X-RAY IMAGING SYSTEM WITH FOREIGN OBJECT REDUCTION

Abstract

An improved X-ray imaging system. The system comprises an X-Ray radiation source configured to emit an X-ray beam towards an object to be imaged and an X- ray detector configured to detect X-rays which have passed through the object. It further comprises a reconstruction processing means configured to reconstruct an image of the object based on the detected X-rays, wherein the reconstruction processing means is further configured to determining presence of at least one foreign object located in the object or located between a surface of the object and the X-Ray radiation source and/or the X-ray detector, obtaining a three-dimensional profile of the determined foreign object from a server-based foreign object database, and reconstructing an image of the object by acquiring a plurality of projection images of the object from the X-ray detector and reducing impact on image quality of an artefact that can be caused by the foreign object in the image of the object based on at least the obtained three-dimensional profile of the foreign object.

Claims

1. X-ray imaging system, comprising an X-Ray radiation source configured to emit an X-ray beam towards an object to be imaged, an X-ray detector configured to detect X-rays passed through the object, a reconstruction processor configured to reconstruct an image of the object based on the detected X-rays, wherein the reconstruction processor is further configured to: determine presence of at least one foreign object located in the object or located between a surface of the object and at least one of the X-Ray radiation source and the X-ray detector; obtain a three-dimensional profile of the determined foreign object from a server-based foreign object database; and reconstuct an image of the object by acquiring a plurality of projection images of the object from the X-ray detector and reducing impact on image quality of an artefact caused by the foreign object in the image of the object based on at least the obtained three-dimensional profile of the foreign object; wherein the reconstruction processor is further configured to at least partly subtract the artefact from the image of the object.

2. The X-Ray imaging system according to claim 1, wherein the three-dimensional profile comprises density data and/or material data of the foreign object.

3. The X-Ray imaging system according to claim 1, wherein the reconstruction processor comprises a classifier for identifying the foreign object based on at least a feature extraction of the foreign object derived from the acquired image of the object including the foreign object.

4. The X-Ray imaging system according to claim 1, wherein the reconstruction processor is further configured to identify the foreign object based on a read-out of a computer-readable identifier provided along with the foreign object.

5. The X-Ray imaging system according to claim 1, wherein the reconstruction processor is further configured to determine at least a 6 DoF-position of the foreign object relative to the object before reducing the impact of the foreign object.

6. The X-Ray imaging system according to claim 5, wherein the reconstruction processor is further configured to determine the 6 DoF-position based on a first image acquiring scan provided with a first resolution, and based on the 6 DoF-position to subtract the foreign object from a second image acquiring scan provided with a second resolution higher than the first resolution.

7. The X-Ray imaging system according to claim 5, wherein the reconstruction processor is further configured to adapt scan parameters of the X-Ray imaging system based on the 6 DoF-position.

8. Th X-Ray imaging system according to claim 1, wherein the artefact is caused by at least one foreign object including an electronic device arranged between a surface of the object and at least one of the X-Ray radiation source and the X-ray detector.

9. A method for imaging an object by an X-ray imaging system, the method comprising: determining presence of at least one foreign object located in the object or located between a surface of the object and at least one of the X-Ray radiation source and the X-ray detector; obtaining a three-dimensional profile of the determined foreign object from a server-based foreign object database; and reconstructing an image of the object by acquiring a plurality of projection images of the object from the X-ray detector and reducing impact on image quality of an artefact caused by the foreign object in the image of the object based on at least the obtained three-dimensional profile of the foreign object; wherein the artefact is at least partly subtracted from the image of the object.

10. The method according to claim 9, wherein the three-dimensional profile is obtained from at least a first scan on a first radiation dosage level and a second scan on a second radiation dosage level different to the first radiation dosage level of the X-ray imaging system.

11. The method according to claim 9, further comprising determining a photon counting based scatter profile of the foreign object before reconstructing the image.

12. The method according to claim 9, further comprising determining a phase contrast information of the foreign object is before reconstructing the image.

