Loosening of moving parts of switchable devices in MRI systems

Abstract

An apparatus 100 for loosening a moving part 104 in a first position within a switchable device 106 of a magnetic resonance imaging system 300 is disclosed. The apparatus 100 includes a moving part 104, an inductor 102, and an AC source 108. The moving part 104 moves from a first position to a second position within the switchable device 106, thereby switching the switchable device 106 from at least a first state to a second state. The inductor 102 is connected to the AC source 108 via an electrical connection 110. The AC source 108 provides AC to the inductor 102 via the electrical connection 110. The inductor 102 further loosens the moving part 104 by inducing vibration of the moving part 104 upon receiving AC from the AC source 108 via the electrical connection 110.

Description

[Technical field]

[0001] The present invention relates to hardware and software for magnetic resonance imaging systems, and in particular to hardware and software for loosening moving parts of switchable devices in magnetic resonance systems. [Background technology]

[0002] Magnetic resonance imaging (MRI) systems include various types of switchable devices, such as valves and relays, with moving parts. By moving the moving parts from one position to another, such switchable devices switch from one state to another. For example, a valve, such as a valve in a cryostat cooling line, may switch from a closed state, in which the flow of cryogenic fluid through the valve is blocked, to an open state, in which the cryogenic fluid flows through the valve, or vice versa. For example, a relay may switch from a connected state, in which a contact is established by the relay, to a disconnected state, in which the contact is disconnected by the relay, or vice versa. Summary of the Invention [Problem to be solved by the invention]

[0003] In such switchable devices there is a risk that the moving parts get stuck, for example by getting stuck or frozen. In particular in cryostats there is a high risk of sticking due to the low temperature of the cryogenic fluid. In the case of valves the moving parts may even be located in the flow of the cryogenic fluid. If the moving parts get stuck in one position there will be problems switching the switchable device to another state, for example there will be problems opening or closing the valve or problems with the relay making or breaking contacts.

[0004] International application WO2020 / 193415 discloses a cryostat for a magnetic resonance examination system including a thermal switch with a ball valve integrated in a loop tube between a persistent current switch and a heat exchanger, the ball valve including a ferromagnetic ball. [Means for solving the problem]

[0005] The invention provides an apparatus, a cryostat, a magnetic resonance imaging system, a method and a computer program in the independent claims. Exemplary embodiments are set out in the dependent claims.

[0006] The apparatus allows loosening moving parts of a switchable device in an MRI system without requiring direct access to the switchable device. The apparatus realizes, for example, an electromechanical vibrator that acts on the moving parts when they are mechanically stuck, inducing vibration of the moving parts to loosen them. Thus, when the moving parts are stuck, they can be vibrated or rocked loose without the need to open or even disassemble the section of the MRI system that contains the switchable device.

[0007] In one aspect of the invention, there is provided an apparatus for loosening a moving part in a switchable device of a magnetic resonance imaging system, the apparatus including a moving part, an inductor, and an AC source. The moving part switches the switchable device from at least a first state to a second state by moving from a first position to a second position in the switchable device. The inductor is connected to the AC source via an electrical connection. The AC source provides AC to the inductor via the electrical connection. The inductor is further adapted to loosen the moving part by inducing vibration of the moving part when the inductor receives AC from the AC source via the electrical connection.

[0008] This is beneficial to loosen stuck moving parts of switchable devices placed in an MRI system or to prevent such moving parts from getting stuck. This is particularly beneficial for switchable devices that are not directly accessible, such as valves and relays in a cryostat or superconducting magnet in an MRI system. If an actuator of the switchable device, which moves the moving part from its current (first) position in the switchable device to a target (second) position, is unable to move the moving part from its current position due to mechanical jamming, the moving part may get stuck. Due to mechanical jamming caused by ice formation, sticking, etc., the static friction overcome by the actuator to move the moving part may exceed the force provided by the actuator. Vibrating the moving part, i.e., applying vibration to the moving part in its current position, may loosen the moving part. That is, the mechanical jamming may be released or reduced. This allows the force provided by the actuator to be sufficient to overcome the remaining static friction of the moving part in its current position and move it to the target position. The movement of the moving part may include rotation about a rotation axis and translation along a translation vector.

[0009] An inductor is understood as an electromagnet, i.e. a component that generates a magnetic field when it receives an electric current. Inductors are provided in the form of a coil, such as a solenoid. For example, a current flowing through the inductor's wire wound in the coil generates a magnetic field. The inductor's wire is wound around a magnetic core, for example made from a ferromagnetic or ferrimagnetic material. Using a core containing a ferromagnetic or ferrimagnetic material increases the inductance of the inductor. When an inductor receives an alternating current (AC), it generates an alternating magnetic field.

[0010] When the inductor is placed in a static magnetic field, for example provided by a permanent magnet of the apparatus, an actuator of the switchable device, or a superconducting magnet of an MRI system in the form of a B0 field, AC flowing through the inductor causes the inductor to vibrate due to the Lorentz force, which is mechanically transferred to the moving parts to loosen them.

[0011] For example, an alternating magnetic field, generated by an AC flowing through an inductor, causes a vibration of the switchable device, which is mechanically transferred to the moving parts, or a vibration of the moving parts, due to magnetic interactions, for example when the switchable device or moving parts include permanent magnets, ferromagnetic sections, and / or ferrimagnetic sections. The vibration of the switchable device or moving device is generated, for example, by an alternating current induced in a conductor included in the switchable device or moving device. The alternating magnetic field generates an alternating current (such as eddy currents) in a conductor located, for example, in the permanent magnets of the device and / or the switchable device, the actuator of the switchable device, or in a static magnetic field provided by a superconducting magnet of an MRI system in the form of a B0 field.

[0012] Thus, the electrically driven inductor provided by the device, when mechanically stuck, induces mechanical vibrations acting on the moving part to loosen it. For example, the vibrations acting on the moving part are generated by the inductor by vibrating itself and mechanically transmitting the vibrations of the inductor to the mechanically stuck moving part. For example, the inductor induces vibrations in the switchable device. The vibrations of the switchable device are mechanically transmitted to the mechanically stuck moving part in the switchable device. For example, the inductor can directly induce vibrations in the moving part by directly interacting with the mechanically stuck moving part in the switchable device via an alternating magnetic field generated by the inductor.

[0013] The moving parts may vibrate loose when mechanically stuck. The moving parts may get stuck due to ice formation or mechanical jamming, i.e. the movement of the moving parts actuated by the actuator of the switchable device may get jammed. Thus, the risk of jamming of moving parts of the switchable device integrated in enclosed parts of the MRI system (such as the cryostat or the superconducting magnet of the MRI system) is reduced or even prevented.

[0014] For example, the switchable device is a switchable device of a cryostat and / or a superconducting magnet of a magnetic resonance imaging system. Magnetic resonance imaging (MRI) systems, and in particular MRI cryostats, include several different components with moving parts for switching from one state to another. Without loss of generality, these components are hereinafter referred to as switchable devices or switches.

[0015] The switchable device may be, for example, electrically driven. The switchable device may include, for example, an electrically driven actuator that moves a moving part when triggered. An actuator is a component that moves a moving part. For example, an actor opens or closes a valve. For example, an actor establishes or breaks an electrical contact. An actuator requires, for example, a control signal to trigger the actor to move the moving part and a source of energy to move the moving part. The control signal may be, for example, a direct current (DC) pulse. The energy source may be, for example, an electric current (such as DC). For example, the control signal simultaneously provides the energy required to move the moving part. For example, the actor may include an electromagnet that uses magnetic forces to generate a static magnetic field to move the moving part. For example, the actuator may be provided in the form of a coil. When the actuator is triggered, i.e. when it receives a control signal, it responds by converting the energy of a source, such as DC, into a mechanical movement of the moving part. For example, an actuator such as an electromagnet uses DC to generate a static magnetic field. The moving part is attracted or repelled by the static magnetic field generated by the actuator.

