Field of view for mobile 3D imaging

Abstract

The present invention relates to matching imaging fields of view for mobile 3D imaging, e.g., mobile C-arm 3D imaging. To provide improved image data for comparison purposes, for example, when using a mobile X-ray imaging system, first position information of a first reconstruction volume based on a first X-ray image sequence of a region of interest of a subject acquired along a first trajectory at a first position of an X-ray imaging device is received. A planned second trajectory for acquiring a second X-ray image sequence at a second position of the X-ray imaging device is then received, and a resulting second reconstruction volume for the second X-ray image sequence is calculated. Second position information for the second reconstruction volume is then determined. A degree of equivalence between the first reconstruction volume and the second reconstruction volume is determined based on the first position information and the second position information. An adapted second trajectory that results in an increased degree of equivalence between the first reconstruction volume and the second reconstruction volume is calculated. The adapted second trajectory for acquiring the second X-ray image sequence at the second position of the X-ray imaging device is provided.

Description

[Technical field]

[0001] The present invention relates to matching of imaging fields of view for mobile 3D imaging, and in particular to a device for optimizing an X-ray imaging trajectory, an X-ray imaging system, and a method for optimizing an X-ray imaging trajectory. [Background technology]

[0002] In surgical applications, mobile C-arm imaging systems are frequently used. As an example, a motorized system can be used to build a 3D volume reconstruction after a given sequence of projection images has been recorded. Often, such an acquisition can be difficult, since many devices and systems, as well as clinical staff, are present around the subject's table. Further difficulties can arise when a second 3D acquisition is to be performed, for example, to evaluate the treatment result or progress. The mobile C-arm can be freely moved by the operator, and therefore the acquisition may require performing another trajectory, since the mobile C-arm cannot be in the same position during the second acquisition as during the first acquisition. However, this indicates that it can be cumbersome to compare both reconstructed 3D volumes. Summary of the Invention [Problem to be solved by the invention]

[0003] Thus, it may be necessary to provide improved image data for comparison purposes.

[0004] The object of the present invention is solved by the subject matter of the independent claims, further embodiments are incorporated in the dependent claims. It should be noted that the below described aspects of the present invention also apply to a device for optimizing an X-ray imaging trajectory, an X-ray imaging system and a method for optimizing an X-ray imaging trajectory. [Means for solving the problem]

[0005] According to the present invention, a device for optimizing an X-ray imaging trajectory is provided. The device includes a position information receiver, a processor, and a trajectory adapter. The position information receiver is configured to receive first position information of a first reconstruction volume based on a first X-ray image sequence of a region of interest of a subject acquired along a first trajectory at a first position of the X-ray imaging device. The position information receiver is also configured to receive a planned second trajectory for acquiring a second X-ray image sequence at a second position of the X-ray imaging device. The processor is coupled to the position information receiver and the trajectory adapter and configured to calculate a resulting second reconstruction volume for the second X-ray image sequence. The processor is also configured to determine second position information for the second reconstruction volume. The processor is further configured to determine a degree of equivalence between the first reconstruction volume and the second reconstruction volume based on the first position information and the second position information. The processor is still further configured to calculate an adapted second trajectory that results in an increased degree of equivalence between the first reconstruction volume and the second reconstruction volume. For the optimized x-ray imaging trajectory, a trajectory adapter is configured to provide a matched second trajectory for acquiring a second x-ray image sequence at a second position of the x-ray imaging device.

[0006] This provides improved equivalence of the first and second reconstructed volumes, thereby providing an improvement for comparison purposes.

[0007] In one example, a second trajectory adapted to the optimized X-ray imaging trajectory is used in a mobile C-arm 3D imaging system.

[0008] According to one example, the degree of similarity is provided as a degree of overlap between the first and second reconstructed volumes.

[0009] According to one example, the degree of overlap relates to the degree of spatial overlap between the first reconstructed volume and the second reconstructed volume.

[0010] According to one example, a position information receiver is configured to receive spatial information of an X-ray imaging device during acquisition of a first sequence of X-ray images along a first trajectory, and a processor is configured to determine the first trajectory based on the spatial information and to determine a resulting first reconstruction volume.

[0011] According to one example, a position information receiver is configured to receive a first image sequence captured by a camera representing an X-ray imaging device during acquisition of a first X-ray image sequence along a first trajectory, and a processor is configured to determine the first trajectory based on the image sequence and determine a resulting first reconstruction volume.

[0012] According to the present invention, there is also provided an X-ray imaging system, comprising an X-ray imaging device with an X-ray source and an X-ray detector movable along a trajectory for acquiring an X-ray image sequence of an area of ​​interest, and a device for optimizing an X-ray imaging trajectory according to one of the previous examples, wherein the X-ray imaging device provides a first X-ray image sequence of an area of ​​interest of a subject, and a trajectory adapter provides a second trajectory adapted to the X-ray imaging device for acquiring a second X-ray image sequence at a second position of the X-ray imaging device.

[0013] According to one example, the X-ray imaging system is a mobile X-ray system with a base that is freely movable along a floor surface, the X-ray imaging device includes a mobile C-arm with an X-ray source and an X-ray detector mounted on opposite ends of the C-arm, and a drive mechanism is provided to move the C-arm to move the X-ray source and the X-ray detector along the corresponding second trajectory.

[0014] The X-ray system may be provided as a mobile C-arm 3D imaging system.

[0015] According to one example, at least one optical camera is provided to provide a captured first image sequence showing the x-ray imaging device during acquisition of the first x-ray image sequence along the first trajectory, and a processor determines the first trajectory based on the image sequence and determines a resulting first reconstruction volume.

