Patent Description:
Bedside X-ray is a standard procedure that is performed everywhere where the patient cannot stand upright for a conventional X-ray radiography examination. An example of a bedside X-ray procedure is for chest examinations, since pulmonary disorders are quite common in patients who are immobile. An X-ray detector unit is placed behind the patient lying on the bed, thus typically between the patient and the mattress, and where the mattress could be hinged in the middle thereby inclining the patient and therefore the X-ray detector need not be horizontal. An X-ray source is then positioned in front of the patient and an X-ray image or radiogram is acquired. An example of known radiography devices is shown in <CIT>, which discloses an X-ray source, an X-ray detector with a sensor unit and a processing unit.

One of the problems that is associated with an optimal acquisition of bedside X-rays with such a mobile X-ray system is the correct positioning of the field of view. In particular, as discussed above the X-ray detector is positioned behind the patient's back and the X-ray source or tube has to be positioned and its collimation adapted in such a manner that the chest of the patient is properly imaged. Misalignment of the X-ray tube with the detector leads to cut-off images that hamper proper image reading. A proper alignment between the detector and the X-ray tube/source is difficult to achieve, since the exact position of the detector is typically not visible behind the patient's back. Hence, a significant number of X-ray images have suboptimal patient positioning, which in its turn leads to missed diagnosis and suboptimal workflow as some images have to be retaken. An example of a cut-off image is shown in <FIG>.

It would be advantageous to have an improved medical imaging system for acquiring bedside X-ray images of patients, that provides utility to mobile medical imaging systems. It should be noted that the following described aspects and examples of the invention apply to the medical imaging system, and also to the medical imaging method as well as to the computer program element and the computer readable medium.

In a first aspect, there is provided a medical imaging system, comprising:.

The X-ray detector unit is configured to be placed relative to the X-ray source to acquire X-ray image data of a patient (P) positioned between the X-ray detector unit and the X-ray source unit. The reference structure is part of the X-ray detector unit or the reference structure is configured to be fixedly connected to the X-ray detector unit. An orientation of the sensor unit is known with respect to an orientation of the X-ray source unit. The sensor unit is configured to acquire a sensor image when the X-ray detector unit is placed relative to the X-ray source unit and the patient is positioned between the X-ray detector unit and the X-ray source unit, and the sensor image comprises image data of the reference structure. The sensor unit is configured to provide the sensor image to the processing unit. The processing unit is configured to determine a position of the X-ray detector unit with respect to a position of the X-ray source unit. The determination comprises utilization of the orientation of the sensor unit with respect to the orientation of the X-ray source unit and the image data of the reference structure.

Thus, the system is configured such that when the detector unit is behind a patient, a reference structure that is a part of the detector unit or that has been fixedly attached or connected to the detector unit can be imaged. The processing unit can then determine the position and orientation of the sensor unit with respect to the detector unit through interpretation of the imaged reference structure. Then, because the orientation of the sensor unit with respect to the source unit is known, the processing unit can determine the position and orientation of the detector unit with respect to the source unit. It can then be determined if the detector unit is correctly positioned, or if it is off-centered and/or twisted or tilted, and also the applied collimation can be checked with respect to the detector position.

In an example, the processing unit is configured to determine a required movement of the X-ray source unit on the basis of the determined position of the X-ray detector unit with respect to the position of the X-ray source unit.

In this manner, an automatic or semi-automatic solution can be provided. Thus, the required movement can be in the form of a required movement provided to an operator, who then moves the source unit. However, the source unit can be mounted in a mechanical movement system providing for at least some movement of the source unit. Thus, the processing unit can determine how the source unit needs to be moved and can then control the movement of the source unit to move it to a new required and optimized position with respect to the detector unit.

Also, it is normally required to have a pre-defined or required source to image distance (SID) for proper imaging results, and the system enables it to be checked if the distance between the source and the detector are suitable. Thus, the required movement can be a translational movement sideways and/or a movement forwards backwards.

In an example, the system comprises a visual display unit (VDU), and the sensor image comprises image data of the patient. The processing unit is configured to project the image data of the patient onto the VDU with respect to the position of the X-ray source unit and the processing unit is configured to display on the VDU a representation of the position of the X-ray detector unit with respect to the position of the X-ray source unit.