[0016] In any such switchable device there is a risk that the moving parts will get stuck, for example caused by freezing, i.e. ice formation or jamming. If the force of the actuator of the switchable device is insufficient to free the moving parts on the switchable device itself, i.e. to move the moving parts from their current position to their target position, this will be problematic for the operation of the MRI system.

[0017] For example, the inductor is provided by an actuator of the switchable device. The actuator provides an inductor in the form of a coil, for example a solenoid. For example, the inductor receives AC to loosen the moving part and DC to move the moving part, for example after unblocking. For example, AC is applied first to loosen the moving part, followed by DC to trigger the actuator to move the moving part. For example, the actuator is triggered with DC to move the moving part. If it is detected that the movement of the moving part is mechanically jammed and the moving part is stuck, AC can be applied to the actuator to loosen the moving part and then DC can be repeatedly applied to re-trigger the actuator to move the freed moving part to a target position. By moving the moving part to a target position, the switchable device is switched to a target state.

[0018] For example, the device further includes a vibrating component including at least any one of a permanent magnet, a ferromagnetic section, a ferrimagnetic section, and a conductor disposed within the first static magnetic field.

[0019] This has the beneficial effect that vibration of the vibrating component is induced by the inductor receiving the AC. The inductor generates an alternating magnetic field that interacts with the vibrating component, causing the component to vibrate. The alternating magnetic field interacts with, for example, permanent magnets, ferromagnetic sections, ferrimagnetic sections, and / or conductors of the vibrating component.

[0020] For example, the moving part may include a vibrating component and the apparatus may use an alternating current received by an inductor to generate an alternating magnetic field that causes the vibrating component to vibrate, thereby causing vibration of the switchable device. The vibration of the switchable device induces vibration of the moving part.

[0021] For example, the apparatus vibrates the switchable device by inducing vibration of a vibrating component with a permanent magnet. The apparatus uses an alternating current received by an inductor to generate an alternating magnetic field that vibrates the permanent magnet, thereby causing vibration of the switchable device. For example, a housing of the switchable device contains the permanent magnet.

[0022] For example, the apparatus vibrates the switchable device by inducing vibration of a vibrating component in the ferromagnetic section. The apparatus uses an alternating current received by an inductor to generate an alternating magnetic field that vibrates the ferromagnetic section, thereby causing vibration of the switchable device. For example, a housing of the switchable device includes the ferromagnetic section.

[0023] For example, the apparatus vibrates the switchable device by inducing vibration of a vibrating component in the ferrimagnetic section. The apparatus uses an alternating current received by an inductor to generate an alternating magnetic field that vibrates the ferrimagnetic section, thereby causing vibration of the switchable device. For example, a housing of the switchable device includes the ferrimagnetic section.

[0024] For example, the apparatus vibrates the switchable device by inducing vibration of a vibrating component in a conductor. The conductor is disposed within a first static magnetic field. The apparatus uses an alternating current received by an inductor to generate an alternating magnetic field that induces an alternating current in the conductor that causes the conductor to vibrate, thereby causing the switchable device to vibrate. For example, the alternating current induced in the conductor included in the switchable device is an eddy current. For example, a housing of the switchable device includes the conductor.

[0025] For example, the moving part may include a vibrating component and the device may use an alternating current received by an inductor to generate an alternating magnetic field that causes the vibrating component to vibrate, thereby causing vibration of the moving part.

[0026] For example, the moving part includes a vibrating component having a permanent magnet, and the device uses an alternating current received by an inductor to generate an alternating magnetic field that causes the permanent magnet to vibrate, thereby causing the moving part to vibrate.

[0027] For example, the moving part includes a vibrating component having a ferromagnetic section, and the device uses an alternating current received by an inductor to generate an alternating magnetic field that causes the ferromagnetic section to vibrate, thereby causing the moving part to vibrate.

[0028] For example, the moving part includes a vibrating component having a ferrimagnetic section, and the device uses an alternating current received by an inductor to generate an alternating magnetic field that causes the ferrimagnetic section to vibrate, thereby causing vibration of the moving part.

[0029] For example, the moving part includes a vibrating component having a conductor. The first conductor is disposed within a first static magnetic field. The apparatus uses an alternating current received by the inductor to generate an alternating magnetic field that induces an alternating current in the first conductor that causes the conductor to vibrate, thereby causing the moving part to vibrate. For example, the alternating current induced in the conductor of the moving part is an eddy current.

[0030] For example, the first static magnetic field is provided by a permanent magnet. For example, the permanent magnet is included in the apparatus. For example, the permanent magnet is included in the switchable device. For example, the housing of the switchable device includes the permanent magnet.

[0031] For example, the first static magnetic field may be provided by an actuator of the switchable device, the actuator generating a first static magnetic field to move the moveable part from a first position to a second position.

[0032] For example, the first static magnetic field is generated by a magnetic resonance imaging system. The first static magnetic field generated by the magnetic resonance imaging system is, for example, the B0 magnetic field of the magnetic resonance imaging system, i.e., a strong static magnetic field for aligning atomic nuclear spins as part of a procedure for acquiring magnetically responsive imaging data. The magnetic resonance imaging data is used to reconstruct, for example, a magnetically responsive image of an internal tissue structure of a patient's body.

[0033] For example, the apparatus further includes a switchable device, the apparatus further vibrates the switchable device, the switchable device mechanically transmits the vibration of the switchable device to a moving part of the switchable device, causing the moving part to vibrate.

[0034] This has the beneficial effect that vibrating the switchable device can cause the moving parts to vibrate, for example the apparatus can induce vibrations in the housing of the switchable device which are mechanically transferred to moving parts within the switchable device, for example which are mechanically stuck.

[0035] For example, an inductor is mechanically connected to the switchable device. The inductor is disposed within the second static magnetic field. The inductor oscillates due to an alternating current received from an alternating current source. The apparatus mechanically transfers the oscillation of the inductor to the switchable device via the mechanical connection of the inductor, thereby oscillating the switchable device.

[0036] This has the beneficial effect that the vibrations of the inductor are mechanically transmitted via the switchable device to the moving part.

[0037] The inductor is configured as an oscillating device because it is AC driven within a background static magnetic field. The AC driven inductor (such as an AC driven oscillating coil) is provided to the static magnetic field of a permanent magnet, an actuator of a switchable device (such as a solenoid), or a superconducting magnet of an MRI system (i.e., the B0 field of the MRI system).

[0038] An inductor, such as a solenoid, is mechanically connected to or included in the switchable device, such that vibrations of the inductor are mechanically transferred to the switchable device. The inductor is placed in a background static magnetic field, provided by, for example, a permanent magnet or an electromagnet. The inductor is driven by AC received from an AC source. The Lorentz force resulting from electrons moving in the static magnetic field B creates vibrations of the inductor, which are mechanically transferred to the switchable device. The resulting vibrations of the switchable device cause a stuck moving part to shake loose, i.e. induce vibrations of the moving part to loosen it.

[0039] For example, the inductor is mechanically connected to the housing of the switchable device.

