Device, system, and method for controlling the position of a scatter radiation removal grid in an X-ray image acquisition system

Abstract

The present invention relates to a device for controlling the position of an anti-scatter grid in an X-ray image acquisition system, the device 10 comprising a measurement unit 12, a control unit 14 and a shift unit 16, the measurement unit 12 is configured to determine an X-ray beam focal position 37 of an X-ray radiation source of the X-ray image acquisition system relative to an X-ray detector of the X-ray image acquisition system, the control unit 14 is configured to generate a shift signal based on a displacement 18 between the X-ray beam focal position 37 and a grid focal position 35 of the anti-scatter grid, and based on the shift signal the shift unit 16 is configured to shift the anti-scatter grid of the X-ray image acquisition system in at least one direction to align the anti-scatter grid with the X-ray beam focal position 37, and provides an improved anti-scatter grid for an X-ray acquisition system. The present invention provides the use of an improved anti-scatter grid 26 for an X-ray acquisition system 20.

Description

Technical Field

[0001] The present invention relates to a device, a system, and a method for controlling the position of a scatter removal grid in an X-ray image acquisition system.

Background Art

[0002] To acquire an X-ray image, an X-ray radiation source emits X-ray radiation from a focal spot determined by the position where an electron beam hits the anode of the X-ray radiation source. The X-ray radiation travels through an object and a grid to an X-ray detector. Along the path of travel, the X-ray radiation scatters, thereby generating a significant source of noise in the X-ray image. Scattering can be reduced using a scatter removal grid, which is a plate in front of the X-ray detector, and the scatter removal grid is positioned such that only the X-ray radiation generated from the focal spot can pass through, and other (scattered) X-ray radiation is absorbed, and has a material with similarly high absorbency such as lead or tungsten pieces.

[0003] In a computed tomography system, a two-dimensional scatter removal grid having a height of several centimeters that absorbs a significant amount of scatter is used. However, in a C-arm system, the scatter removal grid has a height of only 2 - 3 mm because the C-arm type X-ray system is not infinitely fixed. Depending on the orientation, speed, and acceleration, the exact position of the focal spot relative to the X-ray detector varies.

[0004] U.S. Patent No. 5,469,429(A) relates to a device for aligning a focal spot at a predetermined position in a computed tomography system. The device detects the focal spot of the X-ray radiation on the anode of the X-ray tube. Then, the device adjusts the position of the focal spot to a predetermined position by repositioning the anode or by changing the path of the electron beam.

Summary of the Invention

Problems to be Solved by the Invention

[0005] There is a need for devices and methods that provide for the use of an improved scatter radiation removal grid for an X-ray acquisition system.

[0006] The object of the present invention is solved by the subject matter of the independent claims, and further embodiments are incorporated into the dependent claims. It should be noted that the aspects of the present invention described below also apply to systems, X-ray image acquisition systems, methods, computer program elements, and computer-readable media.

Means for Solving the Problem

[0007] According to one aspect of the present invention, there is provided an X-ray image acquisition system comprising an X-ray radiation source and an X-ray detector connected to at least one C-arm as a support structure, and a scatter radiation removal grid disposed between an object accommodation space and the X-ray detector. The X-ray image acquisition system further comprises a device for controlling the position of the scatter radiation removal grid, the device comprising a measurement unit, a control unit, and a shift unit. The measurement unit is configured to determine the X-ray beam focus position of the X-ray radiation source with respect to the X-ray detector. The control unit is configured to generate a shift signal based on the displacement between the X-ray beam focus position and the grid focus position of the scatter radiation removal grid. The shift unit is configured to shift the scatter radiation removal grid in at least one direction based on the shift signal in order to align the scatter radiation removal grid with the X-ray beam focus position.

