J. Bazoma et al.: Radioprotection 2026, 61( 2), 105 – 112 107
Table 1. CT techniques used.
Examination |
kVp |
mAs |
Pitch |
Revolution time( s) |
Slice thickness( mm) |
CTDI vol( mGy) |
DLP( mGy cm) |
Head |
120.3 ± 4.1 |
233.0 ± 15.3 |
0.4 |
0.75 |
0.5 |
53.5 ± 6.8 |
1180.2 ± 131.2 |
Chest |
100.0 ± 0.0 |
133.2 ± 54.2 |
0.8 |
0.5 |
1 |
3.5 ± 2.5 |
166.9 ± 102.2 |
AP |
100.9 ± 4.3 |
91.7 ± 29.9 |
0.8 |
0.5 |
1 |
3.6 ± 1.8 |
195.1 ± 135.3 |
CAP |
100.5 ± 6.7 |
98.3 ± 33.5 |
0.8 |
0.5 |
1 |
3.7 ± 2.0 |
240.7 ± 127.6 |
For kVp, mAs, CTDI vol and DLP, the results are given as mean ± 1 standard deviation. Table 2. Patient demographics.
|
|
Number of examinations |
|
|
Age( y) � Mean( Min-Max) |
|
Examination |
Male |
Female |
Overall |
Male |
Female |
Overall |
Head |
104 |
95 |
199 |
55( 17 – 96) |
58( 19 – 85) |
56( 17 – 96) |
Chest |
15 |
18 |
33 |
52( 18 – 84) |
48( 18 – 73) |
50( 18 – 84) |
AP |
20 |
23 |
43 |
57( 31 – 78) |
44( 28 – 88) |
50( 28 – 88) |
CAP |
11 |
22 |
33 |
60( 35 – 83) |
54( 19 – 83) |
56( 19 – 83) |
Total |
150 |
158 |
308 |
55( 17 – 96) |
54( 18 – 88) |
55( 17 – 96) |
AP = abdomen-pelvis; CAP = chest-abdomen-pelvis.
where H M T and HF T are equivalent doses( H T = W R D T, W R = 1 for photons) evaluated for organ or tissue T of the reference male and reference female, respectively. In this study, sexrelated equivalent doses( male: prostate and testes; female: uterus, ovaries) were not averaged.
3 Results and discussion
3.1 CT techniques and patient demographics
The CT techniques applied and patient demographics are presented in Tables 1 and 2, respectively. Table 3 shows the statistical comparison between the data collected for female and male patients. A low variation of the kVp is observed for all the types of examinations involved in the study( coefficient of variation, CV, < 7 %). Contrarywise, a relatively significant variation of the mAs was observed( from ≈ 7 % for head scan to ≈ 41 % for chest scan). The variation is even more pronounced for CTDI vol( from ≈ 13 % for head scan to ≈ 71 % for chest scan) and DLP( from ≈ 11 % for head scan to ≈ 69 % for AP scan).
As shown in Table 2, the study involved 308 adult patients of which 51 % were female patients and 49 % were male patients. The age varied from 17 to 96 years with an overall average of 55 years. Examination with the highest number of patients was head scan( 65 %), and examinations with the lowest number of patients were chest and CAP scans( 11 %).
Statistical comparison between the data collected for female and male patients is presented in Table 3 below.
Since the p-values are all ≥ a = 0.05, the statistical significance level, therefore the distributions of the data collected( mAs, CTDI vol and DLP) for female and male patients are not statistically different. This means that the data for female and male patients can be combined.
Table 3. Statistical comparison( p-value) between the data collected for female and male patients.
Examination |
mAs |
CTDI vol |
DLP |
Head |
0.08 |
0.05 |
0.94 |
Chest |
0.96 |
0.14 |
0.11 |
AP |
0.84 |
0.29 |
0.36 |
CAP |
0.57 |
0.07 |
0.10 |
3.2 Typical( DRL) values
Figure 1 shows the distributions of CTDI vol and DLP per examination type. Values considered as abnormal are shown in red points. The range of CTDI vol collected and the computed mean values ± 1 standard deviation were 40.1 – 57 mGy and 53.5 ± 6.8 mGy, 1.5 – 15.5 mGy and 3.5 ± 2.5 mGy, 2.2 – 13 mGy and 3.6 ± 1.8 mGy, 2.2 – 12.1 mGy and 3.7 ± 2.0 mGy for head, chest, AP and CAP scans, respectively. The range of DLP collected and the calculated mean values ± 1 standard deviation were 488.3 – 1542.6 mGy cm and 1180.2 ± 131.7 mGy cm, 64 – 460.3 mGy cm and 166.9 ± 102.2 mGy cm, 98.3 – 888.6 mGy cm and 195.1 ± 135.3 mGy cm, 134 – 786.6 mGy cm and 240.7 ± 127.6 mGy cm for head, chest, AP and CAP scans, respectively. Apart from the case of head scan, a large variation( CV range, CTDI vol: 50 – 71 %, DLP: 53 – 69 %) in CTDI vol and DLP values was observed.
Tables 4 and 5 present the median and 75 th percentile values of the distribution of CTDI vol and DLP per examination type, respectively. It is observed that the values for female patients are greater than those for male patient globally. However, as shown in Table 3, these values are not statistically different from each other. Therefore, the overall median values were considered as typical values, i. e., 57 mGy, 2.7 mGy,