The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation
Validation of process of medical product sterilization includes absorbed dose mapping in a phantom made of material representative of the object to be processed. Commonly, such measurements are carried out using the disposable chemical dosimeters placed in the phantom at the nodes of the 3D grid. Su...
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| Цитувати: | The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation / R.I. Pomatsalyuk, S.K. Romanovsky, V.A. Shevchenko, A.Eh. Tenishev, D.V. Titov, V.L. Uvarov, A.A. Zakharchenko, V.Ph. Zhyglo // Problems of Atomic Science and Technology. — 2022. — № 3. — С.94-99. — Бібліогр.: 11 назв. — англ. |
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irk-123456789-1954002023-12-05T11:47:56Z The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation Pomatsalyuk, R.I. Romanovsky, S.K. Shevchenko, V.A. Tenishev, A.Eh. Titov, D.V. Uvarov, V.L. Zakharchenko, A.A. Zhyglo, V.Ph. Detectors and nuclear radiation detection Validation of process of medical product sterilization includes absorbed dose mapping in a phantom made of material representative of the object to be processed. Commonly, such measurements are carried out using the disposable chemical dosimeters placed in the phantom at the nodes of the 3D grid. Such a procedure is very laborious and costly in terms of the consumption of dosimeters. In the work, we investigated the possibility of using pyrometric method for prompt mapping of the absorbed dose. The studies were carried out using a rectangular phantom in the form of a set of expanded polystyrene plates, which is exposed to a scanned electron beam. The temperature and absorbed dose distributions in the phantom were measured. A linear dependence between them has been established. The calculation of the absorbed dose profile was also performed by MC simulations. Satisfactory agreement of the calculated dose distribution with the measured one is shown. The limitations of applicability of the proposed method are determined. Валідація процесу стерилізації виробів медичного призначення включає картування просторового розподілу поглинутої дози у фантомі з матеріалу, який є репрезентативний до оброблюваного об’єкту. Зазвичай такі вимірювання проводяться з використанням одноразових хімічних дозиметрів, що розміщені у фантомі у вузлах 3D-сітки. Ця процедура є досить трудомісткою та затратною щодо витрати дозиметричних систем. Вивчена можливість застосування пірометричного методу для оперативного картування поглинутої дози. Дослідження проводилися з використанням прямокутного фантома у вигляді набору пластин з пінополістиролу, на який діє сканований пучок електронів. Проведено спільне вимірювання розподілу температури і поглинутої дози у фантомі. Встановлено лінійну залежність між ними. Розрахунок профілю поглинутої дози виконано також методом MC-моделювання. Показана задовільна відповідність розрахункового розподілу дози з виміряним. Визначено граничні умови застосування запропонованого методу. Валидация процесса стерилизации продукции медицинского назначения включает картографирование пространственного распределения поглощенной дозы в фантоме из материала, репрезентативного к обрабатываемому грузу. Обычно такие измерения проводятся с использованием одноразовых химических дозиметров, размещаемых в фантоме в узлах 3D-сетки. Эта процедура является весьма трудоемкой и затратной по расходу дозиметрических систем. Изучена возможность применения пирометрического метода для оперативного картографирования поглощенной дозы. Исследования проводились с использованием прямоугольного фантома в виде набора пластин из пенополистирола, на который воздействует сканируемый пучок электронов. Проведены совместные измерения распределения температуры и поглощенной дозы в фантоме. Установлена линейная зависимость между ними. Расчет профиля поглощенной дозы выполнен также методом MC-моделирования. Показано удовлетворительное соответствие расчетного распределения дозы с измеренным. Определены граничные условия применимости предложенного метода. 2022 Article The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation / R.I. Pomatsalyuk, S.K. Romanovsky, V.A. Shevchenko, A.Eh. Tenishev, D.V. Titov, V.L. Uvarov, A.A. Zakharchenko, V.Ph. Zhyglo // Problems of Atomic Science and Technology. — 2022. — № 3. — С.94-99. — Бібліогр.: 11 назв. — англ. 1562-6016 PACS: 07.05.Tp; 29.27.-a; 81.40.Wx http://dspace.nbuv.gov.ua/handle/123456789/195400 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| topic |
