Online calibration of x-ray imaging

Abstract

This invention relates to calibration for X-ray imaging. To provide facilitated calibration of an X-ray imager, an X-ray source (10) for online calibration of X-ray imaging is provided. The X-ray source includes a source housing (12), an X-ray generating unit (14), and a calibration pattern (16). The X-ray generating unit is arranged within the source housing and configured to generate an X-ray beam (18) of multi-energy spectral radiation for energy spectrum imaging along a beam path (20). The housing includes an X-ray aperture (22) for transmitting the X-ray beam toward an X-ray detector along the X-ray beam path. The calibration pattern is arranged within the X-ray beam path in the source housing. The calibration pattern is a 2D geometric pattern (24) made of X-ray absorbing material. Furthermore, the 2D geometric pattern includes a plurality of linear elements (26) arranged in a predetermined configuration, thereby allowing inference, based on the image, of at least one of the following: the distance, tilt, and distortion between the detector plane and the X-ray source.

Description

Technical Field

[0001] This invention relates to the calibration of X-ray imagers, such as in-line calibration of X-ray imaging; particularly to X-ray sources for in-line calibration of X-ray imaging, X-ray imaging systems, calibration kits for X-ray imaging systems, and methods for performing calibration during X-ray imaging. Background Technology

[0002] In X-ray imaging, precise geometric arrangements are required for multiple imaging procedures in certain tasks. For example, precise source-detector calibration may be necessary to create a 2D roadmap for DSA or for CBCT 3D reconstruction. However, it has been shown that performing such calibrations can be cumbersome, considering the workload of the personnel involved. Summary of the Invention

[0003] Therefore, it may be necessary to facilitate the calibration of X-ray imaging.

[0004] The object of the invention is achieved through the subject matter of the independent claims; further embodiments are incorporated in the dependent claims. It should be noted that the aspects of the invention described below are also applicable to X-ray sources for online calibrated X-ray imaging, X-ray imaging systems, calibration kits for X-ray imaging systems, and methods for calibration during X-ray imaging.

[0005] According to one aspect of the invention, an X-ray source for online calibration of X-ray imaging is provided. The X-ray source includes a source housing, an X-ray generating unit, and a calibration pattern. The X-ray generating unit is arranged within the source housing and configured to generate an X-ray beam of multi-energy spectral radiation for energy spectral imaging along a beam path. The housing includes an X-ray aperture for transmitting the X-ray beam toward an X-ray detector along the X-ray beam path. The calibration pattern is arranged within the X-ray beam path in the source housing. The calibration pattern is a geometric pattern made of an X-ray absorbing material. The geometric pattern includes a plurality of graphic elements arranged in a predetermined configuration.

[0006] Specifically, an X-ray imaging system including such a source is provided. In addition to the aforementioned X-ray source, the X-ray imaging system also includes an X-ray detector, a holding device for the X-ray source and the X-ray detector, and an image data processing unit. The X-ray source and the X-ray detector are mounted to the holding device. The X-ray source is configured to provide spectral imaging X-ray radiation to image an object of interest arranged between the X-ray source and the X-ray detector. The X-ray detector is configured to receive X-ray radiation after at least partially passing through the object of interest and to detect spectral imaging data, which includes an image portion representing a calibration pattern. The image data processing unit is configured to identify the image portion representing the calibration pattern based on the detected spectral imaging data and to segment the calibration pattern within the image data based on the spectral imaging data. The image data processing unit is configured to provide the segmented calibration pattern for further geometric calibration calculation steps.

[0007] Specifically, the holding device includes a robotic device with a source robotic arm and a detector robotic arm. The X-ray source is mounted to the source robotic arm, and the X-ray detector is mounted to the detector robotic arm.

[0008] Therefore, calibration is provided without additional X-ray dose but during the actual imaging process. Since energy spectrum imaging is provided, the appropriate information for calibration can be derived from the acquired X-ray image data.

[0009] The advantage lies in providing options for real-time calibration, which addresses potential problems that may arise in X-ray imaging systems used, for example, in minimally invasive interventions or surgeries. Conventionally, such systems rely on so-called C-arms to hold the source and detector. However, lighter and smaller holding devices, such as robotic arms, are currently anticipated. In this case, as an example, if the ceiling and floor of a room (such as a catheterization lab) make it not optimally fixed to the robotic arms that mount the X-ray source and detector to the floor and ceiling respectively, relative to each other, real-time calibration allows for the detection of possible misalignments and, at least partially, for consideration of the detected misalignments to perform further image processing steps, such as providing options to compensate for image artifacts caused by such misalignments.

