Signal processing method and imaging system for scatter correction in computed tomography
A signal processing method is disclosed, which includes detecting a total intensity of X-rays passing through an object comprising multiple materials; obtaining at least one set of basis information of basis material information of the multiple materials and basis component information of photon-electric absorption basis component and Compton scattering basis component of the object; estimating a scatter intensity component of the detected X-rays based on the at least one set of basis information and the detected total intensity; and obtaining an intensity estimate of primary X-rays incident on a detector based on the detected total intensity and the estimated scatter intensity component. An imaging system adopting the above signal processing method is also disclosed.
1. A signal processing method, comprising:
detecting a total intensity of X-rays passing through an object comprising multiple materials via a detector of a computed tomography system;
obtaining, via a computer, at least one set of basis information of basis material information of the multiple materials and basis component information of photon-electric absorption basis component and Compton scattering basis component of the object, wherein obtaining the basis material information of the multiple materials comprises obtaining projection data of the basis material information used to characterize each of the multiple materials along each projection beam of the X-rays;
estimating, via the computer, a scatter intensity component of the detected X-rays based on the at least one set of basis information and the detected total intensity; and
obtaining, via the computer, an intensity estimate of primary X-rays incident on a detector based on the detected total intensity and the estimated scatter intensity component;
wherein estimating the scatter intensity component comprises using a weighting model to weight the obtained projection data of each material, determining a scatter intensity component of each material based on individual single-material scatter models for each material, weighting the scatter intensity component of each material determined by the single-material scatter models with the weighted projection data of each material, and estimating the scatter intensity component of the detected X-rays based on the weighted scatter intensity component of each material.
2. The method of claim 1 , wherein obtaining the basis material information of the multiple materials comprises obtaining projection data of at least one of a path length, an integral of a linear attenuation coefficient, and an integral of a density distribution of each of the multiple materials for each projection beam of the X-rays.
3. The method of claim 2 , wherein obtaining the projection data of at least one of a path length, an integral of a linear attenuation coefficient, and an integral of a density distribution of each of the multiple materials for each projection beam of the X-rays comprises performing a material decomposition process.
4. The method of claim 1 , comprising reconstructing, via the computer, an X-ray image based on the intensity estimate.
5. The method of claim 1 , comprising detecting an additional total intensity of X-rays passing through air, and wherein each individual single-material scatter model utilizes the detected additional total intensity in estimating the scatter intensity component.
6. The method of claim 1 , wherein each individual single-material scatter model is established based on at least the detected total intensity.
7. The method of claim 1 , wherein obtaining the basis material information of the multiple materials comprises obtaining projection data, a path length or a path length sequence of each of the multiple materials for each projection beam of the X-rays, and obtaining the projection data, the path length or the path length sequence of each of the multiple materials for each projection beam of the X-rays comprises performing a temporary image reconstruction based on the detected total intensity, segmenting the multiple materials based on the temporary image reconstruction, and reprojecting images of the segmented multiple materials to obtain the projection data, the path lengths or the path length sequences for the multiple materials.
8. The method of claim 1 , wherein obtaining the basis material information of the multiple materials comprises obtaining projection data, a path length or a path length sequence of each of the multiple materials for each projection beam of the X-rays from direct segmentation of projection data of the detected total intensity.
9. The method of claim 1 , wherein detecting the total intensity of the X-rays passing through the object comprising the multiple materials comprises detecting a total intensity of low-energy X-rays passing through the object comprising the multiple materials, and detecting a total intensity of high-energy X-rays passing through the object comprising the multiple materials, and wherein obtaining the basis material information of the multiple materials comprises performing a material decomposition process based on the detected total intensity of the low-energy X-rays and the detected total intensity of the high energy X-ray.
10. The method of claim 9 , wherein before performing the material decomposition process, the method further comprises performing data conversion and calibration for the total intensity of the low-energy X-rays, and performing data conversion and calibration for the total intensity of the high-energy X-rays, and wherein performing the material decomposition process is based on the calibrated total intensity of the low-energy X-rays and the calibrated total intensity of the high-energy X-rays.
11. The method of claim 1 , wherein the multiple materials is characterized by a low effective atomic number material and a high effective atomic number material.
12. The method of claim 11 , wherein the low effective atomic number material comprises a soft tissue, and the high effective atomic number comprises at least one of bone, a metal and a contrast agent.
13. A computed tomography imaging system, comprising:
a detector configured to detect a total intensity of X-rays passing through an object comprising multiple materials; and
a computer configured to obtain at least one set of basis information of basis material information of the multiple materials and basis component information of photon-electric absorption basis component and Compton scattering basis component of the object, estimate a scatter intensity component of the detected X-rays based on the at least one set of basis information and the detected total intensity, and obtain an intensity estimate of primary X-rays incident on the detector based on the detected total intensity and the estimated scatter intensity component, wherein the computer is configured to obtain the basis material information of the multiple materials by obtaining projection data of the basis material information used to characterize each of the multiple materials along each projection beam of the X-rays;
wherein the computer is configured to estimate the scatter intensity component by using a weighting model to weight the obtained projection data of each material, determining a scatter intensity component of each material based on individual single-material scatter models for each material, weighting the scatter intensity component of each material determined by the single-material scatter models with the weighted projection data of each material, and estimating the scatter intensity component of the detected X-rays based on the weighted scatter intensity component of each material.
14. The computed tomography imaging system of claim 13 , wherein the computer is configured to reconstruct an X-ray image based on the intensity estimate.
15. The computed tomography imaging system of claim 13 , wherein the computer is configured for performing a material decomposition process for the detected total intensity of the X-rays to obtain the projection data of at least one of a path length, an integral of the linear attenuation coefficient, and an integral of the density distribution of each of the multiple materials along each projection beam of the X-rays.
16. The computed tomography imaging system of claim 13 , wherein the computer is configured for obtaining projection data, a path length or a path length sequence of each of the multiple materials for each projection beam of the X-rays, and obtaining the projection data, the path length or the path length sequence of each of the multiple materials for each projection beam of the X-rays comprises:
performing a temporary image reconstruction based on the detected total intensity;
segmenting the multiple materials based on the temporary image reconstruction; and
reprojecting images of the segmented multiple materials to obtain the projection data, the path lengths or the path length sequences for the multiple materials.
17. The computed tomography imaging system of claim 13 , wherein the computer is configured for performing a material decomposition process for the detected total intensity of the X-rays to obtain projection data of the basis material information of each material for each projection beam of the X-rays.
18. The computed tomography imaging system of claim 13 , wherein the multiple materials is characterized by a low effective atomic number material and a high effective atomic number material.
19. The computed tomography imaging system of claim 18 , wherein the low effective atomic number material comprises a soft tissue, and the high effective atomic number comprises at least one of bone, a metal and a contrast agent.
20. The computed tomography imaging system of claim 13 , wherein the detector is configured to detect an additional total intensity of X-rays passing through air, and wherein each individual single-material scatter model is configured to utilize the detected additional total intensity in estimating the scatter intensity component.