[0016] According to the present invention there is also provided a method for optimizing an X-ray imaging trajectory, the method comprising: receiving first position information of a first reconstruction volume based on a first sequence of X-ray images of a region of interest of the subject acquired along a first trajectory at a first position of an X-ray imaging device; receiving a planned second trajectory for acquiring a second sequence of X-ray images at a second position of the X-ray imaging device; calculating a resulting second reconstruction volume for a second sequence of X-ray images; determining second position information for a second reconstruction volume; determining a degree of similarity between the first reconstructed volume and the second reconstructed volume based on the first position information and the second position information; calculating a fitted second trajectory resulting in an increasing degree of similarity between the first reconstructed volume and the second reconstructed volume; and providing a second adapted trajectory for acquiring a second sequence of X-ray images at a second position of the X-ray imaging device.

[0017] According to one embodiment, in one example, it is provided to estimate a field of view for a planned 3D volume reconstruction based on an external camera image before a corresponding projection sequence is acquired. The estimated field of view for the planned 3D volume reconstruction is compared with a previous 3D reconstruction to assess whether sufficient overlap of a diagnostically relevant region is provided. A planned trajectory for the planned 3D volume reconstruction is adapted to improve the overlap of the field of view of the estimated reconstruction with the previous acquisition. A visual indicator may provide feedback to the clinician when the C-arm system needs to be repositioned to build a second 3D reconstruction with sufficient overlap with the first 3D reconstruction.

[0018] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0019] Exemplary embodiments of the invention are described below with reference to the following drawings: [Brief description of the drawings]

[0020] [Figure 1] 1 shows an example of a device for optimizing an X-ray imaging trajectory. [Diagram 2] An example of an X-ray imaging system is shown. [Figure 3a] 1 illustrates an example of overlapping reconstructed volumes. [Figure 3b] 1 illustrates an example of overlapping reconstructed volumes. [Figure 4a] 1 shows an example of overlapping scanning trajectories. [Figure 4b] 1 shows an example of overlapping scanning trajectories. [Figure 5a] An example of a planned second trajectory is shown. [Figure 5b] An example of a suitable second trajectory is shown below. [Figure 6] 1 illustrates the basic steps of an example method for optimizing an X-ray imaging trajectory. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Specific embodiments will now be described in more detail with reference to the accompanying drawings. In the following description, similar drawing reference numbers are used for similar elements in different drawings. Matters described herein, such as detailed configurations and elements, are provided to aid in a comprehensive understanding of the exemplary embodiments. Also, well-known functions or configurations are not described in detail, since they would obscure the embodiments in unnecessary detail. Moreover, expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements, and not individual elements of the list.

[0022] Mobile X-ray imaging systems are frequently used in surgical applications. Motorized systems can be used to obtain a 3D volume reconstruction after a given scan or projection image sequence has been recorded along a specific trajectory. This movement along the trajectory can often be difficult since many devices and systems, as well as clinical staff, are present around the subject's table. For such X-ray imaging, fixed installation systems with movable components are provided, as are mobile systems, such as mobile C-arm imaging systems. Similar images can be useful for clinical staff if imaging is required to allow comparison. As an example, a second 3D acquisition should be performed, for example, to evaluate the outcome or progress of a procedure. Pre- and post-operative volume 3D reconstructions may not show the same 3D region of interest, since the positioning of the C-arm, the subject, or surrounding obstacles may change. As another example, since the mobile C-arm can be freely moved by the operator, the system may not be in the same position in the second acquisition as it was in the first acquisition. This can be cumbersome or even a challenge if both reconstructed 3D volumes are to be compared.

[0023] The term "subject" may also be referred to as an individual. Additionally, a "subject" may also be referred to as a "patient," although it should be noted that this term does not indicate whether any disease or illness is actually present with the subject.

[0024] FIG. 1 shows an example of an apparatus 10 for optimizing an X-ray image trajectory. The device 10 includes a position information receiver 12, a processor 14, and a trajectory adapter 16. The position information receiver 12 is configured to receive first position information of a first reconstruction volume based on a first X-ray image sequence of a region of interest of a subject acquired along a first trajectory at a first position of an X-ray imaging device. The position information receiver 12 is also configured to receive a planned second trajectory for acquiring a second X-ray image sequence at a second position of the X-ray imaging device. The processor 14 is coupled to the position information receiver 12 and the trajectory adapter 16 and is configured to calculate a resulting second reconstruction volume for the second X-ray image sequence. The processor 14 is also configured to determine second position information for the second reconstruction volume. The processor 14 is further configured to determine a degree of equivalence between the first reconstruction volume and the second reconstruction volume based on the first position information and the second position information. Furthermore, the processor 14 is configured to calculate an adapted second trajectory resulting in an increased degree of equivalence between the first and second reconstructed volumes. For the optimized X-ray imaging trajectory, the trajectory adapter 16 is configured to provide an adapted second trajectory for acquiring a second X-ray image sequence at a second position of the X-ray imaging device.

[0025] As a result, instead of moving the complete X-ray imaging device, the trajectory is optimized. The goal is to improve the comparison, which also involves accepting a certain degree of uncertainty. We are trying to get a kind of compromise.

[0026] The term "position information" relates to information about the spatial location of each reconstructed volume. To assess the degree of similarity, e.g. the spatial overlap of two reconstructed volumes, i.e. to compare two reconstructed volumes, the spatial locations at least indirectly refer to the same spatial reference. For example, the spatial location of a first reconstructed volume may be related to the reference coordinates of an imaging device at a first location, and the spatial location of a second reconstructed volume may be related to the reference coordinates of an imaging device at a second location, while the displacement between the first and second locations is also provided (or determined). The spatial locations provide information about the three-dimensional arrangement and rotation. As an example, the position information may be provided with respect to a fixed base in the examination room, e.g. a reference point of a 3D coordinate grid in the examination room. As another example, the position information may be provided with respect to a moving base in the examination room, such as a support for the subject, e.g. a patient table.

