Patient monitoring during scanning

Abstract

The imaging system is for capturing images of a patient during a medical scan. A set of one or more cameras captures images of the patient, after applying distortion and perspective correction steps, such that pixel rows correspond to positions along an axis parallel to a direction of movement of the patient support and pixel columns correspond to positions along an axis perpendicular to the patient support. Patient motion of interest can then be identified based on image movement in the pixel column direction between successive captured images. A measure of patient motion can then be derived.

Description

[Technical Field]

[0001] The present invention relates to monitoring a patient during a medical scan, and in particular to detecting movement. [Background technology]

[0002] In many medical imaging procedures, it is important to monitor the patient during the imaging procedure, for example, to monitor the patient's movement during the procedure or to monitor the patient's health during the imaging procedure. For example, surveillance images, such as video images provided by a camera, such as a wide field of view camera, are used for monitoring.

[0003] As an example, it is desirable to detect respiratory-related motion to prevent and correct motion artifacts, ensure optimal image quality, and support respiratory-induced scanning. Indeed, unwanted patient motion is one of the main reasons for image quality issues and safety events (such as finger pinching).

[0004] Furthermore, in these monitoring applications, it is particularly important to monitor a predetermined region of interest of the patient. For example, if respiratory motion is to be monitored, the patient's chest must be monitored, or if the patient's health condition is to be monitored, the patient's face must be monitored. To monitor the patient's region of interest during certain medical imaging procedures, such as CT or MR imaging procedures, the patient must be tracked in the provided monitoring images. Summary of the Invention [Problem to be solved by the invention]

[0005] One problem with tracking a patient's region of interest in a monitoring image is that as the patient is moved through the medical imaging device during a medical scan procedure, the shape and position of the region of interest change in the monitoring image during the imaging procedure due to changes in the monitoring camera's perspective relative to the region of interest. This makes purely image-based tracking of the region of interest to be monitored more difficult. Another problem with tracking a region of interest using a regular monitoring camera is the presence of occlusions, especially as the treatment couch moves through the bore. Therefore, it is very difficult to obtain a free, unoccluded view of the patient's face throughout the examination using a regular monitoring camera mounted on the wall of the scanning room, for example.

[0006] Typically, two or more surveillance cameras are mounted in the scanning room to capture both front and rear views of the scanner, for example, the cameras are mounted at an angle such that there is at least a partial view through the scanning system, e.g., through the bore of the CT scanner gantry.

[0007] Approaches where the camera is mounted on the wall or ceiling of a room can provide, at best, a partial view of the patient during the scan, with much of the anatomy likely to be occluded by the patient's own shape, the limited diameter of the bore through the scanning system, and the presence of positioning or medical devices.

[0008] Therefore, the surveillance system does not have a continuous view of the relevant body parts of the patient throughout the examination, especially as the patient support moves through the scanning system.

[0009] Mounting a camera on the front or rear end of the patient support has the advantage of providing a stable view of the patient while the patient support is moving. However, this option is undesirable because these portions of the patient support are used to position medical devices or head supports. Furthermore, with a heavy patient, the view to either the upper or lower part of the patient is most likely to be obstructed by the abdomen.

[0010] Therefore, there is a need for imaging systems that can better capture patient images during medical scans. These images can be subject to manual inspection to assess patient motion. However, in some cases, automatic patient motion detection can be used as input for image reconstruction algorithms and / or to drive the scanning process. It is also an important clinical input parameter for respiratory-gated and respiratory-triggered scans, such as lung scans and 4D CT scans used in CT simulation of radiation therapy.

[0011] One option is to place the camera on the scanning system, e.g., on the gantry facing the patient. The main challenge then is separating apparent motion due to horizontal displacement of the patient support, such as occurs during helical CT scans, from true patient motion. Because the patient is reclining, the patient motion typically has a significant anterior-posterior component. However, due to the projection geometry of the camera system, these two motions overlap in the final camera image, making motion extraction difficult.

[0012] Therefore, there is also a need for a motion sensing solution that accounts for different patient orientations and patient support positions.

[0013] WO 2021 / 110613 discloses a system and method for monitoring a patient during a medical scan, which uses a wide-field camera to capture images of the patient, and the location and shape of the region of interest are mapped while the patient support is moving.

