1. No category

HealthMED - Volume 5 / Number 6 / 2011
Effects of dispersed radiation on
the thyroid and the gonads during
mammography
Suad Kunosic1,2, Denis Ceke3, Adnan Beganovic4, Begzada Basic5
1
2
3
4
5
Department of Physics, Faculty of Natural Sciences and Mathematics, University of Tuzla, Bosnia and
Herzegovina,
Department of Biophysics, Medical Faculty, University of Tuzla, Bosnia and Herzegovina,
Center for quality assurance and self-evaluation, University of Tuzla, Bosnia and Herzegovina,
Department of Medical Physics and Radiation Safety, Clinical Centre of Sarajevo University,
Bosnia and Herzegovina,
Institute for Public Health FBiH, Sarajevo, Bosnia and Herzegovina.
The study aimed to explore effects of dispersed radiation on radiosensitive organs
during mammography. The thyroid and the gonads
are determined as key organs for exploration of dis
the dispersion zone and the second ones due to their
symmetrical position in regard to the thyroid, which
enables an assessment of distribution of dispersed
radiation in regard to a compression plate.
Entrance skin doses
thermoluminescent dosimeters attached to the skin
surface above the thyroid and the gonads for the purpose of exploration of dispersed radiation effects.
Results obtained indicate that medium entrance skin doses on skin around the thyroid
were 0,211 ± 0,107 mGy per woman and 0,017
± 0,012 mGy per woman on skin around the go cant correlation between entrance skin doses for
the thyroid and total applied mAs during mammography (r = 0,802, p<0,01).
dispersed radiation was directed towards the area
above breasts and the thyroid and only a small
amount covered the area under the breasts and went
towards the gonads. Entering skin doses for the
thyroid ranged from 0.10 to 0,51 mGy while the
dose received by the thyroid varied from 0,7 % to
1,6 % of the MGD dose. Entrance skin doses for the
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gonads can be 13 times less than the thyroid dose
and cannot be concerned dangerous for the gonads.
mammography, dispersed radiation,
entrance skin dose, dosimetry in mammography.
Introduction
Application of x –rays in diagnostics had fun
radiology. Contemporary radiology is based on
prevention of all kinds of diseases examined through their early detection. Mammography is used
as the most reliable radiological diagnostic method
in breast cancer prevention and detection. Since
breast cancer is currently the second leading cause
of death from cancer for women [1], a number of
mammographic examinations [2] with a purpose
of breast cancer early detection [3] has increased.
It is a key for a long-term control and good results in breast cancer treatment, which requires a
high quality mammography. To achieve necessary
requirements for the high quality mammography
timized [4]. Optimization means that exposure of
a patient to radiation must be as little as possible,
but it must comply with quality of imaging necessary for an adequate diagnosis.
Therefore, measuring patient doses received
by a breast during mammography represented an
important segment of ensuring mammographic
Journal of Society for development in new net environment in B&H
HealthMED - Volume 5 / Number 6 / 2011
patients doses in mammography undeniably brought a certain degree of risk [5, 6, 7, 8, 9] which
is relatively small with application of adequate
equipment and technique. Most mammographic
!"#"""$"&"'*
mean glandular dose (MGD) was a base for radiation risk assessment.
+ / mography one has to examine effects of dispersed radiation on surrounding radiosensitive organs
during mammography. Dispersed radiation is interesting due to detection of its adverse impact on
radiosensitive organs during mammography and
possible designing of their protectors [15]. Contribution of dispersed radiation to radiosensitive
organs around the area interesting for mammographic diagnostics increases with an increase of a
number of mammographic examinations. Several
authors examined effects of dispersed radiation
on radiosensitive organs during mammography
[16, 17, 18, 19]. They mainly examined effects of
dispersed radiation on the thyroid, eyes, stomach,
lungs and esophagus while very little study included the gonads. In medical radiology the thyroid
has been marked as a radio sensitive organ since
: during radiological diagnostics of neck, shoulders
and oral cavity. Typical doses for the thyroid were
documented in dentistry [20, 21], through radiological examinations in cardiology [22] and they
proved to be interesting for personnel included in
radiological procedures [23].
This study used TLD [24] as the most suitable
method for direct measuring of doses absorbed on
the surface of the thyroid and the gonads during
mammographic screening.
(Mo/Mo). During a routine mammographic control, we collected data about entrance skin doses
in the area of the thyroid and the gonads for 68
patients between the age of 34 and 80. To collect
data about entrance skin doses we used the same
technique with thermoluminescent dosimeters as
in personal dosimetry.
