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Jeffrey H. Siewerdsen - One of the best experts on this subject based on the ideXlab platform.

  • convergence criterion for mbir based on the local Noise Power Spectrum theory and implementation in a framework for accelerated 3d image reconstruction with a morphological pyramid
    15th International Meeting on Fully Three-Dimensional Image Reconstruction in Radiology and Nuclear Medicine Fully3D 2019, 2019
    Co-Authors: A Sisniega, J W Stayman, Sarah Capostagno, Clifford R Weiss, Tina Ehtiati, Jeffrey H. Siewerdsen
    Abstract:

    Model-based iterative reconstruction (MBIR) offers improved Noise-resolution tradeoffs and artifact reduction in conebeam CT compared to analytical reconstruction, but carries increased computational burden. An important consideration in minimizing computation time is reliable selection of the stopping criterion to perform the minimum number of iterations required to obtain the desired image quality. Most MBIR methods rely on a fixed number of iterations or relative metrics on image or cost-function evolution, and it would be desirable to use metrics that are more representative of the underlying image properties. A second front for reduction of computation time is the use of acceleration techniques (e.g. subsets or momentum). However, most of these techniques do not strictly guarantee convergence of the resulting MBIR method. A data-dependent analytical model of Noise-Power Spectrum (NPS) for penalized weighted least squares (PWLS) reconstruction is proposed as an absolute metric of image properties for the fully converged volume. Distance to convergence is estimated as the root mean squared error (RMSE) between the estimated NPS and an NPS measured on a uniform region of interest (ROI) in the evolving volume. Iterations are stopped when the RMSE falls below a threshold directly related with the properties of the target image. Further acceleration was achieved by combining the spectral stopping criterion with a morphological pyramid (mPyr) in which the minimization of the PWLS cost-function is divided in a cascade of stages. The algorithm parameters (voxel size in this work) change between stages to achieve faster evolution in early stages, and a final stage with the target parameters to guarantee convergence. Transition between stages is governed by the spectral stopping criterion.

  • a simple approach to measure computed tomography ct modulation transfer function mtf and Noise Power Spectrum nps using the american college of radiology acr accreditation phantom
    Medical Physics, 2013
    Co-Authors: Saul N Friedman, Jeffrey H. Siewerdsen, George S K Fung, B M W Tsui
    Abstract:

    Purpose: To develop an easily-implemented technique with free publicly-available analysis software to measure the modulation transfer function (MTF) and Noise-Power Spectrum (NPS) of a clinical computed tomography (CT) system from images acquired using a widely-available and standardized American College of Radiology (ACR) CT accreditation phantom. Methods: Images of the ACR phantom were acquired on a Siemens SOMATOM Definition Flash system using a standard adult head protocol: 120 kVp, 300 mAs, and reconstructed voxel size of 0.49 mm × 0.49 mm × 4.67 mm. The radial (axial) MTF was measured using an edge method where the boundary of the third module of the ACR phantom, originally designed to measure uniformity and Noise, was used as a circular edge. The 3D NPS was measured using images from this same module and using a previously-described methodology that quantifies Noise magnitude and 3D Noise correlation. Results: The axial MTF was radially symmetrical and had a value of 0.1 at 0.62 mm−1. The 3D NPS shape was consistent with the filter-ramp function of filtered-backprojection reconstruction algorithms and previously reported values. The radial NPS peak value was ∼115 HU2mm3 at ∼0.25 mm−1 and dropped to 0 HU2mm3 by 0.8 mm−1. Conclusions: The authors have developed an easily-implementable technique to measure the axial MTF and 3D NPS of clinical CT systems using an ACR phantom. The widespread availability of the phantom along with the free software the authors have provided will enable many different institutions to immediately measure MTF and NPS values for comparison of protocols and systems.

