Method of overlay rendering on spinal hardware implant on image generated by CBCT scanner system

Abstract

A method and system for identifying an implant in an x-ray image of an anatomical structure displayed on a display screen. The method includes: displaying an image including artifacts of the implant; prompting a user to input parameters of the implant; displaying the rendering of the implant on the image; prompting the user to position the rendering on the artifact at an accurate position corresponding to the actual position of the implant; alerting the user when the rendering is in an inaccurate location; prompting the user to reposition the rendering from an inaccurate position to an accurate position; alerting the user when the rendering is manipulated by the user to the accurate position; and after the rendering has been manipulated by the user to the accurate position, reconstructing the x-ray image to replace the artifact with the rendering attached in the accurate position.

Description

Technical Field

[0001] The present disclosure relates to methods and systems for overlay rendering on spinal hardware implants in x-ray images. Background Art

[0002] This section provides background information related to the present disclosure, which is not necessarily prior art.

[0003] A subject (such as a human patient) may elect or be required to undergo a surgical procedure to correct or enhance the subject's anatomy. Enhancement of the anatomy may include various procedures such as movement or augmentation of bone, insertion of an implantable device, or other suitable procedures. A surgeon may perform a procedure on the subject using images of the patient, which may be acquired using an imaging system such as a magnetic resonance imaging (MRI) system, a computed tomography (CT) system, a fluoroscopy (e.g., C-arm imaging system), or other suitable imaging system.

[0004] Images of the patient can assist the surgeon in performing the procedure, including planning the procedure and performing the procedure. The surgeon may select a two-dimensional or three-dimensional image representation of the patient. By allowing the surgeon to view the patient's anatomy during the procedure without removing overlying tissue (including skin and muscle tissue), the images can assist the surgeon in performing the procedure using less invasive techniques. Summary of the Invention

[0005] This section provides a general overview of the present disclosure and is not a complete disclosure of the full scope of the present disclosure or all of its features.

[0006] The present teachings provide a method for identifying an implant in an x-ray image of an anatomy to be displayed on a display screen. The method includes: receiving, in a processing system, the x-ray image of the anatomy based on a computed tomography (CT) projection of the anatomy; displaying, on the display screen, the x-ray image of the anatomy, the x-ray image including an artifact of the implant; prompting a user to input parameters of the implant into the processing system via a user interface; displaying, on the display screen, a rendering of the implant together with the x-ray image, the size and shape of the rendering being set to correspond to the implant; prompting the user to position the rendering of the implant on the artifact at an accurate position corresponding to an actual position of the implant in the anatomy; warning the user when the rendering is manipulated by the user to an inaccurate position beyond a predetermined distance from the accurate position; prompting the user to reposition the rendering from the inaccurate position to the accurate position; warning the user when the rendering is manipulated by the user to the accurate position or within the predetermined distance of the accurate position; and after the rendering has been manipulated by the user to the accurate position, reconstructing the x-ray image to replace the artifact with the rendering at the accurate position.

[0007] The present teachings also provide an image processing system for identifying implants in x-ray images of anatomical structures displayed on a display screen. The system includes a computer processor having a memory storage device and an image processing software module, an implant database accessible by the processor, a display, and an input device. The processor is configured to: prompt a user to input parameters of the implant into the processor via the input device; display a rendering of the implant on the display along with the image, the size and shape of the rendering being set to correspond to the implant; prompt the user to position the rendering of the implant on the artifact at an accurate position corresponding to the actual position of the implant in the anatomical structure; warn the user when the rendering is manipulated by the user to an inaccurate position beyond a predetermined distance from the accurate position; prompt the user to reposition the rendering from the inaccurate position to the accurate position; warn the user when the rendering is manipulated by the user to the accurate position or within the predetermined distance of the accurate position; and, after the rendering has been manipulated by the user to the accurate position, reconstruct the image to replace the artifact with the rendering attached at the accurate position.

[0008] Based on the description provided herein, additional fields of applicability will become apparent. The description and specific examples in this summary are intended for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations and are not intended to limit the scope of the present disclosure.

[0010] Figure 1 is an environmental view of an exemplary imaging system;

[0011] Figure 2 is with Figure 1 the exemplary computer system used with the imaging system;

[0012] Figure 3 is an environmental view of an exemplary pedicle screw;

[0013] Figure 4 is an environmental view of an exemplary spinal fixation implant including a pedicle screw;

[0014] Figure 5A is a first scanned image slice showing an artifact caused by the implant;

[0015] Figure 5B is showing by Figure 5A the second scanned image slice of the artifact caused by the implant;

[0016] Figure 5Cis a second scan image slice showing artifacts caused by the Figure 5A implant;

[0017] Figure 5D is a second scan image slice showing artifacts caused by the Figure 5A implant;

[0018] Figure 5E is a second scan image slice showing artifacts caused by the Figure 5A implant;

[0019] Figure 5F is a second scan image slice showing artifacts caused by the Figure 5A implant;

[0020] Figure 6 is a scan image slice showing correction of artifacts caused by an implant according to the present teachings;

[0021] Figure 7 is a flowchart of an exemplary method according to the present teachings;

[0022] Figure 8 is a flowchart of an additional exemplary method according to the present teachings;

[0023] Figure 9 is a scan image slice showing artifacts caused by scanning an implant and an implant rendering that can be moved by a user in the image; and

[0024] Figure 10 is a scan image slice showing replacement of the Figure 10 artifact with an implant rendering.