[0014] EP 3 832 602 discloses an apparatus for monitoring a subject during imaging, in which a region of interest is determined using two monitoring units at different support positions and a position map based on a calibration object at a calibration support position. [Means for solving the problem]

[0015] The invention is defined by the claims.

[0016] According to an example in accordance with one aspect of the present invention, there is provided an imaging system for capturing images of a patient during a medical scan using a scanner having a scanning system and a patient support, the imaging system comprising: a set of one or more cameras for mounting in a fixed position relative to the scanning system directed towards the patient support to capture images, each camera of the set having an optical axis orthogonal to a direction of displacement of the patient support when the scanner is in use, and a row of pixels in an image captured by each camera corresponding to a position along an axis parallel to the direction of movement of the patient support; A processor, the processor comprising: performing image post-processing to correct distortions in the captured images due to width of field of view of the one or more cameras and to provide perspective correction; identifying patient motion based on image motion in the pixel column direction between successive captured images; outputting a measure of patient movement; a processor configured to execute An imaging system is provided, comprising:

[0017] This imaging system captures images in which movement of the patient support results in displacement along the pixel rows. This is orthogonal to typical patient motion, which, in the case of respiration, is primarily vertical. Therefore, this movement is along the pixel columns. This makes motion analysis simpler in that motion can be extracted simply from analyzing image changes in pixel columns; that is, patient motion is identified based on image movement of only pixel columns between successive captured images. In this way, the anterior-posterior component of patient motion, which is the main component of patient motion for recumbent examinations, can be optimally detected and quantified. Perspective correction accounts for the fact that the camera may not be oriented exactly perpendicular to the gantry's main axis (also the direction of table motion) due to inaccuracies in positioning and orientation. After perspective correction, the direction of table motion is exactly aligned with the desired axis (line) of the output image. By ensuring the correct orientation of the field of view of the output image, it is possible to quantify the detected motion along the pixel columns (vertical). If the field of view is not properly aligned, patient support movement will also result in small motion along the pixel columns, which should be avoided.

[0018] The processor is configured, for example, to identify at least one region of interest within the image and to identify patient motion relative to the at least one region of interest.

[0019] In this way, the movement of a particular region of the patient can be monitored, for example, a region that moves with breathing.

[0020] The processor may, for example, be further configured to track at least one region of interest on the patient during displacement of the patient support, so that the same region can be monitored over time to detect local motion.

[0021] The processor may be configured to perform the tracking.

[0022] It uses inputs indicative of patient support motion or is based on image-based feature identification and tracking.

[0023] Thus, tracking may be based on image processing or may use external patient support position information from the scanner.

[0024] The region of interest may for example include the abdomen, so that a respiratory motion signal can be derived from image processing.

[0025] The region of interest may include, for example, the region comprising the scan plane region of the imaging system, ie, the portion of the imaging system from which data is acquired for image formation.

[0026] At least one camera in the set is equipped with, for example, a fisheye lens with a field of view of more than 150 degrees, so the patient support (and the patient on the patient support) can be imaged by a small set of cameras, even a single camera.

[0027] The processor may further be configured to calculate the depth of the moving part relative to the camera. Based on the depth, the movement may be quantified, meaning that the physical amplitude and direction of the movement may be calculated. The spatial coordinates of points belonging to the moving part may be calculated. Furthermore, based on the depth, a 3D model may be calculated, if desired.

[0028] To calculate the depth map, principles known from stereo vision are applied: the inputs are two images acquired with the table at two different positions. The corresponding table displacement (e.g., a number in mm) is obtained from the scanning system and input. Since the perspective-corrected images are such that the table displacement is only along the lines of the image, the correspondence between the two images is found by calculating the horizontal shift between corresponding pixels. This is the disparity. Depth is calculated from the disparity using camera-specific parameters (e.g., focal length).

[0029] The processor may, for example, be further configured to determine the location and magnitude of local patient motion and to derive global motion from the local patient motion.

[0030] The processor may be configured to perform a calibration process that involves capturing one or more calibration images that allow distortion and perspective correction to be performed for analysis of motion of different patient regions at different positions within the field of view at different times.

[0031] Calibration is typically performed once after camera installation. It can be repeated as needed (e.g., after a service visit), but is not required every time movement is calculated.