[0040] For example, the switchable device is included in a cryostat of a magnetic resonance imaging system. For example, the switchable device is included in a superconducting magnet of a magnetic resonance imaging system. The superconducting magnet is cooled by the cryostat. An apparatus may include the switchable device.

[0041] For example, the inductor may be included in a cryostat of a magnetic resonance imaging system. For example, the inductor may be included in a superconducting magnet of a magnetic resonance imaging system. The superconducting magnet is cooled by the cryostat.

[0042] For example, the device may be included in a cryostat of a magnetic resonance imaging system. For example, the device may be included in a superconducting magnet of a magnetic resonance imaging system. The superconducting magnet is cooled by a cryostat.

[0043] This has the beneficial effect of being able to loosen stuck moving parts, even in enclosed parts of an MRI system that are difficult to access. In particular, stuck moving parts in the cryostat and / or superconducting magnet of an MRI system can be loosened. In the case of a cryostat, there is a high risk of the moving parts becoming stuck, for example by ice formation, due to the low temperature of at least certain parts of the cryostat. Such jams can be effectively freed by vibrating the stuck moving parts.

[0044] For example, the electrical connection is provided by an electrical supply line. The electrical supply line is further electrically connected to a direct current supply source. The supply line supplies the switchable device with direct current for an actuator of the switchable device. The actuator moves the movable part from a first position to a second position. The direct current supplied via the supply line is superimposed with an alternating current supplied via the supply line.

[0045] This is beneficial because DC and AC are provided through the same supply line. In the case of a DC-driven switchable device, i.e. a switchable device with a DC-driven actuator that moves a moving part of the switchable device to switch the switchable device, the supply line itself is necessary to provide the switchable device with DC. By superimposing the DC current and the AC current of the inductor in the same supply line, no additional supply line is required to provide AC. As a result of the superposition of DC and AC, both currents are supplied simultaneously. Thus, a vibration for loosening the moving part can be induced and the switchable device can be actuated at the same time, i.e. the movement of the moving part to be loosened is started. In the case of a switchable device with a permanent magnet, only an additional capacitor is required to allow the superposition of DC and AC that oscillates the inductor. The vibration of such a conductor is transferred to the moving part, for example mechanically.

[0046] The combination of an AC-powered vibrator and a DC-operated switchable device using a common supply line for supplying AC and DC eliminates a pair of leads compared to when the inductor of the AC-powered vibrator and the DC-powered actuator of the switchable device are supplied with current through separate supply lines, which is particularly advantageous in the case of cryostats, where feedthrough into the cryostat is problematic given the increased complexity and increased heat load.

[0047] For example, the device may further include a capacitor arranged in series with the inductor to form a resonant circuit that provides a resonance at a predefined vibration frequency for vibration of the moving part.

[0048] A resonant circuit (also called an LC circuit) with a resonance at a predefined target frequency is used to maximize the current through the inductor with alternating currents at the target frequency, while alternating currents with frequencies deviating from the target frequency are attenuated and rejected. At resonance, the impedance of the series resonant circuit is at a minimum. Thus, the series resonant circuit only accepts alternating currents whose alternating frequency is equal to the resonant frequency. For example, DC is excluded. If DC is superimposed with AC at the resonant frequency, the series resonant circuit only sees AD at resonance.

[0049] For example, the capacitor of the device is placed in parallel with a second inductor included in the actuator of the switchable device. Thus, an additional parallel resonant circuit is provided with a resonant frequency at a predefined vibration frequency for the vibration of the moving part. At resonance, the impedance of the parallel resonant circuit is at a maximum, so that alternating current at a frequency equal to the resonant frequency is suppressed or rejected. AC at the resonant frequency is therefore rejected by the actuator, i.e. the actuator does not see AC. If DC is supplied with superimposed AC at the resonant frequency, the actuator sees only DC.

[0050] For example, the switchable device is a valve of a cryostat of a magnetic resonance imaging system. This has the beneficial effect that moving parts of the cryostat valve are loosened. Typically, the cryostat is an enclosed part of the MRI system and difficult to access due to the need for insulation. However, due to the low temperature of at least certain parts of the cryostat, there is a high risk of the moving parts becoming clogged, for example by ice formation. This is particularly the case for valves in the cooling lines of the cryostat through which the cryogenic fluid flows. Such clogging can be effectively released by vibrating the clogged moving parts. The apparatus comprises a switchable device, for example in the form of a valve.

[0051] An MRI system includes a superconducting magnet, e.g. a superconducting cylindrical magnet with a bore running through it. A superconducting magnet is an electromagnet made of a coil of superconducting wire. The superconducting wire must be cooled to cryogenic temperatures during operation. At cryogenic temperatures, the superconducting wire reaches its superconducting state. In the superconducting state, the wire has no electrical resistance, allowing it to carry a much larger current than a normal wire, making it possible to generate a strong magnetic field. A cryostat is used to cool the superconducting magnet to cryogenic temperatures.

[0052] A cryostat maintains a cryogenic fluid (such as a cryogen) in a liquid state with minimal evaporation. The cryogenic fluid can be, for example, liquid helium. The cryogenic bath provided by the cryostat can keep the superconducting wires that form the superconducting magnets of an MRI system in their superconducting state. To maintain superconductivity, the superconducting wires must be kept below their transition temperature by immersing them in the cryogenic fluid (such as liquid helium).

[0053] The valve is a valve in a cooling line of a cryostat that controls the flow of cryogenic fluid through the cooling line. When the moving part is in a first position, for example, the valve is open, allowing the cryogenic fluid to flow through the cooling line. When the moving part is in a second position, for example, the valve is closed, preventing the cryogenic fluid from flowing through the cooling line.

[0054] For example, when the moving part is in a first position, the valve is in a closed state, preventing cryogenic fluid from flowing through the cooling line, and when the moving part is in a second position, the valve is in an open state, for example, allowing cryogenic fluid to flow through the cooling line.

[0055] The switchable device may be, for example, a valve in a cooling circuit of a magnet persistent current switch (MPCS) of an MRI system. The apparatus may include, for example, the switchable device. The MRI system may include a superconducting magnet with an MPCS. The MPCS may include a cooling circuit controlled by a valve provided by the switchable device to bleed heat during ramping of the superconducting magnet.

[0056] MPCS is used to shunt the superconducting coil of a superconducting magnet using a superconducting short circuit so that the superconducting coil and the superconducting short circuit form a closed circuit with no resistance. To charge the superconducting coil, the short circuit is temporarily switched to a resistive state. The short circuit is heated above the superconducting temperature, for example by a heating element, so that it develops a small finite resistance. The circuit thus becomes an RL circuit, and a power supply is used to inject current into the superconducting coil. Since the magnet's coil is superconducting with virtually zero resistance, the injected current flows through the coil, but little or no current flows through the short circuit. The external current is increased to the target current level, and the target magnetic field strength is obtained. The current is increased slowly (e.g., over 24-48 hours) to avoid quenches, until the target current level of, for example, 500-1000 A is reached.

[0057] Once the target current level is reached, the short circuit switches to the superconducting state, shorting the circuit across the superconducting coil. For example, the heating element is turned off and the temperature of the short circuit is cooled to cryogenic temperatures by a cryostat. The external power supply is disconnected and the current in the superconducting loop provided by the superconducting coil and the short circuit continues in persistent mode, possibly indefinitely. In the superconducting state, the current flowing in persistent mode is in principle stable and low noise. Therefore, the magnetic field induced by the current flowing in the superconducting coil is also stable and low noise.