  • modeling and control of nonstationary Noise characteristics in filtered backprojection and penalized likelihood image reconstruction
    Proceedings of SPIE, 2013
    Co-Authors: Jeffrey H. Siewerdsen, J W Stayman, Grace J Gang, W Zbijewski
    Abstract:

    Purpose: Nonstationarity of CT Noise presents a major challenge to the assessment of image quality. This work presents models for imaging performance in both filtered backprojection (FBP) and penalized likelihood (PL) reconstruction that describe not only the dependence on the imaging chain but also the dependence on the object as well as the nonstationary characteristics of the signal and Noise. The work furthermore demonstrates the ability to impart control over the imaging process by adjusting reconstruction parameters to exploit nonstationarity in a manner advantageous to a particular imaging task. Methods: A cascaded systems analysis model was used to model the local Noise-Power Spectrum (NPS) and modulation transfer function (MTF) for FBP reconstruction, with locality achieved by separate calculation of fluence and system gain for each view as a function of detector location. The covariance and impulse response function for PL reconstruction (quadratic penalty) were computed using the implicit function theorem and Taylor expansion. Detectability index was calculated under the assumption of local stationarity to show the variation in task-dependent image quality throughout the image for simple and complex, heterogeneous objects. Control of Noise magnitude and correlation was achieved by applying a spatially varying roughness penalty in PL reconstruction in a manner that improved overall detectability. Results: The models provide a foundation for task-based imaging performance assessment in FBP and PL image reconstruction. For both FBP and PL, Noise is anisotropic and varies in a manner dependent on the path length of each view traversing the object. The anisotropy in turn affects task performance, where detectability is enhanced or diminished depending on the frequency content of the task relative to that of the NPS. Spatial variation of the roughness penalty can be exploited to control Noise magnitude and correlation (and hence detectability). Conclusions: Nonstationarity of image Noise is a significant effect that can be modeled in both FBP and PL image reconstruction. Prevalent spatial-frequency-dependent metrics of spatial resolution and Noise can be analyzed under assumptions of local stationarity, providing a means to analyze imaging performance as a function of location throughout the image. Knowledgeable selection of a spatially-varying roughness penalty in PL can potentially improve local Noise and spatial resolution in a manner tuned to a particular imaging task. Keywords: cascaded systems analysis, nonstationarity, filtered backprojection, penalized-likelihood reconstruction, Noise-Power Spectrum, covariance matrix, imaging task, detectability index

  • a framework for Noise Power Spectrum analysis of multidimensional images
    Medical Physics, 2002
    Co-Authors: Jeffrey H. Siewerdsen, Ian A Cunningham, David A Jaffray
    Abstract:

    A methodological framework for experimental analysis of the Noise-Power Spectrum (NPS) of multidimensional images is presented that employs well-known properties of the n-dimensional (nD) Fourier transform. The approach is generalized to n dimensions, reducing to familiar cases for n = 1 (e.g., time series) and n = 2 (e.g., projection radiography) and demonstrated experimentally for two cases in which n = 3 (viz., using an active matrix flat-panel imager for x-ray fluoroscopy and cone-beam CT to form three-dimensional (3D) images in spatiotemporal and volumetric domains, respectively). The relationship between fully nD NPS analysis and various techniques for analyzing a "central slice" of the NPS is formulated in a manner that is directly applicable to measured nD data, highlights the effects of correlation, and renders issues of NPS normalization transparent. The spatiotemporal NPS of fluoroscopic images is analyzed under varying conditions of temporal correlation (image lag) to investigate the degree to which the NPS is reduced by such correlation. For first-frame image lag of approximately 5-8%, the NPS is reduced by approximately 20% compared to the lag-free case. A simple model is presented that results in an approximate rule of thumb for computing the effect of image lag on NPS under conditions of spatiotemporal separability. The volumetric NPS of cone-beam CT images is analyzed under varying conditions of spatial correlation, controlled by adjustment of the reconstruction filter. The volumetric NPS is found to be highly asymmetric, exhibiting a ramp characteristic in transverse planes (typical of filtered back-rojection) and a band-limited characteristic in the longitudinal direction (resulting from low-pass characteristics of the imager). Such asymmetry could have implications regarding the detectability of structures visualized in transverse versus sagittal or coronal planes. In all cases, appreciation of the full dimensionality of the image data is essential to obtaining meaningful NPS results. The framework may be applied to NPS analysis of image data of arbitrary dimensionality provided the system satisfies conditions of NPS existence.

