Anisotropic imaging performance in indirect x-ray imaging detectors

Badano, Aldo; Kyprianou, Iacovos S.; Sempau, J.

doi:10.1118/1.2208925

Cited by 34 publications

(35 citation statements)

References 36 publications

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“…Furthermore, for geometries with stationary detector, 5,7 the MTF decreases as the source angle increases. 18,19 The effect of these physical factors on MC detectability has not been investigated, either for human detection or for CADe.…”

mentioning

confidence: 99%

Automated detection of microcalcification clusters for digital breast tomosynthesis using projection data only: A preliminary study

et al. 2008

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Digital breast tomosynthesis ͑DBT͒ is a promising modality for breast imaging in which an anisotropic volume image of the breast is obtained. We present an algorithm for computerized detection of microcalcification clusters ͑MCCs͒ for DBT. This algorithm operates on the projection views only. Therefore it does not depend on reconstruction, and is computationally efficient. The algorithm was developed using a database of 30 image sets with microcalcifications, and a control group of 30 image sets without visible findings. The patient data were acquired on the first DBT prototype at Massachusetts General Hospital. Algorithm sensitivity was estimated to be 0.86 at 1.3 false positive clusters, which is below that of current MCC detection algorithms for full-field digital mammography. Because of the small number of patient cases, algorithm parameters were not optimized and one linear classifier was used. An actual limitation of our approach may be that the signal-to-noise ratio in the projection images is too low for microcalcification detection. Furthermore, the database consisted of predominantly small MCC. This may be related to the image quality obtained with this first prototype.

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confidence: 99%

Automated detection of microcalcification clusters for digital breast tomosynthesis using projection data only: A preliminary study

et al. 2008

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“…The results obtained for PSF 0 from the best fit are slightly distinguishable from the observed data. Previously published simulation work [8] inspires confidence that the results obtained for PSF 0 are believable. This can be explained by the existence of a very narrow Gaussian in PSF 0 (ν~7-11 µm) which is probably difficult to measure using the edge and slit methods when the fill factor is less than 100%.…”

Section: Discussionmentioning

confidence: 79%

“…This structure is probably related to the columnar structure of the detector X-ray converter. In the simulation study [8], the existence of a narrow component in PSF 0 was also related to light transport in the columns of the CsI converter. The value obtained for the standard deviation is slightly larger for the column with diameter ~10 µm.…”

Section: Spatial Resolutionmentioning

confidence: 99%

“…1), and Ω 00 is the area of the central pixel. It can be expected that PSF 0 will be a symmetric function approximating a columnar scintillation X-ray converter [8].…”

Section: Appendix Cmentioning

confidence: 99%

“…The determination of the simultaneous detection probability allows determination of the two-dimensional symmetric PSF 0 . For detectors using columnar scintillators, the previous statement should be considered as an approximation [8].…”

Section: Introductionmentioning

confidence: 99%

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Simultaneous pixel detection probabilities and spatial resolution estimation of pixelized detectors by means of correlation measurements

Grabski

2008

Nuclear Instruments and Methods in Physics Research Section A:

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On the basis of the determination of statistical correlations between neighboring detector pixels, a novel method of estimating the simultaneous detection probability of pixels and the spatial resolution of pixelized detectors is proposed. The correlations are determined using noise variance measurement for isolated pixels and for the difference between neighboring pixels. The method is validated using images from two image-acquisition devices, a General Electric Senographe 2000D and a SD mammographic unit. The pixelized detector is irradiated with X-rays over its entire surface. It is shown that the simultaneous pixel detection probabilities can be estimated with an accuracy of 0.001-0.003, with an estimated systematic error of less than 0.005. The two-dimensional presampled point-spread function (PSF ) 0 is determined using a single Gaussian approximation and a sum of two Gaussian approximations. The results obtained for the presampled PSF 0 show that the single Gaussian approximation is not appropriate, and the sum of two Gaussian approximations providing the best fit predicts the existence of a large (~50%) narrow component. Support for this observation can be found in the recent simulation study of columnar indirect digital detectors by Badano et al. The sampled two-dimensional PSF is determined using Monte Carlo simulation for the L-shaped, uniformly distributed acceptance function for different fill-factor values. The calculation of the presampled modulation transfer function based on the estimated PSF 0 shows that the observed data can be reproduced only by the single Gaussian approximation, and that when the sum of two Gaussians is used, significantly larger values are apparent in the higher-frequency region for images from both detection devices. The proposed method does not require a precisely, constructed tool. It is insensitive to beam collimation and to system physical size and may be indispensable in cases where thin absorption slits or edges are difficult to use. It could therefore be very useful for regular detector verification.