[0058] In the case of an MRI cryostat valve, applying AC to the device's inductor to loosen stuck moving parts has the beneficial effect of solving and / or preventing problems resulting from stuck moving parts without the need to open the cryostat of the MRI system's superconducting magnet.

[0059] For example, the cooling circuit of an MRI cryostat is provided with an inductor that operates within the magnetic field of the superconducting magnet of the MRI system to loosen moving parts of the switchable device (e.g., a valve in the cryostat) when the moving parts become stuck. The moving parts in the cryostat may become stuck, for example, due to ice formation in the switchable device. The AC-driven inductor allows the moving parts to be loosened without the need to open the cryostat of the superconducting magnet.

[0060] For example, the switchable device is a relay in a magnetic resonance imaging system. A relay is an electrically operated switch. It may have one or more input terminals for one or more control signals. It may further have one or more operating contact terminals. Relays are used to control circuits by independent low power signals, i.e. trigger signals. Relays are used, for example, to control multiple circuits with a single signal. Relays may include one or more moving parts. A relay may include, for example, a coil, such as a solenoid, as an actuator to move the moving part of the relay. An apparatus may include a switchable device, for example, in the form of a relay.

[0061] For example, a relay is a contactor. A contactor is a relay, i.e. an electrically controlled switch, used to switch power circuits. A contactor is controlled by a circuit with a much lower power level than the switched circuit. A contactor may be directly connected to a high current load device. An apparatus may include a switchable device, for example in the form of a contactor.

[0062] For example, the apparatus further includes a control module for controlling the apparatus, the control module detecting that the moving part is stuck in a first position and controlling the apparatus to loosen the moving part in response to the detection. Additionally or alternatively, the control module triggers an actuator of the switchable device to move the moving part from the first position to the second position and controls the apparatus to preemptively loosen the moving part prior to or concurrently with the triggering of the actuator, prior to or concurrently with the movement of the moving part.

[0063] Proactively controlling the apparatus to loosen the moving parts may for example include transmitting vibrations of an inductor to a switchable device of a potentially stuck moving part, where the inductor generates vibrations in the switchable device, causing the moving part to vibrate and loosen if the moving part is stuck.

[0064] For example, the moving parts may become frozen or stuck in the first position.

[0065] The movable part may be movable by a translational movement, for example moving the movable part from a first position to a second position comprises a translational movement, for example the movable part moves along a translation vector.

[0066] The movable part may be movable by a rotational movement. For example, moving the movable part from a first position to a second position comprises a rotational movement. For example, the movable part may be rotated. For example, the movable part may be rotated about an axis of rotation. The axis of rotation may be provided, for example, by a hinge that allows the movement of the movable part.

[0067] The movable part may be, for example, a bendable part. For example, moving the movable part from a first position to a second position may include bending the bendable part from the first position to the second position. For example, the bendable part may be bent about a bending axis.

[0068] In another aspect, the invention provides a cryostat for a magnetic resonance imaging system. The cryostat includes a switchable device and an apparatus for loosening a moving part in a first position within the switchable device. The apparatus includes a moving part, an inductor, and an AC source. The moving part switches the switchable device from at least a first state to a second state by moving from a first position to a second position within the switchable device. The inductor is connected to the AC source via an electrical connection. The AC source provides AC to the inductor via the electrical connection. The inductor is further configured to loosen the moving part by inducing vibration of the moving part upon receiving AC from the AC source via the electrical connection.

[0069] For example, the cryostat may include an apparatus according to any of the previous examples of the apparatus.

[0070] In another aspect, the invention provides a magnetic resonance imaging system. The magnetic resonance imaging system includes a switchable device and an apparatus for loosening a moving part in a first position within the switchable device. The apparatus includes a moving part, an inductor, and an AC source. The moving part switches the switchable device from at least a first state to a second state by moving from a first position to a second position within the switchable device. The inductor is connected to the AC source via an electrical connection. The AC source provides AC to the inductor via the electrical connection. The inductor is further configured to loosen the moving part by inducing vibration of the moving part upon receiving AC from the AC source via the electrical connection.

[0071] For example, the cryostat may include an apparatus according to any of the previous examples of an apparatus.

[0072] In another aspect, the invention provides a method of loosening a moving part in a switchable device of a magnetic resonance imaging system using an apparatus. The apparatus includes a moving part, an inductor, and an AC source. The moving part is in a first position in the switchable device and switches the switchable device from at least a first state to a second state by moving from the first position to a second position in the switchable device. The inductor is connected to the AC source via an electrical connection. The AC source provides AC to the inductor via the electrical connection. The inductor is further configured to loosen the moving part by inducing vibration of the moving part when the inductor receives AC from the AC source via the electrical connection.

[0073] The method includes the step of activating an AC source of the device to supply AC to an inductor, the AC flowing through the inductor causing vibration of the moving part.

[0074] For example, the method may use an apparatus according to any of the above examples of an apparatus.

[0075] For example, the moving part may be stuck in the first position, e.g., frozen or stuck. A method for loosening the moving part, e.g., is performed in response to detecting that the moving part is stuck in the first position.

[0076] For example, the moving part is moved from a first position to a second position by an actuator. For example, the method of loosening the moving part is preemptively performed prior to triggering the actuator to move the moving part from the first position to the second position. The method further includes triggering the actuator after preemptively loosening the moving part.

[0077] For example, a method of loosening a moving part is performed simultaneously with triggering an actuator to move the moving part from a first position to a second position, such that the moving part is vibrated and loosened while its movement is initiated.

[0078] In another aspect, the invention provides a computer program comprising machine executable instructions for execution by a processor of a magnetic resonance imaging system. The machine executable instructions control an apparatus included in the magnetic resonance imaging system to loosen a moving part within a switchable device of the magnetic resonance imaging system. The apparatus comprises a moving part, an inductor, and an AC source. The moving part is in a first position within the switchable device and switches the switchable device from at least a first state to a second state by moving within the switchable device from the first position to a second position. The inductor is connected to the AC source via an electrical connection. The AC source provides AC to the inductor via the electrical connection. The inductor is further adapted to loosen the moving part by inducing vibration of the moving part upon receiving AC from the AC source via the electrical connection.

[0079] Execution of the machine-executable instructions causes the processor to control an apparatus of a magnetic resonance imaging system to operate an alternating current source of the apparatus to supply alternating current to an inductor, the alternating current flowing through the inductor causing vibration of the moving parts.

[0080] For example, the machine-executable instructions may control a device according to any of the above-mentioned examples of devices.

[0081] For example, the moving part may become stuck in the first position, e.g., frozen or stuck. For example, the machine executable instructions execute a method for loosening the moving part in response to detecting that the moving part is stuck in the first position.

[0082] For example, the moving part is moved from a first position to a second position by an actuator. For example, the machine executable instructions perform a method for preemptively loosening the moving part before triggering the actuator to move the moving part from the first position to the second position. The machine executable instructions further include triggering the actuator after preemptively loosening the moving part.

[0083] For example, the machine executable instructions further include loosening the moving part simultaneously with triggering the actuator to move the moving part from the first position to the second position, such that the moving part is vibrated loose while its movement is initiated.

[0084] It is understood that one or more of the above embodiments can be combined, as long as the combined embodiments are not mutually exclusive.

[0085] As will be appreciated by those skilled in the art, aspects of the present invention may be embodied as an apparatus, a method, or a computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which are generally referred to as a "circuit," "module," or "system." Additionally, aspects of the present invention may take the form of a computer program product embodied in one or more computer-readable medium(s) having computer-executable code embodied therein.

