6.2.1 Unroll stent

A stent is a medical device used to reopen narrowed arteries. The vast majority of stents are balloon-expandable, which means that the metal structure is deployed by inflating a balloon, located inside the stent. Figure 6.7 shows an example of such a stent prior to expansion (balloon not shown). The 3D surface is obtained by micro CT and consists of triangles.

Figure 6.7: Triangulated mesh of a stent
 
cypher-stent.png

The structure of such a device can be quite complex and difficult to analyse. The same functions pyFormex offers for creating geometries can also be employed to investigate triangulated meshes. A simple unroll operation of the stent gives a much better overview of the complete geometrical structure and allows easier analysis (see figure 6.8).

F = F.toCylindrical().scale([1.,2*radius*pi/360,1.])

Figure 6.8: Result of unroll operation
 
cypher-stent-unroll.png

This unrolled geometry can then be used for further investigations. An important property of such a stent is the circumference of a single stent cell. The clip() method can be used to isolate a single stent cell. In order to obtain a line describing the stent cell, the function intersectionLinesWithPlane() has been used. The result can be seen in figure 6.9.

Figure 6.9: Intersection of stent cell with plane and inner line of stent cell
 
stent-cell-full.png stent-cell.png

Finally, the length() function returns the circumference of the cell, which is 9.19 mm.