Patent Description:
X-ray imaging systems include an X-ray source and an X-ray detector. The X-ray source and the X-ray detector are separated by an examination region. An object may be disposed in the examination region in order to perform an X-ray imaging operation on the object. In order to avoid the need for repeat X-ray images and the associated increase in X-ray dose, it is important that the object to be imaged is correctly positioned with respect to the X-ray detector.

More specifically, X-ray detectors include radiation-sensitive regions that are used for generating X-ray image data, and it is important that the object is correctly positioned with respect to these radiation-sensitive regions in order to generate an X-ray image of the object.

Some X-ray detectors also include radiation dose-measurement regions that are used to generate dose data during generation of the X-ray image data. The dose data is sometimes used to automatically control a duration of the emission of X-ray radiation, and thereby provide a desired signal-to-noise ratio in the resulting X-ray image. This operation is sometimes referred to as automatic exposure control "AEC". The correct positioning of the patient with respect to these radiation dose-measurement regions is also important, particularly when performing an X-ray imaging procedure on an object that includes density variations.

By way of an example, when performing a lateral thorax imaging operation, it is important to firstly position a patient's thorax such that it overlaps the radiation sensitive regions of the X-ray detector, and to secondly position the X-ray detector's radiation dose-measurement region on the posterior side of the spine with little or no overlap with the spine. If the spine obscures the radiation dose measurement region, X-ray attenuation by the high density spine suppresses the measured dose data. If the dose data is used to automatically control the duration of the emission of X-ray radiation via automatic exposure control, the resulting prolongation of this duration can degrade the contrast in the X-ray image, rendering it inaccurate for diagnostic purposes.

The positioning of objects with respect to X-ray detectors is conventionally performed either by eye, or via a monitor that displays a visible, or red-green-blue "RGB" camera image of the object. Depth images that are generated by depth cameras may likewise be displayed on a monitor and used to position objects with respect to X-ray detectors in a similar manner. The extent of an X-ray detector's radiation-sensitive region and its radiation dose-measurement region is typically marked on the radiation-receiving surface of the detector. In-use, an operator positions the object with respect to the detector by eye, or via the monitor using the markings on the detector's surface.

However, conventional approaches for positioning objects with respect to X-ray detectors have drawbacks. In order to avoid obscuring the path between the X-ray source and the X-ray detector, the camera, and similarly the human eye, typically views the examination region between the X-ray source and X-ray detector from a position that is offset with respect to the X-ray source. With the depth camera in such an offset position, it is difficult for the operator to ascertain whether X-ray radiation emitted by the X-ray source will create a desired projection image of the object on the X-ray detector, particularly when the offset is large. Moreover, the object can obscure the markings on the radiation-receiving surface of the detector. Such issues can result in the object being sub-optimally positioned with respect to the detector, and the need to re-take the X-ray image. This hampers workflow, and increases the radiation dose to the object.

Consequently, there is a need to improve the way in which objects are positioned with respect to an X-ray detector.

<CIT> may be considered to disclose a synthetic depth camera image which is projected to the detector, wherein the image is adjusted to be the view as it would be from the X-ray source.

According to one aspect of the present disclosure, an X-ray imaging system is provided. The X-ray imaging system includes an X-ray source, an X-ray detector, a depth camera, and a processor. The X-ray source and the X-ray detector are separated by an examination region for performing an X-ray imaging operation on an object when the object is received within the examination region. The depth camera is configured to view the examination region for generating depth camera image data representing the object when the object is received within the examination region. The processor is configured to:.

Further aspects, features, and advantages of the present disclosure will become apparent from the following description of examples, which is made with reference to the accompanying drawings.

Examples of the present disclosure are provided with reference to the following description and figures. In this description, for the purposes of explanation, numerous specific details of certain examples are set forth. Reference in the specification to "an example", "an implementation" or similar language means that a feature, structure, or characteristic described in connection with the example is included in at least that one example. It is also to be appreciated that features described in relation to one example may also be used in another example, and that all features are not necessarily duplicated in each example for the sake of brevity. For instance, features described in relation to an X-ray imaging system, may be implemented in a computer implemented method, and in a computer program product, in a corresponding manner.

