A static real-time CT imaging system and imaging method thereof

Abstract

The present invention discloses a static real-time CT imaging system and an imaging method thereof. The system includes two ray source rings and a detector ring; on the Z axis, the left ray source ring and the right ray source ring are arranged on the left and right sides of the detector ring; the left ray source ring and the right ray source ring are respectively annular multi-focus X-ray sources with multiple X-ray sources and the same number of focuses are evenly arranged; the detector ring is composed of multiple X-ray detectors arranged in a ring, and on the Z axis, the multiple X-ray detectors together form a left detector sub-ring, a middle detector sub-ring and a right detector sub-ring; an X-ray source of the left ray source ring is placed between any two adjacent X-ray detectors of the left detector sub-ring; an X-ray source of the right ray source ring is placed between any two adjacent X-ray detectors of the right detector sub-ring; and any two adjacent X-ray detectors of the middle detector sub-ring are in close contact. By using the present invention, a wider Z-direction coverage can be achieved, and cone angle artifacts can be effectively suppressed.

Description

Technical Field

[0001] The invention relates to a static real-time CT imaging system and also to a corresponding static real-time CT imaging method, belonging to the technical field of medical imaging. Background Art

[0002] CT (Computed Tomography) is the abbreviation of computer tomography technology. Its imaging principle is as follows: X-ray beams and highly sensitive X-ray detectors are used to perform layer-by-layer section scanning around a certain part of the human body. The X-rays that pass through the layer are received by the X-ray detector and converted into electrical signals by the photoelectric converter. After amplification, they are converted into digital signals through analog / digital conversion and input into the computer for processing. In the computer, the selected layer is divided into several cubes of the same volume, called voxels. After the information obtained from the layer-by-layer section scanning is calculated, the X-ray attenuation coefficient or absorption coefficient of each voxel is obtained, and then arranged into a matrix, namely the voxel digital matrix. The digital information in the voxel digital matrix is ​​converted into small squares with varying grayscales from black to white, which are called pixels on a two-dimensional projection. Arranged in a tomographic manner to form a CT image.

[0003] In order to increase the scanning speed, improve the imaging accuracy and speed, avoid the influence of the centrifugal force caused by mechanical rotation, and reduce the signal tailing effect and overlapping crosstalk during high-speed rotation, the applicant disclosed a static real-time CT imaging system in the Chinese patent No. ZL 201410425061.2. The static real-time CT imaging system includes an annular X-ray detector, an annular scanning X-ray source and a scanning timing controller. During the scanning process of the above-mentioned static real-time CT imaging system, the annular scanning X-ray source does not need to rotate significantly, and the X-ray projection position is switched in sequence through electronic control, so that the scanning speed is increased by dozens of times, and a dynamic three-dimensional stereo image can be obtained: using an X-ray detector, absorption data and energy data can be obtained, and real-time data reconstruction can be achieved.

[0004] In addition, in the Chinese patent application with application number 201910865387.X, a static real-time CT imaging system and imaging control method with paired ray source rings are disclosed. It arranges a ray source on the left and right sides of the detector ring, and reconstructs the projection areas of the two ray source rings to obtain two reconstructed FOVs. However, there is a gap area between the two FOVs. Although the gap area can be supplemented in the spiral scanning mode, there is no way to supplement the gap area in a single axial scan. Therefore, there are certain limitations in the application of expanding the scanning coverage. Summary of the invention

[0005] The primary technical problem to be solved by the present invention is to provide a static real-time CT imaging system.

[0006] Another technical problem to be solved by the present invention is to provide a static real-time CT imaging method.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] According to a first aspect of an embodiment of the present invention, there is provided a static real-time CT imaging system, comprising at least two ray source rings and one detector ring;

[0009] Wherein, on the Z axis, the left ray source ring and the right ray source ring are arranged on the left and right sides of the detector ring, and the two ray source rings share one detector ring;

[0010] The left ray source ring and the right ray source ring are respectively annular multi-focus X-ray sources with multiple X-ray sources, and the same number of focal spots are evenly arranged on the left ray source ring and the right ray source ring; the detector ring is composed of multiple X-ray detectors arranged in a ring, and on the Z axis, the multiple X-ray detectors together form a left detector sub-ring, a middle detector sub-ring and a right detector sub-ring;

[0011] On the left detector sub-ring, a first gap is formed between any two adjacent X-ray detectors for placing the X-ray source of the left ray source ring; on the right detector sub-ring, a second gap is formed between any two adjacent X-ray detectors for placing the X-ray source of the right ray source ring; on the middle detector sub-ring, any two adjacent X-ray detectors are in close contact.

