LOCAL COIL FOR A MAGNETIC RESONANCE SYSTEM

Description

[0001] Diseases of the teeth and periodontium, such as caries or periodontitis, are nowadays usually diagnosed using X-ray-based imaging techniques. These techniques primarily involve conventional or digital projection X-ray methods, as well as, more recently, three-dimensional X-ray methods. Digital volume tomography (DVT) is one example of a three-dimensional X-ray method, which can be used to image teeth and the viscerocranium.

[0002] A major disadvantage of X-ray procedures is the necessity of using ionizing radiation for imaging. Magnetic resonance imaging (MRI) is an imaging technique that avoids ionizing radiation. It typically provides better soft tissue contrast than X-rays and routinely supports three-dimensional imaging of the patient. Furthermore, MRI allows for the imaging of cysts and the detection of dentin degradation even before it is visible with X-rays. MRI thus represents a potential alternative to conventional X-ray methods for imaging the dentition and / or jaw region, as well as for diagnosing dental diseases.

[0003] Magnetic resonance imaging (MRI) is a well-known imaging technique used to generate magnetic resonance images of the interior of an object under investigation. To perform MRI, the object is typically positioned within a strong, static, and homogeneous background magnetic field (B0 magnetic field) of a magnetic resonance device. The background magnetic field can have strengths ranging from 0.2 Tesla to 7 Tesla, causing the nuclear spins of the object to align along this field. To induce nuclear spin resonances, high-frequency signals, known as excitation pulses (B1 magnetic field), are applied to the object. Each excitation pulse causes a deviation in the magnetization of specific nuclear spins within the object from the background magnetic field by an amount known as the flip angle.An excitation pulse can exhibit an alternating magnetic field with a frequency corresponding to the Larmor frequency at the respective static magnetic field strength. The excited nuclear spins can exhibit a rotating and decaying magnetization (nuclear magnetic resonance), which can be detected as a magnetic resonance signal using special antennas. To spatially encode the nuclear magnetic resonances of the object under investigation, magnetic gradient fields can be superimposed on the fundamental magnetic field.

[0004] The received magnetic resonance signals are typically digitized and stored as complex values ​​in a k-space matrix. This k-space matrix can be used as the basis for reconstructing magnetic resonance images and determining spectroscopy data. Reconstructing a magnetic resonance image is typically performed using a multidimensional Fourier transform of the k-space matrix.

[0005] Magnetic resonance imaging (MRI) is particularly suitable for frequent or continuous diagnostic monitoring of dental diseases and / or tooth development due to the avoidance of ionizing radiation. However, diagnostically relevant areas of a patient's jaw, such as the oral cavity, dentition, dental arch, or individual teeth, offer a small volume available for generating MRI signals. Furthermore, conventional volume and surface coils, such as head coils and surface coils, are positioned at a relatively large distance from the diagnostically relevant area. For these reasons, conventional volume and surface coils exhibit a relatively low signal-to-noise ratio, which results in poor image quality when using MRI devices with low field strengths (e.g., between 0.2 and 0.7 T).

[0006] The publication DE 20 2015105111 U1 describes a wireless RF coil for MR measurements at a target volume in an oral area of ​​an object under investigation, which can be inductively coupled to a receiving coil of an evaluation unit for further signal processing.

[0007] AGAZI SAMUEL TESFAI et al. ("Intra-oral flexible coil for improved visibility of dental root canals in MRI", PROCEEDINGS OF THE 2021 ISMRM & SMRT ANNUAL MEETING & EXHIBITION, 15-20 MAY 2021, ISMRM, 2030 ADDISON STREET, 7TH FLOOR, BERKELEY, CA 94704 USA, No. 3946, April 30, 2021 (2021-04-30), XP040725963) describe a thin and flexible, inductively coupled intraoral coil that is adapted to the dental anatomy and allows improved visibility of the dental pulp and root canals.

[0008] In the publication DE 10 2007 047020 A1, an arrangement for the transmission of magnetic resonance signals is disclosed, comprising a local coil with a number of individual antennas and preamplifiers provided for amplifying the high-frequency signals, and with a transmission device designed for transmitting the high-frequency signals from the local coil to the preamplifiers.

[0009] Document WO 2021 / 219340 A1 discloses an antenna arrangement consisting of at least one signal conductor and a support element connected to the antenna arrangement. The support element is shaped like a part of the dentition of an object under investigation and can be positively connected to the patient's dentition in an application position.

[0010] Document US 2019 / 339345 A1 relates to an inductive feed of an RF coil for magnetic resonance imaging as well as a system with an RF coil for magnetic resonance imaging and a feed coil for inductively feeding the RF coil with an RF signal.

[0011] It is therefore an object of the invention to provide a local coil which improves the quality of captured magnetic resonance images.

[0012] This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments and expedient further developments are the subject matter of the dependent claims.

[0013] The local coil according to the invention comprises a first antenna unit and a second antenna unit, wherein the first antenna unit and the second antenna unit are galvanically isolated and are configured to receive magnetic resonance signals from an object under investigation.

[0014] The first and second antenna units each comprise one or more receiving elements configured as signal conductors. A receiving element can act as a coupling element between electromagnetic waves guided in signal conductors and those unguided, i.e., located in free space. The receiving element is preferably configured to receive electromagnetic waves in the range of the magnetic resonance frequency of a magnetically resonant atomic nucleus. For example, a high-frequency signal is considered to be an electromagnetic wave with a frequency between 1 and 500 MHz, preferably between 10 and 300 MHz. The magnetic resonance signal of typical atomic nuclei under investigation can have a low power output ranging from a few microwatts to several milliwatts.

[0015] A signal conductor preferably comprises an electrically conductive wire. The wire of the signal conductor can have an oval or polygonal cross-section suitable for the continuous transmission of the aforementioned power levels. It is conceivable that the signal conductor is implemented as a conductor track on a printed circuit board of the first antenna unit and / or the second antenna unit. The signal conductor can be made of copper. However, other electrically conductive metals, such as gold, silver, or aluminum, are also conceivable. Preferably, a receiving element comprises at least one signal conductor.

[0016] The first antenna unit and the second antenna unit are galvanically isolated from each other. This means that a galvanic or electrical connection between the first and second antenna units is avoided.

[0017] It is conceivable that the first antenna unit and the second antenna unit are mechanically connected. Such a mechanical connection can be provided by means of any force-fit, form-fit, and / or material-fit connection. A mechanical connection between the first antenna unit and the second antenna unit is preferably designed to reduce or prevent the conduction of electrical current between the first and second antenna units.

[0018] In a preferred embodiment, a mechanical connection between the first and second antenna units is avoided. This can mean that the first and second antenna units are mechanically unconnected. With the local coil positioned appropriately on the object under investigation, the first and second antenna units can be located separately from each other, e.g., at a distance of a few centimeters or a few millimeters.

[0019] When the local coil is positioned as intended relative to the object under investigation, the second antenna unit at least partially surrounds the first antenna unit along one of its circumferential directions. This can mean that a projection of the second antenna unit along a direction of a surface normal of a principal surface of the first antenna unit at least partially surrounds the first antenna unit along one of its circumferential directions. It is also conceivable that a body of the second antenna unit at least partially surrounds a body of the first antenna unit along its circumferential direction.