[0010] X-ray imaging systems without a C-arm are also known as C-less setups. One aspect of a C-less setup that differs from a traditional C-arm is that the source and detector are not directly fixed to each other. While the C-arm can exhibit some deformation, this is very limited and reproducible, allowing it to be accounted for in the imaging processing steps.

[0011] However, in C-less setups, spatial consistency depends partly on the room, as the source and detector are connected to the floor and ceiling respectively, both external to the system. This means that consistency can vary significantly between installations, and spatial errors may not always be reproducible. This is where real-time calibration offers advantageous improvements in terms of workflow and accuracy.

[0012] Therefore, calibration using actual patient data is advantageous. Even if this introduces some image artifacts, it can potentially remove these artifacts caused by energy dispersive imaging. As an example, real-time calibration results in improved calibration compared to, for example, routine calibration prior to the procedure. Real-time calibration is suitable in situations where, for example, pre-calibration based on some calibration scheme over time will not lead to sufficient accuracy due to non-reproducible errors between calibration and patient scans.

[0013] In the example, the material of the geometric pattern is distinguishable from human anatomy on the energy spectrum, allowing for the inference of at least one of the following groups based on the image: the distance, tilt, and distortion between the detector plane and the X-ray source. Therefore, the calibration pattern can remain in place during the operation of the X-ray imaging system, whereby energy spectrum imaging processes such as material decomposition algorithms can separate the calibration pattern from the image of the examined anatomical structure in the X-ray image.

[0014] According to the example, the calibration pattern is fixedly arranged in the source housing within the X-ray path.

[0015] According to the example, the geometric pattern includes a 2D geometric pattern, such as multiple linear elements arranged in a predetermined configuration. For example, a 2D geometric pattern is a square-based line pattern with two intersecting axes of symmetry. Multiple line segments form multiple open area segments.

[0016] Alternatively, a 2D geometric pattern comprising multiple points or pixels arranged in a predetermined configuration can be provided. As yet another alternative, instead of a 2D geometric pattern, a 3D structure can be conceived as a geometric pattern.

[0017] In one option, the geometric pattern is made of tungsten elements, such as tungsten filaments. Tungsten elements are distinguished from human anatomy in energy-dispersive X-ray imaging. In particular, the tungsten material of the geometric pattern can be distinguished from tissue, bone, and water, for example, by processing the energy-dispersive image data with a material decomposition algorithm.

[0018] As an example, the imaging system is configured to perform calibration in a regular manner during X-ray imaging. In one option, calibration is provided during each X-ray imaging run.

[0019] According to the example, the X-ray source is configured to provide X-ray radiation of at least a first energy spectrum and a second energy spectrum. The X-ray detector is configured to detect first image data relating to the first energy spectrum and second image data relating to the second energy spectrum. The image data processing unit is configured to combine the first image data and the second image data for detecting a calibration pattern in the image data.

[0020] According to the example, in the first option, the X-ray source is configured to provide multi-spectral imaging, and the X-ray detector is a multilayer detector configured to detect different X-ray energy levels. In the alternative second option, the X-ray source is configured to provide radiation based on a switching voltage, and the X-ray detector is configured to detect different X-ray energy levels in a time-separated manner.

[0021] According to the present invention, a calibration kit for an X-ray imaging system is also provided. The kit includes a calibration pattern and an image data processing unit. The calibration pattern is a geometric pattern made of an X-ray absorbing material. The geometric pattern includes a plurality of graphic elements configured to be arranged in a predetermined configuration, thereby allowing inference based on an image of at least one of the following: the distance, tilt, and distortion between the detector plane and the X-ray source. The calibration pattern is configured to be disposed within the X-ray path of an X-ray generating unit located within the source housing and configured to generate an X-ray beam of multi-energy spectral radiation for energy spectrum imaging. Optionally, the calibration pattern is configured to be fixedly disposed within the source housing. The housing includes an X-ray aperture for sending an X-ray beam toward the X-ray detector along the X-ray path. The image data processing unit is configured to identify image portions detected by the detector that represent the calibration pattern and to segment the calibration pattern within the image data based on energy spectrum imaging data. The image data processing unit is configured to provide the segmented calibration pattern for further geometric calibration calculation steps.

[0022] Depending on one option of the kit, the 2D geometric pattern includes multiple linear elements arranged in a predetermined configuration.

