[en] In this review paper, basic configurations of gamma detectors in SPECT and PET systems were reviewed together with key performance parameters of the imaging system, such as the detection efficiency, the spatial resolution, the contrast resolution, and the data acquisition time for quick understanding of the system-component relationship and future design of advanced systems. Also key elements of SPECT and PET detectors, such as collimators, gamma detectors were discussed in conjunction with their current and future trend. Especially development trend of new scintillation crystals, innovative silicon-based photo-sensors and futuristic room temperature semiconductor detectors were reviewed for researchers who are interested in the development of future nuclear medical imaging instruments

[en] This book deals with current situation and prospect of market on the latest radiation measuring instrument. The contents of this book are basic of technology on radiation measuring instrument with basic principle of various measuring instrument, current situation of technology and prospect of radiation measuring instrument, effect of spreading and application field of radiation measuring instrument, facility for making and research and development of radiation measuring instrument, prospect of market about radiation measuring instrument, strategy for market entry with the latest radiation measuring instrument and general prospect for the future.

[en] This paper presents preliminary results on the degradation of BJTs(Bipolar Junction Transistors) and MOSFETs(Metal Oxide Semiconductor Field Effect Transistors) by 1MeV electron beam. Exposure experimental results show that the change of minority-carrier life time in base region dominates the behavior of BJTs and that the buildup of charges in oxide region can affect the value of threshold voltage for MOSFETs. It was possible to correlate the decrease of the minority-carrier life time to BJTs with irradiation dose, while the shift of MOSFETs' threshold voltage was not only a function of charge buildup in oxide region

[en] Self-Powered Neutron Detectors (SPNDs) are currently used to estimate the power generation distribution and fuel burn-up in several nuclear power reactors in Korea. In this paper, Monte Carlo simulation is accomplished to calculate the escape probability of beta particle as a function of their birth position for the typical geometry of rhodium-based SPNDs. Also, a simple numerical method calculates the initial generation rate of beta particles and the change of generation rate due to rhodium burn-up. Using the simulation and the numerical method, the burn-up profile of rhodium density and the neutron sensitivity are calculated as a function of burn-up time in the reactor. The sensitivity of the SPNDs decreases non-linearly due to the high absorption cross-section and the non-uniform burn-up of rhodium in the emitter rod. In addition, for improvement of some properties of rhodium-based SPNDs which are currently used, this paper presents a new material. The method used here can be applied to the analysis of other types of SPNDs and will be useful in the optimum design of new SPNDs for long term usage

[en] When a-Si:H p-i-n diodes are used for radiation detection for medical imaging, the leakage current is a sensitive characteristic of diode performance, and the transient current behavior may limit the sensitivity and stability of the p-i-n diode. Because of defect states within the band gap, the leakage current shows transient behavior. We investigate this behavior by introducing a time-dependent electric field, which originates from the variation of the ionized dangling bond density due to trapped charge emission. We assume the components of the leakage current to be the thermal generation current and the injection current at the p-i interface. The transient leakage current was calculated using this analytical model and was compared with the experimental results

[en] So as to develop a gamma camera for fuctional imaging, which consists of a collimator, a scintillation crystal, an optical guide, PMT array and position determination circuit, the total response of this system has been estimated using several simulation programs. MCNP4B, DETECT97, and Anger program were used to investigate the response of each component. A collimator for general purpose. 12'x12'x3/8' NaI(TI) crystal, and 23 PMTs for charge amplification with each 5' diameter were considered as the components of gamma camera detector in this work. Interactions of gamma photons in the collimator and crystal were simulated using MCNP4B for estimating the distribution of energy absorption in crystal and interactions of optical photons in the crystal and optical guide were simulated using DETECT97 for estimating the distribution of optical photons out of crystal. The position determination of source was investigated using our own Anger program, which was developed to calculate positions of incident photons in the gamma camera. The main code which is integrated three simulation codes, named INCOGAM (Integrated Code for Gamma Camera Design), automatically creates each inputs and analyzes each outputs. INCOGAM provides 2-D digital image of source finally. The proto-type gamma camera has been developed based on the simulation results. The two images of planar source, acquired by simulation and experimental measurement with Co-57 source, are agreed well to each other. INCOGAM may be used to estimate total response of gamma camera as well as other imaging systems having similar detector structure

[en] In dual-energy radiography using an area detector, it is needed to remove or correct scatter effects for proper separation of soft- and dense-component images. We suggest a new scatter correction method in dual-energy radiography. In the method, two-material object is separated as thickness images by dual-energy algorithm. Using this thickness information and a look-up table of scatter spread functions, scatter components are estimated and corrected in high- and low-energy radiographic images. We have simulated aluminum and water phantom images using MCNP code, and compared uncorrected and corrected resultant separated images. Average thickness-relative errors decrease from 32 % to 3.4 % for aluminum and 41 % to 2.8 % for water

[en] For the application of the neutron flux mapping, an accurate calculation of the sensitivity is required because the sensitivity is proportional to the neutron flux density. Sensitivity is defined as the current per unit length per unit neutron flux and it mainly depends on the depression factor(f), the escape probability from the emitter(ε 1) and the charge build-up factor of the insulator layer(c). A Monte Carlo simulation was accomplished to calculate the sensitivity of rhodium emitter material and alumina(Al₂O₃) insulator with a cylindrical geometry, based on the (n,β) interaction and on other interaction including the secondary electron generation for the more accurate estimation of the sensitivity. From the simulation results, factors for the sensitivity were accurately calculated and compared with other theoretical and experimental values. In addition, the sensitivity linearly increases and saturates as the emitter radius increases. The accomplished method is useful in the analysis for the change of SPND sensitivity as a function of burn-up and in the optimum design of SPND

[en] A tomography algorithm to maximize the entropy of image using Lagrangian multiplier technique and conjugate gradient method has been designed for the measurement of 2D spatial distribution of intense neutral beams of KSTAR NBI (Korea Superconducting Tokamak Advanced Research Neutral Beam Injector), which is now being designed. A possbile detection system was assumed and a numerical simulation has been implemented to test the reconstruction quality of given beam profiles. This algorithm has the good apllicability for sparse projection data and thus, can be used for the neutral beam tomograpy

[en] The importance of decontamination is emphasized because the site of disposal require a large land. The scintillation detector is widely used for radioactive waste monitor. Many scintillation detectors are needed to identify the position of the radioactive contamination although it widely used for dose measurement. Large-area detectors are also needed to inspect wide field-of-view (FOV). There is, therefore, a limitation to detect the hot spot accurately. This problem can overcome by gamma camera which detects and visualizes of the radioactive sources emitting the gamma ray. Therefore, using the gamma camera, the contamination distribution of the radioactive waste can be visualized and evaluated. The high resolution gamma camera is essential for effective decontamination and cost reduction. The purpose of this study is to optimize the high resolution pinhole collimator for radioactive waste monitor. The spatial resolution, collimator efficiency, and angle-dependent efficiency were investigated a using Monte Carlo N-Particle Transport code, version 6. The pinhole collimator for high resolution and high energy gamma ray imaging was introduced and its characteristics were evaluated by Monte Carlo simulation.