In other words, an image of the patient is displayed on a VDU as if the X-ray source had acquired the image of the patient and at the same time a representation of the position of the detector, such as an outline of the outer extent of the detector area is also displayed on the VDU. In this way an operator can quickly and effectively see if the detector is correctly aligned with respect to the X-ray source and whether the patient is correctly aligned with respect to the X-ray source and/or the detector.

In an example, the reference structure comprises a handle of the X-ray detector unit.

In an example, the reference structure comprises a structure extending laterally from an edge of the X-ray detector unit.

In an example, the reference structure comprises one or more markers.

In an example, the one or more markers extend perpendicularly to the structure extending laterally from the edge of the X-ray detector unit.

In an example, the reference structure comprises three markers.

In an example, the one or more markers comprises a plurality of markers and wherein a first marker is oriented perpendicularly to a second marker.

In an example, the first marker is oriented perpendicularly to the third marker.

Thus, the reference structure is in effect a calibration structure, and image data of the reference structure enables the distance to and orientation of the reference structure to be determined, from which the distance to and orientation of the detector can be determined because the reference structure is at a known location and orientation with respect to the detector itself. Then, as detailed above this can be used to determine the relative positions of the X-ray source unit and X-ray detector unit enabling it to be determined if they are correctly aligned one with the other.

In an example, the sensor unit is integrated with the X-ray source unit.

In this manner, a simple combined source/sensor unit is provided. However, the sensor unit and source unit need not be in a combined unit.

In an example, the sensor image comprises image data of the patient. The processing unit is configured to determine a collimation of the X-ray source unit comprising utilization of the orientation of the sensor unit with respect to the orientation of the X-ray source unit and the image data of the patient.

In this manner, not only can it be determined if the x-ray source is correctly aligned with the X-ray detector it can be determined if the patient is correctly aligned with respect to the X-ray source and its collimation adjusted if required.

In an example, the processing unit is configured to determine a required movement of the X-ray source unit on the basis of the determined collimation of the X-ray source unit.

In an example, the processing unit is configured to determine a required movement of the X-ray detector unit on the basis of the determined collimation of the X-ray source unit.

Thus, the new collimation could then lead to the X-ray source unit not then being correctly aligned with respect to the X-ray detector unit. However, now the X-ray source and/or the X-ray detector unit can then be moved with respect to each other and indeed with respect to the patient, and indeed if necessary the patient could be moved, in order to provide for correct exposure. This can lead to a further slight adjustment in the required collimation of the X-ray source and to further movements of the X-ray source/X-ray detector, which is facilitated by the new system. The collimation and movement of the X-ray source unit can be fully automated and controlled by the processing unit, or information can be provided to an operator to adjust the collimation and move the source etc..

In a second aspect, there is provided a medical imaging method, comprising:.

According to another aspect, there is provided a computer program element controlling one or more of the systems as previously described which, if the computer program element is executed by a processor, is adapted to perform the method as previously described.

According to another aspect, there is provided a computer readable medium having stored computer element as previously described.

The computer program element can for example be a software program but can also be a FPGA, a PLD or any other appropriate digital means.

<FIG> shows a schematic example of a medical imaging system <NUM>. The medical imaging system comprises an X-ray source unit <NUM>, an X-ray detector unit <NUM>, a sensor unit <NUM>, a reference structure <NUM>, and a processing unit <NUM>. The X-ray detector unit <NUM> is configured to be placed relative to the X-ray source unit <NUM> to acquire X-ray image data of a patient (P) positioned between the X-ray detector unit <NUM> and the X-ray source unit <NUM>. The reference structure <NUM> is part of the X-ray detector unit <NUM> or the reference structure <NUM> is configured to be fixedly connected to the X-ray detector unit <NUM>. An orientation of the sensor unit <NUM> is known with respect to an orientation of the X-ray source unit <NUM>. The sensor unit <NUM> is configured to acquire a sensor image when the X-ray detector unit <NUM> is placed relative to the X-ray source unit <NUM> and the patient is positioned between the X-ray detector unit <NUM> and the X-ray source unit <NUM>, and the sensor image comprises image data of the reference structure <NUM>. The sensor unit <NUM> is configured to provide the sensor image to the processing unit <NUM>. The processing unit <NUM> is configured to determine a position of the X-ray detector unit <NUM> with respect to a position of the X-ray source unit <NUM>. The determination of the position of the X-ray detector unit <NUM> with respect to the position of the X-ray source unit <NUM> comprises utilization of the orientation of the sensor unit <NUM> with respect to the orientation of the X-ray source unit <NUM> and the image data of the reference structure <NUM>.

