Determining the value of an imaging parameter using an anatomical landmark

Abstract

Method for determining at least one value of at least one imaging parameter for an X-ray image of a patient (5) lying on a patient bed (6), comprising - S1: contactless scanning of at least part of the patient's surface (5) using at least one electromagnetic sensor (31), - S2: Calculating the three-dimensional contour of the scanned surface, - S3: Identify at least one anatomical landmark of the patient (5) using the three-dimensional contour, - S4: Determining the position of the anatomical landmark in the coordinate system of the patient bed (6), as well as - S5: Determining the value of the recording parameter based on the position of the anatomical landmark, - S6: Calculating a patient model based on the three-dimensional contour for the pictorial representation of the patient (5), - S7: Highlighting the identified landmark in the patient's image (5), - S8: Providing a graphical user interface (23) with a button (1,2,7,10) wherein the button (1,2,7,10) represents the identified landmark, wherein the button (1,2,7,10) is designed to trigger the determination of the recording parameter value through user interaction.

Description

[0001] The invention relates to both a method and an imaging system for determining the value of an image parameter.

[0002] Computed tomography (CT) is an imaging technique primarily used for medical diagnostics. In CT, an X-ray source and an X-ray detector, which interacts with the X-ray source, rotate around a patient lying on a table. Images are taken at various angular positions of the X-ray source and detector, and the patient can be moved along the axis of rotation, also known as the system axis. Each image is a projection of a specific area of ​​the patient being imaged; therefore, the angular position of the X-ray source and detector is also called the projection angle. At the end of the series of images, also called a "scan," the projections are processed to create a three-dimensional (3D) tomographic X-ray image.Therefore, the process of taking a series of images is also referred to as a tomographic image. However, taking an X-ray image also includes taking a single projection or multiple projections, each taken from the same angle. In particular, the term "X-ray image" can also refer to an overview image in the form of a so-called topogram.

[0003] The quality of an X-ray image is influenced by the selection of the relevant acquisition parameters. A scan protocol includes values ​​for acquisition parameters that define the precise sequence of the tomographic acquisition of an X-ray image. Furthermore, a scan protocol can include values ​​for acquisition parameters that influence the subsequent reconstruction of the X-ray image. These acquisition parameters can include, for example, the dose to be applied or the intensity values ​​of the X-ray radiation. Such intensity values ​​can be modulated, in particular, depending on the projection angle. Additionally, the acquisition parameters can include settings for filters or apertures, as well as the initial and final positions of the patient table.In medical settings, selecting appropriate imaging parameters is crucial not only for the quality of the resulting X-ray image but also for avoiding unnecessary radiation exposure for the patient. Such parameters are often determined by choosing a predefined scan protocol or by analyzing a topogram. However, acquiring a topogram does expose the patient to radiation; furthermore, a topogram provides only limited information about the patient's surface contours.

[0004] From German patent application DE 10 2012 201 798 A1, a method for planning an X-ray imaging of an examination area of ​​an object is known, wherein the object is mounted on a support for an X-ray imaging device. The method comprises: S1) Obtaining setting parameters for the X-ray imaging device; S2) Determining the position of at least one part of the object; S3) Determining at least one irradiated area of ​​the object as a function of the setting parameters for the X-ray imaging device and the position of at least one part of the object.

[0005] Furthermore, from the publication WO 2012 / 023 088 A1, an object support for an imaging device with an identification unit for determining the acquisition position is known. The identification unit generates a signal that indicates at least a start position or an end position of an examination area. The signal is generated based on the position of the examination region on a movable unit of the object support.

[0006] The object of the invention is to determine a value of an imaging parameter for taking an X-ray image with the lowest possible radiation exposure for the patient, as well as quickly and in a technically simple manner.

[0007] The problem is solved by a method according to claim 1 and by an imaging system according to claim 10.

[0008] The inventive solution to the problem is described below with respect to both the claimed system and the claimed method. Features, advantages, or alternative embodiments mentioned herein are also applicable to the other claimed subject matter and vice versa. In other words, the claims (which, for example, relate to a system) can also be further developed with the features described or claimed in connection with a method. The corresponding functional features of the method are thereby implemented by corresponding material modules.

