Inner-focusing reconstruction method for grating-based phase-contrast CT.

Grating-based phase-contrast imaging has been a hot topic for several years due to its excellent imaging capability for low-density materials and easy implementation with a laboratory x-ray source. Compared with traditional x-ray computed tomography (CT) systems, the standard data collection procedure, "phase-stepping" (PS), in the grating-based phase-contrast CT (GPC-CT) is time consuming. The imaging time of a GPC-CT scan is usually up to hours. It is unacceptable in clinical CT examinations, and will cause serious motion artifacts in the reconstructed images. Additionally, the radiation dose delivered to the object with the PS-based GPC-CT is several times larger than that by a conventional CT scan. To address these problems, in this paper, we followed the interlaced PS method and proposed a novel image reconstruction method, namely the inner-focusing (IF) reconstruction method. With the interlaced PS method, the sample rotation and the grating stepping in GPC-CT occur at the same time. Thus, the interlaced GPC-CT scan can have a comparable temporal resolution with existing CT systems. Without any additional requirements, the proposed IF reconstruction method can prevent the artifacts existing in the conventional interlaced PS method. Both numerical simulations and real experiments were carried out to verify the proposed IF reconstruction method. And the results demonstrated it was effective in archiving a fast and low-dose GPC-CT.