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Deriving depth‐dependent light escape efficiency and optical Swank factor from measured pulse height spectra of scintillators

et al. 2017

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Purpose Pulse height spectroscopy has been used by investigators to deduce the imaging properties of scintillators. Pulse height spectra (PHS) are used to compute the Swank factor, which describes the variation in scintillator light output per x-ray interaction. The spread in PHS measured below the K-edge is related to the optical component of the Swank factor, i.e. variations in light escape efficiency from different depths of x-ray interaction in the scintillator, denoted ε̄(z). Optimizing scintillators for medical imaging applications requires understanding of these optical properties, as they determine tradeoffs between parameters such as x-ray absorption, light yield, and spatial resolution. This work develops a model for PHS acquisition such that the effect of measurement uncertainty can be removed. This method allows ε̄(z) to be quantified on an absolute scale and permits more accurate estimation of the optical Swank factor of scintillators. Methods The pulse height spectroscopy acquisition chain was modeled as a linear system of stochastic gain stages. Analytical expressions were derived for signal and noise propagation through the PHS chain, accounting for deterministic and stochastic aspects of x-ray absorption, scintillation, and light detection with a photomultiplier tube. The derived expressions were used to calculate PHS of thallium-doped cesium iodide (CsI) scintillators using parameters that were measured, calculated, or known from literature. PHS were measured at 25 and 32 keV of CsI samples designed with an optically-reflective or absorptive backing, with or without a fiber-optic faceplate (FOP), and with thicknesses ranging from 150–1000 μm. Measured PHS were compared with calculated PHS, then light escape model parameters were varied until measured and modeled results reached agreement. Resulting estimates of ε̄(z) were used to calculate each scintillator’s optical Swank factor. Results For scintillators of the same optical design, only minor differences in light escape efficiency were observed between samples with different thickness. As thickness increased, escape efficiency decreased by up to 20% for interactions furthest away from light collection. Optical design (i.e. backing and FOP) predominantly affected the magnitude and relative variation in ε̄(z). Depending on interaction depth and scintillator thickness, samples with an absorptive backing and FOP were estimated to yield 4.1–13.4 photons/keV. Samples with a reflective backing and FOP yielded 10.4–18.4 keV−1, while those with a reflective backing and no FOP yielded 29.5–52.0 keV−1. Optical Swank factors were approximately 0.9 and near-unity in samples featuring an absorptive or reflective backing, respectively. Conclusions This work uses a modeling approach to remove the noise introduced by the measurement apparatus from measured PHS. This method allows absolute quantification of ε̄(z) and more accurate estimation of the optical Swank factor of scintillators. The method was applied to CsI scintillators with different thicknes...

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Anisotropic imaging performance in indirect x-ray imaging detectors

Cited by 34 publications

References 36 publications

Automated detection of microcalcification clusters for digital breast tomosynthesis using projection data only: A preliminary study

Automated detection of microcalcification clusters for digital breast tomosynthesis using projection data only: A preliminary study

Simultaneous pixel detection probabilities and spatial resolution estimation of pixelized detectors by means of correlation measurements

Deriving depth‐dependent light escape efficiency and optical Swank factor from measured pulse height spectra of scintillators

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