[0009] The inventive method for determining at least one value of at least one acquisition parameter for an X-ray image of a patient lying on a treatment table utilizes the contactless scanning of at least a portion of the patient's surface by means of at least one electromagnetic sensor to calculate the three-dimensional contour of the scanned surface without additional radiation exposure. The inventors have recognized that at least one anatomical landmark of the patient can be identified based on the three-dimensional contour and that the position of the anatomical landmark in the coordinate system of the treatment table can be determined. The value of the acquisition parameter can be determined based on the position of the anatomical landmark.Determining the value of the recording parameter in this way is quick and technically simple, since contactless surface scanning can be accomplished quickly and easily. This is particularly true if the at least one electromagnetic sensor is designed as a stereo camera, a triangulation system, or a time-of-flight measurement system, or if the electromagnetic sensor is designed to scan a surface using structured illumination. Furthermore, the method according to the invention offers great flexibility, as various recording parameters can be determined based on the position of the anatomical landmark.

[0010] The landmark can be, in particular, a body region of the patient, such as the head, eyes, thorax, chest, legs, or a single knee joint. In at least one embodiment of the invention, determining the position of the landmark also includes determining the relative position of several identified landmarks to one another. Furthermore, the identity and position of other landmarks can be deduced from already identified landmarks whose positions have been determined. For example, the position and orientation of the thorax can be used to determine the position of the heart or a lung.

[0011] The method according to the invention comprises calculating a patient model based on the three-dimensional contour for the visual representation of the patient. Such a patient model can be easily modified; for example, the corresponding visual representation can be taken from different angles, so that a user of an imaging system according to the invention or a treating person can take the information of the three-dimensional contour into account when planning the scan or further treatment.

[0012] The method according to the invention comprises highlighting the identified landmark in the image of the patient. This provides the user of an imaging system according to the invention or a treating person with additional information about the identity and position of the landmark in a particularly intuitive manner.

[0013] The method according to the invention comprises providing a graphical user interface with a button, wherein the button represents the identified landmark and is designed to trigger the determination of the value of the acquisition parameter through user interaction. Furthermore, the button is designed to trigger the acquisition of the X-ray image through user interaction. This allows the method according to the invention to be carried out particularly intuitively and quickly, and the X-ray acquisition to be started particularly intuitively and quickly.

[0014] According to a further aspect of the invention, determining the value of the acquisition parameter comprises the automatic selection of a retrievable, stored value of an acquisition parameter based on the identity and / or the position of the anatomical landmark. Such determination by automatic selection allows, in particular, the simultaneous selection of multiple acquisition parameters and thus entire scan protocols through classification.

[0015] According to an advantageous aspect of the invention, the acquisition parameter includes the applied dose for acquiring the X-ray image. The applied dose can be determined because the three-dimensional contour of the scanned surface allows the patient's X-ray absorption to be calculated along the various irradiation directions. In particular, the applied dose can be determined as a function of the projection angle, a type of angle-dependent adjustment of the applied dose also known as dose modulation. An advantage of the present invention over conventional dose modulation methods is that the patient's contour can be determined with exceptional accuracy, thus providing a wealth of information for calculating the dose. Furthermore, dose modulation can be achieved by modulating the emitted intensity of the X-ray radiation.The intensity values ​​are achieved, for example, by controlling the X-ray source, i.e., by controlling the current or voltage of an X-ray tube.

[0016] According to a further advantageous aspect of the invention, the acquisition parameter includes the volume of a contrast agent for contrast-enhanced X-ray imaging. This is because the volume of contrast agent to be administered also depends on the patient's body weight. The patient's three-dimensional contour allows for a direct determination of the patient's body weight.

[0017] According to a particularly advantageous aspect of the invention, the acquisition parameter includes the position of the patient table for acquiring the X-ray image. If a specific area of ​​the patient is to be imaged, the position of this area can be determined using landmarks, particularly within the coordinate system of the patient table or an X-ray machine used for acquiring the image. According to the invention, the determination of the position of the patient table, especially the starting and ending positions, is particularly precise. Furthermore, this determination of the patient table's position is especially flexible, since the patient can be easily rescanned and the position of the patient table re-determined without radiation exposure if the patient moves.

[0018] According to a further advantageous aspect of the invention, the acquisition parameter includes the patient's orientation. This orientation specifically includes the relative orientation of the head and feet with respect to the path of the patient table. However, it also includes the patient's position, such as supine, right lateral, left lateral, prone, etc. The quick and easy determination of the patient's orientation or position allows for the particularly rapid and simple determination of other acquisition parameters, such as the dose to be administered. Furthermore, determining the orientation or position serves as a check to ensure that the patient is in the desired orientation or position.

