Method for determining a position of at least one coil element of a radio-frequency coil that can be introduced into a patient receiving area of ​​a magnetic resonance device by means of an effective area with a similarity measure

Abstract

Method for determining a position of at least one coil element of a radio-frequency coil insertable into a patient receiving area of ​​a magnetic resonance device for a magnetic resonance measurement, comprising the following steps: - Playing back a magnetic resonance sequence by means of a radio-frequency antenna which is fixedly arranged within a scanner unit of the magnetic resonance device, - Acquiring first magnetic resonance data by means of the radio-frequency antenna and acquiring second magnetic resonance data by means of the at least one coil element of the radio-frequency coil, - determining first magnetic resonance images from the first magnetic resonance data and determining second magnetic resonance images from the first magnetic resonance data and the second magnetic resonance data, - Determining an effectiveness range of the at least one coil element of the radio-frequency coil from the first magnetic resonance images and the second magnetic resonance images, wherein the effectiveness range comprises a position of the at least one coil element of the radio-frequency coil, wherein a similarity measure (LCI) is calculated to determine the effectiveness range, wherein the similarity measure (LCI) comprises an average difference between all pixels of the first magnetic resonance image and all pixels of the second magnetic resonance image at a position of the at least one spatial direction.

Description

[0001] The present invention relates to a method for determining a position of at least one coil element of a radio-frequency coil that can be introduced into a patient receiving area of ​​a magnetic resonance device for a magnetic resonance measurement. Furthermore, the present invention relates to a magnetic resonance device comprising a scanner unit with a radio-frequency antenna, a patient receiving area, a local radio-frequency coil that can be introduced into the patient receiving area, and an evaluation unit, wherein the magnetic resonance device is configured to carry out the method for determining a position of at least one coil element of the radio-frequency coil that can be introduced into the patient receiving area.Furthermore, the invention is based on a computer program product which comprises a program and can be loaded directly into a memory of a programmable control unit, with program means for controlling a method for determining a position of at least one coil element of a radio-frequency coil which can be introduced into a patient receiving area of ​​a magnetic resonance device when the program is executed in the control unit, and an electronically readable data carrier on which a corresponding computer program is stored.

[0002] For various magnetic resonance examinations, it is helpful and / or a prerequisite to know the position of local radiofrequency coils and / or individual coil elements of the local radiofrequency coils. This is particularly important when multiple local radiofrequency coils and / or a local radiofrequency coil with multiple coil elements are positioned on the patient and these multiple local radiofrequency coils and / or these multiple coil elements are to be used for different measurements and / or different examination areas. If, for example, MR images of different organs are taken on a patient during a magnetic resonance examination, it is advantageous to activate only those local radiofrequency coils and / or only those coil elements that are spatially closest to the respective organ to be examined.However, when positioning the patient and / or the local radiofrequency coils, it is not immediately apparent which local radiofrequency coil, in particular which coil elements, are positioned particularly close to which organ.

[0003] In addition, methods are known for determining the position of a local radio-frequency coil. However, the center point of the local radio-frequency coil is usually only determined in the z-direction. However, such a position determination does not include information regarding orientation and / or extent in the y-direction and / or x-direction.

[0004] From DE 102 07 736 A1 a method is known for determining the position of at least one local antenna in an examination room of a magnetic resonance system, in which magnetic resonance signals emitted by a body arranged in the examination room are received spatially coded in at least one coordinate direction by the local antenna, spatially resolved intensity values ​​are generated from the received magnetic resonance signals in the coordinate direction and the position of the local antenna in the coordinate direction is determined from a course of the intensity values, which may have been subjected to post-processing, along the coordinate direction.

[0005] The present invention is based, in particular, on the object of providing an improved automatic determination and / or selection of a coil element and / or a local radio-frequency coil. This object is achieved by the features of the independent claims. Advantageous embodiments are described in the subclaims.

[0006] The invention is based on a method for determining a position of at least one coil element of a radio-frequency coil that can be introduced into a patient receiving area of ​​a magnetic resonance device for a magnetic resonance measurement, comprising the following steps: - Playing back a magnetic resonance sequence by means of a radio-frequency antenna which is fixedly arranged within a scanner unit of the magnetic resonance device, and - Acquiring first magnetic resonance data by means of the radio-frequency antenna and acquiring second magnetic resonance data by means of the at least one coil element of the radio-frequency coil, - determining first magnetic resonance images from the first magnetic resonance data and determining second magnetic resonance data from the first magnetic resonance data and the second magnetic resonance data, - Determining an effective range of the at least one coil element of the radio-frequency coil from the first magnetic resonance images and the second magnetic resonance images, wherein the effective range comprises a position of the at least one coil element of the radio-frequency coil.

[0007] The magnetic resonance device preferably comprises a medical and / or diagnostic magnetic resonance device that is designed and / or configured to acquire medical and / or diagnostic image data, in particular medical and / or diagnostic magnetic resonance image data, of a patient. The magnetic resonance device comprises the scanner unit. The scanner unit of the magnetic resonance device preferably comprises a detector unit, in particular a magnet unit, for acquiring the medical and / or diagnostic image data. The scanner unit, in particular the magnet unit, comprises a base magnet, a gradient coil unit, and a radio-frequency antenna. The radio-frequency antenna is fixedly arranged within the scanner unit.

[0008] The base magnet is designed to generate a homogeneous base magnetic field with a defined magnetic field strength, such as a magnetic field strength of 3 T or 1.5 T, etc. In particular, the base magnet is designed to generate a strong, homogeneous, and constant base magnetic field. The homogeneous base magnetic field is preferably arranged and / or located within a patient receiving area of ​​the magnetic resonance device. The gradient coil unit is designed to generate magnetic field gradients that are used for spatial encoding during imaging.

