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The Design by the Monte Carlo Method of the Filter <strong>for</strong> Fluorescence Glass Dosimeters
K. Ejiri 1♣ , K. Minami 1 , M. Shimo 1 , K.Terada 2 , S. Maeda 2 , Y. Takeuchi 2 ,
H. Toyama 3 and K. Katada 3
1 Faculty of Radiological Technology, Fujita health university school of health sciences,
E-mail: kejiri@fujita-hu.ac.jp
2 Fujita health university hospital,
3 Department of Radiology,Fujita health university school of medicine,
Toyoake, Japan
Abstract. Sensitivity compensation filters <strong>for</strong> fluorescence glass dosimeters corresponding to measurement of
an effective dose or a dose equivalent were designed using the Monte Carlo simulation code of Electron Gamma
Shower version 4 (EGS4). Dose Ace GD-300 series made in Asahi Techno Glass Company was used as
materials <strong>for</strong> creating the simulation model of the fluorescence glass dosimeter. Tin (Sn, Z= 50) was adopted as
the filter material. EGS4 <strong>for</strong> mathematically simulation was used <strong>for</strong> getting energy absorption characteristics of
the glass element. First, a basic model equipped with the filter with uni<strong>for</strong>m thickness was created, next, to this
model the simulation which irradiates 100 million photons of single energy uni<strong>for</strong>mly was carried out, and nine
characteristics in the photon energy range of 0.01-10 MeV were obtained by the nine different filter thicknesses
(0-7.5mm), respectively. Synthetic characteristics were made from these nine characteristics using the weighted
average method, and the load coefficients were experientially set that these synthetic characteristics resemble the
characteristics required <strong>for</strong> measurements of the effective dose or the dose equivalent. In the process of design of
a practical use filter model, these coefficients were used in order to determine the area of each thickness part of
the filter which covers an effective domain of the glass element. Although the characteristic of the practical use
filter model checked by the Monte Carlo method had a difference to the characteristic required <strong>for</strong> the
measurement of an effective dose or a dose equivalent, in the photon energy range of 0.03-1.0 MeV, the error
was less than ±5%. This method that applied Monte Carlo simulation to development of a filter <strong>for</strong> fluorescence
glass dosimeters is suitable <strong>for</strong> getting to know the detailed energy absorption characteristics of the glass
element, and is effective in the design of the filters.
1.Introduction
There is sensitivity dependability over photon energy in a fluorescence glass dosimeter [1,2,3].
There<strong>for</strong>e, when the photon which has a broad energy spectrum is carrying out incidence in
measurement area, the compensation filter <strong>for</strong> controlling sensitivity must be used. However, the filter
supports only air absorbed dose, it is not suitable to measure an effective dose or a dose equivalent.
Then, we investigated the energy absorbed in a fluorescence glass dosimeter at the various photon
energies by the photon transportation Monte Carlo calculation code, and searched the energy
absorption characteristics of the dosimeter equipped with uni<strong>for</strong>m thickness filters. We designed new
filters based on these characteristics, and examined whether these characteristics would be suitable to
measurement of an effective dose or a dose equivalent.
2. Materials and Methods
2.1. A dosimeter model and the Monte Carlo calculation code
As materials <strong>for</strong> creating the simulation model of the fluorescence glass dosimeter, GD-300 series of
Dose Ace made in Asahi Techno Glass was adopted. Tin (Sn: Z=50) was used as the quality of the
material of the sensitivity compensation filter. Electron Gamma Shower version 4 with LSCAT
(following "EGS4") [4,5] which is the Monte Carlo calculation code added the low-energy photonscattering
expansion function improved by Y. Namito et al. was used <strong>for</strong> the development of the filter.
2.2. Design procedure of the compensation filter
♣ Present address: Fujita Health University Schoool, Faculty of Health Sciences,1-98, Dengakugakubo,
kutsukake-cho, Toyoake, 470-<strong>11</strong>92 (Japan)
1

First, in order to acquire the characteristic of the glass dosimeter which equipping with a filter of
uni<strong>for</strong>m thickness, a basic model which covered the reading portion of the glass element with a
uni<strong>for</strong>m thickness filter of Sn in the range of 0-0.75 mm was created, and this model was included in
the EGS4 code <strong>for</strong> per<strong>for</strong>ming a photon irradiation simulation. Next, the simulation which irradiates
monochromatic photons in the range of 0.01-10 MeV to the model was carried out, and the amount of
energy absorption in the dose reading portion of the glass element was calculated. The characteristic of
this model was obtained by breaking that absorption energy by the air Kama. This operation was
carried out to the other model to which the thickness of Sn filter was changed, and some different
characteristic curves were collected. These characteristic curves were used <strong>for</strong> the development of a
practical filter model which gives a new characteristic required <strong>for</strong> the measurement of an effective
dose or a dose equivalent. The new characteristic was calculated by the method of weight averaging
those characteristics with the suitable coefficients defined experientially. The coefficients were used
<strong>for</strong> the design of the practical filter, and determined the area of each part of a filter which covers the
dose reading part of the glass element. The glass dosimeter equipped with the new designed filter was
built into the EGS4 code, and it was examined whether the characteristic of the glass element shows
the target characteristic.
