282 F . Poursoltani et al .: Radioprotection 2024 , 59 ( 4 ), 278 – 286 Fig . 3 . Comparison of CT number shift ( a ) and noise increase (%) ( b ) in different ROIs : ( 1 ) anterior , ( 2 ) posterior , ( 3 ) left peripheral , ( 4 ) right peripheral , ( 5 ) the middle in the CTDI phantom .
who survived the atomic bombings of Japan and on patients who underwent multiple radiographs for benign conditions such as tuberculosis and scoliosis have shown the prevalence of cancer in breast tissue after exposure to ionizing radiation ( Hoffman et al ., 1989 ; Miller et al ., 1989 ). Therefore , the use of dose reduction techniques for radiosensitive organs is important during CT imaging . IRA and TCM are techniques used to reduce dose in CT scanners . However , these techniques have limitations and are not also existed in all CT scanners ( Foley et al ., 2013 ; Lambert et al ., 2016 ). Another method is to use a shield that is placed on the surface organ and reduces the dose to that organ by reducing the radiation intensity in the underlying tissues . In this research , various compositions of Cu and BaSO 4 were made in order to reduce the dose for the breast in CT examination . It should be mentioned that for the analysis of dose reduction , in some studies , organ dose and in some other studies , such as this study , the ESD has been reported .
4.1 The effect of new breast radiation shields in dose reduction
Based on data in Table 1 , different composition , constructed breast shields reduces the surface dose of breast by 14.77 %– 51.69 %. The difference between the dose reduction of these shields has a maximum of 37.52 %. Based on the data presented in Table 3 , the efficiency of the