Metal artifact correction

Abstract

To correct a metal artifact.SOLUTION: The metal artifact correction includes projecting X-rays to scan a volumetric region of an object, the projecting generating corresponding cone beam computed tomography (CBCT) image data, reconstructing from the CBCT image data an extended CBCT volume representing the volumetric region and a volume outside the volumetric region, generating from the extended CBCT volume and a projection geometry a maximum intensity projection on a virtual plane, detecting attenuation image areas in the maximum intensity projection corresponding to metal, matching the detected attenuation image areas corresponding to metal to the CBCT image data, and reconstructing a final CBCT volume using the CBCT image data by suppression of areas of the CBCT image data corresponding to the detected attenuation image areas of the maximum intensity projection.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001]

[0001] This disclosure relates to metal artifact correction, and more particularly to correcting metal artifacts caused by metal inside and outside the scanned volume. [Background technology]

[0002] Cone beam computed tomography (CBCT) systems are widely used in medical, dental, and industrial applications to provide high-resolution, three-dimensional images. CBCT imaging is particularly useful in dental and maxillofacial imaging, where it can provide detailed visualization of bone structures, teeth, and surrounding tissues. This technology uses a cone-shaped x-ray beam and a flat-panel detector to acquire volumetric data in rotation around the patient.

[0003] CBCT volumes can contain metal artifacts that distort the volume. The artifacts can be caused by the high density and radiopacity of metal objects such as dental implants, orthodontic brackets, surgical screws, and other metal hardware. These artifacts can appear as streaks, stars, shadows, etc. in the reconstructed volume or 3D image. Summary of the Invention

[0004]

[0004] According to an exemplary embodiment, a method involves irradiating an object with X-rays to scan a volumetric region and generate cone beam computed tomography (CBCT) image data, reconstructing an expanded CBCT volume that includes the volumetric region and an area outside it, creating maximum intensity projections onto a virtual plane from the expanded CBCT volume and projection geometry, detecting attenuated image areas corresponding to metal within these projections, transferring the (i.e., corresponding) locations of these detected areas to the CBCT image data, and reconstructing a final CBCT volume by suppressing areas of the CBCT image data that correspond to the attenuated image areas.

[0005]

[0005] In one embodiment, the reconstructing includes modifying the CBCT image data by changing areas of the CBCT corresponding to attenuated image areas corresponding to the metal to reduce the effect of the metal in subsequent reconstruction, reconstructing an intermediate volume using the modified CBCT image data, correlating the image area of ​​the maximum intensity projection or the image area of ​​the CBCT image data corresponding to the metal with the intermediate volume, reinserting the metal or metal modification (such as blending / weighting / smoothing pixel information of the metal) to modify the intermediate volume, and displaying the modified intermediate volume as the final volume.

[0006]

[0006] According to an exemplary embodiment, an X-ray system includes a processor and a memory having instructions that enable the system to project X-rays to scan a volumetric region of an object to generate cone beam computed tomography (CBCT) image data, reconstruct an enlarged CBCT volume representing the scanned region and an area outside it, create maximum intensity projections onto a virtual plane from the enlarged CBCT volume and projection geometry, detect metal-related attenuation image areas within these projections, correspond these areas to CBCT image data, and reconstruct a final CBCT volume by suppressing areas corresponding to the attenuation image areas.

[0007]

[0007] According to an exemplary embodiment, a non-transitory computer-readable storage medium includes instructions that, when executed by a computer, cause the computer to project X-rays to scan a volumetric region of an object and generate cone beam computed tomography (CBCT) image data, reconstruct an enlarged CBCT volume representing the volumetric region and an area outside it, generate a maximum intensity projection on a virtual plane from the enlarged CBCT volume and projection geometry, detect attenuated image areas corresponding to metal in the projection, correspond these detected areas to CBCT image data, and reconstruct a final CBCT volume by suppressing areas corresponding to the attenuated image areas. [Brief explanation of the drawings]

[0008] To easily identify the description of any particular element or operation, the most significant digit(s) of a reference number refers to the figure number in which that element or operation is first introduced. [Figure 1]

[0009] FIG. 1 depicts a block diagram of a network of data processing systems in accordance with an illustrative embodiment. [Figure 2]

[0010] FIG. 2 depicts a block diagram of a data processing system in accordance with an illustrative embodiment. [Figure 3]

[0011] FIG. 3 illustrates a block diagram of an X-ray system in accordance with an exemplary embodiment. [Figure 4]

[0012] FIG. 4 illustrates an x-ray system for scanning a volumetric region, in accordance with an example embodiment. [Figure 5]

[0013] FIG. 5 illustrates an expanded CBCT volume and corresponding maximum intensity projection, according to an exemplary embodiment. [Figure 6]

[0014] FIG. 6 illustrates a slice through an expanded CBCT volume in accordance with an exemplary embodiment. [Figure 7]

[0015] FIG. 7 illustrates a maximum intensity projection of an expanded CBCT volume, according to an exemplary embodiment. [Figure 8]

[0016] FIG. 8 illustrates a slice through an expanded CBCT volume in accordance with an exemplary embodiment. [Figure 9]

[0017] FIG. 9 illustrates a maximum intensity projection of an expanded CBCT volume in accordance with an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009]

[0018] In the following detailed description, for purposes of illustration, numerous specific details are set forth in order to provide a thorough understanding of the relevant teachings. However, it should be apparent that the present teachings may be practiced without such details. In other instances, well-known methods, procedures, and / or components have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings.