[0019] According to a further advantageous aspect of the invention, the image is acquired through a tomographic scan using a CT scanner, wherein the CT scanner comprises an X-ray source rotatable about a system axis, the system axis centrally penetrating a region of the patient to be imaged in the specific position of the patient's table. This increases the homogeneity of the X-ray image quality and furthermore keeps the radiation exposure for the patient low while maintaining consistent image quality.

[0020] According to a further aspect of the invention, the image is acquired using a tomographic CT scanner, wherein the CT scanner has a tiltable gantry with an X-ray source rotatable about a system axis, wherein the anatomical landmark is a particularly radiosensitive area of ​​the patient's body, and wherein the acquisition parameter includes the tilt angle of the gantry, the tilt angle being determined such that the radiosensitive area of ​​the body is not, or only to a small extent, in the beam path of the X-ray source. This reduces the radiation exposure for the particularly radiosensitive area of ​​the patient's body.

[0021] Furthermore, the invention can be implemented in the form of an imaging system. The imaging system comprises an X-ray device, in particular a CT scanner with a tilting gantry, for acquiring an X-ray image of a patient lying on a patient table, as well as comprising at least one electromagnetic sensor, and a computer with a processing unit, wherein the processing unit is designed to carry out the method according to the invention by means of a computer program stored on a data carrier or in the computer's memory. The at least one electromagnetic sensor can, for example, be a stereo camera, a triangulation system, or a time-of-flight measurement system, or the electromagnetic sensor can be configured to scan a surface using structured illumination.The at least one electromagnetic sensor can be designed as a component of the CT scanner or positioned without a fixed connection to the CT scanner. Advantageously, the at least one electromagnetic sensor is positioned such that the depth information obtained by the contactless scanning is as homogeneous as possible.

[0022] The invention will now be described and explained in more detail with reference to the exemplary embodiments shown in the figures.

[0023] They show: Fig. 1 an exemplary imaging system according to the invention, Fig. 2 a flowchart of the method according to the invention, Fig. 3. An exemplary graphical user interface with a pictorial representation of a patient, Fig. 4 an exemplary imaging system according to the invention with a tiltable gantry.

[0024] Fig. Figure 1 shows an exemplary imaging system according to the invention, comprising a CT scanner. During the tomographic acquisition of an X-ray image, the patient 5 lies on a patient table 6, which is connected to a table base 16 such that the table base supports the patient table 6 with the patient 5. During the tomographic acquisition, the patient table 6 moves the patient 5 in spiral mode along a system axis 17 through the opening 18 of the gantry 19 of the CT scanner 7. During this movement, a plurality of projection images of a body part of the patient 5 are acquired. During the tomographic acquisition of an X-ray image, the X-ray detector 9 and the X-ray source 8, which interacts with the X-ray detector 9, move about the system axis 17. The X-ray source 8 and the X-ray detector 9 are arranged in a gantry 19 such that they are opposite each other and the X-rays 20 from the X-ray source 8 are detectable by the X-ray detector 9.The X-ray detector 9 of a CT device 7 shown here is a detector with multiple rows and columns.

[0025] Furthermore, the gantry 19 can be designed to tilt about an axis, in particular about an axis perpendicular to the system axis 17. In the embodiment of the invention shown here, the gantry 19 is tiltable about the tilting axis 14 extending through the system axis 17, wherein the tilting axis 14 is oriented parallel to the Earth's surface and perpendicular to the system axis 17. A tiltable gantry 19 is understood to be a gantry 19 in which at least the rotatable part of the gantry 19, which also includes the X-ray source 8 and the X-ray detector 9, is designed to tilt. The rotatable part of the gantry 19 is also referred to as the "drum". Furthermore, the CT scanner can have a frame 24 in which at least a part of the gantry 19 is mounted to tilt.

[0026] An X-ray detector 9 is typically designed as a scintillator counter, in which the high-energy X-ray photons are converted into low-energy photons in the optical spectrum by means of a scintillator and subsequently detected by means of a photodiode. Alternatively, the X-ray detector 9 can be designed as a direct-converting detector, which directly converts the high-energy X-ray photons into an electrical signal current by means of internal photoexcitation using a semiconductor material, utilizing the photovoltaic principle. The X-ray source 8 is typically an X-ray tube; however, other X-ray sources 8 suitable for tomographic imaging can also be used.