In the following description, reference is made to an X-ray imaging system. The X-ray imaging system may for example be the DigitalDiagnost C90 marketed by Philips Healthcare, Best, the Netherlands, or another type of X-ray imaging system. In some example arrangements, the X-ray source of the X-ray imaging system is mounted to a ceiling via a gantry, and the corresponding X-ray detector is mounted to a stand and held in the vertical position. However, examples of the present disclosure are not limited to this particular arrangement, and it is to be appreciated that the X-ray source and X-ray detector may alternatively be mounted in a different manner, and also held in different positions.

In the following description, reference is made to various methods that are implemented by a processor, i.e. a computer. It is noted that the computer-implemented methods disclosed herein may be provided as a non-transitory computer-readable storage medium including computer-readable instructions stored thereon, which, when executed by at least one processor, cause the at least one processor to perform the method. In other words, the computer-implemented methods may be implemented in a computer program product. The computer program product can be provided by dedicated hardware, or hardware capable of running the software in association with appropriate software. When provided by a processor, the functions of the method features can be provided by a single dedicated processor, or by a single shared processor, or by a plurality of individual processors, some of which can be shared. The explicit use of the terms "processor" or "controller" should not be interpreted as exclusively referring to hardware capable of running software, and can implicitly include, but is not limited to, digital signal processor "DSP" hardware, read only memory "ROM" for storing software, random access memory "RAM", a non-volatile storage device, and the like. Furthermore, examples of the present disclosure can take the form of a computer program product accessible from a computer-usable storage medium, or a computer-readable storage medium, the computer program product providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable storage medium or a computer readable storage medium can be any apparatus that can comprise, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or a semiconductor system or device or propagation medium. Examples of computer-readable media include semiconductor or solid state memories, magnetic tape, removable computer disks, random access memory "RAM", read-only memory "ROM", rigid magnetic disks and optical disks. Current examples of optical disks include compact disk-read only memory "CD-ROM", compact disk-read/write "CD-R/W", Blu-Ray™ and DVD.

As mentioned above, in order to avoid the need for repeat X-ray images and the associated increase in X-ray dose, it is important that an object to be imaged is correctly positioned with respect to an X-ray detector.

<FIG> is a schematic diagram illustrating a first perspective of an example X-ray imaging system <NUM> including an X-ray source and an X-ray detector <NUM>, in accordance with some aspects of the present disclosure. The X-ray imaging system <NUM> also includes a depth camera <NUM>, and a processor <NUM>. The X-ray source <NUM> and the X-ray detector <NUM> are separated by an examination region <NUM> for performing an X-ray imaging operation on an object <NUM> when the object is received within the examination region. The X-ray source and X-ray detector are typically maintained in a static position during the imaging operation. The object may for example be a portion of the human body, or indeed any object. In the illustrated example, the X-ray source is mounted to the ceiling via a gantry, and the X-ray detector is mounted to a stand and held in the vertical position. Alternative arrangements, mounting arrangements, and positions of the X-ray source <NUM> and the X-ray detector <NUM> may also be used.

<FIG> is a schematic diagram illustrating a second perspective of an example X-ray imaging system <NUM> including an X-ray source and an X-ray detector <NUM>, in accordance with some aspects of the present disclosure. As compared to <FIG>, the perspective of <FIG> more clearly illustrates the position of the X-ray source <NUM> and the depth camera <NUM>. Also, in <FIG>, an example object <NUM> in the form of a patient, is received within the examination region <NUM> in order to perform an X-ray imaging operation, in the illustrated case, a chest X-ray imaging operation, on the patient. The solid lines extending between the X-ray source <NUM> and the X-ray detector <NUM> in <FIG> indicate the volumetric extent of the overlap between the X-ray beam emitted by the X-ray source <NUM>, and the X-ray radiation-sensitive region of the X-ray detector <NUM>, and within which the X-ray image data may be generated. The volumetric extent of this overlap defines the examination region <NUM>. A perimeter of the X-ray radiation-sensitive region <NUM> of the X-ray detector may be marked on the radiation-receiving surface of the X-ray detector, as illustrated by the rectangular outline on the X-ray detector in <FIG>. In some examples, the X-ray detector <NUM> also includes one or more radiation dose-measurement regions <NUM> for generating X-ray dose measurement data. These are sometimes referred-to as automatic exposure control "AEC" chambers. In the illustrated example in <FIG>, there are five circular radiation dose-measurement regions, although in other examples these may have a different shape, and there may be a different number of radiation dose-measurement regions, or even none at all.

