Radioprotection No 59-2 | Page 67

126 S . Semghouli et al .: Radioprotection 2024 , 59 ( 2 ), 123 – 130
Table 4 . Distribution of CTDI vol , DLP and effective dose per type of thorax CT scan . Min Max Mean SD
Radiotherapy planning CT-scans
Pulmonary embolism
Diagnostic CT-scans Infectious lung disease
COPD
CTDI vol ( mGy )
4.00
35.20
14.58
8.68
DLP ( mGy . cm )
215.0
1606.80
735.23
352.63
Effective dose ( mSv )
3.80
28.44
13.01
6.24
CTDI vol ( mGy )
5.48
15.83
9.64
3.29
DLP ( mGy . cm )
205.35
643.10
367.15
137.60
Effective dose ( mSv )
3.63
11.38
6.49
2.43
CTDI vol ( mGy )
7.08
12.27
9.14
1.69
DLP ( mGy . cm )
244.74
686.21
380.05
133.40
Effective dose ( mSv )
4.33
12.14
6.72
2.36
CTDI vol ( mGy )
4.55
10.63
6.53
2.17
DLP ( mGy . cm )
133.80
403.70
250.94
82.87
Effective dose ( mSv )
2.36
7.14
4.44
1.46
Table 5 . : DRLs calculated in terms of CTDI vol and DLP per type of Thorax CT scan .
Radiotherapy planning CT-scans
Diagnostic CT-scans Pulmonary embolism Infectious lung disease COPD
DRLs in term of CTDIvol ( mGy ) DRLs in term of DLP ( mGy . cm )
19.37 11.13 10.26 7.37
851.9 417.73 451.9 317.78
Table 6 . Mean Cancer risk calculated per 1 million of Thoracic CT-scan .
Mean risk ( Per1 million exams )
Radiotherapy planning CT-scans
Diagnostic CT-scans
Pulmonary embolism
Infectious lung disease
COPD
715 ( 209 – 1564 )
357 ( 199 – 626 )
369 ( 238 – 668 )
244 ( 130 – 393 )
Table 7 . Correlation coefficients ( p-values ) for gender of patients , clinical indication , age , BMI and the effective dose .
Effective dose ( p-value )
Radiotherapy planning CT
Diagnostic CT
Gender
Clinical indication
Student ’ s t-test
0.076
0.111
0.001
Age
BMI
Spearman correlation
0.216
0.000
0.036
0.231
** Correlation is significant at the 0.05 level ( two-tailed ).
4.1 Population studied
In fact , body mass influences the dose received by the patient . In this context , it is essential to assess the patient ’ s morph type as accurately as possible in order to select and apply the appropriate examination protocol according to the machine ’ s capabilities , with the aim of limiting doses to the patient ( OTIMROEPMQ , 2016 ).
4.2 Acquisition parameters
The results of this study show that the voltage used during diagnostic and radiotherapy planning CT-scans is 120 kV for all patients , and the intensity is modulated according to patient morphology and the protocol used . The average intensity is 100 mAs for radiotherapy planning CT-scans . In diagnostic CT-scans , the average intensity is 125 mAs for the pulmonary