[0086] Any combination of one or more computer readable media may be utilized. A computer readable medium is a computer readable signal medium or a computer readable storage medium. As used herein, a "computer readable storage medium" encompasses any tangible storage medium capable of storing instructions executable by a processor or a computing system of a computing device. A computer readable storage medium is also referred to as a computer readable non-transitory storage medium. A computer readable storage medium is also referred to as a tangible computer readable medium. In some embodiments, a computer readable storage medium may also store data that can be accessed by a computing system of a computing device. Examples of computer readable storage media include, but are not limited to, floppy disks, magnetic hard disk drives, solid state hard disks, flash memory, USB thumb drives, random access memory (RAM), read only memory (ROM), optical disks, magneto-optical disks, and register files of a computing system. Examples of optical disks include compact disks (CDs) and digital versatile disks (DVDs), such as CD-ROM, CD-RW, CD-R, DVD-ROM, DVD-RW, or DVD-R disks. The term computer-readable storage medium also refers to various types of recording media that can be accessed by a computer device over a network or communication link. For example, data may be obtained via a modem, the Internet, or a local area network. Computer executable code embodied in a computer-readable medium can be transmitted using any medium, including but not limited to wireless, wireline, fiber optic cable, RF, etc., or any suitable combination thereof.

[0087] A computer-readable signal medium may include a propagated data signal in which computer-executable code is embodied, such as, for example, in baseband or as part of a carrier wave. Such a propagated signal may take a variety of forms, including, but not limited to, electromagnetic, optical, or any suitable combination thereof. A computer-readable signal medium is not a computer-readable storage medium, but may be any computer-readable medium that can communicate, propagate, or transfer a program for use in or in connection with an instruction execution system, apparatus, or device.

[0088] "Computer memory" or "memory" is an example of a computer-readable storage medium. Computer memory is any memory that is directly accessible by a computing system. "Computer storage" or "storage" is an example of a computer-readable storage medium. Computer storage is any non-volatile computer-readable storage medium. In some embodiments, computer storage is also computer memory and vice versa.

[0089] As used herein, a "computing system" encompasses electronic components capable of executing programs, machine-executable instructions, or computer-executable code. References to a computing system, including examples of a "computing system," should be interpreted as potentially including multiple computing systems or processing cores. A computing system is, for example, a multi-core processor. A computing system may also refer to a collection of computing systems within a single computer system, or a collection of computing systems distributed across multiple computer systems. The term computing system should also be interpreted as potentially referring to a collection or network of computing devices, each of which includes a processor or computing system. Machine-executable code or instructions may be executed by multiple computing systems or processors within the same computing device, or even distributed across multiple computing devices.

[0090] Machine-executable instructions or computer-executable code may include instructions or programs that cause a processor or other computing system to perform aspects of the invention. Computer-executable code for carrying out operations of aspects of the invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and traditional procedural programming languages ​​such as the "C" programming language or similar programming languages, and compiled into machine-executable instructions. In some cases, the computer-executable code may be in a high-level language or compiled form and used in conjunction with an interpreter that generates the machine-executable instructions on the fly. In other cases, the machine-executable instructions or computer-executable code may be in the form of a programmable logic gate array programming.

[0091] The computer executable code may run entirely on the user's computer, partially on the user's computer, as standalone software, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or a connection to an external computer may be established (e.g., via the Internet using an Internet Service Provider).

[0092] Aspects of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block or part of the blocks of the flowcharts, diagrams, and / or block diagrams, where applicable, can be implemented in the form of computer executable code by computer program instructions. Furthermore, combinations of blocks in different flowcharts, diagrams, and / or block diagrams can be combined if not mutually exclusive. These computer program instructions are provided to a computing system of a general purpose computer, special purpose computer, or other programmable data processing device, such that the instructions are executed via the computing system of the computer or other programmable data processing device to generate a machine that creates means for performing the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams.

[0093] These machine-executable instructions or computer program instructions may also be stored on a computer-readable medium that can direct a computer, other programmable data processing apparatus, or other device to function in a particular manner, such that the instructions stored on the computer-readable medium generate an article of manufacture that includes instructions that implement the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams.

[0094] The machine-executable instructions or computer program instructions may also be loaded into a computer, other programmable data processing apparatus, or other device to cause the computer, other programmable apparatus, or other device to perform a series of operational steps to generate a computer-implemented process, whereby the instructions executing on the computer or other programmable apparatus provide a process for performing the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams.

[0095] A "user interface" as used herein is an interface that allows a user or operator to interact with a computer or computer system. A "user interface" is also referred to as a "human interface device." A user interface can provide information or data to an operator and receive information or data from an operator. A user interface can be used to allow a computer to receive input from an operator and provide output from the computer to a user. That is, a user interface can be used to allow an operator to control or operate a computer, or the interface can be used to allow a computer to show the effects of an operator's control or operation. Displaying data or information on a display or graphical user interface is an example of providing information to an operator. Receiving data via a keyboard, mouse, trackball, touchpad, pointing stick, graphics tablet, joystick, gamepad, webcam, headset, pedals, wired gloves, remote control, and accelerometer are all examples of user interface components that allow for the reception of information or data from an operator.

[0096] As used herein, a "hardware interface" encompasses an interface that allows a computing system of a computer system to interact with and control external computing devices and / or devices. A hardware interface allows a computing system to send control signals and commands to external computing devices and / or devices. A hardware interface also allows a computing system to exchange data with external computing devices and / or devices. Examples of hardware interfaces include, but are not limited to, a universal serial bus, an IEEE 1394 port, a parallel port, an IEEE 1284 port, a serial port, an RS-232 port, an IEEE-488 port, a Bluetooth® connection, a wireless local area network connection, a TCP / IP connection, an Ethernet connection, a control voltage interface, a MID interface, an analog input interface, and a digital input interface.

[0097] As used herein, a "display" or "display device" encompasses an output device or user interface adapted for displaying images or data. A display can output visual, audio, or tactile data. Examples of displays include, but are not limited to, computer monitors, television screens, touch screens, tactile electronic displays, Braille screens, cathode ray tubes (CRTs), storage tubes, bi-stable displays, electronic paper, vector displays, flat panel displays, vacuum fluorescent displays (VFs), light emitting diode (LED) displays, emissive displays (ELDs), plasma display panels (PDPs), liquid crystal displays (LCDs), organic light emitting diode displays (OLEDs), projectors, and head mounted displays.

[0098] A magnetic resonance imaging (MRI) system is a system for acquiring magnetic resonance imaging data. An MRI system further reconstructs the acquired magnetic resonance imaging data into an MRI image (also called an MR image). An MRI image is defined herein as a reconstructed two- or three-dimensional visualization of structural data (such as anatomical data) contained in the magnetic resonance imaging data. This visualization is performed using a computer. [Brief description of the drawings]

[0099] Preferred embodiments of the invention will now be described, by way of example only, with reference to the drawings in which:

[0100] [Figure 1] FIG. 1 shows an example of an apparatus for loosening the moving parts of a switchable device. [Diagram 2] FIG. 2 shows an example of an apparatus for loosening the moving parts of a switchable device. [Diagram 3] FIG. 3 shows an example of an apparatus for loosening the moving parts of a switchable device. [Figure 4] FIG. 4 shows an exemplary circuit diagram of an apparatus for loosening the moving parts of a switchable device. [Diagram 5] FIG. 5 shows an exemplary frequency dependence of the amount of current flowing through the circuit of FIG. [Figure 6] FIG. 6 illustrates an exemplary MRI system. [Figure 7] FIG. 7 illustrates an exemplary computer system that controls the MRI system of FIG. [Figure 8] FIG. 8 illustrates an exemplary cryostat. [Figure 9] FIG. 9 shows a flow chart illustrating an exemplary method for loosening moving parts. [Figure 10] FIG. 10 shows a flow chart illustrating an exemplary method for loosening moving parts. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0101] Elements with the same number in these figures are equivalent elements or perform the same function. Elements already described are not necessarily described in subsequent figures if their functionality is equivalent.

