阅读说明：本技术 加压气体供电的磁共振成像天线 (Pressurized gas powered magnetic resonance imaging antenna ) 是由 B·格莱希 S·魏斯 于 2020-04-28 设计创作，主要内容包括：公开了一种包括一个或多个线圈元件(115)的磁共振成像天线(114)。该磁共振成像天线还包括耦合到一个或多个线圈元件的射频系统(116)。该磁共振成像天线还包括被配置用于接收加压气体的气体入口(200)。该磁共振成像天线还包括被配置用于排放加压气体的气体出口(202)。该磁共振成像天线还包括被配置用于在存在外部磁场时将由所述加压气体从所述气体入口传送到所述气体出口所产生的机械能转换成电能的发电机(117)。该发电机被配置为使用该电能向射频系统供电。(A magnetic resonance imaging antenna (114) comprising one or more coil elements (115) is disclosed. The magnetic resonance imaging antenna further includes a radio frequency system (116) coupled to the one or more coil elements. The magnetic resonance imaging antenna further comprises a gas inlet (200) configured for receiving pressurized gas. The magnetic resonance imaging antenna further comprises a gas outlet (202) configured for discharging pressurized gas. The magnetic resonance imaging antenna further comprises a generator (117) configured for converting mechanical energy generated by the pressurized gas transmitted from the gas inlet to the gas outlet into electrical energy in the presence of an external magnetic field. The generator is configured to use the electrical energy to power a radio frequency system.)

1. A magnetic resonance imaging antenna (114), comprising:

one or more coil elements (115);

a radio frequency system (116) coupled to the one or more coil elements;

a gas inlet (200) configured for receiving pressurized gas;

a gas outlet (202) configured for discharging the pressurized gas;

a generator (117) configured for converting mechanical energy generated by the pressurized gas passing from the gas inlet to the gas outlet into electrical energy in the presence of an external magnetic field, wherein the generator is configured to use the electrical energy to power the magnetic resonance imaging antenna.

2. The magnetic resonance imaging antenna of claim 1, wherein the generator comprises a turbine (400) configured for rotation by the pressurized gas conveyed from the gas inlet to the gas outlet, wherein the turbine is configured for rotating an electrically conductive element (406, 600), wherein the electrically conductive element is configured for generating electrical energy when rotated in the external magnetic field.

3. The magnetic resonance imaging antenna of claim 2, wherein the conductive element is a conductive loop (406).

4. The magnetic resonance imaging antenna of claim 3, wherein the turbine includes paddles (402), and wherein the conductive loops are attached to at least two of the paddles.

5. The magnetic resonance imaging antenna of claim 3 or 4, wherein the generator comprises a switching circuit (500) in series with the conductive loop, wherein the switching circuit is configured for being powered by the switching circuit, wherein the switching circuit is configured for electronically opening and electronically closing the conductive loop at a predetermined frequency, wherein the generator further comprises one or more stationary pickup coils (502) configured for receiving an electrical energy switched at the predetermined frequency, wherein the at least one stationary pickup coil is configured for supplying the electrical energy to the radio frequency system.

6. The magnetic resonance imaging antenna of claim 2, wherein the turbine has a rotational axis (404), wherein the electrically conductive element (600) is asymmetric about the rotational axis, wherein the generator further comprises one or more stationary pickup coils (502) configured for receiving electrical energy caused by rotation of the electrically conductive element, wherein the at least one stationary pickup coil is configured for supplying the electrical energy to the radio frequency system.

7. The magnetic resonance imaging antenna of any one of claims 2 to 6, wherein there is any one of:

the turbine comprises a rotor (401), wherein the rotor has a diameter of less than 2mm or less than 1 mm;

the turbine is configured to have a rotation rate of at least 1200 million revolutions per minute; and

combinations of the above.

8. The magnetic resonance imaging antenna of claim 1, wherein the generator comprises:

a resonant cavity (700) configured for generating acoustic resonance in response to the transfer of pressurized gas from the gas inlet to the gas outlet;

a mechanical member (702, 702') configured to vibrate in response to the acoustic resonance, wherein the mechanical member is suspended within the resonant cavity;

at least one conductive path (900, 502) configured such that movement of the mechanical member causes the generation of the electrical energy in the external magnetic field.

9. The magnetic resonance imaging antenna of claim 8, wherein the resonant cavity is a whistle tuned to an ultrasonic frequency.

10. The magnetic resonance imaging antenna of claim 8 or 9, wherein the mechanical member (702') comprises an electrically conductive element, wherein the electrically conductive element is configured to vibrate torsionally, wherein the at least one electrically conductive path is one or more stationary pick-up coils configured for receiving electrical energy generated by the vibration of the electrically conductive element, wherein the at least one stationary pick-up coil is configured for supplying the electrical energy to the radio frequency system.

11. The magnetic resonance imaging antenna of claim 8 or 9, wherein each of the at least one conductive path (900) is at least partially on the mechanical member.

12. The magnetic resonance imaging antenna of any one of the preceding claims, wherein the generator is arranged such that the pressurized gas conveyed from the gas inlet to the gas outlet cools the radio frequency system.

13. The magnetic resonance imaging antenna of any one of the preceding claims, wherein there is any one of:

the radio frequency system comprises a receiver coupled to at least a portion of the one or more coil elements; and

the radio frequency system comprises a transmitter coupled to at least a portion of the one or more coil elements;

the magnetic resonance imaging system comprises a fiber optic communication system (125) configured for controlling the radio frequency system;

the magnetic resonance imaging system comprises a wireless communication system configured for controlling the radio frequency system; and

combinations of the above.

14. A magnetic resonance imaging system (100) comprising a magnetic resonance imaging antenna (114) according to any one of the preceding claims, wherein the magnetic resonance imaging system comprises a main magnet (104), wherein the main magnet is configured for generating the external magnetic field, and wherein the magnetic resonance imaging system further comprises a pressurized gas system (122) for providing pressurized gas to the gas inlet (200) of the magnetic resonance imaging coil.

