System and method for calibrating camera feature detection system of an x-ray system
By employing a camera-based feature detection system and laser projection indication in the DXA/DEXA imaging system, combined with image processing algorithms, the component requirements caused by optical marking were resolved, achieving efficient and accurate camera calibration and simplifying system deployment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GE PRECISION HEALTHCARE LLC
- Filing Date
- 2023-04-26
- Publication Date
- 2026-06-12
Smart Images
Figure CN116999077B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of medical diagnostic imaging. More specifically, this disclosure relates to systems and methods for medical imaging related to body composition analysis and / or bone mineral density measurement. Background Technology
[0002] In medical x-ray imaging (e.g., body composition and / or bone mineral density measurement systems), the x-ray source and x-ray detector are typically mounted at opposite ends of a generally C-shaped gantry. Scanning radiographic techniques (such as those commonly used with densitography) use narrow collimated radiation beams formed, for example, fan-shaped beams. The emitted fan-shaped radiation beam (typically x-rays) is incident on and can be detected by the x-ray detector, although other configurations of x-ray imaging systems are known. A small array is typically used for the x-ray detector, and the x-ray source and x-ray detector move relative to the patient. In this implementation, this allows for scanning or data collection from a wide area of the patient, including the entire patient, compared to other conventional radiographic techniques. The source and detector are positioned such that when an object (e.g., a part of the human body) is between them and irradiated with x-rays, the detector produces data representing the characteristics of the object between them.
[0003] In specific applications of density measurement, when using X-rays of two (or more) energies, information about bone and tissue can be obtained due to the differences in absorption of X-rays of different energies. Measuring the X-ray absorption of an object at two different X-ray energies can reveal information about the object's composition, if broken down into two selected basic substances. In the medical field, the selected basic substances are often bone and soft tissue. The ability to distinguish bone from surrounding soft tissue allows X-ray images to provide quantitative information about bone density in the body for the diagnosis of osteoporosis and other bone diseases.
[0004] like Figure 1The depicted exemplary X-ray system, such as a dual-energy X-ray absorptiometry (DXA or DEXA) / density measurement system 1010, can be configured to include a generally C-shaped or semi-circular gantry or C-arm 1012. The C-arm 1012 movably supports a source 1014 and a detector 1018 mounted opposite each other at opposite ends. A patient 1022 is placed between the source 1014 and the detector 1018, such as on an examination table 1020. In many systems 1010, the positions of the source 1014 and the detector 1018 are variable to accommodate different patient morphologies, different orientations of the source 1014 and the detector 1018 for imaging different parts of the patient, etc. Movement of the source 1014 and the detector 1018 is typically controlled by a motor (not shown) located within the system 1010 to control and maintain alignment of the source 1014 and the detector 1018 during operation and / or changes in the orientation of the system 1010.
[0005] To assist and / or improve one or more of the following: proper positioning of the patient on examination table 1020, automatic positioning of source 1014 and detector 1018 relative to the patient, and / or determination of the current field of view (FOV) of the position of source 1014 relative to the patient 1022, system 10 may employ a camera 1024 disposed outside system 1010 (such as disposed on the ceiling of the space where system 1010 is located). Camera 1024 provides optical images of system 1010 and the patient to provide information to system 1010 and / or the operator of system 1010, thereby streamlining the operation of system 1010 and reducing errors.
[0006] In order for camera 1024 to provide information about the relative positions of source 1014 / detector 1018 and patient, camera 1024 must be calibrated with reference to system 1010 so that the position of objects in the image obtained by camera 1024 can be referenced relative to the same objects in the image obtained by system 1010.
[0007] To perform calibration, system 1010 may employ calibration optical markers 1026 (such as those disclosed in U.S. Patent No. 10,835,199 ('199 Patent) entitled "Optical Geometry Calibration Devices, Systems, and Related Methods for Three-Dimensional X-Ray Imaging," the entire contents of which are incorporated herein by reference for all purposes). Calibration optical markers 1026 are positioned on a portion of system 1010, i.e., on inspection table 1020, and have a configuration such as a checkerboard pattern with known features (e.g., square position and size), capable of being imaged by camera 1024, and whose position relative to image region 1018 or inspection table 1020 is known.
