gamma rays emitted from the spent fuel assembly to identify the characteristics of the spent fuel and verify the authenticity of the operation history. In order to improve the current fork detection system, we are developing a system that applies CZT, a room temperature semiconductor detector, and a stilbene detector, which is an organic scintillator. Depletion calculations were performed using the ORIGEN code to determine the radiological characteristics emitted from spent nuclear fuel assembly. The flux of radiation emitted from the spent nuclear fuel assembly was calculated by changing the conditions such as initial enrichment, burnup, and cooling time, which are major variables of spent fuel assembly. The calculated result is used as the source term of the particle transport code. Considering the general operating conditions of the pressurized light water reactor, the conditions were changed in the range of 3-5% for initial enrichment and 30-72 GWD/MTU for burnup, and the cooling time was given within 10 years. MCNP 6.2, a Monte Carlo simulation code, was used to simulate the detector response to radiation emitted from spent nuclear fuel assembly. According to the shape, size, and position of the CZT detector, the gamma counts incident on the detector were calculated and derived the initial design of our fork detection system.

CZT를 이용한 국내 가압경수로형 원전 냉각재계통 선원 항 분석

강화윤,문진수,강서곤,김정인 대한방사선방어학회 2013 대한방사선방어학회 학술발표회 논문요약집 Vol.2013 No.04

국내원전의 계획예방정비기간 중 CZT를 이용한 신규원전 및 노후원전 1차계통의 핵종분석

강화윤,강서곤,김정인 대한방사선방어학회 2013 대한방사선방어학회 학술발표회 논문요약집 Vol.2013 No.11

CZT 반도체 검출기를 활용한 중성자 및 감마선 측정과 분석 기술에 관한 연구

진동식(Dong-Sik Jin),홍용호(Yong-Ho Hong),김희경(Hui-Gyeong Kim),곽상수(Sang-Soo Kwak),이재근(Jae-Geun Lee) 대한방사선과학회(구 대한방사선기술학회) 2022 방사선기술과학 Vol.45 No.1

CZT detectors, which are compound semiconductors that have been widely used recently for gamma-ray detection purposes, are difficult to detect neutrons because direct interaction with them does not occur unlike gamma-rays. In this paper, a method of detecting and determining energy levels (fast neutrons and thermal neutrons) of neutrons, in addition of identifying energy and nuclide of gamma-rays, and evaluating gamma dose rates using a CZT semiconductor detector is described. Neutrons may be detected by a secondary photoelectric effect or compton scattering process with a characteristic gamma-ray of 558.6 keV generated by a capture reaction (113Cd + 1 n → 114Cd + γ) with cadmium (Cd) in the CZT detector. However, in the case of fast neutrons, the probability of capture reaction with cadmium (Cd) is very low, so it must be moderated to thermal neutrons using a moderator and the material and thickness of moderator should be determined in consideration of the portability and detection efficiency of the equipment. Conversely, in the case of thermal neutrons, the detection efficiency decreases due to shielding effect of moderator itself, so additional CZT detector that do not contain moderator must be configured. The CZT detector that does not contain moderator can be used to evaluate energy, nuclide, and gamma dose-rate for gamma-rays. The technology proposed in this paper provides a method for detecting both neutrons and gamma-rays using a CZT detector.

Preliminary Research of CZT Based PET System Development in KAERI

조우진,정만희,김한수,김상열,하장호 대한방사선방어학회 2016 방사선방어학회지 Vol.41 No.2

Background: For positron emission tomography (PET) application, cadmium zinc telluride (CZT) has been investigated by several institutes to replace detectors from a conventional system using photomultipliers or Silicon-photomultipliers (SiPMs). The spatial and energy resolution in using CZT can be superior to current scintillator-based state-of-the-art PET detectors. CZT has been under development for several years at the Korea Atomic Energy Research Institute (KAERI) to provide a high performance gamma ray detection, which needs a single crystallinity, a good uniformity, a high stopping power, and a wide band gap. Materials and Methods: Before applying our own grown CZT detectors in the prototype PET system, we investigated preliminary research with a developed discrete type data ac-quisition (DAQ) system for coincident events at 128 anode pixels and two common cath-odes of two CZT detectors from Redlen. Each detector has a 19.4×19.4×6 mm3 volume size with a 2.2 mm anode pixel pitch. Discrete amplifiers consist of a preamplifier with a gain of 8 mV·fC-1 and noise of 55 equivalent noise charge (ENC), a CR-RC4 shaping amplifier with a 5 μs peak time, and an analog-to-digital converter (ADC) driver. The DAQ system has 65 mega-sample per second flash ADC, a self and external trigger, and a USB 3.0 interface. Results and Discussion: Characteristics such as the current-to-voltage curve, energy reso-lution, and electron mobility life-time products for CZT detectors are investigated. In ad-dition, preliminary results of gamma ray imaging using 511 keV of a 22Na gamma ray source were obtained. Conclusion: In this study, the DAQ system with a CZT radiation sensor was successfully developed and a PET image was acquired by two sets of the developed DAQ system.