[0027] In another embodiment, the CT scanner 7 has two interacting pairs of X-ray source 8 and X-ray detector 9, making the CT scanner 7 particularly suitable for multi-energy imaging. In an alternative embodiment, not shown here, the X-ray scanner is a C-arm X-ray scanner. A different type of X-ray source 8 and a different type of X-ray detector 9 can be used in a C-arm X-ray scanner. For example, a flat-panel detector can be used as the X-ray detector 9. The X-ray radiation from a computed tomography scanner 7 or a C-arm X-ray scanner typically has a fan, pyramid, or cone shape. The shaping of the X-ray radiation is typically achieved by means of an aperture system.

[0028] In addition, the embodiment of the CT device 7 shown here also has a contrast agent injector 11 for injecting contrast agent into the patient's 5 bloodstream. This allows the X-ray image to be acquired using a contrast agent in such a way that, for example, the patient's 5 vessels, in particular the heart chambers of the beating heart, can be visualized with increased contrast. Contrast agents are generally understood to be agents that improve the visualization of bodily structures and functions in imaging procedures. Within the scope of this application, contrast agents include both conventional contrast agents such as iodine and tracers such as... 18 F, 11 C or 19 To understand N.

[0029] Furthermore, the imaging system according to the invention has at least one electromagnetic sensor 31, which is designed for contactless scanning of at least a part of the surface of the patient 5. An electromagnetic sensor 31 is designed for the detection of electromagnetic radiation, in particular for the detection of electromagnetic radiation in a low-frequency spectral range compared to X-rays, for example, in the visible or infrared spectral range. The electromagnetic sensor 31 can thus be one or more cameras or video cameras. In the example shown here, the electromagnetic sensor 31 is a 3D camera mounted on the gantry, which is designed, for example, as a stereo camera or as a time-of-flight camera.In a further embodiment of the invention, the electromagnetic sensor 31 is configured to scan a surface using structured illumination. In this embodiment, the imaging system additionally includes an illumination unit for generating structured illumination of at least a portion of the patient's surface 5. Furthermore, in this case, the electromagnetic sensor 31 and the illumination unit are positioned and configured in their emission and detection properties such that the electromagnetic sensor 31 is designed to detect the radiation reflected from the surface of the patient 5.

[0030] In a further embodiment of the invention, the electromagnetic sensor 31 is fixedly integrated into the gantry 19 of the CT scanner 7. In an alternative embodiment, the electromagnetic sensor 31 is integrated into the rotatable part of the gantry 19 in such a way that the electromagnetic sensor 31 rotates with the X-ray source 8 or with the X-ray detector 9 during the acquisition. This allows the surface of the patient 5 to be scanned particularly easily and quickly from different perspectives. The additional surface information enables the three-dimensional contour of the scanned surface to be calculated with particular precision, so that the method according to the invention can also be carried out particularly easily, quickly, and precisely.

[0031] The electromagnetic sensor 31 can also be positioned elsewhere in the room where the CT scanner 7 is located; for example, it can be mounted on or suspended from the ceiling, or placed on a positioning device such as a tripod. For instance, the electromagnetic sensor 31 can be positioned centrally above the patient 5 or centrally above the patient table 6. It is generally advantageous if the electromagnetic sensor 31 is positioned in such a way that the quality of the depth information about the scanned surface of the patient 5, and thus also the quality of the three-dimensional contour, is as homogeneous as possible. The noise or error of depth information acquired by scanning or subsequently calculated contour information should depend as little as possible on the depth or contour information itself or on the position of the scanned area.

[0032] To determine the appropriate value of the acquisition parameter for a patient 5, the imaging system according to the invention, in the embodiment shown here, comprises a first computer 15 on which a plurality of values ​​of various acquisition parameters are stored and can be retrieved, or which the computer 15 can access via a network. According to the invention, the computer 15 is designed to retrieve at least one value of an acquisition parameter into its internal memory. Furthermore, the computer 15 is equipped with a processing unit 22, wherein the computer 15 is designed to load a computer program into its internal memory. The computer program comprises instructions readable by the computer 15 and is itself part of a computer program product. For example, the computer program product can be stored on a computer-readable medium 21.The instructions of the computer program, which are readable by the computer 15, are designed to carry out the method according to the invention when the instructions are executed on the computer 15.

