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Modelling the penumbra in computed tomography
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Kueh, Audrey, Warnett, Jason M., Gibbons, Gregory John, Brettschneider, Julia, Nichols, Thomas E., Williams, M. A. and Kendall, W. S. (2016) Modelling the penumbra in computed tomography. Journal of X-Ray Science and Technology, 24 (4). pp. 583-597. doi:10.3233/XST-160576
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Official URL: http://dx.doi.org/10.3233/XST-160576
Abstract
Background:
In computed tomography (CT), the spot geometry is one of the main sources of error in CT images. Since X-rays do not arise from a point source, artefacts are produced. In particular there is a penumbra effect, leading to poorly defined edges within a reconstructed volume. Penumbra models can be simulated given a fixed spot geometry and the known experimental setup.
Objective:
This paper proposes to use a penumbra model, derived from Beer’s law, both to confirm spot geometry from penumbra data, and to quantify blurring in the image. Methods: Two models for the spot geometry are considered; one consists of a single Gaussian spot, the other is a mixture model consisting of a Gaussian spot together with a larger uniform spot. Results: The model consisting of a single Gaussian spot has a poor fit at the boundary. The mixture model (which adds a larger uniform spot) exhibits a much improved fit. The parameters corresponding to the uniform spot are similar across all powers, and further experiments suggest that the uniform spot produces only soft X-rays of relatively low-energy.
Conclusions:
Thus, the precision of radiographs can be estimated from the penumbra effect in the image. The use of a thin copper filter reduces the size of the effective penumbra.
| Item Type: | Journal Article | ||||||
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| Subjects: | R Medicine > R Medicine (General) | ||||||
| Divisions: | Faculty of Science > Statistics Faculty of Science > WMG (Formerly the Warwick Manufacturing Group) |
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| Library of Congress Subject Headings (LCSH): | Tomography -- Data processing | ||||||
| Journal or Publication Title: | Journal of X-Ray Science and Technology | ||||||
| Publisher: | I O S Press | ||||||
| Official Date: | 20 July 2016 | ||||||
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| Volume: | 24 | ||||||
| Number: | 4 | ||||||
| Page Range: | pp. 583-597 | ||||||
| DOI: | 10.3233/XST-160576 | ||||||
| Status: | Peer Reviewed | ||||||
| Publication Status: | Published | ||||||
| Access rights to Published version: | Open Access | ||||||
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