Elsevier

Academic Radiology

Volume 13, Issue 7, July 2006, Pages 811-821
Academic Radiology

Original investigation
Patient-Specific Computational Modeling of Cerebral Aneurysms With Multiple Avenues of Flow From 3D Rotational Angiography Images

https://doi.org/10.1016/j.acra.2006.03.011Get rights and content

Rationale and Objectives

Previous studies of aneurysm flow dynamics based on three-dimensional (3D) rotational angiography (RA) images were limited to aneurysms with a single route of blood inflow. However, aneurysms of the circle of Willis frequently involve locations with more than one source of inflow, such as aneurysms of the anterior communicating artery. The highest resolution images of cerebral vessels are from RA images, but this technique is limited to visualizing only one route of inflow at a time, leaving a significant limitation in the application of 3DRA image sets for clinical studies of patient-specific computational fluid dynamics (CFD) simulations. In this report, subject-specific models of cerebral aneurysms with multiple avenues of flow are constructed from RA images by using a novel combination of image coregistration and surface merging techniques.

Materials and Methods

RA images are obtained by means of contrast injection in each vessel that provides inflow to the aneurysm. Anatomic models are constructed independently of each of these vascular trees and fused together into a single model. The model is used to construct a finite element grid for CFD simulations of hemodynamics.

Results

Three examples of patient-specific models are presented: an anterior communicating artery aneurysm, a basilar tip aneurysm, and a model of an entire circle of Willis with five coincident aneurysms. The method is evaluated with a numeric phantom of an aneurysm in the anterior communicating artery.

Conclusion

These examples show that this new technique can be used to create merged network numeric models for CFD modeling. Furthermore, intra-aneurysmal flow patterns are influenced strongly by merging of the two inflow streams. This effect decreases as distance from the merging streams increases.

Section snippets

Patient and Image Data

Three patients with cerebral aneurysms for which multiple 3DRA images had been obtained were selected from our database. These multiple selective angiographic images were chosen to have visualization of all avenues of flow into the aneurysms. Patient 1 is a 54-year-old man with an incidentally discovered 10-mm anterior communicating artery (ACoA) aneurysm treated with elective endosaccular coiling. For this patient, two rotational angiograms were obtained by using contrast injection in the left

Numeric Phantom

The model newly constructed from the simulated angiography was found to be in good agreement with the original anatomic model. Figure 2 (bottom right) shows a surface rendering of the distance between the two geometric models. The maximum distance between the two models is of the order of the voxel size (0.02 cm) used to create the virtual angiograms. It also can be seen that regions of maximum distance between models coincide with regions of poor overlap between the virtual angiograms, in this

Discussion

Current technology cannot provide in vivo intra-aneurysmal hemodynamic information whether using invasive or noninvasive measurements. Therefore, researchers have turned to CFD simulations to gain a better understanding of intra-aneurysmal hemodynamics. Computational-based models provide an attractive tool that can model and study any possible geometry (10). Until recently, computational studies were performed on only idealized aneurysm geometries or approximations of a specific patient

Acknowledgment

The authors thank Philips Medical Systems and The Whitaker Foundation (BRG-01-0085) for financial support and encouragement.

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