  • Signal, Noise Power Spectrum, and detective quantum efficiency of indirect-detection flat-panel imagers for diagnostic radiology
    Medical Physics, 1998
    Co-Authors: Jeffrey H. Siewerdsen, John Yorkston, Larry E Antonuk, Yoshiyuki Mohri, W Huang, I. A. Cunningham
    Abstract:

    The performance of an indirect-detection, active matrix flat-panel imager (FPI) at diagnostic energies is reported in terms of measured and theoretical signal size, Noise Power Spectrum (NPS), and detective quantum efficiency (DQE). Based upon a 1536 x 1920 pixel, 127 microns pitch array of a-Si:H thin-film transistors and photodiodes, the FPI was developed as a prototype for examination of the potential of flat-panel technology in diagnostic x-ray imaging. The signal size per unit exposure (x-ray sensitivity) was measured for the FPI incorporating five commercially available Gd2O2S:Tb converting screens at energies 70-120 kVp. One-dimensional and two-dimensional NPS and DQE were measured for the FPI incorporating three such converters and as a function of the incident exposure. The measurements support the hypothesis that FPIs have significant potential for application in diagnostic radiology. A cascaded systems model that has shown good agreement with measured individual pixel signal and Noise properties is employed to describe the performance of various FPI designs and configurations under a variety of diagnostic imaging conditions. Theoretical x-ray sensitivity, NPS, and DQE are compared to empirical results, and good agreement is observed in each case. The model is used to describe the potential performance of FPIs incorporating a recently developed, enhanced array that is commercially available and has been proposed for testing and application in diagnostic radiography and fluoroscopy. Under conditions corresponding to chest radiography, the analysis suggests that such systems can potentially meet or even exceed the DQE performance of existing technology, such as screen-film and storage phosphor systems; however, under conditions corresponding to general fluoroscopy, the typical exposure per frame is such that the DQE is limited by the total system gain and additive electronic Noise. The cascaded systems analysis provides a valuable means of identifying the limiting stages of the imaging system, a tool for system optimization, and a guide for developing strategies of FPI design for various imaging applications.

Ehsan Samei - One of the best experts on this subject based on the ideXlab platform.

  • su d 217a 03 nuclear medicine uniformity assessment using 2d Noise Power Spectrum
    Medical Physics, 2012
    Co-Authors: John W Nelson, O Christianson, Beth A Harkness, Mark T Madsen, Eugene Mah, Stephen R Thomas, Habib Zaidi, Ehsan Samei
    Abstract:

    Purpose: Nuclear medicinequality control programs require daily evaluation for the presence of potential non‐uniformities by commonly utilizing a traditional pixel value‐based assessment (Integral CFOVUniformity). While this method effectively captures regional non‐ uniformities in the image, it does not adequately reflect subtle periodic structures that are visually apparent and clinically unacceptable, therefore requiring the need for additional visual inspection of the image. The goal of this project was to develop a new uniformity assessment metric by targetingstructural patterns and more closely correlating with visual inspection.Methods: The new quantitative uniformity assessment metric is based on the 2D Noise Power Spectrum (NPS). A full 2D NPS was performed on each image. The NPS was thresholded to remove quantum Noise and further filtered by the visual response function. A score, the Structure Noise Index (SNI), was then applied to each based on the average magnitude of the structured Noise in the processed image. To verify the validity of the new metric, 50 daily uniformity images with varying degrees of visual structured and non‐structured non‐uniformity were scored by 5 expert nuclear medicinephysicists. The correlation between the visual score and SNI were assessed. The Integral CFOV was also compared against the visual score. Results: Our new SNI assessment metric compared to the Integral CFOV showed in increase in sensitivity from 67% to 100% in correctly identifying structured non‐uniformities. The overall positive predictive value also increased from 55% to 72%. Conclusions: Our new uniformity metric correlates much more closely with visual assessment of structured non‐ uniform NM images than the traditional pixel‐based method. Using this new metric in conjunction with the traditional pixel value‐based assessment will allow a more accurate quantitative assessment of nuclear medicineuniformity.

