Parallax correction

Abstract

Method for controlling a medical imaging modality (1) with a radiation unit (4), comprising a radiation source (50) and a camera (40), for acquiring images of an examination object (10), comprising the steps: - Capturing a camera image of the object under investigation (10) using the camera (40) in a camera position (18) and - Positioning the radiation unit (4) at a number of acquisition positions (13) in an acquisition plane (12), wherein the acquisition plane (12) includes the camera position (18) and extends substantially perpendicular to a parallax direction (D).

Description

[0001] The invention relates to a method for controlling a medical imaging modality, a control unit and a medical imaging modality.

[0002] Medical examinations encompass diagnostic activities and procedures performed and initiated by a physician as part of patient care. A physician can make a diagnosis using both physical and instrumental examinations. Instrumental examinations include, among other things, device-based procedures. The umbrella term "medical imaging modality" therefore encompasses the various medical devices used for instrumental imaging procedures in medical diagnostics, such as X-ray machines, X-ray scanners, CT scanners, MRI scanners, ultrasound machines, and the like. Medical examinations using such medical imaging modalities are applied to both animals and humans.

[0003] In an examination using a medical imaging modality, for example, a person's upper body is positioned accordingly for the medical device, and an image is acquired in this position. For this purpose, X-rays are generated and emitted, for example, using an X-ray source. When the subject is X-rayed, the intensity of these X-rays is attenuated depending on the type and structure of the tissue being penetrated, and the resulting image is then captured by a detector.

[0004] Such radiation, to which a body must be exposed for this type of examination, should be used as infrequently and to the smallest possible extent whenever possible. Therefore, X-rays should preferably be used only in a selected area of ​​interest within the object being examined, in order to keep the overall radiation exposure of the object low.

[0005] Consequently, this necessitates the ability to adjust the recording area of ​​the medical imaging modality so that precisely an area of ​​interest on the object under investigation is irradiated.

[0006] In X-ray optics, a collimator is used to reduce scattered radiation. The collimator is located on the radiation unit and often includes, among other things, a collimator light field illumination system, a resulting collimator light field, and a collimator mirror. Typically, only a portion of the area to be imaged on an object, the size of a so-called radiation field, can be optically marked for the subsequent examination using such a light field or collimator light field. For this purpose, a user aligns a radiation field marked by the light field onto the area of ​​interest on the object for a subsequent X-ray image. The radiation field refers to the area covered by a single X-ray image from an X-ray source.This area is therefore irradiated by the X-ray source – also called the radiation source – during each individual X-ray examination. This approach is generally sensible, as it ensures that only the area of ​​interest within the object being examined is exposed to the minimum required amount of radiation.

[0007] One disadvantage of this approach arises with continuous X-ray images or more complex sequences, such as an orthoscopic scan. An orthoscopic scan is a large X-ray image composed of several individual images, each with its own aligned detector, taken during an orthoscopic scan. With current technology, the object being examined must be painstakingly aligned with the light field in several steps to define the boundaries for the entire selected scan area. This often involves multiple mechanical movements of the radiation unit by the operator. Overall, this approach is error-prone and time-consuming for such a sequence.

[0008] In X-ray optics, a diaphragm is also commonly used. This serves to limit the radiation field to a small imaging area if necessary.

[0009] Another known approach involves measuring the distance between the patient and the radiation unit. This distance is measured, for example, using integrated 3D measurement functionality. Structured light or a stereo camera is used for this purpose. The captured visual camera image is then corrected according to the actual distance. Problems arise both from determining the point on the patient to which the distance is measured and from the visual camera image itself. Even after distance correction, the image still exhibits minor deviations because the patient's body surface is not flat. Furthermore, strategies must be developed to account for patient movement.

[0010] Camera systems are also used in medical technology, particularly in radiography. They are used to capture patients, their characteristics, and the fields of view and radiation.

[0011] First, a camera image of the patient is captured. Based on this image, the radiation field of the radiation source is then adjusted, and an X-ray image is taken at this position. Typically, the distance between the camera and the radiation source, or the arrangement of these two components relative to each other, results in a deviation or shift between the camera image and the X-ray image. This effect is generally referred to as parallax. Simultaneously, the camera's optical axis and the central beam of the radiation source are also offset by this deviation or shift. The central beam of the radiation source extends in the center of the radiation field in the direction of irradiation. The camera's optical axis extends in the direction of the camera image, where its focus lies—that is, in the direction of the camera lens where the camera captures its image.The camera is often positioned laterally relative to a radiation source, as the radiation source is the central component of the medical imaging modality. From now on, the term "radiation unit" refers to and encompasses such a unit consisting of a radiation source and a camera, which are arranged at a fixed distance and in a specific orientation relative to each other. They are designed to acquire images of an object under examination. The camera and the radiation source are essentially aligned in the same direction.

[0012] The previously described deviation could be avoided by positioning the camera very close to the collimator light field illumination and capturing the camera image via a collimator mirror. While such an arrangement, in which the central beam of the radiation source coincides exactly with the optical axis of the camera, is generally possible, a disadvantage is that the camera must be integrated both electrically and mechanically, and the light field generation must be significantly modified. This solution is not only very complex to implement but also incurs higher costs, for example, when retrofitting or replacing the relevant components in an existing medical imaging modality.