[0025] In several views of all the figures, corresponding reference numerals indicate corresponding parts. DETAILED DESCRIPTION

[0026] The following description is merely exemplary in nature. It should be understood that in all the figures, corresponding reference numerals represent the same or corresponding components and features. As indicated above, the present teachings relate to imaging systems, such as the O-arm imaging system commercially available from Medtronic Navigation, Inc., Louisville, CO, USA. However, it should be noted that the present teachings may be applicable to any suitable imaging device, such as a C-arm imaging device. Further, as used herein, the term "module" may refer to a computer-readable medium accessible by a computer device, an application specific integrated circuit (ASIC) that executes one or more software or firmware programs, an electronic circuit, a processor (shared, dedicated, or grouped) and memory, combinational logic circuitry, and / or other suitable software, firmware programs, or components that provide the described functionality.

[0027] This teaching includes the disclosure of U.S. Patent No. 8,891,847, which was authorized and assigned to Medtronic Navigation, Inc. of Louisville, Kentucky, USA on November 18, 2014, and is incorporated herein by reference. This teaching relates to a method of correcting artifacts caused by hardware, such as screws or other implants, in a portion of the anatomical structure of an object imaged by a scanning method using an x-ray source. Such implants tend to obscure the underlying anatomical structure of the reconstructed three-dimensional (3D) image and make critical assessments of conditions, such as defects or other pathologies, or the delivered treatment, including assessment of the implant's positioning, difficult.

[0028] Artifacts from implants cause problems, for example, in x-ray computed tomography (CT), including cone beam CT (CBCT), and in other imaging methods using an x-ray source. Artifacts from implants are generated because the attenuation coefficients of the materials used for implants, such as, for example, metals, metal alloys, ceramics, etc., are higher than the attenuation coefficients of bone and soft tissue within the x-ray intensity range used in such CT imaging. The flat panel detector used to capture the image can also cause scatter, which results in artifacts at the implant location. Various methods for metal artifact reduction rely on computationally complex algorithms to remove the artifacts, use interpolation methods to fill in the gaps, and re-project the image during 3D image reconstruction. Such methods are generally difficult to implement in an operative / diagnostic imaging environment.

[0029] This teaching provides a method for identifying implants associated with artifacts in one or more CT slices (axial plane segments of the 3D image) after 3D image reconstruction using an optimal fit and / or reliability method. After selecting the optimal fit implant from the database, an image of the selected implant is overlaid on the corresponding artifact. This correction is performed after processing the CT images for 3D reconstruction. As a post-processing operation, the correction is performed on the reconstructed CT slices. In other words, the processing of the images is separated from the intraoperative or real-time diagnostic scanning protocol, although the processing of the images can be performed on the same computer / processor used in the imaging system 10 immediately after the scan, or at a later time on a different computer / processor.

[0030] Briefly, Figure 1 Various components of an exemplary CBCT imaging system 10 including an x-ray source 36 and a flat panel detector 33 are illustrated. Figure 2 A computer system for image processing is illustrated, which can be part of the imaging system 10 or can be a separate system capable of communicating with the computer or processing module of the imaging system. Figure 3 and Figure 4Illustrated is an exemplary metal implant associated with the spine. Although a spinal implant such as a pedicle screw will be used to describe the method, the present teachings apply to and cover any implant that can produce x-ray artifacts, including, for example, implants for the hip, knee, shoulder, ankle, knee, and other joints. The present teachings may also include other therapeutic implantable devices, such as cardiac pacing devices, defibrillation devices, and resynchronization devices, or other implantable devices that deliver therapies (including therapies via electrical signals or pulses). Figures 5A to 5F Illustrated are exemplary CT slices that show artifacts associated with pedicle screws. Figure 6 Illustrated is a CT slice of an image of an identified implant overlaid on an artifact image. Figure 7 Is an exemplary flowchart of a method according to the present teachings.

[0031] Referring Figure 1 , user 12 (such as a medical professional, clinician, or other assistant) may perform a procedure on a subject (such as human patient 14). In performing the procedure, user 12 may use imaging system 10 to acquire image data of patient 14 for use in performing the procedure. The acquired image data of patient 14 may include two-dimensional (2D) projections acquired using an x-ray imaging system (including those disclosed herein). However, it should be understood that 2D forward projections of a volume model may also be generated, as also disclosed herein.

[0032] In one example, the acquired image data may be used to generate a model. The model may be a three-dimensional (3D) volume model generated based on the acquired image data using various techniques (including algebraic iterative techniques), and the model may generate image data (referred to as the displayed image data 18) that can be displayed on a display. The displayed image data 18 may be displayed on display device 20 and additionally may be displayed on a display device 32a associated with imaging computing system 32. The displayed image data 18 may be a 2D image, a 3D image, or a four-dimensional image that varies over time. The displayed image data 18 may also include the acquired image data, the generated image data, both, or a combination of these two types of image data.

