Generating material hardening effect data

1. A method for generating material hardening effect data, comprises:

obtaining actual X-ray attenuation values of a universal phantom corresponding to different angles at each of channels;

according to theoretical X-ray attenuation values and the actual X-ray attenuation values corresponding to different angles at each of the channels, determining equivalent filtration thicknesses corresponding to each of the channels in such a way that minimizes errors between the theoretical X-ray attenuation values and the actual X-ray attenuation values corresponding to different angles at each of the channels; and

according to a predetermined length of a material, a number of sampling points and the equivalent filtration thicknesses corresponding to each of the channels, generating hardening effect data corresponding to the material.

2. The method of claim 1 wherein determining the equivalent filtration thicknesses corresponding to each of the channels in the way that minimizes errors between the theoretical X-ray attenuation values and the actual X-ray attenuation values corresponding to different angles at each of the channels comprises:

according to a spectral curve generated by a bulb under a scanning voltage, lengths of the universal phantom passed by X-ray beams corresponding to different angles and each of the channels, a material spectral attenuation curve of the universal phantom, and the equivalent filtration thicknesses corresponding to each of the channels, establishing a mathematical relationship of the theoretical X-ray attenuation values corresponding to different angles at each of the channels;

based on the mathematical relationship, obtaining a value that minimizes a sum of squared differences between the theoretical X-ray attenuation values and the actual X-ray attenuation values corresponding to different angles at each of the channels, and

using the value as the equivalent filtration thicknesses corresponding to each of the channels.

3. The method of claim 2 , wherein the lengths of the universal phantom passed by X-ray beams corresponding to different angles and each of the channels are determined by:

according to two channels respectively corresponding to maximum actual X-ray attenuation values at two angles, determining an intersection point of the two channels as a center point of the universal phantom; and

according to the center point of the universal phantom, a rotation center and a position of the bulb, determining the lengths of the universal phantom passed by X-ray beams corresponding to different angles and each of the channels.

4. The method of claim 1 , wherein generating the hardening effect data comprises:

generating hardening effect data corresponding to two or more materials based on following equation:

P

k

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(

L

1

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L

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(

∑

i

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(

i

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exp

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(

-

μ

filter

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i

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filter

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k

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filter

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i

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(

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1

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(

i

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exp

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(

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filter

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i

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filter

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k

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μ

air

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(

i

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air

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;

wherein P k (L 1 , . . . , L M ) represents the hardening effect data corresponding to M materials at the k th channel, k represents a channel index, M represents a number of species of materials, and M is an integer greater than 1;

I 0 (i) represents the i th spectral intensity value of X-ray beam emitted by the bulb, i=1˜N, and N represents an aliquot number of X photons with various energy levels contained in the X-ray beam;

μ filter (i) represents an attenuation coefficient of the i th spectrum corresponding to a filter;

L filter,k represents the equivalent filtration thickness corresponding to the k th channel;

μ air (i) represents an attenuation coefficient of the i th spectrum corresponding to air;

μ 1 (i) represents an attenuation coefficient of the i th spectrum corresponding to the first material;

μ M (i) represents an attenuation coefficient of the i th spectrum corresponding to the M th material;

L 1 represents a predetermined length of the first material, and L M represents a predetermined length of the M th material;

L air represents a predetermined length of air; and

D represents a distance between the bulb and a detector.

5. The method of claim 1 , wherein generating the hardening effect data comprises:

generating hardening effect data corresponding to a material based on following equation:

P

k

⁡

(

L

1

)

=

ln

(

∑

i

=

1

N

⁢

⁢

I

0

⁡

(

i

)

*

exp

⁡

(

-

μ

filter

⁡

(

i

)

*

L

filter

,

k

-

μ

filter

⁡

(

i

)

*

(

D

-

L

filter

,

k

)

)

)

-

ln

(

∑

i

=

1

N

⁢

⁢

I

0

⁡

(

i

)

*

exp

⁡

(

-

μ

filter

⁡

(

i

)

*

L

filter

,

k

-

μ

air

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(

i

)

*

L

air

-

μ

1

⁡

(

i

)

*

L

1

)

;

wherein P k (L 1 ) represents the hardening effect data corresponding to the material at the k th channel, and k represents a channel index;

I 0 (i) represents the i th spectral intensity value of X-ray beam emitted by the bulb, i=1˜N, and N represents an aliquot number of X photons with various energy levels contained in the X-ray beam;

μ filter (i) represents an attenuation coefficient of the i th spectrum corresponding to a filter;

L filter,k represents the equivalent filtration thickness corresponding to the k th channel;

μ air (i) represents an attenuation coefficient of the i th spectrum corresponding to air;

μ 1 (i) represents an attenuation coefficient of the i th spectrum corresponding to the material;

L 1 represents a predetermined length of the material;

L air represents a predetermined length of air; and

D represents a distance between the bulb and a detector.

6. The method of claim 1 , further comprises:

according to the hardening effect data corresponding to the material, fitting a mathematical relationship between a material path length and a hardening effect attenuation value by using a polynomial fitting algorithm.

