Introduction Durability of coiling procedures varies widely, and a better understanding of coil dynamics may help improve the treatment strategy. The goal of this study is to evaluate how packing density (PD) and coil uniformity impact aneurysm occlusion efficiency, which is conceptually associated with coil mass permeability.
Materials and methods Experimental A1 aneurysm models were coiled using Guglielmi detachable coils (GDC) or Target coils. Coiled aneurysms were connected to a flow system filled with 1 µm fluorescent microsphere solution. The coil permeability was defined as the ratio of the microspheres that passed through the coil mass to the microspheres that circulated in the parent vessel. One neck section and 2 dome sections were obtained from each aneurysm for image analysis, including surface area fraction (SAF) and uniformity measurements. SAF was defined as the ratio of coil mass cross-sectional area to aneurysm cross-sectional area, and uniformity was determined from fractal-based heterogeneity measure, lacunarity. Lacunarity values closer to 0 indicate a homogeneously distributed coil mass. A statistical model was used to predict coil mass permeability as the outcome, with packing and uniformity measures as predictor variables. If the packing and uniformity measures exhibited statistically significant correlation, then principal component regression analysis was used for statistical modeling.
Results All aneurysm PDs fell within the range of 27.1% to 45.5%, with a mean PD of 34.3 ± 4.4%. Permeability varied as a function of spatial coil uniformity for a given packing density (36%, Figure 1). With a higher uniformity (lacunarity: 0.06 vs. 0.09), the Target coiled aneurysm allowed less microspheres through the coil mass, as compared to the GDC coiled aneurysm. The lacunarity measures showed that in general, the coil distribution at the cross section of the neck was less uniform than in the dome. Coil mass permeability was statistically correlated with PD, SAF of dome and lacunarity of dome. Principal component regression analysis identified a primary factor with similar weights for PD, SAF of dome, and lacunarity of dome (range: 0.55–0.61). Coil mass permeability was modeled better with principal component regression incorporating the above measures (r2 = 0.7) than linear regression with PD alone (r2 = 0.46). The analysis indicates the importance of including a uniformity measure for coil distribution in the dome along with packing measures.
Conclusion In addition to packing density, coil mass distribution has an important impact on excluding the aneurysm from the circulation.
Disclosures J. Chueh: None. S. Vedantham: None. A. Puri: None. A. Wakhloo: 1; C; NIH, Philips Healthcare. 2; C; Stryker Neurovascular. M. Gounis: 1; C; eV3/Covidien, Philips Healthcare, NIH, Silk Road, Stryker Neurovascular. 2; C; fee-per-hour: Stryker Neurovascular, fee-per-hour: Codman Neurovascular.