High technology to simplify the planning and delivery of radiotherapy

Two techniques for the automatic selection of individual leaf positions of a Philips multi-leaf collimator are described. Target volumes are identified either on simulator images or on cross-sectional images from CT or MR scanners. The setting of each leaf is computed to position the beam edge to cover the target with an appropriate, user defined, margin. An important consideration in the development of the system was its robustness and so the applications initially implemented have been relatively simple, comprising single field, parallel opposed fields and coplanar 4 field box techniques. Attention has been paid to the overall integrity of the planning and treatment delivery process. Before treatment commences, the beam shapes, which have been generated by the computer and transferred to the MLC control computer over a local area network, are checked against a printed template representing each beam. All data used for planning is archived and is accessible for review or, if necessary, for treatment modification.