Patient monitoring during scans

Abstract

An imaging system is used to capture an image of a patient during a medical scan. Image post-processing corrects distortion within images captured from one or more static cameras and tracks at least one region of interest of the patient during patient support displacement. A corresponding distortion-corrected image sequence of the region of interest is then output.

Description

Technical Field

[0001] The present invention relates to monitoring patients during medical scans and, in particular, to detecting motion. Background Art

[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, monitoring 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 respiration-related motion in order to prevent and correct motion artifacts, ensure optimal image quality, and support respiration-triggered scanning. In fact, unwanted patient motion is one of the main causes of image quality issues and safety events such as pinched fingers.

[0004] Furthermore, for these monitoring applications it is particularly important to monitor a predetermined region of interest of the patient. For example, if respiratory motion should be monitored, the patient's chest needs to be monitored, or if the patient's health should be monitored, the patient's face needs to be monitored. Since during certain medical imaging procedures (such as CT imaging procedures or MR imaging procedures) the patient may be moved through the imaging device for monitoring the patient's region of interest, this region of the patient needs to be tracked in the provided monitoring images.

[0005] One of the problems with tracking a patient's region of interest in a monitoring image as the patient is moved through a medical imaging device during a medical scanning procedure is that the shape and position of the region of interest in the monitoring image will change during the imaging procedure due to the changing viewing angle of the monitoring camera relative to the region of interest. This makes it more difficult to monitor the tracking of the region of interest based purely on the image. Another problem with tracking the region of interest using a conventional monitoring camera is that there is occlusion, especially because the couch is moving through the bore. Thus, for example, using a conventional monitoring camera mounted on the wall of the scanning room, it is very difficult to have an unobstructed view of the patient's face throughout the examination.

[0006] Typically, two or more surveillance cameras are installed in the scanning space to capture the front and rear views of the scanner. Figure 2 For example, the camera is mounted at an angle so that there is at least a partial view through the scanning system (e.g., through the bore of a CT scanner gantry).

[0007] In scenarios where the camera is mounted on a room wall or ceiling, only the best partial view of the patient is provided during scanning. Much of the anatomy may be obscured due to the patient's own size, the limited diameter of the bore through the scanning system, and the presence of positioning or medical equipment.

[0008] Therefore, the monitoring system is unable to provide a continuous view of the patient's body part of interest throughout the examination, particularly as the patient support travels through the scanning system.

[0009] Mounting the camera at the front or rear end of the patient support would have the advantage of providing a stable view of the patient when the patient support is moved. However, this option is undesirable because these parts of the patient support are used to position medical equipment or head supports. Furthermore, in the case of critically ill patients, the view of the upper or lower part of the patient will most likely be obscured by the abdomen.

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

[0011] One option is to place the camera on the scanning system, for example on a gantry facing the patient. In this case, the main challenge is to distinguish the apparent motion that occurs during spiral CT scanning due to the horizontal displacement of the patient support from the real patient motion. Since the patient is lying down, patient motion usually has a significant front-to-back motion component. However, due to the projection geometry of the camera system, these two motions overlap in the final camera image, making it difficult to extract the motion.

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

[0013] WO 2021 / 110613 discloses a system and method for monitoring a patient during a medical scan. It uses a wide field of view camera to capture images of the patient. The position and shape of the region of interest are mapped while the patient support is moved.

[0014] EP 3 832 602 discloses a device for monitoring an object during imaging. A region of interest is determined using two monitoring units at different support positions and based on a position map of a calibration object at a calibration support position.

[0015] US 2010 / 002071 discloses a system with a wide-angle field of view camera and data processing to perform correction of distortion in an image introduced by the wide-angle field of view camera. Summary of the invention

[0016] The invention is defined by the claims.

[0017] According to one aspect of the present invention, according to an example, there is provided an imaging system for capturing an image of a patient during a medical scan using a scanner having a scanning system and a patient support, the imaging system comprising:

[0018] a collection of one or more cameras mounted in a fixed position relative to the scanning system and directed toward a patient support to capture images;

[0019] A processor, wherein the processor is configured to:

[0020] performing image post-processing to correct distortion within the captured image caused by width of the field of view of the one or more cameras and perspective distortion;

[0021] tracking at least one region of interest of the patient during displacement of the patient support; and

[0022] generating a corresponding sequence of distortion corrected images of the or each region of interest; and

[0023] An output unit is used to output the distortion-corrected image sequence or each distortion-corrected image sequence of the or each region of interest for display.

