CN113081012A - X-ray tomography system - Google Patents
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Abstract
The invention relates to the technical field of medical imaging, and discloses an X-ray tomography system. The method comprises the following steps: the X-ray imaging module is configured to acquire a multi-angle two-dimensional image of a specified inspection part of an object to be imaged by adopting an X-ray imaging device; a two-dimensional image receiving module configured to receive a multi-angle two-dimensional image of a specified examination part acquired in the X-ray imaging module; and the three-dimensional image reconstruction module is configured to reconstruct a three-dimensional image from a plurality of two-dimensional images at different angles by adopting an image reconstruction algorithm to form voxel data in the imaging region. The advantages of high shooting efficiency and lower dosage than CT of the Tomosynthesis technology in the aspect of three-dimensional imaging are effectively utilized, the limitation of the Tomosynthesis three-dimensional imaging range is broken through, continuous pulse shooting and three-dimensional imaging of a longer area of a human body are met, and the requirements of specific clinical diagnosis scenes including the full length of the human body, the full length of a spine or the full length of lower limbs are met.
Description
Technical Field
The invention relates to the technical field of medical imaging, in particular to an X-ray tomography system. The X-ray source and the flat panel detector can be controlled to continuously move in the same direction along the vertical or horizontal direction, and pulse shooting is carried out according to the specified time interval in the moving process, so that continuous shooting of any specified region of the whole body of the subject is realized, and a plurality of X-ray plane images of the examined region are obtained. By means of the three-dimensional reconstruction algorithm, the collected X-ray plane images are processed, and a three-dimensional image of the checked area is constructed.
Background
Tomosynthesis (Tomosynthesis) is a technique for generating tomographic images from very low dose projections obtained from different angles using the imaging technique of standard X-ray equipment with digital flat panel detectors. These images are parallel to the plane of the detector. The bulb tubes shoot at discontinuous positions in multiple angles to obtain images, and by moving and overlapping the shot images, a tomographic image of an object with any set height can be reconstructed. For example, in the large flat panel gastrointestinal island sonialysis safire ii shown in fig. 1 and 2, high-definition tomographic images of successive slices are obtained in one scan.
However, in the existing X-ray imaging system capable of implementing Tomosynthesis function, when performing tomographic image acquisition, some systems adopt a flat panel detector to move in a reverse direction with a ray source, accompanied by the rotation of the ray source angle; some flat panel detectors have a constant position, and the radiation source rotates around the flat panel detector. No matter which prior art is adopted, the three-dimensional imaging range is not large, the three-dimensional imaging of a longer region of a human body (such as the whole body, the whole spine, the whole lower limb and the like) is difficult to meet, and certain limitations exist in clinical application.
In addition, the existing Tomosynthesis equipment is complex in control mode, and the cost of the rack structure design and software control is high.
Disclosure of Invention
In view of the above problems, it is an object of the present invention to provide an X-ray tomography system. The X-ray transmitting end and the X-ray receiving end continuously move in the same direction along the vertical direction or the horizontal direction, and in the moving process, X-pulse rays are continuously transmitted to an imaging area positioned between the transmitting end and the receiving end to form a plurality of two-dimensional plane images distributed in the whole imaging area at different angles; acquiring voxel data from a plurality of two-dimensional images distributed in the whole imaging space at different angles through an image reconstruction algorithm, and reconstructing a three-dimensional image; when the slice of a specific plane needs to be obtained, the pixel values of the voxel data in the specific plane are obtained through a multi-plane cutting algorithm, and slice images of different faults are obtained. The invention can break through the limitation of the existing Tomosynthesis system on the three-dimensional imaging area to a great extent.
The above object of the present invention is achieved by the following technical solutions:
a tomographic imaging system comprising: the X-ray imaging module, the two-dimensional image receiving module and the three-dimensional image reconstruction module are connected with the X-ray imaging module;
the X-ray imaging module is configured to adopt an X-ray imaging device to acquire a multi-angle two-dimensional image of a specified inspection part of an object to be imaged;
the two-dimensional image receiving module is configured to receive the two-dimensional images of the designated examination part acquired in the X-ray imaging module from multiple angles;
the three-dimensional image reconstruction module is configured to reconstruct the two-dimensional images at a plurality of different angles by adopting any one image reconstruction algorithm including a translation-superposition method, a filtering back projection method and an iterative reconstruction method to form a three-dimensional image and voxel data in an imaging area.