[0020] The second antenna unit can, in particular, have a curved or bent shape. It is conceivable that a projection of a surface enclosed by the second antenna unit when two endpoints of the second antenna unit are connected, along the direction of the surface normal of the main surface of the first antenna unit, has a non-empty intersection with the main surface of the first antenna unit or completely encloses it.

[0021] A circumferential direction can be any direction that follows the perimeter of a basic shape or the base area of ​​the first antenna unit.

[0022] A cross-section of the second antenna unit preferably has a convex-concave shape. This can mean that the second antenna unit has a convex shape on a side facing away from the first antenna unit, while a side of the second antenna unit facing the first antenna unit has a concave shape. When the local coil is positioned relative to the object under investigation as required, the first antenna unit is preferably positioned such that the first antenna unit is at least partially surrounded or enclosed by a surface of the second antenna unit with the concave shape.

[0023] The surface contour of the side with the concave shape of the second antenna unit can, for example, be shaped like a circular arc, an elliptical arc, an open triangle (V-shape), or another open polygon. According to the invention, when the local coil is positioned relative to the object under investigation as required, the first antenna unit is located inside the object and the second antenna unit is located on an outer surface of the object.

[0024] The first antenna unit is designed to be positioned inside the object under investigation. This may mean that the first antenna unit meets requirements regarding dimensions, protection against contact, and / or biocompatibility, depending on the object under investigation.

[0025] The subject of the investigation is a patient, in particular a human or an animal. With the local coil positioned as required, the first antenna unit is located intraorally within the patient. The second antenna unit is preferably designed to conform to the outer surface of a body region of the patient that surrounds or covers the first antenna unit and / or to at least partially enclose it.

[0026] In one example, the first antenna unit is shaped to resemble a patient's dental arch. With the local coil positioned as intended, the first antenna unit is located relative to the patient along an occlusal plane between an upper and lower dental arch, while the second antenna unit at least partially encloses a jaw region of the patient along an outer contour of that region.

[0027] Preferably, the first antenna unit and the second antenna unit are galvanically and mechanically unconnected or separated.

[0028] By avoiding a mechanical and galvanic connection between the first antenna unit and the second antenna unit, the risk of injury to a patient, which is associated with positioning the first antenna unit inside the patient and leading mechanical and / or electrical structures out of the patient's interior, can be advantageously avoided.

[0029] The second antenna unit has an inductive coupling with the first antenna unit, wherein the second antenna unit is configured to detect a magnetic resonance signal received from the first antenna unit by means of the inductive coupling.

[0030] The first antenna unit can comprise one or more receiving elements according to an embodiment described above. Through interaction with excited nuclear spins, electric currents or magnetic resonance signals can be induced in a receiving element of the first antenna unit. The magnetic resonance signals received by the receiving element of the first antenna unit can themselves generate a magnetic field as electric currents, which causes an electric current flow in one or more receiving elements of the second antenna unit. The electric currents induced in the second antenna unit in this way can be correlated with or correspond to the received magnetic resonance signal of the first antenna unit.It is also conceivable that the electrical currents induced in the second antenna unit in this way contain information about the received magnetic resonance signal of the first antenna unit.

[0031] The quality of the magnetic resonance signal acquired by means of inductive coupling (e.g., signal strength or signal-to-noise ratio) and / or the quality of the inductive coupling can depend in particular on the relative position and / or orientation of the first antenna unit to the second antenna unit.

[0032] The second antenna unit can also be configured to directly receive magnetic resonance signals from the object under investigation. This can mean that, in addition to the magnetic resonance signals acquired by the first antenna unit via inductive coupling, the second antenna unit can also directly acquire magnetic resonance signals from the object under investigation.

[0033] It is conceivable that the local coil according to the invention also comprises a transmitter unit. The transmitter unit can have at least one transmitter element with a signal conductor. The transmitter element can be configured to emit high-frequency signals into the object under investigation within the frequency and power range of a magnetic resonance device. A high-frequency signal emitted by the transmitter unit can, depending on the fundamental magnetic field of the magnetic resonance device, for example, have a power range from a few watts to several kilowatts. The signal conductor of the transmitter unit can, for example, be energized with an alternating current to emit a high-frequency signal, the so-called B1 magnetic field, into the object under investigation.

[0034] A receiving element and / or a transmitting element of the local coil according to the invention preferably has a touch guard which protects the object under investigation from voltages and / or burns. For this purpose, the signal conductor can, for example, have a coating and / or a covering made of plastic. Suitable plastics include, for example, polytetrafluoroethylene (PTFE), various polysiloxanes, or the like.

[0035] The first antenna unit and / or the second antenna unit can each have a support structure that is mechanically connected to a receiving element of the first antenna unit and / or the second antenna unit. For example, one or more receiving elements can be embedded, suspended, clamped, or inserted into the support structure and / or glued or welded to it. A support structure can advantageously increase the structural or dimensional stability of one or more receiving elements.

[0036] Suitable materials for the support structure include, for example, polycarbonates, glass fiber reinforced plastics, polyethylene, polytetrafluoroethylene, polymethyl methacrylate, or similar plastics. However, it is also conceivable that the support structure could consist of a natural material, such as rubber or natural fibers, or even a ceramic.

[0037] Preferably, the support structure of the second antenna unit is shaped to conform to at least part of the outer contour of the object under investigation, such as a patient's jaw region. It is conceivable that the support structure could be shaped to conform to at least part of the outer contour of the object under investigation, such as a jaw region, a mouth / nose region, and / or a chin region. The second antenna unit can at least partially enclose or surround the object under investigation along its outer contour. In particular, providing a second antenna unit shaped to conform to the outer contour of the object under investigation ensures that the second antenna unit maintains close contact with the object along its outer contour.

[0038] This allows for a beneficial reduction in the average distance between the second antenna unit and the outer contour of the object under investigation and / or the first antenna unit. Furthermore, a particularly high signal-to-noise ratio of received magnetic resonance signals can be advantageously achieved by maintaining a small distance between the second antenna unit and the outer contour of the object under investigation and / or the first antenna unit.

[0039] Preferably, the second antenna unit is electrically connected to a magnetic resonance device for signal transmission. It is conceivable that the electrical connection between the second antenna unit and the magnetic resonance device is made by means of an electrical connecting cable. Such an electrical connecting cable could, for example, be a coaxial cable with shielding to prevent electromagnetic interference from the environment.

[0040] The first antenna unit is preferably galvanically isolated from the magnetic resonance device. This can mean that an electrical and / or galvanic connection between a receiving element of the first antenna unit and the magnetic resonance device is avoided. In particular, this can mean that a signal or a magnetic resonance signal from the first antenna unit is provided to a magnetic resonance device exclusively by means of inductive coupling with the second antenna unit.

[0041] It is also conceivable that the first antenna unit is mechanically separated from the magnetic resonance device and / or the second antenna unit.

[0042] In one embodiment, the first antenna unit and / or the second antenna unit comprise an electronic circuit connected to a signal conductor. The electronic circuit may include a single electronic component or an assembly of several electronic components, such as transistors, resistors, capacitors, diodes, conductors, and the like. The electronic circuit may, in particular, include a protection circuit suitable for protecting a signal conductor against overload. To prevent magnetic attraction, standing waves, heating, and similar undesirable effects, the electronic circuit may incorporate a high proportion of non-magnetic materials as well as appropriate common-mode chokes and / or baluns.The electronic circuit preferably comprises a printed circuit board (PCB) or a comparable substrate suitable for accommodating the electronic components in a predetermined position relative to each other.