[0032] The present invention also provides A scanning system; a patient support extending through the scanning system; a drive system for driving the patient support through the scanning system; an imaging system as defined above; A medical scanner including:

[0033] Each camera of the set is mounted on the scanning system, for example, with its optical axis oriented perpendicular to the direction of displacement of the patient support when the medical scanner is in use, and the pixel rows of the image captured by each camera correspond to positions along an axis parallel to the direction of movement of the patient support.

[0034] This provides the desired pixel row alignment with the scanner patient support motion axis, so that the pixel columns contain the associated patient motion information.

[0035] The present invention also provides an imaging processing method for processing images of a patient during a medical scan using a scanner having a scanning system, a patient support, and a set of one or more cameras mounted in a fixed position relative to the scanning system and directed towards the patient support, each camera of the set having an optical axis orthogonal to a direction of displacement of the patient support when the scanner is in use, the method comprising: receiving an image from one or more cameras of the set, wherein rows of pixels in the image correspond to positions along an axis parallel to a direction of movement of the patient support; performing image post-processing to correct distortions in the captured images due to the width of the field of view of the one or more cameras and to provide perspective correction; identifying patient motion based solely on image motion in the pixel column direction between successive captured images; outputting a measure of patient movement; The present invention provides a method comprising:

[0036] The method is: identifying at least one region of interest within the image; identifying patient movement relative to the at least one region of interest; It can have:

[0037] The region of interest may include, for example, the rib cage.

[0038] The method may also include performing a calibration process by capturing one or more calibration images.

[0039] Horizontal shifts are also calculated, for example, to obtain depth information and to quantify the movement (magnitude, orientation, and spatial coordinates).

[0040] The invention also provides a computer program comprising computer program code adapted to perform the above method when the program is run on a processor of an imaging system as defined above.

[0041] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0042] For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Brief explanation of the drawings]

[0043] [Figure 1] 1 illustrates a schematic diagram of an example medical scanner. [Figure 2] Three example images of a rectified image sequence are shown. [Figure 3] 1 shows a side view of a CT scanner with a single camera located on one side of the gantry. [Figure 4] 1 shows a side view of a CT scanner having two cameras, the first camera located on one side of the gantry and the second camera located on the opposite side of the gantry. [Figure 5] 1 shows two cameras positioned in the gantry bore with lateral positions. [Figure 6] 1 shows a pattern for use in the calibration stage. [Figure 7] 2 shows a second example of a medical scanner. [Figure 8] 1 shows a camera and its field of view to illustrate one design aspect of the scanner. [Figure 9] A series of images of a patient are shown, showing the region of interest as a block in the abdominal region. DETAILED DESCRIPTION OF THE INVENTION

[0044] The present invention will now be described with reference to the drawings.

[0045] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems, and methods, are for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the figures are schematic only and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.

[0046] The present invention provides an imaging system for capturing optical images of a patient during a medical scan. A set of one or more cameras captures images of the patient, after applying distortion and perspective correction steps, such that pixel rows correspond to positions along an axis parallel to the direction of patient support movement and pixel columns correspond to positions along an axis perpendicular to the direction of patient support movement. Patient motion of interest can then be identified based on image movement in the pixel column direction between successive captured images. A measure of patient motion can then be derived.

[0047] The present invention generally relates to the analysis of patient motion. Two aspects related to motion analysis are described below. The first aspect relates to the generation of a set of images that most easily allows motion to be visually inspected. The second aspect relates to the automatic derivation of a measure of patient movement, which can be used, for example, to trigger an imaging process.

[0048] The two aspects may be implemented separately or may be combined, and although both aspects are described below, the present invention is particularly directed to the second aspect.

[0049] 1 illustrates a schematic diagram of an example of a medical scanner 100 for obtaining medical images of a subject, the medical scanner further including an imaging system for capturing optical images of the subject during a medical scan. The images are generated for the purpose of determining patient motion.

[0050] The medical scanner 100 comprises a scanning system, such as a CT imaging system 140, adapted to acquire medical images, i.e., CT images in this example, of a patient 121 disposed on a patient support 120. The patient support 120 is adapted to move the patient 121 through the CT imaging system 140 during a CT imaging procedure. To this end, the medical scanner has a drive system 124 for driving the patient support through the scanning system.

