A CT system and CT imaging method

Abstract

The present invention relates to a CT system and a CT imaging method, belonging to the field of X-ray computed tomography imaging technology, and solves the problem in the prior art that when the number of detector rows is too large, the cone angle of the radiation source is difficult to cover the detector or the cone angle is too large, causing cone angle artifacts. A CT system includes an object conveying component, an object inlet and outlet, and a CT device; the CT device includes a rotating body, a detector, and a radiation source; the detector and the radiation source are both fixed on the rotating body; the radiation source is a multi-focus radiation source, including multiple radiation source focal points; the detectors are arranged in sequence along the direction of the rotation axis of the rotating body to form a detector row; each radiation source focal point radiates a partial area of ​​the detector row. The present invention achieves the purpose of effectively suppressing cone angle artifacts in reconstructed images when using large-width multi-row detectors.

Description

Technical Field

[0001] The present invention relates to the technical field of X-ray computed tomography imaging, and in particular to a CT system and a CT imaging method. Background Art

[0002] Among X-ray explosives detection technologies, X-ray computed tomography (CT) is highly regarded in the security inspection field due to its unique advantages. The only EDS (Explosive Detection System) security inspection equipment certified by the U.S. Transportation Security Administration (TSA) is a CT device, demonstrating the importance of X-ray CT technology in the security inspection field.

[0003] Current CT equipment primarily utilizes spiral CT scans based on slip ring technology. The X-ray source and detectors are typically mounted on a rotating gantry, using slip ring technology to address the issue of continuous gantry rotation. To increase the field of view within a single rotation of the gantry and cover a larger scanning area, the number of detector rows is typically increased. Currently, the maximum number of detector rows in medical CT scans on the market is 320, with a Z-axis coverage of approximately 16 cm. However, since the X-ray source used in these devices is mostly point-source, increasing the number of rows increases the angle between the edge detector and the X-ray source, resulting in increasingly severe cone-angle artifacts in the reconstructed image. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a CT system and a CT imaging method, which solve the problem in the prior art that when there are too many detector rows, the cone angle of the radiation source is difficult to cover the detector or the cone angle is too large, causing cone angle artifacts.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] On the one hand, the present invention provides a CT system, including an object conveying component, an object inlet and outlet, and a CT device; the CT device includes a rotating body, a detector, and a radiation source; the detector and the radiation source are both fixed to the rotating body; the radiation source is a multi-focus radiation source, including multiple radiation source focal points; the detectors are arranged in sequence along the direction of the rotation axis of the rotating body to form a detector row; each of the radiation source focal points radiates a partial area of ​​the detector row.

[0007] Optionally, the focus of the ray source is turned on at different times.

[0008] Optionally, the object conveying component includes a motion motor and a conveyor belt.

[0009] Optionally, the object transport component includes a motion motor and a CT scanning bed.

[0010] Optionally, the ray source includes a carbon nanotube-based cold cathode X-ray tube.

[0011] Optionally, a scattering limiter is provided at the detector.

[0012] Optionally, the scatter limiting element is arranged in front of the detector and is aligned with the focus of the ray source.

[0013] Optionally, areas of the detector rows irradiated by adjacent ray source focal points overlap.

[0014] Optionally, the radiation shielding device is a lead curtain.

[0015] Optionally, a partial area of ​​the detector array forms a certain angle with the focus of the ray source at the focus of the ray source, and the angle is no greater than 15°.

[0016] Optionally, a radiation limiting member is provided at the focus of the ray source.

[0017] Optionally, the radiation limiting component is provided at the beam outlet of the radiation source.

[0018] Optionally, the radiation limiter is made of heavy metal material.

[0019] Optionally, the heavy metal material includes lead and tungsten.

[0020] Optionally, the ray source includes a hot cathode X-ray tube based on grid control technology.

[0021] Optionally, the detector is a single-energy detector.

[0022] Optionally, the detector is a photon counting detector.

