&lt;title&gt;Statistical processes limiting the noise of a screen-film system&lt;/title&gt;

Beutel, Jacob; Yampolsky, Michael; Shaw, Rodney

doi:10.1117/12.174284

Cited by 3 publications

(4 citation statements)

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“…The energy dependence of the photon attenuation coefficients includes a term proportional to E −3 responsible for photoelectric absorption and a constant fraction responsible for the Compton effect (Beutel et al 2000). Therefore, for small lesions and calcifications, the energy dependence of the weighting factor in (5) can also be expressed analytically as w(E) = aE −3 + b, where a and b are the empirical coefficients that depend on the density, effective Z and atomic number of the background and contrast material.…”

Section: Proposed Msms Breast Ct Designmentioning

confidence: 99%

“…The photon counting detector could improve the signal-to-noise ratio (SNR) due to the rejection of electronics noise by setting an optimal threshold level. It is also free of pulse height (Swank) noise (Beutel et al 2000) which further increases the SNR. The energy-resolved detector can count the x-ray photons with different energies separately, and corresponding digital data can be stored, and post-processed.…”

Section: Introductionmentioning

confidence: 99%

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Computed tomography with energy-resolved detection: a feasibility study

2008

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The feasibility of computed tomography (CT) with energy-resolved x-ray detection has been investigated. A breast CT design with multi slit multi slice (MSMS) data acquisition was used for this study. The MSMS CT includes linear arrays of photon counting detectors separated by gaps. This CT configuration allows for efficient scatter rejection and 3D data acquisition. The energy-resolved CT images were simulated using a digital breast phantom and the design parameters of the proposed MSMS CT. The phantom had 14 cm diameter and 50/50 adipose/glandular composition, and included carcinoma, adipose, blood, iodine and CaCO3 as contrast elements. The x-ray technique was 90 kVp tube voltage with 660 mR skin exposure. Photon counting, charge (energy) integrating and photon energy weighting CT images were generated. The contrast-to-noise (CNR) improvement with photon energy weighting was quantified. The dual energy subtracted images of CaCO3 and iodine were generated using a single CT scan at a fixed x-ray tube voltage. The x-ray spectrum was electronically split into low- and high-energy parts by a photon counting detector. The CNR of the energy weighting CT images of carcinoma, blood, adipose, iodine, and CaCO3 was higher by a factor of 1.16, 1.20, 1.21, 1.36 and 1.35, respectively, as compared to CT with a conventional charge (energy) integrating detector. Photon energy weighting was applied to CT projections prior to dual energy subtraction and reconstruction. Photon energy weighting improved the CNR in dual energy subtracted CT images of CaCO3 and iodine by a factor of 1.35 and 1.33, respectively. The combination of CNR improvements due to scatter rejection and energy weighting was in the range of 1.71-2 depending on the type of the contrast element. The tilted angle CZT detector was considered as the detector of choice. Experiments were performed to test the effect of the tilting angle on the energy spectrum. Using the CZT detector with 20 degrees tilting angle decreased the tailing of the measured x-ray spectrum as compared to a conventional CZT detector. It was concluded that the energy-resolved MSMS CT with tilted angle CZT detector is potentially feasible and could provide a unique combination of photon counting, energy weighting, scatter rejection and single kVp dual energy subtraction CT imaging.

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Section: Proposed Msms Breast Ct Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Computed tomography with energy-resolved detection: a feasibility study

2008

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“…The optimal threshold values estimated form the composite LSF method were verified against the expected values determined from the standard s-curve calibration method from threshold scans [8]. Finally, the Modulation Transfer Function (MTF) given by the modulus of the Fourier transform of the LSF [15] has been calculated for the various thresholds and photon energies. For an ideal LSF, represented by a box function, the MTF can be expressed as:…”

Section: Methodsmentioning

confidence: 99%

Comparator threshold settings and the effective pixel width of the PICASSO detector

et al. 2014

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Charge sharing plays an important role in the performance of single-photon counting microstrip detectors, since the comparator threshold defines the effective pixel width. In this contribution, the PICASSO (Phase Imaging for Clinical Application with Silicon detector and Synchrotron radiatiOn) single-photon counting microstrip detector oriented in edge-on configuration has been used to study its spatial resolution as a function of the comparator threshold. The experiment was carried out with monochromatic x-rays at the SYRMEP beamline of the Elettra synchrotron radiation facility in Trieste (Italy). The Edge Spread Function (i.e. the integral of the Line spread Function, LSF) was measured by horizontally translating vertical slits from a bar-pattern test-object in front of the detector, at four different photon energies (19, 20, 22, and 25 keV) and for several different values of the comparator threshold. The effect of charge sharing between strips on the spatial resolution has been quantified by calculating the horizontal Modulation Transfer Function (MTF). Moreover, the composite LSF from neighboring pixels was obtained: this allowed estimating the optimal threshold for each photon energy by selecting the threshold at which the composite LSF would approach unity along the entire width of the pixel. The results show that at

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“…Last year, at this same conference, we presented a paper [1] which was the result of an experimental attempt to understand the behavior ofthe probability distribution functions associated with imaging noise resulting from direct light exposures and screen/film exposures at various conversion efficiencies. Conventional wisdom led us to believe that the effect of so-called quantum mottle could be varied in terms of a broadening of the probability distribution function.…”

Section: Introductionmentioning

confidence: 98%

<title>Statistical processes limiting the noise of a screen-film system: II</title>

Beutel¹,

Shaw²,

Yampolsky³

1995

SPIE Proceedings

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In a recent publication we demonstrated that the increase in image noise which results from exposing a film via a phosphor screen can be attributed entirely to the increased extent of the autocorrelation interval introduced by the screen, and not to any change in the shape or scale ofthe probability distribution function which governs the fluctuations about the mean level. This result implies that the (0,0)-value of the autocovariance function is independent of the degree of so-called quantum mottle and since the autocovariance function, ACV(x,y), and the Wiener Spectrum, WS(u,v), are Fourier transform pairs, it follows that the integral of the Wiener Spectrum over all spatial frequencies (u,v) must share this independence.Since this result was counterintuitive to existing assumptions ofthe role ofscreen and film in defining the Wiener Spectrum (i. e., a simple additive combination of quantum mottle and film grain), we now investigate this relationship in more detail in order to provide a more complete insight. For this purpose we have simulated a set of controlled images which correspond to a wide range of screen correlation intervals, from 192 jim down to uncorrelated film noise. Included in this simulation we have also explored the role of the overall amplification factor, i. e., the average number of image grains associated with an x-ray quantum. The results of these simulations are presented here, and confirm our previous findings, by establishing the invariance ofthe scale (0,0) value ofthe ACV.

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<title>Statistical processes limiting the noise of a screen-film system</title>

Cited by 3 publications

References 10 publications

Computed tomography with energy-resolved detection: a feasibility study

Computed tomography with energy-resolved detection: a feasibility study

Comparator threshold settings and the effective pixel width of the PICASSO detector

<title>Statistical processes limiting the noise of a screen-film system: II</title>

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