Further, in the X-ray imaging module, the adopted X-ray imaging device specifically includes:
the X-ray emitting end is used for emitting X-rays to the specified examination part;
the X-ray receiving end is used for receiving X-rays after the X-rays emitted by the X-ray emitting end penetrate through the designated inspection part, meanwhile, the X-ray receiving end and the X-ray emitting end move in parallel and synchronously during imaging, the designated inspection part is irradiated by pulses at a certain time interval in the moving process, and along with the relative movement of the X-ray emitting end, the X-ray receiving end and the designated inspection part, the projection imaging of the X-rays on the X-ray receiving end continuously changes to obtain the two-dimensional images at a plurality of different angles.
Further, still include: the X-ray imaging device adopts any one of two forms including standing and lying to image the appointed examination part.
Further, when the X-ray imaging apparatus performs imaging in a standing mode, the X-ray imaging apparatus further includes: a vertical transmission mechanism;
the vertical transmission mechanism is used for fixing the X-ray transmitting end and the X-ray receiving end and realizing the simultaneous operation of the X-ray transmitting end and the X-ray receiving end by utilizing a motion control system;
wherein the vertical transmission mechanism may include one or two vertical transmission units; when the number of the vertical transmission units is one, the X-ray transmitting end and the X-ray receiving end are fixed in a mode including a C-shaped arm to form a stable C-shaped structure which is fixed on the vertical transmission units, and a motion control system is adopted to control the C-shaped structure to move up and down; when the number of the vertical transmission units is two, the X-ray transmitting end and the X-ray receiving end are respectively fixed on the two vertical transmission units, and the motion control system is adopted to control the X-ray transmitting end and the X-ray receiving end to operate simultaneously.
Further, still include: the vertical transmission mechanism adopts any one form including a stand column type and a suspension type.
Further, when the X-ray imaging apparatus performs imaging in a lying-down form, the X-ray imaging apparatus further includes: c-arm and hospital bed;
the C-shaped arm is configured to fix the X-ray emitting end and the X-ray receiving end in an opposite form;
the patient bed is configured to be laid down for the object to be imaged;
wherein at least one of the C-arm and the patient bed is horizontally movable.
Further, the three-dimensional image reconstruction module has a specific reconstruction mode:
dispersing the space where the specified inspection part is located into a plurality of cuboid units with the same size, and marking as voxels; a group of rectangular planes of the voxels are parallel to the X-ray receiving end, the absorption rate of all centroids in the voxels to the X-ray is the same, the central coordinate V (X, y, z) of the voxels represents the spatial position of the voxels, X represents the horizontal position of the voxels, y represents the vertical height position of the voxels, and z represents the distance from the voxels to the X-ray receiving end;
the image reconstruction means solving the problem of the X-ray absorption rate a (X, y, z) of all or part of voxels of the specified examination part, including methods such as a translation-superposition method, a filtered back-projection method, and an iterative reconstruction method, and specifically includes:
a: a translation-superposition method, wherein K target planes are obtained by intercepting the space of the specified inspection part by using K planes which are parallel to the X-ray receiving end at equal intervals, each target plane contains M voxels to be solved, the vertical distances from all the voxels in the target plane to the X-ray receiving end are the same, and the vertical distances from the X-ray emitting end to the X-ray receiving end are the same, so that the amplification rates of the voxels shooting the same target plane are the same;
z for the target planekInner arbitrary voxel V (x)i,yi,zk) Projection v (X) in the X-ray receiver planeij,yij) Comprises the following steps:
in the formula HjThe height position of the jth X-ray emitting end is represented, D represents the vertical distance from the X-ray emitting end to the X-ray receiving end, and assuming that N rays penetrate through a voxel V (X) in the whole process of the movement of the X-ray emitting end and the X-ray receiving endi,yi,z0) At the X-ray emitting endAt a height HjProjecting data P obtained by emitting X-rays penetrating voxelsjThen, the target voxel absorption rate A (x) can be obtained by the following translation-superposition methodi,yi,zk):
In the formula hjRepresenting the central height position of the jth X-ray receiving end, traversing all voxels V to be solved in the target planeiObtaining the X-ray absorption rate A of all voxels to be solved in the target planei(i-1, 2, …, M), traversing all of the object planes z-z to be solvedk(K ═ 1,2, …, K), that is, three-dimensional volume data of the space in which the specified examination site is located can be obtained;
