A particle portal imaging (PPI) system and method are provided that can be used to provide a “beam's eye view” of a patient's anatomy as a charged particle beam is delivered to a target region of the patient's body. The PPI system is capable of performing real-time image acquisition and in-situ dose monitoring using at least exit neutrons generated within the patient. The PPI system can perform charged particle treatment (PT) monitoring to monitor the particle beam being used for PT.