Apparatus, method and computer program for monitoring a subject during a medical imaging procedure

Abstract

The invention relates to an apparatus for monitoring an object 121 during an imaging procedure, e.g. CT imaging. The apparatus 110 comprises a monitoring image providing unit 111 providing a first monitoring image and a second monitoring image acquired at different support positions, a monitoring position providing unit 112 providing a first monitoring position of a region of interest in the first monitoring image, a support position providing unit 113 providing support position data of support positions, a position map providing unit 114 providing a position map mapping calibration support positions to calibration monitoring positions, and a region of interest position determining unit 115 determining a position of the region of interest in the second monitoring image based on the first monitoring position, the support position data and the position map. This allows determining the position of the region of interest in an accurate and low computational effort manner.

Description

Technical Field

[0001] This invention relates to apparatus, methods, and computer programs for monitoring a subject during a medical imaging procedure. Additionally, this invention relates to systems for acquiring medical images of a subject and including the aforementioned apparatus, as well as apparatus for providing a location map for use in the apparatus. Background Technology

[0002] In many medical imaging procedures, it is important to monitor the patient during the procedure, for example, to monitor patient movement or health status, using monitoring images (e.g., video images provided by a camera, such as a wide-field-of-view camera). Furthermore, for these monitoring applications, monitoring a predetermined region of interest (ROI) on the patient is particularly important. For example, if respiratory movements are to be monitored, the patient's chest must be monitored, or if health status is to be monitored, the patient's face must be monitored. Since the patient may be moved through the imaging equipment during some medical imaging procedures (e.g., CT or MR procedures) to monitor the patient's RIO, this region must be tracked in the provided monitoring images. One problem with tracking the RIO in monitoring images when the patient is moved through the medical imaging equipment during the procedure is that the shape of the RIO changes due to changes in the viewing angle of the monitoring camera relative to the RIO during the imaging process. This makes methods that rely solely on images for tracking the RIO to be monitored during the medical imaging procedure rigid.

[0003] US 2008 / 095416 discloses a marking system in which a marker is moved from a first predetermined position to a second predetermined position. This marking system is used to determine the position of a camera in a multi-camera system. The first camera is selected as a reference position based on its local coordinate system, and the position and orientation of another camera are based on this reference position.

[0004] US 2011 / 154569 discloses a mobile patient support system. A positioning system is used to determine the actual location of the patient support relative to a multidimensional coordinate system. Summary of the Invention

[0005] The object of the present invention is to provide an apparatus, an imaging system, a method, and a computer program that allow for the accurate and cost-effective monitoring of regions of interest of a subject during the acquisition of medical images.

[0006] This invention is defined by the claims.

[0007] In a first aspect of the invention, an apparatus is provided for monitoring an object during a medical imaging procedure using a medical imaging device, wherein the imaging device includes a support for supporting and moving the object during the imaging procedure, wherein the apparatus includes: a) a monitoring image providing unit for providing monitoring images of the object, the monitoring images including a first monitoring image and a second monitoring image of the object, wherein the first monitoring image is acquired at a first support location and the second monitoring image is acquired at a second support location; b) a monitoring position providing unit for providing a first monitoring position and shape, the first monitoring position and shape indicating... The region of interest is defined as follows: c) a support location providing unit, which provides support location data indicating the location of the second support; d) a location mapping unit, which provides a location mapping, wherein the location mapping provides a mapping between the calibration support location and the calibration monitoring location, wherein the calibration monitoring location indicates the location of the calibration target in the calibration monitoring image acquired at the corresponding calibration support location; e) a region of interest location determining unit, which determines the location and shape of the region of interest in the second monitoring image based on the first monitoring location and shape, the support location data, and the location mapping.

[0008] Since the region of interest (ROI) location determination unit is adapted to determine the location of the ROI in the second monitoring image based on a first monitoring position, support position data indicating the location of the support in the second monitoring image where the acquired object is located, and a location mapping map that maps the calibrated support position to the calibrated monitoring position, information about the location of the support in the second monitoring image can be taken into account for tracking the ROI in the second monitoring image. This provides a computationally efficient method for accurately tracking the ROI during object monitoring. Furthermore, since the location mapping map is used to determine the ROI in the second monitoring image, the location can be determined in a computationally efficient manner. Therefore, the location of the ROI in the second monitoring image can be determined accurately and with low computational workload.

[0009] This device is suitable for monitoring a subject during a medical imaging procedure using a medical imaging device. The medical imaging device can be, for example, a CT system, an MR imaging system, a PET system, etc. The imaging device includes a support (e.g., a patient table) for supporting and moving the subject during the imaging procedure. Preferably, during the imaging procedure, the subject is moved by the support through the medical imaging device (e.g., through the chamber of the imaging device). Alternatively, the support can also be adapted to move the subject relative to an open-type medical imaging device (e.g., a C-arm CT system). The support can be an integral part of the imaging device or an optional part that can be attached to or detached from the imaging device. The subject being imaged by the medical imaging device can be an animal or a human. Preferably, the subject is a human patient.

[0010] The monitoring image providing unit is adapted to provide monitoring images of an object. The monitoring image providing unit can be a storage unit on which monitoring images are stored and can be retrieved. Furthermore, the monitoring image providing unit can be a retrieval unit for retrieving monitoring images, for example, from a monitoring camera adapted to provide monitoring images. Preferably, the same monitoring camera is used to acquire all monitoring images, particularly the same monitoring camera for acquiring a first monitoring image and a second monitoring image. The monitoring camera can be provided as part of an imaging device and positioned, for example, within the chamber of the imaging device; alternatively, the monitoring camera can be separated from the imaging device and positioned, for example, in a corner of a room including the imaging device. In an alternative embodiment, multiple different cameras can be used to acquire monitoring images of the object. In one embodiment, a first camera can be provided at a first position relative to a medical imaging device, and the first camera provides monitoring images for multiple first support positions, and a second camera can be provided at a second position relative to the medical imaging device, and the second camera provides monitoring images for multiple second support positions. Typically, different cameras can be used to provide monitoring images for different support positions.

[0011] The monitoring images include a first monitoring image and a second monitoring image. Additionally, the monitoring images can include extra monitoring images for the same support location or other support locations. Any monitoring image provided by the monitoring image providing unit can be defined as the first monitoring image; therefore, any location of the support during the imaging process can also be defined as the first support location. Preferably, the first support location where the first monitoring image is acquired refers to a general starting location of the support for the medical imaging process. For example, the first support location can refer to the location of the support used to prepare the patient for the medical imaging process. Alternatively, the first support location can refer to a first location of the support that allows the acquisition of a monitoring image of the patient's region of interest, or it can refer to the support location where medical image acquisition begins. The first support location can also be defined, for example, as the last location of the support during medical image acquisition, or a middle location of the support during medical image acquisition, etc. Any monitoring image provided by the monitoring image providing unit that is not defined as the first monitoring image can be defined as the second monitoring image, such that any location of the support where the defined second monitoring image is acquired can be defined as the second support location. Preferably, if the first support position refers to the starting position of the support at the start of medical imaging, then the second support position can be any of the other positions assumed for the support during the medical imaging process for which monitoring images have been acquired.

[0012] A monitoring location providing unit is adapted to provide a first monitoring location, wherein the first monitoring location indicates the position of a region of interest (ROI) in a first monitoring image. The monitoring location providing unit can be a storage unit on which the first monitoring location is stored and can be retrieved. Furthermore, the monitoring location providing unit can be a retrieval unit for retrieving the first monitoring location, for example, from a user interface on which a user of the medical device can indicate the position of the ROI in the first monitoring image. The first monitoring location can be, for example, a point in the first monitoring image located in the center of the ROI. Moreover, the first monitoring location can be defined by the boundaries surrounding the ROI. For example, if the ROI is a patient's chest, the user interface can provide the user of the medical device with the first monitoring image, where the user then draws the patient's chest in the first monitoring image. In this example, the first monitoring location can be a point in the center of the drawn ROI. However, in other examples, the first monitoring location can also refer to a point on the outline of the drawn ROI, for example, a point at a corner of the drawn ROI. Preferably, the monitoring location providing unit is adapted to provide more than one first monitoring location, wherein the more than one first monitoring location can correspond, for example, to different locations along the boundary of the region of interest, or to different corners of the bounding box surrounding the region of interest.