[0010]

[0019] The exemplary embodiments recognize that metal detection in x-ray operations can be performed by threshold detection within a volume, followed by projection of the metal location onto the image for correction before using the corrected image to reconstruct another volume. However, this only detects metal within the scanned volume of interest and may miss metal and artifacts outside the volume. The exemplary embodiments recognize that metal outside the volume may still lead to artifacts within the volume. However, attempting to increase the scanned volume of interest to capture all metal outside the volume may increase the x-ray dose used on the patient. Furthermore, metal detection within the volume may be made more difficult by strong "cupping artifacts" caused by metal.

[0011]

[0020] An exemplary embodiment discloses metal artifact detection and correction for a dental x-ray machine, which involves projecting x-rays to scan a volumetric region of an object, the projections generating corresponding cone beam computed tomography (CBCT) two-dimensional (2D) image data. The CBCT image data is projection data (2D), also referred to as sinograms, CBCT raw data, or CBCT projection data. An augmented CBCT volume (three-dimensional data) is reconstructed from the CBCT image data, the augmented CBCT volume representing the scanned volumetric region and a volume outside the volumetric region. A maximum intensity projection is generated on a virtual plane from the augmented CBCT volume and projection geometry, and attenuated image areas in the maximum intensity projection corresponding to metals are detected. As used herein, the attenuated image areas corresponding to metals generally refer to attenuated image areas corresponding to radiopaque or nearly radiopaque structures, where metals may be most common. In an exemplary embodiment, the detected attenuated image areas corresponding to metals are matched to the CBCT image data, and a final CBCT volume is reconstructed based on the CBCT image data by suppressing areas of the CBCT image data corresponding to the attenuated image areas of the maximum intensity projections.

[0012]

[0021] The exemplary embodiments are described with respect to particular types of machines. The exemplary embodiments are also described with respect to other scenes, objects, measurements, devices, data processing systems, environments, components, and applications, by way of example only. Any specific manifestation of these and other similar things is not intended to limit the present disclosure. Any suitable manifestation of these and other similar things may be selected within the scope of the exemplary embodiments.

[0013]

[0022] Furthermore, exemplary embodiments may be implemented with respect to any type of data, data source, or access to a data source via a data network. Any type of data storage device may provide data to embodiments of the present disclosure, either locally at a data processing system or via a data network, within the scope of the present disclosure.

[0014]

[0023] The exemplary embodiments are described using specific code, hardware, algorithms, designs, architectures, protocols, layouts, circuit diagrams, and tools as examples only, and are not limited to the exemplary embodiments. Furthermore, the exemplary embodiments are described in some instances using specific software, tools, and data processing environments as examples only for clarity of explanation. The exemplary embodiments may be used in conjunction with other equivalent or similar purpose structures, systems, applications, or architectures. For example, other equivalent devices, structures, systems, applications, or architectures thereof may be used in conjunction with such embodiments of the present disclosure within the scope of the present disclosure. The exemplary embodiments may be implemented in hardware, software, or a combination thereof.

[0015]

[0024] The examples in this disclosure are used for clarity of explanation only and are not intended to limit the exemplary embodiments. Additional data, operations, actions, tasks, activities, and operations are contemplated by this disclosure and are contemplated within the scope of the exemplary embodiments.

[0016]

[0025] Any advantages listed herein are merely examples and are not intended to be limiting to example embodiments. Additional or different advantages may be realized by certain example embodiments. Furthermore, certain example embodiments may have some, all, or none of the above-listed advantages.

[0017]

[0026] 1 is a block diagram of a data processing system environment in which exemplary embodiments may be implemented. Data processing environment 100 is a network of engines and computers in which exemplary embodiments may be implemented. Data processing environment 100 may include a network / communications infrastructure 102. Network / communications infrastructure 102 is the medium used to provide communications links between the various devices, databases, and computers connected to each other within data processing environment 100. Network / communications infrastructure 102 may include connections such as wired connections, wireless communication protocols, or other suitable data connections.

[0018]

[0027] The X-ray system 118 can implement the embodiments described herein. The X-ray system 118 can include a metal artifact engine 116, which can further include an embedded application for using data from the X-ray system 118 to detect and correct metal artifacts. The embedded application can also run in one of the data processing systems (server 104 or server 106, client 110), such as a server application 112 in the server 104 or a client application 120 in the client 110.

