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Concept Verification of Three-Layer DOI Detectors for Small Animal PET
Hong, Seong Jong,Kwon, Sun Il,Ito, Mikiko,Lee, Geon Song,Sim, Kwang-Souk,Park, Kwang Suk,Rhee, June Tak,Lee, Jae Sung IEEE 2008 IEEE transactions on nuclear science Vol.55 No.3
<P> Improved spatial resolution without sacrificing sensitivity is one of the most challenging developmental goals for small animal PET scanners. The 3-layer configuration that we propose here utilizes relative offsets of half a crystal pitch in x- and y-directions, and pulse shape discrimination to obtain depth of interaction (DOI). Three layers of crystals with a dimension 1.5<TEX>$\,\times\,$</TEX>1.5<TEX>$\,\times\,$</TEX>7.0mm <TEX>$^{3}$</TEX> were composed of a L <TEX>$_{0.2}$</TEX> GSO (Lu<TEX>$_{0.4}$</TEX> Gd<TEX>$_{1.6}$</TEX> SiO<TEX>$_{4}$</TEX>: Ce) crystal layer and a L<TEX>$_{0.9}$</TEX> GSO (Lu<TEX>$_{1.8}$</TEX> Gd <TEX>$_{0.2}$</TEX> SiO<TEX>$_{4}$</TEX> : Ce) crystal layer aligned with each other, and a L <TEX>$_{0.9}$</TEX> GSO crystal layer offset at half a crystal pitch in x- and y-directions. The L<TEX>$_{0.9}$</TEX> GSO crystal layer was attached to a Hamamatsu H9500 flat-panel PMT. The devised small animal PET scanner has a diameter of 84 mm with one detector ring, and can be upgraded to two detector rings. GEANT4 Monte-Carlo simulation was used to estimate sensitivities of <TEX>$\sim 12\hbox{\%}$</TEX> and <TEX>$\sim 20\hbox{\%}$</TEX>, respectively, at the center of one and two PMT ring system with an energy window of 350 <TEX>$\sim$</TEX> 750 keV. We present flood images with peak-to-valley ratios of about 5–6 obtained using <TEX>$^{22}$</TEX> Na and layer identification capability of <TEX>$\sim 99\hbox{\%}$</TEX> with pulse shape analysis, and verified the basic concepts of multi-layer small animal PET. </P>
Track Distiribution of Recoil Protons in PN-3 Dosimeters Etched in NaOH Solution
Yoo, Done-Sik,Sim, Kwang-Souk Korean Society of Medical Physics 1991 의학물리 Vol.2 No.2
중성자 선원에 의한 되튕긴 양성자의 궤적을 PN-3 검출기를 이용하여 화학적 부식방식으로 검출하는 방법에 대해 논의해 보았다. 또한 PN-3 의 부식 및 검출특성을 부식된 궤적지름과 여러 변수들로 표시하여 보았다. 본 연구를 통해 고체 비적 검출기에 검출된 입자를 분석하기 위해 입자의 전하, 에너지, 질량과 궤적 부식 비율 결정 및 궤적 구조 형성 과정 사이의 관계식에 대한 자세한 정보를 얻을 수 있었다. 또한 하전입자를 보다 정확하게 검출하기 위해 입자의 종류 및 에너지에 대한 부식 조건을 변화시키면서 이에 대응하는 최적의 부식조건을 경험적으로 찾아내었다. 아울러 기대되는 기술 저변 확대 효과로는 고분자플라스틱 검출기를 이용한 저준위 중성자 측정기술의 축적 및 개발을 통해 원자력발전소, 비파괴검사기관 및 의료기관 동 방사선 동위원소 취급기관의 중성자 선량측정계로의 유용한 응용 가능성이 예상된다. The method of etching tracks in PN-3 dosimeter has been applied to tracks of recoil protons from a neutron source. Both the etch and the detection response of PN-3 has been studied as a function of etched-track diameters against various parameters. We could obtain very useful informations about charge, energy, and mass of particles and the relationship between the track etching rate and the track forming procedure in order to analyze the particle recorded in the solid state track detector. The best etching condition could be found by means of changing the etching circumstances for various energies and particles in order to detect the charged particle accurately. It could be influenced widely that the polymer plastic detector could develep the detecting technique for the low energy level neutron and could be used as a neutron dosimeter in the radiation field such as the nuclear power station, the medical institute and the nondtructive testing institute.
Sensitivity of a Gd-Coated Resistive Plate Chamber to Low-Energy Neutrons
홍병식,Ji Hyun Kim,Kwang Bok Lee,Kwang Souk Sim,이경세,Min Sang Ryu,Seong Jong Hong,Sung Keun Park 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.3
We present the design and the construction of a resistive plate chamber (RPC) with a Gdcoated electrode for the detection of low-energy neutrons. The signals were read out by using two perpendicular strip planes. The sensitivity of the RPC was tested by using the 252Cf source at the Korea Atomic Energy Research Institute. After the background had been properly subtracted, the neutron detection efficiency was determined to be about 3 % and 2 % for the backward and the forward scattered electron configurations, respectively, at an incident energy of about 75 meV.
