Device and method for optimizing X-ray imaging trajectory and X-ray imaging system

Abstract

The present invention relates to field of view matching for mobile 3D imaging (such as mobile C-arm 3D imaging). In order to provide improved image data for comparison purposes, for example when using a mobile X-ray imaging system, first position information of a first reconstructed volume that receives a first sequence of X-ray images of a region of interest of a subject acquired along a first trajectory in a first position of an X-ray imaging device is received. In addition, a planned second trajectory for acquiring a second sequence of X-ray images in a second position of the X-ray imaging device is received, and a generated second reconstructed volume for the second sequence of X-ray images is calculated. Then, second position information for the second reconstructed volume is determined. In addition, based on the first position information and the second position information, a degree of comparability between the first reconstructed volume and the second reconstructed volume is determined. An adjusted second trajectory is calculated, which results in an increased degree of comparability between the first reconstructed volume and the second reconstructed volume. The adjusted second trajectory is used to acquire the second sequence of X-ray images in the second position of the X-ray imaging device.

Description

Technical Field

[0001] The present invention relates to field of view matching for mobile 3D imaging. In particular, the present invention relates to an apparatus for optimizing an X-ray imaging trajectory, an X-ray imaging system and a method for optimizing an X-ray imaging trajectory. Background Art

[0002] In surgical applications, mobile C-arm imaging systems are often used. As an example, a motorized system can be used to create a 3D volume reconstruction after recording a predefined sequence of projection images. Such acquisitions can be challenging because there are often many devices and systems as well as clinical staff around the subject table. Further challenges can arise when a second 3D acquisition is required to evaluate, for example, surgical results or progress. The mobile C-arm can be freely moved by the operator and may thus not be in the same position at the second acquisition as at the first acquisition and may require another trajectory to be executed. However, it has been shown that this can be cumbersome for comparing two reconstructed 3D volumes. Summary of the Invention

[0003] Therefore, there may be a need to provide improved image data for comparison purposes.

[0004] It should be noted that the following aspects of the present invention also apply to an apparatus for optimizing an X-ray imaging trajectory, an X-ray imaging system and a method for optimizing an X-ray imaging trajectory.

[0005] According to the present invention, there is provided an apparatus for optimizing an X-ray imaging trajectory. The apparatus 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 reconstructed volume, the first position information being based on a first sequence of X-ray images of a region of interest of a subject acquired along a first trajectory in a first position of an X-ray imaging device. The position information receiver is further configured to receive a planned second trajectory for acquiring a second sequence of X-ray images in a second position of the X-ray imaging device. The processor, coupled to the position information receiver and the trajectory adapter, is configured to calculate a second reconstructed volume resulting from the second sequence of X-ray images. The processor is further configured to determine second position information for the second reconstructed volume. The processor is further configured to determine a degree of comparability between the first reconstructed volume and the second reconstructed volume based on the first position information and the second position information. The processor is further configured to calculate an adjusted second trajectory that results in an increased degree of comparability between the first reconstructed volume and the second reconstructed volume. For the optimized X-ray imaging trajectory, the trajectory adapter is configured to provide the adjusted second trajectory for acquiring the second sequence of X-ray images in the second position of the X-ray imaging device.

[0006] This provides improved comparability between the first reconstructed volume and the second reconstructed volume, thus providing an improvement for comparison purposes.

[0007] In one example, for an optimized X-ray imaging trajectory, an adjusted second trajectory is used for a mobile C-arm 3D imaging system.

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

[0009] According to one example, the degree of overlap is related to the 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. A processor is configured to determine the first trajectory based on the spatial information and determine the resulting first reconstructed volume.

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

[0012] According to the present invention, an X-ray imaging system is also provided. The system includes an X-ray imaging device having an X-ray source and an X-ray detector capable of moving along a trajectory to acquire a sequence of X-ray images of a region of interest. The system further includes means for optimizing an X-ray imaging trajectory according to one of the foregoing examples. The X-ray imaging device provides a first sequence of X-ray images of a region of interest of a subject. In addition, a trajectory adapter provides an adjusted second trajectory to the X-ray imaging device for acquiring a second sequence of X-ray images in 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 having a base that can move freely along a floor surface. The X-ray imaging device includes a movable C-arm, and the X-ray source and the X-ray detector are mounted at opposite ends of the C-arm. In addition, a drive mechanism is provided for moving the C-arm so that the X-ray source and the X-ray detector move along the adjusted second trajectory.

[0014] The X-ray system can 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 first image sequence of the X-ray imaging device during acquisition of a first sequence of X-ray images of a subject along a first trajectory. A processor determines the first trajectory based on the image sequence and determines a resulting first reconstructed volume.

[0016] According to the present invention, there is also provided a method for optimizing an X-ray imaging trajectory. The method includes the following steps:

[0017] Receiving first position information of a first reconstructed volume, the first position information being based on a first sequence of X-ray images of a region of interest of a subject acquired along a first trajectory in a first position of an X-ray imaging device;

[0018] Receiving a planned second trajectory for acquiring a second sequence of X-ray images in a second position of the X-ray imaging device;

[0019] Calculating a resulting second reconstructed volume for the second sequence of X-ray images;

[0020] Determining second position information for the second reconstructed volume;

[0021] Based on the first position information and the second position information, determining a degree of comparability between the first reconstructed volume and the second reconstructed volume;

[0022] Calculating an adjusted second trajectory that results in an increased degree of comparability between the first reconstructed volume and the second reconstructed volume; and

[0023] Providing the adjusted second trajectory for acquiring a second sequence of X-ray images in a second position of the X-ray imaging device.