[0023] According to the present invention, a method for calibration during X-ray imaging is also provided. The method includes the following steps: - Arrange the calibration pattern within the X-ray beam path; the calibration pattern is a 2D geometric pattern made of X-ray absorbing material; - X-ray radiation generated by an X-ray source along the beam path toward the detector for energy spectrum imaging; the object is positioned between the X-ray source and the X-ray detector. - The detector detects the energy spectrum of X-ray radiation, thereby providing the detected image data; - Determine the geometric patterns in the detected image data; - Based on the determined geometric pattern, infer at least one of the following data: the distance, tilt, and distortion between the detector plane and the X-ray source; and - Provide inferred data for calibration purposes.

[0024] According to one option of the method, the geometric pattern comprises a plurality of linear elements arranged in a predetermined configuration.

[0025] According to one approach, when the subject (e.g., a patient) is on a support (e.g., a patient table), the X-ray system itself is used to perform calibration measurements. By incorporating the calibration pattern onto the patient image, the requirement that all radiation must be used for imaging is resolved. While it may be difficult to remove the calibration pattern from the subject in a standard X-ray image, providing spectral imaging improves detectability and thus achieves sufficient improvement to at least partially remove the pattern.

[0026] Using multi-spectral imaging allows for the differentiation of calibration pattern components from patient components in X-ray images, for example, by applying appropriate material decomposition algorithms to the spectral X-ray image data, thereby separating the calibration pattern material from materials commonly found in the patient's anatomy, such as water, bone, and (soft) tissue. In this way, more information can be obtained than simply following a predefined geometric pattern and its variations in Hounsfield values. This allows for a) more efficient (sub-pixel) segmentation of the calibration pattern and subsequent high-precision geometric compensation, and b) more efficient removal of the calibration pattern from the patient's (multi-spectral) X-ray images with fewer artifacts.

[0027] The applications are basically any X-ray system that requires on-the-fly calibration and can perform multi-energy spectral imaging. However, specific examples involve interventional imaging systems that rely on robotic arms to mount the source and detector (so-called C-catheterless chamber systems).

[0028] According to one aspect, the relative position between the X-ray tube (source) and the detector can be accurately measured based on energy spectrum imaging data, and thus calibration efforts can be reduced through services also used for 3D reconstruction calibration and roadmap calibration.

[0029] In one option, multi-spectral imaging is used to distinguish the calibration pattern component from the patient component in the spectral X-ray image, thereby more accurately tracking the calibration pattern and performing better compensation. Based on the spectral image information, the calibration pattern can be removed from the patient's image with fewer artifacts.

[0030] In one option, multi-spectral calibration is performed using a switched kV source. For example, fluorescence imaging or X-ray exposure is performed at low kV. Alternatively, fluorescence imaging or X-ray exposure is performed at high kV. Material values ​​are then calculated and separated based on the absorption distribution at different kV values. The material pattern is then used for geometric correction. Furthermore, the calibration pattern is subtracted from the X-ray patient image.

[0031] In another option, a multi-spectral (e.g., dual-layer) X-ray detector is provided along with an X-ray source having a sufficiently broad energy spectrum. In this case, X-ray switching is not required, but calculating different absorption distributions of the calibration pattern works in the same way.

[0032] In the example, by processing the image data using a suitable material decomposition algorithm, the material of the geometric pattern is distinguished from the object of interest (such as the human anatomy) based on the multi-energy spectral image data.

[0033] These and other aspects of the invention will become apparent from the embodiments described below and will be illustrated with reference to the embodiments described below. Attached Figure Description

[0034] Exemplary embodiments of the present invention are described below with reference to the accompanying drawings.

[0035] Figure 1 An example of an X-ray source for online calibration of X-ray imaging is illustrated schematically.

[0036] Figure 2 It shows in Figure 1 An example of a calibration pattern provided in an X-ray source.

[0037] Figure 3 It shows having Figure 2 An illustration of another example of an X-ray source with a calibration pattern.

[0038] Figure 4a and Figure 4b Different image data from energy dispersive spectroscopy are shown, in which calibration patterns are indicated against the background of the anatomical region of interest in the subject.

[0039] Figure 5 An example of an X-ray imaging system with an optional robotic arm for movably holding the source and detector is shown schematically.