[0013] From DE102013215516A1, an X-ray device and a method for controlling an X-ray device are known, in which the X-ray device is configured to position a table, an X-ray source, and a camera relative to each other depending on user input, wherein, among other things, the X-ray source and the camera can only be moved along a longitudinal direction of the table and / or essentially along a plane normal perpendicular to the table's surface, as well as rotated or tilted relative to each other. Parallax correction perpendicular to the acquisition plane in which the X-ray source is positioned for acquisition does not take place.

[0014] It is an object of the present invention to provide an alternative parallax correction for medical imaging modalities.

[0015] This problem is solved by a method for controlling a medical imaging modality according to claim 1, by a control unit according to claim 9 and a medical imaging modality according to claim 10.

[0016] The aforementioned method involves controlling a medical imaging modality, in particular an X-ray machine or an X-ray scanner, with a radiation unit comprising a radiation source and a camera, to acquire images of an object under examination. It includes at least the following steps: In one step, a camera image of the object under examination is captured using the camera.

[0017] The radiation unit is positioned with the camera in a camera position. In a further step, the radiation unit is positioned in a number of acquisition positions in an acquisition plane, where the acquisition plane encompasses the camera position and extends substantially perpendicular to a parallax direction.

[0018] The aforementioned method for controlling a medical imaging modality begins with the acquisition of a camera image. For this purpose, the object under investigation is captured using, for example, a standard (digital) camera, a 3D camera, or similar device. The camera image shows, for instance, an overview of the object in its entirety. Preferably, the camera image depicts only a specific area of ​​interest within the object. The acquisition process takes place at a single camera position.

[0019] The camera position refers to a position in which the camera is advantageously positioned, i.e., essentially within the acquisition plane where the acquisition using the radiation source will later take place. If the camera has already been pre-positioned, an image of the object under investigation can be captured immediately. If pre-positioning has not yet occurred, the camera position can be set manually by a user or, preferably, pre-positioning can be performed automatically.

[0020] The radiation unit is preferably positioned or moved as quickly and safely as possible, following a logical and time-saving sequence. When selecting a suitable starting position for the radiation unit, the fastest and safest path is given preference. The starting position corresponds to a first acquisition position in the acquisition plane. The acquisition plane is a two-dimensional plane that encompasses all acquisition positions, in particular the starting position and the camera position. Furthermore, the acquisition plane is essentially orthogonal to a parallax direction. This allows for the correction of effects in X-ray images of the radiation source in the acquisition plane that would otherwise arise due to the differing positions of the camera and radiation source in this direction. These effects are referred to as parallax.

[0021] The parallax direction extends in the shortest, i.e., essentially perpendicular, connecting line between a point on the optical axis of the camera and the nearest point on the central ray of the radiation source.

[0022] Depending on the requirements, capturing a specific area of ​​interest (which will be explained in more detail later) with the radiation source may require one or more X-ray images. For example, if the area of ​​interest is large, the radiation source is preferably repositioned automatically between individual X-ray images. This allows a medical imaging modality to be controlled for one or more conventional X-ray images to cover a larger area.

[0023] The aforementioned control unit serves to control a medical imaging modality comprising a radiation unit and a positioning unit. The control unit is configured to control the camera, which includes the radiation unit, such that the camera captures a camera image of the object under examination at a specific camera position. The control unit is further configured to control the positioning unit so that it positions the radiation unit at a number of acquisition positions within the acquisition plane, wherein the acquisition plane encompasses the camera position and extends substantially perpendicular to a parallax direction. The control unit has interfaces to the components of the medical imaging modality. The control unit thus comprises all components for controlling the method according to the invention described above.

[0024] The aforementioned medical imaging modality comprises a control unit and a radiation unit according to the invention. It further comprises a positioning unit. This preferably includes means for positioning the radiation unit in three translational directions and three rotational directions. For the acquisition of X-ray images, the radiation unit is positioned by means of the positioning unit, for example, by means of motors, rails, rotary bearings, telescopic arms, joints, or the like.

[0025] The control unit according to the invention can advantageously be retrofitted into existing medical imaging modalities. However, it is also possible to equip newly manufactured medical imaging modalities with a control unit according to the invention during the manufacturing process.

[0026] The essential components of the control unit according to the invention can be predominantly implemented as software components. However, these components can also be partially implemented as software-supported hardware, such as FPGAs or the like, particularly when very fast calculations are required. Likewise, the necessary interfaces, for example, when it is only a matter of transferring data from other software components, can be implemented as software interfaces. Alternatively, they can be implemented as hardware interfaces controlled by suitable software.

[0027] In particular, the control unit according to the invention can be part of a user terminal of a medical imaging modality.

[0028] A largely software-based implementation has the advantage that existing control units can be easily retrofitted via a software update to operate according to the invention. In this respect, the problem is also solved by a corresponding computer program product comprising a computer program that can be directly loaded into a memory device of a control unit of a medical imaging modality, with program sections to execute all steps of the inventive method when the program is run in the control unit. In addition to the computer program, such a computer program product may optionally include additional components such as documentation and / or additional components, including hardware components such as hardware keys (dongles, etc.) for using the software.

