Abstract: A system/apparatus and a positioning method for the determination of the delivery of protons within a mammalian body or inanimate medium, as well as a treatment method which comprises the delivery of protons to a mammalian body. The system/apparatus necessarily comprise the use of a detector which is placed in the proximity of the body or medium which is responsive to a signal emitted from a fiducuial marker which his positioned within or in the near proximity of target tissue within the body or target volume within the medium. A signal emitted from the fiducial marker is responsive to the impingement of protons thereon received from a controlled proton beam, the signal may be used to modify the subsequent operative characteristics of the source of protons.