Preparation of an MR elastography with an MR elastography device

Abstract

The invention relates to a method for preparing an MR elastography of a liver according to the following method steps: - Creating a photographic image of an object under investigation, - Determination of the position of the liver based on the photograph, - Providing information regarding a target position of a vibration generator based on the position of the liver, - Positioning the vibration generator on the object under investigation depending on the information regarding the target position, - Introducing the examination object with the vibration generator into a patient receiving area of a magnetic resonance device, - Acquisition of overview MR image data of the examination subject, - Selection of an examination region for transverse slices covering at least a partial area of the liver for acquisition of MRE image data based on the overview MR image data.

Description

[0001] The invention relates to a method and an MR elastography device for preparing an MR elastography of a liver of an examination subject.

[0002] In a magnetic resonance scanner, the body of a subject to be examined, particularly a patient, is typically exposed to a relatively high main magnetic field, for example, 1.5 or 3 Tesla, using a main magnet. During magnetic resonance imaging (MR imaging), gradient pulses are generated using a gradient coil unit. In addition, high-frequency radio-frequency pulses (RF pulses), particularly excitation pulses, are then emitted via a radio-frequency antenna unit using suitable antenna devices. This causes the nuclear spins of certain atoms resonantly excited by these RF pulses to be tilted by a defined flip angle relative to the magnetic field lines of the main magnetic field. During the relaxation of the nuclear spins, radio-frequency signals, so-called magnetic resonance signals (MR signals), are emitted, which are received by suitable radio-frequency antennas and then further processed.The desired image data can then be reconstructed from the raw data acquired in this way. For a specific measurement, a specific magnetic resonance control sequence (MR control sequence) must be transmitted. This sequence consists of a sequence of radiofrequency pulses, such as excitation pulses and refocusing pulses, as well as coordinated gradient pulses emitted in different gradient axes along different spatial directions. Readout windows are set to match this timing, specifying the time periods during which the induced magnetic resonance signals are acquired.

[0003] MR elastography (MRE) exploits the fact that the phase of magnetic resonance signals changes as a result of mechanical waves acting on the object under examination. The extent of this change depends on the deflection (i.e., the displacement from the rest position) of the tissue as a result of the mechanical waves. Thus, information about certain mechanical parameters of the tissue, such as elasticity, can be derived from the MR phase images, i.e., images that depict the phase of nuclear magnetization. MRE is therefore a non-invasive method for quantifying the elasticity and stiffness of tissue. In addition to a conventional magnetic resonance scanner, MRE requires an oscillation generator to generate the mechanical waves, particularly in the examination area of the object.The vibration generator can, for example, comprise a flexible membrane, as described in US7034534B2, which is excited to vibrate by acoustic energy. The vibration generator can be designed as a gravitational vibration generator, as described, for example, in US20230305090A1.

[0004] The generation, acquisition and / or recording of MRE image data from an examination area comprises a transmission of mechanical waves into the examination area using a vibration generator and a time-coordinated MR imaging using a magnetic resonance device comprising a generation of magnetic resonance signals in the examination area, an acquisition of corresponding raw data and reconstruction thereof into image data, such image data being referred to as MRE image data.

[0005] MRE of the liver is particularly relevant for the non-invasive diagnosis of chronic liver diseases, fibrosis, and inflammation. The liver typically has its maximum spatial extent approximately parallel to the transverse axis of the examination subject. This region of the liver is of particular interest within the scope of MRE, so MRE image data must be acquired from this area, the examination region, within the scope of MRE. In MRE imaging of the liver, this examination region is typically covered by transverse slices, which must be positioned according to the position and anatomy of the liver and surrounding organs. Furthermore, such an arrangement of the vibration generator on the body surface of the examination subject must ensure that the mechanical waves generated by the vibration generator penetrate the examination region, particularly the spatial extent of the transverse slices.Thus, for MRE, especially for MRE of the liver, coordinated and precise positioning of the transverse slices for MR imaging and the vibration generator on the body surface is essential. US20240090823A1 discloses a method for the enhanced interpretation of shear wave elastography using two imaging modalities. DE102005001325A1 discloses a method for aligning a graphic object on an overview image of an object, which defines parameters for subsequent imaging of at least parts of the object.

[0006] The invention is based on the object of providing a particularly simple and robust method for preparing and performing an MRE of the liver using an MR elastography device. This object is achieved by the features of the independent claims. Advantageous embodiments are described in the subclaims.