[0024] According to one aspect, in one example, it is provided to estimate a field of view of a planned 3D volume reconstruction based on an external camera image before acquiring a corresponding projection sequence. The estimated field of view of the planned 3D volume reconstruction is compared with a previous 3D reconstruction, and it is evaluated whether there is sufficient overlap of diagnostically relevant regions. The planned trajectory of the planned 3D volume reconstruction is adjusted to improve the overlap between the estimated reconstruction field of view and the previously acquired one. In the case where the C-arm system needs to be repositioned, a visual indicator can provide feedback to a clinician to create a second 3D reconstruction with sufficient overlap with the first 3D reconstruction.

[0025] These and other aspects of the present invention will become apparent and be elucidated from the embodiments described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Exemplary embodiments of the present invention will be described below with reference to the following drawings:

[0027] Figure 1Shows an example of an apparatus for optimizing an X-ray imaging trajectory.

[0028] Figure 2 Shows an example of an X-ray imaging system.

[0029] Figures 3a and 3b show two examples of overlapping reconstructed volumes.

[0030] Figures 4a and 4b show two examples of overlapping scan trajectories.

[0031] Figure 5a shows an example of a planned second trajectory, and Figure 5b shows an example of an adjusted second trajectory.

[0032] Figure 6 Shows the basic steps of an example of a method for optimizing an X-ray imaging trajectory. Detailed Description

[0033] Certain embodiments will now be described in more detail with reference to the accompanying drawings. In the following description, the same reference numerals are used for the same elements even in different drawings. Matters defined in the description, such as detailed structures and elements, are provided to assist in a comprehensive understanding of the exemplary embodiments. Also, well-known functions or structures are not described in detail because they would obscure the embodiments with unnecessary detail. Additionally, expressions such as "at least one", when placed in front of a list of elements, modify the entire list of elements without modifying the individual elements in the list.

[0034] Mobile X-ray imaging systems are often used in surgical applications. Motorized systems can be used to achieve 3D volume reconstruction after recording a predetermined sequence of scan or projection images along a certain trajectory. Movement along the trajectory can be challenging because there are often many devices and systems as well as clinical staff around the subject table. For such X-ray imaging, fixed-mounted systems with movable parts as well as mobile systems, such as mobile C-arm imaging systems, are provided. If imaging allowing comparison is needed, similar images can be helpful to clinical staff. As an example, a second 3D acquisition is to be performed to evaluate, for example, surgical results or progress. 3D volume reconstructions before and after surgery may not show the same 3D region of interest because the positioning of the C-arm, the subject, or surrounding obstacles may have changed. As another example, since the mobile C-arm can be freely moved by the operator, the system may not be in the same position at the second acquisition as at the first acquisition. If two reconstructed 3D volumes are to be compared, this can be troublesome and may even be a problem.

[0035] The term "subject" may also be referred to as an individual. The "subject" may also be referred to as a patient, but it should be noted that this term does not indicate whether the subject actually has any disease or disorder.

[0036] Figure 1 An example of an apparatus 10 for optimizing an X-ray imaging trajectory is shown. The apparatus 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 reconstructed volume, the first position information being based on a first sequence of X-ray images of a region of interest of a subject acquired along a first trajectory in a first position of an X-ray imaging device. The position information receiver 12 is further configured to receive a planned second trajectory for acquiring a second sequence of X-ray images in a second position of the X-ray imaging device. The processor 14, which is coupled to the position information receiver 12 and the trajectory adapter 16, is configured to calculate a second reconstructed volume for the second sequence of X-ray images. The processor 14 is further configured to determine second position information for the second reconstructed volume. The processor 14 is further configured to determine a degree of comparability between the first reconstructed volume and the second reconstructed volume based on the first position information and the second position information. The processor 14 is further configured to calculate an adjusted second trajectory that results in an increased degree of comparability between the first reconstructed volume and the second reconstructed volume. For the optimized X-ray imaging trajectory, the trajectory adapter 16 is configured to provide the adjusted second trajectory for acquiring the second sequence of X-ray images in the second position of the X-ray imaging device.

[0037] Thus, the trajectory is optimized rather than moving the entire X-ray imaging device. The goal is to improve the comparison, which also includes accepting a certain degree of uncertainty. An attempt is made to achieve a compromise.

[0038] The term "position information" relates to information about the spatial position of a corresponding reconstructed volume. To evaluate the degree of comparability, such as the spatial overlap of two reconstructed volumes, i.e., to compare two reconstructed volumes, the spatial positions refer at least indirectly to the same spatial reference. For example, the spatial position of the first reconstructed volume may be related to the reference coordinates of the imaging device in the first position, and the spatial position of the second reconstructed volume may be related to the reference coordinates of the imaging device in the second position, while the displacement between the first position and the second position is also provided (or determined). The spatial position provides information about the three-dimensional arrangement and rotation. As an example, the position information may be provided relative to a fixed base in the examination room, such as a reference point of a 3D coordinate grid in the examination room. As another example, the position information may be provided relative to a moving base in the examination room, such as a subject support, e.g., a patient table.

[0039] The term "reconstructed volume" refers to an area for which data is available and can be used for reconstructing the volume's image data. As an example, multiple image projections involving different imaging orientations are provided. The 3D volumes traversed by the projection rays sufficiently overlap such that 3D data can be retrieved from the 2D projections. As an example, the reconstructed volume refers to an area of a subject for which image data is generated by, for example, computed tomography. The reconstructed volume is also referred to as the 3D field of view.

[0040] The first reconstructed volume is also referred to as the previous reconstructed volume, and the second reconstructed volume is referred to as the estimated reconstructed volume.

[0041] In one example, the first reconstructed volume relates to the pre - operative situation, while the second reconstructed volume relates to the post - operative situation. Examinations, interventions, treatments, or other procedures may have occurred between the pre - operative and post - operative situations.