[0019]

[0028] In CBCT, an x-ray source and corresponding detector rotate around the patient, recording multiple projection images, which can be used to reconstruct a 3D volume. In scenarios where metal, such as metal fillings, is present in the patient volume, metal artifacts, such as artifacts appearing as metal streaks, shadows, and / or inaccurate shapes, may appear in subsequent volume reconstructions due to the presence of the metal. Therefore, the information in the subsequent reconstructions may be incomplete because they prevent some relevant patient anatomical structures from being properly visualized. As described herein, the metal artifact engine 116 described herein is adapted with logic to detect and correct metal artifacts caused by metal inside and outside the initial physically scanned volume, thereby reducing or eliminating the need to increase the volume area of ​​the object being scanned. Essentially, the metal may be visible in the CBCT image data. The metal and corresponding metal artifacts may also be visible in the reconstructed volume data. To suppress the metal artifacts in the reconstructed volume, the metal in the CBCT image data may be suppressed prior to reconstruction. To detect metals in CBCT image data, maximum intensity projections can be generated for subsequent processing as described herein.

[0020]

[0029] 1 , client or server are merely exemplary roles for particular data processing systems connected to network / communications infrastructure 102 and are not intended to exclude other configurations or roles of these data processing systems. Server 104 and server 106, along with storage unit 108, couple to network / communications infrastructure 102. Software applications may execute on any computer within data processing environment 100. Client 110 is also coupled to network / communications infrastructure 102. Data processing systems, such as server 104, server 106, or client 110, may contain data and may have software applications or software tools executing thereon.

[0021]

[0030] Merely by way of example, and without implying any limitation to such architecture, Figure 1 depicts certain components that may be used in an exemplary implementation of the embodiments. As another example, the embodiments may be distributed across several data processing systems and data networks as shown, while other embodiments may be implemented on a single data processing system within the scope of the exemplary embodiments.

[0022]

[0031] Data processing environment 100 may include additional servers, clients, and other devices not shown. Server 104 includes a server application 112 that may be configured to implement one or more of the functionality described herein for displaying restoration suggestions in accordance with one or more embodiments.

[0023]

[0032] Server 106 may include a search engine configured to search stored files, such as images of a patient's teeth, for comparison in response to a request to detect a dental defect. In the depicted example, data processing environment 100 may be the Internet. Network / communications infrastructure 102 may represent a collection of networks and gateways that communicate with each other using Transmission Control Protocol / Internet Protocol (TCP / IP) and other protocols. Figure 1 is intended as an example, and not as an architectural limitation for different illustrative embodiments.

[0024]

[0033] Among other uses, data processing environment 100 can be used to implement a client-server environment in which exemplary embodiments can be implemented. A client-server environment allows software applications and data to be distributed across a network, such that applications function using interactivity between client and server data processing systems. Data processing environment 100 may also employ a service-oriented architecture in which interoperable software components distributed across a network can be packaged together as a coherent business application. Data processing environment 100 may also take the form of a cloud and employ a cloud computing model of service delivery to enable convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, network bandwidth, servers, processing, memory, storage, applications, virtual machines, and services) that can be rapidly provisioned and released with minimal administrative effort or interaction with a service provider.

[0025]

[0034] 2, which illustrates a block diagram of a data processing system in which exemplary embodiments may be implemented. Data processing system 200 is an example of a computer, such as X-ray system 118, client 110, server 104, or server 106 of FIG. 1, or another type of device in which computer-usable program code or instructions implementing the processes for exemplary embodiments may be located.

[0026]

[0035] Data processing system 200 is described as a computer by way of example only, and not limitation. Implementations in the form of other devices may modify data processing system 200, such as by adding a touch interface, and may even omit certain illustrated components from data processing system 200 without departing from the general description of the operation and functionality of data processing system 200 described herein.

[0027]

[0036] In the depicted example, data processing system 200 uses a hub architecture including a northbridge and memory controller hub (NB / MCH) 202 and a southbridge and input / output (I / O) controller hub (SB / ICH) 204. A processing unit 206, a main memory 208, and a graphics processor 210 are coupled to northbridge and memory controller hub (NB / MCH) 202. Processing unit 206 may include one or more processors and may be implemented using one or more heterogeneous processor systems. Processing unit 206 may be a multi-core processor. In a particular implementation, graphics processor 210 may be coupled to northbridge and memory controller hub (NB / MCH) 202 via an accelerated graphics port (AGP).

[0028]

[0037] In the illustrated example, a local area network (LAN) adapter 212 is coupled to southbridge and input / output (I / O) controller hub (SB / ICH) 204. An audio adapter 216, a keyboard and mouse adapter 220, a modem 222, a read-only memory (ROM) 224, a universal serial bus (USB) and other ports 232, and PCI / PCIe devices 234 are coupled to southbridge and input / output (I / O) controller hub (SB / ICH) 204 via bus 218. A hard disk drive (HDD) or solid state drive (SSD) 226a and a CD-ROM 230 are coupled to southbridge and input / output (I / O) controller hub (SB / ICH) 204 via bus 228. PCI / PCIe devices 234 may include, for example, an Ethernet adapter, an add-in card, and a PC card for a notebook computer. PCI uses a card bus controller, while PCIe does not. Read-only memory (ROM) 224 may be, for example, a flash binary input / output system (BIOS). Hard disk drive (HDD) or solid-state drive (SSD) 226a and CD-ROM 230 may use, for example, integrated drive electronics (IDE), serial advanced technology attachment (SATA) interfaces, or variations such as external SATA (eSATA) and micro SATA (mSATA). Super I / O (SIO) device 236 may be coupled to southbridge and input / output (I / O) controller hub (SB / ICH) 204 via bus 218.