[0012] Preferably, the sizes of the multiple X-ray detectors are the same, and the multiple X-ray detectors are arranged in a staggered manner to form the left detector sub-ring, the middle detector sub-ring and the right detector sub-ring; the foci of the left ray source ring and the right ray source ring are relatively staggered.

[0013] Preferably, the X-ray detector includes a short-size X-ray detector and a long-size X-ray detector; wherein a plurality of the short-size X-ray detectors and a plurality of long-size X-ray detectors are cross-arranged in sequence to form the left detector sub-ring, the middle detector sub-ring and the right detector sub-ring; and the left ray source ring and the right ray source ring are symmetrically arranged on the left and right sides of the detector ring.

[0014] Preferably, the X-ray detector includes a main detector and a scattering detector, and the scattering detector is arranged on one side or both sides of the main detector;

[0015] A beam limiter is provided between the X-ray source and the X-ray detector to limit the ray coverage of the X-ray source to only cover the main detector.

[0016] Preferably, the beam limiter specifically comprises:

[0017] A Z-direction beam limiting device, which can open and close on the Z axis to limit the coverage of the X-ray source beam in the Z direction;

[0018] An X-axis beam limiting device, which can open and close on the X-axis to limit the coverage of the X-ray beam of the X-ray source in the X-axis;

[0019] The Z direction is the axial direction of the detector ring, and the X direction is the tangential direction of the detector ring.

[0020] Preferably, the Z-direction beam limiting device comprises a Z-direction fixed portion and a Z-direction movable portion, wherein the Z-direction fixed portion is fixedly arranged along the Z-axis direction, and the Z-direction movable portion approaches or moves away from the Z-direction fixed portion along the Z-axis direction to adjust the size of the opening between the Z-direction fixed portion and the Z-direction movable portion;

[0021] The X-direction beam limiting device comprises two X-direction movable parts, and the two X-direction movable parts are moved closer to or farther away from each other along the X-axis direction to adjust the size of the opening between the two X-direction movable parts.

[0022] Preferably, the multiple X-ray sources in the left ray source ring and the right ray source ring perform axial scanning in any of the following ways:

[0023] ① Expose a ray source on the left, expose a ray source on the right, then expose a ray source on the left, and so on. In this way, all ray sources are exposed alternately from left to right to obtain projection images of all ray sources;

[0024] ② The K ray sources on the left are exposed at the same time, and the X-ray detectors corresponding to the light field coverage of the K ray sources on the left are not shared. Then the K ray sources on the right are exposed at the same time, and the X-ray detectors corresponding to the light field coverage of the K ray sources on the right are not shared, and so on. In this way, all ray sources are exposed alternately on the left and right to obtain the projection diagrams of all ray sources; where K is a positive integer and not less than 2;

[0025] ③ The left ray source is exposed in turn, and only the projection image of the left ray source is obtained;

[0026] ④ The ray sources on the right are exposed in turn, and only the projection image of the ray sources on the right is obtained.

[0027] Preferably, the static real-time CT imaging system further comprises a scanning timing controller, and the exposure timing of the multiple focal points in the left ray source ring and the right ray source ring and the acquisition timing of the corresponding X-ray detectors in the detector ring are controlled by the scanning timing controller.

[0028] According to a second aspect of an embodiment of the present invention, a static real-time CT imaging method is provided, which is implemented based on the above-mentioned static real-time CT imaging system and includes at least the following steps:

[0029] The scanning timing controller controls the X-ray sources in the left and right ray source rings and the corresponding X-ray detectors in the detector ring to work in a predetermined scanning timing:

[0030] The multiple X-ray sources in the left ray source ring and the right ray source ring emit X-rays according to a predetermined exposure sequence, and the corresponding X-ray detectors collect projection information on the X-ray detectors after the X-rays pass through the object to be measured.

[0031] Preferably, the projection information includes left-side local projection information collected by the left detector sub-ring, complete projection information collected by the middle detector sub-ring, and right-side local projection information collected by the right detector sub-ring.

[0032] Compared with the prior art, the present invention has the following technical features:

[0033] 1. Due to the use of a double-ray source ring structure, the scanning coverage in the Z-axis direction is increased, and the left and right Z-direction coverage can be achieved without gaps. A single axis scan can achieve a wider Z-direction coverage range, and can further reduce the projection cone angle, effectively suppressing cone angle artifacts.

[0034] 2. The multiple X-ray sources (i.e., multiple focal points) in the left and right ray source rings can realize one-axis scanning in a variety of ways to meet different scanning requirements. In addition, the multiple focal points in the left and right ray source rings can realize energy spectrum scanning in a variety of ways.

