Method and device for calculating the radiation dose distribution for a radiation treatment system for the purpose of radiation therapy of an animal body
A method for calculating the radiation dose distribution for a radiation treatment system for the purpose of radiation therapy of an animal body, wherein the radiation beam of the radiation treatment system exhibits a specific beam field size and shape at different depths as well as to a device for calculating the radiation dose distribution for a radiation treatment system for the purpose of radiation therapy of an animal body, wherein the radiation beam of the radiation treatment system exhibits a specific beam field size and shape at different depths. The method is characterized by the steps of i) determining at least one beam quality index being representative for the radiation beam being used, and ii) calculating the radiation dose distribution in the specific beam field using parameterized dose deposition kernels based on the at least one beam quality index.
1. A method for calculating a radiation dose distribution of a radiation beam for a radiation treatment system for the purpose of radiation therapy of an animal body, wherein said radiation beam of the radiation treatment system exhibits a size and a shape of a specific beam field at different depths, wherein the method is characterized by the steps of:
i) determining one beam quality index being representative for said radiation beam being used, and
ii) calculating said radiation dose distribution in said specific beam field using parameterized dose deposition kernels based on said one beam quality index;
iii) using for different devices pre-collected measured radiation beam data, said measured radiation beam data comprising:
a) measured phantom dose data at different depths, for different field shapes and sizes and at different energies;
b) calculated dose deposition kernel parameters;
c) measured head scatter factors and output factors that are transformable into phantom scatter factors for the corresponding field sizes,
iv) determining said one beam quality index according to step i) using the pre-collected measured radiation beam data according to step iii);
v) expressing the dose deposition kernel parameters as a mathematical function of said one beam quality index being determined.
2. The method according to claim 1 , further characterized by step vi) using Monte Carlo simulations to simulate said measured radiation beam data according to step iii).
3. The method according to claim 1 , further characterized in that said one beam quality index is determined by a ratio (TPR 20,10 ) between a tissue phantom ratio (TPR) measured at d 1 =20 cm and a tissue phantom ratio (TPR) measured at d 2 =10 cm depth.
4. The method according to claim 1 , further characterized in that said at least one beam quality index is determined by the percentage depth dose (PDD) at d 3 =10 cm (PDD 10 ).
5. The method according to claim 1 , further characterized in that the dose deposition kernels are pencil dose deposition kernels.
6. The method according to claim 1 , further characterized in that the dose deposition kernels are point dose deposition kernels.
7. The method according to claim 1 , characterized in that a dose per energy fluence at the central axis of the radiation beam is determined as:
D
Ψ
(
r
=
0
)
∝
2
π
∫
0
R
r
Ψ
(
r
)
Ψ
(
r
=
0
)
k
(
r
,
z
)
ⅆ
r
with
(
7
a
)
k
(
r
,
z
)
=
A
(
z
)
exp
[
-
a
(
z
)
r
]
+
B
(
z
)
exp
[
-
b
(
z
)
r
]
r
(
7
b
)
wherein the parameters are defined as:
A
a
=
A
1
[
1
-
exp
[
A
2
z
2
+
A
5
2
]
]
exp
[
A
3
z
+
A
4
z
2
]
and
(
7
c
)
B
b
=
B
1
[
1
-
exp
[
B
2
z
2
+
B
5
2
]
]
exp
[
B
3
z
+
B
4
z
2
]
and
(
7
d
)
a
=
a
1
+
a
2
z
and
where
(
7
e
)
b
=
b
1
[
1
-
exp
[
b
2
z
2
+
b
5
2
]
]
exp
[
b
3
z
+
b
4
z
2
]
.
(
7
f
)
8. The method according to claim 7 , characterized in that the parameters are expressed through μ, which is a function of TPR (d 2 , d 1 ) (TPR 20,10 ) with the following expressions:
μ=−0.363009·TPR 20,10 3 +0.709250·TPR 20,10 2 −0.259794·TPR 20,10 −0.090314
A 1 =−0.0042·μ 3 −0.46571·μ 2 −0.099992·μ+0.0002918
A 2 =−1605.6·μ 2 −64.40·μ−1.239
A 3 =−0.016·μ 4 −0.0055·μ 3 −0.01246·μ 2 +0.991726·μ+0.0002103
A 4 =0.007·μ 3 0.1081·μ 2 0.01211·μ−0.000208
A 5 =0.003·μ 2 0.805·+0.23061
a 1 =−2852·μ 3 +1641·μ 2 +47.00·μ+2.007
a 2 =−0.010·μ−0.016
B 1 =−69680.47·μ 4 −12517.918·μ 3 −780.2216·μ 2 −20.948788·μ−0.20531052
B 2 =−16.675·μ 2 −2.0546·μ−0.06840
B 3 =1.0011·μ+8.1·10 −5
B 4 =0.0033·μ 3 −0.11080·μ 2 −0.012183·μ−0,0002067
B 5 =2290·μ 2 +225.17·μ+7.084
b 1 =5415900·μ 5 +1573050·μ 4 +180100.6·μ 3 +10207.44·μ 2 +285.8012·μ+3.35788
b 2 =−267.83·μ 2 −26.215·μ−0.93285
b 3 =462400·μ 5 +87700·μ 4 +5070.5·μ 3 +9.641·μ 2 −6.3843·μ−0.15488
b 4 =−12319·μ 5 +2953.1·μ 4 −263.64·μ 3 −10.2445·μ 2 −0.158854·μ−0.0003494
and
b 5 =14.15·μ+1.17168.