2.3. Acquisition of the basic characteristic data based on a simulation
The glass dosimeter model which equipped with the filter of uni<strong>for</strong>m thickness as shown in the
following Figure 1 was created into the EGS4 code. Then, 100 million photons were equally irradiated
from the 2 m away point of the model sides to the area of 3x3 cm 2 centering on the model, the energy
absorption characteristic of the glass element was acquired <strong>for</strong> 42 kinds of photon energy in the range
of 0.01~10MeV. Moreover, nine kinds of thickness of a tin (Sn) filter was gradually changed with 0,
0.1, 0.2,..., 0.7, and 0.75 mm, and the characteristic fi(x) (i=1to9) about each case was calculated,
respectively. Where, x is photon energy of a MeV unit.
Sn
Sn
dose reading domain
Sn
hν hν
Sn
ABS
ID No.
glass element
Fig.1.A composition figure of a basic model (the right is a short axis section and the left is a long axis
section.), and photon irradiation.
2.4. Composition of the characteristic corresponding to an effective dose or the dose equivalent
The nine characteristics fi(x) (i=1 to 9) were multiplied by the coefficients ki and a new characteristic
F(x) was compounded from those sums, as shown in following equation.
F(x)=k1f1(x)+k2f2(x)+ +k9f9(x) ---------- (1)
where, k1, k2, , k9 were load coefficients which determined experientially and required <strong>for</strong>
obtaining the new characteristic suited to an effective dose or a dose equivalent. The sum total of ki
2
Sn

was standardized so that it was set to 1.0. Then, the ki were used <strong>for</strong> the design of a filter with a new
characteristic of the glass dosimeter.
2.5. Creation of a practical use filter model
A practical use model consist of the combination of the various thickness filters were created, as
shown in Figure 2. In this model, ki values were reflected in each size of the filter with various
thicknesses. The characteristic of the practical use model was investigated by the EGS4 simulation,
and evaluated whether the characteristic resembled F(x).
3.Results
Sn
Sn
S
kiS
S
dose reading domain
3.1. The simulation by the basic model
Sn
Sn
ID No.
Full length of an effective filter domain : 2S
Length of each filter ingredient : kiS
Full length of an effective filter domain : 2S
Length of each filter ingredient : kiS
Fig. 2. The composition figure of a practical use model.
The characteristics fi(x) (i=1to9) of the glass dosimeter when changing filter thickness gradually based
on the basic glass dosimeter model in Figure 1 are shown in Figure 3. In this figure, the relative
response is expressed so that the value of the characteristic f1(x) in 0.662MeV (gamma ray energy of
137 Cs) may become equal to 1.0.
relative response
4
3.5
3
2.5
2
1.5
1
0.5
0.0mm, f1(x)
0.1mm, f2(x)
0.2mm, f3(x)
0.3mm, f4(x)
0.4mm, f5(x)
0.5mm, f6(x)
0.6mm, f7(x)
0.7mm, f8(x)
0.75mm, f9(x)
0
0.01 0.1
photon energy [MeV]
1 10
Fig.3. Characteristic curves fi (x) (i=1to9) of a glass element when changing the thickness of a
uni<strong>for</strong>m Sn filter to 0.0 to 7.5 mm.
3

3.2. Composition of characteristic F(x) corresponding to an effective dose or a dose equivalent
A compound characteristic F(x) was obtained by defining the coefficients of the <strong>for</strong>mula (1). Six kinds
of characteristics by this method are shown in Figure 4. Although the characteristics were not able to
obtain sufficient approximation to the conversion coefficients of ICRP in energy higher than 1.0MeV
and lower than 0.03MeV, the approximation were less than 5% of error in the middle energy
range of 0.03-1.0MeV.
