阅读说明：本技术 减少异物的x射线成像系统 (Foreign body reduction X-ray imaging system ) 是由 S·K·武帕拉 R·巴特 G·福格特米尔 R·S·西索迪亚 S·乔杜里 于 2019-09-23 设计创作，主要内容包括：一种改进的X射线成像系统。所述系统包括：X射线辐射源,其被配置为朝向要被成像的目标发射X射线束；以及X射线探测器,其被配置为探测已经穿过所述目标的X射线。所述系统还包括：重建处理单元,其被配置为基于探测到的X射线来重建所述目标的图像,其中,所述重建处理单元还被配置为：确定位于所述目标中或者位于所述目标的表面与所述X射线辐射源和/或所述X射线探测器之间的至少一个异物的存在；从基于服务器的异物数据库获得所确定的异物的三维概况；并且通过以下操作来重建所述目标的图像：从所述X射线探测器采集所述目标的多幅投影图像,并且至少基于所获得的所述异物的三维概况来减小所述目标的所述图像中的能够由所述异物引起的伪影对图像质量的影响。(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 that have passed through the object. The system further comprises: a reconstruction processing unit configured to reconstruct an image of the object based on the detected X-rays, wherein the reconstruction processing unit is further configured to: determining the presence of at least one foreign object located in the object or 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 the effect of artifacts in the image of the object, which can be caused by the foreign object, on image quality at least based on the obtained three-dimensional profile of the foreign object.)

1. An X-ray imaging system (100), comprising:

an X-ray radiation source (150) configured to emit an X-ray beam towards an object (140) to be imaged,

an X-ray detector (160) configured to detect X-rays that have passed through the object,

a reconstruction processing unit (170) configured to reconstruct an image of the object (140) based on the detected X-rays, wherein the reconstruction processing unit (170) is further configured to:

determining the presence of at least one foreign object (190, 200) located in the object (140) or between a surface of the object (140) and the X-ray radiation source (150) and/or the X-ray detector (160),

obtaining a three-dimensional profile of the determined foreign object (190, 200) from a server-based foreign object database (182), and

reconstructing an image (I) of the object (140) by: acquiring a plurality of projection images of the object (140) from the X-ray detector (160) and reducing the effect of artifacts (192, 202) in the image of the object (140) which can be caused by the foreign object (190, 200) on image quality at least based on the obtained three-dimensional profile of the foreign object (190, 200);

wherein the reconstruction processing unit (170) is further configured to at least partially subtract the artifact (192, 202) from the image of the object (140).

2. The X-ray imaging system (100) of claim 1,

wherein the three-dimensional profile comprises density data and/or material data of the foreign object (190, 200).

3. X-ray imaging system (100) according to claim 1 or 2,

wherein the reconstruction processing unit comprises a classification unit (174) for identifying the foreign object (190, 200) derived from the acquired image of the object comprising the foreign object (190, 200) based at least on a feature extraction of the foreign object (190, 200).

4. X-ray imaging system (100) according to one of the preceding claims,

wherein the reconstruction processing unit (170) is further configured to identify the foreign object based on a read-out of a computer-readable identifier provided with the foreign object.

5. X-ray imaging system (100) according to one of the preceding claims,

wherein the reconstruction processing unit (170) is further configured to determine at least 6DoF position of the foreign object relative to the target before reducing the effect of the foreign object.

6. The X-ray imaging system (100) of claim 5,

wherein the reconstruction processing unit (170) is further configured to:

determining the 6DoF position based on a first image acquisition scan provided with a first resolution, and

subtracting the foreign object from a second image acquisition scan provided with a second resolution higher than the first resolution based on the 6DoF position.

7. X-ray imaging system (100) according to claim 5 or 6,

wherein the reconstruction processing unit (170) is further configured to adjust scan parameters of the X-ray imaging system based on the 6DoF position.

8. X-ray imaging system (100) according to one of the preceding claims,

wherein the artifact is caused by the at least one foreign object (190, 200) comprising electronics arranged between a surface of the object and the X-ray radiation source (150) and/or the X-ray detector (160).