Detectors and nuclear radiation detection Detectors and nuclear radiation detection |
| spellingShingle |
Detectors and nuclear radiation detection Detectors and nuclear radiation detection Pomatsalyuk, R.I. Romanovsky, S.K. Shevchenko, V.A. Tenishev, A.Eh. Titov, D.V. Uvarov, V.L. Zakharchenko, A.A. Zhyglo, V.Ph. The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation Вопросы атомной науки и техники |
| description |
Validation of process of medical product sterilization includes absorbed dose mapping in a phantom made of material representative of the object to be processed. Commonly, such measurements are carried out using the disposable chemical dosimeters placed in the phantom at the nodes of the 3D grid. Such a procedure is very laborious and costly in terms of the consumption of dosimeters. In the work, we investigated the possibility of using pyrometric method for prompt mapping of the absorbed dose. The studies were carried out using a rectangular phantom in the form of a set of expanded polystyrene plates, which is exposed to a scanned electron beam. The temperature and absorbed dose distributions in the phantom were measured. A linear dependence between them has been established. The calculation of the absorbed dose profile was also performed by MC simulations. Satisfactory agreement of the calculated dose distribution with the measured one is shown. The limitations of applicability of the proposed method are determined. |
| format |
Article |
| author |
Pomatsalyuk, R.I. Romanovsky, S.K. Shevchenko, V.A. Tenishev, A.Eh. Titov, D.V. Uvarov, V.L. Zakharchenko, A.A. Zhyglo, V.Ph. |
| author_facet |
Pomatsalyuk, R.I. Romanovsky, S.K. Shevchenko, V.A. Tenishev, A.Eh. Titov, D.V. Uvarov, V.L. Zakharchenko, A.A. Zhyglo, V.Ph. |
| author_sort |
Pomatsalyuk, R.I. |
| title |
The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation |
| title_short |
The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation |
| title_full |
The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation |
| title_fullStr |
The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation |
| title_full_unstemmed |
The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation |
| title_sort |
possibility of application of pyrometric method in industrial dosimetry of electron beam radiation |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2022 |
| topic_facet |
Detectors and nuclear radiation detection |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/195400 |
| citation_txt |
The possibility of application of pyrometric method in industrial dosimetry of electron beam radiation / R.I. Pomatsalyuk, S.K. Romanovsky, V.A. Shevchenko, A.Eh. Tenishev, D.V. Titov, V.L. Uvarov, A.A. Zakharchenko, V.Ph. Zhyglo // Problems of Atomic Science and Technology. — 2022. — № 3. — С.94-99. — Бібліогр.: 11 назв. — англ. |
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Вопросы атомной науки и техники |
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94 ISSN 1562-6016. ВАНТ. 2022. №3(139
DETECTORS AND NUCLEAR RADIATION DETECTION
https://doi.org/10.46813/2022-139-094
THE POSSIBILITY OF APPLICATION OF PYROMETRIC METHOD
IN INDUSTRIAL DOSIMETRY OF ELECTRON BEAM RADIATION
R.I. Pomatsalyuk, S.K. Romanovsky, V.A. Shevchenko, A.Eh. Tenishev, D.V. Titov,
V.L. Uvarov, A.A. Zakharchenko, V.Ph. Zhyglo
National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine
E-mail: rompom@kipt.kharkov.ua
Validation of process of medical product sterilization includes absorbed dose mapping in a phantom made of mate-
rial representative of the object to be processed. Commonly, such measurements are carried out using the disposable
chemical dosimeters placed in the phantom at the nodes of the 3D grid. Such a procedure is very laborious and costly in
terms of the consumption of dosimeters. In the work, we investigated the possibility of using pyrometric method for
prompt mapping of the absorbed dose. The studies were carried out using a rectangular phantom in the form of a set of
expanded polystyrene plates, which is exposed to a scanned electron beam. The temperature and absorbed dose distri-
butions in the phantom were measured. A linear dependence between them has been established. The calculation of the
absorbed dose profile was also performed by MC simulations. Satisfactory agreement of the calculated dose distribu-
tion with the measured one is shown. The limitations of applicability of the proposed method are determined.
