Cerebral Aneurysm Occlusion at 12-Month Follow-Up After Flow-Diverter Treatment: Statistical Modeling for V&V With Real-World Data

Abstract

Background: Flow-Diverter (FD) porosity has been pointed as a critical factor in the occlusion of cerebral aneurysms after treatment. Objective: Verification and Validation of computational models in terms of predictive capacity, relating FD porosity and occlusion after cerebral aneurysms treatment. Methods: Sixty-four aneurysms, with pre-treatment and follow-up images, were considered. Patient demographics and aneurysm morphological information were collected. The computational simulation provided by ANKYRAS provided FD porosity, expansion, and mesh angle. FD occlusion was assessed and recorded from follow-up images. Multiple regression Logit and analysis of covariance (ANCOVA) models were used to model the data with both categorical and continuous models. Results: Occlusion of the aneurysm after 12 months was affected by aneurysm morphology but not by FD mesh morphology. A Time-To-Occlusion (TTO) of 6.92 months on average was observed with an SE of 0.24 months in the aneurysm population surveyed. TTO was estimated with statistical significance from the resulting model for the data examined and was capable of explaining 92% of the data variation. Conclusions: Porosity was found to have the most correction power when assessing TTO, proving its importance in the process of aneurysm occlusion. Still, further Verification and Validation (V&V) of treatment simulation in more extensive, multi-center, and randomized databases is required.

Keywords: cerebral aneurysms; device porosity; device sizing; flow diverter; time-to-occlusion.

Figure 1

Graphical interface of ANKYRAS, presenting the centerline extraction tools and the quantitative analysis visualization (in this case, cross-section perimeter). The interface of ANKYRAS is 100% hosted by a standard web-browser and can be accessed from any operative system.

Figure 2

Flow diverter braiding structure, being L the length of the stent at the nominal position and ϕ the nominal diameter of the stent. Right: detailed definition of a unit pore cell, translations and reflections of the unit cell along the surface of the stent covers its whole surface. Being S the constant length of the strut, ω the width of the strut, α the angle with the longitudinal direction of the stent, and S_y and S_y the projections of the wire at the crossing point. A and B are the non-occupied areas of the unit cell.

Figure 3

Four sample cases, one for each FD brand used. The first column presents the XA with contrast dilution and the FD. Second column presents the FD highlighted in red. Third column shows the 3D representation of the angiography with the simulated stent implanted at the same distal location as the actual FD. Fourth column shows a close-up of the simulated FD model labeled by porosity. FD, Flow-Diverter.

Figure 4

Box-plot of the porosity for each FD, grouped by FD brand. FD, Flow-Diverter.