Placement of fiducial markers is a procedure guided by imaging to prepare for specific forms of radiation therapy, including stereotactic radiosurgery (SRS), stereotactic body radiotherapy (SBRT), or proton therapy.
Fiducial markers, typically small gold spheres, coils, or cylinders resembling the size of a grain of rice, are inserted into or close to a tumour to assist in treatment guidance.
Due to the size and material of these markers they are considered as MR conditional and can be scanned up to 3 T.