[0033] It should be understood that the acquired image data of patient 14 may be acquired as 2D projections, for example, using an x-ray imaging system. The 2D projections may then be used to reconstruct 3D volume image data of patient 14. Additionally, theoretical or forward 2D projections may be generated from the 3D volume image data. Thus, it should be understood that the image data may be either or both 2D projections or 3D volume models.

[0034] Display device 20 may be part of computing system 22, which may be associated with Figure 2is the same as the image processing computing system 100 shown. The computing system 22 may include various computer-readable media. A computer-readable medium can be any available medium that can be accessed by the computing system 22, and can include volatile and non-volatile media as well as removable and non-removable media. Computer-readable media can include, for example, computer storage media and communication media. Storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disk (DVD) or other optical disk storage, magnetic tape cartridges, magnetic tape, magnetic disk storage devices or other magnetic storage devices, or any other medium that can be used to store computer-readable instructions, software, data structures, program modules and other data and can be accessed by the computing system 22. A computer-readable medium can be accessed directly or through a network such as the Internet.

[0035] In one example, the computing system 22 may include an input device 24 (such as a keyboard) and one or more processors 26 that can be combined with the computing system 22 (the one or more processors may include a multi-processing core processor, a microprocessor, etc.). The input device 24 may include any suitable device that enables a user to interface with the computing system 22, such as a touchpad, a stylus, a touch screen, a keyboard, a mouse, a joystick, a trackball, a wireless mouse, audible controls, or a combination thereof. In addition, although the computing system 22 is described and illustrated herein as including an input device 24 separate from the display device 20, the computing system 22 may include a touchpad or a tablet computing device, and furthermore, the computing system 22 may be integrated within or may be a part of an imaging computing system 32 associated with the imaging system 10 or the image processing computing system 100 shown in Figure 2 The imaging computing system 32. A wired or wireless connection 28 may be provided between the processor 22 and the display device 20 for data communication to allow driving the display device 20 to illustrate the image 18.

[0036] The imaging system 10 including an O-arm imaging system or other suitable imaging system used during a selected procedure is also described in U.S. Patent Application No. 12 / 465,206 (U.S. Publication No. 2010-0290690) entitled "System And Method For Automatic Registration Between An Image And A Subject" filed on May 13, 2009, which is incorporated herein by reference. Additional descriptions of the O-arm imaging system or other suitable imaging systems can be found in U.S. Pat. Nos. 7,188,998, 7,188,998, 7,106,825, 7,001,045, and 6,940,941, each of which is incorporated herein by reference.

[0037] Reference Figure 1 , the imaging system 10 can include a mobile cart 30 that includes an imaging computing system 32 and an imaging gantry 34 having a source 36, a collimator 37, a flat panel detector 33 (or other type of detector), and a rotor 35. Reference Figure 1 , the mobile cart 30 can be moved from one operating room to another operating room, and the gantry 34 can be moved relative to the cart 30, as further discussed herein. This allows the imaging system 10 to be movable such that the imaging system can be used at multiple locations and in multiple procedures without the capital expenditure or space dedicated to a fixed imaging system.

[0038] Continuing to refer Figure 1 , the gantry 34 can define the isocenter of the imaging system 10. In this regard, a centerline C1 passing through the gantry 34 can define the isocenter or center of the imaging system 10. Generally, the patient 14 can be positioned along the centerline C1 of the gantry 34 such that the longitudinal axis of the patient 14 can be aligned with the isocenter of the imaging system 10.

[0039] Reference Figure 2, provides a diagram illustrating an exemplary embodiment of an image processing computing system 100, which may include an imaging computing system 32 or a computing system 22, or may be a separate computing system. The imaging computing system 100 may include various computer-readable media. The computer-readable media can be any available media accessible by the imaging computing system 100 and includes volatile and non-volatile media as well as removable and non-removable media. By way of example and not limitation, the computer-readable media may include computer storage media and communication media. Storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disks (DVDs) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store computer-readable instructions, software, data structures, program modules and other data and can be accessed by the imaging computing system 32. The computer-readable media can be accessed directly or through a network such as the Internet.

[0040] In one example, the image processing computing system 100 includes a display device 102 and a system unit 104. As shown, the display device 104 may include a computer video screen or monitor. The image processing computing system 100 may also include at least one input device 106. As shown in the exploded view, the system unit 104 may include a processor 108 and a memory 110, and the memory may include software having an image processing module (software) 112, an implant database 114, and other data 116, as Figure 2 shown.

[0041] In this example, the at least one input device 106 includes a keyboard. However, it should be understood that the at least one input device 106 may include any suitable device that enables a user to interface with the image processing computing system 100, such as a touchpad, a stylus, a touch screen, a keyboard, a mouse, a joystick, a trackball, a wireless mouse, audible controls, or a combination thereof. Additionally, although the image processing computing system 100 is described and illustrated herein as including a system unit 104 having a display device 102, the image processing computing system 100 may include a touchpad or a tablet computing device or use a display device 20.