[0008] Accordingly, the device adapts the position of the anti-scatter grid so as to align the grid focus position of the anti-scatter grid with the X-ray beam focus position. The device first measures the focus position of the X-ray radiation beam at the X-ray source. Further, a displacement between the measured X-ray beam focus position and the grid focus position of the anti-scatter grid of the X-ray image acquisition system is determined. A shift signal is generated that includes information on how much the anti-scatter grid should be shifted in order to align the grid focus position with the X-ray beam focus position according to the displacement. The shift unit then shifts the anti-scatter grid according to the information of the shift signal. Accordingly, for example, the displacement between the X-ray source and the anti-scatter grid caused by deformation of the structure of the X-ray image acquisition system is corrected by shifting the anti-scatter grid to the position where the X-ray radiation passes through the anti-scatter grid. By correcting the misalignment between the X-ray beam focus position and the grid focus position, a thick anti-scatter grid, i.e., an anti-scatter grid having a high grid ratio, is used. Using an anti-scatter grid having a high grid ratio improves the contrast of the X-ray image due to the reduction of scatter, thus improving the image quality.

[0009] In one example, the anti-scatter grid is disposed between the object accommodation space and the X-ray detector, and the object accommodation space is the space between the X-ray source and the X-ray detector. The anti-scatter grid is disposed, for example, in proximity in front of the X-ray detector. In another example, the anti-scatter grid is disposed on the X-ray detector.

[0010] In one example, the shift unit is connected to the anti-scatter grid of the X-ray image acquisition system.

[0011] According to one example, the control unit is configured to determine the displacement based on an analysis of the X-ray image acquired by the X-ray detector.

[0012] In one example, the analysis of the X-ray image includes contrast analysis.

[0013] In one example, the determination of the displacement is performed based on the position of the scatter removal grid with respect to the X-ray radiation source.

[0014] In one example, the control unit is configured to determine whether the X-ray image shows the shadow of the scatter removal grid, and the shadow indicates the displacement.

[0015] According to one example, the shift unit is configured to shift at least one scatter removal grid arranged in a plane parallel to the X-ray collision surface of the X-ray detector in at least one direction.

[0016] In one example, the scatter removal grid is a 1D grid.

[0017] According to one example, the shift unit is configured to shift the scatter removal grid in two directions. In one example, the scatter removal grid is a 2D grid. This further improves scatter removal.

[0018] According to one example, the shift unit includes at least one control member configured to move the scatter removal grid.

[0019] In one example, the control member is a motor.

[0020] According to one example, the measurement unit is configured to determine the X-ray beam focus position during the acquisition of the X-ray image by the X-ray image acquisition system. Thus, during the acquisition of the X-ray image, the misalignment between the X-ray beam focus position and the grid focus position is corrected. Thus, repeated image acquisitions at the same position due to low contrast are avoided.

[0021] In one example, the measurement unit is configured to determine the actual position during the calibration procedure before the acquisition of the X-ray image by the image acquisition system.

[0022] According to one example, the X-ray radiation source and the X-ray detector are mounted on opposing sections of a C-arm as at least one support structure, and the support structure is configured to rotate these two opposing mounting sections around an object receiving space.

[0023] In one example, X-ray image acquisition is one of a group of two-dimensional image acquisition systems, three-dimensional image acquisition systems, or mobile systems.

[0024] According to one example, the control unit is configured to generate a shift signal based on the angular position, speed, and / or acceleration of the X-ray detector.

[0025] In one example, the anti-scatter grid has a grid ratio in the range of 8:1 to 16:1, preferably has a grid ratio in the range of 10:1 to 16:1, and most preferably has a grid ratio in the range of 12:1 to 16:1. The grid ratio is defined as the ratio of the grid height to the grid interspace width.

[0026] In one example, the anti-scatter grid is a high-ratio grid, i.e., a "thick" anti-scatter grid.

[0027] Further examples and advantages of the X-ray image acquisition system are derived from the above description. Therefore, reference is made to the above description for that.

[0028] According to the present invention, there is also provided a method for controlling the position of an anti-scatter grid in a C-arm type X-ray image acquisition system, the method comprising: a) determining, using a measurement unit, the X-ray beam focus position of the X-ray radiation source of the X-ray image acquisition system relative to the X-ray detector of the X-ray image acquisition system; b) generating, using a control unit, a shift signal based on the displacement between the X-ray beam focus position and the grid focus position; and c) shifting, using a shift unit, the position of the anti-scatter grid in at least one direction based on the shift signal to align the anti-scatter grid with the X-ray beam focus position at the X-ray radiation source.

