Medical Imaging and Radiotherapy Journal (MITRJ) 37 (1) 5
 
Original article
HOW DOES THE REDUCTION OF GLANDULAR TISSUE EFFECT 
THE FORCE AND BREAST THICKNESS IN MAMMOGRAPHY?
KAKO VPLIVA ZMANJŠANJE ŽLEZNEGA TKIVA NA SILO IN DEBELINO DOJKE PRI 
MAMOGRAFSKEM SLIKANJU?
Manca Pišek, Pia Pšenič Pikelj, Nejc Mekiš, Erna Alukić*
University of Ljubljana, Faculty of Health Sciences, Department of Medical Imaging and Radiotherapy, Zdravstvena pot 5, 
1000 Ljubljana, Slovenia
*Corresponding author: erna.alukic@zf.uni-lj.si
Received: 8. 11. 2019
Accepted: 29. 4. 2020
https://doi.org/10.47724/MIRTJ.2020.i01.a001
IZVLEČEK
Namen: Ugotoviti, ali se debelina dojke z leti po menopavzi 
zmanjšuje glede na zmanjšanje žleznega tkiva pri 
mamografskem slikanju. Zanimalo nas je tudi, kako zmanjšanje 
debeline dojke vpliva na kompresijsko silo in povprečno 
žlezno dozo.
Metode: V nalogi so bili zajeti podatki o kompresijski sili, 
debelini dojke in povprečni žlezni dozi 300 pacientk, ki so 
imele opravljeno mamografsko slikanje v dveh projekcijah, 
tj. CC (kraniokavdalna) in MLO (mediolateralna poševna) 
projekcija. Podatke smo razdelili v tri starostne skupine po 100 
pacientk: od 50 do 55 (skupina 1), 60 do 65 (skupina 2) in 70 do 
75 let (skupina 3). Za izračun smo uporabili osnovne statistične 
teste; za preverjanje normalnosti vzorca Shapiro-Wilk test, za 
primerjavo razlik pa Kruskal-Wallis test. 
Rezultati in razprava: Pri CC projekciji obeh dojk smo 
ugotovili, da obstajajo statistično značilne razlike v debelini 
med 1. in 3. skupino, ter razlike v MGD med skupinama 1 in 2 
ter 1 in 3. Pri MLO projekciji obeh dojk so bile razlike statistično 
značilne pri MGD, in sicer med 1. in 2. ter 1. in 3. skupino. Pri 
CC in MLO projekciji leve in desne dojke smo ugotovili, da se 
kompresijska sila ne viša z višjo starostjo pacientk, kar se da 
pripisati različnim strukturam dojk in različni sili kompresije. 
Posledično bi se vidneje znižala tudi povprečna žlezna doza 
in debelina. 
Zaključek: Pri primerjavi kompresijske sile pri CC projekciji 
leve in desne dojke ni statistično značilnih razlik med 
skupinami, debelina in MGD pa se med nekaterimi starostnimi 
skupinami razlikujeta. Pri MLO projekciji se spreminja le 
MGD. Za nadaljnje raziskave v prihodnosti priporočamo 
zajem meritev na večjem vzorcu ter sočasno upoštevanje in 
preučitev še ostalih faktorjev, ki lahko vplivajo na debelino 
dojke, silo kompresije in MGD.
Ključne besede: mamografi ja, kompresijska sila, povprečna 
žlezna doza, debelina dojke, žlezno tkivo
ABSTRACT
Purpose: To determine whether breast thickness decreases 
with menopause after the reduction of glandular tissue. We 
also wanted to know how the decrease in breast thickness 
aff ects the compression force and the average glandular dose.
Methods: In this project, we collected data regarding the 
compression force, breast thickness and mean glandular 
dose of 300 patients who had mammographic imaging in 
two views: CC (craniocaudal) and MLO (mediolateral oblique) 
view. The data were divided into three age groups: 100 
patients aged 50 to 55, 100 patients aged 60 to 65 and 100 
patients aged 70 to 75 years. We used basic statistical tests for 
measurement purposes, while we used the Shapiro–Wilk test 
to check normality and the Kruskal–Wallis test to compare the 
diff erences.
