The effect of scatter and glare on image quality in contrast‐enhanced breast imaging using an  full‐field flat panel detector

Carton, Ann-Katherine; Acciavatti, Raymond J.; Kuo, Johnny; Maidment, Andrew D. A.

doi:10.1118/1.3077922

Cited by 41 publications

(45 citation statements)

References 37 publications

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“…Beam stop method. The scatter fractions in the output image (SF out ) were determined experimentally with the beam stop method (Carton et al 2009, Salvagnini et al 2012. A series of lead discs with radii R between 3 and 10 mm were imaged on top of the PMMA, at the centre of the plate, followed by an image without a lead disc.…”

Section: Scatter Fraction In the Image (Sf Out )mentioning

confidence: 99%

A comprehensive model for x-ray projection imaging system efficiency and image quality characterization in the presence of scattered radiation

et al. 2017

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A comprehensive model for x-ray projection imaging system efficiency and image quality characterization in the presence of scattered radiation AbstractThis work proposes a method for assessing the detective quantum efficiency (DQE) of radiographic imaging systems that include both the x-ray detector and the antiscatter device. Cascaded linear analysis of the antiscatter device efficiency (DQE ASD ) with the x-ray detector DQE is used to develop a metric of system efficiency (DQE sys ); the new metric is then related to the existing system efficiency parameters of effective DQE (eDQE) and generalized DQE (gDQE). The effect of scatter on signal transfer was modelled through its point spread function (PSF), leading to an x-ray beam transfer function (BTF) that multiplies with the classical presampling modulation transfer function (MTF) to give the system MTF. Expressions are then derived for the influence of scattered radiation on signal-difference to noise ratio (SDNR) and contrast-detail (c-d) detectability.The DQE sys metric was tested using two digital mammography systems, for eight x-ray beams (four with and four without scatter), matched in terms of effective energy. The model was validated through measurements of contrast, SDNR and MTF for poly(methyl)methacrylate thicknesses covering the range of scatter fractions expected in mammography. The metric also successfully predicted changes in c-d detectability for different scatter conditions. Scatter Institute of Physics and Engineering in MedicineOriginal content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. 5 Author to whom any correspondence should be addressed. fractions for the four beams with scatter were established with the beam stop method using an extrapolation function derived from the scatter PSF, and validated through Monte Carlo (MC) simulations. Low-frequency drop of the MTF from scatter was compared to both theory and MC calculations. DQE sys successfully quantified the influence of the grid on SDNR and accurately gave the break-even object thickness at which system efficiency was improved by the grid. The DQE sys metric is proposed as an extension of current detector characterization methods to include a performance evaluation in the presence of scattered radiation, with an antiscatter device in place.

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Section: Scatter Fraction In the Image (Sf Out )mentioning

confidence: 99%

A comprehensive model for x-ray projection imaging system efficiency and image quality characterization in the presence of scattered radiation

et al. 2017

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“…A SEDM system may be implemented with a similar technique we used previously with the SEDR imaging [37][38][39][40] to improve the visibility of micro-calcifications in denser tissue areas and the low-contrast performance of soft tissue masses in digital mammography. To achieve exposure equalization, a narrow fan-beam x-ray (oriented parallel to the anode-cathode axis) can be used to scan the breast phantom in the direction perpendicular to the anode-cathode axis during the x-ray exposure.…”

Section: Iie Assessment Of Primary and Scattered Radiationmentioning

confidence: 99%

“…The details of the FFDM imaging system along with physical imaging characteristics and perception performance have been previously investigated and reported. 29,35,37,42 Before acquiring images, we performed a complete system calibration (correction for dark current bias, gain, and defective pixels/lines) according to the manufacturer's guidelines. The source-to-image distance (SID) was maintained at 66 cm.…”

Section: Iia Imaging Systemmentioning

confidence: 99%

“…16,20,21 Over the past two decades, the developments in advanced electronics and computer technology have led digital detection technology to gain rapid acceptance in radiology departments and to gradually replace SF systems. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] Digital detectors can overcome certain fundamental limitations associated with SF systems by providing a wide dynamic range and enabling contrast enhancement and the postprocessing of images. In digital format, image contrast can be freely manipulated by varying the window/level.…”

