심근 관류 SPECT에서 핵종에 따른 Uniformity correction map 설정을 통한 영상의 질 비교

송재혁,김경식,이동훈,김성환,박장원,Song, Jae hyuk,Kim, Kyeong Sik,Lee, Dong Hoon,Kim, Sung Hwan,Park, Jang Won 대한핵의학기술학회 2015 핵의학 기술 Vol.19 No.2

SPECT에서 Uniformity는 균일한 방사능을 갖는 선원에 대하여 균일한 영상을 제공하는 능력이다. 영상에서 다양한 이유로 불균일이 발생하게 되고, 불균일은 artifacts를 발생시켜 임상적으로 진단하는데 영향을 줄 수 있다. Uniformity correction map은 검사에 사용되는 방사성 동위원소를 이용하여 영상에서 Uniformity의 변동폭을 최소화 시켜주는 역할을 한다. 본원에서 시행되고 있는 $^{201}Tl$을 이용한 심근 SPECT에서는 $^{99m}Tc$으로 기본 설정되어 있는 Uniformity correction map을 사용하고 있으며, 이에 따라 본 연구에서는 $^{201}Tl$과 $^{99m}Tc$ 두 가지 핵종으로 Uniformity correction map을 각각 설정하였을 때 영상의 질에 차이가 있는지 비교 분석하고, 영상의 질을 최적화 할 수 있는 방법에 대하여 모색해 보고자 한다. 장비는 GE Ventri Gamma camera, Flood phantom, Jaszczak ECT phantom을 이용하였다. 실험에 앞서 Collimator를 제거한 상태에서 Detector 표면 중심으로부터 2.5 m 떨어진 지점에 1 cc 주사기에 $^{99m}Tc$ 25.9 Mbq, $^{201}Tl$ 14.8 Mbq의 방사성 동위원소를 주입한 point source를 이용하여 장비사에서 권고하는 $6{\times}10^7count$로 $^{99m}Tc$와 $^{201}Tl$ 각각의 방사성 동위원소로 Uniformity Mapping을 실시하였다. Flood phantom에는 $^{201}Tl$ 21.3 kBq/mL, Jaszczak ECT phantom에는 $^{201}Tl$ 33.4 kBq/mL를 주입하여 phantom을 제작하였다. Flood Phantom으로 획득된 데이터는 Xeleris ver 2.05 프로그램을 이용하여 Integral uniformity, Differential uniformity을 두 가지 항목에 대하여 분석하였다. Jaszczak ECT Phantom으로 획득된 데이터를 본원에서 자체 개발한 Interactive Data Language 프로그램에 입력하여 Integral uniformity, Contrast, Coefficient of variation, Spatial Resolution을 4가지 항목에 대하여 분석하였다. Flood phantom test 에서는 $^{99m}Tc$에서의 Flood I.U값은 3.6%, Flood D.U값은 3.0%으로 나타났고, $^{201}Tl$ Flood I.U값은 3.8%, Flood D.U값은 2.1%으로 나타났다. 이를 통해 $^{201}Tl$으로 Uniformity correction map을 설정하였을 때, Flood I.U값은 감소하였으나 Flood D.U은 향상되어 Flood 영상에서는 크게 영상의 질이 개선되었는지는 알 수 없었다. 반면 Jaszczak ECT Phantom test에서는 $^{99m}Tc$에서의 SPECT I.U값은 13.99%, Coefficient of variation값은 4.89%, contrast값은 0.69, $^{201}Tl$에서의 SPECT I.U값은 11.37%, Coefficient of variation값은 4.79%, contrast값은 0.78로 나타났으며, 육안 분석을 실시한 Spatial Resolution 항목에서는 육안으로 큰 차이를 보이지 않았다. 이를 통해 $^{201}Tl$으로 Uniformity correction map을 설정하였을 때, Spatial Resolution 을 제외한 SPECT I.U, Coefficient of variation, Contrast 세 항목에서 각각 18%, 2%, 13%의 향상된 수치를 보였다는 점에서 영상의 질이 개선되었음을 알 수 있었다. Uniformity correction map이 영상의 질을 크게 좌우할 수 없으나, 개선의 효과를 가져다 준다는 점에서 임상적으로 진단에 영향을 주는지 또한 다른 검사에서 또 다른 방사성 동위원소로 Uniformity correction map을 설정했을 경우 영상의 질을 개선시킬 수 있는지에 관하여 추가적인 연구가 필요할 것으로 사료된다. Purpose When the patients takes myocardial perfusion SPECT using $^{201}Tl$, the operator gives the patients an injection of $^{201}Tl$. But the uniformity correction map in SPECT uses $^{99m}Tc$ uniformity correction map. Thus, we want to compare the image quality when it uses $^{99m}Tc$ uniformity correction map and when it uses $^{201}Tl$ uniformity correction map. Materials and Methods Phantom study is performed. We take the data by Asan medical center daily QC condition with flood phantom including $^{201}Tl$ 21.3 kBq/mL. After postprocessing with this data, we analyze CFOV integral uniformity(I.U) and differential uniformity(D.U). And we take the data with Jaszczak ECT Phantom by American college of radiology accreditation program instruction including $^{201}Tl$ 33.4 kBq/mL. After post processing with this data, we analyze spatial Resolution, Integral Uniformity(I.U), coefficient of variation(C.V) and Contrast with Interactive data language program. Results In the flood phantom test, when it uses $^{99m}Tc$ uniformity correction map, Flood I.U is 3.6% and D.U is 3.0%. When it uses $^{201}Tl$ uniformity correction map, Flood I.U is 3.8% and D.U is 2.1%. The flood I.U is worsen about 5%, but the D.U is improved about 30% inversely. In the Jaszczak ECT phantom test, when it uses $^{99m}Tc$ uniformity correction map, SPECT I.U, C.V and contrast is 13.99%, 4.89% and 0.69. When it uses $^{201}Tl$ uniformity correction map, SPECT I.U, C.V and contrast is 11.37%, 4.79% and 0.78. All of data are improved about 18%, 2%, 13% The spatial resolution was no significant changes. Conclusion In the flood phantom test, Flood I.U is worsen but Flood D.U is improved. Therefore, it's uncertain that an image quality is improved with flood phantom test. On the other hand, SPECT I.U, C.V, Contrast are improved about 18%, 2%, 13% in the Jaszczak ECT phantom test. This study has limitations that we can't take all variables into account and study with two phantoms. We need think about things that it has a good effect when doctors decipher the nuclear medicine image and it's possible to improve the image quality using the uniformity correction map of other radionuclides other than $^{99m}Tc$, $^{201}Tl$ when we make other nuclear medicine examinations.