In an example, the medical imaging system <NUM> is a mobile medical imaging system.

In an example, the sensor unit <NUM> is a camera unit and the sensor image is a camera image.

In an example, the camera unit is a 3D camera unit. Thus, the camera unit can have two cameras <NUM>, <NUM> and the camera image is then an image generated from the two images of the 3D camera, providing an efficient means to determine the distance to and orientation of the reference structure <NUM> with respect to the camera unit and hence the position and orientation of the X-ray detector unit <NUM> with respect to the camera unit, and as detailed above then translate this into the position and orientation of the X-ray detector unit <NUM> with respect to the X-ray source unit <NUM>. However, the camera unit need not be a 3D camera and a 2D image can be utilized.

In an example, the reference structure <NUM> has for example a stalk <NUM> of a known length, or segments of known length, then image data of this structure can be used to determine a distance of the reference structure <NUM> from the camera unit. Then, parts <NUM> of the reference structure <NUM> can extend in a known way from a stalk and image data of these parts can be used to determine a rotational aspect of the reference structure <NUM> to the camera unit. Thus, then a distance and orientation of the reference structure <NUM> and hence the distance and orientation of the X-ray detector unit <NUM> from the camera unit can be determined on the basis of this 2D image, and then as detailed above the position and orientation of the X-ray detector unit <NUM> with respect to the X-ray source unit <NUM> can then be determined.

In an example, the camera unit comprises one or more radiation sources <NUM>, <NUM>. In an example, the one or more radiation sources are infrared radiation sources.

Thus, the system can operate in all light conditions.

In an example, the reference structure <NUM> has reflector segments. In an example the reflector segments are designed to reflect radiation emitted by the one or more radiation sources.

In an example, the sensor unit <NUM> is a LIDAR unit, and the sensor image is an image constructed from laser range information.

In an example, the sensor unit <NUM> is a radar unit, and the sensor image is a radar range constructed image.

According to an example, the processing unit <NUM> is configured to determine a required movement of the X-ray source unit <NUM> on the basis of the determined position of the X-ray detector unit <NUM> with respect to the position of the X-ray source unit <NUM>.

In an example, the processing unit <NUM> is configured to determine a required movement of the X-ray detector unit <NUM> on the basis of the determined position of the X-ray detector unit <NUM> with respect to the position of the X-ray source unit <NUM>.

According to an example, the system comprises a visual display unit (VDU). The sensor image can comprise image data of the patient, and the processing unit <NUM> is configured to project the image data of the patient onto the VDU with respect to the position of the X-ray source unit <NUM> and the processing unit <NUM> is configured to display on the VDU a representation of the position of the X-ray detector unit <NUM> with respect to the position of the X-ray source unit <NUM> and also with respect to the patient.

In an example, the processing unit <NUM> is configured to project a field of view of the X-ray source unit <NUM> onto the VDU.

According to an example, the reference structure <NUM> comprises a handle <NUM> of the X-ray detector unit <NUM>.

According to an example, the reference structure <NUM> comprises a structure <NUM>, <NUM> extending laterally from an edge of the X-ray detector unit <NUM>.

In an example, the structure <NUM>, <NUM> extending laterally from an edge of the X-ray detector unit comprises a stalk <NUM>.

In an example, the stalk <NUM> has known length and/or segments of known length, and the determination of the position of the X-ray detector unit <NUM> with respect to the position of the X-ray source unit <NUM> can comprise utilization of the known length of the stalk <NUM> and/or known length of the segments of the stalk <NUM>.

According to an example, the reference structure <NUM> comprises one or more markers <NUM>.

In an example, the one or more markers <NUM> are located at known positions and orientations with respect to the stalk <NUM> of the reference structure <NUM>, and the determination of the position of the X-ray detector unit <NUM> with respect to the position of the X-ray source unit <NUM> can comprise utilization of the known positions and orientations of the one or more markers <NUM> with respect to the stalk <NUM> of the reference structure <NUM>.

According to an example, the one or more markers <NUM> extend perpendicularly to the structure extending laterally from the edge of the X-ray detector unit <NUM>.