[0029] For transport to and / or storage on or in the control unit, a computer-readable medium, such as a memory stick, a hard drive, or other portable or permanently installed data storage device, can be used, on which the program sections of the computer program that can be read and executed by a computing unit of the control unit are stored. The computing unit can, for example, include one or more cooperating microprocessors or similar components.

[0030] Further, particularly advantageous embodiments and developments of the invention result from the dependent claims and the following description, wherein the independent claims of a claim category may also be further developed analogously to the dependent claims and embodiments of another claim category, and in particular individual features of different embodiments or variants may be combined to form new embodiments or variants.

[0031] Preferably, the camera position is chosen such that perspective distortions are minimized during image capture. This means the camera image is preferably captured from a favorable angle so that the distance to the surface of the object under investigation is as similar as possible throughout the image. Particularly preferably, the camera image is captured essentially perpendicular to the object. For example, the image is captured in a frontal plane, as used in anatomical terminology, of a standing patient. The patient may also be positioned with their back or one shoulder facing the camera. Similarly, the patient may be lying down.

[0032] For reading and executing commands for the control unit, the medical imaging modality preferably includes a computer unit.

[0033] Preferably, the captured camera image is transmitted and displayed on a medium available to the user, such as a screen, display, touchscreen display, or similar device. Subsequently, the user preferably defines the outer boundaries for the subsequent recording area of ​​the radiation source in the displayed camera image or marks them directly on the display. Furthermore, the previously defined boundaries of the recording area are preferably automatically transmitted to the control unit of the medical imaging modality according to the invention for the execution of the positioning.

[0034] The imaging area refers to the region of an object being examined that is irradiated by the radiation source. Therefore, the imaging area is selected as the region of interest within the object being examined. Depending on the size of the selected imaging area, several or, for example, only a single X-ray image may be necessary. The object being examined can, in principle, be any object that can be examined using a medical imaging modality. For example, the object being examined could be an animal. However, the preferred object of examination is a human patient or a part thereof.

[0035] The transmission and display of the camera image to a user is at least partially, and preferably fully, automated. The camera image is transmitted, for example, to a computer unit. For instance, the camera image can be displayed on a screen in an adjacent control room; preferably, the camera image is displayed directly on a touchscreen display of the radiation unit or the medical imaging modality itself.

[0036] Preferably, the radiation field of the radiation unit is set based on the captured camera image of the object under examination. A user preferably not only sets the boundaries of the entire imaging area in the camera image, but can also, and even more preferably, shift the boundaries between the individual positions of the radiation field for each X-ray image (asymmetrically). This prevents, for example, a transition between two X-ray images from lying precisely in a joint space, thus avoiding diagnostic problems. Particularly preferably, the radiation source is positioned by the user based on the defined boundaries of the imaging area, and, if necessary, the aperture settings and / or collimator settings, etc., are adjusted. Most preferably, the radiation source is positioned or adjusted only for a specific area of ​​interest within the object under examination.This should be given special consideration during an examination or assessment. This could include, for example, anomalies in the body such as bone fractures, dislocated joints, or similar conditions.

[0037] Preferably, the medical imaging modality for acquiring X-ray images includes a detection unit. The detection unit comprises at least one detector, a column, and AEC measurement fields for acquiring X-ray images. The detector or the detection unit is particularly preferably controlled such that X-rays emitted by a radiation source during operation in an examination are detected by the detector.

[0038] A maximum acquisition position is preferably chosen as the starting position, from which the radiation unit only needs to be moved in one direction to acquire X-ray images from different positions. "Maximum" here refers to the maximum acquisition angle or the maximum translation of the radiation unit.

[0039] The acquisition angle refers to the orientation angle of the radiation source in the acquisition plane relative to the object under investigation or, if applicable, to a detector. The angle increment by which the acquisition angle is adjusted or positioned for acquiring X-ray images is preferably selected depending on the opening angle of the radiation unit. The opening angle of ordinary radiation sources is often limited to 10°. Therefore, the angle increment is preferably chosen to be correspondingly small so that the individual X-ray images always overlap or at least adjoin each other.

[0040] Aligning the radiation source into a starting position in the acquisition plane can preferably involve a rotational movement of the radiation unit. The radiation source rotates clockwise and / or counterclockwise until it reaches the desired position.

[0041] The alignment of the radiation source to the starting position can preferably also include a translational movement – ​​also called linear movement – ​​of the radiation unit. Pure linear movement, in this context, refers to a rectilinear movement of the radiation unit, specifically without rotation.

[0042] However, aligning the radiation unit is not limited to either movement alone, but can preferably also include a combination of several rotational and translational movements if aligning the radiation unit requires both movements or if a combination is safer and faster. Thus, the positioning unit is preferably designed to simultaneously rotate and linearly move the radiation unit. Such a combined movement corresponds to a pivoting or swiveling motion.

[0043] Preferably, the alignment into a starting position is achieved through the shortest possible flowing sequence of these movements.

[0044] In a preferred variant of the positioning procedure for acquiring multi-part X-ray images, the radiation source can be repeatedly positioned linearly in one spatial direction. In an alternative variant, it can be positioned at different acquisition angles relative to the object being examined. The radiation unit is rotated within the acquisition plane. By imaging the area from different angles, medical diagnosis can be facilitated or supported. This is particularly helpful when individual body parts, for example, are obscured in an X-ray image taken from a specific angle because they are located behind a body part in front of it. Preferably, however, the radiation source can also be positioned using a combination of the two variants described above.Among other things, the radiation source can preferably be positioned in the camera position, at least once for an X-ray image.