[0008] During calibration, an image of the optical mark 1026 is acquired via camera 1024. Using the known distance between detector 1018 or inspection table 1020 and the mark 1026, and subsequently all the intersections of squares on 1026 (based on the known position (i.e., height) of detector 1018 relative to inspection table 1020 caused by movement of a motor (not shown) controlled by system 1010 and the position of detector 1018 along inspection table 1020), and the calculated distance from camera 1024 to the optical mark 1026 determined from the camera image (e.g., disclosed in '199 patent), the camera image can be registered with the detector image so that the coordinates in the camera image are directly correlated with the coordinates in the detector image. Using this registration, in any subsequent imaging process using system 1010, the image obtained by camera 1024 can be used to determine the patient's position relative to source 1014 / detector 1018 and the FOV of source 1014, so as to provide the operator with any necessary adjustments to the patient's position on examination table 1020 to allow system 1010 to provide the patient with the desired X-ray image.
[0009] However, although the use of optical marker 1026 as described above enables the calibration of camera 1024 relative to system 1010, the requirement for optical marker 1026 is undesirable because it creates the need to manufacture additional components and deliver them to the deployment location of system 10 for use during the calibration process.
[0010] Therefore, there is a need to develop a camera calibration system and method for DXA / DEXA imaging systems that avoids the need for separate optical markings. Summary of the Invention
[0011] According to one aspect of an exemplary embodiment of this disclosure, an x-ray system includes: a support surface and a frame operatively connected to the support surface and including an x-ray source, an x-ray detector alignable to the x-ray source, and a laser disposed on the frame adjacent to the x-ray detector, the frame defining a system reference; an image processing system operatively connected to the frame to control the operation of the laser, the x-ray source, and the x-ray detector in generating x-ray image data, the image processing system including: a processing unit for processing the x-ray image data from the detector; a database operatively connected to the processing unit and storing instructions for operating a calibration system; and a display operatively connected to the image processing unit. The image processing system includes a system for presenting information to a user; a user interface operatively connected to the image processing system to allow user input to reach the image processing system; and a camera-based feature detection system including a camera spaced apart from and operatively connected to the image processing system, the camera defining a camera reference, the support surface and the frame being positioned within the camera reference and operable to generate one or more camera images of the support surface and the frame, wherein the calibration system is operable to register the camera reference to the system reference; wherein the calibration system is configured to determine multiple locations indicated within the camera image reference, to determine multiple locations of the indication within the system reference, and to register the camera reference to the system reference.
[0012] According to another aspect of an exemplary embodiment of this disclosure, a method for a camera-based feature detection system for calibrating an x-ray system includes the following steps: providing an x-ray system comprising: a support surface and a frame, the frame being operatively connected to the support surface and including an x-ray source, an x-ray detector alignable to the x-ray source, and a laser disposed on the frame adjacent to the x-ray detector, the frame defining a system reference; an image processing system operatively connected to the frame to control the operation of the laser, the x-ray source, and the x-ray detector in generating x-ray image data, the image processing system including: a processing unit for processing the x-ray image data from the detector; a database operatively connected to the processing unit and storing instructions for operating the calibration system; and a display that can... The system comprises: an image processing system operatively connected to an image processing system for presenting information to a user; a user interface operatively connected to the image processing system to allow user input to reach the image processing system; a camera-based feature detection system including a camera spaced apart from and operatively connected to the image processing system, the camera defining a camera reference, the support surface and the frame positioned within the camera reference and operable to generate one or more camera images of the support surface and the frame, wherein the calibration system is operable to register the camera reference to the system reference; operating a laser to position an indication on a support surface; acquiring multiple camera images of the indication on the support surface; determining multiple positions of the indication within a camera image reference; determining multiple positions of the indication within a system reference; and registering the camera reference to the system reference.
[0013] These and other exemplary aspects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. Attached Figure Description
[0014] The accompanying drawings illustrate the currently conceived best mode for practicing the present invention.
[0015] In the attached diagram:
[0016] Figure 1 This is a schematic diagram of a DXA system that includes an external camera in the prior art.
[0017] Figure 2 Is with Figure 1 A schematic diagram of an optical mark used in the DXA system.
[0018] Figure 3 This is a schematic block diagram of an exemplary imaging system including a camera feature detection system and a calibration system according to an exemplary embodiment of the present disclosure.
[0019] Figure 4This is a schematic diagram of an exemplary DXA system including a camera feature detection system and a calibration system according to an exemplary embodiment of the present disclosure.
[0020] Figure 5 It is based on an exemplary embodiment of this disclosure and Figure 4 A schematic diagram of a positioning laser used in conjunction with a DXA system.
[0021] Figure 6 This is based on an exemplary embodiment of the present disclosure. Figure 4 A top-view plan view of the positioning laser as observed from an external camera during the calibration process of the camera feature detection system and calibration system.
[0022] Figure 7 This is an observation from an external camera during the calibration process of a camera feature detection system and a calibration system, according to an exemplary embodiment of this disclosure. Figure 4 A schematic diagram of the movement of the positioning laser and detector in the DXA system.
