Abstract: An on-board proton imaging system may include a continuous rotation gantry configured to generate proton beams during rotation thereof to penetrate a patient object, a beam detector arranged opposite of the gantry around the object and configured to receive residual proton beams having passed through the object, and a controller in communication with the gantry and a multilayer detector. The controller may be configured to instruct the gantry to generate the proton beams based on patient factors, receive data from the detector indicating at least an energy level of the residual beams, and generate a three-dimensional image based on the received data.