[0102] FIG. 1 illustrates an exemplary apparatus 100 for loosening a moving part 104 of a switchable device 106. The apparatus 100 includes a moving part 104, an inductor 102, and an AC source 108. The moving part 104 switches the switchable device 106 from at least a first state to a second state by moving from a first position to a second position within the switchable device 106. The inductor 102 is provided in the form of a coil, for example a solenoid. The inductor 102 is connected to the AC source 108 via an electrical connection 110. The AC source 108 supplies AC to the inductor 102 via the electrical connection 110. The inductor 102 further loosens the moving part 104 by inducing vibration of the moving part 104 when receiving AC from the AC source 108 via the electrical connection 110. The switchable device 106 is a switchable device of an MRI system. For example, the switchable device 106 is a valve of a cryostat of the MRI system. For example, the switchable device 106 is a relay, such as a contactor of an MRI system. In particular, the switchable device 106 is a relay of a cryostat or a superconducting magnet of an MRI system. The apparatus 100 includes, for example, the switchable device 106.

[0103] 1 vibrates the switchable device 106. The switchable device 106 mechanically transfers the vibrations of the switchable device 106 to the moving part 104, causing the moving part 104 to vibrate.

[0104] The inductor 102 is mechanically connected to the switchable device 106 via a mechanical connection 112. The mechanical connection 112 may be provided in the form of an external connection connecting the inductor 102 to the switchable device 106 when the inductor 102 is disposed outside the switchable device 106, or in the form of an internal connection when the inductor 102 is disposed within the switchable device 106. The switchable device includes the inductor 102. The inductor 102 is disposed within a static magnetic field B. The static magnetic field B may be provided by a permanent magnet or an electromagnet. For example, an electromagnet of an actuator of the switchable device or a superconducting magnet of an MRI system provides the static magnetic field B. The inductor 102 oscillates due to an alternating current received from an alternating current source 108. The apparatus 100 mechanically transmits the oscillation of the inductor 102 to the switchable device 106 via the mechanical connection of the inductor 102, thereby oscillating the switchable device 106.

[0105] Thus, the Lorentz force resulting from electrons moving in the static magnetic field B creates vibrations in the inductor 102, which are mechanically transferred to the switchable device 106. The resulting vibrations in the switchable device 106 cause the stuck moving part 104 to shake loose, i.e. induce vibrations in the moving part 104 that loosen the moving part 104.

[0106] 1 may be movable by a hinge that provides an axis of rotation about which the movable part 104 may rotate. Alternatively, the movement of the movable part 104 may include translating the movable part 104 or deforming (e.g., bending) the movable part 104. In the case of a valve, the movable part 104 may translate, for example, from a position that blocks fluid flow to a position where fluid flows around the movable part 104.

[0107] FIG. 2 shows a further exemplary apparatus 100 for loosening the moving part 104 of the switchable device 106. The apparatus 100 vibrates the switchable device 106. In the case of the apparatus 100 of FIG. 2, the vibration of the switchable device 106 is not based on the transmission of the vibration of the inductor 102 via a mechanical connection. Rather, the vibration of the switchable device 106 is based on the interaction of the switchable device 106 with an alternating magnetic field generated by an AC flowing through the inductor 108. For example, the switchable device 106 includes a vibrating component with a permanent magnet, a ferromagnetic section, a ferrimagnetic section, and / or a conductor arranged in a static magnetic field. The alternating magnetic field causes the vibration of the vibrating component of the switchable device 106, so that the vibration of the switchable device 106 is mechanically transmitted to the moving part 104. In the case of a conductor, the alternating magnetic field generates an alternating current, e.g., an eddy current, in the conductor, which generates a Lorentz force that causes the conductor to vibrate. The static magnetic field is provided by a permanent magnet or an electromagnet. For example, a superconducting magnet in an MRI system provides the static magnetic field.

[0108] 3 shows a further exemplary apparatus 100 for loosening a moving part 104 of a switchable device 106. The apparatus 100 vibrates a vibrating component of the moving part 104, causing the moving part 104 to vibrate. The vibrating component includes a permanent magnet, a ferromagnetic section, a ferrimagnetic section, and / or a conductor disposed in a static magnetic field. An alternating magnetic field generated by an inductor 102 causes the vibrating component of the moving part 104 to vibrate. In the case of a conductor, the alternating magnetic field generates alternating currents, e.g., eddy currents, in the conductor, creating Lorentz forces that cause the conductor to vibrate. The static magnetic field is provided by a permanent magnet or an electromagnet. For example, an electromagnet in an actuator of the switchable device 106 or a superconducting magnet in an MRI system provides the static magnetic field.

[0109] FIG. 4 shows an exemplary circuit diagram illustrating the electrical circuit of an exemplary apparatus for loosening a moving part of a switchable device. The switchable device may be a DC-operated switchable device. An inductor L2 is incorporated in the same circuit as an actuator L2 (such as an actuating electromagnet) of the switchable device. R1 is a wire resistance, L2 is an inductor, C1 is a shorting capacitor, and L1 is an actuator (e.g., provided by a solenoid).

[0110] A switchable device (such as a valve or relay) is actuated by an actuator L1. A capacitor C1 is in series with an inductor L2 to generate a resonance at the target vibration frequency. When a DC voltage V1 with superimposed AC is applied, the capacitor C1 shorts out the actuator L1 for AC such that the actuator L1 sees only the DC component of the voltage V1 and performs its actuation action as is, while the inductor L2 sees only the AC component and receives a corresponding AC current at the target vibration frequency, and thus oscillates. If the switchable device includes a permanent magnet, the switchable device can be simplified since the permanent magnet can provide the background magnetic field necessary for the inductor L2 to generate the oscillations.

[0111] Inductor L2 and capacitor C1 form a series resonant circuit, and inductor L1 and capacitor C1 form a parallel resonant circuit.

[0112] For example, R1 is 0.1 Ω, L2 is 10 mH, C1 is 10 μF, and L1 is 300 mH.

[0113] Figure 5 shows the current in actuator L1 and inductor L2, showing how AC flows mainly through inductor L2, while capacitor C1 shorts out actuator L1, the solenoid it operates on, for AC.

[0114] FIG. 6 illustrates an exemplary MRI system 100 including an apparatus 100 for loosening a moving part of a switchable device of the MRI system 100. The switchable device may comprise, for example, a cryostat 302 or a superconducting magnet 304 of the MRI system 100. The switchable device may be, for example, a valve or a relay. The MRI system 300 is shown as being controlled by a computer 402 having a processor 404. The computer 402 is shown as having an optional hardware interface 406 and an optional user interface 408 in communication with the processor 404. The hardware interface 406 may be used, for example, to control other components of the MRI system 300 illustrated in FIG. 6. The user interface 408 may be used by an operator to control or interact with the computer 102, for example, to control the MRI system 300. The computer 402 is further shown as including a memory 410 in communication with the processor 404. The memory 410 is intended to represent one or more different types of memory in communication with the processor 404.

