Adjustable MR local coil

Abstract

MR local coil with multiple substrates forming a common virtual area, wherein at least one conductor loop is arranged on each of the substrates, wherein the MR local coil is designed such that a displacement of the substrates relative to each other tangential to the virtual surface is possible, wherein the MR local coil includes a casing that at least partially encloses the substrates, where the shell limits the possible displacement of the substrates relative to each other tangentially to the virtual surface.

Description

[0001] The invention relates to an MR local coil and a magnetic resonance device.

[0002] In medical technology, magnetic resonance imaging (MRI), also known as magnetic resonance tomography (MRI), is characterized by high and variable soft tissue contrast. In this process, high-frequency excitation pulses are emitted into the subject, usually a patient, using a magnetic resonance device. This induces magnetic resonance signals within the patient. These signals are received as measurement data by the MRI device and used to reconstruct magnetic resonance images.

[0003] Magnetic resonance signals are often received using so-called MR local coils, also known as surface coils. These are typically antenna systems positioned in close proximity to (anterior to) and / or (posterior to) the patient. Such an antenna system usually comprises one or more electrical conductor loops, often also called coil elements or antenna elements. During an MR scan, the magnetic resonance signals induce a voltage in the individual conductor loops of the MR local coil. This voltage is read out as measurement data and transmitted to a processing unit of the MRI scanner for the reconstruction of magnetic resonance images.

[0004] A general goal in receiving magnetic resonance signals is to position the coil elements as close as possible to the patient in order to achieve the highest possible signal-to-noise ratio. Known solutions can be divided into rigid and flexible local MR coils.

[0005] Rigid local MR coils, such as those used for head examinations, are optimally adapted to the patient's anatomy to cover the largest possible proportion of potential patients. For patients with small or medium anatomical dimensions, optimal image quality is generally not achieved because the coil elements are located too far from the patient.

[0006] Flexible conventional MR local coils can adapt to the patient's anatomy, but only to a certain extent. In particular, adaptation to three-dimensionally shaped anatomies is often inadequate. For example, this can lead to bulges and / or protrusions of parts of the MR local coil.

[0007] German patent application DE 10 2006 027 189 A1 discloses a head coil arrangement for a magnetic resonance device, comprising at least two housing parts that are movable relative to each other. Furthermore, patent application US 2014 / 0191757 A1 discloses a flexible local coil arrangement, which is held in shape by a mechanical holder.

[0008] The object of the present invention can be considered to be, in particular, to improve the formability of MR local coils.

[0009] The problem is solved by the features of the independent claims. Advantageous embodiments are described in the dependent claims.

[0010] Accordingly, an MR local coil is proposed that comprises several substrates. At least one conductor loop is arranged on each substrate. The multiple substrates form a common virtual surface. The MR local coil is designed such that the substrates can be displaced relative to each other tangentially to the virtual surface. Thus, the substrates are displaceable relative to each other tangentially to the virtual surface.

[0011] In particular, the substrates are connected in such a way that a displacement of the substrates relative to each other tangential to the virtual surface is possible.

[0012] A substrate can be understood to be a support material, particularly a planar one, for the conductor loops. The conductor loops are preferably firmly and / or rigidly and / or planarly bonded to the substrates. For example, the conductor loops are printed and / or glued onto the substrates. The conductor loops can be applied to the substrates, in particular, on one or both sides. Conductor loops applied to both sides can be connected from one side to the other by vias to prevent short circuits at the intersection points of two conductor loops.

[0013] The substrates are typically electrically insulating. The conductor loops are typically electrically conductive. This advantageously allows electromagnetic signals to induce an electrical voltage in the conductor loop.

[0014] The substrates can be arranged in a two-dimensional matrix. The substrates, and in particular their surfaces, preferably have a two-dimensional structure that is arranged parallel to the virtual surface of the substrates.

[0015] Ideally, the normal vector at each point on the surface of the substrate is parallel to the normal vector of the virtual surface at the projection point of that point on the surface of the substrate.

[0016] The virtual surface can be planar or curved. Preferably, the virtual surface is a regular and / or differentiable surface, such that a tangent plane can be defined at any point on the substrate surface. Ideally, the virtual surface has no corners and / or edges.

[0017] The real surfaces of the substrates may well have corners and / or edges. The virtual surface can be understood, in particular, as a theoretical and / or idealized two-dimensional geometric object that may differ in detail from the real surfaces of the substrates. Specifically, the virtual surface can be understood as a median surface of an envelope of the substrates.

[0018] Preferably, the projections of the substrates, in particular the conductor loops, onto the virtual surface overlap at least partially.

