• Title/Summary/Keyword: digital accuracy

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Development of Regularized Expectation Maximization Algorithms for Fan-Beam SPECT Data (부채살 SPECT 데이터를 위한 정칙화된 기댓값 최대화 재구성기법 개발)

  • Kim, Soo-Mee;Lee, Jae-Sung;Lee, Soo-Jin;Kim, Kyeong-Min;Lee, Dong-Soo
    • The Korean Journal of Nuclear Medicine
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    • v.39 no.6
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    • pp.464-472
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    • 2005
  • Purpose: SPECT using a fan-beam collimator improves spatial resolution and sensitivity. For the reconstruction from fan-beam projections, it is necessary to implement direct fan-beam reconstruction methods without transforming the data into the parallel geometry. In this study, various fan-beam reconstruction algorithms were implemented and their performances were compared. Materials and Methods: The projector for fan-beam SPECT was implemented using a ray-tracing method. The direct reconstruction algorithms implemented for fan-beam projection data were FBP (filtered backprojection), EM (expectation maximization), OS-EM (ordered subsets EM) and MAP-EM OSL (maximum a posteriori EM using the one-step late method) with membrane and thin-plate models as priors. For comparison, the fan-beam protection data were also rebinned into the parallel data using various interpolation methods, such as the nearest neighbor, bilinear and bicubic interpolations, and reconstructed using the conventional EM algorithm for parallel data. Noiseless and noisy projection data from the digital Hoffman brain and Shepp/Logan phantoms were reconstructed using the above algorithms. The reconstructed images were compared in terms of a percent error metric. Results: for the fan-beam data with Poisson noise, the MAP-EM OSL algorithm with the thin-plate prior showed the best result in both percent error and stability. Bilinear interpolation was the most effective method for rebinning from the fan-beam to parallel geometry when the accuracy and computation load were considered. Direct fan-beam EM reconstructions were more accurate than the standard EM reconstructions obtained from rebinned parallel data. Conclusion: Direct fan-beam reconstruction algorithms were implemented, which provided significantly improved reconstructions.

Relationship Analysis between Lineaments and Epicenters using Hotspot Analysis: The Case of Geochang Region, South Korea (핫스팟 분석을 통한 거창지역의 선구조선과 진앙의 상관관계 분석)

  • Jo, Hyun-Woo;Chi, Kwang-Hoon;Cha, Sungeun;Kim, Eunji;Lee, Woo-Kyun
    • Korean Journal of Remote Sensing
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    • v.33 no.5_1
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    • pp.469-480
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    • 2017
  • This study aims to understand the relationship between lineaments and epicenters in Geochang region, Gyungsangnam-do, South Korea. An instrumental observation of earthquakes has been started by Korea Meteorological Administration (KMA) since 1978 and there were 6 earthquakes with magnitude ranging 2 to 2.5 in Geochang region from 1978 to 2016. Lineaments were extracted from LANDSAT 8 satellite image and shaded relief map displayed in 3-dimension using Digital Elevation Model (DEM). Then, lineament density was statistically examined by hotspot analysis. Hexagonal grids were generated to perform the analysis because hexagonal pattern expresses lineaments with less discontinuity than square girds, and the size of the grid was selected to minimize a variance of lineament density. Since hotspot analysis measures the extent of clustering with Z score, Z scores computed with lineaments' frequency ($L_f$), length ($L_d$), and intersection ($L_t$) were used to find lineament clusters in the density map. Furthermore, the Z scores were extracted from the epicenters and examined to see the relevance of each density elements to epicenters. As a result, 15 among 18 densities,recorded as 3 elements in 6 epicenters, were higher than 1.65 which is 95% of the standard normal distribution. This indicates that epicenters coincide with high density area. Especially, $L_f$ and $L_t$ had a significant relationship with epicenter, being located in upper 95% of the standard normal distribution, except for one epicenter in $L_t$. This study can be used to identify potential seismic zones by improving the accuracy of expressing lineaments' spatial distribution and analyzing relationship between lineament density and epicenter. However, additional studies in wider study area with more epicenters are recommended to promote the results.

