Artifact Reduction in Phase Contrast Tomography

Pascal Bienz

Semester Project

Microengineering section, EPFL

July 2012

Abstract

Differential phase contrast tomography based on grating interferometer is a recent imaging modality which is extraordinarily sensitive to density variations in the sample. The method is especially suited for imaging of biomedical samples and will play an indispensable role in future X-ray imaging applications. However, the high sensitivity to variations in the sample is accompanied by a high sensitivity to intensity fluctuations during image acquisition. It leads to artifacts in the 3D reconstructions, which in turn constitutes a major obstacle for 3D data visualization and analysis.
In this project one outlines the basics of X-ray phase imaging with a grating interferometer and briefly explains the mathematical model of a direct reconstruction process. One then relates the implementation of a 3D projection using MATLAB, C and MEX-files to interface them and presents some results. One finally introduces a lead to remove the artifacts : an iterative reconstruction method using the alternating direction method of multipliers. A brute force computation would, however, be too costly which drives us to parallelize the 3D projection in a sum of 2D projection.

Cuts of a 3D Projection of a part of a human body in the y-theta plane and in the y-z plane respectively