  • ct performance as a variable function of resolution Noise and task property for iterative reconstructions
    Proceedings of SPIE, 2012
    Co-Authors: Baiyu Chen, S Richard, O Christianson, Xiaodong Zhou, Ehsan Samei
    Abstract:

    The increasing availability of iterative reconstruction (IR) algorithms on clinical scanners is creating a demand for effectively and efficiently evaluating imaging performance and potential dose reduction. In this study, the location- and task-specific evaluation was performed using detectability index (d') by combining a task function, the task transfer function (TTF), and the Noise Power Spectrum (NPS). Task function modeled a wide variety detection tasks in terms of shape and contrast. The TTF and NPS were measured from a physical phantom as a function of contrast and dose levels. Measured d' values were compared between three IRs (IRIS, SAFIRE3 and SAFIRE5) and conventional filtered back-projection (FBP) at various dose levels, showing an equivalent performance of IR at lower dose levels. AUC further calculated from d' showed that compared to FBP, SAFIRE5 may reduce dose by up to 50-60%; SAFIRE3 and IRIS by up to 20-30%. This study provides an initial framework for the localized and task-specific evaluation of IRs in CT and a guideline for the identification of optimal operating dose point with iterative reconstructions.

  • detector or system extending the concept of detective quantum efficiency to characterize the performance of digital radiographic imaging systems
    Radiology, 2008
    Co-Authors: Ehsan Samei, Nicole T Ranger, Alistair Mackenzie, Ian D Honey, James T Dobbins, Carl E Ravin
    Abstract:

    Purpose: 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 beam-stop 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 ran...

  • intercomparison of methods for image quality characterization ii Noise Power Spectrum
    Medical Physics, 2006
    Co-Authors: James T Dobbins, Ehsan Samei, Nicole T Ranger, Ying Chen
    Abstract:

    Second in a two-part series comparing measurement techniques for the assessment of basic image quality metrics in digital radiography, in this paper we focus on the measurement of the image Noise Power Spectrum (NPS). Three methods were considered: (1) a method published by Dobbins et al. [Med. Phys. 22, 1581-1593 (1995)], (2) a method published by Samei et al. [Med. Phys. 30, 608-622 (2003)], and (3) a new method sanctioned by the International Electrotechnical Commission (IEC 62220-1, 2003), developed as part of an international standard for the measurement of detective quantum efficiency. In addition to an overall comparison of the estimated NPS between the three techniques, the following factors were also evaluated for their effect on the measured NPS: horizontal versus vertical directional dependence, the use of beam-limiting apertures, beam Spectrum, and computational methods of NPS analysis, including the region-of-interest (ROI) size and the method of ROI normalization. Of these factors, none was found to demonstrate a substantial impact on the amplitude of the NPS estimates ( 0.15 mm(-1).

  • determination of the detective quantum efficiency of a digital x ray detector comparison of three evaluations using a common image data set
    Medical Physics, 2004
    Co-Authors: Ulrich Neitzel, Susanne Guntherkohfahl, Giovanni Borasi, Ehsan Samei
    Abstract:

    The detective quantum efficiency (DQE) of an x-ray digital imaging detector was determined independently by the three participants of this study, using the same data set consisting of edge and flat field images. The aim was to assess the possible variation in DQE originating from established, but slightly different, data processing methods used by different groups. For the case evaluated in this study differences in DQE of up to +/-15% compared to the mean were found. The differences could be traced back mainly to differences in the modulation transfer function (MTF) and Noise Power Spectrum (NPS) determination. Of special importance is the inclusion of a possible low-frequency drop in MTF and the proper handling of signal offsets for the determination of the NPS. When accounting for these factors the deviation between the evaluations reduced to approximately +/-5%. It is expected that the recently published standard on DQE determination will further reduce variations in the data evaluation and thus in the results of DQE measurements.

Norbert J Pelc - One of the best experts on this subject based on the ideXlab platform.

  • cnn based ct denoising with an accurate image domain Noise insertion technique
    Medical Imaging 2021: Physics of Medical Imaging, 2021
    Co-Authors: Byeongjoon Kim, Norbert J Pelc, Sarah E Divel, Jongduk Baek
    Abstract:

    Convolutional neural network (CNN)-based CT denoising methods have attracted great interest for improving the image quality of low-dose CT (LDCT) images. However, CNN requires a large amount of paired data consisting of normal-dose CT (NDCT) and LDCT images, which are generally not available. In this work, we aim to synthesize paired data from NDCT images with an accurate image domain Noise insertion technique and investigate its effect on the denoising performance of CNN. Fan-beam CT images were reconstructed using extended cardiac-torso phantoms with Poisson Noise added to projection data to simulate NDCT and LDCT. We estimated local Noise Power spectra and a variance map from a NDCT image using information on photon statistics and reconstruction parameters. We then synthesized image domain Noise by filtering and scaling white Gaussian Noise using the local Noise Power Spectrum and variance map, respectively. The CNN architecture was U-net, and the loss function was a weighted summation of mean squared error, perceptual loss, and adversarial loss. CNN was trained with NDCT and LDCT (CNN-Ideal) or NDCT and synthesized LDCT (CNN-Proposed). To evaluate denoising performance, we measured the root mean squared error (RMSE), structural similarity index (SSIM), Noise Power Spectrum (NPS), and modulation transfer function (MTF). The MTF was estimated from the edge spread function of a circular object with 12 mm diameter and 60 HU contrast. Denoising results from CNN-Ideal and CNN-Proposed show no significant difference in all metrics while providing high scores in RMSE and SSIM compared to NDCT and similar NPS shapes to that of NDCT.

  • local and global 3d Noise Power Spectrum in cone beam ct system with fdk reconstruction
    Medical Physics, 2011
    Co-Authors: Jongduk Baek, Norbert J Pelc
    Abstract:

    Purpose: The authors examine the nonstationary Noise behavior of a cone-beam CT system with FDK reconstruction. Methods: To investigate the nonstationary Noise behavior, an analytical expression for the NPS of local volumes and an entire volume was derived and quantitatively compared to the NPS estimated from experimental air and waterimages. Results: The NPS of local volumes at different locations along the z -axis showed radial symmetry in the f x - f y plane and different missing cone regions in the f z direction depending on the tilt angle of rays through the local volumes. For local volumes away from the z -axis, the NPS of air and waterimages showed sharp transitions in the f x - f y and f y - f z planes and lack of radial symmetry in the f x - f y plane. These effects are mainly caused by varying magnification and different Noise levels from view to view. In the NPS of the entire volume, the f x - f y plane showed radial symmetry because the nonstationary Noise behaviors of local volumes were averaged out. The nonstationary sharp transitions were manifested as a high-frequency roll-off. Conclusions: The results from Noise Power analysis for local volumes and an entire volume demonstrate the spatially varying Noise behavior in the reconstructed cone-beam CTimages.

  • the Noise Power Spectrum in ct with direct fan beam reconstruction
    Medical Physics, 2010
    Co-Authors: Jongduk Baek, Norbert J Pelc
    Abstract:

    The Noise Power Spectrum (NPS) is a useful metric for understanding the Noise content in images. To examine some unique properties of the NPS of fan beam CT, the authors derived an analytical expression for the NPS of fan beam CT and validated it with computer simulations. The nonstationary Noise behavior of fan beam CT was examined by analyzing local regions and the entire field-of-view (FOV). This was performed for cases with uniform as well as nonuniform Noise across the detector cells and across views. The simulated NPS from the entire FOV and local regions showed good agreement with the analytically derived NPS. The analysis shows that whereas the NPS of a large FOV in parallel beam CT (using a ramp filter) is proportional to frequency, the NPS with direct fan beam FBP reconstruction shows a high frequency roll off. Even in small regions, the fan beam NPS can show a sharp transition (discontinuity) at high frequencies. These effects are due to the variable magnification and therefore are more pronounced as the fan angle increases. For cases with nonuniform Noise, the NPS can show the directional dependence and additional effects.

Kirsten L. Boedeker - One of the best experts on this subject based on the ideXlab platform.

  • application of the Noise Power Spectrum in modern diagnostic mdct part i measurement of Noise Power spectra and Noise equivalent quanta
    Physics in Medicine and Biology, 2007
    Co-Authors: Kirsten L. Boedeker, V N Cooper, Michael F Mcnittgray
    Abstract:

    Dose reduction efforts in diagnostic CT have brought the tradeoff of dose versus image quality to the forefront. The need for meaningful characterization of image Noise beyond that offered by pixel standard deviation is becoming increasingly important. This work aims to study the implementation of the Noise Power Spectrum (NPS) and Noise equivalent quanta (NEQ) on modern, multislice diagnostic CT scanners. The details of NPS and NEQ measurement are outlined and special attention is paid to issues unique to multislice CT. Aliasing, filter design and effects of acquisition geometry are investigated. While it was found that both metrics can be implemented in modern CT, it was discovered that NEQ cannot be aptly applied with certain non-traditional reconstruction filters or in helical mode. NPS and NEQ under a variety of conditions are examined. Extensions of NPS and NEQ to uses in protocol standardization are also discussed.

