DE102021205916A1 - Magnetic resonance device with a thermally coupled radio frequency unit - Google Patents

Abstract

The invention relates to a magnetic resonance device, having a magnetic field unit with a superconducting main magnet and a high-frequency unit, wherein the superconducting main magnet is designed to provide a static magnetic field and the high-frequency unit is designed to receive magnetic resonance signals in a frequency and power range of a magnetic resonance measurement, wherein the high-frequency unit is thermally coupled to a cooling system for the superconducting main magnet of the magnetic resonance apparatus.The invention also relates to a high-frequency unit having at least one antenna element which is designed to receive a high-frequency signal in the frequency and power range of a magnetic resonance measurement, the antenna element having a superconducting Has element which is thermally coupled to a cooling system of a magnetic resonance apparatus according to any one of the preceding claims.

Description

The invention relates to a magnetic resonance device, having a magnetic field unit with a superconducting main magnet and a high-frequency unit, the superconducting main magnet being designed to provide a static magnetic field and the high-frequency unit being designed to receive magnetic resonance signals in a frequency and power range of a magnetic resonance measurement. The invention also relates to a high-frequency unit, having at least one antenna element which is designed to receive a high-frequency signal in the frequency and power range of a magnetic resonance measurement.

Magnetic resonance tomographs are imaging devices which, in order to image an examination object, align nuclear spins of the examination object with a strong external magnetic field and excite them to precess around this alignment by means of an alternating magnetic field. The precession or return of the spins from this excited state to a lower-energy state in turn generates an alternating magnetic field in response, also known as a magnetic resonance signal, which is received via antennas.

With the help of magnetic gradient fields, a spatial coding is impressed on the signals, which subsequently enables the received signal to be assigned to a volume element. The signal received is then evaluated and a three-dimensional imaging representation of the examination object is provided.

To generate the strong external magnetic field with field strengths greater than 0.5 or 1 Tesla, superconducting magnets are usually used, which have to be cooled below a transition temperature of a few Kelvin. Despite the thermal insulation, permanent cooling or the removal of thermal energy from the superconducting element is required in order to ensure the required temperature. Among other things, so-called pulse tube coolers are used for cooling, which achieve a temperature gradient from room temperature to the temperature of liquid helium in one stage. The thermal energy is usually at a hot side of the pulse tube cooler, such. B. a heat exchanger, dissipated. In order to cool the pulse tube cooler, it is usually connected to a building cooling system which includes a chiller or a combination of chillers.

Today's magnetic resonance devices are largely designed as whole-body systems with a high-field magnet (eg, 1.5 T and more). Such whole-body systems with a high field have a considerable weight and complex system technology, such as e.g. B. a required electrical and thermal infrastructure. In the case of smaller magnetic resonance devices with a low-field magnet (eg less than 1.5 T), the weight and the outlay for the system technology can be reduced accordingly. In particular, by using low-field magnets, costs and space requirements can be reduced compared to conventional high-field magnets, and new areas of application, such as e.g. B. dedicated magnetic resonance devices for an imaging examination of specific body regions of a patient. However, lower magnetic field strengths are associated with a lower signal-to-noise ratio of acquired magnetic resonance signals, which can represent a significant limitation for the usability of such low-field magnets.

It is therefore an object of the present invention to increase a signal-to-noise ratio of a magnetic resonance device.

This object is achieved according to the invention by the subject matter of the independent patent claims. Advantageous embodiments and expedient developments are the subject matter of the dependent claims

The magnetic resonance device according to the invention has a magnetic field unit with a superconducting main magnet and a high-frequency unit, the superconducting main magnet being designed to provide a static magnetic field.

The static magnetic field of the magnetic resonance device can represent a main magnetic field (B0 magnetic field) of the magnetic resonance device. For example, the static magnetic field of the magnetic resonance device can be designed as a homogeneous main magnetic field or have a predetermined magnetic field gradient. In one embodiment, the static magnetic field of the superconducting main magnet has a magnetic field strength in a range between 0.01 and 1.5 Tesla. The static magnetic field preferably has a magnetic field strength of between 0.1 and 1 Tesla. It is also conceivable that the static magnetic field has a magnetic field strength between 0.3 and 0.5 Tesla. The superconducting main magnet can have one or more magnets or magnet segments to provide the static magnetic field.

The superconducting main magnet of the magnetic resonance device can have a superconducting wire which is wound in a coil shape is. The superconducting wire may be wound in a predetermined pattern. Preferably, the superconducting main magnet is in the form of a solenoid. In this case, the superconducting main magnet can enclose an essentially cylindrical image recording area of the magnetic resonance device along at least part of a cylinder axis of the image recording area. However, the superconducting main magnet can also have any other desired shape. For example, the superconducting wire may be wound and/or arranged as a substantially planar loop or as a tubular segment. It is also conceivable that the superconducting main magnet or a segment of the superconducting main magnet has the shape of a tube with an oval or polygonal cross-section. The superconducting main magnet may be thermally coupled to a cryostat cooling fluid to cool the superconducting main magnet to a predetermined temperature or temperature range. It is conceivable that the superconducting main magnet is cooled with liquid helium by means of the cryostat to ensure a temperature of about 4 K. In this case, the superconducting main magnet can be embodied as a so-called low-temperature superconductor. However, it is also conceivable that the superconducting main magnet is designed as a high-temperature superconductor, which is cooled in a temperature range between 40 to 100 K or 20 to 60 K.

The imaging area can represent a volume in which a patient is positioned in order to carry out a magnetic resonance examination of the patient. The magnetic resonance device can have an opening which provides access to the imaging area. The opening can represent an oval or polygonal hole. For example, the opening is positioned at one end of a cylindrical imaging area. The opening is preferably dimensioned in such a way that a head and/or a shoulder area of a patient can be passed through the opening into the imaging area.

It is also conceivable that the magnetic resonance device has one or more gradient magnets, which are designed to generate a magnetic gradient field in the image recording area. A gradient magnet can represent a coil with an electrical conductor. The electrical conductor of the gradient magnet may be arranged such that the gradient magnetic field is generated in the imaging area when a predetermined current is passed through the electrical conductor. For this purpose, the electrical conductor of the gradient magnet can be connected to a suitable power supply. The magnetic gradient field can be used in particular for spatial coding of magnetic resonance signals which are acquired from the imaging area. It is also conceivable that the gradient magnetic field is configured to manipulate a phase and/or a frequency of spins in the imaging region in a detuned manner. The gradient magnet can be thermally coupled to a cooling system for the superconducting main magnet of the magnetic resonance device.

The high-frequency unit can be designed to receive magnetic resonance signals in a frequency and power range of a magnetic resonance measurement from the image recording area of the magnetic resonance device. For this purpose, the high-frequency unit can have at least one antenna element, which detects received magnetic resonance signals and forwards them to a preamplifier or an amplifier. The preamplifier and/or the amplifier are preferably connected electrically and/or mechanically to the high-frequency unit. The preamplifier and/or the amplifier can be designed to raise a low signal level of a magnetic resonance signal and to make it available to a processing unit of the magnetic resonance device. In one embodiment, the high-frequency unit is also designed to emit a high-frequency excitation pulse into the imaging area. The amplifier and/or the preamplifier can be designed accordingly to provide and/or condition an electrical current for the high-frequency unit.