[0042] Briefly, with reference to Figure 1, the source 36 can emit x-rays through the patient 14 to be detected by the flat panel detector 33. The x-rays can be emitted by the source 36 in a cone beam and can be further shaped by an optional collimator 37 for detection by the flat panel detector 33. An exemplary collimator 37 is commercially available as a Compact Square Field Collimator, sold by Collimare Engineering of Wheat Ridge, CO, USA, and includes the O-arm imaging system sold by Medtronic Navigation of Louisville, KY, USA. Briefly, the collimator 37 can include one or more blades that can be controlled to shape the x-rays emitted by the source 36. As will be discussed, the collimator 37 can be used to shape the x-rays emitted by the source 36 into a beam corresponding to the shape of the flat panel detector 33. The source 36, the collimator 37, and the flat panel detector 33 can each be coupled to the rotor 35.

[0043] Generally, the flat panel detector 33 can be coupled to the rotor 35 so as to be diametrically opposed to the source 36 and the collimator 37 within the gantry 34. The flat panel detector 33 can be rotationally moved in a 360° motion generally about the patient 14 in the direction of arrow E, and the source 36 and the collimator 37 can move in unison with the flat panel detector 33 such that the source 36 and the collimator 37 remain generally 180° away from and opposite the flat panel detector 33.

[0044] The gantry 34 can be rocked or oscillated (also referred to herein as isocentric rocking) equidistantly generally in the direction of arrow A relative to the patient 14, who can be placed on a patient support or table 15. The gantry 34 can also be tilted relative to the patient 14, as shown by arrow B, can be longitudinally moved relative to the patient 14 and the mobile cart 30 along line C, can be moved vertically generally along line D relative to the mobile cart 30 and transverse to the patient 14, and can be moved vertically generally in the direction of arrow F relative to the patient 14 to permit positioning of the source 36, the collimator 37, and the flat panel detector 33 relative to the patient 14.

[0045] The imaging system 10 can be precisely controlled by the image processing computing system 32 to move the source 36, the collimator 37, and the flat panel detector 33 relative to the patient 14, thereby generating precise image data of the patient 14. Additionally, the imaging system 10 can be connected to the processor 26 via the connection 31, which can include a wired or wireless connection or physical media transfer from the imaging system 10 to the processor 26. Thus, the image data collected using the imaging system 10 can also be transferred from the image processing computing system 32 (or 100) to the computing system 22 (or 100) for navigation, display, reconstruction, post-processing, etc.

[0046] Briefly, continuing to refer to Figure 1 , according to various embodiments, the imaging system 10 can be used with non-navigational or navigational procedures. In a navigational procedure, a locator (including either or both of the optical locator 60 and the electromagnetic locator 62) can be used to generate a field or receive or transmit signals within a navigational domain relative to the patient 14. If desired, components associated with performing the navigational procedure can be integrated within the imaging system 10. The navigational space or domain relative to the patient 14 can be registered to the image data 18 to permit registration of the navigational space defined within the navigational domain and the image space defined by the image data 18. A patient tracker or dynamic reference frame 64 can be connected to the patient 14 to permit dynamic registration and maintenance of the registration of the patient 14 with the image 18.

[0047] The instrument 66 can then be tracked relative to the patient 14 to permit the navigational procedure. The instrument 66 can include tracking devices, such as an optical tracking device 68 and / or an electromagnetic tracking device 70, to permit tracking of the instrument 66 using either or both of the optical locator 60 or the electromagnetic locator 62. The instrument 66 can include a communication line 72 having a navigation interface device 74 that can communicate with the electromagnetic locator 62 and / or the optical locator 60. Using the communication lines 72, 78 respectively, the navigation interface device 74 can then communicate with the processor 26 via the communication line 80. It should be understood that any one of the connection or communication lines 28, 31, 76, 78 or 80 can be wired, wireless, physical medium transmission or mobile, or any other suitable communication. However, a suitable communication system can be equipped with corresponding locators to permit tracking of the instrument 66 relative to the patient 14, thereby permitting tracking of the position of the illustrated instrument 66 relative to the image 18 to perform the procedure.

[0048] It should be understood that the instrument 66 can be an interventional instrument and / or an implant. The implant can include ventricular or vascular stents, spinal implants, nerve stents, etc. The instrument 66 can be an interventional instrument, such as a deep brain or nerve stimulator, an ablation device or other suitable instrument. Tracking the instrument 66 permits viewing of the position of the instrument 66 relative to the patient 14 using the registered image 18 without directly viewing the instrument 66 within the patient 14. For example, the instrument 66 can be graphically depicted as an icon superimposed on the image data 18.

[0049] In addition, the imaging system 10 may include tracking devices, such as an optical tracking device 82 and / or an electromagnetic tracking device 84, to perform tracking using a corresponding optical locator 60 or electromagnetic locator 62. The tracking devices 82, 84 may be directly associated with the source 36, flat panel detector 33, rotor 35, gantry 34, or other suitable parts of the imaging system 10 to determine the positioning or location of the source 36, flat panel detector 33, rotor 35, and / or gantry 34 relative to a selected reference frame. As shown, the tracking devices 82, 84 may be positioned on the exterior of the housing of the gantry 34. Thus, the imaging system 10 may be tracked relative to the patient 14, and the instrument 66 may also be tracked to allow for initial registration, automatic registration, or continued registration of the patient 14 relative to the image data 18. Registration and navigation procedures are discussed in U.S. Patent Application No. 12 / 465,206, filed May 13, 2009, which is incorporated herein by reference.

