Effect of the initial energy layer and spot placement parameters on IMPT delivery efficiency and plan quality.

Purpose: Improving efficiency of intensity modulated proton therapy (IMPT) treatment can be achieved by shortening the beam delivery time. The purpose of this study is to reduce the delivery time of IMPT, while maintaining the plan quality, by finding the optimal initial proton spot placement parameters.

Methods: Seven patients previously treated in the thorax and abdomen with gated IMPT and voluntary breath-hold were included.