Variation in external beam treatment plan quality: An inter-institutional study of planners and planning systems.

Purpose: This study quantifies variation in radiation treatment plan quality for plans generated by a population of treatment planners given very specific plan objectives.

Methods And Materials: A "Plan Quality Metric" (PQM) with 14 submetrics, each with a unique value function, was defined for a prostate treatment plan, serving as specific goals of a hypothetical "virtual physician." The exact PQM logic was distributed to a population of treatment planners (to remove ambiguity of plan goals or plan assessment methodology) as was a predefined computed tomographic image set and anatomic structure set (to remove anatomy delineation as a variable).