[0013] The monitoring location providing unit can also be adapted to automatically determine a first monitoring location based on predefined characteristics of the region of interest (ROI). For example, if a patient's face needs to be monitored, the monitoring location providing unit can be adjusted to use a facial recognition algorithm to provide the location of the object's face in a first monitoring image as the first monitoring location. Furthermore, if the movement of a patient's ROI (e.g., respiratory movement in the patient's chest region) needs to be monitored, the monitoring image providing unit can be adjusted to provide multiple first monitoring images, each of which is acquired at the same support location. In this embodiment, the monitoring location providing unit can be adjusted to search for movement in multiple first monitoring images and determine the ROI based on the movement detected in the multiple first monitoring images. Furthermore, the ROI can also be determined based on predefined characteristics of the movement detected at a specific movement frequency, amplitude, or sequence. The monitoring location providing unit can then be adjusted to provide the location of the thus determined ROI as the first monitoring location.

[0014] The support position providing unit is adapted to provide support position data indicating the position of a second support. The support position providing unit can be a storage unit where support position data is already stored and can be retrieved. Furthermore, the support position providing unit can be a receiving unit for receiving support position data, for example, from a position sensor adapted to acquire the position of the support during an image acquisition process. The support position can be acquired, for example, in a world coordinate system (e.g., the coordinate system of the room providing the medical imaging equipment), or relative to another support position (e.g., a first support position). Moreover, the support position data can also indicate the first support position; for example, the support position data can include the coordinates of both the first and second support positions.

[0015] The position mapping unit is adapted to provide a position mapping. The position mapping unit can be a storage unit where position mappings are already stored and can be retrieved. Preferably, the position mapping is acquired during the calibration process, and the calibration support position is mapped to a calibration monitoring position. The mapping provided by the position mapping can refer to any type of mapping; for example, the mapping can include a mathematical function relating the calibration support position to at least one calibration monitoring position. Preferably, the mapping refers to providing a lookup table relating the calibration support position to the calibration monitoring position.

[0016] The position map is determined during a calibration procedure, which can be a real or virtual calibration procedure. During a real calibration procedure, real medical imaging equipment and real calibration targets can be used. In this embodiment, the calibration support location refers to the actual location of the support at which images are acquired during the calibration procedure to determine the position map, monitoring images, and particularly calibration monitoring images. Typically, the calibration support location corresponds to the support locations that can also be assumed during the acquisition phase of the medical imaging procedure. The calibration monitoring location indicates the position of the calibration target supported by the support in the calibration monitoring image (i.e., the monitoring image acquired during the calibration procedure at the corresponding calibration support location). The calibration target can be particularly suitable for calibration (i.e., determining the position map). For example, the calibration target can be a frame or patient phantom that can be positioned on a support during the calibration procedure. Alternatively, the calibration target can also be an animal or human placed on a support during the calibration procedure to determine the position map.

[0017] Preferably, the calibration monitoring image in which the calibration monitoring position is determined during the calibration procedure corresponds to the monitoring image provided during the medical imaging procedure. In particular, it is preferred that the calibration monitoring image includes the same field of view as the monitoring image acquired during the medical imaging procedure, which can be achieved, for example, by acquiring the calibration monitoring image using the same camera used to acquire the monitoring image during the medical imaging procedure. Alternatively, if a different field of view or a different camera is used to acquire the calibration monitoring image, a registration function can be determined to register the calibration monitoring image with the monitoring image acquired during the medical imaging procedure, and this registration function can be incorporated into a position map. The position map thus provides a relationship between the position of the support and the position of the target or portion of the target positioned on the support in the monitoring image acquired during the medical imaging procedure. Additionally or alternatively, a common coordinate system can be defined for both the monitoring image and the calibration monitoring image, and a first monitoring position and a calibration monitoring position can be provided in the common coordinate system.

[0018] Alternatively, a location mapping can be determined during the virtual calibration process, wherein a virtual computer model can be used on a general-purpose or special-purpose computer system to simulate the real calibration process as described above. For example, a virtual calibration target including multiple virtual calibration locations can be selected, and the position of the virtual calibration target in a virtual monitoring image or a real monitoring image of the camera can be calculated (i.e., simulated) for determining the location mapping according to the principles described above.

[0019] The region of interest (ROI) location determination unit is adapted to determine the location of the ROI in the second monitoring image based on the first monitoring location, the support location data, and the location mapping. Therefore, the ROI location determination unit is adapted to use information provided by the location mapping regarding where the target is located in the monitoring image relative to a certain support location, information about the actual support, and information about the location of the ROI in a current monitoring image within the current monitoring image, to determine and thus monitor the ROI in monitoring images acquired during the medical imaging process. Preferably, the ROI location determination unit is adapted to determine a second monitoring location in the second monitoring image, wherein the second monitoring location is determined by mapping the first monitoring location in the first monitoring image to the second monitoring image using the location mapping. Furthermore, it is preferred that the ROI location determination unit is adapted to determine the ROI in the second monitoring image based on the second monitoring location. For example, the ROI in the second monitoring image can be defined by the following relationship with the second monitoring location: this relationship between the ROI in the second monitoring image and the second monitoring location is the same as the relationship where the ROI in the first monitoring image must be established with the first monitoring location. In a preferred embodiment, the ROI location determination unit is adapted to determine the ROI in the second monitoring image based on the second monitoring location and also based on the second support location. For example, the shape and / or size of the region of interest (ROI) in the second monitoring image can be determined based on information about the expected distortion of the RIO at the location of the second support. In an example, if the RIO is defined as a rectangular region in the first monitoring image and the first monitoring position is located at a corner of the rectangular region, the RIO location determination unit can determine the RIO image in the second monitoring image as a rhombus-shaped region, where the second monitoring position refers to the corresponding corner of the rhombus. For example, information about the expected distortion of the RIO can be determined during the calibration process, and this information can be stored and associated with a specific support location. Alternatively, the RIO location determination unit can be adapted to determine the RIO in the second monitoring image by registering the contents of the RIO with the second monitoring image, where the first and second monitoring positions provide a starting point for registration.

[0020] In an embodiment, the monitoring images include multiple second monitoring images acquired at at least one second support location, wherein the support location providing unit is adapted to provide support location data for each of the at least one second support location, and wherein the region of interest location determining unit is adapted to determine the location of the region of interest in each of the second monitoring images. Preferably, the monitoring image providing unit is adapted to provide monitoring images in the form of a monitoring video, wherein each monitoring image in the video that is not defined as a first monitoring image can be defined as a second monitoring image. Each second monitoring image in the monitoring video can be correlated with a support location, for example, by using timing information of acquiring the monitoring images and acquiring the support locations.

[0021] In a preferred embodiment, the apparatus further includes a monitoring unit for monitoring changes in the region of interest (ROI) of the object, wherein the changes are monitored based on the second monitoring image and the position of the RIO within the second monitoring image. Because the monitoring unit is adapted to monitor changes based on the second monitoring image and the position of the RIO within the second monitoring image, it can very accurately distinguish between changes caused by movement of the support (e.g., motion) and changes caused by the object. Therefore, changes caused by the object's movement can be determined very accurately based on the monitoring image. In an embodiment, the monitoring unit is adapted to monitor changes while further considering the first monitoring image. Furthermore, considering the first monitoring image can provide a basis for evaluating measurements in the second monitoring image. For example, if temperature should be monitored in the second monitoring image, the first monitoring image can provide a baseline value at the beginning of the imaging process, allowing subsequent temperature values ​​determined based on the second monitoring image to be compared with this baseline value.