15. The magnetic resonance imaging system of claim 14, wherein the magnetic resonance imaging system further comprises:

a memory (134) storing machine executable instructions (140) and pulse sequence commands (142) configured for controlling the magnetic resonance imaging system to acquire magnetic resonance imaging data using the magnetic resonance imaging antenna; and

a processor (130) for controlling the magnetic resonance imaging system, wherein execution of the machine executable instructions causes the processor to:

acquiring (300) the magnetic resonance imaging data by controlling the magnetic resonance imaging system with the pulse sequence commands; and is

Powering (302) the magnetic resonance imaging coil by controlling the pressurized gas system to supply the pressurized gas during the acquisition of the magnetic resonance imaging data.

Technical Field

The present invention relates to magnetic resonance imaging, in particular to an antenna for magnetic resonance imaging.

Background

As part of the procedure for generating images within a patient's body, a large static magnetic field is used by a Magnetic Resonance Imaging (MRI) scanner to align the nuclear spins of atoms. This large static magnetic field is referred to as the B0 field or main magnetic field. Various physical quantities or properties of the object, such as proton density or various relaxation times, such as T1, T2, or T2-star values, may be spatially measured using MRI.

In addition to using the B0 field, there is an antenna for transmitting and receiving Radio Frequency (RF) signals. The transmitted RF signal (B1 field) is used to manipulate the orientation of the spins. The received RF signals (recorded as magnetic resonance imaging data) are received from the spins and used to reconstruct a magnetic resonance image. When receiving RF signals, it is beneficial to place electronic components such as preamplifiers and digitizers as close as possible to the respective antenna elements. However, the presence of large magnetic and RF fields can make powering of these circuits difficult.

US patent publication US 10175313B 2 discloses an MRI apparatus comprising a power transmitting unit, a signal receiving unit and an image reconstruction unit. The power transmitting unit wirelessly transmits electric power to the RF coil device by magnetically coupled resonance-type wireless power transmission. The signal receiving unit wirelessly receives the digitized nuclear magnetic resonance signal wirelessly transmitted from the RF coil device. The image reconstruction unit obtains the nuclear magnetic resonance signal received by the signal receiving unit and reconstructs image data of the object based on the nuclear magnetic resonance signal.

Disclosure of Invention

The invention provides a magnetic resonance imaging antenna and a magnetic resonance imaging system.

As described above, it can be difficult to provide power to electronic circuitry within an imaging zone of a magnetic resonance imaging system. Embodiments of the present invention may provide an improved means of powering a magnetic resonance imaging antenna by using a generator powered by compressed gas. This has the advantage that there is no need to be protected from magnetic resonanceAn affected electrical lead of an RF signal within the imaging system. In addition, B₀The presence of the field eliminates the need for the generator to have its own magnets. The use of compressed gas enables the generator to be powered as required and constantly supplied even during long magnetic resonance imaging examinations. This may eliminate the need to have a battery or capacitor to store energy to power the magnetic resonance imaging antenna.

In one aspect, the invention provides a magnetic resonance imaging antenna comprising one or more coil elements. The magnetic resonance imaging antenna further comprises a radio frequency system connected to the one or more coil elements. The magnetic resonance imaging antenna further comprises a gas inlet configured for receiving pressurized gas. The magnetic resonance imaging antenna further comprises a gas outlet configured for discharging the pressurized gas. The magnetic resonance imaging antenna further comprises a generator configured for converting mechanical energy generated by the pressurized gas passing from the gas inlet to the gas outlet into electrical energy in the presence of an external magnetic field.

The generator is configured to use the electrical energy to power a magnetic resonance imaging antenna including a radio frequency system. Depending on the configuration, the magnetic resonance imaging antenna may comprise components such as: tuning/detuning circuits, AD converters, DA converters, digital-to-digital optical converters, sensors, and/or other electrical accessories. All of which may be powered by a generator.

The generator is unique in that it does not have its own magnets. Magnetic resonance imaging systems typically include a main magnet that generates the large magnetic fields necessary to perform magnetic resonance imaging. The external magnetic field may be the main magnetic field of the magnetic resonance imaging system. This embodiment may be beneficial because it provides a means for supplying power to the magnetic resonance imaging antenna that is fully compatible with the large magnetic and radio frequency fields present in the magnetic resonance imaging system. Which may avoid the problems and difficulties of charging a battery or capacitor to power a magnetic resonance imaging antenna.

In another embodiment, the generator includes a turbine configured to be rotated by pressurized gas communicated from the gas inlet to the gas outlet. The turbine is configured to rotate the electrically conductive member. The conductive element is configured to generate electrical energy when rotated in an external magnetic field. This embodiment may be beneficial because it provides an intuitive means of providing electrical power to the radio frequency system.

In another embodiment, the conductive element is a conductive loop. For example, since the loop is rotated by a turbine, it may act as a generator.

In another embodiment, the turbine includes a paddle. The conductive loops are attached to at least two of the paddles. For example, the conductive loop may be integrated into the paddle of the turbine. This may be beneficial as it may reduce the size of the turbine and make it more compact. Incorporating conductive loops into the paddle may also make them more durable.

In another embodiment, the generator includes a switching circuit in series with the conductive loop. The switching circuit is configured to be powered by the conductive loop. The switching circuit is configured to electronically open and electronically close the conductive loop at a predetermined frequency. The generator also includes one or more stationary pick-up coils configured to receive the electrical energy switched at the predetermined frequency. At least one stationary pick-up coil is configured to power a radio frequency system. This embodiment may be beneficial because it may eliminate the need for brushes in the generator. Furthermore, by opening and closing the loop at a predetermined frequency using an electrical circuit, a frequency can be selected that is, for example, very efficient and outside the range used for the magnetic resonance imaging procedure. For example, 1MHz would be very effective in transferring energy from the conductive loop to the stationary pick-up coil. 10MHz may work even better.

In another embodiment, the generator includes brushes for supplying electrical energy from the conductive loop to the radio frequency system.