At every diagnostic examination one TLD
was attached to a patient’s skin surface above the
> " ?
diagnostic examinations, TLD dosimeters were
attached to the patient’s neck (area of the thyroid) and around the waist (area of the gonads) with
thin rubber ribbon (Figure 1.). Dosimeters at the
thyroid and the gonads, respectively, were used to
collect data about dispersed radiation during the
complete diagnostic examination.
Data collection
Experimental measuring of dispersed radiation
during routine mammographic diagnostic examinations was conducted at the Department of Thoracic Diagnostics and Breast of the Radiology Clinic (Clinical Centre of the University of Sarajevo).
A mammography machine used for diagnostic examinations was Siemens Mammomat 1000
Figure 1. Positions of a TLD detector during diagnostic examinations
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HealthMED - Volume 5 / Number 6 / 2011
The following data were recorded during measuring of dispersed radiation at diagnostic examinations:
(1) Patient’s age, mass and size
(2) Applied clinical spectrum
(3) Compressed breast thickness (CBT)
(4) Exposition factors and charge (mAs),
anode voltage (kVp), clinical spectrum
J
K
Q
JWQXY
(6) Distance from the surface of the upper
compression plate to the thyroid in each
individual projection
JZQ?
plate to the gonads in each individual
projection
Quality control
Anode voltage value, reproducibility of doses
J\^_Q hout returnable radiation during the period of data
collection. The compression plate was checked for
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K
nation following recommendations of the European
Protocol (25), which recommends measuring methodology and frequency. Accuracy of reading of
compressed breast thickness was checked according
to recommendations of the mentioned Protocol. All
of quality control tests and dosimetry in diagnostic
radiology were done with a Barracuda instrument.
The safest method to monitor persons professionally exposed to ionizing radiation (in medicine,
industry, science) is personal dosimetry. Personal
dosimetry is closely related to exposure of people working with sources of ionizing radiation in
medicine, industry, science etc. TLDs are suitable
for obtaining important information about dose
distribution during radiotherapy or diagnostic use
of radiation.
Dosimeters used in personal dosimetry are Li
`{J_|Q
? tration systems. The TLDs are small and enable
1776
measuring of entrance skin doses at any point of a
patient’s skin. They can be used to estimate a dose
for organs located immediately under skin surface
(such as the thyroid, the gonads or the breasts),
which was the basis for their application. We used
TLDs to obtain information about entrance skin
doses on the surface of the thyroid and the gonads
during mammographic diagnostics. ESDs were
/persed radiation on these two radio sensitive organs during mammography.
The data were statistically processed in SPSS
17.0 and they were presented as a standard de
~
correlation between the ESDs and total mAs. A
value of p<0.05 was considered as an indicator of
!"
The examined patients were between 34 and 80
years of age. This variation of age was followed by
a symmetric distribution of compressed breast thickness which varied from 25 to 77 mm. A deviation
/ ± 1 mm. Mean value of compressed breast thickness was 52,88 mm (SD: 11,08). The examined
patients’ height ranged from 154 to 175 cm, while
mean value was 164,09 cm (SD: 6,21). An average
body mass per a patient was 73, 91 kg (SD: 11,58).
Beam energies and X-ray technique
Voltage applied during the diagnostic examinations of female patients ranged from 29 to 32
kV, depending on compressed breast thickness.
^
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exposures and mainly for compressed breast thickness up to 45 mm. The most frequently applied
Journal of Society for development in new net environment in B&H
HealthMED - Volume 5 / Number 6 / 2011
voltage of 30 kV was applied in 128 (50%) exposures and voltage of 31 kV in 71(27,73%) exposures. Minimum voltage used was 32 kV and it was
applied 19 (7,42%) times for extreme compressed
breast thickness which varied from 70 to77 mm.
There were 256 diagnostic images made (130
MLO and 126 CC images) for an examination of
68 patients during a routine mammography. Four
images were used for the complete diagnostic examination: two for an MLO projection and two for
a CC projection. A compete examination of both
breasts was done for 56 patients, which involved
224 (87,5%) images (two MLO and two CC). A
control examination of one breast was done for 10
$# JZ"‚Q (one MLO and one CC). Remaining two patients
were diagnostically examined with 12 (4,69%)
J'_ƒ $ „„ Q size and repetition of some images.
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Table 1. represents regarding mean doses absorbed by the skin around the thyroid and the gonads
with all other parameters that can be related to a
potential risk caused by dispersed radiation during
†
/
‡
$W‡
:mination. Mean entrance skin dose on skin surface
around the thyroid was 211,16 μGy (SD : 107,19)
and 14,90 μGy (SD : 7,18) on skin surface around
ˆ
difference in the ratio of the ESDs for the thyroid
:
arches [15] claiming that most of dispersed radiation is emitted vertically backwards towards the area
of the thyroid. Donald McLean [26] assessed the
origin of dispersed radiation in mammography in
his researches and concluded that 85 % of dispersed radiation originates from the compression plate.