In-use, it is desirable that the object <NUM> is correctly positioned with respect to the X-ray detector <NUM>, or more specifically with respect to the X-ray radiation-sensitive region <NUM> and/or the one or more radiation dose-measurement regions <NUM>, in order to obtain reliable X-ray images of the object <NUM>.

The depth camera <NUM> illustrated in <FIG> is configured to view the examination region <NUM> in order to generate depth camera image data representing the object <NUM> when the object is received within the examination region <NUM>. In other words, the depth camera <NUM> has a field of view, which overlaps with a portion of the examination region <NUM>. In general, the depth camera image data generated by a depth camera represents the range between the depth camera and points on the surfaces of objects within the depth camera's field of view. With reference to <FIG>, the depth camera image data may therefore represent a three-dimensional shape of a surface of the object <NUM>. In the example arrangement illustrated in <FIG>, the minimum extent of the field of view of the depth camera is indicated by the dashed lines extending between the depth camera <NUM> and the X-ray detector <NUM>.

The depth camera <NUM> in the example arrangement illustrated in <FIG> is mechanically coupled to the X-ray source <NUM>. However the depth camera <NUM> may alternatively be positioned elsewhere in order to view the examination region <NUM>. The depth camera may for example be mechanically coupled to a wall, or to a ceiling of a room in which the X-ray imaging system <NUM> is located, or it may be mechanically coupled to a floor-based stand in the room. The depth camera may alternatively be mobile. In some examples, the depth camera may therefore be capable of being moved around a room in which the X-ray imaging system <NUM> is located. In each of these alternative arrangements, the depth camera is able to view the examination region <NUM>.

The use of various types of depth camera is contemplated for depth camera <NUM>. The camera may for example employ a time-of-flight, or LIDAR principle, or a structured light principle, or a binocular stereo vision principle. In the time-of-flight, or LIDAR principle, the time taken for emitted light pulses to travel from the position of the camera to objects in a scene and back again, is used to generate depth camera image data representing the range to the objects. The Azure Kinect DK depth camera, and the Intel RealSense™ LiDAR Camera L515 are examples of depth cameras that employ this principle. In the structured light principle, an optical pattern is projected onto the surface of objects within a scene, and the disparity between the original projected pattern, and the pattern that is deformed by the surface of the objects is imaged by one or more cameras. In the binocular stereo vision principle, different views of a scene are used to compute a depth map of the scene.

In some examples, the depth camera <NUM> also generates optical image data representing the object <NUM> when the object is received within the examination region <NUM>. This optical image data may be provided by the aforementioned cameras in addition to the depth camera image data that they provide. Such cameras may be referred-to as RGB-D cameras. The optical image data may represent a visible or infrared portion of the optical spectrum.

The processor <NUM> illustrated in <FIG> is configured to receive the depth camera image data. The processor may receive the depth camera image data via any form of digital communication. The processor <NUM> may receive the depth camera image data from the depth camera <NUM>. The communication path may be direct, or indirect. The processor <NUM> and the depth camera <NUM> may for example include a direct wired or wireless communication path, such as an electrical cable or ethernet, or a wireless infrared or RF communication path such as Bluetooth, as illustrated by the arrows connecting these items in <FIG>. Alternatively, the communication path may be indirect, and the processor <NUM> and the depth camera <NUM> may be in communication with one another via the internet, the cloud, or a computer readable storage memory.

Moreover, the processor <NUM> is configured to:.

In so doing, an image representation <NUM> is provided that obviates one or more challenges involved in positioning the object with respect to the X-ray source. These are described with reference to <FIG>.