[0029] Further examples and advantages of the method are derived from the above description. Therefore, reference is made to the above description for that.

[0030] According to the present invention, there is also provided a computer program element for controlling the device according to the above description, wherein the computer program element is adapted to implement the method according to the above description when being executed by a processing unit.

[0031] According to the present invention, there is also provided a computer-readable medium storing the computer program element according to the above description.

[0032] These and other aspects of the present invention will become apparent from and will be elucidated with reference to the embodiments described hereinafter.

[0033] Exemplary embodiments of the present invention will be described hereinafter with reference to the following drawings.

Brief Description of the Drawings

[0034]

Figure 1a

Figure 1b

Figure 2a

Figure 2b

Figure 2c

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0035] Figures 1a and 1b show an X-ray image acquisition system 20 including an X-ray radiation source 22, an X-ray detector 24, a scatter radiation removal grid 26, at least one support structure 32, and a device 10 for controlling the position of the scatter radiation removal grid in the X-ray image acquisition system. The device 10 includes a measurement unit 12, a control unit 14, and a shift unit 16.

[0036] In one embodiment of the present invention, the X-ray image acquisition system 20 is a two-dimensional X-ray image acquisition system.

[0037] In another embodiment of the present invention, the X-ray image acquisition system 20 is a three-dimensional X-ray image acquisition system.

[0038] In a further embodiment of the present invention, the X-ray image acquisition system 20 is a mobile X-ray image acquisition system.

[0039] The X-ray radiation source 22 emits X-ray radiation 30 from an X-ray beam focus position 37. The X-ray radiation 30 travels through, for example, an object accommodation space 36 where a patient to be examined is present and the scatter radiation removal grid 26, and then reaches an X-ray collision surface 43 of the X-ray detector 24. The scatter radiation removal grid 26 filters scattered X-ray radiation and allows only the X-ray radiation 30 emitted from a grid focus position 35 of the scatter radiation removal grid 26 to pass through.

[0040] The scatter radiation removal grid 26 has a grid ratio in the range of 8:1 to 16:1, preferably has a grid ratio in the range of 10:1 to 16:1, and most preferably has a grid ratio in the range of 12:1 to 16:1. The grid ratio is defined as the ratio of the grid height to the grid gap width. The scatter radiation removal grid 26 having a high grid ratio is called a thick scatter radiation removal grid. The thick scatter radiation removal grid greatly reduces scatter in the X-ray image, which will greatly improve the quality of the X-ray image due to the reduced signal-to-noise ratio.

[0041] In FIG. 1a, at least one support structure 32 is a C-arm 38. The C-arm includes two opposing sections 31, 33 disposed at opposing ends of the C-arm 38. The X-ray source 22 is attached to the first opposing section 31. The X-ray detector 24 is attached to the second opposing section 33. At least one support structure 32 rotates two opposing sections 31, 33 each having an X-ray source 22 and an X-ray detector 24 around an object accommodation space 36. The rotation is performed around an axis 34 that serves as a rotary bearing for the support structure 32.

[0042] In FIG. 1b, at least one support structure 32 includes two robotic arms 39, 41. The X-ray source 22 is attached to the first robotic arm 39. The X-ray detector 24 is attached to the second robotic arm 41. The robotic arms 39, 41 rotate the X-ray source 22 and the X-ray detector 24 around the object accommodation space 36. Further, the robotic arms 39, 41 are configured to arrange the X-ray source 22 and the X-ray detector 24 on opposing sides of the object accommodation space 36 during an image acquisition process. Thus, the X-ray radiation 30 emitted by the X-ray source 22 travels through the object accommodation space 36 to the X-ray detector 24.

[0043] As long as the X-ray beam focus position 37 and the grid focus position 35 coincide, the X-ray radiation 30 passing through the scatter removal grid 26 provides a high-quality image of the object within the object accommodation space 36. This is shown in FIG. 2a.

[0044] FIG. 2b shows a situation where the X-ray beam focus position 37 is displaced by 18 from the grid focus position 35. In that case, the scatter removal grid 26 filters a part of the X-ray radiation 30 emitted from the X-ray beam focus position 37, and as a result, the image quality on the X-ray detector 24 is reduced. Such a displacement is caused by deformation of at least one support structure 32 during image acquisition. The deformation occurs, for example, due to acceleration and / or gravity during rotation of at least one support structure 32 around the object accommodation space 36.

