<i>In vivo</i> verification of proton beam path by using post‐treatment PET/CT imaging

Abstract

Systematic analyses of proton-activated positron emission distributions provide patient-specific information on prostate motion (sigmaM) and patient position variability (sigmap) during daily proton beam delivery. The less than 2 mm of displacement variations in the good cases indicates that population-based values of sigmap and sigmaM, used in margin algorithms for treatment planning at the authors' institution are valid for the majority of cases. However, a small fraction of PET/CT studies (approximately 14%) with -4 mm displacement variations may require different margins. Such data are useful in establishing patient-specific planning target volume margins.