[0009] The patient receiving area is designed and / or configured to accommodate the patient, in particular the area of ​​the patient to be examined, for a medical magnetic resonance examination. For example, the patient receiving area is cylindrical and / or surrounded by the scanner unit in a cylindrical manner.

[0010] A field of view (FOV) and / or an isocenter of the magnetic resonance device is preferably arranged within the patient acquisition area. The FOV preferably comprises a detection region of the magnetic resonance device within which the conditions for detecting medical image data, in particular magnetic resonance image data, are present, such as a homogeneous basic magnetic field. The isocenter of the magnetic resonance device preferably comprises the region and / or point within the magnetic resonance device that has the optimal and / or ideal conditions for detecting medical image data, in particular magnetic resonance image data. In particular, the isocenter comprises the most homogeneous magnetic field region within the magnetic resonance device.

[0011] Furthermore, the magnetic resonance apparatus comprises a patient support device configured for positioning and / or supporting the patient for a magnetic resonance examination. The patient support device may comprise a patient table configured to be retractable into the patient receiving area. For a magnetic resonance examination, the patient is positioned on the patient table such that, after positioning the patient table within the patient receiving area, the area to be examined is arranged and / or positioned within the isocenter of the patient receiving area.

[0012] For a magnetic resonance examination, local radiofrequency coils are positioned on the patient, in particular around the area of ​​the patient to be examined. These local radiofrequency coils often have multiple coil elements that can be selected for acquiring magnetic resonance data based on their position relative to the body region to be examined. In particular, those coil elements of a local radiofrequency coil and / or the local radiofrequency coil for acquiring magnetic resonance data that are closest to the area to be examined should be selected. An example of a local radiofrequency coil with multiple coil elements is a local body coil. The local radiofrequency coils arranged on the patient are brought into the patient acquisition area, in particular into the isocenter, together with the patient for the magnetic resonance examination.

[0013] The method for determining a position of at least one coil element of a radiofrequency coil that can be inserted into the patient receiving area of ​​the magnetic resonance device is preferably performed before the planned magnetic resonance examination, so that the position of the at least one coil element can be determined for the planned and / or upcoming magnetic resonance examination. For this purpose, the patient, together with the local radiofrequency coil, is already located within the patient receiving area, in particular within the isocenter of the magnetic resonance device.

[0014] The magnetic resonance sequence used to determine the position of the at least one coil element can be any magnetic resonance sequence, such as a GRE sequence. The first magnetic resonance data are acquired exclusively using the radio-frequency antenna arranged fixedly within the scanner unit. The second magnetic resonance data are acquired exclusively with the at least one coil element of the radio-frequency coil, in particular the local radio-frequency coil. If the radio-frequency coil, in particular the local radio-frequency coil, has two or more coil elements, second magnetic resonance data can be acquired for each of the two or more coil elements, which second magnetic resonance data can be assigned to the respective coil element.

[0015] The first magnetic resonance images are acquired and / or determined exclusively from the first magnetic resonance data. The second magnetic resonance images are acquired and / or determined from both the first magnetic resonance data and the second magnetic resonance data. If the radio-frequency coil has multiple coil elements, different second magnetic resonance data are also acquired for the different coil elements, and the position determination is performed separately for each of the coil elements.

[0016] For determining and / or determining the first magnetic resonance images from the first magnetic resonance data and for determining and / or determining the second magnetic resonance images from the second magnetic resonance data, the magnetic resonance device has an evaluation unit configured to evaluate the acquired magnetic resonance data, in particular the first magnetic resonance data and the second magnetic resonance data. Preferably, the effective range of the at least one coil element of the radio-frequency coil is also determined from the first magnetic resonance images and the second magnetic resonance images using the evaluation unit.

[0017] The effective range of the at least one coil element of the radio-frequency coil is determined in particular in a location-dependent manner in at least one spatial direction, particularly advantageously in a location-dependent manner in all three spatial directions. To determine the effective range of the at least one coil element of the radio-frequency coil, the first magnetic resonance images are compared with the second magnetic resonance images in order to determine an influence of the at least one coil element of the radio-frequency coil in the magnetic resonance data. A comparison of the first magnetic resonance data with the second magnetic resonance data is preferably carried out in a location-dependent manner in at least one spatial direction. The effective range, in particular a location-dependent effective range, of the at least one coil element of the radio-frequency coil is then determined by the evaluation unit.For example, comparing the first magnetic resonance images and the second magnetic resonance images includes a difference between the first magnetic resonance images and the second magnetic resonance images to determine a match and / or a similarity between the first magnetic resonance images and the second magnetic resonance images.

[0018] The effective range indicates the positions at which a coil element of the local radio-frequency coil acquires magnetic resonance data in relation to the radio-frequency antenna of the scanner unit and / or in relation to a patient's anatomy. An effective range at a position in the at least one spatial direction for the at least one coil element only exists if the first magnetic resonance images differ from the second magnetic resonance images at this position in the at least one spatial direction. If no magnetic resonance data is acquired for a position in the at least one spatial direction by the at least one coil element of the local radio-frequency coil, the second magnetic resonance images are essentially the same as the first magnetic resonance images at this position in the at least one spatial direction, so that a location-dependent comparison of the first magnetic resonance images and the second magnetic resonance images does not reveal any significant difference.

[0019] The evaluation unit comprises at least one computing module and / or a processor. Thus, in particular, the evaluation unit is configured to execute computer-readable instructions for evaluating the acquired magnetic resonance data and determining the effective range. In particular, the evaluation unit comprises a memory unit, wherein computer-readable information is stored on the memory unit. The evaluation unit is configured to load the computer-readable information from the memory unit and execute the computer-readable information in order to evaluate the acquired magnetic resonance data and determine the effective range.