[0040] Figure 6 The basic steps of an example method for calibration during X-ray imaging are shown. Detailed Implementation

[0041] Certain embodiments will now be described in more detail with reference to the accompanying drawings. In the following description, the same reference numerals are used for the same elements, even in different drawings. Matters defined in the specification, such as detailed constructions and elements, are provided to aid in a comprehensive understanding of the exemplary embodiments. Furthermore, well-known functions or constructions are not described in detail, as such unnecessary detail would obscure the embodiments of the invention. Additionally, expressions such as "at least one" preceding the listing of elements modify the overall listing of elements but do not modify the individual listed elements.

[0042] Figure 1 An example of an X-ray source 10 for online calibration X-ray imaging is schematically shown. The X-ray source 10 includes a source housing 12, an X-ray generating unit 14, and a calibration pattern 16. The X-ray generating unit 14 is arranged within the source housing 12 and configured to generate an X-ray beam 18 of multi-energy spectral radiation for energy spectrum imaging along a beam path 20. The source housing 12 includes components for directing the X-ray beam towards an X-ray detector along the X-ray beam path 20. Figure 1 (Not shown in the image) The X-ray aperture 22 of the X-ray beam 18 is used to transmit the X-ray beam 18. A calibration pattern 16 is arranged at the source housing 12 within the X-ray beam path 20. The calibration pattern 16 is a geometric pattern 24 made of X-ray absorbing material (see example...). Figure 2 The geometric pattern 24 in this example is a 2D geometric pattern that includes a plurality of graphic elements arranged in a predetermined configuration. As shown, an exemplary 2D geometric pattern includes a plurality of linear elements 26 arranged in a predetermined configuration.

[0043] The term "source housing" refers to the enclosure that houses an X-ray generating device (also known as an X-ray source). The source housing 12 can be configured as a non-transmissive housing or enclosure.

[0044] The term "X-ray generating unit" refers to a source or tube that provides X-ray radiation.

[0045] The term "calibration mode" refers to a device that provides information for achieving accurate calibration.

[0046] The term “aperture” refers to a portion of the source housing 12 that is transparent to or attenuates only to a minimum extent with respect to the energy spectrum radiation generated by the X-ray source (i.e., the X-ray generating unit 14).

[0047] The term "geometric pattern" refers to a graphic or otherwise generated pattern characterized by a simple and clearly identifiable form that differs from the form that could be expected when radiating an object.

[0048] The term "linear element" refers to a component or part provided as a line segment.

[0049] In the example, calibration pattern 16 is permanently fixed within the X-ray path 20. The provided calibration is suitable for X-ray systems where deviations from the planned geometry are irreproducible and therefore cannot be removed by pre-calibration. For example, real-time calibration, along with the patient in the view, allows at least some mitigation of the effect of deviation from calibration.

[0050] The calibration pattern 16 can be seen by the detector in the X-ray field, thus allowing the differentiation of calibration patterns 16 with absorption characteristics different from those of blood, bone, soft tissue, and iodine in a multi-energy spectral field. This enables the inference of at least one of the following groups based on the image: the distance, tilt, and distortion between the detector plane and the X-ray source 10.

[0051] exist Figure 1 In one of the example options, calibration pattern 16 is fixedly arranged in the source housing 12 within the X-ray path 20.

[0052] In an alternative option, calibration pattern 16 is removably arranged at source housing 12 within X-ray path 20.

[0053] Figure 2 It shows in Figure 1 An example of the calibration pattern 16 provided in the X-ray source 10.

[0054] In one option, geometric pattern 16 is a square-based line pattern 28 with two intersecting axes of symmetry. Multiple line segments 30 form multiple open area segments 32.

[0055] The term "square-based line pattern" refers to a grid-like arrangement based on a rectangular form, such as a grid-like arrangement based on a square basic form.

[0056] In one example, the central open area segment 32a is surrounded by outer area segments (corner segment 32b and middle segment 32c). For example, the outer area segments have at least two different sizes.

[0057] In one example, the central open area segment 32a is square; the corner segment 32b of the outer area segment is also square, and the middle segment 32c of the outer area segment is rectangular.

[0058] As an example, the central open area 32a and the corner segment 32b have an edge length ratio of 4:3.

[0059] As an example, a 10x10mm grid size is provided. The central open area 32a has a size of 4mm×4mm, while the corner segment 32b has a size of 3mm×3mm. The middle segment 32c of the outer area has a size of 3mm×4mm.

[0060] In one example, the calibration pattern 16 is made of a filament with a diameter of 0.25 mm, and the pattern is set with an outer grid size of approximately 10 mm. For a 0.25 mm filament, the outer size is 10.25 mm.