13. The method according to claim 9, wherein the three-dimensional profile is at least partly obtained by manufacturing a model of the determined foreign object and scanning the model by the X-ray imaging system.

14. (canceled)

15. A non-transitory computer-readable medium for storing executable instructions, when executed by processing circuitry, cause the processing circuitry to perform a method for for imaging an object by an X-ray imaging system, the method comprising: determining presence of at least one foreign object located in the object or located between a surface of the object and at least one of the X-Ray radiation source and the X-ray detector; obtaining a three-dimensional profile of the determined foreign object from a server-based foreign object database; and reconstructing an image of the object by acquiring a plurality of projection images of the object from the X-ray detector and reducing impact on image quality of an artefact caused by the foreign object in the image of the object based on at least the obtained three-dimensional profile of the foreign object, wherein the artefact is at least partly subtracted from the image of the object.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Exemplary embodiments of the invention will be described in the following with reference to the following drawings:

[0053] FIG. 1 shows schematically an X-ray system according to an exemplary embodiment of the invention in a perspective view.

[0054] FIG. 2 shows schematically a further embodiment of an X-ray imaging system in a side view.

[0055] FIG. 3 shows schematically a block diagram of an exemplary operation of an X-ray imaging system.

[0056] FIG. 4 shows schematically a block diagram of another exemplary operation of an X-ray imaging system.

[0057] FIG. 5 shows schematically images of an object to be imaged at several points during a reconstruction and/or correction process.

[0058] FIG. 6 shows a flow chart of a method of imaging an object by an X-ray imaging system.

[0059] The figures are merely schematic representations and serve only to illustrate embodiments of the invention. Identical or equivalent elements are in principle provided with the same reference signs.

DETAILED DESCRIPTION OF EMBODIMENTS

[0060] FIG. 1 shows schematically an X-ray imaging system 100, which is in this embodiment a computed tomography imaging scanner. The X-ray imaging system 100 comprises a stationary housing 110 and a rotatable gantry 120 which is rotatable over an angular range of about 360° about an object support 130, which is in this embodiment a support table. In this embodiment, an object 140 to be imaged, which is exemplarily a human patient, is located on an upper surface of the object support 130. The object support 130 is at least translationally movable along a z-axis to selectively move the object 140 into the housing 110. It is noted that the object support 130 may have 6 DoF (six degrees of freedom) in some embodiments. The X-ray imaging system 100 further comprises a radiation source 150 that is configured to emit an X-ray radiation beam towards the object 140 to be imaged, and in particular configured to generate the radiation beam to be directed into an examination region. The radiation beam interacts with a region of interest of the object 140 disposed in the examination region (see FIG. 2), wherein spatially varying absorption of the radiation is generated, as it passes through the examination region.

[0061] The X-ray imaging system 100 further comprises an X-ray detector 160 configured to detect X-rays which have passed through the object 140 and in particular configured to detect an absorption-attenuated radiation after having passed through the examination region. In this embodiment, the radiation source 150 and the X-ray detector 160 are mounted to the gantry 120 and are arranged opposite each other, so that the X-ray detector 160 continuously receives X-rays from the radiation source 150. The X-ray detector 160 may comprise a two-dimensional array of detector elements, wherein other embodiments may be contemplated.

[0062] The X-ray imaging system 100 further comprises one or more computational means, wherein in this embodiment mainly a reconstruction processing means 170 will be described. The reconstruction processing means 170 is connected to at least the X-ray detector 160 and/or the radiation source 150 to control these and/or to obtain data therefrom, in particular from the X-ray detector 160. The reconstruction processing means 170 may also be formed by several subsystems, function modules or units, software modules or units, or the like (not further detailed here), and is configured to reconstruct an image of the object 140 based on the X-rays detected by the X-ray detector 160, and in particular based on a plurality of acquired projection images of the object 140. In this embodiment, the reconstruction processing means 170 comprises at least one processor 171, such as a back-projection processor, or the like, at least one memory 172 for storing image data and at least one memory 173 for storing one or more program elements. The reconstruction processing means 170 comprises at least one image reconstruction algorithm which, in this embodiment, is stored as a program element in the memory 173. Reconstruction processing means 170 is, in this embodiment, configured to reconstruct the image using a filtered backprojection. However, also other reconstruction algorithms can be used for reconstructing.