[0035] 3. The photon counting detector is composed of a scattering detector and a main detector, so that the scattering detector can be used to measure the distribution of the scattering signal to achieve scattering correction.

[0036] 4. The beam limiter can adjust the radiation coverage of the X-ray source to meet different FOV range requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of the three-dimensional structure of a static real-time CT imaging system provided by the first embodiment of the present invention;

[0038] Figure 2 A partial top view of a static real-time CT imaging system in the first embodiment of the present invention;

[0039] Figure 3 It is a projection schematic diagram of a single ray source ring structure in the prior art;

[0040] Figure 4 It is a projection diagram of a double-ray source ring structure in the first embodiment of the present invention;

[0041] Figure 5 In the first embodiment of the present invention, the detector sub-ring is missing Z in the Z-axis direction. L The projection relationship diagram of the X-ray beam and the detector ring in the state;

[0042] Figure 6 In the first embodiment of the present invention, the detector sub-ring is missing Z in the Z-axis direction. R The projection relationship diagram of the X-ray beam and the detector ring in the state;

[0043] Figure 7 This is a projection relationship diagram of the X-ray beam and the detector ring in the first embodiment of the present invention, when the detector sub-ring is not missing in the Z-axis direction;

[0044] Figure 8 This is a projection relationship diagram of the X-ray beam and the detector ring in the first embodiment of the present invention, when the detector sub-ring is not missing in the X-axis direction;

[0045] Fig. 9 In the first embodiment of the present invention, the detector sub-ring lacks Z in the X-axis direction. L or missing Z R The projection relationship diagram of the X-ray beam and the detector ring under the state;

[0046] Fig.10 This is a schematic diagram of the timing of a single X-ray source emitting X-rays in sequence in the first embodiment of the present invention;

[0047] Fig.11 This is a timing diagram of three X-ray sources emitting X-rays synchronously in the first embodiment of the present invention;

[0048] Fig.12 This is a timing diagram of six X-ray sources emitting X-rays synchronously in the first embodiment of the present invention;

[0049] Fig.13 This is a schematic diagram of the structure of an X-ray detector in the first embodiment of the present invention;

[0050] Fig.14 Schematic diagram of beam limitation of an X-ray source and an X-ray detector in the first embodiment of the present invention;

[0051] Fig.15 This is a schematic diagram of the structure of the arrangement of the scattering detectors in the ZX plane using a sparse matrix in the first embodiment of the present invention;

[0052] Fig.16 This is a diagram showing the beam limiting principle of the Z-direction beam limiting device in the first embodiment of the present invention;

[0053] Fig.17 This is a beam limiting principle diagram of the X-direction beam limiting device in the first embodiment of the present invention;

[0054] Fig.18 A partial top view of a static real-time CT imaging system provided in the second embodiment of the present invention. DETAILED DESCRIPTION

[0055] The technical content of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] <First Embodiment>

[0057] like Figure 1 As shown, a static real-time CT imaging system provided by the first embodiment of the present invention comprises at least two ray source rings, a detector ring 3 and a scanning timing controller. In the Z-axis direction, the left ray source ring 1 and the right ray source ring 2 are arranged on the left and right sides of the detector ring 3, and the two ray source rings share one detector ring 3. Among them, the left ray source ring 1, the right ray source ring 2 and the detector ring 3 are installed on the rotating bracket through the bearing 1a, and the three are on the same axis, which is the Z axis commonly known in the CT field.

[0058] Specifically, in this embodiment, the left ray source ring 1 and the right ray source ring 2 are respectively annular multi-focus X-ray sources with multiple X-ray sources. N focal points are arranged on the left ray source ring 1 and the right ray source ring 2, that is, there are 2N focal points on the two ray source rings. Each focal point of the left ray source ring 1 is denoted as F Li , the foci of the right ray source ring 2 are denoted as F Ri , where i∈[1,N], and N foci F Li and N focal points F Ri Relatively staggered arrangement. Figure 2 As shown, the detector ring 3 is composed of a plurality of X-ray detectors 31 arranged in a ring shape, and the sizes of the plurality of X-ray detectors are the same. The plurality of X-ray detectors 31 are arranged alternately to form a left detector sub-ring Z. L , the detector sub-ring Z C and the right detector subring Z R Specifically, in the left detector sub-ring Z LA first gap 101 is formed between any two adjacent X-ray detectors for placing an X-ray source of a left ray source ring 1; R A second gap 102 is formed between any two adjacent X-ray detectors for placing an X-ray source of a right ray source ring 2; C Any two adjacent X-ray detectors are in close contact.

