3D X-ray device and method for producing 3D X-ray images

Abstract

The invention relates to a 3D X-ray device (1) comprising an X-ray detector (2), an X-ray source (3) and a computer (4), wherein the X-ray detector (2) and the X-ray source (3) are moved around an object volume (6) to be recorded on a movement path (5, 7) by a rotation of at least 185°, and a plurality of X-ray projection images are recorded from different irradiation directions (8), whereby X-rays (9) generated by the X-ray source (3) irradiate the object volume (6) in one of the irradiation directions (8) and are captured by the X-ray detector (2), and a 3D X-ray image (10) of the object volume (6) is calculated from the recorded X-ray projection images by a reconstruction method. The X-ray detector (2) is positioned asymmetrically with respect to a central axis (12) passing through the center of rotation (13) of the 3D X-ray device (1), a first fan beam (14) and an opposing second fan beam (17) rotated 180° form an overlap region (18), and at least one X-ray filter (21) is disposed between the X-ray source (3) and the object volume (6) to attenuate the X-ray dose within the overlap region (18).

Description

[Technical Field]

[0001] The invention relates to a 3D X-ray device comprising an X-ray detector, an X-ray source and a computer, wherein the X-ray detector and the X-ray source are moved around an object volume to be recorded on a movement path by a rotation of at least 185°, and a plurality of X-ray projection images are recorded from different irradiation directions, whereby X-rays generated by the X-ray source irradiate the object volume in one of the irradiation directions and are captured by the X-ray detector, and a 3D X-ray image of the object volume is calculated from the recorded X-ray projection images by means of a reconstruction method. [Background technology]

[0002] Several 3D X-ray devices and measurement methods are known from the state of the art.

[0003] U.S. Patent No. 8,238,522 (B2) discloses a filter changing assembly that can be used, for example, in an X-ray device, the filter changing assembly comprising a shaping filter that can be used to generate a radiation beam and that can, for example, be moved back and forth. The filter changing assembly also includes, for example, a beam hardening filter that can be used to change the energy spectrum of the radiation beam and that can also be moved back and forth. The filter changing assembly includes a control system that can be used to select at least one of the filters and to move the selected filter.

[0004] US Patent Application Publication No. 2014 / 0270069(A1) discloses an X-ray device comprising an X-ray source, a collimator for modifying the X-rays, and a motorized system operable to control the collimator. The leaves of the collimator can be configured to modulate the beam quality of the X-rays. The individual leaves of the collimator can be made of different metals, such as aluminum, copper, or tin, and can have different thicknesses so that radiation absorption can be influenced as desired.

[0005] US Patent Application Publication No. 2007 / 0172104(A1) discloses a CT device equipped with an X-ray filter for improving the image quality of 3D X-ray images. The X-ray filter serves to reduce the dose of the irradiated object.

[0006] One drawback of the mentioned method is that for rotations of more than 180°, the X-ray machine irradiates the overlapping area twice, so objects inside the overlapping area are irradiated with a higher dose.

[0007] It is therefore an object of the present invention to provide a method and a 3D X-ray device for recording 3D X-ray images with a homogeneous dose distributed over the object volume. Summary of the Invention

[0008] The present invention relates to a 3D X-ray device comprising an X-ray detector, an X-ray source, and a computer, wherein the X-ray detector and the X-ray source are moved around an object volume to be recorded on a movement path by a rotation of at least 185°. Multiple X-ray projection images are recorded from different irradiation directions, whereby X-rays generated by the X-ray source irradiate the object volume in one of the irradiation directions and are captured by the X-ray detector. A 3D X-ray image of the object volume is then calculated from the recorded X-ray projection images by a reconstruction method. The X-ray detector is positioned asymmetrically with respect to a central axis passing through the center of rotation of the 3D X-ray device, and a first fan beam and an opposing second fan beam rotated by 180° form an overlap region. At least one X-ray filter is disposed between the X-ray source and the object volume to attenuate the X-ray dose inside the overlap region. do.

