• The Korean Journal of Nuclear Medicine
• /
• v.38 no.5
• /
• pp.338-343
• /
• 2004

Purpose: The purpose of this study was to develop a small animal PET using dual layer phoswich detector to minimize parallax error that degrades spatial resolution at the outer part of field-of-view (FOV). Materials and Methods: A simulation tool GATE (Geant4 Application for Tomographic Emission) was used to derive optimal parameters of small PET, and PET was developed employing the parameters. Lutetium Oxyorthosilicate (LSO) and Lutetium-Yttrium Aluminate-Perovskite(LuYAP) was used to construct dual layer phoswitch crystal. $8{\times}8$ arrays of LSO and LuYAP pixels, $2mm{\times}2mm{\times}8mm$ in size, were coupled to a 64-channel position sensitive photomultiplier tube. The system consisted of 16 detector modules arranged to one ring configuration (ring inner diameter 10 cm, FOV of 8 cm). The data from phoswich detector modules were fed into an ADC board in the data acquisition and preprocessing PC via sockets, decoder block, FPGA board, and bus board. These were linked to the master PC that stored the events data on hard disk. Results: In a preliminary test of the system, reconstructed images were obtained by using a pair of detectors and sensitivity and spatial resolution were measured. Spatial resolution was 2.3 mm FWHM and sensitivity was 10.9 $cps/{\mu}Ci$ at the center of FOV. Conclusion: The radioactivity distribution patterns were accurately represented in sinograms and images obtained by PET with a pair of detectors. These preliminary results indicate that it is promising to develop a high performance small animal PET.

• Defense and Technology
• /
• no.9 s.271
• /
• pp.39-49
• /
• 2001

미래에는 정보전자전을 대비해서 전자기펄스탄(EMP 탄), 탄소섬유탄, 고섬광 발생탄과 같이 물리화학적 파괴 능력을 갖는 특수 전용 탄두들이 소요될 것이다. 세계 대전의 가능성은 희박하나 지역분쟁이 발생했을 때 전후방과 군과 민이라는 구분이 없어지고, 전쟁상황이 실시간으로 전파되기 때문에 다양한 비살상 탄두가 주요 전술탄두로 등장할 수 있다. 따라서 전자기 펄스탄(EMP 탄), 탄소섬유탄과 같은 대 정보.전자전 탄두들이 우리가 미래를 대비하는 하나의 수단이 되리라 확신한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2013.06a
• /
• pp.31-33
• /
• 2013

종래의 전구식 등명기의 경우 중량이 많이 나갈 뿐만 아니라 전구의 교체시기가 짧고 전력소모가 심하다는 문제가 있었다. 또한 5mm 포탄형 저휘도 LED램프의 경우에는 수명이 길고 저전력이라는 장점이 있으나, 근래에는 해상의 배후광이 높아져 개당 소비전력이 1W(와트) 이상인 고휘도 파워 LED를 광원으로서 채택하는 등명기가 등장하고 있는 실정이다. 그런데, 이러한 고휘도 파워 LED의 경우 종래의 포탄형 LED에 비하여 광도는 매우 높으나, 소비전력이 상대적으로 매우 높으며, 그에 따라 발열이 심하다는 문제가 있다. 따라서, 고휘도 파워 LED를 채용하여 등명기의 광도를 높이는 경우에는 반드시 방열 문제를 고려해야 한다. 그렇지 않으면, 고휘도 파워 LED의 발열로 인하여 제품이 안정적으로 구동할 수 없으며, 결국에는 관련 부품의 고장이나 파손으로 이어지기 때문이다. 본 연구는 종래의 전구식 램프나 저전력 포탄형 LED램프를 대체하여 고휘도 파워 LED램프를 광원으로 적용함에 있어, 등명기의 중량을 증가시키지 않는 구조로서 보다 효과가 우수한 방열기술을 개발하기 위한 것이다.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.15 no.2
• /
• pp.201-207
• /
• 2012

Pulsed lasers at the 613 nm and 1064 nm wavelengths on nanoseconds have been utilized to characterize the damage on Si photodiode exposed to intense illumination. Morphological damages and structural changes at sites on the photodiode irradiated during microseconds of laser pulses were analyzed by FE-SEM images and XRD patterns, respectively. The removal of oxide coating, ripple, melting marks, ridges, and crater on photodiodes were definitely observed in order of increasing the pulse intensities generated above the damage threshold. Then, the degradation in photosensitivity of the Si photodiode irradiated by high power density pulses was measured as a function of laser irradiation time at the various wavelengths. The free charge carrier and thermal diffusion mechanisms could have been invoked to characterize the damage. The relative photosensitivity data calculated using the thermal diffusion model proposed in this paper have been compared with the experimental data irradiated above the damage threshold.

