X-ray photographing apparatus

Abstract

The invention relates to an X-ray apparatus (10). The following is described: placing (110) an X-ray source (20) relative to an X-ray detector (30) to form an examination region for accommodating an object, wherein a reference spatial coordinate system is defined based on geometric parameters of the X-ray apparatus; positioning (120) a camera (40) at a position and orientation to view the examination region; acquiring (130) a depth image of the object with the camera in a camera spatial coordinate system, wherein in the depth image a pixel value represents a distance for a corresponding pixel; transforming (140) the depth image of the object in the camera spatial coordinate system to the reference spatial coordinate system with a processing unit (50) using a mapping function, wherein the position and orientation of the camera have been calibrated relative to the reference spatial coordinate system to produce a mapping function that maps a spatial point within the camera spatial coordinate system to a corresponding spatial point in the reference spatial coordinate system; generating (150) a composite image in the reference spatial coordinate system; outputting (160) the composite image with an output unit (60).

Description

[0001] This application is a divisional application of the invention patent application filed on June 15, 2018, with application number 201880039405.2 and title "X-ray imaging device". Technical Field

[0002] The present invention relates to an X-ray radiographic apparatus, a method for providing images for an X-ray radiographic apparatus, and a computer program unit and a computer-readable medium. Background Technology

[0003] The general background of this invention is radiography. In radiographic examinations, it is necessary to accurately position the patient relative to the X-ray detector and adjust the geometry and system parameters to suit the patient's anatomy. For example, the exposure chamber used for automatic exposure control (AEC) needs to be precisely positioned behind the target anatomical structure. Similarly, the size of the collimation window needs to be adjusted to fit the size of the body part to be imaged.

[0004] In current systems, existing technology uses visual markers (e.g., a drawing of the exposure chamber on the detector cover) and visible light projected directly onto the scene (detector, patient) as a means of guiding the operator. For example, light sources and slide-like devices are used in the scene to project collimation windows and exposure chambers, allowing the operator to check the current setup by observing the projected shape on the patient.

[0005] Current technology has significant limitations: it cannot provide all the necessary information, and the visibility of the projected light field can be very limited—depending on the lighting conditions of the examination room and the patient's clothing. Furthermore, ideally, the operator needs to view the patient from a position equal to the X-ray source to avoid any visual obstruction, requiring iterative back-and-forth operation between the system configuration panel and the observation point.

[0006] Other methods using conventional video cameras and overlays also suffer from geometric inaccuracies and obstructions because the video camera cannot be placed at the location of the X-ray source and the captured scene view is oblique.

[0007] WO 2015 / 081295 A1 describes a system or method for improving the quality of projection and computed tomography X-rays, comprising: a depth sensing device for measuring the depth of at least one body part from a patient using the depth sensing device; and a control unit for using the depth information to calculate the thickness and / or circumference of the body part. The calculated thickness and circumference information is used to determine an optimal X-ray exposure level for the body part. The system or method also includes: a camera for identifying the body part to be examined and detecting any movement of the identified body part. However, there is a need to improve the images provided to the operator of the X-ray imaging apparatus.

[0008] WO 2016 / 001130 A1 describes a method for automatically configuring an X-ray imaging system for capturing X-ray images of an object. First, one or more depth images are acquired from one or more depth cameras covering at least one area covered by an X-ray beam from an X-ray source. Then, the thickness of the object is determined based on the one or more depth images. This thickness value is then converted into a dose configuration for the X-ray imaging system by taking into account the transmission length of the X-ray beam through the object and knowledge about the type of tissue being imaged. Summary of the Invention

[0009] It would be advantageous to have an improved device for providing images to the operator of the X-ray imaging apparatus.

[0010] The objectives of this invention are achieved through the subject matter of embodiments of this disclosure. It should be noted that the aspects and examples described below also apply to X-ray imaging apparatuses, methods for providing images to X-ray imaging apparatuses, and computer program units and computer-readable media.

[0011] According to a first aspect, an X-ray imaging apparatus is provided, comprising:

[0012] X-ray source;

[0013] X-ray detector;

[0014] camera;

[0015] Processing unit; and

[0016] Output unit.

[0017] The X-ray source is configured to be positioned relative to the X-ray detector to form an examination area for accommodating an object. A reference spatial coordinate system is defined based on the geometric parameters of the X-ray imaging apparatus. The camera is configured to be positioned and oriented to view the examination area, and the camera is configured to acquire depth images in a camera spatial coordinate system, wherein pixel values ​​in the depth images represent distances relative to corresponding pixels. The position and orientation of the camera have been calibrated relative to the reference spatial coordinate system to generate a mapping function that maps spatial points in the camera spatial coordinate system to corresponding spatial points in the reference spatial coordinate system. The camera is configured to acquire a depth image of the object in the camera spatial coordinate system and provide the depth image to the processing unit. The processing unit is configured to use the mapping function to transform the depth image of the object in the camera spatial coordinate system to the reference spatial coordinate system and generate a composite image in the reference spatial coordinate system. The output unit is configured to output the composite image.