In another embodiment, the turbine has a rotating shaft. The conductive element is asymmetric about the axis of rotation. The generator also includes one or more stationary pick-up coils. The stationary pick-up coil is configured to receive electrical energy caused by rotation of the conductive element. At least one stationary pick-up coil is configured to supply electrical energy to the radio frequency system. In this embodiment, an object that is asymmetric about the axis of rotation may have the effect of having eddy currents as it rotates. These eddy currents may generate a radio frequency field that may be picked up by a stationary pick-up coil. For example, the disk-like structure may be rotated. This may for example not be as efficient as using a loop, but it is nevertheless an extremely robust option.

In another embodiment, the turbine includes a rotor. The rotor has a diameter of less than 2mm, and in some cases less than 1 mm. Using a rotor of less than 2mm or 1mm means that the rotor can have a very high rotation rate. This means that the noise generated by it can be above the audible range.

In another embodiment, the turbine is configured to have a rotation rate of at least 1200 million revolutions per minute. This embodiment may be beneficial because the noise generated by the turbine can then be higher than 20000Hz, which is higher than the hearing range of a normal human.

In another embodiment, the magnetic resonance imaging antenna includes a plurality of turbines. For example, the turbines may be mounted such that their axes of rotation are perpendicular to each other. This may be advantageous in case the magnetic resonance imaging antenna may be placed in a different orientation with respect to the magnetic resonance imaging magnet. Having multiple turbines may have the following advantages: regardless of the position of the magnetic resonance imaging antenna, it is still able to generate electrical energy for powering the radio frequency system.

In another embodiment, the generator comprises a resonant cavity configured to generate an acoustic resonance in response to the transfer of pressurized gas from the gas inlet to the gas outlet. The generator also includes a mechanical member configured to vibrate in response to the acoustic resonance. The mechanical member is suspended within the resonant cavity. The generator further comprises at least one conductive path configured such that movement of the mechanical member causes generation of electrical energy in an external magnetic field. This may take different forms, for example. In some examples, the conductive path runs at least partially over the mechanical member such that as the mechanical member moves in an external magnetic field it causes electrical energy to be generated in the at least one conductive path.

In other examples, the mechanical member may have a torsional or rotational movement, for example, in the resonant cavity, and its movement within the magnetic field may result in radio frequency disturbances that can be picked up, and in this case the at least one conductive path is a pick-up coil used to collect such electrical energy.

In another embodiment, the resonant cavity is a whistle to an ultrasonic frequency. This embodiment may be beneficial because the resonant cavity may then be constructed such that it cannot be heard by a typical person.

In another embodiment, the mechanical member comprises a conductive element. The conductive element is configured to vibrate and/or torsionally vibrate with the rotating component. Vibrating the mechanical member rotationally and/or torsionally may be equivalent to a local or rotational movement. This can lead to perturbations in the magnetic field. The at least one conductive path is one or more stationary pick-up coils configured to receive electrical energy generated by vibration of the conductive element.

At least one stationary pick-up coil is configured to supply electrical energy to the radio frequency system. This embodiment may be beneficial because it does not require any electrical connection between the mechanical member and the at least one stationary pick-up coil. For example, when mechanical components become worn, it is possible to replace the part without any changes to the circuitry of the magnetic resonance imaging antenna.

In another embodiment, each of the at least one conductive paths is at least partially on the mechanical member. As the mechanical member vibrates, the area enclosed by the conductive path may change, because when the magnetic resonance imaging antenna is placed in an external magnetic field (such as the field from a magnetic resonance imaging system), such movement of the conductive path on the mechanical member will result in the generation of electrical energy. In other words, each of the at least one conductive path is configured such that movement of the mechanical member causes a region enclosed by the conductive path to change.

In another embodiment, the at least one conductive path is two conductive paths. The two conductive paths are electrically isolated. When the two conductive paths are configured, the two conductive paths are configured to independently generate electrical energy. For example, the mechanical member may be positioned such that two vertical regions each surrounded by a conductive path may be defined. This may enable the generator to function regardless of the orientation of the magnetic field relative to the magnetic resonance imaging system.

In another embodiment, the generator is arranged such that pressurized gas conveyed from the gas inlet to the gas outlet cools the radio frequency system. For example, the generator may also act as a heat sink. This may be beneficial as it may provide an effective means of reducing the amount of heat in the vicinity of the subject during a magnetic resonance imaging examination.

In another embodiment, the radio frequency system includes a receiver coupled to at least a portion of the one or more coil elements.

In another embodiment, the radio frequency system further comprises a transmitter coupled to at least part of the one or more coil elements. For example, the coil may act as a transmitter, receiver, or transceiver.

In another embodiment, the magnetic resonance imaging antenna comprises a fiber optic communication system configured for controlling a radio frequency system. This may be beneficial because the optical fiber does not disturb the electric or magnetic fields present during the magnetic resonance examination.

In another embodiment, the magnetic resonance imaging antenna comprises a wireless communication system configured for controlling a radio frequency system. This may be beneficial as it may provide a means of illuminating the wires extending to and from the magnetic resonance imaging antenna.

In another aspect, the invention provides a magnetic resonance imaging system comprising a magnetic resonance imaging antenna according to an embodiment. The magnetic resonance imaging system comprises a main magnet. The main magnet is configured to generate an external magnetic field. The magnetic resonance imaging system further comprises a pressurized gas system for providing pressurized gas to the magnetic resonance imaging coil. This embodiment may be beneficial because the magnetic resonance imaging system provides pressurized gas and an external magnetic field required by the generator to generate electrical energy.

In another embodiment the magnetic resonance imaging system further comprises a memory storing machine executable instructions and pulse sequence commands. The pulse sequence commands are configured for controlling the magnetic resonance imaging system to acquire magnetic resonance imaging data using the magnetic resonance imaging antenna. The magnetic resonance imaging system further comprises a processor configured for controlling the magnetic resonance imaging system.

Execution of the machine-executable instructions causes the processor to acquire magnetic resonance imaging data by controlling the magnetic resonance imaging system with pulse sequence commands. Execution of the machine-executable instructions further causes the processor to power the magnetic resonance imaging coil by controlling the pressurized gas system to supply pressurized gas during acquisition of magnetic resonance imaging data.

It is to be understood that one or more of the above-described embodiments of the invention can be combined, as long as the combined embodiments are not mutually exclusive.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as an apparatus, method or computer program product. Accordingly, various aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit," module "or" system. Furthermore, various aspects of the invention may take the form of a computer program product embodied in one or more computer-readable media having computer-executable code embodied thereon.