PACS: 07.05.Tp; 29.27.-a; 81.40.Wx
INTRODUCTION
Radiation sterilization of medical devices relates to
technologies with high degree of responsibility. Its vali-
dation under the conditions of a specific radiation facili-
ty is carried out in accordance with the ISO 11137-
1:2006/Amd 2:2018 standard [1]. One of the stages of
validation is the qualification of the operating equip-
ment. It includes irradiation in a specified mode of a
homogeneous object (phantom) representative to the
sterilized product, and measuring of the spatial distribu-
tion of the absorbed dose (dose mapping) in it in ac-
cordance with the standard ISO/ASTM 52303:2015 [2].
This procedure, in addition to confirming the characteris-
tics of the radiation, also allows one to check the accura-
cy of the software product used to simulate and optimize
the irradiation mode [3]. Since the main volume of steri-
lized products is made up of materials with average den-
sity of ~102 kg/m3 (dressings, clothing, coatings, etc.),
expanded polystyrene (EPS) with a close density was
chosen as the phantom material. Its advantage is also
high radiation resistance, that enables multiple reuse of
the phantom without changing its characteristics [3].
The mapping procedure involves the placement of a
large number of disposable dosimeters at the nodes of a
3-dimensional grid in the phantom. Therefore, it is very
laborious and costly in terms of consumption of dosime-
ters and execution time. This is particularly true when
the radiation source is an electron accelerator, which
parameters determining the dose distribution may vary
within wide limits.
The purpose of this paper is to study the conditions
of application of pyrometry technique using the thermal
imager for operational mapping of the absorbed dose in
the phantom.
1. CALORIMETRIC DOSIMETRY
OF ELECTRON RADIATION
In technological dosimetry of electron radiation, the
calorimetric method with the use of polystyrene (PS) as
a material for the sensitive volume of the dosimeter is
used [4]. The advantage of PS, in addition to high radia-
tion resistance, is also its low thermal conductivity.
The method is based on establishing the average
value of the absorbed dose D in the sensitive volume
from the temperature difference after irradiation T1 and
before it T0 using the expression:
( ) ( )0101 ,TTCTTD −= , (1)
where C is the heat capacity of the PS, depending on
temperature [5]. Commonly, this dependence is present-
ed in a linearized form:
( )
+
+=
2
)0(, 01
01
TT
KTCTTC , (2)
where K – is the coefficient determined during calibra-
tion of the dosimeter.
The heat capacity of PS is ~ 103 J/kg·deg. Thus, the
sensitivity of the PS calorimeter dosimeter makes
~1 deg/kGy.
In the calorimetric dosimetry, the temperature meas-
urement is usually carried out in off-line mode with a
time delay ∆t of several minutes, which corresponds to
the dosimeter transfer from the irradiation zone to a
measuring device. Therefore, the uncertainty of the ab-
sorbed dose measurement depends on the accuracy of
restore the temperature T1. The problem can be solved
by fitting the cooling process when the condition
Ct , (3)
where τС is the cooling constant.
If the condition (3) is satisfied when mapping the dose
in the phantom, then its distribution can in principle be
reconstructed from the temperature profile in different
planes inside the phantom. Such measurements are pro-
vided by modern infrared (IR) cameras (thermal imagers)
at a temperature error of ~ 0.1ºC. In terms of the absorbed
dose, this corresponds to ~ 102 Gy. The dose value usual-
ly realized in the technological processes (for example,
during sterilization) is about 10 kGy. Therefore, it can be
expected that the error in dose determination by the py-
rometric method does not exceed a few percent. This is
quite enough for adequate reproduction of the dose dis-
tribution in the phantom volume.
ISSN 1562-6016. ВАНТ. 2022. №3(139) 95
1.1. THERMAL MODEL
OF PS-CALORIMETRIC DOSIMETER
From the point of view of reconstructing the temper-
ature distribution inside the irradiated calorimeter, the
problem is reduced to solving a nonstationary heat con-
duction equation with a given initial distribution deter-
mined by the absorbed dose profile and nonlinear
boundary conditions. The task is complicated by the lack
of accurate data on the thermophysical parameters of both
PS and its foam modifications, as well as their depend-
ence on temperature and manufacturing technology [6].