[0023] On the other hand, the present invention also provides a CT imaging method, which adopts the above-mentioned CT system, including a ray source focus, which is turned on and off in sequence according to a set order. By quickly switching the ray source focus, only one ray source focus is turned on at a single time; or multiple ray source focuses are turned on at the same time, but the ray emission ranges corresponding to the two ray source focuses received by the detector do not overlap.

[0024] The present invention can achieve at least one of the following beneficial effects:

[0025] (1) Medical CT detectors are usually multi-row detectors. The number of rows of existing medical CT detectors is up to 320, with a Z-axis coverage of about 16 cm. Since the radiation sources used in the equipment are mostly point sources, as the number of rows increases, the angle between the edge detector and the radiation source increases, resulting in increasingly serious cone angle artifacts in the reconstructed image. The present invention breaks through the inherent cognition that the radiation source of spiral CT can only be a point source radiation source, and innovatively adopts a multi-focus radiation source as the radiation source of spiral CT. By limiting the area irradiated by each radiation source focus, each radiation source focus does not irradiate all detectors on the entire detector row, but only irradiates detectors in a partial area, that is, a partial area of ​​the detector row forms a certain angle (not greater than 15°) with the radiation source focus at the radiation source focus, so that when using multi-row detectors (more than the existing 320 rows of detectors), the reconstructed image is free from cone angle artifacts, thereby ensuring the reproduction of a clear image.

[0026] (2) The present invention limits the area radiated by each ray source focus by setting a radiation limiting member at each ray source focus, or setting a scattering limiting member at the detector, thereby ensuring that each ray source focus radiates a partial area.

[0027] (3) The present invention can meet the integrity requirements of the scanned object data by controlling the overlap of the areas of the detector rows irradiated by adjacent ray source focal points.

[0028] (4) The present invention can ensure that when the number of detector rows is greater than 320 and the Z-axis coverage exceeds 16 cm, the reproduced image is clear and no cone angle artifacts appear.

[0029] (5) In the imaging method of the present invention, the CT ray source turns on and off the focus in a set order (for example, adjacent ray sources are turned on and off in turn, in a cycle). By quickly switching the focus of the ray source, it is achieved that only one ray source focus is turned on at a single time, or multiple ray source focuses are turned on at the same time, but the ray emission ranges corresponding to the two ray source focuses received by the detector do not intersect, thereby avoiding the problem of cone angle artifacts caused by the rays from multiple ray source focuses irradiating the same detector at the same time, and ensuring the reconstruction of a clear image.

[0030] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages will become apparent from the description or be understood through practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the embodiments of the description and the contents particularly pointed out in the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0032] Figure 1 This is a schematic diagram of the positional relationship between a multi-focus ray source and multiple rows of detectors according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the distribution range of multiple ray sources and the corresponding detector area structure according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic structural diagram of a capacitively coupled slip ring according to an embodiment of the present invention;

[0035] Figure 4 A partial cross-sectional view of a rotating disk according to an embodiment of the present invention;

[0036] Figure 5 A diagram showing the relationship between the spacing between adjacent transmitting antennas and antenna width in the prior art;

[0037] Figure 6 This is a partial cross-sectional view of a rotating disk with an embedded transmitting antenna according to an embodiment of the present invention.

[0038] Reference numerals:

[0039] 1-detector; 2-multi-focus radiation source; 3-focus of radiation source; 4-rotation axis direction; 7-detector array; 8-rotating disk; 9-transmitting antenna; 10-first groove; 11-second groove; 12-receiving unit. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0041] Example 1

[0042] See also Figure 1 A specific embodiment of the present invention discloses a CT system comprising an object transport component, an object inlet and outlet, and a CT device. The CT device includes a rotating body, a detector 1, and a radiation source. Both the detector 1 and the radiation source are fixed to the rotating body. The detectors 1 are arranged in multiple rows along the rotation axis 4 of the rotating body, forming detector rows 7.

[0043] The radiation source is a multi-focus radiation source 2, comprising a plurality of radiation source focal points 3 arranged along the rotation axis 4 of the rotating body. Preferably, the radiation source can be a cold cathode X-ray tube based on carbon nanotubes or a hot cathode X-ray tube based on grid control technology.