The Accuracy Evaluation according to Dose Delivery Interruption and Restart for Volumetric Modulated Arc Therapy (용적변조회전 방사선치료에서 선량전달의 중단 및 재시작에 따른 정확성 평가)

  • Lee, Dong Hyung;Bae, Sun Myung;Kwak, Jung Won;Kang, Tae Young;Back, Geum Mun
    • The Journal of Korean Society for Radiation Therapy
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    • v.25 no.1
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    • pp.77-85
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    • 2013
  • Purpose: The accurate movement of gantry rotation, collimator and correct application of dose rate are very important to approach the successful performance of Volumetric Modulated Arc Therapy (VMAT), because it is tightly interlocked with a complex treatment plan. The interruption and restart of dose delivery, however, are able to occur on treatment by various factors of a treatment machine and treatment plan. If unexpected problems of a treat machine or a patient interrupt the VMAT, the movement of treatment machine for delivering the remaining dose will be restarted at the start point. In this investigation, We would like to know the effect of interruptions and restart regarding dose delivery at VMAT. Materials and Methods: Treatment plans of 10 patients who had been treated at our center were used to measure and compare the dose distribution of each VMAT after converting to a form of digital image and communications in Medicine (DICOM) with treatment planning system (Eclipse V 10.0, Varian, USA). We selected the 6 MV photon energy of Trilogy (Varian, USA) and used OmniPro I'mRT system (V 1.7b, IBA dosimetry, Germany) to analyze the data that were acquired through this measurement with two types of interruptions four times for each case. The door interlock and the beam-off were used to stop and then to restart the dose delivery of VMAT. The gamma index in OmniPro I'mRT system and T-test in Microsoft Excel 2007 were used to evaluate the result of this investigation. Results: The deviations of average gamma index in cases with door interlock, beam-off and without interruption on VMAT are 0.141, 0.128 and 0.1. The standard deviations of acquired gamma values are 0.099, 0.091, 0.071 and The maximum gamma value in each case is 0.413, 0.379, 0.286, respectively. This analysis has a 95-percent confidence level and the P-value of T-test is under 0.05. Gamma pass rate (3%, 3 mm) is acceptable in all of measurements. Conclusion: As a result, We could make sure that the interruption of this investgation are not enough to seriously affect dose delivery of VMAT by analyzing the measured data. But this investigation did not reflect all cases about interruptions and errors regarding the movement of a gantry rotation, collimator and patient So, We should continuously maintain a treatment machine and program to deliver the accurate dose when we perform the VMAT for the many kinds of cancer patients.

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The Improvement of Real-time Updating Methods of the National Base Map Using Building Layout Drawing (건물배치도를 이용한 국가기본도 수시수정 방법 개선)

  • Shin, Chang Soo;Park, Moon Jae;Choi, Yun Soo;Baek, kyu Yeong;Kim, Jaemyeong
    • Journal of Cadastre & Land InformatiX
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    • v.48 no.1
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    • pp.139-151
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    • 2018
  • The National Base Map construction consists of the regular correction work of dividing the whole country into two regions and carrying out the modification Plotting by aerial photographs every two years as well as the real time updating work of correcting the major change feature within two weeks by the field survey and the As-Built Drawing. In the case of the Building Layout Drawing of Korea Real estate Administration intelligence System(KRAS) used for real time updating work of the National base map, the coordinate transformation error is included in the positional error when applied to the National Base Map based on the World Geodetic Reference System as the coordinate system based on the Regional Geodetic Reference System. In addition, National Base Map is registered based on the outline(eaves line) of the building in the Digital Topographic Map, and the Cadastral and Architecture are registered based on the building center line. Therefore, the Building Object management standard is inconsistent. In order to investigate the improvement method, the network RTK survey was conducted directly on a location of the Building Layout Drawing of Korea Real estate Administration intelligence System(KRAS) and the problems were analyzed by comparing with the plane plotting position reference in National Base Map. In the case of the general structure with the difference on the Building center line and the eaves line, beside the location information was different also the difference in the ratio of the building object was different between Building center line and the eave. In conclusion, it is necessary to provide the Base data of the double layer of the Building center line and the outline of the building(eaves line) in order to utilize the Building Layout Drawing of Korea Real estate Administration intelligence System(KRAS). In addition, it is necessary to study an organic map update process that can acquire the up-to-dateness and the accuracy at the same time.