[0007] The method according to the invention for preparing an MR elastography of a liver of an examination subject with an MR elastography device comprising a vibration generator and a magnetic resonance device having a patient receiving area provides the following method steps: - producing a photographic image of at least part of the object under investigation, - Determination of the position of the liver based on the photograph, - Providing information regarding a target position of the vibration generator based on the position of the liver, - Positioning the vibration generator on the object under investigation depending on the information regarding the target position, - Bringing the examination object with the vibration generator into the patient admission area, - Acquisition of overview MR image data of the examination subject, - Selection of an examination region for transverse slices covering at least a partial area of the liver for acquisition of MRE image data based on the overview MR image data.

[0008] During the photographic recording, at least the upper body of the subject is typically captured. The photographic recording typically captures the body surface of the subject.

[0009] Determining the position of the liver typically involves analyzing the body surface depicted in the photograph. Based on externally recognizable features such as joints, shoulders, arms, and / or the position of the neck, the position of the liver can be extracted, estimated, and / or approximated.

[0010] Providing information regarding a target position of the vibration generator based on the position of the liver typically comprises determining the information regarding the target position of the vibration generator. The target position of the vibration generator preferably corresponds to the optimal position of the vibration generator on the body surface of the examination subject. The target position of the vibration generator is typically arranged laterally on the upper body, in particular laterally on the thorax, wherein a transverse plane of the liver includes an intersection area with the target position of the vibration generator. The information regarding the target position of the vibration generator can comprise the target position of the vibration generator itself. The information regarding the target position of the vibration generator can comprise a position of the liver, in particular a center point, for example in the longitudinal direction, of the liver.Based on the position of the liver, i.e., based on such information, the actual target position of the vibration generator can be derived. In particular, the vibration generator can be positioned on the examination subject depending on the position of the liver.

[0011] Arranging the vibration generator on the examination subject based on the information regarding the target position typically involves arranging the vibration generator at the target position. If the information regarding the target position indirectly encompasses the target position, arranging the vibration generator on the examination subject can involve extracting the target position from the information regarding the target position. Arranging the vibration generator on the examination subject typically involves securing the vibration generator to the body surface of the examination subject, for example, by means of a belt. The vibration generator is preferably arranged such that it has direct contact with the skin of the examination subject.

[0012] Overview MR image data is typically acquired using a magnetic resonance imaging scanner. Overview MR image data typically includes MR image data in a coronal orientation. The spatial resolution of overview MR image data is typically lower than the spatial resolution of diagnostic image data such as MRE image data.

[0013] The selection of the examination region typically includes a selection of transverse slices. The examination region is preferably subdivided into transverse slices. There may be a gap between adjacent transverse slices within the examination region. Adjacent transverse slices within the examination region may be directly adjacent to one another.

[0014] The method steps within the scope of the method according to the invention for preparing an MR elastography are therefore preferably carried out before performing an MRE. In particular, the examination subject and the vibration generator are positioned for the acquisition of MRE image data, and the examination region is selected to suit and individually match the examination subject. In particular, the method according to the invention enables automated specification of a correct position of the vibration generator and automated selection of the examination region, thus enabling standardized preparation and performance of an MRE of the liver. Furthermore, typically only the actual positioning of the vibration generator on the examination subject is carried out manually, depending on a specific specification, the information provided regarding a target position of the vibration generator.This enables a simple and robust method for preparing an MRE and reduces the likelihood of incorrect positioning of the vibration generator and / or the examination area, making MRE preparation particularly time-efficient. In particular, the positions of the vibration generator and the examination area can be well coordinated and individually tailored to the location of the liver of the subject being examined. This procedure is particularly easy to perform and independent of the medical staff's experience.

[0015] One embodiment of the method provides that the selection of the examination area takes into account at least one of the following properties: - Exclusion of the lungs from the examination area, - Coverage of a transverse plane of the liver with maximum spatial extent parallel to the transverse axis of the object under examination.

[0016] A transverse plane of the liver with maximum spatial extent parallel to the transverse axis of the subject typically encompasses the maximum lateral extent of the liver. The liver is typically located distally, particularly inferiorly, to the lung.

[0017] The examination region is preferably a cuboid-shaped area distal to the lung. The examination region is preferably selected such that the lung is outside the examination region. This is advantageous for subsequent acquisition of MR signals, particularly MRE image data, since the air and thus the missing tissue within the lung impairs the quality of the MR signals due to susceptibility. Excluding the lung from the examination region reduces artifacts in the MRE image data. In addition, the position of the transverse plane ensures comprehensive information regarding the elasticity of the entire organ.

