Image Reconstruction Method for a Medical System

Abstract

The present invention is an image reconstruction method for a medical system comprising a medical imaging system and, in particular, a tracking device fixedly or movably attached, for example, to the medical imaging system, the method comprising calibrating (S11) a coordinate system C2 of the tracking device for marker-based tracking to a coordinate system C1 of the medical imaging system, performing (S12) a scan by the medical imaging system, which performing the scan includes acquiring a plurality of medical images I_i (i = 1...n), obtaining (S13), by the tracking device, for each of the plurality of medical images I_i, corresponding tracking coordinates in C2 using one or more markers, converting (S14) the medical images based on the tracking coordinates and the calibration between C1 and C2, and reconstructing (S15) a 3D image based on the images converted with respect to a reference position.

Description

Technical Field

[0001] Field of the Invention The present invention relates to an image reconstruction method for a medical system, a corresponding computer program product and computer-readable medium, and a (medical) system.

Background Art

[0002] Background Art In the context of medical imaging, motion artifacts pose a common problem. Therefore, tracking is often used to detect motion. The detected motion can be used to reduce motion artifacts. Known methods require a high degree of periodicity in the motion pattern. The movement of the subject can be tracked using a stationary tracking device.

[0003] However, more flexible medical imaging systems are currently in use. An example is the Loop X system with a gantry that can move freely on wheels and can be tilted. To add flexibility, it is necessary to consider the position of the imaging system when capturing each respective image and the movement of the subject during scanning, which is very difficult for image reconstruction, especially motion compensation.

[0004] Known systems and methods are prone to various motion artifacts in such difficult scenarios.

[0005] Therefore, an object of the present invention is to reduce motion artifacts and improve image quality.

[0006] The present invention can be used in medical imaging, particularly in relation to loop X imaging systems or navigation in medical procedures to enable periodic or aperiodic movement of the imaged subject and / or the imaging device, and / or in systems for image-guided radiation therapy, for example, together with VERO® and ExacTrac®, both products of Brainlab.

[0007] Aspects, embodiments, and exemplary processes of the present invention, and their embodiments, are disclosed below. Various exemplary features of the present invention can be combined in accordance with the present invention, provided that they are technically appropriate and feasible. Summary of the Invention Means for Solving the Problems

[0008] Brief Exemplary Description of the Invention In the following, specific features of the present invention will be briefly described, but it should not be understood that the present invention is limited only to the features or combinations of features described in this section.

[0009] The present invention provides an image reconstruction method for a medical system including a medical imaging system and a tracking device, for example, attached to the medical imaging system. The method includes calibrating a coordinate system C2 of the tracking device for marker-based tracking to a coordinate system C1 of the medical imaging system; performing a scan by the medical imaging system, the step of performing the scan including obtaining a plurality of medical images I_i (i = 1...n); obtaining, by the tracking device, for each of the plurality of medical images I_i, corresponding tracking coordinates in C2 using one or more markers; converting the medical images based on the tracking coordinates and the calibration between C1 and C2; and reconstructing a 3D image based on the images converted with respect to a reference position.

[0010] General Description of the Invention In this section, a description of the general features of the present invention is given, for example, by referring to possible embodiments of the present invention.

[0011] The present invention provides an image reconstruction method, a medical system, a computer program product, and a computer-readable medium according to the independent claims. Preferred embodiments are described in the dependent claims.

[0012] The present invention provides an image reconstruction method for a medical system comprising a medical imaging system and a tracking device firmly attached to the medical imaging system. The method includes calibrating a coordinate system C2 of the tracking device for marker-based tracking to a coordinate system C1 of the medical imaging system, performing a scan by the medical imaging system (S12), including acquiring a plurality of medical images I_i (i = 1...n), obtaining, by the tracking device, for each of the plurality of medical images I_i, corresponding tracking coordinates in C2 using one or more markers, transforming the medical images based on the tracking coordinates and the calibration between C1 and C2, and reconstructing a 3D image, for example, based on the transformed images with respect to a reference position that may be associated with a reference medical image.

[0013] Thus, movements detected in C2 based on the tracking coordinates are taken into account during 3D image reconstruction that utilizes the calibration between C1 and C2 and the reference position (and corresponding medical image) to which the movement is compensated.

[0014] The claimed method is highly reliable and efficient in reducing motion artifacts.

[0015] This method is suitable for periodic and aperiodic movements. For example, other techniques reduce motion artifacts by using the detected movement to gate the image scan (i.e., interrupt the scan when movement occurs and resume the scan when the movement stops and returns to the position where the scan was interrupted), or by binning the acquired raw images into different phases of movement (e.g., the exhalation and inhalation phases of the respiratory cycle) to obtain a plurality of reconstructed phase-specific datasets. The latter technique enables motion compensation by warping all the reconstructed datasets to one phase (e.g., by using non-rigid image registration). However, such techniques require a high degree of periodicity in the movement pattern.

[0016] The method of the present disclosure can include temporary binning of medical images acquired by a medical imaging device by assigning medical images to specific respiratory cycle phases and reconstructing a plurality of 3D images, each corresponding to a respective respiratory cycle phase, in particular using intrinsic or extrinsic binning techniques, and each respiratory cycle phase can be optionally specified within a specific time window size, resulting in effective pixel-based binning in the spatial region of the reconstructed 3D images. In one example, a tracking device can track markers, and the current respiratory phase and the 3D image corresponding to the current respiratory phase can be selected based on the correlation between the movement of the markers and the respiratory phase, in particular for use in tool tracking, and the method can include displaying an overlay of a tool model and the 3D image corresponding to the current respiratory phase. According to the present disclosure, gated navigation may be provided by performing or providing a navigation function only for a subset of respiratory cycle phases, in particular only at one of the respiratory cycle phases.

[0017] Examples related to binning and gating are shown below. An example of a method for tracking a tool such as a needle (e.g., a resection device or a biopsy needle) in a spatial and temporal domain is provided below. In this example, 4D CBCT is acquired and a plurality of CBCT datasets are reconstructed using intrinsic (e.g., using an Amsterdam shroud filter) and / or extrinsic (e.g., based on an optical tracking marker using a tracking system attached to a medical imaging device, e.g., a gantry-mounted tracking device) binning of projections, i.e., assignment of projections to specific respiratory cycle phases (e.g., inhalation phase and exhalation phase), each corresponding to a specific (and sensed) respiratory cycle phase (e.g., inhalation phase, exhalation phase). Regardless of which intrinsic or extrinsic projection binning method is used, the correlation between the movement of the markers (e.g., one or more markers attached to the patient's chest - patient reference markers) and the respiratory phase is established / derived from the acquired data, i.e., the X-ray projections and the corresponding tracked marker positions. Thereby, in a later phase, it becomes possible to derive in which respiratory phase the patient is currently in, for example, simply by observing the patient reference using a tracking device. Based on the above information (i.e., the correlation describing the relationship between the movement of the patient reference markers and the corresponding respiratory cycle, and the 4D CBCT, i.e., the plurality of 3D CBCTs), tool (e.g., needle) tracking (navigation) may be performed. Tool tracking can include that both the tool (e.g., a needle) and the patient reference are tracked in the coordinate system of the imaging system using, for example, a gantry-mounted tracking system, and based on this, a model of the tool (e.g., a CAD model) can be displayed on the upper screen of the acquired CBCT dataset (e.g., in a cross-sectional image view).

[0018] In contrast to known methods, not only is spatial information based on the perceived current patient and tool positions used for display, but further, the current respiratory cycle phase of the patient may be obtained. Based thereon, the currently overlaid CBCT image on the display can be replaced with the most appropriate CBCT image of the 4D CBCT set based on the respiratory cycle phase. That is, for example, if it is sensed that the patient is currently in the inhalation phase, a CBCT of the inhalation phase (consisting of binned projections) can be used. As another example, if it is sensed that the patient is currently at 30% after inhalation but 70% before the exhalation phase, an interpolated CBCT (and thus mixed by corresponding deformation vector interpolation between phases) can be displayed as the overlay image (this can be compared to a live "movie" during playback, the speed and current playback position of which are determined by proxy of the sensed respiratory cycle). Further, for example, in such an interpolation scenario, implicit pixel-based binning can be applied to the displayed CBCT for image noise reduction. As an example, if a 30% inhalation phase is shown, all phases within the window having the window size, for example, all phases from 20% to 40%, can be binned (i.e., averaged) into the displayed CBCT. The window size may be selectable by the user. The selection of the window size is an effective means for controlling the trade-off between visible motion artifacts and visible pixel intensity noise.

[0019] Similarly to the above, spatial and temporal navigation can be realized with respect to gated navigation. For example, gated navigation may involve that the navigation is available or executable only during a specific respiratory cycle of the patient (e.g., only the inhalation phase, which may also be referred to as the deep inspiration breath hold technique).

[0020] The medical image I_i according to the present disclosure may be a medical 2D projection image. Thus, the term "medical image" should be understood to particularly refer to a medical 2D projection image.

[0021] Here, the reference position refers to the reference position at C2, that is, the tracking position. In the present disclosure, the medical image of the reference position can be referred to as the corresponding medical image or the reference medical image.

[0022] In the present disclosure, the position C2 can also be referred to as the position at the tracking position or the tracking coordinates. Hereinafter, the terms "tracking device" and "tracking system" are used interchangeably.

[0023] As an example, the medical imaging system may be, for example, an X-ray based imaging system such as a CT (Computed Tomography) imaging system. In particular, the medical imaging system can include CBCT (Cone Beam CT).

[0024] As an example, the tracking device may be, for example, a camera in the infrared (IR) or visible spectrum configured to track markers.

[0025] The tracking device may be detachably attached to the medical imaging system. The tracking device may be attached to the medical imaging system at a fixed relative position (including orientation) with respect to a part of the medical imaging system.

[0026] The tracking device may be configured to generate the coordinates of the markers within the coordinate system C2 of the tracking device. The coordinate system C1 of the medical imaging system can have a fixed relationship with respect to C2 that can be determined, for example, during the calibration process.

[0027] Therefore, the conversion between the coordinates of C1 and the coordinates of C2 can be defined based on the calibration.

[0028] The medical imaging system can perform a scan. During the scan, the medical imaging system, the patient's bed, or the subject may change position in an unintended (careless) way, which can lead to motion artifacts.

[0029] As an example, the (residual) respiratory movement of a patient, particularly the sagging of the patient's hospital bed that may gradually occur over time, the patient's cough, and flatulence may lead to motion artifacts.

[0030] In addition, saddle trajectories and spiral scans may result in motion artifacts unless motion correction is performed.

[0031] A tracking device can be used to account for such inadvertent movements. Specifically, for each image, the tracking device can record tracking coordinates. From the perspective of the tracking device, the marker has changed its position in the coordinate system C2, that is, the tracking coordinates have changed.

[0032] The tracking coordinates represent the relative movement between the tracking device (and the medical imaging system) and the marker.

[0033] Based on calibration and tracking coordinates, specifically the detected movement, the conversion of medical images can be performed. The conversion can, for example, combine the captured medical images to reconstruct a 3D image from the converted images that take into account any (intentional and / or unintentional) movement with respect to a reference position.

[0034] It will be understood that known marker-based tracking techniques can be used. Similarly, known conversion methods and reconstruction methods may be employed.

[0035] The method can include determining a reference position, and determining the reference position can include selecting one or more images from a plurality of medical images and determining the reference position based on the corresponding tracking positions of the selected images.

[0036] In particular, determining the reference position can include selecting the initial medical image I_1 as the reference image and using the corresponding tracking position as the reference position, or selecting the last medical image I_n as the reference image and using the corresponding tracking position as the reference position.

[0037] That is, in a series of medical images, the first image may be used as a reference image, and the corresponding tracking position may be used as a reference position. This may be particularly advantageous when real-time reconstruction is desired, in which case it may be detrimental to delay until further medical images are captured. Alternatively, in a series of medical images, the last image may be the image used as the reference image, and the corresponding tracking position may be the reference position.

[0038] As another example, determining a reference position can include calculating a reference position based on a set of tracking positions corresponding to a set of medical images I_1,... I_x, using statistical methods such as specifically determining an average tracking position and using it as the reference position.

[0039] As a further example, determining a reference position can include calculating a reference position based on one or more tracking positions at a specific time or within a specific time frame.