[0023] Figure 8 This is according to another exemplary embodiment of the present disclosure. Figure 4 A top-view plan view of the positioning laser as observed from an external camera during the calibration process of the camera feature detection system and calibration system.
[0024] Figure 9 yes Figure 4 A schematic diagram illustrating the operation of the camera feature detection system and calibration system.
[0025] Figure 10 This is a schematic diagram of the operation method of the calibration system, which registers the coordinates of points in the camera reference with the coordinates of points in the system reference. Detailed Implementation
[0026] One or more specific implementations will be described below. To provide a concise description of these implementations, not all characteristics of the actual implementation may be described in the specification. It should be understood that, as in any engineering or design project, numerous implementation-specific decisions must be made in the development of any such implementation to achieve the developer's specific objectives, such as complying with system-related and business-related constraints that may differ between implementations. Furthermore, it should be understood that such development efforts may be complex and time-consuming, but remain routine tasks of design, fabrication, and manufacturing for those skilled in the art who benefit from this disclosure.
[0027] When describing elements of various embodiments of the invention, the articles “a,” “an,” “the,” and “the” are intended to indicate the presence of one or more such elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and indicate that additional elements may exist in addition to those listed. Furthermore, any numerical examples in the following discussion are intended to be non-limiting, and therefore any additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments.
[0028] This document describes various implementations of medical imaging systems. Specifically, methods and systems are provided for use as, for example, single-energy X-ray absorptiometry (SXA) systems for measuring breast density, or dual-energy X-ray absorptiometry (DXA) systems for measuring bone mineral density. While DXA is used as an example, it should be recognized that other modalities such as radiography and / or medical imaging may be employed in other implementations. These may include, for example, PET, SPECT, C-arm angiography, mammography, ultrasound, etc. The discussion of DXA in this document is provided as an example of a suitable application scenario.
[0029] Reference Figure 3 and Figure 4 Exemplary embodiments of System 10 (such as those disclosed in U.S. Patent Application Publication No. US2019 / 0000407 entitled “Variable Distance Imaging,” the entire contents of which are incorporated herein by reference for all purposes) can be used to measure at least bone area, bone length, bone mineral content (BMC), bone mineral density (BMD), or tissue thickness or density. BMD is calculated by dividing BMC by the area of bone. During operation, an object, such as a human patient, is scanned using an X-ray beam with broadband energy levels to image the patient's bones. The acquired bone images are used to diagnose medical conditions such as osteoporosis. These images may be generated in part from determined bone density information acquired during dual-energy X-ray scanning. As further detailed herein, the positions of source 14, detector 18, and / or the examination stage can be adjusted to achieve further desired imaging purposes, including but not limited to magnification, increased image resolution, or spatial resolution. For illustrative purposes, the imaging system 10 may be described as a dual-energy X-ray absorption measurement (DXA) system, but it should be recognized that various other systems may also be implemented in a similar manner.
[0030] The imaging system 10 is shown as including a frame 12. The frame may be a generally C-shaped or semi-circular frame or a C-arm frame. The frame 12 movably supports a source 14 and a detector 18 mounted opposite each other at opposite ends. Furthermore, a subject 22 is disposed between the source 14 and the detector 18.
[0031] The gantry 12 includes an X-ray source 14 that projects a beam of X-rays 16 toward a detector array 18. The gantry 12 exemplarily includes a lower end 13 positioned below a subject 22 (such as a patient) and an upper end 15 positioned above the subject 22. X-rays pass through the subject 22 to generate attenuated X-rays. Figure 3 As depicted, the X-ray source 14 can be secured to the upper end 15, and the X-ray detector 18 can be secured to the lower end 13. For example... Figure 4 As depicted, detector 18 can be secured to upper end 15, and x-ray source 14 can be secured to lower end 13. Each detector element 20 is exemplary, but not limited to, a cadmium telluride (CdTe) detector element that generates an electrical signal representing the intensity of attenuated x-rays.
[0032] During scanning for image data acquisition, the gantry 12 and / or components mounted on it are movable relative to the patient 22 and / or the examination table 46. The examination table 46 may include a scanning surface on which the patient 22 may be positioned. For example, during image data acquisition, the gantry 12 is movable to change the position and / or orientation of the source 14 and / or detector 18 relative to the patient. In one exemplary embodiment, the gantry 12 may move the source 14 and detector 18 along the major axis 48 and minor axis 49 of the examination table 20 in a lateral scan path, a progressively overlapping scan path, or a zigzag (e.g., raster) scan path 24. Figure 3 and Figure 4 As shown. It should be understood that other forms of image data acquisition may utilize other forms of scanning paths, which may include, but are not limited to, rotation or tilting of gantry 12. It should be understood that in other exemplary imaging systems within this disclosure, one of the sources or detectors may be held in a fixed position, while the other of the sources or detectors may be movable relative to the patient. In other exemplary embodiments as disclosed herein, the examination table configured to support the patient may be further movable to achieve the desired image acquisition.