[0018] In this way, images of objects such as human subjects can be presented to the operator as if the image were acquired by a camera positioned at the location of the X-ray source, rather than by a camera at its actual location. Alternatively, if needed, images of the object can be presented to the operator as if the image were acquired by a camera positioned at another location of the X-ray source. This facilitates optimal and efficient positioning of the object within the examination area, where parallax effects are mitigated. In this way, the patient can be accurately positioned relative to the X-ray detector, and the geometry and system parameters of the X-ray apparatus can be appropriately adjusted for the patient's anatomy. Therefore, since the operator is provided with an image of the patient's position within the examination area as seen from the X-ray source, the operator can ensure that the exposure chamber used for automatic exposure control is precisely positioned behind the patient's anatomy. Furthermore, the operator can optimally adjust the X-ray source collimation window to fit the size of the object (the patient's body part).

[0019] In a first aspect, the X-ray source has a collimator configured to limit the range of the X-rays, and the processing unit is configured to generate a representation of the range of the X-rays within the reference spatial coordinate system, and the processing unit is configured to generate a composite image having the representation of the range of the X-rays.

[0020] In other words, the X-ray source has a collimation window, and the composite image has an indication of the size of the collimation window at the object location superimposed on it. In this way, the operator can move the object within the inspection area and / or change the size of the collimation window to provide optimal radiographic examination.

[0021] In the first aspect, the processing unit is configured to generate a composite image having a representation of the range of X-rays at the location of the object.

[0022] In other words, the X-ray source is configured to emit X-rays in both angular and spatial extent, and the processing unit is configured to generate a composite image representing the extent of the X-rays at the object's location. Therefore, the operator is provided not only with an indication of the size of the collimation window from the X-ray source's angle, but also with the size of that window at the object. This takes into account both objects very close to the X-ray detector or portions of objects as well as objects farther from the detector.

[0023] In the example, the X-ray detector has at least one exposure chamber configured to measure the exposure level of X-rays, and the processing unit is configured to generate a representation of the extent of the at least one exposure chamber within the reference spatial coordinate system. The processing unit is then configured to generate a composite image having the representation of the extent of the at least one exposure chamber.

[0024] In this way, the operator can ensure that the object (e.g., a patient) is correctly positioned relative to the exposure chamber used for automatic exposure control, taking into account the actual path of the X-ray from the X-ray source to the detector, since the composite image is acquired from the perspective of the X-ray source and its relationship to the X-ray detector.

[0025] In the example, the processing unit is configured to generate a composite image having a representation of the range of the at least one exposure chamber at the location of the object.

[0026] In the example, the X-ray detector has an active region configured to detect X-rays, and the processing unit is configured to generate a representation of the extent of the active region within the reference spatial coordinate system. The processing unit is then configured to generate a composite image having the representation of the extent of the active region.

[0027] In the example, the processing unit is configured to generate a synthetic image having a representation of the range of the active region at the location of the object.

[0028] In the example, the X-ray detector has a horizontal axis and a vertical axis, and the processing unit is configured to generate representations of the horizontal axis and / or the vertical axis within the reference spatial coordinate system. The processing unit is then configured to generate a composite image having representations of the horizontal axis and / or the vertical axis.

[0029] In this way, the operator is provided with another means to help achieve proper alignment of the object (e.g., the patient) with the device.

[0030] In other words, the axis of symmetry used for the X-ray detector can be used to check whether the patient is properly aligned with the X-ray detector.

[0031] In the example, the camera is configured to acquire 2D images and provide the images to the processing unit, wherein the processing unit is configured to generate a composite image, including utilizing the 2D images.

[0032] In this way, it is possible to generate synthetic images with realistic textures.

[0033] Therefore, although a depth image can be considered a 2D image (since a depth image has two dimensions), additional images are acquired here in addition to the depth image. These additional images can be, for example, multi-channel (color) images or single-channel (monochrome) images, where pixel values ​​represent properties of the scene other than depth, such as the amount of reflected light within a given spectral range, and thermal images.

[0034] According to a second aspect, a method (100) for providing an image for an X-ray radiographic apparatus is provided, comprising:

[0035] a) An X-ray source is positioned relative to an X-ray detector to form an inspection area for accommodating an object, wherein a reference spatial coordinate system is defined based on the geometric parameters of the X-ray imaging apparatus;

[0036] b) Position the camera at a specific location and orientation to view the inspection area;

[0037] c) Using the camera, acquire a depth image of the object in the camera space coordinate system, wherein in the depth image, pixel values ​​represent distances relative to the corresponding pixels;

[0038] d) Using a processing unit, the depth image of the object in the camera space coordinate system is transformed to the reference space coordinate system using a mapping function, wherein the position and orientation of the camera have been calibrated relative to the reference space coordinate system to generate a mapping function that maps spatial points in the camera space coordinate system to corresponding spatial points in the reference space coordinate system.