[0019] Preferably, the substrates are aligned parallel to each other in an overlap area of ​​the projections of the substrates onto the virtual surface.

[0020] The substrates can be displaced tangentially to the virtual surface relative to each other, i.e., the substrates can change their relative position. Tangential displacement can also include, in particular, lateral displacement within the virtual surface or parallel to the virtual surface.

[0021] Such a possible displacement of the substrates can in particular comprise a translation and / or a rotation of the substrates. Preferably, a possible displacement of the substrates comprises a component that cannot be described by a rotation.

[0022] Preferably, the possible displacement of two substrates relative to each other is at least 5 mm. Preferably, the possible displacement of two substrates relative to each other is at most 30 mm.

[0023] The tangential displacement of the substrates allows for improved three-dimensional shaping of the MR local coil, as the freedom of movement afforded by the displacement enables more flexible adaptation of the substrates. A wide variety of shapes and / or diameters of examination objects can be enclosed even more closely.

[0024] For example, when an operator of a magnetic resonance imaging (MRI) device positions the MR local coil on a patient, the substrates advantageously align themselves relative to each other by shifting in such a way that the conductor loops can be brought closer to the patient. Any measurement data that can be acquired by the conductor loops advantageously exhibit a higher signal-to-noise ratio.

[0025] The improved conformability increases the flexibility in the application of the MR local coil (e.g., examination of both large and small knees, with and without bandages, different joint angles, etc.). Functional imaging can be enabled or improved.

[0026] Furthermore, in an MR local coil according to the invention, compared to a conventional MR local coil which has a continuous substrate, the pressure that arises when conforming to an object is less transferred to the substrate material, but rather absorbed by the movable areas. A potential advantage is the reduction of the risk of conductor loop breakage.

[0027] Another embodiment of the MR local coil provides that at least one of the substrates has two or more conductor loops. Preferably, each substrate has three to four conductor loops. Several conductor loops on one substrate can thus form a cluster of conductor loops. Several clusters can, in turn, form an antenna array. Preferably, the area of ​​a substrate is between 50 and 3000 cm². 2 , especially between 100 and 500 cm 2

[0028] By grouping several conductor loops on a substrate or forming a cluster, more space can be provided for the possible displacement, thus increasing the length of the possible displacement between two adjacent substrates.

[0029] Preferably, each substrate has at most 12, and in particular at most 6, conductor loops. As the number of conductor loops on a substrate increases, the size of the substrate generally also increases, which can impair the formability of the overall system.

[0030] Another embodiment of the MR local coil provides that the substrates and / or the conductor loops are bendable. Preferably, the substrates and / or the conductor loops are reversibly and / or non-destructively bendable. Preferably, the substrate consists of one or more flexible materials. Preferably, the substrate is sufficiently thin, in particular between 50 and 300 µm, to ensure sufficient flexibility. The flexibility of the substrate allows the MR local coil to conform better to the object under investigation.

[0031] Depending on the bending state of the substrates, the shape of the virtual surface to which the possible tangential displacement of the substrates refers also changes, of course.

[0032] Preferably, the substrates are not stretchable tangentially to the virtual surface. This allows for better control of the substrates' displacement tangentially to the virtual surface.

[0033] Another embodiment of the MR local coil provides that the substrates comprise a printed circuit board (PCB) material, such as FR4, PEN, PET, and / or polyimide. Preferably, the substrates consist of PCB material. PCB material is inexpensive and can be processed with high precision, reproducibly, and fully automatically. Furthermore, PCB material can be made fire-resistant (in particular, according to fire protection class UL-V0) without significant effort.

[0034] Another embodiment of the MR local coil provides that the MR local coil includes means to limit any possible displacement tangential to the virtual surface. This allows for better control of the substrate's displacement tangential to the virtual surface.

[0035] Another embodiment of the MR local coil provides that adjacent substrates are connected by at least one connecting device which limits a possible displacement of the substrates tangentially to the virtual surface.

[0036] Such a connecting device can be used, in particular, to connect substrates and to control possible displacement.

[0037] Another embodiment of the MR local coil provides that the at least one connecting device comprises a connecting element which is guided through a recess of adjacent substrates.

[0038] The connecting element can be designed, for example, as a pin, double mushroom head, rivet, and / or snap fastener. A potential advantage is that it allows for precise, adjustable lateral displacement.

[0039] Another embodiment of the MR local coil provides that at least one of the recesses has a greater extent in a first direction tangential to the virtual surface than in a direction perpendicular to it. The recess can, for example, be oval or have the shape of an elongated slot.

