Radioprotection No 59-2 | Page 47

106 Z . Tahiri et al .: Radioprotection 2024 , 59 ( 2 ), 104 – 110
Table 2 . c-factors for breasts simulated with PMMA ( based on Dance et al ., 2000 , 2009 , 2011 ).
Thick . PMMA ( mm )
Equivalent breast thickness ( mm )
Breast glandularity (%) c-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
0.89
0.903
0.90
0.912
0.91
0.921
0.92
0.928
0.93
0.93
30
32
67
0.940
0.94
0.945
0.94
0.949
0.95
0.953
0.95
0.959
0.96
0.96
40
45
41
1.043
1.04
1.040
1.03
1.037
1.03
1.034
1.03
1.030
1.02
1.02
45
53
29
1.109
1.10
1.102
1.09
1.096
1.09
1.088
1.08
1.078
1.07
1.06
50
60
20
1.164
1.16
1.151
1.15
1.144
1.13
1.134
1.12
1.117
1.11
1.10
60
75
9
1.254
1.24
1.235
1.23
1.225
1.21
1.207
1.19
1.186
1.17
1.16
70
90
4
1.299
1.29
1.282
1.27
1.270
1.26
1.249
1.23
1.225
1.21
1.20
80
103
3
1.307
1.29
1.292
1.28
1.283
1.27
1.262
1.24
1.238
1.22
1.21
Table 3 . Typical HVL measurements for different combinations of tube voltage and anode / filter combination / s-factors for clinically used spectra ( Dance et al ., 2000 ,).
kV
HVL ( mm Al ) for anode / filter combination Mo Mo Mo Rh Rh Rh W Rh W Ag W Al ( 0.5mm ) W Al ( 0.7mm )
25
0.32 ±. 02
0.38 ±. 02
0.37 ±. 02
0.50 ±. 03
0.51 ±. 03
0.34 ±. 03
0.42 ±. 03
28
0.35 ±. 02
0.42 ±. 02
0.42 ±. 02
0.53 ±. 03
0.58 ±. 03
0.39 ±. 03
0.49 ±. 03
31
0.38 ±. 02
0.45 ±. 02
0.45 ±. 02
0.56 ±. 03
0.61 ±. 03
0.44 ±. 03
0.55 ±. 03
34
0.40 ±. 02
0.47 ±. 02
0.47 ±. 02
0.59 ±. 03
0.64 ±. 03
0.49 ±. 03
0.61 ±. 03
37
0.62 ±. 03
0.67 ±. 03
0.53 ±. 03
0.66 ±. 03
Target material Filter material Filter thickness ( mm ) S-Factor
Mo
Mo
30
1.000
Mo
Rh
25
1.017
Rh
Rh
25
1.061
W
Rh
50-60
1.042
W
Ag
50-75
1.042
The values of the g , c and s factors , used are shown in Tables 1 – 3 , respectively .
2.2 Procedure
The study included 1100 standard screening mammographic incidences performed on 365 women who underwent mammography in the 5 units listed in Table 4 , located in the Rabat-Salé-Zemmour-Zaër region . The standard screening mammographic examinations encompassed bilateral breast examinations , consisting of both craniocaudal ( CC ) and mediolateral oblique ( MLO ) incidences for each breast .
The mammography units that participated in the study underwent regular quality control and maintenance to ensure proper functioning , with a particular focus on the automatic exposure control ( AEC ) system . The AEC system was carefully monitored and maintained to deliver consistent and appropriate radiation doses while upholding high image quality standards . All images used in the study were validated by both the resident and senior radiologist to ensure they met the necessary quality criteria . The study focused on standard bilateral breast examinations , primarily for breast cancer screening , which involved two radiological incidences : craniocaudal ( CC ) and mediolateral oblique ( MLO ). The use of automatic exposure control ( AEC ) helped ensure that the examinations met the required quality and dose standards for breast cancer screening , and the images were subject to thorough validation by the radiology team .
2.3 Data analysis
The data collected were recorded on Microsoft Excel and classified for each mammography unit , examination and imaging modality . Data processing was performed to analyze the median values , the standard deviation of the means and other measurements of different variables , technical parameters and radiation dose received .
3 Results
Data collected from the 5 mammography units used for breast cancer screening included 365 patients , for a total of 1100 images . The majority ( 99.2 %) of the women were within the standard screening age range recommended in the early