oa Harmonic-field Based Artery Separation From Cerebral Aneurysm For Stent Deployment

Background & Objective: Cerebral aneurysms are one of the prevalent and devastating cerebrovascular diseases of adult population worldwide. The resulting effect is subarachnoid hemorrhage, intra- cerebral hematoma and other complications leading to a high mortality rate. When the aneurysm is fusiform, having wide neck or is large in shape, deploying stent in the parent artery to bypass aneurysm is considered as the most suitable treatment. The stent graft is designed to seal tightly with your artery above and below the aneurysm. The graft is stronger than the weakened artery and it allows your blood to pass through it without pushing on the bulge. So that blood cannot flow through the aneurysm to cause any future complication including rupture. Therefore, separation of parent artery from the aneurysm is immensely desired. This paper presents a method to separate parent artery from the aneurysm. Method: It has been challenging to distinguish the parent artery from the aneurysm geometry using a computer algorithm [1]. To date, only a few approaches to accomplish this task have been proposed. In our method, an initial surface mesh of the parent artery with aneurysm is first generated. Then the following steps are subsequently performed to separate the artery from the aneurysm. Step 1. The user specifies foreground and background on the mesh by placing centerline (Figure (a)) on the parent artery and aneurysm; it is also useful for generating Voronoi diagram (Figure (b) and (c)). Step 2. A feature preserving harmonic field based on the user specification is generated (Figure (d)). The resultant harmonic (i.e., "intensity") field over the artery geometry contains large variations not only at these concave and high curvature regions but also at the borders between the normal parent artery and the aneurysm. Since the parent artery centerline is nominally influenced by the presence of an aneurysm, the parent centerline is reconstructed; deviation is recorded and used while finalizing the average isoline or cutting boundary. Step 4. The isolines are generated with the help of Voronoi diagram (from which the average isoline is extracted); see Figure (e). We consider the isolines of the resultant harmonic field as the potential cutting boundary of the parent artery from the aneurysm. Along an isoline, the field variation is minimum. Step 5. A graph-based technique [2] is applied on the harmonic field to segment the parent artery from the aneurysm utilizing the average isoline and distance metric, where we define the energy function according to the harmonic field on the mesh. Results & Conclusion: For testing the method, we collected CTA slices with average thickness of 0.29mm, pixel spacing of 0.29mm x 0.29mm, and matrix size 512x512 on five subjects at the Hamad Medical Corporation using the Siemens Axiom Artis Interventional suite. The average time required by MATLAB R14 to perform segmentation is 2 m for one subject by a 2 GB RAM and core2duo processor (without optimization). Experimental results have shown satisfactory results for meshes with either simple or complicated model.