<FIG> is a schematic diagram illustrating a comparative example of an arrangement including an X-ray source, an X-ray detector <NUM> and a depth camera <NUM>. In <FIG>, the X-ray source and the X-ray detector are separated by an examination region <NUM>. The X-ray source and the X-ray detector may be used to perform an X-ray imaging operation on an object <NUM> that is disposed in the examination region <NUM>. The X-ray source <NUM> generates X-ray radiation within a volumetric beam defined by solid angle Ωx, and which is detected by X-ray detector <NUM> in order to generate X-ray image data. A depth camera <NUM>, or alternatively an optical camera, is located at an offset position with respect to an axis <NUM> passing through the X-ray source <NUM> and a centre of the X-ray detector. The depth camera <NUM> is arranged so as to view the examination region <NUM>, and also the object <NUM>. Depth camera images, or indeed optical camera images, that are generated from this offset position provide some assistance to an operator in positioning the object <NUM> with respect to the detector <NUM> in order to generate X-ray images of the object <NUM>. However, with the depth camera in this offset position, it is difficult for the operator to ascertain whether X-ray radiation emitted by the X-ray source will create a desired projection image of the object <NUM> on the X-ray detector <NUM>, particularly when the offset is large. The <FIG> arrangement may therefore lead to the object <NUM> being mis-positioned with respect to the X-ray detector, and the need to re-take the X-ray image with the object <NUM> in a better position.

In order to address this issue, in one prior art approach it has been proposed to transform the depth camera image data, and to view the depth camera image data from the perspective of the X-ray source. This approach, however, results in a view of the object <NUM> that is unintuitive. Moreover, it suffers from the drawback of missing depth camera image data in occluded regions of the detector's surface. With reference to the arrangement illustrated in <FIG>, the solid angle Ωc and the dashed lines extending from the depth camera <NUM> define the extent of the boundary of the object <NUM> on the X-ray detector's surface, as seen from the perspective of the depth camera. The solid lines extending from the X-ray source indicate the extent of the boundary of the object <NUM> on the surface of the detector <NUM> when viewed from the perspective of the X-ray source <NUM>. When viewed from this perspective, depth camera image data is missing from the hatched occluded region in <FIG>. In order to compensate for the missing depth camera image data in the occluded region, the occluded region may be in-painted with data that is obtained in the absence of the object <NUM>. This adds further complexity to approaches that involve viewing the depth camera image data from the perspective of the X-ray source.

<FIG> is a schematic diagram illustrating an example arrangement including an X-ray source, an X-ray detector <NUM>, a depth camera <NUM>, and a processor <NUM>, in accordance with some aspects of the present disclosure. As in the comparative example of <FIG>, in <FIG>, a depth camera <NUM> is positioned in order to view the examination region <NUM>. In contrast to the comparative example described with reference to <FIG>, in the approach of the present disclosure, the depth camera image data is projected onto a radiation-receiving surface of the X-ray detector <NUM>, from a perspective of the X-ray source <NUM>. An image representation <NUM> is then generated of the projected depth camera image data on the radiation-receiving surface of the X-ray detector <NUM>, from a perspective of the depth camera <NUM>. The projection is performed in a mathematical sense, based on the relative positions of the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>. With reference to <FIG>, this is illustrated by way of the portion of the surface <NUM> of the object <NUM> and which is viewed by the depth camera <NUM>, being projected onto the radiation-receiving surface of the X-ray detector <NUM> in order to provide projected image data <NUM>. An image representation is subsequently generated of this projected image data <NUM>, from the perspective of the depth camera <NUM>. This image representation is more intuitive than a view of the depth camera image data from the perspective of the X-ray source. Consequently, the use of this image representation reduces the opportunity for the object <NUM> to be mis-positioned with respect to the X-ray detector <NUM>, alleviating the need to re-take the X-ray image. Moreover, because the image representation is provided from the perspective of the depth camera, there is no need for in-painting because this is the same perspective as that from which the depth camera image data was acquired.

