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RISS 인기검색어
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- 저자 : 손철호(Cheol Ho Son) (검색결과 12 건)
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3.OT MR 기기를 이용한 확산강조영상에서 b Value의 증가에 따른 정상 뇌의 신호강도의 변화
손철호,Son, Cheol-Ho 대한영상의학회 2003 대한영상의학회지 Vol.49 No.6
목적:확산강조영상에서 b value를 증가시켰을 때 정상 성인 뇌의 신호강도의 변화를 알아보고 대상과 방법:임상적으로 신경학적 증상이 없고 T2 강조영상에서 이상 소견이 관찰되지 않는 21명의 건강한 지원자를 대상으로 하였다.자기공명영상은 3.0T MR 기기를 이용하였다.스핀에코 EPI 기법을 이용하여,b value를 0,1,000,1,500,2,000,2,500,3,000 s/mm$^2$으로 점점 증가시키면서 축상으로 6쌍의 확산강조영상을 얻었다.영상조건중 TE를 제외한 모든 다른 조건은 동일하게 사용하였다.영상의 분석은,정성적으로는 각각의 b value 확산강조영상에서 정상 뇌회백질의 신호변화를 시각적으로 보았고,정량적으로는 각각의 b value 확산강조영상에서 6군데의 해부학적 위치 (전두부 및 두정부 백질,뇌량의 슬 및 팽부,내포의 후변연,시상)에서 신호대잡음비를 구하여 이들의 평균 신호대잡음비를 b value 1,000 s/mm$^2$의 신호대잡음비와 비교하였다. 결과:정성적 분석에서는,b value를 증가시킴에 따라 뇌 회질과 백질의 모든 구조물의 신호가 감소하였다.특히 b=3,000 s/mm$^2$에서의 영상은 잡음이 매우 심했다.뇌 백질은 회질에 비해 경사자장을 증가시킴에 따라 점차 신호강도가 높게 관찰되었다.특히 난형중심,내포의 후변연, 시방사,상소뇌각교차,뇌량의 팽부등의 구조물이 고신호강도로 관찰되었지만 예외적으로 뇌량의 슬부는 중간 저음영을 보였다.정량적 분석에서도,경사자장을 증가시킴에 따라 각각의 해부학적 위치의 평균신호대잡음비는 b value가 1,000 s/mm$^2$일 때의 확산강조영상에 비해 각각평균 0.71(b=1,500 s/mm$^2$),0.52 (b=2,000 s/mm$^2$),0.41 (b=2,500 s/mm$^2$),0.33 (b=3,000s/mm$^2$)으로 감소되었다. 결론:확산강조 경사자장의 세기를 증가시킴에 따라 영상의 신호대잡음비는 감소하며 특히 b value 3,000 s/mm$^2$에서 심하게 나타났고,백질은 회질에 비해 상대적으로 신호강도가 점점 높게 관찰되었다.이러한 정상 뇌회백질 신호변화의 인지는 판독의 오류를 막는데 매우 중요할것으로 생각된다. Purpose: Using diffusion-weighted MR imaging (DWI), to evaluate the signal intensity characteristics of normal adult brain as diffusion gradient strength (b value) increases from 1,000 to 3,000 s/mm$^2$. Materials and Methods: Twenty-one healthy volunteers with neither neurologic symptoms nor pathologic findings at axial and sagittal T2-weighted MR imaging were involved in this study. All images were obtained with a 3.0T MR scanner. Six sets of spin-echo echo-planar images were acquired in the axial plane using progressively increasing strengths of diffusion-sensitizing gradients (corresponding to b values of 0, 1,000, 1,500, 2,000, 2,500, and 3,000 s/mm$^2$). All imaging paremeters other than TE remained constant. Changes in normal white-gray matter signal intensity observed at variable b-value DWI were qualitatively analysed, and the signal-to-noise ratios (SNRs) in six anatomic regions (frontal and parietal white matter, genu and splenium corporis callosi, the posterior limb of the internal capsule, and the thalamus) quantitatively, and the ratios were averaged and compared with the average SNR of 1,000 s/mm DWI. Results: As gradient strength increased from 1,000 to 3,000 s/mm$^2$, both gray-and white-matter structures diminished in signal intensity, and images obtained at a b value of 3,000 s/mm$^2$ appeared very noisy. White matter became progressively hyperintense to gray matter as the diffusion sensitizing gradient increased, especially at the centrum semiovale, the posterior limb of the internal capsule, and the splenium corporis callosi, but the genu corporis callosi, showed exceptional intermediate low signal intensity. At quantitative assessment, the signal-to-noise ratio decreased as the diffusion sensitizing gradient increased. Relative to the images obtained at a b value of 1,000 s/mm$^2$, average SNRs were 0.71 (b=1,500 s/mm$^2$), 0.52 (b=2,000 s/mm$^2$), 0.41(b=2,500 s/mm$^2$), 0.33 (b=3,000 s/mm$^2$). Conclusion: As the diffusion sensitizing gradient increased, the signal-to-noise ratio of brain structures diminished, especially at a b value of 3,000 s/mm$^2$, and white matter became relatively hyperintense compared to gray matter. In order to avoid misdiagnosis, it is important to be aware of the nature of normal changes in the signal intensity of gray-white matter occurring at high-b-value DWI
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WTO 체제하의 임업부문 직접지불제도 도입필요성에 관한 연구
이경일 ( Lee Gyeong Il ),손철호 ( Son Cheol Ho ) 한국산림과학회 2003 한국산림과학회지 Vol.92 No.6
The purpose of research is to examine direct payment been coming in agriculture under WTO, and to suggest introduction necessity of that in forestry. As a result, direct payment in agriculture is magnified rapidly laying stress on developed country, and also our country has been enforcing that in agriculture since 1997. Under the wicked management status of forestry in Korea, for propelling sustainable forest management and income compensation to nonproductive forest land, it is needed to introduce direct payment in forestry.