[0042] The term "trajectory" refers to a path in space along which an image source and an image detector move to acquire multiple projections so as to cover the region of interest from different directions in order to be able to generate 3D image data of the region of interest. In one example, "trajectory" relates to the movement of a C - arm (also known as a C - arc) and the corresponding movement paths of the source and detector mounted on the C - arm. The trajectory can be a rotational movement, a sliding movement along an arc, a slewing movement, or any combination provided by the corresponding bearings and support schemes of the C - arm.

[0043] 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 adjusted second trajectory is referred to as the adjusted upcoming trajectory, the adjusted planned trajectory, or the adjusted trajectory.

[0044] In one example, the planned second trajectory is provided as the first trajectory for the second position of an X - ray imaging device.

[0045] The term "planned" refers to the second trajectory as defined before adjustment. For example, the planned trajectory can be the same trajectory as the one used for the first scan (e.g., relative to the base). However, due to misalignment of the X - ray imaging device between the first and second positions, the resulting reconstructed volumes will not match identically. Instead, a deviation between the first and second reconstructed volumes is anticipated. In another example, the planned trajectory may be a predefined trajectory (e.g., having a certain predefined relationship with the base), but due to possible misalignment of the X - ray imaging device between the first and the planned second positions, the resulting reconstructed volumes will also not match identically.

[0046] The term "degree of comparability" relates to the spatial position and orientation of two reconstructed volumes (i.e., a first reconstructed volume and a second reconstructed volume), and their ability (or suitability) to produce projections for comparing the first reconstructed volume and the second reconstructed volume, i.e., for comparing the first reconstructed volume and the second reconstructed volume.

[0047] Thus, the term "degree of comparability" also relates to taking into account the degree of similarity of the comparison.

[0048] In one example, the degree of comparability is provided as the degree of overlap (also referred to as the overlap degree).

[0049] The term "degree of overlap" relates to the spatial position and orientation of two reconstructed volumes (i.e., a first reconstructed volume and a second reconstructed volume). For example, the overlap is determined as a spatial overlap, i.e., an overlap in 3D space. The overlap can be defined as those positions in space that are covered by both reconstructed volumes.

[0050] The term "adapted" relates to the modification of a second trajectory according to a target to improve the overlap, despite the misalignment of a first position and a second position of an X-ray imaging device. The second trajectory can be used as a starting point, and then the trajectory can be modified, i.e., changed, such that an improved spatial overlap is provided.

[0051] In one example, the second position of the X-ray imaging device is reserved for an adjusted trajectory. Instead of modifying the position and orientation of the X-ray imaging device, such as a mobile base, the trajectory is modified at least within given geometric constraints, while the position of the X-ray imaging device does not change.

[0052] The "position" of the X-ray imaging device relates to the arrangement or position of the components of the X-ray imaging device that do not move during an imaging scan.

[0053] In one example, the adjustment of a planned trajectory is provided in an automated manner.

[0054] In one example, a position information receiver is configured to receive a first trajectory for a first reconstructed volume. A processor is configured to determine the resulting first reconstructed volume.

[0055] As an example, a planned second trajectory is the same trajectory as the first trajectory, but (theoretically or practically) is applied to a second position or a second location of the X-ray imaging device. Then, the planned second trajectory is adjusted to achieve a better match to a volume of interest, i.e., a reconstructed volume, and this adjustment results in a generated adjusted second trajectory, and then the adjusted second trajectory is used to perform a second scan.

[0056] In one example, the position information receiver is configured to receive position information of a second position of the X-ray imaging device. For a planned second trajectory, the processor is configured to apply a first trajectory to the second position of the X-ray imaging device.

[0057] In one example, the position information receiver is configured to receive position information for a second reconstruction volume when applying a planned second trajectory.

[0058] In one example, the position information receiver is configured to receive position information for a planned second reconstruction volume, and for a planned second trajectory, calculate a trajectory that results in achieving the planned second reconstruction.

[0059] In one example, the planned second trajectory is a trajectory manually provided by a staff member.

[0060] In another example, the planned second trajectory is a trajectory proposed by the processor taking into account avoiding possible collisions in the current situation.

[0061] In another example, the trajectory is timed relative to respiratory motion, cardiac motion, or contrast agent motion. Thus, comparability is improved if, for example, the cardiac phase or contrast agent level recorded in two scans is comparable. If the scans show slightly different regions of the body, the arrival time of the contrast agent may be different. Or, if the second scan starts at a different position on the same cycle as the first scan, synchronization with, for example, the heartbeat may still be inconsistent. This may even require additional input. The trajectory can be slowed down accordingly at the start.

[0062] In Figure 1 a display or interface 18 (shown in dashed lines) is provided as an option and is configured to display information about the adjusted second trajectory to an operator.

[0063] In addition, a first arrow 20 (shown in dashed lines) indicates data output, i.e., a data connection.

[0064] A second arrow 22 (shown in dashed lines) indicates data input. A box 24 surrounding the position information receiver 12, the processor 14, and the trajectory adapter 16 indicates that the information receiver 12, the processor 14, and the trajectory adapter 16 can be integrated into a common structure (such as a common housing) to be provided. In one example, the information receiver 12, the processor 14, and the trajectory adapter 16 are provided in an integrated manner. In another example, the information receiver 12, the processor 14, and the trajectory adapter 16 are provided separately.

[0065] In one option, the degree of set comparability is provided as the degree of overlap between a first reconstruction volume and a second reconstruction volume.

[0066] In another option, setting the degree of overlap involves the spatial overlap degree between the first reconstructed volume and the second reconstructed volume.

[0067] In one example, a part of the first reconstructed volume is selected as the first reference part, and a part of the second reconstructed volume is selected as the second reference part; the degree of overlap is determined based on the first reference part and the second reference part.

[0068] In one example, for the first position information, the position information receiver 12 is configured to receive the first trajectory and its spatial position; and the processor 14 is configured to determine the generated first reconstructed volume and the first position information of the first reconstructed volume based on the first trajectory and its spatial position.

