Missing tissue compensation with wax filter compensators in radiotherapy of the head and neck region

Background. In the conventional radiotherapy of the head and neck region, the inhomogeneity of the absorbed dose in certain clinical situations can exceed ? 5% of the nominal dose. Depending on the pattern of dose inhomogeneity, treatment related toxicity is more pronounced and disease control reduced. The aim of our report is to present the wax filter compensation technique used in our department. Case report. A 46-year-old male with inoperable carcinoma of the oropharynx of clinical stage T3N2c was irradiated with 5 MV linear accelerator photon beams and conventional 3-field technique. In order to obtain more homogenous dose distribution in treated volume, the opposed lateral fields were modified using 2Dwax filter compensators. Results. Using conventional wedge filter compensation, the planed absorbed dose deviations in the treated volume were in the range of 94% to 113% of the prescribed dose. By modification of the opposed lateral fields with 2D wax filter compensators, the variations of the absorbed dose were reduced to the range from 93% to 105% of the prescribed dose. In the article, the planning and manufacturing as well as dosimetric checking of wax filter compensators are described. Conclusions. With the use of 2D wax filter compensators, the inhomogeneity of absorbed dose distribution was significantly reduced, and the quality of treatment considerably improved. (author)