B) the filtering back projection method is based on the Rodon transformation, projection data are processed by using a filtering function in a Fourier space, and then the filtered projection data are back projected to reconstruct target volume data;
the X-ray emission end generates cone-shaped beam X-rays, linear projection sampling is carried out on the space of the specified inspection part, however, the X-rays emitted by the X-ray emission end at a certain height are not parallel to each other, the X-rays are required to be rearranged to form a parallel projection environment, a filtering back projection method can be used, the X-rays emitted by the X-ray emission end at a certain height can be uniquely determined by a space direction angle, the ray direction angle range depends on the view field size of a radioactive source, and the space direction angle (phi, theta) of the X-rays and the view field angle alpha of the radioactive source have the following characteristics:
wherein W represents the height dimension of the X-ray receiving end, and D represents the distance from the X-ray emitting end to the X-ray receiving endVertical distance of receiving end, the X-ray emitting end vertically moving to different heights HiCan emit rays I (phi, theta, H) with the same direction anglei) A set of rays L for parallel linear scanning of the specified examination region space may be formed satisfying:
rearranging the projection data of all the rays in the ray group L to obtain a one-dimensional back projection environment; and traversing all the direction angle combinations to obtain a three-dimensional back projection environment T (phi, theta, H), wherein for the three-dimensional space voxel absorption rate A (x, y, z) and the three-dimensional projection data P (x, y, z) of the specified inspection part:
via a three-dimensional fourier transform, one can obtain:
AF(ωx，ωy，ωz)＝TF(ωx，ωy，ωz)·PF(ωx，ωy，ωz)
in the formula PF，TF，AFThe three-dimensional Fourier transformation of P, T and A is respectively expressed, and the following filters are designed to realize the spatial filtering processing of the three-dimensional projection data:
T′F＝TS(ωx，ωy)·TP(ωz)·TI·TF
in the formula TI，TP，TS，T’FRespectively represents TFAn approximation of the inverse matrix, a modulation filter function in the z-direction, a modulation filter function in the x-y plane,and (3) an actual filtering back projection function, namely performing filtering back projection on the three-dimensional projection data in a Fourier space, and obtaining the three-dimensional volume data to be reconstructed through inverse Fourier transform:
A(x，y，z)＝FT-1(Ts·TP·TI·TF·PF)
c: the iterative reconstruction method is used for reconstructing an iterative method with low projection data completeness, the reconstruction mode comprises an algebraic iterative reconstruction method, a target reconstruction object is set to be discrete volume data, each voxel is a uniform substance, and the following relationship between the reconstruction data and a projection image is established:
the matrix A is a system matrix and determined for the whole image equipment, the matrix T is image data to be solved, P is projection data, N in the matrix is the number of detection units, M is the number of voxels, an algebraic iterative reconstruction target is the solution of the equation set, iterative correction is performed on the target reconstruction image by adopting errors of the projection data and real data, and the iterative formula is as follows:
wherein gamma is a relaxation factor, the adjustment is carried out according to the expected reconstruction speed and precision, the above formula is that the error of only one ray is considered, the image of all rays to the voxel is comprehensively considered, and the following iterative formula of joint iterative reconstruction can be adopted for solving:
further, the X-ray emitting end is a bulb tube.
Furthermore, the X-ray receiving end is a flat panel detector.
Furthermore, the system of the invention also comprises an image cutting module;
the image cutting module is configured to, when a slice image on a specific plane in the three-dimensional image needs to be acquired, acquire a pixel value of the specific plane in the three-dimensional image, and obtain the slice images of different faults.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides an X-ray tomography system, which not only effectively utilizes the advantages of high shooting efficiency and lower CT dose of Tomosynthesis technology in the aspect of three-dimensional imaging, but also breaks through the limitation of the Tomosynthesis three-dimensional imaging range, meets the continuous pulse shooting and three-dimensional imaging of a longer region of a human body, and meets the requirements of specific clinical diagnosis scenes comprising the full length of the human body, the full length of the spine or the full length of lower limbs.