The projection of the depth camera image data onto the radiation-receiving surface of the X-ray detector <NUM>, and the generation of the image representation <NUM> of the projected depth camera image data, may in general be performed based on a predetermined spatial relationship between the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>. The predetermined spatial relationship may be used to compute a spatial transformation that is applied to the relevant data to perform the projection.

The predetermined spatial relationship between the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM> may be determined in different ways.

In some examples, the positions of one or more of the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM> are fixed positions, and the predetermined spatial relationship is determined using calibration data that represents the fixed position(s). In some examples, the positions of all three of the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM> are fixed. In these examples, the predetermined spatial relationship between the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>, may be determined based on calibration data representing the relative positions of the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>.

The positions of the X-ray source <NUM>, X-ray detector <NUM>, and depth camera <NUM>, may be fixed by for example mechanically attaching the relevant item to a reference position, such as the wall, the ceiling, the floor, and so forth. In some examples, it is contemplated to permit one or more of these items to be positioned in one of multiple selectable fixed positions, and to provide calibration data representing each of the fixed positions. For example, the X-ray source <NUM> and/or X-ray detector <NUM> may be moved into one of multiple selectable fixed positions. Calibration data representing the positions or the relative positions may be stored in a database, for example as a lookup table, and accessed by the processor in order to compute the aforementioned spatial transformation.

In some examples, the positions of one or more of the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera may be movable to any position, and the predetermined spatial relationship between the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>, is determined using a position sensor. Various types of position sensors are contemplated in this respect, including position sensors that employ optical, radiofrequency "RF", or ultrasound tracking techniques. Examples of suitable position sensors include laser-based optical rangefinders, RF and ultrasound ranging transponders, and optical cameras that are configured to track the positions of fiducial markers disposed on one or more of the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>. In one example, a further depth camera is used to track the positions of one or more of the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>.

In one example, a spatial relationship between the depth camera <NUM> and the X-ray detector <NUM> is determined from depth camera image data that is generated by the depth camera <NUM>. In this example, the depth camera <NUM> is further configured to view at least a portion of the radiation-receiving surface of the X-ray detector <NUM>, and the depth camera <NUM> is further configured to generate depth camera image data representing the at least a portion of the radiation receiving surface of the X-ray detector <NUM>. The processor <NUM> is further configured to determine a spatial relationship between the depth camera <NUM> and the X-ray detector <NUM> from the generated depth camera image data representing the at least a portion of the radiation receiving surface of the X-ray detector <NUM>, and to determine the spatial relationship between the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>, using the determined spatial relationship between the depth camera <NUM> and the X-ray detector <NUM>.

In this example, the depth camera <NUM> may view the portion of the surface of the X-ray detector <NUM> whilst the object <NUM> is received within the examination region <NUM>, or in the absence of the object <NUM>. In the latter case, the spatial relationship between the between the depth camera <NUM> and the X-ray detector <NUM> may be determined before the object is received within the examination region <NUM>. For example, the spatial relationship may be determined immediately prior to the object being received within the examination region <NUM>, or once per hour, once per day, or at a different time interval. As in the example above, calibration data representing the determined spatial relationship may be stored in a database, for example as a lookup table, and accessed by the processor <NUM> in order to compute the aforementioned spatial transformation.

Continuing with this example, the spatial relationship between the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>, may be determined using the spatial relationship between the depth camera <NUM> and the X-ray detector <NUM> that is determined from the generated depth camera image data, and based further on calibration data representing the relative positions of the X-ray source <NUM> and the depth camera <NUM> and/or the relative positions of the X-ray source <NUM> and the X-ray detector <NUM>. By using this calibration data in combination with the spatial relationship between the depth camera <NUM> and the X-ray detector <NUM> that is determined from the generated depth camera image data, the relative positions of all three of the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>, may be determined. The calibration data may be stored in a database and accessed by the processor <NUM> in order to determine the aforementioned spatial transformation.