For a semiquantitative analysis of the factors deter-
mining the cooling constant, consider a simplified ther-
mal model of a standard PS absorbed dose calorimeter
(Fig. 1). It consists of a working medium (capsule) 1 in
the form of a PS disk with a density of 854 kg/m3 and a
mass of 230 g. The capsule is surrounded by a rectangu-
lar heat-insulating shield 2 made of expanded polysty-
rene with dimension 292910 cm. The density of EPS
is 24 kg/m3, weight is 190 g. The shield consists of two
parts. The working medium is tightly set in one part,
and the second part (cover) can be removed, providing
access to it. Inside the working medium there is a ther-
mistor with contacts brought out to the protection sur-
face and calibrated with accuracy of 0.01ºC. This design
of the calorimeter allows it to be used to compare the
temperature of the working media measured with the
thermistor and an IR camera.
Fig. 1. Structure of the PS-calorimetric dosimeter [4]
Consider a simplified thermal model of a PS calo-
rimeter. Taking into account that the surface density of
its thermal insulation at the surface of the capsule is no
more than 10% of the surface density of the capsule
itself, in the first approximation we will assume that
heat transfer in the calorimeter is determined by the
temperature of the capsule T1 and takes place mainly
between the planes of the capsule and the thermal
shield. We will also consider the case of moderate val-
ues of the absorbed dose (~10 kGy), when the increase
in the calorimeter temperature does not exceed ~10°C
and the change in the thermophysical parameters of the
material can be neglected. Due to of the symmetric de-
sign of the calorimeter with a closed lid, the heat flux to
both sides of the capsule is assumed to be the same. In
this case, the heat conduction equation can be represent-
ed as:
( )
d
TT
=
dt
dT
mc S−
− 121
11
2
, (4)
where c1 is the heat capacity of the PS-capsule, m1 is its
mass, 2 is the thermal conductivity coefficient of the
EPS thermal shield, ТS is the temperature of its surface,
d is the thickness of the shield (d = 4.1 cm).
For the quasi-stationary case, the condition of equal-
ity of heat fluxes from the capsule and from the protec-
tion surface can be written in the form:
( )0
1
11 2 TTS=
dt
dT
mc S −− , (5)
where is the heat transfer coefficient on the shield
surface, S is the area of the lateral surface of the cap-
sule, Т0 is the ambient temperature. By joint solution of
the equations (4) and (5), we obtain:
( ) 011
211
11
2
exp)0()( Tt
dmc
S
T=tT +
+ −−
, (6)
where T1(0) is the steady-state temperature of the cap-
sule immediately after irradiation. Thus, the cooling
constant of the capsule with the closed lid is:
)α+λ(dρc=τ 11
2
Sclosed
c
−−110.5 , (7)
where 1
S is the surface density of the capsule.
In turn, for the calorimeter with the removed cover,
the main heat flux in the capsule is directed towards its
open surface, and the cooling constant takes the form:
)α+λ(bρc=τ 11Sopen
c
−− 111 , (8)
where b is the thickness of the capsule, 1 is the coeffi-
cient of thermal conductivity of PS.
Table 1 lists some available data on the thermophys-
ical parameters of polystyrene and its modifications.
Table 1
Thermophysical parameters of polystyrene [6]
Parameter PS EPS
C, kJ/kgºC (1.11…1.33) 1.65103
, W/mºC 0.165 (2.8…4.4) 10-2
, kg/m3 (854…1060) 10…200
The heat transfer coefficient is determined by two
processes − convection and radiation. At a temperature
of ~30ºC, the convection makes the main contribution.
The value is ~10 W/m2·ºC and increases with the in-
crease of the air velocity at the calorimeter surface and
the calorimeter temperature. As follows from the formu-
las (7) and (8), the value of does not significantly
change the estimate of the cooling constant, which is
~1.4×104 s for the PS calorimeter with the closed ther-
mal shield and ~3.7×103 s with the one opened.
2. STUDY OF THE PYROMETRIC
DOSIMETER PROTOTYPE
To test the proposed method, a prototype of the py-
rometric dosimeter based on the RISO polystyrene calo-
rimeter [7] and a thermal imager was developed and
fabricated.
