The Study of Field Equivalence Determined by the Modeled Percentage Depth Dose in Electron Beam Radiation Therapy

Figure 6

The depth dose curves move toward the left significantly when the field size is reduced to less than 5.9 cm of 15 MeV. It is concluded that for the field that is required for lateral scatter equilibrium (LSE) to remain PDD constant, once the LSE is reached, PDD is independent of field size.