[0029]

[0038] Memory such as main memory 208, read-only memory (ROM) 224, or flash memory (not shown) are some examples of computer-usable storage devices. Hard disk drives (HDD) or solid-state drives (SSD) 226a, CD-ROM 230, and other similarly usable devices are some examples of computer-usable storage devices, including computer-usable storage media.

[0030]

[0039] An operating system executes on processing unit 206. The operating system coordinates and provides control of various components within data processing system 200 of FIG. 2. The operating system may be a commercially available operating system for any type of computing platform, including, but not limited to, server systems, personal computers, and mobile devices. An object-oriented or other type of programming system may work in conjunction with the operating system and provide calls to the operating system from programs or applications executing on data processing system 200.

[0031]

[0040] 1 may be located on a storage device, such as in the form of code 226b on a hard disk drive (HDD) or solid-state drive (SSD) 226a, and loaded into at least one of one or more memories, such as main memory 208, for execution by processing unit 206. The processes of the exemplary embodiments may be performed by processing unit 206 using computer-implemented instructions, which may be located in a memory such as main memory 208, read-only memory (ROM) 224, or one or more peripheral devices.

[0032]

[0041] Further, in some cases, code 226b may be downloaded from remote system 214b via network 102a (e.g., network / communications infrastructure 214), and similar code 214c is stored in storage device 214d; in other cases, code 226b may be downloaded to remote system 214b via network 214a, and the downloaded code 214c is stored in storage device 214d.

[0033]

[0042] The communications unit may include one or more devices used to send and receive data, such as a modem or a network adapter. The memory may be, for example, main memory 208 or a cache, such as the cache of northbridge and memory controller hub (NB / MCH) 202. The processing unit may include one or more processors or CPUs.

[0034]

[0043] When a computer or data processing system is described as a virtual machine, virtual device, or virtual component, the virtual machine, virtual device, or virtual component operates like data processing system 200 using virtualized manifestations of some or all of the components depicted in data processing system 200. For example, in a virtual machine, virtual device, or virtual component, processing unit 206 is manifested as a virtualized instance of all or some of the hardware processing unit 206 available in the host data processing system, main memory 208 is manifested as a virtualized instance of all or some portions of main memory 208 that may be available in the host data processing system, and hard disk drive (HDD) or solid state drive (SSD) 226 a is manifested as a virtualized instance of all or some portions of hard disk drive (HDD) or solid state drive (SSD) 226 a that may be available in the host data processing system. The host data processing system in such a case is represented by data processing system 200 .

[0035]

[0044] Figure 3 illustrates the architecture of the X-ray system 118. The X-ray system 118 may operate in a manner similar to that shown in Figure 4. Once a patient or object 406 is positioned so that an area of ​​interest (volume region 408) is within the field of view of an X-ray source 402, the X-ray source 402 operates to emit an X-ray beam 410 that passes through the object and is captured by a detector 404 on the opposite side. The X-ray source 402 and detector may rotate around the patient, for example, through an angle of 180 degrees, to capture multiple 2D images (CBCT image data) that can be used for reconstruction into a 3D model.

[0036]

[0045] 3, the x-ray system 118 may be configured to detect metal (radio-opaque or substantially radio-opaque objects) and remove metal artifacts corresponding to the metal from the reconstruction if metal is present in the object 406 being scanned (such as a portion of a dental cavity). The x-ray system 118 may operate by using the projection engine 302 to project x-rays 410 to scan a volumetric region 408 of the object 406, the projections generating corresponding cone-beam computed tomography (CBCT) image data.

[0037]

[0046] The metal artifact engine 116 of the X-ray system 118 may include a first reconstruction module 304 configured to reconstruct an enlarged CBCT volume 502 from the CBCT image data (see FIG. 5 , the enlarged volume may have, for example, the size of a typical human head. In one embodiment, the size is approximately (e.g., + / −1%, or + / −5%, or + / −10%, or + / −20%, or + / −50%, or + / −1-100%) 20×20×h cm, where h is height), representing the volume region 408 as well as the volume outside the volume region 408. Specifically, a significantly enlarged 3D volume may be reconstructed using a reconstruction method (such as Feldkamp reconstruction) to detect metal inside and outside the volume region 408. In one example, a 20×20×h cm volume may be generated to image the patient's entire head, where h is the height of the enlarged CBCT volume 502. For example, the size of the expanded CBCT volume may be at least 1.5 times, or at least 2.0 times, or 1 time or more larger than the volume region.