[0027] The term "reconstruction volume" refers to a region for which data is available that can be used to reconstruct image data of that volume. As an example, multiple image projections are provided for different imaging directions. The 3D volumes traversed by the projection lines overlap sufficiently to allow 3D data to be extracted from the 2D projections. As an example, the reconstruction volume refers to a region of a subject for which image data is generated, for example by computed tomography. The reconstruction volume is also referred to as the 3D imaging field of view.

[0028] The first reconstructed volume is also referred to as the previous reconstructed volume, and the second reconstructed volume is also referred to as the estimated reconstructed volume.

[0029] In one example, the first reconstructed volume relates to a pre-operative scenario and the second reconstructed volume relates to a post-operative scenario, between which an examination, intervention, treatment, or other procedure may be initiated.

[0030] The term "trajectory" refers to the path in space along which an image source and an image detector move to obtain multiple projections covering a region of interest from different directions so as to be able to generate 3D image data of the region of interest. In one example, "trajectory" refers to the motion of a C-arm (also called a C-arc) and the respective motion path of the source and detector mounted on the C-arm. The trajectory can be a rotational motion, a sliding motion along an arc, a pivoting motion, or any combination provided by the respective bearing and support concept of the C-arm.

[0031] The first trajectory is also referred to as the initial trajectory, the second trajectory is also referred to as the upcoming trajectory or the planned trajectory, and the adapted second trajectory is also referred to as the adapted upcoming trajectory, the adapted planned trajectory, or the adapted trajectory.

[0032] In one example, the planned second trajectory is provided as the first trajectory for the second position of the X-ray imaging device.

[0033] The term "planned" refers to the second trajectory defined before the fitting. For example, the planned trajectory can be the same trajectory (e.g., with respect to the base) used for the first scan. However, due to misalignment of the X-ray imaging device between the first and second positions, the resulting reconstructed volumes do not match exactly the same. Rather, the misalignment of the first and second reconstructed volumes is to be expected. In another example, the planned trajectory can be a predetermined trajectory (e.g., in a specific, predetermined relationship with respect to the base), but due to possible misalignment of the X-ray imaging device between the first and second planned positions, the resulting reconstructed volumes also do not match exactly the same.

[0034] The term "degree of equivalence" relates to the spatial position and orientation of two reconstructed volumes, i.e. a first reconstructed volume and a second reconstructed volume, and their resulting ability (or compatibility) to compare the first reconstructed volume and the second reconstructed volume, i.e. to compare the projections of the first reconstructed volume and the second reconstructed volume.

[0035] Thus, the term "degree of equivalence" also relates to the degree of similarity in terms of comparison.

[0036] In one example, the degree of similarity is provided as a degree of overlap, also referred to as an overlap degree.

[0037] The term "overlap degree" refers to the spatial position and orientation of two reconstruction volumes, i.e., a first reconstruction volume and a second reconstruction volume. For example, the overlap is determined as a spatial overlap, i.e., an overlap in a 3D space. The overlap can be defined as those positions in the space covered by both reconstruction volumes.

[0038] The term "adapted" refers to the modification of the second trajectory according to the target to improve overlap despite misalignment of the first and second positions of the X-ray imaging device. The second trajectory can be used as a starting point and then the trajectory can be modified, i.e. changed, to provide improved spatial overlap.

[0039] In one example, the second position of the X-ray imaging device remains on the adapted trajectory. Instead of modifying the position and orientation of the X-ray imaging device, such as a mobile base, the position of the X-ray imaging device is not changed, but the trajectory is modified, at least within given geometric constraints.

[0040] The term "position" of the X-ray imaging device refers to the placement or location of the part of the X-ray imaging device that is not moving during an imaging scan.

[0041] In one example, the fitting of the planned trajectory is provided in an automated manner.

[0042] In one example, the position information receiver is configured to receive a first trajectory for use in the first reconstruction volume, and a processor is configured to determine a resulting first reconstruction volume.

[0043] As an example, the planned second trajectory is the same trajectory as the first trajectory, but applied (theoretically or practically) to a second location or to a second position of the X-ray imaging device. The planned second trajectory is then adapted to obtain a better matching volume of interest, i.e., reconstructed volume, and this adaptation results in an adapted second trajectory, which is then used to perform the second scan.

[0044] In one example, the position information receiver is configured to receive position information about a second position of the X-ray imaging device. For the planned second trajectory, the processor is configured to apply the first trajectory to the second position of the X-ray imaging device.

[0045] In one example, a position information receiver is configured to receive position information for the second reconstruction volume when applying the planned second trajectory.

[0046] In one example, a position information receiver is configured to receive position information about the planned second reconstruction volume, and a trajectory that will obtain the planned second reconstruction volume is calculated relative to the planned second trajectory.

[0047] In one example, the planned second trajectory is a trajectory manually provided by a staff member.

[0048] In another example, the planned second trajectory is a trajectory suggested by the processor with a view to avoiding a possible collision in the current situation.

[0049] In another example, the trajectory is timed with reference to respiratory motion, cardiac motion, or contrast motion. In this way, if the recorded cardiac phase, or contrast level, etc., is comparable in the two scans, the comparability is improved. If the scans show slightly different regions of the body, the arrival time of the contrast may be different. Or, if the second scan starts from a different position on the same circle as the first scan, for example, the synchronization with the heartbeat may still be off. This may then even require additional input. The trajectory can be slowed down accordingly at first.

[0050] In FIG. 1, a display or interface 18 (shown in dashed lines) is optionally provided and configured to display information regarding the matched second trajectory to an operator.

[0051] Furthermore, a first arrow 20 (shown in dashed lines) indicates a data output, ie a data connection.