9. A method of imaging an object by an X-ray imaging system (100), comprising:

determining the presence of at least one foreign object (190, 200) located in the object or between a surface of the object and the X-ray radiation source (150) and/or the X-ray detector (160),

obtaining a three-dimensional profile of the determined foreign object (190, 200) from a server-based foreign object database (182), and

reconstructing an image (I) of the object by: acquiring a plurality of projection images of the object from the X-ray detector (160) and reducing the effect of artifacts in the image of the object, which can be caused by the foreign object, on image quality at least based on the obtained three-dimensional profile of the foreign object (190, 200);

wherein the artifact (192, 202) is at least partially subtracted from the image of the object (140).

10. The method of claim 9, wherein the first and second light sources are selected from the group consisting of,

wherein the three-dimensional profile is obtained at least from a first scan of the X-ray imaging system (100) at a first radiation dose level and a second scan at a second radiation dose level different from the first radiation dose level.

11. The method according to claim 9 or 10,

wherein a photon-count-based scatter profile of the foreign object (190, 200) is determined prior to reconstructing the image.

12. The method of any one of claims 9 to 10,

wherein phase contrast information of the foreign object (190, 200) is determined prior to reconstructing the image.

13. The method of any one of claims 9 to 12,

wherein the three-dimensional profile is obtained at least in part by: -additively manufacturing a model of the determined foreign object, and-scanning the model by means of the X-ray imaging system (100).

14. A computer program element, which, when being executed by at least one processing unit, is adapted to cause the processing unit to carry out the method according to any one of claims 9 to 13.

Technical Field

The invention relates to an X-ray imaging system, a method of imaging an object by an X-ray imaging system and a computer program element.

Background

X-ray imaging can be used to provide anatomical information, particularly in diagnostic and/or therapeutic applications. In particular in Computed Tomography (CT) systems, 3D data reconstructions of acquired cross-sectional images can be combined into a three-dimensional image of the object and three-dimensional volume information can be provided.

During imaging, the presence of metal and/or other foreign material can interfere with reconstruction and can lead to severe artifacts (often streak artifacts) that can affect image information and reduce image quality, and thus diagnostic quality. Such foreign bodies may be, for example, implants of a patient to be imaged. Such foreign bodies may be, for example, dental implants, bone screws, etc.

There are a number of artifact reduction solutions for X-ray imaging. Some of these solutions are based on the following operations: a three-dimensional volume of a foreign body is algorithmically identified in a reconstructed image of the object, and the reconstruction then needs to be rerun taking into account the identified three-dimensional volume of the foreign body.

Such methods are not only computationally intensive, but are also limited to relatively large, high density foreign matter.

Disclosure of Invention

Accordingly, there is a need for improved imaging, particularly with respect to image quality associated with foreign matter.

The object of the invention is solved by the subject matter of the independent claims, wherein further embodiments are incorporated in the dependent claims. It should be noted that the following described aspects of the invention apply equally to the X-ray imaging system, the method of imaging an object by means of an X-ray imaging system and the computer program element.

According to one aspect, there is provided an 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 that have passed through the object,

a reconstruction processing unit configured to reconstruct an image of the object based on the detected X-rays, wherein the reconstruction processing unit is further configured to:

determining the presence of at least one foreign object located in the object or between the surface of the object and the X-ray radiation source and/or the X-ray detector,

obtaining a three-dimensional profile (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 the effect of artifacts in the image of the object, which can be caused by the foreign object, on image quality at least based on the obtained three-dimensional profile of the foreign object.

An X-ray imaging system may be configured for CT applications or other X-ray applications to image a target that may cause artifacts due to foreign objects. In medical imaging, the target may also be referred to as a patient, wherein the foreign object may be located inside the patient (e.g. as an implant) or may be located outside the patient (e.g. as an electronic or metallic component, such as a sensor, a patient monitoring unit, a patient fixation unit, etc.).

The reconstruction processing unit may comprise one or more processors, a memory for storing at least one program unit, a memory for storing a series of cross-sectional images of the object and/or a memory for storing reconstructed three-dimensional images or the like, a data interface, and a reconstruction software module or the like. The reconstruction processing unit may be configured to: the X-ray absorption effect of, for example, foreign objects, etc. is calculated and corresponding correction data is provided for reconstruction algorithms, etc. without being truncated.

