Figure 3.

Balloon surface $({\mathrm{D}}_{\text{sur}})$ and air cavity surface $({\mathrm{D}}_{\text{sur‐ac}})$ dose differences (solid lines) and inverse square factor (dashed lines) results with various air cavity sizes (in radius) in different balloon sizes. The y‐axis is calculated by $({\mathrm{D}}_{\text{sur‐ac}}-{\mathrm{D}}_{\text{sur}})/{\mathrm{D}}_{\text{sur}}(\%)$.