Virtual Micro MLC Commissioning

Abstract

The resolution of multileaf collimators (MLCs) is limited by their finite leaf width. A commercial package (HD-270) uses three dimensional couch translation and leaf adjustments to emulate smaller leaf widths. In this paper we report on the commissioning of this feature using software testing, dial-gauge measurements and film dosimetry and identify a variety of limitations. The limitations include software bugs and truncation artifacts, MLC leaf positioning uncertainties (random variations, systematic gantry dependence and backlash), and uncertainties in couch positioning. These reduce the capabilities of this implementation below that achievable theoretically.