CN104318972B

CN104318972B - A kind of X-ray expansion device method for designing

Info

Publication number: CN104318972B
Application number: CN201410610085.5A
Authority: CN
Inventors: 代志力; 申济菘; 陈研
Original assignee: CHONGQING ZHENCE SCIENCE AND TECHNOLOGY Co Ltd
Current assignee: CHONGQING ZHENCE SCIENCE AND TECHNOLOGY Co Ltd
Priority date: 2014-10-29
Filing date: 2014-10-29
Publication date: 2017-07-18
Anticipated expiration: 2034-10-29
Also published as: CN104318972A

Abstract

The present invention relates to a kind of X-ray expansion device method for designing, this method is for time-consuming present in traditional expansion device method for designing, high cost, and the shortcoming of expansion effect difference, the design of multi-stage taper expansion device is realized using the method such as monte carlo method and data fitting.The design method can reach good expansion effect, whole process clear process, it is easy to accomplish；Meanwhile, design cost is relatively low, and the cycle is shorter.

Description

A kind of X-ray expansion device method for designing

Technical field

The present invention relates to a kind of X-ray expansion device method for designing, especially for cone-beam x-ray, based on Monte Carlo, number The method for designing of multi-stage taper expansion device is realized according to methods such as fittings.

Background technology

Traditional expansion device method for designing is empirically to design a taper expansion device for being no more than three-level, by repeatedly Expansion effect is reached after ground modification expansion device structure, test of many times measurement.Time-consuming for this method, high cost, and expansion is imitated It is really poor.

Also it is proposed that a kind of expansion device method for designing.This method designs one with many by the way of generating step by step The expansion device of level frustum structure.It will be taken longer by repeatedly adjustment per one-level frustum.Further, since the shadow of ray scattering Ring, often newly increasing one-level frustum can all impact to frustum before.Therefore one-level frustum is often increased newly to be required for before Frustum is modified, and further increases the time of design, and whole design needs square of the number of times changed about with frustum quantity n It is directly proportional.With the requirement and the increase of frustum quantity of flatteness, the global design time will also increase substantially.It is simultaneously this The design process of method of formation is also very complicated step by step.

The content of the invention

In view of this, it is an object of the invention to provide a kind of X-ray expansion device method for designing, this method is based on Meng Teka The method such as Lip river method and data fitting realizes the design of multi-stage taper expansion device.

To reach above-mentioned purpose, the present invention provides following technical scheme：

A kind of X-ray expansion device method for designing, comprises the following steps：

1) X-ray forms cone-beam x-ray after front collimation device, and by plane where expansion device bottom surface, spatially angle is divided At n, n is corresponding with expansion device frustum number, records each corresponding space angle θ₁, θ₂..., θ_n；

2) distance of the base that the plane setting thickness where expansion device base is m, base and radiographic source is L；Penetrated according to X The parameters such as line source beam energy, target structure, X-ray is calculated on expansion device base plane by step using monte carlo method The roentgen dose X A of position and expansion device center at the rapid n 1) divided₀, A₁... .., A_n, A₀For the ray agent at center Amount；

3) X-ray is calculated in the power spectrum at this n+1 on position using monte carlo method：

4) an one-level frustum is designed, thickness is d₀So that the dosage of center ray by this frustum decay after with side Roentgen dose X A at edge_nIt is equal, A₀'=A_n

5) wide beam modifying factor B is calculated

Wherein, A_j0Centered on ray energy spectrum component；μ_jFor corresponding attenuation coefficient；d₀For frustum thickness, above-mentioned side is solved Journey is that can obtain wide beam modifying factor B；

6) the attenuation length d of each frustum is calculated_i

d_iFor unique unknown number in formula, it is the attenuation length d that can obtain frustums at different levels to solve above-mentioned equation_i；

7) according to the attenuation length d of frustums at different levels_iAnd corresponding space angle θ_iCalculate the radius r of frustums at different levels_iAnd thickness Spend l_i；

8) according to the parameter r of frustums at different levels_iAnd l_iExpansion device model is set up, calculating ray using monte carlo method passes through The uniformity after expansion device；Adjust the attenuation length d of frustums at different levels_iSo that simulation calculates obtained flatteness and reaches requirement；

9) expansion device is processed according to the later parameter of adjustment, expansion device is arranged on to the position set and measured； If actual

Flatteness reaches requirement then without modification；On this basis to expansion device if actual flatteness is not up to requirement It is modified slightly so that the actual flatteness of ray reaches requirement.

Further, the material used by expansion device is metal material.

Further, the material used by expansion device is copper or stainless steel.

Further, step 2) in X-ray energy scope from 50keV to 200MeV.

Further, step 7) in frustums at different levels radius r_iWith thickness l_iAnd the attenuation length d of frustums at different levels_iAnd it is right The Space Angle θ answered_iThere is following recurrence relation in degree：

θ₀=0

l_i=d_i-1cosθ_i-1-d_i cosθ_i, i=1,2 ..., n

Further, step 1) to roentgen dose X and power spectrum and expansion device model in 8) foundation in Geant4, or Carried out in EGS, or other softwares based on monte carlo method.

The beneficial effects of the present invention are：The X-ray expansion device method for designing that the present invention is provided can reach well Whole effect, whole process clear process, it is easy to accomplish；Meanwhile, design cost is relatively low, and the cycle is shorter.

Brief description of the drawings

In order that the purpose of the present invention, technical scheme and beneficial effect are clearer, the present invention provides drawings described below and carried out Explanation：

Fig. 1 is expansion device schematic diagram；

Fig. 2 is 6MeV medical accelerator expansion device structural section figures in embodiment；

Fig. 3 is the schematic flow sheet of the method for the invention.

