Abstarct: X-ray radiographic systems have from a long time ago used for many per formance's in various fields such as, x-ray crystallography, agriculture, medicine and so on. Because of the ionizing nature these rays, they can be dangerous to the health of the personnel and ordinary people, in terms of radiation safety. In this thesis, with an review and verification of the effect lead protections used to protect workers and patients and radiology departments personnels, In the first step of the work with dosimetry, we began the radiation from the general radiology in the hospital, which was tested experimentally with a dosimeter for energies of 60 to 120 kVP without use of the lead shields Significant doses were observed for each scan more than 100 (µSv)/h at time interval of 1 second, and for a dosimeter in the presence of a lead cap for energy exceeding 100 kVP, a significant passage was observed. So design of the MCNPX code was similar to the solution. In the second step, by simulating the parameters from real computer tomography to room simulation, this system was performed by MCNPX code and Mird computational phantom to evaluate absorption dose of staff and patients for energies of 80 to 140keV. baxsed on the results of numerical calculations and simulations, the amount of absorbed dose to the bladder was observed in the abdominal scan in the patient's phantom compared to other radiation-sensitive tissues. Therefore, by designing lead shields at thicknesses of 1.5, 2.5 and 3.5 mm at the end, a revised method was presented to patients to improve the dose reduction, Indicates need for a modified shield or lead curtain to be modified in application to the protection and safety of patients undergoing CT examinations in this range of energies.