2.1. MEASUREMENTS WITH THE RISO
CALORIMETER
The thermal imager includes a module with an IR
sensor type MLX90640, a Raspberry Pi mini-computer,
a power supply, a web camera with LED backlight, a
temperature and humidity sensor (Fig. 2). The resolu-
96 ISSN 1562-6016. ВАНТ. 2022. №3(139
tion of the IR sensor is 3224 pixels, the viewing angle
is 55º×45º. The mini-computer runs an I/O controller of
an EPICS system [8], and the data from the IR sensor
are transmitted to the operator's computer via a local
network. The maximal frame rate from the thermal im-
ager is about 8 frames/s. It is also possible to average
over frames and write data to a file at a rate of
~1 frame/s. Software is developed using Python scripts
and runs in the EPICS system. A Control System Studio
package is used as GUI to display information from the
thermal imager.
Raspberry PI
IR sensor
MLX90640
Power
supply
5V, 2,5А
Network
I2C
WEB camera
with LED
Humidity and
temperature
sensor AМ2320
USB
1-wire
Fig. 2. Block diagram of the thermal imager
of the pyrometric dosimeter
2.2. MEASUREMENT PROCEDURE
The studies were carried out on an industrial elec-
tron accelerator LU-10 NSC KIPT [9], equipped with a
conveyor for the transfer of the processed products to
the irradiation zone. The thermal imager was located in
the labyrinth of radiation shield of the accelerator be-
hind the turn of the conveyor line at a distance of 55 cm
from the front plane of the transport container with the
object being processed. Such an object was the RISO
calorimeter. The frame size in the front plane of the
object was 5642 cm. The thermistor of the RISO calo-
rimeter was connected via a 4-wire circuit to a multime-
ter located in the control room. The measurement pro-
cedure was as follows:
• The initial temperature of the disk surface of the
calorimeter was measured with the lid open before irra-
diation (~ 10 min).
• The calorimeter with the lid closed was passed
through the irradiation zone at a certain conveyor speed
and the irradiation time was recorded.
• Then transport container with the calorimeter was
moved to the thermal imager to measure the temperature
of the latter with the lid closed (~10 min).
• After that, the cover was removed. The tempera-
ture on the surface and inside of the calorimeter was
measured (~ 30…60 min).
Irradiation of the RISO calorimeter was carried out
at a conveyor speed of 3.72, 2.48, 1.24 cm/s. The time
between irradiation was ~1 h. During the measurements,
the temperature and humidity of the ambient air near the
thermal imager were recorded. The absorbed dose was
determined by the method [10].
2.3. RESULTS OF THE MEASUREMENTS
Fig. 3,a shows the temperature inside the calorimeter
(black square) measured with the thermistor, and the
maximum temperature on the surface of the calorimeter
disk (red circles) measured with the thermal imager.
The moment of irradiation and the moment of opening
the calorimeter cover are seen as the temperature jump.
Fig. 3,b demonstrates the averaged temperature of
the calorimeter disk surface during cooling and their
approximation by function (9). At the initial moment
after removing the cover (5…6 min), a transient process
of establishing the temperature of the calorimeter is ob-
served.
The temperature inside and on the surface of the
cooling calorimeter disk was approximated by an expo-
nential function (see Fig. 3,b):
0
1
1 exp y
t
x
Ay +
−
= , (9)
where A1 is the temperature difference, y0 is the ambient
temperature, t1 is the time constant (s).
15:10 15:20 15:30 15:40 15:50 16:00 16:10 16:20 16:30 16:40 16:50 17:00
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
T
e
m
p
e
ra
tu
re
,
C
Time, h:min
T RISO
Tmax IR camera
V=200
1000 2000 3000 4000 5000
18
20
22
24
26
28
30
32
34
36
38
T
e
m
p
e
ra
tu
re
,
C
Time, s
T RISO
t36 IR camera
ExpDec1 fit of V200RISO_C
ExpDec1 fit of V200IR_E
a b
Fig. 3. T RISO − temperature inside the calorimeter
(square); Tmax IR camera − the maximum surface tem-
perature of the calorimeter (circles) during irradiation at
a conveyor speed of 1.24 cm/s (a). Temperature of the
RISO calorimeter measured with open lid and fitted by an
exponential function (b). t36 − average temperature of
the calorimeter surface in the center of the disk (circles)
As a result, the dependence of the absorbed dose on
the difference in the surface temperature of the RISO
calorimeter, measured by the IR camera, was obtained.
Table 2 shows the parameters of temperature approxi-
mation during cooling of the calorimeter.
