Modeling of ‘patient-specific’ blood flow in the brain: Are we there yet?

A brain aneurysm is a focal weakening of the arterial wall, and rupture is associated with high rates of mortality and morbidity. Roughly 5% of the population harbors these asymptomatic ‘ticking-bombs’, with an annual rupture risk of 1%. Cost benefit analyses do not support intervention, so what to do individually when incidentally detected? Wall shear stresses are well known to correlate with vessel wall remodeling and rupture, but cannot be measured. Instead, patient-specific medical images are routinely available and have been widely used in combination with computational fluid dynamics (CFD) to reveal adverse “patient-specific” hemodynamic environments correlated with disease initiation, progression, and outcome. However, results are equivocal and clinicians question whether CFD is actually ‘confounding factor dissemination’. In this talk, we present a brief review of the state of the art and also provide an alternative perspective on the results. We discuss basic assumptions, sources of variability, and variability of community challenge results. In short, inconsistency seems to be the only consistency, which begs for standardization. We also address whether results from (bio-) engineering tools really reflect the physics of fluids. Finally, we outline future directions that are essential for translating engineering tools to clinical practice.