Geometric correction method for 3d in-line X-ray phase contrast image reconstruction

Abstract

BackgroundMechanical system with imperfect or misalignment of X-ray phase contrast imaging (XPCI) components causes projection data misplaced, and thus result in the reconstructed slice images of computed tomography (CT) blurred or with edge artifacts. So the features of biological microstructures to be investigated are destroyed unexpectedly, and the spatial resolution of XPCI image is decreased. It makes data correction an essential pre-processing step for CT reconstruction of XPCI.MethodsTo remove unexpected blurs and edge artifacts, a mathematics model for in-line XPCI is built by considering primary geometric parameters which include a rotation angle and a shift variant in this paper. Optimal geometric parameters are achieved by finding the solution of a maximization problem. And an iterative approach is employed to solve the maximization problem by using a two-step scheme which includes performing a composite geometric transformation and then following a linear regression process. After applying the geometric transformation with optimal parameters to projection data, standard filtered back-projection algorithm is used to reconstruct CT slice images.ResultsNumerical experiments were carried out on both synthetic and real in-line XPCI datasets. Experimental results demonstrate that the proposed method improves CT image quality by removing both blurring and edge artifacts at the same time compared to existing correction methods.ConclusionsThe method proposed in this paper provides an effective projection data correction scheme and significantly improves the image quality by removing both blurring and edge artifacts at the same time for in-line XPCI. It is easy to implement and can also be extended to other XPCI techniques.

Correction of micro‐CT image geometric artefacts based on marker

“…represents the coordinate of the jth non-overlap projection of the ith ball's mass centre, given by (9) and (10). (ū i j , v¯i j ) represents the coordinate of the jth not-overlap projection's mass centre of the ith ball, given by (17) and (18).…”

“…In addition, some papers assume that the CT turntable axis is parallel to the detector plane or only part of these geometric parameters are estimated. The second strategy [16][17][18][19][20][21][22][23][24][25], generally uses the projection data features of the measured sample to establish the optimisation model and estimate geometric parameters. Then the CT image geometric artefacts can be eliminated by using the estimated geometric parameters or correcting the scanning CT data.…”