Any combination of one or more computer-readable media may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. "computer-readable storage medium" as used herein encompasses any tangible storage medium that can store instructions executable by a processor of a computing device. The computer-readable storage medium may be referred to as a computer-readable non-transitory storage medium. The computer readable storage medium may also be referred to as a tangible computer readable medium. In some embodiments, the computer-readable storage medium may also be capable of storing data that may be accessed by a processor of a computing device. Examples of computer-readable storage media include, but are not limited to: a floppy disk, a magnetic hard drive, a solid state disk, flash memory, a USB thumb drive, Random Access Memory (RAM), Read Only Memory (ROM), an optical disk, a magneto-optical disk, and a register file for a processor. Examples of optical disks include Compact Disks (CDs) and Digital Versatile Disks (DVDs), e.g., CD-ROMs, CD-RWs, CD-R, DVD-ROMs, DVD-RWs, 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 via a network or a communication link. For example, the data may be retrieved over a modem, the internet, or a local area network. Computer executable code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wired, fiber optic cable, RF, etc., or any suitable combination of the foregoing.

A computer readable signal medium may include a propagated data signal with computer executable code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. The computer readable signal medium may be any computer readable medium that: is not a computer-readable storage medium and is capable of communicating, propagating or transporting a program for use by or in connection with an instruction execution system, apparatus, or device.

"computer memory" or "memory" is an example of computer-readable storage media. Computer memory is any memory that is directly accessible by a processor. A "computer storage device" or "storage device" is another example of a computer-readable storage medium. The computer storage device is any non-volatile computer-readable storage medium. In some embodiments, the computer storage device may also be computer memory, or vice versa.

"processor," as used herein, encompasses an electronic component capable of executing a program or machine-executable instructions or computer-executable code. References to a computing device comprising "a processor" should be interpreted as being capable of containing more than one processor or processing core. The processor may be, for example, a multi-core processor. A processor may also refer to a collection of processors within a single computer system or distributed among multiple computer systems. The term computing device should also be read to be able to refer to a collection or network of computing devices each comprising one or more processors. The computer executable code may be executed by multiple processors, which may be within the same computing device or even distributed among multiple computing devices.

The computer executable code may include machine executable instructions or programs that cause the processor to perform aspects of the present invention. Computer executable code for performing operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C + + or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. In some instances, the computer executable code may be in a high level language or in a pre-compiled form and used in conjunction with an interpreter that generates machine executable instructions when operated.

The computer executable code may execute entirely on the user's computer, partly on the user's computer (as a stand-alone software package), partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet service provider).

Aspects of the present invention are described with reference to flowchart illustrations, pictorial 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 portion of the blocks of the flowcharts, illustrations and/or block diagrams, when applicable, can be implemented by computer program instructions in the form of computer-executable code. It will also be understood that combinations of blocks in different flow diagrams, illustrations, and/or block diagrams, when not mutually exclusive, may be combined. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

As used herein, a "user interface" is an interface that allows a user or operator to interact with a computer or computer system. The "user interface" may also be referred to as a "human interface device". The user interface may provide information or data to and/or receive information or data from an operator. The user interface may enable input from an operator to be received by the computer and may provide output from the computer to a user. In other words, the user interface may allow an operator to control or manipulate the computer, and the interface may allow the computer to indicate the effect of the operator's control or manipulation. The display of data or information on a display or graphical user interface is an example of providing information to an operator. The receipt of data by a keyboard, mouse, trackball, touchpad, pointing stick, tablet, joystick, gamepad, webcam, headphones, pedals, wired gloves, remote control, and accelerometer are all examples of user interface components that enable the receipt of information or data from an operator.

As used herein, "hardware interface" encompasses an interface that enables a processor of a computer system to interact with and/or control an external computing device and/or apparatus. The hardware interface may allow the processor to send control signals or instructions to an external computing device and/or apparatus. The hardware interface may also enable the processor to exchange data with external computing devices and/or apparatus. 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 MIDI interface, an analog input interface, and a digital input interface.

"display" or "display device" as used herein encompasses an output device or user interface suitable for displaying images or data. The display may output visual, audio, and/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), memory tubes, bi-stable displays, electronic paper, vector displays, flat panel displays, vacuum fluorescent displays (VFs), Light Emitting Diode (LED) displays, electroluminescent displays (ELDs), Plasma Display Panels (PDPs), Liquid Crystal Displays (LCDs), organic light emitting diode displays (OLEDs), projectors, and head mounted displays.

Magnetic Resonance (MR) data is defined herein as measurements of radio frequency signals emitted by atomic spins recorded using an antenna of a magnetic resonance apparatus during a magnetic resonance imaging scan. MRF magnetic resonance data is magnetic resonance data. Magnetic resonance data is an example of medical image data. A Magnetic Resonance Imaging (MRI) image or MR image is defined herein as a reconstructed two-dimensional or three-dimensional visualization of anatomical data contained within magnetic resonance imaging data. This visualization can be performed using a computer.

Drawings

Preferred embodiments of the present invention will be described hereinafter, by way of example only, and with reference to the accompanying drawings, in which:

figure 1 illustrates an example of a magnetic resonance imaging system;

figure 2 illustrates an example of a magnetic resonance imaging antenna;

figure 3 shows a flow chart illustrating a method of operating the magnetic resonance imaging system of figure 1;

FIG. 4 illustrates an example of a generator;

FIG. 5 illustrates a further example of a generator;

FIG. 6 illustrates a further example of a generator;

FIG. 7 illustrates a further example of a generator;

FIG. 8 illustrates a further example of a generator;

FIG. 9 illustrates a further example of a generator;

FIG. 10 illustrates a further example of a generator; and is

Fig. 11 illustrates a further example of a generator.