[0043] By inductively coupling the first antenna unit and the second antenna unit according to the invention, a larger coverage of a volume of the object under investigation, in particular a volume inside the object under investigation, can be advantageously achieved in a magnetic resonance examination.

[0044] Preferably, the magnetic resonance signals received by the first antenna unit are transmitted exclusively by means of inductive coupling to the second antenna unit and / or a magnetic resonance device.

[0045] Furthermore, avoiding a galvanic and / or mechanical connection between the first and second antenna units can advantageously simplify the design of the local coil. This reduces the costs and / or manufacturing effort associated with the local coil.

[0046] Furthermore, the quality of recorded magnetic resonance images can be advantageously improved by positioning the first antenna unit appropriately in close proximity to a diagnostically relevant structure inside the object under investigation, such as a tooth root, gums, or the like.

[0047] In one embodiment, the local coil according to the invention has a holding element. The holding element is designed to hold the second antenna unit in a predetermined relative position to the first antenna unit on the outer surface of the object under investigation.

[0048] A retaining element preferably provides a rigid mounting device for the second antenna unit. The retaining element can be mechanically connected to the second antenna unit and / or a receiving element of the second antenna unit. The mechanical connection between the retaining element and the second antenna unit can be any positive-locking, force-locking, and / or material-locking connection. It is conceivable that the second antenna unit is bonded and / or screwed to the retaining element. However, the second antenna unit and the retaining element can also be manufactured as a single piece.

[0049] The retaining element is specifically designed to hold the second antenna unit in a predetermined relative position to the first antenna unit. A predetermined relative position between the first and second antenna units can be characterized by a relative orientation and / or position of the first antenna unit relative to the second antenna unit that enables sufficient inductive coupling between the first and second antenna units.

[0050] By providing the retaining element, the second antenna unit, in particular a receiving element of the second antenna unit, can be advantageously fixed or fastened in a predetermined relative position to the first antenna unit.

[0051] In one embodiment of the local coil according to the invention, the holding element is designed to hold the second antenna unit on the outer surface of the object under investigation when the local coil is positioned relative to the object under investigation in the manner required, such that a surface normal of a main surface of the first antenna unit is oriented essentially orthogonally to a surface normal of a main surface of the second antenna unit.

[0052] A main surface can represent a side or a surface with a significant area.

[0053] A main surface of the second antenna unit is preferably a side or surface of the second antenna unit which faces the object under investigation when the local coil is positioned as required.

[0054] According to the invention, the first antenna unit has a substantially planar shape. The main surface of the first antenna unit is preferably defined by a side or surface of the first antenna unit which is aligned parallel to the planar shape of the first antenna unit.

[0055] Preferably, when the local coil is positioned according to the application, the first antenna unit and the second antenna unit are aligned relative to each other such that the surface normal of the main surface of the first antenna unit is essentially orthogonal to the surface normal of the main surface of the second antenna unit.

[0056] Small deviations of the angle between the surface normal of the main surface of the first antenna unit and the surface normal of the main surface of the second antenna unit from an orthogonal orientation are tolerable. For example, the angle between the surface normal of the main surface of the first antenna unit and the surface normal of the main surface of the second antenna unit can lie in a range between 85° and 95°, 80° and 100°, 70° and 110°, or 60° and 120°.

[0057] The holding element preferably includes a positioning unit configured to set the position and / or orientation of a receiving element of the second antenna unit relative to the object under investigation and / or the first antenna unit. This allows the angle between the surface normal of the main surface of the first antenna unit and the surface normal of the main surface of the second antenna unit, and thus the quality of the inductive coupling, to be advantageously adjusted depending on the geometry of the object under investigation.

[0058] The positioning unit can be designed, for example, as a rail, a hinge, or a joint.

[0059] According to another embodiment of the local coil, the holding element is designed to hold the second antenna unit on the outer surface of the object under investigation in such a way that a geometric center point of the first antenna unit is arranged at an intersection of a surface normal of the main surface of the second antenna unit with a surface normal of the main surface of the first antenna unit.

[0060] By aligning the first antenna unit and the second antenna unit according to the invention, with the local coil positioned relative to the object under investigation as appropriate, the inductive coupling of the first antenna unit and the second antenna unit can be advantageously improved or optimized.

[0061] In a preferred embodiment of the local coil according to the invention, the second antenna unit is shaped like a hollow cylinder sector and, when the local coil is positioned relative to the object under investigation as required, at least partially surrounds the object under investigation along an outer contour of the object under investigation.

[0062] The second antenna unit can be configured according to an embodiment described above. The hollow cylindrical sector can, for example, have a C-shaped, a U-shaped, or an approximately V-shaped base. In particular, it is conceivable that, when the local coil of the first antenna unit is positioned as required, the cross-section of the second antenna unit follows a segment of a circular arc, an elliptical arc, or the outer contour of a polygon.

[0063] The outer contour of the object under investigation is preferably characterized by a two-dimensional or three-dimensional profile of the object's outer surface. For example, the outer surface of the object can be defined by a patient's skin surface, particularly the skin surface of a jaw region. By providing a second antenna unit in the form of a hollow cylindrical sector, the average distance between the second antenna unit and the outer surface of the object and / or the first antenna unit can be advantageously reduced or minimized for objects with curved surfaces or outer contours.

[0064] According to the invention, the first antenna unit of the local coil according to the invention has a substantially planar shape, wherein in one embodiment a receiving element of the first antenna unit is arranged in a plane which intersects the first antenna unit and is aligned parallel to a main surface of the first antenna unit, wherein a geometric center point of the second antenna unit lies in the plane of the receiving element of the first antenna unit when the local coil is positioned relative to the object under investigation in accordance with the application.

[0065] Preferably, the second antenna unit comprises a retaining element according to an embodiment described above. The retaining element can be configured to hold the second antenna unit on the outer surface of the object under investigation such that the geometric center of the second antenna unit lies in the plane of the receiving element of the first antenna unit. The retaining element can further comprise a positioning unit configured to set a position and / or orientation of the second antenna unit relative to the object under investigation and / or the first antenna unit, such that the geometric center of the second antenna unit lies in the plane of the receiving element of the first antenna unit.

[0066] It is also conceivable that the center of gravity of the second antenna unit lies in the plane of the receiving element of the first antenna unit.

[0067] By aligning the first antenna unit and the second antenna unit according to the invention, with the local coil positioned relative to the object under investigation as appropriate, the inductive coupling of the first antenna unit and the second antenna unit can be further improved or optimized in an advantageous manner.

[0068] In one variant of the local coil according to the invention, the second antenna unit has at least one receiving element, wherein the at least one receiving element is designed as a butterfly coil.

[0069] A butterfly coil can be characterized by the shape of a lemniscate. For example, a signal conductor of at least one receiving element can overlap itself at a crossing point, so that the signal conductor forms two loops that are opposite each other at the crossing point.

[0070] In this embodiment of the invention, the intersection point of the butterfly coil is arranged in a plane with the first antenna unit. It is further conceivable that the intersection point corresponds to the geometric center and / or the centroid of the second antenna unit.

