Skin dose measurements for head and neck radiotherapy.

The use of immobilization plastic masks in head and neck radiotherapy can partially eliminate skin benefits derived from the utilization of megavoltage photon beams. Filters and blocks between the patient and the accelerator can further increase the skin dose value. In this study, the increase in surface dose due to 2 and 3.2 mm of plastic material utilized for patient immobilization was measured. Then, the effect of blocking trays, wedges, and blocks on skin dose in typical conditions for head and neck irradiation was evaluated. The measurements were obtained with a NE2534 chamber (Markus type) on a perspex phantom for 6 MeV x-rays from an accelerator.