List of reference numerals

100 magnetic resonance imaging system

104 magnet

106 magnet bore

108 imaging zone

109 region of interest

110 magnetic field gradient coil

112 magnetic field gradient coil power supply

114 magnetic resonance imaging antenna

115 coil element

116 radio frequency system

117 generator

118 object

120 object support

122 pressurized gas system

124 gas line

125 optical fiber communication system

126 computer system

128 hardware interface

130 processor

132 user interface

134 computer memory

140 machine-executable instructions

142 pulse sequence commands

144 magnetic resonance imaging data

146 magnetic resonance image

200 gas inlet

202 gas outlet

204 optional muffler

206 communication system

300 acquiring magnetic resonance imaging data by controlling a magnetic resonance imaging system with pulse sequence commands

302 power a magnetic resonance imaging coil by controlling a pressurized gas system to supply pressurized gas during acquisition of magnetic resonance imaging data

400 turbine

401 rotor

402 paddle

404 rotating the shaft

406 conductive loop

500 switching circuit

502 fixed pickup coil

600 conductive plate

700 resonant cavity

702 mechanical component

702' mechanical component

900 conductive path

902 rectification circuit

1000 conductive part

1002 elastic element

1100 single point of attachment

Detailed Description

In the drawings, like numbered elements are equivalent elements or perform the same function. Elements that have been previously discussed will not necessarily be discussed in subsequent figures if they are functionally equivalent.

Figure 1 shows an example of a magnetic resonance imaging system 100 with a magnet 104. The magnet 104 is a superconducting cylindrical magnet having a bore 106 therethrough. It is also possible to use different types of magnets; it is also possible to use, for example, both split cylindrical magnets and so-called open magnets. A split cylindrical magnet is similar to a standard cylindrical magnet except that the cryostat has been split into two parts to allow access to the iso-plane of the magnet, such a magnet may be used, for example, in conjunction with charged particle beam therapy. The open magnet has two magnet parts, one above the other, with a space in between large enough to accommodate the object: the arrangement of the two partial regions is similar to the arrangement of helmholtz coils. Open magnets are popular because objects are less restricted. Inside the cryostat of the cylindrical magnet there is a collection of superconducting coils. Within the bore 106 of the cylindrical magnet 104, there is an imaging zone 108 in which the magnetic field is strong and uniform enough to perform magnetic resonance imaging. A region of interest 109 within the imaging zone 108 is shown. Magnetic resonance data are typically acquired for a region of interest. The object 118 is shown supported by an object support 120 such that at least a portion of the object 118 is within the imaging region 108 and the region of interest 109.

Also within the bore 106 of the magnet is a set of magnetic field gradient coils 110 for acquiring preliminary magnetic resonance data for spatially encoding magnetic spins within the imaging zone 108 of the magnet 104. The magnetic field gradient coils 110 are connected to a magnetic field gradient coil power supply 112. The magnetic field gradient coils 110 are intended to be representative. Typically the magnetic field gradient coils 110 comprise three separate coil sets for spatially encoding in three orthogonal spatial directions. A magnetic field gradient power supply supplies current to the magnetic field gradient coil. The current supplied to the magnetic field gradient coils 110 is controlled as a function of time and may be ramped or pulsed.

Within the imaging zone 108, a magnetic resonance imaging antenna 114 is visible. The magnetic resonance imaging antenna 114 includes one or more coil elements 115, a radio frequency system 116 and a generator 117. The radio frequency system 116 is coupled to the coil element 115 and may act as a receiver and/or transmitter in different examples. The magnetic resonance imaging antenna 114 is connected to a computer 126 via a fiber optic connection 125 or a communication system. The fiber optic connection 125 may be used to exchange digital information between the computer 126 and the magnetic resonance imaging antenna 114. The fiber optic connection 125 may be replaced with a wireless connection, such as a Wi-Fi network or a bluetooth connection, for example.

The magnetic resonance imaging antenna may be a transmit coil and/or a receive coil.

Outside the magnet 104 there is a pressurized gas system 122. There is a gas line 124 between the pressurized gas system 122 and the generator 117. The pressurized gas provides gas pressure to the generator 117, which the generator 117 converts to electrical energy for powering the radio frequency system 116. The magnetic resonance imaging antenna 114 may also have multiple receive/transmit elements capable of transmitting and/or receiving on separate channels. The sub-antennas for each of these channels are referred to herein as coil elements.

The magnetic resonance imaging antenna 114, the magnetic field gradient coil power supply, and the pressurized gas system 122 are shown connected to a hardware interface 128 of a computer system 126. The computer system also includes a processor 130 in communication with the hardware system 128, memory 134, and user interface 132. Memory 134 may be any combination of memory accessible to processor 130. This may include things such as main memory, cache memory, but also non-volatile memory such as flash RAM, hard drives, or other storage devices. In some examples, memory 134 may be considered a non-transitory computer-readable medium.

The memory 134 is shown as containing machine executable instructions 140. The machine executable instructions 140 enable the processor 130 to perform various control tasks for the magnetic resonance imaging system 100 and to perform various numerical and image processing tasks. Memory 134 is also shown as containing pulse sequence commands 142. The pulse sequence commands may be commands or data converted into commands that enable the processor 130 to control the magnetic resonance imaging system 100 to acquire magnetic resonance imaging data. The memory 134 is also shown as containing magnetic resonance imaging data 144 that has been acquired by controlling the magnetic resonance imaging system 100 with pulse sequence commands 142. The memory 134 is also shown as containing a magnetic resonance image 146 that has been reconstructed from the magnetic resonance imaging data 144.

Figure 2 shows a more detailed view of the magnetic resonance imaging antenna 114 present in figure 1. The magnetic resonance imaging antenna 114 is shown as including a plurality of coil elements 115. These coil elements 115 are coupled to a radio frequency system 116. Depending on the particular example, the radio frequency system 116 may be a transmitter and/or a receiver. The radio frequency system 116 is shown with an optional communication system 206. The communication system 206 may be, for example, a connection for an optical fiber or for a wireless communication system such as Wi-Fi. This may enable the magnetic resonance imaging antenna 114 to be controlled without using a wired connection.

The generator 117 is on top of the radio frequency system 116. The generator 117 has a gas inlet 200 and a gas outlet 202. Pressurized gas enters the gas inlet 200 and exits through the gas outlet 202. The mechanical work thus performed is converted into electrical energy by the generator 117. In this example there is an optional muffler 204 attached to the gas outlet 202. This may be useful, for example, in reducing the amount of audible acoustic noise from the generator 117.