[0045] The method for controlling a medical imaging modality is particularly well-suited for parallax correction in orthographs. An orthograph is a composite image acquired, for example, during an ortho-radiography procedure. This procedure may involve translation and rotation of the X-ray source within a single plane.

[0046] In a preferred application example, the inventive method for controlling a medical imaging modality is used in a so-called ortho sequence. An ortho sequence is particularly advantageous, for example, in the area of ​​the spine ("full spine") or legs ("long leg") during an X-ray examination, since the acquisition area is large. In an ortho sequence, the radiation unit acquires several X-ray images of an object within the acquisition plane according to one of the following two variants. A combination of the two variants is also possible.

[0047] Preferably, positioning the radiation unit between different acquisition positions for acquiring X-ray images comprises—most preferably only—a rotational movement or tilting of the radiation unit to different acquisition angles. In other words, it can be rotated or turned over a set angular range. After alignment, the radiation source is in a starting position. Subsequently, for example, only one X-ray image can be taken in the first acquisition position from a desired acquisition angle. However, several X-ray images are usually provided, as this makes the application of the method particularly time-saving. These X-ray images collectively encompass the area of ​​interest of the object under investigation, if this cannot be captured with a single X-ray image or if the area of ​​interest consists of different settings or...Angles are to be captured. A selected angle increment can thus be used to acquire a complete angular range stepwise. The angle increment is chosen, for example, based on the size of the desired imaging area, the resulting number of X-ray images, and a configurable overlap between the individual X-ray images. For example, a value of 1 cm can be selected for the overlap. Preferably, the areas for the individual X-ray images are chosen to take the patient's physiological characteristics into account. This means, for example, that a transition between two X-ray images is not located in the area of ​​a joint or a similar position relevant to the diagnosis. Alternatively, regular angular intervals can also be used.For example, specific preferred angles (0°, 5°, 15°, 25°) can be used, within which the radiation unit is positioned to acquire X-ray images. Certain preferred angles can also be acquired automatically in sequence.

[0048] Preferably, positioning between different acquisition positions comprises – and most preferably only comprises – a translational movement parallel to an object under investigation in the acquisition plane. That is, alternatively or additionally to rotation, the radiation unit can preferably be moved linearly over a defined recording area in the acquisition plane to acquire X-ray images. Starting again from the initial position, X-ray images are subsequently acquired at different acquisition positions. For this linear movement, the radiation source can be oriented at a fixed angle, e.g., perpendicular to the object under investigation or to the detector, and is positioned in one direction, e.g., between floor and ceiling, essentially parallel to the object under investigation or detector at different acquisition positions.

[0049] The distance between the object being examined and the radiation unit is also referred to as the examination distance. An orthoscopic scan can, in principle, be performed at different examination distances. For this purpose, the radiation unit can preferably be positioned at the desired examination distance to the patient using the positioning unit. If required, a preferred examination distance can thus be selected for an orthoscopic scan to acquire an orthoscopic image, and the orthoscopic images can be acquired at that distance.

[0050] In the case of a large imaging area, several X-ray images may be required. Consequently, the radiation unit must be repositioned multiple times. The individual X-ray images are therefore single images of a large, contiguous imaging area. Preferably, the individual images are combined after acquisition to form a composite X-ray image—for example, an orthophoto—of the entire imaging area. For example, the X-ray images can then preferably be displayed individually and / or as a composite image to a user.

[0051] The camera can, for example, be mounted parallel to the radiation source, preferably keeping its distance to the source as small as possible. This already reduces the parallax effect. Preferably, however, the camera is positioned at an angle to the radiation source, such that the optical axis and the central ray intersect. The point where the optical axis and central ray intersect is called the intersection point. The angle between the optical axis and the central ray is referred to as the intersection angle. Preferably, the camera is permanently installed or mounted on the radiation unit at this intersection angle. This already reduces parallax errors at the intersection point.

[0052] Preferably, the examination distance is chosen such that the intersection point is located at a distance from the radiation unit. At this preferred examination distance – also called the preferred distance – parallax errors are consequently reduced. Particularly preferably, the preferred distance is continuously controlled or regulated during positioning for X-ray image acquisition by means of a distance sensor (e.g., TOF, structured light, laser, ultrasound, etc.).

[0053] Preferably, the camera image can be acquired in an arrangement perpendicular to the object under investigation in the acquisition plane. The radiation unit with the camera is preferably arranged centrally to the object under investigation or on a normal to the surface of the object under investigation. For example, with a standing patient as the object under investigation, the radiation unit is arranged such that the optical axis of the camera runs substantially centrally or through the middle of the patient in the acquisition plane.

[0054] A focal spot is the point where the electron beam from the radiation source strikes an anode of the radiation source. This spot is positioned so that it always lies in the acquisition plane during X-ray image acquisition. Preferably, the radiation unit is positioned such that the distance to the focal spot of the radiation source is equal to the distance to the camera's focus in the camera position. This positioning of the radiation unit may involve, for example, a number of rotational and / or translational movements before an X-ray image is taken by the radiation source.