[0024] The imaging system creates a distortion-corrected view of the patient's region of interest as the patient moves with the patient support. Static cameras are used (i.e., fixed relative to the scanning system, such as the scanner gantry). Thus, one or more cameras are close to the patient, and they generate intentionally distorted images to achieve a wide field of view so that the region of interest can be tracked. The position and orientation of each camera relative to the scanner coordinate system is known to enable post-processing.

[0025] For perspective correction, it is desirable to select a projection plane parallel to the direction of motion of the patient support. In this case, the apparent displacement of the patient support and the patient will be along the horizontal axis of the output image, thus emulating the illusion of traveling from left to right or right to left.

[0026] The precise inclination of the projection plane about the principal axis of motion of the patient support may be selected depending on the desired application. For example, a projection plane may be selected corresponding to a top view, which is of interest for monitoring the face. Alternatively, a projection plane may be selected corresponding to a side view.

[0027] The (or each) sequence of distortion corrected images preferably comprises an enlarged cropped image of a corresponding region of interest.

[0028] By tracking the region of interest, the part of the image intended to be viewed is located at a static position within the output image. This means that the region of interest can be easily inspected in the distortion corrected image sequence. The or each region of interest distortion corrected image sequence is a video stream of images containing the tracked region of interest cropped from the distortion corrected image. Therefore, to someone observing the cropped image stream, it looks like the camera is travelling with the table, as the body part in the region of interest no longer appears to be moving. The cropped image sequence appears to be from a static camera position, i.e. the images correspond to a static virtual camera position generated by distortion correction, tracking and sequence generation.

[0029] The set of at least one camera comprises a fisheye lens having a field of view greater than 150 degrees.Thus, a patient support (and a patient on the patient support) can be imaged by a small group of cameras, even with only a single camera.

[0030] The one or more regions of interest may include one or more of the following:

[0031] face;

[0032] Hands;

[0033] The thoracic cavity, including the diaphragm area (to visualize breathing movements);

[0034] the area of ​​the body to be scanned; and

[0035] The area of ​​the body where an IV is present.

[0036] The processor may be configured to perform tracing by:

[0037] Using input indicating movement of a patient support; or

[0038] Based on feature recognition and tracking based on images.

[0039] Thus, the tracking may be based on image processing, or it may use external patient support position information from a medical scanner.

[0040] The processor may be configured to perform a calibration process involving imaging a calibration image, for example mounted on a patient support.The calibration process enables the required distortion correction function to be derived.

[0041] The imaging system may further comprise a communications system for transmitting the or each sequence of distortion corrected images of the or each region of interest to a screen or a remote system.For example, the remote system may perform automatic image analysis.

[0042] The present invention also provides a medical scanner, comprising:

[0043] Scanning system;

[0044] a patient support extending through the scanning system;

[0045] a drive system for driving the patient support through the scanning system; and

[0046] The imaging system described above.

[0047] For example, the medical scanner includes a CT scanner, a PET scanner, or an MRI scanner.

[0048] The set of cameras of the imaging system may comprise a first camera, which is mounted above a patient support on one side of the scanning system, facing the patient support. The set of cameras may have only this single camera. For example, the camera is at the edge of an opening through the scanning system, in particular at the edge of the upper side of the scanning system. The camera is at least partially facing downwards. It may face vertically downwards, or it may be tilted relative to the vertical, for example giving a side view of the patient from above. It is desirable that the camera looks orthogonally to the table, i.e. the optical axis of the camera is perpendicular to the direction of movement of the table. This is not necessary, but facilitates distortion correction.

[0049] Alternatively, the set of cameras of the imaging system may also include a second camera mounted above the patient support at the opposite side of the scanning system, facing the patient support. Likewise, the second camera may be located at the edge of an opening through the scanning system, in particular the upper side of the scanning system. The use of two cameras (one in front and one in the back) enables an increased combined field of view (or equivalently enables the use of a smaller field of view). The use of two (or more) cameras also enables an unobstructed view of the patient, regardless of the table position, as the front or rear camera will have a direct line of sight to the patient, in particular to the face.