[0039] i) Generate a composite image within the reference spatial coordinate system; and

[0040] j) The synthesized image is output using the output unit.

[0041] In the second aspect, the X-ray source has a collimator configured to limit the range of X-rays, and the method includes step (e): generating a representation of the range of the X-rays in the reference spatial coordinate system using the processing unit, and wherein step i) includes generating a composite image having the representation of the range of the X-rays.

[0042] In the second aspect, step i) includes generating a composite image having a representation of the range of the X-rays at the location of the object.

[0043] In the example, the X-ray detector has at least one exposure chamber configured to measure the exposure level of X-rays; and wherein the method includes step (f): generating a representation of the extent of the at least one exposure chamber in the reference spatial coordinate system using the processing unit, and wherein step i) includes generating a composite image having the representation of the extent of the at least one exposure chamber.

[0044] In the example, the X-ray detector has an active region configured to detect X-rays, and the method includes step (g): generating a representation of the extent of the active region in the reference spatial coordinate system using the processing unit, and wherein step i) includes generating a synthetic image having a representation of the extent of the active region.

[0045] According to another aspect, a computer program unit is provided for controlling the apparatus and / or system as described above, the computer program unit being adapted, when run by a processing unit, to perform the steps of the method as described above.

[0046] According to another aspect, a computer-readable medium storing computer program units as described above is provided.

[0047] Advantageously, the benefits provided by any of the above aspects also apply to all other aspects, and vice versa.

[0048] The above aspects and examples will become apparent and illustrated with reference to the embodiments described below. Attached Figure Description

[0049] Exemplary embodiments will now be described with reference to the following figures:

[0050] Figure 1 A schematic setup of an example X-ray imaging apparatus is shown;

[0051] Figure 2 A method for providing images for an X-ray imaging apparatus is shown;

[0052] Figure 3 An example of an X-ray source (X-ray tube) with a 3D camera mounted on an X-ray tube support is shown;

[0053] Figure 4 Images with and without overlays are shown, as well as overlays that have been geometrically corrected within a single image; and

[0054] Figure 5 Images with overlays that have not been geometrically corrected and images with overlays that have been geometrically corrected are shown. Detailed Implementation

[0055] Figure 1 An example of an X-ray radiography apparatus 10 is shown. The X-ray radiography apparatus includes an X-ray source 20, an X-ray detector 30, a camera 40, a processing unit 50, and an output unit 60. The X-ray source 20 is configured to be positioned relative to the X-ray detector 30 to form an examination area for accommodating an object. A reference spatial coordinate system is defined based on the geometric parameters of the X-ray radiography apparatus 10. The camera 40 is configured to be positioned at a location and orientation to view the examination area, and the camera 40 is configured to acquire a depth image within the camera spatial coordinate system, where pixel values ​​represent distances relative to corresponding pixels. The position and orientation of the camera have been calibrated relative to the reference spatial coordinate system to generate a mapping function that maps spatial points in the camera spatial coordinate system to corresponding spatial points in the reference spatial coordinate system. The camera 40 is configured to acquire a depth image of the object within the camera spatial coordinate system and provide this depth image to the processing unit 50. The processing unit 50 is configured to use the mapping function to transform the depth image of the object in the camera spatial coordinate system to the reference spatial coordinate system and generate a composite image within the reference spatial coordinate system. Output unit 60 is configured to output a composite image.

[0056] In the example, the mapping function maps spatial points in the reference spatial coordinate system to corresponding spatial points in the camera spatial coordinate system.

[0057] In the example, the geometric parameters used to define the X-ray imaging system of the reference spatial coordinate system include one or more of the following: the position of the X-ray source relative to the X-ray detector; geometric parameters related to the source-image receiver distance (SID); the height of the X-ray detector; the width of the X-ray detector; the height of the X-ray source; the width of the X-ray source; the rotation angle of the X-ray source; the longitudinal and lateral positions of the X-ray detector; the longitudinal and lateral positions of the X-ray source; and the rotation angles (roll, pitch, yaw) of the X-ray detector and / or the X-ray source. In this way, the X-ray detector and the X-ray source can be completely defined within the reference spatial coordinate system.

[0058] In the example, in addition to acquiring depth images, the camera is configured to acquire “regular” images of the scene, such as color images or grayscale (monochrome or infrared) images in color spaces like R, G, or B. In the example, the camera is configured to acquire 3D depth (also known as range) data images and is able to calculate 3D point coordinates from the depth data images using the camera system’s internal parameters. In the example, the regular images are used to generate a composite image on which an overlay is shown. A correspondence (mapping function) between pixels in the regular images and pixels in the depth images is used. This is necessary because regular images can be acquired by sensors other than the depth sensor, and both have different positions and orientations. However, this is a standard problem in computer vision and modern 3D camera systems, and this mapping can be provided by the 3D camera system manufacturer. However, in the example, the regular images are acquired by a regular camera that is not a fixed component of a 3D video camera system; in this case, the mapping function needs to be calculated once, which is called camera system calibration. It should also be noted that more than one additional regular image can be used, such as an RGB image and an infrared image.