In an example, the one or more markers <NUM> extend a known length perpendicularly to the structure extending laterally from the edge of the X-ray detector unit <NUM> (such as the stalk <NUM>). The determination of the position of the X-ray detector unit <NUM> with respect to the position of the X-ray source unit <NUM> can then comprise utilization of the known length of the one or more markers <NUM> that extend perpendicularly to the structure extending laterally from the edge of the X-ray detector unit <NUM>.

According to an example, the reference structure <NUM> comprises three markers <NUM>.

According to an example, the one or more markers <NUM> comprises a plurality of markers and wherein a first marker is oriented perpendicularly to a second marker.

According to an example, the first marker is oriented perpendicularly to the third marker.

According to an example, the sensor unit <NUM> is integrated with the X-ray source unit <NUM>.

According to an example, the sensor image comprises image data of the patient. The processing unit <NUM> is configured to determine a collimation of the X-ray source unit <NUM> comprising utilization of the orientation of the sensor unit <NUM> with respect to the orientation of the X-ray source unit <NUM> and the image data of the patient.

According to an example, the processing unit <NUM> is configured to determine a required movement of the X-ray source unit <NUM> on the basis of the determined collimation of the X-ray source unit <NUM>. Additionally, or alternatively, the processing unit <NUM> is configured to determine a required movement of the X-ray detector unit <NUM> on the basis of the determined collimation of the X-ray source unit <NUM>.

<FIG> shows an example of a medical imaging method <NUM> in its basic steps. The method comprise:.

In an example, the medical imaging system is a mobile medical imaging system.

In an example, the camera unit is a 3D camera unit.

In an example, the method comprises determining by the processing unit <NUM> a required movement of the X-ray source unit <NUM> on the basis of the determined position of the X-ray detector unit <NUM> with respect to the position of the X-ray source unit <NUM>.

In an example, the method comprises determining by the processing unit <NUM> a required movement of the X-ray detector unit <NUM> on the basis of the determined position of the X-ray detector unit <NUM> with respect to the position of the X-ray source unit <NUM>.

In an example, the reference structure <NUM> comprises a handle of the X-ray detector unit.

In an example, the sensor image comprises image data of the patient, and the method comprises projecting by the processing unit <NUM> the image data of the patient onto a visual display unit (VDU) with respect to the position of the X-ray source unit <NUM> and displaying by the processing unit <NUM> on the VDU a representation of the position of the X-ray detector unit <NUM> with respect to the position of the X-ray source unit <NUM>.

In an example, the method comprises projecting by processing unit <NUM> a field of view of the X-ray source unit <NUM> onto the VDU.

In an example, the reference structure <NUM> comprises a structure <NUM>, <NUM> extending laterally from an edge of the X-ray detector unit <NUM>.

In an example, the reference structure <NUM> comprises one or more markers <NUM>.

In an example, the one or more markers <NUM> extend perpendicularly to the structure extending laterally from the edge of the X-ray detector unit <NUM>.

In an example, the reference structure <NUM> comprises three markers.

In an example, the one or more markers <NUM> comprises a plurality of markers and wherein a first marker is oriented perpendicularly to a second marker.

In an example, the sensor unit <NUM> is integrated with the X-ray source unit <NUM>.

In an example, the sensor image comprises image data of the patient, and the method comprises determining by the processing unit <NUM> a collimation of the X-ray source unit <NUM>. This determining can comprise utilizing the orientation of the sensor unit <NUM> with respect to the orientation of the X-ray source unit <NUM> and the image data of the patient.

In an example, the method comprises determining by the processing unit <NUM> a required movement of the X-ray source unit <NUM> on the basis of the determined collimation of the X-ray source unit <NUM>.

In an example, the method comprises determining by the processing unit <NUM> a required movement of the X-ray detector unit <NUM> on the basis of the determined collimation of the X-ray source unit <NUM>.

The medical imaging system and medical imaging method are further explained in specific detail, where reference is made to <FIG>. The medical imaging system and method are described with respect to a mobile imaging system and method, however the system and method also apply to a "normal" X-ray tube that is used in order to acquire an X-ray image of a patient lying in bed with a portable detector that is placed behind the patient. Also, the medical imaging system and method are described with respect to a sensor unit in the form of a 3D camera unit or system, but a 2D camera, radar sensor or lidar sensor, or other range sensor could be utilized.

