• 대한핵의학회지
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• 제33권3호
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• pp.327-336
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• 1999

목적: 이 연구의 목적은 3D FDG-PET 뇌영상의 정량적 정확도와 임상적 유용성을 연구하는 것이다. 대상 및 방법: 24명의 환자에게 약 370 MBq의 FDG를 주사하고 섭취되기까지 30분을 대기한 후 GE $Advance^{TM}$ PET을 사용하여 30분간의 2D 영상과 10분간의 3D 영상을 얻었다. 백질, 회백질, 병변, 정상조직의 관심영역 분석을 통하여 영상대비와 FDG 섭취비를 구하여 비교하였다. 3D PET의 효율을 최대화하기 위하여 투과스캔을 사용한 경우와 사용하지 않은 경우의 감쇠보정 효과를 비교하였다. 결과 3D 영상의 영상대비는 2D 영상이 1 일 때 산란보정을 실행한 경우 회백질 대 백질에서 $0.95{\pm}0.12$, 정상 대 병변에서 $0.96{\pm}0.05$이었다. 2D 영상의 FDG 섭취비가 1일 때 3D 영상의 FDG 섭취비는 산란보정을 실행한 경우 $1.02{\pm}0.08$이었다. 3D 영상은 영상대비, 분해능, 영상 잡음에 대한 순위 척도평가에서 각각 81%, 83%, 81%에 해당되는 등급을 받아 선호도가 우수하였다. 3D 영상에서 계산감쇠보정 방법은 측정감쇠보정 방법에 필적하는 결과를 얻었다. 결론: 산란보정과 계산감쇠보정을 실시한 3D 영상은 일반적인 2D 영상과 비교하여 정량적으로 정확한 결과를 나타냈으며 정성적으로 유용하였다. 3D 영상은 일상 임상환경에 충분히 적용할 수 있으며 환자 스캔 시간을 단축하고 방사능 피폭량을 감소시키는 장점이 있었다.

• Agricultural and Biosystems Engineering
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• 제4권2호
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• pp.45-49
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• 2003

Achievements in the real-time soil spectro-photometer are: an improved soil penetrator to ensure a uniform soil surface under high speed conditions, real-time collecting of underground soil reflectance, getting underground soil color images, use of a RTK-GPS, and all units are arranged for compactness. With the soil spectrophotometer, field experiments were conducted in a 0.5 ha paddy field. With the original reflectance, averaging and multiple scatter correction, Kubelka-Munk (KM) transformation as soil absorption, its 1st and 2nd derivatives were calculated. When the spectra was highly correlated with the soil parameters, stepwise regression analysis was conducted. Results include the best prediction models for moisture, soil organic matter (SOM), nitrate nitrogen ($NO_3-N$), pH and electric conductivity (EC), and soil maps obtained by block kriging analysis.

• Journal of Biosystems Engineering
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• 제23권1호
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• pp.49-56
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• 1998

The objectives of this study were to develop models to predict the contents of moisture and protein of single kernel of brown rice based on visible/NIR (near-infrared) spectroscopic technique. The reflectance spectra of rice were obtained in the range of the wavelength 400 to 2,500 nm with 2 nm intervals. Multiple linear regression(MLR) and partial least squares (PLS) were used to develop the models. The MLR model using the first derivative spectra(10 nm of gap) with Standard Normal Variate and Detrending (SNV and Drt.) preprocessing showed the best results to predict moisture content of the sin린e kernel brown rice. To predict the protein content of a single kernel of brown ricer the PLS model used the raw spectra with multiplicative scatter correction(MSC) preprocessing over the wavelength of 1,100~1,500 nm.

• Journal of Biosystems Engineering
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• 제33권1호
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• pp.63-68
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• 2008

This study was carried out to find a useful method to predict hardness of tomato using optical spectrum data. Optical spectrum of reflectance and transmittance data were collected processed by 9 kind of preprocessing methods-normalizations of mean, maximum and range, SNV (standard normal variate), MSC (multiplicative scatter correction), the first derivative and second derivative of Savitzky-Golay and Norris-Gap. With the preprocessed and non-processed original spectrum data, prediction models of hardness of tomato were developed using analytical tools of PLS (partial least squares) and MLR (multiple linear regression) and tested for their validation. The test of validation resulted that the analytical tools of PLS and MLR output similar performances while the transmittance spectra showed much better result than the reflectance spectra.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1199-1201
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• 2005

In the synthetic aperture radar (SAR) system, the motion error is the main phase error sources and the motion compensation is very important. The phase gradient autofocus (PGA) is a state of art technique for phase error correction of SAR. It exploits the redundancy of the phase-error information among range bins by selecting the strongest scatter for each range bin and synthesizes them. The motivation of this paper is based on the observation that the redundancy of phase error is also among the cross-range direction. Moreover, the proposed method applies the weighting function to better utilize the phase error information. The validity of the proposed scheme for PGA is tested with some numerical simulation.

• Agricultural and Biosystems Engineering
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• 제4권1호
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• pp.28-33
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• 2003

Achievements in the real-time soil spectro-photometer are: an improved soil penetrator to ensure a uniform soil surface under high speed conditions, real-time collecting of underground soil reflectance, getting underground soil color images, use of a RTK-GPS, and all units are arranged for compactness. With the soil spectrophotometer, field experiments were conducted in a 0.5 ha paddy field. With the original reflectance, averaging and multiple scatter correction, Kubelka-Munk (KM) transformation as soil absorption, its 1st and 2nd derivatives were calculated. When the spectra was highly correlated with the soil parameters, stepwise regression analysis was conducted. Results include the best prediction models for moisture, soil organic matter (SOM), nitrate nitrogen (NO$_3$-N), pH and electric conductivity (EC), and soil maps obtained by block kriging analysis.