The X-ray tomography system realizes that the X-ray transmitting end and the X-ray receiving end continuously move in the same direction along the vertical or horizontal direction, and continuously transmits X-pulse rays to an imaging area positioned between the transmitting end and the receiving end in the moving process to form a plurality of two-dimensional plane images distributed in the whole imaging area at different angles; acquiring voxel data from a plurality of two-dimensional images distributed in the whole imaging space at different angles through an image reconstruction algorithm, and reconstructing a three-dimensional image; when the slice of a specific plane needs to be obtained, the pixel values of the voxel data in the specific plane are obtained through a multi-plane cutting algorithm, and slice images of different faults are obtained. The invention can break through the limitation of the existing Tomosynthesis system on the three-dimensional imaging area to a great extent.
Drawings
FIG. 1 is a schematic view of a wheelchair patient photography of the Sonilialvision safire II large flat panel gastrointestinal machine island;
FIG. 2 is a schematic view of a patient in a stretcher with Soneriavian cuff II;
FIG. 3 is an overall block diagram of a tomographic imaging system of the present invention;
FIG. 4 is a schematic view of the present invention showing a multi-angle shot of a designated examination part;
FIG. 5 is a schematic diagram of multi-angle shooting of a designated examination part according to the present invention;
FIG. 6 is a schematic view of a stand mode X-ray imaging apparatus of the present invention;
fig. 7 is a schematic view of the X-ray imaging apparatus of the present invention in a lying mode with the patient bed 15 movable and the C-arm 14 stationary;
FIG. 8 is a schematic view of the present invention in a lying mode with the C-arm 14 movable and the patient bed 15 stationary;
fig. 9 is a schematic view of the X-ray imaging apparatus of the present invention in a lying mode in which both the C-arm 14 and the patient bed 15 are movable.
Reference numerals:
11. an X-ray emitting end; 12. an X-ray receiving end; 13. a vertical transmission unit; 14. a C-shaped arm; 15. a hospital bed; 16. and (6) stepping on the platform.
Detailed Description
Unless otherwise defined, technical or scientific terms used herein in the specification and claims should have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.
Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It is noted that in the detailed description of these embodiments, in order to provide a concise description, all features of an actual implementation may not be described in detail.
Examples
As shown in fig. 3, the present embodiment provides a tomographic imaging system comprising: the X-ray imaging module 1, the two-dimensional image receiving module 2 and the three-dimensional image reconstruction module 3;
the X-ray imaging module 1 is configured to acquire a multi-angle two-dimensional image of a designated examination part of an object to be imaged by using an X-ray imaging device.
Specifically, the X-ray imaging module is a two-dimensional image acquisition module at the front end of the invention, so as to acquire a multi-angle two-dimensional image for a specified inspection part and provide data support for the reconstruction of a subsequent three-dimensional image.
It should be noted that the present invention does not specifically limit the X-ray imaging device used by the X-ray imaging module, and only needs to be able to acquire a multi-angle two-dimensional image of a designated examination portion.
The following are specific examples of specific X-ray imaging devices:
in the X-ray imaging module, the adopted X-ray imaging device specifically includes:
an X-ray emitting end 11 for emitting X-rays to the specified examination part;
the X-ray receiving end 12 is configured to receive X-rays after the X-rays emitted by the X-ray emitting end pass through the designated examination portion, and meanwhile, the X-ray receiving end and the X-ray emitting end move in parallel and synchronously during imaging, the designated examination portion is irradiated with pulses at a certain time interval during the movement, and along with the relative movement of the X-ray emitting end 11, the X-ray receiving end 12 and the designated examination portion, the projection imaging of the X-rays on the X-ray receiving end 12 continuously changes, so that the two-dimensional images at a plurality of different angles are obtained.
As shown in fig. 4 and 5, when the X-ray emitting end 11 and the X-ray receiving end 12 move relative to the designated examination portion, the projection imaging of the X-ray on the X-ray receiving end 12 changes continuously, and the specific principle of obtaining a plurality of multi-angle two-dimensional images is as follows: the X-ray transmitting end 11 is a bulb tube, the transmitted X-rays are scattered out in a conical column mode by taking the bulb tube as a center, when the X-ray transmitting end 11 moves relative to the designated inspection part, X-rays with different angles are injected into the designated inspection part, and therefore two-dimensional images with different angles are shot on the designated inspection part.
Further, the X-ray imaging device can image the appointed examination part in any one of two forms including standing and lying.
