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최창락 ( Chang-rak Choi ),김지수 ( Ji-soo Kim ),김수형 ( Soo-hyung Kim ),심철무 ( Cheul-muu Sim ) 한국정보처리학회 2007 한국정보처리학회 학술대회논문집 Vol.14 No.2
현재 우리나라는 원자력 발전에 대한 의존도가 매우 높고 그 기술 또한 우수하다. 그러나 중성자 스펙트럼을 사용하여 폭발물 탐지를 위한 시스템 개발 기술은 미흡한 실정이다. 본 논문은 신경망(Neural Networks)을 한국 원자력 연구소 중성자 스펙트럼 패턴을 분류하는 시스템에 적용하였다. 데이터 획득 방법을 달리하여 두 개의 신경망을 구현하였고 그 결과를 분석하여 보았다. 먼저 폭발물에 다량 포함되어 있는 C(Carbon), N(Nitrogen), O(Oxygen) 3개의 물질을 중심으로 중성자 스펙트럼을 분석하였다. 다른 하나는 중성자 스펙트럼을 전체 영역으로 획득한 데이터를 바탕으로 신경망을 구현하여 인식률을 확인하였다. 실험결과 전자의 경우 62.5%의 인식률을, 후자의 경우 신경망은 83.48%의 인식률을 나타내었다.
중성자 보안검색 장치를 위한 신경망 기반의 γ-스펙트럼 분류 방법
최창락(Chang-Rak Choi),김지수(Ji-Soo Kim),김수형(Soo-Hyung Kim),심철무(Cheul-Muu Sim) 한국정보과학회 2007 한국정보과학회 학술발표논문집 Vol.34 No.2C
본 논문은 한국 원자력 연구소 중성자 스펙트럼 패턴을 분류하는 시스템에 신경망(Neural Networks)을 적용하였다. 중성자 스펙트럼 분석시 3개의 신경망을 하나로 결합하여 각 신경망의 인식률을 확인하였다. 신경망1은 폭발물 판별을, 신경망2는 폭발물의 종류를, 신경망3은 비 폭발물 종류를 구별하도록 시스템을 설계하였다. 중성자 스펙트럼을 통해 실험한 결과 신경망1은 83.48%를, 신경망2는 84.6%를, 신경망3은 91.67%의 인식률을 얻어 본 논문에서 제안한 시스템의 우수성을 입증하였다.
교차소뇌해리현상 : SPECT와 MRI 소견의 비교와 임상징후
손형선,김의녕,신광현,나형균,최창락,Sohn, Hyung Sun,Kim, Euy Neyng,Shin, Kwang Hyun,Rha, Hyung Kyun,Choi, Chang Rack 대한신경외과학회 2000 Journal of Korean neurosurgical society Vol.29 No.6
Objectives : The purpose of our study was to compare findings of brain SPECT representing crossed cerebellar diaschisis(CCD) with brain MRI, to evaluate relation between CCD and location of lesions on MRI and to elucidate clinically apparent cerebellar sign in patients with CCD. Methods : The study population was 20 patients representing CCD on SPECT. Percentage differences(${\triangle}%$) of activity on each cerebellar hemisphere were obtained from ipsilateral and contralateral cerebellum[${\triangle}%cbll=(IL-CL)/IL{\times}100$] and from cerebrum [${\triangle}%cbr=(CL-IL)/CL{\times}100$]. From MR studies, the percentage differences of signal intensity were also calculated as the same method. We compared the degree of percentage differences with location of cerebral lesions and with clinical cerebellar signs of the patients. Results : Among those representing CCD, the parietal lesions were the most common. There was significant correlation of the percentage differences in cerebellum between SPECT($18.8{\pm}7.22$) and MRI($4.4{\pm}3.38$) (p<0.05) and in cerebrum between SPECT($28.7{\pm}15.35$) and MRI($42.8{\pm}10.94$) (p<0.05). Cerebellar signs were observed in 3 of the 20 patients. However, there was no statistically significance between degree of percentage differences of each cerebellar hemisphere on SPECT and clinical cerebellar sign(p>0.05). Conclusion : Using the percentage differences in the cerebellum, the CCD evaluation can be easily done. On MRI, the signal changes of cerebellum were not as definite as SPECT. Despite of our assumption, there was no significant correlation between clinical cerebellar signs and CCD on SPECT.
파킨슨환자의 자기공명영상과 미세전극기록을 이용한 담창구 파괴술
이경진,손형선,박성찬,조경근,박해관,최창락,Lee, Kyung Jin,Son, Hyung Sun,Park, Sung Chan,Cho, Kyung Keun,Park, Hae Kwan,Choi, Chang Rak 대한신경외과학회 2001 Journal of Korean neurosurgical society Vol.30 No.1
Objective : The exact position of the lesion during the pallidotomy is critical to obtain the clinical improvement of parkinson's disease without damage to surrounding structure. Ventriculogrphy, CT(computed tomograpy) or MRI(magnetic resonance imaging) have been used to determine the initial coordinates of stereotactic target for pallidotomy. The goal of this study was to determine whether microelectrode recording significantly improves the neurophysiologic localization of the target obtained from MRI. Methods : Twenty patients were studied. They underwent a unilateral pallidotomy. Leksell frame was applied and T1 axial images parallel to the AC-PC(anterior commissure-posterior commissure) plane using a 1.5 Tesla MRI with 3mm slice thickness were obtained. Anteroposterior coordinate of target was chosen at 2mm in front of the midcommissural point and lateral coordinate between 19 and 22mm from the midline. The vertical coordinate was calculated on coronal slice using a fast spin echo inversion recovery sequence(FSEIR) related to the position of the choroidal fissure and ranged over 4-5mm below the AC-PC plane. Confirmation of the anatomical target was done on axial slices using the same FSEIR sequence . Microrecording was done at the pallidum contralateral to the symptomatic side using an electrode with a tip diameter of $1{{\mu}m}$ diameter tip and 1.1-1.4 mOhm impedance at 1000Hz. Electrophysiologic localization of the target was also confirmed intraoperatively by macrostimulation. Results : Microrecording techniques were reliable to define the transition from the base of the pallidum which was characterized by the disappearance of spike activity and by the change of the audible background activity. Signals from high amplitude neurons firing at 200-400Hz were recorded in the pallidal base. X, Y and Z coordinates of target obtained from the MRI were within 1mm from the X, Y, Z coordinates obtained with microrecording in 16 patients (80%), 15 patients(75%), 10 patients(50%) respectively. The difference of Y coordinate between on MRI and on microrecording was 4mm in only one patient. Conclusion : The MRI was accurate to localize the target within 1mm of the error from microrecording target in 70% of the patients. 4mm discrepancy was observed only once. We conclude that MRI alone can be used to determine the target for pallidotomy in most patients. However, microrecording technique can still be extremely valuable in patents with aberrant anatomy or unusual MRI coordinates. We also consider physiologic confirmation of the target using macrostimulation to be mandatory in all cases.