Method and device for calculating the radiation dose distribution for a radiation treatment system for the purpose of radiation therapy of an animal body

• US 20060203964A1
• Filed: 12/13/2005
• Published: 09/14/2006
• Est. Priority Date: 12/23/2004
• Status: Active Grant

• Current Assignee: Nucletron Operations BV
• Original Assignee: Nucletron Holding BV (New Nucletron Company BV)
• Inventors: Karlsson, Mikael, Ahnesjo, Anders, Olofsson, Jorgen, Nyholm, Tufve
• Granted Patent: US 7,542,545 B2
• Time in Patent Office: Days
• US Class Current: 378/65
• CPC Class Codes: A61N 2005/1034 Monte Carlo type methods; particle tracking
• CPC Class Codes: A61N 5/1031 using a specific method of dose optimization
• CPC Class Codes: G01T 1/29 Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation

Abstract

The invention relates to a method for calculating the radiation dose distribution 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 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 said radiation beam of the radiation treatment system exhibits a specific beam field size and shape at different depths. It is an object of the invention to provide a method and device according to the above allowing the calculation of a radiation dose distribution for a radiation treatment system using a limited amount of data whilst preserving the required accuracy. According to the invention the method is characterized by the steps of i) determining at least 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 at least one beam quality index.

Claims

1. Method for calculating the radiation dose distribution 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 specific beam field size and shape at different depths, wherein the method is characterized by the steps of:

i) determining at least 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 at least one beam quality index.

2. Method according to claim 1, further characterized by the steps of

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 can be transformed into phantom scatter factors for the corresponding field sizes,

iv) determining said at least one beam quality index according to step

i) using the pre-collected measured radiation beam data according to step iii);

v) associating the dose deposition kernel parameters to said one or a few beam quality index being determined.

3. Method according to claim 1, further characterized by step

vi) using Monte Carlo simulations to simulate said measured data according to step iii).

4. Method according to claim 1, further characterized in that said at least one beam quality index is determined by the ratio between the tissue phantom ratio (TPR) measured at d₁=20 cm and d₂=10 cm depth (TPR_20,10).

5. 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 d₃=10 cm (PDD₁₀).

6. Method according to claim 2, further characterized in that the dose deposition kernels are pencil dose deposition kernels.

7. Method according to claim 2, further characterized in that the dose deposition kernels are point dose deposition kernels.

8. Method according to claim 1, characterized in that the dose per energy fluence at the central axis of the radiation beam is determined as:

$\begin{array}{cc}\frac{D}{\mathrm{\Psi <br><br>}<br><br>\left(r=0\right)}\propto <br><br>2<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}<br><br>{\int <br><br>}_0^R<br><br>r<br><br>\frac{\mathrm{\Psi <br><br>}<br><br>\left(r\right)}{\mathrm{\Psi <br><br>}<br><br>\left(r=0\right)}<br><br>k<br><br>\left(r,z\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>r<br><br><br><br>\mathrm{with}& \left(7<br><br>a\right)\\ k<br><br>\left(r,z\right)=\frac{A<br><br>\left(z\right)<br><br>\exp <br><br>\text{\hspace{1em}<br><br>}\left[-a<br><br>\left(z\right)<br><br>r\right]+B<br><br>\left(z\right)<br><br>\exp <br><br>\text{\hspace{1em}<br><br>}\left[-b<br><br>\left(z\right)<br><br>r\right]}{r}& \left(7<br><br>b\right)\end{array}$

wherein the parameters are defined as;

$\begin{array}{cc}\frac{A}{a}=A_1<br><br>\left[1-\exp <br><br>\text{\hspace{1em}<br><br>}\left[A_2<br><br>\sqrt{z^2+A_5^2}\right]\right]<br><br>\exp <br><br>\text{\hspace{1em}<br><br>}\left[A_3<br><br>z+A_4<br><br>z^2\right]<br><br><br><br>\mathrm{and}& \left(7<br><br>c\right)\\ \frac{B}{b}=B_1<br><br>\left[1-\exp <br><br>\text{\hspace{1em}<br><br>}\left[B_2<br><br>\sqrt{z^2+B_5^2}\right]\right]<br><br>\exp <br><br>\text{\hspace{1em}<br><br>}\left[B_3<br><br>z+B_4<br><br>z^2\right]<br><br><br><br>\mathrm{and}& \left(7<br><br>d\right)\\ a=a_1+a_2<br><br>z<br><br><br><br>\mathrm{and}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{where}& \left(7<br><br>e\right)\\ b=b_1<br><br>\left[1-\exp <br><br>\text{\hspace{1em}<br><br>}\left[b_2<br><br>\sqrt{z^2+b_5^2}\right]\right]<br><br>\exp <br><br>\text{\hspace{1em}<br><br>}\left[b_3<br><br>z+b_4<br><br>z^2\right].& \left(7<br><br>f\right)\end{array}$

9. Method according to claim 8, characterized in that the parameters are expressed through μ

, which is a function of TPR (d₂,d₁) (TPR_20,10) with the following expressions;

μ

=−

0.363009·

TPR_20,10³+0.709250·

TPR_20,10²−

0.259794·

TPR_20,10−

0.090314

A₁=−

0.0042·

μ

³−

0.46571·

μ

²−

0.099992·

μ

+0.0002918

A₂=−

1605.6·

μ

²−

64.40·

μ

−

1.239

A₃=−

0.016·

μ

⁴−

0.0055·

μ

³−

0.01246·

μ

²+0.991726·

μ

+0.0002103

A₄=0.007·

μ

³0.1081·

μ

²0.01211·

μ

−

0.000208

A₅=0.003·

μ

²0.805·

+0.23061

a₁=−

2852·

μ

³+1641·

μ

²+47.00·

μ

+2.007

a₂=−

0.010·

μ

−

0.016

B₁=−

69680.47·

μ

⁴−

12517.918·

μ

³−

780.2216·

μ

²−

20.948788·

μ

−

0.20531052

B₂=−

16.675·

μ

²−

2.0546·

μ

−

0.06840

B₃=1.0011·

μ

+8.1·

10<sup>−

5</sup>

B₄=0.0033·

μ

³−

0.11080·

μ

²−

0.012183·

μ

−

0,0002067

B₅=2290·

μ

²+225.17·

μ

+7.084

b₁=5415900·

μ

⁵+1573050·

μ

⁴+180100,6·

μ

³+10207,44·

μ

²+285,8012·

μ

+3,35788

b₂=−

267,83·

μ

²−

26.215·

μ

−

0.93285

b₃=462400·

μ

⁵+87700·

μ

⁴+5070.5·

μ

³+9.641·

μ

²−

6.3843·

μ

−

0,15488

b₄=−

12319·

μ

⁵+2953.1·

μ

⁴−

263.64·

μ

³−

10.2445·

μ

²−

0.158854·

μ

−

0.0003494

and

b₅=14.15·

μ

+1.17168.

10. Device for calculating the radiation dose distribution 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 specific beam field size and shape at different depths, characterized in that the device further comprising inputting means arranged for inputting at least one beam quality index being representative for said radiation beam being used to calculating means, said calculating means being arranged for calculating said radiation dose distribution using parameterized dose deposition kernels being based on said at least one beam quality index.

11. Device according to claim 10, characterized in that the device is a monitor unit (MU) checking device.

12. Device according to claim 10, characterized in that the device is a IMRT treatment MU checking device.