[0020] The components of the evaluation unit can predominantly be implemented as software components. In principle, however, these components can also be implemented partly in the form of software-supported hardware components, such as FPGAs or the like, particularly when particularly fast calculations are required. Likewise, the required interfaces, for example when only transferring data from other software components, can be implemented as software interfaces. However, they can also be implemented as hardware interfaces that are controlled by suitable software. Of course, it is also conceivable for several of the aforementioned components to be implemented together in the form of a single software component or software-supported hardware component.

[0021] The invention advantageously enables improved automatic determination and / or selection of a coil element and / or a local radio-frequency coil. In particular, a particularly precise position for the at least one coil element, in particular for each coil element, of the local radio-frequency coil that can be introduced into the patient receiving area can be determined in this way. This makes it possible to provide position information for the at least one coil element of the local radio-frequency coil for a magnetic resonance examination that goes beyond position information of a center point of the local radio-frequency coil. In addition, a user, in particular medical personnel, can also be advantageously supported in selecting the local radio-frequency coils and / or the individual coil elements for an upcoming magnetic resonance examination.For example, based on provided position information for the coil elements and / or the radio-frequency coils, it is particularly easy to select the coil element and / or those coil elements that have the shortest distance to the area of ​​the patient to be examined.

[0022] In an advantageous development of the method according to the invention, it can be provided that the effective range of the at least one coil element of the radio-frequency coil is determined location-dependently in at least one spatial direction. Preferably, the effective range of the at least one coil element of the radio-frequency coil is determined location-dependently in all three spatial directions. In this case, the acquisition of the first magnetic resonance data and the acquisition of the second magnetic resonance data comprises the acquisition of magnetic resonance data for a plurality of, preferably consecutive, slice images in the at least one spatial direction, preferably in all three spatial directions. In this case, N slice images are determined and / or acquired exclusively from the first magnetic resonance data of the radio-frequency antenna in at least one spatial direction.Preferably, N slice images are acquired and / or determined in each of the three spatial directions exclusively from the first magnetic resonance data of the radio-frequency antenna. The first magnetic resonance images comprise N slice images SliceBC_Z. n with 1 ≤ n ≤ N in z-direction, N slice images SliceBC_X n with 1 ≤ n ≤ N the N in x-direction and N slice images SliceBC_Y n with 1 ≤ n ≤ N in the y-direction.

[0023] Furthermore, N slice images are acquired and / or determined from the first magnetic resonance data of the radio-frequency antenna and the second magnetic resonance data of the at least one coil element of the radio-frequency coil in at least one spatial direction. Preferably, N slice images are acquired and / or determined in each of the three spatial directions from the first magnetic resonance data of the radio-frequency antenna and the second magnetic resonance data of the at least one coil element of the radio-frequency coil. The second magnetic resonance data comprise N slice images SliceLC_Z. n with 1 ≤ n ≤ N in z-direction, N slice images SliceLC_X n with 1 ≤ n ≤ N in x-direction and N slice images SliceBC_Y n with 1 ≤ n ≤ N in y-direction, where each of the N slice images SliceLC_Z n first magnetic resonance data and second magnetic resonance data at position z n includes each of the N slice images SliceLC_X nfirst magnetic resonance data and second magnetic resonance data at position x n and each of the N slice images SliceLC_Y n first magnetic resonance data and second magnetic resonance data at position y n includes.

[0024] This configuration enables a particularly precise determination of a position of the at least one coil element of the high-frequency coil in at least one spatial direction, preferably in all three spatial directions.

[0025] In an advantageous development of the method according to the invention, it can be provided that a similarity measure is calculated to determine the effective range, wherein the similarity measure comprises a mean difference between all pixels of a first magnetic resonance image and all pixels of a second magnetic resonance image at a position in at least one spatial direction. The similarity measure LCI is determined from a mean square difference between all pixels of a first magnetic resonance image and all pixels of a second magnetic resonance image as follows: LCI=∑r=1R∑c=1C(SliceBCr,c−SliceLCr,c)2

[0026] The first magnetic resonance images and the second magnetic resonance images each have R rows and C columns. The smaller the similarity measure, in particular the LCI value, the more similar the first and second magnetic resonance images are. The more similar the first magnetic resonance images and the second magnetic resonance images are, the smaller the influence of the at least one coil element of the radio-frequency coil on the acquisition of magnetic resonance data.

[0027] In this way, a measure for a deviation and / or for a similarity can advantageously be determined and thus also a measure for determining the effective range, in particular an extent and / or a position of the effective range, of the at least one coil element of the radio-frequency coil, in particular of the local radio-frequency coil, can be determined.

[0028] In an advantageous development of the method according to the invention, it can be provided that a minimum value in the similarity measure and a maximum value in the similarity measure are determined in at least one spatial direction and if a difference between the maximum value and the minimum value is smaller than a predetermined first threshold value, the effective range of the at least one coil element of the radio-frequency coil is set to the value zero.

[0029] In this case, a similarity measure LCI is preferably first determined from all first and second magnetic resonance images in one spatial direction. Subsequently, the minimum value in the similarity measure for one spatial direction is determined from the total similarity measures LCI, wherein the minimum value in the similarity measure comprises the smallest value for the similarity measure LCI from the total similarity measures LCI in one spatial direction. In addition, the maximum value in the similarity measure for one spatial direction is also determined from the total similarity measures LCI, wherein the maximum value in the similarity measure comprises the largest value for the similarity measure LCI from the total similarity measures LCI in one spatial direction. Preferably, a minimum value in the similarity measure and a maximum value in the similarity measure are determined for all three spatial directions.The predetermined first threshold value may, for example, comprise half the maximum value in the similarity measure or comprise further first threshold values ​​that appear appropriate to the person skilled in the art.

