Multilayer X-ray detectors and X-ray systems

Abstract

To provide a multilayer X-ray detector which enables improved quantum efficiency of X-ray detection, in addition to sufficient spectrum separation of an X-ray image by means of a dual energy X-ray source.SOLUTION: There is provided a multilayer X-ray detector, in which sensor layers are arranged behind in an X-ray projection direction, a first sensor layer 10 is designed to convert an X-ray quantum of a first light-emission spectrum into a first signal, a second sensor layer 11 is designed to convert an X-ray quantum of a second light-emission spectrum into a second signal, and the multilayer X-ray detector incudes an intermediate space 14 arranged between the two sensor layers, at least one layer belt 15 which has at least two filter regions 16 having a plurality of material compositions and / or coatings and is designed to be bendable, and a transport mechanism for giving either the first filter region 16 or the second filter region 17 to the intermediate space 14.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The invention relates to a multi-layer X-ray detector according to claim 1 and to an X-ray system comprising a multi-layer X-ray detector according to claim 12. [Background technology]

[0002] Modern X-ray technology uses dual-energy X-ray tubes, i.e., X-ray tubes capable of emitting two different emission spectra. One of the emission spectra is generally high-energy, the other somewhat lower-energy. The distinct energy difference between the two sensor layers is particularly important. For example, the soft tissue fraction can be subtracted from the two multiple X-ray images thus generated, thus allowing bone density to be measured. The material composition of whole-body tissues can also be calculated.

[0003] In addition to a dual-energy X-ray tube, a dual-energy X-ray detector is also required to be able to read out the corresponding signal. Such a known dual-energy X-ray detector 9 (see FIG. 1) typically has two scintillator-based sensor layers, one behind the other in the X-ray projection direction 13. During recording, first the first sensor layer 10 and then the second sensor layer 11 are penetrated by the X-ray beam along the projection direction 13. To achieve sufficient spectral separation for dual-energy recording, a filter layer is typically present between the two sensor layers (e.g., a 1 mm thick copper filter layer 12). Such multi-layer X-ray detectors: For example, it is known from Stehr, Fredrik et al., "Performance Characterization of a Prototype Dual-Layer Cone-Beam Computed Tomography System," (Medical Physics Vol. 48, 11 (2021), pp. 6740-6754).

[0004] A drawback of multi-layer X-ray detectors is that the high absorption of the filter layers reduces the quantum efficiency of X-ray detection. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide a multi-layer X-ray detector that allows improved quantum efficiency of X-ray detection as well as sufficient spectral separation of X-ray images by means of a dual energy X-ray source. [Means for solving the problem]

[0006] This object is achieved according to the invention by a multi-layer X-ray detector as defined in claim 1 and by an X-ray system comprising a multi-layer X-ray detector as defined in claim 12. Advantageous embodiments of the invention are the subject matter of the respective associated dependent claims.

[0007] The multi-layer X-ray detector according to the present invention comprises at least first and second sensor layers, which are arranged behind each other in the X-ray projection direction, the first sensor layer designed to convert X-ray quanta of a first spectrum (e.g., X-ray radiation spectrum) into a first signal and the second sensor layer designed to convert X-ray quanta of a second spectrum (e.g., X-ray radiation spectrum) into a second signal, an intermediate space arranged between the two sensor layers, at least one layer belt designed to be bendable and having at least two filter regions with multiple material compositions and / or coatings, and a transport mechanism capable of bringing either the first filter region or the second filter region into the intermediate space.

[0008] The layer belt is particularly flexible and can be bent, folded, or rolled up without damaging the layer belt itself or any possible coating. The filter regions can be designed to have a large surface area, in particular a surface area that roughly corresponds to the surface area of ​​the second sensor layer, so that the entire intermediate space can be covered by one of the filter regions, if necessary. The layer belt itself generally preferably has at least twice the area of ​​the second sensor layer (at least two filter regions), and can also be significantly larger (for example, filter regions or neutral areas between three or more filter regions). The layer belt is preferably arranged in the area of ​​the intermediate space so that the surface normal of the layer belt is parallel to the X-ray projection direction.

[0009] The transport mechanism allows either the first or second filter region, with its respective material composition and therefore filter effect, to be introduced into the intermediate space between the two sensor layers as needed. In this way, the user can select the filtering required for the current application and set it quickly and easily. Even during an ongoing procedure, rapid switching between the two filter regions can be performed within a few seconds, for example. The X-ray detector offers a high degree of flexibility in terms of spectral separation of at least two spectra for X-ray recording. The filter regions have as uniform a composition or filter effect as possible.

