Base image TV model based CT (Computed Tomography) beam hardening correcting method

A technology of beam hardening correction and base image, applied in 2D image generation, image enhancement, image data processing, etc., can solve problems such as low actual value and large deviation of hardening degree

Active Publication Date: 2012-07-25
THE PLA INFORMATION ENG UNIV
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Problems solved by technology

[0006] The present invention aims at the deficiencies of the prior art, by analyzing the influence of beam hardening on the original projection data, it is found that the beam hardening causes the actual value in the original projection to be lower than the ideal value, and the greater the degree of hardening, the more serious the deviation, and proposes a problem based on CT Beam Hardening Correction Method Based on TV Model of Base Image

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  • Base image TV model based CT (Computed Tomography) beam hardening correcting method
  • Base image TV model based CT (Computed Tomography) beam hardening correcting method
  • Base image TV model based CT (Computed Tomography) beam hardening correcting method

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Embodiment 1

[0068] Embodiment 1: In a CT imaging system, X-ray hardening causes cupping and striping artifacts in reconstructed images, seriously affecting image quality. In this paper, by analyzing the influence of beam hardening on the original projection data, it is found that the beam hardening causes the actual value in the original projection to be lower than the ideal value, and the greater the degree of hardening, the more serious the deviation. The CT beam hardening correction method based on the basic image TV model of the present invention is completed by the following steps on the basis of establishing a beam hardening correction model with adjustable parameters: first, under different adjustable parameter conditions, the original The projection data is preprocessed and transformed by the model to obtain multiple sets of preprocessed projection sequences, and then the preprocessed projection sequences are reconstructed to obtain a series of corrected base images, and the total ...

Embodiment 2

[0070] Embodiment 2: The CT beam hardening correction method based on the basic image TV model in this embodiment first analyzes the influence of beam hardening on projection data, and then establishes a beam hardening correction model on this basis, and adopts the following method Perform an analysis of the effect of beam hardening on projection data:

[0071] The intensity attenuation formula of monoenergetic X-rays passing through homogeneous matter can be expressed by Beer’s law, as shown in formula (1),

[0072] I 1 =I 0 e -μx (1)

[0073] where I 0 Indicates the initial intensity of monoenergetic rays; I 1 Indicates the transmitted ray intensity; μ is the material attenuation coefficient, which is related to the density of the material and the energy of the ray; x indicates the length of the material that the ray passes through. Then, from formula (1), we can get:

[0074] μx = - ln I ...

Embodiment 3

[0083] Embodiment 3: The CT beam hardening correction method based on the base image TV model of this embodiment, on the basis of analyzing the influence of beam hardening on projection data in Embodiment 2, establishes a hardening correction model through the following steps:

[0084] Let P be the original projection obtained under the condition of multi-energy spectral rays, P′ be the corresponding projection data after P correction, and define the following functional relationship between P′ and P:

[0085] P'=S(P) (6)

[0086] Among them, S is a pre-correction function, S is a linear function, an exponential function or a power function, combined with a power function and an exponential function, the form of the design function S is as follows:

[0087] S(P)=P (7)

[0088] Add variable parameter n(n ∈ N + ), namely S n (P)=P n (n∈N + ), using S n (P) Fitting the calibration curve, taking different values ​​of n to get different S n (P), which means that the projecti...

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Abstract

The invention relates to a CT (Computed Tomography) transmission imaging beam hardening correcting method and particularly relates to a base image TV minimized model based CT beam hardening correcting method. On the basis of establishing a beam hardening correcting model with an adjustable parameter, the base image TV model based CT beam hardening correcting method comprises the following steps: firstly, converting an original projection data through the model pretreatment so as to obtain sets of pretreated projection sequences under different adjustable parameter conditions; respectively reconstructing the pretreated projection sequences, thereby obtaining a series of corrected base images; taking a full-variation function of a target image as a cost function and obtaining an optimal solution of a weighting coefficient according to an iterative method; and lastly, summing the weights of the obtained series of base images, thereby forming a final reconstructed image. Compared with the traditional method, the method provided by the invention has the advantages that the priori knowledge, such as scanning copy material, radiation source condition, and the like, is unnecessary, the method is unlimited by external conditions and is strong in universality, and the linear combination is solved when a weighting coefficient is confirmed, so that the method has the advantages of small computation complexity and short operation time.

Description

technical field [0001] The invention relates to a beam hardening correction method for CT transmission imaging, in particular to a CT beam hardening correction method based on a base image TV minimization model. Background technique [0002] CT (Computed Tomography, CT) technology is an imaging technology that uses a detector to perform a series of ray projection measurements at different angles on the detected object, and directly calculates all slice images of the object through a three-dimensional image reconstruction algorithm. It is used in industrial non-destructive testing and medical applications. There is a wide range of applications in the field. [0003] The CT reconstruction algorithm is based on the following assumptions: the X-rays used are monoenergetic, the ray intensity decays exponentially with the increase of the thickness of the absorbing material, and the attenuation coefficient is constant. The rays emitted by the actual X-ray source are multi-energy s...

Claims

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Application Information

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IPC IPC(8): G06T5/00G06T11/00G01N23/04
Inventor 闫镔李庆亮潘冬存李磊孙红胜张俊
Owner THE PLA INFORMATION ENG UNIV
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