Radioprotection No 59-2 | Page 46

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 .