Detector Choice for Depth Dose Curves Including the Build-Up Region of Small MV Photon Fields

The right detector choice is an issue in all situations without charged-particle equilibrium, such as in the build-up region of photon fields. As the field size decreases, typically chosen plate parallel ionization chambers are no longer feasible due to volume averaging effects. Alternatively, one of the numerously available small field detectors is recommended. Here, it is necessary to know how the different detectors respond as a function of field size and depth and which factors influence the signal.