[0071] By providing a second antenna unit with a butterfly coil, improved or optimized inductive coupling between the second and first antenna units can be advantageously achieved. In particular, the penetration of the second antenna unit by a magnetic field generated by the first antenna unit can be improved compared to alternative arrangements of receiving elements.

[0072] According to a further variant of the local coil according to the invention, the second antenna unit has at least two receiving elements which are arranged next to each other along a surface contour of the second antenna unit or which at least partially overlap.

[0073] In this embodiment of the invention, the at least two receiving elements of the second antenna unit define a plane of symmetry or a line of intersection which is oriented essentially parallel to the main surface of the first antenna unit. A line of intersection can be a straight line defined by the points where signal conductors of two superimposed receiving elements intersect. A plane of symmetry can be a plane in which the at least two receiving elements are mirror images of each other.

[0074] Preferably, the at least two receiving elements are arranged along the surface contour of the second antenna unit such that the plane of symmetry or the line of intersection of the at least two receiving elements is arranged parallel to and / or coincides with the plane of the receiving coil of the first antenna unit.

[0075] The at least two receiving elements of the second antenna unit are designed to be read independently of each other. The at least two receiving elements of the second antenna unit can be spaced apart from each other. It is also conceivable that the at least two receiving elements are galvanically isolated from each other.

[0076] In another embodiment, the at least two receiving coils are decoupled by a superposition or crossing of signal conductors or capacitively.

[0077] By providing at least two receiving elements, the dependence between the quality of the inductive coupling and a relative position or arrangement of the second antenna unit and the first antenna unit can be advantageously reduced.

[0078] Furthermore, if at least two receiving elements are present, the geometry of the second antenna unit can be improved and adapted to the outer contour of the object under investigation.

[0079] According to a further embodiment of the local coil according to the invention, the second antenna unit has at least three receiving elements.

[0080] Preferably, at least one of the at least three receiving elements is configured as a butterfly coil. However, it is equally conceivable that at least one receiving element has a signal conductor with an oval or polygonal shape or base.

[0081] The at least three receiving elements are arranged side by side along a surface contour of the second antenna unit or overlap at least partially.

[0082] Preferably, the at least three receiving elements are arranged side by side or partially superimposed along the surface contour of the second antenna unit (or the support structure) when the local coil is positioned relative to the object under investigation in accordance with the application, following a usual X-direction of a magnetic resonance device.

[0083] It is particularly conceivable that, when the local coil is positioned as required, the at least three receiving elements are arranged next to each other or partially overlapping along a transverse plane of the patient.

[0084] In one example, the second antenna unit, when laid flat or spread out, can essentially have the shape of a flat cuboid with a rectangular base. However, it is equally conceivable that the second antenna unit has a cross-section other than a rectangle. For instance, the second antenna unit can have a V-shaped base (e.g., a rectangular base with a kink or bend) to improve or simplify the process of shaping or attaching the second antenna unit to a test object with a curved outer surface, particularly a patient's head or jaw region. The at least three receiving elements of the antenna unit are preferably arranged side by side or partially overlapping, following the basic shape (e.g., rectangle or V-shape) of the second antenna unit when spread out.It is particularly conceivable that the geometric centers of at least three receiving elements are arranged side by side or partially overlapping along a surface or outer contour of the second antenna unit and / or the support structure, following a typical X-direction of a magnetic resonance device.

[0085] Partial overlap of two receiving elements can mean that two receiving elements overlap in such a way that a proportion of more than 5%, more than 10%, more than 15% or more than 20% of an enclosed area of ​​a first receiving element is covered by a second receiving element.

[0086] In one embodiment of the local coil according to the invention, the second antenna unit has at least five receiving elements or at least seven receiving elements which are arranged side by side along the surface contour of the second antenna unit or which at least partially overlap.

[0087] In a preferred embodiment, the at least three receiving elements are designed to be read independently of one another.

[0088] By providing a second antenna unit with at least three receiving elements, the inductive coupling between the first antenna unit and the second antenna unit can be advantageously improved or optimized.

[0089] According to the invention, the object of investigation is a jaw region of a patient. According to the invention, when the local coil is positioned relative to the jaw region as required, the first antenna unit is arranged along an occlusal plane in the patient's oral cavity.

[0090] According to the invention, the first antenna unit has a substantially planar shape, preferably with a U-shaped or C-shaped base. For example, the first antenna unit can be shaped to resemble a patient's dental arch. In particular, the first antenna unit can be configured such that a surface and / or base of the first antenna unit substantially coincides with a surface formed by a dental arch along the occlusal plane. However, the first antenna unit can also project slightly, e.g., a few hundredths of a millimeter or a few millimeters, beyond a surface of the dental arch along the occlusal plane.

[0091] The second antenna unit is shaped to follow the outer contour of the patient's jaw region and at least partially encloses the jaw region along the outer contour.

[0092] The second antenna unit, as well as the support structure, can be shaped to resemble the patient's jaw region according to an embodiment described above and at least partially enclose it along an outer contour.

[0093] The local coil according to the invention allows for an advantageous increase in the coverage of a volume of the patient's jaw region with receiving elements compared to purely intraoral local coils, as well as volume or surface coils. This enables the provision of higher-quality magnetic resonance images of parts of the jaw region, as well as the entire jaw region.

[0094] Furthermore, the signal-to-noise ratio of received magnetic resonance signals can be advantageously increased by a small distance between receiving elements of the local coil according to the invention and anatomical structures of the jaw region, such as the teeth, gums, palate, jawbones, temporomandibular joint and the like.

[0095] In one embodiment of the local coil according to the invention, the geometric centers of at least two receiving elements of the second antenna unit are arranged along a sagittal plane of the patient. The at least two receiving elements are arranged side by side or overlap at least partially.

[0096] When the patient is positioned as required in a magnetic resonance imaging (MRI) device, the sagittal plane of the MRI device can be aligned parallel to a direction of the device's main magnetic field and / or a Z-direction of the MRI device. Preferably, the geometric centers of the at least two receiver elements are arranged along the same sagittal plane of the patient.

[0097] A geometric center point of a receiving element can, for example, be a crossing point of a butterfly coil, but also a center point or axis of rotation of a receiving element with an oval or polygonal base.

[0098] Preferably, at least one of the at least two receiving elements is configured as a butterfly coil. The two loops of the signal conductor of the butterfly coil are preferably arranged substantially parallel to the sagittal plane of the patient. This can mean that the geometric centers of the two loops are arranged along the same sagittal plane of the patient.

[0099] In one embodiment of the local coil according to the invention, the geometric centers of at least three receiving elements of the second antenna unit are arranged along a transverse plane of the patient. According to the invention, the at least three receiving elements are arranged side by side or partially overlap.

[0100] Preferably, the geometric centers of the at least three receiving coils are arranged along the same transverse plane of the patient.

[0101] Preferably, the transverse plane on which the geometric centers of at least two or at least three receiving elements are arranged is positioned relative to the patient at a predetermined distance above and / or below the patient's occlusion plane or a plane that intersects the first antenna unit and is aligned parallel to a main surface of the first antenna unit, when the local coil is positioned as required. The predetermined distance can be designed such that the intersection of signal conductors of the at least two receiving elements with the patient's occlusion plane or the plane that intersects the first antenna unit and is aligned parallel to the main surface of the first antenna unit is avoided. Such an arrangement is particularly preferred for receiving elements that have an oval or polygonal arrangement of the signal conductor.

