Research and application of beam auto-modeling method for three-dimensional conformal radiation therapy treatment planning system

To insure the accuracy of irradiation, the three-dimensional conformal radiation therapy (3DCRT) treatment planning system (TPS) should, based on the types and orientations of the beam, automatically calculate the source position and the field size of the irradiation beam to cover the target (tumor) volume while avoiding excessive irradiation of the surrounding tissues. A beam modeling method was developed: first, based on the derived matrix of coordinate system transformation, the 3D patient model is tranfered from the patient coordinate system to the beam coordinate system; then, the iso-center coordinate of the target is caculated, from which the coordinate of the beam source is derived; finally, the target volume is projected onto the iso-center plane to identify the field size of the irradiation beam. By implementing of this method, the beam modeling module was developed with features of 3D visualization and a friendly user interface. The accuracy and efficiency of this module was verified based on the benchmark cases of the AAPM report 55 and the clinical patient image data by testing and comparing it with the beam modeling module of a commercial 3DCRT TPS.