• Progress in Medical Physics
• /
• v.21 no.1
• /
• pp.93-98
• /
• 2010

The aim of this work was to establish the methodology for event positioning by measuring depth of interaction (DOI) information and to evaluate the system sensitivity and spatial resolution of the new detector for I-125 and Tc-99m imaging. For this purpose, a Monte Carlo simulation tool, DETECT2000 and GATE were used to model the energy deposition and light distribution in the detector and to validate this approach. Our proposed detector module consists of a monolithic CsI(Tl) crystal with dimensions of $50.0{\times}50.0{\times}3.0\;mm^3$. The results of simulation demonstrated that the resolution is less than 1.5 mm for both I-125 and Tc-99m. The main advantage of the proposed detector module is that by using 3 mm thick CsI(Tl) with maximum-likelihood position-estimation (MLPE) method, high resolution I-125 imaging and high sensitivity Tc-99m imaging are possible. In this paper, we proved that our new detector to be a reliable design as a detector for a multi-energy SPECT.

• Journal of radiological science and technology
• /
• v.28 no.1
• /
• pp.9-12
• /
• 2005

In this study, film type radiation sensor tips are fabricated for remote sensing of X or g-ray with inorganic scintillators and plastic optical fiber. The visible range of light from the inorganic scintillator that is generated by X and g-ray is guided by the plastic optical fiber and is measured by optical detector and power-meter. It is expected that the fiber-optic radiation sensor which is possible to be developed based on this study is used for remote, fast and exact sensing of X or g-ray because of its characteristics such as very small size, light weight and no interference to electromagnetic fields.

• Journal of radiological science and technology
• /
• v.40 no.4
• /
• pp.621-626
• /
• 2017

In this paper, an optical dosimetric system for radiation dose measurement is developed and characterized for 100 MeV proton beams in KOMAC(Korea Multi-Purpose Accelerator Complex). The system consists of 10 wt% Ultima GoldTM liquid organic scintillator in the ethanol, a camera lens(50 mm / f1.8), and a high sensitivity CMOS(complementary metal-oxide-semiconductor) camera (ASI120MM, ZWO Co.). The FOV(field of view) of the system is designed to be 150 mm at a distance of 2 m. This system showed sufficient linearity in the range of 1~40 Gy for the 100 MeV proton beams in KOMAC. We also successfully got the percentage depth dose and the isodose curves of the 100 MeV proton beams from the captured images. Because the solvent is not a human tissue equivalent material, we can not directly measure the absorbed dose of the human body. Through this study, we have established the optical dosimetric procedure and propose a new volume dose assessment method.

• 대한방사선방어학회:학술대회논문집
• /
• 2009.04a
• /
• pp.232-233
• /
• 2009

• Korean Journal of Optics and Photonics
• /
• v.18 no.4
• /
• pp.241-245
• /
• 2007

In this study, a two-dimensional fiber-optic radiation sensor has been developed using water-equivalent organic scintillators for photon beam therapy dosimetry. Two-dimensional photon beam distributions and percent depth doses(PDD) are measured according to the energies and field sizes of the photon beam. This sensor has many advantages such as high resolution, real-time measurement and ease of calibration over conventional radiation measurement devices.

• Journal of Radiation Protection and Research
• /
• v.20 no.4
• /
• pp.275-283
• /
• 1995

PERALS(Photon Electron Rejecting Alpha Liquid Scintillation) spectrometry coupled with solvent extraction method has been set up for the analysis of $^{222}Rn\;and\;^{226}Ra$ in the groundwater. This analytical method offers low background, better energy resolution and lower quenching problem than the other techniques. By the analysis of NIST SRM 4966 $^{226}Ra$ standard, the analytical accuracy and precision were found to be 3% and 1%, respectively, and the relative standard deviation of the recovery of Rn extraction between pH2 and pH10 was 7%. Detection limits of $^{222}Rn$ and $^{226}Ra$ for 10 hours counting were counted to be $0.42 pCi/{\iota}\;and\;0.016 pCi/{\iota}$, respectively. For the test analysis of $^{222}Rn\;and\;^{226}Ra$ in the graundwater, hot spring water samples of 17 regions were analyzed. The concentration of $^{222}Rn$ were in the range of $90{\sim}5200pCi/{\iota}$ and average value was $1470pCi/{\iota}\;^{226}Ra$ concentration showed a peak value of $97.9pCi/{\iota}$ in a Kangwon region, but the average value was $1.14pCi/{\iota}$ except that region.