Individual Field Simultaneous Optimization (IFSO) in spot scanning proton therapy of head and neck cancers.

In order to better spare organs at risk in the head and neck, the application of proton beam therapy is of great interest. In this study we report the clinical utilization of a novel and robust scanning proton beam therapy treatment planning method called Individual Field Simultaneous Optimization (IFSO) that incorporates the advantages of field patching technique integrated with simultaneous optimization of multiple fields. A treatment planning intercomparison between a conventional Intensity Modulated Proton Therapy Treatment Plan with single target volume vs a split target volume utilizing IFSO method demonstrates superiority of IFSO with regards to sparing of organs at risk and plan robustness.