The magnetic resonance device is preferably designed to acquire magnetic resonance signals from an examination subject, which is positioned in the imaging area, by means of the high-frequency unit. However, the magnetic resonance device can also have further components which are usually required for carrying out a magnetic resonance measurement and for processing acquired magnetic resonance signals. The magnetic resonance device can in particular have a computing unit which is designed to reconstruct a magnetic resonance image as a function of the magnetic resonance signals recorded from the image recording region.

The high-frequency unit is thermally coupled to the cooling system for the superconducting main magnet of the magnetic resonance device, the high-frequency unit being able to be cooled to a temperature level below an ambient temperature by means of the thermal coupling to the cooling system. An ambient temperature can at be between 280 and 300 K, for example. A temperature level that is below the ambient temperature can therefore be lower than 290 K, 280 K or 270 K. It is also conceivable that the temperature level is below 200 K, 150 K or 100 K. The temperature level can correspond to a temperature level of cryogenic cooling. The high-frequency unit can preferably be cooled to a temperature level below a critical temperature of a superconducting element.

In particular, it is conceivable for the preamplifier and/or the amplifier to be thermally coupled to the cooling system for the main magnet of the magnetic resonance device. The cooling system for the superconducting main magnet can in particular be a cryostat. A cryostat may have a cooling fluid thermally coupled to the superconducting main magnet and the radio frequency unit. For example, the cryostat can include a vessel or container which is designed to hold and/or store the cooling fluid at a temperature level required for superconducting properties. The receptacle or container can enclose at least a section of the superconducting main magnet, but also a section of the high-frequency unit. The cryostat preferably has a heat-insulating element, which reduces a transfer of heat energy to the superconducting main magnet and/or the high-frequency unit from an environment and/or from components of the magnetic resonance apparatus. In a preferred embodiment, the cooling fluid is a low boiling point fluid such as e.g. B. argon, nitrogen, neon, helium or the like. The cooling fluid can be in a liquid and/or a gaseous state. The cryostat can in particular be a refrigeration unit such. B. have a pulse tube cooler, a Gifford-McMahon cooler, a Sterling cooler, a Joule-Thomson cooler or the like, which is designed to provide a predetermined temperature of the cooling fluid.

The high-frequency unit of the magnetic resonance device is preferably mechanically connected to the magnetic resonance device in a predetermined relative position. However, it is also conceivable for the high-frequency unit to have a positioning unit which is designed to position the high-frequency unit along at least one spatial direction, with a thermal coupling between the cooling system for the superconducting main magnet and the high-frequency unit being maintained.

A thermal coupling can be any connection that enables thermal energy to be transported between the cooling system for the superconducting main magnet and the radio frequency unit. The thermal coupling can in particular be provided passively. For example, the thermal coupling is provided by means of a heat-conducting element, which is designed to transport heat energy between the high-frequency unit and the cooling system by means of heat conduction. A heat pipe and/or a fluid channel, which transport thermal energy as a function of convection processes between the high-frequency unit and the cooling system for the superconducting main magnet of a suitable working fluid, are also considered passive thermal coupling. The thermal coupling can, of course, include other components that are suitable for transporting thermal energy between two materials and/or systems. An example of such a component is a heat exchanger. The thermal coupling is preferably designed such that at least part of the high-frequency unit can be cooled to a temperature level of below 100K, 80K, 60K, 40K or 20K.

In a preferred embodiment, the magnetic resonance device according to the invention is adapted to a specific body region of a patient and designed to carry out a magnetic resonance device in the specific body region. This can mean that the imaging area, the superconducting main magnet and/or at least a part of the high-frequency unit are shaped to match the specific body region of the patient and/or an imaging volume of the magnetic resonance device is matched to the specific body region. In one example, the magnetic resonance device according to the invention can be designed as a dedicated head scanner, a dental scanner or a dedicated extremity scanner.

An imaging volume can be characterized by a predetermined magnetic field direction and/or a predetermined magnetic field strength. For example, the imaging volume can include a volume with a substantially homogeneous magnetic field direction and/or a substantially homogeneous magnetic field strength. An imaging volume can in particular be an isocenter of the magnetic resonance device. However, it is also conceivable that the imaging volume has a predetermined magnetic field gradient. Such a magnetic field gradient can, for. B. for a spatial coding of magnetic resonance signals, which are received from an examination subject in the imaging area, are used.

A cost-efficient and/or space-efficient implementation of a high-frequency unit with a superconducting element can be provided by means of the magnetic resonance device according to the invention. Furthermore, a signal-to-noise ratio of acquired magnetic resonance signals can advantageously be increased in comparison to conventional magnetic resonance devices with the same magnetic field strength. This can in particular be associated with an improved sensitivity of the high-frequency unit and/or an improved quality of acquired magnetic resonance images. Furthermore, a specific absorption rate of the patient can be advantageously reduced during a magnetic resonance examination with the same image quality. Further advantages can be a reduction in susceptibility problems and/or improved contrast behavior, e.g. B. in an imaging of the heart represent.

In one embodiment of the magnetic resonance device according to the invention, the high-frequency unit has a superconducting element which is designed to receive high-frequency signals in a frequency and power range of a magnetic resonance measurement, the superconducting element of the high-frequency unit comprising a low-temperature superconductor or a high-temperature superconductor.

The superconducting element of the high-frequency unit is preferably designed to receive high-frequency signals in a frequency and power range of a magnetic resonance measurement. For this purpose, the superconducting element can comprise at least one antenna element, which is designed to receive electromagnetic waves in the range of a magnetic resonance frequency of a magnetic resonance-active atomic nucleus. Such electromagnetic waves can have a frequency between 1 and 500 MHz, preferably between 1 and 300 MHz. The magnetic resonance signal of the usual atomic nuclei to be examined can have a low power of a few microwatts to several milliwatts. The at least one antenna element can also be designed to emit a high-frequency signal. Depending on the basic magnetic field of a magnetic resonance device, the high-frequency signal emitted by the at least one antenna element can be in a power range between a few watts and several kilowatts and have a frequency between 1 and 500 MHz, preferably 1 and 300 MHz.

The superconducting element preferably comprises a material with superconducting properties. In particular, the superconducting element of the high-frequency unit can have a superconducting material which corresponds to a superconducting material of the superconducting main magnet. Examples of materials with high-temperature superconducting properties are barium copper oxides (e.g. YBCO, ReBCO), calcium copper oxides (e.g. BSCCO), but also other materials such as fullerides (e.g. Cs ₂ RbC ₆₀ ) , magnesium diborides and the like. Examples of materials with low-temperature superconducting properties are niobium-titanium, niobium-tin or magnesium diboride. Filaments or wires of the superconducting material can be in an electrical conductor such. B. copper, gold, aluminum or the like embedded.

By providing a radio-frequency unit with a superconducting element, a signal-to-noise ratio of the radio-frequency unit can be increased in an advantageous manner when receiving magnetic resonance signals from the imaging area. Furthermore, a required temperature level can be increased by means of a high-temperature superconductor compared to conventional low-temperature superconductors. As a result, the efficiency of the cooling system can be increased and/or energy costs for operating the cooling system can be advantageously reduced.

• • als eine Körperspule, welche einen Bildaufnahmebereich der Magnetresonanzvorrichtung zumindest teilweise außenumfänglich umschließt, und/oder
• • ein Antennenelement, welches zumindest einer Körperregion eines Patienten nachgeformt ist und in einer anwendungsgemäßen Position in dem Bildaufnahmebereich an der Körperregion des Patienten positioniert ist,

ausgebildet.According to one embodiment of the magnetic resonance device according to the invention, the superconducting element is the high-frequency unit

• • as a body coil, which at least partially encloses an image recording area of the magnetic resonance device on the outside, and/or
• • an antenna element, which is shaped after at least one body region of a patient and is positioned in an application-appropriate position in the image recording area on the body region of the patient,

educated.