As shown in fig. 6, which is a schematic diagram of an X-ray imaging apparatus in a standing mode, when the X-ray imaging apparatus performs imaging in a standing mode, the X-ray imaging apparatus further includes: a vertical transmission mechanism 13;
the vertical transmission mechanism 13 is used for fixing the X-ray transmitting end 11 and the X-ray receiving end 12 and realizing the simultaneous operation of the X-ray transmitting end and the X-ray receiving end by utilizing a motion control system;
wherein the vertical transmission mechanism 13 may include one or two vertical transmission units; when the number of the vertical transmission units 13 is one, the X-ray emitting end 11 and the X-ray receiving end 12 are fixed in a manner of including a C-shaped arm (not shown in the figure), so as to form a stable C-shaped structure fixed on the vertical transmission unit 13, and the C-shaped structure is controlled to move up and down by a motion control system; when the number of the vertical transmission units 13 is two, the X-ray transmitting end 11 and the X-ray receiving end 12 are respectively fixed on the two vertical transmission units 13, and the motion control system is adopted to control the X-ray transmitting end and the X-ray receiving end to operate simultaneously.
Further, the vertical transmission mechanism 13 may be of any type, including a column type or a suspension type.
As shown in fig. 7 to 9, when the X-ray imaging apparatus performs imaging in a lying state, the X-ray imaging apparatus further includes: a C-arm 14 and a patient bed 15;
the C-shaped arm 14 is configured for fixing the X-ray emitting end 11 and the X-ray receiving end 12 in an opposite manner;
the patient bed 15 configured to lie flat for the object to be imaged;
at least one of the C-shaped arm 14 and the sickbed 15 can move horizontally (as shown in fig. 7, the sickbed 15 is movable, and the C-shaped arm 14 is not movable; as shown in fig. 8, the C-shaped arm 14 is movable, and the sickbed 15 is not movable; as shown in fig. 9, both the C-shaped arm 14 and the sickbed 15 are movable).
The two-dimensional image receiving module 2 is configured to receive the two-dimensional images of the designated examination part acquired in the X-ray imaging module 1 from multiple angles.
Specifically, the two-dimensional image receiving module 2 is configured to obtain and receive a multi-angle two-dimensional image of a designated examination portion photographed in the X-ray imaging module 1, and provide the multi-angle two-dimensional image to the subsequent three-dimensional image reconstruction module 3 for reconstructing a three-dimensional image.
The three-dimensional image reconstruction module 3 is configured to reconstruct a three-dimensional image from a plurality of two-dimensional images at different angles by using any one image reconstruction algorithm including a translation-superposition method, a filtered back-projection method, and an iterative reconstruction method, so as to form voxel data in an imaging region.
Further, the three-dimensional image reconstruction module has a specific reconstruction mode:
dispersing the space where the specified inspection part is located into a plurality of cuboid units with the same size, and marking as voxels; a group of rectangular planes of the voxels are parallel to the X-ray receiving end, the absorption rate of all centroids in the voxels to the X-ray is the same, the central coordinate V (X, y, z) of the voxels represents the spatial position of the voxels, X represents the horizontal position of the voxels, y represents the vertical height position of the voxels, and z represents the distance from the voxels to the X-ray receiving end;
the image reconstruction means solving the problem of the X-ray absorption rate a (X, y, z) of all or part of voxels of the specified examination part, including methods such as a translation-superposition method, a filtered back-projection method, and an iterative reconstruction method, and specifically includes:
a: a translation-superposition method, wherein K target planes are obtained by intercepting the space of the specified inspection part by using K planes which are parallel to the X-ray receiving end at equal intervals, each target plane contains M voxels to be solved, the vertical distances from all the voxels in the target plane to the X-ray receiving end are the same, and the vertical distances from the X-ray emitting end to the X-ray receiving end are the same, so that the amplification rates of the voxels shooting the same target plane are the same;
z for the target planekInner arbitrary voxel V (x)i,yi,zk) Projection v (X) in the X-ray receiver planeij,yij) Comprises the following steps:
in the formula HjThe height position of the jth X-ray emitting end is represented, D represents the vertical distance from the X-ray emitting end to the X-ray receiving end, and assuming that N rays penetrate through a voxel V (X) in the whole process of the movement of the X-ray emitting end and the X-ray receiving endi,yi,z0) The X-ray emitting end is at highDegree HjProjecting data P obtained by emitting X-rays penetrating voxelsjThen, the target voxel absorption rate A (x) can be obtained by the following translation-superposition methodi,yi,zk):