[0038]

[0047] The maximum intensity projection module (MIP module 306) is configured to generate a maximum intensity projection 506 on a virtual plane 510 from the enlarged CBCT volume 502 and the projection geometry 504. The maximum intensity projection 506 is obtained by projecting onto the virtual plane 510 voxels of the enlarged CBCT volume 502 that meet a threshold intensity criterion and that are in the way of a ray (virtual ray) traced from the viewpoint 512 of the projection geometry 504. Because multiple voxels may project onto the same detector pixel in the virtual plane, an operation to select a "maximum value" may also be performed. The projection geometry 504 may be the geometry used during reconstruction of the enlarged CBCT volume 502. Furthermore, the virtual plane 510 corresponds to the detector in terms of position, orientation, size, resolution, etc. Generally, the geometry used during reconstruction is the geometry of the physical scan. Using the projection geometry of the physical scan enables subsequent transfer of positional information from the maximum intensity projection to the CBCT image data. In one aspect, the projection geometry 504 can include multiple projection matrices (3x4 matrices) that can project any point in 3D patient coordinate space (such as a homogeneous coordinate space with coordinates (x, y, z, l)) to a corresponding detector position.

[0039]

[0048] Furthermore, the enlarged CBCT volume 502 exhibits limited-angle artifacts in the outer regions, which can make it difficult to detect metal within the volume itself. However, the maximum intensity projection 506 may not exhibit this limited-angle artifact because its projection geometry typically corresponds to the projection geometry used for reconstruction (the projection direction is the same, and therefore the information within the enlarged volume is highly accurate relative to the projection direction). The information in the maximum intensity projection is also not affected by limited-angle artifacts for these projection directions. Furthermore, metal detection within the volume may be made more difficult by cupping artifacts caused by metals, but cupping artifacts can be further reduced or eliminated herein by projecting voxels with maximum intensity along each ray. Thus, in the case of cupping artifacts, bright values ​​representing the item's boundaries are projected onto the virtual plane 510, in contrast to the less bright / weaker signals representing the item's central portion.

[0040]

[0049] The MIP module 306 may further detect attenuated image areas 508 within the maximum intensity projection 506 that correspond to metals. Detection may include using a predetermined threshold to determine areas that correspond to metals. Detection may alternatively involve the use of a trained neural network that is trained on a number of example training attenuated image areas that correspond to metals and tested and validated using a dataset of test and validation attenuated image areas.

[0041]

[0050] The detected attenuated image areas 508 corresponding to the metal can be suppressed in the CBCT image data so as to cause fewer artifacts in subsequent volume reconstruction. This can be achieved by matching or masking (e.g., shifting) the detected attenuated image areas 508 corresponding to the metal to the CBCT image data and reconstructing the volume using the CBCT image data. For matching, if the same projection geometry 504 is used to generate the maximum intensity projection 506 as was used for the physical scan when the CBCT image data was generated, matching the image areas is straightforward because the image areas are identical. For example, if there has been an adaptation, such as a resolution adaptation, a corresponding adaptation, such as upsampling / downsampling / smoothing, may be required when (or after) matching the image areas.

[0042]

[0051] After the attenuation image area 508 corresponding to the metal is mapped to the CBCT image data, the second reconstruction module 308 reconstructs the final CBCT volume using the CBCT image data by suppressing the area of ​​the CBCT image data corresponding to the attenuation image area of ​​the maximum intensity projection corresponding to the metal. More specifically, the second reconstruction module 308 first reconstructs the final volume by modifying the CBCT image data, including the location of the attenuation image area corresponding to the metal, by modifying the area of ​​the CBCT image data corresponding to the attenuation image area to completely remove or reduce the influence or artifacts of the metal in subsequent reconstructions. The modification may include, for example, restoration, in which pixels or areas of the CBCT image data corresponding to the attenuation image area are replaced with artificial data. In one example, interpolation of surrounding pixel / 2D information may be performed. In another example, interpolation of surrounding pixel information in the sinogram may be performed taking into account temporally adjacent projection images. In some cases, the interpolation may be linear, using splines, or using AI. In other cases, for example, in the case of slightly lower absorption, the original pixel values ​​may be modified with an additive offset or multiplied by a predetermined weighting factor. The modification therefore ensures that subsequent reconstructions using the corrected CBCT image data will have no metal or fewer metal artifacts in the reconstructed volume.

[0043]

[0052] Thus, in response to modifying the CBCT image data, the second reconstruction module 308 reconstructs an intermediate volume using the modified CBCT image data. This can be done using a reconstruction algorithm such as the "Feldkamp" algorithm. In this intermediate volume, metal and metal artifacts are absent or suppressed due to the modification of the CBCT image data. Then, image areas or image areas of the maximum intensity projection of the CBCT image data corresponding to the metal before modification are separately mapped to the intermediate volume to modify the intermediate volume. This can be achieved by backprojecting the image areas (e.g., generated as a binary mask) onto the intermediate volume using the projection geometry 504. The intersection of the backprojected image areas can be segmented within the intermediate volume (e.g., by applying a threshold or other segmentation technique) to obtain volume areas within the intermediate volume corresponding to the backprojected image areas. The voxel values ​​inserted into these volume areas can be obtained by interpolating from the expanded CBCT volume 502 (which may have a different voxel size than the intermediate volume). Alternatively, an extra, non-expanded volume can be reconstructed to copy the masked voxel values. Additionally, blending may be performed to smooth the transition of voxel values ​​from the intermediate volume to the reinserted voxel values. Separate reinsertion of metal based on the correspondence of the image area to the intermediate volume ensures that only metal is represented in the intermediate volume, and no metal artifacts are present. Metal artifacts typically exist at some distance from the metal object (as streaks or shadows in the "far field"). These may not be reintroduced when reinserting metal voxels (the "near field"). The modified intermediate volume may then be displayed as the final volume.