[0040] For example, determining a reference position can include calculating a reference position based on a set of tracking positions corresponding to a specific time frame, using statistical methods such as specifically determining an average (tracking) position and using it as the reference position, for example, before medical imaging.

[0041] That is, in a series of medical images, for example, considering the position of each selected medical image, a series as a whole or a subset thereof can be selected and used to obtain a reference position, or independently of any medical image, a series of tracking positions from a specific time frame can be selected and used to obtain a reference position. For example, when vibrational motion such as breathing occurs during scanning, it may be possible to use the position where the vibration occurs as the reference position. The calculation of the average may be limited to a subset of the possible degrees of freedom, for example, only with respect to a specific translational direction.

[0042] Of course, image reconstruction can also be performed using different reference positions (e.g., at a later time). Alternatively or additionally, a 3D image reconstructed using a reference position can be transformed (e.g., rigidly) so as to obtain the 3D image from a different reference position, i.e., without requiring reconstruction at a different reference position.

[0043] The reconstruction of the 3D image may be performed in real time, and the initial imaging system coordinates are used as the reference position.

[0044] As briefly described above, in real-time applications, unacceptable delays may occur when using coordinates obtained later.

[0045] The method of the present disclosure can include storing, together with the medical image, the respective imaging system coordinates and the corresponding tracking coordinates of one or more markers.

[0046] Thereby, a 3D image can be reconstructed later for a different reference position. The method of the present disclosure can include storing, together with the reconstructed 3D image, the respective reference positions. Thus, subsequent analysis of the 3D image can be improved.

[0047] The method of the present disclosure can further include reconstructing a second 3D image from the transformed image using a second reference position different from the reference position.

[0048] This may be done simultaneously, or, particularly when the respective coordinates are stored together with the medical image, the second 3D image may be constructed later.

[0049] The method of the present disclosure can include reconstructing a 3D image with respect to a reference position determined from a marker attached to a patient near the imaged ROI such that the marker to be tracked is a valid surrogate signal for any movement occurring in the region of interest (ROI) during acquisition of a medical image (i.e., during imaging).

[0050] The method of the present disclosure can include utilizing a tracking device to track a tool used in a medical procedure in an imaging coordinate system.

[0051] That is, for example, the tool can also be tracked using a tracking device via a marker attached to the tool. The tool position can be obtained in the coordinate system of the tracking device and optionally reflected in the coordinate system of the medical imaging device based on calibration. This enables, for example, visualization of the tool in accurate spatial relationships, for example, for navigation purposes.

[0052] According to the present disclosure, the tool may be a pointer tool, and tracking of the tool may be used to visualize the pointer tool with respect to medical images acquired before and / or during a medical procedure, particularly for use in a pointer planning workflow.

[0053] The pointer tool can be tracked, and the medical imaging device can be arranged to adjust the current projection geometry with respect to the direction indicated by the pointer tool based on calibration between C1 and C2.

[0054] The method of the present disclosure can include using a shared reference marker for obtaining tracking coordinates and for tracking by a tracking camera of a surgical navigation system, and the surgical navigation system performs registering image data acquired by the surgical navigation system during a medical procedure with medical image data acquired before the medical procedure to enable navigation during the medical procedure.

[0055] Since surgical navigation systems can be used for a wide variety of applications, they are often provided separately from medical imaging systems. It is advantageous to be able to utilize the capabilities of these navigation systems along with the capabilities of a tracking device. The methods proposed herein enable doing so in a reliable and efficient manner.

[0056] According to the present disclosure, a shared fiducial marker can be selected to avoid artifacts in the reconstructed image and to provide accurate alignment of medical image data acquired prior to a medical procedure and / or image data acquired during the procedure.

[0057] The method of the present disclosure can include the surgical navigation system providing an alignment time to the medical imaging system, for example as a signal, and the medical imaging system using a position related to the alignment time as a reference position for motion compensation when reconstructing a 3D image or as a reference position for deriving a reference position from a plurality of tracked positions within an alignment time frame.

[0058] Since changes may occur after alignment and may significantly affect accuracy, reliability can be enhanced thereby.

[0059] According to the present disclosure, the medical imaging system may be a self - movable wheeled system, and the method may include using a tracking device to provide position recognition of the medical imaging system.

[0060] In particular, the medical imaging system can be configured to enable acquisition of medical images of the saddle track.

[0061] As an example, the medical imaging system may be configured to have several degrees of freedom, including one or more of C-arm tilt, gantry tilt, C-arm yaw, gantry yaw, and longitudinal translational movement of the gantry or C-arm. The trajectory of the gantry or C-arm that combines two or more of these movements of the gantry or C-arm can be called a saddle trajectory.

[0062] Even in the absence of such a trajectory, calibration is difficult, for example, due to gravity and sag that can cause deviations from the nominal trajectory. Composite movements, such as saddle trajectories, add complexity and uncertainty with respect to the actual trajectory (e.g., due to the influence from the floor on which the system moves) compared to, for example, the nominal trajectory. Thus, the projection geometry may not be known very accurately in essence.

[0063] The method according to the present disclosure enables addressing such challenges, in particular, by using tracking devices together with static markers attached, for example, to the floor or the patient's bed and / or markers attached to the patient, and enables efficient motion compensation when scanning using a trajectory such as a saddle trajectory.

[0064] Specifically, this makes it possible to accurately determine the relative motion in the same way as motion compensation without motion except for the rotation of the radiation source and the detector.

[0065] Static markers attached, for example, to the floor or the patient's bed enable very focused images especially when the subject is not moving, and when the markers are attached to the patient, very accurate determination of motion compensation and projection geometry can be achieved simultaneously.

[0066] Generally, tracking a system that can move autonomously is important for accurate image reconstruction. Since the method proposed in this specification is a high-precision method for determining the position relative to the markers, by using appropriately arranged markers, via a tracking device, a medical imaging system can obtain accurate position recognition for positions that can be easily selected by each marker arrangement, even in difficult arrangements.

[0067] According to the present disclosure, a medical imaging system can include a gantry or a C-arm that can be tilted, particularly a gantry configured such that its rotation plane can be tilted or a C-arm configured such that its rotation plane can be tilted.

[0068] An example of such an imaging system is Loop X. Generally, a medical imaging system enables rotation of a radiation source and a detector in a plane. Further, some imaging systems enable translational movement, for example, in a direction perpendicular to the plane. According to the present disclosure, the gantry or the C-arm may be configured and mounted such that the plane itself can be tilted. For example, the gantry can rotate around an axis parallel to the longitudinal axis of the patient bed. Further, the gantry can represent translational movement in a direction parallel to the longitudinal axis. The gantry may also tilt around a horizontal axis perpendicular to the longitudinal axis, for example, towards and against the direction of translational movement.

[0069] For example, the tilting rotation of the C-arm or the gantry can be a rotation around a hinge attached to a fixed or movable support structure, such as one or more legs, particularly a support structure movable on wheels, used for attaching the C-arm or the gantry.

[0070] According to the present disclosure, the medical imaging system may include a gantry or a C-arm, particularly a tiltable gantry or a tiltable C-arm as described above, and the medical imaging system may be configured such that the gantry or the C-arm is movable so as to represent a yaw rotation. For example, the yaw rotation may be achieved by a wheeled support structure to which the C-arm or the gantry is attached. In particular, the wheeled support structure may be driven by traction, for example, using the rear wheels. As an example, all the wheels may be set at 45° so as to form a circular yaw rotation.

[0071] According to the present disclosure, the tracking device may be firmly attached to a component of the medical imaging system fixed within the imaging coordinate system or a component of the imaging system movable within the imaging coordinate system.

[0072] That is, the medical imaging system may include components movable relative to each other, and the tracking device may be firmly attached to one of the components. As an example, the imaging coordinate system C1 may be selected such that the tracking device coordinate system C2 remains fixedly related. Alternatively, the relationship between the coordinate systems C1 and C2 may not have a constant fixed relationship. In that case, each relationship between the coordinate systems C1 and C2 is tracked based on, for example, the control of movement so that a 3D image can be reconstructed.

[0073] According to the present disclosure, the medical imaging system can include a radiation source and a radiation detector movable relative to each other, and the tracking device is firmly attached to the medical imaging system such that it has a fixed spatial relationship with respect to one of the radiation source and the radiation detector. The relationship between the coordinate systems C1 and C2 is a function of the current position (angle) of the source or the detector and may be calibrated in advance.

[0074] This can enable high flexibility with respect to the imaging geometry while also enabling accurate 3D image reconstruction using the tracking device.

[0075] According to the present disclosure, a medical imaging system can include a radiation source and a radiation detector having a fixed relative spatial position, and a tracking device is rigidly attached to the medical imaging system so as to have a fixed spatial relationship with respect to the radiation source and the radiation detector. The relationship between coordinate systems C1 and C2 can be a function of the current position (angle) of the source or detector and may be calibrated in advance.

[0076] This (i.e., the fixed relative relationship between the radiation source and the detector) is somewhat less flexible with respect to imaging geometry, but can reduce the calibration complexity.

[0077] According to the present disclosure, the tracking device may be configured for pose tracking and / or may comprise in particular at least one of a (near) infrared tracking system comprising one or more cameras, a video camera tracking system comprising one or more cameras, an electromagnetic tracking system. The tracking system may be, for example, a monocular or stereo tracking system.

[0078] According to the present disclosure, one or more markers can include markers attached to the patient's bed and / or markers attached to the floor and / or markers attached to one or more parts of the patient, in particular parts of the patient inside the region of interest and / or parts of the patient outside the region of interest of the medical imaging device.

[0079] Which markers to use can depend on the desired criteria for reconstruction and / or position recognition. Furthermore, as described above, it can depend on whether cooperation with a marker-based surgical navigation system is envisaged.

[0080] According to the present disclosure, one or more markers can comprise markers attached to the patient's chest and / or the patient's spine and / or the patient's skull and / or markers attached to the patient's extremities.

[0081] Since the patient may move during the procedure, the reconstruction accuracy can be improved by attaching markers to the part of the patient related to imaging, for example near or within the region of interest. That is, the perceived position of the imaging system with respect to spatially fixed markers may be different from the perceived position of the imaging system with respect to markers within the region of interest. By taking both into account, an appropriate perspective for reconstruction becomes possible, and the patient's movement can also be taken into account. This can be particularly relevant in the context of cooperation with a surgical navigation system that can be configured to function with markers attached to the patient.

[0082] According to the present disclosure, one or more markers can further comprise markers attached to a treatment device, such as a radiation treatment device, and / or markers attached to tools for use in a medical procedure.

[0083] This can make it possible to accurately track the positions of the treatment device and the tools within the coordinate systems of the tracking device and the medical imaging system.

[0084] According to the present disclosure, one or more markers may be attached at a position such as to enable at least one of taking into account the tilt of the gantry or C-arm, taking into account the sag of the gantry or C-arm, taking into account the yaw of the device, motion compensation during longitudinal scanning, taking into account the slip of the wheels of the medical imaging system on the floor, and in particular taking into account the uneven floor under the medical imaging system when the medical imaging system is a wheeled system.

[0085] Therefore, the tracking camera can be used for position control of a medical imaging device, such as a device that can move autonomously (for example, when very accurate position recognition of the device is important). The medical imaging system can perform guided motion using markers that are static or even movable markers enabling a following function, for example based on the tracking camera.

[0086] As described above, according to the present disclosure, the medical imaging system may be a wheeled system that can move autonomously, and the method according to the present disclosure may include using a tracking device to provide position recognition of the medical imaging system. In such a case, for example, the method according to the present disclosure may include the medical imaging system automatically repositioning itself to the target position, for example, the medical imaging position, after being moved from the target position. The repositioning may include, during repositioning, acquiring an image of one or more markers by the tracking device and determining the current marker position from the image, and using the previous marker position determined from an image of the marker acquired by the tracking device before or during movement from the target position, wherein the image of the marker and / or the marker position of the marker and / or the marker ID of the marker are optionally stored together with the corresponding medical image, and determining a trajectory for repositioning the medical imaging system based on the current marker position and the previous marker position.