[0010] The use of such layered belts also ensures a high reliability of the filtering effect and there is a low risk of artifacts in the resulting X-ray images.

[0011] According to one embodiment of the present invention, the layer belt comprises a first spectral filter material having a first X-ray transmittance in a first filter region and a second spectral filter material having a second X-ray transmittance in a second filter region, the first X-ray transmittance being different from the second X-ray transmittance. The multiple X-ray transmittances allow for multiple filter effects to be selected as needed.

[0012] In particular, the first filter region has a transmittance of less than 25% based on an X-ray photon energy of 50 keV, resulting in a particularly effective X-ray absorption. In this way, when the first filter region is positioned within the intermediate space, particularly good spectral separation of the emission spectrum, and therefore particularly good dual-energy resolution, can be achieved, thereby enabling accurate analysis of the material composition of the object being examined. For this purpose, the first filter material may contain or be made of at least one of the elements copper, tantalum, lead, aluminum, tin, brass, or iron. For example, the first filter region may be designed to be sufficiently thick to absorb low-energy (e.g., 40-80 keV) photons sufficiently well while simultaneously providing the lowest possible absorption of high-energy photons (e.g., 100-120 keV), thereby ensuring sufficient penetration of the second sensor layer for detection and dose efficiency reasons.

[0013] In an advantageous embodiment, the second filter region has a particularly large X-ray transmittance of more than 60%, especially more than 90%, based on an X-ray photon energy of 50 keV, so that the second filter region has only a weak or no X-ray absorption effect. When the second filter region is located in the intermediate space, particularly good quantum efficiency can be achieved in X-ray recording. This allows an X-ray detector having a first filter region with low X-ray transmittance and a second filter region with high X-ray transmittance to ensure good spectral separation in dual-energy operation and high quantum efficiency in normal operation, depending on the transport belt configuration, and can be used for a variety of applications with the same high quality.

[0014] According to a further embodiment of the present invention, the layer belt is designed to be able to be wound up and / or unwound. For this purpose, the transport mechanism can have, for example, rollers on which the layer belt is wound up and unwound. In addition, there can also be one or more motors, for example, which can rotate the rollers and thus move the layer belt. For example, rollers can be present on both sides of the sensor layer outside the intermediate space, and the rolling of the transport belt on one roller and simultaneously on the other roller can carry the respective filter area into the intermediate space.

[0015] According to a further embodiment of the present invention, the conveying mechanism has rollers, and the layer belt is designed to be movable via the rollers so that either the first filter region or the second filter region is conveyed into the intermediate space. In particular, the layer belt and the conveying mechanism are designed as conveyor belts, particularly as motorized conveyor belts. In this embodiment, the layer belt can be designed as a continuous endless conveyor belt tensioned by two rollers and partially positioned in the intermediate space, with the two filter regions positioned on different sides of the rollers. The two rollers are driven by a motor to rotate, moving the conveyor belt so that one of the filter regions can be positioned in the intermediate space depending on its position.

[0016] According to a further embodiment of the present invention, the first sensor layer comprises a first scintillator material of a first thickness and a first readout circuit designed to detect photons generated by the first scintillator material from X-ray quanta of a first spectrum and generate a first signal therefrom, and the second sensor layer comprises a second scintillator material of a second thickness and a second readout circuit designed to detect photons generated by the second scintillator material from X-ray quanta of a second spectrum and generate a second signal therefrom. The operating principle of the sensor layers of X-ray detectors is known in principle.

[0017] According to a further embodiment of the present invention, a multi-layer X-ray detector includes a flexible second layer belt having at least two filter regions with different material compositions and / or coatings, and a transport mechanism for inserting either the first or second filter region into the intermediate space. Different filter effects can be generated by the two or more layer belts, depending on which filter region is simultaneously positioned in the intermediate space in each case. Such an X-ray detector offers multiple possibilities and variations between strong spectral separation and particularly high quantum efficiency.

[0018] According to a further embodiment of the present invention, the multi-layer X-ray detector is designed as either an X-ray flat detector or a fan detector. In an X-ray flat detector for a cone beam X-ray source, the sensor surface is generally flat and relatively large, e.g., 20x30cm or 30x40cm, and as a result, the conveyor belt and filter area are similarly large. application The fan detector for is generally curved in the shape of a segment of a circle, e.g., long and narrow. The conveyor belt and filter area are similarly curved.