The superconducting element of the high-frequency unit can be designed as a body coil, which at least partially encloses the image recording area along a cylinder axis of an essentially cylindrically shaped image recording area. The superconducting element of the high-frequency unit is preferably thermally coupled to the cooling fluid for cooling the superconducting main magnet. However, it is also conceivable that the body coil of the high-frequency unit is arranged in a separate cryostat, which is thermally coupled to the cooling fluid for cooling the superconducting main magnet and/or the cooling unit by means of a heat-conducting element and/or a heat pipe. A body coil with a superconducting element can be advantageous Way to arrange a cylindrical imaging area of the magnetic resonance device according to the invention and thermally connect to the cooling system for the superconducting main magnet.

It is also conceivable that the superconducting element is designed as an antenna element which is directed to a specific body region of the patient, such as e.g. B. a head, a leg, an arm, a jaw region or the like, and this at least partially encloses. The high-frequency unit can be designed in particular as a local coil, which is positioned in a position appropriate to the application in the image recording area on the body region of the patient. In this case, the local coil can have one or more superconducting antenna elements, which are arranged next to one another and/or partially overlapping in a matrix. It is further conceivable that the matrix of superconducting antenna elements has a three-dimensional shape which is shaped after the specific body region of the patient.

By providing a local coil with a superconducting antenna element, which is positioned in the application-appropriate position on the specific body region of the patient, a particularly high signal-to-noise ratio of detected magnetic resonance signals can be achieved in an advantageous manner.

• • im Wesentlichen mit einem Temperaturniveau des supraleitenden Hauptmagneten übereinstimmt oder welches
• • das Temperaturniveau des supraleitenden Hauptmagneten überschreitet, wobei das Temperaturniveau unterhalb einer kritischen Temperatur des supraleitenden Elements der Hochfrequenzeinheit liegt.

According to a further embodiment of the magnetic resonance device according to the invention, the cooling system is designed to cool the superconducting element of the high-frequency unit to a temperature level which

• • essentially corresponds to a temperature level of the superconducting main magnet or which
• • exceeds the temperature level of the superconducting main magnet, the temperature level being below a critical temperature of the superconducting element of the high-frequency unit.

A critical temperature of the superconducting element of the high-frequency unit is preferably characterized by a maximum temperature at which the superconducting element of the high-frequency unit exhibits superconducting properties. Such a temperature can in particular represent a temperature level of cryocooling or require cryocooling. Preferably, the superconducting element of the high-frequency unit is a high-temperature superconductor when the main superconducting magnet is a high-temperature superconductor, and a low-temperature superconductor when the main superconducting magnet is a low-temperature superconductor. It is also conceivable that the main superconducting magnet comprises a low-temperature superconductor, while the superconducting element of the high-frequency unit is a high-temperature superconductor. In this embodiment, the high-temperature superconductor of the high-frequency unit is preferably cooled by means of a separate branch of the cooling system.

For example, a vaporized phase of the cooling fluid for the superconducting main magnet can be used to cool the superconducting element of the radio frequency unit. It is also conceivable that the cooling unit of the cryostat has a separate stage and/or a heat exchanger, which cool the cooling fluid and/or a second cooling fluid to a temperature level suitable for cooling the high-temperature superconducting element of the high-frequency unit. For example, the separate stage and/or the heat exchanger can be characterized by a temperature level which is set by the cooling fluid absorbing heat energy from a low-temperature superconducting main magnet. The cooling unit of the cryostat can have a first coupling point for heat transfer with the cooling fluid for the superconducting main magnet and a second coupling point for heat transfer with the cooling fluid for the superconducting element of the high-frequency unit. A first coupling point may represent a first stage of the chiller, while a second coupling point represents a second stage of the chiller. A temperature of the second stage of the cooling unit can exceed a temperature of the first stage of the cooling unit. A coupling point can be viewed in particular as a heat exchanger and/or a heat-conducting element, which are designed to support or improve a transfer of thermal energy.

It is also conceivable that the cooling fluid for cooling the superconducting main magnet is thermally coupled to the second cooling fluid for the superconducting element of the high-frequency unit by means of a heat exchanger, a heat pipe and/or the heat conducting element. A heat transfer surface between the cooling fluid and the second cooling fluid can be designed in such a way that the superconducting main magnet and the superconducting element of the high-frequency unit are cooled to predetermined temperature levels in each case. In particular, a predetermined temperature level for the superconducting main magnet can be about 4K, while the predetermined temperature level for the superconducting element of the high-frequency unit has a value between 40 and 100K or between 20 and 60K. The predetermined temperature level of a high-temperature superconducting magnets can of course also be higher or lower depending on a material used or a material composition of the high-temperature superconductor.

By using a high-frequency unit with a superconducting element, the cooling system for a superconducting main magnet of the magnetic resonance apparatus can also be used for cooling the high-frequency unit. As a result, expenditure on a separate cooling system for cooling the high-frequency unit can be avoided in an advantageous manner.

In a further embodiment of the magnetic resonance device according to the invention, the cooling system has a heat pipe which is designed to thermally couple the cooling system to the superconducting element of the high-frequency unit.

A heat pipe can be in the form of a hollow cylinder or a hose which is closed in a fluid-tight manner at both ends and encloses a working fluid in an interior. The working fluid can vaporize by absorbing thermal energy at a first end and release the thermal energy with condensation at a second end. The evaporating working fluid is transported from the first end to the second end due to pressure and temperature differences and thus enables a material-bound heat transport within the heat pipe. Examples of possible working fluids are helium, nitrogen and the examples described above for the cooling fluid or the second cooling fluid.

It is conceivable that the superconducting element of the high-frequency unit is thermally coupled to the cooling system by means of a heat pipe. The superconducting element of the high-frequency unit can of course also be thermally coupled to the cooling unit by means of a plurality of heat pipes 22, for example 5, 10, 15, 20 or more. The heat pipe or the plurality of heat pipes are preferably mechanically connected to the high-frequency unit and a component of the cooling system, such as a cooling system, via one or more heat-conducting elements. B. a cooling fluid, a cooling unit, a cryostat, a cryoshield or the like connected.

In one embodiment, the cooling system for the superconducting main magnet can have a heat-conducting element, with the heat-conducting element being designed to thermally couple the cooling system to the high-frequency unit

The heat-conducting element can be designed, for example, as a heat exchanger, which enables heat transfer between the cooling fluid and the second cooling fluid. However, it is also conceivable that the heat-conducting element is designed to thermally connect the superconducting element of the high-frequency unit to the cooling fluid and/or the cooling unit. For this purpose, the heat-conducting element can be a heat-conducting material, e.g. B. aluminum, silver, copper, gold or the like having. A thermal coupling can mean that there is a possibility of transferring thermal energy. In the case of the heat-conducting element, a transport of heat energy can essentially be characterized by heat conduction.

A thermal coupling between the cooling system and the superconducting element of the high-frequency unit can be realized, for example, by means of a heat transfer between the cooling fluid and the second cooling fluid at a heat exchanger. However, it is also conceivable that the thermal coupling of the superconducting element of the high-frequency unit to the cooling system is implemented by the cooling fluid and/or the cooling unit. The thermal coupling can in particular take place indirectly through a heat-conducting element and/or a heat pipe, which separate the superconducting element of the high-frequency unit from the cooling fluid and/or the cooling unit.

