In pencil beam scanning single proton beam with a width of a few millimeters is used. Using a number of systems changing proton beam position it is possible to cover tumor volume with uniform radiation dose. Another thing is rotating gantry which allows to deliver proton beam at an optimum angle. Tumor area is divided into layers which correspond to different proton beam energy. Each of such layers is very precisely covered with dose by moving single proton beam step by step over entire area. The transition to the next layer is performed by changing the beam energy. In this way it is possible to irradiate the entire tumor very fast.
Cyclotron Center Bronowice has two gantries in which it is possible to use pencil beam scanning to irradiate tumors in both adults and children.