Figure 3 shows a flow chart illustrating a method of operating the magnetic resonance imaging system 100 of figure 1. The magnetic resonance imaging data 144 is first acquired in step 300 by controlling the magnetic resonance imaging system 100 with pulse sequence commands 142. The magnetic resonance imaging coil 114 is next powered in step 302 by controlling the pressurized gas system 122 to supply pressurized gas during acquisition of the magnetic resonance imaging data 144.

Fig. 4 illustrates an example of the generator 117. In this example, the generator 117 comprises a turbine 400 with a rotor 401. Pressurized gas entering at the inlet and exiting at the gas outlet 202 causes the turbine 400 to rotate. It rotates about an axis of rotation 404. The turbine 400 includes a plurality of paddles 402. There is a conductive loop 406 within two opposing paddles 402. As paddle 402 rotates, there is a current generated into conductive loop 406. In the example shown in fig. 4, brushes, for example, may be used to complete the electrical connection to the conductive loop 406 and provide power to the rf system.

Fig. 5 shows an alternative generator 117. The example in fig. 5 is similar to the example in fig. 4, except that the version in fig. 4 does not require brushes. In this example, the conductive loop 406 is connected to a switching circuit 500, the switching circuit 500 being configured to electrically connect and disconnect the loop 406. This results in an oscillating electromagnetic field that can be picked up using a stationary pick-up coil 502. Stationary pick-up coil 502 is shown embedded in the housing of generator 117.

Conductive loop 406 provides power to switching circuit 500. This may be beneficial, for example, because it not only enables brushless communication, but also may arbitrarily select the electromagnetic energy generated by the generator 117 by setting the switching circuit 500 to switch at a predetermined frequency. A frequency such as 1MHz or 10MHz may be selected such that it efficiently transfers electrical power and avoids noise in the frequency band used for magnetic resonance imaging.

Fig. 6 shows a further alternative of the generator 117. The view in fig. 6 does not show the turbine, however the structure shown is connected to the turbine. In this example, the turbine causes the conductive plate 600 to rotate about the axis of rotation 404. In the presence of a magnetic field, this causes eddy currents, which then generate an electromagnetic field, which can then be picked up by the stationary pick-up coil 502. The example shown in fig. 6 has the disadvantage that the frequency of the electromagnetic radiation is set by the rotational speed of the turbine. However, the example shown in fig. 6 has the great advantage of its mechanical simplicity. The design is very robust and does not require any additional electrical components in the rotor.

Optional or supplemental MRI coils (such as surface coils, head coils, or other dedicated coils) are almost always used in magnetic resonance imaging. Although the handling of the coils is simple, the connection cables are cumbersome. The reason for this is that a high frequency potential well is required to make the cable safe for the patient.

To avoid bulky cables, pure wireless technology has been proposed. Battery power is feasible, but makes the coil heavy and/or dangerous. Wireless power transfer at larmor frequencies or higher seems infeasible, while at lower frequencies it makes the coil heavy and stiff. There is also a concept of supplying power through a thin wire cable using a high frequency signal. These concepts suffer from inefficiencies and therefore undesirable coil heating.

ExamplesMeans may be provided for transferring power to the magnetic resonance imaging coil (i.e., MRI receive coil) using compressed air or other pressurized gas. Some kind of turbine may be used to expand the air at the coils. A generator utilizing the main magnetic field as a stator field may be attached (or integrated) to the turbine. Thus, ferromagnetic materials may not be required, and for 16 element coils, turbine/generator units are expected to have masses below 2 grams and 1cm³The volume of (a). The air flow is expected to be about 0.5l/s at atmospheric pressure. This means that the compressed air flow at 10 atmospheres is only 50 ml/s. This mass flow can be very close to the breathing action of humans, so it is feasible to suppress noise emissions to a very low level. This gas flow can provide an effective cooling means to keep the coil at ambient temperature accurately at all times.

The energy generated by the adiabatic expansion of the diatomic gas is:

(n: molar weight of molecule; R: universal gas constant; T: absolute temperature; P: pressure).

At a pressure ratio of 10, in order to generate 50W of power at room temperature, a flux of about 0.02mol/s, i.e. an exhaust flow of about 0.5l/s (similar to human breathing action), is required. Even with efficiency considerations, 50W can be sufficient to power a 16 element coil. During expansion, the gas stream is significantly cooled. Starting at about 300K to a finishing temperature of approximately 150K. But when all losses are taken into account, there should be enough power available to return the gas to 300K. There may be no risk to the patient and the problem of coil heating is solved. However, it may be beneficial to use only sufficiently dry air to avoid turbine clogging.

Typical material strengths of commonly used engineering materials allow for turbine blade tip speeds of 100m/s while still having sufficient safety margins. In the case of a turbine diameter of 1cm, this translates into a frequency of 3.1 kHz. Area mounted on turbine is 1cm²May be a single loop coilA peak voltage of 2.9V is generated in an external field of 1.5T. Assume 1mm²The coil resistance may be about 5m omega and thus the short circuit power is about 800W. This may be more than the available power from the turbine. Thus, by reducing the current, with very high efficiency and using very low copper quality: (<400mg) to extract energy may be possible. Copper may be distributed over more windings and/or coils to regulate voltage and smooth the waveform.

An efficient fast rotating turbine design may be used. One inexpensive example is a simple tesla turbine, which has a rather low efficiency with respect to a multi-stage axial turbine. The axial design with vanes may provide a good compromise between efficiency and simplicity. In such a design, the coil(s) (conductive loops) can be easily wound on the rotor or on the blades of the rotor.

This type of power supply is not expected to negatively affect MR imaging. The rotor and turbine housing may be made of non-magnetic materials such as high strength plastics and ceramics. The current in the coil can be no higher than the usual feed current in a classical power supply. Thus, the image may not be distorted more than in current designs.

The generator may be constructed such that the acoustic noise generated in the design has a very high frequency. High frequency acoustic noise can be absorbed fairly well using fiber/cloth or using a muffler. The turbine may be packed in the fibrous material and all of the exhaust air may pass through the dense fibrous material. It is feasible that there is some pressure drop through the material and still generate sufficient power.