[0050] When no patient is present, the set of cameras preferably captures in its combined field of view all parts of the patient support that are to support one or more of the regions of interest of the patient in all patient support positions. This enables tracking of the one or more regions of interest throughout the patient support range of motion.

[0051] The present invention also provides an image processing method for processing an image 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 facing the patient support, the method comprising:

[0052] performing image post-processing to correct distortion within images captured by the set of cameras caused by width of the field of view of the one or more cameras and perspective distortion;

[0053] tracking the at least one region of interest of the patient during displacement of a patient support;

[0054] generating a corresponding sequence of distortion corrected images of the or each region of interest; and

[0055] The distortion-corrected image sequence is output for display.

[0056] The method may further include performing tracking using input indicative of patient support motion or image-based feature recognition and tracking.The method may further include performing a calibration process by imaging one or more calibration images.

[0057] The present invention also provides a computer program, comprising computer program code, wherein the computer program code is configured to implement the above method when the program is run on a processor of the imaging system defined above.

[0058] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] For a better understanding of the invention, and to more clearly show how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0060] Figure 1 An example of a medical scanner is schematically shown;

[0061] Figure 2 An example of three images of a distortion-corrected image sequence is shown;

[0062] Figure 3 shows a side view of a CT scanner having a single camera located on one side of the gantry;

[0063] Figure 4 A side view of a CT scanner having two cameras is shown; a first camera located on one side of the gantry and a second camera located on an opposite side of the gantry;

[0064] Figure 5 Two cameras are shown located within the bore of the frame having a transverse position;

[0065] Figure 6 The pattern used for the calibration phase is shown;

[0066] Figure 7 A second example of a medical scanner is shown;

[0067] Figure 8 The cameras and their fields of view are shown to explain Figure 8 a design aspect of a scanner; and

[0068] Fig. 9 A sequence of images of a patient is shown, and a region of interest is shown as a block at the abdominal region. DETAILED DESCRIPTION

[0069] The present invention will be described with reference to the accompanying drawings.

[0070] It should be understood that the detailed description and specific examples are intended for illustrative purposes only while indicating exemplary embodiments of the device, system and method, and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the device, system and method of the present invention will be better understood through the following description, the appended claims and the accompanying drawings. It should be understood that the drawings are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to indicate the same or similar components.

[0071] The present invention provides an imaging system for capturing optical images of a patient during a medical scan. Image post-processing corrects distortion within the images captured from one or more static cameras and tracks at least one region of interest of the patient during displacement of a patient support. A corresponding sequence of distortion-corrected images of the region of interest is then output.

[0072] The present invention generally relates to the analysis of the movement of a patient. Two aspects related to the analysis of movement are described below. The first aspect relates to generating a set of images that most easily allow visual inspection of movement. The second aspect relates to automatically deriving a measure of the amount of movement of the patient, and this can be used to trigger an imaging process, for example.

[0073] These two aspects can be implemented separately or in combination.Although these two aspects are described below, the present invention is particularly related to the first aspect.

[0074] Figure 1 An example of a medical scanner 100 for acquiring medical images of an object is schematically shown and additionally comprises an imaging system for capturing optical images of a patient during a medical scan. The images are generated for the purpose of determining patient motion.

[0075] The medical scanner 100 comprises a scanning system, such as a CT imaging system 140, which is adapted to acquire medical images, i.e. CT images in this example, 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 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.

[0076] The imaging system comprises an optical camera 130 and a processor 150, the optical camera 130 being adapted to acquire monitoring images of the patient 121 during a CT imaging procedure. The operation of the system will be explained with a single camera, but there may also be multiple cameras, as further explained below. The camera may be a color or monochrome camera. It may use visible light or infrared light.

[0077] The camera 130 has a wide field of view so that it captures a complete view of the patient support 120 or at least the portion of the patient support 120 on which the region of interest of the patient is to be positioned. Furthermore, the movement of the patient support 120 means that a wider field of view is required so that the desired portion of the patient support remains in the field of view of the camera (which is statically mounted to the scanning system) throughout the medical scan.

