ABSTRACT
The relative reduction in percentage transmission through lead for 4-MeV electrons produced from a linear accelerator for different field sizes has been measured both with and without buildup. For our study a parallel plate chamber with Farmer dosimeter in polymethylmethacrylate phantom was used. Lead strips were used as a shielding material. The result of this study shows that as (i) the depth of measurement in phantom, (ii) the gap width between lead shielding material and phantom increases, the lead thickness required for the same percentage of reduction in transmission decreases due to energy loss of scattered electrons and decreased scattered electrons reaching the detector. The 95% and 98% reduction in transmission was evaluated and found to increase with increasing field size due to higher lateral scattering. From our study it was concluded that the reduction in transmission with lead was found to depend upon the field size, the depth at which measurements are made, the gap width between lead shielding and phantom, and the focus to skin distances.