Table 2
Parameters of approximation of RISO temperature
(RISO) and calorimeter surface temperature (IR)
V conv. y0 A1 t1
1.24 IR 16.07 ±0.20 15.15 ± 0.16 2695 ± 72
1.24 RISO 14.15 ± 0.06 23.88 ± 0.04 2567 ± 13
2.48 IR 17.51 ± 0.37 7.22 ± 0.28 1877 ± 192
2.48 RISO 15.30 ± 0.08 13.56 ± 0.07 2895 ± 26
3.72 IR 16.46 ± 2.48 5.17 ± 2.26 2093 ±1518
3.72 RISO 12.80 ± 0.12 9.51 ± 0.12 3484 ± 55
3. THE MEASUREMENTS
WITH THE PHANTOM
3.1. MEASUREMENT PROCEDURE
To test the possibility of using the thermal imager
for mapping the dose in an object, the phantom was
ISSN 1562-6016. ВАНТ. 2022. №3(139) 97
irradiated with an electron beam, and the temperature
distribution inside the phantom was measured. The
phantom consists of 5 stacked plates of expanded poly-
styrene each by 6.5 cm in thickness t with density of
125 kg/m3. On the front plane of the phantom, in the
center of each plate, there was a 20 cm long a dosimetry
film B3 (Fig. 4 on the left) and one more film on the
back surface of the last plate. A measuring stand was
preliminarily assembled to ensure the fixation of the
phantom plates in the field of view of the thermal im-
ager (see Fig. 4 on the right).
The motionless phantom was irradiated with a elec-
tron beam scanned in the vertical plane with an energy
of 9.3 MeV and an average current 0.73 mA. The scan-
ning amplitude at the exit window was ±8.4 cm, which
corresponds to the width of the scanning area on the
front surface of the phantom of 47 cm. After irradiation
for 15 s, the phantom was removed and moved to the
stand (see Fig. 4 on the right)
The surface temperature of each plate was measured
for 10 seconds. The interval between measurements was
~1 min. The IR sensor pixel corresponded to a
2.62.9 cm cell on the plate surface.
Phantom F2N Stand for measurements
IR camera
Support
9
1
3
0
W=33
L=76
H=38.5
е-
В3
Fig. 4. Phantom (left) and measuring stand (right)
As an example, Fig. 5 shows the temperature distri-
bution on the surface of the 2nd plate.
18
20
22
24
26
28
30
2
4
6
8
10
12
14
16
18
20
22
24
1
8
2
0
2
2
2
4
2
6
2
8
3
0
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
2
4
6
8
10
12
14
16
18
20
22
24
Fig. 5. Surface temperature profiles of the 2nd phantom
plate (L2)
3.2. RESULTS OF THE MEASUREMENTS
Data processing from the thermal imager consisted
in determining the boundaries of the phantom, building
temperature profiles (horizontal and vertical) for each
phantom plate.
The obtained horizontal temperature profiles were
approximated by a Gaussian in the form:
−
−+=
2
0
2
1
exp
w
xcx
Ayy , (10)
where A is the peak amplitude, y0 is the displacement
along the vertical axis (Y), w is the standard deviation,
xc is the position of the peak on the X-axis.
Fig. 6 shows the horizontal temperature profiles and
their Gaussian approximation. After approximation, the
width of the beam profile along the X-axis, the position
and height of the distribution peak were obtained (Ta-
ble 3). The value of full width at half maximum
(FWHM) was calculated using expression:
wwFWHM == 2.3548)4ln(2 . (11)
0 10 20 30 40 50 60 70 80 90
22
24
26
28
30
32
34
36
38
40
T
e
m
p
e
ra
tu
re
,
C
Phantom Length (X), cm
L1
L2
L3
L4
L5
L6
Gaussian Fit
Fig. 6. Horizontal profiles of the surface temperature
of phantom plates (L1-L6),
solid lines − Gaussian approximation (10)
Table 3
Parameters of approximation by function (10) of the
horizontal temperature profile of the phantom plates
№
plate
Offset
y0
err
<0.19
Center
xc
err
<0.21
SD
w
err
<0.53
Peak
Height,
А
err<0.35
FWHM
err <1.2
1 25.18 37.54 7.25 12.94 17.07
2 24.85 38.61 7.30 14.56 17.19
3 24.74 38.00 8.41 13.03 19.81
4 24.34 38.01 9.91 11.74 23.34
5 24.09 37.99 12.20 9.26 28.73
6 24.27 38.00 13.70 6.19 32.26
The absorbed dose was measured with the B3 do-
simetry films using a photo scanner (Table 4, Fig. 7).