Results and discussion: We presented the results and 
comparisons in the tables and box plot graphs for CC and 
MLO views of the left and right breast for compression force, 
breast thickness and MGD. In the CC view of the both breasts, 
we found that there were statistically signifi cant diff erences 
in thickness between groups 1 and 3, and diff erences in 
MGD between groups 1 and 2, and 1 and 3. In the MLO view 
of both breasts we found that compression force does not 
increase with the age of patients, which can be attributed 
to the diff erent size and density of breasts, and diff erent 
compression force. Higher compression force results in lower 
MGD and breast thickness. 
Conclusion: In the CC view of left and right breast, there is 
no statistically signifi cant diff erences in compression force, 
but thickness and MGD changed between some groups. In 
the MLO view, only MGD changed. For further research, we 
recommend taking measurements on a larger sample, and 
concurrently considering and examining other factors that 
may aff ect breast thickness, compression force and MGD.
Keywords: mammographic imaging, compression force, 
mean glandular dose, breast thickness, glandular tissue
6 Medical Imaging and Radiotherapy Journal (MITRJ) 37 (1)
Pišek M. et al./ How does the reduction of glandular tissue effect the force and breast thickness in mammography?
INTRODUCTION
Mammography is a radiology examination of the breast using 
X-rays. The exam is fast, reliable and accessible (1). It is the 
most effi  cient method for (early) breast cancer screening. 
Tumours with a diameter of only a few millimetres (mm) can 
be detected. This method has led to a decrease in the breast 
cancer mortality rate by 20 to 40% (2). Compression is used in 
mammography and it is applied using a compression paddle 
to fi x and compress the breast, which facilitates a better 
signal-to-noise-ratio, the higher homogeneity of the fi eld and 
thus a high-quality diagnostic mammogram, as well as a lower 
average glandular dose (3, 4).
The breast is essentially composed of fatty, connective 
and glandular tissue. Over the years, the glandular tissue 
may undergo atrophy and is transformed into fatty tissue, 
the connective tissue becomes less fi rm and the amount 
of collagen is reduced (5). Glandular, i.e. epithelial tissue is 
composed of lobules - TDLU (terminal ductal lobular unit), 
lobuli glandulae mammariae (lobules of mammary gland) and 
ductuli lactiferi (lactiferous ducts)(6).
A mammogram not only depends on the technical quality 
of the examination, but also on the tissue content of the 
examined breast. Younger breasts are composed of more 
glandular and less fatty tissue, and thus produce an image 
of dense and relatively homogenous tissue. During and 
after menopause when fatty tissue is prevalent in breasts, a 
mammogram is relatively transparent (7). A mammogram 
image of glandular tissue is radiopaque, whereas fatty tissue is 
radiolucent, which means that a higher content of fatty tissue 
results into a more dark and transparent mammogram (6).
When preparing for imaging, it is important for the radiographer 
to place the patient in an appropriate position, which can have 
a signifi cant eff ect on the quality of a mammogram, dose load 
and the patient’s perception of imaging (8).
Our aim is to determine whether mammography detects 
a decrease of breast thickness over the years in the 
postmenopausal period and how the reduced breast thickness 
aff ects the compression force and the mean glandular dose 
(MGD). 
METHODS
A retrospective research method was used, combined with 
secondary data analysis. The research was conducted between 
Table 1: Descriptive statistical properties for compression force for all three age groups of patients
Age group Average (N) Standard deviation (N) Median (N) Minimum (N) Maximum (N)
From 50 to 55 106.23 24.01 107.50 9.70 164.00
From 60 to 65 108.55 24.37 106.50 53.00 158.00
From 70 to 75 104.86 22.85 105.00 1.07 174.00
Table 2: Descriptive statistical properties for thickness for all three age groups of patients
Age group Average (mm) Standard deviation (mm) Median (mm) Minimum (mm) Maximum (mm)
From 50 to 55 53.69 13.04 56.00 20.00 76.00
From 60 to 65 51.57 12.24 53.00 24.00 79.00
From 70 to 75 49.19 12.65 49.50 16.00 79.00
Table 3: Descriptive statistical properties for mean glandular dose for all three age groups of patients
Age group Average (mGy) Standard deviation (mGy) Median (mGy) Minimum (mGy) Maximum (mGy)
From 50 to 55 1.40 0.55 1.31 0.66 3.90
From 60 to 65 1.16 0.34 1.08 0.65 2.49
From 70 to 75 1.13 0.33 1.08 0.59 2.85
Table 4: Statistical analysis of results for the CC view of left breast
Variable Pair Percentage diff erence Kruskal-Wallis test Post hoc analysis
Compression 
force
1-2 2%
0.4601-3 -1.3%
2-3 -3.4%
Thickness
1-2 -4%
0.043
0.653
1-3 -8% 0.037
2-3 -5% 0.661
MGD
1-2 -17%
< 0.001
< 0.001
1-3 -19% < 0.001
2-3 -3% 1.000
Medical Imaging and Radiotherapy Journal (MITRJ) 37 (1) 7
Pišek M. et al./ How does the reduction of glandular tissue effect the force and breast thickness in mammography?
