Preparation of MR elastography with MR elastography device

Abstract

The invention relates to a method for preparing MR elastography of the liver according to the following method steps: generating a recording of the examination object, determining the position of the liver on the basis of the recording, providing information with respect to the target position of the vibration generator on the basis of the position of the liver, the vibration generator is arranged on the examination object according to the information of the target position, the examination object with the vibration generator is introduced into the patient accommodating area of the magnetic resonance apparatus, and summary MR image data of the examination object is detected. An examination region for covering a cross section of at least one sub-region of the liver is selected based on the summary MR image data to record MRE image data.

Description

TECHNICAL FIELD

[0001] The application relates to a method and to an MR elastography device for preparing an MR elastography of a liver of an examination object. BACKGROUND

[0002] In a magnetic resonance device, the body of an examination object, in particular a patient, to be examined is subjected to a relatively high main magnetic field, for example to a main magnetic field of 1.5 or 3 Tesla, by means of a main magnet. During magnetic resonance imaging (MR imaging), gradient pulses are emitted by means of gradient coil units. Additionally, a high-frequency radio frequency pulse (HF pulse), in particular an excitation pulse, is then transmitted via a radio frequency antenna unit by means of a suitable antenna device, which causes the nuclear spins of the atoms resonantly excited by the HF pulse to flip by a defined flip angle with respect to the field lines of the main magnetic field. In the case of nuclear spin relaxation, a radio frequency signal, the so-called magnetic resonance signal (MR signal), is emitted, which is received by means of a suitable radio frequency antenna and then further processed. Finally, the desired image data can be reconstructed from the raw data thus acquired. For a specific measurement, therefore, a specific magnetic resonance control sequence (MR control sequence) should be transmitted, which consists of a series of radio frequency pulses, for example excitation pulses and refocusing pulses, and gradient pulses to be transmitted in coordination with this, matched to the different gradient axes in different spatial directions. A read window is set in time with this, which prescribes a period of time in which the induced magnetic resonance signal is detected.

[0003] At MR elastography (MRE), the fact is utilized that the phase of the magnetic resonance signal changes due to a mechanical wave acting on the examination object. The scale of the change depends on the displacement of the tissue due to the mechanical wave, that is to say the movement from the rest position. From the MR phase image, that is to say the image showing the phase of the nuclear magnetization, it is thus possible to derive information about specific mechanical parameters of the tissue, for example about the elasticity. MRE is thus a non-invasive method for quantifying the elasticity and stiffness of tissue. For MRE, in addition to the conventional magnetic resonance device, a vibration generator is additionally required for generating a mechanical wave, in particular in the examination region of the examination object. The vibration generator can comprise, for example, as described in US 7034534 B2, a flexible membrane which is excited to vibrate by means of acoustic energy. The vibration generator can be configured as a gravity vibration generator, as described, for example, in US 20230305090 A1.

[0004] The generating, acquiring and / or detecting of the MRE image data of the examination region comprises transmitting mechanical waves into the examination region according to the vibration generator and performing MR imaging in temporal coordination therewith according to the magnetic resonance device, said MR imaging comprising generating magnetic resonance signals in the examination region, acquiring corresponding raw data and reconstructing it into image data, wherein this image data is referred to as MRE image data.

[0005] MRE of the liver is of particular importance for non-invasive diagnosis of chronic liver diseases, fibrosis and inflammation. The liver typically has its largest spatial extension approximately parallel to the transversal axis of the examination object. In particular, said region of the liver is of interest in the course of MRE, so that MRE image data can be acquired in the course of MRE from said region, the examination region. Said examination region is typically covered by a transversal slice in the course of MRE imaging of the liver, wherein said transversal slice can be positioned according to the position and anatomy of the liver and also according to surrounding organs. Furthermore, it is ensured that the vibration generator is arranged at the body surface of the examination object in such a way that the mechanical waves generated by the vibration generator penetrate the spatial extension of the examination region, in particular the transversal slice. Thus, for MRE, in particular for MRE of the liver, a coordinated and precise positioning of the transversal slice for MR imaging and the vibration generator at the body surface is of importance. SUMMARY

[0006] The object underlying the present application is to specify a particularly simple and robustly applicable method for preparing and performing MRE of the liver by means of a MR elastography device. Said object is achieved by the present application. Advantageous design schemes are described in the following.

