In orthopedic research into screw implants in bone, it is often the goal to examine osteointegration, that is, the status of bone immediately surrounding the implant. MicroCT can provide 3D image data of the implant and surrounding bone to facilitate such peri-implant analysis.
Frequently the implant is metallic, which poses a challenge to microCT imaging, since artefacts are created surrounding the metal due to its high x-ray absorption and consequent extreme beam hardening. The new SkyScan2211 multiscale nanoCT has an X-ray applied voltages up to 190 kV allowing artefact-free analysis of the bone immediately adjacent to the implant surface.
For this, the reference level function in CTAn can help simplify the selection of the cross-section height range in the Z axis, relative to your selected landmark.
In short, a VOI mask is created based on the binary of the metal implant. This binary is filled and dilated to create an ROI surface at a constant distance from the metal surface, set by the pixel value of the dilation. (Some dilation is always needed since the gradient of attenuation from the highly dense metal extends a few pixels away from the implant surface.) This dilated mask allows direct measurement of the bone implant contact (BIC). Running this analysis in 2D restricts the analysis to the sides of the implant in contact with skeletal tissue.