29 April 2019 and 30 May 2019 in the Ljubljana Community 
Health Centre (Unit Centre), on a SIEMENS MAMMOMAT 
INSPIRATION mammogram machine.
We obtained the permission of the head of the Radiology 
Department in the Ljubljana Community Health Centre, the 
chief radiographer of the same centre and the Commission 
of the Republic of Slovenia on Medical Ethics prior to the 
research. In this study, we collected data regarding patients 
who had mammographic imaging in two views, i.e. the CC 
(craniocaudal) and MLO (mediolateral oblique) projection. 
We collected data regarding the compression force, breast 
thickness and MGD of 300 patients. They were divided into 
three age groups: 100 patients aged 50 to 55 (Group 1), 100 
patients aged 60 to 65 (Group 2) and 100 patients aged 70 to 
75 years (Group 3). All data were captured from anonymised 
DICOM fi les and processed using the IBM SPSS STATISTICS 
program (version 25). We used basic statistical tests for 
measurement purposes, while we used the Shapiro–Wilk test 
to check sample normality. The Kruskal–Wallis test and the 
Dunn Bonferroni post hoc analysis were used to compare the 
diff erences in data. The results were shown in form of tables 
and graphs. A standard statistical level of risk of 5% was taken 
into account in verifying hypotheses.
RESULTS
The measurement results of the CC and MLO views of left 
and right breasts were presented. The data are broken down 
according to the compression force, breast thickness and 
mean glandular dose for each breast separately. The results 
were compared for each age group.
Craniocaudal view of left breast (CC)
Tables 1-3 show the basic descriptive statistical properties for 
compression force, breast thickness during the compression 
and MGD. Table 4 shows the results of statistical analysis.
Craniocaudal view of right breast (CC)
Tables 5-7 show the basic descriptive statistical properties for 
compression force, breast thickness and MGD. Table 8 shows 
the results of statistical analysis.
Table 5: Descriptive statistical properties for compression force for all three age groups of patients
Age group Average (N) Standard deviation (N) Median (N) Minimum (N) Maximum (N)
From 50 to 55 107.31 18.93 108.00 46.00 146.00
From 60 to 65 113.18 21.09 110.00 63.00 166.00
From 70 to 75 108.05 19.16 105.50 55.00 180.00
Table 6: Descriptive statistical properties for thickness for all three age groups of patients
Age group Average (mm) Standard deviation (mm) Median (mm) Minimum (mm) Maximum (mm)
From 50 to 55 53.75 13.25 55.50 20.00 83.00
From 60 to 65 50.94 12.42 50.00 23.00 78.00
From 70 to 75 49.46 11.79 51.00 17.00 77.00
Table 7: Descriptive statistical properties for mean glandular dose for all three age groups of patients
Age group Average (mGy) Standard deviation (mGy) Median (mGy) Minimum (mGy) Maximum (mGy)
From 50 to 55 1.42 0.56 1.35 0.70 4.01
From 60 to 65 1.15 0.31 1.12 0.67 1.99
From 70 to 75 1.12 0.26 1.07 0.68 2.05
Table 8: Statistical analysis of results for the CC view of right breast
Variable Pair Percentage diff erence Kruskal-Wallis test Post hoc analysis
Compression 
force
1-2 -5%
0.1061-3 -1%
2-3 5%
Thickness
1-2 5%
0.028
0.317
1-3 8% 0.024
2-3 3% 0.910
MGD
1-2 19%
< 0.001
< 0.001
1-3 21% < 0.001
2-3 3% 1.000
8 Medical Imaging and Radiotherapy Journal (MITRJ) 37 (1)
Mediolateral oblique view of left breast 
(MLO L)
Tables 9-11 show the basic descriptive statistical properties 
for compression force, breast thickness and MGD. Table 12 
shows the results of statistical analysis.
