Radioprotection No 59-2 | Page 59

118 M . Benamar et al .: Radioprotection 2024 , 59 ( 2 ), 117 – 122

Table 1 . Volumetric CT dose index ( CTDI vol ) ( mGy ) and dose length product ( DLP ) ( mGy . cm ) dosimetric indicators for abdominal exams . Hospital Number of acquisitions CTDIvol per acquisition DLP per acquisition

75 th percentile Range 75 th percentile Range

probabilistic nature , with no threshold , and with a frequency that increases proportionally with the radiation dose . For detriment-adjusted cancer risk , the ICRP proposes a nominal risk coefficient equal to 5.5 10 �2 Sv �1 for the population as a whole . For hereditary effects , the nominal risk coefficient adjusted for detriment is estimated at 0.2 10 �2 Sv �1 for the population as a whole ( ICRP 2007 ).

In line with ICRP recommendations , the aim of this study was to assess the effective dose delivered to patients during an abdominopelvic examination , as well as the renal dose , in order to estimate the likely stochastic effects .

2 Materials and methods

We conducted a retrospective quantitative multicenter study , covering a four-month period from June 01 to September 31 , 2022 . Data collection was carried out on DICOM ( Digital Imaging and Communication in Medicine ) consoles in the medical imaging departments of three Moroccan hospitals .

The examinations were carried out on three scanners , two of which were of the same brand , HITACHI Supria , while the third was GE . All three scanners were multi-slice , 16-slice , 1.2516 collimation and helical acquisition mode . Examinations were carried out according to predefined standard protocols , the only parameter that could be modified was the acquisition length adapted to the patient ’ s size . Voltage was set at 120 kV for scans carried out in hospitals H1 and H2 , and 130 kV for the examinations in hospital H3 . The tube current was modulated automatically by IntelliEC ( 3D ), a software package integrated into the scanners .

Information on dosimetric indicators was recorded manually from a post-acquisition dosimetric report , on which the CTDIvol and DLP for each acquisition and for the entire examination were recorded , along with voltage ( kV ) and effective load ( mAs ).

Mean effective doses , mean renal doses , Cancer and Hereditary Risks Assessment were estimated using the weighting factors defined in ICRP Publication 103 ( ICRP , 2007 ), the formulas used are :

E ef f ðmSvÞ ¼ 0:0152 DLP ð1Þ

E kidney ðmSvÞ ¼ 0:0086 CTDI w mAs ð2Þ

C risks ¼ E ef f ðSvÞ 5:510 �2 � Sv �1 ð3Þ

H risks ¼ E ef f ðSvÞ 0:210 �2 � Sv �1 ð4Þ

With : E eff : The effective dose received per patient for a given CT scan ; DLP : Dose length product for a given scan examination ; E kidney : Renal dose received per patient for a given CT scan ; CTDIw : Computed Tomography Dose Index weighted ; mAs : Load for a given CT scan ; C risks : The overall cancer risk per procedure ; H risks : The risk for hereditary diseases up to the second generation per procedure .

The collected data was entered into an Excel spreadsheet and analyzed using statistical analysis software ( Statistical Package for Social Sciences ( SPSS )). The examinations are divided into four groups according to the location where the examination was conducted .

3 Results

Our study included 287 abdominopelvic examinations of adult patients of both genders ( 46.38 % male and 53.62 % female ). The average age of the sample is 48 years ( 17 � 82 years ).

Table 1 shows the 75 th percentile CTDIvol and dose length product ( DLP ) values per abdominopelvic scan for the three hospitals , H1 , H2 , H3 and all H . These values are compared to the NRD published in other countries . The 75 th percentile CTDIvol values per abdominopelvic scan for the three hospitals , H1 , H2 , H3 and all H were 8.6 , 11.3 , 9.56 , and 9.4 m Gy respectively ( Tab . 1 ). These values are lower than the locally reported values in Morocco , France ( IRSN 2023 ) and Australia ( Lee et al ., 2020 ), Only the hospital H2 at a CTDIvol value higher than the value obtained by the El Mansouri study ( Tab . 2 ).

Similarly , the 75 th percentile DLP values per acquisition were 423.8 , 517.4 , 472.5 , 464.65 mGy . cm for H1 , H2 , H3 and all H respectively ( Tab . 1 ). These values are lower than those observed locally in Morocco ( El Mansouri et al ., 2022 ), France ( IRSN 2023 ) and Australia ( Lee et al ., 2020 )( Tab . 2 ).

The mean values for CTDIvol per acquisition varied between 7.68 and 8.29 mGy , and DLP per examination varied between 591.22 and 795.93 mGy . cm ( Tab . 3 ). H3 ’ s CTDIvol and DLP values were higher compared to those of the other hospitals .