[0087] The method of the present disclosure can include a tracking device attached to a medical imaging system obtaining an image of a marker disposed at a fixed position in a room, and using the marker position determined from the image to determine the position of the medical imaging system. Alternatively, the method can include a fixed-position tracking device attached to, for example, a wall or ceiling or floor of the room or a device in the room having a known position in the room obtaining an image of one or more markers attached to the medical imaging system by the fixed-position tracking device, and determining the position of the medical imaging system in the room based on the marker positions in the obtained image. Further alternatively, a tracking device attached to the medical imaging system and a fixed-position tracking device attached to, for example, a wall or ceiling or floor of the room or a device in the room having a known position in the room can each obtain an image of the same one or more markers disposed at a fixed position in the room, or the marker positions determined from the dynamic markers and the images can be combined with the marker positions determined using the medical imaging system and the marker positions determined using the fixed-position tracking device to obtain the position of the medical imaging system relative to the fixed-position tracking device (e.g., within the room) to determine the position of the medical imaging system. Optionally, the position of the medical imaging system can be determined relative to a room coordinate system and / or relative to a tool having a position calibrated relative to the room coordinate system.

[0088] In some cases, a medical imaging device, particularly a device that can move autonomously (e.g., Loop X), has to be moved from the imaging position (e.g., after imaging) and, for example, repeatedly returned for re-imaging (e.g., when clearing the surgical space for a clinician or surgeon). In these cases, it is advantageous to approach the position of the same imaging device as before, especially for re-imaging. This can be achieved when the medical imaging device can accurately relocate itself within the room. Since the accuracy of the basic repositioning of a medical imaging device based on an internal and intrinsic wheel-based coordinate system is affected by the state of the floor, the repositioning accuracy of the medical imaging device may not be met if the state is not good. This problem can be addressed, inter alia, as follows.

[0089] A tracking system attached to a medical imaging device (e.g., gantry-mounted) can continuously detect optical markers placed in its field of view (FOV) using, in particular, a tracking camera attached to the gantry to obtain marker data and store the marker data in the corresponding X-ray projection. The stored optical marker data of an image acquired previously (i.e., before leaving the imaging position) can be compared with the same optical tracking markers visible to the tracking system during repositioning. Subsequently, a correction trajectory for repositioning the medical imaging device can be calculated from this data, for example, by subtracting the currently sensed optical tracking marker position from the stored optical tracking marker position of the previously acquired image. This enables high-precision repositioning of the medical imaging device for re-acquiring an image and can improve the comparability between images taken at different times. To be complete, it is assumed that the optical tracking markers used for this purpose do not move between image acquisition and repositioning movement, which is usually the case for a navigated workflow. The above can also prevent additional patient dose and save time since another image acquisition is required if the basic repositioning is too far.

[0090] For example, as described in detail above, the gantry-mounted tracking system of the present disclosure enables determination of the tool position and / or the relative movement (motion compensation) of the patient in the coordinate system of the imaging device.

[0091] Since the medical imaging device (e.g., Ring X) may be a movable imaging device, it does not necessarily provide information on the movement of the tool or the patient in the outer room coordinate system (i.e., when the medical imaging device is moved). The reference markers may be provided statically in the room (i.e., at known fixed positions within the room). By using these markers as a reference, this problem can be solved.

[0092] Alternatively or additionally, the position of the imaging device within the room may be determined only by a tracking system (e.g., using an IR camera array) statically attached to the ceiling or wall or floor of the room, or by a (non)movable device (referred to as a room tracking system) arranged within the room at a known position, in combination with markers attached to, for example, a gantry of a medical imaging device, where the markers are captured by the room tracking system.

[0093] Alternatively, the position of the imaging device within the room can be determined by combining information obtained by a tracking system attached to a medical imaging device (e.g., a gantry-mounted tracking system) with one or more tracking systems statically attached to the room. In this example, instead of or in addition to static markers, dynamic markers can be placed in the room, and the dynamic markers are captured by both a tracking system attached to a medical imaging device (e.g., a gantry-mounted tracking system) and the room tracking system during imaging. These two pieces of information enable accurate localization of the medical imaging device within the room, and thereby also enable an accurate relationship with other components and devices having known positions within the room, such as a fixed particle therapy beam. The advantage of dynamic markers is that the position of this marker can be adjusted situationally as needed, thereby overcoming various problems.

[0094] By using a room tracking system (either alone or in combination with a tracking system attached to a medical imaging device), it is possible to address issues such as reliably capturing the position of a medical imaging device within a room over the entire range of movement of a generally very large device (e.g., yaw, translation).

[0095] The present invention provides a method for image reconstruction for a medical system comprising a medical imaging system and, in particular, a tracking device fixedly or movably attached to the medical imaging system. The method comprises calibrating a coordinate system C2 of the tracking device for marker-based tracking to a coordinate system C1 of the medical imaging system, performing a scan (S12) by the medical imaging system, including acquiring a plurality of medical images I_i (i = 1...n), obtaining, by the tracking device, for each of the plurality of medical images I_i, corresponding tracking coordinates in C2 using one or more markers, transforming the medical images based on the tracking coordinates and the calibration between C1 and C2, and reconstructing a 3D image, for example, based on the transformed images with respect to a reference position that may be associated with a reference medical image.

[0096] Accordingly, the above features apply to this method. As described above, the present disclosure also provides a medical system, a computer program product, and a computer-readable medium as recited in the independent claims.

[0097] In particular, the present disclosure also provides a medical system comprising a medical imaging system and a tracking device attached to the medical imaging system, in particular fixedly attached, the system being configured to perform the method according to any of the preceding claims.

[0098] In particular, the present disclosure also provides a medical system comprising a medical imaging system and a tracking device attached to the medical imaging system, in particular fixedly or movably attached, the system being configured to perform the method according to any of the preceding claims.

[0099] According to the present disclosure, a medical system can further include a medical imaging system configured to perform a scan and a tracking device configured to acquire corresponding tracking coordinates.

[0100] For example, the medical imaging system can include an X-ray based system, such as a CT scanner. In particular, the medical imaging system may be cone beam CT, CBCT. Even more particularly, the medical imaging system may be a system that can move autonomously. The medical imaging system can have a tiltable gantry or C-arm.

[0101] The tracking device may include a camera, such as a monocular or stereo camera. This can include an infrared camera and / or a camera that uses the visible spectrum or other EM spectrum.

[0102] Optionally, the medical system may further include tracking markers for use by the tracking device, and the tracking markers are attached to the patient's bed, one or more body parts of the patient, the floor, one or more tools for use in medical procedures, one or more components of a treatment device, such as one or more of a radiation treatment device or a tissue disruption device. Potential configurations of the markers are described later in the terminology section.

[0103] According to the present disclosure, a medical system can further include a navigation system for a medical procedure, the navigation system uses one or more navigation markers, and at least a subset of the navigation markers corresponds to at least a subset of the tracking markers, particularly a subset of the tracking markers attached to the patient.

[0104] Thus, as described above, a highly reliable and accurate synergistic effect of the capabilities of the navigation system and the medical imaging system can be achieved.

[0105] According to the present disclosure, the tracking device can comprise one or more cameras surrounded by a housing, in particular completely surrounded by the housing, the housing being configured to block non-marker related reflections from the image sensors of the one or more cameras, in particular reflections from an integrated light source.

[0106] The present disclosure also provides a computer program product comprising instructions which, when executed by a computer, cause the computer to control and / or execute the steps of the method according to the present disclosure, in particular any of the claims of the method.

[0107] The present disclosure also provides a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to control and / or execute the steps of the method according to the present disclosure, in particular any of the claims of the method.

[0108] The present disclosure also relates to the use of the method and / or system according to the present disclosure for medical imaging and / or the performance of navigation, positioning and / or alignment of a subject and various objects, such as pieces of equipment or tools.

[0109] For example, the present invention represents a substantial physical interference with the body that requires specialized medical expertise to implement, and does not include, particularly does not provide for, or does not encompass invasive steps that involve substantial health risks even when implemented using the required specialized care and expertise. For example, the present invention does not include the step of positioning a medical implant to fix it to an anatomical structure, or the step of fixing a medical implant to an anatomical structure, or the step of preparing an anatomical structure for fixing the medical implant thereto. More specifically, the present invention does not include, particularly does not provide for, or does not encompass any surgical or therapeutic activities. Instead, the present invention is directed to be applicable to medical imaging, navigation, positioning, and / or alignment. For this reason alone, by implementing the present invention, surgical or therapeutic activities are not required, particularly surgical or therapeutic steps are not required or implied.

[0110] The features and advantages outlined above in the context of the method are equally applicable to the medical system, computer program product, and computer-readable medium of the present disclosure.

[0111] Definitions In this section, definitions of specific terms used in the present disclosure are provided, which also form part of the present disclosure.

[0112] Computer-implemented method The method according to the present invention is, for example, a computer-implemented method. For example, all steps or only a part of the steps (i.e., less than the total number of steps) of the method according to the present invention can be executed by a computer (e.g., at least one computer). One embodiment of a computer-implemented method is the use of a computer for executing a data processing method. One embodiment of a computer-implemented method is a method regarding the operation of a computer such that the computer operates to execute one, multiple, or all steps of the method.

[0113] A computer comprises, for example, at least one processor and, for example, at least one memory for (technically) processing data, for example, electronically and / or optically. The processor is made of a substance or composition that is, for example, a semiconductor, for example, at least partially an n-type and / or p-type doped semiconductor, for example, a type II, III, IV, V, VI semiconductor material, for example, at least one of (doped) silicon and / or gallium arsenide. The described calculating or determining steps are, for example, executed by a computer. The step of determining or calculating is, for example, a step of determining data within the framework of a technical method, for example, within the framework of a program. A computer is, for example, any kind of data processing device, for example, an electronic data processing device. A computer can generally be considered as such devices, for example, a desktop PC, a notebook, a netbook, etc., but can also be any programmable device, for example, a mobile phone or an embedded processor. A computer can, for example, include a system (network) of "sub-computers", and each sub-computer represents a computer itself. The term "computer" includes cloud computers, for example, cloud servers. The term "cloud computer" includes a cloud computer system that includes, for example, a system of at least one cloud computer and, for example, a plurality of operably interconnected cloud computers such as a server farm. Such a cloud computer is preferably connected to a wide area network such as the World Wide Web (WWW), and is arranged within a so-called cloud of computers all connected to the World Wide Web. Such an infrastructure represents "cloud computing", which provides computing, software, data access, and storage services without the end user having to know the physical location and / or configuration of the computers providing the specific services. For example, the term "cloud" is used here as a metaphor for the Internet (World Wide Web).For example, the cloud provides computing infrastructure as a service (IaaS). The cloud computer can function as a virtual host for the operating system and / or data processing applications used to execute the method of the present invention. The cloud computer is, for example, the Elastic Compute Cloud (EC2) provided by Amazon Web Services (trademark). The computer is provided with an interface for receiving or outputting data, for example, and / or for performing analog-to-digital conversion. The data is, for example, data representing physical characteristics and / or data generated from technical signals. Technical signals are generated, for example, by (technical) detection devices (such as devices for detecting marker devices) and / or (technical) analysis devices (such as devices for performing (medical) imaging methods), and the technical signals are, for example, electrical signals or optical signals. The technical signals represent, for example, data received or output by the computer. The computer is preferably operatively coupled to a display device that enables the information output by the computer to be displayed to a user, for example. An example of the display device is a virtual reality device or an augmented reality device (also called virtual reality glasses or augmented reality glasses) that can be used as "Google" for navigation. A specific example of such augmented reality glasses is Google Glass (trademark of Google). The augmented reality device or virtual reality device can be used both for inputting information into the computer by user interaction and for displaying the information output by the computer. Another example of the display device is, for example, a standard computer monitor equipped with a liquid crystal display that is operatively coupled to the computer for receiving display control data from the computer in order to generate a signal for displaying image information content on the display device. A specific embodiment of such a computer monitor is a digital light box.An example of such a digital light box is Buzz (registered trademark) by Brainlab. The monitor may also be a monitor of a portable device such as a smartphone, a portable information terminal, or a digital media player, for example, a hand-held device.

[0114] The present invention also relates to a program which, when executed on a computer, causes the computer to execute one or more or all of the method steps described herein, and / or a program storage medium (in particular in a non-transitory form) in which the program is stored, and / or a computer comprising the program storage medium, and / or a signal wave (physical, for example electrical, for example technically generated) which conveys information representing a program comprising code means adapted to execute any or all of the method steps described above, for example the program described above, for example the program described herein.