[0030] This advantageously makes it possible to determine in a simple manner whether the at least one coil element of the radio-frequency coil is superimposed on a patient's anatomy and whether the acquired second magnetic resonance data therefore also result from the patient's anatomy or only comprise the noise behavior of the at least one coil element of the radio-frequency coil. If the second magnetic resonance data is not based on any patient's anatomy, in particular if the at least one coil element of the radio-frequency coil does not superimpose the patient's anatomy, the minimum values ​​in the similarity measure and the maximum values ​​in the similarity measure result exclusively from noise of the coil element. In such a case, the difference between the maximum value in the similarity measure and the minimum value in the similarity measure would be smaller than the predetermined first threshold value.This would also mean that there would be no effective range for the at least one coil element of the radio-frequency coil for the upcoming magnetic resonance examination, so that the effective range for the at least one coil element of the radio-frequency coil can be set to the value zero. This can be the case, for example, if a radio-frequency coil is incorrectly positioned and / or arranged next to the patient. If, however, the second magnetic resonance data contains magnetic resonance data resulting from the patient's anatomy, the difference between a maximum value and a minimum value in the similarity measure is greater than the predetermined first threshold value, and an effective range for the at least one coil element of the radio-frequency coil can be determined.

[0031] In an advantageous development of the method according to the invention, it can be provided that an effective range for the at least one coil element of the radio-frequency coil exists only for those positions in at least one spatial direction if the similarity measure for these positions in the at least one spatial direction is greater than a second threshold value. As a result, an effective range can preferably only be determined for those positions in the at least one spatial direction at which the at least one coil element of the radio-frequency coil detects a significant signal. This second threshold value ensures that an effective range exists only for the positions in the at least one spatial direction at which the at least one coil element of the radio-frequency coil is active and / or arranged, i.e. can also detect magnetic resonance data.In regions and / or positions in the at least one spatial direction in which the at least one coil element of the high-frequency coil is no longer active and / or the at least one coil element of the high-frequency coil is no longer arranged and / or positioned, a determined similarity measure at this position is also very small and remains below the second threshold value.

[0032] This second threshold can be determined relative to a maximum value in the similarity measure. For example, the second threshold can be determined by the maximum value in the similarity measure multiplied by a similarity factor. For example, the second threshold in the z-direction can be determined by the formula: SWZ=LCI_Zmax−LCI_Factor The LCI factor can be 0.05, for example. The threshold value for the x-direction and the y-direction can also be determined analogously. If the similarity measure at a position is smaller than the second threshold in at least one spatial direction, particularly advantageously in all three spatial directions, the effective range for this position is set to zero.

[0033] In an advantageous development of the method according to the invention, it can be provided that a smallest position in the at least one spatial direction is determined at which the similarity measure is greater than the second threshold value, and a largest position in the at least one spatial direction is determined at which the similarity measure is greater than the second threshold value, wherein the smallest position and the largest position delimit the effective range of the at least one coil element in the at least one spatial direction. The smallest position and the largest position in the at least one spatial direction comprise a spatial limitation and / or extent of the effective range and thus a spatial limitation and / or extent for the at least one coil element of the radio-frequency coil.Preferably, a smallest position for the at least one coil element of the high-frequency coil with a similarity measure greater than the second threshold value is determined for all three spatial directions and a largest position for the at least one coil element of the high-frequency coil with a similarity measure greater than the second threshold value is determined for all three spatial directions, so that a spatial extent and / or limitation of the at least one coil element of the high-frequency coil is present and / or can be determined for all three spatial directions.

[0034] This embodiment of the invention has the advantage that exact position information, in particular a spatial extent, for the at least one coil element of the radio-frequency coil can be provided in at least one spatial direction, particularly advantageously in all three spatial directions, for the upcoming magnetic resonance examination.

[0035] In an advantageous development of the method according to the invention, it can be provided that the effective range of the at least one coil element of the radio-frequency coil is provided. The effective range of the at least one coil element of the radio-frequency coil is preferably provided automatically by the evaluation unit. In this case, the effective range of the at least one coil element of the radio-frequency coil can be provided to a user for manual selection of a coil element for the upcoming magnetic resonance examination via a user interface. Alternatively, the effective range of the at least one coil element of the radio-frequency coil can also be provided for automatic selection of a coil element.

[0036] In an advantageous development of the method according to the invention, it can be provided that, for a magnetic resonance examination, a spatial extent of the effective range of the at least one coil element is superimposed with a field of view and / or a region of the patient to be examined. The superimposition can be carried out by medical operators, for example at a user interface of the magnetic resonance device. Furthermore, the superimposition can also be carried out at least partially automatically by means of the evaluation unit. Based on the effective range for the individual coil elements, a position of the coil elements with respect to the field of view and / or the region to be examined can be determined and taken into account when selecting at least one coil element. This also allows for a simple selection of a coil element for a magnetic resonance measurement.

[0037] Furthermore, the invention is based on a magnetic resonance device comprising a scanner unit with a radio-frequency antenna, a patient receiving area, a local radio-frequency coil that can be introduced into the patient receiving area and an evaluation unit, wherein the magnetic resonance device is designed to carry out the method for determining a position of at least one coil element of the radio-frequency coil that can be introduced into the patient receiving area.

[0038] This advantageously allows improved automatic determination and / or selection of a coil element and / or a local radiofrequency coil for a magnetic resonance examination. In particular, a particularly precise position for the at least one coil element, in particular for each coil element, of the local radiofrequency coil that can be introduced into the patient receiving area can be determined in this way. This makes it possible to provide position information for the at least one coil element of the local radiofrequency coil for a magnetic resonance examination that goes beyond position information of a center point of the local radiofrequency coil. This also makes it possible to advantageously support a user in selecting the coil elements for the upcoming magnetic resonance examination.

