A computing system determines a full motion range of a target, wherein the full motion range of the target defines an internal target volume (ITV). The computing system identifies a partial motion range of the target, wherein the partial motion range is a subset of the full motion range of the target. The computing system generates a partial-ITV based on the identified partial motion range, wherein the partial-ITV is a volume swept by the target as the target moves through the partial motion range, the partial-ITV being smaller than the ITV. The computing system generates a treatment plan to deliver treatment to the partial-ITV.