Fig 1.
Reconstructed μCT data of a stent cast and registration.
A: Theuse of PDMS casts of model vessels provided μCT scan data of accurate geometry and captured fine stent strut detail, including prolapsed struts (red arrow). Top: Optimising μCT scan and reconstruction parameters for homogeneous PDMS casts produced an image of the lumen with a clearly defined wall boundary. Bottom: Cutaway of a section of wall boundary reconstructed from a 9.92 μm resolution scan of a Coroflex Blue coronary stent cast. B: Rigid body registration was performed on models of a Coroflex Blue coronary stent and its associated cast, reconstructed from data from separate μCT scans. The two were aligned in an effort to measure the ability of casts to recreate the geometry of stents.
Fig 2.
Tracked particle streamlines in coronary stents.
Particles were tracked moving through coronary stents deployed within model vessels. Tracking was performed for two 30-second-long sequences (red and blue tracks) on two stent faces, with the stent rotated by 90° between the two faces. A: BiodivYsio OC stent; B: Chroma stent; C: Coroflex Blue stent; D: Coroflex Blue Neo stent; E: Matrix stent; F: Orsiro stent; G: Penchant stent; H: Pro Kinetic Energy stent; I: Velocity stent; J: XTRM-Track stent. Flow direction indicated with arrows. Re = 68 (equivalent to blood flow with 1 Pa wall shear stress). Representative images are mid-stent length and the plane of focus on the bottom of the vessel.
Fig 3.
Complex flow within coronary stent geometry.
Particle tracking revealed areas of complex flow patterns local to struts within coronary stent geometry. A: Recirculation seen within a valley structure of a Coroflex Blue stent. B: Flow reversal seen between Coroflex Blue main ring and bridge struts. C: Flow reversal and recirculation seen within a bridge strut of a BiodivYsio OC stent. Flow from left to right, Re = 68 (equivalent to blood flow with 1 Pa wall shear stress). Scale bar: 100 μm.
Fig 4.
Particle track orientation in coronary stents.
The orientationof tracked particle streamlines moving through coronary stents deployed within model vessels was measured to determine whether the workflow can assess the impact of stent design on the direction of flow. The length of tracks at an angle greater than ±5° of the direction of flow (0°) is shown as a percentage of the total length of tracks within each stent. This threshold was applied to ensure that stent-induced flow deviation was captured while minor deviations, due to equipment disturbance or manual tracking errors, were omitted.
Fig 5.
Locations of particle accumulation within coronary stents.
After cessation of flow, accumulated particles (green) within coronary stents deployed in model vessels were imaged and counted within 1 mm segments (red lines) in order to assess whether the workflow can be used to analyse particle accumulation. No pattern in the location or distribution of particles throughout each model was seen, with the exception of the Chroma and Matrix stents shown here, in which accumulation was almost exclusively seen immediately up or downstream of struts. Top: Chroma stent. Bottom: Matrix stent.
Fig 6.
Wall shear stress within coronary stents.
In silico models were created from reconstructed μCT scans of coronary stent casts and used for CFD analysis to plot wall shear stress along the vessel. A: Coroflex Blue stent, showing elevated shear stress on the luminal surface of prolapsed struts; B: Matrix stent, showing reduced shear stress downstream of struts; C: Pro Kinetic Energy stent, showing reduced shear stress downstream of struts; D: XTRM-Track stent, showing reduced shear stress downstream of struts and within areas of complex geometry. Flow from left to right, 1 Pa average wall shear stress. Note: the maximum value of the scale bar is set to 3 Pa to better illustrate regions of low flow.
Fig 7.
Velocity vectors around coronary stent struts.
In silico models were reconstructed from Coroflex Blue stent strut μCT data and used for CFD analysis. Velocity fields are depicted at the vessel wall [dark blue arrows] and at a fluid layer positioned nearer to the lumen [light blue arrows], with the length of each arrow being proportional to velocity. Vectors revealed that while stent struts had relatively modest effects on velocity magnitude, they greatly impacted direction as flow moved up and over struts, leading to reduced wall shear stress in those regions. Flow from left to right, 1 Pa average wall shear stress. Scale bar: 100 μm.
Fig 8.
Wall shear stress along reference lines within a Matrix coronary stent.
In silico models were reconstructed from coronary stent μCT data and used for CFD analysis. Plotting data along reference lines in the direction of flow revealed elevated wall shear stress on stent struts, greatly reduced shear stress immediately up and downstream of struts, and recovery of shear stress in inter-strut regions. A: Matrix stent, with two reference lines (red and blue); B: Wall geometry (top) and shear stress along the upper, red reference line; C: Wall geometry (top) and shear stress along the lower, blue reference line. Flow from left to right, 1 Pa average wall shear stress.