There are many quick-lock pressurized air connectors available (e.g., from Festo). The outer diameter of the hose may be somewhere between 3mm and 6 mm. The signal may be transmitted through glass fibers, and the fibers penetrate the hose at the end of the hose and enter a separate standard connector. If an attempt is made to unplug the plug to avoid the generation of sound, a sensor system may be used to depressurize the hose.

The exhaust may be treated by letting the device escape from a plurality of pieces of cloth covering holes distributed over the surface of the magnetic resonance imaging coil.

There is a trend towards more flexible and higher channel number MRI coils. However, as mentioned above, the connection cable with the RF trap is still bulky and stiff and requires careful wiring for RF safety. The turbine can operate in the audio frequency band, thereby generating undesirable noise directly at the patient. Sirens and similar oscillators (acoustic resonators) operating at ultrasonic frequencies with pressurized air are proposed here as alternative generators. Voltage can be oscillated in the conductive film in the acoustic cavity by B₀The field induces an oscillation that is excited by the air flow, for example similar to blowing a whistle on a grass blade. In addition to being inaudible, such a device can avoid any macro moving parts, bearings and tight tolerances of the turbine concept. Which makes them cheaper and more robust. The advantageous cooling concept of providing exactly as much local cooling power as is dissipated locally by all loads, thereby solving the cooling problem in the MR coil.

The problem of powering and cooling of the magnetic resonance imaging antenna increases with the number of channels (number of coil elements) because each pre-amplification/digitization/detuning unit increases the dissipated energy. The above air turbine proposal solves this problem well because energy conservation requires that all the energy generated by the thermodynamic engine during adiabatic expansion reduces the internal energy of the air. Thus, neglecting the small joule-thomson effect, the air provides exactly as much cooling "energy" as the heat dissipated by all connected electrical loads (turbine bearings, generators) during the energy conversion.

The main problem with the turbine solution is that unless it is very small (rotor diameter less than 2mm), it is limited to the audio frequency band, producing undesirably high tonal monotonous noise. Typical material strengths in common engineering materials allow for a turbine blade tip speed of 100 m/s. At a turbine diameter of 1cm, this translates to a frequency of 3.1 kHz. The turbine diameter can still be reduced by two thirds, resulting in near 10kHz, but it is difficult to reach 25kHz and still achieve efficient energy conversion. However, such a frequency is beneficial as it can be inaudible and also safe for the human auditory system.

In a magnetic resonance imaging antenna, the MR signal from each coil element (or channel) is pre-amplified, digitized, and converted to an optical signal in many current MR coils, but this and coil detuning can use considerable power supplied electrically. The corresponding electrical coil connections pose RF safety issues and can therefore be carefully wired (not too close to the patient or body coil leads, preferably parallel to the B0 field) and equipped with thick insulation layers and RF traps, making them bulky and inflexible.

In general, one example generator includes an acoustic resonator excited by an air flow, and a conductive element oscillating within the resonator, with the effect of inducing a voltage by means of an external magnetic field.

In particular, whistles operating with pressurized air at ultrasonic frequencies are proposed for such generators. Ultrasonic operation makes them inaudible and this concept avoids the tight tolerances of any rotating or macroscopic moving parts, the corresponding bearings and the turbine concept. Which makes them cheaper and more robust. The advantageous cooling concept of providing exactly as much local cooling power as is dissipated locally by all loads.

As mentioned above, the above is given by a diatomic gas (e.g., having 79% N)₂20% of O₂Air) is generated. At a pressure ratio of 10, in order to generate 50W of thermodynamic power at room temperature, a flux of about 0.02mol/s, i.e. an exhaust flow of about 0.5l/s (similar to human breathing action), is required. The total power consumption of a 16-channel coil array with RXE can be about 16W, so that 50W can suffice to power such coils, also taking into account typical conversion losses.

Several different types of generators using resonant cavities can be constructed. They may also have different types of mechanical members that move mechanically in response to resonance in the resonant cavity.

1. The first type of generator is a "blade of grass" or reed type resonator.

In a first example, a power generation similar to a whistle represented by a grass blade is proposedAs shown in fig. 7 below. Here, the blade (mechanical component 702) is made of a high tensile strength, high yield strength, electrically conductive, non-ferromagnetic material (e.g., copper-beryllium or copper-cobalt-beryllium as used for electrically conductive springs). With its long axis oriented perpendicular to the static magnetic field provided by the MR system. The air flow is oriented parallel to the magnetic field and excites lateral vibration of the blades. This induces a voltage along the long axis of the blade, which is used to drive the AC current. The vane is designed to be at about f₀With its fundamental resonance at 25 kHz. To limit acoustic losses, it may be located in a cavity with matching acoustic resonances. The width of the cavity, l, may be:

where c is the speed of sound, which results in a width of about 7mm, which is quite small for use in an MR coil.

The resonant frequency of the blade itself can be controlled by appropriate selection of its length, thickness and material properties similar to those of a guitar string. The fundamental resonance frequency is given by:

the blade length and cross section d is 1cm and A is 1cm 50 μm, the tension F in the blade, the density and elastic modulus rho of the copper-beryllium are 8250kg/m³And E130 GPa, the resonance at 25kHz will use the following strain

Is only 1.6%, while the elastic range in CuBe and CuCoBe is as high as 20% in range depending on the alloy used. The most advantageous seems to be the choice of cuco0.5be because of its combination of high yield stress and high conductivity.

The cross-section of the blade may be shaped similar to the profile of an aircraft wing to minimize turbulence. The blade may also be designed so that one end (the windward or leeward end) is thicker than the other, or reinforced by steel with an even higher modulus of elasticity, making the respective side so stiff that it does not oscillate significantly. This can lead to additional twisting of the blade and higher resonant frequencies.