[0009] The 3D X-ray device can be, for example, a CT device or a DVT device, and two-dimensional X-ray projection images are generated from different irradiation directions. During rotation, the X-ray detector and the X-ray source are rotated at least 185° around the object volume. During rotation, the X-ray detector and the X-ray source describe, for example, a circular or elliptical movement around the object volume, such that the center of rotation of the 3D X-ray device is defined by the circular movement. A central axis of the 3D X-ray device extends from the X-ray source through the center of rotation. The X-ray detector is positioned asymmetrically with respect to this central axis, for example, such that a first distance from the central axis to a first edge of the X-ray detector is smaller than a second distance from the central axis to a second edge of the X-ray detector. The 3D X-ray device can include an aperture, which is controlled to irradiate the entire sensor surface of the X-ray detector so that the fan beam is also positioned asymmetrically with respect to the central axis. Thus, for any given first fan beam from a particular irradiation direction, there is an opposing second fan beam rotated 180°, thereby positioning the first and second fan beams asymmetrically relative to the central axis. Within the overlap region, both the first and second fan beams irradiate the object volume. An X-ray filter is therefore shaped and positioned within the overlap region so that the X-ray dose attenuation within the overlap region results in a dose distribution that is as homogeneous as possible within the entire object volume. Therefore, one advantage of a 3D X-ray system is that the asymmetric X-ray detector arrangement and the selection and placement of the X-ray filter within the overlap region make it possible to achieve a dose distribution that is as homogeneous as possible within the entire object volume. The dose burden to the patient is therefore reduced.

[0010] Therefore, in regions of the object volume outside the overlap region, no X-ray filters are arranged to attenuate the X-ray dose, since said regions are irradiated only once and not twice as in the overlap region. It is also possible to arrange additional X-ray filters with constant or variable width and constant or variable attenuation in these regions outside the overlap region, whereby the X-ray filters are arranged inside the overlap region appropriately shaped to attenuate the dose inside the overlap region to a dose value within the values ​​outside the overlap region, so that the progression of the dose inside the object volume is as homogeneous as possible.

[0011] The 3D X-ray device can advantageously be a CT device or a DVT device.

[0012] Thus, the 3D X-ray device can be a conventional computed tomography (CT) device or a conventional digital volume tomography (DVT) device, whereby the 3D X-ray device of the present invention can be produced from a conventional CT or DVT device without much technical effort by equipping said device with the described X-ray filter.

[0013] The shape of the X-ray filter may advantageously be selected so that the transmission curve of the X-ray filter is monotonically decreasing or increasing over the overlap region.

[0014] This shape of the x-ray filter results in the desired dose reduction in the overlap region.

[0015] The shape of the X-ray filter may advantageously be chosen so that the transmission curve of the X-ray filter is point symmetric about the centre of rotation and has an attenuation of 50% of the X-ray dose at the centre point of the overlap region.

[0016] In particular for beam lobes with spatially constant or nearly constant intensity, this configuration ensures a dose distribution that is as homogeneous as possible within the object volume.

[0017] The transmission curve of the X-ray filter is a function of the transmission or attenuation of X-ray radiation depending on the X-coordinate along the entire length of the X-ray filter. Therefore, the X-ray filter is shaped and positioned relative to the fan beam so that the transmission curve is point-symmetric about the center of rotation and has an attenuation of 50% of the X-ray dose at the center point of the overlap region.

[0018] The center point of the overlap region is the projection of the center of rotation onto the X-ray detector.

[0019] The dose of the first fan beam and the dose of the second opposing fan beam are thus summed such that the sum of the doses results in a homogeneous dose progression inside the overlap region.

[0020] The shape of the X-ray filter may advantageously be selected such that the transmission curve of the X-ray filter increases monotonically inside the overlap region, for example from 0% to 100%.

[0021] The shape of the X-ray filter can advantageously be a rectangular parallelepiped, a wedge, a staircase, or a shape adapted to the weighting curve of the 3D reconstruction method.

[0022] The X-ray filter can thus have, for example, a rectangular parallelepiped shape, whereby the transmission curve has a constant attenuation of 50% of the X-ray dose along the entire length of the overlap region. In the case of a wedge-shaped X-ray filter, the width of the X-ray filter along the length is selected so that the transmission curve produces, for example, a straight line from 0% to 100% transmission along the length of the X-ray filter. In the case of a step-shaped X-ray filter, the width of the X-ray filter along the entire length is selected so that the transmission curve has a step-like progression. The transmission curve can have, for example, a uniform step-like increase arranged point-symmetrically with respect to the center of the overlap region. The shape of the X-ray filter can be adapted to the weighting curve of the 3D reconstruction method, whereby the width of the X-ray filter along the length is selected to produce a point-symmetric transmission curve with a selected progression.