[0059] Therefore, the camera can acquire a single depth image and extract 3D points from that depth image, meaning it can calculate the 3D spatial coordinates of these points. The 3D point coordinates of objects within the image can be used to perform a transformation from the camera space coordinate system to a reference space coordinate system. Furthermore, the depth image and the calculated 3D points can be used to provide a 3D point representation, for example, using a point cloud. Thus, in effect, the depth image can be used to provide a 3D image. A composite image can then be generated in the reference space coordinate system using a 2D projection of that 3D image. Alternatively, the camera can acquire a second 2D image (a conventional image) simultaneously with the depth image. As described above, the depth image is used to perform the transformation from the camera space coordinate system to the reference space coordinate system, while the conventional image is used (e.g., from the perspective of an X-ray source) to generate a composite image in the reference space coordinate system, on which, for example, an overlay can be shown.

[0060] Typically, this requires integrating two different sensors into the camera system. Only in the infrared case is a single sensor sufficient.

[0061] In the example, the camera uses time-of-flight technology (e.g., LiDAR) to determine the 3D image. In the example, the camera uses structured light to determine the 3D image. In the example, the term "camera" actually refers to two or more 2D cameras used together to provide 3D images, such as a stereo system.

[0062] According to the example, the X-ray source has a collimator configured to limit the range of X-rays, and a processing unit is configured to generate a representation of the range of X-rays within a reference spatial coordinate system. The processing unit is then configured to generate a composite image having the representation of the range of X-rays.

[0063] According to the example, the processing unit is configured to generate a synthetic image having a representation of the range of X-rays at the location of the object.

[0064] According to the example, the X-ray detector has at least one exposure chamber configured to measure the exposure level of X-rays, and wherein a processing unit is configured to generate a representation of the extent of the at least one exposure chamber within a reference spatial coordinate system. The processing unit is then configured to generate a composite image having the representation of the extent of the at least one exposure chamber.

[0065] According to the example, the processing unit is configured to generate a synthetic image having a representation of the range of at least one exposure chamber at the location of the object.

[0066] According to the example, the X-ray detector has an active region configured to detect X-rays, and a processing unit is configured to generate a representation of the extent of the active region within a reference spatial coordinate system. The processing unit is then configured to generate a composite image having the representation of the extent of the active region.

[0067] According to the example, the processing unit is configured to generate a synthetic image having a representation of the range of the active region at the location of the object.

[0068] According to the example, the X-ray detector has a horizontal axis and a vertical axis, and the processing unit is configured to generate representations of the horizontal axis and / or the vertical axis within a reference spatial coordinate system. The processing unit is then configured to generate a composite image having representations of the horizontal axis and / or the vertical axis.

[0069] According to the example, the camera is configured to acquire a 2D image and provide that image to the processing unit. The processing unit is then configured to generate a composite image, including utilizing the 2D image.

[0070] In the example, the 2D image is a monochrome image. In the example, the 2D image is a color image.

[0071] Figure 2 A method 100 for providing an image to an X-ray imaging apparatus is shown with basic steps. Method 100 includes:

[0072] In placement step 110 (also referred to as step (a)), X-ray source 20 is placed relative to X-ray detector 30 to form an inspection area for accommodating an object, wherein a reference space coordinate system is defined based on the geometric parameters of the X-ray imaging apparatus.

[0073] In positioning step 120 (also referred to as step (b)), camera 40 is positioned at a location and orientation to view the inspection area;

[0074] In acquisition step 130 (also referred to as step (c)), a depth image of the object is acquired using a camera in the camera space coordinate system, wherein the pixel value in the depth image represents the distance to the corresponding pixel;

[0075] In transformation step 140 (also referred to as step (d)), the processing unit 50 uses a mapping function to transform the depth image of the object in the camera space coordinate system to the reference space coordinate system, wherein the position and orientation of the camera have been calibrated relative to the reference space coordinate system to generate a mapping function that maps spatial points in the camera space coordinate system to corresponding spatial points in the reference space coordinate system.

[0076] In generation step 150 (also referred to as step (i)), a composite image is generated in the reference space coordinate system; and

[0077] In output step 160 (also referred to as step (j)), the composite image is output using output unit 60.

[0078] According to the example, the X-ray source has a collimator configured to limit the range of X-rays. And wherein the method includes step (e): generating a representation of the range of 170 X-rays in a reference spatial coordinate system using a processing unit, and wherein step i) includes generating a composite image having the representation of the range of X-rays.

[0079] According to the example, step i) includes generating a composite image having a representation of the range of X-rays at the location of the object.

