Correcting phase contrast artefacts in X-ray CT imaging

When going to higher resolution in X-ray transmission CT, one of the biggest problems is the appearance of phase contrast. Achieving high resolution usually means scanning very small and thus very low absorbing objects, especially in medical and biological applications. Since the absorption signal for such samples becomes very small, the contribution of the phase contrast signal to the projection image is no longer negligible. This phase signal, which is due to small angle refraction of the X-rays in the sample, results in severe artifacts in the reconstructed slices when using conventional reconstruction algorithms for transmission CT. The appearance of such phase artifacts can be prevented by using a method called Bronnikov Aided Correction, which applies a filtering operation on the projection images that almost completely removes the phase signal. This method is used to reconstruct a CT scan of a horse biopsy. Results are compared with those of a standard reconstruction.