[0102] In contrast, geometric centers or intersection points of butterfly coils are preferably arranged on a transverse plane which coincides with the occlusion plane of the patient or the plane which intersects the first antenna unit and is aligned parallel to the main surface of the first antenna unit.

[0103] It is conceivable that the at least three receiving coils are arranged next to each other, offset along a typical Y-direction of the magnetic resonance device.

[0104] By using an increased number of receiver elements arranged offset along the transverse plane, magnetic resonance signals from the entire jaw region, and in particular from one or both temporomandibular joints, can be advantageously captured.

[0105] In one embodiment, geometric centers of at least two receiving elements of the second antenna unit are arranged along a straight line which is aligned parallel to a main surface of the first antenna unit and / or an occlusion plane of the patient.

[0106] Preferably, when the local coil is positioned as required, the main surface of the first antenna unit is oriented essentially parallel to a transverse plane of the patient. It is also conceivable that the patient's occlusal plane is oriented parallel to the transverse plane.

[0107] In a particularly preferred embodiment, the second antenna unit of the local coil according to the invention has at least three receiving elements or at least five receiving elements, the geometric centers of which are arranged along the transverse plane of the patient.

[0108] The geometric centers of the at least two receiving elements, the at least three receiving elements, or the at least five receiving elements can be arranged side by side along a direction that is oriented parallel to the main surface of the first antenna unit and / or the occlusion plane of the patient.

[0109] In one embodiment of the invention, at least one receiving element of the second antenna unit is configured as a butterfly coil. In a particularly preferred embodiment of the local coil, the at least one butterfly coil is flanked along a section of the patient's sagittal plane and / or along the Z-direction of the magnetic resonance device by two receiving elements. The two receiving elements flanking the butterfly coil preferably have a single oval or polygonally arranged signal conductor.

[0110] In one embodiment of the local coil according to the invention, the at least two receiving elements of the second antenna unit arranged along the sagittal plane are each flanked by at least one receiving element when the local coil is positioned relative to the patient in the Y-direction of the magnetic resonance device as applicable.

[0111] By providing a second antenna unit according to the invention, the inductive coupling between the second antenna unit and the first antenna unit can be advantageously improved or optimized.

[0112] The magnetic resonance device according to the invention comprises a local coil according to an embodiment described above. The magnetic resonance device is designed to detect magnetic resonance signals of the object under investigation received by the first antenna unit by means of inductive coupling with the second antenna unit.

[0113] Preferably, the second antenna unit of the local coil is also configured to directly receive magnetic resonance signals from the object under investigation. It is conceivable that magnetic resonance signals from the object under investigation received directly by the second antenna unit superimpose, at least partially, as electrical currents in a receiving element of the second antenna unit with the magnetic resonance signals detected by the first antenna unit via inductive coupling.

[0114] The second antenna unit preferably has an electrical connection to a processing unit and / or a control unit. The processing unit and / or control unit of the magnetic resonance device are preferably configured to generate magnetic resonance images of the object under investigation based on signals from the second antenna unit.

[0115] For example, the magnetic resonance device according to the invention has at least one electrical connecting line which is designed to electrically connect the second antenna unit to the magnetic resonance device.

[0116] An electrical or galvanic connection between the first antenna unit and the magnetic resonance device is preferably avoided. This can mean that the magnetic resonance signals received by the first antenna unit are transmitted to the magnetic resonance device exclusively via inductive coupling with the second antenna unit.

[0117] In one embodiment, a transmitter unit of the local coil is connected to a high-frequency unit of the magnetic resonance device via an electrical connecting cable. The high-frequency unit can provide an alternating current, which is emitted as a high-frequency signal from the transmitter unit into a volume in the patient's jaw region, generating a B1 magnetic field.

[0118] In another embodiment, a receiving element of the second antenna unit is connected to a receiver channel of the magnetic resonance device via an electrical connecting cable. The magnetic resonance device is thus able to receive magnetic resonance signals from the patient's jaw region and generate magnetic resonance images based on the received magnetic resonance signals.

[0119] The magnetic resonance device according to the invention enables time-efficient and repeatable acquisition of magnetic resonance images of an object under investigation. The magnetic resonance device according to the invention shares the advantages of the local coil according to the invention.

[0120] In a preferred embodiment, the magnetic resonance device according to the invention includes a patient positioning device.

[0121] A patient positioning device is preferably designed to support the subject of the examination during a magnetic resonance imaging (MRI) scan and / or to hold it in a predetermined position relative to the MRI scanner. The patient positioning device can be, for example, a patient table, a patient couch, or a patient chair.

[0122] According to one embodiment, the retaining element of the local coil is mechanically connected to the patient positioning device, wherein the patient positioning device and / or the retaining element have a positioning unit which is configured to change a relative position and / or orientation of the second antenna unit to the patient positioning device.

[0123] The holding element can be mechanically connected to the magnetic resonance device, in particular a patient table. However, it is equally conceivable that the holding element is a separate component from the magnetic resonance device.

[0124] In this case, the mounting element can be attached to a wall and / or ceiling of an examination room of the magnetic resonance imaging (MRI) device or be reversibly connected to the patient positioning device. Preferably, the mounting element has at least one positioning unit configured to change the position of the mounting element and / or the second antenna unit of the local coil relative to the patient table and / or the object being examined. It is particularly conceivable that the positioning unit is designed to change the spatial position and / or orientation of the second antenna unit relative to the first antenna unit.

[0125] By providing a magnetic resonance device with a holding element and / or a positioning unit, the position and / or orientation of the second antenna unit relative to a patient positioning device with a specimen can be adjusted. This allows for the advantageous improvement or optimization of the quality of inductive coupling between the first and second antenna units for magnetic resonance imaging of a specimen, particularly a patient's jaw region.

[0126] Furthermore, the second antenna unit can be advantageously positioned precisely and repeatably in the application-specific position relative to an object under investigation by providing a holding element and / or a positioning unit according to the invention.

[0127] Further advantages and details will become apparent from the following description of exemplary embodiments in conjunction with the drawings. These show, in schematic representation: Fig. 1 a possible embodiment of a magnetic resonance system according to the invention, Fig. 2 a possible embodiment of a local coil according to the invention, Fig. 3 a possible embodiment of a local coil according to the invention, Fig. 4 a possible embodiment of a local coil according to the invention, Fig. 5 a possible embodiment of a local coil according to the invention, Fig. 6 a possible embodiment of a local coil according to the invention, Fig. 7 a possible embodiment of a local coil according to the invention, Fig. 8 an embodiment of a magnetic resonance device according to the invention with a local coil according to the invention.

[0128] In Fig. 1 Figure 1 schematically illustrates a possible embodiment of a magnetic resonance system 1 with a magnetic resonance device 10 and a local coil 26. The magnetic resonance device 10 comprises a magnet unit 11, which, for example, has a permanent magnet, an electromagnet, or a superconducting main magnet 12 for generating a strong and, in particular, homogeneous fundamental magnetic field 13 (B0 magnetic field). The magnetic resonance device 10 also includes a patient reception area 14 for receiving a test subject 15, in particular a patient 15. In the present embodiment, the patient reception area 14 is cylindrical and surrounded in a circumferential direction by the magnet unit 11. However, in principle, other configurations of the patient reception area 14 are also conceivable.