Table 4
Parameters of approximation of the horizontal dose
profile (B3 film) by function (10). The parameter y0
(offset) was assumed being zero during the approximation
№
plate
Center,
cm
err<0.02
SD,
cm
err<0.03
Peak
Height, kGy
err<0.03
FWHM,
cm
err<0.7
1 38.02 4.95 30.39 11.65
2 37.83 5.39 29.27 12.68
3 37.74 6.09 25.53 14.35
4 38.17 7.36 22.18 17.34
5 38.00 8.86 16.70 20.87
6 38.08 8.39 10.85 19.75
98 ISSN 1562-6016. ВАНТ. 2022. №3(139
10 15 20 25 30 35 40 45 50 55 60 65 70
0
5
10
15
20
25
30
D
o
s
e
,
k
G
y
Length, cm
L1
L2
L3
L4
L5
L6
Gaussian Fit
B3
Fig. 7. Dose profiles measured with B3 film
and their Gaussian approximations (10)
3.3. COMPUTER SIMULATION
To study of the correctness of restoring the 3D dose
distribution in the phantom via the temperature profile
after irradiation with a scanned electron beam, the com-
puter simulation of the interaction process of the
scanned electron beam and the phantom was carried out
using a Geant4 transport code [11]. In the simulations,
the radiation parameters corresponded to the actual
beam parameters during phantom irradiation.
Fig. 8 shows the distributions of the absorbed dose
on the surface of the phantom plates obtained by simu-
lations.
-15 -10 -5 0 5 10 15 20
0
5
10
15
20
25
30
t = 15 s, Ж = 1.0 cm, Emax = 9.3 MeV
spectrum LU10E8P58ZERO
scan cos 8.4
Ti foil = 75 mm
D0, L1, FWHM = 11.6 ± 0.3 cm
D6, L2, FWHM = 12.8 ± 0.4 cm
D12, L3, FWHM = 14.8 ± 0.4 cm
D18, L4, FWHM = 18.0 ± 0.5 cm
D24, L5, FWHM = 22.0 ± 0.4 cm
D29, L6, FWHM = 24.4 ± 0.2 cm
D
o
se
,
k
G
y
X-axis, cm
Fig. 8. The distribution of the absorbed dose along
the X-axis of phantom (simulations),
solid lines − Gaussian approximation
As it can be seen from Table 5, the calculated pa-
rameters of the horizontal profile of the absorbed dose
and those measured by the B3 film are in good agree-
ment.
Table 5
Parameters of approximation by function (10)
of the experimental and calculated dose profiles
№
plate
Calculated
Peak Height,
kGy
err<0.8
Calculated
FWHM,
cm
err<0.5
B3 Peak
Height,
kGy
err<0.03
B3
FWHM,
cm
err <0.7
1 30.2 11.6 30.39 11.65
2 27.5 12.8 29.27 12.68
3 24.1 14.8 25.53 14.35
4 20.3 18.0 22.18 17.34
5 16.6 22.0 16.70 20.87
6 12.4 24.4 10.85 19.75
Fig. 9 shows the dependence of the dose (film B3)
on the temperature increment ∆Т after irradiation. The
measurement result of the first plate was not used in the
approximation process as its cooling through the outer
surface.
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
8
10
12
14
16
18
20
22
24
26
28
30
32
L6
L5
L4
L3
L2
Linear Regression for Data3_B:
Y = A + B * X
Parameter Value Error
-------------------------------------------
A -3,00073 0,03124
B 2,1728 0,00286
-------------------------------------------
R SD N P
0,99798 27,966 5 1,0898E-4
D
o
s
e
,
k
G
y
Temperature rise T, C
Dose B3
Linear Fit of Data3_B
Fig. 9. Dependence of the dose (film B3)
on the temperature increment at the surface
of the phantom plates (L2-L6) after irradiation
(data from Tables 3 and 4)
and approximation by a linear function
CONCLUSIONS
1. The panoramic pyrometry method can be used to
map the absorbed dose in the phantom made of a mate-
rial with low thermal conductivity, such as expanded
polystyrene, provided that the interval between irradia-
tion of the phantom and temperature measurement is
significantly less than the cooling constant of the phan-
tom. The temperature difference inside the phantom
before and after irradiation depends linearly on the ab-
sorbed dose with a proportionality coefficient of
~0.5 deg/kGy.