[0078] For example, the camera includes a fisheye lens having a field of view greater than 150 degrees (e.g., 160 degrees or greater).Thus, the patient support (and the patient on the patient support) can be imaged by a single camera as shown or by a small collection of cameras.

[0079] Wide angle lenses cause image distortions, causing the shapes of objects to appear differently at different regions of the camera's field of view. Thus, as the positions of objects or regions of interest change in the camera's field of view due to movement of the patient support, the shapes of those objects or regions of interest will change.

[0080] To address this issue, the processor 150 performs image post-processing to correct for those distortions within the captured image (i.e., caused by the width of the camera's field of view). This is shown as a 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.

[0081] 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 achieved by a tracking unit 162. The (or each) region of interest is a body part to be monitored, such as a face, an area to be scanned, an area for IV injection, or a hand. The position of the region of interest in the initial image may be defined manually or automatically by an appropriate algorithm (e.g., using a keypoint detection algorithm) that locates selected anatomical features of interest.

[0082] The processor then generates a sequence of distortion corrected images of the (or each) region of interest. This is achieved by an image sequence generator 164.

[0083] The movement of the patient support is used for tracking and for generating a distortion corrected image sequence. For example, the movement of the patient support is provided by a scanning system. Alternatively, the tracking of the region of interest may be based on an automatic image-based detection and tracking algorithm.

[0084] The distortion corrected image sequence is provided as output 170 for display on a display 180. The display 180 may be part of the medical scanner, or it may be a separate device, such as a technician's mobile device, or it may be part of a remote operation center to which the image data is transmitted by wired or wireless data transmission.

[0085] The output 170 comprises a continuous video stream. There may be one or more video streams of a region of interest.

[0086] Figure 2 An example of three images of a distortion corrected image sequence is shown, wherein the region of interest is the face of a patient. There may be separate image sequences for separate regions of interest.

[0087] As shown, the camera (or each camera) is oriented towards the patient support and covers a wide range of views. The position, orientation and intrinsic parameters of the camera are obtained by a calibration step performed once when the system is installed. This calibration enables the required image post-processing to be derived, which in turn enables tracking of the region of interest during displacement of the patient support.

[0088] For example, the distortion corrected image sequence is an enlarged crop of the full distortion corrected camera image and it provides consecutive views of the same anatomical structure.

[0089] As in Figure 2, although the patient support moves relative to the camera, the region of interest is located at a static position within the image cropped from the distortion corrected image sequence. Due to the table displacement, the region of interest moves within the distortion corrected image. After tracking the region of interest, a cropped image around the region of interest is generated so that the body part within the region of interest appears to be static. Therefore, it appears that the cropped distortion corrected image sequence has been obtained from a camera that has traveled with the patient support during the scan. However, the viewing angle will change because the region of interest is viewed from different directions due to the movement.

[0090] In the most basic version, perspective changes are tolerated since movement occurring within the region of interest will still be easily discernible.

[0091] More preferably, the perspective is corrected by adapting the tilt of the output image in three dimensions so that it has a specified viewing angle of the scene. The perspective correction provides a fix for a single z-plane (where z is the depth from the camera viewpoint). Since the motion to be detected occurs in an area wider than a single plane, the overall perspective still changes. When the perspective is corrected relative to a central plane, the perspective changes around it are anyway reduced to a minimum so that actual movement can still be detected.

[0092] In this way, the display output provides a way to accurately monitor the position and movement of a patient during a medical scan, which was previously difficult during scans where the patient support moves back and forth. The system ensures optimal image quality and safe examination conditions.

[0093] There are various options for camera placement. Figure 3 A side view of a CT scanner is shown with a single camera 130 located on one side of a gantry 200 having an opening 202 through which a patient support 120 extends.

[0094] The camera 130 has a field of view that is wide enough in the length direction of the patient support to cover the entire length of the patient support, and wide enough in the width direction of the patient support to cover the entire width of the patient support. In addition, the field of view covers the entire patient support over its range of motion (thus, the patient support 120 is Figure 3 represented by the full range of positions it can adopt).