[0051] The imaging system includes an optical camera 130 adapted to acquire monitoring images of the patient 121 during a CT imaging procedure, and a processor 150. While operation of the system with a single camera is described, there may be multiple cameras, as described further below. The camera may be a color or monochrome camera. Visible or infrared light may be used.

[0052] The camera 130 has a wide field of view so as to capture a full view of the patient support 120, or at least the portion of the patient support 120 where the patient's region of interest is located. Furthermore, the movement of the patient support 120 means that an even wider field of view is required so that the desired portion of the patient support remains within the field of view of the camera (which is statically attached to the scanning system) throughout the medical scan.

[0053] The camera may, for example, have a fisheye lens with a field of view of more than 150 degrees, such as 160 degrees or more. Thus, the patient support (and the patient on the patient support) may be imaged by a single camera, as shown, or by a small set of cameras.

[0054] Wide-angle lenses introduce image distortion such that the shapes of objects appear differently in different regions of the camera's field of view, and as a result, the shapes of objects or regions of interest change when the position of those objects or regions of interest changes within the camera's field of view as a result of patient support movement.

[0055] To address this issue, processor 150 performs image post-processing to correct distortions in the captured images, i.e., distortions resulting from the width of the camera's field of view, shown as post-processing unit 160. For the purposes of post-processing, the cameras are calibrated so that geometric distortions are corrected by post-processing, and the position and orientation of each camera relative to the scanner coordinate system is known.

[0056] According to a first aspect, the processor tracks at least one region of interest of the patient during displacement of the patient support. This is performed by the tracking unit 162. The (or each) region of interest is a body part to be monitored, such as the face, the area to be scanned, the area of ​​IV injection, or the hand. The location of the region of interest in the initial image can be defined manually or automatically by a suitable algorithm (e.g., using a keypoint detection algorithm) that locates a selected anatomical feature of interest.

[0057] The processor then generates a distortion-corrected image sequence of the (or each) region of interest, which is performed by image sequence generator 164.

[0058] The patient support motion is used for tracking and to generate the distortion-corrected image sequence. The patient support motion can be provided, for example, by the scanning system. Alternatively, tracking of the region of interest can be based on automated image-based detection and tracking algorithms.

[0059] The distortion-corrected image sequence is provided as output 170 for display on a display 180. This display 180 may be part of the medical scanner, or may be a separate device such as a technician's mobile device, or may be part of a remote operation center to which image data is transmitted by wired or wireless data transfer.

[0060] The output 170 comprises a continuous video stream. There may be video streams of one or more regions of interest.

[0061] Figure 2 shows an example of three images of an image sequence where the region of interest has been dewarped with the patient's face. There may be separate image sequences for separate regions of interest.

[0062] As shown, the camera (or each camera) is oriented towards the patient support and covers a wide range of views. The camera's position, orientation, and intrinsic parameters are obtained by a calibration step performed once during system installation. This calibration allows for the necessary image post-processing to be derived, which allows for tracking of the region of interest during displacement of the patient support.

[0063] The dewarped image sequence may be, for example, a zoomed-in crop of the overall dewarped camera image, providing successive views of the same anatomical structure.

[0064] As can be seen in Figure 2, despite the movement of the patient support relative to the camera, the region of interest remains stationary in the images cropped from the distortion-corrected image sequence. The region of interest moves within the distortion-corrected image as a result of table displacement. After tracking the region of interest, a cropped image is generated around the region of interest so that the body part within this region of interest appears static. Thus, the cropped distortion-corrected image sequence appears to have been obtained from a camera that moved with the patient support during the scan. However, the viewpoint changes because the region of interest is viewed from different directions as a result of the movement.

[0065] In the most basic version, perspective changes are tolerated since the motion occurring within the region of interest is still easily discernible.

[0066] More preferably, perspective is corrected by adapting the tilt of the output image to a three-dimensional representation of the scene, so that it has a specified viewing angle. Perspective correction provides fixation to a single z-plane (where z is the depth from the camera's viewpoint). Because the motion to be detected occurs within a larger area than this single plane, the overall perspective still changes. However, when perspective is corrected relative to a central plane, the perspective changes around it are minimized so that actual motion can still be detected.

[0067] In this way, the display output provides a way to accurately monitor the patient's position and activity during a medical scan, which has been particularly difficult during scans where the patient support is moving back and forth. The system ensures optimal image quality and safe examination conditions.