[0080] In the example, the representation of the range of generated X-rays includes the use of a ray tracing algorithm.

[0081] According to the example, the X-ray detector has at least one exposure chamber configured to measure the exposure level of X-rays; and wherein the method includes step (f): generating a representation of the extent of at least one exposure chamber within a reference spatial coordinate system using a processing unit, and wherein step i) includes generating a composite image having the representation of the extent of at least one exposure chamber.

[0082] In the example, step i) includes generating a synthetic image having a representation of the range of at least one exposure chamber at the location of the object.

[0083] In the example, generating a representation of the extent of at least one exposure chamber involves utilizing a ray tracing algorithm.

[0084] According to the example, the X-ray detector has an active region configured to detect X-rays, and the method includes step (g): generating a representation of the extent of the active region in reference spatial coordinates using a processing unit, and wherein step i) includes generating a synthetic image having the representation of the extent of the active region.

[0085] In the example, step i) includes generating a synthetic image having a representation of the range of the active region at the location of the object.

[0086] In the example, the representation of the range of the generated active region involves using a ray tracing algorithm.

[0087] In the example, the X-ray detector has a horizontal axis and a vertical axis, and the method includes step (h): generating a representation of 200 horizontal and / or vertical axes in a reference spatial coordinate system using a processing unit, and wherein step i) includes generating a synthetic image having the representation of the horizontal and / or vertical axes.

[0088] In the example, the camera is configured to acquire 2D images, and the method includes providing the image to a processing unit, wherein step i) includes utilizing the 2D image.

[0089] Now combine Figure 3-5 To describe in more detail the X-ray radiographic apparatus and the methods for providing images for the X-ray radiographic apparatus.

[0090] A depth camera capable of acquiring 3D images, a 3D computer vision method, and a display are used to present an augmented reality synthetic image with high geometric accuracy to an operator according to the following steps:

[0091] Position a depth camera that provides depth data and regular video data at an appropriate frame rate so that (e.g., on top of the collimator) the inspection area can be imaged with minimal obstruction. Figure 3 The image shows an example of a 3D camera (depth camera) mounted on an X-ray source (X-ray tube).

[0092] The camera's position and orientation have been calibrated relative to the geometry of the imaging system. This process incorporates real-time values ​​of the imaging system's geometric parameters to generate a mapping function that allows point coordinates to be transformed from the camera coordinate system to the X-ray reference coordinate system.

[0093] In the next step, known computer vision methods and the coordinate transformations obtained above are used to reconstruct a synthetic image that shows the geometrically accurate location and shape (as an overlay) of the patient and detectors such as the exposure chamber, collimation window, and active area.

[0094] Therefore, a composite image seen from the X-ray source can be reconstructed from a depth image, but it is also possible to reconstruct a composite image seen from other vantage points, without requiring it to be a composite image seen from the X-ray source. Overlays are generated in the scene by applying central projection centered on the X-ray source.

[0095] It can also generate a composite image representing the patient's projection onto the X-ray detector based on depth images. Then, an overlay is generated by calculating the size, shape, and position of different patterns projected onto the plane of the X-ray detector.

[0096] The augmented reality composite image is displayed to the operator on the monitor. Different colors can be used to represent each type of overlay among different overlay types.

[0097] Figure 4 An example is shown of an overlay that can be generated using depth data captured by a 3D camera, targeting the exposure chamber and collimation window. Figure 4 Three images are shown. The left image shows an image captured by a 3D camera. The middle image shows the superposition of the exposure chamber and collimation window as viewed from the 3D camera's perspective (i.e., in the camera space coordinate system) without applying the proposed mapping function. In the right image, the superposition has been geometrically corrected based on the mapping function derived from the camera calibration and the geometric parameters of the X-ray imaging apparatus, and the geometrically corrected superposition is now precisely positioned at the correct pixel location.

[0098] Figure 5 Two images with collimated superimposed objects are shown, where the left image is the collimated, uncorrected image, and the right image is the collimated, corrected image. The left image shows the 3D scene as seen from the camera. Because the camera is positioned to the side of the X-ray source, the position and size of the collimated superimposed object (the rectangle projected onto the back of the object) depend on the distance to the X-ray source (which is chosen as the reference). This is represented by two different rectangles. After transforming from the camera space coordinate system to the reference space coordinate system, as shown in the right image, the 3D scene as seen from the X-ray source is now shown. Now, the position and size of the collimated superimposed object are independent of the distance to the X-ray source (which is chosen as the reference) and further accurately match the position and size obtained using the projector.

[0099] Camera calibration

[0100] Typically, it is desirable to express the coordinates of 3D points in a coordinate system specified relative to the examination room or relative to the medical imaging system or X-ray imaging apparatus. In the following text, this reference space coordinate system, as opposed to the camera space coordinate system, is referred to as the "world" coordinate system.

