Practical evaluation of image quality in computed radiographic (CR) imaging systems (original) (raw)
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Comparison of imaging properties of several digital radiographic systems
2001
Digital radiography is a field of great interest; a wide range of different imaging systems is now becoming available and it is very important to have powerful instruments to characterize and compare their imaging properties. We have evaluated imaging properties for several digital radiographic systems in terms of resolution and noise properties. For the resolution properties, we have used the Modulation Transfer Function (MTF) and the presampling MTF, for undersampled systems. We have characterized noise properties by Detective Quantum Efficiency, that is an absolute parameter that allows comparison between different systems. # : S 0 1 6 8 -9 0 0 2 ( 0 1 ) 0 0 8 3 0 -0 SECTION II.
A comparison of digital radiography systems in terms of effective detective quantum efficiency
Medical Physics, 2012
Purpose: The purpose of this study is to compare digital radiography systems using the metric effective detective quantum efficiency (eDQE), which better reflects digital radiography imaging system performance under clinical operating conditions, in comparison with conventional metrics such as modulation transfer function (MTF), normalized noise power spectra (NNPS), and detective quantum efficiency (DQE). Methods: The eDQE was computed by the calculation of the MTF, the NNPS, the phantom attenuation and scatter, and estimation of x-ray flux. The physical characterization of the systems was obtained with the standard beam conditions RQA5 and RQA9, using the PA Chest phantom proposed by AAPM Report # 31 simulating the attenuation and scatter characteristics of the adult human thorax. The MTF (eMTF) was measured by using an edge test placed at the frontal surface of the phantom, the NNPS (eNNPS) was calculated from images of the phantom acquired at three different exposure levels covering the operating range of the system (E 0 , which is the exposure at which a system is normally operated, 1/3 E 0 , and 3 E0), and scatter measurements were assessed by using a beam-stop technique. The integral of DQE (IDQE) and eDQE (IeDQE) was calculated over the whole spatial frequency range. Results: The eMTF results demonstrate degradation due to magnification and the presence of scattered radiation. The eNNPS was influenced by the grid presence, and in some systems, it contained structured noise. At typical clinical exposure levels, the magnitude of eDQE(0) with respect to DQE(0) at RQA9 beam conditions was 13%, 17%, 16%, 36%, and 24%, respectively, for Carestream DRX-1, Carestream DRX-1C, Carestream Direct View CR975, Philips Digital Diagnost VM, and GE Revolution XR/d. These results were confirmed by the ratio of IeDQE and IDQE in the same conditions. Conclusions: The authors confirm the robustness and reproducibility of the eDQE method. As expected, the DR systems performed better than the CR systems due to their superior signal-tonoise transfer characteristics. The results of this study suggest the eDQE method may provide an opportunity to more accurately assess the clinical performance of digital radiographic imaging systems by accounting for factors such as the presence of scatter, use of an antiscatter grid, and magnification and focal spot blurring effects, which are not reflected in conventional DQE measures.
Diagnostics, 2021
The aim of this study was to determine the quantitative image quality metrics of the low-dose 2D/3D EOS slot scanner X-ray imaging system (LDSS) compared with conventional digital radiography (DR) X-ray imaging systems. The effective detective quantum efficiency (eDQE) and effective noise quantum equivalent (eNEQ) were measured using chest and knee protocols. Methods: A Nationwide Evaluation of X-ray Trends (NEXT) of a chest adult phantom and a PolyMethylmethacrylate (PMMA) phantom were used for the chest and knee protocols, respectively. Quantitative image quality metrics, including effective normalised noise power spectrum (eNNPS), effective modulation transfer function (eMTF), eDQE and eNEQ of the LDSS and DR imaging systems were assessed and compared. Results: In the chest acquisition, the LDSS imaging system achieved significantly higher eNEQ and eDQE than the DR imaging systems at lower and higher spatial frequencies (0.001 ≤ p ≤ 0.044). For the knee acquisition, the LDSS imag...