[0007] The method according to the present application for preparing MR elastography of the liver of an examination object by means of a MR elastography device, said MR elastography device comprising a vibration generator and a magnetic resonance device having a patient receiving region, proposes the following method steps:

[0008] - generating a photographic record of at least a portion of the examination object,

[0009] - determining the position of the liver on the basis of the photographic record,

[0010] - providing information in respect of a target position of the vibration generator on the basis of the position of the liver,

[0011] - arranging the vibration generator at the examination object in accordance with the information in respect of the target position,

[0012] - introducing the examination object with the vibration generator into the patient receiving region,

[0013] - detecting summary MR image data of the examination object,

[0014] - selecting a cross-sectional examination region for recording MRE image data based on the summary MR image data covering at least one sub-region of the liver.

[0015] Typically, at least the upper body of the examination object is detected during the photographic recording. The photographic recording typically detects the body surface of the examination object.

[0016] Determining the position of the liver typically comprises analyzing the body surface imaged on the photographic recording. The position of the liver can be extracted and / or estimated and / or approximated based on features identifiable on the outside, such as for example the position of joints, shoulders, arms and / or neck.

[0017] Providing information in terms of the target position of the vibration generator based on the position of the liver typically comprises determining information in terms of the target position of the vibration generator. The target position of the vibration generator preferably corresponds to an optimal position of the vibration generator at the body surface of the examination object. The target position of the vibration generator is typically laterally arranged at the upper body, in particular at the thorax, wherein the cross-section of the liver comprises a sectional area with the target position of the vibration generator. The information in terms of the target position of the vibration generator can comprise the target position of the vibration generator itself. The information in terms of the target position of the vibration generator can comprise the position of the liver, in particular the midpoint of the liver, for example in the longitudinal direction. Based on the position of the liver, i.e. based on such information, the true target position of the vibration generator can be derived. In particular, the vibration generator can be arranged to the examination object in accordance with the position of the liver.

[0018] Arranging the vibration generator to the examination object in accordance with the information in terms of the target position typically comprises arranging the vibration generator at the target position. As long as the information in terms of the target position indirectly comprises the target position, arranging the vibration generator to the examination object can comprise extracting the target position from the information in terms of the target position. Arranging the vibration generator at the examination object typically comprises fixing the vibration generator at the body surface of the examination object, for example by means of a belt fixation. The vibration generator is preferably arranged such that it has a direct contact to the skin of the examination object.

[0019] The summary MR image data is typically detected by means of an acquisition of a magnetic resonance device. The summary MR image data typically comprises MR image data in a coronal orientation. The spatial resolution of the summary MR image data is typically smaller than the spatial resolution of diagnostic image data, such as for example MRE image data.

[0020] Selecting the examination region typically comprises selecting the cross-sectional examination region. The examination region is preferably subdivided into cross-sections. There can be gaps between adjacent cross-sections within the examination region. Adjacent cross-sections within the examination region can directly adjoin each other.

[0021] The method steps in the course of the method for preparing MR elastography according to the application are thus preferably performed before the MRE is performed. In particular, the positioning of the examination object and the vibration generator is used to record the MRE image data and to select the examination region for the examination object in matching and individualized fashion. In particular, the method according to the application enables the correct position of the vibration generator to be preset automatically and the examination region to be selected automatically, so that standardized preparation and performance of MRE of the liver is achieved. Furthermore, the actual setting of the vibration generator at the examination object is typically performed manually only on the basis of the specific preset, the information provided in respect of the target position of the vibration generator. This enables a simple and robustly executable method for preparing MRE to be achieved and reduces the probability of incorrect positioning of the vibration generator and / or the examination region, so that, in particular, the preparation of MRE can be performed time-efficiently. In particular, the position of the vibration generator and of the examination region can thus be well coordinated with one another and individualized in respect of the orientation of the liver of the examination object. The method can in particular be performed simply and independently of the experience of the medical personnel.

[0022] One embodiment of the method proposes that the selection of the examination region takes into account at least one of the following properties:

[0023] - exclusion of the lung from the examination region,

[0024] - covering a cross section of the liver having the greatest spatial extension parallel to the transverse axis of the examination object.

[0025] The cross section of the liver having the greatest spatial extension parallel to the transverse axis of the examination object typically comprises the greatest lateral extension of the liver. The liver is typically disposed distally, in particular inferiorly, of the lung.

[0026] The examination region is preferably a square region distal of the lung. The examination region is preferably selected such that the lung is outside the examination region. This is advantageous for the following recording of MR signals, in particular MRE image data, since air, and thus the tissue missing in the lung, impairs the quality of the MR signals. The exclusion of the lung from the examination region reduces artifacts in the MRE image data. Additionally, the position of the cross section comprises information in respect of the elasticity of the entire organ.