[0039] The advantages of the medical magnetic resonance device according to the invention essentially correspond to the advantages of the inventive method for determining a position of at least one coil element of a radio-frequency coil that can be introduced into a patient receiving area of ​​the magnetic resonance device for a magnetic resonance measurement, which methods have been described in detail above. Features, advantages, or alternative embodiments mentioned herein can also be applied to the other claimed subject matter, and vice versa.

[0040] Furthermore, the invention is based on a computer program product which comprises a program and can be loaded directly into a memory of a programmable control unit, with program means for controlling a method for determining a position of at least one coil element of a radio-frequency coil which can be introduced into a patient receiving area of ​​a magnetic resonance device for a magnetic resonance measurement when the program is executed in the control unit. The computer program may require program means, e.g. libraries and auxiliary functions, in order to implement the corresponding embodiments of the method. The computer program can comprise software with a source code which still needs to be compiled and linked or which only needs to be interpreted, or an executable software code which only needs to be loaded into a corresponding computing unit for execution.

[0041] The computer program product according to the invention can be loaded directly into a memory of a programmable computing unit and has program code means for executing a method according to the invention when the computer program product is executed in the computing unit. The computer program product can be a computer program or comprise a computer program. As a result, the method according to the invention can 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 computing unit. The computing 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 a computer-readable medium or on a network or server, from where it can be loaded into the processor of a local computing unit, which can be directly connected to the magnetic resonance device or formed as part of it. 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 designed such that it executes a method according to the invention when the data carrier is used in a computing unit. Thus, the computer program product can also represent the electronically readable data carrier. Examples of electronically readable data carriers are a DVD, a magnetic tape, a hard disk, or a USB stick on which electronically readable control information, in particular software (see above), is stored.If this control information (software) is read from the data carrier and stored in a controller and / or processing unit, all embodiments of the methods described above can be carried out. Thus, the invention can also be based on said computer-readable medium and / or said electronically readable data carrier.

[0042] Furthermore, the invention is based on a computer-readable data carrier which comprises a program which is intended to carry out a method for determining a position of at least one coil element of a radio-frequency coil which can be introduced into a patient receiving area of ​​a magnetic resonance device for a magnetic resonance measurement.

[0043] Further advantages, features and details of the invention will become apparent from the embodiment described below and from the drawings.

[0044] They show: Fig. 1 a magnetic resonance device according to the invention in a schematic representation, Fig. 2 shows a method according to the invention for determining a position of at least one coil element of a radio-frequency coil that can be introduced into a patient receiving area of ​​the magnetic resonance device for a magnetic resonance measurement, Fig. 3 a schematic representation of an arrangement of a radio-frequency antenna with a coil element of a radio-frequency coil for acquiring magnetic resonance data, Fig. 4 slice images from first magnetic resonance data and second magnetic resonance data in the effective range of the coil element, and Fig. 5 Layer images from first magnetic resonance data and second magnetic resonance data outside the effective range of the coil element.

[0045] In the Fig. 1 schematically shows a magnetic resonance apparatus 10. The magnetic resonance apparatus 10 comprises a scanner unit 11 formed by a magnet unit. In addition, the magnetic resonance apparatus 10 has a patient receiving area 12 for receiving a patient 13. The patient receiving area 12 in the present exemplary embodiment is cylindrical and is surrounded in a circumferential direction by the scanner unit 11, in particular by the magnet unit. In principle, however, a different design of the patient receiving area 12 is conceivable at any time. The patient 13 can be pushed and / or moved into the patient receiving area 12 by means of a patient support device 14 of the magnetic resonance apparatus 10. For this purpose, the patient support device 14 has a patient table 15 designed to be movable within the patient receiving area 12.In particular, the patient table 15 is mounted so as to be movable in the direction of a longitudinal extension of the patient receiving area 12 and / or in the z-direction.

[0046] The scanner unit 11, in particular the magnet unit, comprises a superconducting base magnet 16 for generating a strong and in particular constant base magnetic field 17. Furthermore, the scanner unit 11, in particular the magnet unit, has a gradient coil unit 18 for generating magnetic field gradients that are used for spatial encoding during imaging. The gradient coil unit 18 is controlled by a gradient control unit 19 of the magnetic resonance device 10. The scanner unit 11, in particular the magnet unit, further comprises a radio-frequency antenna 20 for exciting a polarization that arises in the base magnetic field 17 generated by the base magnet 16. The radio-frequency antenna 20 is controlled by a radio-frequency antenna control unit 21 of the magnetic resonance device 10 and radiates radio-frequency magnetic resonance sequences into the patient receiving area 12 of the magnetic resonance device 10.The high-frequency antenna 20 is fixedly arranged within the scanner unit 11.

[0047] The magnetic resonance apparatus 10 further comprises a local radiofrequency coil 22 comprising at least one coil element 23. The local radiofrequency coil 22 can be mounted in the patient receiving area 12 for a magnetic resonance examination on the patient 13. The local radiofrequency coil 22 can comprise only a single coil element 23 or two or more coil elements 23. Magnetic resonance data are acquired during a magnetic resonance examination using the local radiofrequency coil 22. For this purpose, the local radiofrequency coil 22 is arranged and / or positioned around the region of the patient 13 to be examined. The local radiofrequency coil 22 can also be adapted to the region of the patient 13 to be examined, for example, in the case of a local head radiofrequency coil and / or a local knee radiofrequency coil.

[0048] The magnetic resonance apparatus 10 has a system control unit 24 for controlling the base magnet 16, the gradient control unit 19, and the radio-frequency antenna control unit 21. The system control unit 24 centrally controls the magnetic resonance apparatus 10, such as performing a predetermined imaging gradient echo sequence. The system control unit 24 also includes evaluation software (not shown in detail) for evaluating medical image data acquired during the magnetic resonance examination.