[0068] There are various options for camera placement. Figure 3 shows a side view of a CT scanner with a single camera 130 located on one side of a gantry 200 having an opening 202 through which the patient support 120 passes.

[0069] Camera 130 has a field of view wide enough along the length of the patient support to cover the entire length of the patient support, and wide enough across the width of the patient support to cover the entire width of the patient support, and the field of view covers the entire patient support over its range of motion (thus, patient support 120 is represented in FIG. 3 by the full range of positions it can adopt).

[0070] The camera field of view may instead cover only the areas of the patient support where the regions of interest are located, eg, the face and abdomen, but still include all positions of these areas of the patient support during displacement of the patient support.

[0071] FIG. 4 shows a side view of a medical scanner with two cameras, a first camera 130a located on one side of the gantry 200 and a second camera 130b located on the opposite side of the gantry, where the "sides" are at different positions along the patient support, i.e., one side facing the head end of the patient support and one side facing the foot end of the patient support.

[0072] There may also be multiple cameras, even at the same location along the patient support. Figure 5 shows two cameras 130c, 130d, which may be located within the gantry bore or on one side of the gantry. They face the patient support, but from the side, not directly above. As explained further below, this ensures that vertical movement is apparent in the image. For example, the cameras may be oriented 90 degrees relative to each other (in a plane perpendicular to the long axis of the patient support).

[0073] The cameras are therefore pointing to the side and above the patient.

[0074] As described above, a calibration process is used to derive post-processing requirements for correcting image distortion. One approach is to apply a known pattern to the patient support, such as the checkerboard pattern shown in FIG. 6. Image distortion, particularly noticeable at the edges of the field of view, can be corrected by deriving a correction function that returns captured images to a known "correct" image. By calibrating the camera with this checkerboard pattern and combining the calibration results with the respective positions of the patient support provided by the scanning system, regions of interest in one or more body parts can be tracked over time, even when the patient support is moving, as described above.

[0075] The second embodiment also uses a scanning system, calibration approach, and one or more cameras with a wide field of view, as described above.

[0076] FIG. 7 shows an example of a medical scanner according to the second embodiment.

[0077] 1, the medical scanner 300 includes a scanning system, such as a CT system 140, adapted to acquire CT images of a patient 121 positioned on a patient support 120. The patient support 120 is adapted to move the patient 121 through the CT imaging system 140 by a drive system 124.

[0078] The wide field camera 130 is adapted to acquire monitoring images of the patient 121 during the CT imaging procedure, and the processor 150 processes the images.

[0079] Processor 150 performs image post-processing, as described above, to correct for distortions in the captured image due to the width of the camera or the field of view of the camera. This is again performed by post-processing unit 160, and to enable post-processing, the same calibrations can be performed as described above.

[0080] In this embodiment, the motion detection unit 210 provides automatic identification of patient motion based on image motion.

[0081] A measurement 212 of patient movement is output by the system.

[0082] This aspect relies on the specific configuration of the camera(s) to simplify the automatic extraction of the motion signal.

[0083] 8 shows a camera 130 and its field of view 220. The camera has a central axis 222 that extends to the center of the field of view. This is the optical axis of the camera. This optical axis 222 is, for example, a vector that is perpendicular to the plane of the array of image sensing elements and projects from the center of the array of image sensing elements.

[0084] The optical axis 222 is perpendicular to the direction of displacement of the patient support when the scanner is in use, e.g., the length of the patient support in the form of a treatment couch. Furthermore, a row of pixels in the image captured by the camera corresponds to a position along an axis parallel to the direction of movement of the patient support. A line 224 across the field of view is mapped to a row of pixels in the generated image, and this line 224 in the field of view (e.g., when the camera is imaging an empty patient support) is parallel to the direction of displacement of the patient support, i.e., parallel to the length of the patient support.

[0085] This defines a particular orientation of the camera relative to the patient support, meaning that in a captured image of an empty patient support, pixel rows correspond to horizontal lines along the length of the patient support, and pixel columns include a vertical component.

[0086] Thus, motion can be measured automatically by analyzing the change in patient position in the pixel column direction, such as between successive captured images.

[0087] For this purpose, the cameras should not be directly overhead, as they will not capture vertical displacement. The configuration of Figure 5 may be used, for example, with two cameras capturing a partial side view of the patient, so that vertical patient movement results in a component of pixel column-wise movement in the captured image.

