Integrating particle tracking with computational fluid dynamics to assess haemodynamic perturbation by coronary artery stents- COROFLEX BLUE STENT, MICROCT

µCT scans were performed with a SkyScan 1172 high-resolution desktop µCT scanner (Bruker). Stented vessels (with or without contrast agent) and casts were secured to an 8 mm diameter rotating stage within the machine with double-sided tape, oriented vertically (Figure 2.6A). The x-ray source was turned on and control software was opened to provide a live image via an 11 megapixel x-ray camera, as well as the means to alter scan parameters: voltage, current, resolution, the use of aluminium filters, etc.

The vertical position of the stage, the camera pixel size (large, 1000 x 500; medium, 2000 x 1000; small, 4000 x 2000) and the proximity of the camera to the sample were set to maximise resolution while ensuring that the region of interest (i.e. the full length of the stent or cast) remained within the field of view. When the sample extended beyond the widest field of view (typically models containing stents longer than 13 mm) multiple oversize scans were performed. The stage, being metallic, was always kept outside of the field of view to reduce interference.

The stage was set to rotate 180°, in 0.7° steps. Additional settings were varied, to optimise parameters for the type of sample being scanned (Table 2.1). Voltage determined the intensity of the x-ray beam, its penetration, and the contrast of the resultant image. Current determined the number of emitted x-ray photons and the brightness of the resultant image. Filters blocked low intensity x-rays when required, improving contrast and reducing noise.

The scan was started and as the stage rotated the camera captured an x-ray tomography projection image of the sample at each rotation step (Figure 2.6B). Scan time was dependent on the settings used and ranged from 10 minutes to several hours.