Obtaining the determined three-dimensional profile of the foreign object from the foreign object database may also be referred to as downloading the determined three-dimensional profile of the foreign object from a corresponding server, which may be a local computer system, a cloud computing system, or the like. The three-dimensional profile may be provided by the manufacturer of the foreign object and/or may be determined, for example, by scanning by means of an X-ray system. The three-dimensional profile may comprise an image, in particular a three-dimensional image, preferably an X-ray image, of the foreign body. In other words, the determined foreign object may have been previously measured and/or analyzed and may be recorded to a foreign object database, and/or such data may be provided by a supplier of the foreign object to have, for example, an exact material and/or geometric model of the foreign object, so as to be able to be used for improving the reconstruction.

Reducing the influence of foreign objects on the image quality may be performed directly during the reconstruction process and may be understood as at least partly avoiding the appearance of artifacts in the image of the object and/or at least partly removing artifacts from the image, etc.

An X-ray imaging system may improve image correction and hence image quality, in particular with respect to artifact reduction. In particular, a correction of artifacts which may be caused by foreign bodies located between the X-ray radiation source and the X-ray detector may be improved. The three-dimensional profile of the foreign object can be provided with a high level of detail, thereby improving the overall accuracy of the correction target image. For example, the system may improve the sharpness of the target image. The system may distinguish small foreign objects from the target image and/or the acquired image. The system can reduce the artifacts of low-density thin-wall metal.

According to the above aspect, the reconstruction processing unit is further configured to at least partially subtract the artifact from the image of the object to reduce an effect of the artifact on image quality. The reconstruction processing unit may comprise a subtraction module configured to subtract at least a portion of the artifact of the foreign object. The subtraction module may for example be implemented as a software module. The artifact may be included in one or more of the acquired images.

In further examples, the three-dimensional profile may include density data and/or material data of the foreign matter. The density data may vary in or relative to the imaging direction. The material data may include a single material or a composite material. The density data may comprise a density map, in particular a multi-dimensional density map. Therefore, more information about the foreign substance can further improve the image quality.

In another example, a three-dimensional profile and/or a scattering profile including a foreign object. Optionally, the scattering profile may comprise different intensities. The scatter profile may be determined prior to acquiring an image of the target. The reconstruction processing unit may be further configured to reduce artifacts based on the obtained scatter profile of the foreign object. Therefore, more information about the foreign substance can further improve the image quality.

In one example, the identifier may be associated with the three-dimensional profile in a foreign object database, wherein the reconstruction processing unit may be further configured to determine the identifier of the foreign object to obtain the three-dimensional profile data from the foreign object database.

In further examples, the reconstruction processing unit may be further configured to determine the identifier from one or more acquired images of the object including the foreign object. Thus, foreign objects may have been identified based on the acquired images.

In another example, the reconstruction processing unit comprises a classification unit for identifying the foreign object at least based on feature extraction of the foreign object derived from one or more acquired images of the object comprising the foreign object (which may reveal shape, material properties, density, etc.). The classification unit may be implemented as a software module, in particular an artificial intelligence module — AI module. The AI module may comprise a machine learning component implemented in an artificial neural network, in particular in a convolutional neural network, or may alternatively be arranged to support a vector machine, a linear regression algorithm, or other items. The classification unit may be pre-trained with a suitable training data set. In addition, the classification unit may be configured to compare the identified foreign object with records of a foreign object database to automatically obtain a correct three-dimensional profile and optionally to automatically obtain other information (e.g., material properties, density distribution, etc.) to reduce the effects of artifacts caused by the foreign object.

In one example, X-ray absorption measurements from the image data may be used to give a first analysis of the material and/or spatial distribution of the material of the foreign object. Such information may be used to perform or assist in the classification of foreign matter.

In a further example, the reconstruction processing unit may be further configured to identify the foreign object based on a shape-independent property of the foreign object derived from the acquired image and matching the foreign object database. This may be used as a single identification method or may be combined with the identification method of the classification unit to verify the classification and/or to improve the match with foreign objects in the corresponding database.