[0055] In a preferred embodiment, the radiation unit comprises a camera with an opening angle of approximately 60° to 90°. Furthermore, the camera's focus is preferably arranged at a minimal distance from the central beam of the radiation source. Preferably, the distance between the camera's focus and the object under investigation corresponds essentially to the distance between the focal spot of the radiation source and the object under investigation. This advantageously shortens the path required for positioning the camera to the starting position.

[0056] The invention is explained in more detail below with reference to the accompanying figures and exemplary embodiments. The same components are designated with identical reference numerals in the various figures. The figures are generally not to scale. They show: Fig. 1 a roughly schematic representation of an embodiment of a medical imaging modality according to the invention, Fig. 2 a block diagram of an embodiment of a medical imaging modality according to the invention, Fig. 3 a schematically represented top view of a top surface of the radiation unit made of Fig. 1 in a camera position, Fig. 4 a schematically represented top view of a top surface of the radiation unit made of Fig. 1 in a starting position, Fig. 5 a roughly schematic side view of a translational movement in an embodiment of a method according to the invention for controlling a medical imaging modality, Fig. 6 a roughly schematic side view of a rotational movement in an embodiment of a method according to the invention for controlling a medical imaging modality, Fig. 7 a schematically represented top view of the front of a detection unit of an embodiment of a medical imaging modality according to the invention, Fig. 8 a schematic block diagram for the sequence of an embodiment of a method according to the invention for controlling a medical imaging modality and Fig. 9 a schematic block diagram of a step of the process of an embodiment of a method according to the invention for controlling a medical imaging modality.

[0057] In Fig. Figure 1 shows an exemplary and roughly schematic representation of a medical imaging modality 1 according to the invention. Relative directional terms such as "up", "down", etc., refer to a medical imaging modality 1 set up as intended for operation, e.g., in an examination room. The medical imaging modality 1 is configured here as an X-ray device or X-ray scanner for carrying out the control method according to the invention. It comprises a radiation unit 4, a positioning unit 3, a detection unit 6, and a control unit 2 (see block diagram). Fig. 2).

[0058] The radiation unit 4 comprises a radiation source 50 and a camera 40. With a housing of the radiation unit 4 being essentially cuboid in shape, the camera 40 is located, for example, centrally on one side of the radiation unit 4 at a distance from the radiation source 50 – in camera position 18 with the optical axis 42 parallel to the acquisition plane 12. The radiation unit 4 is furthermore movable in space via the positioning unit 3.

[0059] The positioning unit 3 has means for positioning in three translational directions and at least two rotational directions. These three translational directions and at least two rotational directions are, for example, the three spatial directions X, Y, Z, and the rotational directions around the spatial directions Y, Z. The orientation of these directions is also illustrated by most of the other figures. The positioning unit 3 comprises a telescopic arm 30, a pivot bearing 33, and at least two movement rails 31, 32. The radiation unit 4 is attached to the ceiling via the telescopic arm 30 and the movement rails 31, 32. This allows for virtually any desired positioning of the radiation unit 4 in the room.

[0060] The motion rails 31 and 32 are arranged with their longest extensions parallel to the spatial direction X and parallel to the spatial direction Y, respectively, and perpendicular to each other in the XY plane. They are designed to allow the medical imaging modality to move in both spatial directions X and Y, if necessary. One motion rail 31 is attached to the ceiling with its mounting side. The second motion rail 32 is attached to its opposite underside. Both motion rails 31 and 32 are mounted in such a way as to enable virtually any two-dimensional movement in the XY plane. Essentially, the movement range of the radiation unit 4 is limited only by the dimensions of the motion rails 31 and 32.

[0061] The lower motion rail 31 is itself connected to the telescopic arm 30, so that the latter moves along with the motion rails 31 and 32. The radiation unit 4 is attached to the lower free end of the telescopic arm 30. The telescopic arm 30 allows the radiation unit 4 to be moved upwards or downwards in the Z-direction. Furthermore, the radiation unit 4 is rotatably mounted on pivot bearings 33, so that it can be rotated in the XZ-plane, among other directions. For example, it can be moved along the motion rails 31 and 32 in the Z-direction, i.e., towards the floor or vice versa, regardless of its current position in the XY-plane.

[0062] Control unit 2 is described in detail using the following: Fig. 2 is described. It is designed to control the medical imaging modality 1. Individual components of the positioning unit 3, driven by motors in three translational directions and at least two rotational directions, can be moved in space, thus positioning the radiation unit 4. This allows desired X-ray images to be acquired, i.e., for example, of an area of ​​interest of an object of study 10. The control unit 2 controls the radiation unit 4, for example, in an ortho-sequence, so that several individual, partially overlapping, or at least adjacent X-ray images of the area of ​​interest are acquired. These can then be displayed in a single, coherent X-ray image.

[0063] The detection unit 6 comprises a support column 61 and a detector 60. The support column 61 is connected to the detector 60 so that it can be moved in at least one direction. During operation, the support column 61 stands on the floor of the examination room. The detector 60 has AEC measuring fields 62. For an examination, a test object 10 is positioned between the detector 60 and the radiation unit 4. The test object 10 is the body of a standing patient.