Mediolateral oblique view of right breast 
(MLO R)
Tables 13-15 show the basic descriptive statistical properties 
for compression force, breast thickness and MGD. Table 16 
shows the results of statistical analysis.
DISCUSSION
A CC projection of the left breast showed that the compression 
force does not increase with respect to our three age groups. 
By increasing the force, the thickness of the compressed 
breast reduces, which means that the mean glandular dose 
should decrease. In our case, the thickness diff ers in the fi rst 
and the third group, where the thickness of the breast in the 
fi rst group is highest and lowest in the third group. Waade et 
al. (4) determined that at some level a higher compression 
force no longer leads to a lower breast thickness; it only 
causes a more painful and unpleasant examination for the 
patient. Our study established that the MGD of the fi rst 
group is higher than the MGD of the second and third group, 
while there are no diff erences in MGD between the second 
and third group. Compared to other tissues, glandular breast 
tissue is most sensitive to ionising radiation. Therefore, the 
highest mean glandular dose is expected in the fi rst group 
and the lowest in the third group. A Sydney study compared 
the diff erences in compression force in cases when patients 
alone compress the breast and on the other hand when 
radiographers perform the compression. It was determined 
that the compression force is many times lower when the 
compression is done by radiographers. Consequently, the 
breast thickness diff ered by up to 11 mm (9). According 
to a six-year study by Mercer et al., (10, 11) the applied 
force also depends on the radiographer who performs 
the examination. When a patient was imaged by diff erent 
radiographers, statistically signifi cant diff erences occurred. It 
is likely that a higher compression force on the breast could 
have been applied more often in our study, without causing 
discomfort or pain to the patient. However, it would to some 
Pišek M. et al./ How does the reduction of glandular tissue effect the force and breast thickness in mammography?
Table 9: Descriptive statistical properties for compression force for all three age groups of patients
Age group Average (N) Standard deviation (N) Median (N) Minimum (N) Maximum (N)
From 50 to 55 126.14 30.88 122.50 32.00 188.00
From 60 to 65 129.94 32.06 132.00 1.30 187.00
From 70 to 75 125.04 29.99 122.50 1.30 191.00
Table 10: Descriptive statistical properties for thickness for all three age groups of patients
Age group Average (mm) Standard deviation (mm) Median (mm) Minimum (mm) Maximum (mm)
From 50 to 55 54.61 14.33 57.50 22.00 81.00
From 60 to 65 52.69 14.62 54.00 24.00 82.00
From 70 to 75 52.97 14.02 54.50 16.00 84.00
Table 11: Descriptive statistical properties for mean glandular dose for all three age groups of patients
Age group Average (mGy) Standard deviation (mGy) Median (mGy) Minimum (mGy) Maximum (mGy)
From 50 to 55 1.45 0.56 1.35 0.67 3.64
From 60 to 65 1.23 0.38 1.16 0.64 2.22
From 70 to 75 1.25 0.37 1.18 0.68 3.21
Table 12: Statistical analysis of results for the MLO view of left breast
Variable Pair Percentage diff erence Kruskal-Wallis test Post hoc analysis
Compression 
force
1-2 -3%
0.2701-3 1%
2-3 4%
Thickness
1-2 4%
0.3311-3 3%
2-3 -1%
MGD
1-2 15%
0.002
0.004
1-3 14% 0.016
2-3 -2% 1.000
Medical Imaging and Radiotherapy Journal (MITRJ) 37 (1) 9
extent cause a reduction in breast thickness as well as in 
mean glandular dose. Poulos and McLean (9) discovered a 
connection between the size of a breast and the force that 
can be applied. Larger breasts allow for a higher force. Since 
numerous data were obtained from anonymous DICOM 
fi les, it is not clear whether older women had larger breasts, 
which could be one of the reasons for a non-decreasing 
compression force in age groups. 