[0023] The X-ray detector and the X-ray source can advantageously be moved around the object volume to be recorded on a movement path by a rotation of at least 360°.

[0024] As a result of the rotation of at least 360°, the entire recorded object volume is measured twice so that for any given first radiation beam there is a second opposing radiation beam, creating a homogeneous dose progression inside the overlap region.

[0025] To attenuate the X-ray dose inside the overlap region, multiple X-ray filters of different widths and shapes may advantageously be disposed between the X-ray source and the object volume.

[0026] The individual X-ray filters can be, for example, two wedge-shaped X-ray filters and a rectangular parallelepiped X-ray filter arranged inside an overlapping region one above the other in the X-ray direction, so that the X-ray filters arranged one above the other also generate the desired transmission curve.

[0027] It is important that there is no discontinuity in the dose progression at the transition between the overlap region and the remaining regions of the first and second opposing fan beams.

[0028] The X-ray filter can advantageously be constructed of multiple layers, with each layer being made of materials having different X-ray absorption characteristics, whereby the individual layers of the X-ray filter are constructed to produce a desired transmission curve.

[0029] X-ray filters are therefore constructed from multiple layers of different materials, such as copper or aluminum, to produce a desired, possibly point-symmetric, transmission curve. The individual layers of the X-ray filter may be positioned parallel to the X-rays of the X-ray fan beam, such that the different X-ray absorption properties of the materials and the widths of the individual layers produce the desired transmission curve.

[0030] The 3D X-ray device may advantageously comprise an aperture between the X-ray source and the object volume to form a fan beam, whereby the X-ray filter is arranged between the aperture and the X-ray source or between the aperture and the object volume.

[0031] The fan beam is therefore collimated by the aperture, whereby the X-rays striking the aperture are absorbed. The X-ray filter can therefore be arranged in front of or behind the aperture.

[0032] The computer may advantageously be configured such that the attenuation of the X-ray dose by the at least one X-ray filter is taken into account in the calculation of the 3D X-ray image by the reconstruction method.

[0033] The attenuation or transmission curve of the X-ray filter is therefore taken into account in the calculation of the 3D X-ray image so that potential distortions and imaging errors are avoided, and the calculation by the reconstruction method thus infers the correct X-ray filtered attenuated dose for each voxel of the object volume.

[0034] The X-ray filter may advantageously be made of copper or aluminium.

[0035] Copper and aluminum materials are particularly advantageous for the targeted attenuation of X-rays.

[0036] The X-ray filter can advantageously be moved automatically by a control unit and a drive unit to a desired position relative to the radiation beam.

[0037] The drive unit may, for example, comprise an electric motor so that the X-ray filter is positioned relative to the radiation beam as desired under the control of the control unit. This may be necessary, for example, if the size of the fan beam is changed by adjusting an aperture. The X-ray filter is thus positioned relative to the radiation beam in a desired manner, for example, so that the transmission curve is point-symmetric and has a 50% attenuation of the X-ray dose at the center point of the overlap region.

[0038] The present invention further relates to a method for generating a 3D X-ray image by a 3D X-ray device according to the inventive method discussed above, whereby the attenuation of the X-ray dose by the X-ray filter is taken into account in the calculation of the 3D X-ray image from the individual X-ray projection images by a reconstruction method.

[0039] Thus, one advantage of the method of the present invention is that the 3D X-ray image is recorded with reduced dose burden using the above-described 3D X-ray device with the described X-ray filter, and the calculation by the reconstruction method thus estimates the X-ray filtered attenuated dose for each voxel of the object volume.