[0044]

[0053] 6-9, an exemplary slice 608 through the enlarged CBCT volume 502 and a corresponding maximum intensity projection 506 are shown. FIG. 6 discloses an axial volume slice 608 through the enlarged CBCT volume 502 illustrating a section 610 of the slice corresponding to the volume region 408. The figure also illustrates an inner metal region 602 representing metal within the volume region 408. A first outer metal region 604 and a second outer metal region 606 illustrate metal and / or metal artifacts within the enlarged CBCT volume 502. In FIG. 6, the enlarged CBCT volume 502 is generated using a filtered backprojection, which produces sharp edges or contours of the metal structures outside the section 610, but with less reliable brightness or gray values ​​for the metal areas. In contrast, in FIG. 8, the enlarged CBCT volume 502 from which the slice 608 is obtained is generated using an unfiltered backprojection, which produces relatively fuzzy contours but has more consistent or brighter gray values ​​for the metal areas outside the section 610. FIG. 7 depicts a maximum intensity projection 506 of the enlarged CBCT volume 502 of FIG. 6 created using filtered backprojection geometry, and FIG. 9 depicts a maximum intensity projection 506 of the enlarged CBCT volume 502 of FIG. 8 created using unfiltered backprojection.

[0045]

[0054] Therefore, exemplary embodiments recognize that different types or combinations of maximum intensity projections can be generated and utilized in the methods described herein. For example, in exemplary embodiments, at least two enlarged CBCT volumes 502 can be generated, including a first enlarged CBCT volume and an additional enlarged CBCT volume. At least one of the at least two enlarged CBCT volumes can be generated using filtered backprojection, and at least another of the at least two enlarged CBCT volumes can be generated using unfiltered backprojection. For example, the first enlarged CBCT volume can be generated using filtered backprojection, and the additional enlarged CBCT volume can be generated using unfiltered backprojection. At least two sets of maximum intensity projections corresponding to the at least two enlarged CBCT volumes are then generated, and attenuated image areas 508 corresponding to metal can be detected using characteristics of the at least two enlarged CBCT volumes, such as the brightness and contour of the corresponding areas.

[0046]

[0055] Of course, the examples described herein are not intended to be limiting, as other examples may be obtained in light of the description herein. For example, other examples include:

[0047]

[0056] Example 1: A method comprising: projecting X-rays to scan a volumetric region of an object; generating corresponding cone beam computed tomography (CBCT) image data; reconstructing from the CBCT image data an enlarged CBCT volume representing the volumetric region and a volume outside the volumetric region; generating a maximum intensity projection on a virtual plane from the enlarged CBCT volume and projection geometry; detecting attenuated image areas in the maximum intensity projection corresponding to metal; matching the detected attenuated image areas corresponding to the metal to the CBCT image data; and reconstructing a final CBCT volume using the CBCT image data by suppressing the areas of the CBCT image data that correspond to the attenuated image areas of the maximum intensity projection.

[0048]

[0057] Example 2: The method of example 1, wherein the expanded volume represents the entire object.

[0049]

[0058] Example 3: The method of any previous example, wherein the augmented volume is generated using filtered or unfiltered backprojection.

[0050]

[0059] Example 4: The method of any previous example, wherein the generating comprises, for each maximum intensity projection, projecting voxels of the expanded CBCT volume onto the virtual plane along virtual projection rays that satisfy one or more thresholds.

[0051]

[0060] Example 5: The method of any previous example, wherein the one or more thresholds comprise a maximum intensity threshold.

[0052]

[0061] Example 6: The method of any previous example, wherein reconstructing the final CBCT volume comprises modifying the CBCT image data by changing areas of the CBCT image data corresponding to the attenuation image areas corresponding to the metal so as to remove or reduce the effect of the metal in subsequent reconstructions; reconstructing an intermediate volume using the modified CBCT image data; matching the maximum intensity projection or image areas of the CBCT image data corresponding to the metal to the intermediate volume; reinserting the metal to modify the intermediate volume; and displaying the modified intermediate volume as a final volume.

[0053]

[0062] Example 7: The method of Example 6, further comprising displaying the intermediate volume along with the final volume.

[0054]

[0063] Example 8: The method of Example 6 or 7, wherein modifying the area of ​​the CBCT image data corresponding to the attenuation image area includes, for example, interpolating, extrapolating, or inputting meaningful information based on surrounding image areas surrounding the area.

[0055]

[0064] Example 9: The method of Examples 6 to 8, wherein at least two enlarged CBCT volumes are generated, including the enlarged CBCT volume and an additional enlarged CBCT volume. At least one of the at least two enlarged CBCT volumes is generated using filtered back projection, and at least another of the at least two enlarged CBCT volumes is generated using unfiltered back projection. At least two sets of maximum intensity projections corresponding to the at least two enlarged CBCT volumes are generated, including the maximum intensity projection and the additional maximum intensity projection. The attenuated image area is detected using both the maximum intensity projection and the additional maximum intensity projection.

