207 Extension of Sherouse's GRATIS™ three-dimensional treatment planning system for use with a multileaf collimator

Abstract

In February 1995, a linear accelerator (Philips SL25) was retrofitted with a Philips multileaf collimator (MLC). MLC reduces workload (decreases the numbers of cerrobend blocks) and increases throughput (avoids tray placements). However, programming the leaf settings is a labur intensive procedure on the Philips MLC, as settings have to be derived manually from simulator films. We use the GRATIS 3D planning system by George W. Sherouse and have written an extension to plan the leaf settings in beam's eye view mode. From a tool implemented in GRATIS' last release, which draws a conformal block around the target with a predefined margin, we developed a feature for automatic or interactive leaf setting. After virtual simulation, a file with the leaf settings is transferred to the MLC computer over a local network. The advantages of this system are efficiency, automatization and elimination of transfer errors. Within the philosophy of GRATIS, we will make our tool freely available to the GRATIS users.