[0040] One possible advantage is that it allows for better and more comprehensive control of the direction of the possible displacement tangential to the virtual surface.

[0041] Furthermore, it is provided that the MR local coil includes a casing that at least partially, and in particular completely, encloses the substrates. Specifically, the substrates can be arranged within the casing. A potential advantage of the casing is that the substrates and conductor loops can be better protected.

[0042] Furthermore, the enclosure is designed to limit any potential displacement of the substrates tangentially to the virtual surface. Advantageously, in addition to its protective function, particularly against mechanical damage, the enclosure can be designed to simultaneously limit the potential displacement of the substrates.

[0043] Another possible advantage is that it is possible to do without a connecting device to limit the possible displacement of the substrates.

[0044] Another embodiment of the MR local coil provides that the casing comprises a first layer and a second layer arranged parallel to the virtual surface. wherein the substrates are arranged between the first layer and the second layer, wherein the first layer has a first edge and the second layer has a second edge, wherein the first edge and the second edge are connected to each other and form a common edge.

[0045] The common boundary limits a possible displacement of the substrates tangentially to the virtual surface.

[0046] In particular, the substrate can have an edge that, in a mid-position, is a certain distance from the common edge of the shell. A mid-position can be, for example, a position where the smallest distance between the edge of the substrate and a common edge of the shell is maximized.

[0047] Starting from this central position, the substrate can then be moved by this distance until the edge of the substrate meets the common edge of the shell, thus limiting the movement.

[0048] Preferably, the common edge of the casing limits a perforation in the casing. This allows the perforations to simultaneously improve air circulation. Furthermore, the perforation can reduce the weight of the MR local coil.

[0049] Preferably, the substrate also has a perforation whose extent is greater than the extent of the perforation in the casing. The difference in extents then preferably determines the distance between the edge of the common edge of the casing and the edge of the substrate.

[0050] For example, if the opening in the shell has the shape of a circle with diameter D1 and the opening in the substrate has the shape of a circle with diameter D2 < D1, and the circles are arranged concentrically so that the substrate is in a central position, then the edge of the substrate is spaced from the common edge of the shell by (D1-D2) / 2. From this central position, the substrate can be displaced by a maximum of this distance, provided it does not encounter another obstacle, in particular another edge.

[0051] Another embodiment of the MR local coil provides that at least two substrates have the same shape. By reusing a single substrate shape, the MR local coil can be manufactured more cost-effectively.

[0052] Another embodiment of the MR local coil provides that an electronic unit is arranged on at least part of the substrate. The electronic unit can, for example, include a preamplifier.

[0053] Preferably, the electronic unit is connected and / or coupled to several conductor loops of a substrate. This advantageously allows the electronics to be bundled and / or concentrated overall. This, for example, permits a greater number of openings in the MR local coil and thus improved air circulation.

[0054] Furthermore, a magnetic resonance device with at least one previously described MR local coil is proposed.

[0055] Further advantages, features, and details of the invention will become apparent from the exemplary embodiments described below and from the drawings. Corresponding parts are designated with the same reference numerals in all figures.

[0056] They show: Fig. 1 a magnetic resonance device with an MR local coil, Fig. 2 an MR local coil with substrates that can be moved relative to each other, Fig. 3-7 different means to limit a possible shift, Fig. 8 a substrate with three electrical conductor loops, Fig. 9-10 an array with 8 substrates with three electrical conductor loops, Fig. 11 substrates with different numbers of electrical conductor loops.

[0057] In Fig. Figure 1 schematically depicts a magnetic resonance imaging (MRI) device 10. The MRI device 10 comprises a magnetic unit 11, which includes a main magnet 12 for generating a strong and, in particular, time-constant main magnetic field 13. The MRI device 10 also includes a patient receiving area 14 for receiving a patient 15. In the present embodiment, the patient receiving area 14 is cylindrical and is cylindrically surrounded in one circumferential direction by the magnetic unit 11. However, a different configuration of the patient receiving area 14 is conceivable. The patient 15 can be moved into the patient receiving area 14 by means of a patient positioning device 16 of the MRI device 10. For this purpose, the patient positioning device 16 has a patient table 17 that is movably designed within the patient receiving area 14.