According to Hofl ehner et al., (12) there are two categories of 
breasts: fi rm and soft. The thickness of soft breasts after the 
applied force of 80 N accounts for 40 mm, while it is higher for 
fi rm breasts. For each subsequent 30 N, the thickness changes 
by 1 to 4 mm. The thickness of soft breasts under similar 
conditions changes by more than 4 mm (9). In our research, 
the patients were divided into age groups. However, the 
category (fi rm or soft breasts) was not determined for patients 
from individual age groups. 
There were no diff erences in the compression force nor in 
the thickness of the compressed breast in the mediolateral 
oblique projection for any of the age groups, but there were 
statistical diff erences in mean glandular dose between the 
fi rst and the second group, and the fi rst and the third group. 
The dose and quantity of glandular tissue were lower. 
Pišek M. et al./ How does the reduction of glandular tissue effect the force and breast thickness in mammography?
Menstrual function and thus reproductive abilities of women 
cease in menopause, which is connected to undesired 
changes in body weight and its composition. Generally, the 
body weight increases and results in higher body fat (13). If we 
assume that the women in our study also gained weight and 
breast density during the menopausal period, our results are 
fairly expected. The larger and denser the breast is, the higher 
the thickness and consequently the mean glandular dose will 
be. The diff erence in breast density for women from the fi rst, 
second and third groups is therefore smaller or non-existent. 
Thus, the diff erences between data for the three age groups 
are smaller. 
CONCLUSION
According to literature, it was expected that a higher age 
group and thus a greater atrophy of glandular tissue would 
result in an increasing compression force on the breast, a 
decreasing tissue thickness as well as a mean glandular dose. 
We determined that there are no statistically signifi cant 
diff erences in the CC view of left and right breasts. The only 
exceptions were thickness, which only decreases between the 
fi rst and third age group, and MGD, which decreases between 
Table 13: Descriptive statistical properties for compression force for all three age groups of patients
Age group Average (N) Standard deviation (N) Median (N) Minimum (N) Maximum (N)
From 50 to 55 122.34 34.13 125.00 1.01 186.00
From 60 to 65 124.68 23.99 122.50 65.00 182.00
From 70 to 75 127.40 34.40 123.00 1.06 190.00
Table 14: Descriptive statistical properties for thickness for all three age groups of patients
Age group Average (mm) Standard deviation (mm) Median (mm) Minimum (mm) Maximum (mm)
From 50 to 55 54.28 13.94 57.00 18.00 78.00
From 60 to 65 51.45 13.78 53.00 22.00 86.00
From 70 to 75 52.71 14.09 54.00 18.00 82.00
Table 15: Descriptive statistical properties for mean glandular dose for all three age groups of patients
Age group Average (mGy) Standard deviation (mGy) Median (mGy) Minimum (mGy) Maximum (mGy)
From 50 to 55 1.45 0.58 1.32 0.71 3.86
From 60 to 65 1.22 0.37 1.14 0.66 2.76
From 70 to 75 1.24 0.33 1.18 0.70 2.54
Table 16: Statistical analysis of results for the MLO view of right breast
Variable Pair Percentage diff erence Kruskal-Wallis test Post hoc analysis
Compression 
force
1-2 -2%
0.6421-3 -4%
2-3 -2%
Thickness
1-2 5%
0.2461-3 3%
2-3 -2%
MGD
1-2 16%
0.001
0.002
1-3 14% 0.017
2-3 -2% 1.000
10 Medical Imaging and Radiotherapy Journal (MITRJ) 37 (1)
the fi rst and second group and between the fi rst and third 
group. In the MLO view of left and right breasts, only the 
MGD changes between the fi rst and the second group, and 
the fi rst and the third group, while the other two parameters 
remain the same. Our research did not prove that the breast 
thickness decreases over time in the postmenopausal period 
and therefore does not aff ect the compression force and dose 
load for the patient, as expected. Since the results failed to 
meet our expectations, it would be recommended in further 
studies to increase the sample and also take other factors 
into account. By reviewing literature, we came across the 
following factors: breast size, categorisation into soft and fi rm 
breasts, appropriately applied compression force, review of 
mammograms. It would also be advisable to conduct research 
in another fi eld of mammographic diagnostics.
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Pišek M. et al./ How does the reduction of glandular tissue effect the force and breast thickness in mammography?