[0115] Within the framework of the present invention, computer program elements can be embodied by hardware and / or software (which includes firmware, resident software, microcode, etc.). Within the framework of the present invention, a computer program element can take the form of a computer-usable, e.g., computer-readable program product embodied by a computer-usable, e.g., computer-readable data storage medium, having, for use on or in relation to an instruction execution system, computer-usable, e.g., computer-readable program instructions, "code", or "computer program". Such a system can be a computer, and the computer can be a data processing device comprising means for executing the computer program elements and / or programs according to the present invention, e.g., a digital processor (central processing unit or CPU) for executing computer program elements, and optionally, a volatile memory (e.g., random access memory or RAM) for storing data used in and / or generated by the execution of the computer program elements. Within the framework of the present invention, a computer-usable, e.g., computer-readable data storage medium can be any data storage medium capable of storing, communicating, propagating, or transporting a program for use on or in relation to an instruction execution system, apparatus, or device. A computer-usable, e.g., computer-readable data storage medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a propagation medium such as the Internet.A computer-usable or computer-readable data storage medium can, for example, electronically capture a program by optically scanning paper or other appropriate media and then can be compiled, interpreted, or otherwise processed in an appropriate manner, so it can be, for example, paper or other appropriate media on which the program is printed. The data storage medium is preferably a non-volatile data storage medium. The computer program products as well as any software and / or hardware described herein form various means for performing the functions of the present invention in exemplary embodiments. A computer and / or a data processing device can include, for example, a guidance information device including means for outputting guidance information. The guidance information can be output to the user, for example, visually by visual indication means (such as a monitor and / or a lamp), and / or acoustically by acoustic indication means (such as a speaker and / or a digital voice output device), and / or tactilely by tactile indication means (such as a vibration element or a vibration element incorporated in the device). For the purposes of this document, a computer is, for example, a technical computer comprising technical, for example tangible, components, for example mechanical and / or electronic components. Any device referred to as such herein is a technical, for example tangible, device.

[0116] Data acquisition The expression "data acquisition" encompasses, for example, scenarios where data is determined by a computer-implemented method or program (within the framework of a computer-implemented method). Determining data includes, for example, measuring a physical quantity and converting the measurement value into data, such as digital data, and / or calculating (and, for example, outputting) data by a computer, for example, within the framework of a method according to the present invention. The meaning of "data acquisition" also includes scenarios where data is received or acquired (for example, input) by a computer-implemented method or program from, for example, another program, a previous method step, or a data storage medium for further processing by a computer-implemented method or program. The generation of the acquired data may be part of the method according to the present invention, but it is not necessary. Thus, the expression "data acquisition" can also mean, for example, waiting for the reception of data and / or receiving data. The received data can be input, for example, via an interface. The expression "data acquisition" also means that a computer-implemented method or program executes steps to (actively) receive or acquire data from a data source, such as a data storage medium (for example, ROM, RAM, database, hard drive, etc.) or via an interface (for example, from another computer or network). The data respectively acquired by the disclosed method or apparatus can be obtained from a database arranged in a data storage device operable with a computer for data transfer between the database and the computer, for example, from the database to the computer. The computer acquires the data and uses it as an input for the step of determining the data. The determined data can be output again to the same or another database for later use.The database used to implement the database or the disclosed method can be arranged on a network data storage device or a network server (e.g., a cloud data storage device or a cloud server) or a local data storage device (such as a mass storage device operably connected to at least one computer that executes the disclosed method). The data can be made "ready for use" by performing an additional step before the acquisition step. According to this additional step, data is generated for acquisition. The data is detected or captured, for example, by an analyzer. Alternatively or additionally, the data is input according to an additional step, for example, via an interface. The generated data can be input, for example, into a computer. According to an additional step (preceding the acquisition step), it is also possible to provide the data by performing an additional step of storing the data on a data storage medium (such as ROM, RAM, CD, and / or hard drive), thereby preparing it for use within the framework of the method or program according to the present invention. Therefore, the "data acquisition" step can also include instructing the device to acquire and / or provide the data to be acquired. In particular, the acquisition step represents a substantial physical interference with the body that requires specialized medical expertise to implement, and does not include invasive steps that involve substantial health risks even when implemented using the required specialized care and expertise. In particular, the step of acquiring data, for example, the step of determining data, does not include surgical steps, and in particular, does not include steps of treating the human or animal body using surgery or treatment. To distinguish different data used by this method, the data is denoted (i.e., referred to) as "XY data" etc., defined in terms of the information they describe, which is then preferably called "XY information" etc.

[0117] Registration The n-dimensional image of the body is registered when the image data points of the images (such as CT, MR, etc.) stored in the navigation system are assigned to the spatial positions of the actual objects in the space, for example, each point of the body part in the operating room.

[0118] Image registration Image registration is the process of converting different data sets into one coordinate system. The data can be from multiple photos and / or different sensors, data from different times or different viewpoints. This is used in computer vision, medical imaging, as well as the compilation and analysis of images and data from satellites. Registration is necessary to enable the comparison or integration of data obtained from these different measurements.

[0119] Marker This is the function of the marker detected by a marker detection device (such as a camera or an ultrasonic receiver, or an analysis device such as a CT or MRI device) so that the spatial position of the marker (i.e., its spatial position and / or alignment) can be confirmed. The detection device is, for example, part of a navigation system. The marker can be an active marker. An active marker can emit electromagnetic radiation and / or waves that can be, for example, in the infrared, visible, and / or ultraviolet spectral ranges. However, the marker can also be passive, i.e., it can reflect electromagnetic radiation in the infrared, visible, and / or ultraviolet spectral ranges, or can block X-ray radiation. For this purpose, the marker can be provided with a surface having corresponding reflection characteristics, or can be made of metal to block X-ray radiation. It is also possible for the marker to reflect and / or emit electromagnetic radiation and / or waves in the radio frequency range or ultrasonic wavelengths. The marker preferably has a spherical and / or ellipsoidal shape and can thus be called a marker sphere, but the marker can also exhibit an angular shape, for example, a cube shape.

[0120] Marker device The marker device can be, for example, preferably a reference star or a pointer or a single marker or a plurality of (individual) markers in a predetermined spatial relationship. The marker device comprises one, two, three or more markers, and two or more such markers are in a predetermined spatial relationship. This predetermined spatial relationship is known, for example, in a navigation system and is stored, for example, in a computer of the navigation system.

[0121] In another embodiment, the marker device includes an optical pattern, for example, on a two-dimensional surface. The optical pattern can include a plurality of geometric shapes such as circles, rectangles and / or triangles. The optical pattern can be identified within an image captured by a camera, and the position of the marker device relative to the camera can be determined from the size of the pattern in the image, the orientation of the pattern in the image, and the distortion of the pattern in the image. This makes it possible to determine the relative position of up to three rotational dimensions and up to three translational dimensions from a single two-dimensional image.

[0122] The position of the marker device can be confirmed, for example, by a medical navigation system. When the marker device is attached to an object such as a bone or a medical instrument, the position of the object can be determined from the position of the marker device and the relative position between the marker device and the object. Determining this relative position is also called aligning the marker device and the object. The marker device or the object can be tracked, which means that the position of the marker device or the object is confirmed two or more times over time.

[0123] Marker holder The marker holder is understood to mean an attachment device for individual markers that serves to attach the markers to an instrument, a part of the body, and / or a holding element of a fiducial star, and can be attached in a fixed manner, advantageously in a manner that allows it to be removed. The marker holder can be, for example, rod-shaped and / or cylindrical. A fastening device for the marker device (for example, a latch mechanism, etc.) can be provided at the end of the marker holder facing the marker, and helps to arrange the marker device on the marker holder by force fitting and / or form fitting.

[0124] Pointer The pointer is a rod that has one or more, advantageously two, markers fixed thereto and can be used to measure the individual coordinates of a part of the body, for example spatial coordinates (i.e., three-dimensional coordinates). The user can guide the pointer (for example, a part of the pointer that has a defined and advantageously fixed position with respect to at least one marker attached to the pointer) to a position corresponding to the coordinates so that the position of the pointer can be determined by detecting the markers on the pointer using a surgical navigation system. The relative position between the marker of the pointer and the part of the pointer used to measure the coordinates (for example, the tip of the pointer) is, for example, known. The surgical navigation system then enables the assignment of the position (of the three-dimensional coordinates) to a predetermined body structure, and the assignment can be performed automatically or by user intervention.

[0125] Fiducial star A "reference star" refers to a device having a number of markers, preferably three markers, attached thereto, the markers being (e.g., removably) attached to the reference star such that they are stationary and thus provide a known (preferably fixed) position of the markers relative to each other. The position of the markers relative to each other can be different for each reference star used within the framework of a surgical navigation method in order to enable the surgical navigation system to identify the corresponding reference star based on the position of the markers relative to each other. Thus, it is also possible to identify and / or distinguish the object (e.g., instrument and / or part of the body) to which the reference star is attached accordingly. In a surgical navigation method, the reference star serves to attach a plurality of markers to an object (e.g., bone or medical instrument) in order to be able to detect the position (i.e., its spatial position and / or alignment) of the object. Such a reference star is characterized, for example, by the way it is attached to the object (e.g., clamp and / or thread), and / or by a holding element that ensures the distance between the marker and the object (e.g., to assist the visibility of the marker for a marker detection device), and / or by a marker holder that is mechanically connected to the holding element and to which the marker can be attached.

[0126] Navigation system The present disclosure can be applied in the context of a navigation system for computer-assisted surgery. This navigation system preferably comprises the aforementioned computer for processing data provided according to any one of the computer-implemented methods described in the embodiments described herein. The navigation system preferably comprises a detection device for detecting the positions of detection points representing a main point and an auxiliary point, so that the computer can determine absolute main point data and absolute auxiliary point data based on the received detection signals, generate the detection signals, and supply the generated detection signals to the computer. The detection points are points on the surface of an anatomical structure detected, for example, by a pointer. In this way, absolute point data can be provided to the computer. The navigation system also preferably comprises a user interface for receiving calculation results (for example, the position of the main plane, the position of the auxiliary plane, and / or the position of the standard plane) from the computer. The user interface provides the received data to the user as information. Examples of the user interface include a display device such as a monitor and a speaker. The user interface can use any type of indication signal (for example, a visual signal, an audio signal, and / or a vibration signal). An example of the display device is an augmented reality device (also called augmented reality glasses) that can be used as a so-called "goggles" for navigation. A specific example of such augmented reality glasses is Google Glass (a trademark of Google). The augmented reality device can be used both for inputting information to the computer of the navigation system by user interaction and for displaying the information output by the computer.

[0127] The present invention also relates to a navigation system for computer-assisted surgery, the system comprising a computer for processing absolute point data and relative point data, and a detection device for detecting the positions of a main point and an auxiliary point to generate absolute point data and supply the absolute point data to the computer. A data interface for receiving relative point data and supplying the relative point data to a computer, A user interface for receiving data from a computer in order to provide information to a user, the received data being generated by the computer based on the result of processing executed by the computer, the user interface.

[0128] Surgical navigation system Navigation systems such as surgical navigation systems include at least one marker device, a transmitter that emits electromagnetic waves and / or radiation and / or ultrasonic waves, a receiver that receives electromagnetic waves and / or radiation and / or ultrasonic waves, and an electronic data processing device connected to the receiver and / or transmitter. The data processing device (e.g., a computer) includes, for example, a processor (CPU), a working memory, and advantageously, an indicating device for issuing an instruction signal (e.g., a visual display device such as a monitor, and / or an acoustic display device such as a speaker, and / or a tactile display device such as a vibrator), and a permanent data memory. The data processing device processes the navigation data transferred by the receiver and can advantageously output guiding information to the user via the indicating device. It is understood to mean a system that can include the data processing device. The navigation data can be stored in the permanent data memory and can be compared, for example, with data pre-stored in the memory.

[0129] Landmark A landmark is a defined element of an anatomical body part that is always the same or is repeated with a high degree of similarity in the same anatomical body parts of multiple patients. Typical landmarks are, for example, the epicondyle of the femur or the tip of the transverse process and / or spinous process of the vertebra. A point (main point or auxiliary point) can represent such a landmark. A landmark on the characteristic anatomical structure (e.g., on its surface) of the body part can also represent the said structure. A landmark can represent the anatomical structure as a whole or only a point or a part thereof. A landmark can also be present, for example, on an anatomical structure that is a prominent structure. An example of such an anatomical structure is the posterior surface of the iliac crest. Another example of a landmark is a landmark defined by the edge of the acetabulum, for example by the center of said edge. In another example, a landmark represents the bottom or deepest point of the acetabulum derived from a number of detection points. Thus, one landmark can represent, for example, a number of detection points. As described above, a landmark can represent anatomical characteristics defined based on the characteristic structure of the body part. Furthermore, a landmark can also represent anatomical characteristics defined by the relative movement of two body parts, such as the center of rotation of the femur when it moves relative to the acetabulum.