[0018] One embodiment of the method provides that the examination area is selected based on landmarks.

[0019] The landmarks preferably comprise at least one of the following liver segments and / or positions within the liver: dome of the liver, right liver lobe, left liver lobe, laterale segment, quadrate lobe, caudate lobe, anterior segment, and posterior segment. The landmarks may also comprise features of other organs, such as the position and / or location of the lungs. Alternatively and / or in addition to the landmarks, a segmentation of the liver may be taken into account when selecting the examination region. The selection of the examination region may comprise a segmentation of the overview MR image data with regard to the liver, wherein the segmented liver may be taken into account when selecting the examination region. Such a selection of the examination region is easily automated and can be carried out robustly and repeatably by an algorithm.

[0020] One embodiment of the method provides that the examination region is selected using a first trained function. This embodiment typically comprises providing the first trained function. The first trained function can, for example, comprise a neural network and / or a U-network and / or a convolutional neural network. The first trained function can be designed to identify landmarks and / or organs and / or a position of the arranged vibration generator in the overview MR image data and to determine an optimal position and spatial extent of the examination region and / or a position, orientation, thickness and / or number of transverse slices. The first trained function is preferably applied to the overview MR image data. The first trained function can optionally be designed to take the photographic image into account.According to this embodiment, the examination region and / or the transverse slices are preferably output as the result of the first trained function. Such a selection of the examination region is easily automated and can be applied individually for each examination object.

[0021] According to the invention, a patient model is additionally provided, wherein the position of the liver is determined taking the patient model into account.

[0022] The patient model typically comprises at least one correlation between a photographic image of an examination subject, in particular its body surface, and a position and / or location and / or spatial extent of the liver. The patient model can also comprise a position and / or location and / or spatial extent of other organs. According to the invention, the patient model comprises a correlation between external features, in particular features externally recognizable in photographic images, such as a position of the neck, shoulder, hip and / or hands, and a position and / or location and / or spatial extent of the liver. The patient model can be generated and / or provided using a third trained function. In particular, an artificial neural network can have been used to generate the patient model.Such a determination of the position of the liver takes into account individual characteristics of the object under investigation, in particular due to the photographic image, and is easily automatable and can be carried out robustly and repeatably by an algorithm.

[0023] An embodiment of the method additionally comprises providing a second trained function, wherein the determination of the position of the liver is carried out using the second trained function. The second trained function typically comprises a correlation between a position and / or location and / or spatial extent of the liver and a photographic image of an examination subject. In particular, the second trained function can be combined and / or integrated with the patient model. The second trained function can, for example, comprise a neural network and / or a U-network and / or a convolutional neural network. Such a determination of the position of the liver takes into account individual properties of the examination subject, in particular based on the photographic image, and is easily automated and can be precisely executed by an algorithm.

[0024] An embodiment of the method provides that the magnetic resonance device comprises a marking device and a patient support device to support positioning of the examination subject in the patient receiving area, the examination object is positioned at least partially outside the patient receiving area on the patient support device during the photographic recording, and the provision of information regarding a target position of the vibration generator comprises a visualization of the position of the liver and / or the target position of the vibration generator by marking the position of the liver and / or the target position of the vibration generator on the body surface of the examination subject by means of a marking device.

[0025] The marking device can comprise a laser. The marking device can be designed to optically mark, in particular by means of a photon beam, the position of the liver on the body surface. The marking device can be designed to mark the center of the liver and / or the center of the liver along the longitudinal axis of the body of the examination subject. The patient support device can be designed to displace the examination subject along the longitudinal axis of the magnetic resonance scanner as part of marking the position of the liver on the body surface. In particular, if the marking device is typically used as part of isocentric positioning of the examination subject, it can be designed to provide only a vertical marking.The patient positioning device can perform a horizontal displacement of the examination object along the longitudinal axis of the magnetic resonance device in the horizontal direction and is thus designed together with the marking device for marking the position of the liver.

[0026] The coordinate of the longitudinal axis of the liver position typically corresponds to the coordinate of the longitudinal axis of the target position of the vibration generator. The coordinate of the transverse axis of the target position of the vibration generator is typically determined by the lateral extent of the rib cage. Preferably, the target position of the vibration generator is located laterally on the rib cage at the level of the liver, typically on the side of the rib cage facing the right lobe of the liver. This target position of the vibration generator is clearly identifiable for medical personnel when the position of the liver is marked, so that the vibration generator can be clearly positioned at its target position.This embodiment of the method preferably uses a marking device typically available on the magnetic resonance device for other purposes to mark the position of the liver and thus to provide information regarding a target position of the vibration generator.