[0022] Preferably, the monitoring unit is adapted to monitor the movement of the subject (e.g., respiratory movement, cardiac movement, limb movement, etc.) as changes. In particular, if the region of interest is defined as the patient's chest region, the patient's respiratory movements can be monitored very accurately. Alternatively, the region of interest can also be any other part of the patient in which movement must be detected very accurately. In another example, the patient's region of interest can be the patient's face, wherein the device can also include a monitoring unit for monitoring movement in the patient's face based on a second monitoring image and the position of the region of interest in the second monitoring image, to determine, for example, the patient's state (e.g., whether the patient is asleep or awake, or whether the patient is tense or relaxed, etc.). As a supplement or alternative to monitoring changes caused by the subject's movement, other changes, such as changes in the patient's temperature, changes in the patient's skin color, etc., can also be monitored. For example, such monitoring is helpful for monitoring the patient's health condition; for example, when the patient's skin becomes pale, this can indicate, for example, heart or circulatory problems caused by tension or panic. Furthermore, it is possible to use, for example, a patient's face to monitor cardiac activity, where, in this case, color changes (specifically, changes in the patient's skin color) in the monitored area of ​​interest are monitored, and these color changes indicate blood flow and thus indicate cardiac processes or cardiac activity.

[0023] In an embodiment, the location map maps multiple calibration monitoring locations to each calibration support location, with each calibration monitoring location indicating the location of a different portion of the calibration target. For example, if the calibration target is a real or virtual calibration box, the calibration monitoring locations can correspond to the corner positions of the calibration box in the calibration monitoring image. In a preferred embodiment, the real or virtual calibration target is a box comprising a checkerboard pattern, wherein the location map maps the corner positions of each area of ​​the checkerboard pattern in the corresponding calibration monitoring image to each calibration support location as calibration monitoring locations. Providing more than one calibration monitoring location for each calibration support location in the location map allows for more accurate monitoring of the region of interest in the monitoring image.

[0024] In an embodiment, the first region of interest providing unit is adapted to provide a first monitoring position in the first monitoring image, the first monitoring position corresponding to a calibration monitoring position in a calibration monitoring image within the calibration monitoring image. For example, the user interface can provide the first monitoring image to a user, and the user interface can be adapted to allow only the user to select the first monitoring position in the first monitoring image corresponding to one of the calibration monitoring positions in the location map. Alternatively, determining the position of the region of interest in the second monitoring image includes determining the first calibration monitoring position, wherein the first calibration monitoring position corresponds to a calibration monitoring position in the location map derived from the first monitoring position in the first monitoring image, wherein determining the position of the region of interest is also based on the first calibration monitoring position. Preferably, the first monitoring position is derived from the first monitoring position by searching for calibration monitoring positions within a proximity of the first monitoring position, wherein the proximity to be searched can be predetermined. For example, it can be predetermined whether the calibration monitoring position is within a first proximity threshold, such as whether it is within a first radius around the first monitoring position. If no calibration monitoring position is found within a first proximity threshold, a search for a calibration monitoring position is conducted within a second proximity threshold, and so on, until a calibration monitoring position is found. The found calibration monitoring position is then determined as the first calibration monitoring position. Alternatively, the calibration monitoring position closest to the first monitoring position is derived as the first calibration monitoring position. The closest calibration monitoring position can be determined, for example, by determining the Euclidean distance between the first monitoring position and all calibration monitoring positions provided by the location map, where the closest calibration monitoring position is the one with the smallest Euclidean distance to the first monitoring position. Other distance metrics can also be used to determine the closest calibration monitoring position as the first calibration monitoring position. Furthermore, the distance between the first calibration monitoring positions and / or the difference between the first calibration monitoring positions can be stored, for example, relative to the x and y coordinates of the positions in the monitoring image. The region of interest location determination unit can then be adapted to use this stored difference and the first calibration monitoring position to determine the location of the region of interest. This allows for very accurate determination of the location of the region of interest in the second monitoring image using only a small number of calibration monitoring positions.

[0025] In an embodiment, determining the location of the region of interest in the second monitoring image includes: determining at least two calibration monitoring locations derived from the first monitoring location as first calibration monitoring locations, wherein the location of the region of interest is then determined by interpolation between the location map and the monitoring locations determined in the second monitoring image based on the first calibration monitoring location. The at least two first calibration monitoring locations can be derived, for example, by defining all or part of the calibration monitoring locations within a proximity of the first monitoring location as first calibration monitoring locations. For example, proximity can be predefined as a region surrounding the first calibration monitoring location, wherein all calibration monitoring locations within that region are defined as first calibration monitoring locations. Additionally or alternatively, the calibration monitoring location closest to the first monitoring location can be defined as the first calibration monitoring location. If more than one first calibration monitoring location should be determined from multiple calibration monitoring locations, the closest first calibration monitoring location refers to the closest calibration monitoring location, the second closest calibration monitoring location, the third closest calibration monitoring location, and so on, until a predetermined number of closest calibration monitoring locations are reached. In a preferred example, the calibration monitoring positions are evenly spaced in at least a portion of the calibration monitoring image of the calibration support position. In this case, it is preferable to determine the calibration monitoring position corresponding to the corner of the square surrounding the first monitoring position as the first calibration monitoring position. Based on the first calibration monitoring positions and the position mapping diagram, the monitoring position for each of the first calibration monitoring positions can be determined in the second monitoring image. By interpolating between these thus determined monitoring positions, the location of the region of interest in the second monitoring image can be determined very accurately.

[0026] In an embodiment, determining the position of the region of interest (ROI) in the second monitoring image includes: determining a virtual first support position based on the first monitoring position and the position mapping; and determining the position of the ROI in the second monitoring image based on the virtual first support position, the support position data, and the position mapping. For example, the virtual first support position can be determined by mapping the first monitoring position to the support position using the position mapping. Therefore, the virtual first support position does not necessarily correspond to the first support position. For example, if the calibration monitoring position of the position mapping is determined based on a calibration target positioned in the middle of the support, while the first monitoring position of the ROI is determined at one end of the support, the position mapping will provide a position different from the first support position as the virtual first support position. Then, the accurate position of the ROI can be determined based on the virtual first support position. For example, in such a case, the difference between the second support position and the first support position included in the support position data can be determined, and the position of the ROI in the second monitoring image can be determined based on this difference and the virtual first support position according to the position mapping. Preferably, the support location data includes the difference between the first support location and the second support location, and the region of interest location determination unit is adapted to determine the location of the region of interest in the second monitoring image based on the first monitoring location, the difference, and the location mapping.

[0027] In an embodiment, the support location providing unit is adapted to provide support location data based on the first monitoring image and the second monitoring image by identifying the support in the respective monitoring image. For example, the support location providing unit can be adapted to provide support location data based on the monitoring image by tracking the support in the monitoring image using a known target tracking algorithm or by markings provided on the support on the imaging device. In both cases, the support can be easily tracked in the monitoring image with very little computational effort. Providing support location data based on monitoring images allows each monitoring image to be directly associated with the support location without providing additional hardware (e.g., a support location sensor).

[0028] In this embodiment, each monitoring image is acquired by the same camera, wherein the field of view of each monitoring image is identical and covers all locations of interest within the region of interest during the medical imaging process. Preferably, the camera is attached to the medical imaging device. Alternatively, the camera can be provided independently of the medical imaging device, for example, on the ceiling or in a corner of the room including the medical imaging device. Furthermore, it is preferable to use the same camera with the same field of view to acquire calibration monitoring images. In one embodiment, the camera can be a wide field-of-view camera.

