A system for carrying out or monitoring irradiation of a moving object using a particle beam is provided. A particle beam may be directed onto the moving object from a beam outlet. X-ray images from different directions are recorded by an imaging unit. The imaging unit may include an x-ray detector and an x-ray emitter opposite the x-ray detector. The imaging unit may be positioned around the object independently of the position of the beam outlet, for example, during application of the particle beam. The X-ray images may be used to reconstruct a series of digital tomosynthesis images of the moving object online. The reconstructed digital tomosynthesis images are evaluated so that movement of the moving object is captured and the irradiation profile is controlled.