[0130] Imaging geometry Information regarding the imaging geometry preferably includes information that enables an analysis image (X-ray image) to be calculated taking into account the known relative position between the imaging geometry analysis apparatus and the analysis object (anatomical body part) analyzed by X-ray radiation, where "known" means that the spatial geometry (size and shape) of the analysis object is known. This means, for example, that three-dimensional "spatially resolved" information regarding the interaction between the analysis object (anatomical body part) and the analysis radiation (X-ray radiation) is known, and "interaction" means, for example, that the analysis radiation is blocked or passes through the analysis object partially or completely. The position and especially the orientation of the imaging geometry are defined, for example, by the position of the X-ray apparatus, for example by the position of the X-ray source and the X-ray detector, and / or by the position of a multiplicity (manifold) of X-ray beams that pass through the analysis object and are detected by the X-ray detector. The imaging geometry represents, for example, a multiplicity (manifold) of positions (i.e., positions, especially orientations) and shapes (e.g., a conical shape with a specific tilt angle). The position can be represented, for example, by the position of the X-ray beam passing through the center of the multiplicity or by the position of a geometric object (such as a frustum of a cone) representing the multiplicity of X-ray beams. The information regarding the above-mentioned interaction is preferably three-dimensional and is known, for example, from three-dimensional CT, and describes the interaction in a spatially resolved manner for points and / or regions of the analysis object, for example for all points and / or regions of the analysis object. Knowledge of the imaging geometry enables, for example, the position of the radiation source (e.g., the X-ray source) to be calculated relative to the image plane (e.g., the plane of the X-ray detector). Regarding the connection between the three-dimensional analysis object defined by the imaging geometry and the two-dimensional analysis image, reference is made, for example, to the following publications.

[0131] 1. "An Efficient Accurate Camera Calibration Technique for 3D Machine Vision", Roger Y. Tsai, Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition. Miami Beach, Florida, 1986, pp. 364 - 374 2. "A Vesatile Camera Calibraion Technique For High-Accuracy 3D Machine Vision Metrology Using Off-the-Shelf TV Cameras and Lenses", Roger Y. Tsai, IEEE Journal of Robotics and Automation, Volume RA - 3, No. 4, August 1987, pp. 323 - 344.

[0132] 3. "Fluoroscopic X-ray Image Processing and Registration for Computer-Aided Orthopedic Surgery", Ziv Yaniv 4. European Patent Specification No. 08156293.6 5. United States Patent Specification No. 61 / 054,187 Shape representation Shape representations represent characteristic aspects of the shape of an anatomical structure. Examples of shape representations include lines, planes, geometric figures, etc. Geometric figures can be, for example, one-dimensional such as an axis or an arc, two-dimensional such as polygons and circles, or three-dimensional such as a cuboid, a cylinder, and a sphere. The relative positions between shape representations can be described in a reference system, for example, by coordinates or vectors, or can be described by geometric variables such as length, angle, area, volume, and ratio. Characteristic aspects represented by shape representations are, for example, symmetry characteristics represented by a plane of symmetry. Another example of a characteristic aspect is the elongation direction of an anatomical structure represented by, for example, a longitudinal axis. Another example of a characteristic aspect is the cross-sectional shape of an anatomical structure represented by, for example, an ellipse. Another example of a characteristic aspect is the surface shape of a part of an anatomical structure represented by, for example, a plane or a hemisphere. For example, a characteristic aspect constitutes an abstraction of an actual shape or an abstraction of characteristics of an actual shape (e.g., its symmetry or longitudinal elongation). For example, a representative shape represents this abstraction.

[0133] Reference When determining a position means notifying the navigation system of the position within the reference system of the navigation system, it is called referring.

[0134] Atlas / Atlas segmentation Preferably, atlas data is obtained that describes (e.g., defines, and more specifically, represents, and / or is) the general three-dimensional shape of an anatomical body part. Thus, the atlas data represents an atlas of the anatomical body part. An atlas typically consists of a plurality of general models of an object, and the general models of the object together form a complex structure. For example, an atlas comprises a statistical model of a patient's body (e.g., a part of the body) generated from anatomical information collected from a plurality of human bodies, such as medical image data including images of such human bodies. Thus, in principle, the atlas data represents the result of a statistical analysis of such medical image data for a plurality of human bodies. This result can be output as an image, and thus the atlas data either includes or is comparable to the medical image data. Such a comparison can be performed, for example, by applying an image fusion algorithm that performs image fusion between the atlas data and the medical image data. The result of the comparison can be used as a measure of similarity between the atlas data and the medical image data. The atlas data can be aligned, for example, with image information (e.g., position image information) included in the medical image data (e.g., by applying an elastic or rigid image fusion algorithm) in order to determine, for example, by comparing the atlas data with the medical image data, the position of the anatomical structure in the medical image data corresponding to the anatomical structure defined by the atlas data.

[0135] The human body whose anatomical structure functions as an input for generating atlas data advantageously shares common features such as at least one of gender, age, ethnicity, body measurements (e.g., size and / or mass), and pathological conditions. The anatomical information describes, for example, the anatomical structure of the human body and is extracted from, for example, medical image information regarding the human body. For example, a femur atlas can comprise a head, a neck, a body, a greater trochanter, a lesser trochanter, and a lower limb as objects that together constitute a complete structure. For example, a brain atlas can include a telencephalon, a cerebellum, a diencephalon, a pons, a midbrain, and a medulla oblongata as objects that together constitute a complex structure. One use of such an atlas is the segmentation of medical images, where the atlas is matched with medical image data, and the image data is compared with the matched atlas to assign points (pixels or voxels) of the image data to the objects of the matched atlas, thereby segmenting the image data into objects.

[0136] Analytical device The movement of the treatment body part is caused, for example, by movements hereinafter referred to as "biological movements". In this regard, reference is also made to European Patent Application Publication No. 2189943 and European Patent Application Publication No. 2189940, which are respectively published as US Patent Application Publication No. 2010 / 0125195 and US Patent Application Publication No. 2010 / 0160836, which discuss these biological movements in detail. To determine the position of the treatment body part, an analysis device such as an X-ray device, a CT device or an MRT device is used to generate an analysis image of the body (such as an X-ray image or an MRT image). For example, the analysis device is configured to perform a medical imaging method. The analysis device is, for example, a device for analyzing a patient's body by using a medical imaging method, for example, by using waves and / or radiation and / or energy beams, for example, electromagnetic waves and / or radiation, ultrasonic waves and / or particle beams. The analysis device is, for example, a device for generating an image (for example, a two-dimensional or three-dimensional image) of a patient's body (and for example, the internal structure and / or anatomical parts of a patient's body) by analyzing the body. The analysis device is used, for example, in medical diagnosis, for example, in radiology. However, it may be difficult to identify the treatment body part in the analysis image. For example, it may be easier to identify an indicator body part that correlates with the position and for example, changes in the movement of the treatment body part. Therefore, by tracking the indicator body part, the movement of the treatment body part can be tracked based on a known correlation between the change in the position (for example, movement) of the indicator body part and the change in the position (for example, movement) of the treatment body part. Instead of or in addition to tracking the indicator body part, a marker device (which can be used as an indicator and is therefore referred to as a "marker indicator") can be tracked using a marker detection device. The position of the marker indicator has, for example, a known (predetermined) correlation with the position of an indicator structure (for example, the chest wall, for example, the true or false ribs, or the diaphragm or intestinal wall) that changes their positions due to biological movements.

[0137] Treatment beam Furthermore, the present invention can also be used in the field of controlling therapeutic beams. The therapeutic beam treats a body part to be treated, hereinafter referred to as the "treatment body part". These body parts are, for example, parts of a patient's body, i.e., anatomical body parts.

[0138] The present invention relates to the field of medicine and, for example, to the use of beams such as radiation beams for treating a part of a patient's body, also referred to as a therapeutic beam. The therapeutic beam treats a body part to be treated, hereinafter referred to as the "treatment body part". These body parts are, for example, parts of a patient's body, i.e., anatomical body parts. Ionizing radiation is used, for example, for therapeutic purposes. For example, the therapeutic beam contains or consists of ionizing radiation. Ionizing radiation includes or consists of particles (e.g., subatomic particles or ions) or electromagnetic waves having sufficient energy to separate electrons from atoms or molecules and ionize them. Examples of such ionizing radiation include X-rays emitted from radioactive elements, high-energy particles (high-energy particle beams) and / or ionizing radiation. Therapeutic radiation, such as a therapeutic beam, is used, for example, in radiotherapy or radiation therapy, such as in the field of oncology. In particular, for treating cancer, body parts containing pathological structures or tissues such as tumors are treated using ionizing radiation. A tumor is an example of a treatment body part.

[0139] The therapeutic beam is preferably controlled to pass through the treatment body part. However, the therapeutic beam can potentially have an adverse effect on body parts outside the treatment body part. These body parts are referred to herein as "outer body parts". Generally, the therapeutic beam has to pass through the outer body parts in order to reach the treatment body part and pass through the treatment body part as such.

[0140] Regarding this, please also refer to the following web pages, http: / / www.elekta.com / healthcare_us_elekta_vmat.php and http: / / www.varian.com / us / oncology / treatments / treatment_techniques / rapidarc.

[0141] Treatment beam arrangement The treatment body part can be treated by one or more treatment beams emitted one or more times from one or more directions. Thus, the treatment by at least one treatment beam follows a specific spatial and temporal pattern. Therefore, the term "beam arrangement" is used to cover the spatial and temporal characteristics of the treatment by at least one treatment beam. The beam arrangement is the arrangement of at least one treatment beam.

[0142] "Beam position" describes the position of the treatment beam of the beam arrangement. The arrangement of beam positions is called position arrangement. The beam position is preferably defined by the beam direction and additional information that enables, for example, the assignment of a specific position in three-dimensional space to the treatment beam, such as information regarding its coordinates in a defined coordinate system. The specific position is a point, preferably a point on a line. This line is called the "beam line" and extends in the beam direction, for example, along the central axis of the treatment beam. The defined coordinate system is preferably defined with respect to the treatment device or at least a part of the patient's body. The position arrangement includes, for example, consists of at least one beam position, such as a discrete set of beam positions (e.g., two or more different beam positions), or a continuous multiplicity (manifold) of beam positions.

[0143] For example, one or more treatment beams adopt treatment beam positions defined by the positioning, either simultaneously or sequentially during treatment (e.g., sequentially if there is only one beam source for emitting the treatment beam). If there are several beam sources, it is also possible that at least a subset of the beam positions are adopted simultaneously by the treatment beams during treatment. For example, one or more subsets of the treatment beams can adopt the beam positions of the positioning according to a predetermined sequence. A subset of the treatment beams comprises one or more treatment beams. A complete set of treatment beams comprising one or more treatment beams that adopt all beam positions defined by the positioning is a beam arrangement.

[0144] Imaging method In the medical field, imaging methods (also referred to as imaging modalities and / or medical imaging modalities) are used to generate image data (e.g., two-dimensional or three-dimensional image data) of anatomical structures of the human body (e.g., soft tissues, bones, organs, etc.). The term "medical imaging method" is understood to mean, for example, (advantageously device-based) imaging methods such as computed tomography (CT), cone beam computed tomography (CBCT, e.g., volumetric CBCT), X-ray tomography, magnetic resonance tomography (MRT or MRI), conventional X-ray examinations, acoustic examinations and / or ultrasonic examinations, as well as positron emission tomography. For example, the medical imaging method is performed by an analysis device. Examples of medical imaging modalities applied by the medical imaging method are, as mentioned by Wikipedia, X-rays, magnetic resonance imaging, medical ultrasound or sonography, endoscopy, elastography, tactile imaging, thermography, medical photography, and nuclear medicine functional imaging techniques such as positron emission tomography (PET) and single photon emission computed tomography.