[0033] The computer-readable medium 21 can be, for example, a DVD, a USB stick, a hard drive, or a floppy disk. The computer 15 is connected to an output unit 13, for example, for the graphical output of tomographic images. The output unit 13 is, for example, one (or more) LCD, plasma, or OLED screen(s). Furthermore, the computer 15 is connected to an input unit 4. The input unit 4 serves, for example, to confirm a specific value of an acquisition parameter through user interaction and thus start the acquisition of the X-ray image. The input unit 4 is, for example, a keyboard, a mouse, a touchscreen, or a microphone for voice input.

[0034] The computing unit 22 can be implemented as either hardware or software. An interface enables the computing unit 22 to communicate with the CT scanner 7. In the embodiment shown here, the computing unit 22, or computer 15, has further interfaces for communicating with the input unit 4 or an output unit 13. These interfaces are commonly known hardware or software interfaces, such as PCI bus, USB, or FireWire hardware interfaces.

[0035] Fig. Figure 2 shows a flowchart of the method according to the invention. The method according to the invention for determining at least one value of at least one acquisition parameter for an X-ray image of a patient 5 lying on a patient table 6 uses, in step S1, the contactless scanning of at least a part of the surface of the patient 5 by means of at least one electromagnetic sensor 31 in order to calculate the three-dimensional contour of the scanned surface without additional radiation exposure in step S2. In step S3, at least one anatomical landmark of the patient 5 is identified based on the three-dimensional contour. Common methods for identifying a landmark are, for example, so-called "support vector machines" or so-called "point cloud" techniques. In step S4, the position of the anatomical landmark in the coordinate system of the patient table 6 is determined.The value of the recording parameter can be determined in step S5 based on the position of the anatomical landmark.

[0036] The position of the anatomical landmark in the coordinate system of the patient table 6 can be easily determined if a correlation is known between the coordinate system of the data acquired by the electromagnetic sensor 31 by scanning and the coordinate system of the patient table 6 or the CT scanner 7. Such a correlation can be determined by a calibration that precedes the method according to the invention.

[0037] The method according to the invention comprises, in step S6, the calculation of a patient model based on the three-dimensional contour for the visual representation of the patient; in step S7, the highlighting of the identified landmark in the visual representation of the patient 5; and in step S8, the provision of a graphical user interface 23 with a button, wherein the button represents the identified landmark and is designed to trigger the determination of the value of the acquisition parameter through user interaction. In a further embodiment, the button in step S9 is designed to trigger the acquisition of the X-ray image through user interaction. This allows the method according to the invention to be carried out particularly intuitively and quickly, and the X-ray acquisition to be started particularly intuitively and quickly.

[0038] An advantage of the invention is that, if the patient 5 is moved or repositioned, the corresponding values ​​for the acquisition parameters can be easily and quickly recalculated. The method according to the invention can be used both to prepare for the acquisition of a topogram in order to define the scan area along the system axis 17 for a topogram. It is also suitable for replacing the acquisition of a topogram for planning the acquisition of a diagnostic X-ray image.

[0039] The following embodiment of the invention can be applied to the acquisition of a tomographic X-ray image using a CT scanner 7 following the inventive method. The contour of the patient 5 and information about the anatomical landmark or the patient model are used to determine a value for a reconstruction parameter for reconstructing the X-ray image from the individually acquired projections. The reconstruction parameter can, for example, be information about the surface of the patient 5, which simplifies the determination of the patient's surface in the image to be reconstructed. Furthermore, the reconstruction center can be determined depending on the position of the patient 5 or a landmark.If part of the area of ​​patient 5, which is actually to be recorded, lies outside the scanning area of ​​the CT device 7, so that only an incomplete data set is available for this area, a reconstruction can be carried out in the extended measurement field taking into account the information about the surface of patient 5.

[0040] In another embodiment of the invention, information about the patient's surface 5 and about landmarks is used to improve the value of a processing parameter for downstream image processing. For example, the determined patient model is used to pass the spatial location of organs such as the lungs or the heart to an algorithm, for example, a segmentation algorithm. Currently, image processing algorithms often have to start without initial information, which causes problems, especially when information is missing or incomplete. By providing additional or initial information that cannot be obtained from the X-ray projections, the method according to the invention offers the advantage of more reliable and faster image reconstruction and image processing.