[0052] A second arrow 22 (shown in dashed lines) indicates data input. A frame 24 enclosing the position information receiver 12, the processor 14, and the orbital adapter 16 indicates that the information receiver 12, the processor 14, and the orbital adapter 16 can be provided integrated into a common structure, such as a common housing. In one example, the information receiver 12, the processor 14, and the orbital adapter 16 are provided in an integrated manner. In another example, the information receiver 12, the processor 14, and the orbital adapter 16 are provided separately.

[0053] Optionally, it is defined that the degree of similarity is provided as a degree of overlap between the first reconstructed volume and the second reconstructed volume.

[0054] In a further option, the degree of overlap is defined as relating to the degree of spatial overlap between the first reconstructed volume and the second reconstructed volume.

[0055] In one example, a portion of the first reconstruction volume is selected as a first reference portion, a portion of the second reconstruction volume is selected as a second reference portion, and an overlap portion is determined based on the first reference portion and the second reference portion.

[0056] In one example, for the first position information, the position information receiver 12 is configured to receive a first trajectory and its spatial position, and the processor 14 is configured to determine a resultant first reconstruction volume and first position information of the first reconstruction volume based on the first trajectory and its spatial position.

[0057] In one example, the position information receiver 12 is configured to receive spatial information of the X-ray imaging device during acquisition of a first X-ray image sequence along a first trajectory, and the processor 14 is configured to determine the first trajectory based on the spatial information and to determine a resulting first reconstruction volume.

[0058] In one example, the position information receiver 12 is configured to receive a first image sequence taken by a camera representing an X-ray imaging device during acquisition of a first X-ray image sequence along a first trajectory, and the processor 14 is configured to determine a first trajectory based on the image sequence and to determine a resulting first reconstruction volume.

[0059] In one example, the X-ray imaging device includes a movable C-arm and the images show the movement of the C-arm.

[0060] In one example, the X-ray imaging system is a mobile X-ray imaging system, and a first position of the X-ray imaging device is determined based on an image of the X-ray imaging system taken by a camera, and a second position of the X-ray imaging device is determined based on at least one second image taken by a camera showing the X-ray imaging device at a second X-ray imaging system prior to acquisition of the second X-ray image sequence.

[0061] A mobile X-ray system is provided with many degrees of freedom for movement, for example a movable C-arm mounted on a carriage. In one example, the system is not motorized with respect to the floor and does not track movement along the floor. The position difference between the first position and the second position is detected based on an external detection system, such as a camera, providing an optical tracking system. In another example, electromagnetic tracking is provided to track the first and second positions within the examination room.

[0062] In one example, the subject on the subject support is also tracked by an optical camera. Optionally, the subject is tracked by image. In another option, the subject is tracked by electromagnetic tracking.

[0063] To compare the first and second reconstructed volumes, a first scanning movement is captured by one or more cameras. In one example, a camera captures where the first reconstructed volume is located. After a relative movement between the imaging device and the subject, a repetition of the same scanning movement leads to an offset or displaced second reconstructed volume.

[0064] The modification, i.e. adapting the trajectory for the (second) scan, provides an improvement by providing a second reconstruction volume with more overlap compared to applying a non-adapted trajectory. At least to a certain extent, this avoids the need to give an instruction to an operator, e.g. a doctor or a nurse, to move the X-ray imaging device. The adapted second trajectory then replaces the repositioning instruction. The imaging procedure is then facilitated and the staff member is relieved from further work.

[0065] With respect to X-ray imaging, information or a warning that the current position is not suitable for imaging may be considered as a first support step or support stage, providing instructions how to obtain an improved position for X-ray imaging (i.e. relation guidance) may be considered as a second support step or support stage, while providing a suitable trajectory may be considered as a third support step or support stage.

[0066] In this way, the external camera can be used to estimate and verify that the imaging fields of view of the two 3D reconstructions have sufficient overlap for diagnostic purposes, which can be improved by using the camera information to define a specific trajectory for the second acquisition or by instructing the operator to change the starting position of the system.

[0067] An external camera may be provided on the system or in the operating room and may be used to facilitate finding the optimal trajectory around all obstacles while still capturing projections from all angles required.

[0068] In one example, the movement of the X-ray imaging between the first and second positions is detected by sensors in the wheel drives or bearings that provide spatial information of the movement.

[0069] In one example, the first position information includes first subject-related spatial information at a first position of the X-ray imaging device, the position information receiver 12 is configured to receive second subject-related spatial information at a second position of the X-ray imaging device, and the processor 14 is configured to determine a degree of overlap between the first and second reconstructed volumes related to the subject.

[0070] This provides the advantage that overlap can be assessed in terms of image data comparison applications.

[0071] The (first and second) reference portions are also referred to as (first and second) core regions of interest within the (first and second) regions of interest covered by the (first and second) reconstruction volumes.

[0072] In one example, the processor 14 is configured to determine whether the degree of equality is outside a predetermined range of equality. A repositioning indicator is provided that is configured to indicate that repositioning of the x-ray imaging device is required.

[0073] As an example, a minimum overlap of 30% is provided. In a further example, the minimum is 50%.

[0074] In one example, the type of imaging task is also taken into consideration to determine and assess the degree of overlap. For example, for certain imaging purposes, a lesser degree of overlap may be required.

[0075] In a further example, the reconstruction volumes are both cylindrical regions and the overlap is a spherical region.

[0076] In a further example, the reconstruction volumes are both cylindrical regions arranged perpendicular to each other.

[0077] For example, C-arm imaging is provided. The first and second positions include a lateral orientation of the imaging device, such as a first position at a side of a patient support and a second position at an end of the subject support, or vice versa. One trajectory is then defined by a propeller motion of the C-arm and the other trajectory is defined as a roll motion of the C-arm.