By using a thermally conductive element and/or a heat pipe, thermal energy from the high-frequency unit can be dissipated to the cooling unit in a particularly cost-effective manner and/or with a relatively high output. Furthermore, the high-frequency unit can be positioned on a patient in an advantageous manner, with a positioning of the cooling unit in direct proximity to the image recording region being advantageously avoided.

In a further embodiment of the magnetic resonance apparatus according to the invention, the cooling system is designed as a cryostat, with the cryostat having a cooling unit which is designed to cool a cooling fluid of the cryostat, with the heat pipe being designed to thermally connect the high-frequency unit with the cooling fluid and/or to be coupled to the cooling unit of the cryostat.

The cooling unit preferably has a heat-conducting element, in particular a heat exchanger, which is designed to thermally couple the cooling unit, in particular a working fluid of the cooling unit, with the cooling fluid of the cryostat. The cooling fluid can in particular be present separately from the working fluid of the cooling unit and by means of the heat transfer be thermally coupled with the working fluid. In an alternative embodiment, the cooling fluid represents a working fluid of the cooling unit.

It is conceivable that the superconducting element of the high-frequency unit is thermally coupled to a first end of the heat pipe, while the second end of the heat pipe is thermally coupled to the cooling fluid and/or the heat-conducting element of the cooling unit. However, it is also conceivable that the first end of the heat pipe is coupled to the second cooling fluid, which at least partially encloses the superconducting element of the high-frequency unit on the outside.

By providing a heat pipe, which thermally couples the superconducting element of the high-frequency unit to the cooling unit, a heat transport speed can be increased in an advantageous manner compared to heat transport based on heat conduction. As a result, the occurrence of temperature jumps, which can occur due to an increased heat input during a magnetic resonance measurement, can be reduced or avoided.

In a preferred embodiment, the magnetic resonance apparatus according to the invention is positioned on a substantially horizontal reference surface, with a first vertical distance between the cooling unit and the horizontal reference surface exceeding a second vertical distance between the high-frequency unit and the horizontal reference surface, with the heat pipe being arranged in such a way that it produces a monotonous slope.

It is conceivable that a portion of the heat pipe is tilted less than 10°, less than 20°, or less than 30° from a straight line oriented parallel to the vector of gravity. The heat pipe may also include one or more bends. Preferably, an imaginary course of the heat pipe, which is characterized by a straight connection between a connection point of the heat pipe to the superconducting magnet of the high-frequency unit and a connection point of the heat pipe to the cooling unit and/or the cooling fluid, deviates by less than 30° from a straight line which parallel to the vector of gravity. It is also conceivable that the heat pipe is designed to increase monotonically. This can mean that a tangent through any point on a surface of the heat pipe in the direction of the second end of the heat pipe always has a non-zero, positive angle to the surface of the heat pipe. In particular, the heat pipe can have an internal capillary structure, which enables a capillary-driven material transport of the condensed working fluid in the heat pipe.

In a further embodiment of the magnetic resonance device according to the invention, at least one section of the heat pipe is aligned essentially parallel to a vector of gravity, so that a transport speed of a condensed phase of a working fluid in the heat pipe is increased.

Preferably, at least a portion of a heat pipe is positioned in a perpendicular manner between the chiller and the superconducting element of the radio frequency unit. It is also conceivable that a predominant portion of the heat pipe is oriented substantially parallel to the vector of gravity.

In accordance with a further embodiment, the heat pipe has an inner capillary structure which is designed to increase a speed of mass transport of the working fluid in the heat pipe at a point with a slight incline.

By positioning the cooling unit at a geodetic height that exceeds the geodetic height of the superconducting element of the high-frequency unit, a gravitation-dependent mass transport of the condensed phase of the working fluid of the heat pipe can be advantageously improved. Furthermore, a transport of the condensed phase of the working fluid of the heat pipe can be advantageously improved by means of an inner capillary structure, in particular in an area of bends.

According to a further embodiment, the magnetic resonance apparatus according to the invention has a coupling point which is thermally coupled to the cooling system at least by means of a heat-conducting element, with a third perpendicular distance of the coupling point to the horizontal reference surface exceeding at least the second perpendicular distance of the radio-frequency unit to the horizontal reference surface, wherein a a first end of the heat pipe is mechanically connected to the radio frequency unit and a second end of the heat pipe is thermally coupled to the coupling point.

A first end and a second end of the heat pipe can be designed according to an embodiment described above. In some configurations of the magnetic resonance apparatus, thermal coupling of the superconducting element of the high-frequency unit by means of a continuous heat pipe may be impossible. In such cases, a Kop plungspunkt be provided which thermally couples the heat pipe with a second heat pipe, the cooling fluid and / or a heat conducting element. For example, thermal energy of the superconducting element of the high-frequency unit can be transported by means of the heat pipe to the coupling point, from where the thermal energy is transferred to the cooling unit and/or the cooling fluid by means of the second heat pipe, the cooling fluid and/or the heat-conducting element. Preferably, at least a portion of the heat pipe is oriented substantially parallel to the vector of gravity. In one embodiment, a geodetic elevation of the coupling point (third plumb distance) may exceed the geodetic elevation of the chiller (first plumb distance). However, it is also conceivable that the geodetic height of the cooling unit exceeds the geodetic height of the coupling point. The coupling point can in particular be designed as a heat-conducting element or a heat exchanger and/or represent part of a heat-conducting element or a heat exchanger. In a preferred embodiment, the coupling point provides a mechanical connection of the heat pipe to the heat conducting element. It is conceivable that the heat-conducting element is mechanically connected to the cooling unit in order to enable thermal coupling of the high-frequency unit to the cooling unit.

By providing a coupling point, thermal energy can be transferred in an advantageous manner in any relative position, but also larger distances between the superconducting element of the high-frequency unit and the cooling unit.

In a further embodiment of the magnetic resonance device according to the invention, at least the radio-frequency unit has a heat-insulating element, in particular a Dewar vessel, which is designed to reduce a transfer of thermal energy from an image recording area of the magnetic resonance device to the radio-frequency unit.

A heat-insulating element can be designed to limit and/or prevent heat transfer based on heat conduction, heat convection and/or heat radiation. For this purpose, the heat-insulating element can in particular have a material with low thermal conductivity and/or a double-walled structure. It is also conceivable that in a gap of the double-walled heat-insulating element there is a negative pressure compared to the environment in order to reduce heat transfer by convection. It is also conceivable that at least one surface and/or one side in the gap has a reflective layer which is designed to reflect at least part of the incident heat rays. The heat-insulating element can be designed in particular as a Dewar vessel, which delimits the superconducting element of the local coil from the imaging area and/or the patient. It is also conceivable that the heat-insulating element at least partially encloses the outer circumference of a part of the superconducting element that faces the imaging area and/or the patient. The heat-insulating element can also contain the preamplifier or the amplifier of the high-frequency unit, as well as other components of the magnetic resonance device, such as e.g. B. the superconducting main magnet, a gradient magnet, the cryostat and the like, enclose the outer circumference.