[0088] As mentioned above, there may be one or more cameras on only one side of the gantry, or there may be one or more cameras on each side of the gantry.

[0089] This imaging system thereby captures images in a direction orthogonal to typical patient motions such as breathing, primarily vertical, with the result that movement of the patient support results in displacements in the pixel rows.

[0090] As above, the processor can additionally identify at least one region of interest within the image or divide the image into blocks, and then identify patient motion for at least one region of interest or block. For each region of interest, the overall horizontal pixel shift induced by patient support motion between successive frames is corrected by using known patient support motion. The vertical motion component between successive regions of interest is then calculated as a measure of patient motion. The images can be processed in real time or retrospectively to detect patient motion between successive frames.

[0091] FIG. 7 shows a module 230 for tracking a region of interest.

[0092] Different algorithms can be applied to detect motion along pixel columns, such as optical flow algorithms or cross-correlation algorithms.

[0093] In this way, specific regions of the patient, such as regions that move with respiration, can be automatically monitored for movement. For respiration detection, the region of interest can include, for example, the abdomen. Thus, a respiration movement signal can be derived from image processing. The processor can track at least one region of interest on the patient during displacement of the patient support.

[0094] As explained above, tracking can use inputs indicative of patient support motion or can be based on image-based feature identification and tracking.

[0095] 9 shows a series of images of a patient, showing a region of interest 240 as a block in the abdominal region. A motion signal can be derived specifically for this region of interest and used for gating or triggering purposes, in known manner.

[0096] Based on the known horizontal shift between successive frames during couch displacement, an optional additional image processing step can be applied. This step creates a mapping from the 2D image to 3D (world) coordinates. In particular, the sequence of images is from different viewpoints relative to the patient, so that even a single camera can function as a time-multiplexed camera system. Therefore, 3D images can be generated based on the stereo principle. In this way, the position and size of moving subject parts can be calculated.

[0097] 3D modeling uses known table motion as a prerequisite. The assumption is that there is no motion in the x-axis (pixel row) direction, separate from the patient support motion. From the relationship between the pixel shift per pixel obtained from the motion detection algorithm and the true table motion (in mm), the relative size of the pixel in mm can be derived. Together with the camera focal length (known from the calibration step), this relative size can be converted into a value indicating the distance to the camera, which is equal to the depth. Since this calculation only uses the detected changes in pixel row direction, motion in pixel column direction does not directly affect 3D modeling. Therefore, patient motion between different images does not interfere with the generation of the 3D image.

[0098] As mentioned above, a calibration procedure is used. The output of the calibration process is a set of camera-specific parameters that describe the optical properties and dimensions of the sensor, such as focal length, optical center, and distortion coefficients. These parameters can be used as input for calculating an undistorted image. The calibration process also makes it possible to calculate the exact position and orientation of the camera relative to the scanner coordinate system, which is typically linked to the scanner's isocenter. This step is called calculating the camera's extrinsic parameters (orientation matrix) and makes it possible to correct for perspective effects.

[0099] Based on external parameters, the spatial coordinates of the moving part can be expressed in the scanner coordinate system, which in particular makes it possible to detect whether the movement is occurring in or near the scan plane.

[0100] Here, we describe a simplified method for calculating the physical amplitude of the motion. For each pixel, the lateral and vertical displacements between two images acquired at two consecutive time points are first calculated using means known from the state of the art, such as optical flow or cross-correlation. The horizontal shift is due to the table displacement. The vertical shift is due to the patient's movement (if any). The horizontal shift pixel amplitude depends on the depth of the corresponding part relative to the camera: the closer the part is to the camera, the larger the pixel shift. In other words, the horizontal shift amplitude, together with the value of the table displacement between the two images, provides the physical optical resolution of the camera at this position. This can therefore be used to calculate the physical amplitude of the vertical shift. This last step is obtained simply by dividing the vertical pixel shift by the horizontal pixel shift and multiplying this quotient by the table displacement in millimeters.

[0101] Based on the location and magnitude of patient motion in one or more regions of interest, an overall motion signal can be derived over the time of the scan, thus detecting significant patient motion. This calculated motion signal can then be used to inform the operator about patient motion either before or during the scan. It can be used to predict which slices of the imaged volume will be affected by motion. It can also be used as input for data reconstruction (e.g., gating or motion correction) and for 4D CT scans.