[0078] In one example, the first position and the second position of the x-ray imaging device relate to a placement of the x-ray imaging device relative to the subject, the second position being different from the first position.

[0079] The difference may be due to motion of the x-ray imaging device, the difference may be due to motion of the subject being imaged, and the difference may be due to motion of both the x-ray imaging device and the subject being imaged.

[0080] For example, a subject may be positioned in a different position after an intervention or treatment. In another example, the X-ray imaging device may be moved away for an intervention or treatment and then moved back for a further imaging procedure, but with at least a slight shift in position and / or orientation.

[0081] In one example, a subject is provided in a first position during a first X-ray image sequence. Further, the subject remains in the first position during a second X-ray image sequence. An X-ray imaging device is positioned in a first position during the first X-ray image sequence. Further, the X-ray imaging device is positioned in a second position during the second X-ray image sequence.

[0082] In another example, a subject is presented in a first pose during a first x-ray image sequence and in a second pose during a second x-ray image sequence, and an x-ray imaging device is disposed in a first position during the first x-ray image sequence and remains in the first position during the second x-ray image sequence.

[0083] In a further example, the subject is presented in a first pose during a first x-ray image sequence and in a second pose during a second x-ray image sequence, and an x-ray imaging device is disposed in a first position during the first x-ray image sequence and in a second position during the second x-ray image sequence.

[0084] FIG. 2 shows an example of an X-ray imaging system 50. The system 50 comprises an X-ray imaging device 52 with an X-ray source 54 and an X-ray detector 56 movable along a trajectory for acquiring an X-ray image sequence of an area of ​​interest. Furthermore, the system 50 comprises an example of a device 10 for optimizing an X-ray imaging trajectory according to one of the previous examples. The device 10 is shown, as an example, diagrammatically as a separate frame. The device 10 can be provided in a separate housing or in an integrated manner. The line 58 shows a data connection between the X-ray imaging device 52 and the device 10 for optimizing the X-ray imaging trajectory. The X-ray imaging device 52 provides a first X-ray image sequence of an area of ​​interest of a subject. The trajectory adapter 16 provides the X-ray imaging device 52 with a second trajectory adapted to acquire a second X-ray image sequence at a second position of the X-ray imaging device 52.

[0085] As an advantage, the projections of the two 3D volumes generated based on each scan along the X-ray imaging trajectory are insensitive to small movements of the C-arm or the imaged subject between the first and second scans due to the adaptation of the trajectory.

[0086] 2, the X-ray imaging system 50 is a mobile X-ray system 60 with a base 62 that is freely movable along a floor surface. The X-ray imaging device 52 includes a mobile C-arm 64 with the X-ray source 54 and the X-ray detector 56 mounted on opposite ends of the C-arm 64. A drive mechanism 66 is provided for moving the C-arm 64 to move the X-ray source 54 and the X-ray detector 56 along a compatible second trajectory.

[0087] 2 there is shown a first reconstructed volume 68 and a second reconstructed volume 70. As can be seen, the two volumes 68, 70 partially overlap.

[0088] The first reconstruction volume 68 shows results from a first scan of the subject with the X-ray imaging system 50 positioned in a first position relative to the subject (e.g., positioned on a subject support (not shown)). For example, the first scan has already been performed.

[0089] The second reconstruction volume 70 shows results from a second scan of the subject with the X-ray imaging system 50 positioned at a second position relative to the subject (e.g., also positioned on a subject support (not shown)). For example, the second scan is performed as a next step.

[0090] The first and second reconstruction volumes 68, 70 are shown in a free-floating manner to show overlap, and therefore equivalence, possible. In one example, the mobile X-ray system includes a motorized support wheel arrangement, which provides position information for the second position of the X-ray system.

[0091] In one example, the X-ray imaging system is a fixed X-ray system with a movable support structure for the C-arm. The movable support structure provides position information about the second position of the X-ray system.

[0092] In an option also shown in Fig. 2, at least one optical camera 71 is provided to provide a captured first image sequence showing the X-ray imaging device during acquisition of the first X-ray image sequence along the first trajectory. The camera is data connected to the device 10 for optimizing the X-ray imaging trajectory. A processor determines the first trajectory based on the image sequence and determines a resulting first reconstruction volume.

[0093] Note that at least one camera is not further shown in Figures 5A and 5B, thus capturing or detecting where the first reconstruction volume is located, and capturing or detecting where the second reconstruction volume is suitably located.

[0094] Figures 3a and 3b show two further examples of overlapping reconstruction volumes. In the example shown in Figures 3a and 3b, a first cylindrical reconstruction volume 68', 68" and a second cylindrical reconstruction volume 70', 70" are provided that overlap in the middle.

[0095] In the first option, shown in FIG. 3a, the two cylinders, ie the cylindrical reconstruction volumes 68', 70', are oriented perpendicular to each other.

[0096] In a second option, shown in Fig. 3b, the two cylinders, i.e. cylindrical reconstruction volumes 68'' and 70'', are co-oriented, i.e. the underlying projections are recorded in the same orientation.

[0097] Thus, although the actual spatial overlap may be smaller in the second option (FIG. 3b) than in the first option (FIG. 3a), the second option may still have a higher degree of equivalence since the projection directions are similar. In this example, only small core regions are important. Thus, a large extra overlap would not improve the equivalence. However, the fact that the projection directions in the second option are similar improves the equivalence since directional imaging artifacts (partial volumes, beam hardening, scattering, metal streaks, etc.) and absolute voxel values ​​(e.g., Hounsfield units) can be better compared. Improved equivalence in this example does not mean improved spatial overlap, but improved equivalence of the x-ray attenuation properties of tissues recorded in the two reconstructed images.