[0095] Alternatively, the camera field of view may cover only the areas of the patient support where the areas of interest (eg, face and abdomen) will be located, but also include all positions of those areas of the patient support during displacement of the patient support.

[0096] Figure 4A side view of a medical scanner with two cameras is shown; a first camera 130a located on one side of a gantry 200 and a second camera 130b located on an opposite side of the gantry, where the "sides" are at different locations along a patient support, i.e., one side faces the leading end of the patient support, and one side faces the trailing end of the patient support.

[0097] There may be multiple cameras even at the same location along the patient support. Figure 5 Two cameras 130c, 130d are shown, which may be located within the bore of the gantry, or on one side of the gantry. However, they face the patient support from the outside, rather than from directly above. As explained further below, this ensures that vertical motion in the image is apparent. For example, the cameras may be oriented at 90 degrees relative to each other (in a plane perpendicular to the long axis of the patient support).

[0098] As described above, a calibration process is used to derive post-processing requirements to correct for image distortion. One approach is to apply a known pattern to a patient support, such as Figure 6 The checkerboard pattern shown. Image distortions that are particularly prominent at the edges of the field of view can be corrected to derive a correction function that returns the captured image to a known "correct" image. By calibrating the camera using this checkerboard pattern, and combining the calibration results with the corresponding position of the patient support provided by the scanning system, a region of interest for one or more body parts can be tracked over time, even when the patient support moves, as described above.

[0099] The second aspect also uses a scanning system, calibration method and one or more cameras with a wide field of view as described above.

[0100] Figure 7 An example of a medical scanner according to the second aspect is shown.

[0101] As in Figure 1 In the present invention, the medical scanner 300 includes a scanning system, such as a CT system 140, which is 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.

[0102] Wide field of view camera 130 is adapted to acquire monitoring images of patient 121 during a CT imaging procedure, and processor 150 processes the images.

[0103] The processor 150 performs image post-processing to correct for distortion within the captured image caused by the width of the field of view of the camera or cameras, as discussed above. This is also accomplished by the post-processing unit 160, and the same calibration may be performed as described above to accomplish post-processing.

[0104] In this regard, there is automatic recognition of patient motion based on image movement by the motion detection unit 210 .

[0105] A measure 212 of patient motion is output by the system.

[0106] This aspect relies on a specific configuration of the camera(s) to simplify the automatic extraction of motion signals.

[0107] Figure 8 A camera 130 and its field of view 220 are shown. The camera has a central axis 222 extending to the center of the field of view. This is the optical axis of the camera. For example, the optical axis 222 is a vector normal to the plane of the image sensing element array and projected from the center of the imaging sensing element array.

[0108] In use of the scanner, the optical axis 222 is orthogonal to the direction of displacement of the patient support, for example, the length of a patient support in the form of a couch. Furthermore, the pixel rows of the image captured by the camera correspond to positions along an axis parallel to the direction of movement of the patient support. Lines 224 across the field of view are mapped to pixel rows in the generated image, and such lines 224 within the field of view (for example, when the camera is imaging an empty patient support) are parallel to the direction of displacement of the patient support, i.e., parallel to the length of the patient support.

[0109] This defines a specific orientation of the camera relative to the patient support. This means that in a captured image of an empty patient support, the rows of pixels correspond to horizontal lines along the length of the patient support, while the columns of pixels comprise a vertical component.

[0110] Thus, movement may be automatically measured by analyzing changes in the patient's position in the direction of the pixel columns, such as between sequentially captured images.

[0111] For this purpose, the camera should not be directly overhead, as it would not capture vertical displacements. For example, Figure 5 An arrangement whereby the two cameras capture a partial lateral view of the patient such that vertical patient movement will result in a movement component in the pixel column direction of the captured images.

[0112] As described above, there may be one or more cameras on only one side of the rack, or there may be one or more cameras on each side of the rack.

[0113] Thus, the imaging system captures images in which patient support movements result in displacements in the direction of the pixel rows, while typical patient movements (such as breathing) are in orthogonal directions, primarily the vertical direction.