[0049] Furthermore, the magnetic resonance device 10 comprises a user interface 25 connected to the system control unit 24. Control information such as imaging parameters and reconstructed magnetic resonance images can be displayed on a display unit 26, for example, on at least one monitor, of the user interface 25 for medical personnel. Furthermore, the user interface 25 has an input unit 27, by means of which information and / or parameters can be entered by the medical personnel during a measurement process.

[0050] The illustrated magnetic resonance apparatus 10 may, of course, include additional components that magnetic resonance apparatuses 10 typically have. A general mode of operation of a magnetic resonance apparatus 10 is also known to those skilled in the art, so a detailed description of the additional components is omitted.

[0051] In Fig. 2 schematically illustrates a method for determining a position of at least one coil element 23 of a radio-frequency coil 22 that can be introduced into the patient receiving area 12 of the magnetic resonance device 10 for a magnetic resonance measurement. To carry out the method, the patient 13 is already positioned on the patient support device 14, in particular on the patient table 15 of the patient support device 14. Furthermore, all local radio-frequency coils 22 required for the upcoming magnetic resonance examination are already positioned on the patient 13, in particular around the area to be examined and / or the areas of the patient 13 to be examined. In addition, the patient 13, together with the local radio-frequency coils 22, is already located within the patient receiving area 12. Preferably, the area of ​​the patient 13 to be examined is already arranged within the FOV of the patient receiving area 12.

[0052] To carry out the method, the magnetic resonance apparatus 10 also has an evaluation unit 28. In the present exemplary embodiment, the evaluation unit 28 is designed separately from the system control unit 24. In an alternative embodiment of the magnetic resonance apparatus 10, the evaluation unit 28 can also be included in the system control unit 24. For executing and / or controlling the method, the evaluation unit 28 has evaluation software and control software stored in a memory unit (not shown in detail) of the evaluation unit 28. Furthermore, in an alternative embodiment of the evaluation unit 28, the memory unit can also be designed separately from the evaluation unit 28, for example in the form of an external electronically readable data carrier.For execution and / or control of the method, the evaluation unit 28 also has a processor and / or a computing module that executes the corresponding evaluation software and control software.

[0053] In a first method step 101 of the method according to the invention, a magnetic resonance sequence is played back by means of the radio-frequency antenna 20 of the scanner unit 11. The magnetic resonance sequence used can be any magnetic resonance sequence, such as a GRE sequence.

[0054] In a second method step 101, which follows the first method step 100, first magnetic resonance data are acquired by means of the radio-frequency antenna 20 of the scanner unit 11 and second magnetic resonance data are acquired by means of the at least one coil element 23 of the radio-frequency coil 22. The first magnetic resonance data are acquired exclusively by means of the radio-frequency antenna 20 of the scanner unit 11. The second magnetic resonance data are acquired exclusively by means of the at least one coil element 23 of the radio-frequency coil 22. The acquisition of the first magnetic resonance data and the acquisition of the second magnetic resonance data comprise the acquisition of magnetic resonance data for a plurality of, preferably successive, slice images in at least one spatial direction x, y, z, preferably in all three spatial directions x, y, z.

[0055] In a subsequent, further, third method step 102, first magnetic resonance images are determined and / or identified from the first magnetic resonance data, and second magnetic resonance images are determined and / or identified from the first magnetic resonance data and the second magnetic resonance data. The first magnetic resonance images are determined exclusively from the first magnetic resonance data. In this case, N slice images are determined and / or identified in each of the three spatial directions exclusively from the first magnetic resonance data of the radio-frequency antenna 20. The first magnetic resonance images comprise N slice images SliceBC_Z. n with 1 ≤ n ≤ N in z-direction, N slice images SliceBC_X n with 1 ≤ n ≤ N the N in x-direction and N slice images SliceBC_Y n with 1 ≤ n ≤ N in y-direction, where each of the N slice images SliceBC_Z n first magnetic resonance data at position z nincludes each of the N slice images SliceBC_X n first magnetic resonance data at position x n and each of the N slice images SliceBC_Y n first magnetic resonance data at position y n includes.

[0056] Furthermore, N slice images are determined and / or acquired from the first magnetic resonance data of the radio-frequency antenna 20 and the second magnetic resonance data of the at least one coil element 23 of the radio-frequency coil 22, preferably in all three spatial directions x, y, z. The second magnetic resonance images always comprise first magnetic resonance data and second magnetic resonance data. The second magnetic resonance data comprise N slice images SliceLC_Z. n with 1 ≤ n ≤ N in z-direction, N slice images SliceLC_X n with 1 ≤ n ≤ N in x-direction and N slice images SliceBC_Y n with 1 ≤ n ≤ N in y-direction, where each of the N slice images SliceLC_Z nfirst magnetic resonance data and second magnetic resonance data at position z n includes each of the N slice images SliceLC_X n first magnetic resonance data and second magnetic resonance data at position x n and each of the N slice images SliceLC_Y n first magnetic resonance data and second magnetic resonance data at position y n includes.

[0057] In the Fig. 3, the radio-frequency antenna 20 and a coil element 23 of the radio-frequency coil 22 are schematically illustrated. In this embodiment, five slice images at positions z1, z2, z3, z4, z5 are acquired in the z-direction by means of the radio-frequency antenna 20 of the scanner unit 11, and five slice images at positions z1, z2, z3, z4, z5 are acquired by means of the coil element 23 of the radio-frequency coil 22. Fig. 4 shows the second magnetic resonance images for the positions z2 and z3 in the area of ​​influence of the coil element 23 of the radio frequency coil 22. In Fig. 5 shows the second magnetic resonance images for the positions z1, z4 and z5 outside the range of influence of the coil element 23 of the radio-frequency coil 22.