[0041] In further embodiments, individual or even all steps of the method according to the invention can be executed automatically. "Automatic" in the context of this application means that the respective step is carried out independently by a computer 15, and essentially no user interaction with the computer 15 is necessary for the respective step. In other words, the computational activity underlying the steps essential to the invention is performed by the computer 15 or by the computing unit 22. The user only needs to confirm the results calculated in the individual steps according to the invention or perform intermediate steps. In further embodiments of the invention with "fully automatic" steps, no user interaction with the computer 15 is necessary at all to carry out these steps essential to the invention.Regardless of whether the individual steps are performed "automatically" or "fully automatically," the method according to the invention can be part of a workflow that additionally requires user interaction. This user interaction can consist of the user manually selecting a class of scan protocols and / or a clinical question, for example, from a menu presented by the computer 15.

[0042] Fig. Figure 3 shows an example graphical user interface with a pictorial representation of a patient. In one variant, the pictorial representation of patient 5 can be based on a patient model calculated from the three-dimensional contour. In a second variant, the pictorial representation of patient 5 can also be a direct reproduction of an image of patient 5 captured with a camera. In the second variant, the identified landmark can be displayed or highlighted by marking or emphasizing an area within the reproduced image of patient 5. Alternatively, the reproduced image of patient 5 can be overlaid with a virtual representation of the landmark, which is particularly advantageous if the landmark is located within the patient's body, for example, an internal organ.

[0043] The graphical user interface 23 can be displayed on an output unit 13 by means of a computer 15. In the embodiment shown here, the invention is designed to provide a graphical user interface 23 with buttons 1, 2, 7, and 10, each button representing an identified landmark. In the example shown here, four different landmarks have been identified: head, eyes, thorax, and heart. When a button is activated by user interaction, step S5, i.e., determining the value of the acquisition parameter, is triggered. In a further embodiment of the invention, the button is designed to trigger the acquisition of the X-ray image through user interaction. Such user interaction can be performed, for example, by selecting with a graphic pointer or on a so-called "touchscreen."

[0044] In various embodiments of the invention, the landmarks displayed in the graphical user interface 23 can be highlighted in different ways. For example, the landmarks can assume a specific color value or a specific brightness value. Furthermore, the corresponding highlighting features, such as color and brightness, can also change after user interaction. Additionally, a specific highlighting feature can also provide specific information about the respective landmark. For example, an arm positioned outside the scanning area of ​​the CT scanner 7 can be highlighted with a warning feature. Such a warning feature can be implemented, for example, by highlighting the respective landmark in red or by making the landmark flash. Furthermore, the highlighting feature can also change after the value of the acquisition parameter has been determined.If a specific value of the recording parameter is above or below a certain threshold, the relevant landmark can be highlighted with a warning feature. Furthermore, highlighting can also include marking the landmark, for example, with a graphic symbol displayed next to or overlaid on the landmark.

[0045] Fig.Figure 4 shows an exemplary imaging system according to the invention with a tiltable gantry. In one embodiment of the invention, the image acquisition is a tomographic image acquired using a CT scanner 7, wherein the CT scanner 7 has a tiltable gantry 19 with an X-ray source rotatable about a system axis, and wherein the anatomical landmark is a particularly radiation-sensitive area of ​​the patient 5. Such a particularly radiation-sensitive area could be, for example, the gonads or the eyes 12. In such a case, the acquisition parameter includes the tilt angle of the gantry 19, the tilt angle being determined such that the radiation-sensitive area is not, or only to a small extent, in the beam path of the X-ray source 8. This reduces the radiation exposure for the particularly radiation-sensitive areas of the patient 5.

[0046] In the example shown here, the landmark "head" is identified in step S2. The acquisition parameter is then the angle by which the tiltable part 25 of the gantry 19 is to be tilted about a tilting axis 14 for the subsequent acquisition. The tiltable part of the gantry is mounted in a frame 24. In step S5, the value of the corresponding angle is then determined so that the X-rays 20 emitted by the X-ray source 8 do not penetrate the eyes 12 of the patient 5, or only to a negligible extent. Furthermore, in the embodiment shown here, the value for the position of the patient table 6 is determined as a further acquisition parameter, with the patient table 6 being supported by a table base 16 designed as a foot.