In the formula hjRepresenting the central height position of the jth X-ray receiving end, traversing all voxels V to be solved in the target planeiObtaining the X-ray absorption rate A of all voxels to be solved in the target planei(i-1, 2, …, M), traversing all of the object planes z-z to be solvedk(K ═ 1,2, …, K), that is, three-dimensional volume data of the space in which the specified examination site is located can be obtained;
B) the filtering back projection method is based on the Rodon transformation, projection data are processed by using a filtering function in a Fourier space, and then the filtered projection data are back projected to reconstruct target volume data;
the X-ray emission end generates cone-shaped beam X-rays, linear projection sampling is carried out on the space of the specified inspection part, however, the X-rays emitted by the X-ray emission end at a certain height are not parallel to each other, the X-rays are required to be rearranged to form a parallel projection environment, a filtering back projection method can be used, the X-rays emitted by the X-ray emission end at a certain height can be uniquely determined by a space direction angle, the ray direction angle range depends on the view field size of a radioactive source, and the space direction angle (phi, theta) of the X-rays and the view field angle alpha of the radioactive source have the following characteristics:
wherein W represents the height dimension of the X-ray receiving end, and D represents the distance from the X-ray emitting end to the X-ray receiving endThe X-ray emitting end moves vertically to different heights HiCan emit rays with the same direction angle l (phi, theta, H)i) A set of rays L for parallel linear scanning of the specified examination region space may be formed satisfying:
rearranging the projection data of all the rays in the ray group L to obtain a one-dimensional back projection environment; and traversing all the direction angle combinations to obtain a three-dimensional back projection environment T (phi, theta, H), wherein for the three-dimensional space voxel absorption rate A (x, y, z) and the three-dimensional projection data P (x, y, z) of the specified inspection part:
via a three-dimensional fourier transform, one can obtain:
AF(ωx，ωy,ωz)＝TF(ωx，ωy，ωz).PF(ωx，ωy,ωz)
in the formula PF,TF,AFThe three-dimensional Fourier transformation of P, T and A is respectively expressed, and the following filters are designed to realize the spatial filtering processing of the three-dimensional projection data:
T′F＝Ts(ωx，ωy)·TP(ωz)，TI·TF
in the formula TI,TP,TS,T’FRespectively represents TFApproximation of the inverse matrix, modulation filter function in the z-direction, modulation filter function in the x-y plane, actual filtered back-projection function, in the fourier spaceCarrying out filtering back projection on the three-dimensional projection data in the middle, and obtaining the three-dimensional volume data to be reconstructed through inverse Fourier transform:
A(x，y，z)＝FT-1(Ts·TP·TI·TF·PF)
c: the iterative reconstruction method is used for reconstructing an iterative method with low projection data completeness, the reconstruction mode comprises an algebraic iterative reconstruction method, a target reconstruction object is set to be discrete volume data, each voxel is a uniform substance, and the following relationship between the reconstruction data and a projection image is established:
the matrix A is a system matrix and determined for the whole image equipment, the matrix T is image data to be solved, P is projection data, N in the matrix is the number of detection units, M is the number of voxels, an algebraic iterative reconstruction target is the solution of the equation set, iterative correction is performed on the target reconstruction image by adopting errors of the projection data and real data, and the iterative formula is as follows:
wherein gamma is a relaxation factor, the adjustment is carried out according to the expected reconstruction speed and precision, the above formula is that the error of only one ray is considered, the image of all rays to the voxel is comprehensively considered, and the following iterative formula of joint iterative reconstruction can be adopted for solving:
the above is a specific example of the three-dimensional reconstruction algorithm, and other three-dimensional reconstruction methods can be applied to the present invention, which is not limited in particular.
Further, the X-ray emitting end is a bulb tube.
Furthermore, the X-ray receiving end is a flat panel detector.
Further, the system of the present invention further comprises: an image cutting module 4;
the image segmentation module 4 is configured to, when a slice image on a specific plane in the three-dimensional image needs to be acquired, acquire a pixel value of the specific plane in the three-dimensional image, and obtain the slice images of different slices.