[0061] In another option, the 2D geometric pattern 16 is a triangle-based line pattern (not shown) with three intersecting axes of symmetry.

[0062] In another option, the 2D geometric pattern 16 is a circle-based line pattern (also not shown) with at least two intersecting axes of symmetry.

[0063] In the case of distance offset, the size of calibration pattern 16 is a calibration indicator.

[0064] In the case of tilt offset, the deviation in the form of a pattern is a calibration indicator.

[0065] As in the previous example, calibration pattern 16 allows for the determination of offsets relative to at least one set of X, Y, and Z positions and at least one set of X, Y, and Z rotations, relative to the X-ray source and the X-ray detector. Preferably, offsets can be determined simultaneously for all degrees of motion freedom with respect to position and rotation.

[0066] In particular, a calibration pattern having multiple linear elements 26 arranged in a predetermined configuration allows for the robust and accurate determination of the offsets of all motion degrees of freedom, even for systems with relatively large source-detector distances, such as “C-less” systems as described herein, which include robotic arms that mount sources and detectors.

[0067] In one example provided as an option, the 2D geometric pattern 16 is made of a material that is distinguishable from human anatomy on the energy spectrum.

[0068] In another option, the 2D geometric pattern 16 is made of tungsten filaments.

[0069] In one option not shown in detail, an X-ray imaging apparatus is provided, comprising an X-ray source, an X-ray detector, and an image data processing unit according to one of the foregoing examples. The X-ray source is configured to provide spectral imaging X-ray radiation for imaging an object of interest arranged between the X-ray source and the X-ray detector. The X-ray detector is configured to receive X-ray radiation after it has at least partially passed through the object of interest; and to detect spectral imaging data including image portions representing a calibration pattern. The image data processing unit is configured to identify the image portions representing the calibration pattern and to segment the calibration pattern within the image data based on the spectral imaging data. The image data processing unit is configured to provide the segmented calibration pattern for further geometric calibration calculation steps.

[0070] Figure 3 It shows having Figure 2 An illustration of another example of an X-ray source 10 with calibration pattern 16 is shown. A tubular X-ray absorbing housing 34 with mounting and assembly screws 36 is shown. A central portion 38 is configured as an X-ray window for emitting X-ray radiation. An example of calibration pattern 16 is arranged at the center of the central portion 38 forming the X-ray window. Thus, calibration pattern 16 is arranged within the possible beam path when X-ray radiation is generated inside housing 34. The X-ray source 10 provides energy spectral imaging for imaging regions of interest of an object under examination.

[0071] Figure 4a and Figure 4b Different image data 40 of spectral imaging are shown, in which calibration pattern 16 is indicated against the background of the anatomical region of interest of the subject. The spectral image data show anatomical structures 42, such as tissue structures, organs, blood vessels, or bone structures 42. As an example, Figure 4a It shows the relationship with Figure 4b Image data of the same region of interest; Figure 4a The image content involves the first energy spectrum range of X-ray radiation, and Figure 4b Image data involving a second energy spectrum range of X-ray radiation are shown. It can be seen that the anatomical structure 42 and the calibration pattern 16 are each visible in different ways in the two images. By combining the energy spectrum image data, the calibration pattern 16 can be identified in an enhanced manner, and calibration data, such as in terms of distance, tilt, etc., can then be determined. Alternatively, segmentation and subtraction of the calibration pattern 16 from the rest of the image are also provided to provide improved image data of the anatomical structure 42.

[0072] Figure 5 An example of an X-ray imaging system 100 is schematically shown. The X-ray imaging system 100 includes an example of an X-ray source 10 according to one of the examples described above, an X-ray detector 102, a holding device 104 for the X-ray source 10 and the X-ray detector 102, and an image data processing unit 106. The X-ray source 10 and the X-ray detector 102 are mounted to the holding device 104. The X-ray source 10 is configured to provide spectral imaging X-ray radiation for imaging an object of interest arranged between the X-ray source 10 and the X-ray detector 102. The X-ray detector 102 is configured to receive X-ray radiation after at least partially passing through the object of interest 108 and to probe spectral imaging data, which includes an image portion representing a calibration pattern. The image data processing unit 106 is configured to identify the image portion representing the calibration pattern 16 and segment the calibration pattern within the image data based on the spectral imaging data. The image data processing unit 106 is also configured to provide the segmented calibration pattern for further geometric calibration calculation steps.