[0063] The reconstruction processing means 170 further comprises an artificial intelligence module, AI-module, which for better illustration is denoted by reference sign 174. The AI-module 174 comprises a classification means, which is configured to identify objects within the images, in particular within the images reconstructed by the reconstruction processing means 170. The classification means of the AI-module 174 exemplarily comprises a machine learning component implemented in an artificial neural network, in particular a convolutional neural network, which may be arranged instead as a support vector machine, linear regression algorithm or otherwise. The classification means may be pre-trained with suitable training data sets.

[0064] The X-ray imaging system 100 further comprises a server-based computing device 180, which may be a local or, as exemplarily indicated in FIG. 1, a cloud computing system. The server-based computing device 180 is connected to at least the reconstruction processing means 170, wherein this connection may be established by wire or wireless. The server-based computing device 180 comprises a processor, memory etc. which are collectively designated by reference sign 181. The server-based computing device 180 further comprises a database 182 configured to associate an identifier of a foreign object 190, 200, which will be described in more detail below, with a corresponding three-dimensional profile of the foreign object 190, 200. The foreign object database 182 comprises the three-dimensional profile, geometric data, such as shape and/or dimensional data, material data, density data, density contribution data, X-ray absorption data, a scattering profile, or the like. These data may be measured and/or analyzed prior during a scout or examination scan of the X-ray imaging system 100 or may be provided by a manufacturer and/or supplier of the foreign object 190, 200. In this embodiment, a first foreign object 190 is located outside the object 140 between an outer surface of the object 140 and the radiation source 140. By way of example, the first foreign object 190 is an electronic device, such as sensor, a camera, or the like. Further exemplarily, a second foreign object 200 is located inside the object 140 and is formed, for example, as a metal implant, such as a metal clip, a high-density dental filling, an artificial hip, or the like. It is noted that the first and second foreign object 190, 200 may cause artefacts, in particular if the imaged region of interest contains their high density regions. Typically, the second foreign object 190 may appear as a metal artefact in a reconstructed image as streaks emanating from the high density region (see FIG. 5).

[0065] Referring to FIG. 2, which schematically shows a further embodiment of the X-ray imaging system 100 without occlusion through the housing 110, the first foreign object 190, which is located outside the object 140, exemplarily further comprises a computer-readable identifier 191 that is provided along with the first foreign object 190. It is noted that the size of the computer-readable identifier 191 is only exaggerated for better illustration. The computer-readable identifier 191 may be provided as an electronic or-non electronic device, such as barcode, QR code, NFC tag, RFID tag, or the like, or may comprise an accelerometer, a magnetic sensor, or the like, and may further be configured to be read-out by a detection means 210, as schematically indicated in FIG. 2. Depending on the design of the identifier 191, the detection means 210 may be provided as a barcode or QR code scanner, a NFC module, a radio module, a camera, or the like. It is noted that the detection means 210 may be arranged outside or inside the housing 110. In this embodiment, the detection means 210 is connected to the reconstruction processing means 170. It is noted that the detection means 210 may also be connected directly to the server-based computing device 180. The same or a further detection means 210 may be configured to detect the foreign object 190 based on EM tracking, radar based triangulation, light based triangulation, ultrasound based triangulation, or the like.

[0066] Further referring to FIG. 2, in this embodiment, the X-ray imaging system 100 further comprises an additive manufacturing device 220, which is configured to form a physical model, e.g. by 3D printing technology, of the foreign object 190, 200 imaged by the X-ray imaging system 100. By way of example, the additive manufacturing device 220 is connected on one side to the reconstruction processing means 170 and on another side to the server-based computing device 180. The additive manufacturing device 220 is configured to generate a 3D model of the foreign object 190, 200 based on a foreign object image reconstructed by the reconstruction processing means 170. Such a 3D model of the foreign object 190, 200 may be imaged by the X-ray imaging system 100 and provided to server-based computing device 180.