Continuing with this example, in <FIG>, the depth camera <NUM> may be mechanically coupled to the X-ray source <NUM>, and the calibration data may represent the relative positions of the X-ray source <NUM> and the depth camera <NUM>. The depth camera <NUM> may alternatively be mechanically coupled to the X-ray source <NUM> and be movable into one of multiple selectable fixed positions. In this example, the calibration data may represent the multiple relative positions. Calibration data representing fixed relative positions of the X-ray source <NUM> and the X-ray detector <NUM> may be stored and used in a similar manner in combination with the spatial relationship between the depth camera <NUM> and the X-ray detector <NUM> that is determined from the generated depth camera image data, in order to determine the relative positions of all three of the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>.

<FIG> illustrate various example image representations in accordance with the present disclosure. In general, it is noted that an image representation may be provided as a two-dimensional image, or a three-dimensional image.

<FIG> is a schematic diagram illustrating a first example of an image representation <NUM> of projected depth camera image data on the radiation-receiving surface of an X-ray detector <NUM>, from a perspective of the depth camera <NUM>, in accordance with some aspects of the present disclosure. In <FIG>, the image representation <NUM> includes projected depth camera image data corresponding to the surface of the patient, as well as part of the radiation-receiving surface of the X-ray detector <NUM>. The <FIG> image representation permits an operator to position the patient with respect to the outer perimeter of the X-ray detector.

In some examples, the X-ray detector <NUM> includes one or more radiation-sensitive regions <NUM> for generating X-ray image data and/or one or more radiation dose-measurement regions <NUM> for generating X-ray dose measurement data. In one example, the processor <NUM> is configured to generate an overlay image representation including the one or more X-ray radiation-sensitive regions <NUM> and/or a representation of the one or more X-ray radiation dose-measurement regions <NUM>, and the image representation <NUM> of the projected depth camera image data. This is illustrated in <FIG>, which is a schematic diagram illustrating a second example of an image representation <NUM> of projected depth camera image data on the radiation-receiving surface of an X-ray detector <NUM>, from a perspective of the depth camera <NUM>, in accordance with some aspects of the present disclosure.

As compared to <FIG>, in <FIG>, the projected depth camera image data is overlaid on top of the example five X-ray radiation dose-measurement regions <NUM> and the radiation-sensitive region <NUM>. In <FIG>, the patient is displayed in semi-transparent form. The X-ray detector <NUM> appears in the background, and the projected object <NUM>, i.e. the patient, is provided as a semi-transparent overlay on top of the background. Alternatively, the projected object <NUM>, i.e. the patient, may appear in the background, and the X-ray radiation-sensitive region(s) <NUM> and/or X-ray radiation dose-measurement region(s) <NUM>, may be overlaid on top of the patient. The <FIG> image representation permits an operator to position the patient with respect to the X-ray radiation-sensitive regions <NUM>, and with respect to the example five X-ray radiation dose-measurement regions <NUM>.

With reference to the <FIG> example, the overlaying of the X-ray radiation-sensitive region(s) <NUM> and/or the X-ray radiation dose-measurement region(s) <NUM>, and the projected depth camera image data, may be performed by i) detecting the radiation-receiving surface of the X-ray detector in the projected depth camera image data, and ii) mapping the positions of the X-ray radiation-sensitive region(s) <NUM> and/or the X-ray radiation dose-measurement region(s) <NUM> onto the detected radiation-receiving surface of the X-ray detector based on a knowledge of their positions respective the radiation-receiving surface of the X-ray detector <NUM>. The positions of the X-ray radiation-sensitive region(s) <NUM> and/or the X-ray radiation dose-measurement region(s) <NUM> respective the radiation-receiving surface of the X-ray detector <NUM>, may be determined by generating a reference depth camera image that includes the radiation-receiving surface of the X-ray detector <NUM> in the absence of the object <NUM>, i.e. the illustrated patient, and determining the positions of the X-ray radiation-sensitive region(s) <NUM> and the X-ray radiation dose-measurement region(s) <NUM> respective the reference depth camera image from a corresponding RGB image. Alternatively, the position of the X-ray radiation-sensitive region(s) <NUM> and the X-ray radiation dose-measurement region(s) <NUM> respective the radiation-receiving surface of the X-ray detector <NUM> may be known from calibration data representing a geometric model of their positions.