Ito, Mikiko,Lee, Jae Sung,Park, Min-Jae,Sim, Kwang-Souk,Hong, Seong Jong Institute of Physics in association with the Ameri 2010 Physics in medicine & biology Vol.55 No.13
<P>PET detectors with depth-of-interaction (DOI) encoding capability allow high spatial resolution and high sensitivity to be achieved simultaneously. To obtain DOI information from a mono-layer array of scintillation crystals using a single-ended readout, the authors devised a method based on light spreading within a crystal array and performed Monte Carlo simulations with individual scintillation photon tracking to prove the concept. A scintillation crystal array model was constructed using a grid method. Conventional grids are constructed using comb-shaped reflector strips with rectangular teeth to isolate scintillation crystals optically. However, the authors propose the use of triangularly shaped teeth, such that scintillation photons spread only in the <I>x</I>-direction in the upper halves of crystals and in the <I>y</I>-direction in lower halves. DOI positions can be estimated by considering the extent of two-dimensional light dispersion, which can be determined from the multiple anode outputs of a position-sensitive PMT placed under the crystal array. In the main simulation, a crystal block consisting of a 29 × 29 array of 1.5 mm × 1.5 mm × 20 mm crystals and a multi-anode PMT with 16 × 16 pixels were used. The effects of crystal size and non-uniform PMT output gain were also explored by simulation. The DOI resolution estimated for 1.5 × 1.5 × 20 mm<SUP>3</SUP> crystals was 2.16 mm on average. Although the flood map was depth dependent, each crystal was well identified at all depths when a corner of the crystal array was irradiated with 511 keV gamma rays (peak-to-valley ratio ∼9:1). DOI resolution was better than 3 mm up to a crystal length of 28 mm with a 1.5 × 1.5 mm<SUP>2</SUP> or 2.0 × 2.0 mm<SUP>2</SUP> crystal surface area. The devised light-sharing method allowed excellent DOI resolutions to be obtained without the use of dual-ended readout or multiple crystal arrays.</P>
Systematic Studies of Aging Effects in RPCs for the CMS/LHC Experiment
Sungkeun Park,이경세,Byung Il Kim,홍병식,Dong Ho Mun,Duk Kil Koo,Jeong Ku Lim,이준택,Kwang Bok Lee,Kwang-Souk Sim,Mikiko Ito,MIn Sang Ryu,Sang Ryeol Bahk,이석재,홍성종,남순권,Sunghwan Ahn,Tae Im Kang,Woo Jin Park,김용은,김 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.2
An intensive aging study for the forward resistive plate chambers (RPCs) was performed by using a 200 mCi 137Cs gamma-ray source. For the systematic aging study, four double-gap RPCs, 40 £ 40 cm2, were manufactured and tested for cosmic muons and the gamma rays irradiated from the source. The aging of the RPC gap is expected to be proportional to the integrated avalanche charge per unit area of the RPC. In this paper, a few diagnostic methods to observe aging phenomena are discussed, and the test result for a gamma irradiation of 150 days are presented. The integrated avalanche charge per unit area induced by the gamma rays in the RPC gap was 0.23 C/cm2/gap on average, which is equivalent to approximately 12 years of Compact Muon Solenoid (CMS) RPC operation.
A Four-Layer DOI Detector With a Relative Offset for Use in an Animal PET System
Mikiko Ito,Jae Sung Lee,Sun Il Kwon,Geon Song Lee,Byungsik Hong,Kyong Sei Lee,Kwang-Souk Sim,Seok Jae Lee,June Tak Rhee,Seong Jong Hong IEEE 2010 IEEE transactions on nuclear science Vol.57 No.3
<P>For animal PET systems to achieve high sensitivity without adversely affecting spatial resolution, they must have the ability to measure depth-of-interaction (DOI). In this paper, we propose a novel four-layer PET system, and present the performances of modules built to verify the concept of the system. Each layer in the four-layer PET system has a relative offset of half a crystal pitch from other layers. Performances of the four-layer detector were estimated using a GATE Monte Carlo simulation code. The proposed system consists of six H9500 PMTs, each of which contains 3193 crystals. A sensitivity of 11.8% was obtained at the FOV center position of the proposed system. To verify the concept, we tested a PET module constructed using a H9500 flat panel PMT and LYSO crystals of cross-sectional area 1.5 × 1.5 mm<SUP>2</SUP>. The PET module was irradiated with a 1.8 MBq <SUP>22</SUP>Na radiation source from the front or side of the crystals to obtain flood images of each crystal. Collimation for side irradiation was achieved using a pair of lead blocks of dimension 50 × 100 × 200 mm<SUP>3</SUP>. All crystals in the four layers were clearly identified in flood images, thus verifying the DOI capability of the proposed four-layer PET system. We also investigated the optimal combination of crystal lengths in the four-layer PET system using the GATE Monte Carlo simulation code to generate events from simulated radiation sources, and using the ML-EM algorithm to reconstruct simulated radiation sources. The combination of short crystal lengths near radiation sources and long crystal lengths near the PMT provides better spatial resolution than combinations of same crystal lengths in the four-layer PET system.</P>
CHAN MI LEE,홍성종,HYUN SUK YOON,Mikiko Ito,SUN IL KWON,SANG KEUN PARK,이동수,Kwang Souk Sim,이재성 한국원자력학회 2012 Nuclear Engineering and Technology Vol.44 No.1
The aim of this study was to explore the spatial and energy resolutions of a PET scanner that we have recently developed. The scanner, which consists of six detector modules with 1-layer LGSO crystals, has a hexagonal configuration with a faceto-face distance of 86.4 mm between two opposite PET modules; such properties facilitate the imaging of small animals. A 22Na point source was employed to estimate horizontal and vertical spatial resolutions. To assess the energy resolution, a uniform 18F cylindrical phantom was scanned. A software-based spectrum analysis of list-mode data was used to assign a local energy window centered on the photopeak position for every single crystal. For the image reconstruction, an ML-EM algorithm was used. The spatial resolutions at the center of the scanner were 0.99 mm in the horizontal direction and 1.13mm in the vertical direction. The energy resolution averaged over each PMT ranged from 13.3%-14.3%, which gave an average value of 13.8%. These results show that this simple system is promising for small animal imaging with excellent spatial and energy resolutions.