[0029] In an alternative embodiment, monitoring images are acquired by at least two cameras with different fields of view, wherein the different fields of view may overlap to allow monitoring of the entire medical imaging process. Preferably, the cameras are attached to the medical imaging equipment. Alternatively, the cameras can be provided independently of the medical imaging equipment, for example, on the ceiling or in a corner of the room including the medical imaging equipment. Additionally, it is preferable to use the same camera to acquire calibration monitoring images at the same location as used during monitoring.

[0030] In one aspect of the invention, a calibration apparatus (and an apparatus further comprising the calibration apparatus as described above) is provided for providing a position mapping for use in the apparatus described above, wherein the apparatus comprises: a) a calibration monitoring image providing unit for providing calibration monitoring images, wherein each calibration monitoring image is acquired at a different calibration support location and indicates the location of a calibration target supported by the support; b) a calibration support location providing unit for providing calibration support location data, wherein the calibration support location data indicates the support location during the calibration; and c) a position mapping determining unit for determining a position mapping by determining a mapping between the location of the calibration target and the corresponding calibration support location for each calibration monitoring image.

[0031] The calibration monitoring image providing unit can be a storage unit on which calibration monitoring images are stored and can be retrieved. Furthermore, the calibration monitoring image providing unit can be a retrieval unit for retrieving calibration monitoring images, for example, from a monitoring camera intended for monitoring the object during the medical imaging process. Preferably, each calibration monitoring image has the same field of view as the monitoring images acquired at the same support location during the medical imaging process. During such a calibration process, a calibration target is provided on the support of the medical device, and the camera monitors the calibration target to provide calibration monitoring images. The calibration target can be, for example, a dedicated calibration target, preferably including a checkerboard pattern, a phantom, or a human cube.

[0032] The calibration support position providing unit is adapted to provide calibration support position data, which indicates the position of the support during the calibration process. The calibration support position providing unit can also be a storage unit on which the calibration support position data is stored and can be retrieved. Furthermore, the calibration support position providing unit can be a receiving unit, configured to receive the calibration support position data, for example, from a support position sensor of a medical device or, as described above, from a monitoring image (e.g., a calibration monitoring image).

[0033] The position mapping determination unit is then adapted to determine a position mapping by determining a mapping between the position of the calibration target and the corresponding calibration support position for each calibration monitoring image. For example, the position mapping determination unit can be adapted to provide a table linking each calibration support position to the position of the calibration target in the corresponding calibration monitoring image as a position mapping. Preferably, the position mapping determination unit is adapted to determine a mapping between the calibration support position and more than one position of the calibration target in the corresponding calibration monitoring image, wherein each position of the calibration target refers to the position of a different portion of the calibration target in the calibration monitoring image. For example, if the calibration target includes a checkerboard pattern, the position mapping determination unit can be adapted to map the position of each corner of each checkerboard area of ​​the calibration target in the corresponding calibration monitoring image to each calibration support position.

[0034] In one aspect of the invention, a system is provided for acquiring medical images of a subject during a medical imaging procedure using a medical imaging device, wherein the system comprises: a) a medical imaging device for acquiring medical images, wherein the medical imaging device includes a support for supporting the patient during the medical imaging procedure; b) a camera for acquiring monitoring images of the subject during the medical imaging procedure; and c) the apparatus as described above.

[0035] In another aspect of the invention, a method for monitoring an object during a medical imaging procedure using a medical imaging device is provided, wherein the imaging device includes a support for supporting and moving the object during the imaging procedure, the method comprising: a) providing monitoring images of the object, the monitoring images including a first monitoring image and a second monitoring image of the object, wherein the first monitoring image is acquired at a first support location and the second monitoring image is acquired at a second support location; b) providing a first monitoring position and shape, the first monitoring position and shape indicating the position and shape of a region of interest in the first monitoring image; c) providing support position data indicating a second support position; d) providing a position map, wherein the position map provides a mapping between a calibration support position and a calibration monitoring position, wherein the calibration monitoring position indicates the position of a calibration target in a monitoring image acquired at the corresponding calibration support location; and e) determining the position and shape of the region of interest in the second monitoring image based on the first monitoring position and shape, the support position data, and the position map.

[0036] In another aspect of the invention, a computer program for monitoring an object during a medical imaging procedure using a medical imaging device is provided, wherein the computer program includes program code modules that, when the computer program is run by the device as described above, cause the device to perform the steps of the method as described above.

[0037] It should be understood that the apparatus, method and computer program of the present invention have similar and / or identical preferred embodiments, particularly those defined in the dependent claims.

[0038] It should be understood that the preferred embodiments of the present invention can also be any combination of the dependent claims or the foregoing embodiments with the corresponding independent claims.

[0039] These and other aspects of the invention will become apparent and will be elucidated with reference to the embodiments described below. Attached Figure Description

[0040] In the following figures:

[0041] Figure 1 An embodiment of a system for acquiring medical images of a subject during a medical imaging procedure is illustrated schematically and exemplary, including means for monitoring the subject.

[0042] Figure 2 A system including means for providing a location mapping map of the present invention is illustrated schematically and exemplary;

[0043] Figure 3 The principles of the invention are illustrated schematically and exemplary;

[0044] Figure 4 A flowchart illustrating an exemplary embodiment of a method for monitoring an object during a medical imaging procedure is shown; and

[0045] Figure 5 A flowchart illustrating an exemplary embodiment of a method for providing a location mapping map for use with a device for monitoring an object is shown. Detailed Implementation

[0046] Figure 1An embodiment of a system for acquiring medical images of a subject during a medical imaging procedure, including means for monitoring the subject, is illustrated schematically and exemplary. In the following embodiment, system 100 includes a CT system 140 as a medical imaging device, 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 during the CT imaging procedure. Additionally, the CT imaging system includes a camera 130, which, as an example of a system arranged to acquire monitoring images provided to a monitoring image providing unit, is adapted to acquire monitoring images of the patient 121 during the CT imaging procedure. Furthermore, system 100 includes means 110 adapted to process the acquired monitoring images and derive physiological parameters for monitoring the patient 121 during CT image acquisition.

[0047] The device 110 includes a monitoring image providing unit 111, a monitoring position providing unit 112, a support position providing unit 113, a position mapping providing unit 114, and a region of interest position determining unit 115. In this embodiment, the device 110 optionally includes a monitoring unit 116. Additionally, the device 110 may also include an input module 118 (e.g., a mouse, keyboard, or touchscreen) for inputting data into the device 110 and an output module 117 (e.g., a display) for outputting monitoring images for monitoring the patient.

[0048] The monitoring image providing unit 111 is configured as a receiving unit for receiving monitoring images of patient 121 from camera 130. Camera 130 can be a wide field-of-view camera capable of imaging the entire medical imaging process. Preferably, camera 130 is positioned and adjusted such that the patient is within the camera's field of view throughout the medical imaging process, particularly without moving or changing the camera's position. The monitoring images of patient 121 include a first monitoring image of patient 121 and multiple second monitoring images, wherein the first monitoring image is acquired at a first support location, and the multiple second monitoring images are acquired at different second support locations. Preferably, camera 130 provides a video stream, wherein each image in the video stream provided by camera 130 can be considered a monitoring image. The first monitoring image can be any of the monitoring images of patient 121 provided, but preferably refers to the monitoring image provided by camera 130 that first shows the region of interest of patient 121 to be monitored. In this case, all images provided by camera 130 after the first monitoring image can be defined as second monitoring images of patient 121. Alternatively, only the monitoring image provided by camera 130 selected after the first monitoring image has been provided can be defined as the second monitoring image of patient 121. For example, only one monitoring image can be selected as the second monitoring image of patient 121 for each support location.