[0115] The memory is shown as including machine executable instructions 420 for controlling the MRI system 300. The machine executable instructions 420 control the MRI system 300 to acquire MRI data 426 using pulse sequence commands 424. The MRI data 426 is used to reconstruct an image 426. The machine executable instructions 420 include a computer program 422 having machine executable instructions for controlling an apparatus 100 included in the magnetic resonance imaging system 300.

[0116] Machine-executable instructions 420 enable processor 404 to perform various tasks such as data processing, image processing, and control of other components.

[0117] The magnetic resonance imaging system 300 further includes a magnet 304. The magnet 304 is a superconducting cylindrical magnet having a bore 306 therein. The superconducting magnet 304 is cooled by a cryostat 302. Different types of magnets can be used, for example both segmented cylindrical magnets and so-called open magnets. A segmented cylindrical magnet is similar to a standard cylindrical magnet, except that the cryostat is split into two sections to allow access to the isoplane of the magnet, and such magnets can be used in combination with charged particle beam therapy, for example. An open magnet has two magnet sections, one above the other, with enough space between them to accommodate the subject. The arrangement of the two sections is similar to that of a Helmholtz coil. Open magnets are popular because the subject is less confined. Inside the cryostat of the cylindrical magnet is a collection of superconducting coils.

[0118] Within the bore 306 of the cylindrical magnet 304 is an imaging zone 308 where the magnetic field is sufficiently strong and uniform to perform magnetic resonance imaging. Within the imaging zone 308 is shown a region of interest 309. Typically, magnetic resonance data is acquired about the region of interest. A subject 318 is shown as being supported by a subject support 320 such that at least a portion of the subject 318 is within the imaging zone 308 and the region of interest 309.

[0119] Also within the magnet bore 306 are a set of magnetic field gradient coils 310 used to acquire preliminary magnetic resonance data for spatially encoding magnetic spins within an imaging zone 308 of the magnet 304. The magnetic field gradient coils 310 are connected to a magnetic field gradient coil power supply 312. The magnetic field gradient coils 310 are intended to be representative. Typically, the magnetic field gradient coils 310 will include three separate coil sets for spatially encoding in three orthogonal spatial directions. The magnetic field gradient power supply supplies electrical current to the magnetic field gradient coils 310. The electrical current supplied to the magnetic field gradient coils 310 is controlled as a function of time and may be ramped or pulsed.

[0120] Adjacent to the imaging zone 308 is a radio frequency coil 314 for manipulating the orientation of magnetic spins in the imaging zone 308 and for receiving radio transmissions from the spins in the imaging zone 308. A radio frequency antenna may include multiple coil elements. A radio frequency antenna is also referred to as a channel or an antenna. The radio frequency coil 314 is connected to a radio frequency transceiver 316. The radio frequency coil 314 and the radio frequency transceiver 316 may be replaced by separate transmit and receive coils and separate transmitters and receivers. The radio frequency coil 314 and the radio frequency transceiver 316 are understood to be representative. The radio frequency coil 314 is also intended to represent a dedicated transmit antenna and a dedicated receive antenna. Similarly, the transceiver 316 may represent separate transmitters and receivers. The radio frequency coil 314 may have multiple transmit / receive elements and the radio frequency transceiver 316 may have multiple receive / transmit channels. For example, if a parallel imaging technique such as SENSE is performed, the radio frequency coil 314 has multiple coil elements.

[0121] The transceiver 316 and gradient controller 312 are shown as being connected to a hardware interface 406 of the computer 402 .

[0122] The memory 410 is further shown as including pulse sequence commands 424. The pulse sequence commands are commands or data that are converted into commands that enable the processor 404 to control the magnetic resonance imaging system 300 to acquire MRI data 426 (e.g., k-space data). The pulse sequence commands 424 acquire the MRI data 426 that encodes a number of magnetic resonance images 428 that are reconstructed using the MRI data 426.

[0123] 7 illustrates an exemplary computer 402 for controlling an MRI system, such as the exemplary MRI system 300 illustrated in FIG. 6. The exemplary computer 402 uses a computer program 422 having machine executable instructions to control the apparatus 100 included in the MRI system 300 to loosen moving parts in a switchable device of the MRI system 330. The computer program 422 is stored in a memory 410 of the computer 402. The computer 402 receives the computer program 422, for example, from a server, such as a cloud server, over a network connection, or from a computer program product. The computer program product may include a computer readable storage medium. The computer readable storage medium may have embodied program instructions of the computer program 422. The storage medium included in the computer program product may be, for example, an exchangeable storage medium.

[0124] FIG. 8 illustrates an exemplary cryostat 302 with MPCS for an MRI system such as the exemplary MRI system 300 illustrated in FIG. 6. The MRI system includes a superconducting magnet 304. The superconducting magnet 304 is disposed in a cryogenic bath 330 provided by the cryostat 302. The MPCS shorts the superconducting windings of the superconducting magnet 304 with a piece of superconductor 338 provided by the MPCS when the superconducting magnet 304 is energized. The windings of the superconducting magnet 304 form a closed superconducting loop with the piece of superconductor 338, and the power supply 336 supplying current to the superconducting magnet 304 is turned off while a persistent current flows through the superconducting loop in a persistent mode, preserving the static magnetic field generated by the superconducting magnet 304 of the MRI system. The advantage of such a persistent mode is that no additional energy needs to be supplied to the superconducting magnet to power the windings, and a very stable magnetic field is provided.

[0125] The short circuit is established using the MPCS, a piece of superconductor 338 in the superconducting magnet 304, connected across the windings and attached to a heating element 340. As the magnet 304 rises, the piece of superconductor 338 is heated by the heating element 340 to a temperature above its transition temperature. The heated piece of superconductor 338 therefore becomes resistive. The windings of the superconducting magnet 304 itself are cooled by the cryogenic bath 330 to a temperature below its transition temperature, so the windings are superconducting without resistance. As a result, no or very little current flows through the piece of superconductor 338. The supply current supplied to the superconducting magnet 304 is increased until it reaches a target current level that produces a target magnetic field strength. The heating element 340 is then turned off and the MPCS with the piece of superconductor 338 is cooled by the cryostat 302 to its superconducting temperature, shorting the windings of the superconducting magnet 304 through the now conductive piece of superconductor 338. The power supply 336 of the shorted superconducting magnet 304 is then turned off. The winding current flowing in a permanent state through the windings of the superconducting magnet 304 and the resulting magnetic field slowly decay according to a normal inductive time constant (L / R), where R is the small residual resistance in the superconducting windings due to, for example, joints and flux motion resistance.

[0126] Cryogenic fluid for cooling the superconducting magnet 304 is supplied via cooling line 332. The flow of cryogenic fluid through cooling line 332 is controlled by a switchable device in the form of a valve. Cryostat 302 includes apparatus 100 for loosening a moving part of the switchable device. Alternatively or additionally, cryostat 302 may include a switchable device in the form of a relay having a moving part that is loosened by apparatus 100.

[0127] 9 shows a flow chart illustrating an exemplary method of loosening a moving part in a switchable device of a magnetic resonance imaging system using an apparatus. The apparatus includes a moving part, an inductor, and an AC source. The moving part is in a first position in the switchable device and switches the switchable device from at least a first state to a second state by moving from the first position to a second position in the switchable device. The inductor is connected to the AC source via an electrical connection. The AC source supplies AC to the inductor via the electrical connection. The inductor further loosens the moving part by inducing vibration of the moving part when the inductor receives AC from the AC source via the electrical connection.

