Abstract: Systems and methods of treating a patient, including a proton treatment system having a proton delivery unit to direct protons to a target area of a patient, the proton treatment system including a positron emission tomography (PET) system having a detector unit to scan for radiotracers introduced into a patient's body, a processing unit to generate location information corresponding to a target area of the patient based on a scanned radiotracer, a guidance unit to receive the location information from the PET system and to instruct the proton delivery unit to direct protons to the target area according to the location information.