Quantitative assessment of computed radiography quality control parameters
Physics in Medicine and Biology, 2006
Quality controls for testing the performance of computed radiography (CR) systems have been recommended by manufacturers and medical physicists' organizations. The purpose of this work was to develop a set of image processing tools for quantitative assessment of computed radiography quality control parameters. Automatic image analysis consisted in detecting phantom details, defining regions of interest and acquiring measurements. The tested performance characteristics included dark noise, uniformity, exposure calibration, linearity, low-contrast and spatial resolution, spatial accuracy, laser beam function and erasure thoroughness. CR devices from two major manufacturers were evaluated. We investigated several approaches to quantify the detector response uniformity. We developed methods to characterize the spatial accuracy and resolution properties across the entire image area, based on the Fourier analysis of the image of a fine wire mesh. The implemented methods were sensitive to local blurring and allowed to detect a local distortion of 4% or greater in any part of an imaging plate. The obtained results showed that the developed image processing tools allow us to implement a quality control program for CR with short processing time and with absence of subjectivity in the evaluation of the parameters.
2016
The standards EN 14784-1:2005 and ISO 16371-1:2011 describe the classification of Computed Radiography systems for industrial applications. After 10 years of classification experience, it can be concluded that all certified NDT CR systems achieve the best classification result: IP 1. The measured basic spatial resolution is different depending on the manufacturer’s brand and the IP used. Therefore, a revision was recommended to obtain a better gradation for the different brands. Users in USA and Europe classify the CR systems based on different parameters. Consequently, a new revision of ASTM E 2446-15 was finalized in 2015, which describes the characterization of CR systems based on CR performance levels. The key parameters are the normalized Signal to Noise Ratio (SNRN), the interpolated basic spatial resolution (iSRb) and the achieved equivalent penetrameter sensitivity (aEPS). A series of further tests is required for complete characterization by manufacturers or certifying labo...
Modeling the Performance Characteristics of Computed Radiography (CR) Systems
IEEE Transactions on Medical Imaging, 2000
Computed radiography (CR) using storage phosphors is widely used in digital radiography and mammography. A cascaded linear systems approach wherein several parameter values were estimated using Monte Carlo methods was used to model the image formation process of a single-side read ;;flying spot'' CR system using a granular phosphor. Objective image quality metrics such as modulation transfer function and detective quantum efficiency were determined using this model and show good agreement with published empirical data. A model such as that addressed in this work could allow for improved understanding of the effect of storage phosphor physical properties and CR reader parameters on objective image quality metrics for existing and evolving CR systems.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2020
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Radiology, 2008
To develop an experimental method for measuring the effective detective quantum efficiency (eDQE) of digital radiographic imaging systems and evaluate its use in select imaging systems. Materials and Methods: A geometric phantom emulating the attenuation and scatter properties of the adult human thorax was employed to assess eight imaging systems in a total of nine configurations. The noise power spectrum (NPS) was derived from images of the phantom acquired at three exposure levels spanning the operating range of the system. The modulation transfer function (MTF) was measured by using an edge device positioned at the anterior surface of the phantom. Scatter measurements were made by using a beamstop technique. All measurements, including those of phantom attenuation and estimates of x-ray flux, were used to compute the eDQE. Results: The MTF results showed notable degradation owing to focal spot blur. Scatter fractions ranged between 11% and 56%, depending on the system. The eDQE(0) results ranged from 1%-17%, indicating a reduction of up to one order of magnitude and different rank ordering and performance among systems, compared with that implied in reported conventional detective quantum efficiency results from the same systems. Conclusion: The eDQE method was easy to implement, yielded reproducible results, and provided a meaningful reflection of system performance by quantifying image quality in a clinically relevant context. The difference in the magnitude of the measured eDQE and the ideal eDQE of 100% provides a great opportunity for improving the image quality of radiographic and mammographic systems while reducing patient dose.
A phantom study of image quality versus radiation dose for digital radiography
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2007
In the present work, a contrast-detail phantom was used to study the image quality and the radiation dose for digital X-ray imaging systems. The phantom consists of a 265 mm (H) Â 265 mm (W) Â 10 mm (D) acrylic sheet with drilled holes of various depths and diameters. At each setting of exposure techniques, three images were taken and evaluated subjectively by three independent radiologists. The average image quality figure (IQF) was then calculated. In addition, a computer program was developed to evaluate objectively the same images. This program, written in MATLAB, was based on a statistical method with variance analysis of the image pixels. Corrections of the parallax effect were made. Results showed that the computer program proved more sensitive than the radiologists. In addition to image analyses, the entrance surface dose (ESD) was measured using the Harshaw thermoluminescent dosimeters TLD-100H. Two 75 mm-thick acrylic slabs were used with the contrast-detail phantom in between. Optimization analyses on the image quality and the radiation dose were performed. r