[0050] In one example, the image data 18 may include a single 2D image. In another example, an image control / processing module (such as the image processing module 112( Figure 2 )) may perform an automatic reconstruction of an initial three-dimensional model of the region of interest of the patient 14. The reconstruction of the three-dimensional model may be performed in any suitable manner, such as using algebraic techniques for optimization. Suitable algebraic techniques include expectation maximization (EM), ordered subset EM (OS-EM), simultaneous algebraic reconstruction technique (SART), and total variation minimization. Their application for performing 3D volume reconstruction based on 2D projections allows for efficient and complete volume reconstruction.

[0051] Generally, the algebraic techniques may include an iterative process to perform the reconstruction of the patient 14 for display as the image data 18. For example, pure or theoretical image data projections, such as those generated based on or from an atlas or stylized model of a "theoretical" patient, may be repeatedly altered until the theoretical projection image matches the acquired 2D projection image data of the patient 14. Then, the stylized model may be appropriately altered to a 3D volume reconstruction model of the acquired 2D projection image data of the selected patient 14 and may be used for surgical treatment, such as navigation, diagnosis, or planning. In this regard, the stylized model may provide additional details about the anatomy of the patient 14, which may enable the user to more effectively plan a surgical intervention. The theoretical model may be associated with the theoretical image data to construct the theoretical model. In this way, the model or image data 18 may be constructed based on the image data of the patient 14 acquired using the imaging system 10. The image processing module 112 may output the image data 18 to the display device 32a or 102.

[0052] Refer to Figure 3 and Figure 4, an exemplary implant 200 that can cause imaging artifacts in a CT scan is illustrated in a top view of the lumbar vertebra 90 (e.g., the L2 vertebra). The vertebra 90 includes a vertebral body 91, a spinous process 94, transverse processes 96, pedicles 92 located between the vertebral body 91 and the transverse processes 96, and superior articular processes 98. The vertebra has a cortical bone contour 93 surrounding the internal trabecular (cancellous) bone. The cortical bone contour 93 appears brighter than the spongy trabecular bone on an x-ray image due to its greater density. The implant 200 is a pedicle screw ( Figure 3 Two pedicle screws 200 are shown in Figure 4 ). The pedicle screw 200 includes a head 206 and a threaded shaft 202 having a longitudinal axis A. The pedicle screw 200 is inserted through the pedicle such that the axes of these pedicle screws point toward the apex of the vertebral body 91. The head of the screw 206 is captured by a receiver or seat 204, which is also used to couple to Figure 4 the elongated rod 250 of the spinal fixation system shown in

[0053] Referring to Figures 5A to 5F , images of six 833.00 μm thick CT slices at six corresponding positions -84.97 mm,.85.40 mm, -86.63 mm, -87.47 mm, -88.30 mm, and -89.13 mm relative to a marked or reference image (not shown) are illustrated. These images are of a postmortem spine with two implanted pedicle screws, such as those discussed in conjunction with Figure 3 and Figure 4 . In the following description, reference numerals from Figure 3 are used to describe Figures 5A to 5F the corresponding elements of the vertebrae and pedicle screws in the CT images of Figure 3 . In each CT slice, the left and right sides of the patient are identified by the letter L and the letter R. To avoid confusion, the left side L and the right side R will be referred to as the radiological left and radiological right (opposite to the left and right sides of the drawing). The artifact 300 around the pedicle screw 200, i.e., the area of increased brightness and "frosting" effect, varies according to the position of the CT slice. In some CT slices, the image of the cortical contour 93' of the vertebral body (shown as 93 in Figure 5B , Figure 5C , Figure 5D and Figure 5EThe CT slices have worse artifacts 300, in the sense that the frosting effect becomes wider and blurs the image of the cortical contour 93', making it difficult to determine whether the pedicle screw 200 is correctly positioned. In Figure 5A , although there are still many artifacts 300, the contour or edge of the pedicle screw 200 is visible. In Figure 5B , the frosting effect is wider, blurring the cortical contour 93' and determining the orientation and position of the left pedicle screw 200 (the radiological left is marked as L; appears on the Figure 5B right side). In Figure 5C and Figure 5D , the frosting effect becomes worse and then gradually improves from Figures 5E to 5F . For example, evaluating Figure 5A and Figure 5F , we can determine that the (radiological) right pedicle screw has deviated significantly medially from the right pedicle 92. Similarly, the (radiological) left pedicle screw 200 appears to be misoriented and very close to the spinal canal.