Comparison of Three Kinds of Methods on Estimation of Forest Carbon Stocks Distribution Using National Forest Inventory DB and Forest Type Map (국가산림자원조사 DB와 임상도를 이용한 산림탄소저장량 공간분포 추정방법 비교)

  • Kim, Kyoung-Min;Roh, Young-Hee;Kim, Eun-Sook
    • Journal of the Korean Association of Geographic Information Studies
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    • v.17 no.4
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    • pp.69-85
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    • 2014
  • Carbon stocks of NFI plots can be accurately estimated using field survey information. However, an accurate estimation of carbon stocks in other unsurveyed sites is very difficult. In order to fill this gap, various spatial information can be used as an ancillary data. In South Korea, there is the 1:5,000 forest type map that was produced by digital air-photo interpretation and field survey. Because this map contains very detailed forest information, it can be used as the high-quality spatial data for estimating carbon stocks. In this study, we compared three upscaling methods based on the 1:5,000 forest type map and 5th national forest inventory data. Map algebra(method 1), RK(Regression Kriging)(method 2), and GWR(Geographically Weighted Regression)(method 3) were applied to estimate forest carbon stock in Chungcheong-nam Do and Daejeon metropolitan city. The range of carbon stocks from method 2(1.39~138.80 tonC/ha) and method 3(1.28~149.98 tonC/ha) were more similar to that of previous method(1.56~156.40 tonC/ha) than that of method 1(0.00~93.37 tonC/ha). This result shows that RK and GWR considering spatial autocorrelation can show spatial heterogeneity of carbon stocks. We carried out paired t-test for carbon stock data using 186 sample points to assess estimation accuracy. As a result, the average carbon stocks of method 2 and field survey method were not significantly different at p=0.05 using paired t-test. And the result of method 2 showed the lowest RMSE. Therefore regression kriging method is useful to consider spatial variations of carbon stocks distribution in rugged terrain and complex forest stand.

A 1.1V 12b 100MS/s 0.43㎟ ADC based on a low-voltage gain-boosting amplifier in a 45nm CMOS technology (45nm CMOS 공정기술에 최적화된 저전압용 이득-부스팅 증폭기 기반의 1.1V 12b 100MS/s 0.43㎟ ADC)

  • An, Tai-Ji;Park, Jun-Sang;Roh, Ji-Hyun;Lee, Mun-Kyo;Nah, Sun-Phil;Lee, Seung-Hoon
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.7
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    • pp.122-130
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    • 2013
  • This work proposes a 12b 100MS/s 45nm CMOS four-step pipeline ADC for high-speed digital communication systems requiring high resolution, low power, and small size. The input SHA employs a gate-bootstrapping circuit to sample wide-band input signals with an accuracy of 12 bits or more. The input SHA and MDACs adopt two-stage op-amps with a gain-boosting technique to achieve the required DC gain and high signal swing range. In addition, cascode and Miller frequency-compensation techniques are selectively used for wide bandwidth and stable signal settling. The cascode current mirror minimizes current mismatch by channel length modulation and supply variation. The finger width of current mirrors and amplifiers is laid out in the same size to reduce device mismatch. The proposed supply- and temperature-insensitive current and voltage references are implemented on chip with optional off-chip reference voltages for various system applications. The prototype ADC in a 45nm CMOS demonstrates the measured DNL and INL within 0.88LSB and 1.46LSB, respectively. The ADC shows a maximum SNDR of 61.0dB and a maximum SFDR of 74.9dB at 100MS/s, respectively. The ADC with an active die area of $0.43mm^2$ consumes 29.8mW at 100MS/s and a 1.1V supply.

An Area-Efficient Time-Shared 10b DAC for AMOLED Column Driver IC Applications (AMOLED 컬럼 구동회로 응용을 위한 시분할 기법 기반의 면적 효율적인 10b DAC)