[0019] Furthermore, the present invention comprises an X-ray system comprising a multi-layer X-ray detector according to one of the preceding claims, a dual-energy X-ray source designed to be able to switch from emitting light in a first emission spectrum to emitting light in a second emission spectrum and vice versa, and a system controller for controlling the multi-layer X-ray detector and the dual-energy X-ray source.

[0020] The invention and further advantageous embodiments according to the features of the dependent claims are explained in more detail below with the help of exemplary embodiments shown schematically in the drawings, but the invention is not consequently limited to these exemplary embodiments. [Brief explanation of the drawings]

[0021] [Figure 1] 1 shows a cross-sectional view of a multi-layer X-ray detector according to the prior art. [Figure 2] 1 shows a cross-sectional view of a multi-layer X-ray detector according to the invention having a layer belt with two filter regions in a first state; [Figure 3] 3 shows a cross-sectional view of a multi-layer X-ray detector according to the invention with a layer belt having two filter regions in a second state. [Figure 4] 3 shows a cross-sectional view of a further multi-layer X-ray detector according to the invention having a layer belt with two filter regions in a first state; [Figure 5] 1 shows a cross-sectional view of a multi-layer X-ray detector according to the present invention having a two-layer belt. [Figure 6] 3 shows a cross-sectional view of a further multi-layer X-ray detector according to the invention having two layer belts; [Figure 7] 1 shows an X-ray system having a multi-layer X-ray detector and a dual-energy X-ray source. DETAILED DESCRIPTION OF THE INVENTION

[0022] As already explained, Figure 1 shows a known dual-energy X-ray detector 9 in which, to achieve sufficient spectral separation for dual-energy recording, a fixed high X-ray absorption filter layer is present between a first scintillator-based sensor layer 10 and a second scintillator-based sensor layer 11. However, such a dual-energy X-ray detector 9 does not provide sufficient quantum efficiency in normal operation.

[0023] 2-6 show a multi-layer X-ray detector 19 having a layer belt 15, in which the filter region of the flexible layer belt 15 can be transported by various transport mechanisms into the intermediate space 14 between the first sensor layer 10 and the second sensor layer 11. Depending on the coating or composition of the filter region, various filters can be produced that achieve different effects, for example, these filters can ensure spectral separation in dual-energy operation or can provide sufficient quantum efficiency in normal operation.

[0024] 2 and 3 show a multi-layer X-ray detector 19 having a first scintillator-based sensor layer 10 and a second scintillator-based sensor layer 11, which are arranged one behind the other in the X-ray projection direction 13. An intermediate space 14 is arranged between the two sensor layers 10, 11, for example, across the entire length and width of the sensor layers. The multi-layer X-ray detector 19 can also be designed as a flexible, retractable, "endless" conveyor belt, for example, with a layer belt 15 tensioned via two rollers 18, which are arranged on both sides of the sensor layers 10, 11, in particular the second sensor layer 11. The rollers 18 are preferably arranged outside the angle of incidence of the X-ray radiation. The conveyor belt is at least partially arranged in the intermediate space 14 between the two sensor layers 10, 11, and extends at least partially, in particular completely, across the length and width of the sensor layers 10, 11. The rotation of the rollers 23 causes the conveyor belt to roll over the rollers 18, thereby changing its position.

[0025] The conveyor belt has at least two filter regions with different spectral filter materials (different compositions, thicknesses, densities, etc.) with, for example, different X-ray transmittances. In this case, for example, the first filter region 16 can have a first filter material with low X-ray transmittance, and the second filter region 17 can have a second filter material with high X-ray transmittance. The filter materials can be applied to the conveyor belt, for example, as a coating. The layer belt 15 can be designed as a conveyor belt and have the form of a film. The conveyor belt itself can also have multiple material compositions and / or multiple thicknesses and / or densities in the corresponding filter regions.

[0026] The first filter region 16 can have a coating containing, or be at least partially made of, one or more of copper, tantalum, lead, aluminum, brass, tin, or iron. The coating can be thick enough to provide a significant filtering effect (e.g., 1 mm of copper). The second filter region 17 can have only a very thin coating of a material with high X-ray transmittance, or no coating at all (e.g., only a layer belt / film), and thus have nearly 100% X-ray transmittance. Alternatively, the first filter region can have a thick coating, and the second filter region can have a thin coating of the same material.