[0040] The present invention will now be described with reference to the following figures. [Brief explanation of the drawings]

[0041] [Figure 1] Sketch of a 3D X-ray machine. [Figure 2] FIG. 1 is a diagram of a rectangular embodiment of an X-ray filter. [Figure 3] FIG. 1 is a diagram of a wedge-shaped embodiment of an X-ray filter. [Figure 4] FIG. 1 is a diagram of a stepped embodiment of an X-ray filter. [Figure 5] FIG. 1 is a diagram of a wedge-shaped embodiment of an X-ray filter. [Figure 6] FIG. 1 is a diagram of a stepped embodiment of a two-part X-ray filter. [Figure 7] FIG. 1 is a diagram of a wedge-shaped embodiment of a three-layer x-ray filter. DETAILED DESCRIPTION OF THE INVENTION

[0042] FIG. 1 shows a sketch of a 3D X-ray device 1, comprising an X-ray detector 2, an X-ray source 3, and a computer 4. The X-ray detector 2 is moved clockwise around the object volume 6 to be recorded on a first movement path 5 by a rotation of at least 360°, while the X-ray source 3 is moved in a corresponding manner around the object volume 6 to be recorded on a second movement path 7 by a rotation of at least 360°. During the rotation, multiple X-ray projection images are recorded from different irradiation directions 8, whereby X-rays 9 generated by the X-ray source 3 irradiate the object volume 6 in the corresponding irradiation directions 8 and are captured by the X-ray detector 2. A 3D X-ray image 10 of a patient 11 positioned within the object volume 6 is then calculated from the recorded X-ray projection images of the different irradiation directions by a reconstruction method and using the computer 4. The X-ray detector 2 is positioned asymmetrically with respect to a central axis 12 of the 3D X-ray device 1, which passes through a center of rotation 13. A first fan beam 14 of X-rays 9 irradiates the object volume 6. The X-ray source 3 is rotated 180° along the travel path 7 to reach the opposing position 15. The X-ray detector 2 is correspondingly rotated 180° to reach the opposing position 16 of the X-ray detector 2. At the opposing position 15, the X-ray source emits a second opposing fan beam 17, which irradiates the object volume 6. The first fan beam 14 and the second fan beam 17 irradiate a common overlap region 18. This overlap region 18 is therefore measured and irradiated twice, whereas a first remaining region 19 of the first fan beam 14 and a second remaining region 20 of the second fan beam 17 inside the object volume 6 are irradiated and recorded only once. Thus, for each first fan beam 14 in the irradiation direction 8, there is an opposing second fan beam 17 and overlap region 18. The superposition of all of the overlap regions 18 of the different illumination directions creates a cylindrical volume of overlap regions 18, which is shown in plan view as a circle around the center of rotation 13. Similarly, the superposition of all of the fan beams 14, 17 of the different illumination directions 8 results in a cylindrical volume of object volume 6, which is shown in plan view as a circle.While the X-ray detector 2 moves around the object volume 6, between 30 and 1000 X-ray projection images may be recorded every few seconds at angular increments between, for example, 0.01° and 10°.

[0043] To attenuate the X-ray dose inside the overlap region 18, an X-ray filter 21 is disposed at a fixed position relative to the X-ray source 3 and thus the first fan beam 14. The X-ray dose inside the overlap region 18 is thereby attenuated as part of the first fan beam 14, as indicated by the dotted line 22. As a result of the rotation of the X-ray source 3 and the opposing position 15, the X-ray filter 21 is moved to an opposing position 23 so that the overlap region 18 of the opposing second fan beam 17 is attenuated. In this case, the X-ray filter 21, which may be made of copper, for example, has a rectangular parallelepiped shape so that the X-ray dose in the overlap region 18 of the first fan beam 14 is attenuated by 50%, and accordingly the opposing second fan beam 17 inside the overlap region 18 is also attenuated by 50%. Thus, a total homogeneous X-ray dose of 100% is achieved inside the overlap region 18. To generate the fan beam 14, an aperture 24 is disposed in a fixed position relative to the x-ray source 3, whereby the aperture 24 may be made of tungsten or lead. As the x-ray source 3 rotates, the aperture 24 is also moved to an opposing position 25 to generate a second opposing fan beam 17.