In one example, the reconstruction processing unit is further configured to identify the foreign object based on a read-out of a computer-readable identifier provided with the foreign object. The identifier may be unique and may be provided as a barcode, QR code, RFID tag, NFC tag, etc., which can be read by a barcode scanner, camera, radio module, etc., of the X-ray imaging system. If the foreign object is an implant, such code or information obtained by the patient information system may be used to identify the foreign object. This may be used as a single identification method or may be combined with the identification method of the classification unit to verify the classification and/or to improve the match with the foreign object in the corresponding database.

In a further example, the reconstruction processing unit may be further configured to determine at least a 6DoF position (six degree of freedom position) of the foreign object relative to the target, optionally also alternatively or additionally determining an orientation of the foreign object relative to the target, before reducing the effect of the foreign object. For example, information about the relative position and/or orientation of the foreign object may be determined based on one or more of the acquired images of the object comprising the foreign object, in particular prior to reconstruction. To this end, a few orthogonal images may be acquired to reduce computational requirements, or low resolution three-dimensional images may be generated (e.g., reconstructed) to reduce computational requirements and increase speed. Alternatively, a full reconstruction is performed without artifact reduction (e.g., artifact subtraction).

In one example, an X-ray imaging system (e.g., a reconstruction processing unit or a separate module) may be configured to acquire the 6DOF position and/or orientation of the foreign object using one or more of the following methods: electromagnetic tracking, radar and/or light and/or ultrasound based triangulation. Additionally or alternatively, acceleration sensors, magnetic sensors, etc. may provide additional 6DOF information.

In further examples, the reconstruction processing unit may be further configured to: determining the 6DoF position and optionally the orientation of the foreign object based on a first image acquisition scan provided with a first resolution; and subtracting the foreign object from a second image acquisition scan provided with a second resolution higher than the first resolution based on the 6DoF position. The first image acquisition scan may also be referred to as a scout scan, which may be faster than the second scan. Since the 6DoF position and/or orientation is determined based on scout scans, the definition of quality and position may lead to patient and/or scanner guidance information. After the scout scan is processed and information derived therefrom, a second, subsequent or final high resolution diagnostic scan may be automatically performed.

Typically, data obtained from such scout scans may be used to determine an identifier of the foreign object. Based on the determined identifier, corresponding data of the foreign object database may be obtained.

In another example, the reconstruction processing unit may be further configured to adjust scan parameters of the X-ray imaging system based on the 6DoF position. The scan parameters may include at least one of: patient position, tilt angle, start and end of scan, etc.

In one example, the artifact is caused by the at least one foreign object comprising electronics arranged between a surface of the target and the X-ray radiation source and/or the X-ray detector. The electronic device may be a sensor, a camera, etc. Thus, a foreign object located outside the target can be determined, and the image of the target can be corrected accordingly.

In further examples, the foreign object may comprise at least a portion of a patient monitoring system. The patient monitoring system may be a sensor, a camera, etc. Alternatively or additionally, the patient monitoring system may include fiducial markers or the like.

In another example, the foreign object may comprise a patient fixation unit.

In further examples, the foreign object may be an implant located inside the object to be imaged. Such implants may be patient-specific (e.g., titanium alloy hip joints, etc.) and may generate metal artifacts. The three-dimensional model may include at least the geometry and/or material data (e.g., density information, etc.) of the implant. In some embodiments, the patient implant may be manufactured using additive manufacturing/3D printing.

According to one aspect, there is provided a method of imaging an object by an X-ray imaging system, comprising the steps of:

determining the presence of at least one foreign object located in the object or between the 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 the effect of artifacts in the image of the object, which can be caused by the foreign object, on image quality at least based on the obtained three-dimensional profile of the foreign object. At least partially subtracting the artifact caused by the foreign object from the image of the target.

The method may be performed using the system described above. For example, in some embodiments, the method may be stored as a program element on a computer readable medium, which, when being executed by a processor (e.g. a processor of an X-ray system, in particular a processor of a reconstruction processing unit), is adapted to carry out the steps of the method described above and below.

In one example, the three-dimensional profile may be obtained from at least a first scan of the X-ray imaging system of the foreign object at a first radiation dose level and a second scan of the foreign object at a second radiation dose level different from the first radiation dose level. Alternatively or additionally, a three-dimensional profile of the foreign object may be obtained by scanning the foreign object at a plurality of energy settings, in particular a plurality of scans at a plurality of kV settings. Information for different radiation dose levels and/or multiple energy settings may be stored as additional information in the foreign object database.

