Eurographics Conference on Visualization (EuroVis) 2014 H. Carr, P. Rheingans, and H. Schumann (Guest Editors) Volume 33 (2014), Number 3 Comparative Blood Flow Visualization for Cerebral Aneurysm Treatment Assessment R. van Pelt 1 , R. Gasteiger 2 , K. Lawonn 2 , M. Meuschke 2 , and B. Preim 2 1 Biomedical Engineering, Eindhoven University of Technology, The Netherlands 2 Visualization Group, Otto-von-Guericke University Magdeburg, Germany Abstract A pathological vessel dilation in the brain, termed cerebral aneurysm, bears a high risk of rupture, and is as- sociated with a high mortality. In recent years, incidental findings of unruptured aneurysms have become more frequent, mainly due to advances in medical imaging. The pathological condition is often treated with a stent that diverts the blood flow from the aneurysm sac back to the original vessel. Prior to treatment, neuroradiol- ogists need to decide on the optimal stent configuration and judge the long-term rupture risk, for which blood flow information is essential. Modern patient-specific simulations can model the hemodynamics for various stent configurations, providing important indicators to support the decision-making process. However, the necessary visual analysis of these data becomes tedious and time-consuming, because of the abundance of information. We introduce a comprehensive comparative visualization that integrates morphology with blood flow indicators to facilitate treatment assessment. To deal with the visual complexity, we propose a details-on-demand approach, combining established medical visualization techniques with innovative glyphs inspired by information visualiza- tion concepts. In an evaluation we have obtained informal feedback from domain experts, gauging the value of our visualization. Categories and Subject Descriptors (according to ACM CCS): I.3.8 [Computer Graphics]: Applications—Cerebral Blood Flow I.6.8 [Simulation and Modeling]: Types of Simulation—Combined 1. Introduction Blood flow information is increasingly consulted for diag- nosis and treatment assessment of cardiovascular disease [MFK * 12] – currently the leading cause of death worldwide. This work focuses on cerebrovascular conditions, which can cause stroke through blockage or hemorrhage, accounting for approximately one out of nineteen deaths in the USA [GMRea13]. Specifically, we are concerned with cerebral aneurysms, which bear a high risk of rupture, and are there- fore related to high morbidity and mortality [SPC09]. An increased number of patient examinations and ad- vances in medical imaging have led to more incidental findings of the mostly asymptomatic cerebral aneurysms [Wie03]. Today, these lesions are often treated with flow di- verting stents combined with a coil, promoting thrombosis in the cavity. Initial clinical trials showed promising results, but recent findings show an increased risk of post-treatment hemorrhaging due to a pressure increase [CMR * 11]. Neuroradiologists have to assess the treatment risk, decid- ing on the type of stent and its placement; bearing in mind the long-term safety. This process mainly relies on mor- phological indicators, such as aneurysm size or sphericity. However, this is not reliable in all cases, and the hemody- namics are also evidently important. Current research thus acquires indicators such as pressure and wall-shear stress (WSS) using blood flow simulations [JRST13]. These com- putational fluid dynamics (CFD) simulations rely on the patient-specific aneurysm morphology, and enable prognos- tic comparison between different stent configurations. Besides the quantitative assessment of the simulation out- come, visual analysis is essential to understand the spa- tial relations between the hemodynamics and morphology [GLvP * 12], and is of importance for simulation researchers, stent design engineers and neuroradiologists. The simula- tions, however, provide an abundance of time-varying hemo- dynamic information, which should be compared between the stent configurations. To support the visual analysis, a comprehensive visualization is therefore essential. c  2014 The Author(s) Computer Graphics Forum c  2014 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.