[0059] The exposure sequence of multiple focal points in the left ray source ring 1 and the right ray source ring 2 and the data acquisition sequence of the corresponding X-ray detectors in the detector ring 3 are controlled by the same scanning timing controller. The multiple X-ray sources in the left ray source ring 1 and the right ray source ring 2 emit X-rays according to the predetermined exposure sequence, and the corresponding X-ray detectors 31 in the detector ring 3 collect the projection information of the X-rays on the X-ray detector 31 after the X-rays pass through the object to be measured. It can be understood that the projection information in this embodiment includes the projection information according to the left detector sub-ring Z. L The local projection information on the left side is collected according to the detector sub-ring Z C The complete projection information collected and based on the right detector sub-ring Z R The right side local projection information is collected. Therefore, through the construction of the double ray source ring, the scanning coverage in the Z-axis direction is increased, and the left and right Z-direction coverage can be achieved without gaps. A single axis scan can achieve a wider Z-direction coverage, and can further reduce the projection cone angle, effectively suppressing cone angle artifacts.

[0060] The following is a detailed description of the differences between a single-ray source structure and a dual-ray source structure:

[0061] Figure 3 It is a schematic diagram of the Z-direction projection of a single ray source ring structure in the prior art. Figure 4 Fi is a Z-direction projection diagram of the dual-ray source ring structure in this embodiment. Li and F Ri are the two focal points in the Z direction of the dual-ray source ring structure in this embodiment, the rectangular dotted area is the image range that can be reconstructed in the Z direction corresponding to the two structures, and α1 and α2 correspond to the cone angles of projection in the two modes respectively. Figure 3 and Figure 4 It can be seen that when the detector Z-width remains unchanged and the vertical distance between the focus and the detector remains unchanged, α1>α2, Figure 3 Z-direction coverage< Figure 4 The Z-direction coverage range, that is, the Z-direction coverage range in this embodiment is larger and the cone angle of the ray beam is smaller, which can reduce the problem of cone angle artifacts in image reconstruction.

[0062] In addition, it can be understood that, due to the structure of the double ray source ring in this embodiment, the scanning coverage in the Z-axis direction is increased. Figure 4 It can be seen that the image range that can be reconstructed in the Z direction is larger to ensure the Z-direction coverage requirements of the CT machine in clinical applications.

[0063] Reference Figures 5 to 7 As shown in the figure, in the Z-axis direction, the X-ray beam and the detector ring are L , Z C and Z R Specifically, when the Z of the X-ray detector is L When the photosensitive element in the area is missing, the X-ray beam and the X-ray detector Z C and Z R Zone formation Figure 5 Similarly, when the X-ray detector's Z R When the photosensitive element in the area is missing, the Z of the X-ray beam and the X-ray detector C and Z L Formed as Figure 6 When the X-ray detector has a complete Z L , Z C and Z R The photosensitive element in the area, the ray beam and the X-ray detector form a Figure 7 The projection relationship shown.

[0064] Reference Figure 8 and Fig. 9 As shown, in the X-axis direction, the X-ray beam and the detector ring are L , Z C and Z R Two possible corresponding relationships are formed, wherein the X-axis direction is the tangential direction of the detector ring 3. Specifically, Figure 8 As shown, in the X-ray projection, the oblique line segment from the upper left to the lower right illustrates the actual X-ray projection geometry, the detector Z C The projection geometry corresponding to the area is a projection covering the entire FOV. Fig. 9 As shown, the detector ring Z L Zone and Z R In the projection of the radiation source, due to the partial loss of the detector photosensitive element, the detector ring Z L and Z R The projection of the region is missing in the X-axis direction (ie, the tangential direction). In this embodiment, the partial missing of the projection can be solved by a sparse sampling reconstruction algorithm, thereby achieving the integrity of the reconstructed image in the X-direction FOV.

[0065] In the above embodiment, the X-ray sources (i.e., multiple focal points) in the left ray source ring 1 and the right ray source ring 2 can achieve an axial scan in the following multiple ways. Specifically, at least the following four axial scan ways are included:

[0066] ① Expose a ray source on the left, then a ray source on the right, then another ray source on the left, and so on. In this way, all ray sources are exposed alternately from left to right to obtain projection images of all ray sources;

[0067] ② A group of K ray sources on the left are exposed at the same time, and the photon counting detectors 31 corresponding to the light field coverage range of the K ray sources on the left are not shared, then a group of K ray sources on the right are exposed at the same time, and the photon counting detectors 31 corresponding to the light field coverage range of the K ray sources on the right are not shared, then another group of ray sources on the left are exposed at the same time, and so on. In this way, all ray sources are exposed alternately from left to right to obtain projection images of all ray sources; where K is a positive integer and not less than 2;

[0068] ③ The left ray source is exposed in turn, and only the projection image of the left ray source is obtained;

[0069] ④ The ray sources on the right are exposed in turn, and only the projection image of the ray sources on the right is obtained.

