Hello Djalal,

great question, I think it is the size of and the complex flow patterns with multiple vortices with lack of current quantitative markers to describe these intra-aneurysmal flow patterns. Flow patterns have inter individual variances based on the bifurcations e.g. which might increase even more these flow pattern deviations influencing development or aneurysm progression. 

hope this helps 

Filip

Thanks you for the answer