Considering combined effect of phton scattering in phantom and constraint conditions for organ(s) at risk
it is difficult to optimize the intensity of beam profiles and weight of segments or conformal fields during the process of radiotherapy planning design.In this paper
a two-step method is proposed.First
the prescription dose of PTV
constraint conditions of OAR and dose matrix without considering the scattering in phantom are used to optimize the dose distribution which is called the voxel-by-voxel-based objective dose.With the new objective dose and consider-ing the scattering
the intensity or the weight could be well optimized.The second step is an optimization process without constraint conditions and the optimization can be finished rapidly.Because the new objective dose satisfies the constraint condition in Step 1 and the dose matrix is calculated by accurately dose calculation algorithm in Step 2
the results are satisfying and credible
as verified by applying the method to a typical example.