[0128] The apparatus includes a control module for controlling the apparatus. In step 500, the control module detects that the moving part is stuck in a first position. In step 502, the control module controls the apparatus to loosen the moving part in response to the detection. The control module activates an AC source of the apparatus to supply AC to an inductor. The AC flowing through the inductor causes vibration of the moving part. In step 504, the control module triggers an actuator of the switchable device to move the moving part from the first position to the second position. Thus, in step 504, switching of the switchable device is triggered.

[0129] 10 shows a flow chart illustrating a further exemplary method of loosening a moving part in a switchable device of a magnetic resonance imaging system. In step 510, the control module controls the apparatus to preemptively loosen the moving part before or simultaneously with a movement of the moving part. After the moving part is loosened, the control module triggers an actuator of the switchable device in step 512 to move the moving part from a first position to a second position. For example, the loosening of the moving part in step 510 is performed simultaneously with the triggering of the actuator in step 512. Thus, the moving part is vibrated and loosened while its movement is initiated.

[0130] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments.

[0131] Other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the singular elements do not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be used to advantage. The computer program can be stored / distributed on any suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless communication systems. Any reference signs in the claims should not be interpreted as limiting the scope.

[0132] 100 devices 102 Inductor 104 Moving parts 106 Switchable Devices 108 AC supply 110 Electrical Connections 112 Mechanical Connection 120 Cooling Line 300 MRI System 302 Cryostat 304 Magnet 306 Magnet Bore 308 Imaging Zone 309 Areas of Interest 310 Magnetic field gradient coil 312 Magnetic field gradient coil power supply 314 Radio Frequency Coil 316 Transceiver 318 Subject 320 Specimen Support 330 Cryogenic bath 332 Cooling Line 334 Power supply 336 Power supply 338 Superconductors 340 heating element 402 Computer 404 Processor 406 Optional Hardware Interface 408 Optional User Interface 410 Memory 420 Machine Executable Instructions 422 Program 424 Pulse sequence command 426 MRI data 428 images

Claims

1. 1. A cryostat for a magnetic resonance imaging system, comprising: a switchable device; and an apparatus for loosening a moveable part of the magnetic resonance imaging system in a first position within the switchable device, the apparatus comprising: the device includes the moving part, an inductor, and an AC source; the movable part moves from the first position to a second position within the switchable device to switch the switchable device from at least a first state to a second state; the inductor is connected to the AC source via an electrical connection, the AC source providing AC to the inductor via the electrical connection; The inductor further loosens the moving part by inducing vibration of the moving part when the inductor receives the alternating current from the alternating current source via the electrical connection.

2. The apparatus further comprises: Permanent magnets, Ferromagnetic section, Ferrimagnetic section, a conductor disposed within the first static magnetic field; 10. The cryostat of claim 1, further comprising a vibration component comprising at least one of:

3. the switchable device includes the oscillating component, and the apparatus uses the alternating current received by the inductor to generate an alternating magnetic field that causes the oscillating component to oscillate, thereby causing vibration of the switchable device, the vibration of the switchable device inducing the vibration of the moving part, or 3. The cryostat of claim 2, wherein the moving part includes the vibrating component, and the apparatus uses the alternating current received by the inductor to generate an alternating magnetic field that vibrates the vibrating component, thereby causing the vibration of the moving part.

4. 4. A cryostat as described in any one of claims 1 to 3, wherein the apparatus further comprises the switchable device, the apparatus further comprising: vibrating the switchable device, the switchable device mechanically transmitting the vibration of the switchable device to the moving part of the switchable device, causing the vibration of the moving part.

5. 5. The cryostat of claim 4, wherein the inductor is mechanically connected to the switchable device, the inductor is disposed within a second static magnetic field, the inductor is caused to vibrate by the alternating current received from the alternating current source, and the apparatus vibrates the switchable device by mechanically transmitting the vibration of the inductor to the switchable device via the inductor's mechanical connection.

6. 6. The cryostat of claim 1, wherein the electrical connection is provided by an electrical supply line, the electrical supply line being further electrically connected to a DC supply source, the electrical supply line supplying to the switchable device a DC for an actuator of the switchable device, the actuator moving the moveable part from the first position to the second position, the DC supplied via the electrical supply line being superimposed with the AC supplied via the electrical supply line.

7. 7. The cryostat of claim 1, further comprising a capacitor arranged in series with the inductor to form a resonant circuit providing a resonance at a predefined vibration frequency for the vibration of the moving part.

8. 8. The cryostat of claim 1, wherein the switchable device is a valve of a cryostat of the magnetic resonance imaging system.

9. 9. The cryostat of claim 1, wherein the switchable device is a relay of the magnetic resonance imaging system.

10. The apparatus further includes a control module for controlling the apparatus, the control module comprising: detecting when the moveable part is stuck in the first position, and controlling the apparatus to release the moveable part in response to said detection; triggering an actuator of the switchable device to move the movable part from the first position to the second position, and controlling the apparatus to preemptively release the movable part before or simultaneously with the triggering of the actuator, before or simultaneously with the movement of the movable part.

10. The cryostat of claim 1 , configured for at least one of the following:

11. 1. A magnetic resonance imaging system having a switchable device and including an apparatus for loosening a moveable part in a first position within the switchable device, comprising: The device includes the moving part, an inductor, and an AC source; the movable part moves from the first position to a second position within the switchable device to switch the switchable device from at least a first state to a second state; the inductor is connected to the AC source via an electrical connection, the AC source providing AC to the inductor via the electrical connection; The inductor further loosens the moving part by inducing vibration of the moving part when the inductor receives the alternating current from the alternating current source via the electrical connection.

12. 1. A method of loosening a moving part in a switchable device of a cryostat of a magnetic resonance imaging system using an apparatus, comprising: The device includes the moving part, an inductor, and an AC source; the movable part is in a first position within the switchable device and is adapted to switch the switchable device from at least a first state to a second state by moving from the first position to a second position within the switchable device; the inductor is connected to the AC source via an electrical connection, the AC source providing AC to the inductor via the electrical connection; the inductor further comprises: upon receiving the alternating current from the alternating current source via the electrical connection, inducing a vibration in the moving part thereby loosening the moving part; The method includes activating the AC source of the apparatus to supply the AC to the inductor, the AC flowing through the inductor causing the vibration of the moving part.

13. 1. A computer program comprising machine executable instructions for execution by a processor of a magnetic resonance imaging system, comprising: The machine executable instructions control an apparatus included in the magnetic resonance imaging system to loosen a moving part within a switchable device within a cryostat of the magnetic resonance imaging system; The device includes the moving part, an inductor, and an AC source; the movable part is in a first position within the switchable device and is adapted to switch the switchable device from at least a first state to a second state by moving from the first position to a second position within the switchable device; the inductor is connected to the AC source via an electrical connection, the AC source providing AC to the inductor via the electrical connection; the inductor further comprises: upon receiving the alternating current from the alternating current source via the electrical connection, inducing a vibration in the moving part thereby loosening the moving part; A computer program product that, when executing the machine-executable instructions, causes the processor to control the device of the magnetic resonance imaging system to operate the alternating current source of the device to supply the alternating current to the inductor, the alternating current flowing through the inductor causing the vibration of the moving part.

Images