Technical Note: Relationships between gamma criteria and action levels: Results of a multicenter audit of gamma agreement index results

Abstract

This work provides a method (and a large sample of results) for calculating equivalent action levels for different gamma evaluation criteria. This work constitutes a valuable guide for clinical decision making and a means to compare published gamma evaluation results from studies using different evaluation criteria. More generally, the data provided by this work support the recommendation that gamma criteria that specifically prioritize the property of greatest clinical importance for each treatment modality of anatomical site should be selected when using gamma evaluations for modulated radiotherapy QA. It is therefore suggested that departments using the gamma evaluation as a QA analysis tool should consider the relative importance of dose difference and distance to agreement, when selecting gamma evaluation criteria.