Cardiovascular diseases are the leading cause of death worldwide. Treatment options such as replacement of the vascular tissue with a synthetic graft, intravascular stent deposition or balloon angioplasty often tend to fail. The hypothesis is that this failure is partly due to a mechanical mismatch between the biomaterial and the native tissue, or the application of too large mechanical forces on the vascular tissue during treatment. However, the exact mechanisms are not yet fully understood. To better understand these mechanisms and to evaluate potential new treatment techniques, biomechanical characterization of vascular tissue could provide a solution. The goal of this thesis is, therefore, two-fold. The first aim is to develop, validate and apply a novel methodology for dynamic testing of vascular tissues, named 4D contrast-enhanced 3D microfocus X-ray computed tomography (4D CECT). 4D CECT combines in-situ mechanical testing of soft tissues with CE-CT imaging. It allows to obtain a 3D visualization of the different subtissues (collagen and elastin fibres, calcifications, adipocytes, …) within native and diseased vascular tissues, and it provides information on the microstructural changes of the tissue during loading. It also allows to quantify the local strain distribution at different stages of the loading. The second objective is to create a more comprehensive computational model to evaluate and predict the outcome of a medical treatment. For this, we will use the microstructural information provided by CE-CT of native and diseased vascular tissues. The results of the 4D CECT imaging will serve as validation of the model. The combined imaging and modelling approach should improve the insights into the failure mechanisms of some of the current treatments of cardiovascular diseases.