[0101] External camera parameters describe the 3D point P in the world coordinate system w To the 3D point P in the camera coordinate system c Transformation. These parameters are given by the following equation:

[0102]

[0103]

[0104] and This represents the rotation and translation that define the external camera parameters, and they have the following relationship:

[0105]

[0106] Translation vector The coordinates can be viewed as the origin of the world coordinate system expressed in camera coordinates. Each column of the rotation matrix represents the coordinates (in camera coordinates) of a unit vector oriented along the principal axis of the world coordinate system.

[0107] To determine the extrinsic parameters for a given camera's position and orientation, the following method can be used. In this method, it is assumed that the camera's intrinsic parameters, which define the mapping from 2D points in image coordinates to 3D points in camera coordinates, are already known. These parameters can be calculated using known methods, such as images based on a checkerboard pattern. See: http: / / docs.opencv.org / 2.4 / doc / tutorials / calib3d /

[0108] camera_calibration / camera_calibration.html.

[0109] First, a camera is used to acquire depth images of the known object. Within this image, multiple calibration points with known coordinates in the world coordinate system are identified. These points can be located, for example, at specific known locations in the world coordinate system, such as the corner of the detector's front cover. These calibration points constitute N pairs... (in, The calibration dataset was obtained, thus yielding A system of N equations of type [N]. The linear system can then be solved for the unknown coefficients of the rotation matrix R and the translation vector T. An example of the computational algorithm can be found in Berthold KP Horn's "Closed-form solution of absolute orientation using unitquaternions" (J. Opt. Soc. Am. A., Vol. 4, No. 4, pp. 629-642, 1987).

[0110] Enhanced robustness can be achieved by using a number N greater than 3 (where the system is over-determined) and by ensuring that the calibration points are not coplanar.

[0111] Other methods are also possible. For example, instead of using a well-defined set of calibration points, a point cloud describing world coordinates can be used, such as a reference 3D object with a known pattern (e.g., a portion of the detector's front cover). First, candidate calibration points that may be located on the reference object are extracted from the acquired images using, for example, an edge detector. Then, an iterative nearest-point algorithm can be used to compute the match between these candidate calibration points and the reference 3D point cloud in world coordinates, along with the unknown rotation matrix R and translation vector T. This iterative nearest-point algorithm is described in "Efficient Variants of the ICP algorithms" (International Conference on 3D Digital Imaging and Modeling (3DIM)) by Rusinkiewicz et al. (Szymon Rusinkiewicz and Marc Levoy, 2001).

[0112] In another exemplary embodiment, a computer program or computer program unit is provided, characterized in that it is configured to run method steps of the method according to one of the foregoing embodiments on a suitable system.

[0113] Therefore, the computer program unit can be stored in the computer unit, and this computer program unit can also be part of the embodiment. The computing unit can be configured to execute or cause the execution of steps of the above-described method. Furthermore, the computing unit can be configured to operate components of the above-described apparatus and / or system. The computing unit can be configured to automatically operate and / or execute user commands. The computer program can be loaded into the working memory of the data processor. Therefore, the data processor can be equipped to execute the method of one of the foregoing embodiments. The computer program or output unit can be integrated into an imaging system or a navigation system.

[0114] This exemplary embodiment of the invention covers both computer programs that use the invention from the outset and computer programs that are converted from existing programs to use the invention.

[0115] In addition, the computer program unit may be able to provide all the necessary steps to complete the process of the exemplary embodiments of the method described above.

[0116] According to another exemplary embodiment of the present invention, a computer-readable medium, such as a CD-ROM, a USB flash drive, etc., is provided, wherein the computer-readable medium has computer program units stored on the computer-readable medium, the computer program units being described in the preceding sections.

[0117] Computer programs can be stored and / or distributed on suitable media, such as optical storage media or solid-state media supplied together with or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0118] However, computer programs can also exist on networks (such as the World Wide Web) and can be downloaded from such networks to the working memory of a data processor. According to another exemplary embodiment of the invention, a medium is provided for making computer program units available for download, said computer program units being arranged to perform a method according to an embodiment of the previously described embodiments of the invention.

[0119] Several examples of this disclosure are listed below:

[0120] Example 1. An X-ray imaging device (10), comprising:

[0121] X-ray source (20);

[0122] X-ray detector (30);

[0123] Camera (40);

[0124] Processing unit (50); and

[0125] Output unit (60);

[0126] The X-ray source is configured to be positioned relative to the X-ray detector to form an inspection area for accommodating an object, wherein the X-ray source has a collimator configured to limit the range of the X-rays;

[0127] The reference space coordinate system is defined based on the geometric parameters of the X-ray imaging device.

[0128] The camera is configured to be positioned at a location and orientation to view the inspection area, and the camera is configured to acquire a depth image in a camera space coordinate system, wherein in the depth image, pixel values ​​represent distances relative to corresponding pixels;

[0129] The position and orientation of the camera have been calibrated relative to the reference spatial coordinate system to generate a mapping function that maps spatial points in the camera spatial coordinate system to corresponding spatial points in the reference spatial coordinate system.