감마카메라의 중장기 외인성 균일도 분석

김윤재,정우영,이동훈,Yoon-Jae Kim,Woo-Young Jung,Dong-Hoon Lee 대한핵의학기술학회 2023 핵의학 기술 Vol.27 No.1

Purpose The long-term trend of extrinsic uniformity by type of gamma camera was analyzed, and the factors affecting uniformity were investigated. Based on this, the purpose was to predict the life of the gamma camera, pay attention to factors that affect uniformity, and obtain better quality images. Materials and methods Four of the gamma cameras in operation at a senior general hospital in Seoul were selected and the trend of extrinsic uniformity from the first operation date to the present was analyzed. In order to minimize various factors affecting uniformity, a detailed analysis was conducted by calculating the monthly and annual average of the uniformity values. Results Two Symbia E gamma cameras from SIEMENS, one Symbia Evo Excel gamma camera, and one Symbia Intevo16 gamma camera were selected and analyzed. The uniformity of Symbia E₁ (2012 warehousing) changed unevenly, and the uniformity of Symbia E₂ (2014 warehousing) changed according to the replacement cycle of ⁵⁷Co sheet sources. The uniformity of Symbia Evo Excel (received in 2017) and Symbia Intevo 16 (received in 2017) was constant compared to Symbia E. Conclusion The extrinsic uniformity of the gamma camera gradually increased over time. However, there was a difference in uniformity for each type of gamma camera, and there was a change in uniformity in which the cause could not be accurately identified. In order to improve the quality of the image, it is necessary to periodically check changes in uniformity and minimize factors that affect uniformity.

압력에 따른 스프링클러 살수 분포 및 관개 효율 평가

가마자신토빈센트필립 ( Jacinto Vicente Filipe Gama ),홍성구 ( Seonggu Hong ) 한국농공학회 2020 한국농공학회 학술대회초록집 Vol.2020 No.-