  • Application of the Noise Power Spectrum in modern diagnostic MDCT: Part II. Noise Power spectra and signal to Noise
    Physics in Medicine and Biology, 2007
    Co-Authors: Kirsten L. Boedeker, Michael F. Mcnitt-gray
    Abstract:

    Balancing dose and image quality requires signal-to-Noise (SNR) metrics which incorporate both the variance and the spatial frequency characteristics of Noise. In this study, the non-prewhitening matched filter SNR metric is calculated for 2 mm slices of a 1 cm diameter sphere under three different conditions: (1) constant pixel standard deviation, (2) constant dose and (3) constant reconstruction filter. For the constant pixel standard deviation condition, an increase of 260% in SNR was found with increasing filter sharpness. For constant dose, the SNR remained level for smooth to medium filters, then declined by up to 55% with increasing filter sharpness. For a constant reconstruction filter, the SNR increased with dose, but not as high as photon statistics would predict. However, when structured Noise was removed from the Noise Power Spectrum, the SNR did vary with quanta statistics. These results offer protocol design guidance for low-frequency-dominated objects.

James T Dobbins - One of the best experts on this subject based on the ideXlab platform.

  • detector or system extending the concept of detective quantum efficiency to characterize the performance of digital radiographic imaging systems
    Radiology, 2008
    Co-Authors: Ehsan Samei, Nicole T Ranger, Alistair Mackenzie, Ian D Honey, James T Dobbins, Carl E Ravin
    Abstract:

    Purpose: 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 beam-stop 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 ran...

  • intercomparison of methods for image quality characterization ii Noise Power Spectrum
    Medical Physics, 2006
    Co-Authors: James T Dobbins, Ehsan Samei, Nicole T Ranger, Ying Chen
    Abstract:

    Second in a two-part series comparing measurement techniques for the assessment of basic image quality metrics in digital radiography, in this paper we focus on the measurement of the image Noise Power Spectrum (NPS). Three methods were considered: (1) a method published by Dobbins et al. [Med. Phys. 22, 1581-1593 (1995)], (2) a method published by Samei et al. [Med. Phys. 30, 608-622 (2003)], and (3) a new method sanctioned by the International Electrotechnical Commission (IEC 62220-1, 2003), developed as part of an international standard for the measurement of detective quantum efficiency. In addition to an overall comparison of the estimated NPS between the three techniques, the following factors were also evaluated for their effect on the measured NPS: horizontal versus vertical directional dependence, the use of beam-limiting apertures, beam Spectrum, and computational methods of NPS analysis, including the region-of-interest (ROI) size and the method of ROI normalization. Of these factors, none was found to demonstrate a substantial impact on the amplitude of the NPS estimates ( 0.15 mm(-1).

  • imaging characteristics of an amorphous silicon flat panel detector for digital chest radiography
    Radiology, 2001
    Co-Authors: Carey E Floyd, James T Dobbins, Richard J Warp, Harrell G Chotas, Ala H Aydush, Rene Vargasvoracek, Carl E Ravi
    Abstract:

    PURPOSE: To evaluate the imaging characteristics of an amorphous silicon flat-panel detector (FPD) for digital chest radiography. MATERIALS AND METHODS: The 41 × 41-cm digital FPD is constructed on a single monolithic glass substrate with a structured cesium iodide scintillator layer and an amorphous silicon thin-film transistor array for image readout. Basic imaging characteristics of the FPD and associated image processing system were assessed on acquired images, including linearity, repeatability, uniformity of response, modulation transfer function (MTF), Noise Power Spectrum, detective quantum efficiency (DQE), contrast sensitivity, and scatter content. Results with the FPD system were compared to those with a storage phosphor computed radiography (CR) system. RESULTS: Images obtained with the FPD demonstrated excellent uniformity, repeatability, and linearity, as well as MTF and DQE that were superior to those with the storage phosphor CR system. The contrast and scatter content of images acquired w...