[0130] The camera is configured to acquire a depth image of the object within the camera space coordinate system and provide the depth image to the processing unit.

[0131] The processing unit is configured to use the mapping function to transform the depth image of the object in the camera space coordinate system to the reference space coordinate system and generate a composite image in the reference space coordinate system;

[0132] The processing unit is configured to generate a representation of the extent of the X-rays within the reference spatial coordinate system, and the processing unit is configured to generate a composite image having a representation of the extent of the X-rays at the location of the object.

[0133] The output unit is configured to output the synthesized image.

[0134] Example 2. The apparatus according to Example 1, wherein the X-ray detector has at least one exposure chamber configured to measure the exposure level of X-rays, and wherein the processing unit is configured to generate a representation of the extent of the at least one exposure chamber in the reference spatial coordinate system, and wherein the processing unit is configured to generate a composite image having the representation of the extent of the at least one exposure chamber.

[0135] Example 3. The apparatus according to Example 2, wherein the processing unit is configured to generate a composite image having a representation of the range of the at least one exposure chamber at the location of the object.

[0136] Example 4. An apparatus according to any one of Examples 1-3, wherein the X-ray detector has an active region configured to detect X-rays, and wherein the processing unit is configured to generate a representation of the extent of the active region in the reference spatial coordinate system, and wherein the processing unit is configured to generate a composite image having a representation of the extent of the active region.

[0137] Example 5. The apparatus according to Example 4, wherein the processing unit is configured to generate a synthetic image having a representation of the range of the active region at the location of the object.

[0138] Example 6. An apparatus according to any one of Examples 1-5, wherein the X-ray detector has a horizontal axis and a vertical axis, and wherein the processing unit is configured to generate a representation of the horizontal axis and / or the vertical axis in the reference spatial coordinate system, and wherein the processing unit is configured to generate a composite image having the representation of the horizontal axis and / or the vertical axis.

[0139] Example 7. An apparatus according to any one of Examples 1-6, wherein the camera is configured to acquire 2D images and provide the images to the processing unit, and wherein the processing unit is configured to generate a composite image, including utilizing the 2D images.

[0140] Example 8. A method (100) for providing an image for an X-ray imaging apparatus, comprising:

[0141] a) An X-ray source (20) is placed (110) relative to an X-ray detector (30) to form an inspection area for accommodating an object, wherein the X-ray source has a collimator configured to limit the range of X-rays, wherein a reference space coordinate system is defined based on the geometric parameters of the X-ray imaging apparatus;

[0142] b) Position the camera (40) (120) at a location and orientation to view the inspection area;

[0143] c) Using the camera, acquire (130) a depth image of the object in the camera space coordinate system, wherein in the depth image, the pixel value represents the distance to the corresponding pixel;

[0144] d) Using the processing unit (50), the depth image of the object in the camera space coordinate system is transformed (140) to the reference space coordinate system using a mapping function, wherein the position and orientation of the camera have been calibrated relative to the reference space coordinate system to generate a mapping function that maps spatial points in the camera space coordinate system to corresponding spatial points in the reference space coordinate system.

[0145] e) Using the processing unit, a representation of the range of the X-rays (170) is generated within the reference spatial coordinate system;

[0146] i) Generate (150) a composite image in the reference spatial coordinate system having a representation of the range of the X-rays at the location of the object; and

[0147] j) The output unit is used to output the synthesized image (160).

[0148] Example 9. The method according to Example 8, wherein the X-ray detector has at least one exposure chamber configured to measure the exposure level of X-rays; and wherein the method includes step (f): generating (180) a representation of the extent of the at least one exposure chamber in the reference spatial coordinate system using the processing unit, and wherein step i) includes generating a composite image having the representation of the extent of the at least one exposure chamber.

[0149] Example 10. The method according to any one of Examples 8-9, wherein the X-ray detector has an active region configured to detect X-rays, and wherein the method includes step (g): generating (190) a representation of the extent of the active region in the reference spatial coordinate system using the processing unit, and wherein step i) includes generating a synthetic image having a representation of the extent of the active region.

[0150] Example 11: A computer program unit for controlling an apparatus according to any one of Examples 1-7, the computer program unit being configured, when run by a processor, to perform the method according to any one of Examples 8-10.

[0151] It should be noted that embodiments of the present invention are described with reference to different subjects. In particular, some embodiments are described with reference to method claims, while others are described with reference to apparatus claims.

[0152] In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality. A single processor or other unit can perform the functions of several items recited in the claims. Although certain measures are recited in different dependent claims, this does not indicate that combinations of these measures cannot be advantageously used. No reference numerals in the claims should be construed as limiting the scope.

