In collaboration with hospitals we try to investigate various topics in medicine by means of visualization or visual analytics. Due to the increasing amount of data generated by hospital information systems, visualization becomes successively more important. Extracting certain trends from such highly diverse data by suitable visual mappings is one of the primary goals of medical visualization. The data is usually acquired by computed tomography, magnetic resonance imaging or ultrasound. Currently, our research addresses the analysis of blood vessels such as the inspection of possible stenotic regions or their spatial arrangement as in the Circle of Willis. Furthermore, we investigate aneurysm classification and lesion detection as well as visualization. Another research area deals with realistic prenatal visualization of the fetus in-vivo and in real-time. Due to the high variability of medical imaging data, we further focus on high-level correction of segmentation defects.