Spatial Projection Ratio: A Novel Shape Index to Evaluate Aneurysm Rupture Risk Using Three-dimensional Geometry.

Area of Science:

• Medical Imaging
• Radiology
• Biomedical Engineering

Background:

• Traditional 2D shape indices for aneurysm rupture assessment can be biased by observation direction.
• A need exists for more accurate, direction-independent morphological parameters to evaluate aneurysm rupture risk.

Purpose of the Study:

• To introduce and validate a novel 3D morphological parameter, the spatial projection ratio, for assessing aneurysm rupture status and risk.
• To compare the diagnostic performance of spatial projection ratio against traditional indices and primary variables.

Main Methods:

• Retrospective analysis of 225 aneurysms using 3D computed tomography angiography.
• Calculation of spatial projection ratio based on 3D geometry (neck orifice center to furthest point, divided by equivalent neck diameter).
• Statistical analysis including Brunner-Munzel tests, ROC curve analysis, and Spearman's rank correlation.

Main Results:

• Ruptured aneurysms showed significantly higher primary variables and shape indices than unruptured ones.
• Spatial projection ratio demonstrated high diagnostic accuracy (AUC = 0.791) for rupture status, outperforming primary variables.
• Spatial projection ratio correlated significantly with the traditional size ratio (r = 0.575, p < 0.01).

Conclusions:

• Spatial projection ratio is a robust 3D morphological parameter for evaluating aneurysm rupture status.
• This novel index may enhance the prediction of aneurysm rupture risk, offering improved clinical insights.