Physics Bucharest 2017

Summary Basic Dose Calculation Principles For equal number of MU : Dose decrease with depth (beyond d max )  Dose absorption and inverse square law Dose increase with larger field sizes  More scatter to contribute to dose (Output factors) Dose decrease with larger SSD  inverse square law Dose increase with energy (beyond d max )  less attenuation for higher energies Dose increase off central axis – most at d max  Flattening filter, Beam spectrum is “softer” off axis (off axis factors)

less at depth.