Improved dose homogeneity in the head and neck using computer controlled radiation therapy

Computer-controlled radiation therapy techniques are demonstrated which improve dose homogeneity throughout the nasopharynx when compared to conventional treatment techniques. The typical approach using a heavily weighted anterior field and opposed wedged lateral fields results in a dose gradient from 95% to 110% or greater. All three of the computer-controlled techniques investigated improved the dose uniformity to a range from 95% to 105% or less. Multiple overlapping fields are used to compensate for patient anatomy and treatment beam characteristics. Treatment planning and monitor unit calculations are quite time-consuming at this stage of development. Actual treatment time is not unreasonably long and can be improved in future releases of the therapy machine control software.