[0067] FIG. 3 shows a schematic block diagram of an exemplary operation of the X-ray imaging system 100 for generating a corrected image I of the object 140 (see FIG. 1 or 2) from the acquired projection data, in particular the acquired projection images. Preferably, the projection images comprise projection data, which correspond to an angular illumination range of each image element, i.e. of each pixel or voxel, of at least 360°.

[0068] However, reconstruction of a reduced projection data set providing, for example, projection data corresponding to an angular illumination range of each image element of at least 180° is also contemplated. The X-ray detector 160 provides the acquired projection images upon detection of X-rays which have passed through the object 140 and the foreign object 190, 200 to the reconstruction processing means 170, wherein the X-rays are emitted by the radiation source 150. Based on the acquired projection images, the reconstruction processing means 170 determines the presence of the foreign object 190, 200, e.g. by use of the classification means or, in general, by a feature extraction and/or recognition algorithm, or the like. Upon determining the presence it further determines an identifier of the foreign object 190, 200 by use of the classification means of the AI-module 174, which may reveal a shape, material property, density, or the like, of the foreign object 190, 200. Based on the unique identifier, the reconstruction processing means 170 obtains a three-dimensional profile of the foreign object 190, 200 matching the unique identifier by downloading from the foreign object database 182 the server-based computing device 180. Based on the three-dimensional profile that comprises in particular geometric data, such as the shape, dimension, or the like, material data, such as the density, the density distribution, the material properties, or the like, and at least a subset of the acquired projection images, the reconstruction processing means 170 determines, e.g. by a position determining module, the position and/or orientation of the imaged foreign object 190, 200. For this, the reconstruction processing means 170 uses a few orthogonal images of the acquired projection images, a low-resolution three-dimensional image reconstructed by the reconstruction processing means 170 based on the acquired projection images, or the like. At least based on the position and/or the orientation of the imaged foreign object 190, 200, the reconstruction means 170 at least reduces an impact of the foreign object 190, 200 on the reconstructed image quality by subtracting an artefact from the reconstructed image, either during or after the final reconstruction of the image. The reconstructed and corrected image of the object 140, in which artefacts caused by the foreign object 190, 200 are reduced or from which the artefacts are substantially removed, is detonated by reference sign I in FIG. 3.

[0069] FIG. 4 shows a schematic block diagram of another exemplary operation of the X-ray imaging system 100 for generating a corrected image I of the object 140 (see FIG. 1 or 2) from the acquired projection data, in particular the acquired projection images. In order to avoid repetition, mainly the differences to the operation according to FIG. 3 will be described below. In addition to the detection of the foreign object 190, 200 (or its identifier), data obtained by the further detection means 210 is used to detect and/or identify the foreign object 190, 200. These additional data may be based on a read-out of a computer-readable identifier as the above-mentioned barcode, QR code, NFC tag, RFID tag, or the like. In addition to the position and/or orientation determination of the foreign object 190, 200 based on the image data, which comprise the image of the object 140 and the foreign object 190, 200, the further detection means 210, preferably in another configuration (not shown), is used to acquire the 6 DoF position and/orientation base on EM tracking, radar or light or ultrasound triangulation, or the like. Apart from these differences, again, the reconstruction processing means 170 generates the reconstructed and corrected image I of the object 140 as explained above.

[0070] It is noted that the exemplary operations described with reference to FIGS. 3 and 4 may also be combined with each other.