[0145] The image data thus generated is also called "medical imaging data". The analysis device is used, for example, to generate image data in a device-based imaging method. The imaging method is used for medical diagnosis, for example, to analyze the anatomical body to generate an image described by the image data. The imaging method is also used, for example, to detect pathological changes in the human body. However, some of the changes in anatomical structures, such as pathological changes in structures (tissues), may not be detectable and may not be visible, for example, in the images generated by the imaging method. A tumor represents an example of a change in an anatomical structure. When a tumor grows, it can be said to represent an expanded anatomical structure. This expanded anatomical structure may not be detectable, and for example, only a part of the expanded anatomical structure may be detectable. Primary / high-grade brain tumors are usually visible on an MRI scan, for example, when a contrast agent is used to infiltrate the tumor. The MRI scan represents an example of an imaging method. In the case of an MRI scan of such a brain tumor, the signal enhancement in the MRI image (due to the contrast agent infiltrating the tumor) is considered to represent a solid tumor mass. Thus, the tumor is detectable and, for example, distinguishable in the images generated by the imaging method. In addition to these tumors called "expanded" tumors, about 10% of brain tumors are not distinguishable on a scan and are considered not visible, for example, to a user looking at the images generated by the imaging method.

[0146] Mapping Mapping describes the transformation (e.g., a linear transformation) of elements (e.g., pixels or voxels) of a first dataset in a first coordinate system, e.g., the position of the elements, to elements (e.g., pixels or voxels) of a second dataset in a second coordinate system (which may have a different basis than the basis of the first coordinate system), e.g., the position of the elements. In one embodiment, the mapping is determined by comparing (e.g., matching) the color values (e.g., gray values) of the respective elements by an elastic or rigid fusion algorithm. The mapping is embodied, for example, by a transformation matrix (such as a matrix defining an affine transformation).

[0147] Elastic fusion, image fusion / morphing, rigidity Image fusion can be either elastic image fusion or rigid image fusion. In the case of rigid body image fusion, the relative positions between the pixels of a 2D image and / or the voxels of a 3D image are fixed, and in the case of elastic image fusion, the relative positions can vary.

[0148] In this application, the term "image morphing" is also used as an alternative to the term "elastic image fusion" and has the same meaning.

[0149] Elastic fusion transformation (e.g., elastic image fusion transformation) is designed to enable seamless transition from one dataset (e.g., a first dataset such as a first image) to another dataset (e.g., a second dataset such as a second image). The transformation is designed such that, for example, one of the first and second datasets (images) is deformed so that corresponding structures (e.g., corresponding image elements) are placed at the same position as the other of the first and second images. The transformed (converted) image transformed from one of the first and second images is, for example, as similar as possible to the other of the first and second images. Preferably, a (numerical) optimization algorithm is applied to find the transformation that yields the optimal similarity. The similarity is preferably measured by a measure of similarity (also hereinafter referred to as "similarity measure"). The parameters of the optimization algorithm are, for example, vectors of the deformation field. These vectors are determined by the optimization algorithm to yield the optimal similarity. Thus, the optimal similarity represents a condition, e.g., a constraint, for the optimization algorithm. The basis of the vector is, for example, at the voxel position of one of the first and second images to be transformed, and the tip of the vector is at the corresponding voxel position in the transformed image. A plurality of these vectors are preferably provided, for example, exceeding 20 or a hundred or a thousand or ten thousand, etc. Preferably, there are (other) constraints on the transformation (deformation), for example, to avoid pathological deformations (e.g., all voxels are shifted to the same position by the transformation). These constraints include, for example, the constraint that the transformation is regular, meaning that the Jacobian determinant calculated from the matrix of the deformation field (e.g., vector field) is greater than zero, and the constraint that the transformed (deformed) image does not self-intersect, and the constraint that the transformed (deformed) image does not contain defects and / or breaks, for example. The constraints include, for example, the constraint that the grid cannot be folded to any of its positions when the regular grid is transformed in a corresponding manner with the image. The optimization problem is solved, for example, iteratively by an optimization algorithm that is a first-order optimization algorithm, such as a gradient descent algorithm, for example.Other examples of optimization algorithms include optimization algorithms that do not use derivatives, such as the downhill simplex algorithm, or algorithms that use higher-order derivatives, such as Newton-like algorithms. The optimization algorithm preferably performs local optimization. If there are multiple local optima, global algorithms such as simulated annealing or general-purpose algorithms can be used. In the case of a linear optimization problem, for example, the simplex method can be used.

[0150] In the process of the optimization algorithm, the voxel is shifted in size, for example, in a direction such that the similarity increases. This size is preferably less than a predetermined limit, for example, less than 1 / 10 of the diameter of the image or 1 / 100 or 1 / 1000, for example, less than the distance between adjacent voxels. For example, due to a large number of (iterative) processes, large deformations can be implemented.

[0151] The determined elastic fusion transformation can be used, for example, to determine the similarity (or similarity measure, see above) between the first and second data sets (first and second images). For this purpose, the deviation between the elastic fusion transformation and the identity transformation is determined. The degree of deviation can be calculated, for example, by determining the difference between the determinant of the elastic fusion transformation and the identity transformation. The greater the deviation, the lower the similarity, and thus the degree of deviation can be used to determine a measure of similarity.

[0152] The measure of similarity can be determined, for example, based on the determined correlation between the first data set and the second data set.

[0153] Fixed (relative) position As used herein, a fixed position, also referred to as a fixed relative position, means that two objects at the fixed position have a relative position that does not change unless a change is explicitly and intentionally initiated. A fixed position is particularly given when a force or torque exceeding a predetermined threshold must be applied to change the position. This threshold can be 10 N or 10 Nm. In particular, the position of the sensor device remains fixed relative to the target while the target is being aligned or while two targets are moving relative to each other. A fixed position can be achieved, for example, by firmly attaching one object to another object. The spatial position, which is part of the position, can be described particularly only by the distance (between two objects) or only by the direction of the vector (linking two objects). The alignment, which is another part of the position, can be described particularly only by the angle of the relative orientation (between two objects).

[0154] Medical workflow A medical workflow includes a plurality of workflow steps that are executed during a medical treatment and / or a medical diagnosis. The workflow steps are not necessarily executed in a predetermined order. Each workflow step means, for example, a specific task and may be a single action or a set of actions. Examples of workflow steps are the capture of a medical image, the positioning of a patient, the attachment of a marker, the execution of an excision, the movement of a joint, the placement of an implant, etc.

[0155] Brief description of the drawings In the following, the background will be explained and the present invention will be described with reference to the accompanying drawings that represent specific embodiments of the present invention. However, the scope of the present invention is not limited to the specific features disclosed in the context of the figures.

Brief description of the drawings

[0156]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying out the Invention

[0157] Description of Embodiments FIG. 1 shows the basic steps of an image reconstruction method for a medical system comprising a medical imaging system according to the present disclosure and a tracking device attached to, in particular firmly attached to, the medical imaging system. Alternatively, the tracking device may not be attached to the medical imaging system.

[0158] Step S11 includes calibrating the coordinate system C2 of the tracking device for marker-based tracking to the coordinate system C1 of the medical imaging system.

[0159] Subsequent step S12 includes performing a scan by the medical imaging system, and performing the scan includes acquiring a plurality of medical images I_i (i = 1...n).

[0160] Step S13 includes, for each of the plurality of medical images I_i, obtaining corresponding tracking coordinates within C2 using one or more markers by the tracking device.

[0161] The method can optionally include (S13a) storing, together with the medical images, the respective imaging system coordinates and the corresponding tracking coordinates of one or more markers.

[0162] The method can include determining a reference position in an optional step S10. The reference position can be determined, for example, by selecting a medical image, for example the first medical image I_1, and using the corresponding tracking position as the reference position. Alternatively, the reference position may be determined by selecting a part or all of the medical image, determining the corresponding average tracking position, and using the average tracking position as the reference position.

[0163] Alternatively, the reference position may be based on a tracked position at a given time or a time frame that tracks the position independent of medical image acquisition.

[0164] Step S14 includes converting a medical image based on the tracking coordinates and the calibration between C1 and C2.

[0165] Step S15 includes reconstructing a 3D image based on the converted image with respect to a reference position. The reconstruction may be performed first in step S15a, for example, in real time, for example, using the first image I_1 as a reference image. Alternatively or additionally, the reconstruction may be performed at a later time in step S15b for optionally different reference positions.

[0166] The method may optionally include, in step S16, storing each reference position together with the reconstructed 3D image.

[0167] The method may also optionally include step S17 of tracking a tool, such as a pointer tool, by a tracking device, for example, for visualization and / or selection of a reference position.

[0168] Optional step S18 may involve the surgical navigation system performing marker-based tracking simultaneously with a tracking system attached to a medical imaging device that performs the tracking.

[0169] In this example, the method may include step S18a of using a shared reference marker that is also used by a tracking device attached to the medical imaging system by the surgical navigation system, and step S18b of performing alignment of the image data acquired during the medical procedure and the pre-procedure image data.

[0170] In an optional step S19, a pointer plan may be executed. That is, the medical imaging device may be positioned / aligned based on a pointer tracked by a tracking device, and then optionally, a planar X-ray image may be acquired (step S19a), or CBCT imaging may be performed from said direction / at said position (step S19b). Step 19b may involve returning to step S11. Figure 2 shows in detail an example of transformation and 3D reconstruction. This can be used in the manner described in the context of Figure 1.

[0171] In step S21, the coordinate system C1 of the imaging system is defined. For example, it may be defined with respect to the imaging geometry.

[0172] In step S22, the coordinate system C2 of a rigidly attached tracking device / system is defined. For example, the coordinate system may be defined with respect to the line-of-sight direction of the tracking camera of the tracking device.

[0173] The order and timing of these steps can be freely selected. In step S23, the coordinate systems C1 and C2 may be calibrated. This may involve determining a transformation that converts a position in one coordinate system to a position in the other coordinate system. Specifically, since tracking coordinates are obtained in C2, a transformation for representing the position or movement (described by the tracking coordinates) in C1 may be determined.

[0174] In step S24, medical imaging data having spatial information in the coordinate system C1 is acquired. At the same time, in step S25, the tracking device tracks the position of the marker in the coordinate system C2 and determines the relative movement. The synchronization mechanism between the tracking device and the imaging device ensures that the tracked position of the marker is clearly associated with the correct medical (projection) imaging data frame. If it is impossible to associate the tracked position of the marker with one medical (projection) image data frame, the tracked position of the marker in the previous frame shall be used.

[0175] In step S26, the medical (projection) imaging data, together with the relevant positions of the markers (converted to C1 by the calibration established in S21), is used for 3D image reconstruction.

[0176] For each medical (projection) image, its spatial information (S24) is corrected by converting its projection geometry before 3D reconstruction. The conversion is determined by subtracting the reference position of the marker from the perceived tracking position of the marker in the medical (projection) image.

[0177] Alternatively, for each medical (projection) image, its original spatial information (S24) is used for 3D reconstruction. However, in this case, the position (including orientation) of the 3D reconstruction is corrected by the inverse transformation of the above-mentioned conversion before each reconstruction step.

[0178] Finally, S26 results in a motion-compensated 3D reconstruction with the tracked marker positions of the underlying medical (projection) images incorporated.

[0179] FIG. 3 discloses a medical system 1 according to the present disclosure. The medical system can be configured to execute the method of the present disclosure, particularly as outlined in the context of FIGS. 1 and 2.

[0180] The medical system comprises a medical imaging system 2, for example a CT imaging system. As an example, a loop X imaging system can be used. An exemplary radiation source 2a and an exemplary detector 2b arranged on a gantry 2c are shown. The gantry may have a loop shape. The medical system further comprises a tracking device 3, in this example an infrared tracking camera. The tracking device is attached to the medical imaging system 3 in an optionally removable manner, particularly firmly attached. Alternatively, the tracking device may not be attached to the medical imaging system.

[0181] The figure also shows that the medical system may optionally include a surgical navigation system 4. Markers 5a - 5e are also shown as being respectively placed on the floor, attached to the patient bed 6, attached to a part of the patient 7 within the region of interest 8, or attached to a part of the patient outside the region of interest, or attached to the medical tool 9. It should be understood that any one of the markers 5a - 5e, and any combination of at least some of them, can be used.

[0182] The tracking device of the surgical navigation system is labeled 4a. The medical imaging system is shown as a wheeled system and as a system having a gantry 2c that can be tilted, in particular a gantry having a tiltable plane of rotation (seen from the side in this figure) indicated by the dashed line 10.

[0183] The tracking device 3 and the medical imaging system 2 can communicate via a data connection 11a. The surgical navigation system and the medical imaging system can communicate via a data connection 11b. Each data connection can be wired or wireless.