<FIG> is a schematic diagram illustrating a third example of an image representation <NUM> of projected depth camera image data on the radiation-receiving surface of an X-ray detector <NUM>, from a perspective of the depth camera <NUM>, in accordance with some aspects of the present disclosure. As compared to <FIG>, in the <FIG> image representation <NUM>, the surface of the patient is replaced by its silhouette on the surface of the X-ray detector <NUM>.

<FIG> is a schematic diagram illustrating a fourth example of an image representation <NUM> of projected depth camera image data on the radiation-receiving surface of an X-ray detector <NUM>, from a perspective of the depth camera <NUM>, in accordance with some aspects of the present disclosure. As compared to <FIG>, in the <FIG> image representation <NUM>, the surface of the patient is replaced by its outline where it overlaps the surface of the X-ray detector.

<FIG> is a schematic diagram illustrating a fifth example of an image representation <NUM> of projected depth camera image data on the radiation-receiving surface of an X-ray detector <NUM>, from a perspective of the depth camera <NUM>, in accordance with some aspects of the present disclosure. As compared to <FIG>, in the <FIG> image representation <NUM>, provides a schematic visualisation of the position of the object <NUM> respective the X-ray radiation-sensitive region <NUM> and the X-ray radiation dose-measurement regions <NUM>. In the schematic visualisation, the object is identified in the depth camera image data and substituted with a schematic illustration of the object.

In one example, one or more corrective actions for obtaining a more-optimal position of the patient with respect to the X-ray detector <NUM> are also generated. In this example, the processor <NUM> is further configured to compute a displacement between a position of one or more features in the image representation <NUM> of the projected depth camera image data, and an expected position of the one or more features respective i) the representation of the one or more X-ray radiation-sensitive regions <NUM> and/or ii) the representation of the one or more X-ray radiation dose-measurement regions <NUM>. The processor <NUM> is further configured to generate, based on the computed displacement, an output representing one or more corrective actions for reducing the displacement.

In this example, image processing techniques may be used identify features such as a silhouette of the patient on the surface of the X-ray detector, or the position of a limb, or the head, and so forth, from the depth camera image data. The expected position of the feature may be determined based on user input of the type of imaging operation taking place, based on the automatic detection of a current position of an anatomical landmark or region of the patient, based on a classification of the view of the patient, or a combination of these factors. For example, if a chest imaging operation is taking place, the silhouette of the patient's torso on the surface of the detector may be identified, and the corrective actions may include "move torso to the right by <NUM> centimetres" in order to align the patient's torso with the X-ray radiation-sensitive region <NUM>. The corrective actions may be outputted in the form of audio instructions, or displayed on a monitor. For example, directional arrows accompanied by a distance by which the object should be moved may be overlaid on the relevant portion of the image representation <NUM>.

In one example, the depth camera <NUM> also generates optical image data. In this example, the processor <NUM> generates the image representation <NUM> of the projected depth camera image data, such that the image representation includes the optical image data. An RGB-D camera may for example be used to provide the optical image data in addition to the depth camera image data. The optical image data may be in the visible or infrared potion of the electromagnetic spectrum. The optical image data may be included in the image representation <NUM> by generating an overlay of the optical image data and the representation of the projected depth camera image data. The overlay may further assist a user in positioning the patient with respect to the X-ray detector <NUM>.

Returning to <FIG>. In most situations, the portion of the surface <NUM> of the object <NUM> that is "visible" from the perspective of the X-ray source <NUM>, and which is projected onto the surface of the X-ray detector <NUM>, can be determined to a very good approximation from the depth camera image data, despite its offset position. However, if the offset is large, the projected surface of the object may be incomplete on the opposite side of the X-ray source to the offset, i.e. at the lower portion of the projected image data <NUM> in <FIG>. In such situations, a more complete projection of the depth camera image data onto the radiation-receiving surface of the X-ray detector <NUM>, from a perspective of the X-ray source <NUM>, can be obtained by combining the projection data that is obtained from different rotational positions of the depth camera with respect to the X-ray source <NUM>. Thus, in one example, the depth camera is mechanically coupled to the X-ray source <NUM>, and the depth camera <NUM> is offset in a radial direction with respect to an axis <NUM> passing through the X-ray source <NUM> and a centre of the X-ray detector <NUM>, or the depth camera <NUM> is offset in a radial direction with respect to an axis passing through a centre of a radiation beam emitted by the X-ray source <NUM>. The depth camera <NUM> is rotatable about said axis <NUM> for generating the depth camera image data from different rotational positions with respect to the axis.