[0064] The radiation source 50 and the detector 60 are arranged for an X-ray examination such that, during operation, X-rays emitted from a focal spot 51 of the radiation source 50 strike the detector 60. During operation, the detector 60 detects X-rays emitted by the radiation source 50, at least some of which have penetrated the patient located between the radiation source 50 and the detector 50. Furthermore, the AEC measuring fields 62 ensure that the patient 10 is exposed to only the minimum necessary radiation dose. These fields are designed, among other things, to switch off the radiation source 50 after a specific minimum necessary amount of radiation has been detected.

[0065] The radiation source 50 can be rotated relative to the detector 60 in a 360° angle by means of a rotary bearing 33.

[0066] In an additional coordinate system, the orientation of the three spatial directions X, Y, Z and a rotation direction R (clockwise and counterclockwise) around the spatial direction Y are schematically shown. The medical imaging modality 1 can be positioned and rotated in at least these directions, and thus also swiveled.

[0067] In Fig. Figures 3 to 6 also depict the spatial directions X, Y, Z, oriented according to the respective perspective. The choice of coordinate system serves as an example and for better illustration. It is made without limitation of generality.

[0068] In Fig. Figure 2 shows an exemplary block diagram of a medical imaging modality 1 according to the invention. It comprises a control unit 2, which is connected via suitable interfaces to the positioning unit 3, the radiation unit 4, the detection unit 6, and a computer unit 7 for control purposes. The components of the medical imaging modality 1 are connected either directly, e.g., via a central bus, or indirectly. In the case of indirect connection, the components of the medical imaging modality 1 are connected to each other as needed.

[0069] Computer unit 7 is designed to display and process the captured camera image and X-ray images. Furthermore, computer unit 7 is designed to detect or, preferably, automatically define the boundaries of an imaging area.

[0070] In Fig. Figure 3 is an exemplary and schematic top view of the medical imaging modality 1 according to the invention. Fig. Figure 1 shows the acquisition plane 12. The acquisition plane 12 is initially arranged in the optical axis 42 of the camera 40 and is located in the XZ plane. The acquisition plane 12 thus extends into the drawing plane and can be oriented parallel to the optical axis 42 of the camera 40. Furthermore, the acquisition plane 12 extends substantially perpendicular to the parallax direction D. The parallax direction D extends along the shortest, i.e., substantially perpendicular, connecting line between a point on the optical axis 42 of the camera 40 and the nearest point on the central ray 52 of the radiation source 50.

[0071] The radiation unit 4 comprises a radiation source 50 and a camera 40. The radiation source 50 is located in the center of the radiation unit 4, while the camera 40 is located at one side. The camera 40 has an optical axis 42. This axis extends from the focus 41 inside the camera 40 in a direction in which other optical components are arranged and in which the camera captures its image. The radiation source 4 has a central beam 52, which originates from an internal focal spot 51 (not visible). The optical axis 42 of the camera 40 is fixed at an angle 16 to the central beam 52 of the radiation source 50. As a result, the optical axis 42 and the central beam 52 intersect at a point 17. The radiation unit 4 is positioned such that the optical axis 42, at camera position 18, is substantially perpendicular to the object under investigation 10.

[0072] Fig. Figure 4 shows an exemplary and schematic view according to Fig. 3 in a modified starting position 15. Here, the radiation unit 4 is positioned such that the central beam 52 strikes the object 10 essentially perpendicularly. The central beam 52 travels in the spatial direction X. With this arrangement in the starting position 15, parallax errors E are corrected or do not occur in an X-ray image taken in this position. In other words, the radiation source 50 is, so to speak, positioned in the camera position 18 from this perspective, so that the parallax effect disappears.

[0073] Such an arrangement within the acquisition plane 12 implies that a radiation source 50 can also be positioned in different acquisition positions 13 along the spatial direction Z without causing parallax errors E. Furthermore, it follows that the radiation source 50 can be rotated about the spatial direction Y without causing parallax errors E. It also follows that the starting position 15 can be an acquisition position 13 shifted in the spatial direction Z relative to the camera position 18.

[0074] The alignment of the radiation unit 4 from a camera position 18 to an acquisition position 13, in particular a starting position 15 in the acquisition plane 12, can be carried out by means of a rotational movement R, a translational movement T or a combination of both movements.

[0075] In Fig. Figure 5 shows a roughly schematic side view of a translational movement T in an embodiment of a method according to the invention.

[0076] The radiation source 50 is positioned at an examination distance 11 from the object under investigation 10. A detection unit 6 for recording the radiation emitted by the radiation source 50 is also positioned accordingly. The radiation source 50 is positioned in an acquisition position 13 by means of solid lines. Further acquisition positions 13 are schematically indicated by dashed lines, shifted linearly along the Z-axis. The starting position 15 designates a first acquisition position 13, from which the radiation source 50 has been linearly shifted to the further acquisition positions 13. The translational movement T – also called linear movement – ​​of the radiation source 50 in a spatial direction Z is achieved by extending or retracting the telescopic arm 30 (see Figure 1). Fig. 1) realized.

