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Phys Med Biol. 2011 Apr 7;56(7):2219-44. doi: 10.1088/0031-9155/56/7/020. Epub 2011 Mar 14.

Analytical evaluation of the signal and noise propagation in x-ray differential phase-contrast computed tomography.

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Siemens AG Healthcare Sector, H IM CT R&D PA, Siemensstrasse 1, D-91301 Forchheim, Germany.


We analyze the signal and noise propagation of differential phase-contrast computed tomography (PCT) compared with conventional attenuation-based computed tomography (CT) from a theoretical point of view. This work focuses on grating-based differential phase-contrast imaging. A mathematical framework is derived that is able to analytically predict the relative performance of both imaging techniques in the sense of the relative contrast-to-noise ratio for the contrast of any two materials. Two fundamentally different properties of PCT compared with CT are identified. First, the noise power spectra show qualitatively different characteristics implying a resolution-dependent performance ratio. The break-even point is derived analytically as a function of system parameters such as geometry and visibility. A superior performance of PCT compared with CT can only be achieved at a sufficiently high spatial resolution. Second, due to periodicity of phase information which is non-ambiguous only in a bounded interval statistical phase wrapping can occur. This effect causes a collapse of information propagation for low signals which limits the applicability of phase-contrast imaging at low dose.

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