[0044] FIG. 2 shows a diagram of the width 30 of the X-ray filter 21 along the central axis 12 of FIG. 1 as a function of the length 31 of the X-ray detector 2 in the direction of movement 5 of FIG. 1. The progression of the width 30 of the X-ray filter 21 as a projection onto the X-ray detector 2, i.e., depending on the length of the X-ray detector, is plotted in a first function 32. In this case, the average energy of the X-ray photons of the fan beam 14 is 60 keV. The X-ray filter is made of copper. It can therefore be seen from the first function 32 that the width of the X-ray filter 21 is a constant 0.5 mm within the overlap region 18, thereby eliminating the X-ray filter within the first remaining region 19. The transmission 33 between 0% and 100% is plotted on the second y-axis. The transmission curve 34 therefore shows the dependence of the transmission on the length coordinate 31 of the X-ray detector 2, whereby 50% attenuation occurs inside the overlap region, or more specifically, the transmission is 50% and the transmission in the first remaining region 19 is 100%.

[0045] 3 shows a diagram like that in FIG. 2, where the width 30 function 32 drops off sharply based on the length coordinate 31 of the X-ray detector 2. The X-ray filter therefore has a wedge shape 40. The transmission curve 34 therefore increases linearly from 0% to 100% inside the overlap region 18 and remains constant at 100% within the remaining region 19. The transmission at the center point 41 of the overlap region 18 is 50%. The linearly increasing function 34 is therefore point-symmetric inside the overlap region 18 with respect to the center point 41 of the overlap region, such that the addition of the dose of the first fan beam 14 and the dose of the second fan beam 17 of FIG. 1 results in a 100% homogeneous dose distribution.

[0046] 4 shows a further embodiment of an X-ray filter having a step shape 50 with a variable width 30, whereby the associated diagram shows a step function 32 of the width 30 depending on the length coordinate of the X-ray detector 2. The transmission curve 34 consequently shows a stepwise increase inside the overlap region 18, which is point-symmetric about the center point 41 of the overlap region 18. The transmission within the remaining region 19 is 100%. The transmission at the center point 41 of the overlap region is consequently 50%.

[0047] 5 shows a further embodiment of an X-ray filter having a second wedge shape 60, whereby the width 30 is reduced compared to the X-ray filter of FIG. 3. The progression of the function 32 of the width 30 depending on the length coordinate 31 thus results in an increasing transmission curve 34 that is point-symmetric inside the overlap region 18 relative to the center point 41 of the overlap region. The transmission at the center point 41 of the overlap region 18 is 50%. The transmission inside the remaining region 19 remains at 100%.

[0048] 6 shows a further embodiment of an X-ray filter 70 comprising a first portion 71 and a second portion 72, whereby the first portion 71 is made, for example, of aluminum and the second portion 72 is made, for example, of copper. The different X-ray absorption properties of the two portions 71 and 72 as well as the selected function 32 of the width 30 depending on the adjacent coordinates 31 result in a desired stepped transmission curve 34 that extends point-symmetrically inside the overlap region 18 relative to a center point 41 of the overlap region 18. The transmission 33 at the center point 41 is 50%.

[0049] 7 shows a further embodiment of an X-ray filter 80 comprising a first portion 81, a second portion 82 and a third portion 83, whereby the individual portions 81, 82 and 83 are arranged one above the other in the irradiation direction 8. The portions 81, 82 and 83 can be made of different materials. The function 32 of the width 30 depending on the length coordinate 31 as well as the individual materials are therefore selected so that a desired linear progression of the transmission curve 34 inside the overlap region 18 is achieved. The transmission 33 at the center point 41 of the overlap region 18 is 50%. [Explanation of symbols]