[0045] To align the grid focus position 35 of the scatter radiation removal grid 26 with the X-ray beam focus position 37, the shift unit 16 shifts the scatter radiation removal grid 26 by a distance 19 according to FIG. 2c so that the X-ray radiation 30 emitted from the X-ray beam focus position 37 passes through the scatter radiation removal grid 26. The shift of the scatter radiation removal grid 26 is performed parallel to the X-ray collision surface 43.

[0046] FIG. 3 shows the device 10 in more detail. The measurement unit 12 comprises two elements arranged at the X-ray radiation source 22 and the X-ray detector 24. The measurement unit 12 is configured to determine the X-ray beam focus position 37 at the X-ray radiation source 22 with respect to the X-ray detector 24. The X-ray beam focus position 37 is determined by the position at the X-ray radiation source 22 where the electron beam 28 emitted from the cathode 21 reaches the anode 23.

[0047] The measurement unit 12 determines the position of the X-ray detector 24 and compares the position of the X-ray detector 24 with the X-ray beam focus position 37 to determine the displacement between the X-ray beam focus position 37 and the X-ray detector 24. The measurement unit 12 makes its determination during the image acquisition process.

[0048] To determine the displacement between the X-ray beam focus position 37 and the X-ray detector 24, an initial alignment is made between the X-ray beam focus position 37 at the X-ray radiation source 22 and the grid focus position 35 of the scatter radiation removal grid 26 arranged near or on the X-ray detector 24 respectively. The measurement unit 12 determines the deviation of the initial spatial alignment between the X-ray radiation source 22 and the X-ray detector 24 during image acquisition, i.e., during the rotation of the X-ray radiation source 22 and the X-ray detector 24 around the object accommodation space 36. Then, the measurement unit 12 determines the displacement with respect to the initial alignment during image acquisition.

[0049] Furthermore, in one example, the displacement 18 between the X-ray beam focus position 37 and the grid focus position 35 is determined by analyzing the acquired X-ray image of the X-ray detector 24 during image acquisition. A reduction in the quality of the X-ray image indicates a misalignment between the X-ray beam focus position 37 and the grid focus position 35. The reduction in quality is caused by a reduction in the contrast of the X-ray image and / or the presence of the shadow of the anti-scatter grid 26 in the X-ray image. This improves the determination of the displacement between the X-ray beam focus position 37 and the grid focus position 35.

[0050] The control unit 14 analyzes the measured displacement 18 between the X-ray beam focus position 37 and the grid focus position 35. Based on the displacement 18, the control unit 14 generates a shift signal. The shift signal includes information about the distance 19 by which the anti-scatter grid 26 has to be shifted in order to align the grid focus position 35 with the X-ray beam focus position 37.

[0051] The control unit 14 also bases the shift signal on the angular position, speed, and / or acceleration of the X-ray detector 24. The angular position, speed, and acceleration are acquired by sensors on at least one support structure 32.

[0052] The shift unit 16 is attached to the anti-scatter grid 26. Furthermore, the shift unit 16 comprises at least one control member that is a motor. The control member is configured to reposition the anti-scatter grid 26 in one dimension, i.e., along one direction.

[0053] The shift unit 16 receives the shift signal from the control unit 14 and shifts the anti-scatter grid 26 by the distance 19. This shifts the grid focus position 35 towards the X-ray beam focus position 37. As a result, the X-ray beam focus position 37 and the grid focus position 35 of the anti-scatter grid 26 are realigned.

[0054] Figures 4a and 4b show different types of scatter radiation removal grids 26. Figure 4a shows a one-dimensional scatter radiation removal grid 26. This one-dimensional scatter radiation removal grid 26 includes a single row of X-ray radiation transmission sections 25 divided by X-ray radiation absorption sections 27. The X-ray radiation transmission sections 25 are arranged such that the X-ray radiation transmission sections 25 are aligned with the grid focal position 35. The one-dimensional scatter radiation removal grid 26 reduces scatter in one dimension.

