Confidence map tool for gradient-based X-ray phase contrast imaging.

We present a graphical tool that we call a "confidence map". It allows to evaluate locally the quality of a phase image retrieved from the measurement of its gradients. The tool is primarily used to alert the observer to the presence of artifacts that could affect his interpretation of the image. It can also be used to optimize a phase imager since it associates a cause with the creation of each artifact: dislocation, under-sampling and noise. An illustration of the use of the confidence map tool is presented, based on a microfocus X-ray tube using multilateral shearing interferometry, a gradient based phase contrast technique employing a single 2D-grating.