[0050] 1 3DX ray device 2 X-ray detector 3 X-ray source 4. Computer 5. Travel Route 6 Object Volume 7 Second migration route 8 Irradiation direction 9 X-ray 10 3DX ray image 11 patients 12 Center axis 13 Center of rotation 14 First Fan Beam 15 Opposite position of X-ray source 3 16 Opposite position of X-ray detector 2 17 Second opposing fan beam 18 Overlapping area 19 First Remaining Region 20 Second Remaining Area 21 X-ray filter 22 dotted line 23 Opposite position of X-ray filter 24 aperture 25 Opposite positions of X-ray sources 30 X-ray filter width 31 X-ray detector length 32 First Function 33 Transparent 34 Transmission curve 40 Wedge-shaped X-ray filter 41 Center point of overlapping area 50 Stepped X-ray filter 60 Second wedge-shaped X-ray filter 70 Additional X-ray filters, 2 pieces 71 First part of X-ray filter 72 Second part of the X-ray filter 80 additional x-ray sections, 3 sections 81 First part of X-ray filter 82 Second part of the X-ray filter 83 X-ray filter third part The following is a summary of the claims as originally filed: [1] A 3D X-ray device (1) comprising an X-ray detector (2), an X-ray source (3), and a computer (4), 3D X-ray device, wherein the X-ray detector (2) and the X-ray source (3) are moved around an object volume (6) to be recorded in the craniomaxillofacial region on a movement path (5, 7) by a rotation of at least 185°, and a plurality of X-ray projection images are recorded from different irradiation directions (8), whereby X-rays (9) generated by the X-ray source (3) irradiate the object volume (6) in one of the irradiation directions (8) and are captured by the X-ray detector (2), and a 3D X-ray image (10) of the object volume (6) is calculated from the recorded X-ray projection images by a reconstruction method, a first fan beam (14) and a second fan beam (17) rotated 180° to form an overlap region (18); at least one X-ray filter (21) is disposed between the X-ray source (3) and the object volume (6) to attenuate the amount of X-rays within the overlap region (18); and a second X-ray filter (21) having a width different from a width (30) of the X-ray filter (21) disposed within the overlap region (18) is disposed within a region (19, 20) of the two fan beams (14, 17) outside the overlap region (18). [2] The 3D X-ray device (1) according to [1], characterized in that the 3D X-ray device (1) is a CT device or a DVT device. [3] The 3D X-ray device (1) according to [1] or [2], characterized in that the shape of the X-ray filter (21) is selected so that the transmission curve (34) of the X-ray filter (21) monotonically decreases or increases over the overlap region. [4] The 3D X-ray device (1) according to any one of [1] to [3], characterized in that the shape of the X-ray filter (21) is selected so that a transmission curve (34) of the X-ray filter (21) is point-symmetric with respect to the center of rotation (13) and so that an attenuation of the X-ray dose of 10 to 75% is exhibited within a center point (41) of the overlap region (18). [5] The 3D X-ray device (1) according to any one of [1] to [4], characterized in that the shape of the X-ray filter (21) is a rectangular parallelepiped, a wedge (40, 60, 80), a staircase (50, 70), or a shape fitted to a weighting curve. [6] A 3D X-ray device (1) according to any one of [1] to [5], characterized in that the X-ray detector (2) and the X-ray source (3) are moved around the object volume (6) to be recorded on a movement path (5, 7) by a rotation of at least 360°. [7] A 3D X-ray device (1) according to any one of [1] to [6], characterized in that a plurality of X-ray filters (71, 72) of different widths and shapes are arranged between the X-ray source (3) and the object volume (6) to attenuate the X-ray amount inside the overlap region (18). [8] The 3D X-ray device (1) according to any one of [1] to [7], characterized in that the X-ray filter (80) is constructed from a plurality of layers (81, 82, 83), each of which is made of a material having different X-ray absorption characteristics, and the individual layers (81, 82, 83) of the X-ray filter (80) are constructed so as to generate a desired transmission curve (34). [9] The 3D X-ray device (1) according to any one of [1] to [8], characterized in that the 3D X-ray device (1) comprises an aperture (24) between the X-ray source (3) and the object volume (6) to form the fan beam (14, 17), and the X-ray filter (21) is arranged between the aperture and the X-ray source (3) or between the aperture (24) and the object volume (6).

[10] The 3D X-ray device (1) according to any one of [1] to [9], characterized in that the computer (4) is configured so that the attenuation of the X-ray dose by the at least one X-ray filter (21) is taken into account in the calculation of the 3D X-ray image (10) by the reconstruction method.

[11] The 3D X-ray device (1) according to any one of [1] to

[10] , characterized in that the X-ray filter (21) is made of copper or aluminum.

[12] The 3D X-ray device (1) according to any one of [1] to

[11] , characterized in that the X-ray filter (21) is automatically moved to a desired position relative to the radiation beam (14) by a control unit and a drive unit.

[13] A method for generating a 3D X-ray image (10) by a 3D X-ray device (1) according to any one of [1] to

[12] , characterized in that the attenuation of the X-ray dose by an X-ray filter (21) is taken into account in the calculation of the 3D X-ray image (10) from the individual X-ray projection images by a reconstruction method.