[0070] In addition, in the axial scanning modes ①②③④, the exposure sequence of single or multiple focal points in different areas of a single ray source ring can also adopt a scanning sequence of simultaneous or time-sharing operation, point-by-point or point-by-point, line-by-line or line-by-line emission of X-rays. Each X-ray source in the left ray source ring 1 and the right ray source ring 2 can emit X-rays in sequence along the circumferential direction, or can emit X-rays in sequence with a plurality of X-ray sources spaced apart. The X-ray sources in the left ray source ring 1 and the right ray source ring 2 can emit X-rays only by a single X-ray source (refer to Fig.10 As shown), multiple X-ray sources can also emit X-rays in parallel (see Fig.11 and Fig.12 The maximum number of X-ray sources emitting X-rays in parallel is based on the premise that the X-rays emitted in parallel do not interfere with each other on the X-ray detector 31, and the circumferential distribution of the X-ray sources emitting X-rays in parallel is preferably uniform.

[0071] The X-rays emitted by the X-ray sources in the left ray source ring 1 and the right ray source ring 2 pass through the object to be measured and then irradiate the corresponding X-ray detector 31 in the detector ring 3. The data acquisition and processing unit is composed of multiple distributed subsystems, and an embedded GPU is integrated in the subsystem. The X-ray detector 31 collects the received X-ray projection information and performs image reconstruction processing on the data acquisition and processing unit, and the reconstructed image information is then transmitted to the image data storage unit and the human-computer interaction unit, and the image storage and visual reproduction are completed in the image data storage unit and the human-computer interaction unit. Of course, it is also possible to follow the existing CT data acquisition and processing method: the data acquisition and processing unit only collects data, and then transmits the data information to the image reconstruction unit and the data storage unit for reconstruction and storage.

[0072] The static real-time CT imaging system can realize energy spectrum scanning in various ways by using the multi-focus in the left ray source ring 1 and the right ray source ring 2. First, the left ray source ring 1 and the right ray source ring 2 can use the energy level instantaneous switching of a single X-ray source to perform energy spectrum scanning, and can instantaneously switch multiple energy levels (for example, switching between 80kV, 100kV, 120kV, and 140kV). The specific number of switched energy levels is determined by the design requirements. After a certain X-ray source performs energy spectrum scanning by instantaneous energy level switching, the next X-ray source under the scanning timing control performs energy spectrum scanning in the same way until the entire scanning work is completed. Secondly, the left ray source ring 1 and the right ray source ring 2 can use circular intermittent energy level switching to perform energy spectrum scanning, that is, after each X-ray source of the left ray source ring 1 and the right ray source ring 2 completes a circular scan at the same energy level under timing control, then all switch to another energy level, and repeat the next circular scan until all energy level switching is completed. Thirdly, the left ray source ring 1 and the right ray source ring 2 can also use a circular multi-energy spectrum scanning method to perform energy spectrum scanning, that is, the scanning X-ray sources distributed on the circumference are divided into several groups, each group is unified into one energy level, and after completing a circular scan under timing control, the energy level of each group of scanning X-ray sources is switched to the corresponding next energy level, and the next circular scan is repeated until all energy level switching is completed. Finally, the left ray source ring 1 and the right ray source ring 2 can also use two different energy levels at the same time. Specifically, the multiple focal spots in the left ray source ring 1 use one energy level (A kV), and the multiple focal spots in the right ray source ring 2 use another energy level (B kV, B≠A), and one scan realizes energy spectrum images of two energy levels.

[0073] It should be noted that the X-ray detector 31 in this embodiment can be a photon flow detector or can be replaced by an energy integrating detector to achieve the same function.