7. A device for generating material hardening effect data, comprises:

a processor which invokes machine readable instructions corresponding to a control logic for generating material hardening effect data stored on a non-transitory storage medium and executes the machine readable instructions to:

obtain actual X-ray attenuation values of a universal phantom corresponding to different angles at each of channels;

according to theoretical X-ray attenuation values and the actual X-ray attenuation values corresponding to different angles at each of the channels, determine equivalent filtration thicknesses corresponding to each of the channels in such a way that minimizes errors between the theoretical X-ray attenuation values and the actual X-ray attenuation values corresponding to different angles at each of the channels; and

according to a predetermined length of a material, a number of sampling points and the equivalent filtration thicknesses corresponding to each of the channels, generate hardening effect data corresponding to the material.

8. The device of claim 7 , wherein said machine readable instructions further cause the processor to:

according to a spectral curve generated by a bulb under a scanning voltage, lengths of the universal phantom passed by X-ray beams corresponding to different angles and each of the channels, a material spectral attenuation curve of the universal phantom, and the equivalent filtration thicknesses corresponding to each of the channels, establish a mathematical relationship of the theoretical X-ray attenuation values corresponding to different angles at each of the channels;

based on the mathematical relationship, obtain a value that minimizes a sum of squared differences between the theoretical X-ray attenuation values and the actual X-ray attenuation values corresponding to different angles at each of the channels, and

use the obtained value as the equivalent filtration thicknesses corresponding to each of the channels.

9. The device of claim 8 , wherein said machine readable instructions further cause the processor to:

according to two channels respectively corresponding to maximum actual X-ray attenuation values at two angles, determine an intersection point of the two channels as a center point of the universal phantom; and

according to the center point of the universal phantom, a rotation center and a position of the bulb, determine the lengths of the universal phantom passed by X-ray beams corresponding to different angles and each of the channels.

10. The device of claim 7 , wherein said machine readable instructions further cause the processor to:

generate hardening effect data corresponding to two or more materials based on following equation:

P

k

⁡

(

L

1

,

…

⁢

,

L

M

)

=

ln

⁡

(

∑

i

=

1

N

⁢

⁢

I

0

⁡

(

i

)

*

exp

⁡

(

-

μ

filter

⁡

(

i

)

*

L

filter

,

k

-

μ

filter

⁡

(

i

)

*

(

D

-

L

filter

,

k

)

)

)

-

ln

(

∑

i

=

1

N

⁢

⁢

I

0

⁡

(

i

)

*

exp

⁢

(

-

μ

filter

⁡

(

i

)

*

L

filter

,

k

-

μ

air

⁡

(

i

)

*

L

air

-

μ

1

⁡

(

i

)

*

L

1

⁢

⁢

Λ

⁢

⁢

…

⁢

-

μ

M

⁡

(

i

)

*

L

M

)

;

wherein P k (L 1 , . . . , L M ) represents the hardening effect data corresponding to M materials at the k th channel, k represents a channel index, M represents a number of species of materials, and M is an integer greater than 1;

I 0 (i) represents the i th spectral intensity value of X-ray beam emitted by the bulb, i=1˜N, and N represents an aliquot number of X photons with various energy levels contained in the X-ray beam;

μ filter (i) represents an attenuation coefficient of the i th spectrum corresponding to a filter;

L filter,k represents the equivalent filtration thickness corresponding to the k th channel;

μ air (i) represents an attenuation coefficient of the i th spectrum corresponding to air;

μ 1 (i) represents an attenuation coefficient of the i th spectrum corresponding to the first material;

μ M (i) represents an attenuation coefficient of the i th spectrum corresponding to the M th material;

L 1 represents a predetermined length of the first material, and L M represents a predetermined length of the M th material;

L air represents a predetermined length of air; and

D represents a distance between the bulb and a detector.

11. The device of claim 7 , wherein said machine readable instructions further cause the processor to:

generate hardening effect data corresponding to a material based on following equation:

P

k

⁡

(

L

1

)

=

ln

(

∑

i

=

1

N

⁢

⁢

I

0

⁡

(

i

)

*

exp

⁡

(

-

μ

filter

⁡

(

i

)

*

L

filter

,

k

-

μ

filter

⁡

(

i

)

*

(

D

-

L

filter

,

k

)

)

)

-

ln

(

∑

i

=

1

N

⁢

⁢

I

0

⁡

(

i

)

*

exp

⁡

(

-

μ

filter

⁡

(

i

)

*

L

filter

,

k

-

μ

air

⁡

(

i

)

*

L

air

-

μ

1

⁡

(

i

)

*

L

1

)

;

wherein P k (L 1 ) represents the hardening effect data corresponding to the material at the k th channel, and k represents a channel index;

I 0 (i) represents the i th spectral intensity value of X-ray beam emitted by the bulb, i=1˜N, and N represents an aliquot number of X photons with various energy levels contained in the X-ray beam;

μ filter (i) represents an attenuation coefficient of the i th spectrum corresponding to a filter;

L filter,k represents the equivalent filtration thickness corresponding to the k th channel;

μ air (i) represents an attenuation coefficient of the i th spectrum corresponding to air;

μ 1 (i) represents an attenuation coefficient of the i th spectrum corresponding to the material;

L 1 represents a predetermined length of the material;

L air represents a predetermined length of air; and

D represents a distance between the bulb and a detector.

12. The device of claim 7 , wherein said machine readable instructions further cause the processor to:

according to the hardening effect data corresponding to the material, fit a mathematical relationship between a material path length and a hardening effect attenuation value by using a polynomial fitting algorithm.