Specifically, after the three-dimensional reconstruction by the three-dimensional image reconstruction module 3, the pixel value of any one point in the entire three-dimensional space can be obtained. When the slice image on the specific plane in the three-dimensional image needs to be acquired, the pixel value of the specific plane in the three-dimensional image is acquired, and the slice images of different faults are obtained.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (10)
1. A tomographic imaging system, comprising: the X-ray imaging module, the two-dimensional image receiving module and the three-dimensional image reconstruction module are connected with the X-ray imaging module;
the X-ray imaging module is configured to adopt an X-ray imaging device to acquire a multi-angle two-dimensional image of a specified inspection part of an object to be imaged;
the two-dimensional image receiving module is configured to receive the two-dimensional images of the designated examination part acquired in the X-ray imaging module from multiple angles;
the three-dimensional image reconstruction module is configured to reconstruct the two-dimensional images at a plurality of different angles by adopting any one image reconstruction algorithm including a translation-superposition method, a filtering back projection method and an iterative reconstruction method to form a three-dimensional image and voxel data in an imaging area.
2. The tomography system of claim 1, wherein in the X-ray imaging module, the X-ray imaging device employed comprises in particular:
the X-ray emitting end is used for emitting X-rays to the specified examination part;
the X-ray receiving end is used for receiving X-rays after the X-rays emitted by the X-ray emitting end penetrate through the designated inspection part, meanwhile, the X-ray receiving end and the X-ray emitting end move in parallel and synchronously during imaging, the designated inspection part is irradiated by pulses at a certain time interval in the moving process, and along with the relative movement of the X-ray emitting end, the X-ray receiving end and the designated inspection part, the projection imaging of the X-rays on the X-ray receiving end continuously changes to obtain the two-dimensional images at a plurality of different angles.
3. The tomography system of claim 2, further comprising: the X-ray imaging device adopts any one of two forms including standing and lying to image the appointed examination part.
4. The tomography system of claim 3, wherein when the X-ray imaging device is in a standing configuration for imaging, the X-ray imaging device further comprises: a vertical transmission mechanism;
the vertical transmission mechanism is used for fixing the X-ray transmitting end and the X-ray receiving end and realizing the simultaneous operation of the X-ray transmitting end and the X-ray receiving end by utilizing a motion control system;
wherein the vertical transmission mechanism may include one or two vertical transmission units; when the number of the vertical transmission units is one, the X-ray transmitting end and the X-ray receiving end are fixed in a mode including a C-shaped arm to form a stable C-shaped structure which is fixed on the vertical transmission units, and a motion control system is adopted to control the C-shaped structure to move up and down; when the number of the vertical transmission units is two, the X-ray transmitting end and the X-ray receiving end are respectively fixed on the two vertical transmission units, and the motion control system is adopted to control the X-ray transmitting end and the X-ray receiving end to operate simultaneously.
5. The tomography system of claim 4, further comprising: the vertical transmission mechanism adopts any one form including a stand column type and a suspension type.
6. The tomography system of claim 3, wherein when said X-ray imaging apparatus is in a lay-flat form for imaging, said X-ray imaging apparatus further comprises: c-arm and hospital bed;
the C-shaped arm is configured to fix the X-ray emitting end and the X-ray receiving end in an opposite form;
the patient bed is configured to be laid down for the object to be imaged;
wherein at least one of the C-arm and the patient bed is horizontally movable.
7. The tomography system of claim 2, wherein the three-dimensional image reconstruction module has the following specific reconstruction modes:
dispersing the space where the specified inspection part is located into a plurality of cuboid units with the same size, and marking as voxels; a group of rectangular planes of the voxels are parallel to the X-ray receiving end, the absorption rate of all centroids in the voxels to the X-ray is the same, the central coordinate V (X, y, z) of the voxels represents the spatial position of the voxels, X represents the horizontal position of the voxels, y represents the vertical height position of the voxels, and z represents the distance from the voxels to the X-ray receiving end;
the image reconstruction means solving the problem of the X-ray absorption rate a (X, y, z) of all or part of voxels of the specified examination part, including methods such as a translation-superposition method, a filtered back-projection method, and an iterative reconstruction method, and specifically includes:
a: a translation-superposition method, wherein K target planes are obtained by intercepting the space of the specified inspection part by using K planes which are parallel to the X-ray receiving end at equal intervals, each target plane contains M voxels to be solved, the vertical distances from all the voxels in the target plane to the X-ray receiving end are the same, and the vertical distances from the X-ray emitting end to the X-ray receiving end are the same, so that the amplification rates of the voxels shooting the same target plane are the same;