[0054] The present teachings provide a method that can identify a specific implant that causes artifacts 300 and overlay a CAD, graphic, or other scaled image 200' in the contour on the artifacts 300, thereby indicating the actual position and orientation of the implant, such as as shown in Figure 6 . In Figure 6 , the contour of the pedicle screw is overlaid on the radiological left frosting artifact 300, thereby reliably indicating the actual position of the implanted left pedicle screw 200' and the shape, size, and / or type of the implanted pedicle screw 200 on the CT slice displayed on the display (such as the Figure 2 display 102). The implementation of the method for positioning the overlay is outlined in the flowchart of Figure 7 .

[0055] As described with reference to Figure 1 , the x-ray source 36 can direct a cone beam of x-rays towards the flat panel detector 36. The subject 14 is positioned such that the region of interest is within the cone beam. By rotating the x-ray source and detector around the subject 14, multiple 2D projections of the region of interest are acquired at Figure 7 box 500. These projections can be processed by CBCT reconstruction software to obtain a 3D image of the corresponding anatomy of the subject 14. As described above, the reconstruction software can be incorporated in the image computing system 32 or computing system 22 or image processing system 100, which can be separate and can be a communication system, an overlapping system, or can be integrated in one system.

[0056] Automatically or by user input (e.g., byFigure 2 input device 106), start identifying voxels having higher intensities than the expected intensity thresholds of bone and tissue relative to the patient's anatomy in one or more selected CT slices of the 3D image. At block 502, a post-processing software module configured to execute image processing commands is incorporated into the image processing module 112 and is capable of identifying and localizing clusters of voxels that are brighter or have higher contrast than the average brightness of the surrounding voxels in the CT slices for a particular intensity range of the x-ray source 36. Isolated voxels above a given threshold intensity can be discarded, and adjacent voxels above a given threshold intensity can be grouped together for further analysis and identification. To determine whether a cluster of voxels is an artifact of an implant (i.e., an implant candidate), such as a metal or ceramic screw or other implant, at block 504, various factors or characteristics of the cluster can be compared to the corresponding characteristics of artifacts from potential implants. Comparable characteristics include image intensity, mass attenuation, density, and material composition. These characteristics can be stored in the implant database 114( Figure 2) In this case, the implant database can include a table of such characteristics for common implants for a particular anatomical structure (such as spinal implants, hip and knee implants, or orthopedic and non-orthopedic implants). For example, when a portion of a patient's lumbar spine is imaged, the characteristics of various fixation implants (such as pedicle screws, fixation rods, and other implants) can be included in the database. For example, in the case of a pedicle screw, the database can include composition, size, shape, and orientation relative to the vertebral body in an exemplary spinal fixation or other spinal correction procedure for comparison, as well as the expected artifact shape, size, brightness, attenuation, density, etc. Based on this comparison, voxels potentially related to implant artifacts are selected on the CT slice at block 506, and these voxels are grouped into implant candidates (or artifact candidates for the implant) at block 508. At block 510, implant candidates (i.e., the selected voxel clusters) can be selected using best-fit analysis and optionally statistical and reliability assessments of the available data for various characteristics (such as those discussed above). At block 510, the implant candidates are compared with the images and artifacts of potential implants from the implant database 114, and at block 512, the best-fit implant is selected from the implant database 114. The best-fit selection of the implant candidates and the corresponding implants can be based on least squares, iterative, weighted, or other optimization or probability algorithms. The best-fit algorithm can employ a weighted metric that includes image intensity, mass density, material composition, and / or other characteristics with corresponding weight factors. The weight factors can be optional or selected based on information available in the database of previous results or other knowledge and experience. The weight factors can be equal, unequal, and include zero and non-zero combinations. For example, in some embodiments, image intensity and mass composition can each be equally weighted at 50%, while mass density is weighted at 0%. In other embodiments, all factors can be equally weighted. In addition to the inherent characteristics of the selected implant (such as shape, size, type, material composition, etc.), the selection of the best-fit implant also includes determining the orientation and position of the implant relative to the artifacts and / or anatomical landmarks on the CT slice. The stylized, CAD, graphical, or other image of the selected implant 200' can be overlaid and registered with the orientation and position determined on the CT slice at block 514, as also shown in Figure 6 as shown. At block 516, the image of the selected implant can be presented with a selectable color and a selectable transparency.

[0057] Referring to Figure 2, the image processing module 112 uses the reconstructed 3D image as input and provides one or more CT slices to perform the method in an automated manner, the one or more CT slices showing an image of the detected and identified implant overlaid on the CT slice. Optionally, interactive input from the user at the input device 106 can be enabled at the start of the method. For example, such input can be provided at blocks 502 to 516 to take advantage of the sometimes excellent image recognition capabilities of the human eye, or to verify the selections made by the image processing module 112. Additionally, input regarding the position of the CT slice in the 3D image can be provided as user input.

[0058] Figure 8 Generally illustrated is an additional method for identifying implants in an x-ray image of an anatomical structure for display on a display screen according to the present disclosure. The method generally begins at block 610, where an x-ray image of the anatomical structure is received by Figure 2 the image processing computing system 100. The x-ray image is a 3D image reconstructed from a 2D projection taken using the imaging system 10. At block 614, the x-ray image is displayed, such as on the display 102 of the image processing computing system 100. The x-ray image includes one or more implants in the imaged anatomical structure, such as spinal screws (the spinal screws may include tulip-shaped heads). Any other suitable implants can also be imaged. At least for the reasons described above, the implants are blurred by artifacts 300 in the image, and thus the exact position of the implants cannot be clearly seen in the x-ray image. Figure 9 An exemplary x-ray image showing an artifact 300 of a spinal screw with a blurred implant is illustrated.

