for my research I will perform a motion capture and I will make MRI scans of my subjects. I would prefer to leave the spherical, retro-reflective markers that I will use for my motion capture on the subject while making the MRI scan. It is therefore essential that these markers are MRI-compatible and visible on the scans. We don't have those markers and I am not aware of their existence. A search on the internet did not lead to any results. Do you have any suggestions? Does anyone know for example of markers that can be filled by contrast agent? Any tips would be much appreciated! Thanks!