Modulated beam conformal therapy for head and neck tumors.

摘要: Abstract Purpose: The goal of modulated-beam conformal therapy is to reduce the dose healthy tissue and sensitive structures around a uniformly irradiated target volume. Multiple intensity-modulated fields offer improved tissuesparing distributions. New computer-based systems for planning delivering such treatments may soon be available from different commercial sources that will make formulation an treatment plan its execution widely at any facility has resources acquire necessary equipment. This work reports on study integration two systems. Methods Materials: Treatment was done using commercially inverse algorithm based simulated annealing. plans arbitrarily assumed nine coplanar x-ray beams nonopposed gantry angles. Intensity modulation computed each beam. modulated field angle broken down into series uniform (nonmodulated) subfields, which could delivered as sequence produce desired distribution. Because large number subfields delivered, multileaf collimator (MLC) used shaping. allowed rapid accurate shaping made up several hundred sublields. Computer control MLC linear accelerator delivery d less than .01 Gy per subfield. prototype, computer-controlled system. Resulting distributions were analyzed film anatomically specific, homogeneous phantom. Results: evaluated dose-volume histogram analysis. provided acceptably irradiation volume without exceeding tolerances nearby critical structures. successfully by prototype dynamic MLC. time needed deliver one ranged 0.7 2.0 min. Isodoses agreed reasonably well with planned isodose Conclusions: It feasible fixed gantry, head neck tumors being developed commercially. exhibit significant potential sparing closely spaced normal in neck.