The heat-insulating element preferably has a material which has little or no interaction with electromagnetic waves in the frequency and power range of a magnetic resonance measurement. Preferred materials are plastics, fiber composites, but also natural materials and/or amorphous solids. Examples include glass, wood, natural and synthetic polymers, glass fiber composites, and the like. A reflective layer can in particular represent a metal layer. The metal layer is preferably made very thin in order to avoid the occurrence of significant electrical currents during a magnetic resonance examination. It is also conceivable that the metal layer has slits in order to suppress or avoid the occurrence of eddy currents.

By providing the thermally insulating element, a patient in the imaging area can be advantageously protected from contact with cold components and/or a transfer of thermal energy from the imaging area to the superconducting element of the high-frequency unit can be reduced.

According to a further embodiment of the magnetic resonance apparatus according to the invention, the high-frequency unit has a fluid distribution system, the fluid distribution system being designed to thermally couple a cooling fluid of the cooling system to the high-frequency unit and the fluid distribution system being thermally coupled to the cooling fluid of the cooling system, in particular to a temperature level of cryogenic cooling is coolable.

The fluid distribution system can have one or more fluid channels which thermally communicate with the cooling fluid and/or the second cooling fluid couple to the superconducting antenna element of the radio frequency unit. The cooling fluid can in particular represent a cooling fluid of a cryostat according to an embodiment described above. The fluid distribution system is preferably configured to thermally couple a plurality of superconducting antenna elements to the cooling fluid and/or the second cooling fluid. The superconducting element of the high-frequency antenna is preferably cooled to a temperature level which is below the critical temperature of the superconducting element of the high-frequency unit. Such a temperature level can represent a temperature level of a cryocooling. A temperature level of cryogenic cooling can be below 100K, 150K, 200K or 250K, for example.

In one embodiment, the fluid distribution system is oversized with respect to an expected, continuously introduced heat output from the environment, so that the fluid distribution system also functions as a cold store. For example, the fluid distribution system can be oversized by a factor of 1.5, a factor of 2, a factor of 3, a factor of 4 or more with regard to the expected, continuously introduced heat output. A thermal coupling between the fluid distribution system and the superconducting antenna element can be implemented in particular by means of a thermally conductive element. The heat-conducting element is preferably designed as part of a carrier structure of the high-frequency unit, in particular the superconducting antenna element and/or the local coil. However, it is also conceivable that the radio frequency unit has a heat pipe which is thermally coupled to the fluid distribution system of the radio frequency unit and the cooling system for the superconducting main magnet. The thermal energy of the superconducting element and/or the amplifier of the high-frequency unit can thus be absorbed locally by the fluid distribution system and transferred to the heat pipe or the heat-conducting element in a particularly efficient manner. The heat pipe or the heat conducting element can accordingly dissipate the heat energy of the high-frequency unit to the cooling system.

The high-frequency unit and/or a support structure of the high-frequency unit can in particular have at least one fluid channel which is designed to enable thermal energy to be transferred between the cooling fluid and/or the second cooling fluid and the superconducting element of the high-frequency unit. It is conceivable for the cooling fluid and/or the second cooling fluid to be transported through the fluid channels by means of a compressor, a pump or a comparable delivery unit. A fluid channel may represent a hole, tunnel, cavity, chamber, conduit, or the like. In particular, a fluid channel can have one or more branches or strands. Several fluid channels can be connected to one another by means of branches or strands. In a preferred embodiment, the at least one fluid channel comprises a three-dimensional network of tunnels, cavities, chambers and/or branches, which is integrated or embedded in a carrier structure of the local coil and/or the body coil. Preferably, the fluid channel is positioned close to the superconducting element of the high-frequency unit in order to achieve sufficient thermal coupling between the cooling fluid and/or the second cooling fluid and the superconducting element. The cooling fluid and/or the second cooling fluid can be present in a liquid or gaseous phase, which is transported through the at least one fluid channel by means of the delivery unit. The at least one fluid channel can in particular have an inlet and an outlet which are connected to the delivery unit in such a way that the cooling fluid and/or the second cooling fluid can be transported continuously through the at least one fluid channel.

By providing a fluid distribution system, cooling of superconducting antenna elements of the local coil can advantageously also be implemented outside of a cryostat for the superconducting main magnet of the magnetic resonance device. As a result, the local coil can be positioned in the image recording area in such a way that direct proximity to the specific body region of the patient is made possible. Furthermore, a precise thermal coupling between the superconducting element of the high-frequency unit and the cooling fluid and/or the second cooling fluid can be provided by using fluid channels. As a result, a required volume of the high-frequency unit and/or an impairment of the patient during the magnetic resonance examination can advantageously be reduced.

In one embodiment, the magnetic resonance device according to the invention also has a heat-conducting element, which is designed to thermally couple the cooling system to the high-frequency unit, with the cooling system being designed as a cryostat, with the cryostat having a cooling unit which is designed to pump a cooling fluid of the To cool cryostats, the high-frequency unit being thermally connected to the cooling unit of the cooling system by means of the heat-conducting element.

In this embodiment, the heat-conducting element can be interpreted as a “cold bus” or a “cold rail”, which consists of a consists of highly thermally conductive material and dissipates thermal energy of the superconducting element of the high-frequency unit to the cooling unit. A highly thermally conductive material can, in particular, consist of a high-purity metal, such as e.g. B. copper, silver, gold or aluminum exist. The heat-conducting element is preferably mechanically and thermally connected to the cooling unit. The heat-conducting element can also be mechanically and thermally coupled to the superconducting magnet of the high-frequency unit. It is conceivable that a thermally conductive but electrically insulating layer is positioned between the superconducting element of the high-frequency unit and the heat-conducting element. The cooling unit can be configured according to one of the embodiments described above.

By providing a “cold bus” or a “cold rail” based on a heat-conducting element, a particularly cost-effective and/or easy-to-implement solution for cooling the superconducting element of the high-frequency unit can be provided. In particular, a “dry” local coil can be provided by means of the heat conducting element, which avoids the effort and costs for operating liquefied gases (such as helium or nitrogen).

In one embodiment, the magnetic resonance device according to the invention also has an image recording area, which is at least partially surrounded on the outside by the superconducting main magnet and thereby defines an access direction for an examination object to an imaging volume of the magnetic resonance device, the access direction being oriented at an angle to a vector of gravity, the angle having a value between 10° and 40°.

In one embodiment, the magnetic resonance apparatus has a substantially cylindrical imaging area, which is at least partially surrounded on the outside by the superconducting main magnet, with a cylinder axis of the cylindrical imaging area being oriented at an angle to a vector of gravity. The cylinder axis can in particular be aligned parallel to the access direction and/or essentially coincide with it.

The magnetic resonance device according to the invention is preferably oriented in an examination room in such a way that the access direction is aligned at an angle of between 10° and 40° to the vector of gravity. It is conceivable that the magnetic resonance device also has a positioning unit which is designed to adapt an orientation and/or a position of the magnetic resonance device. An angle of the access direction with respect to the vector of gravity can in particular be correlated with an angle of a backrest of a patient positioning device and/or essentially correspond to it. It is conceivable that the magnetic resonance device is designed as a dedicated head scanner and/or a dedicated dental scanner. The high-frequency unit can be designed in particular as a head coil. The head coil is preferably in the form of a drum, a hollow cylinder or a birdcage and encloses the patient's head at least partially on the outside circumference when the patient's head is stored in the head coil in a position appropriate for use. However, the high-frequency unit can also be designed as a dedicated dental coil, which is shaped to match a jaw region of the patient. The dental coil can be shaped in such a way that the patient's eyes and/or a region of the forehead are not covered by the local coil when the local coil is in a position in accordance with the application.