[0058] In a subsequent, further, fourth method step 103, an effective range of the at least one coil element 23 of the radio-frequency coil 11 is determined from the first magnetic resonance images and the second magnetic resonance images by means of the evaluation unit 28. The effective range of the at least one coil element 23 of the radio-frequency coil 22 is preferably determined location-dependently in all three spatial directions x, y, z. To determine the effective range of the at least one coil element 23 of the radio-frequency coil 22, for example, the first magnetic resonance images are compared with the second magnetic resonance images and / or a difference is formed between the first magnetic resonance images and the second magnetic resonance images in order to determine an influence, in particular a location-dependent influence, of the at least one coil element 23 of the radio-frequency coil 22 in the magnetic resonance data.

[0059] To determine the effective range, a similarity measure LCI is calculated in this fourth method step 105, wherein the similarity measure LCI comprises a mean difference between all pixels of the first magnetic resonance image and all pixels of the second magnetic resonance image at a position in a spatial direction x, y, z. Preferably, the similarity measure LCI is calculated and / or determined for all positions for which first magnetic resonance data and second magnetic resonance data were acquired, in all three spatial directions x, y, z.

[0060] The similarity measure LCI is determined as follows: LCI=∑r=1R∑c=1C(SliceBCr,c−SliceLCr,c)2 The first magnetic resonance images and the second magnetic resonance images each have R rows and C columns. The smaller the similarity measure LCI and / or the LCI value, the more similar the first and second magnetic resonance images are, as is also the case in Fig. 5. The more similar the first magnetic resonance images and the second magnetic resonance images are, the smaller the influence of the second magnetic resonance data of the at least one coil element 23 of the radio-frequency coil 22 in determining the similarity measure LCI.

[0061] Subsequently, in this fourth method step 103, the minimum value in the similarity measure LCI is determined from the total similarity measures LCI min for each of the three spatial directions x, y, z, where the minimum value in the similarity measure LCI min This includes the smallest value for the similarity measure LCI from the total similarity measures LCI for the individual spatial directions x, y, z. In addition, the maximum value in the similarity measure LCI is also calculated from the total similarity measures LCI. max for each of the three spatial directions x, y, z, where the maximum value in the similarity measure LCI maxwhich includes the largest value for the similarity measure LCI from the total similarity measures LCI for the individual spatial directions x, y, z. Furthermore, for each spatial direction x, y, z, a difference between the maximum value in the similarity measure LCI max and the minimum value in the similarity measure LCI min If the difference between the maximum value in the similarity measure LCI max and the minimum value in the similarity measure LCI min is smaller than a predetermined first threshold value, the effective range, in particular the entire effective range, of the at least one coil element 23 of the radio-frequency coil 22 is then set to the value zero. The predetermined first threshold value can, for example, be half the maximum value in the similarity measure LCI max include.

[0062] If the second magnetic resonance data are not based on an anatomy of the patient 13, in particular if the at least one coil element 23 of the radio-frequency coil 22 does not overlap the anatomy of the patient 13, for example in the case of incorrect positioning of the radio-frequency coil 22, the minimum values ​​in the similarity measure LCI result min and the maximum values ​​in the similarity measure LCI max solely due to noise. In such a case, the difference between the maximum value in the similarity measure LCI max and the minimum value in the similarity measure LCI min smaller than the predetermined first threshold value and the entire effective range for the at least one coil element 23 of the high-frequency coil 22 is set to the value zero.

[0063] If the difference between the maximum value in the similarity measure LCI max and minimum value in the similarity measure LCI minis greater than the first threshold value, in this fourth method step 103 the similarity measure LCI for all positions in each spatial direction x, y, z is compared with a second threshold value SW. Only if the similarity measure LCI at a position is greater than the second threshold value SW, is there an effective range for the at least one coil element 23 of the radio-frequency coil 22 for that position. The second threshold value SW is set in the present exemplary embodiment relative to a maximum value in the similarity measure LCI max The second threshold SW is determined from the maximum value in the similarity measure LCI max multiplied by a similarity factor LCI_Factor, where the similarity factor LCI_Factor has the value 0.05. For example, the second threshold SW in the z-direction is determined by: SWZ=LCImax−LCI_factor

[0064] In an analogous manner, the second threshold value SW for the x-direction and the y-direction can also be determined. If the similarity measure LCI at a position in one of the three spatial directions x, y, z is smaller than the second threshold value SW, the effective range for this position is set to the value zero. As a result, an effective range is preferably only determined for those positions in the three spatial directions x, y, z at which the at least one coil element of the radio-frequency coil detects a significant signal. This second threshold value SW ensures that an effective range exists only for those positions in the spatial directions x, y, z at which the at least one coil element 23 of the radio-frequency coil 22 is active, i.e., can also detect magnetic resonance data. Illustrated by the Fig.3 to 5, the similarity measure LCI would therefore only be above the second threshold value SW for positions Z2 and z3, since the coil element 23 of the high-frequency coil 22 contributes a significant signal for determining the similarity measure LCI here and thus an effective range exists for the coil element 23 of the high-frequency coil 22. In contrast, in this exemplary embodiment, the similarity measure LCI would be below the second threshold value SW at positions Z1, z4 and z5, since the coil element 23 of the high-frequency coil 22 does not contribute a significant signal for determining the similarity measure LCI and thus no effective range exists for the coil element 23 of the high-frequency coil 22.

[0065] Subsequently, in this fourth method step 103, a smallest position x min , y min , e.g. minfor each of the three spatial directions x, y, z, where the similarity measure LCI is greater than the second threshold SW. In addition, a largest position x max , y max , e.g. max for each of the three spatial directions x, y, z, where the similarity measure LCI is greater than the second threshold SW. The smallest position x min y min , e.g. min and the largest position x max , y max , e.g. max the effective range of the at least one coil element 23 of the high-frequency coil 22 in each of the three spatial directions x, y, z. By the smallest positions x min , y min , e.g. min and the largest positions x max , y max , e.g. maxa spatial extent and / or limitation of the effective area is determined for all three spatial directions x, y, z and thus also a spatial extent and / or limitation and / or a position for the at least one coil element 23 of the high-frequency coil 22 is determined and / or ascertained.