[0098] 4a and 4b show a first scanning path 72, 72' and a second scanning path 74, 74' around a region of interest 76 of a subject, where limited angular segments are used for the first and second reconstruction volumes. The scanning directions are indicated by curved, i.e. circular arrows. The resulting directions of partial angle artifacts of the first and second scans are indicated by a first straight arrow 78, 78' for the first scan and a second straight arrow 80, 80' for the second scan.

[0099] In FIG. 4a, the scan directions are opposite, as are the resulting artefact directions.

[0100] In Figure 4b, the scan direction is the same but at a different angle, and the resulting artefact orientation is now angled.

[0101] Optionally, the restricted angle segments are as similar as possible, or at least in opposite directions, in this embodiment the comparison is improved since the orientation of the artifacts is more similar.

[0102] Figures 5a and 5b show a subject 82 positioned on a subject support 84. Partially shown is a movable C-arm X-ray imaging device 86. The C-arm can be moved such that the X-ray source and X-ray detector rotate around the subject's region of interest, thus forming an isocenter.

[0103] FIG. 5a shows an example of a planned second trajectory 88, which results in a second reconstruction volume that overlaps with the first reconstruction volume, but with a much lower degree of similarity.

[0104] FIG. 5b shows an example of an adapted second trajectory 90, which improves the degree of similarity. In the illustrated example, a scan is provided around a subject 82 positioned on a subject support 84. The initially planned second trajectory shown in FIG. 5a is a circular rolling motion M around the subject 82.R The second fitted trajectory shown in FIG. 5b is a trajectory of the propeller motion M around the subject 82. P In this way, a second reconstructed volume that has a better matching degree with the first reconstructed volume can be achieved. R Propeller operation from M P is an example for adapting the second trajectory.

[0105] 6 shows the basic steps of an example of a method 100 for optimizing an X-ray imaging trajectory. The method 100 comprises the following steps: In a first step 102, also referred to as step a), first position information of a first reconstruction volume based on a first X-ray image sequence of a region of interest of a subject acquired along a first trajectory at a first position of an X-ray imaging device is received. In a second step 104, also referred to as step b), a planned second trajectory for acquiring a second sequence of X-ray images at a second position of the X-ray imaging device is received. In a third step 106, also called step c), a resulting second reconstructed volume for the second X-ray image sequence is calculated. In a fourth step 108, also called step d), second position information for the second reconstruction volume is determined. A fifth step 110, also referred to as step e), involves determining a degree of similarity between the first and second reconstructed volumes based on the first and second position information. In a sixth step 112, also called step f), a fitted second trajectory is calculated which results in an increasing degree of equivalence between the first and second reconstructed volumes. A seventh step 114, also referred to as step g), includes providing a second adapted trajectory for acquiring a second sequence of X-ray images at a second position of the X-ray imaging device.

[0106] The first step 102 of receiving the first position information and the second step 104 of receiving the planned second trajectory may be provided simultaneously, or the second step 104 may be provided before the first step 102.

[0107] In one example, a first trajectory and its spatial position are provided for the first position information, and a resulting first reconstruction volume and first position information of the first reconstruction volume are determined based on the first trajectory and its spatial position.

[0108] In one example, the first position information also includes first subject-related spatial information at a first position of the X-ray imaging device. Additionally, second subject-related spatial information at a second position of the X-ray imaging device is provided. A degree of similarity for the subjects, for example a degree of overlap between the first and second reconstructed volumes, is determined.

[0109] As an example, based on a camera, e.g. an external camera, the trajectory of the detector and the trajectory of the source acquiring 3D X-rays relative to the imaged subject are recorded. Optionally, the camera is placed fixedly in the operating room or mounted on a C-arm to view the patient. This can be facilitated by special markers on the C-arm system and / or the patient to capture and track the movements and actions. It can also be facilitated by natural features identifiable in the camera image. As dedicated markers, one or more QR Code markers can be attached to one or more dedicated positions on the detector, the source, and / or the subject. For example, on each side of the detector housing, on each side of the tube housing, and in the center of the subject's skin. The natural markers that can be extracted from the image can be a number of image features that can be recognized from different perspectives. For example, edges, ridges, corners, markings on the tube housing and the detector housing. For the subject, features such as eyes, fingers, wrinkles, skin spots, navel, etc. can be used.

[0110] Based on the trajectory, the 3D imaging field to be acquired for the patient's anatomy is estimated. This can be done by tracking features of the optical images using the special or natural markers mentioned above according to: Multiple optical images are acquired when performing a first trajectory. In each image, image features can be detected and correlated with other optical images acquired from different viewpoints. For example, as another option, a camera is attached to the C-arm, which "sees" the patient when performing the first trajectory. In one image, for example, the patient's fingertip can be detected. The C-arm is then moved along the first trajectory and further optical images are acquired. In all of these images, an attempt is made, now from different viewpoints, to find the patient's fingertip. All detected fingertips from the different views can be matched and thus the patient's fingertip can be located in 3D space (relative to the C-arm). By repeating this method for all possible markers, it is possible to generate a point cloud, i.e. a cloud of points, of the positions of the 3D markers.

[0111] Additionally, for the second acquisition, a planned C-arm trajectory for the second 3D acquisition is calculated.

[0112] Based on the second planned trajectory, a second 3D imaging field to be acquired is estimated with respect to the patient's anatomy. In this step, the detection of the 3D marker positions as described above is repeated.

[0113] Then, the overlap between the first and second 3D imaging fields is calculated. This can be achieved by calculating the overlap between the point cloud of all 3D marker positions from the first acquisition and the point cloud from the second acquisition, i.e. there must be sufficient feature correspondence between both point clouds. In other words, it is analyzed whether sufficient overlap for a given diagnostic purpose is provided. The term sufficient overlap may depend on the desired diagnostic purpose. It may be expressed by a volume percentage, for example, if a general characteristic such as tissue iodine concentration is to be investigated. It may also be defined by specific anatomical landmarks that must all be within the overlapping volume, i.e. all anatomical landmarks that are required for a specific purpose. For example, two specific vertebrae of interest must be completely within the overlapping imaging fields in order to compare them in the two images. Or, specific points of interest in the vascular structure (lesions, bifurcations, implants, aneurysms) must all be included within the overlapping volume.

