• Journal of radiological science and technology
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• v.33 no.3
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• pp.173-178
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• 2010

In projection radiography, two types of digital imaging systems are currently available, computed radiography (CR) and digital radiography (DR): a difference between them can be stated in terms of dose and image quality. In the Department of Radiology our hospital, a flat-panel DR equipment (Digital diagnost, Philips) and two CR systems (ADC Compact plus digitizer, AGFA) are employed. Eight standard radiographic examinations (Skull AP, Skull LAT, Chest PA, Chest LAT, Abdomen AP, L-spine AP, L-spine LAT, Pelvis AP) were considered: doses delivered to patients in terms of both entrance skin dose (ESD) were calculated and compared in order to study the dosimetric discrepancies between CR and DR. Assessment of image quality is undertaken by Consultant Radiologists to ensure that the quality criteria for diagnostic radiographic images of the European guidelines were met. Results showed that both ESD in DR are lower than that in CR; all images met the criteria in the European Guidelines for both modalities and were used for reporting by the radiologists. Since the operators are the same and the image quality is comparable in both modalities, this study shows that in the considered examinations, DR can perform better than CR from a dosimetric point of view.

• Korean Journal of Digital Imaging in Medicine
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• v.10 no.2
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• pp.23-31
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• 2008

Computed radiography(CR) has been widely used in the field of diagnostic radiography since digital X-ray image was introduced. The imaging performance of CR system was studied by analyzing the digital image data of the CR images which are the outcomes of the whole imaging system composed of image plate(IP), laser digitizer, analoge-digital convertor, and a given image processing unit. In this study, we used a conventional CR system made by Agfa. From the flat field image of 150$\times$150 image pixels, signal-to-noise ratio(SNR) was calculated. SNR of the CR image increases in proportion to logarithm value of the X-ray exposure irradiated on the IP. SNR is less than about 6 at the exposure below 0.2mR and is more than 10 at the exposure above 0.54mR. In our study, most of images obtained by the smaller exposures less than 2.0mR can not be readable. In general, the minimum value of the SNR ranges from 3 to 5. We obtained modulation transfer function(MTF) by analyzing the bar pattern image which was made under conditions as follows: X-ray tube potential was 55kVp, the IP exposure was 0.54 mR, and the distance between X-ray source to IP was 2m, where bar pattern was located on the IP. MTF is 23% at 2.5lp/mm spatial frequency. Provided that the MTF of noise equivalent modulation is 10%, the CR system has the limiting spatial resolution of 3.2lp/mm. If the image sharpness is evaluated by the spatial frequency where MTF is 50%. the corresponding spatial frequency is 0.5$\sim$0.75lp/mm. MTFA(Modulation Transfer Function Area) is 1.0lp/mm. Compared with the Fuji CR whose MTFA is 1.1lp/mm, Agfa CR in this study shows almost same MTFA performance.

• Journal of Radiation Protection and Research
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• v.35 no.1
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• pp.26-33
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• 2010

A computed Radiography (CR) system by use of reusable Image Plate (IP) offers a convenient and reliable way to replace a conventional film-screen system for NDT (non-destructive testing) field. The quality of a radiography to detect a defect of welded objects depends on the procedure embracing several factors such as measurement conditions, image plate type/class, radiation energy, radiation type, and source to image plate distance. Also, the ability of images to detect a flaw reduces with increasing object thickness. In the study, the properties of gamma ray source were summarized for NDT field and inspection images of CR image system manufactured by FUJI were acquired using $^{75}Se$ and $^{192}Ir$ with welded objects. We analyzed the gray scale of hole defect image by using XCAP image processing program and calculated the image contrast and SNR in definition. Also the sesitivities of image quality indicator(IQI) were calculated for hot and cooling tube image of $^{75}Se$ and $^{192}Ir$.

• Journal of Conservation Science
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• v.37 no.3
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• pp.220-231
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• 2021

The use of digital copies of film-based analog images and the introduction of digital radiographic imaging systems using image plates gradually replace the non-destructive radiationirradiation method of Cultural Heritage. The quality of images obtained from this technique is affected by conditions such as tube voltage, tube current, and exposure time, type of image acquisition medium, distance of the artifacts from the image acquisition medium, and thickness of artifacts. In this study, we evaluated the grayscale image obtained using GE's Computed Radiograhpy (CR) imaging system, the transmission characteristics of the X-ray source for each tree type (pine, chestnut, sawtooth oak, ginkgo) used in wooden Cultural Heritage, and the signal-to-noise ratio (SNR) and contrast. The GE's CR imaging were analyzed using the Duplex wire image quality indicator, line-pair gauges.