[0027] One embodiment of the method provides for the photographic image to be generated using a 3D camera. Photographic images captured using a 3D camera provide a spatial impression and can enable the determination of a depth map. A 3D camera can therefore capture a surface in three dimensions, allowing the body surface of the subject to be determined with particular precision. Based on such a photographic image, the position of the liver can be determined with particular precision, according to the invention.

[0028] One embodiment of the method provides for the generation of the photographic image to be time-resolved. In particular, a camera designed as a video camera, preferably a 3D camera designed as a video camera, enables a time-resolved image of the examination object. According to this embodiment, the positioning of the vibration generator on the examination object depending on the information regarding the target position preferably takes place at least partially simultaneously with a time-resolved photographic image of the examination object. This enables continuous monitoring and continuous comparison of the current position of the vibration generator during positioning at the target position with the provided target position of the vibration generator. This reduces the probability of incorrect positioning of the vibration generator within the scope of the method according to the invention.

[0029] One embodiment of the method provides that the magnetic resonance device has a display unit, and the provision of information regarding a target position of the vibration generator a representation of the photographic recording and a representation of the target position of the vibration generator on the display unit.

[0030] The display unit typically comprises a monitor and / or a display. The photographic image is preferably shown on the display unit as soon as it is created and / or with a delay of less than 5 seconds. The photographic image is preferably acquired in a time-resolved manner and shown continuously on the display unit. The target position of the vibration generator is preferably shown superimposed on the photographic image. The information regarding a target position of the vibration generator is preferably provided while the examination subject is positioned on the patient support device and with which patient support device it is introduced into the patient receiving area of the magnetic resonance scanner, typically without active movement of the examination subject.This embodiment enables continuous monitoring of the process of positioning the oscillator at the target position specified for the oscillator through a visual representation of the oscillator and the target position specified for the oscillator on the display unit. This embodiment provides medical personnel positioning the oscillator on the examination subject with continuous feedback regarding the position of the oscillator, thus avoiding the need to reposition the oscillator and / or acquire erroneous MRE image data.

[0031] One embodiment of the method provides that the representation of the photograph includes a visualization in at least two viewing directions, in particular two views. The display unit can be segmented and / or subdivided so that the target position for the vibration generator can be displayed in two views, thus better supporting navigation for positioning the vibration generator. In particular, the display unit can visualize a frontal and lateral view of the examination object and the target position of the vibration generator. This enables particularly precise positioning of the vibration generator.

[0032] An embodiment of the method additionally comprises - determining a comparison result by analyzing the overview MR image data with regard to a position of the oscillator relative to the liver, and - Output of a note regarding repositioning of the vibration generator depending on the comparison result.

[0033] According to the invention, the overview MR image data is acquired after the oscillation generator has been positioned at its target position. The oscillation generator is preferably configured such that it emits MR signals that are recognizable in image data, in particular in overview MR image data, at least for an algorithm and / or visually. Analysis of the overview MR image data with regard to a position of the oscillation generator relative to the liver typically comprises determining a position of the oscillation generator and a position of the liver in the overview MR image data. In particular, based on the position of the liver extracted from the overview MR image data, an updated target position of the oscillation generator can be determined, and this can be compared with the position of the oscillation generator.In the event of deviations, particularly deviations greater than a threshold, the repositioning notification may include a request to reposition the vibration generator. This allows for repositioning of the vibration generator before performing the actual MRE, particularly before acquiring the MRE image data.

[0034] One embodiment of the method provides that - the determination of the comparison result is a determination of a difference between a position of the vibration generator and a position of the liver in the longitudinal direction, and - the output of the note a length indication for a displacement of the vibration generator in the longitudinal direction, According to this embodiment, the comparison result comprises a difference between the positions of the oscillator and the liver in the longitudinal direction. The output of the indication typically comprises providing the difference, optionally dependent on a threshold value. The indication regarding repositioning can comprise an indication of an offset by which the oscillator is to be moved in the longitudinal direction. Medical personnel can reposition the oscillator according to the specified offset. This enables particularly precise repositioning.

[0035] One embodiment of the method additionally comprises performing MR elastography using the MR elastography device, comprising acquiring MRE image data of the examination region and synchronously controlling the vibration generator. For this purpose, the magnetic resonance scanner is typically controlled according to an MR control sequence, and synchronously, the examination region is exposed to mechanical waves and / or vibrations generated by the vibration generator. A vibration generator positioned according to the invention enables particularly homogeneous penetration of the selected examination region, which covers the relevant areas of the liver. Such acquired MRE image data are particularly diagnostically meaningful.