[0066] If the radio-frequency coil 22 has more than one coil element 23, the method is performed for each of the coil elements 23 of the radio-frequency coil 22 for position determination. If multiple radio-frequency coils 22 are arranged on the patient 13 for a magnetic resonance measurement, the method is performed for each radio-frequency coil 22 and / or each coil element 23 of the multiple radio-frequency coils 22 for position determination.

[0067] In a further, fifth method step 104, the effective range for the at least one coil element 23 of the radio-frequency coil 22 is provided. In particular, a position and / or an extent of the at least one coil element 23 of the radio-frequency coil 22 is provided. The effective range of the at least one coil element 23 of the radio-frequency coil 22 can be provided automatically, for example, by the evaluation unit 28. The effective range of the at least one coil element 23 of the radio-frequency coil 22 can be provided to a user for manual selection of a coil element 23 for the upcoming magnetic resonance examination via the user interface 25. Alternatively, the effective range of the at least one coil element 23 of the radio-frequency coil 22 can also be provided for automatic selection of a coil element 23.

[0068] In a further, optional sixth method step 105, a spatial extent of the effective range of the at least one coil element 23 of the radio-frequency coil 22 is superimposed on an FOV and / or the region of the patient 13 to be examined for the upcoming magnetic resonance measurement. The superimposition can be performed by medical personnel, such as at the user interface 25 of the magnetic resonance device 10. Furthermore, the superimposition can also be performed at least partially automatically by means of the evaluation unit 28. If the superimposition of the effective range of the at least one coil element 23 of the radio-frequency coil 22 on the FOV and / or the region of the patient 13 to be examined results in a positional match, the at least one coil element 23 of the radio-frequency coil 22 can be selected for the upcoming magnetic resonance measurement.

[0069] Although the invention has been illustrated and described in detail by the preferred embodiment, 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.

Claims

[1] Method for determining a position of at least one coil element of a radio-frequency coil that can be introduced into a patient receiving area of ​​a magnetic resonance device for a magnetic resonance measurement, comprising the following steps: - Playing back a magnetic resonance sequence by means of a radio-frequency antenna which is fixedly arranged within a scanner unit of the magnetic resonance device, - Acquiring first magnetic resonance data by means of the radio-frequency antenna and acquiring second magnetic resonance data by means of the at least one coil element of the radio-frequency coil, - determining first magnetic resonance images from the first magnetic resonance data and determining second magnetic resonance images from the first magnetic resonance data and the second magnetic resonance data, - Determining an effectiveness range of the at least one coil element of the radio-frequency coil from the first magnetic resonance images and the second magnetic resonance images, wherein the effectiveness range comprises a position of the at least one coil element of the radio-frequency coil, wherein a similarity measure (LCI) is calculated to determine the effectiveness range, wherein the similarity measure (LCI) comprises an average difference between all pixels of the first magnetic resonance image and all pixels of the second magnetic resonance image at a position of the at least one spatial direction. [2] Method according to claim 1, characterized by that the determination of the effective range of the at least one coil element of the high-frequency coil is carried out location-dependently in at least one spatial direction. [3] Method according to one of the preceding claims, characterized bythat the acquisition of the first magnetic resonance data and the acquisition of the second magnetic resonance data comprises an acquisition of magnetic resonance data for a plurality of slice images in the at least one spatial direction. [4] Method according to one of the preceding claims, characterized by that in at least one spatial direction a minimum value in the similarity measure and a maximum value in the similarity measure are determined and if a difference between the maximum value and the minimum value is smaller than a predetermined first threshold value, the effective range of the at least one coil element of the radio-frequency coil is set to the value zero. [5] Method according to one of the preceding claims, characterized bythat an effective range for the at least one coil element of the radio-frequency coil is present only for those positions in at least one spatial direction if the similarity measure for these positions in the at least one spatial direction is greater than a second threshold value. [6] Method according to claim 5, characterized by that a smallest position in the at least one spatial direction is determined at which the similarity measure is greater than the second threshold value, and a largest position in the at least one spatial direction is determined at which the similarity measure is greater than the second threshold value, wherein the smallest position and the largest position limit the effective range of the at least one coil element of the radio-frequency coil in the at least one spatial direction. [7] Method according to one of the preceding claims, characterized by that the effective range of the at least one coil element of the high-frequency coil is provided. [8] Method according to one of the preceding claims, characterized by that for a magnetic resonance measurement, a spatial extent of the effective area of ​​the at least one coil element is superimposed with a field of view and / or an area of ​​the patient to be examined. [9] Magnetic resonance apparatus comprising a scanner unit with a radio-frequency antenna, a patient receiving area, a local radio-frequency coil that can be introduced into the patient receiving area and an evaluation unit, wherein the magnetic resonance apparatus is designed to carry out the method for determining a position of at least one coil element of the radio-frequency coil that can be introduced into the patient receiving area according to one of the preceding claims. [10] Computer program product comprising a program and being directly loadable into a memory of a programmable control unit, with program means for controlling a method for determining a position of at least one coil element of a radio-frequency coil insertable into a patient receiving area of ​​a magnetic resonance apparatus according to one of claims 1 to 8 when the program is executed in the control unit. [11] Electronically readable data carrier with electronically readable control information stored thereon, which is designed such that, when the data carrier is used in a control unit, it carries out the method for determining a position of at least one coil element of a radio-frequency coil that can be introduced into a patient receiving area of ​​a magnetic resonance device according to one of claims 1 to 8.

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