[0033] The movement of the gantry 12 and the operation of the x-ray source 14 are controlled by the imaging controller 26 of the imaging system 10. The imaging controller 26 includes an x-ray controller 28 that provides power and timing signals to the x-ray source 14. The x-ray controller 28 may also provide operating and / or control signals to the adjustable collimator 25 to shape the x-ray beam from the source 14 according to the imaging process to be performed. In some embodiments, the x-ray beam may be shaped (collimated) into a fan-shaped beam. In one exemplary embodiment, the fan-shaped beam 16 may be a narrow fan-shaped beam to limit the divergence between x-rays in the beam, which has proven beneficial for improving parallax and image overlap blur.
[0034] The imaging controller 26 also includes a gantry motor controller 30, which controls the movement, speed, and position of the gantry 12 via one or more suitable motors (shown) operably connected to the gantry 12 or a designated portion thereof and to the gantry motor controller 30. In some embodiments, the gantry motor controller 30 may utilize one or more motors to control the movement of the gantry 12 in multiple degrees of freedom, including the tilt angle of the gantry 12. The system 10 may also include a table motor controller 44, operably connected to the table 46 via a table motor (not shown) and connected to the imaging controller 26. Under control signals from the table motor controller 44, the table motor is operable to translate, rotate, and / or tilt the table 46 in multiple degrees of motion. In one embodiment, the table motor is operable to move the table 46 in three degrees of freedom (e.g., horizontal translation, vertical translation, and depth translation), while in another embodiment, rotational degrees of freedom of movement (e.g., pitch, yaw, and roll) may be available. It should be recognized that the inspection table motor may include one or more mechanical or electromechanical systems to perform these movements of the inspection table 46, including but not limited to track and intention-driven, screw-driven or chain-driven actuators.
[0035] The X-ray source 14 and X-ray detector 18 (e.g., gantry 12) can be moved according to a grating pattern 24 to track a series of lateral scans 27 of the subject 22, during which dual-energy X-ray data is collected by the X-ray detector 18. The lateral scanning process generates a single image or a quantitative dataset, forming multiple scan images acquired from the patient's whole body, wherein the X-ray source 14 and detector 18 are longitudinally aligned with the patient's upper-lower axis or laterally aligned from the patient's left to right. Using lateral movement to scan the patient helps to minimize the time between the acquisition of adjacent scan images because the lateral direction of the patient's whole body is shorter than the longitudinal direction. Therefore, lateral scanning can reduce the severity of patient motion artifacts between scan images, thus allowing for more accurate image merging.
[0036] The transverse scanning motion is generated through coordination between: gantry motor controller 30 controlling the motion of gantry 12, x-ray source 14, and x-ray detector 18, and stage motor controller 44 optionally controlling stage 46 via stage motors. During operation, x-ray source 14 generates a fan-shaped beam 16 having a plane exemplarily parallel to longitudinal axis 48. Optionally, fan-shaped beam 16 may have a plane perpendicular to longitudinal axis 48. The grating pattern 24 is adjusted such that there is some overlap (e.g., 10% overlap) between successive scan lines of fan-shaped beam 16. Furthermore, the range of motion of gantry 12 and source 14 / detector 18 defines system reference 31, which includes a space that can be observed / imaged by system 10.
[0037] The data acquisition system (DAS) 32 in the imaging controller 26 samples and digitizes data from the detector element 20, converting the data into sampled and digitized data for subsequent processing. In some embodiments, the DAS 32 may be positioned adjacent to the detector array 18 on rack 12. A preprocessor 33 receives the sampled and digitized data from the DAS 32 to preprocess the sampled and digitized data. In one embodiment, preprocessing includes, but is not limited to, bias correction, original velocity correction, reference channel correction, air calibration, and / or application of negative logarithmic operations. As used herein, the term processor is not limited to those integrated circuits referred to as processors in the art, but broadly refers to controllers, microcontrollers, microcomputers, programmable logic controllers, application-specific integrated circuits, and any other programmable circuits, and these terms are used interchangeably herein. The preprocessor 33 preprocesses the sampled and digitized data to generate preprocessed data.