[0027] One embodiment of the method proposes that the selection of the examination region is based on a marker.

[0028] The landmarks preferably comprise at least one of the following segments and / or locations within the liver: hepatic dome, right liver lobe, left liver lobe, lateral segment, quadrate lobe, caudate lobe, anterior segment, posterior segment. The landmarks can also comprise features of other organs like e.g. locations and / or orientations of the lungs. Alternatively and / or additionally to the landmarks, segmenting the liver can be considered when selecting the examination region. Selecting the examination region can comprise segmenting the summary MR image data in respect of the liver, wherein the segmented liver can be considered when selecting the examination region. This selection of the examination region can be well automated and robustly and reproducibly performed by an algorithm.

[0029] One embodiment of the method proposes selecting the examination region using the trained first function. The embodiment typically comprises providing the trained first function. The trained first function can for example comprise a neural network and / or a U-Net and / or a convolutional neural network. The trained first function can constitute a means for identifying the landmarks and / or organs and / or locations of the vibration generator in the summary MR image data and determining the optimal location and spatial extension and / or the direction, orientation, thickness and / or number of the cross-sections of the examination region. The trained first function is preferably applied to the summary MR image data. The trained first function can optionally constitute a means for considering the photographic record. The examination region and / or the cross-sections are preferably output as a result of the trained first function according to the embodiment. This selection of the examination region can be well automated and individualized applied for each examination subject.

[0030] One embodiment of the method additionally comprises providing a patient model, wherein the location of the liver is determined considering the patient model.

[0031] The patient model typically comprises at least one association between the photographic record of the examination subject, in particular of its body surface, and the location and / or orientation and / or spatial extension of the liver. The patient model can also comprise the location and / or orientation and / or spatial extension of other organs. In particular, the patient model can comprise an association between the location of external features, in particular features which are externally identifiable on the photographic record, like e.g. the neck, the shoulder, the hip and / or the hand, and the location and / or orientation and / or spatial extension of the liver. The patient model can be generated and / or provided using a trained third function. In particular, an artificial neural network can be used for generating the patient model. This determination of the location of the liver considers individualized characteristics of the examination subject, in particular based on the photographic record, and can be well automated and robustly and reproducibly performed by an algorithm.

[0032] One embodiment of the method additionally comprises providing a trained second function,

[0033] wherein the position of the liver is determined using the trained second function. The trained second function typically comprises a correlation between the position and / or orientation and / or spatial extension of the liver and the recorded data of the examination object. In particular, the trained second function can be executed in combination and / or integrated with the patient model. The trained second function can for example comprise a neural network and / or a U- network and / or a convolutional neural network. This determination of the position of the liver takes into account individualized characteristics of the examination object, in particular based on the recorded data, and can be well-automated and accurately performed by an algorithm.

[0034] One embodiment of the method proposes that 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,

[0035] the examination object is at least partially arranged outside the patient receiving area on the patient support device during the recording of the data,

[0036] and providing the information on the target position of the vibration generator comprises visualizing 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 object by means of the marking device.

[0037] The marking device can comprise a laser. The marking device can be configured for optically marking the position of the liver on the body surface, in particular by means of a photon beam. The marking device can be configured for marking a midpoint of the liver and / or a center of the liver along a longitudinal axis of the body of the examination object. The patient support device can be configured for moving the examination object along a longitudinal axis of the magnetic resonance device during marking of the position of the liver on the body surface. In particular when the marking device is used typically during isocenter positioning of the examination object, the marking device can be configured only for vertical marking. The patient support device can perform a horizontal movement of the examination object along a longitudinal axis of the magnetic resonance device in a horizontal direction to thereby be configured together with the marking device for marking the position of the liver.

[0038] The coordinates of the longitudinal axis of the position of the liver typically correspond to the coordinates of the longitudinal axis of the target position of the vibration generator. The coordinates of the transversal axis of the target position of the vibration generator are typically determined by a transversal extension of the thorax. Preferably, the target position of the vibration generator is laterally at the thorax at the level of the liver, typically at the side of the thorax facing the right liver lobe. The target position of the vibration generator can be explicitly identifiable for a medical person when marking the position of the liver, so that the vibration generator can be explicitly arranged at its target position. The described embodiment of the method preferably uses the marking device, which is typically available at the magnetic resonance device for other purposes, for marking the position of the liver to thereby provide the information on the target position of the vibration generator.