[0114] In the same manner as described above, the processor may additionally identify at least one region of interest within the image or divide the image into tiles, and then identify patient motion for the at least one region of interest or tile. For each region of interest, the global horizontal pixel shift caused by the patient support motion between consecutive frames is corrected by using the known patient support motion. The vertical motion component between consecutive regions of interest is then calculated as a measure of patient motion. The images may be processed in real time or retrospectively to detect patient motion between consecutive frames.

[0115] Figure 7 A module 230 for tracking a region of interest is shown.

[0116] Different algorithms can be applied to detect movement in the direction of pixel columns, such as an optical flow algorithm or a cross-correlation algorithm.

[0117] In this way, the movement of a specific area of ​​the patient, such as an area that moves with breathing, is automatically monitored. For breathing detection, for example, one or more regions of interest include the abdomen. Thus, a respiratory motion signal can be derived from the image processing. The processor can track at least one region of interest of the patient during displacement of the patient support.

[0118] As described above, tracking may use input indicative of movement of the patient support or it may be based on feature recognition and tracking from images.

[0119] Fig. 9 A sequence of images of a patient is shown and a region of interest 240 is shown as a block at the abdominal region. A motion signal is derived specifically for this region of interest and can be used for gating or triggering purposes in a known manner.

[0120] Based on the known horizontal offset between consecutive frames during couch displacement, an optional additional image processing step can be applied. This step creates a mapping from 2D images to 3D (world) coordinates. In particular, the image sequences are from different viewpoints relative to the patient, so that even a single camera can perform as a multi-camera system over time. Thus, 3D images can be generated based on the stereo principle. In this way, the position and amplitude of the moving object parts can be calculated.

[0121] 3D modeling uses known table movement as a prerequisite. The assumption is that there is no movement in the x-axis (pixel row) direction that is separate from the patient support movement. According to the relationship between the pixel offset for each single pixel obtained from the motion detection algorithm and the real movement of the table (in mm), the relative size of the pixel in mm can be derived. Together with the focal length of the camera (which is 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 the calculation only uses the changes in the direction of the detected pixel row, the movement in the direction of the pixel column has no direct effect on the 3D modeling. Therefore, the movement of the patient between different images does not hinder the generation of 3D images.

[0122] As described above, a calibration process is used. The output of the calibration process is a set of camera intrinsic parameters, which describe the optical properties and length of the sensor, such as focal length, optical center and distortion coefficients. These parameters can then be used as input to calculate the distortion-free image. The calibration process also allows the calculation of the exact position and orientation of the camera relative to the scanner coordinate system, which is usually linked to the isocenter of the scanner. This step is called calculating the extrinsic parameters of the camera (pose matrix) and allows correction of perspective effects.

[0123] Based on the external parameters, the spatial coordinates of the moving part can be expressed in the scanner coordinate system. In particular, this allows detecting whether the movement occurs at or near the scanning plane.

[0124] A simplified way of calculating the physical magnitude of the motion is described here. For each pixel, the horizontal and vertical offsets between two images acquired at two consecutive time points are first calculated using means known from the prior art (such as optical flow or cross-correlation). The horizontal offset is due to the table displacement. The vertical offset is due to patient motion, if any. The amplitude in the pixel of the horizontal offset depends on the depth of the corresponding part relative to the camera: the closer the part is to the camera, the larger the pixel offset will be. In other words, together with the value of the table displacement between the two images, the amplitude of the horizontal offset provides the physical optical resolution of the camera at that position. Therefore, it can be used to calculate the physical amplitude of the vertical offset. This last step is obtained simply by dividing the vertical pixel offset by the horizontal pixel offset and multiplying the quotient by the table displacement (in millimeters).

[0125] Based on the position and magnitude of patient movement in one or more regions of interest, an overall motion signal can be derived for the time of the scan, and thus significant patient motion can be detected. This calculated motion signal can then be used to inform the operator about patient motion 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 reconstruction data (e.g., gating or motion correction) and for 4D CT scans.

[0126] The present invention can be applied to any medical scanner in which a patient support moves during the imaging process, such as a PET imaging device, an MR imaging device, a SPECT imaging device, and a CT scanner as described above. The medical scanner may include a C-arm or a closed bore. One or more cameras may be located within the bore or the inner surface of the C-arm, or outside the bore or C-arm housing. 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 may not be mounted directly to the medical scanner, but may instead be in a fixed position relative to the medical scanner by a separate mounting.