[0058] The magnet unit 11 further comprises a gradient coil unit 18 for generating magnetic field gradients, which 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 magnet unit 11 also includes a high-frequency antenna unit 20, which in the present embodiment is designed as a body coil permanently integrated into the magnetic resonance device 10. The high-frequency antenna unit 20 is designed to excite atomic nuclei that are established in the main magnetic field 13 generated by the main magnet 12. The high-frequency antenna unit 20 is controlled by a high-frequency antenna control unit 21 of the magnetic resonance device 10 and transmits high-frequency magnetic resonance sequences into an examination space, which is essentially formed by a patient acquisition area 14 of the magnetic resonance device 10.The high-frequency antenna unit 20 is further designed for receiving magnetic resonance signals.

[0059] The magnetic resonance imaging (MRI) device 10 includes a system control unit 22 for controlling the main magnet 12, the gradient control unit 19, and the high-frequency antenna control unit 21. The system control unit 22 centrally controls the MRI device 10, for example, by performing a predetermined imaging gradient echo sequence. The system control unit 22 also includes an evaluation unit (not shown) for evaluating measurement data acquired during the MRI scan. Furthermore, the MRI device 10 includes a user interface 23 connected to the system control unit 22. Control information, such as imaging parameters, and reconstructed MRI images can be displayed on a display unit 24, for example, on at least one monitor, of the user interface 23 for medical personnel.Furthermore, the user interface 23 has an input unit 25 by means of which information and / or parameters can be entered by the medical operating personnel during a measurement process.

[0060] The magnetic resonance device further comprises an MR local coil 100, which is connected to the high-frequency antenna control unit 21. The MR local coil 100 is designed for transmitting high-frequency signals (RF signals) and / or for receiving magnetic resonance signals and is described in more detail by way of example in the following figures. In Fig. Figure 2 shows an MR local coil 100 with three substrates 101, 102, 103. Two conductor loops 150 are arranged on each of the substrates 101, 102, 103. The substrates 101, 102, 103 form a common virtual surface F and are tangentially displaceable relative to each other. In this example, a possible displacement can occur along direction T1, along direction T2, or along a combination of both directions T1 and T2.

[0061] The projections of substrates 101 and 102, as well as of substrates 102 and 103, onto the virtual surface F overlap. Furthermore, the projections of conductor loops 150 of adjacent substrates 101 and 102, as well as 102 and 103, overlap.

[0062] Substrates 101, 102, 103 are flexible, so that they can, for example, reversibly change from a flat state to the in Fig. The curved state shown in Figure 2 can be achieved. To enable this, the substrates 101, 102, 103 can, for example, consist of a thin printed circuit board material.

[0063] The MR local coil 100 further comprises means 110 to limit any possible displacement tangential to the virtual surface F. Various versions of such means 110 are explained in more detail in the following figures.

[0064] In Fig. Figure 3 shows two adjacent substrates 101 and 102. The virtual surface here runs horizontally, for example, perpendicular to the plane of the drawing. The possible tangential displacement T of the substrates 101 and 102 tangential to the virtual surface is limited by means of a device 110. This device 110 also serves to connect the substrates 101 and 102, i.e., it represents a possible connecting device.

[0065] The connecting device comprises a connecting element in the form of a pin 111, which is guided through a recess in each of the substrates 101, 102. To fix the pin to the substrates 101, 102, the connecting device further has a mushroom-shaped head 112 on both sides of the pin.

[0066] The upper substrate 101 can, for example, be moved to the right until the left edge of the recess of this substrate 101 abuts the pin 111. The lower substrate 102 can, for example, be moved to the left until the right edge of the recess of this substrate 102 abuts the pin 111.

[0067] As in Fig. As shown in Figure 4, the means 110 can also include a pin 110 which is attached at one end to a substrate 102 and guided through a recess in the substrate 101. In the upper state, the upper substrate 101 is tangential to the virtual surface, which again runs in a horizontal direction, and is displaced maximally to the left relative to the substrate 102, and in the lower state, it is displaced maximally to the right.

[0068] In Fig. Figure 5 shows a top view of two substrates 101 and 102, which are connected to each other tangentially to the virtual surface via a means for limiting the displacement of the substrates 101 and 102. The virtual surface lies in the plane of the drawing. The substrate has a recess that has a greater extent dx in the x-direction than its extent dy in the perpendicular y-direction. This allows the direction of the possible displacement tangentially to the virtual surface to be precisely adjusted.

[0069] In Fig. 6 and Fig. Figure 7 shows an MR local coil 100 with a shell 115 in which the substrates 101, 102 are arranged. Here, the shell 115 limits a possible displacement of the substrates 101, 102 tangentially to the virtual surface, which is shown in Fig. 6 perpendicular to the drawing plane in a horizontal direction and in Fig. 7 runs in the drawing plane.

