A method for rapid determination of the energy of electron beams from medical linear accelerators

A method has been developed using a Varian Clinac-18 LINAC for the rapid determination of electron beam energy for clinically used linear accelerators. The method involves measuring the ionization values in a water or polystyrene phantom with an ion chamber at two predetermined depths. Then with predetermined Bremsstrahlung "tail" values which are presented here or which can be developed by the user, the practical range, Rp can be measured. With the Rp, the effective surface energy Eo of the electron beam can be determined by the Markus range-energy formula. Thus, by measuring just two depth ionization values, one is quickly able to determine the Eo of an electron beam without plotting a full depth ionization curve.