[0055] The shift unit 16 attached to the scatter radiation removal grid 26 relocates the scatter radiation removal grid 26 in the direction indicated by the arrow.

[0056] Figure 4b shows a two-dimensional scatter radiation removal grid 26. The two-dimensional scatter radiation removal grid 26 has multiple rows of X-ray radiation transmission sections 25 divided by X-ray radiation absorption sections 27. Similarly, the multiple rows of X-ray radiation transmission sections 25 are divided by the X-ray radiation absorption sections 27. The two-dimensional scatter radiation removal grid 26 reduces scatter in two dimensions.

[0057] The shift unit 16 includes a first shift component 162 and a second shift component 164. The first shift component 162 and the second shift component 164 are control members.

[0058] The first shift component 162 shifts the scatter radiation removal grid 26 in the first dimension, and the second shift component 164 shifts the scatter radiation removal grid 26 in the second dimension. The first dimension and the second dimension are orthogonal to each other as indicated by the arrow. However, the first dimension and the second dimension are also non-parallel while being non-orthogonal.

[0059] Figure 5 shows a flowchart of a method 100 for controlling the position of a scatter radiation removal grid in an X-ray image acquisition system.

[0060] In step a), the X-ray beam focal position of the X-ray radiation source of the X-ray image acquisition system is determined relative to the X-ray detector of the X-ray image acquisition system using a measurement unit in 101. The position of the X-ray detector and the position of the X-ray radiation source are determined in order to determine the change in alignment of an anti-scatter grid, which is arranged near or on the X-ray detector, respectively, to the X-ray beam focal position. This means that in step a), the displacement between the grid focal position and the X-ray beam focal position is determined.

[0061] In one example, the acquired x-ray image is further analyzed at 102 to determine any reduction in image quality caused by reduced contrast in the x-ray image due to changes in alignment and / or shadowing of the anti-scatter grid, which improves the determination of the displacement between the grid focal position and the x-ray beam focal position.

[0062] In step b), a shift signal is generated 103 from the displacement between the X-ray beam focal position and the grid focal position. The generation 103 is performed by the control unit. The shift signal contains information about how much the anti-scatter grid has to be shifted in order to align the grid focal position of the anti-scatter grid with the X-ray beam focal position.

[0063] In step c), the position of the anti-scatter grid is shifted in at least one direction based on the shift signal at 104. The shift is performed by a shift unit, which aligns the grid focus position of the anti-scatter grid with the X-ray beam focus position at the X-ray radiation source.

[0064] In another exemplary embodiment of the invention, a computer program or computer program element 40 as shown in FIG. 1 is provided, characterized in that it is adapted to execute, on a suitable system, the steps of the method according to one of the preceding embodiments.

[0065] Accordingly, the computer program element 40 is stored in a computer unit which is also part of an embodiment of the present invention. This computing unit is adapted to perform or induce the performance of the steps of the method described above. Further, the computing unit is adapted to operate the components of the device described above. The computing unit may be adapted to operate automatically and / or execute the instructions of a user. The computer program is loaded into the working memory of a data processor. Accordingly, the data processor is equipped to perform the method of the present invention.

[0066] This exemplary embodiment of the present invention covers both a computer program that uses the present invention from the very beginning and a computer program that, by way of an update, changes an existing program into a program that uses the present invention.

[0067] Furthermore, the computer program element can provide all the necessary steps for carrying out the procedure of an exemplary embodiment of the method described above.

[0068] According to a further exemplary embodiment of the present invention, a computer-readable medium 50 according to FIG. 1, such as a CD-ROM, is presented, the computer-readable medium storing a computer program element, the computer program element being described by the foregoing sections. The computer program is stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0069] However, a computer program may also be presented via a network such as the World Wide Web and downloaded from such a network into the working memory of a data processor. According to a further exemplary embodiment of the invention, a medium is provided for making computer program elements available for download, the computer program elements being configured to carry out a method according to one of the embodiments described previously of the invention.

