Techniques are generally described for particles with a surface including an adhesion material. The adhesion material may be selectively activated in response to radiation. The particles may be distributed proximate to a target through a fluid system. Radiation may be emitted toward the target causing the adhesion material to activate. The activated adhesive material on the surface of the particles may adhere to the target providing a fiducial mark or reference point. The fiducial mark may be visible through a medical imaging technique. In some examples, the particles may be nanoparticles. In some examples, the radiation may be infrared radiation.
