Three-dimensional photon radiotherapy planning for laryngeal and hypopharyngeal cancers. 1. Conventional rotational technique.

Abstract

Three-dimensional dose distributions have been computed for the photon radiation therapy of laryngeal and hypopharyngeal cancers, using biaxial and eccentric rotatory techniques. Treatment plans obtained under various conditions of irradiation with a 15 MV linear accelarator (MEVATRON 77, Siemens) are analysed and compared. Dose delivery to the tumour and the degree of spinal cord protection are evaluated for both treatment techniques. The eccentric plan is somewhat superior to the biaxial one, suggesting a justifiable preference to use this method in the radiation treatment of these tumours. Simulations show that extreme care is needed in positioning the axis: an accuracy of +/- 3 mm is required in the sagittal plane.