[0039] One embodiment of the method proposes that the recording is generated by means of a 3D camera. The recording taken by means of the 3D camera has a spatial stereoscopic impression and makes it possible to determine a depth map. The 3D camera can therefore detect the body surface of the examination object stereoscopically, so that the position of the liver can be determined particularly precisely on the basis of this recording.

[0040] One embodiment of the method proposes that the recording is generated time-resolved. In particular, a camera configured as a video camera, preferably a 3D camera configured as a video camera, makes it possible to record the examination object time-resolved. The setting of the vibration generator to the examination object in accordance with the information in terms of the target position takes place, according to the embodiment, preferably at least partially simultaneously with the time-resolved recording of the examination object. This makes it possible to continuously monitor and continuously compare the current position of the vibration generator during the setting to the target position with the provided target position of the vibration generator. This reduces the probability of incorrect positioning of the vibration generator in the method according to the application.

[0041] One embodiment of the method proposes that the magnetic resonance device has a display unit,

[0042] and the provision of the information in terms of the target position of the vibration generator comprises the representation of the recording and the representation of the target position of the vibration generator on the display unit.

[0043] The display unit typically comprises a monitor and / or a display. The recording is preferably represented on the display unit as soon as it is generated and / or with a delay of less than 5 seconds. The recording is preferably detected time-resolved and continuously represented on the display unit. The target position of the vibration generator is preferably represented superimposed on the recording. Preferably, the information in terms of the target position of the vibration generator is provided during the positioning of the examination object on the patient support device and the introduction into the patient receiving region of the magnetic resonance device by means of the patient support device, typically without active movement of the examination object. The continuous monitoring of the process of setting the vibration generator at the target position predetermined for the vibration generator is achieved by visually representing the vibration generator and the target position predetermined for the vibration generator on the display unit. The embodiment gives the medical personnel setting the vibration generator at the examination object continuous feedback in terms of the position of the vibration generator, so that it is possible to avoid the need to reposition the vibration generator and / or to acquire incorrect MRE image data.

[0044] One embodiment of the method proposes that the representation of the photographic record comprises a visualization in at least two viewing directions, in particular two perspectives. The display unit can be segmented and / or subdivided, so that the target position for the vibration generator can be shown in both perspectives and navigation for positioning the vibration generator is better supported. In particular, the display unit can visualize a front view and a lateral view of the examination object and the target position of the vibration generator. This enables a particularly precise positioning of the vibration generator.

[0045] One embodiment of the method additionally comprises

[0046] - determining a comparison result by analyzing the summary MR image data with respect to the position of the vibration generator relative to the liver, and

[0047] - outputting an indication in terms of repositioning the vibration generator depending on the comparison result.

[0048] According to the application, the summary MR image data is recorded after the vibration generator is arranged at its target position. The vibration generator is preferably designed such that it emits an MR signal which is recognizable in the image data, in particular in the summary MR image data, at least for an algorithm and / or visually. Analyzing the summary MR image data with respect to the position of the vibration generator relative to the liver typically comprises determining the position of the vibration generator and the position of the liver in the summary MR image data. In particular, an updated target position of the vibration generator can be determined based on the position of the liver extracted from the summary MR image data and compared to the position of the vibration generator. In case of a deviation, in particular in case of a deviation greater than a threshold value, the indication in terms of repositioning can comprise a request to reposition the vibration generator. This enables repositioning the vibration generator before performing a true MRE, in particular before recording MRE image data.

[0049] One embodiment of the method proposes

[0050] - determining the comparison result comprises determining a difference of the position of the vibration generator and the position of the liver in the longitudinal direction, and

[0051] - outputting the indication comprises providing a length specification for moving the vibration generator in the longitudinal direction.

[0052] The comparison result according to the embodiment comprises a difference of the positions of the vibration generator and the liver in the longitudinal direction. Outputting the indication typically comprises providing the difference, optionally depending on a threshold value.

[0053] The indication in terms of repositioning can comprise a specification of a shift in order to move the vibration generator in the longitudinal direction by which shift. The medical person can reposition the vibration generator corresponding to the specified shift. This enables a particularly precise repositioning.