In developing the new system and method it was realized that optical tracking systems could be utilized, along with a modified detector housing or unit, in order to improve the acquisition of bedside X-rays using mobile X-ray systems. Such optical tracking systems are based for example on 3D cameras, here called a camera unit. A new technique was developed, using such an optical tracking system, to improve the acquisition of bedside X-rays using mobile X-ray systems by enabling the position of the X-ray tube, also called an X-ray source unit, to be determined with respect to the X-ray detector unit. It can then be established if the components of the system are positioned correctly with respect to each other and that the correct field of view of the patient will be captured, or if adjustment is required. Reference is made above to an optical tracking system, however it was established that an appropriate radar based system or LIDAR system can be utilized.

<FIG> shows an example of a sensor unit <NUM> in the form of a camera unit and indeed in the form of a 3D camera. It is to be noted that although 3D imagery is acquired, 2D imagery can be utilized with an appropriate reference structure <NUM>, <NUM>, <NUM>, <NUM> - shown in <FIG>.

Continuing with <FIG>, the optical tracking system or camera unit <NUM> typically consists of two light sources <NUM>, <NUM> and two cameras <NUM>, <NUM> that are positioned at a certain distance from each other, resulting in a 3D camera. The emitted light can be both in the visible or in the infrared range or indeed in both of these parts of the spectrum. A commercially available optical tracking system is provided for example by Polaris Spectra.

The camera unit <NUM> of <FIG> is utilized with a modified detector unit <NUM> of <FIG>. The modified detector unit <NUM> has a reference structure <NUM> with for example markers <NUM> of a known geometry positioned on the end of a stalk <NUM>, or the reference structure <NUM> can be in the form of an enlarged handle <NUM> of the detector unit <NUM>. The reference structure <NUM> has a known geometrical arrangement with respect to the detector unit <NUM> structure, and can be an integral part of the detector unit <NUM> or be attachable to the detector unit <NUM>. The reference structure <NUM>, or at least the markers <NUM>, must be visible to the camera unit <NUM>. Optical tracking is then utilized to localize the markers <NUM> in space, with for example <NUM> accuracy. Triangulation for example is used in this location determination in order to determine the 3D location of each marker <NUM> and this is then matched to the known geometry of the markers <NUM> to determine the pose of the reference structure <NUM> with respect to a coordinate system of the camera unit <NUM>. As the manner in which the reference structure <NUM> is positioned relative to the detector unit <NUM> is known, the position and pose, or orientation, of the detector unit <NUM> with respect to the camera unit <NUM> is then known.

As the camera unit's position and pose is known with respect to the X-ray source unit's, which is most conveniently achieved by having both mounted fixedly in the same unit, the position and pose of the detector unit <NUM> with respect to the source unit <NUM> can be determined, enabling it to be determined if the field of view will correctly fill the required part of the detector.

Thus in a specific example the optical tracking system or camera unit <NUM> is in effect integrated into the tube-head or X-ray source unit <NUM> of a mobile system and a processing unit <NUM> can control movement of the collimation shutters, and indeed the X-ray source unit <NUM> can be on a mobile motorized gantry allowing for the X-ray source unit <NUM> to be moved right/left/up/down and even tilted as required under the control of the processing unit <NUM>. Currently, as discussed above the exact position of the detector behind the patient is difficult to estimate as the detector is completely hidden behind the patient.

As shown in <FIG>, in addition to having a source unit <NUM> operating with a camera unit <NUM>, a modified detector unit <NUM> is utilized. The detector unit <NUM>, which here includes the housing of the detector, has been adapted or has a connected part such that a reference structure part <NUM> is visible to the camera unit even after placing the detector unit behind the patient. As discussed above the reference structure can be in the form of an enlarged handle <NUM>, or a structure in the form of a stalk <NUM> with markers <NUM> at the end. Conveniently, the stalk <NUM> and markers <NUM> can be designed to fold into the main body of the detector unit <NUM>.