• Korean Journal of Digital Imaging in Medicine
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• v.7 no.1
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• pp.7-13
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• 2005

Purpose : Image plate (IP) is substituted for film in computed radiography. This study is to investigate into a variation of contrast and detail by the number used of image plate in computed radiography. Materials and Methods : A Contrast-Detail(CD)-RAD 2.0 phantom(Nijmegen hospital, The Netherlands) was used for this study. The computed radiography(CR) CD-RAD phantom images were acquired at 40 kVp, 160 mA, 1.6 mAs, and small focus with the Shimadzu general radiography UD-150B-10 system and Fuji FCR 5000 image process system with speed of 200. The IP used including once, 5000 times, and 10000 times also was used. The numerical value of image quality figures (IQF) was produced by CD-RAD analyser(the program is installed in the directory), and then contrast-detail curve was drawn. Results : In this study, the value of IQF was 3.53 in IP used once, 3.40 in 5000 times, and 3.22 in 10000 times. Conclusions : There was a variation of contrast-detail curve by the number used of IP with contrast-detail phantom in computed radiography. Therefore, it is necessary that the IP with lower IQF and a shift of contrast-detail curve to the lower left part is used.

• Journal of the Korean Society of Radiology
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• v.1 no.1
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• pp.31-37
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• 2007

The purpose of this research was to compare and analyze image quality for each Detector of CR(Computed Radiography) and DR(Digital Radiography). The results showed that CR(AGFA MD 4.0 General plate, JAPAN) was superior to DR(HOLOGIC nDirect Ray, USA) based on the quantitative values and comparison of MTF(Modulation Transfer Function), NPS(Noise Power Spectrum), Photon fluence and DQE(Detective Quantum Efficiency) which have been widely accepted for the estimation of CR and DR. Quantitative evaluations of CR and DR system were obtained and they may be very helpful for QA and QC of general X-ray systems.

• Korean Journal of Digital Imaging in Medicine
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• v.2 no.1
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• pp.92-95
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• 1996

Computed Radiography(CR) is a relatively new technology that relies on an image plate(IP) as an alternate x-ray sensor to screen/film. Standard CR cassettes do not have lead foil behind the IP to control scatter radiation. The result of this study indicate that such control is needed. In most screen/film cassettes, that lines the rear of the cassette eliminates back scatter radiation. This study was performed to Investigate on the effects of back scatter in CR images by size of exposure field, distance between the CR cassette and the wall of radiography room. 1. It showed artifacts from hinges and clips located on the back of CR cassette by back scatter radiation. 2. The greater effects of back scatter radiation in CR images was attributed to the greater size of exposure field and the longer distance between the CR cassette and the wall of radiography room.

• Progress in Medical Physics
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• v.20 no.4
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• pp.199-207
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• 2009

It is important to initialize Image Plate (IP) completely for removing residual latent image by sodium lamp for reliability and repeatability of computed radiography (CR) system. The purpose of this study was to evaluate latent images of computed radiography (CR) images respect to delay time after erasure of foregone latent image and its effect, and erasure level. Erasure thoroughness for CR acceptance test from American Association of Physicist in Medicine (AAPM) Report 93 (2006) was also evaluated. Measurements were made on a CR (Agfa CR 25; Agfa, BELGIUM) system. Chest postero-anterior (PA), Hand PA, L-spine lateral radiographs were chosen for evaluation. Chest phantom (3D-torso; CIRS, USA) was used for Chest PA and L-spine lateral radiography. For Hand PA radiography, projections was done without phantom. Except Hand PA radiographs, noise was increased with delay time, and ghost image was appeared on overexposed area. Effect of delay after erasure on latent image was not seen on naked eye, but standard deviation (SD) of pixel value on overexposed area was relatively higher than that of other areas. On Hand PA and Chest PA radiographs, noise were not occurred by adjustment of erasure level. On L-spine lateral images at lower erasure level than standard level, noise including ghost image were occurred because of high tube current. Erasure thoroughness of CR system in our department was to be proved by these evaluation. The results of this study could be used as a baseline for IP initialization and reliability of CR images.

• Journal of radiological science and technology
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• v.40 no.3
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• pp.363-370
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• 2017

We aimed to evaluate the physical imaging properties in various digital radiography systems with charged coupled device (CCD), computed radiography (CR), and indirect flat panel detector (FPD). The imaging properties measured in this study were modulation transfer function (MTF) wiener spectrum (WS), and detective quantum efficiency (DQE) to compare the performance of each digital radiography system. The system response of CCD were in a linear relationship with exposure and that of CR and FPD were proportional to the logarithm of exposure. The MTF of both CR and FPD indicated a similar tendency but in case of CCD, it showed lower MTF than that of CR and FPD. FPD showed the lowest WS and also indicated the highest DQE among three systems. According to the results, digital radiography system with different type of image receptor had its own image characteristics. Therefore, it is important to know the physical imaging characteristics of the digital radiography system accurately　to obtain proper image quality.

• Journal of radiological science and technology
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• v.45 no.5
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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.