• 대한방사선기술학회지:방사선기술과학
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• 제45권5호
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• pp.397-405
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• 2022

Computed radiography (CR) systems, which convert an analog signal recorded on a cassette into a digital image, combine the characteristics of analog and digital imaging systems. Compared to digital radiography (DR) systems, CR systems have presented difficulties in evaluating system performance because of their lower detective quantum efficiency, their lower signal-to-noise ratio (SNR), and lower modulation transfer function (MTF). During the step of energy-storing and reading out, a baseline offset occurs in the edge area and makes low-frequency overestimation. The low-frequency offset component in the line spread function (LSF) critically affects the MTF and other image-analysis or qualification processes. In this study, we developed the method of baseline correction using mathematical morphology to determine the LSF and MTF of CR systems accurately. We presented a baseline correction that used a morphological filter to effectively remove the low-frequency offset from the LSF. We also tried an MTF evaluation of the CR system to demonstrate the effectiveness of the baseline correction. The MTF with a 3-pixel structuring element (SE) fluctuated since it overestimated the low-frequency component. This overestimation led the algorithm to over-compensate in the low-frequency region so that high-frequency components appeared relatively strong. The MTFs with between 11- and 15-pixel SEs showed little variation. Compared to spatial or frequency filtering that eliminated baseline effects in the edge spread function, our algorithm performed better at precisely locating the edge position and the averaged LSF was narrower.

• Journal of Radiation Protection and Research
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• 제48권1호
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• pp.9-14
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• 2023

Background: The detectors of both computed radiography (CR) and direct digital radiography (DR) have a wide dynamic range that could tolerate high values of exposure factors without an adverse effect on image quality. Therefore, this study aims to assess patient radiation dose and proposes institutional diagnostic reference levels (DRLs) for two teaching hospitals in Ghana. Materials and Methods: CR and DR systems were utilized in this study from two teaching hospitals. The CR system was manufactured by Philips Medical Systems DMC GmbH, while the DR system was manufactured by General Electric. The entrance skin doses (ESDs) were calculated using the standard equation and the tube output measurements. Free-in-air kerma (µGy) was measured using a calibrated radiation dosimeter. The proposed institutional DRLs were estimated using 75^th percentiles values of the estimated ESDs for nine radiographic projections. Results and Discussion: The calculated DRLs were 0.4, 1.6, 3.4, 0.5, 0.4, 1.1, 1.0, 1.2, and 1.7 mGy for chest posteroanterior (PA), lumbar spine anteroposterior (AP), lumbar spine lateral (LAT), cervical spine AP, cervical spine LAT, skull PA, pelvis AP, and abdomen AP, respectively in CR system. In the DR system, the values were 0.3, 1.6, 3.1, 0.4, 0.3, 0.7, 0.6, 0.9, and 1.3 for chest PA, lumbar spine AP, lumbar spine LAT, cervical spine AP, cervical spine LAT, skull PA, pelvis AP, and abdomen AP, respectively. Conclusion: Institutional DRLs in nine radiographic projections have been proposed for two teaching hospitals in Ghana for the first time. The proposed DRLs will serve as baseline data for establishing local DRLs in the hospitals and will be a valuable tool in optimizing patient doses.

• 대한방사선기술학회지:방사선기술과학
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• 제28권4호
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• pp.273-277
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• 2005

디지털 의료 영상의 빠른 발전은 새로운 기술-비정질 평판형 측정기-에 대한 최적의 기술이 동행되지 못했다. 이번 실험으로 비정질 평판형 측정기를 사용한 흉부 방사선 영상의 대한 환자선량과 영상의 화질에 대하여 비교하였다. 모든 실험은 비정질 평판형 측정기를 사용하였다. 흉부 팬텀을 사용한 흉부 방사선영상은 관전압 $60{\sim}150\;kVp$에서 획득하였다. 이번 실험을 통하여 획득된 비정질 평판형 측정기를 사용한 X-선 에너지에 대한 영상의 질과 환자선량에 관련된 정보들을 보고한다. 이 정보는 비정질 평판형 측정기를 사용한 시스템에서 최적의 관전압의 선정에 효과적인 정보를 제공하며, 특히 일반적인 흉부 검사에 적용될 수 있을 것이다.

• 대한족부족관절학회지
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• 제16권1호
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• pp.53-57
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• 2012

Purpose: To study computerized measurements of angular parameters on 100% and 150% resized digital radiography of hallux valgus deformity Materials and Methods: 30 digital radiography of standing foot anteroposterior view of hallux valgus patients were included. Two observers(A, B) independently measured hallux valgus angle (HVA), 1-2 intermetatarsal angle (IMA), and distal metatarsal articular angle (DMAA) in two times on both 100%-size and 150% magnified images respectively, using computerized measurement software tools. The results were interpreted with the statistical software program, Statistical Analysis System, version 9.2. Results: In repeated measurements of each observer, measurements on 150% magnified image showed no differences of all three parameters and with 100%-size image, there were differences of HVA (observer A) and 1-2 IMA (observer B) (p>0.05). When testing interobserver reliability, both observers showed differences in measurement of HVA and DMAA (p<0.05), but no differences in measurement of 1-2 IMA in both images. Within the 95% confidence interval, limits of error of measurements between two observers on HVA, IMA and DMAA were $2.7^{\circ}$ $1.4^{\circ}$ and $5.0^{\circ}$ respectively in 100%-size images, and $2.6^{\circ}$, $1.6^{\circ}$ and $4.7^{\circ}$ respectively in 150% magnified images. Conclusion: In computerized measurements for angular parameters of hallux valgus with digital radiography, 150% magnified images showed intraobserver reliability. Both 100% and 150% magnified images failed to show interobserver reliability. Measurement of 1-2 IMA in both 100% and 150% images showed less interobserver error.