In this example, both the depth camera <NUM> and the X-ray source may be rotatable about the axis together; i.e. there is no relative movement between the X-ray source and the X-ray detector during the rotation, or the depth camera <NUM> may be independently rotatable with respect to the X-ray source; and in which case the X-ray detector remains static whilst the depth camera is rotated. In this example, the depth camera may be freely rotated to any angular position, or indeed the depth camera may be rotated to one of multiple selectable fixed rotational positions. The rotational positions may for example be separated by <NUM> degrees, or by <NUM> degrees, or by another angle. In so doing, a more accurate positioning of the object <NUM> with respect to the X-ray detector <NUM>, may be achieved.

In one example, a further image representation of the projected depth camera image data may also be provided. In this example, the processor <NUM> generates an image representation <NUM> of the projected depth camera image data, from a perspective of the X-ray source <NUM>. This projection may be determined based on the aforementioned predetermined spatial relationship between the X-ray source <NUM>, the X-ray detector <NUM>, and the depth camera <NUM>. This further image representation may also be used to assist an operator to position the object with respect to the X-ray detector.

In one example, X-ray images may also be generated. In this example, the X-ray detector <NUM> is configured to generate X-ray image data representing the attenuation of X-ray radiation emitted by the X-ray source <NUM>, within the examination region <NUM>, and the processor <NUM> is further configured to generate an X-ray image representation of the X-ray image data.

In another example, a computer-implemented method is provided for use with the X-ray imaging system <NUM>. The computer-implemented method of generating an image representation <NUM> using an X-ray imaging system comprising an X-ray source <NUM>, an X-ray detector <NUM>, and a depth camera <NUM>, wherein the X-ray source <NUM> and the X-ray detector <NUM> are separated by an examination region <NUM> for performing an X-ray imaging operation on an object when the object is received within the examination region, and wherein the depth camera <NUM> is configured to view the examination region <NUM> for generating depth camera image data representing the object when the object is received within the examination region; includes:.

In another example, a computer program product is provided for use with the X-ray imaging system <NUM>. The computer program product comprises instructions which when executed by one or more processors <NUM>, cause the one or more processors <NUM> to carry out a method of generating an image representation <NUM> using an X-ray imaging system comprising an X-ray source <NUM>, an X-ray detector <NUM>, and a depth camera <NUM>, wherein the X-ray source <NUM> and the X-ray detector <NUM> are separated by an examination region <NUM> for performing an X-ray imaging operation on an object when the object is received within the examination region, and wherein the depth camera <NUM> is configured to view the examination region <NUM> for generating depth camera image data representing the object when the object is received within the examination region. The method comprises:.

Claim 1:
An X-ray imaging system (<NUM>) comprising:
an X-ray source (<NUM>);
an X-ray detector (<NUM>);
a depth camera (<NUM>); and
a processor (<NUM>);
wherein the X-ray source (<NUM>) and the X-ray detector (<NUM>) are separated by an examination region (<NUM>) for performing an X-ray imaging operation on an object (<NUM>) when the object is received within the examination region;
wherein the depth camera (<NUM>) is configured to view the examination region (<NUM>) for generating depth camera image data representing the object when the object is received within the examination region; and
wherein the processor (<NUM>) is configured to:
receive the depth camera image data;
project the depth camera image data onto a radiation-receiving surface of the X-ray detector (<NUM>), from a perspective of the X-ray source (<NUM>); and to
generate an image representation (<NUM>) of the projected depth camera image data on the radiation-receiving surface of the X-ray detector (<NUM>), from a perspective of the depth camera (<NUM>).