[0184] The floor is shown as having some unevenness. This is only for explaining the problems related to the position tracking of the medical imaging device. Other problems can arise from the slipping of the wheels on a potentially wet floor. These problems can be overcome by the methods and systems of the present disclosure.

[0185] In the following, more examples and advantages are described to explain the methods and systems of the present disclosure.

[0186] According to the present disclosure, there are provided an imaging system such as a CT system having a coordinate system (C1), and a tracking device such as a tracking camera firmly attached to the imaging system (C2), in particular, its components that are fixed components with respect to C1 or movable components with respect to C1. For example, the tracking device may include a camera such as an optical stereo camera, a monocular camera, an EM tracking device, or an infrared camera. The tracking device can be attached, for example, to a gantry or a C-arm to which the radiation source and / or detector of the imaging system are attached.

[0187] In particular, the tracking device may be attached to the imaging system such that the relationship between C1 and C2 is clearly defined. Even more specifically, the tracking device may be attached such that the tracking camera tilts together with the gantry or the C-arm such that the relationship between C1 and C2 remains constant when the gantry or the C-arm tilts.

[0188] As an example, C2 is optionally calibrated to C1 via the inherent calibration of another coordinate system such as C3, for example, a detector or a light source with respect to C1.

[0189] Therefore, the optical coordinate system C2 and the radiation coordinate system C1 are mutually calibrated, in particular, for example, using static mutual calibration.

[0190] The markers used by the tracking device may be arranged statically (e.g., on the patient's bed or on the floor) or on the patient, in particular, near a moving body part or removed from a moving body part. The markers can be arranged on the patient inside or outside the ROI of the imaging device.

[0191] To address the problem that accurate internal calibration of the imaging device is difficult or impossible for some orbit types or device axes, static attachment of markers can be used. For example, problems arise when considering the tilt of the gantry (e.g., due to sagging caused by residual variable gravity), the yaw of the device, or the longitudinal / lateral scan and movement (due to wheel slip and unpredictable floor surface). Therefore, the imaging device can be tracked during scanning to improve the image quality by more accurate "encoding" of each device axis.

[0192] Optionally, the marker is placed on a tool such as a radiotherapy treatment device or a treatment device.

[0193] According to the present disclosure, (medical) images (I_i) can be acquired and stored together with the imaging system coordinates.

[0194] The tracking coordinates of the (patient or static) marker are acquired and stored in I_1. The tracking coordinates of the (patient or stationary) marker are acquired and stored in I_2, and so on.

[0195] As the reference position image I_ref, image I_1 or another I_n (which may be virtual or may be derived by statistical means such as the average of a set of images I_x) is selected.

[0196] All images I_i are transformed, for example, using the transformation of trackingCoordinates(I_i) - trackingCoordinates(I_ref), and I_i_transf is obtained.

[0197] As described above, or for each medical (projection) image, its original spatial information can be used for 3D reconstruction. However, in this case, the position (including orientation) of the 3D reconstruction is corrected by the inverse transformation of the above transformation before each reconstruction step.

[0198] A 3D image can be reconstructed based on the transformed image I_i_transf. The reconstructed 3D image may be stored with respect to the selected / computed reference position.

[0199] As an example, live reconstruction can be performed based on I_1 as I_ref. Optionally, the reference position, e.g., the average position, first, last, can be changed later based on the tracking of patient markers and the similarity between the current position and the imaging position.

[0200] As described above, a combination with a surgical navigation system is conceivable. The surgical navigation system can have its own tracking camera and can perform an independent alignment of the pre-treatment image dataset.

[0201] Without tracking of the imaging system with respect to the patient, the intra-treatment image data may be blurred and / or misaligned with the pre-treatment data. Thus, tracking of the imaging system with respect to the patient having the same (shared) reference marker (or a marker firmly attached to the reference) provides intra-treatment image data that is correctly aligned with and / or not blurred with respect to the pre-treatment data. "Blurred" in this context can generally refer to a reconstructed image showing image artifacts. Thus, this is not ideal for navigation purposes and potentially introduces uncertainty and as a result inaccuracy into the navigation process.

[0202] The alignment time point may be provided as a signal from the surgical navigation system to the imaging system, such that the imaging system can store and use this to determine the corresponding tracking position as a reference position for motion correction, i.e., for the transformation of medical images and the execution of 3D image reconstruction.

[0203] Optionally, a tracking device attached to a medical imaging system on a gantry, for example, can replace or complement an external navigation system.

[0204] The tracking device can be used to track tools within the imaging coordinate system C1. Markers attached to the tools can be used for that purpose.

[0205] This can be used for live visualization of the pointer tool on an image acquired during or before the operation. Similarly, a "pointer planning" workflow is also possible. As an example, a medical imaging system can adjust the projection geometry based on the tracked pointer tool.

[0206] As another example, a treatment device such as a LINAC can have markers attached to it, and the patient motion correction markers can function as a reference for an alternative navigation system.

[0207] The tracking device may also be used for position control of the imaging system independent of imaging, for example, when very accurate position recognition of the imaging system is important.

[0208] Although the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description should be considered illustrative and not restrictive. The present invention is not limited to the disclosed embodiments. It will be apparent to those skilled in the art that various modifications can be made within the scope of the present invention as defined by the claims, considering the foregoing description and the drawings.

Claims

1. An image reconstruction method for a medical system comprising a medical imaging system and a tracking device firmly attached to the medical imaging system, calibrating a coordinate system C2 of the tracking device for marker-based tracking to a coordinate system C1 of the medical imaging system (S11); performing a scan by the medical imaging system (S12), where performing the scan includes acquiring a plurality of medical images I_i (i = 1...n) (S12); acquiring, by the tracking device, corresponding tracking coordinates in C2 for each of the plurality of medical images I_i using one or more markers (S13); converting the medical image based on the tracking coordinates and the calibration between C1 and C2 (S14); reconstructing a 3D image based on the converted image with respect to a reference position (S15); A method comprising the above steps.

2. The method according to claim 1, further comprising determining the reference position, where determining the reference position includes selecting one or more images from the plurality of medical images and determining the reference position based on the corresponding tracking positions of the selected images.

3. Determining the reference position includes selecting an initial medical image I_1 as a reference image and using the corresponding tracking position as the reference position, and / or selecting the last medical image I_n as a reference image and using the corresponding tracking position as the reference position, and / or in particular, using a statistical method such as determining an average tracking position and using it as the reference position to calculate the reference position based on a set of tracking positions corresponding to a set of medical images I_1,..., I_x, and / or calculating the reference position based on one or more tracking positions at a specific time or within a specific time frame. The method according to claim 1 or 2, comprising the above steps.

4. The method according to claim 3, wherein the reconstruction of the 3D image is performed in real time and the initial imaging system coordinates are used as the reference position.

5. Storing, using the medical image, the imaging system coordinates and the corresponding tracking coordinates of each of the one or more markers, and / or Storing the respective reference positions together with the reconstructed 3D image. The method according to any of the preceding claims, comprising the above steps. Claim 6 The method according to any of the preceding claims, further comprising reconstructing a second 3D image from the transformed image using a second reference position different from the reference position. Claim 7 The method according to any of the preceding claims, comprising reconstructing the 3D image with respect to a reference position determined from a marker attached to the patient and in the vicinity of the imaged region of interest ROI, and providing an effective alternative signal for any patient movement within the ROI that occurs during acquisition of the medical image. Claim 8 The method according to any of the preceding claims, comprising using the tracking device to track a tool used in a medical procedure in the imaging coordinate system. Claim 9 The tool is a pointer tool, and the tracking of the tool is used to visualize the pointer tool with respect to medical images acquired before and / or during the medical procedure, particularly for use in a pointer planning workflow. The method according to claim 8. Claim 10 The method according to any of the preceding claims, comprising using a shared reference marker to obtain the tracking coordinates and for tracking by a tracking camera of a surgical navigation system, the surgical navigation system performing alignment of image data acquired by the surgical navigation system during the medical procedure with medical image data acquired before the medical procedure to enable navigation during the medical procedure. Claim 11 The method according to claim 10, wherein the shared reference marker is selected to avoid artifacts in the reconstructed image and to provide accurate alignment of the medical image data acquired before the medical procedure and / or the image data acquired during the procedure. Claim 12 The method according to any of the preceding claims, comprising the surgical navigation system providing an alignment time to the medical imaging system, for example as a signal, and the medical imaging system using tracking positions associated with the alignment time as a reference position for motion compensation when reconstructing the 3D image, or as a reference position for deriving a reference position from a plurality of tracking positions within an alignment time frame. Claim 13 The medical imaging system is a wheeled system capable of autonomous movement, and the method includes using the tracking device to provide position recognition of the medical imaging system, according to any of the preceding claims.

14. The method includes the medical imaging system automatically repositioning itself to the target position, for example, a medical imaging position, after being moved from the target position. The repositioning includes during repositioning, acquiring an image of one or more markers by the tracking device and determining the current marker position from the image; and using the previous marker position determined from an image of the marker acquired by the tracking device before or during movement from the target position, wherein the image of the marker and / or the marker position of the marker and / or the marker ID of the marker are optionally stored together with the corresponding medical image. determining a trajectory for repositioning the medical imaging system based on the current marker position and the previous marker position. The method according to any of the preceding claims, particularly the method according to claim 13.

15. The tracking device attached to the medical imaging system acquires an image of a marker arranged at a fixed position in the room and uses the marker position determined from the image to determine the position of the medical imaging system, or for example, a fixed position tracking device attached to a wall or ceiling or floor of the room or a device in the room having a known position in the room acquires an image of one or more markers attached to the medical imaging system using the fixed position tracking device, and determines the position of the medical imaging system based on the marker positions in the acquired image, and is used to track the position of the medical imaging system in the room, or Each of the tracking device attached to the medical imaging system and, for example, a fixed-position tracking device attached to a wall or ceiling or floor of the room or a device in the room having a known position in the room acquires an image or a dynamic marker of the same one or more markers arranged at a fixed position in the room, and the marker position determined from the image combines the marker position determined using the medical imaging system and the marker position determined using the fixed-position tracking device to obtain the position of the medical imaging system relative to the fixed-position tracking device, and is used to determine the position of the medical imaging system. The method according to any one of the preceding claims. Claim 16 The method according to claim 15, wherein the position of the medical imaging system is determined with respect to a room coordinate system and / or with respect to a tool having a position calibrated with respect to the room coordinate system. Claim 17 Temporal binning of the medical images acquired by the medical imaging device by assigning the medical images to specific respiratory cycle phases and reconstructing a plurality of 3D images, each corresponding to a respective respiratory cycle phase, in particular using an endogenous or exogenous binning technique, wherein each of the respective respiratory cycle phases can be optionally specified within a specific time window size, resulting in effective pixel-based binning in the spatial region of the reconstructed 3D images, including temporal binning of medical images. The method according to any one of the preceding claims. Claim 18 The tracking device tracks a marker, and the current respiratory phase and the 3D image corresponding to the current respiratory phase are selected based on the correlation between the movement of the marker and the respiratory phase, in particular for use in tool tracking, and the method includes displaying an overlay of a tool model and the 3D image corresponding to the current respiratory phase. Claim 19 Gated navigation is provided by performing or providing a navigation function only for a subset of the respiratory cycle phases, in particular only in one of the respiratory cycle phases. Claim 20 The medical imaging system comprises a gantry or a C-arm that can be tilted, in particular a gantry configured such that its plane of rotation can be tilted, or a C-arm configured such that its plane of rotation can be tilted, and / or The medical imaging system comprises a gantry or a C-arm, in particular a gantry or a C-arm that can be tilted, and the medical imaging system is configured such that the gantry or the C-arm is movable so as to describe a yaw rotation. The method according to any one of the preceding claims.

21. The method according to any one of the preceding claims, wherein the tracking device is firmly attached to a component of the imaging system fixed within the imaging coordinate system C1 or a component of the imaging system movable within the imaging coordinate system C1.

22. The medical imaging system comprises a radiation source and a radiation detector movable relative to each other, and the tracking device is firmly attached to the medical imaging system so as to have a spatial relationship fixed with respect to one of the radiation source and the radiation detector, or The medical imaging system comprises a radiation source and a radiation detector having a fixed relative spatial position, and the tracking device is firmly attached to the medical imaging system so as to have a spatial relationship fixed with respect to the radiation source and the radiation detector. The method according to any one of the preceding claims.