Access of the patient's head to the imaging area of the magnetic resonance device can advantageously be simplified by means of the described alignment of the access direction. Furthermore, the orientation of the access direction described advantageously simplifies an approximately vertical orientation of heat pipes along the access direction of the imaging area.

According to a further embodiment, the magnetic resonance device according to the invention has a substantially cylindrical image recording area with an opening, the opening being positioned on a base surface of the cylindrical image recording area and being designed to accommodate a patient, the cooling system having a cooling unit and the cooling unit being connected to a the opening opposite base surface of the cylindrical of the image recording area is arranged.

The cooling unit is preferably aligned essentially along the cylinder axis of the image recording area. It is conceivable that the cooling unit projects out of the image recording area on the base surface of the cylindrical image recording area opposite the opening.

The cooling unit can be aligned particularly easily with the local coil and/or thermally coupled by positioning the cooling unit on a base surface of the cylindrical image recording area opposite the opening. Further a breakthrough can be avoided in an advantageous manner by cladding the image recording area for connecting the local coil to the cooling system of the magnetic resonance device in the image recording area.

The high-frequency unit according to the invention has at least one antenna element which is designed to receive a high-frequency signal in the frequency and power range of a magnetic resonance measurement, the antenna element having a superconducting element which is thermally coupled to a cooling system of a magnetic resonance device according to one of the preceding claims.

The high-frequency unit according to the invention can be designed according to a high-frequency unit of a magnetic resonance device according to the invention, as described above, and can be correspondingly thermally coupled to the cooling system of the magnetic resonance device. The high-frequency unit can be viewed in particular as a local coil. A local coil can be characterized in that it is positioned in an application-appropriate position or relative position in an image recording area of the magnetic resonance device on a body region of a patient. The antenna element of the high-frequency unit preferably has a superconducting wire which is arranged in a loop shape. The superconducting wire may be made of a high-temperature superconducting material or a low-temperature superconducting material. It is conceivable that the high-frequency unit is mechanically connected to the magnetic resonance device according to the invention in a predetermined relative position. However, it is also conceivable that the superconducting element of the high-frequency unit is thermally coupled to the cooling system of the superconducting main magnet of the magnetic resonance device by means of a fluid distribution system. In this case, the radio-frequency unit and/or the magnetic resonance device can have a positioning unit which is designed to position the radio-frequency unit along at least one spatial direction, with at least part of the fluid distribution system being deformed and/or displaced and with a thermal coupling of the superconducting element with the cooling system of the superconducting main magnet is maintained.

A dedicated magnetic resonance device with a low magnetic field strength can be provided in an advantageous manner by means of the local coil according to the invention, with a signal-to-noise ratio of the high-frequency unit being improved in comparison to conventional local coils.

In a further embodiment, the high-frequency unit according to the invention has a heat-conducting element, a heat pipe and/or a fluid distribution system, which are designed to thermally couple the at least one antenna element to the cooling system.

According to one of the embodiments described above, the at least one antenna element of the high-frequency unit can be thermally coupled to the cooling system of the magnetic resonance device according to the invention by means of a heat-conducting element and/or a heat pipe. In particular, it is conceivable that the high-frequency unit has a plurality of antenna elements, which are thermally coupled to the cooling system of the magnetic resonance apparatus by means of one or more heat-conducting elements and/or one or more heat pipes. The high-frequency unit can also have a support structure with fluid channels that thermally couple the antenna element or the plurality of antenna elements with a second cooling fluid. According to an embodiment described above, the second cooling fluid can be coupled to the cooling system of the magnetic resonance apparatus.

By providing a heat conducting element and/or a heat pipe, which thermally couple the at least one antenna element to the cooling system of the magnetic resonance device, installation and/or positioning of the high-frequency unit in the imaging area can be simplified in an advantageous manner. Furthermore, free space for the patient in the imaging area can be advantageously increased, since a volume for an additional cryostat, in which the at least one antenna element of the high-frequency unit can be immersed, can be reduced or avoided.

• 1 eine schematische Darstellung einer Magnetresonanzvorrichtung,
• 2 eine schematische Darstellung einer erfindungsgemä-ßen Magnetresonanzvorrichtung mit einer erfindungsgemäßen Hochfrequenzeinheit,
• 3 eine schematische Darstellung einer erfindungsgemä-ßen Magnetresonanzvorrichtung mit einer erfindungsgemäßen Hochfrequenzeinheit,
• 4 eine schematische Darstellung einer erfindungsgemä-ßen Magnetresonanzvorrichtung mit einer erfindungsgemäßen Hochfrequenzeinheit,
• 5 eine schematische Darstellung einer erfindungsgemä-ßen Magnetresonanzvorrichtung mit einer erfindungsgemäßen Hochfrequenzeinheit,
• 6 eine schematische Darstellung einer erfindungsgemä-ßen Magnetresonanzvorrichtung mit einer erfindungsgemäßen Hochfrequenzeinheit,
• 7 eine schematische Darstellung einer erfindungsgemä-ßen Magnetresonanzvorrichtung mit einer erfindungsgemäßen Hochfrequenzeinheit.

Further advantages and details result from the following description of exemplary embodiments in conjunction with the drawings. They show in principle:

• 1 a schematic representation of a magnetic resonance device,
• 2 a schematic representation of a magnetic resonance device according to the invention with a high-frequency unit according to the invention,
• 3 a schematic representation of a magnetic resonance device according to the invention with a high-frequency unit according to the invention,
• 4 a schematic representation of a magnetic resonance device according to the invention tion with a high-frequency unit according to the invention,
• 5 a schematic representation of a magnetic resonance device according to the invention with a high-frequency unit according to the invention,
• 6 a schematic representation of a magnetic resonance device according to the invention with a high-frequency unit according to the invention,
• 7 a schematic representation of a magnetic resonance device according to the invention with a high-frequency unit according to the invention.

1 shows an embodiment of a magnetic resonance device 10 with a superconducting main magnet 11. The superconducting main magnet 11 is arranged in a cryostat 14 for cooling. The superconducting main magnet 11 can be cooled by a cooling unit or a cryogenic cooling system to such an extent that the superconducting main magnet 11 is in a superconducting state. A pulse tube cooler 13 can be provided as a cooling unit, for example, which produces the required temperature difference between a cold head (an end cooled by the pulse tube cooler) and a hot head in one stage. The hot head here encompasses an area in which thermal energy is to be dissipated. This can e.g. B. also include a compressor required to operate the cooling unit. It is also conceivable that the refrigeration unit includes one of the technologies described above and/or has one or more stages by means of which heat energy is absorbed and/or dissipated by the refrigeration system at different temperature levels.

In the example shown, the cold head of the pulse tube cooler 13 has a heat-conducting element 12 or is thermally coupled to one. In the present case, the heat-conducting element 12 is thermally coupled to the superconducting main magnet 11 . It is also conceivable that the heat-conducting element is thermally coupled to a helium bath containing liquid helium. The helium bath is cooled by the pulse tube cooler 13 and surrounds the superconducting main magnet 11. If the cooling system and/or the pulse tube cooler 13 fails, the evaporation of the liquid helium can bridge a longer period of time without external cooling.

the inside 1 The pulse tube cooler 13 shown may have a heat exchanger 50 which is thermally coupled to the hot head of the pulse tube cooler 13 and is designed to cool the hot head below an intended operating temperature. Since the pulse tube cooler 13 is usually operated with oil lubrication, the cooling of the pulse tube cooler 13 via an oil circuit 16 is appropriate. This oil circuit 16 is driven by a pump 15 and dissipates the waste heat energy from the pulse tube cooler 13, for example via the heat exchanger 50, to an external cooling system. The external cooling system can include a refrigeration machine, which continuously cools an inlet of the oil cooling circuit 16 to a desired temperature. In addition to the pulse tube cooler 13 shown, other components that require cooling can be connected to the oil circuit 16 and/or the external cooling system.

