RADIOTHERAPY TREATMENT PLANNING WITH DYNAMIC WEDGES - AN ALGORITHM FOR GENERATING WEDGE FACTORS AND BEAM DATA

If the jaws of a linear accelerator are moved under computer control d uring irradiation, dose distributions similar to those with wedge filt ers can be produced. Varian linear accelerators utilize this effect to give a 'dynamic wedge', using segmented treatment tables (STTs). An a lgorithm is described to generate the dose per monitor unit at any poi nt in a beam, using the STT values. Dynamically wedged beams are model led as the superposition of static asymmetric beams, using an algorith m based on beam data measured for symmetric beams. Predictions of wedg e factors, depth doses and profiles generated using the algorithm are compared with measurements. Good agreement is found between prediction s and measurements. The calculation time is typically 5 ms/dose point on a PC with a 486DX processor.