In a method of constructing a head shield for a radiation machine, the angular distribution of radiation propagating from a source and the angular function of thickness of a material in attenuating the radiation to a certain level of its original value are determined. Based on the angular distribution of radiation from the source and the angular function of thickness of the material, the thicknesses of the material at a plurality of angular locations around the source and distances from the source can be calculated for attenuating the radiation to or less than a predetermined threshold value. A shield around the source is constructed based on the calculated thicknesses of the material through iterative steps to ensure a cost-saving, weight-efficient, optimal solution. A method of designing a local radiation shield for a point of interest in a radiation system is also described to improve the machine reliability, regardless of the motion component of the POI with respect to the main radiation source and the secondary radiation source created by the patient scatter.