[0044] The detector 1 of this embodiment can be any one or more combinations of a single-energy detector, a dual-energy detector, and a photon counting detector, and can also be a flat-panel detector or a multi-row detector.

[0045] In a specific system, in addition to the multi-focal radiation source 2, additional multi-focal radiation sources may be arranged at other locations on the rotating body. Furthermore, the focal points within the multi-focal radiation source 2 may be arranged in a planar array, for example, with the focal points arranged in a 3x2 pattern along a plane parallel to the rotation axis of the rotating body.

[0046] It should be noted that, if no restriction is imposed, each ray source focus 3 will correspond to the entire detector row 7 , which will increase the angle between the edge detector and the ray source, resulting in very serious cone-angle artifacts in the reconstructed image.

[0047] In order to solve the technical problem of very serious cone angle artifacts in the reconstructed image due to the increase in the angle between the edge detector and the ray source. Figure 2 In one possible implementation, the radiation area of ​​each radiation source focus is limited. Instead of corresponding to the entire detector array 7, each radiation source focus corresponds to a detector in a partial area. That is, each radiation source focus 3 corresponds to a unit at a different position on the detector array 7. Specifically, each radiation source focus can only irradiate the detector within a certain angle range, such as Figure 2 As shown, a partial area of ​​the detector array forms a certain angle with the focus of the radiation source at the focus of the radiation source, and the angles of the detectors irradiated by the three radiation source focuses are α, β and θ respectively.

[0048] Specifically, Figure 2 The detector array 7 and the multiple radiation source focal points 3 are located in the same two-dimensional plane parallel to the rotation axis 4 of the rotating body. The range of the cone angles α, β and θ of each radiation source focal point 3 in the figure is preferably not greater than 15°. The detector unit within the cone angle range is the detector corresponding to the radiation source focal point, for example Figure 2 In the example, the detector unit corresponding to the first ray source focus 3 is the portion of the cone angle α corresponding to the upper and lower edges of the detector. Due to the requirement for completeness of the scanned object data, the detector areas corresponding to adjacent ray source focuses 3 overlap.

[0049] In order to limit the radiation range of the radiation source focus, in a possible embodiment, a radiation limiting element is provided at each radiation source focus, or a scattering limiting element is provided at the detector.

[0050] The radiation limiting component is set at the beam outlet of the radiation source and is made of heavy metal materials such as lead and tungsten. It is used to limit the radiation beam to a narrow range, thereby controlling the solid angle of the beam.

[0051] The specific structure of the radiation limiting member can take various forms, as long as it can achieve the purpose of controlling the solid angle of the beam and limiting the ray beam to a narrow range.

[0052] The scatter limiting element is set in front of the detector and is shaped like a set of grids. It is arranged to align with the focus of the radiation source, thereby blocking the deviated original X-ray photons (primary photons) from entering the detector.

[0053] In order to increase operational safety, this embodiment further provides a radiation shielding device at the object entrance and exit. For example, the radiation shielding device can be a lead curtain.

[0054] The CT system of this embodiment can be applied in both the security inspection field and the medical field. When applied in the security inspection field, the object conveying components are usually a motion motor and a conveyor belt; when applied in the medical field, the object conveying components are usually a motion motor and a CT scanning bed.

[0055] Example 2

[0056] Another specific embodiment of the present invention discloses a multi-row detector imaging method based on a multi-focus radiation source, which can reconstruct images without cone angle artifacts when using multiple rows of detectors. The imaging method is implemented using the CT system of Example 1 and includes the following steps:

[0057] Step 1: Place the object (baggage) on the conveyor belt. Driven by the conveyor belt motor, the object (baggage) moves at a constant speed along the conveyor belt.

[0058] Step 2: The object (baggage) enters the CT scanning area. The slip ring motor controls the CT slip ring to rotate at a constant speed. The CT radiation source turns on and off in a set sequence (for example, adjacent radiation sources turn on and off in a cycle). By rapidly switching the radiation source focus, only one focus is active at a time, avoiding the problem of cone angle artifacts caused by radiation from multiple focuses simultaneously irradiating the same detector. Alternatively, multiple radiation source focuses may be turned on simultaneously, but the radiation emission ranges corresponding to the radiation sources detected by the detector do not overlap.