[0049] The monitoring location providing unit 112 is adapted to provide a first monitoring location, which indicates the position of the region of interest in the first monitoring image. Preferably, in order to provide the first monitoring location, the monitoring location providing unit 112 is adapted to display the first monitoring image on the display 117 and receive the first monitoring location as input from a user. For example, the user can mark the chest of patient 121 as a region of interest by drawing a box on the chest region of patient 121 on the first monitoring image displayed on the display 117 using the input module 118. The corner of the box drawn by the user can then be regarded as the first monitoring location defining the region of interest to be monitored. Alternatively, the first monitoring location can also be provided by the first monitoring providing unit based on, for example, information about where the region of interest is typically expected to be located in the first monitoring image. In such embodiments, the first monitoring location is preferably determined by the monitoring location providing unit based on the patient's patient data (e.g., height, age, weight, etc.) and / or configuration data (e.g., the height and starting position of the support 120 and the spatial relationship between the camera 130 and the support 120). Based on this data, it is possible to estimate the location of the region of interest (e.g., chest region) of the patient 120 in the first monitoring image, and the monitoring location providing unit 112 is adapted to provide the first monitoring location based on this estimation.

[0050] The support position providing unit 113 is adapted to provide support position data indicating a plurality of second support positions. In this embodiment, the support 120 includes a support marker 122, and the support position providing unit is adapted to provide support position data based on tracking the support marker 122 in a monitoring image of the camera 130. In an alternative embodiment, a support position sensor, which is part of the support 120 or part of the imaging device 140, can also be provided to measure the position of the support and provide the support position to the support position providing unit. In this case, the support position providing unit can be adapted to determine which support positions are related to a second monitoring image provided by the monitoring image providing unit and provide the determined support positions as second support positions. This determination can be based, for example, on the support position data and the timestamp of the provided monitoring image.

[0051] The position mapping unit 114 is adapted to provide a position mapping. The position mapping provides a mapping between calibration support locations and calibration monitoring locations, wherein the calibration monitoring locations indicate the location of the calibration target in a monitoring image acquired at the corresponding calibration support location during the calibration process. The position mapping can be, for example, using... Figure 2 The data was collected by the calibration system shown.

[0052] Figure 2 A system including means for providing a position mapping map for use in device 110 is illustrated schematically and exemplary. Calibration system 200 includes... Figure 1 The imaging device 140, support 120, and camera 130 are described. During the calibration procedure, a calibration target 221 (not the patient 121) is placed on the support 120, preferably in a portion of the support 120 where the patient 121 is intended to be placed during the imaging procedure. The calibration target 221 can be a marked box, for example, a box in the form of a checkerboard with alternating black and white areas. In other embodiments, other forms can also be selected for the calibration target 221, for example, a medical phantom of a patient or a portion of a patient can be used.

[0053] The calibration system 200 also includes a calibration device 210, which includes a calibration monitoring image providing unit 211, a calibration support position providing unit 212, and a position mapping determination unit 213. The calibration monitoring image providing unit 211 is adapted to provide calibration monitoring images. These calibration monitoring images correspond to monitoring images provided by the camera 130 during the medical imaging process. Preferably, providing calibration monitoring images involves selecting calibration monitoring images from the monitoring images provided by the camera 130 during the calibration process, such that each calibration monitoring image is acquired at different support positions on the support 120 (i.e., at different calibration support positions) during the calibration process.

[0054] The calibration support position providing unit 112 is adapted to provide calibration support position data indicating the position of the support during calibration. Figure 2 In the illustrated embodiment, the calibration support position providing unit is adapted to provide calibration support position data based on tracking of the support marker 122 in the monitoring image provided by the camera 130. As described above, if a support position sensor is provided, the calibration support position providing unit 112 can also be adapted to provide calibration support position data based on the measurement results of the support position sensor.

[0055] The position mapping determination unit 213 is adapted to determine a position mapping by determining a mapping between the position of the calibration target 221 and the corresponding calibration support position for each calibration monitoring image. Preferably, the position mapping determination unit 213 is adapted to automatically determine the position of the calibration target by identifying different portions of the calibration target 221 in the calibration monitoring image using, for example, a known target recognition or tracking algorithm. Figure 2In the illustrated embodiment, the position mapping determination unit 213 is adapted, for example, to identify a checkerboard pattern on the calibration target 221 and determine the corner of each checkerboard piece as the position of the calibration target 221. Alternatively, the position mapping determination unit 213 is adapted to present a calibration monitoring image to a user, whereby the user can then indicate the calibration position (i.e., the position of the target) on the calibration monitoring image. Thus, for each calibration monitoring image, the position mapping determination unit 213 can determine multiple positions of the calibration target 221. The position mapping determination unit 213 is then adapted to map these multiple positions of the calibration target 221 in the calibration monitoring image to the calibration support position of the support 120 where the calibration monitoring image has been acquired. The position mapping can then be determined as a list or table classifying the positions of the calibration targets 221 to the corresponding calibration support positions. In other embodiments, the position mapping determination unit 213 is adapted to determine a function between the position of the calibration target 221 and the corresponding calibration support position, where, in this case, the position mapping refers to the determined function. After the calibration process is performed using the calibration system 200, the location map can be stored and used in the imaging process, for example, to image the patient 121. Figure 1 The position mapping providing unit 114 of system 100 is then adapted to provide the stored position mapping acquired using calibration system 200.

[0056] The region of interest location determination unit 115 is adapted to determine the location of the region of interest of the patient 121 in the second monitoring image provided by the monitoring image providing unit 111 based on a first monitoring location provided by the monitoring location providing unit 112, support location data provided by the support location providing unit 113, and a location mapping provided by the mapping map providing unit 114. (The following will discuss...) Figure 3 This describes a preferred embodiment for determining the location of the region of interest in a second monitoring image.

[0057] Figure 3 The principles of the invention are illustrated schematically and exemplary. The same reference numerals are used to identify and refer to [other parts of the invention]. Figure 1 and Figure 2 The components shown are those of the parts. For example, Figure 3 Imaging device 140, camera 130, patient 121, and patient support 120 are also shown. Additionally, Figure 3The field of view 300 of camera 130 during the imaging process is schematically shown. Within the field of view 300, two plots are provided of the patient 121 and the patient support 120, each plot relating to different monitoring images and different support positions during medical image acquisition. Specifically, the left plot of patient 121 and support 120 indicates the position where patient 121 may be seen in the first monitoring image, and the right plot of patient 121 and support 120 indicates the position where patient 121 may be seen in a second monitoring image. A box 310 shown in the left plot of the patient then indicates the region of interest to be monitored. In this example, the upper left corner is provided as the first monitoring position p0. The actual support position where the first monitoring image has been acquired is indicated by point xA. In this example, the region of interest location determination unit is adapted to determine a virtual first support position x0 based on the first monitoring position p0 and a location map mt. Specifically, the virtual first support position x0 can be determined by applying the location map to the first monitoring position p0 such that x0 = mt(p0). For example, if the location mapping refers to a list, the region of interest location determination unit can be adapted to search for a calibration monitoring location corresponding to the first monitoring location p0 in the entries of the list and determine the calibration support location corresponding to the found calibration monitoring location indicated by the list as the virtual first support location x0.