[0114] If the overlap is not sufficient, corrective actions can be triggered by adjusting the planned trajectory or by giving instructions to the operator, e.g., depending on the freedom of movement of the system, the user may be advised to manually change the position of the C-arm, thus improving the overlap with the first trajectory and allowing the second trajectory to be executed.

[0115] The automatic trajectory adaptation depends on the motorized degrees of freedom that can be controlled by the mobile C-arm unit. For example, if a motorized translational motion is possible, the C-arm can be positioned to obtain two isocenters as close as possible.

[0116] If the first trajectory is a roll motion of the C-arm and the repositioned C-arm is in a significantly different orientation before the second acquisition, a propeller motion may be preferred for the second acquisition to better align the source and detector trajectories in 3D space, which results in a better overlap of the reconstruction volumes. Also, a combination of roll and propeller motion may be a solution to optimize the second trajectory.

[0117] For limited angle reconstructions (less than 180° + fan angle), the non-imaged directions in each acquisition should ideally be the same. However, depending on the repositioning of the C-arm, this may mean different motor motions.

[0118] A different biaxial trajectory may be used to reconstruct the same 3D volume. If a new obstacle is placed in the path of the original trajectory in the second acquisition, a second biaxial trajectory may be selected to image the same volume, but avoiding the obstacle.

[0119] If the repositioning of the C-arm does not allow automatic acquisition of projections from sufficient angles of the initial reconstruction volume for a complete second reconstruction, the second acquisition can be reduced to a limited angle segment, i.e. only those angle segments that also have the first reconstruction volume in their imaging field of view are imaged. A limited angle reconstruction of the initial volume can then be built for comparison. The acquisition of unnecessary data, i.e. data not related to the first acquisition during the second acquisition, is avoided.

[0120] The present invention relates to matching of imaging fields of view for mobile 3D imaging, e.g., mobile C-arm 3D imaging. In order to provide improved image data for comparison purposes, e.g., when using a mobile X-ray imaging system, first position information of a first reconstruction volume based on a first X-ray image sequence of a region of interest of a subject acquired along a first trajectory at a first position of an X-ray imaging device is received. Further, a planned second trajectory for acquiring a second X-ray image sequence at a second position of the X-ray imaging device is received, and a resulting second reconstruction volume for the second X-ray image sequence is calculated. Then, second position information for the second reconstruction volume is determined. Further, a degree of equivalence between the first reconstruction volume and the second reconstruction volume is determined based on the first position information and the second position information. An adapted second trajectory that results in an increased degree of equivalence between the first reconstruction volume and the second reconstruction volume is calculated. The adapted second trajectory for acquiring a second X-ray image sequence at a second position of the X-ray imaging device is provided. In an exemplary embodiment, a computer program is provided that enables a processor to perform the method of the above example.

[0121] In an exemplary embodiment, a computer program or program element for controlling an apparatus according to one of the above examples is provided, which program or program element is adapted to perform the method steps of one of the above example methods when executed by a processing unit.

[0122] In an exemplary embodiment, a computer readable medium having stored thereon program elements of one of the above embodiments is provided.

[0123] In another exemplary embodiment of the invention, a computer program or a computer program element is provided, characterized in that it is adapted to execute, on a suitable system, the method steps of the method according to one of the previous embodiments.

[0124] Thus, a computer program element can be stored on a computing unit or distributed across two or more computing units, which can also be part of an embodiment of the present invention. This computing unit can be adapted to effect or direct the execution of the steps of the above-mentioned method. Moreover, it can be adapted to operate the components of the above-mentioned apparatus. The computing unit can be adapted to operate automatically and / or to execute user instructions. The computer program can be loaded into the working memory of a data processor. Thus, the data processor can be equipped to perform the method of the present invention.

[0125] Aspects of the present invention may be embodied in a computer program product, which may be a collection of computer program instructions stored on a computer-readable storage device that may be executed by a computer. The instructions of the present invention may be any interpretable or executable code mechanism, including, but not limited to, a script, an interpretable program, a dynamic link library (DLL), or a Java class. The instructions may be provided as a complete executable program, a partial executable program, as a modification (e.g., an update) to an existing program, or as an extension (e.g., a plug-in) to an existing program. Moreover, parts of the processing of the present invention may be distributed across multiple computers or processors.

[0126] As mentioned above, a processing unit, e.g., a controller, implements the control method. The controller can be implemented in numerous ways, using software and / or hardware to perform the various functions required. The processor is one example of a controller that uses one or more microprocessors that can be programmed using software (e.g., microcode) to perform the required functions. However, the controller can be implemented with or without a processor, and can also be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions.

[0127] Examples of controller components that may be used in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field programmable gate arrays (FPGAs).

[0128] This exemplary embodiment of the invention covers both computer programs that use the invention from the very beginning and computer programs that, by modern means, transform existing programs into programs that use the invention.

[0129] Moreover, the computer program element may provide all the steps required to fulfill the actions of the exemplary embodiments of the methods described above.

[0130] According to a further exemplary embodiment of the present invention, a computer readable medium, such as a CD-ROM, is presented, having stored thereon a computer program element, which is described by the previous section. The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0131] However, the computer program may also be presented over a network such as the World Wide Web and downloaded from such a network into the working memory of a data processor. According to a further exemplary embodiment of the invention, a medium for making a computer program element available for downloading is provided, which computer program element is arranged to perform a method according to one of the aforementioned embodiments of the invention.