[0073] For example, the image data processing unit 106 is connected to the X-ray detector 102 via data connection 110. Alternatively, an additional data connection 112 may be arranged to data connect the X-ray source 10 to the image data processing unit 106.

[0074] The object of interest 108 (e.g., the object under inspection) can be arranged on a movable object support 114 attached to the base 116, such as... Figure 5 As shown. In addition, the display device 118 is located near the object under inspection support 114.

[0075] The term "subject" can also refer to an individual. "Subject" can also refer to a patient; however, it should be noted that this term does not indicate whether the subject actually has any discomfort or disease.

[0076] The term "holding device" refers to providing a movable mounting for the X-ray source 10 and X-ray detector 102 of the X-ray imaging system 100.

[0077] Based on energy-spectral imaging, relative absorption can be detected in the image, and this allows for the differentiation of bones based on the contrast of the calibration pattern.

[0078] exist Figure 5 In the example shown as an option, the holding device 104 includes a robotic device having a source robotic arm 120 and a detector robotic arm 122. The X-ray source 10 is mounted to the source robotic arm 120, and the X-ray detector 104 is mounted to the detector robotic arm 122.

[0079] The term "robotic arm" refers to a robot used to move and hold the X-ray source 10 or the X-ray detector 102.

[0080] The term "source robotic arm" refers to a robot used to move and hold the X-ray source 10. In the example, the robot is mounted to the floor, and the X-ray source 10 is mounted at the free end of the robot. The robot may have the form of an arm with several movable joints that allow for a high degree of freedom of movement.

[0081] The term "detector robotic arm" refers to a robot used to move and hold the X-ray detector 102. In the example, the robot is mounted to the ceiling, and the X-ray detector 102 is mounted on the free end of the robot. The robot may have the form of an arm with several movable joints that allow for a high degree of freedom of movement.

[0082] like Figure 5 The imaging system 100 shown is configured to perform calibration in a regular manner during X-ray imaging.

[0083] The term "routine approach" refers to providing calibration in a routine manner, such as once a week, once a day, or during each run.

[0084] One option is to provide calibration during each X-ray imaging run.

[0085] In another option, the image data processing unit 106 is configured to use additional energy spectrum information to detect patterns in the image data.

[0086] In another option, the X-ray source 10 is configured to provide X-ray radiation of at least a first energy spectrum and a second energy spectrum. The X-ray detector 102 is configured to detect first image data relating to the first energy spectrum and second image data relating to the second energy spectrum. Furthermore, the image data processing unit 106 is configured to combine the first image data and the second image data for detecting a calibration pattern in the image data.

[0087] The terms "first energy spectrum" and "second energy spectrum" refer to X-ray radiation that provides different energy ranges.

[0088] In another option, the X-ray source 10 is configured to provide multi-spectral imaging, and the X-ray detector 102 is a multilayer detector configured to detect different X-ray energy levels. Furthermore, the X-ray source 10 is configured to provide radiation based on a switching voltage, and the X-ray detector 102 is configured to detect different X-ray energy levels in a time-separated manner.

[0089] The term "multilayer detector" refers to a detector that includes multiple (i.e., at least two) detector panels arranged in a stacked manner.

[0090] The term "switching voltage" refers to generating X-ray radiation with different characteristics by changing the voltage setting.

[0091] In one option, the image data processing unit is configured to execute a material decomposition algorithm to distinguish geometric patterns from human anatomy as objects of interest.

[0092] In another example, not shown in detail, a calibration kit for an X-ray imaging system is provided. The kit includes a calibration pattern and an image data processing unit. The calibration pattern is a 2D geometric pattern made of X-ray absorbing material. The 2D geometric pattern includes multiple graphic elements arranged in a predetermined configuration, which allows inference of at least one of the following: the distance, tilt, and distortion between the detector plane and the X-ray source. The calibration pattern is configured to be fixedly arranged within the source housing within the X-ray path of an X-ray generating unit, which is arranged within the source housing and configured to generate an X-ray beam of multi-energy spectral radiation for energy spectrum imaging. The housing includes an X-ray aperture for sending the X-ray beam toward the X-ray detector along the X-ray path. The image data processing unit is configured to identify image portions detected by the detector that represent the calibration pattern and to segment the calibration pattern within the image data based on energy spectrum imaging data. The image data processing unit is configured to provide the segmented calibration pattern for further geometric calibration calculation steps.

[0093] Depending on one option of the kit, the 2D geometric pattern includes multiple linear elements arranged in a predetermined configuration.