[0058] Determining the virtual first support position x0 has the following advantages: even if the calibration target 221 is not positioned in the same area as the region of interest to be monitored on the support during the calibration process, the region of interest can still be monitored very accurately based on the virtual first support position, as shown below. In this example, the region of interest position determination unit 115 is then adapted to determine the position p0' of the region of interest in a second monitoring image acquired with the patient support 120 located at the actual second support position xA'. For example, the region of interest position determination unit 115 is adapted to determine the difference between the two support positions (i.e., determine Δx = xA' – xA) based on support position data including the first support position xA and the second support position xA'. Alternatively, the support position data provided by the support position providing unit 113 can already include support position data indicating the difference Δx as the second support position data. The region of interest position determination unit 115 can then be adapted to apply the inverse operation of the position map to the sum of the virtual first support position x0 and the difference Δx (i.e., p0' = mt). -1 (x0+Δx) is used to determine the location p0' of the region of interest (i.e., the second monitoring location). The provided formula uses mt... -1The term indicates the inverse operation of the search in the location map. When the region of interest location determination unit 115 has determined the second monitoring position p0' of the region of interest, it can also provide the bounding box 310' of the region of interest in the second monitoring image. For example, if the second monitoring image is not expected to be strongly distorted compared to the first monitoring image due to camera specifics or only due to a small difference Δx, the bounding box can be simply copied from the first monitoring image, with p0' as the starting point. Then, if a change in viewing angle is expected due to camera specifics or a large difference Δx, the size and shape of the bounding box marking the region of interest can be adjusted according to the expected distortion of the region of interest due to the change in viewing angle. For example, the size and shape changes of the region of interest used to provide the calibration map during the same calibration process can be predetermined, and then such size and shape changes can be stored with respect to the second support position, either as part of the calibration map or as additional information independent of the calibration map. Alternatively, a function describing the shape distortion within the camera's field of view can be known based on theoretical thinking or computational simulation, and the corresponding function can be applied to the bounding box marking the region of interest to determine the region of interest in the second monitoring image.

[0059] In other embodiments, the region of interest (ROI) location determination unit 115 can also be adapted to determine the location of the ROI in the second monitoring image based on other methods (e.g., without calculating the location of the virtual first support). In such embodiments, the monitoring location providing unit can be adapted to determine, for example, a calibration monitoring location that corresponds as closely as possible to or is the user's input to the ROI and provide that calibration monitoring location as the first monitoring location. For example, the monitoring location providing unit can be adapted to search for a calibration monitoring location in the calibration monitoring locations in the location map that corresponds to the indicated location of the ROI at the same support location. In this case, the determination of the virtual first support location can be omitted. Furthermore, to improve the accuracy of the determined ROI location, the ROI location determination unit 115 can be adapted to determine the calibration monitoring location derived from the first monitoring location in the location map, for example, if the first monitoring location is located between the corners of one of the checkerboard pieces in the checkerboard puzzle used as the calibration monitoring location, then these four corners can be derived as the first calibration monitoring location. To determine the location of the ROI, the ROI location determination unit 115 can then be adapted to interpolate between the locations determined for the first calibration monitoring location in the second monitoring image. The preferred possibility for determining the first calibrated monitoring location of the first monitoring location is to determine the nearest neighbor of the first monitoring location in the location map.

[0060] Based on the location of a region of interest determined in multiple second monitoring images, monitoring unit 116 is adapted to derive physiological parameters (e.g., respiratory rate) from the acquired monitoring images, thereby enabling (e.g., by tracking upward and downward movement within the determined region of interest) monitoring, for example, the respiratory movements of an object within the region of interest. Additionally or alternatively, monitoring unit 116 can also be adapted to monitor other movements of patient 121 or the health status of patient 121. For example, if monitoring unit 116 is adapted to monitor the health status of patient 121, the patient's face can be defined as a region of interest, and monitoring unit 116 can be adapted to determine the patient's health status based on the second monitoring images and the position of the face in the second monitoring images, for example, by monitoring facial movement, changes in facial expression, temperature changes in parts of the face, or skin color.

[0061] Figure 4 A flowchart illustrating an exemplary embodiment of a method for monitoring a subject during a medical imaging process is shown. The method 400 for monitoring a subject according to the principles of the invention already described above includes a first step 410: providing monitoring images of the subject, the monitoring images including a first monitoring image and a second monitoring image of a patient 121. The first and second monitoring images can be acquired by a camera 130. Furthermore, the first monitoring image is acquired at a first support position of a patient support 120, and the second monitoring image is acquired at a second support position of the patient support 120. Additionally, the method includes a step 420: providing a first monitoring position, the first monitoring position indicating the location of a region of interest in the first monitoring image. The first monitoring position can be provided, for example, by a user displaying the first monitoring image on a monitor, or it can be provided automatically by identifying a region of interest that should be monitored. For example, if respiratory movements should be monitored, multiple first monitoring images, all acquired at the first support position, can be provided, and the first monitoring position can be automatically determined by identifying the region of interest showing the greatest movement in the first monitoring images. Alternatively, if the patient's health status should be monitored, the first monitoring location can be automatically determined by applying a facial recognition algorithm to the first monitoring image. Additionally, method 400 includes step 430: providing support location data, which indicates the location of a second support. For example, support location data can be provided based on tracking of marker 122 in the monitoring image provided by camera 130. Furthermore, method 400 includes step 440: providing the support location data as described above. Figure 1 and Figure 2 A location mapping map. This can be based, for example, on the following description regarding... Figure 5The calibration method 500 determines the position mapping. The method 400 then includes step 450: determining the location of the region of interest in the second monitoring image based on the first monitoring location, support location data, and the position mapping, according to the principles explained above.

[0062] Figure 5 A flowchart illustrating an exemplary embodiment of a method for providing a position map for use with an apparatus for monitoring an object is shown. The method 500 for providing a position map for use in the method for monitoring an object as described above includes a first step 510: providing calibration monitoring images, wherein each calibration monitoring image is acquired at a different calibration support location and indicates the location of a calibration target supported by the support. Additionally, the method 500 includes a step 520: providing calibration support location data, wherein the calibration support location data indicates the location of the calibration support during calibration. In step 530, the method 500 then includes (e.g., as explained with respect to calibration apparatus 210) determining the position map by determining a mapping between the location of the calibration target and the corresponding calibration support location for each calibration monitoring image.

[0063] Medical imaging techniques (such as CT or MR) capture multiple imaging data points from a patient, which are then combined to reconstruct the final scan image. The examination may last from a few seconds to several minutes, during which time the patient is required to remain as still as possible, sometimes even holding their breath, so that all images are taken under the most similar conditions, resulting in a clear and artifact-free final scan. For example, if a CT scan is used to obtain a three-dimensional scan of a patient's chest, projection data acquired from different angles are combined. If all projection data are acquired instantaneously, all data will represent the patient in the exact same position, thus the combination of projection data will yield a clear and accurate scan image.

[0064] However, the examination can last for several seconds or minutes, during which time the patient may move, even involuntarily (e.g., due to breathing or heartbeat), which can degrade the quality of the final reconstructed scan image. Of course, if imaging data obtained at the point of movement during maximal exhalation is combined with imaging data obtained at the point of movement during maximal inspiration, the reconstructed scan image may be blurry or contain artifacts because the patient's shape has changed. Even when asked to hold their breath, not all patients can remain still and hold their breath for as long as the examination itself. In such cases, some degree of image quality degradation must be accepted.

[0065] To prevent image quality degradation caused by movement due to breathing, existing medical imaging systems monitor patient respiration and adjust the examination accordingly, for example, by attaching a measuring band to the patient's chest. However, attaching sensors can cause discomfort to the patient and requires trained personnel to attach and remove them, increasing overall examination time and cost. If the sensor is not properly attached, the obtained respiratory signal will be degraded and unusable during the examination. This can lead to reduced image quality or significant time loss.

[0066] As an alternative to contact sensors, camera-based non-contact respiratory monitoring solutions have been proposed and successfully applied to certain medical imaging modalities (e.g., MR imaging). Existing camera-based non-contact respiratory monitoring solutions measure a patient's respiratory signal by tracking respiratory-induced movements in the chest region (specifically, the repetitive expansion and contraction of the chest during each respiratory cycle). Such algorithms require the patient to remain still so that motion is not superimposed on respiratory-induced movements.

[0067] In some imaging techniques (e.g., CT or MR), the patient lies on a patient support (also known as a table or couch), and during a CT imaging procedure, the patient support is moved across the CT gantry, or during an MR imaging procedure, the patient support is moved across the MR imaging gantry. The patient support can be moved stepwise, enabling the acquisition of imaging data during periods of no movement, a technique known as "step-and-shoot," or the patient support can be moved continuously while images are being acquired, a technique particularly used in helical CT scans. In either case, continuous respiratory monitoring based on a fixed camera is not feasible with existing respiratory algorithms because they require the patient not to move within the camera's field of view (i.e., translational movement is not allowed to superimpose on the respiratory signal). From the camera's perspective, translational movement masks the movement caused by respiration, where the movement of the support is much greater, thus camera monitoring algorithms cannot isolate the respiratory signal.