[0074] Reference Fig.13As shown, in the above embodiment, preferably, the X-ray detector 31 includes a main detector 311 and a scattering detector 312, and the scattering detector 312 is arranged on one side or both sides of the main detector 311. Fig.14 As shown, in this embodiment, a beam limiter 10 is provided between the X-ray source and the X-ray detector 31 to limit the coverage of the main beam of the X-ray source, so that the coverage of the main beam of the X-ray source only covers the main detector 311. As a result, the scattering detector 312 is not covered by the main beam, and the signal measured by it is the X-ray scattering distribution generated after the interaction between the main beam and the scanned object. In this way, the scattering distribution information is obtained while obtaining the projection image, forming a scattering matrix, and integrating it with the projection matrix obtained by the main detector, and uploading it to the data acquisition server in the form of a data stream, and then the data acquisition server separates the scattering information and the image information, restores the complete scattering information and removes it from the image information, and realizes scattering correction.

[0075] It can be understood that in the above-mentioned embodiments, the scattering detector 312 and the main detector 311 do not depend on the specific implementation form, and can be a variety of situations. For example: it can be an independent PD array; it can also be various detector photosensitive element arrays (including but not limited to CMOS+PD, TFT+PD; indirect X-ray detectors, direct X-ray detectors, such as: amorphous selenium, cadmium telluride (CdTe), cadmium zinc telluride (CdZnTe, CZT) and cadmium selenide (CdSe), IGZO, etc.). In this embodiment, the pixels of the main detector 311 are uniformly arranged, and the pixel matrix of the main detector 311 can be represented as I (R*M), that is, R rows and M columns; the pixel matrix of the scattering detector 312 is represented as S (r*m), that is, r rows and m columns. When m=M, the number of columns of the main detector and the scattering detector is the same; when m<M, the arrangement of the scattering detector 312 in the ZX plane can be in the form of a sparse arrangement (such as Fig.15 As shown). Due to the sparse arrangement of the scatter detectors 312, combined with the low-frequency characteristics of the scatter signal, scatter estimation based on scatter measurement is performed in the X direction and the Z direction and removed from the image information. The method includes steps S10 to S30:

[0076] S10: Measurement and completion of scattered signals in the X direction

[0077] In a single X-ray detector 31, in the X direction, the scattered signals can be supplemented by interpolation to obtain the same number of scattering matrix columns as the main detector columns, and the scattered signals of S(r*m) can be corrected to S(r*M);

[0078] Between the X-ray detectors 31, in the X direction, due to D Li and D Ri The Z direction is not aligned, DLi The amount of scattering between Ri The scattering amount of D is filled by interpolation. Ri The amount of scattering between Li The scattering amount is filled by interpolation.

[0079] S20: Measurement and completion of scattered signals in the Z direction

[0080] In the Z direction, the number of rows r of the scattering detectors arranged on both sides must be ≥ 3 rows, and the scattering detectors must avoid the penumbra of the main ray. The scattering signals on the entire Z-direction image column are fitted by the distribution trend of the scattering signals on both sides to obtain the scattering signal matrix S (R*M).

[0081] S30: Removal of scattered signals

[0082] The image matrix I(R*M) and the extracted scattering signal S(R*M) are subtracted to remove the scattering information.

[0083] like Fig.16 and Fig.17 As shown, in the above embodiment, the beam limiter 10 includes: a Z-direction beam limiter 110 and an X-direction beam limiter 120. The Z-direction beam limiter 110 can be opened and closed in the Z direction to limit the ray coverage of the X-ray source in the Z direction; the X-direction beam limiter 120 can be opened and closed in the X direction to limit the ray coverage of the X-ray source in the X direction. Specifically, in this embodiment, Fig.16 As shown, the Z-direction limiting device 110 includes a Z-direction fixed portion 111 and a Z-direction movable portion 112. The Z-direction fixed portion 111 is fixedly arranged along the Z-axis direction, and the Z-direction movable portion 112 is moved closer to or away from the Z-direction fixed portion 111 along the Z-axis direction to adjust the size of the opening between the Z-direction fixed portion 111 and the Z-direction movable portion 112. Fig.17 As shown, the X-direction beam limiting device 120 includes two X-direction movable parts 121, and the two X-direction movable parts 121 are moved closer to or farther from each other along the X-axis direction to adjust the size of the opening between the two X-direction movable parts 121. It can be understood that the larger the opening, the larger the ray beam coverage range (i.e., FOV range) of the X-ray source; the smaller the opening, the smaller the ray beam coverage range (i.e., FOV range) of the X-ray source, so that adaptive adjustment can be performed according to actual clinical needs.

[0084] In summary, the static real-time CT imaging system provided by the first embodiment of the present invention has the following beneficial effects:

[0085] 1. The scanning coverage in the Z-axis direction is increased, and the left and right Z-axis coverage can be achieved without gaps. A single axis scan can achieve a wider Z-axis coverage range, and can further reduce the projection cone angle, effectively suppressing cone angle artifacts.