[0059] Step 3: The X-ray source emits an X-ray beam that penetrates the object. The CT detector receives the attenuation signal from the object and continuously transmits the received signal to the data processing computer.

[0060] Step 4: Reconstruct the data in the data processing computer to obtain the tomographic data at different positions of the object, and then display the three-dimensional data composed of all the tomographic data on the screen.

[0061] The imaging method of this embodiment turns on the focus in a set order to ensure that only one focus is turned on at a single moment. The scan is completed by quickly switching the focus, thereby avoiding the situation where rays from multiple focuses simultaneously illuminate the same detector; or multiple ray source focuses are turned on at the same time, but the ray emission ranges corresponding to the two ray source foci received by the detector do not intersect, thereby avoiding the occurrence of cone angle artifacts and ensuring the reconstruction of a clear image.

[0062] The fast switching of focus can be achieved by controlling the hardware, for example, by setting a grid-controlled switch to control the exposure time and release sequence of the X-ray tube.

[0063] Example 3

[0064] Another specific embodiment of the present invention adopts the CT rotating body of the first embodiment, wherein the CT rotating body is a capacitive coupling slip ring using slip ring technology, and includes a rotating disk 8, a transmitting unit, and a receiving unit.

[0065] like Figure 3 As shown, the transmitting unit includes a transmitting antenna 9 and a transmitting data processing unit. The transmitting data processing unit includes a transmitting circuit board and a data line. The transmitting antenna 9 and the data line are both connected to the transmitting circuit board. For example, the transmitting antenna 9 and the transmitting circuit board are connected via a connector. The transmitting circuit board is fixed to the rotating disk.

[0066] The transmitting antenna used in the present invention is in a flat shape, or in a strip shape.

[0067] The rotating disk is a large-aperture ring with a hollow interior. A circumferentially arranged first groove 10 is provided on its outer surface. The shape of the first groove 10 matches the shape of the transmitting antenna 9 , and the transmitting antenna 9 is placed in the first groove 10 .

[0068] It should be noted that, depending on the diameter of the rotating disk, the transmitting antenna located within first groove 10 can be a single antenna or multiple transmitting antennas forming a complete circle. Specifically, the circuit board has two pathways, with adjacent antennas connected to each pathway. The receiving unit includes a receiving circuit board and a data cable, which is connected to the receiving circuit board.

[0069] The receiving unit 12 includes two parts: a receiving end data processing unit and a receiving antenna. The two parts can be integrated into a printed circuit or connected in a plug-in form.

[0070] The receiving unit includes a first receiving unit and a second receiving unit. The first receiving unit is arranged near the outer surface of the rotating disk and is 1.5-5 mm away from the transmitting antenna in the first groove.

[0071] In a possible embodiment, the inner surface of the rotating disk 8 is also provided with a circumferentially arranged groove (second groove 11), such as Figure 4 The shape of the second groove 11 matches the shape of the transmitting antenna, and the transmitting antenna is placed in the second groove.

[0072] It should be noted that the transmitting antenna 9 in this embodiment is fixed in the groove. For example, the transmitting antenna can be fixed in the groove by gluing.

[0073] The second receiving unit is arranged near the inner surface of the rotating disk and is 1.5-5 mm away from the transmitting antenna in the second groove.

[0074] It should be noted that the number of the first groove 10 and the second groove 11 is at least one. For example, 1 first groove and 1 second groove; or 1 first groove and 2 second grooves; 2 first grooves and 1 second groove; or 2 first grooves and 2 second grooves, such as Figure 4 The position of the second groove may correspond to the position of the first groove, or may not correspond to the position of the first groove.