2 shows a schematic representation of a magnetic resonance apparatus 10 according to the invention with a high-frequency unit according to the invention, which is embodied as a local coil 20 in the present case. In the present example, the magnetic resonance device 10 is designed as a dedicated head scanner, which is designed to acquire magnetic resonance signals from a head region of a patient 15, in particular a jaw region and/or a set of teeth of the patient 15. The patient 15 can be positioned on a patient table 17 of a patient positioning device 16 . The patient support device 16 can be designed in particular to position the patient 15 in an image acquisition area 21 of the magnetic resonance device 10 . The patient support device 16 is preferably designed to adjust a position and/or a posture of the patient 15 in a desired manner for a magnetic resonance examination, so that the head of the patient 15 is positioned relative to the magnetic resonance device 10 in a manner appropriate to the application.

In the present example, the heat conducting element 12 of the pulse tube cooler 13 is thermally coupled to a heat pipe 22 which transports thermal energy from the superconducting element (not shown) of the local coil 20 to the pulse tube cooler 13 . The heat pipe 22 is preferably oriented parallel to a vector of gravity. As a result, a gravitation-dependent mass transport of a condensed phase of a working fluid within the heat pipe 22 from a second end on the heat-conducting element 12 in the direction of the first end on the local coil 20 in the heat pipe 22 can be improved or optimized.

In one example, the superconducting element of the local coil 20 according to the invention is shaped after an outer contour of the jaw region of the patient 15 and encloses it at least partially when the local coil is in an application-appropriate position on the patient 15 . It's imaginable, that an eye region and/or a forehead region of the patient 15 are uncovered when the local coil 20 is positioned on the patient 15 in accordance with the application, in order to avoid restricting the patient's 15 comfort.

in the in 2 example shown, the pulse tube refrigerator 13 has a single stage. Since both the superconducting element of the local coil 20 and the superconducting main magnet 11 are thermally coupled to the cold head of the pulse tube cooler 13, the superconducting element of the local coil 20 is cooled to a temperature level which essentially corresponds to the temperature level of the superconducting main magnet. For example, the superconducting main magnet 11 and the superconducting element of the local coil 20 in the in 2 shown embodiment may be high-temperature superconducting magnets or low-temperature superconducting magnets, which are cooled to the same temperature level.

In an alternative embodiment, the superconducting element of the high-frequency unit can also be designed as a body coil, which at least partially encloses the image recording region 21 of the magnetic resonance apparatus 10 along the cylinder axis 30 on the outside. In this embodiment, the superconducting element is preferably thermally coupled to a cooling fluid and/or a second cooling fluid. The cooling fluid and/or the second cooling fluid can be present in particular in the cryostat 14 of the magnetic resonance device 10 or in a cryostat (not shown) separated therefrom. The cryostat 14 can be designed in particular as a bath cryostat, an evaporator cryostat or a mixture cryostat. The magnetic resonance device 10 can also have a liquid distribution system with at least one fluid channel in which the first cooling liquid and/or the second cooling liquid is/are transported.

in the in 3 In the example shown, the superconducting element of the local coil 20 is thermally coupled to the pulse tube cooler 13 by means of two heat pipes 22a and 22b and a heat conducting element 12b. The heat pipe 22a is aligned approximately parallel to a vector of gravity, while the heat pipe 22b is oriented at an angle to the vector of gravity. The two heat pipes 22a and 22b are mechanically and thermally connected by means of the heat-conducting element 12b. However, it is also conceivable for the superconducting element of the local coil 20 to be thermally coupled to the pulse tube cooler 13 by means of a continuous heat pipe 22, with the continuous heat pipe 22 being able to have at least one bend or angle. It is of course conceivable that the superconducting element is thermally coupled to the cooling unit by means of a plurality of heat pipes 22, for example 5, 10, 15, 20 or more.

The local coil 20 can have one or more fluid channels with a second cooling fluid, which thermally couple the superconducting element of the local coil 20 to the heat pipe 22a. In this case, the fluid channels can be arranged in the immediate vicinity of the superconducting elements of the local coil 20 and/or can be connected to them by means of a heat-conducting element (not shown).

4 shows an embodiment of the magnetic resonance device 10 according to the invention, in which the cylinder axis 30 of the image recording area 21 is aligned at an angle 33 to a parallel of a vector of the gravitational force 35 . In the present example, the angle 33 is selected in such a way that the head of the patient 15 can be positioned in a comfortable sitting position in the image recording area 21 . The magnetic resonance device 10 shown can be embodied in particular as a dedicated head scanner and/or dental scanner.

The heat pipe 22 thermally couples the heat conducting element 12c to the heat conducting element 12b. The heat conducting element 12b can be thermally coupled to the cold head (eg the heat conducting element 12a) of the cooling unit and/or represent a second stage of the cooling unit. The second stage can have a different temperature level from the first stage (eg the heat-conducting element 12a), in particular a higher temperature level. For example, the superconducting element of the local coil 20 can be a high-temperature superconductor, while the superconducting main magnet 11 of the magnetic resonance device 10 is a low-temperature superconductor. In this case, the superconducting main magnet 11 is thermally coupled to the heat-conducting element 12a, while the superconducting element of the local coil 20 is thermally coupled to the heat-conducting element 12b of the cooling unit by means of the heat pipe 22 and the heat-conducting element 12c.

It is also conceivable that the heat-conducting elements 12b and 12c represent heat exchangers. The heat conducting element 12c can thermally couple the heat pipe 22 to a second cooling fluid for cooling the superconducting element of the local coil 20 , while the heat conducting element 12b thermally couples the heat pipe 22 to a cooling fluid for cooling the superconducting main magnet 11 . The cooling fluid and the second cooling fluid preferably differ at least in a state of aggregation and/or a molecular composition of matter.

In 4 the magnetic resonance device 10 is positioned relative to a substantially horizontal reference surface 31 . A first vertical distance between the cooling unit and the horizontal reference surface 31 exceeds a second vertical distance between the superconducting element of the local coil 20 and the horizontal reference surface 31. The heat pipe 22 is aligned essentially parallel to the direction of gravity, so that a transport speed of a condensed phase of the Working fluid in the heat pipe 22 is increased.

5 shows an embodiment of the magnetic resonance device 10 according to the invention with a coupling point 12k, which thermally couples the heat pipe 22a to the heat-conducting element 12a of the cooling unit. In the present example, a third perpendicular distance of the coupling point 12k to the horizontal reference surface 31 exceeds at least the second perpendicular distance of the superconducting element of the local coil 20 to the horizontal reference surface 31. The coupling point 12k preferably provides a mechanical and thermal connection of the heat pipe 22a to the heat-conducting element 12b. In an alternative embodiment, the coupling point 12b can also be a heat exchanger, which enables thermal energy to be transferred between a cooling fluid for cooling the superconducting main magnet 11 and a second cooling fluid for cooling the superconducting element of the local coil 20. In this case, the cooling fluid can be thermally coupled to the cooling unit, while the second cooling fluid is thermally coupled to the superconducting element of the local coil 20 . Instead of the heat pipe 22a, a fluid channel (not shown) can also be provided here, which transports the second cooling fluid between the superconducting element of the local coil 20 and the coupling point 12k. It is also conceivable that the coupling point 12k and the superconducting element of the local coil 20 are thermally coupled via a liquid bath. The liquid bath can have the second cooling fluid, which is continuously cooled at the coupling point 12k by means of the heat-conducting elements 12a and/or 12b.

