Abstract
The aim of this experiment is to solve the problem of lacking of skin sparing in electron beam therapy and to increase the tolerance of skin to radiation by using grid technique. The method of the electron grid therapy is to place a grid on the end of an electron cone. Film dosimetry was used to measure the relative surface optical density and depth profile for grid electron beam with energies from 6 to 14 MeV. Different grid hole diameters (d = 0.45, 1.0, 1.5 cm), grid spaces (s = 0.4, 0.2 cm), grid materials, field sizes and air gaps (0, 3, 6 cm) were investigated for various electron energies. The experimental results indicate that electron grid therapy can decrease the relative surface optical density at each electron energy. The degradations of the relative surface optical density depend on the percentage of open area of the grid portal. The cerrobend grid with 1.5 cm diameter holes and grid space 0.2 cm can conform to the demands of clinical radiotherapy. With this design one can decrease the surface dose and the range of nonhomogeneous dose can be limited to a depth so that the target volume would receive a homogeneous dose. Grid technique can lessen the surface dose in electron beam radiotherapy indeed. We can deliver higher radiation dose with electron beams without damaging the skin by grid technique.