z for the target planekInner arbitrary voxel V (x)i,yi,zk) Projection v (X) in the X-ray receiver planeij,yij) Comprises the following steps:
in the formula HjThe height position of the jth X-ray emitting end is represented, D represents the vertical distance from the X-ray emitting end to the X-ray receiving end, and assuming that N rays penetrate through a voxel V (X) in the whole process of the movement of the X-ray emitting end and the X-ray receiving endi,yi,z0) The X-ray emitting end is at a height HjProjecting data P obtained by emitting X-rays penetrating voxelsjThen, the target voxel absorption rate A (x) can be obtained by the following translation-superposition methodi,yi,zk):
In the formula hjRepresenting the central height position of the jth X-ray receiving end, traversing all voxels V to be solved in the target planeiCan obtain theX-ray absorption rate A of all voxels to be solved in the target planei(i-1, 2, …, M), traversing all of the object planes z-z to be solvedk(K ═ 1,2, …, K), that is, three-dimensional volume data of the space in which the specified examination site is located can be obtained;
B) the filtering back projection method is based on the Rodon transformation, projection data are processed by using a filtering function in a Fourier space, and then the filtered projection data are back projected to reconstruct target volume data;
the X-ray emission end generates cone-shaped beam X-rays, linear projection sampling is carried out on the space of the specified inspection part, however, the X-rays emitted by the X-ray emission end at a certain height are not parallel to each other, the X-rays are required to be rearranged to form a parallel projection environment, a filtering back projection method can be used, the X-rays emitted by the X-ray emission end at a certain height can be uniquely determined by a space direction angle, the ray direction angle range depends on the view field size of a radioactive source, and the space direction angle (phi, theta) of the X-rays and the view field angle alpha of the radioactive source have the following characteristics:
wherein W represents the height dimension of the X-ray receiving terminal, D represents the vertical distance from the X-ray transmitting terminal to the X-ray receiving terminal, and the X-ray transmitting terminal vertically moves to different heights HiCan emit rays I (phi, theta, H) with the same direction anglei) A set of rays L for parallel linear scanning of the specified examination region space may be formed satisfying:
rearranging the projection data of all the rays in the ray group L to obtain a one-dimensional back projection environment; and traversing all the direction angle combinations to obtain a three-dimensional back projection environment T (phi, theta, H), wherein for the three-dimensional space voxel absorption rate A (x, y, z) and the three-dimensional projection data P (x, y, z) of the specified inspection part:
via a three-dimensional fourier transform, one can obtain:
AF(ωx，ωy，ωz)＝TF(ωx，ωy，ωz)·PF(ωx，ωy，ωz)
in the formula PF，TF，AFThe three-dimensional Fourier transformation of P, T and A is respectively expressed, and the following filters are designed to realize the spatial filtering processing of the three-dimensional projection data:
T′F＝Ts(ωx，ωy)·TP(ωz)·TI·TF
in the formula TI，TP，TS，T’FRespectively represents TFApproximation of an inverse matrix, a modulation filtering function in the z direction, a modulation filtering function in an x-y plane, and an actual filtering back-projection function, filtering back-projection is performed on three-dimensional projection data in a Fourier space, and three-dimensional volume data to be reconstructed can be obtained through Fourier inverse transformation:
A(x，y，z)＝FT-1(TS·TP·TI·TF·PF)
c: the iterative reconstruction method is used for reconstructing an iterative method with low projection data completeness, the reconstruction mode comprises an algebraic iterative reconstruction method, a target reconstruction object is set to be discrete volume data, each voxel is a uniform substance, and the following relationship between the reconstruction data and a projection image is established:
the matrix A is a system matrix and determined for the whole image equipment, the matrix T is image data to be solved, P is projection data, N in the matrix is the number of detection units, M is the number of voxels, an algebraic iterative reconstruction target is the solution of the equation set, iterative correction is performed on the target reconstruction image by adopting errors of the projection data and real data, and the iterative formula is as follows:
wherein gamma is a relaxation factor, the adjustment is carried out according to the expected reconstruction speed and precision, the above formula is that the error of only one ray is considered, the image of all rays to the voxel is comprehensively considered, and the following iterative formula of joint iterative reconstruction can be adopted for solving:
8. the tomography system of claim 2, further comprising: the X-ray emitting end is a bulb tube.
9. The tomography system of claim 2, further comprising: the X-ray receiving end is a flat panel detector.
10. The tomography system of claim 1, further comprising: an image cutting module;
the image cutting module is configured to, when a slice image on a specific plane in the three-dimensional image needs to be acquired, acquire a pixel value of the specific plane in the three-dimensional image, and obtain the slice images of different faults.
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