2. The values of the cooling constant (~4 h) obtained
in the work on the basis of a simple analytical model are
very approximate, taking into account the accepted limi-
tations, as well as the lack of accurate data on the ther-
mophysical characteristics of the material. At the same
time, they qualitatively agree with the results of the ex-
periments.
3. Under the conditions of the LU-10 accelerator of
NSC KIPT, when a phantom moves from the irradiation
zone to the IR camera for ~15 min, the decrease in its
temperature does not exceed 6…7%. This allows the
prompt absorbed-dose mapping in the phantom by the
pyrometric technique providing its calibration with the
standard film dosimeters.
REFERENCES
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2. ISO/ASTM 52303:2015 Guide for absorbed-dose
mapping in radiation processing facilities. [Electron-
ic resource] Verified 29.04.2021. URL:
https://www.iso.org/ru/standard/67807.html
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tions”. 2008, № 5, p. 150-154.
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metric dosimetry systems for dose measurements
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Article received 16.02.2022
ПРО МОЖЛИВІСТЬ ЗАСТОСУВАННЯ ПІРОМЕТРИЧНОГО МЕТОДУ В ПРОМИСЛОВІЙ
ДОЗИМЕТРІЇ ЕЛЕКТРОННОГО ВИПРОМІНЮВАННЯ
Р.І. Помацалюк, С.К. Романовський, В.О. Шевченко, А.Е. Тенішев, Д.В. Тітов, В.Л. Уваров,
О.О. Захарченко, В.Ф. Жігло
Валідація процесу стерилізації виробів медичного призначення включає картування просторового розпо-
ділу поглинутої дози у фантомі з матеріалу, який є репрезентативний до оброблюваного об'єкту. Зазвичай
такі вимірювання проводяться з використанням одноразових хімічних дозиметрів, що розміщені у фантомі у
вузлах 3D-сітки. Ця процедура є досить трудомісткою та затратною щодо витрати дозиметричних систем.
Вивчена можливість застосування пірометричного методу для оперативного картування поглинутої дози.
Дослідження проводилися з використанням прямокутного фантома у вигляді набору пластин з пінополісти-
ролу, на який діє сканований пучок електронів. Проведено спільне вимірювання розподілу температури і
поглинутої дози у фантомі. Встановлено лінійну залежність між ними. Розрахунок профілю поглинутої дози
виконано також методом MC-моделювання. Показана задовільна відповідність розрахункового розподілу
дози з виміряним. Визначено граничні умови застосування запропонованого методу.
О ВОЗМОЖНОСТИ ПРИМЕНЕНИЯ ПИРОМЕТРИЧЕСКОГО МЕТОДА В ПРОМЫШЛЕННОЙ
ДОЗИМЕТРИИ ЭЛЕКТРОННОГО ИЗЛУЧЕНИЯ
Р.И. Помацалюк, С.К. Романовский, В.А. Шевченко, А.Э. Тенишев, Д.В. Титов, В.Л. Уваров,
А.А. Захарченко, В.Ф. Жигло
Валидация процесса стерилизации продукции медицинского назначения включает картографирование
пространственного распределения поглощенной дозы в фантоме из материала, репрезентативного к обраба-
тываемому грузу. Обычно такие измерения проводятся с использованием одноразовых химических дозимет-
ров, размещаемых в фантоме в узлах 3D-сетки. Эта процедура является весьма трудоемкой и затратной по
расходу дозиметрических систем. Изучена возможность применения пирометрического метода для опера-
тивного картографирования поглощенной дозы. Исследования проводились с использованием прямоуголь-
ного фантома в виде набора пластин из пенополистирола, на который воздействует сканируемый пучок элек-
тронов. Проведены совместные измерения распределения температуры и поглощенной дозы в фантоме.
Установлена линейная зависимость между ними. Расчет профиля поглощенной дозы выполнен также мето-
дом MC-моделирования. Показано удовлетворительное соответствие расчетного распределения дозы с изме-
ренным. Определены граничные условия применимости предложенного метода.
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