[0069] In one example, the position information receiver 12 is configured to receive the spatial information of the X-ray imaging device during acquiring the first sequence of X-ray images along the first trajectory; and the processor 14 is configured to determine the first trajectory based on the spatial information and determine the generated first reconstructed volume.

[0070] In one example, the position information receiver 12 is configured to receive the first image sequence showing the X-ray imaging device captured by a camera during acquiring the first sequence of X-ray images along the first trajectory; and the processor 14 is configured to determine the first trajectory based on the image sequence and determine the generated first reconstructed volume.

[0071] In one example, the X-ray imaging device includes a movable C-arm, and the image shows the movement of the C-arm.

[0072] In one example, the X-ray imaging system is a mobile X-ray imaging system, and for the first position of the X-ray imaging device, the first position of the X-ray imaging system is determined based on the image captured by a camera. In addition, for the second position of the X-ray imaging device, the second position of the X-ray imaging system is determined based on at least one second image showing the X-ray imaging device captured by a camera before acquiring the second sequence of X-ray images.

[0073] The mobile X-ray system, such as a movable C-arm mounted on a carriage, has multiple degrees of freedom of movement. In one example, the system is not motorized relative to the floor, and the movement along the floor is not tracked. 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 position and the second position in the examination room.

[0074] In one example, the subject on the subject support is also tracked by an optical camera. In one option, the subject is tracked by images. In another option, the subject is tracked by electromagnetic tracking.

[0075] To compare the first reconstructed volume and the second reconstructed volume, the first scan movement is captured by one or more cameras. In one example, the camera captures where the first reconstructed volume is set. After the imaging device and the subject move relative to each other, repeating the same scan movement will result in a second reconstructed volume that is offset (i.e., shifted).

[0076] By changing, i.e., adjusting, the trajectory of the (second) scan, an improvement is achieved by providing a second reconstructed volume with more overlap compared to when the unadjusted trajectory is applied. At least to some extent, this avoids the need to provide an indication to the operator (such as a doctor or nurse) to move the mobile X-ray imaging device. Thus, the adjusted second trajectory replaces the indication of repositioning. Subsequently, the imaging operation is facilitated and the staff is also freed from further tasks.

[0077] Regarding X-ray imaging, information or warnings that the current position is not suitable for imaging can be regarded as support for the first step or stage. While providing an indication of how to achieve an improved position for X-ray imaging (i.e., relationship guidance) can be regarded as support for the second step or stage, and providing an adjusted trajectory can be regarded as support for the third step or stage.

[0078] Therefore, an external camera can be used to estimate and verify that there is sufficient overlap between two 3D reconstruction fields of view for diagnostic purposes. The overlap can be improved by using the camera information to define a specific trajectory for the second acquisition, or by indicating to the operator to change the starting position of the system.

[0079] The external camera can be set on the system or in the operating room. The external camera can also be used to facilitate finding a preferred trajectory around all obstacles while still obtaining projections from all required angles.

[0080] In one example, the movement of the X-ray imaging device between the first position and the second position is detected by drive wheels or sensors in the bearings, and these sensors provide spatial information about the movement.

[0081] In one example, the first position information includes first spatial information related to the subject in the first position of the X-ray imaging device. The position information receiver 12 is configured to receive second spatial information related to the subject in the second position of the X-ray imaging device; and the processor 14 is configured to determine the degree of overlap between the first reconstructed volume and the second reconstructed volume related to the subject.

[0082] This provides an evaluation of the effect of the overlap taking into account the intended use of the image data comparison.

[0083] (The first and second) reference portions may also be referred to as (the first and second) core regions of interest within (the first and second) regions of interest covered by (the first and second) reconstructed volumes.

[0084] In one example, the processor 14 is configured to determine whether the degree of comparability is outside a predetermined range of comparability. A repositioning indicator is provided, which is configured to indicate that the X-ray imaging device needs to be repositioned.

[0085] As an example, a minimum overlap of 30% is provided. In another example, the minimum value is 50%.

[0086] In one example, in order to determine and evaluate the degree of overlap, the type of imaging task is also considered. For example, for certain imaging purposes, a smaller degree of overlap may be required.

[0087] In a further example, the reconstructed volumes are all cylindrical regions, and the overlap results in a spherical region.

[0088] In another example, the reconstructed volumes are all cylindrical regions, which are arranged perpendicular to each other.

[0089] For example, C-arm imaging is provided. The first position and the second position have a cross-orientation of the imaging device, such as the first position being on one side of the patient support and the second position being at the end of the subject support, or vice versa. Then, one trajectory will be defined by the propeller movement of the C-arm, and the other trajectory will be defined as the rolling movement of the C-arm.

[0090] In one example, the first position and the second position of the X-ray imaging device are related to the arrangement of the X-ray imaging device relative to the subject. The second position is different from the first position.

[0091] This difference may be caused by the movement of the X-ray imaging device. This difference may also be caused by the movement of the subject being imaged. This difference may also be caused by the movement of both the X-ray imaging device and the subject being imaged.

[0092] For example, after an intervention or treatment, the subject may be arranged in a different posture. In another example, the X-ray imaging device may be moved away for an intervention or treatment and then moved back for further imaging operations, but with at least a slight deviation in position and / or orientation.

[0093] In one example, during a first sequence of X-ray images, the subject is set in a first position. Additionally, during a second sequence of X-ray images, the subject also remains in the first position. In the first sequence of X-ray images, the X-ray imaging device is arranged in a first position. Additionally, in the second sequence of X-ray images, the X-ray imaging device is arranged in a second position.