[0047] In one embodiment of the invention, a warning is issued when the specified value for the recording parameter exceeds or falls below a limit value. Such a limit value can be predefined by a user, or it can be stored in the internal memory of the computer 15 and be retrievable. A computer program according to the invention compares the specified value with the stored value to perform the method according to the invention. Furthermore, a warning can be issued when the limit value is exceeded or fallen below, and this warning can be audible, visual, or otherwise. For example, the value specified according to the invention for the angle of the tiltable part 25 of the gantry 19 can be greater than the maximum angle by which the tiltable part of the gantry 19 can be tilted.Furthermore, the method according to the invention can analyze the position of the landmark, for example the head or the eyes 12, and suggest a repositioning of the patient 5 or the identified landmark. For example, an output can be generated with the suggestion "Turn head further to the left" or "Lower head further towards chest".

Claims

[1] Method for determining at least one value of at least one imaging parameter for an X-ray image of a patient (5) lying on a patient bed (6), comprising - S1: contactless scanning of at least part of the patient's surface (5) using at least one electromagnetic sensor (31), - S2: Calculating the three-dimensional contour of the scanned surface, - S3: Identify at least one anatomical landmark of the patient (5) using the three-dimensional contour, - S4: Determining the position of the anatomical landmark in the coordinate system of the patient bed (6), as well as - S5: Determining the value of the recording parameter based on the position of the anatomical landmark, - S6: Calculating a patient model based on the three-dimensional contour for the pictorial representation of the patient (5), - S7: Highlighting the identified landmark in the patient's image (5), - S8: Providing a graphical user interface (23) with a button (1,2,7,10) wherein the button (1,2,7,10) represents the identified landmark, wherein the button (1,2,7,10) is designed to trigger the determination of the recording parameter value through user interaction. [2] Method according to claim 1, wherein the button (1,2,7,10) is designed to trigger the acquisition of the X-ray image through user interaction. [3] Method according to one of claims 1 to 2, wherein determining the value of the recording parameter comprises the automatic selection of a retrievable stored value of a recording parameter based on the identity and / or the position of the anatomical landmark. [4] Method according to any one of claims 1 to 3, wherein the acquisition parameter comprises the dose to be applied for the acquisition of the X-ray image. [5] Method according to any one of claims 1 to 4, wherein the recording parameter comprises the volume of a contrast medium for contrast-enhanced X-ray imaging. [6] Method according to any one of claims 1 to 5, wherein the recording parameter comprises the position of the patient bed (6) for recording the X-ray image. [7] Method according to any one of claims 1 to 6, wherein the recording parameter comprises the orientation of the patient (5). [8] Method according to claim 6, wherein the recording is a tomographic recording using a CT device, wherein the CT device comprises an X-ray source (8) rotatable about a system axis (17), wherein in the determined position of the patient table (6) the system axis (17) centrally penetrates an area of ​​the patient (5) to be recorded. [9] Method according to any one of claims 1 to 8, wherein the recording is a tomographic recording using a CT device, wherein the CT device has a tiltable gantry (19) with an X-ray source (8) rotatable about a system axis (17), wherein the anatomical landmark is a particularly radiosensitive area of ​​the patient's body (5), wherein the recording parameter includes the tilt angle of the gantry (19), wherein the tilt angle is determined such that the radiosensitive area of ​​the body is not or only to a small extent in the beam path of the X-ray source (8). [10] Imaging system comprising an X-ray device for taking an X-ray image of a patient (5) lying on a patient bed (6), and comprising at least one electromagnetic sensor (31), and comprising a computer (15) with a computing unit (22), wherein the computing unit (22) is designed to carry out a method according to one of claims 1 to 7 by means of a computer program stored on a data carrier (21) or on the memory of the computer (15). [11] Imaging system comprising a CT device for tomographic acquisition of an X-ray image, wherein the CT device has a tiltable gantry (19) with an X-ray source (8) rotatable about a system axis (17), wherein the imaging system comprises at least one electromagnetic sensor (31) and a computer (15) with a computing unit (22), wherein the computing unit (22) is designed to carry out a method according to one of claims 8 or 9 by means of a computer program stored on a data carrier (21) or on the memory of the computer (15). [12] Imaging system according to claim 10 or 11, wherein the at least one electromagnetic sensor (31) is configured in the form of a stereo camera or a triangulation system or a time-of-flight measurement system, or wherein the electromagnetic sensor (31) is configured by means of structured illumination for scanning a surface.

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