Inadequate information about sprinklers especially in terms of coefficient uniformity and distribution uniformity is usually not given by the manufacturers, thus engineers are gettng into difficulty in correctly selecting appropriate sprinkler systems. The manufacturers provide the sprinkler specifications (throw or wetted radius of nozzle for different pressure, discharge volume, and precipitation for each nozzle). The main goal of this study is to evaluate water distribution uniformity, coefficient uniformity, and water application rates of a sprinkler system. The single sprinkler nozzl, HE-VAN of Rain bird^TM 15 series was evaluated through a set of experiments. The pressure is one of the most important factors that strongly affect irrigation uniformity and efficiency in a sprinkler irrigation system. The sprinklers were operated under different pressure and nozzle angle as recommended by the manufacture. The water depths were measured using catch cans which are located from the nozzle to the wetted radius for different pressures (1, 1.4, 1.7, and 2.1 bars) for 15 minutes. The results showed changes in both distribution coefficient and the coefficient of uniformity. The lowest coefficient uniformity (CU) and (DU) on nozzle 360°for the pressures 1.7 bar were 52% and 22%, respectively. The highest value of CU and DU were 70% and 34%, respectively at 1.4 bar. At the spray angles of 360°and 270°, higher water depth near to the nozzle and th depths decreased sharply along with the distance from the sprinkler. Meanwhile at the angles of 90°and 180°, higher water depths were located at 1.3 meters from the nozzle and then decreased at end of wetted radius. Wind influence affected distribution uniformity and coefficient uniformity. The results showed that irrigation engineers should take into serious consideration of the changes in the uniformity of water distribution by different pressures in designing and installation to achieve efficient irrigation.

Assessment of Irrigation Efficiency and Water Distribution by the Different Pressures and Nozzles angle of the Sprinkler Irrigation System

가마자신토빈센트필 ( Jacinto Vicente Filipe Gama ),홍성구 ( Seonggu Hong ) 한국농공학회 2020 한국농공학회 학술대회초록집 Vol.2020 No.-

Inadequate information about sprinklers especially in terms of coefficient uniformity and distribution uniformity is usually not given by the manufacturers, thus making an engineer difficult to correctly select a sprinkler. The manufacturers mention the sprinkler specifications (pressures for each nozzle with a radius of throwing wetted, discharge volume, and precipitation for each nozzle). The main goal of this study is to evaluate water distribution uniformity, coefficient uniformity, and water application rate surrounding a sprinkler on the single sprinkler. The single sprinkler Rain bird 15 series HE-VAN was evaluated under outdoor experimental conditions by measuring water depth. The pressure is one of the most important factors that strongly affect irrigation uniformity and efficiency in a sprinkler irrigation system. The sprinklers were operated under different pressure and nozzle angle as recommended by the manufacture. The Measurements of water depth using a catch can for sprinkler surroundings to the wetted radius have been done for different respective pressures (1bar, 1.4bar, 1.7 bar, and 2.1 bar) each within 15 minutes. The results show that the change in the distribution coefficient, the coefficient of uniformity change also. The lowest and highest coefficient uniformity (CU) and (DU) on nozzle 360°for the respecting pressure 1.7 bar & 1.4 bar is 22%, 52% of CU, and 70%,34% respectively. For the water application rate show that on 360° and 270° high water dept near to sprinkler and decreased sharply with the increasing distance from the sprinkler, while on 180° and 90°, high water dept increase in 1.3 meters from the sprinkler and then decrease at end of wetted area. Weather influence, causing low efficiency of distribution uniformity and coefficient uniformity. By this individual sprinkler evaluation, the irrigation system uniformity can be an input for an engineer to ensuring proper spacing is used in design and installation to meet the maximum irrigation efficiency.

Effects of superimposed dual-frequency (13.56/2 MHz) inductively coupled plasma source on the uniformity of Ar/CF₄ plasma

Yang, Kyung Chae,Shin, Ye Ji,Tak, Hyun Woo,Lee, Wonseok,Lee, Seung Bae,Yeom, Geun Young Pergamon Press [etc.] 2019 Vacuum Vol.168 No.-

<P><B>Abstract</B></P> <P>As one of the methods for controlling the plasma uniformity, superimposed dual frequencies of 13.56 and 2 MHz were used on an inductively coupled plasma (ICP) source, and the effects of the superimposed dual-frequency ICP on the plasma and etch uniformities were investigated and compared with a conventional single-frequency ICP operation at 13.56 MHz using Ar/CF<SUB>4</SUB>. The superimposed dual-frequency ICP operated at 13.56 and 2 MHz improved the plasma uniformity compared to the single-frequency ICP for both Ar and Ar/CF<SUB>4</SUB> by improving the plasma density near the center region of the wafer close to the edge region. In addition, for Ar plasma, a change in the power ratio of 2/13.56 MHz during the superimposed dual-frequency operation changed the EEDF of the plasma and the IED toward the wall. When SiO<SUB>2</SUB> was etched using Ar/CF<SUB>4</SUB> with the superimposed dual-frequency ICP while biasing the substrate with a separate radio frequency power of 12.56 MHz, similar to the results on the plasma uniformity, the SiO<SUB>2</SUB> etch uniformity within a 300 mm diameter wafer was improved by using the superimposed dual-frequency ICP operated at 13.56 and 2 MHz, as compared to that using a single-frequency ICP of 13.56 MHz.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The superimposed dual-frequency ICP operated at 13.56 and 2 MHz improved the plasma uniformity by improving plasma density near the center region of the wafer close to the edge region. </LI> <LI> Also when SiO<SUB>2</SUB> was etched using Ar/CF<SUB>4</SUB> while biasing the substrate with a separate RF power, the ICP operated using superimposed dual frequencies showed a better etch uniformity. </LI> <LI> Using superimposed dual frequencies of 13.56 and 2 MHz showed a better plasma and etch uniformity. </LI> </UL> </P>