[0027] The sensor layers 10, 11 are configured as in known multi-layer X-ray detectors. Thus, the first sensor layer 10 can comprise a first scintillator material of a first thickness and can include a first readout circuit, and the second sensor layer 11 can comprise a second scintillator material of a second thickness and can include a second readout circuit. Each readout circuit is designed to detect photons generated by the first scintillator material from X-ray quanta of a respective associated emission spectrum and generate a signal therefrom, which is used to generate an X-ray image.

[0028] If necessary, either the first filter region 16 or the second filter region 17 can be moved within the intermediate space 14, for example, by motor-driven rollers 18, both of which rotate in the same direction of rotation 23. For this purpose, the rollers can have a drive (not shown). When the first filter region 16, which has low X-ray transmittance, is located in the intermediate space 14 (shown in FIG. 2) and extends across the entire sensor surface of the second sensor layer 11, irradiation with a dual-energy X-ray source with different emission spectra results in spectral filtering, by which tissue composition can be determined (e.g., by subtraction) from the resulting X-ray image. When the second filter region 17, which has high X-ray transmittance, is located in the intermediate space 14 (shown in FIG. 3), a composite X-ray image with high quantum efficiency can be generated from the two X-ray images.

[0029] The transport mechanism can also be designed so that two rollers 18 are rotatably arranged on both sides of the second sensor layer 11 outside the intermediate space 14 (as shown in FIG. 4), and the layer belt 15 is wound by being wound from one roller 18 to the other roller 18, respectively. This is done, for example, by motor-driven rotation of the two rollers 18 in the same direction of rotation 23. In this way, one filter area 16, 17 can also be arranged between the rollers 18, so that the filter area is completely located within the intermediate space 14 and extends, for example, over the second sensor surface 11. filtering To ensure this, the ply belt 15 has a (e.g., predetermined) tension between the rollers 18. To maintain such tension, for example, one or both of the rollers 18 may be provided with a spring mechanism.

[0030] 5 and 6 show a further exemplary embodiment of a multi-layer X-ray detector 19 having two transport mechanisms, each with a layer belt, whose filter regions can be arranged behind one another in the X-ray projection direction 13 in the intermediate space 14. In this way, further filter options can be created.

[0031] For example, FIG. 5 shows two layer belts: a first layer belt 15.1, designed as an endless conveyor belt and tensioned via two rollers 18, with a first filter region 16 and a second filter region 17; and a second layer belt 15.2, also designed as an endless conveyor belt and tensioned via two rollers 18, with a third filter region 16.2 and a fourth filter region 17.2. The first layer belt 15.1 is, for example, positioned within the second layer belt 15.2. In this case, the filter regions can be arranged overlapping and combined as needed within the intermediate space 14 in the X-ray projection direction 13. For example, the first filter region 16 of the first layer belt 15.1 can be combined with the third filter region 16.2 of the second layer belt 15.2, or with the fourth filter region 17.2 of the second conveyor belt 15.2. The overlapping provides a combined filtering effect. Depending on the combination and the individual filters, up to four different filter variants are possible here.

[0032] In this case, the conveyor belt may have a filter region with low X-ray transparency and a filter region with high X-ray transparency. The conveyor belt may be made of, for example, a film or belt, with the filter region coated accordingly, or may be assembled from multiple components. The filter region materials may vary in composition, density, and thickness. The conveyor belt and its coating should be flexible and bendable and not crack or break when rolled.

[0033] FIG. 6 shows two ply belts 15.1, 15.2 arranged behind each other in the X-ray projection direction 13. Each ply belt has two rollers 18 with a transport mechanism similar to that shown in FIG. 4. When both rollers 18 are driven by a motor in the same direction of rotation 23, each of the two ply belts 15.1, 15.2 can be wound up by winding it from one roller 18 to the other depending on the position of the ply belt, thereby moving one of the filter areas into the intermediate space 14. In this way, the filter area of ​​the first ply belt 15.1 and the filter area of ​​the second ply belt 15.2 can always be arranged behind each other and can overlap in terms of X-ray absorption effect. With two filter areas per ply belt, up to four different filter configurations are also possible.

[0034] Each layer belt can also have more than two filter regions, for example, three or four. The motor-driven rollers 18 can be controlled by a controller with respect to their movement, for example, to set specific positioning of the filter regions.

[0035] FIG. 7 shows an X-ray system having a multi-layer X-ray detector 19 and a dual-energy X-ray source 21 controlled by a system controller 24. The multi-layer X-ray detector 19 and dual-energy X-ray source 21 can be fixedly positioned on a C-arm 22, for example, which can be spatially adjustable (e.g., orbitally, rotationally, or translationally). In this case, the dual-energy X-ray source 21 can be designed to emit a cone beam, and the multi-layer X-ray detector 19 can be designed as a flat detector. In the case of a flat detector, the sensor layer is also designed as a flat detector. The system controller can also be used to control the positioning of the filter region, for example, by moving the motorized rollers 18 according to the planned application.