[0054] One embodiment of the method additionally comprises performing MR elastography by means of the MR elastography device, said performing MR elastography comprising recording MRE image data of the examination region and temporally coordinated actuation of the vibration generator. To this end, the magnetic resonance device is typically actuated in accordance with a MR control sequence and, in synchronism therewith, the examination region is subjected to mechanical waves and / or vibrations generated by means of the vibration generator. The vibration generator positioned in accordance with the application enables particularly uniform penetration of the selected examination region, which covers an important region of the liver. Such recorded MRE image data is particularly diagnostically compelling.

[0055] Furthermore, the application is based on a MR elastography device, said MR elastography device comprising

[0056] - a vibration generator, which is configured to generate mechanical waves,

[0057] - a magnetic resonance device, which is configured to detect summary MR image data and MRE image data,

[0058] - a camera, which is configured to generate a photographic recording,

[0059] - a determination unit, which is configured to determine a position of the liver on the basis of the photographic recording, and

[0060] - a provision unit, which is configured to provide information in respect of a target position of the vibration generator, in particular on the basis of the position of the liver,

[0061] - a selection unit, which is configured to select an examination region.

[0062] The MR elastography device according to the application is thus configured to perform the method according to the application.

[0063] The determination unit, the provision unit and the selection unit can be configured as part of the control unit and / or together be referred to as the control unit. The determination unit, the provision unit and the selection unit can be configured at least partially independently of one another and / or independently of the control unit.

[0064] The control unit typically has an input, a processor unit and an output.

[0065] The determination unit, the provision unit and / or the selection unit typically each have an input, a processor unit and an output and / or can have a connection to the input, the processor unit and / or the output of the control unit.

[0066] The determination unit can thus be provided with the shot record and the position of the liver output by the determination unit. The provision unit is preferably configured to derive and provide information on the target position of the vibration generator on the basis of the position of the liver. The selection unit is typically configured to provide the selected examination region. Via the input, the control unit and / or the determination unit and / or the selection unit and / or the provision unit can be provided with further functions, algorithms or parameters required in the method.

[0067] The control unit and / or the determination unit and / or the selection unit and / or the provision unit can be integrated into the MR elastography device. The control unit and / or the determination unit and / or the selection unit and / or the provision unit can also be installed independently of the MR elastography device. The control unit and / or the determination unit and / or the selection unit and / or the provision unit can be connected to the MR elastography device.

[0068] The embodiments of the MR elastography device according to the application are configured analogously to the embodiments of the method according to the application. The MR elastography device can have further control components which are necessary and / or advantageous for carrying out the method according to the application. The MR elastography device can also be configured to transmit control signals and / or to receive and / or to process control signals in order to carry out the method according to the application. On the memory unit of the control unit, a computer program and further software can be stored by means of which the processor unit of the control unit automatically controls and / or carries out the method flow of the method according to the application.

[0069] The computer program product according to the application can be directly loadable into the memory of a programmable control unit and has program code means which, when the computer program product is executed in the control unit, perform the method according to the application. The method according to the application can thus be performed quickly, identically and reproducibly and robustly. The computer program product is configured in such a way that it can perform the method steps according to the application by means of the control unit. The control unit must have the prerequisites here, such as, for example, a corresponding working memory, a corresponding graphics card or a corresponding logic unit, so that the respective method steps can be performed efficiently. The computer program product is stored, for example, on an electronically readable medium or on a network or server, from which the computer program product can be loaded into the processor of a local control unit, which can be connected directly to the MR elastography device or form part of the MR elastography device. Furthermore, the 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 designed in such a way that, when the data carrier is used, the control information performs the method according to the application in the control unit of the MR elastography device. Examples of electronically readable data carriers are DVDs, magnetic tapes or USB sticks, on which electronically readable control information, in particular software, is stored. When the control information (software) is read by the data carrier and stored in the control unit of the MR elastography device, all embodiments according to the application of the above-described method can be performed.

[0070] Furthermore, the application is based on an electronically readable data carrier, on which a program is stored, which is set up to perform the method according to the application.

[0071] The advantages of the MR elastography device according to the application, the computer program product according to the application and the electronically readable data carrier according to the application according to the application correspond essentially to the advantages of the method according to the application, which are stated in detail above. The features, advantages or alternative embodiments mentioned here can likewise be transferred to the other claimed subject matters and vice versa. BRIEF DESCRIPTION OF DRAWINGS

[0072] Further advantages, features and details of the application result from the embodiments described hereinafter and according to the drawings.