[0038] Image processor 34 receives preprocessed data from preprocessor 33 and performs image analysis, including image analysis involving optical density measurement and / or absorbance measurement through one or more image processing operations. Acquired bone and tissue information (e.g., image and density information) can be processed and displayed in real time to image processor 34 and / or processing unit 36. Processing unit 36 is exemplarily operated to store reconstructed images in mass storage device 38, wherein, as a non-limiting example, mass storage device 38 may include hard disk drives, floppy disk drives, optical disc read / write (CD-R / W) drives, digital versatile optical disc (DVD) drives, flash memory drives, and / or solid-state storage devices. As used herein, the term "computer" is not limited to those integrated circuits referred to in the art as computers, but broadly refers to processors, microcontrollers, microcomputers, programmable logic controllers, application-specific integrated circuits, and any other programmable circuits, and these terms are used interchangeably herein. It should be recognized that any one or more processors and / or controllers as described herein may be performed by or in conjunction with processing unit 36, for example by executing computer-readable code stored on a computer-readable medium accessible and executable by processing unit 36. For example, computer / processing unit 36 may include a processor configured to execute machine-readable instructions stored in mass storage device 38, which may be non-transitory memory. Processor unit / computer 36 may be single-core or multi-core, and programs executed thereon may be configured for parallel or distributed processing. In some embodiments, processing unit 36 may optionally include individual components distributed across two or more devices that may be remotely located and / or configured for coordinated processing. In some embodiments, one or more aspects of processing unit 36 may be virtualized and executed by a remotely accessible networked computing device configured in a cloud computing configuration. According to other embodiments, processing unit / computer 36 may include other electronic components capable of performing processing functions, such as digital signal processors, field-programmable gate arrays (FPGAs), or graphics boards. According to other embodiments, processing unit / computer 36 may include multiple electronic components capable of performing processing functions. For example, the processing unit / computer 36 may include two or more electronic components selected from a list of electronic components, including: a central processing unit, a digital signal processor, a field-programmable gate array, and a graphics board. In yet another embodiment, the processing unit / computer 36 may be configured as a graphics processing unit (GPU) including a parallel computing architecture and parallel processing capabilities.
[0039] The processing unit 36 also receives commands and scan parameters from a user (such as an operator) via a console 40, which includes a user interface device such as a keyboard, mouse, voice-activated controller, touchscreen, or any other suitable input device. An associated display 42 allows the user (such as an operator) to view images and densitometric data from the processing unit 36. Commands and scan parameters are used by the processing unit 36 to provide control signals and information to the imaging controller 26 (including the DAS 32, X-ray controller 28, and gantry motor controller 30). Furthermore, the processing unit 36 can operate the table motor controller 44 (exemplarily the imaging controller 26), which controls a movable patient support (exemplarily the motorized table 46) to position the patient 22 within the gantry 12. Specifically, the table motor controller 44 adjusts the table 46 to move multiple parts of the patient 22.
[0040] During operation, system 10 is configured to operate in either dual-energy X-ray mode or single-energy X-ray mode. In single-energy mode, the X-ray source 14 emits X-rays with a narrow band energy of a few keV and within a diagnostic imaging range of approximately 20 keV to 150 keV. In dual-energy mode, the X-ray source 14 emits radiation with two or more energy bands emitted simultaneously or in rapid succession. The X-ray source 14 can also be configured to emit a single broadband energy exceeding a few keV within the diagnostic imaging range. System 10 can be switched between dual-energy and single-energy modes by increasing or decreasing the voltage and / or current of the X-ray source 14. System 10 can also be switched between dual-energy and single-energy modes using a K-side filter and an energy discrimination detector. It should be noted that the X-ray source 14 can emit X-rays of different energies or energy ranges.
[0041] X-ray source 14 can be configured to output a fan-shaped beam 16 of X-rays. X-ray source 14 can also be configured to output a pencil beam (not shown), a cone beam, or other configurations of X-rays. In some embodiments, processing unit 36 controls system 10 to operate in single-energy or dual-energy mode to determine at least some bone or tissue information of the scanned body. Generally, the image resolution in system 10 can be based on detector element size, source focal spot size, and object-to-detector distance. The acquired images can then be used to measure, for example, bone density or other bone and tissue properties or contents. As described above, dual-energy X-ray scanning can be a linear scan of the entire patient's body, which can be performed in a transverse scanning sequence as described above. During dual-energy X-ray scanning, images of the entire patient's body can be acquired, including image information related to bones and tissues in the body. Whole-body or circumferential scans of the entire body can be performed as a single scan operation, which can be a low-dose mode scan. In some embodiments, instead of whole-body or circumferential scans, individual rectangular regions of the body can be scanned, which can be single-scan scans. Once a scan of the patient or a portion thereof is complete, the dual-energy signal provided by detector 18 is decomposed into images of two basic materials, such as bone and soft tissue. The high-energy and low-energy signals can be combined to provide a single-energy mode with an excellent signal-to-noise ratio for imaging purposes.
