• Journal of Biomedical Engineering Research
• /
• v.17 no.2
• /
• pp.165-172
• /
• 1996

A scanning slot digital mammography system Luing a plastic scintillating fiber screen (SFS) is currently being developed To improve the x-ray interaction efficiency and absorption efficiency of an SFS, high Z elements can be added into the scintillating fiber core. In this paper, we investigated theoretically the zero spatial frequency detective quantum efficiency, DQE(0), and modulation transfer function, MTF(f), of three 2 cm thick SFSs made of polystyrene, polystyrene loaded with 5% by weight of lead, and polystyrene Loaded with 10% by weight of tin scintillating fibers. X-ray interaction efficiency, scintillating light intensity distributions and line spread functions were generated using Monte Carlo simulation. DQE(0) and MTF(f) were computed for x-ray energies ranging from 15 to 50 keV. Loading high Z elements into the SFS markedly increased the DQE(0). For x-ray energies used for mammovaphy, DQE(0) values of both high Z element loaded SFSs are about a factor of three higher than the DQE(0) of an Min-R screen. At mammographic x-ray energies, MTF(f) values of all three SFSs are Venter than 50% at 25 Ip/mm spatial frequency, and were found to be dominated by the 20 um individual scintillating fiber diameter used The results show that both hiP DQE(0) and spatial resolution can be achieved with the high Z element loaded SFSs, which make these SFSs attractive for use in a scanning slot detector for digital mammography.

• Progress in Medical Physics
• /
• v.19 no.4
• /
• pp.219-226
• /
• 2008

In this study, we have conducted characterization of imaging performance for a flat panel digital X-ray detector using amorphous Selenium and a-Si TFT which was developed by the authors. The procedures for characterization were in concordance with internationally recommended standards such as IEC (international electrotechnical commission). The measures used for imaging performance characterization include response characteristic, modulation transfer function (MTF), detective quantum efficiency (DQE), noise power spectrum (NPS), and quantum limited performance. The measured DQEs at lowest and highest spatial frequencies were 40% and 25% respectively, which was superior to that of commercial products by overseas vendor. The MTF values were significantly superior to that of CR and indirect type DRs. The quantum limited performance showed the detector was limited by quantum noise at the entrance exposure level below 0.023 mR, which is sufficiently low for general X-ray examination.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.1
• /
• pp.11-21
• /
• 2008

• Journal of radiological science and technology
• /
• v.40 no.3
• /
• pp.363-370
• /
• 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
• /
• v.39 no.3
• /
• pp.415-420
• /
• 2016

The purpose of this study was to evaluation of the performance characteristic for mammography by using edge device that mammography equipment improves essential in the correct diagnosis for the maintenance. We measured the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE) using the 61267 RQA-M2 based on commission standard international electro-technical commission (IEC). As a results, spatial resolution of elenia demensions tomo and lorad selenia mammography were maintained at $10mm^{-1}$ and NPS and DQE including the low nyquist frequency indicated to $6.0mm^{-1}$. Therefore, regulary QA of mammography system should be necessary. This study can be contribute to evaluate QA for performance characteristic of mammography of DDR system.

• Journal of radiological science and technology
• /
• v.35 no.2
• /
• pp.109-117
• /
• 2012

The purpose of this work was to evaluate an amorphous silicon cesium iodide based indirect flat-panel detector (FPD) in terms of their modulation transfer function (MTF), Wiener spectrum (WS, or noise power spectrum, NPS), and detective quantum efficiency (DQE). Measurements were made on flat-panel detector using the International Electrotechnical Commission (IEC) defined RQA3, RQA5, RQA7, and RQA9 radiographic technique. The MTFs of the systems were measured using an edge method. The WS(NPS) of the systems were determined for a range of exposure levels by two-dimensional (2D). Fourier analysis of uniformly exposed radiographs. The DQEs were assessed from the measured MTF, WS(NPS), exposure, and estimated ideal signal-to-noise ratios. Characteristic curve in the RQA3 showed difference in the characteristic curve from RQA5, RQA7, RQA9. MTFs were not differences according to x-ray beam quality. WS(NPS) was reduced with increasing dose, and RQA 3, RQA5, RQA7, RQA9 as the order is reduced. DQE represented the best in the 1mR, RQA 3, RQA5, RQA7, RQA9 decrease in the order. The physical imaging characteristics of FPD may also differ from input beam quality. This study gives an initial motivation that the physical imaging characteristics of FPD is an important issue for the right use of digital radiography system.

• Progress in Medical Physics
• /
• v.21 no.3
• /
• pp.261-273
• /
• 2010

For the use of Indirect-conversion CMOS (complementary metal-oxide-semiconductor) detectors for digital x-ray radiography and their better designs, we have theoretically evaluated the spatial-frequency-dependent detective quantum efficiency (DQE) using the cascaded linear-systems transfer theory. In order to validate the developed model, the DQE was experimentally determined by the measured modulation-transfer function (MTF) and noise-power spectrum, and the estimated incident x-ray fluence under the mammography beam quality of W/Al. From the comparison between the theoretical and experimental DQEs, the overall tendencies were well agreed. Based on the developed model, we have investigated the DQEs values with respect to various design parameters of the CMOS x-ray detector such as phosphor quantum efficiency, Swank noise, photodiode quantum efficiency and the MTF of various scintillator screens. This theoretical approach is very useful tool for the understanding of the developed imaging systems as well as helpful for the better design or optimization for new development.

• Journal of radiological science and technology
• /
• v.32 no.1
• /
• pp.17-24
• /
• 2009

Noise evaluation for an image has been performed by root mean square (RMS) granularity, autocorrelation function (ACF), and Wiener spectrum. RMS granularity stands for standard deviation of photon data and ACF is acquired by integration of 1 D function of distance variation. Fourier transform of ACF results in noise power spectrum which is called Wiener spectrum in image quality evaluation. Wiener spectrum represents noise itself. In addition, along with MTF, it is an important factor to produce detective quantum efficiency (DQE). The proposed evaluation method using Wiener spectrum is expected to contribute to educate the concept of Wiener spectrum in educational organizations, choose the appropriate imaging detectors for clinical applications, and maintain image quality in digital imaging systems.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.26 no.7
• /
• pp.112-124
• /
• 1989

In order to evaluate imaging performance of newly developed digital radiography system which requires scanning time as short as 0.7 sec and patient exposure as low as 3 mR, we have investigated its imaging and physical properties such as sensitivity characteristic, scatter fraction, detective quantum efficiency, modulation transfer function, and contrast detail diagram. The results show that the digital radiography system has linear sensitivity to the incident energy, and superior contrast resolving power with less X-ray exposure than conventional film-screen system. These performances are resulted from excellent scatter rejection capability and high detective quantum efficiency of digital radiography system.

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