[0129] The patient 15 can be positioned in the patient reception area 14 of the magnetic resonance imaging (MRI) device 10 using a patient positioning system 16. For this purpose, the patient positioning system 16 includes a patient table 17 that is movable within the patient reception area 14. Of course, the MRI device can also include alternative patient positioning devices, such as a patient bed, a patient chair, a patient couch, or the like, in addition to the patient table 17 shown.

[0130] The magnet unit 11 further comprises a gradient coil 18 for generating magnetic gradient fields, which are used for spatial encoding during a magnetic resonance imaging (MRI) scan. The gradient coil 18 is controlled by a gradient control unit 19 of the MRI scanner 10. The magnet unit 11 can also include a high-frequency antenna, which in the present embodiment is designed as a body coil 20 permanently integrated into the MRI scanner 10. The body coil 20 is designed to excite atomic nuclei located in the fundamental magnetic field 13 generated by the main magnet 12. The body coil 20 is controlled by a high-frequency unit 21 of the MRI scanner 10 and transmits high-frequency signals into an examination space, which is essentially formed by a patient acquisition area 14 of the MRI scanner 10.The body coil 20 can also be configured to receive magnetic resonance signals.

[0131] The magnetic resonance device 10 includes a control unit 22 for controlling the main magnet 12, the gradient control unit 19, and the radio frequency unit 21. The control unit 22 is configured to control the execution of a sequence, such as an imaging gradient echo sequence, a TSE sequence, or a UTE sequence. Furthermore, the control unit 22 comprises a processing unit 28 for evaluating digitized magnetic resonance signals acquired during the magnetic resonance examination. The processing unit 28 can also be configured to employ reconstruction methods to reconstruct image data from reduced sets of k-space data when using parallel imaging techniques.

[0132] Furthermore, the magnetic resonance device 10 includes a user interface 23, which has a signal connection to the control unit 22. Control information, such as imaging parameters and reconstructed magnetic resonance images, can be displayed to a user on a display unit 24, for example, on at least one monitor, of the user interface 23. The user interface 23 also includes an input unit 25 by means of which the user can enter parameters of a magnetic resonance examination.

[0133] Furthermore, the magnetic resonance device 10 has a local coil 26, which is located in the Fig. 1 The example shown is positioned in an application-oriented position on a jaw region 43 of a patient 15 (see below). Fig. 2 The local coil 26 transmits magnetic resonance signals based on nuclear magnetic resonances from a volume of the jaw region 43 to the magnetic resonance device 10. The local coil 26 is preferably connected to an electrical connecting cable 27, which provides a signal connection to the high-frequency unit 21 and also to the control unit 22. Like the body coil 20, the local coil 26 can also be configured to excite atomic nuclei and receive magnetic resonance signals. For this purpose, the local coil 26 can, for example, have a transmitter unit (not shown) which is controlled by the high-frequency unit 21 to transmit high-frequency signals. The local coil 26 can at least partially encircle the patient's head 15 along a longitudinal extent of the patient 15. The local coil 26 can also have a retaining element 35 (see figure). Fig. 7 ), which is designed to hold or fix the local coil 26 or the second antenna unit 32 of the local coil 26 in an application-appropriate relative position to the first antenna unit 31 and the patient 15.

[0134] The depicted magnetic resonance device 10 can, of course, include further components that magnetic resonance devices typically have. It is also conceivable that the magnetic resonance device 10 has a C-shaped, a triangular, or an asymmetrical arrangement of the magnetic field-generating components instead of a cylindrical structure. In particular, the magnetic resonance device 10 can be a dedicated magnetic resonance device 10 designed to perform magnetic resonance imaging of the jaw region 43 of a standing or seated patient 15.

[0135] Fig. 2 Figure 1 shows a sectional view of a patient 15 with a local coil 26 according to the invention in a position suitable for use relative to the patient 15. The first antenna unit 31 is shaped to resemble a dental arch of the patient 15 and has a substantially planar form. In this case, the first antenna unit 31 is positioned in an occlusal plane between an upper and a lower dental arch of the patient 15. Preferably, a surface of the first antenna unit 31 is designed with regard to biocompatibility and touch protection such that the patient 15 can bite down on the first antenna unit to lock it in place during the magnetic resonance examination.

[0136] The second antenna unit 32 is positioned in a predetermined relative position to the first antenna unit 31. With the local coil 26 positioned as required, the angle between a surface normal of a main surface of the first antenna unit 31 and a surface normal of a main surface of the second antenna unit 32 lies in a range between 60° and 120°. Preferably, the surface normal of the main surface of the first antenna unit 31 is oriented substantially orthogonally to the surface normal of the main surface of the second antenna unit 32.In the present case, the first antenna unit 31 and the second antenna unit 32 are arranged relative to the patient 15 in such a way that a geometric center 41 of the first antenna unit 31 lies at an intersection of a surface normal of the main surface of the second antenna unit 32 with a surface normal of the first antenna unit 31.

[0137] In the example shown, the second antenna unit 32 has at least one receiving element 33. According to one embodiment of the invention, the receiving element 33 is configured as a butterfly coil. The second antenna unit 32 can have a plurality of receiving elements 33. Preferably, the second antenna unit 32 comprises a support structure 30, which is mechanically connected to the receiving element 33 or the plurality of receiving elements 33. The receiving element 33 or the plurality of receiving elements 33 can further be embedded in the support structure 30. The support structure 30 can be configured as part or a section of a retaining element 35 (see [reference]). Fig. 6 ), which is designed to hold the second antenna unit 32 in a predetermined relative position to the first antenna unit 31, so that inductive coupling between the first antenna unit 31 and the second antenna unit 32 is achieved. The support structure 30 can also be mechanically connected to the holding element 35.

[0138] As in Fig. 2 As shown, the second antenna unit 32 is preferably shaped like a hollow cylindrical sector. The second antenna unit 32 can thus at least partially enclose or surround the jaw region 43 of the patient 15, as well as the first antenna unit 31, along the outer contour of the jaw region 43. A cross-section of the second antenna unit 32 can have a convex-concave shape, as shown. When the local coil 26 is positioned relative to the patient 15 as required, the first antenna unit 31 is at least partially surrounded or enclosed by the concave surface of the second antenna unit 32 along one circumferential direction of the first antenna unit 31.

[0139] Fig. 3 Figure 1 shows a frontal view of a patient 15 with a local coil 26 according to the invention. The second antenna unit 32 is positioned in a typical application position on the jaw region 43 of the patient 15. A representation of a support structure 30 has been omitted for the sake of clarity regarding the arrangement of the receiving elements 33. With the local coil 26 positioned as applicable, the support structure 30 can be located a short distance from the skin surface of the jaw region 43 of the patient 15. The distance between the second antenna unit 32 and the skin surface of the jaw region 43 of the patient can be, for example, between one millimeter and ten millimeters. However, it is also conceivable that the distance between the second antenna unit 32 and the skin surface of the jaw region 43 of the patient 15 is less, or that the second antenna unit 32 is at least partially in contact with the skin surface of the patient 15.

[0140] In the Fig. 3 In the example shown, the second antenna unit 32 has a receiving element 33c, which is designed as a butterfly coil. A crossing point of the signal conductor of the butterfly coil is arranged in the same plane as the first antenna unit 31. The two loops of the signal conductor of the butterfly coil 33 are preferably arranged on a lower jaw and an upper jaw of the patient 15, respectively.