[0094] In another example, during a first sequence of X-ray images, the subject is set in a first position, and during a second sequence of X-ray images, the subject is in a second position. The X-ray imaging device is arranged in a first position during the first sequence of X-ray images and also remains in the first position during the second sequence of X-ray images.

[0095] In another example, during a first sequence of X-ray images, the subject is set in a first position, and during a second sequence of X-ray images, the subject is in a second position. The X-ray imaging device is arranged in a first position during the first sequence of X-ray images and is arranged in a second position during the second sequence of X-ray images.

[0096] Figure 2 An example of an X-ray imaging system 50 is shown. System 50 includes an X-ray imaging device 52 having an X-ray source 54 and an X-ray detector 56 that are movable along a trajectory to acquire a sequence of X-ray images of a region of interest. Additionally, system 50 includes an example of a device 10 for optimizing an X-ray imaging trajectory according to one of the foregoing examples. As an example, device 10 is schematically shown as a separate box. Device 10 may be provided in a separate housing or in an integrated manner. Line 58 represents 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 sequence of X-ray images of the region of interest of the subject. The trajectory adapter 16 provides an adjusted second trajectory to the X-ray imaging device 52 for acquiring a second sequence of X-ray images in a second position of the X-ray imaging device 52.

[0097] As an effect, due to the adjustment of the trajectory, the projections of two 3D volumes generated based on the respective scans along the X-ray imaging trajectory are not affected by small movements of the C-arm or the object being imaged between the first and second scans.

[0098] In one example, in Figure 2Shown as an option, the X-ray imaging system 50 is a mobile X-ray system 60 having a base 62 that can move freely along the floor surface. The X-ray imaging device 52 includes a movable C-arm 64, and an X-ray source 54 and an X-ray detector 56 are mounted at opposite ends of the C-arm 64. A drive mechanism 66 is provided for moving the C-arm 64 so that the X-ray source 54 and the X-ray detector 56 move along an adjusted second trajectory.

[0099] In Figure 2 it is indicated the first reconstruction volume 68 and the second reconstruction volume 70. It can be seen that these two volumes 68, 70 partially overlap.

[0100] The first reconstruction volume 68 indicates the result of a first scan of a subject (e.g., arranged on a subject support (not further shown)), while the X-ray imaging system 50 is arranged in a first position relative to the subject. For example, the first scan has been performed.

[0101] The second reconstruction volume 70 indicates the result of a second scan of a subject (e.g., also arranged on a subject support (not further shown)), while the X-ray imaging system 50 is arranged in a second position relative to the subject. For example, the second scan will be performed as the next step.

[0102] The first reconstruction volume 68 and the second reconstruction volume 70 are indicated in a free-floating manner to indicate the overlap and the achievable comparability.

[0103] In one example, the mobile X-ray system includes a motor-driven support wheel device, and the support wheel device provides position information of the second position of the X-ray system.

[0104] In one example, the X-ray imaging system is a fixed X-ray system that includes a movable support structure for the C-arm. The movable support structure provides position information of the second position of the X-ray system.

[0105] In one option, also shown in Figure 2 it, at least one optical camera 71 is provided to provide a first image sequence of the X-ray imaging device being photographed during acquisition of a first sequence of X-ray images along a first trajectory. The camera is data-connected to a device 10 for optimizing the X-ray imaging trajectory. A processor determines the first trajectory based on the image sequence and determines the resulting first reconstruction volume.

[0106] It should be noted that in Figure 5A and Figure 5BAt least one camera is not further shown. The camera thus captures (i.e., detects) where the first reconstruction volume is arranged. The camera also captures (i.e., detects) where the second reconstruction volume will be arranged in the case of adjustment.

[0107] Figures 3a and 3b show two further examples of overlapping reconstruction volumes. In the examples shown in Figures 3a and 3b, a first cylindrical reconstruction volume 68', 68'' and a second cylindrical reconstruction volume 70', 70'' overlapping in the middle are provided.

[0108] In the first option, as shown in Figure 3a, two cylinders, i.e., the cylindrical reconstruction volumes 68', 70', are oriented perpendicular to each other.

[0109] In the second option, as shown in Figure 3b, two cylinders, i.e., the cylindrical reconstruction volumes 68'' and 70'', have the same orientation. For example, the following projections are recorded in a similar direction.

[0110] Thus, in the second option (Figure 3b), the actual spatial overlap may be smaller than in the first option (Figure 3a), but the second option may still have a higher degree of comparability because the projection directions are similar. In this example, only a small core region is of interest. Therefore, a large special overlap does not improve comparability. However, the fact that the projection directions in the second option are similar improves comparability because the directional imaging artifacts (partial volume, beam hardening, scattering, metal streaks, etc.) and the absolute voxel values (e.g., Hounsfield units) will be more comparable. In this example, the improved comparability does not refer to the improved spatial overlap, but to the comparability of the X-ray attenuation characteristics of the tissues recorded in the two reconstructed images.

[0111] Figures 4a and 4b show a first scan path 72, 72' and a second scan path 74, 74' around the region of interest 76 of the subject, where for the first reconstruction volume and the second reconstruction volume, limited angled segments are used. The scan directions are indicated by curved (i.e., circular) arrows. The directions of the partial angle artifacts generated by the first scan and the second scan are indicated by a first straight arrow 78, 78' for the first scan and a second straight arrow 80, 80' for the second scan.

[0112] In Figure 4a, the scan directions are in opposite directions, and the directions of the generated artifacts are in opposite directions.

[0113] In Figure 4b, the scan directions are the same, but with different angles. The directions of the generated artifacts are arranged at an angle.

[0114] In one option, the limited angled sections are as similar as possible, or at least in opposite directions. In this example, the comparability is improved because the artifact directions are more similar.

[0115] Figures 5a and 5b indicate a subject 82 disposed on a subject support 84. A movable C-arm X-ray imaging device 86 is partially shown. The C-arm can be moved so that the X-ray source and the X-ray detector rotate around the region of interest of the subject to form an isocenter.