Claims

1. An X-ray imaging device (10), comprising: X-ray source (20); X-ray detector (30); Camera (40); Processing unit (50); as well as Output unit (60); The X-ray source is configured to be positioned relative to the X-ray detector to form an inspection area for accommodating an object; The X-ray detector has at least one exposure chamber configured to measure the exposure level of X-rays; or the X-ray detector has an active region configured to detect X-rays. The reference space coordinate system is defined based on the geometric parameters of the X-ray imaging device. The camera is configured to be positioned at a location and orientation to view the inspection area, and the camera is configured to acquire a depth image in a camera space coordinate system, wherein in the depth image, pixel values ​​represent distances relative to corresponding pixels; The position and orientation of the camera have been calibrated relative to the reference spatial coordinate system to generate a mapping function that maps spatial points in the camera spatial coordinate system to corresponding spatial points in the reference spatial coordinate system. The camera is configured to acquire a depth image of the object within the camera space coordinate system and provide the depth image to the processing unit. The processing unit is configured to use the mapping function to transform the depth image of the object in the camera space coordinate system to the reference space coordinate system and generate a synthetic 2D image in the reference space coordinate system. The processing unit is configured to generate the synthetic 2D image by utilizing the depth image or a regular 2D image acquired by the camera. The processing unit is configured to generate a representation of the extent of the at least one exposure chamber within the reference spatial coordinate system, and the processing unit is configured to generate the composite 2D image having the representation of the extent of the at least one exposure chamber at the location of the object; or, respectively, the processing unit is configured to generate a representation of the extent of the active region within the reference spatial coordinate system, and the processing unit is configured to generate the composite 2D image having the representation of the extent of the active region at the location of the object. The output unit is configured to output, respectively, a representation of the range of the at least one exposure chamber at the location of the object to the operator of the device, or a representation of the range of the active area at the location of the object to the operator of the device.

2. The apparatus according to claim 1, wherein, The X-ray source has a collimator configured to limit the range of the X-rays, and the processing unit is configured to generate a representation of the range of the X-rays in the reference spatial coordinate system, and the processing unit is configured to generate the synthetic 2D image having the representation of the range of the X-rays.

3. The apparatus according to claim 2, wherein, The processing unit is configured to generate the synthetic 2D image having the representation of the range of X-rays at the location of the object.

4. The apparatus according to any one of claims 1-3, wherein, The X-ray detector has a horizontal axis and a vertical axis, and the processing unit is configured to generate a representation of the horizontal axis and / or the vertical axis in the reference space coordinate system, and the processing unit is configured to generate the synthetic 2D image having the representation of the horizontal axis and / or the vertical axis.

5. The apparatus according to any one of claims 1-3, wherein, The camera is configured to acquire 2D images and provide the images to the processing unit, wherein the processing unit is configured to generate the synthesized 2D image, including utilizing the 2D image.

6. A method (100) for providing an image to an X-ray imaging apparatus, comprising: a) An X-ray source (20) is placed (110) relative to an X-ray detector (30) to form an inspection area for accommodating an object, the X-ray detector having at least one exposure chamber configured to measure the exposure level of X-rays; Alternatively, the X-ray detector may have an active region configured to detect X-rays, wherein a reference space coordinate system is defined based on the geometric parameters of the X-ray imaging apparatus. b) Position the camera (40) (120) at a location and orientation to view the inspection area; c) Using the camera, acquire (130) a depth image of the object in the camera space coordinate system, wherein in the depth image, the pixel value represents the distance to the corresponding pixel; d) Using the processing unit (50), the depth image of the object in the camera space coordinate system is transformed (140) to the reference space coordinate system using a mapping function, wherein the position and orientation of the camera have been calibrated relative to the reference space coordinate system to generate a mapping function that maps spatial points in the camera space coordinate system to corresponding spatial points in the reference space coordinate system. f) Using the processing unit to generate (180) a representation of the extent of the at least one exposure chamber in the reference spatial coordinate system; or g) Using the processing unit to generate (190) a representation of the extent of the active region in the reference spatial coordinate system; i) Generate (150) in the reference spatial coordinate system a composite 2D image having a representation of the range of the at least one exposure chamber at the location of the object or a representation of the range of the active area at the location of the object, wherein generating the composite 2D image includes using the depth image or a 2D conventional image acquired by the camera; and j) The synthesized 2D image is output to the operator of the device using the output unit.

7. The method according to claim 6, wherein, The X-ray source has a collimator configured to limit the range of the X-rays; and wherein the method includes step (e): generating (170) a representation of the range of the X-rays in the reference spatial coordinate system using the processing unit, and wherein step i) includes generating the synthetic 2D image having the representation of the range of the X-rays.

8. The method according to claim 7, wherein, Step i) includes generating the synthetic 2D image having the representation of the range of the X-rays at the location of the object.

9. A computer program product storing a computer program for controlling an apparatus according to any one of claims 1-5, the computer program being configured, when run by a processor, to perform the method according to any one of claims 6-8.

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