  • Kim, Won-Kang;An, Tai-Ji;Lee, Seung-Hoon
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.5
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    • pp.87-97
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    • 2016
  • This work proposes a time-shared 10b DAC based on a two-step resistor string to minimize the effective area of a DAC channel for driving each AMOLED display column. The proposed DAC shows a lower effective DAC area per unit column driver and a faster conversion speed than the conventional DACs by employing a time-shared DEMUX and a ROM-based two-step decoder of 6b and 4b in the first and second resistor string. In the second-stage 4b floating resistor string, a simple current source rather than a unity-gain buffer decreases the loading effect and chip area of a DAC channel and eliminates offset mismatch between channels caused by buffer amplifiers. The proposed 1-to-24 DEMUX enables a single DAC channel to drive 24 columns sequentially with a single-phase clock and a 5b binary counter. A 0.9pF sampling capacitor and a small-sized source follower in the input stage of each column-driving buffer amplifier decrease the effect due to channel charge injection and improve the output settling accuracy of the buffer amplifier while using the top-plate sampling scheme in the proposed DAC. The proposed DAC in a $0.18{\mu}m$ CMOS shows a signal settling time of 62.5ns during code transitions from '$000_{16}$' to '$3FF_{16}$'. The prototype DAC occupies a unit channel area of $0.058mm^2$ and an effective unit channel area of $0.002mm^2$ while consuming 6.08mW with analog and digital power supplies of 3.3V and 1.8V, respectively.

Development of a Small Gamma Camera Using NaI(T1)-Position Sensitive Photomultiplier Tube for Breast Imaging (NaI (T1) 섬광결정과 위치민감형 광전자증배관을 이용한 유방암 진단용 소형 감마카메라 개발)

  • Kim, Jong-Ho;Choi, Yong;Kwon, Hong-Seong;Kim, Hee-Joung;Kim, Sang-Eun;Choe, Yearn-Seong;Lee, Kyung-Han;Kim, Moon-Hae;Joo, Koan-Sik;Kim, Byuug-Tae
    • The Korean Journal of Nuclear Medicine
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    • v.32 no.4
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    • pp.365-373
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    • 1998
  • Purpose: The conventional gamma camera is not ideal for scintimammography because of its large detector size (${\sim}500mm$ in width) causing high cost and low image quality. We are developing a small gamma camera dedicated for breast imaging. Materials and Methods: The small gamma camera system consists of a NaI (T1) crystal ($60 mm{\times}60 mm{\times}6 mm$) coupled with a Hamamatsu R3941 Position Sensitive Photomultiplier Tube (PSPMT), a resister chain circuit, preamplifiers, nuclear instrument modules, an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a standard resistive charge division which multiplexes the 34 cross wire anode channels into 4 signals ($X^+,\;X^-,\;Y^+,\;Y^-$). Those signals were individually amplified by four preamplifiers and then, shaped and amplified by amplifiers. The signals were discriminated ana digitized via triggering signal and used to localize the position of an event by applying the Anger logic. Results: The intrinsic sensitivity of the system was approximately 8,000 counts/sec/${\mu}Ci$. High quality flood and hole mask images were obtained. Breast phantom containing $2{\sim}7 mm$ diameter spheres was successfully imaged with a parallel hole collimator The image displayed accurate size and activity distribution over the imaging field of view Conclusion: We have succesfully developed a small gamma camera using NaI(T1)-PSPMT and nuclear Instrument modules. The small gamma camera developed in this study might improve the diagnostic accuracy of scintimammography by optimally imaging the breast.

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The Measurement of Normal Talus in Korean Cadaver (한국인 사체에서의 정상 거골의 실측)

  • Ha, Dong-Jun;Gwak, Heui-Chul;Kim, Jeon-Gyo;Kim, Jung-Han;Lee, Chang-Rak;Kim, Young-Jun;Lee, Jeong-Han;Ha, Byung-Ho;Kim, Ui-Cheol
    • Journal of Korean Foot and Ankle Society
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    • v.20 no.4
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    • pp.163-169
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    • 2016
  • Purpose: To investigate the measured values of the talus in Koreans. Materials and Methods: We measured 88 tali from 44 cadavers that have been donated between December 2012 and December 2015. Of the cadavers, 27 were male and 17 were female. Their mean age was 73 years. The length and width of the talus were measured using a digital goniometer and vernier caliper. Results: The values of cadaveric measurement, mean maximal width and length, width and length of the dome anterior, width and length of the posterior facet, height and length of the trochlear medial facet, and height and length of the trochlear lateral facet were $43.6{\pm}2.6mm$, $56.5{\pm}3.3mm$, $32.5{\pm}2.0mm$, $42.2{\pm}2.7mm$, $22.2{\pm}2.2mm$, $34.7{\pm}2.0mm$, $15.3{\pm}1.3mm$, $33.3{\pm}2.9mm$, $25.3{\pm}3.3mm$, and $30.8{\pm}2.4mm$ for men and $38.9{\pm}1.6mm$, $53.6{\pm}2.4mm$, $27.9{\pm}2.1mm$, $37.4{\pm}3.2mm$, $20.6{\pm}0.8mm$, $31.9{\pm}1.2mm$, $13.6{\pm}2.6mm$, $28.4{\pm}2.5mm$, $24.9{\pm}2.1mm$, and $28.9{\pm}1.4mm$ for women, respectively. The size of the talus showed an accuracy of 86% when anteroposterior diameter was greater than 59 mm. A difference in the size of the right and left talus was not observed. The mean inclination and declination angles were $24.4^{\circ}{\pm}4.2^{\circ}$ and $28.2^{\circ}{\pm}5.4^{\circ}$ for men, and $24.6^{\circ}{\pm}3.6^{\circ}$ and $24.7^{\circ}{\pm}6.7^{\circ}$ for women (p=0.980, p=0.018), respectively, at least $15^{\circ}$, which showed a big difference for every object up to $37^{\circ}$. Conclusion: This paper, to the best of our knowledge, is the first study to measure the talus in Koreans. There were differences by gender and ethnicity in the in measured talus values. The measurements were smaller than European-Americans and greater than Japanese.