[0116] Figure 5a shows an example of a planned second trajectory 88 that will result in the generation of a second reconstructed volume that will overlap with the first reconstructed volume but only with a relatively low degree of comparability.

[0117] Figure 5b shows an example of an adjusted second trajectory 90 that will result in an improved degree of comparability. In the example shown, the scan is provided around a subject 82 disposed on a subject support 84. The initially planned second trajectory, as shown in Figure 5a, is shown as a circular rolling movement M around the subject 82 R . The adjusted second trajectory, as shown in Figure 5b, is shown as a propeller movement M around the subject 82 P . Thus, a second reconstructed volume is achievable that has a better match with the first reconstructed volume. The change from the rolling movement M R to the propeller movement M P is an example of the adjustment of the second trajectory.

[0118] Figure 6 Shows the basic steps of an example of a method 100 for optimizing an X-ray imaging trajectory.

[0119] Method 100 includes the following steps:

[0120] In a first step 102, also referred to as step a), receive first position information of a first reconstructed volume, the first position information being based on a first sequence of X-ray images of a region of interest of a subject acquired along a first trajectory in a first position of an X-ray imaging device.

[0121] In a second step 104, also referred to as step b), receive a planned second trajectory for acquiring a second sequence of X-ray images in a second position of the X-ray imaging device.

[0122] In a third step 106, also referred to as step c), calculate a second reconstructed volume for the generation of the second sequence of X-ray images.

[0123] In a fourth step 108, also referred to as step d), determine second position information for the second reconstructed volume.

[0124] In a fifth step 110, also referred to as step e), a degree of comparability of a first reconstructed volume and a second reconstructed volume is determined based on first position information and second position information.

[0125] In a sixth step 112, also referred to as step f), an adjusted second trajectory is calculated, which results in an increased degree of comparability of the first reconstructed volume and the second reconstructed volume.

[0126] In a seventh step 114, also referred to as step g), the adjusted second trajectory is provided for acquiring a second sequence of X-ray images in a second position of an X-ray imaging device.

[0127] The first step 102 of receiving the first position information and the second step 104 of receiving a planned second trajectory may also be provided simultaneously, or the second step 104 may be provided before the first step 102.

[0128] In an example, for the first position information, a first trajectory and its spatial position are provided, and the first position information of the resulting first reconstructed volume and the first reconstructed volume is determined based on the first trajectory and its spatial position.

[0129] In an example, the first position information further includes first spatial information related to a subject in a first position of the X-ray imaging device. In addition, second spatial information related to the subject in a second position of the X-ray imaging device is also provided. The degree of comparability, for example, the degree of overlap of the first reconstructed volume and the second reconstructed volume, is determined to be related to the subject.

[0130] As an example, based on a camera, such as an external camera, trajectories of a detector and a source for 3D X-ray acquisition relative to an imaged subject are recorded. In one option, the camera is fixedly placed inside an operating room or attached to a C-arm and sees the patient. This can be facilitated by a C-arm system and / or special markings on the patient to capture and track movement and motion. It can also be facilitated by natural features recognizable in the camera image. As dedicated markings, one or more QR code markings 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 at a central position on the skin of the subject. Natural markings that can be extracted from the image can be numerous image features that can be recognized from different perspectives. For example, edges, ridges, corners, markings on the tube and the detector housing. For the subject, features such as their eyes, fingers, wrinkles, skin spots, navel can be used.

[0131] Based on the trajectory, a 3D field of view relative to the patient's anatomy to be acquired is estimated. This can be done by tracking optical image features using the above-mentioned special or natural markers as follows. When performing the first trajectory, multiple optical images are acquired. In each image, image features can be detected and associated with other optical images acquired from different perspectives. For example, as another option, the camera is attached to the C-arm and, when performing the first trajectory, the camera "looks" at the patient. In one image, we can, for example, detect the fingertip of the patient. Then, the C-arm moves along the first trajectory and additional optical images are acquired. In all these images, the fingertip of the patient is now sought from different perspectives. All the fingertips detected from different perspectives can be matched, so that the fingertip of the patient can be located in 3D space (relative to the C-arm). By repeating this method for all possible markers, a point cloud, i.e., a digital point cloud of 3D marker positions, can be generated.

[0132] Furthermore, for the second acquisition, a planned C-arm trajectory for the second 3D acquisition is calculated.

[0133] Based on the planned second trajectory, a second 3D field of view to be acquired relative to the patient's anatomy is estimated. In this step, the detection of the above-mentioned 3D marker positions is repeated.

[0134] Then, the overlap between the first 3D field of view and the second 3D field of view is calculated. This can be achieved by calculating the overlap between the point cloud of all 3D marker positions acquired in the first acquisition and the point cloud acquired in the second acquisition, i.e., there needs to be sufficient feature correspondence between the two point clouds. In other words, it is analyzed whether sufficient overlap is provided for a predetermined diagnostic purpose. The term sufficient overlap may depend on the desired diagnostic purpose. It can be expressed as a percentage of volume, for example, when investigating general characteristics such as tissue iodine concentration. It can also be defined by specific anatomical landmarks that must all be within the overlapping volume, i.e., all the anatomical landmarks required for a specific purpose. For example, two specific vertebral bodies of interest must be completely within the overlapping field of view in order to compare them in the two images. Or, specific points of interest (lesions, bifurcations, implants, aneurysms) in the vascular structure must all be included in the overlapping volume.

[0135] If the overlap is insufficient, a corrective action can be triggered by adjusting the planned trajectory or by issuing an indication to the operator. For example, depending on the degrees of freedom of movement of the system, the user is advised to manually change the position of the C-arm so that the second trajectory can be executed, improving the overlap with the first trajectory.