Fig. 7 shows a further example of a generator 117. In this example again there is an inlet 200 and an outlet 202 for pressurised gas. In this example there is a resonant cavity 700. The passage of pressurized gas results in resonance that causes the mechanical member 702 to oscillate. This mechanical vibration of the mechanical member 702 is used to generate electrical energy. The mechanical member 702 is similar to a grass blade or reed. The oscillating vane 702 is fixed at the top and bottom of the cavity and is designed to have a resonance that matches that of the cavity. The air flow excites the resonance and by means of the main field B₀Inducing a voltage U_ind。

Alternatively, the generator may be designed as a pipe or whistle as in fig. 8 below or a variant thereof. Figure 8 shows an alternative structure for resonant cavity 700. In this configuration, the generator 117 is configured like an organ tube. In this design, the pressurization causes resonant oscillation of the air column in the tube, which can be transferred to the movement of the membrane at the location of maximum air motion amplitude. The external field causes a voltage U_ind. The generator may also be designed such that the membrane is positioned elsewhere therein, for example further towards or at its upper end.

Power generation:

for the grass blade profile, the amplitude of the blade when oscillating in its fundamental mode is:

this results in the induced voltage:

thereby obtaining a maximum voltage ofBlade length, frequency f for d 1cm₀25kHz, field B₀1.5T and a₀This amounts to a peak voltage of 1.5V, an expected lateral oscillation amplitude of 1 mm.

The resistance of the blade can be estimated using the following equation:

and when d is 1cm, a is 1cm by 50 μm, and ρ is 8.5E to 8 Ω m for CuBe2, R is 1.7m Ω, and theoretical short-circuit power exceeding 660W is obtained. This is much greater than the available thermodynamic power of a reasonable air flow and much less than what is required electrically. To get 16W of electrical power, an AC current of about 16W/1.5V sqrt 2-16A is required through the blades, resulting in 0.45W of heat dissipation, which is easily cooled by the cold air flow.

During adiabatic expansion, the air is significantly cooled. If a pressure ratio of 10 is provided at about 300K, it cools to approximately 150K. But when considering all losses, there is simply enough power available to bring the air back to 300K. Thus, in the case of an MR coil, there is no risk to the patient because the air is released at ambient temperature.

Generally, it is recommended to locate the generator at those components that require the most cooling (CPU, GPU or RXE in the case of MR coils) and provide air ducts projecting in common with the electrical leads to power and cool locally adjacent components.

This type of power may be MR imaging compatible. Assuming a square loop of 1cm size, a required AC current of about I-16A through the blade loop can generate an alternating dipole magnetic field with the following strength at its center:

it can be shielded to 0.7% of its original value with a copper shell of thickness of about 2mm (═ 5 times the skin depth). Furthermore, the residual accumulation phase of adjacent spins during MR imaging can be rephased to 1/f₀Within 40 mus, i.e. typically within a few sample points. This residual sinusoidal phase modulation is not phase locked across the individual k-space lines, resulting in locally virtually increased noise levels.

Trace amounts of water and CO in the feed air can be removed₂To avoid any icing of the components in the generator by water ice or dry ice. Methods known in the art, for example, techniques used in industrial liquid air production, may be used for this purpose.

Alternatively or additionally, the generator may be periodically flushed with low pressure air for a short period of time to remove any ice.

Fig. 9 shows a further example of a generator 117 of the type depicted in fig. 7. In this example, there is a conductive path 900 on a portion of the side of the resonant cavity 700 and also along the mechanical member 702. As acoustic resonances accumulate in resonant cavity 700, mechanical member 702 can oscillate back and forth, and the region surrounded by conductive path 900 can change. This may result in a current flow in the conductive path 900. In this example, there is a rectifier circuit 902 for supplying electrical power to the radio frequency system. The rectifying circuit 902 is not shown in all examples, but it should be understood that the rectifying circuit 902 may be present if alternating current is supplied by the generator 117 within the generator or within the radio frequency circuit.

Fig. 10 shows a further example of a generator 117. The example in fig. 10 is similar to the example depicted in fig. 9, except that the conductive path 900 is connected to the switch circuit 500. The mechanical member in this example includes a conductive portion 1000 having a conductive path 900, the conductive path 900 being located entirely on the mechanical member 702. Conductive portion 1000 is attached to resonant cavity 700 by a resilient element 1002. Such a design may be achieved, for example, by forming the mechanical member 702 as a metallic or mostly metallic blade (conductive portion 1000) that may be suspended by a resilient material (resilient element 1002) having high durability. Acoustic resonance in resonant cavity 700 may cause mechanical member 702 to vibrate. For some designs, the resilient element 1002 may enable the conductive portion 1000 to vibrate with a rotating and/or twisting component. This may facilitate the generation of electrical energy.

The conductive path supplies power to the switching circuit 500, and the switching circuit then opens and closes the circuit. This may be done at a predetermined frequency and this may result in electromagnetic radiation of the same frequency. A stationary pick-up coil 502 is used to couple to the radio frequency energy and is then used to provide electrical energy to the radio frequency system. This example may be beneficial where, in some cases, mechanical components 702 may wear out. By having the switching circuit 500, the stationary pick-up coil 502 can be located on a different mechanical component than the mechanical member 702. This means that the mechanical member 702 can for example be replaced without any modification of the electronics of the radio frequency system. Fig. 11 shows a further example of a generator 117. In this example, the mechanical member 702' is at least partially made of an electrically conductive material. The mechanical member 702' may be made of, for example, an electrically conductive material or a partially electrically conductive material. As acoustic resonances accumulate in resonant cavity 700, mechanical member 702 'vibrates back and forth causing eddy currents in the electrically conductive portions of mechanical member 702'. This results in an electromagnetic field that can be picked up by the stationary pick-up coil 502. The stationary pick-up coil is in this case a conductive path 900. The example of fig. 11 works when the mechanical member 702' has a rotational or torsional movement. To obtain this twisting movement, the mechanical members 702' are connected at the top and only at one point at the bottom 1100. This enables portions of the mechanical member 702' to oscillate back and forth in a rotational or quasi-rotational or torsional movement.

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

Other variations to 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 word "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. Although specific elements are recited in mutually different dependent claims, this does not indicate that a combination of these elements cannot be used to advantage. A computer program may be stored and/or distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. Any reference signs in the claims shall not be construed as limiting the scope.