[0070] The shell 115 comprises a first layer 116 and a second layer 117, which are arranged parallel to the virtual surface, with the substrates 101 and 102 positioned between the first layer 116 and the second layer 117. The first layer 116 has a first edge and the second layer 117 has a second edge, the first and second edges being connected and forming a common edge 118. The substrates 101 and 102 also have lateral edges, which, in a maximal displacement position, touch the common edge 108 of the shell 115. Thus, the common edge 118 limits any possible displacement of the substrates tangentially to the virtual surface. In the depicted situation, substrate 101 is maximally displaced to the right and substrate 102 maximally to the left.

[0071] A substrate can have a different number of conductor loops, as in Fig. Figure 10 shows examples where a substrate 101 has between one and four conductor loops. A bundling of three conductor loops on one substrate is considered particularly advantageous.

[0072] In the middle of the grouping of conductor loops (or at the edge in the case of only one conductor loop) there is a rigid area for an electronic unit 130, in particular an electronic connection.

[0073] Signals from the electronic unit 130 can, for example, be passed from substrate to substrate and bundled internally, or individually routed from substrates and bundled externally.

[0074] For example, in Fig. Figure 8 shows a substrate 101 with three conductor loops 150 and an electronic unit 150.

[0075] For example, an MR local coil can comprise eight such substrates 101, 102, 103, 104, 105, 106, 107, 108 by assembling them into an 8x3 coil array, as shown in Fig. Figure 9 is shown. The eight substrates 101, 102, 103, 104, 105, 106, 107, 108 all have the same shape.

[0076] The areas indicated by the dashed lines contain movable sections or overlaps of the conductor loops. Furthermore, fixed overlaps 151 within a substrate are also possible, as shown in Fig. 8 is shown.

[0077] Fig. Figure 10 shows an arrangement of substrates 101, 102, 103, 104, 105, 106, 107, 108 adapted to a three-dimensional body, which are connected by means of connecting devices which simultaneously serve as means 110 to limit their tangential displacement.

[0078] Finally, it should be noted once again that the MR local coils described in detail above are merely exemplary embodiments which can be modified in various ways by those skilled in the art without departing from the scope of the invention. Furthermore, the use of the indefinite articles "a" or "an" does not preclude the possibility that the features in question may be present multiple times. Likewise, the term "unit" does not preclude the possibility that the components in question consist of several interacting sub-components, which may also be spatially distributed.

Claims

[1] MR local coil with multiple substrates forming a common virtual area, wherein at least one conductor loop is arranged on each of the substrates, wherein the MR local coil is designed such that a displacement of the substrates relative to each other tangential to the virtual surface is possible, wherein the MR local coil includes a casing that at least partially encloses the substrates, where the shell limits the possible displacement of the substrates relative to each other tangentially to the virtual surface. [2] MR local coil according to claim 1, wherein at least one of the substrates has two or more conductor loops. [3] MR local coil according to one of the preceding claims, wherein the substrates and / or the conductor loops are bendable. [4] MR local coil according to one of the preceding claims, wherein the substrates comprise a printed circuit board material. [5] MR local coil according to one of the preceding claims, wherein the MR local coil comprises means to limit the possible displacement of the substrates relative to each other tangentially to the virtual surface. [6] MR local coil according to one of the preceding claims, wherein adjacent substrates are connected by at least one connecting device which limits the possible displacement of the substrates relative to each other tangentially to the virtual surface. [7] MR local coil according to claim 6, wherein the at least one connecting device comprises a connecting element which is guided through a recess of adjacent substrates. [8] MR local coil according to claim 7, wherein at least one of the recesses has a greater extent in a first direction tangential to the virtual surface than in a direction perpendicular to it tangential to the virtual surface. [9] MR local coil according to any of the preceding claims, wherein the shell comprises a first layer and a second layer arranged parallel to the virtual surface, wherein the substrates are arranged between the first layer and the second layer, wherein the first layer has a first edge and the second layer has a second edge, where the first edge and the second edge are connected to each other and form a common edge, where the common boundary limits the possible displacement of the substrates relative to each other tangentially to the virtual surface. [10] MR local coil according to one of the preceding claims, wherein the projections of the substrates, in particular the conductor loops, onto the virtual surface overlap at least partially. [11] MR local coil according to one of the preceding claims, wherein the substrates are aligned parallel to each other in an overlap region of the projections of the substrates onto the virtual surface. [12] MR local coil according to one of the preceding claims, wherein at least two substrates have the same shape. [13] MR local coil according to one of the preceding claims, wherein at least a part of the substrates has an electronic unit arranged. [14] Magnetic resonance device with at least one MR local coil according to any one of claims 1 to 13.

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