[0036] Furthermore, the invention is based on an MR elastography device comprising - a vibration generator designed to generate mechanical waves, - a magnetic resonance imaging device designed to acquire overview MR image data and MRE image data, - a camera designed to produce a photographic image, - a determination unit configured to determine a position of a liver based on the photograph, and - a provision unit designed to provide information regarding a target position of a vibration generator, in particular based on the position of the liver, - a selection unit trained to select an area of investigation.

[0037] The MR elastography device according to the invention is therefore designed to carry out a method according to the invention.

[0038] The determination unit, the provision unit, and the selection unit can be configured as part of a control unit and / or collectively referred to as a control unit. The determination unit, the provision unit, and the selection unit can be configured at least partially separately from one another and / or separately from a control unit.

[0039] The control unit typically has an input, a processor unit and an output.

[0040] The determination unit, the provision unit and / or the selection unit typically each have an input, a processor unit and an output and / or may have a connection to the input, the processor unit and / or the output of the control unit.

[0041] A photograph can be provided to the determination unit, and the position of the liver can be output by the determination unit. The provision unit is preferably designed to determine and provide information regarding a target position of a vibration generator based on the position of the liver. The selection unit is typically designed to provide the selected examination region. Additional functions, algorithms, or parameters required in the method can be provided to the control unit and / or determination unit and / or selection unit and / or provision unit via the input.

[0042] The control unit and / or determination unit and / or selection unit and / or provision unit can be integrated into the MR elastography device. The control unit and / or determination unit and / or selection unit and / or provision unit can also be installed separately from the MR elastography device. The control unit and / or determination unit and / or selection unit and / or provision unit can be connected to the MR elastography device.

[0043] Embodiments of the MR elastography device according to the invention are designed analogously to the embodiments of the method according to the invention. The MR elastography device can have further control components that are necessary and / or advantageous for carrying out a method according to the invention. The MR elastography device can also be designed to transmit control signals and / or receive and / or process control signals in order to carry out a method according to the invention. Computer programs and other software can be stored on a memory unit of the control unit, by means of which the processor unit of the control unit automatically controls and / or executes a method sequence of a method according to the invention.

[0044] A computer program product according to the invention can be loaded directly into a memory unit of a programmable control unit and has program code means for executing a method according to the invention when the computer program product is executed in the control unit. This allows the method according to the invention to be executed quickly, identically repeatably, and robustly. The computer program product is configured such that it can execute the method steps according to the invention by means of the control unit. The control unit must have the prerequisites, such as a corresponding main memory, a corresponding graphics card, or a corresponding logic unit, so that the respective method steps can be executed efficiently.The computer program product is stored, for example, on an electronically readable medium or on a network or server, from where it can be loaded into the processor of a local control unit, which can be directly connected to the MR elastography device or formed as part of the MR elastography device. Furthermore, control information of the computer program product can be stored on an electronically readable data carrier. The control information of the electronically readable data carrier can be configured such that, when the data carrier is used in a control unit of an MR elastography device, it carries out a method according to the invention. Examples of electronically readable data carriers are a DVD, a magnetic tape, or a USB stick on which electronically readable control information, in particular software, is stored.If this control information (software) is read from the data carrier and stored in a control unit of an MR elastography device, all embodiments of the methods described above can be carried out.

[0045] Furthermore, the invention is based on an electronically readable data carrier on which a program is stored which is intended to carry out a method according to the invention.

[0046] The advantages of the MR elastography device according to the invention, the computer program product according to the invention, and the electronically readable data carrier according to the invention essentially correspond to the advantages of the method according to the invention, which have been detailed above. Features, advantages, or alternative embodiments mentioned herein can also be applied to the other claimed subject matter, and vice versa.

[0047] Further advantages, features and details of the invention will become apparent from the exemplary embodiments described below and from the drawings.

[0048] They show: Fig. 1 shows a schematic representation of an MR elastography device according to the invention, Fig. 2 a flowchart of a first embodiment of a method according to the invention, Fig. 3 a flowchart of a second embodiment of a method according to the invention, Fig. 4 a flowchart of a third embodiment of a method according to the invention, and Fig. 5 a relative position of an examination area comprising transverse slices in a schematic representation.