response [Sv/Gy]
response [Sv/Gy]
response [Sv/Gy]
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
ICRP E/Ka
E type F(x)
0.01 0.1 1 10
photon energy [MeV]
ICRP Hp(10,0°)/Ka
Hp(10,0°) type F(x)
0.01 0.1 1 10
photon energy [MeV]
ICRP Hp(0.07,0°)/Ka
Hp(0.07,0°) F(x)
0.01 0.1 1 10
photon energy [MeV]
response [Sv/Gy]
response [Sv/Gy]
response [Sv/Gy]
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
ICRP H*(10)/Ka
H*(10) type F(x)
0.01 0.1 1 10
photon energy [MeV]
ICRP H'(10,0°)/Ka
H'(10,0°) type F(x)
0.01 0.1 1 10
photon energy [MeV]
ICRP H'(0.07,0°)/Ka
H'(0.07,0°) F(x)
0.01 0.1 1 10
photon energy [MeV]
Fig.4. Comparison of the characteristics F(x)/Ka acquired by optimizing ki and the dose conversion
coefficients of the ICRP Publication 74.
3.3. Load coefficients ki of F(x) corresponding to an effective dose or a dose equivalent
measurement
Lord coefficients ki of the characteristic F(x) corresponding to the measurement of an effective dose or
a dose equivalent were shown in Table 1. In the work which obtains optimal F(x), all of the fi(x)
did not need to be used, and fi(x) more than a half were not used <strong>for</strong> the design of the filter.
4

Table 1. Coefficients ki of the characteristic F(x) respectively developed <strong>for</strong> measurement of the
effective dose or the five kinds of dose equivalent.
Load coefficient k 1 k 2 k 3 k 4 k 5 k 6 k 7 k 8 k 9
Thickness of Sn
filter [mm]
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.75
E type 0.06 0.33 0.61 1.00
H *(10) type 0.24 0.24 0.52 1.00
H p(10,0°) type 0.25 0.22 0.40 0.13 1.00
H '(10,0°) type 0.26 0.12 0.18 0.44 1.00
H p(0.07,0°) type 0.30 0.04 0.24 0.42 1.00
H '(0.07,0°) type 0.30 0.05 0.14 0.51 1.00
E : effective dose, H : dose equivalent
3.4. The characteristic Fp(x) of the practical use model obtained in the simulation by EGS4
By the method as shown in Fig. 2, a practical use model according to ki shown in Table 1 was built,
the practical model was included in EGS4, and photon irradiation simulation was carried out. In
Figure 5, each of the six characteristic curves Fp(x) acquired in the simulations was approximated very
well to the conversion coefficients of ICRP in the energy rage of 0.03-1.0MeV, respectively, and the
error was less than 5%r.
response [Sv/Gy]
response [Sv/Gy]
response [Sv/Gy]
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.01 0.1 1 10
photon energy [MeV]
ICRP E/Ka
E type Fp(x)
0.01 0.1 1 10
photon energy [MeV]
ICRP Hp(10,0°)/Ka
Hp(10,0°) type Fp(x)
ICRP Hp(0.07,0°)/Ka
Hp(0.07,0°) type Fp(x)
0.01 0.1 1 10
photon energy [MeV]
response [Sv/Gy]
response [Sv/Gy]
response [Sv/Gy]
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.01 0.1 1 10
photon energy [MeV]
ICRP H'(0.07,0°)/Ka
H'(0.07,0°) type Fp(x)
0.01 0.1 1 10
photon energy [MeV]
ICRP H*(10)/Ka
H*(10) type Fp(x)
0.01 0.1 1 10
photon energy [MeV]
ICRP H'(10,0°)/Ka
H'(10,0°) type Fp(x)
Fig.5. Comparisons with the characteristics Fp(x) of the practical use filter models, and the dose
conversion coefficients in the Publication 74 of ICRP.
Total
5

3.5 Comparison with the characteristic F(x) of a basic model, and the characteristic Fp(x) of a
practical use model
In order to investigate the difference of the characteristic Fp(x) and the characteristic F(x), the ratio
Fp(x)/F(x) was calculated. The details were shown in Fig. 6, in many calculating points, the ratios were
less than 1.0±0.02, and the maximum ratio was 1.0+0.054.
sensitivity ratio
sensitivity ratio
sensitivity ratio
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
E type model
Fp(x)/F(x)
0.01 0.1 1 10
photon energy [MeV]
Hp(10,0°) type model
Fp(x)/F(x)
0.01 0.1 1 10
photon energy [MeV]
Hp(007,0°) type model
Fp(x)/F(x)
0.01 0.1 1 10
photon energy [MeV]
sensitivity ratio
sensitivity ratio
sensitivity ratio
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
H*(10) type model
Fp(x)/F(x)
0.01 0.1 1 10
photon energy [MeV]
H'(10,0°) type model
Fp(x)/F(x)
0.01 0.1 1 10
photon energy [MeV]
H'(0.07,0°) type model
Fp(x)/F(x)
0.01 0.1 1 10
photon energy [MeV]
Fig.6. Comparison of the synthetic characteristic F(x) created from the combination of the
characteristics from the basic model, and the characteristic Fp(x) of the practical use model based on
the ki values.