[0068] Furthermore, it is impossible to track a patient's chest region based on simple automated images. The shape of the chest region, in which respiratory signals can be measured, can vary considerably among different patients, making it difficult for automated image-based tracking algorithms to automatically identify the chest region from different perspectives. Even if the chest region is manually selected for each patient, the viewing angle on the chest changes due to the movement of the support during the examination (i.e., the target to be tracked becomes another target during tracking). Currently, in such situations, target-based images cannot accurately track the target, therefore, methods relying on target tracking algorithms to identify the chest are not feasible for identifying translational movements.

[0069] This invention provides a method and system that allow monitoring of a region of interest (e.g., chest) on a monitoring image using additional information about the position of a support. The tracking of the region of interest can then be used to isolate respiratory signals, for example, from translational signals. Specifically, it is proposed to determine an initial one-time calibration (i.e., a calibration map) and use this calibration during tracking.

[0070] In embodiments, a system according to the principles of the invention may include, for example: a medical imaging device; a camera fixed to the medical imaging device or fixed in a room; a patient support or patient table, preferably including a positioning sensor indicating the exact position of the patient on the patient support at any given time, and for moving the patient through the medical imaging device; a control system for the medical imaging device, the control system being able to provide a signal indicating the exact position of the patient support at any given time; and a processing unit (e.g., the apparatus described above) that combines information captured by the camera, for example in a video stream, with the patient support position signal and provides the patient's respiratory signal. Preferably, the medical imaging device is equipped with a camera having a wide field of view lens (typically a fisheye lens). The camera can be fixed to the medical imaging device, and from the fixed position of the camera, the patient's chest should be visible in all patient support positions of interest. Alternatively, the camera can be fixed in a room, or it can be provided on a tripod near the medical imaging device.

[0071] In embodiments of the invention, the method according to the principles of the invention can include performing an initial calibration based on an easily identifiable target (i.e., a calibration target) and creating a position map. This position map determines which locations (e.g., pixels in video images (i.e., monitoring images)) correspond to the calibration target positioned on the patient support for each patient support location. Based on this position map, any target lying on the patient support during support movement can be tracked in the video stream (i.e., in the monitoring images) by simply identifying the target once (e.g., before movement begins) and then analyzing the support location. Preferably, the target of interest is identified first before support movement begins, for example, by placing a bounding box around the target. It can be assumed that there is no relative movement between the patient support and the target, and the target can be tracked by moving the bounding box in the monitoring images according to the actual support location (i.e., by shifting the bounding box by mapping the actual support movement (i.e., location) to an offset calculated in the pixels). The chest (i.e., the region of interest) should then appear static within the identified bounding box, with at least limited support movement between subsequent monitoring images.

[0072] Preferably, the initial calibration, whether real or virtual, only needs to be performed once, for example, when the camera is fixed to the imaging device and cannot be moved. In this case, if the tolerance in the manufacturing process is small enough, calibration may even only need to be performed once for each design. Further preferably, the movement of the support is restricted, for example, by moving the patient support along a rail fixed to the imaging device itself. A unique target can be used to perform the initial calibration. In the example, a target with a checkerboard pattern is used because it is commonly used in camera calibration and imaging tracking algorithms, while corner recognition algorithms are also widely applicable. Different calibration targets can also be used. During an exemplary embodiment of the calibration method, the patient support is moved to one end, and then the calibration target is placed on the patient support. It is possible to suggest placing the calibration target in the center. However, calibration can also be used based on relative position. The initial calibration can then be performed once by specific software (i.e., software for providing a position map). Software running on the calibration system, as described above, can receive video streams from the camera and synchronously receive support position signals, making it possible to know the support position corresponding to each acquired monitoring image. The support is then moved to the other end of the imaging device. As the support moves, the camera captures the entire motion. Ideally, each support position would be captured in at least one monitoring image. However, it is not necessary to capture all positions. For example, for each monitoring image captured by the camera, the calibration device described above can accurately identify the position (e.g., pixel value) of the calibration target in the monitoring image and link it to the actual support position. In this way, a position map can be created.

[0073] In real-world conditions, different patients will lie in slightly different positions, and even then, they may be tall, short, fat, thin, etc. To account for all these differences, a large calibration target can be used. This large calibration target (e.g., a box on which a checkerboard pattern is drawn) can then cover all possible chest positions (i.e., the location of the region of interest) on the patient support, taking into account the expected variability in the patient's body shape, weight, orientation (e.g., head first, legs first), etc. In this way, several position maps can be created at once (e.g., once for each corner of the checkerboard) (i.e., position maps that map more than one calibration position to the support position). When using this position map, the bounding box can then be moved based on the position map or a combination of position maps that best approximates the actual position of the bounding box in the first monitoring image. Note that in a simple calibration method, only one position map can be created for only one calibration position.

[0074] In an alternative embodiment, the camera may not be fixed to the medical imaging device, but rather to the room. In this case, all the above procedures can be applied similarly, even if the calibration is only effective for the time when the camera does not move relative to the medical imaging device.

[0075] In one embodiment, the use of a location map in a real-world inspection can be accomplished in multiple steps. For example, by identifying the chest region, one or more bounding boxes containing regions of interest (e.g., the chest region) are defined, and then the bounding boxes are moved accordingly once the boundaries of the region to be monitored are known and support movement begins, thus enabling tracking of the target of interest. Note that the boundaries of the region of interest can even be represented by a single point in the image.

[0076] Since the calibration will use only a limited set of locations (which represent a limited set of possible locations for a region of interest), the method can include performing interpolation of the locations used in the location map. For example, given an initial location of the chest region, it is possible to identify the four nearest neighbors in the location map. Then, the new location of the region of interest after support movement can be found by interpolating the new locations of the four nearest neighbors given by the location map. In another embodiment, instead of receiving the support location as a signal from the control system, the support location is extracted by the camera system using, for example, a marker fixed to the support. This marker can be tracked during a one-time calibration and during actual inspection to provide an indication of the support location.

[0077] While in the embodiments described above the camera is provided as part of the imaging device or positioned within the imaging device, the camera can also be positioned independently of the imaging device, for example, in a corner of the room where the imaging device is located or on a tripod near the imaging device. Furthermore, more than one camera can be provided to provide monitoring images. For example, two cameras can be positioned on different sides of the imaging device to monitor different support positions.

[0078] Although the imaging device is described as a CT imaging device in the above embodiments, the imaging device can also be any other medical imaging device that moves the patient support during the imaging process, such as a PET imaging device, an MR imaging device, a SPECT imaging device, etc.

[0079] Although in the above embodiments, the patient support is always the one on which the patient lies during medical image acquisition, the patient support can also be configured to allow the patient to sit or stand on it.

[0080] Although in the above embodiments, the first monitoring image is the image initially provided by the camera before or at the start of the imaging process, the first monitoring image can also be defined as a monitoring image acquired by the camera during, at the end of, or after the imaging process. Furthermore, the second monitoring image can then be correspondingly defined as a monitoring image acquired, for example, before the acquisition of the first monitoring image.

[0081] While the location map providing unit provides only one location map in the above embodiment, in other embodiments, the location map providing unit can also be adapted to provide multiple location maps. For example, the location map providing unit can be adapted to provide different location maps for different imaging systems or for different configurations of imaging systems. The location map providing unit can also provide location maps for different camera positions and fields of view and / or different calibration targets placed at different positions on the patient support. Then, the location map providing unit can be adapted to select one of the provided location maps, for example, based on user input, imaging system configuration data, information about the patient, region of interest, etc.