Claims

1. A 3D X-ray device (1) comprising an X-ray detector (2), an X-ray source (3), and a computer (4), a 3D X-ray device (1) in which the X-ray detector (2) and the X-ray source (3) are moved around an object volume (6) to be recorded in the craniomaxillofacial region on a movement path (5, 7) by a rotation of at least 185°, and a plurality of X-ray projection images are recorded from different irradiation directions (8), whereby X-rays (9) generated by the X-ray source (3) irradiate the object volume (6) in one of the irradiation directions (8) and are captured by the X-ray detector (2), and a 3D X-ray image (10) of the object volume (6) is calculated from the recorded X-ray projection images by a reconstruction method, 1. A 3D X-ray device (1), characterized in that the X-ray detector (2) is arranged asymmetrically with respect to a central axis (12) passing through a center of rotation (13) of the 3D X-ray device (1) and the X-ray source (3), a first fan beam (14) and an opposing second fan beam (17) rotated by 180° form an overlap region (18), at least one X-ray filter (21) is arranged between the X-ray source (3) and the object volume (6) to attenuate the X-ray amount inside the overlap region (18), and a second X-ray filter is provided in regions (19, 20) of the two fan beams (14, 17) outside the overlap region (18).

2. 3D X-ray device (1) according to claim 1, characterized in that the 3D X-ray device (1) is a CT device or a DVT device.

3. 3D X-ray device (1) according to claim 1 or 2, characterized in that the shape of the X-ray filter (21) is selected such that the transmission curve (34) of the X-ray filter (21) monotonically decreases or increases over the overlap region.

4. 4. The 3D X-ray device (1) according to claim 1, wherein the shape of the X-ray filter (21) is selected so that the transmission curve (34) of the X-ray filter (21) relative to the center of rotation (13) is point-symmetric and exhibits an attenuation of the X-ray dose of 50% within the center point (41) of the overlap region (18).

5. 3D X-ray device (1) according to any one of claims 1 to 4, characterized in that the shape of the X-ray filter (21) is a rectangular parallelepiped, a wedge (40, 60, 80) or a step shape (50, 70).

6. 6. The 3D X-ray device (1) according to any one of claims 1 to 5, characterized in that the X-ray detector (2) and the X-ray source (3) are moved around the object volume (6) to be recorded on a movement path (5, 7) by a rotation of at least 360°.

7. 7. The 3D X-ray device (1) according to claim 1, wherein a plurality of X-ray filters (71, 72) of different widths and shapes are arranged between the X-ray source (3) and the object volume (6) to attenuate the X-ray amount inside the overlap region (18).

8. 8. The 3D X-ray device (1) according to claim 1, wherein the X-ray filter (80) is constructed from a plurality of layers (81, 82, 83), each layer (81, 82, 83) being made of a material having different X-ray absorption properties, and wherein the individual layers (81, 82, 83) of the X-ray filter (80) are constructed in such a way that a desired transmission curve (34) is generated.

9. 9. The 3D X-ray device (1) according to claim 1, characterized in that the 3D X-ray device (1) comprises an aperture (24) between the X-ray source (3) and the object volume (6) to form the fan beam (14, 17), and the X-ray filter (21) is arranged between the aperture and the X-ray source (3) or between the aperture (24) and the object volume (6).

10. 10. The 3D X-ray device (1) of claim 1, wherein the computer (4) is configured such that the attenuation of the X-ray dose by the at least one X-ray filter (21) is taken into account in the calculation of the 3D X-ray image (10) by the reconstruction method.

11. 3D X-ray device (1) according to any one of claims 1 to 10, characterized in that the X-ray filter (21) is made of copper or aluminium.

12. 3D X-ray device (1) according to any one of claims 1 to 11, characterized in that the X-ray filter (21) is automatically moved to a desired position relative to the radiation beam (14) by a control unit and a drive unit.

13. 13. A method for generating a 3D X-ray image (10) by means of a 3D X-ray device (1) according to any one of claims 1 to 12, characterized in that the attenuation of the X-ray dose by an X-ray filter (21) is taken into account in the calculation of the 3D X-ray image (10) from individual X-ray projection images by a reconstruction method.

Images