[0056]

[0065] Example 10: The method of any preceding example, wherein the detection of the attenuated image areas is performed using thresholding or a neural network.

[0057]

[0066] Example 11: An X-ray system comprising a processor and a memory storing instructions that, when executed by the processor, configure the device to perform any of Examples 1 to 10.

[0058]

[0067] Example 12: A non-transitory computer-readable storage medium containing instructions that, when executed by a computer, cause the computer to perform any of Examples 1 to 10.

[0059]

[0068] Thus, computer-implemented methods, systems or apparatus, and computer program products for correcting metal artifacts and other related features, functions, or operations are provided in exemplary embodiments. Where an embodiment or portion thereof is described with respect to a certain type of device, the computer-implemented method, system, or apparatus, computer program product, or portion thereof, is adapted or configured for use with suitable and equivalent manifestations of that type of device.

[0060]

[0069] The present invention may be a system, method, or computer program product at any possible level of technical detail integration. The computer program product may include a computer-readable storage medium having computer-readable program instructions for causing a processor to perform aspects of the present invention.

[0061]

[0070] A computer-readable storage medium can be a tangible device that can hold and store instructions for use by an instruction execution device. The computer-readable storage medium can be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of computer-readable storage media includes: portable computer diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disk (DVD), memory sticks, floppy disks, mechanically encoded devices such as punch cards or ridge structures in grooves with instructions recorded thereon, and any suitable combination of the foregoing. As used herein, computer-readable storage media, including but not limited to computer-readable storage devices, should not be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses passing through fiber optic cables), or electrical signals transmitted through wires.

[0062]

[0071] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device or to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical transmission fiber, wireless transmission, routers, firewalls, switches, gateway computers, or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in the respective computing / processing device.

[0063]

[0072] The computer-readable program instructions for carrying out the operations of the present invention may be either source code or object code written in any combination of one or more programming languages, including assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state-setting data, configuration data for an integrated circuit, or object-oriented programming languages ​​such as Smalltalk, C++, and procedural programming languages ​​such as the "C" programming language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or a connection may be made to an external computer (e.g., through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA) can execute computer readable program instructions by utilizing state information in the computer readable program instructions to personalize the electronic circuitry to perform aspects of the present invention.

[0064]

[0073] Aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0065]

[0074] These computer-readable program instructions may be provided to a general-purpose computer, a special-purpose computer processor, or other programmable data processing apparatus to produce a machine, whereby the instructions, executing via the computer processor or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram blocks. These computer-readable program instructions may also be stored in a computer-readable storage medium that can direct a computer, programmable data processing apparatus, and / or other device to function in a particular manner, whereby the computer-readable storage medium having instructions stored therein comprises an article of manufacture containing instructions that implement aspects of the functions / acts specified in the flowchart and / or block diagram blocks.

[0066]

[0075] The computer-readable program instructions may also be loaded into a computer, other programmable data processing apparatus, or other device to cause the computer, other programmable apparatus, or other device to perform a series of operational steps to create a computer-implemented process, such that the instructions, which execute on the computer, other programmable apparatus, or other device, perform the functions / operations specified in the flowchart or block diagram blocks.

[0067]

[0076] The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowcharts or block diagrams may represent a module, segment, or portion of instructions, comprising one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may be executed in the reverse order, depending on the functionality involved. It should also be noted that each block of the block diagrams and / or flowchart diagrams, and combinations of blocks in the block diagrams and / or flowchart diagrams, may be implemented by a dedicated hardware-based system that performs the specified functions or operations or executes a combination of dedicated hardware and computer instructions.

Claims

1. projecting x-rays to scan a volumetric region of an object, wherein said projecting generates corresponding cone beam computed tomography (CBCT) image data; reconstructing from the CBCT image data an enlarged CBCT volume representing the volumetric region and a volume outside the volumetric region; generating a maximum intensity projection onto a virtual plane from the expanded CBCT volume and projection geometry; detecting attenuated image areas within the maximum intensity projection corresponding to metal; Corresponding the detected attenuation image area corresponding to the metal to an area of ​​the CBCT image data; and reconstructing a final CBCT volume using the CBCT image data by suppression of the area of ​​the CBCT image data corresponding to the detected attenuation image area of ​​the maximum intensity projection.

2. The method of claim 1 , wherein the expanded CBCT volume represents the entire object.

3. The method of claim 1 , wherein the expanded CBCT volume is generated using filtered or unfiltered backprojection.

4. Generating the maximum intensity projections includes, for each of the maximum intensity projections:

4. The method of claim 1, comprising projecting voxels of the expanded CBCT volume onto the virtual plane along virtual projection rays that satisfy one or more thresholds.

5. The method of claim 4 , wherein the one or more thresholds comprise a maximum intensity threshold.

6. Reconstructing the final CBCT volume comprises: (a) modifying the CBCT image data by changing the areas of the CBCT image data corresponding to the detected attenuation image areas to remove or reduce the influence of the metal in subsequent reconstructions; (b) reconstructing an intermediate volume using the modified CBCT image data; and (c) matching the attenuation image area of ​​the maximum intensity projection or the area of ​​the CBCT image data corresponding to the metal to the intermediate volume; (d) transferring information about the metal based on (c) to modify the intermediate volume; and The method of claim 1 , further comprising: (e) displaying the modified intermediate volume as a final volume.