[0059] At block 616, the system 100 prompts the user to input parameters of the implant via any suitable user interface, such as the input device 106. Any suitable parameters can be input, such as but not limited to the following parameters: implant system, implant group, implant type, implant diameter, and implant length. At block 618, the system 100 selects a rendering of the implant that matches the implant parameters input by the user from the implant database 114. For example, if the implant parameters match implant 200, the system 100 displays rendering 200' on the display 102. The rendering 200' is displayed over the x-ray image on the anatomical structure (see Figure 9 ). The size and shape of the rendering 200' are set to correspond to the input parameters of the implant. Using the input device 106 or any suitable input device, the user can move the rendering 200' with respect to the x-ray image, for example, as Figure 9 shown. At block 620, the system 100 prompts the user to position the rendering over the artifact 300 at an accurate position corresponding to the actual position where the user believes the actual implant 200 is or should be.

[0060] At block 622, system 100 compares the position of rendering 200’ with the actual position of implant 200. If the rendering 200’ is at an inaccurate position outside a predetermined distance from the accurate position, system 100 generates a notification to the user. And at block 624, system 100 prompts the user to reposition the rendering 200’ to the accurate position. The predetermined distance from the accurate position can be any suitable distance. For example, with respect to spinal screws, the predetermined distance can be + / -2 mm for the tip of the rendered screw from the actual position of the tip of the implant, and the predetermined distance can be + / -10° for the head of the rendered screw from the actual position of the head of the implant. Using the rendered position at block 620, a pre-check algorithm checks whether an actual implant is present on the x-ray image of the anatomical structure in a specific region at the rendered position. This is done by comparing the volumetric ROI with the image of the selected implant in the implant database. System 100 will continue to prompt the user to reposition the rendering at block 624 until the user positions the rendering 200’ within the predetermined distance from the accurate position of the implant. Once the user positions the rendering 200’ at the accurate position corresponding to the actual position of implant 200, system 100 generates an alert notifying the user that the rendering 200’ is correctly positioned.

[0061] After the rendering 200’ has been accurately positioned by the user on the x-ray image, at block 628, system 100 reconstructs the x-ray image to replace the artifact 300 with the rendering 200’ attached at the accurate position. Figure 10 An exemplary x-ray image is illustrated where two of the artifacts 300 have each been replaced with an attached rendering 200’ positioned by the user. System 100 can be configured to allow the user to position each rendering 200’ one at a time. After the user successfully positions one of the renderings 200’ at the accurate position, system 100 will begin to reconstruct the x-ray image to replace the corresponding artifact with the attached rendering 200’. While system 100 is reconstructing the image, the user and system 100 can at least repeat the steps from block 616 to block 626 to position another rendering 200’ for an additional implant 200, and then perform an additional reconstruction of the x-ray image for the additional implant 200 at block 628.

[0062] Additional advantages of the present disclosure include the following: (1) The user can select which implants in the x-ray image require artifact correction for clinical purposes, as opposed to automatic positioning which automatically applies artifact correction to all implants presented on the x-ray volume; (2) Ambiguity in implant selection is avoided; (3) The pre-check mechanism (block 622) ensures that implants with artifact reduction are placed within the specified tolerance.

[0063] The present teachings provide a computer-implemented method for identifying and displaying implants from artifacts in CT slices of 3D images of a patient's anatomy. The 3D images can be reconstructed from 2D projections of a CT or CBCT imaging system (such as imaging system 10) in a processor (such as Figure 1 the computing system 32 or 22 shown in Figure 2 or the computing system 100 shown in Figure 2 the processor 108 of) associated with the imaging system. Although 3D image reconstruction can be performed during an imaging session (intraoperatively), the identification of implants that cause artifacts is a post-processing procedure performed using axial segments or CT slices. The processor 108 compares the intensity and contrast characteristics of the voxels in the 3D image with various CT slice positions and selects clusters of voxels having characteristics associated with known implant artifacts. The characteristics of each identified cluster of voxels are compared with the similar characteristics of the artifacts of known implants in an implant database (such as Figure 2 the implant database 114 shown in). Least squares or other optimization and reliability algorithms can be used to select the best-fit implant for the selected artifacts that are candidates for implants. The image of the identified implant can be registered and overlaid at the scale of the CT slice on the image of the CT slice on the display 102 of the image processing computing system 100. The image of the implant can be a wire or solid CAD drawing of the implant or other digital rendering and includes colorization of the outline of the image or filled colorization of the image of the implant, with selected transparency, contrast, and chromaticity to enhance the identification and recognition of the implant in the CT slice.