[0036] A computed tomography X-ray system is also possible having a gantry on which the multi-layer X-ray detector 19 and the dual-energy X-ray source 21 are arranged. In such a case, the X-ray detector is designed as a line detector and the sensor layer is designed to be curved.

[0037] The material of the coating of the filter region can also be mixed with other materials that increase flexibility and / or elasticity to allow for damage-free rolling. The filter material can be applied to an elastic carrier material.

[0038] The term includes individuals who identify as male, female, or any other gender identity, regardless of grammatical usage of the term.

[0039] The present invention can be briefly summarized as follows. For particularly flexible usability with regard to dual energies, a multi-layer X-ray detector is provided which includes at least first and second sensor layers, which are arranged behind the other in the X-ray projection direction, the first sensor layer designed to convert X-ray quanta of a first emission spectrum into a first signal and the second sensor layer designed to convert X-ray quanta of a second emission spectrum into a second signal, an intermediate space arranged between the two sensor layers, at least one layer belt designed to be bendable and having at least two filter regions with a plurality of material compositions and / or coatings, and a transport mechanism capable of bringing either the first filter region or the second filter region into the intermediate space.

Claims

1. at least a first sensor layer (10) and a second sensor layer (11), one of which is arranged behind the other in an X-ray projection direction (13), the first sensor layer (10) being designed to convert X-ray quanta of a first spectrum into a first signal, and the second sensor layer (11) being designed to convert X-ray quanta of a second spectrum into a second signal; an intermediate space (14) arranged between the two sensor layers (10, 11); At least one layer belt (15) designed to be flexible, having at least two filter regions (16; 17) with multiple material compositions and / or coatings, and a conveying mechanism capable of conveying either the first filter region (16) or the second filter region (17) into the intermediate space (14); A multi-layer X-ray detector (19) comprising: a second layer belt (15.2) designed to be flexible and having at least two filter areas (16.2; 17.2) with multiple material compositions and / or coatings; a conveying mechanism capable of placing one of the filter regions (16.2; 17.2) of the second layer belt (15.2) into the intermediate space (14); A multi-layer X-ray detector (19) comprising:

2. the layer belt (15) comprises a first spectral filter material having a first X-ray transmittance in the first filter region (16) and a second spectral filter material having a second X-ray transmittance in the second filter region (17), the first and second X-ray absorption coefficients are different; The multi-layer X-ray detector of claim 1 .

3. The multi-layer x-ray detector of claim 2 , wherein the first x-ray transmission is less than 25% based on a photon energy of 50 keV.

4. The multi-layer x-ray detector of claim 2 , wherein the first filter material includes at least one element of copper, tantalum, lead, aluminum, tin, brass, or iron.

5. The multi-layer x-ray detector of claim 2 , wherein the second x-ray transmission is greater than 60% based on a photon energy of 50 keV.

6. 2. A multi-layer X-ray detector according to claim 1, wherein the layer belt (15) is designed to be able to be wound up and / or unwound.

7. 2. The multi-layer X-ray detector according to claim 1, wherein the transport mechanism has rollers (18) via which the layer belt (15) is designed to be movable so that either the first filter region (16) or the second filter region (17) is transported into the intermediate space.

8. 2. The multi-layer X-ray detector according to claim 1, wherein the layer belt (15) and the transport mechanism are designed as conveyor belts.

9. the first sensor layer (10) having a first scintillator material of a first thickness and a first readout circuit designed to detect photons generated by the first scintillator material from X-ray quanta of the first spectrum and generate a first signal therefrom; the second sensor layer (11) comprises a second scintillator material of a second thickness and a second readout circuit designed to detect photons generated by the second scintillator material from X-ray quanta of the second spectrum and to generate a second signal therefrom; The multi-layer X-ray detector of claim 1 .

10. 10. The multi-layer X-ray detector according to claim 1, which is designed as either an X-ray flat detector or a fan detector.

11. a dual-energy X-ray source (21) designed to be able to switch from emitting radiation of the first spectrum to emitting radiation of the second spectrum and vice versa; a system controller (24) for controlling the multi-layer X-ray detector (19) and the dual-energy X-ray source (21); An X-ray system comprising a multi-layer X-ray detector (19) according to claim 1.

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