Modeling Risks in Cerebral Aneurysms

Overview

Unruptured cerebral aneurysms can represent a significant health risk for patients if not properly diagnosed and treated. A study was carried out to determine if significant geometrical differences could be measured between a soft (close to the rupture) aneurysm and a stiff (healthy) aneurysm. The biomechanical properties of soft and stiff tissues of the aneurysm sac were determined experimentally. Image processing of MRI scans was carried out in Simpleware ScanIP to create a model suitable for simulating fluid-structure (FSI) interactions and evaluation of tissue rupture risk based on its mechanical properties.

Characteristics:

  • 3D models from MRI
  • Visualization of segmented image data of aneurysm
  • Cropping and processing of segmented data
  • Export of image data for simulation in ANSYS©

Thanks to

IRRAs Technology, Philips Healthcare, University of Montpellier:
M. Sanchez • D. Ambard • V. Costalat • S. Mendez • F. Jourdan • F. Nicoud

Image Processing

The geometry of the aneurysm was obtained from an MRI patient scan. This data was imported into ScanIP, where automated thresholding and flood fill tools were used to separate out regions of interest, keeping only the parent artery. Cropping was then employed to reduce the region of interest for analysis. A low-pass (Gaussian) filter was applied to segmented data to reduce the noise-to-signal ratio and smooth the image. Processed image data was exported to ANSYS© for further analysis.

FSI Simulation

Boundary conditions were set for modelling fluid structure interaction (FSI) on the mechanical properties of aneurysm tissue material. Simulations were carried out in ANSYS to determine whether significant geometrical differences are measurable between a soft (close to the rupture) aneurysm and a stiff (healthy) aneurysm. Differences were observed based on volume variations and maximal mesh displacements for two aneurysm models along a typical cardiac cycle, and in the context of parametric tests.

Results

Testing indicated that, based on comparisons with real intracranial artery tissues extracted during surgery, there is a strong correlation between the mechanical properties of aneurysm materials and their risk of rupture.

FSI computations demonstrated a significant difference in volume variations corresponding to high risk soft and lower risk stiff aneurysm cases.

The results demonstrated the potential of assessing a patient-specific risk of rupture based on a comparison of computed volume variations and patient medical images.