ABSTRACT
Proton therapy has been developed and was performed initially in nuclear physics laboratories that were equipped with a particle accelerator, such as a cyclotron or a synchrotron, like in Berkeley, Cambridge, Paul Scherrer Institute, and Uppsala. Several important specifications of the accelerator and beam delivery system depend on the chosen technique to apply the proton dose to the tumor. In accelerators such as cyclotrons and synchrocyclotrons this is not possible, since the machines developed for proton therapy can work at one specific proton energy only, which is the maximum to be used in the facility. The best coverage of the target volume in combination with the lowest dose in the surrounding normal tissue is obtained with the pencil beam scanning technique. Unexpected fluctuations or interruptions in the beam intensity or a pulsed beam are not desired. The characteristics of a proton beam from any accelerator will be subject to time-dependent variations.
