A model for computer-controlled delivery of 3-D conformal treatments.

Three-dimensional conformal radiation treatments are highly complex and may comprise a large number of coplanar and noncoplanar beams, virtually all of which are shaped and may also employ arbitrary intensity modulation. The delivery of such treatments with conventional means is highly labor intensive and limited to a relatively small number of fields. A generalized model for a system that can deliver 3-D conformal treatments rapidly and safely using a computer-controlled treatment machine equipped with a multileaf collimator is presented. The model emphasizes the separation of tasks between an external computer programmed by the user institution and a control computer proprietary to the treatment machine manufacturer. The treatment scheme that is employed consists of a sequence of fixed fields, called segments, which are delivered in succession without human intervention. Settings for all segments, derived from a 3-D conformal treatment planning system, are downloaded by the external computer into the control computer of the treatment machine. During patient setup, the control computer enables the operator to step through computer-controlled setup of the segments without radiation to ensure the absence of collisions, and to allow the adjustment of setup parameters if necessary. The external computer verifies the treatment setup and permits the control computer to carry out the treatment segment by segment. Safety aspects of the model and anomalous situations which may arise are discussed.