[0073] The drawings show:

[0074] Figure 1 a schematic diagram of an MR elastography device according to the application,

[0075] Figure 2 a flowchart of a first embodiment of the method according to the application,

[0076] Figure 3a flow chart showing a third embodiment of the method according to the application, and

[0077] Figure 4 a flow chart showing a third embodiment of the method according to the application, and

[0078] Figure 5 a schematic diagram showing the relative position of the examination region including the cross-section. DETAILED DESCRIPTION

[0079] Figure 1 a schematic diagram showing an MR elastography device according to the application. The MR elastography device comprises a magnetic resonance device 33. The magnetic resonance device 33 comprises according to the embodiment a hollow cylindrical probe unit 31 which encloses, in particular concentrically surrounds, a cylindrical patient receiving region 40. The cylindrical patient receiving region 40 constitutes a recording region for the examination object 17. The examination object 17 can be pushed into the patient receiving region 40 by means of a patient support device 16 of the magnetic resonance device 33. The patient support device 16 constitutes a device for introducing the examination object 17, in particular the examination object 17 with the vibration generator 21, into the patient receiving region 40. The probe 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, which constitutes a device for emitting excitation pulses.

[0080] For controlling the probe unit 31, the magnetic resonance device 33 has a control unit 32. The control unit 32 centrally controls the magnetic resonance device 33, as for example performs MR control sequences in order to generate and detect MR signals. Furthermore, the control unit 32 comprises a reconstruction unit, not shown in detail, for reconstructing image data from the MR signals, or raw data. Thus, according to the manipulation of the vibration generator 21 and the probe unit 31, the magnetic resonance device 33 constitutes a device for detecting summary 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 constitute a device for evaluating the MRE image data.

[0081] The MR elastography device additionally comprises a vibration generator 21 which constitutes a device for generating mechanical waves. The vibration generator 21 is typically flexibly positionable and / or can be fixed at the examination object 17 and / or the patient support device 16. The vibration generator 21 can be constituted as a passive vibration generator. The vibration generator 21 is in the shown embodiment manipulated and / or activated by means of a vibration generator unit 30, for example comprising a stepper motor. For this purpose, the vibration generator 21 is connected with the vibration generator unit 30 via a connector 28. The connector 28 can be constituted as a flexible rotary lead.

[0082] The MR elastography device additionally comprises a camera 18 which is configured to generate a photographic recording. The camera 18 is in the case shown arranged at a 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 area which is to be directed towards the examination object 17, wherein the camera 18 can record a photographic recording within the detection area. The camera 18 can be configured as a video camera and thus configured to record a temporally resolved photographic recording. The camera 18 can alternatively and / or additionally be configured as a 3D camera, i.e. configured to three-dimensionally detect a body surface of the examination object 17.

[0083] The magnetic resonance device 33 in the case shown optionally additionally comprises a marking device 19. The marking device 19 typically comprises a laser which supports in particular in positioning the examination object 17. Thus, the examination object 17 can be placed in such a position when positioned at least partially outside the patient accommodation region 40, such that a region of the examination object 17 which is to be examined is marked by the marking device 19 and subsequently automatically introduced into an optimal position in the patient accommodation region 40. The marking device 19 can be used according to one embodiment of the application to visualize the position of the liver 12 by marking the position 20 of the liver 12 on a body surface of the examination object 17 in the process of providing information in respect of the target position of the vibration generator 21.

[0084] The magnetic resonance device 33 in the case shown optionally additionally comprises a display unit 38. The display unit 38 is configured to show a photographic recording of the examination object 17 and at the same time to visualize the target position 22 of the vibration generator 21, for example by superimposition. In particular, showing a photographic recording of the examination object 17 can also comprise marking the position 20' of the liver 12 on the photographic recording. The display unit 38 can display in at least one first viewing direction 23, in particular for a first orientation. Additionally, the display unit 38 can optionally visualize the showing in at least one second viewing direction 23', i.e. a second orientation. The second viewing direction 23' is preferably configured perpendicular to the first viewing direction 23.

[0085] The magnetic resonance device 33 shown can obviously comprise further components which the magnetic resonance device 33 usually has. Furthermore, the general mode of operation of the magnetic resonance device 33 is known to the person skilled in the art, such that the further components do not have to be described in detail.

[0086] The MR elastography device comprises a determination unit 34 which is configured to determine the position of the liver 12 on the basis of the photographic recording and a provision unit 35 which is configured to provide information in respect of the target position of the vibration generator 21.

[0087] Furthermore, the MR elastography device comprises a selection unit 36 configured for selecting an examination region. The determination unit 34, the provision unit 35 and the selection unit 36 can be configured as part of a control unit 32 of the magnetic resonance device 33.

