Techniques are described herein for delivering a particle beam composed of a plurality of beamlets from a continuously rotating gantry towards a target, by determining a plurality of predefined spots on the target and configuring them into a set of smaller spots on the outside of the target and a set of larger spots on the inside of the target, optimizing the delivery of the rotating particle beam such that the inside edge and the outside edge of the arc of the rotating beam are delivered to the spots located at the center of the target, and the central component of the arc of the beam is delivered to the spots located at the outside of the target.