[0070] It should be noted that the embodiments of the present invention have been described with respect to different subjects. In particular, some embodiments have been described with respect to method type claims, while other embodiments have been described with respect to device type claims. However, those skilled in the art will understand from the above and the following description that, unless otherwise notified, any combination of features belonging to one type of subject, as well as any combination between features related to different subjects, is considered to be disclosed by this application. However, all features can be combined and provide a synergistic effect beyond a mere addition of features.

[0071] The present invention has been shown and described in detail in the drawings and the above description, but such illustrations and descriptions should be considered illustrative or exemplary and not restrictive. The present invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and implemented by those skilled in the art when practicing the claimed invention from a consideration of the drawings, the disclosure, and the dependent claims.

[0072] In the claims, the words "comprising", "having", "including" do not exclude other elements or steps, and the singular does not exclude the plural. A single processor or other unit may perform the functions of several items recited in the claims. The mere fact that several measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously. No reference signs in the claims should be construed as limiting the scope thereof.

Claims

1. an X-ray radiation source and an X-ray detector connected to at least one C-arm as a support structure, a scatter radiation removal grid disposed between an object accommodation space and the X-ray detector, a device for controlling the position of the scatter radiation removal grid, comprising a measurement unit, a control unit, and a shift unit, an X-ray image acquisition system comprising: the measurement unit determines an X-ray beam focus position of the X-ray radiation source with respect to the X-ray detector during acquisition of an X-ray image by the X-ray image acquisition system, the control unit generates a shift signal based on a displacement between the X-ray beam focus position and a grid focus position of the scatter radiation removal grid, the shift unit shifts the scatter radiation removal grid in at least one direction based on the shift signal such that the grid focus position coincides with the X-ray beam focus position, an X-ray image acquisition system.

2. The X-ray image acquisition system according to claim 1, wherein the scatter radiation removal grid has a grid ratio in the range of 8:1 to 16:

1.

3. The X-ray image acquisition system according to claim 1, wherein the control unit determines a displacement based on an analysis of an X-ray image acquired by the X-ray detector.

4. The X-ray image acquisition system according to claim 1, wherein the shift unit shifts the scatter radiation removal grid disposed in a plane parallel to an X-ray collision surface of the X-ray detector in at least one direction.

5. The X-ray image acquisition system according to claim 1, wherein the shift unit shifts the scatter radiation removal grid in two directions.

6. The X-ray image acquisition system according to claim 1, wherein the shift unit comprises at least one control member for moving the scatter radiation removal grid.

7. The X-ray radiation source and the X-ray detector are mounted on opposing sections of the at least one C-arm, and the C-arm rotates these two opposing mounting sections around the object accommodation space. The X-ray image acquisition system according to claim 1.

8. A method for controlling the position of a scatter radiation removal grid in a C-arm type X-ray image acquisition system, the method comprising: a) Using a measurement unit, determining an X-ray beam focus position of the X-ray source of the C-arm type X-ray image acquisition system with respect to the X-ray detector of the C-arm type X-ray image acquisition system during acquisition of an X-ray image by the X-ray image acquisition system; b) Using a control unit, generating a shift signal based on a displacement between the X-ray beam focus position and a grid focus position; c) Using a shift unit, shifting the position of the scatter radiation removal grid in at least one direction based on the shift signal such that the grid focus position coincides with the X-ray beam focus position. Method. **Claim 9** An X-ray source and an X-ray detector connected to at least one C-arm as a support structure; A scatter radiation removal grid disposed between an object accommodation space and the X-ray detector; A device for controlling the position of the scatter radiation removal grid, comprising a measurement unit, a control unit, and a shift unit; An X-ray image acquisition system comprising: The measurement unit determines an X-ray beam focus position of the X-ray source with respect to the X-ray detector during acquisition of an X-ray image by the X-ray image acquisition system; The control unit generates a shift signal based on a displacement between the X-ray beam focus position and a grid focus position of the scatter radiation removal grid; The shift unit shifts the scatter radiation removal grid in at least one direction based on the shift signal such that the grid focus position coincides with the X-ray beam focus position. A computer program for controlling an X-ray image acquisition system, which, when executed by a processing unit, implements the method according to claim 8. **Claim 10** A non-transitory computer-readable medium storing the computer program according to claim 9.

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