[0077] For the sake of simplicity, radiation source 50 is shown here only symbolically. Therefore, only five acquisition positions 13, including the starting position 15, are indicated. However, the positioning of radiation source 50 is not limited to a specific number of acquisition positions 13, but in principle includes any number of acquisition positions 13 that can be implemented as intended.

[0078] Fig. Figure 6 shows a roughly schematic side view of a rotational movement R in an embodiment of a method according to the invention.

[0079] Unlike Fig. The inventive method for controlling the radiation source 50 comprises a rotational movement R. The radiation source 50 is rotated from a starting position 15 (shown with dashed lines) through an acquisition position 13 (shown with solid lines) to another acquisition position 13 (shown with dashed lines). An acquisition angle 14 of the radiation source 50 can, for example, be specified as an angle to a normal of the object under investigation 10. The rotational movement R comprises a rotation about the spatial direction Y. The direction of rotation is arbitrary; it can be clockwise or counterclockwise. The two outermost positions (indicated by dashes) correspond to a maximum acquisition angle. This can be selected as required.

[0080] A radiation source 50 controlled according to the invention is preferably rotated from a maximum acquisition position, i.e., a starting position 15, in one direction to another maximum acquisition position. The acquisition area therefore corresponds to the area between the two maximum acquisition positions. The two maximum acquisition positions are included in the acquisition area. Preferably, when taking an X-ray image of a large acquisition area, the radiation field 19 of the radiation source 50 is repeatedly positioned such that the individual X-ray images within the large acquisition area, for example, partially overlap or at least adjoin each other.

[0081] In Fig. Figure 7 shows a schematic top view of the front of a detection unit 6. The detection unit 6 comprises a detector 60, which has a number of AEC measuring fields 62 and a reticle 63. The AEC measuring fields 62 are essentially rectangular and arranged around the center point of a reticle 63. They are designed to detect the radiation from the radiation source 50 and to terminate the irradiation by the radiation source 50 if a maximum radiation dose is exceeded. The area irradiated by the radiation source 50 and detected by the detector 60 is referred to as the radiation field 19.

[0082] In an examination, the object of investigation 10 is typically a patient's body positioned between the detector 60 and a radiation source 50, which, in an examination not covered by the invention, emits X-rays through the patient's body onto the detector 60. Without a patient, the distance between the radiation unit 4 and the detector 60 is known. However, the distance of the radiation unit 4 to a patient is unknown, since the patient's surface is not flat and therefore varies. This results in a so-called parallax error E. This error arises, firstly, from the misalignment of the camera 40 and the radiation source 50, and secondly, from the unknown distance between the camera 40 and the object of investigation 10. This parallax error E is corrected by means of the positioning method according to the invention.This circumvents the parallax error, so that the exemplary shift between the camera image and the X-ray image is preferably no longer present. The parallax error E is indicated as a shift between the radiation field 19 of the radiation source 50 and the actual camera image of the camera 50.

[0083] Fig. Figure 8 shows an exemplary block diagram of a method according to the invention for controlling the medical imaging modality, here an X-ray scanner. After preparatory positioning in a camera position 18, a camera image of an object of examination 10, in particular of an area of ​​interest, is captured in a first step I. The captured camera image is transmitted directly to a computer unit 7 available to the user and subsequently displayed on a screen.

[0084] In a second step (II), the user specifies boundaries for the subsequent recording area of ​​the radiation source 50 in the displayed, captured camera image. These boundaries are graphically marked, for example, on a display available to the user, preferably a touchscreen display for operating the radiation unit 4. The marking is done, for example, by means of a frame or lines drawn around the area of ​​interest in the displayed camera image. After subsequent confirmation by the user, the defined boundaries of the recording area are transmitted to the control unit 2.

[0085] In a third step III, the radiation unit 4 is aligned or positioned for the acquisition of X-ray images based on the previously set imaging area. This third step III comprises further substeps III.a to III.c, which are illustrated in the following schematic block diagram. Fig. 9 will be explained.

[0086] Steps I and III can be repeated iteratively until a defined termination criterion is reached. This means, for example, until a recording area is completely covered and step II is proceeded.

[0087] Fig. Figure 9 shows an example block diagram of the substeps III.a to III.c included in a third step III. In a first substep III.a, the radiation unit 4 is initially positioned so that the radiation source 50 is in a starting position 15 according to Fig.The alignment to a starting position 15 can be achieved based on the limits of the recording area previously defined by the user. Furthermore, it can be controlled so that the focal spot 51 of the radiation source 50 is located at the same distance to the object 10 or detector 60 during an X-ray image as the focus 41 of the camera 40 was previously. The control unit 2 controls the positioning unit 3, which then linearly moves and / or rotates the radiation unit 4 to the starting position 15 in the acquisition plane 12 along the most efficient path. The starting position 15 is an acquisition position 13, from which the radiation unit 4 is later linearly moved to the further acquisition positions 13 by means of a translational movement T in only one direction.

[0088] In a second sub-step III.b, an X-ray image of the object 10 can be acquired using the radiation source 50 at the respective acquisition position 13. Furthermore, by controlling an aperture of the radiation unit 4, only an area of ​​interest of the object 10 can be imaged.

