3D Shape Analysis of Intracranial Aneurysms Using the Writhe Number as a Discriminant for Rupture

Abstract

Abstract-Intracranial aneurysms are polymorphic focal arterial dilations, which harbor a variable risk of rupture leading to high morbidity and mortality. Increased detection of incidental aneurysms by non-invasive imaging has created a need for rupture risk stratification tools, in addition to simple aneurysm size, to guide optimal treatment strategy. To this end, shape analysis has emerged as a possible differentiator of rupture likelihood. A novel set of morphological parameters based on the writhe number are introduced here to describe aneurysms and discriminate rupture status. Classification in 117 saccular aneurysms (52 ruptured and 65 unruptured) is based on statistical analysis of writhe number distribution on the aneurysm surface. Aneurysms are analyzed both in isolation and including a portion of their parent vessel. Sidewall and bifurcation aneurysm subtypes were found to be best described by disjoint sets of shape parameters, yielding a morphological dichotomy between the two aneurysm classes. Writhe number analysis results in 86.7% accuracy on sidewall (SW) aneurysms and 71.2% accuracy on bifurcation (BF) aneurysms. This represents a 12% accuracy increase for both subtypes compared to the performance of seven established 2D and 3D indexes. The results support the utility of writhe number aneurysm shape analysis, with potential clinical value in rupture risk stratification.

Suggested Connections Between Risk Factors of Intracranial Aneurysms: A Review

“…They analyzed sidewall and bifurcation aneurysms separately and found a classification accuracy of 80% and 70%, respectively 71 . Similarly, the use of the writhe number, which measures the extent to which a curve twists and coils around itself, to characterize aneurysm shapes and predict aneurysm rupture status resulted in approximately 86% accuracy for sidewall aneurysms and 71% accuracy for bifurcation aneurysms 74 .…”

Three-Dimensional Reconstruction and Characteristics Computation of Corn Ears Based on Machine Vision

“…Other shape features of interest can also be identified and each feature is quantified by one or more indices. For example, the non-sphericity index (NSI) can express how closely the shape of the corn ear resembles a sphere [12]. The NSI is defined as:…”

Physical Factors Effecting Cerebral Aneurysm Pathophysiology

“…4,34,153,177 There is some evidence that the longitudinal axis of aneurysms clusters around specific angles with respect to the parent artery 166 and that more distal aneurysms have smaller sizes, 17 but the effect of the perianeurysmal environment 154 must be considered along with such results. Advancements in software and hardware have enabled the quantification of much more sophisticated geometrical variables (or sophisticated combinations of geometrical variables) of the 3D aneurysm-parent vessel complex with relative ease 104,111,138,139 and although it is difficult to imagine that a critical threshold predicting aneurysm rupture (or initiation) could be derived from purely geometrical factors, future evaluation may yield a geometrical predictive test with acceptable sensitivity and specificity to be clinically useful.…”