[0049] Fig. 1 shows a schematic representation of an MR elastography device according to the invention. The MR elastography device comprises a magnetic resonance device 33. According to this embodiment, the magnetic resonance device 33 comprises a hollow cylindrical detector unit 31 enclosing, in particular concentrically surrounding, a cylindrical patient receiving area 40. The cylindrical patient receiving area 40 is designed to receive an examination subject 17. The examination subject 17 can be pushed into the patient receiving area 40 by means of a patient support device 16 of the magnetic resonance device 33. The patient support device 16 is designed to Examination object 17, in particular with the vibration generator 21, into the patient receiving area 40. The detector unit 31 typically comprises a main magnet (not shown in detail), a gradient coil unit (not shown in detail) and / or a radio-frequency antenna unit (not shown in detail) designed to emit excitation pulses.

[0050] The magnetic resonance scanner 33 has a control unit 32 for controlling the detector unit 31. The control unit 32 centrally controls the magnetic resonance scanner 33, for example, performing MR control sequences and thus generating and acquiring MR signals. Furthermore, the control unit 32 includes a reconstruction unit (not shown in detail) for reconstructing image data from the MR signals or raw data. The magnetic resonance scanner 33 is therefore configured, depending on the control of the vibration generator 21 and the detector unit 31, to acquire overview MR image data and MRE image data. The control unit 32 can have a display (not shown in detail) and an input unit (not shown in detail). Furthermore, the control unit 32 can be configured to evaluate MRE image data.

[0051] The MR elastography device additionally comprises a vibration generator 21 configured to generate mechanical waves. The vibration generator 21 can typically be flexibly positioned and / or fixed to the examination object 17 and / or the patient support device 16. The vibration generator 21 can be configured as a passive vibration generator. In the illustrated embodiment, the vibration generator 21 is controlled and / or activated by a vibration generator unit 30, for example, comprising a stepper motor. For this purpose, the vibration generator 21 is connected to the vibration generator unit 30 via a connector 28. The connector 28 can be configured as a flexible rotary supply line.

[0052] The MR elastography device additionally comprises a camera 18 configured to generate a photographic image. In the illustrated case, the camera 18 is arranged at the longitudinal end of the housing of the detector unit 31. The camera 18 can also be freely positioned in space. The camera 18 typically has a detection range directed at the examination subject 17, wherein the camera 18 can record a photographic image within the detection range. The camera 18 can be configured as a video camera and thus for recording time-resolved photographic images. The camera 18 can alternatively and / or additionally be configured as a 3D camera, i.e. for three-dimensional recording of the body surface of the examination subject 17.

[0053] In the illustrated case, the magnetic resonance device 33 optionally additionally comprises a marking device 19. The marking device 19 typically comprises a laser, which particularly assists in positioning the examination object 17. Thus, the The examination object 17, when at least partially positioned outside the patient receiving area 40, can be brought into a position such that the area of the examination object 17 to be examined is marked by the marking device 19 and is then automatically introduced into an optimal position in the patient receiving area 40. According to one embodiment of the invention, the marking device 19 can be used to visualize a position of the liver 12 by marking the position 20 of the liver 12 on the body surface of the examination object 17 as part of the provision of information regarding a target position of the vibration generator 21.

[0054] In the illustrated case, the magnetic resonance scanner 33 optionally additionally comprises a display unit 38. The display unit 38 is designed to display the photographic image of the examination subject 17 and, at the same time, to visualize a target position 22 of the vibration generator 21, for example by superimposition. In particular, the display of the photographic image of the examination subject 17 can also include a marking of a position 20' of the liver 12 on the photographic image. The display unit 38 can display the image in at least a first viewing direction 23, in particular for a first orientation. In addition, the display unit 38 can optionally display the image in at least a second viewing direction 23', i.e., a second orientation. The second viewing direction 23' is preferably perpendicular to the first viewing direction 23.

[0055] The illustrated magnetic resonance device 33 may, of course, include additional components that magnetic resonance devices 33 typically have. The general functioning of a magnetic resonance device 33 is also known to those skilled in the art, so a detailed description of the additional components is omitted.

[0056] The MR elastography device comprises a determination unit 34 configured to determine a position of a liver 12 based on the photographic image and a provision unit 35 configured to provide information regarding a target position of a vibration generator 21.

[0057] The MR elastography device also includes a selection unit 36 configured to select an examination region. The determination unit 34, the provision unit 35, and the selection unit 36 can be configured as part of the control unit 32 of the magnetic resonance scanner 33.

