Study Of Orientation Optimization In Radiation Therapy

Radiation therapy is a difficult problem. The 3 dimensional conformal radiation therapy (3D-CRT) and the intensity modulate radiation therapy (IMRT) emerge in the last decade years, which significantly boost the technical as well as the optional parameters in radiation therapy such as beam energy, beam orientation, beamlet size, beam weight, and conformal field are too much to be decided. Specializing the radiation therapy plan for every patient becomes an impossible mission for physicists. So developing some optimization algorithms to aid physicists is very necessary.This thesis mainly concerns the optimization problem in radiation therapy, such as optimization algorithm for the multi-leaf collimator(MLC) conformal field, optimization algorithm for gantry angle in conformal radiation therapy, as well as in intensity modulate radiation therapy.In this work, the effect on the conformality by rotating the collimator angle was studied. A method, in which multiple MLC fields of various rotation angles are applied, has been proposed to have the targets more uniformly irradiated and thus eliminate the cold spots on the targets and hot spots in normal tissues. By simulation cases, it has been shown that the multiple MLC field method can eliminate the stepped leaf edges and improve the conformality significantly. Moreover, the PTV can receive a more uniform delivery with cold spot eliminated.