## 4 Discussion  
Although numerous studies have been conducted to reduce radiation exposure in CT imaging procedures, concerns among medical professionals still exist when the delivered doses are evaluated in CT scanning. These diagnostic parameters were observed critically between two periods: pre-optimization and post-optimization of the exposed radiation.  
In this single-center cohort study, the authors evaluated ED and organ radiation doses to create an institutional benchmark and compared it with NDRLs [16] at a tertiary academic hospital in Saudi Arabia (Table 1).  
Dose parameters determine the average absorbed dose in the scanned region CTDIvol and the integrated absorbed dose along a line parallel to the axis of rotation for the complete CT examination. Nonetheless, DLP can provide a method for comparing patient radiation doses from different diagnostic procedures. Establishing DRLs would minimize the overall dosage in clinical practice. [35; 36]  
In our sample, the CTDIvol values were 75% lower after applying NDRLs [16], except for the head examinations, where the CTDIvol values were higher after applying NDRLs [16]. However, when comparing our results to NDRLs, the CTDIvol values for head examinations were lower than those for NDRLs [16]. Nevertheless, the chest, abdomen, and pelvic examination values were consistent with the NDRLs [16] (Table 2).  
When comparing our study results with those of previous studies in Nigeria [26], ICRP [11], the United States of America (USA) [27], Japan [28], the EU [29], Greece [30], Italy [33], Egypt [31], and the United Kingdom (UK) [32], the CTDIvol values in head examinations were lower than those in all other studies, with the exception of those in Egypt [31]. The CTDIvol values in abdomen/pelvic exams were lower than those reported in studies from Nigeria [26], ICRP [11], USA [27], Japan [28], EU [29], Italy [33], and Greece [30]. However, these values were consistent with NDRLs in the UK [28]. Regarding chest examinations, the CTDIvol values were equivalent to NDRLs, higher than those in the study from Egypt [31], and lower than those in other studies [26; 27; 28; 29; 30; 31; 32].  
DLP reflects the total energy absorbed (and thus the potential biological effect) attributable to complete scan acquisition. In the current study, after the application of NDRLs [16], the DLP was lower than that before applying NDRLs, except in head examinations. The DLP values in the head and abdominal examinations were lower than those reported in previous studies.  
The values in chest examinations were higher in the current study than those in studies from the USA [27], Egypt [31], Italy [33], and the UK [32], but lower than NDRLs and values  
Figure 2: Distribution of effective dose across the study period. Linear histogram showing the distribution of effective dose across the study period (Middle: to separate pre- and post- optimization phases).  
reported in studies from Nigeria [24], ICRP [11], Japan [28], the EU [29], Italy [33], and Greece [30]. It is important to recognize that the potential biological effects of radiation depend not only on the radiation dose received by a tissue or organ but also on the biological sensitivity of the irradiated tissue or organ.  
ED is a dose descriptor that reflects differences in biological sensitivity. It is a single-dose parameter that represents the risk of non-uniform exposure in relation to an equivalent whole-body exposure. Therefore, an ED can be used to estimate the risk factors. In this study, the ED after applying NDRLs [16] was lower than it had been before applying NDRLs, except in the case of head examinations.  
Applying NDRLs remarkably reduced the patient dose in most CT examinations. The mean organ dose compared to similar studies from other countries (e.g., Tanzania [34], UK [32], and ICRP [11]) showed that the organ dose was lower in chest, abdomen/pelvic, and head examinations than in examinations from all other countries [28].