[0058] The MR elastography device is accordingly designed to carry out a method according to the invention, wherein only the method step 140 comprising the arrangement of the vibration generator 21 on the examination object 17 is to be carried out manually depending on the information regarding the target position.

[0059] The control unit 24, and in particular the determination unit 34, the provision unit 35, and the selection unit 36, also have computer programs and / or software that can be loaded directly into a memory unit (not shown in detail) of the control unit 24, with program means for carrying out a method according to the invention when the computer programs and / or software are executed in the control unit 24. For this purpose, the control unit 24 has a processor (not shown in detail) that is designed to execute the computer programs and / or software. Alternatively, the computer programs and / or software can also be stored on an electronically readable data carrier 14 that is designed separately from the control unit 24, wherein data access from the control unit 24 to the electronically readable data carrier 14 can take place via a data network.The MR elastography device is thus designed together with the control unit 24 to carry out a method according to the invention.

[0060] A method according to the invention can also be in the form of a computer program product that implements the method on the control unit 24 when it is executed on the control unit 24. Likewise, an electronically readable data carrier 14 with electronically readable control information stored thereon can be provided, which comprises at least one such computer program product as just described and is configured such that it carries out the described method when the data carrier 14 is used in a control unit 24 of an MR elastography device.

[0061] Fig. 2 shows a flowchart of a first embodiment of a method according to the invention for preparing an MR elastography of a liver 12 of an examination subject using an MR elastography device, wherein the MR elastography device comprises a vibration generator 21 and a magnetic resonance device 33 having a patient receiving area 40.

[0062] The method provides, with method step 110, the generation of a photographic image of at least a portion of the examination object 17. Method step 110 is typically carried out using the camera 18. In method step 120, a position of the liver 12 is determined based on the photographic image. Method step 120 is typically carried out using the determination unit 34. Method step 130 comprises the provision of information regarding a target position of the vibration generator 21 based on the position of the liver 12. Method step 130 is typically carried out using the provision unit 35.

[0063] In the following method step 140, the vibration generator 21 is arranged on the examination subject 17 depending on the information regarding the target position. Method step 140 is typically performed manually by medical personnel. Method step 150 provides for the introduction of the examination subject 17 with the vibration generator 21 into the patient receiving area 40. Method step 150 is typically performed using the patient support device 16. In method step 160, overview MR image data of the examination subject 17 is acquired. Method step 160 is typically performed by the magnetic resonance scanner 33 and in particular the detector unit 31.

[0064] In the following method step 170, an examination region 11 for transverse slices 10 covering at least a partial region of the liver 12 is selected for acquisition of MRE image data based on the overview MR image data. This method step 170 typically takes landmarks into account. Method step 170 is typically executed by means of the selection unit 36.

[0065] Fig. Figure 3 shows a flowchart of a second embodiment of a method according to the invention. The second embodiment differs from the one shown in Fig. 2, in particular by the additional method steps 121, 131, 132, 171, wherein the additional method steps 121, 131, 132, 171 can also be carried out independently of one another.

[0066] Method step 121 comprises the provision of a patient model, which is taken into account in method step 120 when determining the position of the liver 12. Method step 171 comprises the provision of a trained function, which is taken into account in method step 170 when Selection of the study area 11 is taken into account.

[0067] The provision of information regarding a target position of the vibration generator 21 based on the position of the liver 12 according to method step 130 can be carried out according to method step 131 and / or method step 132. Method step 131 requires a marking device 19 and a patient support device 16 to support positioning of the examination subject 17 in the patient receiving area 40, and that the examination subject 17 is arranged on the patient support device 16 at least partially outside the patient receiving area 40 during the photographic recording. Method step 131 provides for the visualization of a position of the liver 12 by marking the position 20 of the liver 12 on the body surface of the examination subject 17 by means of the marking device 19. Method step 132 requires a display unit 38, on which, according to method step 132, a representation of the photographic recording and a representation of the target position 22 of the vibration generator 21.

[0068] Fig. Figure 4 shows a flowchart of a third embodiment of a method according to the invention. The third embodiment differs from the one shown in Fig. 2, in particular by the additional method steps 180, 182, 190, wherein at least method step 190 can also be carried out independently of the other two. Method step 180 provides that the overview MR image data generated in method step 160 are analyzed with regard to a position of the vibration generator 21 relative to the liver 12, wherein a comparison result is determined. This can be done, for example, by determining a difference between a position of the vibration generator 21 and a position of the liver 12 in the overview MR image data in the longitudinal direction. Optionally, in method step 182, an indication can be output, in particular comprising a length specification for a displacement of the vibration generator 21 in the longitudinal direction, regarding a repositioning of the vibration generator 21 depending on the comparison result.Finally, in method step 190, MR elastography is performed, wherein the MR elastography device is used to record MRE image data of the examination area 11 and to control the vibration generator 21 in a time-coordinated manner.

