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Proceedings Paper

Investigation of source grating stepping for differential phase-contrast cone-beam CT (DPC-CBCT) system
Author(s): Weixing Cai; Yang Yu; Ruola Ning; Jiangkun Liu; David Conover
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Paper Abstract

Differential phase contrast (DPC) imaging, which utilizes phase shift information of X-ray, has the potential of dramatically increasing the contrast in biological sample imaging compared to attenuation-based method that relies on X-ray absorption information, since the X-ray phase is much more sensitive than the attenuation during transmission. In a DPC imaging system, the phase stepping method is widely used to obtain DPC images: at each angle the phase grating is shifted incrementally to produce a set of images and then the so obtained images are used to retrieve DPC image. However, DPC imaging requires a high mechanical precision to perform phase stepping, which is generally one order higher than the period of phase grating. Given that phase grating period is generally 2-4 um, the requirement of mechanical accuracy and stability are very demanding (<0.5um) and difficult to meet in a system with rotating gantry. In this paper, we present a method that is able to greatly relax the requirement of mechanical accuracy and stability by stepping the source grating rather than the analyzer grating. This method is able to increase the system's mechanical tolerance without compromising image quality and make it feasible to install the system on a rotating gantry to perform differential phase-contrast cone beam CT (DPC-CBCT). It is also able to increase the grating shifting precision and as a result improve the reconstructed image quality. Mechanical tolerance investigation and image quality investigation at different phase stepping schemes and different dose levels will be carried out on both the original modality and the new modality, the results will be evaluated and compared. We will deliberately create random mechanical errors in phase stepping and evaluate the resulting DPC images and DPC-CBCT reconstructions. The contrast, noise level and sharpness will be evaluated to assess the influence of mechanical errors. By stepping the source grating, the system is expected to tolerate an error of 6-7 times bigger than that with analyzer grating stepping.

Paper Details

Date Published: 9 March 2012
PDF: 6 pages
Proc. SPIE 8313, Medical Imaging 2012: Physics of Medical Imaging, 83132S (9 March 2012); doi: 10.1117/12.911422
Show Author Affiliations
Weixing Cai, Univ. of Rochester Medical Ctr. (United States)
Yang Yu, Univ. of Rochester (United States)
Ruola Ning, Univ. of Rochester Medical Ctr. (United States)
Univ. of Rochester (United States)
Jiangkun Liu, Univ. of Rochester (United States)
David Conover, Koning Corp. (United States)


Published in SPIE Proceedings Vol. 8313:
Medical Imaging 2012: Physics of Medical Imaging
Norbert J. Pelc; Robert M. Nishikawa; Bruce R. Whiting, Editor(s)

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