[0136] Automatic trajectory adjustment will depend on the motorized degrees of freedom that can be controlled on the mobile C-arm unit. For example, if motorized translation is possible, the C-arm is positioned such that the isocenters of two acquisitions are as close as possible.

[0137] If the first trajectory is a rolling movement of the C-arm and the C-arm repositioned before the second acquisition is in a significantly different orientation, a propeller movement for the second acquisition may be preferred in order to better align the source and detector trajectories in 3D space. This will result in better overlap of the reconstructed volumes. Additionally, a combination of a rolling movement and a propeller movement may be a solution to optimize the second trajectory.

[0138] In the case of limited-angle reconstruction (less than 180° plus the fan angle), the direction not imaged in each acquisition is ideally the same. However, depending on the repositioning of the C-arm, this may imply different motor movements.

[0139] Different bi-axial trajectories can be used to reconstruct the same 3D volume. If a new obstacle is placed in the path of the original trajectory during the second acquisition, a second bi-axial trajectory can be selected to image the same volume but avoid the obstacle.

[0140] In cases where the repositioning of the C-arm does not allow for automatic acquisition of projections from a sufficient angle of the initial reconstructed volume for a complete second reconstruction, the second acquisition can be reduced to a limited angled section. That is, only the angled section that also has the first reconstructed volume in the field of view is imaged. Then a limited-angle reconstruction of the initial volume can be created for comparison. During the second acquisition, unnecessary data, i.e., data unrelated to the first acquisition, is avoided.

[0141] The present invention relates to field-of-view matching for mobile 3D imaging, such as 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 reconstructed volume is received, the first position information being based on a first sequence of X-ray images of a region of interest of a subject acquired along a first trajectory in a first position of the X-ray imaging device. Additionally, a planned second trajectory for acquiring a second sequence of X-ray images in a second position of the X-ray imaging device is received, and a second reconstructed volume for the generation of the second sequence of X-ray images is calculated. Then, second position information for the second reconstructed volume is determined. Furthermore, based on the first position information and the second position information, a degree of comparability between the first reconstructed volume and the second reconstructed volume is determined. An adjusted second trajectory is calculated, which results in an increased degree of comparability between the generated first reconstructed volume and the second reconstructed volume. The adjusted second trajectory is used to acquire the second sequence of X-ray images in the second position of the X-ray imaging device.

[0142] In an exemplary embodiment, a computer program is provided that enables a processor to execute the method of the above embodiment.

[0143] In an exemplary embodiment, a computer program or program unit is provided for controlling a device according to one of the above embodiments. When the program or program unit is executed by a processing unit, it is adapted to execute the method steps of one of the above method embodiments.

[0144] In an exemplary embodiment, a computer-readable medium is provided that stores a program unit of one of the above embodiments.

[0145] In another exemplary embodiment of the present invention, a computer program or computer program unit is provided, characterized in that it is adapted to execute the method steps of the method according to one of the foregoing embodiments on a suitable system.

[0146] Therefore, the computer program unit can be stored on a computer unit or distributed over more than one computer unit, which can also be part of an embodiment of the present invention. The computing unit can be adapted to execute or induce the execution of the steps of the above method. In addition, it can be adapted to operate the components of the above device. The computing unit can be adapted to automatically operate and / or execute user commands. The computer program can be loaded into the working memory of a data processor. Therefore, the data processor can be configured to execute the method of the present invention.

[0147] Multiple aspects of the present invention can be implemented in a computer program product, which can be a collection of computer program instructions stored on a computer-readable storage device and executable by a computer. The instructions of the present invention can be any interpretable or executable code mechanism, including but not limited to scripts, interpretable programs, dynamic link libraries (DLLs) or Java classes. The instructions can be provided as a complete executable program, a partially executable program, a modification to an existing program (such as an update) or an extension to an existing program (such as a plugin). In addition, part of the processing of the present invention can be distributed over multiple computers or processors.

[0148] As described above, a processing unit (such as a controller) implements a control method. The controller can be implemented in various ways, using software and / or hardware, to perform the various required functions. A processor is an example of a controller, which employs one or more microprocessors that can be programmed with software (such as 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 for performing certain functions and a processor for performing other functions (for example, one or more programmed microprocessors and associated circuits).

[0149] Examples of controller components that may be employed 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).

[0150] This exemplary embodiment of the invention covers both computer programs that use the invention from the start and computer programs that turn existing programs into programs using the invention by way of update.

[0151] Furthermore, the computer program unit is capable of providing all the necessary steps to carry out the operations of the exemplary embodiments of the method described above.

[0152] According to another exemplary embodiment of the invention, there is provided a computer-readable medium, such as a CD-ROM, having stored thereon a computer program unit as described in the foregoing part.

[0153] The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium provided 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 telecommunication systems.

[0154] However, the computer program may also be provided via a network such as the World Wide Web and may be downloaded into the working memory of a data processor from such a network. According to another exemplary embodiment of the invention, there is provided a medium for making available for download a computer program unit arranged to carry out the method according to one of the foregoing embodiments of the invention.

[0155] It should be noted that the embodiments of the invention have been described with reference to different subject matters. In particular, some embodiments have been described with reference to method-type claims, while other embodiments have been described with reference to apparatus-type claims. However, those skilled in the art will derive from the foregoing and following descriptions that, unless otherwise indicated, any combination between features related to different subject matters is also considered to be disclosed by this application, in addition to any combination of features belonging to one type of subject matter. However, all features may be combined to provide a synergistic effect that is more than a simple sum of the features.

[0156] Although the invention has been illustrated and described in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. By studying the drawings, the disclosure, and the dependent claims, those skilled in the art will be able to understand and implement other variations of the disclosed embodiments when practicing the claimed invention.