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윤여창(Yeo Chang Youn),손철호(Cheol Ho Son),이진규(Jin Kue Lee) 한국산림과학회 1994 한국산림과학회지 Vol.83 No.1
To investigate the effects of national forest management on the regional community, the inter-relationship between the local communities and neighbouring forest owned by the state was surveyed in the three locations, namely pyungchang-gun, Bonghwa-gun, and Kwangyang-gun, which have a large area of national forest. The effect of national forest management on the local community was different depending upon the relationship between the local community and the national forest the resource base and infrastructure and facilities installed within the national forest. The major contribution of the national forest to regional society is the provision of land resources, forest products, employment opportunities, and social functions of forest. The supply of land resource from `he national forest has been increasing steadily due to the increase in demand for public facilities. About one quarter of household income in the forest villages surveyed came out of the sales of forest products, mainly non-timber products. Due to the low level of forest operations for timber production, there are very limited opportunities of employment provided by the national forest. And the use of forest roads by local residents was also to a limited extent. Therefore, it is suggested that the national frosts should be managed such that help to revive the economy of local communities which are disadvantaged in the national investment priority due to the low economic returns .
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뇌혈관 조영CT에 대한 320-MDCT에서의 영상의 질 및 방사선량
차영경(Yeong Kyeong Cha),이민수(Min Su Lee),이성주(Seong Joo Lee),임흥선(Heung Seon Im),손철호(Cheol Ho Son) 대한CT영상기술학회 2012 대한CT영상기술학회지 Vol.14 No.2
목적 본 연구는 뇌혈관 조영CT에 대한 320-MDCT와 64-MDCT에서의 영상의 질과 방사선량을 비교하고자 한다. 대상 및 방법 320-MDCT와 64-MDCT에서 뇌혈관 조영CT를 실시한 60명의 환자(남성 28명, 여성 32명; 연령분포, 20-84세; 평균나이 58±14.8세)를 대상으로 320-MDCT 그룹과 64-MDCT 그룹으로 나누었다. 횡단 다면 재구성 영상과 볼륨 렌더링 혈관조영CT 영상을 획득하여 영상의 질을 평하였다. 중대뇌동맥과 기저동맥에서 각각 CT number와 Noise, SNR을 측정하였고, DLP값과 유효선량(ED)을 비교하였다. 유효선량은 DLP값과 두부 촬영 변환계수(k=0.0021 mSv/mGy×cm)로 계산하였다. 정량적 영상분석을 위해 영상의학과 교수 한명이 4점 척도를 이용하여 영상의 질을 평가하였다. 정량적 분석과 정성적 분석을 위해 각각 Independent t-test를 사용하여 통계적 유의성을 검정하였다. 결과 중대뇌동맥과 기저동맥에서의 CT number값은 두 그룹간 통계적으로 유의한 차이를 보였다. (p=0.000) 중대뇌동맥 Noise는 64-MDCT 보다 320-MDCT에서 유의하게 낮게 나타났다(p=0.016). 중대뇌동맥과 기저동맥의 SNR은 320-MDCT에서 모두 유의하게 높게 나타났다(p=0.000). 각 그룹에서 측정한 유효선량은 64-MDCT보다 다 320-MDCT에서 유의한 차이를 보이며 14% 낮게 나타났다(p=0.000). 영상의 질은 두 그룹 모두 우수했고 64-MDCT보다 320-MDCT에서 유의하게 높게 나타났다(p=0.000). 결론 320-MDCT에서의 뇌혈관 조영CT는 64-MDCT보다 낮은 선량으로 높은 영상의 질을 제공함으로써 뇌혈관 질환의 진단에 있어 유용한 검사라고 생각된다. I. Purpose The purpose of this study was to compare image quality and radiation dose of 320- and 64-MDCT for whole brain CT angiography. II. Meterial and Methods A total of 60 patients (28 men, 32 women; age range, 20~84 years; mean age, 58±14.8 years) who underwent contrast-material-enhanced brain CT angiography with 320- and 64-MDCT were randomized into two groups: the 320-MDCT group and the 64-MDCT group. Transaxial multiplanar reformatted images and volume-rendered CT angiogram; were obtained and evaluated image quality, CT numbers in middle cerebral artery, basilar artery; Noise; signal-to-noise ratio(SNR); and dose-length product(DLP), Effective dose(ED) were compared. ED was calculated from the DLP and a conversion factor (k=0,0021 mSv/mGy×cm). To qualitative image analysis, One observer indepen-dently assessed image quality using a 4-point scale. Independent t-test was used for quantitative and qualitative analysis, respectively. III. Result Significant difference in mean CT numbers of the middle cerebral artery and basilar artery was noted between the two groups(p=0.000). Noise of middle cerebral artery was significantly lower in the 320-MDCT group than in the 64-MDCT group(p=0.016). SNR of the both cerebrovasculars was significantly higher in the 320-MDCT group than in the 64-MDCT group(p=0.000). ED was 14% significantly lower in the 320-MDCT group than in the 64-MDCT group(p=0,000). Image quality was acceptable in both groups and was significantly better in the 320-MDCT group than in the 64-MDCT group(p=0,000). IV. Conclusions A 320-MDCT for brain CT angiography is a useful method for the diagnosis of cerebrovascular diseases with better image quality and lower radiation dose than 64-MDCT.
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