[0141] Fig. 4 Figure 1 shows an embodiment of the local coil 26 according to the invention, in which the second antenna unit 32 has two receiving elements 33a and 32b (32a-b). The geometric centers 51 of the two receiving elements 33a-b are arranged on the jaw region 43 along a sagittal plane 50 of the patient 15 when the second antenna unit 32 is positioned as per application. In the example shown, the at least two receiving elements 33a-b partially overlap.

[0142] The at least two receiving elements 33a-b can be arranged along the surface contour of the second antenna unit 32 such that a line of intersection 52 of the at least two receiving elements 33a-b is arranged parallel to a main surface of a receiving coil of the first antenna unit 31 and / or coincides with a plane of the first antenna unit 31.

[0143] It is conceivable that, in addition to the ones in Fig. 3 and Fig. 4 In addition to the receiver elements 33 shown, further receiver elements 33 are arranged along the surface contour of the second antenna unit 32 and / or the support structure 30.

[0144] Fig. 5 Figure 1 shows a further embodiment of the local coil 26 according to the invention. The second antenna unit 32 has three receiving elements 33c, 33d and 33e (33c-e). The receiving element 33c is designed as a butterfly coil, which is essentially the same as the one shown in Figure 2. Fig. 3 corresponds to the embodiment shown.

[0145] The geometric centers 51 of the three receiving elements 33c-e are arranged along the transverse plane 53 of the patient 15. Furthermore, the geometric centers 51 of at least two receiving elements 33d and 33e are arranged along a straight line oriented parallel to a main surface of the first antenna unit 31 and / or the occlusion plane of the patient 15.

[0146] In the present example, the two receiving elements 33d and 33e flank the receiving element 33c along the Z-direction. The signal conductors of the receiving elements 33d and 33e can connect to the signal conductor of the receiving element 33c as shown in Fig. 5 The signal conductors shown cross or overlap. However, it is also conceivable that the signal conductors of the receiving elements 33d and 33e are arranged next to the signal conductor of the receiving element 33c in such a way that a crossing of signal conductors is avoided.

[0147] It is also conceivable that, instead of the butterfly coil 33c, two receiving elements 33a and 33b are arranged along the surface contour of the second antenna unit 32. In this case, the second antenna unit 32 has four receiving elements 33a, 33b, 33d, and 33e. The geometric centers 51 of the two receiving elements 33d and 33e can be arranged along a straight line oriented parallel to a main surface of the first antenna unit 31 and / or an occlusion plane of the patient 15. It is equally conceivable that the geometric centers 51 of two receiving elements 33d and 33e configured as butterfly coils lie essentially in the same plane as a main surface of the first antenna unit 31.

[0148] Furthermore, the geometric centers 51 of the two receiving elements 33a and 33b can be arranged along the sagittal plane 50 of the patient 15 (cf. Fig. 4 ).

[0149] Preferably, the second antenna unit 32 has, instead of the receiving elements 33d and 33e shown, two receiving elements 33d.1 and 33d.2 as well as 33e.1 and 33e.2 (not shown), the geometric centers of which are as shown in Fig. 4 The antenna elements are shown offset along a sagittal plane of the patient 15. The geometric centers 51 of the two receiving elements 33d.1 and 33e.1 or 33d.2 and 33e.2 can each be arranged along a straight line that is parallel to and at a distance above or below a main surface of the first antenna unit 31 and / or an occlusion plane of the patient 15.

[0150] Fig. 6 Figure 1 shows a further embodiment of the local coil 26 according to the invention. In this example, the second antenna unit 32 has a total of nine receiving elements 33f to 33j (33f-j). The three receiving elements 33f, 33g and 33h (33f-h) are configured as butterfly coils whose geometric centers or intersection points (not shown) are arranged along the transverse plane 53 of the patient 15. In particular, the geometric centers of the two butterfly coils 33f and 33h are arranged along a straight line that is oriented parallel to the main surface of the first antenna unit 31 and / or an occlusion plane of the patient 15.

[0151] Furthermore, each butterfly coil 33f-h is flanked along the X-direction by two receiving elements 33i and 33j. The signal conductors of a butterfly coil 33f, 33g, or 33h can intersect with signal conductors of the receiving elements 33i and / or 33j. However, it is also conceivable that the receiving elements 33f-j are arranged in such a way that an overlap of receiving elements 33 or an intersection of signal conductors is avoided.

[0152] It is also conceivable that the second antenna unit 32 has two receiving coils 33a and 33b each, instead of one or more butterfly coils 33f-h, according to an embodiment described above.

[0153] Preferably those in the Figuren 3 bis 6 The butterfly coils 33c, 33f, 33g and / or 33h shown and the receiving elements 33a, 33b, 33d, 33e, 33i and / or 33j are galvanically isolated to allow separate reading of individual receiving elements 33.

[0154] Each pair of receiving elements 33 of an embodiment described above can, for example, have an overlap area with a dimension of 0.5 cm to 2 cm. It is further conceivable that the support structure 30 has a compensation mechanism (not shown) which adjusts the overlap area between the two adjacent receiving elements 33 in the event of deformation of the support structure 30. The receiving elements 33 can be inductively decoupled from each other by means of the overlap area.

[0155] The receiving elements 33 of the second antenna unit 32 can be embedded in a material of the support structure 30 and / or be connected to the support structure 30 in a form-fitting, force-fitting and / or material-fitting manner.

[0156] Fig. 7 Figure 1 shows an embodiment of the local coil 26 according to the invention, in which the second antenna unit 32 is mechanically connected to a holding element 35. The holding element 35 is designed to hold the second antenna unit 32 in a predetermined relative position to the first antenna unit 31 and the jaw region 43 of the patient 15.

[0157] For example, the second antenna unit 32 and the retaining element 35 can have complementary plug-in elements 36a and 36b, which interlock when the second antenna unit 32 and the retaining element 35 are properly assembled. This prevents the second antenna unit 32 from being involuntarily shifted or moved by the patient 15. The plug-in elements 36a and 36b can also be configured to provide an electrical connection between the second antenna unit 32 and the electrical connecting line 27. In the example shown, received magnetic resonance signals from the second antenna unit 32 are transmitted to the processing unit 28 of the magnetic resonance device 10 via the electrical connecting line 27a. The processing unit 28 can then reconstruct a magnetic resonance image from the received magnetic resonance signals.

[0158] If the second antenna unit 32 has a transmitter unit, an alternating current can be transmitted via the electrical connecting line 27b from the high-frequency unit 21 via the plug-in elements 36a and 36b to the transmitter unit of the local coil 26, which then sends a high-frequency signal into the jaw region 43 of the patient 15.

[0159] In the Fig. 7 In the example shown, the electrical connecting lines 27a and 27b are arranged on opposite sides of the mounting element 35 for better clarity. Naturally, the second antenna unit 32 can be connected to the electrical connecting lines 27a and 27b by means of separate or shared connectors (36a, 36b) and / or at any position on the second antenna unit 32 or the support structure 30.

[0160] In the present example, the retaining element 35 has a plurality of mechanically separated components. In addition to the two struts 35a and 35b, which have the plug-in elements 36b, the retaining element 35 also includes a head cup 35c, which is designed to restrict or prevent movement of the patient's head 15 during the magnetic resonance examination.

