An example particle therapy system includes: a particle accelerator to output a beam of charged particles and a scanning system to scan the beam across at least part of an irradiation target. An example scanning system includes: a scanning magnet to move the beam during scanning and a control system (i) to control the scanning magnet to produce uninterrupted movement of the beam over at least part of a depth-wise layer of the irradiation target so as to deliver doses of charged particles to the irradiation target and (ii) to determine, in synchronism with delivery of a dose, information identifying the dose actually delivered at different positions along the depth-wise layer.
