Physical Image Simulation of Human Brain in Case of Acute Stroke

In an acute stroke parts of the human brain undergo subtle physiological changes, which are often visible as hypo- or hyperdense regions in Computed Tomography (CT) images. In the case of ischemic stroke usually an edema develops due to undersupplied cells forming regions of a core (dead tissue) and a penumbra (salvable tissue). For stroke diagnosis and outcome control it is very important to know the location and size of these different kinds of damaged tissue. We have modelled the changes in elemental composition of brain tissue in different phases of an ischemic stroke. Influence of a number of factors on the absolute Hounsfield units is investigated as possible causes of intra- and interpatient variation. The modeled pathological changes are included in different software brain models. Subsequently we have simulated X-ray images of these brain models acquired by dual energy Cone Beam Computed Tomography (CBCT). Our modelling is based on a combination of analytical and Monte-Carlo methods. As an example of spectral processing virtual monoenergetic images are reconstructed from the simulated projections. Simulated images are intended to optimize acquisition parameters for clinical studies beforehand and to develop new image processing algorithms to enhance the diagnostic value. As example a water map is calculated to better visualize the formation of an edema after ischemic stroke.