23. The method according to any one of the preceding claims, wherein the tracking device is configured for pose tracking and / or comprises in particular at least one of an infrared tracking system comprising one or more cameras, a video camera tracking system comprising one or more cameras, and an electromagnetic tracking system.

24. The method according to any one of the preceding claims, wherein the one or more markers include markers attached to the patient's bed and / or markers attached to the floor and / or markers attached to one or more parts of the patient, in particular parts of the patient inside the region of interest and / or parts of the patient outside the region of interest of the medical imaging device.

25. The method according to any of the preceding claims, wherein the one or more markers comprise markers attached to the patient's chest and / or the patient's spine and / or the patient's skull and / or markers attached to the patient's hands and feet.

26. The method according to any of the preceding claims, wherein the one or more markers further comprise markers attached to a treatment device, such as a radiation treatment device, and / or markers attached to a tool for use in a medical procedure.

27. The method according to any of the preceding claims, wherein the one or more markers are attached at a position enabling at least one of taking into account the tilt of the gantry or C-arm, taking into account the sag of the gantry or C-arm, taking into account the yaw of the device, motion compensation during a longitudinal scan, taking into account the slip of the wheels of the medical imaging system on the floor, and in particular taking into account a non-uniform floor under the medical imaging system when the medical imaging system is a wheeled system.

28. An image reconstruction method for a medical system comprising a medical imaging system and in particular a tracking device attached, for example, rigidly or movably to the medical imaging system, the method comprising: calibrating a coordinate system C2 of the tracking device for marker-based tracking to a coordinate system C1 of the medical imaging system (S11); performing a scan by the medical imaging system (S12), wherein performing the scan includes acquiring a plurality of medical images I_i (i = 1...n); acquiring, by the tracking device, for each of the plurality of medical images I_i, corresponding tracking coordinates in C2 using one or more markers (S13); converting the medical images based on the tracking coordinates and the calibration between C1 and C2 (S14); reconstructing a 3D image based on the converted images with respect to a reference position (S15); and including.

29. The method according to claim 28, including determining the reference position, wherein determining the reference position includes selecting one or more images from the plurality of medical images and determining the reference position based on the corresponding tracking positions of the selected images.

30. Determining the reference position comprises Selecting the initial medical image I_1 as the reference image and using the corresponding tracking position as the reference position, and / or Selecting the last medical image I_n as the reference image and using the corresponding tracking position as the reference position, and / or In particular, calculating the reference position based on a set of tracking positions corresponding to a set of medical images I_1,..., I_x using a statistical method that determines the average tracking position and uses it as the reference position, and / or Calculating the reference position based on one or more tracking positions within a specific time or specific time frame, The method according to claim 28 or 29, comprising.

31. The method according to claim 30, wherein the reconstruction of the 3D image is performed in real time and the initial imaging system coordinates are used as the reference position.

32. Using the medical image to store the imaging system coordinates and corresponding tracking coordinates of each of the one or more markers, and / or Storing the respective reference positions together with the reconstructed 3D image, The method according to any of the preceding claims, comprising.

33. The method according to any of claims 28 to 32, further comprising reconstructing a second 3D image from the transformed image using a second reference position different from the reference position.

34. Reconstructing the 3D image with respect to a reference position determined from a marker attached to the patient and near the imaged region of interest ROI to provide an effective alternative signal for any patient movement within the ROI that occurs while acquiring the medical image. The method according to any of claims 28 to 33, comprising.

35. The method according to any of claims 28 to 34, wherein the method includes using the tracking device to track a tool used in a medical procedure in the imaging coordinate system.

36. The tool is a pointer tool, and the tracking of the tool is used to visualize the pointer tool with respect to medical images acquired before and / or during the medical procedure, particularly for use in a pointer planning workflow. The method according to claim 35.

37. The method includes using a shared reference marker to obtain the tracking coordinates and for tracking by a tracking camera of a surgical navigation system, and the surgical navigation system performs aligning image data acquired by the surgical navigation system during the medical treatment with medical image data acquired before the medical treatment to enable navigation during the medical treatment, the method according to any one of claims 28 to 36.

38. The shared reference marker is selected to avoid artifacts in the reconstructed image and to provide accurate alignment of the medical image data acquired before the medical treatment and / or the image data acquired during the treatment, the method according to claim 37.

39. The method includes the surgical navigation system providing an alignment time to the medical imaging system, for example as a signal, and the medical imaging system using a tracking position related to the alignment time as a reference position for motion compensation when reconstructing the 3D image, or as a reference position for deriving a reference position from a plurality of tracking positions within an alignment time frame, the method according to any one of claims 28 to 38.

40. The medical imaging system is a wheeled system capable of autonomous movement, and the method includes using the tracking device to provide position recognition of the medical imaging system, the method according to any one of claims 28 to 39.

41. The method includes the medical imaging system automatically repositioning to the target position, for example a medical imaging position, after being moved from the target position, The repositioning includes, during repositioning, obtaining an image of one or more markers by the tracking device and determining a current marker position from the image; using a previous marker position determined from an image of the marker acquired by the tracking device before or during movement from the target position, wherein the image of the marker and / or the marker position of the marker and / or the marker ID of the marker are optionally stored together with the corresponding medical image, using. Determining a trajectory for repositioning the medical imaging system based on the current marker position and the previous marker position; The method according to any one of claims 28 to 40, in particular the method according to claim 40, comprising.

42. The tracking device attached to the medical imaging system acquires an image of a marker arranged at a fixed position in the room, and the marker position determined from the image is used to determine the position of the medical imaging system, or For example, a fixed position tracking device attached to a wall or ceiling or floor of the room, or a device in the room having a known position in the room, acquires an image of one or more markers attached to the medical imaging system using the fixed position tracking device, and the position of the medical imaging system in the room is determined based on the marker position in the acquired image, or, Each of the tracking device attached to the medical imaging system and, for example, a fixed position tracking device attached to a wall or ceiling or floor of the room, or a device in the room having a known position in the room, acquires an image or dynamic markers of the same one or more markers arranged at a fixed position in the room, and the marker position determined from the image combines the marker position determined using the medical imaging system and the marker position determined using the fixed position tracking device to obtain the position of the medical imaging system relative to the fixed position tracking device, and is used to determine the position of the medical imaging system. The method according to any one of claims 28 to 41.

43. The method according to claim 42, wherein the position of the medical imaging system is determined relative to a room coordinate system and / or relative to a tool having a position calibrated relative to the room coordinate system.

44. Temporal binning of the medical images acquired by the medical imaging device by assigning the medical images to specific respiratory cycle phases and reconstructing a plurality of 3D images, each corresponding to a respective respiratory cycle phase, in particular using an endogenous or exogenous binning technique, wherein the respective respiratory cycle phases can be optionally specified within a specific time window size, so that effective pixel-based binning in the spatial region of the reconstructed 3D images is brought about, the method according to any of claims 28 to 43, comprising temporal binning of the medical images.

45. The tracking device tracks markers, and the current respiratory phase and the 3D image corresponding to the current respiratory phase are selected based on the correlation between the movement of the markers and the respiratory phase, in particular for use in tool tracking, and the method comprises displaying an overlay of the tool model and the 3D image corresponding to the current respiratory phase, the method according to claim 44.

46. Gated navigation is provided by performing or providing the navigation function only for a subset of the respiratory cycle phases, in particular only at one of the respiratory cycle phases, the method according to claim 44 or 45.

47. The medical imaging system comprises a gantry or C-arm that can be tilted, in particular a gantry configured such that its plane of rotation can be tilted, or a C-arm configured such that its plane of rotation can be tilted, and / or The medical imaging system comprises a gantry or C-arm, in particular a gantry or C-arm that can be tilted, and the medical imaging system is configured such that the gantry or the C-arm is movable so as to describe a yaw rotation. The method according to any of claims 28 to 46.

48. The tracking device is attached to a component of the imaging system fixed within the imaging coordinate system C1 or a component of the imaging system movable within the imaging coordinate system C1, the method according to any of claims 28 to 47.

49. The medical imaging system includes a radiation source and a radiation detector that are movable relative to each other, and the tracking device is attached to the medical imaging system such that the tracking device has a spatial relationship that is at least partially fixed, e.g., with respect to one or more degrees of freedom, to one of the radiation source and the radiation detector, or The medical imaging system includes a radiation source and a radiation detector having a fixed relative spatial position, and the tracking device is attached to the medical imaging system such that the tracking device has a spatial relationship that is at least partially fixed, e.g., with respect to one or more degrees of freedom, to the radiation source and the radiation detector. The method according to any one of claims 28 to 48.

50. The tracking device is configured for pose tracking and / or comprises at least one of an infrared tracking system comprising one or more cameras, a video camera tracking system comprising one or more cameras, and an electromagnetic tracking system, the method according to any one of claims 28 to 49.

51. The one or more markers include markers attached to the patient's bed and / or markers attached to the floor and / or markers attached to one or more parts of the patient, in particular parts of the patient inside the region of interest and / or parts of the patient outside the region of interest of the medical imaging device, the method according to any one of claims 28 to 50.

52. The one or more markers comprise markers attached to the patient's chest and / or the patient's spine and / or the patient's skull and / or markers attached to the patient's extremities, the method according to any one of claims 28 to 51.

53. The one or more markers further comprise markers attached to a treatment device, e.g., a radiation treatment device, and / or markers attached to a tool for use in a medical procedure, the method according to any one of claims 28 to 52.

54. The one or more markers of claim 28 to 53, are mounted in a position enabling at least one of: taking into account the tilt of the gantry or C-arm, taking into account the sag of the gantry or C-arm, taking into account the yaw of the device, motion compensation during longitudinal scanning, taking into account the slip of the wheels of the medical imaging system on the floor, especially when the medical imaging system is a wheeled system, and taking into account an uneven floor under the medical imaging system.

55. A medical system (1) comprising a medical imaging system (2) and a tracking device (3) rigidly attached to the medical imaging system, the medical system (1) being configured to perform the method according to any one of claims 1 to 27.

56. The medical imaging system (2) configured to perform the scan, The tracking device (3) configured to obtain the corresponding tracking coordinates, Optionally, tracking markers (5a-5e) for use by the tracking device, the tracking markers (5a-5e) being attached to a patient's bed, one or more body parts of the patient, the floor, one or more tools for use in a medical procedure, one or more components of a treatment device, such as one or more of a radiation treatment device or a tissue disruption device. The system according to claim 55, further comprising.

57. The system according to claim 56, further comprising a navigation system (4) for a medical procedure, the navigation system using one or more navigation markers, at least a subset of the navigation markers corresponding to at least a subset of the tracking markers, especially a subset of the tracking markers attached to the patient.

58. The system according to claim 56 or 57, wherein the tracking device comprises one or more cameras surrounded by a housing, especially completely surrounded by the housing, the housing being configured to block non-marker-related reflections from the image sensors of the one or more cameras, especially reflections from an integrated light source.

59. A medical system (1) comprising a medical imaging system (2), and in particular a tracking device fixedly or movably attached to the medical imaging system, for example, and the system is configured to execute the method according to any one of claims 28 to 54.

60. The medical imaging system (2) configured to perform the scan, The tracking device (3) configured to obtain the corresponding tracking coordinates, Optionally, tracking markers (5a to 5e) for use by the tracking device, which are attached to the patient's bed, one or more body parts of the patient, the bed, one or more tools for use in medical treatment, one or more components of a treatment device, for example one or more of a radiation treatment device or a tissue disruption device Tracking markers (5a to 5e). The system according to claim 59, further comprising.

61. Further comprising a navigation system (4) for medical treatment, the navigation system using one or more navigation markers, at least a subset of the navigation markers corresponding to at least a subset of the tracking markers, in particular a subset of the tracking markers attached to the patient. The system according to claim 60.

62. The tracking device comprises one or more cameras surrounded by a housing, in particular completely surrounded by the housing, and the housing is configured to block non-marker-related reflections from the image sensors of the one or more cameras, in particular reflections from an integrated light source. The system according to claim 60 or 61.

63. A computer program product comprising instructions that, when executed by a computer, cause the computer to execute and / or control the method according to any one of claims 1 to 54.

64. A computer-readable medium comprising instructions that, when executed by a computer, cause the computer to execute and / or control the method according to any one of claims 1 to 54.

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