[0094] In the example, a kit is provided to enable the conversion of an energy-spectral X-ray imaging system into... Figure 5 An example of an X-ray imaging system 100 is shown.

[0095] The calibration kit can be used to upgrade existing X-ray imaging systems that provide energy-spectral imaging. In particular, the calibration kit can be used to upgrade existing X-ray imaging systems with separately mounted X-ray sources and X-ray detectors that provide energy-spectral imaging.

[0096] The term "kit" refers to a number of separate components that, when used together, provide additional functionality to a previously existing system.

[0097] Figure 6 The basic steps of an example of a method 200 for calibration during X-ray imaging are shown. Method 200 includes the following steps: - In the first step 202, a calibration pattern is arranged within the X-ray beam path; the calibration pattern is a 2D geometric pattern made of X-ray absorbing material.

[0098] - In the second step 204, X-ray radiation for energy spectrum imaging is generated by an X-ray source along the beam path toward the detector; the object is positioned between the X-ray source and the X-ray detector.

[0099] - In the third step 206, the detector detects the energy spectrum X-ray radiation, thereby providing the detected image data.

[0100] - In step 208, a 2D geometric pattern is determined from the detected image data.

[0101] - In the fifth step 210, for calibration, based on the image data, at least one of the following groups is inferred: the distance, tilt, and distortion between the detector plane and the X-ray source.

[0102] - In step 6, 212, the inferred data is provided for calibration purposes.

[0103] In one option of the fifth step, the 2D geometric pattern comprises multiple linear elements arranged in a predetermined configuration.

[0104] In another exemplary embodiment, a computer program or computer program element is provided, characterized in that it is adapted to perform method steps of the method according to one of the foregoing embodiments on a suitable system.

[0105] In another exemplary embodiment, a computer-readable medium storing a computer program is provided.

[0106] Therefore, computer program elements can be stored on a computer unit or distributed across more than one computer unit, which may also be part of embodiments of the present invention. The computing unit can be adapted to perform or induce the execution of the steps of the described method. Furthermore, it can be adapted to operate components of the described apparatus. The computing unit can be adapted to automatically operate and / or execute user commands. The computer program can be loaded into the working memory of the data processor. Therefore, the data processor can be configured to perform the methods of the present invention.

[0107] Various aspects of this invention can be implemented as a computer program product, which may be a collection of computer program instructions stored on a computer-readable storage device and executable by a computer. The instructions of this invention can be any interpretable or executable code mechanism, including but not limited to scripts, interpretable programs, dynamic link libraries (DLLs), or Java classes. The instructions can be provided as a complete executable program, a partial executable program, a modification (e.g., an update) of an existing program, or an extension (e.g., a plugin) of an existing program. Furthermore, some processing of this invention can be distributed across multiple computers or processors.

[0108] As described above, processing units, such as controllers, implement control methods. Controllers can be implemented in various ways, using software and / or hardware, to perform a variety of required functions. A processor is an example of a controller employing one or more microprocessors, which can be programmed using software (e.g., microcode) to perform desired functions. However, controllers can be implemented with or without a processor, and can also be implemented as a combination of dedicated hardware for performing some functions and processors (e.g., one or more programmed microprocessors and associated circuitry) for performing other functions.

[0109] Examples of controller components that may be employed in various embodiments of this disclosure include, but are not limited to, conventional microprocessors, application-specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).

[0110] This exemplary embodiment of the invention covers computer programs that begin to use the invention and computer programs that convert existing programs into programs that use the invention through updates.

[0111] Furthermore, computer program elements may be able to provide all the necessary steps to complete the exemplary embodiment of the method as described above.

[0112] According to another exemplary embodiment of the invention, a computer-readable medium, such as a CD-ROM, is provided, wherein the computer-readable medium has computer program elements stored thereon, the computer program elements being described in the preceding section. The computer program may be 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.

[0113] However, computer programs can also be presented via networks like the World Wide Web and downloaded from such networks to the working memory of a data processor. According to another exemplary embodiment of the invention, a medium is provided for making computer program elements available for download, these computer program elements being arranged to perform a method according to one of the previously described embodiments of the invention.

[0114] It should be noted that embodiments of the invention are described with reference to different subject matter. In particular, some embodiments are described with reference to method-type claims, while other embodiments are described with reference to device-type claims. However, those skilled in the art will understand from the above and following description that, unless otherwise stated, any combination of features related to multiple features of different subject matter is also considered part of the disclosure of this application, in addition to any combination of features belonging to one type of subject matter. However, all features can be combined to provide a synergistic effect that is more than the sum of the features.