[0075] The transmission unit and the receiving unit are connected through the principle of capacitive coupling, that is, the electric field coupling between the transmitting and receiving antennas. If the distance between different groups of transmitting and receiving antennas is too close, crosstalk between different transmitting and receiving modules will occur, resulting in abnormal communication. Therefore, in order to prevent signal interference between different transmitting antennas on the same side, the spacing D between different transmitting antennas on the same side in the prior art is not less than three times the width W of the transmitting antenna (i.e. 3W), and the dielectric thickness H between the transmitting antennas on different sides is not less than three times the width of the transmitting antenna, such as Figure 5 As shown (for the sake of convenience, the transmitting antenna is shown as protruding from the outer surface of the rotating disk).

[0076] However, due to space limitations, it is impossible to infinitely increase the distance between different transceiver modules. Therefore, in one possible embodiment of the present invention, a solution of embedding the receiving antenna is adopted, that is, the depth of the groove is not the same as the thickness of the transmitting antenna, but the depth of the groove is greater than the thickness of the transmitting antenna, such as Figure 6 Thus, after the transmitting antenna is placed in the groove, there is a height difference between the upper surface of the transmitting antenna and the outer surface of the rotating disk, that is, the upper surface of the transmitting antenna is not flush with the outer surface of the rotating disk, but lower than the outer surface of the rotating disk.

[0077] Specifically, the antenna is 2mm thick, and the groove is 3mm deep. This places the surface of the transmitting antenna 1mm from the side of the rotating disk. This arrangement effectively reduces the radiation field of the transmitted signal. Therefore, even when the spacing between different groups of transmitting antennas is reduced, interference between different transceiver modules is reduced, effectively improving the utilization rate of the electric slip ring disk while ensuring normal signal communication.

[0078] Through experimental research, the present invention has found that with the above-mentioned embedded structural setting, the spacing between the transmitting antennas on the same side does not need to reach 3 times the width of the transmitting antenna (i.e. 3W), and only needs to be 1-2 times the width of the transmitting antenna to ensure normal communication.

[0079] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in the present invention should be covered by the scope of protection of the present invention.

Claims

1. A CT system, characterized in that: Including object transport components, object inlet and outlet, and CT device; The CT device includes a rotating body, a detector and a radiation source; the detector and the radiation source are both fixed on the rotating body; The ray source is a multi-focus ray source, including multiple ray source focuses; The detectors are arranged in sequence along the direction of the rotation axis of the rotating body to form a detector row; Each of the radiation source focal points irradiates a partial area of ​​the detector row; The rotating body is a capacitive coupling slip ring using slip ring technology, and the capacitive coupling slip ring includes a rotating disk, a transmitting unit and a receiving unit; The transmitting unit includes a transmitting antenna; The rotating disk is annular with a hollow interior, and a first groove is provided on its outer surface in a circumferential direction. The shape of the first groove matches the shape of the transmitting antenna, and the transmitting antenna is placed in the first groove. The depth of the first groove is greater than the thickness of the transmitting antenna. There is a height difference between the upper surface of the transmitting antenna and the outer surface of the rotating disk. The spacing between the transmitting antennas on the same side is 1-2 times the width of the transmitting antenna.

2. The CT system according to claim 1, wherein: The focus of the ray source is turned on at different times.

3. The CT system according to claim 1, wherein: The object conveying component includes a motion motor and a conveyor belt.

4. The CT system according to claim 1, wherein: The object conveying component includes a motion motor and a CT scanning bed.

5. The CT system according to any one of claims 1 to 4, characterized in that: The ray source includes a carbon nanotube-based cold cathode X-ray tube.

6. The CT system according to claim 1, wherein: A scattering limiter is provided at the detector.

7. The CT system according to claim 6, characterized in that The scatter limiting component is arranged in front of the detector and is aligned with the focus of the ray source.

8. The CT system according to claim 1, wherein: The areas of the detector rows irradiated by the focal points of adjacent radiation sources overlap.

9. The CT system according to claim 8, characterized in that The radiation shielding device is a lead curtain.

10. A CT imaging method, characterized in that: A CT system according to any one of claims 1 to 9, comprising a radiation source focus, wherein the radiation source focus is turned on and off in a set order, and by rapidly switching the radiation source focus, only one radiation source focus is turned on at a single time; Or multiple ray source focuses are turned on at the same time, but the ray emission ranges corresponding to the two ray source focuses received by the detector do not intersect.

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