[0088] Thus, the MR elastography device is configured for performing the method according to the application, wherein only the method step 140 of providing the vibration generator 21 at the examination object 17 is performed manually according to the information in terms of the target position.

[0089] Furthermore, the control unit 24 and in particular the determination unit 34, the provision unit 35 and the selection unit 36 have a computer program and / or software which can be directly loaded into a not shown memory unit of the control unit 24, which has program means for performing the method according to the application when the computer program and / or software is executed in the control unit 24. The control unit 24 for this has a not shown processor which is designed for executing the computer program and / or software. Alternatively thereto, the computer program and / or software can also be stored on an electronically readable data carrier 14 which is configured separately from the control unit 24, wherein the data access of the electronically readable data carrier 14 by the control unit 24 can take place via a data network. Thus, the MR elastography device together with the control unit 24 is designed for performing the method according to the application.

[0090] The method according to the application can also be present in the form of a computer program product which implements the method on the control unit 24 when the method is executed on the control unit 24. Likewise, the electronically readable data carrier 14 can exist together with the electronically readable control information stored thereon, which comprises at least one such above-mentioned computer program product and is designed such that it executes the method in the control unit 24 of the MR elastography device in the case of use of the data carrier 14.

[0091] Figure 2 A flow chart showing a first embodiment of a method for preparing MR elastography of a liver 12 of an examination object by means of an MR elastography device is shown, wherein the MR elastography device comprises a vibration generator 21 and a magnetic resonance device 33 having a patient containing region 40.

[0092] The method proposes in a method step 110 generating a photographic record of at least a portion of the examination object 17. The method step 110 is typically performed by means of the camera 18. In a method step 120 the position of the liver 12 is determined on the basis of the photographic record. The method step 120 is typically performed by means of the determination unit 34. The method step 130 comprises providing information in respect of the target position of the vibration generator 21 on the basis of the position of the liver 12. The method step 130 is typically performed by means of the provision unit 35.

[0093] In a following method step 140 the vibration generator 21 is set to the examination object 17 in accordance with the information in respect of the target position. The method step 140 is typically performed manually by medical personnel. The method step 150 proposes introducing the examination object 17 with the vibration generator 21 into the patient accommodation region 40. The method step 150 is typically performed by means of the patient support device 16. In a method step 160 overview MR image data of the examination object 17 is detected. The method step 160 is typically performed by means of the magnetic resonance device 33 and in particular the detector unit 31.

[0094] In a following method step 170 the examination region 11 of the cross section 10 for covering at least one sub-region of the liver 12 is selected on the basis of the overview MR image data to record MRE image data. The method step 170 is typically performed taking into account the marker. The method step 170 is typically performed by means of the selection unit 36.

[0095] Figure 3 A flow chart of a second embodiment of the method according to the application is shown. The second embodiment differs from the first embodiment shown in Figure 2 in particular in the additional method steps 121, 131, 132, 171, wherein the additional method steps 121, 131, 132, 171 can also each be performed independently of one another. Figure 2 The method step 121 comprises providing a patient model, which is taken into account in the method step 120 in determining the position of the liver 12. The method step 171 comprises providing a trained function, which is taken into account in the method step 170 in selecting the examination region 11.

[0096]

[0097] ​The provision of information 21 in terms of a target position of the vibration generator based on the position of the liver 12 after the method step 130 can be performed in accordance with a method step 131 and / or a method step 132. The method step 131 requires the marking device 19 and the patient support device 16 for supporting the positioning of the examination object 17 in the patient receiving area 40 and for at least partially setting the examination object 17 outside the patient receiving area 40 on the patient support device 16 during the taking of the recording. The method step 131 proposes visualizing the position of the liver 12 by marking the position 20 of the liver 12 on the body surface of the examination object 17 by means of the marking device 19. The method step 132 requires the display unit 38 on which the recording is shown in accordance with the method step 132 and the target position 22 of the vibration generator 21 is shown.

[0098] Figure 4 A flow chart showing a third embodiment of the method according to the application is shown. The third embodiment differs from the first embodiment shown in Figure 2 particular in the additional method steps 180, 182, 190, wherein at least the method step 190 can also be performed independently from the other two method steps. The method step 180 proposes analyzing the summary MR image data generated in the method step 160 in terms of the position of the vibration generator 21 relative to the liver 12, wherein a comparison result is determined. This can be performed for example by determining the difference of the position of the vibration generator 21 in the longitudinal direction and the position of the liver 12 in the summary MR image data. Optionally, an indication in terms of a repositioning of the vibration generator 21 can be output in the method step 182 in accordance with the comparison result, in particular comprising an indication of a length specification for a movement of the vibration generator 21 in the longitudinal direction. Subsequently, the MR elastography imaging is performed in the method step 190, wherein the MRE image data of the examination region 11 is recorded by means of the MR elastography device and the vibration generator 21 is manipulated in time coordination.