[0042] System 10 also includes a camera 80 disposed on a surface 82 of the space in which system 10 is located. Figures 3 to 5 In an exemplary embodiment, camera 80 is disposed in a canopy 84 above system 10 such that system 10 and imaging volume 31 are entirely positioned within an area observable by camera 80, which defines camera reference 83. Camera 80 is operatively connected to computer / processing unit 36 to form part of a camera-based feature detection system 85 for system 10, operable to detect and provide information regarding the proper positioning of patient 22 on examination table 20, automatic positioning of source 14 and detector 18 relative to the region of interest of patient 22, and / or determination of the current field of view (FOV) of source 14 relative to patient 12. Camera 80 may operate in response to signals transmitted from computer / processing unit 36 to camera 80, wherein image-forming data acquired by camera 80 can be transmitted to computer / processing unit 36. Camera 80 may be any suitable type of camera for acquiring images of system 10 and patient 22 located on system 10, such as an RBG depth infrared camera capable of acquiring images in the visible and infrared spectra and providing depth information, etc.
[0043] Images from camera 80 are transmitted to a camera-based feature detection system 81 within computer / processing unit 36. This system can be used to provide one or more pieces of information regarding the proper positioning of patient 22 on examination table 20, the automatic positioning of source 14 and detector 18 relative to patient 22, and / or the determination of the current field of view (FOV) of source 14 relative to patient 22. This information is calculated using known relationships or registrations between a reference frame or system reference 33 of system 10 defined by components of system 10 (e.g., rack 12, source 14, and detector 18) and a reference frame or camera reference 83 of camera 80 defined by the position of camera 80. Using this known relationship, the computer / processing unit 36 can associate the information / data provided by the images from the camera 80 (e.g., the position of the patient 22 and / or the body part of interest (e.g., the knee) on the examination table 20) with the known positions of the source 14 and detector 18 of the system 10, so as to adjust the position of the source 14 / detector 18 and / or the patient 22 / examination table 20 before and / or during any imaging procedure performed on the patient 22 using the system 10.
[0044] To provide a known relationship between the system reference and the camera reference, the positions of system 10 and its components within camera reference 83 must be registered or calibrated. For example... Figure 5 As best shown, the upper end 15 of the rack 12 includes a light source 85, such as a target laser 86 positioned adjacent to the detector 18. In operation, the laser 86 projects a beam 88 onto the examination table 20 or onto a portion of the patient 22 on the examination table 20 to provide an indication 90 of the point on the path of the X-rays from the source 14 that will pass through the examination table 20 on the way to the detector 18.
[0045] When operating laser 86, such as Figure 6 As best illustrated, due to the configuration of system 10 and the positioning of components under the control of computer / processing unit 36, the position of the indicator 90 generated by laser 86 relative to components of system 10 (e.g., source 14, detector 18, and inspection table 20) within system reference 33 is known. Furthermore, the position of indicator 90 within camera image reference 83 can also be determined using an image of indicator 90 projected onto inspection table 20 obtained by camera 80. Figure 7As shown, by moving the frame 12 along the long axis of the inspection table 20 and moving the detector 18 within the frame 12 to move the indicator to different points along the short axis of the inspection table 20 as different points along the long axis, the camera 80 can acquire multiple images of the indicator 90 along the path of the frame 12, thereby providing multiple reference points for the indicator 90 within the camera image reference 83 corresponding to the known position of the indicator 90 within the system reference 33. Depending on the position of the camera 80, there may be an area 92 on the inspection table 20 that is obscured by the frame 12, so that the indicator 90 is not observed by the camera 80. However, the number of points on either side of the area 92 that can be obtained for the position of the indicator 90 is sufficient to calculate the necessary correspondence between the position of the indicator 90 in the system reference 33 and the position of the indicator in the camera image reference 83, thereby registering the camera reference 83 to the system reference 33.
[0046] In a particular exemplary embodiment of the invention, a camera 80 operating in the visible and / or infrared spectrum can be used (such as when the camera 80 utilized is...). RealSense TM (The camera is used to obtain each camera image of the indicator 90 in order to obtain the best view of the position of the indicator 90.) Using a suitable 2D to 3D pose or model correspondence process, the pose / position of the indicator 90 relative to the system 10 can be determined using the positioning of the indicator 90 in the 2D image obtained by the camera 80 together with the corresponding 3D coordinates of the indicator in the system reference.
