It is well known that, when accelerated electrons from a linear accelerator interact with a high atomic number (Z) target material, electromagnetic radiation (bremsstrahlung) is produced. In the present work some aspects of the generation of the bremsstrahlung radiation by linear accelerators of electrons are studied, namely the relation between the dose and parameters of the accelerating structure and beam characteristics is investigated. We carry out numerical simulations of the relative dose rate at fixed maximal beam energy and analyze its dependence on the length of the accelerating cells, power of the electromagnetic field dissipated in them and average energy and energy spread of the output beam. The simulation of the acceleration of the electrons in the accelerator is done with the RTMTRACE code.