• Radiation Oncology Journal
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• 제7권2호
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• pp.287-291
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• 1989

Radiation dosimetry has been extended to small fields less than $4\times4cm^2$ which may be suitable for irradiation of small intracranial tumors. Special consideration was given to the percentage depth dose and scatter correction factors with 0.14ml ion chamber, film dosimetry and TLD measurement. Calculated dose distributions were compared with measured data.

• Nuclear Engineering and Technology
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• 제47권7호
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• pp.939-944
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• 2015

The calibration methods of neutron-measuring devices such as the neutron survey meter have advantages and disadvantages. To compare the calibration factors obtained by the shadow cone method and semi-empirical method, 10 neutron survey meters of five different types were used in this study. This experiment was performed at the Korea Atomic Energy Research Institute (KAERI; Daejeon, South Korea), and the calibration neutron fields were constructed using a $^{252}Californium$ ($^{252}Cf$) neutron source, which was positioned in the center of the neutron irradiation room. The neutron spectra of the calibration neutron fields were measured by a europium-activated lithium iodide scintillator in combination with KAERI's Bonner sphere system. When the shadow cone method was used, 10 single moderator-based survey meters exhibited a smaller calibration factor by as much as 3.1-9.3% than that of the semi-empirical method. This finding indicates that neutron survey meters underestimated the scattered neutrons and attenuated neutrons (i.e., the total scatter corrections). This underestimation of the calibration factor was attributed to the fact that single moderator-based survey meters have an under-ambient dose equivalent response in the thermal or thermal-dominant neutron field. As a result, when the shadow cone method is used for a single moderator-based survey meter, an additional correction and the International Organization for Standardization standard 8529-2 for room-scattered neutrons should be considered.

• 핵의학기술
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• 제17권1호
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• pp.25-29
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• 2013

SPECT/CT에서 140 kVp를 사용하는 CT 평균 에너지를 60 keV로 가정하고, CT 평균 에너지와 $^{201}Tl,\;^{99m}Tc,\;^{131}I$의 각기 다른 3가지 에너지를 서로 비교하여 감쇠 보정과 산란 보정의 정확도를 평가하고자 한다. Cylindrical phantom 에 $^{201}Tl$은 55.5 MBq (2 mCi), $^{99m}Tc$은 281.2 MBq (7.6 mCi), $^{131}I$은 96.2 MBq (2.66 mCi)를 주입하고 장비는 GE사의 Hawkeye 4 SPECT/CT를 사용하였다. 모든 SPECT는 frame 당 약 50 kcounts, CT는 140 kVp, 2.5 mA로 하여 영상을 얻었다. 영상은 OSEM (iteration: 2, subset: 10)으로 재구성하였고, 이때 감쇠 보정 적용 유무, 산란 보정 적용 유무를 서로 비교했다. 전체 phantom 영상의 uniformity를 모두 측정하고, center to peripheral ratio (CPR)를 구하여 평가하였다. $^{201}Tl$과 $^{99m}Tc$의 재구성 영상에 감쇠 보정만 적용한 경우 약 10-20% 정도 uniformity가 향상되지만, SC만 적용한 경우에는 약 2% 감소하였다. $^{131}I$의 uniformity는 감쇠 보정과 산란 보정을 모두 적용한 경우에 조금 향상되었다. 또한 CPR은 $^{201}Tl$과 $^{99m}Tc$에서 감쇠 보정만 적용한 경우에 1에 가까웠고, $^{131}I$의 영상에서는 감쇠 보정만 적용한 경우 1에 가깝지 않은 결과가 나타났다. SPECT/CT에서 140 kVp의 CT 평균 에너지를 60 keV이라고 가정했을 때, 대체적으로 에너지가 낮은 $^{201}Tl$과 $^{99m}Tc$은 감쇠 보정만 적용한 경우에 uniformity가 향상되었고, 에너지가 높은 $^{131}I$ 은 감쇠 보정과 산란 보정을 모두 적용한 경우에만 향상되었다.

• 천문학회지
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• 제42권6호
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• pp.161-174
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• 2009

Observation of standard stars is of crucial importance in stellar photometry. We have studied the standard transformation relations of the UBV RI CCD photometric system at the Maidanak Astronomical Observatory in Uzbekistan. All observations were made with the AZT-22 1.5m telescope, SITe 2k CCD or Fairchild 486 CCD, and standard Bessell UBV RI filters from 2003 August to 2007 September. We observed many standard stars around the celestial equator observed by SAAO astronomers. The atmospheric extinction coefficients, photometric zero points, and time variation of photometric zero points of each night were determined. Secondary extinction coefficients and photometric zero points were very stable, while primary extinction coefficients showed a distinct seasonal variation. We also determined the transformation coefficients for each filter. For B, V, R, and I filters, the transformation to the SAAO standard system could be achieved with a straight line or a combination of two straight lines. However, in the case of the U filter and Fairchild 486 CCD combination, a significant non-linear correction term - related to the size of Balmer jump or the strength of the Balmer lines - of up to 0:08 mags was required. We found that our data matched well the SAAO photometry in V, B - V, V - I, and R - I. But in U - B, the difference in zero point was about 3.6 mmag and the scatter was about 0.02 mag. We attribute the relatively large scatter in U -B to the larger error in U of the SAAO photometry. We confirm the mostly small differences between the SAAO standard UBV RI system and the Landolt standard system. We also attempted to interpret the seasonal variation of the atmospheric extinction coefficients in the context of scattering sources in the earth's atmosphere.