[0082] Although the location map was determined using a real calibration process in the above embodiments, in other embodiments, the location map can also be determined during a virtual calibration process (i.e., during the calculation of the monitoring position based on the virtual calibration target, virtual monitoring image, and virtual support). In the virtual calibration process, a model can be used to simulate the position of the virtual calibration target in the virtual monitoring image to determine the location map.

[0083] Those skilled in the art, through studying the accompanying drawings, the disclosure, and the claims, can understand and implement other variations of the disclosed embodiments when practicing the claimed invention.

[0084] In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude multiple.

[0085] A single unit or device can perform the functions of several items recited in the claims. Although certain measures are recited in different dependent claims, this does not mean that combinations of these measures cannot be used advantageously.

[0086] Processes such as providing monitoring images or determining the location of a region of interest in a second monitoring image, which are performed by one or more units or devices, can also be performed by any other number of units or devices. For example, these processes can be performed by a single device. These processes and / or controls of the apparatus for monitoring the object can be implemented as program code modules of a computer program and / or dedicated hardware.

[0087] Computer programs can 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 can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0088] No reference numerals in the claims should be construed as limiting the scope.

[0089] This invention relates to an apparatus for monitoring an object during an imaging process (e.g., CT imaging). The apparatus includes: a monitoring image providing unit that provides a first monitoring image and a second monitoring image acquired at different support locations; a monitoring location providing unit that provides a first monitoring location of a region of interest (ROI) in the first monitoring image; a support location providing unit that provides support location data for the support location; a location mapping providing unit that provides a location mapping that maps the calibrated support location to the calibrated monitoring location; and a ROI location determining unit that determines the location of the ROI in the second monitoring image based on the first monitoring location, the support location data, and the location mapping. This allows for the accurate and computationally efficient determination of the ROI location.

Claims

1. An apparatus for monitoring a subject (121) during a medical imaging procedure using a medical imaging device (140), wherein, The imaging device includes a support (120) for supporting and moving the object (121) during the imaging process, and the device (110) includes: A monitoring image providing unit (111) is used to provide monitoring images of the object (121), the monitoring images including a first monitoring image and a second monitoring image of the object (121), wherein the first monitoring image is acquired at a first support position and the second monitoring image is acquired at a second support position; A monitoring location providing unit (112) is used to provide a first monitoring location and shape, wherein the first monitoring location and shape indicate the location and shape of the region of interest in the first monitoring image; A support position providing unit (113) is used to provide support position data, the support position data indicating the position of the support; A position mapping unit (114) is used to provide a position mapping, wherein the position mapping provides a mapping between calibration support positions and calibration monitoring positions during a calibration process, wherein calibration monitoring images are acquired at different calibration support positions having a calibration target (221) supported by the support (120), wherein the calibration monitoring position indicates the position of the calibration target (221) in the calibration monitoring image at the corresponding calibration support position indicated by the calibration support position data; The region of interest location determination unit (115) is used to determine the location and shape of the region of interest in the second monitoring image based on the first monitoring location and shape, the support location data, and the location mapping map. The device further includes a monitoring unit (116) for monitoring changes in the size and shape of the region of interest of the object (121), wherein the changes are monitored based on the second monitoring image and the position of the region of interest in the second monitoring image.

2. The apparatus according to claim 1, wherein, The monitoring images include multiple second monitoring images acquired at at least one second support location, wherein the support location providing unit is adapted to provide support location data for each of the at least one second support location, and wherein the region of interest location determining unit is adapted to determine the location and shape of the region of interest in each of the second monitoring images.

3. The apparatus according to any one of the preceding claims, wherein, The location mapping map maps multiple calibration monitoring locations relative to each calibration support location, with each calibration monitoring location indicating the location of a different part of the calibration target supported by the support.

4. The apparatus according to claim 3, wherein, The monitoring location providing unit is adapted to provide the first monitoring location in the first monitoring image based on a first monitoring location received from the user or based on information about where the region of interest is typically expected to be located in the first monitoring image.

5. The apparatus according to claim 3, wherein, Determining the location of the region of interest in the second monitoring image includes: determining a first calibration monitoring location, wherein the first calibration monitoring location corresponds to a calibration monitoring location in the location mapping derived from the first monitoring location in the first monitoring image; and further determining the location of the region of interest based on the first calibration monitoring location.

6. The apparatus according to claim 5, wherein, Determining the location of the region of interest in the second monitoring image includes: determining at least two calibration monitoring locations derived from the first monitoring location as the first calibration monitoring location, wherein the location of the region of interest is then determined by interpolation between the location map and the monitoring location determined in the second monitoring image based on the first calibration monitoring location.

7. The apparatus according to claim 1 or 2, wherein, Determining the location of the region of interest in the second monitoring image includes: Determine the location of a virtual first support, the location of which includes the result of processing the first monitoring location using the location mapping map; and The location of the region of interest in the second monitoring image is determined based on the location of the virtual first support, the support location data, and the location mapping.

8. The apparatus according to claim 1 or 2, wherein, The support location data includes the difference between the first support location and the second support location, and wherein the region of interest location determination unit is adapted to determine the location of the region of interest in the second monitoring image based on the first monitoring location, the difference, and the location mapping.

9. The apparatus according to claim 1 or 2, wherein, The support location providing unit is adapted to provide support location data by identifying the support in the corresponding image based on the first monitoring image and the second monitoring image.

10. The apparatus according to claim 1 or 2, wherein, Each monitoring image is acquired by a camera (130), wherein, during the medical imaging process, the field of view of each monitoring image is the same and covers all locations of interest in the region of interest.

11. The apparatus of claim 1 or 2, further comprising a calibration device for providing the position map, the calibration device comprising: A calibration monitoring image providing unit (211) is used to provide the calibration monitoring image; A calibration support position providing unit (212) for providing the calibration support position data; and The position mapping determination unit (213) is used to determine the position mapping by determining the mapping between the position of the calibration target (221) and the corresponding calibration support position for each calibration monitoring image.

12. A system (121) for acquiring medical images of a subject (121) during a medical imaging procedure using a medical imaging device (140), comprising: A medical imaging device (140) for acquiring medical images, wherein the medical imaging device (140) includes a support (130) for supporting the object during the medical imaging process; Camera (130), used to acquire monitoring images of the object (121) during the medical imaging procedure; and The apparatus (110) according to any of the preceding claims.

13. A method for monitoring a subject during a medical imaging procedure using a medical imaging device (140), wherein, The imaging device includes a support for supporting and moving the object during the imaging process, and the method (400) includes: Provide (410) monitoring images of the object, the monitoring images including a first monitoring image and a second monitoring image of the object, wherein the first monitoring image is acquired at a first support location and the second monitoring image is acquired at a second support location; Provides (420) a first monitoring location and shape, the first monitoring location and shape indicating the location and shape of the region of interest in the first monitoring image; Provide (430) support position data, the support position data indicating the position of the second support; Provide (440) a location mapping map, wherein the location mapping map provides a mapping between calibration support locations and calibration monitoring locations during the calibration process, during which calibration monitoring images are acquired at different calibration support locations having a calibration target (221) supported by the support (120), wherein the calibration monitoring location indicates the position of the calibration target in the monitoring image acquired at the corresponding calibration support location indicated by the calibration support location data; Based on the first monitoring location and shape, the support location data, and the location mapping, the location and shape of the region of interest in the second monitoring image are determined (450), and The size and shape changes of the region of interest of the object (121) are monitored based on the second monitoring image and the position of the region of interest in the second monitoring image.

14. A computer-readable medium storing a computer program for monitoring an object during a medical imaging procedure using a medical imaging device, wherein, The computer program includes a program code module, which, when the computer program is run by the apparatus according to claim 1, is used to cause the apparatus to perform the steps of the method according to claim 13.

Images