• 대한의용생체공학회:의공학회지
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• 제3권1호
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• pp.49-50
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• 1982

In this paper, the information capacity, the intergrate performance measure of digital radiography system has been quantitatively analyzed. The effect of various factors affecting the information capacity of the digital radiography system in multi-stage detection processes has been considered and analyzed in detail. The results show that the more information capacity can be obtained with the smaller detector cell area, despite of the reduced signal to noise ratio due to the reduced number of X-ray photons per detector cell. Considering the limit of human visual acuity. however, the sufficient resolution will be obtained when the detector cell size in 0.2${\times}$0.2mm with 8 bit quantizaion. And also the results indicates that the information capacity may be severely reduced by the mixture of electric noise in final read-out stage.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2006년도 제33회 추계학술대회 발표논문집
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• pp.40-40
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• 2006

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.655-668
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• 2023

In radiography, an antiscatter grid is a well-known device for eliminating unexpected x-ray scatter. We investigate a new stationary grid artifact suppression method based on a nonsubsampled contourlet transform (NSCT) incorporated with Gaussian band-pass filtering. The proposed method has an advantage that extracts the Moiré components while minimizing the loss of image information and apply the prior information of Moiré component positions in multi-decomposition sub-band images. We implemented the proposed algorithm and performed a simulation and an experiment to demonstrate its viability. We did this experiment using an x-ray tube (M-113T, Varian, focal spot size: 0.1 mm), a flat-panel detector (ROSE-M Sensor, Aspenstate, pixel dimension: 3032 × 3800 pixels, pixel size: 0.076 mm), and carbon graphite-interspaced grids (JPI Healthcare, 18 cm × 24 cm, line density: 103 LP/inch and 150 LP/inch, ratio: 5:1, focal distance: 65 cm). Our results indicate that the proposed method successfully suppressed grid artifacts by reducing them without either reducing the spatial resolution or causing negative side effects. Consequently, we anticipate that the proposed method can improve image acquisition in a stationary grid x-ray system as well as in extended x-ray imaging.

• 동력기계공학회지
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• 제13권5호
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• pp.95-102
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• 2009

A steam generator (boiler) in thermal power plants, consisting of more than 30,000 parts and components, can lead to the plant shutdown with damage to even the small part of the components; esp., like weld failures on boiler tubes. Consequently it is greatly demanded to improve the quality of the weld on the boiler tube for the stable operation of the power plants. Because of the feature of the welding, which is done past by melting the work pieces and adding a filler material that cools to become a strong coalescence, there is a great possibility that weld failures take place. As a result, it is regulated to make a non-destructive testing, like radiography test, to detect defects and flaws in the weld. The current film radiography test provides a lower image quality exceeding 2.0% of a basic quality level for a penetrameter, it is very likely to fail to detect micro defect. As a result, the prevention for the boiler tube failure has not been made effectively. In this study, computed radiography technology has been applied as a digital radiography test to the boiler tube weld, and Se-75 radiation source was used to improve the image quality, instead of Ir-192 source. As a result of this study, it is proven to save the time and cost for test and to enhance the quality level of penetrameter penetrating image, which enables to upgrade the quality of radiography test to the boiler tube weld.

• 한국방사선학회논문지
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• 제2권2호
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• pp.5-10
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• 2008

최근의 진단의료용 방사선영상은 대부분 디지털영상으로 변환되었으나, 영상획득을 위한 조사조건 등 영상화질에 영향을 미치는 요소들에 관련하여서는 여전히 대부분 필름-스크린 시스템의 기준을 그대로 따르고 있으며, 실정이다. 뿐만 아니라 획득된 디지털영상에 대한 객관적인 화질평가 또한 임상에서 적용되고 있지 않은 실정이다. 본 연구에서는 디지털영상의 화질을 평가함에 있어 기본이 되는 요소인 화질의 균일성, NPS(noise power spectrum), MTF(modulation transfer function), NEQ(noise equivalent quanta) 등에 대한 평가를 임상에서 활용할 수 있도록 사용자 친화적인 윈도우 환경의 디지털영상화질 평가 프로그램을 MatLab을 이용하여 개발하였다.

• 대한방사선기술학회지:방사선기술과학
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• 제44권1호
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• pp.39-46
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• 2021

This study confirmed the usefulness of the copper filter according to the mode change by comparing and analyzing the energy change according to the application of the copper filter and the change in effective dose and image quality according to the distance to the subject in the DR(Digital Radiography) system. The average energy increased when the copper filter was applied and the reduction rate by 50% of mAs was increased as the thickness of the copper filter increased according to the application of the 10 kVp rule in AEC mode. The effective dose decreased as the thickness increased when the copper filter was applied in AEC(Automatic Exposure Control) mode and manual mode according to the application of the 10 kVp rule, and the decrease rate decreased with increasing 10 kVp increments. As a result of analyzing the dicom images for AEC mode and manual mode with Image J. the PSNR(Peak Signal to Noise Ratio) values were approximate values of less than 30 dB for each mode and for each copper filter thickness. When the copper filter was applied, the average energy increased, so when the 10 kVp rule was applied, the mAs for each mode could be reduced, and the effective dose could also be reduced. However, as the distance and tube voltage increased, the reduction rate of mAs decreased, and the quality of the image was found to decrease when the copper filter was applied, but there was no difference in quality of the image when the copper filter thickness increased.