In further examples, a photon count based scatter profile of the foreign object may be determined prior to reconstructing the image from the projection images. A photon count based scatter profile may be used during image reconstruction to further improve the accuracy of artifact and/or streak reduction (e.g., removal, subtraction, etc.). The scatter profile may be used in combination with a three-dimensional profile of the foreign object, which may improve image quality, in particular the accuracy of subtracting artifacts from the image of the target. For example, using a scatter profile may improve image correction for small metal artifacts.

In another example, phase contrast information of the foreign object is determined prior to reconstructing the image. In other words, dark-field X-ray imaging based on phase contrast information may be used in conjunction with a three-dimensional profile and/or a scatter profile of the foreign object. This may further improve the image correction and thus the image quality.

In one example, a three-dimensional profile of the foreign object may be obtained by scanning the foreign object using an X-ray imaging system. Thus, the three-dimensional profile of the foreign object may be corrected based on the scatter profile, dark-field X-ray imaging, or a combination thereof. This may further improve the image correction and thus the image quality.

In a further example, the presence of the foreign object may be determined during a scout scan provided with a first radiation dose, and an image of the object is acquired by an examination scan provided with a second radiation dose higher than the first radiation dose. After the presence of foreign matter is determined, the foreign matter may be identified as described above. For example, the foreign matter may be classified using the above-described classification means or the like. Scout scans may take less time and may provide patient and/or scanner guidance information. When the foreign matter can be identified, the inspection scan can be automatically performed.

In one example, the three-dimensional profile is obtained, at least in part, by: a model of the determined foreign object is additively manufactured (e.g. 3D printed) and the model is scanned by means of the X-ray imaging system. For example, the foreign object may be determined manually prior to scanning (i.e., performing a scout scan and/or an inspection scan). In some embodiments, the foreign object may be automatically determined as described above. The manufactured model may be scanned to obtain a scatter profile, density information, and the like.

According to an aspect, a computer program element is provided, which, when being executed by at least one processing unit (e.g. a processor of an X-ray imaging system, in particular a processor of a reconstruction processing unit), is adapted to cause the processing unit to carry out the method as described above. The computer readable medium may be a floppy disk, a hard disk, a USB (universal serial bus) memory device, a RAM (random access memory), a ROM (read only memory), and an EPROM (erasable programmable read only memory). The computer readable medium may also be a data communication network, e.g. the internet, which allows downloading the program code.

A further aspect of the invention relates to a program element (e.g. a computer program) for controlling an X-ray system, which program element, when being executed by a processor (e.g. a processor of an X-ray imaging system), is adapted to carry out the steps of the methods described above and below.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

Drawings

Exemplary embodiments of the invention will be described below with reference to the following drawings:

fig. 1 schematically shows, in a perspective view, an X-ray system according to an exemplary embodiment of the present invention.

Fig. 2 schematically shows a further embodiment of an X-ray imaging system in side view.

Fig. 3 schematically shows a block diagram of an exemplary operation of an X-ray imaging system.

Fig. 4 schematically illustrates a block diagram of another exemplary operation of an X-ray imaging system.

Fig. 5 schematically shows an image of an object to be imaged at several points during a reconstruction process and/or a correction process.

Fig. 6 shows a flow chart of a method of imaging an object by an X-ray imaging system.

The drawings are only schematic representations and are intended to illustrate embodiments of the present invention. In principle, identical or equivalent elements are provided with the same reference numerals.