Therefore, it was very interesting to take two positions to be assessed in this research: the area of the
thyroid and the area of the gonads.
Mean ESD of 211,16 μGy for the thyroid is
ch conducted by a group of authors [18] due to
less exposure during mammography per a patient.
ˆ
ference in mean ESD for the thyroid arose as a
Table 1. A summary of statistics regarding a number of images, It, compressed breast thickness, distance
from organs to the compression plate, ESDs for the thyroid and the gonads for the whole sample.
%
Number
$
It
'(
'(
)
'(
Mean ± SDc
Mean ±SDc
Mean ± SDc
Total
256
30,8 ±13,90 11,40±4,33* 52,88±11,08
CCb
126
26,40±10,38 15,44±2,12* 50,20±10,16
MLOa
130
35,10±15,49 7,48 ± 1,15* 55,48±11,34
2 IMAGES 20(10x2) 31,30±13,21 11,8±4,79* 54,60±12,69
4 IMAGES 224(56x4) 30,20±13,93 11,38±4,33* 51,95±10,59
6IMAGES 12(2x6)
41,4±10,56 11,04±3,88* 67,42±6,34
Total
256
30,8 ±13,90 41,20±6,17** 52,88±11,08
Gonades
CCb
126
26,40±10,38 36,97±4,60** 50,20±10,16
MLOa
130
35,10±15,49 45,30±4,50** 55,48±11,34
2 IMAGES 20(10x2) 31,30±13,21 41,10±6,61** 54,60±12,69
4 IMAGES 224(56x4) 30,20±13,93 40,93±6,05** 51,95±10,59
6IMAGES 12(2x6)
41,4±10,56 46,46±5,60** 67,42±6,34
* Distance from the surface of the upper compression plate to the thyroid
a
MLO: Mediolateral oblique view.
b
CC: Craniocaudal view.
c
SD: Standard deviation.
d
CBT: Compressed breast thickness.
ESD
"*"'+,(
Mean ± SDc
./d
)
-
+,
211,16±107,19 211,16±25,47 283,13
Thyroida
Journal of Society for development in new net environment in B&H
120,66± 77,07
220,54±100,48
401,02± 46,46
17,15 ± 12,45
120,66±47,77 168,65
220,54±26,31 284,32
401,02±64,38 417,44
17,15 ± 2,96 22,96
14,90 ± 7,18 14,90 ± 4,45
17,67 ± 13,37 17,67 ± 3,50
13,92 ± 2,27 13,92 ± 3,14
22,98
23,78
14,72
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HealthMED - Volume 5 / Number 6 / 2011
consequence of the fact that this study applied one
TLD to register dispersed radiation while the other
one [18] applied three TLDs on skin around the
thyroid, which could cause the mentioned difference in the entrance doses. An additional analysis
:
there were not any such differences between these
two studies in examinations that were done with 2
to 6 images, which can realistically be applied for
a complete mammographic examination of breasts. The mentioned differences appeared as a consequence of an increased number of exposures per
a patient, which caused somewhat increased ESDs
for the thyroid in the mentioned situation [18].
It was not possible to compare mean ESD for
the gonads due to a lack of relevant data from other authors. We selected the gonads as the second
critical point exposed to dispersed radiation during
mammography due to their symmetric position in
regard to the thyroid. This approach enables us
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dispersed radiation is emitted vertically upwards
from the compression plate towards the thyroid.
Mean distance between the compression plate
and the TLD on the thyroid was 15,44 cm (SD :
2,12) for CC projection and 7,48 cm (SD: 1,15)
for MLO projection. Mean distance from a detec
'W&#
(SD: 4,50) for MLO and 36,97 cm (SD: 4,60) for
„„
+
between entrance skin doses for the thyroid and
the total mAs, which was shown with a regression
line (r = 0,801 ; p<0,01) in Figure 2.
Tables 2. and 3. represent mean skin doses in
JQ the thyroid and the gonads. Mean skin dose per
an image is 0,061 mGy for the thyroid and it is
13 times higher than the corresponding dose for
the gonads. For the thyroid, distribution of mean
/
is somewhat uniform for mammographic examinations with two, four, and six images while it is
totally opposite with the gonads.
Table 2. Distribution of an average thyroid skin
!
per examination
No of
)
"
1-
0
,.
0
2
4
6
Total
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0,121 ± 0,077
0,220 ± 0,010
0,401 ± 0,046
0,060
0,055
0,067
0,061±0,006
?
/ such that a dose decreases with application of
greater number of images so that the highest skin
with two images and the lowest for procedures
with 6 images. Such result provides an additional
/
for the gonads is small with multiple exposures.
Table 3. Distribution of an average gonad skin
!
per examination
No of
,
1-
"0
0
,.