[0047] In addition, Figure 8 In other exemplary embodiments shown, the position of indicator 90 within the camera image reference 83 can be determined by obtaining a first camera image of system 10 that does not include indicator 90 (which may be a first infrared camera image), then operating laser 86 at the same position on rack 12 and obtaining a second camera image of system 10 that includes indicator 90 (which may be a second infrared image), and then subtracting pixels from the first image that do not include indicator 90 from the second image that includes indicator 90 to produce a third image within the camera image reference 83 that only has indicator 90.
[0048] By inputting the image of indicator 90 from camera 80 and the corresponding indicator coordinates into system reference 33 (at least three (3) images are required), a transformation matrix can be calculated to establish a correspondence between any point in camera reference 83 and a point within system reference 33. For example, for each camera image, based on the construction of gantry 12 along with any movement of gantry 12 via suitable motors under the control of imaging controller 32 and / or computer / processing unit 36, the position of gantry 12 (and the position of laser 86 thereon) is known, and consequently the position of indicator 90 in each of the X, Y, and Z axes of system reference 33 is known, thus determining the position of indicator 90 in the X and Y axes, where the Z-axis position is defined as 0, i.e., the surface of inspection table 20. Using these known coordinates of indicator 90 in system reference 33 and the corresponding position of indicator in camera image reference 83, camera reference 83 can be registered relative to system reference 33, such as by employing any suitable known method to determine the perspective n-point (PnP) of camera 80.
[0049] For example, such as Figure 9 As shown in the exemplary embodiment, the calibration system 81 can operate in step 200 to obtain one or more camera images of the indicator 90, such as those previously described and / or as described in the infrared or visible spectrum operating modes of the camera 80. In step 202, one or more images are image-processed by the system 10 (such as the processing unit 36), wherein the X and Y coordinates of the indicator 90 in the images are determined based on image processing algorithms or manual detection. Simultaneously, in step 204, the gantry 12 is moved to a desired position using one or more motors so that the position of the gantry 12 within the system reference 33 can be known based on the precise operation of the motor positioning of the gantry 12. Accordingly, the position or coordinates of the emitted X-rays passing through the inspection table 20 can be known from the structure and position of the gantry 12. In step 206 (which can be performed before, simultaneously with, or after step 202), the computer / processing unit 36 can use the precise position of the laser 86 relative to the detector 18 (i.e., laser offset) to determine the precise position of the indicator 90 within the system reference 33 relative to the X-ray intersection point on the inspection table 20. Steps 200 to 204 of this process can be repeated for multiple different positions of indicator 90 on inspection table 20 in order to provide a sufficient number of coordinate pairs 210, such as at least three coordinate pairs, for use in conjunction with the P3P algorithm employed in calibration system 81 for the indication 90 in camera image reference 83 and system reference 33.
[0050] In the presence of a specified number of coordinate pairs, in step 208, the computer / processing unit 36 may provide the coordinate pairs 210 as input, along with various intrinsic parameters 214 of the camera 80, to a suitable algorithm 212, such as a random sample consensus algorithm (or RANSAC algorithm), or a PnP solution, or a combination thereof, such as those described in the following literature: https: / / en.wikipedia.org / wiki / Perspective-n-Point (the entire contents of which are incorporated herein by reference in their entirety for all purposes), in order to create or output a transformation matrix 216 from the artificial intelligence / algorithm 208 for transforming the coordinates in the system reference 33 into the camera reference 83, and vice versa.
[0051] Now refer to Figure 10 The transformation matrix 216 / registration enables the computer / processing unit 36 to correlate images from camera 80 with images and / or suggested images from detector 18 to accurately identify the location of anatomical structures of patient 22 shown in the camera images within system reference 33. Specifically, in the camera image 300 of a point of interest P on patient / subject 22 obtained by camera 80, the image provides pixel information (X,Y) and depth information (Z) about the point of interest P, which provides the coordinates (X,Y,Z) of the point of interest P in camera reference 83. The transformation matrix 216 can be applied to the coordinates of point P in camera reference 83 to convert those coordinates into coordinates within system reference 33 for use by system 10.
[0052] Furthermore, since the system and method do not require additional components for performing camera calibration (i.e., excluding optical markings), the camera calibration system and method of the present invention provide a more efficient calibration process than previously employed.
[0053] It should be understood that the compositions, apparatus, and methods described herein are not limited to the specific embodiments and methods, as these are subject to variation. It should also be understood that the terminology used herein is for the purpose of describing specific exemplary embodiments only and is not intended to limit the scope of this disclosure, which will be limited only by the appended claims.