List of reference numerals

100X-ray imaging system

110 casing

120 rack

130 target support

140 target

150 radiation source

160X-ray detector

170 reconstruction processing unit

171 processor

172 memory

173 memory

174 artificial intelligence module

180 server-based computing device

181 processor, memory, etc

182 foreign object database

190 foreign matter

191 computer readable identifier

192 ghost image

200 foreign matter

202 artifact

210 detection unit

220 additional detection unit

Detailed Description

Fig. 1 schematically shows an X-ray imaging system 100, which in this embodiment is a computed tomography imaging scanner. The X-ray imaging system 100 includes a stationary housing 110 and a rotatable gantry 120, the rotatable gantry 120 being capable of rotating within an angular range of about 360 ° about a target support 130, the target support 130 being a support table in this embodiment. In this embodiment, a target 140 to be imaged (which is, for example, a human patient) is located on the upper surface of the target support 130. The target support 130 is movable in translation along at least the z-axis to selectively move the target 140 into the housing 110. Note that in some embodiments, the target support 130 may have 6DoF (six degrees of freedom). The X-ray imaging system 100 further comprises a radiation source 150, the radiation source 150 being configured to emit an X-ray radiation beam towards the object 140 to be imaged, and in particular to generate a radiation beam to be directed into the examination region. The radiation beam interacts with a region of interest of a target 140 (see fig. 2) disposed in an examination region, wherein a spatially varying absorption of the radiation occurs as the radiation traverses the examination region.

The X-ray imaging system 100 further comprises an X-ray detector 160, the X-ray detector 160 being configured to detect X-rays that have passed through the object 140, and in particular to detect absorption-attenuated radiation after the radiation has 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 such that the X-ray detector 160 continuously receives X-rays from the radiation source 150. The radiation detector 160 may comprise a two-dimensional array of detector elements, wherein other embodiments are envisioned.

The X-ray imaging system 100 further comprises one or more calculation units, wherein, in this embodiment, the reconstruction processing unit 170 will be mainly described. The reconstruction processing unit 170 is connected at least to the X-ray detector 160 and/or the radiation source 150 for controlling these elements and/or for obtaining data from these elements, in particular from the X-ray detector 160. The reconstruction processing unit 170 may further be formed by several subsystems, functional modules or units, software modules or units or the like (not described in further detail herein) 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 to reconstruct an image of the object 140 based on a plurality of acquired projection images of the object 140. In this embodiment, the reconstruction processing unit 170 comprises at least one processor 171 (e.g. a backprojection 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 unit 170 comprises at least one image reconstruction algorithm, which in this embodiment is stored as a program unit in the memory 173. In this embodiment, the reconstruction processing unit 170 is configured to reconstruct an image using filtered back-projection. However, other reconstruction algorithms can be used for reconstruction.

The reconstruction processing unit 170 also includes an artificial intelligence module, the AI module, which is designated by the reference numeral 174 for better illustration. The AI module 174 comprises a classification unit configured to identify objects within the image, in particular objects within the image reconstructed by the reconstruction processing unit 170. The classification unit of the AI module 174 illustratively comprises a machine learning component implemented in an artificial neural network, particularly in a convolutional neural network, which may alternatively be arranged to support a vector machine, a linear regression algorithm, or other terms. The classification unit may be pre-trained with a suitable training data set.

The X-ray imaging system 100 further includes a server-based computing device 180, the server-based computing device 180 may be 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 unit 170, wherein such connection may be established in a wired manner or a wireless manner. The server-based computing device 180 includes a processor, memory, etc., collectively designated with the reference numeral 181. The server-based computing device 180 also includes a database 182, the database 182 configured to associate identifiers of the foreign objects 190, 200 (which will be described in greater detail below) with corresponding three-dimensional profiles of the foreign objects 190, 200. The foreign object database 182 includes three-dimensional profiles, geometric data (e.g., shape and/or size data), material data, density contribution data, X-ray absorption data, scattering curves, and the like. These data may be measured and/or analyzed in advance during a scout scan or an inspection scan of the X-ray imaging system 100, or may be provided by the manufacturer and/or supplier of the foreign object 190, 200. In this embodiment, the first foreign object 190 is located outside of the target 140 between the outer surface of the target 140 and the radiation source 140. As an example, the first foreign object 190 is an electronic device (e.g., a sensor, a camera, etc.). Additionally, illustratively, the second foreign body 200 is located inside the target 140 and is formed, for example, as a metal implant (e.g., a metal clip, a high density dental filling, an artificial hip joint, etc.). Note that the first and second foreign objects 190, 200 may cause artifacts, particularly if the region of interest being imaged contains a high density region of them. Typically, the second foreign object 190 may appear as a metal artifact in the reconstructed image, such as a streak emanating from a high density region (see fig. 5).