[0086] 2. The X-ray sources (i.e., multiple focal spots) in the left ray source ring 1 and the right ray source ring 2 can realize a single axial scan in a variety of ways to meet different scanning requirements. In addition, the multiple focal spots in the left ray source ring 1 and the right ray source ring 2 realize energy spectrum scanning in a variety of ways.

[0087] 3. The X-ray detector 31 is composed of a scatter detector 312 and a main detector 311 , so that scatter correction can be achieved using the scatter detector 312 .

[0088] 4. The beam limiter 10 can adjust the ray coverage range of the X-ray source to meet different FOV range requirements.

[0089] <Second Embodiment>

[0090] like Fig.18 As shown, a static real-time CT imaging system provided by the second embodiment of the present invention includes two ray source rings, a detector ring 3 and a scanning timing controller. Compared with the first embodiment, the difference of this embodiment is that the arrangement of the ray source ring and the detector ring 3 is different.

[0091] Specifically, in this embodiment, the plurality of X-ray detectors include a plurality of short-size X-ray detectors 31a and a plurality of long-size X-ray detectors 31b, and the plurality of short-size X-ray detectors 31a and the plurality of long-size X-ray detectors 31b are arranged crosswise in sequence to form a left detector sub-ring, a middle detector sub-ring, and a right detector sub-ring. In addition, the left radiation source ring 1 and the right radiation source ring 2 are symmetrically arranged on the left and right sides of the detector ring 3.

[0092] It can be understood that in this embodiment, when performing X-ray exposure scanning, the short-size X-ray detector 31a can only measure the projection of the area where the middle detector sub-ring is located, and the long-size X-ray detector 31b can measure the projection of the entire area of ​​the left detector sub-ring, the middle detector sub-ring, and the right detector sub-ring. That is, the Z-direction expansion is achieved in the area where the long-size X-ray detector 31b is located, which is conducive to improving the imaging quality.

[0093] In addition, compared with the first embodiment, due to the occupation of the X-ray source in this embodiment, when the number N of X-ray source focal points increases, the corresponding arc interval between the focal points decreases, so that the area where the long-size X-ray detector 31b is located gradually becomes smaller. If the area where the long-size X-ray detector 31b is located disappears, the function of Z-direction expansion will be lost, so it is necessary to adaptively set the number N of focal points of the X-ray source according to needs. In addition, the layout method in the first embodiment can achieve the complementary effect of the projection diagram, and the projection diagram in this embodiment has no complementary effect. The imaging effect of this embodiment is slightly worse than that of the first embodiment, but Z-direction expansion can still be achieved, and the imaging effect is better than that of the CT imaging system without Z-direction expansion in the prior art.

[0094] Except for the above structure, the rest of the structure of this embodiment is the same as that of the first embodiment and will not be described again.

[0095] <Third Embodiment>

[0096] The third embodiment of the present invention provides a static real-time CT imaging method, which is implemented based on the static real-time CT imaging system in the first embodiment or the second embodiment, and at least includes steps S1 to S2:

[0097] S1: The scanning timing controller controls the X-ray sources in the left ray source ring 1 and the right ray source ring 2 and the corresponding X-ray detectors 31 in the detector ring 3 to work in a predetermined scanning timing:

[0098] S2: Multiple X-ray sources in the left ray source ring 1 and the right ray source ring 2 emit X-rays according to a predetermined exposure sequence, and the corresponding X-ray detectors 31 collect projection information on the X-ray detectors 31 after the X-rays pass through the object to be measured.

[0099] It can be understood that the projection information in this embodiment includes left-side local projection information collected by the left detector sub-ring, complete projection information collected by the middle detector sub-ring, and right-side local projection information collected by the right detector sub-ring.

[0100] The above is a detailed description of the static real-time CT imaging system and imaging method provided by the present invention. For those skilled in the art, any obvious changes made to it without departing from the essence of the present invention will constitute an infringement of the patent right of the present invention and will bear corresponding legal liabilities.

Claims

1. A static real-time CT imaging system, characterized in that It includes at least two ray source rings and one detector ring; Wherein, on the Z axis, the left ray source ring and the right ray source ring are arranged on the left and right sides of the detector ring, and the two ray source rings share one detector ring; The left ray source ring and the right ray source ring are respectively annular multi-focus X-ray sources with multiple X-ray sources, and the same number of focal spots are evenly arranged on the left ray source ring and the right ray source ring; the detector ring is composed of multiple X-ray detectors arranged in a ring, and on the Z axis, the multiple X-ray detectors together form a left detector sub-ring, a middle detector sub-ring and a right detector sub-ring; On the left detector sub-ring, a first gap is formed between any two adjacent X-ray detectors for placing the X-ray source of the left ray source ring; on the right detector sub-ring, a second gap is formed between any two adjacent X-ray detectors for placing the X-ray source of the right ray source ring; on the middle detector sub-ring, any two adjacent X-ray detectors are in close contact.

