The optimized beam weights in the target volume

If the same weight is used in parallel opposed 6 and 10 MV x-ray beams, the lowest dose is achieved at SAD. Therefore, dose homogeneity in the target volume is decreased when SAD is taken at center of target volume than center of phantom or patient. With Standard deviation of ±6% that represented the dose homogeneity in target volume, we studied the optimized beam weights at which hot spot dose was least in parallel opposed beams. The optimized beam weights that maximally decrease the hot spot dose, were 1.29, 1.19, 2.71, 3.50, and 4.70 in 6 MV x-ray and 1.25, 1.53, 1.90, 2.36, 3.01, and 3.7 in 10 MV x-ray, respectively, when center of target volume was changed to 2,4,6,8,10, and 12 cm from center plan of phantom along the centeral axis of beams.