7. The method of claim 6 further comprising displaying the intermediate volume along with the final volume.

8. 8. The method of claim 6 or 7, wherein modifying the area of ​​the CBCT image data comprises interpolating based on surrounding image areas surrounding the area.

9. At least two enlarged CBCT volumes are generated, including the enlarged CBCT volume and an additional enlarged CBCT volume, wherein at least one of the at least two enlarged CBCT volumes is generated using filtered backprojection and at least another of the at least two enlarged CBCT volumes is generated using unfiltered backprojection; generating at least two sets of maximum intensity projections corresponding to the at least two expanded CBCT volumes, the sets including the maximum intensity projections and additional maximum intensity projections; The method according to claim 6 , wherein the attenuated image area is detected using both the maximum intensity projection and the additional maximum intensity projection.

10. The method of claim 1 , wherein the detection of the attenuated image areas is performed using thresholding or neural networks.

11. The method of claim 1 , further comprising configuring the size of the expanded CBCT volume to the size of a human head.

12. a processor; and a memory storing instructions, the instructions, when executed by the processor, causing the apparatus to: projecting x-rays to scan a volumetric region of the object and generating corresponding cone beam computed tomography (CBCT) image data; reconstructing from the CBCT image data an enlarged CBCT volume representing the volumetric region and a volume outside the volumetric region; generating a maximum intensity projection onto a virtual plane from the augmented CBCT volume and projection geometry; detecting attenuated image areas within said maximum intensity projection corresponding to metal; Corresponding the detected attenuation image area corresponding to the metal to an area of ​​the CBCT image data; an x-ray system configured to reconstruct a final CBCT volume using the CBCT image data by suppression of the areas of the CBCT image data corresponding to the detected attenuation image areas of the maximum intensity projection.

13. 13. The x-ray system of claim 12, wherein the processor causes the device to generate the expanded volume using filtered or unfiltered backprojection.

14. 13. The x-ray system of claim 12, wherein the processor causes the device to generate each of the maximum intensity projections by using a virtual projection ray to project a voxel of the expanded CBCT volume having a maximum intensity along the virtual projection ray onto the virtual plane.

15. The processor may cause the device to: (a) modifying the CBCT image data by changing the areas of the CBCT image data corresponding to the detected attenuation image areas to remove or reduce the influence of the metal in subsequent reconstructions; (b) reconstructing an intermediate volume using the modified CBCT image data; and (c) matching the attenuation image area of ​​the maximum intensity projection or the area of ​​the CBCT image data corresponding to the metal to the intermediate volume; (d) transferring information about the metal based on (c) to modify the intermediate volume; and 15. The x-ray system of claim 12, wherein the final CBCT volume is reconstructed by: (e) displaying the modified intermediate volume as a final volume.

16. The processor may cause the device to:

16. The x-ray system of claim 15, wherein the intermediate volume is displayed together with the final volume.

17. The processor may cause the device to: generating at least two enlarged CBCT volumes including the enlarged CBCT volume and an additional CBCT volume, wherein at least one of the at least two enlarged CBCT volumes is generated using filtered backprojection and at least another of the at least two enlarged CBCT volumes is generated using unfiltered backprojection; generating at least two sets of maximum intensity projections corresponding to the at least two enlarged CBCT volumes, the sets including the maximum intensity projections and additional maximum intensity projections; 16. The x-ray system of claim 15, wherein both the maximum intensity projection and the additional maximum intensity projection are used to detect the attenuated image area.

18. The x-ray system of claim 12 , wherein the expanded CBCT volume is the size of a human head.

19. A non-transitory computer-readable storage medium containing instructions that, when executed by a computer, cause the computer to: projecting x-rays to scan a volumetric region of the object and generating corresponding cone beam computed tomography (CBCT) image data; reconstructing from the CBCT image data an enlarged CBCT volume representing the volumetric region and a volume outside the volumetric region; generating a maximum intensity projection onto a virtual plane from the expanded CBCT volume and projection geometry; detecting attenuated image areas within said maximum intensity projection corresponding to metal; Corresponding the detected attenuation image area corresponding to the metal to an area of ​​the CBCT image data; A non-transitory computer-readable storage medium for reconstructing a final CBCT volume using the CBCT image data by suppression of the areas of the CBCT image data that correspond to the detected attenuation image areas of the maximum intensity projection.

20. The computer further comprises: (a) modifying the CBCT image data by changing the area of ​​the CBCT image data corresponding to the detected attenuation image area so as to remove or reduce the effect of the metal in subsequent reconstruction; (b) reconstructing an intermediate volume using the modified CBCT image data; and (c) associating the attenuation image area of ​​the maximum intensity projection or the image area of ​​the CBCT image data corresponding to the metal with the intermediate volume; (d) transferring information about the metal based on (c) to modify the intermediate volume; and 20. The non-transitory computer-readable storage medium of claim 19, wherein the final CBCT volume is reconstructed by: (e) displaying the modified intermediate volume as a final volume.

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