[0069] Fig.Figure 5 shows a relative position of an examination region 11 of an examination object 17 comprising transverse slices 10 in a schematic representation. The examination region 11 is selected such that the lung 13 lies outside the examination region 11, and the lung 13 is therefore not covered by the transverse slices 10. The liver 12 of the examination object 17, however, is covered by the examination region 11 at the position in the longitudinal direction of the examination object 17, at which position the liver 12 has the maximum spatial extent parallel to the transverse axis of the examination object 17. Furthermore, a target position 22 for the vibration generator 21 is marked in this figure.

[0070] Although the invention has been illustrated and described in detail by the preferred embodiments, the invention is not limited to the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention. Regardless of the grammatical gender of a particular term, this includes persons of male, female, or other gender identities.

Claims

[1] Method for preparing an MR elastography of a liver of an examination subject with an MR elastography device comprising a vibration generator and a magnetic resonance device having a patient receiving area according to the following method steps: - Provision of a patient model comprising a correlation between externally recognizable features on photographic images and a position and / or location and / or spatial extent of the liver, - producing a photographic image of at least part of the object under investigation, - Determination of the position of the liver based on the photographic image and taking into account the patient model, - Providing information regarding a target position of the vibration generator based on the position of the liver, - Positioning the vibration generator on the object under investigation depending on the information regarding the target position, - Bringing the examination object with the vibration generator into the patient admission area, - Acquisition of overview MR image data of the examination subject, - Selection of an examination region for transverse slices covering at least a partial area of the liver for acquisition of MRE image data based on the overview MR image data. [2] Method according to claim 1, wherein the selection of the examination area takes into account at least one of the following properties: - Exclusion of the lungs from the examination area, - Coverage of a transverse plane of the liver with maximum spatial extent parallel to the transverse axis of the object under examination. [3] Method according to one of the preceding claims, wherein the selection of the examination area is based on landmarks. [4] Method according to one of the preceding claims, wherein the selection of the examination region is carried out using a first trained function. [5] Method according to one of the preceding claims, additionally comprising a provision of a second trained function, where the position of the liver is determined using the second trained function. [6] Method according to one of the preceding claims, wherein the magnetic resonance device comprises a marking device and a patient support device for supporting positioning of the examination object in the patient receiving area, the examination object is positioned at least partially outside the patient receiving area on the patient support device during the photographic recording, and the provision of information regarding a target position of the vibration generator comprises a visualization of the position of the liver and / or the target position of the vibration generator by marking the position of the liver and / or the target position of the vibration generator on the body surface of the examination subject by means of a marking device. [7] Method according to one of the preceding claims, wherein the photographic image is generated by means of a 3D camera. [8] Method according to one of the preceding claims, wherein the production of the photographic image is time-resolved. [9] Method according to one of the preceding claims, wherein the magnetic resonance device has a display unit, and the provision of information regarding a target position of the vibration generator a representation of the photographic recording and a representation of the target position of the vibration generator on the display unit. [10] Method according to claim 9, wherein the representation of the photographic image comprises a visualization in at least two viewing directions. [11] Method according to one of the preceding claims, additionally comprising - determining a comparison result by analyzing the overview MR image data with regard to a position of the oscillator relative to the liver, and - an output of a hint regarding the repositioning of the vibration generator depending on the comparison result. [12] Method according to claim 11, where - the determination of the comparison result is a determination of a difference between a position of the vibration generator and a position of the liver in the longitudinal direction, and - the output of the note a length indication for a displacement of the vibration generator in the longitudinal direction, include. [13] Method according to one of the preceding claims, additionally comprising carrying out the MR elastography by means of the MR elastography device comprising recording MRE image data of the examination area and a time-coordinated control of the vibration generator. [14] MR elastography device comprising a vibration generator designed to generate mechanical waves, a magnetic resonance imaging device designed to acquire overview MR image data and MRE image data, a camera designed to produce a photographic image, a determination unit configured to determine a position of a liver based on the photograph, and a provision unit designed to provide information regarding a target position of a vibration generator, a selection unit designed to select an examination area and thus designed to carry out a method according to one of the preceding claims.

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