Embodiment

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.

Fig. 1 is expansion device schematic diagram, and Fig. 3 is the schematic flow sheet of the method for the invention.

The method of the invention is specifically described by taking the design of 6MeV accelerator for electron therapy expansions device as an example, Fig. 2 is 6MeV medical accelerators expansion device structural section figure in the present embodiment, the technical requirements of the figure are：1st, cone boss portion size Tolerance is by IT8 grades of processing, and remaining dimensional tolerance is by IT10 grades of processing；2nd, material is brass.

Specifically include following steps：

1) expansion device base is apart from radiographic source target spot apart from L=128mm, and ray subtended angle is 14 °.Setting one has 10 The expansion device of level frustum structure, the corresponding space angle θ of each frustum_iRespectively 1 °, 2 °, 3 °, 4 °, 5 °, 6 °, 8 °, 10 °, 12 °, 14 °.Expansion equipment material selects copper.

2) dosage A of the 6MeV rays in corresponding position is calculated using monte carlo method₀,A₁,.....,A₁₀, A₀For Roentgen dose X at center.Calculate respective spectral distribution simultaneously.

3) it is d to design a thickness₀One-level frustum so that the dosage of the ray of center decay through frustum after with side Roentgen dose X at edge is equal.

A′₀=A₁₀ d₀=20mm

4) wide beam modifying factor B is calculated

5) attenuation length of frustums at different levels is calculated

6) according to the attenuation length d of frustums at different levels_iAnd corresponding space angle θ_iCalculate the radius r of frustums at different levels_iWith Thickness l_i。

7) according to the parameter r of frustums at different levels_iAnd l_iExpansion device model is set up, calculating ray using monte carlo method passes through The uniformity after expansion device.Adjust the attenuation length d of frustums at different levels_iSo that simulation calculates obtained flatteness and reaches requirement.

8) expansion device is processed according to the later parameter of adjustment, expansion device is arranged on to the position set and measured. Expansion device structure is once finely tuned on the basis of measurement result so that actual flatteness is less than 6%, as shown in Figure 3, Reach design requirement.

Finally illustrate, preferred embodiment above is merely illustrative of the technical solution of the present invention and unrestricted, although logical Cross above preferred embodiment the present invention is described in detail, it is to be understood by those skilled in the art that can be Various changes are made to it in form and in details, without departing from claims of the present invention limited range.

Claims

1. a kind of X-ray expansion device method for designing, it is characterised in that：Comprise the following steps：

1) X-ray forms cone-beam x-ray after front collimation device, and by plane where expansion device bottom surface, spatially angle is divided into n Place, n is corresponding with expansion device frustum number, records each corresponding space angle θ₁, θ₂..., θ_n；

2) distance of the base that the plane setting thickness where expansion device base is m, base and radiographic source is L；According to x-ray source The parameters such as beam energy, target structure, X-ray is calculated on expansion device base plane by step 1 using monte carlo method) The roentgen dose X A of position and expansion device center at the n of division₀, A₁... .., A_n, A₀For the roentgen dose X at center；

A_{i} = Σ_{j = 1}^{k} A_{j i}, i = 0, 1, 2..... n

4) an one-level frustum is designed, thickness is d₀So that the dosage of center ray by this frustum decay after with edge Roentgen dose X A_nIt is equal, A₀'=A_n

5) wide beam modifying factor B is calculated

{A_{0}}^{'} = A_{n} = B Σ_{j = 1}^{k} A_{j 0} e^{- μ_{j} d_{0}}

Wherein, A_j0Centered on ray energy spectrum component；μ_jFor corresponding attenuation coefficient；d₀For frustum thickness, above-mentioned equation is solved Obtain wide beam modifying factor B；

6) the attenuation length d of each frustum is calculated_i

{A_{i}}^{'} = A_{n} = B Σ_{j = 1}^{k} A_{j i} e^{- μ_{j} d_{i}}

7) according to the attenuation length d of frustums at different levels_iAnd corresponding space angle θ_iCalculate the radius r of frustums at different levels_iWith thickness l_i；

8) according to the parameter r of frustums at different levels_iAnd l_iExpansion device model is set up, calculating ray using monte carlo method passes through expansion The uniformity after device；Adjust the attenuation length d of frustums at different levels_iSo that simulation calculates obtained flatteness and reaches requirement；

9) expansion device is processed according to the later parameter of adjustment, expansion device is arranged on to the position set and measured；If real Border flatteness reaches requirement then without modification；Expansion device is slightly repaiied on this basis if actual flatteness is not up to requirement Change so that the actual flatteness of ray reaches requirement；

Material used by the expansion device is copper or stainless steel；

Step 2) in X-ray energy scope from 50keV to 200MeV；

Step 7) in frustums at different levels radius r_iWith thickness l_iAnd the attenuation length d of frustums at different levels_iAnd corresponding Space Angle θ_i There is following recurrence relation in degree：

θ₀=0

l_i=d_i-1cosθ_i-1-d_icosθ_i, i=1,2 ..., n

r_{i} = (L - d_{0} + Σ_{j = 1}^{i} l_{j}) {tanθ}_{i}, i = 1, 2, ...., n .

2. a kind of X-ray expansion device method for designing according to claim 1, it is characterised in that：Step 1) to ray in 8) The foundation of dosage and power spectrum and expansion device model in Geant4, either EGS or other based on the soft of monte carlo method Carried out in part.