[0099] Figure 5 A schematic diagram showing the relative position of the examination region 11 of the examination object 17 comprising the transverse layer 10 is shown. The examination region 11 is chosen such that the lung 13 is outside the examination region 11, the lung 13 is thus not covered by the transverse layer 10. In contrast, the liver 12 of the examination object 17 is covered by the examination region 11 at a position in the longitudinal direction of the examination object 17 at which the liver 12 has the largest spatial extension parallel to the transverse axis of the examination object 17. Furthermore, a target position 22 for the vibration generator 21 is marked in the diagram.

[0100] Although the details of the application have been described and illustrated with respect to preferred embodiments, the application is not limited to the disclosed examples and other variations can be deduced by the person skilled in the art without departing from the scope of the application. Irrespective of the grammatical gender of the specific terms, also persons with a male or female gender are included.

Claims

1. A method for preparing an MR elastography of the liver of an examination subject by means of an MR elastography system, the MR elastography system comprising a vibration generator and a magnetic resonance system having a patient receiving area, the method being performed according to the following method steps: - generating a recording of at least a portion of the object under examination, - determining the position of the liver based on the imaging record, - providing information on the target position of the vibration generator based on the position of the liver, - placing the vibration generator at the inspection object based on the information about the target position, - introducing the examination subject with the vibration generator into the patient accommodation area, - detecting summary MR image data of the examination object, - selecting an examination region for a transverse slice covering at least a subregion of the liver for acquiring MRE image data based on the summary MR image data.

2. The method according to claim 1, The selection of the inspection region takes into account at least one of the following characteristics: - excluding the lungs from the examination region, - covering a transverse section of the liver having a maximum spatial extent parallel to the transverse axis of the examination object.

3. The method according to any one of the preceding claims, The examination region is selected based on the marker.

4. The method according to any one of the preceding claims, The examination region is thereby selected using a trained first function.

5. The method according to any one of the preceding claims, The method additionally includes providing a patient model, The position of the liver is determined in this case taking into account the patient model.

6. The method according to any one of the preceding claims, The method additionally includes providing a trained second function, The position of the liver is thereby determined using the trained second function.

7. The method according to any one of the preceding claims, The magnetic resonance apparatus comprises a marking device and a patient support device for supporting the positioning of the examination subject in the patient receiving area. During the recording, the examination subject is arranged on the patient support device at least partially outside the patient receiving area, And providing information on the target position of the vibration generator includes visualizing 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.

8. The method according to any one of the preceding claims, The recordings are produced with the aid of a 3D camera.

9. The method according to any one of the preceding claims, The recordings are generated in a time-resolved manner.

10. The method according to any one of the preceding claims, The magnetic resonance system comprises a display unit. And providing the information on the target position of the vibration generator includes showing the photographing record and showing the target position of the vibration generator on a display unit.

11. The method according to claim 10, It is shown therein that the recording includes a visualization in at least two viewing directions.

12. The method according to any one of the preceding claims, The method additionally includes - determining a comparison result by analyzing the summary MR image data with respect to the position of the vibration generator relative to the liver, and - outputting an instruction for repositioning the vibration generator based on the comparison result.

13. The method according to claim 12, in - determining the comparison result comprises determining a difference between the position of the vibration generator and the position of the liver in the longitudinal direction, and - outputting the instruction includes a length specification for moving the vibration generator in the longitudinal direction.

14. The method according to any one of the preceding claims, The method additionally includes performing MR elastography by means of an MR elastography device, wherein the performing of the MR elastography includes recording MRE image data of the examination region and actuating the vibration generator in a temporally coordinated manner.

15. An MR elastography device, comprising A vibration generator configured to generate mechanical waves, a magnetic resonance system configured to detect summary MR image data and MRE image data, A camera configured to produce a photographic record, a determining unit configured to determine a position of the liver based on the imaging record, and providing a unit configured to provide information on a target position of the vibration generator, A selection unit configured to select an inspection area, The MR elastography device is thus designed to carry out the method according to one of the preceding claims.

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