[0089] In a third sub-step III.c, the radiation unit 4 is moved or positioned in a further acquisition position 13 by means of the positioning unit 3, controlled by the control unit 2. This movement can be performed by means of a translational movement T. It is implemented using the telescopic function of the telescopic arm 30. For this purpose, the telescopic arm 30 is extended or retracted in the spatial direction Z. For example, with a patient lying down, the translational movement T can also be performed using one or both of the motion rails 31, 32.

[0090] In an alternative or additional step III.c, the radiation unit 4 can also be rotated or turned into further acquisition angles 14 by means of a rotational movement R instead of a translational movement T. The rotational movement R is realized by means of the rotary bearings 33. The radiation unit 4 is turned into an acquisition position 13 by means of the rotary bearings 33. During the rotational movement R, the radiation unit 4 is not moved in the spatial direction Z, but rotated about the spatial direction Y. However, with a patient lying down, the rotation can also be about the Z-axis.

[0091] In another embodiment of the process, the radiation unit 4 is repeatedly rotated between the acquisition positions 13 by means of a rotational movement R. After being aligned to a starting position 15 in step III.a, which corresponds to a first acquisition position 13, a first X-ray image is acquired in step III.b. Subsequently, in step III.c, the radiation source 50 is rotated from the starting position 15 to a second acquisition position 13 with a changed acquisition angle 14. The angle increment used during the rotation can be set by a user or automatically based on the previously defined acquisition area. In the second acquisition position 13, an X-ray image is acquired by repeating step III.b. Steps III.b and III.c are then repeated until a complete acquisition of the selected acquisition area has been achieved.Preferably, the acquired X-ray images are directly and automatically combined into a single, coherent image of the scan area. This coherent image is then displayed to a user on a screen and / or stored on the memory of computer unit 7 and / or on a connected network storage device.

[0092] Finally, it should be noted once again that the devices and methods described in detail above are merely exemplary embodiments, which can be modified in various ways by a person skilled in the art without departing from the scope of the invention. For example, only an X-ray system was described above, but the invention can, in principle, relate to any medical imaging modality in which parallax errors can occur. Furthermore, the use of the indefinite articles "a" or "an" does not preclude the possibility that the features in question may be present multiple times. Likewise, the terms "device," "unit," "arrangement," and "system" do not preclude the possibility that the component in question consists of several interacting sub-components, which may also be spatially distributed.

Claims

[1] Method for controlling a medical imaging modality (1) with a radiation unit (4), comprising a radiation source (50) and a camera (40), for acquiring images of an object under investigation (10), comprising the steps: - Capturing a camera image of the object under investigation (10) using the camera (40) in a camera position (18) and - Positioning the radiation unit (4) at a number of acquisition positions (13) in an acquisition plane (12), wherein the acquisition plane (12) includes the camera position (18) and extends substantially perpendicular to a parallax direction (D). [2] Method according to claim 1, wherein a radiation field (19) of the radiation unit (4) is set on the basis of the captured camera image of the object under investigation (10). [3] Method according to claim 1 or 2, wherein aligning the radiation source (50) into a starting position (15) in the acquisition plane (12) comprises a rotational movement (R) of the radiation unit (4). [4] Method according to one of the preceding claims, wherein aligning the radiation source (50) into a starting position (15) in the acquisition plane (12) comprises a translational movement (T) of the radiation unit (4). [5] Method according to one of the preceding claims, wherein the positioning of the radiation unit (4) is such that, as a result, the distance of a focal spot (51) of the radiation source (50) is equal to the distance of a focus (41) of the camera (40) in the camera position (18). [6] Method according to one of the preceding claims, wherein an optical axis (42) of the camera (40) is preferably arranged at an angle of intersection (16) with a central ray (52) of the radiation source (50). [7] Method according to one of the preceding claims, wherein the positioning between different acquisition positions (13) comprises a rotational movement (R) of the radiation unit (4) into a number of acquisition angles (16) in the acquisition plane (12). [8] Method according to one of the preceding claims, wherein the positioning between different acquisition positions (13) comprises a translation movement (T) parallel to an object of investigation (10) in the acquisition plane (12). [9] Control unit (2) for controlling a medical imaging modality (1) with a radiation unit (4) comprising a camera (40) and a positioning unit (3), wherein the control unit (2) is configured - to control the camera (40) so that it captures a camera image of an object under investigation (10) in a camera position (18) and - the positioning unit (3) to position the radiation unit (4) at a number of acquisition positions (13) in an acquisition plane (12), wherein the acquisition plane (12) includes the camera position (18) and extends substantially perpendicular to a parallax direction (D). [10] Medical imaging modality (1) comprising a control unit (2) according to claim 9 - a radiation unit (4) comprising a camera (40) configured to capture a camera image of the object under investigation (10) in a camera position (18), and - a positioning unit (3) configured to position the radiation unit (4) in a number of acquisition positions (13) in the acquisition plane (12). [11] Medical imaging modality (1) according to claim 10, comprising a detector (60) which is controlled by the control unit (2). [12] Computer program product comprising a computer program which can be directly loaded into a storage device of a control unit (2), comprising program sections to execute all steps of a method according to any one of claims 1 to 8 when the computer program is executed in the control unit (2). [13] Computer-readable medium on which program sections readable and executable by a computer unit (7) are stored to execute all steps of a method according to any one of claims 1 to 8 when the program sections are executed by the computer unit (7).

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