Preliminary Research of CZT Based PET System Development in KAERI

Jo, Woo Jin,Jeong, Manhee,Kim, Han Soo,Kim, Sang Yeol,Ha, Jang Ho The Korean Association for Radiation Protection 2016 방사선방어학회지 Vol.41 No.2

Background: For positron emission tomography (PET) application, cadmium zinc telluride (CZT) has been investigated by several institutes to replace detectors from a conventional system using photomultipliers or Silicon-photomultipliers (SiPMs). The spatial and energy resolution in using CZT can be superior to current scintillator-based state-of-the-art PET detectors. CZT has been under development for several years at the Korea Atomic Energy Research Institute (KAERI) to provide a high performance gamma ray detection, which needs a single crystallinity, a good uniformity, a high stopping power, and a wide band gap. Materials and Methods: Before applying our own grown CZT detectors in the prototype PET system, we investigated preliminary research with a developed discrete type data acquisition (DAQ) system for coincident events at 128 anode pixels and two common cathodes of two CZT detectors from Redlen. Each detector has a $19.4{\times}19.4{\times}6mm^3$ volume size with a 2.2 mm anode pixel pitch. Discrete amplifiers consist of a preamplifier with a gain of $8mV{\cdot}fC^{-1}$ and noise of 55 equivalent noise charge (ENC), a $CR-RC^4$ shaping amplifier with a $5{\mu}s$ peak time, and an analog-to-digital converter (ADC) driver. The DAQ system has 65 mega-sample per second flash ADC, a self and external trigger, and a USB 3.0 interface. Results and Discussion: Characteristics such as the current-to-voltage curve, energy resolution, and electron mobility life-time products for CZT detectors are investigated. In addition, preliminary results of gamma ray imaging using 511 keV of a $^{22}Na$ gamma ray source were obtained. Conclusion: In this study, the DAQ system with a CZT radiation sensor was successfully developed and a PET image was acquired by two sets of the developed DAQ system.

Development of an efficient method of radiation characteristic analysis using a portable simultaneous measurement system for neutron and gamma-ray

Dong-Sik Jin,Yong-Ho Hong,Hui-Gyeong Kim,Sang-Soo Kwak,Jae-Geun Lee,Young-Suk Jung 한국분석과학회 2022 분석과학 Vol.35 No.2

The method of measuring and classifying the energy category of neutrons directly using raw data acquired through a CZT detector is not satisfactory, in terms of accuracy and efficiency, because of its poor energy resolution and low measurement efficiency. Moreover, this method of measuring and analyzing the characteristics of low-energy or low-activity gamma-ray sources might be not accurate and efficient in the case of neutrons because of various factors, such as the noise of the CZT detector itself and the influence of environmental radiation. We have therefore developed an efficient method of analyzing radiation characteristics using a neutron and gamma-ray analysis algorithm for the rapid and clear identification of the type, energy, and radioactivity of gamma-ray sources as well as the detection and classification of the energy category (fast or thermal neutrons) of neutron sources, employing raw data acquired through a CZT detector. The neutron analysis algorithm is based on the fact that in the energy-spectrum channel of 558.6 keV emitted in the nuclear reaction 113Cd + 1n → 114Cd + in the CZT detector, there is a notable difference in detection information between a CZT detector without a PE modulator and a CZT detector with a PE modulator, but there is no significant difference between the two detectors in other energy-spectrum channels. In addition, the gamma-ray analysis algorithm uses the difference in the detection information of the CZT detector between the unique characteristic energy-spectrum channel of a gamma-ray source and other channels. This efficient method of analyzing radiation characteristics is expected to be useful for the rapid radiation detection and accurate information collection on radiation sources, which are required to minimize radiation damage and manage accidents in national disaster situations, such as large-scale radioactivity leak accidents at nuclear power plants or nuclear material handling facilities.

A modeling study on utilizing SnS₂ as the buffer layer of CZT(S, Se) solar cells

Haghighi, Maryam,Minbashi, Mehran,Taghavinia, Nima,Kim, Dae-Hwan,Mahdavi, Seyed Mohammad,Kordbacheh, Amirhossein Ahmadkhan Elsevier 2018 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.167 No.-

<P><B>Abstract</B></P> <P>CdS is conventionally used as the n-type buffer layer in chalcopyrite (CIG(S, Se)) and Kesterite (CZT(S, Se)) solar cells. CdS is toxic and there are wide attempts to find substitutes for it. Here, we suggest SnS<SUB>2</SUB> as a possible alternative. SnS<SUB>2</SUB> films were deposited by pulsed laser deposition (PLD), characterized to estimate carrier concentration and electron affinity values, and the obtained values were used to model a CZT(S, Se) solar cell. The experimental values of a benchmark CZT(S, Se) cell with efficiency of 12.3% were employed to obtain the density and energy position of defects in CZT(S, Se) and validating the model. We observed that SnS<SUB>2</SUB> results in almost identical performance as CdS, showing slightly better current density, due to smaller conduction band offset of 0.21 eV compared to 0.28 eV for CdS.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CZT(S, Se) solar cell is modeled with vertically graded absorber composition based on experimental data. </LI> <LI> The non-toxic and inexpensive SnS<SUB>2</SUB> has been introduced as a new buffer layer and appropriate alternative for CdS. </LI> <LI> The measured conduction and valence band positions of PLD grown SnS<SUB>2</SUB> layers are 4.26 eV and 6.11 eV. </LI> <LI> SnS<SUB>2</SUB> compares well with CdS as the buffer layer of CZT(S, Se) solar cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>