The use of ions in radiation therapy aims at improving the selectivity of the irradiation thanks to a
favourable depth-dose profile and, in case of heavy ions, to their enhanced radiobiological effect.
The treatment modality employing actively scanned pencil beams provides highly conformal dose
distributions but is sensitive to uncertainties in the dose calculation, delivery and measurement.
During the treatment, the delivery of the beam has to be controlled in real time and monitored with
high accuracy, including any effect due to patient positioning and motion. Based on the experience
gained in the collaboration with the CNAO (Centro Nazionale di Adroterapia Oncologica, Pavia,
Italy), this paper is intended to give an overview of recent techniques and trends for the delivery,
measurement and verification of the dose distribution in charged particle therapy with scanned
ion beams, focusing in particular on real time and online techniques.