[0132] It should be noted that the embodiments of the present invention are described with reference to different subject matters. In particular, some embodiments are described with reference to claims of the type of method, while other embodiments are described with reference to claims of the type of device. However, a person skilled in the art will infer from the above and following description that, unless otherwise indicated, any combination of features belonging to one type of subject matter, as well as any combination between features relating to different subject matters, is considered to be disclosed in the present application. However, all features can be combined to provide a synergistic effect that is greater than the simple sum of the features.

[0133] While the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered as illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

[0134] In the claims, the word "comprises" does not exclude other elements or steps, and the singular does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be interpreted as limiting the scope.

Claims

1. 1. A device for optimizing an X-ray imaging trajectory, said device comprising: A location information receiver; A processor; a track adapter; the position information receiver receives first position information of a first reconstruction volume based on a first X-ray image sequence of a region of interest of a subject acquired along a first trajectory at a first position of an X-ray imaging device, and receives a planned second trajectory for acquiring a second X-ray image sequence at a second position of the X-ray imaging device; the processor is coupled to the position information receiver and the trajectory adapter, and is configured to calculate a resulting second reconstructed volume for the second X-ray image sequence, determine second position information for the second reconstructed volume, determine a degree of equivalence between the first reconstructed volume and the second reconstructed volume based on the first position information and the second position information, the degree of equivalence being provided as a degree of overlap between the first reconstructed volume and the second reconstructed volume, and calculate an adapted second trajectory resulting in an increased degree of equivalence between the first reconstructed volume and the second reconstructed volume; A device, wherein for an optimized X-ray imaging trajectory, the trajectory adapter provides a second trajectory adapted for acquiring the second X-ray image sequence at the second position of the X-ray imaging device.

2. The device of claim 1 , wherein the degree of overlap relates to a degree of spatial overlap between the first reconstruction volume and the second reconstruction volume.

3. The device of claim 1 or 2, wherein the degree of overlap is provided for a predetermined diagnostic purpose.

4. The device of claim 1 , wherein for the first position information, the position information receiver receives a first trajectory and its spatial information, and the processor determines a resultant first reconstruction volume and the first position information of the first reconstruction volume based on the first trajectory and its spatial information.

5. 5. The device of claim 1, wherein the position information receiver receives spatial information of the X-ray imaging device during acquisition of the first X-ray image sequence along the first trajectory, and the processor determines the first trajectory based on the spatial information and determines the resulting first reconstruction volume.

6. 5. The device of claim 1, wherein the position information receiver receives a first image sequence showing the X-ray imaging device photographed by a camera during acquisition of the first X-ray image sequence along the first trajectory, and the processor determines the first trajectory based on the image sequence and determines the resulting first reconstruction volume.

7. the first position information includes first subject-related spatial information at the first position of the X-ray imaging device; the location information receiver receiving second subject-related spatial information at the second location of the X-ray imaging device; The device of claim 1 , wherein the processor determines a degree of overlap between the first reconstructed volume and the second reconstructed volume for the subject.

8. 8. The device of claim 1, wherein the processor determines if the degree of equality is outside a predetermined range of equality and a repositioning indicator is provided to indicate that repositioning of the X-ray imaging device is required.

9. 9. The device of claim 1, wherein the first and second positions of the X-ray imaging device relate to an orientation of the X-ray imaging device relative to the subject, and the second position is different from the first position.

10. an x-ray imaging device having an x-ray source and an x-ray detector movable along a trajectory for acquiring a sequence of x-ray images of a region of interest; 10. An X-ray imaging system comprising: a device for optimizing an X-ray imaging trajectory according to any one of claims 1 to 9, the x-ray imaging device providing the first sequence of x-ray images of a region of interest of a subject; An X-ray imaging system, wherein the trajectory adapter provides the second trajectory adapted to the X-ray imaging device for acquiring the second X-ray image sequence at the second position of the X-ray imaging device.

11. the X-ray imaging system is a mobile X-ray system having a base that is freely movable along a floor surface; the x-ray imaging device comprises a moveable C-arm with the x-ray source and the x-ray detector mounted at opposite ends of the C-arm; The X-ray imaging system of claim 10 , further comprising a drive mechanism for moving the C-arm to move the X-ray source and the X-ray detector along the adapted second trajectory.

12. at least one optical camera is provided, and during acquisition of the first sequence of X-ray images along the first trajectory, the at least one optical camera provides a captured first sequence of images showing the X-ray imaging device; 12. The X-ray imaging system of claim 10 or 11, wherein the processor is configured to determine the first trajectory based on the image sequence and to determine the resulting first reconstruction volume.

13. 1. A method for optimizing an x-ray imaging trajectory, the method comprising: receiving first position information of a first reconstruction volume based on a first sequence of X-ray images of a region of interest of the subject acquired along a first trajectory at a first position of an X-ray imaging device; receiving a planned second trajectory for acquiring a second sequence of X-ray images at a second position of the X-ray imaging device; calculating a resulting second reconstruction volume for the second X-ray image sequence; determining second position information for the second reconstruction volume; determining a degree of similarity between the first reconstructed volume and the second reconstructed volume based on the first location information and the second location information, the degree of similarity being provided as a degree of overlap between the first reconstructed volume and the second reconstructed volume; calculating a fitted second trajectory resulting in an increasing degree of similarity between the first reconstructed volume and the second reconstructed volume; providing the adapted second trajectory for acquiring the second X-ray image sequence at the second position of the X-ray imaging device to a display or user interface, or to a trajectory adapter for providing the adapted second trajectory to the X-ray imaging device and acquiring the second X-ray image sequence at the second position of the X-ray imaging device; The method comprising:

14. A computer program enabling a processor to carry out the method according to claim 13.

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