108 J. Bazoma et al.: Radioprotection 2026, 61( 2), 105 – 112 Fig. 1. Overall distribution of CTDI vol and DLP per examination type.
Table 4. Median and 75 th percentile( in mGy) of the distribution of CTDI vol per examination type. Female Male Overall
Examination |
Q2 |
Q3 |
Q2 |
Q3 |
Q2 |
Q3 |
Head |
57 |
57 |
57 |
57 |
57 |
57 |
Chest |
3.6 |
4.8 |
2.6 |
3.7 |
2.7 |
3.9 |
AP |
3.5 |
4.1 |
2.9 |
3.3 |
3.2 |
3.7 |
CAP |
3.3 |
4.4 |
3.2 |
3.3 |
3.2 |
3.7 |
Q2 = Second quartile = Median; Q3 = Third quartile = 75 th percentile.
Table 5. Median and 75 th percentile( in mGy cm) of the distribution of DLP per examination type. Female Male Overall
Examination |
Q2 |
Q3 |
Q2 |
Q3 |
Q2 |
Q3 |
Head |
1172.2 |
1243.5 |
1172.2 |
1260.1 |
1172.2 |
1257.7 |
Chest |
161.8 |
225.625 |
131.2 |
168.7 |
158.3 |
176.3 |
AP |
177.6 |
214.9 |
141.6 |
170.1 |
163.2 |
193.9 |
CAP |
208.9 |
272.5 |
201.7 |
226.3 |
203.6 |
264.1 |
Q2 = Second quartile = Median; Q3 = Third quartile = 75 th percentile.
3.2 mGy and 3.2 mGy for head, chest, AP and CAP scans, respectively( CTDI vol). For DLP, the typical values were 1172.2 mGy cm, 158.3 mGy cm, 163.2 mGy cm and 203.6 mGy cm.
It is worth noting that setting DRLs has been shown to be an effective tool for identification of examinations for which optimization of protection should be undertaken( ICRP, 2017). Sindi et al.( 2024) has undertaken a study that aimed to evaluate the effect of implementing national diagnostic reference levels for adult chest CT scans at a major Saudi Arabia hospital. They showed that 83.5 % of scans passed DRL criteria( CTDIvol = 12 mGy, DLP = 430 mGy cm), with higher pass rates for contrast( 91.8 %) versus non-contrast( 81.5 %) scans. Furthermore, they compared effective dose before and after DRL implementation. They showed that, for non-contrast scans, the effective dose declined by 2.43 %. For contrast scans, the effective dose declined by 6.77 %. It will be of interest to undertake a similar study in Congo that assesses the effect of implementing DRLs in CT installations.
Finally, it is important to stress that in the country there are 15 CT machines in service, of which 8 are located in the capital city Brazzaville. The present study involved only 1 CT machine installed in the largest hospital( the most frequented by patients) in the Republic of Congo. A larger study is needed to provide reference values at the national level. However, the present study provide a first set of reference values for the radiation protection of patients in our country.
3.3 Size-specific dose estimates
Figure 2 shows the distribution of SSDE per examination type for overall patients. Mean SSDE value ± 1 standard deviation for overall patients were 5.2 ± 4.3 mGy( range: 0.52 – 26.8 mGy; p-value = 0.25), 5.3 ± 2.4 mGy( range: 3.6 – 18.8 mGy;