Laboratory experiments carried out at the LMR-EPFL on thick-walled hollow cylindrical samples aim at modelling at small-scale conditions similar to those that will be experienced by host rocks around disposal galleries for heat emitting radioactive waste. The paper presents results on a Boom Clay sample cored parallel to the bedding planes and subjected to a decrease of the confining pressure in the central hole of the hollow cylinder. It focuses on medium resolution X-Ray Computed Tomography (XRCT) scans of the sample inside the testing cell that were carried out with a medical scanner. By comparing the scans before and after the mechanical unloading (tracking of the movement of pyrite inclusions), quantitative analyses of the displacements undergone by the clay can be performed. The observations point out a significant mechanical anisotropy of Boom Clay related to its bedding planes.