A Improved Scene based Non-uniformity Correction Algorithm for Infrared Camera

Ho-Jin Hyun(현호진),Byung-In Choi(최병인) 한국컴퓨터정보학회 2018 韓國컴퓨터情報學會論文誌 Vol.23 No.1

In this paper, we propose an efficient scene based non-uniformity correction algorithm which performs the offset correction using the uniform obtained from input scenes for Infrared camera. In general, pixel outputs of a infrared detector can not be uniform. Therefore, the non-uniformity correction procedure need to be performed to make the image outputs uniform. A typical non-uniformity correction method uses a black body at the laboratory to obtain the output of the infrared detector’s pixels for two temperatures, HOT and COLD, and calculates the non-uniformity correction parameters. However, output characteristics of the Infrared detector changes while the Infrared camera is operated, the fixed pattern noise of the Infrared detector and dead pixels are generated. To remove the noise, the offset correction is generally performed. The offset correction procedure usually need the additional device such as a thermo-electric cooler, shutter, or non-uniformity correction lens. Therefore, we introduce a general scene based non-uniformity correction technique without additional equipment, and then we propose an improved non-uniformity correction algorithm based on image to solve the problem of the existing technique.

CFD simulation and optimization on airflow uniformity of material drying room used in steam blanching and hot-air vacuum drying equipment

Dong Wang,Libin Tan,Yuejin Yuan,Yuming Lu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.10

Airflow velocity uniformity in material drying room used in steam blanching and hot-air vacuum drying equipment is crucial for obtaining a good drying quality of fruits and vegetables. To analyze the airflow velocity uniformity and give the optimization design for improving the airflow uniformity, CFD method is used for the flow field analysis of material drying room and the velocity non-uniformity coefficient is used as the evaluation indicator for the velocity uniformity. Results show that the airflow velocity distribution in the material drying room at the original inlet airflow distribution chamber is relatively uneven and the airflow velocity nonuniformity coefficient in drying area is 34 %. For reducing the airflow velocity non-uniformity, the airflow velocity distribution of three structural modification directions with 12 designs in total are analyzed and compared. The minimum airflow velocity non-uniformity coefficient for adding a spoiler model, reducing the closed end width and adding nozzle baffles are 17.1 %, 30.2 %, 10.4 %, respectively. Through comparison, adding the nozzle baffle with a width of 11 mm at the rear end of each nozzle outlet is considered as the optimal designs to conduct the experimental validation. Experimental validation results shows the the relative error between the simulated value and the measured value is within 10 %, proving that the CFD prediction results is reliable and the research results can give a theoretical reference for the designers to evaluate and optimize the structure of inlet airflow distribution chamber for improving the airflow uniformity in drying area.

SPECT/CT에서 CT를 기반으로 한 Attenuation Correction의 정확도 평가

김승정,김재일,김정수,김태엽,김수미,우재룡,이재성,김유경,Kim, Seung Jeong,Kim, Jae Il,Kim, Jung Soo,Kim, Tae Yeop,Kim, Soo Mee,Woo, Jae Ryong,Lee, Jae Sung,Kim, Yoo Kyeong 대한핵의학기술학회 2013 핵의학 기술 Vol.17 No.1