Referring to fig. 2, which schematically shows a further embodiment of the X-ray imaging system 100, wherein the first foreign object 190 located outside the target 140 further exemplarily comprises a computer readable identifier 191 provided along with the first foreign object 190, passing through the housing 110 without occlusion. Note that only the size of the computer readable identifier 191 is exaggerated for better illustration. The computer-readable identifier 191 may be provided as an electronic device or a non-electronic device (e.g., a barcode, QR code, NFC tag, RFID tag, etc.), or may include an accelerometer, magnetic sensor, etc., and may also be configured to be read by the detection unit 210 as schematically indicated in fig. 2. Depending on the design of the identifier 191, the detection unit 210 may be provided as a barcode or QR code scanner, an NFC module, a radio module, a camera, or the like. Note that the detection unit 210 may be disposed outside or inside the housing 110. In this embodiment, the detection unit 210 is connected to the reconstruction processing unit 170. Note that the detection unit 210 may also be directly connected to the server-based computing device 180. The same or another detection unit 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.

With further reference to fig. 2, in this embodiment, the X-ray imaging system 100 further comprises an additive manufacturing device 220, the additive manufacturing device 220 being configured to form a physical model of the foreign object 190, 200 imaged by the X-ray imaging system 100 (e.g. by 3D printing techniques). For example, additive manufacturing device 220 is connected to reconstruction processing unit 170 on one side and server-based computing device 180 on the other side. The additive manufacturing device 220 is configured to generate a 3D model of the foreign object 190, 200 based on the foreign object image reconstructed by the reconstruction processing unit 170. Such 3D models of the foreign objects 190, 200 may be imaged by the X-ray imaging system 100 and may be provided to the server-based computing device 180.

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 a target 140 (see fig. 1 or fig. 2) from acquired projection data, in particular acquired projection images. Preferably, the projection image comprises projection data corresponding to an angular illumination range of at least 360 ° per image element (i.e. per pixel or voxel). However, it is also contemplated to reconstruct a reduced projection data set providing projection data corresponding to, for example, an angular illumination range of at least 180 ° for each image element. The X-ray detector 160 provides projection images acquired when X-rays that have passed through the object 140 and the foreign objects 190, 200 are detected to the reconstruction processing unit 170, wherein the radiation source 150 emits X-rays. Based on the acquired projection images, the reconstruction processing unit 170 determines the presence of a foreign object 190, 200 (e.g. by using a classification unit or typically by a feature extraction and/or recognition algorithm, etc.). Upon determining the presence of the foreign object, the reconstruction processing unit 170 also determines an identifier of the foreign object 190, 200, which may reveal the shape, material properties, density, etc. of the foreign object 190, 200, by using the classification unit of the AI module 174. Based on the unique identifier, the reconstruction processing unit 170 obtains a three-dimensional profile of the foreign object 190, 200 that matches the unique identifier by downloading the server-based computing device 180 from the foreign object database 182. Based on the three-dimensional profile, which comprises in particular geometrical data (e.g. shape, size, etc.), material data (e.g. density, density distribution, material properties, etc.), and the at least one subset of the acquired projection images, the reconstruction processing unit 170 determines the position and/or orientation of the imaged foreign object 190, 200, e.g. by means of a position determination module. For this reason, the reconstruction processing unit 170 uses a few orthogonal images of the acquired projection images, a low-resolution three-dimensional image reconstructed by the reconstruction processing unit 170 based on the acquired projection images, and the like. Based at least on the position and/or orientation of the imaged foreign object 190, 200, the reconstruction unit 170 at least reduces the effect of the foreign object 190, 200 on the reconstructed image quality by subtracting the artifact from the reconstructed image during or after the final image reconstruction. In fig. 3, a reconstructed and corrected image of the object 140 is denoted by reference character I, in which artifacts caused by foreign bodies 190, 200 are reduced or substantially removed.

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 a target 140 (see fig. 1 or fig. 2) from acquired projection data, in particular acquired projection images. In order to avoid repetition, differences from the operation according to fig. 3 will be mainly described below. In addition to the detection of the foreign object 190, 200 (or an identifier thereof), the foreign object 190, 200 is detected and/or identified using data obtained by a further detection unit 210. These additional data may be based on reading a computer readable identifier such as a barcode, QR code, NFC tag, RFID tag, etc. as described above. In addition to determining the position and/or orientation of the foreign object 190, 200 based on image data, including images of the target 140 and the foreign object 190, 200, a further detection unit 210, preferably in another configuration (not shown), is used for acquiring the 6DoF position and/or orientation based on EM tracking, radar triangulation or light triangulation or ultrasound triangulation, etc. In addition to these differences, the reconstruction processing unit 170 again generates a reconstructed and corrected image I of the object 140 as described above.