[0161] Fig. 8 shows an embodiment of the magnetic resonance device 10 according to the invention, in which the holding element 35 is mechanically connected to the patient table 17 of the patient positioning system 16 (see Fig. 1 ) is connected. In the example shown, the patient 15 is lying on the patient table 17. The head of the patient 15 can be positioned on a headrest 35c or any head support designed to receive, support, and / or stabilize the head of the patient 15. The support element 35, for example, has a one-piece body or struts 35a and 35b (see Figure 1). Fig. 7 ) which places the antenna unit 32 in a predetermined relative position to the first antenna unit 31 and the jaw region 43 of the

[0162] Patient 15 is held. The second antenna unit 32 can be connected to the struts 35a and 35b or to the body of the holding element 35 by means of a plug connection (36a, 36b) or any reversible mechanical connection.

[0163] Furthermore, the retaining element 35 in this case has a positioning unit 40, which is designed to change the position of the retaining element 35 and / or the second antenna unit 32 at least along the Z-direction relative to the patient table 17. The positioning unit 40 can, for example, be designed as a guide mechanism, such as a rail, which enables manual and / or automated movement of the second antenna unit 32 along the Z-direction.

[0164] The positioning unit 40 can further be configured to enable relative alignment of the second antenna unit 32 with respect to the first antenna unit 31, the patient 15, and / or the patient table 17. The positioning unit 40 can, for example, have a hinge, a joint, and / or a pivoting mechanism (not shown) configured to tilt or pivot the second antenna unit 32 in one or more spatial directions.

[0165] It is conceivable that the local coil 26 according to the invention comprises a single positioning unit 40, which is configured to change the orientation and / or position of the second antenna unit 32 relative to the first antenna unit 31 and / or the patient 15. It is also conceivable that the positioning unit 40 comprises at least a first adjustment mechanism and a second adjustment mechanism. The first adjustment mechanism can, for example, be configured to change the position of the second antenna unit 32 along the Z-direction, while the second adjustment mechanism is configured to change the orientation of the second antenna unit 32 relative to the patient 15 and / or the patient positioning device 16.

[0166] Although the invention has been illustrated and described in detail by the preferred embodiments, the invention is nevertheless not limited by the disclosed examples and other variations can be derived by the person skilled in the art without leaving the scope of protection of the invention as defined by the claims.

Claims

1. Local coil (26), comprising a first antenna unit (31) and a second antenna unit (32), wherein the first antenna unit (31) and the second antenna unit (32) are galvanically separated and are embodied to receive magnetic resonance signals of an examination object (15), wherein the examination object (15) is a jaw region of a patient, wherein when the local coil (26) is positioned relative to the examination object (15) as per the application: • the second antenna unit (32) encloses the first antenna unit (31) at least partially along a peripheral direction of the first antenna unit (31), wherein • the first antenna unit (31) has a substantially planar design and is embodied to be arranged along an occlusion plane in an oral cavity of the examination object (15), wherein • the second antenna unit (32) is arranged on an outer surface of the examination object (15), and wherein • the second antenna unit (32) has an inductive coupling to the first antenna unit (31); wherein the second antenna unit (32) is embodied to detect a magnetic resonance signal received by the first antenna unit (31) by means of the inductive coupling, wherein • the second antenna unit (32) has at least one receive element (33), wherein the at least one receive element (33) is designed as a butterfly coil and wherein a point of intersection of the butterfly coil is arranged in a plane with the first antenna unit or wherein • the second antenna unit (32) has at least two receive elements (33), which are arranged adjacent to one another along a surface contour of the second antenna unit (32) or at least partially overlap, wherein the at least two receive elements (33) are embodied to be read out independently of one another and wherein the at least two receive elements define a plane of symmetry or a line of intersection, which is aligned substantially parallel to a main surface of the first antenna unit.

2. Local coil according to claim 1, further having a holding element (35), which is embodied to hold the second antenna unit (32) in a predetermined position relative to the first antenna unit (31) against the outer surface of the examination object (15).

3. Local coil according to claim 2, wherein the holding element (35) is embodied to hold the second antenna unit (32) against the outer surface of the examination object (15), when the local coil (26) is positioned relative to the examination object (15) as per the application, such that a surface normal of a main surface of the first antenna unit (31) is aligned substantially orthogonally to a surface normal of a main surface of the second antenna unit (32).

4. Local coil according to one of the preceding claims 2 or 3, wherein the holding element (35) is embodied to hold the second antenna unit (32) against the outer surface of the examination object (15) in such a way that a geometric centre point (41) of the first antenna unit (31) is arranged in a point of intersection of a surface normal of the main surface of the second antenna unit (31) with a surface normal of the main surface of the first antenna unit (31).

5. Local coil according to one of the preceding claims, wherein the second antenna unit (32) is shaped to match a hollow cylinder sector and encloses the examination object (15) at least partially along an outer contour of the examination object (15) when the local coil (26) is positioned relative to the examination object (15) as per the application.

6. Local coil according to one of the preceding claims, wherein a receive element of the first antenna unit (31) is arranged in a plane, which intersects the first antenna unit (31) and is aligned parallel to a main surface of the first antenna unit (31), wherein a geometric centre point of the second antenna unit (32) lies in the plane of the receive element of the first antenna unit (31) when the local coil (26) is positioned relative to the examination object (15) as per the application.

7. Local coil according to one of the preceding claims, wherein the second antenna unit (32) has at least three receive elements (33), wherein the at least three receive elements (33) are arranged adjacent to one another along a surface contour of the second antenna unit (32) or at least partially overlap.

8. Local coil according to one of the preceding claims, wherein the second antenna unit (32) is shaped to match an outer contour of the jaw region (43) of the patient (15) and at least partially encloses the jaw region (43) along the outer contour.

9. Local coil according to claim 8, wherein geometric centre points (51) of at least two receive elements (33) of the second antenna unit (32) are arranged along a sagittal plane (50) of the patient (15) and wherein the at least two receive elements (33) are arranged adjacent to one another or at least partially overlap.

10. Local coil according to one of claims 8 or 9, wherein geometric centre points (51) of at least three receive elements (33) of the second antenna unit (32) are arranged along a transversal plane (53) of the patient (15) and wherein the at least three receive elements (33) are arranged adjacent to one another or partially overlap.

11. Local coil according to one of claims 8 to 10, wherein geometric centre points (51) of at least two receive elements (33) of the second antenna unit (32) are arranged along a straight line, which is aligned parallel to a main surface of the first antenna unit (31) and / or an occlusion plane of the patient (15).

12. Magnetic resonance apparatus (10), having a local coil (26) according to one of the preceding claims, wherein the magnetic resonance apparatus (10) is embodied to detect magnetic resonance signals of the examination object (15) received by the first antenna unit (31) by means of the inductive coupling to the second antenna unit (32).

13. Magnetic resonance apparatus (10) according to claim 12 with a local coil (26) according to claim 2, further having a patient support apparatus (17), wherein the holding element (35) of the local coil (26) is connected mechanically to the patient support apparatus (17), and wherein the patient support apparatus (17) and / or the holding element (35) have a positioning unit (40) which is embodied to change a position and / or alignment of the second antenna unit (32) relative to the patient support apparatus (17).