Fig 1.
Schematic illustration of the dogboning ratio during stent deployment.
A: Crimped stent inside an artery. B: Stent expansion with pronounced dogboning ratio. C: Overstretching of the artery due to the dogboning ratio. D: Final cylindrical expanded stent configuration inside slightly overstretched artery. E: Exemplary detailed illustration of the determination of dogboning ratio.
Fig 2.
Model set-up of the balloon folding process.
A: Isometric illustration of the initial balloon inside the folding jaws with the representation of the balloon mesh. B: Isometric illustration of the folded balloon inside the pleating jaws and the resulting balloon mesh after folding.
Table 1.
Material parameters used for modeling the constitutive material behavior of the balloon (Grilamid L25).
Fig 3.
Schematic illustration of the boundary condition during the balloon folding simlation.
A: Schematic illustration of the initial balloon and catheter inside the three folding jaws with the pivot point/RP of the jaws (indicated by “x”) which are connected to the jaws by a rigid body constraint (blue dashed line). B: Application of the rotation boundary condition urot at the pivot point/RP of the folding jaws, which causes the jaws to rotate by the angle α and thus creates the three balloon folds. The initial position of the folding jaws is indicated with a dotted line. C: Schematic illustration of the folded balloon and catheter inside the ten pleating jaws with the pivot point/RP of the jaws (indicated by “x”) which are connected to the jaws by a rigid body constraint (blue dashed line). D: Application of the rotation boundary condition urot at the pivot point/RP of the pleating jaws, which causes the jaws to rotate by the angle α and thus wraps the three balloon folds around the catheter. The initial position of the pleating jaws is drawn with a dotted line.
Fig 4.
Model set-up of and schematic illustration of the boundary condition during the stent crimping simulation.
A: Stent placed over the balloon-catheter system. B: Folded balloon, catheter and stent inside the twelve crimping jaws with the pivot point/RP of the jaws (indicated by “x”) and the connection of the jaws to the pivot points/RP via a rigid body constraint (blue dashed line). C: Application of the rotation boundary condition urot at the pivot points/RP of the crimping jaws, which causes the jaws to rotate by the angle α and thus creates the three balloon folds.
Table 2.
Material parameters used for modeling the constitutive material behavior of the stent (stainless steel 316L).
Fig 5.
Successive simulation results of the balloon folding process.
A: Balloon cross section of the initial cylindrical balloon. B: Cross section after the folding process. C: Cross section after the vacuum generation and retraction of the folding jaws. D: Cross section after the pleating process. E: Cross section of the final folded balloon configuration after retraction of the pleating jaws.
Fig 6.
Validation of the balloon folding simulation.
A: Superimposition of a section of the predicted folded balloon (yellow) with CT Data (blue). B: Superimposition of a section of the predicted folded balloon (black) with a section of an embedded balloon.
Table 3.
Validation of the predicted stent dimensions after crimping with experimental measurements.
Fig 7.
Successive simulation results of the stent crimiping process.
A: Initial balloon-stent configuration before crimping. B: Maximum compressed stent configuration after rotating the crimp jaws (not visualized) around their pivot point and thereby reducing the diameter of the crimp iris. C: Holding phase. D: Final crimped stent-balloon configuration after retraction of the crimping jaws and stent recoil.
Fig 8.
Validation of the crimping simulation.
A: Comparison of the numerical results of stent crimping (grey) with CT data of a crimped stent (blue). B: Superimposition of the numerical results of stent crimping (black) with the section of an embedded stent.
Fig 9.
Comparison of the predicted stent expansion behavior (left) with high-speed recordings (right).
A: Detailed stent life-cycle simulation of stent V1. B: Detailed stent life-cycle simulation of stent V2. C: Detailed stent life-cycle simulation of stent V1 with an assymmetric positioning of the stent on the balloon catheter D: Displacement-controlled expansion of stent V1. For reasons of conformity with Fig 10, the given time labels were related to the entire simulation of the stent life-cycle. Therefore, stent expansion starts at a step time t of 4 s.
Fig 10.
Numerically determined diameter course within the simulation of the entire stent life-cycle.
A: Detailed stent life-cycle simulation of stent V1. B: Detailed stent life-cycle simulation of stent V2. C: Detailed stent life-cycle simulation of an asymmetrical positioned stent V1. D: Displacement-controlled expansion of stent V1. Within the evaluation of the results from the detailed simulation approach (A, B, C), a distinction was also made between the diameter progression of the stent ends (red) and the central part of the stent.
Table 4.
Validation of the predicted stent dimensions after stent expansion with experimental measurements (mean value and standard deviation(SD)).
Fig 11.
Determination of the dogboning ratio for stent within the stent life-cycle simulation.
A: Stent V1 with a typical pronounced dogboning ratio, B: Stent V2 with a rather untypical dogboning ratio due to the heterogenous stent design.
Fig 12.
Comparison of stress distribution in the maximum expanded state.
A: Overview of the stress distribution and localization of the following close-up representations. B: Stress distribution obtained from the detailed stent life-cycle simulation of stent V1. C: Stress distribution obtained from the displacement controlled expansion simulation of stent V1. D: Stress distribution obtained from the detailed stent life-cycle simulation of stent V2.
Fig 13.
Qualitative validation of stent deformation with scanning electron microscope images of an expanded V1 stent.
A: Scanning electron microscope images and B: Plastic equivalent strain distribution resulting from the detailed simulation of stent V1.