Note that the exemplary operations described with reference to fig. 3 and 4 may also be combined with each other.

Fig. 5 schematically shows an image of the object 140 to be imaged at several points during a reconstruction process and/or a correction process using the reconstruction processing unit 170. As shown on the left side of fig. 5, the X-ray detector 160 provides acquired images, which are represented as already reconstructed images for better illustration only. As indicated, the acquired projection images include artifacts 192, 202 caused by the foreign object 190, 200. Since the metal implant represented by foreign object 200 has a high density, artifact 202 is a streak artifact. As described above, based on the acquired projection images, the reconstruction processing unit 170 determines the presence of a foreign object 190, 200, for example by using a classification unit or typically by a feature extraction and/or recognition algorithm or the like. Upon determining the presence of the foreign object, the reconstruction processing unit 170 also determines an identifier of the foreign object 190, 200, which may reveal the shape, material properties, density, etc. of the foreign object 190, 200, by using the classification unit of the AI module 174. Based on the unique identifier, the reconstruction processing unit 170 obtains a three-dimensional profile of the foreign object 190, 200 that matches the unique identifier by downloading the server-based computing device 180 from the foreign object database 182. Based on the three-dimensional profile, the reconstruction processing unit 170 determines the position and/or orientation of the imaged foreign object 190, 200, e.g. by a position determination module. Based at least on the position and/or orientation of the imaged foreign object 190, 200, the reconstruction unit 170 at least reduces the effect of the foreign object 190, 200 on the reconstructed image quality by subtracting the artifact from the reconstructed image during or after the final image reconstruction. As a result, a reconstructed and corrected image I of the object 140 (see also fig. 1 or fig. 2) is obtained in which artifacts caused by the foreign bodies 190, 200 are reduced or substantially removed therefrom.

Fig. 6 shows a flow chart of a method of imaging an object by the X-ray imaging system 100. In step S1, the presence of a foreign object 190, 200 located in the object 140 or between the surface of the object 140 and the X-ray radiation source 150 and/or the X-ray detector 160 is determined. In step S2, a three-dimensional profile of the determined foreign object 190, 200 is obtained from the server-based foreign object database 182. In step S3, an image I of the object 140 is reconstructed by: a plurality of projection images of the object 140 are acquired from the X-ray detector 160 and the effect on the image quality of artifacts 192, 202 in the image of the object 140, which can be caused by foreign objects, is reduced at least on the basis of the obtained three-dimensional profile of the foreign object 190, 200.

In optional step S4 (not shown), a three-dimensional profile is obtained from at least a first scan of the X-ray imaging system at a first radiation dose level and a second scan at a second radiation dose level different from the first radiation dose level. The dosage levels may include different intensities and/or different electromagnetic spectra.

In an optional step S5 (not shown), a photon count bin based scatter profile of the foreign object 190, 200 is determined prior to reconstructing the image I.

In an optional step S6 (not shown), the phase contrast information of the foreign object 190, 200 is determined prior to reconstructing the image I.

In an optional step S6 (not shown), the presence of a foreign object 190, 200 is determined during a scout scan provided with a first radiation dose, and an image of the target is acquired by an examination scan provided with a second radiation dose higher than the first radiation dose.

In optional step S7 (not shown), a three-dimensional profile is obtained, at least in part, by: a model of the determined foreign object 190, 200 is additively manufactured and scanned by means of the X-ray imaging system 100.

It should be noted that embodiments of the present 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 apparatus type claims. However, unless otherwise indicated, a person skilled in the art will gather from the above and the following description that, in addition to any combination of features belonging to one type of subject-matter, also any combination between features relating to different subject-matters is considered to be disclosed with this application.

All of the features can be combined to provide a synergistic effect more than a simple addition of the features.

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.

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 appended claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. Although some measures are recited in mutually different dependent claims, this does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope.