Z . Tahiri et al .: Radioprotection 2024 , 59 ( 2 ), 104 – 110 105
Table 1 . g-factors for breasts simulated with PMMA ( based on Dance et al ., 2000 , 2009 , 2011 ).
Thick . PMMA ( mm )
Equivalent breast thickness ( mm )
Breast glandularity (%) g-factors ( mGy / mGy ) HVL ( mm Al ) 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80
20 |
21 |
97 |
0.889 |
0.895 |
0.903 |
0.908 |
0.912 |
0.917 |
0.921 |
0.924 |
0.928 |
0.933 |
0.937 |
30 |
32 |
67 |
0.940 |
0.943 |
0.945 |
0.946 |
0.949 |
0.952 |
0.953 |
0.956 |
0.959 |
0.961 |
0.964 |
40 |
45 |
41 |
1.043 |
1.041 |
1.040 |
1.039 |
1.037 |
1.035 |
1.034 |
1.032 |
1.030 |
1.028 |
1.026 |
45 |
53 |
29 |
1.109 |
1.105 |
1.102 |
1.099 |
1.096 |
1.091 |
1.088 |
1.082 |
1.078 |
1.073 |
1.068 |
50 |
60 |
20 |
1.164 |
1.160 |
1.151 |
1.150 |
1.144 |
1.139 |
1.134 |
1.124 |
1.117 |
1.111 |
1.103 |
60 |
75 |
9 |
1.254 |
1.245 |
1.235 |
1.231 |
1.225 |
1.217 |
1.207 |
1.196 |
1.186 |
1.175 |
1.164 |
70 |
90 |
4 |
1.299 |
1.292 |
1.282 |
1.275 |
1.270 |
1.260 |
1.249 |
1.236 |
1.225 |
1.213 |
1.200 |
80 |
103 |
3 |
1.307 |
1.299 |
1.292 |
1.287 |
1.283 |
1.273 |
1.262 |
1.249 |
1.238 |
1.226 |
1.213 |
for the breast ( ICRP , 2007 ). This change is the result of several research studies that revealed the increased radio-sensitivity of breast gland tissues and the fact that malignant breast tumors account for nearly one quarter of the total cancer incidence in women ( Siegel et al ., 2018 ). The association between radiation-induced breast malignancies and radiation dose is the product of several factors such as age at exposure , latency period ( time after exposure ) and other hormonal factors . Age at exposure is the most important factor , with young girls being at higher risk than women approaching menopause . In light of the potential risks associated with radiation exposure during pregnancy , particularly from medical procedures , it becomes imperative to scrutinize practices such as mammography examinations . The Moroccan national cancer prevention and control plan proposes a mammography screening examination starting at the age of 40 . The reason for this rather young age ( usually 45 – 50 in other countries ) is that the incidence rate for breast cancer in Moroccan women shows a significant rise at this age ( Khalis et al ., 2016 ). While the Moroccan Ministry of Health recommends mammography at an age beyond 40 , it is crucial to recognize that age may play a pivotal role in future processes of optimization of radiation-based procedures for women of childbearing age ( Applegate et al ., 2021 ).
Although the assessment of ionizing radiation exposures of patients undergoing radiological examinations is recommended for dose optimization and benefit-risk assessment , few large studies have been published regarding the doses received by patients during mammography examinations in Morocco . Moreover , recent local studies , have brought attention to the critical importance of evaluating physicians ’ understanding of radiation doses and potential health risks and underscore the urgent need for enhanced training initiatives aimed at improving healthcare professionals ’ knowledge and practices ( Tahiri et al ., 2022 ).
The aim of this study is to investigate and quantify the radiation exposure during mammography for breast cancer screening in Morocco . Specifically , the study aims to assess the mean glandular dose ( MGD ) received by patients undergoing mammographic examinations and to explore the factors that contribute to dose variation among different mammography units . By analyzing the radiation dose data and examining technical parameters such as exposure factors , anode / filter combinations , breast thickness , and imaging modalities , this research aims to provide valuable insights into the level of radiation exposure faced by women during breast cancer screening in Morocco . This research forms a crucial foundation for the future optimization of mammography processes , prioritizing patient safety and informing strategies for refining our country ’ s mammography screening programs .
2 Materials and methods
2.1 Dose assessment
Patient data were retrieved from DICOM ( Digital Imaging and Communication in Medicine ) headers recorded during mammographic examinations acquired in automatic exposure control ( AEC ) mode . The technical parameters collected for each mammogram were the following : charge ( mAs ) and voltage ( kVp ) selected by the AEC , anode / filter combination , compressed breast thickness , type of cranial projection caudal ( CC ) or mediolateral-oblique ( MLO ) for each breast and compression force ( N ).
The collected patient data were used to calculate the MGD for the compressed breasts . The choice of the method of calculation depends mainly on the availability of measurement equipment , access to values for estimation or calculation and other technical criteria . In this study , we have used the well known method proposed by Dance et al ., :
MGD = K . g . c . s
where K is the kerma in incident air ( without backscattering ) at the upper surface of the breast and g , c and s are conversion factors ( Dance et al ., 2000 ).
The MGD is calculated from the kerma in the air measured at the surface of the breast , measured by using a polymethyl methacrylate ( PMMA ) phantom with 25 , 28 , and 34 kV W / Rh techniques , multiplied by a coefficient ( g ) as a function of the thickness of the breast under compression and the quality of the X ray beam used ( anode / filtration material , kV and CDA ). The use of the two other factors allows the improvement of the accuracy of the estimate , the factor ( c ) which takes into account the density of the breast and the factor ( s ) which characterizes the influence of the quality of the X-ray beam ( Talbi et al ., 2021 ; Dance et al ., 2000 ; Perry et al ., 2008 ). These factors depend on the half value layer ( HVL ), i . e ., the thickness of the material required to reduce the air kerma to half its original value .