2
4
6
Total
Figure 2. A correlation between the ESD and the
total mAs for the thyroid.
10
56
2
68
10
56
2
68
0,0149±0,0072
0,0177±0,0134
0,0139±0,0023
0,0074
0,0044
0,0023
0,0047±0,0026
The research registered the ESD in a range
from 0,10 to 0,510 mGy on the skin around the
thyroid and from 5 to 70 μGy on the skin around
the gonads. The highest registered individual ESD
was 503,91 μGy for the thyroid and 67,17 μGy
for the gonads.
Entrance skin doses (ESDs) for the gonads
are very small in comparison to the entrance skin
doses for the thyroid. The results obtained do not
exceed the maximum value of 67,17 μGy and vary
Journal of Society for development in new net environment in B&H
HealthMED - Volume 5 / Number 6 / 2011
from 0,01 mGy to 0,05 mGy and they are up to
13 times less than those of the thyroid. This result
enables us to claim with certainty that there is not
any need to wear protectors on the gonads during
mammography.
Figure 3. A histogram of skin doses absorbed by
the thyroid (a) and the gonads (b).
In more than 40% of measuring entrance skin
doses on the thyroid (Figure 3.) ranged from 0,3
to 0,4 mGy, which complies with the previously
documented results [18]. Skin doses over 0,4 mGy
were very rare and they were registered only in situations with 6 images used for a mammographic
examination or with extremely huge thickness of
a compressed breast.
Bearing in mind anatomic characteristics of the
thyroid described in literature [27], it is clear that
one can make an estimation of a dose received by
the thyroid during a mammography on this basis.
An underlined problem is non-regular size and position of the thyroid [28]. A typical length of both
parts of the thyroid is about 5 – 6 cm, width is 1,5
– 2 cm and thickness 2 – 3 cm [28,29]. Individual variations among patients do exist [28, 29, 30,
31]. Thickness of frontal surface part of the area
around the thyroid varies from 1 to 3 cm so that
an estimation of a dose received by the thyroid being 10 % of the entrance skin dose is acceptable
[18]. Applying the mentioned estimation in the
paper proved that a dose received by the thyroid
during mammography is 0,05 mGy or approximately about 1,6 % of the mean glandular dose for
a complete mammographic examination with the
same apparatus [13]. According to the same estimation, mean dose received by the thyroid during
mammography is 0,021 mGy or 0,7 % of the mean
glandular dose for a complete mammographic
examination [13]. A dose received by the thyroid
during pediatric tomography ranges from 0,10 to
0,29 mGy [32] and 0,53 mGy, but is decreased to
0,23 mGy with usage of a protective collar [32].
A similar measuring done in radiography gave results ranging from 0,34 to 0,73 mGy [21] with a similar reduction of entrance skin doses with usage
of the thyroid collar. Results of these researches
indicate that measuring dispersed radiation around
the thyroid one establishes a new quality in analyses of effects which mammography, as a diagnostic radiology discipline, has on patients. Entrance
skin doses ranging from 0,1 to 0,5 mGy are not
negligible but they are not ultimately dangerous
for patients. Dispersed radiation mostly originates
from the compression plate and the breast.
The results prove that in most cases entrance
skin dose for the thyroid ranges from 0,2 to 0,5
mGy. Bearing in mind anatomic characteristics of
the thyroid and its position and size, estimation
that the thyroid receives 10 % of the entrance skin
dose is acceptable. It is approximately represented
that the highest dose received by the thyroid during mammography is 0,05 mGy or about 1,6 % of
mean glandular dose for a complete mammographic examination. ESD for the gonads is very low
in comparison with the entrance skin dose for the
thyroid. The results obtained in this paper do not
exceed the maximum value of 70 μGy while they
usually range from 5 to 70 μGy and are up to 13
times less than those for the thyroid. During mammography, most of dispersed radiation goes back
to the thyroid and only a small part goes down
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HealthMED - Volume 5 / Number 6 / 2011
towards the gonads. Skin dose for the gonads rarely, and almost never, exceeds 0,1 mGy. However,
it can be noticed that the entrance skin dose for
the thyroid varies according to compressed breast
thickness for a complete examination.
This study was supported by the Clinical Centre of the University of Sarajevo, Radiology Clinic
and Department of Thoracic Diagnostics and Breast in Sarajevo.
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2$3
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ESD - entrance skin dose
TLD - thermoluminescent dosimeter
MLO - mediolateral projection
CC - craniocaudal projection
CBT - compressed breast thickness
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Corresponding author
Suad Kunosic,
Department of Physics,
Faculty of Natural Sciences and Mathematics,
University of Tuzla,
Bosnia and Herzegovina,
E-mail: suad.kunosic@untz.ba
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