[0127] Although in the above-described embodiments the patient support is always a patient support on which the patient lies during acquisition of medical images, the patient support may also be configured for a sitting or standing patient.

[0128] Variations of the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed invention, based on a study of the drawings, the present 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.

[0129] The functions implemented by a processor may be implemented by a single processor or by multiple separate processing units, which may be collectively considered to constitute a “processor.” In some cases, such processing units may be remote from each other and communicate with each other in a wired or wireless manner.

[0130] 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.

[0131] The computer program may be stored / distributed on suitable media such as optical storage media or solid-state media supplied together with or as part of other hardware, but may also be distributed in other forms such as via the Internet or other wired or wireless telecommunications systems.

[0132] If the term "suitable for" is used in the claims or description, it should be noted that the term "suitable for" is intended to be equivalent to the term "configured to". If the term "arranged" is used in the claims or description, it should be noted that the term "arranged" is intended to be equivalent to the term "system" and vice versa.

[0133] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. An imaging system for capturing an image of a patient during a medical scan using a scanner having a scanning system (140) and a patient support (120), the imaging system comprising: a collection of one or more optical cameras (130) mounted in a fixed position relative to the scanning system, facing the patient support, to capture images; as well as The processor (150) is characterized in that the processor is configured to: performing image post-processing to correct distortion within the captured images caused by width of the field of view of the one or more cameras and perspective distortion; tracking at least one region of interest of the patient during displacement of a patient support; and generating a corresponding sequence of distortion-corrected images of the or each region of interest; and Characterized in that the imaging system further comprises an output unit, which is used to output the distortion-corrected image sequence or each distortion-corrected image sequence of the region of interest or each region of interest for display.

2. The imaging system according to claim 1, wherein: At least one camera of the set includes a fisheye lens having a field of view greater than 150 degrees.

3. The imaging system according to any one of claims 1 to 2, wherein: The one or more regions of interest include one or more of the following: face; Hands; the thoracic cavity, including the diaphragm area; The body area to be scanned; The area of ​​the body where an IV is present.

4. The imaging system according to any one of claims 1 to 3, wherein: The processor (150) is configured to perform the tracking by: Using input indicating movement of a patient support; or Based on feature recognition and tracking based on images.

5. The imaging system according to any one of claims 1 to 4, wherein: The processor (150) is configured to perform a calibration process involving imaging one or more calibration images.

6. An imaging system according to any one of claims 1 to 5, comprising a communication system for transmitting the sequence of distortion corrected images of the or each region of interest to a screen or a remote system.

7. A medical scanner comprising: Scanning system (140); a patient support (120) extending through the scanning system; a drive system (124) for driving the patient support through the scanning system; and An imaging system according to any one of claims 1 to 6.

8. The medical scanner of claim 7, wherein: The set of cameras of the imaging system comprises: a first camera mounted above the patient support on one side of the scanning system, facing the patient support; and optionally, A second camera is mounted above the patient support on an opposite side of the scanning system, facing the patient support.

9. The medical scanner according to claim 7 or 8, wherein: When no patient is present, the set of cameras captures in their combined field of view all portions of the patient support that are to support one or more of the regions of interest of the patient in all patient support positions.

10. An imaging processing method for processing an image of a patient during a medical scan using a scanner having a scanning system, a patient support and a collection of one or more cameras, the collection of one or more cameras being mounted in a fixed position relative to the scanning system, facing the patient support, characterized in that The method comprises: performing image post-processing to correct distortion within said images captured by said set of cameras caused by width of the field of view of said one or more cameras and perspective distortion; tracking at least one region of interest of the patient during displacement of a patient support; generating a corresponding sequence of distortion corrected images of the or each region of interest; and The distortion-corrected image sequence is output for display.

11. The method of claim 10, comprising performing the tracking using input indicative of movement of the patient support or based on feature recognition and tracking from images.

12. A computer program comprising computer program code configured to implement the method according to any of claims 10-11 when said program is run on the processor of the imaging system according to any of claims 1-7.

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