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. Purpose: In this study, we evaluated the accuracy of CT-based attenuation correction (AC) under the conventional CT protocol (140 kVp, on average 50-60 keV) by comparing the SPECT image qualities of different energy of radioisotopes, $^{201}Tl,\;^{99m}Tc$ and $^{131}I$. Materials and Methods: Using a cylindrical phantom, three different SPECT scans of $^{201}Tl$ (70 keV, 55.5 MBq), $^{99m}Tc$ (140 keV, 281.2 MBq) and $^{131}I$ (364 keV, 96.2 MBq) were performed. The CT image was obtained with 140 kVp and 2.5 mA in GE Hawkeye 4. The OSEM reconstruction algorithm was performed with 2 iterations and 10 subsets. The experiments were performed in the 4 different conditions; non-AC and non-scatter correction (SC), only AC, only SC, AC and SC in terms of uniformity and center to peripheral ratio (CPR). Results: The uniformity was calculated from the uniform whole region in the reconstructed images. For $^{201}Tl$ and $^{99m}Tc$, the uniformities were improved by about 10-20% AC was applied, but these were decreased by about 2% as SC was applied. The uniformity of $^{131}I$ was slightly increased as both AC and SC were applied. The CPR of the reconstructed image was close to one, when AC was applied for $^{201}Tl$ and $^{99m}Tc$ scans and $^{131}I$ was distant from 1 and that is only AC. Conclusion: The image uniformity improved by AC on low energy likely to $^{201}Tl$ and $^{99m}Tc$. However, image uniformity of high energy such as $^{131}I$ was improved, when both AC and SC was applied.

NEW EVALUATION METHODS FOR RADIAL UNIFORMITY IN NEUTRON TRANSMUTATION DOPING

HAKSUNG KIM,JAE-YONG LIM,CHEOL HO PYEON,TSUYOSHI MISAWA,SEIJI SHIROYA,SANG-JUN PARK,MYONG-SEOP KIM,SOO-YOUL OH,BYUNG-JIN JUN 한국원자력학회 2010 Nuclear Engineering and Technology Vol.42 No.4

Recently, the neutron irradiation for large diameter silicon (Si)-ingots of more than 8" diameter is requested to satisfy the demand for the neutron transmutation doping silicon (NTD-Si). By increasing the Si-ingot diameter, the radial non-uniformity becomes larger due to the neutron attenuation effect, which results in a limit of the feasible diameter of the Si-ingot. The current evaluation method has a certain limit to precisely evaluate the radial uniformity of Si-ingot because the current evaluation method does not consider the effect of the Si-ingot diameter on the radial uniformity. The objective of this study is to propose a new evaluation method of radial uniformity by improving the conventional evaluation approach. To precisely predict the radial uniformity of a Si-ingot with large diameter, numerical verification is conducted through comparison with the measured data and introducing the new evaluation method. A new concept of a gradient is introduced as an alternative approach of radial uniformity evaluation instead of the radial resistivity gradient (RRG) interpretation. Using the new concept of gradient, the normalized reaction rate gradient (NRG) and the surface normalized reaction rate gradient (SNRG) are described. By introducing NRG, the radial uniformity can be evaluated with one certain standard regardless of the ingot diameter and irradiation condition. Furthermore, by introducing SNRG, the uniformity on the Si-ingot surface, which is ignored by RRG and NRG, can be evaluated successfully. Finally, the radial uniformity flattening methods are installed by the stainless steel thermal neutron filter and additional Si-pipe to reduce SNRG.

NEW EVALUATION METHODS FOR RADIAL UNIFORMITY IN NEUTRON TRANSMUTATION DOPING

Kim, Hak-Sung,Lim, Jae-Yong,Pyeon, Cheol-Ho,Misawa, Tsuyoshi,Shiroya, Seiji,Park, Sang-Jun,Kim, Myong-Seop,Oh, Soo-Youl,Jun, Byung-Jin Korean Nuclear Society 2010 Nuclear Engineering and Technology Vol.42 No.4

Recently, the neutron irradiation for large diameter silicon (Si)-ingots of more than 8" diameter is requested to satisfy the demand for the neutron transmutation doping silicon (NTD-Si). By increasing the Si-ingot diameter, the radial non-uniformity becomes larger due to the neutron attenuation effect, which results in a limit of the feasible diameter of the Si-ingot. The current evaluation method has a certain limit to precisely evaluate the radial uniformity of Si-ingot because the current evaluation method does not consider the effect of the Si-ingot diameter on the radial uniformity. The objective of this study is to propose a new evaluation method of radial uniformity by improving the conventional evaluation approach. To precisely predict the radial uniformity of a Si-ingot with large diameter, numerical verification is conducted through comparison with the measured data and introducing the new evaluation method. A new concept of a gradient is introduced as an alternative approach of radial uniformity evaluation instead of the radial resistivity gradient (RRG) interpretation. Using the new concept of gradient, the normalized reaction rate gradient (NRG) and the surface normalized reaction rate gradient (SNRG) are described. By introducing NRG, the radial uniformity can be evaluated with one certain standard regardless of the ingot diameter and irradiation condition. Furthermore, by introducing SNRG, the uniformity on the Si-ingot surface, which is ignored by RRG and NRG, can be evaluated successfully. Finally, the radial uniformity flattening methods are installed by the stainless steel thermal neutron filter and additional Si-pipe to reduce SNRG.