Section: Introductionmentioning

confidence: 99%

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Effects of exposure equalization on image signal‐to‐noise ratios in digital mammography: A simulation study with an anthropomorphic breast phantom

et al. 2011

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Purpose: The scan equalization digital mammography (SEDM) technique combines slot scanning and exposure equalization to improve low-contrast performance of digital mammography in dense tissue areas. In this study, full-field digital mammography (FFDM) images of an anthropomorphic breast phantom acquired with an anti-scatter grid at various exposure levels were superimposed to simulate SEDM images and investigate the improvement of low-contrast performance as quantified by primary signal-to-noise ratios (PSNRs). Methods: We imaged an anthropomorphic breast phantom (Gammex 169 "Rachel," Gammex RMI, Middleton, WI) at various exposure levels using a FFDM system (Senographe 2000D, GE Medical Systems, Milwaukee, WI). The exposure equalization factors were computed based on a standard FFDM image acquired in the automatic exposure control (AEC) mode. The equalized image was simulated and constructed by superimposing a selected set of FFDM images acquired at 2, 1, 1/2, 1/4, 1/8, 1/16, and 1/32 times of exposure levels to the standard AEC timed technique (125 mAs) using the equalization factors computed for each region. Finally, the equalized image was renormalized regionally with the exposure equalization factors to result in an appearance similar to that with standard digital mammography. Two sets of FFDM images were acquired to allow for two identically, but independently, formed equalized images to be subtracted from each other to estimate the noise levels. Similarly, two identically but independently acquired standard FFDM images were subtracted to estimate the noise levels. Corrections were applied to remove the excess system noise accumulated during image superimposition in forming the equalized image. PSNRs over the compressed area of breast phantom were computed and used to quantitatively study the effects of exposure equalization on low-contrast performance in digital mammography. Results: We found that the highest achievable PSNR improvement factor was 1.89 for the anthropomorphic breast phantom used in this study. The overall PSNRs were measured to be 79.6 for the FFDM imaging and 107.6 for the simulated SEDM imaging on average in the compressed area of breast phantom, resulting in an average improvement of PSNR by $35% with exposure equalization. We also found that the PSNRs appeared to be largely uniform with exposure equalization, and the standard deviations of PSNRs were estimated to be 10.3 and 7.9 for the FFDM imaging and the simulated SEDM imaging, respectively. The average glandular dose for SEDM was estimated to be 212.5 mrad, $34% lower than that of standard AEC-timed FFDM (323.8 mrad) as a result of exposure equalization for the entire breast phantom. Conclusions: Exposure equalization was found to substantially improve image PSNRs in dense tissue regions and result in more uniform image PSNRs. This improvement may lead to better lowcontrast performance in detecting and visualizing soft tissue masses and micro-calcifications in dense tissue areas for breast imaging tasks.

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“…[30][31][32] At our institution we have measured the effect of veiling glare on the flat panel detector used in this study.…”

Section: Introductionmentioning

confidence: 99%

A digitally reconstructed radiograph algorithm calculated from first principles

Staub

Murphy

2012

Medical Physics

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Purpose: To develop an algorithm for computing realistic digitally reconstructed radiographs (DRRs) that match real cone-beam CT (CBCT) projections with no artificial adjustments. Methods: The authors used measured attenuation data from cone-beam CT projection radiographs of different materials to obtain a function to convert CT number to linear attenuation coefficient (LAC). The effects of scatter, beam hardening, and veiling glare were first removed from the attenuation data. Using this conversion function the authors calculated the line integral of LAC through a CT along rays connecting the radiation source and detector pixels with a ray-tracing algorithm, producing raw DRRs. The effects of scatter, beam hardening, and veiling glare were then included in the DRRs through postprocessing. Results: The authors compared actual CBCT projections to DRRs produced with all corrections (scatter, beam hardening, and veiling glare) and to uncorrected DRRs. Algorithm accuracy was assessed through visual comparison of projections and DRRs, pixel intensity comparisons, intensity histogram comparisons, and correlation plots of DRR-to-projection pixel intensities. In general, the fully corrected algorithm provided a small but nontrivial improvement in accuracy over the uncorrected algorithm. The authors also investigated both measurement-and computation-based methods for determining the beam hardening correction, and found the computation-based method to be superior, as it accounted for nonuniform bowtie filter thickness. The authors benchmarked the algorithm for speed and found that it produced DRRs in about 0.35 s for full detector and CT resolution at a ray step-size of 0.5 mm. Conclusions:The authors have demonstrated a DRR algorithm calculated from first principles that accounts for scatter, beam hardening, and veiling glare in order to produce accurate DRRs. The algorithm is computationally efficient, making it a good candidate for iterative CT reconstruction techniques that require a data fidelity term based on the matching of DRRs and projections.

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The effect of scatter and glare on image quality in contrast‐enhanced breast imaging using an full‐field flat panel detector

Cited by 41 publications

References 37 publications

A comprehensive model for x-ray projection imaging system efficiency and image quality characterization in the presence of scattered radiation

A comprehensive model for x-ray projection imaging system efficiency and image quality characterization in the presence of scattered radiation

Effects of exposure equalization on image signal‐to‐noise ratios in digital mammography: A simulation study with an anthropomorphic breast phantom

A digitally reconstructed radiograph algorithm calculated from first principles

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