MICROLEAKAGE AND WATER STABILITY OF RESIN CEMENTS

  • Choi Sun-Young;Lee Sun-Hyung;Yang Jae-Ho;Han Jung-Suk
    • The Journal of Korean Academy of Prosthodontics
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    • v.41 no.3
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    • pp.369-378
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    • 2003
  • Statement of Problem: Recently, resin cements have become more widely used and have been accepted as prominent luting cements. Current resin cements exhibit less microleakage than conventional luting cements. However, the constant contact with water and exposure to occlusal forces increase microleakage even in resin cements inevitably. Most bonding resins have been modified to contain a hydrophilic resin such as 2-hydroxyethylmethacrylate (HEMA) to overcome some of the problems associated with the hydrophobic nature of bonding resins. By virtue of these modifications, bonding resins absorb a significant amount of water, and there may also be significant stresses at bonding interfaces, which may adversely affect the longevity of restorations. Therefore the reinforcement of water stability of resin cement is indispensable in future study. Purpose: This study was conducted to examine the influence of water retention on microleakage of two resin cements over the period of 6 months. Materials and Methods: 32 extracted human teeth were used to test the microleakage of a single full veneer crown. Two resin cements with different components and adhesive properties - Panavia F (Kuraray Co., Osaka, Japan) and Super-Bond C&B (Sun Medical Co., Kyoto, Japan)- were investigated. The storage medium was the physiological saline solution changed every week for 1 month, 3 months, and 6 months. One group was tested after storage for 1 day. At the end of the each storage period, all specimens were exposed to thermocycling from $5^{\circ}C$ to $55^{\circ}C$ of 500 cycles and chewing simulation of 50,000 cycles, and then stained with 50% silver nitrate solution. The linear penetration of microleakage was measured using a stereoscopic microscope at ${\times}40$ magnification and a digital traveling micrometer with an accuracy of ${\pm}3{\mu}m$. Values were analyzed using two-way ANOVA test, Duncan's multiple range tests (DMRT). Results : Statistically significant difference of microleakage was shown in the 3-month group compared with the1-day or 1-month group in both systems (p<0.05) and there were statistically significant differences in microleakage between the 3-month group and the 6-month group in both systems (p<0.05). The two systems showed different tendency in the course of increased microleakage during 3 months. In Panavia F, microleakage increased slowly throughout the periods. In Super-Bond C&B, there was no significant increase of microleakage for 1 month, but there was statistically significant increase of microleakage for the next 2 months. For the mean microleakage for each period, in the 3-month group, microleakage of Super-Bond C&B was significantly greater than that of Panavia F. On the other hand, in the 6-month group, microleakage of Panavia F was significantly greater than that of Super-Bond C&B (p<0.05). Conclusion: Within the limitation of this study, water retention of two different bonding systems influence microleakage of resin cements. Further studies with the longer observation periods in viro are required in order to investigate water stability and the bonding durability of the resin cement. CLINICAL IMPLICATIONS Microleakage at the Cement-tooth interfaces did not necessarily result in the failure of the crowns. But it is considered to be a major factor influening the longerity of restorations. Further clinical approaches for decreasing the amount of microleakage are required.