[0157] In a claim, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may implement the functions of several items recited in the claim. Reciting certain measures in mutually different dependent claims does not mean that a combination of these measures cannot be used advantageously. Any reference signs in the claims shall not be construed as limiting the scope.

Claims

1. An apparatus (10) for optimizing an X-ray imaging trajectory, comprising: a position information receiver (12); a processor (14); and a trajectory adapter (16); wherein the position information receiver is configured to receive first position information of a first reconstructed volume, the first position information being based on a first sequence of X-ray images of a region of interest of a subject acquired along a first trajectory in a first position of an X-ray imaging device; and to receive a planned second trajectory for acquiring a second sequence of X-ray images in a second position of the X-ray imaging device; wherein the processor, coupled to the position information receiver and the trajectory adapter, is configured to: calculate a second reconstructed volume for generation of the second sequence of X-ray images; and determine second position information of the second reconstructed volume; and determine a degree of comparability between the first reconstructed volume and the second reconstructed volume based on the first position information and the second position information, the degree of comparability being provided as a degree of overlap between the first reconstructed volume and the second reconstructed volume; and calculate an adjusted second trajectory that results in an increased degree of comparability between the first reconstructed volume and the second reconstructed volume; and wherein, for an optimized X-ray imaging trajectory, the trajectory adapter is configured to provide the adjusted second trajectory for acquiring the second sequence of X-ray images in the second position of the X-ray imaging device.

2. The apparatus according to claim 1, wherein, the degree of overlap is related to a spatial overlap degree between the first reconstructed volume and the second reconstructed volume.

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

4. The apparatus according to claim 1 or 2, wherein, for the first position information, the position information receiver is configured to receive the first trajectory and its spatial position; and the processor is configured to determine the generated first reconstructed volume and the first position information of the first reconstructed volume based on the first trajectory and its spatial position.

5. The apparatus according to claim 1 or 2, wherein, the position information receiver is configured to receive spatial information of the X-ray imaging device during acquisition of the first sequence of X-ray images along the first trajectory; and the processor is configured to determine the first trajectory based on the spatial information and determine the generated first reconstructed volume.

6. The apparatus according to claim 1 or 2, wherein, the position information receiver is configured to receive a first image sequence of the X-ray imaging device captured by a camera during acquisition of the first sequence of X-ray images along the first trajectory; and the processor is configured to determine the first trajectory based on the image sequence and determine the generated first reconstructed volume.

7. The apparatus according to claim 1 or 2, wherein, the first position information includes first spatial information related to the subject in the first position of the X-ray imaging device; wherein the degree of comparability is provided as an overlap degree between the first reconstructed volume and the second reconstructed volume; wherein the position information receiver is configured to receive second spatial information related to a subject in the second position of the X-ray imaging device; and wherein the processor is configured to determine the overlap degree between the first reconstructed volume and the second reconstructed volume with respect to the subject.

8. The apparatus according to claim 1 or 2, wherein, the processor is configured to determine whether the degree of comparability is outside a predetermined comparability range; and wherein a repositioning indicator is provided, and the repositioning indicator is configured to indicate that repositioning of the X-ray imaging device is required.

9. The apparatus according to claim 1 or 2, wherein, the first position and the second position of the X-ray imaging device are related to the arrangement of the X-ray imaging device relative to the subject; and wherein the second position is different from the first position.

10. An X-ray imaging system (50), comprising: an X-ray imaging device (52) having an X-ray source (54) and an X-ray detector (56) capable of moving along a trajectory to acquire a sequence of X-ray images of a region of interest; and an apparatus for optimizing an X-ray imaging trajectory according to any one of the preceding claims; wherein the X-ray imaging device provides the first sequence of X-ray images of the region of interest of the subject; and wherein the trajectory adapter provides the adjusted second trajectory to the X-ray imaging device for acquiring the second sequence of X-ray images in the second position of the X-ray imaging device.

11. The X-ray imaging system (50) according to claim 10, wherein, the X-ray imaging system (50) is a mobile X-ray system (60) having a base (62) capable of freely moving along a floor surface; wherein the X-ray imaging device includes a movable C-arm (64), and the X-ray source and the X-ray detector are mounted at opposite ends of the C-arm; and wherein a drive mechanism is provided for moving the C-arm so that the X-ray source and the X-ray detector move along the adjusted second trajectory.

12. The X-ray imaging system (50) according to claim 10 or 11, wherein, at least one optical camera (66) is provided to provide a first sequence of images showing the X-ray imaging device during acquisition of the first sequence of X-ray images along the first trajectory; and wherein the processor determines the first trajectory based on the sequence of images and determines the resulting first reconstructed volume.

13. A method for optimizing an X-ray imaging trajectory, comprising the steps of: receiving first position information of a first reconstructed volume, the first position information being based on a first sequence of X-ray images of a region of interest of a subject acquired along a first trajectory in a first position of an X-ray imaging device; Receive a planned second trajectory for acquiring a second sequence of X-ray images in a second position of the X-ray imaging device; Calculate a second reconstructed volume for the generation of the second sequence of X-ray images; Determine second position information of the second reconstructed volume; Based on the first position information and the second position information, determine a degree of comparability between the first reconstructed volume and the second reconstructed volume, the degree of comparability being provided as a degree of overlap between the first reconstructed volume and the second reconstructed volume; Calculate an adjusted second trajectory that results in an increased degree of comparability between the first reconstructed volume and the second reconstructed volume; And Provide the adjusted second trajectory to a display or a user interface, or to a trajectory adapter for acquiring the second sequence of X-ray images in the second position of the X-ray imaging device, the trajectory adapter being configured to provide the adjusted second trajectory to the X-ray imaging device and acquire the second sequence of X-ray images in the second position of the X-ray imaging device.

14. A computer program product that enables a processor to execute the method according to claim 13.

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