[0064] In summary, the present teachings provide a method for detecting and identifying implants in CT slices of a reconstructed 3D image of a patient's anatomy. The method analyzes and identifies voxels associated with image artifacts and compares the selected clusters of voxels with artifact characteristics associated with implants in an implant database. The best-fit implant is determined and the image of the best-fit implant is registered and overlaid on the CT slice and viewed on the display of the image processing computing system. This information enables the user to better evaluate and assess the status of recent or old treatments or procedures and to plan corrective or new procedures taking into account the position and orientation of the implant and its characteristics.

[0065] Although specific examples have been described in the specification and illustrated in the drawings, those of ordinary skill in the art should understand that various changes can be made without departing from the scope of the teachings and that elements thereof can be replaced by equivalents. In addition, the mixing and matching of features, elements, and / or functions between various examples are expressly contemplated herein, such that those of ordinary skill in the art will recognize from the teachings that, unless otherwise described above, the features, elements, and / or functions of one example can be appropriately incorporated into another example. Moreover, many modifications may be made to adapt a particular situation or material to the teachings without departing from the basic scope thereof. Accordingly, it is intended that the teachings not be limited to the specific examples shown in the drawings and described in the specification, but that the scope of the teachings will include any implementation falling within the foregoing description.

Claims

1. A method for identifying an implant in an x-ray image of an anatomical structure for display on a display screen, the method comprises: receiving, in a processing system, the x-ray image of the anatomical structure based on computed tomography (CT) projections of the anatomical structure; displaying, on the display screen, the x-ray image of the anatomical structure, the x-ray image including an artifact of the implant; prompting a user to input parameters of the implant into the processing system via a user interface; displaying, on the display screen, a rendering of the implant together with the x-ray image, the size and shape of the rendering being set to correspond to the implant; prompting the user to position the rendering of the implant on the artifact at an accurate position corresponding to the actual position of the implant in the anatomical structure; warning the user when the rendering is manipulated by the user to an inaccurate position beyond a predetermined distance from the accurate position; prompting the user to reposition the rendering from the inaccurate position to the accurate position; warning the user when the rendering is manipulated by the user to the accurate position or within the predetermined distance of the accurate position; and after the rendering has been manipulated by the user to the accurate position, reconstructing the x-ray image to replace the artifact with the rendering in the accurate position.

2. The method according to claim 1, wherein the implant is a spinal screw.

3. The method according to claim 1, wherein the implant is a spinal screw, the spinal screw including a tulip-shaped head.

4. The method according to claim 1, wherein the parameters of the implant include at least one of an implant system, an implant group, an implant type, an implant diameter, and an implant length.

5. The method according to claim 1, wherein the predetermined distance is + / -2 mm for the tip of the rendered screw from the tip of the implant, and + / -10° for the head of the rendered screw from the head of the implant.

6. The method according to claim 1, the method further comprising prompting the user to input parameters of an additional implant, and prompting the user to position an additional rendering of the additional implant during reconstruction of the x-ray image.

7. The method according to claim 1, the method further comprising prompting the user to switch between the reconstructed x-ray image and the original x-ray image including the artifact.

8. The method according to claim 1, wherein the implant is a spinal screw configured to mount a spinal rod; and wherein the method is performed after the spinal screw has been implanted and before the spinal rod has been mounted to the spinal screw.

9. The method according to claim 1, wherein the rendering of the implant is three-dimensional.

10. An image processing system for identifying an implant in an x-ray image of an anatomical structure displayed on a display screen, the system comprises: A computer processor including a memory storage device and an image processing software module, an implant database accessible by the processor, a display, and an input device, wherein the processor is configured to: Prompt a user to input parameters of the implant into the processor via the input device; Select a rendering of the implant from a database stored in the memory storage device; Display the rendering of the implant together with the image on the display, the size and shape of the rendering being set to correspond to the implant; Prompt the user to position the rendering of the implant on the artifact at an accurate position corresponding to the actual position of the implant in the anatomical structure; Warn the user when the rendering is manipulated by the user to an inaccurate position beyond a predetermined distance from the accurate position; Prompt the user to reposition the rendering from the inaccurate position to the accurate position; Warn the user when the rendering is manipulated by the user to the accurate position or within the predetermined distance of the accurate position; And After the rendering has been manipulated by the user to the accurate position, reconstruct the image to replace the artifact with the rendering attached at the accurate position.

11. The system according to claim 10, wherein the implant is a spinal screw.

12. The system according to claim 10, wherein the implant is a spinal screw, and the spinal screw includes a tulip-shaped head.

13. The system according to claim 10, wherein the parameters of the implant include at least one of an implant system, an implant group, an implant type, an implant diameter, and an implant length.

14. The system according to claim 10, wherein the predetermined distance is + / -2 mm for the tip of the rendered screw from the tip of the implant, and + / -10° for the head of the rendered screw from the head of the implant.

15. The system according to claim 10, the system further comprising prompting the user to input parameters of an additional implant, and prompting the user to position an additional rendering of the additional implant during the reconstruction of the image.

16. The system according to claim 10, the system further comprising prompting the user to switch between the reconstructed image and the original image including the artifact.

17. The system according to claim 10, wherein the rendering is three-dimensional.

Images