2. The static real-time CT imaging system according to claim 1, characterized in that: The sizes of the plurality of X-ray detectors are all the same; The plurality of X-ray detectors are arranged in an interlaced manner to form the left detector sub-ring, the middle detector sub-ring and the right detector sub-ring; The foci of the left ray source ring and the right ray source ring are arranged in a staggered manner relative to each other.

3. The static real-time CT imaging system according to claim 1, characterized in that: The X-ray detector includes a short-size X-ray detector and a long-size X-ray detector; wherein, a plurality of the short-size X-ray detectors and a plurality of the long-size X-ray detectors are arranged crosswise in sequence to form the left detector sub-ring, the middle detector sub-ring and the right detector sub-ring; the left ray source ring and the right ray source ring are symmetrically arranged on the left and right sides of the detector ring.

4. The static real-time CT imaging system according to claim 1, characterized in that: The X-ray detector includes a main detector and a scattering detector, wherein the scattering detector is arranged on one side or both sides of the main detector; A beam limiter is provided between the X-ray source and the X-ray detector to limit the coverage of the X-ray beam of the X-ray source to only cover the main detector.

5. The static real-time CT imaging system according to claim 4, characterized in that The beam limiter comprises: A Z-direction beam limiting device, which can open and close on the Z axis to limit the coverage of the X-ray beam of the X-ray source in the Z direction; An X-axis beam limiting device, which can open and close on the X-axis to limit the coverage of the X-ray beam of the X-ray source in the X-axis; The Z direction is the axial direction of the detector ring, and the X direction is the tangential direction of the detector ring.

6. The static real-time CT imaging system according to claim 5, characterized in that: The Z-direction beam limiting device comprises a Z-direction fixed portion and a Z-direction movable portion, wherein the Z-direction fixed portion is fixedly arranged along the Z-axis direction, and the Z-direction movable portion approaches or moves away from the Z-direction fixed portion along the Z-axis direction to adjust the size of the opening between the Z-direction fixed portion and the Z-direction movable portion; The X-direction beam limiting device comprises two X-direction movable parts, and the two X-direction movable parts are moved closer to or farther from each other along the X-axis direction to adjust the opening size between the two X-direction movable parts.

7. The static real-time CT imaging system according to claim 1, characterized in that The multiple X-ray sources in the left ray source ring and the right ray source ring perform axial scanning in any of the following ways: ① Expose a ray source on the left, then a ray source on the right, and then another ray source on the left, and so on, alternately expose all ray sources left and right to obtain projection images of all ray sources; ② The K ray sources on the left are exposed at the same time, and the X-ray detectors corresponding to the light field coverage range of the K ray sources on the left are not shared. Then the K ray sources on the right are exposed at the same time, and the X-ray detectors corresponding to the light field coverage range of the K ray sources on the right are not shared. In this way, all ray sources are exposed alternately from left to right to obtain projection images of all ray sources; wherein K is a positive integer and not less than 2; ③ The left ray source is exposed in turn, and only the projection image of the left ray source is obtained; ④ The ray sources on the right are exposed in turn, and only the projection image of the ray sources on the right is obtained.

8. The static real-time CT imaging system according to claim 1, characterized in that It also includes a scanning timing controller, and the exposure timing of multiple focal points in the left ray source ring and the right ray source ring and the collection timing of the corresponding X-ray detectors in the detector ring are controlled by the scanning timing controller.

9. A static real-time CT imaging method, implemented based on the static real-time CT imaging system according to any one of claims 1 to 8, characterized in that The steps include: The scanning timing controller controls the X-ray sources in the left and right ray source rings and the corresponding X-ray detectors in the detector ring to work in a predetermined scanning timing: The multiple X-ray sources in the left ray source ring and the right ray source ring emit X-rays according to a predetermined exposure sequence, and the corresponding X-ray detectors collect projection information on the X-ray detectors after the X-rays pass through the object to be measured.

10. The static real-time CT imaging method according to claim 9, characterized in that: The projection information includes left-side local projection information collected by the left detector sub-ring, complete projection information collected by the middle detector sub-ring, and right-side local projection information collected by the right detector sub-ring.

Images