[0102] The present invention can be applied to any medical scanner in which the patient support moves during the imaging procedure, such as PET imaging devices, MR imaging devices, SPECT imaging devices, and the CT scanners mentioned above. The medical scanner can have a C-arm or closed bore. One or more cameras can be located within the bore, on the inner surface of the C-arm, or outside the bore or C-arm envelope. However, in all cases, the camera is static relative to the body of the scanning system, and therefore the patient support moves relative to the camera. The camera does not have to be directly attached to the medical scanner, but instead can be in a fixed position relative to the medical scanner by a separate attachment.

[0103] Although in the above-described embodiments the patient support is always the one on which the patient lies during acquisition of medical images, the patient support can also be configured for a sitting or standing patient.

[0104] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0105] The functions implemented by a processor may be implemented by a single processor or by multiple separate processing units, which may be considered to constitute a “processor.” Such processing units may possibly be remote from each other and may communicate with each other in wired or wireless manner.

[0106] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0107] The computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as over the Internet or other wired or wireless telecommunications systems.

[0108] It should be noted that when the term "adapted to" is used in the claims or description, it is intended to be equivalent to the term "configured for." When the term "apparatus" is used in the claims or description, it is intended to be equivalent to the term "system," and vice versa.

[0109] Any reference signs in the claims should not be construed as limiting the scope. The following describes embodiments of the present invention. (Appendix 1) 1. An imaging system for capturing images of a patient during a medical scan using a scanner having a scanning system and a patient support, the imaging system comprising: a set of one or more cameras for mounting in a fixed position relative to the scanning system directed towards the patient support to capture images, each camera of the set having an optical axis orthogonal to a direction of displacement of the patient support when the scanner is in use, and a row of pixels in an image captured by each camera corresponding to a position along an axis parallel to the direction of movement of the patient support; A processor, the processor comprising: performing image post-processing to correct distortions in the captured images due to width of field of view of the one or more cameras and to provide perspective correction; identifying patient motion based solely on image motion in the pixel column direction between successive captured images; outputting a measure of patient movement; a processor configured to execute An imaging system comprising: (Appendix 2) 10. The imaging system of claim 1, wherein each camera of the set of cameras faces the patient support from the side and from above. (Appendix 3) The processor: identifying at least one region of interest within the image; identifying patient motion relative to the at least one region of interest; tracking at least one region of interest on the patient during displacement of the patient support; 3. The imaging system of claim 1, configured to perform the following: (Appendix 4) The processor: using an input indicative of movement of the patient support; or Based on the image-based feature identification and tracking, 4. The imaging system of claim 3, configured to perform the tracking. (Appendix 5) 5. The imaging system of claim 3, wherein the region of interest comprises an abdomen. (Appendix 6) 6. The imaging system of any one of claims 1 to 5, wherein at least one camera of the set is equipped with a fisheye lens having a field of view greater than 150 degrees. (Appendix 7) 7. The imaging system of any one of claims 1 to 6, wherein the processor is further configured to calculate a depth of a moving part relative to the camera. (Appendix 8) The processor further comprises: determining the location and magnitude of local patient motion; deriving global motion from the local patient motion; 8. The imaging system of claim 1, configured to perform the following: (Appendix 9) 9. The imaging system of any one of claims 1 to 8, wherein the processor is configured to perform a calibration process including capturing one or more calibration images. (Appendix 10) 1. A medical scanner comprising: A scanning system; a patient support extending through the scanning system; a drive system for driving the patient support through the scanning system; An imaging system according to any one of Supplementary Notes 1 to 9; A medical scanner comprising: (Appendix 11) 11. The medical scanner of claim 10, wherein each camera of the set is mounted on the scanning system with an orientation such that the optical axis is perpendicular to a direction of displacement of the patient support when the medical scanner is in use, and a pixel row of an image captured by each camera corresponds to a position along an axis parallel to the direction of movement of the patient support. (Appendix 12) 1. An imaging processing method for processing images of a patient during a medical scan using a scanner having a scanning system, a patient support, and a set of one or more cameras mounted in a fixed position relative to the scanning system and directed towards the patient support, each camera of the set having an optical axis orthogonal to a direction of displacement of the patient support when the scanner is in use, the method comprising: receiving an image from one or more cameras of the set, wherein rows of pixels in the image correspond to positions along an axis parallel to a direction of movement of the patient support; performing image post-processing to correct distortions in the captured images due to the width of the field of view of the one or more cameras and to provide perspective correction; identifying patient motion based solely on image motion in the pixel column direction between successive captured images; outputting a measure of patient movement; A method comprising: (Appendix 13) identifying at least one region of interest within the image; identifying patient motion relative to the at least one region of interest; 13. The method of claim 12, comprising: (Appendix 14) 14. The method of claim 12 or 13, comprising performing a calibration process by capturing a calibration image. (Appendix 15) 15. A computer program having computer program code adapted to perform the method of any one of claims 12 to 14 when the program is run on a processor of an imaging system of any one of claims 1 to 9.