4. Discussion
The latest photon transportation Monte Carlo calculation code is very highly precise, and can per<strong>for</strong>m
a simulation reliable if a user code is constructed strictly. Moreover, since it is a simulation, irradiation
conditions with difficult realization can be set up easily, and detailed in<strong>for</strong>mation can be acquired
compared with an irradiation experiment. We applied the advantage of such a calculation code to the
sensitivity compensation filter design <strong>for</strong> fluorescence glass dosimeters, and tried the design of the
6

filter which can measure an effective dose or a dose equivalent. It was started from acquisition of basic
data and the procedure of composition of the characteristic needed <strong>for</strong> the dose measurement from the
data subsequently acquired, planning of the practical use model which can maintain the compounded
characteristic, and evaluation of the model per<strong>for</strong>med the design. It was thought that this procedure
was useful in order to be able to design a new filter certainly and to raise the efficiency of a filter
design. The method of using the calculation code <strong>for</strong> the design does not need large-scale equipment,
but can also save the time and ef<strong>for</strong>t of an experiment. So, the effect which reduces the expense of
development sharply is expected. In the simulation of the basic model, the details of the energy
characteristic could be known and the filter was designed based on this basic data. In the practical use
model, the characteristic as expected was obtained and it was suggested that this method can serve as a
leading means <strong>for</strong> the design of a filter. For this designed filter model, the characteristic was examined
in the photon energy range of 0.01-10.0MeV. However, the energy range which can use the designed
filter was narrowed by the photon absorption characteristic which a tin filter has at 0.03-1.0MeV, and
the utility value became low.In the domain in which photon energy exceeds 1.0MeV(s), it was
considered as a cause in which shortage of filter thickness weakens sensitivity, and in the domain
below 0.029 MeV with photon energy lower than K absorption edge of tin, since the K absorption did
not take place, the rise of partial sensitivity was observed. It was the result of reflecting the K
absorption edge in this characteristic that the characteristic of a glass element became discontinuous at
the photon energy of 0.029MeV. These problems may be able to be conquered by examining the
quality of the material of a filter, and are due to be examined further from now on. Since the trial
production of the practical use filter is not per<strong>for</strong>med now, the characteristic shown by actual
measurement with the designed filter is not clear. However, the error of an old experience to an actual
measurement and a simulation is very small, and it is sure that this method can use <strong>for</strong> a design in a
comparatively simple model like the design of a filter. Even if slight gap arose between the
measurement and the simulation, from the energy range which the gap produced, if which of the
coefficients of the <strong>for</strong>mula (1) is adjusted, it can presume easily whether the characteristic improves.
The technique which we adopted by this research does not need large-scale equipment in the
development stage of a filter, but if there are a personal computer and a reliable Monte Carlo
simulation code, it can carry it out. It will greatly be used <strong>for</strong> development of various measuring
instruments which need the new characteristic in the radiation field by this technique in the near future.
5.Conclusion
Development of the sensitivity compensation filter <strong>for</strong> glass dosimeters was tried using the reliable
Monte Carlo calculation code. Collecting required in<strong>for</strong>mation through the gradual process from
acquisition of basic data, the technique of us which compounds the target characteristic based on the
in<strong>for</strong>mation carried out the purpose achievement, without inducing a big error in the specific photon
energy range. Development of the filter corresponding to various doses is due to be tried from now on
in a different photon energy range using the same technique.
6.References
1. Perry, J.A., Radiophotoluminescence in health physics, Series in Medical Physics and Biomedical
engineering, (1987).
2. Juto, N., The Large Scale Personal Monitoring Service Using The Latest Personal Monitor
GLASS BADGE, Proceedings of AOCRP-1, Korea (2002)
3. Piesch, E., Burgkhardt, B., and Vilgis, M., Progress in Phosphate Glass Dosimetry: Experiences
and Routine Monitoring with a Modern Dosimetry System, Radiation Protection Dosimetry, 47,
409-414, (1993)
4. Namito,Y., Hirayama, H., and Ban, S., Improvements of Low-energy Photon Transport in
EGS4sytem, Proceedings of The first international Workshop on EGS4, KEK proceeding 97-16,
2-50 , (1997)
5. Nelson, W.R., Hirayama, H., and Rogers D.W.O., The EGS4 Code System, SLAC Report
265(1985)
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