Claims
1. A method for calibrating a camera-based feature detection system for an X-ray system, the method comprising the following steps: a. Providing an x-ray system, the x-ray system comprising: i. A support surface and a frame, the frame being operatively connected to the support surface and including an x-ray source, an x-ray detector alignable to the x-ray source, and a light source disposed on the frame adjacent to the x-ray detector, the frame defining a system reference; ii. An image processing system operatively connected to the rack for controlling the generation of x-ray image data by the light source, the x-ray source, and the x-ray detector, the image processing system comprising: a processing unit for processing the x-ray image data from the detector; a database operatively connected to the processing unit and storing instructions for operating a calibration system; a display operatively connected to the image processing system for presenting information to a user; and a user interface operatively connected to the image processing system to enable user input to reach the image processing system; and iii. A camera-based feature detection system comprising a camera spaced apart from the frame and operably connected to the image processing system, the camera defining a camera reference, the support surface and the frame being positioned within the camera reference and operable to generate one or more camera images of the support surface and the frame, wherein the calibration system is operable to register the camera reference to the system reference; b. Operate the light source to position the indicator on the support surface; c. Acquire the multiple camera images indicated on the support surface; d. Determine multiple locations of the indicated position within the camera reference; e. Determine multiple locations of the indication within the system reference; and f. Register the camera reference to the system reference.
2. The method of claim 1, wherein the step of registering the camera reference to the system reference includes determining a transformation matrix between the camera reference and the system reference.
3. The method of claim 2, wherein the step of determining the transformation matrix between the camera reference and the system reference comprises the following steps: a. Providing the indications to the algorithm within the calibration system at the plurality of locations within the camera reference; g. Providing the algorithm within the calibration system with the indication at the plurality of locations within the system reference; as well as b. Operate the calibration system to generate the transformation matrix.
4. The method of claim 1, wherein the light source is a laser, and wherein the step of determining the position indicated within the system reference comprises: a. Determine the location of the detector within the system reference; b. Determine the position of the laser relative to the position of the detector within the system reference; as well as c. Determine the position of the indication relative to the laser within the system reference.
5. The method of claim 1, wherein the step of determining the position of the indication relative to the detector within the system reference includes applying a light source offset to the position of the detector.
6. The method of claim 5, wherein the light source offset is the difference between the position of the detector on the rack and the position of the light source on the rack.
7. The method according to claim 1, further comprising the following steps: a. Operate the light source to position the indicator at a first location on the support surface; b. Acquire a first camera image indicating a first position on the support surface; c. After acquiring the first camera image, move the frame relative to the supporting surface; d. Operate the light source to position the indicator at a second location on the support surface; e. Acquire a second camera image indicating a second position on the support surface.
8. The method of claim 7, wherein the step of moving the frame relative to the support surface comprises moving the frame along at least one of the long axis or the short axis of the support surface.
9. The method of claim 7, further comprising the step of: The frame is repeatedly moved to obtain camera images at the minimum number of positions indicated on the support surface.
10. The method according to claim 7, further comprising the step of: The frame is repeatedly moved to obtain camera images indicating at least three locations on the support surface.
11. The method of claim 1, wherein no optical markings are attached to the support surface or the frame.
12. The method of claim 1, wherein the x-ray system is a DXA system.
13. An x-ray system, the x-ray system comprising: a. A support surface and a frame, the frame being operatively connected to the support surface and including an x-ray source, an x-ray detector alignable to the x-ray source, and a light source disposed on the frame adjacent to the x-ray detector, the frame defining a system reference, the light source being capable of positioning an indication on the support surface; b. An image processing system operatively connected to the rack for controlling the generation of x-ray image data by the light source, the x-ray source, and the x-ray detector, the image processing system comprising: a processing unit for processing the x-ray image data from the detector; a database operatively connected to the processing unit and storing instructions for operating a calibration system; a display operatively connected to the image processing system for presenting information to a user; and a user interface operatively connected to the image processing system to enable user input to reach the image processing system; and c. A camera-based feature detection system comprising a camera spaced apart from the frame and operably connected to the image processing system, the camera defining a camera reference, the support surface and the frame being positioned within the camera reference and operable to generate one or more camera images of the support surface and the frame, wherein the calibration system is operable to register the camera reference to the system reference; The calibration system is configured to determine multiple locations of the indication within the camera reference, to determine multiple locations of the indication within the system reference, and to register the camera reference to the system reference.
14. The x-ray system of claim 13, wherein the x-ray system does not include optical markers.
15. The x-ray system of claim 13, wherein the calibration system is configured to register the camera reference to the system reference by determining a transformation matrix between the camera reference and the system reference.