Claims

1. 1. An imaging system for capturing images of a patient during a medical scan using a scanner having a scanning system and a patient support, the imaging system comprising: a set of one or more cameras for mounting in a fixed position relative to the scanning system directed towards the patient support to capture images, each camera of the set having an optical axis orthogonal to a direction of displacement of the patient support when the scanner is in use, and a row of pixels in an image captured by each camera corresponding to a position along an axis parallel to the direction of movement of the patient support; A processor, the processor comprising: performing image post-processing to correct distortions in the captured images due to width of field of view of the one or more cameras and to provide perspective correction; identifying patient motion based solely on image motion in the pixel column direction between successive captured images; outputting a measure of patient movement; a processor configured to execute An imaging system comprising:

2. 10. The imaging system of claim 1, wherein each camera of the set of cameras faces the patient support from the side and from above.

3. The processor: identifying at least one region of interest within the image; identifying patient motion based on a location and magnitude of the patient motion in the at least one region of interest; tracking at least one region of interest on the patient during displacement of the patient support; The imaging system of claim 1 , configured to perform the following:

4. The processor may perform the tracking by: using an input indicative of movement of the patient support; or Based on the image-based feature identification and tracking, 4. The imaging system of claim 3 configured to perform:

5. The imaging system of claim 3 , wherein the region of interest comprises an abdomen.

6. 6. The imaging system of claim 1, wherein at least one camera of the set is equipped with a fisheye lens with a field of view greater than 150 degrees.

7. 6. The imaging system of claim 1, wherein the processor is further configured to calculate a depth of a moving part relative to the camera.

8. The processor further comprises: determining the location and magnitude of local patient motion; deriving global motion from the local patient motion; 6. The imaging system of claim 1, configured to perform the following:

9. 6. The imaging system of claim 1, wherein the processor is configured to perform a calibration process that includes capturing one or more calibration images.

10. 1. A medical scanner comprising: A scanning system; a patient support extending through the scanning system; a drive system for driving the patient support through the scanning system; The imaging system according to any one of claims 1 to 5; A medical scanner comprising:

11. 11. The medical scanner of claim 10, wherein each camera of the set is mounted on the scanning system with an orientation such that the optical axis is perpendicular to a direction of displacement of the patient support when the medical scanner is in use, and wherein pixel rows of an image captured by each camera correspond to positions along an axis parallel to the direction of movement of the patient support.

12. 1. An imaging processing method for processing images of a patient during a medical scan using a scanner having a scanning system, a patient support, and a set of one or more cameras mounted in a fixed position relative to the scanning system and directed towards the patient support, each camera of the set having an optical axis orthogonal to a direction of displacement of the patient support when the scanner is in use, the method comprising: receiving an image from one or more cameras of the set, wherein rows of pixels in the image correspond to positions along an axis parallel to a direction of movement of the patient support; performing image post-processing to correct distortions in the captured images due to the width of the field of view of the one or more cameras and to provide perspective correction; identifying patient motion based solely on image motion in the pixel column direction between successive captured images; outputting a measure of patient movement; A method comprising:

13. identifying at least one region of interest within the image; identifying patient motion relative to the at least one region of interest; 13. The method of claim 12, comprising:

14. The method of claim 12, comprising performing the calibration process by taking a calibration image.

15. A computer program having a computer program code adapted to perform the method of any one of claims 12 to 14 when the program is run on a processor of an imaging system according to any one of claims 1 to 5.

Images