Thus, this visible reference structure <NUM>, <NUM>, <NUM>, <NUM>, that is used to calculate the position of the detector unit <NUM> can be for example a stalk <NUM> of known length at the end of which are markers <NUM> of known geometrical arrangement. This can be permanently positioned, or be connected and disconnected as required, but being positioned in a known position, or fold inwards to the main body of the detector unit <NUM>. Thus, at the tip of this reference structure <NUM> the markers <NUM> in the form of reflectors enable position tracking to be carried out to enable the position and pose of the reference structure <NUM> and hence of the detector unit <NUM> to be calculated with respect to the camera unit <NUM> and thence with respect to the source unit <NUM>. Alternatively, the handle <NUM> of the detector unit <NUM> could be adapted/enlarged, so that it is visible after placement and the reflective spheres can also if necessary be attached to the detector handle <NUM> in order to form a reference structure <NUM>. Thus, after the detector unit <NUM> has been placed behind the patient the optical tracking system that consists of a 3D camera <NUM>, <NUM>, <NUM> and light emitters <NUM>, <NUM> can find and locate the visible reference structure <NUM> and due to the rigid connection calculate the exact position of the detector unit <NUM>.

By motorizing for example the column with the X-ray tube or X-ray source unit <NUM>, the positioning of the X-ray tube can be automatically adjusted in such a manner in order to ensure that the detector within the detector unit <NUM> is optimally illuminated. Furthermore, the 3D camera unit <NUM> and optical tracking can be further used to determine and apply the optimal collimation for the X-ray source <NUM>. To achieve this, the 3D camera unit <NUM> detects landmarks on the human thorax, that can for example be markers placed on the patient's body, and calculate the optimal collimation. Therefore, the X-ray shutters or collimators can be automatically adapted in order to achieve the calculated optimal collimation.

Thus, this enables a completely new manner in which to provide for optimized and automatic field of view positioning, where the detector is optimally illuminated with X-rays and at the same time the required part of the patient is illuminated with X-rays, and all in a mobile medical imaging system that can be utilized for bedside radiogram acquisition. Thus, the new approach has the advantage that it not only allows to track the position of the detector behind the patient but also to allow for an optimal collimation.

The new approach can be summarized as following:
Place the detector unit <NUM> behind the patient Ensure that either the handle <NUM> as a reference structure <NUM>, or a specific reference structure <NUM>, <NUM> is visible behind the patient.

The 3D camera <NUM> detects the detector handle <NUM> or the reference structure <NUM>, <NUM> and calculates the position of the detector unit <NUM> and the detector itself.

Based on the calculated position of the detector unit <NUM>, the X-ray source unit / tube <NUM> is either.

The 3D camera <NUM> detects the landmarks of the patient and choses the proper collimation and checks if the proper collimation is covered by the current detector position. In the situation where the current detector position is not suitable to cover the field of view, a notice is provided to the user to adapt the detector position and the process is repeated again from step <NUM>) - it is to be noted that the detector unit <NUM> can also be moved automatically in mounted in an appropriate motorized outer housing.

Thus, the described method ensures proper choice of field of view and improved the clinical workflow.

This computing unit may be configured to perform or induce performing of the steps of the method described previously.

This exemplary embodiment of the invention covers both, a computer program that right from the beginning uses the invention and computer program that by means of an update turns an existing program into a program that uses the invention.

Claim 1:
A medical imaging system (<NUM>), comprising:
- an X-ray source unit (<NUM>);
- an X-ray detector unit (<NUM>);
- a sensor unit (<NUM>);
- a reference structure (<NUM>); and
- a processing unit (<NUM>);
wherein the X-ray detector unit is configured to be placed relative to the X-ray source to acquire X-ray image data of a patient (P) positioned between the X-ray detector unit and the X-ray source unit;
wherein the reference structure is part of the X-ray detector unit or the reference structure is configured to be fixedly connected to the X-ray detector unit;
wherein an orientation of the sensor unit is known with respect to an orientation of the X-ray source unit;
wherein the sensor unit is configured to acquire a sensor image when the X-ray detector unit is placed relative to the X-ray source unit and the patient is positioned between the X-ray detector unit and the X-ray source unit, and wherein the sensor image comprises image data of the reference structure;
wherein the sensor unit is configured to provide the sensor image to the processing unit; and
wherein the processing unit is configured to determine a position of the X-ray detector unit with respect to a position of the X-ray source unit, and wherein the determination comprises utilization of the orientation of the sensor unit with respect to the orientation of the X-ray source unit and the image data of the reference structure.