Radioprotection No 59-1 | Page 20

14 M . EL Fahssi et al .: Radioprotection 2024 , 59 ( 1 ), 13 – 18

medical exposure of patients for diagnostic and interventional procedures ( ICRP , 2017 ).

The use of DRLs reduces the overall dose and the range of doses observed in clinical practice . In the United Kingdom , the 2005 DRLs for radiography , fluoroscopy , and dental x-rays were approximately 16 % lower than those in 2000 and approximately half of those in the mid-1980s ( Kanal et al ., 2017 ).

In Morocco , medicine accounts for more than 80 % of the installations and activities that use ionizing radiation sources . The field of health records includes over 300 scanners , 40 electron accelerators used for treatment and 24 nuclear medicine centers . These figures are expected to increase in the future with the construction of new regional centers and the expansion of mandatory health insurance ( Mrabit , 2022 ).

Several previous studies have examined diagnostic reference levels in Moroccan hospitals . In this context , El Mansouri et al . found that the established DRLs in Morocco in terms of CTDIvol were 57.4 , 12.3 and 10.9 for CT examinations of the head , chest , and abdomen , respectively ( El Mansouri et al ., 2021 ). For DLP , they were 1020 , 632 and 714 , respectively . For their part , Benamar et al . found that the DRLs in terms of CTDIvol for head , chest , abdomen-pelvis , chest-abdomen-pelvis , and lumbar examinations were 57.7 , 11.1 , 11.3 , 11.6 and 20 mGy respectively . In terms of DLP , they were 1250.4 , 392.2 , 517.1 , 833.27 and 707.37 mGy . cm , for the mentioned types of examinations respectively ( Benamar et al ., 2022 ).

This study , which aims to estimate the doses received by adult patients during CT examinations , completes the study carried out by EL Fahssi et al ., 2023 which calculated the doses delivered to patients in conventional radiology in the Souss Massa region . This study covers 6 routine CT examinations : Brain without contrast media , chest without contrast media , abdomen without contrast media , abdomen with contrast media , abdomen and pelvis ( AP ) with contrast media , and chest abdomen and pelvis ( CAP ) with contrast media .

2 Method

Data of this study were collected between January and June 2023 at the Souss Massa Regional Hospital . A total of 360 patients ’ data were collected from the Optima General Electric 16-slice scanner , covering 6 routine CT examinations : Brain without contrast media , chest without contrast media , abdomen without contrast media , abdomen with contrast media , abdomen and pelvis ( AP ) with contrast media , and chest abdomen and pelvis ( CAP ) with contrast media .

Patient data were specified for each type of CT scan , including age , sex , weight , and height , as well as scanner acquisition parameters including number of series , use of contrast media , rotation time plus slice thickness , the displayed Computed Tomography Dose Index ( CTDI vol ), and the Dose Length Product ( DLP ).

DRLs were calculated for each type of CT examination by estimating the 75 % percentile of CTDI vol and DLP . The effective dose is calculated using the following formula :

E ( mSv ) = EDLP DLP ( mGy . cm ) ( Delchambre , 2012 ). Where EDLP is the millisievert per second conversion factor .

Table 1 . Conversion factors for the anatomical regions scanned ( Delchambre , 2012 ).

Table 1 presents the conversion factor according to the type of CT-scan .

Student ’ s t-test was used to examine the association between patient gender and effective dose . To study the association between age and body mass index ( BMI ), Pearson ’ s parametric test was used after confirmation of the normal distribution of all variables . A linear regression test was then performed to understand and model the relationship between these variables .

2.1 Data analysis

The data were statistically analyzed by SPSS software version 21.0 . The third quartile ( 75th percentiles ) is considered according to ICRP publication 135 as the reference value for setting diagnostic reference levels in terms of CTDI vol and DLP .

3 Results

Epdl ( mSv . mGy �1 . cm �1 )

Table 2 . The Summary of acquisition parameters per type of CT scan .

Parameters Brain C�

CT examinations

Chest Abdomen Abdomen C� Cþ C�

AP CAP Cþ Cþ

The mean tube voltage ( Kv ), electric charge ( mAs ), pitch , and slice thickness are indicated for each CT examination . Cþ : with contrast media . C� : without contrast media .

360 patients who underwent a CT scan of one of the anatomical regions already mentioned took part in this study . All patients were adults aged over 18 years and weighing between 50 and 90 kg .

Table 2 shows that the voltage is invariable for all examinations ( 120 kV ). The charge is fixed on 125 mAs for chest CT , and 120 mAs for the rest of examinations . The pitch is equal to 1 for the Brain CT and equal to 1,75 for the rest of