[0071] FIG. 5 shows a schematically images of the object 140 to be imaged at several points during the reconstruction and/or correction process using the reconstruction processing means 170. As indicated on the left side of FIG. 5, the X-ray detector 160 provides the acquired projection images, which only for better illustration are indicated as being already reconstructed. As indicated, the acquired projection images comprise artefacts 192, 202 caused by the foreign objects 190, 200. The artefact 202 is a streak artefact due to the high density of the metal implant which is represented by the foreign object 200. As explained above, based on the acquired projection images, the reconstruction processing means 170 determines the presence of the foreign object 190, 200, e.g. by use of the classification means or, in general, by the feature extraction and/or recognition algorithm, or the like. Upon determining the presence it further determines the identifier of the foreign object 190, 200 by use of the classification means of the AI-module 174, which may reveal a shape, material property, density, or the like, of the foreign object 190, 200. Based on the unique identifier, the reconstruction processing means 170 obtains the three-dimensional profile of the foreign object 190, 200 matching the unique identifier by downloading from the foreign object database 182 the server-based computing device 180. Based on the three-dimensional profile, the reconstruction processing means 170 determines, e.g. by the position determining module, the position and/or orientation of the imaged foreign object 190, 200. At least based on the position and/or the orientation of the imaged foreign object 190, 200, the reconstruction means 170 at least reduces an impact of the foreign object 190, 200 on the reconstructed image quality by subtracting an artefact from the reconstructed image, either during or after the final reconstruction of the image. As a result, the reconstructed and corrected image I of the object 140 (see also FIG. 1 or 2), in which artefacts caused by the foreign object 190, 200 are reduced or from which the artefacts are substantially removed, is obtained.

[0072] FIG. 6 shows a flow chart of a method of imaging an object by the X-ray imaging system 100. In a step S1, presence of the foreign object 190, 200 located in the object 140 or located between a surface of the object 140 and the X-Ray radiation source 150 and/or the X-ray detector 160 is determined. In a step S2, the three-dimensional profile of the determined foreign object 190, 200 is obtained from the server-based foreign object database 182. In a step S3, the image I of the object 140 is reconstructed by acquiring the plurality of projection images of the object 140 from the X-ray detector 160 and reducing impact on image quality of an artefact 192, 202that can be caused by the foreign object in the image of the object 140 based on at least the obtained three-dimensional profile of the foreign object 190, 200.

[0073] In an optional step S4 (not shown), the three-dimensional profile is obtained from at least a first scan on a first radiation dosage level and a second scan on a second radiation dosage level different to the first radiation dosage level of the X-ray imaging system. The dosage level may comprise a different intensity and/or a different electromagnetic spectrum.

[0074] In an optional step S5 (not shown), a photon counting bin based scatter profile of the foreign object 190, 200 is determined before reconstructing the image I.

[0075] In an optional step S6 (not shown), a phase contrast information of the foreign object 190, 200 is determined before reconstructing the image I.

[0076] In an optional step S6 (not shown), determining the presence of the foreign object 190, 200 is performed during a scout scan provided with a first radiation dose, and acquiring the image of the object is performed by an examination scan provided with a second radiation dose higher than the first radiation dose.

[0077] In an optional step S7 (not shown), the three-dimensional profile is at least partly obtained by additive manufacturing a model of the determined foreign object 190, 200 and scanning the same by means of the X-ray imaging system 100.

[0078] It should to be noted that embodiments of the invention are described with reference to different subject-matters. In particular, some embodiments are described with reference to method-type claims, whereas other embodiments are described with reference to device-type claims. However, a person skilled in the art will gather from the above, and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject-matter, also other combinations between features relating to different subject-matters is considered to be disclosed with this application.

[0079] All features can be combined to provide a synergetic effect that is more than the simple summation of the features.

[0080] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary, and not restrictive. The invention is not limited to the disclosed embodiments.

[0081] Other variations to the disclosed embodiments can be understood, and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

[0082] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor, or other unit, may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

LIST OF REFERENCE SIGNS

[0083] 100 X-ray imaging system

[0084] 110 housing

[0085] 120 gantry

[0086] 130 object support

[0087] 140 object

[0088] 150 radiation source

[0089] 160 X-ray detector

[0090] 170 reconstruction processing means

[0091] 171 processor

[0092] 172 memory

[0093] 173 memory

[0094] 174 artificial-intelligence-module

[0095] 180 server-based computing device

[0096] 181 processor, memory etc.

[0097] 182 foreign object database

[0098] 190 foreign object

[0099] 191 computer-readable identifier

[0100] 192 artefact

[0101] 200 foreign object

[0102] 202 artefact

[0103] 210 detection means

[0104] 220 further detection means