[0115] While the invention has been described and illustrated in detail in the accompanying drawings and the foregoing description, such description is to be considered illustrative or exemplary rather than limiting. The invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments will be understood and implemented by those skilled in the art in practicing the claimed invention upon studying the drawings, the disclosure, and the dependent claims.

[0116] In the claims, the word "comprising" does not exclude other elements or steps, and the quantifiers "a" or "an" do not exclude multiple. A single processor or other unit can perform the functions of several items recited in the claims. The fact that certain measures are recited only in mutually different dependent claims does not mean that combinations of these measures cannot be used to obtain their advantages. Any reference numerals in the claims should not be construed as limiting the scope of protection.

Claims

1. An X-ray imaging system (100), comprising: -X-ray source (10); -X-ray detector (102); - A holding device (104) for the X-ray source and the X-ray detector, the holding device comprising a robotic device having a source robotic arm (120) and a detector robotic arm (122), wherein the X-ray source is mounted to the source robotic arm, and the X-ray detector is mounted to the detector robotic arm; and - Image data processing unit (106); The X-ray source includes -Source shell (12); -X-ray generating unit (14); and - Calibration pattern (16); The X-ray generating unit is arranged within the source housing and configured to generate an X-ray beam (18) along the X-ray beam path (20) for energy spectral imaging of an object of interest arranged between the X-ray source and the X-ray detector. The source housing includes an X-ray aperture (22) for sending an X-ray beam toward the X-ray detector along the X-ray beam path; The calibration pattern is a geometric pattern (24) made of X-ray absorbing material, which is arranged in the source housing within the X-ray beam path and includes a plurality of elements arranged in a predetermined configuration. The X-ray detector is configured to receive X-ray radiation that has passed at least partially through the object of interest and to detect energy spectrum imaging data, which includes an image portion representing the calibration pattern. The image data processing unit is configured to identify the image portion representing the calibration pattern and to segment the calibration pattern within the image data based on the energy spectrum imaging data; and The image data processing unit is configured to provide segmented calibration patterns for further geometric calibration calculation steps.

2. The X-ray imaging system according to claim 1, wherein, The X-ray absorbing material of the geometric pattern is distinguishable from human anatomy in terms of energy spectrum, so as to enable image-based inference of at least one of the following: the distance, tilt, and distortion between the detector plane and the X-ray source.

3. The X-ray imaging system according to claim 1 or 2, wherein, The calibration pattern is fixedly arranged in the source housing within the X-ray path.

4. The X-ray imaging system according to any of the preceding claims, wherein, The geometric pattern is a 2D geometric pattern, which includes a plurality of linear elements (26) arranged in a predetermined configuration.

5. The X-ray imaging system according to claim 4, wherein, The 2D geometric pattern is a square-based line pattern with two intersecting axes of symmetry; and Among them, multiple line segments form multiple open area segments (32).

6. The X-ray imaging system according to any of the preceding claims, wherein, The geometric pattern is made of tungsten elements.

7. The X-ray imaging system according to any of the preceding claims, wherein, The imaging system is configured to be calibrated in a regular manner during X-ray imaging; and Calibration is provided during each X-ray imaging run.

8. The X-ray imaging system according to any of the preceding claims, wherein, The image data processing unit is configured to use additional energy spectrum information to detect the pattern in the image data.

9. The X-ray imaging system according to any of the preceding claims, wherein, The X-ray source is configured to provide X-ray radiation of at least a first energy spectrum and a second energy spectrum; The X-ray detector is configured to detect first image data related to the first energy spectrum and second image data related to the second energy spectrum; and The image data processing unit is configured to combine the first image data and the second image data to detect the calibration pattern in the image data.

10. The X-ray imaging system according to any of the preceding claims, wherein, The X-ray source is configured to provide multi-spectral imaging, and the X-ray detector is a multilayer detector configured to detect different X-ray energy levels.

11. The X-ray imaging system according to any one of claims 1-9, wherein, The X-ray source is configured to provide radiation based on a switching voltage, and the X-ray detector is configured to detect different X-ray energy levels in a time-separated manner.

12. The X-ray imaging system according to any of the preceding claims, wherein, The image data processing unit is configured to execute a material decomposition algorithm to distinguish the geometric pattern from the human anatomical structure that is the object of interest.

13. The X-ray imaging system according to any of the preceding claims, wherein, The robotic arm was mounted on the floor of the room.

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