In one embodiment, the local coil 20 has a heat-insulating element 32, in particular a Dewar vessel. The heat-insulating element 32 is designed to reduce a transfer of heat energy from the imaging area 21 , in particular from the patient 15 , to the local coil 20 . The heat-insulating element 32 can cover the head of the patient 15, as in 5 shown, at least partially enclose the outer circumference. The heat-insulating element 32 preferably also encloses the superconducting element of the local coil 20 on the outside.

6 12 shows an embodiment in which the superconducting element of the local coil 20 is thermally coupled to the cold head (eg the heat conducting element 12a) of the cooling unit by means of the heat conducting element 12b. However, it is also conceivable that the superconducting element of the local coil 20 is thermally coupled to the cooling fluid, which cools the superconducting main magnet 11, by means of the heat conducting element 12b. The heat conducting element 12b can be understood as a “cold bus” or a “cold rail” which transports thermal energy from the superconducting element of the local coil and/or the superconducting main magnet 11 to the cooling unit.

7 10 shows an embodiment of the magnetic resonance device 10 according to the invention, in which the cooling unit (such as, for example, the pulse tube cooler 13) is arranged on a base surface of the cylindrical image recording area 21 opposite the opening 34. The cooling unit is aligned essentially parallel to the cylinder axis 30 and protrudes beyond the cylindrical imaging area 21 on a side of the magnetic resonance device 10 opposite the opening 34 . In the example shown, the heat pipe 22, which thermally couples the superconducting element of the local coil 20 to the heat-conducting element 12a of the cooling unit, is aligned approximately parallel to a vector of gravity in order to support gravitation-dependent mass transport of a working fluid in the heat pipe 22.

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 therefrom by those skilled in the art without departing from the scope of the invention.

Claims (15)

Magnetic resonance device (10), having a magnetic field unit with a superconducting main magnet (11) and a high-frequency unit, wherein the superconducting main magnet (11) is designed to provide a static magnetic field and the high-frequency unit is designed to generate magnetic resonance signals in a frequency and power range of a To receive magnetic resonance measurement, characterized in that the high-frequency unit is thermally connected to a cooling system for the superconducting main magnet (11) of the magnetic resonance apparatus Device (10) is coupled, wherein the high-frequency unit can be cooled to a temperature level below an ambient temperature by means of the thermal coupling with the cooling system. Magnetic resonance device (10) after claim 1 , wherein the high-frequency unit has a superconducting element which is designed to receive high-frequency signals in a frequency and power range of a magnetic resonance measurement and wherein the superconducting element of the high-frequency unit comprises a low-temperature superconductor or a high-temperature superconductor. Magnetic resonance device (10) after claim 2 , wherein the superconducting element of the high-frequency unit • as a body coil, which at least partially encloses an image recording area (21) of the magnetic resonance device (10) on the outside, and/or • an antenna element, which is shaped after at least one body region of a patient (15) and in an application-specific manner Position in the imaging area (21) is positioned on the body region of the patient (15) is formed. Magnetic resonance apparatus (10) according to any one of the preceding claims 2 or 3 , wherein the cooling system is designed to cool the superconducting element of the high-frequency unit to a temperature level which • essentially corresponds to a temperature level of the superconducting main magnet (11) or which • exceeds the temperature level of the superconducting main magnet (11), the temperature level being below a critical temperature of the superconducting element of the high-frequency unit. Magnetic resonance device (10) according to one of the preceding claims, wherein the cooling system has a heat pipe (22) which is designed to thermally couple the cooling system to the high-frequency unit. Magnetic resonance device (10) after claim 5 , wherein the cooling system is designed as a cryostat (14), the cryostat (14) having a cooling unit which is designed to cool a cooling fluid of the cryostat (14), the heat pipe (22) being designed to the high-frequency unit thermally coupled to the cooling fluid and / or the cooling unit of the cryostat (14). Magnetic resonance device (10) after claim 6 , wherein the magnetic resonance device (10) is positioned on a substantially horizontal reference surface (31) and wherein a first perpendicular distance of the cooling unit to the horizontal reference surface (31) exceeds a second perpendicular distance of the high-frequency unit to the horizontal reference surface (31), wherein the Heat pipe (22) is arranged such that it has a monotonic slope. Magnetic resonance device (10) according to one of Claims 5 until 7 wherein at least a portion of the heat pipe (22) is oriented substantially parallel to a vector of gravity (35) such that a transport speed of a condensed phase of a working fluid in the heat pipe (22) is increased. Magnetic resonance device (10) according to one of Claims 7 or 8th , wherein the magnetic resonance device (10) has a coupling point which is thermally coupled to the cooling system at least by means of a heat-conducting element, wherein a third perpendicular distance of the coupling point to the horizontal reference surface (31) is at least the second perpendicular distance of the high-frequency unit to the horizontal reference surface (31 ) wherein a first end of the heat pipe (22) is mechanically coupled to the radio frequency unit and a second end of the heat pipe (22) is thermally coupled to the coupling point. Magnetic resonance device (10) according to one of the preceding claims, wherein at least the high-frequency unit has a heat-insulating element (32), in particular a Dewar vessel, which is designed to transfer thermal energy from an image recording region (21) of the magnetic resonance device (10). to reduce the high frequency unit. Magnetic resonance apparatus (10) according to one of the preceding claims, wherein the radio-frequency unit has a fluid distribution system, wherein the fluid distribution system is designed to thermally couple a cooling fluid of the cooling system to the radio-frequency unit and wherein the fluid distribution system is thermally coupled to the cooling fluid of the cooling system in particular on a Temperature level of a cryogenic cooling can be cooled. Magnetic resonance device (10) according to any one of the preceding claims, further comprising a heat conducting element (12) which is designed to thermally couple the cooling system to the high-frequency unit and wherein the cooling system is designed as a cryostat (14), the cryostat (14) has a cooling unit, which is designed to a cooling fluid of the cryostat (14), the high-frequency unit being thermally connected to the cooling unit of the cooling system by means of the heat-conducting element (12). Magnetic resonance device (10) according to one of the preceding claims, further comprising an image recording region (21), which is at least partially surrounded on the outside by the superconducting main magnet (11) and thereby defines an access direction for an examination subject to an imaging volume of the magnetic resonance device (10), wherein the Access direction at an angle (33) to a vector of gravity (35) is aligned, wherein the angle (33) has a value between 10 ° and 40 °. High-frequency unit, having at least one antenna element, which is designed to receive a high-frequency signal in the frequency and power range of a magnetic resonance measurement, wherein the antenna element has a superconducting element, which is thermally coupled to a cooling system of a magnetic resonance device (10) according to one of the preceding claims . High frequency unit after Claim 14 , Having a heat-conducting element (12), a heat pipe (22) and/or a fluid distribution system, which are designed to thermally couple the at least one antenna element to the cooling system.

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